JPH01272940A - Powder supply amount controller - Google Patents

Abstract

PURPOSE:To evaluate a difference in the particle concentration of the powder in a high-concentration supply pipe and to remove a measurement error by providing a detection pipe for taking part of powder within a prescribed concentration range out of piping and returning it to the piping after light transmission is detected. CONSTITUTION:The pulverized coal supply amounts of plural pulverized coal supply pipes 100a-100c are varied by opening/closing valves 101a-101c, and irregular particle concentration distributions generated in the supply pipes 100 are uniformed by particle concentration uniforming devices 102a-102c. Then detection pipes 103a-103c sample part of particles in the supply pipes 100 and particle concentration meters 106a-106c as detecting means detect the particle concentration. A signal processor 107 calculates the ratios of the intensity values of light photodetected by detectors 105a-105c to the intensity values of incident light from projectors 104a-104c. Then the intensity ratios are compared 108 and an opening extent regulator 109 adjusts the opening/closing valves 101 to equalize the intensity ratios of the respective pipes.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a powder supply rate control device, and particularly to a powder supply rate control device suitable for maintaining an appropriate powder supply rate in a plurality of pipes. .

[Conventional technology]

A pulverized coal-fired boiler will be described in detail as a conventional device of this type. This has multiple stages of supply pipes that supply pulverized coal and air, and each stage has multiple burners.The pulverized coal (hereinafter referred to as pulverized coal) is usually However, one pulverizer supplies pulverized coal to multiple burners by conveying air.

Since this pulverized coal contains about 1 to 3% nitrogen in its fuel, nitrogen compounds (NOx) are generated when it is combusted. For this reason, NO! due to improved burner performance! reduction (so-called low NO
x burner), a method of burning pulverized coal in a part of the boiler with insufficient air (the so-called two-stage combustion method), a method of reducing NOx to nitrogen by spraying ammonia, etc. into the combustion exhaust gas (the so-called, Attempts have been made to reduce the degree of NoxlA released into the atmosphere by various techniques such as ex-furnace denitrification. Among these, low NOx burners and two-stage combustion methods are often used from the viewpoint of reducing operating costs of pulverized coal boilers.

A pulverized coal-fired boiler with multiple stages and multiple rows of burners.
In order to effectively operate the low NOx burner and two-stage combustion method described above, the air flow rate and the pulverized coal flow for conveying pulverized coal to each burner must be made equal to the designed values.

For example, to explain the operation of low NOx combustion using the two-stage combustion method, burner rows with a ratio of the actual air flow rate (hereinafter referred to as the air ratio) to the air flow rate required to burn the supplied fuel are higher than 1. , a burner row with an air ratio of less than 1 is provided, and the burner row with an air ratio of 1 or more releases the nitrogen content in the coal into the flame in the form of NOx, and the burner row with an air ratio of 1 or less releases the nitrogen content into ammonia (NH3). ) and cyanide (HcN), and further products of combustion such as -carbon oxide (Co), hydrogen (H2), and methane (cH4) are produced. These substances are well known to reduce NOx in oxygen-deficient regions, and by forming a flame with an air ratio of 1 or less inside the boiler furnace, they effectively reduce NOx by 9 degrees.

Since the number of crushers is smaller than the total number of burners, usually 1
The pulverized coal produced in one pulverizer is supplied to multiple burners, but in order to make the above-mentioned two-stage combustion method effective, the burners in the same row are supplied with pulverized coal produced in the same pulverizer. It is assembled in such a way that it is supplied with

However, the pressure loss caused by the total length of the supply pipe that supplies pulverized coal from the pulverizer to each burner, as well as the curvature and number of bends, is different for each supply pipe, and the pulverized coal from the pulverizer is distributed to each burner. The amount of pulverized coal supplied to each burner is unbalanced due to poor performance of the distributor. Therefore, the air ratio of each burner corresponds to the imbalance in the amount of pulverized coal supplied, and differs from the set air ratio.

For example, if the aforementioned air ratio imbalance occurs in a burner stage with an air ratio of 1 or higher, the total amount of combustion intermediate products in the burner with an air ratio higher than the set air ratio will decrease, and therefore will be discharged from the boiler. The N 0xllJ degree increases, while the total amount of combustion intermediates in the burner below the set air ratio increases. Excessive combustion intermediate products, especially excessive CO gas, take time to burn out compared to NOx'a degree,
Sometimes it is released outside the boiler furnace. Moreover, since the proportion of combustible components in the pulverized coal increases at the same time, problems such as a decrease in combustion efficiency and a decrease in the dust collection efficiency of a dust collector installed downstream of the boiler furnace occur.

The example in 1-2 describes a burner stage with an air ratio of 1 or less in the two-stage combustion method, but in general, an imbalance in the amount of pulverized coal supplied between each burner is considered to be a decrease in the combustion efficiency of the boiler furnace. To avoid this, it is necessary to develop a distributor that distributes pulverized coal to each burner, and to reduce the amount of pulverized coal a downstream of the distributor.
A device has been devised to control the supply amount to be equal by observing the degree.

An example of the latter device is disclosed in Japanese Patent Application No. 58-123323. This is done so that the ratio of light transmission detected by the detection device that detects light transmission in the piping directly attached to the piping that supplies pulverized coal to each burner is equal in each piping. It is characterized by controlling the opening degree of an on-off valve that is provided to control the amount of powder supplied.

[Problem to be solved by the invention]

However, the above-mentioned device has the following two practical problems.

The first problem is that due to the large diameter of the pulverized coal supply pipe, the light transmission rate of the detection device directly attached to the supply pipe hardly changes even if the pulverized coal supply amount is changed.
There is a problem.

In the case of a boiler that supplies pulverized coal with a crusher, the pulverized coal weight flow rate (Ckg/h) flowing in the supply pipe and the conveying air weight flow +
The ratio C/A of i (A kg/h) is usually set to 0.3 to 0.4 due to boiler system constraints. Further, the flow velocity of the conveying air is set to about 19 m/s so as not to cause the pulverized coal to settle on the pipe wall. From these two conditions,
Calculating the diameter of the pulverized coal supply pipe is 0.37-0.33 m for a burner that burns 3 t/h of pulverized coal, 10 t/h.
In case of h burner, it will be 0.77-0.69m.

On the other hand, the light intensity ■ when particles are present is the light intensity ■ when particles are not present. It is known that the relationship of equation 0 is established between the particle diameter χ2, the number n of particle diameters χ, and the tube diameter d.

In order to roughly estimate this equation 0, the equation 0 is simplified using the average diameter χ3□ defined by the equation (2) for the particle diameter χ and the total number N of particles existing in the optical path, resulting in the equation (2).

(c, c' are constants) fn・χ3dχ χ32'''''''' (Program 1) fn・χ2dχ ■When the right side of the equation becomes 1 or more, the particle concentration becomes optically high, and the light scattered by the particles It has been experimentally revealed that the particles scatter again into the light transmission detector of the detection device.This condition is generally called multiple scattering, and the particle concentration cannot be accurately identified. From the limit particle number concentration that does not cause multiple scattering in the charcoal supply pipe, the C/A in the supply pipe is calculated as C' = 2 + Z, +z = 20 pm from (the right side of the equation) = 1, and it is approximately 3. /h burner C/A is 0.022--0.025, l OL
/h bar-1-(7)C/Δ is Q, Q1] ~ 0.01
It becomes 2.

In other words, simply attaching a detection device that transmits light directly to the supply pipe is not only incapable of determining high particle concentrations such as those in the pulverized coal supply pipe, but moreover, the above-mentioned multiple scattering is caused by the light intensity. (The energy of light per unit area) occurs regardless of the intensity of the transmitted light. The ratio to the total amount does not change much even if the particle concentration is changed.

A second problem is that particles do not necessarily pass through the light of the detection device due to inertial forces. For example, consider a case where a straight pipe with a -like particle concentration bends to the right in the flow direction.

While the conveying air can pass through the curved pipe section while maintaining the flow velocity distribution of the straight pipe section, the particles have a large inertial force, so the particle concentration after passing through the curved pipe is higher on the left side in the flow direction. At this time, if the detection device passes light in the vertical direction including the center of the tube, even though particles are present in the tube, the detection device can only output a signal indicating that no particles are present.

Furthermore, even if the detection device is installed at a position where a signal indicating the presence of particles is generated, the distribution of particle concentration will be different from the distribution before the bend, and the particle concentration distribution will change depending on the operating conditions, so it will only output a signal containing errors. It cannot be done.

Considering the fact that the shape of the supply pipe that supplies pulverized coal to each burner is different, the actual amount of pulverized coal supplied will not necessarily be the same even if the signals from the detection device are controlled to be equal using the known method. .

When the concentration of a single particle increases in this way, the ratio of the intensity of light received by the detection device to the intensity of incident light becomes almost constant due to the influence of multiple scattering, which makes it impossible to accurately measure the difference in actual concentration. No consideration was given to the uneven distribution of particles due to the curved pipe upstream of the detection device, and there was a problem in that the amount of pulverized coal supplied flowing through the supply pipe could not be evaluated.

The purpose of the present invention was to solve the above-mentioned problems, and it is possible to evaluate the difference in the particle concentration of powder in a high-concentration supply pipe, and to eliminate measurement errors in particle concentration due to uneven distribution of particles. An object of the present invention is to provide a powder supply amount control device.

[Means to solve the problem]

In order to achieve the above object, the present invention includes an on-off valve that controls the amount of powder supplied, which is provided in each of a plurality of pipes that supply powder, and an on-off valve that is provided downstream from the installation position of this on-off valve to supply powder. Comparing the detection means that detects the light transmission in each pipe from time to time, the calculation means that calculates the light transmittance of each pipe based on the output from this detection means, and the light transmittance output from this calculation means, In the powder supply amount control device having an opening degree adjuster that adjusts the opening degree of the on-off valve according to the light transmittance of each pipe based on the signal output from the comparator, The present invention is characterized in that a detection tube is provided for taking out a part of the powder in the concentration range, detecting light transmission, and then returning it to the pipe (claim 1).

Further, a particle concentration homogenizing means for adjusting the concentration of powder particles in the piping to a predetermined concentration range is disposed in the piping at a position downstream of the on-off valve and upstream of the detection means. (Eft term 2).

This particle concentration homogenizing means has an opening smaller than the inner diameter of the pipe, and makes the powder a predetermined concentration by passing the powder through the opening (claim 3); A plurality of gas ejection holes are arranged on the inner wall of the powder, and the powder is brought to a predetermined concentration by ejecting gas from the ejection holes (claim 4).

There is also a detection tube provided with a suction means for sucking powder (claim 5).

Some of these devices are characterized in that pulverized coal is used as the powder (claim 6).

[Effect]

The above configuration has the following effects.

(Claim 1) When measuring light transmission, it is possible to take out powder in a predetermined concentration range using the detection tube, so that inaccurate identification due to multiple scattered light can be prevented.

(Claim 2) Since the powder taken into the detection tube can be brought to a predetermined concentration by the particle concentration homogenizing means, accurate detection can be performed by light transmission.

(Claim 3) When powder flows through the piping leading to the detection tube inlet, the flow is restricted by this opening, preventing uneven distribution of particles caused by, for example, bends in the piping on the upstream side, and reducing the concentration of particles in the piping. almost homogenized within.

(Claim 4) Moreover, instead of the opening, gas can be ejected from a plurality of gas ejection holes to mix the powder flowing in the pipe, thereby preventing particles from being unevenly distributed.

(Claim 5) When taking out a part of the powder from the piping into the detection tube, it can be sucked into the detection tube, so regardless of the diameter of the piping or detection tube, or the flow rate of the powder, there is no powder in the piping. be sure to incorporate
Check the concentration? J5 can be done.

(Claim 6) Since fine powder can be used as the powder, these devices can be applied to a pulverized coal-fired boiler.

〔Example〕

Hereinafter, as an example of the present invention, an example in which pulverized coal is used as the powder will be described in detail.

First, before explaining a specific example, the principle of preventing uneven distribution of powder particles and measuring transmitted light in multiple scattered light according to this embodiment will be explained.

To prevent uneven distribution of powder particles, a constriction part such as a venturi or orifice whose opening diameter is not equal to the inner diameter of the pulverized coal supply pipe, or This can be achieved by providing a plurality of air jet holes, which are characterized by forming a swirling flow, inside the pulverized coal supply pipe.

In addition, regarding the measurement of transmitted light in multiple scattered light, the length L of the transmitted light emitted from the light source of the detection device passing through the pulverized coal particles is shorter than satisfying the following equation 0. This is achieved by locating the detector of the light source.

X3□ρ 3 Here, C' in equation 0 is a constant of approximately 2, and C/A is the weight of pulverized coal.
The ratio of the weight flow rate of the conveying air to the IT flow rate, L is the length of light passing through the pulverized coal (m), X3□ is the average particle diameter of the pulverized coal (m) defined by the above formula 0, and ρ is the pulverized coal The density of (
kg/m).

The particle concentration materializing device, such as the aperture section or a plurality of air jet holes, provided on the upstream side of the detection device suppresses the uneven distribution of particle concentration caused by piping, such as a curved pipe, on the upstream side of the particle concentration homogenizing device. It operates so that the particle concentration inside the pipe is homogeneous or symmetrical with respect to the central axis of the pipe.

In detail, the constriction part once collects the unevenly distributed particles and the conveying air in the center of the pipe, and then the cross section of the flow path becomes equal to the cross section of the flow path at the inlet of the constriction part, thereby reducing the particle concentration inside the pulverized coal supply pipe. They can be made almost equal. On the other hand, compressed air is ejected from the plurality of air ejection holes so as to form a swirling flow with each other so as not to reduce the C/A inside the pipe.

Since the swirling flow disperses the unevenly distributed pulverized coal in the airflow, it is possible to form a particle concentration distribution in which the particle concentration is high on the pipe wall and low in the center. This particle concentration homogenization device uses the detection signal of the detection device as the measurement result of the average particle concentration in the pipe, so
The detection device will not malfunction.

Furthermore, a detection device installed to satisfy the above formula 0 has a C/A of 0.3 to 0.4, which prevents multiple scattered light from particles from entering the detector of the detection device even in a state where the particle concentration is high. It doesn't seem to work. As a result, fluctuations in the particle concentration of the pulverized coal supply pipes can be detected, so that the particle concentrations of the plurality of pulverized coal supply pipes can be made equal.

Specific examples will be explained below with reference to the drawings.

FIG. 1 is a system diagram of a fuel supply amount control device for a pulverized coal burner according to a first embodiment. In this embodiment, a plurality of pulverized coal supply pipes 100 (in the figure, individual pipes are indicated by numbers followed by a, b, c)
an on-off valve 101 that changes the supply amount of pulverized coal, which is installed sequentially in the direction in which the pulverized coal particles flow;
Particle concentration homogenization device 1 that makes uniform the uneven particle concentration distribution in the pulverized coal supply pipe 100 caused by the on-off valve 101
02, a detection tube 103 for collecting part of the particles in the pulverized coal supply pipe so that the amount of light transmitted changes with the concentration of particles within the usage conditions, and a floodlight for detecting the concentration of particles in this detection tube. 104, a particle concentration measuring device 106 as a detection means composed of a detector 105 and the like, and the intensity (■) of light incident on the projector 104 from the signal of this particle concentration measuring device 106; A signal processor 107 that calculates the ratio of the intensity I of the light passed through the detection tube 103 and received by the detector 105 (hereinafter referred to as intensity ratio I/I), and a plurality of signals output from the signal processor 107. Strength ratio I/I of pulverized coal supply pipe. A comparator 108 compares the intensity ratio I/I of each pipe and receives the output signal of the comparator 108.

It consists of an opening adjuster 109 that adjusts the on-off valve 101 so that the opening and closing valves are equal.

Pulverized coal produced by a pulverized coal pulverizer (not shown in the figure) is conveyed by conveying air and distributed to a plurality of pulverized coal supply pipes 100 by a distributor (not shown in the figure) (in FIG. 100a, 1ooob.

(distributed to three pulverized coal supply pipes of 100c).

The flow rate of pulverized coal in the pulverized coal supply pipe 100 is adjusted by an on-off valve 101 that changes the cross-sectional area of the flow path and changes the pressure loss of the flow path.

The coal particles that have passed through the on-off valve 101 are passed through a particle concentration homogenizer 10 that passes through a flow path smaller than the flow path area of the pulverized coal supply pipe 100, such as a venturi or orifice.
2, the particles are changed to have a predetermined particle concentration distribution. This particle concentration homogenizing device 102 operates to make the uneven distribution of particle concentration generated on the upstream side into a predetermined particle concentration distribution.

Pulverized coal supply pipe of particle concentration homogenizing device 102] FIG. 3 explains the operation regarding Oa.

FIG. 3 shows a flow path cross section A-A on the upstream side of the on-off valve 101, a flow path cross section B-B located between the on-off valve 101 and the particle concentration homogenization device 102, and a flow path cross section downstream of the particle concentration homogenization bag +i 102. It is a diagram showing the particle concentration distribution of the side channel cross section C-C,
The vertical axis shows the particle concentration, which is the pulverized coal concentration made dimensionless by the maximum pulverized coal concentration in the cross section in the pipe, and the horizontal axis is the radius, which is made dimensionless by the radius in the cross section by the radius of the supply pipe of the flow path. ,0
corresponds to the center of the tube, and 1 or -1 corresponds to the tube wall. The pulverized coal particle concentration in the A-A cross section is high in the center because the distance from the distributor is long, so the flow generally develops and the velocity distribution becomes similar.

However, due to the reduction of the flow path area due to the on-off valve, uneven distribution of particles due to the inertial force of particles moving in the bent pipe section, etc.
The particle concentration distribution after the opening/closing valve shows a maximum value at a position shifted from the center of the piping, as shown by the curve B-B. In the case of this example,
The maximum value of the BB curve corresponds to radius/supply pipe diameter=-0.5. This uneven distribution of particle sensitivity varies in a complex manner depending on the shape of the pipe, the degree of opening of the on-off valve, etc., making it impossible to accurately measure the particle concentration.

However, in the particle concentration homogenizing device 102, since the particles once pass through the center of the tube, the particles that were unevenly distributed near the tube wall are also collected at the center of the tube.

As a result, the maximum value of the concentration distribution in the C-C portion is located approximately at the center of the tube. In other words, the particle concentration materializing device 102 works to change the distribution of particles that are unevenly distributed in the upstream portion so that the concentration becomes higher almost at the center of the pipe.

Now, as described above, after the particle concentration distribution becomes high in the center of the pipe flow path, the pulverized coal particles reach the particle concentration i-1 measuring device 106 that measures the particle concentration. The particle concentration measuring device 106 in this embodiment is a pulverized coal supply pipe 10
A particle sample tube 110 for collecting some of the particles in 0 and (
The position of the particle sample tube 110 at which the particles are sucked can be set at any location within the pulverized coal supply tube 1], the straight tube 1 connected to the particle sample tube 110.
11, and a return pipe 1 for returning the particles to the pulverized coal supply pipe 100 again.
A particle sample system consisting of 1-2, a light emitter 104 that emits light for measuring particle concentration attached to a corresponding arbitrary wall surface of the straight pipe 111, and light from the light emitter is incident. It consists of a detector 105 installed at a position where it can be detected.

At this time, the locations where the particle sample pipe 110 collects particles from the pulverized coal supply pipe 100 are the locations where the pulverized coal supply amount of each pipe is made equal (in this example, 100a, ), OOb
, 100 c), from the center of the pipe to the particle sample tube], It is important to ensure that the ratio of the pipe inner diameter to the distance from the center of the pipe to the particle sample tube is equal.

Furthermore, when the particle concentration in the pipe is high, if particles are collected from a relatively low concentration area such as the part near the pipe wall of the concentration distribution in the C-C section shown in Figure 3, the apparent -1- Since the particle concentration can be made equivalent to a low particle concentration, the limit of measurable particle concentration can be increased.

In the figure, 113 is a detection signal cable, 114 is a cable that connects the signal processor 107 and the comparator 108, 1]5 is a cable that connects the comparator 108 and the opening adjuster 109, 116
117 is an opening adjustment signal cable connecting the opening adjustment device 109 and the on-off valve 101, and 117 is a fiber to the projector 104.

FIG. 2 shows the detailed structure of the particle concentration detection section of the particle concentration measuring device 106 in the first embodiment. The light output from the light source 201 that generates light for measuring particle concentration is
The pulverized coal is distributed to 111 pulverized coal supply pipes by the optical distributor 202 (three in the first embodiment). At this time,
The light source 201 can be anything that generates light, but
Preferably, laser light is used. divided light 20
3, only the operation related to the pulverized coal supply pipe 100a will be described below, but the other lights 203b and 203c also operate on the same principle.

The distributed light 203a is divided into light for measuring the particle concentration and light for measuring the intensity of the distributed light by the Be-11 splitter 204, and a rod lens for guiding the light to the fiber 205. 206 and enters the light intensity measuring device 207.

Light for measuring particle concentration is guided by an optical fiber 205 to a projector 104a attached to a straight pipe 111a, and is attached to an end surface of the optical fiber 205 opposite to the incident light end surface (=I). Light is generated from the light unit 208, passes through the light emitting hole 209 provided in the straight pipe 11]a, passes through the light receiving hole 210 and the protective crow 211, and is transmitted to the detector 105a.
The light enters the detection unit 212 of.

The detection unit 212 generates a signal (usually an electrical signal) with an intensity corresponding to the incident light, and this signal is transmitted to the detection signal cable 11.
3a, and is input to the signal processor 107 through an amplifier 213 that increases the signal strength and a filter 214 that removes noise contained in the signal. On the other hand, the signal generated from the light intensity measuring device 207 for measuring the intensity of the distributed light is passed through an amplifier 213 that increases the signal intensity and a filter 2]4 that removes noise contained in the signal. The signal is input to processor 107.

The light intensity ratio (I/Io) of the supply pipe 100a is, for example, the light intensity ratio (I/Io) of the other pulverized coal supply pipes 10ob and 100c.
I. ), it indicates that the amount of pulverized coal supplied from the pulverized coal supply pipe 100a is small, so the opening regulator 109 instructs to open the on-off valve 101a, and the amount of pulverized coal supplied from the pulverized coal supply pipe 100a is It operates to increase the amount of pulverized coal supplied, or conversely, increases the strength ratio (I/1) of the pulverized coal supply pipe 100a.
．． , ) is smaller than the intensity ratio, it indicates that the supply amount of pulverized coal is large, so the opening regulator 109 is set to the on-off valve 1.
It is possible to give an instruction to close 01a and operate it so that the light intensity ratio (I/1.) of all the pulverized coal supply pipes becomes equal.

Here, a method for measuring the light intensity ratio (I/I) will be explained. First, when no particles are present in the straight pipe 11''a, the intensity of the light incident on the detection unit 212 is Il'l, and the intensity of the light incident on the light intensity measuring device 2078 is 11. shall be. Amplifier 21
3 is the signal strength according to the strength IB and the strength ■. The amplification ratio is adjusted so that the signal strength according to the The characteristics of the device that converts the intensity of light 207 into a signal are corrected. When performing a relative comparison of particle concentrations within the pulverized coal supply pipe, a signal corresponding to the light intensity ratio (I/1.) may be output.

On the other hand, when calculating the particle concentration, the constant value C of the following formula (■)
It is necessary to calibrate n in advance.

Qn(In/I)=C''NX, 2'd -■Here, X j 2 is the average particle diameter determined by the above formula 0, d is the pipe diameter, N
corresponds to the number of particles located in the optical path.

C" is a physical property constant that changes depending on the shape and surface properties of particles, and changes depending on the type of particles passing through the pipe.Constant C
'' is obtained, the particle source degree Cp can be obtained by dividing the number of particles N obtained by the following 0 formula by the flow rate per 1L hour calculated based on the conveying air velocity measured by another means. .

N=L/(C"・XJ," d)・Q n (I o
/I) -1B+The diameter d of the straight pipe 111a is set using the physical property constant C'' obtained by calibration so that the right side of the equation (■) is 1 or less.By setting the pipe diameter d using this method, , multiple scattering of light caused by the presence of many particles in the optical path is prevented, making it possible to sensitively measure changes in particle concentration, and reducing the intensity of transmitted light, which was a problem with conventional technology. This solves the problem of no change even if the particle concentration is changed.

When coal particles adhere to the surfaces of the light projecting section 208 and the detecting section 212, the above method for measuring particle concentration causes a significant error. For this reason, the method of mounting the light emitting section 2.8 and the detecting section 212 must be structured to prevent particle adhesion to a minimum. This embodiment has a structure in which a purge gas is supplied to prevent particle adhesion, and the light projecting section 208 and the detecting section 212 are not exposed to the inner wall of the straight pipe 1'J]a. That is, the light projecting section 208 and the detecting section 212 have an opening (light projecting hole 209 or light receiving hole 2) in the inner wall of the straight pipe 111a.
10), and a purge gas pipe 216 for introducing purge scum into the gas reservoir 215 is attached. The diameter of the inner wall of the gas retainer 215 is largest at the position where the purge gas pipe 216 is attached.
An inner wall of a gas reservoir 215 smaller in diameter than the above diameter is provided on the straight pipe 111a side. Further, the purge gas pipe 216 is installed so as to be substantially perpendicular to the direction in which the light travels.

By having such a structure of the gas retainer 215,
Since the purge gas uniformly flows around the outer periphery of the light projecting section 208 and the detecting section 212 and is ejected from the light projecting hole 209 and the light receiving hole 210, adhesion of particles can be prevented.

Since the diameter of the light receiving hole 2100 is made larger than the diameter of the light emitting hole 209, manufacturing and assembly of the particle concentration measuring device 106 can be easily performed.

The protective glass 211 is for preventing damage to the detection section 212.

As a second embodiment, the particle concentration homogenization device 1.02 can also be achieved by an air jet swirling type particle temperature homogenization device shown in FIGS. 4 and 5.

FIG. 4 is a side view, and FIG. 5 is a sectional view taken along line L-D in FIG. 4.

In this embodiment, the plurality of air jet holes 51 are connected to the pulverized coal supply pipe 1.
The pipe is arranged so that the angle between the jetting direction and the central axis flow direction is 90° or less with respect to the central axis of the pipe, and the jetted air is supplied so as to form a swirling flow with respect to each other. The air jet moves the unevenly distributed particles in a swirling flow, and the concentration distribution of the C-C section curve in Fig. 3 or
The distribution is such that the concentration is high at the pipe wall and low at the center of the pipe so that the concentration of each coal particle is axially symmetrical. As a result, measurement errors due to uneven distribution of particles can be eliminated.

A modification of the straight pipe 111 is shown in FIG. 6 as a third embodiment. In FIG. 6, a venturi 71 having an opening smaller than the inner diameter of the straight pipe 111 is installed, and a nozzle 72 that blows out high-speed air is installed on the upstream side.
The nozzle 72 is positioned so that the flow passes through the center of the opening. According to the modification shown in FIG.
Since the pressure of 1.10 can be lower than that of the first embodiment, the pulverized coal particles can be easily guided to the measurement section of the straight pipe 1.11. Furthermore, since the concentration of particles can be lowered using the compressed air 73, it is possible to measure with higher accuracy even under conditions where the concentration of particles is higher than in the first embodiment.

Another modification of the straight pipe 111 is shown in FIG. 7 as a fourth embodiment. This embodiment is characterized in that the pump 81 is disposed on the downstream side of the measuring section of the straight pipe 111.

Since the suction flow rate of the pump can be made variable, the measurement range of pulverized coal particle concentration can be widened.

As a fifth example, the above example is a particle concentration reduction @1
The tube diameter d, that is, the length of the optical path, was made small so that the particle concentration measurement condition of 06 was such that the right side of equation 0 was 1 or less, but the optical path length between the detector 105 and the projector 104 was If the above conditions are satisfied, the pulverized coal supply pipe may be installed inside the OO. In this case, the projector 104 or the detector 1
05 protrudes into the inside of the pulverized coal supply pipe 100, so it is necessary to provide a protective wall made of ceramic or the like on the surface to prevent wear caused by particle collisions.

〔Effect of the invention〕

As described above, according to the present invention, the following effects can be achieved.

By providing a detection tube for taking out powder in a predetermined concentration range, accurate concentration measurement can be performed even in the state of multiple scattered light (claim 1).

In addition, by providing particle concentration homogenization means in the piping, the powder particles in the piping can be kept within a predetermined concentration range, allowing accurate light transmission measurement and eliminating measurement errors in particle concentration. It is possible (Claim 2).

As this particle concentration homogenization means, an opening smaller than the inner diameter of the pipe is provided (Claim 3) or gas is ejected from multiple locations on the inner wall of the pipe (Claim 4). The powder within can be set within a predetermined concentration range.

On the other hand, since particles can be reliably sucked into the detection tube by the powder suction means provided in the detection tube, reliable measurement is possible (claim 5).

By using pulverized coal as the powder, it can also be applied to pulverized coal-fired boilers, and the particle concentration can be measured with high accuracy even under conditions where the concentration of pulverized coal particles is high. The amount can be controlled (
Claim 6).

[Brief explanation of the drawing]

Fig. 1 is a system diagram of a fuel supply amount control device showing an embodiment of the present invention, Fig. 2 is a structural diagram of a particle concentration measuring device, Fig. 3 is a concentration distribution diagram of pulverized coal in a supply pipe, and Fig. 4 is a diagram of a concentration distribution diagram of pulverized coal in a supply pipe. The figure is an explanatory diagram of a modification of the particle concentration homogenizing device of the second embodiment, and FIG.
Between arrows D and D in the figure, FIG. 6 is an explanatory diagram of a modification of the straight pipe of the third embodiment, and FIG. 7 is an explanatory diagram of another modification of the straight pipe of the fourth embodiment. be. 100 Pulverized coal supply pipe, 101 On-off valve, 102 Particle concentration homogenizer, 103 Detection tube, 104 Floodlight,
105・Detector, 106 Particle concentration measuring device, 107・Signal processor, 10
8 Comparator, 109 Opening degree adjuster, 201-Light source, 202-Light distributor, 203 Light, 20
4-beam splinter, 205/fiber, 206
Rod lens, 207 Light intensity measuring device, 208... Light projecting unit, 209 Light projecting hole, 210 Light receiving hole, 2] 1 Protective glass, 212 Detecting unit, 213 Amplifier, 214 Filter, 51 Air blowout hole, 71-・Venturi, 72 nozzles, 73...compressed air, 8 pumps.

Claims (1)

[Claims] 1. An on-off valve for controlling the supply amount of powder provided in each of a plurality of pipes for supplying powder, and an on-off valve provided downstream from the installation position of this on-off valve for controlling the amount of powder supplied during each powder supply. a detection means for detecting light transmission in the piping; a calculation means for calculating the light transmittance of each piping based on the output from the detection means; and a comparator for comparing each light transmittance output from the calculation means; In the powder supply amount control device having an opening degree adjuster that adjusts the opening degree of the on-off valve according to the light transmittance of each pipe based on the signal output from the comparator, A powder supply amount control device characterized by being provided with a detection tube that takes out a portion of powder in a concentration range, detects light transmission, and then returns it to the pipe. 2. A claim characterized in that a particle concentration homogenizing means for adjusting the powder particles in the piping to a predetermined concentration is disposed in the piping at a position downstream of the on-off valve and upstream of the detection means. Item 1. Powder supply amount control device. 3. The particle concentration homogenizing means has an opening smaller than the inner diameter of the pipe, and the powder is made to have a predetermined concentration by passing the powder through the opening. Item 2. Powder supply control device according to item 2. 4. The particle concentration homogenizing means is characterized in that a plurality of gas ejection holes are arranged on the inner wall of the piping, and the powder is brought to a predetermined concentration by ejecting gas from the ejection holes. Item 2. Powder supply amount control device. 5. The powder supply amount control device according to claim 1, wherein the detection tube is provided with suction means for sucking the powder. 6. The powder supply amount control device according to claim 1, wherein pulverized coal is used as the powder.