The hydrogen content in the inlet gas of the methanol synthesis tower is very high
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The hydrogen-to-carbon ratio of the feed gas is required to be around 2.1; then why is the hydrogen content in the inlet gas of the methanol synthesis tower so high?
Hydrogen is initially present in excess; after methanol synthesis, compared to CO which is already present in small quantities, the percentage of unreacted hydrogen increases significantly, and this percentage becomes even higher due to the accumulation in the recycle gas. This is normal; the hydrogen-to-carbon ratio of the syngas fed into the tower is generally 4 to 8
The reaction equation for synthesizing methanol is: CO + H2 = CH3OH. This is a reversible reaction, and an excess of H2 favors the reaction proceeding in the direction of forming CH3OH; therefore, an excess of H2 is used! Generally, a hydrogen-to-carbon ratio of 4 to 5 is considered the most suitable; of course, this can vary from plant to plant depending on actual conditions, and it may be higher or lower!
Hello! The reason for maintaining such a high hydrogen-to-carbon ratio is that although the diffusion rate of H2 is greater than that of CO, its adsorption rate at the catalyst’s active sites is much lower than that of CO. To achieve a H2/CO ratio of 2 at the adsorbed phase interface, an excess of H2 is required in the synthesis system; this excess is necessary to ensure that the H2/CO ratio at the interface equals 2, which corresponds to the H2/CO ratio in the actual reaction. Experiments have shown that only when the H2/CO ratio is greater than 3 can a higher yield of methanol be obtained. The specific values for H2/CO should ideally be determined through practical operation in different methanol plants, in order to achieve the optimal production capacity of methanol. On the other hand, excess H2 can also suppress the occurrence of side reactions.
The 4th floor is good; in theory, everything is correct, but I’m not sure about the actual situation
How high is the hydrogen content in the inlet gas of the methanol synthesis tower? It is desirable for the hydrogen-to-carbon ratio in a single tower to be greater than 5, while the requirement for the fresh gas is that this ratio be greater than 2. Hydrogen-based high-syngas has good thermal conductivity, few impurities, and low cyclic pneumatic consumption.