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Basic Oxygen Process
Water Treatment
JOHN R. BROUGH, Director
Air and Water Control
THOMAS F. VOGES, Assistant Superintendent
Power Steam and Combustion Department
Inland Steel Company
East Chicago, Illinois
INTRODUCTION
Although the subject of this paper is water treatment for a Basic Oxygen Furnace,
(BOF) a discussion of water treatment would not be complete without including
comments on air pollution abatement. The need for water in the operation of a BOF
arises mainly because it is necessary to clean the gases evolved during the steelmaking
operation in order to prevent air pollution.
The furnace is charged with molten iron, scrap steel and fluxing materials. High
purity, high pressure oxygen is then introduced through a water cooled lance to
remove carbon, silicon, manganese and phosphorus. The oxidation of these elements
also provides the heat that is necessary for the process.
During the oxygen blowing period, iron oxide is formed which is carried out of
the furnace along with the flue gas and other dust from the process. The facilities
necessary to collect and recover this dust require over 90 per cent of the water that
is used by Inland's Basic Oxygen Furnace Shop.
Inland's BOF Shop has two furnaces which have a nominal capacity of 230 tons;
however, the average heat size is 254 tons. Only one furnace is operated at a time.
The average tap to tap time is 37 min, which results in an average production rate of
412 tons/hr. The total water use is approximately 70 mgd. Of this quantity, 50 per
cent is in recirculated water and 50 per cent is water withdrawn from Lake Michigan.
There are five major water systems. Each of these systems has different treatment
requirements, and these systems and their treatment requirements will each be discussed. These major systems are: 1) Hood Cooling; 2) Oxygen Lance Cooling; 3)
Spark Box Spray Cooling; 4) Gas Scrubbing; and 5) Gas After Cooling.
HOOD COOLING
The purpose of the hood is to contain the gases which are discharged from the
BOF vessel so that they can be conveyed into the gas cleaning system for removal of
the iron oxide and other dust generated in the steelmaking process. The gases leaving
the vessel are about 2800 F. The major component of these gases is carbon monoxide,
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