Methanol synthesis system pressure
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I would like to ask everyone: What factors influence the pressure in a methanol synthesis system? The designed pressure for this system is 5.2 MPa, while it is currently operating at 4.8 MPa; I hope to reach the designed value. A reciprocating compressor is used for compressing the fresh gas, and I intend to increase the pressure of the fresh gas by raising the power of this compressor, thereby increasing the system pressure. However, the equipment indicates that the pressure is related to the pressure within the synthesis system itself – if the system pressure doesn’t increase, then the outlet pressure of the compressor cannot be raised either. I would like to know what factors affect the system pressure. Is it possible to increase the system pressure by raising the pressure of the fresh gas, without adjusting the vent gas flow?
The circuit can be closed to reduce venting and increase pressure
System pressure is related to the following factors! Operating temperature, inert gas content, opening degree of system bypasses, air injection volume of the circulator, catalyst activity level, amount of fresh gas added, and volume of vent gas!
The pressure drop or differential pressure in the synthesis tower (or synthesis system) serves as an indicator of the one-pass conversion rate of CO; the greater the differential pressure, the higher the one-pass conversion rate of CO. An excessive differential pressure can lead to increased resistance in the catalysts and pipelines, or to an excessively high conversion rate of syngas. If the first issue is at fault, it is necessary to identify and address the cause promptly, with load adjustments being made in very small increments. If the second issue is responsible, it indicates that the hydrogen-to-carbon ratio is too low, which may result in an increase in methanol production or an increase in ether and lipid by-products over a short period. In either case, this leads to elevated temperatures at the active sites of the catalysts, causing them to age or even sinter. The solution is to increase the space velocity and the recycling ratio, that is, to gradually reduce the amount of off-gas released. As a result, the hydrogen-to-carbon ratio increases in the synthesis system, the one-pass conversion rate decreases, and the pressure rises gradually, but the overall conversion rate increases. If conversion rate is not a concern and the goal is merely to increase pressure, there are two methods: 1) Increase the hydrogen-to-carbon ratio by temporarily reducing the amount of gas released, thereby raising the content of inert gases in the system; 2) Reduce the catalyst’s activity by lowering the pressure in the steam drum, which in turn lowers the catalyst temperature. Increasing the pressure of the fresh gas is beneficial for the inlet pressure of the synthesis tower, but the effect is limited. In terms of energy efficiency, using a circulator is the more energy-saving and convenient approach
It is normal for the new catalyst to exhibit good initial activity, a high conversion rate, and low system pressure.