Chemical nature of raw material from biomass

Before detailing the pyrolysis processes and its reactors, it is necessary to specify the origin, properties, and chemical compositions of the raw material, as well as products from biomass. Several experimental studies have reported cases on the composition of biomass. A review was quite extensive and recently studied by Vassilev et al. (2010). Naturally, the composition of the vapors and gases produced depends on the characteristics of the raw material, the pyrolysis process, and operating conditions. Therefore, knowledge of the chemical nature is the first and essential step in this process. 

Vegetative biomass is comprised primarily of cellulose, hemicellulose, and lignin along with lesser amounts of extractives (e.g., tannins, fatty acids, oils, and resins), moisture, and mineral matter (Orfao et ah, 1999). Most of the results published in the literature are based on lignin and cellulose (Naik et ah, 2010). 

The lignin biopolymer consists of a complex network of cross-linked aromatic molecules, which serves to inhibit the absorption of water through cell walls. The structure and chemical composition of lignin are determined by the type and age of the plant from which the lignin is isolated (White et al., 2011). 

The first step in converting biomass is very fast and its results indicate the presence of unstable intermediates, which are difficult to quantify experimentally. The formation of these compounds occurs in a very short contact time and with a high rate of 

The conversion of biomass produces carbon, gases, and vapors in the first stage, and then these products are transformed into other compounds, which depend on the operating conditions. Some authors argue that intermediaries, called complex active, are unstable and rapidly converted into vapors and gases. The lifetime of these intermediate materials is less than 10 ms. Vapors intermediates are converted into gases at elevated temperatures and, if rapidly quenched, form complex liquid (bio-oil). For that, the contact time between the components must be less than 1 s. 

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