Practical application of semi-self-grinding process

Superiority and suitability for ore type

The semi-self-grinding process is a form of self-grinding process. The medium consists of two parts: the ore and the added steel ball. The two media themselves are impact-sliding between the lining and the lining, so that the ore is ground. Wet grinding and conventional crushing ratio, less dust, good environment, low energy consumption, convenient material transportation, good management and easy maintenance, many advantages, and a wide range of applications. The grain size of the ore is 200mm-350mm. After a single grinding, the particle size of the product can be up to several millimeters. The crushing ratio is large, which can significantly shorten the process. It has certain advantages in space saving, capital investment, maintenance and other aspects. The superiority.

The addition of a small amount of steel balls can eliminate the accumulation of hard stones, improve the mill capacity, and reduce the consumption of the liner. SAG ball mill filling rate is generally 2% to 8%, 70% -80% speed, crushing ratio up to 100-150, the amount of ball mill, a self-loading semi gold ore 6 tons, fitted The ball rate is 6%, the grid hole width is 12 mm, the rotation speed is 17 rotations per minute, the rotation speed is 70%-80%, the crushing ratio is about 145, and the grinding concentration is 75%-85%. Due to the limitation of the type of ore to be treated, the application range is still very limited compared with the conventional crushing and grinding process. In the production practice, the problems in the semi-self-grinding process should be solved according to the ore properties and production conditions of the mine, so that it can be continuously improved. In order to show its superiority.

The semi-self-grinding process is suitable for the treatment of ore types: ore with high moisture content, high viscosity, and difficult to crush and screen; the ore body is altered by petrochemical green curtain, green mud, actinolite and kaolin ; Mineral ore with coarse grain size, dissociation development, relatively high density ore; corrosive ore.

Working mechanism and lining, etc.

The main force of the internal crushing ore in the semi-autogenous grinding machine is the impact force when the ore and the steel ball are free to fall. The mutual grinding and stripping force between the granular steel balls and the instantaneous stress of the ore from the pressure state to the tension state realize the ore nugget. The granules are graded, the large pieces are in the rotating inner layer (near the center of the mill), and the ore particles are drilled to the outer layer for self-grinding, medium grinding or mutual grinding. The diameter is large, and the large potential energy is generated, so that the ore block is impacted, ground and pulverized; the cylinder is short, anti-segregation, and the size is blended, which is convenient for discharging.

Under the condition that the semi-autogenous mill specifications and speed are fixed, the feed amount of the material and the ratio of the size of the ore block directly affect the grinding process. Practice shows that the material filling rate is between 30% and 40%, and the ore supply stability is basically unchanged in terms of quantity and particle size ratio. The general size blocks each account for 50%. One is the quantity, and the other is that the ratio of the particles is basically stable. However, the capacity is low, the liner is consumed more, and the treatment of hard ore is prone to the accumulation of hard stones, becoming "hard-to-wear particles" or critical particles. The length-to-diameter ratio of the semi-autogenous mill is generally between 0.30 and 0.35, and most of them are L/D ≤ ​​1.5, which are mostly short cylindrical mills.

A MQG4014 semi-self-grinding process plant is based on the processing capacity of 1651 pits. The ball diameter of the semi-autogenous grinding machine has been increased from 100 mm to 120 mm, and the medium gravity is increased in the 4 m high grinding chamber space. Potential energy, improve the effectiveness of "crush". The filling rate was also raised from 8% to 12.88%, the load increased, the current was basically maintained at 340 amps - 360 amps, and the ball diameter of the second-stage ball mill was reduced from 80 mm and 60 mm to 60 mm and 40 mm. The ratio is changed from 3:1 to 2:5, so that the medium and the mineral are fully "grinded", the filling rate is increased to 42%, the current is increased from 320 amps to 350 amps, and the size of the cyclone grit nozzle is 30. The mm adjustment is 40 mm, resulting in an increase of 50 tons per day, reaching 430 tons per day.

The lining is described by taking the MQG4014 semi-self-grinding as an example. The end lining is 4.212 tons, the outer ring is matched with the inner ring, and the feeding end has a hole diameter of about 1.5 meters, that is, the feeding material can be inserted into the cavity to change the lining plate, and the service life is 2 months; the lining is 7.794 tons, and the row is arranged at a high edge and a low edge. The cloth will be smashed and cracked by the steel ball in less than 3 months. After being replaced by high ribs and 2 flat edges, the life is extended by 1 month. The specification is 1090×220× (thickness 60+ rib 60) A total of 54 pieces; lattice lining 4.095 tons, the outer ring pressure-mixed plate protrudes 2 edges, the pressure plate and 2 along the level, the two 2 along the assembly fit, the inner ring lattice small lining lattice part and the edge flush, large pressure plate lattice Partially protruding 2 edges, the small lining and the large pressure plate are assembled along the assembly, the service life is 4 months; the lining is 4.68 tons, and the two side plates are close to the four large screws, and the outer ring and the inner ring can be added. The grid version mainly enhances the pulp, so that the qualified person passes through the center hole and enters the discharge cylinder screen; the manhole lining is 0.268 tons, one piece.

Excavation cylinder screen: ∮ 1130 × (diameter 16 threaded steel mesh 1700 + non-porous end 250), cylinder screen center diameter, inlet 25 mm, outlet 50 mm. The inverted mesh of the threaded steel bar is welded on the screen to make the ore particles larger than the mesh size of 10 mm return to the semi-autogenous grinding machine for re-grinding.

Heavy sand grade, when the ore is 2 g / ton - 3 g / ton, 11.28 g / ton - 30.25 g / ton between steel balls; lining plate gap 222.52 g / ton - 1090.59 g / ton; mill - classifier chute 158.60 g / ton - 166.95 g / ton.

Electronic belt scale, magnetic arc and spiral classifier

They all take the semi-autogenous grinding machine as the core, or regulate the ore, or the magnetic ball to break the ball, or form a loop, which is an important component of the semi-self-grinding process. The electronic belt scale carries the electromagnetic speed controller of the same heavy plate feeder to ensure that the semi-self-grinding machine supplies the right amount, uniform and stable, and the magnetic arc magnetic to semi-self-grinding machine discharges the broken ball fragments, spiral classifier and semi-self The mill constitutes a closed circuit, and the amount of sand returned is directly related to the scale of production.

The electronic belt scale consists of a steel mechanical scale, a speed sensor, a high-precision load cell, and an electronic belt scale control display instrument. When weighing, the load-bearing device transmits the gravity of the material on the belt to the load cell, and converts it into a digital quantity A after being amplified; after the material speed is input to the speed sensor, the number of pulses is output B; A, B are sent to the calculator after calculation , the total weight of the material is obtained cumulatively.

First of all, we must do a series of work before and after the school scale, including scales, scales, etc. for the scales. Secondly, pay attention to the timely cleaning of foreign objects or dust on the scales to ensure that the zero point of the scale is within the permitted range. For the heavy plate feeder to feed the belt, the electromagnetic speed control motor controller should be adjusted to control the speed of the chain plate to ensure the proper supply of the semi-autogenous mill. The specification of the heavy plate feeder of a mine selection plant is 1000×9500 (mm), the chain plate speed is 0.044 m/s, the motor power is 15 kW, the production capacity is 80 tons/hour, and the corresponding processing amount of the electromagnetic controller instrument pointer is shown in the table. 2.

The broken small ball discharged from the semi-autogenous mill not only consumes energy but also affects the amount of treatment. More dangerous is damage to the pipeline and the pump impeller. Only when it is repaired, it is picked up from the chute, and the cost is not cleaned. Magnetic arc is in semi-permanent installation of a magnetic iron mill outfall, when the ball is broken adsorbed magnetic force to the highest point, it will automatically fall to connect the Di inclined chute, automatically slides crushed ball box.

When the residual ball ore is circularly moved around the semi-autogenous mill barrel, it is subjected to three forces below the centerline of the cylinder: gravity mg, magnetic force F, support force N, and the angle between the gravity and the tangent of the cylinder is  Then, the centripetal force mv2/R=N-mgsin-F, when at the lowest point =∏/2 sin=1, at this time N=mv2/R+ mgsin+F. It is also affected by three forces above the centerline of the cylinder: gravity mg, magnetic force F, support force N, and the angle between the gravity and the tangent of the cylinder is ∏-, then the centripetal force is mv2/R=F-mgsin -N, when at the highest point =∏/2 SIN=1, at this time N=F-mv2/R-mgsin, since N=0 at the highest point, then F=mv2/R+mgsin.

According to the manufacturers technical personnel magnetic arc, neodymium-iron-boron rare-earth magnetic materials, the strength of 0.2T, and 1Oe≈ (1000 / 4Π) A / m 1T = 1N / Am 1T = 1 / (4) × 107A / m 1T ≈104 Oe The magnetic field is divided by 240kA/m, which is less than the weak magnetic field. If the greater than the strong magnetic field is substituted into the above relation, it can be known that 0.2T=159.24kA/m belongs to the weak magnetic field 0.3T=238.85 kA/m, which is also a weak magnetic field. 0.7T = 557.32 kA / m is a strong magnetic field.

A gold processing plant semi-autogenous mill workers introduction, just installed on a magnetic arc, crushing the ball residual class plane take up to 20 pouches, each pouch 25kg, class total 0.5t. Preliminary analysis block mostly crushed ore pyrite, copper ore, ore block size occupied by the magnetic take weight percentage: greater than 70, less than 20, 20%, 80% between 35-45. The gold grades were determined to be 8.82 g/t, 1.64 g/t, and 6.58 g/t, respectively. The fine grain adhered to the test has a gold grade of 182.47 g/t. The magnetic rate was measured by magnetite. The magnetic minerals after the sample was crushed accounted for 79/1462=5.40% of the total amount of 90/1550=5.81%, indicating that the magnetic rate is in the range of 5%-6%, mostly hematite.

The FG-20 classifier of a mine has a shaft diameter of 500 mm, a wall thickness of 32 mm and an inner diameter of 436 mm. It has been twisted several times for various reasons. Even if the manufacturer sends technicians to the site to guide the repair, it will not solve the problem at all. The shaft length of 19 meters in the near future is 9 meters below the shaft head. The brother mine uses 50 thick steel plate to process the flange fittings. The shaft is made of 30 thick 16 manganese steel sheets. The shaft is inserted into a positioning tube to connect the inner and outer walls. The weld is smoothed and the outer wall flange is placed for seamless welding. In order to increase the degree of firmness, the flange bolts on both sides are welded to each other and a total of 24 pieces are welded. The result was only a week. To this end, the mine relies on its own strength to weld itself. After one month of use, as the new shaft arrives, it is replaced with a new one. It is said that the classifier shaft should be replaced once every two years.