Use Of Polyols For Improving A Process For Reverse Froth Flotation Of Iron Ore

Abstract

This invention relates to use of a water-miscible polyhydric alcohol having two or three hydroxyl groups for improving the collector performance of a collector composition for the reverse iron ore flotation comprising at least one alkyl ether amine of formula (I) and/or alkyl ether diamine of formula (II)

R.sup.1—(O-A)-NH.sub.2  (I)

R.sup.2—(O-A)-NH—R.sup.3—NH.sub.2  (II)

wherein
R.sup.1 is a hydrocarbyl group with 6 to 24 carbon atoms,
R.sup.2 is a hydrocarbyl group with 6 to 24 carbon atoms,
R.sup.3 is an aliphatic hydrocarbyl group with 2 to 4 carbon atoms
A is an alkylene group with 2 to 6 carbon atoms.

Claims

1.-23. (canceled)

24. A process for improving collector performance of a collector composition for enriching an iron ore through reverse flotation of a silicate containing iron ore, wherein the collector composition comprises at least one alkyl ether amine of formula (I) and/or alkyl ether diamine of formula (II)
R.sup.1—(O-A)-NH.sub.2  (I)
R.sup.2—(O-A)-NH—R.sup.3—NH.sub.2  (II) wherein R.sup.1 is a hydrocarbyl group with 6 to 24 carbon atoms, R.sup.2 is a hydrocarbyl group with 6 to 24 carbon atoms, R.sup.3 is an aliphatic hydrocarbyl group with 2 to 4 carbon atoms, and A is an alkylene group with 2 to 6 carbon atoms, and wherein the process comprises the step of adding to the collector composition at least one water-miscible polyhydric alcohol having two or three hydroxyl groups, wherein improving collector performance means (i) an increase of recovery rate of iron ore when the at least one water-miscible polyhydric alcohol having two or three hydroxyl groups is present, compared to the case when the at least one water-miscible polyhydric alcohol having two or three hydroxyl groups is absent, (ii) a higher selectivity in removal of silicate, which means that the collector composition comprising the at least one water-miscible polyhydric alcohol enables a higher proportion of the iron to be retained and a higher proportion of the silicate to be removed, compared to the case when the at least one water-miscible polyhydric alcohol having two or three hydroxyl groups is absent; (iii) that the amount of iron retained and the amount of silicate removed in the flotation process according to the second aspect in the presence of the at least one water-miscible polyhydric alcohol remains essentially unchanged when the temperature at which said process is executed drops to temperatures of below 10° C., compared to the case when the at least one water-miscible polyhydric alcohol having two or three hydroxyl groups is absent in which case the amount of iron retained and the silicate removed becomes poorer; (iv) that the froth formed by the collector composition comprising the at least one water-miscible polyhydric alcohol is less voluminous, and after separation from the flotation cell it collapses faster, compared to the case when the at least one water-miscible polyhydric alcohol having two or three hydroxyl groups is absent, and wherein improvement of collector performance and improving the collector performance is assumed to occur if one or more of conditions (i) to (iv) are met.

25. The process according to claim 24, wherein the component A and component B are added to a finely ground iron ore combined with water or a suitable aqueous liquid and mixed using mechanical mixing means to form a homogenous slurry called pulp, in a total amount of 1 to 1,000 g/to in respect to the amount of iron ore present.

26. The process according to claim 24, wherein the iron ore is selected from the group consisting of magnetite, hematite and goethite.

27. The process according to claim 25, wherein a dispersant, a chain extender, a frother, a defoamer, a co-collector and/or a depressant is present in the pulp.

28. The process according to claim 24, wherein R.sup.1 and R.sup.2 independently from each other comprise 7 to 18 carbon atoms.

29. The process according to claim 24, wherein component A) is an alkyl ether amine of formula (I).

30. The process according to claim 24, wherein component A) is an alkyl ether diamine of formula (II).

31. The process according to claim 24, wherein component A) is a mixture of an alkyl ether amine of formula (I) and an alkyl ether diamine of formula (II).

32. The process according to claim 24, wherein R.sup.1 and/or R.sup.2 independently from each other are aliphatic hydrocarbyl residues.

33. The process according to claim 24, wherein R.sup.1 and/or R.sup.2 are linear or branched hydrocarbyl residues.

34. The process according to claim 24, wherein the alkyl ether amine (I) and/or the alkyl ether diamine (II) is derived from a branched synthetic alcohol.

35. The process according to claim 24, wherein A is a group of the formula —CH.sub.2—CH.sub.2— or of the formula —CH.sub.2—CH.sub.2—CH.sub.2—.

36. The process according to claim 24, wherein R.sup.2 is a group of the formula —CH.sub.2—CH.sub.2— or of the formula —CH.sub.2—CH.sub.2—CH.sub.2—.

37. The process according to claim 24, wherein the alkyl ether amine (I) and/or the alkyl ether diamine have been partially neutralized.

38. The process according to claim 37, wherein the acid used for neutralization of the alkyl ether amine (I) and/or the alkyl ether diamine (II) is a carboxylic acid having between 1 and 6 carbon atoms.

39. The process according to claim 24, wherein R.sup.1 and/or R.sup.2 is a branched alkyl residue.

40. The process according to claim 24, wherein the collector composition comprises an alkyl ether amine of formula (I) and an alkyl ether diamine of formula (II) in a weight ratio between 1:100 and 100:1.

41. The process according to claim 24, wherein the water-miscible polyhydric alcohol has 2 to 20 carbon atoms.

42. The process according to claim 24, wherein the water-miscible polyhydric alcohol is selected from the group consisting of ethylene glycol, propylene glycol and glycerol.

43. The process according to claim 24, wherein the composition contains 50-99 wt.-% of the alkyl ether amine (I) and/or the alkyl ether diamine (II) and 1 to 50 wt.-% of the water-miscible polyhydric alcohol (component B) are present.

Description

EXAMPLES

[0080] The percentages given refer to percent by weight unless indicated otherwise.

Materials Used

[0081]

TABLE-US-00001 Ether(di)amines A1) (3-Isononyloxy)propylamine A A2) N-[3-(isononyloxy)propyl]-1,3-propanediamine (“Isononyl ether diamine”) A3) (3-Isotridecyloxy)propylamine (“Isotridecylether amine”) A4) N-[3-(isotridecyloxy)propyl]-1,3- propanediamine (“Isotridecyl ether diamine”) A5) Coco fatty alcohol based N-dodecyl/ tetradecyl ethylenediamine (comparative) Polyhydric B1) Ethylene glycol alcohol B B2) Propylene glycol B3) Glycerol B4) 2-Ethyl hexanol (comp.) B5) 1-Hexanol (comp.) B6) Fatty alcohol mixture containing as main components 68 wt.-% C.sub.12 and 23 wt.-% C.sub.14- fatty alcohol, being alkoxylated with 2 moles of ethylene oxide and 4 moles of propylene oxide (comp.)
From the components A1 to A5 and B1 to B5 the various collector compositions given in Table 1 were prepared by mixing the components in the given weight ratios at 2000.

TABLE-US-00002 TABLE 1 Composition and characterization of collector compositions Composition A B CC1 80% A1 20% B3 CC2 70% A1 30% B3 CC3 90% A1 10% B3 CC4 95% A1 5% B3 CC5 80% A1 20% B1 CC6 80% A1 20% B2 CC7 80% A2 20% B3 CC8 80% A3 20% B3 CC9 80% A4 20% B3 CC10 (comp.) 80% A5 20% B3 CC11 (comp.) 100% A1 — CC12 (comp.) 100% A2 — CC13 (comp.) 100% A3 — CC14 (comp.) 100% A4 — CC15 (comp.) 100% A5 — CC16 (comp.) 80% A1 20% B4 CC17 (comp.) 80% A1 20% B5 CC18 (comp.) 80% A1 20% B6 comp. = comparative experiments, not according to the invention.

[0082] The collector compositions according to Table 1 were tested in reverse iron ore flotation. The iron ore samples used for this study were characterized in terms of chemical analysis and particle size analysis with the results given in Table 2 (hereinafter also referred to as crude iron ore).

[0083] The content of SiO.sub.2 in the ores was determined by a gravimetric method. The ore was decomposed by an acid attack (HCl) leading to the dissolution of metal oxides and metal hydroxides, and leaving insoluble SiO.sub.2 as the residue.

[0084] The iron content of the ores was determined by a titration method wherein the sample was decomposed by an acid attack (HCl), trivalent iron was reduced to bivalent iron by addition of stannous chloride (SnCl.sub.2) and mercury chloride (HgCl) and the iron content was determined by titration with potassium dichromate (K.sub.2Cr.sub.2O.sub.7).

[0085] The particle size was determined by wet sieving according to ASTM E276-13 wherein sieves of different openings were used. The results of this analysis are given in the table 2 below. P80 represents the diameter of openings through which eighty percent of the particles pass; D50 represents the diameter of the particle that 50 wt.-% of a sample's mass is smaller than and 50 wt.-% of a sample's mass is larger than; %-38 μm represents the percentage of particles smaller than 38 μm.

TABLE-US-00003 TABLE 2 Characterization of the crude iron ores used for flotation tests iron ore 1 iron ore 2 iron content 43.0% 41.2% SiO.sub.2 content 34.8% 41.0% P80 97 μm 137 μm D50 49 μm  69 μm %-38 μm 39.6% 22.0%

[0086] The flotation tests were done in laboratory scale using a Denver Flotation Cell D12 apparatus at a temperature of about 25° C. according to the following procedure: A sample with 1.1 kilograms of the respective crude iron ore was charged to the flotation cell of 1.5 l volume and water was added in order to prepare a pulp of 50 wt.-% of solids content. The stirrer was set to a speed of 1100 rpm and the pulp was homogenized for 1 minute. Then, a depressant (corn starch alkalized with NaOH in a weight ratio of starch to NaOH of 5:1) was added in a dosage rate of 600 mg/kg in respect to the dried ore. The pulp was conditioned under stirring for 5 minutes. The pH of the pulp was controlled and, if necessary, adjusted to 10.0 by further addition of NaOH. A collector composition according to Table 1 was added in a dosage of 70 mg/kg of dry ore for crude iron ore 1 respectively 120 mg/kg for crude iron ore 2. For ease of handling the collector compositions were applied as aqueous solutions of 1 wt.-% by weight active. The collector was conditioned in the ore pulp for 1 minute. Then air flow was started and froth flotation was done for 3 minutes. The floated mass (tailings) and the depressed mass (concentrated iron ore) were collected in separate bowls and dried in a lab oven. Both samples (depressed and floated) were then analyzed in respect to weight, SiO.sub.2 content and iron content according to the methods described above. The results are given in terms of the following parameters: [0087] Yield (wt.-%): percentage of concentrated ore (depressed mass) in relation to the total mass of crude iron ore. [0088] SiO.sub.2 content (wt.-%): content of SiO2 present in the concentrated iron ore (depressed mass). [0089] Fe.Rec. (wt.-%): weight ratio of iron mass recovered in the concentrated iron ore (depressed mass) in relation to the total mass of iron in the crude iron ore.

TABLE-US-00004 TABLE 3 Results of flotation experiments with iron ore 1 Dosage yield SiO.sub.2 content Fe. Rec Example Collector [g/to] [wt.-%] [wt.-%] [wt.-%] 1 CC1 70 48.1 2.96 72.2 2 CC2 70 48.9 2.92 72.6 3 CC3 70 47.3 2.84 71.3 4 CC4 70 47.1 2.81 71.4 5 CC7 70 44.3 1.14 67.4 6 (comp.) CC11 (comp.) 70 43.7 2.99 65.2 7 (comp.) CC12 (comp.) 70 40.4 1.57 61.4 comp. = comparative experiments, not according to the invention.

TABLE-US-00005 TABLE 4 Results of flotation experiments with iron ore 2 Dosage yield SiO.sub.2 content Fe. Rec Example Collector [g/to] [wt.-%] [wt.-%] [wt.-%]  8 CC1 120 39.0 2.73 65.8  9 CC5 120 38.6 3.18 64.6 10 CC6 120 38.1 3.30 63.1 11 CC8 120 45.8 1.24 75.2 12 CC9 120 46.4 1.35 75.7 13 (comp.) CC10 (comp.) 120 76.0 35.4 83.4 14 (comp.) CC11 (comp.) 120 37.4 3.38 62.0 15 (comp.) CC13 (comp.) 120 43.9 1.69 73.7 16 (comp.) CC14 (comp.) 120 44.3 1.78 74.0 17 (comp.) CC15 (comp.) 120 75.5 32.3 86.6 18 (comp.) CC16 (comp.) 120 41.2 4.05 67.6 19 (comp.) CC17 (comp.) 120 41.8 4.24 68.2 20 (comp.) CC18 (comp.) 120 42.3 4.67 71.2 comp. = comparative experiments, not according to the invention.

[0090] In this table, e.g. comparative Example 15 is to be compared to Example 11. It becomes apparent that in Example 11 the yield is higher, the SiO.sub.2 content is lower and the Fe recovery is higher than in comparative Example 15.

Performance Testing at Different Temperatures

[0091] Flotation tests according to the general description given above were repeated at different temperatures. The results are given in Table 5.

TABLE-US-00006 TABLE 5 Results of flotation tests at different temperatures with iron ore 1 temper- SiO.sub.2 Fe. dosage ature yield content Rec Example Collector [g/to] [° C.] [wt.-%] [wt.-%] [wt.-%] 21 CC1 70 25 48.1 2.96 72.2 22 CC1 70 5 49.7 2.83 74.3 23 CC7 70 25 44.3 1.14 67.4 24 CC7 70 5 44.2 1.32 68.0 25 (comp.) CC11 70 25 43.7 2.99 65.2 26 (comp.) CC11 70 5 61.9 13.82 82.5 27 (comp.) CC12 70 25 40.4 1.57 61.4 28 (comp.) CC12 70 5 47.5 7.28 69.3 comp. = comparative experiments, not according to the invention.

Evaluation of Foaming Behavior

[0092] Determination of the collector compositions foaming behavior was evaluated using the following procedure: a pulp consisting of 50 g of crude iron ore 1 and 50 g of tap water was prepared in a graduated cylinder. A 1 wt.-% active solution of the collector composition according to Table 1 was added to the pulp in a dosage of 50 mg/kg of ore. The cylinder was tilted 15 times with an angle of 180° within 20±2 seconds. Immediately after the last movement a chronometer was started. The foam height was measured immediately and after 30 seconds, 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes and 10 minutes. The results are given in Table 6.

TABLE-US-00007 TABLE 6 Collapse time of the froth obtained foam height [mm] ½ 1 2 3 5 10 Example Collector t = 0 min min min min min min 29 CC1 19 13 11 10 10 10 10 30 CC7 20 19 17 14 14 14 14 31 CC11 24 20 19 17 17 17 17 32 CC12 26 22 21 19 19 19 19 33 CC15 70 63 60 58 58 58 58

[0093] The experimental results show that by substitution of part of the alkyl ether amine and/or alkyl ether diamine with a water-miscible polyhydric alcohol the recovery rate of iron is raised, i.e. a higher proportion of the iron is retained. Simultaneously the content of SiO.sub.2 in the concentrate is reduced. Taken together the selectivity of the process is improved.

[0094] Although giving a superior iron recovery rate the froth formed with the collector compositions according to the invention has a lower initial volume and afterwards collapses faster than the froth formed by the application of alkyl ether amine (I) respectively alkyl ether diamine (II) in absence of the water-miscible polyhydric alcohol.

[0095] With the collector compositions according to the invention the superior performance is maintained under cold weather conditions while the ether(di)amine alone loses its selectivity at low temperatures. This is particularly important for many major mining operations located in areas with cold winters as for example in Northern US states as Michigan, Minnesota, and in Canada.