A fixed source VOCs sampling device and sampling method for coal-fired power plants

Abstract

The present invention relates to the technical field of fixed source volatile gas sampling, and in particular to a fixed source VOCs sampling device and sampling method for coal-fired power plants. The device comprises a Summa tank, a sampling gun, a primary gas diluter and a secondary gas diluter. The flue gas outlet of the sampling gun is connected to a first air inlet of the primary diluter via a sampling pipeline, and the flue gas outlet of the sampling gun is respectively connected to a second air inlet of the primary diluter and an air inlet of the secondary diluter via another sampling pipeline. The air outlet of the primary diluter and the air outlet of the secondary diluter are both connected to the Summa tank. The present invention samples VOCs emissions from fixed sources in coal-fired power plants, and can be used together with the currently more advanced cold trap pre-concentration air intake system to achieve qualitative analysis of more than 100 types of VOCs, providing technical support for China's research and development and formulation of targeted VOCs control technologies and policies for coal-fired power plants.

Description

Technical Field

[0001] The present invention relates to the technical field of fixed source volatile gas sampling, and in particular to a fixed source VOCs sampling device and a sampling method for a coal-fired power plant. Background Art

[0002] In addition to emitting large amounts of conventional pollutants, coal combustion in coal-fired power plants also releases significant concentrations of volatile organic compounds (VOCs). These are important precursors of atmospheric ozone and secondary organic aerosols, contributing to complex atmospheric pollution such as photochemical smog and haze. Furthermore, most VOCs are highly toxic, posing a significant threat to human health. China has a large number of coal-fired power plants, and their emissions are substantial. The impact of VOCs on these plants cannot be ignored, making monitoring and controlling VOC concentrations from these plants crucial. Currently, atmospheric VOC sampling in China uses air bags, adsorption tubes, and Suma canisters, while stationary source VOC sampling uses air bags and adsorption tubes. Suma canisters, with their inertized inner walls, prevent background contamination and can be subsequently combined with state-of-the-art cold trap pre-concentration intake systems to enable qualitative analysis of over 100 VOC species. These canisters are an advanced and effective sampling tool for collecting and storing VOCs. However, a device and method for sampling VOCs from stationary coal-fired power plants using Suma canisters is currently unavailable. Summary of the Invention

[0003] The purpose of the present invention is to provide a VOCs sampling device and sampling method for a coal-fired power plant stationary source, so as to solve the problem in the prior art that VOCs of a coal-fired power plant stationary source cannot be sampled by a Suma tank.

[0004] The technical solution of the present invention:

[0005] A fixed source VOCs sampling device for a coal-fired power plant includes a Summa tank, a sampling gun, a primary gas diluter, and a secondary gas diluter. The flue gas outlet of the sampling gun is connected to the first air inlet of the primary diluter through a sampling pipeline, and the flue gas outlet of the sampling gun is connected to the second air inlet of the primary diluter and the air inlet of the secondary diluter through another sampling pipeline. The air outlet of the primary diluter and the air outlet of the secondary diluter are both connected to the Summa tank.

[0006] Preferably, the sampling gun is a stainless steel heated sampling gun with a heating temperature of 120°C ± 5°C, and a brushless diaphragm pump is provided inside the sampling gun.

[0007] Preferably, a glass wool filter head is provided at the air inlet end of the sampling gun, and the pore size of the glass wool filter head is ≤10 μm.

[0008] Preferably, the second air inlet of the first-stage diluter and the air inlet of the second-stage diluter are both connected to the liquid nitrogen bottle.

[0009] Preferably, a sealing cap is installed on the top of the Suma tank; and a vacuum pressure gauge is provided on the Suma tank.

[0010] Preferably, a flow limiting valve and an exhaust pipe are provided on the sampling pipeline connecting the first-stage diluter outlet and the second-stage diluter outlet to the Suma tank.

[0011] Preferably, the first-stage gas diluter is a gas diluter with a fixed dilution multiple; and the second-stage gas diluter is a gas diluter with an adjustable dilution multiple.

[0012] Preferably, a mass flow controller is provided in the secondary gas diluter.

[0013] Preferably, the inner wall of the Suma tank is inerted.

[0014] Preferably, a valve is provided on the sampling pipeline connecting the smoke outlet of the sampling gun with the second air inlet of the first-stage diluter and the air inlet of the second-stage diluter.

[0015] The sampling method of the stationary source VOCs sampling device of a coal-fired power plant includes the following steps:

[0016] S1, before VOCs sampling, clean the sampling pipeline;

[0017] S2, VOCs sampling;

[0018] S3: After VOCs sampling, clean the sampling pipeline.

[0019] Preferably, step S1 specifically comprises connecting the flue gas outlet of the sampling gun to the first air inlet of the first-stage diluter, the second air inlet of the first-stage diluter, and the air inlet of the second-stage diluter through the sampling pipeline, extending the sampling gun into the flue of the coal-fired power plant, and placing the flue gas inlet of the sampling gun close to the center of the flue as a sampling point. The power supply of the heating tape and the brushless diaphragm pump is turned on, and the brushless diaphragm pump pumps the flue gas in the flue into the sampling gun, so that the flue gas enters the sampling pipeline of the sampling device, and the sampling pipeline is flushed with flue gas, and the flue gas is diluted by the two-stage gas diluter to complete the pre-flushing process. Before performing this step, the Suma tank is disconnected from the sampling pipeline, and the valve on the liquid nitrogen bottle is closed.

[0020] Preferably, step S2 specifically involves first cleaning and vacuuming the Suma tank, and then connecting the first-stage diluter outlet and the second-stage diluter outlet to the Suma tank through sampling pipes; when sampling, opening the flow limiting valve on the sampling pipe at the front end of the Suma tank, starting sampling, and after the vacuum pressure gauge shows that the pressure in the Suma tank is consistent with the atmospheric pressure at the sampling point, closing the flow limiting valve, sealing it with a sealing cap, and recording the sampling time, location, temperature and humidity, atmospheric pressure and working condition information.

[0021] Preferably, step S3 specifically opens the valve of the liquid nitrogen bottle, passes high-purity nitrogen into the sampling pipeline, and turns on the power supply and valve of the brushless diaphragm pump. The brushless diaphragm pump pumps high-purity nitrogen into the sampling pipeline, sampling gun and two-stage gas diluter of the device, flushes the sampling pipeline, dilutes the nitrogen by the two-stage gas diluter, and finally discharges it into the air through the exhaust pipe to complete the cleaning process; before this step is performed, the Suma tank is disconnected from the sampling pipeline.

[0022] Preferably, before performing step S1, the air tightness test of the sampling device is performed. If the sampling device is leak-free, subsequent steps can be performed.

[0023] Preferably, after the air tightness test of the sampling device is performed, nitrogen samples are collected, and then step S1 is executed. The nitrogen sample collection is specifically as follows: first, the Suma tank is cleaned and vacuumed, and then the first-stage diluter outlet and the second-stage diluter outlet are connected to the Suma tank through the sampling pipeline; the power supply and valve of the brushless diaphragm pump are turned on, the valve and the flow limiting valve are opened, and the valve on the liquid nitrogen bottle is opened to pass high-purity nitrogen into the pipeline, and the nitrogen is diluted by the first-stage gas diluter and the second-stage gas diluter, and then the high-purity nitrogen enters the Suma tank, and finally the flow limiting valve is closed, and the Suma tank is sealed with a sealing cap to complete the nitrogen sample collection. Before this step is performed, the sampling gun is disconnected from the sampling pipeline.

[0024] Beneficial effects of the present invention: Compared with the prior art:

[0025] Compared with the existing technology, the invention has the following significant advantages: it provides a VOCs sampling device and sampling method for fixed sources of coal-fired power plants, which can sample VOCs emissions from fixed sources of coal-fired power plants. It can be used with the currently more advanced cold trap pre-concentration air intake system to achieve qualitative analysis of more than 100 types of VOCs, providing technical support for China's research and development and formulation of targeted VOCs control technologies and policies for coal-fired power plants. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic structural diagram of the sampling device of the present invention;

[0027] Figure 2 This is a schematic diagram of the connection process of the sampling device of the present invention for flushing before VOCs sampling and the VOCs sampling process;

[0028] Figure 3 This is a schematic diagram of the system connection process of the sampling pipeline cleaning process after VOCs sampling by the sampling device of the present invention;

[0029] In the figure: 1. Flue of a coal-fired power plant, 2. Sampling gun, 201. Glass wool filter head, 3. First-stage gas diluter, 301. First air inlet of first-stage diluter, 302. Valve, 303. Second air inlet of first-stage diluter, 304. Air outlet of first-stage diluter, 4. Second-stage gas diluter, 401. Air inlet of second-stage diluter, 402. Air outlet of second-stage diluter, 5. Suma tank, 501. Flow limiting valve, 502. Sealing cap, 503. Vacuum pressure gauge. DETAILED DESCRIPTION

[0030] The following is a further detailed description of the specific embodiments of the present invention, such as the shapes and structures of the various components involved, the relative positions and connection relationships between the various parts, the functions and working principles of the various parts, the manufacturing process and the operation and use methods, etc., through the description of the embodiments with reference to the accompanying drawings, so as to help those skilled in the art to have a more complete, accurate and in-depth understanding of the concept and technical solution of the present invention:

[0031] One embodiment of the present invention provides a stationary source VOCs sampling device for a coal-fired power plant, comprising a coal-fired power plant flue 1, a sampling gun 2, a glass wool filter head 201, a primary gas diluter 3, a first air inlet 301 of the primary diluter, a valve 302, a second air inlet 303 of the primary diluter, an air outlet 304 of the primary diluter, a secondary gas diluter 4 with a mass flow controller, an air inlet 401 of the secondary diluter, an air outlet 402 of the secondary diluter, a Suma tank 5, a flow limiting valve 501, a sealing cap 502, and a vacuum pressure gauge 503;

[0032] VOCs generated in the power plant flue 1 are considered as stationary source VOCs;

[0033] In this embodiment, the flue gas outlet of the sampling gun 2 is connected to the first air inlet 301 of the first-stage diluter through a sampling pipeline, and the flue gas outlet of the sampling gun 2 is respectively connected to the second air inlet 303 of the first-stage diluter and the air inlet 401 of the second-stage diluter through another sampling pipeline. A glass wool filter head 201 is provided at the end of the air inlet of the sampling gun 2, and the air outlet 304 of the first-stage diluter and the air outlet 402 of the second-stage diluter are both connected to the Suma tank 5; a sealing cap 502 is installed on the top of the Suma tank 5; a vacuum pressure gauge 503 is provided on the Suma tank 5; a limiting flow valve 501 and an exhaust pipe are provided on the sampling pipeline connecting the air outlet 304 of the first-stage diluter and the air outlet 402 of the second-stage diluter and the Suma tank, and a valve 302 is provided on the sampling pipeline connecting the flue gas outlet of the sampling gun 2 and the second air inlet 303 of the first-stage diluter and the air inlet 401 of the second-stage diluter.

[0034] In this embodiment, the sampling gun 2 is a stainless steel heated sampling gun with a heating temperature of 120°C ± 5°C. A brushless diaphragm pump is provided inside the sampling gun 2. The brushless diaphragm pump can automatically adjust the flow rate to transport the flue gas in the flue.

[0035] In this embodiment, the glass wool filter head 201 has a pore size of ≤10 μm and removes particulate matter in the flue gas.

[0036] In this embodiment, the second air inlet 303 of the first-stage diluter and the air inlet (401) of the second-stage diluter are both connected to the liquid nitrogen bottle.

[0037] In this embodiment, the primary gas diluter 3 is a fixed dilution ...

[0038] In this embodiment, a mass flow controller is provided in the secondary gas diluter 4. The mass flow controller can accurately measure and control the mass flow of the flue gas / gas.

[0039] In this embodiment, the inner wall of the Suma tank (5) is inertized, the volume is 3.2L or 6L, and the pressure resistance value is greater than 241KPa; before sampling, the Suma tank is humidified or heated to clean the tank to reduce the active adsorption of the tank body. After cleaning, the Suma tank is evacuated to a vacuum (less than 10Pa);

[0040] In this embodiment, all sampling pipelines are Teflon tubes (made of polytetrafluoroethylene); the Teflon tubes are used to prevent impurities in the flue gas from being adsorbed on the inner wall of the sampling pipeline.

[0041] Another embodiment of the present invention provides a method for sampling VOCs from a stationary source in a coal-fired power plant, specifically comprising the following steps:

[0042] Step S1, perform air tightness test on the sampling device. If the sampling device is leak-proof, proceed to the subsequent steps.

[0043] Step S2, collect two groups of nitrogen samples, one as a laboratory blank and the other as a transport blank, specifically: first clean and vacuum the Suma tank 5, then connect the first-stage diluter outlet 304 and the second-stage diluter outlet 402 to the Suma tank 5 through a sampling pipeline; turn on the power supply and valve of the brushless diaphragm pump, open the valve 302 and the flow limiting valve 501, open the valve on the liquid nitrogen bottle to pass high-purity nitrogen into the sampling pipeline, and dilute the nitrogen by the first-stage gas diluter 3 and the second-stage gas diluter 4, and then the high-purity nitrogen enters the Suma tank 5, finally close the flow limiting valve 501, seal the Suma tank with a sealing cap 502, and complete the nitrogen sample collection. Before this step is performed, disconnect the sampling gun 2 from the sampling pipeline.

[0044] Step S3: Before VOCs sampling, clean the sampling pipeline:

[0045] The flue gas outlet of the sampling gun 2 is connected to the first air inlet 301 of the first-stage diluter, the second air inlet 303 of the first-stage diluter, and the air inlet 401 of the second-stage diluter through the sampling pipeline, and the sampling gun 2 is extended into the flue 1 of the coal-fired power plant. The flue gas inlet of the sampling gun 2 is close to the center of the flue 1 of the power plant as the sampling point. The power of the heating tape and the brushless diaphragm pump is turned on. The brushless diaphragm pump pumps the flue gas in the flue into the sampling gun 2, so that the flue gas enters the sampling pipeline of the sampling device. The sampling pipeline is flushed with flue gas, and the flue gas is diluted by the two-stage gas diluter to complete the pre-flushing process. Before this step is performed, the Suma tank 5 is disconnected from the sampling pipeline and the valve on the liquid nitrogen bottle is closed.

[0046] Step S4, VOCs sampling:

[0047] First, clean and evacuate the Summa tank 5, then connect the first-stage diluter outlet 304 and the second-stage diluter outlet 402 to the Summa tank 5 through sampling pipes. When sampling, open the flow limiting valve 501 on the sampling pipe at the front end of the Summa tank 5 and start sampling. After the vacuum pressure 503 gauge shows that the pressure inside the Summa tank 5 is consistent with the atmospheric pressure at the sampling point, close the flow limiting valve 501 and seal it with the sealing cap 502. Record the sampling time, location, temperature and humidity, atmospheric pressure and working condition information.

[0048] Step S5: After VOCs sampling, the sampling pipeline is cleaned:

[0049] Open the valve of the liquid nitrogen bottle, pass high-purity nitrogen into the sampling pipeline, and turn on the power and valve of the brushless diaphragm pump. The brushless diaphragm pump pumps high-purity nitrogen into the sampling pipeline, sampling gun 2 and two-stage gas diluter of the device to flush the sampling pipeline. The nitrogen is diluted by the two-stage gas diluter and finally discharged into the air through the exhaust pipe to complete the cleaning process. Before this step, disconnect the Suma tank 5 from the sampling pipeline.

[0050] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for sampling VOCs from stationary sources in coal-fired power plants, characterized in that: The method is implemented by using a fixed source VOCs sampling device, which comprises a Suma tank (5), a sampling gun (2), a primary gas diluter (3) and a secondary gas diluter (4); the smoke outlet of the sampling gun (2) is connected to the first air inlet (301) of the primary diluter through a sampling pipeline, the smoke outlet of the sampling gun (2) is connected to the second air inlet (303) of the primary diluter and the air inlet (401) of the secondary diluter through another sampling pipeline, and the air outlet (304) of the primary diluter and the air outlet (402) of the secondary diluter are both connected to the Suma tank (5); The method comprises the following steps: S1, before VOCs sampling, clean the sampling pipeline: connect the flue gas outlet of the sampling gun (2) to the first air inlet (301) of the first-stage diluter, the second air inlet (303) of the first-stage diluter, and the air inlet (401) of the second-stage diluter through the sampling pipeline, extend the sampling gun (2) into the flue (1) of the coal-fired power plant, and the flue gas inlet of the sampling gun (2) is close to the center of the flue (1) as the sampling point, turn on the power of the heating cable and the brushless diaphragm pump, and the brushless diaphragm pump pumps the flue gas in the flue (1) into the sampling gun (2), so that the flue gas enters the sampling pipeline of the sampling device, and uses the flue gas to flush the sampling pipeline. The flue gas is diluted by the two-stage gas diluter to complete the pre-flushing process. Before this step is performed, disconnect the Suma tank (5) from the sampling pipeline and close the valve on the liquid nitrogen bottle; S2, VOCs sampling: first clean and vacuum the Suma tank (5), then connect the first-stage diluter outlet (304) and the second-stage diluter outlet (402) to the Suma tank (5) through sampling pipes; when sampling, open the flow limiting valve (501) on the sampling pipe at the front end of the Suma tank (5) and start sampling. After the vacuum pressure gauge (503) shows that the pressure inside the Suma tank (5) is consistent with the atmospheric pressure at the sampling point, close the flow limiting valve (501), seal it with a sealing cap (502), and record the sampling time, location, temperature and humidity, atmospheric pressure and working condition information; S3: After VOCs sampling, clean the sampling pipeline.

2. The sampling method according to claim 1, characterized in that: The sampling gun (2) is a stainless steel heated sampling gun with a heating temperature of 120°C ± 5°C. A brushless diaphragm pump is provided inside the sampling gun (2).

3. The sampling method according to claim 2, characterized in that: A glass wool filter head (201) is provided at the air inlet end of the sampling gun (2), and the pore size of the glass wool filter head (201) is ≤10 μm.

4. The sampling method according to claim 1, wherein: The second air inlet (303) of the first-stage diluter and the air inlet (401) of the second-stage diluter are both connected to the liquid nitrogen bottle.

5. The sampling method according to claim 4, characterized in that: A sealing cap (502) is installed on the top of the Suma tank (5); and a vacuum pressure gauge (503) is provided on the Suma tank (5).

6. The sampling method according to claim 5, characterized in that: A flow limiting valve (501) and an exhaust pipe are provided on the sampling pipeline connected to the first-stage diluter air outlet (304) and the second-stage diluter air outlet (402) and the Suma tank.

7. The sampling method according to claim 1, characterized in that: The first-stage gas diluter (3) is a gas diluter with a fixed dilution multiple; the second-stage gas diluter (4) is a gas diluter with an adjustable dilution multiple.

8. The sampling method according to claim 1, wherein: A mass flow controller is provided in the secondary gas diluter (4).

9. The sampling method according to claim 5, characterized in that: The inner wall of the Suma tank (5) is inerted.

10. The sampling method according to claim 1, characterized in that: A valve (302) is provided on a sampling pipeline connecting the smoke outlet of the sampling gun (2) with the second air inlet (303) of the first-stage diluter and the air inlet (401) of the second-stage diluter.

11. The sampling method according to claim 1, characterized in that: Step S3 specifically involves opening the valve of the liquid nitrogen bottle, passing high-purity nitrogen into the sampling pipeline, and turning on the power supply and valve of the brushless diaphragm pump. The brushless diaphragm pump pumps the high-purity nitrogen into the sampling pipeline, the sampling gun (2) and the two-stage gas diluter of the device, flushing the sampling pipeline, diluting the nitrogen by the two-stage gas diluter, and finally exhausting it into the air through the exhaust pipe to complete the cleaning process. Before this step is performed, the Suma tank (5) is disconnected from the sampling pipeline.

12. The sampling method according to claim 1, wherein: Before performing step S1, the air tightness test of the sampling device is performed. If the sampling device is leak-free, the subsequent steps can be performed.

13. The sampling method of the stationary source VOCs sampling device of a coal-fired power plant according to claim 12, characterized in that: After the air tightness test of the sampling device is performed, nitrogen samples are collected, and then step S1 is performed. The nitrogen sample collection is specifically as follows: first, the Suma tank (5) is cleaned and vacuumed, and then the first-stage diluter gas outlet (304) and the second-stage diluter gas outlet (402) are connected to the Suma tank (5) through the sampling pipeline; the power supply and valve of the brushless diaphragm pump are turned on, the valve (302) and the flow limiting valve (501) are opened, and the valve on the liquid nitrogen bottle is opened to pass high-purity nitrogen into the pipeline, and the nitrogen is diluted by the first-stage gas diluter (3) and the second-stage gas diluter (4), and then the high-purity nitrogen enters the Suma tank (5), and finally the flow limiting valve (501) is closed, and the Suma tank (5) is sealed with a sealing cap (502) to complete the nitrogen sample collection. Before this step is performed, the sampling gun (2) is disconnected from the sampling pipeline.

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