UNDERSTANDING THE REACTIVITY OF PYROLYSIS TARS FROM BIOMASS AND LOW RANK COALS IN A VIEW POINT OF FREE RADICALS

摘要

It is well accepted that pyrolysis is a simple and an effectnmethod to produce tar and consequently fuels and chemicals fromnbiomass and low rank coals, and fast heating speeds up the processnand results in a higher liquid yield. Many fast pyrolysis processesnhave been developed worldwide in decades, including fluidized bed,nmoving bed, transported bed and rotating cone with scales up tonthousands kg/h, such as Ensyn of Canada (4000 kg/h) andnDynamotive of Canada (8000 kg/h) for biomass, and COED of USAn(1500 kg/h) and Lurgi-Ruhrgas of Germany (416 kg/h) for coal. Itnwas found, however, that the tars collected in most of the processes,nif not all, were of low quality and poor stability, [1,2] and difficult tonbe upgraded at an acceptable cost. Furthermore the product linesnwere frequently clogged by solid deposition causing operation andnsafety problems.[3-6] Technical efforts made to solve these problemsnwere found not effective, which halted commercialization of many ofnthese processes. It is certain that new insight should be gained tonsolve the problems especially on the fundamental chemistry involved.