Design and construction of a gas filter system for hospital incinerators

An incinerator is designed to burn combustible waste materials such as municipal solid waste and infectious waste into inert ash. The design reduces waste volumes and subsequently destroys pathogens. A gas filtering unit is designed, constructed, and fitted on an existing incinerator for cleaning the smoke from medical waste treatment. Its main components are a framework whose material is made of galvanized diamond, three wire meshes, made of steel, to serve as filter bed supports, an inlet and 2 sampling holes of diameter 1.5cm beneath the wire meshes, and an outlet and 2 sampling holes of 1.5 cm above the wire meshes. As part of the gas filter design considerations, the amounts of dry volumetric gas discharged during combustion, and of particulate matter produced per cycle of combustion in the chosen incinerator were estimated to be 12,051.86 m3 /cycle, and 2.17 kg PM/cycle of incineration respectively. The novelty in this design consisted in adapting the impingement plate type of wet scrubbing unit for dry adsorption of organic pollutants in smoke using locally-activated charcoal powder. The incorporation of powdered activated charcoal in the filter unit as adsorbent material significantly reduces the emission of harmful pollutants into the atmosphere. As a result, pollution of the environment is minimized. The smoke was sampled before and after filtration, and the samples were later tested in the laboratory for 14 polychlorinated biphenyls, namely PCB 18, PCB 28, PCB 31, PCB 44, PCB 52, PCB 101, PCB 118, PCB 138, PCB 149, PCB 153, PCB 170, PCB 180, PCB 194 and PCB 209. The three charcoal filter beds used in the evaluation study achieved target pollutant reductions in smoke ranging from 2.03 % - 71.85%. An Air Pollution Control Device with such pollutant reductions should justify the continued use of incinerators if they are properly mounted and secured on the incinerators and can curb the problem of air pollution from point sources.