Low-temperature trap device for direct-method non-methane total hydrocarbon analyzer

Abstract

The utility model discloses a low-temperature trapping trap device for a direct-method non-methane total hydrocarbon analyzer, which comprises an outer frame, a refrigeration heat conduction block is arranged in the outer frame, a U-shaped groove is arranged in the refrigeration heat conduction block, a trapping pipe is arranged in the U-shaped groove, semiconductor chilling plates are respectively mounted on two sides of the refrigeration heat conduction block, and the semiconductor chilling plates are arranged in the trapping pipe. Radiators are tightly attached to the two sides of the semiconductor chilling plate and fixedly installed on the outer side of the outer frame in an exposed mode. According to the direct-method non-methane total hydrocarbon low-temperature trapping trap provided by the utility model, the refrigeration efficiency is improved, the working temperature is controlled to be about-10 to-20 DEG C for long-time stable operation, and the adsorption and thermal desorption capabilities of the trapping trap on low-boiling-point and polar organic matters are improved; non-methane total hydrocarbon peaks of substances such as propane, trichloro ethylene, methylbenzene and ethyl acetate meet the file requirements of a master station, the structure of the trapping trap is redesigned, and the waterproof sealing performance and the heat preservation performance of the trapping trap are improved.

Description

TECHNICAL FIELD

[0001] The utility model relates to low temperature trapping trap device technical field especially relates to a low temperature trapping trap device for direct method non -methane total hydrocarbon analyzer. BACKGROUND

[0002] In recent years, environmental air pollution problems have become the social problems that people pay more and more attention to. Volatile organic compounds (VOCs) pollution in the environment air not only affects human health, but also as a photochemical pollution precursor is an important factor causing ozone concentration exceeding standard. Volatile organic compounds (VOCs) monitoring is generally divided into total monitoring and characteristic factor monitoring, wherein total monitoring takes total volatile organic compounds (TVOC) and non-methane total hydrocarbon (NMHC) as environmental pollution evaluation index.

[0003] In the "HJ1013-2018 stationary sources of waste gas non-methane total hydrocarbon continuous monitoring system technical requirements and detection method", non-methane total hydrocarbon (NMHC) definition: under the conditions stipulated in HJ38 standard, the sum of other gaseous organic compounds (except otherwise specified, the result is calculated in carbon) that have response on hydrogen flame ionization detector. Non-methane total hydrocarbon monitoring has a long history in the field of environmental monitoring, and the methods are various, and most countries mainly use gas chromatography (difference method). In HJ38-2017 and HJ604-2017, it is stipulated that the detection principle of difference method: the gas sample is directly injected into the gas chromatograph with hydrogen flame ionization detector, and the content of total hydrocarbon and methane is measured on total hydrocarbon column and methane column respectively, and the difference between the two is the content of non-methane total hydrocarbon. The method defaults that the response value of oxygen on non-methane total hydrocarbon is constant, and the interference of oxygen on non-methane total hydrocarbon is excluded by deducting the absolute value of oxygen response, but the actual situation is that the interference of oxygen is not a simple cumulative relationship, and cannot be solved by directly deducting, which also leads to the negative value of non-methane total hydrocarbon monitored by difference method.

[0004] In 2018 Shanghai area "DB31 / T1090-2018 environmental air non-methane total hydrocarbon online monitoring technical specification" and 2021 China environmental protection station "environmental air non-methane total hydrocarbon continuous automatic monitoring technology regulation (trial)" file clearly stipulates that the analysis method of the instrument should adopt the direct method. The common direct method is column back flushing method and low temperature pre-concentration method: 1) column back flushing method uses carrier gas to carry the sample into the chromatographic column, when the methane peak is out, the valve is cut to make the chromatographic column reverse into the carrier gas, the remaining components except methane are back flushed out of the chromatographic column and detected by the detector, and the non-methane total hydrocarbon peak signal is generated; 2) adsorbent low temperature pre-concentration method pumps the sample into the quantitative ring and the low temperature trapping tube, and the sample in the quantitative ring enters the chromatographic column through valve cutting to generate oxygen peak and methane peak, the remaining components are discharged by back flushing, the low temperature trapping tube traps non-methane total hydrocarbon, and the non-methane total hydrocarbon peak is detected by the detector through rapid heating and thermal desorption. However, the existing two schemes cannot perfectly meet the requirements of the total station file. The column back flushing method cannot meet the requirements of the non-methane total hydrocarbon peak width and tailing factor due to the adsorption of the chromatographic column. The adsorbent low temperature pre-concentration method has high requirements for the low temperature trapping module, and the existing low temperature trapping module has the following defects: 1) the semiconductor refrigeration effect is poor, and generally only the temperature of the trapping module can be controlled at 0-10 DEG C. The continuous operation of the online instrument causes the refrigeration component to age rapidly, the cooling time is lengthened, the service life of the refrigeration component is shortened, if the compressor refrigeration is changed, the compressor has high energy consumption, large volume and is very heavy; 2) the adsorbent has poor adsorption and thermal desorption effect on low boiling point and polar organic matter; 3) condensate water is easy to appear around the trapping tube, and the poor waterproofness causes the heating component to be short-circuited, which has safety hidden danger; 4) condensate water is easy to appear on the surface of the trapping module due to poor heat preservation, and the internal trapping tube has poor cooling effect. Practical new type content

[0005] To solve the above technical problems, the utility model designs a low temperature trapping trap device for direct method non-methane total hydrocarbon analyzer.

[0006] The utility model adopts the following technical scheme:

[0007] A low temperature trapping trap device for direct method non-methane total hydrocarbon analyzer, including outer frame, the outer frame is provided with refrigeration heat conduction block, the refrigeration heat conduction block is provided with U-shaped groove, the U-shaped groove is provided with trapping tube, the both sides of refrigeration heat conduction block are respectively installed with semiconductor refrigeration piece, the both sides of semiconductor refrigeration piece are closely installed with radiator, and the radiator is exposed and fixedly installed on the outside of outer frame. Improve the refrigeration efficiency, prolong the service life of semiconductor refrigeration piece, make the working temperature of refrigeration trapping trap module can be stabilized at about-10-20 DEG C, reduce the cooling time of trapping tube after thermal desorption aging, and shorten the analysis cycle.

[0008] As preferred, the outside of the refrigeration and heat conduction block is coated with a layer of high-temperature resistant waterproof glue. The surrounding condensed water is prevented from penetrating into the cavity, thereby avoiding the risk of short circuit of the trapping tube heating assembly.

[0009] As preferred, the outer frame is a heat preservation frame, and the gap between the refrigeration and heat conduction block and the outer frame is filled with foaming glue. The foaming glue is used to fill the gap in the frame, thereby improving the overall heat preservation effect of the module.

[0010] As preferred, the trapping tube is wrapped with a heating wire. The heating output power is adjusted and the appropriate heating wire specification is selected, so that the heating rate of the trapping tube is greater than 50℃ / s.

[0011] As preferred, the heat sink is a pure copper heat sink.

[0012] As preferred, a heat dissipation fan is installed outside the heat sink.

[0013] As preferred, the refrigeration and heat conduction block and the semiconductor refrigeration sheet are adhered through heat conduction silicone grease.

[0014] As preferred, the semiconductor refrigeration sheet is a Peltier.

[0015] As preferred, the trapping tube is filled with one or more of graphitized carbon black, carbon molecular sieve, high molecular polymer and activated carbon. The proportion of the combined filler is tested, and appropriate sampling temperature, sampling volume, thermal desorption temperature, thermal desorption time, aging temperature and time are matched, so that the non-methane total hydrocarbon peak type (peak width and tailing factor) meets the requirements of the total station trial document. The trapping tube material is selected to reduce the influence of the trapping trap background on the system blank test.

[0016] As preferred, the refrigeration and heat conduction block and the outer frame are respectively formed by two half modules symmetrically distributed and bolted. The modular design facilitates the overall installation and part disassembly and replacement of the utility model.

[0017] The direct method non-methane total hydrocarbon low-temperature trapping trap provided by the utility model improves the refrigeration efficiency, controls the working temperature at about-10 to-20℃ for long-time stable operation, improves the adsorption and thermal desorption capacity of the trapping trap for low-boiling-point and polar organic matters, makes the non-methane total hydrocarbon peaks of substances such as propane, trichloroethylene, toluene and ethyl acetate meet the requirements of the total station document, redesigns the structure of the trapping trap, and improves the waterproof sealing and heat preservation performance of the trapping trap. BRIEF DESCRIPTION OF DRAWINGS

[0018] Fig. 1 is a structural schematic view of the utility model;

[0019] Fig. 2 is a structural schematic view of the inside of the outer frame of the utility model;

[0020] Fig. 3 is a side view of the utility model after removing the outer frame, radiator and cooling fan;

[0021] In the figure: 1, outer frame, 2, capture tube, 3, pure copper radiator, 4, cooling fan, 5, refrigeration heat conducting block, 6, foaming glue, 7, high temperature resistant waterproof glue, 8, heat-conducting silicone grease, 9, peltier. DETAILED DESCRIPTION

[0022] The technical scheme of the utility model will be further described in detail below by specific embodiments and in conjunction with the drawings:

[0023] Embodiment: as Figs. 1-3 Indicated, a low-temperature capture trap device for direct method non-methane total hydrocarbon analyzer, including outer frame 1, capture tube 2, pure copper radiator 3, cooling fan 4, refrigeration heat conducting block 5, foaming glue 6, high temperature resistant waterproof glue 7, heat-conducting silicone grease 8 and peltier 9.

[0024] Capture tube is filled with one or several selected from graphitized carbon black, carbon molecular sieve, high molecular polymer, activated carbon, the proportion of combined filler is tested, and suitable sampling temperature, sampling volume, thermal desorption temperature, thermal desorption time, aging temperature and time are matched, so that the non-methane total hydrocarbon peak type (peak width and tailing factor) meets the requirements of the total station trial document.

[0025] The capture tube material is selected to reduce the influence of the capture trap background on the system blank test.

[0026] The heating wire is wound around the capture tube, the heating output power is adjusted, and the appropriate heating wire specification is selected, so that the capture tube heating rate reaches more than 50 DEG C / s.

[0027] The refrigeration heat conducting block is provided in the outer frame, the U-shaped groove is provided in the refrigeration heat conducting block, and the capture tube is arranged in the U-shaped groove.

[0028] Two high-power semiconductor peltiers and pure copper radiators are adhered to both sides of the heat conducting block through heat-conducting silicone grease, and the cooling fan is installed outside the pure copper radiator; the refrigeration efficiency is improved, the service life of the peltier is prolonged, the working temperature of the refrigeration capture trap module can be stabilized at about-10~20 DEG C, the cooling time after the capture tube thermal desorption aging is reduced, and the analysis cycle is shortened.

[0029] The outer frame of the capture trap adopts a heat preservation frame, and the gap between the outer frame and the refrigeration heat conducting block is filled with foaming glue, so that the overall heat preservation effect of the module is improved.

[0030] The working process of the utility model:

[0031] 1, sampling stage, the refrigeration temperature of the trap is controlled at about -10 to -20 DEG C, the heating assembly does not work, the sample after condensation and water removal is pumped into the trap, and the trap traps and adsorbs volatile organic compounds in the sample except methane in the trap tube;

[0032] 2, thermal desorption stage, the refrigeration temperature of the trap is controlled at about -10 to -20 DEG C, the heating assembly works, the trap tube is rapidly heated to about 180 to 200 DEG C, and reverse carrier gas is connected at the same time, so that volatile organic compounds desorbed and analyzed are taken out of the trap tube;

[0033] 3, aging backflushing stage, the refrigeration temperature of the trap is controlled at about -10 to -20 DEG C, the temperature of the trap tube is increased by 20 to 40 DEG C again, carrier gas is connected, the trap tube is cleaned by aging and washing, and the high concentration residual of the trap module is reduced.

[0034] The above-described embodiment is only a preferred scheme of the utility model, and does not limit the utility model in any form, and other variants and modifications can be made without exceeding the technical scheme recorded in the claims.

Claims

1. A cryogenic trap device for a direct non-methane total hydrocarbon analyzer, comprising an outer frame, characterized in that: A cooling and heat-conducting block is provided in the outer frame, a U-shaped groove is provided in the cooling and heat-conducting block, a collection tube is placed in the U-shaped groove, semiconductor refrigeration plates are installed on both sides of the cooling and heat-conducting block, radiators are installed tightly on both sides of the semiconductor refrigeration plates, and the radiators are exposed and fixed on the outside of the outer frame.

2. The low-temperature trap device for a direct non-methane total hydrocarbon analyzer according to claim 1, characterized in that: The outer side of the refrigeration heat conducting block is coated with a layer of high temperature resistant and waterproof glue.

3. The low-temperature trap device for a direct non-methane total hydrocarbon analyzer according to claim 1, characterized in that: The outer frame is a heat-insulating frame, and the gap between the cooling and heat-conducting blocks and the outer frame is filled with foam glue.

4. The low-temperature trap device for a direct non-methane total hydrocarbon analyzer according to claim 1, characterized in that: A heating wire is wound around the outside of the collecting tube.

5. The low-temperature trap device for a direct non-methane total hydrocarbon analyzer according to claim 1, characterized in that: The radiator is a pure copper radiator.

6. The low-temperature trap device for a direct non-methane total hydrocarbon analyzer according to claim 1, characterized in that: A cooling fan is installed outside the radiator.

7. The low-temperature trap device for a direct non-methane total hydrocarbon analyzer according to claim 1, characterized in that: The refrigeration heat conduction block and the semiconductor refrigeration plate are adhered to each other through heat-conducting silicone grease.

8. The low-temperature trap device for a direct non-methane total hydrocarbon analyzer according to claim 1, characterized in that: The semiconductor refrigeration sheet adopts Peltier.

9. The low-temperature trap device for a direct non-methane total hydrocarbon analyzer according to claim 1, characterized in that: The cooling heat conducting block and the outer frame are respectively formed by two symmetrically distributed half modules which are assembled by bolts.

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