Specialized metallurgical processes – compositions for use therei – Processes – Consolidating metalliferous material by agglomerating,...
Patent
1997-03-18
1999-08-10
Ryan, Patrick
Specialized metallurgical processes, compositions for use therei
Processes
Consolidating metalliferous material by agglomerating,...
75746, 75 1, 75 3, 75 4, 75 5, 75 24, 75 25, C22B 702
Patent
active
059352965
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention is concerned with bonded media. Certain inorganic materials are sometimes present in a form in which they are difficult to handle and use. For example, basic oxygen steelmaking sludge (which is a waste product from the basic oxygen steelmaking process), contains up to 30% moisture and solids, including ferrous sulfide, iron oxide and various foundry additives, as well as other metals such as zinc.
Basic oxygen steelmaking sludge is generally considered to be a waste product, for which disposal is very expensive and difficult, partly because of its zinc content. We have now devised a way of using such basic oxygen steelmaking sludge, and other mineral and inorganic materials.
According to the present invention therefore, there is provided a method of forming thermally shock stable bonded solid materials, which comprises mixing a solid mineral or inorganic material in an aqueous medium with a lignosulfonate, treating the aqueous medium with a polyvalent or polydentate cationic complexing agent for lignosulfonate, with application of heat sufficient to maintain said lignosulfonate in fluid form, so as to produce an intimate mix of said complexing agent with said lignosulfonate and said mineral or inorganic material, and thoroughly mixing the resulting substantially dry material with a substantially dry further reagent comprising urea or a urea derivative, so as to cause the mix to agglomerate.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The resulting agglomerates can be shaped into, for example, briquettes (formed between shaped dies or the like) or pellets, or similar bodies formed by extrusion, pan agglomeration or the like.
The lignosulfonate may be used in method according to the invention in the form of a solution (such as an aqueous solution). Alternatively, when the mineral or organic material is itself aqueous, the lignosulfonate may be used in powder form. The lignosulfonate may include any suitable cation(s); examples of suitable cations are ammonium, calcium, magnesium, sodium or potassium. Of these, calcium is most preferred.
The cationic complexing agent may comprise a transition metal or an alkaline earth metal; the metal is preferably of the fourth period of the Periodic Table of the elements, such as calcium, iron or the like. Of these, calcium is preferred, preferably in the form of the oxide (preferably as lime, which has the advantage of reacting with any free water in the mix).
When lime is used, it is preferably added to the aqueous medium in such an amount as to produce a saturated slaked mix, having a pH typically in excess of 10.
The further reagent is preferably added in powdered form and mixed with the saturated slaked mix by contra-rotating blade mixing or by tumbling, until the mix becomes plastic; this mixing may be carried out at a temperature ranging from ambient to up to about 80.degree. C. The further reagent is preferably urea or a urea derivative (such as an alkyl urea).
When the mineral or inorganic material treated by the method according to the invention is basic oxygen steelmaking sludge, then the resulting shaped agglomerates can undergo direct reduction to a ferrous metal source, for addition to molten steel or iron in a steelmaking process. The direct reduction with carbon as reducing agent, which is typically carried out at about 900-1000.degree. C., is advantageously without disintegration of the agglomerates because of their highly advantageous thermal shock resistance. Any zinc, furthermore, may be volatilised off from the shaped agglomerates during the direct reduction phase.
It is a particular advantage of the present invention, when applied to the process of forming agglomerates from basic oxygen steelmaking sludge or other inorganic or mineral materials, that highly thermal shock-resistant agglomerates can be formed. Such agglomerates are substantially dry and can be added to high temperature direct reduction processes or the like without any deleterious water evolution (which could otherwise have potentially
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Photocopy of PCT International Search Report dated Jan. 12, 1996.
Elve M. Alexandra
Ryan Patrick
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