Method of recycling iron-bearing waste material back into a basic oxygen furnace
AssigneeBethlehem Steel Corporation
InventorsJohn D. Lynn, Colvin W. Smith, Glenn C. Keyser
Life of this patent
Estimating the term…
Abstract
The invention is directed to a process for dehydrating and recycling back into a BOF converter wet BOF scrubber sludge to produce a steelmaking revert having an improved flow rate when handled in a recycle stream. Wet sludge is combined with hot BOF slag to provide a slag/sludge mixture. The wet sludge causes the mixture to have a moisture content greater than 10% water by weight, and the hot slag, having a temperature below the molten liquid state, vaporizes the water in the mixture and reduces the moisture content to about 4% water by weight or less. The dehydrated mixture has improved flow rate properties when it is recycled as a steelmaking revert.
Claims30
A process for dehydrating a wet sludge to produce a revert for recycling back into a steelmaking furnace, the dehydrating steps producing a revert having an improved flow rate when handled in a recycle stream, the steps of the process comprising:
- a) combining wet sludge with hot slag to provide a slag/sludge mixture having a moisture content greater than 10% water by weight, the hot slag having a temperature below the molten liquid state;
- b) discontinuing said step of combining wet sludge and hot slag and resting the slag/sludge mixture for a time period to enable radiant energy emitted from the hot slag to vaporize water in the slag/sludge mixture to produce a dehydrated slag/sludge mixture having a reduced moisture content of about 10% water by weight or less;
- and
- charging the dehydrated slag/sludge mixture into a furnace during a steelmaking oxidation phase so that oxidation phase temperatures volatilize heavy metals in the dehydrated slag/sludge mixture and remaining iron-bearing materials in the dehydrated slag/sludge mixture fall into and become entrained within the molten metal bath.
A process for recycling iron-bearing waste material back into a steelmaking furnace heat, the steps of the process comprising:
- a) charging steel scrap into the steelmaking furnace;
- b) charging molten iron into the steelmaking furnace;
- c) blowing O.sub.2 into the molten iron contained in the steelmaking furnace;
- d) charging an iron-bearing waste material derived from slag and sludge into the steelmaking furnace during the O.sub.2 blow, the waste material having a moisture content of about 10% by weight or less water;
- e) volatilizing and discharging through a furnace exhaust non-ferrous materials contained in said iron-bearing waste material;
- and
- f) reducing to steel ferrous materials contained in the steelmaking furnace.
A process for recycling iron-bearing waste materials, having concentrations of not more than about 200,000 ppm zinc by weight, back into a steelmaking furnace and producing a heat of finished steel product having a concentration of less than about 43 ppm zinc by weight, the steps of the process comprising:
- a) charging steel scrap into the steelmaking furnace;
- b) charging molten iron into the steelmaking furnace;
- c) blowing O.sub.2 into the molten iron contained in the steelmaking furnace and reducing the molten iron to a steel product;
- d) charging an iron-bearing waste material derived from slag and sludge containing zinc into the steelmaking furnace during the O.sub.2 blow, the waste material having a moisture content of about 10% by weight or less water;
- e) volatilizing and discharging through a furnace exhaust zinc contained in the iron-bearing waste material;
- f) reducing to steel ferrous materials contained in the iron-bearing waste material, the reduced ferrous materials being combined with the steel product in the steelmaking furnace;
- and
- g) tapping the combined steel product, the combined steel product having a zinc content of less than 43-ppm zinc by weight.
Dependencies are inferred from the claim text.