RU2516423C2 - Method of in-situ leaching of oxidised nickel-cobalt ores - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: invention relates to extraction of nonferrous metal ore. Proposed method comprises ore body exposure by the system of injection and evacuation works, feed of leaching solution in evacuation works, forcing the production solution via evacuation works and processing the latter. Deposit is divided in ore blocks to be successively processed. Note here that injection and evacuation works are located across groundwater flows. Note also that nickel-cobalt solution is evacuated in pH range that ensures in-situ settling-out of ballast admixtures, mainly, iron and aluminium ions.

EFFECT: lower costs, better ecology.

7 cl, 6 dwg, 2 tbl

Description

The invention relates to mining, and in particular to geological methods for the extraction of non-ferrous metal ores.

Geotechnical methods for the extraction of non-ferrous metals are the most promising, allowing to work out ore deposits and technogenic formations without causing significant damage to the environment, where the content of valuable components is small, and mining by traditional methods is unprofitable.

A known method (US patent No. 3309140, class. 299-4.1967), according to which the opening of the ore body is carried out by the pumping well system - injection wells with subsequent supply of leaching solution through injection wells, and pumping the productive solution through the pumping. The disadvantage of this method is the lack of information on controlling the process of underground leaching, and therefore, the possibility of obtaining a given pH value for further processing of the productive solution.

A known method of leaching metals from ores (AS SU No. 1491076 class. E21B 43/28), according to which the productive horizon is opened by a system of pumping and injection wells and sequentially injected formation water and oxygen into the injection wells, then a solution of sulfuric acid, divalent iron and oxygen, withstand the solution in contact with the productive horizon until the acid is neutralized and the ferrous iron is oxidized, sulfuric acid is supplied and the production solution is pumped through the pumping wells. The disadvantage of this method is its multi-stage and the difficulty of regulating the pH of the productive solution.

A known method of underground and heap leaching of sulfide copper-containing polymetallic ores, in which the leaching is carried out with a solution of sulfuric acid in the presence of copper compounds, iron, etc. (AS No. 1308639, CL C22B 3/08). The disadvantage of this method is the increased concentration of acid in the production solution, leading to a low recovery of useful components during further processing.

According to patent RU No. 2075522, leached pyrite ores containing carbonate materials are leached. Due to the high acid intensity of such ores, difficulties arise in achieving the required pH value of the production solution, which leads to significant losses of recoverable components.

According to patent RU No. 2073790, the ore body is opened with alternating rows of pumping and injection wells, supplying a leach solution to the injection wells and pumping a production solution through the pumping wells. The injection of the solution begins with the maximum concentration of leachable reagent with its subsequent decrease. The disadvantage of this method is the increase in the time of development of the field and the difficulties in processing solutions with a high content of leaching reagent at the stage of its filing with high concentration.

According to patent RU No. 2355793 with heap leaching, the first stack of ore is leached with an acid solution of an increased concentration. If the pH of the effluent is more than 2.0, the solution is sent to the extraction of Nickel. If the pH value is less than 2.0, then this solution can be sent to the next ore stack to increase the pH value.

The closest in technical essence to the claimed method for underground leaching of oxidized nickel-cobalt ores, adopted as a prototype, is the "Method of underground leaching of non-ferrous metal ores" (patent RU No. 2293844), according to which injection and pumping facilities are constructed at the place of extraction of oxidized nickel-cobalt ore mining workings. Leaching solutions of acid are fed into injection openings with acidification and subsequent mining of the ore body, the product solution is discharged through the pumping openings, while acidification with sulfuric solutions with their aging in the ore body is carried out at a pH of not more than 1.5, and the output of production solutions is carried out at pH not more than 1.0.

When acidified with sulfuric acid solutions with their aging in the ore body at a pH of not more than 1.5, nickel leaches. At the same time, a significant amount (from 10 to 30 g / dm ³ ) of ferric iron and 1-3 g / dm ³ aluminum, which must be removed for iron cleaning operations using limestone, calcium oxide, magnesium, brucite, dolomite at pH values in the range of 3.5-4.5. This, in turn, entails additional technological operations for separating the formed solid phase from the nickel-containing productive solution and its storage, which presents significant difficulties, and the removal of productive solutions at a pH of not more than 1.0 further aggravates this situation.

The problem to which the invention is directed, is the development of a method for underground leaching of oxidized nickel-cobalt ores.

The technical result of the proposed technical solution is to reduce the cost of leaching nickel-cobalt ores at the site and improving the environmental situation at the place of work.

The technical result is achieved by the fact that the ore body to be mined is divided into ore blocks and worked out sequentially, injection and pumping openings are arranged crosswise to the movement of groundwater, while the production of nickel-cobalt production solutions is pumped out in the pH range, ensuring precipitation in the bowels of the ballast impurities transferred into the solution, represented mainly by iron and aluminum ions. In the event that the pH of the production solution decreases below the hydrate formation of ballast impurities, the pumping is transferred to new neighboring pumping excavations located on and against the groundwater flow, while the previously used pumping excavations are used as observational, and when nickel and substandard contents appear in the latter cobalt injection is transferred to them.

When mining the ore block adjacent to the barren zone, pumping excavations are located in the latter.

A variant of the method is the construction in the barren zone of a system of injection and pumping openings or an oreless pile of rock on the surface and, accordingly, the supply and pumping of production nickel-cobalt solution from them for subsequent redistribution.

At the final stage, water washing of the worked blocks is carried out.

The proposed method is as follows.

The deposit of oxidized nickel-cobalt ores to be mined is divided into ore blocks and drilled with a system of injection and pumping openings located across the groundwater flow, a solution of sulfuric acid is pumped into the pumping openings, and a production solution is pumped to the surface whose pH is greater than the hydroformation of the main ballast impurities to the appearance of solutions with a lower pH of their hydrate formation. This is due to the fact that at appropriate pH values, ballast impurities precipitate, forming metal hydroxides, while nickel and cobalt remain in solution even at pH values of 7.0-8.0.

This allows, by controlling and maintaining the optimum pH of the production solution pumped to the surface, to clear it of ballast impurities, which significantly complicate its further processing, simplify the technological scheme and avoid the construction of a sludge storage facility for collecting and storing ballast impurities.

As leaching occurs, the pH of the production solution decreases, and when it reaches its corresponding values, the content of ballast impurities increases, thereby deteriorating the quality indicators of the production solution. This leads to the need to transfer the pumping to new adjacent pumping excavations, and the previously used pumping excavations should be used as observational ones to control the completeness of mining of the leached part of the ore block.

When substandard nickel and cobalt contents appear in these observational mines, this part of the ore block is considered to be spent and the leachate solution is transferred to them.

When mining the ore block adjacent to the contour of the field, pumping wells are built in its barren zone. The transfer of pumping openings to a new place with a decrease in the pH of the product solution is less than the pH of hydrate formation of ballast impurities is carried out both in the direction of groundwater flow and in the opposite direction. At the same time, both directions are used simultaneously to accelerate field development.

To compensate for the excess acidity of the production solutions, it is possible to use enclosing (barren) rocks with increased reagent capacity. For this purpose, the barren zone of the field is drilled with injection and pumping mine systems and production solutions are supplied to the injection workings, the pH of which is less than the pH of hydrate formation of ballast impurities from any stage of leaching of the processed block of the field. The purified solutions from the pumping openings are fed for processing.

A similar option for the extinction of acidity by a production solution is the use of barren rocks built on the surface of stacks. The product solutions pumped from the ore block are fed to the barren stack by known methods, the purified production solutions are collected and sent from its lower part for processing.

At the end of the mining of the ore block, the sorbed nickel and cobalt rocks are washed using acidified groundwater with a pH in the range 2.0-3.0.

The possibility of implementing the proposed technical solution is illustrated by the arrangement of rows of injection and pumping openings in the process of underground leaching and examples explaining the possibility of implementing the claimed process parameters.

Figures 1-6 show the schematic diagrams of successive changes in the purpose of the rows of injection and pumping mine workings of ore blocks located opposite and against the movement of groundwater, depending on the pH and the content of nickel and cobalt in the production solution during leaching, as well as possible schemes for reducing acidity production solutions and their conditioning.

), откачных (

) и невовлеченных в отработку новых (

) выработок при кондиционных содержаниях никеля и кобальта и величине pH продукционного раствора в выработках ряда 2 не менее 3,0.Figure 1 - Location of injection (

), pumping (

) and not involved in the development of new (

) workings at conditioned contents of nickel and cobalt and the pH of the production solution in workings of row 2 not less than 3.0.

), откачных (

) и наблюдательных (

) выработок при величине pH продукционного раствора в выработках ряда 2 менее 3,0.Figure 2 - Location of injection (

), pumping (

) and observational (

) workings when the pH of the production solution in the workings of row 2 is less than 3.0.

), откачных (

) и выведенных из отработки закачных (

) выработок при появлении в выработках ряда 2 некондиционных содержаний по никелю и кобальту.Figure 3 - Location of injection (

), pumping (

) and withdrawn from mining injection (

) workings when a number of 2 substandard contents of nickel and cobalt appear in the workings.

), откачных (

) и выведенных из отработки закачных (

) выработок смежного с контуром месторождения рудного блока при появлении в наблюдательных выработках (

) некондиционных содержаний по никелю и кобальту.Figure 4 - Location of injection (

), pumping (

) and withdrawn from mining injection (

) the workings of the ore block adjacent to the contour of the deposit when it appears in the observational workings (

) substandard nickel and cobalt contents.

) и откачных (

) выработок при величине pH продукционного раствора в откачном ряду 2 менее 3,0.Figure 5 - Location of injection (

) and pumping (

) workings when the pH of the production solution in the pumping row 2 is less than 3.0.

) и откачных (

) выработок и безрудного штабеля при величине pH продукционного раствора в откачном ряду 2 менее 3,0.Figure 6 - Location of injection (

) and pumping (

) workings and barren stack at a pH of the production solution in the pumping row 2 less than 3.0.

The dependence of the content of Nickel, iron and aluminum on the pH of the production solution is illustrated in example 1.

Example 1

The initial production solution obtained by leaching of oxidized nickel ore and containing, g / l: Ni - 1.9; Co - 0.02; Fe - 4.6; Al - 1.2; pH and Eh values of 1.2 and 600 mV, respectively, were treated with limestone while stirring on a magnetic stirrer. In the process of neutralizing acidity, pH and Eh were measured, samples were taken and analyzed. The determination results are presented in table 1.

Table 1 The dependence of the content of Ni, Co, Fe, Al in the production solution on the pH Content, g / l PH value 1,2 2.0 2,5 3.0 4.0 4,5 6.0 7.0 Ni 1.90 1.90 1.90 1.89 1.89 1.89 1.87 1.86 Co 0.02 0.02 0.02 0.02 0.02 0.019 0.019 0.017 Fe ³⁺ 4.60 3.80 2.60 0.04 0.04 0.009 0.00 0.00 Al 1.20 1.20 1.10 0.20 0.15 0.10 0.01 0.01 Eh, mV 630 614 562 451 373 356 284 154

As can be seen from the data in table 1, at a pH in the range of 3.0-7.0, the nickel and cobalt contents practically do not change, and the contents of iron and aluminum (the main ballast impurities) are reduced to values that allow nickel and cobalt to be extracted by known methods with high economic indicators.

A similar picture (the neutralization process) is observed during underground leaching during the movement of leaching solutions from injection to pumping out. When the pH of the product solution appears in the pumping unit less than 3.0, accompanied by a significant increase in the iron and aluminum contents (the main elements that interfere with the process of processing solutions), pumping is carried out from new pumping units, which makes it possible to increase the pH value of the recovered product solution and clean it from interfering impurities.

The possibility of neutralizing production solutions by filtering them through barren host rocks, provided that nickel and cobalt are retained in the solution by underground leaching of oxidized nickel-cobalt ores, is illustrated in Example 2.

Example 2

Aliquots of a production solution containing, g / l: Ni - 1.9; were added to sample samples of barren host rock weighing 100 g each; Co - 0.02; Fe - 4.6; Al - 1.2 to W: T = 5, 10 and 15. The initial pH of the production solution was 1.4, 2.0 and 2.5. Contact time - 10, 20 and 40 days with periodic stirring. After each period of time, the nickel and cobalt contents were determined, and the pH and Eh of the solution were measured. The determination results are shown in table 2.

table 2 The results of changes in the contents of Nickel and cobalt in the solution depending on the initial pH of the solution and the value of W: T PH initial value Indicator Time, day 10 twenty 40 W: T = 5 1.4 Ni, g / l 2,145 2,014 1,994 Co, g / l 0,022 0,023 0.019 pH 2.6 3.37 3.68 Eh, mV 542 511 438 2.0 Ni, g / l 2,103 2,003 1,946 Co, g / l 0,021 0,020 0.019 pH 2.82 3.82 3,821 Eh, mV 530 472 426 2,5 Ni, g / l 1,969 1,942 1,923 Co, g / l 0,021 0,020 0.019 pH 3.10 4.02 4.28 Eh, mV 498 461 4.17 W: T = 10 1.4 Ni, g / l 2,278 2,052 2,008 PH initial value Indicator Time, day 10 twenty 40 Co, g / l 0.024 0,023 0,021 pH 2,37 2.92 3.00 Eh, mV 564 528 448 2.0 Ni, g / l 2,278 2,031 1,975 Co, g / l 0.024 0,021 0,021 pH 2.72 3.36 3,58 Eh, mV 571 484 444 2,5 Ni, g / l 1,984 1,966 1,940 Co, g / l 0,023 0,022 0,021 pH 2.92 3.81 4.01 Eh, mV 540 488 429 W: T = 15 1.4 Ni, g / l 2,296 2,135 2,027 Co, g / l 0,026 0,026 0.024 pH 2.27 2.74 2.89 Eh, mV 612 598 530 2.0 Ni, g / l 2,286 2,061 1,985 Co, g / l 0,026 0.024 0,023 PH initial value Indicator Time, day 10 twenty 40 pH 2.64 3.12 3.20 Eh, mV 598 496 487 Ni, g / l 1,996 2,000 1,961 2,5 Co, g / l 0,026 0,025 0.024 pH 2.75 2.94 3.40 Eh, mV 592 498 469

As can be seen from the data in Table 2, for almost all initial pH values of the production solutions and W: T values after their contact with the barren host rock represented by serpentinite, the pH values reach 3.0 or more with additional extraction of nickel. In this case, the production solutions are cleaned of the main impurities that interfere with the processing process - iron and aluminum.

Next, a sample of barren host rock after contact with the production solution for 30 days according to example 2 was divided into liquid and solid phases. The solid phase was treated acidified to pH = 2.0 with formation water containing no nickel and cobalt at a ratio of W: T = 2.0. The content of nickel, cobalt, iron, aluminum in the solution, respectively, amounted to, g / l: Ni - 0.842; Co - 0.084; Fe - 0.044; Al - 0.023. As can be seen from the results of the analysis, carrying out a washing operation with acidified water with a pH value of 2.0 at the final stage of leaching makes it possible to extract additional nickel and cobalt and improve the environmental situation at the work site. A similar result was obtained using acidified water to a pH value of 3.0.

The same picture is observed in the case of neutralization of production solutions with a pH value of less than 3.0 by passing them through an oreless rock stack built on the surface.

Thus, the above schemes for mining a deposit of oxidized nickel-cobalt ores and examples of the implementation of the claimed process parameters show the advantages and feasibility of the proposed method for leaching oxidized nickel-cobalt ores.

Claims (7)

1. A method of underground leaching of oxidized nickel-cobalt ores, including opening the ore body with a system of injection and pumping openings, feeding the leach solution to the pumping openings, lifting the production solution through the pumping openings and processing it, characterized in that the deposit is divided into ore blocks and sequentially work out, while the pumping and injection workings are arranged across the groundwater movement and pump out the nickel-cobalt-containing solution in the pH range, providing drop in the pellet in the interior transferred into solution in the leaching of impurities ballast represented mainly ions of iron and aluminum. 2. The method according to claim 1, characterized in that when the pH of the production solution is less than the pH of hydrate formation of ballast impurities, its pumping is transferred to new pumping excavations located on and against the groundwater flow, and previously used pumping excavations are used as observational ones. 3. The method according to claim 1, characterized in that when mining the ore block adjacent to the contour of the deposit, the pumping excavations are located in the barren zone. 4. The method according to claim 1, characterized in that when the pH of the production solution is less than the pH of hydrate formation of ballast impurities, it is supplied to the injection workings and the subsequent rise from the pumping workings located in the barren zone. 5. The method according to claim 1, characterized in that when the value of the production solution is less than the pH of hydrate formation of ballast impurities, it is fed to an barren stack with subsequent processing of the solutions filtered through it. 6. The method according to claim 1, characterized in that at the end of the mining of ore blocks, they are washed with formation water at a pH in the range of 2.0-3.0. 7. The method according to claim 2, characterized in that when the substandard contents of nickel and cobalt appear in the observational workings, the injection of the leach solution is transferred to the latter.

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