【Ten Years of Great Development in Chemical Engineering Equipment】The New “High-Chlorine Coal” Gasifier Developed by China Aerospace Changzheng from 1967 to 2017

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Witnessing the decade-long rapid development of chemical engineering equipment; praising the prosperity and strength of modern China. Replies will be rewarded – discussions are welcome. ------------------------------------------- In May 2017, the R&D team at the Equipment Department of Aerospace Changzheng Chemical Engineering Co., Ltd., which is affiliated with the China Academy of Launch Vehicle Technology (hereinafter referred to as “the Academy”), developed a new type of gasifier for \"high-chloride coal\" using a special stainless steel material with excellent corrosion resistance. It fills the research gap in the field of gasifier materials and breaks the foreign monopoly. The area around Urumqi in Xinjiang is a concentrated zone for coal chemical industries. Due to the high chloride ion content in the coal produced in the Zhundong mining region there, the coal produced in this area is known as \"high-chloride coal\". This type of coal is highly corrosive to gasifiers and other equipment; as a result, the local chemical industrial parks can only use it in combination with other coals or discard it altogether. This undoubtedly increases the cost of raw materials, which is not conducive to the localization of raw coal. 　Since May 2013, the equipment R&D team at the Aerospace Engineering Company of the Rocket Research Institute has been conducting research on \"high-chlorine coal\". During the 4-year research and development process, they compared various steel grades suitable for resisting chloride corrosion in gasifiers, and ultimately selected a specific type of specialty stainless steel. To apply this type of special stainless steel in gasifiers, the R&D team conducted research on the manufacturing processes for gasifiers. At high temperatures, this type of special stainless steel precipitates carbon and nitrogen compounds as well as σ-intermetallic phases, which results in a **reduction in its resistance to chloride corrosion, with performance that is much lower than that in its original state. After numerous tests, the R&D team finally determined a process that involves heat treatment after explosive bonding and post-weld heat treatment at temperatures below 650°C. This approach not only preserves the corrosion-resistant properties of this type of special stainless steel but also meets the mechanical requirements of the underlying Cr-Mo steel, resulting in a gasifier that is highly resistant to chloride corrosion. Nickel-based alloys, which are commonly used in gasification furnaces as materials resistant to chloride corrosion, are expensive. The import price of special stainless steels identified by aerospace engineering companies is significantly lower than that of nickel-based alloys, resulting in a reduction in the total manufacturing cost of gasification furnaces by over 3 million yuan. Vaporization furnaces using this type of special stainless steel have been deployed in areas with \"high-chlorine coal,\" resolving the issue of local availability of such coal and breaking the monopoly held by foreign products. 　　Since the material selection plan was finalized in 2015, the R&D team has conducted in-depth research and exploration. Through experiments, they determined the corrosion resistance data of various materials at different chloride ion concentrations, and compiled a database on the corrosion resistance of these materials under various chloride ion levels. Guidelines for selecting materials resistant to chloride ions have now been developed, which will be useful for coal chemical enterprises in areas with high chloride content in coal.