Air preheater with wide turndown ratio using heat pipe heat exchange

Abstract

The present application discloses an air preheater with a wide modulation ratio utilizing heat pipe heat exchange, comprising an air preheater body and a heat exchange unit, wherein the air preheater body comprises a smoke cavity and an air cavity, wherein the air cavity comprises a primary air cavity and a secondary air cavity, which are respectively located on both sides of the smoke cavity, wherein the smoke cavity comprises a primary air side smoke cavity close to the primary air cavity and a secondary air side smoke cavity close to the secondary air cavity, and an insulating sealed partition wall is provided at the connection between the smoke cavity and the air cavity; the heat exchange unit comprises a high-temperature heat exchange unit group, a medium-temperature heat exchange unit group and a low-temperature heat exchange unit group, wherein the heat exchange unit comprises a smoke side heat exchange portion and an air side heat exchange portion connected to each other, and an insulating sealed partition wall is provided at the connection between the smoke side heat exchange portion and the air side heat exchange portion; the present application can achieve zero air leakage, no cold end blockage and can realize a wide modulation ratio according to changes in coal quality.

Description

Technical Field

[0001] The present application belongs to the technical field of boiler air preheaters, and in particular, relates to a wide modulation ratio air preheater utilizing heat pipe heat exchange. Background Art

[0002] After years of development, different types of sealing methods and sealing devices have emerged in an endless stream for Ljungker air preheaters, and the sealing effect of air preheaters has been greatly improved. For example, flexible seals, rigid seals, dredge fan seals, and four compartments are all conducive to reducing the air leakage rate of air preheaters. The air leakage of some air preheaters can be reduced to 4%. However, the small sealing gap of the air preheater can easily lead to wear and fall off of the sealing components. After long-term operation, the air leakage rate of the air preheater will increase significantly. When the air leakage rate is high, it can exceed 10%, which seriously affects the energy consumption of the unit and the safety of the fan. When the air preheater is designed, about 30% of the primary air leaks to the flue gas side and the secondary air side. The main reason is the high differential pressure between the primary air and the flue gas and the secondary air. The tubular air preheater has a small air leakage rate, but occupies a large space. In the later stage, due to wear and tear, the air leakage is serious. Therefore, the tubular air preheater is not suitable for large-capacity units.

[0003] Under the current situation, power plants are under great pressure in production and operation. In order to control production costs, most power plants purchase a large proportion of economic coal and reduce production costs by blending economic coal, which leads to a significant deviation of the coal quality entering the plant and the furnace from the designed coal quality and frequent changes in coal quality parameters. Affected by the supply and demand relationship and production costs of the coal market, even many units originally designed for anthracite and lean coal are blended with a large amount of bituminous coal or even lignite, resulting in insufficient drying output of the pulverizing system, which in turn affects the output of the grinding and pulverizing system, and the initial ignition and burnout of the pulverized coal are affected; in order to control costs, some power plants purchase a large amount of high-sulfur, high calorific value, low-moisture lean coal, resulting in a high outlet temperature of the pulverizing system. In order to control the outlet temperature of the coal mill, a large amount of cold air is mixed, resulting in a significant increase in the exhaust gas temperature. In the case of uncontrollable coal quality, the main reason for the above problems is that the primary air volume and primary air temperature of the Junkers air preheater cannot be adjusted, and the hot primary air temperature can only be reduced by adjusting the cold air. It cannot be flexibly adjusted to changes in coal types, so the adaptability to coal types is poor.

[0004] How to solve the key problems of traditional rotary air preheaters, such as blockage, high air leakage rate, cold end corrosion and poor coal adaptability, is particularly important for improving the operating performance, operating safety and adaptability of air preheaters. So far, various forms of air preheater-related technical transformation have not completely solved the above problems fundamentally. In order to completely solve the stubborn problems of air preheaters, it is particularly urgent to invent an air preheater that can achieve zero air leakage, no cold end blockage and can achieve a wide adjustment ratio according to changes in coal quality. Summary of the invention

[0005] In view of the above problems, the embodiment of the present application provides a wide adjustment ratio air preheater using heat pipe heat exchange, which can achieve zero air leakage, no cold end blockage and can achieve a wide adjustment ratio according to changes in coal quality. The technical solution is as follows:

[0006] The present application provides a wide modulation ratio air preheater using heat pipe heat exchange, comprising an air preheater body and a heat exchange unit, the air preheater body comprising a smoke cavity and an air cavity, the air cavity comprising a primary air cavity and a secondary air cavity, which are respectively located on both sides of the smoke cavity, the smoke cavity comprising a primary air side smoke cavity close to the primary air cavity and a secondary air side smoke cavity close to the secondary air cavity, and insulation is provided at the connection between the primary air cavity and the primary air side smoke cavity, and at the connection between the secondary air cavity and the secondary air side smoke cavity Sealed partition wall; the heat exchange unit includes a high-temperature heat exchange unit group, a medium-temperature heat exchange unit group and a low-temperature heat exchange unit group, which are arranged in the air preheater body in sequence from upstream to downstream in the order of the flue gas flow in the flue gas cavity. The high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group all include a connected flue gas side heat exchange part and an air side heat exchange part, the flue gas side heat exchange part is located in the flue gas cavity, and the air side heat exchange part is located in the air cavity. An insulating sealed partition wall is provided at the junction of the flue gas side heat exchange part and the air side heat exchange part.

[0007] For example, in the wide modulation ratio air preheater using heat pipe heat exchange provided in one embodiment, a high-temperature heat exchange unit group, a medium-temperature heat exchange unit group and a low-temperature heat exchange unit group arranged in sequence are provided in the primary air cavity and the primary air side smoke cavity, wherein the smoke side heat exchange parts of the high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group are located in the primary air side smoke cavity, and the air side heat exchange parts of the high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group are located in the primary air cavity for heating the primary air; a high-temperature heat exchange unit group, a medium-temperature heat exchange unit group and a low-temperature heat exchange unit group arranged in sequence are provided in the secondary air cavity and the secondary air side smoke cavity, wherein the smoke side heat exchange parts of the high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group are located in the secondary air side smoke cavity, and the air side heat exchange parts of the high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group are located in the secondary air cavity for heating the secondary air.

[0008] For example, in the wide modulation ratio air preheater using heat pipe heat exchange provided in one embodiment, the primary air side smoke chamber and the secondary air side smoke chamber are independent of each other, and the hot smoke that transports smoke to the smoke chamber is divided into two paths, one path transports smoke to the primary air side smoke chamber through a bypass flue, and the other path transports smoke to the secondary air side smoke chamber through a hot smoke gas duct.

[0009] For example, in the wide modulation ratio air preheater using heat pipe heat exchange provided in one embodiment, a bypass flue gas remote control adjustment baffle is provided on the bypass flue to adjust the amount of flue gas delivered to the primary air side smoke cavity.

[0010] For example, in the wide modulation ratio air preheater using heat pipe heat exchange provided in one embodiment, a flue partition wall is provided in the flue gas cavity, and the flue partition wall divides the flue gas cavity into the primary air side smoke cavity and the secondary air side smoke cavity.

[0011] For example, in the wide modulation ratio air preheater utilizing heat pipe heat exchange provided in one embodiment, a primary air side remote control smoke regulating baffle is provided downstream of the low-temperature heat exchange unit group in the primary air side smoke cavity, and a secondary air side remote control smoke regulating baffle is provided downstream of the low-temperature heat exchange unit group in the secondary air side smoke cavity, so as to adjust the amount of smoke delivered to the primary air side smoke cavity and the secondary air side smoke cavity.

[0012] For example, in the wide adjustment ratio air preheater using heat pipe heat exchange provided in one embodiment, the heat exchange unit includes a plurality of heat pipes, and the plurality of heat pipes are fixed through a heat exchange unit box frame to form a prefabricated assembly module, the flue gas side heat exchange portion is the evaporation section of the heat pipe, the air side heat exchange portion is the condensation section of the heat pipe, the evaporation section of the heat pipe is a bare pipe, and spiral fins are provided on the outer surface of the condensation section of the heat pipe.

[0013] For example, in the wide modulation ratio air preheater utilizing heat pipe heat exchange provided in one embodiment, the heat exchange unit is installed obliquely in the air preheater body, and the condensation section is higher than the evaporation section. The angle between the heat exchange unit and the horizontal direction is 5 to 10°, and the air side heat exchange portion of the heat exchange unit extends out of the air preheater body, and an insulating sealing baffle is provided at the junction of the air side heat exchange portion and the external air.

[0014] For example, in the wide adjustment ratio air preheater using heat pipe heat exchange provided in one embodiment, a regeneration outlet pipe and an opening and closing core are provided at the end of the condensing section extending out of the air preheater body, and the outside of the opening and closing core is protected by a nut.

[0015] For example, in the wide adjustment ratio air preheater using heat pipe heat exchange provided in one embodiment, several fixed partitions are arranged at intervals on the heat exchange unit box frame to support the heat pipe, the heat pipe in the heat exchange unit includes round tubes and elliptical tubes, the spacing between two adjacent heat pipes in the high-temperature heat exchange unit group and the medium-temperature heat exchange unit group is 8mm-16mm, and the spacing between two adjacent heat pipes in the low-temperature heat exchange unit group is 10mm-20mm.

[0016] The beneficial effects brought about by the wide modulation ratio air preheater using heat pipe heat exchange in the present application are as follows: the present application adopts high vacuum regenerative heat pipes as the heat exchange elements in the heat exchange units, the junctions of the evaporation section and the condensation section of the heat pipes in different heat exchange units are fixed with double-layer insulation sealing partition walls, and insulation sealing partitions are arranged at the junctions between the air side and the environment of the heat exchange units. Through the joint action of the insulation sealing partitions and the insulation sealing partitions, zero air leakage of the air preheater can be achieved; by arranging a remote control adjustment baffle in the flue gas cavity to change the flue gas volume of the heated primary air and the temperature of the hot primary air, the requirements of different coal qualities for the pulverizer inlet air temperature are met, thereby achieving the purpose of improving the wide modulation ratio of coal quality adaptability. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 Schematic diagram of the layout of the independent cavity type air preheater of the present application;

[0019] Figure 2 Schematic diagram of the layout of the integral cavity air preheater of the present application;

[0020] Figure 3 The heat exchange unit of the present application and its layout schematic diagram;

[0021] Figure 4 Schematic diagram of the high vacuum regenerative heat pipe structure of the present application.

[0022] Figure 5a It is a schematic diagram of the arrangement of circular high vacuum regenerative heat pipes;

[0023] Figure 5b It is a schematic diagram of the arrangement of an elliptical high vacuum regenerative heat pipe;

[0024] Figure numerals: 1-air preheater body, 2-hot flue gas flue, 3-secondary air side smoke cavity, 4-high temperature heat exchange unit group smoke side heat exchange part, 5-medium temperature heat exchange unit group smoke side heat exchange part, 6-low temperature heat exchange unit group smoke side heat exchange part, 7-high temperature heat exchange unit group air side heat exchange part, 8-medium temperature heat exchange unit group air side heat exchange part, 9-low temperature heat exchange unit group air side heat exchange part, 10-primary air side smoke cavity, 11-secondary air cavity, 12-primary air cavity, 13-insulated sealed partition wall, 14-secondary air side remote control smoke adjustment damper, 15-primary air side remote control smoke adjustment damper, 16 -cold flue gas duct, 17-dust collector, 18-induced draft fan, 19-supply fan, 20-primary fan, 21-cold primary air duct, 22-hot primary air duct, 23-cold secondary air duct, 24-hot secondary air duct, 25-bypass flue gas remote control adjustment damper, 26-bypass flue, 27-bypass cold flue gas duct, 28-heat pipe, 29-evaporation section, 30-condensation section, 31-spiral fin, 32-regeneration outlet pipe, 33-nut, 34-opening and closing core, 35-insulating sealing partition, 36-heat exchange unit, 37-heat exchange unit box frame, 38-fixed partition, 39-flue duct partition. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0026] Unless otherwise defined, the technical terms or scientific terms used in the present disclosure should be understood by people with ordinary skills in the field to which the present disclosure belongs. The "first", "second" and similar words used in the present disclosure do not indicate any order, quantity or importance, but are only used to distinguish different components. "Include" or "comprise" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used to indicate relative positional relationships. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0027] As the country's environmental emission requirements become increasingly stringent, coal-fired power plants have all been equipped with denitrification and nitrogen reduction facilities in order to meet the requirements of NOx emissions. In order to effectively control the NOx concentration at the denitrification outlet, the ammonia nitrogen ratio is generally controlled to be higher than the design value during operation, which can easily cause high ammonia escape at the denitrification outlet. NH3 reacts with sulfuric acid vapor to form ammonium bisulfate (ABS for short). This type of ammonium bisulfate is in a gaseous state at high temperatures, becomes solid at low temperatures, and is liquid at intermediate temperatures [150-200℃ (high dust content)]. Liquid ammonium bisulfate is viscous; another type of ABS is generated by the reaction of sulfuric acid condensed in the cold section of the thermal storage element with ammonia or ammonia and ammonium sulfate adsorbed by fly ash, and is mainly deposited in the area where the wall temperature of the cold section is lower than the acid dew point. When ammonium bisulfate is slightly heated (about 200℃), the decomposition reaction is NH4HSO4=NH3↑+H2SO4. When it is above 400℃, H2SO4=H2O+SO3. When the surface temperature of the heat storage element at the cold end of the air preheater is lower than 200℃, the ammonium bisulfate adhering to the heat storage element captures the fly ash in the flue gas and accumulates on the surface of the heat storage element. The Junkers-type three-compartment air preheater commonly equipped in power plants uses plate heat exchange elements. In order to ensure the heat exchange performance, the plate gap is designed to be small. Ammonium bisulfate is easy to adhere to the heat exchange element of the air preheater, which eventually leads to the blockage of the heat exchange element of the air preheater. After the air preheater is blocked, the heat exchange capacity is reduced, the exhaust gas temperature is increased, and the differential pressure of the air preheater is increased, which affects the boiler efficiency and increases the power consumption of the fan. In severe cases, the insufficient output of the fan affects the operating oxygen content and the negative pressure of the boiler, affecting the safe and economical operation of the unit. Once the air preheater is blocked, adding soot blowing cannot be completely solved, and long-term soot blowing will cause large-scale blowing damage to the heat storage element of the air preheater, which will further affect the heat exchange effect.

[0028] In view of this, the present application provides a wide adjustment ratio air preheater using heat pipe heat exchange, such as Figure 1-2As shown, it includes an air preheater body 1 and a heat exchange unit 36, the air preheater body 1 includes a smoke cavity and an air cavity, the air cavity includes a primary air cavity 12 and a secondary air cavity 11, which are respectively located on both sides of the smoke cavity, the smoke cavity includes a primary air side smoke cavity 10 close to the primary air cavity 12 and a secondary air side smoke cavity 3 close to the secondary air cavity 11, and an insulating sealing partition wall 13 is provided at the connection between the primary air cavity 12 and the primary air side smoke cavity 10, and at the connection between the secondary air cavity 11 and the secondary air side smoke cavity 3, so that the smoke cavity and The air cavity is divided into independent cavities; the heat exchange unit 36 ​​includes a high-temperature heat exchange unit group, a medium-temperature heat exchange unit group and a low-temperature heat exchange unit group, which are arranged in the air preheater body 1 in sequence from upstream to downstream in the order of the flue gas flow in the flue gas cavity, and the high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group all include a connected flue gas side heat exchange part and an air side heat exchange part, the flue gas side heat exchange part is located in the flue gas cavity, and the air side heat exchange part is located in the air cavity, and an insulating sealing partition wall 13 is provided at the junction of the flue gas side heat exchange part and the air side heat exchange part.

[0029] like Figure 1-2 As shown, the high-temperature heat exchange unit group is arranged at the upper part of the air preheater body 1, the medium-temperature heat exchange unit group is arranged at the middle part of the air preheater body 1, and the low-temperature heat exchange unit group is arranged at the lower part of the air preheater body 1. According to the above embodiment, the secondary air side smoke cavity 3 and the secondary air cavity 11, and the primary air side smoke cavity 10 and the primary air cavity 12 in the air preheater body 1 are separated by a double-layer insulation sealing partition wall 13, which can ensure that the air leakage on the smoke side and the air side of the air preheater is zero.

[0030] For example, in the wide turndown ratio air preheater using heat pipe heat exchange provided in one embodiment, Figure 1-2 As shown, in the primary air cavity 12 and the primary air side smoke cavity 10, a high-temperature heat exchange unit group, a medium-temperature heat exchange unit group and a low-temperature heat exchange unit group are provided, which are arranged in sequence, wherein the smoke side heat exchange parts of the high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group are located in the primary air side smoke cavity 10, and the air side heat exchange parts of the high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group are located in the primary air cavity 12 for heating the primary air; in the secondary air cavity 11 and the secondary air side smoke cavity 3, a high-temperature heat exchange unit group, a medium-temperature heat exchange unit group and a low-temperature heat exchange unit group are provided, which are arranged in sequence, wherein the smoke side heat exchange parts of the high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group are located in the secondary air side smoke cavity 3, and the air side heat exchange parts of the high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group are located in the secondary air cavity 11 for heating the secondary air.

[0031] Specifically, Figure 1-2 As shown, the high-temperature heat exchange unit group air side heat exchange part 7, the medium-temperature heat exchange unit group air side heat exchange part 8 and the low-temperature heat exchange unit group air side heat exchange part 9 are arranged in sequence from top to bottom in the primary air cavity 12 and the secondary air cavity 11, and the high-temperature heat exchange unit group smoke side heat exchange part 4, the medium-temperature heat exchange unit group smoke side heat exchange part 5 and the low-temperature heat exchange unit group smoke side heat exchange part 6 are arranged in sequence from top to bottom in the primary air side smoke cavity 10 and the secondary air side smoke cavity 3. Among them, the high-temperature heat exchange unit group air side heat exchange part 7 in the primary air cavity 12 and the high-temperature heat exchange unit group smoke side heat exchange part 4 in the primary air side smoke cavity 10 are an integrated structure, the medium-temperature heat exchange unit group air side heat exchange part 8 in the primary air cavity 12 and the medium-temperature heat exchange unit group smoke side heat exchange part 5 in the primary air side smoke cavity 10 are an integrated structure, and the low-temperature heat exchange unit group air side heat exchange part 9 in the primary air cavity 12 and the low-temperature heat exchange unit group smoke side heat exchange part 6 in the primary air side smoke cavity 10 are an integrated structure. Structure: the high-temperature heat exchange unit group air side heat exchange part 7 in the secondary air cavity 11 and the high-temperature heat exchange unit group smoke side heat exchange part 4 in the secondary air side smoke cavity 3 are an integrated structure, the medium-temperature heat exchange unit group air side heat exchange part 8 in the secondary air cavity 11 and the medium-temperature heat exchange unit group smoke side heat exchange part 5 in the secondary air side smoke cavity 3 are an integrated structure, and the low-temperature heat exchange unit group air side heat exchange part 9 in the secondary air cavity 11 and the low-temperature heat exchange unit group smoke side heat exchange part 6 in the secondary air side smoke cavity 3 are an integrated structure.

[0032] The wide modulation ratio air preheater using heat pipe heat exchange in the present application can be divided into independent cavity type and integral cavity type according to different flue gas cavity layout modes. Figure 1 The figure shows an independent cavity type, that is, the primary air side smoke cavity 10 and the secondary air side smoke cavity 3 are independently arranged. Figure 2 The example shown is an integral cavity type, that is, the primary air side smoke cavity 10 and the secondary air side smoke cavity 3 share one cavity.

[0033] For example, in the wide turndown ratio air preheater using heat pipe heat exchange provided in one embodiment, Figure 1 An independent cavity type is shown, in which the primary air side smoke cavity 10 and the secondary air side smoke cavity 3 are independent of each other, and the hot smoke transporting smoke to the smoke cavity is divided into two paths, one path transporting smoke to the primary air side smoke cavity 10 through the bypass flue 26, and the other path transporting smoke to the secondary air side smoke cavity 3 through the hot smoke duct 2.

[0034] For example, in the wide modulation ratio air preheater using heat pipe heat exchange provided in one embodiment, a bypass flue gas remote control adjustment damper 25 is provided on the bypass flue duct 26 to adjust the amount of flue gas delivered to the primary air side smoke chamber 10. According to the above embodiment, by adjusting the opening of the bypass remote control adjustment damper 25 to change the amount of flue gas heated primary air, the temperature of the hot primary air can be changed to meet the requirements of different coal qualities for the coal mill inlet air temperature, thereby achieving the purpose of improving the adaptability of coal quality.

[0035] For example, in the wide turndown ratio air preheater using heat pipe heat exchange provided in one embodiment, Figure 2 The figure shows an integral cavity type, in which a flue partition wall 39 is provided in the smoke cavity, and the flue partition wall 39 divides the smoke cavity into the primary air side smoke cavity 10 and the secondary air side smoke cavity 3. According to the above embodiment, the flue partition wall 39 installed inside the smoke cavity separates the smoke for heating the primary air and the smoke for heating the secondary air, and the flue partition wall 39 can separate the flue left and right or front and back.

[0036] For example, in the wide modulation ratio air preheater using heat pipe heat exchange provided in one embodiment, a primary air side remote control smoke gas adjustment damper 15 is provided downstream of the low temperature heat exchange unit group in the primary air side smoke cavity 10, and a secondary air side remote control smoke gas adjustment damper 14 is provided downstream of the low temperature heat exchange unit group in the secondary air side smoke cavity 3, so as to adjust the amount of smoke delivered to the primary air side smoke cavity 10 and the secondary air side smoke cavity 3. According to the above embodiment, the ratio of smoke heated primary air and secondary air is adjusted by the primary air side remote control smoke gas adjustment damper 15 and the secondary air side remote control smoke gas adjustment damper 14, and the temperature of the hot primary air is adjusted.

[0037] For example, in the wide turndown ratio air preheater using heat pipe heat exchange provided in one embodiment, Figure 3-4 As shown, the heat exchange unit 36 ​​includes a plurality of heat pipes 28, and the plurality of heat pipes 28 are fixed by a heat exchange unit box frame 37 to form a prefabricated assembly module, the flue gas side heat exchange portion is the evaporation section 29 of the heat pipe 28, and the air side heat exchange portion is the condensation section 30 of the heat pipe 28, the evaporation section 29 of the heat pipe 28 is a bare pipe, and a spiral fin 31 is provided on the outer surface of the condensation section 30 of the heat pipe 28.

[0038] Among them, the high-temperature heat exchange unit group is composed of high-temperature heat pipes, the medium-temperature heat exchange unit group is composed of medium-temperature heat pipes, and the low-temperature heat exchange unit group is composed of low-temperature heat pipes. The heat pipes 28 in the high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group of the present application are high-vacuum regenerative heat pipes. Unlike traditional air preheater heat exchange elements, the high-vacuum regenerative heat pipes in the present application are made of precision rolled pipes. The internal medium includes preservatives, corrosion inhibitors, hydrogen absorbers and heat exchange media. The heat exchange media are different according to the heat exchange temperature. The high-vacuum regenerative heat pipes in different heat exchange units are suitable for different temperature ranges. The applicable temperature range of the heat pipes in the high-temperature heat exchange unit group is 300℃-420℃, the applicable temperature range of the heat pipes in the medium-temperature heat exchange unit group is 180℃-300℃, and the applicable temperature range of the heat pipes in the low-temperature heat exchange unit group is 80℃-180℃.

[0039] like Figure 3-4 As shown, the junction of the evaporation section 29 and the condensation section 30 of the heat pipe 28 is fixed by a double-layer insulation sealing partition wall 13, and the two ends of the heat pipe 28 are arranged in a free expansion manner, ensuring that the insulation sealing partition wall 13 is sealed and airtight while the two ends of the heat pipe 28 can expand freely.

[0040] According to the above embodiment, by arranging spiral fins 31 on the outer surface of the condensing section 30 of the heat pipe 28, the heat exchange area on the air side is increased, the length of the heat pipe on the air side is reduced, and it is convenient for on-site layout; the evaporation section 29 of the heat pipe 28 is a bare pipe, which can effectively avoid flue gas blockage and cold end corrosion.

[0041] According to the above embodiment, the heat exchange unit 36 ​​is fixed by the heat exchange unit box frame 37 to form a prefabricated assembly module. During installation, it is only necessary to stack the different heat exchange units in sequence and place them in the air preheater body 1. The installation is quick and convenient. The heat exchange unit frame 37 is connected to the outer shell of the air preheater body 1 by welding. The number of high, medium and low temperature heat exchange units is arranged according to design requirements.

[0042] For example, in the wide turndown ratio air preheater using heat pipe heat exchange provided in one embodiment, Figure 3As shown, the heat exchange unit 36 ​​is installed obliquely in the air preheater body 1, and the condensing section 30 is higher than the evaporating section 29. The angle between the heat exchange unit 36 ​​and the horizontal direction is 5-10°. The air side heat exchange part of the heat exchange unit 36 ​​extends out of the air preheater body 1, and an insulating sealing baffle 35 is provided at the junction of the air side heat exchange part and the external air. According to the above embodiment, by arranging the insulating sealing baffle 35 at the junction of the air side heat exchange part of the heat exchange unit 36 ​​and the external air, it is ensured that there is no air leakage between the heat exchange unit 36 ​​and the outside world. Through the combined action of the insulating sealing baffle 35 and the insulating sealing partition wall 13, zero air leakage of the air preheater can be achieved; by obliquely installing the heat exchange unit 36, and the installation angle is 5°-10°, the heat exchange efficiency of the heat pipe is high within the angle range, the space required for on-site installation is small, and it is not easily limited by on-site space.

[0043] For example, in the wide turndown ratio air preheater using heat pipe heat exchange provided in one embodiment, Figure 4 As shown, a regeneration outlet pipe 32 and an opening and closing core 34 are provided at the end of the condensing section 30 extending outside the air preheater body 1, and the outside of the opening and closing core 34 is protected by a nut 33. According to the above embodiment, by providing the regeneration outlet pipe 32 and the opening and closing core 34 at the head of the condensing section 30, and the regeneration outlet pipe 32 and the opening and closing core 34 are located outside the air preheater body 1, it is possible to ensure that the heat pipe failure detection and the regeneration operation after failure are performed during the operation of the unit, and the outside of the opening and closing core 34 is protected by the nut 33 to prevent the heat pipe from leaking.

[0044] For example, in the wide turndown ratio air preheater using heat pipe heat exchange provided in one embodiment,

[0045] like Figure 3 , Figure 5a , Figure 5b As shown, several fixed partitions 38 are arranged at intervals on the heat exchange unit box frame 37 to support the heat pipe 28. The heat pipe 28 in the heat exchange unit 36 ​​includes a round tube and an elliptical tube. The spacing between two adjacent heat pipes in the high-temperature heat exchange unit group and the medium-temperature heat exchange unit group is 8mm-16mm, and the spacing between two adjacent heat pipes in the low-temperature heat exchange unit group is 10mm-20mm. According to the above embodiment, by arranging several fixed partitions 38 at intervals on the heat exchange unit box frame 37, the heat pipe 28 is supported to prevent deformation, and at the same time, the flow of smoke and wind fluid is balanced and rectified; by arranging the heat pipes of the high-temperature, medium-temperature, and low-temperature heat exchange units at centimeter-level spacing, and by differentially arranging the spacing between the heat pipes in different heat exchange units, the heat exchange needs and the flexibility of small space layout are guaranteed, and the blockage of the cold end of the air preheater and the low temperature corrosion caused by the low temperature of the cold end caused by the blockage can be prevented.

[0046] Figure 5aA schematic diagram of the arrangement of circular high vacuum regenerative heat pipes is given; Figure 5b A schematic diagram of the arrangement of elliptical high vacuum regenerative heat pipes is given;

[0047] The working principle of the wide modulation ratio air preheater using heat pipe heat exchange in the present application is: Figure 1 , the primary air enters the cold primary air duct 21 through the primary fan 19, and then enters the hot primary air duct 22 after being heated by the low-temperature heat exchange unit group air side heat exchange part 9, the medium-temperature heat exchange unit group air side heat exchange part 8 and the high-temperature heat exchange unit group air side heat exchange part 7 in the primary air cavity 12; the secondary air enters the cold secondary air duct 23 through the secondary fan 20, and then enters the hot secondary air duct 24 after being heated by the low-temperature heat exchange unit group air side heat exchange part 9, the medium-temperature heat exchange unit group air side heat exchange part 8 and the high-temperature heat exchange unit group air side heat exchange part 7 in the secondary air cavity 11;

[0048] When the smoke chamber is Figure 1 In the independent cavity shown in the figure, a part of the flue gas passes through the hot flue gas duct 2 and successively passes through the high-temperature heat exchange unit group flue gas side heat exchange part 4, the medium-temperature heat exchange unit group flue gas side heat exchange part 5 and the low-temperature heat exchange unit group flue gas side heat exchange part 6 in the secondary air side flue cavity 3 to release heat, and then enters the cold flue gas duct 16; another part of the flue gas enters the bypass flue duct 26, and then successively passes through the high-temperature heat exchange unit group flue gas side heat exchange part 4, the medium-temperature heat exchange unit group flue gas side heat exchange part 5 and the low-temperature heat exchange unit group flue gas side heat exchange part 6 in the primary air side flue cavity 10 to release heat, and then enters the bypass cold flue gas duct 27, and finally enters the cold flue duct 16 to mix with the other part of the flue gas, and then passes through the dust collector 17 and the induced draft fan 18 in sequence, wherein the amount of flue gas entering the bypass flue duct 26 can be controlled by the bypass flue gas remote control adjustment baffle 25, so as to achieve the purpose of adjusting the hot primary air at the inlet of the coal mill, thereby improving the adaptability of the pulverizing system to the coal quality.

[0049] When the smoke chamber is Figure 2In the case of the integral cavity shown, the hot flue gas is diverted through the flue gas partition wall 39. A part of the flue gas passes through the hot flue gas duct 2 and sequentially passes through the high-temperature heat exchange unit group flue gas side heat exchange part 4, the medium-temperature heat exchange unit group flue gas side heat exchange part 5 and the low-temperature heat exchange unit group flue gas side heat exchange part 6 in the secondary air side flue cavity 3 to release heat, and then enters the cold flue gas duct 16. The other part of the flue gas enters the high-temperature heat exchange unit group flue gas side heat exchange part 4, the medium-temperature heat exchange unit group flue gas side heat exchange part 5 and the low-temperature heat exchange unit group flue gas side heat exchange part 6 in the primary air side flue cavity 10 to release heat, and then enters the cold flue duct 16 to mix with the other part of the flue gas, and then passes through the dust collector 17 and the induced draft fan 18 in sequence. Among them, the amount of smoke entering the primary air side smoke chamber 10 and the secondary air side smoke chamber 3 can be adjusted by the primary air side remote-controlled smoke regulating baffle 15 located at the outlet of the primary air side smoke chamber 10 and the secondary air side remote-controlled smoke regulating baffle 14 located at the outlet of the secondary air side smoke chamber 3. By coordinated control of the primary air side remote-controlled smoke regulating baffle 15 and the secondary air side remote-controlled smoke regulating baffle 14, the amount of smoke entering the primary air side smoke chamber 10 and the secondary air side smoke chamber 3 is adjusted, so as to achieve the purpose of adjusting the hot primary air at the inlet of the coal mill, thereby improving the adaptability of the pulverizing system to coal quality.

[0050] Although the embodiments of the present application have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.

Claims

1. A wide-turndown ratio air preheater utilizing heat pipe heat exchange, characterized in that: include: The air preheater body comprises a smoke cavity and an air cavity, wherein the air cavity comprises a primary air cavity and a secondary air cavity, which are respectively located on both sides of the smoke cavity, and the smoke cavity comprises a primary air side smoke cavity close to the primary air cavity and a secondary air side smoke cavity close to the secondary air cavity, and an insulating sealing partition wall is provided at the connection between the primary air cavity and the primary air side smoke cavity, and at the connection between the secondary air cavity and the secondary air side smoke cavity; The heat exchange unit includes a high-temperature heat exchange unit group, a medium-temperature heat exchange unit group and a low-temperature heat exchange unit group, which are arranged in the air preheater body in sequence from upstream to downstream of the flue gas flow in the flue gas cavity. The high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group all include a connected flue gas side heat exchange part and an air side heat exchange part. The flue gas side heat exchange part is located in the flue gas cavity, and the air side heat exchange part is located in the air cavity. An insulating sealing partition wall is provided at the junction of the flue gas side heat exchange part and the air side heat exchange part.

2. The wide turndown ratio air preheater using heat pipe heat exchange according to claim 1, characterized in that: A high-temperature heat exchange unit group, a medium-temperature heat exchange unit group and a low-temperature heat exchange unit group arranged in sequence are provided in the primary air cavity and the primary air side smoke cavity, wherein the smoke gas side heat exchange parts of the high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group are located in the primary air side smoke cavity, and the air side heat exchange parts of the high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group are located in the primary air cavity for heating the primary air; a high-temperature heat exchange unit group, a medium-temperature heat exchange unit group and a low-temperature heat exchange unit group arranged in sequence are provided in the secondary air cavity and the secondary air side smoke cavity, wherein the smoke gas side heat exchange parts of the high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group are located in the secondary air side smoke cavity, and the air side heat exchange parts of the high-temperature heat exchange unit group, the medium-temperature heat exchange unit group and the low-temperature heat exchange unit group are located in the secondary air cavity for heating the secondary air.

3. The wide turndown ratio air preheater using heat pipe heat exchange according to claim 1, characterized in that: The primary air side smoke cavity and the secondary air side smoke cavity are independent of each other, and the hot smoke that transports smoke to the smoke cavity is divided into two paths, one path transports smoke to the primary air side smoke cavity through a bypass flue, and the other path transports smoke to the secondary air side smoke cavity through a hot smoke duct.

4. The wide turndown ratio air preheater using heat pipe heat exchange according to claim 3, characterized in that: A bypass smoke remote control regulating baffle is provided on the bypass smoke duct to regulate the amount of smoke delivered to the primary air side smoke cavity.

5. The wide turndown ratio air preheater using heat pipe heat exchange according to claim 1, characterized in that: A flue partition wall is provided in the smoke cavity, and the flue partition wall divides the smoke cavity into the primary air side smoke cavity and the secondary air side smoke cavity.

6. The wide turndown ratio air preheater using heat pipe heat exchange according to claim 5, characterized in that: A primary air side remote-controlled smoke regulating baffle is provided downstream of the low-temperature heat exchange unit group in the primary air side smoke cavity, and a secondary air side remote-controlled smoke regulating baffle is provided downstream of the low-temperature heat exchange unit group in the secondary air side smoke cavity, so as to adjust the amount of smoke delivered to the primary air side smoke cavity and the secondary air side smoke cavity.

7. The wide turndown ratio air preheater using heat pipe heat exchange according to claim 2, characterized in that: The heat exchange unit comprises a plurality of heat pipes, which are fixed by a heat exchange unit box frame to form a prefabricated assembly module. The flue gas side heat exchange portion is the evaporation section of the heat pipe, and the air side heat exchange portion is the condensation section of the heat pipe. The evaporation section of the heat pipe is a bare pipe, and spiral fins are provided on the outer surface of the condensation section of the heat pipe.

8. The wide turndown ratio air preheater using heat pipe heat exchange according to claim 7, characterized in that: The heat exchange unit is installed obliquely in the air preheater body, and the condensation section is higher than the evaporation section. The angle between the heat exchange unit and the horizontal direction is 5 to 10 degrees. The air side heat exchange part of the heat exchange unit extends out of the air preheater body, and an insulating sealing baffle is provided at the junction of the air side heat exchange part and the external air.

9. The wide turndown ratio air preheater using heat pipe heat exchange according to claim 8, characterized in that: A regeneration outlet pipe and an opening and closing core are provided at the end of the condensing section extending out of the air preheater body, and the outside of the opening and closing core is protected by a nut.

10. The wide turndown ratio air preheater using heat pipe heat exchange according to claim 7, characterized in that: Several fixed partitions are arranged at intervals on the heat exchange unit box frame to support the heat pipes. The heat pipes in the heat exchange unit include round tubes and elliptical tubes. The spacing between two adjacent heat pipes in the high-temperature heat exchange unit group and the medium-temperature heat exchange unit group is 8mm-16mm, and the spacing between two adjacent heat pipes in the low-temperature heat exchange unit group is 10mm-20mm.

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