The four major processes for converting coal into raw materials are reaching maturity

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Source: China Chemical Industry News (Author is an expert from the Coal Chemicals Committee of the China Petroleum and Chemical Industry Federation, director of the Engineering Research Center for Efficient Utilization of Hydrocarbon Resources in the petroleum and chemical industry under the same federation, and a leading expert in coal chemicals at Yanchang Petroleum Group). Since the beginning of this year, coal-producing provinces have successively introduced policies to increase the rate of on-site conversion of coal, thereby further promoting its use as a raw material. The conversion of coal into raw materials has become an important approach for the clean utilization of coal. 　　The coal raw material utilization approach makes use of integrated pyrolysis and gasification technologies to efficiently convert coal into two types of products: gas (industrial fuel gas or syngas) and liquid (low-temperature coal tar). These gas and liquid products are then further processed to produce high-value-added products such as clean fuels, natural gas, and chemical substances. This creates a new industrial framework for the simultaneous production of oil, electricity, chemicals, and heat from coal, thereby enabling efficient and clean utilization of coal throughout its entire life cycle, while minimizing energy consumption and emissions. Currently, there are mainly four processes for converting coal into raw materials. 　　The first is a green power generation scheme based on the coal pyrolysis-gasification integration (CCSI) technology. 　　　This approach organically combines coal pyrolysis technology with coal gasification technology through a reactor, converting coal directly into two products—industrial gas and coal tar—in a single step. The calorific value of the generated gas is 1,200 kcal per standard cubic meter, with an effective gas content of over 35% ； The coal tar yield exceeds 15%, which is equivalent to a crude oil price of $20 per barrel. This technology has already undergone 72 hours of on-site calibration of the industrial test unit organized by the China Petroleum and Chemical Industry Federation, and successfully passed the evaluation for scientific and technological achievements. 　　　If CCSI technology is integrated with power plants, coal is first pyrolyzed to produce coal tar (which is then further processed), while the heat semi-coke generated by pyrolysis is fed directly into the lower section of an integrated reactor for gasification, thereby producing industrial gas. This gas is used in boilers or gas turbines to generate electricity with ultra-high purity. As a result, a new integrated production model that combines clean and efficient conversion of coal, further processing of coal tar, and green power generation is created. This approach not only significantly improves the economic efficiency of power plants but also greatly reduces their emissions of SO2, NOX, and particulate matter. 　　The second is a coal-based natural gas solution to replace direct coal combustion, based on the integrated technology of coal tar extraction and methanation from coal (CCMI). 　　The core of this approach is to carry out coal pyrolysis, gasification, and partial methanation in a single reactor, converting coal into gaseous and liquid products in one step. Among them, the methane content in the syngas is over 12%, and the yield of coal tar is around 15%. By utilizing methanation technology to convert the remaining components of the syngas into methane gas, the overall methane yield increases significantly, thereby making the economics of coal-to-gas production highly favorable. 　　According to this technical approach, one 5,000 tons/day CCMI unit can be paired with a production facility capable of producing 600 million cubic meters of natural gas per year, while also generating 250,000 tons of coal tar per year as a by-product. Compared with conventional coal-to-natural gas production processes, this approach reduces investment costs by 25%, features a shorter process route, fewer pieces of equipment, and less land usage. Moreover, since coal tar produced per cubic meter of natural gas can generate sales revenue of 1.75 yuan after processing, the profitability of the project is significantly improved, with the cost of natural gas able to be kept below 1 yuan per cubic meter. If it is widely adopted in the future, it will not only significantly improve the efficient and clean use of coal but also greatly enhance domestic natural gas supply capacity, meeting the natural gas needs of urban and rural residents and ensuring an adequate and affordable supply of natural gas to replace the use of coal for heating. 　　Third is an innovative approach to the construction of coal chemical industrial parks based on the ultra-large-scale pulverized coal fluidized bed gasification (KSY) technology. 　　The KSY technology uses oxygen as a gasifying agent, enabling a daily processing capacity of 5,000 tons of coal per furnace. It offers advantages such as large furnace size, high coal conversion efficiency, low costs, and reduced water consumption. Currently, this technology has completed industrial trials at a rate of 100 tons per day, and the preparation of the process package for 5,000 tons per day is essentially finished. 　　The KSY technology is employed to construct gasification islands at pit sites for the centralized production of syngas, which is then transported via pipelines to nearby energy and chemical enterprises, or through long-distance pipelines to enterprises that require gas (or coal) and are located near target markets but far from coal production areas, thereby replacing the previous practice of building and operating gasification islands in a dispersed manner with a unified and centralized approach ； Replacing the previous decentralized and multi-step coal transportation methods via roads, railways, and waterways by centralized pipeline gas delivery, and shifting from coal transport to gas transport, enables long-distance delivery. This will facilitate the establishment and development of large-scale coal chemical projects such as those for producing olefins from syngas, aromatics from syngas, and petroleum products through F-T synthesis in various regions. 　　　Fourth is a comprehensive utilization plan for pyrolyzed coal tar based on maximum benefit. 　　　As various pyrolysis technologies in our country become increasingly mature, particularly with the engineering breakthroughs in large-scale coal powder pyrolysis techniques that yield higher liquid yields, the production and further processing of coal tar will enter a golden age of development. 　　Based on the physical properties of low-temperature coal tar and market demands, and following the principle of \"using oil where appropriate, using chemical processing where suitable, and carrying out staged conversion,\" the phenolic compounds that are present in high concentrations in the light fractions of coal tar and are easy to separate can be extracted. The heavy fractions (which contain high levels of asphaltenes and resins and are difficult to convert) are sent to a suspension bed for efficient conversion, while the middle fractions, along with the light fractions from which phenols have been removed and the light components resulting from conversion in the suspension bed, are sent to a fixed bed for further processing. This hierarchical conversion addresses the problems of high hydrogen consumption and large amounts of wastewater generated during the hydrogenation process due to the presence of phenolic substances. In addition to producing high-quality refined oil, it is also possible to further process it into aromatics, aviation fuel, lubricants, and other products, thereby enriching the industrial chain and increasing added value. 　　Based on preliminary estimates, constructing a 1 million tons per year medium- and low-temperature coal tar processing plant using this approach would involve producing products such as phenol, cresol, gasoline, diesel, and aviation fuel. Assuming an yield of 85% for these oil-based products, a average price of 6,000 yuan per ton, and a cost of 1,000 yuan per ton for coal tar, the total investment required for the project is approximately 4 billion yuan. The annual sales revenue could reach 5.1 billion yuan. Moreover, the project’s energy consumption, water usage, hydrogen consumption, and wastewater generation are significantly reduced compared to traditional coal tar processing methods. 　　Overall, in the coming years, if it is possible to convert 2 billion tons of coal per year into fuel through the aforementioned methods, thereby turning those previously unclean energy sources into clean ones, then, without changing the current proportions of oil, natural gas, coal, and new energy sources in China’s energy consumption structure, the share of clean energy in China could rise from 17.9% in 2016 to 49.9%, reaching a level roughly comparable to that of developed countries. During this process, an additional 300 million tons of low-cost coal tar can be produced, at a cost equivalent to $20 per barrel for international oil prices, thereby helping to address the gap between oil supply and demand in our country.