Technological method for preparing food-grade CO2 based on high-concentration carbon dioxide exhaust gas

Abstract

The invention relates to a technological method for preparing food-grade CO2 based on high-concentration carbon dioxide exhaust gas, wherein, the technological method solves the problems of complicated preparation technology, high energy consumption, high equipment investment, high running cost and large occupied area of prior food-grade CO2. The technological method adopts the technical scheme as follows: feed gas of high-concentration carbon dioxide is processed through compression, purification edulcoration, dehydration, rectification and cooling, and then the food-grade CO2 is obtained. The technological method is characterized in that part of feed gas enters a CO2 medium-pressure low-temperature rectifying tower in a rectification step so as to supply heat to a reboiler at the tower bottom after feed gas is compressed to reach the gage pressure of 4 to 6 MpaG; and then part of feed gas that is processed through heat exchange and residual feed gas are mixed and then enter the purification edulcoration step. The technological method has the advantages of simple technological process, low energy consumption of system operation, small occupied area, low equipment investment and low running cost.

Description

technical field [0001] The invention relates to a method for preparing food-grade CO 2 The process method, specifically the preparation of food-grade CO2 from high-concentration carbon dioxide emission gas 2 process method. Background technique [0002] The possible harm of global warming to human beings and the entire earth environment has increasingly attracted widespread attention from all over the world. In order to curb the trend of global warming, the "Kyoto Protocol" passed in 1997 will reduce the global carbon dioxide (CO 2 ) emission is determined as the future work target. How to reduce CO 2 emissions have become the primary concern of governments and scientists. domestic CO emissions 2 It mainly comes from fertilizer factory tail gas, refinery tail gas, fermentation tail gas, etc., which can be used in food, medicine, welding and cutting industries after recycling through appropriate technology, which can reduce CO 2 emissions, which can be used in industri...

AI Technical Summary

Problems solved by technology

Medium-pressure production of food-grade CO 2 The pressure is generally 2.5MPaG. For example, Yan Xiaoru et al. ("Chemical Design", 2008, 18(6)) proposed a pressurized rectification process. Firstly, the raw material gas is compressed to 2.4MPaG, and then sent to the refining process after purification. Distillation device, and use low-pressure steam as the heat source of the reboiler of the rectification device, the product purity can reach 99.99%, but due to the need to consume low-pressure steam as the heat source of the rectification tower, the energy consumption of the device increases

The high-pressure method produces food-grade CO 2 when CO 2 The preparation pressure is about 8.0MPaG, which exceeds CO 2 Although it can be cooled and liquefied with normal temperature water, at least 4 to 5 stages of compression are required, which not only consumes too much power for the compressor, but also requires high pressure resistance for the system, and higher requirements for equipment, pipelines, and instruments.

To sum up, so far, the above-mentioned preparation processes under pressure have a large energy consumption loss, which leads to the problems of complex preparation process, large floor area, high equipment investment and operation cost

Moreover, the non-condensable gas treated by rectification is usually discharged directly, and the cooling capacity is not well recovered and utilized, resulting in increased energy consumption

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