Oklahoma Gas & Electric Muskogee Generating Station Best ...

Oklahoma Gas & Electric
Muskogee Generating Station – BART Determination
May 28, 2008
WESP has not been widely used in utility applications, and has only been proposed on
boilers firing high sulfur coals and equipped with SCR. Muskogee Units 4 & 5 fire lowsulfur
subbituminous coal. Based on the fuel characteristics listed in Table 4-1, and
assuming 1% SO2 to SO3 conversion in the boiler, potential uncontrolled H2SO4 emissions
from Muskogee Units 4 & 5 will only be approximately 5 ppm. This emission rate does
not take into account inherent acid gas removal associated with alkalinity in the
subbituminous coal fly ash. Based on engineering judgment, it is unlikely that a WESP
control system would be needed to mitigate visible sulfuric acid mist emissions from
Muskogee Units 4 & 5, even if WFGD control was installed.
WESPs have been proposed to control condensable particulate emissions from boilers
firing a high-sulfur bituminous coal and equipped with SCR and wet FGD. This
combination of coal and control equipment results in relatively high concentrations of
sulfuric acid mist in the flue gas. WESP control systems have not been proposed on units
firing subbituminous coals, and WESP would have no practical application on a
subbituminous-fired units. Therefore, the combination of WFGD+WESP will not be
evaluated further in this BART determination.
Wet FGD Scrubbing - Conclusions
Wet FGD technology is an established SO2 control technology. Wet scrubbing systems
have been designed to utilize various alkaline scrubbing solutions including lime,
limestone, and magnesium-enhanced lime. Wet scrubbing systems may also be designed
with spray tower reactors or reaction vessels (e.g., jet bubbling reactor). Although the flue
gas/reactant contact systems may vary, the chemistry involved in all wet scrubbing systems
is essentially identical. A large majority of the wet FGD systems designed to remove SO2
from existing high-sulfur utility boilers have been designed as wet limestone scrubbers with
spray towers and forced oxidation systems.
Wet scrubbing systems using limestone as the reactant have demonstrated the ability to
achieve control efficiencies of greater than 95% on large pulverized coal-fired boilers firing
high-sulfur bituminous coals. The chemistry of wet scrubbing consists of a complex series
of kinetic and equilibrium-controlled reactions occurring in the gas, liquid and solid phases.
In general, the amount of SO2 removed from the flue gas is governed by the vapor-liquid
equilibrium between SO2 in the flue gas and the absorbent liquid. If no soluble alkaline
species are present in the liquid, the liquid quickly becomes saturated with SO2 and
absorption is limited. 25 Likewise, as the flue gas SO2 concentration goes down, absorption
25 Combustion Fossil Power – A Reference Book on Fuel Burning and Steam Generation, edited by Joseph P.
Singer, Combustion Engineering, Inc., 4 th ed., 1991 (pp. 15-41).
43