pa1778data.pdf

U.S. STEEL DUQUESNE WORKS
HAER No. PA-115
(Page 2 07)
and pumped under high pressure into a Dorrclone. Shaped like a
cone and set at a slight angle to a horizontal plane, the
Dorrclone separated the heavy solids from the quencher slurry by
centrifugal force. The solids dropped through the small end of
the cone into a chute leading to a sludge dump, while the
filtrate exited at the top, or large end of the cone, and flowed
by gravity to a 90'-0" diameter clarifier. All slurry from the
dual venturi scrubber and gas cooling tower passed by gravity
into the clarifier. Clarified water exited into the basin's
launderer and was directed to a sewer leading back to the
Monongahela River. Sludge was pumped from the clarifier by
underflow pumps to the filter cake house where it was dried and
deposited into a dumping area by vacuum drum filters. The drum
filters operated in the same way as the disc filters in the blast
furnace plant. 2
Shortly after the basic oxygen steelmaking facility went
into production, several important changes were made to its by-
product (slag handling, gas cleaning, and water treatment) and
teeming operations. In 1966, an ill-fated slag granulating and
separation facility was constructed on the site. Designed by the
company 1 s research center in Monroeville, Pennsylvania, to
separate steel tailings or residue from BOP slag, the system
included two slag granulating tanks, a 12'-0" diameter stand
pipe, and slag separation eguipment. The process began by
feeding slag from the oxygen furnace into a tundish leading to
one of the granulating tanks. The slag was sprayed with water,
thereby granulating it, as it entered the tank and was pumped
with the water to the standpipe. From the standpipe, which acted
as a surge tank, the slurry was pumped to the magnetic separator
at the top floor of the slag separation building. The
separator's magnetic drums segregated steel tailings from the
slag. Both the steel and the slag were subsequently delivered by
chute to their respective horizontal filters located on the floor
below. The filters separated the filtrate from the solid
materials. The slag and steel were then gravity fed through
chutes to their respective holding bins while the filtrate was
fed into a receiving tank and delivered to the clarifier at the
water treatment facility. Periodically, the granulated slag and
the steel tailings were removed from the holding bins by truck.
The granulated slag was delivered to the United States Steel
Corporation's Universal Cement Company, while the steel tailings
were charged back into the oxygen furnace with the scrap charge.
Despite best efforts by system operators to make the
facility work, the slag granulating and separation complex was
shut down after only two years of operation. The process never
achieved the required seven percent yield of steel tailings from
the by-product mass in order to be profitable. 3