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News – What`s happening in energy research

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Project head Olaf Schulze shows the sampling point for samples at a height of 12 metres.
© Christina Geimer, BINE Informationsdienst
Coal conversion
22.07.2013

Hanging a horse shoe on the testing facility (from the left): Envirotherm Managing Director Dr Georg Daradimos, Saxony State Minister Sven Morlok and Professor Bernd Meyer, Director of the Department of Energy Process Engineering and Chemical Engineering (IEC).
© TU Bergakademie Freiberg

In the slag bath gasifier the scientists are investigating the ash behaviour under real process conditions.
© TU Bergakademie Freiberg

The coal enters the gasifier via the feed system using sluices (blue).
© Christina Geimer, BINE Informationsdienst

New testing facility using coal gasification technology

Coal is not just combusted but can also be used for generating chemical products such as methanol or methane. Until now these processes have been principally used in China and India. With its new testing facility, the Technische Universität Bergakademie Freiberg is now creating a database for a new design of coal gasifiers in Germany.

Visitors to Freiberg in Saxony will notice the hill with the “Reiche Zeche” mine – a symbol of the century-long tradition of silver mining in the small town between Chemnitz and Dresden. Since the summer of 2013, the new 20.45-metre-high slag bath gasifier has overlooked the decommissioned winding tower at the top of the hill. The Department of Energy Process Engineering and Chemical Engineering (IEC) at the TU Bergakademie Freiberg wants to expand the testing facility to convert another resource, namely coal.

The coal is added to the head of the 12-metre-long slag bed gasifier. First of all it is enclosed in a chamber that acts as a sluice, where it is brought up to a pressure of 40 bar that also prevails in the slag bed gasifier itself. The other end of the feed system then opens at a height of 11.20 metres and the coal falls into the actual slag bed gasifier below. The gasification agent is injected at a height of 7.40 metres. The temperature in the gasifier ranges between 1,200 and 1,600 degrees Celsius, so that gas forms from the coal. The mineral components, i.e. the ashes, are completely removed as viscous slag.

The slag drips from the gasifier into a water bath like thick honey, where it cools. The scientists at IEC are investigating which components make up the slag and how its composition can be influenced. It is the first research establishment to investigate the slag under real process conditions. At a high pressure of 40 bar, they remove samples from the slag at special points, before the slag falls into the water. Particularly the melting behaviour of the ash and the properties of the hot, liquid slag are important for operating gasifiers and are often the cause of problems.

Testing facility aims to lower technology costs

Until now it was only possible to conduct investigations without pressure or once the slag was immersed in water. The Freiberg facility intends to change this. Here, for example, it is planned to optimise the flow behaviour of the slag. The test plant will also be used to test new approaches in order to lower the costs of the technology. A further aim is to increase the conversion of the carbon from a maximum of 95 per cent at the moment to 99 per cent. The scientists also want to increase the tolerance regarding the fuel quality. For this purpose, they are testing not just various types of coal but also biomass. Until now every gasifier has been designed for a specific fuel.

On conclusion of all the research work, a comprehensive database on the composition of the slag will be available for different coal types. The knowledge shall open the way to optimising and further developing gasifiers and will contribute to improving the plant availability.
The project is being sponsored by the Saxony State Ministry for Economic Affairs, Labour and Transport using money from the European Regional Development Fund (ERDF).

(cg)

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