Removing Contaminants from Natural Gas

Abstract

A process is described for removing contaminants from a natural gas feed stream including water. The process includes the steps of cooling the natural gas feed stream in a first vessel to a first operating temperature at which hydrates are formed, heating the hydrates to a temperature that is above the first operating temperature by introducing a warm liquid to the first vessel so as to melt the hydrates and liberate a dehydrated gas and a water-containing liquid, and removing from the first vessel a stream of dehydrated gas.

1 . A process for removing contaminants from a natural gas feed stream including water, which process comprises the steps of:
 cooling the natural gas feed stream in a first vessel to a first operating temperature at which hydrates are formed; and,   heating the hydrates to a temperature that is above the first operating temperature by introducing a warm liquid to the first vessel so as to melt the hydrates and liberate a dehydrated gas and a water-containing liquid; and,   removing from the first vessel a stream of dehydrated gas.   
     
     
         2 . The process of  claim 1 , wherein the warm liquid is a natural gas liquid. 
     
     
         3 . The process of  claim 2 , further comprising the step of separating natural gas liquids from the natural gas feed stream upstream of the first vessel and using the separated natural gas liquid as the warm liquid introduced to the first vessel to melt the hydrates. 
     
     
         4 . The process of  claim 1 , further comprising the step of removing the water-containing liquid from the first vessel and recovering natural gas liquids from the water-containing liquid. 
     
     
         5 . The process of  claim 4 , wherein the natural gas liquids recovered from the water-containing liquid are heated and recycled as the warm liquid introduced to the first vessel to melt the hydrates. 
     
     
         6 . The process of  claim 1 , wherein the step of cooling the natural gas feed stream in a first vessel to a first operating temperature comprises introducing the natural gas feed stream into the first vessel at a temperature that is below the first operating temperature. 
     
     
         7 . The process of  claim 1 , wherein the step of cooling the natural gas feed stream comprises expanding the natural gas feed stream through an expansion device. 
     
     
         8 . The process of  claim 1 , wherein the step of cooling the natural gas feed stream in a first vessel to a first operating temperature comprises introducing a sub-cooled liquid into the first vessel in addition to introducing the natural gas feed stream to the first vessel, the sub-cooled liquid being introduced at a temperature that is below the first operating temperature. 
     
     
         9 . The process of  claim 8 , wherein the first vessel includes an inlet for the natural gas feed stream and the sub-cooled liquid is introduced through a sub-cooled liquid inlet located in the first vessel above the inlet for the natural gas feed stream. 
     
     
         10 . The process of  claim 8 , wherein the sub-cooled liquid is sprayed into the first vessel. 
     
     
         11 . The process of  claim 8 , wherein the sub-cooled liquid is a natural gas liquid. 
     
     
         12 . The process of  claim 11 , further comprising the step of cooling the dehydrated gas removed from the first vessel to form a two-phase mixture of gas and condensate at a temperature higher than −56° C. and separating condensate from the two-phase mixture in a second flash tank. 
     
     
         13 . The process of  claim 12 , further comprising the step of recycling the separated condensate from the second flash tank as the sub-cooled liquid. 
     
     
         14 . The process of  claim 1 , wherein the natural gas feed stream further includes sour gas species, and the process further comprises the step of sweetening the stream of dehydrated gas removed from the first vessel by removal of the sour gas species.