pa1778data.pdf

U.S. STEEL DUQUESNE WORKS
HAER NO. PA-115
(Page 208)
An important change to the gas cleaning system occurred in
1976 when a second dual venturi washer and gas cooling tower were
added, thus greatly increasing the system's capacity.
Significant changes to the water treatment facilities took place
in 1966 and 1979. In the former year, the Dorrclone was replaced
by a grizzly and two reciprocating rake classifiers.
Difficulties with the Dorrclone centered on its inability to
efficiently separate entrained particulate from the gas quencher
wastewater by the centrifugal force method, and by excessive
maintenance costs caused by the highly abrasive matter entrained
in the fumes emanating from the oxygen furnace. The new
equipment solved these problems by handling the quencher
wastewater in three stages. During the first stage, quencher
wastewater was delivered from the rough gas main through the
scupper to the top opening of the grizzly, which was nothing more
than a vertical cylinder outfitted with a screen to catch and
divert large entrained particulate to a dumping area. After
passing through the grizzly's screen, the slurry was next fed to
one of the reciprocating rake classifiers. The classifier
consisted of an hydraulically powered rake which swept solids
that had settled in a shallow, rectangularly shaped basin up an
incline into a dewatering hopper while the remaining filtrate was
delivered by gravity to the clarifier for further treatment.
Additional water treatment equipment was added in 1979 for
the purpose of meeting E.P.A. clean water standards. Designed to
partially recycle wastewater from the gas cleaning system, major
additions to the water treatment complex included a 6,175 gallon
capacity neutralization tank, a 18,000 gallon capacity wet well,
a gravity filter, and a variety of chemical feed equipment. The
expanded system began with the feeding of polymer additions to
the water overflowing into the clarifier's launderer. From the
launderer, water at a rate of 900 gpm was delivered to the
neutralization tank where it was treated with sulfuric acid in
order to prevent scaling in the system's equipment, and to assure
that the wastewater remain within an acceptable pH range before
being gravity fed to the quencher supply pumps. The remainder of
water in the system (from 750 to 1800 gpm) was sent to the wet
well and treated with a calcium dispersant to control scaling.
Wet well water was subsequently blown back to the river after it
passed through a gravity filter. 4
Finally, in 1982, a clean steel production building was
built onto the northern wall of the near west teeming aisle. The
building housed a teeming platform and was equipped with argon
delivery facilities. Argon was used to provide a shield for the
molten steel as it was teemed from the ladle to the ingot moulds.
This was done because exposure to the oxygen during the teeming
process had a tendency to create defects in the form of