Specialized metallurgical processes – compositions for use therei – Processes – Electrothermic processes
Reexamination Certificate
1998-10-13
2001-05-15
King, Roy (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Electrothermic processes
C075S750000, C075S961000, C075S962000
Reexamination Certificate
active
06231634
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to additives for an electric arc furnace, and more particularly to additives containing metallic oxides which are adapted to be introduced to the furnace.
2. Prior Art
In our patent EP-A-0499779 there is a described and claimed: a method for treating a mixture consisting of solid and liquid waste materials, which contains at least one metal, in particular Fe, and/or its compounds, more especially oxides, whereby the mixture is in a state in which it is unusable or usable only with difficulty, characterised in that the mixture is at least largely homogenised and to is added at least one ultra-fine-grained dry substance comprising fly ash and/or coke, in such quantity, and blended therewith until the resulting mixture is predominantly in the form of briquettes, of which at least part can be supplied for reutilisation in a thermal process; and a method for treating a first mixture consisting of solid and liquid waste materials; which contains at least one metal, in particular Fe, and/or its compounds, more especially oxides, whereby the mixture is in a condition in which it is unusable or usable only with difficulty, characterised in that the first mixture is at least largely homogenised and to it is added at least one ultra-fine-grained dry substance, comprising fly ash and/or coke, in such quantity and blended therewith until the resulting mixture exhibits a nature which enables the classification of the resulting mixture to provide at least one fraction which can be supplied for reutilisation in a thermal process.
The method of the earlier patent works well but when other materials need to be included for addition to the furnace there are disadvantages. Usually one would mix a baghouse dust (which contains valuable recoverable toxic metals such as lead and zinc) with the mixture and then process the blend as described. The need to blend the dust with the mixture means that very large mixing plant is required, which aggravates the capital cost. Because there is much loose dust in the atmosphere there is a health hazard for operators.
GB-A-928084 discloses mixing together metallic oxide, a carbonaceous reducing agent, a hydraulic binding agent and water to form pellets which are allowed to harden without added heat. Storage takes place over one to seven days, but the conditions of storage are not identified. WO 96/31630 discloses a similar process using waste materials. Again the conditions of storage are not mentioned.
It is one object of the invention to provide a method of forming a substantially dry injectable particulate composition from waste materials in a more convenient and economic way.
SUMMARY OF THE INVENTION
In one aspect the invention provides a method of making an additive for addition to an electric arc furnace from a waste material mixture consisting of solid and liquid containing at least one metal, comprising breaking up the mixture into wet particles of substantially the same size, mixing the particles with a carbonaceous substance and a hydratable substance to form a particulate composition, and storing the composition in containers having gas permeable walls in a substantially dry atmosphere and allowing the composition to chemically cure therein to form injectable substantially dry particles.
Preferably the waste material mixture is broken up by passage through a frame having rotary parallel bars which have generally star shaped lobes, the mixture being passed in the passageway between adjacent lobes.
Typically the waste material mixture has a water content of about 10% to about 30% by weight. Typically the mixture comprises an oily millscale.
Preferably the ingredients are mixed in the weight ratios of about 70 to about 80 parts millscale or the like; about 20 to about 25 parts carbonaceous substance: balance hydratable substance.
Preferably the particles are allowed to chemically cure for a period of about 72 hours. The composition is stored in containers, typically air permeable bags, in a substantially dry atmosphere.
Preferably the cured dry particles have an average diameter of about 5 mm which makes them particularly suitable for pneumatic injection.
In another aspect the invention provides the method as described and including the subsequent step of mixing the cured particles with baghouse dust.
Preferably the ingredients are mixed in a blender, most usefully a ribbon blender. The dust is housed in a sealed hopper having an air current to encourage material flow. The particles are housed in a hopper having a stirrer to encourage the material to flow. Both materials are supplied to a screw feed into the blender. Volumetric rotary valves may be present to adjust the relative proportions.
The baghouse dust is mainly iron oxide and silica but contains useful quantities of zinc and lead.
The particles made in the first step and those made incorporating baghouse dust may be pneumatically injected into an Electric Arc Furnace.
REFERENCES:
patent: 4273575 (1981-06-01), Litzinger et al.
patent: 5380351 (1995-01-01), Fisher
patent: 5538552 (1996-07-01), Osing et al.
patent: 5573576 (1996-11-01), Krofchak
patent: 5626664 (1997-05-01), Osing et al.
patent: 5695543 (1997-12-01), Shields
patent: 5882374 (1999-03-01), Hendrix
patent: 928084 (1963-06-01), None
patent: 2324081 (1998-10-01), None
patent: WO 9631630 (1996-10-01), None
Eckert Seamans Cherin & Mellott , LLC
Heckett Multiserv plc
Jenkins David C.
King Roy
McGuthry-Banks Tima
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