Thermochemical processing of biomass

Torrefaction can be defined as “a thermochemical process in an inert or limited oxygen environment where biomass is slowly heated to within a specified temperature range and retained there for a stipulated time such that it results in near complete degradation of its hemicellulose content while maximizing mass and energy yield of solid product”. Biomass torrefaction is considered as a pre-treatment technology. Torrefaction can significantly reduce the energy requirement for grinding biomass. The equilibrium moisture content (EMC) and the immersion tests are two tests commonly used to measure the hydrophobicity of torrefied biomass. Pyrolysis is a thermal decomposition of organic materials in the absence of oxygen, producing a solid residue rich in carbon, condensable volatiles (bio-oil) and non-condensable gases (producer gas). The design and optimization of biomass pyrolysis reactors requires analytical description of the process. Simplifications have led to the development of lumped models containing conceptual or pseudo-reactions for modeling pyrolysis. Available models can be arranged into three main groups: one step models, model with competing reactions and models with secondary reactions. Gasification is a partial combustion process that converts carbonaceous materials like biomass into useful gaseous fuels with a useable heating value or chemical feedstock. Combustion of biomass proceeds in various forms: evaporation combustion, decomposition combustion, surface combustion and smoldering combustion.