An ORC system for recovering waste heat from TCA / FGH gas turbines in combined cycle units

Abstract

The present invention discloses an ORC system for recovering waste heat from a TCA / FGH gas turbine of a combined cycle unit, comprising a TCA / FGH gas turbine system and an ORC waste heat utilization system; the ORC waste heat utilization system comprises a waste heat utilization heat exchanger and an ORC working medium circulation device, wherein the hot side inlet and outlet of the waste heat utilization heat exchanger are respectively connected in parallel with the waste heat pipeline of the TCA / FGH gas turbine system, and the cold side of the waste heat utilization heat exchanger is connected to the ORC working medium circulation device, and the hot side of the waste heat utilization heat exchanger utilizes the waste heat of the TCA / FGH gas turbine system to heat the organic working medium on the cold side of the ORC working medium circulation device to generate steam, and simultaneously utilizes steam extraction from a steam turbine to supplement heating to generate superheated steam, thereby driving the ORC expander to perform work and driving the generator to output additional electrical energy, thereby increasing the power generation power and power generation efficiency of the combined cycle unit and improving the peak regulation performance of the unit, and the other part of the waste heat is normally discharged through the chimney, thereby effectively improving the operation economy of the unit.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste energy recovery and utilization of energy systems, and in particular relates to an ORC system for recovering waste heat from a TCA / FGH gas turbine in a combined cycle unit. Background Art

[0002] Currently, the turbine inlet temperature of H-class and F-class gas turbines is generally as high as around 1500°C. To ensure the safe and reliable operation of hot-path components such as the combustion chamber liner, nozzle, and rotor blades in such high-temperature environments, these components are designed with cooling air ducts. The cooling air in these ducts is typically extracted from the intermediate stages of the gas turbine compressor. To reduce cooling air usage and reduce compressor power consumption, some gas turbine models, such as Mitsubishi's M701F gas turbine, are equipped with a TCA / FGH system (Turbine Rotor Cooling Air / Fuel Performance Heater). In this TCA / FGH system, the induced draft fan draws in low-temperature air, which then exchanges heat with the compressor exhaust air in the TCA heat exchanger to form high-temperature air. This high-temperature air then exchanges heat with the low-temperature fuel in the FGH heat exchanger before being discharged into the atmosphere. Generally speaking, the low-temperature fuel in the FGH heat exchanger can only recover about 60% of the compressor exhaust heat in the TCA heat exchanger. Under the unit design conditions, the TCA / FGH system will still discharge waste hot air at around 180°C into the atmosphere, which not only wastes energy but also causes certain thermal pollution to the environment. Summary of the Invention

[0003] In response to the problems existing in the prior art, the present invention provides an ORC system for recovering waste heat from TCA / FGH gas turbines of a combined cycle unit, which can effectively improve the operating economy of the unit.

[0004] The present invention is achieved through the following technical solutions:

[0005] An ORC system for recovering TCA / FGH waste heat from a combined cycle unit gas turbine, comprising a gas turbine TCA / FGH system and an ORC waste heat utilization system;

[0006] The ORC waste heat utilization system includes a waste heat utilization heat exchanger and an ORC working fluid circulation device. The hot side inlet and outlet of the waste heat utilization heat exchanger are respectively connected in parallel with the waste heat pipeline of the gas turbine TCA / FGH system, and the cold side of the waste heat utilization heat exchanger is connected to the ORC working fluid circulation device. The hot side of the waste heat utilization heat exchanger uses the waste heat of the gas turbine TCA / FGH system to heat the working fluid on the cold side of the ORC working fluid circulation device. The heated working fluid drives the ORC working fluid circulation device to generate electricity.

[0007] Preferably, the ORC working medium circulation device includes an ORC evaporator, an ORC expander, an ORC condenser and an ORC liquid storage tank;

[0008] The ORC liquid storage tank is connected to the cold side of the ORC evaporator through an ORC working fluid pump, the hot side of the ORC evaporator is connected to the cold side of the waste heat utilization heat exchanger, the cold side outlet of the ORC evaporator is connected to the inlet of the ORC expander, the outlet of the ORC expander is connected to the ORC condenser, and the ORC condenser is connected to the inlet of the ORC liquid storage tank.

[0009] Preferably, the cold side outlet of the ORC evaporator is connected to the cold side inlet of the ORC subcooler, and the cold side outlet of the ORC subcooler is connected to the inlet of the ORC expander;

[0010] The hot side of the ORC superheater utilizes the heat from the steam pipeline of the absorption combined cycle unit to heat the working medium again.

[0011] Preferably, the hot side of the ORC superheater is connected to the cold side of the steam turbine extraction heat exchanger to form a circulation pipeline, and the hot side of the steam turbine extraction heat exchanger is arranged on the steam pipeline of the combined cycle unit.

[0012] Preferably, the exhaust end of the ORC expander is connected to the ORC regenerator, and the outlet of the ORC regenerator is connected to the ORC condenser.

[0013] Preferably, a waste heat utilization control valve group is provided at the inlet of the waste heat utilization heat exchanger, and the water supply pipeline of the ORC condenser is connected to the cooling tower through the circulating water control valve group. The operating state of the ORC waste heat utilization system is controlled by the waste heat utilization control valve group and the circulating water control valve group.

[0014] Preferably, the gas turbine TCA / FGH system comprises a heat exchanger housing, and a TCA heat exchanger and a FGH heat exchanger disposed therein;

[0015] An air inlet is provided at the bottom of the heat exchanger housing and is connected to the induced draft fan A. The air outlet of the heat exchanger housing is connected to the chimney of the waste heat boiler through a waste heat pipeline. The hot side air inlet end of the TCA heat exchanger is connected to the gas turbine compressor exhaust, the hot side air outlet end of the TCA heat exchanger is connected to the gas turbine compressor, and the cold side air outlet end of the FGH heat exchanger is connected to the gas turbine combustion chamber.

[0016] Preferably, the working fluid is at least one of alkanes, hydrofluorocarbons, hydrocarbons and chlorofluorocarbons.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects:

[0018] The present invention provides an ORC system for recovering waste heat from a combined cycle unit's gas turbine TCA / FGH. The system connects a waste heat utilization heat exchanger to the waste heat pipeline of the gas turbine TCA / FGH system in parallel. When the gas turbine TCA / FGH waste heat utilization ORC system is not operating, the waste heat from the gas turbine TCA / FGH system is discharged normally through the chimney. When the gas turbine TCA / FGH waste heat utilization ORC system is operating, the waste heat from the gas turbine TCA / FGH system is recovered using the principle of heat energy exchange, heating the organic working fluid of the ORC waste heat utilization system to produce steam. Simultaneously, steam extraction from a steam turbine is used to supplement heating and generate superheated steam, which drives the ORC expander to perform work and drives the generator to output additional electrical energy, thereby increasing the combined cycle unit's power generation power and efficiency and improving the unit's peak-shaving performance. Another portion of the waste heat is discharged normally through the chimney, effectively improving the unit's operating economy.

[0019] Furthermore, the cold-end circulating water of the ORC system for TCA / FGH waste heat utilization of gas turbines can be realized by using it in parallel with the cold-end circulating water of the combined cycle unit, and can be regulated by the circulating water control valve group. This not only saves equipment investment, but also reduces the system footprint. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a schematic diagram of an ORC system for recovering waste heat from a TCA / FGH gas turbine in a combined cycle unit according to the present invention.

[0021] In the figure: 1 is the gas turbine; 2 is the waste heat boiler; 3 is the gas turbine; 4 is the condenser; 5 is the cooling tower; 6 is the feed water pump; 7 is the chimney; 8 is the gas turbine TCA / FGH system; 8A is the induced draft fan; 8B is the TCA heat exchanger; 8C is the FGH heat exchanger; 9 is the waste heat utilization heat exchanger; 10 is the waste heat utilization control valve group; 11 is the steam turbine extraction heat exchanger; 12 is the steam turbine extraction control valve group; 13 is the ORC evaporator; 14 is the ORC superheater; 15 is the ORC expander; 16 is the ORC regenerator; 17 is the ORC condenser; 18 is the ORC liquid storage tank; 19 is the ORC working fluid pump; and 20 is the circulating water control valve group. DETAILED DESCRIPTION

[0022] The present invention will be further described in detail below with reference to the accompanying drawings, which are intended to explain rather than limit the present invention.

[0023] See Figure 1 An ORC system for recovering waste heat from a combined cycle unit's gas turbine TCA / FGH includes a combined cycle unit, a gas turbine TCA / FGH system 8, and an ORC waste heat utilization system. The gas turbine TCA / FGH system 8 is connected to the combined cycle unit, and the ORC waste heat utilization system is connected in parallel to the waste heat pipeline of the gas turbine TCA / FGH system.

[0024] The combined cycle unit includes a gas turbine 1 , a waste heat boiler 2 , a steam turbine 3 , a condenser 4 , a cooling tower 5 and a feed water pump 6 .

[0025] The gas turbine 1 is coaxially connected to the steam turbine 3, the output end of the steam turbine 3 is connected to the generator G, the waste heat boiler 2 is connected to the air inlet end of the steam turbine 3 through a steam pipeline, the exhaust end of the steam turbine 3 is connected through the hot side inlet of the condenser 4, the hot side outlet of the condenser 4 is connected to the water feed pipeline of the waste heat boiler 2 through the feed water pump 6, and the cold side of the condenser is connected to the cooling tower 5.

[0026] The steam pipeline is provided with a steam turbine extraction control valve group 12, which includes a first valve and a second valve. The steam pipeline is divided into two steam branches through the first valve and the second valve. The two steam branches are respectively connected to the air inlet end of the steam turbine 3.

[0027] The gas turbine TCA / FGH system 8 includes a heat exchanger housing, and a TCA heat exchanger 8B and an FGH heat exchanger 8C arranged therein. An air inlet is provided at the bottom of the heat exchanger housing and is connected to the induced draft fan 8A. The air outlet of the heat exchanger housing is connected to the chimney of the waste heat boiler 2 through a waste heat pipeline. The TCA heat exchanger 8B is provided with a compressed air inlet and outlet, and the FGH heat exchanger 8C is provided with a fuel inlet and outlet. The hot side air inlet end of the TCA heat exchanger 8B is connected to the exhaust of the gas turbine compressor, the hot side air outlet end of the TCA heat exchanger 8B is connected to the compressor of the gas turbine 2, and the cold side air outlet end of the FGH heat exchanger 8C is connected to the combustion chamber of the gas turbine 2.

[0028] In the gas turbine TCA / FGH system 8, the induced draft fan 8A draws in low-temperature air, which then exchanges heat with the compressor exhaust air on the hot side of the TCA heat exchanger 8B to form high-temperature air. The high-temperature air then exchanges heat with the low-temperature fuel in the FGH heat exchanger 8C and is discharged into the atmosphere.

[0029] The ORC waste heat utilization system includes a waste heat utilization heat exchanger 9 and an ORC working fluid circulation device. The hot side inlet and outlet of the waste heat utilization heat exchanger 9 are respectively connected in parallel with the waste heat pipeline of the gas turbine TCA / FGH system 8, and the cold side of the waste heat utilization heat exchanger 9 is connected to the ORC working fluid circulation device. The waste heat utilization heat exchanger 9 uses the waste heat of the gas turbine TCA / FGH system 8 to heat the working fluid of the ORC working fluid circulation device. The heated working fluid drives the ORC working fluid circulation device to generate electricity, thereby realizing the waste heat utilization of the gas turbine TCA / FGH system 8.

[0030] The waste heat outlet of the gas turbine TCA / FGH system 8 is provided with a waste heat utilization control valve group 10, which includes a third valve and a fourth valve. The third valve is provided at the inlet of the waste heat pipeline, and the fourth valve is provided at the hot side inlet of the waste heat utilization heat exchanger 9. When the third valve is opened and the fourth valve is closed, the waste heat of the gas turbine TCA / FGH system 8 enters the chimney through the waste heat pipeline and is discharged to the atmosphere. When the third valve is closed and the fourth valve is opened, the waste heat of the gas turbine TCA / FGH system 8 enters the waste heat utilization heat exchanger 9 to heat the working fluid in the ORC working fluid circulation device.

[0031] The ORC working medium circulation device includes an ORC evaporator 13 , an ORC superheater 14 , an ORC expander 15 , an ORC regenerator 16 , an ORC condenser 17 , an ORC liquid storage tank 18 and an ORC working medium pump 19 .

[0032] The outlet of the ORC liquid storage tank 18 is connected to the inlet of the ORC working fluid pump 19, the outlet of the ORC working fluid pump 19 is connected to the cold side inlet of the ORC evaporator 13, the hot side of the ORC evaporator 13 is connected to the cold side of the waste heat utilization heat exchanger 9 to form a circulation pipeline, the cold side outlet of the ORC evaporator 13 is connected to the cold side inlet of the ORC subcooler 14, the hot side of the ORC superheater 14 is connected to the cold side of the steam turbine extraction heat exchanger 11 to form a circulation pipeline, the hot side of the steam turbine extraction heat exchanger 11 is arranged on the steam pipeline at the inlet of the steam turbine 3, the cold side of the ORC superheater 14 is connected to the cold side of the steam turbine extraction heat exchanger 11 The side outlet is connected to the air inlet end of the ORC expander 15, the exhaust end of the ORC expander 15 is connected to the ORC regenerator 16, the outlet of the ORC regenerator 16 is connected to the ORC condenser 17, the outlet of the ORC condenser 17 is connected to the inlet of the ORC liquid storage tank 18, and the water supply pipeline of the ORC condenser 17 is connected to the cooling tower through the circulating water control valve group 20. The circulating water control valve group 20 includes a fifth valve and a sixth valve. The fifth valve is arranged on the water inlet pipeline of the ORC condenser 17, and the sixth valve is arranged on the return water pipeline of the ORC condenser 17.

[0033] When the ORC waste heat utilization system is working, the ORC working fluid pump 19 boosts the pressure and delivers the working fluid in the ORC liquid storage tank 18 to the cold side of the ORC evaporator 13. The hot side of the ORC evaporator 13 exchanges heat with the waste heat utilization heat exchanger to heat the working fluid on the cold side and boil it. The heated high-temperature working fluid enters the cold side of the ORC superheater 14 and is supplemented by the heat of the steam pipeline. The heated working fluid then enters the ORC expander to perform work and drive the generator. After the work is done and the temperature is reduced, the working fluid enters the ORC regenerator, and then enters the ORC condenser 17 to exchange heat with condensed water for cooling and condensation, and returns to the ORC liquid storage tank, completing the cycle.

[0034] The working fluid in the ORC waste heat utilization system is an organic working fluid, which is not limited to pure working fluids such as alkanes, hydrofluorocarbons, hydrocarbons, and chlorofluorocarbons. Non-azeotropic mixed working fluids can also be selected. The temperature glide phenomenon during the evaporation and condensation process is used to improve the matching degree of the cold and heat source temperatures and reduce the irreversible loss of the system.

[0035] The ORC waste heat utilization system's waste heat exchangers, turbine extraction heat exchangers, and other equipment must be designed based on detailed heat exchange calculations. Similarly, the ORC evaporator, ORC superheater, and ORC regenerator in a TCA / FGH waste heat utilization ORC system also require detailed heat exchange calculations.

[0036] This ORC system for recovering waste heat from the TCA / FGH waste heat recovery system of a combined cycle unit connects a waste heat utilization heat exchanger in parallel with the waste heat pipeline of the TCA / FGH system. This system is controlled by a waste heat utilization control valve assembly 10, a steam turbine extraction control valve assembly 12, and a circulating water control valve assembly. When the TCA / FGH waste heat recovery ORC system is not operating, the waste heat from the TCA / FGH system is normally discharged through the chimney. When the TCA / FGH waste heat recovery ORC system is operating, it utilizes the principle of heat energy exchange to recover waste heat from the TCA / FGH system, heating the organic working fluid of the ORC waste heat recovery system to generate steam. Simultaneously, steam turbine extraction steam is used to supplement heating to generate superheated steam, which drives the ORC expander to produce work and drives the generator to output additional electricity, thereby increasing the combined cycle unit's power generation capacity and efficiency and improving the unit's peak-shaving performance. The remaining waste heat is normally discharged through the chimney, effectively improving the unit's operating economy. At the same time, the cold-end circulating water of the ORC system for utilizing waste heat from gas turbine TCA / FGH can be realized by using it in parallel with the cold-end circulating water of the combined cycle unit, and can be regulated by the circulating water control valve group. This not only saves equipment investment, but also reduces the system footprint.

[0037] The present invention recycles and rationally utilizes the waste heat of the TCA / FGH system, which can not only prevent environmental pollution, but also effectively improve the overall power generation efficiency of the unit. At present, the technologies for converting thermal energy into kinetic energy or electrical energy driven by low-temperature heat sources mainly include organic Rankine cycle systems (ORC), Stirling systems, Kalina systems, and thermoelectric conversion materials. Compared with other methods, the ORC system has the advantages of relatively simple structure, high safety and stability, and low operating costs. The working principle of the ORC system is basically the same as that of the traditional Rankine cycle. It also constitutes a thermodynamic cycle system through four processes: adiabatic compression, isentropic expansion, isobaric heating, and work and heat release. Its characteristic is that a low-boiling point organic working fluid is used as the system circulating working fluid. When the heat source temperature is low, it can boil and generate steam to drive the expander to do work, thereby driving the generator to output electrical energy. The present invention utilizes the ORC system to rationally recover waste heat from the gas turbine TCA / FGH system, thereby improving the power generation efficiency of the combined cycle unit. This not only complies with the principle of cascade utilization of energy, but also improves the economic efficiency of the unit operation, thus having great energy-saving and environmental protection significance and high promotion value.

[0038] The above content is only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. An ORC system for recovering waste heat from TCA / FGH gas turbines in a combined cycle unit, characterized in that: Including gas turbine TCA / FGH system (8) and ORC waste heat utilization system; The ORC waste heat utilization system includes a waste heat utilization heat exchanger (9) and an ORC working medium circulation device. The hot side inlet and outlet of the waste heat utilization heat exchanger (9) are respectively connected in parallel with the waste heat pipeline of the gas turbine TCA / FGH system (8). The cold side of the waste heat utilization heat exchanger (9) is connected to the ORC working medium circulation device. The hot side of the waste heat utilization heat exchanger (9) utilizes the waste heat of the gas turbine TCA / FGH system (8) to heat the working medium on the cold side of the ORC working medium circulation device. The heated working medium drives the ORC working medium circulation device to generate electricity. The ORC working fluid circulation device includes an ORC evaporator (13), an ORC expander (15), an ORC condenser (17) and an ORC liquid storage tank (18); The ORC liquid storage tank (18) is connected to the cold side of the ORC evaporator (13) via the ORC working fluid pump (19), the hot side of the ORC evaporator (13) is connected to the cold side of the waste heat utilization heat exchanger (9), the cold side outlet of the ORC evaporator (13) is connected to the inlet of the ORC expander (15), the outlet of the ORC expander (15) is connected to the ORC condenser (17), and the ORC condenser (17) is connected to the inlet of the ORC liquid storage tank (18); The cold side outlet of the ORC evaporator (13) is connected to the cold side inlet of the ORC superheater (14), and the cold side outlet of the ORC superheater (14) is connected to the inlet of the ORC expander (15); The hot side of the ORC superheater (14) utilizes the heat of the steam pipeline of the absorption combined cycle unit to reheat the working medium.

2. The ORC system for recovering waste heat from TCA / FGH gas turbines of a combined cycle unit according to claim 1, characterized in that: The hot side of the ORC superheater (14) is connected to the cold side of the steam turbine extraction heat exchanger (11) to form a circulation pipeline, and the hot side of the steam turbine extraction heat exchanger (11) is arranged on the steam pipeline of the combined cycle unit.

3. The ORC system for recovering waste heat from TCA / FGH gas turbines of a combined cycle unit according to claim 1, characterized in that: The exhaust end of the ORC expander (15) is connected to the ORC regenerator (16), and the outlet of the ORC regenerator (16) is connected to the ORC condenser (17).

4. The ORC system for recovering waste heat from TCA / FGH gas turbines of a combined cycle unit according to claim 1, characterized in that: The inlet of the waste heat utilization heat exchanger (9) is provided with a waste heat utilization control valve group (10), and the water supply pipeline of the ORC condenser (17) is connected to the cooling tower through the circulating water control valve group (20). The operating state of the ORC waste heat utilization system is controlled by the waste heat utilization control valve group (10) and the circulating water control valve group (20).

5. The ORC system for recovering waste heat from TCA / FGH gas turbines of a combined cycle unit according to claim 1, characterized in that: The gas engine TCA / FGH system (8) includes a heat exchanger housing, and a TCA heat exchanger (8B) and an FGH heat exchanger (8C) arranged inside the housing; The bottom of the heat exchanger housing is provided with an air inlet and is connected to the induced draft fan (8A); the air outlet of the heat exchanger housing is connected to the chimney of the waste heat boiler (2) through a waste heat pipeline; the hot side air inlet of the TCA heat exchanger (8B) is connected to the exhaust of the gas turbine compressor; the hot side air outlet of the TCA heat exchanger (8B) is connected to the compressor of the gas turbine (2); and the cold side air outlet of the FGH heat exchanger (8C) is connected to the combustion chamber of the gas turbine (1).

6. The ORC system for recovering waste heat from TCA / FGH gas turbines of a combined cycle unit according to claim 1, characterized in that: The working fluid is at least one of alkanes, hydrofluorocarbons, hydrocarbons and chlorofluorocarbons.

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