Effect of hydrogen-to-carbon ratio
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If the circulation rate is increased, will the hydrogen-to-carbon ratio increase or decrease, and how does it change?
It increases because an increase in the circulation rate leads to a rise in the proportion of inert gases, thereby reducing the amounts of the active components CO and CO2. Hydrogen levels also decrease. Overall, however, the hydrogen-to-carbon ratio increases
In my opinion, the hydrogen-to-carbon ratio should remain at its previous level; it can only be increased slightly within certain limits, depending on the actual conditions. If the circulation rate increases, that means more load is applied, and the amount of effective gas produced still remains within a certain proportion. As mentioned earlier, the amount of inert gas increases, but I think the amount of off-gas also increases, so the proportion of inert gas isn’t that high. You can adjust the hydrogen-to-carbon ratio appropriately based on the temperature of the bed layer.
I agree with what was said on the 2nd floor. Since the volume of the feed gas is fixed, increasing the amount of recycle gas undoubtedly reduces the amount of off-gas. The unreacted gases resulting from synthesis are sent back into the recycling system; the concentration of the components useful for methanol synthesis in these unreacted gases is certainly lower than that in the feed gas, as they contain more inert gases. Therefore, it makes sense that an increase in the recycling volume leads to an increase in the amount of inert gases, but the hydrocarbon ratio will not change significantly.
The hydrocarbon ratio remains essentially unchanged; considering that an increase in the circulation rate leads to an increase in system pressure, this results in a decrease in the effective components CO and CO2, while there is a slight increase relative to the hydrogen-to-carbon ratio. I think the amount of exhaust gas decreases when the flow rate is first adjusted, but once it stabilizes, the amount of exhaust gas remains fairly constant.
Components: CO, CO2, H2, N2, CH4, Ar, CH3OH, H2O; Total. Flow rate: Nm3/h – 11902.30, 6690.36, 150277.25, 6045.96, 918.74, 442.85, 116.71, 2.02; Total flow: 20163.27. Composition (%V): 6.28, 3.53, 79.29, 3.19, 4.79, 2.31, 0.61, 0.01; 100% in total
The main reaction of methanol is CO + 2H2 = CH3OH; this is a reversible reaction. Generally, the hydrocarbon ratio is (H2/CO2)/(CO/CO2) = S. According to this reaction, this ratio should be greater than 2 in order to favor the formation of methanol. Additionally, it is an exothermic reaction, and the release of heat facilitates methanol synthesis. However, there is now a new liquid-phase methanol synthesis method that allows for the production of methanol in a CO-rich environment, by taking advantage of rapid heat removal. The recycle ratio of methanol, when within an appropriate range, is beneficial for improving methanol synthesis.
Whether the hydrogen-to-carbon ratio increases or decreases after the increase in the circulation gas volume depends on the change in the temperature of the catalyst bed. When the circulation volume increases, there is no significant change in the effective components of the circulation gas; only the proportion of inert gases may increase as the circulation volume rises, but this does not affect the gas composition entering the synthesis tower.
When the temperature in the synthesis tower remains constant, increasing the circulation rate raises the hydrogen-to-carbon ratio; as a result, the synthesis rate increases, production rises, and the amount of hydrogen in the loop also increases.
I agree with what was said on the third floor; it is necessary to consider the changes in conversion rate and the amount of vent gas following an increase in the circulation volume. It can’t be simply said whether it increases or decreases.
The circulation rate is driven by the recycle gas compressor; as the circulation rate increases, the power consumption of the compressor rises. The relationship between these two factors is taken into account during process design to determine a reasonable value. In production, an increase in the circulation rate leads to a higher methanol yield, but it also results in an increase in the amount of inert gases, while the amounts of the active components CO and CO2 decrease. This increases the hydrogen-to-carbon ratio. However, the circulation rate cannot be too high, as it is necessary to consider power consumption and the thermal balance of the synthesis process, as well as the type of synthesis equipment, in order to prevent excessive reactions and the accumulation of heat that could damage the catalyst
I support the view from the second floor: as the hydrogen-to-carbon ratio increases and the circulation volume rises, the proportion of inert gases also increases, while the amounts of the active components CO and CO2 decrease. Hydrogen levels also drop.