KR20040013429A - Cooling air system and method for combined cycle power plants - Google Patents

Abstract

PURPOSE: A composite cycle generator and an operation method thereof are provided to reduce stress of a tube sheet, to increase the life span and reliability of components, to simplify the control of a system, and to reduce the size of a heat exchanger and the cost of the system. CONSTITUTION: A composite cycle generator comprises a combustion turbine system(10), a vapor generator(32), a vapor turbine system(34) for receiving at least one vapor flow, and a cooling air current path for orienting a compressed air portion(156) toward at least one compressor(14) and a gas turbine(24) from the compressor to cool a part. The combustion turbine system has the compressor for producing compressed air(16); a burner(18) burning fuel in the compressed air and producing combustion air; and the gas turbine expanding combustion air and producing mechanical energy and exhaust gas(30). The vapor generator has an inlet for receiving the exhaust gas and plural regions sequentially arranged in a flow path of exhaust gas, to remove the heat from the exhaust gas and produce at least one vapor flow(38). The cooling air current path includes a heat exchange system(154) for receiving the compressed air portion, for removing the heat from the compressed air portion, and for producing a heated fluid flow(202) and a cooled compression air current(168). The heat exchange system includes a chamber(158) having at least one tube(160) for making water flow to exchange heat with high-temperature compressed air disposed in the chamber. The chamber includes a compressed air inlet(176) and a compressed air outlet(178).

Description

COOLING AIR SYSTEM AND METHOD FOR COMBINED CYCLE POWER PLANTS

The present invention relates to a gas turbine cycle using a cooling air (CCA) system for cooling the extracted hot cooling air to cool the turbine or compressor portion.

In modern high efficiency gas turbine cycles, hot compressor air is extracted to cool the compressor or turbine portion. With regard to reliability, improved CCA system architectures are required due to difficulty of control and expensive CCA systems.

1 is a schematic diagram of a combined cycle system having a prior art cooled cooling air system (hereinafter referred to as a CCA system) for cooling the extracted hot compressor air to cool the turbine and compressor portions. In the generator shown, a gas turbine system 10 is provided that includes a compressor 14, a combustion system 18, and a gas turbine expander 24, the steam turbine system of which is schematically shown at 34. . More specifically, the compressed air 16 generated as air 12 enters the axial flow compressor 14 enters the combustion system 18, where fuel is injected into the combustion system 18 so that combustion It is done. Combustion mixer 22 exits combustion system 18 and enters turbine 24. In the turbine section, the energy of the hot gas is converted to work. This conversion occurs in two stages, where the hot gas is expanded and a portion of the thermal energy is converted into kinetic energy in the nozzle section of the turbine. Then, in the bucket section of the turbine, part of the kinetic energy is transferred to the rotating bucket and converted into work. Thus, part of the work developed by the turbine drives the compressor 14, while the rest is used for example for a generator or mechanical load device 28. The exhaust gas 30 flows out of the turbine and flows into the heat recovery device. The heat recovery apparatus may take the form of any of a variety of known heat exchange systems, including, for example, other conventional multiple compressed heat recovery system generators (HRSG) 32. In the figure, the gas turbine system 10 and the steam turbine system 34 each drive a separate generator (or other load device) 28, 36. The steam turbine system 34 is combined with a conventional scheme with multiple compression HRSGs 32. Thus, steam 38 enters or exits steam turbine system 34, where steam turbine system 34 exhausts to condenser 40, and the condensate is conduit 42 by condensate pump 44. Is fed from the condenser 40 to the HRSG 32. In this example only low pressure evaporator 46, medium pressure evaporator 48 and high pressure evaporator 50 are shown and are well understood as a number of economizers, with superheaters and coupled conduit light valves typically provided to HRSGs. And are simply omitted because they are not directly relevant to the description herein.

As described above, heat is provided to the HRSG 32 by the gas turbine exhaust gas 30 injected into the HRSG 32 and exits the HRSG 52 and passes through an exhaust pipe (not shown). Other descriptions of such conventional systems will generally limit such components provided as a coupling part of the CCA system 54.

In the illustrated CCA system 54, as shown schematically, the hot compressor air is extracted by a conduit 56 at a temperature of, for example, 850 ° F. to 900 ° F., and in a pot-type boiler shell and tube heat exchanger. Cooled to about 500 ° F. to 550 ° F. The pot-type boiler 58 has a U-shaped tube bundle 60, shown schematically as a tube, immersed in the water 62 of the pool on the side of the cell, with hot compressor air inside the tube. The hot air stream in the tube causes hot water in the pool 62, and the generated saturated vapor 64 is received in a medium compression (IP) evaporator 48 vapor drum in a heat recovery steam generator (HRSG) 32. The IP economizer discharge 66 constitutes the vapor 64 generated by being received in the cell of the boiler 58. Cooled air 68 exiting the CCA heat exchanger 58 is used for the compressor and / or turbine portion by conduits 70 and 72 as schematically shown. Side tubes 74 on the air side are also provided to control the air temperature exiting the CCA system 54. Since the CCA system is designed to pressure drop the low system air side, two passage U-shaped tube bundles are commonly used for power cycle thermal efficiency.

There is a potential area of progress with respect to the CCA system described above.

The two passage tube structure described above allows one half of the tube sheet to be exposed to the incoming hot air while the other half is exposed to the cooled air exiting the heat exchanger on the air side. This results in high thermal stress on the tube sheet. Single passage cooker boilers overcome this problem, and single passage construction will require cell expansion joints or slide tube sheets for reliability.

Accurate water level control on the side of the cell is required to prevent excess transport of water in saturated steam and to prevent the tubes in the water pool from being exposed and the hot air tubes being exposed to water only temporarily. In this regard, drum levels are generally calculated by measuring different pressures in the drum and calculating the density of the drum water. However, because there is steam bubbles in the hot water pool of water, accurate calculation of evasion rate is required for accurate density and level calculation. The calculation of evasion rate is useful for this type of application, especially in transient situations.

As also described below, the air side is configured so that the low pressure drop is low. Therefore, the rate of heat transfer on the air side is low because the velocity of air in the tube is low. Heat exchanger size can be advantageously reduced by applying an extended surface (such as a side vane) on the low heat transfer side. The extended surface can be economically applied on the outer tube surface.

The present invention provides a CCA system for application in modern gas turbine cycles, overcoming the reliability, control and cost associated with those identified above.

In particular, in an embodiment of the present invention the CCA system comprises a cell and tube heat exchanger, where water flow is provided inside the tube and air flow is provided on the cell side of the heat exchanger. In such a system, the water discharged from the heat exchanger is partially evaporated. Thus, as another feature of the invention, the final two-phase water / vapor flow is received in a separator / flash drum such that steam and water are separated. Saturated steam exiting the separator generally flows to the HRSG after being pumped to a higher pressure by a recycle water pump.

Since airflow is provided outside the tube, the side winged tube can reduce the overall heat exchanger size.

The present invention provides a compressor for generating compressed air, a combustor for combusting fuel in the compressed air to generate combustion air, a gas turbine for expanding combustion air to generate mechanical energy and exhaust gas, and exhaust gas. A steam generator having an inlet for accommodating the fuel cell, a plurality of sections sequentially positioned in the flow path of the exhaust gas to remove heat from the exhaust gas and to generate at least one vapor flow, and to receive at least one vapor flow. A steam turbine system for cooling and a cooling air flow path for directing a portion of the compressed air from the compressor to the at least one compressor and the gas turbine to cool a portion thereof; The cooling airflow path includes a heat exchange system for receiving the compressed air portion and removing heat from the compressed air portion to generate a heated fluid flow and a cooled compressed air stream, wherein the heat exchange system includes a compressed air inlet and a compressed air stream. A chamber having an air outlet, implemented as a combined cycle generator comprising a chamber having at least one tube for flowing water for heat exchange with hot compressed air disposed within the chamber.

The invention also provides a heat exchange system comprising a chamber having a compressed air inlet and a compressed air outlet, the chamber having at least one tube for flowing water for heat exchange with hot compressed air disposed within the chamber. Providing a combustor, operating a combustion turbine system to combust the fuel to generate a flow of hot compressed air, mechanical energy and exhaust gas, and to generate cooled compressed air and heated fluid flow. A combined cycle generator having an internal combustion engine system, a heat recovery steam generator and a steam turbine system, comprising directing a portion through the heat exchange system and directing the cooled compressed air to cool a portion of the combustion turbine system. Is implemented in a way that works.

1 is a schematic diagram of a combined cycle generator in combination with a conventional cooled cooling air system,

2 is a schematic diagram of a combined cycle generator in combination with a cooled cooling air system according to the present invention.

Explanation of symbols for main parts of the drawings

10 combustion turbine system 14 compressor

18 combustor 24 gas turbine

32: HRSG34: steam turbine system

48: second section 50: first section

154: cooled cooling air system

158: heat exchanger 160: tube heat exchanger

176: air inlet 178: air outlet

204 Separator 206 Valve

208: Pump

The following description of the invention generally defines such components provided or added as an embodiment of the invention. Reference numerals shown in FIG. 2, which are not described below as being substantially identical to corresponding components of the system of FIG. 1, are indicated by providing a frame for reference. Components generally corresponding to the components shown in FIG. 1 are denoted by the same reference numerals as the components used in FIG. 1, and components changed according to an embodiment of the present invention are displayed with an increment of 100.

The CCA system 154 according to the present invention includes a tube heat exchanger and a cell 158 that is adjusted for water flow inside the tube and airflow on the cell side. Airflow is extracted from the compressor and flows through the conduit 156 to the air inlet 176 in the cell 158. The hot compressed air flows around it between the heat exchangers 160 and the final cooled air flows through the outlet 178. Cooling air flows through conduit 168 as shown schematically in flow paths 170 and 172 for use as cooling air. Side tubes 174 are formed of conduits 156-168 to control the cooling air temperature.

In the illustrated embodiment, water enters a heat exchanger with a small secondary cooling (ie, lower than saturation temperature) at 200 and is partially evaporated in the heat exchanger (10% to 20% mass ratio). The final two-phase water / vapor flow 202 is then received into a separator / flash drum 204 where steam and water are separated. Separated vapor 164 exits the separator and is received in an IP evaporation drum in HRSG 32. IP economizer discharge 166 constitutes the steam generated received in the separator, and this water flow is controlled by, for example, valve 206 to maintain a constant level in separator 204.

Separator water 162 is pumped to higher pressure by recycle water pump 208 and is received as heat exchanger 158 at 200 as described above. The pump discharge pressure is selected to overcome the circulating water system pressure drop.

Airflow outside the tube allows the use of side vane tubes (not shown in detail) to reduce the overall heat exchanger size. For example, an extra pump, which is the pump 208, is used to increase the reliability of the system. Although the vertical separator 204 is shown in FIG. 2, the horizontal separator may be used for this embodiment with the added advantage that horizontal separation can be stacked on top of the heat exchanger.

In an exemplary embodiment, the water flow rate in the recycle water circuit is maintained at a constant rate for the entire gas turbine operating mode, including part load operation. The water flow rate (constant) is selected such that the maximum tube side water evaporation is limited to approximately 10% to 20% (ie, the circulation ratio is between 5: 1 to 10: 1) over the entire gas turbine operating envelope. .

Key features / advantages of the system architecture and control proposed herein throughout the flow system are as follows. Providing water on the tube side eliminates the tube sheet temperature gradient encountered when water flows in the tube in the pot-like boiler structure. The temperature increase on the tube side of the tube sheet is less than 10 ° F. and the high temperature drop on the airflow side of the heat exchanger spreads throughout the entire tube sheet. Thus, the stress on the tube sheet is significantly reduced and the life and reliability of the component will increase.

The water level control in the system shown is in separator 204, where hot water is not achieved and therefore it is possible to reliably calculate the density of the water without the uncertainty of the avoidance rate encountered in the water hot water pool. This makes the level control and level control accurate from different pressure measurements. While accurate level control is possible, it should be noted that the heat exchanger tube is not very important in the proposed system structure because it is not immersed in water as in conventional pot boilers.

As mentioned above, the control method disclosed herein significantly simplifies the control of the system by maintaining a constant water flow rate in the recirculating water circuit for all operations of the gas turbine.

The airflow on the cell side reduces the size and system cost of the heat exchanger by allowing the use of extended surface tubes, ie side vanes.

Although the description of the system is referred to above as generating the IP vapor 164 by the CCA system, the system can be used for LP vapor EH vapor. The pressure level of steam generated will be determined by the air temperature (inside / outside of the CCA heat exchanger) required for the individual application.

It will be appreciated that the illustrated assembly is only one embodiment of a generator that can be applied to a CCA system. In this regard, the combined cycle system may be a multiple pressure reheating combined cycle and / or gas turbine, steam turbine and generator that may be arranged in a longitudinal connection to a single generator on a single shaft rather than the multiple shaft structure shown.

Although the present invention has been described in terms of what is currently recognized as the most practical and preferred embodiment, the invention is not limited to the above-described embodiments, but rather includes several modifications and equivalent arrangements included within the spirit and scope of the appended claims. It will be understood.

According to the present invention, there is an effect of overcoming the reliability, control and cost associated with the above identified by providing a CCA system for application in modern gas turbine cycles.

Claims (11)

In a combined cycle generator, A compressor (14) for generating compressed air (16), a combustor (18) for generating combustion air (22) by burning fuel (20) in the compressed air, and expanding the combustion air A combustion turbine system 10 having a gas turbine 24 for generating mechanical energy and exhaust gas 30, An inlet for receiving the exhaust gas 30 and a plurality of sections sequentially located in the flow path of the exhaust gas to remove heat from the exhaust gas to generate at least one vapor flow 38. A steam generator 32, A steam turbine system 34 for receiving the at least one steam flow, A cooling air flow path for directing a portion of the compressed air (156) from the compressor (14) to the at least one compressor (14) and the gas turbine (24) to cool a portion thereof; The cooling airflow path includes a heat exchange system 154 for receiving the compressed air portion and for removing heat from the compressed air portion to generate a heated fluid flow 202 and a cooled compressed air stream 168. Wherein the heat exchange system is a chamber 158 having a compressed air inlet 176 and a compressed air outlet 178, and at least one for flowing water for heat exchange with hot compressed air disposed within the chamber. The chamber 158 having a tube 160 of Combined cycle generator. The method of claim 1, The plurality of sections includes a first section 50 and a second section 48, wherein the first section generates a vapor flow at a higher pressure in the second section. Combined cycle generator. The method of claim 2, And further comprising a first conduit 164 for flowing at least a portion of the heating fluid flow 202 generated by the heat exchange system into the second section 48. Combined cycle generator. The method of claim 3, wherein A second conduit 166 for supplying feed water from the second section 48 to the heat exchanger 154. Combined cycle generator. The method of claim 1, The at least one tube 160 is a side winged tube for increased heat exchange Combined cycle generator. In a combined cycle generator, A combustion turbine 10 operable to combust fuel 20 to generate mechanical energy 28 and hot exhaust gas 30, A heat recovery steam generator (32) having a plurality of sections (48, 50), operable to receive the hot exhaust gas and to generate steam (38) at a plurality of pressures; A steam turbine 34 operable to receive the steam 38 and generate the mechanical energy 36; A cooling air flow path for directing the compressed air portion 154 from the compressor 14 to the combustion turbine 10 to cool a portion thereof; The cooling airflow path is for receiving the compressed air portion 156 and for removing heat from the compressed air portion 156 to generate a heated fluid flow 202 and a cooled compressed air stream 168. A heat exchange system 154, which is a chamber 158 having a compressed air inlet 176 and a compressed air outlet 178, for heat exchange with hot compressed air disposed within the chamber. Comprising the chamber 158, having at least one tube 160 for flowing a fluid Combined cycle generator. In a method of operating a combined cycle generator comprising a combustion turbine system 10, a heat recovery steam generator 32, and a steam turbine system 34, A chamber 158 having a compressed air inlet 176 and a compressed air outlet 178 and at least one tube 160 for flowing water for heat exchange with hot compressed air disposed within the chamber. Providing a heat exchange system 154, Operating the combustion turbine system 10 to combust fuel 20 to generate a flow of hot compressed air 156, 16, mechanical energy 28 and exhaust gas 30; Orienting a portion 156 of the hot compressed air through the heat exchange system 154 to generate cooled compressed air 168 and heated fluid flow 202; Orienting the cooled compressed air 168 to cool a portion of the combustion turbine system 10. How a combined cycle generator works. The method of claim 7, wherein Providing the feed 166 for the heat exchange system from the heat recovery steam generator 32. How a combined cycle generator works. The method of claim 8, The heat recovery steam generator 32 has a high pressure section 50, an intermediate pressure section 48 and a low pressure section 46, wherein the step of providing the feed water is supplied from the medium pressure section 48 Comprising the steps of providing How a combined cycle generator works. The method of claim 9, The heat exchange system further includes a flow separator 204 for separating the heated fluid flow 202 into water 162 and a first vapor flow 164, and separating the water 162 into the tube in the chamber. Further comprising recycling to 160 How a combined cycle generator works. The method of claim 10, Directing the first steam flow 164 to the intermediate pressure section 48 of the heat recovery steam generator 32. How a combined cycle generator works.