Regulation of the catalyst bed temperature
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Dear sea friends: In the production of methanol from coke oven gas, the amount of gas fed into the synthesis tower can be controlled by adjusting the circulation volume, and the temperature of the catalyst bed can also be adjusted by regulating the pressure in the drum. What is the exact relationship between these factors?
As the circulation gas volume increases, more heat is carried away, causing the temperature of the catalyst bed to drop. (If the circulation gas volume is too low, the temperature of the catalyst bed will also drop.) As the pressure in the drum increases and the temperature difference decreases, the temperature of the catalyst bed rises.
What is the structural design of the synthesis tower? Overall, the volume of circulating gas is large, which results in a significant amount of heat being carried away. In the case of a shell-and-tube design, the temperature of the synthesis tower is proportional to the pressure in the drum.
In a synthesis tower with a shell-and-tube structure, for every 0.1 Mpa change in the drum pressure, the bed temperature changes by approximately 1.5°C. If the circulation rate is too high, too much heat is removed from the tower, and the bed temperature cannot be maintained ； If it is too small, heat cannot be removed adequately, leading to overheating. Generally, the bed temperature is controlled based on the drum pressure, which is relatively intuitive and the changes are also quite noticeable.
In a shell-and-tube type synthesis tower, the volume of circulating gas remains essentially constant; the reaction heat can only be removed by adjusting the pressure in the drum
As the volume of circulating gas increases, more heat is carried away, causing the temperature of the catalyst bed to drop. The pressure in the steam drum decreases as well, and the temperature of the steam drops accordingly; the increase in temperature difference leads to a further decrease in the temperature of the catalyst bed.
The inlet temperature of the synthesis tower is adjusted by the amount of circulating gas, while the catalyst bed temperature is adjusted by the pressure in the steam drum
The temperature of the synthesis tower is mainly regulated by the steam drum. Relatively speaking, an increased circulation gas volume and a higher space velocity result in more heat being carried away, so the temperature drop is not significant; only when the circulation gas volume is excessively high is it possible for the temperature to drop. The drum pressure is directly proportional to the synthesis outlet temperature; for every 0.1 Mpa increase in drum pressure, the synthesis temperature increases by 1.5°C (with the composition of the syngas remaining unchanged).
First and foremost, it should be clear that adjusting the circulation rate of the synthesis system is not intended to regulate the temperature of the catalyst bed; rather, the goal is to achieve the highest possible overall conversion rate of carbon monoxide and carbon dioxide. The regulation of the catalyst bed temperature relies primarily on the pressure in the steam drum.
The circulation rate is not a means of regulating the catalyst bed temperature; the catalyst bed temperature is primarily controlled by adjusting the pressure in the steam drum. Increasing the pressure in the steam drum reduces the amount of heat carried away by the steam, thereby raising the bed temperature.
Q=Km△t; changing the circulation rate affects m, while changing the drum pressure affects △t – both of these factors influence temperature regulation. The change in one of them is proportional to Q, whereas the changes in both are related by a multiplicative relationship.