ENHANCED BIOLOGICAL TREATMENT SYSTEM FOR
COKE PLANT WASTEWATER ACHIEVING COMPLETE NITRIFICATION
A. Bhattacharyya, Donner-Hanna Coke Joint Venture
Buffalo, New York
A.C. Middleton, Koppers Company, Inc.
Pittsburgh, Pennsylvania
INTRODUCTION
Coke plant wastewaters generate mainly from coke oven gas cleaning and by-product
recovery process steps. They contain varying levels of ammonia, phenols, sulfide, thiosulfate,
thiocyanate, cyanide, chloride and many other compounds. Effluent limitations guideUnes,
for discharge of coke plant effluents to navigable waters, are expected to be based on Best
Avadable Technology Economically Achievable (BATEA). Several possible alternate routes
have been proposed as BATEA with low required effluent Umits in view. BasicaUy they can
be divided into two groups: (a) physico-chemical; and (b) biological.
Physico-chemical processes conventionally consist of solvent extraction for phenol
removal, lime or caustic distdlation for ammonia removal, alkaline chlorination for ammonia
and cyanide removal and a few others. More recently activated carbon is also being used.
Physico-chemical processes, properly conceptualized and designed, are capable of achieving
high purification efficiency at a high operational reliabdity. NormaUy, however, they are
associated with high operating costs.
Biological treatment, on the other hand, is considered as a cost effective process provided
the feasibdity study indicates the compatibdity of the waste to biological degradation. A
literature review on research and operating experiences of pdot plant and full-scale treatment
systems indicated consistent nitrification of coke plant waste waters has not been widely
demonstrated. It is the objective of the paper to describe a bench-scale treatabdity study
that achieved consistent reliable nitrification.
BACKGROUND
The Donner-Hanna Coke Plant, Buffalo, New York, operates three batteries totaUing 151
ovens. Batches of crushed, specially blended coals are carbonized in these ovens producing
as much as 3000 tons of coke per day.
Volatile organic matter and moisture from coal leave the ovens during carbonization and
are taken through the by-product recovery system to produce raw ammonia liquor, tar,
ammonium sulfate, light oils and coke oven gas.
Figure 1 is a schematic diagram of the Donner-Hanna coking process with by-product
recovery systems. The primary component is the coke battery where carbonization of coal
takes place. The coal blend is "charged" in measured amounts to individual ovens and is
"pushed" as coke at the end of a coking cycle of the oven. A "hot car" carries this coke to
a quenching station where it is cooled by water sprays. Evaporation takes place in the
quenching tower and the remainder of the sprayed water flows to a settling basin where
particles settle out and are removed periodically. The clarified water is mixed with required
make-up water and is recycled to the quench tower.
Crude gas, consisting of the products of destructive distillation of coal and moisture, are
withdrawn from the ovens through individual stand pipes connected to the coUecting main.
This crude gas is cooled by sprayed recirculated raw ammoniacal Uquor called "flushing
Uquor." CooUng is effected mainly by adiabatic evaporation of water in flushing liquor and
the temperature of gas goes down to about 100 C. Up to about 2000 gallons of flushing
liquor are used per ton of coal carbonized. Most of the tar is condensed out of gas in the
collecting main, and the flushing liquor dissolves almost all of the "fixed ammonia" and
some "free ammonia" from the gas. The raw ammonia liquor and tar, separated from gas, go
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