synthesis
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Why is it necessary to control the bleed air, and what components are present in the bleed air? What impact does it have on synthesis?
Due to the low one-way conversion rate in methanol synthesis, the amount of inert components in the synthesis loop increases, which affects the bed temperature; therefore, it is necessary to remove some of these inert components after methanol synthesis. The off-gases typically consist of methane, hydrogen, CO, CO2, N2, and methanol, 1# m353387456
This is mainly due to the issue of methanol synthesis conversion rate. The synthesis of methanol requires a certain hydrogen-to-carbon ratio; too high or too low a ratio will affect the conversion rate of methanol. Therefore, the system must remove excess hydrogen or inert gases. The gases released mainly include CO, CO2, H2, and inert gases.
In the synthesis cycle reaction, inert gases such as N2 and CH4 accumulate and occupy the reaction space. It directly affects the synthesis reaction; by controlling the amount of exhaust gas, it regulates the quantity of inert gas, thereby ensuring the efficiency of the synthesis reaction. Synthesis mainly adjusts the reaction atmosphere of synthesis by controlling H/C. The vent gas volume also indirectly adjusts H/C. Excessive venting carries away too much heat from the synthesis reaction, affecting its efficiency. Too low a amount of vent gas leads to the accumulation of inert gases, which not only prevents an increase in reaction efficiency but also raises the energy consumption per compression cycle
Inert gases such as N2, Ar, CH4, etc.: To prevent the accumulation of these gases in the synthesis loop, it is necessary to remove a portion of them from the circulating gas. These gases to be removed are extracted separately from the high-pressure separator downstream, where the concentration of inert gases is highest.
It is mainly to increase the conversion rate of methanol synthesis
The off-gas should not contain excessive amounts of inert gases such as N2, Ar, and CH4; too much of these inert gases can lead to an increase in synthesis pressure and a decrease in reaction efficiency, which is why they need to be removed
The bleed gas should be the cycle gas, with the same components.
Use purge gas to control the synthesis pressure! The composition of the vent gas is that of the gas emitted from the synthesis process; it contains a high proportion of inert gases, as well as plenty of H2 and inert gases, with little CO and CO2. If no venting occurs, the synthesis pressure will continue to rise, and an excessive amount of inert gases in the syngas will affect the reaction!