Thermal precipitator

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A thermal precipitator is a device used to measure the amount of dust in the air . The measurement result is output as the number of particles per volume unit.

Measuring principle and application

The measuring principle is based on the fact that a defined amount of dusty air is conveyed through a narrow channel, the width of which is a few tenths of a millimeter, in which there is a heating wire . Due to thermophoresis , the particles contained in the air are transported across the direction of flow and deposited on a collecting plate. The collecting plate is then evaluated microscopically .

In particular, particles with a diameter of less than 1 µm can be quantified very well with the thermal precipitator. Due to the prevailing low speeds, no destruction of particle agglomerates is to be expected. Particles and any agglomerates formed do not experience any measurable thermal or mechanical stress.

However, when measuring mixed dusts containing transparent particles such as quartz , errors can occur in the evaluation. The entire collection plate must also always be evaluated microscopically, since the separated particles are fractionated due to the transport mechanism. The fractionation effect is usually less than it would have to be if there was a thermal equilibrium .

In addition to measuring dust , thermal precipitators can also be used for quality control of test aerosols .

The thermal precipitator was introduced into dust measurement technology in 1935. The dust measuring devices working according to this principle were standard devices in the mining industry in Great Britain for a long time . A VDI guideline from 1968 on measuring the dust concentration with a thermal precipitator was withdrawn in October 2009.

literature

  • VDI 2266 sheet 1: 1968-08 Measurement of the dust concentration at the workplace; Measurement of particle number; Measure with the thermal precipitator. VDI-Verlag Düsseldorf.

Individual evidence

  1. ↑ a b D. Hasenclever: Investigations into the suitability of various dust measuring devices for the operational measurement of mineral dusts. In: dust . No. 41, 1955, pp. 388-435.
  2. ↑ Heinrich Thürmer, Norbert Kersten: Measurement of ultrafine aerosols with the thermal precipitator. In: Hazardous substances - cleanliness. Air . 61, No. 6, 2001, ISSN  0949-8036 , pp. 275-279.
  3. ↑ Walter Lorenz Hartmann: Investigations into the comparability of the results of different dust measurement methods. In: dust. 19, No. 10, 1959, pp. 345-351.
  4. ↑ H. Thürmer: The fractionation effect in the thermal precipitator and the conclusions for an electromicroscopic grain analysis method. In: dust. 20, No. 1, 1960, pp. 6-8.
  5. ↑ Ingo Westerboer: On the physics of dust separation in the thermal precipitator. In: dust. 21, No. 10, 1961, pp. 466-473.
  6. ↑ VDI 3491 sheet 3: 1980-11 measurement of particles; Production of latex aerosols using nozzle atomizers. VDI-Verlag, Düsseldorf, p. 3.
  7. ↑ Karlheinz Schmitt: Basic investigations on the thermal precipitator. In: dust. 19, No. 12, 1959, pp. 416-421.
  8. ^ Gustav Kühnen, Wolfgang Pfeiffer, Edgar Rudolf: Development of the dust measurement technology at the workplace. In: Dust - cleanliness. Air . 46, No. 4, 1986, ISSN  0949-8036 , pp. 177-181.
  9. ^ Association of German Engineers : VDI guideline: VDI 2266 sheet 2 Measurement of the dust concentration at the workplace; Measurement of particle number; Measuring with the thermal precipitator , accessed on December 22, 2016