First, the dressing workshop process

(1) Overview of the mineral processing workshop

The dressing workshop currently has two plants of 200 tons/day and 600 tons/day. The daily handling capacity of 200 tons/day plant is 300 tons, and the daily processing capacity of 600 tons/day plant is 900 tons, and the total daily processing capacity is 1200 tons.

The main positions of the ore dressing workshop include feeding, crushing, grinding classification, flotation and pressure filtration. The main equipment consists of jaw crusher , rotary disc crusher , ball mill , classifier, flotation machine and filter press.

(II) Introducing the process flow chart of the mineral processing workshop with the 600 tons/day selection plant as an example (see Figure 1)

(3) Main tasks of each position

1. Feeding position: The large ore (unqualified material) in the original ore from each mining area is crushed and passed through the sieve to become the qualified material that meets the requirements of the inlet of the crusher.

2. Broken screening position: The material is further pulverized to make it a qualified material that meets the grinding requirements.

3. Grinding and grading post: further processing the qualified materials from the crushing to achieve the particle size requirement of effective floating flotation.

4. Flotation post: Through the action of certain chemicals, the effective floating of the target mineral is achieved.

5, dehydration post: dehydration of the flotation of the bubble product, so that its water content reduced from about 80% to about 15%.

Second, the basic knowledge of mineral processing

(1) Concept

1. Scale of the concentrator

Generally refers to the quantity of raw ore processed by the mining plant each year. The gold selection plant is generally expressed in tons/day.

2. What is concentrate, medium mine, tailings?

Concentrate refers to the final product of the concentrator; medium ore refers to the intermediate product of the beneficiation process; tailings refers to the abandoned part of the concentrator.

3. What is rough selection, selection, and sweeping?

The rough selection refers to the sorting operation of the slurry treated by the medicament; the selection refers to the operation of re-selecting the rough-selected bubble products; the sweep selection refers to the operation of re-selecting the rough-selected underflow.

4. What is the calculation method of yield and concentrate yield:

In the process of beneficiation, the percentage of the weight of a product obtained and the weight of the ore is called the yield of the product.

Calculation method of concentrate yield:

--original grade

--concentrate grade

θ - tailings grade

5. What is the calculation method of mineral recovery rate and theoretical recovery rate?

The ore recovery rate refers to the amount of metal in the concentrate or the amount of useful components as a percentage of the amount of metal or useful component in the ore.

The calculation method of theoretical recovery rate:

--original grade

--concentrate grade

Θ-tailing grade

6. What is the calculation method of fineness and fineness of grinding?

Fineness refers to the percentage of all particles in a material that are smaller than a certain particle size.

Method for calculating grinding fineness

G _{pot + pulp} : the concentration of the pot filled with the total weight of the pulp

G _{pot + sieve top} : the total weight of the sieve topping up the water

G _{pot + water} : the total weight of the pot filled with water

7, mill filling rate

The ratio of the volume occupied by the steel ball to the effective volume of the mill.

8, grading

The process of dividing the material into several levels of granularity according to the different settling speed of the ore particles in the medium.

9, grading efficiency

That is, after the material is classified, the amount of the fine fraction in the overflow product obtained is the same as the percentage of the fine fraction of the same grade in the material fed to the classifier.

10. Critical pH

Under certain conditions, minerals can float and non-floating PH boundaries.

11. Flotation and flotation process

The main principle is to make use of the difference in physical and chemical properties of the mineral surface to selectively attach one or a group of minerals in the ore to the bubble and rise to the surface of the ore to separate the useful mineral from the gangue mineral. Because the sorting process must be carried out in the slurry, it is called floating ore dressing, referred to as flotation.

(2) Flotation reagents used in the beneficiation workshop and their effects

1. Adjusting agent: The main role of lime is to adjust the pH value of the slurry. The modifier includes an activator and an inhibitor, and the main function is to change the properties of the surface of the ore and affect the action of the mineral and the collector .

2. Collector: The main role of butyl xanthate is to increase the hydrophobicity of the mineral surface, so that the target mineral adheres to the bubble and effectively floats as the bubble rises.

3, foaming agent: 11 # oil its main role to improve bubble stability.

(3) Flotation process

The flotation process is completed in the flotation machine. It is a continuous process and can be divided into the following four stages.

1. Raw material preparation. Preparation of raw materials before flotation includes grinding, mixing, dosing, stirring, and the like. After grinding, the particle size of the raw material must meet certain requirements. The main purpose is to dissociate most of the useful minerals from the inlaid state. The other purpose is to enable the bubbles to carry the ore particles up, which is generally required to be ground to less than 0.2 mm. Slurrying refers to the mixing of raw materials into pulp of suitable concentration. Various flotation agents are added later to enhance the difference in floatability of useful minerals and gangue minerals. The purpose of the agitation is to make the flotation agent and the surface of the ore particles fully effective.

2. Stir the aeration. The stirring aerator of the flotation machine is used for agitation and air is sucked in, and a special compressor device can also be provided to press the air in. The purpose is to make the ore particles in suspension, and at the same time produce a large number of suitable and relatively stable bubbles, causing the mineral particles to collide with the bubbles.

3. Mineralization of bubbles. After acting on the flotation agent, the surface hydrophobic mineral particles can adhere to the bubbles and gradually rise to the slurry surface to form a mineralized foam. The surface hydrophilic ore particles cannot adhere to the bubbles and remain in the slurry. This is the most basic behavior of flotation separation of minerals.

4. The scraping of mineralized foam. In order to maintain continuous production, the mineralized foam is discharged in time, and the scraper of the flotation machine scrapes it out. This product is called “foam concentrate”. The product left in the pulp and then discharged is called “tailings”.

(4) Factors affecting the mineral processing process

1. Factors affecting screening operations

(1) The nature of the material

a material particle size characteristics

The particle size composition of the sieved material has a decisive influence on the screening process. Under any conditions, the fine particles always pass through the sieve holes more easily than the coarse particles. Therefore, as the content of fines in the material increases, the productivity of the sieve also increases significantly.

b water content and mud content of the sieved material

The external moisture attached to the surface of the material has a certain influence on the screening of the material; the moisture in the pores and cracks of the material and the combined moisture of the material have no effect on the screening process.

The surface moisture of the material increases within a certain range, and the viscosity increases. The surface moisture of the material can make the fine particles stick to each other and adhere to the large block, and the sticky material will also block the mesh hole. These reasons greatly reduce the efficiency of screening.

When the same material is sieved on different sizes of sieve surfaces, the effect of moisture on the screening efficiency is different. The larger the mesh size, the smaller the effect of moisture. This is because the larger the mesh size, the less likely the mesh is blocked. In addition, the more important reason is because the distribution of moisture in each particle size is not uniform. The smaller the particle size, the larger the specific surface area and the higher the moisture content. Therefore, when the mesh opening is large, the fine particle level having a high moisture content can be quickly sieved off, and the water content of the sieved material is greatly reduced so as not to affect the progress of the screening process. Therefore, when the water content of the material is high, which seriously affects the screening process, it may be considered to increase the screening efficiency by appropriately expanding the mesh size.

c particle shape of the material

Round particles are easy to permeate through square holes and round holes: the crushed products are mostly polygonal, and it is easier to pass through square holes or round holes than through rectangular holes; strips, plates and flakes are difficult to penetrate square holes and round holes. It is easier to pass through the rectangular hole. Therefore, the influence of the shape of the particles can be overcome by selecting an appropriate mesh shape.

(2) Screen type and working parameters

a sieve surface type

There are usually three types of working faces on the screen surface: steel rod (or strip), steel plate punching and steel wire weaving. Their effect on the screening process is primarily related to their effective area.

The effective area of ​​the sieve is the ratio of the area occupied by the sieve holes to the area of ​​the sieve surface, which is referred to as an effective sieve surface. The larger the effective sieve surface, the more the number of sieve holes on the unit sieve surface, and the more chance that the material passes through the sieve hole, the higher the unit production capacity and the screening efficiency of the sieve surface, but the shorter the service life. Which screen surface to use should be determined according to specific requirements. When screening large pieces of material or causing serious wear, wear-resistant bar sieves or steel plate punching screens should be used; when sieving medium and fine particles, steel wire woven sieves are often used.

b mesh shape

In the screening practice, the commonly used mesh holes have a circular shape, a square shape, and a rectangular shape. The mesh shape of the punched screen surface is mostly round; and the woven screen surface has two shapes of rectangle and square. The choice of mesh shape depends on the size of the sieved product and the production capacity of the sieve.

The particle size of the particles passing through the rectangular mesh is larger than the particle size of the circular and square mesh having the same size. The circular mesh has a smaller particle size of the undersize product that passes through the mesh in the case of the same nominal size compared to other shaped mesh openings. It is generally believed that the maximum particle size of the particles actually passing through the circular mesh is on average only 80% to 85% of the particle size of the square mesh through the same size.

The shape of the mesh has an effect on the effective area of ​​the screen and the possibility of the particles passing through the screen. The rectangular mesh has the largest effective area, followed by a square and a minimum of a circle. Therefore, the productivity per unit area is also sequentially decreased in the above order. Another advantage of the rectangular mesh hole is that the mesh hole is not easily blocked, and the ore particles only need to be in contact with three or two sides of the mesh hole, and the resistance is small. The length of the hole is along the direction of movement of the material on the screen surface. Its disadvantage is that it easily penetrates the strip or flakes, making the undersize products uneven. Therefore, the rectangular mesh can only be used if the sieve product size requirements are not particularly strict.

When selecting the shape of the mesh, it is best to match the shape of the material.

c mesh size

The larger the sieve opening, the higher the productivity of the unit sieve surface and the higher the screening efficiency.

d screen surface motion characteristics

The sieve used in the ore dressing machine can be divided into: fixed screen with fixed screen surface and vibrating screen with strong vibration on screen surface. The fixed screen surface is fixed, the ore particles move parallel to the screen surface, the screening efficiency is very low, and the vibrating screen is vibrated in the direction close to the vertical screen hole due to the strong vibration of the screen surface, and the vibration frequency Higher, so the screening efficiency is the highest.

The screening efficiency of the sieve of the same nature differs depending on the strength of the sieve surface. The excessive or too small movement of the sieve surface is not conducive to the passage of fine particles through the sieve.

e screen width and length

For a certain material, the productivity depends mainly on the width of the screen surface, and the screening efficiency depends mainly on the length of the screen surface. In the case of sieve productivity and constant movement speed of the material along the screen surface, the larger the screen width, the thinner the thickness of the layer; the larger the length, the longer the screening time. The reduction of the thickness of the layer and the lengthening of the screening time are all beneficial to improve the screening efficiency. When the sieve surface is narrow and long, the thickness of the material layer on the sieve surface is increased, so that the fine particles are difficult to access the sieve surface and pass through the sieve hole, and the ore content and the screening efficiency are lowered; otherwise, the sieve surface is wide and short, the sieve surface The thickness of the upper material layer is reduced, so that the fine particles are easily passed through the sieve holes, but at this time, the residence time of the particles on the sieve surface is short, and the probability of passing through the sieve holes is reduced, so the screening efficiency is also lowered. Usually, the length to width ratio of the screen surface is 2 to 3.

f inclination of the screen surface

In general, the screen is installed obliquely to facilitate discharge of the material on the screen. The inclination angle should be suitable, the inclination angle is too small, and the movement speed of the material on the sieve surface is too slow. Although the screening efficiency is high, the productivity of the sieve is reduced; on the contrary, the inclination angle is too large, the material discharge is too fast, and the screening efficiency is lowered. Therefore, the inclination of the screen surface should be appropriate.

(3) Operating conditions

a give amount

As the amount of ore is increased, the productivity of the sieve increases, but the screening efficiency decreases. Production practice has shown that as the screen load increases, the screening efficiency initially declines slowly and then decreases rapidly. When the ore amount is too large, the screen surface becomes a chute, and actually only serves as a transport material. The number of products entering the sieve through the sieve hole is extremely small, and the screening efficiency drop due to the increase of the ore supply amount on the sieve surface of the small sieve hole is more remarkable. Therefore, for screening operations, both high productivity and high screening efficiency should be ensured.

b feed uniformity

It is a very important factor in the screening process to uniformly feed the material to the screen surface and evenly distribute it over the screen width. The uniformity of the feed means that the weight of the material fed into the sieve should be equal in any of the same time intervals; the distribution of the sieve material along the width of the screen surface should be uniform. Let the material spread a thin layer along the width of the whole sieve, which not only makes full use of the sieve surface, but also facilitates the passage of fine particles through the sieve hole to ensure high productivity and screening efficiency. In order to ensure the uniformity and continuity of the feed, the direction of movement of the material before it enters the sieve should be consistent with the direction of the flow on the screen surface, and the width of the material entering the screen surface should be as close as possible to the width of the screen surface.

c sieve amplitude and vibration times

Within a certain range, the screening efficiency and productivity increase as the sieve amplitude and vibration times increase. However, the excessive amplitude makes the ore particles stay in the air for a long time, but reduces the probability of screening the mineral particles and reduces the screening efficiency. Also, excessive amplitude and vibration can damage the components. In the production, the amplitude of the sieve can be appropriately adjusted according to the specific conditions of the material. The principle of adjustment is: a large amplitude is difficult for a difficult-to-screen material with a coarse particle size, a thick layer, a high density, and a large viscosity; and a small amplitude is used for a sieve material having a fine particle size, a thin material layer, and a small density. Large amplitude and small vibration times should be used when sieving coarse materials; small amplitude high vibration times should be used when sieving fine particles.

2. Factors affecting the working index of the crushing operation

There are three main aspects: the physical and mechanical properties of the ore, the working parameters of the crusher and the operating conditions.

(1) Mechanical and physical properties of ore

a ore hardness

The hardness of the ore is expressed by the compressive strength or the Platt hardness coefficient of the ore. During the beneficiation process, the ore is divided into five grades: soft, soft, medium hard, hard and very hard. The harder the ore is, the higher the compressive strength, the lower the productivity, and the higher the productivity.

b material humidity

Humidity itself has little effect on the crushing, but when there is a lot of mud and fine ore in the material, the fine material will agglomerate or stick to the coarse particles due to the increase of humidity, thereby increasing the viscosity and reducing the discharge speed. The productivity declines, and when it is serious, it will cause blockage of the discharge port and affect the normal production.

c ore density

The production capacity of the crusher is directly proportional to the density of the ore. The same crusher has a high production capacity when crushing ore with high density. On the contrary, the production capacity is low.

Deconstruction of d ore

The degree of development of ore cleavage also directly affects the production capacity of the crusher. Since the ore is easily broken along the cleavage plane when it is broken, the ore with developed cleavage surface is broken, and the crusher has a higher production capacity than the compacted ore. Much more.

e particle size composition of broken materials

When the content of coarse particles (greater than the size of the discharge port) in the crushed material is high and the ratio of the maximum mass of the ore to the ore width is large, the crushing ratio to be completed is large, so the production capacity is low. On the contrary, the production capacity is high.

(2) Working parameters of the crusher

a crushing machine

The angle between the jaw and the cone crusher , which is the closest between the two broken working faces, is called the angle of the teeth. The angle of the crusher is an important condition for determining whether the crusher can successfully break the ore. The smaller the angle, the larger the discharge port, the smaller the crush ratio, the easy passage of the ore, and the greater the production capacity. On the contrary, the production capacity is small. If the angle is too large, when the ore is broken, the ore will be jumped up and cannot be broken, and even a safety accident will occur. If the angle of the teeth is too small, the crushing ratio is too small to meet the requirements of the process.

The ultimate angle of the various crushers should be less than twice the friction angle.

The jaw crusher has a working angle of 15 to 25 and a cone crusher of about 18.

bThe number of revolutions of the crusher

The eccentric shaft of the jaw crusher and the number of revolutions of the eccentric bushing of the cone crusher determine the number of swings of the moving jaw and the moving cone, which have a great influence on productivity. The number of revolutions of various crushers has a certain range, and too high or too low will affect productivity.

c parallel strip length

For the medium and fine crusher cone crusher, in order to ensure a certain degree of fineness and uniformity of the crushed product, a parallel strip crushing area is arranged in the lower part of the crushing chamber, so that the ore is at least once squeezed in the parallel belt before being discharged. Parallel belt length B is related to the size of the crusher (bottom maximum diameter D) and type

Medium crush cone crusher B=0.085D

Fine cone crusher B=0.16D

d crusher feed and discharge port

The width of the crusher feed port is determined by the maximum block size of the feed. Generally, the maximum ore mass of the crusher is 80% to 85% of the width of the crusher feed port.

The size of the crusher discharge port is related to the crusher's angle of the crusher and the crushing ratio. Within the allowable range, if the discharge port is appropriately increased, the angle of the nail and the crushing ratio are reduced, and the productivity is improved. On the contrary, productivity is reduced.

(3) Operating conditions

In order to give full play to the production capacity of the crusher, the operating conditions of the crusher should be properly mastered, and the mine should be evenly distributed, and the crusher should work under the condition of large crushing ratio and high load factor. The so-called load factor is the percentage of the actual production capacity of the crusher and the ratio of the production capacity that can be achieved.

3. Factors affecting the grinding effect

Can be summarized in three aspects: the nature of the ore, the structure of the mill and the operating conditions

(1) Effects of ore properties, feed size and product size

a ore nature

The effect of the nature of the ore on the work of the mill can be compared and measured by the grindability of the ore (ie the difficulty of grinding the ore from a certain particle size to the specified particle size). Different ores have different grindability, and she is mainly related to the mineral composition, mechanical strength, embedding characteristics and grinding ratio of the ore itself. The ore with dense structure, small crystal and high hardness has small grindability, and it needs to consume more energy to grind it. The productivity of the grinding machine is low. Conversely, the ore with coarse and loose crystals is grindable. The productivity of the mill is high and the unit energy consumption of the grinding is low.

b feed size

The size of the mill feedstock has a great influence on the grinding process. The smaller the grain size of the ore, the shorter the time required to grind to the specified fineness, the higher the processing capacity of the mill, and the lower the energy consumption per unit of grinding.

However, the appropriate grain size of the grinding machine should be determined after considering the total cost of crushing and grinding.

c product granularity

When the ore size and other conditions are the same, the finer the grinding product, the lower the productivity of the grinding machine and the higher the unit energy consumption.

(2) Influence of the structure of the grinding machine

Grinding is carried out in a grinding machine. The structure of the grinding machine (including its type, diameter, length and shape of the lining) has a great influence on the grinding effect.

a type of grinding machine

Under the same conditions, the lattice ball mill is 10% to 25% higher than the production capacity of the overflow mill of the same specification.

b diameter and length of the grinding machine

The diameter of the grinding machine directly determines the ball loading pressure of the material to be ground and the impact force of the steel ball falling. The larger the diameter, the greater the pressure and impact force of the ore particles subjected to the grinding medium, and the higher the working efficiency of the grinding machine.

The length and diameter of the mill determine the volume of the mill and therefore its production capacity. Ball mills of the same diameter, if their length increases, their productivity increases proportionally.

The length of the mill also affects the fineness of the milled product. When the amount of mineral is fixed, the longer the length of the grinding machine, the longer the ore stays in the cylinder, and the finer the grinding product.

c grinding machine liner

Since the external energy is transmitted to the grinding medium through the liner lining to produce a movement state in accordance with the grinding requirements, the shape and material of the lining plate affect the working effect, energy consumption and steel consumption of the grinding machine. Both have a big impact.

(3) Influence of grinding operation conditions

The operational factors affecting the grinding process include: grinding medium loading system, grinding concentration, feeding speed, grinding machine speed, sand return ratio, classification efficiency, and addition of grinding aids.

a grinding medium loading system

The extremely high loading system of grinding media is a prerequisite for obtaining good grinding index. Therefore, each concentrating plant must find the most suitable medium through industrial production test according to the characteristics of the ore and the quality of the grinding products. Into the system.

(a) The shape and material of the grinding medium as a grinding medium that directly grinds the material. It should meet and meet the requirements of both aspects: First, it has the largest possible surface area to provide contact with the material to be ground. The appropriate surface; the second is to have as much mass as possible to have the energy necessary to grind the material. It goes without saying that the requirements of these two aspects must be related to the shape of the medium and the material used.

(b) Size and proportion of grinding medium The size of the grinding medium is related to the strength of impact, extrusion and grinding on the material in the grinding machine, which directly affects the grinding effect. When determining the size of the medium, the main consideration is the nature and particle size composition of the ground ore. Taking a ball mill as an example, when dealing with ore with high hardness and coarse grain size, a large impact force is required, and a steel ball of a larger size should be loaded; when the ore is soft, the ore size is small, and the required grinding product is required. When the particle size is finer, the steel ball with smaller size should be loaded to increase the contact surface of the steel ball with the material to be ground, and enhance the grinding effect. The size of the media and the speed of the mill should also be considered when selecting the media size. A grinding machine with a large diameter and a high rotational speed has a large energy to be transmitted to the medium, and a medium having a smaller size can be used to increase the number thereof and improve the grinding efficiency.

The feedstock for industrial production mills is composed of different sizes of ore particles, so the grinding media loaded into the mill should also have different sizes. A good grinding effect can be achieved only by maintaining the proportion of the medium of various sizes of the grinding machine in accordance with the particle size composition of the material to be ground. The experience gained from long-term grinding practice is that coarse ore particles should be broken with large steel balls, and fine ore particles should be ground with small steel balls. When the quality of the steel ball loaded into the grinding machine is constant, the number of steel balls with small diameter is large, the number of hits of each batch of steel balls is also large, and the grinding area is also large, but the impact force of each ball is small; The number of shots is small, the number of hits per batch of steel balls is small, and the grinding area is small, but the impact of each ball is large. The ratio of steel balls of various diameters to the grinding machine should have sufficient impact force, just break the coarse ore in the feed, and have more hits and stronger grinding effect. To finely grind finer ore particles.

(c) Loading amount of grinding media

When the diameter, length and rotation rate of the grinding machine are constant, the useful power of the grinding machine increases with the increase of the ball loading rate and the production capacity increases with the ball loading rate not exceeding 50%. However, different speeds have different limit ball loading rates. When operating within the critical speed, the ball ball loading rate is usually 40% to 50%.

(d) Reasonable addition of grinding media

In the process of grinding the material, the grinding medium is constantly worn by itself, and the larger the size gradually becomes smaller, and finally completely worn out or turned into pieces and discharged from the grinding machine. In order to keep the grinding machine in the grinding process with a proper proportion of the medium of different sizes and keep the filling rate of the medium constant, it is necessary to add a certain amount of new medium to the grinding machine every day to compensate for the wear. The amount of media.

Practice has proved that the grinding effect can be improved by adding steel balls of several sizes in an appropriate ratio.

In order to make a reasonable addition of steel balls, the site should regularly check the ball load of the ball mill and its particle size composition to understand the wear of the steel balls of various sizes, so as to continuously correct the quality and proportion of the added steel balls in production. The particle size composition of the steel balls in the mill is maintained to approximate the particle size composition at the time of initial loading. If the broken ball with irregular shape after wear is too much in the ball mill, it will affect the grinding effect and should be removed regularly. The cleaning cycle varies with the material of the ball. The iron ball is usually cleaned once every 2 to 4 months, while the steel ball is 6 to 10 months.

b influence of grinding machine speed

When other conditions are constant, the state of motion of the grinding media in the cylinder depends on the rotational speed of the mill. The movement state of the medium is different, and the grinding effect is different. When the grinding machine rotates at a low speed, the medium is mainly in the leeching movement, the impact is small, the grinding is mainly grinding, the grinding machine has low production capacity, and is suitable for fine grinding; when the rotation speed is high, the medium is throwing motion. The proportion of the method is large, the impact effect is strong, the grinding effect is mainly impact, and the grinding and stripping is second, which is beneficial to crushing coarse-grained materials, and the grinding machine has high production capacity.

The suitable working speed of the grinding machine is 76% and 88% of the critical speed respectively. The current rate of ball mills manufactured in China is mostly between 75% and 80%, which is slightly lower than the theoretical calculation. In actual production, the suitable speed of the grinding machine should be determined through long-term production comparison test. When comparing, it is necessary to look at the production capacity of the grinding machine, but also the power consumption, steel consumption and economic benefits.

Of course, if the grinding machine production capacity does not reach the design output quota, properly increasing the rotation speed of the grinding machine is still one of the effective measures to improve the processing capacity of the processing plant. However, after the grinding machine speed is increased, vibration and wear are intensified, and care must be taken to strengthen management and maintenance. Conversely, if the grinding machine has ample production capacity, the rotation speed should be appropriately reduced to reduce energy consumption and steel consumption and reduce grinding costs.

c influence of grinding concentration

Grinding concentration refers to the concentration of pulp in the grinding machine during normal operation. It can be expressed as the percentage of solid content (by mass) in the slurry, or by the ratio of liquid mass to solid mass in the slurry (referred to as liquid-solid ratio). concentration). The ore concentration of the mill is its grinding concentration.

The concentration of the slurry in the grinding machine has a direct impact on the grinding effect of the medium, the flow performance of the slurry itself and the sedimentation speed of the ore particles. When the grinding concentration is high, the buoyancy of the medium in the slurry is large, the effective density is reduced, the impact force of the drop is weakened, and the impact effect is poor. When the content of solid ore particles in the concentrated slurry is high, the viscosity of the slurry is large, and there are many ore particles adhering around the medium. The probability of attacking and grinding the ore particles is increased, and the grinding efficiency is improved. This is because the fine grinding action of the grinding machine mainly depends on the grinding and shattering action of the grinding medium in the circular motion. However, the grinding concentration should not be too high, otherwise the impact force and grinding activity of the medium will be greatly reduced, and the grinding efficiency will be reduced; and the pulp is too concentrated, the slurry fluidity is poor, the coarse material sinks slowly, and the overflow ball mill is easy to run. In the case of coarse sand, the lattice type ball mill may block and cause "bloat". When the concentration of pulp is low, the effective density of the medium in the pulp is relatively large, and the impact force is strong when falling, but the viscosity of the slurry is low, the number of ore particles adhering to the surface of the medium is less, the grinding effect is reduced, and the medium and the liner are Increased wear. At the same time, when the pulp is too thin, the fine ore particles in the overflow ball mill are also easy to sink, resulting in excessive pulverization. Therefore, the concentration of the slurry is too high or too low, and the appropriate grinding concentration should be determined according to the nature of the ore, the feedstock and product size, and the characteristics of the medium. Generally speaking, when processing ore with coarse grain size, high hardness and high density, the grinding concentration should be higher; when the ore with fine grain size, small hardness and small density is treated, the grinding concentration is lower.

Effect of sand return ratio and classification efficiency in d grinding cycle

The classification efficiency and the ratio of sand returning in the closed-circuit grinding cycle have a great influence on the production capacity of the grinding machine and the quality of the grinding product: the higher the classification efficiency or the sand-return ratio, the larger the grinding machine production capacity, the product The less pulverized grains are in the middle. At present, the classification efficiency of the ore dressing plant is generally 40% to 60%, and the return sand ratio of closed-circuit grinding is preferably 200% to 350%.

e impact on mine speed

The ore feeding rate refers to the amount of ore fed into the mill per unit time. When the ore-feeding speed is too low, when the ore quantity is insufficient, the medium will be lining up in the grinding machine, the wear will be intensified, and the product will be crushed seriously; if the ore is too fast, if the ore is too much, the grinding machine will be overloaded. The grinding process was destroyed when there was a discharge of steel balls, spit out of large ore and gushing of slurry.

f grinding aid effect

Adding certain chemicals during the grinding process can improve grinding efficiency, reduce grinding energy consumption and steel consumption. In addition to seeing the effect of grinding aids on improving grinding efficiency, it also considers its source, price, toxicity, and adverse effects on subsequent operations (such as sorting and dewatering) and the environment.

4. Factors affecting the classification process of the spiral classifier

It is mainly divided into three aspects, namely the nature of ore (including the mud content and particle size composition of the graded feed, the density and shape of the ore, etc.); the equipment structure (refers to the size of the groove inclination, the height of the overflow weir and the rotation speed of the spiral, etc.) Operation method (concentration of slurry, amount of ore and uniformity of ore supply)

(1) The mud content and particle size composition of the graded feedstock.

The more sludge or fine fraction in the graded feed, the greater the viscosity of the slurry, the smaller the sedimentation rate of the ore in the slurry, and the coarser the size of the overflow product; in this case, to ensure compliance The required overflow fineness can be appropriately increased to increase the concentration of the slurry. If the amount of mud in the feed is small, or after de-sludge treatment, the slurry concentration should be appropriately increased to reduce the excessive fine-grained material in the return sand.

(2) Density and particle shape of the ore.

In the case of the same concentration and other conditions, the density of the graded material is smaller, the viscosity of the slurry is larger, and the particle size of the overflow product becomes coarser. Conversely, the density of the graded stream is larger, the viscosity of the slurry is smaller, and the size of the overflow is finer. The fine fraction content in the return sand increases. Therefore, when classifying ore with a high density, the classification concentration should be appropriately increased; when the ore having a small classification density is used, the classification density should be appropriately lowered. Since the flat ore is slower than the original or near-original ore, the classification is the concentration of the slurry to be used, or the rate of discharge of the overflow product is accelerated.

(3) The inclination of the classifier slot.

The inclination angle of the trough not only determines the settlement area of ​​the classification, but also affects the degree of agitation of the slurry by the spiral blade, thus affecting the quality of the overflow product. The inclination angle of the trough is small, the settlement area of ​​the classifier is large, and the fineness of the overflow is fine. The content of fine particles in sand increases; on the contrary, the inclination angle of the groove increases, the settlement area decreases, the chance of the coarse material decreases, and the overflow particle size becomes thicker, but the sand return is less fine. Of course, after the classifier is installed, its inclination angle is not changed, and it can only adapt to the determined inclination angle under the operating conditions.

(4) The level of overflow weir.

Adjust the height of the weir to change the size of the settlement area. When the weir is increased, the sedimentation area of ​​the ore particles is increased, and the volume of the classification zone is also increased. Therefore, the agitation of the slurry to the slurry surface is relatively weak, and the overflow particle size is made fine. When the overflow particle size is required to be coarse, the height of the weir should be reduced.

(5) The speed of the spiral.

The rotational speed of the helix not only affects the particle size of the overflow product, but also the ability to transport the grit. Therefore, when selecting the screw speed, it is necessary to satisfy both the overflow fineness and the returning sand productivity. The faster the speed, the higher the production capacity according to the sand return meter, but the stronger the agitation of the slurry, the larger the entrainment of the coarse particles in the overflow, which is suitable for the classifier used in the rough grinding cycle. The classifier used in the second stage of grinding or fine grinding cycle requires a finer overflow product, and the screw speed should be slowed down as much as possible.

(6) Concentration of pulp.

The slurry concentration is one of the most important adjustment factors in the operation of the classifier. It is usually used to control the graded overflow fineness. Generally, the slurry concentration is low, the fineness of the overflow is fine, the concentration is increased, and the overflow is overflow. The particle size becomes coarse. This is because in the thicker slurry, the viscosity of the slurry is larger, the interference of the particle sedimentation is large, and the sedimentation speed is slow. Some of the coarser ore particles are too late to sink, and the horizontally flowing pulp is brought out of the overflow weir. The overflow particle size is made thicker. However, when the slurry concentration is very low, there may be cases where the overflow particle size becomes coarse. This is because the concentration is too low, in order to maintain a certain capacity calculated according to the solid mass, the amount of slurry is inevitably large, causing the slurry flow rate in the classifier to increase, thereby flushing the coarser ore to the overflow. Go in. Therefore, in actual production, for the classifier that processes the specified ore, there is an optimum graded slurry concentration at which the maximum productivity can be obtained while maintaining a certain graded particle size; while maintaining a certain productivity, The smallest separation particle size is obtained. This concentration is called the critical concentration. The critical concentration value of the actual production shall be determined by testing and referring to the index of similar concentrating operations of the concentrator.

(7) The uniformity of the ore supply and the ore supply.

When the concentration of the slurry is constant, if the amount of ore fed to the classifier increases, the ascending flow rate and the horizontal flow rate of the slurry also increase, thereby making the overflow particle size coarse. On the contrary, when the amount of ore is reduced, the overflow particle size becomes finer, and the fine particle content in the returning sand increases. Therefore, the ore-feeding amount of the classifier should be appropriate, and it must be kept even and stable, so that the classification process can be carried out normally, and a good classification effect can be obtained.

5. Process factors affecting the flotation process

It mainly includes: the selected particle size composition of the ore, namely the grinding fineness; the selected concentration of the slurry; the addition and adjustment of the agent, that is, the pharmaceutical system; the regulation of bubbles and foam; the temperature of the slurry; the flotation process; the water quality.

(1) Effect of particle size on flotation

Flotation requires not only the dissociation of mineral monomers, but also the appropriate inclusion size. The ore is too thick, even if the mineral has been dissociated from the monomer, it will not float because it exceeds the floating capacity of the bubble. The ore particles are too fine, causing muddy, which also affects the flotation index.

(2) Effect of slurry concentration on flotation

As one of the important process factors of the flotation process, the slurry concentration affects the following technical and economic indicators.

a recovery rate In the flotation of various minerals, the slurry concentration and recovery rate have obvious regularity. When the concentration of the slurry is very thin, the recovery rate is low. As the concentration of the slurry increases, the recovery rate also increases gradually and reaches a maximum. However, after the optimum pulp concentration is exceeded, the recovery rate is lowered. This is because the concentration of the slurry is too high or too low, which will deteriorate the aeration condition of the flotation machine.

b Concentrate quality The general rule is that the quality of concentrate is higher when flotation is carried out in a thinner slurry, while the quality of concentrate is decreased when flotation is carried out in a thicker slurry.

c dosage of the agent In the flotation, the concentration of the agent must be maintained in a balanced manner in order to obtain a good flotation index.当矿浆浓度较高时，液相中药剂增加，处理每吨矿石的药量可减少，反之，当矿浆浓度较低时，处理每吨矿石的用药量就增加。

d浮选机的生产能力 随着矿浆浓度的增加，浮选机按处理量生产的生产能力也增加。

e浮选时间 在矿浆浓度较高时，浮选时间会增加，有利于提高回收率，增加了浮选机的生产率。

f水电消耗 矿浆浓度愈高，处理每吨矿石的水电消耗将愈低。

在实际生产过程中，浮选时除保持最适宜的矿浆浓度外，还须考虑矿石性质和具体的浮选条件。一般原则是：浮选密度大、粒度粗的矿物，往往用较高的矿浆浓度；当浮选密度较小、粒度细或矿泥时，则用较低的矿浆浓度；粗选作业采用较高的矿浆浓度，可以保证获得高的回收率和节省药剂，精选用较低的浓度，则有利于提高精矿品位。扫选作业的浓度受粗选作业影响，一般不另行控制。

（3）药剂制度对浮选的影响

生产过程中对所需添加药剂种类、药剂用量、配制、添加位置和方式等的总称，称为药剂制度，俗称“药方”。

在自然界中，天然可浮性好的矿物不多，大多数硫化矿、氧化矿等本身就亲水难浮，经过矿床中的温度、压力、地下水、风化等作用以及破碎磨矿过程，表面受污染，它的可浮性受到影响。即使是天然可浮性好的矿物，受到氧化和水化作用，可浮性也会降低。为了实现各类矿物的浮选，就需要改变矿物的可浮性，目前在有效的方法就是通过加入浮选药剂，造成矿物表面的“人为可浮性”，调节矿物的可浮性和改善气泡的性质，从而达到控制浮选过程的目的。

（4）矿浆酸碱度对浮选的影响

矿浆酸碱度的变化直接或间接影响其浮选过程中矿物的可浮性，其浮选矿物的回收率与一定范围内的PH值有密切的关系。

（5）矿浆温度对浮选的影响

矿浆温度在浮选过程中常常起重要的作用，也是影响浮选的一个重要因素。调节矿浆温度条件主要来自两个方面的要求，一是药剂的性质，有些药剂要在一定的温度下才能发挥其有效作用；二是有些特殊的工艺，要求提高矿浆的温度，以达到分选矿物的目的。

（6）浮选用水对浮选的影响

水是浮选过程中的重要介质，水质的好坏往往对浮选指标产生影响。在大多数情况下，江河、湖泊的水都适合浮选的要求。

选矿厂利用回水进行循环使用，无论从环境保护，还是从工业用水的降低成本都是十分必要的。浮选回水的特点是含有较多的有机和无机药剂，其中浮选药剂的含量有时比自然水高出50～100倍，但其中所含的细粒矿泥对浮选是有害的。一般要求循环使用的水，含固体颗粒不超过0.2～0.38g/L，如果回水的PH值过高，必要时还要中和处理。

（7）浮选时间对浮选的影响

浮选时间的长短对浮选指标的好坏影响很大，浮选工艺中，浮选时间长，对精矿中有用成分的回收率有所增加，但精矿质量降低。

在选矿厂的实际工作中，浮选时间的长短主要由单位时间内所处理的矿石量和入选矿浆浓度来决定，单位时间处理量增加或矿浆浓度降低，都会使浮选时间缩短。一般认为，原矿品位高，需要较长的浮选时间。浮选细粒比粗粒矿物的时间长。

（8）浮选操作对浮选的影响

The flotation operation is the degree of control of flotation production by flotation workers, and is adjusted in time according to the changes in the production process, and finally obtains good production technical indicators.

浮选操作中在常遇到的是维持设备的正常运转，通过浮选过程表现出的各种现象，判断浮选泡沫产品的质量，并根据出现的不同情况，及时调整浮选药剂、矿浆的浓度和粒度、确定泡沫的刮出量。在长期的浮选操作中，掌握必要的操作可以使浮选过程得到有效控制，即应该做好的“三会”、“四准”、“四好”、“两及时”、“一不动”。

“三会”是指：会观察泡沫，会测浓度、粒度，会调整。

“四准”是指：药剂配制和添加准，品位变化看的准，发生变化原因找得准，泡沫刮出量掌握准。

“四好”是指：浮选与处理量控制好，浮选与磨矿分级联系好，浮选与药台联系好，浮选各作业联系好。

“两及时”是指：出现问题发现及时，解决处理问题及时。

“一不动”是指：生产正常不乱动。

600吨/日选厂工艺流程图

figure 1

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