A steam reinjection gas-steam combined cycle system with waste heat recovery

Abstract

The present invention discloses a steam-reinjection gas-steam combined cycle system with waste heat recovery. The system comprises: a gas turbine FGH / TCA system, a combustion chamber steam reinjection device, and a waste heat boiler combined heat exchange module. The gas turbine FGH / TCA system is equipped with an FGH heat exchanger and a TCA heat exchanger. The cold-side inlet of the FGH heat exchanger is connected to a cold natural gas pipeline, and the outlet is connected to the combustion chamber. The hot side of the FGH heat exchanger is connected to the compressor extraction pipeline, and the cold side is connected to the hot-side outlet of the FGH heat exchanger. Part of the outlet water from the high- and medium-pressure economizers of the waste heat boiler is heated to a set temperature in the FGH, and then fed into the cold side of the TCA heat exchanger to absorb the heat of the compressor extraction to become superheated steam, which is then injected into the combustion chamber and the cold re-header. The present invention solves the heat imbalance problem of the FGH / TCA system, performs steam injection modification on the combustion chamber, and improves the system output power and efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of gas turbine energy regulation, and in particular to a waste heat recovery steam reinjection type gas-steam combined cycle system. Background Art

[0002] A gas-steam combined cycle power plant is a highly efficient energy conversion device, consisting of a Brayton cycle consisting of a gas turbine and a Rankine cycle consisting of a waste heat boiler and steam turbine. The high-temperature exhaust gas from the gas turbine serves as the heat source for the bottoming cycle, heating feedwater to produce superheated steam at various pressure levels. This steam then enters the steam turbine for expansion and work, thus achieving cascaded energy utilization. Currently, advanced combined cycle units can achieve efficiencies of up to 60%. Most domestic gas-fired units operate as peak-shaving units due to their superior peak-shaving performance.

[0003] Advanced turbine cooling technology is crucial for increasing gas turbine turbine inlet temperature (TIT) and achieving higher efficiency and thermal performance. Currently, cooling air for gas turbine moving parts is extracted from the final stage of the compressor. After passing through the turbine rotor cooling air system (TCA system), it exchanges heat with an external coolant before being fed into the turbine blades and rotor for cooling. The coolant absorbs heat and heats up, which is then used to heat natural gas to a certain temperature before being fed into the gas turbine combustion chamber, achieving cascaded energy utilization. This is known as the fuel heater heat exchange system (FGH system). Gas turbine TCA and FGH systems often experience an energy imbalance. For example, in a Mitsubishi M701F3 gas turbine system, the TCA air cooling load is approximately 11,300 kW, while the FGH natural gas heating load is approximately 5,600 kW. This results in the FGH heat exchange outlet air still retaining unused excess heat of approximately 160°C, dissipating over 5,300 kW of heat to the air and causing thermal pollution.

[0004] In addition, when the gas-steam combined cycle unit is running at partial load, there is a problem that the exhaust temperature of the gas turbine does not match the heat exchange of the waste heat boiler, and the temperature difference is too large. It can be considered to transfer part of the heat of the bottom cycle to the top cycle, extract the steam from the waste heat boiler and inject it back into the combustion chamber to improve the thermal efficiency of the top cycle, thereby reducing the temperature difference between the flue gas inlet temperature of the waste heat boiler and the main steam, and reducing heat transfer. In summary, the flexible transformation of the gas-steam combined cycle system by flexibly allocating appropriate-grade working fluids in the bottoming cycle to achieve a balance between heat absorption and supply in the FGH / TCA system and generate steam for reinjection into the combustion chamber has broad prospects. Summary of the Invention

[0005] In order to overcome the defects and shortcomings of the existing technology, the present invention provides a steam reinjection gas-steam combined cycle system with waste heat recovery, which realizes the cascade and efficient utilization of energy and improves the operating performance and economy of the unit.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention provides a waste heat recovery steam reinjection type gas-steam combined cycle system, comprising: a gas turbine FGH / TCA system, a combustion chamber steam reinjection device and a waste heat boiler combined heat exchange module;

[0008] The combustion chamber steam reinjection device is provided with a combustion chamber and a third three-way valve, and the gas turbine FGH / TCA system is provided with an FGH heat exchanger and a TCA heat exchanger;

[0009] The hot side inlet of the FGH heat exchanger is connected to the waste heat boiler water extraction pipeline, the hot side outlet of the FGH heat exchanger is connected to the cold side inlet of the TCA heat exchanger, the cold side inlet of the FGH heat exchanger is connected to the cold natural gas pipeline, and the cold side outlet of the FGH heat exchanger is connected to the combustion chamber;

[0010] The hot side inlet of the TCA heat exchanger is connected to the compressor exhaust pipe, the hot side outlet of the TCA heat exchanger is connected to the gas turbine, the compressor outlet is connected to the combustion chamber, and the cold side outlet of the TCA heat exchanger is connected to the combustion chamber and the waste heat boiler cold reheader via a third three-way valve.

[0011] The waste heat boiler on the hot side of the FGH heat exchanger draws water to heat the natural gas on the cold side. The cooled waste heat boiler water absorbs the heat of the compressor extraction air in the TCA heat exchanger and turns into superheated steam, achieving heat balance in the gas turbine FGH / TCA system.

[0012] The combustion chamber obtains hot natural gas from the cold side outlet of the FGH heat exchanger, air from the compressor outlet, and superheated steam from the cold side outlet of the TCA heat exchanger, and burns the mixed gas to produce flue gas which is fed into the gas turbine to produce work and drive the generator to output electricity.

[0013] The waste heat boiler combined heat exchange module is equipped with multiple pressure modules for generating steam of different pressures and temperature grades to drive the corresponding pressure cylinders to generate power;

[0014] The flue gas containing water vapor output by the gas turbine is input into the waste heat boiler combined heat exchange module for heat exchange;

[0015] A condensing heat exchanger is installed at the outlet of the waste heat boiler to recover the water vapor in the flue gas of the waste heat boiler combined heat exchange module and return it to the waste heat boiler.

[0016] As a preferred technical solution, the hot side inlet of the FGH heat exchanger is further connected to a third flow control valve, a first temperature sensor, and a first pressure sensor;

[0017] The third flow control valve is used to adjust the pumping water flow to change the supplied heat so that the cold natural gas is heated to a set temperature. The first temperature sensor and the first pressure sensor are used to detect the temperature and pressure of the pumping water respectively.

[0018] As a preferred technical solution, the cold side inlet of the FGH heat exchanger is connected to a natural gas pipeline provided with a first three-way valve, and is connected in parallel with a cold natural gas pipeline provided with a first flow control valve;

[0019] The first three-way valve is used to divide the cold natural gas in the natural gas pipeline into two paths, one path entering the cold side inlet of the FGH heat exchanger, and the other path entering the cold natural gas pipeline provided with the first flow control valve. The two paths of natural gas are mixed at the cold side outlet of the FGH heat exchanger and then fed into the combustion chamber.

[0020] The first flow control valve is used to regulate the temperature of the natural gas entering the combustion chamber.

[0021] As a preferred technical solution, the hot side inlet of the TCA heat exchanger is connected to the compressor exhaust pipe equipped with a second three-way valve, and is connected in parallel with the hot air pipe equipped with a second flow control valve;

[0022] The second three-way valve is used to divide the compressor hot air into two paths, one path entering the hot side of the TCA heat exchanger, and the other path entering the parallel pipeline equipped with a second flow control valve. The two air paths converge in a pipeline equipped with a second pressure sensor and a second temperature sensor at the hot side outlet of the TCA heat exchanger, and are then sent to the gas turbine to cool the moving blades and rotor. The second pressure sensor and the second temperature sensor are used to detect the pressure and temperature of the air in the pipeline, respectively.

[0023] As a preferred technical solution, the combustion chamber steam reinjection device is further provided with a fourth flow control valve, which is connected to the waste heat boiler cold re-header and the third three-way valve respectively, and is used to control the amount of steam entering the combustion chamber;

[0024] And / or, the cold side outlet of the TCA heat exchanger is further provided with a third pressure sensor and a third temperature sensor, which are used to detect the pressure and temperature of the steam at the cold side outlet, respectively.

[0025] As a preferred technical solution, the compressor inlet is provided with an air throttle valve for controlling the pressure and mass flow of air entering the compressor.

[0026] As a preferred technical solution, the waste heat boiler combined heat exchange module includes a reheat module, a high pressure module, a medium pressure module and a low pressure module;

[0027] The high-pressure module, medium-pressure module and low-pressure module generate steam of different pressures and temperature grades to drive the high-, medium- and low-pressure cylinders of the corresponding steam turbines to generate power. The exhaust steam is condensed in the condensing heat exchanger and pressurized by the condensate pump to enter the low-pressure module.

[0028] The low-pressure saturated steam in the waste heat boiler combined heat exchange module flows through the low-pressure superheater to generate low-pressure superheated steam. The low-pressure drum is divided into two water routes. One route is boosted by the medium-pressure feed water pump to form medium-pressure feed water, which flows through the medium-pressure evaporation section and the superheating section to generate medium-pressure superheated steam. The other route is boosted by the high-pressure feed water pump to form high-pressure feed water, which is then passed through the high-pressure module to generate high-pressure superheated steam.

[0029] The high-pressure superheated steam enters the high-pressure cylinder of the steam turbine to expand. The high-pressure exhaust steam after doing work is mixed with the medium-pressure superheated steam of the waste heat boiler into the cold reheader to form cold reheated steam. The reheated steam after being heated by the reheat module enters the intermediate-pressure cylinder of the steam turbine to expand and do work. The exhaust steam of the intermediate-pressure cylinder is mixed with the low-pressure superheated steam of the waste heat boiler and enters the low-pressure cylinder of the steam turbine to do work.

[0030] As a preferred technical solution, the high-pressure economizer outlet of the high-pressure module is provided with a fourth three-way valve, and the medium-pressure economizer outlet of the medium-pressure module is provided with a fifth three-way valve;

[0031] The fourth three-way valve and the fifth three-way valve are both connected to the sixth three-way valve, and the sixth three-way valve is connected to the hot side inlet of the FGH heat exchanger. The high-pressure economizer extraction water and the medium-pressure economizer extraction water are sent to the hot side inlet of the FGH heat exchanger through the sixth three-way valve.

[0032] As a preferred technical solution, a fifth flow control valve is further provided on the high-pressure economizer outlet water extraction pipeline to control the water flow rate at the high-pressure economizer outlet.

[0033] The present invention also provides another waste heat recovery steam reinjection type gas-steam combined cycle system, comprising: a TCA heat exchanger, a combustion chamber steam reinjection device and a waste heat boiler combined heat exchange module;

[0034] The combustion chamber steam reinjection device is provided with a combustion chamber, a steam injection nozzle, and a third three-way valve;

[0035] The cold side inlet of the TCA heat exchanger is connected to the exhaust water pipeline of the waste heat boiler. The exhaust water of the waste heat boiler absorbs the heat of the compressor exhaust to generate superheated steam. The cold side outlet of the TCA heat exchanger is connected to the combustion chamber and the cold re-header of the waste heat boiler via a third three-way valve. Part of the steam at the cold side outlet of the TCA heat exchanger is fed into the combustion chamber through a steam injection nozzle. The hot side inlet of the TCA heat exchanger is connected to the exhaust pipe of the compressor. The hot side outlet of the TCA heat exchanger is connected to the gas turbine, and the outlet of the compressor is connected to the combustion chamber.

[0036] The combustion chamber obtains natural gas, compressor outlet air and steam from the cold side outlet of the TCA heat exchanger, and burns the mixed gas to produce flue gas which is fed into the gas turbine to produce work and drive the generator to output electricity.

[0037] The waste heat boiler combined heat exchange module is equipped with multiple pressure modules for generating steam of different pressures and temperature grades to drive the corresponding pressure cylinders to generate power;

[0038] The flue gas containing water vapor output by the gas turbine is input into the waste heat boiler combined heat exchange module for heat exchange;

[0039] A condensing heat exchanger is installed at the outlet of the waste heat boiler to recover the water vapor in the flue gas of the waste heat boiler combined heat exchange module and return it to the waste heat boiler.

[0040] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0041] (1) The present invention achieves full absorption of heat from the gas turbine TCA system and full supply of heat to the FGH system by flexibly scheduling the water extraction from the waste heat boiler, thereby solving the waste heat waste problem of the traditional FGH / TCA system, eliminating the thermal pollution caused by insufficient waste heat utilization, and achieving energy conservation and environmental protection.

[0042] (2) Compared with the traditional heat exchange system, the present invention adopts a combined heat exchange system of FGH / TCA and waste heat boiler, which inverts the traditional FGH / TCA heat exchange sequence, first supplies heat to the FGH heat exchanger and then absorbs air heat from the TCA heat exchanger, avoiding the problem of excessive heat in the TCA heat exchanger and generating additional superheated steam for production use.

[0043] (3) The present invention utilizes the FGH / TCA system to generate additional superheated steam, realizes the steam reinjection control in the gas turbine combustion chamber, reduces the gas turbine exhaust temperature, optimizes the top and bottom cycle thermal parameter configuration, and improves the top cycle thermal efficiency and system power output. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 Schematic diagram of the overall architecture of the steam reinjection type gas-steam combined cycle system with waste heat recovery in Example 1;

[0045] Figure 2 Schematic diagram of the overall architecture of the steam reinjection type gas-steam combined cycle system with waste heat recovery in Example 2.

[0046] Among them, 1- compressor, 2- gas turbine, 3- combustion chamber, 4- generator, 5- TCA heat exchanger, 6- FGH heat exchanger, 7- first three-way valve, 8- first flow control valve, 9- second three-way valve, 10- second flow control valve, 11- third three-way valve, 12- third flow control valve, 13- fourth flow control valve, 14- cold reheader, 15- high-pressure steam drum, 16- medium-pressure steam drum, 17- low-pressure steam drum, 18- fourth three-way valve, 19- fifth three-way valve, 20- high-pressure feed water pump, 21- medium-pressure feed water pump, 22- reheat module, 23- high-pressure module, 24- medium-pressure module, 25- low-pressure module, 26- fifth flow control valve, 27- sixth three-way valve, 28- air throttle valve, 29- condensing heat exchanger, 30- condensate, 31- cooling water, 32- seventh three-way valve, 33- booster water pump. DETAILED DESCRIPTION

[0047] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0048] Example 1

[0049] like Figure 1 As shown, this embodiment provides a steam reinjection type gas-steam combined cycle system for FGH / TCA waste heat recovery, comprising: a gas turbine FGH / TCA system, a combustion chamber steam reinjection device and a waste heat boiler combined heat exchange module;

[0050] In this embodiment, the gas turbine FGH / TCA system includes an FGH heat exchanger 6 and a TCA heat exchanger 5. The FGH heat exchanger 6 is a countercurrent heat exchanger located between the cold natural gas transmission pipeline and the gas turbine combustion chamber 3. The hot side inlet of the FGH heat exchanger 6 is connected to the waste heat boiler extraction water pipeline and is equipped with a third flow control valve 12, a temperature sensor, and a pressure sensor. The third flow control valve 12 is used to adjust the extraction water flow rate to ensure that sufficient heat is supplied to heat the cold natural gas to the set temperature.

[0051] The cold-side inlet and outlet of the FGH heat exchanger 6 are connected to the cold natural gas pipeline, and the cold-side outlet of the FGH heat exchanger 6 is connected to the combustion chamber 3. The cold-side inlet of the FGH heat exchanger 6 is connected to the natural gas pipeline with a first three-way valve 7 and is connected in parallel with the cold natural gas pipeline with a first flow control valve 8. The two converge at the cold-side outlet of the FGH heat exchanger 6. Specifically, before entering the FGH heat exchanger 6, the cold natural gas is divided into two paths by the first three-way valve 7. One path enters the cold side of the FGH heat exchanger, and the other path is connected in parallel with it. The two paths of natural gas are mixed at the cold-side outlet of the FGH heat exchanger 6 and are sent to the combustion chamber 3 after being monitored by pressure and temperature sensors to meet the standards. In addition, the first flow control valve 8 provided on the cold natural gas parallel pipeline is used to regulate the amount of natural gas entering the FGH heat exchanger 6.

[0052] The waste heat boiler on the hot side of the FGH heat exchanger 6 draws water to supply the heat required by the cold natural gas on the cold side of the FGH system. At the same time, by changing the flow rate, the first flow control valve 8 is coordinated to control the natural gas temperature at the combustion chamber inlet. The flow control valve on the cold side of the FGH heat exchanger can control the flow of natural gas entering the FGH heat exchanger.

[0053] The hot side of the TCA heat exchanger 5 is connected to the exhaust pipe of the compressor 1. Specifically, the hot side inlet of the TCA heat exchanger 5 is connected to the compressor exhaust pipe with a second three-way valve 9 and is connected in parallel with the hot air pipe with a second flow control valve 10. The TCA heat exchanger 5 is a countercurrent heat exchanger located between the outlet of the compressor 1 and the inlet of the turbine 2. The working medium on the hot side of the TCA heat exchanger 5 is the air extracted from the compressor 1. The outlet hot air is divided into two parts by the second three-way valve 9 in the hot air pipe. One part enters the hot side of the TCA heat exchanger 5, and the other part enters the parallel pipe with the second flow control valve 10. The two parts of air are heat exchanged in the TCA. The pipeline with pressure and temperature sensors converges at the hot side outlet of the TCA heat exchanger 5 to monitor the parameters of the cooling air entering the gas turbine 2, and then sends it to the gas turbine 2 to cool the moving blades and rotor. The cold side inlet of the TCA heat exchanger 5 is connected to the hot side outlet of the FGH heat exchanger 6, that is, the cold side working medium of the TCA heat exchanger 5 is the waste heat boiler pumped water after cooling at the hot side outlet of the FGH heat exchanger 6. The cold side inlet is connected to the FGH heat exchanger 6, and the cold side outlet is connected to the steam pipeline with pressure and temperature sensors. After being cooled in the FGH heat exchanger 6, the waste heat boiler pumped water absorbs the heat of the hot side air of the TCA heat exchanger 5, and is heated to become superheated steam, which flows out from the cold side outlet of the TCA heat exchanger 5.

[0054] In this embodiment, the cold-side inlet of the TCA heat exchanger 5 is connected to the hot-side outlet of the FGH heat exchanger 6. Part of the outlet water from the high- and medium-pressure economizers of the waste heat boiler heats the cold natural gas to the set temperature in the FGH heat exchanger 6. The water is then fed into the cold side of the TCA heat exchanger 5 to absorb the heat of the compressor extraction gas and convert it into superheated steam, thus achieving heat balance in the FGH / TCA system and fully recovering waste heat.

[0055] In this embodiment, a flow control valve is provided on the hot side of the TCA heat exchanger 5 to control the air flow entering the TCA heat exchanger 5, and on the cold side of the TCA heat exchanger 5 to cool down the hot side compressor of the TCA heat exchanger 5 and to regulate the turbine inlet cooling air temperature.

[0056] In this embodiment, the heat exchange between the cold and hot fluids in the FGH / TCA heat exchanger follows the heat balance equation, and the heat exchange capacity of the heat exchanger can be expressed as:

[0057]

[0058] The left side of the equation (1) represents the heat transfer on the cold side or hot side of the heat exchanger, and the right side of the equation (1) represents the heat transfer on the cold side or hot side of the heat exchanger. and They represent the fluid flow rate on the hot side and the fluid flow rate on the cold side of the heat exchanger, respectively. hot,in and h hot,out are the inlet and outlet enthalpies of the hot side fluid, h cold,in and h cold,out They represent the inlet and outlet specific enthalpies of the cold side fluid respectively.

[0059] In this embodiment, the heat transfer efficiency of the FGH / TCA heat exchanger can be expressed as:

[0060]

[0061] Among them, T on the right side of formula (2) hot,in and T hot,out are the inlet and outlet temperatures of the hot side fluid, T cold,in and T cold,out represent the inlet and outlet temperatures of the cold side fluid, respectively.

[0062] The heat exchangers are all arranged in countercurrent flow, where the logarithmic mean temperature difference and heat exchange area are:

[0063]

[0064] Where U is the heat transfer coefficient.

[0065] The combustion chamber steam reinjection device includes a steam injection nozzle of the gas turbine, a combustion chamber 3, a third three-way valve 11, a fourth flow control valve 13, a steam pipe, a pressure sensor, a temperature sensor, etc.;

[0066] The waste heat boiler at the cold side outlet of the TCA heat exchanger 5 draws water, which absorbs the heat from the compressor exhaust and then heats up to become superheated steam. The water flows to the pipes equipped with temperature and pressure sensors, with one part injected into the combustion chamber 3 and the other part sent to the cold reheader 14.

[0067] In this embodiment, steam reinjection into the combustion chamber involves installing a steam injection nozzle in the combustion chamber 3. Steam from the cold-side outlet of the TCA heat exchanger 5 flows through a pipeline equipped with a temperature sensor, a pressure sensor, and a third three-way valve 11. A portion of the steam is delivered to the combustion chamber 3 through the steam injection nozzle, while the remaining portion is returned to the cold reheader 14 of the waste heat boiler. A fourth flow control valve 13 is used to control the amount of steam entering the combustion chamber 3. Within the combustion chamber 3, the hot natural gas from the FGH heat exchanger 6, the air at the outlet of the compressor 1, and the steam at the cold-side outlet of the TCA heat exchanger 5 are mixed and combusted to produce high-temperature, high-pressure flue gas, which is then fed into the gas turbine 2 to produce work, driving the generator 4 to output electricity.

[0068] In this embodiment, the reinjection steam pipe entering the combustion chamber 3 is equipped with pressure and temperature sensors. On the one hand, it ensures that the reinjection steam pressure is higher than the combustion chamber pressure. On the other hand, the injected hot steam is mixed with the gas. During the process, it is necessary to consider the pressure drop of the high-pressure injected steam entering the combustion chamber and the temperature difference between the hot steam and the gas during heat exchange.

[0069] In this embodiment, an air throttle valve 28 is installed at the front end of the inlet of the compressor 1 to control the pressure and mass flow of air entering the compressor to solve the problem that the amount of reinjected steam is limited by the maximum steam output of the waste heat boiler.

[0070] In this embodiment, steam is reinjected into the combustion chamber, and the mass conservation before and after combustion is:

[0071] Gc+Gsteam+Gfuel=Gt (5)

[0072] Among them, G c Indicates the mass flow rate of compressed air entering the combustion chamber; G steam Indicates the steam mass flow rate injected back into the combustion chamber; G fuel Indicates the fuel mass flow rate entering the combustion chamber; G t Indicates the mass flow rate of mixed gas before entering the gas turbine.

[0073] In this embodiment, steam is reinjected into the combustion chamber, and the energy conservation before and after combustion is:

[0074] Gc·hc+Gsteam·hsteam+etafuel·Gfuel·hfuel=Gt·ht (6)

[0075] Among them, h c ,h steam ,h fuel ,h t Represent the specific enthalpy of air, steam, fuel and mixed gas respectively; η fuel Indicates combustion efficiency.

[0076] The waste heat boiler combined heat exchange module includes a reheat module 22, a high-pressure module 23, a medium-pressure module 24, and a low-pressure module 25. The high-pressure module 23, the medium-pressure module 24, and the low-pressure module 25 are each equipped with a high-pressure steam drum 15, a medium-pressure steam drum 16, and a low-pressure steam drum 17. The moisture at the economizer outlet of each pressure module enters the corresponding steam drum. Except for the reheat module 22, the other pressure modules are respectively composed of a feed water preheating section (economizer), an evaporation section, and a steam superheating section, thereby generating steam of different pressures and temperature grades, which are sent to the corresponding high, medium, and low-pressure cylinders of the steam turbine to generate power. The exhaust steam is condensed in the condenser, pressurized by the condensate pump, and enters the low-pressure economizer of the waste heat boiler.

[0077] In this embodiment, the low-pressure saturated steam in the waste heat boiler combined heat exchange module flows through the low-pressure superheater to produce low-pressure superheated steam. The low-pressure saturated water is divided into two paths. One path is pressurized by the medium-pressure feedwater pump 21 to form medium-pressure feedwater, which flows through the medium-pressure evaporation section and superheating section to produce medium-pressure superheated steam. The other path of low-pressure saturated water is pressurized by the high-pressure feedwater pump 20 to form high-pressure feedwater, and finally passes through the high-pressure module to produce high-pressure superheated steam. The high-pressure superheated steam enters the high-pressure cylinder of the steam turbine for expansion. After performing work, the high-pressure exhaust steam and the medium-pressure superheated steam from the waste heat boiler enter the cold reheader to mix and form cold reheated steam. The reheated steam, after being heated by the reheat module, enters the intermediate-pressure cylinder of the steam turbine to expand and perform work. The intermediate-pressure cylinder exhaust steam mixes with the low-pressure superheated steam from the waste heat boiler and then enters the low-pressure cylinder of the steam turbine to perform work.

[0078] In this embodiment, the waste heat boiler extraction water, that is, the waste heat boiler combined heat exchange module, is provided with a fourth three-way valve 18 at the high-pressure economizer outlet of the high-pressure module and a fifth three-way valve 19 at the medium-pressure economizer outlet of the medium-pressure module. The fourth three-way valve 18 and the fifth three-way valve 19 are both connected to the sixth three-way valve 27, which divides the economizer outlet water into two parts, entering the corresponding steam drum and the extraction water. The high-pressure economizer extraction water and the medium-pressure economizer extraction water are combined into the same pipeline with temperature and pressure sensors and the third flow control valve 12 through the sixth three-way valve 27, and are connected to the hot side inlet of the FGH heat exchanger 6.

[0079] In this embodiment, a fifth flow control valve 26 is further provided on the extraction water pipeline at the high-pressure economizer outlet to control the water flow at the high-pressure economizer outlet. This valve cooperates with the third flow control valve 12 before the hot-side inlet of the FGH heat exchanger 6 to control the extraction water flow entering the FGH heat exchanger and adjust the temperature of the mixed extraction water.

[0080] In this embodiment, after steam is reinjected into the combustion chamber 3 for combustion, the exhaust gas of the gas turbine 2 containing water vapor passes through each waste heat boiler pressure module in sequence for heat exchange. A condensing heat exchanger 29 is set at the outlet of the waste heat boiler to recover water vapor in the flue gas and return it to the waste heat boiler. Cooling water 31 circulates in the condensing heat exchanger 29, and condensed water 30 returns to the waste heat boiler combined heat exchange module for recycling.

[0081] Example 2

[0082] like Figure 2 As shown, this embodiment provides a steam reinjection type gas-steam combined cycle system with FGH / TCA waste heat recovery. For some small and medium-sized gas-steam combined cycle units that do not have FGH systems, the cold natural gas from the natural gas station is pressurized and directly fed into the combustion chamber 3. For this purpose, the above reference Figure 1 Based on Example 1, a flexible modification is proposed, considering pumping water from a suitable location in the waste heat boiler to directly absorb the heat from the TCA, generating superheated steam. A portion of this steam is injected into the combustion chamber 3, and the remaining portion is sent to the cold reheader 14. To reduce the impact on the work performed by the bottoming cycle high-grade steam, water is considered to be pumped from the outlet of the low-pressure economizer. This water is sent to the booster water pump 33 through the seventh three-way valve 32. After being boosted by booster water pump 33, it is sent to the cold side of the TCA heat exchanger 5 to absorb the heat from the compressor exhaust. The remaining specific implementation methods are similar to those of Example 1.

[0083] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A waste heat recovery steam reinjection type gas-steam combined cycle system, characterized in that: include: Gas turbine FGH / TCA system, combustion chamber steam reinjection device and waste heat boiler combined heat exchange module; The combustion chamber steam reinjection device is provided with a combustion chamber and a third three-way valve, and the gas turbine FGH / TCA system is provided with an FGH heat exchanger and a TCA heat exchanger; The hot side inlet of the FGH heat exchanger is connected to the waste heat boiler water extraction pipeline, the hot side outlet of the FGH heat exchanger is connected to the cold side inlet of the TCA heat exchanger, the cold side inlet of the FGH heat exchanger is connected to the cold natural gas pipeline, and the cold side outlet of the FGH heat exchanger is connected to the combustion chamber; The hot side inlet of the TCA heat exchanger is connected to the compressor exhaust pipe, the hot side outlet of the TCA heat exchanger is connected to the gas turbine, the compressor outlet is connected to the combustion chamber, and the cold side outlet of the TCA heat exchanger is connected to the combustion chamber and the waste heat boiler cold reheader via a third three-way valve. The waste heat boiler on the hot side of the FGH heat exchanger draws water to heat the natural gas on the cold side. The cooled waste heat boiler water absorbs the heat of the compressor extraction air in the TCA heat exchanger and turns into superheated steam, achieving heat balance in the gas turbine FGH / TCA system. The combustion chamber obtains hot natural gas from the cold side outlet of the FGH heat exchanger, air from the compressor outlet, and superheated steam from the cold side outlet of the TCA heat exchanger, and burns the mixed gas to produce flue gas which is fed into the gas turbine to produce work and drive the generator to output electricity. The waste heat boiler combined heat exchange module is equipped with multiple pressure modules for generating steam of different pressures and temperature grades to drive the corresponding pressure cylinders to generate power; The flue gas containing water vapor output by the gas turbine is input into the waste heat boiler combined heat exchange module for heat exchange; A condensing heat exchanger is installed at the outlet of the waste heat boiler to recover the water vapor in the flue gas of the waste heat boiler combined heat exchange module and return it to the waste heat boiler.

2. The waste heat recovery steam reinjection type gas-steam combined cycle system according to claim 1, characterized in that: The hot side inlet of the FGH heat exchanger is also connected to a third flow control valve, a first temperature sensor, and a first pressure sensor; The third flow control valve is used to adjust the pumping water flow to change the supplied heat so that the cold natural gas is heated to a set temperature. The first temperature sensor and the first pressure sensor are used to detect the temperature and pressure of the pumping water respectively.

3. The waste heat recovery steam reinjection type gas-steam combined cycle system according to claim 1, characterized in that: The cold side inlet of the FGH heat exchanger is connected to a natural gas pipeline provided with a first three-way valve, in parallel with a cold natural gas pipeline provided with a first flow control valve; The first three-way valve is used to divide the cold natural gas in the natural gas pipeline into two paths, one path entering the cold side inlet of the FGH heat exchanger, and the other path entering the cold natural gas pipeline provided with the first flow control valve. The two paths of natural gas are mixed at the cold side outlet of the FGH heat exchanger and then fed into the combustion chamber. The first flow control valve is used to regulate the temperature of the natural gas entering the combustion chamber.

4. The waste heat recovery steam reinjection type gas-steam combined cycle system according to claim 1, characterized in that: The hot side inlet of the TCA heat exchanger is connected to the compressor exhaust pipe provided with a second three-way valve, and is connected in parallel with the hot air pipe provided with a second flow control valve; The second three-way valve is used to divide the compressor hot air into two paths, one path entering the hot side of the TCA heat exchanger, and the other path entering the parallel pipeline equipped with a second flow control valve. The two air paths converge in a pipeline equipped with a second pressure sensor and a second temperature sensor at the hot side outlet of the TCA heat exchanger, and are then sent to the gas turbine to cool the moving blades and rotor. The second pressure sensor and the second temperature sensor are used to detect the pressure and temperature of the air in the pipeline, respectively.

5. The waste heat recovery steam reinjection type gas-steam combined cycle system according to claim 1, characterized in that: The combustion chamber steam re-injection device is further provided with a fourth flow control valve, which is connected to the waste heat boiler cold re-header and the third three-way valve respectively, and is used to control the amount of steam entering the combustion chamber; And / or, the cold side outlet of the TCA heat exchanger is further provided with a third pressure sensor and a third temperature sensor, which are used to detect the pressure and temperature of the steam at the cold side outlet, respectively.

6. The waste heat recovery steam reinjection type gas-steam combined cycle system according to claim 1, characterized in that: The compressor inlet is provided with an air throttle valve for controlling the pressure and mass flow of air entering the compressor.

7. The waste heat recovery steam reinjection type gas-steam combined cycle system according to claim 1, characterized in that: The waste heat boiler combined heat exchange module includes a reheat module, a high pressure module, a medium pressure module and a low pressure module; The high-pressure module, medium-pressure module and low-pressure module generate steam of different pressures and temperature grades to drive the high-, medium- and low-pressure cylinders of the corresponding steam turbines to generate power. The exhaust steam is condensed in the condensing heat exchanger and pressurized by the condensate pump to enter the low-pressure module. The low-pressure saturated steam in the waste heat boiler combined heat exchange module flows through the low-pressure superheater to generate low-pressure superheated steam. The low-pressure drum is divided into two water routes. One route is boosted by the medium-pressure feed water pump to form medium-pressure feed water, which flows through the medium-pressure evaporation section and the superheating section to generate medium-pressure superheated steam. The other route is boosted by the high-pressure feed water pump to form high-pressure feed water, which is then passed through the high-pressure module to generate high-pressure superheated steam. The high-pressure superheated steam enters the high-pressure cylinder of the steam turbine to expand. The high-pressure exhaust steam after doing work is mixed with the medium-pressure superheated steam of the waste heat boiler into the cold reheader to form cold reheated steam. The reheated steam after being heated by the reheat module enters the intermediate-pressure cylinder of the steam turbine to expand and do work. The exhaust steam of the intermediate-pressure cylinder is mixed with the low-pressure superheated steam of the waste heat boiler and enters the low-pressure cylinder of the steam turbine to do work.

8. The waste heat recovery steam reinjection type gas-steam combined cycle system according to claim 7, characterized in that: A fourth three-way valve is provided at the high-pressure economizer outlet of the high-pressure module, and a fifth three-way valve is provided at the medium-pressure economizer outlet of the medium-pressure module; The fourth three-way valve and the fifth three-way valve are both connected to the sixth three-way valve, and the sixth three-way valve is connected to the hot side inlet of the FGH heat exchanger. The high-pressure economizer extraction water and the medium-pressure economizer extraction water are sent to the hot side inlet of the FGH heat exchanger through the sixth three-way valve.

9. The waste heat recovery steam reinjection type gas-steam combined cycle system according to claim 8, characterized in that: A fifth flow control valve is also provided on the high-pressure economizer outlet water extraction pipeline to control the water flow at the high-pressure economizer outlet.

10. A waste heat recovery steam reinjection type gas-steam combined cycle system, characterized in that: include: Combined heat exchange module of TCA heat exchanger, combustion chamber steam reinjection device and waste heat boiler; The combustion chamber steam reinjection device is provided with a combustion chamber, a steam injection nozzle, and a third three-way valve; The cold side inlet of the TCA heat exchanger is connected to the exhaust water pipeline of the waste heat boiler. The exhaust water of the waste heat boiler absorbs the heat of the compressor exhaust to generate superheated steam. The cold side outlet of the TCA heat exchanger is connected to the combustion chamber and the cold re-header of the waste heat boiler via a third three-way valve. Part of the steam at the cold side outlet of the TCA heat exchanger is fed into the combustion chamber through a steam injection nozzle. The hot side inlet of the TCA heat exchanger is connected to the exhaust pipe of the compressor. The hot side outlet of the TCA heat exchanger is connected to the gas turbine, and the outlet of the compressor is connected to the combustion chamber. The combustion chamber obtains natural gas, compressor outlet air and steam from the cold side outlet of the TCA heat exchanger, and burns the mixed gas to produce flue gas which is fed into the gas turbine to produce work and drive the generator to output electricity. The waste heat boiler combined heat exchange module is equipped with multiple pressure modules for generating steam of different pressures and temperature grades to drive the corresponding pressure cylinders to generate power; The flue gas containing water vapor output by the gas turbine is input into the waste heat boiler combined heat exchange module for heat exchange; A condensing heat exchanger is installed at the outlet of the waste heat boiler to recover the water vapor in the flue gas of the waste heat boiler combined heat exchange module and return it to the waste heat boiler.

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