RAPID STARTUP HEAT RECOVERY STEAM GENERATOR

1 . A rapid startup heat recovery steam generator (HRSG) comprising:

a gas inlet;

a high pressure section comprising a high pressure steam-water separator and a plurality of high pressure evaporator tubes in fluid communication with the high pressure steam-water separator;

an optional intermediate pressure section comprising an intermediate pressure steam-water separator a plurality of intermediate pressure evaporator tubes in fluid communication with the intermediate pressure steam-water separator;

an optional low pressure section comprising a low pressure steam-water separator a plurality of low pressure evaporator tubes in fluid communication with the low pressure steam-water separator; and

a gas outlet;

wherein at least one of the high pressure steam-water separator, the intermediate pressure steam-water separator, and the low pressure steam-water separator is a vertical steam separator.

2 . The HRSG of claim 1 , wherein the high pressure steam-water separator is a vertical steam separator.

3 . The HRSG of claim 2 , wherein the intermediate pressure steam-water separator and the low pressure steam-water separator are both vertical steam separators.

4 . The HRSG of claim 2 , wherein the intermediate pressure steam-water separator and the low pressure steam-water separator are both steam drums.

5 . The HRSG of claim 1 , wherein the intermediate pressure steam-water separator is the vertical steam separator.

6 . The HRSG of claim 5 , wherein the high pressure steam-water separator and the low pressure steam-water separator are both steam drums.

7 . The HRSG of claim 1 , wherein the low pressure steam-water separator is the vertical steam separator.

8 . The HRSG of claim 7 , wherein the high pressure steam-water separator and the intermediate pressure steam-water separator are both steam drums.

9 . The HRSG of claim 1 , wherein the intermediate pressure steam-water separator and the low pressure steam-water separator are both vertical steam separators.

10 . The HRSG of claim 9 , wherein the high pressure steam-water separator is a steam drum.

11 . The HRSG of claim 5 , wherein the high pressure steam-water separator is a steam drum.

12 . The HRSG of claim 7 , wherein the high pressure steam-water separator is a steam drum.

13 . The HRSG of claim 1 , wherein the vertical steam separator comprises:

a vertically extending cylindrical vessel having a top and a bottom portion;

means for providing a steam/water mixture to the vessel for swirling the steam/water mixture in the separator for separating steam from water in the separator;

vertically oriented scrubber means for removing water from steam located in the top portion of the vessel and arranged around an inside circumference of the separator;

saturated steam connection means for conveying saturated steam from the vessel;

feedwater supply means connected through a wall of the separator for conveying feedwater to the vessel; and

means for conveying the feedwater and water separated from the steam from the vessel.

14 . The HRSG of claim 13 , wherein the scrubber means comprises an array of vertically oriented individual scrubber elements arranged around the inside circumference of the separator, spaced from the inside surface of the wall of the separator so as to create a substantially open, annular region therebetween.

15 . The HRSG of claim 1 , wherein the vertical steam separator comprises:

a vertically extending cylindrical vessel having a top and a bottom portion;

at least one level of tangentially oriented nozzles connected to a wall of the vessel for providing a steam/water mixture to the vessel for swirling the steam/water mixture in the separator for separating steam from water in the separator;

vertically oriented scrubber means for removing water from steam, located in the top portion of the vessel and arranged around an inside circumference of the separator;

saturated steam connection means for conveying saturated steam from the vessel;

feedwater supply means connected for conveying feedwater to the vessel; and

means for conveying the feedwater and water separated from the steam from the vessel.

16 . The HRSG of claim 15 , wherein the tangentially oriented nozzles are inclined downwardly at an angle with respect to the horizontal direction.

17 . The HRSG of claim 15 , wherein the vertical steam separator comprises plural levels of inclined, tangentially oriented nozzles connected to the wall of the vessel, the nozzles of one level being staggered with respect to the nozzles of an adjacent level so as to avoid interference between jets of steam/water being conveyed by the nozzles from various levels.

18 . The HRSG of claim 1 , wherein the vertical steam separator comprises:

a vertically extending cylindrical vessel having a top and a bottom portion;

means for providing a steam/water mixture to the vessel for swirling the steam/water mixture in the separator for separating steam from water in the separator;

vertically oriented scrubber means for removing water from steam, located in the top portion of the vessel and arranged around an inside circumference of the separator;

a stripper ring positioned within the vessel below the scrubber means and above at least one level of tangentially oriented nozzles connected to a wall of the vessel for providing a steam/water mixture to the vessel for swirling the steam/water mixture in the separator for separating steam from water in the separator;

saturated steam connection means for conveying saturated steam from the vessel;

feedwater supply means connected for conveying feedwater to the vessel; and

means for conveying the feedwater and water separated from the steam from the vessel.

19 . The HRSG of claim 18 , wherein the stripper ring has a solid, annular portion adjacent an inside surface of the vessel and a conical, perforated portion in the center region of the separator.

20 . The HRSG of claim 1 , wherein the vertical steam separator comprises:

a vertically extending cylindrical vessel having a top and a bottom portion;

means for providing a steam/water mixture to the vessel for swirling the steam/water mixture in the separator for separating steam from water in the separator;

vertically oriented scrubber means for removing water from steam, located in the top portion of the vessel and arranged around an inside circumference of the separator;

saturated steam connection means for conveying saturated steam from the vessel;

feedwater supply means connected for conveying feedwater to the vessel;

vortex inhibitor means for reducing rotation of the feedwater and water as it is conveyed from the vessel; and

means for conveying the feedwater and water separated from the steam from the vessel.

21 . The HRSG of claim 1 , wherein the vertical steam separator is configured for receiving feedwater and a steam/water mixture, separating the steam from the water, conveying the separated steam from the separator, and mixing the feedwater with the separated water and conveying same from the separator, the vertical steam separator comprising:

a vertically extending cylindrical vessel having a top and a bottom portion and defining a plurality of zones therein, said zones including;

a secondary steam/water separation zone having scrubber means for removing a final portion of water from the steam;

an entrainment separation zone, located below the scrubber means and above a boiler steam/water entry zone, which provides the steam/water mixture into the separator via a plurality of inclined tangential nozzles;

a primary steam/water separation zone, located below the boiler steam/water entry zone, where water spirals downwardly to the bottom of the separator;

a vertical separator water level operation zone, located below the primary steam/water separation zone, which will be substantially filled with water having a fluctuating water level, during boiler operation;

a feedwater injection zone, located below the vertical separator water level zone, where the feedwater is introduced into the separator for mixing with the separated water; and

a lower vortex elimination zone, located below the feedwater injection zone, for reducing rotation of the feedwater and water as it is conveyed from the separator.

22 . The HRSG of claim 1 , wherein a flow path extending from the gas inlet to the gas outlet is substantially horizontal.

23 . The HRSG of claim 1 , wherein a flow path extending from the gas inlet to the gas outlet is substantially vertical.

24 . The HRSG of claim 1 , wherein the vertical steam separator is fluidly connected to the high pressure evaporator tubes via a plurality of tangential riser connections.

25 . The HRSG of claim 1 , wherein the vertical steam separator is fluidly connected to the high pressure evaporator tubes via a plurality of straight riser connections.

26 . A method of retrofitting a HRSG, comprising:

removing a steam drum from the HRSG; and

replacing the steam drum with a vertical steam separator.

27 . The method of claim 26 :

wherein one or more steam drums selected from the group consisting of a high pressure steam drum, intermediate pressure steam drum, and low pressure steam drum is replaced with one or more vertical steam separators.

28 . A rapid start heat recovery steam generator comprising a high pressure section, an intermediate pressure section, and a low pressure section;

wherein the high pressure section comprises a vertical steam separator, a high pressure evaporator fluidly connected to the vertical steam separator via a plurality of high pressure risers at a top end and via a high pressure recycle line at a bottom end, and a high pressure superheater fluidly connected to the vertical steam separator via a high pressure dry steam conduit;

wherein the intermediate pressure section comprises an intermediate pressure steam drum, an intermediate pressure economizer fluidly connected to the intermediate pressure steam drum, an intermediate pressure evaporator fluidly connected to the intermediate pressure steam drum via intermediate pressure risers and an intermediate pressure recycle line, and an intermediate pressure superheater fluidly connected to the intermediate pressure steam drum via an intermediate pressure dry steam conduit; and

wherein the low pressure section comprises a low pressure steam drum, a low pressure economizer fluidly connected to the low pressure steam drum, a low pressure evaporator fluidly connected to the low pressure steam drum via low pressure risers and a low pressure recycle line, and a low pressure dry steam conduit extending from the low pressure steam drum.