Wet scrubbers, which separate particles, liquids or gaseous constituents from exhaust air streams, were already in use 160 years ago. Historical records show that the use of water as a natural binder for dust was already in use over 2000 years ago.
Today, legal requirements such as the Federal Immission Control Act (BImsch) or the Technical Instructions on Air Quality Control (TA Luft) demand the use of scrubbers in various forms in a wide range of industrial applications. Today’s industrial applications already require the reduction of particles down to 1 micrometer, i.e. 0.001 mm.
So-called countercurrent scrubbers are particularly suitable for removing particles from the exhaust air and reducing the exhaust air temperature, e.g. in roasting plants. Column scrubbers, on the other hand, are suitable for removing ammonia and smoke.
Gas scrubber or wet separator
A gas scrubber or wet separator is a system in which a gas stream is brought into contact with a liquid stream in order to absorb constituents of the gas stream in the liquid. The components of the gas stream that are transferred can be solid, liquid or gaseous substances. Water, but also suspensions can be used as scrubbing liquid. Gas scrubbers can be used simultaneously for dust removal and for the separation of harmful gases. As a rule, a droplet separator is installed downstream.
The scrubber operation aims to produce the largest possible liquid surface area for the best possible mass transfer. The efficiency of the gas scrubber is determined by
- the contact time,
- the surface area of the scrubbing liquid
- the diffusion distance in the gas phase
- the concentration difference between gas phase and liquid phase, or
- an admixed chemical that serves as a reaction partner for the absorbed substance.
The efficiency can therefore be increased by
- a longer residence time,
- maximizing the surface area of the wash solution
- by using special nozzles, internals and packing, or
- a reduction of the concentration in the liquid phase
by using more scrubbing liquid or a chemical reaction.
In scrubbers that operate with droplet generation, for example, the droplets produced are usually much larger than the particles to be separated and can be separated comparatively easily at the apparatus outlet by means of a droplet separator.
Clean smokehouse exhaust air
During smoking, a mixture of gases and aerosols of incompletely burned or pyrolytically decomposed smoking agents, such as wood or other plant parts, acts on the material to be smoked. The smoke is generated either from wood or a liquid smoke concentrate in the smoke generation unit.
A scrubber with tar separator, the UV/ozone module with reaction tube and a downstream catalyst is suitable for cleaning this complex exhaust air.
Roasting air
During the roasting process, on the one hand the silver skins adhering to the green coffee flake off, and on the other hand, on the basis of the Maillard reaction, the conversion of peptides with reducing sugars from the starch, lipids and proteins to aroma substances and melanoidins takes place.
During roasting, between 45 and 73 g of water, 50 to 110 g of organic compounds (total C) and 15 to 35 g of other substances (inorganic gases, organic dusts, especially silver skins) are released per kilogram of green coffee. Organic compound classes in the exhaust air include aldehydes, ketones, phenols, alcohols, organic acids, and anime and mercaptans.
The roasting and quenching air can be successfully treated with a UV/ozone module, which is additionally equipped with an upstream air-to-air heat exchanger and scrubber as well as a downstream catalyst.
Ammonium polluted exhaust air
Exhaust air from laboratories, animal stables, slaughterhouses and animal processing plants is heavily contaminated with ammonium. Our exhaust air scrubbing system effectively removes water-soluble and odor-bearing particles in the exhaust air.
Pharmaceutical industry
The production of heparin from intestinal mucus gives rise to unpleasant odors which are not only of organic origin but also contain ammonia. Here, the combination of scrubber and UV/ozone system leads to odor-free exhaust air.
Smoke scrubber for cleaning smoke exhaust air
This system consists of an automated exhaust air scrubber plus a downstream UV ozone system. It eliminates the highly tar-containing fumigant exhaust air from manufacturing processes in the food industry (smoking ovens) and the associated high odor emissions.
Clean Washer Air
This exhaust air scrubber system has proven itself especially for ammonium-contaminated exhaust air from laboratories, animal stables, slaughterhouses and animal processing plants. Chlorine gas, ammonia and hydrochloric acid vapors are removed at a rate of more than 99 %.
The scrubbing liquid sprays against the air stream, achieving the highest levels of scrubbing for toxic gases and odors. The washed out ingredients are concentrated and separated via a sump receiver.
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