Combustible flue gas self-circulation heating system for kiln

Abstract

The invention discloses a combustible smoke self-circulation heating system for a kiln. The combustible smoke self-circulation heating system comprises a smoke discharging unit, a combustion unit and a tail gas discharging unit. One end of the smoke exhaust unit hermetically penetrates into a hearth of the kiln, and the other end is connected to the combustion unit; the combustion unit and the tail gas emission unit are oppositely arranged on the two sides of the kiln, and the combustion unit comprises an ignition part, a flame sleeve and a radiation protection pipe; one end of the radiation protection pipe is communicated with the smoke exhaust unit, the other end of the radiation protection pipe hermetically penetrates through the hearth in the width direction of the hearth and then is connected with the tail gas exhaust unit, the ignition component is nested and connected to one end of the flame sleeve, the flame sleeve is nested in the radiation protection pipe, and the ignition component is used for realizing smoke combustion in the radiation protection pipe to release heat; and the tail gas emission unit is used for cooling and discharging combustion tail gas. Traditional huge and complex incinerator tail gas treatment equipment is omitted, kiln tail gas is introduced into the radiation protection pipe in a simpler mode for secondary combustion, and self-circulation of sintering flue gas is achieved.

Description

Technical Field

[0001] This invention relates to the field of kiln thermal energy utilization technology, specifically to a self-circulating heating system for combustible flue gas in kilns. Background Technology

[0002] Kilns are thermal equipment used in industrial production processes to heat, melt, and sinter materials or workpieces. During sintering, the reactants produce a significant amount of combustible substances. For example, lithium iron phosphate or silicon-carbon anode reactants generate large quantities of non-methane hydrocarbons and other combustibles during sintering, with an average calorific value of approximately 40,000 kJ / kg. Currently, the main method for treating waste gas is through incineration. This method is expensive, requires a large area, and cannot directly and efficiently utilize the combustion heat of the combustibles in the flue gas. Even with a waste heat recovery system installed after the incinerator, the waste heat recovery efficiency is low, and the system is relatively complex. Designing a self-circulating heating system to introduce the combustible flue gas generated during the sintering process into the kiln for combustion would allow for the direct utilization of flue gas heat (including sensible heat and combustion chemical heat), thus reducing both the energy consumption of the kiln equipment and the initial investment cost.

[0003] Taking a 5000 t / year lithium iron phosphate roller furnace as an example, the equipment cost of configuring a waste gas incinerator is around 700,000 yuan. From the perspective of heat utilization, the average temperature of the flue gas discharged during the production process is 300℃, and the flow rate is Qv=1200 m³ / h. 3 The concentration of combustible substances in the flue gas is ρ = 0.012 kg / m³ / h. 3 The average calorific value is H = 40000 kJ / kg. The theoretically available heat of combustion (Q) and power (W) can be calculated using the following formulas: M f =Q v ×ρ=1200×0.012=14.4 kg / h Q=M f ×H=576000 kJ / h W = Q / 3600 = 57600 / 3600 = 160 kW In conclusion, if a self-circulating combustion gas heating system for kilns can be designed to directly introduce the flue gas generated during the sintering process into the combustion heating system of the kiln, allowing it to burn in the kiln heating system and using the heat released from combustion to directly heat the materials, then the energy consumption of the kiln equipment and the initial investment cost of the equipment can be greatly reduced, resulting in high economic benefits. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a kiln combustible flue gas self-circulation heating system that is compact in structure, easy to operate and conducive to improving thermal energy utilization, in order to overcome the shortcomings of the existing technology.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A self-circulating combustible flue gas heating system for a kiln includes: a flue gas exhaust unit, a combustion unit, and a tail gas emission unit. The inlet end of the flue gas exhaust unit is sealed and extends into the furnace chamber of the kiln, and the exhaust end of the flue gas exhaust unit is connected to the combustion unit. The combustion unit and the tail gas emission unit are arranged opposite each other on both sides of the kiln. The combustion unit includes an ignition component, a flame sleeve, and a radiant protection tube. One end of the radiant protection tube is connected to the flue gas exhaust unit to transport the flue gas in the furnace chamber to the radiant protection tube. The other end of the radiant protection tube is sealed and extends through the furnace chamber along its width and then connected to the tail gas emission unit. The ignition component is nested and connected to one end of the flame sleeve, and the flame sleeve is nested inside the radiant protection tube. After the ignition component is ignited, the flue gas in the radiant protection tube burns and releases heat to heat the kiln. The tail gas emission unit is used to cool and discharge the flue gas after combustion.

[0006] As a further improvement of the present invention, the ignition component includes a burner, a gas assembly, and a combustion air assembly; the burner is nested at one end of the flame sleeve, and the gas assembly and the combustion air assembly provide natural gas and combustion air to the burner, respectively.

[0007] As a further improvement of the present invention, the radiation protection tube includes a protection tube body, a flue gas inlet is provided on one side of the front end of the protection tube body to connect to the smoke exhaust unit, and a flame sleeve is nested in the front end of the protection tube body, and the rear end of the protection tube body is connected to the exhaust gas emission unit; multiple guide vanes are provided inside the protection tube body.

[0008] As a further improvement of the present invention, the combustion unit further includes a kiln exhaust fan and a flue gas supply pipe; the inlet of the kiln exhaust fan is connected to the exhaust unit, and the outlet of the kiln exhaust fan is connected to the flue gas supply pipe; the furnace is divided into multiple temperature zones, and each temperature zone is equipped with a flame sleeve and a radiation protection pipe; the flue gas supply pipe adopts a one-inlet-multiple-outlet branch pipe structure, and the outlet of the branch pipe of the flue gas supply pipe is connected to the flue gas inlet, so as to realize the flue gas being transported to the radiation protection pipes of different temperature zones.

[0009] As a further improvement of the present invention, a pneumatic proportional valve is provided at the end of the branch pipe of the smoke supply pipe to adjust the proportion of flue gas entering the radiation protection pipe.

[0010] As a further improvement of the present invention, the flue gas exhaust unit includes a main flue gas exhaust pipe disposed at the top of the kiln along the length of the kiln, and multiple branch flue gas exhaust pipes are provided on the main flue gas exhaust pipe. The branch flue gas exhaust pipes are sealed and penetrate into the furnace to collect the flue gas generated in the furnace. The outlet end of the main flue gas exhaust pipe is connected to the inlet of the kiln flue gas exhaust fan.

[0011] As a further improvement of the present invention, the main exhaust pipe is provided with an air supply regulating port with a pneumatic proportional valve to supplement air for combustion.

[0012] As a further improvement of the present invention, the exhaust gas emission unit includes an exhaust pipe, an exhaust gas fan, and an exhaust gas pipe. The intake port of the exhaust gas fan is connected to the exhaust pipe, and the exhaust port of the exhaust gas fan is connected to the exhaust gas pipe. The exhaust pipe is connected to a radiation protection pipe to realize the exhaust of combustion exhaust gas inside the radiation protection pipe.

[0013] As a further improvement of the present invention, the exhaust pipe is provided with an air injection cooling port to achieve mixing of combustion exhaust gas and external cold air.

[0014] As a further improvement of the present invention, the exhaust pipe is provided with pressure monitoring points and temperature monitoring points.

[0015] Compared with the prior art, the advantages of the present invention are as follows: The kiln combustible flue gas self-circulation heating system of this invention directly introduces the flue gas generated during the sintering process into the kiln combustion system for secondary combustion, achieving efficient closed-loop utilization of sensible heat and chemical energy (combustion heat) from the flue gas. This design can replace auxiliary equipment such as independent incinerators required by traditional processes, significantly reducing initial equipment investment costs. Simultaneously, by recovering waste heat from the flue gas to directly provide heat for material sintering, it greatly reduces the energy consumption of kiln operation. The integrated system of this invention combines the dual advantages of equipment simplification and efficient energy utilization, possessing significant economic benefits and promotional value. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the main structural principle of the flue gas self-circulation heating system in a specific embodiment of the present invention; Figure 2 This is a side view schematic diagram of the flue gas self-circulation heating system in a specific embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the structural principle of the radiation protection tube in a specific embodiment of the present invention.

[0017] Legend: 1. Smoke exhaust unit; 11. Smoke exhaust branch pipe; 12. Smoke exhaust main pipe; 13. Air supply regulating port; 2. Combustion unit; 21. Burner; 22. Flame sleeve; 23. Radiant protection pipe; 231. Flue gas inlet; 232. Guide vane; 233. Protective pipe body; 24. Gas assembly; 25. Combustion air assembly; 26. Kiln smoke exhaust fan; 27. Smoke supply duct; 3. Exhaust gas emission unit; 31. Exhaust duct; 32. 33. Air supply cooling port; 34. Pressure monitoring point; 35. Temperature monitoring point; 36. Exhaust gas exhaust fan; 47. Exhaust gas discharge pipe; 48. Upper temperature control point of the first temperature zone; 49. Lower temperature control point of the first temperature zone; 40. Upper temperature control point of the second temperature zone; 41. Lower temperature control point of the second temperature zone; 52. First pneumatic proportional valve; 53. Second pneumatic proportional valve; 54. Third pneumatic proportional valve; 55. Fourth pneumatic proportional valve; 100. Kiln; 101. Furnace chamber. Detailed Implementation

[0018] The present invention will be further described below with reference to the accompanying drawings and specific preferred embodiments, but this does not limit the scope of protection of the present invention.

[0019] In the description of this invention, it should be understood that the terms "side", "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0020] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more unless otherwise explicitly specified.

[0021] Example like Figure 1 and Figure 2As shown, the kiln combustible flue gas self-circulation heating system of the present invention includes: a flue gas exhaust unit 1, a combustion unit 2, and a tail gas emission unit 3. The flue gas exhaust unit 1 includes a main flue gas exhaust pipe 12 arranged along the length of the kiln 100 at the top of the kiln 100. Multiple branch flue gas exhaust pipes 11 are provided on the main flue gas exhaust pipe 12, which are sealed and penetrate into the furnace chamber 101 to collect the flue gas generated during the sintering of materials within the furnace chamber 101. The outlet end of the main flue gas exhaust pipe 12 is connected to the inlet of the kiln exhaust fan 26 of the combustion unit 2. It is understood that both the branch flue gas exhaust pipes 11 and the main flue gas exhaust pipe 12 can be made of SUS304 stainless steel welded pipes or seamless pipes, and the pipe diameter is related to the exhaust volume.

[0022] like Figure 1 As shown, the main exhaust pipe 12 is equipped with an air supply regulating port 13 with a pneumatic proportional valve to supply air for combustion. By installing a pneumatic proportional valve on the air supply regulating port 13, the amount of air supplied can be remotely adjusted according to the different processes and production capacities of the sintered materials, ensuring complete combustion of the flue gas. In this embodiment, the exhaust volume of the main exhaust pipe 12 is approximately Q = 470 m³. 3 / h, where the concentration of combustibles in the flue gas is C=0.012 kg / m³. 3 The average calorific value of the combustible material is E = 20000 kJ / kg.

[0023] like Figure 2 As shown, the combustion unit 2 and the exhaust gas emission unit 3 are arranged opposite each other on both sides of the kiln 100. The combustion unit 2 includes a burner 21, a flame sleeve 22, a radiant protection tube 23, a gas assembly 24, and a combustion air assembly 25. The radiant protection tube 23 is made of SUS310S stainless steel. One end of the radiant protection tube 23 is connected to the exhaust gas unit 1 to transport the flue gas in the furnace 101 into the radiant protection tube 23. The other end of the radiant protection tube 23 is sealed and passes through the furnace 101 along its width and is then connected to the exhaust gas emission unit 3. The burner 21 is nested in one end of the flame sleeve 22, and the flame sleeve 22 is nested in the radiant protection tube 23. The gas assembly 24 and the combustion air assembly 25 provide natural gas and combustion air to the burner 21, respectively. The flame sleeve 22 is made of silicon carbide and is installed inside the radiation protection tube 23. The side wall of the flame sleeve 22 has openings, and its length is similar to the inner width of the furnace 101. This helps to constrain the flame shape, ensuring the flame length completely covers the width of the furnace 101 and improving temperature uniformity. After the burner 21 is ignited, the flue gas inside the radiation protection tube 23 burns and releases heat to heat the kiln 100. The exhaust gas unit 3 is used to cool the flue gas after combustion and then discharge it externally. This eliminates the need for traditional, large, and complex incinerator exhaust gas treatment equipment, allowing the kiln exhaust gas to be introduced into the radiation protection tube 23 for secondary combustion in a simpler way. This achieves self-circulation of the flue gas during the sintering process, reducing the equipment's footprint and cost.

[0024] In this embodiment, the gas assembly 24 consists of a gas regulating valve, a gas pressure reducing valve, a flow meter, a solenoid valve, a high / low pressure switch, a gas pipeline plug, an air-fuel proportional valve, and a gas fine-tuning valve, among other pipes and accessories. All system components are commercially available and selected according to the burner 21's power rating. Its main function is to provide gas to the burner 21 and, in conjunction with the gas control system, control the combustion power of the burner 21. The combustion air assembly 25 consists of a combustion air fan, combustion air ducts, a manual butterfly valve, and an automatic butterfly valve. All system components are commercially available and selected according to the burner 21's power rating. Its main function is to provide combustion air to the burner 21 and, in conjunction with the gas system, regulate the combustion power of the burner 21.

[0025] The flue gas temperature inside furnace 101 is generally 200–400℃, and it contains a large amount of non-methane total hydrocarbons and other combustible substances. These combustible substances burn and release heat in the radiation protection tube 23. Under normal circumstances, the heat utilization rate of the radiation protection tube 23 is between 60% and 80%, and the heat released by the combustion of the combustible flue gas is E = Q × C × H × η = 470m³. 3 / h × 0.012 kg / m 3 × 20000 kJ / kg × 70% ≈ 22 kW. The circulating heating system in this embodiment can utilize part of the sensible heat and latent heat of chemical combustion in the flue gas to provide heat for the kiln heating section. Moreover, this part of the heat is considerable and can significantly reduce the kiln's heating energy consumption, achieving energy-saving effects.

[0026] The inner diameter of the radiation protection tube 23 should not be too small; if the inner diameter is too small, the gas flow rate will be too fast, which will not only fail to meet the residence time of the flue gas in the tube (generally > 1 s), but also easily extinguish the burner flame when the burner 21 is running at low flame. Figure 3 As shown, the radiation protection pipe 23 includes a pipe body 233. A flue gas inlet 231 is located on one side of the front end of the pipe body 233, connecting to the exhaust unit 1. Flue gas enters the pipe body 233 through the flue gas inlet 231 and burns inside. A flame sleeve 22 is nested within the front end of the pipe body 233. The rear end of the pipe body 233 is connected to the exhaust unit 3. Multiple guide vanes 232 are arranged along the length of the pipe body 233, which serve both as pipe reinforcement and increase flow resistance within the pipe, thereby increasing the residence time of the flue gas. The residence time is generally above 1.0 s, ensuring complete combustion and efficient heat release of the flue gas.

[0027] Combustion unit 2 also includes a kiln exhaust fan 26 and a flue gas supply duct 27. The intake of the kiln exhaust fan 26 is connected to the exhaust unit 1, and the exhaust outlet of the kiln exhaust fan 26 is connected to the flue gas supply duct 27. The furnace chamber 101 is divided into four temperature zones, and each temperature zone is equipped with a flame sleeve 22 and a radiation protection pipe 23. The flue gas supply duct 27 adopts a one-inlet, four-outlet branch pipe structure. The outlet of the branch pipe of the flue gas supply duct 27 is connected to the flue gas inlet 231 to realize the separate delivery of flue gas to the radiation protection pipes 23 of the four temperature zones.

[0028] Furthermore, a pneumatic proportional valve is provided at the end of the branch pipe of the smoke supply duct 27 to adjust the proportion of flue gas entering the radiation protection pipe 23.

[0029] like Figure 1 As shown, the furnace 101 is divided into four different temperature zones. Each of the four zones has an upper temperature control point 41, a lower temperature control point 42, an upper temperature control point 43, and a lower temperature control point 44. Each temperature control point is equipped with a thermocouple to monitor the temperature of the corresponding zone in real time. The branch pipes of the flue gas supply duct 27 are equipped with a first pneumatic proportional valve 51, a second pneumatic proportional valve 52, a third pneumatic proportional valve 53, and a fourth pneumatic proportional valve 54 to regulate the flow rate of flue gas entering the radiation protection pipes 23 of the four temperature zones.

[0030] In this embodiment, the flue gas generated during the sintering of materials in the kiln is first collected into the main flue gas pipe 12 through the exhaust branch pipe 11. Air enters the main exhaust gas pipe 12 through the air supply regulating port 13 to mix with the flue gas. The power source is the kiln exhaust fan 26. The temperature of the mixed gas is about 300°C. It is blown into the radiant protection pipe 23 and ignited after encountering the flame of the burner 21. The combustion of the mixed gas releases heat, which is used to heat the temperature zone of the kiln heating section through the radiant protection pipe 23. The combustible substances in the mixed gas are completely burned off. The combustion exhaust gas is discharged into the exhaust gas emission unit 3 and mixed with cold air to cool it down, forming exhaust gas that meets the emission standards, and finally discharged into the atmosphere.

[0031] like Figure 2 As shown, the exhaust unit 3 includes an exhaust pipe 31, an exhaust fan 35, and an exhaust pipe 36. The intake of the exhaust fan 35 is connected to the exhaust pipe 31, and the exhaust outlet of the exhaust fan 35 is connected to the exhaust pipe 36. The exhaust pipe 31 is connected to the radiation protection tube 23 to allow the combustion exhaust gas inside the radiation protection tube 23 to be discharged externally. Both the exhaust pipe 31 and the exhaust pipe 36 are made of SUS304 stainless steel.

[0032] Furthermore, the exhaust pipe 31 is equipped with an air injection cooling port 32, a pressure monitoring point 33, and a temperature monitoring point 34. The air injection cooling port 32 is used to inject cold air to achieve mixing and cooling of the combustion exhaust gas with the external cold air. The pressure monitoring point 33 and the temperature monitoring point 34 are respectively equipped with a digital display pressure gauge and a thermocouple for real-time monitoring of the pressure and temperature of the exhaust pipe 31.

[0033] In this embodiment, the flue gas is treated by combustion to form exhaust gas that meets emission standards, which then enters the exhaust gas emission unit 3. Pressure monitoring point 33 monitors the pressure inside the exhaust pipe 31 in real time, ensuring that the pressure remains within the range of -20 to -50 Pa. If the exhaust pipe 31 is under positive pressure, the exhaust gas will leak out from the air supply cooling port 32. Therefore, the control logic of the exhaust gas emission unit 3 is as follows: when the pressure in the exhaust pipe 31 is greater than -20 Pa, pressure monitoring point 33 feeds this signal back to the external controller, which then issues a control signal to increase the frequency of the exhaust gas fan 35; when the pressure in the exhaust pipe 31 is less than -50 Pa, pressure monitoring point 33 feeds this signal back to the external controller, which then issues a control signal to decrease the frequency of the exhaust gas fan 35.

[0034] In this embodiment, the outer surfaces of the high-temperature pipes, such as the smoke exhaust branch pipe 11, the smoke exhaust main pipe 12, the air supply regulating port 13, the smoke supply pipe 27, and the exhaust pipe 31, are all covered with fire-resistant fiber material to prevent burns during system operation.

[0035] In this embodiment, both the kiln exhaust fan 26 and the tail gas exhaust fan 35 are high-temperature resistant, fully sealed variable frequency fans with a temperature resistance of 400℃. The fan casing and blades are made of SUS304 stainless steel to meet the requirements of high temperature resistance, corrosion resistance, and sealing. Both the exhaust fan 26 and the tail gas exhaust fan 35 are equipped with cleaning ports and glue discharge ports to facilitate future maintenance.

[0036] The operation and control principle of the combustible flue gas self-circulation heating system implemented in this embodiment are as follows: The set temperatures of the first and second temperature zones are SV=300℃ and 400℃, respectively. The upper and lower limits of the temperature zone settings are ±10℃. The heating elements in the upper and lower parts of the first and second temperature zones are 30 kW burners. When the temperature zone starts heating, the gas assembly 24 and the combustion air assembly 25 provide natural gas and combustion air to the burner 21, and the burner 21 is ignited for heating. When the actual temperature PV of the temperature zone is greater than the set upper limit (SV+10℃), the gas supply of the gas assembly 24 and the combustion air assembly 25 decreases, the heating power of the burner 21 decreases, and the temperature of the temperature zone drops; when the actual temperature PV of the temperature zone is less than the set lower limit (SV-10℃), the gas supply of the gas assembly 24 and the combustion air assembly 25 increases, and the heating power of the burner 21 increases.

[0037] Assuming the burner 21 operates at a stable power of 20 kW, its power will decrease when overheating and increase when underheating to maintain furnace temperature balance. When reactants enter the furnace for heating, they react to produce combustible substances such as non-methane hydrocarbons and hydrocarbons. The flue gas mixes with air entering from the air supply regulating port 13 in the exhaust pipe 12. The amount of air supplied is related to the opening of the pneumatic proportional valve installed therein; after installation, the commissioning personnel need to adjust the proportional valve opening to a suitable position to achieve an appropriate combustion ratio between the combustible flue gas and air. If the reactant process changes subsequently, the valve opening can be adjusted accordingly. The mixed flue gas is then sent to the flue gas supply pipe 27 via the kiln exhaust fan 26, which delivers the flue gas to the radiant protection pipes 23 in the four temperature zones for combustion. The combustion of the flue gas releases heat, raising the temperature of each zone. When the temperature in a temperature zone exceeds the set upper limit (SV+10℃), the upper temperature control point 41 of the first temperature zone, the lower temperature control point 42 of the first temperature zone, the upper temperature control point 43 of the second temperature zone, and the lower temperature control point 44 of the second temperature zone collect temperature signals and feed them back to the external controller. The external controller gives a control signal to reduce the gas supply of the gas assembly 24 and the combustion air assembly 25, and the power of the burner 21 is reduced. At this time, due to the release of the heat of combustion of combustibles in the flue gas, the power required by the burner 21 is reduced, and the consumption of natural gas is reduced, thereby realizing the utilization of waste heat. In order to better control the flow rate of flue gas entering the radiant protection pipe of each temperature zone and make the flue gas flow rate distributed in the high and low temperature zone radiant protection pipes more reasonable, this embodiment proposes an automatic control logic: during the combustion process of the burner 21 in each temperature zone, the average consumption of natural gas flow is fed back to the external controller; the external controller calculates the ratio of the average natural gas consumption of each temperature zone, and then feeds back the data to the actuator to control the opening of the pneumatic proportional valve of the air supply branch pipe of each temperature zone. For example, the average natural gas consumption ratio of the upper part of the first temperature zone, the lower part of the first temperature zone, the upper part of the second temperature zone, and the lower part of the second temperature zone is 1:1:2:2. The controller feeds this ratio signal back to the actuator, controlling the opening ratio of the first pneumatic proportional valve 51 on the upper air supply branch pipe of the first temperature zone, the second pneumatic proportional valve 52 on the lower air supply branch pipe of the first temperature zone, the third pneumatic proportional valve 53 on the upper air supply branch pipe of the second temperature zone, and the fourth pneumatic proportional valve 54 on the lower air supply branch pipe of the second temperature zone to be 1:1:2:2. Reasonable distribution of flue gas flow is beneficial to improving the stability of burner 21 control and the combustion effect of flue gas.

[0038] The above description is merely a preferred embodiment of the present invention. The scope of protection of the present invention is not limited to the above embodiments. All technical solutions falling within the scope of the present invention's concept are within the scope of protection of the present invention. It should be noted that for those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A self-circulating combustion gas heating system for kilns, characterized in that, include: The furnace includes a flue gas exhaust unit (1), a combustion unit (2), and a tail gas emission unit (3). The inlet of the flue gas exhaust unit (1) is sealed and extends into the furnace chamber (101) of the kiln (100), and the exhaust end of the flue gas exhaust unit (1) is connected to the combustion unit (2). The combustion unit (2) and the tail gas emission unit (3) are arranged opposite to each other on both sides of the kiln (100). The combustion unit (2) includes an ignition component, a flame sleeve (22), and a radiation protection tube (23). One end of the radiation protection tube (23) is connected to the flue gas exhaust unit (1) to achieve the connection between the furnace chamber (101) and the combustion unit (2). The flue gas in the furnace is transported to the radiation protection tube (23). The other end of the radiation protection tube (23) is sealed through the furnace (101) along the width direction and connected to the exhaust gas emission unit (3). The ignition component is nested and connected to one end of the flame sleeve (22). The flame sleeve (22) is nested in the radiation protection tube (23). After the ignition component is ignited, the flue gas in the radiation protection tube (23) is burned to release heat and heat the kiln (100). The exhaust gas emission unit (3) is used to cool and discharge the flue gas after combustion.

2. The self-circulating combustible flue gas heating system for kilns according to claim 1, characterized in that, The ignition components include a burner (21), a gas assembly (24), and a combustion air assembly (25); the burner (21) is nested at one end of a flame sleeve (22), and the gas assembly (24) and the combustion air assembly (25) provide natural gas and combustion air to the burner (21), respectively.

3. The self-circulating combustible flue gas heating system for kilns according to claim 2, characterized in that, The radiation protection tube (23) includes a protection tube body (233), a flue gas inlet (231) is provided on one side of the front end of the protection tube body (233) to connect to the smoke exhaust unit (1), and a flame sleeve (22) is nested in the front end of the protection tube body (233), and the rear end of the protection tube body (233) is connected to the exhaust gas emission unit (3); multiple guide vanes (232) are provided inside the protection tube body (233).

4. The self-circulating combustible flue gas heating system for kilns according to claim 3, characterized in that, The combustion unit (2) also includes a kiln exhaust fan (26) and a flue gas duct (27); the inlet of the kiln exhaust fan (26) is connected to the exhaust unit (1), and the outlet of the kiln exhaust fan (26) is connected to the flue gas duct (27); the furnace (101) is divided into multiple temperature zones, and each temperature zone is equipped with a flame sleeve (22) and a radiation protection tube (23). The flue gas duct (27) adopts a branch pipe structure with one inlet and multiple outlets. The outlet of the branch pipe of the flue gas duct (27) is connected to the flue gas inlet (231) so as to realize the flue gas being transported to the radiation protection tube (23) of different temperature zones.

5. The self-circulating combustible flue gas heating system for kilns according to claim 4, characterized in that, The branch end of the smoke supply pipe (27) is equipped with a pneumatic proportional valve to adjust the proportion of flue gas entering the radiation protection pipe (23).

6. The kiln combustible flue gas self-circulation heating system according to claim 4, characterized in that, The exhaust unit (1) includes an exhaust main pipe (12) arranged along the length of the kiln (100) at the top of the kiln (100). The exhaust main pipe (12) is provided with multiple exhaust branch pipes (11). The exhaust branch pipes (11) are sealed and penetrate into the furnace (101) to collect the flue gas generated in the furnace (101). The outlet end of the exhaust main pipe (12) is connected to the inlet of the kiln exhaust fan (26).

7. The kiln combustible flue gas self-circulation heating system according to claim 6, characterized in that, The exhaust pipe (12) is equipped with an air supply regulating port (13) with a pneumatic proportional valve to supply air for combustion.

8. The self-circulating combustible flue gas heating system for kilns according to claim 4, characterized in that, The exhaust gas emission unit (3) includes an exhaust pipe (31), an exhaust gas fan (35), and an exhaust gas discharge pipe (36). The intake port of the exhaust gas fan (35) is connected to the exhaust pipe (31), and the exhaust port of the exhaust gas fan (35) is connected to the exhaust gas discharge pipe (36). The exhaust pipe (31) is connected to the radiation protection pipe (23) to realize the exhaust of combustion exhaust gas in the radiation protection pipe (23).

9. The self-circulating combustible flue gas heating system for kilns according to claim 8, characterized in that, The exhaust pipe (31) is provided with an air supply cooling port (32) to achieve the mixing of combustion exhaust gas with external cold air.

10. The kiln combustible flue gas self-circulation heating system according to claim 8, characterized in that, The exhaust pipe (31) is equipped with a pressure monitoring point (33) and a temperature monitoring point (34).

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