Use of geothermal energy from coal dumps

Smouldering fires in coal dumps occur when coal is oxidized by the oxygen of the air. In succession the developing heat in the dump lights the residual coal in the dumps of the coal mines. They are polluting the environment and require a long-term monitoring and special securing that needs to continue after the mining of coal has already ended.

Smouldering fires in coal dumps present not only a risk, but also a chance to use the thermal potential, which has been unnoticed: the stored heat in the dump and the occurring combustion gases were not used and released into the atmosphere. To develop the potential of the geothermal heat in the dump, the R&D Cooperation Project “Climate Protection: Thermal use of smouldering dumps” within the scope of the “klimazwei” program of the Ministry of Education and Research (BMBF) has been initiated by a research group from industry and sciences. Commissioned by the Unit of Technology of Fuels (Teer, RWTH Aachen University) FUMINCO performed “Field Laboratory Experiments, Modelling and Simulation of smouldering fires in coal dumps, Analysis of Optimum Stability of the dump”.

Aim of the project was the utilization of the thermal energy in smouldering fires in coal dumps combined with the reduction of greenhouse gases. The focus of the technical product development was the testing of production techniques and energetic use of the thermal dump heat. In a field experiment a heat-probe prototype and a product in the scale-up phase have been tested. This product should have ecological and economic advantages to the previous concept of the stability of the dump. Technical, legal, ecological and economic parameters have been examined to develop an alternative safety and energetic use concept. Besides the improvement of the knowledge on long-term safety on smouldering fires in coal dumps, concepts for the utilization of the thermal potential in generating electricity, cold or thermal heat were developed and tested.

The focus of the work of the Unit of Technology of Fuels was based on the basic evaluation of laboratory and field experiments and the setting and calibration of a numeric simulation model. Based on our long experience in the area of simulation processes we supported the research work of the Unit of Technology of Fuels. Together we developed a 3D-Simulation of the smouldering dump on the basis of empirical generated algorithms. The calculations and the model of the smouldering fires in a coal dump were implemented in a simulation model.