I would appreciate some guidance on the issue of methanol synthesis
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I would appreciate some guidance on the relationship between air velocity and volumetric flow rate – is it a perfectly proportional relationship? I always get confused about the effect of air velocity on the one-way conversion rate and the overall conversion rate; maybe I’m a bit silly!
With a high air velocity, the catalyst will not experience local overheating； A large number of empty cycles results in a high overall carbon conversion rate ； The one-way conversion rate depends only on the system’s CO2 content and the catalyst itself. Some personal understanding
With a high air velocity, the gas has longer contact time with the catalyst, resulting in good synthesis reactions and a high one-pass conversion rate. A large circulation volume enables effective removal of the reaction heat from the synthesis tower
Air velocity refers to the ratio of the gas flowing into the tower to the catalyst per unit volume, that is, the amount of gas flowing through a unit volume of catalyst per unit time； The inlet gas refers to the sum of the synthetic fresh gas and the recycled gas ； Fresh gas refers to the synthetic feed gas supplied from the upstream purification unit ； Circulating gas refers to the gas entering the tower, minus the amount of gas used to produce crude alcohol, minus the amount of gas released from the methanol separator (such as vent gas and fuel gas for various processes). It can be seen that the air velocity is not entirely proportional to the circulation gas volume. Within the design space velocity range of the catalyst, as the space velocity increases, the single-pass conversion rate tends to decrease, while the overall conversion rate increases.
I largely agree with the comments above; I would just like to add one thing: the one-way conversion rate decreases as the space velocity increases, and the overall conversion rate should be discussed with reference to the optimal overall conversion rate. As for the circulation gas volume, generally the higher the circulation volume, the higher the content of inert gases in the reaction gas, and thus the lower the one-pass conversion rate at the same space velocity. Therefore, the greater the amount of recycled gas, the lower the one-pass conversion rate will inevitably be; however, the optimal total conversion rate should be determined based on actual on-site data, and the amount of recycled gas should then be adjusted accordingly!