Project Leader:	Professor Dr-Ing Otto Geisler
Research Assistant:	Dipl-Ing K Wilbrand
Duration:	01.01.1991-30.06.1994

 

In Saarbrücken a model remediation of the grounds of the Burbach Foundry was undertaken, a facility used before as iron foundry. Until the 1970s on these grounds hard and brown coals were pyrolysed and processed further. The soils were at parts heavily contaminated by substances (organics and heavy metals) involved in the production.

The Stadtwerken Saarbrücken engaged the Institute to scientifically lead, oversee and evaluate the pilot measurements of the Firms participating in the project. The pilot plant types tested were a rotary pyrolyser, a stationary fluidised bed, a rotary pan facility as well as a rotary combustion kiln.

In the pilot measurements performed it was shown that thermal processes at high temperatures (> 750 °C) are very appropriate for the decontamination of soils containing organic contaminants. A scientific evaluation was performed of the various pilot plants above as regards decontamination efficiency of the soils and the elutriation characteristics of the facilities, their exhaust gas emissions and energy requirements.

Within the project a mathematical model for the dynamic simulation of the operation of direct-fired rotary kilns was developed. This necessitated physical modelling of the heat and mass transfer in the rotary kiln and the downstream components such as, for example, the afterburner, the exhaust gas cleaning apparatus and the heat exchangers.

Aim was the development of a general model which allows simulation of different rotating kilns. Measurements were performed at two thermal rotating driers and in addition available measurement results from a rotary kiln for thermal soil decontamnation were also analysed. This enabled the adjustement and validation of the model to facilities with different construction characteristics and throughput rates.

Whereas in thermal driers emphasis is given to reducing primary energy consumption through optimised process configuration, for soil decontamination also the residence time of the solids under certain temperature levels to ensure safe destruction of the contaminants is very important. Through simulation it is possible to determine the optimal operating conditions such as the solid mass flows, the burner loading and the proportion of exhaust gas recirculation, towards reducing the number of necessary tests.