Method and system for removing impurities from gas streams using rotating packed beds

Abstract

The present invention relates to a method and system for removing an impurity from a feed gas stream. Various embodiments include, for example, using a rotating packed bed, a pressure reducing device such as a turbine and/or control valve, a regenerator, and novel internal seal designs and liquid distributors. Advantageously, at least a portion of any energy produced is recycled for use in the process or elsewhere.

What is claimed is: 
     
         1 . A method for removing an impurity from a feed gas stream, which comprises:
 contacting in a rotating packed bed absorber a liquid solution capable of absorbing an impurity and a feed gas comprising an impurity; wherein the rotating packed bed absorber comprises a packed bed with one or more rotatable packing rings having an interior region within the packed bed characterized by (1) at least one liquid inlet for infusing liquid into the interior region, (2) at least one gas inlet for infusing a feed gas into the interior region; (3) at least one gas outlet for removing gas from the interior region; and (4) at least one liquid outlet for removing liquid from the interior region;   
       wherein said contacting occurs under conditions such that the liquid solution absorbs impurity to produce an impurity-rich liquid solution;
 removing the impurity-rich liquid solution; and 
 reducing the pressure of the impurity-rich liquid solution and recovering at least a portion of any energy produced. 
 
     
     
         2 . The method of  claim 1  which further comprises removing impurities and regenerating the impurity-rich liquid solution. 
     
     
         3 . The method of  claim 1  wherein at least a portion of the recovered energy is utilized in the method. 
     
     
         4 . The method of  claim 3  wherein at least a portion of the recovered energy is utilized to rotate the one or more rotatable packing rings. 
     
     
         5 . The method of  claim 4  wherein a turbine recovers the energy and operates the rotating packed bed absorber. 
     
     
         6 . The method of  claim 2  wherein the de-sorbing of absorbed impurity from the impurity-rich liquid solution occurs in a rotating packed bed regenerator. 
     
     
         7 . The method of  claim 1  wherein the impurity to be removed from the feed gas stream is selected from the group consisting of H 2 S, CO 2 , H 2 O, and mixtures thereof. 
     
     
         8 . The method of  claim 1  wherein the feed gas stream comprises CH 4 , natural gas, a mixture of hydrocarbons, or hydrogen. 
     
     
         9 . The method of  claim 1  wherein the liquid solution comprises an amine, a glycol, a physical solvent, or a mixture thereof. 
     
     
         10 . The method of  claim 1  wherein the pressure of the impurity-rich liquid solution is reduced from a pressure of from about 300 psig to about 2000 psig to a reduced pressure of from about 0 psig to about 30 psig. 
     
     
         11 . A system for removing an impurity from a feed gas stream, which system comprises:
 a rotating packed bed absorber with one or more rotatable packing rings, said absorber configured for contacting a feed gas stream comprising one or more impurities with a liquid to produce (1) an impurity-rich liquid solution comprising one or more absorbed impurities and (2) purified gas; and   a pressure reducing device in fluid communication with the rotating packed bed absorber for receiving and reducing the pressure of the impurity-rich liquid solution and recovering energy therefrom and wherein at least some of the energy recovered in the pressure reducing device may be employed to rotate the one or more rotatable packing rings of the rotating packed bed absorber.   
     
     
         12 . The system of  claim 11 , which further comprises a regenerator for regenerating the impurity-rich liquid solution by de-sorbing the impurity from the liquid solution, the regenerator is operably linked to the pressure reducing device and the packed bed absorber so that liquid solution can be directed to the rotating packed bed absorber for reuse. 
     
     
         13 . The system of  claim 12  wherein said regenerator comprises a rotating packed bed with one or more rotatable packing rings. 
     
     
         14 . The system of  claim 13  wherein the regenerator and pressure reducing device are configured such that at least some of the energy recovered in the pressure reducing device may be employed in the regenerator. 
     
     
         15 . The system of  claim 11  wherein the pressure reducing device comprises a turbine, a control valve, or a combination thereof. 
     
     
         16 . The system of  claim 15  wherein the pressure reducing device comprises a turbine and control valve and wherein the turbine and rotating packed bed absorber each comprise a separate rotatable shaft. 
     
     
         17 . The system of  claim 15  wherein the pressure reducing device comprises a turbine and control valve and wherein the turbine and rotating packed bed absorber are operably connected to a common rotatable shaft. 
     
     
         18 . A system for removing an impurity from a feed gas stream, which system comprises:
 a rotating packed bed absorber with one or more rotatable packing rings, said absorber configured for contacting a feed gas stream comprising one or more impurities with a liquid to produce (1) an impurity-rich liquid solution comprising one or more absorbed impurities and (2) purified gas; and   a pressure reducing device in fluid communication with the rotating packed bed absorber for receiving and reducing the pressure of the impurity-rich liquid solution and recovering energy therefrom; and   a regenerator for regenerating the impurity-rich liquid solution operably linked to the pressure reducing device for regenerating the impurity-rich liquid solution for reuse in the rotating packed bed absorber, wherein the regenerator and pressure reducing device are configured such that at least some of the energy generated in the pressure reducing device may be employed in regeneration.   
     
     
         19 . The system of  claim 18  wherein the pressure reducing device comprises a turbine, a control valve, or a combination thereof. 
     
     
         20 . The system of  claim 19  wherein the pressure reducing device comprises a turbine and control valve and wherein the turbine and rotating packed bed absorber each comprise a separate rotatable shaft. 
     
     
         21 . The system of  claim 19  wherein the pressure reducing device comprises a turbine and control valve and wherein the turbine and rotating packed bed absorber are operably connected to a common rotatable shaft. 
     
     
         22 . The system of  claim 19 , wherein the pressure reducing device comprises a turbine operably connected to the one or more rotatable packing rings of the rotating packed bed absorber such that at least some of the energy generated in the pressure reducing device may be employed to rotate the one or more rotatable packing rings of the rotating packed bed absorber. 
     
     
         23 . The system of  claim 18 , which further comprises one or more additional, parallel connected rotating packed bed absorbers wherein the pressure reducing device comprises a turbine and wherein two or more rotating packed bed absorbers are operably connected to a common rotatable shaft. 
     
     
         24 . The system of  claim 18 , wherein the regenerator comprises two or more parallel connected rotating packed bed regenerators and wherein the pressure reducing device comprises a turbine and wherein two or more rotating packed bed regenerators are operably connected to a common rotatable shaft. 
     
     
         25 . The system of  claim 18  wherein the rotating packed bed absorber comprises a liquid distributor comprising: a pipe having a central conduit and an annulus about the conduit, the annulus is in fluid communication with a plurality of protruding tabs that extend into an interior region of the rotatable packing rings, the protruding tabs having a plurality of outlets for introducing liquid solution into the interior region, the central conduit in fluid communication with the interior region for removing a purified gas from the interior region. 
     
     
         26 . The system of  claim 25  wherein the liquid distributor further comprises one or more internal seals to prevent feed gas from passing between the rotating packed bed and the pipe, wherein said internal seal comprises indentations sufficient to create a pressure drop within said space between the rotating packed bed and the pipe. 
     
     
         27 . The system of  claim 18  wherein the regenerator comprises a chamber, a rotating packed bed within the chamber, and a heater for heating at least a portion of the impurity-rich liquid solution. 
     
     
         28 . The system of  claim 27 , wherein the heater is disposed within the chamber. 
     
     
         29 . The system of  claim 27 , wherein the heater comprises a reboiler external to the chamber and a condenser. 
     
     
         30 . The system of  claim 18  wherein the regenerator comprises a packed tower.