Process and apparatus for removal of sour species from a natural gas stream

Abstract

A process for removal of sour species from a dehydrated natural gas feed stream is provided. The dehydrated natural gas feed stream is cooled to conditions where a slurry of solid sour species and hydrocarbon liquids is formed together with a gaseous stream containing gaseous sour species. The gaseous stream containing gaseous sour species is then separated from the slurry and treated with a liquid solvent, thereby forming a liquid solution of the sour species and a dehydrated sweetened natural gas product stream. An apparatus for removing sour species from a dehydrated natural gas feed stream is also provided. The apparatus has a vessel with a solids formation zone in fluid communication with a gas solvation zone. The solids formation zone is configured to facilitate formation of a slurry of solid sour species and hydrocarbon liquids and a gaseous stream containing gaseous sour species. The gas solvation zone is configured to facilitate formation of a liquid solution of sour species. The apparatus has an inlet for introducing the dehydrated natural gas feed stream to the solids formation zone, a conduit configured to direct the gaseous stream from the solids formation zone to the gas solvation zone, and an inlet for introducing liquid solvent into the gas solvation zone.

1 .- 37 . (canceled) 
     
     
         38 . A process for removing a sour species from a dehydrated natural gas feed stream comprising the steps of:
 (a) cooling the dehydrated natural gas feed stream and forming a slurry of solid sour species and hydrocarbon liquids, and a gaseous stream containing gaseous sour species;   (b) separating the gaseous stream containing gaseous sour species and the slurry; and,   (c) treating the gaseous stream containing gaseous sour species with a liquid solvent and forming a dehydrated sweetened gas stream and a liquid solution of the sour species.   
     
     
         39 . The process according to  claim 38 , wherein the step of cooling the dehydrated natural gas feed stream comprises adiabatically expanding the dehydrated natural gas feed stream. 
     
     
         40 . The process according to  claim 38 , wherein the step of separating the solid sour species and the liquid condensate from the gaseous feed stream containing the gaseous sour species is conducted under gravity, centrifugal force, or other suitable separation techniques known in the art. 
     
     
         41 . The process according to  claim 38 , wherein the process further comprises a step of removing the solid sour species from the slurry. 
     
     
         42 . The process according to  claim 41 , wherein the step of removing the solid sour species comprises heating the slurry and melting the solid sour species, thereby forming a liquid rich in sour species. 
     
     
         43 . The process according to  claim 42 , wherein the slurry is heated to a temperature just above the melting point of the solid sour species. 
     
     
         44 . The process according to  claim 42 , wherein a warm liquid is added to the slurry. 
     
     
         45 . The process according to  claim 42 , wherein a heater is immersed in the slurry. 
     
     
         46 . The process according to  claim 38 , wherein the step of treating the gaseous stream containing gaseous sour species with the liquid solvent comprises contacting the gaseous stream containing the gaseous sour species with the liquid solvent. 
     
     
         47 . The process according to  claim 38 , wherein the step of contacting the gaseous stream containing the gaseous sour species with the liquid solvent facilitates forming a liquid solution of the sour species in the liquid solvent. 
     
     
         48 . The process according to  claim 38 , wherein the liquid solvent comprises a solvent in which the gaseous sour species is more soluble than in the natural gas stream. 
     
     
         49 . The process according to  claim 38 , wherein the liquid solvent comprises any one of methanol, ethanol, dimethyl sulfoxide, ionic liquids selected from a group comprising imidazolium, quaternary ammonium, pyrrolidinium, pyridinium, or tetra alkylphosphonium, or a NGL [natural gas liquids] condensate comprising a mixture of C2, liquefied petroleum gas components, C3 and C4 and C5+ hydrocarbon components, or a combination thereof. 
     
     
         50 . The process according to  claim 38 , wherein the process further comprises a step of separating the gaseous sour species from the liquid solution of the sour species. 
     
     
         51 . The process according to  claim 50 , wherein the liquid solution of the gaseous sour species undergoes a stripping process to separate the sour species from the liquid solution. 
     
     
         52 . The process according to  claim 38 , wherein the sour species comprises any one of, or a mixture of any two or more of, CO 2 , H 2 S, mercaptans, COS, CS 2 , aromatic hydrocarbons and mercury. 
     
     
         53 . An apparatus for removing a sour species from a dehydrated natural gas feed stream comprising:
 a vessel with a solids formation zone in fluid communication with a gas solvation zone, wherein the solids formation zone is configured to facilitate formation of a slurry of solid sour species and hydrocarbon liquids, and a gaseous feed stream containing gaseous sour species, and the gas solvation zone is configured to facilitate formation of a liquid solution of sour species;   an inlet for introducing the dehydrated natural feed gas stream to the solids formation zone;   a fluid communication device configured to direct the gaseous stream containing gaseous sour species from the solids formation zone to the gas solvation zone;   an inlet for introducing liquid solvent into the gas solvation zone;   a first outlet for removing the liquid solution of the sour species from the gas solvation zone; and,   a second outlet for removing a dehydrated sweetened gas product stream from the gas solvation zone.   
     
     
         54 . The apparatus according to  claim 53 , wherein the solids formation zone is disposed in a first vessel and the gas solvation zone is disposed in a second vessel. 
     
     
         55 . The apparatus according to  claim 53 , wherein the apparatus further comprises a gas cooler for cooling the dehydrated natural gas feed stream entering the solids formation zone. 
     
     
         56 . The apparatus according to  claim 55 , wherein the gas cooler comprises a gas expander for adiabatically expanding the dehydrated natural gas feed stream. 
     
     
         57 . The apparatus according to  claim 56 , wherein the gas expander comprises a Joule-Thomson valve, an orifice or venturi, a turbo expander, or a turbo expander in sequential combination with a Joule-Thomson valve. 
     
     
         58 . The apparatus according to  claim 56 , wherein the gas expander defines the inlet for introducing the dehydrated natural gas feed stream into the solids formation zone. 
     
     
         59 . The apparatus according to  claim 56 , wherein the solids formation zone further comprises a collection zone into which the solid sour species and liquid concentrate collect and form a slurry. 
     
     
         60 . The apparatus according to  claim 59 , wherein the apparatus further comprises a heater disposed in the collection zone to heat the slurry and melt the solid sour species. 
     
     
         61 . The apparatus according to  claim 60 , wherein the heater comprises an immersion heater or a heat exchanger. 
     
     
         62 . The apparatus according to  claim 59 , wherein the collection zone is configured to facilitate ingress of a warm liquid into the slurry to heat the slurry and melt the solid sour species. 
     
     
         63 . The apparatus according to  claim 60 , wherein the apparatus further comprises an outlet from which the liquid sour species can be removed from the collection zone. 
     
     
         64 . The apparatus according to  claim 59 , wherein the apparatus further comprises an outlet from which the liquid hydrocarbon can be removed from the collection zone. 
     
     
         65 . The apparatus according to  claim 64 , wherein the outlet from which the liquid hydrocarbon can be removed is disposed above the outlet from which the liquid sour species can be removed. 
     
     
         66 . The apparatus according to  claim 53 , wherein the apparatus is configured to provide fluid communication between the solids formation zone and the gas solvation zone via a fluid communication device, the fluid communication device being configured to prevent return of liquid phase from the gas solvation zone to the solids formation zone. 
     
     
         67 . The apparatus according to  claim 66 , wherein the fluid communication device comprises a chimney tray or a non-return valve. 
     
     
         68 . The apparatus according to  claim 56 , wherein the apparatus further comprises a liquid-gas contactor disposed in the gas solvation zone. 
     
     
         69 . The apparatus according to  claim 68 , wherein the liquid-gas contactor comprises a plurality of trays or random packing or structured packing disposed in the gas solvation zone. 
     
     
         70 . The apparatus according to  claim 68 , wherein the inlet for introducing the liquid solvent into the gas solvation zone is disposed above the liquid-gas contactor. 
     
     
         71 . The apparatus according to  claim 53 , wherein the inlet comprises a plurality of spray nozzles or a liquid distributor. 
     
     
         72 . The apparatus according to  claim 53 , wherein the first outlet for removing the liquid solution of the sour species from the gas solvation zone is in fluid communication with a stripper to remove the sour species from the liquid solution and recover liquid solvent. 
     
     
         73 . The apparatus according to  claim 72 , wherein the apparatus further comprises a recirculator to recycle the recovered liquid solvent to the inlet for introducing liquid solvent to the gas solvation zone. 
     
     
         74 . A process for recovering liquid carbon dioxide from a dehydrated natural gas feed stream comprising the steps of:
 (a) cooling the dehydrated natural gas feed stream and forming a slurry of solid carbon dioxide particles and hydrocarbon liquids, and a gaseous stream containing gaseous carbon dioxide;   (b) separating the gaseous stream containing gaseous carbon dioxide and the slurry;   (c) treating the gaseous stream containing gaseous carbon dioxide with a liquid solvent and forming a liquid solution of carbon dioxide; and,   (d) heating the slurry and melting the solid carbon dioxide particles and forming liquid carbon dioxide.