Gasification: Difference between revisions

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[[Category:Technologies & Solutions]]

[[Gasification]] is the thermal ~~breakdown~~ of a material into a gas via partial oxidation under the application of heat. It Involves the sub-stoichiometric oxidation or steam reformation of a substance to produce a gaseous mixture containing two or more of the following: (i) oxides of carbon, (ii) methane and (iii) hydrogen<ref>[[DEFRA]] 2018. [https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/765494/ACT_Guidance_-_Compliance_with_the_ACT_Efficiency_Standard_criterion.pdf Guidance Note for Advanced Conversion Technologies Compliance with the ACT Efficiency Standard criterion in the Contract for Difference scheme.] London. </ref>. The gas is then generally burnt to raise steam and create electricity, but many plants are exploring the option of cleaning the gas for use in a gas engine or separating the gas into usable fractions such as hydrogen for use, as an example, of liquid fuels which in ~~turn may be eligible under~~ the [[~~RTFO~~]].

[[Gasification]] is a form of [[treatment|thermal treatment]] of a material into a gas via partial oxidation under the application of heat.

==Overview==

[[Gasification]] is a form of [[treatment|thermal treatment]] of a material into a gas via partial oxidation under the application of heat. It Involves the sub-stoichiometric oxidation or steam reformation of a substance to produce a gaseous mixture containing two or more of the following: (i) oxides of carbon, (ii) methane and (iii) hydrogen<ref>[[DEFRA]] 2018. [https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/765494/ACT_Guidance_-_Compliance_with_the_ACT_Efficiency_Standard_criterion.pdf Guidance Note for Advanced Conversion Technologies Compliance with the ACT Efficiency Standard criterion in the Contract for Difference scheme.] London. </ref>. The gas is then generally burnt to raise steam and create electricity, but many [[Energy from Waste]] plants are exploring the option of cleaning the gas for use in a gas engine or separating the gas into usable fractions such as hydrogen for use, as an example, as liquid fuels.

== History ==

[[Gasification]] was originally developed in the early 1800s for the production of town gas, which was a gaseous product manufactured from coal. It provided gas for lighting, cooking and heating for the industrialising Europe and North America in the 19th century. The first use of town gas produced via gasification occurred in 1807 where it was used in Pall Mall, London as the first public street lighting.

[[Gasification]] moved to producing synthetic fuels and chemicals in the 1920s. The process was used widely during World War II to produce transportation fuels from coal via the [[Fischer Tropsch Process]]. It has been used in the last 40-60 years to convert coal and oil into hydrogen for use in the production of fertilisers (mainly ammonia) and for [[feedstock]] preparation in the chemical and refinery industries.

At the start of the 21st century, [[Gasification|gasification]] began commercial scale use by the power industry in Integrated [[Gasification]] Combined Cycle (IGCC) plants. IGCC plants convert carbonaceous materials/waste into electricity, with the raw [[syngas]] cleaned of particulate matter and pollutants<ref>[https://www.mdpi.com/1996-1073/3/2/216 Gasification Processes Old and New]</ref>.

~~Gasification can be considered~~ a ~~process between~~ [[~~Pyrolysis~~|~~pyrolysis~~]] ~~and conventional~~ [[~~EfW~~]] ~~in that it involves the partial oxidation of~~ a ~~substance. This means~~ that ~~oxygen is added but the amounts are not enough to allow the fuel to be completely oxidised and full combustion to occur. The temperatures employed are typically above 650°C. Generally,~~ the [[Syngas~~|syngas~~]] ~~generated from Gasification will have~~ a [[~~Net Calorific Value~~]] ([[~~NCV~~]]) of ~~4-10MJ~~/~~Nm3 <~~ref>[[~~DEFRA~~]], ~~2013.~~ [https://~~assets.publishing.service~~.gov.uk/~~government~~/~~uploads~~/~~system/uploads/attachment_data/file/221035/pb13888~~-~~thermal~~-~~treatment~~-~~waste~~.~~pdf Advanced Thermal Treatment~~ of ~~Municipal Solid~~ Waste.] ~~London. </ref>~~.

==Context and Definition==

In legal terms, a '''‘waste incineration plant’''' means any stationary or mobile technical unit and equipment dedicated to the [[Treatment|thermal treatment]] of waste, with or without recovery of any energy generated, or whether the gases resulting from the thermal [[treatment]] are subsequently incinerated <ref>As an example, a [[Pyrolysis]] facility that burnt the produced [[Syngas]] to generate electricity would be Incineration, whereas a [[Pyrolysis]] facility that processed [[Syngas]] for vehicle fuel would not be classed as an incinerator</ref><ref name='ref01'>European Commission, 2010 Industrial Emissions Directive 2010/75/EU of the European Parliament and of the Council of 24 November 2010 on industrial emissions (integrated pollution prevention and control). Official Journal of the European Union.</ref>. If the [[Incineration|Incinerator]] can be shown to meet the energy efficiency measurement of [[R1]] it can be classified as a [[recovery]] facility, if it cannot it is classified as a [[disposal]] facility<ref>https://data.gov.uk/dataset/8287c81b-2288-4f14-9068-52bfda396402/r1-status-of-incinerators-in-england</ref>. This means that an incinerator that generates power, and is a net exporter of power, can be described as an '''[[Energy from Waste]]''' ([[EfW]]) facility. An incinerator that is an [[EfW]] facility that meets the [[R1]] criteria is the only type of incinerator under the legislation that can legitimately describe itself as an '''[[Energy Recovery Facility]]''' ([[ERF]]).

=~~= History ==~~

The most recent recent [[BAT|BREF]] guidance<ref name="Inc">[https://eippcb.jrc.ec.europa.eu/sites/default/files/2020-01/JRC118637_WI_Bref_2019_published_0.pdf BAT and BREF for Waste incineration]</ref> also sets out how incinerators can be described by:

* waste origin (e.g. Municipal Incinerators), '''and in WikiWaste includes [[Residual Waste EFW]] and [[Biomass Waste EFW]]''',

* the nature of the waste (e.g. Hazardous Waste Incinerators),

* the method/type of incineration (e.g. High Temperature Incinerators)

~~The~~ [[~~Gasification|gasification~~]] concept was originally developed in the early 1800s for the production of town gas which was a gaseous product manufactured from coal. It provided gas for lighting, cooking and heating for the industrialising Europe and North America in the 19th century. The first use of town gas produced via gasification occurred in 1807 where it was used in Pall Mall, London as the first public street lighting.

In WikiWaste these last two bullet points are covered in '''[[High Temperature and Clinical Waste Incineration]]'''.

[[Gasification]] moved to producing synthetic fuels and chemicals in the 1920s. The process was used widely during World War II to produce transportation fuels from coal via the [[Fischer Tropsch Process]]. It has been used in the ~~last 40-60 years~~ to ~~convert coal and oil into hydrogen for use in the production of fertilisers (mainly ammonia) and for [[feedstock]] preparation in the chemical and refinery industries.~~

However, there are a range of other terms used in the sector to describe different types of incineration, the kiln/furnace used, and the [[subsidy]] that may apply to them, and these are captured in the table below:

~~At the start~~ of ~~the 21st century~~, ~~[[Gasification|gasification]] began commercial scale use by~~ the ~~power industry in Integrated [[Gasification]] Combined Cycle (IGCC) plants. IGCC plants convert carbonaceous materials~~/~~waste into electricity~~, ~~with~~ the ~~raw~~ [[~~syngas~~]] ~~cleaned of particulate matter~~ and ~~pollutants. This emissions free, renewable process allows~~ the ~~production of clean energy while solving waste problems simultaneously. <ref>[https://www.mdpi.com/1996-1073/3/2/216 Gasification Processes Old and New]</ref>~~

~~ ~~

~~==Context==~~

{|class="wikitable"

!colspan=2|Definitions in Legislation!!rowspan=7 style="padding: 50px"| !!Types!!Temp. Range °C!!Category!!rowspan=7 style="padding: 50px"|  !!Kiln/Furnace/Reactor

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|[[Fluidised Bed]]

|-

|rowspan=2|[[Gasification]]||rowspan=2|500 - 1600||rowspan=2| [[Advanced Thermal Treatment]] ([[ATT]] and [[ACT]])||[[~~Reciprocating &~~ Rotary]]

|rowspan=2|[[Gasification]]||rowspan=2|500 - 1600||rowspan=2| [[Advanced Thermal Treatment]] ([[ATT]] and [[ACT]])||[[Rotary Kiln]]

|-

|rowspan=3|[[Incineration without Energy Recovery|Without Energy Recovery]]||[[Plasma]]

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|[[Surface contact]]

|}

~~== Autothermal Gasifiers ==~~

Autothermal (direct) gasifiers provide the necessary heat of conversion by adding an oxidant to achieve partial oxidation of the fuel within the gasification reactor. This releases energy directly in the reactor where it is consumed. Autothermal conditions are easy to achieve using air or oxygen. Overall the complexity of the process is reduced compared to allothermal gasifiers, however the heat release occurs in the zone of contact between the oxidant and a combustible which requires a good internal heat transfer to even out the temperature or causes a temperature gradient inside the gasifier.

~~Types~~ of autothermal gasifier:

Gasification can be considered a process between [[Pyrolysis|pyrolysis]] and conventional [[Combustion]] in that it involves the partial oxidation of a substance. This means that oxygen is added but the amounts are not enough to allow the fuel to be completely oxidised and full combustion to occur. The temperatures employed are typically above 650°C. Generally, the [[Syngas|syngas]] generated from Gasification will have a [[Net Calorific Value]] ([[NCV]]) of 4-10MJ/Nm3 <ref>[[DEFRA]], 2013. [https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/221035/pb13888-thermal-treatment-waste.pdf Advanced Thermal Treatment of Municipal Solid Waste.] London. </ref>.

==Principles of Gasification==

Most of the main gasification reactions are endothermic. These are reactions that absorb heat energy from their surroundings. An exception is the oxidation (the loss of electrons during a reaction) of char or [[Combustion|combustible]] gases by oxygen and also the water gas shift towards hydrogen and the [[pyrolysis]] in certain temperature windows, which are exothermic (reactions that release heat energy into their surroundings). Therefore, there is a need to supply to or generate energy within the gasifier to balance the overall conversion.

===Autothermal Gasifiers===

Autothermal (direct) gasifiers provide the necessary heat of conversion by adding an oxidant (a reactant that removes electrons from other reactants) to achieve partial oxidation (when oxygen is fed at a below level of which is required for complete oxidation) of the fuel within the gasification reactor. This releases energy directly in the reactor where it is consumed. Autothermal conditions are easy to achieve using air or oxygen. Overall the complexity of the process is reduced compared to allothermal gasifiers. However, the heat release occurs in the zone of contact between the oxidant (a reactant that removes electrons from other reactants) and a [[Combustion|combustible]] which requires a good internal heat transfer to even out the temperature.

===Allothermal Gasifiers===

Allothermal (indirect) gasifiers are characterized by the fact that heat is provided from an external source (the processes of heat production and heat consumption are physically separated). The heat is generated by [[combustion]] and transferred to the gasification reactor with a heat carrier (e.g. circulating bed material) or a heat exchanger (e.g. heat pipe exchanger)<ref>[https://www.sciencedirect.com/science/article/pii/B9780128155547000076 Waste Gasification Process for SNG Production]</ref>. In contrast to autothermal gasifiers where only one product gas stream is produced, allothermal gasifiers generally produce two separate gas streams: a medium calorific product gas stream having a low nitrogen content from the gasification reactor and a [[Flue Gas|flue gas]] stream from the [[combustion]] reactor. Both streams need to be cleaned to the standard required for the gas end user (product gas), or for release to the stack ([[Flue Gas|flue gas]]), respectively.

There are two main types of allothermal reactor. One uses a solid heat carrier (sand or larger aggregates) that is circulated between the gasification and [[combustion]] reactors, respectively. The hot energy carrier coming into the gasification reactor releases heat to drive the gasifier reactions, and when leaving to the [[combustion]] reactor also withdraws a major part of the remaining solid residue/char (a). The second type is the heat-integrated gasifier, where part of the product gas/char residues are separated from the product gas and are burnt. Then via an indirect heat exchanger, the energy in the hot [[Flue Gas|flue gas]] is transferred to the gasifier by a combination of radiation and convective heat transport (b).

==Kiln/Reactor Types in Gasification ==

There are several configurations for gasification kilns/reactors. Gasifiers are typically grouped according to their flow pattern and gas-solid contact.

Gasifier Kiln/Reactor Types:

#Co-current flow (downdraft) moving bed gasifier

#Counter flow (updraft) moving bed gasifier

#Fluidised bed gasifier

#Fluidised bed gasifier (Stationary and Static)

#Entrained flow

#Grate gasifier

Further detail of each type is expanded on below.

=== Co-current flow (downdraft) moving bed gasifier ===

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<ref name="ref1">[https://www.ieabioenergy.com/wp-content/uploads/2019/01/IEA-Bioenergy-Task-33-Gasification-of-waste-for-energy-carriers-20181205-1.pdf Gasification of Waste for Energy Carriers (IEA Bioenergy)]</ref>

~~ ~~

~~=== Allothermal Gasifiers ===~~

Allothermal (indirect) gasifiers rely on the fact that the heat necessary for running the gasification reactions is delivered to the gasification reactor from an external source. The heat is generated by combustion and transferred to the gasification with a heat carrier (e.g. circulating bed material) or a heat exchanger (e.g. heat pipe exchanger)<ref>[https://www.sciencedirect.com/science/article/pii/B9780128155547000076 Waste Gasification Process for SNG Production]</ref>. There are two main types of allothermal reactor. One uses a solid heat carrier (sand or larger aggregates) that is circulated between the gasification and combustion reactors, respectively. The hot energy carrier coming into the gasification reactor releases heat to drive the gasifier reactions, and when leaving to the combustion reactor also withdraws a major part of the remaining solid residue (char). The second type is the heat-integrated gasifier, where part of the product gas or char residues are separated from the product gas and are burnt, and via some form of indirect heat exchanger the energy in the hot flue gas is transferred to the gasifier by a combination of radiation and convective heat transport.

Allothermal/ indirect fluidized beds can have different combinations of fluidization types in the two beds, such as two stationary fluidized bed reactors, one stationary fluidized bed gasifier and circulating bed combustor, one circulating fluidized bed gasifier and one stationary bed combustor or two circulating fluidized beds. Indirect double fluidized beds function in the same way as a fluidized bed, the difference being that there is no oxidant, instead typically steam is added to the gasifier, since the energy required is instead provided by hot sand bed material being transferred at high rate from the second, combustor bed.

~~<ref name="ref1" />~~

@@ Line 1: / Line 1: @@
 [[Category:Technologies & Solutions]]
-[[Gasification]] is the thermal breakdown of a material into a gas via partial oxidation under the application of heat. It Involves the sub-stoichiometric oxidation or steam reformation of a substance to produce a gaseous mixture containing two or more of the following: (i) oxides of carbon, (ii) methane and (iii) hydrogen<ref>[[DEFRA]] 2018. [https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/765494/ACT_Guidance_-_Compliance_with_the_ACT_Efficiency_Standard_criterion.pdf Guidance Note for Advanced Conversion Technologies Compliance with the ACT Efficiency Standard criterion in the Contract for Difference scheme.] London. </ref>. The gas is then generally burnt to raise steam and create electricity, but many plants are exploring the option of cleaning the gas for use in a gas engine or separating the gas into usable fractions such as hydrogen for use, as an example, of liquid fuels which in turn may be eligible under the [[RTFO]].
+[[Gasification]] is a form of [[treatment|thermal treatment]] of a material into a gas via partial oxidation under the application of heat.
+==Overview==
+[[Gasification]] is a form of [[treatment|thermal treatment]] of a material into a gas via partial oxidation under the application of heat. It Involves the sub-stoichiometric oxidation or steam reformation of a substance to produce a gaseous mixture containing two or more of the following: (i) oxides of carbon, (ii) methane and (iii) hydrogen<ref>[[DEFRA]] 2018. [https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/765494/ACT_Guidance_-_Compliance_with_the_ACT_Efficiency_Standard_criterion.pdf Guidance Note for Advanced Conversion Technologies Compliance with the ACT Efficiency Standard criterion in the Contract for Difference scheme.] London. </ref>. The gas is then generally burnt to raise steam and create electricity, but many [[Energy from Waste]] plants are exploring the option of cleaning the gas for use in a gas engine or separating the gas into usable fractions such as hydrogen for use, as an example, as liquid fuels.
+[[File:IGCC System.png|700px|center|IGCC System. All rights reserved.]]
+<br clear=all />
+== History ==
+[[Gasification]] was originally developed in the early 1800s for the production of town gas, which was a gaseous product manufactured from coal. It provided gas for lighting, cooking and heating for the industrialising Europe and North America in the 19th century. The first use of town gas produced via gasification occurred in 1807 where it was used in Pall Mall, London as the first public street lighting.
+[[Gasification]] moved to producing synthetic fuels and chemicals in the 1920s. The process was used widely during World War II to produce transportation fuels from coal via the [[Fischer Tropsch Process]]. It has been used in the last 40-60 years to convert coal and oil into hydrogen for use in the production of fertilisers (mainly ammonia) and for [[feedstock]] preparation in the chemical and refinery industries.
+At the start of the 21st century, [[Gasification|gasification]] began commercial scale use by the power industry in Integrated [[Gasification]] Combined Cycle (IGCC) plants. IGCC plants convert carbonaceous materials/waste into electricity, with the raw [[syngas]] cleaned of particulate matter and pollutants<ref>[https://www.mdpi.com/1996-1073/3/2/216 Gasification Processes Old and New]</ref>.
-Gasification can be considered a process between [[Pyrolysis|pyrolysis]] and conventional [[EfW]] in that it involves the partial oxidation of a substance. This means that oxygen is added but the amounts are not enough to allow the fuel to be completely oxidised and full combustion to occur. The temperatures employed are typically above 650°C. Generally, the [[Syngas|syngas]] generated from Gasification will have a [[Net Calorific Value]] ([[NCV]]) of 4-10MJ/Nm3 <ref>[[DEFRA]], 2013. [https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/221035/pb13888-thermal-treatment-waste.pdf Advanced Thermal Treatment of Municipal Solid Waste.] London. </ref>.
+==Context and Definition==
+In legal terms, a '''‘waste incineration plant’''' means any stationary or mobile technical unit and equipment dedicated to the [[Treatment|thermal treatment]] of waste, with or without recovery of any energy generated, or whether the gases resulting from the thermal [[treatment]] are subsequently incinerated <ref>As an example, a [[Pyrolysis]] facility that burnt the produced [[Syngas]] to generate electricity would be Incineration, whereas a [[Pyrolysis]] facility that processed [[Syngas]] for vehicle fuel would not be classed as an incinerator</ref><ref name='ref01'>European Commission, 2010 Industrial Emissions Directive 2010/75/EU of the European Parliament and of the Council of 24 November 2010 on industrial emissions (integrated pollution prevention and control). Official Journal of the European Union.</ref>. If the [[Incineration|Incinerator]] can be shown to meet the energy efficiency measurement of [[R1]] it can be classified as a [[recovery]] facility, if it cannot it is classified as a [[disposal]] facility<ref>https://data.gov.uk/dataset/8287c81b-2288-4f14-9068-52bfda396402/r1-status-of-incinerators-in-england</ref>. This means that an incinerator that generates power, and is a net exporter of power, can be described as an '''[[Energy from Waste]]''' ([[EfW]]) facility. An incinerator that is an [[EfW]] facility that meets the [[R1]] criteria is the only type of incinerator under the legislation that can legitimately describe itself as an '''[[Energy Recovery Facility]]''' ([[ERF]]).
-== History ==
+The most recent recent [[BAT|BREF]] guidance<ref name="Inc">[https://eippcb.jrc.ec.europa.eu/sites/default/files/2020-01/JRC118637_WI_Bref_2019_published_0.pdf BAT and BREF for Waste incineration]</ref> also sets out how incinerators can be described by:
+* waste origin (e.g. Municipal Incinerators), '''and in WikiWaste includes [[Residual Waste EFW]] and [[Biomass Waste EFW]]''',
+* the nature of the waste (e.g. Hazardous Waste Incinerators),
+* the method/type of incineration (e.g. High Temperature Incinerators)
-The [[Gasification|gasification]] concept was originally developed in the early 1800s for the production of town gas which was a gaseous product manufactured from coal. It provided gas for lighting, cooking and heating for the industrialising Europe and North America in the 19th century. The first use of town gas produced via gasification occurred in 1807 where it was used in Pall Mall, London as the first public street lighting.
+In WikiWaste these last two bullet points are covered in '''[[High Temperature and Clinical Waste Incineration]]'''.
-[[Gasification]] moved to producing synthetic fuels and chemicals in the 1920s. The process was used widely during World War II to produce transportation fuels from coal via the [[Fischer Tropsch Process]]. It has been used in the last 40-60 years to convert coal and oil into hydrogen for use in the production of fertilisers (mainly ammonia) and for [[feedstock]] preparation in the chemical and refinery industries.
+However, there are a range of other terms used in the sector to describe different types of incineration, the kiln/furnace used, and the [[subsidy]] that may apply to them, and these are captured in the table below:
-At the start of the 21st century, [[Gasification|gasification]] began commercial scale use by the power industry in Integrated [[Gasification]] Combined Cycle (IGCC) plants. IGCC plants convert carbonaceous materials/waste into electricity, with the raw [[syngas]] cleaned of particulate matter and pollutants. This emissions free, renewable process allows the production of clean energy while solving waste problems simultaneously. <ref>[https://www.mdpi.com/1996-1073/3/2/216 Gasification Processes Old and New]</ref>
-[[File:IGCC System.png|700px|left|IGCC System. All rights reserved.]]
-<br clear=all />
-==Context==
 {|class="wikitable"
 !colspan=2|Definitions in Legislation!!rowspan=7 style="padding: 50px"|&nbsp;!!Types!!Temp. Range °C!!Category!!rowspan=7 style="padding: 50px"|&nbsp; !!Kiln/Furnace/Reactor
@@ Line 21: / Line 31: @@
 |[[Fluidised Bed]]
 |-
-|rowspan=2|[[Gasification]]||rowspan=2|500 - 1600||rowspan=2| [[Advanced Thermal Treatment]] ([[ATT]] and [[ACT]])||[[Reciprocating & Rotary]]
+|rowspan=2|[[Gasification]]||rowspan=2|500 - 1600||rowspan=2| [[Advanced Thermal Treatment]] ([[ATT]] and [[ACT]])||[[Rotary Kiln]]
 |-
 |rowspan=3|[[Incineration without Energy Recovery|Without Energy Recovery]]||[[Plasma]]
@@ Line 29: / Line 39: @@
 |[[Surface contact]]
 |}
-== Autothermal Gasifiers ==
-Autothermal (direct) gasifiers provide the necessary heat of conversion by adding an oxidant to achieve partial oxidation of the fuel within the gasification reactor. This releases energy directly in the reactor where it is consumed. Autothermal conditions are easy to achieve using air or oxygen. Overall the complexity of the process is reduced compared to allothermal gasifiers, however the heat release occurs in the zone of contact between the oxidant and a combustible which requires a good internal heat transfer to even out the temperature or causes a temperature gradient inside the gasifier.
-Types of autothermal gasifier:
+Gasification can be considered a process between [[Pyrolysis|pyrolysis]] and conventional [[Combustion]] in that it involves the partial oxidation of a substance. This means that oxygen is added but the amounts are not enough to allow the fuel to be completely oxidised and full combustion to occur. The temperatures employed are typically above 650°C. Generally, the [[Syngas|syngas]] generated from Gasification will have a [[Net Calorific Value]] ([[NCV]]) of 4-10MJ/Nm3 <ref>[[DEFRA]], 2013. [https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/221035/pb13888-thermal-treatment-waste.pdf Advanced Thermal Treatment of Municipal Solid Waste.] London. </ref>.
+==Principles of Gasification==
+Most of the main gasification reactions are endothermic. These are reactions that absorb heat energy from their surroundings. An exception is the oxidation (the loss of electrons during a reaction) of char or [[Combustion|combustible]] gases by oxygen and also the water gas shift towards hydrogen and the [[pyrolysis]] in certain temperature windows, which are exothermic (reactions that release heat energy into their surroundings). Therefore, there is a need to supply to or generate energy within the gasifier to balance the overall conversion.
+===Autothermal Gasifiers===
+Autothermal (direct) gasifiers provide the necessary heat of conversion by adding an oxidant (a reactant that removes electrons from other reactants) to achieve partial oxidation (when oxygen is fed at a below level of which is required for complete oxidation) of the fuel within the gasification reactor. This releases energy directly in the reactor where it is consumed. Autothermal conditions are easy to achieve using air or oxygen. Overall the complexity of the process is reduced compared to allothermal gasifiers. However, the heat release occurs in the zone of contact between the oxidant (a reactant that removes electrons from other reactants) and a [[Combustion|combustible]] which requires a good internal heat transfer to even out the temperature.
+===Allothermal Gasifiers===
+Allothermal (indirect) gasifiers are characterized by the fact that heat is provided from an external source (the processes of heat production and heat consumption are physically separated). The heat is generated by [[combustion]] and transferred to the gasification reactor with a heat carrier (e.g. circulating bed material) or a heat exchanger (e.g. heat pipe exchanger)<ref>[https://www.sciencedirect.com/science/article/pii/B9780128155547000076 Waste Gasification Process for SNG Production]</ref>. In contrast to autothermal gasifiers where only one product gas stream is produced, allothermal gasifiers generally produce two separate gas streams: a medium calorific product gas stream having a low nitrogen content from the gasification reactor and a [[Flue Gas|flue gas]] stream from the [[combustion]] reactor. Both streams need to be cleaned to the standard required for the gas end user (product gas), or for release to the stack ([[Flue Gas|flue gas]]), respectively.
+[[File:Allothermal gasifiers.png|300px|right|Different allothermal gasifiers: a)double bed indirect gasifier and b)indirect heat fluidised bed gasifier. All rights reserved.]]
+There are two main types of allothermal reactor. One uses a solid heat carrier (sand or larger aggregates) that is circulated between the gasification and [[combustion]] reactors, respectively. The hot energy carrier coming into the gasification reactor releases heat to drive the gasifier reactions, and when leaving to the [[combustion]] reactor also withdraws a major part of the remaining solid residue/char (a). The second type is the heat-integrated gasifier, where part of the product gas/char residues are separated from the product gas and are burnt. Then via an indirect heat exchanger, the energy in the hot [[Flue Gas|flue gas]] is transferred to the gasifier by a combination of radiation and convective heat transport (b).
+<ref name="ref1" />
+<br clear=all />
+==Kiln/Reactor Types in Gasification ==
+There are several configurations for gasification kilns/reactors. Gasifiers are typically grouped according to their flow pattern and gas-solid contact.
+Gasifier Kiln/Reactor Types:
 #Co-current flow (downdraft) moving bed gasifier
 #Counter flow (updraft) moving bed gasifier
-#Fluidised bed gasifier
+#Fluidised bed gasifier (Stationary and Static)
 #Entrained flow
 #Grate gasifier
+Further detail of each type is expanded on below.
 === Co-current flow (downdraft) moving bed gasifier ===
@@ Line 72: / Line 101: @@
 <ref name="ref1">[https://www.ieabioenergy.com/wp-content/uploads/2019/01/IEA-Bioenergy-Task-33-Gasification-of-waste-for-energy-carriers-20181205-1.pdf Gasification of Waste for Energy Carriers (IEA Bioenergy)]</ref>
-<br clear=all />
-=== Allothermal Gasifiers ===
-[[File:Allothermal gasifiers.png|400px|right|Different allothermal gasifiers: a)double bed indirect gasifier and b)indirect heat fluidised bed gasifier. All rights reserved.]]
-Allothermal (indirect) gasifiers rely on the fact that the heat necessary for running the gasification reactions is delivered to the gasification reactor from an external source. The heat is generated by combustion and transferred to the gasification with a heat carrier (e.g. circulating bed material) or a heat exchanger (e.g. heat pipe exchanger)<ref>[https://www.sciencedirect.com/science/article/pii/B9780128155547000076 Waste Gasification Process for SNG Production]</ref>. There are two main types of allothermal reactor. One uses a solid heat carrier (sand or larger aggregates) that is circulated between the gasification and combustion reactors, respectively. The hot energy carrier coming into the gasification reactor releases heat to drive the gasifier reactions, and when leaving to the combustion reactor also withdraws a major part of the remaining solid residue (char). The second type is the heat-integrated gasifier, where part of the product gas or char residues are separated from the product gas and are burnt, and via some form of indirect heat exchanger the energy in the hot flue gas is transferred to the gasifier by a combination of radiation and convective heat transport.
-Allothermal/ indirect fluidized beds can have different combinations of fluidization types in the two beds, such as two stationary fluidized bed reactors, one stationary fluidized bed gasifier and circulating bed combustor, one circulating fluidized bed gasifier and one stationary bed combustor or two circulating fluidized beds. Indirect double fluidized beds function in the same way as a fluidized bed, the difference being that there is no oxidant, instead typically steam is added to the gasifier, since the energy required is instead provided by hot sand bed material being transferred at high rate from the second, combustor bed.
-<ref name="ref1" />
 <br clear=all />