EP0456565A1 - Method for enriching andalusite by flotation - Google Patents

Abstract

In this process andalusite is separated from a gangue of an ore containing it and also containing other silicate components, especially micas. According to the invention this process essentially comprises the following stages: a) wet milling of the ore so as to convert this ore into a pulp of given particle size, b) desliming this pulp so as to retain only a deslimed useful pulp, c) treatment of this useful pulp in a flotation cell, this treatment comprising the substages of: . stirring in the presence of a collecting agent, then . flotation of the mass thus stirred, so as to separate a froth therefrom, and finally . removal of the froths produced by the flotation, and d) recovery, at the bottom of the cell, of a final andalusite concentrate. s

Description

The present invention relates to a process for the enrichment of andalusite, which is a particular variety of anhydrous aluminum silicate.

This mineral is found naturally in a gangue also containing other silicate elements, in particular micas (which are potassium, iron or magnesium silico-aluminates) and other constituents, in particular ferrifere constituents .

More specifically, the present invention relates to a process for enriching andalusite by flotation, a technique - conventional as such - consisting in separating the ore from its gangue by finely grinding it and stirring the particles obtained, in the presence of an appropriate additive, in a liquid flow which will cause a separation between the hydrophobic elements, which will be recovered in the form of a scum, and the hydrophilic elements, which will remain at the bottom.

FR-A-2 625 115, in the name of the Applicant, describes an application of this flotation technique to the enrichment of andalusite.

The process described in this prior document, however, requires prior conditioning of the pulp, in particular by substantially modifying its pH by adding a strong mineral acid and then mixing it with an alkyl sulfonate so that, when bubbling through the flotation cell, andalusite can be entrained on the surface of the bath and recovered in the form of foam.

This previous process is effective - it allows in particular to concentrate andalusite to a content higher than 90% -, but requires a delicate control of the physicochemical parameters making it possible to adequately ensure the separation of andalusite, collected on the surface in the form foam, with its gangue which must remain at the bottom of the cell.

One of the aims of the present invention is to propose a simplified process for the enrichment of andalusite which uses the known flotation technique but which, in particular, can be implemented without modification or regulation of the natural pH of the pulp. obtained after grinding.

Another characteristic of the present invention is that, as will be explained below, the andalusite ore is no longer collected at the surface of the flotation bath, as taught by FR-A-2 625 115, but at the bottom of the cell, which facilitates collection.

• a) broyage humide du minerai, de manière à transformer ce minerai en une pulpe de granulométrie donnée,
• b) déschlammage de cette pulpe, de manière à n'en conserver qu'une pulpe utile déschlammée,
• c) traitement de cette pulpe utile dans une cellule de flottation, ce traitement comprenant les sous-étapes de :
  • . brassage en présence d'un agent collecteur, puis
  • . flottation de la masse ainsi brassée, de manière à en séparer une écume, et enfin
  • . élimination des écumes produites par la flottation, et
• d) récupération, en fond de cellule, d'un concentré final d'andalousite.

To this end, the method of the present invention essentially comprises the following steps:

• a) wet grinding of the ore, so as to transform this ore into a pulp of given particle size,
• b) de-flaming this pulp, so as to keep only one de-flammable useful pulp,
• c) treatment of this useful pulp in a flotation cell, this treatment comprising the sub-steps of:
  • . stirring in the presence of a collecting agent, then
  • . flotation of the mass thus stirred, so as to separate a foam, and finally
  • . removal of scum produced by flotation, and
• d) recovery, at the bottom of the cell, of a final andalusite concentrate.

The collecting agent of the brewing sub-step of step (c) is preferably introduced only during the sub-step, after prior mixing of the pure pulp.

This collecting agent can in particular comprise a quaternary ammonium salt.

Very advantageously, step (c) is repeated at least once by reprocessing the non-floated product from the previous step.

In the latter case, the last iteration of step (c) is preferably carried out with a concentration of collecting agent and / or a duration of flotation greater than that of the previous iteration or iterations, the first iteration being able in particular be performed with a brewing time greater than that of the next iteration or of the following iterations.

We will now describe in more detail three examples of implementation of the method of the invention.

Example 1

In this first example, the andalusite ore is introduced (for example an amount of 1 kg for this test) to be enriched in a steel ball mill, with water in an amount necessary to obtain a mass concentration of solids of the order of 50% (typically, between 40 and 70%).

The ball load is adjusted so that, after 8 minutes of grinding, a pulp is obtained at the outlet of the grinder, the particle size of which is 80% by weight less than 270 μm. It is thus possible to load a steel mill with a volume of 10 liters per 56 steel balls with a total mass of 11.1 kg.

The pulp is then de-ignited by passing it through a 63 µm mesh sieve (typically 20 - 70 µm, but with as small a quantity of fines as less than 20 µm in the rejection of the sieve).

The sieving pass, essentially composed of sterile and iron-rich schlamms, is rejected.

The refusal of sieving, on the other hand, constitutes the deslammed useful pulp which is put by adding water to a mass concentration of solids of the order of 36 to 37%, then introduced into a flotation cell such as a Minemet cell . H 130 with self-aspirating turbine rotating at 1900 rpm.

The cell is then switched on so as to effect stirring first for 2 min of the pulp alone, then for 5 min of the pulp added with a collecting agent such as a quaternary ammonium salt dosed at 100 g per tonne of solid (the quantities of collecting agent introduced are determined as a function of the solid concentrations used during the different flotation steps).

R étant un radical alkyl dérivé du suifOne can in particular use for this purpose Noramium MS 50 marketed by the company CECA, and whose developed formula is of the form:

R being an alkyl radical derived from tallow

Other agents of the same nature (amine salts or amines), collectors of quartz and feldspar, can also be used with success.

The mass thus stirred is floated for 30 s, which makes it possible to separate and recover the scum mainly composed of fine white and black micas.

The resulting pulp obtained after removal of the scum is again conditioned in the flotation cell by stirring for 2 min with the same collector as above, dosed at 100 g / t.

The following flotation, also 30 s, eliminates the rest of the micas.

Finally, we proceed to a third treatment of the pulp by stirring it for 2 min with a dose of 300 g / t of collector.

The last flotation step, lasting 2.5 minutes, which follows this mixing allows most of the gangue to be recovered in foam with good resistance.

Note that the flotation takes place at a natural pH, between 7 and 9, which does not need to be modified or regulated (although it is possible to do so). It will also be noted that the pH will depend on the type of collector used, the values given here corresponding to the Noramium mentioned above.

At the end of the treatment, a final andalusite concentrate titrating 82.8% can be recovered from the bottom of the cell, for a recovery rate of 40.4% compared to the bulk.

The processing temperatures can be ambient temperatures (15 to 20 ° C), which are the temperatures generally used for flotation; it is preferable to avoid heating the pulp, which would increase the cost of the treatment.

• en sortie du broyeur,
• dans les schlamms ayant traversé le tamis,
• au chargement de la cellule de flottation, avant tout conditionnement par celle-ci, et
• en fin de traitement, dans le concentré récupéré en fond de cellule.

Table I below shows the development of the respective contents and recovery rates of andalusite, alumina and ferric oxide at the various stages of the process, namely:

• at the outlet of the mill,
• in the schlamms that have passed through the sieve,
• loading the flotation cell, before any conditioning by it, and
• at the end of treatment, in the concentrate recovered at the bottom of the cell.

Example 2

This second example shows the influence of the solid concentration of the pulp before flotation, this concentration being adjusted by the addition of water to the rejection of sieving, before loading into the cell.

For this purpose, instead of a mass percentage of solids of 36 to 37%, as in the first example, a value of 60% is chosen, therefore corresponding to a much thicker pulp during packaging by the collecting agent.

The other parameters of the treatment, in particular the times flotation, the dosages in collecting agent and the material used, are the same as in example n ° 1.

The results are given in Table II below, which is homologous to Table I of Example No. 1.

We can see, on examining the last line of this table, that the Andalusite recovery rate could have been greatly increased, going from 40.4% to 68.1%, to the detriment nevertheless of the quality of the Andalusite concentrate, the content of which decreases (but in much smaller proportions: from 82.8% to 74.6%).

Example 3

This third example shows the influence of grinding on the quality of the final concentrate.

For this purpose, instead of loading a steel mill with steel balls, we load a porcelain mill with porcelain balls. It is thus possible to load a porcelain grinder with a volume of approximately 7 liters per 52 massa porcelain balls totaling 2.9 kg.

The milling water is added to the ore in an amount necessary to give a mass concentration of 70%, and the ball load is adjusted to deliver at the outlet of the grinder, after 50 minutes of grinding, a pulp whose particle size is for 80% by weight less than 270 μm (therefore with the same particle size qualities as in the two examples previous).

The rest of the process is identical in all respects to that of Example 2, including as regards the concentration of solids in the pulp before loading into the flotation cell (mass percentage of solids of 60%).

The results are given in Table III below, which is homologous to Table II of Example 2.

It can be seen, on examining the last line of this table, that grinding with porcelain balls in a porcelain grinder significantly improves the quality of the Andalusite concentrate (its content increasing from 74.6% to 82.2%), with a slight loss nonetheless with regard to the recovery rate (which went from 68.1% to 64.4%).

It can thus be seen that, under the conditions of this third example, it is possible to obtain a quality of concentrate comparable to that obtained in the case of Example 1 (82.2% against 82.8%), but with a very much higher recovery rate (64.4% against 40.4%).

• en sortie du broyeur,
• au chargement de la cellule de flottation, avant tout conditionnement par celle-ci, et
• en fin de traitement, dans le concentré récupéré en fond de cellule, pour chacun des trois exemples ci-dessus.

Furthermore, Table IV below indicates the different contents and recovery rates of sodium and potassium oxides at the different stages of the process, namely:

• at the outlet of the mill,
• loading the flotation cell, before any conditioning by it, and
• at the end of treatment, in the concentrate recovered at the bottom of the cell, for each of the three examples above.

Claims (7)

A process for enriching andalusite by separating it from a gangue of an ore containing it and also containing other silicate elements, in particular micas,
process characterized in that it essentially comprises the following steps: a) wet grinding of the ore, so as to transform this ore into a pulp of given particle size, b) de-flaming this pulp, so as to keep only one de-flammable useful pulp, c) treatment of this useful pulp in a flotation cell, this treatment comprising the sub-steps of: . stirring in the presence of a collecting agent, then . flotation of the mass thus stirred, so as to separate a foam, and finally . removal of scum produced by flotation, and d) recovery, at the bottom of the cell, of a final andalusite concentrate The method of claim 1, wherein the collecting agent of the brewing sub-step of step (c) is introduced only during the sub-step, after prior mixing of the pure pulp. The method of claim 1, wherein the collecting agent comprises a quaternary ammonium salt. The method of claim 1, wherein step (c) is repeated at least once by reprocessing the non-floated product from the previous step. The method of claim 4, wherein the last iteration of step (c) is carried out with a higher concentration of collecting agent than for iteration previous or previous iterations. The method of claim 4, wherein the last iteration of step (c) is carried out with a flotation duration greater than that of the previous iteration or iterations. The method of claim 4, wherein the first iteration of step (c) is carried out with a brewing time greater than that of the next iteration or the following iterations.