AU2009100586A4 - Mining and Mineral Process, System and Method - Google Patents

Description

1 MINING AND MINERAL PROCESS, SYSTEM AND METHOD FIELD OF INVENTION The present invention relates to the field of mining and mineral processes, systems and methods related thereto. 5 In one form, the invention relates to recovery of tailings and/or fines from, for example, a mining or mineral processing operation. In one particular aspect the present invention is suitable for the production of substantially dewatered cake. It will be convenient to hereinafter describe the invention in relation to the 10 production of substantially dewatered cake, however it should be appreciated that the present invention is not limited to that use only. BACKGROUND ART Throughout this specification the use of the word "inventor" in singular form may be taken as reference to one (singular) inventor or more than one (plural) 15 inventor of the present invention. Mine tailings are waste fine material left over after the metals of interest such as lead, zinc, copper, silver, gold and others, have been extracted from the mineral rocks that contained them. The mineral separation process, especially in older mining operations, is only partially efficient. As a result, after the crushing, 20 grinding and subsequent extraction processes, some of the metal-containing minerals, clays and other non-valuable fractions are left behind as small tailings particles. In the states of California, Arizona and Nevada in USA alone, there are some 420,000 abandoned mines. Of these, some 13,000 are considered 25 potentially hazardous. The mine tailings and their associated metal contaminants, such as arsenic, lead, and cadmium,, are prone to potential leaching through tailings dam walls. In another process, tailings may be dewatered. Dewatering tailings to 30 higher degrees than paste like products produces a filtered wet (saturated) and dry (unsaturated) cake that can no longer be transported by pipeline due to its low moisture content. A typical moisture content of less than 20% is achieved by using a combination of belt, drum, horizontal and vertical stacked pressure plates 2 and vacuum filtration systems. The term 'dry cake' or 'dry stack' is used to describe tailings that have a moisture content several percent below saturation. These dewatered tailings are normally transported by conveyor or truck, deposited, spread and compacted to form an unsaturated tailings deposit. This 5 type of tailings storage produces what is considered to be a stable deposit requiring no retention bunding and is referred to as 'dry stack'. A further method used to reduce dust problems is to deposit tailings (and water) into a dam. However this also has problems, such as: - A dam is expensive to construct and maintain to prevent future 10 degradation of the dam itself; e a dam occupies further land, often quite some distance from the mining and mineral processing operation, which may be used for other purposes; e a dam must be maintained for decades after the mining operation has finished. A mining company may not have sufficient funds in the long term 15 future to properly maintain a tailings storage site; e once one dam is full, further dam(s) must be constructed to hold additional mine tailings or expensive modification of the existing dam would be required to expand it's holding capacity; e depositing tailings into a dam does not easily allow for the recovery of 20 valuable minerals in the tailings with subsequently improved extraction technologies; e a poorly constructed dam can result in seepage into underground water systems. Figure 1 illustrates schematically a typical mining process in which ore 11 25 is extracted from the mine, crushed and/or sized 12 after which the desired mineral(s) are extracted 13 using known techniques (which are not further described in this specification). Tailings 14 result from the extraction process and these are typically deposited as waste to landfill 15, dam(s) 16 and/or deposited back in parts of the mine as backfill 17. 30 There is a significant risk associated with the pumping of mine tailings over long distances, which is very typical in terms of the location for tailings dams. These risks can include potential for rupture of the pipe lines and the consequent 3 environmental impact can be catastrophic. This invention can substantially reduce the risk by either eliminating or substantially reducing the use and/or size of tailings dams. Tailings Dams by the nature of their operation contain large bodies of 5 process liquor throughout their structure and on the surface which may contain toxic chemicals which present a danger to local fauna. Tailings storage facilities are exposed to potentially large rain events which present potential stability issues if not managed appropriately. The discussion throughout this specification comes about due to the 10 realisation of the inventor and/or the identification of certain related art problems by the inventor and, moreover, any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the invention. It should not be taken as an admission that any of the material forms a part of the prior art base or the common general knowledge in the relevant art in Australia or 15 elsewhere on or before the priority date of the disclosure and claims herein. Throughout this specification the use of the word "inventor" in singular form may be taken as reference to one (singular) inventor or more than one (plural) inventor of the present invention. It is to be appreciated that any discussion of documents, devices, acts or 20 knowledge in this specification is included to explain the context of the present invention. Further, the discussion throughout this specification comes about due to the realisation of the inventor and/or the identification of certain related art problems by the inventor. Moreover, any discussion of material such as documents, devices, acts or knowledge in this specification is included to explain 25 the context of the invention in terms of the inventor's knowledge and experience and, accordingly, any such discussion should not be taken as an admission that any of the material forms part of the prior art base or the common general knowledge in the relevant art in Australia, or elsewhere, on or before the priority date of the disclosure and claims herein. 30 SUMMARY OF INVENTION It is an object of the embodiments described herein to overcome or alleviate at least one of the above noted drawbacks of related art systems or to at least provide a useful alternative to related art systems.

4 An object of the present invention is to provide an improved mining or mineral process, system and/or method. In a first aspect of embodiments described herein there is provided a method of, system and/or apparatus for recovering tailings from, for example, a 5 mining or mineral processing operation, comprising providing the tailings as an input stream to a hydrocyclone; and dewatering at least one of the output streams of the hydrocyclone. In another aspect of embodiments described herein there is provided a system, apparatus and/or method adapted to process tailings, comprising a first 10 hydrocyclone adapted to receive, as an input stream, the tailings, and a screen adapted to dewater an output stream of the first hydrocyclone. Preferably, a Discharge Regulator is also provided to regulate the output stream of the hydrocyclone. In yet a further aspect of embodiments described herein there is provided a 15 kit of parts adapted to provide the system, apparatus and/or method as herein disclosed. Other aspects and preferred forms are disclosed in the specification and/or defined in the appended claims, forming a part of the description of the invention. In essence, embodiments of the present invention stem from the 20 realization that a process of combining hydrocyclonic separation, and dewatering technologies can be used to concentrate solids in tailings to produce a dewatered cake. Advantages provided by the present invention comprise the following: " Dewatered cake can be produced from very fine tailings streams 25 0 Dewatered cake can be transported to other locations for reprocessing, blending with other materials to form a cementitious blend for concrete, or disposal without the concern associated with large volumes of water e The waste liquid stream from this novel processing combination can 30 be further clarified by second stage hydrocyclonic separation or more traditional clarification technologies such as thickeners and can then either be returned to the processing circuit to allow for 5 significant reduction in process water usage or pumped into shallow evaporation pans significantly smaller than previously utilised tailings storage facilities * The removal of the majority of the solids from the tailings stream 5 could substantially reduce the loading or even eliminate the use of tailings dams * This novel processing combination could allow the economic treatment of solids in existing tailings dams or waste solids from operating plants to produce paste like products without the need for 10 extremely expensive low capacity alternative equipment such as belt presses, vacuum filters etc. * Recovery of valuable minerals from existing tailings dams may be more possible and may avoid the need to introduce large volumes of water to pump these solids long distances. 15 Throughout this specification, 'tailings' includes tailings, fines and/or other mineral or mining operations material and/or residue. Throughout this specification, 'mineral' includes elements or compounds which are sought to be extracted from a mining operation. Further scope of applicability of embodiments of the present invention will 20 become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure herein will become apparent to those skilled in the art from this detailed 25 description. BRIEF DESCRIPTION OF THE DRAWINGS Further disclosure, objects, advantages and aspects of preferred and other embodiments of the present application may be better understood by those skilled in the relevant art by reference to the following description of embodiments 30 taken in conjunction with the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the disclosure herein, and in which: Table 1 illustrates an example of slurry particle size distribution; 6 Figure 1 illustrates schematically a process associated with the prior art; Figure 2 illustrates schematically a process according to one aspect of the present invention; Figure 3 illustrates schematically a process according to another aspect of 5 the present invention. DETAILED DESCRIPTION Figure 2 illustrates schematically a process according to one aspect of the present invention. Tailings 20 are sourced from any or any combination of sources, such as without limitation: 10 0 Tailings dam * Mine residue * Landfill * Dry stack * Fines stacks 15 0 Mine processing residue or waste e Other sources The tailings 20 are then processed in a separator 21. This serves to concentrate the solids of the tailings prior to discharge via the underflow onto the vibrating screen. The separator is designed with a discharge regulator built in. 20 This discharge regulator consists of a slotted rubber "seal" which allows the separator to be operated under vacuum and retain the solids that are separated in the unit until such time as the mass of the solids is sufficient to overcome the vacuum at which time the solids 22 are discharged onto the vibrating screen 23. The vibrating screen is fitted with fine slotted panels, or wire mesh, on which a 25 bed of dewatered solids will form. The screen design can be optimised to allow various shapes of initial and subsequent dewatering zones, including use of different aperture sizes on the screen panels or mesh as has been the practise in the industry. The dewatered solids are thereby treated to produce dewatered cake 24. The dewatered cake 24 is not necessarily devoid of moisture, it just has 30 a reduced moisture content as compared with the solids 22 that are output from the separator 21. The dewatered cake may be used, without limitation in a variety of applications and/or products, including building and/or construction 7 applications or used in combination with cementitious products to produce concrete which is the subject of other technologies not covered in this invention. The dewatered cake can also be recovered as usable product for example coal fines can be recovered to produce a saleable product, other cake material 5 can be used as road base or as filler. The dewatered cake may also be stored in a separate dam, dry stack or landfill, if required, In one aspect of the present invention, a tailings stream from, for example, a previous processing step (such as mining) is fed to a feed regulating sump. A slurry is then pumped from the sump to a hydocyclone, such as for example, a 10 Linatex T M Hydrocyclone G4 DW fitted with a Discharge Regulator. In one embodiment, the discharge regulator is a LinatexTM fishtail, however, it is to be understood that any suitable discharge regulator may be used in association with the present invention. The density of the feed may be up to approximately 40% solids by weight, however it is preferred that the density is below 25% to ensure 15 maximum recovery to underflow. The feed is pumped to the LinatexTM Hydrocyclone and preferably operated at a pressure between 40 and 10OKpa. This is considered a preferred range to achieve a relatively high underflow density whist achieving a relatively high recovery to underflow. The thickened underflow from the Discharge Regulator is then fed directly 20 onto the dewatering screen where the deck is preferably sloped to assist in dewatering. In one embodiment, the deck is sloped at, for example 45 degrees decline. There is also a further screen section sloped at approximately 5 to 10 degrees incline. As the thickened underflow begins to move up the 5-10 degree incline, a bed of coarse solids form. This bed then acts similar to a sand filter and 25 captures many of the particles including those finer than the apertures on the screen deck. Dewatering screens are configured in this way, the first part is a 45 degree decline to assist in building the bed, and then the particles travel up a incline of between 5-10 degrees which helps to slow the travel of material and again assist in retention time and thus dewatering efficiency. This bed or "cake" 30 then moves to the end of the screen where a discharge lip assists to further form a bed depth and maximise the dewatered cake density. The cake is labelled a "drip free product" and this would equate to somewhere between 7 to 15% moisture depending on the material being treated.

8 The screen is preferably fitted with 500 micron slotted aperture decks however smaller apertures can be fitted for the treatment of finer feed size distributions. It is preferred to have about 5-10% of the feed particles coarser than the apertures on the screen deck. Additionally vibration stroke, dewatering 5 screen inclination angle, discharge weir height and other settings can be varied on the screen to achieve the desired result. The fine particles that pass through the screen whilst the bed is forming are captured in the feed sump and may be re-pumped to the hydrocyclone or to another hydrocyclone for re feeding back to the screen. 10 In a further embodiment, any finer particles overflowing from a first hydrocyclone can be captured in an additional sump and then fed into further hydrocyclone(s), this time with or without the Discharge Regulator. These further hydrocyclone(s) would be operated at high pressure, up to 30OKpa to capture an additional component of these fine particles to their an additional underflow. The 15 fine particles captured at this stage could then be fed back the dewatering screen for recovery. To assist the capture of the finer particles on the screen bed, the finer particles may be deposited on the bed further towards the discharge end of the screen on top of an already formed coarse bed. They are then dewatered and captured in the one dewatered cake. 20 Figure 3 illustrates schematically a process according to another aspect of the present invention. Tailings 30 are obtained from a variety of sources. These are then processed in a first separator 31, providing solids 32 to the vibrating screen to be further dewatered 33, resulting in dewatered cake 34. The waste 35 from the first separator may be further processed by a second separator (s) 36 in 25 order to obtain further solids 37 for dewatering. The waste 38 from the dewatering process 33 may also be fed back to the first separator 31 and/or the second separator(s) 36 (not shown). A thickener (not shown) may be optionally used to concentrate the waste 39. Concentrated solids collected in the second separator, thickener or other solids concentrating unit may then be retumed to the 30 dewatered cake bed as it is forming on the vibrating screen for further dewatering, or treated by more conventional means in much smaller belt presses, vacuum filters or the like or even sent to tailings dams with significantly lower solids loadings than the original tailings stream solids being treated.

9 It is also possible to configure an arrangement whereby waste 35 from the first separator is discharged to a separate processing stage to remove remaining solids or indeed returned with or without further processing to either the tailings dam or evaporation ponds. Similarly waste 38 from the second separator could 5 be treated in the same manner. It may be possible to provide artificial solids concentration aids by way of chemical flocculants or coagulants prior to the separator or vibrating screen stages. Similarly it may be possible to provide such aids in the processing of the waste solids from any and all stages in this process to assist in the clarification of 10 the ultimate water effluent and/or densification of the various solids streams. In a further embodiment of the present invention, copper tailings slurry from a mineral processing operation containing approximately 47% solids and with particle size distribution as shown in Table 1 below was transferred into the feed regulating sump. The 'cyclone feed' column of Table 1 indicates an 15 exemplary percentage passing of particles. The present invention should not be limited to the disclosure of Table 1. The tailings slurry was pumped into the hydrocyclone of the following general dimensions 150mm cyclone body with 30mm inlet, a 35mm spigot and 50mm vortex finder, and fitted with a Discharge Regulator at a rate of 5 tonnes per hour at a pressure of 70 - 90 kPa. The 20 overflow pipe from the hydrocyclone was arranged to enable the discharge level to be below that of the bottom of the Discharge Regulator by approximately 2 meters in order to create a vacuum at the bottom of the hydrocyclone. The overflow pipe is fitted with the Linatex Overflow Rubber Syphon Boot, which ensures the overflow pipe is always full of water and the vacuum is maintained 25 over a range of operating condition. A vacuum is preferably formed to enable the solids to be concentrated sufficiently prior to discharge from the hydrocyclone underflow. The underflow discharge from the hydrocyclone Discharge Regulator was discharged under gravity when the solid loading was sufficient to open the Discharge Regulator onto the sloped section of the screen deck which was at an 30 angle of approximately 45 deg. The screen deck was 2.1 m long and 0.3 m wide and fitted with polyurethane panels with a slotted apertures approximately 250 microns wide and 1.4 mm long on the sloped section which extended 0.9 m and then fitted with similar 500 micron panels on the 5 deg inclined section following 10 the 45 deg section. The screen deck was also fitted with dual out of balance vibration motors of 1.3 kW capacity each. The screen created a Stoke of 3.5 m. Overflow from the hydrocyclone and material that passed through the screen whilst forming the cake on the screen deck were collected in the feed regulating 5 sump and pumped back up to the hydrocyclone. The dewatered cake product was approximately 85% solids with what is considered to be an excellent recovery efficiency of those particles fed to the screen from the hydrocyclone underflow. Other attempts were also made to treat tailings from a similar operation without passing these tailings through the hyrdocyclone however no bed could be 10 formed on the vibrating screen. When these same tailings were combined with the copper tailings mentioned in the example above and passed through the hydrocylone complete with Discharge Regulator, a suitable bed was formed and dewatered cake produced. While this invention has been described in connection with specific 15 embodiments thereof, it will be understood that it is capable of further modification(s). This application is intended to cover any variations uses or adaptations of the invention following in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be 20 applied to the essential features hereinbefore set forth. As the present invention may be embodied in several forms without departing from the spirit of the essential characteristics of the invention, it should be understood that the above described embodiments are not to limit the present invention unless otherwise specified, but rather should be construed broadly 25 within the spirit and scope of the invention as defined in the appended claims. The described embodiments are to be considered in all respects as illustrative only and not restrictive. Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention and appended claims. 30 Therefore, the specific embodiments are to be understood to be illustrative of the many ways in which the principles of the present invention may be practiced. In the following claims, means-plus-function clauses are intended to cover structures as performing the defined function and not only structural equivalents, but also 11 equivalent structures. For example, although a nail and a screw may not be structural equivalents in that a nail employs a cylindrical surface to secure wooden parts together, whereas a screw employs a helical surface to secure wooden parts together, in the environment of fastening wooden parts, a nail and a 5 screw are equivalent structures, It should also be noted that where a flowchart is used herein to demonstrate various aspects of the invention, it should not be construed to limit the present invention to any particular logic flow or logic implementation. The described logic may be partitioned into different logic blocks (e.g., programs, 10 modules, functions, or subroutines) without changing the overall results or otherwise departing from the true scope of the invention. Often, logic elements may be added, modified, omitted, performed in a different order, or implemented using different logic constructs (e.g., logic gates, looping primitives, conditional logic, and other logic constructs) without changing the overall results or otherwise 15 departing from the true scope of the invention. Various embodiments of the invention may be embodied in many different forms, including computer program logic for use with a processor (e.g., a microprocessor, microcontroller, digital signal processor, or general purpose computer), programmable logic for use with a programmable logic device (e.g., a 20 Field Programmable Gate Array (FPGA) or other PLD), discrete components, integrated circuitry (e.g., an Application Specific Integrated Circuit (ASIC)), or any other means including any combination thereof. In an exemplary embodiment of the present invention, predominantly all of the communication between users and the server is implemented as a set of computer program instructions that is 25 converted into a computer executable form, stored as such in a computer readable medium, and executed by a microprocessor under the control of an operating system. Computer program logic implementing all or part of the functionality where described herein may be embodied in various forms, including a source code 30 form, a computer executable form, and various intermediate forms (e.g., forms generated by an assembler, compiler, linker, or locator). Source code may include a series of computer program instructions implemented in any of various programming languages (e.g., an object code, an assembly language, or a high- 12 level language such as Fortran, C, C++, JAVA, or HTML) for use with various operating systems or operating environments. The source code may define and use various data structures and communication messages. The source code may be in a computer executable form (e.g., via an interpreter), or the source code 5 may be converted (e.g., via a translator, assembler, or compiler) into a computer executable form. The computer program may be fixed in any form (e.g., source code form, computer executable form, or an intermediate form) either permanently or transitorily in a tangible storage medium, such as a semiconductor memory 10 device (e.g, a RAM, ROM, PROM, EEPROM, or Flash-Programmable RAM), a magnetic memory device (e.g., a diskette or fixed disk), an optical memory device (e.g., a CD-ROM or DVD-ROM), a PC card (e.g., PCMCIA card), or other memory device. The computer program may be fixed in any form in a signal that is transmittable to a computer using any of various communication technologies, 15 including, but in no way limited to, analog technologies, digital technologies, optical technologies, wireless technologies (e.g., Bluetooth), networking technologies, and inter-networking technologies. The computer program may be distributed in any form as a removable storage medium with accompanying printed or electronic documentation (e.g., shrink wrapped software), preloaded 20 with a computer system (e.g., on system ROM or fixed disk), or distributed from a server or electronic bulletin board over the communication system (e.g., the Internet or World Wide Web). Hardware logic (including programmable logic for use with a programmable logic device) implementing all or part of the functionality where described herein 25 may be designed using traditional manual methods, or may be designed, captured, simulated, or documented electronically using various tools, such as Computer Aided Design (CAD), a hardware description language (e.g., VHDL or AHDL), or a PLD programming language (e.g., PALASM, ABEL, or CUPL). Programmable logic may be fixed either permanently or transitorily in a 30 tangible storage medium, such as a semiconductor memory device (e.g., a RAM, ROM, PROM, EEPROM, or Flash-Programmable RAM), a magnetic memory device (e.g., a diskette or fixed disk), an optical memory device (e.g., a CD-ROM or DVD-ROM), or other memory device. The programmable logic may be fixed in 13 a signal that is transmittable to a computer using any of various communication technologies, including, but in no way limited to, analog technologies, digital technologies, optical technologies, wireless technologies (e.g., Bluetooth), networking technologies, and internetworking technologies. The programmable 5 logic may be distributed as a removable storage medium with accompanying printed or electronic documentation (e.g., shrink wrapped software), preloaded with a computer system (e.g., on system ROM or fixed disk), or distributed from a server or electronic bulletin board over the communication system (e.g., the Internet or World Wide Web). 10 "Comprises/comprising" and "includes/including" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. Thus, unless the context clearly requires otherwise, throughout the description and the claims, the 15 words 'comprise', 'comprising', 'includes', 'including' and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

Claims (5)

1. A method of recovering tailings from, for example, a mining or mineral processing operation, the method comprising the steps of: 5 providing the tailings as an input stream to a hydrocyclone; and dewatering at least one of the output streams of the hydrocyclone, wherein the dewatering step produces a substantially dewatered cake.

2. A method as claimed in claim 1, wherein the output stream of the 10 hydrocyclone is regulated to discharge when there is a predetermined solid loading.

3. A system adapted to process tailings, the system comprising: a first hydrocyclone adapted to receive, as an input stream, the tailings 15 a screen adapted to dewater an output stream of the first hydrocyclone, further comprising a discharge regulator adapted to regulate the output stream of the hydrocyclone,.

4. A system as claimed in claim 3, wherein the discharge regulator is 20 operable to discharge the output stream of the hydrocyclone when the solids in the hydrocyclone provide a sufficient loading to open the Discharge Regulator.

5. A system as claimed in anyone of claims 3 or 4, wherein the discharge regulator is a fishtail. 25