CN211013928U - Small ion collection type dust monitoring device based on α radioactive source - Google Patents
Small ion collection type dust monitoring device based on α radioactive source Download PDFInfo
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Abstract
The utility model provides a small-size ion collection formula dust monitoring devices based on α radiation source, including sensing system, utilize the tubulose to be used for attracting the air and measure the dust content in the air, including the section of admitting air and the section of giving vent to anger, and be located the electric field section in the middle of and arranged the negative pole silk on the axis of electric field section, arranged the absorption wall on the circumference inside wall, measurement system, for the negative pole silk provides appointed negative pressure, simultaneous measurement the negative pressure variation of negative pole silk, data processing system receives the negative pressure variation value calculates the voltage (induced-current) of negative pole silk output obtains the linear relation of test place dust concentration and induced-current, and then reachs the dust concentration value in test place now, the utility model discloses an organic combination of radioisotope characteristic and ion collection formula sensor technique forms a novel work place productivity dust monitoring sensing system, and this sensing system has very high sensitivity, and 1 mu m particle diameter dust measurement lower limit is about 0.1mg/m 3.
Description
Technical Field
The utility model relates to an environment dust measurement field, in particular to ion collection type dust small-size monitoring devices based on α radiation source real-time measurement dust concentration.
Background
The dust is solid particles suspended in the air, and the high-concentration dust can cause the continuous rise of the temperature of the near-surface space, thereby being an environmental factor causing the global 'greenhouse effect' and also being one of the main causes of environmental pollution and ecological deterioration of working and living places in China.
Dust widely existing in workplaces can induce various occupational diseases, workers can seriously harm body health by passively inhaling excessive respirable dust in the professional activities, and finally develop irreversible occupational silicosis and pneumoconiosis, lose labor capacity and aggravate social and family burdens; in addition, the concentration of productive dust is further increased, and the possibility of explosion is also existed, thus seriously threatening the production safety of industrial and mining enterprises.
At present, the mature dust monitoring technology comprises a filter membrane weighing method, a light scattering and absorption method, an acoustic method, a piezoelectric vibration method, an β ray mass absorption method and the like, and the technical principles of the methods are analyzed as follows:
(1) and (3) a filter membrane weighing method: the dust concentration level is calculated by weighing the mass difference of the filter membranes before and after sampling.
(2) Light scattering and absorption methods: the optical absorption method is that a laser is used to generate incident light to irradiate a light splitter, the light splitter divides the incident light into two beams of light with equal intensity, one beam of light is used as a signal beam to irradiate a measuring area and then enters a photoelectric detector, the other beam of light is used as a reference beam and directly enters the photoelectric detector, and due to the absorption and scattering effects of dust, the light intensity of the signal beam is weakened, and the difference value of the two signals is compared to carry out quantitative analysis.
The light scattering method is characterized in that a solid light source emits a near infrared ray or a laser parallel beam modulated by a pulse modulator, the near infrared ray or the laser parallel beam irradiates a measured object, dust particles scatter light in the direction, the scattered light is focused on a detector for detection, a voltage or current signal is amplified and output, and the signal is proportional to the dust concentration in a certain range. The angle between the receiver and the light source can be classified into forward scattering, side scattering and backward scattering.
(3) An acoustic method: a detection sound source and a receiver are placed in a dust area to be measured, when the detection sound source vibrates and penetrates through the dust area to be measured, the detection sound source is obstructed by solid particles to cause sound energy value loss, and at the moment, a corresponding function relation exists between the sound energy loss value of the sound source and the concentration content of the dust particles, so that a measurement signal can be obtained.
(4) Piezoelectric vibration method: two identical piezoelectric crystals (quartz crystal resonators) were used, one for reference comparison and the other as a measuring device placed in the sampling chamber. The filter belt is placed in the sampling chamber positioned in the area to be measured, and when the measured dust passes through the filter belt, the dust can be adsorbed on the filter belt, so that the change of the quality of the dust is caused, the change of the vibration frequency of the piezoelectric crystal in the sampling chamber is caused, the variation of the vibration frequency and the dust concentration are in a linear relation, and the mass concentration of the dust is obtained through measurement.
(5) β ray quality absorption method, when the ray passes through the test area, it interacts with dust particles, and the attenuation degree of ray beam intensity has an e-exponential function relation with dust particle concentration, the dynamic range of ray absorption method is wide, it can be measured in most spectral range, and it has the advantages of high measuring accuracy and high sensitivity, and β radioactive isotope is commonly used.
In the method, in order to meet the constant-speed sampling requirement given by the standard, the filter membrane weighing method needs to adjust the control of the sampling flow of the air pump (the sampling flow is comparable to the actual gas flow and flow field distribution of a place), and the measurement result is an average value after long-time accumulation and cannot reflect the real-time change of the dust concentration of the place. The filter membrane sample obtained by sampling needs to be analyzed and processed in a laboratory, belongs to an off-line measurement mode, and has a hysteresis effect. The requirement of real-time and continuous monitoring of the technology and a working place is greatly different, and although the technology is a standard method widely adopted at present, the field application of the technology is limited by a method principle.
Although the light scattering and light absorption method has high sensitivity and can realize on-line measurement, the measurement accuracy is affected by multiple factors such as light source monochromaticity deviation, dust particle size and morphology, distribution condition, medium non-uniformity, measured object color and the like, the reliability of long-term measurement results is not high, and the requirement of continuous measurement is difficult to meet. Generally, the method is only suitable for measuring low-concentration dust (environment level) and high-concentration gas-solid two-phase flow, and is not suitable for dust monitoring in a workplace because physical and chemical properties of a measured object are changed and a measurement result is distorted due to easy interaction among particles in a dust environment with large dust concentration change and complex components.
The acoustic method is to measure the dust concentration by using the acoustic energy loss value, and the accuracy of the measurement result is influenced by the changes of the speed, the pressure, the humidity and the temperature of the dust-containing gas, the dispersion degree difference of the dust particle size and the like, and the measurement result is unreliable.
The piezoelectric vibration method needs to remove dust particles deposited on the piezoelectric crystal during each measurement so as to obtain a reliable result. Therefore, the operation is complicated and the degree of automation is low, and it is not suitable for real-time on-line, long-time monitoring of dust concentration.
In addition, according to the conventional technical level achieved by the method, instruments and equipment are relatively precise and heavy, the maintenance and management cost is high, the requirements of the development trend of distributed sampling measurement cannot be met, meanwhile, under complex use conditions, the radiation protection management related to a large number of radiation source items has certain practical difficulties (for example, multiple data channels are integrated, the radiation source is likely to be unevenly distributed, multiple sets of monitoring systems are needed in places with large concentration variation differences, namely multiple sets of monitoring systems need to be configured), therefore, the β ray mass absorption method does not reflect the reliability of results and the radiation protection of work places in a contradiction manner, the balance application condition is very limited in the aspect of the radiation source distribution, the concentration variation difference is very large, the dust concentration distribution is still limited in real-time by using a large-flow field sampling speed measurement mode, and the dust concentration change principle is not limited in the field, no matter the dust concentration change is not limited by the real-time dust extraction speed measurement mode, the dust concentration change is still limited by the real-time dust extraction speed measurement mode, and the dust concentration change is not limited by the real-time dust-sampling principle.
In conclusion, the working place conditions are different, the dust concentration changes obviously along with the change of the production condition, in general conditions, the frequency and the time of dust exposure hazard of workers and the working state of microscopic labor are difficult to accurately master, the data obtained by conventional sampling detection (annual detection, evaluation detection, daily detection and the like) is greatly different from the actual level of dust exposure hazard of workers, and the risk degree of the occupational hazard of the working place caused by dust can not be accurately evaluated by the data, and appropriate and timely prevention and treatment measures can be guided to be taken. How to realize real-time and long-term continuous collection and online scientific analysis of dust concentration level data in a workplace gradually becomes a key point and a difficult point of dust monitoring technology development.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing a small-size monitoring devices of ion collection formula dust based on α radiation source real-time measurement dust concentration.
Particularly, the utility model provides a small-size ion collection formula dust monitoring devices based on α radiation source, including sensing system, utilize the tubulose to be used for attracting the air and measure the dust content in the air, include to the air that gets into utilize the α radiation source to carry out the air inlet section of ionization, the section of giving vent to anger of exhaust air, and one end with the air inlet section is connected the electric field section that the other end is connected with the section of giving vent to anger, arrange the negative pole silk that absorbs positive ion on the axis of electric field section, arrange the absorption wall that absorbs negative electron on the circumference inside wall;
the measuring system is used for providing specified negative pressure for the cathode wire and measuring the negative pressure variation of the cathode wire;
and the data processing system is used for receiving the negative pressure change value, calculating the voltage (induced current) output by the cathode wire according to the amount of motion of the charged dust particles in the detection cavity to the electrode with opposite polarity under the composite action of the electric field force and the air drag force formed by the air suction pump, obtaining the linear relation between the dust concentration of the test site and the induced current, and further obtaining the dust concentration value of the current test site.
The utility model discloses an in one embodiment, the electric field section with the section of admitting air with the section of giving vent to anger is movable threaded connection the dead lever that passes the centre of a circle is installed perpendicularly respectively to the both ends mouth of electric field section, the both ends of high-pressure negative pole silk are fixed respectively on the dead lever at both ends.
In one embodiment of the present invention, the two ends of the housing are conical contraction structures respectively.
In one embodiment of the present invention, the length ratio of the air inlet section, the electric field section and the air outlet section is 1: 1: 1, the total weight of the sensor is less than 100g, and the volume of the housing is Φ 1.0-5.0 cm × 5.0.0-15.0 cm.
In one embodiment of the present invention, the α radiation sources are arranged in an array on an inner surface of the air intake section of the housing.
In one embodiment of the present invention, the α radioactive source has a total activity of 1 × 105～1×106Bq, the cathode filament phi is made of metal materials with the thickness of 0.01-0.1 mm, negative high voltage loaded on the cathode filament is 0-2260V, and the output end of the cathode filament is connected with 1-20G of resistor.
The utility model discloses an in an embodiment, the port of the section of giving vent to anger is connected with the aspiration pump, the extraction flow speed of aspiration pump is less than or equal to 1L/min.
In an embodiment of the present invention, the measuring system includes a primary winding for externally connecting voltage, and an advanced winding for connecting the cathode filament, the primary winding is adjusted to output to a rectifier transformer for the advanced winding voltage, and receive the voltage output by the rectifier transformer and the measuring winding for the cathode filament changing voltage, the measuring winding transmits the measuring result to the data processing system.
In an embodiment of the present invention, the voltage algorithm of the cathode filament output is as follows:
wherein Qe is the charge number, Q is the charge saturation value, M is a multiplication factor, N is the number of the dust particles with positive charges, and Q is the charge positive electricity quantity of the dust particles;
the multiplication factor M is calculated as follows:
wherein Δ U is the electric field energy obtained by 2 consecutive collisions of positive ions entering the corona field, k represents the lowest applied electric field strength E/Σ n value that can be multiplied, Σ n being a constant introduced by parameters related to the dust particle diameter, charge-to-mass ratio, and the like, and n is a constant introduced by the particle diameter, charge-to-mass ratio, and the like of the dustcIn terms of dust concentration, mg/m3The delta U and k values are obtained by measuring the relation curve of M and U of charged dust with a certain distribution through experiments, the U external voltage, the radius of the cathode filament a and the radius of the collector b.
The utility model discloses a combine radioisotope characteristic and ion collection formula sensor technique, form a novel workplace production nature dust monitoring sensing system, this sensing system has very high sensitivity, 1 mu m particle diameter dust is measured the lower limit and is about 0.1mg/m 3. measuring object's selectivity is strong, the range of application is extensive, be applicable to the monitoring of different dispersity and different grade type dust concentration, whole sensing system can realize the miniaturization, probe total weight is no longer than 100g, the geometric volume is phi 1.0 ~ 5.0cm × 5.0.0 ~ 15.0 cm. simple to operate is nimble, can realize the distributed setting, the line-collecting type processing of data collection adopts low-activity α radiation source as core component, can accord with the relevant requirement of china's radiation protection standard, effectively reduce radiation protection burden and administrative cost, do not cause ecological environment pollution.
The measurement system works in a low-speed sampling mode, can accurately reflect the natural distribution and concentration change of dust in a workplace, is suitable for various working modes (such as time-weighted average concentration allowable value PC-TWA or short-time exposure concentration limit value STE L and the like), and can provide key support data for dust hazard prevention and control.
Drawings
Fig. 1 is a schematic connection diagram of a dust monitoring system according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of a sensing system according to an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a measurement system according to an embodiment of the present invention;
FIG. 4 is a schematic view of the movement of positively charged dust particles in the electric field section;
FIG. 5 is a graph showing the output signal as a function of the applied voltage (0-2010V) under static conditions;
FIG. 6 is a schematic diagram showing the output value of the induced current signal varying with the intensity of the applied electric field;
FIG. 7 is a linear relationship of dust concentration to induced current;
FIG. 8 is a schematic diagram showing the comparison between the measured data of the filter membrane gravimetric method and the sensor method according to an embodiment of the present invention;
fig. 9 is a schematic diagram of a data transmission process according to an embodiment of the present invention.
Detailed Description
As shown in fig. 1, one embodiment of the present invention provides a small ion collection type dust monitoring system based on α radioactive source, which includes a sensing system for absorbing external dust, a measuring system for measuring the change of the sensing system, and a data processing system for receiving the data of the measuring system and calculating the dust content.
As shown in figure 2, the sensing system 1 comprises a hollow measuring pipe, two ends of the measuring pipe are in a contracted conical shape, the inside of the measuring pipe is sequentially divided into an air inlet section 2, an electric field section 3 and an air outlet section 4, the length ratio of the air inlet section to the electric field section to the air outlet section is 1: 1: 1, the total weight of the sensing system 1 is lower than 100g, and the volume of the measuring pipe is phi 1.0-5.0 cm × 5.0.0-15.0 cm.
In the air intake section 2, α radioactive sources 21 are arranged in an array on the inner circumferential surface of the measuring tube to ionize the incoming air, and the air is ionized to generate a large number of positive and negative ions to form low-density non-equilibrium space plasma.
Two ends of the electric field section 3 are respectively provided with a fixing rod in a mode of being vertical to the axial lead, the centers of the two fixing rods are provided with cathode filaments 31 which are superposed with the axial lead of the electric field section 3 to collect positive ions, and the inner circumferential surface of the electric field section 3 is covered with a collector 32 for collecting negative ions; the charged dust particles move to the electrode with opposite polarity under the composite action of the electric field force and the air drag force (inertia force) formed by the air suction pump, when the dust particles drift to be close to the cathode wire 31 and the collector 32, the current formed by the induced charges is collected and processed, and finally a voltage signal is output to the measuring system.
The air outlet section 4 is used for discharging the treated air, and an air suction pump is arranged at the outlet end, so that the air can enter the measuring pipe from the air inlet section.
As shown in figure 3, the measuring system mainly comprises a rectifier transformer ZB, a primary winding W1, a cathode high-voltage winding W2 and a measuring winding W3, wherein the primary winding circuit is connected with a power frequency voltage 380V to provide the power and power consumption requirements of the measuring system, a collector of the high-voltage winding is connected with the ground and is supplied with negative high voltage required by the sensing system through a high-voltage silicon rectifier bridge circuit (GZ L), a cathode wire 31 is connected with a negative high-voltage output end of the sensing system, the measuring winding and the high-voltage winding share a grounding end and structurally ensures that the measuring winding and the high-voltage winding have coupling performance, the measuring winding is connected with a magnetoelectric direct-current voltmeter to obtain branch voltage signals after carrying out bridge rectification (Z L) on output signals, the bridge rectifier circuit mainly has the function of shaping alternating current by using a high-voltage silicon diode (or rectifier diode) to form direct-current high voltage and simultaneously prevents damage of the reverse current to the measuring circuit, and the magnetoelectric direct-current voltage fusing resistor.
The data processing system takes a voltage value as an output signal through a linear relation between the dust concentration of a place and an induced current output signal, and can calculate the dust concentration, wherein the specific calculation process is as follows:
1. the dust particle charge and particle number parameter relationship is as follows:
the actual measurement of the dust dispersion at the test site was determined to fit the Rosson-Lamg distribution (bias function).
2. Electrostatic field physical mechanism analysis:
neglecting the influence of gravity and flow field turbulence, the motion of charged dust (charged particles) entering the electrostatic field is divided into:
A) the charged dust particles (charged particles) have a horizontal initial velocity component V0(parallel to the cathode filament and collector) and vertical initial velocity V⊥(perpendicular to cathode filament and collector) composition, dust particles in horizontal direction at velocity V0Making uniform linear motion;
B) the charged particles are subjected to a constant electrostatic field force perpendicular to the cathode filament and make uniform accelerated linear motion in the vertical direction, and the acceleration can be expressed as formula (1).
Wherein q is the charge quantity carried by the dust particles, and the unit mC; u is the static voltage, unit V; d is the distance between the cathode filament and the collector in cm; m is the weight of the dust particles, unit g;
the resultant velocity of the dust particles in the vertical direction is represented by formula (2):
the velocity of the charged dust particles in the vertical direction is thus determined by the combined action of the air drag force (inertial force) and the electrostatic field (electric force), the positively charged dust particles having a combined velocity VΣMaking the cathode filament move centripetally. A schematic of the movement of positively charged dust particles within the electric field section 32 is shown in figure 4.
C) Positive charges are accumulated in the space near the negative high-voltage cathode filament to form an intrinsic electric field (corona field) with the field intensity of ErThe intrinsic electric field strength can be expressed as formula (3);
in the formula: r is the radial distance of a point on the axis from the center point of the sphere in cm. N is the number of positively charged dust particles, q is the amount of positive charge of the dust particles, in mC.
The total electric field intensity is electrostatic field intensity E and intrinsic electric field intensity ErAnd when the E and the Er are in the same order level or the number of electrons emitted by the cathode filament reaches a critical value, glow discharge occurs near the cathode filament, and positive charge accumulation (corona field) is formed, namely the intrinsic electric field. The presence of the intrinsic electric field enhances the electric field strength between the positive charge and the cathode filament, while weakening the electric field strength directed to the ground (collector).
The drift speed of the charged dust particles in the electrostatic field is gradually increased, and the charged dust particles finally enter the corona field. Along with the gradual increase of high pressure, the electrostatic field intensity is constantly strengthened, can divide into 3 regions with the process of ion drift and effect in the electrostatic field.
The I area is called a composite area, the applied voltage U is very small, the ion drift rate is very small, the free diffusion composite effect of charged dust particles plays a main role, the number of positive ions collected on an electrode is very small, the ionization collision effect in a corona field is not severe, and the number of induced charges (induced current) is also very small.
The region II is called a saturation region, when an external voltage reaches a certain value, the composite effect is inhibited, all dust particles (electrons and ions) entering an electrostatic field are collected to reach saturation, the charge saturation value Q is qN, the region is also called a plateau region, the plateau region part is increased along with the external high voltage, and the increase of induced charges (induced current) is not obvious.
The III area is called proportional area, after the applied voltage is raised over a certain value U, the ions are fed into corona field area, the applied electric field and intrinsic electric field make electrons and ions obtain enough energy to produce secondary ionization process several times and produce secondary ions, so that the total charge quantity collected is greater than saturation value, and the number of the charges collected on the electrode is QeAs the applied voltage further increases, the multiplication factor M becomes larger, and the induced charge Q is amplified in proportion to the applied voltagee(induced current) to gradually intensify the ionization discharge. The sensor operates primarily in this region.
In this case, the sensor probe can be regarded as a variable capacitor, and the output voltage signal is expressed by equation (4):
3. multiplying and amplifying the quantitative relation between the M value and the external voltage U in the proportional area;
the charged dust particles drift to the anode and the cathode respectively, and the closer the positively (negatively) charged dust particles drift to the cathode (anode), the larger the electric field, the higher the ion migration rate. When the ion reaches a certain distance (mean free path), the ionization collision probability is extremely high, and the energy obtained by the ion from the electric field is enough to generate multiple ionization collisions with gas molecules, namely more new ion pairs are generated, and a large amount of electrons and positive ions are generated as a result of continuous proliferation. At the moment, the external electric field intensity is in a proportional region, avalanche multiplication occurs, the output voltage signal is exponentially increased and rapidly rises to a saturation voltage, and at the moment, the intrinsic electric field intensity can reach the level of 100 kV-400 kV/cm. Referring to a Diethorn formula of the action of an electrostatic field, and introducing a non-equilibrium plasma reduced electric field theory, the multiplication relation of the sensor can be expressed as a formula (5);
Δ U is the electric field energy obtained in 2 consecutive collisions of positive ions entering the corona field, k represents the lowest applied electric field strength E/Σ n value that can be multiplied, and Σ n is a constant introduced by relevant parameters such as the dust particle diameter and the charge-to-mass ratio. n iscIn terms of dust concentration, mg/m3. Through the relation curve of M and U measured by experiments on charged dust with a certain distribution, the values of delta U and k can be determined. M is a multiplication factor, U is applied with voltage, a is the radius of the cathode filament, and b is the radius of the collector.
Analysis of the field segments 32 shows that positive ions drift into the corona field before multiplication occurs, and that each ion undergoes the same multiplication regardless of where it initially entered the electrostatic field, thereby producing a position-independent amplitude signal of the multiplied saturation value.
The sensing system has very high sensitivity, the lower limit of the 1 mu m particle size dust measurement is about 0.1mg/m < 3 >, the selectivity of a measured object is strong, the application range is wide, and the sensing system is suitable for monitoring different dispersion degrees and different types of dust concentrations.
The measurement system works in a low-speed sampling mode, can accurately reflect the natural distribution and concentration change of dust in a workplace, is suitable for various working modes (such as time-weighted average concentration allowable value PC-TWA or short-time exposure concentration limit value STE L and the like), and can provide key support data for dust hazard prevention and control.
The following examples further illustrate embodiments of the present invention.
(1) Static testing
The particles emitted by the radioactive source ionize the ambient air to generate free electrons and positive ions, and a dynamic reverse process of compounding the positive ions, the electrons and the negative ions exists at the same time. Background test is carried out in a laboratory dust environment (without a pre-separation system), ion pairs are freely diffused to a collecting electric field area (a second area), and the Fick first law shows that the flow of a diffusion substance passing through a unit sectional area perpendicular to the diffusion direction in unit time (called diffusion flux, represented by J) is in direct proportion to the concentration gradient of the section, namely the larger the concentration gradient is, the larger the diffusion flux is;
wherein D is called the diffusion coefficient (m)2S) C is the volume concentration of the diffusing species (constituent element)(number of atoms/m)3Or kg/m3) dC/dx is a concentration gradient, and the "-" indicates that the diffusion direction is opposite to the concentration gradient, i.e., a diffusion component diffuses from a high concentration region to a low concentration region, the total activity of the arrangement inside the linear tube sensor is 1 × 105～1×106The α radioactive source of Bq, the central cathode filament phi is 0.01-0.2 mm metal material, the length of the upstream air inlet section is 5cm, the length of the electric field section is 6cm, the length of the downstream air outlet section is 5 cm., the central cathode filament is loaded with 0-2260V negative high voltage, the output end is connected with 0.1-20G resistor, the voltage value is taken as an output signal, and under the static condition, the change curve of the voltage value along with the load negative high voltage is shown in figure 5.
Analysis of the results of fig. 5 shows that when the negative pressure is applied, the electric field force applied to the ions is small, the ion recombination effect is significant, the number of collected ions in unit time is small, and the output voltage (signal) does not change much in the range of 0-1500V. When the loading negative pressure exceeds 1600V, the electric field is continuously enhanced, the ion recombination is weakened, the migration rate is increased, the number of collected ions in unit time is increased, when the loading negative pressure is higher than 1600V, the output voltage value is increased, and when the loading negative pressure is higher than 2040V, the average value of the output voltage is about 6.5V.
(2) Low flow extraction (background) test
Background micro-dust environment (not connected with the pre-separation system), when air is extracted at low flow speed, the air outlet end is connected with a diaphragm air pump to slowly extract air at the flow rate of less than or equal to 1L/min, the convection multiplication effect is gradually obvious along with the increase of high pressure caused by air extraction, the change of the output voltage obtained by testing is shown in table 1, after micro-dust (the particle size is less than 0.1 mu m) in the background air is charged, the micro-dust reaches a dust collection electric field area through diffusion and convection movement, and when the negative high pressure is 1960V, the saturated output value is 10.8V.
TABLE 1 output signal varying with load voltage (1260-1985V) at low extraction speed
The results of static tests show that fine dust (less than 0.1 μm) has a great influence on the experimental results. The particle size of the dust particles becomes smaller, the particle number is approximately in 3-power growth relation,i.e., the number of particles of dust having a particle size of 0.25 μm or about 2.5 μm (2.5/0.25)31000 times. Through estimation, if the tiny dust enters the charging area without control, the charging total amount of the tiny dust exceeds 92%, and the saturation charging efficiency of the respiratory dust and the accuracy of a measurement result are seriously influenced. Therefore, the fine dust should be pre-separated before sampling.
(3) Respiratory dust test
According to section 2 of determination of dust in workplace air: the requirement of the respiratory dust concentration of GBZ/T192.2-2007 is that the dust concentration measurement pre-separation should achieve the dust aerodynamic diameter distribution below 7.07 μm, and the dust collection efficiency of the aerodynamic diameter 5 μm is 50%. The dust concentration of an ore transfer point (sampling point) in a certain place is measured in a traditional filter membrane mode, and in order to meet the requirement that the particle size distribution of sampled dust meets the requirement, a cyclone separation device is adopted for pre-separation, and a developed sensor is adopted for simultaneous measurement. The signal output of the sensor sensing current with high voltage change is shown in fig. 6.
As can be seen from fig. 6, when the applied electric field strength is 2.6kV/cm, the voltammetric V-I relationship is good, and the corresponding induced current value is y 94.4 × e0.31×2.6≈2.1× 103And fA, which indicates that 2.6kV/cm can be selected as the applied electric field intensity for measurement, the pre-separation system controls the dust particles which can enter the sensor to be mainly distributed in the respiratory dust range, the diaphragm pump is adopted to pump air to provide the inertia force for the dust particles to enter the sensor, when the flow is 0.4L/min, the maximum flow velocity of the charged dust particles is estimated to be about 3cm/s, and the flow velocity range is about 1-3 cm/s, and the obtained test results are shown in Table 2.
Table 2 respirable dust concentration test results units: pA is
According to the table 2, the linear relation between the dust concentration of the place and the output signal of the induced current can be obtained, as shown in fig. 7, the output end is connected with 0.1-20G of resistors, and the voltage value is taken as the output signal, so that the dust concentration can be calculated.
(4) Dust concentration measurement experiment results in different places
For verifying the utility model discloses the sensor system performance of design development has selected several kinds of typical workplaces, has carried out the contrast experiment to its dust concentration. The comparative experiment adopts a filter membrane weight method (weight method for short) and a sensor system (sensor method for short). The experimental data are shown in tables 3 and 4.
TABLE 3 workplace dust concentration measurement data I
Table 4 workplace dust concentration measurement data II
(5) Real-time online monitoring verification
At the same time, the dust concentration is measured at a certain place (a filter membrane weight method and a sensor method). The filter weight method works for 1 hour (15 minutes cumulatively, i.e. 900 s-counts), while the sensor method can measure 360 data (1 n/10s counts per second), and is absolutely advantageous in the comprehensiveness and continuity of the data. The filter membrane gravimetric method cannot measure the dust concentration peak value due to the method principle, so that the continuous measurement is more scientific and effective. The highest concentration obtained by the traditional filter membrane weight method in the experiment is 1.69mg/m3The highest concentration obtained by the sensor method is 1.79mg/m3Showing a clear technical advantage, see fig. 8.
In this embodiment, the measurement system sends the collected data to the data processing system or the remote data receiving center, so that one data processing system can simultaneously control and manage a plurality of sensing systems, as shown in fig. 9. The data processing system can also send alarm signals to the outside through the measuring system or the sensing system when measuring that the dust at the position of a certain sensing system exceeds the standard.
Thus, it should be appreciated by those skilled in the art that while a number of exemplary embodiments of the invention have been shown and described in detail herein, many other variations and modifications can be made, consistent with the principles of the invention, which are directly determined or derived from the disclosure herein, without departing from the spirit and scope of the invention. Accordingly, the scope of the present invention should be understood and interpreted to cover all such other variations or modifications.
Claims (9)
1. Small-size ion collection formula dust monitoring device based on α radiation source, its characterized in that includes:
the sensing system is used for sucking air and measuring the dust content in the air by utilizing a tubular shape, and comprises an air inlet section for ionizing the entering air by utilizing an α radioactive source, an air outlet section for discharging the air, and an electric field section, wherein one end of the electric field section is connected with the air inlet section, the other end of the electric field section is connected with the air outlet section, cathode wires for absorbing positive ions are arranged on the axis of the electric field section, and an absorbing wall for absorbing negative electrons is arranged on the circumferential inner side wall of the electric field section;
the measuring system is used for providing specified negative pressure for the cathode wire and measuring the negative pressure variation of the cathode wire;
and the data processing system is used for receiving the negative pressure change value, calculating the voltage output by the cathode wire according to the amount of motion of the charged dust particles in the detection cavity to the electrode with opposite polarity under the composite action of the electric field force and the air drag force formed by the air suction pump, obtaining the linear relation between the dust concentration of the test site and the induced current, and further obtaining the dust concentration value of the current test site.
2. The compact ion collecting dust monitoring device according to claim 1,
the electric field section is movably connected with the air inlet section and the air outlet section through threads, two end ports of the electric field section are respectively and vertically provided with a fixed rod penetrating through the circle center, and two ends of the cathode filament are respectively fixed on the fixed rods at the two ends.
3. The compact ion collecting dust monitoring device according to claim 2,
two ends of the shell are respectively provided with a conical contraction structure.
4. The compact ion collecting dust monitoring device according to claim 3,
the length ratio of the air inlet segment to the electric field segment to the air outlet segment is 1: 1: 1, the total weight of the sensing system is lower than 100g, and the volume of the shell is phi 1.0-5.0 cm × 5.0.0-15.0 cm.
5. The compact ion collecting dust monitoring device according to claim 4,
the α radiation sources are arranged in an array on an interior surface of the air intake section of the housing.
6. The compact ion collecting dust monitoring device according to claim 5,
the total activity of α radioactive source is 1 × 105～1×106Bq, the cathode filament phi is made of metal materials with the thickness of 0.01-0.1 mm, negative high voltage loaded on the cathode filament is 0-2260V, and the output end of the cathode filament is connected with 1-20G of resistor.
7. The compact ion collecting dust monitoring device according to claim 1,
and the port of the air outlet section is connected with an air pump, and the pumping flow speed of the air pump is less than or equal to 1L/min.
8. The compact ion collecting dust monitoring device according to claim 1,
the measuring system comprises a primary winding externally connected with voltage, an advanced winding connected with the cathode wire, a rectifier transformer for regulating the voltage output from the primary winding to the advanced winding, and a measuring winding for receiving the voltage output from the rectifier transformer and the variation voltage of the cathode wire, wherein the measuring winding transmits the measuring result to the data processing system.
9. The compact ion collecting dust monitoring device according to claim 1,
the voltage algorithm output by the cathode filament is as follows:
wherein Qe is the charge number, Q is the charge saturation value, M is a multiplication factor, N is the number of the dust particles with positive charges, and Q is the charge positive electricity quantity of the dust particles;
the multiplication factor M is calculated as follows:
wherein Δ U is the electric field energy obtained by 2 consecutive collisions of positive ions entering the corona field, k represents the lowest applied electric field strength E/Σ n value that can be multiplied, Σ n being a constant introduced by parameters relating to the particle diameter and charge-to-mass ratio of the dust, and n is a constant introduced by parameters relating to the particle diameter and charge-to-mass ratio of the dustcIn terms of dust concentration, mg/m3The delta U and k values are obtained by measuring the relation curve of M and U of charged dust with a certain distribution through experiments, the U external voltage, the radius of the cathode filament a and the radius of the collector b.
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Denomination of utility model: base on a A Small Ion Collecting Dust Monitoring Device for Radiation Sources Effective date of registration: 20231227 Granted publication date: 20200714 Pledgee: Hebei Bazhou Rural Commercial Bank Co.,Ltd. Pledgor: BAZHOU DIHAI YUNTIAN ENVIRONMENTAL PROTECTION TECHNOLOGY Co.,Ltd. Registration number: Y2023980074557 |