Cooler Control.ppt

Cooler Control

Objectives of Cooler Operation  The primary objectives of cooler operation are to cool

the clinker and maximize heat recuperation.  Functions of a grate cooler are:   

Clinker cooling Recuperation of heat for use within the kiln system Clinker transport away from the kiln system

 Efficient cooler operation is characterized by:   

Maximum heat recuperation Optimum cooling airflow Unrestricted availability 2

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Grate Cooler Control Parameters and Variables Control Parameters Control Variables Exhaust Fan Speed

Kiln Hood Pressure Secondary &Tertiary Air Temperature

Grate Plate Temperatures Undergrate Pressure Air Flowrate

Clinker Discharge Temperature

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Grate Speed Cooling Air Flowrate

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Grate Cooler Control Parameters  Control parameters are indicators which aid in both

monitoring and control of the clinker cooler.  Main control parameters of a grate cooler are:    

Undergrate pressure Kiln hood pressure Cooling airflow Secondary and tertiary air temperature

 Secondary control parameters of a grate cooler are:  

Grate plate temperature Clinker discharge temperature

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Undergrate Pressure (Bed Resistance)  Undergrate pressure is influenced by: 





Depth of the clinker bed on the grates – A thick clinker bed requires more force from the cooling fans to pass through a given clinker bed. Average clinker particle size – A coarse clinker bed has less resistance than a bed composed of fine particles Clinker temperature (increase) – An increase in clinker temperature increases the cooling air volume which increases bed resistance.

 Optimum clinker bed depth should allow free

passage of air through it.

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Undergrate Pressure (Bed Resistance) Illustration of Air Flow as a Function of Clinker Size Low Resistance

High Resistance

clinker

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Range of Operational Parameters (Grate Cooler)

Heat Consumption Efficiency t sec & tert air * t sec air t tert air t waste air grate speed first grate pressure Specific grate load Spec. cooling air * TA extraction from

Modern 3000 3500 71% 76% 1070 990 1230 1170 950 850 300 300 10 - 15 80 - 100 45 - 50 1.8 kiln hood

Conventional 3500 5000 68% 64% 890 610 940 850 240 200 10 - 20 45 - 55 35 - 45 2.3

kJ/kg % °C °C °C °C min-1 mbar t/d m2 Nm3/kg

Installed

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Holcim HGRS Sizing Rules for Clinker Coolers  Grate size / specific loading

<= 45 t/(m2d)

 Grate width load:

1000 – 1500 t/(m d)

 Installed cooling air:

>= 2.0 Nm3/kg cli

 First fan pressure:

>=100 mbar

 Resulting in estimated   

Grate speed Clinker outlet temperature Efficiency at 3100 kJ/kg

10 to 15 strokes/min ~90 oC + t ambient ~70 %

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Cooler Control Variables  Control variables are actuators manipulated to keep

cooler control parameters close to the set point.  Grate clinker cooler variables are: 

Airflow rates



- Provide the cooling air needed to cool the clinker as well as the combustion air for the kiln system. Exhaust fan speed



- Controls kiln hood pressure Grate speed - Influences cooler undergrate pressure with respect to bed resistance.

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Grate Speed Control  Grate speed control prevents the clinker bed

resistance from exceeding the pressure capabilities of the cooling fans by ensuring the bed resistance is kept constant.  Two options for grate speed control are: 



use the undergrate pressure of the 1st compartment to control the 1st grate speed and ratio the downstream grate speed according to the 1st . Control each drive by the undergrate pressure in both the 1st and 2nd compartments of each grate section which then influences the speed of each drive. 10

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Cooler Upset Conditions  Upset conditions are abnormal process conditions

which disturbs operation and lead to loss of production.  Typical cooler upset conditions are:    

Red river Geyser effect Snowman formation High grate plate temperatures

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Red River  A red river is a red-hot layer

of clinker fines on top of a cooled black clinker bed which travels faster toward the discharge end.  Counter Actions 





Increase clinker bed uniformity/distribution by increasing the clinker bed depth within the cooler. Optimize air distribution within cooler to ensure proper aeration is on red river side. Ensure clinker chemistry is correct for given kiln conditions.

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Red River

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Geyser Effect  The Geyser effect is experienced when too much

air is placed on the grate cooler and air blows through the clinker bed.  Counter actions 



Increase undergrate pressure by slowing down the cooler grate speed resulting in a thicker clinker bed. Decrease airflow until the clinker “dances” on the clinker bed. Blow through

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Snowman Formation

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Snowman Formation  A snowman formation is a mound of molten

material within the cooler inlet which disturbs the airflow pattern to the kiln resulting in unstable kiln conditions.  A snowman is detected in the cooler by a sharp

increase in undergrate pressure followed by an increase in grate speed.  Counter actions are:   

Decrease cooler speed Increase cooler airflow Mechanically remove

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Satellite Cooler Operation  Satellite cooler operation cannot be controlled. The

specific quantity of cooling air corresponds to the quantity of combustion air required.  Range of operational parameters for satellite

coolers are: Heat Consumption Efficiency t sec air Spec. cooling air Surface load Cross section load Air velocity in tube Air velocity in elbow

3500 5000 55% 68% 730 600 0.9 1.3 1.8 - 2.0 70 - 80 < 4.5 < 25

kJ/kg % °C Nm3/kg clin t/m2 d t/m2 d m/s m/s 16

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Grate Cooler Control Loops  Automated cooler operation consists of control

loops used to stabilize cooler operation.

FN1

FN2

FN3

FN4

FN5

FN6

FN7

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Cooler High-level Control  Cooler high-level control is a supervisory and

optimizing system which controls the operation of the cooler automatically  Benefits of cooler high-level control are: 

 



Stable cooler operation resulting in stable kiln conditions Lower heat consumption Stable and high secondary and tertiary air temperatures Lower clinker discharge temperatures

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Cooler High-level Control  LINKman (Expert Optimizer) input signals for cooler

control are:     

 

Secondary air temperature Cooling air flow rates Undergrate pressure Kiln hood pressure Clinker discharge temperature Grate speed Grate temperatures

 LINKman (Expert Optimizer) output signals are:   

Undergrate pressure Individual cooling fan set points 2nd grate speed ratio set point 19

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