Boiler air heater system and air preheating method

Abstract

The invention discloses a boiler air heater system and an air preheating method, and the boiler air heater system comprises a plurality of mixing and stirring structures which are sequentially arranged at the position of an air inlet of an air heater in series, at least one mixing and stirring structure exchanges heat with a boiler smoke exhaust pipe, and at least one mixing and stirring structure exchanges heat with a first heating assembly; the air heater is provided with an air heater shell, an air heater air inlet and an air heater air outlet, a second heating assembly is arranged in an inner cavity of the air heater shell, the air heater air inlet and the air heater air outlet communicate with the inner cavity of the air heater shell, and the air heater air inlet communicates with the mixing and stirring structure; an air inlet of the air pre-heater is communicated with an air outlet of the air heater, and an air outlet of the air pre-heater is communicated with the air inlet end of the boiler. The sectional type mixing and stirring structure adopts a dual-heat-source mode combining waste heat recovery with active heating, so that the temperature of air entering the boiler does not change greatly, heat is utilized thoroughly, and energy loss is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of boiler auxiliary, and particularly to a boiler air heater system and an air preheating method. Background Art

[0002] The main function of a boiler air heater is to prevent low-temperature corrosion at the cold end of an air preheater. When the boiler is starting up, operating at low load, or operating in winter, the inlet air temperature of the air preheater may be relatively low, which is likely to cause low-temperature corrosion. The boiler air heater prevents such corrosion by heating the incoming air of the boiler to increase the inlet air temperature of the air preheater. An air preheater is a heat exchanger that uses the waste heat of the flue gas from a boiler or other devices to preheat air. Its function is to reduce the flue gas temperature of devices such as boilers, improve the thermal efficiency, make the fuel easier to ignite, burn stably, and improve the combustion efficiency.

[0003] In the existing boiler air heater system, only the waste heat of the flue gas at the tail of the boiler is used to preheat the incoming air, and then the preheated air is introduced into the boiler. The temperature of the flue gas is usually relatively low, and the quality of the waste heat is limited, resulting in a small temperature rise amplitude after the air is preheated. When the boiler load suddenly increases (such as during the peak load regulation of a generator set), the combustion system needs to inhale a large amount of air in a short time, and the flow rate of cold air passing through the air heater per unit time increases significantly. Since the boiler air heater system only relies on the waste heat of the flue gas, and the amount of waste heat in the flue gas remains unchanged, the temperature rise of the air heated by the boiler air heater system will be significantly reduced. After the air heated by the boiler air heater system enters the boiler, the low-temperature air will cause unstable fuel combustion and incomplete combustion, thereby leading to a problem of decreased combustion efficiency. Summary of the Invention

[0004] In view of this, the present invention provides a boiler air heater system and an air preheating method to solve the problem that the existing boiler air heater system only uses the waste heat of the flue gas at the tail of the boiler to preheat the incoming air, resulting in a relatively low air temperature entering the boiler when the boiler load suddenly increases.

[0005] In a first aspect, the present invention provides a boiler air heater system, comprising:

[0006] A plurality of mixing and stirring structures are arranged in series at the air inlet of the air heater and introduce external air. At least one of the mixing and stirring structures exchanges heat with the boiler flue gas pipe, and at least one of the mixing and stirring structures exchanges heat with the first heating component. Each of the mixing and stirring structures is used to heat the introduced external air, uniformly mix the external air, and then input it into the air heater;

[0007] The air heater has an air heater housing, an air heater air inlet, and an air heater air outlet. A second heating component is provided in the inner cavity of the air heater housing. The air heater air inlet and the air heater air outlet are respectively communicated with the inner cavity of the air heater housing, and the air heater air inlet is communicated with a mixing and stirring structure;

[0008] The air preheater has an air preheater air inlet and an air preheater air outlet. The air preheater air inlet is communicated with the air heater air outlet, and the air preheater air outlet is communicated with the boiler air inlet end.

[0009] The beneficial effects of the above boiler air heater system are as follows:

[0010] The incoming air is successively mixed, stirred, and heated through the segmented mixing and stirring structure, so that the air flow rate and velocity entering the boiler are relatively large, providing sufficient oxygen supply. Multiple series-connected mixing and stirring structures can exchange heat with the boiler flue gas pipe and the first heating component to form a dual heat source mode of "waste heat recovery + active heating". On the one hand, it can effectively utilize the waste heat of the flue gas in the boiler flue gas pipe, and on the other hand, it will not cause the problem that the temperature of the air entering the boiler is too low due to the limited heat of the flue gas in the boiler flue gas pipe. Therefore, when the heated air enters the boiler, the temperature of the boiler will not change significantly, thus ensuring its temperature, and the heat utilization is relatively complete, reducing energy loss.

[0011] When the boiler load suddenly increases and the cold air flow rate increases, the first heating component and the second heating component quickly supplement heat to avoid the temperature rise from dropping. In this embodiment, a multi-stage mixing and stirring structure is used to heat the incoming air in combination with the flue gas waste heat, significantly increasing the final temperature of the air and ensuring combustion stability.

[0012] Multiple series-connected mixing and stirring structures can also mix the air flow by stirring, eliminating the problem of too low local wall temperature caused by uneven air temperature distribution in the traditional system, avoiding low-temperature corrosion of the air preheater. The uniform hot air flow can improve the combustion efficiency and reduce the residual unburned fuel.

[0013] In an optional embodiment, there are three mixing and stirring structures, namely a first mixing and stirring structure, a second mixing and stirring structure, and a third mixing and stirring structure;

[0014] The periphery of the first mixing and stirring structure is wound with waste heat exchange tubes. One side of the waste heat exchange tubes exchanges heat with the boiler flue gas pipe, and the other side exchanges heat with the first mixing and stirring structure;

[0015] A heating box is arranged on the periphery of the second mixing and stirring structure. A first heat exchange medium is arranged between the heating box and the second mixing and stirring structure. The heating box exchanges heat with the air in the inner cavity of the second mixing and stirring structure through the first heat exchange medium;

[0016] A heating resistor is provided on the periphery of the third mixing and stirring structure. A heating chamber is provided on the periphery of the heating resistor. The heating chamber communicates with a heating box. The heating resistor exchanges heat with the air in the inner cavity of the third mixing and stirring structure and is used to heat the second heat exchange medium filled in the heating chamber and the heating box.

[0017] The heating box and the heating resistor are the first heating assembly.

[0018] In an optional embodiment, the first mixing and stirring structure, the second mixing and stirring structure, and the third mixing and stirring structure are arranged in sequence from top to bottom. The first mixing and stirring structure communicates with the external air, which is provided by a blower. The third mixing and stirring structure communicates with the air inlet of the air heater; the position of the heating chamber is lower than that of the heating box.

[0019] In an optional embodiment, the mixing and stirring structure includes a cylinder body. Two spiral grooves with opposite rotation directions and opposite arrangements are provided on the inner side wall of the cylinder body. The air inlets of the two spiral grooves are arranged oppositely, and the air outlets of the two spiral grooves incline towards the central axis of the cylinder body and are arranged oppositely.

[0020] The beneficial effects of the above technical solution are as follows: After the cold air enters the cylinder body, it flows downward along the surfaces of the two opposite spiral grooves, causing the incoming air to form a vortex impact and enabling sufficient heat exchange with the wall surface of the cylinder body. Then it flows out from the air outlets of the spiral grooves. At this time, due to the absence of the limitation of the spiral grooves and the air outlets of the spiral grooves being set as slopes, the gas gathers towards the middle, forming a vortex that collides towards the middle, generating a stirring effect, thereby mixing the gas, and accordingly heating the incoming air, making the heating of the air more uniform.

[0021] In an optional embodiment, at least one of the mixing and stirring structures is connected to the boiler flue gas pipe through a first circulation pipeline, so that the flue gas in the boiler flue gas pipe can circulate into the mixing and stirring structure and be mixed with the air in the mixing and stirring structure; the air preheater is connected to the boiler flue gas pipe through a second circulation pipeline, so that the flue gas in the boiler flue gas pipe can circulate into the air preheater; electromagnetic valves are respectively provided on the first circulation pipeline and the second circulation pipeline.

[0022] In an optional embodiment, the boiler air heater system further includes:

[0023] A first temperature sensor, which is arranged inside the boiler flue gas pipe;

[0024] A second temperature sensor, which is arranged at the air outlet of the air heater;

[0025] A flue gas comprehensive analyzer has a detection end, and the detection end of the flue gas comprehensive analyzer is arranged inside the boiler exhaust pipe. The flue gas comprehensive analyzer is used to detect and analyze the content of combustible gases in the flue gas in the boiler exhaust pipe, and feed back the detection information to the controller;

[0026] A controller, the output ends of the first temperature sensor, the second temperature sensor and the flue gas comprehensive analyzer are respectively connected to the input end of the controller, and the controlled ends of the first heating component, the second heating component and each solenoid valve are respectively connected to the output end of the controller.

[0027] The beneficial effects of the above technical solution are as follows: The controller receives real-time data from the first temperature sensor, the second temperature sensor and the flue gas comprehensive analyzer; according to the set control strategy, it adjusts the working states of the first heating component, the second heating component and each solenoid valve to realize the dynamic optimization of the flue gas circulation flow rate and heating power.

[0028] In an optional implementation manner, a fan blade is arranged at the connection between the air preheater air inlet and the air heater air outlet;

[0029] And / or, the second heating component is an electric heating wire.

[0030] In a second aspect, the present invention provides an air preheating method, which is carried out by using the boiler air heater system, and includes the following steps:

[0031] S1. External air sequentially passes through each mixing and stirring structure, and each mixing and stirring structure heats and mixes the external air. At least one mixing and stirring structure heats the external air by using the waste heat of the flue gas in the boiler exhaust pipe, and at least one mixing and stirring structure heats the external air by using the first heating component;

[0032] S2. The externally mixed and heated air enters the air heater and is reheated by the second heating component in the air heater;

[0033] S3. The externally air heated by the second heating component enters the air preheater, and then enters the boiler through the boiler air inlet end.

[0034] The beneficial effects of the above air preheating method are as follows:

[0035] When the external air flows through each stirring structure, the waste heat heating of the flue gas is combined with the heating of the first heating component. On the one hand, it can effectively utilize the waste heat of the flue gas in the boiler exhaust pipe, and on the other hand, it can avoid the problem that the temperature of the air entering the boiler is too low due to the limited heat of the flue gas in the boiler exhaust pipe.

[0036] The outside air undergoes the heating processes of the mixing and stirring structure, the air preheater, and the air heater in sequence, achieving the multi-stage heating of the air, ensuring that the air entering the boiler reaches the ideal temperature, and further improving the combustion efficiency.

[0037] In an alternative embodiment, the following steps are further included:

[0038] Detect the content of combustible gas in the flue gas inside the boiler exhaust pipe through a flue gas comprehensive analyzer; when the detected content of combustible gas in the flue gas is higher than the set threshold, control at least one solenoid valve to open through a controller, so that the flue gas of the boiler exhaust pipe is introduced into the air preheater and / or at least one mixing and stirring structure.

[0039] In an alternative embodiment, the following steps are further included:

[0040] Detect the temperature of the flue gas inside the boiler exhaust pipe through a first temperature sensor, and detect the temperature of the gas at the air outlet of the air preheater through a second temperature sensor; the controller controls the operating state of the solenoid valve based on the temperature detection information of the first temperature sensor and the second temperature sensor. Description of the Drawings

[0041] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0042] Figure 1 It is a flow block diagram of a boiler air preheater system provided by the present invention;

[0043] Figure 2 It is a structural diagram of the mixing and stirring structure of a boiler air preheater system provided by the present invention.

[0044] Description of the Reference Numerals:

[0045] 1. Air preheater; 2. Electric heating wire; 3. Mixing and stirring structure; 31. First mixing and stirring structure; 32. Second mixing and stirring structure; 33. Third mixing and stirring structure; 34. Cylinder body; 35. Spiral groove; 4. Waste heat heat exchange tube; 5. Heating box; 6. Heating resistor; 7. Heating cavity; 8. Air heater; 9. Boiler air inlet end; 10. Boiler exhaust pipe; 11. First temperature sensor; 12. Flue gas comprehensive analyzer; 13. Second temperature sensor; 14. Fan; 15. Solenoid valve. Detailed Embodiments

[0046] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0047] The main function of the boiler air preheater is to prevent low-temperature corrosion at the cold end of the air preheater. During boiler startup, low-load operation, and winter operation, the inlet air temperature of the air preheater may be relatively low, which can easily lead to low-temperature corrosion. The boiler air preheater prevents this corrosion by heating the boiler inlet air and raising the inlet air temperature of the air preheater.

[0048] Generally, the air preheater uses the tail gas of the boiler to heat the air entering the furnace. Although it utilizes waste heat, it also increases the heat of the boiler flue gas. Since the heat is not fixed due to the change in unit load, its utilization efficiency is relatively low. First, the temperature of the air preheating is unstable, making the thermal efficiency of the boiler unstable. Second, increasing the air volume at the bottom of the boiler can make its combustion more complete, but increasing the flow rate allows a large amount of cold air to enter, thereby reducing the temperature at the bottom of the boiler and affecting its thermal efficiency. Specifically as follows:

[0049] 1) Affect the thermal efficiency

[0050] The main function of the air preheater is to use the heat of the boiler tail gas to heat the air required for combustion. A low inlet temperature means less heat is brought in by the air, which will make the temperature after the fuel and air are mixed during the combustion process relatively low, slow down the combustion speed, and cause incomplete combustion, resulting in increased heat loss and reduced thermal efficiency of the boiler.

[0051] A low air temperature will also increase the flue gas discharge temperature, and more heat is discharged with the flue gas, further reducing the thermal efficiency of the boiler.

[0052] 2) Cause low-temperature corrosion

[0053] When the inlet temperature of the air preheater is too low, water vapor and sulfur oxides in the flue gas will condense at the low-temperature part of the air preheater, forming corrosive substances such as sulfuric acid, which will corrode the heating surface of the air preheater and shorten the service life of the air preheater.

[0054] Long-term low-temperature corrosion will thin and perforate the metal wall of the air preheater, resulting in air leakage and affecting the normal operation of the boiler.

[0055] 3) Cause ash accumulation and blockage

[0056] A lower inlet temperature will make it easier for impurities such as fly ash in the flue gas to deposit on the heating surface of the air preheater, forming fouling. Fouling will increase the flow resistance of air and flue gas, reduce the heat transfer effect of the air preheater, and degrade the performance of the air preheater.

[0057] Severe fouling may also cause blockage of the air preheater, reducing the flow area of air and flue gas, affecting the ventilation and combustion of the boiler, and even possibly forcing the boiler to stop for cleaning.

[0058] 4) Affect combustion stability

[0059] A low inlet temperature of the air preheater will reduce the temperature of the air entering the furnace, lowering the temperature level in the furnace and affecting the ignition and combustion stability of the fuel. For some difficult-to-burn fuels, problems such as difficult ignition, incomplete combustion, and even flameout may occur, affecting the normal operation of the boiler.

[0060] Therefore, to ensure the normal operation of the boiler air heater, the present invention modifies the existing boiler air heater and installs an electric heating as an auxiliary heat source for the air heater, which can effectively increase the inlet air temperature of the boiler air preheater and is of great significance for the safe and stable operation of the boiler.

[0061] According to an embodiment of the present invention, in a first aspect, a boiler air heater system is provided, which includes a mixing and stirring structure 3, an air heater 1, and an air preheater 8 as shown in combination with Figure 1 and Figure 2 The mixing and stirring structure 3 is provided with a plurality of them, which are sequentially connected in series at the air inlet of the air heater and external air is introduced. At least one mixing and stirring structure 3 exchanges heat with the boiler exhaust pipe 10, and at least one mixing and stirring structure 3 exchanges heat with the first heating component. Each mixing and stirring structure 3 is used to heat the introduced external air and uniformly mix the external air and then input it into the air heater 1.

[0062] The air heater 1 has an air heater housing, an air heater air inlet, and an air heater air outlet. A second heating component is arranged in the inner cavity of the air heater housing to further supplement heat. The air heater air inlet and the air heater air outlet are respectively communicated with the inner cavity of the air heater housing, and the air heater air inlet is communicated with the mixing and stirring structure 3.

[0063] The air preheater 8 is used for air preheating and premixing work. The air preheater 8 has an air preheater air inlet and an air preheater air outlet. The air preheater air inlet is communicated with the air heater air outlet, and the air preheater air outlet is communicated with the boiler air inlet end 9.

[0064] The air preheater 8 is used for air preheating and pre - mixing work. The air preheater 8 has an air preheater air inlet and an air preheater air outlet. The air preheater air inlet is communicated with the air heater air outlet, and the air preheater air outlet is communicated with the boiler air inlet end 9.

[0065] The above boiler air preheater system mixes, stirs, and heats the incoming air in sequence through the segmented mixing and stirring structure 3, so that the air flow rate and velocity entering the boiler are relatively large, providing sufficient oxygen supply. Multiple series-connected mixing and stirring structures 3 can exchange heat with the boiler flue gas pipe 10 and the first heating component, forming a dual heat source mode of "waste heat recovery + active heating". On the one hand, it can effectively utilize the waste heat of the flue gas in the boiler flue gas pipe 10, and on the other hand, it will not cause the problem that the temperature of the air entering the boiler is too low due to the limited heat of the flue gas in the boiler flue gas pipe 10. Therefore, when the heated air enters the boiler, the temperature of the boiler will not change significantly, thus ensuring its temperature, and the heat utilization is relatively complete, reducing energy loss.

[0066] When the boiler load suddenly increases and the cold air flow rate increases, the first heating component and the second heating component quickly supplement heat to avoid the decrease in temperature rise. In this embodiment, the multi-stage mixing and stirring structure 3 is used to heat the incoming air in combination with the waste heat of the flue gas, significantly increasing the final temperature of the air and ensuring combustion stability.

[0067] Multiple series-connected mixing and stirring structures 3 can also mix the air flow by stirring, eliminating the problem of too low local wall temperature caused by uneven air temperature distribution in the traditional system, avoiding the low-temperature corrosion of the air preheater 8, and the uniform hot air flow can improve the combustion efficiency and reduce the residual unburned fuel.

[0068] And the multi-stage series-connected mixing and stirring structure forms a "buffer-compensation" mechanism: the front stage uses waste heat to stabilize the basic temperature rise, and the rear stage dynamically adjusts the air temperature entering the boiler through the active heating components (including the first heating component and the second heating component). In load mutation scenarios such as peak shaving of the generator set, the system can quickly respond to changes in air flow rate and maintain the stability of the air temperature entering the boiler.

[0069] In some embodiments, there are three mixing and stirring structures 3, namely the first mixing and stirring structure 31, the second mixing and stirring structure 32, and the third mixing and stirring structure 33.

[0070] The periphery of the first mixing and stirring structure 31 is wound with a waste heat exchange tube 4. One side of the waste heat exchange tube 4 exchanges heat with the boiler flue gas pipe 10, which can be arranged inside the boiler chimney. The other side of the waste heat exchange tube 4 exchanges heat with the first mixing and stirring structure 31. After the waste heat exchange tube 4 exchanges heat with the flue gas in the boiler flue gas pipe 10, it exchanges heat with the first mixing and stirring structure 31 again to realize the heat recovery of the flue gas in the boiler flue gas pipe 10.

[0071] A heating box 5 is arranged on the periphery of the second mixing and stirring structure 32. A first heat exchange medium is arranged between the heating box 5 and the second mixing and stirring structure 32. The heating box 5 exchanges heat with the air in the inner cavity of the second mixing and stirring structure 32 through the first heat exchange medium. Among them, the first heat exchange medium can be water or other media. When the first heat exchange medium is water, the heating box 5 is a water bath heating box, and the heating is more stable through water bath heating.

[0072] A heating resistor 6 is arranged on the periphery of the third mixing and stirring structure 33. Electric heating is used as an auxiliary heat source. A heating cavity 7 is arranged on the periphery of the heating resistor 6. The heating cavity 7 is communicated with the heating box 5 and the second heat exchange medium is filled in both of them. The heating resistor 6 exchanges heat with the air in the inner cavity of the third mixing and stirring structure 33 and is used to heat the second heat exchange medium filled in the heating cavity 7 and the heating box 5. Among them, the second heat exchange medium can be water or other media.

[0073] The above heating box 5 and heating resistor 6 are the first heating components. The air inside the third mixing and stirring structure 33 and the second heat exchange medium in the heating cavity 7 can be heated simultaneously through the heating resistor 6. The second heat exchange medium in the heating cavity 7 exchanges heat with the second heat exchange medium in the heating box 5, and then the air inside the second mixing and stirring structure 32 is heated, so that the heat generated by the heating resistor 6 can be fully utilized.

[0074] The second heating component arranged in the inner cavity of the air heater is an electric heating wire 2. The electric heating wire 2 has high heating efficiency and stable heating performance, and can quickly heat the air inside the air heater to the required temperature and maintain a constant temperature state to meet the operation requirements of the boiler air heater system.

[0075] In some embodiments, the first mixing and stirring structure 31, the second mixing and stirring structure 32 and the third mixing and stirring structure 33 are arranged in sequence from top to bottom. The first mixing and stirring structure 31 is communicated with the external air, and the external air is provided by a fan 14. The air flow is driven by the fan 14. The third mixing and stirring structure 33 is communicated with the air inlet of the air heater. The heating cavity 7 is not in contact with the third mixing and stirring structure 33. The position of the heating cavity 7 is lower than that of the heating box 5, which reduces the influence of the heat absorbed by the heating cavity 7 on the third mixing and stirring structure 33. Secondly, according to the characteristic that hot water rises, the temperature of the heating box 5 is maintained.

[0076] If the mixing and stirring structure 3 is only a straight cylinder structure, when the external air is introduced into the mixing and stirring structure 3, the air near the inner wall of the cylinder of the mixing and stirring structure 3 is more easily heated than the air in the middle of the cylinder of the mixing and stirring structure 3. As a result, the air in the outer circle inside the mixing and stirring structure 3 is hotter than the air in the inner circle, and the air entering the boiler is not evenly heated.

[0077] To solve the above problems, in some embodiments, the mixing and stirring structure 3 includes a cylinder body 34. Two spiral grooves 35 with opposite spiral directions are provided on the inner side wall of the cylinder body 34 to guide the air flow to form a two-way swirling flow in the cylinder body. The two spiral grooves 35 are arranged oppositely, the air inlets of the two spiral grooves 35 are arranged oppositely, and the air outlets of the two spiral grooves 35 incline towards the central axis of the cylinder body 34 and are arranged oppositely. In this embodiment, after the cold air enters the cylinder body 34, it flows downward along the surfaces of the two opposite spiral grooves 35, causing the incoming air to form a vortex impact, and enabling sufficient heat exchange with the wall surface of the cylinder body 34. Then it flows out from the air outlet of the spiral groove. At this time, due to the absence of the limitation of the spiral groove and the air outlet of the spiral groove being set as a slope, the gas gathers towards the middle, forming a vortex that flushes towards the middle, generating a stirring effect, thereby mixing the gas, and accordingly heating the incoming air, making the heating of the air more uniform, and preventing the problem that the temperature of the outer circle is higher than that of the inner circle.

[0078] The swirling flow intensity can also be controlled by controlling the pitch of the spiral groove 35. When it is necessary to enhance the swirling flow intensity, reducing the pitch of the spiral groove 35 can increase the number of rotations of the fluid when flowing in the spiral groove. When it is necessary to weaken the swirling flow intensity, increasing the pitch of the spiral groove 35 can reduce the number of rotations of the fluid when flowing in the spiral groove.

[0079] In some embodiments, at least one mixing and stirring structure 3 is connected to the boiler flue gas pipe 10 through a first circulation pipeline, so that the flue gas in the boiler flue gas pipe 10 can circulate into the mixing and stirring structure 3 and be mixed with the air in the mixing and stirring structure 3. The air preheater 8 is connected to the boiler flue gas pipe 10 through a second circulation pipeline, so that the flue gas in the boiler flue gas pipe 10 can circulate into the air preheater 8, enabling the unburned gas in the flue gas to burn again in a cycle. Solenoid valves 15 are respectively arranged on the first circulation pipeline and the second circulation pipeline.

[0080] In some embodiments, the boiler warm air heater system further includes a first temperature sensor 11, a second temperature sensor 13, a flue gas comprehensive analyzer 12, and a controller.

[0081] The first temperature sensor 11 is arranged inside the boiler flue gas pipe 10 and is used to monitor the flue gas temperature T1, taking this detected value as an important parameter for judging the heat utilization rate of the flue gas.

[0082] The second temperature sensor 13 is arranged at the air outlet of the warm air heater and is used to monitor the outlet temperature T2 of the gas processed by the mixing and stirring structure 3, reflecting the mixing and heating effect and the operating state of the system.

[0083] The flue gas comprehensive analyzer 12 has a detection end, and the detection end of the flue gas comprehensive analyzer 12 is arranged inside the boiler exhaust pipe 10. The flue gas comprehensive analyzer 12 is used to detect and analyze the content of combustible gas in the flue gas in the boiler exhaust pipe 10, and feed back the detection information to the controller. When the concentration of combustible gas exceeds the standard, the controller triggers an alarm or adjusts the combustion condition.

[0084] The output ends of the first temperature sensor 11, the second temperature sensor 13 and the flue gas comprehensive analyzer 12 are respectively connected to the input end of the controller, and the controlled ends of the first heating component, the second heating component and each electromagnetic valve 15 are respectively connected to the output end of the controller. The controller receives real-time data from the first temperature sensor 11, the second temperature sensor 13 and the flue gas comprehensive analyzer 12; according to the set control strategy (such as temperature range, combustible gas concentration threshold), it adjusts the working states of the first heating component, the second heating component and each electromagnetic valve 15 to realize the dynamic optimization of the flue gas circulation flow rate and heating power.

[0085] Among them, the temperature control strategy can be: if T2 is lower than the lower limit, the controller increases the power of the first heating component or opens the electromagnetic valve 15 of the first circulation pipeline to increase the flue gas flow rate to raise the temperature of the mixed gas; if T2 is higher than the upper limit, the controller reduces the power of the first heating component or closes the electromagnetic valve 15 of the first circulation pipeline to reduce the flue gas flow rate to avoid overheating.

[0086] The combustible gas concentration control strategy can be: if the concentration of combustible gas exceeds the threshold, the controller controls the electromagnetic valve 15 on the first circulation pipeline and / or the second circulation pipeline to open to realize the circulating combustion of the combustible fuel in the flue gas.

[0087] The goal of the thermal efficiency control strategy is to maximize the utilization of the waste heat of the boiler exhaust and reduce the exhaust temperature. The thermal efficiency control strategy: according to the detected value T1 of the first temperature sensor 11, dynamically adjust the opening degrees of the electromagnetic valves of the first circulation pipeline and the second circulation pipeline; when T1 is relatively high, preferentially increase the flue gas flow rate of the first circulation pipeline and use the mixing and stirring structure 3 for sufficient heat exchange; when T1 is relatively low, appropriately reduce the flow rate of the first circulation pipeline to avoid excessive cooling of the flue gas and affect the subsequent combustion stability.

[0088] In some embodiments, a fan blade is arranged at the connection between the air preheater air inlet and the air heater air outlet. The fan blade can rotate after receiving the control signal of the controller, so as to adjust the air flow between the air preheater air inlet and the air heater air outlet, and can more accurately control the temperature and flow rate of the gas entering the air preheater, improving the overall efficiency and stability of the boiler air heater system.

[0089] According to an embodiment of the present invention, in a second aspect, an air preheating method is provided. This method is carried out by using a boiler air heater system and includes the following steps:

[0090] S10. Connection: Wind one end of the waste heat exchange pipe 4 around the periphery of the first mixing and stirring structure 31, install the other end of the waste heat exchange pipe 4 in the boiler chimney. At the same time, connect the boiler exhaust pipe 10 to the boiler chimney, and connect the rest of the devices in sequence.

[0091] S20. Detection: Detect the flue gas temperature inside the boiler exhaust pipe 10 through the first temperature sensor 11, and detect the flue gas components inside the boiler exhaust pipe 10 through the flue gas comprehensive analyzer 12.

[0092] S30. Heating: External air sequentially passes through each mixing and stirring structure 3. Each mixing and stirring structure 3 heats and mixes the external air. At least one mixing and stirring structure 3 uses the waste heat of the flue gas in the boiler exhaust pipe 10 to heat the external air, and at least one mixing and stirring structure 3 uses the first heating component to heat the external air. Taking the case where there are three levels of mixing and stirring structures 3 as an example, the first mixing and stirring structure 31 performs low-temperature heating through the waste heat exchange pipe 4, then the temperature is raised to a relatively high temperature through the second mixing and stirring structure 32 by water bath heating, and final heating is performed through the third mixing and stirring structure 33.

[0093] The externally mixed and heated air enters the air heater 1, and is reheated by the second heating component in the air heater 1.

[0094] The externally heated air by the second heating component enters the air preheater 8, and then enters the boiler through the boiler air inlet end 9.

[0095] In the above air preheating method, when the external air flows through each mixing and stirring structure 3, the waste heat heating of the flue gas is combined with the heating of the first heating component. On the one hand, the waste heat of the flue gas in the boiler exhaust pipe 10 can be effectively utilized, and on the other hand, the problem that the air temperature entering the boiler is too low due to the limited heat of the flue gas in the boiler exhaust pipe 10 can be avoided.

[0096] The external air successively undergoes the heating processes of the mixing and stirring structure 3 (waste heat heating of the flue gas and heating of the second heating component), the air heater 1 (heating of the second heating component), and the air preheater 8, realizing multi-stage heating of the air, ensuring that the air entering the boiler reaches the ideal temperature, and further improving the combustion efficiency.

[0097] The above air preheating method further includes the following steps: Detect the content of combustible gas in the flue gas inside the boiler exhaust pipe 10 through the flue gas comprehensive analyzer 12. When the detected content of combustible gas in the flue gas is higher than the set threshold, control at least one solenoid valve 15 to open through the controller, so that the flue gas in the boiler exhaust pipe 10 is introduced into the air heater 1 and / or at least one mixing and stirring structure 3, and then the combustible gas contained in the flue gas is fully burned.

[0098] The above air preheating method further includes the following steps:

[0099] The internal flue gas temperature of the boiler exhaust pipe 10 is detected by the first temperature sensor 11, so that the utilization of the flue gas waste heat can be grasped in real time. If the flue gas temperature is too low, the controller will adjust the operating state of the solenoid valve 15 to reduce or stop the flue gas from entering the mixing and stirring structure 3, avoiding the decline of the air heating effect caused by insufficient heat.

[0100] The gas temperature at the air outlet of the air heater is detected by the second temperature sensor 13 to ensure that the temperature of the air reheated by the air heater 1 reaches the set value. If the temperature is too low, the controller can adjust the power of the solenoid valve 15 or other heating components to improve the heating effect.

[0101] Based on the temperature detection information of the first temperature sensor 11 and the second temperature sensor 13, the controller controls the operating state of the solenoid valve 15. For example, when the flue gas temperature is low, the flue gas flow is reduced; when the flue gas temperature is high, the flue gas flow is increased. This dynamic adjustment mechanism can ensure the stable operation of the system under different working conditions. By real-time monitoring of the flue gas temperature and the temperature at the air outlet of the air heater, the controller can reasonably distribute the flue gas waste heat and the heat of other heating components, minimizing energy waste.

[0102] The above air preheating method further includes a temperature control step: when introducing air, the flow rate and rotation speed of the fan 14 are controlled according to the temperature and the flow rate of the boiler exhaust pipe 10 to achieve more precise temperature control. When the flue gas temperature is high and the flow rate of the boiler exhaust pipe 10 is large, the controller can instruct the fan 14 to increase the flow rate and raise the rotation speed to more effectively utilize the high-temperature flue gas to preheat the air. On the contrary, when the flue gas temperature is low or the flow rate of the boiler exhaust pipe 10 is small, the controller will reduce the flow rate and rotation speed of the fan 14 to prevent the preheated air from being over-cooled. This temperature control step not only improves the preheating efficiency, but also ensures the stability and energy saving of the boiler air heater system under various working conditions.

[0103] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations fall within the scope defined by the appended claims.

Claims

1. A boiler air heater system, characterized in that: include: A plurality of mixing and stirring structures (3) are sequentially arranged in series at the air inlet of the heater and introduce external air, wherein at least one mixing and stirring structure (3) performs heat exchange with the boiler exhaust pipe (10), and at least one mixing and stirring structure (3) performs heat exchange with the first heating component, and each of the mixing and stirring structures (3) is used to heat the introduced external air and evenly mix the external air before inputting it into the heater (1); A heater (1) comprising a heater housing, a heater air inlet and a heater air outlet, wherein the inner cavity of the heater housing is provided with a second heating component, the heater air inlet and the heater air outlet are respectively connected to the inner cavity of the heater housing, and the heater air inlet is connected to a mixing and stirring structure (3); The air preheater (8) has an air preheater air inlet and an air preheater air outlet, wherein the air preheater air inlet is connected to the air heater outlet, and the air preheater air outlet is connected to the boiler air inlet end (9).

2. The boiler air heater system according to claim 1, characterized in that: The mixing and stirring structures (3) are provided with three, namely a first mixing and stirring structure (31), a second mixing and stirring structure (32) and a third mixing and stirring structure (33); A waste heat exchange tube (4) is wound around the periphery of the first mixing and stirring structure (31), one side of the waste heat exchange tube (4) performs heat exchange with the boiler exhaust pipe (10), and the other side of the waste heat exchange tube (4) performs heat exchange with the first mixing and stirring structure (31); A heating box (5) is arranged on the periphery of the second mixing and stirring structure (32), a first heat exchange medium is arranged between the heating box (5) and the second mixing and stirring structure (32), and the heating box (5) performs heat exchange with the air in the inner cavity of the second mixing and stirring structure (32) through the first heat exchange medium; A heating resistor (6) is disposed on the periphery of the third mixing and stirring structure (33), a heating chamber (7) is disposed on the periphery of the heating resistor (6), the heating chamber (7) is connected to the heating box (5), the heating resistor (6) performs heat exchange with the air in the inner chamber of the third mixing and stirring structure (33) and is used to heat the second heat exchange medium filled in the heating chamber (7) and the heating box (5); The heating box (5) and the heating resistor (6) constitute a first heating component.

3. The boiler air heater system according to claim 2, characterized in that: The first mixing and stirring structure (31), the second mixing and stirring structure (32) and the third mixing and stirring structure (33) are arranged in sequence from top to bottom; the first mixing and stirring structure (31) is connected to the external air, and the external air is provided by the fan (14); the third mixing and stirring structure (33) is connected to the air inlet of the heater; the heating chamber (7) is located lower than the heating box (5).

4. The boiler air heater system according to any one of claims 1 to 3, characterized in that: The mixing and stirring structure (3) comprises a cylinder (34), and two spiral grooves (35) with opposite rotation directions and arranged opposite to each other are arranged on the inner side wall of the cylinder (34), the air inlets of the two spiral grooves (35) are arranged opposite to each other, and the air outlets of the two spiral grooves (35) are inclined toward the central axis of the cylinder (34) and are arranged opposite to each other.

5. The boiler air heater system according to any one of claims 1 to 3, characterized in that: At least one of the mixing and stirring structures (3) is connected to the boiler exhaust pipe (10) through a first circulation pipeline, so that the smoke in the boiler exhaust pipe (10) can circulate into the mixing and stirring structure (3) and mix with the air in the mixing and stirring structure (3); the air preheater (8) is connected to the boiler exhaust pipe (10) through a second circulation pipeline, so that the smoke in the boiler exhaust pipe (10) can circulate into the air preheater (8); and the first circulation pipeline and the second circulation pipeline are respectively provided with electromagnetic valves (15).

6. The boiler air heater system according to claim 5, characterized in that: The boiler air heater system also includes: A first temperature sensor (11) is arranged inside the boiler exhaust pipe (10); A second temperature sensor (13) is arranged at the air outlet of the heater; A comprehensive flue gas analyzer (12) having a detection end, wherein the detection end of the comprehensive flue gas analyzer (12) is arranged inside the boiler exhaust pipe (10), and the comprehensive flue gas analyzer (12) is used to detect and analyze the combustible gas content in the flue gas in the boiler exhaust pipe (10), and feed back the detection information to the controller; The controller comprises: the output ends of the first temperature sensor (11), the second temperature sensor (13) and the comprehensive flue gas analyzer (12) are respectively connected to the input end of the controller; the controlled ends of the first heating component, the second heating component and each of the solenoid valves (15) are respectively connected to the output end of the controller.

7. The boiler air heater system according to any one of claims 1 to 3, characterized in that: A fan blade is provided at the connection between the air inlet of the air preheater and the air outlet of the heater; And / or, the second heating component is an electric heating wire (2).

8. An air preheating method, characterized in that: The method is performed using the boiler air heater system according to any one of claims 1 to 7, comprising the following steps: S1. External air passes through each mixing and stirring structure (3) in sequence, and each mixing and stirring structure (3) heats and mixes the external air, wherein at least one mixing and stirring structure (3) heats the external air using waste heat of flue gas in the boiler exhaust pipe (10), and at least one mixing and stirring structure (3) heats the external air using a first heating component; S2, the mixed and heated external air enters the air heater (1) and is heated again by the second heating component in the air heater (1); S3. The external air heated by the second heating assembly enters the air preheater (8), and then enters the boiler through the boiler air inlet (9).

9. The air preheating method according to claim 8, characterized in that: The following steps are also included: The combustible gas content in the flue gas inside the boiler exhaust pipe (10) is detected by a flue gas comprehensive analyzer (12); when the combustible gas content in the flue gas is detected to be higher than a set threshold value, at least one solenoid valve (15) is controlled to open by a controller, so that the flue gas in the boiler exhaust pipe (10) is passed into the heater (1) and / or at least one mixing and stirring structure (3).

10. The air preheating method according to claim 9, characterized in that: The following steps are also included: The first temperature sensor (11) detects the internal smoke temperature of the boiler smoke exhaust pipe (10), and the second temperature sensor (13) detects the gas temperature at the air outlet of the heater; the controller controls the operating state of the solenoid valve (15) based on the temperature detection information of the first temperature sensor (11) and the second temperature sensor (13).

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