3/2011 Saving costs Turbocompressors in wastewater treatment
Newly developed pumps Meeting market trends in the water segment
Prediction of forces Simulation in a pump sump
EDITORIAL
Sulzer today The Sulzer brothers laid the foundations of today's company in 1834 in Winterthur, Switzerland. Sulzer is active in the fields of machinery, equipment manufacturing, and surface technology in more than 160 locations around the world. Its divisions are global leaders in their respective markets, including the oil and gas sector, the hydrocarbon processing industry, power generation, pulp and paper, aviation, and the automotive industry. Sulzer employs more than 17 000 professionals who develop innovative new technical solutions. These products and services enable Sulzer's customers to achieve sustained improvements in their competitive positions. www.sulzer.com
Leveraging the megatrend of water Dear Technology Professionals, Customers, and Partners, The demand for water is a megatrend that we leverage at Sulzer. Sulzer is a leading provider of technology for transportation, production, and treatment of water as well as for energy generation with hydropower. The completed acquisition of Cardo Flow Solutions has established Sulzer as a leading supplier of pumps and related equipment in the wastewater market. Our new technologies increase energy efficiency and help protect the environment. The articles in the current Sulzer Technical Review (STR) present selected new solutions and technologies for the water market. For example, you will learn that using turbocompressors instead of positive displacement blowers for aeration in wastewater treatment leads to significant energy and cost savings. In another article, you will gain insights into the development process of the new SMD water pump for water transportation and desalination plants. In this issue, you will get to know the processes for the purification of industrial wastewater and water quality analysis. Additionally, you will learn more about the coating solutions from Sulzer for hydropower plants and experience how the performance of hydroelectric power plants can be enhanced. I hope you enjoy this issue. Sincerely yours,
Hans-Walter Schläpfer CTO Sulzer
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Sulzer Pumps Sulzer Pumps offers a variety of centrifugal pumps, ranging from custom-built models to standardized series. The division's marketleading position reflects its research and development activities relating to processoriented materials as well as its reliable service. It serves customers in the oil and gas, hydrocarbon processing, pulp and paper, power generation, water distribution and treatment sectors, as well as other specialized areas. www.sulzerpumps.com Sulzer Metco Sulzer Metco specializes in thermal-spray and thin-film processes for surface technology applications. The division coats and enhances surfaces, produces materials and equipment, and develops machining processes for special components. Its customers are active in the aviation and automotive industries, the power generation segment, and other specialized markets. www.sulzermetco.com Sulzer Chemtech Sulzer Chemtech is the market leader in the fields of process technology, separation columns, static mixing, and cartridge technologies. The division has sales, engineering, production, and customer service facilities throughout the world that enable it to meet the needs of its customers in the oil and gas, chemical, petrochemical and plastics industries. www.sulzerchemtech.com Sulzer Turbo Services Sulzer Turbo Services is a leading independent provider of repair and maintenance services for turbomachinery, generators, and motors with expertise in rotating equipment. The division also manufactures and sells replacement parts for gas and steam turbines, compressors, generators, and motors. Sulzer Turbo Services’ customers are located in the oil and gas, hydrocarbon processing, power generation, transport, mining, and other industrial markets. www.sulzerts.com Sulzer Innotec The research and development unit supports the development projects of Sulzer's own divisions as well as projects of industrial companies around the world by providing contract research and special technical services. Sulzer Innotec has considerable expertise in materials engineering, surface engineering, fluid technology, as well as in the field of mechanics. Its core competencies in the area of contract research also focus on these traditional disciplines. www.sulzerinnotec.com
CONTENTS
4
News Exhibitions, Events
Water and Wastewater 6
Saving aeration costs Positive displacement blower vs. turbocompressor
11
Sulzer analogy Walkers in white water
12
World-class water pumps Newly developed pumps meet market trends in the water segment
16
Simulation of the flow in a pump sump Prediction of the dynamic forces acting on a shaft
20
(Dis)Solving the high boiling problem Treating industrial wastewater
25
Sulzer world Welcome to Sulzer Chemtech in Rio Grande do Sul
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Surfaces for longer lifetime and higher energy efficiency The benefits of thermal-sprayed coatings in water turbines
31
Hydro-generator refurbishment Upgrading a power station for improved efficiency
34
Water analysis at Sulzer Innotec Prevention of water-related corrosion
38
Interview Marcos Koyama, Sulzer Pumps
39
Imprint
On the cover: Sulzer is a leading full-line supplier of pumps and related equipment to the water and wastewater industry. Solutions from Sulzer cover the entire water cycle.
Sulzer Technical Review 3 /2011 |
3
Exhibitions, Events
Sulzer completes acquisition of Cardo Flow Solutions
November 29–December 1, 2011, Barcelona, Spain
European Refinery Technology Conference http://ev557.eventive.incisivecms.co.uk/static/home Information for Sulzer Chemtech: Giuseppe Mosca Phone +39 02 6672 13 215 giuseppe.mosca@sulzer.com November 29–December 2, 2011, Geneva, Switzerland
Russian and CUS Refining Conference http://core.theenergyexchange.co.uk Information for Sulzer Chemtech: Albert Hug Phone +7 4967 76 06 00 albert.hug@sulzer.com November 29–30, 2011, Esslingen, Germany
2. ATZ-Fachtagung Reibungsminimierung im Antriebsstrang www.gabler.de/Veranstaltung/618 Information for Sulzer Metco: Nadine Pernhardt Phone +41 56 618 82 97 nadine.pernhardt@sulzer.com November 29–December 2, 2011, Las Vegas, NV, USA
The announced acquisition of Cardo Flow Solutions was completed on July 29, 2011. For a total cash consideration of SEK 5.9 billion (CHF 852 million), Sulzer acquired one of the leading suppliers of pumps and related equipment in the attractive wastewater market. The business has around 1900 employees. Headquartered in Malmö, Sweden, Cardo Flow Solutions is a full-line supplier of pumps and related equipment such as lifters, mixers, aerators, compressors, control and monitoring equipment, and services for the wastewater market, which accounts for around 90% of sales. With this acquisition, Sulzer has entered the highly attractive wastewater
pump market and will become a leading player in it. In addition, Sulzer has further strengthened its global position as a supplier of pumps and related services in the general industry, including the pulp and paper industry. Water and wastewater has become a key strategic market for Sulzer, accounting for approximately 16% of annual sales (proforma combined, based on 2010 numbers). The wastewater market offers growth potential in both mature and emerging markets, driven by longterm trends such as population growth, increasing water consumption, urbanization, and environmental protection. The acquisition creates a strong platform for further growth, driven by global geographic expansion and continued technological development of complete pumping solutions, good aftermarket opportunities by leveraging Sulzer’s existing service network, and cross-selling opportunities with the combined product offering. The acquired businesses will be fully integrated in Sulzer Pumps.
NGWA National Ground Water http://groundwaterexpo.com Information for Sulzer Pumps: Jim Willis Phone +1 318 742 9617 jim.willis@sulzer.com December 13–15, 2011, Las Vegas, NV, USA
PowerGen International 2011 www.power-gen.com/index/conference.html Information for Sulzer Pumps: Jim Willis Phone +1 318 742 9617 jim.willis@sulzer.com Information for Sulzer Turbo Services: Stephanie King Phone +1 713 567 2748 stephanie.king@sulzer.com January 24–25, 2012, Stavanger, Norway
Produced Water Management 2012 www.teknakurs.no Information for Sulzer Chemtech: Daniel Egger Phone +41 52 262 50 08 daniel.egger@sulzer.com
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Scania Euro 6 engine with SUMEBore™ technology Truck manufacturer Scania debuts its new Euro 6 engines that combine innovative technology solutions to radically reduce emissions with low fuel consumption. To help achieve this innovative technology, the cylinder liners of the new Euro 6 engine are enhanced with Sulzer’s SUMEBore™ coating technology to reduce friction, increase fuel efficiency, and improve corrosion and wear resistance. Martin Lundstedt, Executive Vice President of Sales and Marketing at Scania states, “We are proud of this impressive performance by our engineers, and we are happy we can now offer it to our customers. We have done everything possible to avoid increased fuel consumption.” Peter Ernst, Head of Automotive Venture SUMEBore at Sulzer Metco adds, “SUMEBore coating solutions have been successfully used for more than ten years in various engines, including large series applications. Based on our long-standing experience and continuing development efforts, we have reached a high standard of technology and reliability. We have now successfully adapted our coating materials and system engineering developments to the mass production of cylinder liners for the new Scania engines.”
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Successful Sulzer Turbo Machinery Technology Day More than 70 participants joined the Sulzer Turbo Machinery Technology Day organized by Sulzer Innotec on September 15th in Winterthur, Switzerland. Speakers from Sulzer Innotec, Sulzer Turbo Services, Sulzer Metco, EMPA (Swiss Federal Laboratories for Materials Testing and Research) and the Swiss Federal Institute of Technology in Zurich showed outstanding and interesting presentations. The presentations, the discus-
March 11–13, 2012, San Diego, CA, USA
NPRA Annual Meeting sions during the conference, and the subsequent guided tour of Sulzer Innotec, led to many personal contacts and exchanges of ideas between participants from Sulzer Innotec, partners from industry, and associates from the Sulzer divisions.
Sulzer opens its first pumps service center in Russia Sulzer Pumps, one of the world's leading pump companies, is opening its first service center in Russia. Located in Khimki, Moscow, the new service center will provide repair and retrofit service for industrial pumping systems for Russian customers and help to strengthen Sulzer Pumps’ presence in Russia. Operating one of the largest service networks in the industry, Sulzer Pumps has more than 60 service facilities with experienced specialists close to customers around the world. The service center in Moscow was constructed according to Sulzer Pumps global quality standards and meets all local industry regulations. The service engineers working in the service center
Exhibitions, Events
www.npra.org/meetings Information for Sulzer Chemtech: Rodney Alario Phone +1 281 441 5807 rodney.alario@sulzer.com March 12–14, 2012, Weimar, Germany
Jahrestreffen der Fachgruppen Fluidverfahrenstechnik and Computational Fluid Dynamics www.processnet.de Information for Sulzer Chemtech Mass Transfer Technology: Marc Wehrli Phone +41 52 262 67 47 marc.wehrli@sulzer.com Information for Sulzer Chemtech Process Technology: Juan Herguijuela Phone +41 61 486 37 61 juan.herguijuela@sulzer.com March 27–30, 2012, Cologne, Germany
have experience in local refineries and power stations and have also received training in, the wide range of Sulzer Pumps products and capabilities. The service center is equipped for repairs, retrofit, and efficiency improvement activities of existing pumps as well as the complete packaging of new ones. The service center will also offer trainings to employees of local customers.
Anuga Foodtec www.anugafoodtec.de Information for Sulzer Chemtech Mixing and Reaction Technology: Andrea Schwarz Phone +41 52 262 51 79 andrea.schwarz@sulzer.com Information for Sulzer Chemtech Process Technology: Norbert Martin Phone +49 681 6857 0053 norbert.martin@sulzer.com April 1–5, 2012, Houston, TX, USA
Pratt & Whitney signs agreement with Sulzer Eldim Pratt & Whitney signed a long term agreement (LTA) with Sulzer Eldim, a Sulzer Metco Company, to manufacture critical engine components for the F135, F100, F119, PW4000, PW2000, and V2500 jet engines.
AIChE Spring Meeting www.aiche.org/Conferences/SpringMeeting/index.aspx Information for Sulzer Chemtech: Mark Pilling Phone +1 918 447 7652 mark.pilling@sulzer.com
Sulzer Technical Review 3/2011 |
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WATER AND WASTEWATER
Positive displacement blower vs. turbocompressor
Saving aeration costs After comparing the aeration performance of existing positive displacement blowers with the aeration performance of an ABS turbocompressor HST, the Spanish wastewater treatment company FACSA achieved significant reductions in energy and maintenance costs with the turbocompressor.
A
BS, a product brand within Sulzer Pumps, is synonymous with innovation and well-proven solutions for wastewater collection and treatment. The company’s competence in wastewater handling has developed over more than 100 years. Today, the company offers one of the most complete wastewater technology portfolios in the world, and its products and solutions
help solve the challenges in municipal, industrial, commercial, and domestic sectors across the world every day. An important ABS strategy is to provide the wastewater industry with solutions that reduce both energy consumption and carbon footprint and increase both equipment efficiency and reliability. To achieve these goals, a number of world firsts in technology
have been launched. It is known as the ABS EffeX revolution. The first step of this revolution started in 2009 with the launch of the ABS EffeX range of submersible sewage pumps XFP with builtin IE3 premium-efficiency motors. Six models in this range provide motors spanning from 1.3 to 350 kW. In 2010, the medium-speed ABS submersible mixer XRW with an IE3 perma-
The picture shows Castellón de la Plana and the Desert de les Palmes Mountains from the air.
Kai Schreiber | CC-BY-SA
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WATER AND WASTEWATER
130 120 HST 2500
HST 9000
HST 6000
HST 40
110
Pressure (kPa)
100 90 80 70 60 50
nent magnetic motor followed. It gave users a total efficiency improvement of up to 35 % compared with other existing medium-speed mixer designs. Later this year, ABS will be introducing two additional world firsts for saving energy and improving operational processes in wastewater treatment plants (WWTPs).
Outstanding HST turbocompressors A further range of innovative ABS products with proven energy savings, reduced carbon emissions, and lower maintenance cost is the ABS turbocompressor HST series. These turbocompressors are used to powerfully aerate wastewater during the treatment processes. Lower life-cycle costs and easy operation are achieved through: • Magnetic bearings—minimal energy loss and no mechanical wear • Integrated design—compressor, motor, frequency converter, and control cabinet built in; an easy-to-install package • Small footprint—smaller compressor room, lower building cost • Low installation cost—no external starters or controls required. No crane or special foundation needed • System modularity—permits parallel operation of numerous compressors allowing tailor-made installations • Compatibility—can operate in parallel with all types of compressors, which facilitates flexible refurbishment The ABS turbocompressor HST can be configured in groups to suit the aeration
requirements. The ABS Master Control Unit optimizes the compressor operation to match the desired output and controls the group of machines just as one would control a single unit. This optimizes the operation of the whole group in terms of output as well as energy consumption. The performance of four ABS turbocompressor HST models is presented in Figure 1.
40 30 0k
2k
4k
6k
8k
10 k
12 k
14 k
16 k
Airflow rate (Nm3/h)
1 Graph of pressure (kPa) versus airflow rate (Nm3/h) for four ABS turbocompressor HST models.
Aeration devours energy The biggest single cost of running a WWTP is the cost of energy used for running motors. This expense is estimated at between 15 and 30 % of the total operational budget. If the energy costs are broken down, 43 % derive from aeration equipment, 33 % from pretreatment steps, and 24 % from dewatering sludge treatment. Because aeration is the biggest energy consumer, the Spanish WWTP company FACSA decided to compare the performance of its existing positive displacement blowers for aeration with a highspeed ABS turbocompressor HST 6000 to see if a significant saving in energy costs could be achieved with the latter.
2 FACSA’s wastewater treatment plant in Castellón de la Plana, Levante region, Spain.
Aeration at the WWTP The study presented in this article, was performed at the WWTP of Castellón de la Plana, a city in the Levante region of Spain 2. The treatment plant is designed for treating up to 45 000 m3 wastewater/day and has a total power capacity of
Sulzer Technical Review 3/2011 |
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Energy consumption kW•h
WATER AND WASTEWATER
kW • h
EUR
50.00
4.00
40.00
3.73
30.00
2.80
20.00
1.86
10.00
0.83
Energy consumption analysis
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3 Energy consumption of the ABS turbocompressor HST 6000.
1370 kW. The plant, built in 1980, has two lines of biological treatment with volumes of 4428 m3 and 5125 m3 respectively. Air is supplied through fine bubble diffusers by means of 4 positive displacement blowers: two blowers for each line. The power of all blowers is 160 kW, with a nominal flow of 11 238 m3/h for line 1, and 7326 m3/h for line 2 at standard conditions. For this study comparing normal rotating positive-displacement (Rootstype) blowers to high-speed turbocompressors with magnetic-levitation technology, a turbocompressor with a similar capacity to the existing blowers had to
be used. The operating specifications and conditions of the selected ABS turbocompressor HST 6000 are the following: • Design airflow: between 2475 m3/h and 7462 m3/h at standard conditions • Altitude of treatment plant: 0 m (sea level) • Ambient air temperature: between 0 °C and 35 °C • Relative humidity conditions: 50 % to 80 % • Pressure increase: 53 kPa (inlet pressure: 101 325 Pa; outlet pressure: 154 325 Pa) The airflow is regulated by a built-in frequency drive that can vary speed and
Energy consumption kW•h
4 Energy consumption of the positive displacement blower. kW • h
EUR
50.00
4.00
40.00
3.73
30.00
2.80
20.00
1.86
10.00
0.83
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torque to accurately and precisely control the air volume and pressure. It is this that provides significant energy saving at lower speeds.
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To allow correct comparison of both aeration technologies, one treatment line was operated with alternating use of the positive displacement (Roots-type) blower and the magnetic-levitation turbocompressor, after which the ratio kWh/kg BOD5 eliminated was compared. The biochemical oxygen demand or BOD is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. The same concentration of mixed-liquor suspended sludge (MLSS) was used in both cases to facilitate normalizing the results of one technology with those of the other. The energy consumption of both systems was compared using an analyzer that had been set up to measure the equipment operating data every 15 minutes.
Analysis of maintenance costs The analysis of maintenance costs of both technologies was carried out theoretically by comparing the preventive maintenance tasks of both systems. The existing positive displacement blowers have a complete log of performed maintenance. However, such logs do not exist for the ABS turbocompressor HST as it had only recently been installed in the treatment plant (summer 2009). Nevertheless, it should be stressed that since the start-up of the compressor in September 2009, no repair interventions have been made. Also, an important number of references exist of plants where the compressors have been
WATER AND WASTEWATER
1,4
280
1,2
270
Energy consumption
250 0,8
EUR/day
running numerous years without suffering damage or problems.
kWh/kg BOD5 eliminated
260 1,0
0,6
230 0,4
220
0,2
Figures 3 and 4 show results obtained during two days where system conditions were practically identical. As can be seen, the energy consumption of the positive displacement blower is higher than that of the ABS turbocompressor HST. In figures 5 and 6, the energy consumption and characteristics of both technologies are presented. The EUR/day calculation was done applying an energy cost of 0.098 EUR/kWh. Significant results were obtained when comparing the ratio kWh/kg BOD5 eliminated and the ratio EUR/day. Figure 7, the analysis of variance (ANOVA) results, shows that the average value of kWh/kg BOD5 eliminated using the ABS turbocompressor HST (0.86 kWh/kg BOD5 eliminated) is much lower than the average value when using the positive displacement blower (1.23 kWh/kg BOD5 eliminated). The energy consumption is lower by 0.37 kWh/kg BOD5 eliminated for the ABS turbocompressor HST. Figure 8 of ANOVA results shows that the mean EUR/day for the positive displacement
240
0
210
ABS turbocompressor HST 6000
Positive displacement blower
7 ANOVA results for kWh/BOD5 eliminated
for the ABS turbocompressor HST 6000 and the positive displacement pump.
blower (EUR 258/day) is higher than the cost for the ABS turbocompressor (EUR 233/day).
Maintenance costs Given the functioning principle of the ABS turbocompressor HST, the need for preventive and corrective maintenance of its mechanical parts is very low under the correct operating conditions. Considering the maintenance activities listed in system maintenance manuals, the theoretical maintenance costs for a period of five years for a worst-case scenario for a positive displacement blower are about EUR 19 318 in 5 years. Displacement blowers require exhaustive control of the bearings lubricating oil and moving parts in general. To
5 Characteristics of the positive displacement blower.
Positive displacement blower Variable
Mean
Minimum
Maximum
Standard deviation
kWh/kg BOD5
1.1
0.63
1.57
0.306
EUR/day
258.08
210.14
298.08
24.183
6 Characteristics of the ABS turbocompressor HST 6000.
ABS turbocompressor HST 6000 Variable
Mean
Minimum
Maximum
Standard deviation
kWh/kg BOD5
0.78
0.43
1.47
0.193
EUR/day
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187.01
290.59
24.067
200
ABS turbocompressor HST 6000
Positive displacement blower
8 ANOVA results of EUR/day for the ABS turbocompressor HST 6000 turbocompressor and the positive displacement pump.
estimate the maintenance cost of the blower, an approximation was made including the material cost of the maintenance performed over the years and the maintenance personnel costs. A renovation, which costs about EUR 8150, has to be performed on the premises of the supplier when 20 000 operating hours has been reached (approximately 2.5 operating years). Therefore, total maintenance costs for the positive displacement blower are about EUR 27 468. Additionally, it should be mentioned that cranes are required to move a positive displacement blower but only a normal forklift truck is needed to lift an ABS turbocompressor HST.
The ABS turbocompressor HST saves energy On analyzing the data obtained in this study, it can be concluded that the operating costs of an ABS turbocompressor HST are lower than those of a conventional positive displacement blower. The higher energy efficiency results of the turbocompressor derive from the higher optimal operating range of the system, which means that small changes in pressure do not increase energy consumption as is the case for a normal displacement blower. Magnetic bearing technology avoids the use of conventional bearings and the operation of moving
Sulzer Technical Review 3/2011 |
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WATER AND WASTEWATER
parts—such as the belt transmission system in a conventional positive displacement blower—to save significant energy. After several months of running both existing blowers and ABS’s magneticlevitation turbocompressor, FACSA concluded that with the magnetic-levitation technology, between 20 and 30 % energy savings had been obtained. The ratio of power intake divided by the kilograms of biological oxygen demand BOD5, went down from 1.23 kW/kg BOD5 eliminated to 0.86 kW/kg BOD5 eliminated. This means energy savings of EUR 25 146 per year, taking into account a cost of 0.098 EUR/kWh. Additionally, comparing the maintenance cost of 27 468 EUR/5 years for the positive displacement blower with the preventive and corrective maintenance cost of 15 771 EUR/5 years for the ABS turbocompressor HST, EUR 11 697 is saved using the latter.
Satisfied participants All participants in the comparative study described above are very satisfied with the results. David Castell, Manager of the WWTP operated by FACSA in Castellón, gives his views. “I’m very satisfied with the operation of the ABS turbocompressor HST 6000 9, which achieves scientifically proven energy savings of 20–30 %. As a result of our energy reduction, I estimate that our carbon dioxide reduction is now 350–400 tonnes of CO2 per year with the turbocompressor. From a maintenance point of view, the system has been running for 2 years in Castellón and has required no interventions at all since its installation. Two other major benefits are much appreciated. The small size and lighter
10 | Sulzer Technical Review 3/2011
9 ABS turbocompressor HST 6000.
weight of the ABS turbocompressor HST means that this system is much easier to handle manually than a blower. It can moved using just an ordinary trolley— no need for a forklift truck. With a new plant, one can build a smaller room for housing the machine. No cranes or other heavy lifting equipment are required. In addition, the quietness of the ABS turbocompressor HST means that regulations governing noise are more easily complied with. Staff must use protective equipment when working with positive displacement blowers but not with turbocompressors. This means more comfortable working conditions for workers and no complaints from people who live near a WWTP running a turbocompressor. FACSA now has two ABS turbocompressors HST installed, including the one in Castellón, and I’d certainly be glad to be informed of any new technology from Sulzer in the future that improves the performance of wastewater processes.” The ABS sales engineer for the Levante region, Juan Luis Alonso, is also very pleased.
“We have always been confident that the ABS turbocompressors HST series could satisfy the demands of our customers as regards significant energy saving, reduced maintenance costs, and quiet system operation. The success of the ABS turbocompressors HST run by FACSA and the publication of their comparative study has generated a lot of interest, which has led to six further ABS turbocompressor aeration systems being installed in the Levante region. Now that their high performance has been proved without a doubt through our close cooperation with FACSA, we look forward to even greater success in the future.”
Bart Janssen Cardo Flow Solutions Spain C/Madera, 14–16 28522 Madrid Spain Phone +34 620 714 721 bart.janssen@sulzer.com Tom Albrecht Cardo Flow Solutions Finland Tekniikantie 4 D 02150 Espoo Finland Phone +358 50 404 89 17 thom.albrecht@sulzer.com
SULZER ANALOGY
Walkers in white water One would think that the place where the mountain stream thunders down from the cliffs high above and dances foaming over the rocks would be no place for living organisms. However, larvae of a net-winged midge stroll about here on the slippery rocks, like some kind of microcow grazing on a lawn of algae. In the mid-1990s, Andreas Frutiger, then a water biologist at the Swiss Federal Institute of Aquatic Science and Technology (Eawag) in Dübendorf, was looking for such “blephs,” as the family of the net-winged midges (Blepharoceridae) are called in researcher slang, in the white water of Swiss streams. In contrast to the assumption that these highly specialized insects are very rare, Frutiger found representatives of five different species at 400 locations.
© A. Frutiger | Eawag – aquatic research
Hapalothrix larvae live in raging waters, where no enemy can catch them. Six suction cups provide them with footing there.
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Biophysical vacuum pump Blephs have been studied for more than one hundred years in the Alps and in the Rocky Mountains. The solution to the mystery as to how the larvae move about in the raging water is really fascinating: They attach themselves to the slippery rock surface with a row of suction cups. Squids and cuttlefish also make use of adhesion through suction cups; these are pressed flat on contact and thereby stick to smooth surfaces due to the negative pressure. What the blephs have invented, however, is much
more refined. In the middle of each of the six body segments, there is a biophysical vacuum pump in the form of a suction cup. After the application of the suction cup, muscles pull a plunger upwards in fixed tubular pipes made from chitin, thereby creating a vacuum in the pipes. The ring-shaped adhesion discs at the lower end of the tubular pipe stick unshakably to the surface. There has also been speculation as to how the larvae release the suction cup as quickly as possible during their movement. Andreas Frutiger solved this mystery in 1998. In the artificial white water channel in Dübendorf, he filmed the larvae as they walked over a glass plate. Thereby, he saw that the animal already pushed the individual suction cups further while the plunger was still at the top of the tubular pipe—and was thus seemingly still in suction operation. Frutiger ultimately discovered, in the edge of the adhesive disc, a fine notch that opened like a mouth shortly before the end of the adhesion phase: a valve then flooded the vacuum chamber within a split second and quickly ended the adhesion. This is why the body segment can be moved even before the plunger has travelled back to the lower start position.
Mobile in all directions Further analysis of the video sequences demonstrated the wide variety of this suction cup technique. Starting with the rearmost body segment, the animal moves one suction cup after the other in a wave-like action. The most common species in Switzerland, Liponeura cinerascens minor, which is found up to 2300
© Verastuchelova | Dreamstime.com
Despite the foaming water, the larvae a species of a net-winged midge stroll over the rocks.
meters above sea level, only requires one to two seconds for a cycle of all six suction cups, and can thereby travel up to five centimeters in a minute. In order to be able to move sideways, the larvae move some suction cups across their body axis. And, if they are in a particular hurry, they can release several suction cups at the same time and swing their front or rear parts to the side at an angle. Some blephs even have a “reverse gear” that they can select if they unexpectedly come across a weak flow, and want to get back into fast-moving water as quickly as possible. But why go to all this trouble in the raging mountain stream when there is usually calmer water only a few meters away? With this specialization in extremely strong currents, the blephs have conquered an ecological niche where they are relatively safe from predators and from food competitors. If the current reduces with decreasing water levels, they detach themselves from their supporting rock and let themselves be carried along downstream until they find more lively water, where they immediately connect themselves to a rock again with their suction cups. Herbert Cerutti
Sulzer Technical Review 3/2011 | 11
WATER AND WASTEWATER
Newly developed pumps meet market trends in the water segment
World-class water pumps Transportation and treatment of water are essential tasks in many industries, and water is a vital resource for all life on the planet. As the result of targeted product development for the water segment, Sulzer Pumps, a leader in pump design and manufacture, has recently introduced two pump ranges for the applications water transportation and desalination. State-of-the-art design and manufacturing processes make these pumps stand out due to their high efficiency and easy maintenance.
O
f all water on earth, only 2.5 % is not salty, and two-thirds of this freshwater is locked up in ice caps and glaciers 1. Of the remaining approx.0.8 % (ca. one-third of 2.5 %), onefifth is in remote, inaccessible areas or
cannot be used easily because it appears as seasonal rainfall in monsoonal deluges and floods. The world’s total freshwater reserves are estimated at around 35 million km3. Total global withdrawals of water
amount to about 3700 km3 annually—a small fraction of the estimated reserve. Even though water is the most widely occurring substance on earth, the everincreasing demand for water for sanitation, drinking, manufacturing, leisure,
Sulzer is a specialist in transporting large volumes of water over long distances and high geodetic heights.
Š Darren Bradley | Dreamstime.com
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WATER AND WASTEWATER 1 Distribution of earths’s water.
Optimization supports development
Total global water 2.50 % 0.93 % 0.07 % 96.50 %
Freshwater Saline groundwater Saline lakes Oceans
Surface water and other freshwater
Freshwater 1.30 % Surface water and other freshwater 30.10 % Groundwater 68.60 % Glaciers and ice caps
0.44 % Atmospheric and biological water 0.46 % Rivers 2.53 % Swamps and marshes 3.52 % Soil moisture 20.00 % Lakes 73.05 % Ice and snow
Source: Igor Shiklomanov’s chapter “World fresh water resources” in Peter H. Gleick (editor), 1993, Water in Crisis: A Guide to the World’s Fresh Water Resources.
and agriculture requires enormous effort to manage and optimize water usage and to minimize the environmental impact of water consumption.
Specialized in water transportation Agriculture and industry are the two largest users of the world’s freshwater resources, consuming 70 % and 20 % respectively. Municipalities account for the remaining 10 %. According to a study by the International Water Management Institute (IWMI), more than 1.2 billion people, one-fifth of the world’s population, live in areas of physical water scarcity. For a further 1.6 billion people, water scarcity has economic reasons, with lack of investment or insufficient human capacity making it impossible to satisfy the water demand. Lack of clean water supplies and sanitation remain major problems in many parts of the world. The water
sector needs significant investment and funding for water and sanitation. With two new pump ranges specifically developed for water transportation and desalination, Sulzer is able to support the growth of the water market in two important areas. Sulzer Pumps has been specialized in delivering pumps for transporting large volumes of water over long distances and high geodetic heights. Based on its hydraulic knowledge, the division has recently developed a new range of single-stage, double-flow, axially split pumps for water applications—including water transportation, municipal water treatment and distribution systems, desalination plants, and circulation pumps in power plants. Compact in design, these new pumps are specifically developed to provide the high performance and reliability typically required by water applications.
Automatic optimization tools played an important role in the development of these new SMD pumps. The pump range was developed at the product design center in Winterthur (CH) in close cooperation with Sulzer’s global manufacturing locations. State-of-the-art 3D tools including computational fluid dynamics (CFD) 2 for hydraulic design and finite element analysis (FEA) 3 to ensure mechanical integrity were used for the design process. The results were validated through model and prototype testing. This procedure made it possible to integrate the different analysis tools much faster and better. It also improved control of the full production chain, resulting in an innovative design that permits the optimum hydraulic fit for each duty point. This improvement ensures lower energy consumption and optimized hydraulic performance over a wide range of flows.
High level of standardization To provide a very high level of standardization of the new range, hydraulic coverage was ensured using standardized power levels instead of the traditional approach of using standard sizes and hydraulics of chosen specific speeds. While the new range offers 43 hydraulic
2 The pump range was developed at the product design center in Winterthur (CH) in close cooperation with Sulzer’s global manufacturing locations. State-ofthe-art 3D tools including computational fluid dynamics (CFD) for hydraulic design were used for the design process.
3 Finite element analysis (FEA) was used during the design process to ensure mechanical integrity.
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4 Thanks to the robust mechanical design, the new pump offers low vibration levels and a bearing life of over 100 000 hours, which results in lower life-cycle cost.
designs based on 20 different casings with two or three impellers per casing, the new approach to hydraulic coverage has drastically reduced the number of standard parts to only three standardized shaft diameters, sealing systems, and bearing housings. Using such an approach, each pump size requires a specific hydraulic design; whereas it is not possible to use a specific standard speed to systematize these designs. The high number of hydraulic designs required called for a new and faster design process. Sulzer Pumps invested significant development effort in coupling an automatic optimization tool with its proprietary hydraulic design tools for impellers and casings and performance prediction using a Reynolds-averaged Navier–Stokes (RANS) CFD code.
Low life-cycle cost
5 The standard SMD package consists of foundation rails for the motor and a separate base plate for the pump, or a combined base plate for pump and motor.
6 The new MBN-RO multistage ring section pump has special suction impeller for low NPSHr, as well as high-quality cast impellers and stage casings for better efficiency.
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Through this automated design process, the new pump range meets the high expectations regarding suction performance and efficiency while having very compact hydraulic water passages. In addition, the innovative volute and cutwater designs dramatically reduce pressure pulsations, shaft and bearing vibration levels, and mechanical stresses. The compact hydraulic dimensions—in combination with the low number of parts—lead to a cost-effective manufacturing process and to a reduction in product and inventory costs. Sulzer completed extensive model testing to verify the performance of these new hydraulic designs. Because this validation was on the critical path of the development process, model pumps were produced using rapid prototyping methods. Acrylic windows in the models allowed the observation of cavitation development as a function of the net positive suction head available (NPSHa). NPSHa describes the margin between the pressure at the inlet of the pump and the vapor pressure. The relation of incipient cavitation and NPSHa is an important quality measure for a pump. Because the cavitation was observable through the windows, it was possible to determine the NPSH required to avoid cavitation erosion for different impeller materials.
At the same time, dynamic and static components of the axial and radial loads, as well as suction and discharge pressures were measured to verify safe performance of the pumps in their full operating range. Thanks to the robust mechanical design, the new pump offers low vibration levels and a bearing life of over 100 000 hours, which results in lower life-cycle cost 4.
Ensuring mechanical integrity Finite element analysis (FEA) was used to check the mechanical integrity of the new range of pumps. This analysis included several aspects of the pump design. • Stress levels in the casing and the bolting of the pump during normal operation and for the maximum allowable working pressure, as experienced during the hydro test • Analysis of the axial split flange sealing and the internal leakage at maximum working pressure • Natural frequencies of the entire pump and its bearing housings as well as deformation of the casing in the various mode shapes. Particular attention was given to the packaging design, especially to the pump and drive baseplate. The design of the packaging is executed in 3D using a parametric approach, which allows for fast response in designing the complete package specific to each order 5. It also allows for analysis of the mechanical integrity of the package using finite elements in calculating the natural frequencies of the baseplate. Depending on the hydraulic configuration, the new SMD pump can handle flow rates of up to 16 000 m3/h and deliver heads of up to 260 m. Sulzer’s use of fully 3D design and associated modern numerical tools for hydraulic and mechanical design were crucial in developing this new range of compact pumps without compromising efficiency or suction performance. These new designs, together with the reduced number of standard parts, make this range of single-stage, double-flow; axially split pumps a competitive choice in water applications in terms of both cost and performance.
WATER AND WASTEWATER Production of drinking water In addition to water transportation, production of fresh water is a most important field in the water segment. Sulzer Pumps is a full-range supplier of highly efficient pumps for seawater desalination plants using reverse osmosis (RO) or multieffect distillation (MED). Reverse osmosis is a membrane filtration method used to remove larger molecules and ions from solutions by pressurizing the fluid on one side of a selective membrane. The solute is retained on the pressurized side whereas the pure solvent passes through the membrane. This process is widely used to purify drinking water from seawater by removing the salt and other substances from the water. The reverse osmosis process requires high pressure, and, moreover, it requires reliable equipment, as the plants generally operate around the clock. Often, these plants provide water to industrial installations, e.g., mines, or human settlements in areas where no other freshwater resources are available.
Designed for high pressure The newly developed MBN/MBN-RO ring section multistage pumps 6 have been specifically designed for the highpressure and high-efficiency pumping applications in small-to-medium seawater reverse osmosis plants 7. The MBN-RO addresses the special need for a high-pressure pump for the reverse osmosis and desalination markets. It
covers flow ranges up to 1100 m3/h and handles pressures up to 90 bar. Its improved hydraulic performance makes it suitable for any other highpressure application with clean liquids. Particularly its high efficiency, a key requirement in the desalination market, is an exceptional feature of the new pump range. The MBN-RO range is manufactured in duplex or superduplex as standard materials for a variety of seawater qualities to avoid pitting and crevice corrosion. By using the same improved low-NPSH impellers for every stage, the pump becomes highly modular, and its simplicity allows for ease maintenance. Main wear parts, such as mechanical seals or bearings, can be accessed quickly and easily without disassembling suction and discharge nozzle.
Ease of maintenance The new pump is available for the two specific speeds nq 29 and nq 33. Specific speed is a relation of flow rate and head of a pump and describes the geometry of a pump impeller. Low specific-speed radial impellers are generally lowflow/high-head designs, whereas high specific-speed axial flow impellers are high-flow/low-head designs. In order to achieve a modular design with a minimum number of parts and good interchangeability, as many common components as possible are used for both the nq 29 and nq 33 hydraulics 8. Parts such as suction case,
7 The MBN-RO addresses the special need for a high-pressure pump for the reverse osmosis and desalination markets.
8 In order to achieve a modular design with a minimum number of parts and good interchangeability, as many common components as possible are used for both the nq 29 and nq 33 hydraulics.
stage case, shaft, bearing parts, and sleeves, as well as some sealing and balance disk parts are interchangeable between both types. Discharge case, diffuser, and impeller are designed specifically for each specific speed. However, suction and stage impeller use the same hydraulic and mechanical design, thus reducing manufacturing and inventory cost. With the targeted development of new pump ranges for water transportation and desalination, Sulzer Pumps has moved to the forefront in the market for water pumps. Sulzer engineers are aware of the specific requirements for these important applications and have managed to develop highly efficient and cost-competitive pumps. At the same time, these pumps are easy to maintain, thanks to the forward-looking modular design that involves a reduced number of parts.
Philippe Dupont Sulzer Pumps Ltd. Z端rcherstrasse 12 8404 Winterthur Switzerland Phone +41 52 262 67 83 philippe.dupont@sulzer.com Jukka-Pekka Peri Sulzer Pumps Finland Oy P.O. Box 66 48601 Kotka Finland Phone +358 10 234 5395 jukka-pekka.peri@sulzer.com
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Prediction of the dynamic forces acting on a shaft
Simulation of the flow in a pump sump By means of flow simulation, engineers from Sulzer Pumps and Sulzer Innotec have been able to show that a modified pump sump geometry can lead to significantly smoother and uniform inflow at the pump inlet. The radial forces acting on the shaft can therefore be reduced and mainly centered around the zero point, allowing a significant increase in the lifetime of the bearings.
C
omputational fluid dynamics (CFD) has been successfully used for many years in the development and optimization of pumps. CFD is widely used for the prediction of the pump head, power, and efficiency of pump stages. However, exact knowledge of the inflow conditions is necessary in order to be able to correctly calculate these quantities. It is therefore also of interest to correctly
predict through CFD the flow conditions in the sump, from which the vertical pump draws in the water. The continuous development of numerical models, a steady increase in the available computing power, and careful validation based on experimental data with clearly defined boundary conditions are important factors for the successful application of CFD. The latter is nec-
essary in order to be able to reliably design pumps and their hydraulic components through numerical flow simulations.
Calm flow for smooth pump operation Large vertical pumps, such as those used for water supply, for process plants, and in cooling processes of thermal power
1 Pump sump with
a vertical pump: view of the water surface (green) and the streamlines, colored by velocity (increasing velocity: blue, green, red).
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plants, are submerged in a water basin, the so-called pump sump, where they draw in water 1. These semi-axial flow pumps must be reliable for a wide range of operating conditions, from low partload to overload. The behavior of these vertical pumps is strongly influenced by the flow conditions at the pump inlet. The formation of vortices and highvelocity gradients at the inlet of the pump can negatively affect the performance and may lead to shaft vibrations due to the dynamic radial forces. These vibrations can damage the shaft and the bearings and, in the worst case, lead to the failure of these components. Therefore, the industrial standards of the Hydraulic Institute1 define the vortex structures and velocity gradients that are permissible at the pump inlet. Up to now, model tests have been performed to demonstrate to the customer that no impermissible flow phenomena occur upstream of the pump. As these tests are very time consuming and expensive, it is advantageous to complement or replace these experimental tests by numerical flow simulations. Often,
different pump sump configurations have to be investigated before a favorable flow into the pump can be achieved. The investigations of these variants can be carried out much more efficiently using numerical simulations, which reduce development time and costs.
Modeling of the flow conditions for a pump sump on the computer In order to assess the possibilities and limits of numerical flow simulation, the operational behavior of a typical pump sump with a vertical pump has been modeled on the computer. This numerical model has been compared with the results from experiments using a physical model. Engineers have analyzed two pump sump designs to ensure that the numerical methods also provide the correct forecasts under different flow conditions 2 : • The basic geometry, in which the vortices that occur are impermissible according to the industrial standards. • Improved geometry, in which no vortices occur or only such vortices occur that are permissible according to the industrial standards.
The occurrence of these vortex structures should be demonstrated by means of unsteady flow simulations. The real flow within a pump sump includes the free surface of the water that may also be deformed by velocity gradients or by the occurrence of vortices. The modeling of this free surface by means of CFD is possible but is more complex and thereby requires more computer power. This additional effort is required because a two-phase simulation has to be set up that takes the liquid and the gas phases into account, thus, also, the air above the water. In some cases, simpler models can also reliably provide the desired information. Therefore, the free water surface is replaced by a fixed one. However, this simplification means that deformations at the water surface can no longer be reproduced. In addition, to keep the computational costs as low as possible, engineers do not model the impeller of the pump— only the outer and inner contours of the pump housing are taken into account. It is assumed that the impeller has no
2 Inflow to the vertical pumps. On the left, the original sump geometry with distinct vortex structures; on the right, the modified sump geometry with uniform flow.
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significant influence on the flow in the pump sump. Figure 3 compares simulation and experiment for the basic geometry. Five vortex structures can be seen in the model experiments. Two of these can be seen in the photo from the experiments, and they are also indicated in the streamlines from the simulation: the “floor vortex” and the “side-wall vortex”. The vortices are submerged and permanent
(type 2 according HI). The more complex simulation of this geometry with a free surface could predict four of these. With the simpler simulation using a fixed water surface, on the other hand, it was not possible to clearly identify the intermittent vortex described as the “backwall vortex”. The presentation of the streamlines for the case with the modified geometry 4 indicates a much more uniform
flow, which is also confirmed by the pictures from the experiments. As already mentioned, no significant vortex structures arise with this configuration. This behavior can be predicted with both types of CFD modeling— with and without free surface of the water. The results of these simulations show that the numerical models are able to recognize the different types of vortices
Side-wall vortex
Floor vortex
Back-wall vortex
3 Comparison of the vortex structures calculated with CFD and results from the experiments for the basic geometry of the pump sump.
4 Comparison of the vortex structures calculated with CFD and the results from the experiments for the improved geometry of the pump sump.
Uniform inflow
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as defined by the Hydraulic Institute1. The impact of the modification of the geometry of the sump on the vortex formation is also reflected. The validation shows that, in the case of the basic geometry where impermissible vortices structures occur, the CFD modeling with free surface predicts these better than the simpler method with fixed water surface. However, these slightly more accurate results require a significantly larger computational effort. For this reason, it would be sufficient in most cases in industrial practice to carry out the simulation with the more efficient method with fixed surface.
Determination of the dynamic forces acting on the shaft The impact of pump inflow on radial forces acting on shaft and bearings is also of interest in pump design. In order to investigate this, engineers must carry out a transient simulation of the vertical pump with the impeller. The computational domain only includes the pump without the sump and begins at the pump inlet. In order to obtain the correct inflow conditions into the impeller in the simulation, engineers use the inlet velocity profile from a sump simulation. This information is obtained as described above. For comparison, a uniform inlet velocity profile is also used. The forces can be determined by adding the pressures acting on the rotating parts of the pump. The spatial distribution of the force components Fx and Fy is plotted for one impeller revolution. The resulting forces on the shaft during operation with a uniform velocity profile at the inlet are shown in figure 5. It can be seen that the forces are largely centered around the origin, the center point of the shaft. The case with an inflow with a non-uniform velocity profile from a sump simulation is shown
in 6. The resulting forces are, in this case, no longer located around the center point of the shaft. The forces are increased by around a factor of two against the main flow direction. This means that there is a strong dynamic load on the shaft, which may lead to its failure or to damage at the bearings.
10 000
Flow from the sump 5000
0 – 10 000
– 5000
0
5000
Fewer model tests thanks to state-ofthe-art simulation methods Thanks to state-of-the-art simulation methods, it is now possible to considerably reduce the number of expensive physical model tests. Numerical flow simulation is able to predict the vortex structures and the velocity gradients that are relevant for the assessment of sump pumps according to industrial standards. If the inflow profile at the pump inlet is transferred into a simulation for the impeller, the radial forces that act on the shaft can be determined. Coupled flow calculations (sump and pump internals) have shown even larger forces. It is thus possible to determine in the design phase whether any impermissible dynamic loads act on the shaft and, thereby, on the bearings. The precondition for reliable predictions from numerical flow simulations is the thorough validation with experimental data, as well as exact knowledge of the limits of these methods.
10 000 Fx (N)
– 5000
– 10 000 Fy (N)
5 Spatial distribution of the radial forces acting on the impeller during an impeller revolution as calculated with CFD for a uniform velocity profile at the pump inlet.
10 000
Flow from the sump 5000
0 – 10 000
– 5000
0
5000
10 000 Fx (N)
– 5000
– 10 000 Fy (N)
6 Spatial distribution of the radial forces acting on the impeller during an impeller revolution as calculated with CFD for a nonuniform inlet velocity profile from a sump simulation. Felix A. Muggli Sulzer Markets & Technology Ltd. Sulzer Innotec Sulzer Allee 25 8404 Winterthur Switzerland Phone +41 52 262 42 52 felix.muggli@sulzer.com Susanne Krüger Sulzer Pumps Ltd. Zürcherstrasse 12 8401 Winterthur Switzerland Phone +41 52 262 40 10 susanne.krueger@sulzer.com
References 1
ANSI. Pump Intake Design Standards (ANSI/HI 9.8). Parsippany, New Jersey: Hydraulic Institute, 1998.
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Treating industrial wastewater
(Dis)Solving the high boiling problem Sulzer equipment can cost effectively remove pollutants from large wastewater flows. Depending on the boiling points of the pollutants to be removed in relation to that of water, Sulzer recommends either a wastewater stripper or a liquid-liquid extraction unit.
A
large number of pollutants in industrial wastewater are organic chemicals that are dissolved in water. These are only biodegradable in the rarest cases. Therefore, this wastewater cannot be cleaned in a municipal sewage treatment plant together with domestic wastewater. The substances often interfere with the microorganism metabolism or are even toxic. Such pollutants must therefore be removed
before the wastewater is discharged, as, for example, in the case of pollution with organic solvents. Depending on the source of the wastewater, the typical concentrations of the solvents lie in the range of 1–20 % by weight. Such concentrations of pollutants are too low and the calorific value of the wastewater flow is too low for thermal treatment, which is basically incineration. The requirement for a secondary fuel
would be very high—leading to high costs and additional environmental pollution.
Wastewater stripper Stripping represents a well-proven and effective method of treating wastewater contaminated with solvents. In this process, wastewater is fed into the top of a rectification column and steam is passed through the column from the
Part of an extraction column on a truck. During the contact of the two liquids in the extraction column, the phenol is transferred from the water to the extract. The latter has a higher affinity for phenol than water.
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(Concentration figures quoted in % by weight) Vent Cooling water Condenser Decanter
Feed (100 kg/h) 92 % Water 8 % Ethyl acetate
solvent-rich flow. Typical solvents that can be removed through direct stripping without a decanter are alcohols and ketones. A decanter is required for esters, ethers, short-chain hydrocarbons, and other substances that do not mix with water. This process is also well suited for wastewater that is simultaneously polluted with several components.
Problem: high boiling substances If wastewater is polluted with a chemical that has a boiling point above 100 °C at atmospheric pressure, the wastewater stripping process above is of limited use. If the substance forms an azeotrope with water that has a lower boiling point than pure water and that has a sufficiently high enrichment, then wastewater stripping can be performed with a decanter as described earlier. The solvent can thereby be effectively enriched in the distillate of a stripping column and can be removed well, despite the high boiling point. If the thermodynamic equilibrium is less favorable, however, direct stripping cannot be used. Phenol, for example, has a boiling point of 182 °C. Although it forms an azeotrope with water, the boiling point of this azeotrope is only 99 °C with a phenol content of 9 % by weight. This almost corresponds with the solubility of phenol in water at 25 °C 1. No concentration will take place in wastewater saturated with phenol. Because the boiling point of the azeotrope is very close to that of water, the stripping column will also need to have a very high separation performance. This would require a high number of stages and a high reflux ratio. The corresponding column would therefore be high and would consume a great amount of energy. Considering the high water
Stripping column Heat exchanger
Live steam
Bottom product (92 kg/h) > 99.99 % Water
1 Wastewater stripper with optional decanter, including a wastewater example.
content in the azeotrope, direct stripping is therefore not practical. Separation is also difficult in the case of water polluted with acetic acid. Acetic acid has no azeotrope with water and has a higher boiling point than water, so that all the water would be removed as a low boiling substance out of the distillate in direct “stripping.” This process would not be stripping in the true sense, but would be wastewater evaporation and would thereby be extremely energy intensive. Treatment would also be possible using extractive or entrainer distillation, but both are complicated and also require a lot of energy.
2 Flow diagram of a liquid-liquid extraction unit, including solvent treatment and a wastewater stripper.
3
Feed Acetic acid/ Phenol 1
Extractant
bottom in the opposite direction. This steam can be directly fed from an external steam network, but can also be generated in an evaporator. Figure 1 shows a diagram of this process. Simple wastewater stripping is suitable for use for all solvents with a lower boiling point than water and for those that form a low boiling azeotrope with water. The solvent, which will be condensed as a concentrate at the head of the column, accumulates in the vapor phase. The maximum achievable solvent concentration is determined by the thermodynamic equilibrium and by economic considerations. Wastewater that is practically free from solvents can be removed from the bottom of the column. After it has been used for the preheating of the polluted wastewater flow, it can either be fed into the sewer system or be recycled in the process. The concentrate obtained at the head of the column can either be treated further, with the solvent being recycled, or can now be incinerated more cost efficiently. If the solvent forms a heterogeneous azeotrope with water, and shows a miscibility gap, the decanter presented as an option in Figure 1 will be required. The water phase from the decanter is fed back into the stripping column, as it has a composition similar to the feed and is saturated with the solvent. The organic phase can be correspondingly treated further or be disposed of as a concentrate. The costs of this process are mainly determined by the thermodynamics of the water-solvent mix. Depending on the vapor-liquid equilibrium, a different water concentration will result at the head of the column, and will therefore also lead to a different energy requirement for a sufficiently concentrated,
Distillate (8 kg/h) > 97 % Ethyl acetate < 3 % Water
2
4 1 Extraction column 2 Decanter 3 Extractant recovery 4 Wastewater stripper
Wastewater
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3 Internals of the Kühni-type ECR column.
Solution: Extraction In such cases, liquid-liquid extraction offers an elegant solution to the separation problem. This process is based on the different solubility of a substance— the so-called transfer component—in two liquids that cannot be mixed with each other or that can only be partially mixed. If these two liquids are brought into contact with each other, a two-phase liquid-liquid dispersion results, and the transfer component divides itself according to the thermodynamic equilibrium between the two liquids. The liquid that has a higher affinity for the transfer component—and that takes these up—is generally described as the extraction agent, while the liquid phase enriched with the transfer component is described as the extract. The donor phase with depleted transfer component is called the raffinate. Liquidliquid extraction is mostly carried out at ambient temperature and pressure, so that no additional energy is required for heating or cooling.
22 | Sulzer Technical Review 3/2011
In many cases, ketones, esters, or ethers are used as extraction agents for phenol and acetic acid. During the contact between the two liquids in the extraction column, a material transport of the phenol takes place from the water to the extraction agent, as the latter has a higher affinity for the phenol than water. The water will thereby become depleted of phenol and the extraction agent enriched. At the same time, however, the water will become saturated with the extraction agent that is being used, so that the water itself cannot be directly discharged after the extraction. The extraction stage alone cannot purify the water, but the component with a high boiling point can be removed without an evaporation step. The water thereby takes up another material — the extraction agent. This agent has a lower boiling point than water and/or forms a low boiling azeotrope, and therefore it can be simply removed with the stripping process described earlier. In some cases, a solvent that is already present in trace quantities in the feed is used for the extraction. In this way, no additional materials are brought into the process. The transfer component—in this case, phenol or acetic acid—must be removed from the loaded extraction agent in order to make the agent reusable for extraction. This is normally carried out in a rectification unit. Figure 2 shows the basic flow diagram of the complete process.
Comparison Biodegradable solvents can also be removed by means of biological wastewater treatment in a sewage treatment plant. They are, however, mostly recycled for cost reasons. A comparison of the two processes described above, on the basis of the two flow diagrams, indicates that the removal of a high boiling com-
ponent from wastewater using extraction is much more complicated than singlestage stripping. Key factors in an efficient process are the right choice of the extraction agent and the operating conditions of all the connected columns that have been adapted to the separation task. The extraction agent must have certain properties: it must not be miscible with water—or at least be only slightly miscible—it must have a high affinity for the transfer component, and it should be as environmentally friendly
4 Pilot liquid-liquid extraction column with 60 mm diameter.
WATER AND WASTEWATER
and cost-effective as possible. The thermodynamic equilibrium of the extraction agent, water, and transfer component are key determining factors for the energy demand of the complete system, because most of the energy is used for solvent recovery in the rectification column after the extraction column. As a last step, the most suitable type of apparatus must be chosen for each process step. Depending on the origin of the wastewater, the pollutant concentration, volumetric flow rate, and required purity can be very different. The optimal column type for the extraction step must be selected according to these variables. On the one hand, the decisive factor for the selection is the thermodynamic liquid-liquid equilibrium, which, together with the solvent ratio, determines the necessary number of separation stages. On the other hand, the concentration of the transfer component in the feed is of great importance. The physical properties of the liquid phases strongly depend on the concentration of the transfer component. This applies to density, viscosity, and, in particular, to interfacial tension, which have a great impact on the hydrodynamic conditions in the column. In addition, the flow rates of the raffinate and extract phase over the height of the column also change due to the mass transfer in the extraction
5 Loading of a modular system from Sulzer Chemtech for recovery of solvents and purification.
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WATER AND WASTEWATER 6 3D layout of a wastewater stripper in a Sulzer Chemtech modular construction.
column. These changes are often so significant that the internals of the extraction column have to be adapted to these. This is the case when wastewater is polluted with 10 % or more acetic acid by weight, for example. The agitated Kühni column type ECR has proven to be very suitable for applications that require high separation performance and great flexibility. Figure 3 shows internals of this type of column, in which the geometry can be changed in each compartment. In this way, it is possible to compensate for any changes in physical property data and mass flow rates that arise typically in the case of large mass transfer. ECR extraction columns have already been successfully used for wastewater with up to 12 % phenol by weight and 35 % acetic acid by weight. Columns have been built with more than 30 theoretical stages. Columns with structured Sulzer extraction packing type ECP are used for very large wastewater flows with throughputs of several 100 m3/h. This type of column is characterized by a high hydrodynamic capacity but does not allow separation performances as high as ECR columns do. Together with liquid distributors specifically adapted to the packings, very efficient processes can be realized with these columns, in which large material flows can be treated that require only moderate separation performance. Distillation trays are used in the stripper column for the post-treatment of wastewater, as there is often a large liquid load in these columns and a twophase liquid in the upper part. The treatment of the extraction agent is often carried out in a rectification column with Sulzer distillation packing designed for high separation performance. In comparison to biological treatment of municipal wastewater, industrial
24 | Sulzer Technical Review 3/2011
wastewater treatment often requires the use of different thermal separation processes. The optimal selection of the extraction agent, the type of equipment that will be adapted to the task, and the operational parameters require broad knowledge and experience in all areas of thermal separation technology. This is vital in order to be able to combine the individual unit operations to achieve an efficient process. The necessary data for the design and operation of the system is obtained through a comparison with reference installations and, in particular, for the extraction step, through pilot trials in the Sulzer Test Center 2. Figure 4 shows a section of a pilot liquidliquid extraction column in operation. Based on many years of experience, it is thereby possible to find a turnkey solution to remove many high boiling pollutants from a wastewater flow, as shown in Figures 5 and 6.
Jörg Koch Sulzer Chemtech Ltd. Gewerbestrasse 28 P.O. Box 51 4123 Allschwil Switzerland Phone +41 61 486 37 12 joerg.koch@sulzer.com
References 1
Smallwood, I.M. Handbook of Organic Solvent Properties. London: Arnold, 1996.
2
Zuber, L. “The Power of Testing.” Sulzer Technical Review 2/2011, Winterthur: Sulzer Management Ltd., 2011.
SULZER WORLD
Welcome to Sulzer Chemtech in Rio Grande do Sul Sulzer strengthens its Tower Field Services activities with the acquisition and integration of CL Engenharia Ltda. Through local specialists, Sulzer now offers maintenance of vessel internals, welding, modification, and repairs as well as maintenance and fabrication of heat exchangers and boilers throughout Brazil from our base in Rio Grande do Sul.
In April 2010, Sulzer Chemtech acquired CL Engenharia Ltda, a maintenance company in Rio Grande do Sul, the southernmost state of Brazil. Porto Alegre is the capital of Rio Grande do Sul and the closest city to the premises of CL Engenharia. CL Engenharia was founded at the beginning of the 1990s by the father of the latest owners, Jorge Alfredo (since almost the beginning) and Luiz Alberto Celada (since 2006). Their great-grandparents were Spaniards with Italian roots who first moved to Argentina and then settled in the neighboring part of Brazil. At the beginning, the company was operated with approximately 20 employees and rented tools. It provided technical services for the repair and maintenance of electrical and mechanical equipment. A few years later, CL Engenharia increased its line of business by starting to offer maintenance
Vessel fabrication at Sulzer Chemtech in Rio Grande do Sul.
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At work in a plant.
and mechanical assembly, primarily to companies within the petrochemical complex in Triunfo, in the neighborhood of Porto Alegre. The headquarter of CL Engenharia was relocated to Triunfo in 1999. The business success of CL Engenharia shows that the founder had the right idea and testifies the tenacity and perserverance typical of Jorge and all his employees. Today, CL Engenharia is a recognized local specialist in the maintenance of vessel internals, welding, modification, and repairs as well as the maintenance and fabrication of heat exchangers and boilers, mainly in Rio Grande do Sul but also across the whole country. As an example, the company has several long-term maintenance con-
tracts in Triunfo for servicing and maintaining various mechanical systems and industrial boilers. The former owners as well as all other employees (approx. 300) are now part of the North and South American regional organization of Tower Field Services, and the premises serve as basis to support the presence of Sulzer Chemtech in Brazil.
Jorge and Luiz Celada Fabio Secchi
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The benefits of thermal-sprayed coatings in water turbines
Surfaces for longer life and higher energy efficiency Hydroelectric power contributes importantly towards the expansion of renewable energy sources. Sulzer Metco coatings protect many water turbine components from erosion and corrosion damage; thus, they contribute to a safe, economical, and environmentally friendly energy supply.
A
ccording to the World Energy Outlook 2010 report of the International Energy Agency, the worldwide primary energy demand will be 35% higher in 2035 than in 2008 as a result of increasing world population and increasing prosperity, particularly in
the emerging markets. However, on the whole, the proportion of demand for different primary energy sources will change. The study predicts an overall increase in oil consumption of only about 20% â&#x20AC;&#x201D;well below the average predicted rise in demand.
Gas, hydro, and other renewable energies will grow in all countries 1. The share of renewable energies for electricity production will increase from 19% in 2008 to 32% in 2035. But, after the Fukushima nuclear disaster in March 2011 and the declaration of a
Dam of a hydroelectric storage power plant in the Alps.
Š Prochasson Frederic | Dreamstime.com
26 | Sulzer Technical Review 3/2011
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at that time, that the turbines be manufactured from expensive high-alloy steel castings. The technology of today’s power plants differs significantly from that in Northumberland. Tools such as computer modeling optimize component designs to minimize cavitation. On the other hand, the overall stress loads on turbine components have risen. This is caused not least by ambitions to achieve greater profitability, exploit greater heads (water pressures and velocities), and expand weirs into inaccessible mountain regions, such as the Himalayas and the Andes. It is also caused by the desire to build fasterrotating, small turbines as well as large “monster” turbines and power plants in rivers that are contaminated with sand and chemicals. As the expectations of service life, maintenance intervals, and turbine efficiency are constantly rising, wear protection for power plant components is of increasing importance.
Coal Oil Gas Nuclear Hydro Other renewables – 600
– 300
0
300
600
900
1200
1500
Millions tonnes of oil equivalent (Mtoe)
OECD
China
Rest of the world
1 Projected growth in primary energy consumption by technology from 2008 to 2035. (Source: OECD / IEA World Energy Outlook 2010)
PIT
50.00
30.00
CAT
KRT Kaplan
20.00 15.00 10.00
The names Sulzer and Metco have been closely associated with the field of hydropower for a long time. As early as the 1930s, Metco applied steel, chromium steel, bronze, and zinc coatings to Francis runners to investigate the performance of these coatings in cavitation tests. In Germany and Austria during the 1960s, abrasion tests were performed on Kaplan machines using Metcoloy 2 (13% chromium steel wire) coatings at the Inn power plants. Later, these coatings were used successfully in the field. Combustion wire spray has become a standard coating technology in the turbine business and has since been used suc-
RRT
7.00 5.00 3.00 2.00 1.50 1.00
10.00
Francis
Bevel Gear Bulb Turbine and Compact Kaplan
Power (MW)
Longer lifetime of water turbines with coating solutions from Sulzer Metco
Water flow (m3/s)
nuclear phase-out by some of the leading industrial nations, it can be assumed that the growth of renewable energies will occur much faster than was predicted in 2010. One of the most environmentally friendly forms of energy production is hydropower. Water-powered electric utility plants can be differentiated between run-of-the-river power stations, reservoir power stations (e.g., dams), and pumped-storage hydropower stations. Run-of-the-river hydroelectric power plants are built directly in the river and produce energy continuously. Pumped-storage hydropower plants can also be used for energy storage. Energy storage is nowadays an important factor for on-demand electricity consumption. Germany currently has an installed pumped-storage capacity of about 7 GW with a daily operating capacity of 4 to 8 hours. This results in a remarkable overall storage capacity of about 40 GWh. Future projects will notably increase that capacity. Another advantage of pumped-storage power plants is that they are highly efficient, i.e., the excess electrical energy can be stored with an overall efficiency of 80%. Hydropower plants, particularly the turbines, face efficiency losses from corrosion and wear by erosion (hydroabrasion, fluid erosion and cavitation erosion) that depends on the type of power plant, the turbine design (Francis, Kaplan, or Pelton) 2, and the specific operating conditions (e.g., the corrosive potential and the sand, gravel, and stone debris in the water) 3. The first hydroelectric power plant was built in 1880 in Northumberland, England. The high wear on the blades caused by corrosion and erosion required,
5.00
0.70 2.50
0.50
Compact Francis
0.30
1.00
0.20 0.15
Pelton
0.10
0.50
Compact Pelton 0.03
0.05
0.1
0.05
0.25 2
3
5
7
10
20
30
50 70 100 150
300 500
Water fall (m) 2 Conditions of use for water turbines. (Source: Catalog Sulzer Hydro / Sulzer Escher Wyss)
Sulzer Technical Review 3/2011 | 27
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cessfully in almost all types of water turbines. Compared to the formerly used standard technology—weld buildup— the primary benefits were much shorter processing time and reduced detrimental thermal effects to the base material and components. 50 mm
Duk | CC-BY
3 Cavitation damage on a Francis turbine.
DJ Hybrid WCCoCr Jet-Kote WCCoCr
Coating
Weld overlay Oxide 2 Oxide 1 Hard chrome Wire arc Stellite 6 0
50
100
150
200
250
300
80 m/s 62 m/s Erosion resistance relative to X5 Cr Ni 13 4 4 Erosion resistance of different materials and coating systems.
350
Successful launch Toward the end of the 1980s, Metco introduced its new DiamondJet™ highvelocity oxygen fuel spray process (HVOF). This new technology was suited for the workshop and was adequate for everyday use due to its simple design. The first early attempts on sleeves were very promising, and so the range of parts to which coatings such as tungsten carbide materials (of type WCCoCr) were applied expanded very quickly. The component lifetimes achieved using these new HVOF coatings exceeded the boldest expectations. Thus, material erosion was reduced by a factor of 50 from that of turbine steel (1.4313). The transition from the very thick layers that were common at that time (e.g., 10 mm thick wire combustion-sprayed Metcoloy 2) to the thinner, but also more erosion-resistant, HVOF-sprayed carbide coatings was then initiated. Diagram 4 shows a comparison of the wear characteristics of various surface coatings. The dominant position of the HVOF process with WCCoCr as the coating material is evident.
Groundbreaking coating development
5 A Kaplan turbine blade, coated with Sulzer Metco SUME™Turb.
28 | Sulzer Technical Review 3/2011
In the 1990s, Sulzer Innotec, Sulzer Metco, and Sulzer Hydro collaborated to develop groundbreaking coatings and models for hydroturbine applications. An example is the development of
the SUME™Turb coating especially for Kaplan turbine blades 5. This WCCoCr coating is applied with the Sulzer Metco DiamondJet HVOF gun. The coating thickness is 400 µm or less. Additionally, a large percentage of Francis and Pelton turbines parts that are in contact with the water are coated. Some components, such as labyrinth seals on Francis machines, are constructed for optimal ease of coating. In the majority of cases, the coated components can be used without further treatment.
Proven materials Figure 6 provides an overview of the commonly used coating systems for the different types of water turbines. Typical standard Sulzer Metco WCCoCr materials that have proven their value in this area—considering load condition, the specific application, and the HVOF system used— are Diamalloy 5849, Amdry 5843, Sulzer Metco 5847, Woka 3652, Woka 3653, and SUMETurb. Despite practically identical chemical composition, these powder materials have different particle shapes, morphologies, particle size distributions, primary carbide sizes, and bulk densities. Therewith, they differ in production and manufacturing parameters and the starting raw materials used. These differences are clearly visible in wear test results 7. However, these differences are not noticeable through the usual hardness test performed for quality assurance. Thus, it becomes evident that in the water turbine industry high-velocity oxygen fuel spray (in the workshop, with DiamondJet, WokaStar, or WokaJet guns) or wire combustion spray (in the workshop or on-site with 14E, 16E or
WATER AND WASTEWATER
Kaplan turbine EGD-K) are mainly used. Plasma spray, yet another thermal spray process, has largely lost importance in this area whereas it was previously used to apply wear coatings to needles, nozzles, and Francis turbine parts.
Development support As with most mechanical parts, a general recommendation of a suitable coating solution cannot be made without detailed analysis of the application. Depending on the design of the machine, its specific operating parameters, and its specific service conditions, extensive differences in the dominant or overlapping wear mechanisms can prevail. In the worst case, it can happen that the stresses mutually reinforce one another. In general, however, it can be assumed that wear due to hydroabrasion, corrosion, and cavitation erosion increases with the flow velocity, the quantity of entrained solids, and the corrosion potential of the fluid. The wear in operation depends on factors such as size, shape, and hardness of the solid particles. Therefore, predictable limits for individual materials cannot be specified. Because the wear behavior of a material cannot be predicted by its simple physical and mechanical characteristics such as hardness, elastic modulus, and tensile strength, it becomes necessary to employ specialized wear tests. While phenomenological tests are used to determine the basic wear behavior of materials under well-defined loading conditions, application-specific tests are designed for specific conditions and components. The results of these tests can usually be transferred directly to an application1.
Component
Coated area
Coating
Wear mechanism
Discharge ring Partial or entire discharge • Wire combustion-sprayed ring 15 mm thick Metcoloy 2
Kaplan blade
Partial or entire blade
• HVOF 0.4 mm thick WCCoCr Erosion • wire combustion-sprayed (hydroabrasion, 5 mm thick Metcoloy 2 fluid erosion)
Guide vane ring
Between planar surface and draft tube liner
• Wire combustion-sprayed 5 mm thick Metcoloy 2
Protective sleeve
2-part sealing elements
• HVOF 0.3 mm thick WCCoCr Seal area, • wire combustion-sprayed abrasive wear Metcoloy 2
Radial bearing Applied to new or repaired • Wire combustioncomponents sprayed Sprababbitt A Crank Crank pin
Slide bearing area Slide bearing area
• Wire combustionsprayed Sprasteel-LS
Sliding wear
• Wire combustionsprayed Sprasteel-LS
Francis turbine Cheek plate
Complete area
Guide vane
Complete guide vane, also disc and face side seals
Turbine cover
Clearance and labyrinth area, wear ring area
Runner wheel
Clearance and labyrinth area, runner inlet channel
HVOF / WCCoCr
Erosion (hydroabrasion, fluid erosion)
Pelton turbine Pelton bucket
Inside and edge
HVOF / WCCoCr
Pelton needle
Area subject to wear
• HVOF / WCCoCr • Plasma / Cr2 O3
Needle spear
Area subject to wear
• Wire combustionsprayed Metcoloy 2 / Sprabronze
Sliding wear
HVOF / WCCoCr
Erosive and abrasive wear
Nozzle tip
Entire internal contour
Nozzle tip insert ring
Area subject to wear
Jet deflector
Area subject to wear
Jet deflecting cover
Area subject to wear
Erosion (hydroabrasion, fluid erosion)
6 Selection of the most important applications for thermal-sprayed coatings in water turbines.
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data generated from the above-mentioned test beds to develop customized applications. It can be determined, for example, which of the available coating systems is best suited for a given stress. For example, a special cavitation test bed is used at Sulzer Metco 8 especially to assess the cavitation of HVOF-sprayed coatings. Through close and proprietary cooperation, Sulzer Metco provides its customers the ability to select the best solution from a number of existing coatings or to further develop an existing coating to fulfill the customer’s specific turbine requirements. Thus, hydroturbines can operate for longer periods at even greater efficiencies, further contributing to effectiveness of these renewable energy resources.
The authors thank Hans Rinnergschwentner for his valuable contribution to this article.
120 110 100 90 80 70 60 50 40 30 20 10 0
BoR3 WF 12º GWF
8 Cavitation test rig at Sulzer Metco.
Acknowledgment
Black/grey: Sintered WCCoCr Blue: Various Sulzer Metco HVOF coatings Rest: Various WCCoCr coatings sprayed with other market-available systems and materials GWF: Erosion resistance (water jet erosion) under all impact angles WF 12°: Erosion resistance (water jet erosion) at grazing angle of 12° BoR3: Abrasion resistance (3-body wear test)
Relative wear behavior (% of duplex)
Together with its partner Sulzer Innotec, Sulzer Metco is fully equipped with test benches both for phenomenological studies as well as for customerand application-specific coating development. In detail, the following test facilities are currently available: • Cavitation/erosion test per ASTM G32-03 • Abrasion test bench per ASTM G65 (dry sand rubber wheel) • Abrasion/corrosion test (modified ASTM G65 test) • Salt-spray test per ASTM B117, also suitable for ASTM G85, ASTM B368, ASTM G43, and ASTM D2247 • Current-potential measurement • GE erosion test per GE50TF121 • Taber abraser per ASTM G75 • Two-body block-on-ring test (wear of friction pairs under sliding friction) • Water-jet erosion test Sulzer Metco offers its coating application expertise and its expertise analyzing
Hans-Michael Höhle Sulzer Metco Europe GmbH Spreestrasse 2 65451 Kelsterbach Germany Phone +49 172 6212 735 hans-michael.hoehle@sulzer.com Montia C. Nestler Sulzer Metco (US) Inc. 1101 Prospect Ave. Westbury, NY 11590-0201 USA Phone +1 516 338 2305 montia.nestler@sulzer.com
References 1
7 WCCoCr coating wear behavior.
30 | Sulzer Technical Review 3/2011
Kränzler, Thomas: “Ensuring product quality through customized materials tests – Classification of materials”; Sulzer Technical Review 1/2010
WATER AND WASTEWATER
Upgrading a power station for improved efficiency
Hydro-generator refurbishment Since 1882, when one of the first AC hydroelectric power stations was built with a capacity of 12.5 kW, the number of stations has grown very significantly not only in number but also in capacity. Today, for example, the Three Gorges power station has a capacity of 22 500 MW. Many power stations were built in the first half of the 20th century, and several stations have been in operation for over 100 years. Although the dams are relatively unchanged, the efficiency improvements in turbines have resulted in increased shaft power and, therefore, increased generation output.
H
ydro-generator insulation systems have a finite life and generally need to be rewound after 50 years—although some insulation systems have lasted much longer. When the generator is due to be rewound, it is an opportune time to consider increasing the rated output. Modern insulating materials, although thinner than ever, are capable of withstanding greater dielectric stress and higher operating temperatures than the materials used in the original stator and rotor windings. Figure 1 shows how a stator coil from an older machine (1950s) was redesigned to give improved performance and extended insulation life.
Thinner insulation—increased output As can be seen in figure 1, the thinner insulation of today’s insulating systems allows more space for copper, which reduces the resistance of the stator winding. As a result, the winding will run cooler and permit a small increase in output. The higher temperature rating of today’s insulation system permits higher operating temperatures and therefore increased outputs. When a generator is upgraded, the operator needs to have design performance calculations for the new rated output of the generator. These calculations include operating curves, excitation curves, reactances, and time constants,
1 Drawing of coil
redesign for a 1950s generator. 10% increase in copper X-section
Poor fit of coil in slot
25% increase in conductor insulation Too much space between coil sides
11% increase in slot wall insulation
Original copper size with modern insulation
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New copper size with enhanced insulation
etc. Before the output can be increased, a design model needs to be produced for the original machine design and original rated output using data available from the power station operator and from site measurements. This design model has to accurately reflect the electromechanical and thermodynamic performance of the original machine when compared with original performance data and the station’s operating records for temperature rise and excitation current at specific outputs.
Improved performance Once the design model has been produced and verified, it is used to evaluate improvements in the stator coil design and determine the temperature rises when operated at the new rated output. The design program generates the performance data required by the operator. If the refurbishment includes replacement of the stator core, there is an opportunity to use a lower-loss grade of magnetic steel than that used in the original machine construction. When changing stator core material, one must consider the increase in excitation requirements of the lower-loss grade of steel. Occasionally, it is possible to improve performance by some adjustment of the stator slot dimensions, although it is sur-
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2 Entrance to the underground generators in the Barron Gorge power station in Queensland, Australia.
prising how good many original slot designs were, given the methods of design calculation available at the time of construction. Improvement in the control of stray losses can be achieved by changing the method of stator coil transposition in order to reduce circulating current losses, or by changing winding covers to a non-magnetic material. Generally, any increase in generator output requires an increase in rotor excitation current. This increases the total losses within the machine with a resultant increase in stator and rotor operating temperatures.
4 Generator floor at Barron Gorge.
32 | Sulzer Technical Review 3/2011
3 Barron Gorge.
Upgrade at the Barron Gorge power station An example of a hydro-generator rewind and upgrade occurred at the Barron Gorge power station, which is operated within a World Heritage tropical forest site in Queensland, Australia 2 , 3. The power station was constructed in the early 1960s and went into service in 1963. The underground station was originally constructed with two 30 MW vertical 10-pole generators driven by Francis turbines. In 2009, Sulzer rewound and upgraded the first generator from 30 MW to 35 MW, and Sulzer is currently finishing the rewind and upgrade of the second generator. The original work scope was to rewind the generator stator, reinsulate the rotor, and, if necessary, rewind the exciter. When the stator winding was stripped and a stator core test conducted, deficiencies in the core were identified that necessitated the coreâ&#x20AC;&#x2122;s replacement. The customer agreed to an amended work scope and program, including a replacement core. When the core was stripped, further deficiencies in the stator case were identified, which were rectified during the lead time for the replacement stator core. This work included the manufacture and fitting of new building dovetail bars, core bolts, and clamp plate heel system.
The stator coil redesign slightly increased the cross-sectional area of the conductor (3.12 %), and the improved method of stator coil transposition reduced the stray losses. This change enabled the generator output to be increased by 16.67 % within the 65 °C temperature rise limits specified in the tender requirements. The insulation system passed the IEEE 400 hr voltage endurance test. Figure 4 shows the generator floor, and figure 5 shows a station section model. One significant change in the generator design was in the method of control of circulating current losses in the stator
5 Station section model.
WATER AND WASTEWATER
6 Stages of the rewind.
a) Original winding data recording
b) Original winding stripped
c) Rebuilding and consolidating new core
d) All new coils inserted
e) Stator winding connected
f) Stator winding completed
The site rewind was managed by our labour from UK and Australia. The Sulzer Dowding & Mills branch in Brendale, Brisbane, Australia, rewound the field coils and exciter. The location of the site within this unique World Heritage tropical forest site introduced some additional environmental challenges for the project management.
Enhanced generator efficiency The stages of the rewind can be seen in figure 6 a–h. It was possible to enhance the efficiency of the generator from 97.99 % before the rewind to 98.09 % after the rewind. The losses for the generator before and after rewind are shown in figure 7. The first rewind was completed within the revised program as agreed with the customer. The second rewind is currently due to be completed four weeks ahead of schedule. The tests at the completion of the first rewind met the customer’s requirements, and, during the heavy rains earlier this year, the rewound generator ran continuously at maximum output. Generator
g) Reinsulated rotor
h) Generator assembly
Original
Upgraded
MVA
33.33
39.00
MW
30.00
35.00
Fixed losses Friction, windage, and iron losses NL excitation losses
kW
kW
361.00
361.00
24.70
24.70
Variable losses
winding. The original manufacturer’s transposition consisted of two 180° twists of the top and bottom conductor stack one-quarter of the way and threequarters of the way through each phase. The design also swapped and twisted the top and bottom halves of the conductor stack halfway through the phase. The new transposition system had double top-top or bottom-bottom strand transpositions at all coil connections.
10% reduction in losses The replacement core lamination segments were manufactured from a grade of magnetic steel that provides a 10 % reduction in losses over the material used in the original machine construction. The rotor field coils were stripped and reinsulated with Class F insulating materials, as was the DC exciter. The DC exciter was redesigned to enable an increase in field forcing from 150 % to 200 %.
FL excitation losses
60.30
78.10
FL stator and stray losses
173.00
219.70
Total losses
616.00
683.50
97.99
98.09
Efficiency Stator temperature rise
46 °C
53 °C
Rotor temperature rise
43 °C
55 °C
7 Losses for the generator before and after the rewind.
John Allen Sulzer Dowding & Mills Camp Hill, Bordesley Birmingham, B12 0JJ United Kingdom Phone +44 121 766 6161 john.allen@sulzer.com
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Prevention of water-related corrosion
Water analysis at Sulzer Innotec Water is the ideal medium for a variety of purposes thanks to its high heat capacity, environmental friendliness, and easy availability. However, if the water quality is ignored, damage can occur due to corrosion, formation of deposits, or growth of microorganisms. Damage totaling billions of dollars occurs worldwide from water-related corrosion every year.
T
he specialists of Sulzer Innotec have been working for more than 40 years investigating water quality and its impact on materials. Through many years of practical experience, Sulzer Innotec has acquired significant experience in the field of water-related corrosion and cases of damage, and it passes on this know-how
to customers and to workgroups for the specifications of water-conducting equipment and systems. At present, the water laboratory of Sulzer Innotec operates as a contract laboratory for industrial and private customers. Hundreds of water and glycol-water samples from various applications are analyzed here every year.
Among the applications examined are waste incineration plants, industrial factories with heating and cooling circuits, cooling towers, air washers and air-conditioning plants, as well as heating systems in houses. This vast amount of product knowledge is, therefore, one of the strengths of Sulzer Innotec. Clients are advised indi-
1 Photo of a cooling system used in industry.
34 | Sulzer Technical Review 3/2011
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WATER AND WASTEWATER
100 µm
100 µm
100 µm
1mm
2 Piping made from high-alloy stainless steel with clearly visible pitting corrosion.
vidually and receive support in solving their problems—with services ranging from normal standard analyses, through on-site measurements, to customerspecific analyses with the development of specific analytical procedures. Through preventative water analysis, Sulzer Innotec has been able to avert massive damage to various facilities and equipment in many cases over recent years, thereby saving millions of dollars in costs 1.
Water as the cause of pitting corrosion At low temperatures, the presence of water is necessary for the corrosion of metals. Due to the special properties of water (dipole moment, oxygen solubility), dissolved ions (such as chlorides and sulfates) can come into contact with the surface of a metal together with oxygen and cause corrosion. Much of the corrosion damage that occurs could be prevented or delayed if conditioned water of a suitable composition and quality were used and if its quality were monitored regularly. Various cases of damage that have been investigated in recent years have been traced back to the use of unsuitable water. In one of the cases of damage examined by Sulzer Innotec, a piece of pipe had been delivered with various small holes in it. The pipe was part of a cooling
system in a refinery. As the operation of the refinery had been interrupted for a long period due to the damage, a loss of several CHF 100 000 had resulted. The pipe was made of so-called stainless steel. High-alloy stainless steels have a very thin, but nevertheless protective passive layer, which consists mainly of chromium oxides. Despite this protective layer, the surface of the pipe was partially rusted and showed signs of localized corrosion attack (pitting). The examination of the material revealed that the material had the correct specifications and had been properly processed. A material defect could therefore be eliminated as the cause of the damage. In order to find the cause of the corrosion, the customer was asked to provide a water sample from the affected cooling system. A high level of chloride was subsequently found in this water sample. Stainless steel is very susceptible to chloride attack because chloride locally destroys the passive layer and thus causes pitting. If, as a result, even more chloride is accumulated at the said location, a local area arises that is no longer protected by a passive layer. This area is now more susceptible to corrosive attack. Differences in concentration, potential differences, or even a reduced pH value at the location of the attack promote
pitting corrosion and lead to a faster growth of the holes. Small holes can then appear in the steel, even on passivated stainless steel 2. If the water quality had been checked in advance, it would have become clear at the planning stage that this steel was unsuitable for the water quality used 3. The costs of the water analyses and the consultation on the selection of the most suitable material and the conditioning of the cooling water would have only amounted to a fraction of the damage costs.
3 A check of the water quality can indicate whether the steel being used is suitable.
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Problems due to high microbiological contamination of the water Damage to plants can be triggered not only by inorganic constituents in the water, but also by microorganisms. If the water has a high level of microbiological contamination, biofouling can occur through the formation of biofilms. Biofilms consist of a mucus layer (film) in which microorganisms are embedded. The film offers the microorganisms a mechanical anchor and protection from external chemical and physical influences, and it allows them to adapt themselves to changes in the environmental conditions. In this way, the microorganisms can survive extreme pH and temperature fluctuations, pollutants (e.g., bactericides), and even UV radiation and lack of nutrients.
4 Cultivated microorganisms on an agar plate.
This robustness hinders the elimination of the biofilms. The economic damage caused by biofouling is enormous. For example, the flow of water in pipes can be reduced significantly, and the pipes can even clog in extreme cases. In the case of cargo ships, a biofilm of only one-tenth of a millimeter on the hull can reduce the ship's speed by several percent through the increased friction. This also results in increased fuel consumption. Another danger posed by water with a high level of biological contamination is microbiologically induced corrosion (MIC). In MIC, the aggressive metabolic products of bacteria lead to corrosive attack of the metal. Sulfate-reducing bacteria (SRB) prevail, and they form aggressive sulfides. In the case of passive materials, chlorides are also necessary for MIC attack to occur. These chlorides destroy the passive layer locally. Biofilms are a frequent source of MIC. Recent estimates suggest that at least 20 % of corrosion damage is either triggered, or promoted by MIC. As it is difficult to eliminate biofilms, preventative measures are highly recommended. Therefore, Sulzer Innotec offers bacterial count checks in order to be able to detect an increased microbiological contamination in the water in time 4. Biofouling or MIC can then be prevented by appropriate countermeasures.
Water as a cause of microbiologically induced corrosion
10 mm
36 | Sulzer Technical Review 3/2011
A perforated CuNi pipe was delivered to Sulzer Innotec for the investigation of corrosion damage to a condenser of a cooling unit. The condenser was cooled with river water. Neither a material defect nor a manufacturing error could be found in the initial investigation. In
order to find the cause of the damage, a water sample was also examined. The chemical analysis of the water sample revealed no anomaly, and neither the pH value nor the chloride content could be identified as being responsible for the corrosion. Further investigation revealed a strong microbiological contamination of the river water. As the sample had been delivered in non-sterile containers, however, the sampling had to be repeated for verification using sterile containers. A sample of the river water was taken before and after it passed through the condenser. A microbiological investigation was also carried out directly on the corroded tube. A very high level of microbiological contamination was found in both water samples. The sample taken after the water had passed through the heat exchanger also indicated agglomerations of bacteria, which is a clear indication of the formation of biofilms. A significant quantity of microorganisms were also detected at the corrosion locations by means of direct microbiological analysis. After further investigations, microbiologically induced corrosion (MIC) was definitively confirmed as the mechanism for the damage. Recommendations to prevent biofilms and corrosion were provided to the customer. Further corrosion of the system could therefore be successfully avoided. Without the analytical work of Sulzer Innotec, the piping of the condenser would have had to be replaced at regular intervals 5.
Hazard of Legionella in cooling towers and water systems In addition to the hazards of corrosion and fouling, microorganisms can also present problems for human health.
WATER AND WASTEWATER
50 mm
5 CuNi pipe with clearly visible local attacks of microbiologically induced corrosion (MIC).
Legionella 6 are particularly critical, and represent a significant hazard in air conditioning plants, ventilation systems, and cooling towers in particular. Legionella are rod-shaped, gram-negative bacteria that belong to the family Legionellaceae. They have one or more flagella with which they can move around and occur in both freshwater and salt water, where a temperature of 25–50 °C is a precondition. Water standing for long periods (stagnant conditions) also promotes their growth. Forty-eight species and 70 serogroups of legionella are currently known, all
being classified as harmful to human health. The most important type for human illness is the pathogen legionella pneumophila, as this can cause Legionnaires’ disease or the so-called “Pontiac Fever.” In healthy people, Legionnaires’ disease is fatal in approximately 15 % of cases, while mortality can be up to 70 % for people with compromised immune systems. The Legionnaires’ disease was first identified in 1976 at a meeting of the US war veterans association, the “American Legion State Convention,” from which it also received its name. At this meeting,
6 Legionella colonies growing on an agar plate illuminated with ultraviolet light. Photo credit: CDC / James Gathany
10 mm
181 people became ill with severe pneumonia at this meeting. All of the affected people were either participants in the war veterans’ conference, or were guests in the same hotel. As a result of this epidemic, the US American health authorities began investigating the causes, and, in 1978, were able to identify the responsible legionella pneumophila pathogen, which had established itself in the air conditioning system of the hotel. Other epidemics were retrospectively attributed to the same legionella pneumophila pathogen, as well as the Pontiac Fever, which was described for the first time in Pontiac in 1968. Through the routine testing of water for legionella, Sulzer Innotec has been able to identify a number of cases of legionella infestations in the last few years and has thereby been able to prevent illness outbreaks. With the early detection of legionella, the affected system can be cleaned and be refilled with fresh water, so as to ensure safe operation.
Roger Häusermann Sulzer Markets and Technology Ltd. Sulzer Innotec Sulzer-Allee 25 8404 Winterthur Switzerland Phone +41 52 262 21 44 roger.haeusermann@sulzer.com
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INTERVIEW
Marcos Koyama: “Our equipment is efficient and reliable”
Sulzer Pumps is a leading supplier of centrifugal pumps. The product line ranges from standardized pumps through configured pumps to complex customized pumps. We spoke with Marcos Koyama— head of the Water and Wastewater business segment— about Sulzer pump technology and new opportunities after the acquisition of Cardo Flow Solutions.
Sulzer has been building centrifugal pumps since 1857. What are the current core competencies of Sulzer in the water and wastewater business? To answer that, I have to go back in time. Since the beginning, we have had the unique ability to develop pumps optimized for specific applications, as, for example, for water transport. In the water transport business, it is very important that the equipment is highly efficient and robust and that it can provide reliable service for many years. Additionally, when desalination became commercially feasible, we invested in one technology—called reverse osmosis—which today is the relevant technology for water desalination. We entered this business at the beginning, in the mid-1990s, and our talent to engineer highly efficient and reliable pumps allowed us to develop a strong presence there. We were one of the first to use configured pumps in the desalination business and are now one of the market leaders. We recently also entered the market of large thermal desalination
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plants (multieffect distillation, MED). This technology is now at a level to compete with advantages against the MSF (multistage flashing) technology. In 2005, Sulzer acquired Johnston, a major player in the municipal business. Johnston has 100 years of experience in making vertical pumps. Already with this acquisition, we had an extensive product range and the talent to engineer products to solve unique challenges. How does Cardo Flow Solutions enrich the product offering? Sulzer was still not active in a big portion of the market because the wastewater market demanded submersible pumps. Sulzer did not have this technology and we only participated in the wastewater market with tailormade products. We have been looking for a way to penetrate this market for several years. Now with the acquisition of Cardo Flow Solutions and its product brand ABS, we have integrated a company that is one of the leading companies in the market. It designs very efficient products, and it has a complete product portfolio specifically for the wastewater market,
such as aeration products, pumps, and agitators. Where do you see great growth potential in the water and in the wastewater business? The water and wastewater business is big and stable. There is approximately 5 % growth per year on a global basis. Having solutions for both markets gives us very good opportunities to grow in the Americas and in Asia. Wastewater is driven by infrastructure projects, which are abundant in these geographical areas. In Europe, the Middle East, and North Africa we expect to grow with desalination and water pipeline projects in addition to wastewater. Sulzer Pumps manufactures standard and configured pumps, as well as engineered pumps—i.e., pumps that are optimized for a specific application. Which approach prevails in the water and wastewater business? Standard pumps are already fully configured and are mass produced. Configured pumps are something in-between
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a standard and an engineered pump. The pumps are configured using different standard elements such as casings, impellers, materials, accessories, etc., but you need to have experience to be able to do a smart configuration for a specific application. Engineered pumps are specially designed pumps for a specific application. Before the acquisition of Cardo Flow Solutions, Sulzer only had configured and engineered pumps. Coming back to your question: In general terms, engineered products account for ca. 15 % of the market in terms of value. Looking at the specific segments, it varies significantly. For example, in the municipal wastewater business, where ABS is strong, nearly all pumps are standard pumps. In the municipal and industrial water business, a mix between configured products and a smaller portion of standard products is required.
major industrial processes that can take place without water. The growing awareness of the environment leads to stronger regulations in terms of water quality, water treatment, and energy efficiency. These developments lead to major investments. For example, no products that have contact with drinking water should contaminate the drinking water. For that reason, they must be made of certified materials. Moreover, energy consumption is the biggest expense for our customers. Therefore, increased efficiency and reduced consumption is very important for them. On top of that, a lot of energy is dissipated from pressurized water. When the pressure of water in the pipe is too high to use directly in a process, the pressure must be reduced. We are looking at technologies with which we may be able to recover this energy. One last question: How long is the lifetime of a pump, and what is usually done when the lifetime is over? Customers specify the lifetime expectancy of a pump—typically 25–30 years. But, to be honest, the expectation is that it will last longer. For example, a few years ago, I got an inquiry from Argentina from a customer that owned a pump that had been operating since 1929! There is always an increase in demand for water. When a customer needs to pump more water through a given pipeline, we have the competence to redesign the pumping infrastructure. Usually, the strategy is to keep as much as possible of the given infrastructure and only replace where necessary.
How can customers from Sulzer and from the former Cardo Flow Solutions profit from the now extended offering? Our product portfolio now contains all products from Sulzer, Johnston, and ABS. Together, we have more than 300 years of experience and know-how. Our customers can profit from our presence with products and service all over the world. We can cover all processes in the water industry—from production through transportation to freshwater treatment and decontamination. We have a huge spectrum of products and services to meet all their requirements. Furthermore, we are committed to continuous improvement to being even more energy efficient.
Interview: Gabriel Barroso
Are there any technological or legislative developments to which you are paying increased attention? We take water for granted. However, a huge infrastructure is needed to bring water to your tap. Water is essential for life and also for industry. There are no
Marcos Koyama studied in Brazil in the state of São Paulo. He specialized in mechanics with two majors—machine design and production processes —and he holds a masters degree in industrial business management. He has been working in the pump industry for 35 years, and he has been working for Sulzer in various positions and locations for 29 years. He moved to Switzerland six years ago, and his current position is Head of Business Segment Water and Wastewater.
The Sulzer Technical Review (STR) is a customer magazine produced by the Sulzer Corporation. It is published periodically in English and German and annually in Chinese. The articles are also available at: www.sulzer.com/str 3/2011 93rd year of the STR ISSN 1660-9042 Publisher Sulzer Management Ltd. P.O. Box 8401 Winterthur, Switzerland Editor-in-Chief Gabriel Barroso gabriel.barroso@sulzer.com Editorial Assistant Laura Gasperi sulzertechnicalreview@sulzer.com Advisory Board Mia Claselius Ralf Gerdes Thomas Gerlach Hans-Michael Höhle Ernst Lutz Claudia Pröger Hans-Walter Schläpfer Heinz Schmid Shaun West Translations Interserv AG, Zürich Design Concept Partner & Partner AG, Winterthur Design Typografisches Atelier Felix Muntwyler, Winterthur Printers Mattenbach AG, Winterthur © November 2011 Reprints of articles and illustrations are permitted subject to the prior approval of the editor. The Sulzer Technical Review (STR) has been compiled according to the best knowledge and belief of Sulzer Management Ltd. and the authors. However, Sulzer Management Ltd. and the authors cannot assume any responsibility for the quality of the information, and make no representations or warranties, explicit or implied, as to the accuracy or completeness of the information contained in this publication. Circulation: 16 000 copies. Magno Satin 135 g/m2 from sustainably managed forests.
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