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10TECHNICAL SCIENCES
IMPROVING THE QUALITY OF AIR POLLUTION CONTROL AT LIGHT INDUSTRY
ENTERPRISES
Bokanova A.,
Professor of the Engineering Faculty, d.t.s.
Matayev U.,
Ass. professor of the Engineering Faculty, c.t.s.
Eurasian Technological University Abishova A.,
Senior lecturer of Textile Production Technology Faculty, c.t.s.
Almaty Technological University Almaty, Kazakhstan Republic Yermakhanova F.
Ass. professor of the Eurasian National University by name L.N. Gumilev,
c.t.s.
Nur-Suktan, Kazakhstan Republic
Abstract
The article discusses the issues of air purification in dusty workshops of the textile industry. Increasing the efficiency of air purification is achieved by the fact that a method for monitoring the dustiness of premises has been developed, providing high accuracy and a wide range of measurements, The method is implemented in a device in which corona discharge sections of different polarities are created and connected in series: in the first section, dusty air is charged in a negative volumetric charge of the corona discharge, in the second section, the flow of dusty air is discharged in a positive volumetric charge of the corona discharge. The degree of dustiness is determined by the value of the discharge current in the common circuit.
Keywords: air purification, corona discharge, volumetric charge, current, measurement range, accuracy.
Previously, a device for monitoring the counting (piece) concentration of aerosol particles in a gas stream was considered, based on measuring the number of corona discharge current pulses that occur when charging particles in the corona discharge zone and then discharging them on a measuring electrode [1, p.31; 2]. The proposed method was suitable only for monitoring weak flows due to the location of a flat measuring electrode in the path of the gas flow, which disrupted the natural flow of the flow. When several charged particles hit the measuring electrode at the same time, one pulse with a large amplitude was recorded at the output of the device. This position of the measuring process dramatically reduced the accuracy of the control. Thus, the proposed method has low accuracy and a narrow measurement range when monitoring highly polluted gas flows with a high purge rate.
The closest in technical essence was a device for controlling the dustiness of atmospheric air in industrial premises [1, p.32; 2], which contained a chamber for charging aerosol particles with negative oxygen ions and a chamber located sequentially along the passage of a polluted gas stream in which negatively charged aerosol particles were discharged in a positive volumetric charge of a corona discharge. By connecting both chambers electrically in series with volumetric charges of different polarities and measuring the corona discharge current in the common circuit circuit, the degree of atmospheric air pollution passing through the chambers was determined by the current value. The main disadvantage of the proposed device, which significantly reduces the accuracy of control, was the loss of part of the aerosol particles in the charging
chamber, which was due to the defocusing effect of the electric field in it, when some of the charged aerosols are pressed against the outer electrode of the chamber and gives it the charge they received when entering the chamber. Another disadvantage of the device is that it works only with running gas, which required a fan or other technical means to create. This complicates the measurement process and reduces accuracy [2].
In our gas pollution control device, high control accuracy is ensured without the involvement of additional technical means to create flowing gas through it. Here, the corona electrodes in the form of needles are located in the direction of the flow of dusty gas, and the external electrodes in the form of flat metal grids are located opposite the corona needles. This method differs from the known device, which includes two corona discharge chambers made in the form of metal cylinders as external electrodes with an axisymmetrically arranged common corona wire.
The air pollution control is based on the processes of charging aerosol particles when they interact with negative oxygen ions of atmospheric air located in the corona discharge charging chamber, and then their discharge processes occur in the positive volumetric charge of the discharge chamber, where positive oxygen and nitrogen ions are present, in the vast majority [2].
In the case of the prototype, the charging of aerosol particles begins already at the entrance to the charging chamber of a corona discharge with a negative volumetric charge. In the chamber, negatively charged aerosols under the action of the field begin to drift towards
the external electrode and partially settle on the electrode, giving up their acquired charge, thereby leaving the total counting concentration of aerosols in the flow. This position will be fully fulfilled for those aerosols in the flow that pass close to the external electrode [3, p.6; 4, p.233].
In the proposed device, volumetric charges of different polarities in the chambers are formed between corona needles and metal grids serving as external electrodes (figure). In this case, the directions of the flow of polluted air and current lines of aeroions coincide, and if the condition of "transparency" of the grid electrode to aerosol particles is met, the effect of the "aerosol loss" effect on the counting characteristics of the device will be minimal [2]. In addition, it should be assumed that for the processes of charging and discharging aerosols, the unidirectionality of the flows of aerosols and aeroions is, if at their intersections, as was the prototype. Meanwhile, it is unlikely that such a situation can play a significant role in the control processes due to the high ion velocities (5 •lO2 m/s) compared to the flow velocities of aerosol particles.
It should be noted that in this case, the proposed device operates according to the principle of operation of an ion-convection pump [2]. In the device, unlike the prototype, the flow of polluted air through the measuring chambers is created naturally by means of an electric wind arising between the corona needles and flat mesh electrodes (1-3m/s). Ultimately, changes in the air flow velocity through the corona discharge chambers do not affect the accuracy of monitoring due to the equality of the charging and discharging times of aerosols. In the device, the measuring chambers are electrically connected to the power source in parallel, which provides measurements of the charging and discharge chamber currents separately, which distinguishes it from the known ones. Thus, the connection of measuring chambers makes it possible to
determine the effectiveness of certain processes of interaction of aeroions with aerosol particles and to study their dielectric properties, dimensions and charge density. At the same time, one measuring device is used in the control process, which is included in the general circuit of the circuit. The device has a higher control accuracy, since due to the single direction of aerosol and aeroion flows and the use of a flat metal mesh as an external electrode, the effect of "aerosol loss" in the charging chamber is minimized. In addition, the operation of the device does not require forced blowing of polluted air through it. The supply of atmospheric air with aerosol particles is provided by an electric wind formed in the measuring chambers when a corona discharge occurs between the needles and external electrodes. The device is adapted to work with any natural flows of polluted air, since the influence of the flow rate on the measurement result is excluded due to the equality of charging and discharging times of particles. In other devices, high control accuracy is not provided due to the serial connection of two cameras, which leads to a redistribution of voltage between them during operation. The figure shows a functional diagram of a device for monitoring atmospheric air pollution. The proposed device contains a housing made of dielectric material 1, corona needles 2 and external electrodes in the form of metal grids 3. Corona needles 2 are coaxi-ally attached to the grid electrodes 3 with the housing 1.
The grid electrode to which the second needle is attached is simultaneously an external electrode for the first charging chamber and serves as a common electrical circuit for the two chambers due to its grounding through the output device 4. A microprocessor is used as an output device, which allows you to control not only the processes occurring inside the device, but also to control these processes [5, p.4; 6, p.236].
1 -device housing; 2 -corona electrodes; 3 -external electrodes; 4 -microprocessor; 5 - measuring device; 6 -polluted air; 7 - compressor; 8 -ventilation pipe; 9 -purified air Figure -Device for air pollution control
The metal mesh to which the first needle is fixed and the grid electrode 3, which serves as an external electrode for the second discharge chamber, are connected through measuring instruments 5 and ballast resistances R to the negative pole of the power source. After connecting a high voltage and the occurrence of a corona discharge in the chambers, an electric wind is formed in the working volume in the direction of the corona needles 2. When a sufficiently high voltage is applied to the first needle 2, a negative corona discharge occurs between it and the grid electrode 3, while a positive corona discharge appears between the second needle 2 and the grid electrode 3. After that, with the help of an electric wind, the polluted air in which the dust content (aerosols) is measured is drawn into the working volume of the device, where it interacts alternately, first with negative, then with positive volumetric charges of discharge gaps. In the charging chamber, aerosol particles are negatively charged and, being carried away by the electric wind, leave the discharge zone, thereby reducing the discharge current in the general circuit of the circuit. Then the negatively charged particles enter the zone of the second discharge chamber, where they coagulate with positive ions and, being neutralized, reduces the corona discharge current once again [2].
Thus, by the value of the deviation of the output device reading 4 from the initial one, the degree of contamination of the gas passing through the working volume of the device is determined, and due to the use of grid electrodes, the effect of the "aerosol loss" effect on the control accuracy is minimized. In addition, the measuring chambers work independently of each other due to their parallel connection to a power source, and therefore the changes in discharge currents in the chambers during the passage of polluted air are summed up without loss. The proposed device is characterized by simplicity and ease of operation, provides high control accuracy while simplifying measurement processes [6, c. 24; 7, c.504].
The developed device refers to indirect methods of control: it is adapted to perform comparative measurements of the degree of air pollution, for example, more or less, in different industrial premises or at different times. If it is necessary to determine the absolute values of air pollution, it is required to initially calibrate the output device of the device on dusty gases with a known dispersion of aerosols. If the composition and nature of aerosol particles in the atmospheric air are constant, the device must be calibrated once [8, p.20].
Tests and control measurements of the proposed device were carried out in the conditions of dustiness of the air of the weaving factory. The sensitivity of the device measurement to highly dispersed particles turned out to be high, which led to a decrease in the operating current by 4-5 ^A, which does not affect the high efficiency of air purification.
This means that highly dispersed particles are charged with a limiting charge, and its value no longer depends on the increase in the density of aeroions in the discharge gap. With an increase in the dustiness of the
air, by about 2 times, the operating current is already reduced by 6 ^A, which shows the existence of some nonlinearity depending on the discharge current on the degree of atmospheric air pollution, which is the subject of further research by the authors of the article [9, c.947; 10, c.208].
References
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