Compressed Natural Gas

Transcription

1 Compressed Natural Gas 1 Why Use Alternative Fuels? Petroleum Displacement Energy Diversity Air Quality Improvement Greenhouse Gas Emission Reductions Domestic Economic Development 2 Compressed natural Gas 1

2 Urban Pollution 3 Case Study of Delhi 4 Compressed natural Gas 2

3 Smog Became Pervasive 5 6 Compressed natural Gas 3

4 7 FLEET COMPOSITION OF INDIAN VEHICLES (1997) (Source: TERI) (Two wheelers (71%) & Three wheelers (5%) occupy significant places in the Indian transportation sector) 8 Compressed natural Gas 4

5 9 Landmark March 31, 2001, India Supreme Court ruling 10 Compressed natural Gas 5

6 Heavy duty conversion of the entire bus fleet to (CNG). Taxis and auto rickshaws must be replaced with engines running on clean fuels A natural gas pipeline from Mumbai supplies natural gas to New Delhi. 11 Light-duty As of April 1, 2000, non-commercial 4-wheelers must meet Euro II emission standards. Commercial vehicles, such as taxis, must be also meet Euro II emission standards or use CNG In order to be registered in the Capital Region of New Delhi. 12 Compressed natural Gas 6

7 Alternative Fuel Vehicles Available Now Ethanol Natural Gas Propane (LPG) 13 Why Natural Gas Chosen? 1. Natural gas is one of the cleanest of all fuel sources available 2. Huge potential of unexploited natural gas reserves exists in India 3. This presentation explores the possibilities of utilizing unexploited gas reserves by converting them into liquids 14 Compressed natural Gas 7

8 15 Gas Reserves In India 1. Gas reserves of NE region Tripura 2. Gas hydrates in deep sea 3. Gas reserves in deepwater 16 Compressed natural Gas 8

9 NATURAL GAS 17 HISTORY 18 Compressed natural Gas 9

10 19 20 Compressed natural Gas 10

11 21 22 Compressed natural Gas 11

12 23 24 Compressed natural Gas 12

13 Natural Gas Vehicles Dilemma Very Low Emissions Good Performance Lower Cost Fuel Limited Range, but adequate for most Applications Few Refueling Stations Higher Cost Vehicle Indian buses generally use horsepower engines. 25 Forms of Natural gas Storage Natural gas can be used in engines in a liquefied compressed gas (LNG). In order to liquefy it at atmospheric pressure, it is necessary to bring it to a temperature of 162 C. As a result it is used mainly in the form of Compressed Natural gas (CNG) 26 Compressed natural Gas 13

14 CNG tanks CNG tanks are regulated to be steel and no composite material is allowed. A brand new, good quality CNG kit with cylinder costs around 32,000 rupees or $6,400, while a substandard locally-made welded version is half the amount Compressed natural Gas 14

15 Refueling: CNG refueling stations using Tulsa Gas technologies equipment. The India Supreme Court has mandated that at least 90 refueling stations be made available. Taxi cab drivers and rickshaw drivers fill at 68 daughter stations. Natural gas buses are filled at 3 mother stations. The methane content for compressed natural gas is 88 percent Compressed natural Gas 15

16 PROBLEMS WITH CNG DISPENSING STATIONS Uneven distribution of CNG stations Inadequate pressure in daughter stations Overrunning of compressors Non availability of continuous power supply Shortage of trained manpower 31 CNG Induction Techniques 32 Compressed natural Gas 16

17 33 SI Combustion technology 34 Compressed natural Gas 17

18 Gasoline Car Bi Fuel Conversion 35 What does the Conversion kit comprise of? The Cylinder The Vapor Bag The High Pressure Pipe The Refueling Valve The Pressure Regulator The Gas Air Mixer The Petrol Solenoid Valve The Selector Switch 36 Compressed natural Gas 18

19 Typical Gas Conversion Compressed natural Gas 19

20 Typical Gas regulator 39 Typical Gas & Petrol Solenoid 40 Compressed natural Gas 20

21 Various Design of gas mixers 41 Fuel Mode Switch 42 Compressed natural Gas 21

22 Dedicated CNG Conversion of Diesel Engines Replacing injector by Spark plug Machining the piston to decrease CR Gas Conversion Kit installed 43 Transit buses Only two Indian chassis manufacturers exist--tata and Ashok Leyland. Natural gas buses are using stoichometric Cummins engines. private operators are installing conversion kits. Nugas is the certified company for CNG bus conversions. 44 Compressed natural Gas 22

23 45 Tuning up gas engines: Stoichiometric engines (=1), in other words, the air fuel ratio is exactly the theoretical required for combustion Lean mixture engines (normally = 1.4 ) 46 Compressed natural Gas 23

24 Efficiency of CNG Engines The best gas powered engines achieve a level of efficiency in the order of 36 37% Which is above petrol engines Below modern diesel engines 47 Safety with CNG 48 Compressed natural Gas 24

25 49 50 Compressed natural Gas 25

26 Natural Gas What is natural gas? Mainly methane(ch 4 ) also contains heavier gaseous hydrocarbons such as ethane (C 2 H 6 ), propane (C 3 H 8 ) and butane (C 4 H 10 ), as well as other sulphur containing gases, in varying amounts exact composition of natural gas varies between gas fields. Compressed natural Gas 26

27 Composition component % Methane(CH4) Ethane(C2H6) 5-15 Propane(C3H8) and Butane(C4H10) <5 Sources of natural gas It is found in oil fields and natural gas fields, and in coal beds The largest two natural gas fields are probably South Pars Gas Field in Iran and Urengoy gas field in Russia, with reserves on the order of m³ Gas produced from oil wells is called casinghead gas or associated gas Compressed natural Gas 27

28 Storage It can be stored in two forms: Liquefied natural gas (LNG) and compressed natural gas (CNG) CNG Fuel Large scale use since 1960 s Some 3,500,000 CNG vehicles now in operation worldwide Mostly in Italy, Argentina, Brazil, Pakistan, etc. as lower cost fuel Growing rapidly for transit operations in Europe as lower emission fuel Some 7,500 fill stations Compressed natural Gas 28

29 CNG Fuel Temperature Effects Typically stored at 3,600 psi at 70ºF If ambient temperature goes up or down, pressure also correspondingly goes up or down CNG Fuel Filling During filling, gas heats up as it compresses in the tanks Typically, stations only fill to service pressure of 3,600 psi End up with 3,600 psi at some elevated temperature (say 100ºF) in the tanks As gas cools to ambient (say 70ºF), pressure of gas decreases End result is less gas instead of having a fill of 3,600 psi at 70ºF, one has say 3,400 psi at 70ºF Compressed natural Gas 29

30 To prevent underfills Tanks can be slowly filled to allow heat to dissipate Tanks can be pressured beyond service pressure, i.e. fill so that one gets higher pressure at a higher temperature, thus cooling to 3,600 psi at 70ºF Tanks actually designed to be filled up to 1.25 times service pressure (all qualification testing done at 1.25 times) Fuel Tank Technologies 4 basic types of tank designs which design to use depends on need to reduce weight and how much can pay All designs have equivalent safety, as all meet requirements of same standards Design type can also determine how a tank may be handled, and how it may be filled Compressed natural Gas 30

31 Type 1 & Type 2 Tank Designs Type 1 All metal (aluminum or steel) Cheap but heavy Type 2 Metal liner reinforced by composite wrap (glass or carbon fiber) around middle ( hoop wrapped ) Liner takes 50% and composite takes 50% of the stress caused by internal pressurization Less heavy, but more cost Type 3 Tank Design Metal liner reinforced by composite wrap around entire tank ( full wrapped ) Liner takes small amount of the stress Light weight, but expensive Compressed natural Gas 31

32 Type 4 Tank Design Plastic gas tight liner reinforced by composite wrap around entire tank ( full wrapped ) Entire strength of tank is composite reinforcement Light weight, but expensive CNG performance The octane rating for CNG is higher than that for gasoline; in a dedicated engine a CNG vehicle s power, acceleration, and cruise speed can be greater than that of a gasoline powered vehicle. In addition, due to the cleaner burning characteristics of natural gas, CNG vehicle engines can run more efficiently than a gasoline powered vehicle, CNG engines are also generally less noisy than diesel engines. Compressed natural Gas 32

33 Safety CNG has a narrow flammability range, making it an inherently safe fuel. It is non toxic CNG also disperses rapidly, minimizing ignition risk relative to gasoline However, leaks indoor may form flammable mixture in the vicinity of ignition source Emissions Reductions in carbon monoxide emissions of 90 to 97 percent, and reductions in carbon dioxide emissions of 25 percent. Reductions in nitrogen oxide emissions of 35 to 60 percent. Potential reductions in nonmethane hydrocarbon emissions of 50 to 75 percent. Fewer toxic and carcinogenic pollutants, and little to no particulate matter produced. Compressed natural Gas 33

34 Maintenance Proper training is required for all maintenance personnel working on CNG vehicles The oil in a CNG vehicle does not need to be changed as frequently because CNG burns more cleanly than gasoline, producing less deposits in the oil. LNG fuel Liquefied natural gas or LNG is natural gas that has been processed to remove helium, or impurities such as water, and heavy hydrocarbons and then condensed into a liquid at almost atmospheric pressure by cooling it to approximately 163 degrees Celsius LNG is about 1/614th the volume of natural gas at standard temperature and pressure (STP) Much more cost efficient to transport Compressed natural Gas 34

35 Producing LNG by liquefaction Preliminary processes The raw feed gas supply arriving from a producing gas field must be clean and dry before liquefaction can take place It is scrubbed of entrained hydrocarbon liquids and dirt Treated to remove hydrogen sulphide and carbon dioxide Gas is cooled to allowed water to get condensed Compressed natural Gas 35

36 Then it is further dehydrated to remove even small amounts of water. If mercury is present then it is also removed at this stage. Then the gas is filtered to ensure only methane and traces of other hydrocarbons are present. Liquefaction Liquefaction takes place through cooling of the gas using heat exchangers. In these vessels, gas circulating through aluminum tube coils is exposed to a compressed hydrocarbon nitrogen refrigerant. Heat transfer is accomplished as the refrigerant vaporizes, cooling the gas in the tubes before it returns to the compressor. The liquefied natural gas is pumped to an insulated storage tank where it remains until it can be loaded onto a tanker. Compressed natural Gas 36

37 Basic facts on LNG LNG offers energy density comparable to gasoline or diesel. But its high cost of production and need of cryogenic temperatures to store it has prevented its widespread use. Natural gas fed into LNG plant is treated to remove water, hydrogen sulphide, carbon dioxide and other compounds which freeze at low temperatures. Storage LNG above ground tanks are mainly of double wall, high nickel steel construction with extremely efficient insulation between the walls Large tanks are low aspect ratio (height to width) and cylindrical in design with a domed roof. Storage pressures are very low, less than 5psig. Compressed natural Gas 37

38 LNG Storage tank Pipeline system Compressed natural Gas 38

39 Smaller quantities, 70,000 gallons and less, are stored in horizontal or vertical, vacuum jacketed, pressure vessels. These tanks may be at pressures any where from less than 5 psig to over 250 psig LNG must be maintained cold (at least below 117 F) to remain a liquid, independent of pressure. LNG performance There are no discernible differences in LNG vehicle performance, operation, and utility when compared with diesel The high ignition quality of LNG is similar to that of diesel, providing for similar durability and engine life overall. Compressed natural Gas 39

40 Safety A LNG vehicle parked indoors and unmoved for a week or more will vent a flammable gas mixture that could catch fire in the vicinity of an ignition source. refueling vehicles with LNG requires training because of the fuel s ultra low temperature. It can cause frostbite if it contacts skin. Emissions Production of half particulate matter of average diesel vehicles. Can significantly reduce carbon monoxide emissions. Reductions of nitrogen oxide and volatile organic hydrocarbon emissions by 50 percent or more. Potential reductions in carbon dioxide emissions of 25 percent depending on the source of the natural gas. Drastic reductions in toxic and carcinogenic pollutants. Compressed natural Gas 40

41 Maintenance LNG s cleaner burning characteristics can result in longer engine life and reduced maintenance costs. Use of LNG eliminates the periodic tank inspections Because of the fuel s below freezing temperatures, only trained personnel should maintain LNG vehicles. Exhaust emissions CNG emissions are compared with diesel and B20 ( diesel blend with vegetable oil) THC, NOx, and PM emissions of CNG engine are significantly lower than diesel, with a reduction of 67%, 98% and 96% respectively. No significant reduction in CO is observed. Compressed natural Gas 41

42 Unregulated emissions Carbonyl compounds Formaldehyde is most abundant compared to other carbonyl compounds in the exhaust emissions. CNG emits 95% lower formaldehyde with respect to diesel fuel. PAHs and nitro PAHs Use of CNG results in significant decrease in emissions: a reduction of, at least, 98% and 88% was observed for PAHs associated to PM and vapor phase. Compressed natural Gas 42

43 Unregulated emissions PAHs associated with particulate matter PAHs associated with vapour phase Compressed natural Gas 43

44 Carbonyl compounds Compressed Natural Gas: Storage and Dispensing There are two types of CNG refueling systems Slow-fill: In slow fill systems, several vehicles are connected to the output of the compressor at one time. These vehicles are then refilled over several hours of compressor operation. Slow fill is considered practical only for vehicles of single fleet. Fast-fill:In fast systems, enough CNG is stored so that several vehicles can be refueled one after the other, just like refueling from a single gasoline dispenser Compressed natural Gas 44

45 Basic Elements of a Fast Fill CNG Refueling System Compressor Storage Piping Dispensers Control system Leak detection system Fire suppression system Lightning protection Compressors Reciprocating compressor Multistage (usually four stages) Gas is compressed from 35 kpa to as high as 31 MPa. Compressed natural Gas 45

46 Storage Cylinders are made according to either U.S. DOT or ASME pressure vessel code. Cylinders are made only from carbon steel. Cylinders are placed on a concrete slab without enclosure. CNG storage cylinders can also be placed in underground vaults but usually not preferred. Piping Piping must be compatible with natural gas and capable of four times the rated service pressure without failure. Stainless steel seamless tubing is commonly used. Threaded and compression type fittings that do not use gaskets or sealants are also allowed. Compressed natural Gas 46

47 Dispensers Dispensers are used to direct CNG from the storage system into the vehicle (only used for fast fill systems). They typically incorporate a sort of on off switch activated by removal of the refueling nozzle and a meter to measure the amount of CNG dispensed. CNG dispensers are usually made of stainless steel CNG dispenser nozzles are made from aluminum and stainless steel Control Systems Control systems are of two types mechanically controlled and completely computer controlled. Computer controlled systems offers flexibility not possible with mechanical systems. Computer controlled systems provide functions such as accounting of the amount of the fuel dispensed into the vehicle and billing functions. Compressed natural Gas 47

48 Leak Detection Systems Leak detection system usually use methane detectors. Methane detectors are usually placed above the ground level at points where the released gas is likely to pass as methane rises when released. Most methane detectors are set to alarm when 20% lower flammability limit (LFL) of methane in air is detected (about 1% methane in air). Some refueling facilities use two stage approach to methane detection and alarm.first alarm is sounded when 20% LFL is detected and shutdown of refueling system is initiated when 40% LFL is reached. Fire Suppression Systems These systems are dry chemical using infrared detectors A puff test should be normally carried out after installation of fire suppression systems. Puff tests not only shows the coverage that can be obtained but also tests the components of the fire protection systems. Compressed natural Gas 48

49 Lightning Protection CNG refueling systems located outdoor should take lightning protection into account. Lightning strikes can damage the refueling system and cause fuel release and/or fires Fuel Quality and Effect on Exhaust Emission 98 Compressed natural Gas 49

50 Fuel Quality Trends in India Diesel * Cetane number increased from 42 to 45 in 1995 and further increased to 48. Need for further increase in 2005 to be assessed. * Distillation limits became stringent from year 2000 in view of no clear trends further control of T90/T95 to be examined. * Sulphur content reduced from 1% to 0.5% in the year 1996 and further reduced to 0.25% in the year Likely to be 0.05 in 2005 but needs to be linked with engine technology. * Benefits of multifunctional additives being examined. Likely benefits in terms of fuel economy and emission reduction. 99 Gasoline Quality And Emissions Note: (+) Desirable; (-) Undesirable; Blank NO significant effect 100 Compressed natural Gas 50

51 ROLE of Fuel Additives Additives are rapid, economic and easy means for Improving fuel performance properties. Control fuel quality during production, distribution and storage. Control emissions. 101 MFA In Gasoline Gasoline stability problem inclusion of cracked stocks in gasoline gasoline deterioration during storage Results in formation of gum and sediments in storage. Gummy deposits in engine intake system. Engine performance deterioration Loss of fuel economy. Increase in emission. Poor startability. Solution of problem Refinery processing chemical treatment of gasoline with additives 102 Compressed natural Gas 51

52 MFA In Gasoline INTERNATIONAL SCENARIO U.S.A * As per clean air act gasoline must contain certified additives. EUROPE * Growing use of deposit control additives (DCA) ASIA AND AUSTRALIA * Japan, Singapore, S. Korea, New Zealand, Australia USE guidelines from US EPA * In Thailand DCA regulation system is in place 103 Fuel Quality Trends in India Related to Emissions Unleaded gasoline introduced in four metros from APR.1995 and all over the country from Total lead phase out in Delhi from Volatility limits implemented from 1995 further review for evaporative emission control. Use of multifunctional additives in gasoline recommended in 1997 Use of oxygenates like MTBE started in some refineries for producing unleaded gasoline Sulphur limit to be made stringent from year 2000 demand for further control from 2005 Benzene also to be restricted to 5% max. from 2000 demand for reduction upto 1% 104 Compressed natural Gas 52

53 Impact of Diesel Properties on Emissions Note: (+) Desirable; (-) Undesirable; Blank NO significant effect 105 Fuel Sulphur-PM Emission Sulphur 0.25% Sulphur 0.05% Reduction Contribution of sulphate & H 2 0 -Absolute Emission g/kwh % of Euro 1 limit (0.36 g/kwh) % of Euro 2 limit (0.15 g/kwh) Compressed natural Gas 53

54 Conclusion Main conclusion that flows logically from the overview presented is that India along with most of the world will have to switch to alternative fuels for automobiles, sooner or later, the sooner the better for our own environment. There is a need for all the players in the industry to look ahead and formulate a strategy to make this switch smooth and timely. 107 Compressed natural Gas 54