Biomass properties composition

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Complex pyrolysis chemistry takes place in the conversion system of any conventional solid-fuel combustion system. The pyrolytic properties of biomass are controlled by the chemical composition of its major components, namely cellulose, hemicellulose, and lignin. Pyrolysis of these biopolymers proceeds through a series of complex, concurrent and consecutive reactions and provides a variety of products which can be divided into char, volatile (non-condensible) organic compounds (VOC), condensible organic compounds (tar), and permanent gases (water vapour, nitrogen oxides, carbon dioxide). The pyrolysis products should finally be completely oxidised in the combustion system (Figure 14). Emission problems arise as a consequence of bad control over the combustion system. 

Particle physical properties typically change under the impact of smoke plume but these changes may not be specific for the wildfire smoke. In addition to biomass burning, particle mass or number concentration can increase due to the biogenic or other anthropogenic sources, e.g., traffic or industrial emissions. Chemical composition of particles is more unique to particle source, however, particles with similar chemistry can have different origin. Physical and chemical properties of the LRT biomass burning particles observed in Northern Europe are discussed below. Physical properties and the chemical components measured from the smoke particles are summarized in Table 2. The measurements of PM mass concentrations are excluded from Table 2 as nearly all the studies had some measurements of particle mass. 

After release from fires, organic and some inorganic components undergo rapid or more delayed chemical transformation in the atmosphere. The physical properties as well as chemical composition of smoke particles may alter on the way from the source areas (biomass burning areas) to the measurement sites in Northern Europe. There are several reasons why particle properties change. Chemical components can, e.g., become oxidized or substituted in particles, but also the condensation of secondary material onto the LRT particles during the transport changes the particle properties. 

Bio-oil from rapid pyrolysis is usually a dark brown, free-flowing liquid having a distinctive smoky odor. It has significantly different physical and chemical properties compared to the liquid from slow pyrolysis processes, which is more like a tar. Bio-oils are multicomponent mixtures comprised of different size molecules derived primarily from depolymerization and fragmentation reactions of the three key biomass building blocks cellulose, hemicellulose, and lignin. Therefore, the elemental composition of biooil resembles that of biomass rather than that of petroleum oils. Basic properties of biooils are shown in Table 33.7. More detail on fuel-related characteristics is provided in the literature.571... 

Syngas composition, most importantly the H2/CO ratio, varies as a function of production technology and feedstock. Steam methane reforming yields H2/CO ratios of three to one whereas coal and biomass gasification yields ratios closer to unity or lower. Conversely, the required properties of the syngas are a function of the synthesis process. Fewer moles of product almost always occur when H2 and CO are converted to fuels and chemicals. Consequently, syngas conversion processes are more thermodynamically favorable at higher H2 and CO partial pressures. The optimum pressures depend on the specific synthesis process. 

The median elemental compositions of FAs, HAs, and NOM are rather similar, and so consequently are properties such as the average oxidation state of organic carbon and the total unsaturation of these materials. Most of the elemental compositions that were included in this review lie outside the biomass triangle on a van Krevelen plot, indicating that DOM is not simply a residue of biomass. It has clearly gained oxygen and lost hydrogen, as would be expected for partial oxidation of biomass to CO2 and H2O. 

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