Auger reactors for pyrolysis of biomass and wastes

Pyrolysis is one of the most efficient and environmentally attractive thermochemical processes for conversion of both biomass and wastes to energy products. This review focuses on the use of auger reactors, also known as screw reactors, for the pyrolysis of carbonaceous solids into liquid, gaseous and solid products that can be used in the production of fuels and other valued-added products. The auger reactor is attractive for its versatility in transforming a wide range of feedstocks, and has been recognized as one of the technologies with better strengths not only for fast pyrolysis, but also for slow or intermediate pyrolysis. Auger pyrolyzers are of relatively simple design and overcome some of the problems of conveying heat for pyrolyzing biomass or wastes. The mechanical forces associated with auger reactors enhance particle mixing and heat transfer, which are key to successful pyrolysis. This paper presents a comprehensive review of the advantages and challenges of this technology and identify the main characteristics of both single- and twin-screw auger technology. The effect of operating conditions on yield and some properties of pyrolysis products are also provided. The review includes examples of commercial/demonstration-scale auger pyrolysis plants operated around the world.