WO2016079167A1

WO2016079167A1 - Collector for froth flotation of clay minerals from potash ores

Info

Publication number: WO2016079167A1
Application number: PCT/EP2015/076935
Authority: WO
Inventors: Jan Olof Gustafsson
Original assignee: Akzo Nobel Chemicals International BV
Current assignee: Nouryon Chemicals International BV
Priority date: 2014-11-21
Filing date: 2015-11-18
Publication date: 2016-05-26
Anticipated expiration: 2017-05-21
Also published as: ES2642181B2; ES2642181R1; EA032176B1; CA2966387A1; ES2642181A2; EA201791041A1

Abstract

The invention relates to a flotation process for removal of slimes from potash ores wherein a collector is used which is a propoxylated ethoxylated fatty amine having the formula (I) wherein R1 is a hydrocarbyl group having 8-24 C-atoms, the sum of all m is on average 2-6, and the sum of all n is on average at least 15 and at most 100.

Description

COLLECTOR FOR FROTH FLOTATION OF CLAY MINERALS FROM

POTASH ORES

Field of Invention

The present invention relates to a process to remove clay slimes from potash ores by flotation of at least part of said slimes, using one or more specific propoxylated ethoxylated primary fatty amines as collector.

Background of Invention

Potash ore froth flotation is a conventional process for recovering sylvite (KCI) from ore pulps. Examples of potash ores are sylvinite, carnallite, langbeinite, and kainite.

Common gangue minerals in addition to halite (NaCI) are different types of water-insoluble fine-grained minerals, such as clay minerals, silicate-carbonate minerals, anhydrite, iron oxides, etc., often collectively called slime. The siliceous gangue (clay) consists of very fine particles and represents a large surface area, which adversely affects the recovery of sylvite (KCI) in the potash ore froth flotation process. The collector used during the potash flotation typically adsorbs to the clay, which results in high collector consumption and poor metallurgical results. The clay also interferes with other sylvite beneficiation processes such as dissolution procedures.

Several technical developments have addressed the problems arising from the presence of slime. Mechanical methods such as use of hydro cyclones, centrifuges, hydro separators, etc. are unselective and result in losses of fine particle sylvite. Several patents describe a process where clay-containing sylvinite ores are deslimed by a selective flocculation of slime (clay) followed by froth flotation of the slime. Polyacrylamides are mainly used as flocculants, and several compounds are suggested as collectors. Examples of collectors disclosed in the literature are oxyethylated primary amines (US 3,805,951 and RU 2278739), mixtures of non-ionic and anionic collectors (US 4,192,737), oxyethylated fatty acids (SU1304893), and oxyethylated alkyl phenol (RU2237521 ).

US 3 805 951 describes a process for desliming sylvinite ores by selective flocculation, followed by froth flotation of the slime. The process includes treatment of the ore pulp with a high molecular weight acrylamide polymer to flocculate the slime and then with a cationic collector that is for example a condensation product of 1 to 10 moles of ethylene oxide with one mole of a C12-C18 primary or secondary aliphatic amine.

DE 1068191 discloses flotation processes for potassium ores using ethoxylated fatty amines.

RU 2278739 describes a method for enrichment of potassium ores which comprises disintegrating the ore, removing water-insoluble clay-carbonate impurities by formation of a flotation slurry, followed by flotation of potassium chloride. The compounds used for flotation slurry formation are oxyethylated primary amines with 15-50 ethoxy groups per mole of amine. However, there is still a need for more effective collecting agents for desliming potash ores which do not have a negative effect on the recovery of potassium.

Description of Invention

Now it has surprisingly been found that compounds having the formula

C H₃ wherein R1 is a hydrocarbyl group having 8-24, preferably 12-22, and most preferably 16-22, C-atoms, the sum of all m is on average 2-6, preferably 2-5, and the sum of all n is on average at least 15, preferably at least 20, and at most 100, preferably at most 80, more preferably at most 60, even more preferably at most 50, still more preferably at most 40 and most preferably at most 35, are very efficient collectors for removing slime from potash ores. It should be noted that the compounds of formula (I) of the present invention contain two oxyalkylene tails, but that these two tails need not be identical.

Furthermore it should be noted that as these compounds are prepared by subsequent propoxylation of a fatty amine with m equivalents of propoxylation reagent and ethoxylation with n equivalents of ethoxylation reagent, the oxypropyl groups are closer to the nitrogen atom than the oxyethyl groups. Also because the propxylated ethoxylated fatty amines are obtainable by such a process, they need not be pure products of only one compound but they may as well be compositions containing different propoxylated ethoxylated fatty amines which fulfill on average the above values for m and n. In a few prior art documents similar compounds having formula (I) are disclosed. For example, GB 1 ,1 12,390 discloses propoxylated ethoxylated amines as an intermediate to react with hydroxyethane sulfonic acid or hydroxypropane sulfonic acid to so prepare sulfonic acid-functional surface active substances that are said to be of use in ore flotation, and EP 2 444 527 A2 discloses the use of a propoxylated ethoxylated amine surfactant, Ethopropomeen ™ C18/18, in tin plating. None of these prior art documents discloses or suggests the use of propoxylated ethoxylated amines of formula (I) in removing slime from potash ores, let alone suggests the advantages thereof.

Thus the invention pertains to a process for flotating slimes from potash ores by using propoxylated ethoxylated fatty amines having the formula (I) as collectors. In this process the collectors are added to a slurry containing a pulped ore undergoing the flotation process.

Thus, in a first embodiment the invention relates to the process wherein compounds of formula (I) are used as collectors.

One preferred embodiment is a process where the compounds according to formula (I), wherein R1 is a hydrocarbyl group having 16-22 carbon atoms, the sum of all m is 2-5 and the sum of all n is 15-50, are used as collectors. The R1 hydrocarbyl group in a preferred embodiment is an aliphatic group that may be a saturated alkyl or unsaturated alkenyl group and be a straight-chain or branched group.

By using the new collectors it is possible to achieve better recovery of water insolubles (slime), and the recovery of sylvite preferably is not adversely affected. More preferably, sylvite recovery is increased when a process of the invention is compared with a process wherein a collector of the prior art is used.

The process of the present invention typically comprises the steps

a) pulping a crushed potash ore comprising a potassium mineral and a clay component in an aqueous medium, which is typically a saturated brine, preferably a brine saturated with dissolved potash ore from the actual ore deposit;

b) conditioning the pulped ore with a flocculant and the collector having formula (I) as defined above; c) introducing air into the conditioned pulped ore; and

d) skimming off the froth formed.

The collector of the present invention is added to the aqueous slurry containing the ore in an effective amount to obtain flotation of the slimes from the ore. Effective amounts usually comprise 5 to 500 g of collector on 1 ,000 kg of total solid ore. Preferred is the use of 15 to 50 g of collector on 1 ,000 kg of solid ore. During the flotation, the clay component is enriched in the foam, leading to a depletion of the clay component in the cell product.

Flocculants useful in the above-described process are such compounds known to the person skilled in the art that are able to flocculate clay mineral particles in the mineral pulp, such as but not limited to polyacrylannides and copolymers of acrylamide with other ethylenically unsaturated monomers, such as acrylic acid.

In the conditioning step, the flocculant is preferably added to the pulped ore prior to the addition of the collector having formula (I).

The resulting sylvite-enriched cell product will normally be further purified by a second flotation step, wherein the sylvite is flotated.

Thus, in a further embodiment the present invention also relates to the process where a first treatment in accordance with the invention is followed by a further step which comprises a flotation of sylvite using another collector. This other collector is preferably a fatty amine.

The present invention is further illustrated by the following examples and with reference to the enclosed drawings. Brief description of the drawings

Figure 1 is a graphical representation of the results from the Example described below, with the water insolubles (W.I.) recovery in froth product (%) plotted against the number of propylene oxide (PO) units for the collectors.

EXAMPLES

General Experimental

Flotation procedure

Method

In practising the invention, the potash ore is crushed to a desirable flotation size and scrubbed in water that is saturated with dissolved potash ore from the actual ore deposit. The pulp is then charged to a flotation machine and diluted to an appropriate concentration. The machine is started and the required amount of a flocculating polymer is added as a 0.1 to 0.5% water solution; 20 g polyacrylamide per 1 ,000 kg ore is used in the examples. The collector diluted in water is then added and the pulp is conditioned for a few minutes. The air is turned on and the resulting froth containing the slimes (water insolubles) is skimmed off as tailing. The cell product (non-flotated), also known as bottom product, contains the concentrated potash ore ready to be processed further.

Samples of the froth fraction containing mainly slime product and the cell product are dried and analyzed for KCI and water insolubles (W.I.) present in both fractions. The material balance, i.e. recovery of W.I. and KCI, is calculated for the evaluation of results. The content of W.I. and KCI in the flotation feed (the ore sample that was flotated) is calculated as the sum of the found content of both the froth product and the cell product for each test. This differs to some extent when compared with the overall analysis, which can be explained as small variations in the ore sample and variations between the analyses. The results of the tests are presented in the following tables. In the froth product the content and recovery of KCI should be low and the W.I. content and recovery should be high. If this condition is met, it means that the flotation is efficient and selective, and the losses of the valuable mineral KCI are low. The cell product should contain a low grade of W.I. The selectivity index (Recovery KCI/Recovery W.I. for the froth product) is calculated to illustrate the selectivity, and this value should be low. All percentages presented are percentages by weight.

Example

In this example slime is flotated from a potash ore comprising on average 30.5% by weight (%w/w) of KCI and 5.0-5.5 %w/w of water insolubles (W.I.) Polyacrylamide (Accofloc A1 10, molecular weight 1 .9^*10⁶ D) is present as flocculant in an amount of 20 g/1 ,000 kg ore.

The collectors used are displayed in Table 1 .

Table 1

The dosage of collector (A - H) is 35 g/1 ,000 kg ore in all tests.

The content of KCI and W.I. in the froth product and in the cell product was determined. From these values and the weight recovery of the froth and cell products, the total content of KCI and W.I. in the ore sample used in the flotation was calculated (see Table 2B). The recovery of KCI and W.I. in the froth product, determining the selectivity index for the froth product, was then calculated for all flotation experiments. The results are presented in Table 2A. Table 2A

'mole PO added per mole tallow alkylamine

'mole EO added per mole tallow alkylamine or propoxylated tallow alkylamine

Table 2B

When using the same dosage, the recovery for W.I. was higher for the flotation experiment performed with the propoxylated and ethoxylated primary (tallow alkyl) amine according to the invention than for the ethoxylated primary amine (30 EO) that was used as an example of the prior art.

The selectivity index indicates that the selectivity is similar for the tests, both comparison and examples of invention. This means that the product according to the invention is more efficient than the comparison compound in floating away the slime product from the potash ore without giving rise to large losses of KCI. The improved recovery is also illustrated in Figure 1 where the results for the water insolubles (W.I.) recovery in froth product (%) is plotted against the number of propylene oxide (PO) units for the collectors. It is obvious that the results are improved in comparison to the product containing 0 PO and 30 mole EO per mole amine. Surprisingly, the introduction of PO according to the invention gives an improvement of the recovery of water insolubles at a given collector dosage.

Claims

Use of a propoxylated ethoxylated fatty amine having the formula

C H₃ wherein R1 is a hydrocarbyl group having 8-24, preferably 12-22, and most preferably 16-22, C-atoms, the sum of all m is on average 2-6, preferably 2- 5, and the sum of all n is on average at least 15, preferably at least 20, and at most 100, preferably at most 80, more preferably at most 60, even more preferably at most 50, still more preferably at most 40, and most preferably at most 35, as a collector in a froth flotation process for removal of slimes from potash ores.

Use according to claim 1 wherein the propoxylated ethoxylated fatty amine has the formula (I) wherein R1 is a hydrocarbyl group having 12-22 carbon atoms, the sum of all m is 2-5 and the sum of all n is 15-50.

Use according to claim 2 wherein the propoxylated ethoxylated fatty amine has the formula (I) wherein R1 and the sum of all m are as defined in claim 2 and the sum of all n is 20-40.

Use according to claim 3 wherein the propoxylated ethoxylated fatty amine has the formula (I) wherein R1 is a hydrocarbyl group having 16-22 C- atoms.

5. Use according to claim 1 -4 wherein the removal of slime is followed by a further step which comprises a flotation of sylvite using another collector.

6. Use according to claim 5 wherein said collector in the further step is a fatty amine.

7. A froth flotation process for removal of slimes from potash ores using a collector as defined in claims 1 -4. 8. A process according to claim 7 which comprises the steps

a) pulping a crushed potash ore comprising a potassium mineral and a clay component in an aqueous medium;

b) conditioning the pulped ore with a flocculant and the collector having formula (I) as defined in claims 1 -4

c) introducing air into the conditioned pulped ore

d) skimming off the froth.

9. A process according to claim 8 wherein the removal of clay is followed by a further step which comprises a flotation of sylvite using another collector.

10. A process according to claim 9 wherein said collector for flotation of sylvite in the further step is a fatty amine.