Coal gasification is the process of producing syngas-a mixture consisting mainly of carbon monoxide (CO), hydrogen (H 2 ), carbon dioxide (CO 2 ), methane (CH 4 ), and water vapor (H 2 O) -from coal and water, air and/or oxygen.
Historically, gasification coal uses preliminary technology to produce coal gas (also known as "city gas"), which is a flammable gas traditionally used for city lighting and heating prior to the emergence of industrial-scale natural gas production.
In current practice, large-scale examples of coal gasification are primarily for power generation, as in combined combined gasification cycle plants, for the production of chemical raw materials, or for the production of synthetic natural gas. Hydrogen derived from coal gasification can be used for various purposes such as making ammonia, turning on the hydrogen economy, or increasing fossil fuels.
Alternatively, coal-derived syngas can be converted into transportation fuels such as gasoline and diesel by additional treatment through the Fischer-Tropsch process or into methanol which itself can be used as a transportation fuel or fuel additive, or which can be converted to gasoline by methanol process to gasoline. Methane from coal gasification can be converted into LNG for use as fuel in the transportation sector.
Video Coal gasification
Histori
In the past, coal was converted to make coal gas, which was channeled to customers to be burned for lighting, heating, and cooking. High oil and natural gas prices led to increased interest in "BTU Conversion" technologies such as gasification, methanation and liquefaction. The Synthetic Fuels Corporation is a US government funded company founded in 1980 to create a market for imported fossil fuel alternatives (such as coal gasification). The corporation was suspended in 1985.
Initial history of coal gas production with carbonization
Flemish scientist Jan Baptista van Helmont used the name "gas" in his book Origin of Medicine 1609 to describe his discovery of a "wild spirit" escaping heated wood and stone embers, and which is "a little different from the chaos of the ancients". A similar experiment was conducted in 1681 by Johann Becker of Munich and in 1684 by John Clayton of Wigan, England. The latter calls it "Coal Spirit". William Murdoch (later known as Murdock) invented new ways to create, refine, and store gas. Among other things, he illuminated his home in Redruth and his cottage in Soho, Birmingham in 1792, the entrance to the Manchester Police Commissioner's building in 1797, outside the Boulton and Watt factory in Birmingham, and a large cotton mill in Salford, Lancashire in 1805.
Professor Jan Pieter Minckeleers lit his lecture room at Louvain University in 1783 and Lord Dundonald lit his home in Culross, Scotland, in 1787, a gas carried in closed vessels of local tarworks. In France, Philippe le Bon patented a gas fire in 1799 and showed street lighting in 1801. Other demonstrations took place in France and in the United States, but it was generally recognized that the first commercial gas works were built by London and Westminster Gas. Light and Coke Company at Great Peter Street in 1812 installed a wooden pipe to illuminate the Westminster Bridge with gas lamps on New Year's Eve in 1813. In 1816, Rembrandt Peale and four others set up the Cahaya Gas Company of Baltimore, the first gas company produced in America.. In 1821, natural gas was used commercially in Fredonia, New York. The first German gas work was built in Hannover in 1825 and by 1870 there were 340 gas jobs in Germany that made city gas from coal, wood, peat and other materials.
Working conditions at Gas Light and Coke Company Horseferry Road Works, London, in the 1830s were described by a French visitor Flora Tristan in his book Promenades Dans Londres:
Two rows of stoves on each side are lit; the effect is no different from the Vulcan depictions, except that the Cyclops is moved by a divine spark, whereas the dark-horned British slaves are unhappy, silent, and paralyzed.... The mandur told me that the buffer was chosen from among the strongest, all became consumptive after seven or eight years of hard work and died of lung consumption. It explains the sadness and apathy in the face and every movement of the poor man.
The first general gas pipe supply was for 13 gas lamps, each with three glass balls along the Pall Mall, London in 1807. The credit for this was given to inventor and entrepreneur Fredrick Winsor and plumber Thomas Sugg, who made and put a pipe- pipe. Digging roads for plumbing required legislation and this delayed the development of street lighting and gas for household use. Meanwhile, William Murdoch and his student Samuel Clegg installed gas lights in factories and workplaces, did not encounter such obstacles.
Initial history of coal gas production with gasification
In the 1850s every small and medium-sized city and city had a gas plant to provide street lighting. Subscribed customers can also have pipelines to their homes. In this era, gas lighting became acceptable. Gaslight drips into the middle class and then comes the gas stove and stove.
The year 1860 was the golden age of coal gas development. Scientists like KekulÃÆ'Â © and Perkin solve the secrets of organic chemistry to reveal how gases are made and their composition. From this came the better gas factories and Perkin purple dyes, like Mauveine. In the 1850s, the manufacturing process of gas producers and gas water from coke was developed. Unenriched water gas can be described as blue water gas (BWG).
Gas Mond, developed in the 1850s by Ludwig Mond, is a gas producer made of coal instead of charcoal. It contains ammonia and coal tar and is processed to recover this precious compound.
Blue water gas (BWG) burns with non-glowing flames that make it unsuitable for lighting purposes. The Carburetted Water Gas (CWG), developed in the 1860s, is an enriched BWG with gas obtained by spraying oil into a heat retort. It has higher calorific value and burns with luminous flame.
The gas water process of the carburetor was enhanced by Thaddeus S. C. Lowe in 1875. The gas oil was repaired to the BWG via thermocracking in the carburetor and superheater of the CWG generator. CWG was the dominant technology in the US from the 1880s to the 1950s, replacing coal gasification. CWG has a CV of 20 MJ/mÃ,³ i.e. slightly more than half of natural gas.
Development of the coal gas industry in the UK
The appearance of incandescent gas lamps in factories, homes and on the streets, replacing oil lamps and candles with clear light, almost matching the colors of daylight, turning into daylight for many people - makes night shift work possible in industries where light all that matters - in spinning, weaving and making clothes etc. The social significance of these changes is difficult for generations raised with lighting after dark is available with one touch to appreciate. Not only industrial production is accelerated, but roads are made safe, facilitated social relationships and reading and writing become wider. Gas work is being built in almost every city, the main streets lit up brightly and gas flowed in the streets to the majority of urban households. The invention of the gas meter and the pre-payment meter in the late 1880s played an important role in selling city gas to domestic and commercial customers.
Great workforce education and training, attempts to standardize manufacturing and commercial practices and moderation of commercial competition between supplier companies led to the establishment of a gas managers association, first in Scotland in 1861. A British Gas Manager Association was formed in 1863 in Manchester and this, turbulent, became the basis of the Institute of Gas Engineers (IGE). In 1903, the reconstructed Civil Civil Institute (ICE) began a course for gas-making students at City and Guilds of London Institute. IGE was awarded the Royal Charter in 1929. The University was slow to respond to industry needs and it was not until 1908 that the first Professor of Gas Coal and Fuel Industries was established at the University of Leeds. In 1926, Light and Coke Gas Company opened Watson House adjacent to Nine Elms Gas Works. Initially, this was a scientific laboratory. Then it includes a center to train apprentices but its main contribution to industry is its gas equipment testing facility, which is available to all industries, including gas appliance manufacturers. Using this facility, the industry is established not only for safety but also performance standards for the manufacture of gas appliances and servicing in customers' homes and commercial premises.
During World War I, by-products of industrial gases, phenols, toluene and ammonia and sulfur compounds were valuable materials for explosives. A lot of coal for gas work is delivered by sea and vulnerable to enemy attacks. The gas industry is a great employer, especially pre-war men. But the arrival of typewriters and female typists makes other important social changes, unlike the work of women in the war-time industry, to have long-term effects.
The inter-war years are characterized by the development of a continuous vertical retort that replaces many of the batches feeding the horizontal retort. There is an increase in storage, especially the waterless gas holder, and the distribution with the emergence of 2-4 inch steel pipes to drain the gas up to 50 psi (340 kPa) as the main supplier compared to traditional cast iron pipes working on the average of the water meter 2 -3 inches (500-750 Pa). Benzole as a vehicle fuel and coal tar as the main raw material for the emerging organic chemical industry provides the gas industry with large revenues. Petroleum replaces coal tar as the main raw material of the organic chemicals industry after World War II and the loss of this market contributes to the economic problems of the gas industry after the war.
A wide range of equipment and uses for gas developed over the years. Gas fires, gas stoves, refrigerators, washing machines, hand irons, pokers for lighting coal fires, hot gas baths, remote gas-controlled gas clusters, gas engines of various types and, in later years, warm air gases and hot-water heating and air conditioning centers, all of which contribute greatly to improving the quality of life in cities and towns around the world. The evolution of electric illumination that is available from the general supply puts out gas lights, except where color matching is practiced like in a men's clothing store.
Maps Coal gasification
Process
During the gasification process, coal is blown with oxygen and steam (water vapor) while it is being heated (and in some cases pressure). If the coal is heated by an external heat source, this process is called "allothermal", while the "autothermal" process assumes heating of coal through the exothermic chemical reactions occurring within the gasifier itself. It is imperative that the oxidizing agent be inadequate for the full oxidation (burning) of the fuel. During the reaction, oxygen and water molecules oxidize coal and produce a mixture of carbon dioxide gas (CO 2 ), carbon monoxide (CO), water vapor (H 2 O), and molecular hydrogen (H 2 ). (Some by-products such as tar, phenol, etc. Also may be the final product, depending on the specific gasification technology used.) This process has been done in-situ in natural coal seams (referred to as underground coal gasification) and in coal refineries. The desired end product is usually syngas (ie, a combination of H 2 CO), but the resulting coal gas can also be further refined to produce an additional amount of H 2 :
- 3C (that is, coal) O 2 H 2 O -> H 2 3CO
If refiners want to produce alkanes (ie hydrocarbons present in natural gas, gasoline, and diesel), coal gas is collected in this state and fed to the Fischer-Tropsch reactor. If, however, hydrogen is the desired end product, coal gas (mainly CO product) undergoes a gas shift reaction in which more hydrogen is generated by an additional reaction with moisture:
- CO H 2 O -> CO 2 H 2
Although other technologies for coal gasification currently exist, all employ, in general, the same chemical processes. For low grade coal (ie, "coking coal") containing large amounts of water, there is a technology where no steam is needed during the reaction, with coal (carbon) and oxygen being the only reactants. In addition, some coal gasification technologies do not require high pressure. Some use coal powder as fuel while others work with relatively large coal fractions. The gasification technology also varies in the way the blowing is supplied.
"Direct blow" assumes that coal and oxidators are supplied to each other from opposite sides of the reactor ducts. In this case the oxidator passes the coke and (more likely) the ash to the reaction zone where it interacts with the coal. The resulting hot gas then skips the fresh fuel and heats it while absorbing some of the thermal destruction products of fuel, such as tar and phenol. Thus, the gas requires significant purification before use in the Fischer-Tropsch reaction. Product refinement is highly toxic and requires special facilities for its utilization. As a result, factories that utilize the technology described must be enormous to economically efficient. One plant called SASOL is located in the Republic of South Africa (RSA). It was built because the embargo applied to the state prevented it from importing oil and natural gas. RSA is rich in Bituminous and Anthracite coal and is able to regulate the use of the famous high-pressure "Lurgi" gasification process developed in Germany in the first half of the 20th century.
"Reversed blowing" (compared to the previously described type found first) assumes that coal and oxidant are supplied from the same side of the reactor. In this case there is no chemical interaction between coal and oxidators before the reaction zone. The gases generated in the reaction zone pass through the gasification solid products (coke and ash), and CO 2 and H 2 O contained in the gas are also chemically returned to CO and H < sub> 2 . Compared to "direct blowing" technology, there are no toxic byproducts present in the gas: which are disabled in the reaction zone. This type of gasification has been developed in the first half of the 20th century, along with "direct blowing", but the level of gas production in it is much lower than in "direct blowing" and there is no further effort to develop a "reversal process" 1980s when a Soviet research facility KATEKNIIUgol '(Institute of R & D to develop the Kansk-Achinsk coal field) initiated R & amp; D to produce the technology now known as the "TERMOKOKS-S" process. The reason for reviving interest for this type of gasification process is that it is ecologically clean and capable of producing two types of useful products (simultaneously or separately): gas (both flammable or syngas) and medium temperature coke. The former can be used as fuel for gas boilers and diesel generators or as syngas to produce gasoline, etc., the latter - as fuel technology in metallurgy, as a chemical absorber or as a feedstock for household fuel briquettes. The product gas combustion in the gas boiler is ecologically cleaner than the initial coal burning. Thus, factories that utilize gasification technology with "reversed reversal" are able to produce two relatively valuable products that are relatively zero because the latter is covered by competitive market prices from others. When the Soviet Union and its KATEKNIIgol ceased to exist, this technology was adopted by individual scientists who originally developed it and is now being researched further in Russia and distributed commercially to the rest of the world. The industrial plants that utilize them are now known to function in Ulaan-Baatar (Mongolia) and Krasnoyarsk (Russia).
Pressurized air flow gasification technology created through joint development between Wison Group and Shell (Hybrid). For example: Hybrid is a sophisticated powdered coal gasification technology, this technology combined with the existing advantages of the Shell SCGP waste heat boiler, encompassing more than just a carrier system, a coal pressurized coal gasification setting, a lateral type of jet burning wall, and intermittent discharge has been fully validated in existing SCGP mills such as mature and reliable technology, at the same time, it eliminates the existing complication process and in the easily failing syngas cooler filters (fly waste) and combines gasification technology which exists today which is widely used in the synthetic gas quench process. Not only does it retain the original SCGP Shell heat waste heaters from the coal characteristics of strong adaptability, and the ability to improve easily, but also absorb the advantages of existing quench technology.
Underground coal gasification
Underground coal gasification is an industrial gasification process, carried out on non-mining coal layers using the injection of a gas-oxidizing agent, usually oxygen or air, and carrying the product gas produced to the surface through a well-drilled production well from the surface. Gas products can be used as chemical raw materials or as fuel for power generation. This technique can be applied to uneconomical resources to extract and also offers alternatives to conventional coal mining methods for some resources. Compared to traditional coal mining and gasification, UCG has fewer environmental and social impacts, although some concerns including potential aquifer contamination are known.
Carbon capture technology
Carbon collection, utilization, and sequestration (or storage) are increasingly being used in modern coal gasification projects to address greenhouse gas emissions associated with the use of coal and carbon fuels. In this case, gasification has a significant advantage over conventional coal combustion, where CO 2 generated from combustion is greatly diluted by nitrogen and residual oxygen in the exhaust of near-ambient pressure combustion, making it relatively difficult, energy -intensive, and expensive to capture CO 2 (this is known as "post-burning" CO 2 capture).
In gasification, on the other hand, oxygen is usually supplied to gasifiers and only enough fuel is burned to provide heat for the remaining gasification; In addition, gasification is often performed at high pressures. The resulting syngas is usually at a higher pressure and is not diluted by nitrogen, thus allowing the removal of CO 2 easier, more efficient, and cheaper. Integrated gasification and gasification combine the unique ability of the cycle to easily remove CO 2 from syngas before its combustion in a gas turbine (called CO-substitute capture) or its use in materials burning or chemical synthesis is one of its significant advantages over conventional coal utilization systems.
CO 2 capture technology options
All coal-based gasification conversion processes require the release of hydrogen sulphide (H 2 S; acid gas) from syngas as part of the overall plant configuration. The acid gas removal process (AGR) used for gasification design is a chemical solvent system (for example, an amine gas processing system based on MDEA, for example) or a physical solvent system (eg, Rectisol or Selexol). The choice of process depends largely on the requirements and cost of cleaning syngas. Conventional chemical/physical AGR processes using MDEA, Rectisol or Selexol are commercially proven technologies and can be designed for selective removal of CO 2 in addition to H 2 S from syngas flow. For significant CO capture of <2 from a gasification plant (eg, & Gt; 80%) CO in syngas must first be converted to CO 2 and hydrogen (H 2 ) through a water-gas-shift (WGS) transfer step from the AGR plant.
For gasification applications, or IGCC, plant modifications required to increase the capability to capture CO 2 are minimal. Syngas produced by gasifiers needs to be treated through various processes to remove the impurities already present in the gas stream, so all that is needed to remove CO 2 is to add the required equipment, absorber and regenerator, to this process cart. In combustion applications, modifications should be made to the exhaust stack and because the lower CO concentration 2 exists in the exhaust, a volume much larger than the total gas requires processing, requiring larger and more expensive equipment.
IGCC-based project in the United States with CO 2 capture and use/storage
The Mississippi Power Kemper Project is in the final stages of construction. It will be a lignite-fuel IGCC plant, generating 524 MW of net power from syngas, while capturing more than 65% of CO 2 generated using Selexol process. Technology at Kemper facility, Transport-Integrated Gasification (TRIG), developed and licensed by KBR. CO 2 will be sent via pipeline to a thinning oil field in Mississippi to improve oil recovery operations.
Hydrogen Energy California (HECA) will be a 300 MW IGCC polygeneration plant, coal and petroleum coke-fueled (producing hydrogen for power generation and fertilizer manufacture). Ninety percent of the produced CO 2 will be captured (using Rectisol) and transported to Elk Hills Oil Field for the EOR, enabling the recovery of an additional 5 million barrels of domestic oil per year.
The KTT Texas Clean Energy Project (TCEP) will be a 400MW fuel-fired generating/fuel-generating project (also producing urea fertilizer), which will capture 90% of CO 2 in pre-burning capture using the Rectisol process. CO 2 which is not used in the manufacture of fertilizer will be used to improve oil recovery in Permian Basin of West Texas.
Plants such as the Texas Clean Energy Project that use carbon capture and storage have been touted as partial, or interim, solutions to climate change issues if they can be made economically via improved design and mass production. There is opposition by utility regulators and taxpayers due to increased costs and by some environmental activists like Bill McKibben who see the continued use of fossil fuels as counterproductive.
By-products
The by-products of coal gas manufacture include coke, coal tar, sulfur and ammonia; all useful products. Dyes, medicines, including sulfa, saccharin and many organic compounds are therefore derived from coal gas.
Cokes are used as a smokeless fuel and for gas and water gas producers. Coal Tar is subject to fractional distillation to recover various products, including
- tar, for path
- benzole, motor fuel
- creosote, wood preservative
- phenol, used in the manufacture of plastics
- cresols, disinfectants
Sulfur is used in the manufacture of sulfuric acid and ammonia is used in the manufacture of fertilizers.
Commercialization
According to the Gasification and Syngas Technologies Council, a trade association, globally there are 272 operating gasification plants with 686 gasifiers and 74 plants with 238 gasifiers under construction. Most of them use coal as raw material.
In 2017 large-scale expansion of the coal gasification industry occurs only in China where local governments and energy companies are promoting industry for jobs and markets for coal. The central government is aware of the conflict with environmental goals. For most factories located in remote coal-rich areas. In addition to generating a lot of carbon dioxide, plants use a lot of water in areas where water is scarce.
Environmental impact
Environmental impact of the coal gas industry produced
From the original development to the widespread adoption of natural gas, more than 50,000 gas plants produced exist in the United States alone. The gas-making process usually produces a number of byproducts that contaminate soil and ground water in and around the plant, so many former municipal gas factories are a serious environmental problem, and the cost of cleaning and remediation is often high. Prepared gas plants (MGPs) are usually located near or adjacent to waterways used for transporting coal and for disposal of contaminated wastewater with tar, ammonia and/or drops, and tera waste and water emulsions.
In the early days of MGP operations, coal tar is considered waste and is often discharged into the environment in and around the plant site. While the use for coal tar was developed at the end of the 19th century, the market for tar varies and plants that can not sell tar at any given time can save tar for future use, try to burn it as fuel for boilers, or dispose of tar as waste. Generally, the waste layer is disposed in the old gas holder, adit or even the mine shaft (if any). Over time, the waste layer is degraded with phenol, benzene (and other mono-aromatics - BTEX) and aromatic polycyclic hydrocarbons released as pollutants that can pass to the surrounding environment. Other wastes include "blue billy", which is a ferroferricyanide compound - the blue color of Prussia blue, which is commercially used as a dye. Blue billy is usually a granular material and sometimes sold locally with a "guaranteed weed-free" line of straps. The presence of blue billy can provide gas work that removes almond or bitter walnuts or the smell of marzipan associated with cyanide gas.
The shift to the CWG process initially results in reduced output of tar gas water compared to coal tar volume. The emergence of cars reduces the availability of naphtha for carburetor oil, because the fraction is desirable as motor fuel. MGPs shifting to heavier oils often experience problems with the production of water-based emulsions, which are difficult, time-consuming, and expensive to destroy. (The cause of the water-emulsion gel change is complex and is associated with several factors, including free carbon in carburizing oil and bituminous coal substitution as non-coking feedstock.) Production of large volumes of quick-aqueous emulsified emissions filled with storage capacity available at MGP and factory management often discard emulsions in the pits, from which they may or may not then be reclaimed. Even if the emulsion is reclaimed, the environmental damage from placement of t in the striped pit remains. The stockpiling of emulsions (and other terrious residues such as tar sludge, tank bottom, and off-spec tar) into the soil and waters surrounding MGP is a significant factor in the pollution found in FMGP today.
Generally associated with former gas plants produced (known as "FMGPs" in environmental remediation) are contaminants including:
- BTEX
- Spread from coal/gas tar deposits
- Carburetor oil leak/light oil
- Leakage from the drop pot, which collects the condensed hydrocarbons from the gas
- Coal tar waste/sludge
- Usually found in gas containers and pouring ponds.
- Coal tar sludge has no selling value and is always discarded.
- Volatile organic compounds
- Polycyclic aromatic hydrocarbons (PAHs)
- Comes in coal tar, gas tar, and pitch at significant concentrations.
- Heavy metals
- Lead solder for main gas, lead pipe, coal ash.
- Cyanide
- Cleaning garbage has a large number of complex ferrocyanides in it.
- Lampblack
- Only found where crude oil is used as gasification raw material.
- Tar emulsion
Coal tar and tar mud are often more dense than water and are in the environment as non-aqueous solid fluid phase.
In the UK, used gasworks have generally been developed for residential and other uses (including the Millennium Dome), seen as a land that can be developed primarily within the city limits. Situations like this now lead to problems related to planning and the Reaminated Land Regime and were recently debated in the House of Commons.
Environmental impact of modern coal gasification
The coal gasification process requires pollution control and measures to reduce pollutant emissions. Pollutants or emissions of concern in the context of coal gasification include mainly:
- Ash & amp; slag
Non-slagging gasifiers produce dry ash similar to those generated by conventional coal combustion, which can be the environmental responsibility if the ash (usually heavy metals) is leachable or caustic, and if the ash should be stored in a pool of ash. Slagging gasifiers, used in many large coal gasification applications worldwide, have a considerable advantage in the ash component that converges into a glass slag, capture traces of heavy metals in a non-removable glass matrix, thus making the material non-toxic. This harmless slag has many useful benefits such as aggregates in concrete, aggregates in asphalt for road construction, sand in abrasive blasting, roof grinding, etc.
- Carbon dioxide (CO 2 )
CO 2 is very important in global climate change.
- Mercury
- Arsenic
- Particulate material (PM)
Ash is formed in the gasification of inorganic impurities in coal. Some of these impurities react to form microscopic solids that can be delayed in syngas produced by gasification.
- Sulfur dioxide (SO 2 )
Usually coal contains 0.2 to 5 percent sulfur of dry weight, which converts to H 2 S and COS in gasifiers due to high temperatures and low oxygen levels. This "acid gas" is removed from the syngas generated by gasifiers by acid gas-busting equipment before syngas is burned in a gas turbine to generate electricity, or before being used in fuel synthesis.
- Nitrogen oxide (NOT x )
(NOT x ) refers to nitric oxide (NO) and nitrogen dioxide (NOT 2 ). Coal usually contains between 0.5 and 3 percent nitrogen based on dry weight, which mostly turns into harmless nitrogen gas. Small levels of ammonia and hydrogen cyanide are produced, and should be removed during the syngas cooling process. In the case of electricity generation, NO x can also be formed downstream by burning syngas in the turbine.
See also
- History of produced gas
- The Fischer-Tropsch process
- Georgetown Coal Gasification Plant
- Sasol
- Secunda CTL
- Edwardsport Power Station
- The Kemper Project
References
This article incorporates public domain material from websites or documents from the US Department of Energy.
External links
- Gasifipedia, a comprehensive collection of online resources to promote a better understanding of gasification technology (with emphasis on coal gasification), developed and maintained by the National Energy Technology Laboratory of the US Department of Energy (NETL)
- Gasification System Program, from the National Energy Technology Laboratory of the US Department of Energy (NETL)
- "Practical Experience Generated During the First Twenty Years of Gasification Plant Operations and Large Implications for Future Projects" (PDF-3.1MB), DOE Fossil Energy Office, May 2006.
Source of the article : Wikipedia
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