Recovery of gold from flotation gold concentrate by full mud cyanidation

Zhejiang Suichang Gold Mine Co., flotation concentrate cyanidation process of gold recovery of gold, ore processing 300 t, the process used for the two - closed-circuit crushing - stage grinding - and Stage - gold concentrate regrinding - concentrated before dipping - two two-dip wash - zinc powder was replaced with expensive - Filter press cake - lean solution (return portion) of cyanide addition efflux. In 2000, a small whole mud cyanide leaching test was completed. In 2001, an oxygen-enriched leaching test was carried out. In 2003, the original 300t/d flotation-cyanide process was changed to a 150t/d full mud cyanidation process. After the technical transformation, a number of new technologies were adopted: the return of the precious liquid to the grinding, the immersion while grinding; the high-cyanide and alkali-rich oxygen leaching; the dehydration of the tailings of the ceramic filter; the high-efficiency reformation of the thickener; zero discharge of cyanide-containing sewage; For the first time in the South, the cyanide tailings dry stacking technology was used, and the recovery rates of gold and silver were increased by 4%. Meanwhile, the original flotation equipment, the venue transformed into a full mud cyanide, lead and zinc beneficiation process two independent production system, saving investment costs, create the conditions for the production of lead and zinc mineral processing.

First, the nature of the ore

The useful minerals in the ore are natural gold, natural silver and silver gold. Gold and silver minerals include gold and silver, silver and gold, natural gold and silver ore. About 90% of gold is distributed in gold and silver. Metallic minerals include pyrite, pyrrhotite, marcasite, sphalerite, galena, copper ore and the like; gangue minerals are quartz, calcite and dolomite. The results of multi-element chemical analysis of raw ore are shown in Table 1.

Table 1 Multi-element analysis results of raw ore %

Gold and silver minerals are mostly oval, leafy, rod-shaped and irregularly dendritic. The particle size is between 0.01 and 0.038 mm, the maximum particle size is 0.3 mm, and the minimum particle size is 0.003 mm. There are two kinds of occurrence states: inclusions, accounting for about 30%, most of them are distributed in pyrite, and a small amount is dispersed in galena, sphalerite and chalcopyrite crystals, and the particle size is generally less than 0.01mm; The continuous body form, accounting for about 70%, is distributed between gangue minerals and metal sulfides, and the particle size changes greatly, ranging from 0.20 to 0.02 mm. The ore is an easy-to-select leachable ore.

Second, the whole mud cyanide leaching process technical transformation

The whole mud cyanide leaching process is shown in Figure 1.

Figure 1 Flow chart of the whole mud cyanidation production process

(1) Edge grinding and immersion strengthening leaching process

From the perspective of metallurgical kinetics, edge edging has the effect of strengthening leaching, which shortens the leaching time of gold. The reasons for enhanced leaching are as follows: 1. The cyanide complexation reaction of gold is a diffusion-controlled reaction. During the edge-dip immersion process, there is a strong grinding action between the grinding medium and the ore particles, which is destroyed or thinned. The diffusion interface layer on the surface of gold particles in the ore strengthens the diffusion of CN ^- , O ₂ molecules and gold cyanide ions, thereby accelerating the cyanide complexation reaction of gold. 2. The coarse ore material causes the gold particles to continuously expose the fresh surface during the grinding process, so that the surface reactivity is improved, which is favorable for the cyanation complex reaction. 3. The gold particles are continuously ground to increase the surface area of ​​dissolution, thereby shortening the dissolution time of gold. In the production practice, no pre-dip is needed, and some of the precious liquid is directly returned to the ball mill and the staged overflow, which can realize the recycling of the whole system water and achieve zero discharge. The edge grinding and immersion process can leach at least 50% of gold and silver, which can further shorten the leaching time. The poor liquid can be used as a concentrator to wash water, which can effectively reduce the gold content in the liquid discharge. In order to prevent the run, run, drip and leak of the cyanide-containing liquid, an alarm and automatic control device are set in the process.

(2) Use of ceramic filter

The original XMG300×1 250 (300m ² ) chamber filter press has simple structure and convenient solid-liquid separation operation, but has high operating cost, high filter cake moisture (up to 17.92%), low automation, and high labor intensity. There are many problems such as large number of operators, large maintenance workload, easy spraying, poor sanitation, turbidity of the filtrate, etc. The ceramic filter is a new type of equipment developed for solid-liquid separation in recent years, with high degree of automation and operation. Convenient, dehydrated products with low moisture (16.81%) and other advantages, have been widely used in the non-ferrous metallurgy industry. The ceramic filter is used to treat the whole mud cyanide tailings with high degree of automation, convenient operation, complete dehydration, clear filtrate and ideal index.

(3) Drying of tailings

The application of tailings pressure filtration and tailings dry method in domestic gold mines has been used for nearly 10 years, and practice shows. The tailings can bring significant economic and social benefits to the mine through pressure filtration and dry storage, and should be vigorously promoted.

Gold mines, especially those that use the whole mud cyanidation method, use dry chopping after tailings pressure filtration in order to make full use of cyanide wastewater and recover cyanide and dissolved gold. The flotation tailings have a graded effect on the natural settlement in the tailings pond. The coarse particles sink in front of the dam, which is beneficial to the drainage. The cyanide tailings (about 17% water) are not graded and the texture is uniform, which is conducive to consolidation. (in the absence of incoming water) is not conducive to drainage. The cyanide tailings are stored in a dry type, no external water supply, and no water seepage can be discharged, so the stability is improved.

A number of measures have been taken for the management of the tailings dry heap: 1. The interception (row) ditches are set up to completely exclude the external recharge water caused by the rainfall outside the dry storage yard; 2. Strengthen the slope level in the yard and divert water Work, the surface rainwater is set as a drainage ditch in the partition block, and is led to the boundary gutter in a small flow (dispersion) manner to establish a ground surface with a middle high and slowly inclined to the drainage ditch on both sides to avoid water accumulation; 3. In the stack body A number of marks shall be set up to carry out deformation monitoring at regular intervals; 4. During the rainy season, operators must enter the hazardous area and take necessary protective measures and carry out under the supervision of others, and shall not enter the dangerous area independently. 5. Prepare enough bleaching powder to degrade cyanide in an emergency. Once the cyanide-containing cyanide is high, affecting the total discharge index, add bleaching powder; 6. Have clear stacking order and stacking requirements; 7. Rainwater When coming, we must do a good job of covering the cyanide slag yard.

Since the whole mud cyanide production in July 2003, the results of the seepage detection of the yard (most of the time without seepage) indicate that the downstream water quality and the tailings pool total discharge index have improved before the whole mud cyanidation, in 2003. environmental assessment December give a "no impact on the environment deteriorated, wherein Cu, Zn, Cd, Mn, CN - not to decrease the degree of concentration" conclusion.

(4) New configuration auxiliary leaching - oxygen enrichment system

Oxygen-enriched leaching can significantly increase the dissolved oxygen content in the slurry, increase the dissolution rate of gold, significantly reduce the gold grade of cyanide tailings, increase the leaching equipment , reduce the number of leaching tanks, and reduce the aeration power (the oxygen generator power is less than the air pressure) Machine power), reducing power consumption, carbon consumption, and drug consumption. The oxygen-rich leaching process can obtain the leaching index equivalent to the carbon leaching process (CIL) for 24 hours as long as 8 to 16 hours, the gold leaching rate can generally be increased by 1% to 3%, and the amount of sodium cyanide can be reduced by 10% to 30%, thereby improving leaching. The processing capacity of the equipment is more than 1 time, saving construction investment and reducing production costs. The production shows that the oxygen-rich leaching time is 12h, the average leaching grade is 0.50-0.80g/t; the oxygen-rich leaching is 16h, the average leaching rate of gold is 97.18%, which exceeds the index of non-oxygen leaching for 30h. At the same time, according to the characteristics of high content of silver and copper in the noble liquid, the high cyanide and high alkali concentration replacement test was carried out, and the effect was good. Production practice shows that the gold concentration in the poor liquid after replacement is reduced to below 0.02 and 0.08 mg/L, respectively.

Third, the conclusion

The main advantages of the improved all-cyanide leaching technology are:

(1) The process is simple, the intermediate links are few, and the loss of the mine is less, which is conducive to metal recovery;

(2) There is no need for beneficiation, which saves flotation reagents and electricity consumption, reduces production costs, and avoids environmental pollution caused by flotation reagents;

(3) Without pre-dip, lime and sodium cyanide can be directly added to the ball mill , and the precious liquid directly returns to the ball mill and the graded overflow, which provides favorable conditions for realizing water recycling of the whole system and achieving zero discharge;

(4) The leaching index is good, and the comprehensive recovery rate is higher than the mineral processing-cyanide process index;

(5) Configuring an auxiliary leaching-oxygen-rich system, the leaching time is shortened by half compared with the conventional process;

(6) The cyanide tailings are dryly stored and the wastewater is discharged.

The comparison of production technical indicators before and after improvement is shown in Table 2. It can be seen that with the whole mud cyanide leaching process, the total recovery rate of gold and silver is increased by more than 4%, the economic benefit is obvious, and there is no waste water discharge, the tail slag can be dryly stored, and there is no pollution to the environment. Environmental benefits.

Table 2 Process indicators before and after the transformation

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