Fresh air and flue gas proportion adjusting equipment for low-nitrogen combustion

Abstract

The invention relates to low-nitrogen combustion fresh air and flue gas proportion adjusting equipment which comprises a control unit used for adjusting the proportion of air and nitrogen, and the control unit is used for selecting the optimal air and nitrogen proportion by continuously adjusting the proportion of the air and the nitrogen and detecting the yield of nitric oxide generated after boiler combustion in the equipment operation process; wherein the control unit comprises a timing module used for counting the stable operation time of the boiler, rated time is set in the timing module, after the operation time of the boiler reaches the rated time, the control module starts to operate, the proportion of flue gas to air in the mixed gas is adjusted, and the boiler operates stably again after adjustment. And the timing module carries out zero clearing and re-timing. According to the method, the total amount of the nitric oxide generated under each proportion can be detected and compared respectively, so that the proportion generating the minimum nitric oxide is selected, and the low-nitrogen combustion efficiency can be maximized while the yield of the nitric oxide is reduced.

Description

[0001] This case is a divisional application of the invention patent application with the application date of December 28, 2018, application number 201811626207.4, and invention name "Fresh air and flue gas ratio adjustment equipment for low-nitrogen combustion". Technical Field

[0002] The invention relates to the technical field of flue gas recovery, and in particular to a fresh air and flue gas ratio regulating device for low-nitrogen combustion. Background Art

[0003] Traditional denitrification methods use a pre-furnace reduction method or a post-furnace oxidation method, which has high operating costs, large equipment size, and cumbersome installation. In order to improve the denitrification efficiency, the industry generally uses a catalyst-added denitrification (SNCR) method. This method has improved operating efficiency, but after adding a catalyst, the operating cost is increased, and it still does not achieve the optimal state of high reaction efficiency and operating cost. For this reason, a low-nitrogen combustion, fresh air and flue gas matching technology and control equipment are invented.

[0004] Oxygen accounts for 21% of the air. The boiler uses fresh air for combustion, which results in excess oxygen. In addition to meeting the oxygen required for fuel combustion, the excess oxygen and nitrogen are not fully burned, forming a NOX mixture, which is discharged into the atmosphere, causing emissions to exceed the standard. In addition, the chemical oxygen demand and environmental protection require that the oxygen content of flue gas be controlled at 6-9%. In order to meet the above requirements, fresh air and flue gas are matched according to demand to form a mixed wind of fresh air and flue gas, which is blown into the boiler furnace to assist combustion. By adjusting the mixed air ratio, the minimum threshold point for the generation of nitrogen oxides is found, which is used as a new mixed air technology for boiler combustion.

[0005] Chinese Patent Publication No.: CN104501203A discloses a device and method for controlling the gas mixing ratio of oxygen-deficient carbon dioxide-rich gas to achieve low-nitrogen combustion. The device includes an air preheater, a mixed gas box, a blower, a boiler flue gas return pipe, a fresh air duct and a blower duct. One end of the flue gas inlet chamber of the air preheater is connected to the flue gas outlet of the boiler, and is connected to the mixed gas box through the boiler flue gas return pipe. The fresh air outlet of the air preheater is connected to the mixed gas box through the fresh air duct. The mixed gas box is connected to the air inlet of the blower. The blower is connected to the air inlet of the primary air chamber of the boiler through the blower duct. The blower extracts boiler flue gas and fresh air through the boiler flue gas return pipe and the fresh air duct respectively. After being evenly mixed in the mixed gas box, they are sent into the boiler through the blower duct. Various gases undergo oxidation-reduction reactions in the boiler furnace to eliminate or significantly reduce nitrogen oxides. It can be seen that the device has the following problems:

[0006] First, the device merely recycles the flue gas and mixes it with air for secondary use, but cannot adjust the ratio of the two, thereby failing to maximize the efficiency of low-nitrogen combustion.

[0007] Second, the device needs to use manpower to operate the valve when controlling it, the operation process is cumbersome and it is impossible to quantitatively control the gas in the pipeline. Summary of the invention

[0008] To this end, the present invention provides a fresh air and flue gas ratio regulating device for low-nitrogen combustion, so as to overcome the problem of low efficiency of low-nitrogen combustion in the prior art.

[0009] To achieve the above object, the present invention provides a fresh air and flue gas ratio regulating device for low-nitrogen combustion, comprising:

[0010] A control unit for adjusting the ratio of air and nitrogen. During the operation of the equipment, the ratio of air to nitrogen is continuously adjusted and the output of nitrogen oxides produced after boiler combustion is detected to select the best air-nitrogen ratio;

[0011] A flue gas fan for extracting flue gas, which extracts the flue gas generated by the boiler and delivers it to the boiler together with fresh air in different proportions for secondary combustion;

[0012] A fresh air fan for extracting air;

[0013] A mixing duct connected to the flue gas fan and the fresh air fan respectively for mixing the flue gas and the air and conveying the mixed gas to the boiler;

[0014] A boiler disposed at the outlet of the mixing pipe and connected thereto for burning fuel, wherein when the boiler is in operation, the mixing pipe transports the mixed gas to the boiler;

[0015] A chimney connected to the exhaust port of the boiler for discharging the flue gas after combustion.

[0016] Furthermore, the control unit comprises:

[0017] A control module for controlling the power of the flue gas fan and the fresh air fan respectively, wherein the control module controls the flow rates of air and flue gas respectively by adjusting the power of the flue gas fan and the fresh air fan respectively, thereby adjusting the ratio of air and flue gas in the mixed gas transported by the mixing pipeline;

[0018] A timing module used to count the boiler's stable operating time;

[0019] A detection module for detecting nitrogen oxides in flue gas discharged by the equipment;

[0020] A statistical module for collecting data measured by the detection module.

[0021] Furthermore, a rated time is set in the timing module. After the operating time of the boiler reaches the rated time, the control module starts to operate and adjusts the ratio of flue gas and air in the mixed gas by adjusting the power of the flue gas fan and the fresh air fan respectively. After the adjustment, the boiler resumes stable operation, the timing module is reset and the timing is restarted.

[0022] Furthermore, the detection module is externally connected to a production detector, and the production detector is arranged inside the chimney to detect the production of nitrogen oxides in the flue gas generated by the boiler.

[0023] Furthermore, the statistical module will record the power of the flue gas fan and the fresh air fan adjusted by the control module.

[0024] Furthermore, the statistical module is connected to the detection module to count the nitrogen oxide production measured by the detection module. After the detection module detects the nitrogen oxide production output from the chimney, the measured data will be transmitted to the statistical unit. The statistical unit will store the data and correspond the data to the power of the flue gas fan and the fresh air fan adjusted by the control module.

[0025] Furthermore, a return duct is provided between the chimney and the flue gas fan, for drawing the flue gas output from the chimney to the flue gas fan, mixing it with the air in the fresh air fan and conveying it to the boiler for secondary use.

[0026] Furthermore, the boiler is a rectangular tank body, in which an ultrasonic device and a plurality of coils of heating wires are arranged, surrounding the inner side of the boiler; the ultrasonic device is an ultrasonic generator arranged at the tank mouth of the boiler;

[0027] In the process of heating the coal, the ultrasonic generator and the heating wire of this embodiment are controlled as follows, wherein the ultrasonic device vibrates according to the following relationship between the ultrasonic vibration frequency and the heating temperature:

[0028] Among them, in the first temperature section, within the temperature range of 25-40°C:

[0029]

[0030] Wherein, f1 represents the real-time vibration frequency of the first temperature section, T represents the real-time temperature in the first temperature section, T0 represents the reference preset temperature value, the temperature is 30°C, m represents the mass of air in the added mixed gas, M represents the mass of flue gas in the added mixed gas, c represents the concentration of the mixed gas, and f0 represents the preset vibration frequency of the first temperature section, which is 25kHz;

[0031] Among them, in the second temperature section, within the temperature range of 40-45°C:

[0032]

[0033] Where f2 represents the real-time vibration frequency of the second temperature range, T represents the real-time temperature in the second temperature range, and T 10 It indicates the reference preset temperature value, the constant temperature is 40℃, m indicates the mass of air in the mixed gas, M indicates the mass of flue gas in the mixed gas, c indicates the concentration of the mixed gas, f 10 Indicates the preset vibration frequency of the second temperature range, which is 55kHz;

[0034] In the above step d, the vibration frequency in the temperature range from room temperature to 45°C is 25kHz;

[0035] When the temperature rises to 45℃, within the temperature range of 45-55℃:

[0036]

[0037] Where f3 represents the real-time vibration frequency of the third temperature range, T represents the real-time temperature in the third temperature range, and T 20 Indicates the reference preset temperature value, the temperature is 45℃, c indicates the concentration of the mixed gas, f 20 Indicates the preset vibration frequency of the first temperature section, which is 40kHz;

[0038] Among them, during the cooling process, in the temperature range of 25-55℃:

[0039]

[0040] Wherein, f4 represents the real-time vibration frequency of the fourth temperature segment, T represents the real-time temperature in the fourth temperature segment, c represents the specific heat of the mixed liquid, m represents the mass of air added to the mixed gas, M represents the mass of the flue gas added to the mixed gas, and f30 represents the preset vibration frequency of the fourth temperature segment, which is 30kHz.

[0041] Compared with the prior art, the beneficial effect of the present invention lies in that the equipment of the present invention arranges a control unit therein and respectively arranges fans for flue gas and air, and the power of the fans is set by the control unit to adjust the ratio of flue gas to air. At the same time, the total amount of nitrogen oxides generated under each ratio can be detected and compared respectively, so as to select the ratio with the least nitrogen oxide generation, and the efficiency of low-nitrogen combustion can be maximized while reducing the output of nitrogen oxides.

[0042] In particular, the control unit is provided with a control module, a timing module, a detection module and a statistical module. By interconnecting multiple modules, the control unit can more quickly, accurately and efficiently detect, count and compare the total amount of nitrogen oxides in the flue gas generated by flue gas mixtures of different proportions, thereby further improving the low-nitrogen combustion efficiency of the regulating equipment.

[0043] In particular, a rated time is provided in the timing module, so that when comparing data, the flow time of each proportion of flue gas can be fixed, thereby fixing the flow rate. When comparing the nitrogen oxide production, the comparison result can be more intuitive and the judgment method can be simple and efficient.

[0044] In particular, the detection module is externally connected to a yield detector, and the yield detector is arranged in the chimney. In this way, when flue gas is generated after the mixed gas is burned, the yield detector will perform real-time detection of the yield of nitrogen oxides in the flue gas within a specified time. By improving the detection accuracy of the nitrogen oxide yield in the flue gas to obtain the most efficient flue gas-air ratio, the low-nitrogen combustion efficiency of the regulating equipment is further improved.

[0045] In particular, the statistical module will record the power of the flue gas fan and the fresh air fan after adjustment by the control module. In this way, when the nitrogen oxide production is measured at different ratios, the statistical module can correspond different nitrogen oxide productions to different powers. When the minimum nitrogen oxide production is obtained, the corresponding flue gas-air ratio can be quickly found and used directly, reducing the time spent by the device in selecting the flue gas-air ratio.

[0046] Furthermore, a return pipe is provided between the chimney and the flue gas fan, so that after the boiler outputs the flue gas, the conduit can recover the flue gas and transport it to the mixing pipe through the flue gas fan for secondary utilization, thereby reducing the pollution emissions caused by the equipment to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 This is a structural schematic diagram of the fresh air and flue gas ratio adjustment device for low-nitrogen combustion according to the present invention;

[0048] Figure 2 This is a working flow chart of the fresh air and flue gas ratio regulating device for low-nitrogen combustion described in the present invention. DETAILED DESCRIPTION

[0049] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0050] The above and other technical features and advantages of the present invention are described in more detail below in conjunction with the accompanying drawings.

[0051] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0052] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside" and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the drawings. This is merely for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0053] In addition, it should be noted that in the description of the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For those skilled in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0054] See also Figure 1 As shown, it is a structural schematic diagram of the fresh air and flue gas ratio adjustment device for low nitrogen combustion of the present invention, including a control unit 1, a flue gas fan 2, a fresh air fan 3, a mixing pipe 4, a boiler 5, a chimney 6 and a return pipe 7. The control unit 1 is respectively connected to the flue gas fan 2, the fresh air fan 3 and the chimney 6 to control the power of the flue gas fan 2 and the fresh air fan 3 and the output of nitrogen oxides in the flue gas output by the measuring device. The mixing pipe 4 is respectively connected to the output ends of the flue gas fan 2 and the fresh air fan 3 to mix and transport the flue gas output by the flue gas fan 2 and the air output by the fresh air fan 3. The boiler 5 is connected to the output end of the mixing pipe 4 to contain the mixed gas and burn it to generate flue gas. The chimney 6 is arranged at the outlet of the boiler 5 to output the flue gas generated in the boiler 5, and the two ends of the return pipe 7 are respectively connected to the input end of the flue gas fan 2 and the inlet end of the chimney 6 to reflux the flue gas output by the boiler 5 for secondary use.

[0055] When the regulating device starts to operate, the control unit 1 will adjust the operating power of the flue gas fan 2 and the fresh air fan 3, and adjust the power to adjust the flow rate of the gas output by each fan to complete the ratio of flue gas and air in different proportions. After the adjustment is completed, the flue gas fan 2 outputs flue gas, and the fresh air fan 3 outputs air. The flue gas and air will enter from the two pipes of the mixing pipe 4 respectively and mix in the mixing pipe 4 to form a mixed gas. The mixed gas enters the boiler 5 after being transported through the mixing pipe 4, and generates flue gas after being burned in the boiler 5 and is transported to the entrance of the chimney 6. When the smoke enters the chimney 6, the chimney 6 will transport it upward and output the smoke. During the transportation process, the smoke will pass through the return pipe 7, and the return pipe 7 will extract the smoke and re-transport it to the smoke fan to achieve the reuse of the smoke. It can be understood that the ratio regulating device of the present invention can be used not only to regulate the emission of nitrogen oxides, but also to regulate the emission of other compounds, as long as the ratio regulating device can reach its specified working state.

[0056] Please continue reading Figure 1 As shown, the flue gas fan 2 of the present invention is a centrifugal fan, whose input end is connected to the outlet of the return pipe 7, so as to extract the flue gas in the return pipe 7 and transport it together with the air output by the fresh air fan 3 to the mixing pipe 4 for mixing. After the return pipe 7 recovers the flue gas transported by the chimney 6, it will be transported to the flue gas fan 2, and the flue gas fan 2 will transport it to the mixing pipe 4 and mix it with the air output by the fresh air fan 3 to form a mixed gas. It can be understood that the flue gas fan 2 can be a centrifugal fan, or an axial flow, oblique flow, mixed flow, cross flow or other type of fan, as long as the flue gas fan 2 can transport the flue gas to the mixing pipe 4.

[0057] Please continue reading Figure 1 As shown, the fresh air fan 3 of the present invention is a centrifugal fan, and its output end is connected to the delivery pipe 4 to deliver the air outside the equipment to the mixing pipe 4. When the equipment is running, the fresh air fan 3 will draw air from outside the equipment, deliver it to the mixing pipe 4 and mix it with the flue gas output by the flue gas fan 2 to form a mixed gas. It can be understood that the fresh air fan 3 can be a centrifugal fan, or an axial flow, oblique flow, mixed flow, cross flow or other type of fan, as long as the fresh air fan 3 can deliver the air outside the equipment to the mixing pipe 4 and mix it with the flue gas inside it.

[0058] Please continue reading Figure 1As shown, the mixing pipe 4 of the present invention is a pipe with three outlets, which are respectively connected to the output ends of the flue gas fan 2 and the fresh air fan 3, for respectively receiving the flue gas output by the flue gas fan 2 and the air output by the fresh air fan 3, and the other end of the mixing pipe is connected to the boiler 5, for conveying the mixed gas to the inside of the boiler 5. When the equipment is running, the mixing pipe 4 will respectively receive the flue gas output from the connection with the flue gas pipe, and receive the air output from the connection with the fresh air fan 3, and mix the flue gas and the air inside the mixing pipe 4 to form mixed air, and convey the mixed air to the inside of the boiler 5. It can be understood that the material of the mixing pipe 4 can be iron, stainless steel, polyethylene or other types of metal or non-metal materials, as long as the conveying pipe 4 will not be corroded by the mixed gas.

[0059] Please continue reading Figure 1 As shown, the boiler 5 of the present invention is a metal container for burning the mixed gas, and its inlet is connected to the mixing pipe 4 for receiving the mixed gas, and its outlet is connected to the chimney for outputting the smoke after combustion. When the mixed gas is transported to the boiler interior 5 through the mixing pipe 4, the boiler 5 starts to burn and heat the mixed gas. After the heating is completed, the mixed gas forms smoke and is output through the chimney 6.

[0060] Specifically, the boiler is a rectangular tank body, in which an ultrasonic device and a plurality of coils of heating wires are arranged, surrounding the inner side of the boiler; the ultrasonic device is an ultrasonic generator arranged at the tank mouth of the boiler;

[0061] In the process of heating the coal, the ultrasonic generator and the heating wire of this embodiment are controlled as follows, wherein the ultrasonic device vibrates according to the following relationship between the ultrasonic vibration frequency and the heating temperature:

[0062] Among them, in the first temperature section, within the temperature range of 25-40°C:

[0063]

[0064] Wherein, f1 represents the real-time vibration frequency of the first temperature section, T represents the real-time temperature in the first temperature section, T0 represents the reference preset temperature value, the temperature is 30°C, m represents the mass of air in the added mixed gas, M represents the mass of flue gas in the added mixed gas, c represents the concentration of the mixed gas, and f0 represents the preset vibration frequency of the first temperature section, which is 25kHz;

[0065] Among them, in the second temperature section, within the temperature range of 40-45°C:

[0066]

[0067] Where f2 represents the real-time vibration frequency of the second temperature range, T represents the real-time temperature in the second temperature range, and T 10 It indicates the reference preset temperature value, the constant temperature is 40℃, m indicates the mass of air in the mixed gas, M indicates the mass of flue gas in the mixed gas, c indicates the concentration of the mixed gas, f 10 Indicates the preset vibration frequency of the second temperature range, which is 55kHz;

[0068] In the above step d, the vibration frequency in the temperature range from room temperature to 45°C is 25kHz;

[0069] When the temperature rises to 45℃, within the temperature range of 45-55℃:

[0070]

[0071] Where f3 represents the real-time vibration frequency of the third temperature range, T represents the real-time temperature in the third temperature range, and T 20 Indicates the reference preset temperature value, the temperature is 45℃, c indicates the concentration of the mixed gas, f 20 Indicates the preset vibration frequency of the first temperature section, which is 40kHz;

[0072] Among them, during the cooling process, in the temperature range of 25-55℃:

[0073]

[0074] Wherein, f4 represents the real-time vibration frequency of the fourth temperature segment, T represents the real-time temperature in the fourth temperature segment, c represents the specific heat of the mixed liquid, m represents the mass of air added to the mixed gas, M represents the mass of the flue gas added to the mixed gas, and f30 represents the preset vibration frequency of the fourth temperature segment, which is 30kHz.

[0075] Please continue reading Figure 1 As shown, the chimney 6 of the present invention is arranged at the outlet of the boiler 5 and connected thereto to discharge the smoke out of the boiler. A return pipe 7 is provided on the side of the chimney to transport the smoke transported in the chimney to the smoke fan 2.

[0076] See also Figure 2As shown, it is a working flow chart of the control unit 1 of the present invention, and the control unit includes a control module, a timing module, a detection module and a statistical module; wherein the control module is used to control the power of the flue gas fan 2 and the fresh air fan 3 respectively, and change the ratio of flue gas and air in the mixed gas by changing the flow rate of the output gas; the timing module is used to record the stable operation time of the boiler 5; the detection module is externally connected to a production detector, and the production detector is arranged in the chimney 6 and located upstream of the return pipe 7, so as to detect the total amount of nitrogen oxides generated by the boiler 5 during operation; the statistical module is used to count the total amount of nitrogen oxides generated by the mixed gas under different flue gas-air ratios, and compare them.

[0077] Before the equipment of the present invention starts to operate, the ratio range of flue gas and air is set, and the operating time is set. After the setting is completed, the equipment starts to operate. At this time, the control module starts to select the ratio of flue gas and air, and the statistical module will perform statistics on it. After the statistics, the control module will adjust the power of the flue gas fan 2 and the fresh air fan 3 according to the ratio. After the adjustment is completed, the flue gas fan 2 starts to output flue gas, and the fresh air fan 3 starts to output air. The flue gas and air enter the mixing pipe 4 to mix to form a mixed gas and are transported to the boiler 5. After being heated in the boiler 5, flue gas is formed and output by the chimney 6. During the output process of the chimney 6, the reflux pipe 7 will reflux the flue gas and transport it to the inlet of the flue gas fan 2 for secondary use. When the boiler 5 runs stably, the timing module starts timing. At this time, the detection module controls the yield detector to count the total amount of nitrogen oxides in the flue gas flowing through the chimney 6. When the recording time reaches the rated time, the yield detector stops detecting and sends the counted total amount of nitrogen oxides to the statistical module. The statistical module records the total amount of nitrogen oxides generated at this ratio. After the recording is completed, the timing and yield statistics are reset. The control module starts to reselect the ratio and repeats the above steps to record the total amount of nitrogen oxides in the flue gas output by the equipment at this ratio until the set ratio range is fully measured.

[0078] After the determination is completed, the statistical module will compare the total amounts to obtain the minimum nitrogen oxide output and the corresponding ratio of flue gas to air.

[0079] Example 1

[0080] In this embodiment, the equipment is used to measure the nitrogen oxide production in the flue gas, wherein the boiler capacity is selected as 20T, the boiler power is 14MW, the flue gas to air ratio range is selected as 80:20 to 10:90, and each 5% is a level. The method described in the present invention is used to measure it, and the measurement results are shown in Table 1.

[0081] Table 1

[0082]

[0083] After operation, it can be obtained that: the amount of nitrogen oxides generated is reduced by 100-150mg / m3, the denitrification dosage is calculated to be 42.86%, and the operation cost of dosing is reduced: 68% / 42.86%=1.59-1=59%; the proportion of fresh air is reduced by 30%, the heat taken away by exhaust smoke is reduced, and energy saving reaches about 3%.

[0084] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

[0085] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A fresh air and flue gas ratio regulating device for low-nitrogen combustion, characterized in that: include: A control unit for adjusting the ratio of air and nitrogen. During the operation of the equipment, the ratio of air to nitrogen is continuously adjusted and the output of nitrogen oxides produced after boiler combustion is detected to select the best air-nitrogen ratio; Among them, the control unit includes a timing module for counting the stable operation time of the boiler. The timing module is provided with a rated time. After the operation time of the boiler reaches the rated time, the control module starts to operate and adjusts the ratio of flue gas and air in the mixed gas. After the adjustment, the boiler resumes stable operation, the timing module is reset and the timing is restarted.

2. The fresh air and flue gas ratio regulating device for low-nitrogen combustion according to claim 1 is characterized in that: Also includes: A flue gas fan for extracting flue gas, which extracts the flue gas generated by the boiler and delivers it to the boiler together with fresh air in different proportions for secondary combustion; A fresh air fan for extracting air; The mixing pipes are respectively connected to the flue gas fan and the fresh air fan to mix the flue gas and the air and transport the mixed gas to the boiler.

3. The fresh air and flue gas ratio regulating device for low-nitrogen combustion according to claim 2 is characterized in that: Also includes: A boiler disposed at the outlet of the mixing pipe and connected thereto for burning fuel, wherein when the boiler is in operation, the mixing pipe transports the mixed gas to the boiler; A chimney connected to the exhaust port of the boiler for discharging the flue gas after combustion.

4. The fresh air and flue gas ratio regulating device for low-nitrogen combustion according to claim 3 is characterized in that: The control unit also includes: A control module for controlling the power of the flue gas fan and the fresh air fan respectively, wherein the control module controls the flow rates of air and flue gas respectively by adjusting the power of the flue gas fan and the fresh air fan respectively, thereby adjusting the ratio of air and flue gas in the mixed gas transported by the mixing pipeline.

5. The fresh air and flue gas ratio regulating device for low-nitrogen combustion according to claim 4 is characterized in that: The control unit also includes: A detection module for detecting nitrogen oxides in flue gas discharged by the equipment; A statistical module for collecting data measured by the detection module.

6. The fresh air and flue gas ratio regulating device for low-nitrogen combustion according to claim 5 is characterized in that: The detection module is externally connected to a production detector, which is arranged inside the chimney to detect the production of nitrogen oxides in the flue gas generated by the boiler.

7. The fresh air and flue gas ratio regulating device for low-nitrogen combustion according to claim 6 is characterized in that: The statistical module records the power of the flue gas fan and the fresh air fan adjusted by the control module.

8. The fresh air and flue gas ratio regulating device for low-nitrogen combustion according to claim 7 is characterized in that: The statistical module is connected to the detection module and is used to count the nitrogen oxide production measured by the detection module. After the detection module detects the output nitrogen oxide production in the chimney, the measured data is transmitted to the statistical unit.

9. The fresh air and flue gas ratio regulating device for low-nitrogen combustion according to claim 8 is characterized in that: The statistical unit stores data and corresponds the data to the power of the flue gas fan and the fresh air fan adjusted by the control module.

10. The fresh air and flue gas ratio regulating device for low nitrogen combustion according to claim 1 is characterized in that: A return duct is provided between the chimney and the flue gas fan, for drawing the flue gas output from the chimney to the flue gas fan, mixing it with the air in the fresh air fan and conveying it to the boiler for secondary use.

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