Lamtec AEC-TPS, Manual

Page: 208 / 284

207
8 CO/O
2
Control
8 CO/O
2
Control
8.1 For Your Safety
The following factors must be taken into consideration for the assignment of the set-point val-
ues of the actuators for controlling the quantity of fuel and air and for setting the parameters
for correctional intervention:
•
Combustion chamber pressure
• Fuel pressure
• Temperature and pressure of the combustion air
• Calorific value of the fuel
In the process, a safe, stable firing operation must be guaranteed across the entire output
range and in all firing operating modes.
This must be documented by measuring the characteristic values for an operation of the fur-
nace at the shut-off limits of the ratio control, as well as the set limits of the correction circuits
(e.g. an O
2
trim). To help you assess the situation, you should also refer to the informative
commissioning report.
It is essential that the procedure in chapter
6.3.4.1 Run to Shut-off Limits is observed.
For an equipment of the furnace with a failsafe CO controller, the check in the air deficiency
direction can be omitted. Instead, the shut-off limit of the CO controller (0.4 Vol.% O
2
) must
be checked; see chapter 6.3.4.1 Run to Shut-off Limits .
The correction limit in the excess air direction must also be limited to a non-critical range in
the event of CO controller operation.
If two or more systems of the CMS type are combined with a CO control device (e.g. two or
more burners for a combustion chamber), the safe operation of the combustion must be en-
sured with an additional flue gas monitoring system.
8.2 Safety Concept
The CO controller attempts to keep the combustion process within in the range of complete
combustion, i.e. just above the CO edge. To do this, the controller outputs a correction signal
which is evaluated by the electronic ratio control in order to move the positions of the actuating
devices in the direction of less or more air.
The set maximum correction range limits the possible influence of the controller. It is not pos-
sible to leave this range.
The position of the electronic ratio curve and correction range must be set in such a way that
the electronic ratio control can exceed the CO edge towards less air under all operating con-
ditions. The CO edge towards excess air must not be exceeded.
The following figure depicts this once more.