Recovery and purification of ethylene from direct hydration ethanol vent gas streams

Claim 2

A process for recovery of ethylene from vent gases obtained as a by-product of a catalytic ethylene hydration process and having ethylene present therein as a major component, which process comprises: collecting high pressure vent gas containing about 85 percent to 95 percent ethylene and reducing the pressure thereof collecting low pressure vent gas containing a major amount of ethylene therein and elevating the pressure thereof to the value at which the high pressure vent gas has been reduced combining the two vent gases with one another passing the combined vent gases so obtained from the ethylene hydration process to a drying zone drying said combined vent gas in said drying zone to remove substantially all of the moisture present therefrom cooling the dried vent gas passing the cooled dried vent gas to a fractionation zone fractionating all of the dry cooled vent gas to produce an ethylene fraction passing the ethylene taken as a side cut from said fractionation zone in heat exchange relationship with the vent gases to cool same and thereafter passing said ethylene fraction to an ethylene product line.

Claim 3

A process as in claim 3 wherein the reduced pressure of the high-pressure vent gas is 350 PSIG, the pressure of the low-pressure vent gas is 350 PSIG subsequent to pressurization; the pressure in the fractionation recovery tower is 290 PSIG and the temperature gradient in the fractionation tower is from 260*F. to -19*F. and the ethylene is removed from the fractionation recovery tower as a side cut at a temperature of -17*F.

Claim 4

A process as in claim 4 wherein the ethylene-rich liquid which is condensed from the fractionation tower overhead is condensed at a temperature of -20*F. and a pressure of 290 PSIG.