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 group of heat transfer modules is divided into a number of sub-headers by a cold fluid inlet partition plate, and a cold fluid inlet cut-off mechanism that can be independently controlled to open and close 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.

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. The 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 denitrification device 9; an air preheater 10 and a 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] Currently, the most common air preheater in coal-fired power plants is the rotary air preheater, which has the advantages of high heat transfer surface density, compact structure, small volume, and flexible layout. The rotary air preheater usually uses a metal corrugated plate as the heat storage core body, which 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 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 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 static and dynamic components 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 in the figure, the air preheater 10 is a rotary air preheater, and a denitration device 9 is provided upstream of it. The denitration device generally adopts the SCR denitration process. Inevitably, there will be NH3 escape in the SCR denitration device. While the SCR catalyst promotes the reaction of NH3 and NO x to remove 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 with hygroscopicity. After absorbing moisture, it becomes acidic and corrosive. The melting point of ammonium bisulfate is 147 °C. When the flue gas temperature of the rotary air preheater is lower than 147 °C, ammonium bisulfate will solidify, have strong viscosity, and easily deposit and adhere to the surface of the heat exchange plates of the rotary air preheater, causing blockage of the rotary air preheater. Also, because ammonium bisulfate becomes acidic and corrosive after absorbing moisture, it is easy to cause corrosion of the rotary air preheater.

[0008] To solve the air leakage problem of the rotary air preheater, CN210463080U provides a coal-fired power plant air preheater system, which combines a tubular air preheater and a two-compartment rotary air preheater in parallel to form a new air preheater system, realizing the isolation of the primary air system and the flue gas, and reducing the influence of the primary air with a relatively high pressure on the air leakage rate of the air preheater. Although this system can alleviate the air leakage problem to a certain extent, its structure is complex, equipment assembly and maintenance are difficult, and it cannot solve the problems of blockage and corrosion.

[0009] To solve the problems of blockage and corrosion of the rotary air preheater, the commonly taken measures include: First, controlling the flue gas temperature of the rotary air preheater to be higher than the melting point of ammonium bisulfate; its disadvantage is that it will reduce the recovery of flue gas waste heat and is not conducive to improving the boiler efficiency; Second, setting up soot blowers. The soot blowers mainly include acoustic soot blowers, steam soot blowers, shock wave soot blowers, etc. Limited by the soot blowing principle of the soot blowers, the soot blowing range and effect are limited. Even if the air preheater has a soot blower, there are still problems such as ash accumulation and difficulty in long-term operation. To ensure that the effective soot blowing range of the soot blower is fully covered, CN108662927A discloses a plate-type gas-gas heat exchanger, which includes one or more rectangular heat exchange units. Each rectangular heat exchange unit includes a tube bundle module and four heat exchange chambers formed by the corners of the tube bundle module or the extended plates at the corners and the edges of the rectangular columns. The heat exchange chambers on the opposite sides of the tube bundle module flow through the same medium. Since the channel lengths on both sides are basically the same and the flow path is short, it can ensure that the effective soot blowing range of the soot blower is fully covered. However, this heat exchanger still needs to use a soot blower for soot blowing and dust removal, and cannot achieve the self-cleaning function of the heat exchanger. Moreover, frequent soot blowing not only has an unsatisfactory soot blowing effect but also seriously erodes the heat transfer elements. Third, on-line water washing. On-line water washing will waste water resources, and there are also problems in the subsequent treatment of waste water, and it is easy to cause corrosion problems of 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, high energy consumption, and large 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 in the existing boiler flue gas treatment system when using a rotary air preheater, and the problems of high exhaust gas temperature, low utilization rate of flue gas waste heat, low boiler efficiency, high energy consumption, and large 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] The present invention provides an air preheater with a partition self-cleaning function. The air preheater includes 2n heat transfer modules, n≥2, and is characterized in that:

[0014] The heat transfer module is formed by welding a pair 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 pair of opposite sides of the plate pair is not welded, 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 pair of opposite sides; the flow directions of the hot fluid and the cold fluid in the heat transfer module are perpendicular, for cross-flow heat exchange;

[0015] The heat transfer module is formed with a cold fluid inlet, a cold fluid outlet, a hot fluid inlet, and a hot fluid outlet of the heat transfer module;

[0016] The heat transfer modules are assembled in pairs, where:

[0017] The first heat transfer module and the 1' heat transfer module are the first group of heat transfer modules;

[0018] The second heat transfer module and the 2' heat transfer module are the second group of heat transfer modules;

[0019] The third heat transfer module and the 3' heat transfer module are the third group of heat transfer modules;

[0020] The fourth heat transfer module and the 4' heat transfer module are the fourth group of heat transfer modules;

[0021] ……

[0022] The nth heat transfer module and the n' heat transfer module are the Nth group of heat transfer modules;

[0023] The cold fluid inlets of two heat transfer modules within the same group are arranged opposite to each other or the cold fluid outlets are arranged opposite to each other; the heat transfer modules of different groups are connected through a turnover header and a transition header. The turnover header connects the heat transfer module cold fluid outlet of one group of heat transfer modules to the heat transfer module cold fluid inlet of the adjacent group of heat transfer modules, and the transition header connects the heat transfer module hot fluid inlet of one group of heat transfer modules to the heat transfer module hot fluid outlet of the adjacent group of heat transfer modules.

[0024] At the heat transfer module cold fluid inlet of the first group of heat transfer modules, a cold fluid inlet header is provided; at the heat transfer module cold fluid outlet of the Nth group of heat modules, a cold fluid outlet header is provided.

[0025] At the heat transfer module hot fluid outlet of the first group of heat transfer modules, a hot fluid outlet header is provided; at the heat transfer module hot fluid inlet of the Nth group of heat transfer modules, a hot fluid inlet header is provided.

[0026] A cold fluid inlet header partition plate parallel to the heat transfer plates of the first group of heat transfer modules is provided inside the cold fluid inlet header. The cold fluid inlet header partition plate divides the cold fluid inlet header into several sub-headers, and there is no leakage between the sub-headers. A corresponding cold fluid inlet cut-off mechanism is provided in each sub-header, and each cold fluid inlet cut-off mechanism can be independently controlled to open.

[0027] A turnover header partition plate is provided inside the turnover header. The number of turnover header partition plates is the same as that of the cold fluid inlet header partition plates and they correspond one by one. Each turnover header partition plate is in the same plane as the corresponding cold fluid inlet header partition plate.

[0028] Thus, the cold fluid enters the air preheater through the cold fluid inlet header, enters the cold fluid channel through the heat transfer module cold fluid inlet of the first group of heat transfer modules, then flows into the turnover header through the heat transfer module cold fluid outlet, and under the guidance of the turnover header partition plate, enters the cold fluid channel of the second group of heat transfer modules through the heat transfer module cold fluid inlet of the second group of heat transfer modules, then flows into the next turnover header through the heat transfer module cold fluid outlet of the second group of heat transfer modules, and under the guidance of the turnover header partition plate, enters the third group of heat transfer modules, and finally flows out of the air preheater through the heat transfer module cold fluid outlet of the Nth group of heat transfer modules and the cold fluid outlet header.

[0029] At the heat transfer module hot fluid inlet of the Nth group of heat transfer modules, a hot fluid inlet header is provided. The hot fluid enters the hot fluid channel of the Nth group of heat transfer modules through the hot fluid inlet header, then flows through the transition header and enters the hot fluid channel of the N - 1th group of heat transfer modules, and finally flows out of the air preheater through the hot fluid outlet header of the first group of heat transfer modules.

[0030] Preferably, the heat transfer plate is a corrugated plate, and there is no particular limitation on the shape of the corrugation, which can be a corrugation with protrusions or depressions.

[0031] 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.

[0032] 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 in the present invention is not particularly limited.

[0033] The working principle of the air preheater with a partition self-cleaning function described in the present invention is as follows:

[0034] Since the cold fluid inlet header of the first group of heat transfer modules is divided into several sub-headers by the cold fluid inlet header partition plate, and a cold fluid inlet cut-off mechanism that can be independently controlled to open is provided in each sub-header. Therefore, when the cold fluid inlet cut-off mechanism 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 plate. The ammonium bisulfate adhering to the heat transfer plate 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, realizing the self-heating cleaning effect of the corresponding heat transfer plate. When the cold fluid inlet cut-off mechanisms are closed in turn, the partition self-heating cleaning function of all the heat transfer plates can be realized.

[0035] Another object of the present invention is to provide a flue gas treatment system using the above-mentioned air preheater with a partition self-cleaning function.

[0036] In one embodiment, the flue gas treatment system includes the aforementioned air preheater with a partition self-cleaning function.

[0037] 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.

[0038] 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.

[0039] 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. Since the second air preheater has a partition self-cleaning function, the phenomenon of ammonium bisulfate blockage can be avoided.

[0040] During the operation of the flue gas treatment system, the flue gas exits from the boiler and then passes through the first air preheater and the second air preheater, and finally is discharged into the atmosphere.

[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 from 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] 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 duct 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.

[0043] 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 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.

[0044] 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 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 sequentially passes through the second air preheater, the second low-low temperature economizer and the first air preheater and enters 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.

[0045] In the described 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, 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 avoids the blockage and corrosion phenomena caused by ammonium bisulfate while improving the boiler efficiency and the utilization rate of flue gas waste heat, and has broad market application prospects.

[0046] 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 all are of full-welded structure, which can avoid the leakage of secondary air and flue gas. Therefore, the secondary air volume and flue gas volume will be reduced, the power of the secondary 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.

[0047] 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: the flue gas is discharged into the atmosphere after heat exchange through the aforementioned flue gas treatment system.

[0048] In another embodiment, after the flue gas exits from the boiler, it is heat-exchanged through the first air preheater and the second air preheater, and finally 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.

[0049] 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 from the boiler and then enters the atmosphere 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.

[0050] The primary air enters the system through the primary air fan, and then is heat-exchanged through the first air preheater in sequence, 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.

[0051] The secondary air enters the system through the secondary air fan, and then enters the boiler after heat exchange through the second air preheater and the first air preheater in sequence; 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 enters the boiler after passing through the second air preheater, the second low-low temperature economizer, and the first air preheater in sequence. 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.

[0052] 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.

[0053] The first air preheater adopts a conventional two-chamber rotary air preheater for realizing heat exchange between flue gas and 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.

[0054] 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.

[0055] During the operation of the flue gas treatment system, the flue gas is divided into two paths after coming out of the boiler:

[0056] One path of the flue gas passes through the first air preheater and the second air preheater in sequence, and 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, and this path of the 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.

[0057] Preferably, the flue gas treatment system is further provided with a denitration device. 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.

[0058] 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 pass through the first low-low temperature economizer, the dust removal device, the induced draft fan, the desulfurization device, and the chimney in sequence and are discharged into the atmosphere.

[0059] The first low-low temperature economizer is arranged in the downstream flue after the flue gas of the second air preheater and the third air preheater converges, using the flue gas to heat the boiler feed water and 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.

[0060] The primary air enters the system through the primary air fan, and then passes through the third air preheater and the coal feeder into the boiler in sequence, 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.

[0061] The secondary air enters the system through the secondary air fan, and then passes through the second air preheater and the first air preheater into the boiler in sequence.

[0062] 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 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] The present invention has 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 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 blockage and corrosion caused by ammonium bisulfate. The second air preheater and the third air preheater adopt the air preheater with the function of partition 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 uses a three-chamber rotary air preheater, more flue gas heat is recovered, the boiler efficiency is improved, and at the same time, 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 amounts of secondary air, primary air, and flue gas will be reduced, and the powers 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.

[0064] Through the coordinated cooperation of the conventional rotary air preheater and the air preheater with the function of partition self-cleaning provided by the present invention, this system can improve the boiler efficiency and the utilization rate of flue gas waste heat, while avoiding blockage and corrosion caused by ammonium bisulfate, and has broad market application prospects.

[0065] Correspondingly, 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:

[0066] After the flue gas comes out of the boiler, it is divided into two paths: One path of the 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 outlet of the third air preheater converge, it is finally discharged into the atmosphere.

[0067] 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.

[0068] 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 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.

[0069] 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.

[0070] 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 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.

[0071] In a further 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.

[0072] 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.

[0073] During the operation of the flue gas treatment system, the flue gas from the boiler 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 from the outlet of the second air preheater are merged, it is finally discharged into the atmosphere.

[0074] 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.

[0075] 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 from the outlet of the second air preheater are merged, they then pass through the low-low temperature economizer, the dust removal device, the induced draft fan, the desulfurization device, and the chimney in sequence and are discharged into the atmosphere.

[0076] The low-low temperature economizer is arranged in the downstream flue after the flue gas of the first air preheater and the second air preheater is merged, 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.

[0077] The primary air enters the system through the primary air fan, and then passes through the second air preheater and the coal feeder into the boiler in sequence. 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 air volume of the 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.

[0079] By setting two air preheaters with partition self-cleaning functions, which cooperate with each other, it is possible to improve the boiler efficiency and the utilization rate of waste heat recovery of the flue gas, while avoiding blockage and corrosion caused by ammonium bisulfate, and has a broad market application prospect.

[0080] Since the first and second air preheaters in the system are both of all-welded structures, leakage between the primary air and the flue gas, and between the secondary air and the flue gas can be avoided. Therefore, the air volume of the primary air, the air volume of the secondary air, and the flue gas volume will decrease, and the power of the primary air induced draft fan, the secondary air fan, and the induced draft fan will decrease, and the power consumption will correspondingly decrease. At the same time, after the flue gas volume decreases, the flue gas treatment volume of the dust removal device and the desulfurization device downstream of the air preheater decreases, and the device load is reduced.

[0081] Correspondingly, another object of the present invention is to provide a method for flue gas treatment using the above flue gas treatment system, comprising the following steps:

[0082] After the flue gas exits from the boiler, it is divided into two paths: one path of flue gas sequentially 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 converges with the flue gas from the outlet of the second air preheater, it is finally discharged into the atmosphere. The flue gas outlet temperatures of the first air preheater and the second air preheater are controlled to be lower than the melting point of ammonium bisulfate.

[0083] Preferably, the flue gas treatment system is further provided with a denitration device. After the flue gas exits from the boiler, it first enters the denitration device, and after coming out of the denitration device, the flue gas is divided into two paths.

[0084] 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 converges with the flue gas from the outlet of the second air preheater, it sequentially passes through the low-low temperature economizer, the dust removal device, the induced draft fan, the desulfurization device and the chimney and is discharged into the atmosphere.

[0085] The primary air enters the system through the primary air fan, and then sequentially 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 air volume of the primary air entering the second air preheater.

[0086] 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

[0087] Figure 1 : Schematic diagram of the flue gas treatment system of a conventional coal-fired power plant boiler in the prior art;

[0088] Figure 2: Schematic structural diagram of the air preheater with a partition self-cleaning function provided by the present invention;

[0089] Figure 3: Two-dimensional structural diagram of the air preheater with a partition self-cleaning function provided by the present invention;

[0090] Figure 4 : Schematic diagram of the heat transfer module of the air preheater with a partition self-cleaning function provided by the present invention;

[0091] Figure 5 : Figure 4 Schematic diagram of the heat transfer channel of the shown heat transfer module;

[0092] Figure 6: Schematic diagram of the flue gas treatment system provided by the present invention;

[0093] Figure 7 : Another schematic diagram of the flue gas treatment system provided by the present invention;

[0094] Figure 8 : Another schematic diagram of the flue gas treatment system provided by the present invention. Detailed implementation manners

[0095] Now, the present invention will be further described in detail with reference to the accompanying drawings, but the following implementation manners do not constitute a limitation to the present invention.

[0096] Figures 2 - 5 show the schematic structure of the air preheater with a partition self-cleaning function provided by the present invention.

[0097] The present invention provides an air preheater with a partition self-cleaning function. The air preheater includes 2n heat transfer modules, where n ≥ 2, and is characterized in that:

[0098] 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, 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 set of welded opposite sides; the flow directions of the hot fluid and the cold fluid in the heat transfer module are perpendicular, for cross-flow heat exchange;

[0099] The heat transfer module is provided with a cold fluid inlet, a cold fluid outlet, a hot fluid inlet, and a hot fluid outlet of the heat transfer module;

[0100] The heat transfer modules are assembled in pairs, where:

[0101] The first heat transfer module and the 1' heat transfer module are the first group of heat transfer modules;

[0102] The second heat transfer module and the 2' heat transfer module are the second group of heat transfer modules;

[0103] The third heat transfer module and the 3' heat transfer module are the third group of heat transfer modules;

[0104] The fourth heat transfer module and the 4' heat transfer module are the fourth group of heat transfer modules;

[0105] ……

[0106] The nth heat transfer module and the n' heat transfer module are the Nth group of heat transfer modules;

[0107] The cold fluid inlets of two heat transfer modules within the same group are arranged opposite to each other or the cold fluid outlets are arranged opposite to each other; the heat transfer modules of different groups are connected through a reversing header and a transition header. The reversing header connects the heat transfer module cold fluid outlet of one group of heat transfer modules to the heat transfer module cold fluid inlet of the adjacent group of heat transfer modules, and the transition header connects the heat transfer module hot fluid inlet of one group of heat transfer modules to the heat transfer module hot fluid outlet of the adjacent group of heat transfer modules.

[0108] At the heat transfer module cold fluid inlet of the first group of heat transfer modules, a cold fluid inlet header is provided; at the heat transfer module cold fluid outlet of the Nth group of heat modules, a cold fluid outlet header is provided.

[0109] At the heat transfer module hot fluid outlet of the first group of heat transfer modules, a hot fluid outlet header is provided; at the heat transfer module hot fluid inlet of the Nth group of heat transfer modules, a hot fluid inlet header is provided.

[0110] A cold fluid inlet header partition plate parallel to the heat transfer plates of the first group of heat transfer modules is provided inside the cold fluid inlet header. The cold fluid inlet header partition plate divides the cold fluid inlet header into several sub-headers, and there is no leakage between the sub-headers. A corresponding cold fluid inlet cut-off mechanism is provided in each sub-header, and each cold fluid inlet cut-off mechanism can be independently controlled to open.

[0111] A reversing header partition plate is provided inside the reversing header. The number of reversing header partition plates is the same as and corresponds one by one to the cold fluid inlet header partition plates, and each reversing header partition plate is in the same plane as the corresponding cold fluid inlet header partition plate.

[0112] Thus, the cold fluid enters the air preheater through the cold fluid inlet header, enters the cold fluid channel of the heat transfer module of the first group through the heat transfer module cold fluid inlet of the first group, then flows into the reversing header through the heat transfer module cold fluid outlet, and under the guidance of the reversing header partition plate, enters the cold fluid channel of the second group of heat transfer modules through the heat transfer module cold fluid inlet of the second group, then flows into the next reversing header through the heat transfer module cold fluid outlet of the second group of heat transfer modules, and under the guidance of the reversing header partition plate, enters the third group of heat transfer modules, and finally flows out of the air preheater through the heat transfer module cold fluid outlet of the Nth group of heat transfer modules and the cold fluid outlet header.

[0113] At the heat transfer module hot fluid inlet of the Nth group of heat transfer modules, a hot fluid inlet header is provided. The hot fluid enters the hot fluid channel of the Nth group of heat transfer modules through the hot fluid inlet header, then flows through the transition header and enters the hot fluid channel of the N - 1th group of heat transfer modules, and finally flows out of the air preheater through the hot fluid outlet header of the first group of heat transfer modules.

[0114] 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.

[0115] 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 the problem of cross-leakage.

[0116] 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.

[0117] The working principle of the air preheater with a partition self-cleaning function described in the present invention is as follows:

[0118] Since the cold fluid inlet header of the first group of heat transfer modules is divided into several sub-headers by the cold fluid inlet header partition plate, and a cold fluid inlet cut-off mechanism that can be independently controlled to open is provided in each sub-header. Therefore, when the cold fluid inlet cut-off mechanism 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 plate. Therefore, the ammonium bisulfate adhering to the heat transfer plate 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, realizing the self-heating cleaning effect of the corresponding heat transfer plate. When the cold fluid inlet cut-off mechanisms are closed in turn, the partition self-heating cleaning function of all heat transfer plates can be realized.

[0119] Figure 6 Shows a flue gas treatment system using the above-mentioned air preheater with a partition 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.

[0120] The first air preheater 10 adopts a conventional rotary air preheater, which can realize the heat exchange between flue gas and primary air and secondary air.

[0121] 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.

[0122] 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.

[0123] 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 outlet of 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.

[0124] 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 amount of primary air entering the first air preheater.

[0125] 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 decreased, thereby increasing the heat transfer temperature difference of the first air preheater 10.

[0126] 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 outlet of 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.

[0127] 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 flows 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 in sequence after exiting from the outlet of the boiler 1 and is discharged into the atmosphere.

[0128] The primary air enters the system through the primary air fan 3, and then successively passes through the first air preheater 10 for heat exchange, 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 passes through the second air preheater 12 and the first air preheater 10 for heat exchange 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.

[0129] Figure 7 It shows another flue gas treatment system provided by the present invention that adopts 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.

[0130] The first air preheater 10 adopts a conventional two-chamber rotary air preheater for realizing heat exchange between flue gas and 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.

[0131] 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, problems such as blockage and corrosion caused by ammonium bisulfate can be avoided.

[0132] After the flue gas comes out of the boiler 1, it enters the denitration device 9. After coming out of the denitration device 9, the flue gas is divided into two paths:

[0133] One path of flue gas successively passes through the first air preheater 10 and the second air preheater 12. This path of flue gas exchanges heat with the secondary air; the other path of flue gas passes through the third air preheater 14. This path of flue gas exchanges heat with the primary air; after the flue gas coming out of the second air preheater 12 and the flue gas coming out of the outlet of the third air preheater are combined, they are finally discharged into the atmosphere.

[0134] 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. After the flue gas coming out of the second air preheater 12 and the flue gas coming out of the outlet of the third air preheater are combined, they successively 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.

[0135] 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 converges, 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.

[0136] The primary air enters the system through the primary air fan 3, then successively passes through the third air preheater 14 and the coal feeder 2 and enters the boiler 1, and heat exchange occurs between the primary air and the flue gas in the third air preheater 14. 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 primary air volume entering the third air preheater 14.

[0137] The secondary air enters the system through the secondary air fan 4, then successively passes through the second air preheater 12 and the first air preheater 10 and enters the boiler 1.

[0138] 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 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 10, thereby increasing the heat transfer temperature difference of the first air preheater 10.

[0139] 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 successively passes through the first air preheater 10 and the second air preheater 12. In this path, heat exchange occurs between the flue gas and 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 heat exchange occurs between the flue gas and the primary air in this path, and the flue gas outlet temperature of the third air preheater 14 is controlled to be lower than the melting point of ammonium bisulfate. After the flue gas coming out of the second air preheater 12 converges with the flue gas from the outlet of the third air preheater 14, it is finally discharged into the atmosphere.

[0140] 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. After the flue gas coming out of the second air preheater 12 converges with the flue gas from the outlet of the third air preheater, it successively passes 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 is discharged into the atmosphere.

[0141] The primary air enters the system through the primary air fan 3, then successively 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.

[0142] The secondary air enters the system through the secondary air fan 4, then successively 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.

[0143] Figure 8 It shows another flue gas treatment system adopting the air preheater with the partition 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 low-low temperature economizer 11; a second air preheater 12.

[0144] 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, which can avoid the blockage and corrosion caused by ammonium bisulfate.

[0145] 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 the flue gas successively passes through the first air preheater 10, 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 12, and this path of the flue gas exchanges heat with the primary air; after the flue gas coming out of the first air preheater 10 and the flue gas at the outlet of the second air preheater 12 are merged, they are finally discharged into the atmosphere.

[0146] 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. After the flue gas coming out of the first air preheater 10 and the flue gas at the outlet of the second air preheater 12 are merged, they successively 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.

[0147] 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, 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 11 can also be arranged between the induced draft fan 6 and the desulfurization device 7.

[0148] The primary air enters the system through the primary air fan 3, and then successively passes through the second air preheater 12, 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.

[0149] The secondary air enters the system through the secondary air fan 4, and then enters the boiler 1 through the first air preheater 10.

[0150] 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:

[0151] After the flue gas comes out of the boiler 1, it is divided into two paths: one path of the flue gas successively passes through the first air preheater 10, 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 12, and this path of the flue gas exchanges heat with the primary air; after the flue gas coming out of the first air preheater 10 is merged with the flue gas at the outlet of the second air preheater 12, 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.

[0152] 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. After the flue gas coming out of the first air preheater 10 is merged with the flue gas at the outlet of the second air preheater 12, it successively passes 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 is discharged into the atmosphere.

[0153] The primary air enters the system through the primary air fan 3, and then successively passes through the second air preheater 12, 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.

[0154] The secondary air enters the system through the secondary air fan 4, and then enters the boiler 1 through the first air preheater 10.

[0155] The above has introduced the air preheater, flue gas treatment system and treatment method provided by the present invention in detail. 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. An air preheater with a zoned self-cleaning function, comprising 2n heat transfer modules, where n ≥ 2, and characterized by: The heat transfer module has a heat transfer module cold fluid inlet, a heat transfer module cold fluid outlet, a heat transfer module hot fluid inlet and a heat transfer module hot fluid outlet; The heat transfer modules are assembled in groups of two, wherein: The first heat transfer module and the first' heat transfer module are the first group of heat transfer modules; The second heat transfer module and the second' heat transfer module form a second group of heat transfer modules; The third heat transfer module and the 3' heat transfer module form the third group of heat transfer modules; The 4th heat transfer module and the 4' heat transfer module form the fourth group of heat transfer modules; …… The nth heat transfer module and the n'th heat transfer module constitute the Nth group of heat transfer modules; The cold fluid inlets of the heat transfer modules of the two heat transfer modules in the same group are arranged opposite to each other or the cold fluid outlets of the heat transfer modules are arranged opposite to each other; Different groups of heat transfer modules are connected through a flip header and a transition header. The flip header connects the cold fluid outlet of the heat transfer modules of one group with the cold fluid inlet of the heat transfer modules of an adjacent group. The transition header connects the hot fluid inlet of the heat transfer modules of one group with the hot fluid outlet of the heat transfer modules of an adjacent group. A cold fluid inlet header is provided at the cold fluid inlet of the heat transfer module of the first group of heat transfer modules; a cold fluid outlet header is provided at the cold fluid outlet of the heat transfer module of the Nth group of heat transfer modules; A hot fluid inlet header is provided at the hot fluid inlet of the heat transfer module of the Nth group of heat transfer modules; a hot fluid outlet header is provided at the hot fluid outlet of the heat transfer module of the first group of heat transfer modules; A cold fluid inlet manifold partition plate is provided in the cold fluid inlet manifold, parallel to the heat transfer plates of the first group of heat transfer modules. The cold fluid inlet manifold partition plate divides the cold fluid inlet manifold into a plurality of sub-manifolds, preventing leakage between the sub-manifolds. A corresponding cold fluid inlet shut-off mechanism is provided in each sub-manifold, and each cold fluid inlet shut-off mechanism can be independently controlled to open. The flip header is provided with flip header partition plates, the flip header partition plates are the same in number and correspond one to one with the cold fluid inlet header partition plates, and each flip header partition plate is in the same plane as the corresponding cold fluid inlet header partition plate; The cold fluid enters the air preheater through the cold fluid inlet header, passes through the cold fluid channels of the heat transfer modules, and flows into the flip header. Under the guidance of the flip header partition plate, it enters the cold fluid channels of the next group of heat transfer modules and finally flows out of the air preheater through the cold fluid outlet header of the Nth group of heat transfer modules. The hot fluid enters the hot fluid channels of the Nth group of heat transfer modules through the hot fluid inlet header, then flows through the transition header into the hot fluid channels of the N-1th group of heat transfer modules and finally flows out of the air preheater through the hot fluid outlet header of the first group of heat transfer modules. The heat transfer module is formed by welding a group of opposite edges of two heat transfer plates to form a plate pair. Multiple plate pairs are stacked to form a heat transfer module. Cold fluid channels are formed inside the plate pairs. The other group of opposite edges of the plate pairs are not welded, forming a cold fluid inlet and a cold fluid outlet of the heat transfer module; hot fluid channels are formed between the plate pairs along the direction of the welded group of opposite edges.

2. The air preheater according to claim 1, characterized in that: The cold fluid inlet cut-off mechanism is a flap valve, a plug valve or a shutter valve with opening and closing functions.

3. 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 mechanism, all heat transfer plates can be self-cleaned using hot fluid.

4. The air preheater according to claim 1, wherein: The air preheater adopts a fully welded plate heat exchanger structure.

5. The air preheater according to claim 4, characterized in that: The hot fluid flow direction and the cold fluid flow direction in the heat transfer module are perpendicular to each other, which is a cross-flow heat exchange.

6. The air preheater according to claim 5, characterized in that: The heat transfer plate is a corrugated plate.

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

8. The flue gas treatment system according to claim 7, wherein: 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 with a partitioned self-cleaning function.

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

10. The flue gas treatment system according to claim 9, characterized in that: The flue gas treatment system is also provided with a denitrification device, a first 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 from the boiler outlet through the denitrification device, the first air preheater, the second air preheater, the first low-temperature economizer, the dust removal device, the induced draft fan, the desulfurization device and the chimney in sequence.

11. The flue gas treatment system according to claim 8, wherein: 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.

12. The flue gas treatment system according to claim 11, characterized in that: A second low-temperature economizer is also 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 enters the boiler through the second air preheater, the second low-temperature economizer and the first air preheater.

13. The flue gas treatment system according to claim 8, wherein: During flue gas treatment, the flue gas outlet temperature of the first air preheater is controlled to be higher than the melting point of ammonium bisulfate.

14. The flue gas treatment system according to claim 13, wherein: During flue gas treatment, the flue gas temperature of the second air preheater is controlled to be lower than the melting point of ammonium bisulfate.

15. The flue gas treatment system according to claim 7, wherein: 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 to realize heat exchange between flue gas and secondary air; the second air preheater and the third air preheater both adopt the air preheater with partitioned self-cleaning function.

16. The flue gas treatment system according to claim 15, characterized in that: After coming out of the boiler, the flue gas is divided into two paths: one path of flue gas passes through the first air preheater and the second 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 third air preheater, and this path of flue gas exchanges heat with the primary air; the flue gas coming out of the second air preheater merges with the flue gas from the outlet of the third air preheater, and is finally discharged into the atmosphere.

17. The flue gas treatment system according to claim 16, wherein: The flue gas treatment system is also provided with a first low-temperature economizer, a dust removal device, an induced draft fan, a desulfurization device and a chimney; the flue gas coming out of the second air preheater is merged with the flue gas from the outlet of the third air preheater and then passes through the first 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.

18. The flue gas treatment system according to claim 16, wherein: The primary air enters the system through the primary air fan, then passes through the third air preheater and the coal feeder to enter the boiler; the secondary air enters the system through the secondary air fan, then passes through the second air preheater and the first air preheater in sequence to enter the boiler.

19. The flue gas treatment system according to claim 18, wherein: A second low-temperature economizer is provided in the secondary air duct between the first air preheater and the second air preheater, and the secondary air enters the boiler through the second air preheater, the second low-temperature economizer and the first air preheater in sequence.

20. The flue gas treatment system according to claim 15, wherein: During flue gas treatment, the flue gas outlet temperature of the first air preheater is controlled to be higher than the melting point of ammonium bisulfate.

21. The flue gas treatment system according to claim 15, wherein: During flue gas treatment, the flue gas outlet temperature of the second air preheater and the third air preheater is controlled to be lower than the melting point of ammonium bisulfate.

22. The flue gas treatment system according to claim 7, wherein: 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 and the second air preheater both use the air preheater with a zoned self-cleaning function; the flue gas is divided into two paths after coming out of the boiler: 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; the flue gas coming out of the first air preheater merges with the flue gas from the outlet of the second air preheater, and is finally discharged into the atmosphere.

23. The flue gas treatment system according to claim 22, wherein: The flue gas treatment system is also provided with a low-temperature economizer, a dust removal device, an induced draft fan, a desulfurization device and a chimney; the flue gas coming out of the first air preheater is merged with the flue gas coming out of the second air preheater and then passes through the 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.

24. The flue gas treatment system according to claim 22, wherein: The primary air enters the system through the primary air fan, then passes through the second air preheater and coal feeder into the boiler; the secondary air enters the system through the secondary air fan, then passes through the first air preheater into the boiler.

25. A flue gas treatment method, characterized in that: The flue gas treatment system according to claim 7 is used to perform heat exchange treatment on the flue gas and then discharge it into the atmosphere.

26. A flue gas treatment method, characterized in that: The flue gas treatment system according to claim 8 is used to perform heat exchange treatment on the flue gas and then discharge it into the atmosphere.

27. The processing method according to claim 26, characterized in that After the flue gas comes out of the boiler, it is discharged into the atmosphere after heat exchange through the first air preheater and the second air preheater; 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.

28. The processing method according to claim 26, characterized in that The primary air enters the system through the primary air fan, then passes through the first air preheater for heat exchange, and then enters the boiler through the coal feeder.

29. The processing method according to claim 26, characterized in that: The secondary air enters the system through the secondary air fan, and then enters the boiler after heat exchange through the second air preheater and the first air preheater.

30. A flue gas treatment method, characterized in that: The flue gas treatment system according to claim 15 is used to perform heat exchange treatment on the flue gas and then discharge it into the atmosphere.

31. The processing method according to claim 30, characterized in that After coming out of the boiler, the flue gas 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 temperature of the second air preheater and the third air preheater is controlled to be lower than the melting point of ammonium bisulfate; the flue gas coming out of the second air preheater is combined with the flue gas from the outlet of the third air preheater, and finally discharged into the atmosphere.

32. The processing method according to claim 30, characterized in that The primary air enters the system through the primary air fan, then passes through the third air preheater and the coal feeder into the boiler. In the third air preheater, the primary air exchanges heat with the flue gas; the secondary air enters the system through the secondary air fan, then passes through the second air preheater and the first air preheater into the boiler.

33. A flue gas treatment method, characterized in that: The flue gas treatment system according to claim 22 is used to perform heat exchange treatment on the flue gas and then discharge it into the atmosphere.

34. The processing method according to claim 33, characterized in that After coming out of the boiler, the flue gas is divided into two paths: one path of 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; the flue gas coming out of the first air preheater and the flue gas coming out of the second air preheater are merged and finally discharged into the atmosphere; the flue gas outlet temperatures of the first air preheater and the second air preheater are controlled to be lower than the melting point of ammonium bisulfate.

35. The processing method according to claim 33, 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 into the boiler. In the second air preheater, the primary air exchanges heat with the flue gas; the secondary air enters the system through the secondary air fan, then passes through the first air preheater into the boiler.

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