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Measurement of Dust Concentration

#1506


Design and Creation of Measuring Base for Determination of Mass Dust Concentration in Broad Ecological and Industrial Applications

Tech Area / Field

  • ENV-APC/Air Pollution and Control/Environment
  • INS-MEA/Measuring Instruments/Instrumentation

Status
3 Approved without Funding

Registration date
18.04.1999

Leading Institute
NPO Geophysica / Geophisica-Art, Russia, Moscow

Supporting institutes

  • Scientific & Production Association “Typhoon”, Russia, Kaluga reg., Obninsk

Collaborators

  • University of Uppsala / Meteorology Institute, Sweden, Uppsala

Project summary

The constant growth of power consumption and output of various production with use of natural raw resources and with synthesis of manufactured materials essentially changes environment of the person, in particular significantly increases air pollution in a vicinity of the factories and inside their premises. In this connection the determination of mass concentration of a dust in air acquires the greater practical significance. Thus a timeliness at monitoring of the reliable data about a dust air content goes out at first.

The project objective is a research of physical principles, development of a methodology and creation experimental specimens of technical means (devices) for measurement of aerosol particles mass concentration for a broad range of its changes.

Among various methods of aerosol concentration measurement the most broad propagation was received the optical methods, based on the registration of diffused light by each separate particle of light and on the account of impulses (counters of particles), or based on the measurement of direct attenuation of light, transmitting through medium which become muddy by particles (route transparency meters). Devices nephelometer type are known also. They are based on registration of light, diffused in some space of muddy medium (by ensemble of particles) at any angle to a direction of transmitting through this medium light.

The low detectability is a common disadvantage of a dust concentration meters (dust counters), based on listed methods.

It is connected with a fact that slightly muddied mediums only unsignificantly attenuate transmitting through them light in route transparency meters and here there are the difficulties in registration of small distinctions between transmitted through aerosol layer radiation and radiation falling at it.

The main reason of low particles counters detectability is a registration difficulty of light impulses from particles with dimensions less than 0.1...0.2 microns. The small particles contribution to a total dust content is not practically taken into account in these devices, but their concentration in real mediums usually significantly surpasses concentration of particles with dimensions more than 0.2 ...0.5 microns. Moreover the essential increase of information accumulation time is required at the process of measurements of small concentration (the speed of particles account is very small); this brings to nothing the timeliness, that is a main advantage of optical methods.

Part of received by a photocell diffused light flux is small (in relation to a complete diffused flux) in the devices nephelometer type, taking a light flux diffused by particles at some angle to a falling flux direction. It is necessary for increase of measurements accuracy to aspire to a small range of observation angles (diffusion angles) and, hence, to the small apertures of the receiver, that essentially increases a threshold of sensitivity. The diffused at aerosol particles light flux appears comparable and even less the flux diffused at molecules of pure air (not containing a dust particles) in the slightly muddied mediums, for example, in the air of working premises at “especially clean" productions; that requires a low threshold of sensitivity and high sensitivity of the device.

In this connection there are conducted rather intensive developments of new means of air dust content measurements in the world mainly with use of particles account and subsequent calculation of dust mass concentration. The problem of measurement results interpretation is leaved unsufficiently worked until today when takes place the transition from a liquid-trickle (spherical) form of particles to a solid form, nonspherical as a rule.

Within the scope of the present project it is supposed to investigate first of all connection of mass dust concentration with a level of a light flux, diffused on particles ensemble and to develop reliable methods for optical measurements calibration of aerosol concentration with reference to a solid particles with broad fractional structure. Thus the offered project is directed on development of high-effective measuring base for determination of mass dust concentration at broad ecological and industrial applications, methods of calibration and periodic calibration check.

The project bases on availability at the organizations-executors:


1) Unique aerosol chamber and optical equipment for atmosphere optics researches.
2) Certificated equipment complex for production and certification monodispersible sizing aerosol particles.
3) High-technology optical-mechanical and electronic production.

The project participants possess a competent staff, which has a scientific works and investigations in the field of aerosol study, a significant back-log in the whole complex of problems, connected with development of pointed measuring base.

The project goals are completely in agreement with ISTC objectives: a big team of weapon scientists will redirect their talents to peaceful activities, will receive the opportunities to integrate into international scientific community, to conduct applied researches for technology development in a field of environmental protection.

It will be as a result of project realization:


problems are solved at reliable interpretation of results at measurements of mass dust concentration by the optical method;
methods are developed at devices calibration with reference to solid aerosol with broad fractional structure;
experimental specimen of production-type meter of mass dust concentration is developed and made;
metrological researches of dust counter parameters are conducted;
laboratory and full-scale tests of the device are conducted.

Technical approach and methodology.

The research is based on an opportunity of measurement of light, diffused in some small volume of filled with dust air. Thus light is received, that diffused at such angle to the falling light, for which it is observed a small dependence between intensity of diffused light and particles fractional structure. It removes restriction at diffusing particles sizes, as it has a place at the time of measurements, based on sizes determination and account of particles with the subsequent calculation of their concentration. It is supposed to investigate an opportunity of measurement management simultaneously at two angles and to correct measurement results on the basis of the analysis of diffusion asymmetry indicatrix under possible changes of a dust fractional structure.

To our knowledge researches and developments are not executed at the given direction in CIS now.

The analysis of developments of leading western firms shows, that their main efforts are directed at creation of dust counters, working by a principle of direct radiation attenuation at the route (for example, firm SICK, Germany) or by a principle of sizes measurement and account of particles with the subsequent calculation of concentration (for example, firm Grimm Labor Technic). Marked circumstances determine offered nephelometer method in the present project.

The project is directed on the solution of the important technical and ecological problems, connected with monitoring of air or other gas mediums dust content and arising during the realization of especially clean technological processes in electronic, optical, pharmaceutics and similar industries and also in such ecologically dangerous industries, as power, metallurgy, petrochemistry, production of cement, mineral fertilizers etc.


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