Police filter

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Police filter is a term in process engineering . It is connected downstream of another filter (or a series of filtering separators ) and takes on both a final cleaning and a safety function. The latter is necessary if an upstream filter - for example due to damage - is no longer capable of proper filtering.

commitment

In the exhaust gas purification often be activated carbon adsorber used as a police filter, as it not only because of their structure by adsorption can act, but also filternd. In some cases, the chemisorptive properties of the adsorbent are also used. Adsorptive police filters are used both as entrained flow and fixed bed processes. For example, a police filter based on activated coke can be used to further reduce the sulfur dioxide concentration in waste gas leaving the wet scrubbing facility from waste incineration .

In safety-related applications, police filters - for example in cassette form - prevent the formation of an explosive dust mixture . In working areas such filters are used as police filters in recirculation mode, the filter effect of which at least corresponds to the last upstream filter stage. Depth filters are often used in the aforementioned applications .

The disadvantage of police filters lies not only in the sometimes high investments , but also, due to the energy expenditure due to the greater pressure loss , in the increased operating costs . Downstream activated carbon adsorbers also run the risk of catching fire when the exhaust gases are hot.

Individual evidence

  1. ↑ a b VDI 3674: 2013-04 Exhaust gas cleaning through adsorption; Process gas and waste gas cleaning (Waste gas cleaning by adsorption; Process gas and waste gas cleaning). Beuth Verlag, Berlin, p. 47.
  2. ↑ a b VDI 2263 sheet 5.1 Dust fires and dust explosions; Hazards, assessment, protective measures; Explosion protection in fluidized bed systems; Notes and exemplary embodiments for manufacture and operators (Dust fires and dust explosions; Hazards, assessment, protective measures; Explosion protection in fluid bed dryers; Hints and examples of operation). Beuth Verlag, Berlin, p. 11.
  3. ↑ VDI 3674: 2013-04 Exhaust gas cleaning through adsorption; Process gas and waste gas cleaning (Waste gas cleaning by adsorption; Process gas and waste gas cleaning). Beuth Verlag, Berlin, p. 15.
  4. ↑ VDI 3927 sheet 1: 2015-11 exhaust gas cleaning; Reduction of sulfur oxides, nitrogen oxides and halides from exhaust gases from combustion processes (flue gases) (Waste gas cleaning; Reduction of sulfur oxides, nitrogen oxides and halides from combustion flue gases). Beuth Verlag, Berlin, pp. 38-39.
  5. ↑ VDI 2262 sheet 3: 2011-06 Air quality at the workplace; Reduction of exposure to air pollutants; Ventilation technical measures (Workplace air; Reduction of exposure to air pollutants; Ventilation technical measures). Beuth Verlag, Berlin, p. 20.
  6. ↑ VDI 3677 sheet 2: 2004-02 Filtering separators; Depth fiber filters (filtering separators). Beuth Verlag, Berlin, p. 7.
  7. ↑ Götz-Gerald Börger: Smoldering fire in activated carbon adsorbers, Part 1 and Part 2 . Chem.-Ing.-Techn. , ISSN  0009-286X , (69) 1 + 2/97, pp. 130-132 and (69) 3/97, pp. 358-361