CN115288816B - A start-up optimization system and method for combined cycle multi-stage recovery of machine island waste heat - Google Patents

Abstract

The invention provides a combined cycle multi-stage waste heat recovery system for startup optimization, including a gas turbine and a boiler. It is characterized in that the high-temperature compressed cooling air extracted from the compressor outlet is connected to a gas-water heat exchanger, and the gas-water The outlet of heat exchanger one is connected to the inlet of the cooling chamber of the gas turbine. The cooling chamber is connected to the first three stages of stator blades. The outlet of the chamber is connected to the second stage of gas-water heat exchanger. The first three stages are gas-water exchangers. Heater two is connected to gas-water heat exchanger three through a pipeline. A steam-driven Roots blower is installed on gas-water heat exchanger three. The outlet of gas-water heat exchanger three is connected to a high-pressure cylinder and a medium-pressure cylinder. The high-pressure cylinder is equipped with a steam turbine outer box 1 correspondingly, and the medium-pressure cylinder is equipped with a steam turbine outer box 2 correspondingly. The steam turbine outer box 1 and the steam turbine outer box 2 are respectively equipped with preheating channels and rotors. The boiler communicates with gas-water through the outlet of the high-pressure circulating water pump. Heater one, gas-water heat exchanger two and gas-water heat exchanger three are connected.

Description

A start-up optimization system and method for combined cycle multi-stage recovery of machine island waste heat

Technical field

The present invention relates to the technical field of waste heat utilization in power plants, and in particular to a startup optimization system and method for combined cycle multi-stage recovery of machine island waste heat.

Background technique

As a power generation equipment that uses gas turbine exhaust to heat steam and water working fluids, gas-steam combined cycle has a large number of technologies for recycling waste heat on the side of the waste heat boiler (i.e. furnace island). However, at present, domestic high-power combined cycle starts early and stops late. During peak shaving operation, part of the heat generated by the gas turbine side (i.e. the machine island) is often wasted due to the rapid startup of the gas turbine and the lag of the waste heat boiler during the startup process.

At present, the initial gas temperature of H-class/J-class heavy-duty gas turbine combined cycle has far exceeded the endurance limit of turbine blade metal materials. Gas turbine cooling systems generally draw compressed air from the compressor outlet into the turbine cooling air heat exchanger, that is, OTC (Organic Trans-critical Cycle) heat exchanger, which is further cooled and then sent to the turbine for cooling air. The maximum temperature of the turbine blades is reduced by about 200°C.

The OTC heat exchanger generally extracts high-pressure and low-temperature hot water in front of the high-pressure economizer, and leads it to the cooling compressor of the machine island to extract air. Then the compressed air flows into the first three-stage stator chambers, and the cooling air passes through a series of chambers and dampers. The first three-stage blades of the turbine are cooled and then discharged from the fixed part of the main flow channel outside the body. The OTC heat exchanger generates high-pressure hot water or steam, which is sent to the high-pressure steam drum during the normal load of the combined cycle. During startup, in order to control the heating rate of the waste heat boiler, the turbine steam flow is small, and the high-pressure hot water generated by the OTC system is directly discharged to the condensing steam. Moreover, after the gas turbine is started to the initial load stage, the boiler heats up and pressurizes for up to 80 minutes under cold start conditions, and the backwater in the OTC system causes a huge loss of heat and boost pump power.

Currently, the heating heat used for preheating the turbine outer box comes from the air heater. If the OTC system can be used to recover the heat energy on the machine island side and heat the furnace island to start preheating the air, it can be reasonably used for the steam turbine high-pressure and medium-pressure cylinder insulation CHS (i.e. Casings Heating System ) system to reduce the temperature difference between the rotor and the box. Such a system will improve the energy saving and economy of the combined cycle power plant startup process.

The existing relevant technology at this stage is to save the waste heat of the gas turbine during the startup process and low load into a heat storage buffer device. However, it is inevitable to modify the gas circuit structure and introduce high-cost heat storage equipment.

Therefore, for heavy-duty gas turbine power plants, it is urgent to combine the advantages of the existing water circulation system to form a set of high-efficiency, low-cost, easy-to-operate technical solutions that can quantitatively recycle and utilize gas turbine side heat and waste heat.

Contents of the invention

The present invention aims to provide a startup optimization system for combined cycle multi-stage waste heat recovery of machine islands to overcome the shortcomings in the existing technology.

In order to solve the above technical problems, the technical solution of the present invention is: a combined cycle multi-stage recovery machine island waste heat start-up optimization system, including a gas turbine and a boiler, which is characterized in that the outlet of the compressor is connected with a combustion chamber and a gas-water exchanger. Heater one, the combustion chamber and the outlet of gas-water heat exchanger one are connected in parallel with a gas turbine with a built-in chamber, wherein the chamber includes a gas film hole, a gas path inlet guide tube opening and a gas path outlet guide tube, The first three stages of static vanes are spaced in the chamber to form a flow channel for the cooling gas. The cooling gas inlet guide tube and the gas path outlet guide tube are arranged on the same side. The gas path outlet guide tube is connected with an air-water heat exchanger. Device two; the gas-water heat exchanger two is connected to a gas-water heat exchanger three through a pipeline, and a steam-driven Roots blower is provided on the gas-water heat exchanger three. The steam-driven Roots blower is composed of a low-pressure cylinder 1 is driven by the extraction of steam, which can pressurize the air and drain it; the three outlets of the gas-water heat exchanger are connected to a high-pressure cylinder and a medium-pressure cylinder. The high-pressure cylinder is equipped with a turbine outer box, and the medium-pressure cylinder is equipped with a corresponding one. The steam turbine outer box 2, the steam turbine outer box 1 and the steam turbine outer box 2 are equipped with cylinders and rotors correspondingly. The boiler communicates with the gas-water heat exchanger one, the gas-water heat exchanger two and the gas-water heat exchanger three through the circulating water pump. Connected.

As an improvement of the start-up optimization system of the combined cycle multi-stage recovery machine island waste heat of the present invention, a flow valve is provided at the outlet of the gas-water heat exchanger three, and the flow valve is used to adjust the input of the gas-water heat exchanger three. Air flow rate of high-pressure cylinder box and medium-pressure cylinder box.

The present invention aims to provide a startup optimization method for combined cycle multi-stage waste heat recovery of machine islands to overcome the shortcomings in the existing technology.

In order to solve the above technical problems, the technical solution of the present invention is: a startup optimization method for a combined cycle multi-stage waste heat recovery machine island, based on a startup optimization system for a combined cycle multi-stage recovery machine island waste heat, including the following steps:

Step 1. The cooling system extracts high-temperature compressed air from the compressor. The high-temperature compressed air flows to the combustion chamber and air-water heat exchanger one respectively. The high-temperature compressed air flowing to air-water heat exchanger one is heated and flows from the boiler to the air-water heat exchanger. High-pressure water supply to the first, and the heated feed water flows to the air-water heat exchanger two and the air-water heat exchanger three;

Step 2. The high-temperature compressed air flowing out of the combustion chamber and the air-water heat exchanger flows to the blades of the first three-stage stator blades in the chamber, and the high-temperature compressed air flowing out of the chamber is heated by the first three-stage stator blades. The high-temperature compressed air The flow guide pipe in the chamber is directed to the air-water heat exchanger one and the air-water heat exchanger two respectively. The high-temperature compressed air flowing to the air-water heat exchanger two heats the air flowing through the air-water heat exchanger two. water supply;

Step 3. The feed water in Step 2 flows to the air-water heat exchanger three through the pipeline. The feed water heats the air sent to the air-water heat exchanger three through the steam-driven Roots blower. The air is heated and then sent to the steam turbine. The outer box 1 of the high-pressure cylinder and the outer box 2 of the medium-pressure cylinder are used to reduce the temperature difference between the outer boxes 1 and 2 of the steam turbine and its internal rotor.

As an improvement of the start-up optimization method of the combined cycle multi-stage recovery machine island waste heat of the present invention, in step 1, the high-temperature compressed air heats the high-pressure water supply flowing from the boiler to the gas-water heat exchanger one to 300°C, and then the gas turbine is started In the initial load stage, turbine sliding pressure operation, and feed water flow rate of 100%, the OTC feed water flow rate can reach 100 tons/hour.

As an improvement of the start-up optimization method of the combined cycle multi-stage recovery machine island waste heat of the present invention, in step 2, the high-temperature compressed air flowing to the air-water heat exchanger 2 will flow through the water supply of the air-water heat exchanger 2 Heating water at 400°C.

As an improvement of the start-up optimization method of the combined cycle multi-stage recovery machine island waste heat of the present invention, in step 2, a part of the cooling compressed air flows into the cooling gas inlet and flows out of the chamber from the air film hole, and the remaining gas of the cooling compressed air flows from The outlet of the air path flows into the guide tube, which sends the high-temperature air with a certain pressure after cooling through the blades to the second air-water heat exchanger to recover its waste heat.

As an improvement of the start-up optimization method of the combined cycle multi-stage recovery machine island waste heat of the present invention, in step 3, the water supply continuously heats the air sucked into the air-water heat exchanger 3 by the steam-driven Roots blower to 100~380°C. , and the heating flow is adjusted according to the preheating needs of the steam turbine. During the startup process of the combined cycle unit, the feed water of gas-water heat exchanger three finally returns to the condenser.

The specifications of the steam-driven Roots blower are: capacity 25Nm ³ /min, suction air pressure rise of 0.8MPa, and pipes connected to heat exchanger three for heating. Compared with the prior art, the beneficial effects of the present invention are:

1. During the initial load start-up process of the gas turbine of the combined cycle unit, the high-temperature and high-pressure hot water generated by the OTC heat exchanger is used to not return to the waste heat boiler to continue working. It is clever to add a two-stage heat exchanger while maintaining the original water circulation system. The waste heat of the machine island is recycled and used to heat the preheated air of the furnace island steam turbine during the auxiliary steam heating pipe period of the waste heat boiler.

2. The heat exchange efficiency of the air-to-water heat exchanger is higher than that of air-to-air heat exchange. The system proposed by the present invention rationally utilizes the high-temperature and high-pressure compressed air released by the cooling system to the outside for a long time during the startup process of the unit to reheat the startup process. The high-temperature, high-pressure hot water of the TCA system that is originally discharged into the condenser recovers its heat energy in stages, replacing the original gas storage tank that provides turbine preheating, saving the auxiliary heating equipment needed to heat the warm air in the outer box of the turbine, and improving Improves unit operational flexibility and shortens startup time;

3. Without affecting the air cooling effect of the turbine blades, the system proposed by the present invention is based on the existing machine island-furnace island heat exchange water circulation pipeline of the combined cycle cooling system, and only adds two cascade heat recovery heat exchangers and induced draft fans. (Prepared by the power plant), so the cost is low, installation can be completed quickly during power plant maintenance, and the compressor and turbine-related pipelines can be inspected and replaced without opening the cylinder.

Description of the drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are only These are some embodiments recorded in the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a schematic structural diagram of the present invention;

Figure 2 is a schematic structural diagram of the chamber in Figure 1:

Figure 3 is a schematic structural diagram of a gas-water heat exchanger.

Among them, the solid arrows in Figures 1 and 3 represent the flow direction of the feed water, and the short dotted arrows represent the cooling air flow direction.

Reference signs

1. Compressor; 2. Combustion chamber; 3. Gas turbine; 4. Chamber; 5. Boiler; 6. High-pressure cylinder outer box one; 7. Medium-pressure cylinder outer box two; 8. High-pressure cylinder; 9 , medium pressure cylinder; 10. Gas-water heat exchanger one; 11. Gas-water heat exchanger two; 12. Pipeline; 13. Gas-water heat exchanger three; 14. Steam-driven Roots blower; 15. Flow rate Valve; 16. Low-pressure cylinder; 17. Air film hole; 18. Gas path inlet guide tube; 19. Gas path outlet guide tube; 20. Circulation pump.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

As shown in Figures 1 and 2, a combined cycle multi-stage waste heat recovery system starts up and optimizes the system, including a compressor 1 and a boiler 5. The outlet of the compressor 1 is connected to a combustion chamber 2 and a gas-water heat exchanger 10 , the combustion chamber 2 and the outlet of the gas-water heat exchanger 10 are connected in parallel with the gas turbine 3 with a built-in chamber 4. The chamber 4 is provided with the first three-stage stator blades, and the inlet of the chamber 4 is the combustion chamber 2 and the gas-water heat exchanger 10. The outlet of water heat exchanger one 10 is connected. The outlet of chamber 4 is connected with air-water heat exchanger two 11. The air-water heat exchanger two 11 is connected with air-water heat exchanger three 13 through pipe 12. In the air - The air inlet of the water heat exchanger 313 is provided with a steam-driven Roots blower 14. The outlet of the air-water heat exchanger 313 is connected to a high-pressure cylinder 8 and a medium-pressure cylinder 9. The high-pressure cylinder 8 is provided with a steam turbine outer box. 1. The medium-pressure cylinder 9 is provided with a steam turbine outer box 2 corresponding to the steam turbine outer box 1 and the steam turbine outer box 2. There are corresponding cylinders and rotors inside the steam turbine outer box 1. The boiler 5 communicates with the air-water heat exchanger 10 through the circulating water pump, and the air-water exchanger Heater two 11 and gas-water heat exchanger three 13 are connected.

A flow valve 15 is provided at the outlet of the gas-water heat exchanger 313, and the flow valve 15 is used to adjust the air flow rate input by the gas-water heat exchanger 313 to the high-pressure cylinder 8 and the medium-pressure cylinder 9.

As shown in Figure 2, the chamber 4 includes an air film hole 17, a gas path inlet guide tube opening 18 and a gas path outlet guide tube 19. The first three stages of static blades are spaced in the chamber and form a flow channel for the cooling gas. The cooling gas inlet guide tube 18 and the gas path outlet guide tube 19 are arranged on the same side, and the gas path outlet guide tube 19 is connected with the gas-water heat exchanger 211.

The steam-driven Roots blower 14 is driven by the steam extraction from the low-pressure cylinder 16 and can pressurize the air and then divert it.

A startup optimization method for combined cycle multi-stage recovery machine island waste heat, based on a combined cycle multi-stage recovery machine island waste heat startup optimization system, including the following steps,

Step 1: The cooling system extracts high-temperature compressed air from the compressor 1. The high-temperature compressed air flows to the combustion chamber 2 and the gas-water heat exchanger 10 respectively. The high-temperature compressed air flowing to the gas-water heat exchanger 10 is heated and flows from the boiler 5 to the gas. - High-pressure water supply from water heat exchanger one 10, high-temperature compressed air heating flows from boiler 5 to air-water heat exchanger one 10. High-pressure water supply to 300°C, and the heated water supply flows to air-water heat exchanger two 11. -Water heat exchanger three 13. Among them, in the initial load stage of gas turbine startup, steam turbine sliding pressure operation, and 100% feed water flow rate, the OTC feed water flow rate can reach 100 tons/hour.

Step 2. The high-temperature compressed air flowing out of the combustion chamber 2 and the air-water heat exchanger 10 flows to the blades of the first three-stage stator blades in the chamber 4, and the high-temperature compressed air flowing out of the chamber 4 is heated by the first three-stage stator blades. , the high-temperature compressed air is directed to the air-water heat exchanger one 10 and the air-water heat exchanger two 11 respectively through the guide tube 19 of the chamber 4, and the high-temperature compressed air flowing to the air-water heat exchanger two 11 is heated. The feed water flowing through the air-water heat exchanger 2 11 and the high-temperature compressed air flowing to the air-water heat exchanger 2 11 heat the feed water flowing through the air-water heat exchanger 2 11 to 400°C; among which, part of the cooling compressed air is from The cooling gas inlet 16 flows into and flows out of the chamber 4 from the air film hole 17. The remaining gas of the cooling compressed air flows into the guide tube 19 from the air path outlet 18. The guide tube 19 fills the high-pressure and high-temperature air after cooling the blades. The waste heat is recovered in the gas-water heat exchanger 211.

Step 3. The feed water in Step 2 flows to the air-water heat exchanger 3 13 through the pipeline 12. The feed water is heated and introduced into the air flowing to the air-water heat exchanger 3 13 through the steam-driven Roots blower 14. The feed water is heated through the steam-driven Roots blower 14. The blower 14 introduces the air flowing to the air-water heat exchanger 3 13 to 100-380°C. After the air is heated, it is sent to the outer box 1 of the high-pressure cylinder 8 and the outer box 2 of the medium-pressure cylinder 9 of the steam turbine to reduce the pressure of the steam turbine. The temperature difference between outer box one and outer box two and their internal rotors.

The warm air entering the outer box should be as close as possible to the steam temperature during the startup process of the steam turbine to achieve the effect of pre-warming the engine. Pre-warming can reduce the temperature difference between the steam turbine cylinder and its internal rotor. Taking into account the heat dissipation loss of pipe 12 and the heat exchanger Efficiency, the use of recovered waste heat to heat the return water of the OTC system to the temperature required for preheating can fully meet the requirements. Finally, the steam turbine is driven by the steam of the waste heat boiler 5 to increase the speed. As shown in Figure 3, the dotted line represents air and the solid line represents water or steam. Fin-type air-water heat exchangers are selected as air-water heat exchanger one 10, air-water heat exchanger two 11 and air-water heat exchanger 10. Heat exchanger three 13, the high-pressure water supply boosted by the circulating water pump flows in the pipe 12, and the pressure loss is small. The compressed air entering the heat exchanger flows through the fins tangentially to the pipe, and there is a certain pressure loss but there is no pressure loss. Affects fluidity, so the system does not require additional water or air pumps.

It is obvious to those skilled in the art that the present invention is not limited to the details of the above-described exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention. Therefore, the embodiments should be regarded as illustrative and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is therefore intended that all claims falling within the claims All changes within the meaning and scope of equivalent elements are included in the present invention. Any reference signs in the claims shall not be construed as limiting the claim in question.

In addition, it should be understood that although this specification is described in terms of implementations, not each implementation only contains an independent technical solution. This description of the specification is only for the sake of clarity, and those skilled in the art should take the specification as a whole. , the technical solutions in each embodiment can also be appropriately combined to form other implementations that can be understood by those skilled in the art.

Claims (7)

1. A combined cycle multi-stage waste heat recovery system for starting up and optimizing the machine island, including a gas turbine and a boiler, characterized in that the outlet of the compressor is connected with a combustion chamber and a gas-water heat exchanger, and the combustion chamber and gas-water heat exchanger The outlet of the first device is connected in parallel with a gas turbine with a built-in chamber. The chamber includes a gas film hole, a gas path inlet guide tube and a gas path outlet guide tube. The first three stages of static blades are arranged at intervals in the chamber. , and forms a flow channel for the cooling gas. The cooling gas inlet guide pipe and the gas outlet guide pipe are set on the same side. The gas outlet guide pipe is connected with the second air-water heat exchanger; the second air-water heat exchanger passes through The pipeline is connected to a gas-water heat exchanger three, and a steam-driven Roots blower is provided on the gas-water heat exchanger three. The steam-driven Roots blower is driven by the extraction of steam from the low-pressure cylinder and can pressurize the air. Rear drainage; the three outlets of the gas-water heat exchanger are connected to a high-pressure cylinder and a medium-pressure cylinder. The high-pressure cylinder is equipped with a turbine outer box 1, and the medium-pressure cylinder is equipped with a turbine outer box 2. The steam turbine outer box 1 and the steam turbine outer box are arranged correspondingly. There are corresponding cylinders and rotors inside the second box, and the boiler is connected to the first air-water heat exchanger, the second air-water heat exchanger and the third air-water heat exchanger through the circulating water pump. 2. A startup optimization system for combined cycle multi-stage recovery machine island waste heat according to claim 1, characterized in that a flow valve is provided at the outlet of the gas-water heat exchanger three, and the flow valve is used to adjust the gas flow. -Water heat exchanger three inputs the air flow rate of the high-pressure cylinder box and the medium-pressure cylinder box. 3. A startup optimization method for combined cycle multi-stage recovery machine island waste heat, based on a combined cycle multi-stage recovery machine island waste heat startup optimization system as claimed in claim 1, characterized in that it includes the following steps: Step 1. The cooling system extracts high-temperature compressed air from the compressor. The high-temperature compressed air flows to the combustion chamber and air-water heat exchanger one respectively. The high-temperature compressed air flowing to air-water heat exchanger one is heated and flows from the boiler to the air-water heat exchanger. High-pressure water supply to the first, and the heated feed water flows to the air-water heat exchanger two and the air-water heat exchanger three; Step 2. The high-temperature compressed air flowing out of the combustion chamber and the air-water heat exchanger flows to the blades of the first three-stage stator blades in the chamber, and the high-temperature compressed air flowing out of the chamber is heated by the first three-stage stator blades. The high-temperature compressed air The flow guide pipe in the chamber is directed to the air-water heat exchanger one and the air-water heat exchanger two respectively. The high-temperature compressed air flowing to the air-water heat exchanger two heats the air flowing through the air-water heat exchanger two. water supply; Step 3. The feed water in Step 2 flows to the air-water heat exchanger three through the pipeline. The feed water heats the air sent to the air-water heat exchanger three through the steam-driven Roots blower. The air is heated and then sent to the steam turbine. The outer box 1 of the high-pressure cylinder and the outer box 2 of the medium-pressure cylinder are used to reduce the temperature difference between the outer boxes 1 and 2 of the steam turbine and its internal rotor. 4. A start-up optimization method for combined cycle multi-stage recovery machine island waste heat according to claim 3, characterized in that, in step 1, high-temperature compressed air heats the high-pressure water supply flowing from the boiler to the air-water heat exchanger one. to 300°C, during the initial load stage of gas turbine startup, steam turbine sliding pressure operation, and 100% feed water flow rate, the OTC feed water flow rate can reach 100 tons/hour. 5. A start-up optimization method for combined cycle multi-stage recovery machine island waste heat according to claim 3, characterized in that in step 2, the high-temperature compressed air flowing to the air-water heat exchanger two will flow through the air-water heat exchanger. The feed water of water heat exchanger 2 heats water at 400°C. 6. A startup optimization method for combined cycle multi-stage recovery machine island waste heat according to claim 3, characterized in that, in step 2, a part of the cooling compressed air flows into the cooling gas inlet and flows out of the chamber from the air film hole. , the remaining gas after cooling the compressed air flows into the guide tube from the air path outlet. The guide tube will send the high-temperature air with a certain pressure after cooling the blades to the second air-water heat exchanger to recover its waste heat. 7. A start-up optimization method for combined cycle multi-stage recovery machine island waste heat according to claim 3, characterized in that, in step 3, the feed water continuously heats the steam-driven Roots blower suction air-water heat exchanger 3. The air is heated to 100~380°C, and the heating air flow is adjusted according to the turbine preheating needs. During the startup process of the combined cycle unit, the feed water from air-water heat exchanger three finally returns to the condenser.