Process for reducing carbon dioxide emission in a power plant

Abstract

A process for reducing CO 2 emission in a power plant, wherein the power plant comprises at least one gas turbine coupled to a heat recovery steam generator unit and the CO 2 capture unit comprises an absorber and a regenerator, the process comprising the steps of: (a) introducing hot exhaust gas exiting a gas turbine having a certain elevated pressure into a heat recovery steam generator unit to produce steam and a flue gas stream comprising carbon dioxide; (b) removing carbon dioxide from the flue gas stream comprising carbon dioxide by contacting the flue gas stream with absorbing liquid in an absorber having an elevated operating pressure to obtain absorbing liquid enriched in carbon dioxide and a purified flue gas stream, wherein the settings and/or construction of the gas turbine are adjusted such that the hot exhaust gas exiting the gas turbine has a pressure of at least 40% of the elevated operating pressure of the absorber.

1 . A process for reducing CO 2  emission in a power plant, the process comprising the steps of:
 (a) introducing a hot exhaust gas exiting a gas turbine having a certain elevated pressure into a heat recovery steam generator unit to produce steam and a flue gas stream comprising carbon dioxide;   (b) removing carbon dioxide from the flue gas stream comprising carbon dioxide by contacting the flue gas stream with an absorbing liquid in an absorber having an elevated operating pressure in the range of from 50 to 200 mbarg to obtain an absorbing liquid enriched in carbon dioxide and a purified flue gas stream, wherein the settings and/or construction of the gas turbine are adjusted such that the hot exhaust gas exiting the gas turbine has a pressure of at least 40% of the elevated operating pressure of the absorber.   
     
     
         2 . A process according to  claim 1 , wherein the hot exhaust gas exiting the gas turbine has a pressure of at least 50%, of the elevated operating pressure of the absorber. 
     
     
         3 . A process according to  claim 2 , wherein the elevated operation pressure of the absorber is in the range of from 70 to 150 mbarg. 
     
     
         4 . A process according to  claim 3 , further comprising the step of:
 (c) regenerating the absorbing liquid enriched in carbon dioxide by contacting the absorbing liquid enriched in carbon dioxide with a stripping gas at elevated temperature in a regenerator to obtain a regenerated absorbing liquid and a gas stream enriched in carbon dioxide.   
     
     
         5 . A process according to  claim 4 , the process further comprising the step of:
 (d) pressurising the gas stream enriched in carbon dioxide using a carbon dioxide compressor, wherein a first part of the steam produced in the heat recovery steam generator unit is used to drive the carbon dioxide compressor.   
     
     
         6 . A process according to  claim 5 , wherein an amount of fuel is combusted in the heat recovery steam generator unit to produce an additional amount of steam, wherein the amount of fuel combusted in the heat recovery steam generator unit is such that the additional amount of steam is sufficient to provide at least 80% of the heat needed for the regeneration of the absorbing liquid. 
     
     
         7 . A process according to  claim 6 , wherein at least part of the steam produced in the heat recovery steam generator unit is high pressure steam, having a pressure in the range of from 90 to 125 bara. 
     
     
         8 . A process according to  claim 7 , wherein the pressurised gas stream enriched in carbon dioxide is used for enhanced oil recovery. 
     
     
         9 . A process according to  claim 8 , wherein the absorbing liquid comprises an amine, selected from the group consisting of monethanolamine (MEA),diethanolamine (DEA), diglycolamine (DGA), methyldiethanolamine (MDEA), triethanolamine (TEA), N-ethyldiethanolamine (EDEA), N,N′-di(hydroxyalkyl)piperazine, N,N,N′,N′-tetrakis(hydroxyalkyl)-1,6-hexanediamine and tertiary alkylamine sulfonic acid compounds. 
     
     
         10 . A process according to  claim 9 , wherein the absorbing liquid comprises a physical solvent or ammonia.