Energy recovery for waste gas capture systems

Abstract

Processes and units are described for recovering energy from a waste gas capture system. Heat energy generated from the compression of waste gas can be integrated with a waste gas capture system to reduce energy needs of the system. Recovered heat energy is used to produce useful energy sources such as low pressure steam that can be integrated back into the waste gas capture system. The recovered heat energy can be used to produce the waste gas, for instance in a regeneration column and reboiler. The produced waste gas can be fed into the compression units designed to transform the waste gas into a storage fluid.

We claim: 
     
         1 . An energy-recovery process for a waste gas capture system, the process comprising:
 a. releasing waste gas from an absorption solvent;   b. feeding the released waste gas to a waste gas compressor;   c. introducing a heat transfer fluid to a heat exchanger downstream of a waste gas compressor to reduce the temperature of the waste gas compressor discharge, wherein the temperature of the heat transfer fluid exiting the heat exchanger is increased;   d. using the heat transfer fluid exiting the heat exchanger as a heat source for the waste gas capture system.   
     
     
         2 . The process of  claim 1 , the waste gas comprising CO 2  or H 2 S. 
     
     
         3 . The process of  claim 1 , the heat transfer fluid being in a closed loop heat exchange system. 
     
     
         4 . The process of  claim 1 , further comprising using the heat transfer fluid exiting the heat exchanger to generate a first steam source. 
     
     
         5 . The process of  claim 4 , further comprising mixing the first steam source with a second steam source to form a mixed steam source and supplying the mixed steam source to the waste gas capture system to provide a recovered energy source. 
     
     
         6 . The process of  claim 5 , the waste gas capture system having a reboiler for releasing the waste gas from the absorption solvent and the mixed steam source being used as a heat source for producing the waste gas in a regeneration column. 
     
     
         7 . The process of  claim 5 , the waste gas capture system having a thermal reclaimer for regenerating the waste gas, solvent, or other volatiles, wherein the mixed steam source provides the energy to the thermal reclaimer to release the volatiles. 
     
     
         8 . The process of  claim 6 , the produced waste gas being fed to the waste gas compressor. 
     
     
         9 . The process of  claim 5 , the waste gas capture system having a regeneration column, the mixed steam source being used as a heat source for increasing temperature a reflux stream of the regenerating column. 
     
     
         10 . The process of  claim 5 , the waste gas capture system comprising a waste gas absorption solvent, the mixed steam source being used to heat the waste gas absorption solvent prior to the waste gas absorption solvent being introduced to a regeneration column. 
     
     
         11 . The process of  claim 5 , further comprising a steam ejector for mixing the first steam source with the second steam source, wherein the second steam source is at a pressure greater than the first steam source prior to mixing. 
     
     
         12 . The process of  claim 5 , further comprising a compressor for mixing the first steam source with the second steam source, wherein the second steam source is at a pressure greater than the first steam source prior to mixing. 
     
     
         13 . An energy-recovery unit for a waste gas capture system, the unit comprising:
 a. a heat exchange loop containing a heat transfer fluid;   b. a heat exchanger positioned downstream of a waste gas compressor such that the heat exchanger receives the waste gas compressor discharge and the heat transfer fluid flows through the heat exchanger to reduce the temperature of the waste gas compressor discharge;   c. a steam generating apparatus for producing a first steam source, the steam generating apparatus having a heat exchange component for producing steam, the heat exchange component using the heat transfer fluid exiting the heat exchanger;   d. a steam mixing device for combining the first steam source and a second steam source to form a mixed steam source, wherein the mixed steam source is supplied to the waste gas capture system to provide a recovered energy source.   
     
     
         14 . The energy-recovery unit of  claim 13 , the waste gas compressor discharge comprising CO 2  or H 2 S. 
     
     
         15 . The energy-recovery unit of  claim 13 , the steam mixing device being a steam ejector, wherein the second steam source is at a pressure greater than the first steam source prior to mixing. 
     
     
         16 . The energy-recovery unit of  claim 13 , the steam mixing device being a compressor for mixing the first steam source with the second steam source. 
     
     
         17 . The energy-recovery unit of  claim 13 , the steam generating apparatus being a vessel and the heat exchange component comprising a heat coil in the vessel, the heat coil housing the heat transfer fluid exiting the heat exchanger. 
     
     
         18 . The energy-recovery unit of  claim 17 , the heat transfer fluid exiting the heat coil being used in the heat exchanger to reduce the temperature of the waste gas compressor discharge. 
     
     
         19 . The energy-recovery unit of  claim 17 , the vessel containing steam condensate discharged from the waste gas capture system. 
     
     
         20 . The energy-recovery unit of  claim 19 , the steam condensate comprising condensate generated from the mixed steam source being supplied to the waste gas capture system. 
     
     
         21 . The energy-recovery unit of  claim 13 , the waste gas capture system having a waste gas regeneration column for producing waste gas, wherein the waste gas is fed to the waste gas compressor and the mixed steam source is supplied to the waste gas regenerator for producing the waste gas.