Difference between revisions of "Pyrolysis"
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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 == | ||
| Line 15: | Line 30: | ||
=== 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. | ||
Revision as of 11:42, 14 April 2021
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
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 [1]:
- 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
The pyrolysis is an endothermal process which requires the input of energy in form of heat which can either be directly (direct pyrolysis) applied via hot gases or indirectly (indirect pyrolysis) via external heating of the reactor. Compared to gasification, the process takes place in an atmosphere without oxygen or at least under a limitation of oxygen.
In general, pyrolysis can be divided into different steps which includes:
- Evaporation and vapourisation of water and other volatile molecules which is induced at temperatures > 100 °C
- Thermal excitation and dissociation of the molecules induced at temperatures between 100-600 °C, which also may involve the production of free radicals as intermediate stage
- Reaction and recombination of the molecules, and triggering of chain reactions through free radicals
The pyrolysis process and the formation of products can be controlled to a certain extend via different temperature ranges and reaction times as well as by utilising reactive gases, liquids, catalysts, alternative forms of heat application (e.g. via microwaves or plasma), and a variety of reactor designs.
Reactions
A range of different reactions occur during the process such as dehydration, depolymerisation, isomerisation, aromatisation, decarboxylation, and charring[1].
Product
Technology providers
Patents
References
Al Arni, S. 2018: Comparison of slow and fast pyrolysis for converting biomass into fuel. Renewable Energy, Vol. 124 197-201. doi:https://doi.org/10.1016/j.renene.2017.04.060
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:https://doi.org/10.1016/j.tsep.2017.06.003
Speight, J. 2019: Handbook of Industrial Hydrocarbon Processes. Gulf Professional Publishing, Oxford, United Kingdom.
Tan, H., Lee, C. T., Ong, P. Y., Wong, K. Y., Bong, C. P. C., Li, C. and Gao, Y. 2021: A Review On The Comparison Between Slow Pyrolysis And Fast Pyrolysis On The Quality Of Lignocellulosic And Lignin-Based Biochar. IOP Conference Series: Materials Science and Engineering, Vol. 1051 doi:10.1088/1757-899X/1051/1/012075
Waheed, Q. M. K., Nahil, M. A. and Williams, P. T. 2013: Pyrolysis of waste biomass: investigation of fast pyrolysis and slow pyrolysis process conditions on product yield and gas composition. Journal of the Energy Institute, Vol. 86 (4), 233-241. doi:10.1179/1743967113Z.00000000067
Zaman, C. Z., Pal, K., Yehye, W. A., Sagadevan, S., Shah, S. T., Adebisi, G. A., Marliana, E., Rafique, R. F. and Johan, R. B. 2017: Pyrolysis: A Sustainable Way to Generate Energy from Waste. IntechOpen
- ↑ a b Hu, X. and Gholizadeh, M., 2019: Biomass pyrolysis: A review of the process development and challenges from initial researches up to the commercialisation stage. Journal of Energy Chemistry, Vol. 39, 109-143. doi: https://doi.org/doi:https://doi.org/10.1016/j.jechem.2019.01.024