JP3494952B2 - PM sampling measurement device using metal mesh filter and voltage application - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to measurement of fine particles in combustion air such as fine particles in ambient air and diesel exhaust gas, and is used in the field of environmental technology.

[0002]

2. Description of the Related Art Fibrous filter papers such as glass fibers coated with Teflon (registered trademark) have generally been used for sampling fine particles such as ambient air and diesel exhaust gas.

[0003]

[Problems of the prior art] In the conventional filter, the collection of fine particles having a particle size of about 0.05 μm (50 nm) or less, which is important as the number concentration, is inefficient, and it is sufficient to cope with the number concentration which has become a problem recently. You are in a situation where you cannot. Moreover, there is a defect that the filter cannot be reused.

[0004]

The combustion exhaust gas such as diesel exhaust gas contains a lot of particles of about 0.05 μm or less, which efficiently collects fine particles which are difficult to sample in terms of fluidity, and the measurement time. The main problem is to know the change in the internal concentration, and it is also an important problem to make it possible to use the filter repeatedly.

[0005]

Means for Solving the Problems In order to efficiently collect particles of about 0.05 μm or less, charge is used for the motion of particles in the flow of a sample gas having a small Reynolds number, that is, a relatively slow flow velocity to conduct electricity. Adopted a method of attaching to a filter having properties. In order to measure the change in particle concentration, a method of continuously measuring the pressure before and after the filter at a constant flow rate was selected. Furthermore, the filter material has corrosion resistance,
A means that can recycle the filter by washing was used by using a metal mesh having a relatively simple structure and less problem in strength. In particular, in order to increase the collection amount of fine particles, a thinner metal wire fiber was used to increase the surface area. Further, in order to appropriately increase the pressure before and after the filter due to the adhesion of fine particles to facilitate the measurement and improve the sensitivity, a means for using a filter such as a normal glass fiber filter paper on the downstream side of the metal mesh filter. Also made possible.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1, 2, 3, 4, 5, and 6. In the configuration example of the measuring apparatus 1 of FIG. 1, the sample gas 11 of the combustion exhaust gas containing fine particles is guided to the measurement collecting unit 10 via the sampling path 12 whose temperature is kept constant and whose temperature is measured by the thermometer 17. . In the measurement collecting unit 10, a metal material having a high corrosion resistance as shown in FIG.
A collecting filter 100 (hereinafter, simply referred to as a collecting filter 100 for collecting fine particles using a single layer or a plurality of layers of a wire net formed by braiding a fine wire having a wire diameter of m or less at a high density of 200 mesh or more
"Filter 100") is configured and used. The edge of the peripheral portion 105 of the filter 100 is formed by fusing with a laser, an electron beam, or the like to prevent the fine wire at the edge from coming off and to secure the accuracy of the outer peripheral dimension. The filter 100 is used by holding the peripheral portion 105 thereof airtight by using a heat resistant O-ring 106 or the like. The filter 100 is arranged in the insulating filter holder 7 and has a structure that can be easily attached / detached and allows the weight to be precisely measured before and after the measurement.
The wire mesh may be used as a single layer in the filter 100, but it is often used in a plurality of layers in consideration of the direction of the thin wire. In the measuring and collecting unit 10, a conduit 14 and a conduit 15 for measuring the pressure P1 on the upstream side and the pressure P2 on the downstream side of the filter 100 are arranged, and the filter 100 is electrically insulated, so that the high voltage power source (negative) 2, A high voltage is applied by a high-voltage contact terminal 16 from a circuit having a high-voltage power source (positive) 3, a voltmeter 4, a voltmeter 5, and a high-voltage cable 6. Filter 1
On the upstream side of 00, keep an appropriate distance from the filter 100,
An appropriately shaped needle electrode 50 is arranged. The sample gas 11 that has passed through the filter 100 passes through the protective filter 21 and is sucked by the pump 23 and discharged from the discharge pipe 24 while the mass flow controller 22 controls the mass flow rate to be constant. The particles contained in the sample gas 11 are charged in the vicinity of the needle electrode 50 due to the abrupt change in the electric field strength, and become charged particles. For example, a negative voltage of about −2 kV is applied to the needle electrode 50, and the filter 100 has a +1.
A positive voltage of about 5 kV is applied. Inside the measurement and collection unit 10, except for the filter 100 and the needle electrode 50, the potential is kept at 0,
An insulating member 55 for preventing discharge is arranged on the outer periphery of the needle electrode 50. With a slight electric current flowing between the needle electrode 50 and the filter 100, the fine particles flow in a charged state. Some of these particles are large particles 31
The metal wire 10 that constitutes the first-layer flow passage 110 of the filter 100 as shown in the enlarged view of FIG.
Although many particles 32 are trapped between the metal wire 1 and the metal wire 102, many of the particles 32 are affected by the slow flow velocity and the electric charge of the particles, and attach to each part of the surface of the metal wire of the filter 100 by an electric attractive force.
In particular, particles of 0.1 μm or less are more efficiently collected because the influence of electric force is larger than that of fluid force. The particles adhering to the metal wires 101 and 102 of the first layer and the metal wires 103 and 104 of the second layer of the filter 100 successively narrow the channel 110 of the filter, and the resistance of the filter 100 at a constant flow rate, that is, the differential pressure ΔP = ( P1-P2) is increased as in the example of FIG. In the example of FIG. 3, the sample gas has a constant concentration c of fine particles, and the time axis of the horizontal axis corresponds to the mass of the collected fine particles. As for the relationship between the mass of the collected fine particles and ΔP, a constant linear relationship is established within the range below a certain collection amount as in the example of FIG. 3, and the collection amount can be easily obtained from the differential pressure ΔP. . In this way, since the time differential value of the differential pressure is proportional to the concentration of fine particles,
It is possible to continuously measure the change in the particle concentration within the measurement time in real time.

A pressure sensor 8 connected to a conduit 14 and a conduit 15 is used to measure the differential pressure, and the measured value is calculated by a data processing computer 9 to obtain the particle concentration and the like.

[0008] With a metal mesh filter, it may be difficult to measure the amount of fine particles that can be collected with high measurement accuracy due to the limited surface area. In the example of FIG. 4, as a means for remarkably increasing the surface area of the filter, an extremely thin stainless wire is used as a fiber 110 to form a non-woven fabric 111, and two metal meshes 101 ', 102' and 103 ', 1
The structure of the filter sandwiched between 04 'and 04' is shown. In this case, the filter has a large thickness, and the amount of collected fine particles can be increased.

The example shown in FIG. 5 is a metal mesh filter 101 '.
A glass fiber filter 112 is provided on the downstream side of ′ and 102 ″.
The following shows an example of using and overlapping. In this case, fine particles adhere to the metal mesh due to the effect of charging, and particles having a slightly larger diameter mainly adhere to the glass fiber filter paper due to agglomeration or the like, and mainly control the pressure increase by the entire filter. Then, the ratio of the fine particles collected in the metal mesh can be appropriately selected by appropriately selecting the voltage applied to the electrode and the metal mesh.

The temperature Ts of the measuring and collecting unit 10 is measured by the thermometer 2b and controlled by an external heater 25 or the like. By keeping the temperature Ts at a high temperature of 200 ° C. or higher, even the fine particles have a high boiling point. It is also possible to collect only the components, which has the potential for simple component analysis. The temperature of the filter 100 is an important factor related to adsorption / desorption of fine particles to / from the filter.

FIG. 6 shows the same sampling probe 6 from a dilution tunnel 60 for diesel exhaust gas.
1, the measuring device 1 and the measuring device 1 ′ are arranged in parallel, and the temperature of the measurement collecting unit 10 including the temperature of the filter is set to be different in each measuring device, and the fine particle component depending on the temperature It is an example which shows the composition of the device which tries to obtain information. For example, if the measuring unit temperature of one measuring device 1 is set to 35
Set the temperature to ℃ and set the temperature of the measuring part of the other measuring device 1'to 250 ℃.
Then, it becomes possible to easily measure the amount and ratio of the low boiling point component contained in the fine particles.

The filter 100 which has collected the fine particles is removed from the measuring and collecting section, weighed, and an actual measured value of the collected amount within the measuring time, that is, the average fine particle concentration is obtained by comparison with the measured weight before collecting. To be Further, the collected fine particles can be extracted with an appropriate solvent or the like and used for analysis or the like. Further, the filter 100 can completely remove the fine particles collected by using an appropriate detergent or washing machine, and can be reused.

[0013]

In the PM sampling device according to the present invention, fine particles such as ambient air and diesel exhaust gas are efficiently captured by the corrosion-resistant metal mesh filter including extremely fine particles of 0.01 μm or less. Also, it is possible to know the change in the particle concentration during the measurement time by measuring the differential pressure before and after the filter. The filter can be reused and can be said to be an advantageous device in terms of environmental load reduction and cost.

[0014]

[Brief description of drawings]

FIG. 1 is a structural explanatory view showing a PM sampling device according to the present invention.

FIG. 2A is an explanatory view showing a structural example of a metal mesh filter used in the present invention. FIG. 2B is an enlarged view of the structure of a metal mesh filter used in the present invention and adhesion of fine particles.

FIG. 3 is a graph showing a measurement example of the relationship between the differential pressure before and after the filter and the amount of collected fine particles according to the present invention.

FIG. 4 is a structural explanatory view showing another metal mesh filter.

FIG. 5 is a structural explanatory view showing a metal mesh filter incorporating a filter paper.

FIG. 6 is a structural explanatory view showing a PM sampling device according to another embodiment of the present invention.

[Explanation of symbols]

1 Measuring device 2 High voltage power supply (negative) 3 High voltage power supply (positive) 4 voltmeter 5 ammeter 6 high voltage cable 7 Insulation filter holder 8 Pressure sensor 9 computers 10 Measurement collection unit 11 sample gas 12 sampling paths 14 conduits 15 conduits 16 High voltage contact terminal 17 Thermometer 21 Protective filter 22 Mass flow controller 23 pumps 24 discharge pipe 25 External heater 26 Thermometer 30 particles 31 Part of large particles 32 many particles 50 needle electrodes 60 Dilution Tunnel 61 Sampling probe 100 filters 101 metal wire 102 metal wire 103 metal wire 104 metal wire 105 peripheral area 106 Heat resistant O-ring 110 channel 111 Non-woven fabric 111 101 'metal mesh 102 'metal mesh 103 'metal mesh 104 'metal mesh 112 glass fiber filter paper

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI B03C 3/47 B03C 3/14 A (72) Inventor Hidetoshi Urakawa 1-19-4 Tamazutsumi, Setagaya-ku, Tokyo JIJI Kennai (72) Inventor Keizo Saito 1-2, Namiki, Tsukuba-shi, Ibaraki Institute of Mechanical Engineering, Institute of Industrial Technology (72) Inventor Osamu Shinozaki 1-2-2 Namiki, Tsukuba, Ibaraki Institute of Mechanical Engineering (72) ) Inventor Akifumi Seto, 1-2, Namiki, Tsukuba, Ibaraki, Institute of Mechanical Engineering, Institute of Industrial Technology (56) Reference JP-A-11-230888 (JP, A) JP-A-62-5626 (JP, A) Special Kaihei 9-294940 (JP, A) JP-A-8-33856 (JP, A) JP-A-5-117837 (JP, A) JP-A-11-142301 (JP, A) JP-B-5-11899 ( JP, B2) Special public 59-10046 (JP, B2) Japanese Patent Publication 6-21546 (JP, B2) Shigeru Yanagihara, Hidetoshi Urakawa, Tsunemichi Kaba, Nakahiro Uesaka, Osamu Shinozaki, Keiko Saito, Keizo Saito, "1 Nickel of diesel exhaust particulate matter" Sampling with a plate filter ”, Preprints of the Automotive Engineering Conference, Japan, Japan Society of Automotive Engineers, May 19, 1999, No. 1-99, p. 1-4 Shigeru Yanagihara, Michio Okada, Kazuyuki Naruzawa, "Measurement of Diesel Exhaust Particulate Matter Using CO 2 Conversion," Preprints for Academic Conferences of the Society of Automotive Engineers of Japan, Japan Society of Automotive Engineers, April 1994. 20th, 943, p. 113-116 (58) Fields surveyed (Int.Cl. ⁷ , DB name) G01N 1/00-1/44 B03C 3/00-3/88 G01N 5/00-5/04 G01N 15/00-15 / 14 JISST file (JOIS)

Claims (6)

(57) [Claims] 1. A metal mesh filter using a single layer or a plurality of layers of a wire mesh made of a metal material having strength, heat resistance and corrosion resistance, which is braided at a density of 200 mesh or more using a fine wire having a wire diameter of 50 μm or less. In a device for sampling and measuring PM (particulates) by configuring a conductive collecting filter made of, which is arranged in the flow path of the sample gas in the sample collecting section, a needle-like filter is provided upstream of the collecting filter. A single electrode or a plurality of electrodes are arranged, a voltage is applied, a reverse voltage is applied to the collection filter, and fine particles containing fine particles having a particle size of 0.1 μm or less are sampled by the collection filter to measure the mass. At the same time, while continuously sampling the particles under the condition of maintaining a constant flow rate and a constant temperature, the pressure before and after the collection filter is continuously measured to detect the change in the particle concentration during the sampling process. PM sampling measurement apparatus utilizing metal mesh filter and a voltage application possible. 2. The PM sampling apparatus according to claim 1, wherein a plurality of metal mesh filter metal meshes are used, and between the metal mesh layers, metal fibers having a wire diameter of 10 μm or less and having heat resistance and corrosion resistance are used as a non-woven fabric. Conditions for maintaining a constant flow rate and a constant temperature while sampling the fine particles containing fine particles having a particle diameter of 0.1 μm or less by the collecting filter to determine the mass. A PM sampling measuring device using a metal mesh filter and voltage application capable of continuously measuring the front-back pressure of a collecting filter while sampling fine particles and detecting a change in fine particle concentration during sampling. 3. The PM sampling apparatus according to claim 1, wherein one or more metal mesh filter wire meshes are used, and a non-conductive fiber filter made of non-conductive fiber such as non-conductive glass fiber is provided on the downstream side thereof. The filter for collection is constituted so that fine particles having a particle size of 0.1 μm or less are mainly collected by the metal mesh filter of the wire mesh, and the remaining fine particles are collected by the non-conductive fiber filter. A metal mesh filter capable of detecting the change in particle concentration during sampling by continuously measuring the front and rear pressures of the collection filter under the condition that a constant flow rate and a constant temperature are maintained while sampling and measuring the mass. PM sampling measurement device using voltage application. 4. In the PM sampling apparatus according to any one of the above 1, 2 and 3, the temperature condition is from room temperature to 2
Fine particles were sampled under the condition that a constant flow rate and a constant temperature were maintained so that the PM component could be analyzed from the change in the trapped amount due to the difference in temperature, so that it could be changed and set over the range of 00 ° C or higher. Meanwhile, a PM sampling measuring device using a metal mesh filter and voltage application capable of continuously measuring the front and rear pressures of the collecting filter to detect even a change in particle concentration during sampling. 5. The PM sampling device according to claim 3, wherein two or more sets of measuring devices are arranged in parallel, and the temperature conditions of the measuring and collecting section including the temperature conditions of each filter are set to different conditions, and continuous. The PM pressure component can be analyzed in real time of measurement, and the pressure before and after the filter is continuously measured while sampling fine particles under a constant flow rate and temperature condition by the two or more sets of measuring devices, and the sampling is in progress. PM sampling measurement device that uses a metal mesh filter and voltage application that can detect changes in the concentration of fine particles. 6. A stainless steel such as SUS 316, 304 is used as the metal material having heat resistance and corrosion resistance in the metal mesh filter according to any one of the above 1, 2, 3, 4 and 5. A PM sampling device using a characteristic metal mesh filter and voltage application.