Over-temperature issue in one absorption tower
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What are the reasons for the high temperature at point 3 of the absorption tower, and how should it be adjusted in terms of operation?
The temperature at three points in the absorption tower can theoretically be regarded as the boiling point of ammonia water at that pressure; the lower the concentration of ammonia water, the higher its boiling point. Therefore, reducing this temperature serves two purposes: ensuring the appropriate concentration of ammonia water in the second stage and controlling the proper amount of ammonia used for reflux. At the same time, in the bubbling section and the cleaning section of a absorption tower, the absorption efficiency is not sufficient, which results in a small amount of CO2 escaping upward; the temperature at this point also increases.
There are two main reasons for the overheating in the fine washing stage: first, the absorption efficiency in the bubbling stage is poor, which leads to CO2 rising upward and causing overheating. The second reason is related to the fine washing section itself: changes in the amount or composition of the absorbent liquid in this section lead to poor absorption in the bubbling section, and the upward movement of CO2 causes overheating. The best way to deal with it is to dilute it with water.
High CO2 levels cause the temperature to rise by 3 degrees; apart from adding water, should the ammonia level be adjusted to reduce the temperature and absorb CO2?
Let me talk about this: The temperature at point 3 in the first absorption tower is the temperature of the gas phase above the liquid level in the bubbling zone; as the liquid level in this tower rises, the temperature at point 3 increases as well. But when the liquid level is low, CO2 in the gas phase reacts with ammonia water, and the temperature also rises ； When the gas distributor leaks, CO2 gas escapes into the bubbling section where it reacts; as a result, the temperature at point 2 rises rapidly, forcing the absorption tower to be shut down for maintenance.
In addition to the situations described by the residents on the upper floors, there is another scenario: when the liquid level in the absorption tower is too high, the methanol-ammonia solution rises to the tray where the temperature at point 3 is measured. At this point, the temperature displayed at point 3 corresponds to the temperature of the methanol-ammonia solution, resulting in an increase in temperature.