The problems of hydrogen sulfide and carbon dioxide in low-temperature methanol washing
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Explain why the absorption of hydrogen sulfide in low-temperature methanol washing is relatively stable, while the concentration of carbon dioxide in the outlet gas often fluctuates
This is because the concentration of hydrogen sulfide in the shifted gas remains essentially stable; when the type of coal does not change, there is little variation in the hydrogen sulfide content in the shifted gas. In contrast, the concentrations of CO and CO2 in water gas can vary to some extent, and after the shift reaction, these concentrations change even more significantly than in water gas. In other words, the variation in the CO2 content in the shifted gas is much greater than that in the H2S content. As a result, the absorption of hydrogen sulfide during low-temperature methanol washing is relatively stable, while the CO2 content in the outlet gas often fluctuates.
The reason why H2S is present in low amounts in the first place, and why methanol has a strong ability to absorb H2S
1. Fluctuations in the carbon dioxide component in the feed gas. 2. Hydrogen sulfide has a high solubility in methanol. Therefore, the absorption of hydrogen sulfide at the outlet of the scrubber is relatively stable, while the concentration of carbon dioxide in the outlet gas often fluctuates
1. Since methanol’s solubility for hydrogen sulfide is six times that of CO2, it is removed first in the scrubber tower. 2. Within the same scrubber tower, carbon removal is divided into three stages, and each stage is affected by the heat exchange efficiency; as a result, there are many interferences and fluctuations are likely to occur. 3. The gas itself contains a high level of CO2, and there are many influencing factors in the various stages of the process; even a slight change in temperature within the system can trigger a chain reaction, which leads to fluctuations.