A heat storage peak shaving operation system of a gas-steam combined cycle generator set of a steel enterprise

Abstract

The utility model provides a kind of steel enterprise gas steam combined cycle generator set's heat storage peak shaving operation system, solve existing coal gas generator set operating load limited, cannot flexibly adapt to the problem of peak-valley electricity price of power grid.The system includes gas steam combined cycle power electronic system, fuel supply subsystem, storage and heat exchange subsystem, flue gas regulating subsystem, steam main pipe subsystem, water supply main pipe subsystem etc.Storage and heat exchange subsystem uses molten salt as heat storage medium, through flue gas molten salt heat exchanger, double-tank heat storage unit and molten salt steam-water heat exchanger realizes heat energy storage and release.System is based on power grid electricity price signal, stores energy in low electricity price period, stores most flue gas heat energy;Energy release in high electricity price period, simultaneously utilize flue gas heat energy and stored heat energy to generate electricity.Collaborative control through flue gas regulating subsystem, steam regulating valve group and water supply regulating valve group etc., realize system stable switching and reliable operation, improve power generation output, improve energy utilization, increase power generation income, reduce external purchase electricity cost.

Description

Technical Field

[0001] This utility model relates to the field of energy dispatching and optimization technology for steel enterprises, specifically to a thermal storage and peak-shaving operation system for gas-fired steam combined cycle generator sets in steel enterprises, which is suitable for the efficient utilization of surplus coal gas in steel enterprises and economic operation under peak-valley electricity pricing. Background Technology

[0002] Steel companies typically recover and utilize surplus coal gas generated during production through gas-fired combined cycle (GC-COC) power plants. While traditional GC-COC power systems offer high power generation efficiency, their operation is significantly limited. Because coal gas supply is constrained by the main steel production process, the power plants often operate at relatively fixed loads, unable to flexibly adjust output according to grid demand. Especially under time-of-use pricing policies, this rigid operating mode prevents the units from increasing output during peak hours and effectively reducing load during off-peak hours, resulting in low energy efficiency and high electricity purchase costs for the companies.

[0003] Existing combined cycle (CCC) power generation systems typically employ a combination of gas turbine and steam turbine power generation systems, generating steam to drive the turbine and produce electricity by recovering waste heat from the gas turbine's exhaust gas. However, this system operates in a relatively fixed manner, lacking the ability to transfer and redistribute flue gas heat in time and space. During peak grid load periods, companies cannot temporarily increase power generation, resulting in higher costs for purchased electricity; conversely, during off-peak grid load periods, the units cannot effectively store excess energy, leading to energy waste. This operating mode restricts further improvements in the self-generation efficiency of steel companies. Utility Model Content

[0004] The technical problem to be solved by this utility model is to overcome the shortcomings of existing steel enterprises' gas generator sets, which are limited by the amount of gas, cannot flexibly adapt to the peak and valley electricity prices of the power grid, and fail to maximize economic benefits. The present invention provides a thermal storage peak-shaving operation system with a reasonable system structure, flexible operation mode, and can significantly improve peak power generation capacity and reduce the cost of purchased electricity.

[0005] To solve the above-mentioned technical problems, the technical solution provided in this application is as follows: This application provides a thermal storage and peak-shaving operation system for a gas-fired steam combined cycle generator unit in an iron and steel enterprise, comprising:

[0006] A combined cycle gas turbine and steam turbine power generation system, comprising a gas turbine power generation unit, a waste heat boiler unit, and a steam turbine power generation unit connected in sequence;

[0007] The fuel supply subsystem is connected to the fuel inlet of the gas turbine power generation unit via a fuel delivery pipe;

[0008] The heat storage and exchange subsystem is connected in parallel with the waste heat boiler unit on the flue gas outlet side of the gas turbine power generation unit. It is used to store flue gas heat energy during periods of low electricity price and release the stored heat energy during periods of high electricity price to assist in power generation.

[0009] The flue gas conditioning subsystem is connected to the flue gas outlet of the gas turbine power generation unit and diverts it to the flue gas input of the waste heat boiler unit and the heat storage and exchange subsystem for regulating flue gas distribution.

[0010] The steam header subsystem connects the steam output terminals of the waste heat boiler unit and the heat storage and exchange subsystem, and aggregates the steam input terminals of the steam turbine power generation unit.

[0011] The feedwater main pipe subsystem connects to the feedwater output end of the steam turbine generator unit and is branched to the feedwater input end of the waste heat boiler unit and the heat storage and exchange subsystem.

[0012] The flue gas regulation subsystem includes a first flue gas valve installed on the pipeline leading to the waste heat boiler unit and a second flue gas valve installed on the pipeline leading to the heat storage and exchange subsystem. By adjusting the opening of the two valves, the flue gas distribution is controlled, and the system can switch between the two operating modes of energy storage and energy release.

[0013] Preferably, the heat storage and exchange subsystem includes:

[0014] A flue gas molten salt heat exchanger, whose flue gas inlet is connected to the outlet of a second flue gas valve, is used for heat exchange between high-temperature flue gas and molten salt;

[0015] A dual-tank thermal storage unit, comprising a high-temperature storage tank, a low-temperature storage tank, a high-temperature molten salt circulation pump, and a low-temperature molten salt circulation pump;

[0016] Molten salt steam-water heat exchanger, which is used to exchange heat between molten salt and feedwater to generate steam;

[0017] The outlet of the cryogenic storage tank is connected to the molten salt inlet of the flue gas molten salt heat exchanger via a cryogenic molten salt circulation pump, and the molten salt outlet of the flue gas molten salt heat exchanger is connected to the inlet of the high-temperature storage tank, forming a heat storage loop.

[0018] The outlet of the high-temperature storage tank is connected to the molten salt inlet of the molten salt steam-water heat exchanger via a high-temperature molten salt circulation pump, and the molten salt outlet of the molten salt steam-water heat exchanger is connected to the inlet of the low-temperature storage tank, forming a heat release loop.

[0019] Preferably, the molten salt steam-water heat exchanger includes a preheater, a heater, and a superheater that sequentially preheat, evaporate, and superheat the feedwater, for generating steam with parameters consistent with those produced by the waste heat boiler unit.

[0020] Preferably, the steam main pipe subsystem is equipped with a steam regulating valve group, which includes a first steam valve installed in the steam output pipeline of the waste heat boiler unit and a second steam valve installed in the steam output pipeline of the heat storage and exchange subsystem.

[0021] Preferably, the water supply main pipe subsystem is equipped with a water supply regulating valve group, which includes a first water supply valve installed on the water supply pipeline leading to the waste heat boiler unit and a second water supply valve installed on the water supply pipeline leading to the heat storage and exchange subsystem.

[0022] Preferably, the system further includes a flue gas collection and emission subsystem, which connects the flue gas output ends of the waste heat boiler unit and the heat storage and exchange subsystem, and collects the flue gas into the chimney. This subsystem is equipped with a tail gas regulating valve group, including a first tail gas valve installed in the flue gas output pipeline of the waste heat boiler unit and a second tail gas valve installed in the flue gas output pipeline of the heat storage and exchange subsystem.

[0023] Preferably, the gas turbine power generation unit includes a gas compressor, an air compressor, a burner, a gas turbine, and a gas turbine generator, used to generate electricity by consuming surplus gas from the steel plant.

[0024] Preferably, the steam turbine power generation unit includes a steam turbine generator set, a condenser, a circulating cooler, a condensate pump, a regenerative deaerator, and a feedwater pump;

[0025] The exhaust steam output of the steam turbine generator set is connected to the input of the condenser.

[0026] The condensate outlet of the condenser is connected to the input of the regenerative deaerator via a condensate pump, and the exhaust port of the turbine generator set is connected to the regenerative deaerator.

[0027] The feedwater output of the regenerative deaerator is connected to the input of the feedwater main pipe subsystem via a feedwater pump.

[0028] The circulating cooler is coupled to the condenser to condense the exhaust steam in the condenser; thus forming a complete steam-water circulation loop.

[0029] This application also provides a method for thermal storage and peak-shaving operation of a gas-fired combined cycle generator unit in an iron and steel enterprise, which is divided into energy storage mode operation during low electricity price periods and energy release mode operation during high electricity price periods based on the grid electricity price signal. The method specifically includes the following steps:

[0030] Energy storage mode operation includes:

[0031] S1. Flue gas distribution and regulation: Regulate the flue gas regulation subsystem, close the first flue gas valve, open the second flue gas valve, and distribute most of the high-temperature flue gas to the heat storage and exchange subsystem.

[0032] S2, Heat storage circulation: Start the low temperature molten salt circulation pump to pump the molten salt in the low temperature storage tank into the flue gas molten salt heat exchanger, absorb the heat of the flue gas and become high temperature molten salt, which is then stored in the high temperature storage tank.

[0033] S3. Low-load operation of steam and water system: Adjust the feedwater regulating valve group and steam regulating valve group, close the second feedwater valve and the second steam valve, and only the waste heat boiler unit generates steam to drive the steam turbine generator unit to operate at low load.

[0034] S4. Flue gas emission: Keep the first and second tail gas valves open to ensure that the flue gas is collected and then emitted.

[0035] The energy release mode operation includes:

[0036] S5. Flue gas distribution switching: Adjust the flue gas regulation subsystem, open the first flue gas valve, close the second flue gas valve, and distribute all high-temperature flue gas to the waste heat boiler unit.

[0037] S6. Heat release and steam generation: Start the high-temperature molten salt circulation pump to pump the high-temperature molten salt stored in the high-temperature storage tank into the molten salt steam-water heat exchanger to generate steam.

[0038] S7. High-load operation of steam and water system: Adjust the feedwater regulating valve group and steam regulating valve group, open the second feedwater valve and the second steam valve, and the waste heat boiler unit and the heat storage and exchange subsystem jointly generate steam to drive the steam turbine power generation unit to operate at high load.

[0039] S8. Flue gas emission adjustment: Keep the first tail gas valve open and adjust the opening of the second tail gas valve to ensure that the flue gas is collected and then discharged.

[0040] Compared with the prior art, the beneficial effects of this utility model are as follows:

[0041] 1. This application achieves flexible adjustment of the unit's operating mode by introducing a heat storage and exchange subsystem and cleverly integrating it with the gas-fired steam combined cycle power generation system. Through the coordinated control of the first and second flue gas valves in the flue gas regulation subsystem, the system realizes intelligent distribution of flue gas heat between the waste heat boiler unit and the heat storage and exchange subsystem, effectively solving the problem in existing technologies where units cannot flexibly adjust peak loads according to grid demand.

[0042] 2. This application uses molten salt as the heat storage medium. By setting up a heat storage and exchange subsystem including a flue gas molten salt heat exchanger, a dual-tank heat storage unit, and a molten salt steam-water heat exchanger, it achieves efficient storage and utilization of flue gas thermal energy. This design not only maintains the high efficiency characteristics of the original power generation system, but also significantly improves the overall energy utilization rate of the system through the spatial and temporal transfer of heat energy, and significantly increases the power generation output of the unit during periods of high electricity prices.

[0043] 3. This application achieves smooth steam merging and rational feedwater distribution between the waste heat boiler unit and the heat storage and exchange subsystem through optimized design of the steam main pipe subsystem and feedwater main pipe subsystem. The coordinated control of the first and second steam valves in the steam regulating valve group, and the first and second feedwater valves in the feedwater regulating valve group, ensures stable switching and reliable operation of the system under different operating modes.

[0044] 4. This application fully utilizes the time-of-use pricing policy of the power grid and achieves automatic switching of operating modes through intelligent control strategies. During periods of low electricity prices, the system stores most of the flue gas heat energy in the heat storage and exchange subsystem; during periods of high electricity prices, the system simultaneously utilizes both flue gas heat energy and stored heat energy to generate electricity, thereby significantly improving power generation revenue and reducing the enterprise's external power purchase costs while ensuring that the total power generation remains unchanged. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of the structure of a heat storage and peak-shaving operation system for a gas generator set in a steel enterprise, as described in this application.

[0046] As shown in the figure: 1. Fuel supply subsystem, 2. Gas turbine power generation unit, 3-1. First flue gas valve, 3-2. Second flue gas valve, 4. Waste heat boiler unit, 5. Heat storage and exchange subsystem, 5-1. Flue gas molten salt heat exchanger, 5-2. High temperature storage tank, 5-3. Low temperature storage tank, 5-4. High temperature molten salt circulating pump, 5-5. Low temperature molten salt circulating pump, 5-6. Molten salt steam-water heat exchanger, 6. Steam turbine power generation unit, 6-1. Steam turbine generator set, 6-2. Condenser, 6-3. Circulating cooler, 6-4. Condensate pump, 6-5. Regenerative deaerator, 6-6. Feedwater pump, 7. Chimney, 8-1. First steam valve, 8-2. Second steam valve, 9-1. First feedwater valve, 9-2. Second feedwater valve, 10-1. First tail gas valve, 10-2. Second tail gas valve. Detailed Implementation

[0047] The present invention will now be described in further detail with reference to the accompanying drawings.

[0048] The specific embodiments of this utility model will be further described below with reference to the accompanying drawings. Identical components are indicated by the same reference numerals.

[0049] It should be noted that the terms “front,” “back,” “left,” “right,” “up,” and “down” used in the following description refer to the directions shown in the attached diagram, while the terms “inside” and “outside” refer to the directions toward or away from the geometric center of a specific component, respectively.

[0050] To make the content of this utility model easier to understand, the technical solutions in the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings.

[0051] This invention provides a thermal storage and peak-shaving operation system for gas-fired combined cycle generator sets in steel enterprises, belonging to the field of energy conservation and energy dispatching technology in the steel industry. The system integrates a thermal storage and exchange subsystem in parallel within a traditional gas-fired combined cycle generator set, achieving thermal coupling through the steam header and feedwater header. It intelligently switches operating modes based on the time-of-use electricity price signal from the power grid, significantly increasing the unit's power output during periods of high electricity prices while maintaining constant total gas consumption. This substantially reduces the cost of purchased electricity and improves the enterprise's overall energy efficiency and economic benefits.

[0052] Combined with appendix Figure 1 This system mainly includes a gas-fired steam combined cycle power generation system, a heat storage and exchange subsystem 5, a flue gas conditioning subsystem, a steam header subsystem, a feedwater header subsystem, and a flue gas collection and emission subsystem. The gas-fired steam combined cycle power generation system includes a gas turbine power generation unit 2, a waste heat boiler unit 4, and a steam turbine power generation unit 6 connected in sequence; the fuel supply subsystem 1 is connected to the fuel delivery port of the gas turbine power generation unit 2 through a fuel delivery pipe.

[0053] The heat storage and exchange subsystem 5 is connected in parallel with the waste heat boiler unit 4 on the flue gas outlet side of the gas turbine power generation unit 2; the flue gas regulation subsystem is used to regulate the distribution path of high-temperature flue gas; the steam header subsystem and the feedwater header subsystem respectively realize steam convergence and feedwater divergence; the flue gas collection and emission subsystem ensures the safe emission of flue gas after heat exchange.

[0054] In a preferred embodiment of this system, the heat storage and exchange subsystem 5 uses molten salt as the heat storage medium, specifically including a flue gas molten salt heat exchanger 5-1, a high-temperature storage tank 5-2, a low-temperature storage tank 5-3, a high-temperature molten salt circulation pump 5-4, a low-temperature molten salt circulation pump 5-5, and a molten salt steam-water heat exchanger 5-6. The flue gas inlet of the flue gas molten salt heat exchanger 5-1 is connected to the tail flue of the gas turbine through a second flue gas valve 3-2. Its molten salt side forms a closed loop with the dual-tank heat storage unit: low-temperature molten salt is pumped from the low-temperature storage tank 5-3 into the flue gas molten salt heat exchanger 5-1 via the low-temperature molten salt circulation pump 5-5, absorbs heat, becomes high-temperature molten salt, and is stored in the high-temperature storage tank 5-2; during the heat release stage, high-temperature molten salt is pumped from the high-temperature storage tank 5-2 into the molten salt steam-water heat exchanger 5-6 via the high-temperature molten salt circulation pump 5-4, exchanges heat with feedwater, cools down, and returns to the low-temperature storage tank 5-3. Molten salt steam-water heat exchanger 5-6 adopts a modular design, with a preheating section, an evaporation section and a superheating section. It can generate superheated steam with the same pressure and temperature as the main steam at the outlet of waste heat boiler unit 4, ensuring the matching of thermodynamic parameters when the two steam streams are mixed and avoiding thermal stress at the turbine inlet.

[0055] The steam turbine generator unit 6 includes a steam turbine generator set 6-1, a condenser 6-2, a circulating cooler 6-3, a condensate pump 6-4, a regenerative deaerator 6-5, and a feedwater pump 6-6, forming a complete Rankine cycle. After performing work, the exhaust steam is condensed in the condenser 6-2 and then pumped by the condensate pump 6-4 to the regenerative deaerator 6-5. The exhaust port of the steam turbine generator set 6-1 is connected to the regenerative deaerator 6-5 and used to heat the condensate in the regenerative deaerator 6-5. After being reheated and deaerated by the extracted steam, it becomes feedwater, which is finally pressurized by the feedwater pump 6-6 and delivered to the feedwater header.

[0056] The system is equipped with multiple key regulating valve groups to achieve flexible switching of operating modes: flue gas regulating valve group 3 (including the first flue gas valve 3-1 and the second flue gas valve 3-2) controls flue gas distribution; steam regulating valve group (including the first steam valve 8-1 and the second steam valve 8-2) controls steam convergence; feedwater regulating valve group (including the first feedwater valve 9-1 and the second feedwater valve 9-2) regulates feedwater flow; and exhaust gas regulating valve group (including the first exhaust gas valve 10-1 and the second exhaust gas valve 10-2) manages flue gas emissions. All valve groups are connected to the central control system and can automatically adjust according to preset strategies or real-time electricity price signals.

[0057] The system operates by dividing the time-of-use electricity price signal into an energy storage mode during low-price periods and an energy release mode during high-price periods. The specific steps are as follows:

[0058] Energy storage mode typically operates during periods of low grid load and low electricity prices, aiming to store as much flue gas heat energy as possible in molten salt while maintaining stable operation of the turbine generator unit at minimum load. The specific steps are as follows:

[0059] S1. Flue Gas Distribution Regulation: Close the first flue gas valve 3-1 slightly and open the second flue gas valve 3-2 wider, introducing most of the high-temperature flue gas into the flue gas molten salt heat exchanger 5-1 of the heat storage and exchange subsystem 5. During periods of low electricity prices, the grid's demand for electricity is relatively low. At this time, the amount of flue gas entering the waste heat boiler system 4 is reduced, lowering its steam production capacity, and more high-temperature flue gas is guided to the flue gas molten salt heat exchanger 5-1. In this way, without increasing the total gas consumption, the flue gas heat energy that would normally be used for direct power generation can be stored, providing energy reserves for power generation during periods of high electricity prices.

[0060] S2. Thermal Storage Circulation: The cryogenic molten salt circulation pump 5-5 is started, pumping the molten salt in the cryogenic storage tank 5-3 into the flue gas molten salt heat exchanger 5-1 to absorb heat from the flue gas. The resulting high-temperature molten salt is stored in the high-temperature storage tank 5-2. The molten salt has a wide liquid phase temperature range and high thermal stability, enabling it to operate stably at high temperatures for extended periods. The high-temperature flue gas releases sensible heat in the flue gas molten salt heat exchanger 5-1, and this energy is efficiently transferred to the flowing molten salt medium through the heat exchange tube walls. After absorbing heat, the cryogenic molten salt becomes high-temperature molten salt and is stored in the high-temperature storage tank 5-2, thus realizing the storage of thermal energy in the flue gas in the form of sensible heat.

[0061] S3. Low-load operation of the steam-water system: The second feedwater valve 9-2 and the second steam valve 8-2 are closed, allowing steam to be generated solely by the waste heat boiler unit 4 to drive the turbine generator unit 6 to operate near the minimum load rate. Since most of the high-temperature flue gas is allocated to the heat storage and exchange subsystem 5 for heat storage, the flue gas supply to the waste heat boiler system 4 is reduced, resulting in a corresponding reduction in steam production. By closing the second steam valve 8-2 and the second feedwater valve 9-2, the steam-water connection between the heat storage and exchange subsystem 5 and the turbine generator system 6 is severed. This ensures that the small amount of steam generated by the waste heat boiler system 4 can be used entirely to drive the turbine generator unit 6-1 to operate near the minimum load rate, guaranteeing the unit's basic operating condition while reducing unnecessary energy consumption.

[0062] S4. Flue Gas Emission: Keep the first tail gas valve 10-1 and the second tail gas valve 10-2 open to ensure that all flue gas is collected and discharged through chimney 7 after heat exchange. In energy storage mode, both the waste heat boiler system 4 and the flue gas molten salt heat exchanger 5-1 are operating, and both will generate low-temperature flue gas after heat exchange. Keeping both tail gas valves open allows the low-temperature flue gas generated by the two systems to smoothly flow into chimney 7 for discharge, ensuring the environmentally friendly operation of the system and preventing the accumulation of flue gas from affecting equipment and the environment.

[0063] The energy release mode typically operates during peak grid load periods and when electricity prices are high. Its goal is to release stored thermal energy to generate steam in conjunction with a waste heat boiler system, driving the steam turbine generator unit to operate at full load. The specific steps are as follows:

[0064] S5. Flue Gas Distribution Switching: Open the first flue gas valve 3-1 fully and close the second flue gas valve 3-2 partially to allow all high-temperature flue gas to enter the waste heat boiler unit 4. During periods of high electricity prices, the grid's demand for electricity is higher, requiring an increase in the unit's power output. Distributing most of the high-temperature flue gas to the waste heat boiler system 4 enables it to generate more steam and increase power generation. Simultaneously, supplying a minimum amount of flue gas to the heat storage and exchange subsystem 5 maintains its system temperature, ensuring rapid response to mode switching when needed.

[0065] S6. Heat Release and Steam Generation: Start the high-temperature molten salt circulation pump 5-4 to pump the high-temperature molten salt stored in the high-temperature storage tank 5-2 into the molten salt steam-water heat exchanger 5-6 to generate steam. After starting the high-temperature molten salt circulation pump 5-4, the high-temperature molten salt flows into the molten salt steam-water heat exchanger 5-6 and exchanges heat with the feedwater. The high-temperature molten salt transfers its stored heat energy to the feedwater, causing the feedwater to gradually heat up and generate steam, thus realizing the release and conversion of heat energy.

[0066] S7. High-load operation of the steam-water system: Adjust the steam-water pipeline valves, open the second feedwater valve 9-2 and the second steam valve 8-2, and simultaneously adjust the opening of the first feedwater valve 9-1; this allows feedwater to enter the waste heat boiler system 4 and the molten salt steam-water heat exchanger 5-6 to generate steam. The steam generated from both sources merges after opening the first steam valve 8-1 and the second steam valve 8-2, and is then introduced into the steam turbine generator system 6, driving the steam turbine generator set 6-1 to operate at full load or near full load. Opening the second feedwater valve 9-2 and the second steam valve 8-2 creates a steam-water circulation path between the molten salt steam-water heat exchanger 5-6 and the steam turbine generator system 6. The waste heat boiler system 4 and the molten salt steam-water heat exchanger 5-6 simultaneously generate steam. After the two steam sources merge, they enter the steam turbine generator set 6-1, increasing the steam flow and energy, thereby driving the steam turbine generator set 6-1 to operate at full load or near full load, improving the unit's power output, and meeting the grid's electricity demand during periods of high electricity prices.

[0067] S8. Flue Gas Emission Adjustment: Keep the first tail gas valve 10-1 fully open and adjust the opening of the second tail gas valve 10-2 to ensure that all flue gas is collected and discharged into the chimney 7. In energy release mode, the operating status of the waste heat boiler system 4 and the flue gas molten salt heat exchanger 5-1 changes, and the amount of flue gas produced may also differ. Keep the first tail gas valve 10-1 fully open to ensure smooth discharge of flue gas from the waste heat boiler system 4; adjust the opening of the second tail gas valve 10-2, and reasonably control the flue gas emission of the flue gas molten salt heat exchanger 5-1 according to its operating status, so that the flue gas generated by the two systems can be collected and stably discharged into the chimney 7, ensuring the environmentally friendly and safe operation of the system.

[0068] Example:

[0069] Taking the actual application of a 100MW gas-fired combined cycle generator unit in a steel plant as an example. The unit was originally designed with a gas turbine output of 60MW and a steam turbine output of 40MW, with a power generation efficiency of 50%. After thermal storage and peak shaving retrofitting, additional features were added... Figure 1 The heat storage and exchange subsystem shown.

[0070] During off-peak electricity hours at night (assuming 16 hours), the system enters energy storage mode. Approximately 70% of the high-temperature flue gas is switched to the heat exchange subsystem 5 to heat the molten salt energy storage; the remaining flue gas enters the waste heat boiler unit 4 to maintain the steam turbine power generation unit 6 at 33% load rate (approximately 13.2MW). During this period, the total unit output is the sum of the gas turbine output of 60MW and the steam turbine low-load output of 13.2MW, which is 73.2MW.

[0071] During peak daytime electricity price periods (assuming 8 hours), the system switches to energy release mode, with all flue gas entering the waste heat boiler unit 4, causing it to operate at full load and generate steam. Simultaneously, the heat storage and exchange subsystem 5 releases its stored heat energy, generating steam with parameters consistent with the waste heat boiler. After the two steam streams merge, they drive the steam turbine generator unit 6 to operate at over 100% load (40MW), with the actual turbine output reaching 72MW. During this period, the total unit output is the sum of the gas turbine output of 60MW and the high-load steam turbine output of 72MW, which is 132MW.

[0072] In terms of economic benefits, taking Jiangsu's electricity pricing policy as an example, the peak electricity price is 0.9 yuan / kWh, and the off-peak electricity price is 0.3 yuan / kWh. Before the upgrade, the unit operated continuously at 100MW, generating 2400MWh per day, with daily electricity revenue of approximately 1.46 million yuan. After the upgrade, it operates at 132MW for 8 hours during peak hours, generating 1056MWh; and at 73.2MW for 16 hours during off-peak hours, generating 1171.2MWh. The total daily electricity generation remains 2227.2MWh, but the electricity revenue increases to approximately 1.62 million yuan. After deducting the increased costs of equipment depreciation, maintenance, and molten salt replacement due to the thermal storage system, it is estimated that the net increase in revenue will be approximately 53 million yuan for 330 days of operation per year, with an investment payback period of approximately 2-3 years, demonstrating significant economic benefits.

[0073] Furthermore, this invention offers significant environmental benefits and system optimization effects. By enhancing the peak-shaving capacity of the generating unit, it strengthens the steel plant's responsiveness to grid demands, enabling it to participate in demand response or ancillary services markets as needed. During periods of fluctuating gas supply, the thermal storage system acts as a buffer, absorbing gas pressure fluctuations and improving the operational stability of the power generation system. The molten salt system operates at atmospheric pressure, ensuring high safety, and its composition consists of environmentally friendly inorganic salts, generating no additional pollutants during operation.

[0074] In summary, this invention, by introducing a thermal storage subsystem and integrating it in parallel with an existing gas-fired combined cycle power generation system, successfully achieves a significant increase in peak-hour unit output without increasing gas consumption. Furthermore, it optimizes production plans based on electricity price signals, demonstrating high economic efficiency and engineering application value. Those skilled in the art can adapt and adjust system parameters or optimize local structures under the guidance of this invention, such as selecting different types of thermal storage media, adjusting the form of the thermal storage tank, or changing the system layout. These modifications should also fall within the protection scope of this invention.

[0075] In conclusion, if any person skilled in the art, inspired by this invention, designs a similar structure and embodiment without departing from the spirit of this invention, such design should fall within the protection scope of this invention.

Claims

1. A thermal storage and peak-shaving operation system for a gas-fired steam combined cycle generator unit in an iron and steel enterprise, characterized in that, include: A combined cycle gas turbine and steam turbine power generation system, comprising a gas turbine power generation unit (2), a waste heat boiler unit (4), and a steam turbine power generation unit (6) connected in sequence; The fuel supply subsystem (1) is connected to the fuel delivery port of the gas turbine power generation unit (2) via a fuel delivery pipe; The heat storage and exchange subsystem (5) is connected in parallel with the waste heat boiler unit (4) on the flue gas outlet side of the gas turbine power generation unit (2) to store flue gas heat energy during periods of low electricity price and release the stored heat energy during periods of high electricity price to assist in power generation. The flue gas regulation subsystem is connected to the flue gas outlet of the gas turbine power generation unit (2) and is diverted to the flue gas input of the waste heat boiler unit (4) and the heat storage and exchange subsystem (5) for regulating flue gas distribution. The steam header subsystem connects the steam output terminals of the waste heat boiler unit (4) and the heat storage and exchange subsystem (5), and is connected to the steam input terminal of the steam turbine power generation unit (6). The water supply main pipe subsystem is connected to the water supply output end of the steam turbine power generation unit (6) and is diverted to the water supply input end of the waste heat boiler unit (4) and the heat storage and exchange subsystem (5); The flue gas regulation subsystem includes a first flue gas valve (3-1) installed on the pipeline leading to the waste heat boiler unit (4) and a second flue gas valve (3-2) installed on the pipeline leading to the heat storage and exchange subsystem (5). By adjusting the opening of the first flue gas valve (3-1) and the second flue gas valve (3-2), the flue gas distribution is controlled, and the system can switch between the two operating modes of energy storage and energy release.

2. The thermal energy storage and peak-shaving operation system according to claim 1, characterized in that, The heat storage and exchange subsystem (5) includes: The flue gas molten salt heat exchanger (5-1) has its flue gas inlet end connected to the outlet of the second flue gas valve (3-2) for heat exchange between high-temperature flue gas and molten salt; A dual-tank thermal energy storage unit, comprising a high-temperature storage tank (5-2), a low-temperature storage tank (5-3), a high-temperature molten salt circulation pump (5-4), and a low-temperature molten salt circulation pump (5-5); Molten salt steam-water heat exchanger (5-6) is used to exchange heat between molten salt and feedwater to generate steam; The outlet of the cryogenic storage tank (5-3) is connected to the molten salt inlet of the flue gas molten salt heat exchanger (5-1) via a cryogenic molten salt circulation pump (5-5), and the molten salt outlet of the flue gas molten salt heat exchanger (5-1) is connected to the inlet of the high-temperature storage tank (5-2), thus forming a heat storage circuit. The outlet of the high-temperature storage tank (5-2) is connected to the molten salt inlet of the molten salt steam-water heat exchanger (5-6) via a high-temperature molten salt circulation pump (5-4), and the molten salt outlet of the molten salt steam-water heat exchanger (5-6) is connected to the inlet of the low-temperature storage tank (5-3), thus forming a heat release circuit.

3. The thermal energy storage and peak-shaving operation system according to claim 2, characterized in that, The molten salt steam-water heat exchanger (5-6) includes a preheater, a heater, and a superheater that sequentially preheat, evaporate, and superheat the feedwater, and is used to generate steam with parameters consistent with those produced by the waste heat boiler unit (4).

4. The thermal energy storage and peak-shaving operation system according to claim 1, characterized in that, The steam main pipe subsystem is equipped with a steam regulating valve group, which includes a first steam valve (8-1) installed in the steam output pipeline of the waste heat boiler unit (4) and a second steam valve (8-2) installed in the steam output pipeline of the heat storage and exchange subsystem (5).

5. The thermal energy storage and peak-shaving operation system according to claim 1, characterized in that, The water supply main pipe subsystem is equipped with a water supply regulating valve group, which includes a first water supply valve (9-1) installed on the water supply pipeline leading to the waste heat boiler unit (4) and a second water supply valve (9-2) installed on the water supply pipeline leading to the heat storage and exchange subsystem (5).

6. The thermal energy storage and peak-shaving operation system according to claim 1, characterized in that, The system also includes a flue gas collection and emission subsystem, which connects the flue gas output end of the waste heat boiler unit (4) and the heat storage and exchange subsystem (5) and collects the flue gas into the chimney (7). The flue gas collection and emission subsystem is equipped with a tail gas regulating valve group, including a first tail gas valve (10-1) installed in the flue gas output pipeline of the waste heat boiler unit (4) and a second tail gas valve (10-2) installed in the flue gas output pipeline of the heat storage and exchange subsystem (5).

7. The thermal energy storage and peak-shaving operation system according to claim 1, characterized in that, The gas turbine power generation unit (2) includes a gas compressor, an air compressor, a burner, a gas turbine, and a gas turbine generator, which are used to generate electricity by consuming surplus gas from the steel plant.

8. The thermal energy storage and peak-shaving operation system according to claim 1, characterized in that, The steam turbine power generation unit (6) includes a steam turbine generator set (6-1), a condenser (6-2), a circulating cooler (6-3), a condensate pump (6-4), a regenerative deaerator (6-5), and a feedwater pump (6-6); The exhaust steam output terminal of the steam turbine generator set (6-1) is connected to the input terminal of the condenser (6-2); The condensate output end of the condenser (6-2) is connected to the input end of the regenerative deaerator (6-5) through the condensate pump (6-4), and the exhaust port of the steam turbine generator set (6-1) is connected to the regenerative deaerator (6-5). The water supply output end of the regenerative deaerator (6-5) is connected to the input end of the water supply main pipe subsystem via the water supply pump (6-6); The circulating cooler (6-3) is coupled to the condenser (6-2) to condense the exhaust steam in the condenser (6-2); thus forming a complete steam-water circulation loop.

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