Air pre-heater air leakage rate online monitoring system and method based on single meter oxygen amount difference accurate measurement and installation structure

Abstract

The invention discloses an air pre-heater air leakage rate online monitoring system and method based on single meter oxygen amount difference accurate measurement and an installation structure. An air pre-heater air leakage rate online monitoring system based on single-meter oxygen difference accurate measurement comprises an air pre-heater flue gas side inlet grid sampler, an air pre-heater flue gas side outlet grid sampler, a coupling pipeline, an inlet sample gas control valve, an outlet sample gas control valve, a sample gas conveying pipeline, an oxygen meter, an air extractor, a positive pressure air source and a reverse blowing control valve. The flue gas side inlet grid sampler, the air pre-heater flue gas side outlet grid sampler, the inlet sample gas control valve and the outlet sample gas control valve are sequentially connected to the coupling pipeline; the oxygen meter, the air extractor and the blowback control valve are sequentially connected to the sample gas conveying pipeline. According to the invention, only one oxygen meter is needed to complete the measurement of the oxygen amount difference between the inlet and the outlet of the flue gas side of the air pre-heater, the system integration degree is high, the cost is obviously reduced, the system measurement error is obviously reduced, and the measurement accuracy is improved; the structure is simple, and emission is avoided.

Description

TECHNICAL FIELD

[0001] The present application relates to an air preheater leakage rate online monitoring system, method and installation structure based on single-table oxygen difference accurate measurement, belonging to the technical field of air preheater sealing. BACKGROUND

[0002] The rotary air preheater (hereinafter referred to as "air preheater") is a heat exchange equipment used in large power station boilers, which uses the heat of boiler flue gas to heat the air required for combustion, so as to improve the efficiency of the boiler.

[0003] The main problems of air preheater include ash blocking, high leakage rate, low heat transfer efficiency, and serious low-temperature corrosion, which have long affected the safe and economic operation of the air preheater and the entire boiler system.

[0004] The air preheater leakage rate is one of its core performance indicators, which has a greater impact on the economic operation of the coal-fired boiler system: according to the "Energy Saving Evaluation and Energy Audit Manual for Thermal Power Plants" (Li Chun, Zhang Xingying, Liu Xuebing), the air preheater leakage rate increases by 0.20 g / kWh for each 1% increase; Shanghai Boiler Factory's statistical data of nearly 100 units show that for a 1% change in leakage rate, the total current of three large fans of 300MW grade unit changes by 6~8A (6kV), the total current of three large fans of 600MW grade unit changes by 9.5~11A (6kV), and the total current of three large fans of 1000MW grade unit changes by 10.2~11.5A (10kV).

[0005] Currently, there is a lack of online monitoring means for air preheater leakage rate, and generally only 1~3 sets of oxygen meters are arranged at the inlet and outlet of the air preheater. Since the values of a few monitoring points cannot represent the average oxygen content of the entire cross section, and the oxygen meter cannot be accurately measured if it is not calibrated in time, the problem of air preheater leakage rate cannot be solved. SUMMARY

[0006] To solve the above technical problems, the present application provides an air preheater leakage rate online monitoring system, method and installation structure based on single-table oxygen difference accurate measurement, which can online and reliably measure the air preheater leakage rate.

[0007] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0008] An air preheater leakage rate online monitoring system based on single-table oxygen difference accurate measurement, comprising an air preheater flue gas side inlet grid sampler, an air preheater flue gas side outlet grid sampler, a coupling pipeline, an inlet sample gas control valve, an outlet sample gas control valve, a sample gas conveying pipeline, an oxygen meter, an air extractor, a positive pressure gas source and a back flushing control valve.

[0009] One end of the coupling pipeline is communicated with the sample outlet of the inlet grid sampler of the air preheater flue gas side, and the other end is communicated with the sample outlet of the outlet grid sampler of the air preheater flue gas side;

[0010] The inlet sample gas control valve and the outlet sample gas control valve are arranged on the coupling pipeline, and the inlet grid sampler of the air preheater flue gas side, the inlet sample gas control valve, the outlet sample gas control valve and the outlet grid sampler of the air preheater flue gas side are arranged in sequence on the coupling pipeline;

[0011] One end of the sample gas conveying pipeline is communicated with the coupling pipeline between the inlet sample gas control valve and the outlet sample gas control valve, and the number of the oxygen content meter and the air extractor is one set, and they are arranged on the sample gas conveying pipeline, and the air extractor is located downstream of the oxygen content meter; the positive pressure gas source is communicated with the air extractor through a pipeline; the back flushing control valve is arranged on the sample gas conveying pipeline downstream of the air extractor.

[0012] The inlet grid sampler of the air preheater flue gas side and the outlet grid sampler of the air preheater flue gas side have one end as a sample outlet and the other end provided with a grid-distributed sampling port (the grid-distributed sampling port meets the requirements of GB10184).

[0013] The upstream-to-downstream direction of the present application is consistent with the flow direction of the material. The upstream-to-downstream direction of the sample gas conveying pipeline refers to the flow direction of the flue gas during sampling, and is opposite to the back flushing direction during anti-blocking. The back flushing direction during anti-blocking is opposite to the flow direction of the flue gas during sampling.

[0014] The present application only needs one set of oxygen content meter to complete the oxygen content difference measurement of the inlet and outlet of the air preheater flue gas side, which significantly reduces the cost, avoids the accuracy problem caused by the deviation of the measurement accuracy of multiple oxygen content meters, and significantly improves the measurement accuracy.

[0015] In order to facilitate use, the air extractor is a jet device structure, and the air extractor is provided with a working gas inlet, an extracted gas inlet and a mixed gas outlet. The working gas inlet is communicated with the positive pressure gas source through a pipeline, and the extracted gas inlet and the mixed gas outlet are communicated with the sample gas conveying pipeline, and the extracted gas inlet is located upstream of the mixed gas outlet. When the back flushing control valve is opened, the positive pressure gas source is opened, the positive pressure gas enters the working gas inlet of the air extractor, and flows to the mixed gas outlet, so that the extracted gas inlet of the air extractor generates negative pressure, and then the sample gas suction power is increased. When the back flushing control valve is closed, the positive pressure gas source is opened, and the positive pressure gas enters the working gas inlet of the air extractor. Due to the closing of the back flushing control valve, under the action of gas pressure, the high-pressure gas flow flows out from the extracted gas inlet to sequentially flush the sample gas conveying pipeline, the coupling pipeline and the inlet grid sampler of the air preheater flue gas side. The aforementioned upstream-to-downstream direction refers to the flow direction of the flue gas in the sample gas conveying pipeline during sampling.

[0016] In order to facilitate arrangement and provision, and at the same time take into account the cost, the aforementioned positive pressure gas source is preferably an air compressor.

[0017] The air preheater flue gas side inlet grid sampler has a sampling outlet at one end and a grid-distributed sampling port at the other end (the grid-distribution of the sampling port meets the requirements of GB10184); the air preheater flue gas side outlet grid sampler has the same structure as the air preheater flue gas side inlet grid sampler.

[0018] In order to facilitate installation and arrangement, as one of the specific preferred schemes, the air preheater flue gas side inlet grid sampler comprises a sampling pipe, a mixing pipe and a connecting pipe; the number of the sampling pipes is 4-6, which are arranged in parallel; each sampling pipe is provided with 4-8 sampling holes arranged at equal intervals, and the sampling holes on all the sampling pipes are arranged in a grid shape; the mixing pipe has a tubular structure with both ends blocked; one end of each sampling pipe is vertically connected to the side wall of the mixing pipe; one end of the connecting pipe is connected to the side wall of the mixing pipe, and the other end is connected to one end of the coupling pipeline as a sampling outlet; the sampling pipes and the connecting pipe are respectively located on both sides of the mixing pipe. The air preheater flue gas side outlet grid sampler has the same structure as the air preheater flue gas side inlet grid sampler, and the connecting pipe of the air preheater flue gas side outlet grid sampler is connected to the other end of the coupling pipeline.

[0019] The lengths of the sampling pipes are equal, and the sampling pipes are arranged at equal intervals.

[0020] In order to improve the representativeness of the sampled sample, one end of the connecting pipe is connected to the middle position of the length direction of the side wall of the mixing pipe.

[0021] The installation structure of the air preheater air leakage rate online monitoring system based on the precise measurement of the single-table oxygen content difference is as follows: the air preheater flue gas side inlet grid sampler is installed at the air preheater flue gas side inlet, and the air preheater flue gas side outlet grid sampler is installed at the air preheater flue gas side outlet; one end of the sample gas conveying pipeline is connected to the coupling pipeline between the inlet sample gas control valve and the outlet sample gas control valve, and the other end of the sample gas conveying pipeline is connected to the air preheater flue gas side outlet flue downstream of the air preheater flue gas side outlet grid sampler. That is, the connection between the other end of the sample gas conveying pipeline and the air preheater flue gas side outlet flue is located downstream of the air preheater flue gas side inlet grid sampler and the air preheater flue gas side outlet grid sampler. Therefore, whether the inlet or the outlet is sampled, automatic sampling can be completed under the differential pressure, and the measured flue gas returns to the air preheater, without causing pollution. When the sampling pressure is insufficient, the air extractor can be started.

[0022] The present application is provided with grid samplers (grid-distributed sampling ports, which meet the requirements of GB10184) at the inlets and outlets of the air preheater flue gas side, and then through the switching of the valves, the samples are alternately taken to the same set of oxygen content meters for measurement, and the air leakage rate is calculated through the oxygen content difference. The use of the same set of oxygen content meters can avoid the accuracy problem caused by the deviation of the measurement accuracy of different oxygen content meters, and significantly improve the accuracy of the oxygen content difference measurement.

[0023] In order to facilitate installation, the sampling pipe and the mixing pipe are located in the flue, the one end of the connecting pipe is communicated with the side wall of the mixing pipe, and the other end is communicated with the coupling pipeline and the connecting pipe.

[0024] A method for monitoring the air leakage rate of an air preheater on-line without emission by using a set of oxygen meters, which is realized by using the installation structure and comprises the following steps:

[0025] 1) measuring the oxygen content of the inlet of the air preheater on the flue gas side: closing the outlet sample gas control valve, opening the inlet sample gas control valve and the back flushing control valve, under the action of the differential pressure, the flue gas at the inlet of the air preheater on the flue gas side automatically enters the inlet grid sampler of the air preheater on the flue gas side, and then sequentially passes through the coupling pipeline and the sample gas delivery pipeline, and returns to the air preheater, and the measurement is completed when passing through the oxygen meter; when the differential pressure is insufficient, the positive pressure gas source is opened, the positive pressure gas enters the working gas inlet of the air extractor, and flows to the mixed gas outlet, so that the negative pressure is generated at the extracted gas inlet of the air extractor, and then the sample gas suction power is increased;

[0026] 2) measuring the oxygen content of the outlet of the air preheater on the flue gas side: closing the inlet sample gas control valve, opening the outlet sample gas control valve and the back flushing control valve, under the action of the differential pressure, the flue gas at the inlet of the air preheater on the flue gas side automatically enters the inlet grid sampler of the air preheater on the flue gas side, and then sequentially passes through the coupling pipeline and the sample gas delivery pipeline, and returns to the air preheater, and the measurement is completed when passing through the oxygen meter; when the differential pressure is insufficient, the positive pressure gas source is opened, the positive pressure gas enters the working gas inlet of the air extractor, and flows to the mixed gas outlet, so that the negative pressure is generated at the extracted gas inlet of the air extractor, and then the sample gas suction power is increased;

[0027] 3) calculating the air leakage rate by using the difference between the oxygen contents of the inlet and outlet of the air preheater on the flue gas side, and the specific calculation method is the prior art, which will not be described in detail;

[0028] 4) closing the back flushing control valve and the outlet sample gas control valve, and opening the positive pressure gas source, the positive pressure gas enters the working gas inlet of the air extractor, and under the action of the gas pressure, the high-pressure gas flow flows out from the extracted gas inlet to sequentially flush the sample gas delivery pipeline, the coupling pipeline and the inlet grid sampler of the air preheater on the flue gas side due to the closing of the back flushing control valve;

[0029] 5) closing the back flushing control valve and the inlet sample gas control valve, and opening the positive pressure gas source, the positive pressure gas enters the working gas inlet of the air extractor, and under the action of the gas pressure, the high-pressure gas flow flows out from the extracted gas inlet to sequentially flush the sample gas delivery pipeline, the coupling pipeline and the outlet grid sampler of the air preheater on the flue gas side due to the closing of the back flushing control valve.

[0030] The technologies not particularly limited in the present application are all prior art.

[0031] This invention relates to an online monitoring system and method for air preheater leakage rate based on precise measurement of oxygen difference using a single meter. It requires only one oxygen meter to measure the oxygen difference between the flue gas inlet and outlet of the air preheater. The system boasts high integration, significantly reducing costs while also reducing measurement errors and improving accuracy. Furthermore, it can sample the flue gas based on its own pressure difference, and the sampled gas is returned to the air preheater after measurement, resulting in no emissions and no pollution. The ingenious arrangement of the ejector structure not only assists in sampling when pressure is insufficient but also provides backflushing for pipelines and samplers, preventing blockages. The structure is simple, ingenious, and reasonable, facilitating modification and widespread adoption. Attached Figure Description

[0032] Figure 1 This is a schematic diagram of the online monitoring system for air preheater leakage rate based on precise measurement of oxygen difference using a single meter, as per the present invention.

[0033] In the figure, 1 is the air preheater flue gas side inlet grid sampler, 2 is the inlet sample gas control valve, 3 is the air preheater flue gas side outlet grid sampler, 4 is the outlet sample gas control valve, 5 is the oxygen meter, 6 is the ejector, 7 is the backflush control valve, 8 is the positive pressure gas source, 9 is the air preheater, 10 is the coupling pipeline, and 11 is the sample gas delivery pipeline. Detailed Implementation

[0034] In this application, directional terms such as up and down, left and right, horizontal, vertical, top and bottom, front and back, etc., are based on the relative orientation or positional relationship shown in the attached drawings and should not be construed as an absolute limitation on this application.

[0035] Example 1

[0036] like Figure 1 As shown, an online monitoring system for air preheater leakage rate based on precise measurement of oxygen difference using a single meter includes an air preheater flue gas side inlet grid sampler, an air preheater flue gas side outlet grid sampler, coupling pipeline, inlet sample gas control valve, outlet sample gas control valve, sample gas delivery pipeline, oxygen meter, air ejector, positive pressure gas source, and backflush control valve.

[0037] One end of the coupling pipeline is connected to the sampling port of the grid sampler at the flue gas inlet of the air preheater, and the other end is connected to the sampling port of the grid sampler at the flue gas outlet of the air preheater.

[0038] Both the inlet sample gas control valve and the outlet sample gas control valve are located on the coupling pipeline. The air preheater flue gas side inlet grid sampler, the inlet sample gas control valve, the outlet sample gas control valve, and the air preheater flue gas side outlet grid sampler are arranged sequentially on the coupling pipeline.

[0039] The one end of the sample gas conveying pipeline is communicated with the coupling pipeline between the inlet sample gas control valve and the outlet sample gas control valve, the number of the oxygen content meter and the air extractor is one set, and the oxygen content meter and the air extractor are arranged on the sample gas conveying pipeline, and the air extractor is located downstream of the oxygen content meter; the positive pressure gas source is communicated with the air extractor through a pipeline; and the back flushing control valve is arranged on the sample gas conveying pipeline downstream of the air extractor. The one end of the air preheater flue gas side inlet grid sampler and the air preheater flue gas side outlet grid sampler is an outlet, and the other end is provided with a grid distributed sampling port (the grid distribution of the sampling port is required according to GB10184).

[0040] The system only needs one set of oxygen content meter to complete the oxygen content difference measurement of the air preheater flue gas side inlet and outlet, which significantly reduces the cost, avoids the accuracy problem caused by the deviation of the measurement accuracy of multiple oxygen content meters, and significantly improves the measurement accuracy.

[0041] Embodiment 2

[0042] On the basis of embodiment 1, the following improvements are further made: in order to facilitate use, the air extractor is a jet device structure, and the air extractor is provided with a working gas inlet, an extracted gas inlet and a mixed gas outlet; the working gas inlet is communicated with the positive pressure gas source through a pipeline, and the extracted gas inlet and the mixed gas outlet are communicated with the sample gas conveying pipeline, and the extracted gas inlet is located upstream of the mixed gas outlet. When the back flushing control valve is opened, the positive pressure gas source is opened, the positive pressure gas enters the working gas inlet of the air extractor, and flows to the mixed gas outlet, so that the extracted gas inlet of the air extractor generates negative pressure, and then the sample gas suction power is increased. When the back flushing control valve is closed, the positive pressure gas source is opened, the positive pressure gas enters the working gas inlet of the air extractor, and due to the closing of the back flushing control valve, the high pressure gas flow flows out from the extracted gas inlet to sequentially flush the sample gas conveying pipeline, the coupling pipeline and the air preheater flue gas side inlet grid sampler. The aforementioned upstream to downstream direction refers to the flow direction of the flue gas in the sample gas conveying pipeline during sampling. In order to facilitate arrangement and provision, the aforementioned positive pressure gas source is preferably an air compressor.

[0043] Embodiment 3

[0044] On the basis of embodiment 2, the following improvements are further made: the inlet grid sampler on the flue gas side of the air preheater comprises a sampling tube, a mixing tube and a connecting tube; the sampling tube is parallel arranged in 6, each sampling tube is equal in length and arranged at equal intervals, each sampling tube is provided with 8 sampling holes arranged at equal intervals, and the sampling holes on all sampling tubes are distributed in a grid shape (the grid distribution of the sampling holes meets the requirements of GB10184); the mixing tube is a tubular structure with both ends blocked, and each sampling tube is vertically connected to the side wall of the mixing tube at one end; the connecting tube is connected to the middle position of the side wall of the mixing tube in the length direction at one end and connected to one end of the coupling pipeline as a sampling outlet at the other end, and the sampling tube and the connecting tube are respectively located on both sides of the mixing tube. The outlet grid sampler on the flue gas side of the air preheater is the same structure as the inlet grid sampler on the flue gas side of the air preheater, and the connecting tube on the outlet grid sampler on the flue gas side of the air preheater is connected to the other end of the coupling pipeline.

[0045] The installation structure of the above-mentioned air preheater leakage rate online monitoring system based on single oxygen content difference precision measurement, the inlet grid sampler on the flue gas side of the air preheater is installed at the inlet of the flue gas side of the air preheater, and the outlet grid sampler on the flue gas side of the air preheater is installed at the outlet of the flue gas side of the air preheater; one end of the sample gas conveying pipeline is connected to the coupling pipeline between the inlet sample gas control valve and the outlet sample gas control valve, and the other end of the sample gas conveying pipeline is connected to the flue gas outlet of the flue gas side of the air preheater downstream of the outlet grid sampler on the flue gas side of the air preheater. That is, the other end of the sample gas conveying pipeline is connected to the flue gas outlet of the flue gas side of the air preheater downstream of the inlet grid sampler on the flue gas side of the air preheater and the outlet grid sampler on the flue gas side of the air preheater, so that automatic sampling can be completed under the differential pressure regardless of inlet sampling or outlet sampling, and the measured flue gas returns to the air preheater without causing pollution. When the sampling pressure is insufficient, the air extractor can be started. In order to facilitate installation, the sampling tube and the mixing tube are located in the flue, one end of the connecting tube is connected to the side wall of the mixing tube, and the other end of the connecting tube penetrates the flue and is connected to the coupling pipeline.

[0046] A method for online monitoring of air preheater leakage rate without emission by using a set of oxygen meters, which is realized by using the above-mentioned installation structure and comprises the following steps:

[0047] 1) Measuring the oxygen content of the inlet of the flue gas side of the air preheater: closing the outlet sample gas control valve, opening the inlet sample gas control valve and the back flushing control valve, under the action of the differential pressure, the flue gas of the inlet of the flue gas side of the air preheater automatically enters the inlet grid sampler on the flue gas side of the air preheater, and then passes through the coupling pipeline and the sample gas conveying pipeline to return to the air preheater, and the measurement is completed when passing through the oxygen meter; when the differential pressure is insufficient, the positive pressure gas source is started, the positive pressure gas enters the working gas inlet of the air extractor, and flows to the mixed gas outlet, so that the negative pressure is generated at the air extraction gas inlet of the air extractor, and the sample gas suction power is increased;

[0048] 2) Measure the oxygen content of the outlet of the air preheater flue gas side: close the inlet sample gas control valve, open the outlet sample gas control valve and the back flushing control valve, under the action of differential pressure, the flue gas of the air preheater flue gas side inlet automatically enters the air preheater flue gas side inlet grid sampler, and in turn passes through the coupling pipeline and the sample gas delivery pipeline, and then returns to the air preheater, and when passing through the oxygen content meter, the measurement is completed; when the differential pressure is insufficient, the positive pressure gas source is opened, the positive pressure gas enters the working gas inlet of the air extractor, and flows to the mixed gas outlet, so that the negative pressure is generated at the air extraction gas inlet of the air extractor, thereby increasing the sample gas suction power;

[0049] 3) Calculate the air leakage rate by using the difference between the oxygen contents of the inlet and outlet of the air preheater flue gas side;

[0050] 4) Close the back flushing control valve and the outlet sample gas control valve, and open the positive pressure gas source, the positive pressure gas enters the working gas inlet of the air extractor, and under the action of gas pressure, the high pressure gas flows out from the air extraction gas inlet to form a purge of the sample gas delivery pipeline, the coupling pipeline and the air preheater flue gas side inlet grid sampler due to the closing of the back flushing control valve;

[0051] 5) Close the back flushing control valve and the inlet sample gas control valve, and open the positive pressure gas source, the positive pressure gas enters the working gas inlet of the air extractor, and under the action of gas pressure, the high pressure gas flows out from the air extraction gas inlet to form a purge of the sample gas delivery pipeline, the coupling pipeline and the air preheater flue gas side outlet grid sampler due to the closing of the back flushing control valve.

[0052] The above-mentioned grid samplers (grid-distributed sampling ports, which are distributed in a grid according to GB10184) are arranged at the inlet and outlet of the air preheater flue gas side, and then the valves are switched to alternately sample to the same set of oxygen content meters for measurement, and the accuracy of the oxygen content difference measurement is significantly improved by avoiding the accuracy problem caused by the deviation of the measurement accuracy of different oxygen content meters. The sample gas is sampled by the pressure difference of the flue gas, and the sample gas after measurement returns to the air preheater, without emission and pollution; through the ingenious arrangement of the air extractor structure, the sample can be assisted when the pressure is insufficient, and the pipeline, sampler, etc. can be back flushed to prevent blockage; the structure is simple, ingenious and reasonable, and is easy to modify and promote.

Claims

1. An air preheater air leakage rate online monitoring system based on single table oxygen difference accurate measurement, characterized by: The air preheater flue gas side inlet grid sampler, the air preheater flue gas side outlet grid sampler, the coupling pipeline, the inlet sample gas control valve, the outlet sample gas control valve, the sample gas conveying pipeline, the oxygen content meter, the air extractor, the positive pressure gas source and the back flushing control valve are arranged in sequence on the coupling pipeline. One end of the coupling pipeline is communicated with the sample outlet of the air preheater flue gas side inlet grid sampler, and the other end is communicated with the sample outlet of the air preheater flue gas side outlet grid sampler. The inlet sample gas control valve and the outlet sample gas control valve are arranged on the coupling pipeline. The sample gas conveying pipeline is communicated with the coupling pipeline between the inlet sample gas control valve and the outlet sample gas control valve.

2. The system according to claim 1, wherein the system is characterized in that: The air extractor is a jet device structure, and the air extractor is provided with a working gas inlet, an extracted gas inlet and a mixed gas outlet.

3. The system according to claim 1 or 2, characterized in that: The positive pressure gas source is an air compressor.

4. The system according to claim 1 or 2, characterized in that: The air preheater flue gas side inlet grid sampler is provided with a sample outlet at one end and a plurality of sampling ports arranged in a grid at the other end.

5. The system according to claim 1 or 2, characterized in that: The air preheater flue gas side inlet grid sampler comprises a sampling pipe, a mixing pipe and a connecting pipe.

6. The system according to claim 5, wherein the system is characterized in that: The lengths of the sampling pipes are equal and arranged at equal intervals.

7. The system according to claim 5, wherein the system is characterized in that: The connecting pipe is communicated with the mixing pipe at one end and communicated with the other end of the coupling pipeline at the other end.

8. The installation structure of the online monitoring system for the air preheater leakage rate based on the single oxygen difference precision measurement according to any one of claims 1-7, characterized in that: The lengths of the sampling pipes are equal and arranged at equal intervals.

9. The mounting structure according to claim 8, characterized by: The connecting pipe is communicated with the mixing pipe at one end and communicated with the other end of the coupling pipeline at the other end.

10. A method for monitoring the air leakage rate of an air preheater on-line without emission by using a set of oxygen meters, which is implemented by using the installation structure of claim 7 or 8, characterized in that: The air preheater flue gas side inlet grid sampler is arranged at the air preheater flue gas side inlet, and the air preheater flue gas side outlet grid sampler is arranged at the air preheater flue gas side outlet. The sampling pipe and the mixing pipe are arranged in the flue, and the connecting pipe is communicated with the mixing pipe at one end and communicated with the coupling pipeline at the other end. The method comprises the following steps. 1) Measure the oxygen content of the inlet of the air preheater flue gas side: close the outlet sample gas control valve, open the inlet sample gas control valve and the back flushing control valve, under the action of differential pressure, the flue gas of the inlet of the air preheater flue gas side automatically enters the air preheater flue gas side inlet grid sampler, and then passes through the coupling pipeline and the sample gas delivery pipeline, and returns to the air preheater, and the measurement is completed when passing through the oxygen content meter; when the differential pressure is insufficient, open the positive pressure gas source, the positive pressure gas enters the working gas inlet of the air extractor, and flows to the mixed gas outlet, so that the extracted gas inlet on the air extractor generates negative pressure, thereby increasing the sample gas suction power; 2) Measure the oxygen content of the outlet of the air preheater flue gas side: close the inlet sample gas control valve, open the outlet sample gas control valve and the back flushing control valve, under the action of differential pressure, the flue gas of the inlet of the air preheater flue gas side automatically enters the air preheater flue gas side inlet grid sampler, and then passes through the coupling pipeline and the sample gas delivery pipeline, and returns to the air preheater, and the measurement is completed when passing through the oxygen content meter; when the differential pressure is insufficient, open the positive pressure gas source, the positive pressure gas enters the working gas inlet of the air extractor, and flows to the mixed gas outlet, so that the extracted gas inlet on the air extractor generates negative pressure, thereby increasing the sample gas suction power; 3) Calculate the air leakage rate by the difference between the oxygen contents of the inlet and outlet of the air preheater flue gas side; 4) Close the back flushing control valve and the outlet sample gas control valve, and open the positive pressure gas source, the positive pressure gas enters the working gas inlet of the air extractor, due to the closing of the back flushing control valve, under the action of gas pressure, the high pressure gas flows out from the extracted gas inlet, and then forms a purge on the sample gas delivery pipeline, the coupling pipeline and the air preheater flue gas side inlet grid sampler; 5) Close the back flushing control valve and the inlet sample gas control valve, and open the positive pressure gas source, the positive pressure gas enters the working gas inlet of the air extractor, due to the closing of the back flushing control valve, under the action of gas pressure, the high pressure gas flows out from the extracted gas inlet, and then forms a purge on the sample gas delivery pipeline, the coupling pipeline and the air preheater flue gas side outlet grid sampler.

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