Main Aim of this section is to produce Clinker from Raw meal in energy efficient manner
Kiln Operation can be in following mode
Wet Process : Kiln Feed Water 30 - 40%
Semi Dry/Wet process
Dry Process : Kiln Feed Water 2 - 3%
The choice of the process to be used depends upon a complex combination of different factors This includes:
The nature of the raw materials.
The thermal efficiency of the different processes and their variations
fuel and other energy prices
Clinkerization Overview
Three sections in Dry Process
Preheater :
Preheat the Kiln feed Using Waste Heat Gas
Calcination Using Waste heat gas & Coal in Calciner
Kiln :
Clinker Formation from Calcined Kiln feed using Coal fuel.
Cooler :
Heat Recovery from Hot Clinker
Cooling Clinker rapidly to form reactive clinker
Clinkerization Overview
Reactions - Heating
30 - 300
Evaporation of Water
400 - 900
Removal of structural water and OH group from clay minerals
Clacination
above 800
Formation of C2S , intermediate product , aluminate , ferrite
above 1250
Formation of liquid phase (aluminate & Ferrite melt)
Crystalization of Alite ,Belite I.e Completion of phase formation
Clinkerization Overview
Reactions - Cooling
1300 - 1240
Crystalization of liquid phase into mainly aluminate & ferrite
Clinkerization Overview
Clinkerization Overview
Liquid &Phase
CaO + SiO2 -> CaO.SiO2
CaO.SiO2 + CaO -> (CaO)2.SiO2 (CaO)2.SiO2 + CaO -> (CaO)3.SiO2
(CaO)3.(Al2O3) --- C3A (CaO)4.(Al2O3).Fe2O3--- C4AF
Preheater
Different Type of Preheater System
4 , 5 , 6 stage ,One string - With or Without Calciner
4 , 5 stage ,Two String - Calciner String , Kiln String
4, 5 stage ,Two string - Both Calciner String
Typical : 5 stage , Two String - Calciner & Kiln String
More Stages gets added in Preheater String
More Heat Recovery from Waste Heat Gas
More Capital Cost
Less Temperature For Raw Mill Grinding
Preheater
Aim
Maximum Heat Recovery from waste heat gas
Maximum Calcination without melting raw meal
Operational Philosophy
Heat exchange between Waste Heat Gas & Raw Meal takes place through Direct Heat Exchange in Riser Duct
Separation of Raw Meal Solid from Gas is carried out in Cyclone at each stage.
Maximum Calcination is carried out in Pre-Calciner by burning Coal.
Preheater
Process
Gas enters from bottom cyclone
Raw meal enters from top cyclone
Gas is sucked by induced draft fan from kiln
Fan is placed at Preheater Outlet
From Last but One cyclone raw meal goes to Pre-Calciner where coal is fired
Tertiary air is sucked in Calciner from cooler
After Pre-Calciner Raw meal is carried to last cyclone by air & Separated raw meal from this cyclone goes to Kiln
Preheater
Major Operating Parameter
PHOutlet Temp : Heat Recovery
PHOutlet CO : ESP security, Oxygen Shortage
Calciner Outlet Temp : Completion of Calcination
Kiln inlet Material Temp : Material Fusion Temp
PHOutlet Draft / O2 : Excess Air , Leakage
Cyclone Cone Draft : Cyclone Jamming
Handles
PHOutlet Fan Damper /RPM : Air Quantity
Calciner Coal : Heat Quantity
Preheater
MV-CV Relation
Preheater
Abnormal Conditions & control
High PHOutlet CO
Cause:
– Less Oxygen for Coal Combustion – High Calciner Coal Feed rate
Control:
– Cut Calciner Coal
– Increase PHFan RPM or Damper
Preheater
Abnormal Conditions & control
High Kiln inlet material temp
Cause :
– High Calciner Coal Feed rate – Less Raw Meal Rate
– Secondary Burning of Coal in preheater
Control:
– Cut Calciner Coal
Preheater
Abnormal Conditions & control
High Calciner Outlet temp
Cause :
– High Calciner Coal Feed rate – Less Raw Meal Rate
Control:
– Cut Calciner Coal
Preheater
Abnormal Conditions & control
Low Cyclone cone draft
Cause :
– Less Air
– Coating in cyclone
– Brick lining failure , Flap damper Malfunction
Control:
– Cut Raw Meal Feed Rate
Kiln
Aim
Maintain Clinker Quality
Minimize Heat Consumption
Operational Philosophy
Heat is generated by Coal combustion
High residence time i.e. 20 min
High Temp 1500oC
Maximum Contact area of Hot air & Material by circulatory motion (4 rpm)
Kiln
Process
Kiln is cylindrical rotating furnace (60 m length) &
installed slightly slant (3-4degree) to carry the material to lower end when rotating.
At Lower end is the burner where coal is fired through using primary air for conveying.
Cooler Secondary air is sucked into Kiln which is at high temp ( Due to heat recuperation from hot clinker ).
Secondary Air from Cooler & Primary Air gets heated by combustion of coal.
This air travels opposite to material flow & Heat Exchange between air & material takes place
Kiln
Major Operating Parameter
Kiln Torque : Clinker Quality
Burning Zone Temp. : Good Heat Content
Clinker Lt..wt. & Free Lime : Clinker Quality
Kiln Hood Draft : Safety & Maintenance
Kiln inlet CO or O2 : Oxygen Availability
Handles
Kiln Feed
Kiln RPM
Kiln Coal
Kiln
Clinker Quality
Clinker Phase Requirement
C3 S (Alite) - 40 to 60% :Rapid Contribution to strength C2 S (Belite) - 20 to 30% : Slow Contribution to strength C3 A - 5 to 12% : Rapid Contribution to strength C4 AF - 5 to 12% : V. Slow Contribution to strnth
Indirect/Direct Measurement of Good Clinker
Litre Weight (density) - Represent phase%
Free Lime (CaO) - Should be minimized
Kiln
Clinker Quality
Affecting Parameters
Degree of Kiln feed mixing
Kiln Feed Granulometry
Burnability of kiln feed
Degree of heating
Retention time
Clinker Cooling Rate
Kiln
MV-CV Relation
Kiln
Abnormal Conditions & control
High Kiln inlet CO
Cause :
– Less Air
– More Kiln Coal
Control:
– Cut Kiln Coal
– Increase PH fan RPM / Open Damper
Kiln
Abnormal Conditions & control
LOW kiln Torque/ Dusty Kiln
Cause :
– Less Heat Content in Kiln – High Kiln filling
Control:
– Reduce Kiln RPM & Increase Kiln Coal – Decrease Kiln Feed
Kiln
Abnormal Conditions & there control
Red Spot
Cause :
– Coating Deformation – Brick dislodging
Control:
– Reduce Kiln RPM – Stop Kiln
Cooler
Aim
Recuperate Maximum Heat from Clinker
Maintain Clinker Quality
Minimize Clinker Temperature
Operational Philosophy
Maximum Heat Recuperation in first few compartments is achieved by keeping high bed height of Clinker
Lower Clinker temperature is achieved in last few compartments by Low Clinker bed height & High Air volume
Cooler
Process
Types Of Cooler
Reciprocating Grate Cooler
– Perforated Grates moving one over other creating forward motion for clinker.
– Air with high velocity flows vertically up 90 degree to Clinker flow.
IKN Cooler
– Grates Doesn’t move. Forward motion for clinker is created by Horizontal Air Jet with very high velocity.
– Air with very high velocity flows parallel to Clinker flow & then moves vertically up.
Cooler
Major Operating Parameter
Under-Grate Pressure : Clinker Bed
Grate Drive Amps : Clinker Bed
Clinker Temperature : Clinker property , Safety
Secondary Air Temp. : Recuperation
Hood Draft : Safety
Cooler Vent Temperature : Heat Loss
Handles
Air Volume / Fan Damper / Fan RPM
Grate Drive Speed
Vent fan Damper / RPM
Cooler
MV-CV Relation
Cooler
Abnormal Conditions & control
Grate Drive Amps High
Cause :
– High Clinker Bed Height – Lumps
Control:
– Increase Grate Speed