CONTROL OF WATER PROBLEMS IN A STEEL MILL'S
BLAST FURNACE GAS WASH RECIRCULATION SYSTEM
G. R. Brower, Vice President
P. A. Luther, Environmental Engineer
Ryckman/Edgerley/Tomlinson & Associates
Knoxville, Tennessee 63141
S. J. Ryckman, Professor
Civil Engineering Department
Dayton University
Dayton, Ohio 45409
INTRODUCTION
Blast furnaces represent an integral part of the iron and steel industry. The blast furnace
converts iron ore into molten iron as the first step in the production of steel.  Large quantities of gas are generated during normal operations of a blast furnace.  This gas is rich in carbon monoxide and is utUized in the steel making process as a source of fuel. The gases
leaving the blast furnace, however, are contaminated with fine suspended particles consisting
primarily of calcium, sUica and iron salts and undesirable gases, such as hydrogen cyanide,
which must be removed not only to allow the gas to be used as a fuel, but to prevent air pollution. High-energy air scrubbers, using as much as 5000 gallons per minute (gpm) of water,
are used to clean the gases. The scrubber water removes the contaminants from the gases
and carries them to a treatment site which usually is comprised of a series of clarifiers. The
treated water is subsequently recycled back to the scrubbers. This treatment facUity nor-
maUy removes a major portion of the suspended particles but does little to reduce the dissolved solids load of the water. Continuous recirculation of this water results in a buUdup
of dissolved salts. These dissolved salts, in turn, are concentrated further through evaporation, and without significant blowdown from the system, create a potential scale-forming
and corrosive situation. Blowdown cannot in most cases be discharged from the system to
a receiving body of water due to effluent limitations. Thus, the water must be treated to
eliminate a potential scale-forming and corrosive situation, or blowdown must be used elsewhere in the steel plant.
Ryckman/Edgerley/Tomlinson & Associates (RETA) was contracted by a major steel industry to develop a treatment procedure which would prevent scaling and corrosion problems in the mUl's blast furnace gas wash recirculation system. This paper presents the investigations and studies that occurred in an attempt to find a solution to this problem.
PROBLEM DEFINITION
The operation of this steel mUl's blast furnace gas cleaning system, as shown schematicaUy
in Figure 1, has-caused serious scale deposition at critical points in the system. The deposition resulted in blockage of pipes and necessitated a significant blowdown of water from the
system into a receiving body of water. In an attempt to solve this problem, the mUl contracted a chemical company to supply a scale inhibitor to control scale formation in the system. This organic phosphate inhibitor was able to reduce scaling in the system by approximately 95%. However, scaling was still evidenced in exposed areas of the recirculation system.
In addition to the scale problem, on four occasions total cyanide levels in recycled waters
were measured at values greater than 50 mg/1. On numerous occasions chlorides were measured in concentrations greater than 800 mg/1 producing a potentially corrosive situation.
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