South Africa Gold Mine RIP Law Gold Factory

It is the first mine in the West to extract gold from cyanide pulp using the RIP process. The factory is located in the Easten Transvaol region of South Africa. Its processing capacity is about 375t / d, 90% of which is from the open pit mine near the plant, the gold grade is about 1g / t; the rest of the ore is provided by two small high-grade mines about 10km away from the plant, the gold grade is 5~15g/t. Because the clay content in the ore is as high as 50%, it is not appropriate to use conventional cyanidation, zinc replacement or heap leaching to raise gold. Therefore, the detailed intermediate-scale comparison test between RIP and CIP method has further proved that the RIP method is obviously better than the CIP method for the cyanide slurry, so it is transformed into the RIP gold extraction plant. In 1988, it solved various problems in the initial stage of RIP reform and production. In 1989, it entered the normal RIP method to increase gold production. The processing volume gradually increased, almost twice the CIL method, and the economic benefits were greatly improved.
1) The process is grinded in a cyanide medium and classified by a hydrocyclone to form a closed circuit. The dilute slurry of the qualified size is pre-screened by a horizontal vibrating screen to remove wood chips, and then dehydrated by a hydrocyclone. The cyanide leaching tank, the gold-loaded resin adsorbed by the RIP method is washed with Na ₂ Zn(CN) ₄ solution, and the gold is recovered by using the steel wool as the cathode electric storage tank. The lean resin is regenerated by sulfuric acid, washed and returned to the RIP system. The heating desorption, electrowinning and regeneration system is shown in Figure 1.

2) Main equipment and materials 1 Grinding. Add a ball mill Ф 6300mm × 1800mm one, the original ball mill Ф 1800mm × 1800mm spare.
2 cyanide leaching. 180m ³ are newly added three volumes mechanically stirred tank with the original six 55m ³ volume of air are stirred tanks in series, the leaching system configuration, newly added to the front end of the large groove string.
3RIP adsorption system. Four cone-bottom air agitation (ie Pachuca) adsorption tanks with a height-to-diameter ratio of 3 and a volume of 10 m ³ were connected in series to form a RIP system, and it was decided to add two additional adsorption sections.
4 resin. At first, it was A101DU; later changed to A161L, which is a macroporous strong basic resin with a particle size of +0.85mm and 92%.
5 desorption regeneration. One desorption column was regenerated, with a volume of 1000 L. In 1989, another desorption column was constructed; an 1800 L desorption column was also constructed. [next]
6 electric accumulators. The specification is 900m×500m×700mm, the outer casing is made of polypropylene material, and there are 7 steel ash cathodes and 8 stainless steel mesh anodes. Each cathode contains 250g steel wool and is packed in a polypropylene box (width 400mm).
3) Main process parameters 1 Cyanide leaching. The liquid-solid ratio is maintained at about 2:1 because the ore has a high clay content (about 50%), a high viscosity, a leaching time of 24 hours, and a corresponding slurry flow rate of about 36 m ³ /h.
2 slurry adsorption. 500L of resin is injected into each section, which corresponds to a resin concentration of 20g/L, and the average residence time of the slurry in each section is about 20min; the resin flow rate is 300L/d, and the corresponding volumetric flow ratio of the slurry to the resin is about 2900:1.
3 desorption of gold-loaded resin and electricity accumulation gold. The plant uses Na ₂ Zn(CN) ₄ -NaOH as a desorbent, and the desorption and electrowinning gold are connected in series in a large cycle.
4 desorption conditions. The temperature is 60 ° C (the maximum temperature allowed by the resin should not exceed 65 ° C); the concentration of Na 2 Zn (CN) 4 is 0.6 mol / L (almost the saturation concentration of the salt at 60 ° C); the flow rate is 500 L / h, this is electricity The upper limit of the flow allowed by the sump.
5 electrowinning conditions. The current density is 100 A/m ² (cathode surface area); the total current is 300 A; the desorption electron-growth cycle is originally 4 d, and then improved to 2 d.
6 resin-lean regeneration. The regenerant was 1 mol/L H ₂ SO ₄ .
4) Operation of the RIP adsorption system The resin-slurry mixture in the adsorption tank is lifted by an air lifter onto a curved screen located above the tank, and the slurry passes through a 0.5 mm sieve hole and flows from one tank to the next, while the sieve The resin is returned to the original adsorption tank. The resin and some of the slurry are regularly discharged from the valve at the bottom of the adsorption tank, and enter the horizontal adsorption sieve with a sieve hole of 0.3 mm through the inclined chute. The slurry under the sieve returns to the original adsorption tank, and the resin on the sieve is collected and sent to the previous one. The adsorption tank flows backward with the slurry; for the gold-loaded resin in the first tank, the water is eluted and sent to the desorption section.
5) Main results 1 Leaching and slurry adsorption. The liquid gold concentration of the slurry in the 9 leaching tanks and 4 RIP adsorption tanks is shown in Table 1. The leaching tanks 1~3 are large tanks, and the residence time of the slurry in the slurry is 15h, but the leaching rate is only about 80% of the final value, indicating that the leaching speed of the ore is slow. However, although the gold concentration in the liquid phase of the adsorbed tailings is lower than that at the initial stage of the reform (0.05 mg/L), it is still not satisfactory. To this end, the adsorption tank, the desorption column and the electrowinning tank will be newly added to reduce the residual gold concentration in the lean resin, so that the liquid concentration of the adsorbed tailings liquid is finally below 0.01 mg/L. [next]

During the production of RIP and CIL, the average concentration of gold concentration on each adsorbent is shown in Table 2. It can be seen that the gold-loaded resin has a high gold capacity. Therefore, the gold-loaded resin only needs to be desorbed once a week for 48 hours. Since the capacity of the gold-loaded carbon is much lower, the amount of gold-loaded carbon is correspondingly increased, so it is necessary to continuously desorb a large amount of solution every 24 hours, resulting in an increase in the cost of the carbon slurry method. [next]

Desorption, electrowinning and resin-lean regeneration of 2 gold-loaded resins. The results of desorption of 60 batches of gold-loaded resin are shown in Figure 2. As can be seen from the figure, the desorption rate drops sharply for each adsorption 10 or more times, and the residual resin residual gold capacity sharply rises. This is due to the accumulation of by-product NaOH up to 200 g/L when Na ₂ Zn(CN) ₄ was prepared using ZnO and NaCN. In addition, Cu and Fe in the desorbent reached about 10 g/L and about 2 g/L, respectively, due to repeated use.

Therefore, each batch of new desorbent needs to be replenished 5 or 6 times, and the relationship between the concentration of gold in the corresponding typical desorption electrowinning effluent as a function of time is shown in Fig. 3. The best and worst results for desorption are shown in Table 3. The desorption results of other batches are between the two. It can be seen that even if the gold desorption effect is good, the desorption rate of diamond and nickel is only about 60%. In addition, when gold is poorly desorbed, most other elements are also poorly desorbed, especially diamonds, nickel, iron and silicon. However, from the 18-month adsorption-desorption-regeneration cycle at the beginning of the reformation, there is no indication that the diamond, nickel and any other metals will accumulate in the form of harmful substances on the resin, hindering the adsorption of gold. [next]

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