Process for removing acid gas with low-temperature methanol solution

Abstract

The invention relates to a process for removing an acid gas with a low-temperature methanol solution, solving the problem that a low-temperature rectisol plant enriches ammonia and has lower recovery rate of CO2, lower concentration of H2S in acid gases and large solution circulating volume in the traditional process. The process comprises feed gas preprocessing, desulfuration and decarbonizationby an absorption tower, CO2 analysis and gas stripping and hydrogen sulfide concentration by a desorber, regeneration by a heat regenerator and deficient methanol separation by a methanol / water separation tower, wherein the feed gas is conveyed into an ammonia scrubber for deamination and preprocessing. The process can reduce the ammonia enrichment in the low-temperature rectisol plant, increase the recovery rate of CO2, improve the concentration of H2S in acid gases, reduce the circulating volume of the solution and ensure the quality of purified gas products.

Description

technical field [0001] The invention relates to a gas purification process, in particular to a process for removing acid gas by using a low-temperature methanol solution. Background technique [0002] The low-temperature methanol washing method belongs to the physical absorption method. This technology utilizes the physical characteristics of methanol's great solubility to acid gas at low temperature, uses cold methanol as the acid gas absorption liquid, and selectively absorbs H in the raw gas in stages. 2 S and CO 2 And various organic sulfur and other impurities, it is widely used in the production of synthetic ammonia, city gas, natural gas desulfurization, industrial hydrogen production, hydroxyl synthesis, synthetic methanol or some other one-carbon chemicals. This process is an effective gas purification technology jointly developed by Linde and Lurgi in Germany in the 1950s, usually including raw gas pretreatment, absorption tower desulfurization and decarbonization...

AI Technical Summary

Problems solved by technology

But the process still has the following problems: 1. In the actual production process, if the ammonia content in the raw gas is too high, it is easy to be enriched in the low-temperature methanol washing device, and it will react with carbon dioxide to form ammonium bicarbonate, which will cause pollution to downstream equipment and pipeline valves Blockage, or react with hydrogen sulfide to form ammonium sulfide, which will cause the total sulfur content of the purified gas to be unqualified after being decomposed at the top of the washing tower at high temperature; 2. The lean methanol at the bottom of the regeneration tower is used as the absorption liquid of the absorption tower after pressurization and cooling, and the circulation volume is large 3. The recovery rate of carbon dioxide is not high, only 50%-70mol%. The concentration of hydrogen sulfide in the acid gas after thermal regeneration is low, and the concentration of hydrogen sulfide is completely dependent on the CO in the raw gas. 2 / H 2 S ratio

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