US 3811623 A
A process and apparatus for breaking the mechanical bonds between relatively interlocked and embedded mineral ore crystals and gangue crystals are disclosed. Severing the bonds between the crystals is effected by irradiating the rock material with ultrasonic waves in the range of about 300,000 to about 1,200,000 cycles per second. The frequency of the ultrasonic waves is selected to cause one of the ore and gangue crystals to vibrate at about a resonant frequency thereof until oscillations within the resonating crystals and a node condition at the interfaces between crystals causes fracturing of the rock material at about the interfaces. The separation of magnetite and rutile crystals, as contained in black sands material, by ultrasonic irradiation is particularly advantageous, and a magnetic concentrator and separator capable of separation of ferromagntic and non-ferromagnetic particles in a liquid medium is also disclosed.
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Description (OCR text may contain errors)
United States Patent [191 Speer 1 May 21, 1974 2 Filed PROCESS AND APPARATUS FOR SEPARATION OF MINERAL ORE FROM GANGUE MATERIAL Inventor: Rolland Orin Speer, 2254 Wordside Ln. Apt. 6, Sacramento, Calif. 95825 Dec. 4, 1972.
Appl. No.: 312,232
References Cited UNITED STATES PATENTS 7/1962 Burgess 241/1 X 4/1961 Kececioglu et a1. 241/1 l0/l959 Sasaki 24l/l X 11/1955 Myers 24l/l X Chickering 57 ABSTRACT A process and apparatus for breaking the mechanical bonds between relatively interlocked and embedded mineral ore crystals and gangue crystals are disclosed.
Severing the bonds between the crystals is effected byirradiating the rock material with ultrasonic waves in the range of about 300,000 to about 1,200,000 cycles per second. The frequency of the ultrasonic waves is selected to cause one of the ore and gangue crystals to vibrate at about a resonant frequency thereof until oscillations within the resonating crystals and a node condition at the interfaces between crystals causes fracturing of the rock material at about the interfaces. The separation of magnetite and rutile crystals, as contained in black sands material, by ultrasonic irradiation is particularly advantageous, and a magnetic concentrator and separator capable of separation of ferromagntic andnon-ferromagnetic particles in a liquid medium is also disclosed.
PATENTEBMY 2 1 1974 SHEET 1 [1F 2 PROCESS AND APPARATUS FOR SEPARATION OF MINERAL ORE FROM GANGUE MATERIAL BACKGROUND OF THE INVENTION Every year enonnous quantities of mineral bearing alluvial sands are deposited in river delta areas. Certain of these alluvial sands and deposits are known to be very rich in iron ore and titanium. These alluvial sand deposits are commonly referred to as black sands, and they occur in extremely large deposits along the Pacific Coast of the United States, New Zealand, Australia, South Africa, South America and Korea, to name a few locations.
Considerable effort has been made in connection with attempts to recover the highly useful iron ore, found in the black sands as magnetite (Fe O and the titanium ore, found in the black sands as rutile (TiO It has been predicted that by the year 2,000 the demand for primary metals will have increased about four times over the present needs; therefor, the pressure to recover iron and titanium from black sands has and is continually mounting.
Attempts were made as early as 1849 to smelt black sands. A high titanium content in iron ore, however, hampers blast furnace operations, and more than two percent by weight of titanium will make the ore unsuitable for smelting by ordinary techniques. Since the black sands typically contain about 50 percent by weight or less of magnetite and as much as twelve or fifteen percent by weight of titanium oxide (rutile), they are not suitable for direct smelting.
Many hundreds of thousands of dollars have been lost in the United States and abroad attempting to devise techniques for recovering iron ore from black sands. Unfortunately, the crystals of rutile are embedded and interlocked with the crystals of magnetite in the individual sand particles by reason of the origin of the black sands as igneous or metamorphic rocks containing both types of crystals. Usually a sand particle contains only one or two of each type of crystal together with other gangue crystals. Although there are some sand particles which are solely magnetite crystals, attempts at magnetic separation have been unsatisfactory because the sand particles containing interlocked magnetite and rutile crystals are also separated, and the titanium in the rutile crystals is again present. This problem is further complicated by the fact that the rutile crystals are attracted by magnetic separators, although rutile exhibits a magnetic attraction about onethird that of magnetite. The black sands further typically include other gangue material, such as silica or quartz (SiO and ilmenite -(FeTiO which is embedded in and mechanically attached to the magnetite and rutile crystals. It should benoted that ilmenite contains iron and titanium in a single chemically bonded crystal while magnetite and rutile are separate crystals that are mechanically held together. The ilmenite crystals are also unsuitable for direct smelting by conventional techniques because of their titanium content.
Atleast two types of approaches have been taken in the past in attempting to recover useful mineral ores from the black sands. First, iron smelting techniques and apparatus have attempted to be developed which can tolerate the impurities and contaminants found in the black sands, with these impurities and contaminants being reduced to some extent by magnetic ore concentration of separation apparatus and further reduced as part of the smelting process. Secondly, attempts have been made to separate the magnetite crystals from the remaining gangue material by mechanical techniques such as crushing the particulate black sands. The crushing approach has been found to have strong economic disadvantages, and additionally and more importantly, crushing causes relatively indiscriminate fracturing of the sand particles so as to effect a mere reduction in size and not separation of magnetite crystals from rutile, silica or other gangue crystals. Moreover, a reduction in size of the magnetite crystals is often undesirable since it may result in vaporization of the small particles upon smelting or the need for pelletization prior to smelting.
It is further known that the black sands include trace amounts of valuable metals such as gold, platinum, rhodium and silver. Prior processing techniques and apparatus have not found a suitable way of recovering these metals from the black sands. Instead, they act as contaminants and their value is lost during attempts to smelt the iron ore. The result is that these otherwise valuable metals are disregarded as having no value or a negative value in connection with attempts to process black sands.
Accordingly, it is an object of the present invention to provide a process and apparatus for the recovery of iron ore from black sands with such iron ore being suitable for use in conventional iron ore smelting apparatus.
It is a broader object of the present invention to provide a process and apparatus for breaking the mechanical bonds between relativelyinterlocked and embedded one crystals and gangue crystals to enable separation of the ore crystals for subsequent use of the same.
It is another object of the present invention to provide aprocess and apparatus for the recovery of the mineral ore crystals from particulate rock material which is adaptable for use while the rock material is immersed in a liquid medium, and particularly salt water, in which it is commonly found in nature.
It is an additional object of the present invention to provide a process and apparatus for the recovery of a mineral ore from rock material which will require little or no treatment of the rock material prior to entry into the recovery apparatus, will effect recovery of the mineral ore in one continuously operating process, employs virtually no moving mechanical parts, and is readily adaptable to a multitude of ore recovery environments.
It is still a further object of the present invention to provide an ore recovery process and apparatus which will not harm wild life which passes through the system,
destroys harmful bacteria found in the waters passing through the system, and can be used to reduce undesirable build-ups of sand and particulate matter at the mouths of streams, rivers and bays.
It is still a further object of the present invention to provide an ore recovery process and apparatus for the same which enables an ecologically more efficient means of recovering and utilizing valuable trace minerals found in composite mineral ore deposits.
Still a further object of the present invention is to provide an apparatus and process for the separation of intermixed but relatively unbonded ferromagnetic particles from non-ferromagnetic particles in which the purity and efficiency of the separation of the particles is enhanced.
It is a further object of the present invention to provide a mineral ore recovery process and apparatus having great versatility of operation to accommodate changing processing conditions and an economy of operation suitable for processing hundreds of thousands of tons of material.
The process and apparatus of the present invention have other objects and features of advantage which will become more apparent and are set forth in more detail in the drawings and description contained hereinafter.
SUMMARY OF THE INVENTION The process of the present invention includes, briefly, irradiating a rock material containing ore and gangue crystals with ultrasonic waves having a frequency selected to cause one of the ore crystals and gangue crystals to vibrate at about a resonant frequency thereof, with irradiation being maintained until fracturing of the rock material occurs at about the interfaces between the crystals; and separating the ore crystals from the gangue material. The amplitude of the ultrasonic waves is preferably maintained below a level required to cause fracturing or internal fatiguing of the mineral ore crystals to prevent a reduction in the size thereof. Irradiation at a frequency in the range of about 300,000 to about 1,200,000 cycles per second in preferred, with a frequency of about 750,000 cycles per second being employed to separate magnetite ore crystals from rutile and other gangue crystals. A magnetic ore separator or concentrator and process for operating the same is also provided in which the flow of a moving liquid medium is controlled and employed with sequentially applied magnetic forces to vertically reciprocate ferromagnetic particulate material to wash and separate the gangue particles therefrom.
DESCRIPTION OF A DRAWING FIG. 1 is a top plan view of a schematic representation of mineral ore separation apparatus constructed in accordance with the present invention.
FIG. 2 is an enlarged top plan view of the ultrasonic processing portion of the apparatus of FIG. 1.
FIG. 3 gives an enlarged, fragmentary, top plan view of a section of the ultrasonic processing apparatus of FIG. 2.
FIG. 4 is an enlarged, fragmentary, side elevational view of the magnetic separator portion of the apparatus of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT The process of the present invention is briefly comprised of breaking the mechanical bonds between relatively interlocked and embedded ore crystals and gangue crystals by shearing or fracturing these crystals apart at the interfaces therebetween through the use of ultrasonic waves. More particularly, a process which is economically feasible and highly advantageous has been found for the separation of magnetite crystals from rutile and other gangue crystals as contained in black sands rock material. It is known that magnetite and rutile have a substantially differing crystallography. This difference in crystallography affords a basis for separation of the relatively embedded and interlocked crystals, namely, irradiation of the rock material with ultrasonic waves having a frequency selected to cause one of the mineral ore crystals and the gangue crystals to vibrate at about a resonant frequency thereof. As used herein, the expression a resonant frequency shall include the fundamental frequency or any harmonic frequency of the fundamental frequency. While a selected one of the crystals is in fundamental or harmonic resonance .under the irradiation of ultrasonic waves, the remaining crystals, because of their different crystallography, remain relatively stationary. The remaining crystals vibrate under the irradiation; however, the size of their oscillations is considerably less than the crystals in resonance. There, therefore, exists a relative node condition at the interface between the resonating and non-resonating crystals, and the'irradiation can be maintained until oscillations in the resonating crystals are large enough to cause fracturing of the rock material at about the interfaces between the crystals where the node condition occurs.
Ultrasonics have been employed previously in such fieldsv as cleaning and degreasing; the formation of emulsions, including the floatation of mineral ores to effect separation thereof; fatigue testing; and drilling of various materials including metals. Many of these processes depend upon the phenomenon of cavitation in a liquid medium, that is, the rarefaction that occurs in a liquid medium immediately behind a traveling ultrasonic wave. Thus, in U.S. Pat. No. 2,907,455, ultrasonic waves are used to cause cavitation and agitation in a slurry containing carbonaceous fuel particles to effect coagulation and recovery of the same from the slurry. In a similar manner, cavitation may be employed to lift grease and other contaminants ofi of surfaces, to emulsify and suspend materials in solution, and even to generate a food or a liquid fountain. While cavitation occurs in the process of the present invention, it is believed to have only secondary significance. Similarly, in connection with the use of ultrasonic irradiation to effect fatigue testing and/or drilling, the ultrasonic waves are used directly or indirectly to fatigue the crystals and cause internal fracturing and failure thereof. In fatigue testing the crystals of substantially homogeneous materials are simply irradiated until they fatigue at the weakest point thereon or the point of greatest irradiation intensity. In connection with drilling, abrasives are driven by the ultrasonic waves and caused to impinge upon a homogeneous material with the abrasives and the waves combining to destroy the crystalline structure in the path of the ultrasonic beam. The process of the present invention does not depend upon such a fatiguing or destruction of the rock crystals to effect separation of the mineral ore from the gangue material.
Instead the mechanism for severing the mechanical bonds between interlocked crystals depends on the concept that all crystals will oscillate in free vibration at a frequency peculiar to the dimensional characteristics of the individual material. When forced vibrations at about the same frequency as the fundamental frequency or a harmonic frequency of the crystal are impressed upon the crystal, free vibrations in the crystal are enforced and relatively large oscillations result.
It is, therefore, an important feature of the present invention to irradiate the crystals at a resonant frequency of one of them, and preferably at the fundamental frequency, to minimize the power required to obtain oscillations of a magnitude sufficient to cause fracturing at the crystal interface.
By amplifying the forced vibrations sufficiently the molecular activity of the crystals can be increased to a destructive level. It is not necessary, however, to increase the. amplitude of the crystals vibration to the point that will cause internal destruction of the crystal itself. In the situation in which dissimilar crystals are to be sheared apart, the resonating crystal is mechanically bonded to a dissimilar crystal, and the internal sympathetic vibrations in the resonating crystal will cause shear forces at the interface with the dissimilar nonresonating crystal before internal fracturing of the resonating crystal takes place. It is probable that the cavitation produced in the liquid medium in which the crystals are placed by the high intensity ultrasonic waves helps separate the crystals once the mechanical bond is broken or reduces the size of the oscillations required to effect fracturing by impacting the particles containing the crystals. Additionally, cavitation may impact the sand particles and loosen contaminants, such as trace amounts of gold, silver, zirconium, and the like, which contaminants adhere to the sand or crevices therein but are not mechanically bonded in the same manner as would occur in igneous or metamorphic rock.
Magnetite (Fe O has an isometric crystallographic system with the crystals usually taking a hexoctahedral, octahedral, .or dodecahedron form. By contrast, rutile (TiO has a tetragonal crystal system in which the crystals are ditetragonal-dipyramidal in form, and they frequently occur in elbow twins and are slender and acicular. Additionally, quartz (SiO crystals fall into the rhombohedral division of the hexagonal crystal system and take the form of trigonal trapezohedrons and hexagonal trapezohedrons and are commonly prismatic and twinned. As will be apparent, therefore, the crystallography of the three main constituents of black material indicates substantial differences in the crystal structure. These differences result in a substantial difference in the natural resonant or fundamental frequencies of the respective crystals, which differences can be and are employed in the process and apparatus of the present invention.
As also will be understood from the foregoing, crystals of materials other than magnetite and rutile, which are embedded in each other mechanically, such as in the formation of igneous or metamorphic rock, can similarly be separated. The crystallography of such crystals can be determined and used to calculate the natural or fundamental frequencies of the crystals, or the natural frequencies can be imperically determined.
Differences in natural or fundamental frequency will occur whenever the materials are not the same. Once known, dissimilar fundamental frequencies will allow selective sympathetic vibration of one crystal, but not the other.
It should be noted further that as used herein, mineral ore crystals shall mean the crystals of the material which are primarily sought after, and gangue crystals shall means the crystalline material of secondary or perhaps no commercial significance. In the separation of black sands, for example, the magnetite crystals are commonly referred to as themineral ore crystals and rutile crystals are gangue crystals, notwithstanding the fact that rutile is itself a valuable mineral ore which can be of substantial economic significance. As will be seen in more detail hereinafter, it is contemplated in the process of the present invention that the rutile and other mineral ores which are separated from the magnetite be collected and recovered for their substantial eco nomic value. Part of the recovery process for rutile might include ultrasonic irradiation, in which situation the rutile would be the mineral ore crystals and quartz might be regarded as gangue crystals.
Referring now to FIGS. 1, 2 and 3, the ultrasonic processing apparatus can be seen to include a treatment flow channel 31 and a separation flow channel 32, preferably axially aligned and interconnected to allow continuous treatment and separation of mineral ore. Treatment flow channel 31 is formed with an inlet opening 33 defined by conduit 34. Extending from conduit 34 is a splitter section 36 of the treatment flow channel which is formed with partitions or baffles 37, 38 and 39 to divide and separate the flow of incoming material into four'sub-channels 41-44. Greater or fewer subchannels can be provided within the scope of the present invention, depending upon the flow of the material processed. The mainbody 46 of flow treatment channel 31 acts as an ultrasonic cracking chamber and is provided with a plurality of ultrasonic wave generating means 47 arranged in banks along the side walls of the partitions which define the sub-channels 4l44. Finally, flow treatment channel 31 may be provided with an end section 48 which is used to control the speed of the flow of material discharged from the ultrasonic cracking chamber, and section 48 tenninates in discharge opening 49.
In the configuration shown in the drawings, flow control section 48 is converging to increase the flow rate of the material passing out of the cracking chamber in accordance with the basic law of hydraulics that Q AV, where Q represents the quantity of liquid, A represents the cross-sectional area of the conduit or channel, and V represents the velocity of the liquid. While it is possible to vary Q the pumping means or the like, for any given Q separator section 32 in the preferred configuration is more effective if velocity is increased over that in the ultrasonic treatment section.
When processing a sand or gravel, the apparatus is preferably further provided with pump means 51 connected to conduit 34 in orderthat a mixture of the particulate material and a liquid, such as salt water, may be pumped through treatment flow channel 31 for ultrasonic irradiation. Large deposits of black sands, for example, are often found immersed in salt water. Fortunately, salt water is one of the best liquid mediums in which to propagate and transmit ultrasonic waves. In the process of the present invention, therefore, pump 51, which is preferably a jet pump, can be attached to a suction line 52 to drive sand and salt water up to the processing apparatus. The ultrasonic treatment channel 31 and separation channel 32 are preferably positioned on a floating barge anchored above the sand deposit.
In order to enhance the effectiveness of the ultrasonic irradiation inseparating crystals, it is preferred that an ultrasonic wave reflecting means 53 (FIG. 3) be positioned on a side opposite the flow treatment subchannel, such as sub-channel 44, from the probe 54 of the ultrasonic wave generating means. As shown in the preferred form, reflective means 53 is a parabolic reflector joined at the edges 56 and 57 with the side walls of partition 37 so as to present a smooth flow channel which will not impede or trap particles. Reflector S3 is employed to increase the field strength in sub-channel 44. As will be seen by the broken lines in FIG. 3, the parabolic reflector results in a reflected wave pattern which reinforces the wave pattern emanating directly from probe 54. It is also possible to provide a second electronic generating wave transducer positioned opposite transducer 47 with a probe extending through reflector 53. This second transducer could be used with a second parabolic mirror positioned in front of transducer 47 with the result that the particulate liquid slurry or mixture would be subjected to very high intensity irradiation from opposed transducers.
In order to insure complete cracking of the sands into constituent crystals, variation of the frequency of the ultrasonic waves may be required. It is, therefore, preferred that the transducer or wave generating means 47 be driven by a signal generator 58 capable of varying the frequency of the ultrasonic waves produced by the transducer. For the separation of most interlocked mineral crystals, ultrasonic waves in the range of about 300,000 to about 1,200,000 cycles per second can be employed to effect fracturing at the interfaces between the crystals. The best results occur and the least power is required when the frequency is selected in the above range so as to cause one of the crystals to vibrate at about a resonant frequency thereof. When black sands material is being treated, the ultrasonic waves are preferably selected to have a frequency of between about 700,000 to 800,000 cycles per second, with about 750,000 cycles per second being optimum to cause the magnetite crystalsto resonate and become sheared and fractured with respectto the rutile crystals. Alternatively, however, signal generator 58 can be adjusted to drive transducer 47 at a frequency in the range of between about 1,000,000 and 1,200,000 cycles per second so as to cause the rutile crystals to resonate and to shear away from the relatively stationary magnetite crystals. In some configurations the transducer electronics or geometry may have to be modified to get the full range of frequency adjustment. When the rutile crystals are selected, they constitute the mineral ore crystal as used herein and the magnetite crystals, although quite valuable, constitute the gangue crystal material.
Black sands have the advantage of being of relatively uniform and consistent size, making adjustments in frequency less necessary than might be required for other materials. Some adjustment of the resonating frequencies, however, may be required by reason of the composition of the black sands being processed, as well as the volume and the flow rate of the liquid passing in front of the transducer. A single signal generator and amplifier unit 58 will accommodate such variations and can be used to drive a multiplicity of transducers, such as are contained in the banks of transducers shown in the drawing. It is further possible to use multiple signal generators to drive banks of transducers at differing frequencies simultaneously to cover the range in which all sand particles will be effectively treated.
It is preferred to employ a magnetostrictive ultrasonic transducer since these devices are relatively rugged. Piezoelectric transducers can also be employed and may have certain advantages at high frequencies. Both types of transducers are commercially available as are signal generators and amplifiers for driving multiple transducers. Signal generating means 58 are also available which will allow variation of the power and accordingly the amplitude of the ultrasonic waves impinged upon the rock material.
As above noted, it is usually preferable that the fracturing of the rock material by ultrasonic waves take place in a manner which maintains the particle size of the mineral ores as large as is possible. Maintaining the particle size enables direct smelting without pelletization. Therefore, the separation process will eliminate a pelletizing step as long as the amplitude of the ultrasonic waves are below the amplitude required to cause fracturing and a substantial reduction in size of the mineral ore crystals. It should be noted that some sand particles will contain more than one mineral ore crystal. Ultrasonic irradiation of these particles will usually sever the similar as well as the dissimilar crystals, and thus, some particle size reduction will occur in addition to that resulting from severing of the rutile or gangue crystals. Sampling of the end product from the apparatus of the present invention can be used to determine variation of the power at signal generator 58 and transducer 47. When black sands are being irradiated at 750,000 cycles per second, fracturing at the interfaces will occur almost instantaneously as the sand passes in front of the transducers in a 24 inch wide treatment channel without internally fracturing the crystals.
in certain situations, steel processing plants are constructed in a manner which will only accept pelletized ore of substantial size. Accordingly, in these situations, it may be advantageous to not only fracture the magnetite ore from the rutile and other gangue crystals, but to fracture the magnetite crystals themselves so as to facilitate subsequent pelletizing. If this is desired, the amplitude of the ultrasonic waves can be increased until the sympathetic vibration within the crystals, as well as the cavitation, is substantial enough to cause internal fracturing of the crystals and to effect a reduction of the size of the crystals for their use in pelletized applications.
The pump 51 and probes 54 are the only apparatus which will require periodic maintenance or replacement, since the ultrasonic treatment chamber is substantially free of moving parts. Abrasion of the transducer probes by the sand and cavitating salt water will eventually cause destruction of the probes. Since extremely hard materials erode at a higher rate, it is preferable that probes be constructed of an erosion resistant material such as molybdenum steel. It should also be noted that instead of a pump 51, the mixture of liquid and rock can be urged by gravity through the separator system of the present invention.
In order to insure fracturing of the rock material, it is possible to irradiate the rock with ultrasonic waves simultaneously from two ultrasonic wave generating means which have differing frequencies. Thus, adjacent transducers can be formed with overlapping fields of ultrasonic waves with one generator irradiating at a first frequency and a second or additional generator irradiating ultrasonic waves at a second and different frequency. The impressing of a first frequency on the rock material which causes the selected crystal to vibrate at about its natural frequency and simultaneous impressing of a second differing frequency may be used to enhance the cleavage and fracturing between crystals. While side-by-side generators can be employed, it is also possible to position the second transducer directly across from the first in a manner similar to that described above in connection with intensifying the power in the treatment channel.
While it is believed that the primary mechanism inv volved in separating the crystals is sympathetic vibration of a selected crystal, undoubtedly the substantial cavitation produced in the sub-channels 41-44 enhances performance. The cavitation insures circulation of the particulate sand through the ultrasonic field so as to expose the same to irradiation. Moreover, the cavitation will act to clean the severed crystals of contaminants which are deposited in crevices or adhered to the crystal surfaces.
It should be noted further that an important advantage and feature of use of the ultrasonic process is that it is accompanied by a very beneficial ecological effect. The waters in many alluvial plane areas have become contaminated and polluted by raw sewage discharged from nearby population centers. The sands have been deposited to a degree that the flow of the rivers discharging into the ocean are not sufficient to carry away the sewage. Accordingly, it becomes a stagnant breeding ground for serious infectious diseases, including even typhoid fever. The highenergy bombardment in the cracking chamber 31 of the process of the present invention beneficially destroys bacteria contained in the waters passed through the system. Thus, the processing of substantial volumes of water and sand (for example a flow rate of 4,000 gallons per minute) results in a removal of bacteria which ameliorates the health hazard. Additionally, the removal of sand from the mouth of the river further enhances the surge of the river to enablecarrying waste products away from the populated areas; and the'removal .of sand will afford improved access to the rivers for migrating fish, such as salmon.
The type of mineral crystal separated by ultrasonic irradiation in section 31 will determine the'type of concentrating, segregating or separating apparatus into which the severed particulate crystals are discharged through discharge opening 49. if the mineral crystals are non-magnetic, sophisticated and effective 96-stage sluice systems can be employed to selectively gradeand separate ores such as titanium, the noble metals, zirconium and silica. In connection with the extraction of magnetite from black sands material, however, the magnetite crystals are highly ferromagnetic andv yet have a density making them difficult to separate in a multiple stage sluice gate system. It is, therefore, ad-
vantageous to employ a ferromagnetic separator or concentrator in connection with the ultrasonic processor above described. v
The use of magnetic separators orv ore concentrators is well known and hasbeen employed in connection with the separation of magnetite andrutile. One approach is exemplified by US. Pat. Nos. 1,425,235 and 3,552,564 in which ferromagnetic ore is passed underneath a plurality of magnets which have cycling magnetic fields to enable movement of the ore under the influence of gravity and escape of the non-ferromagnetic gangue material. In these systems the ore is held against aplate by the magnets, and the gangue falls in 'air away from the ore to collecting bins. The magnetic forces are maintained so as to hold the ferromagnetic ore against the plate except during short intervals which allows the ore to slip down along the plate to an ore concentration zone. Similar approaches are shown in US. Pat. Nos. 871,301, 871,365 and 2,975,897. It should be noted that dry processing techniques are not well suited for use with black sands material which is immersed in water since it requires an extra drying step. A drying step usually requires heating, if it is to be accomplished within a reasonable period of time, and heating black sand material may give rise to a very un desirable side effect. Both rutile (TiO and ilmenite (FBTiOg), when heated enough to dry them out, undergo a substantial increase in magnetism, and they will be magnetically indistinguishable from magnetite and will be gathered up with the magnetite. Since both rutile and ilmenite contain titanium, the titanium will once again make the iron ore unsuitable for smelting. By contrast, however, if the rutile and ilmenite are kept wet and cold, they will exhibit a magnetic attraction about one-third that of magnetite. Thus, magnetic separation processes which require dry particles, which in turn require heating of the particles to dry the same,-
will be unsuitable for the separation of the magnetite crystals from black sands containing rutile and ilmenite.
Wet magnetic separators have also been employed to separate particulate ferromagnetic mineral ores. Typical of this approach are US. Pat. Nos. 2,714,960 and 3,289,836. The apparatus disclosed in these patents includes a rotating or movable magnetic field which travels in a direction counter to the direction of flow of a washing liquid. While having certain advantages, such systems are susceptible to clogging, require a multiplicity of moving parts and attendant maintenance problems, andhave hydraulic systems which are more difficult to integrate with the flow from an ultrasonic processing or cracking chamber.
Referring now to FIG. 4, the magnetic separating stage 32 of the apparatus of the present invention and the process implemented therebycan be set forth in greater detail. As will be seen, reducing section 48 of the ultrasonic treatment channel is connected to an inlet opening 61 in separation flow channel 32. It should be noted again that FIG. 4 is a side elevational view as opposed to the top plan view of FIGS. 1 and 2. Positioned superjacent flow channel 32 are a plurality of magnetic force generating means 62 formed for application of magnetic forces to the mixture of liquid medium and particulate ore and gangue material as the mixture passes beneath the magnetic force generating means. Flow channel 32 is formed adjacent a second end thereof with ub-channels 63 and 64, with channel 63 acting as an ore receiving portion of the apparatus and channel 64 acting as a gangue receiving portion. As indicated by the arrows, the liquid mixture and particulate materials flow from inlet opening 61 toward ore receiving portion 63 and gangue receiving portion 64.
As will be seen, thelower surface 66 of separation channel 32 diverges from the upper surface 67 with the resultant progressive increase in the area of the flow channel from the inlet to the ore and gangue receiving end thereof. In accordance with the basic laws of hy draulics, the incoming velocity of the mixture of liquid medium and particulate material will be relatively high and will gradually decrease as the mixture moves through the separation channel. As will be understood, the decrease of flow rate of the liquid will tend to cause gravitational settling of the particulate materials as the liquid progresses toward the gangue and ore receiving portions. Similarly, the motion of the liquid will have a component which tends to urge or propel the particulate material toward the ore and gangue receiving portions. It is also possible to enlarge the area of channel 32 in the horizontal dimension to effect a reduction in velocity of the carrier liquid medium, but this type of approach requires a widening of the magnetic field, which may be disadvantageous. Additionally, the downwardly sloping surface 66 insures movement of the gangue material toward portion 64 under gravitational forces, whereas a fiat bottomsurface 66 would have to depend solely on the flow of liquid through the separation channel to move the gangue material. Similarly, upper surface 67 could be upwardly sloped to effect a reduction in velocity, but this can result in turbulence at the upper surface which would interfere to some degree with the matnetic attraction.
In order to effect separation of the ferromagnetic particles from the particulate non-ferromagnetic gangue, magnetic force generating means 62 are connected by conductors 68 to a controller 69, which may be used to apply and terminate (including a nulling of the hysteresis effect) the magnetic forces generated by the generating means intermittently at discrete, relatively spaced apart intervals along flow channel 32. Such cycling of the magnetic forces alternatively and repetitively attracts the ferromagnetic particles toward the magnetic force generating means and release the same to fall under the influence of gravity. in the ferromagnetic particle separator of the present invention, the magnetic forces are applied and then tenninated progressively in the same direction as the flow of the liquid medium in channel 32. Magnetic force generating means 62 is advantageously comprised of a plurality of side-by-side electromagnets, each formed for independent actuation and connected to controller 69. in operation, controller 69 will activate magnet 71 for a first period of time. Thereafter, the controller deenergizes magnet 71 and nulls the same by a nulling coil to effectively terminate the magnetic forces generated, including the magnetic flux remaining in the magnet due to the hysteresis phenomenon. There no longer being a lingering magnetic field in or about magnet 71, the ferromagnetic particles will begin to fall back toward surface 66 away from magnet 71 while being carried downstream by the velocity of the liquid mixture. At about the termination of magnet 71, magnet 74 is activated by the controller and begins to draw the ferromagnetic particles back up toward magnet 74. Momentarily, magnet 74 is de-energized and nulled, and the particles again gravitate downwardly in the liquid medium until magnet 77 is activated and begins to pull the ferromagnetic particles upwardly in the liquid medium. This sequence is repeated for magnets 80, 83 and 86. Upon activation of magnet 77, however, the controller further activates magnet 72 and begins another progressive sequence with magnets 72, 75, 78, etc. Similarly, upon activation of magnet 83 and magnet 78, a third series of magnets, beginning with magnet 73, is progressively and sequentially activated and terminated by controller 69. The third series includes magnet 73, 76, 79, etc. 1
Thus, the ferromagnetic ore is repetitively drawn up toward an electromagnet, allowed to settle and gravitate back down in the moving liquid medium towards the bottom of the flow chamber and then raised upwardly again by the magnets. The sequencing of magnets insures that there is always at least one deenergized and nulled magnet between any two energized magnets. In this manner the ferromagnetic particles flowing downstream in the flow channel are never drawn in a backward direction contrary to the flow. The magnetic action keeps the ferromagnetic material and, particularly magnetite ore, close to the top of separator channel 32, while repeatedly washing the ore upwardly and downwardly transverse to the stream flow to allow trapped gangue material to be washed from the ferromagnetic particles. This washing technique, however, makes use of the flow of the liquid mixture to urge both the magnetic and non-magnetic particles toward the respective collecting portions 63 and 64. The washing effect is particularly desirable so as to clean the ore to as high a degree as possible for blast furnace use. The on-off' action of the magnets further insures that the separator channel 32 does not become clogged with particulate material.
Beginning adjacent ore receiving sub-channel 63, it is possible to cycle the magnets more frequently to keep the magnetic ore in a tight grouping. For example, magnets 87, 88 and 89 can be energized, de-energized and then nulled one after the other without any deenergized magnets therebetween. Additionally, the magnetic flux can be progressively reduced adjacent ore receiving portion 63 to allow the less magnetically responsive rutile and ilmenite to escape the magnetic flux and fall down with the non-magnetic gangue. The reduction in flux of magnets in portion 63 also allows the ore to fall free of the magnetic field for conveyance to a ferromagnetic ore stockpile.
The gangue material will initially be suspended and intermixed with the ferromagnetic ore at inlet opening 61. The turbulence resulting from reciprocation of the ferromagnetic materials and the velocity of the liquid will maintain the gangue in suspension for a period of time which insures that the gangue will not trap an undue quantity of the ferromagnetic particles and gravitate them to the bottom of the separation channel. As the velocity slows, turbulence will decrease, and the gangue will begin gravitating toward surface 66 of the flow channel and will be urged toward the gangue receiving portion.
It is a further feature of the present invention to form an upper surface of the sub-channel 64 to converge toward lower surface 66 so as to increase the velocity of the liquid in gangue receiving channel 64. The increase in velocity of the liquid causes the gangue to again be picked up and maintained in suspension in the liquid medium so as to prevent the piling up or building up of gangue in the conduit to the gangue stockpile or to a non-ferromagnetic separator, such as sluice gate system. It is also possible to pump additional liquid into the separating chamber at portions 63 and 64 through nozzles (not shown) to insure suspension of the particles to prevent clogging.
There are several methods of implementing the control function of controller 69. It is preferable to use bar magnets having coils therearound, with the number of coils determining the field strength. The number of coils can be varied to obtain a field gradient from end 61 to portion 63, or the magnets can be driven at differing levels to change field strength. Similarly, the effective air gap can be increased along the length of the separation chamber to vary field strength. The electromagnets may be cooled in a liquid bath (not shown) to prevent overheating. Controller 69 can be used to energize the electromagnets, and then for a short period of time, a nulling coil activated to reverse the polarity in the core and nullify the magnet. This sequence can be accomplished, for example, electronically, by employing a rotating disc with brushes or rollers, or a photoelectric cell having an element which interrupts the light in accordance with the speed at which the magnets are to be sequenced. The ability to vary the speed of the controller allows cycling of the electromagnets at different rates to accommodate different flow rates through the separation chamber 32. Thus, if. sampling indicated too much gangue was being carried over to the ore receiving portion or too much ore to the gangue receiving portion, it would be possible to alter the rate at which the magnetic field progressively moves down the chamber to obtain better separation.
It should be noted further that while a single treatment or ultrasonic cracking chamber and single magnetic separator are shown, it is quite possible and in some instances advantageous to employ additional ultrasonic cracking chambers, for example, at a location downstream of gangue receiving portion 64 of the magnetic separator. Similarly, it would be possible to again irradiate the materials deposited in ore receiving channel 63 with ultrasonic waves followed by a second magnetic separation to obtain even cleaner ore. Moreover, ultrasonic irradiation of the gangue material traveling down channel 64 could also be selected to insure fracturing of different materials such as the rutile from silica or other gangue crystals. One of the important advantages of the ore recovery system of the present invention is, therefore, that it is susceptible to sequential or series positioning of cracking chambers and separators for continuous flow-through processing of ore.
1. A process for breaking the mechanical bonds between relatively interlocked and embedded mineral ore crystals and gangue crystals contained in a rock material, said crystals having differing fundamental resonant frequencies, to enable separation of said mineral ore crystals from said gangue crystals, comprising:
irradiating said rock material with ultrasonic waves having a frequency selected to cause one of said mineral ore crystals and said gangue crystals to vibrate at about a resonant frequency thereof, said irradiation being maintained until fracturing of said rock material occurs at about the interfaces between said crystals.
2. The process as' defined in claim 1 wherein,
said rock material is selected to contain magnetite ore crystals and rutile gangue crystals.
3. The process as defined in claim 2 wherein, said rock material is black sand.
in size of a substantial quantity of said mineral ore crystals.
6. The process as defined in claim 1 wherein, v said irradiating step is accomplished by irradiating with ultrasonic waves having an amplitude above the amplitude required to cause fracturing of a substantial quantity of said mineral ore crystals to effect reduction in the size thereof.
7. The process as defined in claim 1, and
simultaneously with said irradiating step, subjecting said rock material to ultrasonic waves from an additional source, said ultrasonic waves from said additional source having a frequency selected to differ from the frequency of said ultrasonic waves of said irradiating step.
8. A process for recovery of a mineral bearing ore from rock containing mineral ore crystals interlocked with and embedded in a gangue material comprising:
a. irradiating said rock with ultrasonic waves having a frequency in the range of about 300,000 to about 1,200,000 cycles per second until fracturing occurs at the interfaces between said mineral ore crystals and said gangue material in a substantial quantity of said rock; and
b. separating said mineral ore crystals from said 11. The process as defined in claim 10 wherein,
said frequency is selected to be about 750,000 cycles per second.
12. The process as defined in claim 8 wherein,
said mineral ore crystals are magnetite and said gangue material includes rutile, and said ultrasonic waves have a frequency in the range of between about 1,000,000 and 1,200,000 cycles per second.
13. The process as defined in claim 8 wherein,
said rock is selected as black sands containing magnetite ore crystals and rutile gangue material, and said rock material is immersed in salt water.
14. A process for recovery of a mineralbearing ore as defined in claim 8 wherein,
said mineral ore crystals are ferromagnetic and said gangue material is substantially less magnetic than said mineral ore crystals; and
said separating step is accomplished by:
' i. introducing a mixture of said mineral ore crystals and said gangue material and a liquid medium into a separation apparatus through an inlet portion in a first end thereof, said separation apparatus having an ore receiving portion and a gangue receiving portion adjacent a second end thereof with said ore receiving portion positioned above said gangue receiving portion;
ii. urging said liquid medium to flow from said inlet portion to said ore receiving portion and said gangue receiving portion;
iii. intermittently applying a vertically oriented magnetic force to said mixture from a position above said mixture and terminating'said magnetic force to repetitively move the ferromagnetic mineral ore crystals upwardly through said liquid medium; and
iv. allowing both said ferromagnetic mineral ore crystals and said gangue material to gravitate downwardly through said liquid medium while said magnetic force is terminated, said magnetic force being applied with a frequencycausing said ferromagnetic mineral ore crystals to be maintained in the upper portion of said mixture as said mixture reaches said gangue and said ore receiving portion for deposit of said ferromagnetic ore crystals in said'ore receiving portion.
15. The process for recovery of a mineral bearing ore as defined in claim 14 and the step of:
reducing the rate of flow of said liquid medium as said liquid medium progresses from said inlet portion to said ore receiving portion and said gangue receiving portion.
16. A process for recovery of a mineral bearing ore as defined in claim 14 wherein,
said separation apparatus includes a plurality of magnetic force generating means positioned in relatively spaced apart relation and extending from adjacent said inlet portion to adjacent said ore receiving portion; and
said magnetic force is applied by each generating means sequentially commencing adjacent said inlet portion and progressively applied and then terminated in a direction toward said ore receiving portion.
17. A process for recovery of a mineral bearing ore as defined in claim 16 wherein,
said magnetic force is applied in the following sequence:
a first magnetic force is applied to said mixture by a first generating means while adjacent generating means to said first generating means apply substantially zero magnetic force to said mixture;
said first magnetic force is terminated and a second magnetic force is applied to said mixture by second generating means positioned between said first generating means and said ore receiving portion while adjacent generating means to said second generating means apply substantially zero magnetic force to said mixture; and
said second magnetic force is terminated and subsequent magnetic forces are applied to said mixture by subsequent generating means, each said subsequent generating means being progressively positioned between the next preceding generating means applying a magnetic force and said ore receiving portion and said generating means adjacent said subsequent generating means apply substantially zero magnetic force to said mixture during activation of each of said subsequent generating means. I
18. Apparatus for the formation of a mixture of ferromagnetic ore and non-ferromagnetic gangue material from rock containing said ore and said gangue material and for separation of said ore and said gangue material comprising:
a. a treatment flow channel having an inlet opening for receipt of rock containing said ore and said gangue material, said treatment flow channel being adapted for receipt and flow of a liquid medium therethrough and having a discharge opening communicating with an inlet opening in a separation flow channel; v
b. ultrasonic wave generating means positioned adjacent said treatment flow channel intermediate said inlet and discharge openings and formed for'irradiation of said rock with ultrasonic waves while immersed in said liquid medium and positioned in said treatment flow channel;
. a separation flow channel formed to contain said liquid medium, said ore and said gangue material therein, said flow channel being-formed with an inlet opening at a first end thereof communicating with said discharge opening in said treatment flow channel and terminating in an ore receiving portion and a gangue receiving portion adjacent a second end thereof;
d. means for causing said liquid medium to flow through from said treatment flow channel and said separation flow channel to said ore and gangue receiving portions operatively connected to said separation flow channel;
. magnetic force generating means positioned superjacent said flow channel and formed to apply magnetic forces to said ore and gangue material as immersed in said liquid medium and positioned in said flow channel, said generating means being further formed to apply and terminate said magnetic forces intermittently at discrete intervals along said flow channel intermediate of said inlet opening in said separation flow channel and said ore receiving portion; and
magnetic control means connected to said magnetic force generating means and formed to repetitively cause said magnetic generator means to apply intermittent magnetic forces at discrete intervals along said separation flow channel progressively in a direction from said inlet opening therein to said ore receiving portion.
19. Apparatus as defined in claim 18, and
pump means connected to urge said rock and liquid medium from said inlet opening through said treatment flow channel and to said discharge opening and through said separation flow channel; and ultrasonic wave reflecting means positioned on a side opposite said treatment flow channel from said ultrasonic wave generating means and formed and" treatment flow channel toward said ultrasonic wave generating means.