22nd AFA Int’l. Fertilizers Technology Conference & Exhibition June 30th - July 2nd, 2009 Marrakech, Morocco
Recent Highlights in STAMICARBON’S Urea Technologies
Freddy Buitink Licensing Manager Stamicarbon
The Netherlands
AFA Technical 30 June – 2 July 2009
Recent Highlights of Stamicarbon Urea Technologies
by Freddy Buitink, Stamicarbon B.V.
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AFA Technical 30 June – 2 July 2009
Table of contents 1. Introduction ............................................................................................................................ 3 2. Highlights in Material development. ..................................................................................... 4
2.1 Safurex® as alloy protection for HP equipment .......................................................4 2.2 Safurex® as material of construction for HP piping .................................................4
3. Highlights in technological development. ........................................................................... 5
3.1 Urea2000plus™ Pool condenser and pool reactor technology ...............................5 3.2 Developments leading to the new Avancore® design. ............................................5 3.3 The Avancore®. Design ..........................................................................................6 3.4 Summary ..................................................................................................................7 4. Stamicarbon Granulation technology .................................................................................. 8
4.1. History .....................................................................................................................8 4.2 Feature 1: Runtime of 90 days or more ...................................................................9 4.3 Feature 2: Lower formaldehyde consumption (0.3 %) ...........................................9 4.3 New developments with regard to the granulation process...................................10 4.4 Summary ................................................................................................................10 5. Joint developments.............................................................................................................. 11
5.1 Safurex ...................................................................................................................11 5.2. Radar level measurements ...................................................................................11 5.3 Rotoform urea process ..........................................................................................14 5.4 Integrally geared compressors for CO2 compression in the urea-process............15 5.5 N/C meter ...............................................................................................................15 5.6 New urea operator training simulator.....................................................................15 6. Summary and conclusions.................................................................................................. 16
All technical and other information contained herein is based on general Stamicarbon/DSM experience and within this limit is accurate to the best of our knowledge. However, no liability is accepted therefore and no warranty or guarantee is to be inferred.
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AFA Technical 30 June – 2 July 2009
1. Introduction Stamicarbon is the world leader in urea technology. Leadership in this context also means responsibility. As process licensor we see this responsibility as a continuous effort to ensure that our process plant designs fulfill our customer’s needs defined as; • Strife to make the plant as safe as possible • Maximize the reliability • Minimize the CAPEX • Minimize the OPEX • Maximize the ease of operation Through our investments in research and development and our experiences in revamp projects together with joint developments with different manufactures we are proud to present our most recent achievements in this respect, achievements available for licensing and engineering for new plants as well as for revamp projects.
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AFA Technical 30 June – 2 July 2009
2. Highlights in Material development. 2.1 Safurex® as alloy protection for HP equipment Since urea processes became industrial, the very important issue to be solved was the corrosion resistance of the applied materials under the extreme synthesis process conditions. For most of the materials that have been used as construction material, continuous passivation was required. Continuous passivation is usually done by adding air to the synthesis section, which has a negative influence on the process with respect to reaction conversion and process safety. If no passivation air is needed, no oxygen will be introduced hence no risk anymore in the formation of explosive mixtures. Safurex® material has been Stamicarbon’s standard material since year 2001 and already in use since year 1997 for HP replacement equipment and revamping. Due to the use of Safurex® as alloy protection, the investment of new plants became significantly lower, limitations with respect to operational aspects were widened and although the on stream times of Stamicarbon urea plants were already significant, with Safurex® we have realized on stream times that in the past never have been classified as being realistic. All this means that the efficiency and profitability of a urea plant is upgraded to a maximum level; one can easily talk about a maintenance free urea plant. Safurex® eliminates the risk of active corrosion without consequences for the overall corrosion rate. Due to its higher mechanical strength use of Safurex® is effectively extending the lifetime and reliability of the HP equipment. Also from process point of view there are huge advantages such as intrinsically safe design (no risk on active corrosion), higher reactor conversion and lower emissions. Due to the impressive corrosion resistance Stamicarbon inspectors advises customers with Safurex equipment to extend the inspection interval to 6 years. 2.2 Safurex® as material of construction for HP piping A very successful development has taken place in the fabrication of the HP Synthesis Piping and all its accessories. By using Safurex® Piping advantages have been achieved in several ways. First of all: The corrosion rates are low and the risk for selective corrosion is negligible. Special advantages exist in gas lines; here no condensation corrosion will occur anymore. Secondly: The wall thickness of HP Piping can be reduced substantially when using Safurex® Piping. In case of 316L Urea grade Piping one needs a schedule 160, this wall thickness can be reduced in case of x2CrNiMoN 25.22.2 to schedule 120. By using Safurex® Piping only a schedule 80 is needed. This is the result of the high mechanical strength of Safurex®. The consequence of the reduction in schedule is that the larger size pipes can be scaled down one size; this is valid for sizes of 10 inch and more, a one size smaller diameter piping can be used while maintaining the same inner diameter. Taking into account that the maximum size of piping is one off the bottlenecks that might limit plant capacities the value of this advantage becomes clear. Restrictions in lines can easily be removed by replacing the existing line by a line made of Safurex®. Applying the same outside diameter combined with the reduced wall thickness enables more area available for process
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AFA Technical 30 June – 2 July 2009
flows making replacement of conventional piping through Safurex® piping a ideal tool for revamping. In the third place Safurex® has the same thermal expansion coefficient as Carbon Steel and thus significant lower than austenite steels. That means that one can shorten the lines since expansion loops are no longer needed to the extent as should be taken into account for the full austenite steels. Safurex® Piping can be used in new plants but can of course also be used in operating plants for replacing Piping and its components.
3. Highlights in Technological development. 3.1 Urea2000plus™ Pool condenser and pool reactor technology Since the introduction of the high pressure CO2 stripper in Stamicarbon urea plants in the late sixties the urea solution from the synthesis section has been directly fed to the so called Low Pressure recirculation section. At that time this was a novelty, because up to then an in-line medium pressure recirculation section including ammonia recovery and pure ammonia recycle section was required. From the medium pressure recirculation the resulting urea solution could then be fed to the Low Pressure recirculation section after which it was further concentrated and processed. The introduction of the Stamicarbon CO2 stripper resulted in unprecedented high overall conversion on both CO2 and NH3 lowering the steam consumption per ton of urea with almost 40 % comparing with existing technology in that timeframe. This Stamicarbon technology made it possible to leave out this medium pressure recirculation with its ammonia recovery, ammonia condensation and recycle section reducing overall costs and improving the reliability of urea plant. Stamicarbon started in 1994 the first CO2 stripping urea plant with a pool condenser. The pool condenser combines the functions of a HP carbamate condenser and a urea reactor in one vessel. Integration of HP equipment lowers the total costs of HP equipment en minimizes HP piping lowering further the costs and improving the reliability. Reducing the number of connecting lines in the HP section means a lower risk of leakages and hence an improved reliability. In 1996 the first CO2 stripping urea plant with pool reactor was build. HP scrubber, HP condenser and HP reactor were integrated in one piece of equipment reducing the overall costs of equipment and simplifying operation of the synthesis. 3.2 Developments leading to the new Avancore® design. In 1998 Stamicarbon started the 2nd revamp project of PIC Kuwait, conventional type plant. The synthesis of a conventional plant is the urea reactor operated at about 200 bar. The reactor is located at ground level. This section was modified to CO2 stripping, increasing the capacity from 1065 to 1750mtpd. The project proved that it is possible to have the reactor in a CO2 stripping plant located on ground level, while maintaining gravity flow in the synthesis loop. This is done by installing the Poolcondenser above the original vertical reactor.
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AFA Technical 30 June – 2 July 2009
In 2004 Stamicarbon started the revamp project of MCF, Mangalore. The HP Scrubber had to be replaced. It was deleted and replaced by a MP Absorber. Again successfully costs were saved and reliability was increased in an evolution process to the Avancore® plant design. All the knowledge gained in the last years is now part of the today’s plant design called Avancore®. The HP scrubber is deleted and the overhead vapor of the Poolcondenser or Poolreactor is vented to a simple MP absorber. This is possible because the overhead flow is very small as no passivation air is needed, thanks to Safurex®. This can be explained as follows. Due to elimination of the need for passivation no air is anymore added to the synthesis. Therefore the amount of inert to be vented is reduced drastically. Scrubbing the inert with the relative cold carbamate from the LP section is enough to reduce the ammonia vented to the atmosphere while maintaining a good overall conversion in the synthesis without the need of an additional HP heat exchanger. 3.3 The Avancore®. Design Depending on the plant capacity, the Stamicarbon Synthesis concept Avancore® is a Poolreactor type up to 2300 MPTD and a Poolcondenser with a vertical reactor at grade at higher capacities. Figure 1. Development of Stamicarbon’s CO2 stripping concept Design, late sixties
Poolcondenser (1994)
• Total gravity flow • No HP Scrubber
grade <2300mtpd
>2300mtpd
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AFA Technical 30 June – 2 July 2009
Figure 2: Avancore® lay-out. VAPOUR AND INERTS TO MP ABSORBER POOL REACTOR LP STEA M / STE AM CO NDENS ATE STE AM CONDENSATE
22 mtr. CARBAMATE RECIRCULATIO N SE CTION
NH3
Liquid 14 mtr.
V apour Utilities
MP STEAM
HP STRIPPER MP S TEA M CONDENSATE
SOLUTION TO LP RECIRCULATION SECTION CO2
3.4 Summary With Avancore®, the challenge put forward in the introduction is met. o The Synthesis is very simple with minimum HP piping and process controls. o The Synthesis recycle is on total gravity flow. o For capacities up to 2300 MTPD, only 2 pieces of HP equipment are needed (Stripper and Poolreactor) o For capacities above 2300 MTPD, an additional reactor is located at grade. o The urea solution from the HP stripper is discharged in both cases directly to a low pressure recirculation section. Adding up the effects of the main topics of this chapter, use of Safurex, zero oxygen synthesis operation and the low level synthesis arrangement, it gives ample opportunities for HP equipment replacement and for revamping projects of any type of urea plant.
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4. Stamicarbon Granulation technology 4.1. History There are several processes available for granulation of urea. For a long time the drum granulation process licensed by Girdler was used. Despite of the capacity limitation in this process licenses were granted to companies in the US and Canada. In the late seventies of the previous century the fluid bed granulation process of Stamicarbon was developed in the research facilities of DSM. At the same time the company NSM developed their process in Sluiskil. Stamicarbon developed their proprietary film spraying nozzle, however at that time Stamicarbon decided not to commercialize this process. Later on Stamicarbon started to implement the granulation process in a commercial pilot plant in Belarus in cooperation with the company Grodno Azot. In the year 2002 the first product came out of this plant. The process proved to be very successful and was later accepted by Agrium for introduction in their plant in Fort Saskatchewan. In 2003 the Agrium plant started the commercial production of granules with Stamicarbonâ&#x20AC;&#x2122;s license. In the mean time a number of other granulation plants (> 15) and with capacities up to 3900 MTPD has come on stream or are currently been build or contracted. Figure 3: Process lay out for granulation unit Elevator Urea granules
Coarse
Screen
Cooler Crusher
Fines
Dust scrubber s
Process water
Granulator
Recycle
Cooler
Formaldehyde Urea
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4.2 Feature 1: Runtime of 90 days or more The dust formation is a critical point in the granulation process. The advantage of the Stamicarbon granulation is that due to its granulation nozzle using liquid film layering of the granules there is low dust formation in the granulator. In other processes the urea melt is distributed in the granulator as very fine droplets. If a very fine droplet does not meet a seed particle the droplet crystallizes to a dust particle. This dust particle is blown out and settles down in the top of the granulator. As the dust formation is minimal in the Stamicarbon process the time interval for granulator washing is in the order of 90 days and more. In most situations the granulator is washed only during a plant shut down caused by a trip of the ammonia or the urea plant. Experiences in existing plants show that there is further improvement possible in the on stream time of the plant. Excessive dust formation in other processes results in reduced efficiency of the main screens resulting in the need of cleaning on a regular base. The cleaning has to be done to maintain a good classification of the product. If there is a lot of dust deposits in the plant the final product will contain dust particles on the surface, leading to a dusty product. In the Stamicarbon granulation dust built up in screens and crusher does not cause any problem. The main screens show good performance even without cleaning. 4.3 Feature 2: Lower formaldehyde consumption (0.3 %) Generally the formaldehyde is used for two reasons: 1. Granulation aid in the granulator to suppress dust formation; 2. Stabilizing the final product. In our process the role of formaldehyde is limited to the last point, stabilizing the final product. As our process shows a reduced dust formation there is no reason for the application of formaldehyde to reduce the dust formation in the granulator. We operated the pilot plant without formaldehyde and even in that situation it was possible to operate the plant. Of course the deletion of formaldehyde influences the quality of the final product. This zero formaldehyde product was transported from Klapeida to Antwerp without a complaint from the client, however the crushing strength was somewhat lower and the product showed a slightly increased caking tendency. Stamicarbon recommends a value for the formaldehyde content of 0.30 %. This product is already exported worldwide without any problems and complies with the demand of the customers. The reduction in formaldehyde compared to other processes is an important factor when we consider the operational costs. For a 3000 MTPD plant the saving amounts to 14200 kg urea formaldehyde solution (UF85). For a fair comparison it has to be taken into account that this
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amount of solution contains 3550 kg/h urea, which now has to be produced by the plant. Overall the cost saving for a world scale plant is in the order of 3 mln US$ per year based on UF85 savings only. 4.3 New developments with regard to the granulation process As with the urea melt process Stamicarbon is dedicated to lead the innovation also with regard to their granulation process. To this extent we have set up an intensive research program aiming at improving our process. 1. Lowering energy consumption by applying bulk flow heat exchangers whenever possible. 2. Applying cooling systems to minimize the sizing of the granulation equipment compensating for summer conditions. 3. Investigation of innovative ideas to reduce or eliminate dust and ammonia emissions. 4. Improving the run time even more by optimizing equipment configuration and process conditions. 5. Investigating alternatives for formaldehyde which should be cheaper, accepted in the market 6. Lowering installation costs. Integration of granulator and cooler eliminating cooler fans, cooler, dust scrubber and exhaust fan, lowering the total height of the granulation unit. 4.4 Summary 1. 2. 3. 4.
Higher reliability of the total urea line due to extended run time of a Stamicarbon granulation. Lower operation costs per ton of Urea due to a lower formaldehyde consumption. The final product quality is very good. The granules show a high sphericity and a very smooth surface thanks to the film sprayer. The state of the art granulation thanks to continuous improvements and the dedication of Stamicarbon towards technology development for the benefit of our customers.
Figure 4: Film spraying nozzle, core of the Stamicarbon granulation process
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AFA Technical 30 June – 2 July 2009
5. Joint developments 5.1 Safurex Safurex is developed in close cooperation with Sandvik and became not only a success for Stamicarbon and Sandvik but ultimately for all the people working in the urea business due to the huge benefits with respect to its corrosion resistance. (See paragraph 2) 5.2. Radar level measurements Although radioactive measurements are quite robust and reliable, urea producers have been looking for alternatives for many years due to the ponderous disadvantages of these measurements. Not only the negative image of radioactivity but also the increasing reservation of local authorities to grant permissions for the use of radioactive measurements should be emphasized. Moreover these measurements exhibit some very typical and specific problems like their sensitivity of the detectors for X-rays causing misreading and spurious trips if X-rays are used in the neighborhood. There is also the necessity to replace them every several years due to the half-life time of the radioactive material. As a leading licensor of urea process technology Stamicarbon took up the challenge and decided to pave the road for the elimination of radioactive sources in urea plants. The alternative had to meet the following straight but difficult criteria: • reliable and accurate, • independent on process conditions, • proven technology, • maintenance-free, • urea/carbamate resistant A brief market survey taught that one technology seemed very promising: RADAR. A partner in this development for urea applications was found in German company VEGA Grieshaber KG through its Dutch affiliate. The benefits of radar measurements as an alternative for the traditional level measuring techniques in urea plants are obvious. As the radar technology has been developing over several decades now radar can be considered as a proven and mature technology. Increased processing power and improved electronic components made radar measurements available for the process industry and added reliability and accuracy to level measurement. Figure 5: Principle of Radar measurement
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The accuracy of radar is not affected by changes in the density of the medium or the DK-value of it. Process temperature and pressure have only minor influence so does vapor composition above the medium to be measured. From a maintenance point of view a radar transmitter has no moving parts and does not need any recalibration. The use of SafurexÂŽ for the wetted parts of the radar instrument is a break trough and enables reliable and maintenance free use of Rader measurement systems in Urea plants. Radar measurements have been applied several times already. After the initial new application issues the arrangement shows to be a robust and reliable level measurement system and is since 2006 already used in numerous occasions applied, both in new and existing equipment.
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Figure 6: Rader level measurement in the bottom of the stripper.
Summary Radar
Radioactive
Safety
++
--
Life-cycle cost
++
--
Maintenance
none
yes
Accuracy
good
fair
Proven
>10 applications
> 100 appl.
(de)installation
easy
complicated
Dependent on very minor process conditions
yes
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5.3 Rotoform urea process Stamicarbon and Sandvik Process Systems developed a new finishing technology for urea: the so called Sandvik Rotoform Urea Process.
Specific advantages are: - Very low NH3 and dust emissions - A very low power consumption figure - More uniform product - Good crushing strength even without adding formaldehyde - Flexible production by switching on/off rotoformer lines - Possibility to produce controlled release urea and mixed fertiliser - Lower investment costs - Ideal option if existing prilling of granulation unit is maxed out
The Rotoform principle: Linking a specially designed drop-former to the outstanding attributes of the Sandvik steel belt cooler revolutionized the processing and handling of many products.
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The Rotoform process: Liquid product is pumped through a filtering system onto the continuously running steel belt cooler. The droplets are solidified as they cool down and are discharged at the end of the unit. The resulting premium pastilles are ready for weighing and bagging and subsequent storage and shipment. The entire process is environmentally friendly and dust-free.
5.4 Integrally geared compressors for CO2 compression in the urea-process Cooperation together with MAN-Turbo, Germany 5.5 N/C meter Technology made available to SPIE in the Netherlands. 5.6 New urea operator training simulator Cooperation with Protomation (The Netherlands) was sought to develop a state of the art training simulator. The new urea plant operator training simulator is a valuable tool for training of (in)experienced operators on urea plants based on Stamicarbonâ&#x20AC;&#x2122;s CO2 stripping urea process. The current simulation system uses state of the art simulation technology that facilitates easy and flexible development, maintenance and deployment of the simulator. Since the simulator system is fully PC based there is now the possibility to give simulation based training on the premises of the customer upon request.
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AFA Technical 30 June – 2 July 2009
6. Summary and conclusions •
Research and revamp projects accelerated the use of Safurex® and the Avancore® urea process design for improved performance of the urea plants. The Avancore® urea process combines a low elevation plant concept, whilst maintaining the trouble free principle of full gravity flow for the main recycle within the synthesis section. All process elements used for this new plant concept are proven in revamp projects.
Through the use of Safurex® material of construction, the urea plant design is further simplified since continuous passivation of the synthesis materials of construction becomes history. Consequently the new plant concept is an intrinsically safe and maintenance free plant concept with highest reactor conversion due to the absence of the passivation inerts. Overall, it can be concluded that with these new process developments, Stamicarbon once more shows its dedication to urea process design developments, which focus on our customers needs. - Low CAPEX and Low OPEX: High product quality: assure trouble free acceptance of the product at your customers. - High safety standards: no oxygen present, no explosion risk. - High on-stream time: simple design, less equipment to avoid production losses caused by non-scheduled production interruptions. - Low emission standards: assure your ‘license to operate’, and keep friends with your neighbors! •
And last but not least: Safurex® material of construction is available for replacement projects of critical HP synthesis equipment to take your advantage.
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