Modification of a deethanization plant for enhancing propane and propylene recovery and solving some operational problems

The expected conversion and selectivity of the investigated propane dehydrogenated plant were not achieved due to many causes. One of causes is the inefficient performance of the gas separation and fractionation unit especially the deethanization process. Thus, the primary goal of the present work is to increase the propane and propylene recoveries as well as to overcome some operational problems of this process. In order to accomplish this goal, a change in the process configuration and in some operating conditions was suggested. The simulation tool used in this study to examine the proposed modifications is HYSYS version 8.0 with Peng-Robinson Equation of State (EoS). The validity of simulation is proved by the good correspondence between laboratory and simulation results of the modified plant. The benefits of this study were realized when our proposed modification was applied to the original plant. The results show that the modified plant in operation is capable of recovering 2235 tons/year of propane and propylene more than the original plant. It is also noted that more ethane and ethylene are separated in the modified plant. Furthermore, the modified process provides a solution to some operational problems like increased carryover in the deethanizer rectifying column. The last part of this work considered the investigation of the maximum feed stream CO2 concentration at which the plant can operate properly without freezing.