Steam-explosion process, utilization

The steam explosion process is a recent development in wood processing (1,2). Much attention has been paid to this process from the viewpoint of total wood utilization. Cellulose and hemicellulose from this process can be converted into sugars of commercial value by enzymatic methods (3). However, the conversion of lignin from this process (steam explosion lignin) into useful materials continues to present difficulties. Preparation of adhesives from it is considered to be a feasible way to solve this problem. 

Shimizu, K., Sudo, H. and Fijii, T. (1989). Total utilisation of wood components by steam explosion pre-treatment. In Wood Processing and Utilization, Kennedy, J.F., Phillips, G.O. and Williams, P.A. (Eds.). Ellis Harwood, Chichester, UK, pp. 407 12. 

Steam-explosion lignins have received some attention as adhesives mainly because this process offers some potential for utilizing low-quality hardwoods. Like kraft lignin, these preparations also require activation [e.g., by hydroxymethy-lation (70), isocyanation (75,80)] to achieve any type of acceptable wood composite adhesive properties. 

R. Akiyoshi, S. Nishio, and I. Tanasawa, An Attempt to Produce Particles of Amorphous Materials Utilizing Steam Explosion, in I. Tanasawa and N. Lior (eds.). Heat and Mass Transfer in Materials Processing, pp. 330-343, Hemisphere, New York, 1992. 

Shimizu K, Sudo K, Ono H, Fujii T. Total utilisation of wood components by steam explosion treatment. In Wood processing and utilization. Chichester Ellis Horwood Lim 1989. p. 407—12. 

CHP production The solid residue from the beer column and me concentrated syrup from the evaporation plant can be used to generate heat to the process and electricity in a CHP plant. If necessary, bark from the debarking unit can also be used. The CHP plant (back-pressure steam turbine unit with steam extraction at appropriate pressme levels to supply utility and process steam) was simulated in Aspen Plus (for input dam, see Figure 4.5). Utility steam is used for process heating in, for example, distillation column reboilers and can be merefore replaced by another hot utility at me same temperature. Process steam is used in the process directly as, for example, in the pretreatment step where steam is used for steam explosion to separate to wood components. As steam in this case is an essential part of the process, it cannot be replaced by another utility. 

Table 9 is a very cryptic summary of some of the new emerging technologies. Most of them have been commercialized but not popularized yet. Use of superheated steam instead of air as the drying medium affords numerous advantages, e.g., low net energy consumption if exhaust steam is utilized fully elsewhere in the process, no oxidation/combustion/ /fire/explosion risk, sometimes a better quality product, reduced environmental impact since gaseous emissions can be eliminated. Use of heat pumps to improve energy efficiency and... 

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