Gasification: Difference between revisions
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[[Gasification]] is the thermal | [[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.]] | |||
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== 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>. | |||
==Context and Definition== | |||
In legal terms, a '''‘waste incineration plant’''' means any stationary or mobile technical unit and equipment dedicated to the 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 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]]). | |||
The [[ | The most recent recent [[BAT|BREF]] guidance<ref name="Inc">[https://ec.europa.eu/jrc/en/news/new-eu-environmental-standards-waste-incineration 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), '''and in WikiWaste includes [[Hazardous Waste Incineration]] and [[Clinical Waste Incineration]]''' | |||
* the method/type of incineration (e.g. High Temperature Incinerators). | |||
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: | |||
{|class="wikitable" | {|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 | !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]] | |[[Fluidised Bed]] | ||
|- | |- | ||
|rowspan=2|[[Gasification]]||rowspan=2|500 - 1600||rowspan=2| [[Advanced Thermal Treatment]] ([[ATT]] and [[ACT]])||[[ | |rowspan=2|[[Gasification]]||rowspan=2|500 - 1600||rowspan=2| [[Advanced Thermal Treatment]] ([[ATT]] and [[ACT]])||[[Rotary]] | ||
|- | |- | ||
|rowspan=3|[[Incineration without Energy Recovery|Without Energy Recovery]]||[[Plasma]] | |rowspan=3|[[Incineration without Energy Recovery|Without Energy Recovery]]||[[Plasma]] | ||
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|[[Surface contact]] | |[[Surface contact]] | ||
|} | |} | ||
== | |||
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>. | |||
==Kiln/Reactor Types in Gasification == | |||
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. | 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. | ||
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#Co-current flow (downdraft) moving bed gasifier | #Co-current flow (downdraft) moving bed gasifier | ||
#Counter flow (updraft) moving bed gasifier | #Counter flow (updraft) moving bed gasifier | ||
#Fluidised bed gasifier | #Fluidised bed gasifier (Stationary and Static) | ||
#Entrained flow | #Entrained flow | ||
#Grate gasifier | #Grate gasifier | ||
Further detail of each type is expanded on below. | |||
=== Co-current flow (downdraft) moving bed gasifier === | === Co-current flow (downdraft) moving bed gasifier === | ||