Summary of gold ore beneficiation methods

1 re-election

Reselection method is to divide the mineral beneficiation composition according to the difference in relative density (specific gravity generally known) is. Mineral particles of different densities are subjected to hydrodynamic forces and various mechanical forces in the moving medium (water, air and heavy liquid), resulting in suitable loose delamination and separation conditions, so that different density of ore particles can be separated.

Re-election is one of the oldest and most common methods of gold selection. In the gold deposits, gold is usually in the form of monomeric natural gold. The particle size is generally greater than 16 tons/m3, which is much different from the density of gangue. Therefore, re-election is the most important, most effective and economical method for selecting gold deposits. Methods. However, in Pulse Gold, re-election is rarely used alone, not as part of the joint gold withdrawal process. Generally, in the grinding and grading circuit, the jig and the spiral chute are combined with the shaker to recover the cleavage in advance. Coarse grain monomer gold to facilitate subsequent flotation and hydrogenation operations and to obtain qualified gold concentrates. This method is more commonly used in small-scale gold mines and local group mining, such as Jinchanggouliang and Dashuiqing in Inner Mongolia.

The main equipment for re-election is the various types of chutes, jigs and shakers. In addition to conventional re-election equipment , according to the production characteristics of China's gold mines, based on the digestion and absorption of foreign advanced equipment, China has developed new re-election equipment such as belt chute, Ross chute, round jig, sand gold centrifugal washing unit. In order to achieve good results in gold production. For example, Shandong Jinnan Gold Mine Gold Field Concentrator has set a soft coating (blanket) chute in the grinding classification circuit, and the recovery rate of gold can reach 70%. Soft-faced chutes are also used to treat flotation and amalgam tailings to increase gold recovery. The amalgamation method can be divided into internal mixed mercury and external mixed mercury according to its production mode. In gold mines, amalgamation is commonly used to separate gold and heavy sand minerals. In vein gold mines, amalgamation is usually used as part of a combined process with flotation, re-election, cyanidation, etc., mainly for the capture of coarse-grained singles. Body gold.

1) Jigging gold selection method

The jigging method is a gold selection process for jigs. Jigs are commonly used re-election equipment and come in many types. At present, China's gold-removing plants use Dyval-type diaphragm jigs.

The working principle of the Dyna-type diaphragm jig is: when the eccentric transmission mechanism drives the diaphragm to reciprocate, the water in the jigging chamber passes through the vertical alternating pulsating water flow generated by the screen. The selected materials are fed to the bed layer, and the bed ore and water form a granule system. When the water flow impacts upward, the particles are in a loose suspension state. At this time, the ore particles of different sizes are settled at different speeds, and the large density coarse particles (bed stones) settle in the lower layer. When the water flow drops, inhalation occurs, and the mineral particles with a large density and small particle size pass through the bed gap and enter the lower layer.

2) Shaker gold selection method

The shaker gold selection method is a gold selection process in which the shaker is the main equipment. The shaker is a device for beneficiation in a horizontal medium flow. It consists of two parts, the bed surface and the transmission mechanism (see the figure below). The bed surface is longitudinally reciprocated by the transmission mechanism. The sorting of the mine on the shaker is gradually completed during the reciprocating movement of the bed. The factors contributing to the movement of ore particles, in addition to their own gravity, are mainly the differential movement of the rushing and bed surface. The ore particles undergo a stratification perpendicular to the bed surface and a separation parallel to the bed surface during the movement. The result of both actions is that different ore particles are discharged from different intervals of the bed surface.

The shaker can be divided into three types: coarse sand bed (>0.5 mm), fine sand bed (0.5-0.074 mm) and slime bed (0.074-0.037 mm) depending on the size of other ore selected.

3) Chute selection method

The chute selection method is an old and still used re-election method. The main equipment for the chute selection is the chute. The chute is a wooden (or steel) narrow chute with an inclination of 3° to 4° (maximum of 14° to 16°). The gold industry can be manufactured locally. The principle of sorting is: after the slurry is fed into the chute from the trough, under the combined action of the force of the water flow, the gravity of the ore (or centrifugal force), the friction between the ore and the bottom of the trough, the loose particles of different densities And separation, the density is greater at the bottom of the tank becomes a concentrate, the density is small to become tailings. The chute is intermittent operation. When the bottom concentrate is deposited to a certain height, the ore is stopped and the concentrate is cleared.

The chute is divided into a coarse sand chute and a slime chute. The former is suitable for processing coarse-grained materials, and the latter is suitable for processing fine-grained materials. The bottom of the coarse-grained chute is provided with paving and baffles.

The coarse grain chute is the main equipment for sand gold ore beneficiation and is widely used on land and gold mining vessels. The large chute on the land is generally about 15 meters, and the gold mining ship is generally 4 to 6 meters.

4) Spiral concentrator gold selection method

The spiral concentrator gold selection method is a gold selection process with a spiral concentrator as the main equipment. The spiral concentrator is a chute dressing equipment that uses the combined effects of gravity, friction, centrifugal force and water flow to separate the ore particles by specific gravity, particle size and shape (left side of the figure below). It is characterized in that the entire chute is curved in a spiral shape in the vertical direction. The sorting process is: the slurry fed from above the chute flows downward along the chute in a spiral shape. During the flow, the ore particles are stratified. Large particles with a small density are distributed on the outer edge of the spiral groove, and fine particles having a large density are distributed on the inner edge of the spiral groove (right in the lower figure). The stratified heavy product is discharged by the discharge port of the inner groove bottom by the interceptor, and the light product is discharged by the end of the spiral groove.

The spiral concentrator has a simple structure, is easy to manufacture, has no transmission mechanism, and does not require power. The disadvantage is that the selection of materials with a diameter of more than 6 mm and less than 0.05 mm and flat gangue is inferior. It is widely used abroad to select sand gold mines.

5) Cone concentrator gold selection method

Cone concentrators evolved from the principle of a narrow chute (also known as a fan chute). The tapered chute is fan-shaped, with a groove length of about 1 m, a feeding end width of 125 to 400 mm, and a discharge end width of 25 to 9 mm, and the groove surface is inclined.

The slurry is fed from the center of the upper end, distributed by the distribution cone, and the cone is selected. The ore particles are stratified by density during the flow on the sorting cone, and the final intercepting port separates the light and heavy products. There is also a Reichert Cone Concentrator widely used in sand gold pre-selection. It is a vertical overlap of several cones, which can be completed in a few stages.

2 amalgam selection

The amalgamation method can be divided into internal mixed mercury and external mixed mercury according to its production mode. In the gold mining, mercury is widely used to separate gold and heavy sand minerals. In the vein gold mine, amalgam is usually used as part of the combined process with flotation, re-election, cyanidation, etc., mainly used to promote the collection of coarse grains. Body gold.

The internal amalgamation is carried out in a mercury amalgamation tank or a grinding machine, which can better control mercury pollution.

The main equipment for external amalgamation is a mercury-mixing plate, which consists of a bracket, a bed surface and a mercury plate. Mercury from purple copper plate board material, silver-plated copper, mercury plate, silver-plated copper plate amalgamation best. In order to facilitate silver plating and easy replacement in production, the electrolytic copper plate is often cut into small pieces having a width of 400 to 600 mm and a length of 800 to 1,200 mm. After silver plating, the electrolytic copper plate is laid on the bed surface in the oblique direction of the support.

The determination of the area of ​​the mercury plate is related to the amount of ore processed, the nature of the ore and the role of the amalgamation process in the gold selection process. Generally, the mercury plate area required for treating one ton of ore is 0.05 to 0.5 m 2 /ton·day under the condition that the depth of the slurry flow on the surface of the mercury plate is 5 to 8 mm and the flow rate is 0.5 to 0.7 m/sec. If the amalgam is only for the collection of large particles of free gold, and the tailings still need to be flotation, re-election and cyanidation, the public quota can be set at 0.1-0.2 square meters / ton.

Amalgam operation conditions: the concentration of the ore is 10 to 25%, the grain size of the ore is 3 to 0.4 mm, and the flow rate of the slurry is 0.5 to 0.7 m/s. The mercury consumption is 3-8 g/t.

Mercury read protection: Mercury can invade the body through the skin, mucous membranes and respiratory tract in the form of liquids, salts and vapors. Mercury can be found in kidneys, liver, brain, lungs, bones and other organs to poison people. In particular, mercury vapor is the most harmful to humans and can cause acute or chronic poisoning. In China, the air content is not allowed to exceed 0.01-0.02 mg/m3, and the maximum allowable concentration of mercury and its compounds in industrial wastewater is 0.05 mg/l.

In order to protect the environment from pollution and protect the health of workers, amalgamation should be restricted. Some countries in foreign countries have banned the use of amalgam. China is only a few gold mines and small mines in some places still use amalgam. For the entire site with amalgamation operations, mercury poisoning must be protected: (1) Develop a strict amalgam operation system. Mercury-containing vessels should be sealed to prevent mercury vapor from overflowing; protective equipment must be worn during mercury amalgamation to avoid direct contact between mercury and skin; food, food, and smoking are not stored in rooms with mercury. (2) The amalgamation workshop and the alchemy room should be ventilated, and the operation of mercury paste washing should be carried out in a closed operation cabinet with ventilation. (3) having a factory floor where the job should be selected with mercury does not absorb mercury masonry material, made of ground slope of 1-3%, with the walls should be kept smooth surface, regular use soap and water or a solution of potassium permanganate (1 : 1,000) Washing. (4) Mercury collection devices should be installed in the sewage wells under the operating cabinet and outside, so as not to lose mercury. (5) The workshop with mercury operation should be cleaned regularly by manganese dioxide absorption method, which can absorb 99% of mercury vapor in the air.

1). Internal amalgamation method

The internal amalgamation method refers to a method of mixing mercury and extracting gold while crushing the ore in the grinding equipment . Grinding equipment is usually a rake machine, a rake mining machine, a mixed salary water tank or a dedicated small ball mill , a rod mill, and the like.

The process of internal amalgamation is to add mercury to the ore during the grinding process. The ore is mined and mixed with mercury. The newly exposed gold particles are in contact with mercury and become mercury. After the internal amalgamation, the slurry and the mercury paste are discharged from the internal amalgamation equipment, and then the mercury paste is separated by a trap, a chute, a classifier or the like.

The main disadvantage of the internal amalgamation method is the pulverization of mercury. When the ore is crushed, the mercury is divided into particles. These particles are wrapped and covered with an oxide film of a base metal, a lubricating oil film, and a slime particle, thereby losing the ability to bond with each other to cause pulverization. Mercury is difficult to separate from the ore being processed, most of the mercury is lost, and some gold is taken away.

When the content of copper, lead and zinc minerals in gold-bearing ore is very small, and there is no sulfide which is easy to cause large amount of mercury to be pulverized, and the size of the gold is large, the internal amalgamation method is often used. Gold mines also use internal amalgamation to separate gold from other heavy minerals.

2). External amalgamation method

The external amalgamation method refers to a method of amalgamation and gold extraction performed outside the grinding equipment.

Ammonia is commonly used in gold extraction by external amalgamation. The amalgam plate has a fixed type and a vibrating type. The fixed mercury-mixing plates are divided into three types: flat type, stepped type and intermediate trapping type. At present, fixed flat amalgamation plates are often used in China. The flat fixed mercury amalgamation plate consists of three parts: the bracket, the bed surface and the mercury plate. The structure is shown in the following figure. The bracket and bed surface can be made of wood or steel, and the bed surface must not leak pulp. The mercury plate on the bed is a silver-plated copper plate with a thickness of 3 to 5 mm, a width of 400 to 600 mm, and a length of 800 to 1000 mm. The mercury plates are connected to the bed surface one by one according to the inclination direction of the support.

The operation process of gold extraction by external amalgamation method is: the mercury solution is applied to the silver plating surface of the mercury plate, and the slurry flows through the surface of the plate to contact with mercury. After starting the work, add mercury to the slurry. After a period of time after the amalgamation operation, a layer of mercury paste was conveniently retained on the mercury surface and scraped off in time.

The external amalgamation method is suitable for treating gold-containing polymetallic ore, and is mainly used for capturing coarse gold in it. In the gold selection plant, most of the mercury amalgamation plates are installed in the discharge port of the ball mill to capture the coarse free gold in the grinding products.

3 cyanidation

Since it was applied to mines for gold and silver in 1887, it has a history of nearly one hundred years and the process is relatively mature. Because of its high recovery rate and strong adaptability to ore, it can be used as a real estate gold, so it is still one of the main ways of gold production.

The cyanidation process can be divided into agitating cyanidation and diafiltration cyanidation. Stirring cyanide for the treatment of re-selected, mercury-contained tailings and flotation of gold-bearing concentrates, or for total mud cyanidation; and diafiltration cyanidation for the treatment of flotation tailings and low-grade gold-bearing ores Heap dipping and so on.

The conventional cyanidation process is a very mature process, which includes preparation of leaching raw materials; stirring cyanide leaching; countercurrent washing solid-liquid separation; leaching liquid purification and deoxidation; zinc powder replacement and pickling; and smelting ingots and the like.

a. Preparation of leaching raw materials: Usually, the produced ore is crushed, ground (or ore-elected) to prepare a slurry suitable for cyanidation leaching. Grinding fineness depends on the embedding characteristics of natural gold. Gold-bearing quartz vein of ore, typically 60 to 70% ground to -200 mesh; gold-containing ores and sulfide minerals, the use of flotation enrichment, concentrate regrinding to 90 to 95% -325 mesh; containing arsenic or high pyrrhotite ore flotation concentrate is taken after desulfurization roasting arsenic removal, for the calcine cyanidation; Additionally, there are high-carbon interfere cyanide leaching ores.

b. Stirring cyanide leaching: under conditions of a slurry concentration of 35 to 50%, a pH of 10 to 10.5, and a cyanide concentration of 0.03 to 0.06%, the mixture is fully agitated and leached for more than 24 hours. More than 95% of the gold is dissolved as a gold cyanide complex.

The stirring leaching tank has two types: mechanical stirring type and air stirring type.

c. Countercurrent washing solid-liquid separation: In order to fully separate the cyanide leachate from the gold residue, multiple single-layer or multi-layer thickeners are generally used to form multi-stage countercurrent washing; multi-stage filtration washing is adopted by a filter; The machine and the filter form a combined wash. The latter is more common abroad, while the domestic ones mainly use a single-layer or multi-layer concentrator for multi-stage countercurrent washing.

d. Purification and deoxidation of leachate: The leachate (your liquid) obtained from the washing operation usually contains 70 to 80 ppm or more of a solid suspension. In order to prepare the zinc powder replacement operation, the suspended matter content in the noble liquid must be reduced to 5 to 7 ppm, and the oxygen content is reduced to 1 ppm. Therefore, the noble liquid should be purified and deoxidized.

e, zinc powder replacement and pickling: replacing the gold cyanide complex in the solution with zinc powder to precipitate gold. In order to obtain a more efficient displacement reaction of the zinc powder, a lead salt of about 0.005% and a cyanide concentration of about 0.05% should be maintained in the solution.

F, ingot smelting: gold clay and flux generally 1: 0.8 to 1 ratio, i.e., 30 to 40% borax, saltpeter 25%, 15 to 20% quartz sand, 5 to 10% fluorite, soda other, Manganese oxide, etc. The slag is smelted at a furnace temperature of 1000 to 1100 ° C for about 3 hours to obtain a gold ingot (composite gold) containing 85% or more of gold and silver.

1). Ion exchange resin method

The ion exchange resin method is a method for adsorbing and recovering gold from a cyanide slurry by using an ion exchange resin, and is divided into two types of gold extraction methods: RIP and RIL. RIP is called resin slurry method. It is first leached and adsorbed. It has been used for many years in the former Soviet Union. It is only used by the Jolden Jubilee gold mine in South Africa in the western world. RIL is adsorbed by side leaching. It is said that there is no industrial application. Some people also call RIP and RIL a resin slurry method.

The principle of the ion exchange resin method is that the ion exchange resin can dissociate two ionized groups in a solution: a fixed ion (R) that cannot be ion-exchanged and an exchangeable ion that is electrically opposite to a fixed ion. The ion exchange resin is divided into a cation exchange resin and an anion exchange resin according to the positive and negative charges of the exchangeable ions. In the cyanide slurry, gold exists in the form of an anion complex Au (CN). Therefore, when an ion exchange resin method is used for gold extraction, an anion exchange resin must be used. The ion exchange reaction that takes place from the cyanide solution with an ion exchange resin is:

R-OH+Au(CN)2-═R-Au(CN)2+OH-

The basic process of gold extraction from resin pulp is:

(1) Adsorption: When the gold-containing cyanide solution is passed through the resin column, an ion exchange reaction occurs, and gold is adsorbed on the resin.

(2) Desorption: The desorbent is used to desorb the gold from the resin into the solution. For weakly alkaline gold-loaded resin, it can be desorbed with sodium hydroxide solution with pH=13 under normal temperature and pressure; for strong alkaline gold-loaded resin, sodium hypochlorite method, acid thiourea method, zinc cyanide complex method and sulfur can be used. Desorption by cyano complex method.

(3) Recovery of gold: Gold is recovered from a dehydration solution rich in gold by a zinc powder replacement method, an alkali precipitation method or an electrolysis method.

The ion exchange resins currently used for adsorbing gold from cyanide liquid are: strongly basic anion exchange resin AM, AB-17, weakly basic ion exchange resin AH-18, 704, mixed basic ion exchange resin AM-2B, A-2 and so on. AM-2B is widely used in the production of the former Soviet Union. AM-2B is a macroporous bifunctional resin that combines selectivity, mechanical strength, and adsorption and desorption properties with other resins.

2). Zinc wire replacement method

The basic principle of the zinc wire replacement method is the action of zinc and the gold-containing cyanide leaching solution, and the gold is replaced by zinc to be converted into a metal state and precipitated:

2Au(CN)2-+Zn═2Au+Zn(CN)42-

The zinc wire replacement method is carried out in a zinc wire replacement sedimentation tank (commonly known as a gold cabinet). The zinc wire replacement sedimentation tank is an open rectangular box made of wood, steel or cement. The box is 3.5 to 7 meters long, 0.45 to 1 meter wide and 0.75 to 0.9 meters deep. The box is divided into several (5-20) cells by the transverse wall, and there is a partition in each compartment. The first cell is generally used for clarification of gold-containing solution and addition of cyanide (to increase the cyanide concentration of the solution); the last cell is used for the gold mud taken away by the solution; the remaining cells are placed with a mesh of 6-12 mesh. The iron frame and the screen wire are filled with zinc wire. Such a structure is for the gold-containing solution to flow from front to back into each of the grids containing the zinc wires. The handle is fixed to the screen. It is necessary to gently lift up and down the vibration to loosen the zinc wire and deposit the gold mud from the zinc wire on the bottom of the tank. Gold mud is generally discharged 1 or 2 times a month, and the drain is usually blocked with a wooden box. Gold mud is the raw material for smelting.

The zinc wire replacement method is a conventional method for extracting gold from a gold-containing cyanide solution, and was industrially applied as early as 1888. The method consumes a large amount of zinc wire and NaCN, and the obtained gold mud has a high zinc content and a large floor area, and has been basically replaced by a widely used zinc powder replacement method. However, the method is simple in operation, does not consume power, and the cabinet is easy to manufacture. Therefore, it is still used in some small gold mines and local gold mining in China.

3). Stirring cyanidation

The stirring cyanidation method is one of the processes for cyanide leaching. The slurry obtained by grinding and classifying the gold ore is concentrated to a suitable concentration, placed in a leaching tank, and the cyanide solution is added, and aerated and agitated. This method is applicable to materials with a particle size of less than 0.3 to 0.4 mm.

The main equipment for the stirred cyanide leaching process is a cyanide leaching tank. According to the different mixing methods, cyanide leaching tanks are divided into three types:

(1) The mechanically agitated leaching tank is a leaching tank currently commonly used in gold selection plants.

(2) The air agitated leaching tank utilizes the pneumatic action of compressed air to stir the slurry, and the most commonly used is the Bachuk leaching tank.

(3) The air-mechanical combined stirring leaching tank is a combination of the above two kinds of tanks, and is also an effective mechanical and air stirring device. The main advantage is that gold dissolves quickly.

After the end of the cyanide leaching, the gold-containing solution is separated from the slurry by a washing method. There are three washing methods:

The first is the decantation method: the batch method and the continuous method. The former is rarely used due to shortcomings such as long operating time and large amount of solution used. The continuous decantation method is washed according to the principle of countercurrent, that is, the slurry is sequentially fed into the concentration tank from front to back, and the washing liquid is returned from the back to the front, so that the washing liquid used for each slurry concentration is overflowed by the next concentration. flow. This washing method can be carried out by connecting several single-layer concentrators or multi-layer concentrators in series.

The second is the filtration method: the separation and washing operations are completed by a filter. This is usually done with a continuous vacuum filter.

The third is the fluidization method: the washing process is completed in the washing column. At present, this method is in the experimental stage along the gold selection plant in China.

4). Heap leaching cyanidation method

Heap leaching cyanidation, also known as heap leaching and heap leaching, is one of the cyanide leaching processes and is mainly used to treat low grade gold ore. In 1971, the world's first industrial-scale gold heap leaching site was put into operation in Nevada, USA, and has now developed into a mature process.

The heap leaching cyanidation method is a gold ore with a low grade ore crushed or agglomerated into a 3 to 10 mm lump ore, stacked on a bottom pad of anti-seepage, sprayed with cyanide solution from the top of the heap to dissolve the gold in the ore. The gold-containing precious liquid is percolated from the heap and collected into the pool of precious liquid. The gold-containing noble liquid obtained by heap leaching can be recovered by metal zinc replacement method, activated carbon adsorption method, etc., and the recovered lean liquid is returned to the heap leaching operation for recycling. The heap leaching cyanidation process has low production cost and can be put into production very quickly. The heap leaching scale can be large or small, and the amount of ore per terrane can reach tens of thousands of tons. In the United States, each pile of tons of ore is a standard heap; the grade is less than 0.6 g/ tons of ore crushed directly without asbestos as heap leaching, 0.6 to 1.0 g / t of ore crushed to a certain particle size after leaching, heap leaching higher grade by granulation after grinding.

5) Percolation cyanidation

The diafiltration cyanidation method is one of the processes for cyanide leaching, and is a method for leaching gold in a gold-bearing ore based on a cyanide solution permeating through an ore layer, and is suitable for use in sand ore and loose porous materials.

The main equipment for the diafiltration cyanidation process is a percolation leaching tank. The percolation leaching tank is usually a wooden tank, an iron tank or a cement tank. The bottom of the trough is horizontal or slightly inclined and is round, rectangular or square. The diameter or side length of the trough is generally 5 to 12 meters, the height is generally 2 to 2.5 meters, and the volume is generally 50 to 150 tons.

The process of diafiltration cyanidation:

(1) Loading ore and alkali: The fabric is required to be uniform, the particle size is consistent, and the looseness is consistent. There are two methods of dry and wet. The dry method is suitable for ore with a moisture content below 20%, which can be loaded manually or mechanically. The wet method is to dilute the slurry with water, and then use a sand pump to lift or feed the tank into the tank.

(2) Percolation leaching: After the filling is completed, the cyanide solution can be sent to the tank. There are two kinds of cyanide liquid flow in the tank: one is up and down. That is, the cyanide solution is injected from the top of the tank and passes through the ore layer from top to bottom under the action of gravity; one is to go in and out, and the good cyanide solution passes through the ore layer from bottom to top by pressure. After the leaching is completed, the cyanide tailings are washed with water.

(3) tailings discharge: there are two kinds of dry and wet methods. The dry method discharges the cyanide tailings through the bottom working door; the wet method is to wash the cyanide tailings with high pressure water, and let the tailings slurry flow out along the pre-arranged tailings pipe (tank).

6). Zinc powder replacement method carbon slurry method

The zinc powder replacement method is to mix the zinc powder with the gold-containing solution, the gold is replaced by zinc, and then precipitated, and then the gold powder and the excess zinc powder enter the filter cake (ie, cyanide gold mud), and the liquid is separated from the gold. The basic principle is the same as the zinc wire replacement method. Since the surface area per unit weight of zinc powder is much larger than that of zinc wire, the zinc powder displacement method is much more efficient than the zinc wire replacement method.

In production practice, the gold-containing solution is typically deoxygenated with a deoxygenation column prior to displacement of the precipitate. The deoxidation tower structure is shown on the left.

The equipment for zinc powder replacement is linked to the right. The zinc powder and the gold-containing deoxidation solution are mixed into the mixing tank, and then precipitated and filtered by the zinc powder displacement precipitator through the tube at the bottom of the tank. At this time, the gold mud is deposited on the filter cloth by the suction force of the vacuum pump, and the gold removal solution is The filter cloth is discharged through the branch pipe and the manifold. The gold mud is discharged intermittently, and two to three replacement zinc powder replacement precipitators are required for continuous displacement precipitation.

Zinc powder is obtained by sublimation method to rapidly cool zinc vapor in a large-volume condenser. The particle size is less than 0.01 mm, which is easily oxidized, so it must be tightly sealed during transportation or storage.

7). Carbon slurry method

Carbon in Pulp (CIP) is a new process for recovering gold from activated carbon by cyanide leaching. In 1973, the world's first industrialized CIP plant was put into operation at the Homest Gold Mine in the United States, and was quickly promoted to countries around the world.

(1) Pretreatment: cyanide pulp should be sieved to remove coarse particulate materials (such as sand) and wood chips before adsorption, so as to avoid the influence of these impurities on the adsorption and separation of gold-loaded activated carbon and de-gold slurry, and also avoid the accelerated wear and removal of activated carbon. Gold activated carbon is difficult to regenerate; activated carbon should also be pre-ground to remove sharp corners and edges before entering the adsorption tank. If not pre-ground, these debris will enter the de-gold slurry to cause gold loss.

(2) Adsorption: Activated carbon is added to the fully leached pulp, and the activated carbon adsorbs gold in the cyanide slurry to become gold-loaded charcoal. The adsorption is carried out in an adsorption tank (carbon slurry tank). There are many types of adsorption tanks. For the treatment of fine slurry with fine mud, it is advisable to use a common Dole-type tank stirred at a low speed center; for the treatment of a coarse-grained slurry, a Baqik air agitation tank should be used. The adsorption tanks are used in series during production. After the adsorption is completed, the gold-loaded activated carbon and the de-gold slurry are separated by using a sieve mounted on the carbon slurry tank.

(3) Desorption: De-gold treatment of the gold-loaded charcoal separated from the de-gold slurry is called desorption. Common desorption methods are atmospheric desorption and pressure desorption. Desorption is carried out in a desorption column, and the gold-loaded charcoal washed with water is charged into a desorption column, and then the carbon layer is immersed with 4% NaCN and 2% aqueous NaOH solution, and heated to 90 ° C under normal pressure or pressure. At 95 ° C, after 2 to 4 hours, the gold was washed with water, and the total desorption time was 12 to 24 hours. After desorption, a gold-rich desorbent and desorbed charcoal are obtained.

(4) Shen Jin: Gold is recovered from the gold-rich desorbent. The method of sinking gold from the desorption liquid is mainly the electrowinning method.

(5) Desorption of activated carbon: The depleted carbon of desorbed gold is regenerated and proportioned into new activated carbon and reused in the process.

The activated carbon used in today's gold production is mostly coconut shell charcoal in foreign countries, and most of the domestic is apricot nuclear charcoal. When using activated carbon, the strength (ie wear resistance), adsorption capacity, desorption and regeneration performance, selectivity and price of activated carbon should be considered. Among them, strength is the most important.

The carbon slurry method is mainly applicable to gold-containing oxidized ore with high sludge content. China has studied the carbon slurry method since the 1980s. More than 20 charcoal pulp gold extraction plants have been built in Linghu Gold Mine in Henan and Chiweigou Gold Mine in Jilin.

4 flotation method

The flotation method is based on the difference in physical and chemical properties of the mineral surface, and is treated by a flotation agent to selectively attach the useful mineral to the bubble to achieve the purpose of sorting. Non-ferrous ore dressing, such as copper, lead, zinc, sulfur, molybdenum and other miners to use flotation process; some ferrous metals, rare metals, and some non-metallic minerals, such as graphite ore, apatite, also flotation Law selection.

Flotation is one of the most widely used methods for processing gold ore in gold concentrators. In most cases, the flotation process is used to treat highly reversible sulfide mineral gold-bearing ores with the most significant effect. Because flotation can not only maximize the concentration of gold into sulfide mineral concentrates, but also waste tailings, the cost of ore dressing is low. Flotation is also used to treat multi-metal gold ores, such as gold - copper, gold - lead, gold - antimony, gold - copper - lead - zinc - other minerals such as sulfur. For this kind of ore, the flotation process can effectively identify and select various gold-bearing sulfide concentrates, which is conducive to the comprehensive recovery of mineral resources. In addition, so-called "refractory ores" that cannot be directly treated by amalgamation and cyanidation are also required to be treated by a combined process including flotation. Of course, the flotation method also has limitations; for coarse-grained inlays, ores with a gold particle size greater than 0.2 mm, and for quartz-bearing gold-bearing ores without sulfides, it is difficult to obtain a stable flotation foam after slurrying, using flotation The law has difficulties.

In recent years, the flotation process of gold ore has made great progress, mainly in the innovation of process, the development of new agents, and the improvement of design. The use of cutting-edge grinding; cutting-edge selection process is the current development trend of flotation gold selection, most foreign gold selection often uses two or even three sections, China's Suichang Gold Mine, Xiangxi Gold Mine uses two-stage grinding; two special processes The recovery rate of gold is increased by 2% to 6%; changing the pharmaceutical system, using a mixture of various agents, can also improve the effect of gold selection, and the addition of butylamine black and xanthate in the Suichang Gold Mine and the Jinchang Gold Mine. The recovery rate of gold is increased by 2% to 5%.

The general process of flotation is:

The washed and classified mineral mixture is uniformly stirred in a mixing tank and sent to a flotation machine. The gold ore generally uses sodium carbonate as a conditioning agent to float the gold. At the same time, the butyl xanthate and the amine black medicine are used as a supplement to separate the gold ore powder from the slag and produce gold concentrate powder. In the new flotation machine, the dynamic collision between the bubble and the ore particles and the static separation of the bubble particle combination are better, which is beneficial to the selection of fine or fine grain gold ore. In addition, the flotation machine realizes automatic control, so it is suitable Selected in the gold mine. The mineral concentrate after flotation generally contains more water, and it is necessary to use a new high-efficiency concentrator to reduce the concentrate water to the national standard. Conveyor and feeder can be connected in each production process.

Since the flotation method can only maximize the concentration of gold into various sulfide concentrates, and can not finally obtain the finished gold, there are not many gold selection plants that use a single flotation process, generally the flotation is used as a joint. A process of the process is adopted. At present, the gold selection in China using a single flotation process includes gold deposits such as Suichang and Xiuyan and some small gold mines in local groups.

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