Design Practice of Extraction Technology for Treatment of Low Grade Copper Ore

I. Overview

With the growing consumption of copper metal, copper ore grade decreased, some low-grade copper ore, flotation tailings, the table outside the mine, and even some waste pits, difficult mining veins need to be treated. It is obviously not cost-effective to use the fire rule to refine these materials, and methods such as heap leaching and in-situ leaching are receiving more and more attention. Solvent extraction is an effective method for treating these low concentration copper leaching solutions.

Metal solvent extraction began in the mid-19th century. In the early 100s, solvent extraction was only applied in the field of analytical chemistry. In the 1940s, the nuclear fuel industry developed rapidly in 1940, and was completed in 1942. It also commissioned the world's first commercially available solvent extraction and refined uranium plant. By 1960, more than 20 extraction plants were built around the world. Since then, solvent extraction has been widely used in the nuclear fuel industry. The separation of rare earth elements has also achieved good industrial results. Since the mid-1960s, and especially in the 1970s, the following new situations have emerged, further contributing to the development of solvent extraction technology:

1 metal consumption increased, ore grade decreased;

2 Due to the need of resource exploitation, some low-grade ore mines, tailings, off-balance mines, and even some waste pits and difficult-to-exploit veins need to be treated. It is obviously not cost-effective to use smelting to process these materials, but heap leaching Methods such as ground leaching are gaining more and more attention;

3 increasingly strict environmental protection;

4 The useful components of complex ore must be recovered. The abundant marine resources have yet to be developed, and these materials are often not smelt by fire.

In the late 1960s, the world's first copper extraction plant was put into production. In the next 10 years, many large copper extraction plants in the world were built one after another, establishing the status of metal solvent extraction in copper hydrometallurgy. With the gradual rise of solvent extraction-electrolysis (SX-EW) technology, refined copper is produced by ore leaching, which currently accounts for 13% of total production. In 1998, the refining capacity was 16.228 million tons. From 1980 to 1990, the world's refining capacity averaged 12.331 million tons. After 4a, the refining capacity increased by 26% compared to the average of the past 15a. Extraction-electrolysis production capacity increased by 286%, most of which occurred in Chile.

The above fully illustrates the solvent extraction, which is an effective method for treating these low-concentration copper leaching solutions, and the application of solvent extraction technology in copper smelting is more and more extensive.

Second, the design conditions

The ore copper grade of a mine is 1.81% and the silver is 17-31g/t. Ore consists of three layers: an upper shale ore, 42%, mainly mineral chalcopyrite, bornite times for, Yeyan Cheng divided calcite, clay-based, time quartz; the lower sandstone The ore is mainly composed of free copper oxide and copper oxide. The total oxidation rate of copper in the whole mining area is greater than 70%, and the vulcanization rate is not high. In order to recover the ore and sulfide ore in the ore, through experimental research, it was decided to use the first flotation to select the sulfide ore and silver. The flotation tailings adopt the process of stirring and leaching and extracting the electrowinning. The designed scale has an annual output of 5000t. Copper, the tailings copper grade after flotation is 1.27%, the copper concentration of the leachate after stirring and leaching is 2.5g/L, the iron is 3.5g/L, the liquid volume is 300m ³ /h, and the copper concentration is rich by extraction. Accumulated to the electromagnetism requirement (about 50g / L), the raffinate copper concentration ≤ 0.15g / L, the stripping waste electrolyte containing copper 35g / L.

Third, the extraction process

The extraction process is shown in the figure below.

Extraction process flow chart

Fourth, the choice of extractant

Commonly used industrial extractants are classified into four categories: one type of neutral extractant; two types of alkaline extractants; three types of acid extractants; and four types of chelate extractants. The following factors should be considered when selecting an extractant:

1 The source of the extractant should be sufficient;

2 The price of the extractant should be relatively cheap;

3 The solubility of the extractant in the aqueous phase should be relatively small;

4 The stability of the extractant is good and degradation occurs in the extraction cycle;

5 When mixing, the extractant should not form a stable emulsion with the aqueous phase;

6 extractant has a larger extraction capacity;

7 has good dynamic extraction performance, that is, the extraction balance is fast.

Copper extractants which have been used in industry mainly include Lix64N, SME529, Lix622, P-5000, P5100, Lix864, Lix984 and the like.

The extractant selected in this project has been successfully used for the production of Lix984. Because of its high separation speed, high extraction efficiency and separation coefficient of copper to iron of 2000-2500, the leachate of this project has good pertinence. 260 diluent using coal oil. 10% Lix984 saturated capacity is 5.1 ~ 5.4g / L, net copper exchange capacity ≥ 2.7g / L, extraction equilibrium point ≥ 4.4g / L, extraction speed 30s, extraction phase separation ≤ 70s, stripping acid degree 150 ~ 160g /L, the stripping speed is 30s, and the stripping phase is ≤80s.

Extraction compared: O/A = (215-0115) / 217 = 0187;

Extraction series: 2 grades according to semi-industrial tests;

Counter-extraction compared: O/A=(50-35)/217=516;

The mixing residence time was taken for 3 minutes.

V. Selection and calculation of extraction equipment

The extraction device is a device for achieving two-phase contact and separation during the extraction process. Industrial extraction equipment is divided into a differential extractor and a stage extractor according to the characteristics of the operation. The former is light and heavy two-phase flow, continuous contact balance in the tower body, the spray tower and the packed tower belong to this category; the typical equipment of the stage extractor is the mixing clarifier, which is two phases in the same container (mixed The chamber is internally equilibrated, and then phase separated in another vessel (clarification chamber), and the two phases are respectively flowed into the next mixing clarification stage to contact the equilibrium and phase separation. Nowadays, the extraction equipment with more industrial applications is the mixing clarifier, and the mixing-clarification tank is the earliest.

The mixing-clarification tank has the following advantages:

1 large processing capacity, high efficiency;

2 simple structure, easy to enlarge and operate;

3 Two-phase flow ratio range is large, the operation is stable and reliable, easy to open and stop, good adaptability to the system, and can also be treated for materials containing a small amount of suspended solids;

4 Easy to achieve multi-stage continuous operation, easy to adjust the number of stages, the device does not need tall workshops and complex auxiliary equipment.

The mixing-clarification tank has the following disadvantages:

1 general mixing - clarification tank covers a large area, solvent reserves are large;

2 Due to the need for power mixing equipment and inter-stage logistics transportation equipment, equipment costs and operating costs are high.

There are many factors that affect the extraction operation, such as the nature of the system, the operating conditions and the structure of the equipment. For a certain system, it is necessary to select suitable extraction equipment to meet production requirements under certain operating conditions. The considerations for selecting an extraction device are as follows:

1 stability and residence time;

2 required theoretical series;

3 dispersion and agglomeration characteristics of the system;

4 production capacity;

5 anti-corrosion and anti-pollution requirements;

6 building site requirements.

Taking into account the above factors, combined with production practices, the extraction equipment of this project uses a mixed clarification extraction tank that has been successfully used in production practice.

The size of the extraction tank is determined by calculation and is based on a single-stage calculation.

1, the effective volume of the mixing chamber

V=Qt/60=(300+300×0..87)×3/60=28.05m ³

The effective volume of the V-effective mixing chamber in the formula, m ³ ;

Q-two-phase total liquid flow, m ³ /h;

T-mixing time, 3 min.

2, mixing room size

The square mixing chamber is selected, and the two-phase liquid is introduced from the bottom channel guide tube, and the mixing chamber size can be calculated as follows:

Where B, C, H ₀ - are the effective dimensions of the length, width and height of the mixing chamber, respectively.

The actual height H of the mixing chamber is 1.25H0, ie:

H = 1.25 H0 = 1.25 x 3.04 = 3.8 m.

3, the size of the clarification chamber

The area of ​​the clarification chamber is calculated as follows:

Where S-clarification chamber area, m ² ;

R-clarification rate, m ³ /(m ³ ·h).

The clarification chamber is rectangular, and the length and width of the clarification chamber are:

In the formula, the length and width of the L, W-clarification chamber.

To define the depth of the chamber, a shallow pool type clarification chamber is used, that is, the depth of the clarification chamber is smaller than the depth of the mixing chamber to reduce the unnecessary organic phase occupancy in the clarification chamber. According to empirical data and production practices, the effective depth of the mixing chamber is 900mm and the actual height is 1200mm.

4, stirrer size and stirring power

The agitator uses a turbine agitator with six blades, Z = 6.

Turbine diameter: D=B/3=3.04/3=1.01m

Blade width: B1=0.16×D=0.16×1.01=0.16m

Blade length: L = 0.25D = 0.25 × 1.01 = 0.25m

Stirring power: The input power per unit volume of the extraction system is 0.8 to 1 kW/m ³ , and the stirring power is ²⁷ kW. A 30 kW 6-speed motor is used.

The calculation method of the back extraction tank is the same as above.

The main dimensions of the extraction and back extraction tanks are shown in the table below.

Extraction and back extraction tank size table

Conclusion

1. Through the above design practice, the solvent extraction method is used to extract copper in the copper-containing solution, which has the advantages of high efficiency, automation, low energy consumption, and is easy to operate.

2. Main technical and economic indicators: the production cost of wet copper smelting is about 6,000-8,000 yuan per t copper; the investment per ton of copper is 8,000-10,000 yuan; the construction period is 015~2a; the recovery rate and acid consumption of copper depends on the ore. Taste and nature. The copper recovery rate in the extraction process is 9915%, and the Lix984 consumption is 3 to 4 kg per t copper.

3, the technology can be applied to difficult to choose low-grade copper oxide ore, oxidized-sulfurized mixed ore, low-grade sulfide ore, copper-containing waste rock and wastewater, smelting furnace slag and old tailings, etc., can also be applied in high altitude and cold regions . This technology not only expands the utilization of copper resources, but also has good economic and social benefits. The scale can be large, small, and without environmental pollution.

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