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BR-112021004021-B1 - METHOD AND SYSTEM FOR PRODUCING A STACKABLE WASTE MIXTURE

BR112021004021B1BR 112021004021 B1BR112021004021 B1BR 112021004021B1BR-112021004021-B1

Abstract

METHOD AND SYSTEM FOR WATER REMOVAL. The present invention relates to a method for removing water (dewatering) from tailings and systems for carrying out the same. In certain aspects, the invention relates to methods for producing a dewatered tailings residue or a stackable tailings residue, comprising subjecting tailings to hydrocyclonic separation to produce one or more partially dewatered substreams and a water-rich final overflow; separating the water-rich final overflow, by centrifugation, into a recovered water stream and a low-water residue; and mixing the low-water residue and at least part of one or more partially dewatered substreams to produce a dewatered tailings residue or a stackable tailings residue.

Inventors

  • NILS RICHARD STEWARD
  • Dean Stephenson

Assignees

  • WEIR MINERALS AUSTRALIA LTD

Dates

Publication Date
20260310
Application Date
20190904
Priority Date
20180904

Claims (15)

  1. 1. Method for producing a stackable tailings residue (20) from tailings (13) discarded as waste material from a mining operation, characterized in that it comprises: feeding tailings (13) to a hydrocyclone (11a, 11b) at a feed inlet pressure in a range of 0.75 MPa to 1.5 MPa; subjecting the tailings (13) to hydrocyclonic separation to produce one or more partially water-removed substreams (14, 14a, 14b) and a water-rich final overflow (15, 15b); separating the water-rich final overflow (15, 15b), by centrifugation, into a recovered water stream (22) and a low-water residue (17); mix together the low water content residue (17) and at least part of one or more partially water-removed substreams (14) to produce the stackable tailings residue (20), wherein the stackable tailings residue (20) has a solids content of 75% by weight to 90% by weight.
  2. 2. Method according to claim 1, characterized in that it comprises: injecting gas into the tailings (13), before subjecting the tailings to hydrocyclonic separation, at a pressure higher than the high feed inlet pressure, optionally that the gas is injected at more than 10 m3/hr up to 60 m3/hr.
  3. 3. Method according to claim 2, characterized in that the gas is air.
  4. 4. Method, according to any one of claims 1 to 3, characterized in that said method further comprises injecting a coagulant and/or a flocculant into at least one hydrocyclone (11a, 11b) used in said hydrocyclonic separation.
  5. 5. Method, according to any one of claims 1 to 3, characterized in that said method further comprises injecting a coagulant and/or a flocculant into the tailings (13) prior to said hydrocyclonic separation.
  6. 6. Method, according to any one of claims 1 to 5, characterized in that the tailings (13) are subject to a plurality of hydrocyclonic separation stages, including a first stage and a final stage; wherein each hydrocyclonic separation stage includes at least one hydrocyclone (11a, 11b), each hydrocyclonic separation stage configured to separate an inlet into one of one or more partially removed water substreams (14, 14a, 14b) and the water-rich overflow (15, 15a, 15b); the inlet of the first stage comprising the tailings (13); the water-rich overflow (15, 15a, 15b) of each stage preceding the final stage being an inlet to the next adjacent stage; and the final water-rich overflow (15b) is the water-rich overflow (15, 15a, 15b) of the final stage.
  7. 7. Method according to claim 6, characterized in that at least some of the one or more partially removed water substreams (14, 14a, 14b) from one of the plurality of hydrocyclonic separation stages are collected as a highly removed water product (14a’).
  8. 8. Method according to claim 6, characterized in that the stage from which the highly water-removed product (14a’) is collected is the first stage of hydrocyclonic separation.
  9. 9. Method, according to any one of claims 1 to 8, characterized in that the stackable tailings residue (20) has a solids content of 80% by weight.
  10. 10. System for producing a stackable tailings residue (20) using the method as defined in any one of claims 1 to 9, characterized in that the system comprises: a hydrocyclonic separation unit (10) having a feed inlet pressure in a range of 0.75 MPa to 1.5 MPa for subjecting tailings (13) to hydrocyclonic separation to produce one or more partially dewatered substreams (14, 14a, 14b) and a water-rich final overflow (15, 15b); a centrifugation unit (16) comprising at least one centrifuge (12) configured to separate the water-rich final overflow (15, 15b) into a recovered water stream (22) and a low-water residue (17); a mixer (18) for mixing the low water content residue (17) and at least part of one or more partially water-removed substreams (14, 14a, 14b) to produce the stackable tailings residue, wherein the stackable tailings residue (20) has a solids content of 75% by weight to 90% by weight.
  11. 11. System according to claim 10, characterized in that the system further comprises an injection means for injecting gas into the tailings (13) before the hydrocyclonic separation unit (10), optionally wherein the injection means is further configured to inject a coagulant and/or a flocculant into the tailings (13) before the hydrocyclonic separation unit (10).
  12. 12. System according to claim 10 or 11, characterized in that said system is configured to inject a coagulant and/or a flocculant into at least one of said one or more hydrocyclones (11a, 11b).
  13. 13. System, according to any one of claims 10 to 12, characterized in that: the hydrocyclonic separation has a plurality of hydrocyclonic separation stages, including a first stage and a final stage; for each stage, the hydrocyclonic separation unit (10) has a subunit (10a, 10b) that includes at least one hydrocyclone (11a, 11b) to separate an inlet into one or more partially removed water substreams (14, 14a, 14b) and a water-rich overflow (15, 15a, 15b); the subunit for the first stage (10a) is configured so that the inlet to the first stage includes the tailings (13); the subunits (10a, 10b) are configured to provide the water-rich overflow (15, 15a, 15b) from each preceding stage to the final stage as an input to the next adjacent stage; and the subunit for the final stage (10b) is configured to provide the final water-rich overflow (15, 15b) to the centrifugation unit (16).
  14. 14. System, according to any one of claims 10 to 13, characterized in that the stackable tailings residue (13) has a solids content of 80% by weight.
  15. 15. System, according to any one of claims 10 to 14, characterized in that it further comprises: a pump fluidly connected to a disposal site and configured to pump stackable tailings waste to the disposal site, optionally wherein the pump is a positive displacement pump.

Description

TECHNICAL FIELD [001] The present invention relates to methods for removing water from tailings, and systems for carrying out the same. BACKGROUND OF THE INVENTION [002] Tailings storage facilities are used to store mine tailings, which are waste materials discarded from a mining operation, such as an ore processing plant or coal preparation plant. Wet tailings (e.g., slurries) can be stored in reservoirs such as dams, ponds, diversion channels, spillways, and seepage collection ditches, so that they gradually dehydrate through sedimentation, drainage, and evaporation. A traditional tailings pond occupies a large area of land and requires a lot of maintenance and monitoring. In addition, wet tailings storage is subject to increasing scrutiny in light of the risks of tailings seepage, overflow or leakage, or abrupt failure of tailings storage facilities. Tailings spills, dam failures, seepage, and direct discharges into waterways have resulted in serious and long-term environmental and social consequences. [003] Furthermore, it is increasingly desirable to increase water recovery, particularly where mining operations are located in areas where there is water scarcity. Consequently, processes have been developed for the removal of water from tailings to allow water to be recovered and produce substantially water-free tailings. Substantially water-free tailings may be suitable for disposal through so-called "dry" stacking. [004] Dry stacking facilities may be easier to close and rehabilitate and require a smaller footprint compared to other surface tailings storage options, as removing water from the tailings produces a higher density waste product. Additionally, "dry" stacking can be used in environments where wet tailings storage facilities may be unsuitable, such as undulating and steep terrain. [005] Known water removal processes for the production of stackable tailings waste use filters, such as vacuum filters or filter presses, to produce a dewatered filter cake that meets the geotechnical requirements for stacking the water-removed product. However, the high capital and operating costs of filtration facilities may limit the conversion from wet tailings storage to "dry" stacking. [006] Filtration facilities may have a relatively limited throughput. In addition, the filter cake may require significant new handling to construct the pile geometries, such as being loaded or transported by truck to the tailings storage facility and then moved to the final position in the dry pile using earthmoving equipment. [007] It is desirable to address one or more of the above or, at least, provide a useful alternative to them. SUMMARY [008] The present invention relates to a method for removing water from tailings and a system for doing so. [009] In a first aspect, the present invention relates to a method and a system for removing water from tailings in order to produce a stackable tailings residue. The production of a stackable tailings residue can facilitate the transport, disposal and deposition of the tailings. [0010] In the first aspect, the present invention provides a method for producing a stackable tailings residue, comprising: subjecting tailings to hydrocyclonic separation to produce one or more partially water-removed substreams and a water-rich final overflow; separating the water-rich final overflow, by centrifugation, into a recovered water stream and a low-water residue; and mixing the low-water residue and at least part of one or more partially water-removed substreams to produce a stackable tailings residue. [0011] Typically, there is a plurality of hydrocyclonic separation stages. Consequently, in some embodiments, hydrocyclonic separation has a plurality of hydrocyclonic separation stages, including a first stage and a final stage; each hydrocyclonic separation stage separates an inlet into one of one or more partially removed water substreams and a water-rich overflow; the inlet of the first stage comprises the tailings; the water-rich overflow of each stage prior to the final stage is an inlet to the next adjacent stage; and the final water-rich overflow is the water-rich overflow of the final stage. [0012] In some embodiments, a process generated the waste and the method comprises: supplying the recovered water stream to the process for reuse. [0013] In addition, the present invention provides a system for producing a stackable tailings residue, comprising: a hydrocyclonic separation unit for subjecting tailings to hydrocyclonic separation to produce one or more partially water-removed substreams and a water-rich final overflow; a centrifugation unit comprising at least one centrifuge configured to separate the water-rich final overflow into a recovered water stream and a low-water residue; and a mixer for mixing the low-water residue and at least part of one or more partially water-removed substreams to produce a stackable tailings residue. [0014] In some embodiments of the system, hydrocyclonic