Rotary kiln pyrolysis of straw and fermentation residues in a 3 MW pilot plant - Influence of pyrolysis temperature on pyrolysis product performance

The idea of co-firing biomass in an already existing coal-fired power plant could play a major contribution in the reduction of carbon dioxide emissions. Huge amounts of unused biomass in terms of agricultural residues such as straw, which is a cheap and local feedstock, are often available. But due to the high amount of corrosive ash elements (K, Cl, etc.), the residues are usually not suitable for co-firing in a thermal power plant. Therefore, the feedstock is converted by low temperature pyrolysis into gaseous pyrolysis products and charcoal. A 3 MW pyrolysis pilot plant located next to a coal-fired power plant near Vienna was set up in 2008. For the process, an externally heated rotary kiln reactor with a design fuel power of 3 MW is used which can handle about 0.6-0.8 t/h straw. The aim is to investigate the fundamentals for scale-up to the desired size for co-firing in a coal-fired power plant. In addition to the desired fuel for the process, which is wheat straw, a testing series for DOGS was also performed. The high amount of pyrolysis oil in the gas had positive effects on the heating value of the pyrolysis gas. Chemical efficiencies of this pyrolysis pilot plant of up to 67% for pyrolysis temperatures between 450 degrees C and 600 degrees C can be reached. The focus of this work is set on the pyrolysis products and their behavior at different pyrolysis temperatures as well as the performance of the pyrolysis process. (c) 2012 Elsevier B.V. All rights reserved.