When the reactor effluent comes out the reactor, you are going to get EO as your product, a large amount of unreacted ethylene, some CO2 and water as side reaction products, and inert Argon. The reason for the large amount of unreacted ethylene is that the reaction needs to be controlled in a low conversion+high selectivity fashion so that side reactions are limited. The effluent is then send to a absorber column.
In the absorber column, water is going to be sent in from the top of the column at a large flowrate. Water is used as the absorbent to absorb the gas EO into liquid water, which would exit from the bottom of the column. The unabsorbed gas such as CO2, Aron, and Ethylene are going to exit from the top of the column, in which the CO2 and Argon are going to be purged from the system. The ethylene will be recycled back so mix with the fresh feed, because ethylene is very expensive and it’s best if none of it gets wasted in the process. Since EO and water provides easy absorption, 5 trays are used. The absorber discharges at 12 bar and 25C for the gas on top, 48C for the liquid process water and EO at the bottom. The bottom stream containing EO will enter the distillation column so that EO and water will get separated.
The Txy diagram shows easy separation between water and EO at 12 bar.
The distillation column has 9 stages and the feed stream comes in at stage 4. The column has a condenser at 85.8C with a reflux ratio of 13.8. A reboiler is also used to vaporize the bottom liquid to the top which is then condensed by the condenser. The EO effluent coming out of the column is in gas phase with a purity of 99.5% Ethylene Oxide. The process water exit stream is being divided into two streams. One stream get recycled back to the abosrber to use as absrobent, while the other stream exits out of the system to avoid accumulations of process water.