BTU compensation in coal fired boiler control system

[niko99]

Has anyone had any experience designing and/or modifying a boiler control system that can account for varying BTU content of coal? I am referring specifically to a coal-fired utility boiler that utilizes natural gas reburn with overfire air. Maintaining a target stoichiometry in the primary combustion zone is difficult if the BTU content of the coal is a variable. Is there any way to relate boiler heat release to fuel input rate?

 

[JEB66]

What about using throttle pressure.

Feedwater at a given flow and pressure will require a fixed amount of BTU's. Any change in lbs / hr of fuel flow will be an indication of fuel change.

However this is complicated by the amount of moisture in the coal and a change in boiler efficiency.

One other point is, the amount of air required to complete combustion will change as the carbon content changes. This will effect the burner stoichiometry as well.

 

[25362]

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