Method for recovering CO in low-temperature methanol washing tail gas with low energy consumption

Abstract

The invention provides a method for recycling CO in low-temperature methanol washing tail gas with low energy consumption. The method comprises the following steps: feeding rich methanol from the bottom of an upper tower of a methanol washing tower into a primary flash tank for primary flash evaporation; methanol evaporated by the first-stage flash evaporation tank is respectively fed into a medium-pressure flash evaporation tower, and gas for promoting CO analysis in the methanol is introduced for flash evaporation; a stream of methanol led out from the bottom of the gas-liquid separation tank and lean methanol at an inlet of a lean methanol tank are subjected to heat exchange through a heat exchanger, the stream of methanol enters a flash tank to be subjected to reduced-pressure flash evaporation, flash steam obtained after flash evaporation enters a CO2 product tower to be treated, methanol with the low CO2 content after flash evaporation is pressurized through a pump and then cooled twice, and methanol with the low CO2 content is obtained. And feeding into the top of the middle section of the medium-pressure flash tower for flash steam washing, and reversely contacting with flash steam from the tops of the upper section and the lower section of the medium-pressure flash tower to reduce the quantity of the flash steam. According to the invention, the content of CO in methanol entering the CO2 product tower and the hydrogen sulfide concentration tower is reduced, the methanol productivity is improved, and the field operation environment is effectively improved.

Description

technical field [0001] The invention belongs to the technical field of coal chemical equipment, and in particular relates to a low-energy recovery method for CO in low-temperature methanol scrubbing tail gas. Background technique [0002] In chemical production using coal as raw material, the shifted gas after CO sulfur tolerance shift contains a large amount of excess CO 2 , a small amount of H 2 S, COS and other acid gases, these acid gases are very unfavorable to the production of downstream methanol synthesis, especially sulfide will cause catalyst poisoning in the downstream methanol synthesis reaction, so it must be removed. The low-temperature methanol washing process uses cold lean methanol (methanol ≥ 99.5%, H 2 O≤0.5%) as the absorption solvent, using lean methanol at low temperature for acid gas (CO 2 、H 2 S, COS, etc.) have excellent characteristics such as great solubility, not easy to foam, low viscosity, and wide range of sources. The acid gas in the shift...

AI Technical Summary

Problems solved by technology

Due to the secondary flash and H 2 The amount of flash gas after stripping is large, so the power of the compressor for recovering the flash gas is relatively high, resulting in a huge energy consumption for recovering the flash gas

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