Thermal decomposition behavior and sulfur release characteristics for torrefied wheat straw during pyrolysis process.

Understanding the release characteristics of S for pyrolysis process is crucial to the development of biomass thermochemical conversion. The thermal decomposition behavior and S release characteristics for torrefaction and pyrolysis process as well as the impact of torrefaction on the S release during subsequent pyrolysis process of wheat straw were evaluated. In the case of torrefaction, high reaction temperature promoted the increase in S release percentage, which was linearly proportional to mass loss. For pyrolysis process, the release percentage of S increased rapidly up to 70.50% at 500 ℃, whereas the release percentage curve showed an unchanged trend for further increase of the pyrolysis temperature. Additionally, torrefaction pretreatment enhanced the pore properties of char, which promoted the physical resistance of released S during the diffusion process. Thus, torrefaction pretreatment effectively inhibited the release of S into the gas phase, and has a promoting effect on retaining more S in char.