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Difference between revisions of "Steam explosion"
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<onlyinclude>'''Steam explosion''' is a is a physicochemical method to break the lignocellulose structure by using high-pressure steam to disrupt the bonding between polymeric components (lignin, cellulose) and decompression to break the lignocellulose structure.</onlyinclude> | <onlyinclude>'''Steam explosion''' is a is a physicochemical method to break the lignocellulose structure by using high-pressure steam to disrupt the bonding between polymeric components (lignin, cellulose) and decompression to break the lignocellulose structure. It can be used to pre-treat the lignocellulosic biomass to improve subsequent processes, such as enzymatic hydrolysis.</onlyinclude> | ||
==Feedstock== | ==Feedstock== | ||
Steam explosion is used to pre-treat lignocellulosic biomass like wood, straw and lignocellulosic wastes for industrial processes. Normally the materal will get into the steam explosion process as [[Sizing|chips]], pellets or grinded materials. | Steam explosion is used to pre-treat lignocellulosic biomass like wood, straw and lignocellulosic wastes for industrial processes. Normally the materal will get into the steam explosion process as [[Sizing|chips]], pellets or grinded materials. | ||
==Process and technologies== | == Process and technologies == | ||
In steam explosion, the | Lignocellulosic biomass materials such as wood are composite materials with high mechanical strength composed by cellulose fibres, lignin polymers as a matrix and hemicelluloses in a tightly packed cellular structures of fibers that form fiber bundles. Their natural function is to bear high mechanical loads, and to resist chemical and enzymatic degradation through microorganisms. In steam explosion, the lignocellulosic biomass is treated with high-pressure hot steam for some time and then the vessel is rapidly depressurized to atmospheric pressure. With this explosive decompression and high temperature it causes degradation of hemicellulose, and it is extracted as water-soluble fraction. The cellulose is largely preserved in its original form, and only slight depolymerization occurs at mild reaction condition. The Lignin undergoes depolymerization by cleavage of β–O–4 linkages, and condensation of the fragments occurs to form a more stable polymer.<ref>{{Cite web|title=Steam Explosion - an overview {{!}} ScienceDirect Topics|url=https://www.sciencedirect.com/topics/chemistry/steam-explosion|date accessed=2021-08-30}}</ref> | ||
Steam explosion was introduced and patented as a biomass pre-treatment process in 1926 by Mason et al. (1926).<ref>W.H. Mason WH (1926): ''Process and apparatus for disintegration of wood and the like.'' US Patent: 1578609, 1926.</ref>. The patent describes a steam explosion process for the pre-treatment of wood where wood chips are fed from a bin through a screw loading valve. The chips are then steam heated at a temperature of about 285°C and a pressure of 3.5 MPa for about 2 min. The pressure is increased rapidly to about 7 MPa (70 bar) for about 5 s, and the chips are then discharged and explode at atmospheric pressure into a pulp. The sudden pressure release defibrillates the cellulose bundles, and this result in a better accessibility of the cellulose for enzymatic hydrolysis and fermentation. Depending on residence time and temperature, steam explosion can result in anything from small cracks in the wood structure, to total defibrillation of the wood fibers.<ref>M. Tanahashi (1990): ''Characterization and degradation mechanisms of wood components by steam explosion and utilization of exploded wood.'' Wood Research 77, 1990: p. 49-117. ([https://core.ac.uk/download/pdf/39187461.pdf pdf])</ref><ref>Wolfgang Stelte: ''Steam explosion for biomass pre-treatment.'' Danish Technological Institute</ref><ref>Kun Wang, Jinghuan Chen, Shao-Ni Sun, Run-Cang Sun: ''Steam Explosion. In: ''Pretreatment of Biomass.'' Elsevier, 2015, p. 75–104. ([https://www.researchgate.net/publication/282595810 pdf])</ref> | |||
=== Supercritical CO<sub>2</sub> === | ===Air=== | ||
===Supercritical CO<sub>2</sub>=== | |||
==Product== | ==Product== | ||