JPH06190226A - Method of classifying particles in air flow and method for measuring concentration and particle size distribution of particles in air flow using same - Google Patents

Abstract

PURPOSE:To classify particles in air flow by simple equipment and a simple procedure and to measure the concentration and particle size distribution of particles in air flow. CONSTITUTION:The flow velocity ratio uo/ui of the flow velocity uo of a main flow in a main pipe where gas to be measured is transported to the flow velocity ui of a sucked flow taken in a measuring device is changed, allowing the particle diameter of particulate material collected from air flow to be variable. And the collection of particles in air flow is performed at the flow velocity ratios uo/ui for two or more different conditions. The true particle concentration Co in air flow at the flow velocity ratio=1 is obtained based on the correlation between the particle concentration Ci obtained from the quantity of the collected particulate material and the flow velocity ratios. Or the particle concentration ratio Ci/Co of the particle concentration Ci under each collection condition to the true particle concentration Co in the equal velocity suction is obtained an the particle size distribution in air flow is obtained from the slope of a straight line showing the proportional relationship of the particle concentration ratio Ci/Co to the flow velocity ratio uo/ui.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for classifying particles in an air stream and a method for measuring concentration and particle size distribution. More specifically, the present invention is a classification of the particulate matter in the air stream to be transported in a system for transporting the particulate matter in the air stream such as pulverized coal, combustion exhaust gas, ceramics and the semiconductor industry field. The present invention relates to a method and a method for measuring particle concentration and particle size distribution using the method.

[0002]

2. Description of the Related Art Conventionally, in measuring the concentration of particulate matter in an air stream, a condition (hereinafter referred to as "constant velocity suction") in which the flow velocity of the main flow is equal to the suction flow velocity of a sampling nozzle portion for measurement, This is done by weighing the weight M of the collected particulate matter and the flow rate V of the sucked gas and calculating the ratio M / V.

Further, the particle size distribution is measured by classifying the particles collected by constant velocity suction into several stages according to the particle size using a classifying device such as a cascade impactor or a cascade cyclone, and the amount of each classified particle. Is carried out by weighing.

[0004]

However, in the above-mentioned prior art, when collecting the particulate matter for measurement, it is necessary to always use the constant velocity suction condition in which the main flow velocity and the suction flow velocity are the same. If the suction flow velocity is slightly different from the main flow velocity, there is a problem that an accurate particle concentration and thus a particle size distribution cannot be obtained. Further, when the mainstream flow velocity constantly fluctuates, it is practically difficult to accurately follow the suction condition according to the fluctuation, and the measurement accuracy is reduced.

Further, in the particle size distribution, a complicated classifying device is required, it is difficult to handle, and it is difficult to perform quick measurement because it is necessary to weigh each classified and sampled particulate matter, and continuous measurement is performed. It also hinders the above.

It is an object of the present invention to provide a classification method which can easily classify particles in an air stream by a simple method.
Another object of the present invention is to provide a measuring method capable of obtaining the particle concentration and particle size distribution in an air stream by a simple method.

[0007]

To achieve the above object, the classification method of the present invention uses a main flow velocity u _o and a suction flow velocity u _i.
And the flow velocity ratio u _o / u _i is changed to make the particle diameter of the particulate matter collected from the air flow variable.

[0008] The measuring method of the air flow in the concentration of particles present invention, the flow rate ratio of the main flow velocity u _o and the suction flow rate u _i u _o / u _i
To change the particulate matter in the air flow to two or more different conditions,
Preferably, the sample is collected at a flow velocity ratio u _o / u _i of 3 or more conditions, and based on the correlation between the particle concentration C _i obtained from the amount of the collected particulate matter and the flow velocity ratio, The true particle concentration C _o is determined.

Further, according to the method of measuring the particle size distribution of particles in the air flow of the present invention, the flow rate ratio u _o of the main flow velocity u _o and the suction flow velocity u _i /
By changing u _i , the particulate matter in the air flow is sampled at different flow rate ratios u _o / u _i of 2 or more conditions, preferably 3 or more conditions, and the particle concentration C _{i is} obtained from the amount of the collected particulate matter. And the particle concentration ratio C _i / C _o with the true particle concentration C _o in the air flow obtained by the measuring method of claim 2, the particle concentration ratio C _i / C _o and the flow velocity ratio u _o / u _i The distribution of particle size in the air stream is obtained from the slope of the straight line representing the proportional relationship.

[0010]

When the suction flow velocity of the particulate matter in the air flow is different from the main flow velocity, that is, when the suction is not constant velocity suction, the amount collected by the suction nozzle is different, and the measured particle concentration deviates from the true value. In other words, the influence of the flow of the air flow varies depending on the size of the particle size, and those with a relatively small particle size are less likely to be affected by changes in the flow rate of the sampling amount, that is, particle concentration, but when the particle size is relatively large, the inertial force is It becomes large and is affected by changes in flow velocity.

Therefore, if the flow velocity ratio between the main flow velocity and the suction flow velocity is changed, there is a difference in the amount sucked by the suction nozzle between particles that are hardly affected by changes in the flow velocity and particles that are easily affected. Therefore, the size of the particles to be sucked differs depending on the flow velocity ratio, and the particles are classified during the suction.

Moreover, there is a correlation between the change in the flow velocity ratio between the main flow velocity and the suction flow velocity and the change in the sampling amount. When the relation between the flow velocity ratio at the time of measurement and the measured particle concentration is plotted, FIG.
It has a substantially linear proportional relationship as shown in. Therefore, the value of the particle concentration C _i at different flow velocity ratios u _o / u _i of two or more conditions is obtained, and from the straight line in FIG. 2 showing the correlation between the flow velocity ratio u _o / u _i at each measurement and the particle concentration, When the flow velocity ratio is 1, the true particle concentration C _o, that is, the particle concentration in the mainstream airflow is obtained.

The change in particle concentration when changing the flow velocity ratio to a value deviating from 1 is due to the effect of the change in flow velocity depending on the particle size. Contains. The change in the particle size distribution is shown as a slope of the correlation between the particle concentration ratio and the flow velocity ratio as shown in FIG. In other words, the influence of the change in the suction flow velocity under the main flow velocity on the amount of particulate matter collected is governed by the particle size distribution, and this appears as the slope of the proportional straight line between the particle concentration ratio and the flow velocity ratio. And the particle size distribution is calculated. For example, the particle concentration C _{i and the} particle concentration ratio C _i / C _o at each measured flow velocity ratio u _o / u _i are determined from the difference in the amount of particulate matter collected at different flow velocity ratios u _o / u _i of two or more conditions. , The particle concentration ratio C _i / C _o
And flow rate ratio uo The particle size distribution is obtained from the slope of the proportional relationship with / u _i .

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure of the present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 shows an example of a measuring apparatus for carrying out the measuring method of the present invention. This measuring device is for measuring the particulate matter contained in the flue gas. The measuring device 1 includes a mainstream pipe 8 for flowing an exhaust gas to be measured, a suction nozzle 2 for extracting a measured gas (exhaust gas) flowing in the mainstream pipe 8, and a filter 1 for collecting particulate matter.
Filter holder 3, which incorporates 0, drain pot 4,
It is composed of a gas meter 5, valves 6 and 9, a vacuum pump 7, and a velocity meter (not shown).

The suction nozzle 2 is for extracting a certain amount of the exhaust gas flowing in the main flow pipe 8 and guiding it to the filter holder 3. The suction nozzle 2 is opened in parallel with the flow of the exhaust gas in the main flow pipe 8. It is located in the center of 8. The filter holder 3 is a device for installing a filter for capturing particulate matter contained in exhaust gas. The filter is removably installed to weigh the collected particulate matter. The drain pot 4 is a device for collecting exhaust gas. The gas meter 5 is a device that measures the amount of exhaust gas sucked through the suction nozzle 2. Also, valves 6, 9
Is a device that controls the suction force of the suction nozzle 2 and the suction operation by the vacuum pump 7.

The flue gas, which is the object of measurement, has an inner diameter d.
mainstream pipe 8 middle of the _o being transported with a mainstream flow velocity u _o. For the measurement of the mainstream flow velocity u _o , for example, a Pitot tube, a hot-wire anemometer, or the like is used, although not shown. And
The collection of the particulate matter is performed by sucking the gas at a suction flow rate u _i from the suction nozzle 2 having the nozzle diameter d _c by the suction force of the vacuum pump 7. All the particulate matter is collected in the filter holder 3 having the particle collecting filter 10 built therein. Then, the collected particle amount M _i is obtained from the difference amount by weighing the filter weight before and after the suction.

The suction gas amount V _i is measured by the gas meter 5. The suction flow rate u _i is the suction gas amount V _i.
And suction time T _i and tip nozzle cross-sectional area S (S = π · d
_c ² ) and the relational expression u _i = V _i / (T _i · S). The particle concentration C _{i at} that time is the particle collection amount M _i.
And the suction gas amount V _i , the relational expression C _i = M _i / V _{i is} obtained.

In the measuring device constructed as described above, if the main flow velocity is kept constant and the suction flow velocity is different from the main flow velocity, the amount of particulate matter collected from the exhaust gas of the same flow will differ. In other words, the influence of the flow of the air flow varies depending on the size of the particle size, and those with a relatively small particle size are less likely to be affected by changes in the flow rate of the sampling amount, that is, particle concentration, but when the particle size is relatively large, the inertial force is It becomes large and is affected by changes in flow velocity.

Therefore, when the flow velocity ratio between the main flow velocity and the suction flow velocity is changed, the amount of particles sucked by the suction nozzle differs between the particles that are hardly affected by the change in the flow velocity and the particles that are easily affected. Therefore, the size of the particles to be sucked differs depending on the flow velocity ratio, and the particles are classified during the suction.

Moreover, there is a correlation between the change in the flow velocity ratio between the main flow velocity and the suction flow velocity and the change in the sampling amount. When the relation between the flow velocity ratio at the time of measurement and the measured particle concentration is plotted, FIG.
It has a substantially linear proportional relationship as shown in. Sampling is performed at six different suction flow rates u _{1 to} u ₆ , and the particle concentration measured at that time is C _{1 to} C ₆ , the ratio of the main suction flow velocity u _o / u _{1 to} u _o / u. _As shown in FIG. 2, ₆ always has a linear relationship with C _{1 to} C ₆ . By utilizing this relationship, it is possible to easily obtain the particle concentration C _o under the constant velocity suction condition in which the ratio of the main flow velocity and the suction flow velocity, which is the condition indicating the true particle concentration, is 1 from the graph of FIG. . Here, the measurement of the particle concentration in the air stream of this example was performed as shown in FIG.
Samples are collected at different flow rate ratios u ₀ / u _i at different points, but the present invention is not limited to this. In order to obtain the linear relationship between the particle concentration C _i and the flow velocity ratio u _o / u _i, it can be theoretically obtained by obtaining data on two or more points having different flow velocity ratios. If the plots of the above measured values measured at two or more points, more preferably the plots of three or more points are connected by a straight line and the value of the particle concentration C _i at the point where the flow velocity ratio u _o / u _i is 1 is read, that value is obtained. Is the value C _{o of the} particle concentration in the mainstream air stream.

Further, when the suction flow velocity ratio deviates from 1, the influence on the sampling amount depends on the particle size and the mainstream flow velocity. As shown in FIG. 3, the faster the particle size is large mainstream flow rate, measured particle concentration C _IDP is differs from the true particle concentration C _ODP. The deviation from the true particle concentration is the particle diameter D _p
Is given by the following Davies equation 1.

[0023]

[Equation 1] Here, P is called an inertial parameter, and is calculated by Equation 2.

[0024]

[Equation 2]

The coefficient C _m is given by equation (3).

[Equation 3]

Mainstream flow velocity u_o, Gas concentration, type is constant
The mathematical formula 1 is based on particle size and suction flow rate u_iWill only be a function. Measurement
Specified particle concentration C_iDpIs the particle size D_pParticles of suction flow
Speed u _iThe true particle concentration C
_oDpIs the particle size D_pIs the true particle concentration of the particles. Actual measurement
Target particle size is D_pNot only the particles of each
It is an aggregate of particles (particle group) and its particle size distribution
Is the logarithmic normal distribution of
Fits well.

[0027]

[Equation 4] Here, f (D _p ) in Expression 4 is a particle size distribution function, and indicates the ratio of particles having a particle size D _{p to} the entire particles.
The symbol D _P50 is the average particle size, and σ _g is the geometric standard deviation. If this D _P50 and σ _g are determined, the particle size distribution is uniquely determined. When the true particle density of the entire particles to be measured and C _o, particles having a particle diameter D _p therein C _o · f
Only (D _p ) is included, and naturally _{Co Dp in} Equation 1 is _included.
Will be the same as Therefore, Equation 1 can be rewritten as follows.

[0028]

[Equation 5] Since the mathematical formula 5 shows the measured concentration of only the particles having the particle diameter D _p , the measured concentration C _{i of the} entire particle group is the mathematical formula 5.
Can be obtained by integrating with respect to the particle size.

[0029]

[Equation 6] Formula 6 can be expressed by the ratio of the true particle concentration and the measured concentration of the entire particle group as in the following formula.

[0030]

[Equation 7]

Further, the results measured by experiment, as shown in FIG. 2, since the concentration C _i is a linear function type with respect to u _o / u _i, relation C _i / C ₀ and u _o / u _i 1 as shown in Figure 4
It has the following function form and can be expressed by the following equation.

[0032]

[Equation 8] Comparing Equation 7 and Equation 8, the following Equation 9 and Equation 1
0 holds.

[0033]

[Equation 9]

[Equation 10]

Since A and B are obtained from FIG. 4 which is an experimental result, the unknowns in the equations 9 and 10 are f (D _p ).
Only D _P50 and σ _g included in the above are solved, and by solving the above two equations simultaneously, the particle size distribution of the particle group to be measured can be obtained.

FIG. 5 shows the particle size distribution thus obtained. In the figure, the black circles "●" are plots of the calculation results according to the present invention, and the white circles "○" are plots of the results obtained by the conventional cascade impactor (ASS: Andersen Stack Sampler).
The two show a very good agreement.

The above-mentioned embodiment is an example of the preferred embodiment of the present invention, but the present invention is not limited to this, and various modifications can be made without departing from the gist of the present invention. For example, although a filter is used to collect particles in the air stream in this embodiment, a centrifugal separator may be used. Furthermore, when the measurement target is not the combustion-produced particles of the embodiment but pulverized particles such as pulverized coal, use the Rosin-Rammler distribution equation that is well suited to them as the particle size distribution function instead of Equation 4. Then, the particle size distribution and the like can be easily obtained by the same method.

[0037]

As is apparent from the above description, the classification method of the present invention makes the particle size of the particulate matter sampled from the air flow variable by changing the flow speed ratio between the main flow speed and the suction flow speed. Therefore, it is possible to perform classification by a simple operation of changing the flow velocity ratio of the particle concentration measuring device without using a complicated classifying device.

Further, according to the method for measuring the concentration of particles in the air stream of the present invention, it is not necessary to make the suction flow velocity and the main flow velocity coincident with each other in the particle concentration measurement, which is always necessary. Moreover, since the method of the present invention only needs to weigh each flow rate and the collected amount, accurate measurement can be easily performed by a well-known established measuring method. Therefore, the method of the present invention can be automatically operated because the measurement conditions and the operating conditions of the measuring device can be measured under the same conditions.

Further, in the method for measuring the particle size distribution of airborne particles according to the present invention, since the classification can be performed directly at the sampling portion without using a complicated and expensive classifying device, the measurement is very inexpensive and easy. Moreover, since the method of the present invention only needs to weigh the amount of particles collected under two or more suction conditions,
It is possible to measure many times in a short time, and it is easy to automate like the particle concentration measurement.

Further, in the present invention, since the particle concentration measurement and the particle size distribution measurement can be obtained from the same data, the particle concentration and the particle size distribution can be measured by one measurement.

[Brief description of drawings]

FIG. 1 is a principle view showing an embodiment of a measuring apparatus for carrying out the method of the present invention.

FIG. 2 is a diagram showing a relationship between a flow velocity ratio and a particle concentration measured using the measuring device of FIG.

FIG. 3 is a diagram showing a relationship between a flow velocity ratio and a particle concentration ratio measured using the measuring device of FIG.

FIG. 4 is a diagram showing a relationship by generalizing the characteristics of FIG. 2;

FIG. 5 is a diagram showing a result of particle size distribution obtained by using the measuring apparatus of FIG. 1 in comparison with a result obtained by a conventional measuring method.

[Explanation of symbols]

2 suction nozzle 3 filter holder 5 gas meter 7 vacuum pump 8 main flow pipe 10 filter u _O main flow velocity u _i suction flow velocity d _o main flow pipe inner diameter d _c suction nozzle inner diameter

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] February 24, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0018

[Correction method] Change

[Correction content]

The suction gas amount V _i is measured by the gas meter 5. The suction flow rate u _i is the suction gas amount V _i.
And suction time T _i and tip nozzle cross-sectional area S (S = π · d
Since _c ^2/4) and, equation _{u i = V i / (T} i · S), the obtained. The particle concentration C _{i at} that time is _calculated from the particle collection amount M _i and the suction gas amount V _i by the relational expression C _i = M _i /
V _{i is} obtained.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0024

[Correction method] Change

[Correction content]

[0024]

[Equation 2]

[Procedure 3]

[Document name to be amended] Statement

[Name of item to be corrected] 0029

[Correction method] Change

[Correction content]

[0029]

[Equation 6] Formula 6 can be expressed by the ratio of the true particle concentration and the measured concentration of the entire particle group as in the following formula.

[Procedure amendment 4]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction content]

[0032]

[Equation 8] Comparing Equation 7 and Equation 8, the following Equation 9 and Equation 1
0 holds.

[Procedure Amendment 5]

[Document name to be corrected] Drawing

[Name of item to be corrected] Figure 3

[Correction method] Change

[Correction content]

[Figure 3]

Claims (3)

[Claims] 1. A main flow velocity u _o and the suction flow rate by varying the flow rate ratio u _o / u _i and u _i, stream particles characterized in that the particle size of the particulate matter collected from air stream to the variable Classification method. 2. The particulate matter in the air flow is changed by changing the flow rate ratio u _o / u _i of the main flow velocity u _o and the suction flow velocity u _i.
Were taken at conditions above the flow rate ratio u _o / u _i, the air flow in the flow rate ratio is 1 based on the correlation between the amount particle concentration obtained from C _i of the harvested the particulate matter and the flow rate ratio A method for measuring a particle concentration in an air stream, which comprises obtaining a true particle concentration _Co in the air. 3. The particulate matter in the air flow is changed by changing the flow rate ratio u _o / u _i of the main flow velocity u _o and the suction flow velocity u _i.
The particle concentration C _i obtained at the flow velocity ratio u _o / u _i above the conditions, and the true particle concentration C _o in the air flow obtained by the measuring method according to claim 2 and the particle concentration C _i obtained from the amount of the collected particulate matter. determine the particle concentration ratio C _i / C _o, the particle concentration ratio C _i / C
_A method of measuring a particle size distribution in an air stream, characterized in that a particle size distribution in the air stream is obtained from a slope of a straight line representing a proportional relationship between _o and the flow velocity ratio u _o / u _i .