Comparison of pressure swing adsorption and membrane separation for off-gas treatment
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In the methanol synthesis process, in order to adjust the hydrogen-to-carbon ratio, a portion of the gas is sent to a hydrogen recovery unit; the gas after hydrogen recovery is known as vent gas, and components such as carbon dioxide and methane increase in this vent gas, which is then discharged as vent gas. Personally, I think pressure swing adsorption is a more reasonable option, as it results in less loss of carbon monoxide; however, the investment required is higher than that for membrane recovery. I would appreciate some advice on what might be a better choice.
Since the requirements for the gases used in synthesis are not strict, a small amount of gases such as CH4 and CO2 can be present. Pressure swing adsorption is suitable for extracting high-purity CO; moreover, the CO content in the off-gases is already low and their total volume is small, so pressure swing adsorption can be used to recover hydrogen – but this is like using a sledgehammer to crack a nut.
Agree with the above view; there’s no need to use membrane separation
I still think membrane separation is more cost-effective.
I agree with what was said on the second floor. Additionally, since the operating pressure in pressure swing adsorption is low, it is necessary to reduce the pressure before the material enters the device; after adsorption, the pressure must be increased again to send the material back into the system. This results in excessive energy loss, which is not worth it. .
If it is diol, membrane separation is a better option. A methanol process with conversion does not require hydrogen extraction, as hydrogen is in excess.
After the synthesis reaction, the concentration of useful gases in the gas stream is already very low. Apart from H2, which can be extracted, there aren’t many other gas components that can be utilized. Using pressure swing adsorption would require significant investment and result in high costs; in my opinion, it’s not worth it – membrane separation is a more cost-effective option
The concentrations of methane and carbon dioxide in the off-gas are not high, and they are related to the properties of the methanol synthesis catalyst as well as the control of reaction conditions; hydrogen and carbon monoxide make up the larger portion of the off-gas. If membrane recovery technology is used, the hydrogen purity is low; to maintain the hydrogen-to-carbon ratio in the reaction system, more vent gas is required.
If the requirements for raw material H are not high, there is no need to use pressure swing adsorption; membrane separation will suffice, and membrane separation can definitely be used in this case. If the process requires a H content of over 98.5%, pressure swing adsorption is still used, as it offers high precision.
The levels of methane and carbon dioxide in the off-gas are not high, so membrane separation will suffice.