A method for determining the leachability of coarse-grained wide-grade gold-bearing ores

Abstract

The present invention relates to a method for determining the leachability of coarse-grained, wide-grade gold-bearing ore. The method comprises the following steps: screening the coarse-grained, wide-grade gold-bearing ore into several narrow-grade materials; cyaniding the finest-grade material using mechanical agitation; and cyaniding the remaining grade materials using a percolation column. Cyanidated tailings from each grade are then individually pulverized and analyzed, or combined and pulverized for gold grade analysis. This method avoids the drawback of inaccurate measurement results caused by unnecessary pulverization of coarse-grained material, which exposes encapsulated gold. The method is simple, easy to operate, and produces accurate and reliable measurement results, making it more useful for guiding heap leaching experiments and technical evaluations.

Description

Technical Field

[0001] The invention belongs to the technical field of heap leaching gold, and in particular relates to a method for measuring the leachability of coarse-grained and wide-grade gold-containing ores. Background Art

[0002] Heap leaching involves stacking gold-bearing ore on an impermeable pad and leaching it through a sodium cyanide solution. The basic reaction equation for gold in an oxygen-containing sodium cyanide solution is: 4Au + 8NaCN + O₂ + 2H₂O = 4NaAu(CN)₂ + 4NaOH. In recent decades, heap leaching has gained widespread industrial application worldwide. To determine the economic feasibility of heap leaching of gold-bearing ore, a technical indicator of cyanide-leachable gold content is essential. Laboratories typically conduct column leaching tests and bottle tests to determine this indicator. The column leaching test is to place a certain amount of ore, water and lime in a plexiglass or plastic percolation column, and then use sodium cyanide solution to drip the ore pile at an intensity of 8L / (m2·h) to 20L / (m2·h) to cause it to penetrate and leach downward. The column leaching test can best simulate heap leaching industrial production and can obtain leachability indicators similar to those of industrial production. However, the column leaching test and heap leaching industrial production also have the problem of slow gold leaching rate due to "static" leaching. The leaching cycle is usually 60d to 150d, or even longer. In addition, during the column leaching experiment, the coarse and fine particles of wide-grade materials in the percolation column are very likely to separate and aggregate separately, which is the particle size segregation phenomenon. This not only affects the leaching rate of gold in fine-particle materials, but in severe cases, it may lead to low leachability indicators. The bottle roller test involves rolling a certain amount of ore with water, lime, and sodium cyanide solution on a drum machine for cyanide leaching. The leaching process generally ends in 72 hours. This experiment can provide an indicator of the ore's leachability quite quickly. However, during the test, there is rolling, impact, and abrasion between ore particles. Coarse-grained ore may crack or even be crushed into fine-grained ore, which promotes the exposure of gold encapsulated in the ore. This situation does not occur in heap leaching, so the gold leaching rate in the bottle roller test is often higher than the actual one. Summary of the Invention

[0003] The present invention provides a method for measuring the leachability of coarse-grained and wide-grade gold-containing ores, and aims to solve the technical problem of long test cycle and inaccurate measurement results in column leaching test and bottle rolling test respectively when measuring the leachability index of gold ores.

[0004] In order to solve the above technical problems, the present invention provides a method for determining the leachability of coarse-grained and wide-grade gold-bearing ore, which is characterized by comprising the following steps:

[0005] Step 1: crush the gold-bearing ore to a certain particle size, then mix and reduce it to produce several identical coarse-grained and wide-grade materials;

[0006] Step 2: The coarse-grained wide-grade material obtained in step 1 is screened into several narrow-grade materials. The particle size classification is less than 0.15 mm, 0.15-2.0 mm, 2.0-5.0 mm, 5.0-10.0 mm, and greater than 10.0 mm. The weighing yield of each particle size is calculated as γ i , the gold grade of each particle size material is β i , where i is 1-5, corresponding to the five particle sizes of screening;

[0007] Step 3: Screening the other wide-grade material obtained in step 1 into narrow-grade materials that are exactly the same as those in step 2, wherein the narrow-grade materials smaller than 0.15 mm are stirred in a stirring tank for cyanide leaching, and the narrow-grade materials of 0.15-2.0 mm, 2.0-5.0 mm, 5.0-10.0 mm, and larger than 10.0 mm are leached by filtration in a set of serially connected filtration columns;

[0008] Step 4: Filter, dry, crush, sample and assay the gold grade of each level of cyanide tailings in step 3. i ;

[0009] Step 5: Gold ore grade β 原 =Σγ i β i , tailings gradeζ 尾 =Σγ i ζ i According to the gold leaching rate formula ε = (1-ζ / β) × 100%, the gold ore leachability index is obtained.

[0010] Beneficial effects: The present invention has the following advantages: (1) the coarse-grained and wide-grade gold-containing ores are screened and graded, and the materials with a particle size of less than 0.15 mm are leached with gold by stirring, and the materials with a particle size of greater than 0.15 mm are leached with gold by cyanidation in a percolation column, thereby avoiding the occurrence of particle size segregation and preventing the aggregation of fine-grained materials, so that the gold in all materials can fully contact the sodium cyanide solution; (2) pure oxygen is mixed with the sodium cyanide solution in the form of micron bubbles, and the micron bubbles greatly increase the solubility of oxygen in water due to the self-pressurized dissolution characteristics, and the micron bubbles are matched and adapted to the cyanide concentration in the solution, and together promote the dissolution rate of gold to reach a maximum value; (3) the fast-flowing cyanide solution is used for percolation leaching of gold, and the cross-sectional area of the ore dripping intensity reaches 3000L / (m 2 ·h)~12000L / (m 2h), which is 300 to 1000 times that of column leaching tests and heap leaching industrial production. This not only avoids unnecessary crushing of coarse-grained ore, but also increases the relative velocity V between the cyanide solution and the gold surface, thereby accelerating the dissolution rate of gold. (4) The gold leachability index of multiple narrow-grade materials of coarse-grained gold-containing ore with a wide range of grades can be obtained simultaneously, which is more conducive to the research and analysis of the ore. Therefore, the test cycle of the present invention is short, the measurement results are accurate and reliable, and it is more conducive to guiding technical evaluation and heap leaching production. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram of the structure of the end cover used in the present invention;

[0012] Figure 2 It is a schematic diagram of the process of the present invention.

[0013] Among them: 1-conduit, 2-outer end cover, 3-bolt, 4-nylon screen, 5-rubber ring, 6-inner end cover, 7-plexiglass column. DETAILED DESCRIPTION

[0014] In order to make the purpose, content and advantages of the present invention more clear, the specific embodiments of the present invention are further described in detail below.

[0015] The present invention provides a method for determining the leachability of a coarse-grained, wide-grade gold-bearing ore, comprising the following steps:

[0016] Step 1: crush the gold-bearing ore to a certain particle size, then mix and reduce it to produce several identical coarse-grained and wide-grade materials;

[0017] Step 2: The coarse-grained wide-grade material obtained in step 1 is screened into several narrow-grade materials. The preferred particle size classifications are less than 0.15 mm, 0.15-2.0 mm, 2.0-5.0 mm, 5.0-10.0 mm, and greater than 10.0 mm. The weighing yield of each particle size is calculated as γ i , crushing, sampling and gold grade testing of each particle size i , where i is 1-5, corresponding to the five particle sizes of screening;

[0018] Step 3: Screening the other wide-grade material obtained in step 1 into narrow-grade materials that are exactly the same as those in step 2, wherein the narrow-grade materials smaller than 0.15 mm are stirred in a stirring tank for cyanide leaching, and the narrow-grade materials of 0.15-2.0 mm, 2.0-5.0 mm, 5.0-10.0 mm, and larger than 10.0 mm are leached by filtration in a set of serially connected filtration columns;

[0019] Step 4: Filter, dry, crush, sample and assay the gold grade of each level of cyanide tailings in step 3. i ;

[0020] Step 5: Gold ore grade β 原 =Σγ i β i , tailings gradeζ 尾 =Σγ i ζ i According to the gold leaching rate formula ε = (1-ζ / β) × 100%, the gold ore leachability index is obtained.

[0021] In the step 3, the gold is leached by stirring with cyanide, the slurry mass concentration is 33% to 40%, the slurry pH is 9.5 to 11.0, the activated carbon density is 10 g / L to 20 g / L, the sodium cyanide concentration is 0.5 g / L to 1.5 g / L, and the cyanide leaching time is 12 h to 36 h. The stirring intensity is preferably such that the slurry can move normally without precipitation.

[0022] In the step three, the filtration column has a diameter of 100mm to 150mm and a length of 200mm to 300mm. Two end caps with a thickness of 5mm are provided at each end of the filtration column. The inner end cap is covered with pores with a diameter of 2mm penetrating the end cap. A catheter interface with a diameter of 10mm is provided in the center of the outer end cap. A nylon screen with an aperture of 0.1mm is provided between the inner end cap and the outer end cap. The filtration column, the end cap and the nylon screen are sealed with bolts and rubber rings. The filtration columns are connected by 10mm diameter PVC pipes.

[0023] In step 3, the gold is leached by diafiltration cyanide. The pH of the sodium cyanide solution is 9.5-11.0, the sodium cyanide concentration is 0.5g / L-1.5g / L, and the sodium cyanide solution is pumped into the micron bubble generator at a flow rate of 50L / h-200L / h and oxygen at a flow rate of 5L / h-20L / h. The oxygen-enriched sodium cyanide solution is sprayed out from the nozzle and flows sequentially through a series of diafiltration columns containing four narrow-grade materials and one activated carbon, and finally returns to the sodium cyanide solution storage tank for cyclic diafiltration cyanide leaching. The cyanide leaching time is 120h-240h. It should be noted that if the amount of material in a certain particle size grade is too large, two diafiltration columns can be used for packaging in series.

[0024] Dissolution rate of gold in cyanide solution Where: D CN- and D O2 is the diffusion coefficient of dissolved cyanide and oxygen, cm 2 / s;[CN - ] and [O2] are CN in cyanide solution - and O2 concentration, M; A is the total contact area between cyanide solution and gold, cm 2 ; δ is the thickness of the Nernst interface layer, cm.

[0025] When CN in cyanide solution is increased -and O2 concentration, and maintain D CN- [CN - ]=4D O2 [O2], the gold dissolution rate reaches its limit. The Nernst interface layer thickness δ depends on the relative velocity V between the cyanide solution and the gold surface. When the relative velocity V is high, the interface layer thickness δ becomes thinner, while when the relative velocity V is low, the interface layer thickness δ becomes thicker. The slow gold leaching rate in the column leaching test is precisely due to the low relative velocity V between the cyanide solution and the gold surface.

[0026] There is a gas-liquid interface around the bubbles in the solution. The gas-liquid interface will cause the bubbles to be affected by the surface tension of the liquid. The dissolution of bubbles in the solution is a process in which the bubbles gradually shrink. According to Young-Laplace P=2γ / R, where P represents the interface pressure, γ represents the surface tension, and R represents the bubble diameter, it can be seen that the increase in pressure will increase the dissolution rate of the gas. With the increase in specific surface area, the speed of bubble shrinkage becomes faster and faster, and eventually the bubbles dissolve into the solution.

[0027] Example 1

[0028] Step 1: crush the gold-bearing ore to a maximum particle size of 20.0 mm, then mix and reduce it to produce several portions (30 kg each) of identical coarse-grained and wide-grade materials;

[0029] Step 2: The coarse-grained wide-grade material obtained in step 1 is screened into several narrow-grade materials. The preferred particle size classifications are less than 0.15 mm, 0.15-2.0 mm, 2.0-5.0 mm, 5.0-10.0 mm, and greater than 10.0 mm. The weighing yield of each particle size is calculated as γ i , crushing, sampling and gold grade testing of each particle size i , where i is 1-5, corresponding to the five particle sizes of screening;

[0030] Step 3: Screening the other wide-grade material obtained in step 1 into narrow-grade materials that are exactly the same as those in step 2, wherein the narrow-grade materials smaller than 0.15 mm are stirred in a stirring tank for cyanide leaching, and the narrow-grade materials of 0.15-2.0 mm, 2.0-5.0 mm, 5.0-10.0 mm, and larger than 10.0 mm are leached by filtration in a set of serially connected filtration columns;

[0031] Step 4: Filter, dry, crush, sample and assay the gold grade of each level of cyanide tailings in step 3. i ;

[0032] Step 5: Gold ore grade β original = Σγ i β i , tailings grade ζtail = Σγ i ζ iAccording to the gold leaching rate formula ε = (1-ζ / β) × 100%, the gold ore leachability index is obtained.

[0033] In the step 3, the gold is leached by stirring with cyanide, the slurry mass concentration is 33%, the slurry pH is 9.5, the activated carbon density is 20 g / L, the sodium cyanide concentration is 0.5 g / L, and the cyanide leaching time is 36 hours. The stirring intensity is preferably such that the slurry can move normally without precipitation.

[0034] In the step three, the filtration column has a diameter of 150 mm and a length of 300 mm. Two end caps with a thickness of 5 mm are provided at each end of the filtration column. The inner end cap is covered with pores with a diameter of 2 mm penetrating the end cap. A catheter interface with a diameter of 10 mm is provided in the center of the outer end cap. A nylon screen with an aperture of 0.1 mm is provided between the inner end cap and the outer end cap. The filtration column, the end cap and the nylon screen are sealed with bolts and rubber rings, and the filtration columns are connected by a 10 mm diameter PVC pipe.

[0035] In the step 3, the gold is leached by diafiltration cyanide, 30 L of sodium cyanide solution, the solution pH is 9.5, the initial sodium cyanide concentration is 1.0 g / L, the sodium cyanide solution is pumped into the micron bubble generator at a flow rate of 150 L / h and oxygen at a flow rate of 150 L / h, the oxygen-enriched sodium cyanide solution is sprayed out from the nozzle and flows sequentially through a series diafiltration column group containing five narrow-grade materials and one activated carbon, and finally returns to the sodium cyanide solution storage tank for cyclic diafiltration cyanide leaching, and the cyanide leaching time is 150 hours.

[0036] Three comparative experiments were conducted on a gold-bearing ore. The first group used the method described in Example 1; the second group used a conventional column leaching test. The experimental conditions were as follows: 30 kg of a coarse-grained, wide-grade material identical to that in Example 1 was evenly distributed in a filtration column with a diameter of 200 mm and a height of 800 mm, along with 30 g of lime. A sodium cyanide solution with an initial concentration of 1.5 g / L and a volume of 20 L was used at a rate of 12 L / (m 2 The cyanide tailings were filtered, washed, dried, pulverized, and sampled for gold grade analysis. A third group performed a conventional roller bottle test under the following conditions: 30 kg of the same coarse-grained, wide-grade material as in Example 1, along with 30 L of water, 30 g of lime, and 30 g of sodium cyanide, were placed in a drum with a diameter of 400 mm and a length of 400 mm and subjected to rolling cyanide leaching for 48 hours. The cyanide tailings were then filtered, washed, dried, pulverized, and sampled for gold grade analysis. The comparative experimental results are shown in Table 1.

[0037] Table 1 Leachability index of a gold-bearing ore in Guizhou

[0038]

[0039] Example 2

[0040] Step 1: crush the gold-bearing ore to a maximum particle size of 15.0 mm, then mix and reduce it to produce several portions (20 kg each) of identical coarse-grained and wide-grade materials;

[0041] Step 2: The coarse-grained wide-grade material obtained in step 1 is screened into several narrow-grade materials. The preferred particle size classifications are less than 0.15 mm, 0.15-2.0 mm, 2.0-5.0 mm, 5.0-10.0 mm, and greater than 10.0 mm. The weighing yield of each particle size is calculated as γ i , crushing, sampling and gold grade testing of each particle size i , where i is 1-5, corresponding to the five particle sizes of screening;

[0042] Step 3: Screening the other wide-grade material obtained in step 1 into narrow-grade materials that are exactly the same as those in step 2, wherein the narrow-grade materials smaller than 0.15 mm are stirred in a stirring tank for cyanide leaching, and the narrow-grade materials of 0.15-2.0 mm, 2.0-5.0 mm, 5.0-10.0 mm, and larger than 10.0 mm are leached by filtration in a set of serially connected filtration columns;

[0043] Step 4: Filter, dry, crush, sample and assay the gold grade of each level of cyanide tailings in step 3. i ;

[0044] Step 5: Gold ore grade β original = Σγ i β i , tailings grade ζtail = Σγ i ζ i According to the gold leaching rate formula ε = (1-ζ / β) × 100%, the gold ore leachability index is obtained.

[0045] In the step 3, the gold is leached by stirring with cyanide, the slurry mass concentration is 40%, the slurry pH is 11.0, the activated carbon density is 10 g / L, the sodium cyanide concentration is 1.5 g / L, and the cyanide leaching time is 12 hours. The stirring intensity is preferably such that the slurry can move normally without precipitation.

[0046] In the step three, the filtration column has a diameter of 100 mm and a length of 200 mm. Two end caps with a thickness of 5 mm are provided at each end of the filtration column. The inner end cap is covered with pores with a diameter of 2 mm penetrating the end cap. A catheter interface with a diameter of 10 mm is provided in the center of the outer end cap. A nylon screen with an aperture of 0.1 mm is provided between the inner end cap and the outer end cap. The filtration column, the end cap and the nylon screen are sealed with bolts and rubber rings. The filtration columns are connected by 10 mm diameter PVC pipes.

[0047] In the step 3, the gold is leached by diafiltration cyanide, 25 L of sodium cyanide solution, the solution pH is 11.0, and the initial sodium cyanide concentration is 0.8 g / L. The sodium cyanide solution is pumped into the micron bubble generator at a flow rate of 50 L / h and oxygen at a flow rate of 5 L / h. The oxygen-enriched sodium cyanide solution is sprayed out from the nozzle and flows sequentially through a series diafiltration column group containing five narrow-grade materials and one activated carbon, and finally returns to the sodium cyanide solution storage tank for cyclic diafiltration cyanide leaching. The cyanide leaching time is 240 hours.

[0048] Three comparative experiments were conducted on a gold-bearing ore. The first group used the method described in Example 1; the second group used a conventional column leaching test. The experimental conditions were as follows: 20 kg of a coarse-grained, wide-grade material identical to that in Example 1 was evenly distributed in a filtration column with a diameter of 200 mm and a height of 600 mm, along with 20 g of lime. A sodium cyanide solution with an initial concentration of 2.0 g / L and a volume of 10 L was used at a rate of 10 L / (m 2 The cyanide tailings were filtered, washed, dried, pulverized, and sampled for gold grade analysis. A third group conducted a conventional roller bottle test under the following conditions: 20 kg of the same coarse-grained, wide-grade material as in Example 1, along with 20 L of water, 20 g of lime, and 20 g of sodium cyanide, were placed in a drum 350 mm in diameter and 350 mm in length and subjected to rolling cyanide leaching for 36 hours. The cyanide tailings were then filtered, washed, dried, pulverized, and sampled for gold grade analysis. The comparative experimental results are shown in Table 2.

[0049] Table 2 Leachability index of a gold-bearing ore in Inner Mongolia

[0050]

[0051] The method of the present invention used in the above-mentioned embodiment has a shorter test period than the column leaching test, and provides more accurate and reliable measurement results than the bottle rolling test. It also obtains multiple gold leachability indices for narrow grade materials, which is more conducive to guiding technical evaluation and heap leaching production.

[0052] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for determining the leachability of coarse-grained, wide-grade gold-bearing ores, characterized in that: The following steps are involved: Step 1: crush the gold-bearing ore to a certain particle size, then mix and reduce it to produce several identical coarse-grained and wide-grade materials; Step 2: The coarse-grained wide-grade material obtained in step 1 is screened into several narrow-grade materials. The particle size classification is less than 0.15 mm, 0.15-2.0 mm, 2.0-5.0 mm, 5.0-10.0 mm, and greater than 10.0 mm. The weighing yield of each particle size is calculated as γ i , the gold grade of each particle size material is β i , where i is 1-5, corresponding to the five particle sizes of screening; Step 3: Screening the other wide-grade material obtained in step 1 into narrow-grade materials that are exactly the same as those in step 2, wherein the narrow-grade materials smaller than 0.15 mm are stirred in a stirring tank for cyanide leaching, and the narrow-grade materials of 0.15-2.0 mm, 2.0-5.0 mm, 5.0-10.0 mm, and larger than 10.0 mm are leached by filtration in a set of serially connected filtration columns; Stirring cyanide leaching of gold, the slurry mass concentration is 33% to 40%, the slurry pH is 9.5 to 11.0, the activated carbon density is 10g / L to 20g / L, the sodium cyanide concentration is 0.5g / L to 1.5g / L, the cyanide leaching time is 12h to 36h, and the stirring intensity is suitable for the slurry to move normally without precipitation; Step 4: Filter, dry, crush, sample and assay the gold grade of each level of cyanide tailings in step 3. i ; Step 5: Gold ore grade β 原 =Σγ i β i , tailings gradeζ 尾 =Σγ i ζ i According to the gold leaching rate formula ε=(1-ζ 尾 / β 原 ) × 100%, and obtain the gold-bearing ore leachability index.

2. The method for determining the leachability of coarse-grained, wide-grade gold-bearing ore according to claim 1, characterized in that: The filtration columns were connected by 10 mm diameter PVC tubes.

3. The method for determining the leachability of coarse-grained, wide-grade gold-bearing ore according to claim 1, characterized in that: The filtration column in step three has a diameter of 100 mm to 150 mm and a length of 200 mm to 300 mm.

4. The method for determining the leachability of coarse-grained, wide-grade gold-bearing ores according to claim 3, characterized in that: Two layers of end caps are provided at each end of the filtration column. The inner end cap is covered with pores penetrating the end cap, a catheter interface is provided at the center of the outer end cap, and a nylon screen is provided between the inner and outer end caps.

5. The method for determining the leachability of coarse-grained, wide-grade gold-bearing ore according to claim 1, characterized in that: In step 3, the pH of the sodium cyanide solution is 9.5 to 11.0, the concentration of sodium cyanide is 0.5 g / L to 1.5 g / L, the sodium cyanide solution is pumped into the micron bubble generator at a flow rate of 50 L / h to 200 L / h and oxygen at a flow rate of 5 L / h to 20 L / h, the oxygen-enriched sodium cyanide solution is sprayed out from the nozzle and flows through a series filtration column group containing four narrow-grade materials and an activated carbon in sequence, and finally returns to the sodium cyanide solution storage tank for cyclic filtration cyanide leaching. The cyanide leaching time is 120 h to 240 h.

6. The method for determining the leachability of coarse-grained, wide-grade gold-bearing ores according to claim 5, characterized in that: If the amount of material at a certain particle size level is too large, two filtration columns can be used for packaging and connected in series.

Images