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Application of new technology for low water/gas sulfur tolerance conversion
Due to the growing global demand for energy and the increasing tension in oil resource availability, China's coal chemical industry has entered a phase of rapid development. With various coal gasification technologies emerging, the Shell dry coal gasification process, developed by the Dutch company Shell, has been widely adopted across 17 large-scale coal chemical projects in China within just a decade. However, this technology has also brought about several challenges.
One major issue is the high concentration of carbon monoxide (CO) in the raw synthesis gas produced by the Shell process, often exceeding 60%. This not only increases the load on the CO shift conversion system but also raises the risk of exothermic methanation side reactions, which can lead to overheating of the catalyst bed. Controlling these side reactions becomes critical for the successful application of the Shell process in ammonia or methanol production.
To address this challenge, Qingdao Lixin Chemical Co., Ltd., Guangxi Liuzhou Chemical Industry Co., Ltd., and Sinopec Group Ningbo Engineering Co., Ltd. jointly developed a new low-water/gas-to-sulfur conversion process. This innovative approach effectively solves the problem of excessive CO and methanation risks, offering a more efficient, energy-saving, and environmentally friendly method for producing synthesis gas. The process recently passed an appraisal organized by the China Petroleum and Chemical Industry Association, marking a significant breakthrough in coal gasification technology.
Previously, to prevent methanation side reactions in the Shell process, most designs opted for a high water/gas ratio. Out of the 17 Shell gasifiers installed in China, 15 used this method. While it helps suppress methanation, it also leads to inefficiencies, such as higher energy consumption and unstable temperature control in the catalyst bed. Some early systems experienced overheating due to lower loads or excess catalyst, forcing operators to increase the water/gas ratio, which further worsened energy waste and caused catalyst degradation.
In response, Qingdao Lixin Chemical began researching sulfur-tolerant conversion technologies as early as 2002. Through extensive studies on water/gas ratios, bed temperatures, and catalyst performance, they identified key factors that influence methanation side reactions. Their research led to the development of a new low-water/gas conversion process, which enables effective CO conversion without triggering unwanted side reactions.
This new process was initially overlooked due to limited industrial experience and concerns over temperature control. However, when Sinopec Ningbo Engineering proposed its use at Guangxi Liuzhou Chemical Industry, the company conducted detailed evaluations and eventually adopted the low-water/gas process with QDB-type catalysts from Qingdao Lixin. This marked the first industrial application of the technology in China and globally.
Since then, the process has operated successfully for 14 months at Guangxi Liuzhou’s second ammonia plant. The results show that the QDB-04 catalyst can maintain stable reaction conditions, with water/gas ratios below 0.28, inlet temperatures under 250°C, and bed hot spots between 360–380°C. The final CO content remains below 0.6%, and no methanation occurs. The system runs smoothly, saving energy significantly and proving to be an ideal solution for high-CO synthesis gas applications like methanol or ammonia production.