Magnetic beneficiation for magnesite ores

Abstract

A process for the beneficiation of magnesite ores includes the selective enhancement of the magnetic properties of the gangue constituents so that said constituents can be easily separated by magnetic separators.

Description

BACKGROUND OF THE INVENTION

This invention relates generally to a beneficiation process for ores or minerals, and more particularly to such a process for the recovery of pure magnesite from magnesite ores containing magnesite serpentine and other gangue material.

SUMMARY OF THE INVENTION

In accordance with the invention a mineral is separated from its gangue, or the gangue is separated from the mineral contained therein, by artificially increasing in a selective manner the magnetic properties of the mineral or the gangue. With the present process the magnetic separation of diamagnetic or slightly paramagnetic ores or minerals can be effected by using magnetic separators, e.g., permanent magnets, of low or medium strength. The increase of the magnetic properties of the ore or mineral to be separated is achieved by selective absorption on the surface of one or more constituents of the ore or mineral of a finely divided, highly magnetic substance such as a magnetite or a ferrosilicon. The thusly conditioned ore or mineral therefore has increased magnetic properties.

Such selective absorption is achieved by conditioning the crushed ore or mineral in an aqueous mixture of suitable reagents for activating the surface of the constituents to be magnetically separated. The crushed ore or mineral is again conditioned in an aqueous suspension of a finely divided, strongly magnetic material such as magnetite or ferrosilicon. This strongly magnetic material is selectively absorbed on the surface of one or more constituents of the ore or mineral and thus increases their magnetic properties. The constituents of the ore or mineral that have absorbed the strongly magnetic material are then separated from the remainder of the constituents by means of a magnetic separat r so as to obtain a concentrate of the remainder of the constituents.

After magnetic separation, recovery of the finely ground magnetic material from the surface of the ore or mineral constituents is carried out with water under pressure or with the use of detergents, or by agitation in another magnetic field.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The ore or mineral is crushed into small particles, as for example less than 15 mm., although particles larger than 15 mm. may be subjected to the present process. The crushed ore or mineral is then thoroughly washed and the various sized particles may be classified into fractions of less than 1 mm., 1 mm. to 15 mm., and greater than 15 mm. Each of the fractions are then conditioned for about 10 to 20 minutes in an aqueous mixture of suitable reagents for activation of the surface of the constituents thereof to be magnetically removed. After undergoing such conditioning the material is drained and fed into a second conditioner of a suspension of finely ground magnetite or ferrosilicon materials and is stirred for about 5 to 10 minutes.

After this further conditioning step, during which the selective absorption of the magnetic material on the surface of the particles to be magnetically removed takes place, the material is drained and then fed into wet and dry magnetic separators for separating the absorbed magnetic material from the remainder of the material so as to obtain a concentrate of this remainder of the separated material.

It should be pointed out that the crushed ore or mineral may be first subjected to a mechanical pre-concentration process to further ultimately effect a concentrate of the remainder of the constituents.

This concentrate of non-magnetic material is washed and, according to its purity, constitutes the intermediate or final product. This concentrate can be further subjected to the beneficiation process as above described so as to improve its quality. This will depend on the quality of the first recovery treatment of the ore or mineral, or upon the specifications required of the final product.

The particles which absorbed the magnetic material may be thoroughly washed with water under pressure or with the use of a detergent, or by agitation in a magnetic field, so that the absorbed film of the highly magnetic material may be removed. This recovery of the finely ground magnetic material from the surface of the ore or mineral constituents is carried out by known methods, as for example thickening, washing, magnetic separation or the use of a demagnetizing coil.

The above sequence is carried out separately on each granulometric fraction as set forth hereinabove.

In particular, a magnesite ore containing slightly magnetic serpentine and non-magnetic feldspars and silica was subjected to the beneficiation process as in the manner above-described. The first conditioning was carried out in an aqueous suspension of, by volume, 1 percent diesel oil and 0.15 percent of a mixture of a dialkyl quaternary ammonium chloride such as ARQUAD 2C-75 and primary amines such as ARMAC T and ARMAC C. The first conditioning lasted for ten minutes and the second conditioning step was carried out in an aqueous suspension of finely ground magnetite of 1 percent by volume.

Magnetic separation of for example the 1 to 3 mm. fraction yielded a product of pure magnesite with 0.72 percent SiO.sub.2 and 1.08 percent CaO, by volume, constituting a fraction of 36.4 percent of the magnesite ore feed which has an analysis of 16.92 percent SiO.sub.2 and 4.9 percent CaO. The reagents used for activation of the surface of the constituents of the ore to be magnetically separated are the same as those used for the flotation process disclosed in commonly owned U.S. application Ser. No. 530,396, filed on even date herewith. Only very small quantities of these reagents are required for the present process thereby rendering the first conditioning step quite economical.

Another advantage with the use of the present process is that relatively coarse crushed ore can be used provided that the intended concentration can be carried out for such sized particles. The costly grinding operation normally required for flotation is therefore avoided.

Other advantages of the present process are that simple, high output devices such as wet magnetic separators may be used for the magnetic separation, and an almost complete recovery of the magnetic medium used is accomplished.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

Claims

What is claimed is:

1. A process for the recovery of pure magnesite from magnesite ores containing magnesite, serpentine and other gangue material, comprising:

crushing a quantity of magnesite ore;

conditioning the crushed ore in an aqueous suspension containing by volume 1 percent diesel oil and 0.15 percent of a mixture of cationic collectors comprising quaternary ammonium chlorides and primary amines for activating the surface of the serpentine and the other gangue material;

again conditioning the crushed ore in a suspension of a finely divided strongly ferromagnetic material so as to achieve selective absorption on the surface of the serpentine and the other gangue material as well as on the strongly siliceous and carbonaceous particles of the ore; and

removing the serpentine and the other gangue material as well as the strongly siliceous and carbonaceous particles of the ore from the remainder of the ore by means of a magnetic separator to obtain a concentrate of magnesite.

2. The process according to claim 1, comprising the further step of first classifying the crushed magnesite ore into particle size fractions of less than 1 mm., 1 mm. to 15 mm. and greater than 15 mm., each of the fractions being separately subjected to the recovery process.

3. The process according to claim 1, comprising the further step of first subjecting the crushed magnesite ore to a mechanical pre-concentration process to further effect a concentrate of the magnesite.

4. The process according to claim 1, comprising the further step of repeating the entire beneficiation process on the concentrate obtained to improve its quality.

5. The process according to claim 3, comprising the further step of repeating the entire beneficiation process on the concentrate obtained to improve its quality.