Coal Plant Operators in Times of Need - Today's Combustion Conditions Promote Forced Outages

The major problem is long high load runs at low O₂ or air flow.  Just when the grid needs every last megawatt, you push your boiler to the fan limit, and then operate for several days at maximum megawatts with O₂ set points below 3.0 excess O₂, Sometimes as low as 2.0% O₂ on PRB coals 

Short term you have a forced outage for “green” slag.  Green slag is formed in hot (high load) low oxygen runs for the boiler.  No load drops are done to shed slag before it overwhelms the boiler slopes.  Green slag is the hardest slag I have met, and it takes days to remove, even using explosives.  It does not matter what coal you burn, all boilers can make this slag in hot, high CO, low O₂ flames.

The other issue these low air flow conditions promote is water wall wastage.  Low O₂ environments, weather from fan limitations or low NO_x burning, particularly with over fire air, OFA, due not burn the sulfides like pyrite (FeS₂).  Sulfides are a known water wall attach/wastage concern.  This is true even with low sulfur sub bituminous coals like PRB in the USA, and many Indonesian coals.

Please consider dropping load to meet minimum O₂ levels, and minimize carbon monoxide, CO levels to prevent slag and water wall wastage.