SU1513393A1 - Method of detecting dust content of inert and electropositive gases by submicron particles - Google Patents

Abstract

The invention relates to the analysis of dispersed systems in gases, in particular, to a method for detecting low dustiness of inert and electropositive gases, and can be used in solving environmental problems to control process hygiene and the degree of purity of process gases. The purpose of the invention is to increase the detection sensitivity when measuring low dustiness by increasing the speed of unipolar diffusion charging of particles. To achieve this goal, the particles are unipolarly charged by nonthermal electrons. The charge is carried out at a constant value of the charge parameter, defined as the product of the electron conductivity of the gas and the charge time. According to the measured values of the transfer current in the saturation region of dispersed particles with electrons and the calibration dependence, or the linear dependence of the transfer current on the measurement of the electric field intensity in the range from 50 to 600 V / cm, the dust content of inert and electropositive gases by submicron particles is measured. 2 hp ff, 2 ill.

Description

The invention relates to the field of analysis of dispersed systems in gases, in particular to a method for detecting small quantities of inert and electropositive gases, and can be used in the field of environmental protection, when testing filters, to control process hygiene and cleanliness of process gases.

The purpose of the invention is to increase the detection sensitivity in measuring small quantities by increasing the rate of unipolar diffusion charging of particles.

FIG. 1 shows a diagram of an apparatus for carrying out the method; in fig. 2 - calibration dependence.

The device contains a pipe 1

for introducing the analyzed gas, a grid electrode 2 and a flat electrode 3 connected to a voltage source 4, a high-voltage voltage source 5 connected to a corona-forming wire electrode 6 with a diameter of 25-50 microns, parallel to electrodes 2 and 3, and glass a fiber filter 7 connected to an electrometer 8 for measuring current

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00 with

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Transfer of charged aerosol particles that occur when they are deposited on the filter fibers. Microammeter 9 is designed to determine the electrical conductivity of the gas Gg in the charge zone from the density of the electron current Gg-E, where E is the intensity of the external electric field in the zone 10.JO

The method is carried out as follows.

The test gas flows through the nozzle 1 into the charging zone 10 located between the grounded grid 15 electrode 2 and the flat electrode 3 connected to the voltage source 4. In the charging zone, the particles are charged by electrons, which are formed as a result of the supply of a high negative voltage from a high voltage source 5 to the corona wire 6 with a diameter of 25-50 microns. The electrons are pulled into the charging zone through the grid electrode 25 by an electric field, which is created in zone 10 with the help of a voltage source 4. Particles are charged in zone 10 by unipolar non-thermal electrons in the diffusion mode 30 at a constant value of the charge parameter, defined as the product of the electronic conductivity of the gas and the particle-charge time t. Charging of particles of os1; valid k) t at E 35 50–1300 V / cm and. Avg t 10 –10 4oM) M From the charging zone, the particle enters a glass fiber (type FSV / P) filter 7, connected to an electrometer 8 to measure the particle transport current 40 that occurs when they are deposited on the filter fibers. But the values of the In transfer current, measured at various E at 6 t const by known theoretical formulas or by the calibration curve 45, judge the lower limit and fluctuations of the inert and electropositive gases by submicron particles. Microammeter 9 measures the magnitude of the electron current on the current j Q b E and, accordingly, the conductivity G g in the charging zone.

The calculation of low dustiness is performed as follows.

In the range of K I: 100-500 / cm at

.e

c c: onst HMMt JicHvie Ip - m ii can be approximated by linear dependence with sufficient accuracy for a straight line

1 "k-E + 1c, (1) where k is KOHciaHTa;

(, is the transfer current at.

The value of 1 almost coincides with the magnitude of the current per- hance of the particles of I; , reserve Jix unipolar ions for E - O and 1 CQ t, since

About electron temperature T ,,

T

and electrons are in equilibrium with gas molecules (T is the gas temperature (1 is the ionic conductivity of the gas). From (1) it can be obtained that

i ,, j / -E; - iJ, Ы

where 1 and the transport currents corresponding to the strengths of the electric field E and E.

Thus, measuring Ig current, for example, at E 200 and E 400 V / cm, it is possible to determine 1 o from (2) and then calculate the charge of particles of a known size by the formula obtained to calculate the average charge of particles charged by gas ions diffusion mode:

. q, t- - || -l8 (1.4-10 J: t),

(3)

where Tj is the charge of particles in elementary

units;

, 8 cgse hell. - electron charge; , 38 erg / K — constant Boltzmann;

g is the particle radius, see. Having determined, the countable particle concentration, 7qj & Where

LZ ..

in the gas flow.

The calculation can be carried out using the calibration dependencies. For example, the measured values as a function of E in helium and nitrogen for dibutyl phthalate particles c, 3 µm at (5. (0 m m) c

shown in figure 2.

From the analysis of these data, it follows that the ratio weakly depends on the change in the field from E 1000 to -1300 V / cm, i.e. particle saturation with charge occurs and, accordingly, the transfer current tends to the limiting value — to the point (similar results were obtained for submicron particles in argon). This makes it possible to measure small dust by measuring the BOMHufi curve to estimate rse. Iinqnny

I.

At the same time, there is a lot of fun

The small values of ap1) llei} and) stati increases by an increase of Ig / Ij times compared to the sensitivity of their detection by measuring the current of the transport of particles, the charge, x unynolon non at the same values of E and C.

PRI me R. A stream of dibutyl- particles (and alat with a radius gj; U, 3 microns in helium is passed with a flow rate of 1000 cm through the charging zone, in which the constant value of the electronic conductivity is 6 2.510 (Ohm-m). t 0.1 s. With an increase in the voltage of the electric field in the charge zone from 50 to 500 V / cm, the temperature of the electrons varies from 1200 to 8800 K, the charge of particles qg from 39 to 220 e, and the transfer current increases linearly from 2.5-10 to U .. Respectively,, 2-10 and countable concentration of particles Nlr410 particles / cm, Saturation current I i 2

ten

A. In the case of the charge of particles with positive ions at (-Gg t 2.5.10 (Ohm-m)), the value of Ij increases only from 1.35 liters to 1.8-10 A with increasing E from 50 to 500 V / cm. Thus, the ratio is 7, I at E 500 V / cm, which makes it possible to extend the lower limit of registration of such small particles by almost 8 times.

Claims (3)

1. A method for detecting the dust content of inert X and electropositive gases by sumicronic particles, including the creation of an ionization zone for gases and a particle loading zone, passing the test gas flow through the charging zone, unipolar charging of particles when an external electric field is applied at a constant the value of the charging parameter, defined as the product of the gas conductivity by the charging time, characterized in that, in order to increase the detection sensitivity of low dustiness with H3MepeHvm by increasing the speed by fusional charge of particles, their unipolarly charged by nonthermal electrons at a constant value of the electronic conductivity of the gas, the dependence of the transfer current on the voltage of the electric field, which determines the dust content of gases by sumicron particles, is determined. 2. A method according to claim 1, characterized in that the entrainment of gases is determined by the magnitude of the current values. 3. The method according to claim 1, characterized in that the dust content 1 gas is determined by the linear dependence of the transfer current on the electric field strength of 100-500 V / cm. 500 Editor P. Bobkova Compiled by M.Roganev Tehred A. Kravchuk Order 6075/45 Circulation 789 VNIIPI State Committee for Inventions and Discoveries under the State Committee on Science and Technology of the USSR 113033, Moscow, Zh-35, 4/5 Raushsk nab. Production and Publishing Combine Patent, Uzhgorod, st. Gagarin, 101 WOO E.BJCM Tsig.2 Proofreader E. Lonchakova Subscription