Industrial and hazardous wastes are incinerated predominantly in rotary kilns. Wastes with a wide specification range can be incinerated (2,6). Solid waste, either bulky material or drums, is fed discontinuously via a chute at the front wall of the rotary kiln. Liquid and pasty material is introduced via lances and burners in the kiln and secondary combustion chamber. A boiler and a flue gas cleaning system are mandatory for heat recovery and reduction of emissions. The incineration of high-calorific waste in drums is limited by the emission standards for carbon monoxide and unburned hydrocarbons. The high-calorific waste causes a very rapid oxygen-consumption which can lead to the emission of pollutants such as soot, hydrocarbons and carbon monoxide. Due to the fact that all incineration plants have to comply with very strict emission limits, the CO concentration in the flue gas is the limiting factor for the throughput of drums in the rotary kiln. In order to increase the throughput of drums a new control system has been developed. It is based on a fast registration of parameters describing the combustion process in the rotary kiln (soot, CO, CO2 or H2O). The signal is used to adjust fuel and air flow in the secondary combustion chamber and rotary kiln in order to optimize the combustion conditions during the period of very intense oxygen consumption when drums are incinerated. The new developed control system has been tested intensively at the semi-technical rotary kiln incinerator THERESA of the Research Center Karlsruhe. The results obtained show that an optimization of the combustion process based on fast in-situ detection of soot and CO increases the capacity for drums with high-calorific content by a factor of two and more.
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