Q & A > Question Details
In a sponge absorber why is absorption of LPG by lean oil (naphtha) an exothermic reaction?
21/04/2021 A: Priyank Varghese, Renewable Energy Group, pri_yank@yahoo.com
In a sponge absorber, the LPG (rich gas) stream enters the bottom of the absorber and flows upwards, contacting the countercurrent naphtha (lean oil) stream. The lean oil preferentially absorbs the heavier components from the rich gas stream. As components of the rich gas are absorbed by the lean oil, the temperature of the gas and oil phases will increase due to heat of absorption. The heat released is proportional to the amount of gas absorbed.

20/04/2021 A: Jake Gotham, InSite Technical Services, jake.gotham@insitetechnical.com
The LPG vapour is condensed into the naphtha. The exotherm you observe is the latent heat from the phase change (vapour -> liquid). Just as you need to put heat into something to boil it, when something condenses heat is released.