Rheinbraun's concept for power generation based on biotechnologically converted lignite

Abstract

The main objective of Rheinbraun's research activities with respect to biotechnological lignite upgrading is the large-scale production of liquid and gaseous products in particular for the energy and chemical/refinery sectors. This report outlines Rheinbraun's technical concept for electricity production on the basis of biotechnologically solubilized lignite. Starting out from conventional lignite extraction (opencast mining technology), this concept includes, inter alia, solubilization of the ground coal in bioreactors located near the deposits. The liquid coal reduced in terms of moisture, ash (mainly slag-forming minerals) and inorganic sulphur content is transported via pipeline to the power stations. Power generation is performed in oil-based or gas and steam turbine power plants. A first rough cost estimate based on the assumptions described here and compared with the latest power plant generation shows the general cost-efficiency of this technology despite the additional costs in respect of coal solubilization. The main reasons are: low-cost process techniques for coal conversion (mild reaction condition, low pressure and temperature) on the one hand and cost reductions mainly in power plant technologies (more efficient combustion processes and simplified gas clean-up) but also in coal transport (easy fuel handling) on the other hand. Moreover it is hoped that an extended range of products will make it possible to widen the fields of lignite application. In 1995 Rheinbraun started a research project, 1 1 The research project is financially supported by the North Rhine-Westphalian Ministry of Economics, Medium-Sized Enterprises, Technology and Transport, Germany. in which various leading biotechnological companies and institutes in Germany and the USA are involved. The positive results obtained during the first 10 months of the current project are very promising. So, the first difficult step has been taken: several liters of microbially solubilized Rhenish lignite have been produced. This pre-product with a water content of approximately 95% will now be used to select efficient and low-cost preparation techniques and to perform the first suitability investigations (combustion tests, tests analogous to crude oil preparation). However, it is much too early to determine whether biotechnological lignite upgrading is the ultimate solution or a dead end.