Anti-blocking flue gas and air coupling system based on rotary preheater

Abstract

The utility model belongs to the technical field of power station boilers, and particularly relates to an anti-blocking flue gas and air coupling system based on a rotary preheater. According to the technical scheme, the anti-blocking flue gas and air coupling system based on the rotary preheater comprises the rotary preheater, a plate heat exchanger, a dust remover, a primary / secondary fan, a flue and an air flue, the flue sequentially passes through the rotary preheater, the plate heat exchanger and the dust remover, and the air flue sequentially passes through the primary / secondary fan, the plate heat exchanger and the rotary preheater; the plate heat exchanger comprises a plurality of modules, each module is provided with an inlet air door capable of being opened and closed independently, cold air in an air flue is divided into a plurality of branches to enter the corresponding modules respectively, and smoke in the air flue sequentially passes through all the modules. The utility model provides an anti-blocking flue gas and air coupling system based on a rotary preheater. The anti-blocking flue gas and air coupling system thoroughly solves the problems of ammonium bisulfate blocking, cold end corrosion and the like of the rotary preheater.

Description

Technical Field

[0001] The utility model belongs to the technical field of power station boilers, and in particular relates to an anti-blocking smoke and air coupling system based on a rotary preheater. Background Art

[0002] For large coal-fired boilers, a rotary preheater is typically placed after the economizer and denitrification unit to heat the boiler's supply air, thereby reducing the boiler's exhaust temperature and improving boiler efficiency. To maximize boiler efficiency, the exhaust temperature is typically designed to be relatively low.

[0003] However, for boilers equipped with SCR devices, in order to meet the current ultra-clean exhaust and flexible operation requirements, the amount of ammonia injected is usually large, and the flue gas is not mixed with NO. X The reacting ammonia reacts with SO₃ in the flue gas to form ammonium bisulfate. Ammonium bisulfate is a highly viscous liquid at temperatures between 147°C and 207°C, making it the primary cause of preheater blockage. The flue gas temperature during actual boiler operation is generally between 120°C and 140°C. The cold-end components of the rotary preheater are inevitably within the liquid phase temperature range of ammonium bisulfate. Due to its high viscosity, ammonium bisulfate adheres to the surface of the rotary preheater components and absorbs ash, causing blockage, reduced preheater heat exchange capacity, and increased cold-end corrosion.

[0004] In order to reduce the risk of cold-end corrosion and ammonium bisulfate blockage caused by rotary introduction, a heater is generally installed at the preheater inlet to increase the inlet air temperature of the preheater, thereby increasing the comprehensive temperature of the preheater cold end. However, blindly increasing the inlet air temperature will lead to an increase in the boiler exhaust temperature, and it cannot completely solve the problem of ammonium bisulfate blockage at the cold end. In particular, for boilers burning high-sulfur coal and units with large ammonia escape, the problem of ammonium bisulfate deposition and blockage is particularly serious.

[0005] At present, the problems existing in the rotary preheater are mainly solved by combining various technical means such as optimizing the component plate shape, raising the cold end components, and increasing the air temperature at the preheater inlet. These methods have a good effect on delaying the clogging cycle, but still fail to completely solve the problem of ammonium bisulfate clogging.

[0006] Traditional rotary preheaters suffer from severe ammonium bisulfate clogging and corrosion problems, especially in early preheaters designed for non-denitrification standards. Conventional solutions include optimizing preheater components and installing a heater at the preheater inlet to increase the preheater's inlet air temperature, thereby raising the overall temperature at the preheater's cold end. This prevents corrosion and clogging.

[0007] For early non-denitrification preheaters, the clogging problem was alleviated after component modification, but with increased operating time, certain clogging problems still exist. The main reason is that the early preheater designs were too small. Even after component modification, heat exchange efficiency still needed to be taken into account. The component density did not decrease much, and the inherent resistance was relatively high. When external conditions changed (for example, increased ammonia escape would promote the formation of ammonium bisulfate), the anti-clogging ability was insufficient. On the other hand, although increasing the inlet air temperature can increase the metal wall temperature of the heat exchange element, it is limited by steam consumption and heater output, and the exhaust gas temperature must also be taken into account. Therefore, the inlet air temperature is generally not too high, and the metal wall temperature of the cold-end element cannot avoid the liquid phase of ammonium bisulfate. Therefore, the modification and optimization of the rotary preheater itself can alleviate the clogging problem, but the formation and deposition of ammonium bisulfate cannot be avoided and has not been fundamentally resolved. The clogging problem caused by ammonium bisulfate deposition is particularly serious for boilers burning high-sulfur coal. Utility Model Content

[0008] In order to solve the above problems existing in the prior art, the purpose of the utility model is to provide an anti-blocking smoke and air coupling system based on a rotary preheater, which completely solves the problems of ammonium bisulfate blockage and cold end corrosion of the rotary preheater.

[0009] The technical solution adopted by this utility model is:

[0010] A blockage-proof smoke-air coupling system based on a rotary preheater includes a rotary preheater, a plate heat exchanger, a dust collector, a primary / secondary fan, a flue and an air duct. The flue passes through the rotary preheater, the plate heat exchanger and the dust collector in sequence, and the air duct passes through the primary / secondary fan, the plate heat exchanger and the rotary preheater in sequence. The plate heat exchanger includes several modules, each of which is provided with an independently opened and closed inlet damper. The cold air in the air duct is divided into several branches and enters the corresponding modules respectively. The smoke in the flue passes through all modules in sequence.

[0011] In this utility model, after exiting the economizer and SCR, the flue gas passes through a rotary preheater and a plate heat exchanger before entering the dust collector. After exiting the primary and secondary fans, the cold air passes through a plate heat exchanger and a rotary preheater before entering the boiler. A rotary preheater is placed in the medium- and high-temperature flue gas area at the economizer and SCR outlets, while a plate heat exchanger is placed in the low-temperature area.

[0012] The plate heat exchanger is designed in modules. The air inlet of each module is separated by partitions and interfaces, and an inlet damper is provided. Each module can be opened and closed independently, so that each module can remove ammonium bisulfate online separately.

[0013] The key to the actual operation of the utility model is how to distribute the heating surfaces of the rotary preheater and the plate heat exchanger to ensure that the ammonium bisulfate liquid phase region is transferred to the range of the plate heat exchanger.

[0014] If ammonium bisulfate becomes clogged in the plate heat exchanger, close the inlet damper of the first module, allowing the hotter flue gas from the rotary preheater outlet to heat the plate heat exchanger and remove the ammonium bisulfate online. While one module is removing the ammonium bisulfate online, the remaining modules operate normally. Each module takes turns removing the ammonium bisulfate, and normal operation resumes after all modules have completed the removal.

[0015] The module's removal of ammonium bisulfate does not affect parameters such as heat balance, exhaust temperature, and air leakage rate. This fundamentally differs from existing technologies that use hot air or other heat sources to remove ammonium bisulfate. The present invention utilizes the heat of the flue gas itself, without introducing a heat source. Only the air and smoke distribution channels are altered.

[0016] As a preferred embodiment of the present invention, the rotary preheater and the plate heat exchanger are arranged in series, the rotary preheater is arranged in the medium and high temperature flue gas area, and the plate heat exchanger is arranged in the low temperature flue gas area; the flue gas coming out of the economizer and SCR first passes through the rotary preheater, then passes through the plate heat exchanger, and then enters the downstream dust collector.

[0017] As a preferred solution of the present invention, the air from the primary / secondary fan is first heated by the plate heat exchanger and then enters the rotary preheater.

[0018] As a preferred solution of the present invention, the primary air and the secondary air of the primary / secondary air fan are independent of each other, and the primary air and the secondary air respectively correspond to several different modules of the plate heat exchanger.

[0019] As a preferred solution of the present invention, the air side inlet of each module of the plate heat exchanger is separated by a partition and an interface, the inlet damper is connected to the interface, and each interface corresponds to a module.

[0020] As a preferred solution of the present invention, the plate heat exchanger includes a plurality of plates with wide flow channels. The plate heat exchanger prevents blockage by using the plates with wide flow channels.

[0021] As a preferred solution of the present invention, the flue gas side and the air side of the plate heat exchanger are in the form of a cross-wall structure, the flue gas flows between the plates, and the air flows inside the plates, and the flue gas and air are separated by the plates.

[0022] As a preferred solution of the present invention, the plate heat exchanger is arranged in the vertical flue or the horizontal flue after the rotary preheater.

[0023] As a preferred embodiment of the present invention, the flue gas temperature cutoff point in the design of the rotary preheater and the plate heat exchanger must ensure that ammonium bisulfate does not crystallize in the low-temperature section of the rotary preheater.

[0024] As a preferred solution of the present invention, when the resistance of the plate heat exchanger is higher than the set value, the inlet damper of the first module is closed and online clearing is performed. After the clearing is completed, the inlet damper of the module is opened and the inlet damper of the second module is closed to clear the blockage of the second module. This process is repeated and the normal mode is restored after all modules are cleared.

[0025] As a preferred embodiment of the present invention, a differential pressure transmitter is connected between the flue gas inlet and outlet of the plate heat exchanger. The differential pressure transmitter measures the differential pressure between the flue gas inlet and outlet of the plate heat exchanger and feeds this pressure back to the DCS control system. The control system then controls the opening and closing of the damper based on the plate heat exchanger's resistance to facilitate online removal of ammonium bisulfate.

[0026] As a preferred solution of the present invention, it also includes a control system, and the differential pressure transmitter is electrically connected to the control system.

[0027] The beneficial effects of the utility model are:

[0028] The wide-channel plate heat exchanger employed in this utility model generally requires no deblocking. Even when high resistance requirements are required, ammonium bisulfate can be removed by closing some inlet dampers and "holding back" the airflow, using the heat from the flue gas to raise the metal wall temperature. During the deblocking process, no external heat source is introduced, and the flue gas volume remains unchanged, unaffecting the thermal balance, exhaust temperature, and air leakage rate. No additional air ducting is required, resulting in a simpler system. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural diagram of the present utility model.

[0030] In the figure: 1-rotary preheater; 2-plate heat exchanger; 3-dust collector; 4-primary / secondary fan; 5-inlet damper; 6-differential pressure transmitter. DETAILED DESCRIPTION

[0031] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0032] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but rather merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without inventive effort are within the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features therein may be combined with each other unless there is a conflict.

[0033] According to relevant research, ammonium bisulfate is in liquid form at temperatures between 147 and 207°C, and evaporates from liquid to gas at temperatures above 207°C. Based on this principle, the present invention proposes an air preheating system coupled with a rotary preheater and a plate heat exchanger.

[0034] like Figure 1 As shown, the anti-blocking smoke and air coupling system based on the rotary preheater of this embodiment includes a rotary preheater 1, a plate heat exchanger 2, a dust collector 3, a primary / secondary fan 4, a flue and an air duct. The flue passes through the rotary preheater 1, the plate heat exchanger 2 and the dust collector 3 in sequence, and the air duct passes through the primary / secondary fan 4, the plate heat exchanger 2 and the rotary preheater 1 in sequence; the plate heat exchanger 2 includes several modules, each module is provided with an independently opened and closed inlet damper 5, the cold air in the air duct is divided into several branches and enters the corresponding modules respectively, and the flue gas in the flue passes through all modules in sequence; the flue gas side and the air side of the plate heat exchanger 2 are in the form of a cross-wall structure.

[0035] The rotary preheater 1 is positioned at the outlet of the economizer and denitrification device in the flue. Positioning the rotary preheater 1 in the medium- to high-temperature flue gas region and the plate heat exchanger 2 in the low-temperature flue gas region completely eliminates ammonium bisulfate blockage in the rotary preheater 1. The plate heat exchanger 2 is positioned in the vertical or horizontal flue following the rotary preheater 1.

[0036] Figure 1 In the figure, the plate heat exchanger 2 is schematically illustrated as 4 modules, and in actual engineering, it can be set to more or fewer modules.

[0037] Plate heat exchanger 2 is placed after rotary preheater 1. Flue gas from rotary preheater 1 enters plate heat exchanger 2, while cold air from the blower and primary fan is also heated by plate heat exchanger 2 before entering rotary preheater 1. This ensures a higher flue gas temperature at the outlet of rotary preheater 1, as well as a higher air temperature at its inlet. This significantly increases the metal wall temperature, preventing the deposition of ammonium bisulfate.

[0038] Through the above method, the ammonium bisulfate blockage problem of the rotary preheater 1 is completely solved, but SO3 in the flue gas and excessive sprayed ammonia will continue to form ammonium bisulfate in the downstream plates and adhere to the flue gas side plates of the plate heat exchanger 2.

[0039] Plate heat exchanger 2 utilizes wide-channel plates. Flow simulation analysis indicates that, even with long-term operation, the flue gas at the boiler tail will not clog the channels. Plate heat exchanger 2 utilizes wide-channel plates to prevent clogging. The air-side inlets of adjacent modules are separated by partitions and ports, with inlet dampers 5 connected to the ports.

[0040] For units burning high-sulfur coal or with high ammonia slip, ammonium bisulfate and debris may accumulate on the plate heat exchanger 2, causing a slight increase in resistance. When ammonium bisulfate removal is necessary, the module's inlet damper 5 is closed, allowing only flue gas to flow in, raising the metal wall temperature. Each module then rotates, using flue gas for heating, removing ammonium bisulfate online to prevent ash adsorption and increased resistance.

[0041] The exhaust gas temperature at the outlet of the plate heat exchanger 2 is about 120°C, which is lower than the liquid phase range of ammonium bisulfate (147-207°C). The gaseous ammonium bisulfate heated in the plate heat exchanger 2 will be removed by the electrostatic precipitator 3 together with the ash in the form of solid crystals when entering the electrostatic precipitator 3, preventing the ammonium bisulfate from liquefying and condensing again to clog the dust collector 3.

[0042] Furthermore, a differential pressure transmitter 6 is connected between the flue gas inlet and outlet of the plate heat exchanger 2. The present invention also includes a control system, with the differential pressure transmitter 6 being electrically connected to the control system. The differential pressure transmitter 6 measures the differential pressure between the flue gas inlet and outlet of the plate heat exchanger 2 and feeds this pressure back to the DCS control system. The control system then controls the opening and closing of the damper based on the resistance of the plate heat exchanger 2 to facilitate online removal of ammonium bisulfate.

[0043] The flue gas temperature cutoff point during the design of the rotary preheater 1 and the plate heat exchanger 2 must ensure that ammonium bisulfate does not crystallize in the low-temperature section of the rotary preheater 1 .

[0044] The primary air and secondary air of the primary / secondary air fan 4 are independent of each other, and the primary air and secondary air respectively correspond to several different modules of the plate heat exchanger 2.

[0045] In this utility model, after exiting the economizer and SCR, flue gas passes through rotary preheater 1 and plate heat exchanger 2, and then enters dust collector 3. After exiting the primary / secondary fan 4, cold air passes through plate heat exchanger 2 and rotary preheater 1, and then enters the boiler. Rotary preheater 1 is placed in the medium-high flue gas temperature area at the economizer and SCR outlets, while plate heat exchanger 2 is placed in the low flue gas temperature area.

[0046] The plate heat exchanger is designed as a two-module system. The air inlet of each module is separated by a partition and an interface, and an inlet damper 5 is provided. Each module can be opened and closed independently, so that each module can remove ammonium bisulfate online.

[0047] The key to the actual operation of the present invention is how to allocate the heating surfaces of the rotary preheater 1 and the plate heat exchanger 2 to ensure that the ammonium bisulfate liquid phase is transferred to the range of the plate heat exchanger 2.

[0048] When ammonium bisulfate becomes clogged in plate heat exchanger 2, the inlet damper 5 of the first module of plate heat exchanger 2 is closed (the remaining modules operate normally). Only flue gas flows through this module, raising the metal wall temperature. The flue gas heats the module, vaporizing or decomposing the ammonium bisulfate. After the ammonium bisulfate in this module is cleared, the inlet damper 5 of this module is opened, and the inlet damper 5 of the next module is closed to clear the ammonium bisulfate. This process repeats, with each module taking turns using flue gas heating to clear the ammonium bisulfate online. After all modules are cleared, normal operation resumes.

[0049] After the plate heat exchanger 2 absorbs the waste heat of the flue gas, the exhaust gas temperature is about 120°C, which is lower than the liquid phase range of ammonium bisulfate (147-207°C), ensuring the safe operation of the dust collector 3.

[0050] The module's removal of ammonium bisulfate does not affect parameters such as heat balance, exhaust temperature, and air leakage rate. This fundamentally differs from existing technologies that use hot air or other heat sources to remove ammonium bisulfate. The present invention utilizes the heat of the flue gas itself, without introducing a heat source. Only the air and smoke distribution channels are altered.

[0051] Purpose and application of this utility model:

[0052] 1) It can completely solve the problems of ammonium bisulfate deposition and low-temperature corrosion at the cold end of the rotary preheater 1. Existing solutions (such as installing a low-temperature economizer combined with a heater, steam heater, or heat pipe at the inlet of the rotary preheater 1) can only moderately increase the rotary inlet air temperature, increase the metal wall temperature of components in some areas, and slow down the deposition of ammonium bisulfate, but cannot completely eliminate the formation of ammonium bisulfate on the cold end components of the rotary preheater 1.

[0053] 2) After connecting plate heat exchanger 2 in series with rotary preheater 1, the height of rotary preheater 1 is appropriately lowered to increase the flue gas temperature at its outlet. Simultaneously, plate heat exchanger 2 absorbs the higher flue gas temperature at the rotary preheater 1 outlet and uses it to heat the inlet air temperature of rotary preheater 1. This increased inlet air temperature further increases the flue gas temperature at the rotary preheater 1 outlet, forming a flue-air coupled heating system that significantly increases the metal wall temperature of rotary preheater 1. This transfers the ammonium bisulfate liquid phase to plate heat exchanger 2, fundamentally resolving the blockage problem of rotary preheater 1.

[0054] 3) The plate heat exchanger 2 can use the wide-channel plates independently developed by our company. The plate spacing on the flue gas side is set larger, and the porosity is much larger than that of the rotary preheater 1, so there will be no blockage. Although its heat exchange efficiency is not as good as that of the rotary preheater 1, the flue space behind the rotary preheater 1 can be fully utilized to arrange as many heating surfaces as possible to make up for its heat exchange efficiency.

[0055] 4) Considering that units operating with high-sulfur coal or significant ammonia escape may still experience ammonium bisulfate deposition after years of operation, plate heat exchanger 2 can be divided into several modules. Each module is equipped with a damper (normally open). When ammonium bisulfate removal is required, the damper of the module is closed, allowing only flue gas to pass through, raising the metal wall temperature. Each module is then heated by flue gas in turn, removing ammonium bisulfate online to prevent ash adsorption and channel blockage. To address the severe low-temperature corrosion at the end of plate heat exchanger 2, stainless steel can be designed to improve corrosion resistance.

[0056] 5) The present invention transfers the ammonium bisulfate liquid phase into the plate heat exchanger 2 with a wide flow channel, preventing blockage through the large plate spacing of the wide flow channel. In addition, the ammonium bisulfate on the plate heat exchanger 2 can be removed online by controlling the smoke and air, which is a qualitative change compared to the existing system solutions.

[0057] 6) The present invention is applicable to various coal-fired power generation units, especially medium and large coal-fired units, because the flue after the outlet of the rotary preheater 1 has a larger available space, which can be arranged with more plate-type heating surfaces, resulting in better results. The coupling method proposed by the present invention can effectively solve the blockage problem of the rotary preheater 1 of the coal-fired unit. It can be said that the present invention proposes a new boiler air preheating system that can remove ammonium bisulfate online, solving the pain points of the rotary preheater 1.

[0058] 7) The present invention is applicable to newly built units and modified units, and is particularly applicable to units burning high-sulfur coal and where ammonia escape is high and easily leads to blockage of the rotary preheater 1 .

[0059] 8) The present invention can reasonably adjust the areas of the rotary preheater 1 and the plate heat exchanger 2 according to the on-site space and the sulfur content of the coal being burned, and can appropriately increase the area of ​​the plate heat exchanger 2 to reduce the exhaust gas temperature. The optimal area distribution of the rotary preheater 1 and the plate heat exchanger 2 can be determined through calculation to ensure that the metal wall temperature of the heat exchange element of the rotary preheater 1 is above the acid corrosion temperature and that ammonium bisulfate deposition does not occur.

[0060] The novelty of this utility model and the comparison with similar technologies:

[0061] 1) The main purpose of the conventional heat exchange equipment at the rear of the boiler (after the rotary preheater 1) is to absorb waste heat to heat the cold air or heat medium water and reduce the boiler exhaust temperature, but it does not fundamentally solve the blockage problem at low temperatures.

[0062] The utility model uses a plate heat exchanger 2 as an air-to-air heat exchanger and arranges it after the rotary preheater 1. Its main purpose is to utilize the excellent anti-blocking performance of the wide-channel plate heat exchanger 2. This method is the first of its kind in the industry.

[0063] 2) The existing coupled heat exchange equipment is all tubular heat exchangers, whose flue gas flow and channel direction are perpendicular, and there are blockages and wear. This is an inherent problem in the principle of tubular heat exchangers and cannot be avoided.

[0064] The utility model adopts a wide-channel plate heat exchanger 2, the flue gas flow and the channel direction are consistent, and the plate channel is large, the anti-blocking performance is better, and the wear is smaller.

[0065] 3) There is a blockage problem of ammonium bisulfate on the leeward side of the tubular heat exchanger. Currently, there is a patented technology for introducing high-temperature hot air. The hot air is introduced into the flue gas side through a bypass air duct and valve control to heat and remove the ammonium bisulfate. However, multiple air ducts need to be added, and the original flue gas duct also needs to be modified accordingly. The system is relatively complex. At the same time, the introduction of external heat source will also affect the thermal balance of the entire preheater system. In addition, the high-temperature hot air entering the flue will cause the exhaust gas temperature to increase and the air leakage rate to increase.

[0066] The wide-channel plate heat exchanger 2 adopted in the present invention generally does not require clearing. Even when faced with high resistance requirements, it is possible to remove ammonium bisulfate by closing some inlet dampers 5 and "holding back the air" (as mentioned above, only letting in flue gas without letting in air, see the description of the technical solution for details) using the heat of the flue gas to increase the metal wall temperature. During the entire clearing process, no external heat source is introduced, the flue gas volume does not change, the thermal balance is not affected, the exhaust temperature and the air leakage rate are not affected, and there is no need to add additional air ducts, making the system simpler.

[0067] The implementation of this utility model has the following benefits and effects:

[0068] 1) Completely resolves the ammonium bisulfate blockage and low-temperature corrosion issues in the rotary preheater 1, maintaining the smoke and air resistance within the design range, thereby reducing the current required by the induced draft fan, forced draft fan, and primary fan. Furthermore, severely clogged preheaters often experience reduced heat exchange efficiency. By implementing this utility model, while maintaining a low resistance level, the exhaust gas temperature of the boiler can be lowered, saving coal consumption.

[0069] Boundary conditions: 80% load, 5,000 annual utilization hours, and standard coal price of 1,000 yuan / ton.

[0070] Taking a 300MW unit as an example, the current operating airside resistance is approximately 1.8 kPa, the flue gas resistance is approximately 2.2 kPa, and the exhaust gas temperature is approximately 150°C. Through the design of this utility model, the outlet flue gas temperature of rotary preheater 1 is 200°C, the inlet air temperature is 120°C, the airside resistance is 600 Pa, the flue gas resistance is 800 Pa, and the combined cold end temperature is 320°C, far exceeding the original design requirement of 140°C. This completely eliminates the clogging problem of rotary preheater 1. The outlet flue gas temperature of plate heat exchanger 2 is 125°C, the airside resistance is approximately 900 Pa, and the flue gas resistance is approximately 250 Pa.

[0071] After the transformation, the exhaust gas temperature was reduced by 25°C and the smoke wind resistance was reduced by 1450Pa. The direct economic benefit is saving about 5.7 million yuan in coal consumption and electricity costs each year.

[0072] 2) After implementation, the utility model can eliminate steam heaters, thereby reducing auxiliary steam consumption. Taking the aforementioned 300MW unit as an example, eliminating steam heaters can save 8.5 million yuan per unit per year (assuming the steam heaters are in operation for three months each year).

[0073] 3) After the installation of this utility model, the downtime for flushing can be reduced each year, and the power generation time can be increased by about two weeks. Calculated at a profit of 0.05 yuan per kilowatt-hour, the profit can be increased by 4.03 million yuan.

[0074] 4) The above economic benefits totaled RMB 18.23 million.

[0075] Specific embodiment: Take a 300MW unit as an example for description.

[0076] Due to high ammonia escape in this project, serious ammonium bisulfate blockage occurred, resulting in increased resistance. Ammonium bisulfate adsorbed ash and adhered to the surface of the rotary preheater 1 element, reducing heat exchange efficiency and causing high exhaust gas temperature. According to the utility model, the calculated values ​​are shown in Table 1:

[0077] Table 1 shows the calculated values ​​for a 300MW unit as an example.

[0078]

[0079]

[0080] As can be seen, after implementing this utility model, the inlet air temperature and outlet flue gas temperature of rotary preheater 1 have been significantly improved, ensuring the safety of rotary preheater 1. Furthermore, the plate heat exchanger 2 uses wide-channel plates for anti-clogging and is divided into several modules. Ammonium bisulfate is removed online through alternating heating, meeting anti-clogging requirements. After the modification, the total flue gas resistance was reduced by 1450 Pa and the exhaust gas temperature was lowered by 25°C, achieving excellent economic efficiency.

[0081] The present invention is not limited to the above-mentioned optional implementation methods. Anyone can derive various other forms of products under the inspiration of the present invention. However, no matter what changes are made in the shape or structure, any technical solution that falls within the scope defined by the claims of the present invention shall fall within the scope of protection of the present invention.

Claims

1. An anti-blocking smoke and air coupling system based on a rotary preheater, characterized by: The invention comprises a rotary preheater (1), a plate heat exchanger (2), a dust collector (3), a primary / secondary fan (4), a flue and an air duct, wherein the flue passes through the rotary preheater (1), the plate heat exchanger (2) and the dust collector (3) in sequence, and the air duct passes through the primary / secondary fan (4), the plate heat exchanger (2) and the rotary preheater (1) in sequence; the plate heat exchanger (2) comprises a plurality of modules, each module being provided with an independently opened and closed inlet damper (5), the cold air in the air duct is divided into a plurality of branches and enters the corresponding modules respectively, and the smoke in the flue passes through all the modules in sequence.

2. The anti-blocking smoke-air coupling system based on a rotary preheater according to claim 1 is characterized in that: The rotary preheater (1) and the plate heat exchanger (2) are arranged in series, the rotary preheater (1) is arranged in a medium-high temperature flue gas area, and the plate heat exchanger (2) is arranged in a low temperature flue gas area; the flue gas from the economizer and the SCR first passes through the rotary preheater (1), then passes through the plate heat exchanger (2), and then enters the downstream dust collector (3).

3. The anti-blocking smoke-air coupling system based on a rotary preheater according to claim 1 is characterized in that: The air from the primary / secondary fan (4) is first heated by the plate heat exchanger (2) before entering the rotary preheater (1).

4. The anti-blocking smoke-air coupling system based on a rotary preheater according to claim 1 is characterized in that: The primary air and secondary air of the primary / secondary air fan (4) are independent of each other, and the primary air and secondary air respectively correspond to several different modules of the plate heat exchanger (2).

5. The anti-blocking smoke-air coupling system based on a rotary preheater according to claim 1 is characterized in that: The air side inlet of each module of the plate heat exchanger (2) is separated by a partition and an interface, and the inlet damper (5) is connected to the interface, and each interface corresponds to a module.

6. The anti-blocking smoke-air coupling system based on a rotary preheater according to claim 1 is characterized in that: The plate heat exchanger (2) comprises a plurality of plates with wide flow channels.

7. The anti-blocking smoke-air coupling system based on a rotary preheater according to claim 1 is characterized in that: The flue gas side and the air side of the plate heat exchanger (2) are in the form of a cross-intersecting partition wall structure, the flue gas flows between the plates, and the air flows inside the plates, and the flue gas and air are separated by the plates.

8. The anti-blocking smoke-air coupling system based on a rotary preheater according to claim 1 is characterized in that: The plate heat exchanger (2) is arranged in a vertical flue or a horizontal flue after the rotary preheater (1).

9. The anti-blocking smoke-air coupling system based on a rotary preheater according to claim 1, characterized in that: The flue gas temperature cutoff point when designing the rotary preheater (1) and the plate heat exchanger (2) must ensure that ammonium bisulfate does not crystallize in the low-temperature section of the rotary preheater (1).

10. The anti-blocking smoke-air coupling system based on a rotary preheater according to any one of claims 1 to 9, characterized in that: When the resistance of the plate heat exchanger (2) is higher than the set value, the inlet damper (5) of the first module is closed and the blockage is cleared online. After the blockage is cleared, the inlet damper (5) of the module is opened and the inlet damper (5) of the second module is closed to clear the blockage of the second module. The same process is repeated until all modules are cleared and the system returns to normal mode.

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