Project Leader:	Professor Dr-Ing Otto Geisler
Research Assistant:	Dipl-Ing K Wilbrand
Duration:	01.08.1995 - 31.08.1996

 

Soils contaminated with hydrocarbons were treated in a steam boiler of the brown coal fired CHP plant of Thyssen Henschel GmbH in Kassel, equipped with a circulating fluidised bed (CFB). For this purpose the soils were mixed with raw brown coal and co-fired in the fluidised bed, where they were thermally treated at 850 °C and removed afterwards as FB ash. In this manner the energy content of the soils could be utilised to produce power and heat.

As regards the soil quantities that can be treated in this way, they amount to 2 to 5 % of the mass flow of brown coal. This corresponds anually to 2,000 to 5,000 t. With extensive and systematic measurements at the plant CFB process configurations were investigated, aiming to safeguard that neither in the exhaust gas nor in the ashes non-permitted levels of contaminants and pollutants are left and that the elutriation behaviour of the ashes has not deteriorated.

In the framework of the project different soil types as well as beton and building rubble were co-fired in the CFB, to optimise the most important operational parameters. These parameters included among others also the particle sizing, the preparation of the soil material and the throughput of the different soils and contaminants.

The tests have revealed that soils can be co-fired in the plant and no changes in the mechanical equipment (especially the feeding system) are necessary. Also the thermal behaviour of the plant changes little.

Based on the mass balance it was possible to show that the investigations with beton / building rubble lead also to a reduction in the lime and sand additive requirements. The emissions, measured by TÜV, have not exceeded the limit values applicable. Analyses of the ashes confirmed also the good binding of the toxic contaminants to the FB ash.