Method for producing a zirconium concentrated product from froth treatment tailings

Abstract

A method for processing a heavy mineral concentrate obtained from froth treatment tailings to produce a zirconium concentrated product, including subjecting the heavy mineral concentrate to froth flotation, subjecting a flotation product to initial gravity separation, subjecting an initial gravity separation product to primary dry separation, subjecting a primary dry separation product to finishing gravity separation, and subjecting a finishing gravity separation product to finishing dry separation to produce a finishing dry separation product as the zirconium concentrated product.

Claims

1. A method for processing a heavy mineral concentrate obtained from froth treatment tailings to produce a zirconium concentrated product, wherein the froth treatment tailings result from a process for recovering bitumen from oil sand, wherein the process for recovering bitumen from oil sand is comprised of producing a bitumen froth from the oil sand, wherein the process for recovering bitumen from oil sand is further comprised of separating the froth treatment tailings from the bitumen froth in a froth treatment process, the method comprising: (a) subjecting the heavy mineral concentrate to froth flotation to selectively recover zirconium in order to produce a flotation product; (b) subjecting the flotation product to initial gravity separation to selectively recover zirconium in order to produce an initial gravity separation product; (c) subjecting the initial gravity separation product to primary electrostatic separation to selectively recover zirconium in order to produce a primary electrostatic separation product; (d) subjecting the primary electrostatic separation product to primary magnetic separation to selectively recover zirconium in order to produce a primary magnetic separation product; (e) subjecting the primary magnetic separation product to finishing gravity separation to selectively recover zirconium in order to produce a finishing gravity separation product; (f) subjecting the finishing gravity separation product to finishing electrostatic separation to selectively recover zirconium in order to produce a finishing electrostatic separation product; and (g) subjecting the finishing electrostatic separation product to finishing magnetic separation to selectively recover zirconium in order to produce a finishing magnetic separation product as the zirconium concentrated product.

2. The method as claimed in claim 1 wherein the froth flotation is comprised of a froth flotation circuit comprising a plurality of froth flotation stages.

3. The method as claimed in claim 2 wherein the froth flotation circuit is comprised of at least two froth flotation stages arranged in a configuration which comprises a rougher stage and at least one scavenger stage.

4. The method as claimed in claim 3 wherein the rougher stage of the froth flotation circuit is performed using a plurality of rougher cells, and wherein each of the scavenger stages of the froth flotation circuit is performed using a plurality of scavenger cells.

5. The method as claimed in claim 4 wherein the froth flotation circuit is comprised of two froth flotation stages.

6. The method as claimed in claim 5 wherein the rougher stage of the froth flotation circuit is performed using five rougher cells, and wherein the scavenger stage of the froth flotation circuit is performed using four scavenger cells.

7. The method as claimed in claim 1 wherein the initial gravity separation is comprised of an initial gravity separation circuit comprising a plurality of initial gravity separation stages.

8. The method as claimed in claim 7 wherein the initial gravity separation circuit is comprised of at least four initial gravity separation stages arranged in a configuration which comprises a rougher stage, at least one cleaner stage, and a plurality of scavenger stages.

9. The method as claimed in claim 8 wherein each of the initial gravity separation stages is performed using a spiral separator.

10. The method as claimed in claim 9 wherein the initial gravity separation circuit is comprised of seven initial gravity separation stages.

11. The method as claimed in claim 1 wherein the primary electrostatic separation is comprised of a primary electrostatic separation circuit comprising a plurality of primary electrostatic separation stages.

12. The method as claimed in claim 11 wherein the primary electrostatic separation circuit is comprised of at least four primary electrostatic separation stages arranged in a configuration which comprises a rougher stage, at least one cleaner stage, and a plurality of scavenger stages.

13. The method as claimed in claim 12 wherein each of the primary electrostatic separation stages is performed using a high tension roll separator.

14. The method as claimed in claim 13 wherein the primary electrostatic separation circuit is comprised of five primary electrostatic separation stages.

15. The method as claimed in claim 1 wherein the primary magnetic separation is comprised of a primary magnetic separation circuit comprising a plurality of primary magnetic separation stages.

16. The method as claimed in claim 15 wherein the primary magnetic separation circuit is comprised of at least two primary magnetic separation stages arranged in a configuration which comprises a rougher stage and at least one scavenger stage.

17. The method as claimed in claim 16 wherein each of the primary magnetic separation stages is performed using a rare earth magnet roll separator.

18. The method as claimed in claim 17 wherein the rare earth magnet roll separator used in the rougher stage of the primary magnetic separation circuit is comprised of three rare earth magnet rolls.

19. The method as claimed in claim 17 wherein the rare earth magnet roll separator used in each of the scavenger stages of the primary magnetic separation circuit is comprised of three rare earth magnet rolls.

20. The method as claimed in claim 17 wherein the primary magnetic separation circuit is comprised of two primary magnetic separation stages.

21. The method as claimed in claim 1 wherein the finishing gravity separation is comprised of a finishing gravity separation circuit comprising a plurality of finishing gravity separation stages.

22. The method as claimed in claim 21 wherein the finishing gravity separation circuit is comprised of at least four finishing gravity separation stages arranged in a configuration which comprises a rougher stage, at least one cleaner stage, and a plurality of scavenger stages.

23. The method as claimed in claim 22 wherein each of the finishing gravity separation stages is performed using a shaker table separator.

24. The method as claimed in claim 23 wherein the finishing gravity separation circuit is comprised of four finishing gravity separation stages.

25. The method as claimed in claim 1 wherein the finishing electrostatic separation is comprised of a finishing electrostatic separation circuit comprising a plurality of finishing electrostatic separation stages.

26. The method as claimed in claim 25 wherein the finishing electrostatic separation circuit is comprised of at least four finishing electrostatic separation stages arranged in a configuration which comprises a rougher stage, at least one cleaner stage, and a plurality of scavenger stages.

27. The method as claimed in claim 26 wherein each of the finishing electrostatic separation stages is performed using a high tension roll separator.

28. The method as claimed in claim 27 wherein the finishing electrostatic separation circuit is comprised of four finishing electrostatic separation stages.

29. The method as claimed in claim 1 wherein the finishing magnetic separation is comprised of a finishing magnetic separation circuit comprising a plurality of finishing magnetic separation stages.

30. The method as claimed in claim 29 wherein the finishing magnetic separation circuit is comprised of at least three finishing magnetic separation stages arranged in a configuration which comprises a rougher stage, at least one cleaner stage and at least one scavenger stage.

31. The method as claimed in claim 30 wherein each of the finishing magnetic separation stages is performed using an induced magnet roll separator.

32. The method as claimed in claim 31 wherein the finishing magnetic separation circuit is comprised of four finishing magnetic separation stages.

33. The method as claimed in claim 1, further comprising removing an oversize fraction from the finishing electrostatic separation product before subjecting the finishing electrostatic separation product to the finishing magnetic separation.

34. The method as claimed in claim 33 wherein the oversize fraction has a particle size greater than about 100 microns.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

(2) FIG. 1 is a flow sheet depicting an exemplary embodiment of a froth flotation circuit according to the invention.

(3) FIG. 2 is a flow sheet depicting an exemplary embodiment of a primary gravity separation circuit according to the invention.

(4) FIG. 3 is a flow sheet depicting an exemplary embodiment of a primary electrostatic separation circuit according to the invention.

(5) FIG. 4 is a flow sheet depicting an exemplary embodiment of a primary magnetic separation circuit according to the invention.

(6) FIG. 5 is a flow sheet depicting an exemplary embodiment of a finishing gravity separation circuit according to the invention.

(7) FIG. 6 is a flow sheet depicting an exemplary embodiment of a finishing electrostatic separation circuit according to the invention.

(8) FIG. 7 is a flow sheet depicting an exemplary embodiment of a finishing magnetic separation circuit according to the invention.

(9) FIG. 8 is a Table entitled: Heavy Mineral Concentrate (HMC) Feed Material, which provides examples of heavy mineral concentrate (HMC) samples having compositions which may be suitable for use as a head feed material in the practice of the invention.

(10) FIG. 9 is a Table entitled: Froth Flotation (Operating Conditions), which provides exemplary operating conditions for the exemplary embodiment of the froth flotation circuit depicted in FIG. 1.

(11) FIG. 10 is a Graph entitled: Heavy Mineral Concentrate (HMC)-Particle Size Distribution, which provides an exemplary particle size distribution for a heavy mineral concentrate (HMC) material which may be suitable for use as a head feed material in the practice of the invention.

(12) FIG. 11 is a Graph entitled: Zirconium Concentrated Product-Particle Size Distribution, which provides an exemplary particle size distribution for a zirconium concentrated product which may be produced by the exemplary embodiment depicted in FIGS. 1-7.

(13) FIG. 12 is a Table entitled: Overall Material Balance, which provides an exemplary material balance for the exemplary embodiment depicted in FIGS. 1-7.

(14) FIG. 13 is a Table entitled: Zirconium Recoveries, which provides a summary of zirconium recoveries and cumulative zirconium recoveries from the exemplary material balance of FIG. 12.

DETAILED DESCRIPTION

(15) An exemplary embodiment of the invention is depicted and described in FIGS. 1-13.

(16) As depicted and described in FIGS. 1-13, the exemplary embodiment is comprised of a sequence of mineral processing operations conducted on a heavy mineral concentrate (HMC) as a head feed material. The sequence of mineral processing operations provides a method (10) for processing the heavy mineral concentrate (12) to produce a zirconium concentrated product (14).

(17) Referring to FIGS. 1-7, the sequence of mineral processing operations in the exemplary embodiment is comprised of froth flotation (22), initial gravity separation (24), primary dry separation (26), finishing gravity separation (28), and finishing dry separation (30). Referring to FIGS. 3-4, in the exemplary embodiment, the primary dry separation (24) is comprised of primary electrostatic separation (40) and primary magnetic separation (42). Referring to FIGS. 6-7, in the exemplary embodiment, the finishing dry separation (28) is comprised of finishing electrostatic separation (50) and finishing magnetic separation (52).

(18) In the exemplary embodiment, the heavy mineral concentrate (12) is obtained from processing a coarse mineral material fraction of froth treatment tailings to remove bitumen, water and/or fine mineral material other than heavy minerals, thereby concentrating heavy minerals in the heavy mineral concentrate. An exemplary method for producing a heavy mineral concentrate from a coarse mineral material fraction of froth treatment tailings is described in U.S. Patent Application No. US 2011/0233115 (Moran et al) and corresponding Canadian Patent No. 2,693,879 (Moran et al).

(19) Referring to FIG. 8 and FIG. 10, the heavy mineral concentrate (12) which is used as a head feed material in the exemplary embodiment may comprise a bitumen content of less than about 1 percent by weight of heavy mineral concentrate, a heavy mineral concentration of at least about 50 percent by weight of heavy mineral concentrate, an equivalent zirconia (ZrO.sub.2) concentration of at least about 4 percent by weight of heavy mineral concentrate, and a particle size distribution in which at least about 30 percent by weight of the heavy mineral concentrate has a particle size smaller than about 100 microns.

(20) Referring to FIG. 1 and FIG. 9, in the exemplary embodiment, the heavy mineral concentrate (12) as a head feed material is first subjected to the froth flotation (22) to selectively recover zirconium in order to produce a flotation product (60) and froth flotation tailings (62). In the exemplary embodiment, the flotation product (60) is produced in the froth flotation (22) at least in part by rejecting coarse non-valuable silicates and iron bearing minerals from the heavy mineral concentrate (12).

(21) In the exemplary embodiment, the froth flotation (22) is arranged in a configuration which emphasizes scavenging over cleaning.

(22) Referring again to FIG. 1, in the exemplary embodiment, the froth flotation (22) is comprised of a froth flotation circuit (64) comprising a rougher stage (66) and a scavenger stage (68). Referring to FIG. 9, in the exemplary embodiment, the rougher stage (66) of the froth flotation circuit (64) performed using five rougher cells (70) arranged in series as a froth flotation separator, and the scavenger stage (68) is performed using four scavenger cells (72) arranged in series as a froth flotation separator.

(23) Exemplary operating conditions for the froth flotation circuit (64) in the exemplary embodiment are provided in FIG. 9.

(24) In the exemplary embodiment, the froth flotation circuit (64) is caused to be somewhat selective for zirconium by controlling the pH of the froth flotation slurry in the acidic regime (i.e., a pH of less than about 2) in order to limit interactions between air bubbles and silicates. In the exemplary embodiment, the froth flotation slurry is further modulated in order to improve the selectivity of the froth flotation circuit (64) for zirconium and to suppress the flotation of aluminum and titanium minerals. Unmodified wheat starch is used as a depressant to suppress the flotation of ilmenite and leucoxene. Sodium fluorosilicate is used as an activator to activate the flotation of zirconium bearing minerals. Flotigam 2835 and Flotigam EDA are used as collectors to provide improved selectivity for zirconium over aluminum. C-007 is used as a frothing agent to provide increased stability to the froth produced in the froth flotation circuit (64).

(25) In other embodiments, a different configuration for the froth flotation (22) may be utilized, including the number and configuration of the froth flotation stages, the type of froth flotation separator, the types of froth flotation reagents, and the operating conditions, depending upon the requirements of the head feed material.

(26) Referring to FIG. 2, in the exemplary embodiment, after the froth flotation (22) the flotation product (60) is subjected to the initial gravity separation (24) to selectively recover zirconium in order to produce an initial gravity separation product (80) and initial gravity separation tailings (82). In the exemplary embodiment, the initial gravity separation product (80) is produced in the initial gravity separation (24) at least in part by rejecting aluminosilicates such as kyanite from the flotation product (60).

(27) In the exemplary embodiment, the initial gravity separation (24) is arranged in a configuration which emphasizes scavenging over cleaning.

(28) Referring again to FIG. 2, in the exemplary embodiment, the initial gravity separation (24) is comprised of an initial gravity separation circuit (84) comprising seven initial gravity separation stages. In the exemplary embodiment, the seven initial gravity separation stages are comprised of a rougher stage (86), a cleaner stage (88), and five scavenger stages (90). In the exemplary embodiment, each of the seven initial gravity separation stages is performed using a spiral separator, or alternatively, a shaker table as a gravity separator.

(29) In the exemplary embodiment, the initial gravity separation slurry has a total solid material content of at least about 35 percent in the rougher stage (86) of the initial gravity separation circuit (84).

(30) In other embodiments, a different configuration for the initial gravity separation (24) may be utilized, including the number and configuration of the initial gravity separation stages, the type of gravity separator, and the operating conditions, depending upon the requirements of the flotation product (60).

(31) Referring to FIG. 3, after the initial gravity separation (24), the initial gravity separation product (80) is subjected to the primary electrostatic separation (40) to produce a primary electrostatic separation product (100), primary electrostatic separation tailings (101), and primary electrostatic separation middlings (102). In the exemplary embodiment, the primary electrostatic separation product (100) is produced in the primary electrostatic separation (40) at least in part by rejecting electrically conductive minerals such as ilmenite and leucoxene from the initial gravity separation product (70).

(32) In the exemplary embodiment, the primary electrostatic separation (40) is arranged in a configuration which emphasizes scavenging over cleaning.

(33) Referring again to FIG. 3, in the exemplary embodiment, the primary electrostatic separation (40) is comprised of a primary electrostatic separation circuit (104) comprising five primary electrostatic separation stages. In the exemplary embodiment, the five primary electrostatic separation stages are comprised of a rougher stage (106), a cleaner stage (108) and three scavenger stages (110).

(34) In the exemplary embodiment, each of the five primary electrostatic separation stages is performed using a high tension roll separator such as an Ore Kinetics Coronastat high tension roll separator as an electrostatic separator. In the exemplary embodiment, the high tension roll separators may be operated at an operating temperature of about 90 degrees Celsius, at a voltage of about 23-24 kilovolts, and at a roll speed of about 230-240 rpm.

(35) In other embodiments, a different configuration for the primary electrostatic separation (40) may be utilized, including the number and configuration of the primary electrostatic separation stages, the type of electrostatic separator, and the operating conditions, depending upon the requirements of the initial gravity separation product (80).

(36) Referring to FIG. 4, in the preferred embodiment, after the primary electrostatic separation (40) the primary electrostatic separation product (100) is subjected to the primary magnetic separation (42) to selectively recover zirconium in order to produce a primary magnetic separation product (120) and primary magnetic separation tailings (122). In the exemplary embodiment, the primary magnetic separation product (120) is produced by the primary magnetic separation at least in part by rejecting non-conductive iron-bearing magnetic minerals such as tourmaline and garnet from the primary electrostatic separation product (100).

(37) In the exemplary embodiment, the primary magnetic separation (42) is arranged in a configuration which emphasizes scavenging over cleaning.

(38) Referring again to FIG. 4, in the exemplary embodiment, the primary magnetic separation (42) is comprised of a primary magnetic separation circuit (124) comprising two primary magnetic separation stages. In the exemplary embodiment, the two primary magnetic separation stages are comprised of a rougher stage (126) and a scavenger stage (128).

(39) In the exemplary embodiment, both of the primary magnetic separation stages are performed using a rare earth magnet roll separator as a magnetic separator. In the exemplary embodiment, both of the rare earth magnet roll separators are comprised of three rare earth magnet rolls. In the exemplary embodiment, the rare earth magnet roll separator in the rougher stage (126) is operated at about 200 rpm, and the rare earth magnet roll separator in the scavenger stage (128) is operated at about 225 rpm.

(40) In other embodiments, a different configuration for the primary magnetic separation (42) may be utilized, including the number and configuration of the primary magnetic separation stages, the type of magnetic separator, and the operating conditions, depending upon the requirements of the primary electrostatic separation product (100).

(41) Referring to FIG. 5, in the exemplary embodiment, after the primary magnetic separation (42) the primary magnetic separation product (120) is subjected to the finishing gravity separation (28) to selectively recover zirconium in order to produce a finishing gravity separation product (140) and finishing gravity separation tailings (142). In the exemplary embodiment, the finishing gravity separation product (140) is produced in the initial gravity separation (24) at least in part by rejecting additional aluminosilicates from the primary magnetic separation product (120).

(42) In the exemplary embodiment, the finishing gravity separation (28) is arranged in a configuration which emphasizes scavenging over cleaning.

(43) Referring again to FIG. 5, in the exemplary embodiment, the finishing gravity separation (24) is comprised of a finishing gravity separation circuit (144) comprising four finishing gravity separation stages. In the exemplary embodiment, the four finishing gravity separation stages are comprised of a rougher stage (146), a cleaner stage (148), and two scavenger stages (150). In the exemplary embodiment, each of the four finishing gravity separation stages is performed using a shaker table as a gravity separator.

(44) In the exemplary embodiment, the finishing gravity separation slurry has a total solid material content of at least about 35 percent in the rougher stage (84) of the finishing gravity separation circuit (144).

(45) In the exemplary embodiment, the finishing gravity separation (28) is performed by operating each shaker table carefully to maximize the amount of material which accumulates between each of the riffles of the shaker table. A reason for this is that due to the relatively fine particle size of the zirconium contained in the primary magnetic separation product (120), the zirconium may tend to become commingled with the relatively lighter material having a relatively coarse particle size. By attempting to fill the riffles, it can be ensured that a maximum amount of the zirconium will be captured and transported to the product sides of the shaker tables.

(46) In other embodiments, a different configuration for the finishing gravity separation (28) may be utilized, including the number and configuration of the initial gravity separation stages, the type of gravity separator, and the operating conditions, depending upon the requirements of the primary magnetic separation product (120).

(47) Referring to FIG. 6, after the finishing gravity separation (28), the finishing gravity separation product (140) is subjected to the finishing electrostatic separation (50) to produce a finishing electrostatic separation product (160) and finishing electrostatic separation tailings (162). In the exemplary embodiment, the finishing electrostatic separation product (100) is produced in the finishing electrostatic separation (50) at least in part by rejecting additional non-zirconium contaminants from the finishing gravity separation product (140).

(48) In the exemplary embodiment, the finishing electrostatic separation (50) is arranged in a configuration which emphasizes scavenging over cleaning.

(49) Referring again to FIG. 6, in the exemplary embodiment, the finishing electrostatic separation (50) is comprised of a finishing electrostatic separation circuit (164) comprising four finishing electrostatic separation stages. In the exemplary embodiment, the four finishing electrostatic separation stages are comprised of a rougher stage (166), a cleaner stage (168) and two scavenger stages (170).

(50) In the exemplary embodiment, each of the four finishing electrostatic separation stages is performed using a high tension roll separator such as an Ore Kinetics Coronastat high tension roll separator as an electrostatic separator. In the exemplary embodiment, the high tension roll separators may be operated at an operating temperature of about 90 degrees Celsius, at a voltage of about 23-24 kilovolts, and at a roll speed of about 230-240 rpm.

(51) In other embodiments, a different configuration for the finishing electrostatic separation (50) may be utilized, including the number and configuration of the finishing electrostatic separation stages, the type of electrostatic separator, and the operating conditions, depending upon the requirements of the finishing gravity separation product (140).

(52) Referring to FIG. 7, in the preferred embodiment, after the finishing electrostatic separation (50) the finishing electrostatic separation product (160) is subjected to the finishing magnetic separation (52) to selectively recover zirconium in order to produce a finishing magnetic separation product (180) and finishing magnetic separation tailings (182). In the exemplary embodiment, the finishing magnetic separation product (180) is produced by the finishing magnetic separation (52) at least in part by rejecting additional non-zirconium contaminants from the finishing electrostatic separation product (160).

(53) In the exemplary embodiment, the finishing magnetic separation product (180) is the zirconium concentrated product (14).

(54) Referring again to FIG. 6, in the exemplary embodiment, an oversize fraction (172) is removed from the finishing electrostatic separation product (160) before the finishing electrostatic separation product (160) is subjected to the finishing magnetic separation (52). In the exemplary embodiment, the oversize fraction (172) has a particle size greater than about 100 microns. In the exemplary embodiment, the oversize fraction (172) is removed by screening (174) using a vibrating screen.

(55) In the exemplary embodiment, the finishing magnetic separation (52) is arranged in a configuration which emphasizes scavenging over cleaning.

(56) Referring again to FIG. 7, in the exemplary embodiment, the finishing magnetic separation (52) is comprised of a finishing magnetic separation circuit (184) comprising four finishing magnetic separation stages. In the exemplary embodiment, the four finishing magnetic separation stages are comprised of a rougher stage (186), a cleaner stage (188), and two scavenger stages (188).

(57) In the exemplary embodiment, each of the finishing magnetic separation stages is performed using an induced magnet roll separator as a magnetic separator. In the exemplary embodiment, each of the induced magnet roll separators is comprised of a single induced magnet roll. In the exemplary embodiment, each of the induced magnet roll separators is operated at about 150 rpm.

(58) In other embodiments, a different configuration for the induced magnetic separation (52) may be utilized, including the number and configuration of the induced magnetic separation stages, the type of magnetic separator, and the operating conditions, depending upon the requirements of the finishing electrostatic separation product (160).

(59) Referring to FIG. 12, an exemplary overall material balance is provided for the exemplary embodiment. The exemplary overall material balance in FIG. 12 represents results from experimental pilot plant testing of the exemplary embodiment.

(60) The pilot plant testing was conducted from a 60 kilogram batch of heavy mineral concentrate (12) having a composition consistent with the samples described in FIG. 8 as a head feed material. The method of the exemplary embodiment was performed in a straight-through manner in which each circuit was handled batch-wise with no recombination of materials at any stage. Masses were recorded as appropriate and samples were retained to facilitate material balance closure and recovery calculations.

(61) Samples were collected in replicate to assess variability. Six samples were collected in the froth flotation circuit (64) and the initial gravity separation circuit (84). These samples were subjected to both heavy liquid separation and x-ray fluorescence analyses. Three samples were collected in the primary electrostatic separation circuit (104), the primary magnetic separation circuit (124), the finishing gravity separation circuit (144), the finishing electrostatic separation circuit (164) and the finishing magnetic separation circuit (184). These samples were analyzed by x-ray fluorescence alone.

(62) The entire exemplary embodiment was operated live using a microscope to assess the quality of the process streams, allowing for minor gentle touches to each circuit operation as processing proceeded. These minor gentle touches, where applied, were implemented only at the start of the circuits.

(63) The experimental setup for the pilot plant testing was as follows: 1. the froth flotation (22) was performed using a Denver D-12 laboratory froth flotation unit and a Metso D-12 laboratory froth flotation unit as froth flotation separators, operated in parallel to reduce processing time by half. Both froth flotation units used a standard processing box of 8 liters and were operated at about 12,500 rpm. The air induction was modulated to maintain a froth height that required active paddling to push over the product weir; 2. although the exemplary embodiment contemplates the use of spiral separators as gravity separators in the initial gravity separation (24), both the initial gravity separation (24) and the finishing gravity separation (28) in the pilot plant testing was performed using Holman-Wiley Model 800 laboratory shaker tables as gravity separators. The shaker tables were operated at a titre water rate of about 1.8 kg/min, a stroke rate of about 288/min, a stroke of about 0.5 inches (about 1.3 centimeters), a slurry feed rate of about 2.5 kg/min, and deck angles of about 1.5 degrees parallel to the riffles and about 1 degree perpendicular to the riffles; 3. the primary electrostatic separation (40) and the finishing electrostatic separation (50) in the pilot plant testing were both performed using a laboratory Ore Kinetics Coronastat high tension roll separator as an electrostatic separator, equipped with an EVO II electrode. The high tension roll separator was operated with a roll speed of about 230-240 rpm, a grounded potential at the ionizing element of about 23-25 kilovolts, and a feed rate of about 47 kg/hour; 4. the primary magnetic separation (42) in the pilot plant testing was performed using a Reading rare earth magnet roll separator (Model 300573R) as a magnetic separator, operating at a roll speed of about 225-250 rpm, and a feed rate of about 82 kg/hour; 5. the finishing magnetic separation (52) in the pilot plant testing was performed using an HMD induced magnet roll separator (IMRS: Model 1-1-100) as a magnetic separator, operating at a roll speed of about 150 rpm, a magnetic intensity generated by about 8 amperes across the magnet, and a feed rate of about 42 kg/hour; and 6. a vibrating screen (Eriez) was used in the pilot plant testing to deslime process streams (38 microns) throughout the circuits as well as to remove the oversize fraction (+106 microns) from the finishing electrostatic separation product (160) before performing the finishing magnetic separation (52).

(64) The exemplary material balance in FIG. 12 has been normalized by upscaling to indicate 100 kilograms of heavy mineral concentrate as the head feed material.

(65) Referring to FIG. 11, an exemplary particle size distribution for the zirconium concentrated product (14) is provided. Referring to FIG. 13, zirconium recoveries, based upon the exemplary material balance of FIG. 12, are provided.

(66) From FIG. 11, it can be seen that the zirconium concentrated product (14) has a particle size distribution in which about 70 percent of the particles have a particle size of between about 44 microns and about 100 microns, and about 30 percent of the particles have a particle size smaller than about 44 microns.

(67) From FIG. 12 and FIG. 13, it can be seen that the pilot plant testing of the exemplary embodiment achieved a cumulative zirconium recovery from the heavy mineral concentrate (12) in the zirconium concentrated product (14) of about 71.4 percent, and an equivalent ZrO.sub.2 concentration (or zirconium grade) of greater than about 66 percent (i.e., between about 66 percent and about 67 percent) by weight of the zirconium concentrated product.

(68) From FIG. 12, it can also be seen that the zirconium concentrated product exhibited a TiO.sub.2 concentration of less than about 0.3 percent by weight of the zirconium concentrated product, an Al.sub.2O.sub.3 concentration of less than about 0.2 percent by weight of the zirconium concentrated product, and a Fe.sub.2O.sub.3 concentration of between about 0.09 percent and about 0.1 percent (i.e., less than about 0.1 percent) by weight of the zirconium concentrated product.

(69) The composition of the zirconium concentrated product produced in the pilot plant testing of the exemplary embodiment may therefore be considered as a premium grade zirconium product.

(70) As previously mentioned, in some embodiments, the method of the invention may emphasize scavenging over cleaning, due at least in part to the relatively fine particle size of the zirconium which may be contained in the head feed material (such as heavy mineral concentrate (12)). Scavenging is attractive for recovering minerals having a relatively fine particle size, because minerals having a relatively fine particle size are typically more difficult to recover efficiently than minerals having a relatively coarse particle size, and methods which emphasize cleaning over scavenging often experience reduced recoveries as the particle size of the desired product becomes smaller.

(71) One strategy of the method of the invention is therefore to carry a higher mass of tailings through the circuits than is typical for the recovery of minerals having a relatively coarse particle size, in order to provide opportunities to recover the heavy minerals from the feed materials.

(72) A second strategy of the method of the invention is to provide a plurality of scavenger stages in many of the circuits, since each scavenging stage represents an opportunity to recover additional zirconium. In general, additional scavenging stages in any of the circuits will improve the zirconium recovery.

(73) A third strategy of the method of the invention is generally to provide a relatively wide particle size distribution in the feed materials which are presented to the circuits. The reason for this is that the inventors have discovered that the recovery performance of minerals having a relatively fine particle size may be improved by providing a relatively wide particle size distribution, in comparison with processing only particles having a relatively fine particle size.

(74) For example, referring to FIG. 10, it can be seen that the heavy mineral concentrate (12) has a particle size distribution in which about 40 percent of the particles have a particle size of between about 44 microns and about 100 microns, about 3 percent of the particles have a particle size smaller than about 44 microns, and about 57 percent have a particle size between about 100 microns and about 350 microns.

(75) Without being bound by theory, it is believed that the presence of relatively coarse particles in the feed materials may reduce material handling issues associated with relatively fine particles, such as dusting and entrainment away from active surfaces by adhesion to equipment, while simultaneously providing improved surface area coverage on active surfaces for processing of the relatively fine particles.

(76) More particularly, it is believed that with relatively fine particles, which can become dusty, there may be some entrainment away from actives surfaces (i.e., by being projected from the surfaces of rotating equipment such as electrostatic and magnetic rolls or of reciprocating equipment such as shaker tables). It is believed that relatively coarse particles can: (1) provide some momentum to assist in the transport of relatively fine particles in the desired direction; and (2) provide an ability to obtain a relatively better packing of particles at active surfaces (i.e., the difference between packing uniform spheres and packing a distribution of sphere sizes).

(77) This is achieved in the method of the invention by minimizing the number of sizing operations which are performed on the feed materials in the performance of the method, and by delaying such sizing operations. In the exemplary embodiment, a single sizing operation is conducted between the finishing electrostatic separation (50) and the finishing magnetic separation (52), to remove particles having a particle size greater than about 100 microns. The purpose of this sizing operation in the exemplary embodiment is to assist in polishing in the finishing dry separation, by removing material having a particle size greater than about 100 microns, since such particles are typically not associated with heavy minerals such as zirconium in froth treatment tailings.

(78) In this document, the word comprising is used in its non-limiting sense to mean that items following the word are included, but items not specifically mentioned are not excluded. A reference to an element by the indefinite article a does not exclude the possibility that more than one of the elements is present, unless the context clearly requires that there be one and only one of the elements.