Boiler air heater in air and gas system

Following are the possible reasons

1. Unburnt Fuel in the flue gas (incomplte combustion in the furnace due to inadequate excees air) getting deposited on the tubes.

2. Soots dislodged from heating surfaces due to soot blowing operation caried over by flue gases and getting deposited on the tubes.

3. Oil being the fuel, there may be sulphur content in the fuel. In case of lower mean temperature (Normally during start up and low load operation) at airheater area, the SO 4 in the fluegas liquidified and deposited on the surfaces of the tubes,(IN long run this will lead to airheater tube corrosion)

Above are the some points I can think off immediately.

R.Thiyagarajan

Thanks for your answer but another question, excess air can be caused by auxiliary air damper opening % (curve of aux and fuel air damper with different load) ? , because the combustion oxygen controller is working properly also soot blowing is working in right condition , waiting for your reply

thanks

Is this a regenerative (rotating element) or recouperative (tubular) air heater?

What size is it?

This problem could actually be air in-leakage.

Dear Mr eng aly,

The question is not clear. However I clarify as below.

1. Persume the total combustion air to boiler is in correct quantity as O2 control is working properly.
2. Evaporation is good as soot blowing is working in right condition.
3. The total combustion air to boiler is sent to the furnace in two parts as fuel air (The volume of air required for transporting Fuel} and the balance air as aux. air. Accordingly the dampers are positioned.
4. Hence as such this will not change the quatity of excess air.
5. Excess air air normally being corrected based on percentage of O2 indication or combustibles ( Co + H2 ) in Flue gas if provided.

Regards

R.Thiyagarajan

its a rotating air preheater in steam power plant 393MW total air flow at max load 1200 t/h ,

Do you have steam coil air PREHEATER (SCAH)on suction or discharge side of FD/Combustion Fan? If not operating properly or removed, may be affecting exit gas (cold end) side of Rotary Regenerative Air Heater (RRAH), or keeping exit gas sections too cool allowing for more fouling.

Leak/Seal losses across Rotary unit effect overall unit efficiency. Good source of info on leak/seal/upgrades is Paragon Air Heater Technologies.

I'm a steam coil air heater guy, and the improper operation, leak, or other design issues around steam coil air heater side of issues would be my area to help.

Do you have SCR, ESP, FGD, Scrubber having any problems? All components are linked.