JP7754741B2 - Flotation Method - Google Patents

Description

This specification describes a flotation method for pulp mixed with ore containing copper minerals.

Flotation is used to separate copper minerals from ore containing copper minerals. In this method, ore that has been pulverized in a previous process is mixed with a liquid such as water to form a pulp (sludge), and this pulp is stored in the flotation cell of a flotation device. A foaming agent to form a froth, a collector to float only the desired minerals, a pH adjuster, and other chemicals are then added to the pulp in the flotation cell and stirred. This causes the froth to rise, carrying with it the desired minerals, such as copper minerals. The desired minerals that have risen to the surface are then recovered by overflowing the flotation cell along with the froth.

The timing of froth recovery after flotation begins and the amount recovered are typically managed by workers visually observing the properties of the froth that has risen to the pulp surface and checking measurement data such as the height position of the pulp surface and the height position of the froth on the pulp surface. Based on such worker judgment, flotation operations are generally managed to recover as much copper mineral as possible and to obtain higher-grade copper concentrate.

On the other hand, Patent Document 1 describes the use of a camera and image analysis system as a detector to measure the speed at which the froth overflows from the flotation cell. Furthermore, Patent Document 1 states that there is a correlation between the froth height and the supply gas flow rate to the flotation cell, and between the froth velocity and the supply gas flow rate, and that this correlation is used to calculate the optimal supply gas flow rate.

US Patent Application Publication No. 2014/0110311

Flotation operation management relies on the visual inspection and judgment of workers, so there is concern that responses will vary depending on the worker, especially when the properties of the froth change, making standardization difficult.

Patent Document 1 describes a camera and image analysis system for detecting froth overflow, but it is difficult to say that such cameras are being used effectively in actual operations. Furthermore, since the properties of froth vary depending on the type of ore, it cannot be said that simply using a camera is enough to enable operational management.

This specification provides a flotation method that allows for effective management of flotation operations for ores containing copper minerals.

The above-mentioned flotation method is a flotation method for pulp mixed with ore containing copper minerals, and includes acquiring image information of the froth formed on the pulp surface and managing the flotation operation using the color values of the froth in the L ^* a ^* b ^* color space obtained from the image information , and using ore having a quartz content of 50% by weight or more as the ore .

The above-described flotation method allows for effective management of flotation operations for ores containing copper minerals.

FIG. 1 is a perspective view showing an example of a flotation device that can be used in an ore flotation method according to one embodiment. 2 is a schematic cross-sectional view showing two of the plurality of flotation cells provided in the flotation apparatus of FIG. 1. FIG. 1 is a diagram illustrating an example of actual operation management. 1 is a graph showing the relationship between the color value and the copper grade of a specific ore (sample A) in an example. 1 is a graph showing the relationship between color value and copper recovery rate for a given ore (Sample A) of an example. 1 is a graph showing the color value and copper recovery rate 10 minutes after the start of flotation before brightness adjustment in an example. 1 is a graph showing the color value and copper recovery rate 10 minutes after the start of flotation after brightness adjustment in an example. 1 is a graph showing the relationship between color value and copper grade when another ore (sample B) is used in an example. 1 is a graph showing the relationship between the proportion of Quartz in ore and the flotation rate.

Hereinafter, an embodiment of the above-mentioned flotation method will be described in detail.
One embodiment of the flotation method includes performing flotation on pulp mixed with ore containing copper minerals, acquiring image information of the froth formed on the pulp surface, and managing the flotation operation using the color values of the froth in the L ^* a ^* b ^* color space obtained from the image information.

This is based on the new finding that for ores containing copper minerals, particularly primary copper sulfide ores in which silicon content does not substantially float during flotation, there is a correlation between the color values of the froth in the L ^* a ^* b ^* color space in the froth image information and the copper content of the ore in the froth that has risen to the pulp surface (liquid surface). By utilizing this fact and determining the time and amount of froth recovery based on the color values in the froth image information, flotation operations can be managed more effectively than when relying on the visual inspection and judgment of workers. Furthermore, effective management of flotation operations may improve copper recovery rates, allowing for more effective use of mineral resources.

(ore)
The ore to be subjected to flotation is an ore containing a copper mineral, and is obtained by, for example, crushing ore mined from a specified mine and then grinding it to a specified size. Also, tailings obtained by flotation or other ore-dressing methods for other minerals, or kalami obtained by dry smelting, can also be used as the ore to be subjected to flotation in this embodiment.

Such ores are divided into primary copper sulfide ores and secondary copper sulfide ores. Specifically, copper minerals in primary copper sulfide ores include chalcopyrite, bornite, and enargite. Copper minerals in secondary copper sulfide ores include chalcocite and covellite. Although not always subject to flotation, copper oxide ores also exist in ores containing copper minerals, which can cause contamination. Copper minerals in copper oxide ores include brochantite.

In particular, it is preferable to target ores with a high proportion of primary copper sulfide ore in the copper mineral. This is because it has recently been discovered that there is a strong correlation between the color value and copper content of such ores. The proportions of copper oxide ore, primary copper sulfide ore, and secondary copper sulfide ore in the ore can be measured using a predetermined sequential analysis. This sequential analysis begins with copper oxide ore analysis, in which citric acid is added to a sample of the target mineral crushed to a certain particle size and stirred for a certain period of time. The amount of dissolved copper is quantified, which is defined as the amount of copper oxide ore (CuAC). Next, in secondary copper sulfide ore analysis, sodium cyanide solution is added to the solid portion obtained by solid-liquid separation after copper oxide ore analysis and stirred for a certain period of time. The amount of dissolved copper is quantified, which is defined as the amount of secondary copper sulfide ore (CuCNS). Finally, for primary copper sulfide ore analysis, nitric acid and perchloric acid are added to the solid portion obtained by solid-liquid separation after secondary copper sulfide ore analysis, and the solid is then dried on a hot plate. Hydrochloric acid and distilled water are then added to dissolve the solid, and the amount of dissolved copper is quantified, which is the amount of primary copper sulfide ore (CuINS). In each analysis, the amount of dissolved copper is quantified using inductively coupled plasma atomic emission spectroscopy (ICP-AES). The respective proportions of copper oxide ore, primary copper sulfide ore, and secondary copper sulfide ore in the copper mineral may also be measured using an analytical device such as an MLA (Mineral Liberation Analyzer).

Ore typically contains 0.30% to 1.50% copper by weight. It may also contain 20% to 40% silicon by weight and 1.00% to 5.00% iron by weight. However, since the grade varies depending on the ore, it is not limited to these values.

In particular, it is preferable to target ores in which silicon content is substantially unlikely to float during flotation, i.e., ores with a quartz content of 50% by weight or more. This is because in ores in which silicon content is likely to float, i.e., ores with a quartz content of less than 50% by weight, the correlation between the color value and copper content may be weak. The content of minerals such as quartz can be determined by measuring with an MLA. To achieve reproducibility with MLA, when observing samples to ensure a similar mineral composition, samples embedded in resin are observed vertically. It is also important to confirm that the elemental composition is similar.

For reference, similar flotation was performed on various ores with different quartz percentages, and the float rate of each ore was examined. The results are shown in Table 1 and Figure 9. Table 1 and Figure 9 show that ores with a quartz percentage of 50% or less by weight (high clay content minerals) tend to have a higher float rate than ores with a quartz percentage of more than 50% by weight (low clay content ores).

(flotation)
To perform flotation, the ore described above is mixed with a liquid such as water or lime water to form a pulp, and this pulp is stored in a flotation cell of a flotation device. Chemicals such as a foaming agent to form a froth, a collector to increase the froth's ability to collect copper minerals, and, in some cases, an inhibitor to prevent other minerals from floating are added to the flotation cell. Once a pH adjuster is added to the flotation cell to achieve a predetermined pH, the flotation cell is aerated by forced or self-sufficient air, and the skimmer is rotated to collect the froth. The froth is sometimes collected by allowing the froth to naturally overflow from the flotation cell. The various chemicals described above may also be added in advance when preparing the pulp before it is placed in the flotation cell.

In this embodiment, in order to manage flotation operations using image information of the froth on the surface of the pulp in the flotation cell, image information of the froth is acquired, for example, by installing a photographing device such as a camera above the flotation cell. Image information can be acquired by continuously photographing the froth or by photographing it intermittently at predetermined times. In other words, the froth is monitored using the photographing device.

The image information obtained as described above is transmitted to, for example, a computer, and subjected to image analysis there. The image analysis includes calculating the color values of the floss in the image in the L ^* a ^* b ^* color space (CIE 1976 (L ^* , a ^* , b ^* ) color space). This color value (i.e., Lab color) is calculated using the following formula (1):

(1)

Here, _L0 , _a0 , and _b0 can be set to any coordinates in the L ^* a ^* b ^* color space, but in many cases, the standard white point is used. Also, L ^* , a ^* , and b ^* are coordinates in the L ^* a ^* b ^* color space for the pulp surface in the image of the image information, and can be calculated using image processing software, etc. The color value is calculated as the average color value of each pixel constituting the portion corresponding to the floss in the image of the floss image information within a predetermined time period (e.g., 5 seconds).

As mentioned above, there is a correlation between the color values of the froth in the image information and the copper grade in the froth that floats to the pulp surface in the actual flotation cell. Therefore, the color values can be used to estimate the copper grade in the ore in the froth that was formed on the pulp surface when the image information was acquired. Furthermore, by determining the froth recovery time and/or froth recovery amount based on the color values, it is possible to standardize responses when froth properties change, enabling stable operational management regardless of the operator. Additionally, costs can be reduced by reducing labor costs.

More specifically, it is preferable to obtain multiple images of the froth in the flotation cell at predetermined time intervals and, from these images, obtain in advance graphs or other information about the relationship between color values and the copper grade in the ore in the froth formed on the pulp surface. In this case, when image information of the froth is obtained in a subsequent flotation step, the above-mentioned color values can be calculated from the image information, and the copper grade in the ore in the froth on the pulp surface can be estimated based on the graph or other information about the relationship between the above-mentioned color values and copper grade. Such information is not particularly limited, but could, for example, be a graph with color values (Lab color) on the horizontal axis and copper grade on the vertical axis.

The color values in the L ^* a ^* b ^* color space of the pulp surface obtained from the image information also correlate with the copper recovery rate.

In many cases, the color value decreases as the copper content of the froth in the flotation cell decreases. If the color value reaches zero during flotation, for example, before the cumulative copper recovery rate in the froth formed on the pulp surface reaches its maximum, it may become impossible to estimate the subsequent increase in cumulative copper recovery rate from the color value. Therefore, it is preferable to adjust the brightness of the pulp surface so that the color value does not reach zero until a predetermined time has elapsed from the start of flotation, for example, by installing a lighting fixture that illuminates the pulp surface in the flotation cell or adjusting the output of the lighting fixture. More specifically, it is preferable to set the predetermined time to be equal to or longer than the time from the start of flotation to the time when the copper recovery rate in the froth formed on the pulp surface reaches its maximum. This makes it possible to effectively estimate copper content, etc., using the color value described above over the required period.

For flotation, a flotation apparatus 1 as shown in Fig. 1 may be used. This flotation apparatus 1 includes a plurality of flotation cells 2 arranged side by side from upstream to downstream (from left to right in Fig. 1), and adjacent flotation cells 2 are in communication with each other.
More specifically, as shown in Figure 2, adjacent flotation cells 2 are connected to each other by a communication section 3 provided between them, which allows the flow of pulp P. Each communication section 3 is provided with a valve 4 that controls the flow of pulp P from the upstream flotation cell 2 (the right side in Figure 2) to the downstream flotation cell 2 (the left side in Figure 2). By operating this valve 4, the froth layer FL in the upstream flotation cell 2 can be varied. The froth layer FL is the height-wise region of the froth F formed on the pulp surface PS in the flotation cell 2, and here it is defined as the region between the overlip OL, which is the overflow portion, and the pulp surface PS.

In the illustrated flotation cell 2, when the valve 4 is closed, the pulp surface PS rises as pulp P flows in from the upstream flotation cell 2. As the pulp surface PS rises, much of the froth F on the pulp surface PS overflows the overlip OL and is recovered. When the valve 4 is closed in this way, the amount of recovered froth F increases, and the copper recovery rate also increases.
On the other hand, when the valve 4 is opened, the pulp P flows out into the downstream flotation cell 2, lowering the pulp surface PS. When the pulp surface PS is lowered, the amount of froth F that overflows beyond the overlip OL decreases. Therefore, opening the valve 4 leads to a decrease in the amount of recovered froth F and, ultimately, a decrease in the copper recovery rate.
In this way, in the flotation device 1 of the illustrated example, the amount of froth F recovered can be adjusted by opening and closing the valve 4.

Froth F generally contains a large amount of copper minerals, so increasing the amount of froth F recovered tends to increase the copper recovery rate.

In this embodiment, the color values in the L ^* a*b ^* color space are determined from image information acquired about the froth F on the pulp surface PS in the flotation cell 2 before it overflows the overlip ^OL . As mentioned above, since there is a correlation between the color value of the froth F and the copper grade of the ore in the froth F, it is preferable to open and close each valve 4 between the plurality of flotation cells 2 based on this correlation, and set the froth layer FL of each of the plurality of flotation cells 2. More specifically, after starting flotation using the flotation apparatus 1, when the color value approaches the value at which the copper recovery rate is maximized, it is preferable to perform operational management by varying the froth layer FL so as not to collect too much float. This is because if further float is collected from the flotation cell after the maximum recovery rate has been achieved, the copper grade will decrease.

For example, consider a case where operational management using the color values described above is not performed, as shown in Figure 3 under "1 Normal." In this normal case, the pulp level is set to 20 in the flotation cells of all sections. If image information of the pulp surface is acquired for this case and its color value is calculated, the color values for the flotation cells of each section are obtained as shown under "2 Camera Management." In this case, the color values for the flotation cells of sections 1 and 2, sections 3 and 4, and sections 5 and 6 are relatively high, and it is considered that the maximum recovery rate has not yet been achieved. Therefore, in "3 Improving Recovery Rate through Color Value Management," the pulp level is increased (the distance between the pulp surface and the overflow area is narrowed from 20 to 10), thereby increasing the amount of froth recovered. On the other hand, in the flotation cells in zones 7 and 8 under "2 Camera Control," the color value is small and it is believed that maximum recovery has already been achieved, so the pulp level was lowered (the distance between the pulp surface and the overflow area was increased from 20 to 30) and the amount of froth recovered was reduced. This type of operational control can improve the final copper recovery rate when using multiple flotation cells.

Next, we conducted tests to confirm the effectiveness of the flotation method described above, which are described below. However, the description here is for illustrative purposes only and is not intended to be limiting.

(Relationship between color value, copper grade, and copper recovery rate)
A predetermined ore containing copper minerals (Sample A) was subjected to flotation using a flotation cell.

During flotation, images of the pulp surface in the flotation cell were taken multiple times, and the relationship between the color value calculated from each image and the copper grade and copper recovery rate in the froth at the time the image was taken was investigated. The results are shown in Figures 4 and 5. In the graphs of Figures 4 and 5, as described in the graph legend, the approximation curves of the circle plots are shown as solid lines, the approximation curves of the triangle plots are shown as short dashed lines, and the approximation curves of the square plots are shown as long dashed lines.
4 and 5 show that there is a correlation between the color value and the copper grade and copper recovery rate, respectively.

(Relationship between brightness and color value)
In the above-described flotation, before the brightness adjustment, as shown in Figure 6, the copper recovery rate increased even though the color value was zero 10 minutes after the start of flotation.
In contrast, when the brightness was adjusted to be darker, as shown in FIG. 7, the color value did not reach zero after 10 minutes, making it possible to manage operations using the color value.

(Ore with easily floating Si content)
When a similar flotation process was carried out using an ore (sample B) in which Si content is likely to float, instead of the above-mentioned ore (sample A), no clear correlation was confirmed between the color value and the copper grade, as shown in Figure 8.

The mineral compositions of Samples A and B used in the above-mentioned tests are shown in Table 2. Sample B, which has a tendency for Si to float, was confirmed to have less Quartz than Sample A.

REFERENCE SIGNS LIST 1 Flotation device 2 Flotation cell 3 Communication part 4 Valve P Pulp F Froth FL Froth layer PS Pulp surface OL Overlip

Claims (7)

1. A flotation method for pulp mixed with ore containing copper minerals, comprising:
acquiring image information of the froth formed on the pulp surface, and managing the flotation operation using color values in the L ^* a ^* b ^* color space of the froth obtained from the image information ;
A flotation method using an ore having a quartz content of 50% by weight or more as the ore . The flotation method of claim 1, further comprising estimating the copper content of the ore in the froth from the color value. The flotation method of claim 1 or 2, further comprising obtaining information regarding the relationship between the color value and the copper grade in the ore within the froth from the image information. The flotation method according to any one of claims 1 to 3, further comprising determining the timing and/or amount of the froth to be recovered based on the relationship between the color value and the copper content of the ore in the froth. The flotation method described in any one of claims 1 to 4, further comprising operating a valve in a flotation cell of a flotation device to set the pulp level in the flotation cell based on the relationship between the color value and the copper grade in the ore in the froth. The flotation method described in any one of claims 1 to 5, further comprising adjusting the brightness of the pulp surface so that the color value does not become zero until a predetermined time has elapsed from the start of flotation. The flotation method of claim 6, wherein the predetermined time is set to be equal to or greater than the time from the start of flotation to the time when the copper recovery rate in the froth is maximized.