Control of the bottom temperature in the low-temperature methanol washing heat exchanger
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Our low-mercury washing system operates on a 5-tower process; the temperature of the feed gas is 40 degrees, while the temperature of the purified gas is -64.1 degrees at a pressure of 5.5 MPAG. Some people say that it’s not necessary to control the temperature at the bottom of the heat towers, as what’s important is to maintain proper control over the pressure at the top and the concentration of acidic gases； But some people say that control is necessary, as it is at this temperature that the acidic gases in methanol can be removed. If the regeneration is not thorough, it will affect the absorption of sulfides by the absorption system, which will inevitably lead to trace amounts of such substances. Both viewpoints seem reasonable; please share your opinions, fellow sailors!
It’s not right to consider the two issues in isolation; the latter view is correct. Do you know what the consequences would be if even a small amount exceeds the limit? These five towers form a single unit, and the concentration and pressure of acidic gases at the top are determined by the temperature at the bottom. To understand these issues, the key is to figure out the essence of low-temperature methanol washing, as well as the relationship between the various towers and the subsequent processing stages.
It seems like the person upstairs is very knowledgeable about low-temperature cleaning. Could we exchange some ideas? My QQ number is: 394887841
The heat tower is a single unit without a distinct top or bottom; controlling the pressure at the top and the concentration of acidic gases relies on proper control of the temperature at the bottom. In my opinion, for such a regeneration tower, temperature is the key factor – even if the temperature at the bottom is well controlled, it’s not sufficient if the temperature at the top is not properly managed
In my opinion, the temperature at the bottom of the thermal regeneration tower is influenced by the pressure at that point (i.e., the pressure at the top of the tower plus the pressure difference). The higher the pressure, the higher the temperature – this is true as long as there is sufficient steam supply to the reboiler. Therefore, in theory, it shouldn’t matter as long as the steam supply is adequate. However, low pressure will lead to an increase in the amount of steam at the top of the tower, thereby increasing the load on the condenser at the top of the tower
The low-temperature methanol washing process uses a five-tower configuration, divided into a cold zone and a hot zone. The temperature control of the hot towers is very strict; in particular, the temperature at the bottom of the towers should be maintained between 99 and 102 degrees. If the temperature is too low, it affects the regeneration process, while if it is too high, there is significant waste of methanol. The temperatures at the bottom and middle of the tower must be controlled based on the reboiler at the bottom of the tower.