Grate: Difference between revisions

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[[Category:Technologies & Solutions]]

[[Grate]]-type [[Incineration|incinerators]] are suitable for large irregular-shaped [[Waste|wastes]], which can be supported on a stationary or moving alloy [[Grate]] that allows air to pass through from underneath into the [[Waste|waste]]. The primary furnace is followed by a secondary [[Combustion|combustion]] chamber, where additional air and fuel are added, to ensure complete destruction of all toxic emissions. These types of [[Incineration|incinerators]] are widely used for the [[Incineration|incineration]] of solid mixed [[Municipal Solid Waste|municipal waste]] ([[MSW]]), but can also be applied to [[Sewage Sludge|sewage sludge]], [[Clinical Waste|clinical waste]], and [[Commercial and Industrial Waste|commercial and industrial waste]] (C&I)<ref name="ref1">[https://eippcb.jrc.ec.europa.eu/sites/default/files/2020-01/JRC118637_WI_Bref_2019_published_0.pdf Best Available Techniques (BAT) Reference Document for Waste Incineration]</ref>. They generally have limited application for [[Hazardous Waste|hazardous waste]] [[Incineration|incineration]] due to the high temperatures required in the chamber which could have adverse effects the structure of the [[Grate]]<ref>[https://www.sciencedirect.com/science/article/pii/B9780123736239500034 Sustainable Industrial Design and Waste Management]</ref>.

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===Incineration Grate===

The roles of the [[Incineration|incineration]] [[Grate]] include loosening the materials to be [[Incineration|incinerated]] and transporting the materials to be [[Incineration|incinerated]] in the furnace. The [[Grate]] requires good distribution of the [[Incineration|incineration]] air into the furnace. A primary air blower forces [[Incineration|incineration]] air through the small [[Grate]] layer openings into the fuel layer. More air is usually added above the [[Waste|waste]] bed to complete [[Combustion|combustion]]. The residence time of the [[Waste|wastes]] on the [[Grate~~|grates~~]] generally ~~does not exceed more than~~ 60 minutes.

The roles of the [[Incineration|incineration]] [[Grate]] include loosening the materials to be [[Incineration|incinerated]] and transporting the materials to be [[Incineration|incinerated]] in the furnace. The [[Grate]] requires good distribution of the [[Incineration|incineration]] air into the furnace. A primary air blower forces [[Incineration|incineration]] air through the small [[Grate]] layer openings into the fuel layer. More air is usually added above the [[Waste|waste]] bed to complete [[Combustion|combustion]]. The residence time of the [[Waste|wastes]] on the [[Grate]] is generally around 60 minutes.

Some fine material (referred to as siftings/riddling) may fall through the [[Grate]] which gets recovered in the [[Fly Ash|bottom ash]] remover or is recovered separately. It can be recycled to the [[Grate]] for repeated [[Incineration|incineration]] or removed for disposal. If the siftings are recirculated in the hopper, care is taken not to ignite the [[Waste|waste]] in the hopper.

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There are two main variations for reciprocating [[Grate|Grates]]:

====Reverse reciprocating grate====

The [[Grate]] bars move back and forth in the reverse direction to the flow of [[Waste|waste]]. The [[Grate]] is ~~flopped~~ from the feed end to the ash discharge end and is comprised of fixed and moving grate steps.

The [[Grate]] bars move back and forth in the reverse direction to the flow of [[Waste|waste]]. The [[Grate]] is sloped from the feed end to the ash discharge end and is comprised of fixed and moving grate steps.

====Push forward grate====

The [[Grate]] bars form a series of many steps that move horizontally and push the [[Waste|waste]] in the direction of the [[Fly Ash|ash]] discharge.

===Travelling grate===

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===Roller grate===

The roller [[Grate]] design consists of a perforated roller that traverses the width of the [[Grate]] area. Several rollers are installed in series which rolls or tumbles the material forward, towards the [[Fly Ash|ash]] discharge<ref name="ref1" />.

==Incineration Temperature, Residence Time and Oxygen Content==

[[Incineration|Incinerators]] are designed and operated to ensure good burnout of the [[Combustion|combustion]] gases. This is achieved by maintaining the gases at a maximum temperature for a minimum residence time at a minimum oxygen level. Temperature values typically range between 850°C to ~~1 100°C~~ for at least two seconds at a minimum oxygen level of 6%. Higher temperatures can be associated with [[Hazardous Waste|hazardous waste]]. The carbon monoxide content of the [[Flue Gas|flue gases]] is a main indicator of the quality of [[Combustion|combustion]]<ref name="ref1" />.

[[Incineration|Incinerators]] are designed and operated to ensure good burnout of the [[Combustion|combustion]] gases. This is achieved by maintaining the gases at a maximum temperature for a minimum residence time at a minimum oxygen level. Temperature values typically range between 850°C to 1100°C for at least two seconds at a minimum oxygen level of 6%. Higher temperatures can be associated with [[Hazardous Waste|hazardous waste]]. The carbon monoxide content of the [[Flue Gas|flue gases]] is a main indicator of the quality of [[Combustion|combustion]]<ref name="ref1" />.

==References==

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+[[Category:Technologies & Solutions]]
 [[Grate]]-type [[Incineration|incinerators]] are suitable for large irregular-shaped [[Waste|wastes]], which can be supported on a stationary or moving alloy [[Grate]] that allows air to pass through from underneath into the [[Waste|waste]]. The primary furnace is followed by a secondary [[Combustion|combustion]] chamber, where additional air and fuel are added, to ensure complete destruction of all toxic emissions. These types of [[Incineration|incinerators]] are widely used for the [[Incineration|incineration]] of solid mixed [[Municipal Solid Waste|municipal waste]] ([[MSW]]), but can also be applied to [[Sewage Sludge|sewage sludge]], [[Clinical Waste|clinical waste]], and [[Commercial and Industrial Waste|commercial and industrial waste]] (C&I)<ref name="ref1">[https://eippcb.jrc.ec.europa.eu/sites/default/files/2020-01/JRC118637_WI_Bref_2019_published_0.pdf Best Available Techniques (BAT) Reference Document for Waste Incineration]</ref>. They generally have limited application for [[Hazardous Waste|hazardous waste]] [[Incineration|incineration]] due to the high temperatures required in the chamber which could have adverse effects the structure of the [[Grate]]<ref>[https://www.sciencedirect.com/science/article/pii/B9780123736239500034 Sustainable Industrial Design and Waste Management]</ref>.
@@ Line 24: / Line 25: @@
 ===Incineration Grate===
-The roles of the [[Incineration|incineration]] [[Grate]] include loosening the materials to be [[Incineration|incinerated]] and transporting the materials to be [[Incineration|incinerated]] in the furnace. The [[Grate]] requires good distribution of the [[Incineration|incineration]] air into the furnace. A primary air blower forces [[Incineration|incineration]] air through the small [[Grate]] layer openings into the fuel layer. More air is usually added above the [[Waste|waste]] bed to complete [[Combustion|combustion]]. The residence time of the [[Waste|wastes]] on the [[Grate|grates]] generally does not exceed more than 60 minutes.
+The roles of the [[Incineration|incineration]] [[Grate]] include loosening the materials to be [[Incineration|incinerated]] and transporting the materials to be [[Incineration|incinerated]] in the furnace. The [[Grate]] requires good distribution of the [[Incineration|incineration]] air into the furnace. A primary air blower forces [[Incineration|incineration]] air through the small [[Grate]] layer openings into the fuel layer. More air is usually added above the [[Waste|waste]] bed to complete [[Combustion|combustion]]. The residence time of the [[Waste|wastes]] on the [[Grate]] is generally around 60 minutes.
 Some fine material (referred to as siftings/riddling) may fall through the [[Grate]] which gets recovered in the [[Fly Ash|bottom ash]] remover or is recovered separately. It can be recycled to the [[Grate]] for repeated [[Incineration|incineration]] or removed for disposal. If the siftings are recirculated in the hopper, care is taken not to ignite the [[Waste|waste]] in the hopper.
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 There are two main variations for reciprocating [[Grate|Grates]]:
 ====Reverse reciprocating grate====
-[[File:Reverse feed grate.png|300px|right|Reverse feed grate. All rights reserved.]]
+[[File:Reverse feed grate.png|200px|right|Reverse feed grate. All rights reserved.]]
-The [[Grate]] bars move back and forth in the reverse direction to the flow of [[Waste|waste]]. The [[Grate]] is flopped from the feed end to the ash discharge end and is comprised of fixed and moving grate steps.
+The [[Grate]] bars move back and forth in the reverse direction to the flow of [[Waste|waste]]. The [[Grate]] is sloped from the feed end to the ash discharge end and is comprised of fixed and moving grate steps.
+<br clear=all />
 ====Push forward grate====
-[[File:Forward feed grate.png|300px|right|Forward feed grate. All rights reserved.]]
+[[File:Forward feed grate.png|200px|right|Forward feed grate. All rights reserved.]]
 The [[Grate]] bars form a series of many steps that move horizontally and push the [[Waste|waste]] in the direction of the [[Fly Ash|ash]] discharge.
+<br clear=all />
 ===Travelling grate===
@@ Line 82: / Line 86: @@
 ===Roller grate===
-[[File:Roller grate.png|300px|right|Roller grate. All rights reserved.]]
+[[File:Roller grate.png|200px|right|Roller grate. All rights reserved.]]
 The roller [[Grate]] design consists of a perforated roller that traverses the width of the [[Grate]] area. Several rollers are installed in series which rolls or tumbles the material forward, towards the [[Fly Ash|ash]] discharge<ref name="ref1" />.
+<br clear=all />
 ==Incineration Temperature, Residence Time and Oxygen Content==
-[[Incineration|Incinerators]] are designed and operated to ensure good burnout of the [[Combustion|combustion]] gases. This is achieved by maintaining the gases at a maximum temperature for a minimum residence time at a minimum oxygen level. Temperature values typically range between 850°C to 1 100°C for at least two seconds at a minimum oxygen level of 6%. Higher temperatures can be associated with [[Hazardous Waste|hazardous waste]]. The carbon monoxide content of the [[Flue Gas|flue gases]] is a main indicator of the quality of [[Combustion|combustion]]<ref name="ref1" />.
+[[Incineration|Incinerators]] are designed and operated to ensure good burnout of the [[Combustion|combustion]] gases. This is achieved by maintaining the gases at a maximum temperature for a minimum residence time at a minimum oxygen level. Temperature values typically range between 850°C to 1100°C for at least two seconds at a minimum oxygen level of 6%. Higher temperatures can be associated with [[Hazardous Waste|hazardous waste]]. The carbon monoxide content of the [[Flue Gas|flue gases]] is a main indicator of the quality of [[Combustion|combustion]]<ref name="ref1" />.
 ==References==
 <references />