Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications

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Emil Waters
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1 Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications

3 Contents Abstract...5 MAN B&W ME-GI-S Engines for Dual Fuel Applications...5 ME-GI Injection System...8 High-pressure, Double-wall Piping Gas/Fuel Handling Retrofit Conclusion References Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications 3

5 Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications Abstract This paper deals with the latest development in the MAN B&W ME-GI-S dual fuel high-pressure gas injection MAN B&W two-stroke engines and associated fuel supply systems. The discussion about and interest in lowering CO 2, NO, S and particulate emissions have increased operators and owners interest in investigating future fuel alternatives. The MAN B&W ME-GI-S engine offers the opportunity of utilising such an alternative. The gaseous/liquid fuel flexibility makes the MAN B&W ME-GI-S engine an obvious choice for projects where the engine is connected to interruptible gas supply systems or where a switch among various fuels is required for any reason. MAN B&W ME-GI-S Engines for Dual Fuel Applications The MC-S engine family has been on the market since The stationary installations running on liquid fuels cover any engine output from 4.5 MW to over 50 MW per unit, whether heavy fuel or biofuel, see Fig. 1. In 1987, the first testing of the GI principles was carried out on one cylinder of a 6L35MC engine in Japan and Denmark. At this opportunity, combustion of synthetic gases with LCV down to 11 MJ/Nm 3 was also tested, ref. Table 1. Speed r/min Engine type Hz K98MC-S/ ME-GI-S K90MC-S9/ ME-GI-S K90MC-S/ ME-GI-S K80MC-S9/ ME-GI-S K80MC-S/ ME-GI-S Fig. 1: Engine programme, MAN B&W ME-GI-S Gaseous fuels burned in MAN B&W two-stroke low speed diesel engines Composition Units Natural gas types VOC fuel types CH 4 vol. % C 2 H 6 vol. % C 3 H 8 vol. % C 4 H 10 vol. % C 5+ vol. % CO 2 vol % N 2 vol % Molar mass Kg/kmol Lower calorific value kj/kg 49,170 48,390 7,050 Lower calorific value kj/nm 3 41,460 38,930 11,120 Density 150 K60MC-S/ ME-GI-S K50MC-S/ ME-GI-S L35MC-S/ ME-GI-S At 25 C/ 1 bar abs Kg/m At 25 C/ 200 bar abs Kg/m Engine power MW Table 1 Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications 5

In 1992, the GI systems were installed on a 16V28/32GI stationary medium speed engine at a CHP plant in Hundested, Denmark, where they have been in service for more than 40,000 running hours, see Fig.

For information on these engines please refer to 'Two-stroke Low Speed Diesel Engines for Independent Power Producers and Captive Power Plants'.

6 In 1992, the GI systems were installed on a 16V28/32GI stationary medium speed engine at a CHP plant in Hundested, Denmark, where they have been in service for more than 40,000 running hours, see Fig. 2. The MC/ME/ME-B engine types are well-proven products in the industry. For information on these engines please refer to 'Two-stroke Low Speed Diesel Engines for Independent Power Producers and Captive Power Plants'. The GI solution was developed in parallel and was finished for testing in the early 1990s. In 1994, the first two-stroke GI engine, a 12K80MC-GI-S, was put into service on a power plant at Chiba, Tokyo, Japan. So far, the Chiba engine has operated as a peak load plant for almost 20,000 hours on high-pressure gas, see Fig. 3. Fig. 2: 16V28/32-GI, Hundested, Denmark At the same time, in 1994, all major classification societies approved the GI concept for stationary and marine applications. Technically, there is only a small difference between fuel and gas-burning engines, but the GI engine provides optimal fuel flexibility. Fig. 4 shows the components of an HFO engine which need to be modified for gas operation. The gas supply line is designed with ventilated double-wall piping and HC sensors for safety shutdown. 12K80MC-GI-S Bore Stroke Output 800 mm 2300 mm 40 MW Main data Average reliability 97% Average availability 97% Average load factor 71% The GI control and safety systems are add-on systems to the normal engine systems. Fuels (Main/Pilot): M Natural gas Average efficiency gross 46.1% Average efficiency net 42.6% P Marine diesel oil Fig. 3: 12K80MC-GI-S Chiba Plant 6 Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications

Apart from these systems on the engine, the engine and auxiliaries will comprise some new units.

delivering sealing oil to the gas valves separating control oil and gas Inert gas system, which enables purging of the gas system on the engine with inert gas.

The control and safety system is designed to fail to safe conditions.

7 Apart from these systems on the engine, the engine and auxiliaries will comprise some new units. The most important ones, apart from the gas supply system, are listed below: Ventilation system for venting the space between the inner and outer pipe of the double-wall piping Sealing oil system, delivering sealing oil to the gas valves separating control oil and gas Inert gas system, which enables purging of the gas system on the engine with inert gas. The GI system also includes: Control and safety system, comprising a hydrocarbon analyser for checking the hydrocarbon content of the air in the double-wall gas pipes. The control and safety system is designed to fail to safe conditions. All failures detected during gas fuel running, including failures of the control system itself, will result in a gas fuel stop/shutdown, and a change-over to HFO operation. Blow-out and gas-freeing purging of the high-pressure gas pipes and of the complete gas supply system will follow. The change-over to fuel oil mode is always done without any power loss on the engine. Exhaust receiver Cylinder cover Valve block ELGI valve Double wall gas pipes FIVA Fig. 4: Components to be modified: ME-GI compared to an ME engine Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications 7

The high-pressure gas from the gas supply flows through the main pipe via narrow and flexible branch pipes to each cylinder s gas valve block system and accumulator.

system They act as flexible connections between the stiff main pipe system and the engine structure, safeguarding against extra stresses in the main and branch pipes caused by the inevitable

8 The high-pressure gas from the gas supply flows through the main pipe via narrow and flexible branch pipes to each cylinder s gas valve block system and accumulator. These branch pipes perform two important tasks: They separate each cylinder unit from the rest in terms of gas dynamics, utilising the well-proven design philosophy of the ME-B engine s fuel oil system They act as flexible connections between the stiff main pipe system and the engine structure, safeguarding against extra stresses in the main and branch pipes caused by the inevitable differences in thermal expansion of the gas pipe system and the engine structure. The buffer tank, containing about 20 times the injection amount per stroke at MCR, also performs two important tasks: ME-GI Injection System Dual fuel operation requires the injection of both pilot fuel and gas fuel into the combustion chamber. Different types of valves are used for this purpose. Two are fitted for gas injection and two for pilot fuel. The auxiliary medium required for both fuel and gas operation is as follows: High-pressure gas supply Fuel oil supply (pilot oil) Control oil supply for actuation of gas injection valves Sealing oil supply. The gas injection valve design is shown in Fig. 5. This valve complies with traditional design principles of the compact design. Gas is admitted to the gas injection valve through bores in the cylinder cover. To prevent a gas leakage between the cylinder cover/gas injection valve and the valve housing/ spindle guide, sealing rings made of temperature and gas resistant material have been installed. Any gas leakage through the gas sealing rings will be led through bores in the gas injection valve to the space between the inner and the outer shield pipe of the double-wall gas piping system. This leakage will be detected by HC sensors. The gas acts continuously on the valve spindle at a max. pressure of about 250 bar. To prevent gas from entering the control oil actuation system via the clearance around the spindle, the spindle is sealed by sealing oil at a pressure higher than the gas pressure (25-50 bar higher). The pilot oil valve is a standard ME fuel oil valve without any changes, except for the nozzle. The fuel oil pressure is constantly monitored by the GI safety system in order to detect any malfunctioning of the valve. It supplies the gas amount for injection at a slight, but predetermined, pressure drop. It forms an important part of the safety system. Sealing oil inlet Since the gas supply piping is of the common rail design, the gas injection valve must be controlled by an auxiliary control oil system. This, in principle, consists of the ME hydraulic control oil system and an ELGI (electronic gas injection) valve, supplying high-pressure control oil to the gas injection valve, thereby controlling the timing and opening of the gas valve. Cylinder cover Gas inlet Connection to the ventilated pipe system Control oil Sealing oil Gas spindle Fig. 5: Gas injection valve ME-GI engine 8 Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications

9 The oil valve design allows operation solely on fuel oil up to MCR and 10% overload once each consecutive 12 hours. The gas engine can be run on fuel oil at 100% load at any time, without stopping the engine. For prolonged operation on fuel oil, it is recommended to change the nozzles and gain an increase in efficiency of around 1% when running at full engine load. As can be seen in Fig. 6 (GI injection system), the ME-GI injection system consists of two fuel oil valves, two fuel gas valves, ELGI for opening and closing of the fuel gas valves and a FIVA (fuel injection valve actuator) valve to control via the fuel oil valve the injected fuel oil profile. Furthermore, it consists of the conventional fuel oil pressure booster, which supplies pilot oil in the dual fuel operation mode. The fuel oil pressure booster is equipped with a pressure sensor to measure the pilot oil on the high pressure side. As mentioned earlier, this sensor monitors the functioning of the fuel oil valve. If any deviation from a normal injection is found, the GI safety system will not allow opening for the control oil via the ELGI valve. In this event no gas injection will take place. Under normal operation where no malfunctioning of the fuel oil valve is found, the fuel gas valve is opened at the correct crank angle position, and gas is injected. The gas is supplied directly into an ongoing combustion. Consequently, the risk of having unburnt gas eventually slipping past the piston rings and into the scavenge air receiver is considered to be very low. Monitoring the scavenge air receiver pressure and combustion condition safeguards against such a situation. In the event of a too high combustion pressure, the gas mode is stopped and the engine returns to burning fuel oil only. The gas flow to each cylinder during one cycle is be detected by measuring the pressure drop in the accumulator. By this system, any abnormal gas flow, whether due to seized gas injection valves or blocked gas valves, is be detected immediately. The gas supply is be discontinued and the gas lines purged with inert gas. Also in this event, the engine continues running only on fuel oil without any power loss. Low pressure fuel supply Fuel return Measuring and limiting device. Pressure booster ( bar) Injection Gas supply Position sensor 300 bar hydraulic oil. Common with exhaust valve actuator FIVA valve Bar abs Pilot oil pressure ELGI valve 400 Control oil pressure The system provides: Pressure, timing, rate shaping, main, pre and post injection Fig. 6: ME-GI injection system Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications 9

High-pressure, Double-wall Piping A common rail (constant pressure) gas supply system is to be fitted for highpressure gas distribution to each valve block.

The intervening space, including also the space around the valves, flanges, etc., is equipped with separate mechanical ventilation with a capacity of approx. 30 air changes per hour.

10 High-pressure, Double-wall Piping A common rail (constant pressure) gas supply system is to be fitted for highpressure gas distribution to each valve block. The gas pipes are designed with double-walls, with the outer shielding pipe designed so as to prevent gas outflow to the machinery spaces in the event of rupture of the inner gas pipe. The intervening space, including also the space around the valves, flanges, etc., is equipped with separate mechanical ventilation with a capacity of approx. 30 air changes per hour. The pressure in the intervening space is below that of the engine room with the (extractor) fan motors placed outside the ventilation ducts. The ventilation inlet air is taken from a non-hazardous area. The gas pipes are arranged in such a way that air is sucked into the doublewall piping system from around the pipe inlet, into the branch pipes to the individual gas valve control blocks, via the branch supply pipes to the main supply pipe and via the suction blower into the atmosphere, see Figs. 7 and 8, and Appendix I. Ventilation air is exhausted to a firesafe place. The double-wall piping system is designed so that every part is ventilated. All joints connected with sealings to a high-pressure gas volume are ventilated. Any gas leakage will therefore be led to the ventilated part of the doublewall piping system and detected by the HC sensors. The gas pipes on the engine are designed for 50% higher pressure than the normal working pressure, and are supported so as to avoid mechanical vibrations. Furthermore, the gas pipes are shielded against heavy items falling down, and on the engine side they are placed below the top gallery. The pipes are pressure-tested at 1.5 times the working pressure. The design is to be all-welded, as far as it is practicable, using flange connections only to the extent necessary for servicing purposes. The branch piping to the individual cylinders is designed with adequate flexibility to cope with the thermal expansion of the engine from cold to hot condition. The gas pipe system is also designed so as to avoid excessive gas pressure fluctuations during operation. For the purpose of purging the system after gas use, the gas pipes are connected to an inert gas system with an inert gas pressure of 4-8 bar. In the event of a gas failure, the high-pressure pipe system is depressurised before automatic purging. During a normal gas Protective hose Soldered Ventilation air air Bonded seal Fuel FuelGas flow Ventilation air Outer pipe Ventilation air High pressure gas High pressure gas pipe Fig. 7: Branching of gas piping system 10 Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications

Fig. 8: Gas valve control block stop, the automatic purging is be started after a period of up to 30 minutes.

Minimum fuel mode % Total % Pilot Automatic switchover between gas and pilot oil or fuel injection at 25 % load Gas Fuel Gas/Fuel

11 Fig. 8: Gas valve control block stop, the automatic purging is be started after a period of up to 30 minutes. Time is therefore available for a quick Fuel 100% Fuel-oil-only mode Fuel 100% re-start in gas mode. Minimum fuel mode % Total % Pilot Automatic switchover between gas and pilot oil or fuel injection at 25 % load Gas Fuel Gas/Fuel Handling The MAN B&W ME-GI-S engine is ca- Fuel 100% load 100% load 25 pable of running both on 100% liquid gas and on any ratio of gas to liquid fuel the pilot oil 95-0%, see Fig. 9. In Fuel 100% Speciﬁed gas mode case of gases with a very low energy Gas content, a larger amount of pilot oil might be required. 5% Fuel 100% load Fig. 9: MAN B&W two-stroke dual fuel low speed diesel, fuel type mode Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications 11

12 To drain tank F.O. drain tank To F.W. cooling pump suction Main engine Automatic de-aerating valve Preheater Full flow filter 50 µm Venting tank Circulating pumps Heavy fuel oil service tank Overflow valve Supply pumps From centrifuges Diesel oil service tank Therefore, the plant is usually to be equipped with a full size liquid fuel supply system, see Fig. 10, and a gas fuel supply system, see Fig. 11. The gas supply station is to fulfil the requirements specified in Fig. 12. The sizing and parasitic load of the compressor station mainly depend on the gas pressure at the plant inlet and the Lower Calorific Value (LCV) of the gas, see Fig. 13. Fig. 10: Fuel oil system Internal and external systems for dual fuel operation Gas system on the cylinder Exhaust receiver Cylinder cover Engine room Sealing oil system Outside Double wall pipe Gas pipe Air flow direction Gas flow direction Valve block Compressor unit Fuel oil pressure booster Inert gas line Pipe Ventilation system Gas supply system B.0. gas ELFI valve ELGI valve Servo oil Fig. 11: ME-GI engine and gas handling 12 Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications

13 300 Control of gas delivery pressure General Data for Gas Delivery Condition: Pressure: 250 Nominal 250 bar Max. value 300 bar Gas pressure set point (bar) Engine Load (% of MCR) Pulsation limit ± 2 bar Set point tolerance ± 5% Temperature: Below ambient - or max. 30 o C, whichever is lowest Quality: Condensate free, without oil/water droplets or mist, similar to the PNEUROP recommendation 6611 Air Turbines Fig. 12: Gas supply station, guiding specification kw compressor power (per 1000kg CH4 per hour) Compressor power / Generator output (%) Pressure at compressor outlet LCV 40MJ/Nm 3 LCV 30MJ/Nm 3 LCV 20MJ/Nm 3 LCV 10MJ/Nm Gas pressure at compressor station inlet (bar abs.) Fig. 13: Gas compressor power demand Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications 13

14 As pilot oil, any liquid mineral or biofuel can be used, ref. Tables 2, 3 and 4. Two-stroke guiding liquid fuel specification for MAN B&W two-stroke low speed diesel engines 1) The fuel gas supply system is suggested to comprise two compressors for a single engine installation. Each compressor is to have a 100% capacity for redundancy. In case of a multiple engine plant we suggest installation of one compressor per engine, all feeding a common gas supply line, see Fig. 14. Retrofit For engines operating on HFO/biofuel, it is possible to carry out conversion to dual fuel operation. The engine components shown in Fig. 4 will be affected by a retrofit, and a gas compressor should be installed. Requests for retrofit solutions should be sent to MAN Diesel & Turbo on an ad hoc basis. Designation Diesel engines CIMAC-H55 Density at 15 C kg/ Kinematic viscosity at 100 C cst 55 Flash point C 60 Carbon residue % (mm) 22 Ash % (mm) 0.15 Water % (mm) 1.0 Sulphur % (mm) 5.0 Vanadium ppm (mm) 600 Aluminium + Silicon mg/kg 80 API gravity (min) API * Sodium plus potassium ppm (mm) 200 Calcium ppm (mm) 200 Lead ppm (mm) 10 *) experience, no limitations in official specification Table 2 Two-stroke guiding biofuel specification for MAN B&W two-stroke low speed diesel engines 1) Designation Density at 15 C kg/m Kinematic viscosity at 100 C 2) cst 55 Flash point º C > 60 Carbon residue % (m/m) 22 Ash % (m/m) 0.15 Water % (m/m) 1.0 Sulphur 3) % (m/m) 5.0 Vanadium ppm (m/m) 600 Aluminium + Silicon mg/kg 80 Sodium plus potassium ppm (m/m) 200 Calcium ppm (m/m) 200 Lead ppm (m/m) 10 TAN (Total Acid Number) mg KOH/g 4) < 25 SAN (Strong Acid Number) mg KOH/g 0 1) Maximum values valid at inlet to centrifuge plant 2) Pre-heating down to 15 cst at engine inlet flange is to be ensured 3) Iodine, phosphorus and sulphur content according to agreement with emission control maker 4) TBO of engine fuel systems to be adjusted according to actual value and experience Table 3 14 Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications

15 Two-stroke guiding gas specification for MAN B&W two-stroke low speed diesel engines 1) Designation Lower heat value MJ/kg Minimum 38 if maximum gas fuel is to be obtained, below 38 higher pilot fuel oil amount might be required Gas methane number No limit Methane content (% volume) No limit Hydrogen sulphide (H2S) (% volume) Max Hydrogen (H2) (% volume) No limit Water and hydrocarbon condensates (% volume) 0 Ammonia (mg/nm 3 ) Max. 25 Chlorine + Flourines (mg/nm 3 ) Max. 50 Particles or solid content (mg/nm 3 ) Max. 50 Particles or solid size (μm) Max. 5 Gas inlet temperature ( C) 45 Gas pressure According to MAN Diesel & Turbo specification Table 4 Conclusion The MAN B&W ME-GI-S engines are applicable anywhere, when fuel efficient, reliable and flexible power production is required. Besides traditional fuels such as heavy fuel and natural gas, biofuels and synthetic biofuels and cynthetic biogases from e.g. vegetable garbage or pyrolyses processes can be applied. References Two-stroke Low Speed Diesel Engines for Independent Power Producers and Captive Power Plants, ppr May 2009 Development of the World s First Large- Bore Gas-Injection Engine Service Experience of the World s First Large-Bore Gas-Injection Engine, ISME Tokyo 2000 Compressor Vent Control range 150 to 265 bar g p set Paper: Guidelines for Fuels and Lubes Purchasing, ppr Feb 2009 Shut off valve V1 Pressure regulation valve Gas supply from pipe line Control range 150 to 265 bar g p set ME-GI Compressor ME-GI Fig. 14: Multiple engine installation Stationary MAN B&W ME-GI-S Engines for Dual Fuel Applications 15

20 All data provided in this document is non-binding. This data serves informational purposes only and is especially not guaranteed in any way. Depending on the subsequent specific individual projects, the relevant data may be subject to changes and will be assessed and determined individually for each project. This will depend on the particular characteristics of each individual project, especially specific site and operational conditions Copyright MAN Diesel & Turbo Subject to modification in the interest of technical progress ppr Aug 2010 Printed in Denmark MAN Diesel & Turbo Teglholmsgade Copenhagen SV, Denmark Phone Fax

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