Reburning involves the staged addition
of fuel into two combustion zones: (1) the
primary combustion zone where coal is
fired; and (2) the reburn zone where additional
fuel (the reburn fuel) is added to create
a reducing (oxygen deficient) condition
to convert the NOx produced in the primary
zone to molecular nitrogen (N2) and water.
Above the reburn zone is a burnout zone in
which OFA is added to complete the combustion.
Each zone has a unique stoichiometric
air ratio (the ratio of the air used
to that theoretically required for complete
combustion) as determined by the flows
of primary fuel, burner air, reburn fuel,
and OFA.