FR2532053A1 - METHOD AND APPARATUS FOR DETERMINING DUST CONTENT OF GAS-DUST FLOWS - Google Patents

Abstract

PROCESS FOR DETERMINING THE DUST CONTENT OF GAS-DUST TYPE FLOWS AND DEVICE FOR IMPLEMENTING THIS PROCESS. THIS DEVICE INCLUDES, ARRANGED IN THE DIAMETRAL DIRECTION OF THE GAS DUCT 1, A SOURCE OF BETA RAYS 2 EQUIPPED WITH A COLLIMATOR 3 AND INTENDED TO DETECT THE BRAKING RADIATION INDUCED BY THE DUST PARTICLES DURING IRRADIATION BY THE B SPOKES OF A GROUP OF RADIATION COUNTERS 4. A FILTER 5 INTENDED TO ABSORB THE DIRECTLY TRANSMITTED BETA RADIATION IS PLACED IN BEFORE OF SAID COUNTERS.

Description

The present invention relates to a method and a device for

  determine the dust content of the gas-dust type flows, and aims to carry out a continuous control of the quantity of dust contained in mixtures of dust and gas emitted by industrial units, inter alia, whether upstream or downstream;

  downstream of the corresponding filtering devices.

  There are two main groups of methods and devices known in the art for solving this problem: Methods and Devices for Separating the Solid Phase from the Disperse Medium These methods and devices are based on the principle of weighing;

  the tracer method; and some versions of

ceded optics.

  The disadvantages of said methods and devices lie mainly in the cyclical nature of the measurement, the large manpower required, as well as the low sensitivity due to long sampling times (up to several hours) that are necessary. for

measure low concentrations.

  II Methods and devices not containing

separation of the solid phase.

  The most commonly used methods and devices in this group are: methods and devices that are based on the principle of integrated light scattering, in which the mass concentration of the dust is determined by measuring the total intensity of the scattered light by the flow of

gas-dust type.

  holographic methods and devices which are based on Frauhoffner's holograms which represent superimposed diffraction patterns of the particles of the field and the light source. This method provides information on the number, size and arrangement of particles in space electrical contact methods and devices, which are based on the property of dust particles to electrify when in contact with solids; and the piezoelectric methods and devices These processes and the corresponding devices find their application in the determination of the dust content by means of a totalization of the electrical pulses created by the collisions between the dust particles and the crystal.

  piezoelectric input into the gas-type flow

dust.

  The methods and devices of the latter group meet the requirements of continuous measurement but all have a number of disadvantages which limit their practical applications. Said disadvantages include the strong influence on the results of the measurement by factors such as the physical and chemical properties

  and the size of the particles (in piezo

  electric and holographic); the composition of the dispersion; velocity, temperature and humidity of the particles (in the electrical contact process); and the coloring of the dust gas flow (in optical processes). All these factors result in a considerable limitation of the possibilities of application of the devices developed on the basis of the above methods, especially in the case of the weak ones. dust concentrations. An object of the present invention is to provide a method and a device for the continuous determination of the dust content of the gas-dust flowsprocesses and devices in which neither the physico-chemical properties of dust and gas nor the dynamic parameters of The further object of the invention is to provide the precision required in the measurement of low concentrations, on the one hand, and the possibility automatic recording

results, on the other hand -

  These objectives are achieved by means of a method implemented in a device making it possible to determine the

2532 è 53-

  dust content of the gas-dust flows ç thus making it possible to carry out a continuous control of the quantity of dust contained in the mixtures of dust and gas which are emitted by industrial units, both upstream and downstream of the filtering apparatus This method consists in measuring the braking radiation emanating from the dust particles during the irradiation of the useful volume, by using a beta ray source equipped with a suitable collimator and detector, the transmitted beta rays being absorbed by a particle. corresponding filter arranged in front of said detector, and the signal thus obtained being processed later. The output data may, depending on the case, be in digital form or

  in the form of a continuous recording.

  The advantages of this method are as follows: the measurement is carried out directly in the useful volume of the gas conduit, and the information thus obtained comes from a

  relatively large amount of gas-type flow

  Since a recording of the induced braking radiation is made and there is a unique dependence between the intensity of said radiation and the dust concentration, it becomes possible to obtain greater precision when measuring low concentrations area in which the aforementioned methods

suffer from considerable errors.

  The advantages of the device are as follows the measurement is done automatically and continuously The device allows the necessary collimation of the radiation source and the selection of the radiation to record said device allows to implement the method of

  the invention on an industrial scale.

  The results of the measurements made using the method and the device according to the present invention are not influenced by the diameter of the gas duct, by the size of the particles or by the temperature, humidity,

  coloring and flow velocity of the type, gas-

  In order to achieve maximum sensitivity and precision when implementing the process in a

-2532053

  production, it is necessary to choose an appropriate source of radiation- <ie the half-life, energy and activity of this source) taking into account the chemical composition of the dust, a part, and the

  diameter of the gas duct, on the other hand.

  The method and general operation of the device according to the present invention will be better understood

thanks to the following examples.

Example 1

  Experimental determination of the dust content of the gases emitted in the copper production in shaft furnaces This determination was made in a gas conduit 1500 mm in diameter, placed after the dust collectors in the diametrical direction. of this gas duct (1) (single figure) were mounted in respective holes: a beta ray source (2) equipped with a collimator (3) and a group of radiation counters (detector) (4). ) A filter (5) for absorbing beta rays

  directly transmitted was placed in front of the meters.

  The radiation source was mounted in such a way as to preclude any possibility of contamination of its anterior surface by dust. The radiation meters were fixed on an angle frame (6) and were also protected from dust contamination. beta particles through the mixture of gas and dust, the dust particles induce a radiation of

  braking whose intensity is recorded by the meters.

  The signal thus produced is processed by an intensity meter and is then

  sent to a recorder for continuous recording.

  The results obtained during large-scale trials are listed in Table 1-below.

Table 1

  Indications Density content (graduation) dust dust (normal mg / m 3) (normal mg / m 3) (normal mg / m 3) (weighing method) 13, 0 12.4

12.4

12.0 11.6 11.3 11.4

9.2

  7.6 + 3 + 1 + 10 + 10 The apparatus was calibrated by the well known weighing method (using "NIOGAS" cartridges)

  during a continuous operating period of 14 days.

Example 2

  Similar experiments were made using the same device and gas pipe, except that the measurement was taken in front of dust collectors. The results (Table 2) prove the applicability of the method and device to the determination of high concentrations

  of dust in the flows of the gas-dust type.

Table 2

  Number of impulse content in error content per min dust dust (g / m 3 normal) x 103 (g / m 3 normal) (g / m 3 normal) (weighing method)

1.10 0.55 0.62 0.07

1.20 0.65 0.75 0.10

2.35 3.50 3.50 O

3.25 6.90 6.70 + 0.20

, 00 10.90 10.80 + 0.10

Claims (2)

  A method for determining the dust content of gas-dust type flows, which aims to carry out a continuous control of the quantity of dust contained in the gas and dust mixtures emitted by the industrial units both upstream and downstream. downstream of the corresponding filtering devices, characterized in that it consists in measuring the intensity of the braking radiation induced by the dust particles during the irradiation of the volume   useful using a beta ray source.   2 Device for carrying out the method according to claim 1, characterized in that it comprises a beta ray source (2) anda detector (4), a suitable collimator (3) disposed in front of said beta ray source (2), and a suitable filter (5) mounted in front of said detector (4), said filter (5) providing only the recording of the induced braking radiation, and the   signal thus obtained being processed later.