Thermal use of waste

Project co-ordinator: Dr. Andrej Stergaršek

Total waste management includes a series of different processes and waste incineration is one of the steps. The incineration process developed significantly in the last 15 years. Mostly these improvements have been triggered by new legislative requirements, first of all due to demands for lowering emissions into air. The improvement process is an ongoing one and technical performances are being improved with steady price levels. Public perception is one of the main reasons for the minimal operation of incinerators in Slovenia, although the emission of dioxins is comparable to that of other combustion operations such as coal and oil burning thermal power plants. Therefore a demonstration unit of industrial capacity (about 100 kg of waste per hour) will be built in order to demonstrate the operation of an incineration unit that is acceptable in terms of technology and environmental quality.

The removal of persistent organic pollutants will be the main focus in the proposed research. Fractions/wastes which are of no use and contain burnable mass will be thermally processed. New cleaning steps will be introduced, such as the development of hot filtration of flue gases, where the filtration media will be used as carriers for catalysing degradation of persistent organic substances.

The main steps in incineration are as follows:

1. Drying and volatilisation: in this phase volatile compounds such as water and HCs that are volatile at temperatures 100 to 300 degrees C are removed. Energy is needed for this stage.

2. Pyrolysis and gasification: pyrolysis is the next stage of the degradation of organic substances without oxygen at temperatures of 400-700 degrees C. Gasification is the reaction between waste, carbon dioxide and water taking place at 700 to 1000 degrees C. (External) heating, water vapour and oxygen are required.

3. Oxidation: combustible gases from the previous step are combusted, consuming oxygen and producing heat.

Innovation is expected in new combinations of catalytic effects simultaneously on the filters and in the sand bed. A new, effective POPs removal stage based on absorption into different materials will be sought for. New materials, including waste plastic, will be tested and compared to the efficiency of active charcoal.