Gaseous and Solid Air Pollutants Formed during the Combustion of Heavy Metal Contaminated Oak and Poplar

In recent decades several industrial activities polluted the soil, which caused the accumulation of heavy metals to an extent greater than the natural concentration. This is mainly typical of countries, where mining and industry plays or has played an important role in the economy. The utilization of these lands is an economic interest, since locating the contamination, controlling its spreading and maintaining the area has costs. One of the methods for remediation is phytoextraction, during which heavy metals, especially harmful to water and soil, are removed from the soil by plants capable of accumulating contaminants. However, during the combustion of these plants their heavy metal content is replaced into the formed gaseous and solid combustion remains, so the hazard, composition and treating method of these remains must be defined by the appropriate examinations. In this article we present some part of the results of this research, where we examine the gaseous and solid pollutant content of flue gas formed during combustion, as well as the heavy metal content of fly ash. We made two different experiments for domestic and semiplant usage. We have used oak and poplar from a heavy metal contaminated area in both experiments. The domestic examination was conducted in a 7 kW hearth with a closed combustion chamber, the semiplant examination was carried out in a 0,5 MW capacity furnace equipped with an automatic fuel feeding system and a cyclone dust extractor. We have measured the composition of flue gas in both firing experiments with a HORIBA PG-250 type portable gas analyzer, in the case of the analysis of heavy metal content of fly ash DX4 EDAX EDS microprobe of an AMRAY 1830 I scanning electron microscope and ICP-AES, using a 720 ES instrument was used. Based on our results, it can be determined, that the combustion device used to burn biomass grown on heavy metal polluted areas – brownfield lands – must make it possible to separate fly ash from the flue gas and allow the handling of solid burning residues.