Process for removing a gaseous contaminant from a contaminated gas stream

Abstract

The invention provides a process for removing one or more gaseous contaminants from a contaminated feed gas stream, the process comprising 1) providing the contaminated feed gas stream, 2) cooling the contaminated feed gas stream to a temperature at which liquid contaminant is formed as well as a contaminant depleted gaseous phase, and 3) separating the two phases by introducing them into a gas/liquid separator vessel, comprising a gas/liquid inlet at an intermediate level, a liquid outlet arranged below the gas/liquid inlet and a gas outlet arranged above the gas/liquid inlet, in which vessel a normally horizontal coalescer is present above the gas/liquid inlet and over the whole cross-section of the vessel and in which vessel a centrifugal liquid separator is arranged above the coalescer and over the whole cross-section of the vessel, the liquid separator comprising one or more swirl tubes. The contaminated gas stream can be a methane-containing gas stream, especially a natural gas stream, or a gas stream from a gasification or combustion process. The invention further provides a device for carrying out the process as well as the purified gas stream.

1 . A process for removing one or more gaseous contaminants from a contaminated feed gas stream, the process comprising 1) providing the contaminated feed gas stream, 2) cooling the contaminated feed gas stream to a temperature at which liquid contaminant is formed as well as a contaminant depleted gaseous phase, and 3) separating the two phases by introducing them into a gas/liquid separator vessel, comprising a gas/liquid inlet at an intermediate level, a liquid outlet arranged below the gas/liquid inlet and a gas outlet arranged above the gas/liquid inlet, in which vessel a normally horizontal coalescer is present above the gas/liquid inlet and over the whole cross-section of the vessel and in which vessel a centrifugal liquid separator is arranged above the coalescer and over the whole cross-section of the vessel, the liquid separator comprising one or more swirl tubes. 
     
     
         2 . Process according to  claim 1 , in which the gas inlet comprises an admittance with a supply and distribution assembly extending horizontally in the separator vessel, the assembly consisting of a longitudinal box-like structure connected to the gas inlet and having at least one open vertical side with a grid of guide vanes disposed one behind each other, seen in the direction of the flow. 
     
     
         3 . Process according to  claim 1 , in which the horizontal coalescer consists of one or more layers of gauze. 
     
     
         4 . Process according to  claim 1 , in which the horizontal coalescer consists of a layer of vanes. 
     
     
         5 . Process according to  claim 1 , in which the horizontal coalescer consists of a layer of structured packing. 
     
     
         6 . Process according  claim 1 , in which the centrifugal liquid separator comprises two horizontal trays between which vertical open-ended swirl tubes extend, each from an opening in the lower tray to a distance below a coaxial opening in the upper tray, means for the discharge of secondary gas and of liquid from the space between the trays outside the swirl tubes, and means provided in the lower part of the swirl tubes to impart to the gas/liquid a rotary movement around the vertical axis. 
     
     
         7 . Process according to  claim 6 , in which in the separation vessel a second normally horizontal liquid coalescer is present above the centrifugal liquid separator and over the whole cross-section of the vessel, wherein the second coalescer is arranged to remove liquids from the secondary gas. 
     
     
         8 . Process according to  claim 7 , in which the second coalescer is a bed of one or more layers of gauze. 
     
     
         9 . A process according to  claim 1 , in which the gaseous contaminants are acidic gaseous contaminants, comprising carbon dioxide or hydrogen sulphide, wherein the natural gas stream comprises between 5 and 80 vol % of methane. 
     
     
         10 . A process according to  claim 1 , in which the contaminated gas stream has a temperature between −20 and 150° C., and a pressure between 10 and 150 bara. 
     
     
         11 . A process according to  claim 1 , in which the cooling is done by isenthalpic expansion. 
     
     
         12 . A process according to  claim 11 , in which the feed gas stream is pre-cooled to a temperature between 15 and −35° C. before expansion. 
     
     
         13 . A process according to  claim 1 , in which the cooling is done by heat exchange against a cold fluidum. 
     
     
         14 . A process according to  claim 1 , in which the contaminated gas stream is cooled to a temperature between −30 and −80° C. 
     
     
         15 . (canceled)