Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Reexamination Certificate
2002-05-07
2003-11-04
Mai, Ngoclan (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
C075S392000, C423S001000, C423S020000, C423S068000
Reexamination Certificate
active
06641641
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of producing a metal or a similar substance comprising collecting and refining the metal or substance contained in an ore or a concentrate containing a radioactive substance, and to an ingredient-regulated raw material employed in the method. Particularly, the technical idea of the method and the raw material according to the present invention are usefully applied to production of tantalum, niobium, or compounds thereof.
BACKGROUND ART
A widely-known method of producing a metal or a metal compound from an ore or a concentrate containing a radioactive substance serving as a raw material involves a fluoridation process—i.e., treating the raw material with hydrofluoric acid or a mixed acid containing, as an essential component, hydrofluoric acid, and separating the resultant mixture into an extract into which a metallic component is eluted and a residue—and collection and refinement of the metallic component from the extract.
Typical examples of metals and metal compounds produced through the above method include tantalum and niobium, which are contained in naturally occurring ores, and typical examples of ores employed in the method include rare earth ores containing a plurality of metallic elements; i.e., misch metals. The thus-produced metal, metal compound, or similar material is typically employed as a certain additive.
For example, tantalum, niobium, or compounds thereof (hereinafter these substances may be referred to as simply “tantalum, niobium, or a similar substance”) find use such as an alloying element or compound for producing special steel or material for producing electronic apparatus, and such substances have become of interest. Thus, the range of such applications and the amount of the substances have increased remarkably. This trend has been accompanied by remarkably increasing demand for ores such as tantalite and columbite and concentrates obtained therefrom, which serve as raw material for collecting tantalum, niobium, or a similar substance.
However, in most cases, ores per se which are subjected to the production method contain small amounts (e.g., some wt. %) of radioactive element compounds such as oxides. For example, ores or concentrates which are employed for producing tantalum, niobium, or a similar material have been known to contain uranium oxide (U
3
O
8
) and thorium oxide (ThO
2
). In such a case, these radioactive substances cannot be completely removed even when the ores are refined to corresponding concentrates through flotation, and remain as unavoidable components in the concentrates. Japanese Patent Application Laid-Open (kokai) No. 10-212532 also discloses such unavoidable components.
In terms of material containing at least a certain level of a radioactive substance, properties such as radioactive substance content are strictly limited by a variety of laws. For example, the Basel Convention prohibits cross-border transportation of a substance harmful to the human body. Thus, in some cases, as-prepared concentrate products cannot be imported and cannot be employed in the metal production industry. In such cases, the composition of ore material and concentrate material must be modified in accordance with the radioactive substance content.
In view of the foregoing, regarding ores or concentrates containing a radioactive substance employed for collecting a metal or a metal compound; i.e., the target of the present invention, those containing a large amount of a metal or a metal compound cannot be simply regarded as an excellent raw material in the industry at present. Throughout the industries of modern society, product stability and safety must be assured in consideration of steps of production, consumption, disposal, and further recycling. In addition, safety issues involving the environmental load imposed by wastes must be considered in view of the circumstances.
Specifically, when ores or concentrates contain a metal, a metal compound, or a similar substance at high content, the amount of the residue remaining after completion of extraction and refinement of a target metal, a target metal compound, or a similar substance is small. Given an initial level of radioactive elements in the ore or concentrate is the smaller the amount of generated residue, the higher the concentration of radioactive substances in the residue. Such a high concentration of radioactive substances is problematic in safety of handling the residue, and requires particular apparatus and a strict operational procedure. Thus, the above-described ores or concentrates are not preferred, in that handling the residue becomes more difficult and costs for waste disposal increase.
In addition, in recent years, the raw material situation has disadvantageously been aggravated. Particularly, the raw material situation for tantalum and niobium has become tighter in accordance with an increasing demand therefor, and raw materials of low radioactive element content are difficult to obtain. In view of the foregoing, there has been demand for a technique for safe transportation of concentrates containing a radioactive substance, exerting effects on refinement of tantalum, niobium, and similar substances.
SUMMARY OF THE INVENTION
The present inventors have conducted earnest studies, and as a result have accomplished the present invention as described hereunder.
In claim
1
of the present invention, there is provided a method of producing a metal or a metal compound from an ingredient-regulated raw material obtained by mixing an ore or a concentrate containing a radioactive substance, which method involves a fluoridation process—i.e., treating the ingredient-regulated raw material with hydrofluoric acid or a mixed acid containing, as an essential component, hydrofluoric acid, and separating the resultant mixture into an extract into which a metallic component is eluted and an extraction residue—and collection and refinement of the metallic component from the extract, wherein the employed ingredient-regulating raw material comprises the ore or the concentrate containing a radioactive substance and, as an additive, a substance insoluble to hydrofluoric acid or to a mixed acid containing, as an essential component, hydrofluoric acid, to thereby control to an arbitrary value of 1.0 wt. % or less the ratio of the amount of the radioactive substance remaining in the extraction residue generated through the fluoridation process to the weight of the extraction residue.
In claim
2
of the present invention, there is provided a method of producing tantalum, niobium, or a similar substance from an ingredient-regulated raw material obtained by mixing an ore or a concentrate containing at least one of tantalum and niobium and a radioactive substance, which method involves a fluoridation process—i.e., treating the ingredient-regulated raw material with hydrofluoric acid or a mixed acid containing, as an essential component, hydrofluoric acid, and separating the resultant mixture into an extract into which a metallic component is eluted and an extraction residue—and collection and refinement of tantalum, niobium, or a similar substance from the extract, wherein the employed ingredient-regulating raw material comprises the ore or the concentrate containing a radioactive substance and, as an additive, a substance insoluble to hydrofluoric acid or to a mixed acid containing, as an essential component, hydrofluoric acid, to thereby control to an arbitrary value of 1.0 wt. % or less the ratio of the total amount of the radioactive substances, U
3
O
8
and ThO
2
, remaining in the extraction residue generated through the fluoridation process to the weight of the extraction residue.
The method of producing a metal or a metal compound according to the present invention can be applied to a variety of those methods which employ an ore or a concentrate containing a radioactive substance and involve a fluoridation process; i.e., treating a raw material with hydrofluoric acid or a mixed acid containing, as an essential component, hydrofluoric acid, and s
Isaka Hiromichi
Sohama Yoshio
Watanabe Hiroyuki
Mai Ngoclan
Mitsui Mining & Smelting Co. Ltd.
Rothwell Figg Ernst & Manbeck P.C.
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