RU2656652C1 - Radioisotopic method of measurement of dust development in mine openings and device for implementation - Google Patents

Abstract

FIELD: test and measurement equipment.

SUBSTANCE: invention relates to the technique for controlling the dustiness of the surface at coal, mining and metallurgical and other industries and agricultural production enterprises, where there is explosive dust: coal, sulphide, flour, etc. Surface density of the dust sediment on the collector is calculated from the reduced mathematical expression. Operation of measuring the surface density of the precipitate is repeated until a predetermined critical surface density of the dust sediment is collected σ^u _n. Also disclosed is a device made in the form of a radiometric assembly consisting of a flat circular source of beta-particles radiation and a coaxially located equal-sized detector, located at a distance from each other, sufficient for placing between them a movable carriage with a dust sediment, in the carriage are cut two round holes located one after another on which the reference measure and working collector are placed, alternately moved to the radiometric unit, the movement mechanism of the carriage is made in the form of a screw connected at one end to the micromotor, and the other to the body of the device, and the nut fastened to the carriage, which moves the carriage to the radiometric assembly and vice versa, and motor end switches disposed on the device body fixing the carriage position in the radiometric assembly and the dust collection point. In the case are placed electronic units for calculating and indicating the measurement, controlling the movement mechanism of the carriage and power supply.

EFFECT: increased safety and efficiency of the radioisotope method of measuring the current and critical mass of the dust sediment and the device that implements it, absorption of soft beta radiation by a dust deposit located on a thin substrate-collector, the measurement process is divided into two phases: precipitation of dust particles and measurement of the surface density of the precipitate.

2 cl, 2 dwg

Description

The invention relates to techniques for controlling dustiness of the surface at enterprises of coal, mining and metallurgical and other industries and agricultural production, where explosive dust is present: coal, sulfide, flour, plastic, etc.

Known methods for measuring the dust deposition of coal dust in mine workings, based on the backscattering of beta particles from a substrate on which dust is deposited from an air stream, and a device in the form of an annular source of beta particles placed on the periphery of the ionization chamber applied to the substrate [Brines N .I., Sklyarenko I.P. Development of a method for controlling coal dust deposition in mine workings. In kN. “Security Issues in Coal Mines”, vol. XIII. McNII. M .: Gosgortekhizdat. 1962. S. 219-240].

The disadvantage of this method and device is that the process of continuously performed measurements and tracking the accumulation of dust is impossible without human intervention.

The closest in technical essence and the achieved result is a method and apparatus for measuring the settling dust in time in the workings, comprising a housing, a detector, a dust collecting substrate, an amplifier driver and a signal converter, a radiation source, and beta-scattering from the substrate with dust is also used [ Rassolov N.I., Sklyarenko I.P. Development of a method for controlling coal dust deposition in mine workings. In kN. “Security Issues in Coal Mines”, vol. XIII. McNII. M .: Gosgortekhizdat. 1962. S. 219-240 (prototype)].

The method and device have the following disadvantages:

- the fraction of beta radiation from the source falling on the detector and the efficiency of using the activity of the radionuclide in the radiation source is much less than unity. This fraction of the radiation is determined by solid angles at which the dust sediment from the source and the detector from the scattering beta particles of the substrate are viewed. Therefore, a greater activity of the radionuclide in the source of beta particles is required in comparison with analogs, especially if the intensity of beta radiation is measured, rather than counting the number of particles.

- in this method and device (sensor) the source is open, the radiation is directed away from the side surface of the mine, where people can be, and is dangerous for others;

- the source is not protected from dust, as it is in the dust stream, which affects the error in measuring the mass of the sediment.

Due to the required greater activity of the source, its cost is high.

An object of the invention is to increase the safety and efficiency of measuring the current and critical mass of dust sediment and its device that implements.

The technical problem is solved by using the absorption of soft beta radiation by a dust deposit located on a thin collector substrate, the measurement process is divided into two phases: the deposition of dust particles and the measurement of the surface density of the precipitate. The surface density of the dust sediment on the substrate collector is calculated by the formula:

,

,

where N ₀ is the number of particles passing through the collector substrate during the time Δt;

N _i is the number of particles passing through the dust sediment with the substrate during the time Δt;

μ is the mass attenuation coefficient of radiation;

c = Δt / t;

k is the coefficient due to the design of the radiometric unit and is determined from a comparison of the measured surface density of the sediment with the value obtained by weighing.

The measurement operation σ ^u _{i is} repeated until the specified critical surface density of the dust sediment σ ^u _{n is accumulated} .

The device is made in the form of a radiometric unit, consisting of a flat circular source of beta particle radiation and a coaxially located isometric detector located at a distance from each other sufficient to accommodate a movable carriage between them with two circular holes cut out one after another in the same plane, on which the standard-simulator of dust sediment and the working collector-substrate are placed with the possibility of alternating movement in the radiometric unit, the worm mechanism for moving the caret the ki is connected at one end to the micromotor and the other to the device body, a threaded stand fastened to the carriage moves it to the radiometric unit and vice versa, and motor limit switches located on the device body fixing the position of the carriage in the radiometric unit and dust extraction site . The case contains electronic units for calculating and indicating measurements, controlling the mechanism for moving the carriage and power.

The device can be placed in any position. It is absolutely safe, and it uses radionuclide effectively.

The invention is illustrated by drawings, where in FIG. 1 shows a block diagram of a device for measuring dust deposition in mine workings; in FIG. 2 - shows the calculation of σ ^and - the true amount of dust deposition, determined from the similarity of triangles, where t is the dust deposition time, Δt is the measurement time σ of settled dust, t and Δt = Const.

A device for measuring dust deposition in mine workings contains an information processing unit - 1, a control unit - 2, a power supply unit - 3, a microelectric motor - 4, an indication unit - 5, a worm gear - 6; beta radiation detector -7, a nut fastened to the carriage - 8, a dust sediment simulator-9, a beta radiation source C ¹⁴ - 10, a collector-substrate with dust - 11, a carriage - 12 with it made in one plane two holes with lodgements for placement of a standard of a simulator of dust sediment in them - 9 and a working collector-substrate with dust - 11, limit switches - 13, pillow block bearing - 14.

The method is implemented as follows.

The process of absorption of soft beta radiation by a dust deposit located on a thin collector substrate is used, the measurement process is divided into two phases:

- sedimentation of dust particles;

- measurement of surface density of sediment.

The surface density of the dust sediment on the collector-substrate -11 is calculated by the formula:

(1)

(one)

where N ₀ is the number of particles passing through the collector substrate during the time Δt;

N _i is the number of particles passing through the dust sediment with the substrate during the time Δt;

μ is the mass attenuation coefficient of radiation;

c = Δt / t;

k is the coefficient due to the design of the radiometric unit and is determined from a comparison of the measured surface density of the sediment with the value obtained by weighing.

The surface density σ is measured ^{and is} carried out by placing the collector-substrate -11 in the radiometric unit, and the number of particles N ₀ passed through the collector-substrate during the time Δt is counted. The movable carriage -12 moves the collector-substrate into a dusty atmosphere (near the wall of a mine working), where dust is deposited for a given time t. After this time, the collector-substrate -11 with dust sediment is returned to the radiometric unit, in which the number of particles N _i passed through the collector-substrate -11 with dust sediment is counted over the time Δt. The surface density of the sediment σ _{i is} calculated by the formula:

(2)

(2)

where μ is the mass attenuation coefficient of radiation;

N _i , is the number of particles passing through the dust sediment with the substrate during the time Δt;

N ₀ is the number of particles passing through the substrate during the time Δt.

Since during the time Δt of measuring the surface density of the sediment, the dust did not deposit on the collector-substrate - 11, the true value of the sediment σ ^u _i at the end of measuring its density (at the end t + Δt) is:

(3)

(3)

where Δσ _i is the mass of dust referred to the deposition surface, which should have settled during the time Δt.

Δσ _{i is} determined from the similarity of triangles (see figure 2).

Δσ _i / σ _i = Δt / t = c,

where Δσ _i = σ _i c.

c is a constant value, since Δt and t are set based on the radiation intensity of the beta radiation source C ¹⁴ -10 and the dust deposition rate.

The obtained surface density of the dust sediment is determined from the expressions:

(4)

(four)

or

(1+c) (5)

(1 + c) (5)

In this case, the coefficient k is introduced into expression (4), due to the design of the radiometric unit:

(1)

(one)

k is determined from a comparison of σ ^u _n with a surface density value determined by weighing.

The measurement operation is repeated n times until you reach the specified (critical) surface density of the sediment σ ^u _n .

The source data is processed in the display unit - 5 and displayed on the display in digital form in mg / cm ² or transmitted to the dispatcher. If σ ^u _i approaches a critical value, the danger level is indicated on the display by the colors of the LEDs: green, yellow and red.

For a given ratio c = Δt / t << 1 (much less than unity, for example, 0.01), dust accumulation is determined by the formula

(6)

(6)

In this case, sediment accumulation over time Δt is neglected, and the time interval t of sediment accumulation is set to be greater than the measurement time of the surface density Δt, which, together with the time of movement of the collector-substrate, is -11, for example, no more than 3 s.

In the general case of using formula (5) at real time Δt = 3 s and c = Δt / t = 0.01, the dust accumulation time on the substrate is 5 min, i.e., data on the amount of dust sediment is received every 5 min.

Changing the value of "c", reduce or increase the time of dust sampling on the collector-substrate -11, that is, change the frequency of information.

The implementation of the method is illustrated by an example.

Example.

The amount of sediment in the production area l m for a time t C is estimated by the formula:

where S is the cross section of the development, m ² ;

ν is the velocity of the dust stream (not more than 4 m / s);

t is the time of dust accumulation on the substrate, s;

n is the concentration of dust (mg / m ³ ) in the air entering the production cross section s;

S is the surface (m ² ) of a working length of l m;

P - perimeter of the output, m

At s = 2 × 2.5 = 5 m ² , ν = 4 m / s, t = 300 s, n = 300 mg / m ³ , Рl = 9⋅10 m ² , the average surface density of dust sediment in the production area l = 10 m will be

or

σ = 0.4 mg / cm ² .

When the dust concentration is equal to the lower explosive limit, for example n _in = 30 g / m ³ , the surface density of the sediment will be σ _in = σ⋅30 / 0.3 = 40 mg / cm ² . To measure this surface density, you can use technetium-97, which belongs to the third hazard class.

At c = 0.05, σ _in = 8 mg / cm ² , that is, the critical surface density of the dust sediment can be measured by the absorption of beta radiation emitted by the carbon-14 radionuclide, in which the maximum particle path is 22 mg / cm ² and which is assigned to the fourth hazard class.

A device for measuring dust deposition in mine workings is as follows.

The device is made in the form of a radiometric unit, consisting of a flat circular source of beta particles radiation - 10 and coaxially located equal beta radiation detector - 7 located at a distance from each other, sufficient to accommodate a movable carriage - 12 between them with two round holes cut out, located one after the other in the same plane, and with lodges, in which the standard simulator - 9 dust sediment and the working collector-substrate - 11 are placed with the possibility of alternating movement in the mine and back to the radiometric unit using the worm gear - 6. In this case, the worm gear itself - 6 carriage movements are connected at one end to the micromotor - 4, and to the other end to the device body, the threaded stand - 8 is rigidly fastened to the carriage - 12 and moves it during measurements to the mine workings and back to the radiometric unit using limit switches - 13 micromotors - 4.

Limit switches - 13 are located on the device body and fix the position of the carriage in the radiometric unit and the dust extraction site. Using electronic information processing units -1 located in the housing, the control unit for the carriage moving mechanism -2 and the power supply unit -3, the calculation and indication of measurements are made.

Dust deposition measurements in mine workings are carried out by using direct absorption of beta particles by dust deposited on a thin collector substrate -11, which is placed on a lodgement above the hole made in the movable carriage -12. The carriage -12 is periodically moved from the radiometric unit to the position for collecting dust sediment from the production atmosphere and back to the radiometric unit. The radiometric unit is presented in the form of a flat circular source of beta radiation C ¹⁴ -10 and coaxially located with it is the equal detector of beta radiation -7. In the movable carriage -12 there are two circular holes located in one plane in the direction of movement of the carriage -12. The holes are made lodgment. On the lodgement of one of them impose a standard-simulator of dust sediment - 9, and on the other lodgement place a working thin collector-substrate -11, for example, an AFA-VP-10 filter. In this case, the standard simulator of dust sediment -9 and the working thin collector-substrate - 11 in the holes of the carriage - 12 are flush, i.e. lower or flush with the upper plane of the carriage - 12, and the standard-simulator of dust sediment -9 is installed above the hole that is constantly inside the device for measuring dust deposition in mine workings. The carriage - 12 is moved by means of a micro electric motor drive - 4, attached to one of the ends of the worm gear - 6, passing through the holes of the strut - 8, in which the thread is made, and the other end of the worm gear - 6 is placed in the plain bearing - 14, rigidly attached to the wall of the device. The limit position of movement of the carriage -12 is fixed by limit switches - 13 microelectric motors - 4.

The received data is processed in the display unit - 5 and displayed on the display in digital form in mg / cm ² or transmitted to the dispatcher. If σ ^u _i approaches a critical value, the danger level is indicated on the display by the colors of the LEDs: green, yellow and red.

The device is radiation-safe and can be placed in any position inside the mine.

Claims (9)

1. Radioisotope method for measuring dust deposition in mine workings, based on the use of beta-radiation interaction with a substance, characterized in that direct absorption of soft beta radiation by dust sediment on a collector is used to measure the current mass of dust sediment, the measurement process is divided into two phases: deposition dust and measuring the surface density of dust sediment, and the ratio of the measurement time Δt and deposition t is much less than unity, the surface density of dust sediment on the collector is determined according to the formula:

where N ₀ is the number of particles passing through the collector during the time Δt; N _i is the number of particles passing through the dust sediment with the substrate-collector during the time Δt; μ is the mass attenuation coefficient of radiation; c = Δt / t; k is the coefficient, which is due to the design of the radiometric unit, is determined by comparing the measured surface density of the sediment with the value obtained by weighing; the measurement operation σ ^u _{i is} repeated until a predetermined critical surface density of the dust sediment σ ^u _{n is accumulated} . 2. A device for measuring dust deposition in mine workings, comprising a housing, a beta radiation source, a detector, a dust collecting substrate, an amplifier driver, a signal converter, characterized in that a control unit, an information processing unit from the detector, a power supply unit, a power supply unit are introduced therein indications, a microelectric motor with a worm gear, a stand rigidly fixed to the carriage and limit switches, a C ¹⁴ beta radiation source, a beta radiation detector, a dust sediment simulator and a collector substrate into a single radiometric unit, consisting of a flat circular source of beta-particles radiation and a coaxially located equidistant detector, mounted as close as possible to each other, but sufficient to accommodate a movable collector carriage with dust sediment between them, two circular holes are cut out in the carriage, located one after the other in the same plane and with tool holders, in holes, on tool holders, a dust sediment simulator and working collector substrate are placed, the carriage moving mechanism is made in the form of a worm mechanism with a microelectric resistant rigidly secured to the carriage and the limit switch with the carriage, which is movable in a radiometric node and back, the housing units are arranged electronic calculation and indication of measurement, the control mechanism moving the carriage and nutrition.

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