Bioriesel bed reactor

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A Biorieselbettreaktor (also trickling filter , Tropfkörperbiowäscher , biowashers after the trickling filter process or trickling scrubber ) is a biologically-working reactor for purification of waste air and waste gases . It can be viewed as a special form of the bio-scrubber . Both reactor types use the absorbed air pollutants as substrates . In the bioresel bed reactor, the microorganisms are predominantly on the internals, while in the bioscrubber they are mainly suspended in the washing liquid. In contrast to the biofilter , in which the microorganisms are also fixed, in the bioresel bed reactor there is a specific guidance of the washing liquid, whereas with the biofilter only drying out has to be prevented. A first patent for this type of exhaust air cleaning was applied for in 1934 and granted in 1941. The process principle was adopted from biological wastewater treatment, where wastewater is clarified by using trickling filters .

Procedural bases

Example of a packing

The basic design of a bioriesel bed reactor is a gas scrubber equipped with packing elements , on the surface of which a microorganism flora, which usually consists of a mixed culture, has settled. This microorganism flora is also known as biological lawn and determines the efficiency of the cleaning system. Information on the biological lawn is given in m² surface per m³ installation volume. In contrast to the bio-scrubber, the use of liquids only serves to humidify the microorganisms and to supply them with substances that are not introduced via the exhaust gas. A physical washing out of the air pollutants is, unlike the bio-scrubber, not the primary purpose of the liquid. When selecting the packing, make sure that the gaps are large enough to prevent them from overgrowing. Pall and Raschig rings have not proven themselves for this purpose.

Process scheme of the bio-diesel bed reactor
The exhaust gas to be cleaned (1) flows through the reactor (A) from top to bottom and leaves it as so-called clean gas (2). The irrigation liquid (3) is largely circulated. A nutrient salt solution (4) supplements the part of the liquid that is discharged as waste water (5).

In the bio-diesel bed reactor operation, wash water, which is provided with nutrient salts, is distributed as evenly as possible over the packing of the reactor. The exhaust gas to be cleaned comes into contact with the liquid and the substances to be separated go into the liquid phase. In addition to transporting the exhaust gas constituents to the biological lawn, the washing water also has the task of cleaning it. The so-called excess sludge is removed from the internals. This is to be separated from the washing water and discharged. The air pollutant to be separated serves the microorganisms in the biological lawn as a substrate and is ideally converted by them into carbon dioxide and water.

Bioriesel bed reactors are operated in cocurrent, cross or countercurrent . Just like bio-scrubbers, bio-diesel bed reactors are able to deal with dry, untreated exhaust gases, since in contrast to bio-filters there is no risk of the reactor drying out. The water discharged with the steam-saturated exhaust gas (so-called evaporation loss) can be supplemented with fresh water.

For optimal treatment in the bio-diesel bed reactor, the exhaust gas temperature should be in the mesophilic range. Substances that are toxic to the microorganisms must not be present in the exhaust gas. Concentration and temperature fluctuations in the exhaust gas can lead to a change in the microorganism population and should therefore be avoided. The oxygen concentration in the exhaust gas and thus also in the scrubbing liquid must be high enough so that aerobic conditions can arise.

The construction material of the individual reactor components as well as the internals must be resistant to chemical stress on both the liquid side and the gas side. Concrete, plastic and steel are suitable for this.

Areas of application

The preferred area of ​​application of Bioriesel bed reactors is at air pollutant concentrations of up to 1500 mg / m³ with sufficient water solubility of the pollutants. Bioriesel bed reactors are used, among other things, in the treatment of exhaust air and exhaust gas in paint shops, food processing plants, biowaste treatment plants, pharmaceutical companies and semiconductor manufacturers. The substances contained in the exhaust air that can be easily removed by Bioriesel bed reactors include, for example, representatives of the substance groups

Bioriesel bed reactors are also used for the desulphurisation of biogas .

The bio- diesel bed reactor, which is more expensive than the biofilter, is advantageous if undesired reaction end products such as salts or acids are to be expected for a biofilter. These can more easily be discharged from a bioresel bed reactor.

literature

  • VDI 3478 sheet 2: 2008-04 Biological exhaust gas cleaning; Bioriesel bed reactors (Biological waste gas purification; Biological trickle bed reactors) . Beuth Verlag, Berlin. ( Table of contents , abstract )
  • Klaus Fischer: Biological exhaust air purification: application examples, possibilities and limits for bio filters and bio washers . Expert Verlag, Ehningen bei Böblingen 1990, ISBN 3-8169-0428-9 .

Individual evidence

  1. ^ A b c d Klaus Fischer, Franjo Sabo: Separation of gaseous pollutants through biological reactions. In: Heinz Brauer (Ed.): Handbook of environmental protection and environmental protection technology. Volume 3: Additive environmental protection: treatment of exhaust air and exhaust gases. Springer-Verlag, Berlin / Heidelberg / New York 1996, ISBN 3-540-58060-3 , pp. 594-645.
  2. ^ A b c d Klaus Fischer: Degradation of foreign matter in the air. In: Johannes CG Ottow, Werner Bidlingmaier (Ed.): Environmental biotechnology . Gustav Fischer Verlag, Stuttgart / Jena / Lübeck / Ulm 1997, ISBN 3-437-25230-5 , pp. 317-349.
  3. ^ A b Walter Reineke, Michael Schlömann: Umweltmikrobiologie. Springer-Verlag, Berlin / Heidelberg 2015, ISBN 978-3-642-41764-1 , pp. 411-414.
  4. ↑ H. Kohler: Bio scrubbers to minimize organic gaseous emissions - state of development work using the example of the foundry industry, paint shops, fat melting and fiberglass production. In: Odor substances: sources, spread, effects, olfactometry, technical and administrative measures. VDI-Verlag, Düsseldorf 1985, ISBN 3-18-090561-1 , pp. 169-190.
  5. ↑ Michael Schultes: Exhaust gas cleaning . Springer-Verlag, 1996, ISBN 3-540-60621-1 , p. 218.
  6. ↑ VDI 3896: 2014-06 (draft) emission reduction; Upgrading biogas to natural gas quality. Beuth Verlag, Berlin, p. 15.
  7. ↑ Nikolaus Thissen: Biological exhaust gas cleaning in industry. In: Commission for keeping the air clean in the VDI and DIN - standards committee KRdL (Hrsg.): Biological exhaust gas cleaning - gases, odors, germs . VDI reports 1777, 2003, ISBN 3-18-091777-5 , pp. 73-82.