Process for the selective floatation of kainite from mineral mixtures using sulfated fatty acids as the collector reagent

Abstract

The invention relates to a process for selective flotation of kainite from crushed crude potash salts or, for example, from crystallized salt mixtures obtained by evaporation processes, which in addition to kainite may contain further minerals such as halite, sylvine and other salt minerals, for example, in order to produce a kainite concentrate fraction and a residues fraction. The separation process is characterized in that the crushed or crystallized salt mixture is intensively mixed as a crystallizate suspension with a combination of conditioning agents consisting of a sulfated fatty acid or its alkali metal salt as collecting reagent and a frothing agent known for flotation (for example, glycol ether, monohydric aliphatic alcohols, terpene alcohols, polyglycol ethers, etc.) and is then separated by agitator-driven or pneumatic flotation into a kainite concentrate fraction and a residues fraction. The resulting fractions may be further processed in downstream processes. This process permits industrial-scale processing for selective extraction of kainite from mineral mixtures by means of the flotation process.

Claims

1. A process for processing a kainite-containing crystallized salt mixture for production of a kainite concentrate fraction and a residues fraction comprising a residual mineral that is present in a solids mixture, the process comprising: separating the kainite-containing crystallized salt mixture in a one-stage or multi-stage process of separation by flotation by intensively mixing the kainite-containing crystallized salt mixture in a flotation solution with a combination of conditioning agents comprising a collecting agent comprising a sulfated fatty acid or its alkali metal salt and a frothing agent to obtain a flotation mixture, and then separating the flotation mixture by agitator-driven or pneumatic flotation into a kainite concentrate fraction and a residues fraction, wherein the kainite-containing crystallized salt mixture to be separated by floatation in the separating is a freshly crystallized salt mixture comprising kainite, sylvine, and halide.

2. The process according to claim 1, wherein the kainite concentrate and residues fractions are further processed in a downstream process.

3. The process according to claim 1, wherein at most 500 g/t.sub.solid of the sulfated fatty acid or its alkali metal salt is used as the collecting reagent.

4. The process according to claim 1, wherein at most 75 g/t.sub.solid of the frothing agent is used.

5. The process according to claim 1, wherein a flotation temperature is from 25 C. to 80 C.

6. The process according to claim 3, wherein from 250 to 350 g/t.sub.solid of the sulfated fatty acid or its alkali metal salt is used as the collecting agent.

7. The process according to claim 4, wherein from 25 to 50 g/t.sub.solid of the frothing agent is used.

8. The process according to claim 5, wherein the flotation temperature is from 45 C. to 70 C.

9. The process according to claim 1, wherein the combination of conditioning agents consists of the collecting agent and the frothing agent.

10. The process according to claim 9, wherein the collecting agent consists of the sulfated fatty acid or its alkali metal salt.

Description

EXAMPLE 1

(1) Example 1 shows experiments on selective kainite flotation from an evaporation crystallizate with the combination of conditioning agents used according to the invention in the corresponding flotation solution/mother liquor. The sodium salt of a sulfated fatty acid was used as the kainite collector and a glycol ether was used as the frothing agent (trade name Amerfloc MI of Ashland). The experiments were performed by means of pneumatic flotation on the laboratory scale. The evaporation crystallizate had the following composition: halite (28.5 wt %), kainite (70.5 wt %) and sylvine (1.0 wt %). The solids content of the crystallizate suspension was approx. 20 wt %. The flotation temperatures were set to 45 C. and 27 C. respectively. The conditioning time was 2 minutes and the flotation time 4 minutes.

(2) The flotation parameters are summarized in Table 1.

(3) TABLE-US-00002 TABLE 1 [g/t] Concentrate fraction Residues fraction Collector/ Halite Halite Frothing Kainite K.sub.2O.sub.tot content/ content/ Kainite K.sub.2O.sub.tot content/ content/ agent/ Kainite yield K.sub.2O.sub.tot yield yield Kainite yield K.sub.2O.sub.tot yield yield Expt. Temp. [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] 1 280/20 96.9 99 18.7/99 2.5/7 3.0 1 0.7/1 96.9/92 45 C. 2 370/30 96.0 99 18.5/99 3.4/9 2.0 1 0.6/1 99.0/91 45 C. 3 465/35 95.3 99 18.5/99 4.0/9 2.0 1 0.6/1 99.2/91 45 C. 4 280/20 93.7 99 19.0/95 4.3/11 2.0 1 2.4/5 95.2/89 27 C. 5 465/35 93.7 98 18.3/95 5.0/13 4.6 2 2.6/5 93.0/87 27 C.

(4) All results show good separation of the kainite (kainite yield 98 to 99 wt %) and high kainite contents in the concentrate (93.7 to 96.9%). The highest selectivity (96.9 wt %) in the separation of the kainite is obtained at a temperature of 45 C. together with a collector concentration of 280 g/t and a frothing agent concentration of 20 g/t (Experiment 1).

EXAMPLE 2

(5) In the following, the efficiency of the combination of conditioning agents was tested on the production scale during continuous operation. In this case a suspension of crystallizates obtained by solution evaporation and containing halite, kainite and sylvine mineral phases was processed by flotation according to the invention in the corresponding flotation solution/mother liquor.

(6) Crystallizate suspensions with solids contents of 20 wt % and 17 wt % (percent by weight) respectively were conditioned according to the invention and fed continuously to the pneumatic flotation system. Flotation took place in two stages with cells connected in series.

(7) The sodium salt of a sulfated fatty acid was used as the kainite collector and a glycol ether was used as the frothing agent (trace name Amerfloc MI of Ashland).

(8) The concentrations of conditioning agents used were: sodium salt of a sulfated fatty acid Experiment 1A to 1C=325 g/t.sub.solid; 2A to 2B=445 g/t.sub.solid frothing agents Experiment 1A to 1C=25 g/t.sub.solid; 2A to 2B=34 g/t.sub.solid

(9) The flotation parameters of the experiments are summarized in Table 2.

(10) TABLE-US-00003 TABLE 2 Kainite Kainite Halite Halite Sylvine Sylvine content yield content yield content yield Expt. Fraction [wt %] [wt %] [wt %] [wt %] [wt %] [wt %] Phase distribution of the charge in 28.3 49.1 22.6 Expt. 1A (before flotation) 1A Results Concentrate 93.3 83.4 1.5 0.8 5.2 5.9 (after flotation) Residue 6.3 16.6 65.2 99.2 28.5 94.1 Phase distribution of the charge in 26.2 51.7 22.1 Expt. 1B (before flotation) 1B Results Concentrate 94.0 76.6 1.3 0.5 4.7 4.6 (after flotation) Residue 7.8 23.4 65.4 99.5 26.8 95.4 Phase distribution of the charge in 31.0 47.3 21.7 Expt. 1C (before flotation) 1C Results Concentrate 92.7 75.8 1.8 1.0 5.5 6.4 (after flotation) Residue 10.0 24.2 62.7 99.0 27.2 93.6 Phase distribution of the charge in 44.3 40.7 15.0 Expt. 2A (before flotation) 2A Results Concentrate 93.6 84.2 1.8 1.7 4.7 12.4 (after flotation) Residue 11.6 15.8 66.5 98.3 21.6 87.6 Phase distribution of the charge in 44.8 40.2 15.1 Expt. 2B (before flotation) 2B Results Concentrate 95.0 88.7 1.1 1.1 3.9 10.9 (after flotation) Residue 8.7 11.3 68.3 98.9 23.1 89.1

(11) The results of all experiments show a good kainite yield (75.8 to 88.7 wt %) and high kainite contents in the concentrate (92.7 to 95 wt %). Experiments 2A to 2B, which were performed at a higher temperature (66 C.), show the best results with respect to the kainite yield (84.2 to 88.7 wt %).

(12) Tests 1A to 1C were performed at a temperature of 25 C. and tests 2A to 2B at a temperature of 66 C.

(13) The composition of the flotation solution was chosen such that it lies in the existence range of kainite. In this regard, see below under Table 3, Examples of the composition of the flotation solutions used.

(14) TABLE-US-00004 TABLE 3 Examples of the composition of the flotation solution (in g/L) Temp. [ C.] MgCl.sub.2 MgSO.sub.4 KCl NaCl H.sub.2O 25 305.0 40.1 43.5 26.7 882.7 25 299.7 51.3 46.0 27.2 875.7 45 297.9 31.4 64.2 32.9 864.7 45 264.1 59.3 73.1 42.8 860.0 66 288.6 45.0 86.5 39.7 847.3 66 264.8 50.1 92.6 46.3 843.3

(15) The kainite fraction may be used for potassium sulfate production, for example, while the halite/sylvine fraction may be fed to a further sylvine flotation or to the hot dissolution process.