Effect of feedstock composition on product yields and energy recovery rates of fast pyrolysis products from different straw types

The conversion of different types of straw by fast pyrolysis has been investigated in this study. The mass and energy balance for corn stover, wheat straw and also rape and sunflower stalks are reported. A process development unit with a twin screw mixer reactor has been utilised for the experiments with a feeding rate of 10 kg/h at fixed operation conditions of reactor temperature, cooling temperature, vapour residence time, biomass particle size and heat carrier material. The results in product yields and energy recovery rates are compiled and compared. It can be observed that different types of straw produce different char, condensate and gas mass yields due to their varying ash content and differing lignocellulosic composition. On a dry and ash-free basis elemental formulas for feedstock, char, organic condensate and gas could be defined independent of the feedstock due to similar elemental compositions. Gas flow rate and composition measurements provide additional information on mass yields: a CO/CO2-ratio of 1 (i.e. wood) corresponds to an organic condensate yield of about 50 wt.%, whereas a ratio of 0.3–0.7 (straw) corresponds to about 18–32 wt.%.