Fuel Flexibility Done Right. MAN B&W ME-GI-S and MAN B&W ME-LGI-S for stationary applications

Transcription

1 Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W ME-LGI-S for stationary applications

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3 Contents Abstract...5 Definition of Fuel Gases for Dual Fuel Applications:...5 What is gas in terms of physics?...5 Natural gas (NG)...5 Liquefied natural gas (LNG)...6 Ethane (C 2 H 6 )...6 Liquefied petroleum gas (LPG)...6 Methanol (CH 3 OH)...7 Dimethyl ether (DME)...7 Gas engines...7 Development history of MAN B&W ME-GI-S engines for dual fuel applications...8 Technical description of the gas injection concept (ME-GI-S)...10 Safety features...12 High-pressure, double-wall piping...12 Fuel gas and fuel handling for ME-GI-S...13 Description of the Liquid Gas Injection Concept (ME-LGI-S)...19 Liquid fuel gas and fuel handling for ME-LGI-S...20 Liquid fuel gas supply system (LFSS)...20 The low flashpoint fuel valve train (LFFVT)...21 Purge return system (PRS)...21 Maintenance Work...21 Maintenance of ME-GI-S or ME-LGI-S engines...21 Maintenance work at the power plant...21 Retrofit...22 Conclusion...22 References...23

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5 Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications Abstract This paper deals with the latest developments of the MAN B&W ME-GI-S and ME-LGI-S dual fuel two-stroke low speed diesel engines and associated fuel gas supply systems. Speed r/min Hz Engine type K98ME-GI-S K98ME-LGI-S K90ME-GI-S K90ME-LGI-S9 K90ME-GI-S K90ME-LGI-S The discussion about and the requirement for lowering CO 2, NO x, SO x and particulate emissions have increased operators and owners interest in investigating future fuel alternatives. The MAN B&W ME-GI-S and ME-LGI-S engines offer the opportunity of utilising such alternatives, also for stationary application K80ME-GI-S9 K80ME-LGI-S9 K80ME-GI-S K80ME-LGI-S K60ME-GI-S K60ME-LGI-S K50ME-GI-S K50ME-LGI-S L35ME-GI-S L35ME-LGI-S Engine power MW The gaseous/liquid fuel flexibility makes the MAN B&W ME-GI-S and ME-LGI-S engines an obvious choice for projects where the engine is connected to interruptible gas supply systems or where a switch/mixing ratio among various fuels is required for various reasons. Fig. 1 shows the engine programme for ME- GI-S and ME-LGI-S engines. Definition of Fuel Gases for Dual Fuel Applications: It is important to understand the basic definitions of the various fuel types that can be burned in engines of our design. MAN B&W two-stroke low speed diesel engines are designed to provide optimum fuel flexibility and are an ideal source of power, whether operating on fuel gas, liquid fuel gas, liquid fuel or liquid biofuel. Fig. 1: Engine programme, MAN B&W ME-GI-S and LGI-S What is gas in terms of physics? examples of gases are oxygen at room Gas is one of the four fundamental temperature (approximately 20 C), hydrogen at room temperature and water states of matter (the others being solid, liquid, and plasma). A gas is a sample at standard atmospheric pressure, at a of matter that confines to the shape of temperature above 100 C. a container in which it is held and acquires a uniform density inside the container. If not confined into a container, tive list of various gas types are de- In the following section, a non-exhaus- gaseous matter, also known as vapour, scribed in detail. will disperse into space. The term gas is also used in reference to the state, Natural gas (NG) or conditions, of matter having similar Raw natural gas is defined as gas obtained from a natural underground properties. reservoir. It generally contains a large The atoms or molecules of matter in quantity of methane along with heavier the gaseous state move freely among hydrocarbons such as ethane, propane, each other, and are, in most instances, isobutene, normal butane, etc. Also, in packed more loosely than the molecules of the same substance in solid or erable amount of non-hydrocarbons, the raw state it often contains a consid- liquid state. A sample of gaseous matter such as nitrogen, hydrogen sulphide can be compressed. The most typical and carbon dioxide. These properties Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 5

6 indicate some traces of compounds like helium, carbonyl sulphide and various n~captans. Raw natural gas is also saturated with water. Table 1 gives some examples of analyses of various types of raw natural gas. Natural gas sold for commercial use is quite different in composition from the raw gas given in Table 1. Table 2 lists the typical composition of natural gas sold directly as an industrial fuel. Natural gas sold as industrial fuel is not specified by its chemical composition, but rather by the series of specific properties that must be met, like heating value, dew point, water, H 2 S, CO 2 and O 2 content as well as the Wobbe index. A typical lower heating value of natural gas is 46 MJ/kg. Liquefied natural gas (LNG) Liquefied natural gas (LNG) is a natural gas (predominantly methane, CH 4 ) that has been converted to liquid form for ease of storage or transport. The gas is first extracted and transported to a processing plant where it is purified by removing any condensates, such as water, oil, mud and other gases, like for example CO 2 and H 2 S. The gas is then cooled down in stages until liquefies it has now become LNG. LNG is stored in storage tanks and can be loaded and shipped. LNG typically contains more than 90% methane. It also contains small amounts of ethane, propane, butane, some heavier alkanes and nitrogen. Geological era Mesozoic mole % Paleozoic mole % Nitrogen N Hydrogen sulphide H 2 S Carbon dioxide CO Methane C Ethane C Propane C Isobutane ic n-butane nc Isopentane ic n-pentane nc Hexane C Heptane ++ C Table 1 From a field plant mole % From a straddle plant mole % N C C C ic nc ic Table 2 LNG is principally used when transporting natural gas to markets. When reaching the final destination it is expanded (re-gassified) and distributed as natural gas into pipelines to local distribution companies or independent product of petroleum refining. Its chief use is as petrochemical feedstock for ethylene production. A typical lower heating value of ethane is 47 MJ/kg. In this paper we will designate ethane gas as fuel gas. power plants. Liquefied petroleum gas (LPG) The heating value of LNG depends on the source of gas that is used and the process that is used to liquefy it. A typical lower heating value of LNG is 49 MJ/kg. In this paper, natural gas and LNG is designated as fuel gas. Liquefied petroleum gas, also called LPG, GPL, LP Gas, liquid petroleum gas or simply propane or butane, is a flammable mixture of hydrocarbon gases primarily used as a fuel in heating appliances and vehicles. When specifically used as a fuel in vehicles it is often Ethane (C 2 H 6 ) referred to as autogas. At standard temperatures and pressures, ethane is a colourless, odourless gas. Ethane is isolated on an industrial scale from natural gas, and as a by- Varieties of LPG bought and sold include propane (C3), butane (C4) and most commonly, mixtures consisting of 6 Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications

7 both propane and butane. Propylene, butylenes and other hydrocarbons are usually also present in small concentrations. A powerful odorant, ethanethiol, is added so that leaks can easily be detected. LPG is prepared by refining petroleum or»wet«natural gas, and is almost entirely derived from fossil fuel sources, being manufactured during the refining of petroleum (crude oil) or extracted from petroleum or natural gas streams as they emerge from the ground. As its boiling point is below room temperature, LPG will evaporate quickly at normal temperatures and pressures and is usually supplied in pressurised steel vessels. Unlike natural gas, LPG is heavier than air and, therefore, it will flow along floors and tend to settle in low spots, such as basements. A typical lower heating value of LPG is 46 MJ/kg. In this paper we will designate LPG as liquid fuel gas. Methanol (CH 3 OH) Methanol, also known as methyl alcohol, wood alcohol, wood naphtha or wood spirits, is a chemical with the formula CH 3 OH (often abbreviated MeOH). Methanol acquired the name»wood alcohol«because it was once produced chiefly as a byproduct of the destructive distillation of wood. Modern methanol is produced in a catalytic industrial process directly from carbon monoxide, carbon dioxide and hydrogen. Methanol is the simplest alcohol, and is a light, volatile, colourless, flammable liquid with a distinctive odour very similar to, but slightly sweeter than that of ethanol (drinking alcohol). It is also used for producing biodiesel. Methanol burns in oxygen, including open air, forming carbon dioxide and water: 2 CH 3 OH + 3 O 2 2 CO H 2 O Methanol is one of the most traded chemical commodities in the world, with an estimated global demand of around 27 to 29 million metric tons. In recent years, the production capacity has expanded considerably with new plants coming on-stream in South America, China and the Middle East, the latter based on access to abundant supplies of methane gas. Apart from water, typical impurities include acetone and ethanol. When methanol is delivered by ships or tankers used to transport other substances, contamination by the previous cargo must be expected. A typical lower heating value of methanol is 20 MJ/kg. In this paper we will designate methanol as liquid fuel gas. Dimethyl ether (DME) Dimethyl ether (DME), also known as methoxymethane, is the organic compound with the formula CH 3 OCH 3. The simplest ether is a colourless gas that is a useful precursor to other organic compounds and an aerosol propellant. The simplicity of this short carbon chain compound leads by combustion to very low emission of NO x, and CO, as well as being sulphur-free resulting in no SO x emissions. A typical lower heating value of DME is 29 MJ/kg. In this paper, we will designate DME as liquid fuel gas. For other gases please consult MAN Diesel & Turbo, Copenhagen. Gas engines A gas in this paper and context is a hydrocarbon, or a mixture of hydrocarbons and other gases, like He, N 2 or CO, which at normal ambient pressure and temperature is in a gaseous state and has a defined flashpoint temperature. The physical properties of the gas mixture determines whether it is suitable for either an ME-GI-S or an ME- LGI-S engine. The selection of gas is to be determined in the initial phase of a project. If the gas can be compressed to approximately 300 or 400 bar at 45 +/ 10 C and behave as a single phase, gas state (i.e. compressible), it is suitable for ME-GI-S. Gaseous fuels like natural gas and LNG are suitable for operation at a high gas pressure at engine inlet. We will apply designation fuel gas(es) for these gas types. If the gas (or mixture) can be compressed to approx. 35 bar at 25 to 55 C, and it is in a liquid state (i.e. almost incompressible), it is well-suited for an ME-LGI-S engine. Liquid gas fuels in the form of LPG, DME and methanol are suitable for operation at low gas pressure at engine inlet. It is important to note that the required pressure and temperature of the low pressure fuel system vary slightly with the fuel selected. We will use the designation liquid fuel gas. Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 7

8 Liquid fuels like HFO, diesel, crude biofuel and crude oil are suitable as pilot oil, see Table 5 and 6 on page 17. It is important to note that the MAN B&W two-stroke low speed diesel engines have accumulated millions of operating hours on these liquid fuel types. Development history of MAN B&W ME-GI-S engines for dual fuel applications The MC-S engine family has been on the market since The statio nary installations running on liquid fuels cover any engine output from 4.5 MW to over 50 MW per unit, whether heavy fuel or biofuel. 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 At 25 C/ 1 bar abs Kg/m 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 3. In 1992, the GI systems were installed on a 16V28/32GI stationary medium speed engine at a combined heat and Table 3 power (CHP) plant at Hundested in Denmark, where it has 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 marine market and can be used for stationary application as well. Our paper: Twostroke Low Speed Diesel Engines for Independent Power Producers and Captive Power Plants describes these engine types in more detail. The GI solution was developed in parallel and was first tested in the early 1990s. In 1994, the first MAN B&W two-stroke low speed 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 highpressure 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. 8 Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications

9 12K80MC-GI-S Bore Stroke Output Fuels (main/pilot): M P 800 mm 2300 mm 40 MW Natural gas Marine diesel oil Main data Average reliability 97% Average availability 97% Average load factor 71% Average efficiency 46.1% gross Average efficiency net 42.6% Fig. 3: 12K80MC-GI-S Chiba Plant Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 9

10 Technical description of the gas injection concept (ME-GI-S) Technically, there is only a small difference between conventional fuel and gas-burning engines. The combustion principle in either case follows the diesel cycle principle. On conventional fuel engines, the injected fuel ignites because the temperature of the compressed air in the cylinder is above the auto-ignition temperature of the fuel. The auto-ignition temperature of liquid fuel is approx C. The auto-ignition temperature of pure gases, i.e. metane and ethane, is in the range of approximately 470 to 540 C. This means that a small amount of pilot fuel has to be injected into the cylinder before gas injection because gas does not auto-ignite at the temperature prevailing in the combustion chamber at the time of the injection. 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 enabling inert gas purging of the gas system 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 systems are 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 100% pilot fuel operation. Blow-out and gas-freeing purging of the highpressure 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. The gas from the fuel gas supply flows through the main pipe via chain pipes to each cylinder s gas valve block system and accumulator. These chain pipes perform an important task: The double-wall chain pipes act as flexible connections between the stiff main pipe system and the engine structure, safeguarding against extra stresses in the main and chain pipes caused by the inevitable differences in thermal expansion of the gas pipe system and the engine structure. The engine output and load response remain unchanged compared with operation on liquid fuel. It is important to know that the gross efficiency also remains unchanged. Gas leakage detection Sealing oil inlet Hydraulic oil inlet The gas supply line on the engine proper is designed with ventilated doublewall piping and HC (hydrocarbon) sensors for safety shutdown. The GI control and safety systems are add-on systems to the normal engine systems. It is a precondition that the engines are of the electronic control design, i.e. ME. MAN B&W two-stroke low speed diesel engines of the ME design are the preferred solution in the marine market when placing orders for ships. Cylinder cover Connection to the ventilated pipe system Gas fuel supply Fig. 5: Gas injection valve ME-GI engine 10 Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications

11 The buffer tank, containing about 20 times the injection amount per stroke at MCR, i.e. 100% load, performs two important tasks: It supplies the gas amount for injection at a slight, but predetermined, pressure drop It forms an important part of the safety system. Since the gas supply piping is of the common rail design, the gas injection valve must be controlled by an auxiliary control oil system. In principle, this consists of the ME hydraulic control oil system and an ELGI (ELectrical Gas Injection) valve, supplying highpressure control oil to the gas injection valve, thereby controlling the timing and opening of the gas valve. As already mentioned, dual fuel operation requires injection of both pilot fuel and gas fuel into the combustion chamber. Different types of valves are used for this purpose. Three valves per cylinder are fitted for gas injection and three for pilot fuel for engines with bore sizes larger than 60 cm. The media required for both liquid fuel and fuel gas operation are as follows: Fuel gas supply Liquid fuel 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. Fuel 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. Any leakage will be detected by HC sensors. The gas acts continuously on the valve spindle at a max. pressure of about 300 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. HFO, MGO, MDO, crude oil and crude biofuel can be used as pilot oil. The fuel oil pressure is constantly monitored by the GI safety system in order to detect any malfunction of the fuel oil valve. The fuel oil valve design allows operation solely on fuel oil up to MCR and 10% overload once for every consecutive 12 hours. The gas engine can be run on fuel oil at 100% load, switching from gas to fuel at any time without stopping the engine. As can be seen in Fig. 6 (GI injection system), the ME-GI injection system for Gas injection valves ELWI ELGI Time Low pressure fuel supply Fuel return Injection Gas Press Gas Block Fuel injection valve Proximity position sensor Blow off Window Valve Fuel actuation To Silencer Purge Gas Accu ELWI ELGI FIVA valve Valve Closed 300 bar hydraulic oil. Common with exhaust valve actuator Fig. 6: ME-GI injection system for 50 bore and smaller Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 11

12 50-bore engines and smaller consists of fuel oil valves, fuel gas valves, ELGI for opening and closing of the fuel gas valves, a FIVA (fuel injection valve actuator) valve to control via the fuel oil valve the fuel oil injection profile and last, but not least, the ELWI (ELectrical WIndow and gas shutdown valve) valve to control the position of the window valve as an extra safety feature to prevent gas leakages and ensure a double valve block towards the combustion chamber. 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 pressure 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. pressure, the gas mode is stopped and the engine returns to burning liquid fuel oil only. The purpose is to be warned at an early stage if any gas leaks occur across the gas injection valves. The window valve has a double safety function securing that gas injection into the combustion chamber is only possible at the correct injection timing. In the event of a gas failure, it can also block the gas from entering the combustion chamber, thereby ensuring that only a very small amount of gas will enter. The pressure sensor is located between the window valve and the gas injection valve. The small gas volume in the cylinder cover on each cylinder will reveal the gas pressure during one cycle. By this system, any abnormal gas flow will be detected immediately, whether due to seized gas injection valves, leaking gas valves or blocked gas valves. The gas supply is discontinued and the gas lines are purged with inert gas. Also in this event, the engine continues running only on liquid fuel oil without any power loss. High-pressure, double-wall piping The chain gas pipes are designed with double walls, with the outer shielding pipe designed so as to prevent fuel 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 hall with the (extractor) fan motors placed outside the ventilation ducts. The ventilation inlet air is taken from a non-hazardous area. Gas pipes are arranged in such a way that air is sucked into the doublewalled piping system from around the Safety features 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 fuel gas is injected. The fuel 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 Fig. 7: Branching of gas piping system 12 Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications

13 pipe inlet. Next the air is led to the individual gas valve control blocks and designed for 50% higher pressure than The gas pipes on the engine proper are then returned back into the chain pipes the normal working pressure, and are and into the atmosphere. supported so as to avoid mechanical vibrations. The pipes are pressure-tested Ventilation air is exhausted to a firesafe at 1.5 times the working pressure. place. The double-wall piping system is designed so that every part is ventilated, see Fig. 7 and 8. All joints connecttween the individual cylinders ensures The chain pipe design, see Fig. 7, beed with sealings to a high-pressure gas adequate flexibility to cope with the volume are ventilated. Any gas leakage thermal expansion of the engine from will therefore be led to the ventilated cold to hot condition. The gas pipe system is also designed to avoid excessive part of the double-wall piping system and detected by the HC sensors. gas pressure fluctuations during operation. Window valve 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 approximately 9 bar. In the event of a gas failure, the highpressure pipe system is depressurised before automatic purging. During a normal gas stop, the automatic purging is to be started after a period of up to 30 minutes. Time is therefore available for a quick re-start in gas mode. Fuel gas and fuel handling for ME- GI-S The MAN B&W ME-GI-S engine is capable of running on both 100% liquid fuel oil and on any ratio of gas and fuel/ pilot oil at a ratio of 97-3%, see Fig. 9. In case of fuel gases with very low energy content, a larger amount of pilot oil might be required. Gas outlet Hydraulically actuated purge/blow-off valve Gas areas Ventilation air channel Fig. 8: Gas valve control block Fuel 100% Fuel-oil-only mode Fuel 100% Maximum-gas-amount mode %Total %Pilot Fuel Fuel Gas 3% 100% load 10% 100% load *Automatic switchover between gas and pilot oil or fuel injection at 10% load Fig. 9: MAN B&W two-stroke dual fuel low speed diesel, fuel type mode Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 13

14 Therefore, the power plant is usually to be equipped with a full size fuel oil supply system, see Fig. 10, and a fuel gas supply system, see Fig. 11. The fuel gas supply station must be capable of fulfilling the requirements specified in Fig. 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 Fig. 10: Fuel oil system I Oxidiser II Oxidiser III ME-GI-S engine LNG LNG Reliquefaction* Reliquefaction* NG HP compressor Cryogenic HP pump HP compressor HP vaporiser 300 bar and 45 C To engine Fig. 11: ME-GI-S engine and gas handling 14 Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications

15 Gas supply pressure set point (bar) Control of gas delivery pressure Gas supply pressure set point range % 20% 40% 60% 80% 100% Engine load (% MCR) General Data for Gas Delivery Condition: Pressure: Nominal at 100% load Max. value for design Set point tolerance (dynamic) 300 bar 315 bar ± 5 bar Set point tolerance (static) ± 1% Temperature: 45 C ± 10 C Quality: Condensate free, without oil/water droplets or mist, similar to the PNEUROP recommendation 6611 Air Turbines Fig. 12: Gas supply station, guiding specification Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 15

16 The sizing and power consumption of the compressor station or the LNG cryogenic pump mainly depend on the gas pressure at the plant inlet and the lower calorific value (LCV) of the fuel gas, see Fig. 13. Table 4 lists the guiding gas specifications. As pilot oil, any commercial available liquid mineral or biofuel can be used, ref. Tables 5 and 6. The fuel gas supply system is suggested to comprise two compressors for a single engine installation. Each compressor must have 100% capacity for redundancy. kw compressor power (per 1000kg CH4 per hour) Compressor power / Generator output (%) Pressure at 400 compressor outlet LCV 30MJ/Nm 3 LCV 40MJ/Nm LCV 20MJ/Nm LCV 10MJ/Nm Gas pressure at compressor station inlet (bar abs.) Fig. 13: Guiding gas compressor power demand for natural gas and compressed natural gas 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 16 Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications

17 Two-stroke guiding liquid fuel specification for MAN B&W two-stroke low speed diesel engines 1) Designation Diesel engines ISO8217:2010(E) rmk700 Density at 15 C kg/m Kinematic viscosity at 50 C cst Flash point C 60 Carbon residue % (mm) 20 Ash % (mm) Water % (mm) 0.50 Sulphur % (mm) 5.0 Vanadium mg/kg 450 Aluminium + Silicon mg/kg 60 API gravity (min) API * Sodium mg/kg 100 Calcium ppm (mm) 200 Lead ppm (mm) 10 Free from ULO calsim > 30 and zink > 15 mg/kg or calsium > 30 and phosphorus >15 mg/kg Table 5 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 Table 6 1 1) Max. values at plant entry prior to treatment on site 2) Pre-heating down to 15 cst at engine inlet flange is to be ensured 3) Lodin, phosphorus and sulphur content according to agreement with emissioni control maker 4) TBO of engine fuel systems to be adjusted according to actual value and experience Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 17

18 For multiple engine plants operating on NG or CNG, we suggest the installation of one compressor per engine, all feeding a common gas supply line, see Fig. 14. Compressor Vent Control range 150 to 265 bar g p set Shut off valve V1 For operation on LNG, where a fuel gas pressure of 300 bar is required, the technology method is to pressurise the LNG and evaporate while maintaining the pressure. Technical solutions are available from a number of suppliers. In such a case, the power consumption is estimated to be approximately 0.5% of the engine power. The requirement for redundancy is to be decided together with the end-user. A glycol water system is required for heating the LNG in the vaporiser, see Fig. 15. Gas supply from pipe line Compressor Fig. 14: Multiple engine installation p set Pressure regulation valve Control range 150 to 265 bar g ME-GI ME-GI HT1 Water glycol circuit HT2 Waste heat Pilot fuel Gas LNG tank Fig. 15: High-pressure cryogenic pump 18 Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications

19 Description of the Liquid Gas Injection Concept (ME-LGI-S) The details of high-pressure gas injection have been dealt with in the previous sections of this paper. This chapter focuses on liquid fuel gases such as LPG, DME and methanol, which can be injected into the combustion chamber in liquid form. Just like the conventional operation on an ME-GI-S engine, these gases are combusted according to the diesel cycle principle described previously. In order to be able to combust liquid fuel gases, MAN Diesel & Turbo has developed the fuel booster injection valve (FBIV), see Fig. 16, which is applied on the ME-LGI-S engine design. The FBIV integrates our fuel oil booster design and our slide injection valve design. Both designs are well-proven in the marine market for MAN B&W twostroke low speed diesel engines for propulsion purposes. By application of this design, the total inertia of the fuel injection system reduces and improves the response time of the FBIV. Tests in service on engines for marine application have demonstrated an improved control of the injection profiles. Surfaces requiring lubrication/sealing Lubricating/sealing oil booster piston Cooling oil inlet Nozzle Plunger Control oil Fig. 16: Cross section of fuel booster injection valve (FBIV) LPG, methanol or DME are vented with ventilation air. in the oil system. If LPG or methanol is detected in the system, the engine will switch to fuel oil mode, and the The FBIVs are to be cooled, and their running surfaces must be lubricated. For this purpose, a combined sealing and cooling oil system delivering a 50 bar system oil pressure has been integrated on the engine, and the system both lubricates all running surfaces and controls that the temperature in the booster valve is lower than max. 60 C. The design principle is show in Fig. 16. liquid fuel gas will be purged from the engine. At the same time, the cooling oil pump supply side will be switched to clean system oil, and the oil circuit will be flushed with clean oil. Then, the clean oil will be collected together with the contaminated oil in the cooling oil tank, and the system will only be able to continue operation when no liquid fuel gas is detected in the tank. When operating on LPG or methanol, each of the cylinder covers will be equipped with FBIVs designed for each of the selected liquid fuel gases. An LGI block will be mounted on the cylinder cover. This block contains a control valve for either LPG or methanol for fuel injection, a sealing booster actuation valve, a forced suction valve and an LGI purge valve. All pipes for hydraulic oil and liquid fuel gases are double walled. The double-walled pipes for The sealing oil pressure is generated internally in the FBIV in order to avoid contamination of the hydraulic oil when operating the valve. The sealing oil has further advantages as it avoids LPG, methanol or DME from entering the umbrella system and further down into the drain oil system. The cooling oil and sealing oil system is fully integrated in the engine design, including equipment for continuous monitoring of LPG, methanol or DME contamination To ensure the correct temperature of the FBIV, the system oil is cooled in a heat exchanger connected to, for example, the low-temperature cooling system. When the liquid fuel gas is injected, the combustion condition is monitored with PMI sensors located in each of the cylinder covers. Three combustion conditions are monitored: the compression Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 19

20 pressures, the combustion pressures and the expansion pressures. The pressurised liquid fuel gas is delivered to the engine inlet via doublewalled pipes ventilated with dry air taken from the starting air system. A ventilation system fitted at the outlet sucks in the air. All liquid fuel gas supply equipment is designed with double walls, as any leakage into the atmosphere will develop into vapour. This is monitored by HC sensors located close to the outlet of the double wall piping system. If the LPG, methanol or DME vapour content in the ventilation system gets too high, the safety system will shut down operation on LPG or methanol and return to operate on fuel oil only. This switch is done smoothly and without any power loss. A control and safety system for either LPG, methanol or DME is integrated on the engine. The main operating panel (MOP) is equipped with a user-friendly interface for liquid fuel gas operation. Via this panel, the LGI system monitors and indicates the relevant pressure, temperatures and the position of the different valves. Liquid fuel gas and fuel handling for ME-LGI-S This section describes the specific auxiliary systems for the ME-LGI-S engine. In addition to the systems described here, the normal auxiliary systems for the electronically controlled ME concept will also be required, and since the ME-LGI is a dual fuel concept, a standard supply system for operation on fuel oil is also needed. Fig. 17 gives an overview of the external LGI-S system. In the ME-LGI-S system principle overview diagram, the liquid fuel gas service tank is shown as a ventilated tank. Liquid fuel gas supply system (LFSS) The engine is using temperature-conditioned LPG, methanol or DME at a predetermined supply pressure and varying flow depending on the engine load. The LFSS will have to supply this fuel to the engine while complying with the requirements described regarding temperature, flow, pressure and rampup capabilities. A different system layout could be chosen for this task. In the following, a circulation solution is described as an example only. The LFSS applies the same principle as an ordinary liquid fuel oil supply system. LPG, methanol or DME is taken from a service tank containing liquid fuel gas Air supply 7 bar Vent Fuel valve train Liquid fuel gas Liquid fuel gas service tank Purging nitrogen Cooling oil system Purge return system Supply pressure and temperature according to specification Liquid fuel gas tank Standard piping Double-walled piping, ventilated Double-walled piping Liquid Fuel Gas Supply System Fig. 17: ME-LGI-S system overview. 20 Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications

21 and boosted to a pressure close to the supply pressure. The liquid fuel gas is then circulated by the circulation pump, and the pressure is raised to the engine supply pressure for either LPG, methanol or DME. The delivery pressure must ensure that the liquid fuel gas stays liquid, and that no cavitation occurs at the temperatures that the liquid fuel gas is exposed to until injection into the FBIV. The flow of liquid fuel oil in the circulation circuit should be higher than the liquid fuel oil consumption of the engine at all times. A typical circulation factor is 2-3 times the liquid fuel oil consumption. To ensure the liquid fuel delivery temperature, a heater/cooler is placed in the circulation circuit. It is recommended to connect this through a secondary cooling circuit to the LT cooling system. The low flashpoint fuel valve train (LFFVT) The LFFVT connects the LFSS with the engine through a master fuel valve (MFV) arranged in a double block and bleed configuration. For purging purposes, the valve train is also connected to a nitrogen source. Typically, the LFFVT will be placed outside the engine hall to avoid the need for double safety barriers. From the LFFVT, the fuel is fed to the engine in a double-walled ventilated pipe through the engine hall. Purge return system (PRS) As mentioned, the ME-LGI-S concept involves LPG, methanol or DME on the engine proper. Because of the low flashpoint, there are operation scenarios where the liquid fuel gas piping will have to be emptied and purged with nitrogen. For the ME-LGI-S, the liquid fuel gas piping on the engine and in the engine hall is to be arranged so that it can be purged and, thereby, return the gas to the fuel gas service tank. After the LPG, methanol or DME has been returned to the service tank, full purging with nitrogen is to be conducted through the double-walled piping system. Maintenance Work Maintenance of ME-GI-S or ME- LGI-S engines Proper maintenance planning is essential to satisfy the requirements of the power plant operation. Also with the ME-GI-S and ME-LGI-S engine components, operation and maintenance are straightforward processes for the skilled and experienced operating crew, at least if the maintenance jobs are duly planned, prepared and controlled. In general, superintendents and operating crew must be well-educated, skilled and dedicated professionals. MAN Diesel & Turbo offers education programmes to chief engineers that will keep them updated with the latest information on maintenance and technology. Requests for education programmes can be sent to MAN Diesel & Turbo in Copenhagen. Maintenance work at the power plant When an ME-GI-S engine is stopped, the high-pressure gas pipes will be pressure released and purged with nitrogen to ensure that the engine is gas free and available for all kinds of maintenance works. For an ME-LGI-S engine, if liquid fuel gas operation is expected to be stopped for a certain period, e.g. during minor maintenance work at the power plant, the procedure for switching to gas standby mode is to be followed. However, the LFSS is switched off when the procedure has been completed. Major servicing work involving lifting equipment over the supply lines is not recommended in this mode. The reason is that the liquid fuel gas supply lines in both the engine hall and on the engine proper are expected to contain amounts of LPG or methanol. In the event of a complete shutdown of the liquid gas system, e.g. for major maintenance work at the power plant, all piping must be emptied of LPG or methanol in the LFSS and then the ventilation can be turned off. Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 21

22 Retrofit For engines of the MC-S design already operating on HFO/biofuel, it is technically possible to carry out conversion to dual fuel operation for either ME-GI-S or ME-LGI-S. The engine components shown in Fig. 18 will be affected by a retrofit, and a suitable fuel gas supply should be installed. It is important to note that requests for retrofit solutions must be sent to MAN Diesel & Turbo on an ad hoc basis. Conclusion The two-stroke MAN B&W ME-GI-S or ME-LGI-S engines are applicable anywhere where fuel efficient, reliable and flexible power production is required. Besides traditional fuels, such as heavy fuel and natural gas, biofuels, synthetic biofuels and synthetic biogases from, e.g., vegetable garbage or pyrolyses processes can be applied. Cylinder cover Exhaust reciever Valve block ELGI valve Double wall gas pipes FIVA Fig. 18: Areas affected in retrofit situations 22 Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications

23 References Paper: Service Experience of Mitsui Gas Injection Diesel Engines, Mitsui- MAN B&W 12K80MC-Gi-S and Mitsui 8L42MB-G, Cimac Copenhagen 1998 Paper: Service Experience of the World s First Large-Bore Gas-Injection Engine, ISME Tokyo 2000 Paper: ME Engines - The New Generation of Diesel Engines, P412 Oct 2003 Paper: Guidelines for Fuels and Lubes Purchasing, ppr Feb 2009 Two-stroke Low Speed Diesel Engines for Independent Power Producers and Captive Power Plants, ppr May 2009 Paper: Stationary MAN B&W ME-GI- S, Engines for Dual Fuel Applications, ppr Aug Paper: ME-GI Dual Fuel MAN B&W Engines, A Technical Operational and Cost effective Solution for Ships fuelled by Gas, ppr Oct 2013 Paper: Using Methanol Fuel in the MAN B&W ME-LGI Series, ppr Aug 2014 Fuel Flexibility Done Right MAN B&W ME-GI-S and MAN B&W LGI-S for stationary applications 23

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28 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 ppr Sep 2014 Printed in Denmark MAN Diesel & Turbo Teglholmsgade Copenhagen SV, Denmark Phone Fax MAN Diesel & Turbo a member of the MAN Group