Method for recovering carbon dioxide by multi-stage liquefaction and staged refrigeration of industrial exhaust gas

Abstract

The invention discloses a method for recovering carbon dioxide by multi-stage liquefaction of industrial tail gas and classified refrigeration, which comprises the following steps: the raw material gas first enters the first waste cold recovery device, exchanges heat with non-condensable gas and is pre-cooled to 22°C, and then goes to the second The residual cold recovery device is pre-cooled to 16°C by exchanging heat with non-condensable gas. Then it goes to the primary condenser and is cooled to -18°C by ammonia evaporative refrigeration, then goes to the secondary condenser and is cooled to -25°C by ammonia evaporative refrigeration again. Then go to the rectification tower for rectification and purification. The tail condenser installed on the top of the rectification tower cools the tail gas to -45°C through the vacuum evaporation of ammonia, so that the qualified industrial-grade or food-grade liquid CO can be extracted from the bottom of the rectification tower. 2 product. Then it is sent to the subcooler through the product pipeline, and is subcooled to -25°C by ammonia evaporation refrigeration, and then sent to the product storage tank through the product pipeline. The invention has clear technological process layers, low working pressure and low equipment manufacturing difficulty, improves the refrigeration coefficient of the refrigeration system, and simultaneously increases the CO 2 System yield, to achieve the purpose of energy saving and consumption reduction.

Description

technical field [0001] The invention belongs to the technical field of recovering carbon dioxide, and in particular relates to a method for recovering carbon dioxide through multi-stage liquefaction and graded refrigeration of industrial tail gas. Background technique [0002] At present, coal and oil are still the main energy consumption of human beings. In the primary energy consumption structure, coal accounts for 68.5%, oil accounts for 17.7%, and natural gas accounts for only 4.7%, which is far lower than the world average of 24%. In the late regeneration stage of the decarbonization liquid of the low-temperature methanol eluting carbon device and the early stage of the regeneration of the adsorbent of the PSA decarburization device, a tail gas with a medium and low carbon dioxide concentration (75% to 85%) will be produced. [0003] In response to the above problems, the Chinese patent disclosed a utility model patent on 2018.03.10 called a low-temperature methanol was...

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Problems solved by technology

[0003] In response to the above problems, the Chinese patent disclosed a utility model patent on 2018.03.10 called a low-temperature methanol washing flash tower second-stage flash vapor recovery system (application number: CN201820326875.4), in which the liquid CO 2 The recovery system includes fine desulfurization tower, purification tower, CO 2 Gas compressor, precooler, ammonia condenser, separation column and product CO 2 Storage tank; the flash gas enters the fine desulfurization tower after passing through the water cooling device, and the flash gas after desulfurization goes to the purification tower. In the purification tower, high boiling substances such as methanol and water in the flash gas are absorbed, and the flash gas after passing through the purification tower Vapor enters CO 2 The second stage of the gas compressor is pressurized to 3.4-3.6MPa and then enters the precooler, then the deammonization condenser is cooled and liquefied, and finally enters the separation tower, and the liquid CO 2 Separation from non-condensable gas, liquid CO from the bottom of the separation tower 2 Go to product CO 2 storage tank, which can produce industrial grade liquid CO 2 , the market price is slightly higher than the production cost, while avoiding CO 2 The impact of gaseous emissions on the environment, but the above-mentioned liquid CO 2 The recovery system has a low recovery rate of carbon dioxide and high energy consumption of the device

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