Method for Processing Off Gas

Abstract

A method for recovering C 2 and higher weight hydrocarbons, or alternatively C 3 and higher weight hydrocarbons, from off gas, such as refinery off gas, wherein the method avoids the need to significantly compress contaminated off gas in most cases, and is robust in response to pressure and temperature variations in the off gas feed.

1 . A method for processing an off gas inlet stream to recover C 2  and higher weight hydrocarbons, comprising the steps of
 cooling said off gas inlet stream to form a partially condensed hydrocarbon feed,   separating a condensed portion from said partially condensed hydrocarbon feed, and   distilling said condensed portion to recover C 2  and higher weight hydrocarbons as product.   
     
     
         2 . The method of  claim 1 , wherein the step of cooling said off gas inlet stream to form a partially condensed hydrocarbon feed additionally comprises the step of using a portion of said product as part or all of a refrigerant used to provide said cooling. 
     
     
         3 . The method of  claim 1 , wherein the step of cooling said off gas inlet stream to form a partially condensed hydrocarbon feed additionally comprises the step of using a portion of said off gas inlet stream as part or all of a refrigerant used to provide said cooling. 
     
     
         4 . The method of  claim 1 , wherein the step of cooling said off gas inlet stream to form a partially condensed hydrocarbon feed additionally comprises the step of using a closed loop refrigeration system to provide said cooling. 
     
     
         5 . The method of  claim 1 , additionally comprising the steps of
 recovering vapor from said step of distilling said condensed portion of said partially condensed hydrocarbon feed to recover C 2  and higher weight hydrocarbons as product,   cooling said vapor to form reflux,   separating a vapor portion from said reflux, and   using part of said vapor portion of said reflux as part or all of a refrigerant used to provide said cooling.   
     
     
         6 . The method of  claim 5 , additionally comprising the step of
 distilling a liquid portion of said reflux to recover C 2  and higher weight hydrocarbons as product.   
     
     
         7 . The method of  claim 1 , additionally comprising the steps of
 separating a vapor portion from said partially condensed hydrocarbon feed,   compressing said vapor portion, and   distilling said compressed vapor portion to recover C 2  and higher weight hydrocarbons as product.   
     
     
         8 . The method of  claim 1 , additionally comprising the steps of
 separating a vapor portion from said partially condensed hydrocarbon feed,   compressing said vapor portion,   cooling said compressed vapor portion to partially condense said compressed vapor portion,   separating a liquid portion from said partially condensed vapor portion, and   distilling said separated liquid portion to recover C 2  and higher weight hydrocarbons as product.   
     
     
         9 . A method for processing an off gas inlet stream to recover C 3  and higher weight hydrocarbons, comprising the steps of
 cooling said off gas inlet stream to form a partially condensed hydrocarbon feed,   separating a condensed portion from said partially condensed hydrocarbon feed, and   distilling said condensed portion to recover C 3  and higher weight hydrocarbons as product.   
     
     
         10 . The method of  claim 9 , wherein the step of cooling said off gas inlet stream to form a partially condensed hydrocarbon feed additionally comprises the step of using a portion of said product as part or all of a refrigerant used to provide said cooling. 
     
     
         11 . The method of  claim 9 , wherein the step of cooling said off gas inlet stream to form a partially condensed hydrocarbon feed additionally comprises the step of using a portion of said off gas inlet stream as part or all of a refrigerant used to provide said cooling. 
     
     
         12 . The method of  claim 9 , wherein the step of cooling said off gas inlet stream to form a partially condensed hydrocarbon feed additionally comprises the step of using a closed loop refrigeration system to provide said cooling. 
     
     
         13 . The method of  claim 9 , additionally comprising the steps of
 recovering vapor from said step of distilling said condensed portion of said partially condensed hydrocarbon feed to recover C 3  and higher weight hydrocarbons as product,   cooling said vapor to form reflux,   separating a vapor portion from said reflux, and   using part of said vapor portion of said reflux as part or all of a refrigerant used to provide said cooling.   
     
     
         14 . The method of  claim 13 , additionally comprising the step of
 distilling a liquid portion of said reflux to recover C 3  and higher weight hydrocarbons as product.   
     
     
         15 . The method of  claim 9 , additionally comprising the steps of
 separating a vapor portion from said partially condensed hydrocarbon feed,   compressing said vapor portion, and   distilling said compressed vapor portion to recover C 3  and higher weight hydrocarbons as product.   
     
     
         16 . The method of  claim 9 , additionally comprising the steps of
 separating a vapor portion from said partially condensed hydrocarbon feed,   compressing said vapor portion,   cooling said compressed vapor portion to partially condense said compressed vapor portion,   separating a liquid portion from said partially condensed vapor portion, and   distilling said separated liquid portion to recover C 3  and higher weight hydrocarbons as product.