Rotary Kiln: Difference between revisions

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Rotary kilns can be classified into two general types: direct fire and indirect fire.

===Direct Fire===

The direct fire kiln is a single shell vessel with rings added inside to slow the catalyst as it tumbles from the inlet (elevated part) towards outlet (lower part). The oxidation medium (air) flows counter current to catalyst movement. The oxygen concentration in the medium will decrease in the same direction because of its consumption. Therefore, the zone in the vessel located near the inlet may function as a stripper of volatile components of coke. The kiln is fired by gas burners directly against the outer shell of the vessel. The temperature inside the kiln is controlled by adjusting the burner heat, varying concentration of oxygen in the oxidizing medium (air) and its flow.

The direct fire kiln is a single shell vessel with rings added inside to slow the catalyst/[[feedstock]] as it tumbles from the inlet (elevated part) towards outlet (lower part). The oxidation medium (air) flows counter current to catalyst/[[feedstock]] movement. The oxygen concentration in the medium/[[feedstock]] will decrease in the same direction because of its consumption. Therefore, the zone in the vessel located near the inlet may function as a stripper of volatile components of coke. The kiln is fired by gas burners directly against the outer shell of the vessel. The temperature inside the kiln is controlled by adjusting the burner heat, varying concentration of oxygen in the oxidizing medium (air) and its flow.

===Indirect Fire===

The indirect fire kiln comprises a double-shell cylinder vessel. The inner shell is similar as that of the direct fire kiln. The space between the shells is heated either by [[combustion]] gas or steam. In some cases, the inner cylinder shell is ebullated (fluidised by the continual injection of gas and liquid) allowing hot gases or steam to enter and contact the tumbled catalyst. The catalyst temperatures are controlled by monitoring the temperatures of the inlet and outlet gases. <ref>[https://www.sciencedirect.com/science/article/pii/B9780444535566000069 Handbook of Spent Hydroprocessing Catalysts]</ref>

The indirect fire kiln comprises a double-shell cylinder vessel. The inner shell is similar as that of the direct fire kiln. The space between the shells is heated either by [[combustion]] gas or steam. In some cases, the inner cylinder shell is ebullated (fluidised by the continual injection of gas and liquid) allowing hot gases or steam to enter and contact the tumbled catalyst/[[feedstock]]. The catalyst/[[feedstock]] temperatures are controlled by monitoring the temperatures of the inlet and outlet gases. <ref>[https://www.sciencedirect.com/science/article/pii/B9780444535566000069 Handbook of Spent Hydroprocessing Catalysts]</ref>

==Rotary Kiln with a Post-Combustion Chamber for Hazardous Waste Incineration==

[[File:Rotary (drum-type) kiln with a post combustion chamber for hazardous waste incineration.png|300px|right|Rotary (drum-type) kiln with a post combustion chamber for hazardous waste incineration. All rights reserved.]]

A combination of rotary kilns and post-combustion chambers has proven successful for incineration of [[Hazardous Waste|hazardous waste]] as this combination can treat solid, pasty, liquid and gaseous wastes uniformly. The kiln operating temperature is usually between 850 °C and 1 300 °C. The temperature can be maintained by burning higher calorific (e.g. liquid) [[waste]], waste oils, heating oil or gas. Operation at higher temperatures may result in molten (vitrified) bottom ash (slag), whilst at lower temperatures the bottom ashes are sintered (~~solidify~~).

A combination of rotary kilns and post-combustion chambers has proven successful for [[incineration]] of [[Hazardous Waste|hazardous waste]] as this combination can treat solid, pasty, liquid and gaseous wastes uniformly. The kiln operating temperature is usually between 850 °C and 1 300 °C. The temperature can be maintained by burning higher calorific (e.g. liquid) [[waste]], waste oils, heating oil or gas. Operation at higher temperatures may result in molten (vitrified) bottom ash (slag), whilst at lower temperatures the bottom ashes are sintered (solidified).

Rotary kilns are tilted towards the post-combustion chamber. This along with the slow rotation (between 3-40 rotations per hour), facilitates the transport of solid [[Hazardous Waste|hazardous wastes]] that are fed into the upper end, as well as the bottom ash produced during [[incineration]], in the direction of the post-combustion chamber. These are then removed together with the ash from the post-combustion chamber via a wet bottom ash discharger. The residence time for solid wastes is typically greater than 30 minutes.

Rotary kilns are tilted towards the post-combustion chamber. This, along with the slow rotation (between 3-40 rotations per hour), facilitates the transport of solid [[Hazardous Waste|hazardous wastes]] that are fed into the upper end, as well as the bottom ash produced during [[incineration]], in the direction of the post-combustion chamber. These are then removed together with the ash from the post-combustion chamber via a wet bottom ash discharger. The residence time for solid wastes is typically greater than 30 minutes.

A post-combustion chamber is usually used to increase the disintegration of toxic compounds. Additional firing using liquid [[waste]]/support fuel may be carried out to maintain the temperatures required to ensure the complete destruction of compounds in the exhaust gas. The post-combustion chamber provides the necessary time for the incineration of the flue gasses produced in the kiln, as well as for the [[incineration]] of directly injected liquid and gaseous [[Waste|wastes]]. Due to the high temperatures (900-1200°C) and the secondary air introduction in the post-combustion chamber, the [[combustion]] of the exhaust gases is completed, and organic compounds are destroyed. <ref name="ref1" />

@@ Line 25: / Line 25: @@
 Rotary kilns can be classified into two general types: direct fire and indirect fire.
 ===Direct Fire===
-The direct fire kiln is a single shell vessel with rings added inside to slow the catalyst as it tumbles from the inlet (elevated part) towards outlet (lower part). The oxidation medium (air) flows counter current to catalyst movement. The oxygen concentration in the medium will decrease in the same direction because of its consumption. Therefore, the zone in the vessel located near the inlet may function as a stripper of volatile components of coke. The kiln is fired by gas burners directly against the outer shell of the vessel. The temperature inside the kiln is controlled by adjusting the burner heat, varying concentration of oxygen in the oxidizing medium (air) and its flow.
+The direct fire kiln is a single shell vessel with rings added inside to slow the catalyst/[[feedstock]] as it tumbles from the inlet (elevated part) towards outlet (lower part). The oxidation medium (air) flows counter current to catalyst/[[feedstock]] movement. The oxygen concentration in the medium/[[feedstock]] will decrease in the same direction because of its consumption. Therefore, the zone in the vessel located near the inlet may function as a stripper of volatile components of coke. The kiln is fired by gas burners directly against the outer shell of the vessel. The temperature inside the kiln is controlled by adjusting the burner heat, varying concentration of oxygen in the oxidizing medium (air) and its flow.
 ===Indirect Fire===
-The indirect fire kiln comprises a double-shell cylinder vessel. The inner shell is similar as that of the direct fire kiln. The space between the shells is heated either by [[combustion]] gas or steam. In some cases, the inner cylinder shell is ebullated (fluidised by the continual injection of gas and liquid) allowing hot gases or steam to enter and contact the tumbled catalyst. The catalyst temperatures are controlled by monitoring the temperatures of the inlet and outlet gases. <ref>[https://www.sciencedirect.com/science/article/pii/B9780444535566000069 Handbook of Spent Hydroprocessing Catalysts]</ref>
+The indirect fire kiln comprises a double-shell cylinder vessel. The inner shell is similar as that of the direct fire kiln. The space between the shells is heated either by [[combustion]] gas or steam. In some cases, the inner cylinder shell is ebullated (fluidised by the continual injection of gas and liquid) allowing hot gases or steam to enter and contact the tumbled catalyst/[[feedstock]]. The catalyst/[[feedstock]] temperatures are controlled by monitoring the temperatures of the inlet and outlet gases. <ref>[https://www.sciencedirect.com/science/article/pii/B9780444535566000069 Handbook of Spent Hydroprocessing Catalysts]</ref>
 ==Rotary Kiln with a Post-Combustion Chamber for Hazardous Waste Incineration==
 [[File:Rotary (drum-type) kiln with a post combustion chamber for hazardous waste incineration.png|300px|right|Rotary (drum-type) kiln with a post combustion chamber for hazardous waste incineration. All rights reserved.]]
-A combination of rotary kilns and post-combustion chambers has proven successful for incineration of [[Hazardous Waste|hazardous waste]] as this combination can treat solid, pasty, liquid and gaseous wastes uniformly. The kiln operating temperature is usually between 850 °C and 1 300 °C. The temperature can be maintained by burning higher calorific (e.g. liquid) [[waste]], waste oils, heating oil or gas. Operation at higher temperatures may result in molten (vitrified) bottom ash (slag), whilst at lower temperatures the bottom ashes are sintered (solidify).
+A combination of rotary kilns and post-combustion chambers has proven successful for [[incineration]] of [[Hazardous Waste|hazardous waste]] as this combination can treat solid, pasty, liquid and gaseous wastes uniformly. The kiln operating temperature is usually between 850 °C and 1 300 °C. The temperature can be maintained by burning higher calorific (e.g. liquid) [[waste]], waste oils, heating oil or gas. Operation at higher temperatures may result in molten (vitrified) bottom ash (slag), whilst at lower temperatures the bottom ashes are sintered (solidified).
-Rotary kilns are tilted towards the post-combustion chamber. This along with the slow rotation (between 3-40 rotations per hour), facilitates the transport of solid [[Hazardous Waste|hazardous wastes]] that are fed into the upper end, as well as the bottom ash produced during [[incineration]], in the direction of the post-combustion chamber. These are then removed together with the ash from the post-combustion chamber via a wet bottom ash discharger. The residence time for solid wastes is typically greater than 30 minutes.
+Rotary kilns are tilted towards the post-combustion chamber. This, along with the slow rotation (between 3-40 rotations per hour), facilitates the transport of solid [[Hazardous Waste|hazardous wastes]] that are fed into the upper end, as well as the bottom ash produced during [[incineration]], in the direction of the post-combustion chamber. These are then removed together with the ash from the post-combustion chamber via a wet bottom ash discharger. The residence time for solid wastes is typically greater than 30 minutes.
 A post-combustion chamber is usually used to increase the disintegration of toxic compounds. Additional firing using liquid [[waste]]/support fuel may be carried out to maintain the temperatures required to ensure the complete destruction of compounds in the exhaust gas. The post-combustion chamber provides the necessary time for the incineration of the flue gasses produced in the kiln, as well as for the [[incineration]] of directly injected liquid and gaseous [[Waste|wastes]]. Due to the high temperatures (900-1200°C) and the secondary air introduction in the post-combustion chamber, the [[combustion]] of the exhaust gases is completed, and organic compounds are destroyed. <ref name="ref1" />