Heat storage peak regulation operation system and method for gas generator set of iron and steel enterprise

Abstract

The invention provides a heat storage peak regulation operation system and method for a gas generator set of an iron and steel enterprise. The problems that the operation load of the gas generator set is limited, and economic benefits are not maximized are solved. The system comprises a coal gas power generation subsystem, a heat storage and exchange subsystem connected with a coal gas boiler unit in parallel, a fuel supply subsystem, a water supply subsystem, a main steam subsystem and a flue gas subsystem. The gas distribution amount is adjusted through the fuel adjusting valve set, and switching between the energy storage mode and the energy release mode is achieved. According to the method, time-phased operation is performed according to an electricity price signal, in an energy storage mode, most coal gas stores heat for the molten salt heating furnace, and a small amount of coal gas maintains low-load power generation; in the energy release mode, most coal gas enters the coal gas boiler unit, and meanwhile the heat storage subsystem releases heat to assist power generation. The system breaks through the gas supply constraint, improves the power generation capacity in a high-electricity-price period, reduces the cost of outsourcing electricity, is high in integration level, is flexible in operation, has an obvious advantage of selecting fused salt for heat storage, and improves the energy utilization efficiency and enterprise benefits.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy scheduling and optimization of steel enterprises, and particularly relates to a coal gas generator unit peak shaving operation system and method combined with heat storage technology, which is suitable for efficient utilization of surplus coal gas of a steel enterprise and economic operation under peak-valley electricity price of a power grid. BACKGROUND

[0002] A steel enterprise is a typical high energy consumption and high carbon emission industrial department, and a large amount of coal gas, such as blast furnace gas and converter gas, is by-produced in the production process. The coal gas is usually used to drive a generator unit to realize self-sufficiency of part of electric energy of the enterprise. However, the consumption of the coal gas by the main process of the steel enterprise fluctuates, which causes unstable amount of surplus coal gas for power generation and restricts the output and efficiency of the generator unit. The existing coal gas generator unit usually adopts a scheme of a coal gas boiler combined with a steam turbine generator, and the operation load of the generator unit is directly limited by the amount of the coal gas, so that the generator unit cannot play a greater role in a high peak period of the power grid, and the ability of the enterprise to obtain higher benefits by participating in peak shaving of the power grid is also limited.

[0003] Especially during the peak electricity consumption period such as the peak summer, the power grid implements a time-of-use electricity price policy, and the electricity price in the high peak period is much higher than that in the low valley period. The traditional coal gas generator unit cannot flexibly adjust the power generation load due to the limitation of the total amount of the coal gas, so that the power generation capacity is insufficient in the high peak period, and the coal gas may have to be discharged or inefficiently utilized due to the surplus in the low valley period, which causes energy waste and economic loss. Therefore, there is an urgent need for an operation scheme capable of improving the output of the unit in the high peak period and optimizing the power generation benefits under the premise that the total amount of the coal gas is unchanged. SUMMARY

[0004] The technical problem to be solved by the present application is to overcome the defects that the operation load of the existing coal gas generator unit of a steel enterprise is limited by the amount of the coal gas, the generator unit cannot flexibly adapt to the peak-valley electricity price of the power grid, and the economic benefits cannot be maximized, and to provide a heat storage peak shaving operation system and method which has reasonable system structure, flexible operation mode, can significantly improve the high peak power generation capacity and reduce the cost of purchased electricity.

[0005] To solve the above technical problems, the technical scheme provided by the present application is as follows: the present application provides a heat storage peak shaving operation system for a coal gas generator unit of a steel enterprise, which comprises:

[0006] a coal gas power generation system, which comprises a coal gas boiler unit and a steam turbine power generation unit;

[0007] a heat storage and exchange subsystem, which is arranged in parallel with the coal gas boiler unit, and comprises a molten salt heating furnace, a double-tank heat storage unit and a molten salt heat exchanger unit, and is used for storing chemical energy of the coal gas in a low electricity price period and releasing the stored heat energy to assist power generation in a high electricity price period;

[0008] a fuel supply subsystem connected to the input of the coal gas boiler unit and the molten salt heater through a pipeline for supplying coal gas;

[0009] a feedwater subsystem connected to the input of the coal gas boiler unit and the molten salt heat exchanger unit through a pipeline;

[0010] a main steam subsystem connected to the steam output of the coal gas boiler unit and the molten salt heat exchanger unit and connected to the steam input of the steam turbine power generation unit;

[0011] a flue gas subsystem connected to the flue gas output of the coal gas boiler unit and the molten salt heater and connected to a chimney;

[0012] wherein the fuel supply subsystem is provided with a fuel regulating valve group on the connecting pipeline between the coal gas boiler unit and the molten salt heater for regulating the distribution of coal gas into the coal gas boiler unit and the molten salt heater, thereby controlling the system to switch between energy storage and energy release modes.

[0013] Preferably, the molten salt heater comprises a burner, a furnace, and a molten salt heat exchange coil arranged in the furnace, through which the molten salt flows to absorb the chemical energy released by the combustion of coal gas.

[0014] Preferably, the double-tank heat storage unit comprises a high-temperature storage tank, a low-temperature storage tank, a high-temperature molten salt circulating pump, and a low-temperature molten salt circulating pump.

[0015] The outlet of the low-temperature storage tank is connected to the molten salt inlet of the molten salt heater through a low-temperature molten salt circulating pump, and the molten salt outlet of the molten salt heater is connected to the inlet of the high-temperature storage tank, forming a heat storage circuit.

[0016] The molten salt heat exchanger unit has its molten salt inlet connected to the outlet of the high-temperature storage tank through a high-temperature molten salt circulating pump, and its molten salt outlet connected to the inlet of the low-temperature storage tank, forming a heat release circuit.

[0017] Preferably, the molten salt heat exchanger unit comprises a preheater, a heater, and a superheater for preheating, heating, and superheating the feedwater in sequence, thereby producing steam with parameters consistent with those of the steam produced by the coal gas boiler unit.

[0018] Preferably, the steam turbine power generation unit comprises a steam turbine generator set, a condenser, a circulating cooler, a condensate pump, a regenerative deaerator, and a feedwater pump.

[0019] The exhaust steam output end of the steam turbine generator set is connected to the exhaust steam input end of the condenser; the circulating cooler is coupled with the condenser for condensing the exhaust steam in the condenser; the condensate water output end of the condenser is connected to the regenerative deaerator through the condensate water pump, and the steam turbine generator set is connected to the regenerative deaerator through the extraction port; and the feed water output end of the regenerative deaerator is connected to the feed water subsystem through the feed water pump.

[0020] Preferably, the fuel regulating valve group comprises a first gas valve arranged on a pipeline leading to the coal gas boiler unit and a second gas valve arranged on a pipeline leading to the molten salt heater.

[0021] Preferably, the main steam subsystem is provided with a steam regulating valve group comprising a first steam valve arranged on a steam output pipeline of the coal gas boiler unit and a second steam valve arranged on a steam output pipeline of the molten salt heat exchanger unit.

[0022] Preferably, the feed water subsystem is provided with a feed water regulating valve group comprising a first feed water valve arranged on a feed water pipeline leading to the coal gas boiler unit and a second feed water valve arranged on a feed water pipeline leading to the molten salt heat exchanger unit.

[0023] Preferably, the flue gas subsystem is provided with a tail gas regulating valve group comprising a first flue gas valve arranged on a flue gas output pipeline of the coal gas boiler unit and a second flue gas valve arranged on a flue gas output pipeline of the molten salt heater.

[0024] The application also provides a heat storage peak shaving operation method for a coal gas generator set of a steel enterprise, which is divided into an energy storage mode operation in a low electricity price period and an energy release mode operation in a high electricity price period according to an electricity price signal, and specifically comprises the following steps:

[0025] The energy storage mode operation specifically comprises the following steps:

[0026] S1, fuel distribution adjustment: adjusting the fuel regulating valve group, specifically closing the first gas valve and opening the second gas valve, so that most of the coal gas is distributed to the molten salt heater in the heat storage and exchange subsystem for combustion;

[0027] S2, heat storage cycle: starting the low-temperature molten salt circulating pump to pump the low-temperature molten salt in the low-temperature storage tank into the molten salt heater to absorb the heat released by the combustion of the coal gas, and the heated high-temperature molten salt flows into the high-temperature storage tank for storage, thereby completing the heat storage;

[0028] S3, steam-water system isolation and low-load power generation: adjusting the steam-water pipeline valves, closing the second steam valve and the second feed water valve, and adjusting the opening degree of the first feed water valve; the steam generated by the combustion of a small amount of coal gas entering the coal gas boiler unit is all introduced into the steam turbine unit through the first steam valve to drive the steam turbine generator set to maintain operation at a minimum load rate.

[0029] S4, flue gas treatment: keep the first flue gas valve and the second flue gas valve in the open state to ensure that the flue gas generated by the two systems can be merged into the chimney for emission;

[0030] The energy releasing mode operation specifically comprises the following steps:

[0031] S5, fuel distribution switching: adjust the fuel adjusting valve group, specifically, open the first coal gas valve to near full opening and close the second coal gas valve, so that most of the coal gas enters the coal gas boiler unit for combustion and only the minimum amount of coal gas required to maintain the combustion of the burner of the molten salt heating furnace is supplied to the molten salt heating furnace;

[0032] S6, heat release and steam generation: start the high-temperature molten salt circulating pump to pump the high-temperature molten salt stored in the high-temperature storage tank into the molten salt heat exchanger unit;

[0033] S7, parallel connection of the steam-water system and high-load power generation: adjust the steam-water pipeline valve, open the second feed water valve and the second steam valve, and adjust the opening degree of the first feed water valve; make the feed water enter the coal gas boiler unit and the molten salt heat exchanger unit to generate steam, respectively, and the steam generated by the two routes is merged after the first steam valve and the second steam valve are opened, and then is guided into the steam turbine unit to drive the steam turbine generator set to operate at full load or near full load;

[0034] S8, flue gas treatment adjustment: keep the first flue gas valve fully open and adjust the opening degree of the second flue gas valve to ensure that all the flue gas is merged and then emitted into the chimney.

[0035] Compared with the prior art, the beneficial effects of the present application are as follows:

[0036] 1. The present application breaks through the rigid constraint of the total amount of coal gas supply on the power output of the generator set, realizes the time-space transfer of energy through the heat storage subsystem, significantly improves the power generation capacity of the unit during the high electricity price period without increasing the coal gas consumption, and is equivalent to realizing the expansion of the unit.

[0037] 2. Through intelligent scheduling of coal gas distribution and heat storage / heat release process, the operation strategy of the generator set is perfectly matched with the peak-valley electricity price of the power grid, the power generation income during the peak period is maximized, and the external purchase cost of electricity of the steel enterprise is effectively reduced.

[0038] 3. The system has high integration degree, through parallel connection type modification of the existing coal gas generator set, the heat storage system is newly added, the modification amount is small, the implementation is convenient, and the operation mode switching is flexible and reliable.

[0039] 4. The molten salt is selected as the heat storage medium, which has the advantages of large heat capacity, wide temperature range, good stability and economy, and is especially suitable for large-scale and medium-high temperature heat storage demand of the steel enterprise.

[0040] 5. The utilization efficiency of the whole energy system and the economic benefit of the enterprise are improved, which provides an effective technical path for the green and low-carbon transformation of the steel enterprise and the participation in the demand side response of the power grid. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a structural schematic diagram of a heat storage peak shaving operation system for a coal gas generator set of a steel enterprise.

[0042] As shown in the figure: 1, fuel supply subsystem, 2, coal gas boiler unit, 3, heat storage and heat exchange subsystem, 3-1, molten salt heating furnace, 3-2, double-tank heat storage unit, 3-2-1, high-temperature storage tank, 3-2-2, low-temperature storage tank, 3-2-3, high-temperature molten salt circulating pump, 3-2-4, low-temperature molten salt circulating pump, 3-3, molten salt heat exchanger unit, 4, steam turbine unit, 4-1, steam turbine generator set, 4-2, condenser, 4-3, circulating cooler, 4-4, condensate pump, 4-5, regenerative deaerator, 4-6, feed water pump, 5, chimney, 6-1, first coal gas valve, 6-2, second coal gas valve; 7-1, first steam valve, 7-2, second steam valve; 8-1, first feed water valve, 8-2, second feed water valve, 9-1, first flue gas valve, 9-2, second flue gas valve. DETAILED DESCRIPTION

[0043] The application will be further described in detail below with reference to the accompanying drawings.

[0044] The specific embodiments of the application will be further described below with reference to the accompanying drawings. The same parts are denoted by the same reference numerals.

[0045] It should be noted that the words "front", "back", "left", "right", "up" and "down" used in the following description refer to the directions in the drawings, and the words "in" and "out" refer to the directions towards or away from the geometric center of a particular part.

[0046] In order to make the content of the application more easily understood, the technical solutions in the embodiments of the application will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the application.

[0047] The application relates to a heat storage peak shaving operation system and method for a coal gas generator set of a steel enterprise, and belongs to the technical field of energy saving and energy scheduling in the steel industry, in particular to an operation scheme for improving the output of a coal gas generator set during a high electricity price period through a heat storage system.

[0048] The accompanying drawings Figure 1The application provides a heat storage peak shaving operation system for a steel enterprise coal gas generator set, which mainly comprises a coal gas electronic system, a heat storage and exchange subsystem, a fuel supply subsystem, a feedwater subsystem, a main steam subsystem and a flue gas subsystem. The coal gas electronic system comprises a coal gas boiler unit 2 and a steam turbine electronic unit 4; the heat storage and exchange subsystem 3 is arranged in parallel with the coal gas boiler unit 2, further comprises a molten salt heating furnace 3-1, a double-tank heat storage unit 3-2 and a molten salt heat exchanger unit 3-3, and is used for storing chemical energy in the coal gas in the form of heat energy in high-temperature molten salt during a low electricity price period of an electricity network, and releasing the stored heat energy to heat feedwater to generate steam during a high electricity price period, so as to assist the coal gas boiler to jointly improve the power generation load of the steam turbine unit; the fuel supply subsystem 1 is connected to the coal gas boiler unit 2 and the molten salt heating furnace 3-1 through pipelines respectively, and is responsible for the supply and distribution of the coal gas; the feedwater subsystem provides feedwater to the coal gas boiler unit 2 and the molten salt heat exchanger unit 3-3 through pipelines respectively; the main steam subsystem collects steam from the coal gas boiler and the molten salt heat exchanger, and delivers the steam to the steam turbine electronic unit 4; and the flue gas subsystem is connected to the exhaust outlets of the combustion equipment, and finally flows into a chimney 5 for emission.

[0049] In a specific embodiment of the system, the molten salt heating furnace 3-1 comprises a dedicated burner, a hearth and an embedded molten salt heat exchange coil, the structural design of which can ensure that the coal gas is fully combusted in the hearth, and the released chemical energy is efficiently transferred to the flowing molten salt medium through the coil wall. The molten salt is selected from a mixture of nitrate salts with a wide liquid phase temperature range and high thermal stability, which can be stably operated at high temperature for a long time. The double-tank heat storage unit 3-2 is composed of a high-temperature storage tank 3-2-1, a low-temperature storage tank 3-2-2, a high-temperature molten salt circulating pump 3-2-3 and a low-temperature molten salt circulating pump 3-2-4. The low-temperature molten salt is pumped from the low-temperature storage tank into the molten salt heating furnace, becomes high-temperature molten salt after absorbing heat, and is stored in the high-temperature storage tank, completing the heat storage cycle; in the heat release stage, the high-temperature molten salt is pumped from the high-temperature storage tank into the molten salt heat exchanger unit 3-3, exchanges heat with the feedwater, and returns to the low-temperature storage tank after being cooled. The molten salt heat exchanger unit 3-3 is usually designed in a modular manner, comprising a preheater, an evaporator and a superheater, and can gradually heat the feedwater into main steam with a certain superheat degree. The steam parameters are designed to be consistent with the outlet steam parameters of the coal gas boiler, so that the thermal parameters of the two steam flows are matched when mixed, and the thermal stress of the steam turbine inlet end is not uneven.

[0050] The steam turbine generator unit 4 includes a steam turbine generator set 4-1, a condenser 4-2, a circulating cooling system 4-3, a condensate pump 4-4, a regenerative deaerator 4-5, and a feed water pump 4-6. The spent steam after work is condensed into water in the condenser, and is sent into the regenerative deaerator by the condensate pump, and after multi-stage steam extraction regeneration and deaeration, is boosted by the feed water pump to be supplied to the coal gas boiler and the molten salt heat exchanger again. The steam extraction port of the steam turbine generator set 4-1 is connected with the regenerative deaerator 4-5 and is used for heating the condensate in the regenerative deaerator 4-5.

[0051] To realize flexible switching between the two operation modes, a plurality of key valve groups are provided in the system. The fuel regulating valve group includes a first coal gas valve 6-1 and a second coal gas valve 6-2, which are used for distributing coal gas; the steam regulating valve group includes a first steam valve 7-1 and a second steam valve 7-2, which are used for controlling the convergence and isolation of the two steam paths; the feed water regulating valve group includes a first feed water valve 8-1 and a second feed water valve 8-2, which are used for regulating the amount of feed water supplied to the two heat exchange systems; and the tail gas regulating valve group includes a first flue gas valve 9-1 and a second flue gas valve 9-2, which are used for regulating the flue gas discharge path. All the valve groups can adopt electric or pneumatic actuators and are connected to the central control unit to realize automatic regulation according to the preset strategy or real-time electricity price signal.

[0052] The application also provides a heat storage peak regulation operation method for a coal gas generator set of a steel enterprise, which is realized based on the foregoing system, and by intelligently responding to the time-of-use electricity price signal of the power grid, the operation mode is divided into an energy storage mode in a low electricity price period and an energy release mode in a high electricity price period. The core of the method is to realize the time-space transfer of coal gas energy by adjusting a plurality of key valve groups and subsystems, so that the power generation output of the unit in the high electricity price period is significantly improved on the premise that the total coal gas consumption remains unchanged, and the power generation benefit is maximized. The specific steps of the two operation modes are described in detail below.

[0053] The energy storage mode operation specifically includes the following steps:

[0054] S1, fuel distribution regulation: adjust the fuel regulating valve group, specifically close the first coal gas valve 6-1 and open the second coal gas valve 6-2, so that most of the coal gas is distributed to the molten salt heater 3-1 in the heat exchange sub-system 3 for combustion. In the low electricity price period, the demand for electricity of the power grid is relatively low, at this time, the coal gas supply of the coal gas boiler unit 2 is reduced, the power generation output is reduced, and more coal gas is guided to the molten salt heater 3-1. In this way, the coal gas energy originally used for direct power generation can be stored without increasing the total coal gas consumption, and energy is reserved for power generation in the high electricity price period.

[0055] S2, heat storage cycle: start the low-temperature molten salt circulating pump 3-2-4, and pump the low-temperature molten salt in the low-temperature storage tank 3-2-2 into the molten salt heating furnace 3-1 to absorb the heat released by the combustion of coal gas, and the high-temperature molten salt after being heated flows into the high-temperature storage tank 3-2-1 for storage, and the heat storage is completed. The molten salt has a wide liquid phase temperature range and high thermal stability, and can be stably operated at high temperature for a long time. The coal gas is fully combusted in the molten salt heating furnace 3-1, and a large amount of chemical energy is released, which is transmitted to the molten salt medium flowing through the heat exchange coil in the furnace through the heat exchange coil. The low-temperature molten salt absorbs heat and becomes high-temperature molten salt, which is stored in the high-temperature storage tank 3-2-1, so that the chemical energy in the coal gas is stored in the form of heat.

[0056] S3, steam-water system isolation and low-load power generation: adjust the steam-water pipeline valve, close the second steam valve 7-2 and the second feed water valve 8-2, and adjust the opening degree of the first feed water valve 8-1; make the steam generated by the combustion of a small amount of coal gas entering the coal gas boiler unit 2 all introduced into the steam turbine unit 4 through the opening of the first steam valve 7-1, to drive the steam turbine generator set 4-1 to operate near the minimum load rate. Since most of the coal gas is distributed to the molten salt heating furnace 3-1 for heat storage, the coal gas supply of the coal gas boiler unit 2 is reduced, and the amount of steam generated is also reduced. By closing the second steam valve 7-2 and the second feed water valve 8-2, the steam-water connection between the molten salt heat exchanger unit 3-3 and the steam turbine unit 4 is cut off, so that the small amount of steam generated by the coal gas boiler unit 2 can be used to drive the steam turbine generator set 4-1 to operate near the minimum load rate, to ensure the basic operation state of the unit, and to reduce unnecessary energy consumption.

[0057] S4, flue gas treatment: keep the first flue gas valve 9-1 and the second flue gas valve 9-2 open to ensure that the flue gas generated by the two systems can be discharged into the chimney 5. In the energy storage mode, the coal gas boiler unit 2 and the molten salt heating furnace 3-1 are both running and will generate flue gas. Keeping the two flue gas valves open can make the flue gas generated by the two systems flow smoothly into the chimney 5 for discharge, ensure the environmental protection operation of the system, and avoid the influence of flue gas accumulation on equipment and environment.

[0058] The energy release mode operation specifically includes the following steps:

[0059] S5, fuel distribution switching: adjust the fuel regulating valve group, specifically open the first gas valve 6-1 to near full opening and close the second gas valve 6-2 to a small amount, so that most of the gas enters the gas boiler unit 2 for combustion, and only the minimum amount of gas required to maintain the burner of the molten salt heating furnace 3-1 is supplied to it. During the high electricity price period, the power grid has a high demand for electricity, so the power generation output of the unit needs to be increased. Distribute most of the gas to the gas boiler unit 2 so that it can generate more steam to increase power generation. At the same time, supply the minimum amount of gas to the molten salt heating furnace 3-1 to maintain the burner unextinguished and ensure that the heat release process can be started quickly when needed.

[0060] S6, heat release and steam generation: start the high-temperature molten salt circulating pump 3-2-3 to pump the high-temperature molten salt stored in the high-temperature storage tank 3-2-1 into the molten salt heat exchanger unit 3-3. The high-temperature molten salt stores the heat released by gas combustion during the low electricity price period. When the high-temperature molten salt circulating pump 3-2-3 is started, the high-temperature molten salt flows into the molten salt heat exchanger unit 3-3 and exchanges heat with the feedwater. The high-temperature molten salt transfers its stored heat energy to the feedwater, causing the feedwater to gradually warm up and generate steam, achieving heat release and conversion.

[0061] S7, parallel steam-water system and high-load power generation: adjust the steam-water pipeline valves, open the second feedwater valve 8-2 and the second steam valve 7-2, and adjust the opening of the first feedwater valve 8-1; make the feedwater enter the gas boiler unit 2 and the molten salt heat exchanger unit 3-3 to generate steam, respectively. The two routes of generated steam are combined after opening the first steam valve 7-1 and the second steam valve 7-2, and then introduced into the steam turbine power generation unit 4 to drive the steam turbine generator set 4-1 to full load or near full load operation. Opening the second feedwater valve 8-2 and the second steam valve 7-2 forms a steam-water circulation path between the molten salt heat exchanger unit 3-3 and the steam turbine power generation unit 4. The gas boiler unit 2 and the molten salt heat exchanger unit 3-3 generate steam simultaneously, and the two routes of steam are combined and then enter the steam turbine generator set 4-1, increasing the flow and energy of the steam, thereby driving the steam turbine generator set 4-1 to operate at full load or near full load, increasing the power generation output of the unit and meeting the demand for electricity from the power grid during the high electricity price period.

[0062] S8, flue gas treatment adjustment: keep the first flue gas valve 9-1 fully open and adjust the opening of the second flue gas valve 9-2 to ensure that all flue gas is discharged into the chimney 5. In the energy release mode, the operating state of the gas boiler unit 2 and the molten salt heating furnace 3-1 changes, and the amount of flue gas generated may also be different. Keeping the first flue gas valve 9-1 fully open ensures that the flue gas from the gas boiler unit 2 can be smoothly discharged; adjusting the opening of the second flue gas valve 9-2 according to the operating condition of the molten salt heating furnace 3-1, reasonably controls the amount of flue gas discharged, so that the flue gas generated by the two systems can be stably discharged into the chimney 5 after being combined, ensuring the environmental protection and safe operation of the system.

[0063] Taking the actual application of a 40MW gas-fired power plant unit in a steel plant as an example, the solution of this invention will be specifically described. This unit was originally designed as a conventional gas-fired boiler generator unit. After undergoing thermal storage and peak-shaving modifications, the system added features such as... Figure 1 The heat storage and exchange subsystem is shown. During off-peak electricity hours at night (typically 16 hours), the system enters energy storage mode. Approximately 75% of the gas is switched to the molten salt heater for heating and storing the molten salt; the remaining gas is used by the gas boiler, and the unit's power generation load drops to 33% of its rated output, approximately 13.2 MW. During this period, the combustion system of the molten salt heater maintains stable operation, ensuring efficient heat absorption and storage by adjusting the combustion air distribution and molten salt flow rate, with the high-temperature molten salt temperature reaching over 565℃. Simultaneously, the gas boiler maintains stable operation under low-temperature and low-pressure conditions by adjusting the feedwater flow rate and combustion air distribution. The generated steam is only used to maintain the turbine's minimum load operation, avoiding frequent start-ups and shutdowns or excessively low efficiency under low load conditions.

[0064] During peak electricity pricing periods on the grid during the daytime (assuming 8 hours), the system switches to energy release mode. At this time, approximately 90% of the gas is allocated to the gas boiler, rapidly increasing its load to over 40MW of rated output. Simultaneously, the molten salt heat exchanger unit operates, releasing heat from the high-temperature molten salt to heat the feedwater into superheated steam with parameters consistent with the boiler's main steam (e.g., pressure 9.8MPa, temperature 540℃). The two steam streams mix and enter the turbine, jointly driving the generator unit to operate at 72MW, significantly increasing the unit's output. It is important to note that during high-load operation, the pressure and temperature of the main steam must be monitored in real time to ensure parameter matching during the mixing of the two steam streams, avoiding additional thermal stress on the turbine rotor or cylinder due to parameter deviations. Meanwhile, in this mode, the molten salt heater only supplies a small amount of gas to maintain a low-fired burner, ensuring the system can respond to mode switching again at any time.

[0065] In terms of economic benefits, taking Jiangsu's electricity pricing policy as an example, assuming a peak electricity price of 0.9 yuan / kWh and an off-peak price of 0.3 yuan / kWh, before the upgrade, the unit operated continuously at its rated output of 40MW, generating 960MWh per day, with electricity revenue of approximately 590,000 yuan. After the upgrade, it operates at 72MW for 8 hours during peak hours, generating 576MWh, and at 13.2MW for 16 hours during off-peak hours, generating 211.2MWh. The total daily power generation remains 787.2MWh, but the electricity revenue increases to approximately 740,000 yuan. After deducting the increased costs of equipment depreciation, maintenance, and molten salt replacement due to the investment in the thermal storage system, the estimated net increase in revenue for 330 days of operation per year is approximately 50 million yuan, with an investment payback period of 2-3 years, demonstrating significant economic benefits.

[0066] Furthermore, the system offers significant environmental benefits. By enhancing the peak-shaving capacity of the generator units, it strengthens the steel plant's responsiveness to grid demands, enabling it to effectively participate in demand response or ancillary services markets. During periods of fluctuating gas supply, the thermal storage system can also act as a buffer, appropriately absorbing gas pressure fluctuations and improving the overall operational stability of the power generation system. The molten salt system operates at atmospheric pressure, ensuring high safety, and its molten components are environmentally friendly inorganic salts, generating no additional pollutants during operation.

[0067] In summary, this invention, by introducing a thermal storage subsystem and integrating it in parallel with existing gas-fired power generator sets, successfully achieves a significant increase in peak-hour 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, under the guidance of this invention, adapt and adjust system parameters or optimize local structures, 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.

[0068] The above is a detailed description of the system and method of the present invention, including its composition, operation mode, typical embodiments, and benefit analysis. This invention is particularly suitable for steel enterprises with abundant coal gas energy resources. It can be used for energy-saving and efficiency-improving retrofits of existing generator sets, as well as for design optimization of new projects, and has broad prospects for widespread application.

[0069] In conclusion, if anyone skilled in the art, inspired by this invention, designs a similar structure and embodiment without departing from the spirit of the invention, such design should fall within the scope of protection of this invention.

Claims

1. A thermal storage and peak-shaving operation system for gas-fired generator sets in steel enterprises, characterized in that, include: A gas-fired power generation system, comprising a gas boiler unit (2) and a steam turbine power generation unit (4); The heat storage and exchange subsystem (3) is connected in parallel with the gas boiler unit (2). The heat storage and exchange subsystem (3) includes a molten salt heater (3-1), a double-tank heat storage unit (3-2), and a molten salt heat exchanger unit (3-3). It is used to store the chemical energy of gas during periods of low electricity price and release the stored heat energy during periods of high electricity price to assist in power generation. A fuel supply subsystem (1) is connected via pipeline to the input of the gas boiler unit (2) and the molten salt heater (3-1) for supplying gas; The water supply subsystem is connected to the input terminals of the gas boiler unit (2) and the molten salt heat exchanger unit (3-3) via pipelines; The main steam subsystem connects the steam output terminals of the gas boiler unit (2) and the molten salt heat exchanger unit (3-3), and is connected to the steam input terminal of the steam turbine generator unit (4). The flue gas subsystem connects the flue gas output terminals of the gas boiler unit (2) and the molten salt heater (3-1), and collects the flue gas into the chimney (5); The fuel supply subsystem (1) is connected to the gas boiler unit (2) and the molten salt heater (3-1) by a fuel regulating valve group, which is used to regulate the amount of gas entering the gas boiler unit (2) and the molten salt heater (3-1), thereby controlling the system to switch between the two operating modes of energy storage and energy release.

2. The peak-shaving operation system for gas-fired generator sets in steel enterprises according to claim 1, characterized in that, The molten salt heating furnace (3-1) includes a burner, a furnace chamber, and molten salt heat exchange coils arranged in the furnace chamber. The molten salt flows through the molten salt heat exchange coils to absorb the chemical energy released by the combustion of coal gas.

3. A thermal storage and peak-shaving operation system for a gas generator set in an iron and steel enterprise according to claim 2, characterized in that, The dual-tank thermal storage unit (3-2) includes a high-temperature storage tank (3-2-1), a low-temperature storage tank (3-2-2), a high-temperature molten salt circulation pump (3-2-3), and a low-temperature molten salt circulation pump (3-2-4); The outlet of the cryogenic storage tank (3-2-2) is connected to the molten salt inlet of the molten salt heater (3-1) via a cryogenic molten salt circulation pump (3-2-4), and the molten salt outlet of the molten salt heater (3-1) is connected to the inlet of the high-temperature storage tank (3-2-1), thus forming a heat storage circuit. The molten salt heat exchanger unit (3-3) has its molten salt inlet connected to the outlet of the high-temperature storage tank (3-2-1) via a high-temperature molten salt circulation pump (3-2-3), and its molten salt outlet connected to the inlet of the low-temperature storage tank (3-2-2), forming a heat release circuit.

4. A thermal storage and peak-shaving operation system for a gas generator set in an iron and steel enterprise according to claim 1, characterized in that, The molten salt heat exchanger unit (3-3) includes a preheater, a heater, and a superheater that sequentially preheat, heat, and superheat the feedwater, and is used to generate steam with parameters consistent with those produced by the gas boiler unit (2).

5. A thermal storage and peak-shaving operation system for a gas generator set in an iron and steel enterprise according to claim 1, characterized in that, The steam turbine generator unit (4) includes a steam turbine generator set (4-1), a condenser (4-2), a circulating cooler (4-3), a condensate pump (4-4), a regenerative deaerator (4-5), and a feedwater pump (4-6); The exhaust steam output of the turbine generator set (4-1) is connected to the exhaust steam input of the condenser (4-2); the circulating cooler (4-3) is coupled to the condenser (4-2) and is used to condense the exhaust steam in the condenser (4-2); the condensate output of the condenser (4-2) is connected to the regenerative deaerator (4-5) through the condensate pump (4-4), and the exhaust port of the turbine generator set (4-1) is connected to the regenerative deaerator (4-5); the feedwater output of the regenerative deaerator (4-5) is connected to the feedwater subsystem through the feedwater pump (4-6).

6. A thermal storage and peak-shaving operation system for a gas generator set in an iron and steel enterprise according to claim 1, characterized in that, The fuel regulating valve group includes a first gas valve (6-1) installed on the pipeline leading to the gas boiler unit (2) and a second gas valve (6-2) installed on the pipeline leading to the molten salt heater (3-1).

7. A thermal storage and peak-shaving operation system for a gas generator set in an iron and steel enterprise according to claim 1, characterized in that, The main steam subsystem is equipped with a steam regulating valve group, which includes a first steam valve (7-1) installed in the steam output pipeline of the gas boiler unit (2) and a second steam valve (7-2) installed in the steam output pipeline of the molten salt heat exchanger unit (3-3).

8. A thermal storage and peak-shaving operation system for a gas generator set in an iron and steel enterprise according to claim 1, characterized in that, The water supply subsystem is equipped with a water supply regulating valve group, which includes a first water supply valve (8-1) installed on the water supply pipeline leading to the gas boiler unit (2) and a second water supply valve (8-2) installed on the water supply pipeline leading to the molten salt heat exchanger unit (3-3).

9. A thermal storage and peak-shaving operation system for a gas generator set in an iron and steel enterprise according to claim 1, characterized in that, The flue gas subsystem is equipped with a tail gas regulating valve group, which includes a first flue gas valve (9-1) installed in the flue gas output pipeline of the gas boiler unit (2) and a second flue gas valve (9-2) installed in the flue gas output pipeline of the molten salt heater (3-1).

10. A method for heat storage and peak-shaving operation of gas-fired generator sets in steel enterprises, characterized in that, The method 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. Includes the following steps: The operation of the energy storage mode specifically includes the following steps: S1. Fuel distribution regulation: Adjust the fuel regulating valve group, specifically by closing the first gas valve (6-1) and opening the second gas valve (6-2) to distribute most of the gas to the molten salt heater (3-1) of the heat storage and heat exchange subsystem (3) for combustion; S2, Thermal Storage Circulation: Start the low-temperature molten salt circulation pump (3-2-4) to pump the low-temperature molten salt in the low-temperature storage tank (3-2-2) into the molten salt heating furnace (3-1) to absorb the heat released by the combustion of coal gas. The heated high-temperature molten salt flows into the high-temperature storage tank (3-2-1) for storage, thus completing the thermal energy storage. S3, Isolation of steam and water system and low-load power generation: Adjust the steam and water pipeline valves, close the second steam valve (7-2) and the second feed water valve (8-2), and at the same time adjust the opening of the first feed water valve (8-1); so that the steam generated by the combustion of a small amount of gas entering the gas boiler unit (2) is completely introduced into the steam turbine generator unit (4) through the opening of the first steam valve (7-1), driving the steam turbine generator set (4-1) to maintain operation near the minimum load rate; S4. Flue gas treatment: Keep the first flue gas valve (9-1) and the second flue gas valve (9-2) in the open state to ensure that the flue gas generated by the two systems can be discharged into the chimney (5); The energy release mode operation specifically includes the following steps: S5. Fuel distribution switching: Adjust the fuel regulating valve group, specifically by opening the first gas valve (6-1) to almost full opening and closing the second gas valve (6-2) to allow most of the gas to enter the gas boiler unit (2) for combustion, and only supply the molten salt heating furnace (3-1) with the minimum amount of gas required to keep its burner from going out. S6. Heat release and steam generation: Start the high-temperature molten salt circulation pump (3-2-3) to pump the high-temperature molten salt stored in the high-temperature storage tank (3-2-1) into the molten salt heat exchanger unit (3-3); S7. Parallel connection of steam and water system and high-load power generation: Adjust the valves of the steam and water pipeline, open the second feedwater valve (8-2) and the second steam valve (7-2), and at the same time adjust the opening of the first feedwater valve (8-1); so that the feedwater enters the gas boiler unit (2) and the molten salt heat exchanger unit (3-3) respectively to generate steam. The steam generated by the two paths is combined by opening the first steam valve (7-1) and the second steam valve (7-2), and then introduced into the steam turbine generator unit (4) to drive the steam turbine generator set (4-1) to full load or near full load operation; S8. Flue gas treatment adjustment: Keep the first flue gas valve (9-1) fully open and adjust the opening of the second flue gas valve (9-2) to ensure that all flue gas is collected and discharged into the chimney (5).

Images