Torrefaction is a slow pyrolysis process that is carried out in the relatively low temperature range of 220-300°C. The influence of torrefaction as a pretreatment on biomass gasification technology was investigated using a bench-scale torrefaction unit, a bench-scale laminar entrained-flow gasifier, and the analysis techniques TGA-FTIR and low temperature nitrogen adsorption. A series of experiments were performed to examine the characteristics of the torrefaction process, the properties of torrefaction products, and the effects of torrefaction on gas composition, cold gas efficiency and gasification efficiency. The results showed that during the torrefaction process the moisture content of biomass were reduced, and the wood fiber structure of the material was destroyed. This was beneficial to storage, transport and subsequent treatments of biomass in large scale. For solid products, torrefaction increased the energy density, decreased the oxygen/carbon ratio, and created a more complex pore structure. These improved the syngas quality and cold gas efficiency. Combustible gases accounted for about 50% of non-condensable gaseous torrefaction products. Effective use of the torrefaction gases can save energy and improve efficiency. Overall, biomass torrefaction technology has good application prospects in gasification processes. Energy is the most important basis for economic and social development. With large-scale industrial development, the total exploitable amount of fossil fuel is declining, and environmental pollution is increasing. With the advantages of being clean and CO 2 neutral, biomass is the only renewable energy source that can fix carbon, and biomass has gradually won worldwide attention. However, as a result of its dispersion, low energy density, low bulk density and high moisture content, the costs of logistics and transport are increased. Those factors make large-scale utilization of biomass for bioenergy production inefficient and uneconomic. Consequently, it is necessary to enhance the characteristics of biomass feedstocks through pretreatment.At present, biomass pretreatments include drying, pelletisation, pyrolysis and torrefaction. While drying is a relatively *Corresponding author (email: zhoujs@cmee.zju.edu.cn) mature conventional technology, the moisture content of biomass is as high as typically about 10 wt% after drying [1]. Dried biomass will re-absorb water and start to decompose. In addition, drying has little benefit for the improvement on the properties such as low energy density and bulk density, high oxygen content and grindability. As a slow pyrolysis process at moderate temperatures under atmospheric pressure, torrefaction can solve these problems. Using torrefaction technology, the energy density and bulk density of biomass are increased, and the costs of transportation and storage reduced. Moreover, because of its high process efficiency (94%) compared with pelletisation (84%) and pyrolysis (64%), torrefaction is potentially the best method for improving the economics of the ...

As a clean renewable energy, biomass energy is now gradually being used in electric power, chemicals, heating and other related industries with great potential, and further research is also ongoing in depth. At the same time, because the demand of the construction of environment-friendly society, feed gas from biomass gasification for Fischer-Tropsch fuel synthesis in this way also has gained more and more attention. For the selection of ideal way to obtain synthetic fuels with relatively high system efficiency from biomass, this paper simulation for a variety of processes and different gasification conditions based on Gibbs free energy minimization method. The impacts of pre-treatment of biomass, temperature of gasification and pressure are analyzed. In the evaluation of energy efficiency of the system, an exergy analysis of biomass integrated process is presented. All parts of the process were calculated and compared, which mainly includes the gasification, pre-treatment, HRSG, compression, purification, WGS and FT reactor sections. The results showed that in the process the largest exergy losses take place in the gasifier section, and the pre-treatment of biomass materials for this part will have a greater impact on exergy loss.