Exhaust gas cleaning using biofilter

In foundries, biofilters are applied for the removal of odorous gases, which mainly consist of amines from the off-gas from cold-box core-making processes and for the removal of VOCs (e.g. benzene) from casting shop exhaust gases. 

Permeability of the filter layer Gases need to flow through the bed in good contact with the filter bed material. An excess of fine material in the filter bed may cause clogging, pressure build-up and blowout of bed material 

Wetting of the filter medium A water dispersion system may be installed for continuous or intermittent wetting of the bed material 

Conditioning of the exhaust gas The exhaust gases need to be moistened before entering the filter. For optimum operation, a constant temperature (30 C) has to be maintained. This may require preheating of the exhaust gas 

Adequate water treatment. The biofilter produces residual water, containing phenol and cresol. This is treated in a waste water system before disposal or re-circulation. Recirculation requires an additional salt removal step. 

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