A thermal diffusion tube device and method for removing volatile substances from motor vehicle exhaust

Abstract

The present invention discloses a thermal diffusion tube device and method for removing volatile substances from motor vehicle exhaust gas, which can thermally dilute the exhaust gas and remove volatile substances during the exhaust gas sampling process. The thermal diffusion tube device includes a high-temperature dilution part, a volatile substance adsorption part, and a cooling and dilution part. The sample gas entering the high-temperature dilution device through the sampling tube is mixed with the heated sheath gas in the high-temperature dilution tube, and then heated by the tube wall to reach a preset temperature and have a good temperature distribution. The sample gas after high-temperature dilution leaves the high-temperature dilution device and enters the volatile substance removal device. The volatile substances evaporate at the set high temperature and are adsorbed by the activated carbon in the adsorption device, thereby achieving the effect of removing volatile substances. The exhaust gas from which the volatile substances have been removed finally enters the dilution and cooling device. The cooling and dilution part adjusts the dilution ratio according to the temperature of the inlet sample gas, so that the temperature of the diluted exhaust gas meets the temperature requirement of the rear-end particle number concentration measurement device.

Description

Technical Field

[0001] The invention relates to the technical field of exhaust gas removal, and in particular to a thermal diffusion tube device and a method for removing volatile substances in motor vehicle exhaust gas. Background Art

[0002] In recent years, with the rapid improvement of the national economic level, the number of motor vehicles has increased year by year. The emission of motor vehicle exhaust has a great impact on air quality, and the ultrafine particles contained in its exhaust have a great impact on human health. Studies have shown that the smaller the particle size of the particles, the greater the harm to the human body. The aggregation of particles will also reduce air visibility and seriously interfere with the production and life of human society. Therefore, it is necessary to accurately detect the number concentration of ultrafine particles in motor vehicle exhaust, so as to take effective measures to reduce the content of ultrafine particles in the air. Since the ultrafine particles emitted by motor vehicle exhaust contain volatile and semi-volatile substances, this has a great impact on the measurement of non-volatile particles in the exhaust. Volatile and semi-volatile substances can condense into nuclei or attach to non-volatile particles, thereby changing the particle size distribution and number concentration measurement of non-volatile particles. Therefore, when measuring the number concentration of motor vehicle exhaust particles, the volatile and semi-volatile substances in the exhaust should be removed first to reduce their impact on the measurement results.

[0003] At present, the devices used for removing volatile substances from motor vehicle exhaust are mainly divided into three categories internationally: the first category is the method of combining evaporation tube with rear-end dilution. The volatile substances removed by this method are extremely limited, and most of the volatile substances will eventually reattach or re-nucleate, and it is difficult to miniaturize due to the large volume of the required evaporation tube; the second category is the method of combining heating tube with adsorption tube. The removal efficiency of this method is better than the method of evaporation tube plus rear-end dilution, but the total length of the relevant equipment for commercial and laboratory use is about one meter, and no relevant miniaturization work has been carried out; the thermal diffusion tube mentioned in the existing patent CN113504160A has not optimized the volume of the thermal diffusion tube up to one meter, and its heating tube structure is too complicated to meet the portability requirements. The design of adding a flow-following fan to the heating tube mentioned in the patent is too complicated and unreliable. The high temperature environment will affect the operation of the flow-following fan and the cooling speed of the heating tube will not be greatly improved. The valves used when the two heating tubes are heated alternately also have a certain degree of influence on the airtightness of the device; the third category is the catalytic cracking method, which has the highest removal efficiency for volatile substances. However, due to its complex structure and large number of contact surfaces with the gas, it will cause a large loss of non-volatile particulate matter to be measured, thereby affecting the subsequent particle number concentration measurement. In summary, the use of miniaturized heating tubes and adsorption tubes can not only ensure the portability of the equipment, but also meet the removal efficiency of volatile substances in motor vehicles. Based on the above advantages and disadvantages of the device and method for removing volatile substances from motor vehicle exhaust, the present invention proposes a thermal diffusion tube that can be thermally diluted, miniaturized, and has guaranteed volatile removal efficiency and low particulate matter loss efficiency. Summary of the invention

[0004] The purpose of the present invention is to provide a thermal diffusion tube device and a removal method for removing volatile substances in motor vehicle exhaust gas, which is used for the removal of volatile and semi-volatile substances in the measurement of the number concentration of motor vehicle exhaust particles, and aims to eliminate volatile or semi-volatile substances in motor vehicle exhaust gas, so as to perform true motor vehicle exhaust gas particle number concentration measurement.

[0005] To achieve the above purpose, the technical implementation scheme of the present invention is:

[0006] A thermal diffusion tube device for removing volatile substances in motor vehicle exhaust gas, comprising a high-temperature dilution device, an adsorption device connected to the high-temperature dilution device by a flange, and a cooling dilution device connected to the adsorption device and having the same structure as the high-temperature dilution device;

[0007] The high temperature dilution device comprises a metal tube with a certain tube wall thickness, a circulating sheath gas channel located in the tube wall, a circulating sheath gas elbow with a certain length at the outlet end of the adsorption tube, a sheath gas outlet and inlet welded on the tube wall, a sheath gas sample gas mixing outlet located in the tube wall, a metal shell with an embedded heating coil surrounding the outer wall of the metal tube, and high temperature resistant sealing gaskets at both ends of the metal tube;

[0008] The adsorption device comprises a stainless steel tube, a steel mesh coaxial with the stainless steel tube, activated carbon filled between the stainless steel tube and the coaxial steel mesh for adsorbing volatile substances, gaskets for sealing at both ends of the stainless steel tube and an internally threaded metal cover;

[0009] The cooling and diluting device comprises a metal tube with a certain tube wall thickness, a circulating sheath gas channel located in the tube wall, a sheath gas outlet and an inlet welded on the tube wall, and high temperature resistant sealing gaskets at both ends of the cylinder;

[0010] The heating device of the high temperature dilution device wraps the metal tube to heat the sheath gas and the sample gas;

[0011] The cooling dilution tube wall forms a cooling loop to dilute and cool the sample gas to meet the requirements of the back-end detection instruments;

[0012] A circulating loop sheath gas channel is used in the high temperature dilution device, which can fully heat the sheath gas;

[0013] The heated high-temperature sheath gas is mixed with the sample gas. A cylindrical baffle is used for the dilution gas at the mixing point. After buffering, it is mixed with the sample gas to avoid turbulence caused by direct mixing and resulting in particle loss. The high-temperature sheath gas dilutes and preliminarily heats the sample gas. After mixing evenly, it is heated again in the sample gas channel.

[0014] The circulating sheath gas loop in the high-temperature dilution tube extends into the adsorption tube, so that the front end of the adsorption tube is kept at a certain temperature, ensuring that the temperature of the aerosol drops steadily from the heated dilution tube to the adsorption tube;

[0015] The cylindrical parts of the heating dilution device and the cooling dilution device are both made of stainless steel, and the gasket used for end face sealing in the high-temperature dilution device is made of graphite;

[0016] The inner wall of the cylindrical adsorption device uses a steel mesh with a certain porosity, so that the gaseous volatile substances pass through the steel mesh and are adsorbed by the activated carbon;

[0017] The outlet of the adsorption tube and the outlet of the cooling and dilution device adopt metal ferrule tees for placing thermocouples or PT100 temperature measuring devices;

[0018] The present invention also relates to a method for the above tail gas pretreatment device, the method comprising the following steps:

[0019] (1) The exhaust gas of the motor vehicle is collected through the sampling tube and enters the high-temperature dilution device, where it is mixed with the heated high-temperature sheath gas in the high-temperature dilution device at the inlet;

[0020] (2) After mixing with the high-temperature sheath gas, the gas at the end of the sampling tube is split according to the set flow rates of the sheath gas and the sample gas, and the part that is split and enters the cylindrical adsorption device is the diluted sample gas;

[0021] (3) The diluted sample gas diverted into the sheath gas loop at the end of the high-temperature dilution device passes through a cooling copper tube, a filter, a dehumidifier, a filter, an air pump, and a filter, and then enters the sampling tube again to mix with the sampled tail gas;

[0022] (4) The high-temperature dilution device and the adsorption device are connected and sealed with flanges. The sheath gas loop of the high-temperature dilution tube is extended to the adsorption material layer of the adsorption tube by bending the copper tube, so that the sample gas at the outlet of the high-temperature dilution tube is slowly cooled in the adsorption tube to prevent the evaporated volatile or semi-volatile substances from condensing and re-nucleating or adsorbing on the surface of the particles;

[0023] (5) The diluted sample gas passes through the adsorption device. Due to the high temperature heating, the volatile or semi-volatile substances evaporate into gaseous state, diffuse to the wall of the adsorption device tube and are adsorbed by the activated carbon;

[0024] (6) After the diluted sample gas passes through the adsorption device, the removal efficiency of volatile or semi-volatile substances reaches more than 99%, and then it enters the cooling and dilution device to cool the diluted sample gas to the measurement temperature required by the back-end detection device.

[0025] In summary, the present invention provides an exhaust gas pre-treatment device that can perform high-temperature in-situ dilution sampling of exhaust gas and remove volatile and semi-volatile substances in exhaust gas. The device and method can pre-treat the components of motor vehicle exhaust gas, making the measurement result of the number concentration of motor vehicle exhaust particles more accurate. The device adopts a high-temperature dilution module, eliminating the hot dilution part in the traditional volatile substance removal device. After high-temperature dilution, the sample gas is passed into an adsorption tube containing activated carbon to adsorb the evaporated volatile and semi-volatile substances, and finally passed into a cooling dilution tube to adjust the gas temperature. The device meets the pre-regulation function of the exhaust gas for the measurement of the number concentration of motor vehicle exhaust particles, and improves portability to meet the real-time measurement of motor vehicle exhaust gas.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] (1) Compared with most of the thermal diffusion tubes in previous papers or commercial production, the structure of the present invention is significantly reduced, shortening the mainstream 500mm desorption tube and 500mm adsorption tube to 140mm and 200mm respectively, making it more portable;

[0028] (2) The mainstream thermal diffusion tube does not have the function of diluting the sample gas. The present invention combines the dilution function with the removal of volatile and semi-volatile substances by the thermal diffusion tube, and innovatively uses high-temperature sheath gas to dilute and heat the sample gas at high temperature;

[0029] (3) The high temperature dilution device of the present invention has a good temperature distribution, and can stably maintain a sufficient effective heating distance within a short residence time, so that volatile substances and semi-volatile substances can be fully evaporated;

[0030] (4) The sheath gas circulation loop of the high temperature dilution device of the present invention is connected by a bent copper tube and extends into the adsorption tube for heat dissipation, thereby ensuring a steady drop in temperature at the connection between the heating tube and the adsorption tube, reducing thermophoretic losses of particles, and preventing volatile or semi-volatile substances from re-nucleating due to a sudden drop in temperature;

[0031] (5) A cooling device can be added to the sheath gas circuit of the high temperature dilution device of the present invention. By cooling the cooling copper tube, the temperature of the high temperature dilution device can be quickly reduced, thereby improving the time resolution of the instrument. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a schematic structural diagram of a device for removing volatile substances in the present invention.

[0033] in:

[0034] 11. particle sample gas inlet, 12. high temperature dilution device front cover, 13. particle inlet sealing gasket, 14. metal tube, 15. sheath gas circuit extension tube, 16. particle outlet, 17. sheath gas inlet, 18. sheath gas outlet, 19. sheath gas circuit, 111. heating dilution tube main gas path, 21. adsorption tube inlet, 22. adsorption tube device front cover, 23. adsorption tube body, 24. stainless steel mesh, 25. adsorption tube device rear cover, 26. adsorption tube outlet, 27. adsorption tube main gas path, 31. cooling dilution device inlet, 32. cooling dilution device front cover, 33. inlet sealing gasket, 34. cooling dilution device body, 35. outlet sealing gasket, 36. cooling dilution device outlet, 37. cooling dilution device sheath gas inlet, 38. cooling dilution device sheath gas outlet, 39. cooling sheath gas circuit; DETAILED DESCRIPTION

[0035] like Figure 1A thermal diffusion tube device for removing volatile substances from motor vehicle exhaust is shown, comprising a high-temperature dilution device with a dilution function, an adsorption device (adsorption tube) connected to the outlet of the high-temperature dilution device by a flange and a clamp, and a cooling dilution device connected to the back of the adsorption device and having the same structure as the high-temperature dilution device; wherein the high-temperature dilution device is heated at high temperature by a set heating jacket. Since motor vehicle exhaust contains a certain proportion of volatile and semi-volatile substances in addition to non-volatile carbon particles, these substances will adhere to non-volatile particulate matter or condense themselves into nuclei after the exhaust temperature is reduced, which greatly affects the accurate measurement of the number concentration of motor vehicle exhaust particles. Therefore, the present invention uses high-temperature dilution heating combined with activated carbon adsorption to adsorb and remove volatile and semi-volatile substances in exhaust gas.

[0036] The high temperature dilution device comprises a metal tube 14 with a certain tube wall thickness, a front cover 12 of the high temperature dilution device, a circulating sheath gas loop 19 located in the tube wall of the metal tube, a sheath gas inlet 17, a sheath gas outlet 18 and a sample gas inlet 11 located on the front cover 12 of the high temperature dilution device, a metal jacket with an embedded heating coil surrounding the outside of the cylinder, and a high temperature resistant sealing gasket 13 between the front cover 12 of the high temperature dilution device and the metal tube 14;

[0037] The high temperature dilution device front cover 12 and the metal tube 14 are sealed by a high temperature resistant sealing gasket 13, and the high temperature resistant sealing gasket 13 is made of graphite. After sealing, two No. 3 screws are screwed in from the side of the high temperature dilution device front cover 12 to fix it.

[0038] The circulating sheath gas loop 19 is an air path formed by drilling holes in the wall thickness of the metal tube 14. The circulating sheath gas loop 19 is formed by drilling four through holes in the wall of the metal tube and digging grooves at both ends of the metal tube to connect the through holes. Clean air enters the circulating sheath gas loop 19 through the sheath gas inlet 17, circulates in the four-way through hole gas path and is heated by the heated metal tube 14, and finally enters the main gas path 111 of the high-temperature dilution device metal tube 14 through the sheath gas outlet 18 located on the front cover 12 of the high-temperature dilution device, and is mixed with the exhaust gas sample drawn in at the sample gas inlet 11;

[0039] The heating device of the high temperature dilution device wraps the metal tube to heat the sheath gas and the sample gas;

[0040] The high temperature dilution device adopts a circulating sheath gas loop 19, which can fully heat the sheath gas;

[0041] The sheath gas outlet 18 of the high temperature dilution device is perpendicular to the sample gas inlet 11, so that the sample gas and the sheath gas are fully mixed, thereby achieving the purpose of high temperature dilution and ensuring the mixing uniformity of the dilution;

[0042] The high-temperature dilution device has a moderate ratio of sheath gas to sample gas. The sample gas flow rate is determined under the premise that the sheath gas can be mixed with the sample gas at the set temperature. The total flow of the sample gas and the sheath gas also needs to be defined according to the effective residence time. Therefore, the sample gas and sheath gas flow rate should first be determined to determine the appropriate total flow, and then determine the ratio of the total flow of the sample gas and sheath gas mixed gas to the sample gas, that is, the dilution ratio, which is set to 5; calculated at a total flow of 1L / MIN, the sample gas is drawn in at 0.2L / MIN and the sheath gas is drawn in at 0.8L / MIN under the dilution ratio of 5.

[0043] The high temperature dilution device and the adsorption tube are connected by a sheath gas circulation loop 19 through a bent copper tube, which extends into the adsorption tube for heat dissipation, ensuring a steady drop in temperature at the connection between the heating tube and the adsorption tube, reducing thermophoretic losses of particles, and preventing volatile or semi-volatile substances from re-nucleating due to a sudden drop in temperature;

[0044] The sheath gas that flows back from the adsorption tube to the high-temperature dilution device through the bent copper tube is heated again and mixed with the sample gas. A cylindrical baffle is used for the dilution gas at the mixing point to buffer and mix it with the sample gas to avoid turbulence caused by direct mixing and particle loss. The high-temperature sheath gas dilutes and preliminarily heats the sample gas, and after mixing evenly, it is heated again in the sample gas channel;

[0045] The bent copper tube inserted into the adsorption tube is connected to the circulating sheath gas loop 19 in the high-temperature dilution tube by a metal ferrule. The outlet of the circulating sheath gas loop is screwed into the metal ferrule by an internal thread, and the inlet of the bent copper tube is sealed and connected by a metal ferrule. The outlet of the bent copper tube is connected to another part of the passage in the circulating sheath gas loop, and the connection method is the same as that of the inlet of the bent copper tube.

[0046] The end of the metal tube 14 of the high-temperature dilution tube is connected to the flange, and a graphite gasket is used to seal the two parts, which are fixed by screwing two No. 3 screws into the side of the flange;

[0047] The left side of the adsorption tube body 23 is connected to the flange, and a graphite gasket is used to seal the two parts. Two No. 3 screws are screwed into the side of the flange to fix it;

[0048] The flange connected to the end of the metal tube 14 and the flange connected to the inlet side of the adsorption tube are sealed between the two flanges with a graphite gasket. Then the two flanges are clamped and fixed with a circular clamp.

[0049] The main gas path of the high-temperature dilution tube forms a passage with the flange and the adsorption tube. The sheath gas heated by the circulating gas path is mixed with the sample gas at the entrance of the high-temperature dilution tube, and then further heated by the main gas path of the high-temperature dilution tube, leaves the high-temperature dilution tube, and enters the main gas path 27 of the adsorption tube.

[0050] The adsorption device comprises a metal cylindrical shell 23, a steel mesh 24 coaxial with the metal cylindrical shell, activated carbon filled between the metal cylindrical shell 23 and the coaxial steel mesh 24 for adsorbing volatile substances, gaskets for sealing at both ends of the metal cylindrical shell 23 and internally threaded metal end caps;

[0051] The activated carbon in the adsorption tube is replaced by removing the end caps 22 and 25 at both ends of the adsorption tube;

[0052] The coaxial steel mesh 24 in the adsorption tube ensures a high porosity while ensuring that the activated carbon does not leak, so as to increase the airflow diffusion adsorption area;

[0053] The inner wall of the adsorption device is made of a steel mesh 24 with a certain porosity, so that the gaseous volatile substances pass through the steel mesh 24 and are adsorbed by the activated carbon;

[0054] The two ends of the steel mesh 24 in the adsorption tube are fixed by metal ferrules at the inlet and outlet 21 and 26 of the adsorption tube;

[0055] The temperature of the airflow heated by the high-temperature dilution tube gradually decreases when it enters the adsorption tube. Due to the temperature gradient with the wall of the adsorption tube, there will be a thermophoretic force from the center of the adsorption tube to the wall of the adsorption tube. Under the action of the thermophoretic force and the Brownian motion force of gas diffusion, the volatile particles in the sample gas flow that has been heated to a high temperature and is in a gaseous state will first diffuse into the activated carbon layer in the adsorption tube and be adsorbed, and some particles of the non-volatile particles to be tested will also enter the activated carbon layer and be lost. The remaining non-volatile particles to be tested will gradually cool down and leave the adsorption tube.

[0056] The cooling and diluting device comprises a metal tube 34 with a certain tube wall thickness, a cooling and diluting device front cover 32, a circulating sheath gas loop 39 located in the tube wall, a sheath gas inlet 37 and a sample gas inlet 31 located on the cooling and diluting device front cover 32, a high temperature resistant sealing gasket 33 between the cooling and diluting device front cover 32 and the metal tube 34, a cooling and diluting device rear cover 40, a sheath gas outlet 38 and a sample gas outlet 36 located on the cooling and diluting device rear cover 40, and a high temperature resistant sealing gasket 35 is used to seal between the cooling and diluting device rear cover 40 and the metal tube 34;

[0057] The cooling and diluting device front cover 32 and the metal tube 34 are sealed by a high temperature resistant sealing gasket 33, and the high temperature resistant sealing gasket 33 is made of graphite. After sealing, two No. 3 screws are screwed in from the side of the high temperature diluting device front cover 32 to fix it.

[0058] Two No. 3 screws are screwed into the side of the cooling and diluting device rear cover 40 to fix the cooling and diluting device rear cover, the high temperature resistant sealing gasket 35 and the metal tube 34 together;

[0059] The circulating sheath gas loop 39 is an air path formed by drilling holes in the wall thickness of the metal tube 34. The circulating sheath gas loop 39 is formed by drilling four through holes in the wall of the metal tube and digging grooves at both ends of the metal tube to connect the through holes. Clean air enters the circulating sheath gas loop 39 through the sheath gas inlet 37, circulates in the four-way through hole gas path, and finally leaves the cooling and diluting device through the sheath gas outlet 38 located on the rear cover 40 of the cooling and diluting device;

[0060] The sheath gas outlet 38 of the cooling and dilution device is perpendicular to the sample gas inlet 31, so that the sample gas and the sheath gas are fully mixed, thereby achieving the purpose of cooling and dilution, and ensuring the mixing uniformity of the dilution;

[0061] The cooling and dilution device uses the sheath gas to dilute the sample gas in the same manner as the flow rate of the sheath gas drawn in and discharged out. For example, the sample gas entering the cooling and dilution device through the sample gas inlet 31 of the cooling and dilution device is 1L / MIN, and the sheath gas entering the cooling and dilution device through the sheath gas inlet 37 is 4L / MIN. The sheath gas and the sample gas are mixed in the cooling and dilution device, and finally the 4L / MIN mixed gas leaves the cooling and dilution device through the sheath gas outlet 38, and the 1L / MIN mixed gas leaves the cooling and dilution device through the sample gas outlet 36 of the cooling and dilution device and enters the rear-end particle counting device for measurement. At this time, the dilution ratio is the sheath gas flow plus the sample gas flow to the sample gas flow, and the dilution ratio is 5;

[0062] The metal tubes 14 and 34 of the heating and dilution device and the cooling and dilution device are both made of stainless steel;

[0063] The gaskets 13, 33, 35 used for high-temperature sealing of the end faces in the high-temperature dilution device are made of graphite;

[0064] The high temperature dilution device inlet 11, the adsorption tube outlet 26, and the cooling dilution device outlet 36 are made of metal ferrule tees for placing thermocouples or PT100 temperature measuring devices;

[0065] The present invention also relates to a method for the above tail gas pretreatment device, the method comprising the following steps:

[0066] (1) The exhaust gas of the motor vehicle is collected through the sampling tube and enters the high-temperature dilution device, where it is mixed with the heated high-temperature sheath gas in the high-temperature dilution device at the inlet;

[0067] (2) The total flow after the motor vehicle exhaust gas and the high-temperature sheath gas are mixed is further heated in the main gas path 111 of the high-temperature dilution tube. The volatile substances and semi-volatile substances contained in the heated high-temperature total flow volatilize under high temperature conditions and enter the adsorption tube along with the total flow;

[0068] (3) After the total flow enters the adsorption tube, the volatile and semi-volatile substances diffuse toward the wall of the adsorption tube and are absorbed by the activated carbon filled in the adsorption tube. The removal efficiency of volatile or semi-volatile substances reaches more than 99%, and the remaining non-volatile carbon particles leave the adsorption tube;

[0069] (4) The sheath gas circulation loop of the high-temperature dilution device is connected by a bent copper tube and extends into the adsorption tube for heat dissipation, ensuring a steady drop in the temperature at the connection between the heating tube and the adsorption tube;

[0070] (5) After the total flow leaves the adsorption tube, it is mixed with the sheath gas in the cooling and dilution device to cool and dilute the total flow, and the total flow is cooled to the measurement temperature required by the rear-end detection device;

[0071] (6) A portion of the total flow at the end of the cooling and diluting device leaves the cooling and diluting device through the sheath gas outlet 38 of the cooling and diluting device, passes through the cooling coil, filter, dehydrator, filter, air pump, filter, and finally enters the cooling and diluting device through the cooling and diluting device inlet 37 again to mix with the total flow at the outlet of the adsorption tube.

[0072] In summary, the present invention provides an exhaust gas pre-treatment device that can perform high-temperature in-situ dilution sampling of exhaust gas and remove volatile and semi-volatile substances in exhaust gas. The device and method can pre-treat the components of motor vehicle exhaust gas, making the measurement result of the number concentration of motor vehicle exhaust particles more accurate. The device adopts a high-temperature dilution module, eliminating the hot dilution part in the traditional volatile substance removal device. After high-temperature dilution, the sample gas is passed into an adsorption tube containing activated carbon to adsorb the evaporated volatile and semi-volatile substances, and finally passed into a cooling dilution tube to adjust the gas temperature. The device meets the pre-regulation function of the exhaust gas for the measurement of the number concentration of motor vehicle exhaust particles, and improves portability to meet the real-time measurement of motor vehicle exhaust gas.

[0073] The embodiments described above are merely descriptions of preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A thermal diffusion tube device for removing volatile substances from motor vehicle exhaust, comprising a high-temperature dilution device, an adsorption device and a cooling dilution device, characterized in that: The adsorption device is connected to the high temperature dilution device by flange, and the cooling dilution device is connected to the adsorption device; The high temperature dilution device comprises a metal tube 1, a circulating sheath gas channel located in the wall, and a circulating sheath gas elbow at the outlet end of the metal tube 1, and also comprises a sheath gas outlet and inlet welded on the tube wall, a sheath gas sample gas mixing outlet located in the tube wall, a metal shell with an embedded heating coil surrounding the outer wall of the metal tube 1, and high temperature resistant sealing gaskets at both ends of the metal tube 1; The adsorption device comprises a stainless steel tube, a steel mesh coaxial with the stainless steel tube, activated carbon filled between the stainless steel tube and the coaxial steel mesh for adsorbing volatile substances, gaskets for sealing at both ends of the stainless steel tube and an internally threaded metal cover; The cooling and diluting device comprises a second metal tube, a circulating sheath gas channel located in the tube wall, a sheath gas outlet and an inlet welded on the tube wall, and high temperature resistant sealing gaskets at both ends of the second metal tube; The circulating sheath gas channel is an air path formed by drilling holes in the wall of a metal tube, and a circulating sheath gas loop is formed by drilling four through holes in the wall of the metal tube and digging grooves at both ends of the metal tube to connect the through holes; The sheath gas outlet of the high temperature dilution device is perpendicular to the sample gas inlet.

2. A thermal diffusion tube device for removing volatile substances from motor vehicle exhaust according to claim 1, characterized in that: The sheath gas that flows back to the high-temperature dilution device from the adsorption tube through the bent copper tube is heated again and mixed with the sample gas. A cylindrical baffle is used for the sheath gas at the mixing point.

3. A thermal diffusion tube device for removing volatile substances from motor vehicle exhaust according to claim 1, characterized in that: The bent copper tube inserted into the adsorption tube is connected to the circulating sheath gas loop in the high-temperature dilution tube by a metal ferrule. The outlet of the circulating sheath gas loop is screwed into the metal ferrule by an internal thread, and the inlet of the bent copper tube is sealed and connected by a metal ferrule.

4. A thermal diffusion tube device for removing volatile substances from motor vehicle exhaust according to claim 1, characterized in that: One end of the metal pipe is connected to the flange and sealed with a graphite gasket, and fixed by screwing two No. 3 screws into the side of the flange; The left side of the adsorption tube body is connected to the flange plate 2 and sealed with a graphite gasket. Two No. 3 screws are screwed into the side of the flange plate 2 to fix it; The flange connected to one end of the metal tube and the flange connected to the inlet side of the adsorption tube are sealed between the two flanges using a graphite gasket, and then the two flanges are clamped and fixed using a circular clamp.

5. A thermal diffusion tube device for removing volatile substances from motor vehicle exhaust according to claim 1, characterized in that: The metal tubes of the high-temperature dilution device and the cooling dilution device are both made of stainless steel, and the gasket used for end face sealing in the high-temperature dilution device is made of graphite.

6. A thermal diffusion tube device for removing volatile substances from motor vehicle exhaust according to claim 1, characterized in that: Both ends of the steel mesh are fixed by the inlet and outlet ferrules of the adsorption tube.

7. A thermal diffusion tube device for removing volatile substances from motor vehicle exhaust according to claim 1, characterized in that: The outlet of the adsorption tube and the outlet of the cooling and dilution device adopt metal ferrule tees for placing thermocouples or PT100 temperature measuring devices.

8. A method for removing volatile substances from motor vehicle exhaust, using the thermal diffusion tube device for removing volatile substances from motor vehicle exhaust according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: (1) The exhaust gas from the motor vehicle is collected through the sampling tube and enters the high-temperature dilution device, where it is mixed with the heated high-temperature sheath gas in the high-temperature dilution device at the inlet; (2) After mixing with the high-temperature sheath gas, the gas at the end of the sampling tube is split according to the set flow rates of the sheath gas and the sample gas, and the part that enters the adsorption device is the diluted sample gas; (3) The diluted sample gas diverted into the sheath gas loop at the end of the high-temperature dilution device passes through the cooling copper tube, filter, dehumidifier, filter, air pump, filter, and then enters the sampling tube again to mix with the sampled tail gas; (4) The high-temperature dilution device and the adsorption device are connected and sealed with flanges. The sheath gas loop of the high-temperature dilution tube is extended to the adsorption material layer of the adsorption tube by bending the copper tube, so that the sample gas at the outlet of the high-temperature dilution tube is slowly cooled in the adsorption tube to prevent the evaporated volatile or semi-volatile substances from condensing and re-nucleating or adsorbing on the surface of the particles; (5) The diluted sample gas passes through the adsorption device. Due to high temperature heating, the volatile or semi-volatile substances evaporate into gaseous state, diffuse to the wall of the adsorption device and are adsorbed by the activated carbon; (6) After the diluted sample gas passes through the adsorption device, it enters the cooling and dilution device to cool the diluted sample gas to the measurement temperature required by the back-end detection device.

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