Air preheater, flue gas treatment system using the same, and flue gas treatment method

Abstract

The present invention relates to an air preheater, a flue gas treatment system and a flue gas treatment method with a partition self-cleaning function. The air preheater has a number of heat exchange modules. The cold fluid inlet header of the first heat transfer module is divided into a number of sub-headers by a cold fluid inlet partition plate, and an independently controllable cold fluid inlet cut-off mechanism is provided in each sub-header. By controlling the opening and closing of the cold fluid inlet cut-off mechanism in the sub-header, the self-cleaning function of all the heat transfer modules in the air preheater casing can be realized, solving the problems of air leakage, blockage and corrosion existing in the prior art due to the use of a rotary air preheater, as well as the problems of high flue gas temperature, low utilization rate of flue gas waste heat, low boiler efficiency, high energy consumption and heavy loads on downstream dust removal devices and desulfurization devices caused thereby.

Description

Technical Field

[0001] The present invention relates to the field of air preheaters, and particularly to an air preheater with a partition self-cleaning function, a flue gas treatment system using the air preheater, and a flue gas treatment method. Background Art

[0002] During the operation of a coal-fired power plant boiler, corresponding waste heat utilization devices and desulfurization and denitrification devices are usually equipped to treat the flue gas discharged from the boiler, so as to achieve the purpose of energy conservation and emission reduction.

[0003] The flue gas treatment system of a conventional coal-fired power plant boiler is as Figure 1 shown. This system includes: boiler 1, coal feeder 2, primary air fan 3, secondary air fan 4, dust removal device 5, induced draft fan 6, desulfurization device 7, chimney 8, denitrification device 9; air preheater 10 and low-low temperature economizer 11.

[0004] The air preheater 10 is a core component of the flue gas treatment system, and the operation effect of the air preheater 10 directly affects the efficiency of the boiler. By recovering the heat in the flue gas through the air preheater 10, the recovered heat can preheat the primary air and secondary air entering the boiler 1, improve the boiler thermal efficiency, and reduce energy consumption.

[0005] At present, the most common air preheater in coal-fired power plants is the rotary air preheater. The rotary air preheater has the advantages of high heat transfer surface density, compact structure, small volume, and flexible layout. The rotary air preheater usually uses metal corrugated plates as the heat storage core body, and is generally divided into three compartments, namely the flue gas compartment, the primary air compartment, and the secondary air compartment. When the heat storage core body rotates to the flue gas compartment, the heat in the flue gas is absorbed and accumulated by the heat storage body. When the heat storage core body rotates to the primary air compartment and the secondary air compartment, the accumulated heat is released to the primary air and the secondary air, and the temperature of the heat storage core body decreases, realizing the heat exchange between the flue gas and the primary air and the secondary air.

[0006] One of the disadvantages of the rotary air preheater is the serious air leakage problem. The reason for the air leakage is that the operating pressure on the primary air side is higher than that on the flue gas side and the secondary air side. In this way, the primary air will leak to the flue gas side through the gap between the moving and static parts of the rotary air preheater, forming air leakage. The air leakage rate of the primary air is about 20%. As the equipment usage time prolongs, the air leakage problem will become more serious. In order to maintain the primary air volume, the power of the primary air fan needs to be increased. At the same time, in order to maintain the negative pressure of the boiler system, the power of the flue gas induced draft fan also needs to be increased accordingly. The increase in the power of the primary air fan and the flue gas induced draft fan leads to an increase in the system power consumption, and the loads of the dust removal device and the desulfurization device downstream of the rotary air preheater also increase.

[0007] Another disadvantage of the rotary air preheater is that it is prone to blockage and corrosion. As Figure 1As shown, the air preheater 10 is a rotary air preheater, and a denitrification device 9 is provided upstream thereof. The denitrification device generally adopts an SCR denitrification process. The SCR denitrification device inevitably has NH3 escape. The SCR catalyst promotes the denitrification of NH3 and NO. x While the reaction removes nitrogen oxides, it also promotes the conversion rate of SO2 to SO3. The escaped NH3 reacts with SO3 and H2O to form ammonium bisulfate. Ammonium bisulfate is a sticky substance and is hygroscopic. After absorbing moisture, it becomes acidic and corrosive. The melting point of ammonium bisulfate is 147°C. When the exhaust temperature of the rotary air preheater is lower than 147°C, the ammonium bisulfate will solidify and has strong viscosity. It is very easy to deposit and adhere to the surface of the heat exchange plate of the rotary air preheater, causing the rotary air preheater to be blocked. Because ammonium bisulfate becomes acidic and corrosive after absorbing moisture, it is easy to cause corrosion of the rotary air preheater.

[0008] To address air leakage in rotary air preheaters, CN210463080U proposes a coal-fired power plant air preheater system. This system combines a tubular air preheater with a two-chamber rotary air preheater in parallel. This isolates the primary air system from the flue gas, reducing the impact of high-pressure primary air on the air preheater's leakage rate. While this system can alleviate air leakage to some extent, it is complex in structure, difficult to assemble and maintain, and unable to address clogging and corrosion.

[0009] In order to solve the problems of clogging and corrosion of rotary air preheaters, the measures usually taken include: 1. Controlling the exhaust gas temperature of the rotary air preheater to be higher than the melting point of ammonium bisulfate; the disadvantage is that it will reduce the amount of waste heat recovered from the flue gas, which is not conducive to improving boiler efficiency; 2. Setting up soot blowers. Soot blowers mainly include sonic soot blowers, steam soot blowers, shock wave soot blowers, etc., which are limited by the soot blower cleaning principle, and their cleaning range and cleaning effect are limited. Even if the air preheater is provided with a soot blower, there are still problems such as soot accumulation and difficulty in long-term operation. In order to ensure that the effective soot blowing range of the soot blower is fully covered, CN108662927A discloses a plate-type air-to-air heat exchanger, including one or more rectangular heat exchange units, each of which includes a plate bundle module and four heat exchange chambers formed by the four corners of the plate bundle module or the four corner extension plates and the edges of the rectangular columns, and the heat exchange chambers on the opposite sides of the plate bundle module flow through the same medium. Because the lengths of the channels on both sides are roughly equal and the flow path is short, the sootblower can effectively cover the entire sootblowing range. However, the heat exchanger still requires a sootblower for dust removal, which prevents the heat exchanger from achieving self-cleaning. Frequent sootblowing not only results in poor sootblowing results but also causes severe erosion of the heat transfer components. Third, online water washing: Online water washing wastes water resources, poses problems with subsequent wastewater treatment, and can easily cause equipment corrosion.

[0010] It can be seen from this that none of the existing measures can effectively solve the problems of air leakage, blockage and corrosion existing in the flue gas treatment system using a rotary air preheater, as well as the problems of low recovery rate of flue gas waste heat, high energy consumption, and heavy loads on downstream dust removal devices and desulfurization devices caused thereby. How to overcome the above defects has become an urgent problem to be solved in the current flue gas treatment field. Summary of the Invention

[0011] An object of the present invention is to provide an air preheater with a partition self-cleaning function, as well as a flue gas treatment system and a flue gas treatment method using the air preheater, so as to solve the problems of air leakage, blockage, and corrosion existing when a rotary air preheater is used in an existing boiler flue gas treatment system, and the problems of high exhaust gas temperature, low utilization rate of flue gas waste heat, low boiler efficiency, high energy consumption, and heavy loads on downstream dust removal devices and desulfurization devices caused thereby.

[0012] To solve the above technical problems, the technical solutions provided by the present invention are as follows:

[0013] One object of the present invention is to provide an air preheater with a partition self-cleaning function, the air preheater includes n heat transfer modules, n≥2, and is characterized in that:

[0014] The heat transfer module is formed by welding a set of opposite sides of two heat transfer plates to form a plate pair, and multiple plate pairs are stacked to form a heat transfer module. A cold fluid channel is formed inside the plate pair, and the other set of opposite sides of the plate pair is not welded together to form a cold fluid inlet of the heat transfer module and a cold fluid outlet of the heat transfer module; a hot fluid channel is formed between the plate pairs along the direction of the set of welded opposite sides; the flow direction of the hot fluid and the flow direction of the cold fluid in the heat transfer module are perpendicular, for cross-flow heat exchange.

[0015] The 1st, 2nd, ……, n-1th, and nth heat transfer modules are arranged in sequence; each two heat transfer modules are connected by a transition header, and no heat transfer module is provided inside the transition header.

[0016] At the cold fluid inlet 2’ of the 1st heat transfer module, a cold fluid inlet header 2 is provided;

[0017] At the cold fluid outlet 5’ of the 1st heat transfer module, a 1st flipping header is provided, and the 1st flipping header connects the cold fluid outlet of the 1st heat transfer module and the cold fluid inlet of the 2nd heat transfer module; in the same way, at the cold fluid outlet of the n-1th heat transfer module, an n-1th flipping header is provided, and the n-1th flipping header connects the cold fluid outlet of the n-1th heat transfer module and the cold fluid inlet of the nth heat transfer module; at the cold fluid outlet of the nth heat transfer module, a cold fluid outlet header 5 is provided;

[0018] A cold fluid inlet header 2 is provided with a cold fluid inlet header partition plate 4 parallel to the heat transfer plates of the first heat transfer module. The cold fluid inlet header partition plate 4 divides the cold fluid inlet header 2 into several sub - headers, and there is no leakage between the sub - headers. A corresponding cold fluid inlet cut - off mechanism 3 is provided in each sub - header, and each cold fluid inlet cut - off mechanism 3 can be independently controlled to open.

[0019] The turnover header is provided with a turnover header partition plate 10. The number of turnover header partition plates 10 is the same as and corresponds one - to - one with the cold fluid inlet header partition plates 4, and each turnover header partition plate 10 is in the same plane as a corresponding cold fluid inlet header partition plate 4.

[0020] Thus, the cold fluid passes through The cold fluid inlet header 2 enters the air preheater and is by the heat transfer module cold fluid inlet 2' of the first heat transfer module and enters the cold fluid passage, then flows out from the heat transfer module cold fluid outlet 5' into the first turnover header, and under the guidance of the first turnover header partition plate 10, enters the cold fluid channel of the second heat transfer module through the cold fluid inlet of the second heat transfer module, and finally flows out of the pre - heater through the heat transfer module cold fluid outlet 5' of the nth heat transfer module and the cold fluid outlet header 5.

[0021] A hot fluid inlet header 6 is provided in the direction of a set of opposite sides of the plate pair welding of the nth heat transfer module. The hot fluid enters the hot fluid channel of the nth heat transfer module through the hot fluid inlet header 6, then flows through the transition header and enters the hot fluid channel of the (n - ⅰ)th heat transfer module, and finally flows out through the hot fluid outlet header 1 of the first heat transfer module.

[0022] Preferably, the heat transfer plates are corrugated plates, and there is no special limitation on the shape of the corrugations, which can be corrugations with protrusions or depressions.

[0023] The air pre - heater described in this patent is a plate - type heat exchanger structure with a fully welded structure, and the cold and hot fluids exchange heat through a partition wall, without any leakage problem.

[0024] Preferably, the cold fluid inlet cut - off mechanism is a gate with opening and closing functions, such as a flap valve, a plug valve, a louver valve, etc. The form of the cold fluid inlet cut - off mechanism of the present invention is not particularly limited.

[0025] The working principle of the air pre - heater with a partition self - cleaning function described in the present invention is as follows:

[0026] Since the cold fluid inlet header 2 of the first heat transfer module is divided into several sub - headers by the cold fluid inlet partition plate 4, and a cold fluid inlet cut - off mechanism 3 that can be independently controlled to open is provided in each sub - header. Therefore, when the cold fluid inlet cut - off mechanism 3 in a certain sub - header is closed, the cold fluid will not enter the cold fluid channel corresponding to that sub - header, but the hot fluid can still enter the corresponding hot fluid channel. Since there is no cold fluid passing through the cold fluid channel, there is no heat exchange on the corresponding heat transfer plates. Thus, the ammonium bisulfate adhering to the heat transfer plates can be heated by the high - temperature hot fluid. The ammonium bisulfate melts when heated, and the melted ammonium bisulfate is carried away by the hot fluid, achieving the self - heating cleaning effect of the corresponding heat transfer plates. When the cold fluid inlet cut - off mechanisms 3 are closed in turn, the partitioned self - heating cleaning function of all heat transfer plates can be realized.

[0027] Another object of the present invention is to provide a flue gas treatment system using the air preheater with the above - mentioned partitioned self - cleaning function.

[0028] In one embodiment, the flue gas treatment system includes the aforementioned air preheater with the partitioned self - cleaning function.

[0029] In another embodiment, the flue gas treatment system specifically includes a boiler, a coal feeder, a primary air fan, a secondary air fan, a first air preheater, and a second air preheater.

[0030] The first air preheater uses a conventional rotary air preheater, which can achieve heat exchange between flue gas and primary air and secondary air. Preferably, the flue gas outlet temperature of the first air preheater is higher than the melting point of ammonium bisulfate to avoid the phenomenon of ammonium bisulfate condensation and blockage in the first air preheater.

[0031] The second air preheater is the aforementioned air preheater with the partitioned self - cleaning function. The flue gas outlet temperature of the second air preheater can be lower than the melting point of ammonium bisulfate. Since the second air preheater has the partitioned self - cleaning function, the phenomenon of ammonium bisulfate blockage can be avoided.

[0032] During the operation of the flue gas treatment system, the flue gas passes through the first air preheater and the second air preheater after exiting the boiler and is finally discharged into the atmosphere.

[0033] Preferably, the flue gas treatment system is further provided with a denitration device, a first low - low temperature economizer, a dust removal device, an induced draft fan, a desulfurization device, and a chimney. The flue gas passes through the denitration device, the first air preheater, the second air preheater, the first low - low temperature economizer, the dust removal device, the induced draft fan, the desulfurization device, and the chimney in sequence and is discharged into the atmosphere after exiting the boiler.

[0034] Optionally, the first low-low temperature economizer can also be arranged between the induced draft fan and the desulfurization device. By arranging the first low-low temperature economizer in the flue downstream of the second air preheater, the boiler feed water is heated by the flue gas, and the waste heat in the flue gas is further recovered.

[0035] The primary air enters the system through the primary air fan, and then sequentially passes through the first air preheater and the coal feeder and enters the boiler. Preferably, a bypass is provided at the primary air inlet and outlet of the first air preheater, and there is a valve on the bypass to adjust the primary air volume entering the first air preheater.

[0036] The secondary air enters the system through the secondary air fan, and then sequentially passes through the second air preheater and the first air preheater and enters the boiler. Preferably, a second low-low temperature economizer is provided in the secondary air duct between the first air preheater and the second air preheater. The secondary air enters the system through the secondary air fan, and then sequentially passes through the second air preheater, the second low-low temperature economizer, and the first air preheater and enters the boiler. Through the second low-low temperature economizer, heat exchange between the secondary air and the boiler condensate can be realized, the heat of the secondary air is transferred to the boiler feed water, the temperature of the boiler feed water is increased, and the temperature of the secondary air entering the first air preheater is decreased, thereby increasing the heat transfer temperature difference of the first air preheater.

[0037] In the flue gas treatment system, the first air preheater adopts a conventional rotary air preheater, which can give full play to the advantages of high heat transfer surface density, compact structure, small volume, and flexible arrangement of the rotary air preheater. At the same time, the flue gas outlet temperature of the first air preheater is controlled to be higher than the melting point of ammonium bisulfate, thereby avoiding the phenomena of ammonium bisulfate blockage and corrosion in the first air preheater. The second air preheater adopts the air preheater with the function of zone self-cleaning according to the present invention, so that the flue gas temperature of the second air preheater can be lower than the melting point of ammonium bisulfate. Compared with the conventional process flow that only adopts a three-chamber rotary air preheater to recover flue gas heat, more flue gas heat is recovered, the boiler efficiency is improved, and at the same time, the phenomena of ammonium bisulfate blockage and corrosion are avoided. The coordinated cooperation of the conventional rotary air preheater and the air preheater with the function of zone self-cleaning provided by the present invention can improve the boiler efficiency and the utilization rate of flue gas waste heat, and at the same time avoid the blockage and corrosion phenomena caused by ammonium bisulfate, and has broad market application prospects.

[0038] In addition, the second air preheater in the system adopts the air preheater with the function of zone self-cleaning according to the present invention, and is all-welded structure, which can avoid the leakage of secondary air and flue gas. Therefore, the secondary air volume and the flue gas volume will be reduced, the power of the secondary air fan and the induced draft fan will be reduced, and the power consumption will be correspondingly reduced. At the same time, after the flue gas volume is reduced, the flue gas treatment volume of the dust removal device and the desulfurization device downstream of the air preheater is reduced, and the device load is reduced.

[0039] Accordingly, the present invention provides a method for flue gas treatment using the above flue gas treatment system, which is characterized in that the flue gas treatment process is as follows: the flue gas is discharged into the atmosphere after heat exchange through the aforementioned flue gas treatment system.

[0040] In another embodiment, after the flue gas exits the boiler, it exchanges heat through the first air preheater and the second air preheater, and finally is discharged into the atmosphere; the flue gas outlet temperature of the first air preheater is controlled to be higher than the melting point of ammonium bisulfate, and the flue gas temperature of the second air preheater is controlled to be lower than the melting point of ammonium bisulfate.

[0041] Preferably, the flue gas treatment system is further provided with a denitration device, a first low-low temperature economizer, a dust removal device, an induced draft fan, a desulfurization device, and a chimney. The flue gas exits the boiler and then sequentially passes through the denitration device, the first air preheater, the second air preheater, the first low-low temperature economizer, the dust removal device, the induced draft fan, the desulfurization device, and the chimney and is discharged into the atmosphere.

[0042] The primary air enters the system through the primary air fan, and then sequentially exchanges heat through the first air preheater and then enters the boiler through the coal feeder; preferably, a bypass is provided between the primary air inlet and the primary air outlet of the first air preheater, and there is a valve on the bypass to adjust the amount of primary air entering the first air preheater.

[0043] The secondary air enters the system through the secondary air fan, and then sequentially exchanges heat through the second air preheater and the first air preheater and then enters the boiler; preferably, a second low-low temperature economizer is provided in the secondary air duct between the first air preheater and the second air preheater. The secondary air enters the system through the secondary air fan, and then sequentially passes through the second air preheater, the second low-low temperature economizer, and the first air preheater and enters the boiler. Through the second low-low temperature economizer, heat exchange between the secondary air and the boiler condensate can be achieved, transferring the heat of the secondary air to the boiler feed water, increasing the temperature of the boiler feed water, and reducing the temperature of the secondary air entering the first air preheater, thereby increasing the heat transfer temperature difference of the first air preheater.

[0044] In another embodiment of the present invention, the flue gas treatment system includes: a boiler, a coal feeder, a primary air fan, a secondary air fan, a first air preheater, a second air preheater, and a third air preheater.

[0045] The first air preheater adopts a conventional two-chamber rotary air preheater for realizing heat exchange between the flue gas and the secondary air. The flue gas outlet temperature of the first air preheater is higher than the melting point of ammonium bisulfate, avoiding the phenomenon of ammonium bisulfate condensation and blockage in the first air preheater.

[0046] Both the second air preheater and the third air preheater adopt the air preheater with a partition self-cleaning function described in the present invention. Due to the partition self-cleaning function of the second air preheater and the third air preheater, the phenomenon of ammonium bisulfate blockage can be avoided.

[0047] During the operation of the flue gas treatment system, the flue gas is divided into two paths after coming out of the boiler:

[0048] One path of the flue gas sequentially passes through the first air preheater and the second air preheater, and this path of flue gas exchanges heat with the secondary air; the other path of flue gas passes through the third air preheater, and this path of flue gas exchanges heat with the primary air; after the flue gas coming out of the second air preheater and the flue gas from the outlet of the third air preheater converge, they are finally discharged into the atmosphere.

[0049] Preferably, the flue gas treatment system is also provided with a denitration device. After the flue gas comes out of the boiler, it first enters the denitration device, and after coming out of the denitration device, the flue gas is divided into two paths.

[0050] Preferably, the flue gas treatment system is also provided with a first low-low temperature economizer, a dust removal device, an induced draft fan, a desulfurization device and a chimney. After the flue gas coming out of the second air preheater and the flue gas from the outlet of the third air preheater converge, they sequentially pass through the first low-low temperature economizer, the dust removal device, the induced draft fan, the desulfurization device, and the chimney and are discharged into the atmosphere.

[0051] The first low-low temperature economizer is arranged in the downstream flue after the flue gas from the second air preheater and the third air preheater converges, and uses the flue gas to heat the boiler feed water to further recover the waste heat in the flue gas. Optionally, the first low-low temperature economizer can also be arranged between the induced draft fan and the desulfurization device.

[0052] The primary air enters the system through the primary air fan, and then sequentially passes through the third air preheater and the coal feeder and enters the boiler. In the third air preheater, the primary air exchanges heat with the flue gas. Preferably, bypasses are provided at the primary air inlet and outlet of the third air preheater, and valves are provided on the bypasses to adjust the air volume of the primary air entering the third air preheater.

[0053] The secondary air enters the system through the secondary air fan, and then sequentially passes through the second air preheater and the first air preheater and enters the boiler.

[0054] Preferably, a second low-low temperature economizer is arranged in the secondary air duct between the first air preheater and the second air preheater. The second low-low temperature economizer can realize the heat exchange between the secondary air and the boiler condensate, transfer the heat of the secondary air to the boiler feed water, increase the temperature of the boiler feed water, and reduce the temperature of the secondary air entering the first air preheater, thereby increasing the heat transfer temperature difference of the first air preheater.

[0055] The present invention provides three air preheaters. The first air preheater adopts a conventional rotary air preheater, which can give full play to the advantages of high heat transfer surface density, compact structure, small volume, and flexible layout of the rotary air preheater. At the same time, the flue gas outlet temperature of the first air preheater is controlled to be higher than the melting point of ammonium bisulfate, thereby avoiding blockage and corrosion caused by ammonium bisulfate. The second air preheater and the third air preheater adopt the air preheater with the function of zone self-cleaning provided by the present invention, so that the flue gas temperature of the second air preheater and the third air preheater can be lower than the melting point of ammonium bisulfate. Compared with the conventional process flow that only adopts a three-compartment rotary air preheater, more flue gas heat is recovered, the boiler efficiency is improved, blockage and corrosion phenomena are avoided, and at the same time, the second and third air preheaters are both of all-welded structures, which can avoid the leakage of secondary air and flue gas, and primary air and flue gas. Therefore, the secondary air volume, primary air volume, and flue gas volume will be reduced, the power of the secondary air fan, primary air fan, and induced draft fan will be reduced, and the power consumption will be correspondingly reduced. At the same time, after the flue gas volume is reduced, the flue gas treatment volume of the dust removal device and desulfurization device downstream of the air preheater is reduced, and the device load is reduced.

[0056] Through the coordinated cooperation of the conventional rotary air preheater and the air preheater with the function of zone self-cleaning provided by the present invention, the system can improve the boiler efficiency and the utilization rate of flue gas waste heat, and at the same time avoid blockage and corrosion caused by ammonium bisulfate, and has broad market application prospects.

[0057] Correspondingly, the present invention provides a method for treating flue gas using the above flue gas treatment system, which is characterized in that the flue gas treatment process is as follows:

[0058] After the flue gas comes out of the boiler, it is divided into two paths: one path of flue gas sequentially passes through the first air preheater and the second air preheater. This path of flue gas exchanges heat with the secondary air, and the flue gas outlet temperature of the first air preheater is controlled to be higher than the melting point of ammonium bisulfate; the flue gas outlet temperature of the second air preheater is controlled to be lower than the melting point of ammonium bisulfate; the other path of flue gas passes through the third air preheater. This path of flue gas exchanges heat with the primary air, and the flue gas outlet temperature of the third air preheater is controlled to be lower than the melting point of ammonium bisulfate. After the flue gas coming out of the second air preheater and the flue gas coming out of the third air preheater outlet converge, they are finally discharged into the atmosphere.

[0059] Preferably, the flue gas treatment system is further provided with a denitration device. After the flue gas comes out of the boiler, it first enters the denitration device, and then the flue gas is divided into two paths after coming out of the denitration device.

[0060] Preferably, the flue gas treatment system is further provided with a first low-low temperature economizer, a dust removal device, an induced draft fan, a desulfurization device, and a chimney. After the flue gas coming out of the second air preheater and the flue gas coming out of the third air preheater outlet converge, they sequentially pass through the first low-low temperature economizer, the dust removal device, the induced draft fan, the desulfurization device, and the chimney and are discharged into the atmosphere.

[0061] The primary air enters the system through the primary air fan, and then successively passes through the third air preheater and the coal feeder into the boiler, where heat exchange occurs between the primary air and the flue gas in the third air preheater. Preferably, bypasses are provided at the inlet and outlet of the primary air in the third air preheater, and valves are provided on the bypasses to adjust the flow rate of the primary air entering the third air preheater.

[0062] The secondary air enters the system through the secondary air fan, and then successively passes through the second air preheater and the first air preheater into the boiler. Preferably, a second low-low temperature economizer is provided in the secondary air duct between the first air preheater and the second air preheater. The second low-low temperature economizer can achieve heat exchange between the secondary air and the boiler condensate, transfer the heat of the secondary air to the boiler feed water, increase the temperature of the boiler feed water, and reduce the temperature of the secondary air entering the first air preheater, thereby increasing the heat transfer temperature difference of the first air preheater.

[0063] In another embodiment of the present invention, the flue gas treatment system includes: a boiler, a coal feeder, a primary air fan, a secondary air fan, a first air preheater, and a second air preheater. Both the first air preheater and the second air preheater adopt the air preheater with a partition self-cleaning function described in the present invention.

[0064] Due to the partition self-cleaning function of the first air preheater and the second air preheater, blockage and corrosion caused by ammonium bisulfate can be avoided.

[0065] During the operation of the flue gas treatment system, the flue gas is divided into two paths after coming out of the boiler: one path of flue gas successively passes through the first air preheater, and heat exchange occurs between this path of flue gas and the secondary air; the other path of flue gas passes through the second air preheater, and heat exchange occurs between this path of flue gas and the primary air; after the flue gas coming out of the first air preheater and the flue gas from the outlet of the second air preheater converge, they are finally discharged into the atmosphere.

[0066] Preferably, a denitration device is also provided in the flue gas treatment system. The flue gas enters the denitration device first after coming out of the boiler, and then the flue gas is divided into two paths after coming out of the denitration device.

[0067] Preferably, the flue gas treatment system is also provided with a low-low temperature economizer, a dust removal device, an induced draft fan, a desulfurization device, and a chimney. After the flue gas coming out of the first air preheater and the flue gas from the outlet of the second air preheater converge, they successively pass through the low-low temperature economizer, the dust removal device, the induced draft fan, the desulfurization device, and the chimney and are discharged into the atmosphere.

[0068] The low-low temperature economizer is arranged in the downstream flue after the flue gas from the first air preheater and the second air preheater converges, and uses the flue gas to heat the boiler feed water to further recover the waste heat in the flue gas. Optionally, the low-low temperature economizer can also be arranged between the induced draft fan and the desulfurization device.

[0069] The primary air enters the system via the primary air fan, and then successively passes through the second air preheater and the coal feeder and enters the boiler. In the second air preheater, the primary air exchanges heat with the flue gas. Preferably, bypasses are provided at the inlet and outlet of the primary air in the second air preheater, and valves are provided on the bypasses to adjust the amount of primary air entering the second air preheater.

[0070] The secondary air enters the system via the secondary air fan, and then enters the boiler through the first air preheater.

[0071] By providing two air preheaters with the function of partition self-cleaning and their coordinated cooperation, it can improve the boiler efficiency and the utilization rate of the waste heat recovery of the flue gas, and at the same time avoid the blockage and corrosion caused by ammonium bisulfate, and has broad market application prospects.

[0072] Since the first and second air preheaters in the system are both of all-welded structures, the leakage between the primary air and the flue gas and between the secondary air and the flue gas can be avoided. Therefore, the amounts of the primary air, the secondary air, and the flue gas will be reduced, and the powers of the primary air induced draft fan, the secondary air fan, and the induced draft fan will be reduced, and the power consumption will be correspondingly reduced. At the same time, after the amount of the flue gas is reduced, the flue gas treatment amounts of the dust removal device and the desulfurization device downstream of the air preheater are reduced, and the device load is decreased.

[0073] Correspondingly, another object of the present invention is to provide a method for treating flue gas using the above flue gas treatment system, including the following steps:

[0074] After the flue gas comes out of the boiler, it is divided into two paths: one path of the flue gas successively passes through the first air preheater, and this path of the flue gas exchanges heat with the secondary air; the other path of the flue gas passes through the second air preheater, and this path of the flue gas exchanges heat with the primary air; after the flue gas coming out of the first air preheater and the flue gas coming out of the outlet of the second air preheater are merged, it is finally discharged into the atmosphere. Control the flue gas outlet temperatures of the first air preheater and the second air preheater to be lower than the melting point of ammonium bisulfate.

[0075] Preferably, a denitration device is further provided in the flue gas treatment system. After the flue gas comes out of the boiler, it first enters the denitration device, and after coming out of the denitration device, the flue gas is divided into two paths.

[0076] Preferably, a low-low temperature economizer, a dust removal device, an induced draft fan, a desulfurization device, and a chimney are further provided in the flue gas treatment system. After the flue gas coming out of the first air preheater and the flue gas coming out of the outlet of the second air preheater are merged, they successively pass through the low-low temperature economizer, the dust removal device, the induced draft fan, the desulfurization device, and the chimney and are discharged into the atmosphere.

[0077] The primary air enters the system through the primary air fan, and then successively passes through the second air preheater and the coal feeder into the boiler, where heat exchange occurs between the primary air and the flue gas in the second air preheater. Preferably, bypasses are provided at the primary air inlet and outlet of the second air preheater, and valves are provided on the bypasses to adjust the amount of primary air entering the second air preheater.

[0078] The secondary air enters the system through the secondary air fan, and then enters the boiler through the first air preheater. Description of the Drawings

[0079] Figure 1 : Schematic diagram of the flue gas treatment system of a conventional coal-fired power plant boiler in the prior art;

[0080] Figure 2: Schematic structural diagram of the air preheater with a partition self-cleaning function provided by the present invention;

[0081] Figure 3: Two-dimensional structural diagram of the air preheater with a partition self-cleaning function provided by the present invention;

[0082] Figure 4 : Schematic diagram of the heat transfer module of the air preheater with a partition self-cleaning function provided by the present invention;

[0083] Figure 5 : Figure 4 Schematic diagram of the heat transfer channel of the shown heat transfer module;

[0084] Figure 6 : Schematic diagram of the flue gas treatment system provided by the present invention;

[0085] Figure 7 : Another schematic diagram of the flue gas treatment system provided by the present invention;

[0086] Figure 8 : Another schematic diagram of the flue gas treatment system provided by the present invention. Detailed Embodiments

[0087] The present invention will now be further described in detail with reference to the accompanying drawings, but the following embodiments do not constitute a limitation to the present invention.

[0088] Figures 2-5 show schematic structural diagrams of the air preheater with a partition self-cleaning function provided by the present invention. The air preheater includes n heat transfer modules, n≥2, and is characterized in that:

[0089] The heat transfer module is formed by welding a set of opposite sides of two heat transfer plates to form a plate pair, and multiple plate pairs are stacked to form a heat transfer module. A cold fluid channel is formed inside the plate pair, and the other set of opposite sides of the plate pair are not welded together, forming a cold fluid inlet and a cold fluid outlet of the heat transfer module; a hot fluid channel is formed between the plate pairs along the direction of the welded set of opposite sides; the flow direction of the hot fluid and the flow direction of the cold fluid in the heat transfer module are perpendicular, for cross-flow heat exchange.

[0090] The 1st, 2nd, ……, (n - 1)th, and nth heat transfer modules are arranged in sequence; each two heat transfer modules are connected by a transition header, and no heat transfer module is arranged inside the transition header.

[0091] At the cold fluid inlet 2’ of the 1st heat transfer module, a cold fluid inlet header 2 is provided.

[0092] At the cold fluid outlet 5’ of the 1st heat transfer module, a 1st turning header is provided. The 1st turning header connects the cold fluid outlet of the 1st heat transfer module and the cold fluid inlet of the 2nd heat transfer module; in the same way, at the cold fluid outlet of the (n - 1)th heat transfer module, an (n - 1)th turning header is provided, and the (n - 1)th turning header connects the cold fluid outlet of the (n - 1)th heat transfer module and the cold fluid inlet of the nth heat transfer module; at the cold fluid outlet of the nth heat transfer module, a cold fluid outlet header 5 is provided.

[0093] Inside the cold fluid inlet header 2, a cold fluid inlet header partition plate 4 parallel to the heat transfer plates of the 1st heat transfer module is provided. The cold fluid inlet header partition plate 4 divides the cold fluid inlet header 2 into several sub-headers, and there is no leakage between the respective sub-headers. A corresponding cold fluid inlet cut-off mechanism 3 is provided in each sub-header, and each cold fluid inlet cut-off mechanism 3 can be independently controlled to open.

[0094] Inside the turning header 8, a turning header partition plate 10 is provided. The number of turning header partition plates 10 is the same as and corresponds one-to-one with the cold fluid inlet header partition plates 4, and each turning header partition plate 10 is in the same plane as the corresponding cold fluid inlet header partition plate 4.

[0095] Thus, the cold fluid passes through The cold fluid inlet header 2 enters the air preheater and is by enters through the cold fluid inlet 2’ of the 1st heat transfer module the cold fluid passage, then flows into the 1st turning header through the cold fluid outlet 5’ of the heat transfer module, and under the guidance of the 1st turning header partition plate 10, enters the cold fluid channel of the 2nd heat transfer module through the cold fluid inlet of the 2nd heat transfer module, and finally flows out of the preheater through the cold fluid outlet 5’ of the nth heat transfer module and the cold fluid outlet header 5.

[0096] On a pair of opposite sides of the plate pair group welded in the nth heat transfer module, a hot fluid inlet header 6 is provided. The hot fluid enters the hot fluid channel of the nth heat transfer module through the hot fluid inlet header 6, then flows through the transition header and enters the hot fluid channel of the (n - 1)th heat transfer module, and finally flows out through the hot fluid outlet header 1 of the first heat transfer module.

[0097] Preferably, the heat transfer plates are corrugated plates, and there is no particular limitation on the shape of the corrugations, which can be corrugations with protrusions or depressions.

[0098] The air preheater described in this patent is a plate heat exchanger structure with a fully welded structure, and the hot and cold fluids exchange heat through a partition wall, without any problem of leakage.

[0099] Preferably, the cold fluid inlet cut-off mechanism is a gate with opening and closing functions, such as a flap valve, a plug valve, a louver valve, etc. The form of the cold fluid inlet cut-off mechanism of the present invention is not particularly limited.

[0100] The working principle of the air preheater with a partitioned self-cleaning function described in the present invention is as follows:

[0101] Since the cold fluid inlet header 2 of the first heat transfer module is divided into several sub-headers by the cold fluid inlet partition plate 4, and a cold fluid inlet cut-off mechanism 3 that can be independently controlled to open is provided in each sub-header. Therefore, when the cold fluid inlet cut-off mechanism 3 in a certain sub-header is closed, the cold fluid will not enter the cold fluid channel corresponding to that sub-header, but the hot fluid can still enter the corresponding hot fluid channel. Since there is no cold fluid passing through the cold fluid channel, there is no heat exchange on the corresponding heat transfer plates. Therefore, the ammonium bisulfate adhering to the heat transfer plates can be heated by the high-temperature hot fluid. The ammonium bisulfate melts when heated, and the melted ammonium bisulfate is carried away by the hot fluid, achieving the self-heating cleaning effect of the corresponding heat transfer plates. When the cold fluid inlet cut-off mechanisms 3 are closed in turn, the partitioned self-heating cleaning function of all the heat transfer plates can be realized.

[0102] Figure 6 Shows a flue gas treatment system using the above-mentioned air preheater with a partitioned self-cleaning function provided by the present invention. The flue gas treatment system includes a boiler 1; a coal feeder 2; a primary air fan 3; a secondary air fan 4; a dust removal device 5; an induced draft fan 6; a desulfurization device 7; a chimney 8; a denitration device 9; a first air preheater 10; a first low-low temperature economizer 11; a second air preheater 12; a second low-low temperature economizer 13.

[0103] The first air preheater 10 uses a conventional rotary air preheater, which can realize the heat exchange between flue gas and primary air and secondary air.

[0104] Preferably, the flue gas outlet temperature of the first air preheater 10 is higher than the melting point of ammonium bisulfate to avoid the blockage of the first air preheater 10 caused by the condensation of ammonium bisulfate.

[0105] The second air preheater 12 adopts the air preheater with the partition self-cleaning function described in the present invention. The flue gas outlet temperature of the second air preheater 12 can be lower than the melting point of ammonium bisulfate. Since the second air preheater 12 has the partition self-cleaning function, the blockage phenomenon caused by ammonium bisulfate can be avoided.

[0106] During the operation of the flue gas treatment system, the flue gas flows through the denitration device 9, the first air preheater 10, the second air preheater 12, the second low-low temperature economizer 11, the dust removal device 5, the induced draft fan 6, the desulfurization device 7, and the chimney 8 in sequence after leaving the boiler 1 and is discharged into the atmosphere. Optionally, the first low-low temperature economizer 11 can also be arranged between the induced draft fan 6 and the desulfurization device 7. The first low-low temperature economizer 11 is arranged in the flue downstream of the second air preheater to heat the boiler feed water with the flue gas and further recover the waste heat in the flue gas.

[0107] The primary air enters the system through the primary air fan 3, and then passes through the first air preheater 10 and the coal feeder 2 into the boiler 1 in sequence. Preferably, a bypass is arranged between the primary air inlet and the primary air outlet of the first air preheater 10, and there is a valve on the bypass to adjust the primary air volume entering the first air preheater.

[0108] The secondary air enters the system through the secondary air fan 4, and then passes through the second air preheater 12 and the first air preheater 10 into the boiler 1 in sequence. Preferably, a second low-low temperature economizer 13 is arranged in the secondary air duct between the first air preheater 10 and the second air preheater 12. The secondary air enters the system through the secondary air fan 4, and then passes through the second air preheater 12, the second low-low temperature economizer 13, and the first air preheater 10 into the boiler 1 in sequence. Through the second low-low temperature economizer 13, the heat exchange between the secondary air and the boiler condensate can be realized, the heat of the secondary air is transferred to the boiler feed water, the temperature of the boiler feed water is increased, and the temperature of the secondary air entering the first air preheater 10 is reduced, thereby increasing the heat transfer temperature difference of the first air preheater 10.

[0109] Correspondingly, the present invention provides a method for treating flue gas using the above flue gas treatment system. After the flue gas leaves the boiler 1, it is heat-exchanged by the first air preheater 10 and the second air preheater 12 and finally discharged into the atmosphere; the flue gas outlet temperature of the first air preheater 10 is controlled to be higher than the melting point of ammonium bisulfate, and the flue gas temperature of the second air preheater 12 is controlled to be lower than the melting point of ammonium bisulfate.

[0110] Preferably, the flue gas treatment system is further provided with a denitration device 9, a first low-low temperature economizer 11, a dust removal device 5, an induced draft fan 6, a desulfurization device 7 and a chimney 8. The flue gas exits from the boiler 1 and then successively passes through the denitration device 9, the first air preheater 10, the second air preheater 12, the first low-low temperature economizer 11, the dust removal device 5, the induced draft fan 6, the desulfurization device 7, and the chimney 8 and is discharged into the atmosphere.

[0111] The primary air enters the system through the primary air fan 3, and then successively exchanges heat through the first air preheater 10 and then enters the boiler 1 through the coal feeder 2; the secondary air enters the system through the secondary air fan 4, and then successively exchanges heat through the second air preheater 12 and the first air preheater 10 and then enters the boiler 1; preferably, a second low-low temperature economizer 13 is provided in the secondary air duct between the first air preheater and the second air preheater. The secondary air enters the system through the secondary air fan 4, and then successively passes through the second air preheater 12, the second low-low temperature economizer 13, and the first air preheater and enters the boiler 1.

[0112] Figure 7 Shows another flue gas treatment system provided by the present invention that uses the above-mentioned air preheater with a partition self-cleaning function. The flue gas treatment system includes a boiler 1; a coal feeder 2; a primary air fan 3; a secondary air fan 4; a dust removal device 5; an induced draft fan 6; a desulfurization device 7; a chimney 8; a denitration device 9; a first air preheater 10; a first low-low temperature economizer 11; a second air preheater 12; a second low-low temperature economizer 13, and a third air preheater 14.

[0113] The first air preheater 10 uses a conventional two-compartment rotary air preheater to realize the heat exchange between the flue gas and the secondary air. The flue gas outlet temperature of the first air preheater 10 is higher than the melting point of ammonium bisulfate, avoiding the phenomenon of ammonium bisulfate condensation and blockage in the first air preheater 10.

[0114] Both the second air preheater 12 and the third air preheater 14 use the air preheater with a partition self-cleaning function described in the present invention. Since the second and third air preheaters have a partition self-cleaning function, problems such as blockage and corrosion caused by ammonium bisulfate can be avoided.

[0115] The flue gas exits from the boiler 1 and then enters the denitration device 9. After exiting from the denitration device 9, the flue gas is divided into two paths:

[0116] One path of the flue gas successively passes through the first air preheater 10 and the second air preheater 12. This path of the flue gas exchanges heat with the secondary air; the other path of the flue gas passes through the third air preheater 14. This path of the flue gas exchanges heat with the primary air; after the flue gas exiting from the second air preheater 12 converges with the flue gas exiting from the outlet of the third air preheater, it is finally discharged into the atmosphere.

[0117] Preferably, the flue gas treatment system is further provided with a first low-low temperature economizer 11, a dust removal device 5, an induced draft fan 6, a desulfurization device 7, and a chimney 8. The flue gas coming out of the second air preheater 12 and the flue gas from the outlet of the third air preheater are merged and then sequentially pass through the first low-low temperature economizer 11, the dust removal device 5, the induced draft fan 6, the desulfurization device 7, and the chimney 8 and are discharged into the atmosphere.

[0118] The first low-low temperature economizer 11 is arranged in the downstream flue after the flue gas of the second air preheater 12 and the third air preheater 14 is merged, uses the flue gas to heat the boiler feed water, and further recovers the waste heat in the flue gas. Optionally, the first low-low temperature economizer 11 can also be arranged between the induced draft fan 6 and the desulfurization device 7.

[0119] The primary air enters the system through the primary air fan 3, and then sequentially passes through the third air preheater 14 and the coal feeder 2 and enters the boiler 1. In the third air preheater 14, the primary air exchanges heat with the flue gas. Preferably, bypasses are provided at the primary air inlet and outlet of the third air preheater 14, and valves are provided on the bypasses to adjust the primary air volume entering the third air preheater 14.

[0120] The secondary air enters the system through the secondary air fan 4, and then sequentially passes through the second air preheater 12 and the first air preheater 10 and enters the boiler 1.

[0121] Preferably, a second low-low temperature economizer 13 is arranged in the secondary air duct between the first air preheater 10 and the second air preheater 12. The second low-low temperature economizer 13 can realize the heat exchange between the secondary air and the boiler condensate, transfer the heat of the secondary air to the boiler feed water, increase the temperature of the boiler feed water, and reduce the temperature of the secondary air entering the first air preheater 10, thereby increasing the heat transfer temperature difference of the first air preheater 10.

[0122] Correspondingly, the present invention provides a method for treating flue gas using the above flue gas treatment system. The flue gas treatment process is as follows: The flue gas coming out of the boiler 1 is divided into two paths: One path of flue gas sequentially passes through the first air preheater 10 and the second air preheater 12. This path of flue gas exchanges heat with the secondary air, and the flue gas outlet temperature of the first air preheater 10 is controlled to be higher than the melting point of ammonium bisulfate; the flue gas outlet temperature of the second air preheater 12 is controlled to be lower than the melting point of ammonium bisulfate; the other path of flue gas passes through the third air preheater 14. This path of flue gas exchanges heat with the primary air, and the flue gas outlet temperature of the third air preheater 14 is controlled to be lower than the melting point of ammonium bisulfate. The flue gas coming out of the second air preheater 12 and the flue gas from the outlet of the third air preheater 14 are merged and finally discharged into the atmosphere.

[0123] Preferably, the flue gas treatment system is further provided with a first low-low temperature economizer 11, a dust removal device 5, an induced draft fan 6, a desulfurization device 7, and a chimney 8. The flue gas coming out of the second air preheater 12 and the flue gas from the outlet of the third air preheater are combined and then sequentially pass through the first low-low temperature economizer 11, the dust removal device 5, the induced draft fan 6, the desulfurization device 7, and the chimney 8 and are discharged into the atmosphere.

[0124] The primary air enters the system through the primary air fan 3, and then sequentially passes through the third air preheater 14, the coal feeder 2 and enters the boiler 1. In the third air preheater 14, the primary air exchanges heat with the flue gas. Preferably, bypasses are provided at the inlet and outlet of the primary air in the third air preheater 14, and valves are provided on the bypasses to adjust the amount of primary air entering the third air preheater 14.

[0125] The secondary air enters the system through the secondary air fan 4, and then sequentially passes through the second air preheater 12 and the first air preheater 10 and enters the boiler 1. Preferably, a second low-low temperature economizer 13 is provided in the secondary air duct between the first air preheater 10 and the second air preheater 12. The second low-low temperature economizer 13 can realize the heat exchange between the secondary air and the boiler condensate, transfer the heat of the secondary air to the boiler feed water, and increase the temperature of the boiler feed water.

[0126] Figure 8 Shows another flue gas treatment system provided by the present invention that uses the air preheater with the above-mentioned partition self-cleaning function. The flue gas treatment system includes a boiler 1; a coal feeder 2; a primary air fan 3; a secondary air fan 4; a dust removal device 5; an induced draft fan 6; a desulfurization device 7; a chimney 8; a denitration device 9; a first air preheater 10; a low-low temperature economizer 11; a second air preheater 12.

[0127] Both the first air preheater 10 and the second air preheater 12 adopt the air preheater with the partition self-cleaning function described in the present invention. The blockage and corrosion phenomena caused by ammonium bisulfate can be avoided.

[0128] During the operation of the flue gas treatment system, the flue gas is divided into two paths after coming out of the boiler 1: one path of flue gas sequentially passes through the first air preheater 10, and this path of flue gas exchanges heat with the secondary air; the other path of flue gas passes through the second air preheater 12, and this path of flue gas exchanges heat with the primary air; the flue gas coming out of the first air preheater 10 and the flue gas from the outlet of the second air preheater 12 are combined and finally discharged into the atmosphere.

[0129] Preferably, the flue gas treatment system is further provided with a low-low temperature economizer 11, a dust removal device 5, an induced draft fan 6, a desulfurization device 7 and a chimney 8. The flue gas coming out of the first air preheater 10 and the flue gas from the outlet of the second air preheater 12 are merged and then sequentially pass through the low-low temperature economizer 11, the dust removal device 5, the induced draft fan 6, the desulfurization device 7, and the chimney 8 and are discharged into the atmosphere.

[0130] The low-low temperature economizer 11 is arranged in the downstream flue after the flue gas of the first air preheater 10 and the second air preheater 12 is merged, uses the flue gas to heat the boiler feed water, and further recovers the waste heat in the flue gas. Optionally, the low-low temperature economizer 11 can also be arranged between the induced draft fan 6 and the desulfurization device 7.

[0131] The primary air enters the system through the primary air fan 3, and then sequentially passes through the second air preheater 12 and the coal feeder 2 and enters the boiler 1. In the second air preheater 12, the primary air exchanges heat with the flue gas. Preferably, bypasses are provided at the primary air inlet and outlet of the second air preheater 12, and valves are provided on the bypasses to adjust the primary air volume entering the second air preheater 12.

[0132] The secondary air enters the system through the secondary air fan 4, and then enters the boiler 1 through the first air preheater 10.

[0133] Correspondingly, another object of the present invention is to provide a method for treating flue gas using the above flue gas treatment system, including the following steps:

[0134] After the flue gas comes out of the boiler 1, it is divided into two paths: one path of flue gas sequentially passes through the first air preheater 10, and this path of flue gas exchanges heat with the secondary air; the other path of flue gas passes through the second air preheater 12, and this path of flue gas exchanges heat with the primary air; after the flue gas coming out of the first air preheater 10 and the flue gas from the outlet of the second air preheater 12 are merged, it is finally discharged into the atmosphere. The flue gas outlet temperatures of the first air preheater 10 and the second air preheater 12 are controlled to be lower than the melting point of ammonium bisulfate.

[0135] Preferably, the flue gas treatment system is further provided with a low-low temperature economizer 11, a dust removal device 5, an induced draft fan 6, a desulfurization device 7 and a chimney 8. The flue gas coming out of the first air preheater 10 and the flue gas from the outlet of the second air preheater 12 are merged and then sequentially pass through the low-low temperature economizer 11, the dust removal device 5, the induced draft fan 6, the desulfurization device 7, and the chimney 8 and are discharged into the atmosphere.

[0136] The primary air enters the system through the primary air fan 3, then successively passes through the second air preheater 12, the coal feeder 2 and enters the boiler 1, where heat exchange occurs between the primary air and the flue gas in the second air preheater 12. Preferably, bypasses are provided at the inlet and outlet of the primary air in the second air preheater 12, and valves are provided on the bypasses to adjust the air volume of the primary air entering the second air preheater 12.

[0137] The secondary air enters the system through the secondary air fan 4, and then enters the boiler 1 through the first air preheater 10.

[0138] The above has introduced in detail the air preheater, flue gas treatment system and treatment method provided by the present invention. Specific examples are used in this article to elaborate on the principle and implementation mode of the present invention. The above description of the implementation is only for helping to understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation mode and application scope. It is possible to make changes and improvements to the present invention without exceeding the concept and scope defined by the appended claims. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. An air preheater with a partition self-cleaning function, comprising n heat transfer modules, where n ≥ 2, characterized in that: At the cold fluid inlet (2’) of the first heat transfer module, a cold fluid inlet header (2) is provided. At the cold fluid outlet (5’) of the first heat transfer module, a first turning header is provided. The first turning header connects the cold fluid outlet of the first heat transfer module and the cold fluid inlet of the second heat transfer module. In the same way, at the cold fluid outlet of the (n - 1)-th heat transfer module, an (n - 1)-th turning header is provided, and the (n - 1)-th turning header connects the cold fluid outlet of the (n - 1)-th heat transfer module and the cold fluid inlet of the n-th heat transfer module. At the cold fluid outlet of the n-th heat transfer module, a cold fluid outlet header (5) is provided. Inside the cold fluid inlet header (2), a cold fluid inlet header partition plate (4) parallel to the heat transfer plates of the heat transfer module is provided, which divides the cold fluid inlet header (2) into several sub-headers. In each sub-header, a corresponding cold fluid inlet cut-off mechanism (3) is provided, and the cold fluid inlet cut-off mechanism (3) can be independently controlled to open. Inside the turning header, a turning header partition plate (10) is provided. The number of turning header partition plates (10) is the same as and corresponds one-to-one with the cold fluid inlet header partition plates (4). Each turning header partition plate (10) is in the same plane as a corresponding cold fluid inlet header partition plate (4). The n-th heat transfer module is provided with a hot fluid inlet header (6). The hot fluid enters the hot fluid channels of the n-th heat transfer module through the hot fluid inlet header (6), then flows through the transition header and enters the hot fluid channels of the (n - 1)-th heat transfer module, and finally flows out through the hot fluid outlet header (1) of the first heat transfer module. The heat transfer module is formed by welding a set of opposite sides of two heat transfer plates to form a plate pair, and multiple plate pairs are stacked to form the heat transfer module. A cold fluid channel is formed inside the plate pair, and the other set of opposite sides of the plate pair are not welded together to form the cold fluid inlet and the cold fluid outlet of the heat transfer module. Between the plate pairs, a hot fluid channel is formed along the direction of the set of welded opposite sides. When the cold fluid inlet cut-off mechanisms (3) are alternately opened and closed, the function of self-heating and cleaning the heat transfer plates in zones is realized. The cold fluid inlet cut-off mechanism is a flap valve, a plug valve or a louver valve with opening and closing functions.

2. The air preheater according to claim 1, characterized in that: During the flue gas treatment process, by alternately closing the cold fluid inlet cut-off mechanisms, the self-cleaning of all heat transfer plates can be realized by using the hot fluid.

3. The air preheater according to claim 1, characterized in that: The air preheater adopts a plate heat exchanger structure with a fully welded structure.

4. The air preheater according to claim 3, characterized in that: In the heat transfer module, the flow direction of the hot fluid and the flow direction of the cold fluid are perpendicular, and it is cross-flow heat exchange.

5. The air preheater according to claim 4, wherein: The heat transfer plates are corrugated plates.

6. A flue gas treatment system, characterized in that, The flue gas treatment system is provided with an air preheater having a self-cleaning function in zones as described in any one of claims 1 - 5.

7. The flue gas treatment system according to claim 6, characterized in that: The flue gas treatment system includes a boiler, a coal feeder, a primary air fan, a secondary air fan, a first air preheater and a second air preheater. The first air preheater is a rotary air preheater for realizing heat exchange between flue gas and primary air and secondary air. The second air preheater is the air preheater having the self-cleaning function in zones.

8. The flue gas treatment system according to claim 7, wherein: The boiler flue gas is discharged into the atmosphere finally after heat exchange through the first air preheater and the second air preheater from the boiler outlet.

9. The flue gas treatment system according to claim 8, wherein: The flue gas treatment system is also provided with a denitration device, a first low-low temperature economizer, a dust removal device, an induced draft fan, a desulfurization device and a chimney; the flue gas is discharged into the atmosphere successively through the denitration device, the first air preheater, the second air preheater, the first low-low temperature economizer, the dust removal device, the induced draft fan, the desulfurization device and the chimney from the boiler outlet.

10. The flue gas treatment system according to claim 7, characterized in that: The primary air enters the system through the primary air fan, and then enters the boiler through the first air preheater and the coal feeder; the secondary air enters the system through the secondary air fan, and then enters the boiler through the second air preheater and the first air preheater.

11. The flue gas treatment system according to claim 10, characterized in that: A second low-low temperature economizer is also arranged in the secondary air duct between the first air preheater and the second air preheater. The secondary air enters the system through the secondary air fan, and then enters the boiler through the second air preheater, the second low-low temperature economizer and the first air preheater.

12. The flue gas treatment system according to claim 7, characterized in that: When conducting flue gas treatment, control the flue gas outlet temperature of the first air preheater to be higher than the melting point of ammonium bisulfate.

13. The flue gas treatment system according to claim 12, characterized in that: When conducting flue gas treatment, control the flue gas temperature of the second air preheater to be lower than the melting point of ammonium bisulfate.

14. The flue gas treatment system according to claim 6, characterized in that: The flue gas treatment system includes: a boiler, a coal feeder, a primary air fan, a secondary air fan, a first air preheater, a second air preheater and a third air preheater; the first air preheater adopts a conventional two-chamber rotary air preheater for realizing heat exchange between the flue gas and the secondary air. Both the second air preheater and the third air preheater adopt the air preheater with the partition self-cleaning function.

15. The flue gas treatment system according to claim 14, wherein: The flue gas is divided into two paths after coming out of the boiler: one path of flue gas successively passes through the first air preheater and the second air preheater, and this path of flue gas exchanges heat with the secondary air; the other path of flue gas passes through the third air preheater, and this path of flue gas exchanges heat with the primary air; after the flue gas coming out of the second air preheater converges with the flue gas from the outlet of the third air preheater, it is finally discharged into the atmosphere.

16. The flue gas treatment system according to claim 15, characterized in that: The flue gas treatment system is also provided with a first low-low temperature economizer, a dust removal device, an induced draft fan, a desulfurization device and a chimney; after the flue gas coming out of the second air preheater converges with the flue gas from the outlet of the third air preheater, it successively passes through the first low-low temperature economizer, the dust removal device, the induced draft fan, the desulfurization device and the chimney and is discharged into the atmosphere.

17. The flue gas treatment system according to claim 15, wherein: The primary air enters the system through the primary air fan, and then enters the boiler through the third air preheater and the coal feeder; the secondary air enters the system through the secondary air fan, and then successively passes through the second air preheater and the first air preheater and enters the boiler.

18. The flue gas treatment system according to claim 17, characterized in that: In the secondary air duct between the first air preheater and the second air preheater, a second low-low temperature economizer is arranged, and the secondary air successively passes through the second air preheater, the second low-low temperature economizer and the first air preheater and enters the boiler.

19. The flue gas treatment system according to claim 14, wherein: When conducting flue gas treatment, control the flue gas outlet temperature of the first air preheater to be higher than the melting point of ammonium bisulfate.

20. The flue gas treatment system according to claim 14, wherein: When conducting flue gas treatment, control the flue gas outlet temperatures of the second air preheater and the third air preheater to be lower than the melting point of ammonium bisulfate.

21. The flue gas treatment system according to claim 6, characterized in that: The flue gas treatment system includes: a boiler, a coal feeder, a primary air fan, a secondary air fan, a first air preheater and a second air preheater; both the first air preheater and the second air preheater adopt the air preheater with the function of partition self-cleaning as described above; After the flue gas comes out of the boiler, it is divided into two paths: one path of flue gas passes through the first air preheater, and this path of flue gas exchanges heat with the secondary air; The other path of flue gas passes through the second air preheater, and this path of flue gas exchanges heat with the primary air; after the flue gas coming out of the first air preheater and the flue gas from the outlet of the second air preheater converge, it is finally discharged into the atmosphere.

22. The flue gas treatment system according to claim 21, wherein: The flue gas treatment system is also provided with a low-low temperature economizer, a dust removal device, an induced draft fan, a desulfurization device and a chimney; after the flue gas coming out of the first air preheater and the flue gas coming out of the second air preheater converge, they sequentially pass through the low-low temperature economizer, the dust removal device, the induced draft fan, the desulfurization device and the chimney and are discharged into the atmosphere.

23. The flue gas treatment system according to claim 21, characterized in that: The primary air enters the system through the primary air fan, then passes through the second air preheater and the coal feeder and enters the boiler; the secondary air enters the system through the secondary air fan, and then enters the boiler through the first air preheater.

24. A flue gas treatment method, characterized in that, The flue gas treatment system as claimed in claim 6 is used to perform heat exchange treatment on the flue gas and then discharged into the atmosphere.

25. A flue gas treatment method, characterized in that, The flue gas treatment system as claimed in claim 7 is used to perform heat exchange treatment on the flue gas and then discharged into the atmosphere.

26. The processing method according to claim 25, wherein The flue gas comes out of the boiler, exchanges heat through the first air preheater and the second air preheater and is then discharged into the atmosphere; the flue gas outlet temperature of the first air preheater is controlled to be higher than the melting point of ammonium bisulfate, and the flue gas temperature of the second air preheater is controlled to be lower than the melting point of ammonium bisulfate.

27. The processing method according to claim 25, wherein The primary air enters the system through the primary air fan, then exchanges heat through the first air preheater, and enters the boiler through the coal feeder.

28. The processing method according to claim 25, wherein: The secondary air enters the system through the secondary air fan, and then exchanges heat through the second air preheater and the first air preheater and enters the boiler.

29. A flue gas treatment method, characterized in that, The flue gas treatment system as claimed in claim 14 is used to perform heat exchange treatment on the flue gas and then discharged into the atmosphere.

30. The processing method according to claim 29, wherein After the flue gas comes out of the boiler, it is divided into two paths: one path of flue gas passes through the first air preheater and the second air preheater, and this path of flue gas exchanges heat with the secondary air; the other path of flue gas passes through the third air preheater, and this path of flue gas exchanges heat with the primary air; The flue gas outlet temperature of the first air preheater is controlled to be higher than the melting point of ammonium bisulfate; the flue gas outlet temperatures of the second air preheater and the third air preheater are controlled to be lower than the melting point of ammonium bisulfate; After the flue gas coming out of the second air preheater and the flue gas from the outlet of the third air preheater converge, it is finally discharged into the atmosphere.

31. The processing method according to claim 29, wherein, The primary air enters the system through the primary air fan, then passes through the third air preheater and the coal feeder and enters the boiler, and the primary air exchanges heat with the flue gas in the third air preheater; The secondary air enters the system through the secondary air fan, and then passes through the second air preheater and the first air preheater and enters the boiler.

32. A flue gas treatment method, characterized in that, The flue gas treatment system as claimed in claim 21 is used to perform heat exchange treatment on the flue gas and then discharged into the atmosphere.

33. The processing method according to claim 32, characterized in that, After the flue gas comes out of the boiler, it is divided into two paths: one path of the flue gas passes through the first air preheater in sequence, and this path of flue gas exchanges heat with the secondary air; the other path of flue gas passes through the second air preheater, and this path of flue gas exchanges heat with the primary air; after the flue gas coming out of the first air preheater and the flue gas coming out of the second air preheater converge, it is finally discharged into the atmosphere; Control the flue gas outlet temperatures of both the first air preheater and the second air preheater to be lower than the melting point of ammonium bisulfate.

34. The processing method according to claim 32, wherein, The primary air enters the system through the primary air fan, then passes through the second air preheater and the coal feeder and enters the boiler, and the primary air exchanges heat with the flue gas in the second air preheater; the secondary air enters the system through the secondary air fan, and then enters the boiler through the first air preheater.

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