FUNCTION
The main function of the ID FAN (Induced Draft Fan) is to suck the flue gases coming out of the furnace via economizer, air heater and also it maintain the negative draft (pressure) inside the boiler approximately 10mmWC. The component in the below figure is 26. Normally one independent thermal power plant unit comprises of 2- ID Fans.
At present four different problematic operating zones are identified:
- DURING PARALLEL IN
Problem:-
When one is running in Auto mode, controlling the furnace draft and the additional fan is taken in Auto parallel, there could be the furnace draft get disturbed.
Solution:-
The additional fan should follow the running fan control signal with an optimum rate and the existing fan blade pitch should come down and match with the new one with action of PID controller. And similarly this should continue it number of fans are more than two.
- AFTER PARALLEL IN
Problem:-
Two fans are running at different load though operating in Auto.
Solution:-
Fan operator bias need to be adjusted to minimize the deviation between the load.
- ONE IN AUTO AND THE OTHER IN MANUAL
Problem:-
Auto control of the equipment works fast if tuned for multiple, furnace draft becomes unstable
Solution:-
The gain of the controller to be adjusted by implementing a separate gain adjustment logic based on number of equipment involved
- OTHER FANS STARTED LIKE FD FAN OR PA FAN
Problem:-
Furnace draft increases and makes control unstable
Solution:-
Advancement of FD/PA Fan blade pitch to be adjusted to ID Fan blade pitch, so that any increment in other fans make ID Fan blade pitch advance accordingly. So ratio wise Feed-forward signal to be incorporated to prevent the excursion of Furnace draft due to addition of Air considering start of other fans.
Reference Books that can be followed:
Other problems will be posted soon...
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