Gas Purification System

Gas Clean Purification System

In biological gas purification, microorganisms oxidize organic compounds to carbon dioxide and water in a moist and oxygen-rich environment. The oxidation of sulfur or nitrogen-containing compounds and chlorinated organic compounds also generates inorganic acids. If undegradable compounds are not present, control efficiency greater than 90% can be achieved with reasonable filter volumes and low investment and operation costs. Odors are often completely removed. Advantages of the biological gas purification include low operating temperatures and the possibility of treating gas streams with low organic loads. Due to the low operating costs, bio-filtration can provide significant advantages over other air pollution technologies when the waste gases contain low concentrations of readily biodegradable and water-soluble compounds.Bio treatment is not recommended for gases containing organic sulfur compounds.It is essential that dust, oil, and grease are removed from the waste gas stream before they enter the biological treatment zone.

Equipment types Compost or soil filtersCompost or soil filters
Capacity range, m 3  s −10.3-41.7
Inlet gas concentration, ppmvBelow 100
Removal efficiency, %Over 90
Unsuitable inlet gas characteristics

(a)Water-insoluble compounds

(b)Very high flow rates

(c)High organic concentrations


(a)Low organic concentrations can be treated.

(b)Simple operating concept.


(a)Process automation impossible.

(b)Sensitivity to pH and moisture in a filter.

(c)Excess biomass disposal.

(d)Daily manual operation required.

(e)Lots of space needed.

Biofilters are used for the control of organic compounds, air toxics, and organic and inorganic odors. Most  biofilters  are built as open single-bed systems, the most common filter media being compost and soi1. 19  In biofiltration, effluent gases are vented through a biologically active material, and with sufficient residence time, the contaminants diffuse into a wet, biologically active layer (biofilm) that surrounds the filter particles. Aerobic degradation of pollutants occurs while the microorganisms metabolize them. The system consists of an effluent gas blower, a gas humidifier, and a  biofilter  including an air-distribution system and filter material (Fig. 13.26). For biological purification, bioscrubbers such as fixed- bed bioreactors or trickle-bed bioreactors can also be used.

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