In addition to the failures indicated by the visualization system, process errors may occur that may have a negative impact on the finished product.
The following list contains possible process errors and their probable causes as well as effective countermeasures.
INFORMATION
As the processes performed by the lime kiln are extremely complex, the following list can only contain the most common process errors. It is impossible to list all possible errors and their combinations.
In case of problems or doubts when operating the lime kiln, ask the manufacturer for assistance.
NOTICE
It is the sole responsibility of the kiln operating person to decide whether to act by him or herself or to request technical advice and assistance from the manufacturer.
In the event of an erroneous decision in this respect, the manufacturer cannot be held liable for any accidents or damage thus caused.
Issue Possible cause Countermeasure
Concentrations of residual CO2 in lime of both shafts too high
Insufficient heat input Before increasing the heat input, make sure there is no other cause for this problem Too much cooling air Reduce cooling air
Wrong cooling air distribution Set correct amount of cooling air to be supplied to the centre of the shafts
Waste gas temperature too high Increase stone level in shafts, reduce cooling air
Limestone not to specification Provide limestone according to specifications
Non-uniform burning
temperature throughout burning zone
Adjust excess air correctly
Non-uniform burning
temperature over shaft cross-section
Check fuel distribution
Wrong portions or wrong distribution of small and large stone fractions (fine lime kilns)
Adjust stone distribution
Concentrations of residual CO2 in lime of both shafts too low
Too much heat input Reduce heat input
Concentrations of residual CO2 in lime of one shaft too high
Different amounts of limestone in shaft 1 & 2
Correct stone weighing system
Different amounts of fuel in shaft 1 & 2
Check for clogged burner lances or fuel supply lines
Correct fuel dosing system Different amounts of combustion
air in shaft 1 & 2
Replace silicone rubber gaskets on reverse flaps
Issue Possible cause Countermeasure
Non-uniform lime quality at the discharge tables
Non-uniform burning
temperature over shaft cross-section
Check for clogged burner lances and fuel supply lines
Check fuel supply in each shaft Material in burning zone sticking
together
Check for over-burnt lumps of lime, and reduce heat input if necessary.
Wrong cooling air distribution Set correct amount of cooling air to be supplied to the centre of the shafts
Wrong stone distribution Adjust stone distribution Channels partially clogged Clean connecting and ring
channels Insufficient kiln production
rate
Operating pressure too high Reduce heat input, if possible Reduce air volume, if possible Reduce reversal time
Reduce burn-out time, if possible
Provide limestone according to specifications
Burning temperature too high Heat input too high Reduce heat input
Wrong excess air setting Set correct excess air value Lumps of lime sticking together Reduce heat input
Stone size too large Provide limestone according to specifications
Issue Possible cause Countermeasure
Burning temperature too low Heat input too low Check whether excess air is adjusted correctly. If necessary, increase heat input. But first ensure that there is no other cause for this problem.
Wrong excess air setting Set correct excess air value.
Operating pressure too high Air volume too large Reduce air volume if possible Heat input too high Reduce heat input if possible Burn-out time too long Reduce burn-out time if possible Reversal time too long Reduce reversal time
(hydraulics)
Limestone not to specification Provide limestone according to specifications
Channels partially clogged Clean connecting and ring channels
Operating pressures too low Leakage in air, hot gas, or waste gas lines
Check systems for leaks
Not all blowers operating, or failure of one blower
Check all blowers and all connected devices such as non-return valves, pressure relief valves, and flexible connections Different waste gas
temperatures in shaft 1 & 2
Wrong cooling air distribution Set cooling air distribution to the correct value
Different amounts of limestone supplied to the shafts
Correct stone weighing and charging system
Different amounts of fuel supplied to the shafts
Check the lances for obstructions
Correct fuel dosing system Different amounts of combustion Replace silicone rubber gaskets
Issue Possible cause Countermeasure
Lime temperatures in shaft 1
& 2 different or too high
Wrong cooling air distribution Set cooling air distribution to the correct value
Different lime qualities See similar items in this table Material in burning zone sticking
or clogging together
Reduce heat input and notify the manufacturer
Different operating pressures in shaft 1 & 2
Wrong cooling air distribution Set cooling air distribution to correct value
Different amounts of limestone supplied to the shafts
Correct stone weighing and charging system
Different amounts of fuels supplied to the shafts
Check the lances for obstructions
Correct fuel dosing system Different amounts of combustion
air supplied to the shafts
Replace silicone rubber gaskets on reverse flaps
Check air supply system for leaks
Material in burning zone sticking or clogging together
Reduce heat input and notify the manufacturer
Material inside the shafts not moving downwards
Burning temperature in upper part of the burning zone too high
Adjust excess air correctly
No lime discharged after kiln shut down
Build up and release pressure inside the kiln
Material in burning zone sticking or clogging together
Reduce heat input and notify the manufacturer
Discharge system not set to optimum values
Adjust discharge system such that extended idle times at the discharge tables can be avoided.
Adjust the discharge system such that a slightly higher amount of lime is discharged from the firing shaft
Clogged burner lances Temperature in upper part of the Adjust excess air correctly.
8 Maintenance
8.1 In general
The following provides basic information on how to do maintenance work essential to ensure optimum performance and trouble-free operation of the lime kiln.
Detailed descriptions of the necessary maintenance work for each individual component can be found in Instruction Manual Book-2 Specific Data & Component Description.
Maintenance intervals
The listed maintenance intervals have been determined for the intended performance of the kiln as well as for the intended work and operating conditions. They are based on long-term experience and our first hand inspections at various plants.
If regular inspection of the lime kiln show an increased level of wear, the operating person must adjust intervals as required by the actual constraints on the lime kiln and the indications of wear.
If an irregularity cannot be removed by performing the steps described below, the manufacturer is to be notified immediately.
8.2 Safety
WARNING
Improperly performed maintenance work can lead to severe physical injury or damage to property. Any work related to upkeep and maintenance is to be carried out exclusively by qualified and authorized expert personnel.
When performing maintenance, make sure to observe the following:
- Shut down the kiln and lock against restarting
- Do not perform any work unless the kiln has been shut down.
- Lock moving parts to prevent further motion.
- Attach a well-visible sign warning of work in progress to the main switch and the access areas of the kiln (see figure).
Fig. 71 Sign warning of work in progress (typical)
WARNING
Danger of injury!
Any accidental start of the machine during maintenance or repairs may cause serious injury, permanent bodily impairment or death!
Therefore:
- Remove the key from the key switch and keep it out of reach of third parties by storing it in your own pocket until work has been completed.
- Lock the main switch with a padlock to prevent the machine from restarting. Remove the key and keep it with you.
- Inform the machine operator as well as the supervisor about the expected scope and duration of the maintenance work.