An introduction to the coal chemical industry and its development in various countries

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A process that uses coal as raw material and converts it into gas, liquid and solid fuels and chemicals through chemical processing. It mainly includes coal gasification, liquefaction, carbonization, tar processing and calcium carbide acetylene chemical industry. Coal chemical industry began in the second half of the 18th century, and a complete coal chemical industry system was formed in the 19th century. In the 20th century, many organic chemicals using agricultural and forestry products as raw materials were mostly produced using coal as raw materials, and coal chemical industry became an important part of the chemical industry. After the Second World War, the petrochemical industry developed rapidly, and the production of many chemicals shifted from coal as raw material to oil and natural gas, thus weakening the position of coal chemical industry in the chemical industry. When the price of petroleum increased significantly in the 1970s, coal chemical industry experienced some development (see the history of coal chemical industry development). During the chemical processing of coal, the chemical structure of organic matter in coal is a macromolecular structure with mainly aromatic fused rings as the unit core, connected to each other by bridge bonds, and with various functional groups (see coal chemistry). Through thermal processing and catalytic processing, coal can be converted into various fuels and chemical products. Among the various chemical processing processes of coal, coking is the earliest and still the most important method. Its main purpose is to produce coke for metallurgy. At the same time, gas and aromatic hydrocarbons such as benzene, toluene, xylene, and naphthalene are produced as by-products. ； Coal gasification also plays an important role in the coal chemical industry. It is used to produce city gas and various fuel gases (widely used in machinery, building materials and other industries), and is also used to produce synthesis gas (as a raw material for synthetic ammonia, synthetic methanol, etc.) ； Processes such as low-temperature carbonization of coal, direct coal liquefaction and indirect coal liquefaction mainly produce liquid fuels. They were developed in the first half of the 20th century. After the Second World War, their products came to a standstill because their products could not compete with natural oil economically. Currently, only indirect coal liquefaction plants still exist in South Africa. ； Other direct chemical processing of coal, such as the production of montan wax, sulfonated coal, humic acid and activated carbon, are still used on a small scale. World Coal Chemical Industry Coal produced in the world is mainly used as fuel for power stations and industrial boilers. ； It is used in coal chemical industry in a certain proportion, mainly in the coking and gasification of coal. In the 1980s, the world's annual coke output was about 340Mt, and the annual coal tar output was about 16Mt (the naphthalene extracted from it was about 1Mt). Products processed from coal tar are widely used to make plastics, dyes, spices, pesticides, medicines, solvents, preservatives, adhesives, rubber, carbon products, etc. In 1981, the world's total ammonia production was 95.3 Mt, mainly derived from oil and natural gas. Only about 10% of ammonia is produced from coal. ； The proportion of synthetic methanol produced from coal is also very small, accounting for only about 1% of the total methanol production. The United States coal chemical industry used 717.7Mt of coal in 1984, of which 5.5% was used for coking, reaching 39.5Mt. Benzene, a by-product of coking, accounts for 9% of the total benzene production, and vinyl acetate produced from carbide acetylene accounts for 8% of the total production. In 1984, a plant was built in the United States to produce high calorific value city gas through lignite gasification and methanation. It processed 22kt of lignite per day and produced 3.89Mm3 of gas. In recent years, many new process tests have been carried out in coal gasification and liquefaction. The coal chemical industry of the Federal Republic of Germany in 1984 used 84.8Mt of coal (excluding lignite), of which coking coal accounted for 32.6%, accounting for 27.6Mt. The annual output of coal tar was approximately 1.4Mt. Coal tar produced by coke ovens of steel and other enterprises across the country is concentrated in five tar processing plants for processing, producing more than 500 chemicals. There have been great developments in the chemical industry of calcium carbide and acetylene, and there are still improvements in technology. There are also some new developments in the research on pressurized gasification and direct liquefaction of coal. Japan Coal Chemical Industry In 1984, Japan shared 106.9Mt of coal. Since its steel industry is very developed and there is a large demand for coke for ironmaking and other metallurgical purposes, coking coal accounts for 66%, which is 70.5Mt. The annual coal tar output reaches 2.4Mt, providing the entire industrial source of naphthalene. Vinyl acetate produced from carbide acetylene accounts for 23% of its total output. South Africa Coal Chemical Industry South Africa is the only region in the world that still has indirect coal liquefaction plants. It has three synthetic liquid fuel plants, SASOL-I, SASOL-II, and SASOL-III. It processes a total of about 33Mt of coal annually, produces millions of tons of gasoline, diesel, jet fuel and other oil products, and produces hundreds of thousands of tons of by-products such as gaseous hydrocarbons, ethanol, ammonia, sulfur and other chemicals. China Coal Chemical Industry China ranks among the top in the world in terms of coal reserves and production. In 1984, it produced 789 Mt of coal, of which about 8.2% was used for coking and about 5.6% for gasification. There are more than 120 large, medium and small coking plants in the country, with more than 280 coke ovens and an annual coke production capacity of 39Mt. In 1983, the coke output was 34.4Mt, ranking fourth in the world, of which about 55% was used for blast furnace ironmaking, 13% for synthetic ammonia, 6.7% for casting, and 2.8% each for calcium carbide and ferroalloys. Coal tar is processed into about 50 kinds of products including naphthalene, anthracene, and asphalt. Coke oven gas is mainly used as industrial and city gas, and is also used to synthesize ammonia. The gasification of coal is used to produce fuel gas (industrial and domestic) and synthesis gas. In 1984, the output of synthetic ammonia was 18Mt, and its raw material source was mainly coal (anthracite and coke), accounting for about 66%. China's coal-based ammonia production capacity accounts for about half of the world's production capacity. In 1983, the amount of city gas produced from coal was about 1870 Mm3. Prospects of Coal Chemical Industry Looking at the development history of the chemical industry in the past century, every change in the raw material structure is always accompanied by a huge change in the chemical industry. In 1984, coal accounted for about 74% of the world's proven recoverable reserves of fossil fuels, while oil accounted for about 12% and natural gas about 10%. From a resource perspective, coal will be a potential main raw material for the chemical industry. In which fields and at what speed coal chemical industry will develop in the future will depend on the technological progress of coal chemical industry itself and changes in oil supply and demand conditions and prices. In the short term, the coke used in the steel and other metallurgical industries will still rely on the coking of coal, and coking chemicals such as naphthalene, anthracene and other polycyclic compounds are still organic chemical raw materials that are difficult to replace in the petrochemical industry. ； Coal gasification will continue to be an important aspect of coal chemical industry with the development and application of new gasification technologies. ； The development and research of producing syngas from coal gasification and then synthesizing a series of organic chemical products through carbon-chemistry is an area that has made rapid progress in recent years and attracted attention. ； Preparing liquid fuel from coal, whether using low-temperature carbonization, direct liquefaction or indirect liquefaction, has to depend on technical and economic evaluation.