Fluidized-bed drying

A dry topic hardly promises to be exciting. Not so in the case of fluidized-bed drying with internal waste-heat utilization (WTA), whose development has been driven by RWE for years now. This process also meets with great interest at international level. Several tests have already been successfully completed in the Frechen test plant for customers from abroad.

Smart drying 

Until now, lignite with a moisture content of over 50% has been combusted in the power plant boiler after being milldried. Whereas flue gas at a temperature of 1,000°C is needed for the drying process, the temperature of 110°C in the WTA is well below this and energetically more  favourable. The trick: the heat that the water has absorbed during drying is recovered and used in the power plant process. 

Dual use 

WTA enables highly efficient drying of the raw lignite and creates the conditions for making the conversion of lignite into electricity even more environmentally friendly. RWE's aim is to increase the efficiencies obtained until now by lignite-fired power stations with optimized plant engineering (BoA) by several more percentage points; this will also further lower emissions and help spare resources to the same extent. 

Gain in competitiveness 

WTA lignite drying 

Our engineers have been researching the energetically efficient process since the start of the 1990s. An initial milestone in the development was the operation of a test plant at Frechen in 1993. Further optimization of the technology is an important element in the competitiveness of future lignite-fired power plants. 

Prototype plant at the Niederaußem site 

A WTA prototype plant has been erected next to our BoA unit at the Niederaußem site to test the commercial viability of this technique. This commercial-scale plant supplies the existing 1,000-MW power plant unit with 110 t of dry lignite per hour, thus accounting for approximately 30% of furnace thermal rating. The plant is in regular trial operation.

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