RHEINBRAUNS CONCEPT FOR POWER-GENERATION BASED ON BIOTECHNOLOGICALLY CONVERTED LIGNITE

The main objective of Rheinbraun's research activities with respect to biotechnological lignite upgrading is the large-scale production of l iquid and gaseous products in particular for the energy and chemical/r efinery sectors. This report outlines Rheinbraun's technical concept f or electricity production on the basis of biotechnologically solubiliz ed lignite. Starting out from conventional lignite extraction (opencas t mining technology), this concept includes, inter alia, solubilizatio n of the ground coal in bioreactors located near the deposits. The liq uid coal reduced in terms of moisture, ash (mainly slag-forming minera ls) and inorganic sulphur content is transported via pipeline to the p ower stations. Power generation is performed in oil-based or gas and s team turbine power plants. A first rough cost estimate based on the as sumptions described here and compared with the latest power plant gene ration shows the general cost-efficiency of this technology despite th e additional costs in respect of coal solubilization. The main reasons are: low-cost process techniques for coal conversion (mild reaction c ondition, low pressure and temperature) on the one hand and cost reduc tions mainly in power plant technologies (more efficient combustion pr ocesses and simplified gas clean-up) but also in coal transport (easy fuel handling) on the other hand. Moreover it is hoped that an extende d range of products will make it possible to widen the fields of ligni te application. In 1995 Rheinbraun started a research project,(1) in w hich various leading biotechnological companies and institutes in Germ any and the USA are involved. The positive results obtained during the first 10 months of the current project are very promising. So, the fi rst difficult step has been taken: several liters of microbially solub ilized Rhenish lignite have been produced. This pre-product with a wat er content of approximately 95% will now be used to select efficient a nd low-cost preparation techniques and to perform the first suitabilit y investigations (combustion tests, tests analogous to crude oil prepa ration). However, it is much too early to determine whether biotechnol ogical lignite upgrading is the ultimate solution or a dead end. (C) 1 997 Elsevier Science B.V.