【Ten Years of Rapid Development in Chemical Equipment】1036–2023: The First Large-Scale Cascade Refrigeration Industrial Unit Operates Stably

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The chemical industry has seen significant development over the past decade; let’s praise the prosperity and strength of modern China. By contributing our ideas, we can foster more active participation from everyone. HaiChuan becomes even better with your involvement – we welcome everyone to take part in more forum discussions and exchanges. With the hot weather in July, be careful to prevent fires. ---------------------------------------------- Reporters learned from the 2023 China Nitrogen Fertilizer and Methanol Technology Conference that an innovative technology from the field of modern coal chemistry – cascade refrigeration technology – has been applied in Shandong Ruixing Group Co., Ltd.’s large-scale modern coal chemistry project. This technology was successfully implemented on its first attempt, and the system has been operating steadily for over three months now. 　　Gu Zongqin, president of the China Nitrogen Fertilizer Industry Association, spoke highly of this technology, stating that it can not only help modern coal chemical industries significantly reduce energy consumption but also play a role in achieving carbon capture, utilization, and storage (CCUS). 　　General Manager Pei of Shanghai Xinjinhua Machinery Cascade Refrigeration Equipment Co., Ltd. told reporters that the cascade refrigeration technology was provided by Shanghai Shengwei Technology Development Co., Ltd., which supplied the patent technology and process packages, while Shandong Sanwei Chemical Group Co., Ltd. was responsible for the engineering design. Shanghai Xinjinhua Machinery Cascade Refrigeration Equipment Co., Ltd. was authorized to use this patent technology and equipment for manufacturing purposes. The first set of such systems was applied in the Ruyin Aerospace super-large scale coal gasification project demonstration site operated by Shandong Ruixing Group. 　　According to Mr. Lu, an expert in coal chemical industry, cascade refrigeration technology is an innovative technique with independent intellectual property rights; it uses carbon dioxide in combination with ammonia as a refrigerant to provide extremely low-temperature cooling for low-temperature methanol washing units. Compared with traditional ammonia refrigeration units, cascade refrigeration not only saves energy and reduces costs as well as investment, and is safe and reliable, but it also enables carbon reduction and environmental protection as well as ensures ultra-low temperatures. 　　It is understood that the optimal cooling temperature for low-temperature methanol washing is below -40°C, which is difficult to achieve using ammonia refrigeration. With carbon dioxide, the temperature that can be achieved in a cascade refrigeration system is easily -40°C, which fully meets the requirements for low temperatures; even lower temperatures can be attained. The absorption capacity of the solution increases, and power consumption is reduced by half. 　　In terms of pipeline transportation, the cross-sectional area of pipelines used for transporting gaseous carbon dioxide via cascade refrigeration is about 1/20 that of pipelines used for transporting ammonia. Taking the Ruixing project as an example, for a synthetic ammonia production capacity of 1 million tons per year, if ammonia is used for cooling, the diameter of the pipes for transporting gaseous ammonia is approximately 1,800 millimeters; whereas if carbon dioxide is used for cooling, the diameter of the pipes for transporting gaseous carbon dioxide is only 350 millimeters. This results in a significant reduction in the amount of pipes, valves, and other installation materials needed, as well as a substantial decrease in investment costs. 　　This technology offers safer, more stable, and reliable operation. This is because cascade refrigeration is used, so ammonia no longer enters the low-temperature methanol wash unit, thereby avoiding the risk of carbon ammonium crystals forming and blocking the low-temperature heat exchangers. Furthermore, with the use of cascade refrigeration, the refrigeration unit can almost completely liquefy carbon dioxide, which can play a significant role in achieving the \"dual carbon\" goals and in CCUS technologies. 　　According to coal chemical industry experts, cascade refrigeration can be used not only for methanol washing but also in large-scale ammonia synthesis plants. The large-scale ammonia synthesis plant with a capacity of 4,500 tons per day that is currently under construction by Rising Group also employs cascade refrigeration to reduce the temperature of the syngas to -35°C. The ammonia content in the gas fed into the synthesis tower is only 0.7%, resulting in a 2% increase in the net ammonia content; the overall net ammonia content can reach over 21%, which helps to significantly reduce energy consumption and save on investment costs.