The most common technology is to use a reboiled absorber operating at about 200 to 300 psig (depending on the desired percentage recovery of LPG). The lean oil is a recycled stream of C5+ from the distillation towers downstream of the reboiled absorber.
Any good refinery simulator program should include a reboiled absorber.
You could also contact any of the major refinery engineering and construction firms and ask them for help.
Milton Beychok
(Contact me at www.air-dispersion.com)
Thanks for all your replis. Actually, i want to calculate whether recovering LPG is beneficial or not. I've tried to search the processes using google. Many processes I found were not for refinery application but for Nat Gas.
The reboiled absorber that I mentioned in my previuos reply is exactly what most refineries use in their gas recovery units. The reboiled absorbers in a refinery are usually designed for 90 to 95 percent recovery of propane and 98-99+ percent of butane. Such units are so widely used in refinery gas recovery units that they must indeed be economically justified.
Milton Beychok
(Contact me at www.air-dispersion.com)
I don't think that with a reboiled absorber alone you can win back the LPG fraction in a off gas stream. I think you need also a compression step to first get the LPG fraction in liquid phase first. THen you can use a distillation column to separate various fractions.
To verify wether it is economical or not, you should determine how many piece of equipment you need, estimate their sizes, and finally the total installed cost. You of course also know the price of the LPG. if the difference is positive, then it is economical to win back the LPG is negative, it is not.
