pa1778data.pdf

U.S. STEEL DUQUESNE WORKS
HAER No. PA-115
(Page 106)
Entering near the bottom of the 24*-0" diameter x lOO'-O" high
cooling tower, the washed gas was cooled by a series of water
sprays as it rose up the tower. The cooled gas subsequently left
the top of the cooling tower through the 96" i.d. clean gas main
leading back to the burner connection on the hot blast stoves.
The slurry from the gas washer and gas cooler dropped to the cone
at the bottom of each piece of equipment and was taken out by
means of a pipeline to the clarifier or thickener where it was
joined by the wastewater flowing from what remained of the
centralized system.
After passing through the clarifier in the usual manner, the
separated particulate or sludge was pumped over to a continuous
mechanical dewatering process located in the newly constructed
filter cake house near the clarifier. Taking the place of the
settling basins and located on the upper floor of the filter cake
house, the equipment making up the process included two 2 hp
motor driven filter cake machines, each composed of six equally
spaced 8'-10" diameter cloth covered vacuum disc filters set
inside of an approximately 12'-0" long bifurcated tub consisting
of a slurry side and a discharge side. The process embodied
three stages — forming, drying, and discharge. During the
forming stage, the discs were passed, under vacuum, through the
slurry. As they passed, cake was built up and water was removed
by filtration through the cloth. As the discs emerged from the
slurry, they were dried by air drawn through the cake by the
applied vacuum. At the end of the cycle, compressed air was
admitted into the discs thereby expanding the cloth as it was
passed over a knife edge which discharged the dried particulate
through a chute leading to a dumping area directly below. 7
The gas cleaning system was upgraded further when the Diehl
gas scrubbers were replaced by two new systems at blast furnaces
number three and four in 1971. Designed to clean blast furnace
gas from the aforementioned furnaces as well as from blast
furnace number one, the equipment included a dust catcher, a
venturi scrubber, and a gas cooling tower connected in series.
In order to save water, the new system recycled water from the
gas cooling tower into the venturi scrubber. Spray water from
the gas cooler was diverted by means of a "Chinese hat" located
inside of it to a stand pipe before it was pumped over to the
scrubber where it was sprayed on the gas coming from the dust
catcher at a rate of 150,000 cfm. Both the gas and the slurry
left the scrubber by means of a flooded elbow leading to the gas
cooling tower. The gas rose up the tower and was sprayed,
cooling it to a temperature of 112° F, while the slurry dropped
to its cone before being pumped over to the clarifier.
The principle of recirculating water used in blast furnace