JP2006250661A - Evaluation device and evaluation method for ceramic honeycomb filter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaluation device and an evaluation method for a ceramic honeycomb filter for directly evaluating the filter as a whole without necessitating cutting off a partial sample for measurement from a specimen filter, and rapidly measuring the collection performance of the specimen filter by a simple structure without necessitating any expensive and large-scale installation. <P>SOLUTION: This valuation device 1 for a ceramic honeycomb filter, used for measuring the collection performance of the specimen filter 10a by letting test gas containing test particulates of a grain size equal to or more than a prescribed grain size run through the specimen filter 10, is equipped with a dusty-gas generator 3 for generating a material gas containing particulates, an electric dust collector 4 for obtaining the test gas containing the test particulates by eliminating particulates of a grain size less than the prescribed grain size among the above particulates from the material gas, and a concentration meter 5 for measuring the concentration of grains in the test gas. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an evaluation apparatus and an evaluation method for a ceramic honeycomb filter for evaluating the particle collection characteristics of the ceramic honeycomb filter.

  A ceramic honeycomb filter is described in Patent Document 1. Since such a ceramic honeycomb filter is particularly excellent in heat resistance, it is used as a DPF (diesel particulate filter) for purifying exhaust gas from a vehicle. When evaluating the collection efficiency of such a ceramic honeycomb filter (hereinafter abbreviated as a filter), the diesel engine is actually operated and the actual exhaust gas is used for evaluation. An evaluation apparatus using this diesel engine is shown below.

FIG. 4 is a schematic view of a conventional ceramic honeycomb filter evaluation apparatus.
As shown in the figure, a conventional ceramic honeycomb filter evaluation apparatus 51 includes a diesel engine 52, valves 53 and 54, and a particle sensor 55. When evaluating the DUT filter 56 made of a ceramic honeycomb filter, first, the DUT filter 56 is set in the evaluation device 51. Next, the diesel engine 52 is operated to generate exhaust gas. The switching device 57 switches the flow paths of the valves 53 and 54 (in the direction of arrow A in the figure) to bypass the exhaust gas to the evaluated filter 56. In this state, the exhaust gas is passed through a diluter 58 to dilute the exhaust gas, and the particle sensor 55 measures the concentration of particles in the exhaust gas. Next, the flow paths of the valves 53 and 54 are switched by a switch 57 to allow exhaust gas from the diesel engine 52 to pass through the filter under test 56 (in the direction of arrow B in the figure). Exhaust gas that has passed through the DUT filter 56 is diluted by a diluter 58, and its concentration is measured by a particle sensor 55. The exhaust gas after the measurement is exhausted as indicated by arrow D both by-pass and through the evaluated filter. The concentration measured in this way is compared, and it is evaluated how much particles have been collected by the exhaust gas that has passed through the filter under test 56 compared to the exhaust gas that has not passed.

  However, since such an evaluation apparatus 51 uses an actual diesel engine 52, it is difficult to adjust the exhaust gas concentration to be constant. In addition, the equipment is large and installation space is required. Since harmful exhaust gas is used, it is necessary to pay close attention to the test such as exhaust exhaustion, etc., and so that the exhaust gas is also called “black smoke”, so that the device under test filter and the evaluation device can be soaked in black. The cleanup is also difficult.

  On the other hand, in order to indirectly evaluate the collection efficiency of the filter, a mercury porosimeter (mercury intrusion) method may be used for the pore size distribution of the filter. This is an application of the phenomenon in which liquid mercury infiltrates in order from a large pore as pressure increases, and is widely used as a general-purpose method for measuring pore size distribution. However, this measurement method requires that the sample size used for the measurement is about 2 to 3 mm, and the sample must be taken out by scraping it from the device under test, and the filter product itself is used as the device under test. I can't. Further, since the obtained information is small in sample size, it is limited to local information, and it is impossible to know the collection efficiency of the filter under test as a whole. Also, this method takes a long time and cannot be evaluated quickly.

JP 2004-154647 A

  The present invention enables direct evaluation of the entire filter without the need to cut out a local sample for measurement from the filter under test, and does not require expensive and large-scale equipment. An object of the present invention is to provide an evaluation device and an evaluation method for a ceramic honeycomb filter that can quickly measure the collection efficiency of a filter under test with the configuration.

  In order to achieve the above object, according to the first aspect of the present invention, a test gas containing test fine particles having a particle size equal to or larger than a predetermined particle size is passed through the filter under test, and the collection ability of the filter under test is measured. An evaluation apparatus for a ceramic honeycomb filter, wherein a dust-containing gas generator that generates a raw material gas containing fine particles, and fine particles having a particle size smaller than a predetermined particle size in the fine particles are removed from the raw material gas and the test is performed. There is provided an evaluation apparatus for a ceramic honeycomb filter, comprising: an electrostatic precipitator that uses a test gas containing fine particles; and a densitometer that measures a particle concentration in the test gas.

  According to a second aspect of the present invention, the ceramic honeycomb filter evaluation apparatus according to the first aspect is used, the particle concentration of the test gas containing the test fine particles before passing through the filter under test, and the filter under test. There is provided a ceramic honeycomb filter evaluation method for evaluating the collection ability of the filter under test by comparing the particle concentration of a test gas containing the test fine particles later.

  According to a third aspect of the present invention, in the second aspect of the present invention, the predetermined particle size is controlled by changing an applied voltage of the electrostatic precipitator, and a particle size distribution of the test fine particles contained in the test gas is adjusted. Then, the filter is supplied to a filter to be tested, and the collection ability of the filter according to the particle size distribution is evaluated.

  According to the first aspect of the present invention, among the fine particles contained in the raw material gas generated from the dust-containing gas generator, fine particles having a particle size smaller than a predetermined particle size before passing through the filter under test are collected by the electrostatic precipitator. Since the test gas is removed from the raw material gas to obtain the test gas containing the test fine particles, the particle size of the test fine particles in the test gas passing through the filter under test can be adjusted. Therefore, it is possible to adjust the particle size distribution by adjusting the particle size of the test fine particles in the test gas to be circulated, and to evaluate the filter according to the particle size distribution. If a dust-containing gas generator using vaporization combustion or smoke such as incense is used as the dust-containing gas generator, the equipment does not become large and can be measured at low cost. Further, it is not necessary to cut out a sample for measurement from the filter under test and use it, and it can be set in the apparatus as it is, so that it is possible to work quickly and measure the collection ability of the filter under test as a whole.

  According to the invention of claim 2, among the fine particles generated from the dust-containing gas generator, for example, the fine particles having a particle diameter of less than a predetermined particle size are collected by the electric dust collector before passing through the filter under test. The particle size of the test fine particles that pass through the test specimen filter can be adjusted. Therefore, by comparing the test particle concentration with the test particle concentration after passing through the filter under test, the collection ability of the filter under test can be accurately measured.

  According to the invention of claim 3, the particle size distribution of the test fine particles in the test gas can be easily prepared by adjusting the applied voltage of the electrostatic precipitator. Therefore, by applying a predetermined voltage for a predetermined time, changing the voltage, and applying it for a predetermined time, it is possible to easily and reliably evaluate the filter collection ability according to the particle size distribution.

FIG. 1 is a schematic view of a ceramic honeycomb filter evaluation apparatus according to the present invention.
As shown in the figure, the ceramic honeycomb filter evaluation apparatus 1 according to the present invention basically forms a flow path indicated by an arrow passing through the filter under test 10, and allows a test gas containing test fine particles to flow through the flow path. Is. A filter 2, a dust-containing gas generator 3, an electrostatic precipitator 4, a concentration meter 5, valves 13 and 14, a flow velocity measuring device 9, and a suction fan 6 are provided along the flow path. The electric dust collector 4 is voltage-controlled by a dust collector controller 7 and connected to a personal computer 8 together with a concentration meter 5. The gas in the apparatus 1 is circulated in the apparatus 1 in the direction of the arrow by the suction fan 6. A flow rate measuring device 9 is provided in the gas flow path. The flow velocity measuring device 9 measures the pressure before and after the orifice provided in the flow path and calculates the flow velocity. In the middle of the flow path, the DUT filter 10 to be evaluated by measuring the collection ability is set. At this time, both end faces of the filter under test 10 are held so as not to cover the end faces as much as possible so as not to cause a pressure drop, and a crimping type holder that can be easily attached and detached so as not to leak gas from the end faces is used. Fixed. In this way, since the entire DUT filter 10 can be set and measured as it is in the apparatus 1, the collection ability of the DUT filter 10 as a whole can be measured. Valves 13 and 14 such as three-way valves are provided before and after the device under test filter 10 and branch into a flow path that passes through the device filter 10 and a bypass flow path (B in the figure) that does not pass through the device filter 10. The filter 2 is provided at the inlet of the flow path and prevents inflow of impurities into the flow path.

  The flow path has a portion communicating with the densitometer 5, and the concentration of particles in the gas flowing in the flow path is measured. If the density meter 5 is sensitive enough to measure changes before and after the filter under test 10, the FSN measures dust concentration by attaching dust to a reflection type, transmission type, or a specified filter, and applying light to the attached filter. Any (filter smoke number) meter may be used. When the concentration is small, measurement may be performed using a cascade impactor or an electronic low-pressure impactor.

  In place of the configuration in which the bypass flow path B shown in the figure is provided, a communication position is provided by providing concentration meters before and after the filter under test 10, or by connecting one concentration meter before and after the filter 10 under test. By switching the above, it is possible to measure the concentration before and after the filter under test. Even with such a configuration, the particle concentration that does not pass through the filter 10 and the particle concentration that passes through the filter 10 can be measured, and the filter ability can be evaluated by comparing these. In the case of this configuration, the bypass flow path B is not necessary.

  A raw material gas containing fine particles is generated from the dust-containing gas generator 3. The fine particle concentration in the raw material gas is adjusted by, for example, providing an optical dust sensor on the outlet side of the dust-containing gas generator 3 and supplying the raw material gas having a constant concentration while monitoring the fine particle concentration. The fine particle concentration may be adjusted only by the electric dust collector 4 without providing such a dust sensor. The raw material gas containing fine particles is, for example, incense smoke, and the incense may be a test incense for a fire detector in addition to a normal incense. Because mosquito coils are strong in fat, ordinary incense is preferable. This source gas is supplied from the dust-containing gas generator 3 to the flow path in the apparatus 1. The gas concentration is controlled while monitoring the gas concentration with an optical switch or an optical dust meter that can set an analog level. When the incense smoke is used, the smoke concentration is insufficient and the concentration becomes unstable. Therefore, the incense smoke is preferably supplied from a smoke box (not shown) maintained at a predetermined concentration. As a result, the smoke box becomes a buffer, and smoke having a predetermined concentration is sucked into the flow path. Thus, if the source gas containing fine particles is incense smoke, the filter efficiency of the filter under test 10 can be measured with simple equipment at low cost. As the dust-containing gas generator 3, a dust-containing gas generator using vaporization combustion or a soot generator for a diesel engine may be used.

  The electric dust collector 4 includes an ionization unit and a dust collection unit (not shown). The ionization part is composed of an umbrella-shaped electrode of about 20 to 30 mm and a grid parallel electrode, and a high voltage of about 10 kV direct current is applied to the electrode. As a result, a corona discharge is generated from the positive electrode to the negative electrode, air molecules are charged positively and negatively, and the negative ions generated by the ions are absorbed by the ionization line, but the positive ions fill the parallel electrodes and pass between them. Dust is positively charged. The dust collecting part is composed of a positive electrode charged to about DC 5 kV and a grounded electrode, and the positively charged dust is adsorbed to the negative electrode when entering the dust collecting part. The maximum particle size of the dust particles to be adsorbed is determined according to the applied voltage. That is, fine particles having a particle size or less corresponding to the voltage are collected, and fine particles larger than that are passed.

  The personal computer 8 receives the control signal from the dust collector controller 7 of the electric dust collector, the concentration data from the densitometer 5, the flow velocity and temperature in the flow path, etc., and the evaluation calculation of the filter 10 to be tested is performed. Done.

FIG. 2 is an explanatory diagram of the relationship between the particle size distribution of fine particles in the raw material gas generated from the dust-containing gas generator and the control voltage of the electrostatic precipitator.
(A) is a graph which shows the concept of the particle size distribution of the fine particles in the raw material gas which generate | occur | produces from the dust containing gas generator 3. FIG. The graph shows an example of incense smoke as a source gas, the horizontal axis is the particle size (μm), and the vertical axis is the number of particles. From this graph, it can be seen that the largest number of particles having a particle size of around 1.0 μm are contained. When a raw material gas containing fine particles having this particle size distribution is supplied from a dust-containing gas generator, when a predetermined voltage is applied to the electrostatic precipitator, fine particles having a particle diameter less than the predetermined particle size are collected (one point in the figure). X region on the left side of the chain line). Therefore, the test fine particles in the test gas flowing through the flow path through the electrostatic precipitator 4 are fine particles having a larger particle size (Y region on the right side of the dashed line in the figure). When the voltage is increased, the position of the alternate long and short dash line moves to the right.

  (B) is a graph which shows the relationship between the control voltage (applied voltage) of an electrostatic precipitator, and the particle concentration by a densitometer. As the graph shows, the densitometer output (particle concentration) decreases according to the applied voltage. That is, when the applied voltage of the electrostatic precipitator 4 increases, the Y region decreases and the fine particles collected by the electrostatic precipitator increase. Therefore, the test fine particles that pass through the electrostatic precipitator 4 decrease and the densitometer Output decreases.

(C) is a graph which shows the relationship between time and particulate concentration when the control voltage of an electrostatic precipitator is changed. Assume that the voltage of the electrostatic precipitator 4 is increased as V ₁ <V ₂ . In this case, since the reduced particulate collection amount by the filter as shown by (B), a concentration meter output (particle concentration) it can be seen that decreases towards V ₂ than V _1. (D) is a graph when the voltage of the electrostatic precipitator 4 is further increased as V ₁ <V ₂ <V ₃ , and as in (C), when the voltage is increased (V ₃ ), particulate collection by the filter is performed. It can be seen that the collected amount further decreases and the densitometer output further decreases.

FIG. 3 is a flowchart of a method for evaluating a ceramic honeycomb filter according to the present invention.
Step S1
A device under test filter 10 whose filter capability is to be evaluated is set in the evaluation apparatus 1.
Step S2
The flow paths are switched by the valves 13 and 14 so that the gas in the apparatus passes through the bypass flow path B. Thereby, since the gas in the apparatus does not pass through the DUT filter 10, the concentration of fine particles that do not pass through the filter 10 can be measured by the densitometer 5.
Step S3
Gas (air) is circulated through the flow path in the apparatus 1. The gas is exhausted through the apparatus through the filter 2 when the suction fan 6 is operated. Diameter 144 mm, if the length 152mm in (2.54 ^{cm) 2} per 200 cells of the filter, the flow rate of the gas is about 20 liters / min.

Step S4
A raw material gas (for example, incense smoke) is supplied to the flow path of the evaluation apparatus 1. The source gas is generated from the dust-containing gas generator 3.
Step S5
Fine particles having a predetermined particle diameter or less are collected by the electric dust collector 4 to adjust the particle size distribution and fine particle concentration. The collection is performed by adjusting the applied voltage. Fine particles having a particle size less than that corresponding to the voltage are collected, and larger test fine particles pass through the electric dust collector 4 and flow through the bypass channel B.
Step S6
The fine particle concentration is measured by the densitometer 5. The gas concentration measured here is a fine particle concentration that does not pass through the DUT filter 10 because the flow path is switched to the bypass flow path B.

Step S7
The flow path is switched by the valves 13 and 14 so that the gas in the apparatus passes through the filter under test 10. Thereby, since the gas in the apparatus passes through the test specimen filter 10, the concentration of fine particles passing through the filter 10 can be measured by the densitometer 5.
Step S8
The source gas is supplied to the flow path by the dust-containing gas generator 3 under the same conditions as in step S4. This may be continued while supplying the source gas in step S4.
Step S9
Fine particles are collected using the electric dust collector 4 under the same conditions as in step S5. At this time, by changing the applied voltage of the electrostatic precipitator, the particle size distribution of the fine particles in the raw material gas supplied to the filter to be tested is changed to supply a plurality of types of test gases having different particle size distributions.
Step S10
The fine particle concentration is measured by the densitometer 5. The concentration measured here is the fine particle concentration that has passed through the DUT filter 10. In this case, the concentration is measured for each gas whose particle size distribution is changed by adjusting the applied voltage of the electrostatic precipitator. Thereby, the collection ability of the DUT filter according to the particle size distribution of the test gas containing the test fine particles can be evaluated.

Step S11
Using a personal computer, the measured value of the fine particle concentration passed through the filter 10 obtained in step S6 and step S10 through the filter 10 is compared. Thereafter, the collection ability of the filter under test is analyzed by calculation or the like, and the filter characteristics are evaluated. In this method, the concentration of fine particles generated under the same conditions is compared with the concentration of fine particles that do not pass through the filter under test, so that the collection ability of the filter under test can be accurately measured. In the above-described method, the fine particle concentration of the gas passing through the bypass channel B is measured first, but the fine particle concentration of the gas passing through the filter 10 may be measured first.

  The present invention can be applied to a ceramic honeycomb filter.

1 is a schematic view of a ceramic honeycomb filter evaluation apparatus according to the present invention. Explanatory diagram of the relationship between the particle size distribution of fine particles in the raw material gas generated from the dust-containing gas generator and the control voltage of the electrostatic precipitator The flowchart of the evaluation method of the ceramic honeycomb filter which concerns on this invention. Schematic of a conventional ceramic honeycomb filter evaluation apparatus.

Explanation of symbols

1: Evaluation device for ceramic honeycomb filter, 2: filter, 3: dust-containing gas generator, 4: electric dust collector, 5: concentration meter, 6: suction fan, 7: dust collector controller, 8: personal computer, 9: Flow velocity measuring device, 10: filter under test, 13, 14: valve.

Claims (3)

An evaluation apparatus for a ceramic honeycomb filter for measuring a collecting ability of a test sample filter by passing a test gas containing test fine particles having a particle size equal to or larger than a predetermined particle size through the test sample filter,
A dust-containing gas generator for generating a raw material gas containing fine particles;
An electrostatic precipitator that removes fine particles having a particle size less than a predetermined particle size from the raw material gas to form a test gas containing the test fine particles;
An evaluation apparatus for a ceramic honeycomb filter, comprising: a concentration meter that measures a particle concentration in the test gas.   The apparatus for evaluating a ceramic honeycomb filter according to claim 1, wherein the test gas particle concentration including the test fine particles before passing through the filter under test and the test fine particles after passing through the filter under test are included. A method for evaluating a ceramic honeycomb filter, wherein the collection ability of the filter under test is evaluated by comparing the particle concentration of a test gas. The predetermined particle size is controlled by changing the applied voltage of the electrostatic precipitator, the particle size distribution of the test fine particles contained in the test gas is adjusted, and the particle size distribution is supplied to the filter to be tested. The method for evaluating a ceramic honeycomb filter according to claim 2, wherein the collecting ability of the filter according to the condition is evaluated.

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