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Pyrolysis (from greek ''pyr,'' "fire" and ''lysis,'' "loosing/unbind") is a thermochemical process which is able to convert organic compounds in presence of heat and absence of oxygen into valuable products which can be solid, liquid or gaseous. The chemical transformations of substances are generally accompanied by the breaking of chemical bonds which leads to the conversion of more complex molecules into simpler molecules which may also combine with each other to build up larger molecules again. The products of pyrolysis are usually not the actual building blocks of the decomposed substance, but are structurally modified (e.g. by cyclization or rearrangement). | Pyrolysis (from greek ''pyr,'' "fire" and ''lysis,'' "loosing/unbind") is a thermochemical process which is able to convert organic compounds in presence of heat and absence of oxygen into valuable products which can be solid, liquid or gaseous. The chemical transformations of substances are generally accompanied by the breaking of chemical bonds which leads to the conversion of more complex molecules into simpler molecules which may also combine with each other to build up larger molecules again. The products of pyrolysis are usually not the actual building blocks of the decomposed substance, but are structurally modified (e.g. by cyclization and aromatisation or rearrangement). | ||
== Feedstock == | == Feedstock == | ||
=== Origin and composition === | |||
=== Pre-treatment === | |||
The pre-treatment of the feedstock has an impact on the pyrolysis process, its efficiency, and the yield of certain products. The following pre-treatments may be considered <ref name=":0" />: | |||
* Sizing (e.g. chipping) | |||
* Densification | |||
* Chemical pre-treatment | |||
** Acid and alkali pre-treatment | |||
** Hydrothermal pre-treatment | |||
** Steam explosion | |||
** Ammonia fibre expansion | |||
** Thermal pre-treatment (e.g. drying) | |||
** Biochemical pre-treatment | |||
== Process == | == Process == | ||
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=== Reactions === | === Reactions === | ||
A range of different reactions occur during the process such as dehydration, depolymerisation, isomerisation, aromatisation, decarboxylation, and charring<ref>{{Cite journal|author=Hu, X. and Gholizadeh, M.|year=2019|title=Biomass pyrolysis: A review of the process development and challenges from initial researches up to the commercialisation stage|journal=Journal of Energy Chemistry|volume=39|issue=|page=109-143|doi=doi:https://doi.org/10.1016/j.jechem.2019.01.024}}</ref>. | A range of different reactions occur during the process such as dehydration, depolymerisation, isomerisation, aromatisation, decarboxylation, and charring<ref name=":0">{{Cite journal|author=Hu, X. and Gholizadeh, M.|year=2019|title=Biomass pyrolysis: A review of the process development and challenges from initial researches up to the commercialisation stage|journal=Journal of Energy Chemistry|volume=39|issue=|page=109-143|doi=doi:https://doi.org/10.1016/j.jechem.2019.01.024}}</ref>. | ||
== Product == | == Product == | ||
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Czajczyńska, D., Anguilano, L., Ghazal, H., Krzyżyńska, R., Reynolds, A. J., Spencer, N. and Jouhara, H. 2017: Potential of pyrolysis processes in the waste management sector. Thermal Science and Engineering Progress, Vol. 3 171-197. doi:<nowiki>https://doi.org/10.1016/j.tsep.2017.06.003</nowiki> | Czajczyńska, D., Anguilano, L., Ghazal, H., Krzyżyńska, R., Reynolds, A. J., Spencer, N. and Jouhara, H. 2017: Potential of pyrolysis processes in the waste management sector. Thermal Science and Engineering Progress, Vol. 3 171-197. doi:<nowiki>https://doi.org/10.1016/j.tsep.2017.06.003</nowiki> | ||
Speight, J. 2019: Handbook of Industrial Hydrocarbon Processes. Gulf Professional Publishing, Oxford, United Kingdom. | Speight, J. 2019: Handbook of Industrial Hydrocarbon Processes. Gulf Professional Publishing, Oxford, United Kingdom. | ||