Boiler peak shaving system and method based on thermochemical heat storage

Abstract

According to the boiler peak regulation system and method based on the thermochemical heat storage technology, the service life of the heat storage module and the use efficiency of energy in the system can be both considered. The boiler peak shaving system comprises a boiler, a heat storage device and a heat exchange pipeline, the heat exchange pipeline is arranged in a hearth of the boiler, an outlet of the heat exchange pipeline communicates with the heat storage device, a thermochemical heat storage module is arranged in the heat storage device, the boiler peak shaving system further comprises a reheater arranged at the top of the hearth of the boiler, and an outlet of the reheater communicates with a steam turbine; a hot side inlet of the reheating heat exchanger is communicated with the heat storage device, and a hot side outlet of the reheating heat exchanger is communicated with a flue of the boiler; and the reheater branch pipeline is arranged on the cold side of the reheating heat exchanger, one end of the reheater branch pipeline communicates with an outlet of the reheater, and the other end of the reheater branch pipeline communicates with an inlet of the steam turbine. The boiler peak shaving method comprises a heat storage step and a heat release step.

Description

Technical Field

[0001] The present invention relates to the technical field of boiler peak regulation, and in particular to a boiler peak regulation system and a boiler peak regulation method based on thermochemical heat storage. Background Art

[0002] In recent years, the total installed capacity of renewable energy such as wind power and photovoltaic power has continued to grow. However, the problem of mutual impact between renewable energy and thermal power has also been exposed. With the large-scale development of renewable energy, low-load operation and deep peak regulation of thermal power units have gradually become the norm. Long-term low-load operation will seriously affect the stability of boiler operation and the safety of equipment such as steam turbines and auxiliary machines. Combining traditional thermal power units with new energy storage technologies and using the principle of high generation and low storage can greatly improve the flexible adjustment capacity of conventional thermal power units without affecting the safe and stable operation of the units, increase the space for absorbing renewable energy, and is an effective way to resolve the contradiction between the development of thermal power and renewable energy.

[0003] At present, boiler heat storage and peak regulation mainly include electric boiler solid heat storage technology, water storage energy storage technology, molten salt energy storage technology, etc., which mostly use sensible heat and latent heat materials as energy storage media, have low energy storage density, and the peak regulation system occupies a large area. In addition, the heat release temperature is low, the energy grade is low, and it is difficult to use.

[0004] At present, there are also some boiler peak-shaving systems based on thermochemical heat storage, but there is still much room for improvement. For example, in patent CN114623431A, the thermochemical heat storage device is heated by electric heating, so that the excess power generated by the boiler is stored and then released when needed. However, this method has the disadvantages of multiple energy conversions, low efficiency, and reduced energy quality. Some boiler peak-shaving systems directly introduce the high-temperature heat energy released by the heat storage system into the furnace. Due to the large difference between the furnace temperature (usually 1100-1300°C) and the outlet temperature of the heat storage system (usually 600-800°C), it is easy to disrupt the boiler furnace flow field and temperature field, threatening the safe and stable operation of the boiler. Summary of the invention

[0005] In view of the above problems, the present invention provides a boiler peak-shaving system and a boiler peak-shaving method based on thermochemical heat storage technology, which can take into account the service life of thermochemical heat storage materials and the energy utilization efficiency in the system.

[0006] A first aspect of the present invention provides a boiler peak-shaving system, comprising a boiler, a heat storage device, and a heat exchange pipe, wherein the heat exchange pipe is arranged in the furnace of the boiler, and the outlet of the heat exchange pipe is connected to the heat storage device, and the heat storage device has a built-in thermochemical heat storage module, and also includes: a reheater, arranged at the top of the furnace of the boiler, and the outlet of the reheater is connected to the steam turbine; a reheat heat exchanger, the hot side inlet of the reheat heat exchanger is connected to the heat storage device, and the hot side outlet is connected to the tail flue of the boiler; a reheater branch pipe, the reheater branch pipe is arranged on the cold side of the reheat heat exchanger, one end of which is connected to the outlet of the reheater, and the other end is connected to the inlet of the steam turbine.

[0007] According to the technical solution, firstly, when the grid dispatch requires the thermal power plant to reduce the load, that is, when the electric energy generated by the power generation cycle is greater than the electric energy required by the grid, the heat storage device can be used to store the excess heat energy from the boiler combustion to reduce the online power, thereby ensuring the low-load stable combustion of the boiler and avoiding the load reduction affecting the service life of the boiler; when the grid dispatch is restored or increased, the thermal power plant can also reduce or shut down the heat storage air flow through the heat storage device to increase the power load output to the grid by the power generation cycle, thereby achieving deep peak regulation of the thermal power plant.

[0008] Secondly, because air rather than flue gas is used to participate in the reaction of the thermochemical heat storage module, the service life of the heat storage module can be guaranteed, and the more complex components in the flue gas, such as dust, sulfur oxides, nitrogen oxides and other acidic or toxic pollutants, can be avoided to affect the life and heat storage effect of the thermochemical heat storage material.

[0009] Finally, the hot air at the outlet of the heat storage device heats the steam at the outlet of the reheater, which can further increase the temperature of the reheated steam and improve the relative internal efficiency and absolute internal efficiency of the steam turbine. And because the outlet temperature of the reheater is generally 550℃, which is close to the outlet temperature of the heat storage device, the heat loss of the two fluids during heat exchange is small and the energy utilization rate is high.

[0010] As a preferred technical solution, the thermochemical heat storage module is a metal oxide heat storage module, and the heat storage device has a first heat storage device inlet connected to the external environment, a second heat storage device inlet connected to the outlet of the heat exchange pipe, a first heat storage device outlet connected to the furnace of the boiler, and a second heat storage device outlet connected to the hot side inlet of the reheat heat exchanger.

[0011] According to the technical solution, the oxygen and hot air generated in the heat storage / release reaction of the metal oxide are utilized in a targeted manner. The oxygen released in the heat storage process of the metal oxide is mixed with air to form high-temperature oxygen-rich air. The high-temperature oxygen-rich air can heat the primary air passing through the regenerator in the opposite direction, and then pass into the middle and upper part of the boiler furnace through the oxygen supply pipe to supplement the oxygen in the boiler furnace, thereby enabling the fuel in the boiler to burn stably in an oxygen-rich state.

[0012] As a preferred technical solution, the boiler peak load regulation system based on thermochemical heat storage also includes:

[0013] The regenerator has a hot fluid inlet, a hot fluid outlet, a cold fluid inlet and a cold fluid outlet, the cold fluid inlet is connected to the external environment, the cold fluid outlet is connected to the inlet of the heat exchange pipe, the hot fluid inlet is connected to the first heat storage device outlet of the heat storage device, and the hot fluid outlet is connected to the middle and upper part of the furnace of the boiler.

[0014] According to this technical solution, the residual heat of the high-temperature oxygen generated in the heat storage device can be further utilized through the regenerator to preheat the cold air before entering the heat exchange pipe, thereby achieving full utilization of the energy of the heat storage device.

[0015] As a preferred technical solution, the boiler peak-shaving system based on thermochemical heat storage also includes a fan, which is arranged corresponding to the air inlet, and the air inlet is respectively connected to the first heat storage device inlet of the heat storage device and the cold fluid inlet of the regenerator, and the fan blows air into the regenerator and the heat storage device through the air inlet.

[0016] According to this technical solution, on the one hand, a large amount of air can be quickly blown into the boiler peak-shaving system through the fan, which is beneficial to the thermochemical reaction. On the other hand, the introduction of air through an air inlet can also make the system structure more compact.

[0017] As a preferred technical solution, a first valve is provided between the cold fluid inlet and the air inlet.

[0018] According to the technical solution, when it is necessary to use the heat storage device to store excess heat of the boiler, the first valve is opened, and air enters the regenerator from the air inlet for preheating, and then flows into the heat exchange pipe in the boiler furnace to absorb the combustion heat in the furnace. The high-temperature air enters the heat storage device from the second heat storage device inlet of the heat storage device, contacts and exchanges heat with the thermochemical heat storage module, and the thermochemical heat storage module absorbs heat and converts the thermal energy into chemical energy for storage, thereby realizing heat storage peak regulation of the boiler.

[0019] As a preferred technical solution, a second valve is provided between the inlet of the first heat storage device and the air inlet.

[0020] According to this technical solution, when the heat storage device needs to release the stored heat, the second valve is opened, and air enters the heat storage device through the second valve. The thermochemical heat storage module in the heat storage device contacts the air to undergo a reduction reaction, while releasing heat.

[0021] As a preferred technical solution, a third valve is provided between the outlet of the reheater and the reheat heat exchanger.

[0022] According to the technical solution, when it is necessary to utilize the heat released by the heat storage device to quickly increase the power generation capacity of the boiler, the second valve and the third valve are opened at the same time, and the heat released in the heat storage device enters the hot side of the reheat heat exchanger to heat the reheat steam on the cold side of the reheat heat exchanger. The heated steam is mixed with the steam flowing out of the reheater and then passed into the steam turbine to participate in power generation, thereby realizing the utilization of the heat released by the heat storage device and quickly shaving the peak.

[0023] As a preferred technical solution, the hot side outlet of the reheat heat exchanger is connected to the horizontal flue of the boiler, and the connecting port between the reheat heat exchanger and the boiler is upstream of the economizer and the air preheater.

[0024] According to the technical solution, the low-temperature air after heat exchange merges with the flue gas at the tail end of the horizontal flue, heats the economizer and the air preheater in turn, and can fully utilize the heat energy released by the metal oxides in the heat storage device.

[0025] The second aspect of the present invention provides a boiler peak-shaving method based on thermochemical heat storage, which is applicable to the aforementioned boiler peak-shaving system based on thermochemical heat storage, and comprises the following steps:

[0026] Heat storage step: when the load demand of the external power grid drops below a first specified value, the first valve is opened, and the second valve and the third valve are closed; heat release step: when the load demand of the external power grid rises above a second specified value, the second valve and the third valve are opened, and the first valve is closed. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the composition of a boiler deep peak regulation system based on thermochemical heat storage in an embodiment of the present invention;

[0028] Figure 2 It is a flow chart of a boiler peak-shaving method based on thermochemical heat storage in an embodiment of the present invention.

[0029] Figure numerals: 1-boiler; 2-heat storage device; 3-regenerator; 4-reheater; 5-reheat heat exchanger; 6-heat exchange pipe; 7-air inlet; 8-first valve; 9-second valve; 10-third valve; 11-oxygen supply pipe; 12-waste heat air pipe; 201-first heat storage device inlet; 202-second heat storage device inlet; 203-second heat storage device outlet; 204-first heat storage device outlet; 301-hot fluid inlet; 302-hot fluid outlet; 303-cold fluid inlet; 304-cold fluid outlet; 401-reheater branch pipe; 402-reheater main pipe. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] First embodiment

[0032] In a first embodiment of the present invention, a boiler peak load regulation system based on thermochemical heat storage is provided. Figure 1 Schematic diagram of the composition of the boiler deep peak regulation system based on thermochemical heat storage in this embodiment. Figure 1 As shown, the peak shaving system may include: a boiler 1, a heat storage device 2, a regenerator 3, a reheater 4, a reheat heat exchanger 5, a heat exchange pipe 6, and an air inlet 7.

[0033] The heat storage device 2 has a first heat storage device inlet 201, a second heat storage device inlet 202, a second heat storage device outlet 203 and a first heat storage device outlet 204. The first heat storage device inlet 201 is connected to the air inlet 7 via the second valve 9, so that when the heat storage device 2 is exothermic, air can be introduced into the heat storage device 2. The second heat storage device inlet 202 is connected to the outlet of the heat exchange pipe 6, and the hot air heated by the regenerator 3 and the heat exchange pipe 6 in turn enters the heat storage device 2, transfers the heat to the metal oxide heat storage module in the heat storage device 2, and carries the oxygen generated by the reduction reaction, and transports it to the regenerator 3 via the second heat storage device outlet 203. The first heat storage device outlet 204 is connected to the reheat heat exchanger 5. When the heat storage device 2 releases heat, the heated air after heat release is passed into the reheat heat exchanger 5 to exchange heat with the reheat steam in the reheat branch pipe 401, thereby heating the reheat steam in the reheat branch pipe 401, thereby quickly increasing the power generation capacity of the steam turbine.

[0034] The regenerator 3 has a hot fluid inlet 301, a hot fluid outlet 302, a cold fluid inlet 303 and a cold fluid outlet 304, the cold fluid inlet 303 is connected to the air inlet 6 via the first valve 8, the cold fluid outlet 304 is connected to the inlet of the heat exchange pipe 6, the hot fluid inlet 301 is connected to the second heat storage device outlet 203 of the heat storage device 2, and the hot fluid outlet 302 is connected to the boiler 1 through the oxygen supply pipe 11, wherein the connection port of the oxygen supply pipe 11 and the boiler 1 is arranged in the middle and upper part of the furnace, so that the oxygen entering the boiler 1 through the oxygen supply pipe 11 can participate in the combustion in the furnace.

[0035] The reheater 4 has a reheater branch pipe 401 and a reheater trunk pipe 402. The reheater trunk pipe 402 is directly connected to the steam turbine (not shown). The reheater branch pipe 401 is connected to the reheat heat exchanger 5 through the third valve 10. When the heat storage device 2 releases heat, the heated air passes through the first heat storage device outlet 204 and enters the reheat heat exchanger 5 to heat the reheat steam in the reheater branch pipe 401. The heated low-temperature air passes through the waste heat air pipe 12 and mixes with the flue gas at the tail of the horizontal flue, and heats the economizer and air preheater downstream of the horizontal flue in turn, making full use of the heat energy released by the metal oxide in the heat storage device 2. After being heated, the reheat steam in the reheater branch pipe 401 is re-integrated into the reheater trunk pipe 402, and enters the steam turbine together to perform work, thereby realizing a rapid increase in the output power of the boiler 1.

[0036] The heat storage device 2 has a metal oxide heat storage module inside. The metal oxide can be a binary oxide or a multinary oxide, which is not limited here. The metal oxide can store heat energy through redox reactions, and a variety of metal oxide materials such as manganese-based and copper-based can be used. This embodiment provides an implementation plan based on a multinary oxide mixed with manganese and iron.

[0037] It should be noted that in this embodiment, an example is given of a case where a metal oxide heat storage module is built into the heat storage device 2, but the present invention is not limited to this. The use of other thermochemical heat storage materials, such as perovskite, carbonate, etc. as thermochemical heat storage materials, or the use of a thermochemical heat storage module mixed with multiple materials also falls within the scope of protection of the present invention.

[0038] When the metal oxide stores heat, the metal oxide with a higher valence undergoes a reduction reaction to generate metal oxide with a lower valence and oxygen. The oxygen-enriched air enters the regenerator 3 through the outlet 203 of the second heat storage device, heats the cold air passing through the regenerator 3 in the opposite direction, and then flows through the oxygen supply pipe 11 from the hot fluid outlet 302 of the regenerator 3 to the middle and upper part of the furnace of the boiler 1, replenishing the oxygen in the furnace of the boiler 1, allowing the fuel in the boiler 1 to burn stably in an oxygen-enriched state. When the metal oxide releases heat, air enters the first heat storage device inlet 201 of the heat storage device 2 through the second valve 9, and the metal oxide with a lower valence combines with the oxygen in the air to undergo an oxidation reaction to obtain a metal oxide with a higher valence. The released heat is absorbed by the air, and the heated air passes through the outlet 204 of the first heat storage device into the reheat heat exchanger 5, heating the reheat steam in the reheat branch pipe 401, and the reheat steam is merged into the reheat main pipe 402 and enters the steam turbine to generate electricity, while the low-temperature air after heat exchange passes through the waste heat air pipe 12 and mixes with the flue gas at the tail end of the horizontal flue, heating the economizer and the air preheater in turn, thereby making full use of the heat energy released by the metal oxide in the heat storage device 2.

[0039] For example, when the power grid dispatch requires the thermal power plant to reduce the power load output to the power grid, in order to ensure stable combustion at low load, the power generated in the power generation cycle of the thermal power plant is greater than the power required by the power grid, the first valve 8 is opened, and the fan introduces air into the system through the air inlet 7. The air first enters the cold side of the regenerator 3 for preheating, and then enters the heat exchange pipe 6 to absorb the combustion heat energy in the furnace of the boiler 1. The high-temperature air enters the heat storage device 2 through the second heat storage device inlet 202. The metal oxide in the metal oxide heat storage module receives the heat energy and first heats up. The metal oxide stores the heat energy in the form of sensible heat. When the metal oxide itself When the temperature reaches the reduction reaction temperature, the metal oxide stores heat energy in the form of chemical energy, that is, the metal oxide undergoes a reduction reaction to release oxygen, and the released oxygen mixes with air to form high-temperature oxygen-rich air. The high-temperature oxygen-rich air enters the hot side of the regenerator 3 through the outlet 203 of the second heat storage device, preheats the cold air passing through the regenerator 3 in the opposite direction, and then passes through the hot fluid outlet 302 of the regenerator 3 to the middle and upper part of the furnace of the boiler 1 to supplement the oxygen required for the combustion of the boiler 1, so that the fuel in the boiler 1 can be stably burned in an oxygen-rich state, thereby realizing the peak regulation of the boiler 1 and the stable combustion of the boiler 1 under low load conditions.

[0040] When the grid dispatch requires the thermal power plant to restore or increase the power load output to the grid, the thermal power plant can reduce or shut down the flow of the heat storage air process through the heat storage device 2 to increase the power load output to the grid by the power generation cycle. The heat stored in the heat storage device 2 can be further reused. Specifically, first, the first valve 8 is closed, and the second valve 9 and the third valve 10 are opened. The fan transports air from the air inlet 7 through the first heat storage device inlet 201 into the heat storage device 2. The metal oxide reacts with oxygen in the air to release heat, and the remaining oxygen-depleted air absorbs heat and is discharged from the first heat storage device outlet 204 of the heat storage device 2. The high-temperature air passes through the first heat storage device outlet 204 and enters the reheat heat exchanger 5 to heat the reheat steam in the reheater branch pipe 401. The reheat steam in the reheater branch pipe 402 absorbs heat and then flows into the reheater main pipe 402, and is passed into the steam turbine to generate electricity together. The heated low-temperature air passes through the waste heat air pipe 12 and mixes with the flue gas at the tail end of the horizontal flue, and heats the economizer and the air preheater in turn, so as to make full use of the heat energy released by the metal oxide in the heat storage device 2.

[0041] In this embodiment, when the grid dispatch requires the thermal power plant to reduce the load, that is, when the electric energy generated by the power generation cycle is greater than the electric energy required by the grid, the heat storage device 2 can be used to store the excess heat energy burned by the boiler 1 to reduce the online power, thereby ensuring the low-load stable combustion of the boiler 1 and avoiding the load reduction affecting the service life of the boiler 1; when the grid dispatch is restored or increased, the thermal power plant can also reduce or shut down the heat storage air flow through the heat storage device 2 to increase the power load output to the grid by the power generation cycle, and further, the heat released by the metal oxide module can be combined for power generation, thereby realizing rapid and deep peak regulation of the thermal power plant.

[0042] In addition, in the embodiment of the present invention, the oxygen and heat generated in the heat storage / release reaction of the metal oxide are used in a targeted manner. The oxygen released in the heat storage process of the metal oxide is mixed with air to form oxygen-enriched air. The oxygen-enriched air passes through the hot side of the regenerator 3, passes through the cold air of the regenerator 3 in the opposite direction, and is then sent to the boiler 1, so that the fuel in the boiler 1 can be stably burned in an oxygen-enriched state. The air temperature at the outlet of the heat storage device 2 when releasing heat is generally 600-800°C, and the reheat outlet temperature is generally 550°C, which is similar to the outlet temperature of the heat storage device. Therefore, the heat loss of the two fluids during heat exchange is small, and the energy utilization rate is high. The high-temperature air generated after the heat storage device 2 releases heat is passed into the reheat heat exchanger 5 through the outlet 204 of the first heat storage device, and the reheat steam in the reheat branch pipe 401 is heated, which can further increase the temperature of the reheat steam and improve the relative internal efficiency and absolute internal efficiency of the steam turbine. The low-temperature air after heat exchange merges with the flue gas at the tail end of the horizontal flue, heating the economizer and the air preheater in turn, which can fully utilize the heat energy released by the metal oxides in the heat storage device.

[0043] This embodiment also provides a boiler peak-shaving method applicable to the above boiler peak-shaving system. Figure 2 Flow chart of the boiler peak load regulation method based on thermochemical heat storage in the embodiment of the present invention. Figure 2 As shown in the figure, the boiler deep peak regulation method based on thermochemical heat storage includes:

[0044] Heat storage step S1, when the power load output by the thermal power plant to the external power grid drops below a first specified value, the heat storage air process is started, the first valve 8 is opened, the second valve 9 and the third valve 10 are closed, so that the air enters the boiler 1 through the oxygen supply pipe 11 after undergoing the heat storage air process.

[0045] Heat release step S2, when the power load output by the thermal power plant to the external power grid rises above the second specified value, the heat release air process is started, the first valve 8 is closed, the second valve 9 and the third valve 10 are opened, so that the air undergoes the heat release air process and enters the tail of the horizontal flue of the boiler 1 through the waste heat air duct 12.

[0046] The "first specified value" and the "second specified value" can be freely selected according to the actual application situation and are not limited here. Among them, the "second specified value" is greater than or equal to the "first specified value". For example, the "first specified value" can be the minimum load for the stable operation of the thermal power plant under normal circumstances. When the total power load of the thermal power plant is lower than the minimum load, the total power load of the thermal power plant is no longer reduced, but the heat storage air process is started, the first valve 8 is opened, the second valve 9 and the third valve 10 are closed, and the heat storage of the metal oxide reduction reaction in the heat storage device 2 is used to continue to reduce the power load output from the thermal power plant to the external power grid. The "second specified value" can be a load value higher than the minimum load. When the power load of the thermal power plant is equal to or higher than the minimum load, the heat storage air process is closed, the heat release air process is started, the first valve 8 is closed, the second valve 9 and the third valve 10 are opened, and the metal oxide releases heat. After the heat release air process, it enters the tail of the horizontal flue of the boiler 1 through the waste heat air duct 12 to supplement the external output power of the power plant.

[0047] In this embodiment, when the power load required to be output by the generator to the external power grid is reduced to below the first specified value, the boiler deep peak regulation system executes the heat storage step S1, at which time the heat storage air process is started, the first valve 8 is opened, the second valve 9 and the third valve 10 are closed, and part of the air is transported into the heat storage air process. The heat storage air process includes: part of the air is heated for the first time through the regenerator 3, and then heated for the second time through the heat exchange pipe 6 in the boiler 1, and then passes through the heat storage device 2, the metal oxide in the heat storage device 2 undergoes a reduction reaction, absorbing heat while releasing oxygen, and the air flowing in is cooled and enriched with oxygen when it flows out. At this time, the oxygen-enriched air heats the cold air entering from the cold fluid inlet 303 through the regenerator 3, and its own temperature is reduced, and then enters the middle and upper part of the boiler 1 to supplement the oxygen in the furnace of the boiler 1, supporting the combustion of the boiler 1 under oxygen-enriched conditions. When the power grid dispatch requires the thermal power plant to resume or increase the load, the total power load of the thermal power plant continues to rise. When it rises to the second specified value, the heat release step S2 is executed, the first valve 8 is closed, the second valve 9 and the third valve 10 are opened, and the air or primary air is transported into the heat release air process. The heat release air process includes: air enters the heat storage device 2 through the conveying equipment, the metal oxide in the heat storage device 2 undergoes an oxidation reaction, and releases a large amount of heat. After the input air is heated, the high-temperature air passes through the outlet 204 of the first heat storage device and enters the reheat heat exchanger 5 to heat the reheat steam in the reheater branch pipe 401. After that, the air temperature is reduced and merges with the flue gas at the tail of the horizontal flue. Among them, according to the actual situation, the air is controlled by the second valve 9.

[0048] In the above manner, because the heat exchange pipe 6 is used to indirectly heat the air in the embodiment of the present invention, air is used instead of flue gas to contact and react with the metal oxide, which can ensure the service life of the metal oxide heat storage module and avoid the presence of more complex components in the flue gas, such as dust, sulfur oxides, nitrogen oxides and other acidic or toxic pollutants affecting the life of the heat storage material and the heat storage effect. In addition, the regenerator 3 can recover part of the heat that is not stored, so that the thermal efficiency of the oxygen recovery process is improved, and oxygen-enriched air with a high oxygen concentration is obtained, which helps the stable combustion of the boiler 1. When the heat storage device 2 releases heat, the air temperature at the outlet is generally 600-800°C, and the reheater outlet temperature is generally 550°C. The hot air at the outlet of the heat storage device 2 is used to heat the reheater outlet steam, which can further increase the temperature of the reheated steam and improve the relative internal efficiency and absolute internal efficiency of the steam turbine. The temperatures of the two fluids are similar, the heat loss is small, and the energy utilization rate is high. The low-temperature air after heat exchange merges with the flue gas at the tail end of the horizontal flue of the boiler 1, and heats the economizer (not shown in the figure) and the air preheater (not shown in the figure) in turn, so as to fully utilize the heat energy released by the metal oxide in the heat storage device 2.

[0049] Second embodiment

[0050] In the second embodiment of the present invention, a boiler peak-shaving system and a boiler peak-shaving method are provided, in which a heat storage unit using manganese-based metal oxide as a thermochemical heat storage material is used as a heat storage medium. The boiler peak-shaving system in this embodiment has a structure that is basically the same as that in the first embodiment, and will not be repeated here.

[0051] In this embodiment, the heat storage medium in the heat storage device 2 is a heat storage unit made of manganese-based metal oxide. The heat storage unit can be a cubic honeycomb structure with square through holes, and the size is preferably 100mm*100mm*100mm. When the heat storage unit made of manganese-based metal oxide is used as the heat storage medium, the rapid peak regulation method of the boiler system mainly includes:

[0052] When the grid dispatch requires the thermal power plant to reduce the power load output to the grid, in order to ensure stable combustion at low load, the power generated in the power generation cycle of the thermal power plant is greater than the power required by the grid, the first valve 8 is opened, and the fan introduces air into the system through the air inlet 7. The air first enters the cold side of the regenerator 3 for preheating, and the temperature of the preheated air rises to a first temperature, and then enters the heat exchange pipe 6 to absorb the combustion heat energy in the furnace of the boiler 1. The air at the first temperature is reheated to a second temperature by the furnace, and the high-temperature air at the second temperature enters the heat storage device 2 from the second heat storage device inlet 202. The heat storage unit prepared by manganese-based metal oxide contacts with the high-temperature air, and the heat storage unit heats up. The heat energy is first stored in the form of sensible heat. When the heat storage unit itself When the temperature reaches about 950°C, the heat storage unit stores heat energy in the form of chemical energy, that is, the manganese-based metal oxide undergoes a reduction reaction to release oxygen, and the released oxygen mixes with air to form high-temperature oxygen-enriched air. The temperature of the oxygen-enriched air is a third temperature slightly lower than the second temperature. The oxygen-enriched air enters the hot side of the regenerator 3 through the outlet 203 of the second heat storage device, and preheats the cold air passing through the regenerator 3 in the opposite direction. At the same time, the oxygen-enriched air is cooled to the fourth temperature, and then introduced into the middle and upper part of the furnace of the boiler 1 through the hot fluid outlet 302 of the regenerator 3 to supplement the oxygen required for the combustion of the boiler 1, so that the fuel in the boiler 1 can be stably burned in an oxygen-enriched state, thereby realizing the peak regulation of the boiler 1 and the stable combustion of the boiler 1 under low load conditions.

[0053] When the power grid dispatch requires the thermal power plant to restore or increase the power load output to the power grid, the thermal power plant can reduce or close the flow of the heat storage air process through the heat storage device 2 to increase the power load output to the power grid by the power generation cycle. Furthermore, when it is necessary to quickly restore or increase the power load output to the power grid, the heat stored in the heat storage device 2 can be reused. The specific process is: close the first valve 8, open the second valve 9 and the third valve 10, the fan transports the air from the air inlet 7 through the first heat storage device inlet 201 into the heat storage device 2, the heat storage unit contacts the low-temperature air, the manganese-based metal oxide reacts with the oxygen in the air to release heat, and the remaining oxygen-depleted air absorbs heat and the temperature rises to the fifth temperature, and the high-temperature oxygen-depleted air is discharged from the first heat storage device outlet 204 of the heat storage device 2, and the outlet air temperature (i.e., the fifth temperature) ranges from about 750°C to 820°C, and its temperature can be adjusted by controlling the air flow entering the system through the opening of the first valve 8. The high-temperature air at the fifth temperature passes through the outlet 204 of the first heat storage device and enters the reheat heat exchanger 5, heats the reheat steam in the reheat branch pipe 401, and reduces the temperature to the sixth temperature. Then the reheat steam in the reheat branch pipe 402 absorbs heat and flows into the reheat main pipe 402, and passes into the steam turbine to generate electricity together. After the heat exchange, the air at the sixth temperature passes through the waste heat air pipe 12 and mixes with the flue gas at the tail end of the horizontal flue, heats the economizer and the air preheater in turn, and makes full use of the heat energy released by the metal oxide in the heat storage device 2.

[0054] Among them, preferably, the first temperature is in the range of 650℃~700℃, the second temperature is in the range of 1000℃~1050℃, the third temperature is in the range of 800℃~850℃, the fourth temperature is in the range of 400℃~450℃, the fifth temperature is in the range of 750℃~820℃, and the sixth temperature is in the range of 450℃~500℃.

[0055] In this embodiment, a heat storage unit prepared from manganese-based metal oxide is used, and the heat storage unit has the advantages of high energy storage density, high heat storage temperature, good gas-solid heat exchange performance, and stable heat storage and release temperature. In addition, when the heat storage unit is used as the energy storage medium in the heat storage device 2, the heat storage temperature of the heat storage device is about 950°C, and the heat release temperature is about 850°C. When the heat storage device 2 releases heat, the outlet air temperature of the first heat storage device outlet 204 is about 750°C to 820°C, which has a higher outlet temperature and can increase the temperature of the reheated steam, thereby more quickly improving the power generation efficiency of the steam turbine and realizing rapid peak regulation of the thermal power plant.

[0056] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A boiler peak load regulation system based on thermochemical heat storage, comprising a boiler, a heat storage device, and a heat exchange pipe, wherein the heat exchange pipe is arranged in the furnace of the boiler, and the outlet of the heat exchange pipe is connected to the heat storage device, and the heat storage device is equipped with a thermochemical heat storage module, characterized in that: Also includes: A reheater is arranged at the top of the furnace of the boiler, and the outlet of the reheater is connected to the steam turbine; a reheat heat exchanger, wherein a hot side inlet of the reheat heat exchanger is connected to the heat storage device, and a hot side outlet of the reheat heat exchanger is connected to the flue of the boiler; A reheater branch pipe is arranged on the cold side of the reheat heat exchanger, one end of the reheater branch pipe is connected to the outlet of the reheater, and the other end is connected to the inlet of the steam turbine.

2. The boiler peak load regulation system based on thermochemical heat storage according to claim 1 is characterized in that: The thermochemical heat storage module is a metal oxide heat storage module. The heat storage device has a first heat storage device inlet connected to the external environment, a second heat storage device inlet connected to the outlet of the heat exchange pipe, a first heat storage device outlet connected to the furnace of the boiler, and a second heat storage device outlet connected to the hot side inlet of the reheat heat exchanger.

3. The boiler peak load regulation system based on thermochemical heat storage according to claim 2 is characterized in that: Also includes, The regenerator has a hot fluid inlet, a hot fluid outlet, a cold fluid inlet and a cold fluid outlet, wherein the cold fluid inlet is connected to the external environment, the cold fluid outlet is connected to the inlet of the heat exchange pipe, the hot fluid inlet is connected to the first heat storage device outlet of the heat storage device, and the hot fluid outlet is connected to the middle and upper part of the furnace of the boiler.

4. The boiler peak load regulation system based on thermochemical heat storage according to claim 3 is characterized in that: Also includes, A fan is arranged corresponding to an air inlet, the air inlet is connected to the first heat storage device inlet of the heat storage device and the cold fluid inlet of the heat regenerator respectively, and the fan blows air into the heat regenerator and the heat storage device through the air inlet.

5. The boiler peak load regulation system based on thermochemical heat storage according to claim 4 is characterized in that: A first valve is disposed between the cold fluid inlet and the air inlet.

6. The boiler peak load regulation system based on thermochemical heat storage according to claim 5 is characterized in that: A second valve is provided between the first heat storage device inlet and the air inlet.

7. The boiler peak load regulation system based on thermochemical heat storage according to claim 6 is characterized in that: A third valve is provided between the outlet of the reheater and the reheat heat exchanger.

8. The boiler peak load regulation system based on thermochemical heat storage according to claim 1 is characterized in that: The hot side outlet of the reheat heat exchanger is connected to the horizontal flue of the boiler, and the connecting port between the reheat heat exchanger and the boiler is upstream of the economizer and the air preheater.

9. A boiler peak load regulation method based on thermochemical heat storage, applicable to the boiler peak load regulation system based on thermochemical heat storage according to claim 7, characterized in that: The following steps are involved: Heat storage step: when the load demand of the external power grid decreases below a first specified value, opening the first valve, and closing the second valve and the third valve; Heat release step: when the load demand of the external power grid rises above a second specified value, the second valve and the third valve are opened, and the first valve is closed.

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