## 3 Results and Discussion
### Analysis of Raw and Torrefied Wheat Straw
The improved fluidization of torrefied particles for subsequent thermochemical processes such as pyrolysis, gasification, or combustion is generally associated with this and an absence of little thread or needle-like fibers at the edge of milled torrefied particles, as confirmed by SEM observations. The raw wheat-straw high-heating-rate chars consist mainly of large, distorted fibrous particles that retain the basic shape of the original biomass particles. Small particles show significantly more loss of initial biomass structures during charring than large particles. The high-heating-rate chars' explosive porous structure is generally assumed to be responsible for this higher reactivity. The images clearly reveal that torrefaction significantly changed the particle microstructure by increasing cellulose porosity and surface area. Fourier transform infrared (FTIR) spectra of the solid raw and 300 \({}^{\circ}\)C-torrefied wheat straw also confirmed changes in the chemical structure (Figure 2). FTIR Spectroscopy employs infrared light and is used to detect and identify structural groups and components belonging to molecules of hemicellulose, cellulose and lignin in the torrefied biomass [40]. The infrared light has wavenumber range of 12,800-10 cm\({}^{-1}\)[40]. The absorption radiation of most organic compounds and inorganic ions is within the 4000-400 cm\({}^{-1}\) range [40]. Functional groups of interest were those in the regions where most of the transformation was observed such as in the O-H, C-O, C-C, C-H and C-O-C groups. In general, the 300 \({}^{\circ}\)C-torrefied wheat straw had its functional group vibrations shifted towards lower wave numbers with changes in intensity. The 1700-1740 cm\({}^{-1}\) corresponded to carboxylic  
Figure 1: SEM imagery of 42–60 mesh wheat-straw particles that were (**a**) not torrefied and (**b**) torrefied at 280 \({}^{\circ}\)C.  
acid groups. A shift in the bands at about 1740-1710 cm\({}^{-1}\) was observed, and these were related to the stretching vibrations of the C-O groups [41]. This vibration was largely due to the degradation of carboxylic acids in hemicelluloses, which include xyloglucan, arabinglucuronoxylan and galactoglucomannan [15] and can comprise up to 32% of wheat-straw cell wall components. Torrefaction at 300 \({}^{\circ}\)C eliminated this signal by decreasing the amount of carboxylic acids groups and generating new products, which appeared at the lower 1700 cm\({}^{-1}\) wave number. Torrefaction at 300 \({}^{\circ}\)C also caused the C-C stretch to move to a lower wave number and increase in intensity. Hemicellulose degradation by torrefaction at 300 \({}^{\circ}\)C therefore likely resulted in an increase in unsaturation as more non-polar and unsaturated compounds were generated. Torrefaction at 300 \({}^{\circ}\)C also caused a decrease in intensity of bands in the 1250-1220 cm\({}^{-1}\) region corresponding to the C-O-C vibrations in cellulose. Torrefaction at 300 \({}^{\circ}\)C caused a decrease in intensity of bands corresponding to lignin. For instance, the vibrations at 1269 cm\({}^{-1}\) potentially resulted from the aromatic C-O stretching of methoxyl and phenyl propane units, and those at 1516 cm\({}^{-1}\) and 1508 cm\({}^{-1}\) potentially resulted from the C-C aromatic ring vibrations. Torrefaction at 300 \({}^{\circ}\)C also caused an increase in aliphatic content and in intensity of bands at 800-900 cm\({}^{-1}\) and 1600 cm\({}^{-1}\) that corresponded to a C=C bond common in aromatics. Torrefaction at 300 \({}^{\circ}\)C caused a decrease in intensity for bands between 1030 and 1100 cm\({}^{-1}\) that corresponded to a decrease in C-O bonds, and volatiles and oxygen content. Torrefaction at 300 \({}^{\circ}\)C also caused a decrease in intensity in the 3060-3100 cm\({}^{-1}\) band (data not shown) corresponding to the O-H bonds as H\({}_{2}\)O was removed to make the wheat-straw more hydrophobic and less susceptible to microbial spoilage during storage.