Method for recovering carbon dioxide by multistage liquefaction and staged refrigeration of industrial tail gas

Abstract

The invention discloses a method for recovering carbon dioxide by multistage liquefaction and staged refrigeration of industrial tail gas, wherein the method comprises the following steps: raw material gas firstly enters a first residual cold recoverer, exchanges heat with non-condensable gas, is pre-cooled to 22 DEG C, then enters a second residual cold recoverer, exchanges heat with the non-condensable gas, and is pre-cooled to 16 DEG C; then the pre-cooled raw material gas enters a primary condenser, is cooled to -18 DEG C through ammonia evaporation refrigeration, then enters a secondary condenser, and is cooled to -25 DEG C through ammonia evaporation refrigeration; then the treated gas enters a rectifying tower to be rectified and purified, a tail condenser arranged at the top of therectifying tower cools the tail condensed gas to -45 DEG C through ammonia vacuum evaporation, and a qualified industrial-grade or food-grade liquid CO2 product is extracted from the tower kettle ofthe rectifying tower; the product is sent to a supercooler through a product pipeline, is supercooled to -25 DEG C through ammonia evaporation refrigeration and then is sent to a product storage tankthrough a product pipeline. The technological process is clear in hierarchy, low in working pressure and low in equipment manufacturing difficulty, the refrigeration coefficient of a refrigeration system is increased, meanwhile, the yield of the CO2 system is increased, and the purposes of saving energy and reducing consumption are achieved.

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...

AI Technical Summary

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

Images