The Introduction of Placer Gold Ore Dressing Technology and Equipment
2018-02-05 0 Views (823)
The selection of sand and gold mine is mainly based on the physical properties of minerals, such as grain size, shape and specific gravity, so as to achieve the purpose of sorting in the moving medium flow. This is the oldest method of selection in M
The Introduction of
Placer Gold Ore Dressing Technology and Equipment
1. The Gold Sand General Industrial Goods
Gold dredger mining
Hydraulic giant mining
Cutoff grade of mixed sand g/m3
Min. industrial grade of mixed sand g/m3
Min. mineable thickness m
Rejected width of gangue m
Min. quantity of mineable placer m3
2. Ore Dressing Technology and Equipment
The selection of sand and gold mine is mainly based on the physical properties of minerals, such as grain size, shape and specific gravity, so as to achieve the purpose of sorting in the moving medium flow. This is the oldest method of selection in Mineral Engineering--Gravity concentration method. The main equipment includes chute, jigger, table concentrator and spiral separator etc. The simplest sand gold typical selection process has shown in Figure 9-1; more perfect process flow chart is shown in Figure 9-2.
Because of the action principle is different, the gravity separation process can be divided into washing, grading, chute beneficiation, jigging and tabling and heavy medium separation etc. In addition to washing, grading as long as it is in the process of particle size separation, the other is a mechanical clastic mixture according to the proportion (density) of the process of separation of minerals.
2.1 Chute processing equipment
The other all are the process of separating the mineral by the proportion of the mechanical clastic mixture (density).Chute beneficiation is use the interaction of inclined flow's impulsive force, ore particle gravity, friction or centrifugal force. The heavy mineral sink in different zones in the groove surface becomes concentrate or middling, and light minerals are taken away by water then become tailings.
Figure 9-1: the most simple sand gold typical selection process.
Figure 9-2: Better placer gold ore dressing process
Since the action principle and difference of chute, chute sorting equipment including washing tank and chute, spiral concentrator etc. Most of times are use chute sorting in the gold dressing. According to the sorting granularity of chute types can be divided into coarse sand and mud chute. The performance of several commonly used gold chutes is shown in Table 9-1.
In our country, gulch-gold dressing mainly adopts the coarse baffle chute. Particle size is 6-200 mm or larger. The structure is a long and narrow wood groove, the bottom is provided with a baffle or cotton, wool fabric as auxiliary equipment, in order to increase the flow resistance and friction of heavy minerals, to slow down the speed of movement and deposition at the bottom of the groove, so as to improve the separation effect. At the same time, vortex formed between the baffle helps the mixed light minerals in heavy mineral being turned up to flow away.
Table 9-1: The performance of the selected gold chute
Fan shaped chute
Adjustable metal chute
The width of chute is about 0.9-1.8m which is depended on capacity. The depth of chute is 0.75-0.9m. And the length is generally bigger than 5m; it will be hundred meters when regarded as guide slot. The rough chute can be made of materials in local for its simple structure, its easy installing and transporting without power. So it is used until now.
2.2 Jigging separation equipment
In gulch-gold beneficiation, when processing small size materials with jigger, the minus sieve ore discharge method is applied. And it needs to lay artificial bed. These factors should be noticed to right adjustment as follow: feeding, stroke, jig frequency, feed water quantity, water supply, bed thickness, discharge way etc... Therefore it is easy to get good beneficiation performance.
In recent years, the development of the jigger has been taking a break. By the symmetry of sine curve of jig to zigzag curve, it is good for recycling fine class dense gold-bearing minerals and reducing water consumption.
The lateral external diaphragm type Yuba jigging machine developed by Yuba Company of USA has good effect for beneficiation of placer. The beneficiation lower limit of Yuba jigging machine can be 0.04mm, and it is widely used for beneficiation system of gold dredger. There are some types for chamber of this jigging machine: series connection of double chambers, three chambers and four chambers, screen sizes are 1060×1060mm, 840×840mm and 600×600mm. Moreover, the new circular jigging machine researched by Royal IHC of Holland and Norman Cleave land of USA (China had already developed this type) develops toward large-scale. This machine is round shape, the largest is divided into 12 jigging chambers, and cross sections are trapezoidal. The movement of membrane is not relied on eccentric rod gear, adopts hydraulic piston device instead to make the membrane to rapidly move forward and back off slowly, so there will not be strong sucking effect when backing off. It is proved that capacity per unit area of circular jigging machine is double ordinary jigging machine; efficiency is up to 97.5%. When it is used for gold dredger, there is base adjusting device, excellent anti bump performance makes it keep balanced at any time, this makes it is well received by users.
2.3 Concentrating Table
Concentrating table is one of gravity separation equipment for beneficiation of fine ore. The working principle of concentrating table is making the table surface to do reciprocating motion by using the slope water flow and differential mechanism. When the ore particles move on the table surface, its inertia force is larger than the friction between the ore and the table surface to make sure different grade ores get separated.
In the process of placer gold beneficiation, usually adopting the concentrating table to do concentration to the rough concentrate ore after roughing by chute or jigging machine, the operability is over 98%, and we can get the final concentrate and tailing in this way.
It is worth noting that, before we do the beneficiation, we need to do classification by hydraulic classifier in order to improve the beneficiation effect of concentration table. You should pay attention to the adjustment of related parameters in operation. Usually, the conditions that should be controlled are feed particle size, suitable processing quantity, stroke and speed, water consumption, slope, picking method.
Feed particle size and processing quantity should be controlled according to the technology requirement of the selected type. Stroke and speed are closely linked each other parameters, directly related to the different levels of feed particle size. When separating coarse placer gold, stroke should be bigger, speed should be smaller; the bed slope should be larger. It is contrary when separating thin placer gold. The specific parameter can be controlled in rated adjusting range.
2.4 Gold dredger separating equipment
Gold dredger was created in New Zealand in 1870, with the popularization, application, and continuous improvement, it developed very fast. In terms of operation form, gold dredger is a floating mining and processing plant in the sea. It contains mining equipment, separating equipment; tailings discharge device, relevant hull, water supply, electric supply, signal, and some other auxiliary facilities. For stable operation, the most of gold dredgers for inland placer gold deposit are flat-bottomed. Using for coast and deep sea (the deepest digging depth is 4600m in some countries) placer gold placer, the most of dredgers are self-propelled ship and tugboat instead of flat-bottomed boat, in order to resist stormy waves.
The processing equipment and auxiliary facilities should be deployed according to the gold placer property and relevant technology requirement. It usually contains crusher, washing machine, screening machine, separating machine, processing system, gravel and tailings exclude system, etc.
Crush, screening, desliming are prerequisite before gold placer separation. Screen out the thick gravel firstly and then desliming. Cylindrical drum sieve, cylinder scrubbing machine, groove type washing machine, mineral washing trough, and chute are common when crushing and separating gold placer. Sometimes, as for cementing gold placer, rod mill is more suitable.
Choose gold system according to the ore properties and experimental results of optional choose. It can be made of chute, vibrating screen, jig, shaking table, the amalgamation of gold equipment and appropriate increase or decrease in combination, such as improve transport device and properly configured.
Discharging equipment of gravel and tailing is made up of hopper, cylinder screen, and gravel chute, tailing chute, belt conveyor and hoister. The discharging methods are mainly conventional method, non-conventional method, hybrid method and stratified discharging method. At present the commonly used method is conventional discharging method, namely after separation from cylinder screen, the product is discharged to mine pit by tailing chute, the coarse particle product on the screen will be transferred to the non-mineable region by the belt conveyor. However, the latter two discharging methods are good for soil revivification, and decrease the height of refuse dump, which creates conditions for soil recover and agriculture, and is in favor of reduce pollution, it’s really a good method for both gold mining and people benefits.