Patent Application
20130031910
The present application and the resultant patent relate generally to gas turbine engine systems and more particularly relate to a gas turbine engine system having a selective catalyst reduction system driven by captured carbon dioxide or other types of gases.
Generally described, carbon dioxide (“CO2”) produced in power generation facilities and the like is considered to be a greenhouse gas. As such, governmental regulations generally require the capture and sequestration of the carbon dioxide produced in the overall power generation process as opposed to venting into the atmosphere. Specifically, the carbon dioxide may be compressed and intercooled in a number of stages to reach a supercritical state. The carbon dioxide then may be liquefied and transported for end usage such as deep ocean sequestration, enhanced oil recovery, or other uses.
Likewise, power generation equipment produces nitrogen oxides (NOx) and other gasses. The production of nitrogen oxides also is subject to increasing governmental regulation. One solution for reducing overall nitrogen oxide emissions in gas turbine engines is the use of a selective catalyst reduction (“SCR”) system. Such a SCR system may be connected to the gas turbine exit via ducting and the like. The SCR system adds a reductant, typically ammonia or urea, to the exhaust gas stream before passing the stream through a catalytic bed so as to absorb selectively the nitrogen oxides and the reducing agent. The absorbed components undergo a chemical reaction on the catalyst surface and the reaction products are desorbed. Specifically, the reductant reacts with the nitrogen oxides in the flow of exhaust gas to form water and nitrogen (4NO+4NH3—O2=6H20+4N2 at about 549 degrees Fahrenheit to about 664 degrees Fahrenheit (about 287.2 degrees Celsius to about 351.1 degrees Celsius)). Catalysts that use other types of reductants also are known in the art.
Although known SCR systems generally are efficient at reducing the amount of nitrogen oxides, emissions may be reduced by up to about ninety percent (90%) in some applications, such systems generally require a dedicated atomizing air source, a flue gas recirculation line with a flue gas fan, or both in order to vaporize and atomize the ammonia. As such, the overall SCR system involves at least some parasitic drain on the gas turbine engine system as a whole. Further, nitrogen oxide emissions also may spike during transient operation conditions such as during engine startup, load swing conditions, and the like. These nitrogen oxide output spikes may result with the gas turbine engine system being out of compliance with current governmental emissions regulations.
There is thus a desire for an improved gas turbine engine system using selective catalyst reduction systems and the like. Such SCR systems or other types of emissions reduction systems should maintain overall nitrogen oxide emissions within governmental regulations while eliminating or reducing the parasitical loads on the gas turbine engine system usually required for such systems for increased overall performance and efficiency.
The present application and the resultant patent thus provide a gas turbine engine system. The gas turbine engine system may include a gas turbine engine producing a flow of combustion gases, an emissions reduction system in communication with the gas turbine engine, a flow of ammonia to be injected into the flow of combustion gases, and a source of compressed gas to vaporize the flow of ammonia.
The present application and the resultant patent further provide a method of operating a gas turbine engine system. The method may include the steps of generating a flow of combustion gases, compressing a flow of carbon dioxide, vaporizing a flow of ammonia with the compressed flow of carbon dioxide, and injecting the vaporized flow of ammonia into the flow of combustion gases.
The present application further provides a gas turbine engine system. The gas turbine engine system may include a gas turbine engine producing a flow of combustion gases, a selective catalyst reduction system in communication with the gas turbine engine, a flow of ammonia to be injected into the flow of combustion gases, and a carbon dioxide capture and sequestration system to provide a flow of carbon dioxide to vaporize the flow of ammonia.
These and other features and improvements of the present application and the resultant patent will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims.
Referring now to the drawings, in which like numerals refer to like elements throughout the several views,
If the gas turbine engine 10 is in the form of a combined cycle system 60, a heat recovery steam generator 62 may be in communication with the ducting 54 so as to exchange heat between a flow of steam 64 and the flow of combustion gases 40. The heat recovery steam generator 62 may be in communication with one or more steam turbines 66. The steam turbines 66 may drive the same or a separate load 52. Other components and other configurations may be used herein.
The gas turbine engine system 10 also may include an SCR system 70 or other type of emissions reduction system and the like. The SCR system 70 may include an ammonia injection grid 72 positioned within or about the ducting 54 with a catalyst 74 downstream thereof. The ammonia injection grid 72 may have a number of tubes 76 therein for spraying the ammonia or other reductant into the flow of combustion gases 40 for a reaction within the catalyst 74 so as to reduce the nitrogen oxides therein as described above.
The SCR system 70 also may include a vaporizer 78. The vaporizer 78 may be in communication with an aqueous ammonia flow 80 and an atomizing air flow 82. The vaporizer 78 also may be in communication with a flue gas extraction 84 from the ducting 60 via a flue gas fan 86. The flue gas extraction 84 vaporizes the atomized ammonia flow within the vaporizer 78. The gaseous ammonia then may be delivered to the ammonia injection grid 72 via an ammonia injection grid manifold 88. Other components and other configurations may be used herein.
The gas turbine engine system 10 also may include a carbon dioxide capture and sequestration system 90 or other type of compressed gas source. The carbon dioxide capture and sequestration system 90 may capture the carbon dioxide within the flow of combustion gases 40 downstream of the SCR system 70. The carbon dioxide capture and sequestration system 90 may include a number of carbon dioxide compressors 92, a number of intercoolers 94, and/or other components. As described above, the carbon dioxide capture and sequestration system 90 compresses and cools the flow of carbon dioxide to a supercritical state for storage and transport. The carbon dioxide compressors 92 and the intercoolers 94, however, are considered a parasitic load on the overall gas turbine engine system 10. Other components and other configurations may be used herein.
The gas turbine engine system 100 also may include an emissions reduction system 140. In this example, the emission reduction system 140 may be a selective catalyst reduction system 145. Similar to that described above, the SCR system 145 may include an ammonia injection grid 150 with a catalyst 160 positioned downstream thereof. The ammonia injection grid 150 may include a number of tubes 170 therein in order to inject a flow of ammonia 175 into the ducting 54 and the flow of combustion gases 40 of the gas turbine engine 15. The SCR system 145 also may include a vaporizer 180. The vaporizer 180 may be in communication with an aqueous ammonia line 190. The vaporizer 180 provides vaporized ammonia to a manifold 200 of the ammonia injection grid 150.
The vaporizer 180 also may be in communication with the one or more flows of the carbon dioxide 135. Specifically, a first carbon dioxide line 210 may be positioned downstream of the first carbon dioxide compressor 122 and in communication with the vaporizer 180 while a second carbon dioxide line 220 may be positioned further downstream and in communication with the aqueous ammonia line 190. The second carbon dioxide line 220 thus provides the flow of carbon dioxide 135 so as to atomize the flow of aqueous ammonia from the aqueous ammonia line 190 while the flow of carbon dioxide 135 from the first carbon dioxide line 210 serves to vaporize the ammonia therein for use downstream in the manifold 200 of the ammonia injection grid 150. Other components and other configurations may be used herein.
The SCR system 145 thus eliminates the use of the flue gas extraction 84, the flue gas fan 86, and the atomizing air flow 82 through the use of the flows of carbon dioxide 135 from the first carbon dioxide line 210 and the second carbon dioxide line 220. Moreover higher amounts of the flow of carbon dioxide 135 may be recirculated so as to increase the momentum flux ratio issue through the ammonia injection grid 150 so as to improve mixing between the flow of ammonia 175 and the combustion gases 40. Increased mixing should improve the overall efficiency of the SCR system 145. Other components and other configurations may be used herein.
Instead of the vaporizer 180, however, the SCR system 240 may use an ejector 250. The ejector 250 is a mechanical device with no moving parts. The ejector 250 mixes two fluid steams based on a momentum transfer. A motive air inlet 260 may be in communication with higher pressure air from the second carbon dioxide line 220. The ejector 250 also may include a suction air inlet 270. The suction air inlet 270 may be in communication with the first carbon dioxide line 210 and the aqueous ammonia line 190. The ejector 250 also includes a mixing tube 280 and a diffuser 290. The higher pressure flow of carbon dioxide 135 from the second carbon dioxide line 220 enters the motive air inlet 260 as the motive flow and is reduced in pressure below that of the flow of carbon dioxide 135 from the first carbon dioxide line 210 as the suction flow and is accelerated therewith. The flows are mixed in the mixing tube 280 and flow through the diffuser 290. The ejector 250 thus atomizes and vaporizes the flow of aqueous ammonia therein. Other components and other configurations of the ejector 250 and the like may be used herein.
The pressure created in the ejector 250 is high enough to create a sonic jet through the ammonia injection grid 150. As a result, the number of tubes 170 in the ammonia injection grid 150 may be reduced. For example, as is shown in
A heater 295 also may be used on the first and/or second carbon dioxide lines 210, 220 during transient operations and the like in case the flow of carbon dioxide 135 may not be warm enough to vaporize the flow of ammonia 175. The temperature of the compressor discharge may vary depending upon location and insulation. For example, an electrical heater may be used herein. The heater 295 then may be turned off once the flow of carbon dioxide 135 is sufficiently warm. Steam or any other type of heat source also may be used for vaporization. For example, the flow of steam 64 from the heat recovery steam generator 62 or otherwise could be used either to heat the flow of carbon dioxide 135 or as the motive fluid itself or a portion thereof. An ambient air flow also may be entrained by the ejector 250 for higher efficiency. Alternatively, the flow of carbon dioxide 135 may pass through the heat recovery steam generator 62 and exchange heat therein.
Still referring to
The second carbon dioxide line 220 may be in communication with an aqueous ammonia heat exchanger 340. The aqueous ammonia heat exchanger 340 may be positioned on the aqueous ammonia line 190 upstream of the ejector 250. The flow of carbon dioxide 135 from the second carbon dioxide line 220 thus exchanges heat with the flow of ammonia 175 in the aqueous ammonia line 190 so as to convert the flow to gaseous form. The flow of carbon dioxide 135 then enters the motive air inlet 260 while the flow of ammonia 175 enters the suction inlet 270 in a manner similar to that described above. The flow of carbon dioxide 135 thus creates a sonic jet through the ammonia injection grid 150. The use of the aqueous ammonia heat exchanger 340 also improves overall ejector 250 performance. Other components and other configurations may be used herein.
The IGCC system 380 thus may include a number of nitrogen compressors 430 and intercoolers 440 similar to the carbon dioxide compressors and intercoolers described above. The IGCC system 380 thus may provide the flow of nitrogen 400 to the vaporizer 180 via a first nitrogen line 450 and a second flow of nitrogen 400 via a second nitrogen line 460 in a manner similar to the first carbon dioxide line 210 and the second carbon dioxide line 220. The flow of nitrogen 400 thus may be used for the atomization and vaporization of the aqueous ammonia in the SCR system 145. Because the temperature of nitrogen may be less than about 350 degrees Fahrenheit (about 176.7 degrees Celsius), the temperature will not impact the reaction flue gas and should help in overall control of nitrogen oxide emissions. Other components and other configurations may be used herein.
Although the present application is prescribed in terms of the SCR systems, the same types of delivery systems for the ammonia injection grid described herein also are applicable to other types of combustion systems with emissions reduction systems 140. For example, the emissions reduction system 140 may be in the form of a heat recovery steam generator used in a stoichiometric exhaust gas recovery (SEGR) system 500 and the like. Inert carbon dioxide or nitrogen may be used as a carrier for the ammonia for NOx reduction as opposed to the traditional bypass flows used therein. Other components and other configurations may be used herein.
The use of the flows of compressed carbon dioxide 135 and/or nitrogen 400 thus eliminates or at least reduces the parasitic loads generally found in use of SCR systems and other types of emissions reduction systems. Moreover, the complexity of the overall systems should be reduced herein. As such, overall power plant efficiency and output should improve.
It should be apparent that the foregoing relates only to certain embodiments of the present application and the resultant patent. Numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.
