Minimal sour gas emission for an integrated gasification combined cycle complex

Abstract

Disclosed is a process to start-up, operate, and shut down a gasifier and an integrated gasification combined cycle complex with minimal sour gas emissions while additionally reducing the release of contaminants such as carbon monoxide, hydrogen sulfide, and nitrogen oxides. The process is accomplished by starting up with a sulfur free feedstock and by scrubbing any ventable sour gases free of sulfur contaminants prior to release of any such gases to the atmosphere.

1 . A process for starting up and shutting down an integrated gasification combined cycle complex wherein the integrated gasification combined cycle complex comprises a syngas production zone, shift conversion/low temperature gas cooling zone, acid gas removal zone, sulfur recovery zone and a combined cycle power block zone, wherein each zone has at least one blow down conduit associated with it, wherein the integrated gasification combined cycle complex is started up with a hydrocarbon-containing feedstock not containing contaminants such as sulfur-containing compounds and wherein said startup or shut-down is carried out with sulfur-free or reduced sulfur flaring which process comprises the steps of:
 (a) recovering any sour effluent stream from an applicable zone being started up or shutdown and;   (b) scrubbing such sour gas to reduce the content of sulfur-containing contaminants during the startup or shutdown prior to venting or flaring such gases;   (c) recovering a sweet reducing effluent stream from an applicable zone being started up in the integrated gasification combined cycle complex;   (d) passing the sweet reducing effluent stream from the applicable zone that is being started up through at least one blow down conduit downstream of the applicable zone;   (e) passing the sweet reducing stream recovered from the blow down conduit in step (c) to a flare or vent;   
     
     
         2 . The process of  claim 1  wherein oxidizing streams are collected from the group consisting of sumps, tanks, instrument vents, bridals, and pressure safety valves associated with the various zones in the integrated gasification combined cycle complex and such oxidizing streams are passed to the sulfur recovery zone. 
     
     
         3 . The process of  claim 1  which process further comprises the steps of:
 (a) passing a sulfur-free hydrocarbon feedstock to the syngas production zone to produce a sweet reducing syngas effluent stream; 
 (b) passing the sweet reducing syngas effluent stream to a blow down conduit; 
 (c) passing the sweet reducing stream from the blow down conduit in step (b) to a flare 
 (e) when the feed rate to the syngas production zone reaches a predetermined rate at predetermined conditions including a predetermined pressure and temperature, the syngas zone sweet reducing effluent stream is diverted from the blow down conduit in step (b) to the shift conversion zone having a low temperature gas cooling zone downstream thereof to produce a sweet reducing stream effluent from the low temperature gas cooling zone; 
 (f) passing the sweet reducing stream effluent from the low temperature gas cooling zone to a blow down conduit downstream of the low temperature gas cooling zone; 
 (g) passing the sweet reducing stream from the blow down conduit in step (f) to a flare; 
 (h) starting up the acid gas removal zone with nitrogen or any other inert gas such that when the acid gas removal zone has reached predetermined operating conditions including temperature and pressure the sweet reducing stream effluent from the blow down conduit associated with the low temperature gas cooling zone in step (f) is diverted to the acid gas removal zone to produce a sweet reducing effluent stream; 
 (i) passing the sweet reducing effluent stream from the acid gas removal zone in step (h) to a blow down conduit down stream of the acid gas removal zone; 
 (j) passing the sweet reducing stream from the blow down conduit in step (i) to a flare; 
 (k) starting up the sulfur recovery zone with a start-up gas such as natural gas such that when the sulfur recovery zone has reached operating conditions the sweet reducing effluent stream from the acid gas removal zone is diverted from the blow down conduit in step (j) to the sulfur recovery zone to produce a sweet reducing effluent stream; 
 (l) passing the sulfur recovery zone sweet reducing effluent to a tail gas treatment unit to produce a tail gas treatment unit sweet reducing effluent; 
 (m) passing the tail gas treatment unit sweet reducing effluent to a thermal oxidizer or flare; 
 (n) reducing the amount of sulfur-free containing feedstock to the syngas production zone and passing a sulfur-containing hydrocarbon feed stock to the syngas production zone; 
 (o) diverting the acid gas removal zone sweet reducing effluent stream from the sulfur recovery zone to a sour gas scrubber; 
 (p) passing the effluent from the sour gas scrubber to a flare; 
 (q) when the sulfur concentration of the acid gas removal effluent stream passing to the sour gas scrubber reaches a predetermined value, the stream is diverted back to the sulfur recovery zone while simultaneously reducing start up gas to the sulfur recovery zone; 
 (r) diverting the tail gas treatment unit effluent presently flowing to the thermal oxidizer or flare in step (m) to a point either upstream or down stream of the acid gas removal zone. 
 
     
     
         4 . The process of  claim 1  which process further comprises the steps of:
 (a) passing a sulfur-free hydrocarbon feedstock to the syngas production zone to produce a sweet reducing syngas effluent stream; 
 (b) passing the sweet reducing syngas effluent stream to the shift conversion zone having a low temperature gas cooling zone downstream thereof to produce a sweet reducing stream effluent from the low temperature gas cooling zone; 
 (c) passing the shift conversion zone effluent sweet reducing stream from the low temperature gas cooling zone to a blow down conduit downstream of the low temperature gas cooling zone; 
 (d) passing the sweet reducing stream from the blow down conduit in step (c) to a flare; 
 (e) starting up the acid gas removal zone with nitrogen or any other inert gas such that when the acid gas removal zone has reached predetermined operating conditions including appropriate temperature and pressure, the sweet reducing stream effluent from the blow down conduit associated with the low temperature gas cooling zone is diverted to the acid gas removal zone to produce a sweet reducing effluent stream; 
 (f) passing the sweet reducing effluent stream from the acid gas removal zone to a blow down conduit down stream of the acid gas removal zone; 
 (g) passing the sweet reducing stream from the blow down conduit in step (f) to a flare; 
 (h) starting up the sulfur recovery zone with a start-up gas such as natural gas such that when the sulfur recovery zone has reached operating conditions, the sweet reducing effluent stream from the acid gas removal zone is diverted from the blowdown conduit in step (f) to the sulfur recovery zone to produce a sweet reducing effluent stream; 
 (i) passing the sulfur recovery zone sweet reducing effluent to a tail gas treatment unit to produce a tail gas treatment unit sweet reducing effluent; 
 (j) passing the tail gas treatment unit reducing gas effluent to a thermal oxidizer or flare; 
 (k) reducing the amount of sulfur-free containing feedstock to the syngas production zone and passing a sulfur-containing hydrocarbon feed stock to the syngas production zone; 
 (l) diverting the acid gas removal zone reducing effluent stream from the sulfur recovery zone to a sour gas scrubber; 
 (m) passing the effluent from the sour gas scrubber to a flare 
 (n) when the sulfur concentration of the acid gas removal effluent stream passing to the sour gas scrubber reaches a predetermined value, the stream is diverted back to the sulfur recovery zone while simultaneously reducing start up gas to the sulfur recovery zone; and 
 (o) diverting the tail gas from the tail gas treatment unit effluent presently flowing to the thermal oxidizer or flare in step (j) to a point either upstream or down stream of the acid gas recovery zone. 
 
     
     
         5 . The process of  claim 1  which process further comprises the steps of:
 (a) passing a sulfur-free hydrocarbon feedstock to the syngas production zone to produce a sweet reducing syngas effluent stream; 
 (b) passing the sweet reducing syngas effluent stream to a shift conversion zone having a low temperature gas cooling zone downstream thereof to produce a sweet reducing effluent stream; 
 (c) passing the sweet reducing stream effluent from the low temperature gas cooling zone to the acid gas zone to produce a sweet reducing gas effluent stream; 
 (d) passing the sweet reducing gas effluent from the acid gas removal zone to a blow down conduit down stream of the acid gas removal zone; 
 (e) passing the sweet reducing stream from the blow down conduit to a flare; 
 (f) starting up the sulfur recovery zone with a start-up gas such as natural gas such that when the sulfur recovery zone has reached operating conditions, the sweet reducing effluent stream from acid gas removal zone is diverted from the blown down conduit in step (d) to the sulfur recovery zone to produce a sweet reducing effluent stream; 
 (g) passing the sulfur recovery zone sweet reducing effluent stream to a tail gas treatment unit to produce a tailgas treatment unit sweet reducing effluent; 
 (h) passing the tail gas treatment unit reducing gas effluent to a flare or thermal oxidizer; 
 (i) reducing the amount of sulfur-free containing feedstock to the syngas production zone and passing a sulfur-containing hydrocarbon feed stock to the syngas production zone; 
 (j) diverting the acid gas removal regenerator sweet reducing effluent stream from the sulfur recovery zone to a sour gas scrubber; 
 (k) passing the effluent from the sour gas scrubber to a flare; 
 (l) when the sulfur concentration of the acid gas removal effluent stream passing to the sour gas scrubber reaches a predetermined value, the stream is diverted back to the sulfur recovery zone while simultaneously reducing start-up gas to the sulfur recovery zone; and 
 (m) diverting the tail gas from the tail gas treatment unit effluent presently flowing to the flare or thermal oxidizer in step (h) to a point either upstream or down stream of the acid gas removal zone. 
 
     
     
         6 . A process for shutting down the syngas production zone of an integrated gasification combined cycle complex wherein the integrated gasification combined cycle complex comprises a syngas production zone, shift conversion reaction/low temperature gas cooling zone, acid gas removal zone, sulfur recovery zone and a combined cycle power block zone, wherein each zone has at least one blow down conduit associated with it wherein the complex is being fed a hydrocarbon-containing feedstock which feedstock contains contaminants such as sulfur, wherein the process comprises the steps of:
 (a) switching the feedstock to the syngas production zone to a sulfur-free hydrocarbon containing feedstock such that a sweet reducing stream effluent is created once the syngas from the sulfur-free feedstock displaces the sulfur-containing feedstock; and   (b) diverting and depressurizing the sweet reducing stream effluent from the syngas production zone to a blow down conduit associated with the syngas production zone.   
     
     
         7 . The process of  claim 6  which involves shutting down additional zones and comprises the steps of
 (a) diverting and depressurizing a sweet reducing stream effluent from the low temperature gas cooling zone to the blow down conduit associated with this zone once the sulfur-free syngas from the sulfur-free feedstock displaces the syngas from the sulfur-containing feedstock in syngas production zone; 
 (b) passing the effluent from the low temperature gas cooling zone in step (a) to a flare; 
 (c) diverting and depressurizing the effluent from the acid gas removal zone as follows:
 (i) passing a hydrogen rich syngas to a flare; 
 (ii) passing the acid gas to the sulfur recovery zone; 
 
 (d) depressurizing the sulfur recovery zone to a tail gas treating unit (“TGTU”) absorber; 
 (e) passing the effluent from the low pressure tail gas treatment unit absorber to a thermal oxidizer or flare; 
 (f) switching the fuel to turbines associated with the power block zone from hydrogen to natural gas. 
 
     
     
         8 . The process of  claim 7  which process further comprises the steps of:
 (a) diverting and depressurizing the sweet reducing stream effluent from the acid gas removal zone as follows:
 i) passing a hydrogen rich syngas to a flare; 
 ii) passing the acid gas to the sulfur recovery zone; 
 
 (b) depressurizing the sulfur recovery zone to a tail gas treating unit absorber; 
 (c) passing the effluent from the low pressure tail gas treatment unit absorber to a thermal oxidizer or flare; 
 (d) switching the fuel to turbines associated with the power block zone from hydrogen to natural gas. 
 
     
     
         9 . A process for shutting down the syngas production zone of an integrated gasification combined cycle complex wherein the integrated gasification combined cycle complex comprises a syngas production zone, shift conversion reaction/low temperature gas cooling zone, acid gas removal zone, sulfur recovery zone and a combined cycle power block zone, wherein each zone has at least one blow down conduit associated with it wherein the complex is being fed a hydrocarbon-containing feedstock which feedstock contains contaminants such as sulfur, wherein the process comprises the steps of:
 (a) diverting and depressurizing a sour reducing stream effluent from the syngas production zone to a blow down conduit associated with the syngas production zone;   (b) passing the effluent from the syngas production zone in step (a) to a low pressure scrubber such as amine or caustic scrubber to remove the H 2 S gas;   (c) passing the effluent of the low pressure scrubber to a flare or thermal oxidizer;   
     
     
         10 . The process of  claim 9  of shutting down the entire processing units of the IGCC which process further comprises the steps of:
 (a) diverting and depressurizing a sour reducing stream effluent from the temperature gas cooling zone to the blow down conduit associated with this zone; 
 (b) passing the effluent from the low temperature gas cooling zone to a low pressure scrubber such as amine or caustic scrubber for H 2 S removal; 
 (c) passing the effluent from the low pressure scrubber in step (b) to flare 
 (d) diverting and depressurizing the effluent from the acid gas removal zone as follows:
 (i) passing a hydrogen rich syngas to a flare; 
 (ii) passing the acid gas to the sulfur recovery zone; 
 
 (e) depressurizing the sulfur recovery zone to a tail gas treating unit absorber; 
 passing the effluent from the low pressure tail gas treating unit absorber to a thermal oxidizer or flare; 
 (g) switching the fuel to turbines associated with the power block zone from hydrogen to natural gas. 
 
     
     
         11 . The process of  claim 10  which process further comprises the steps of:
 (a) diverting and depressurizing the sour reducing stream effluent from the acid gas removal zone as follows;
 (i) passing a hydrogen rich syngas to the flare; 
 (ii) passing the acid gas to the sulfur recovery zone; 
 
 (b) depressurizing the sulfur recovery zone to a tail gas treating unit absorber; 
 (c) passing the effluent from the low pressure tail gas treating unit absorber to a thermal oxidizer or flare; and 
 (d) switching the fuel to the turbines associated with the power block zone from hydrogen to natural gas. 
 
     
     
         12 . The process of  claims 9 ,  10  and  11  are also used for unplanned emergency shutdown.