The reporter learned from the recently held 2023 China Nitrogen Fertilizer and Methanol Technology Conference that an innovative achievement in the field of modern coal chemical industry-cascade refrigeration technology has been applied in the ultra-large modern coal chemical project of Shandong Rising Group Co., Ltd. Get the application, achieve a successful start-up, and has been running smoothly for more than 3 months.
Gu Zongqin, chairman of the China Nitrogen Fertilizer Industry Association, spoke highly of this technology. This technology can not only help modern coal chemical industry to greatly reduce energy consumption, but also play a role in realizing carbon capture, utilization and storage (CCUS).
General Manager Pei of Shanghai Xinjin Chemical Machinery Cascade Refrigeration Equipment Co., Ltd. told the reporter that Shanghai Shengwei Technology Development Co., Ltd. provides the patented technology and process package for the cascade refrigeration technology, and Shandong Sanwei Chemical Group Co., Ltd. is responsible for the engineering design. Authorized Shanghai Xinjin Chemical Machinery Cascade Refrigeration Equipment Co., Ltd. to use patented technology and equipment manufacturing, and the first set was applied in the super-large pulverized coal gasification demonstration project of Shandong Rising Group Runyin Aerospace.
According to Mr. Lu, a coal chemical expert, cascade refrigeration technology is an innovative technology with independent intellectual property rights. It uses carbon dioxide coupled with ammonia as a refrigerant to provide deep low-temperature cooling capacity for low-temperature methanol washing equipment. Compared with traditional ammonia refrigeration units, cascade refrigeration not only saves energy and reduces consumption, reduces investment, is safe and reliable, but also achieves carbon reduction, environmental protection and cryogenic guarantee.
According to our understanding, the best supplementary cooling temperature for low-temperature methanol washing is lower than -40°C, and ammonia refrigeration is difficult to meet. However, the temperature of cascade refrigeration using carbon dioxide can easily reach -40°C, which fully meets the low temperature requirements, and can even reach a lower temperature, the solution absorption capacity is improved, and the power consumption is reduced by half.
In terms of pipeline transportation, the cross-sectional area of the gaseous carbon dioxide pipeline for cascade refrigeration is about 1/20 of that for ammonia pipeline. Taking the Rising Project as an example, if ammonia refrigeration is used for the scale of 1 million tons/year of synthetic ammonia, the diameter of the gas ammonia pipeline is about 1800mm; if carbon dioxide refrigeration is used, the diameter of the pipeline for transporting gaseous carbon dioxide is only 350mm, and the pipes, valves and installation materials, etc. The amount of use is greatly reduced, and the investment is also greatly reduced.
The operation of this technology is safer, more stable and more reliable. This is because the cascade refrigeration is adopted, and the ammonia no longer enters the low-temperature methanol washing device, avoiding the risk of clogging of the low-temperature heat exchanger caused by crystallization of ammonium bicarbonate. In addition, after adopting cascade refrigeration, the refrigeration unit can almost completely liquefy carbon dioxide, which can play a major role in realizing the "double carbon" goal and CCUS.
According to coal chemical industry experts, cascade refrigeration can be used not only for methanol washing, but also for large-scale ammonia synthesis units. At present, the 4,500-ton/day large-scale ammonia synthesis unit under construction by Rising Group also uses cascade refrigeration to reduce the temperature of the synthesis gas to -35°C, the ammonia content of the circulating gas entering the synthesis tower is only 0.7%, and the net value of ammonia is increased by 2%. The total ammonia net value can reach more than 21%, which can greatly reduce energy consumption and save investment. (Yu Hong)
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