6.9.1 Kiln stoppage
Select kiln stoppage in the visualisation system in order to stop the kiln. The kiln control system automatically carries out the following steps:
- The fuel supply is immediately interrupted.
- The burn-out time begins immediately, the kiln is flushed with combustion air, cooling air and lance cooling air for the duration of the burn-out time.
- The kiln is depressurised using the relief flaps for combustion air and cooling air.
- The blowers for combustion air, cooling air and transport air (option) are stopped.
- The lance cooling air is switched off after 15 minutes.
- The combustion air / waste gas reversal flaps are moved to the position waste gas to the chimney.
- The filter / direct chimney reversal flap is moved to the direct chimney position.
INFORMATION
If the kiln is stopped, all systems remain in AUTO mode. This means:
All containers continue to be filled with limestone until they are full.
The lime discharge system continues to discharge lime.
The hydraulic system continues working.
NOTE
During long stops the lime may form clumps!
Discharge lime manually from time to time in order to prevent clumping in the shafts. The following table shows the maximum quantities which can be discharged during a kiln stoppage:
- Day 1: 6 tonnes - Day 2: 2 tonnes - Day 3: 1 tonne - Day 4: 1 tonne - Day 5: 0 tonnes
With some kilns this manual discharge is not necessary, as they work even better without it. However, you have to test this yourself for your kiln.
NOTE
The following has to be borne in mind in the case of kilns with suspended cylinders!
As the temperatures in the kiln remain at 1000°C for a long time after a stoppage, the cooling system of the suspended cylinders has to continue running.
Do not switch off the cooling system of the suspended cylinders. Otherwise, the suspended cylinders can be damaged.
If the cooling system of the suspended cylinders fails, the emergency cooling system is automatically switched on (via PLC). In any case the kiln operator must check locally whether the emergency cooling system has switched on.
6.9.2 Restarting
Select kiln start in the visualisation system in order to start up the kiln again after a stoppage. The start-up is carried out as described in the following:
Ensure that everyone is back in the control cabin and nobody is located in the vicinity of the kiln.
Check whether all systems work perfectly.
NOTE
Ensure that the temperature in the connecting channel is over 750°C.
For solid and liquid fuels: Ensure that the lance temperature is 50°C above the ignition temperature.
Set all systems that have previously been switched to OFF to AUTO.
If lime was discharged during the stoppage, replenish the shafts with limestone until the filling level is normal again.
INFORMATION
The energy loss through the kiln shell during the stoppage has a negative effect on the quality of the lime.
The loss through the shell cannot be compensated for by a short-term increase in the heat input.
6.9.3 Kiln stoppage by an alarm
In a dangerous situation the kiln is always stopped automatically. This can be caused by process limit values being exceeded.
NOTE
Avoid kiln stoppages by an alarm!
The initial setting of the limit values must be carried out in the presence of a specialist engineer commissioned by the manufacturer. All subsequent changes to the settings by the personnel operating the kiln require a high level of professional knowledge. In cases of doubt the manufacturer should be consulted.
INFORMATION
As soon as the problem which led to the kiln being switched off has been rectified, the kiln operator must restart all systems in accordance with the above instructions.
6.9.4 Kiln stoppage in the case of a power cut
In the case of a power cut, all systems are stopped, with the exception of the PLC and visualisation system. The PLC and the visualisation system have a UPS
(uninterruptible power supply) and remain in operation for at least 10 minutes.
A dangerous situation in the mechanical system cannot occur.
- Where necessary, flaps (in particular the discharge flaps) are closed by means of counterweights and without any hydraulic pressure.
- Certain types of kiln (depending on the fuel used) require an emergency power generator which is started automatically within one minute.
The following systems are switched on by such an emergency power generator:
- The kiln control system - One of the hydraulic pumps.
Suspended cylinders (if applicable) NOTE
As the temperatures in the kiln remain at 1000°C for a long time after a stoppage, the cooling system of the suspended cylinders has to continue running after a power cut. Otherwise, the suspended cylinders can be damaged.
In the case of a power cut, the emergency cooling system is automatically switched on (via PLC). In all cases the kiln controller must check locally:
- whether the emergency cooling system has switched on.
- whether all of the flaps are in the right position.
INFORMATION
As soon as the main current is available again, the kiln operator must put the system back into operation as soon as possible in accordance with the recommendations contained in the above sections.
6.9.5 Emptying the kiln
NOTE
Emptying the kiln reduces the lifetime of the refractory brick lining!
Complete emptying of the kiln reduces the lifetime of the refractory brick lining significantly. The kiln should never be emptied completely unless this is absolutely necessary. When the kiln is switched off in order to carry out repairs, it is often possible to empty the kiln only partially.
It takes approximately 2 days to empty the kiln.
Set the kiln to PRODUCTION MODE.
Set the kiln operation to OFF Set stone handling to ON
Set the filling process for the rotating bucket to AUTO Set the kiln discharge system to AUTO.
Start hydraulic pump 1 and / or 2
Switch the reversal flaps to chimney (kiln to stop)
Open the doors of the discharge table (in order to create natural ventilation in the kiln). Close the doors in the case of waste gas temperatures > 200°C and charge with cold lime
Manual discharging by means of the manual key
Open the discharge flaps for the lime discharge from time to time in order to discharge the lime
- In the case of a discharge temperature of more than 200°C -> stop manual discharging.
- If all discharge temperatures are below 200°C -> start manual discharging.
NOTE
High waste gas temperatures may damage the seals of the reversal flaps
For waste gas temperatures of more than 195°C -> close the doors of the discharge table in order to stop the ventilation.
If all waste gas temperatures are below 180°C -> open the doors of the discharge table in order to restart the natural ventilation.
6.10 Fine Lime Charging