Betriebserfahrung mit Schnellpyrolyse von Siroh im Technikumsmassstab: Zwei Strategien zur Produktabscheidung im direkten Vergleich

摘要

Two different strategies for the separation of products have been investigated at a pilot plant for fast pyrolysis (10 kg h~(-1)). The aim is a direct comparison of these two strategies and the investigation of their impact on product distribution. One concept separates solid char residues together with condensate whereas the other concept separates the solids prior to condensation of tar vapors. Both strategies include a second downstream condensation of aqueous condensate at lower temperature. For the case of fast pyrolysis of wheat straw, mass, energy, and carbon balances have been set up for both product recovery variants. It was found that there was no change in mass balance whereas there was significantly more carbon recovered with the organic condensate when solids were separated prior to condensation. These contrasting observations can be explained with a change in ash content in the feed between the two experimental runs. The results support the hypothesis that secondary reactions of the organic condensate are promoted at the presence of char particles. Secondary reactions lead to an increase in gas production and solid precipitates, which are balanced together with the char. Both product separation variants can be applied successfully from a technical point of view. However, having separated product fractions increases the flexibility of their use, which might positively affect their economic potential.