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 having a partition self-cleaning function. The air preheater has a heat transfer module, a cold fluid inlet cut-off mechanism and a partition plate; the partition plate is arranged in the cold fluid inlet header of the housing, and divides the cold fluid inlet header of the housing into a plurality of cold fluid inlet sub-headers of the housing. Each cold fluid inlet sub-header of the housing is correspondingly provided with a cold fluid inlet cut-off mechanism, and each cold fluid inlet cut-off mechanism can be independently controlled to open. By separately controlling the cold fluid inlet cut-off mechanism, the self-cleaning function of all the heat transfer modules in the air preheater casing can be realized.

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 stored by the heat storage body. When the heat storage core body rotates to the primary air compartment and the secondary air compartment, the stored 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 arranged 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 viscous substance and is hygroscopic. It becomes acidic and corrosive after absorbing moisture. 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] In order to solve the air leakage problem of the rotary air preheater, CN210463080U provides an air preheater system for coal-fired power plants, which combines a tubular air preheater and a two-chamber rotary air preheater in parallel to form a new air preheater system, realizes the isolation of the primary air system and the flue gas, and reduces the impact of the primary air with a higher pressure on the air leakage rate of the air preheater. Although this system can alleviate the air leakage problem to a certain extent, it has a complex structure, is difficult to assemble and maintain the equipment, and cannot solve the problems of blockage and corrosion.

[0009] In order to solve the problems of clogging and corrosion of the rotary air preheater, the measures usually taken include: 1. Control the exhaust 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 recovery from the flue gas, which is not conducive to improving the efficiency of the boiler; 2. Set up a soot blower. The soot blower mainly includes sonic soot blowers, steam soot blowers, shock wave soot blowers, etc., which are limited by the soot blowing principle of the soot blower. Its soot cleaning range and soot cleaning effect are limited. Even if the air preheater is equipped 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. Since the lengths of the channels on both sides are basically the same and the flow path is short, the effective sootblower can cover the entire sootblowing range. However, the heat exchanger still needs to use a sootblower for sootblowing and dust removal, which cannot achieve the self-cleaning function of the heat exchanger. Frequent sootblowing not only has an unsatisfactory sootblowing effect, but also causes serious erosion of the heat transfer components. 3. Online water washing: Online water washing wastes water resources, and there are also problems with the subsequent treatment of wastewater, which can easily cause corrosion problems for the equipment.

[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, large 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] The 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, large 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 of the objects of the present invention is to provide an air preheater with a partition self-cleaning function, and the air preheater includes:

[0014] A housing and a heat transfer module located inside the housing;

[0015] One end of the housing is a hot fluid inlet of the housing, and the other end of the housing is a hot fluid outlet of the housing;

[0016] A cold fluid inlet header is provided on the side surface of one end of the housing, and a cold fluid outlet header is provided on the side surface of the other end of the housing;

[0017] It is characterized in that:

[0018] The air preheater further includes a cold fluid inlet cut-off mechanism and a partition plate;

[0019] The partition plate is arranged in the cold fluid inlet header of the housing. The partition plate is parallel to the heat transfer plates of the heat transfer module. The partition plate divides the cold fluid inlet header of the housing into several cold fluid inlet sub-headers. A cold fluid inlet cut-off mechanism is correspondingly arranged in each cold fluid inlet sub-header, and each cold fluid inlet cut-off mechanism can be independently controlled to open or close. By closing the corresponding cold fluid inlet cut-off structure, the cold fluid can be prevented from entering the corresponding cold fluid channels of the heat transfer module.

[0020] The heat transfer module is formed by welding two heat transfer plates together along the length and width directions to form a plate pair, and multiple plate pairs are combined to form the heat transfer module. A cold fluid channel is formed inside the plate pair. At both ends of the plate pair in the length direction, a heat transfer module cold fluid inlet and a heat transfer module cold fluid outlet are formed respectively. The cold fluid enters the cold fluid channel from one end of the plate pair and flows out from the other end. Each plate pair can form one heat transfer module cold fluid inlet and one heat transfer module cold fluid outlet, or can form two heat transfer module cold fluid inlets and two heat transfer module cold fluid outlets. A hot fluid channel is formed between the plate pairs, and a heat transfer module hot fluid inlet and a heat transfer module hot fluid outlet are formed respectively in the width direction of the plate pair. The cold fluid enters the heat exchanger from the shell cold fluid inlet header on one side of the shell, then enters the cold fluid channel of the heat transfer module through the heat transfer module cold fluid inlet, and flows out of the heat exchanger through the heat transfer module cold fluid outlet and the shell cold fluid outlet header provided on the other side of the shell; the hot fluid enters the heat exchanger through the shell hot fluid inlet at one end of the shell, enters the hot fluid channel of the heat transfer module through the heat transfer module hot fluid inlet, and then flows out of the heat exchanger through the heat transfer module hot fluid outlet and the shell hot fluid outlet. The flow direction of the hot fluid and the cold fluid in the heat transfer module is opposite, for countercurrent heat exchange.

[0021] Preferably, the heat transfer plate is a corrugated plate, and there is no special limitation on the shape of the corrugation, which can be a corrugation with protrusions or depressions.

[0022] 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.

[0023] The partition plate is arranged in the shell cold fluid inlet header. The partition plate is parallel to the heat transfer plates of the heat transfer module. The partition plate divides the shell cold fluid inlet header into several shell cold fluid inlet sub-headers. Each shell cold fluid inlet sub-header is independent of each other, and a cold fluid inlet cut-off mechanism is correspondingly arranged in each shell cold fluid inlet sub-header. Each cold fluid inlet cut-off mechanism can be independently controlled to open. Since the cold fluid inlet cut-off structure can be independently controlled, by closing the corresponding cold fluid inlet cut-off mechanism, the cold fluid can be prevented from entering the corresponding cold fluid channel of the heat transfer module, but the hot fluid can still enter the hot fluid channel of the heat transfer module.

[0024] Preferably, the cold fluid inlet cut-off mechanism is a flap valve, a plug valve, a louver valve, etc. with opening and closing functions. 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 preheater with the function of zone self-cleaning described in the present invention is as follows:

[0026] The shell cold fluid inlet header is divided into several shell cold fluid inlet sub-headers by a partition plate. During the flue gas treatment process, according to the blockage situation inside the heat exchanger, the opening and closing of the cold fluid inlet cut-off mechanisms in some or all of the shell cold fluid inlet sub-headers are controlled, and then the partition self-cleaning function inside the heat exchanger is realized by using the hot fluid. For example, when some channels of the heat transfer module are blocked, the cold fluid inlet cut-off mechanism in the corresponding shell cold fluid inlet sub-header is closed, and the cold fluid cannot enter the corresponding cold fluid channels of the heat transfer module, while the hot fluid can flow normally. The ammonium bisulfate adhering to the heat transfer plates is removed by heating with the high-temperature hot fluid, realizing the self-cleaning of the corresponding heat transfer module, and the working states of other heat transfer modules are not affected, thereby realizing the partition self-cleaning function of the preheater. By alternately opening and closing the cold fluid inlet cut-off mechanisms in different shell cold fluid inlet sub-headers, the full self-cleaning function inside the air preheater can be realized.

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

[0028] In one embodiment, the flue gas treatment system includes the aforementioned air preheater with a partition 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 adopts a conventional rotary air preheater, which can realize the 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 a partition self-cleaning function. The flue gas outlet temperature of the second air preheater can be lower than the melting point of ammonium bisulfate. Because the second air preheater has a partition 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. The first low-low temperature economizer 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.

[0035] The primary air enters the system through the primary air fan and then successively passes through the first air preheater and the coal feeder into the boiler. 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.

[0036] 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 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 successively passes through the second air preheater, the second low-low temperature economizer, and the first air preheater into the boiler. Heat exchange between the secondary air and the boiler condensate can be achieved through the second low-low temperature economizer, 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.

[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 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, thus 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 of 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 uses 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, having 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 of the present invention, which is a fully welded structure, can avoid the leakage of secondary air and flue gas, so the amount of secondary air and flue gas 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 amount of flue gas is reduced, the flue gas treatment volume of the dust removal device and the desulfurization device downstream of the air preheater will be reduced, and the device load will be 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 from 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, a forced draft fan, a desulfurization device and a chimney. The flue gas exits from the boiler and 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 forced draft fan, the desulfurization device and the chimney.

[0042] The primary air enters the system through the primary air fan, and then exchanges heat through the first air preheater successively, 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 primary air volume entering the first air preheater.

[0043] 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 successively 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 exchanges heat through the second air preheater, the second low-low temperature economizer and the first air preheater successively and then 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.

[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 the function of zone self-cleaning described in the present invention. Due to the function of zone self-cleaning 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, it is finally discharged into the atmosphere.

[0049] 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 after coming out of the denitration device, the flue gas is divided into two paths.

[0050] 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 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 inlet and outlet of the primary air in 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 the blockage and corrosion caused by ammonium bisulfate. The second air preheater and the third air preheater adopt the air preheater with the function of zoning 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, and at the same time, the blockage and corrosion phenomena are avoided. 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, and 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 zoning self-cleaning provided by the present invention, the system can improve the boiler efficiency and the utilization rate of flue gas waste heat, while avoiding the 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 passes through the first air preheater and the second air preheater in sequence. 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, and 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 is combined with the flue gas coming out of the third air preheater outlet, it is 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 after coming out of the denitration device, the flue gas is divided into two paths.

[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 is combined with the flue gas coming out of the third air preheater outlet, it then passes through 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.

[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 amount of 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 the 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 first enters the denitration device 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, a low-low temperature economizer, a dust removal device, an induced draft fan, a desulfurization device, and a chimney are also provided in the flue gas treatment system. 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 through 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 through the secondary air fan, and then enters the boiler through the first air preheater.

[0071] By setting 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 flue gas waste heat recovery, 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 flue gas is reduced, the flue gas treatment amount of the dust removal device and the desulfurization device downstream of the air preheater is 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 flue gas successively 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 coming out of the outlet of the second air preheater converge, 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, 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 after coming out of the denitration device, the flue gas is divided into two paths.

[0076] Preferably, the flue gas treatment system is further 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 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.

[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 and enters 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. Brief 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 : Schematic diagram of the heat transfer channel of the heat transfer module shown in Figure 4;

[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] Now, the present invention will 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 the schematic structural diagram of the air preheater with a partition self-cleaning function provided by the present invention, and the air preheater includes:

[0089] A housing and a heat transfer module 4 located inside the housing;

[0090] One end of the housing is the housing hot fluid inlet 6, and the other end of the housing is the housing hot fluid outlet 1;

[0091] A housing cold fluid inlet header 2 is provided on the side surface of one end of the housing, and a housing cold fluid outlet header 5 is provided on the side surface of the other end of the housing;

[0092] It is characterized in that:

[0093] The air preheater further includes a cold fluid inlet cut-off mechanism 3 and a partition plate 7;

[0094] The partition plate 7 is arranged in the cold fluid inlet header 2 of the shell. The partition plate 7 is parallel to the heat transfer plates of the heat transfer module 4. The partition plate 7 divides the cold fluid inlet header 2 of the shell into several cold fluid inlet sub-headers of the shell. A cold fluid inlet cut-off mechanism 3 is correspondingly arranged in each cold fluid inlet sub-header of the shell. Each cold fluid inlet cut-off mechanism 3 can be independently controlled to open or close. By closing the corresponding cold fluid inlet cut-off structure 3, the cold fluid can be prevented from entering the corresponding cold fluid channel of the heat transfer module.

[0095] The heat transfer module 4 is formed by welding two heat transfer plates along the length direction and the width direction respectively to form a plate pair, and the plate pairs are combined to form a heat transfer module. A cold fluid channel is formed inside the plate pair. At both ends of the plate pair in the length direction, a cold fluid inlet 2' and a cold fluid outlet 5' of the heat transfer module are respectively formed. The cold fluid enters the cold fluid channel from one end of the plate pair and flows out from the other end. Each plate pair can form a cold fluid inlet and a cold fluid outlet of the heat transfer module, or can also form two cold fluid inlets and two cold fluid outlets of the heat transfer module. A hot fluid channel is formed between the plate pairs, and a hot fluid inlet 6' and a hot fluid outlet 1' of the heat transfer module are respectively formed in the width direction of the plate pair. The cold fluid enters the heat exchanger from the cold fluid inlet header 2 on the side of one end of the shell, then enters the cold fluid channel of the heat transfer module through the cold fluid inlet 2' of the heat transfer module, and flows out of the heat exchanger through the cold fluid outlet 5' of the heat transfer module and the cold fluid outlet header 5 arranged on the side of the other end of the shell; the hot fluid enters the heat exchanger through the hot fluid inlet 6 at one end of the shell, enters the hot fluid channel of the heat exchange module through the hot fluid inlet 6' of the heat transfer module, and then flows out of the heat exchanger through the hot fluid outlet 1' of the heat transfer module and the hot fluid outlet 1 of the shell. The flow direction of the hot fluid and the flow direction of the cold fluid in the heat transfer module are opposite, for countercurrent heat exchange.

[0096] 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.

[0097] The air preheater described in this patent is a plate heat exchanger structure with a fully welded structure, and the cold and hot fluids exchange heat through a partition wall, without the problem of leakage.

[0098] The partition plate 7 is arranged in the shell cold fluid inlet header 2. The partition plate 7 is parallel to the heat transfer plates of the heat transfer module. The partition plate 7 divides the shell cold fluid inlet header 2 into several shell cold fluid inlet sub-headers. Each shell cold fluid inlet sub-header is independent of each other, and a cold fluid inlet cut-off mechanism 3 is correspondingly arranged in each shell cold fluid inlet sub-header. Each cold fluid inlet cut-off mechanism 3 can be independently controlled to open. Since the cold fluid inlet cut-off structure 3 can be individually controlled, by closing the corresponding cold fluid inlet cut-off mechanism 3, the cold fluid can be prevented from entering the corresponding cold fluid channels of the heat transfer module, but the hot fluid can still enter the hot fluid channels of the heat transfer module.

[0099] Preferably, the cold fluid inlet cut-off mechanism 3 is a flap valve, a plug valve, a louver valve, etc. with opening and closing functions. The present invention does not particularly limit the form of the cold fluid inlet cut-off mechanism.

[0100] The working principle of the air preheater with the function of zone self-cleaning according to the present invention is as follows:

[0101] The shell cold fluid inlet header 2 is divided into several shell cold fluid inlet sub-headers by the partition plate 7. During the flue gas treatment process, according to the blockage condition inside the heat exchanger, the opening and closing of the cold fluid inlet cut-off mechanisms in some or all of the shell cold fluid inlet sub-headers are controlled, and then the zone self-cleaning function inside the heat exchanger is realized by using the hot fluid. For example, when some channels of the heat transfer module are blocked, the cold fluid inlet cut-off mechanism in the corresponding shell cold fluid inlet sub-header is closed, and the cold fluid cannot enter the corresponding cold fluid channels of the heat transfer module, while the hot fluid can flow normally. The ammonium bisulfate adhered to the heat transfer plates is removed by heating with the high-temperature hot fluid, realizing the self-cleaning of the corresponding heat transfer module, and the working states of other heat transfer modules are not affected, thereby realizing the zone self-cleaning function of the preheater. By alternately opening and closing the cold fluid inlet cut-off mechanisms in different shell cold fluid inlet sub-headers, the full self-cleaning function inside the air preheater can be realized.

[0102] Figure 6 Fig. shows a flue gas treatment system using the above-mentioned air preheater with the function of zone self-cleaning 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 adopts a conventional rotary air preheater, which can realize the heat exchange between the flue gas and the primary air and the secondary air.

[0104] Preferably, the flue gas outlet temperature of the first air preheater 10 is higher than the melting point of ammonium bisulfate, so as to avoid the phenomenon of ammonium bisulfate condensation and blockage in the first air preheater 10.

[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 phenomenon of ammonium bisulfate blockage 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 exiting from 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. By arranging the first low-low temperature economizer 11 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.

[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 in sequence to enter the boiler 1. Preferably, a bypass is provided 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 in sequence to enter the boiler 1. 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 in sequence to enter the boiler 1. 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 exits from the boiler 1, it exchanges heat through the first air preheater 10 and the second air preheater 12, and finally is 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. After the flue gas exits from the boiler 1, it sequentially 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 sequentially 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 sequentially 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 sequentially 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 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 adopts a conventional two-compartment rotary air preheater for realizing 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 adopt 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, the problems of blockage and corrosion caused by ammonium bisulfate can be avoided.

[0115] After the flue gas exits from the boiler 1, it 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 sequentially 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 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 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.

[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 combined, 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 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: 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 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, and 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 combined 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, heat exchange occurs between the primary air and 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 achieve 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 a partition self-cleaning function described above. 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 use the air preheater with a partition self-cleaning function described in the present invention. It can avoid blockage and corrosion caused by ammonium bisulfate.

[0128] During the operation of the flue gas treatment system, 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 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 12, and heat exchange occurs between this path of flue gas and 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 from 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 inlet and outlet of the primary air in the second air preheater 12, and valves are provided on the bypasses to adjust the amount of primary air 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 expound the principle and implementation manner of the present invention. The above description of the implementation is only used to help 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 manner 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. A flue gas treatment system, 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 flue gas and secondary air; both the second air preheater and the third air preheater adopt air preheaters with a partition self-cleaning function; The air preheater with a partition self-cleaning function includes a housing and a heat transfer module located inside the housing; One end of the housing is the housing hot fluid inlet, and the other end is the housing hot fluid outlet; a housing cold fluid inlet header is arranged on the side surface of one end of the housing, and a housing cold fluid outlet header is arranged on the side surface of the other end of the housing; The air preheater with a partition self-cleaning function further includes a cold fluid inlet cut-off mechanism and a partition plate; The partition plate is arranged in the housing cold fluid inlet header, the partition plate is parallel to the heat transfer plates of the heat transfer module, the partition plate divides the housing cold fluid inlet header into several housing cold fluid inlet sub-headers, and a cold fluid inlet cut-off mechanism is correspondingly arranged in each housing cold fluid inlet sub-header, and each cold fluid inlet cut-off mechanism can be independently controlled to open; by closing the corresponding cold fluid inlet cut-off structure, the cold fluid can be prevented from entering the corresponding cold fluid channel of the heat transfer module; The heat transfer module is formed by welding two heat transfer plates along the length direction and the width direction respectively to form a plate pair, and the plate pairs are combined to form a heat transfer module; a cold fluid channel is formed inside the plate pair, a heat transfer module cold fluid inlet and a heat transfer module cold fluid outlet are respectively formed at both ends of the plate pair in the length direction, and the cold fluid enters the cold fluid channel from one end of the plate pair and flows out from the other end; a hot fluid channel is formed between the plate pairs, and a heat transfer module hot fluid inlet and a heat transfer module hot fluid outlet are respectively formed at both ends of the plate pair in the width direction; When performing flue gas treatment, control the flue gas outlet temperature of the first air preheater to be higher than the melting point of ammonium bisulfate; 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; The flue gas is divided into two paths after coming out of the boiler: one path of 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 is combined with the flue gas from the outlet of the third air preheater, it is finally discharged into the atmosphere.

2. The flue gas treatment system according to claim 1, characterized in that: 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 is combined with the flue gas from the outlet of the third air preheater, it sequentially 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.

3. The flue gas treatment system according to claim 1, characterized in that: The primary air enters the system through the primary air fan, and then passes through the third air preheater and the coal feeder and enters the boiler; 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.

4. The flue gas treatment system according to claim 3, 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 provided, and the secondary air sequentially enters the boiler through the second air preheater, the second low-low temperature economizer, and the first air preheater.

5. A flue gas treatment method, characterized in that, The flue gas is heat-exchanged by using the flue gas treatment system described in claim 1 and then discharged into the atmosphere.

6. The flue gas treatment method according to claim 5, characterized in that After coming out of the boiler, the flue gas is divided into two paths: one path of the 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 the 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 converges with the flue gas from the outlet of the third air preheater, it is finally discharged into the atmosphere.

7. The flue gas treatment method according to claim 5, 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, 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 enters the boiler through the second air preheater and the first air preheater.

Images