Half of the 25 coal pyrolysis technologies are industrialized

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Source: China Chemical Industry News. “Our company’s project for the pyrolysis of 1.2 million tons per year of raw coal, as well as the deep processing of coal tar through fluidized-bed hydrocracking to produce aromatics at a rate of 500,000 tons per year, is in the preliminary preparation stage. Construction is expected to begin in September at the Jinjie Industrial Park in Shenmu, Shaanxi.” ”On July 10, a relevant official from Shaanxi Jingyi Chemical Co., Ltd. told a reporter from China Chemical Industry News. 　　As a traditional coal chemical process that has existed for many years, coal pyrolysis has become a popular option for the differentiated utilization of coal in recent years, attracting significant investment from both within and outside the industry. What are the latest developments in coal pyrolysis technology? What other bottlenecks exist? What is the future direction? Could it become a new path for modern coal chemical industry? A reporter from China Chemical Industry News conducted an interview. 　　Processing technologies are diverse. Coal pyrolysis, also known as coal carbonization or thermal decomposition, refers to the process of heating coal in an air-free environment to evaporate the tar and gas contained within it, thereby producing tar, gas, and semi-coke (lignite). That is, by taking advantage of the compositional and structural characteristics of coal, and through thermal effects, control of operating conditions, or catalytic action, the organic macromolecular structures in coal are subjected to \"chemical tailoring.\" The processing conditions are mild, the process is simple, and no oxygen is required. The coal tar, semi-coke, and gas produced can be further processed into fuel oils and high-value chemicals, enabling their use based on their specific properties. 　“Coal is primarily composed of hydrocarbons, and differentiated utilization is one of the approaches for its advanced processing, with coal pyrolysis playing a key role in this process. ”He Yongde, an expert from the Coal Chemicals Committee of the China Petroleum and Chemical Industry Federation, said that China’s annual production of low-grade coal is around 2 billion tons, providing an ample supply of raw materials for the differentiated use of coal. If all low-rank coal were pyrolyzed, 150 million to 180 million tons of tar could be produced, which is equivalent to 90% of the current national oil production. In particular, the coal produced in Yulin has a tar content of around 11%, making it highly suitable for medium- and low-temperature pyrolysis; the production capacity of semi-coke and coal tar accounts for about 80% of the total domestic output. 　　It is understood that in recent years, domestic coal chemical enterprises as well as research institutions have been focusing on technological advancements related to the differentiated utilization of coal. Significant progress has been made in coal pyrolysis techniques, with 25 different methods developed; nearly half of these have been put into industrial use, thus laying the foundation for the differentiated utilization of coal. 　　Since last year, documents such as the \"13th Five-Year Plan for Demonstrating Advanced Coal Processing Industries\" issued by the Energy Bureau, the \"Action Plan for Clean and Efficient Utilization of Coal (2015–2020)\", as well as the \"13th Five-Year Development Guidelines for Modern Coal Chemical Industry\" prepared by the China Petroleum and Chemical Industry Federation, have all identified clean, efficient, and differentiated utilization of coal as one of the key tasks. Five new coal pyrolysis and cogeneration demonstration projects are planned, with a total annual coal consumption of 38.3 million tons; three of these projects will be located in Yulin, accounting for 86% of the total. 　　Multiple bottlenecks remain to be overcome. The technology for the selective utilization of coal through pyrolysis is complex, and it involves high investment and operating costs. There are significant challenges related to the development of large-scale integrated production systems, the removal of dust from pyrolysis gases, and environmental management; further technical optimization, integration, and practical exploration are needed. ”He Yongde told reporters that efforts should be intensified in wastewater treatment and reuse, desalination of highly saline water, and the development of zero-waste-discharge wastewater treatment systems ； Although the localization rate of key equipment reaches 95%, some high-temperature and wear-resistant instruments, valves, and other supporting devices required for coal pyrolysis still need to be imported; joint efforts should be organized to address this issue ； The oil products and electricity generated through coal pyrolysis for combined production are subject to exclusive monopolies; it is necessary to break down industry barriers and obstacles ； There is also a severe lack of industry standards for these products, and there is an urgent need to accelerate the development of such standards and regulations. 　There are still technical issues with current coal pyrolysis. In coal pyrolysis industrial projects, vertical square furnaces are commonly used for pyrolysis, with lump coal serving as the raw material and accounting for over 80% of the total production capacity. This technology requires low investment, but has a small production capacity per furnace and a low tar yield ； Coal tar is difficult to process; solid particles in the tar tend to accumulate on the surface of the catalysts, making separation challenging and affecting long-term stable operation ； High levels of metals, gums, and asphaltenes can cause the catalyst to become deactivated easily. 　　Furthermore, the clean utilization of semicoke (lancang), the main product of coal pyrolysis, is also a bottleneck, serving as a key factor restricting the development of coal pyrolysis and co-production. As the birthplace and largest production base for semi-coke in China, Yulin has a semi-coke production capacity of over 50 million tons. Although efforts are being made to increase the use of semi-coke in areas such as civilian applications, industrial furnaces, boilers, blast furnaces, and gasification, the capacity utilization rate remains around half. Some experts also told reporters that in an effort to obtain coal tar, certain companies have launched pyrolysis projects recklessly, ignoring market conditions; this puts things in the wrong order and exacerbates the overcapacity in lignite carbon production. 　“In recent years, the hydrogenation process for high-temperature coal tar has become increasingly mature, but the hydrogenation technology for medium and low-temperature coal tar still faces issues such as a limited range of products, a short industrial chain, and low added value. ”Ma Xiaoxun, a professor at the School of Chemical Engineering at Northwest University, said that processes such as delayed coking and fixed-bed hydrocracking for producing fuel oil are complex, and approximately 15% of coal tar is converted into coke, resulting in underutilization of this tar resource ； The full distillate of coal tar, when used for hydrogenation to produce fuel oil, has poor adaptability as a raw material; moreover, its catalysts have a short lifespan, which affects the long-term stable operation of the facility ； The more abundant phenols, naphthenes, phenanthrenes, etc. were not separated, resulting in a waste of resources. At the same time, pulverized coal accounts for 70% of coal mining, but the pyrolysis technology of pulverized coal faces bottlenecks such as difficulties in separating oil and dust, solidification of heavy tar, carbon deposition that blocks pipelines, and challenges in wastewater treatment, making industrial application difficult. 　　Deep transformation is the direction. During the 13th Five-Year Plan period, **one of the key tasks for demonstration projects on the selective utilization of coal through pyrolysis was to enhance system optimization and integration, as well as to carry out industrial demonstrations of combined production of oil, gas, chemicals, and electricity. 　　Ding Wu, Secretary-General of the Petrochemical Technology and Equipment Committee of the China Petroleum and Petrochemical Engineering Research Association and Vice President of Guolian Resources Network, said that as macro-control over the coal tar market continues to strengthen, there is an upgrade in the scale, technology, and level of sophistication involved in the deep processing of coal tar. As a result, this processing tends to move toward greater concentration, larger-scale facilities, greater diversity in products, and higher-quality outputs, thereby highlighting the high added value of coal tar and its potential for further development. 　　He Yongde suggested that coal pyrolysis should be used as a key approach to achieve the co-production of oil products, natural gas, chemicals, and electricity, thereby maximizing the value of coal; this is the best option for coal pyrolysis. The development of new technologies should focus on increasing tar yield, with an emphasis on advancing next-generation techniques such as rapid pyrolysis, catalytic (active) pyrolysis, hydrothermal pyrolysis, and pressure-assisted pyrolysis. 　　In 2016, China’s tar production was 18 million tons, but 60% of the value-added processing still remained at a basic level, focusing mainly on naphtha, gasoline, diesel fractions, etc. 　　“Coal tar is a high-quality and valuable raw material oil resource. In addition to conventional oils, it can be used to produce fine chemicals with high added value, especially those that are difficult to obtain through petrochemical routes and in high demand in the market, including naphthalene, **naphthalene, phenanthrene, octahydronaphthalene, pyrene, **pyrene, and others. ”Ma Xiaoxun said that taking phenanthrene as an example, 1,000 kilograms of medium- and low-temperature coal tar can be used to produce 30 kilograms of phenanthrene. At a price of 2,500 yuan per kilogram for phenanthrene, the economic value of this alone amounts to 75,000 yuan. 　　Song Yongyi, director of the Coal Clean Utilization Technology Department at Sinopec Fushun Petrochemical Research Institute, said that the coal tar pretreatment + fixed-bed technology developed by the institute enables a variety of product options; it can be used to produce naphtha with high aromatic potential and diesel with a high cetane number, as well as aviation fuel with a high specific gravity and lubricant base oils with high added value. 　　“China is the largest international supplier of coal tar products, but it has not yet reached the forefront of coal tar technology; companies that only engage in basic processing will not have a future. ”Zhou Xiaoye, deputy general manager of Xinnuolixing Fine Chemicals Co., Ltd. in Huanghua City, Hebei Province, said that the company adheres to the deep processing of tar. The plant processes 600,000 tons of high-temperature coal tar and 300,000 tons of medium-temperature coal tar per year, with an additional capacity for the deep processing of 50,000 tons of washed oil. The products include quinoline, isoquinoline, 2-methylquinoline, industrial fluorene, methylnaphthalene, indole, as well as three main series of products such as polycarboxylic acids, phthalic anhydride, and fluorene. A project to produce 100,000 tons of dioctyl phthalate (DOP) is set to be completed and put into operation this year.