Release characteristics of potassium and chlorine for torrefied wheat straw during a combined pyrolysis-combustion system

The objective is to investigate the release characteristics of potassium (K) and chlorine (Cl) for torrefied wheat straw during a combined pyrolysis-combustion system. Powder and flake wheat straw samples were torrefied at different temperature of 200-300 degrees C. The basic characteristics of torrefied samples and the K and Cl release rates of torrefied samples and their char samples derived from pyrolysis at 400-800 degrees C were analyzed and characterized. The results indicated that release rate of Cl was significantly higher than that of K under the same torrefaction conditions. In order to keep most of K and Cl remaining in biochar as well as the volatiles were completely released, the pyrolysis temperature of 700 degrees C for pyrolysis-combustion system was suitable. The total release rate of K and Cl at the pyrolysis temperature of 700 degrees C both exhibited a change trend of decreasing first and then increasing with the increase of torrefaction severity.