Boiler flue gas heat storage system

Abstract

The invention provides a boiler flue gas heat storage system, which comprises a boiler and a denitration device communicated with an air outlet of the boiler, and particularly, the filtered flue gas heat storage system further comprises a heat storage flue, a filter flue, a heat exchange device, a heat exchange pipeline, a heat exchange pipeline, a heat exchange pipeline, a heat exchange pipeline and a heat exchange pipeline, the inlet end of the heat storage flue is communicated with a furnace arch of the boiler, and the outlet end of the heat storage flue is communicated with the denitration device; the heat storage device is arranged in the heat storage flue and is provided with a flue gas inlet and a flue gas outlet; and the control device is used for controlling opening and closing of the inlet end of the heat storage flue. Due to the fact that the working pressure of the denitration device is lower than the internal pressure of the furnace arch of the boiler, the pressure difference of the two ends of the heat storage flue can drive flue gas to spontaneously flow to the outlet end from the inlet end of the heat storage flue, and the amount of the flue gas entering the heat storage flue can be conveniently controlled through the control device. Flue gas entering the heat storage flue is in contact with the heat storage device for heat exchange, and therefore peak regulation heat storage and flexible dispatching of the thermal power generating unit are achieved. An external heat storage system is not needed, a tail gas treatment device can be shared with a thermal power generating unit, and the improvement cost is low.

Description

Technical Field

[0001] The invention relates to the technical field of thermal power generation, and in particular to a boiler flue gas heat storage system. Background Art

[0002] In the existing technology, the total installed capacity of renewable energy such as wind power and photovoltaic power has continued to grow in recent years. However, the problem of mutual impact between renewable energy and thermal power energy 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. However, under low-load operation, the stable operation of boilers and the safe operation of equipment such as steam turbines and auxiliary machines will be affected. Therefore, by coupling coal-fired power generation and heat storage technology, a certain degree of "thermal and electric decoupling" can be achieved without affecting the heat supply. By using the principle of low storage and high generation, the time and space transfer of electric energy can be realized, and the flexible adjustment capacity of conventional thermal power units can be greatly improved, thereby increasing the absorption space of renewable energy. It is an effective way to resolve the contradiction between the development of thermal power and renewable energy.

[0003] At present, the main boiler heat storage peak regulation technologies include electric boiler solid heat storage technology, water storage technology, molten salt storage technology, etc., which generally use high-temperature flue gas from the boiler, high-temperature steam from the turbine, or excess power from the generator for heating and energy storage. Among them, the method of drawing high-temperature flue gas from the boiler has fewer energy conversion stages and higher heat storage efficiency.

[0004] However, the existing peak-shaving heat storage systems often use exhaust fans to directly extract flue gas from the boiler. The flue gas temperature suitable for thermochemical heat storage is generally 600℃ or above. The high-temperature resistant fan technology in industry is difficult and costly, and it is difficult to directly extract flue gas to heat the heat storage material. In actual solutions, there are also ways to use the cooling effect of heat storage equipment and install induced draft fans at its flue gas outlet, but this takes up space and consumes energy, and the operation and adjustment process affects the internal flame field of the boiler and even threatens the safety of the hydrodynamic cycle. Summary of the invention

[0005] In view of the above problems, the present invention provides a boiler flue gas heat storage system, which does not need to use a fan to extract the flue gas, and has a simple device and low modification cost.

[0006] The present invention provides a boiler flue gas heat storage system, comprising a boiler and a denitrification device connected to the air outlet of the boiler. In particular, the filtered flue gas heat storage system also includes: a heat storage flue, the inlet end of the heat storage flue is connected to the flame deflection angle of the boiler, and the outlet end is connected to the denitrification device; a heat storage device, which is arranged in the heat storage flue and has a flue gas inlet and a flue gas outlet; and a control device for controlling the opening and closing of the inlet end of the heat storage flue.

[0007] According to this technical solution, since the working pressure of the denitrification device is lower than the internal pressure at the flame deflection angle of the boiler, the pressure difference at both ends of the heat storage flue will drive the flue gas to flow spontaneously from the inlet end of the heat storage flue to the outlet end. The amount of flue gas entering the heat storage flue can be conveniently controlled by the control device, and the flue gas entering the heat storage flue contacts with the heat storage device for heat exchange, thereby realizing peak load heat storage and flexible scheduling of thermal power units.

[0008] There is no need to set up an external heat storage system. The heat storage flue can be directly used to connect the flame deflection angle of the boiler of the thermal power unit and the denitrification device. The device is simple and can also share the exhaust gas treatment device with the thermal power unit, with low transformation cost.

[0009] As a preferred technical solution of the present invention, the working pressure of the boiler's denitration device is lower than -800Pa.

[0010] According to this technical solution, generally speaking, the pressure at the boiler flame deflection angle is -100Pa, so that a pressure difference sufficient to drive the flue gas to flow freely can be formed at both ends of the heat storage flue.

[0011] As a preferred technical solution of the present invention, a smoke damper is provided at the inlet end of the heat storage flue, and the control device controls the opening of the smoke damper.

[0012] According to the technical solution, the smoke baffle has a simple structure and is easy to clean, and the opening of the heat storage flue inlet can be controlled by rotating the smoke baffle to achieve deep peak regulation of the thermal power unit.

[0013] As a preferred technical solution of the present invention, the flue gas damper is equipped with a soot blowing device.

[0014] According to the technical solution, by regularly blowing the surface of the flue gas, it is possible to prevent particles in the flue gas from accumulating on the flue gas damper, thereby preventing the flue gas from flowing into the auxiliary flue and even affecting the opening and closing of the flue gas damper.

[0015] As a preferred technical solution of the present invention, the boiler flue gas heat storage system also includes: a dust removal device, which is arranged in the heat storage flue on the upstream side of the heat storage device.

[0016] According to this technical solution, the dust removal device arranged upstream of the heat storage device can remove dust and particulate matter in the flue gas to prevent them from adhering to the heat storage device and affecting the heat storage performance of the heat storage device.

[0017] As a preferred technical solution of the present invention, the operating temperature of the dust removal device is not lower than 1300°C.

[0018] According to this technical solution, since the dust removal device is upstream of the heat storage device, the dust removal device needs to receive high-temperature flue gas. On the one hand, the higher operating temperature can improve the working safety of the dust removal device when receiving high-temperature flue gas. On the other hand, it can also reduce or avoid heat exchange between the dust removal device and the high-temperature flue gas, thereby affecting the heat storage efficiency of the heat storage device.

[0019] As a preferred technical solution of the present invention, the surfaces of the dust removal device and the heat storage device are covered with thermal insulation material.

[0020] According to this technical solution, the heat storage efficiency of the boiler flue gas heat storage system can be further improved by laying thermal insulation materials, thereby avoiding heat loss.

[0021] As a preferred technical solution of the present invention, the heat storage device includes: a heat storage shell, which is provided with a smoke inlet and a smoke outlet; a thermochemical heat storage module, which is built into the heat storage shell; and a support frame, which is staggeredly arranged in the heat storage shell to separate the thermochemical heat storage modules.

[0022] According to the technical solution, the thermochemical heat storage module is a solid heat storage module that stores / releases heat through thermochemical reactions and has a high heat storage density. However, thermal expansion may occur during the heat storage / release process. Therefore, the thermochemical heat storage modules can be separated by a supporting frame to avoid extrusion and crushing between the thermochemical heat storage modules. The flue gas can enter the heat storage shell through the flue gas inlet of the heat storage shell, and directly contact and exchange heat with the thermochemical heat storage module in the heat storage shell. The thermochemical heat storage module absorbs heat to undergo a reduction reaction and stores the heat in the form of chemical energy.

[0023] As a preferred technical solution of the present invention, the thermochemical heat storage module at least includes a metal oxide heat storage material.

[0024] As a preferred technical solution of the present invention, the heat storage device further includes: an air duct connecting the heat storage shell and the external air, and the air duct passes through the reheater and / or superheater of the boiler in sequence.

[0025] According to the technical solution, the metal oxide heat storage material absorbs heat during the heat storage process, undergoes a reduction reaction, and produces oxygen; during the heat release process, it undergoes an oxidation reaction with oxygen to release heat. Air can be introduced into the heat storage device via an air duct, so that the metal oxide heat storage material can react with the oxygen in the air. The released heat then flows through the reheater and superheater via the air duct, thereby realizing the reuse of the heat stored in the heat storage device. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic diagram of the overall structure of a boiler flue gas heat storage system in an embodiment of the present invention;

[0027] Figure 2It is a schematic structural diagram of the connection between the heat storage flue and the boiler in an embodiment of the present invention;

[0028] Figure 3 Schematic diagram of the structure of the heat storage device in the embodiment of the present invention.

[0029] Explanation of the reference numerals: boiler 100; flame folding angle 101; furnace 102; air outlet 103; heat storage flue 1; flue gas damper 2; control device 3; dust removal device 4; heat storage device 5; denitrification device 6; rotating motor 7; transmission structure 8; insulation material 9; thermochemical heat storage module 10; heat storage shell 11; support frame 12; compartment 13; air duct 14; air fan 15; air valve 16; flue gas valve 17; reheater 18; superheater 19. 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] Figure 1 Schematic diagram of the structure of the boiler flue gas heat storage system in the embodiment of the present invention. Figure 1 As shown, a boiler flue gas heat storage system is provided in this embodiment, including a boiler 100 and a denitrification device 6 connected to an air outlet 103 of the boiler 100. A large amount of high-temperature flue gas generated by combustion in the furnace 102 of the boiler 100 rises from the bottom of the furnace 102 to the top of the furnace 102, and is converted into horizontal flow at the flame deflection angle 101 to exchange heat with the circulating medium. The flue gas after heat exchange flows into the denitrification device 6 from the air outlet 103 of the boiler 100 for denitrification treatment, and finally the treated exhaust gas is discharged.

[0032] In particular, the boiler flue gas heat storage system in this embodiment also includes a heat storage flue 1 connecting the flame deflection angle 101 of the boiler 100 and the denitrification device 6, and a heat storage device 5 and a control device 3 for controlling the opening and closing of the inlet end of the heat storage flue 1 are arranged in the heat storage flue 1.

[0033] Specifically, the inlet end of the heat storage flue 1 is connected to the flame bending angle 101 , which refers to a triangular protrusion formed by the lower water-cooled wall at the outlet of the furnace 102 of the boiler 100 bending into the furnace 102 . Preferably, the heat storage flue 1 is directly connected to the furnace 102 of the boiler 100 by removing part of the water-cooled wall at the flame deflection angle 101, so that the high-temperature flue gas in the furnace 102 can be directly drawn out, and the outlet end is connected to the inlet end of the denitrification device 6. Since the working environment of the denitrification device 6 is negative pressure, the pressure at the inlet end of the denitrification device 6 is much lower than the pressure at the flame deflection angle 101 of the furnace 102 of the boiler 100. Driven by the pressure difference, the flue gas in the furnace 102 of the boiler 100 spontaneously flows into the heat storage flue 1 without the need for a separate exhaust device. The high-temperature flue gas entering the heat storage flue 1 contacts the heat storage device 5 in the heat storage flue 1, and the heat storage device 5 absorbs heat to store heat. The flue gas after heat exchange continues to flow to the outlet end of the heat storage flue 1 under the action of the pressure difference, and is discharged after being treated by the denitrification device 6.

[0034] Among them, preferably, Figure 2 Schematic diagram of the structure of the connection between the heat storage flue and the boiler provided in this embodiment. Figure 1 and Figure 2 From the perspective of the heat storage flue 1, the inlet end is connected to the upper slope of the flame bending angle 101 of the boiler 100. Due to the turbulence effect of the flame bending angle 101, the flue gas in the horizontal flue at the top of the furnace 102 flows approximately horizontally. The inlet end of the heat storage flue 1 is located at the upper slope of the flame bending angle 101, which is conducive to the flue gas flowing into the heat storage flue 1 under the action of pressure difference, and can avoid affecting the original turbulence effect of the flame bending angle 101; and the inlet of the heat storage flue 1 is set on the upper slope of the flame bending angle 101. It can also ensure that the temperature of the flue gas leading out of the heat storage is improved while the heat storage efficiency is improved, and it is far away from the combustion part of the furnace 102 of the boiler 100 to the greatest extent, and the operation and adjustment process of the heat storage flue 1 is avoided as much as possible. The influence of the internal flame field of the boiler 100 and even the threat to the safety of the hydrodynamic cycle is avoided. 。 Further preferably, the inventors have found that the pressure at the upper slope of the flame deflection angle 101 of the boiler 100 is about -100Pa, so the working pressure of the denitrification device 6 of the boiler 100 is set to be lower than -800Pa. In some preferred embodiments, the working pressure of the denitrification device 6 of the boiler 100 is -900Pa to -1100Pa, so that a pressure difference sufficient to drive the self-flow of flue gas can be formed at both ends of the heat storage flue 1 without placing excessive burden on the pressure-bearing structure of the equipment.

[0035] The control device 3 is used to control the opening and closing of the inlet end of the heat storage flue 1, and control the amount of flue gas entering the heat storage flue 1, so as to achieve deep peak regulation and flexible scheduling of the thermal power unit. The specific opening and closing structure is not limited here, for example, it can be a valve, a baffle, etc. Preferably, a flue gas baffle 2 is provided at the inlet end of the heat storage flue 1, and one side of the flue gas baffle 2 is rotatably hinged to the edge of the heat storage flue 1. The structure of the flue gas baffle 2 is simple and easy to clean. The control device 3 is a rotating motor 7, which can drive and control the rotation angle of the flue gas baffle 2 through the transmission structure 8, so as to achieve the control of the amount of flue gas entering the heat storage flue 1. Further, preferably, the flue gas baffle 2 is equipped with a soot blowing device (not shown). The soot blowing device can be an air outlet device arranged around the flue gas baffle 2, which can blow air to the surface of the flue gas baffle 2 regularly to prevent particles in the flue gas from accumulating on the flue gas baffle 2, hindering the flue gas from flowing into the heat storage flue 1, and even affecting the opening and closing of the flue gas baffle 2.

[0036] The heat storage device 5 carries a heat storage medium, which exchanges heat with the high-temperature flue gas, thereby absorbing heat from the high-temperature flue gas to complete heat storage. The type of heat storage medium is not limited, and can be a sensible heat storage medium, such as water, molten salt, etc.; it can also be a thermochemical heat storage medium, such as metal oxides, metal hydrides, carbonates, etc., all of which belong to the protection scope of the present invention.

[0037] Figure 3 Schematic diagram of the structure of a preferred heat storage device in an embodiment of the present invention. Figure 1 and Figure 3 The heat storage device 5 includes: a heat storage shell 11, a support frame 12 staggeredly arranged in the heat storage shell 11, and a thermochemical heat storage module 10 arranged in a chamber 13 separated by the support frame 12. The thermochemical heat storage module 10 is a solid heat storage module, which is easy to be placed in the heat storage shell 11, and stores / releases heat through thermochemical reactions. The heat storage density is high, but thermal expansion may occur during the heat storage / release process. Therefore, the heat storage shell 11 can be separated into chambers 13 matching the shape of the thermochemical heat storage module 10 by the support frame 12, thereby avoiding extrusion and crushing between the thermochemical heat storage modules 10. Specifically, the flue gas can enter the heat storage shell 11 from the flue gas inlet of the heat storage shell 11, and directly contact and exchange heat with the thermochemical heat storage module 10 in the heat storage shell 11. The thermochemical heat storage module 10 absorbs heat to undergo a reduction reaction, and stores the heat in the form of chemical energy.

[0038] Among them, preferably, the thermochemical heat storage module 10 includes at least metal oxide heat storage materials, including but not limited to manganese-based, iron-based, copper-based and other metal oxides. When the metal oxide heat storage material stores heat, the high-priced metal oxide absorbs heat, undergoes a reduction reaction, and produces low-priced metal oxides and oxygen; when the metal oxide heat storage material releases heat, the low-priced metal oxide and oxygen undergo an oxidation reaction to generate high-priced metal oxides and release heat.

[0039] Preferably, the heat storage device 5 further includes an air duct 14, which connects the heat storage housing 11 and the external air, and the air duct 14 passes through the reheater 18 and / or the superheater 19 of the boiler 100 in sequence. The air duct 14 can be used to introduce air into the heat storage device 5, so that the metal oxide heat storage material can react with the oxygen in the air, and the released heat then flows through the reheater 18 and / or the superheater 19 of the boiler 100 via the air duct 14, so as to realize the reuse of the heat stored in the heat storage device 5. Furthermore, an air valve 16 is also provided on the air duct 14 to control the opening and closing of the air duct 14, and a flue gas valve 17 is provided at the flue gas outlet of the heat storage device 5. The heat storage device 5 also has an air fan 15 for inhaling air when the air valve 16 is opened.

[0040] In this embodiment, the pressure difference at both ends of the heat storage flue 1 is used to drive the flue gas to flow spontaneously in the heat storage flue 1. The control device 3 can be used to conveniently control the amount of flue gas entering the heat storage flue 1. The flue gas entering the heat storage flue 1 is in contact with the heat storage device 5 for heat exchange, thereby realizing peak load storage and flexible scheduling of the thermal power unit. In addition, there is no need to set up an external fan. The heat storage flue 1 is directly used to connect the flame folding angle 101 of the boiler 100 of the thermal power unit and the denitrification device 6. The structure is simple, and the tail gas treatment device can be shared with the thermal power unit, and the transformation cost is low.

[0041] Among them, preferably, the boiler flue gas heat storage system also includes: a dust removal device 4, including but not limited to a cyclone dust collector, a bag dust collector, and an electrostatic precipitator. The dust removal device 4 is arranged in the heat storage flue 1 on the upstream side of the heat storage device 5, and can remove dust and particulate matter in the flue gas to prevent them from adhering to the surface of the thermochemical heat storage module 10 in the heat storage device 5 and affecting the heat storage performance of the heat storage device 5.

[0042] Further preferably, the working temperature of the dust removal device 4 is not lower than 1300°C, and the surfaces of the dust removal device 4 and the heat storage device 5 are covered with heat insulation material 9. Since the dust removal device 4 is upstream of the heat storage device 5, the dust removal device 4 needs to receive high-temperature flue gas. On the one hand, a higher working temperature can improve the working safety of the dust removal device 4 when receiving high-temperature flue gas. On the other hand, it can also reduce or avoid heat exchange between the dust removal device 4 and the high-temperature flue gas, affecting the heat storage efficiency of the heat storage device 5. Further, by laying the heat insulation material 9, the heat storage efficiency of the boiler flue gas heat storage system can be effectively improved to avoid heat loss.

[0043] Specifically, when the system needs to peak-load heat storage, the air valve 16 is closed, the flue gas valve 17 is opened, and the control device 3 controls the opening of the flue gas damper 2 according to the peak-load demand of the thermal power unit. Under the pressure difference between the denitrification device 6 and the flame angle 101 of the boiler 100, the high-temperature flue gas in the boiler 100 spontaneously flows into the heat storage flue 1. After the high-temperature flue gas is dedusted by the dust removal equipment, it enters the heat storage tank and contacts with the thermochemical heat storage module 10 for heat exchange. The thermochemical heat storage module 10 absorbs heat and releases oxygen, converting the thermal energy of the high-temperature flue gas into the internal energy and chemical energy of the thermochemical heat storage module 10 for storage. The flue gas after heat exchange flows into the denitrification device 6 through the flue gas valve 17 and is discharged after exhaust gas treatment.

[0044] When the system needs to release heat, the air valve 16 is opened, the flue gas valve 17 is closed, and the control device 3 controls the flue gas damper 2 to be in a fully closed state. The flue gas only flows from the main flue through the air outlet 103 into the denitrification device 6. The air fan 15 of the heat storage device 5 is turned on, and fresh air is sucked into the heat storage device 5 through the air channel. The energy storage module undergoes an oxidation reaction with the oxygen in the air to release heat. The oxygen-depleted air after the reaction absorbs heat and its temperature rises. It then flows into the air duct 14 through the air valve 16, and exchanges heat through the reheater 18 and the superheater 19 at the top of the boiler 100 in turn, and is discharged into the air after sufficient heat exchange.

[0045] Through the above method, the boiler flue gas heat storage system provided in this embodiment realizes the conversion of the thermal energy of high-temperature flue gas into energy in the form of high energy storage density and high heat storage temperature for storage, and can release heat to supplement the steam in the boiler 100 when energy is needed, greatly improving the peak-shaving capacity and flexible operation capacity of conventional thermal power units.

[0046] So far, the technical solution of the present invention has been described in conjunction with the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to the above specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A boiler flue gas heat storage system, comprising a boiler and a denitration device connected to an air outlet of the boiler, characterized in that: Also includes: A heat storage flue, wherein the inlet end of the heat storage flue is connected to the flame bending angle of the boiler, and the outlet end of the heat storage flue is connected to the denitration device; A heat storage device, arranged in the heat storage flue, having a smoke inlet and a smoke outlet; A control device is used to control the opening and closing of the heat storage flue inlet.

2. The boiler flue gas heat storage system according to claim 1, characterized in that: The working pressure of the denitration device of the boiler is lower than -800Pa.

3. The boiler flue gas heat storage system according to claim 1, characterized in that: A smoke damper is provided at the inlet end of the heat storage flue, and the control device controls the opening of the smoke damper.

4. The boiler flue gas heat storage system according to claim 3, characterized in that: The flue gas damper is equipped with a soot blowing device.

5. The boiler flue gas heat storage system according to claim 1, characterized in that: Also includes: The dust removal device is arranged in the heat storage flue on the upstream side of the heat storage device.

6. The boiler flue gas heat storage system according to claim 5, characterized in that: The working temperature of the dust removal device is not lower than 1300°C.

7. The boiler flue gas heat storage system according to claim 6, characterized in that: The surfaces of the dust removal device and the heat storage device are covered with heat insulation materials.

8. The boiler flue gas heat storage system according to claim 1, characterized in that: The heat storage device comprises: A heat storage shell, wherein the heat storage shell is provided with the smoke inlet and the smoke outlet; A thermochemical heat storage module, built into the heat storage housing; The support frames are staggeredly arranged in the heat storage shell to separate the thermochemical heat storage modules.

9. The boiler flue gas heat storage system according to claim 8, characterized in that: The thermochemical heat storage module at least includes a metal oxide heat storage material.

10. The boiler flue gas heat storage system according to claim 9, characterized in that: The heat storage device also includes: An air duct connects the heat storage shell and external air, and the air duct passes through the reheater and / or superheater at the top of the boiler in sequence.

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