Acid leaching copper mineral raw materials and process technology

Sulfuric acid leaching can be used as silicate-type processing agent is selected from copper oxide ore difficult. If there is a considerable amount of copper sulfide mineral in addition to the copper oxide mineral, it is preferred to use an oxidizing acid leaching method to decompose the ore. Acid leaching is generally performed at atmospheric pressure, depending on the degree of immersion is difficult, can be heated or not heated, the solid-liquid ratio is generally 1: 1 to 2, of copper sulfate were immersion into shape, the available iron replacement, precipitation - Flotation, extraction - electrowinning to recover copper from the infusion.

I. Acid leaching - displacement (precipitation) - flotation method

The acid leaching-replacement-flotation method is abbreviated as LPE method, which consists of three stages: the first stage leaches the oxidized and mixed copper ore with a dilute sulfuric acid solution; the second stage replaces the leaching solution with iron filings, etc., and replaces the copper by precipitation. The third stage of flotation precipitates copper.

The process of this method can be briefly described as follows:

(1) Grinding. Grinding fineness depends on the nature of the ore and the composition of the copper mineral. If the ore is a pure oxidized ore, such as malachite, azurite and other readily soluble minerals, the grinding particle size should be as large as possible, and the general particle size is about 1 mm. When the hardly decomposable when containing copper sulphide minerals and precious metal, grinding the ore particle size to the same ordinary flotation process, i.e., to ensure that the sulphide ore, gold and silver gangue dissociation with a monomer. In recent years, the process of separate treatment with sediment has been adopted, that is, the ore is first crushed to 8 mm, the sediment is treated separately, the slime is soaked with acid, and the ore can be firstly immersed and floated or only floated.

(2) Leaching. Suitable conditions for leaching, the concentration of sulfuric acid, the liquid-solid ratio of the slurry, and the temperature are determined by tests. In general, acid leaching uses 0.5% to 3% of dilute sulfuric acid as a leaching agent for the purpose of decomposing secondary copper oxide minerals, the residual acid is generally 0.05% to 0.1%, and the solid-liquid ratio is 1:1.
~2. The leaching is carried out at room temperature or under heating to 50 to 80 °C.

(3) Precipitation. In the precipitation, scrap iron, iron filings, sponge iron or burned cans can be used as a precipitating agent, and hydrogen sulfide can also be used as a precipitating agent to precipitate copper in the form of sponge copper or copper sulfide. Main factors such as pH value and amount of precipitant are controlled during precipitation. The solid-liquid ratio during displacement deposition is 1:3, the initial acidity is 2~3g/L, the replacement time is 10~25min, the precipitation of copper is 87%~97%, and the iron loss is mainly determined by the residual acidity of the medium, generally 1.2~ 3.5kg/kg. Inflation should be avoided when replacing the precipitate to prevent the replacement copper from being oxidized and re-dissolved. If the immersion liquid is too high, it can be neutralized with lime first.

(4) Flotation. Metallic copper has good floatability. Flotation of precipitated copper is carried out directly in weakly acidic (pH=3.7~4.5) pulp. Generally, cresol black and bismuth medicin mixed with cresol (1:1) is used as a collector to cresol or pine. The oil acts as a foaming agent, and the undecomposed copper sulfide mineral floats together with the associated precious metal and precipitated copper. The flotation process is simple and usually produces concentrates from the rough tank.

In short, the process is characterized by coarser grinding fineness, thinner leaching agent, leaching slurry without solid-liquid separation, undecomposed copper sulphide minerals and precious metals can be floated and recovered together with the precipitate, and directly floated The selection method can compare the copper concentrate grade and recovery rate.

A chemical beneficiation method for refractory copper ore which is easy to industrialize, leaching-precipitation-carrier flotation method, referred to as LPCF method. Treatment with the aluminum silicate-type, Ca, Mg, Fe, Mn type and refractory-type copper oxide ore and ore, have achieved good results; concentrate grade higher than 20% copper recovery than conventional flotation 6% ~40%.

Dilute sulfuric acid is generally used as a leaching agent during leaching. At the time of precipitation, an alkali or a basic salt is added to the slurry after leaching to neutralize the free acid. Further adding a sulfide base causes the copper ions to form a colloidal copper sulfide precipitate. Carrier flotation, using copper concentrate (as far as possible using the high-grade concentrate produced by the process itself) as a carrier, can eliminate the separation and regeneration of the carrier.

Using this method to test the results of a copper oxide ore, compared with the conventional vulcanization flotation method, the concentrate grade is increased by 5%, and the recovery rate is increased by 6% to 7%. The principle flow of the test is shown in Figure 1.

Figure 1 Flotation - LPCE method test principle process

Second, acid leaching - extraction - electrowinning

Since the BiueBial copper mine in the United States successfully established the world's first copper extraction plant with solvent extraction in March 1968, the basic process of extracting copper by leaching-extraction-electrowinning technology was determined. Since then, although the copper extractant used has been continuously updated, the number of extraction stages and the number of strippings have been decreasing, but the basic process has not changed in principle.

(1) Solvent extraction-electrowinning method

Solvent extraction has the advantages of high extraction rate, good separation effect, simple operation, less "three wastes", easy continuous and automatic, etc. It is a promising new copper extraction process.

1. Extraction process. The extraction process, it is also a balance. The process is that the acid leaching copper solution is mixed with the organic carrier agent, the copper ions enter the organic phase, and the raffinate is recycled. The copper is back extracted from the loaded organic phase, and the regenerated organic agent is recycled, and an electrolyte is prepared for the electrowinned copper.

As briefly mentioned above, solvent extraction involves the following two steps:

(1) Extraction. The leachate is stirred with the immiscible organic extractant to extract the valuable metal from the leachate to the organic phase. After the two phases are separated, the organic phase is retained and the raffinate is recycled or discarded.

(2) Counter extraction. The valuable metal copper is recovered by stirring a small amount of the appropriate stripping solution with the supported organic phase, so that a relatively pure enrichment of the valuable metal copper is obtained. The stripped solution can be recycled.

2. Extractant. Extraction of copper from acid immersion copper. The use of Fix(R) type extractant is widely used in foreign countries. The existing extractants in China are N-510, N-531, O-3045, etc., which are the same as Fix(R). mixture. N-510 is suitable for extracting copper from copper-depleted liquid (1-3g/L), and the extraction rate increases with the increase of pH value, and is generally used for ammonia immersion liquid. N-530 and N-531 are similar in nature and are suitable for extracting copper from copper-rich liquid (about 10g/L). The selectivity of higher acidity (pH=1) O-3045 is better, but the equilibrium time is longer. Suitable for bacterial copper immersion liquid and copper deficiency liquid. When copper is extracted by a chelating agent, the waste electrolyte is usually used for stripping, and the stripping solution contains copper up to about 50 g/L, and then copper is obtained by insoluble anode electrowinning. The counter-extracted organics can be recycled back to the extraction operation.

3. Advantages of solvent extraction. Industrial practice at home and abroad has shown that extracting copper from poor liquids with low copper content (generally 1-5 g/L) has several obvious advantages over solvent removal methods over iron filings:

(1) Extraction process. The iron scrap replacement, liquid-solid separation, drying and fire process are avoided, resulting in an increase in total recovery.

(2) The recovered cathode copper is of high quality and generally can reach more than 99.99%.

(3) The electrowinning process regenerates the sulfuric acid and can be returned for stripping or leaching, which reduces the acid consumption and reduces the total operating cost.

(4) The leaching-extraction-electrowinning process constitutes a closed loop, and only the product and the leaching slag are discharged. It eliminates SO ₂ pollution and exhaust gas emissions that are difficult to avoid by fire treatment, improves the factory labor environment, and facilitates automation.

4, electrowinning. The electrowinning is similar to the electrolytic refining process in general metallurgical plants. The different characteristics are the different anodes used. The anode used in electrolytic refining is a soluble anode made of a crude metal. When the electrolysis is performed, the anode is gradually dissolved, and the pure metal is deposited on the cathode. Accumulating electrically silver anode with 1% copper or antimony-containing insoluble anode 6% to 15% lead-antimony alloy made, when energized electrolysis, the anode does not dissolve, but the electrolyte to be extracted from metallic copper The ions are deposited on the cathode to achieve the purpose of extracting the metal, and the solution to be electrolyzed should contain copper at 25 to 30 g/L or more.

(2) Acid leaching-extraction-electrowinning process and production practice

1. Process flow. This process uses dilute sulfuric acid as the leaching agent, and the principle flow is mostly shown in Figure 2.

Figure 2 Principle flow of the leaching-solvent extraction-electrowinning process

During the entire process, all of the feed liquids were in a closed loop except for the leaching slag discharged and the cathode copper of the product. The raffinate is returned to the leaching section for cyclic leaching, and the organic phase after stripping is returned to the extraction section for cyclic extraction, which fully utilizes the acid generated during the electrolysis process. The entire cycle is continuously operated. In addition to the original ore, the bulk raw material is only sulfuric acid (generally 2 to 3 tons of sulfuric acid per ton of metallic copper). At present, the extraction section mostly uses secondary extraction and primary extraction, and the extraction agent consumption is generally 5-8 kg per ton of metallic copper. The product can reach the quality standard of first grade electrolytic copper.

2. Production practice. Acid leaching-extraction-electrowinning method has many production plants in foreign countries, such as the Blue Bird mine oxidized ore heap leaching in the United States. The immersion liquid contains copper 4g/L and sulfuric acid 3-5g/L, extracted with Fix64, and accumulates copper. t/d, purity 99.9%.

A lot of experimental research and production practices have been carried out on this process in China. For example, the production practice of acid leaching-extraction-electrowinning method for a copper oxide ore shows that the process technology is reliable and economical, and can produce 99.95% of electrolytic copper. .

The raw material processed by the plant is the associated copper oxide ore in the surface layer of an iron ore gangue layer. The main copper-bearing minerals are malachite, azurite and a small amount of chrysocolla. The chemical composition and phase analysis are shown in Table 1. And Table 2.

Table 1 Raw mineral chemical composition

Table 2 Analysis of original mineral phase

It can be seen from Table 2 that copper minerals mainly exist as monomeric copper oxide, copper sulfide only accounts for 1.8%, and acid gangue accounts for 53.4%, which is more suitable for acid leaching treatment.

After the ore is crushed and ground to a suitable particle size, the agitation leaching-extraction-electrowinning treatment is carried out. The principle flow is shown in Fig. 3.

Figure 3 A copper ore acid leaching-extraction-electrowinning principle process

(1) Stirring leaching. The leaching trough is made of granite bricks, lined with acid-resistant ceramic tiles, with a volume of Φ2m×2m, using a turbine agitator. The solid ratio of the leaching solution is 3:1, the acidity of the leaching solution is 20-30 g/L, and the filling is 1t per tank. After stirring for 3 hours, the washing liquid is added with 1m3, which is naturally clarified. After the supernatant is taken out, it is washed twice in reverse flow, and finally the leaching solution (with the washing liquid) Combined) containing Cu4g/L, pH value of 1.6-1.8.

(2) Extraction work. The copper-rich liquid obtained from the leaching operation was extracted using a shallow-pool mixing clarification extraction tank. The main dimensions of the extraction tank are: mixing chamber (effective) 0.9m × 0.9m × 0.9m, clarification chamber (effective) 0.9m × 1.8m × 0.45m, stirring speed is 320r / min. The production conditions of the extraction operation are shown in Table 3.

Table 3 Main parameters of production conditions for extraction operation

(3) Electrostatic operation. The electric accumulator is made of reinforced concrete and is lined with a hard PVC plastic sheet. The size of each groove is length × width × width = 2m × 0.8m × 1m, the cathode size is 0.72m × 0.64m, the anode is lead, bismuth alloy, the size is 0.7m × 0.62m, and the silicon rectifier capacity is 3000A/75V. In order to reduce the acid mist of the electrowinning operation, the plastic float is covered on the groove surface, and 12 kg per tank is added. The electrowinning conditions are shown in Table 4.

Table 4 Operation conditions of electrowinning operation

The raw material consumption of the copper ore by acid leaching-extraction-electrowinning method is shown in Table 5.

Table 5 Consumption of raw materials