As a kind of high-efficiency separation equipment, hydrocyclone has been widely used in many fields such as mineral processing, petroleum, chemical industry, environmental protection and so on, by virtue of its no moving parts, simple structure, large production capacity per unit volume, small footprint, high grading efficiency and fine grading size and many other advantages. In the mineral processing industry, it is mainly responsible for grading, sorting, concentration and desliming and other key tasks; in the petroleum industry, it can be used for crude oil dewatering, desanding and other operations; in the chemical industry, it can achieve solid-liquid separation, product classification and other functions; in the environmental protection industry, it can be used for wastewater treatment, sludge dewatering and other links.
However, in the actual operation process, the working efficiency of hydrocyclone will be affected by a combination of factors. An in-depth study of these influencing factors is of vital significance for optimising equipment performance, improving production efficiency, reducing production costs and achieving efficient use of resources.
一.Factors affecting the efficiency of hydrocyclones
1.Ore properties
(1)Densidad
Ore density has a significant effect on the classification particle size of hydrocyclone. When the density of the ore is large, in the same centrifugal force and fluid resistance, the centrifugal force on the ore particles is relatively larger, easier to overcome the fluid resistance to move to the wall, so as to achieve the separation of fine particles, so the classification size is finer. On the contrary, if the density of the ore is small, the centrifugal force on the ore particles is relatively weak, and it is difficult to separate them effectively, and the classification size will become coarse.
(2)Particle size composition
The particle size composition of the ore is one of the key factors affecting the efficiency of hydrocyclone. If the content of coarse grains in the feed ore is high, the hydrocyclone needs to handle more large particles, which will increase the processing load of the equipment. In order to ensure a better classification effect, it is necessary to appropriately increase the feed pressure, in order to increase the slurry flow rate, and enhance the centrifugal force on the separation of coarse particles. At the same time, the size of the feed port should also be adjusted accordingly, appropriately increasing the ratio of the feed port to the diameter of the hydrocyclone, generally controlled at 0.16 – 0.20, so that coarse-grained materials can enter the cyclone smoothly for separation.
On the contrary, if the fine-grained content in the feed ore is high, the feed pressure can be appropriately reduced to prevent excessive crushing of fine-grained materials, the ratio of the feed opening to the diameter of the hydrocyclone is usually maintained at 0.14 – 0.16, because fine-grained materials in the smaller feed pressure and the appropriate size of the feed opening, can be more effective in the centrifugal force and the role of the resistance to achieve grading of the fluid to avoid the feed pressure is too large or the feed opening is not the right size Avoid too much pressure or inappropriate size of the feed opening, resulting in poor classification effect of fine-grained materials.
(3)Slurry concentration
The slurry concentration has a complicated effect on the efficiency of hydrocyclone. When the slurry concentration is high, the viscosity and density of the slurry increase, which makes the movement resistance of particles in the slurry increase significantly. In this case, the fine particles are difficult to be effectively separated from the coarse particles under the effect of centrifugal force, resulting in coarse grading size. At the same time, the high concentration of slurry may also lead to turbulence in the internal flow field of the cyclone, affecting the separation effect.
On the contrary, if the slurry concentration is too low, although it is conducive to the separation of fine particles, and can obtain a finer classification size, but it will reduce the production capacity of the equipment and increase production costs. Because too low a slurry concentration means that the amount of solid material entering the cyclone per unit time is reduced, and the processing efficiency of the equipment is reduced. Therefore, the appropriate slurry concentration usually needs to be precisely determined by ore dressing test according to the specific ore properties and production requirements.
2.Structural factors
(1)Column diameter and height
Column diameter is the key specification size of the hydrocyclone, which is closely related to the size of other components, and determines the separation size and production capacity of the equipment. When the ratio between the feed pressure, the feed opening, the overflow opening and the cyclone diameter remains unchanged, the production capacity of the hydrocyclone will increase significantly with the increase in the diameter of the column. This is because an increase in diameter increases the volume inside the cyclone, which can hold more slurry, thus increasing the capacity per unit time. However, as the diameter of the column increases, the separation size becomes correspondingly coarser. This is due to the fact that the rotational speed of the slurry inside the cyclone is relatively reduced after the diameter is increased, the centrifugal force is weakened, and the separation ability for fine particles is reduced.
The height of the column mainly affects the length of time that the slurry is subjected to centrifugal force in the cyclone. Generally speaking, the higher the height of the column, the longer the slurry stays in the cyclone, the longer the time by centrifugal force, which is conducive to the separation of fine-grained materials, can make the separation of finer particle size. However, when the height of the column exceeds a certain limit, the feed pressure loss will increase significantly. This is because the slurry flows inside the longer column body and the friction resistance with the vessel wall increases, resulting in excessive pressure consumption. When the pressure loss is too large, it will weaken the effect of centrifugal force on the slurry, thus losing the effect of improving the separation size, and may even affect the normal operation of the equipment.
(2)Feeder size
The size of the feed opening has an important influence on the working efficiency and production capacity of the hydrocyclone. Too large a feed opening will make the slurry flow rate into the cyclone too fast, resulting in too short a residence time of the slurry in the cyclone, too late to fully classify, thus increasing the content of coarse particles in the overflow product, and the classification effect is poor. In addition, too large a feed opening may also destroy the stability of the flow field in the cyclone, affecting the separation effect.
On the contrary, too small a feed opening will limit the amount of slurry entry and reduce the production capacity of the equipment. At the same time, too small a feed opening may lead to slurry clogging at the feed opening, affecting the normal operation of the equipment. For different particle sizes of the feed ore, the ratio of the feed opening to the diameter of the hydrocyclone needs to be reasonably adjusted. When the feed size is coarse, the feed pressure is relatively low, in order to ensure that coarse materials can enter the cyclone smoothly, the ratio of the feed opening and hydrocyclone diameter can be appropriately increased, generally 0.16 – 0.20 appropriate; and when the feed size is fine, the feed pressure is high, the ratio of the feed opening and the hydrocyclone diameter is usually maintained at 0.14 – 0.16, which can make the fine materials in the appropriate This can make the fine-grained materials in the appropriate flow rate and pressure, in the cyclone to get effective classification.
In addition, the shape of the feed opening (often rectangular) and the method of feeding (tangential or involute) also have an effect on the efficiency. Rectangular feed opening can make the slurry enter the cyclone more uniformly than round feed opening, reduce the turbulence of the slurry at the inlet, and thus improve the classification efficiency. Tangent feeding mode can make the slurry enter the cyclone to form a rotating flow field quickly, and make full use of the centrifugal force for separation; involute feeding mode can make the slurry enter the cyclone more smoothly, reduce the impact on the internal flow field, which is conducive to improving the separation effect.
3.Process operating factors
(1)Feed pressure, concentration, particle size composition
Ore feeding pressure is an important factor affecting hydrocyclone throughput and classification particle size. When the feed pressure increases, the slurry flow rate is accelerated. This makes the rotational speed of the slurry in the cyclone increase, and the centrifugal force increases, so that the coarse particles can be separated more effectively and the classification effect of the hydrocyclone can be improved. When dealing with coarse-grained materials, a larger centrifugal force is required to achieve effective separation due to the coarse particles. This is because in the lower pressure, not only can ensure that the coarse particles have enough centrifugal force to be separated, but also to avoid the high pressure leads to increased wear and tear of equipment and increased energy consumption. When dealing with fine particles and muddy materials, due to the greater difficulty in separating fine particles and muddy materials, higher centrifugal force is required to overcome the cohesion between particles and fluid resistance to improve the classification effect.
The concentration of feed ore and its particle size composition are directly related to the concentration and size of the final product. The coarser the grading size, the more mud or fine grains in the graded material, in order to ensure a certain production capacity and grading effect, the feeding concentration should be increased accordingly. However, with the increase of ore concentration, the viscosity of the slurry increases, which will make the particles in the slurry movement resistance increases, and the particle size of the overflow product will be coarser.
(2)Discharge of overflow and sediment
The ideal working condition of hydrocyclone is that the sunken sand is sprayed out in the form of umbrella, and the angle of the umbrella should not be too large, so that it can be dispersed. This discharge method can make the sand uniformly discharged, to avoid clogging or accumulation of sand in the discharge process, to ensure the stable operation of the equipment. When the hydrocyclone is used for thickening operation, the concentration is higher when the sand is discharged in the form of rope. This is because the rope discharge mode can make the water in the sand gradually separated in the discharge process, thus increasing the concentration of the sand. When the hydrocyclone is used for dewatering operations, the sand is discharged in a larger umbrella shape, and the overflow contains the least amount of solids. This is because the larger umbrella discharge mode can make the solid particles in the sand more fully separated from the liquid, reducing the amount of solid particles discharged with the overflow, thus reducing the solid content of the overflow.
In actual production, the operator needs to pay close attention to the overflow and sand discharge, and timely adjust the operating parameters of the equipment to ensure that the discharge method meets the working requirements of the equipment. For example, by adjusting the parameters such as feed pressure, feed concentration, diameter of sand sinking nozzle, etc., to control the discharge state of sand sinking, in order to achieve the best working efficiency.
In practice, in order to improve the efficiency of hydrocyclone, need to consider all aspects of the factors. For different properties of the ore, to choose the appropriate structure parameters of the hydrocyclone, and through the beneficiation test to determine the best process operating parameters. At the same time, according to the operation of the equipment to adjust the parameters, to ensure that the hydrocyclone is always in the best working condition, improve its efficiency and application scope, for the related industries to provide strong support for the efficient production and sustainable development.
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