IMO TIER III SOLUTIONS FOR WÄRTSILÄ 2-STROKE ENGINES – SELECTIVE CATALYTIC REDUCTION (SCR)
THE REVISED MARPOL ANNEX VI The Revised MARPOL Annex VI brings new requirements for marine diesel engines – in particular, the new Tier III standard for NOX emissions requires a step change in technology. The further developments in terms of SOX emissions control, outlined in the same agreement, represent important boundary conditions in this context. Following an overview of potential options for dealing with this challenge, the Wärtsilä SCR solution is presented as a first, readily available approach for achieving compliance with IMO Tier III for Wärtsilä 2-stroke engines.
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The Revised MARPOL Annex VI was adopted in 2008 after extensive discussions within the International Maritime Organization (IMO), further developing emissions control of marine transport on the basis of the original Annex VI of the MARPOL 73/78 treaty, which was introduced in 1997 and entered into force in 2005.
operation, thereby achieving NOX emissions reduction of more than 76% for 2-stroke engines operating at rated speeds of less than 200 rpm, when switching from Tier II to Tier III mode. Moreover, the Tier III requirements are not limited to compliance with respect to the cycle-weighted NOX emissions, but also include an additional not-to-exceed clause stipulating that the NOX values at the individual IMO TIER III REGULATIONS These regulations set the stage for considerable points of the test cycle must not be more than 50% higher than the weighted average. further reductions of the permissible NOX emissions – with the first step (Tier II) already in force since January 2011. Tier III will FUEL SULPHUR LIMIT become applicable after 2016, but only inside At the same time, the Revised MARPOL Annex specifically designated emission control areas VI paves the path towards further reduction (ECAs), whereas, outside of these ECAs, the of SOX and particulate matter (PM) emissions Tier II regulation will continue to apply. by means of prescribing the next steps for This new regulation poses enormous reducing the sulphur content of the fuel used challenges to the engine developers: They in marine diesel engines. Here, the concept of have to optimize their products for both ECAs, already in use with the original Annex VI, requirements, and need to provide technologies is advanced by specifying a sequence of levels allowing for switching between the resulting Tier and introduction dates for the application both II and Tier III operating modes of the engines in on a global scale and inside ECAs.
Tier II: since 1.1.2011, global after 2016, outside emission control areas
Tier III: after 2016, inside emission control areas
Figure 1: NOX emissions limits according to the Revised MARPOL Annex VI. 5
Fuel sulphur content, %
4.5
Global
4 3.5 3 2.5 2 1.5
ECA
1 0.5 0 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 Year
The introduction of the global 0.5% limit is made conditional on the outcome of a review to be completed by 2018. The purpose is to assess the availability of fuel oil in accordance with this requirement on the basis of the global market supply and demand situation at that time and an analysis of the trends in those markets. Based on the outcome of the review, the global limit of 0.5 % will be implemented either in 2020 or 2025.
Figure 2: Global and ECA fuel sulphur limits development according to the Revised MARPOL Annex VI.
EQUIVALENCE CLAUSE The use of measures that can be demonstrated to be at least as effective in terms of emissions reduction as technologies for achieving compliance with the standards of the Revised MARPOL Annex VI is explicitly allowed – provided there are no negative effects on the environment, human health, resources etc.
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TECHNOLOGY OVERVIEW In order to achieve compliance with both the IMO Tier III NOX standards and the requirements for SOX control, a variety of solutions is theoretically conceivable, starting with the choice of fuel and fuel system, including conventional and more advanced tuning concepts, the addition of particular substances and, ultimately, aftertreatment. Switching from liquid to gas fuel, for instance, could be a solution for dealing with both challenges simultaneously, if combined with appropriate measures for controlling the operation of the engine. However, also when considering liquid fuels only, various options need to be taken into account, combining the individual solutions to control the two key pollutants:
Engine internal measures
Low sulphur fuel
Scrubber
SCR
Figure 3: Possible combinations of NOX and SOX control technologies.
182
SOX
RTA
180
zz Low-sulphur fuel zz Scrubber
178
bsfc, g/kWh
176 174
Cost-opt.
172
Standard Delta
170
NOX
zz Engine-internal measures zz SCR
Low-load
168
BASIS FOR FURTHER DEVELOPMENT
166 164 162 160 0
25
50
75
100
125
load, %
Figure 4: Fuel consumption characteristics of various Tier II tuning variants of RT-flex engines and the corresponding RTA version (58T-D example). 30
bsNOX, g/kWh
25
20
15
10
5
Tier II limit
RTA48T-D
RT-flex50-B
RT-flex50-D
RT-flex58T-D
RT-flex60C
RT-flex68-D
RT-flex82C
RT-flex82T eff.-opt.
RT-flex82T cost-opt.
RT-flex84T-D
RT-flex96C
0 25%
50%
75%
100%
Weighted average
Figure 5: NOX emissions characteristics of Tier II compliant engines according to verification test results. 4
As regards NOX emissions control, the Tier II compliant status of Wärtsilä RT-flex and RTA engines represents the basis for further development. This status has been achieved by using a tuning concept based on the combination of individual measures for minimum impact on other performance parameters, thereby particularly exploiting the flexibility of the RT-flex system for realizing the best trade-off between NOX emissions and fuel consumption. This yields clearly superior performance of RT-flex engines compared to their RTA counterparts. Moreover, different tuning variants are offered in order to allow the customer to select the one best suiting his intended operating pattern. Note that all these variants are equally compliant with Tier II NOX emissions standards – this has been demonstrated for the complete portfolio of Wärtsilä 2-stroke engines. Figure 5 shows both the weighted average NOX emissions compared to the applicable limit of 14.4 g/kWh and the values at the individual points of the test cycle. The options for further reducing NOX emissions by means of classical tuning principles are largely exhausted. Therefore, more advanced engine-internal measures or
SCR technology have to be considered. So far only SCR has demonstrated its capability to achieve the target NOX reduction in a reliable and repeatable way as a standalone technology. Other technologies may have the theoretical potential to realize Tier III levels. However, it is highly probable that in practice, combinations of two or more of these technologies are necessary in order to achieve compliance at optimum general performance and for minimum total lifecycle cost.
SCR – GENERAL CONSIDERATIONS SCR technology is based on the reduction of nitrogen oxides by means of a reductant (typically ammonia, generated from appropriate pre-cursor species such as urea) at the surface of a catalyst. For this purpose, the exhaust gas is led through a reactor, containing a sufficiently large number of catalyst blocks for providing the catalyst surface area required. The temperature of the exhaust gas (and hence also the catalyst) is thereby subject to constraints both on the upper side (in order to avoid oxidation of the reductant) and the lower side (for preventing the formation of undesired by-products such as ammonium sulphates, which may subsequently clog and deactivate the catalyst). The latter is particularly an issue with fuels containing higher fractions of sulphur, such as those present in typical heavy fuel oil (HFO) qualities available today, which calls for even higher minimum temperatures in the catalyst. On 2-stroke engines, due to their high efficiency, the temperatures after the engine are generally too low for an SCR unit to work properly, which is why the reactor needs to be put on the high-pressure side, before the turbine. Integrating the SCR reactor before the turbine involves both challenges and opportunities. The presence of an element with non-negligible heat capacity in this region has some impact on the dynamic characteristics of the turbocharging system, which needs to be controlled through appropriate measures. On the other hand, the reactor can be designed in a more compact way compared to a location downstream of the turbine, due to the higher density of the exhaust gas. First installations of 2-stroke engines with SCR have been realized between 1999 and 2000. Three RoRo vessels of Wagenborg have been in operation for more than 10 years, with their SCR-equipped 7RTA52U main engines
certified for NOX emissions below 2 g/kWh, thus realizing NOX emission reductions even beyond Tier III requirements.
ENGINE-INTERNAL MEASURES More advanced concepts required for achieving Tier III NOX emission levels are associated with the application of additional media, components and systems. In particular, the following three main technologies are taken into consideration: zz Extreme Low-NOX Tuning zz Exhaust Gas Recirculation zz Wet Technologies As regards the former, a limiting factor is related to the constraints of single-stage turbocharging in terms of achievable pressure ratio and efficiency. Two-stage turbocharging hence needs to be applied in order to further exploit the potential of this concept, which exhibits some similarity to the Miller system applied on 4-stroke engines. However, it is not associated with the same potential for simultaneously reducing NOX and fuel consumption. Exhaust gas recirculation (EGR) must be considered a proven technology for all types of diesel engines used in land-based vehicles. For marine applications, however, some concerns are often associated with its application in combination with the fuels used in this sector or, more precisely, the exhaust gas composition resulting from the utilization of those fuels. Moreover, recirculating exhaust gas on engines
designed for HFO operation – specifically, if realized on the high-pressure side – requires provisions for overcoming the pressure differential between exhaust and intake side, which is characteristic of the thermodynamic layout of those engines. As a consequence, the system setup for recirculation needs to include an additional exhaust gas cleaning device, an EGR cooler followed by a water separator and a device (e.g. a blower) for pumping the recirculated exhaust gas to the air side. Tests have shown that EGR is associated with a high potential for NOX reduction, but it remains to be seen if this technology can function reliably as a standalone solution or needs to be applied in combination with other technologies. Wet technologies are a well-known means for reducing NOX emissions and, in view of the need for being able to switch between Tier II and Tier III optimized operating modes, the admission of water to the combustion system independent of the air and fuel paths seems to be the most promising approach. The direct water injection (DWI) system developed by Wärtsilä is based on the utilization of a completely separate common-rail injection system for water and has been tested in various development stages on dedicated component test rigs, the RTX-3 lab engine and on a single cylinder of an 8RT-flex96C engine in the field. Confirmation is still pending for whether the target NOX reduction level for Tier III can be achieved by means of DWI alone. 5
ECONOMICAL CONSIDERATIONS Based on considerations of the potential of individual technologies, various possible solutions for achieving the Tier III compliance target can be identified, either as standalone measures (specifically SCR) or by combining several, compatible technologies. Those combinations could e.g. consist of simple superposition of individual technologies, but also be based on advanced integration, such as realized in the WaCoReG concept. This combines exhaust gas retention in the cylinder (sometimes also referred to as internal EGR) with direct water injection, but designed in such a way that the water is used predominately for cooling the retained exhaust gas, e.g. by injecting it early during the compression cycle. Preliminary analyses of the economic viability of such solutions have been performed, thereby considering both investment costs and operating cost effects in order to assess the impact on the total lifecycle cost of those engines. In this context, the operating cost considerations included both the effect on the efficiency of the engine itself, as a consequence of the known bsfc / NOX trade-off, and the purchasing, production and storage costs of any additional media, such as water or reductant. The effect of fuel quality requirements associated with the operation of the respective NOX reduction technologies (HFO allowed or distillate fuel needed) was given particular attention. The results of this analysis can be summarized as follows: zz Sulphur tolerance of Tier III technologies is key for keeping lifecycle cost under control. zz SCR is the most attractive option. zz Some other solutions are in the same range. Hence, already small changes in key parameters such as reductant price may change the result completely. Therefore, even if SCR is considered the technology of choice today, Wärtsilä will put further efforts into the development of potential alternatives. It must be considered highly probable that one solution will not be sufficient, and that at least one alternative will have to be offered for covering the needs of the complete variety of products and applications. 6
THE WÄRTSILÄ SCR SOLUTION FOR IMO TIER III The SCR technology offered by Wärtsilä for marine diesel engine applications is based on the use of a 40% urea solution, which is injected into the hot exhaust gas upstream of the SCR reactor installed between exhaust gas receiver and turbine. Hereby, the amount of reducing agent injected is automatically adjusted according to the operating conditions of the engine.
BASIC CONSIDERATIONS Various aspects of the solution arise from the basic phenomena involved and the requirements associated. MAIN REACTIONS
The main reactions of the process can be seen below: Urea is evaporated and decomposed to become isocyanic acid (HNCO), carbon dioxide (CO2) and ammonia (1). The isocyanic acid is further decomposed into ammonia and carbon dioxide (2). The nitrogen oxides of the exhaust are reduced to N2 and H2O by the reaction with the ammonia ((3) and (4)) over the catalyst. CO(NH2)2 à NH3 + HNCO (1) HNCO + H2O à NH3 + CO2 (2) 4NO + 4NH3 + O2 à 4N2 + 6H2O (3) 6NO2 + 8NH3 à 7N2 + 12H2O (4) Hence, in order to make sure that the evaporation and decomposition of urea is completed and the ammonia formed is
distributed as homogeneously as possible at the entry of the catalyst, the design of the urea injection as well as of the mixing devices needs to be given special attention. CATALYST
The catalytic material is typically titanium dioxide for the carrying substrate, and vanadium pentoxide for the active substance. The temperature of the SCR process is generally between 250 and 500 °C, but the optimum temperature is limited to a narrower window by certain factors. In order to reach sufficient reaction rates, and to avoid deactivation and fouling due to condensation of components in the exhaust gas, the minimum temperature is typically 300–350 °C, with increasing levels required specifically for HFO. If the actual upper temperature limit of 400–450 °C is exceeded, an increased consumption of the reducing agent must be expected as it will start to burn, the catalyst lifetime becomes shorter, and at temperatures above 500 °C even the catalytic material may be damaged. Undesired branch reactions also start to occur at higher temperatures. ARRANGEMENT
As a consequence, the SCR unit needs to be placed between the exhaust manifold and the turbocharger turbine on 2-stroke engines in order to make sure that the minimum temperature can be reached. Moreover, a bypass of the SCR, controlled by appropriate valves, is needed for start-up, shut-down and the operation outside of ECAs. In the design process, attention has to be paid to
minimizing the sensitivity of the SCR and engine combination to fuel composition: On the one hand, the selection of catalyst type and material must be considered essential; on the other hand, the SCR unit needs to be properly integrated with the engine for minimizing heat losses and achieving optimum distribution of the reductant. Finally, the deactivation of the catalyst by means of deposits building up – as well as the potential ageing of the catalyst through small amounts of catalyst poisons included in such deposits – must be counteracted by applying a soot blowing system, which is also needed to keep the pressure loss of the SCR within acceptable limits and to prevent clogging.
SCR SYSTEM LAYOUT The overall SCR system layout is shown schematically in Figure 6. It consists of the following main components: A reducing agent storage tank, a reducing agent feeding and dosing unit, the reducing agent injection and mixing element, a reactor with catalyst elements, a soot blowing system for keeping the catalyst elements clean and the control system. Figure 6 also includes indications with respect to a default scope of supply from Wärtsilä. However, Wärtsilä is open for all kinds of arrangements, up to extending the offering to complete systems if desired. A pump unit transfers urea from the storage tank to the dosing unit, which regulates the flow of urea to the injection system based on the operation of the engine. The dosing unit
2
9
1
8 4
5 7
3
6 (1) Compressed air supply (2) Soot blowing system (3) Urea tank (4) Pump unit (5) Dosing unit (6) Exhaust gas from the engine
(7) Urea injector and mixing element (8) Mixing duct (9) SCR reactor with catalyst elements Default scope of supply consists of items: (2), (4), (5), (6), (7) and (9)
Figure 6: Flow diagram of the SCR system.
(1) Urea inlet (2) Filter
(3) Drain valve (4) Pump
(5) Overflow valve (6) Urea to tan
Figure 7: Flow diagram of the pump unit.
also controls the compressed air flow to the injector. The urea injector sprays reducing agent into the exhaust gas duct. After the injection of reducing agent, the exhaust gas flows through the mixing duct to the reactor, where the catalytic reduction takes place. PUMP UNIT
Besides delivering the reducing agent to the dosing system, the pump unit also maintains the required pressure in the urea lines. The main component of the unit is an electrically driven pump, which is mounted on a frame together with the necessary accessories. A suction filter protects the pump and the downstream equipment from impurities.
Excess urea returns to the storage tank through an overflow line. A schematic flow diagram of the pump unit is provided in Figure 7. The pump unit includes manual inlet and outlet valves, and a drain valve. A non-return valve in the outlet line prevents back-flow of urea from the dosing system. Pressure gauges are installed on both the suction side and the discharge side of the pump. The pump unit is equipped with a control box, which contains a frequency converter for supplying power to the motor of the pump. An emergency stop button for the pump unit is located in the front panel of the control box. 7
DOSING UNIT
(1) Compressed air inlet (2) Air filter (3) Solenoid valve
(4) Air pressure regulator (5) Urea inlet (6) Drain
(7) Flow control valve (8) Flow meter
Figure 8: Flow diagram of the dosing unit.
The dosing unit controls the dosing of reducing agent to the injection system. Figure 8 shows a schematic flow diagram of this unit. The components in the unit are mounted on a module frame. In addition to the equipment for dosing of reducing agent, the unit includes components for compressed air regulation. The flow of reducing agent is regulated by an automatic control valve. A flow meter measures the amount of reducing agent supplied to the injector. The urea circuit is equipped with manual inlet and outlet valves, a solenoid-actuated shutoff valve, a nonreturn valve and a drain valve. In addition to the equipment for dosing of reducing agent, the unit includes components for compressed air regulation. The compressed air line is connected to the urea line through a solenoid valve, which is closed during normal operation. The solenoid valve is used for purging the injection system of urea after a stop, and for cooling the injection nozzle before the urea injection is started in order to minimize the risk of injector clogging due to thermal decomposition of urea. UREA INJECTION UNIT AND MIXING DUCT
(1) Static mixer (2) Injector lance
(3) Injection nozzle (4) Mixing duct
Figure 9: Injector and mixing duct.
Figure 10: CFD simulation result of urea spray evaporation after injection point. 8
The reducing agent is sprayed into the exhaust gas duct and mixed with the exhaust gas before it enters the reactor. The urea injection is performed using compressed air. The urea and the compressed air are mixed in an injection nozzle at the end of the lance, injecting urea solution into the exhaust gas as a fine spray. The static mixer, located in the exhaust duct either before or after the injection point, serves for enhancing the mixing of the reducing agent and the exhaust gas. After the injection of reducing agent, the exhaust gas flow passes through a mixing duct. The mixing duct gives time for the urea to transform into ammonia and mix homogeneously before it reaches the catalyst elements. Figure 9 presents a typical configuration for urea injection in the mixing duct. The layout of injector and mixing duct is an essential part of the design of an SCR system. W채rtsil채 use in-house expertise in Computational Fluid Dynamics (CFD) modelling to determine e.g. correct positioning of urea injectors and spray control to be able to provide best-practice solutions for their 2-stroke engines. Figure 10 presents an example of such optimized urea spray by means of CFD.
SCR REACTOR WITH SOOT BLOWING SYSTEM
The reactor is a steel casing containing an adequate number of catalyst elements, typically of the honeycomb type and arranged in multiple layers, in order to achieve the necessary conversion. As the exhaust gas flows past the catalyst surface, the nitrogen oxides react with the reducing agent. Compressed air connections for soot blowing are installed at each catalyst layer. The reactor is equipped with a differential pressure transmitter for monitoring the condition of the catalyst elements, and a temperature transmitter for monitoring the exhaust gas outlet temperature. Figure 11 shows a typical soot blowing arrangement.
2
5
3
1
6
4
(1) Compressed air inlet (2) Pressure regulator (3) Air filter
(4) Air vessel (5) Solenoid valves (6) Reactor with catalyst elements
Figure 11: Flow diagram of a typical soot blowing system.
CONTROL SYSTEM
The control system regulates the urea dosing as a function of engine load and speed, to ensure that the necessary amount of reducing agent is always injected. It also controls the compressed air supply to the injection system and the soot blowers and involves specific control features for specifying urea injection during start / stop of the engine and transient operation. Moreover, the position control of the exhaust gas by-pass valves is embedded in the control system in order to ensure correct routing of the exhaust gas in all conditions. If the system is in standby mode, the urea injection is automatically activated when the engine starts. The start of the urea injection is triggered by the catalyst temperature. Correspondingly, when the engine stops, the urea dosing is shut off. The injection system is automatically purged of urea after a stop.
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1
3
4
5
6
7 (1) Control unit (2) Soot blowing valves (3) Compressed air control valves (4) Urea tank
(5) Urea pump (6) Urea dosing control valves (7) Engine
Figure 12: Control system layout. 9
Figure 13: Pre-turbine SCR installation on Wärtsilä 7RT-flex40 engine.
INSTALLATION DIMENSIONS INDICATIVE SCR SYSTEM MAIN DIMENSIONS FOR SELECTED WÄRTSILÄ 2-STROKE ENGINES
Engine 6RT-flex50D
Power SCR reactor SCR reactor Mixing duct Mixing pipe kW @100% diameter length diameter length MCR (a) mm (b) mm (c) mm (d) mm 10 470
1900
4200
900
4700
7RT-flex58T
15 820
2200
4000
1100
5200
8RT-flex68D
25 040
2700
4800
1400
6100
7RT-flex82T
31 640
3000
5000
1700
6600
The main challenge with two-stroke marine installations is related to the need for integration of the SCR between exhaust manifold and the turbocharger, including a bypass for start-up, shut-down and non-ECA operation. As an example, Figure 13 shows a 3-D view of the Wärtsilä SCR design on a 7RT-flex40 engine. Such initial designs have been prepared for various engine types and sizes. Figure 14 shows typical SCR arrangements with one and two turbochargers and includes a table listing preliminary SCR and mixing duct dimensions for IMO Tier III compliant designs, to assist in layout studies.
SCR OPERATION AND MAINTENANCE
Figure 14: Preliminary dimensions for SCR system in the case of one TC and two TC engine applications. 10
The SCR catalyst lifetime is relatively long: Typically elements have performance guarantees up to 2 years and 16 000 operation hours depending on the application (fuel and operation profile) and SCR design. Other components in the SCR system (pump unit, urea injection and soot blowing unit) need periodical inspection and maintenance according to the intervals specified in the maintenance manual. It is recommended to monitor and record the following SCR operation data either continuously or at least frequently for identifying potential SCR performance degradation: z urea flow z delta temperature z delta pressure z NOX feedback control (if applicable).
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time of certification. It can take the form of either engine family or group or even single engine approval, with the engine family concept only applicable in cases where the complete engine and SCR system can be tested on the testbed. The scope of additional tests onboard depends on the type of certification chosen.
SCR budgetary price, €/kW
40 35 30 25 20 15 10
WÄRTSILÄ EXPERIENCE AND REFERENCES
5 0
10.000
20.000
30.000
40.000
50.000
60.000
Engine power, kW
Figure 15: SCR budgetary price, €/kW.
INSTALLATION COSTS The Wärtsilä SCR delivery scope can vary depending on the needs and preferences of the client. In the determination of the equipment costs as shown in Figure 15, it is assumed that the default delivery covers the following equipment: zz a reactor housing with catalyst elements zz equipment for injection and mixing of reducing agent zz a unit for dosing of reducing agent zz a pump unit for transfer of reducing agent zz a soot blowing system zz a control and automation system (Control cabinet with PLC) The scope of supply excludes e.g. piping, exhaust gas by-pass valves, support structures, flexible hoses, insulation material and any other parts outside the specified scope. The operation of the system also
requires an air compressor and a tank for storing the reducing agent. Wärtsilä’s scope can be extended to cover these items, or Wärtsilä can assist through specifications or instructions.
OPERATING COSTS Urea costs are the dominating factor in the total O&M costs, depending on the urea market price. The average consumption of urea for reaching the IMO Tier NOX level is approximately 15 l/MWh. If one assumes 40% urea solution price variation between 0.30 and 0.60 €/l, this will result in a typical operating cost of 4.5 to 9 €/MWh.
SCR SYSTEM CERTIFICATION The certification of engines equipped with Wärtsilä SCR systems is done in accordance with guidelines approved by the IMO at the
Wärtsilä has a long and wide experience on SCRs with a total of about 400 SCR systems installed in a large variety of applications: zz Diesel, gas and dual fuel engines zz Marine and stationary applications zz New-building and retrofit applications zz 4- and 2-stroke engine applications. First references on 2-stroke engines date back to 1999/2000, when three RoRo ships were equipped with SCR systems. Each ship has one main engine (Sulzer 7RTA52U) and two auxiliary engines (Wärtsilä 6L20). These installations have received a certificate for low NOX emissions (< 2 g/kWh), already realizing NOX emission reductions even beyond Tier III requirements. The demand for SCR systems is expected to progressively increase in marine applications in 2016, and the ultimate products will be ready to match the current requirements. Wärtsilä already offers and delivers SCR systems for high sulphur applications, and is making big efforts for further development and commercialization of SCRs, in close cooperation with engine development. The clear emphasis is on minimizing total lifecycle costs. 11
marine and energy markets. By emphasising technological innovation and total efficiency, Wärtsilä maximises the environmental and economic performance of the vessels and power plants of its customers. Wärtsilä is listed on the NASDAQ OMX Helsinki, Finland.
WÄRTSILÄ® is a registered trademark. Copyright © 2011 Wärtsilä Corporation.
05.2011 / Bock´s Office / Litoset
Wärtsilä is a global leader in complete lifecycle power solutions for the