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Gaseous Fuel @ Www.07 Met.Tk


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  • 1. Gaseous substance that burns in air and releases enough heat to be useful as a fuel, while also remaining sufficiently stable at ordinary temperature to permit long-term storage without deterioration or undue hazard.
    It is advantageous if a fuel gas is readily transportable through pipes and is easily liquefied. Practically all fuel gases meet the first condition, and some meet the second as well. Natural gas, which occurs alone and in conjunction with petroleum deposits, is an excellent fuel gas in wide commercial use. Liquefied petroleum gas is a manufactured mixture of flammable gases that is easily stored in its liquefied condition. Oil gas is a type of gas made by applying heat to various petroleum distillates. Its principal use is as a supplement to natural gas during periods of heavy demand. Coal gas may be any of a variety of gases produced by heating coal in the absence of air and driving off the volatile constituents. It is not as high in fuel value as other gases and often contains tars, light oils, ammonia, and hydrogen sulfide. Producer gas is made by forcing a mixture of air and steam through burning coal or coke. Water gas, or blue gas, which burns with a bright blue flame, is made by passing steam over glowing coke.
    (A) Naturally Found Gaseous Fuels
    (B) Gaseous Fuels Obtained from Solid Fuels
    (C) Gaseous Fuel Obtained from Petro
    (D) Gases from some fermentation process

    1) Methane from coal mines
    2) Wood gas
    • 3) Goober gas
    • 2. 4) Sewage gas
    • 3. 5) Gas from underground gasification
    • 4. 6) Natural gas
    • 5. 7) Liquefied Petroleum Gas (LPG )
    • 6. 8) Refinery gas
    • 7. 9) Producer gas
    • 8. 10) B.F gas
    • 9. 11) Coke oven gas
    • 10. 12) LD Converter gas
    • 11. 13) Coal gas from coal gasification
    • 12. 14) Oil gas from oil gasification
    Natural Gas
    Naturally occurring gas found in oil fields and coal fields (Fire damp). The quantities of the constituents vary but the principle component is methane. Other components include higher hydrocarbons which can be separated out as a condensate. Some gases also contain hydrogen supplied.
    Terms used to describe gases:
    Dry or lean - high methane content (less condensate)
    Wet - high concentration of higher hydrocarbons (C5 - C10)
    Sour - High concentration of H2S
    Sweet - low conc. of H2S
    Residue gas - gas remaining after the condensing process
    Casing head gas - gas extracted from an oil well by extraction at the surface.
    Total world production of Natural gas in 1986 was 100 trillion m3. It is used as feed stock as well as fuel. It is preferred due to its high CV. Gas from coal mines is of equal quality to oil fields however it is much more difficult to extract. In 1961, 220 mill m3 of coal Nat gas were extracted in the UK. The North Sea gas has smashed the industry.
    Natural gases can be liquefied for distribution by tanker. Liquefied natural gas (LNG) contains mostly methane, LPG (Liquefied petroleum gas) mostly butane and propane.
    Synthetic Gases
    These are gases which are chemically made by some process.
    Increased interest presently in power generation due to the gasification properties of waste and biomass.
    Burner for Synthetic Gas
    A burner, substantially comprising a swirl generator for a combustion air stream and means for introducing fuel into the combustion air stream, the swirl generator having combustion-air inlet openings for the combustion air stream that enters the burner, and the means for introducing fuel into the combustion air stream comprising one or more first fuel feeds having a group of first fuel outlet openings, arranged distributed around the burner axis at a combustion chamber-side end of the burner. The burner is distinguished by the fact that the one or more first fuel feeds having the group of first fuel outlet openings are mechanically decoupled from the swirl generator. The present burner allows reliable and safe use of synthesis gas in both dilute and undiluted form as fuel.
    Producer gas
    The gas is produced by blowing air and sometimes steam through an incandescent fuel bed (the process is self heating). The reaction with air is exothermic but insufficient air is added hence CO is produced. Steam addition results in the formation of hydrogen by the water gas reaction. This is endothermic and hence balances out the exothermic air reaction.
    Producer gas is low CV and is hence is only usually used on site
    Blue Gas or Water Gas
    This is produced in a similar manner to above but allows the production of a higher CV fuel by intermittently blasting the incandescent bed with air and steam such that the overall heat balance is maintained. The products of the air blast contain the nitrogen which reduces CV. These are discharged to atmosphere. The products of the steam blast are kept since they have a higher CV. CV is virtually doubled in this way. Often used as a synthesis gas in the chemical industry.
    Oil Gas
    This is the gas formed by the thermal cracking of crude oil. If oil is sprayed onto heated checker work (refractory) it cracks to form lower gaseous hydrocarbons. These depend entirely on the feed stock but calorific values can increase to as much as 25MJ/m3 but can be as low as half of this.
    Carbureted Water Gas
    Water gas has still to low a CV for most purposes and this makes it unattractive to distribute. Carbureted water gas is the result of combining the water gas and oil gas methods. Oil is sprayed into the hot water gas chamber to result in a good quality gas. The ratio of the two determines the quality. This was the method used to produce the " Town gas" of old and has largely been superseded by natural gas in countries with an abundant supply. AS supplies of natural gas diminish, however, it will become more important again.
    Coal and Coke Oven Gas
    As mentioned previously, gases are liberated in the high temperature carbonization (coking) of coal. These are cleaned, de tarred and scrubbed and used as fuel. If coke is not required (coal gas), steam injection at the end of the cycle reacts with the coke to form blue water gas. This reduces the CV of the gas produced but the thermal efficiency of conversion rises.
    Wood gas is a syn gas also known as producer gas which is produced by thermal gasification of biomass or other carbon containing materials such as coal in a gasified or wood gas generator or producer gas .It is the result of two high-temperature reactions (above 700 °C (1,292 °F)): an exothermic reaction where carbon burns to CO2 but is then reduced partially back to CO (endothermic); and an endothermic reaction where carbon reacts with steam, producing (CO), molecular (H2), and (CO2).
    In several gasifier, the actual gasification process is preceded pyrolysis, where the biomass or coal turns into char, releasing (CH4) and tar rich (PAH). Other gasifiers are fed with previously paralyzed char. Wood gas is flammable because of the carbon monoxide, hydrogen, and methane content.
    C.V = 1660 kCal/M3
    • gober GAS
    • 13. Cow dung gas is 55-65% methane, 30-35% carbon dioxide, with some hydrogen, nitrogen and other traces. Its heat value is about 600 B.T.U.'s per cubic foot.
    • 14. A sample analyzed by the Gas Council Laboratory at Watson House in England contained 68% methane, 31% carbon dioxide and 1% nitrogen. It tested at 678 B.T.U.
    • 15. This compares with natural gas's 80% methane, which yields a B.T.U. value of about 1,000.
    • 16. Gobar gas may be improved by filtering it through limewater (to remove carbon dioxide), iron filings (to absorb corrosive hydrogen sulphide) and calcium chloride (to extract water vapor).
    • 17. Cow dung slurry is composed of 1.8-2.4% nitrogen (N), 1.01.2% phosphorus (P 2 0 5 ), 0.6-0.8% potassium (K 2 0) and from 50-75% organic humus.
    • 18. About one cubic foot of gas may be generated from one pound of cow manure at 75° F. This is enough gas to cook a day's meals for 4-6 people.
    • 19. About 225 cubic feet of gas equals one gallon of gasoline. The manure produced by one cow in one year can be converted to methane which is the equivalent of over 50 gallons of gasoline.
    • 20. Gas engines require 18 cubic feet of methane per horsepower per ho
    Early History of Gas Production by Gasification
    410083067246501850s Every small to medium sized town and city had a gas plant to provide for street lighting. Subscribing customers could also have piped lines to their houses. By this era, gas lighting became accepted. Gaslight trickled down to the middle class and later came gas cookers and stoves.1860 Lenoir Coal Gas Engine is shown in figure.
    1860s were the golden age of coal gas development. Scientists like Kekule and Perkin cracked the secrets of organic chemistry to reveal how gas is made and its composition. From this came better gas plants and Perkin's purple dyes.
    352425051816001850s: Gas producers invented, water gas process discovered. Mond Gas: 1850s Europeans discover that using coal instead of coke in a producer results in producer gas that contains ammonia and coal tar, Ludwig Mond's Mond Gas is processed to recover these valuable compounds.
    Modern History of Gas Production
    In modern age Manufactured gas can be made by two processes: carbonization or gasification. Carbonization refers to the devolatilization of an organic feedstock to yield gas and char. Gasification is the process of subjecting a feedstock to chemical reactions that produce gas
    The first process used was the carbonization and partial paralysis’ of coal. The off gases liberated in the high-temperature carbonization (coking) of coal in coke ovens were collected, scrubbed and used as fuel. Depending on the goal of the plant, the desired product was either a high quality coke for metallurgical use, with the gas being a side product or the production of a high quality gas with coke being the side product. Coke plants are typically associated with metallurgical facilities such as smelters, and blast furnaces, while gas works typically served urban areas.
    A facility used to manufacture coal gas, carbureted water gas (CWG), and oil gas is today generally referred to as a manufactured gas plant (MGP).
    39814502024380In the early years of MGP operations, the goal of a utility gas works was to produce the greatest amount of illuminating gas. The illuminating power of a gas was related to amount of soot-forming hydrocarbons (“illuminants”) dissolved in it. These hydrocarbons gave the gas flame its characteristic bright yellow color. Gas works would typically use oily bituminous coals as feedstock. These coals would give off large amounts of volatile hydrocarbons into the coal gas, but would leave behind a crumbly, low-quality coke not suitable for metallurgical processes. Coal or coke oven gas typically had a calorific value (CV)
    Figure 2: Diagram of a typical industrial distillation tower
    between 10 and 20 MJ/m³ (250-550 Btu/ft3 (std)); with values around 20 MJ/m³ (550 Btu/ft3 (std)) being typical.
    The advent of electric lighting forced utilities to search for other markets for manufactured gas. MGPs that once produced gas almost exclusively for lighting shifted their efforts towards supplying gas primarily for heating and cooking, and even refrigeration and cooling.
    Fischer-Tropsch process
    The Fischer-Tropsch process (or Fischer-Tropsch Synthesis) is a catalyzed chemical reaction in which synthesis gas ( Syngas ), a mixture of carbon monoxide and hydrogen, is converted into liquid hydrocarbons of various forms. The most common catalysts are based on iron and cobalt, although nickel and ruthenium have also been used. The principal purpose of this process is to produce a synthetic petroleum substitute, typically from coal, natural gas or biomass, for use as synthetic lubrication oil or as synthetic fuel. This synthetic fuel runs trucks, cars, and some aircraft engines. (Refer to Sasol.) The use of diesel is increasing in recent years
    Combination of biomass gasification (BG) and Fischer-Tropsch (FT) synthesis is a possible route to produce renewable transportation fuels
    Gas for industrial use
    Fuel gas for industrial use was made using producer gas technology. Producer gas is made by blowing air through an incandescent fuel bed (commonly coke or coal) in a gas producer. The reaction of fuel with insufficient air for total combustion produces carbon monoxide (CO); this reaction is exothermic and self sustaining. It was discovered that adding steam to the input air of a gas producer would increase the CV of the fuel gas by enriching it with CO and hydrogen (H2) produced by water gas reactions. Producer gas has a very low CV of 3.7 to 5.6 MJ/m³ (100-150 Btu/ft3 (std)); because the calorific gases CO/H2 are diluted with lots of inert nitrogen (from air) and carbon dioxide (CO2) (from combustion)
    (Exothermic: Producer gas Reaction)
    (Endothermic: Water gas Reaction)
    (Exothermic: Water gas shift reaction)
    3306445centerThe problem of nitrogen dilution was overcome by the blue water gas (BWG) process, developed in the 1850s by Sir William Siemens. The incandescent fuel bed would be alternately blasted with air followed by steam. The air reactions during the blow cycle are exothermic, heating up the bed, while the steam reactions during the make cycle, are endothermic and cool down the bed. The products from the air cycle contain non-calorific nitrogen and are exhausted out the stack while the products of the steam cycle are kept as blue water gas. This gas is composed almost entirely of CO and H2, and burns with a pale blue flame similar to natural gas. BWG has a CV of 11 MJ/m³ (300 Btu/ft3 (std)).
    Because blue water gas lacked illuminants it would not burn with a luminous flame in a simple fishtail gas jet as existed prior to the discovery of the Welsbach mantle in the 1890s. Various attempts were made to enrich BWG with illuminants from gas oil in the 1860s. Gas oil (an early form of gasoline) was the flammable waste product from kerosene refining, made from the lightest and most volatile fractions (tops) of crude oil.
    In 1875 Thaddeus S. C. Lowe invented the carbureted water gas process. This process revolutionized the manufactured gas industry and was the standard technology until the end of manufactured gas era. A CWG generating set consisted of three elements; a producer (generator), carburetor and a super heater connected in series with gas pipes and valves.
    During a make run, steam would be passed through the generator to make blue water gas. From the generator the hot water gas would pass into the top of the carburetor where light petroleum oils would be injected into the gas stream. The light oils would be thermo cracked as they came in contact with the white hot checker work fire bricks inside the carburetor. The hot enriched gas would then flow into the superheater, where the gas would be further cracked by more hot fire bricks.
    heat production
    Syngas can be used for heat production or for mechanical/electrical power generation. Like any other gaseous fuel, producer gas enables a good control over power levels when compared to solid fuels, paving the way for more efficient and cleaner operation.
    production of electricity
    Gasification is also used industrially in the production of electricity, ammonia and liquid fuels (oil) using Integrated Gasification Combined Cycles (IGCC), with the possibility of producing methane and hydrogen for fuel cells. IGCC is also a more efficient method of CO2 capture as compared to conventional technologies. IGCC demonstration plants have been operating since the early 1970s and some of the plants constructed in the 1990s are now entering commercial service.
    Potential for Renewable Energy
    Gasification can proceed from just about any organic material, including biomass and plastic waste. The resulting syngas burns cleanly into water vapor and carbon dioxide. Alternatively, syngas may be converted efficiently to methane via the Sabatier reaction, or diesel-like synthetic fuel via the Fischer-Tropsch process. Inorganic components of the input material, such as metals and minerals, are trapped in an inert and environmentally safe form as ash, which may have use as a fertilizer.
    From its original development until the wide scale adoption of natural gas, more than 50,000 manufactured gas plants were in existence in the United States alone. The process of manufacturing gas usually produced a number of by-products that contaminated the soil and groundwater in and around the manufacturing plant, so many former town gas plants are a serious environmental concern, and cleanup and remediation costs are often high. MGPs were typically sited near or adjacent to waterways that were used for the discharge of wastewater contaminated with tar, ammonia and/or drip oils, as well as outright waste tars and tar-water emulsions.
    In the earliest days of MGP operations, coal tar was considered a waste and often disposed into the environment in and around the plant locations. While uses for coal tar developed by the late-1800s, the market for tar varied and plants that could not sell tar at a given time could either store tar for future use, attempt to burn it as fuel for the boilers, or dump the tar as waste. Commonly, waste tars were disposed of in old gas holders, adits or even mine shafts (if present). Over time, the waste tars degrade with phenols, benzene (and other mono-aromatics - BTEX) and polycyclic aromatic hydrocarbons released as pollutant plumes that can escape into the surrounding environment. Other wastes included " blue billy" .