Methanol Weekly Topic What is the optimal reaction pressure for methanol production? Why? 2015.12.21--12.27

For low-pressure synthesis, 50 kilograms is generally the optimal amount; from both chemical equilibrium and kinetic perspective, increasing the pressure accelerates the reaction. However, increasing the pressure also facilitates the occurrence of side reactions; when these reactions take place, the degree of volume contraction of the gases before and after the reaction is more pronounced than in the methanol synthesis reaction. Side reactions increase, and paraffins and ethers may be formed, covering the surface of the catalyst and blocking its micropores and voids, thereby reducing the catalyst’s activity. Take measures: maintain stable pressure and minimize fluctuations in operating pressure as much as possible. Under a constant production load, in a synthesis system, factors such as the temperature of the synthesis catalyst layer (controlled by adjusting the pressure in the steam drum), the gas composition (controlled by the amount of gas vented), the space velocity, and the condensation temperature can all cause changes in the system pressure. It is necessary to make accurate judgments and make timely adjustments during operation to ensure that the process operates within the specified parameters. When the synthesis conditions change and the system pressure increases, the production load can be appropriately reduced ； Control the pressure of the synthesis system to prevent overpressure and ensure normal production. When reducing the system capacity, it is necessary to adjust the circulation rate promptly to keep all control temperature points in the specified range. Pressure adjustment must be carried out slowly to ensure that the temperature of the reactor bed remains normal. The general pressure rise and fall rate can be controlled at ≤0.4 MPa/min. However, the synthesis pressure depends on the pressure of the previous system and the pressure of the by-product steam; it is not necessary to keep it at 50 kilograms. It is also related to the catalyst’s service life as well as the amount of inert gas emitted, so a comprehensive consideration is required.

We are at 5 MPA; high pressure is favorable for the forward reaction

The methanol reaction is a reaction with a decrease in the number of molecules, and increasing pressure is favorable for the forward reaction. If the pressure increases, the partial pressure of the components rises, and as a result, the production intensity of the catalyst also increases. For the operation of the synthesis tower, pressure control is adjusted appropriately according to the different catalytic activities at various stages of the catalyst’s usage; at the beginning of catalyst use, when its activity is high, the operating pressure can be lower ； As the catalyst ages, its activity decreases, and higher operating pressures are often used to maintain a certain level of production intensity. In summary, the selection of operating pressure must be determined based on specific factors such as catalyst activity, gas composition, reactor thermal balance, and system energy consumption.

It is generally believed that pressures ranging from 3.5 to 10 MPa are suitable. In terms of the equilibrium constant, a higher equilibrium constant requires a higher effective gas partial pressure; this means that at low pressures it is necessary to ensure high gas purity. Conversely, at high pressures, a certain amount of impurity gases can be allowed to be present. For low-pressure synthesis, 5 to 6 megapascals is often chosen as the pressure for synthesis; this is determined by the compatibility between the compressor and the manufacturing process. For large-scale synthesis, a pressure of around 8.5 megapascals is usually chosen, as this level balances investment costs with operational efficiency.

It is generally believed that pressures ranging from 3.5 to 10 MPa are suitable. In terms of the equilibrium constant, a higher equilibrium constant requires a higher effective gas partial pressure; this means that at low pressures it is necessary to ensure high gas purity. Conversely, at high pressures, a certain amount of impurity gases can be allowed to be present. For low-pressure synthesis, 5 to 6 megapascals is often chosen as the pressure for synthesis; this is determined by the compatibility between the compressor and the manufacturing process. For large-scale synthesis, a pressure of around 8.5 megapascals is usually chosen, as this level balances investment costs with operational efficiency.

Within the design pressure range of the upstream gasifier, the higher the pressure, the better.

5Mpa is commonly used by ordinary users, as it offers good cost-effectiveness. Increasing pressure is beneficial for positive responses, but a negative assessment is needed to achieve better outcomes.

The control of this pressure generally relies on the data provided by the catalyst manufacturer as well as the design parameters of the process. In practice, it is necessary to find the optimal value through experimentation. For example, in our plant, the catalyst is now at the end of its useful life; the synthesis load is only a little over 60%. Although the designed process pressure is 8.3 Mpa, a pressure of 6.1 Mpa is sufficient under these conditions – this results in relatively fewer by-products and a higher production rate. Both higher and lower pressures lead to a decrease in production volume.