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

image credit: Photo by Rod Hatt
Rod Hatt's picture
Chief Coal Combustion, Inc.

Having worked with coal quality and combustion issues in the utility industry for over 40 years I have operated Coal Combustion, Inc. for over 17 years providing sound unbiased consulting and...

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  • May 23, 2022
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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 NOx 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.

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Thank Rod for the Post!
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Michael Keller's picture
Michael Keller on May 31, 2022

The massive load transients caused by renewable energy are also unhelpful to combined cycle (combustion turbines) plants, with cyclic stresses causing more frequent repair of the equipment.

The fundamental driver to provide reliable power to meet consumer and industrial demand has been turned on its head. Now the grid exists to serve renewable energy. Not surprisingly, the cost of energy for the consumer has skyrocketed.

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