Pyrolysis: Difference between revisions
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==Kiln/Reactor Types in Pyrolysis== | ==Kiln/Reactor Types in Pyrolysis== | ||
=== Fixed Bed Reactor === | === Fixed Bed Reactor === | ||
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Fixed bed reactors were traditionally used to produce charcoal due to slow and poor heat transfer resulting in very low liquid charcoal yields. The technology is simple and reliable and utilises relatively uniform particle size. This type of kiln/furnace is divided into downdraft and updraft. | |- | ||
In a downdraft fixed bed reactor, the solid material moves slowly down a vertical shaft, with the solid and product gas move downward in a co-current mode which produces a relatively clean gas with low tar and high carbon conversion rate. In an updraft fixed bed reactor, the [[Feedstock|feedstock]] also moves down a vertical shaft but in a counter-current mode. This results in a dirty product gas with high levels of tars which can be alleviated using tar crackers. However, due to the [[Feedstock|feedstock]] not moving during the process, it is difficult to obtain heating of large quantities of [[Feedstock|feedstock]] material on an industrial scale. This could be solved if the reactor used methods that enable better heat transfer such as heat pipes. <ref>[https://www.sciencedirect.com/journal/thermal-science-and-engineering-progress/vol/3/suppl/C Potential of Pyrolysis Processes in the Waste Management Sector]</ref> | | Fixed bed reactors were traditionally used to produce charcoal due to slow and poor heat transfer resulting in very low liquid charcoal yields. The technology is simple and reliable and utilises relatively uniform particle size. This type of kiln/furnace is divided into downdraft and updraft. In a downdraft fixed bed reactor, the solid material moves slowly down a vertical shaft, with the solid and product gas move downward in a co-current mode which produces a relatively clean gas with low tar and high carbon conversion rate. In an updraft fixed bed reactor, the [[Feedstock|feedstock]] also moves down a vertical shaft but in a counter-current mode. This results in a dirty product gas with high levels of tars which can be alleviated using tar crackers. However, due to the [[Feedstock|feedstock]] not moving during the process, it is difficult to obtain heating of large quantities of [[Feedstock|feedstock]] material on an industrial scale. This could be solved if the reactor used methods that enable better heat transfer such as heat pipes. || [[File:Schematic diagram of a fixed bed pyrolysis reactor.png|250px|right|Schematic diagram of a fixed bed pyrolysis reactor. All rights reserved.]]<br clear=all>''Fixed bed reactor''<ref>[https://www.sciencedirect.com/journal/thermal-science-and-engineering-progress/vol/3/suppl/C Potential of Pyrolysis Processes in the Waste Management Sector]</ref> | ||
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===Fluidised Bed Reactor=== | ===Fluidised Bed Reactor=== | ||
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==== Bubbling ==== | ==== Bubbling ==== | ||
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In bubbling fluidised beds, particles are entered into a bed of hot sand fluidised by a recirculated product gas. The high heat transfer rates from the fluidised sand cause rapid heating of [[Biomass|biomass]] particles and some ablation with the sand particles occurs. This type of reactor is characterised by good temperature control, limited turn down capacity and efficient heat transfer to [[Biomass|biomass]] particles due to high solid density. | | In bubbling fluidised beds, particles are entered into a bed of hot sand fluidised by a recirculated product gas. The high heat transfer rates from the fluidised sand cause rapid heating of [[Biomass|biomass]] particles and some ablation with the sand particles occurs. This type of reactor is characterised by good temperature control, limited turn down capacity and efficient heat transfer to [[Biomass|biomass]] particles due to high solid density. || [[File:Bubbling Fluidised Bed Reactor with an Electrostatic Precipitator.png|250px|right|Bubbling fluidised bed reactor with an electrostatic precipitator. All rights reserved.]]<br clear=all>''Bubbling fluidised bed reactor''<ref>[https://www.researchgate.net/publication/318678876_Review_of_Synthetic_Fuels_and_New_Materials_Production_Based_on_Pyrolysis_Technologies Review of Synthetic Fuels and New Materials Production Based on Pyrolysis Technologies]</ref> | ||
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==== Circulating ==== | ==== Circulating ==== | ||
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| In circulating fluidised beds, [[Biomass|biomass]] particles are introduced into a circulating bed of hot sand. The recirculated product gas, sand and [[Biomass|biomass]] move together in the reactor. The high heat transfer rates from the sand ensure rapid heating of the [[Biomass|biomass]] and ablation is more prevalent than bubbling fluidised beds. This reactor is characterised by good temperature control and high heating rates. The residence time for the tar produced is around the same for the vapour and gas and can be separated by cyclone. || [[File:Circulating Fluidised Bed Reactor.png|250px|Circulating fluidised bed reactor. All rights reserved.]]<br clear=all>''Circulating fluidised bed reactor | | In circulating fluidised beds, [[Biomass|biomass]] particles are introduced into a circulating bed of hot sand. The recirculated product gas, sand and [[Biomass|biomass]] move together in the reactor. The high heat transfer rates from the sand ensure rapid heating of the [[Biomass|biomass]] and ablation is more prevalent than bubbling fluidised beds. This reactor is characterised by good temperature control and high heating rates. The residence time for the tar produced is around the same for the vapour and gas and can be separated by cyclone. || [[File:Circulating Fluidised Bed Reactor.png|250px|Circulating fluidised bed reactor. All rights reserved.]]<br clear=all>''Circulating fluidised bed reactor''<ref name="ref2">[https://www.researchgate.net/publication/330335978_Design_of_A_Fluidized_Bed_Reactor_For_Biomass_Pyrolysis Design of A Fluidized Bed Reactor For Biomass Pyrolysis]</ref> | ||
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