Mathematical modelling of biofilter's temperature regimes

The efficiency of filter functioning to a high extent depends on the location where it is used (within then territory of an enterprise or in its premises) and on the temperature maintained in the filter. That is important for the countries of temperate climate area that have both warm and cold periods, i.e. when temperature changes from below to above zero and vice versa. Thus, when filters are used outside, weather temperature has impact on the temperature maintained in the biocharge which has influence on physical, chemical and biological processes. The aim of the paper is to generate a mathematical modelling of biological air cleaning process and to make regression equations depending on the temperature maintained in the biofilter charge (7, 14 and 28 degrees C), different filter parameters (differing charge height and air flow speed), and injected pollutants (initial concentration, absorption coefficient, and water-solubility). The dependence of the filter efficiency on its charge height (0,15-0,75 in) with different initial pollutant concentrations and at different charge temperatures (7, 14, 28 degrees C) was modelled. Mathematical modelling was carried out on the dependence of the filter efficiency on the speed of the passing air (up to 2 m/s) with different initial pollutant concentrations and different temperatures maintained in the charge (7, 14, 28 degrees C). Similar to experimental tests, the increase in the charge height (from 0,15 to 0,75 in) results in the increase in cleaning efficiency. For example, when the temperature of 28 degrees C is maintained in the filter and the air is being cleaned of xylene (with its initial concentration of 49 mg/m(3)), the efficiency of removal of xylene starting with the height of the charge equal to 0,45 in is 50,43%, starting with the height of 0,75 in it is 63,9%. These results confirm the results of the experimental tests showing that the increase in the passing air flow speed (up to 2 m/s) results in the decreased efficiency of air cleaning. Accordingly, when the temperature of 7 degrees C is maintained in the filter and the air is being cleaned of butanol (with its initial concentration of 51 mg/m(3)), with the speed of the passing air increased from 0,4 to 2 m/s, air cleaning efficiency significantly decreases (from 74 to 62%). Thus, the obtained mathematical expression of efficiency will in future facilitate theoretical calculations, choice of appropriate device parameters and receive maximum air cleaning efficiency.