Device and method for performing multistage flash, resolution and separation on synthetic ammonia decarburization absorption tower bottom pregnant solution

Abstract

The invention discloses a device and a method for performing multistage flash, resolution and separation on a synthetic ammonia decarburization absorption tower bottom pregnant solution. The absorption tower bottom pregnant solution enters into a primary high-pressure flash tank after being decompressed; a flashing gas phase is used as a fuel gas, and a flashing liquid phase enters into a secondary high-pressure flash tank after being subjected to heat exchange; after being cooled and separated, a gas phase of the secondary high-pressure flash tank enters into a CO2 compressor so as to be conveyed to a urea workshop section, and a separated liquid phase flows back to the secondary high-pressure flash tank, and a flashing liquid phase enters into a low-pressure flash tank after being decompressed; after being cooled and separated, the gas phase of the low-pressure flash tank enters into a CO2 recovery device, a separated liquid phase flows back to the low-pressure flash tank, the flashing liquid phase partially enters into a resolution tower after being subjected to heat exchange, and the residual part enters into an absorption tower; resolution tower overhead gas enters into a secondary high-pressure flash tank, the tower bottom solution partially returns to the tower after exchanging heat with low-change gas, the residual part enters the absorption tower after being cooled, and the absorption tower overhead gas is fed into a methanation furnace through a separator. A multistage flash evaporation and resolution process is adopted, so that the CO2 yield is improved and the energy consumption of an absorption tower bottom pregnant solution resolving process is reduced.

Description

technical field [0001] The invention relates to a multi-stage flash analysis and separation method for the rich liquid at the bottom of the absorption tower for decarburization of synthetic ammonia, in particular to realize the CO in the rich liquid at the bottom of the absorption tower by mixing the multi-stage flash analysis and absorption process 2 Gas separation and purification. Background technique [0002] In order to control the purity and ratio of feedstock for ammonia synthesis reaction and avoid catalyst poisoning, the CO in the low-change gas from the reaction part 2 It must be removed in time before the ammonia synthesis process. Alcoholamine (methyldiethanolamine, MDEA, monoethanolamine, MEA) as CO 2 The absorbent has obvious advantages: low absorption and desorption temperature, small solution heat capacity, low regeneration energy consumption, high gas purification purity, no corrosion in the solution, low solvent vapor pressure, and low solvent consumption...

AI Technical Summary

Problems solved by technology

Due to the fact that the analysis process of the rich liquid at the bottom of the decarburization absorption tower of synthetic ammonia lacks the pressure combination with the compressor of the downstream urea section, and the comprehensive optimization process innovation design and global integration of pressure energy are not considered, the main problems of the existing synthetic ammonia decarburization process are as follows: (1 ) is to separate the CO in the rich liquid at the bottom of the absorption tower 2 , the high-pressure rich liquid is decompressed to normal pressure through a hydraulic turbine and a throttle valve to obtain the final low-pressure CO 2 After the product, it needs CO 2 The compressor is boosted and sent to the downstream urea section to complete the synthesis reaction, and the rich liquid at the bottom of the absorption tower is desorbed for CO 2 There are repeated step-down and step-up processes in the process, which invisibly increases the consumption of pressure energy; (2) the high-temperature low-change gas heat is not fully utilized, which increases the temperature of the gas phase entering the bottom of the absorption tower and reduces the temperature of the absorption tower. efficiency, increasing the circulation volume of lean liquid and semi-lean liquid, virtually increasing the processing capacity and energy consumption of the absorption tower

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