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80-440: Ma Tau Kok Road is named after Ma Tau Kok. At the time of the 1911 census, the population of Ma Tau Kok was 212. The number of males was 145. In 1935, a gas work was built at the junction of To Kwa Wan and Ma Tau Kok roads. It was operational until about 1994. Today, Grand Waterfront building stands there. In 1956, a second gas work was built west of To Kwa Wan Road. Later it switched from coal to naphtha gasification . Today, it

160-570: A coal deposit, while enhanced coal bed methane recovery is a method of recovering methane from non-mineable coal seams). It is associated with other hydrocarbon fuels, and sometimes accompanied by helium and nitrogen . Methane is produced at shallow levels (low pressure) by anaerobic decay of organic matter and reworked methane from deep under the Earth's surface. In general, the sediments that generate natural gas are buried deeper and at higher temperatures than those that contain oil . Methane

240-458: A hydrogen halide molecule and a methyl radical ( •CH 3 ). The methyl radical then reacts with a molecule of the halogen to form a molecule of the halomethane, with a new halogen atom as byproduct. Similar reactions can occur on the halogenated product, leading to replacement of additional hydrogen atoms by halogen atoms with dihalomethane , trihalomethane , and ultimately, tetrahalomethane structures, depending upon reaction conditions and

320-661: A few industrial scale biomass gasification plants. Since 2008 in Svenljunga, Sweden, a biomass gasification plant generates up to 14 MW th , supplying industries and citizens of Svenljunga with process steam and district heating , respectively. The gasifier uses biomass fuels such as CCA or creosote impregnated waste wood and other kinds of recycled wood to produces syngas that is combusted on site. Examples of demonstration projects include: Methane Methane ( US : / ˈ m ɛ θ eɪ n / METH -ayn , UK : / ˈ m iː θ eɪ n / MEE -thayn )

400-426: A flexible option for thermal applications, as they can be retrofitted into existing gas fueled devices such as ovens , furnaces , boilers , etc., where syngas may replace fossil fuels. Heating values of syngas are generally around 4–10 MJ/m . Currently Industrial-scale gasification is primarily used to produce electricity from fossil fuels such as coal, where the syngas is burned in a gas turbine. Gasification

480-442: A fuel slurry is gasified with oxygen (much less frequent: air) in co-current flow. The gasification reactions take place in a dense cloud of very fine particles. Most coals are suitable for this type of gasifier because of the high operating temperatures and because the coal particles are well separated from one another. The high temperatures and pressures also mean that a higher throughput can be achieved, however thermal efficiency

560-624: A handful have been implemented as plants processing real waste, and most of the time in combination with fossil fuels. One plant (in Chiba , Japan, using the Thermoselect process ) has been processing industrial waste with natural gas and purified oxygen since year 2000, but has not yet documented positive net energy production from the process. In 2007 Ze-gen erected a waste gasification demonstration facility in New Bedford, Massachusetts . The facility

640-527: A limited amount of oxygen or air is introduced into the reactor to allow some of the organic material to be "burned" to produce carbon dioxide and energy, which drives a second reaction that converts further organic material to hydrogen and additional carbon dioxide. Further reactions occur when the formed carbon monoxide and residual water from the organic material react to form methane and excess carbon dioxide (4CO + 2H 2 O → CH 4 + 3CO 2 ). This third reaction occurs more abundantly in reactors that increase

720-534: A more convenient, liquid fuel, is challenging because the reaction typically progresses all the way to carbon dioxide and water even with an insufficient supply of oxygen . The enzyme methane monooxygenase produces methanol from methane, but cannot be used for industrial-scale reactions. Some homogeneously catalyzed systems and heterogeneous systems have been developed, but all have significant drawbacks. These generally operate by generating protected products which are shielded from overoxidation. Examples include

800-423: A permeable bed, although recent developments have reduced these restrictions to some extent. The throughput for this type of gasifier is relatively low. Thermal efficiency is high as the temperatures in the gas exit are relatively low. However, this means that tar and methane production is significant at typical operation temperatures, so product gas must be extensively cleaned before use. The tar can be recycled to

880-400: A requirement for pure methane can easily be fulfilled by steel gas bottle from standard gas suppliers. Methane is the major component of natural gas, about 87% by volume. The major source of methane is extraction from geological deposits known as natural gas fields , with coal seam gas extraction becoming a major source (see coal bed methane extraction , a method for extracting methane from

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960-399: A resource that is otherwise difficult to transport for its weight, ash content, low calorific value and propensity to spontaneous combustion during storage and transport. A number of similar plants exist around the world, although mostly these plants are targeted towards the production of long chain alkanes for use as gasoline , diesel , or feedstock to other processes. Power to methane

1040-422: A significant role in a renewable energy economy, because biomass production removes the same amount of CO 2 from the atmosphere as is emitted from gasification and combustion. While other biofuel technologies such as biogas and biodiesel are carbon neutral , gasification in principle may run on a wider variety of input materials and can be used to produce a wider variety of output fuels. There are at present

1120-522: A variety of biomass and waste-derived feedstocks can be gasified, with wood pellets and chips, waste wood, plastics and aluminium, Municipal Solid Waste (MSW), Refuse-derived fuel (RDF), agricultural and industrial wastes, sewage sludge, switch grass, discarded seed corn, corn stover and other crop residues all being used. Chemrec has developed a process for gasification of black liquor . Waste gasification has several advantages over incineration: A major challenge for waste gasification technologies

1200-402: Is a chemical compound with the chemical formula CH 4 (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride , the simplest alkane , and the main constituent of natural gas . The abundance of methane on Earth makes it an economically attractive fuel , although capturing and storing it is difficult because it is a gas at standard temperature and pressure . In

1280-406: Is a halogen : fluorine (F), chlorine (Cl), bromine (Br), or iodine (I). This mechanism for this process is called free radical halogenation . It is initiated when UV light or some other radical initiator (like peroxides ) produces a halogen atom . A two-step chain reaction ensues in which the halogen atom abstracts a hydrogen atom from a methane molecule, resulting in the formation of

1360-463: Is a stub . You can help Misplaced Pages by expanding it . Gasification Gasification is a process that converts biomass - or fossil fuel -based carbonaceous materials into gases, including as the largest fractions: nitrogen (N 2 ), carbon monoxide (CO), hydrogen (H 2 ), and carbon dioxide (CO 2 ). This is achieved by reacting the feedstock material at high temperatures (typically >700 °C), without combustion, via controlling

1440-466: Is a plant with seven different processes: biomass processing, fuel delivery, gasification, gas cleaning, waste disposal, electricity generation and heat recovery. Diesel engines can be operated on dual fuel mode using producer gas. Diesel substitution of over 80% at high loads and 70–80% under normal load variations can easily be achieved. Spark ignition engines and solid oxide fuel cells can operate on 100% gasification gas. Mechanical energy from

1520-637: Is a storage facility with a small gasification plant as a backup. A former cattle depot and slaughterhouse has been turned into the Cattle Depot Artist Village . It contains artist studios and hosts exhibitions and art projects. The Kowloon City Ferry Pier and the Ma Tau Kok Public Pier are in Ma Tau Kok. From here, a regular ferry service (every 30 minutes during the day) operated by Sun Ferry goes to North Point . A bus terminus

1600-537: Is a technology that uses electrical power to produce hydrogen from water by electrolysis and uses the Sabatier reaction to combine hydrogen with carbon dioxide to produce methane. Methane can be produced by protonation of methyl lithium or a methyl Grignard reagent such as methylmagnesium chloride . It can also be made from anhydrous sodium acetate and dry sodium hydroxide , mixed and heated above 300 °C (with sodium carbonate as byproduct). In practice,

1680-553: Is abiotic. Abiotic means that methane is created from inorganic compounds, without biological activity, either through magmatic processes or via water-rock reactions that occur at low temperatures and pressures, like serpentinization . Most of Earth's methane is biogenic and is produced by methanogenesis , a form of anaerobic respiration only known to be conducted by some members of the domain Archaea . Methanogens occur in landfills and soils , ruminants (for example, cattle ),

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1760-421: 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 CO 2 capture as compared to conventional technologies. IGCC demonstration plants have been operating since the early 1970s and some of the plants constructed in

1840-589: Is currently widely used on industrial scales to generate electricity. Gasification can generate lower amounts of some pollutants as SO x and NO x than combustion. Energy has been produced at industrial scale via gasification since the early 19th century. Initially coal and peat were gasified to produce town gas for lighting and cooking, with the first public street lighting installed in Pall Mall, London on January 28, 1807, spreading shortly to supply commercial gas lighting to most industrialized cities until

1920-421: Is described by four bonding molecular orbitals (MOs) resulting from the overlap of the valence orbitals on C and H . The lowest-energy MO is the result of the overlap of the 2s orbital on carbon with the in-phase combination of the 1s orbitals on the four hydrogen atoms. Above this energy level is a triply degenerate set of MOs that involve overlap of the 2p orbitals on carbon with various linear combinations of

2000-428: Is easier to store than hydrogen due to its higher boiling point and density, as well as its lack of hydrogen embrittlement . The lower molecular weight of the exhaust also increases the fraction of the heat energy which is in the form of kinetic energy available for propulsion, increasing the specific impulse of the rocket. Compared to liquid hydrogen , the specific energy of methane is lower but this disadvantage

2080-410: Is increasing the amount of methane released from wetlands due to increased temperatures and altered rainfall patterns. This phenomenon is called wetland methane feedback . Rice cultivation generates as much as 12% of total global methane emissions due to the long-term flooding of rice fields. Ruminants, such as cattle, belch methane, accounting for about 22% of the U.S. annual methane emissions to

2160-643: Is located next to the piers. Ma Tau Kok Road runs in a west-northwest-east-southeast direction, connecting Ma Tau Chung and Ma Tau Kok. Ma Tau Kok is in Primary One Admission (POA) School Net 34. Within the school net are multiple aided schools (operated independently but funded with government money) and two government schools: Farm Road Government Primary School and Ma Tau Chung Government Primary School. 22°19′14″N 114°11′34″E  /  22.32061°N 114.19290°E  / 22.32061; 114.19290 This Kowloon -related article

2240-446: Is lower than that of any other hydrocarbon, but the ratio of the heat of combustion (891 kJ/mol) to the molecular mass (16.0 g/mol, of which 12.0 g/mol is carbon) shows that methane, being the simplest hydrocarbon, produces more heat per mass unit (55.7 kJ/g) than other complex hydrocarbons. In many areas with a dense enough population, methane is piped into homes and businesses for heating , cooking, and industrial uses. In this context it

2320-403: Is mixed with the fuel prior to gasification. Addition of a little limestone will usually suffice for the lowering the fusion temperatures. The fuel particles must be much smaller than for other types of gasifiers. This means the fuel must be pulverized, which requires somewhat more energy than for the other types of gasifiers. By far the most energy consumption related to entrained flow gasification

2400-460: Is mostly composed of methane, is used to produce hydrogen gas on an industrial scale. Steam methane reforming (SMR), or simply known as steam reforming, is the standard industrial method of producing commercial bulk hydrogen gas. More than 50 million metric tons are produced annually worldwide (2013), principally from the SMR of natural gas. Much of this hydrogen is used in petroleum refineries , in

2480-641: Is not the milling of the fuel but the production of oxygen used for the gasification. In a plasma gasifier a high-voltage current is fed to a torch, creating a high-temperature arc. The inorganic residue is retrieved as a glass like substance. There are a large number of different feedstock types for use in a gasifier, each with different characteristics, including size, shape, bulk density, moisture content, energy content, chemical composition, ash fusion characteristics, and homogeneity of all these properties. Coal and petroleum coke are used as primary feedstocks for many large gasification plants worldwide. Additionally,

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2560-512: Is obtained by the reaction of CO with water via the water-gas shift reaction : This reaction is mildly exothermic (produces heat, Δ H r = −41 kJ/mol). Methane is also subjected to free-radical chlorination in the production of chloromethanes, although methanol is a more typical precursor. Hydrogen can also be produced via the direct decomposition of methane, also known as methane pyrolysis , which, unlike steam reforming, produces no greenhouse gases (GHG). The heat needed for

2640-433: Is offset by methane's greater density and temperature range, allowing for smaller and lighter tankage for a given fuel mass. Liquid methane has a temperature range (91–112 K) nearly compatible with liquid oxygen (54–90 K). The fuel currently sees use in operational launch vehicles such as Zhuque-2 and Vulcan as well as in-development launchers such as Starship , Neutron , and Terran R . Natural gas , which

2720-430: Is somewhat lower as the gas must be cooled before it can be cleaned with existing technology. The high temperatures also mean that tar and methane are not present in the product gas; however the oxygen requirement is higher than for the other types of gasifiers. All entrained flow gasifiers remove the major part of the ash as a slag as the operating temperature is well above the ash fusion temperature. A smaller fraction of

2800-415: Is that syngas can be more efficient than direct combustion of the original feedstock material because it can be combusted at higher temperatures so that the thermodynamic upper limit to the efficiency defined by Carnot's rule is higher. Syngas may also be used as the hydrogen source in fuel cells, however the syngas produced by most gasification systems requires additional processing and reforming to remove

2880-503: Is then scattered back out. The familiar smell of natural gas as used in homes is achieved by the addition of an odorant , usually blends containing tert -butylthiol , as a safety measure. Methane has a boiling point of −161.5  °C at a pressure of one atmosphere . As a gas, it is flammable over a range of concentrations (5.4%–17%) in air at standard pressure . Solid methane exists in several modifications . Presently nine are known. Cooling methane at normal pressure results in

2960-430: Is to reach an acceptable (positive) gross electric efficiency. The high efficiency of converting syngas to electric power is counteracted by significant power consumption in the waste preprocessing, the consumption of large amounts of pure oxygen (which is often used as gasification agent), and gas cleaning. Another challenge becoming apparent when implementing the processes in real life is to obtain long service intervals in

3040-435: Is under the seafloor in the form of methane clathrates . When methane reaches the surface and the atmosphere , it is known as atmospheric methane . The Earth's atmospheric methane concentration has increased by about 160% since 1750, with the overwhelming percentage caused by human activity. It accounted for 20% of the total radiative forcing from all of the long-lived and globally mixed greenhouse gases , according to

3120-403: Is usually known as natural gas , which is considered to have an energy content of 39 megajoules per cubic meter, or 1,000 BTU per standard cubic foot . Liquefied natural gas (LNG) is predominantly methane ( CH 4 ) converted into liquid form for ease of storage or transport. Refined liquid methane as well as LNG is used as a rocket fuel , when combined with liquid oxygen , as in

3200-542: The Catalytica system , copper zeolites , and iron zeolites stabilizing the alpha-oxygen active site. One group of bacteria catalyze methane oxidation with nitrite as the oxidant in the absence of oxygen , giving rise to the so-called anaerobic oxidation of methane . Like other hydrocarbons , methane is an extremely weak acid . Its p K a in DMSO is estimated to be 56. It cannot be deprotonated in solution, but

3280-586: The Sabatier process . Methane is also a side product of the hydrogenation of carbon monoxide in the Fischer–Tropsch process , which is practiced on a large scale to produce longer-chain molecules than methane. An example of large-scale coal-to-methane gasification is the Great Plains Synfuels plant, started in 1984 in Beulah, North Dakota as a way to develop abundant local resources of low-grade lignite ,

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3360-477: The TQ-12 , BE-4 , Raptor , and YF-215 engines. Due to the similarities between methane and LNG such engines are commonly grouped together under the term methalox . As a liquid rocket propellant, a methane/ liquid oxygen combination offers the advantage over kerosene / liquid oxygen combination, or kerolox, of producing small exhaust molecules, reducing coking or deposition of soot on engine components. Methane

3440-601: The Xe than (literally, "coal car" in Vietnamese ) was a minibus that has been converted to run on coal instead of gasoline . This modification regained popularity in Vietnam during the subsidy period , when gasoline was in short supply. Xe than became much less common during the Đổi Mới period, when gasoline became widely accessible again. In a gasifier, the carbonaceous material undergoes several different processes: In essence,

3520-634: The conjugate base is known in forms such as methyllithium . A variety of positive ions derived from methane have been observed, mostly as unstable species in low-pressure gas mixtures. These include methenium or methyl cation CH + 3 , methane cation CH + 4 , and methanium or protonated methane CH + 5 . Some of these have been detected in outer space . Methanium can also be produced as diluted solutions from methane with superacids . Cations with higher charge, such as CH 2+ 6 and CH 3+ 7 , have been studied theoretically and conjectured to be stable. Despite

3600-518: The residence time of the reactive gases and organic materials, as well as heat and pressure. Catalysts are used in more sophisticated reactors to improve reaction rates, thus moving the system closer to the reaction equilibrium for a fixed residence time. Several types of gasifiers are currently available for commercial use: counter-current fixed bed, co-current fixed bed, fluidized bed , entrained flow, plasma, and free radical. A fixed bed of carbonaceous fuel (e.g. coal or biomass) through which

3680-497: The strength of its C–H bonds, there is intense interest in catalysts that facilitate C–H bond activation in methane (and other lower numbered alkanes ). Methane's heat of combustion is 55.5 MJ/kg. Combustion of methane is a multiple step reaction summarized as follows: Peters four-step chemistry is a systematically reduced four-step chemistry that explains the burning of methane. Given appropriate conditions, methane reacts with halogen radicals as follows: where X

3760-415: The "gasification agent" (steam, oxygen and/or air) flows in counter-current configuration. The ash is either removed in the dry condition or as a slag . The slagging gasifiers have a lower ratio of steam to carbon, achieving temperatures higher than the ash fusion temperature. The nature of the gasifier means that the fuel must have high mechanical strength and must ideally be non-caking so that it will form

3840-463: The 1990s are now entering commercial service. In small business and building applications, where the wood source is sustainable, 250–1000 kWe and new zero carbon biomass gasification plants have been installed in Europe that produce tar free syngas from wood and burn it in reciprocating engines connected to a generator with heat recovery. This type of plant is often referred to as a wood biomass CHP unit but

3920-500: The 1s orbitals on hydrogen. The resulting "three-over-one" bonding scheme is consistent with photoelectron spectroscopic measurements. Methane is an odorless, colourless and transparent gas. It does absorb visible light, especially at the red end of the spectrum, due to overtone bands , but the effect is only noticeable if the light path is very long. This is what gives Uranus and Neptune their blue or bluish-green colors, as light passes through their atmospheres containing methane and

4000-430: The 2021 Intergovernmental Panel on Climate Change report. Strong, rapid and sustained reductions in methane emissions could limit near-term warming and improve air quality by reducing global surface ozone. Methane has also been detected on other planets, including Mars , which has implications for astrobiology research. Methane is a tetrahedral molecule with four equivalent C–H bonds . Its electronic structure

4080-416: The Earth's atmosphere methane is transparent to visible light but absorbs infrared radiation, acting as a greenhouse gas . Methane is an organic compound , and among the simplest of organic compounds. Methane is also a hydrocarbon . Naturally occurring methane is found both below ground and under the seafloor and is formed by both geological and biological processes. The largest reservoir of methane

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4160-977: The Hurlburt Field Florida Special Operations Command Air Force base. The plant, which cost $ 7.4 million to construct, was closed and sold at a government liquidation auction in May 2013. The opening bid was $ 25. The winning bid was sealed. In December 2022, the Sierra BioFuels Plant opened in Reno, Nevada, converting landfill waste to synthetic crude oil. Syngas can be used for heat production and for generation of mechanical and electrical power. Like other gaseous fuels, producer gas gives greater control over power levels when compared to solid fuels, leading to more efficient and cleaner operation. Syngas can also be used for further processing to liquid fuels or chemicals. Gasifiers offer

4240-478: The amount of oxygen and/or steam present in the reaction. The resulting gas mixture is called syngas (from synthesis gas) or producer gas and is itself a fuel due to the flammability of the H 2 and CO of which the gas is largely composed. Power can be derived from the subsequent combustion of the resultant gas, and is considered to be a source of renewable energy if the gasified compounds were obtained from biomass feedstock. An advantage of gasification

4320-572: The ash is produced either as a very fine dry fly ash or as a black colored fly ash slurry. Some fuels, in particular certain types of biomasses, can form slag that is corrosive for ceramic inner walls that serve to protect the gasifier outer wall. However some entrained flow type of gasifiers do not possess a ceramic inner wall but have an inner water or steam cooled wall covered with partially solidified slag. These types of gasifiers do not suffer from corrosive slags. Some fuels have ashes with very high ash fusion temperatures. In this case mostly limestone

4400-419: The ash. In some gasification processes (slagging gasification) this ash has the form of a glassy solid with low leaching properties, but the net power production in slagging gasification is low (sometimes negative) and costs are higher. Regardless of the final fuel form, gasification itself and subsequent processing neither directly emits nor traps greenhouse gases such as carbon dioxide. Power consumption in

4480-426: The atmosphere. One study reported that the livestock sector in general (primarily cattle, chickens, and pigs) produces 37% of all human-induced methane. A 2013 study estimated that livestock accounted for 44% of human-induced methane and about 15% of human-induced greenhouse gas emissions. Many efforts are underway to reduce livestock methane production, such as medical treatments and dietary adjustments, and to trap

4560-679: The breakup of organic matter at elevated temperatures and pressures in deep sedimentary strata . Most methane in sedimentary basins is thermogenic; therefore, thermogenic methane is the most important source of natural gas. Thermogenic methane components are typically considered to be relic (from an earlier time). Generally, formation of thermogenic methane (at depth) can occur through organic matter breakup, or organic synthesis. Both ways can involve microorganisms ( methanogenesis ), but may also occur inorganically. The processes involved can also consume methane, with and without microorganisms. The more important source of methane at depth (crystalline bedrock)

4640-608: The chosen catalyst. Dozens of catalysts have been tested, including unsupported and supported metal catalysts, carbonaceous and metal-carbon catalysts. The reaction is moderately endothermic as shown in the reaction equation below. As a refrigerant , methane has the ASHRAE designation R-50 . Methane can be generated through geological, biological or industrial routes. The two main routes for geological methane generation are (i) organic (thermally generated, or thermogenic) and (ii) inorganic ( abiotic ). Thermogenic methane occurs due to

4720-560: The claims of project proponents did not withstand public and governmental scrutiny of key claims," according to the Global Alliance for Incinerator Alternatives. One facility which operated from 2009–2011 in Ottawa had 29 "emissions incidents" and 13 "spills" over those three years. It was also only able to operate roughly 25% of the time. Several waste gasification processes have been proposed, but few have yet been built and tested, and only

4800-588: The cold gas, the gas at ambient temperature is lighter than air. Gas pipelines distribute large amounts of natural gas, of which methane is the principal component. Methane is used as a fuel for ovens, homes, water heaters, kilns, automobiles, turbines, etc. As the major constituent of natural gas , methane is important for electricity generation by burning it as a fuel in a gas turbine or steam generator . Compared to other hydrocarbon fuels , methane produces less carbon dioxide for each unit of heat released. At about 891 kJ/mol, methane's heat of combustion

4880-810: The contaminants and other gases such as CO and CO 2 to be suitable for low-temperature fuel cell use, but high-temperature solid oxide fuel cells are capable of directly accepting mixtures of H 2 , CO, CO 2 , steam, and methane. Syngas is most commonly burned directly in gas engines , used to produce methanol and hydrogen, or converted via the Fischer–Tropsch process into synthetic fuel . For some materials gasification can be an alternative to landfilling and incineration , resulting in lowered emissions of atmospheric pollutants such as methane and particulates . Some gasification processes aim at refining out corrosive ash elements such as chloride and potassium , allowing clean gas production from otherwise problematic feedstock material. Gasification of fossil fuels

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4960-424: The counter-current type, but the gasification agent gas flows in co-current configuration with the fuel (downwards, hence the name "down draft gasifier"). Heat needs to be added to the upper part of the bed, either by combusting small amounts of the fuel or from external heat sources. The produced gas leaves the gasifier at a high temperature, and most of this heat is often transferred to the gasification agent added in

5040-472: The end of the 19th century when it was replaced with electrical lighting. Gasification and syngas continued to be used in blast furnaces and more significantly in the production of synthetic chemicals where it has been in use since the 1920s. The thousands of sites left toxic residue. Some sites have been remediated, while others are still polluted. During both world wars , especially the World War II ,

5120-649: The engines may be used for e.g. driving water pumps for irrigation or for coupling with an alternator for electrical power generation. While small scale gasifiers have existed for well over 100 years, there have been few sources to obtain a ready-to-use machine. Small scale devices are typically DIY projects. However, currently in the United States, several companies offer gasifiers to operate small engines. In principle, gasification can proceed from just about any organic material, including biomass and plastic waste . The resulting syngas can be combusted. Alternatively, if

5200-491: The formation of methane I. This substance crystallizes in the cubic system ( space group Fm 3 m). The positions of the hydrogen atoms are not fixed in methane I, i.e. methane molecules may rotate freely. Therefore, it is a plastic crystal . The primary chemical reactions of methane are combustion , steam reforming to syngas , and halogenation . In general, methane reactions are difficult to control. Partial oxidation of methane to methanol ( C H 3 O H ),

5280-551: The fuel must be highly reactive; low-grade coals are particularly suitable. The agglomerating gasifiers have slightly higher temperatures, and are suitable for higher rank coals. Fuel throughput is higher than for the fixed bed, but not as high as for the entrained flow gasifier. The conversion efficiency can be rather low due to elutriation of carbonaceous material. Recycle or subsequent combustion of solids can be used to increase conversion. Fluidized bed gasifiers are most useful for fuels that form highly corrosive ash that would damage

5360-434: The gas to use its combustion energy. Most of the subseafloor is anoxic because oxygen is removed by aerobic microorganisms within the first few centimeters of the sediment . Below the oxygen-replete seafloor, methanogens produce methane that is either used by other organisms or becomes trapped in gas hydrates . These other organisms that utilize methane for energy are known as methanotrophs ('methane-eating'), and are

5440-444: The gasification and syngas conversion processes may be significant though, and may indirectly cause CO 2 emissions; in slagging and plasma gasification, the electricity consumption may even exceed any power production from the syngas. Combustion of syngas or derived fuels emits exactly the same amount of carbon dioxide as would have been emitted from direct combustion of the initial fuel. Biomass gasification and combustion could play

5520-449: The guts of termites, and the anoxic sediments below the seafloor and the bottom of lakes. This multistep process is used by these microorganisms for energy. The net reaction of methanogenesis is: The final step in the process is catalyzed by the enzyme methyl coenzyme M reductase (MCR). Wetlands are the largest natural sources of methane to the atmosphere, accounting for approximately 20 - 30% of atmospheric methane. Climate change

5600-401: The halogen-to-methane ratio. This reaction is commonly used with chlorine to produce dichloromethane and chloroform via chloromethane . Carbon tetrachloride can be made with excess chlorine. Methane may be transported as a refrigerated liquid (liquefied natural gas, or LNG ). While leaks from a refrigerated liquid container are initially heavier than air due to the increased density of

5680-482: The main reason why little methane generated at depth reaches the sea surface. Consortia of Archaea and Bacteria have been found to oxidize methane via anaerobic oxidation of methane (AOM); the organisms responsible for this are anaerobic methanotrophic Archaea (ANME) and sulfate-reducing bacteria (SRB). Given its cheap abundance in natural gas, there is little incentive to produce methane industrially. Methane can be produced by hydrogenating carbon dioxide through

5760-451: The need for fuel produced by gasification reemerged due to the shortage of petroleum. Wood gas generators , called Gasogene or Gazogène, were used to power motor vehicles in Europe . By 1945 there were trucks, buses and agricultural machines that were powered by gasification. It is estimated that there were close to 9,000,000 vehicles running on producer gas all over the world. Another example,

5840-422: The plants, so that it is not necessary to close down the plant every few months for cleaning the reactor. Environmental advocates have called gasification "incineration in disguise" and argue that the technology is still dangerous to air quality and public health. "Since 2003 numerous proposals for waste treatment facilities hoping to use... gasification technologies failed to receive final approval to operate when

5920-457: The production of chemicals and in food processing. Very large quantities of hydrogen are used in the industrial synthesis of ammonia . At high temperatures (700–1100 °C) and in the presence of a metal -based catalyst ( nickel ), steam reacts with methane to yield a mixture of CO and H 2 , known as "water gas" or " syngas ": This reaction is strongly endothermic (consumes heat, Δ H r = 206 kJ/mol). Additional hydrogen

6000-469: The reaction can also be GHG emission free, e.g. from concentrated sunlight, renewable electricity, or burning some of the produced hydrogen. If the methane is from biogas then the process can be a carbon sink . Temperatures in excess of 1200 °C are required to break the bonds of methane to produce hydrogen gas and solid carbon. However, through the use of a suitable catalyst the reaction temperature can be reduced to between 550-900 °C depending on

6080-444: The reactor. In the gasification of fine, undensified biomass such as rice hulls , it is necessary to blow air into the reactor by means of a fan. This creates very high gasification temperature, as high as 1000 C. Above the gasification zone, a bed of fine and hot char is formed, and as the gas is blow forced through this bed, most complex hydrocarbons are broken down into simple components of hydrogen and carbon monoxide. Similar to

6160-422: The syngas is clean enough, it may be used for power production in gas engines, gas turbines or even fuel cells, or converted efficiently to dimethyl ether (DME) by methanol dehydration, methane via the Sabatier reaction , or diesel-like synthetic fuel via the Fischer–Tropsch process . In many gasification processes most of the inorganic components of the input material, such as metals and minerals, are retained in

6240-406: The top of the bed, resulting in an energy efficiency on level with the counter-current type. Since all tars must pass through a hot bed of char in this configuration, tar levels are much lower than the counter-current type. The fuel is fluidized in oxygen and steam or air. The ash is removed dry or as heavy agglomerates that defluidize. The temperatures are relatively low in dry ash gasifiers, so

6320-597: The walls of slagging gasifiers. Biomass fuels generally contain high levels of corrosive ash. Fluidized bed gasifiers uses inert bed material at a fluidized state which enhance the heat and biomass distribution inside a gasifier. At a fluidized state, the superficial fluid velocity is greater than the minimum fluidization velocity required to lift the bed material against the weight of the bed. Fluidized bed gasifiers are divided into Bubbling Fluidized Bed (BFB), Circulating Fluidized Bed (CFB) and Dual Fluidized Bed (DFB) gasifiers. A dry pulverized solid, an atomized liquid fuel or

6400-576: Was designed to demonstrate gasification of specific non-MSW waste streams using liquid metal gasification . This facility came after widespread public opposition shelved plans for a similar plant in Attleboro, Massachusetts . Today Ze-gen appears to be defunct, and the company website was taken down in 2014. Also in the US, in 2011 a plasma system delivered by PyroGenesis Canada Inc. was tested to gasify municipal solid waste, hazardous waste and biomedical waste at

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