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Difference between revisions of "Steam explosion"
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Lignocellulosic biomass such as wood exists of composite materials with high mechanical strength composed of cellulose fibres, lignin polymers as a matrix and hemicelluloses in a tightly packed cellular structure of fibres that form fibre bundles. Their natural function is to bear high mechanical loads, and to resist chemical and enzymatic degradation through microorganisms. Steam explosion breaks this structure down to enable these chemical and enzymatic [[Conversion|conversions]]. It converts biomass in a steam atmosphere at elevated temperatures ranging from 140 to 240 °C. The steam pressure is rapidly reduced to atmospheric pressure, whereby a mechanical disruption of the biomass occurs. In steam explosion, the lignocellulosic biomass is treated with high-pressure hot steam for some time and then the vessel is rapidly depressurised to atmospheric pressure. With this explosive decompression and high temperature it causes degradation of hemicellulose, which is extracted as water-soluble fraction. The cellulose is largely preserved in its original form, and only slight depolymerisation occurs at mild reaction condition. The Lignin undergoes depolymerisation 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> | Lignocellulosic biomass such as wood exists of composite materials with high mechanical strength composed of cellulose fibres, lignin polymers as a matrix and hemicelluloses in a tightly packed cellular structure of fibres that form fibre bundles. Their natural function is to bear high mechanical loads, and to resist chemical and enzymatic degradation through microorganisms. Steam explosion breaks this structure down to enable these chemical and enzymatic [[Conversion|conversions]]. It converts biomass in a steam atmosphere at elevated temperatures ranging from 140 to 240 °C. The steam pressure is rapidly reduced to atmospheric pressure, whereby a mechanical disruption of the biomass occurs. In steam explosion, the lignocellulosic biomass is treated with high-pressure hot steam for some time and then the vessel is rapidly depressurised to atmospheric pressure. With this explosive decompression and high temperature it causes degradation of hemicellulose, which is extracted as water-soluble fraction. The cellulose is largely preserved in its original form, and only slight depolymerisation occurs at mild reaction condition. The Lignin undergoes depolymerisation 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 [[Hydrolysis#Enzymatic|enzymatic hydrolysis]], [[Hydrolysis#Acid|acid hydrolysation]]<ref name=":0">David Steinbach, Andrea Kruse, Jörg Sauer, Jonas Storz (2020): ''Is Steam Explosion a Promising Pretreatment for Acid Hydrolysis of Lignocellulosic Biomass?'' Process 8, 1626;, p. 75–104. ([https://www.mdpi.com/2227-9717/8/12/1626 pdf])</ref> or [[Industrial fermentation|fermentation]].<ref name=":1">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 name=":2">Wolfgang Stelte: ''Steam explosion for biomass pre-treatment.'' Danish Technological Institute</ref><ref name=":3">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> | 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 [[Hydrolysis#Enzymatic hydrolysis|enzymatic hydrolysis]], [[Hydrolysis#Acid|acid hydrolysation]]<ref name=":0">David Steinbach, Andrea Kruse, Jörg Sauer, Jonas Storz (2020): ''Is Steam Explosion a Promising Pretreatment for Acid Hydrolysis of Lignocellulosic Biomass?'' Process 8, 1626;, p. 75–104. ([https://www.mdpi.com/2227-9717/8/12/1626 pdf])</ref> or [[Industrial fermentation|fermentation]].<ref name=":1">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 name=":2">Wolfgang Stelte: ''Steam explosion for biomass pre-treatment.'' Danish Technological Institute</ref><ref name=":3">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> | ||
==Product== | ==Product== | ||
Steam explosion is a pre-treatment process that make biomass more suitable for following processes, such as [[Hydrolysis#Enzymatic|enzymatic hydrolysis]], [[Hydrolysis#Acid|acid hydrolysation]]<ref name=":0" /> or [[Industrial fermentation|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 name=":1" /><ref name=":2" /><ref name=":3" /> | Steam explosion is a pre-treatment process that make biomass more suitable for following processes, such as [[Hydrolysis#Enzymatic hydrolysis|enzymatic hydrolysis]], [[Hydrolysis#Acid|acid hydrolysation]]<ref name=":0" /> or [[Industrial fermentation|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 name=":1" /><ref name=":2" /><ref name=":3" /> | ||
=== Post-treatment === | === Post-treatment === | ||