Specialized metallurgical processes – compositions for use therei – Processes – Producing or treating free metal
Reexamination Certificate
2000-09-20
2002-06-11
King, Roy (Department: 1742)
Specialized metallurgical processes, compositions for use therei
Processes
Producing or treating free metal
C075S343000, C075S365000
Reexamination Certificate
active
06402807
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns a smelting method to produce very pure iron or various iron family metals from ores which contain iron, nickel, cobalt, etc., by means of hydrometallurgy.
2. Background Information
Among those means to produce iron from iron ore in great quantity, the blast furnace process is usually adopted to the current and modern iron-making industry. In the case of the blast furnace process, a mixture of iron ore, fluxes, etc. are melted and reduced, then produced molten iron and slag are separated due to the difference of their specific gravity, and iron is extracted.
On the other hand, besides the blast furnace process, there are many so-called direct iron-making processes to extract iron from iron ores. For example, they are the Armco process, the treatment of Laterite and the Hoganas process.
In the case of the blast furnace process, however, a furnace of very large volume equipped with many large accessories is necessary in order to heat and melt the mixture of iron ore, fluxes, etc. with high thermal efficiency at an elevated temperature, so that a high construction cost is necessary. Since the iron produced in this case usually contains 2% or more of carbon, phosphorus, sulfur, etc. the iron is refined once again to make steel.
In contrast thereto, the reduced iron produced by the Armco process, the treatment of Laterite, etc. mostly contains SiO
2
, Al
2
O
3
, etc. that are originally included in the iron ore. In the case of the Hoganas process, it is impossible to completely remove SiO
2
, Al
2
O
3
, etc. that are included in the iron ore. Accordingly, in order to completely remove SiO
2
, Al
2
O
3
, etc. from the reduced iron, it is necessary to carry out refining once again, as in the case of the blast furnace process.
As such, in order to obtain very pure iron which contains no SiO
2
, Al
2
O
3
, etc. from the iron ore, it is required to provide remelting and refining facilities, which results in a high construction cost. Heretofore, there has not been a wet smelting technique for mass-production which does not need such melting and refining process.
SUMMARY OF THE INVENTION
The present invention was developed intending to solve the aforementioned problems, and also to provide a specific refining method by hydrometallurgy, thereby very pure iron or various iron family metals are obtained from ores containing iron family metals.
The inventor made an intense study to solve the aforementioned problems. As a result of the study, it was discovered that if ores containing iron family metals are subjected to an artificially hastening treatment relating to the leaching of iron family metals into acid, namely, an “accelerated weathering treatment”, those metals are eluted easily into acid, whereby a hydrometallurgy method carried out on iron family metals is realized.
The present invention was achieved based on the aforementioned knowledge, and it comprises specific features as set forth in the following procedures:
(a) a grinding process wherein ores containing iron family metals are pulverized into fines of 25 mesh undersize (hereinafter referred to as the “pulverized ore”; the “ore” is a kind of native mineral, but it does not cover processed resources such as iron bearing byproducts of the chemical industry, etc. (e.g., sludge, cinder, residue, or gangue)),
(b) a leaching process wherein iron family metals in the pulverized ore are eluted into at least one inorganic acid, such that the pulverized ore is immersed into an inorganic dilute acid having a concentration of 1N to 8N, preferably 2N to 6N (hereinafter referred to as the “inorganic acid”),
(c) a separation process to obtain a filtrate and gangue individually by filtering the mixture of residue and inorganic acid which contains the eluted iron family metals discussed above,
(d) a precipitation process of a hydroxide of the iron family metals by the addition of an alkali to the filtrate obtained in the preceding step, and a filtration process applied to the suspension composed of the aforementioned hydroxide to collect a hydroxide of the iron family metals, and
(e) reducing process of which the collected hydroxide is heated at a temperature of 600 to 950° C. for 5 minutes or longer in a reducing atmosphere immediately after a pre-reducing process carried out at a temperature of 400 to 500° C. for 5 minutes or longer in the same reducing atmosphere.
The present invention preferably comprises the specific feature of which a hydroxide of the iron family metals is rinsed with a sufficient amount of warm water (water at a temperature of 40 to 60° C., which is defined in JIS K0050 (1991)) before the reducing treatment thereof.
In order to collect an iron hydroxide, usually a centrifugal machine is used for filtration. However, the collected hydroxide is not discharged from the machine right after filtration, but warm water is added into the machine, and it is driven once again. After that the iron hydroxide is taken out. This is explained in more detail as follows.
In the neutralization process, a hydroxide (solid) of iron or an iron family metal and a liquor are produced. The liquor includes such salt(s) as Na
2
SO
4
and NaCl. The kind of salt(s) depends on the kind of alkali used for neutralization.
A first separation by filtration involves charging the mixture of the hydroxide and the liquor described above into a centrifugal separator, sufficiently separating the hydroxide and the liquor, and stopping the revolution of the separator at once. At this moment, the liquor is discharged while the hydroxide remains in the separator. The dehydrated hydroxide thus obtained still includes some of the salt(s) discussed above.
A second separation by filtration involves pouring warm water into the hydroxide in the separator, and driving the separator once again in such manner, at first, slowly, then rapidly. As a result of this operation, the salt(s) absorbed in the hydroxide is eluted into the warm water and separated therefrom. After completion of this separation, the hydroxide from the separator is discharged.
The addition of warm water causes elution of some of the hydroxide. To prevent a decrease of the recovery ratio of iron, the addition of warm water is restricted once.
The present invention preferably comprises the following specific feature: between the steps (a) and (b), the pulverized ore prepared by step (a) is subjected to reducing such that it is heated at a temperature of 600 to 1100° C. for 5 minutes or longer. Further, it is preferable that at the time of reducing, at least any one among an oxide, a hydroxide, or a carbonate of zinc, calcium, lead or potassium is added as a catalyst. Furthermore, after the reducing treatment, the reduced ore is preferably magnetically separated.
Preferably, the present invention further comprises the following specific feature: between the steps (b) and (c), the pulverized ore ground to the desired size as described hereinabove is agitated successively for 30 minutes or longer, as it is immersed in the inorganic acid of the aforementioned concentration.
Furthermore, the invention preferably comprises the following specific feature: between steps (b) and (c), the pulverized ore ground to the desired size as described hereinabove is heated for 1 minute or longer, as it is immersed in the inorganic acid of the aforementioned concentration.
The invention preferably comprises the following specific feature: between the steps (b) and (c), the pulverized ore ground to the desired size as described hereinabove is agitated successively for 30 minutes or longer and also heated for 1 minute or longer, as it is immersed in the inorganic acid of the aforementioned concentration. In this case, the agitating is not always required to be before the heating.
As described hereinabove, according to the present invention a wet smelting process is provided wherein very pure iron or various iron family metals are obtained very economically in a large quantity from ores which contain iron family metals, which is in contrast to the bl
Frishauf Holtz Goodman & Chick P.C.
King Roy
McGuthry-Banks Tima
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