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Removing the bottlenecks in coal gasification technology – A documentary on the development of a 3,000-ton dry pulverized coal pressurized gasification process and its key equipment Authors/Source: ChemNet China Date: December 10, 2021 Page views: 8 Recently, the project titled “Innovative development and industrialization of a 4-million-ton/year coal indirect liquefaction process,” in which China Wuhuan Engineering Co., Ltd., a subsidiary of China National Chemical Engineering Group Corporation, played a key role, was awarded the **First Prize for Scientific and Technological Progress in 2020. The China Five Rings was primarily responsible for developing the most important common technology in this project, namely the large-scale dry coal powder pressurized gasification process, as well as the key equipment associated with it – the 3,000-ton-class dry coal powder pressurized gasification system and its related key equipment. This technology is one of the key core technologies that pose a bottleneck in large-scale indirect coal liquefaction. Breaking monopolies and catering to both high- and low-end markets. Before 2013, foreign countries imposed restrictions on China’s development of large-scale dry coal powder gasification technology for capacities exceeding 2,000 tons. The introduction of foreign gasification units has also revealed issues such as inability to operate for long periods, high investment costs, long construction times, and poor adaptability to different types of coal, all of which severely hinder the development of China’s coal chemical industry. China Five Rings, in collaboration with Shenhua Ningmei Group, focused on addressing the issues encountered in the operation of domestic coal gasification units, and developed a complete set of technologies for large-scale pressurized coal gasification as well as a 3,000-ton dry coal gasifier with a single burner at the top. These advancements helped reduce investment and operating costs, enabling the units to operate for extended periods of time. The successful development of this technology has broken the foreign technological monopoly, achieving a 100% domestic production rate. This technology is applicable to a wide range of coal types; it can gasify various coals such as high-sulfur, high-ash, and high-ash-melting-point lignite and bituminous coal. It can process both low-quality “coarse” coal and high-quality “refined” coal ； It features a high level of intelligence; the entire system has 2,200 detection and control points. Through a rigorous interlock logic control system, intelligent control is achieved throughout the entire process, ensuring the safe and stable operation of the device. Based on physical and chemical property data of various coal types, this technology has established analytical models for gasifier flow fields, studied the enhanced reaction mechanisms between oxygen and pulverized coal, and advanced both the theoretical foundations and engineering applications related to gasifier development. It has thus laid a solid foundation for the development of more large-scale, efficient, energy-saving, and water-conserving advanced coal gasification technologies. Four major breakthroughs leading innovation: This technology has achieved significant innovative breakthroughs in the following four areas. Firstly, a closed-cycle membrane water-cooled wall reaction chamber with high turbulence intensity and a high degree of reaction has been developed. This enables high coupling efficiency between the reaction chamber, the modular burner, and the stable-flow slag removal system, while resulting in a low ash-to-slag ratio and reliable operation. Through theoretical analysis and experimental studies, a structure was determined that features an appropriate height-to-diameter ratio for the reaction chamber, in combination with a swirl burner and a steady-flow slag outlet; this arrangement not only effectively controls the reaction time but also ensures good turbulent mixing and backmixing within the reaction chamber. The design of multiple, independent, closed-loop membrane-type water-cooled wall coil structures ensures uniform distribution of cooling water, eliminates phase changes during the heat transfer process, and allows for measurable and controllable variations in the temperature field inside the furnace. A new approach to heat transfer without phase change in the spiral water wall was proposed, ensuring the reliability of the water wall in resisting slag. The space between the shell and the water wall is filled with syngas or carbon dioxide; there are no connectors in the middle section. This design not only effectively ensures deformation compatibility between the internal components of the reaction chamber and its pressure-bearing shell, but also helps to reduce the diameter of the gasifier shell, thereby lowering investment costs, easing manufacturing difficulties, and accelerating the production process. Second, based on the mechanism of strong momentum transfer in the burner, it reveals the kinetic mechanism of turbulent combustion in the top-mounted swirl gasification field, as well as the enhanced reaction patterns between oxygen and pulverized coal. It features an integrated monitoring system that combines flame detection, flame temperature measurement, and flame imaging for full-process surveillance; the main burner has a service life of over 3 years, the gasifier experiences low heat loss, and slag formation is stable. Third, an advanced water-cooled stepped-diameter flow-stabilizing slag discharge system was invented, which reduced the scattering and vortices that occur as syngas and slag move from the combustion chamber into the quenching chamber. A downcomer protection semi-tube structure was invented to reasonably control the syngas space velocity, thereby preventing wear and rupture of the downcomer caused by unstable operation of the gasifier due to variations in coal type. Fourth, an intelligent control system has been developed to ensure safer and more stable operation of the device. The device enables automatic verification of feeding conditions, one-click initiation of the feeding process, automatic adjustment during operation, and automatic protection in case of abnormalities. A new concept of pressurized ignition and isobaric feeding was proposed, which shortened the feeding time and improved system stability. A new concept for thermal protection of the pilot flame in the furnace was proposed, thereby improving gasification efficiency and the online availability rate of the gasifier. Authorized certification and complete set output: In May 2018, the China Petroleum and Chemical Industry Federation organized experts to conduct on-site verification of the \"Development of 3,000-ton-class dry coal powder pressurized gasification process technology and key equipment.\" Experts conducted high-load operation tests on Gasifier No. 27 at 100% to 115% of its rated capacity. The daily raw coal processing capacity of a single gasifier reached 3,012 tons, making this technology the first top-fired dry coal slurry pressurized gasification technology in the world capable of handling 3,000 tons of raw coal per day. On May 27, 2018, the China Petroleum and Chemical Industry Federation organized an appraisal committee composed of senior experts in China’s coal chemical and petroleum and chemical industries, including Academician Xie Kechang of the Chinese Academy of Engineering and Gu Zongqin, director of the Petroleum and Chemical Industry Planning Institute. The committee held a meeting in Beijing to appraise the scientific and technological achievements related to the development of \"3,000-ton-class dry coal powder pressurized gasification process technology and key equipment.\" The evaluation conclusion is that this technology fills a gap at the international level in the field of 3,000-ton-class dry coal powder pressurized gasification using a single burner, and is at the world’s leading level. In addition, “a type of swirl dry coal powder gasification furnace” won the 19th China Patent Gold Award, and after being evaluated for intellectual property rights by the US-based LD Intellectual Property Law Firm, it was exported to the United States. Currently, the integrated technology for large-scale pressurized gasification of dry coal powder is being applied in multiple fields both domestically and internationally. It has driven the improvement of a number of domestic equipment manufacturing enterprises, changed the long-standing situation where China’s large-scale coal chemical technologies were dependent on foreign companies, and enabled China to export complete sets of large-scale coal-to-oil chemical technologies and equipment to other countries.