【正文】 reated biomass[33]. The aforementioned improved properties of torrefied biomass are favorable for transportation, utilization and storage of biomassbecause of its increased stability and durability.4. GrindabilityThrough deposition of the hemicelluloses coupled with depolymerization of cellulose and thermal softening of lignin, the orientation of microfibrils is displaced during torrefaction. The cell wall in the biomass sample is greatly weakened after torrefaction[37]. The increased brittleness and friability introduced by torrefaction improves the grindability of biomass. The ease of minutionin torrefaction studies is widely examined through the particle distribution of milled samples after being distributed according to its size range. Generally, grindability of biomass improves after torrefaction based on the increased percentages of fine particle as torrefaction condition are raised [26,27,39]. An alternative method is the particle distribution study is coupled with grinding energyconsumption in examining the grindability [47,52]. Specific energy consumption for treated biomass are reduced as much as 10 times after torrefaction [31]. Literature defines the improved grindabilityand reduced energy consumption in minution to a two stage mechanism [52].The improved ease to grind biomass is attributed to the dehydration and physical transformation of lignin at lower , the second stage is the thermal degradation of the cell wall biomass as discussed earlier that contributes to the higher percentage of fine particle after torrefaction [52]. The standard Hardgrove Grindability Index (HGI) used to analyze the grindabilityof coal had been studied in literature for torrefied biomass sample[47]. The modified HGI study adopted volumetric measurement for the sample to be milled in place of mass measurement as biomass are of lower density pared to coal. Although treated sample achieves similar grindability to reference coal samples for extended torrefaction parameter, literature indicate that volumetric HGI may underestimate the grinding property of biomass as large fraction of biomass were removed in the premilling step [47]. The result obtain from volumetric HGI is not representative of all samples, although a general improvement in the grindability of torrefied biomass has been observed.. KineticsReaction kinetics studies the rate of chemical reaction as well as factors affecting the speed of reaction. In the establishment of appropriate thermochemical conversion processes and design of the operational equipments, fundamental knowledge of the reaction mechanism and kinetics is vital. Mathematical model examined for torrefaction kinetic studies were mainly models derived for biomass pyrolysis process [53–55]. Biomass is typically regarded as posed of mainly hemicelluloses, cellulose and lignin. Studies have shown that the biomass pyrolysis process can be subdivided into four main regimes [56,57]. Moisture evolution is the main reaction mechanism at low temperature below220 ?C. Hemicelluloses degradation follows at temperature above 200 ?C with lignin deposing slowly in the background starting from around 160 ?C until 900 ?C. Cellulose deposition continues from 200 ?C to 400 ?C. In literature, torrefaction has been defined as a mild pyrolysis process which improves the fuel properties of biomass [26,44]. Reviewing the torrefaction temperature range of 200–300 ?C, the main reaction activity prise of moisture evolution, hemicelluloses deposition with limited degradation of lignin and cellulose. Table 5 summarizes the kinetic models applied for the torrefaction conditions. One step global model is the simplest form of pyrolysis kinetic model whereby overall biomass thermal degradation is modeled as a single step first order reaction. The one step global model described in Table 5 was examined for the anhydrous weight loss kinetic of two woody biomass (spruce and beech) subject to torrefaction process [53]. Good fitting between the calculated and experimental anhydrous weight loss (R2 of –) was reported. The authors assumed the thermal deposition of spruce and beech to be similar and adopted the activation energy of kJ/mol, as defined in literature for model fitting [58]. The resulting kinetic constant fits the predicted reactivity of hardwood versus softwood。 beech and spruce were 105 kg/kg s and 105 kg/kg s, respectively. However in practical application, this single step model is not applicable for the prediction of product yield due to the assumption of fixed ratio of pyrolytic products [59].Several studies adopted a two step consecutive model, the Di Blasi–Lanzetta model for the weight loss kinetics of woody biomass[22,53,55,59]. An intermediate reaction product accounting for secondarydevolatization reactions is introduced in the model. For the temperature range of 230–300 ?C, the kinetics of torrefaction reactions can be well described by two consecutive first order reactions,depicting hemicelluloses degradation followed by cellulose deposition[55]. Correlation using the Di Blasi–Lanzetta model was reported to fit better (R2 value of –) than the single stepmodel for both hardwood and softwood [53]. The improved fitting of model is attributed to the two step consecutive model taking account of the intermediate pseudoponent [53,55]. Based on the kinetic parameters derived for the willow sample, the rate of the first reaction is higher than the second reaction [60].Within the torrefaction temperature regime, thermal deposition continues under an extended duration. Literature accounts this phenomenon to the deposition of cellulose and lignin possible catalyzed by the inorganic substance or the liquid and gaseous byproducts [60].17