Kiln Optimiztion

STARTING THE MILL PLANT Prerequisites Before start-up of the mill plant, the operator must be fully familiar with the control system and its functions. The performance of all auxiliary machines must be tested for 8 hours prior to the initial start-up of the grinding plant. Main machines must be tested and have performed dry run tests according to the procedures described in their individual manuals, before they are released for operation. The availability of cooling water and compressed air in accordance with the specified requirements must be assured. The plant must not be put into operation until clearance is obtained from electrical, mechanical as well as operational departments. It must be assured that the control system is working according to the stated requirements, and that safety- and process interlocking have been established, ensuring that damage to the machinery, to all extent possible, is avoided. For details regarding safety and process interlocking refer to the block interlocking diagram. Conditions for start-up All machinery must be ready for operation. Reasons for alarms due to safety interlocks must be eliminated. Any alarm from unduly activated emergency switches must be cancelled. Starting up the plant for production is divided in a number of group starts. Each group consists of a number of machines, which will have a sequential start in order to comply with the rules for interlocking. This means that no machine in the sequence will start until the machines succeeding it are in operation. Identical rules apply for the groups, meaning that certain groups must be in operation for other groups to obtain start permission. Start conditions for the individual groups are the following: Product transport to CF-silo Conditions for start-up: Equipment for de-dusting of CF-silo is in operation. No maximum level alarm for the CF-silo. Compressed air available for operation of product transport and silodedusting filter. . Sealing air fan Conditions for start-up: None. . Roller lubrication unit Conditions for start-up: None. Operator can start the oil temperature conditioning alone. Gear lubrication unit Conditions for start-up: None. Operator can start the oil temperature conditioning alone. Hydraulic tensioning system Conditions for start-up: Gear lubrication unit operating. Operator can start the oil temperature conditioning alone. Mill fan and separator Conditions for start up: Sealing air fan operating and sealing air pressure > min1. Raw meal transport system is in operation. Bag house filter, filter fan, and dust transport system are in operation. Shut off dampers before and after the mill circuit to be in open position. Mill exit temperature < max. 2. Material circulation system

Conditions for start-up: The change-over gate set to a position recycling the material. No max alarm in reject bin level. Or Mill fan and separator group running. When the mill feed system has been started the change-over gate will change its position to lead the material to the conveyor belt for new feed. Mill motor Conditions for start-up: All rollers are in top position. Mill exit temperature < max. 2 Mill exit temperature > min. 1 Mill inlet temperature < max. 1 . Mill feed system Conditions for start-up: The mill motor is in operation. Metal detection system for re-circulated material Conditions for start-up: Change over gate position is OK. Metal detector should be OK. Material circulation system running and change over gate in position “Circulation”. Material circulation system stopped and changes over gate in position of dumping outside. . Heat Generator (existing) Condition for start –up: Mill inlet temperature < max1. Mill outlet temperature min1. Mill fan running. Shut-off dampers in mill inlet and outlet should be in open position. . Start Sequence The grinding circuit is started in the sequence as follows: Start the raw meal transport system. Start the sealing air fan. Start the roller lubrication unit and the gear lubrication unit. Start the hydraulic tensioning unit. The rollers are then lifted Automatically to their top positions. Open the two shut-off dampers before and after the mill circuit. Start the separator and the mill fan. The mill fan should be started with Minimum speed. Close the cold air damper at the mill inlet. Stabilize the mill exit temperature at 85-900C by adjusting the speed of The mill fan and adjusting the re-circulation duct damper. Open the Cold air damper at the mill inlet if the mill exit temperature increases to More than 1000C. (The kiln is assumed to be in operation). Start the material circulation system. The change over gate at the end of the long belt conveyor is positioned towards the reject bin. Start the mill motor and subsequently the mill feed system. Since it is a Long belt conveyor the material takes some time to reach the mill. Once it reaches the mill increase the speed of the mill fan in order to obtain The nominal air flow through the mill. If necessary to control the Temperature adjust the louver damper in the re-circulation duct for recirculation Air to the mill inlet. Immediately after this, start the mill motor and subsequently the mill Feed system. Immediately after the mill feed system is started, the Change over gate after the long belt conveyor should be changed

Towards the mill. An increase of mill differential pressure can be observed. Lower the Grinding rollers. Lower the grinding rollers and gradually increase the mill feed rate and grinding pressure to obtain appropriate values of mill differential pressure and roller position, i.e. thickness of the grinding bed. The fan speed and re-circulation duct damper must be adjusted to maintain the proper air flow and to obtain the desired mill exit temperature. Adjust the separator rotor speed to the appropriate value for obtaining the desired fineness of the raw meal. OPERATION Control of operational parameters During the operation the process is monitored by the control system where process values and settings are treated and recorded to be available to the operator. Some of the settings may be controlled automatically by built-in control loops, and others are foreseen to be controlled manually. Alarm and interlocking functions are attached to some of the process parameters. For an overview refer to the enclosed table including expected operational figures, alarm features, and control modes. Control loops: In order to maintain stability of the operation irrespective of changes in parameters that might affect the process, the system is equipped with a number of control loops, which will take corrective action when set to automatic mode. No controller should be set to automatic mode until the input process value has reached stability at the same level as the controller set point. To assist the operator in controlling the process the following control loops are available: A. Air flow, mill and separator The air flow through the mill and the separator is kept constant based on the measured value by the venturi by adjusting the speed of the fan. B. Mill exit temperature The mill exit temperature is kept constant by controlling the position of the louver damper in the recirculation air duct. Adjustment of this damper will change the balance between kiln exhaust gas and re-circulated air to the mill inlet and hence, the mill inlet temperature. The optimum set point for the mill exit temperature taking into account the requirements regarding the moisture content in the raw meal and the process stability. The mill outlet temperature has to be established during commissioning of the grinding plant. However, due to the moisture content of the raw materials a set point of approximately 850C may be appropriate. A mill exit temperature higher than necessary may cause higher mill vibrations. An alarm function is attached to the vibration meter of the mill. The alarm function has three alarm levels: Max. 1: Acoustic alarm. Max. 2: Shut down of the mill circuit after 5 sec with continuous alarm status. Max. 3: Immediate shut down. An alarm function is also attached to the mill exit temperature. Min. 1 and max. 2 alarms will shut down the mill circuit. The min. 1 alarm may however be suspended for up to 30 min. after mill start-up. C. Mill differential pressure The mill differential pressure is kept constant by controlling the rate of new feed to the mill circuit. The optimum differential pressure will be established

during the commissioning of the plant. It can however be expected to be within the range of 505 mmwg. Attached alarm functions: Low alarm (min. 1) and max. 1 alarms for the mill differential pressure will shut down the mill circuit. Min. 1 alarm may however be suspended for up to 30 min. after mill start-up. D. Feed proportioning An automatic controller will maintain a constant ratio between the feed rates for the three raw material components in the mill feed in accordance with the required set-point. The set-point will be maintained on the basis of the chemical analysis of raw mix from on line analyser. E. Pressure after Kiln ID fan The pressure after the kiln ID fan will be controlled by the main EP fan speed Manual settings A few settings of importance to achieve optimum operation have to be made manually: Grinding The grinding pressure exerted by the rollers with their hydraulic tensioning system may be adjusted during operation. A high grinding pressure usually means high power absorption of the mill and consequently a high grinding capacity. However, situations may arise when the grinding pressure should be reduced. Insufficient rate of new feed or abnormal feed characteristics may call for this action. Water injection The mill is provided with a water injection system arranged for spraying water on the grinding table. By using the water injection system an enhanced stability of the grinding bed can be obtained. It is not anticipated that the water injection system will be in use during normal operation. However, situations may arise when water injection is the most suitable means for sustaining a stable operation. Adjustments of mill internals Some of the mill internals - the dam ring and the nozzle ring - are adjustable, although not during operation. Dam ring: The periphery of the grinding table is fitted with a dam ring, which is made up by a number of segmented rings. By adding or removing complete rings, the height of the dam ring can be adjusted. A higher dam ring will retain more material on the grinding table and in this way it may improve the stability of the grinding process. However, with a higher dam ring and the consequently thicker grinding bed the grinding efficiency may suffer. The optimum setting of the dam ring is to be established during the commissioning of the mill. As the wear of the grinding elements proceeds the dam ring may have to be adjusted not to retain too much material on the grinding table. Nozzle Ring The flow area of the nozzle ring is adjustable by means of blanking off plates of various dimensions supplied with mill. Adjustment of the flow area means change of the air velocity through the nozzle ring. The mill should be operated with the largest possible nozzle ring flow area, i.e. with the lowest possible air velocity, provided that the flow of material through the nozzle ring is within the capacity of the material circulation system. The appropriate nozzle ring area will be established during commissioning of the grinding plant. STOP OF THE MILL PLANT The mill circuit may be shut down in two ways.

Unintentional shut down The process and safety interlocks built into the control system may cause an unintentional shut down of the whole grinding circuit or part of it. Refer to the interlocking diagram. . Intentional shut down The mill operator may at his own request execute an intentional shut down of the mill circuit. In the later case the following procedure is to be pursued: Switch the controllers from automatic to manual mode of operation. Reduce the mill feed rate in order to reduce the amount of material in the mill When the mill differential pressure is starting to decrease or the mill vibrations are starting to increase stop the mill feed system and lift the rollers simultaneously. Stop the mill motor. Stop the mill fan and the separator. Stop for longer periods of time If the mill circuit is expected to be out of operation for a longer period of time proceed as follows: Close the shut-off dampers before and after the mill circuit. Stop the mill auxiliaries, i.e. units for lubrication and hydraulic tensioning system.

Stop the raw meal transport system and the material circulation system after it is emptied out. CAUSE/EFFECT DIAGRAMS, OPERATING PARAMETERS AND ALARM LIMITS Various expected operational figures and alarm settings are listed in the following table. The listed figures are only intended as a guide. In practice the operational figures may differ somewhat from those listed. Alarm settings may be adjusted during commissioning of the plant. Notes used in the instrument and alarm tables: a: Refer to mechanical and electrical documentation for the equipment. b: To be set empirically at a level not activating the alarm under normal operating conditions. x: To be evaluated during commissioning.

Heating-up of cold kiln. Conditions prior to start-up. • The kiln, cooler, preheater etc. is closed, and other related machinery is ready for start. • Compressed air is available with min 7 bar pressure.

• Plant water system is operating. • Insulation heating elements (in kiln EP is in operation. • Insulation heating elements in cooler EP is in operation. • Start the HT oil preheating station • Start the fuel oil heat exchanger and ensure that the fuel oil is circulating over the kiln and calciner burner stations .. • Minimum two gas bottles for the kiln gas igniter are available and the gas igniter is connected and in position. • The kiln camera is mounted and connected. • Curve has been made for 24-hour heating-up. • Gas analysers in kiln and after preheater are working properly. • If the grate plates have been cleaned off, enough coarse clinker must be distributed on the grates, at least 100 mm over the cross bar level for heat protection from the flame and eventual flush from the kiln during start-up. The grates should be fully covered at least down to the cooler camera cross section. • The kiln burner is mounted with the 18 mm 60º operational burner nozzle. Check that the nominal cooler fan’s ratio flows is as follow; FN300, 600 Nm3/min. FN305, 765 Nm3/min. K310, 765 Nm3/min. K315, 705 Nm3/min. K325, 705 Nm3/min. K335, 1400 Nm3/min. K340, 1400 Nm3/min. K345, 1300 Nm3/min. Start of heating-up. 1. Start dust transport from kiln ESP and de-dusting filter, groups; (De-dusting. Dust to elevators. . Kiln feed transport I. Kiln feed transport II. Dust transport. CT dust transport.

2. Start the ESP filter fan on minimum speed and open the damper to 40 %. 3. Open the ID-fan’s dampers to 10 %. 4. Start the following kiln groups; Kiln auxiliaries. Kiln fans. Calciner burner cooling fan. 5. In order to secure sufficient combustion air to the kiln burner, open the large man door in the cooler back end. Secure it open and cordon off the area. 6. Start the primary air fan and open the damper to 40 %. Check that the axial damper is 100 % and the radial is 30 % open. 7. Start the coal meal blower 8. Start the gas igniter, and verify ignition on the panel. The pressures should be for; compressed air 40 psi gas 10 psi. 9. Set the kiln oil burner spreader to 2, and open the needle manually a quarter of a revolution. Start the kiln burner and wait for the oil flow to stabilize, and if possible set the oil burner in automatic with a set point of 1000 to 1100kg/h 10. Adjust primary air and kiln draft until a good and steady flame is formed. The oxygen level will initially be around 16 % 11. Turn the kiln according to following scheme ½ – 8 hour 200every 30 min. 8 – 20 hour 200every 15 min. 20 – 24 hour continuous barring. Use the barring automatics with variable timer. In case of heavy rain turn the kiln continuously. If the heating-up schedule is less than 24 hours the above periods must be reduced accordingly. 12. Increase oil to kiln according to heating-up scheme and when the oxygen level comes down maintain this between 4 – 8 % in the kiln with the ID-fan damper. It might be necessary to open up for the oil burner spreader device in order to get more oil flow. There must be no significant CO formation. When the kiln is considered hot enough (after 4 to 6 hours), stop the gas igniter and retract it a meter. 13. After six hours, the cooler grates must be started in order to clean for excess material from the kiln. Start the following sequence if not running; Clinker silo de-dusting. Clinker transport. Cooler water injection. EP filter dust transport. Clinker crusher. If deemed necessary by local observation the grates can be started earlier. 14. Start the excess air fan if not running 15. Open the excess air damper to 40 % and put the kiln hood pressure controller in automatic with a set point of -0.3 mbar. 16. Start the cooler fans if not running, put the fans in automatic and activate the cascade control button. Set the flow ratio to 60 percent. 17. Start the cooler grates and run them with a speed off 5 strokes./min. for 15 min. every 6th hour. Inspect the cooler inlet for possible more frequent operation.

18. When the cooler fans and excess air fan have been started they should not be stopped again before kiln feeding. Start of kiln. Preconditions to kiln start. When the kiln is sufficiently hot (more than 800C in the kiln riser pipe and the kiln is visually considered hot enough, the kiln is ready for start. If not running, start the re-circulation of raw meal at least two hour’s before kiln start with 220 t/h. The dividing gates is positioned at 65 % Start. If not running, start the dust transport for the kiln EP filter. 1. Start both ID-fans 2. Open the tertiary air damper to 15 % and start the calciner burner Give a set point of 20% output. Raise the fuel oil flow to around 1500 kg/h kg/h in manual. The temperature in the calciner and 5th stage will now start to rise slowly. 3. Open the kiln ESP fan damper to 100% and change the set point for the under pressure controller after the ID-fan to –5 mbar. 4. Open the excess air fan damper to 60 % 5. Raise the ratio for the cooler fan flows to 70% 6. Start the cooler grates with a speed set point off 5 strokes/min. 7. Lower the under pressure set point at the kiln hood to –0.4 mbar. 8. Increase the kiln primary air damper to obtain 240 mbar 9. Open the ID-fan dampers to 100% 10. Open the tertiary air damper to 30 % 11. Raise the ID-fans speed to 55% 12. When the ID-fan speed has reached 40 % select the feed to kiln button. 13. Increase kiln fuel oil to 4500 kg/h in automatic. Remember to open up for the spreader on the kiln burner to position 5 fuel oil flow on 4600 kg/h 14. Increase in steps the calciner fuel oil to around 6000 kg/h or in manual. 15. Adjust tertiary air damper and Id-fan speed to balance oxygen in kiln and downcomer (2 – 3 % in kiln and 3 - 4 % in downcomer). 16. Increase kiln speed to 0.5 rpm. 17. If necessary increase calciner fuel to raise 5th stage temperature to 860 ºC When the calciner temperature is reached the controller for the 5th stage outlet temperature can be tried in automatic, with the above mentioned set point. Gradually increase the draft, kiln feed, kiln speed, adjust tertiary air damper, cooler fan flows and grate speed, until the kiln feed is about 300 t/h with proper consideration to the kiln parameters. (Oxygen, NOX, torque etc.). When the kiln is in operation gradually reduce the fuel oil to the kiln until minimum (closed) fuel oil neddle) and increase coal firing accordingly). Kiln stop. In order to stop the kiln the following procedure must be used. Stop the ID-fan. When this is done the following happens; Kiln and calciner burner stops. Kiln feed direct to re-circulation. Kiln speed goes to minimum.

The cooler fans reduce to 60 % of nominal set point. Tertiary air damper closes. Id-fan damper closes. The following must be done manually; Stop the cooler grates or they will stop automatically after 10 minutes. Close the ESP fan damper to 10 % Change from main motor to barring device and bar the kiln every 15 minutes after ten minutes continuous barring. Reduce the set point for the kiln hood under pressure to –0.2 mbar. If the kiln is on stand-by with flame on the kiln must be turned continuously. If not below scheme apply. If the kiln is to be stopped for cold state, the following procedure is to be used; 1. Reduce the primary air damper to 15%. 2. Run the kiln ESP fan in manual with minimum speed and 10% open damper. Open the kiln ID-fan 10 % 3. Bar the kiln according to the following scheme; 0 - ½ hour; Continuous barring. 0 –1 hour; 200 º every 10 min. 1 – 24 hour; 200every 15 min. 24 – 48 hour; 200every 30 min. 48 – 72 hour; barring according to kiln temperature; 100every 30 min. When the kiln shell is below 50 degrees Celsius the kiln and related machinery can be stopped. 4. Run the cooler fans in cascade with a ratio of 0.30. Operation of grates. During the cooling down phase; run the grates 15 min every 6 hours, with 5 strokes/minute. Procedure for cooler operation as mentioned above. Operatinal data Nominal

Maximum

Minimum

Press. Outlet ID-fan Cooling tower outlet temp Kiln feed Outlet temp. Outlet O2 Outlet CO Diverter gates Tert. air gate Fuel calc. Kiln speed Prim. air kiln O2 kiln CO kiln 5. Stage temp

Unit mBar

150

200

120

ºC

315 310 3.4-4.0 0 60-70 30-40

320 475 5 1.2 80 100

150 2.5 40 0

3.4

3.6

.5

3 0 860

5 950

2.5 830

Ton/h ºC % % % % tph rpm mbar % % ºC

Reduction zone temp Prim. air kiln Radial air kiln Axial. air kiln Kiln hood pressure fuel kiln Cooler air Grate speed Grate speed mode Cooler outlet temp.

850

1000

800

ºC

240 30-60 100 -0.5

280 60 100 -0.2

200 20 100 -1.0

mbar % % mbar

15-20 Random mode 280-320

22

400

St./min.

-

ºC

Preconditions. 1. Kiln is on barring device. 2. Gas analyzers are in operation. 3. Kiln/raw mill dust transport is in operation. 4. All cooler fans running (air ratio 0.60). 5. Kiln hood pressure: – 0.2 – 0.3 mbar 6. Hoisting damper fully closed. Initial actions to be taken about 1 hour before kiln feed. 1. All the kiln auxiliaries such as kiln feed system; cooler dust transport and clinker transport are started. 2. Kiln feed in recirculation with set point of 180 t/h (stop Atox mill during that time). Check that the material is flowing from all the extractions. Starting up. 1. When the 5 stage temperature has reached 750°C, which is minimum for starting the calciner, and the kiln heating is approximate to the heating-up program (the kiln is hot– this is determined by the color on the lining), then the kiln is ready for start 2. Start the following in rapid and correct steps. 3. Start the Cooler grates (speed: 5-6 strokes) a) Cooler fans air ratio: min. 0.75 b) Kiln hood pressure: -0.5mbar in auto mode at mentioned hood pressure) 4. Stop the Kiln barring and change to Kiln main drive (speed 0.5 rpm). 5. Adjust kiln gas firing to approximately 4000 Nm3/h (this depends of O2 in kiln inlet). 6. Adjust dampers of the ID fans to 10% 7. Start ID-fans on 10% 8. Start increasing gas on main burner 9. Select kiln feed for permission to start calciner burners 10. Start the Calciner burner. Start-up instruction (cold kiln) 11. When the calciner is started (you see an gas flow indication) a) Open the main EP-fan damper to 100% b) Set point -2.5 in auto c) Open ID fan damper to 100% d) Increase speed of the ID-fan to 60%. 12. Select feed to kiln (180t/h) without waiting for minus pressure out of the preheater but observe the pressure changes in the preheater. 13. Open the TAD damper to 15% (keeping close watch on kiln inlet O2)

14. Start the gas cooling tower. 15. Increase calciner gas flow for a rapidly increasing of fifth stages temperature to 8500 C 16. Increase kiln gas to approximately 4550kg/hr 17. Increase primary air to 250 mbar 18. Open axial air fully and radial air 20% primary air nozzle 35mm open and gas nozzle pressure 0.5 mbar 19. Avoid generating CO in the system and attention must be paid to the Oxygen 20. Increase the speed of the Kiln to 1 rpm. I. Kiln feed is now on and both calciner and kiln burner are in operation. On the kiln mimic we can see the heat consumption which is a good indicator for how much fuel is needed. A cold kiln will initially use up to 1300 kcal/kg cl. 21. Adjust the TAD damper accordingly (the kiln inlet oxygen: 3 – 4% and PH outlet >4%). 22. When the Kiln is stabilized (firing, oxygen) and becoming hotter (kiln torque/NOx starts to climb), increase the Kiln feed and speed. While picking up the kiln production, remember: Fan, Fuel, Feed and Speed. 23. The Cooler fans flows, ratio set points and strokes set point depends of: temperatures of tertiary and kiln hood air, pressure under the grates and thickness of clinker layer They all must to be increased proportional to the Kiln feed. Optimizing the operation Adjust the Kiln and Cooler parameters in a controlled way to obtain nominal and stable production as soon as possible Adjust the auto mode set point of the strokes as per commissioning. 5th stage temperature must be kept constant. Fluctuating of the temperature is Not wanted. Remember this Start- up instruction is only a guidance everything depends of the situation

The optimization of kiln operation 1-increasing production: .How do find out if a production increase is possible? . What action shout you undertake to increase the production? . What criteria do you have respect to keep the proper balance of gas flow and heat? .How do you go about increasing production? The burning process is well balanced (gas and heat flows) .the kiln operation is normal. Nothing in sight to expect an incident -you can take advantage and rest-increasing the production results with a better heat consumption- or you can find out if you can optimize the production - you can think of of increasing the production if you have enough operating margin available - Increasing feeding: Example:

Id fan speed = RPM1

POWER= P1 power 2=p2

Rpm2 Then the equation is: P1=P2*(RPM2/RPM1)^2 Before undertaking an increase of the kiln feed rate .you should make sure -the material the gas temperaute and the decarbonition are normal - the marginal capacity is enough for: .the kiln drive power -the fuel flows -the volumetric flow rate of all fans Don’t forget that the increase of certain parameter is not linear the power of fan is proportional to the square of the speed The kiln feed rate increase must be made is successive steps with complete stabilization of the heat and gas flow system at each step tips during kiln operation 

Every 10% increase in preheater exit temp., increases 7-10 kcal/kg clinker heat consumption.

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Every 10% increase in clinker temperature, increases 2 kcal/kg of clinker heat consumption.

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Every 1% increase in kiln PH exit O2% increases 7 kcal/kg of clinker heat consumption.

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Every 1% increase in residue (kiln feed) in 90 micron, increases 5-10 kcal/kg clinker heat consumption.

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Every 0.1 increase in silica modulus, increases 10kcal/kg clinker heat consumption.

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Every 1% increase in kiln feed LSF increases 15 kcal/kg clinker heat consumption.

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Every 100 blain increase in cement increases 1.5 kwh/MT of power consumption.

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Every 1% reduction in primary air reduces 0.7 kcal/kg clinker heat consumption.

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Every 10 degree centigrade increase in flame temperature increases 1% kiln production.



Every 100 blain increase in cement increases 1.5 Mpa of strength.



Every 1% increase in fine coal moisture reduces 10 to 14 degree centigrade flame temperature.

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Every 1% reduction in clinker-free lime, increases 4.0 % C3S in clinker.

Every 1% increase in C3S reduces 0.3 to 0.5 kwh/MT clinker grinding energy consumption 

Every 1 % reduction in free lime increases 10 – 25 kcal/kg clinker heat consumption.