Should the oil at the bottom of the catalytic absorber go to the cooler or to the desorber?
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Our unit sends the oil at the bottom of the absorption tower together with the compressed rich gas to the cooler, from where they proceed to the gas-liquid separation tank; the liquid then goes to the stripping tower. From the perspective of comprehensive energy utilization, it would be better to feed the oil at the bottom of the absorption tower directly into the stripping tower, thereby avoiding the need to cool it first and then heat it again. I would like to ask fellow sailors what type of process is used in your respective devices, and what are the advantages and disadvantages of the two processes mentioned above?
It is reasonable to cool the material before feeding it into the desorption tower, as the desorption tower only has a stripping section; the composition of the vapor at the top of the tower is directly affected by the feed temperature. If the feed temperature at the tower top is too high, it will result in an increased circulation rate in the absorption and stabilization system, leading to higher energy consumption
In typical systems, the oil at the bottom of the absorber and the compressed rich gas are both sent to a cooler before entering the gas-liquid separation tank; this prevents the rich gas from containing liquid, as the heavier hydrocarbons liquefy after cooling. The second process you mentioned is more difficult to control!
The temperature at the bottom of the absorption tower is generally between 50 and 55 degrees, while the temperature at the top of the desorption tower is also around 50 degrees. Feeding the oil from the bottom of the absorption tower directly into the desorption tower has little impact on the temperature at the top of that tower. After being cooled, the oil at the bottom of the absorption tower has a temperature of around 40 degrees; so, does it require more energy to feed oil at 40 degrees into the desorption tower or oil at 50 degrees? Although the temperature of the analyzed gas is a bit higher and more absorbent is required, I believe the overall energy consumption will be lower in this way. I’m not sure if my analysis is correct.