As a kind of efficient solid-liquid separation equipment, from the purification of chemical raw materials, to the fine treatment of food processing, to the key link of pharmaceutical production, the figure of the pusher centrifuge is ubiquitous, and has become an indispensable core equipment in the production process of many industries. In-depth understanding of the factors affecting the efficiency of its work and the correct operation method, to improve production efficiency, product quality, reduce production costs is of great significance.
一.Multifaceted factors affecting the efficiency of pusher centrifuges
1.Material characteristics
Material particle size, distribution, viscosity, density and other characteristics, each of which is an important factor affecting the efficiency of the centrifuge.
When the material particles are large and uniformly distributed, under the action of centrifugal force, it can be quickly and orderly settled to the inner wall of the drum, forming a compact structure, good permeability of the cake layer. This filter cake layer is like a tightly woven net, which can effectively block the solid-phase material, while allowing the liquid-phase material to pass through smoothly, thus greatly improving the separation efficiency. On the contrary, if the material particles are small and unevenly distributed, under the action of centrifugal force, their trajectory is difficult to predict, easy to intertwine, agglomeration, the formation of the cake layer structure is loose, low porosity, resulting in the liquid phase through the cake layer of resistance to increase, the separation efficiency is significantly reduced. Moreover, these fine particles are also prone to clogging the filter mesh, like small stones blocking the drainage pipe, making the filtration capacity of the centrifuge decreased, further affecting the work efficiency.
Similarly, high viscosity materials have strong cohesion and poor fluidity. In a centrifuge, they are difficult to be quickly dispersed and separated under the action of centrifugal force, and require greater centrifugal force and longer time to achieve solid-liquid separation.
And when the density difference of boring is large, they can be quickly stratified under the action of centrifugal force to achieve efficient separation. However, if the density difference is small, the separation process becomes slow and difficult, requiring higher centrifugal forces and finer operating conditions to facilitate the separation.
2.The decisive influence of equipment operating parameters
Speed and Separation Factor
RPM is one of the core parameters of a pusher centrifuge, and it is closely related to the separation factor. The separation factor is an important indicator of the centrifuge’s separation capacity and is proportional to the square of the rotational speed. Simply put, the higher the rotational speed, the greater the separation factor, the stronger the centrifugal force generated by the centrifuge, and the better the separation effect on the material.
Take the separation of salts in chemical production as an example, when the rotational speed of the centrifuge is increased, the salt particles, under the action of the strong centrifugal force, can be settled more quickly to the inner wall of the drum, and the mother liquor to achieve high efficiency separation, thus improving the purity of the product and the production efficiency. When dealing with some materials with fine particles that are difficult to separate, an appropriate increase in rotational speed can significantly enhance the centrifugal force, overcome the interaction force between the materials, and make the solid-liquid separation more complete.
However, with the increase of rotational speed, firstly, the vibration problem will become more prominent. The high-speed rotating drum is prone to violent vibration under the action of unbalanced force, which not only affects the stability and service life of the centrifuge, but also may lead to equipment failure and jeopardise production safety. Secondly, energy consumption will also increase significantly. Higher rotational speeds require greater power support, which means that the energy consumption of the centrifuge will rise significantly, increasing production costs. In addition, the material and manufacturing process of the equipment also put forward higher requirements. In order to withstand the huge centrifugal force generated by high-speed rotation, the drum and other key components need to use high-strength, high-toughness materials, and the manufacturing process should be more delicate to ensure the reliability and safety of the equipment.
Pushing times and frequency
Pushing times and frequency is another important factor affecting the efficiency of the pusher centrifuge. There is a complex interrelationship between them and the thickness of the cake, moisture content and production efficiency.
Pushing times and frequency directly affect the thickness of the cake and moisture content. When the number of pushes is too little or the frequency is too low, the cake stays in the drum for too long, which will lead to an increase in the thickness of the cake and a decrease in the moisture content. This is because the cake is continuously subjected to centrifugal force inside the drum, the moisture is gradually thrown out and the cake becomes denser. However, too thick filter cake will increase the difficulty of pushing material, reduce the efficiency of pushing material, and may even lead to filter cake blockage of the drum, affecting the normal operation of the centrifuge.
On the contrary, if the number of pushes is too many or the frequency is too high, the residence time of the filter cake in the drum is too short to fully dewater, which will increase the moisture content of the filter cake and reduce the quality of the product. At the same time, frequent pushing action will increase the wear and tear of the equipment, shorten the service life of the equipment.
In actual production, according to the characteristics of the material to accurately adjust the pushing parameters. For large particles, good fluidity of the material, you can appropriately increase the number of pushes and frequency, in order to improve production efficiency; for small particles, viscous materials, you need to reduce the number of pushes and frequency, to extend the residence time of the cake in the drum, to ensure that the cake is fully dewatered, improve product quality.
Feed quantity and concentration
Appropriate feed volume and concentration can ensure stable operation and efficient work of the centrifuge, while excessive or uneven feeding will cause a series of problems.
When the feed volume is too large, the centrifuge will not be able to process all materials in time. This can lead to part of the material is too late in the centrifugal force under the action of solid-liquid separation, was taken out of the centrifuge, resulting in overflow phenomenon. Overflow not only wastes material, but also pollutes the working environment and affects normal production. At the same time, overfeeding will also increase the load of the centrifuge, resulting in uneven force on the drum, vibration, and even damage to the equipment in serious cases.
If the concentration of feed material is high or low, it will lead to unstable separation effect of the centrifuge. Materials of high concentration require greater centrifugal force in the centrifuge to achieve separation, while materials of low concentration are relatively easy to separate. When the feed concentration is not uniform, it is difficult for the centrifuge to effectively separate materials of different concentrations under the same operating conditions, which reduces work efficiency and product quality.
In order to ensure the normal operation of the centrifuge, it is necessary to strictly control the feed volume and concentration. According to the design parameters of the centrifuge and the characteristics of the material, the feed rate and concentration should be reasonably adjusted to ensure that the material can enter the centrifuge uniformly and stably to achieve efficient solid-liquid separation. In chemical production, flow meters and concentration sensors and other equipment are usually used to monitor and control the feed volume and concentration in real time to ensure the stability and efficiency of the production process.
二.The correct operation of the pusher centrifuge guidelines
1.Pre-start-up preparation
Before starting the pusher centrifuge, first of all, the installation of the equipment should be thoroughly checked. Check whether the ground bolts of the equipment are tight to ensure that the equipment will not be displaced or shaken during operation. At the same time, it is important to check whether the various components of the centrifuge are installed correctly and connected firmly to avoid dangerous situations such as loosening and dislodging of components during operation. Secondly, make sure that the pipes and containers are clean. The feeding pipe, the discharge pipe and the container in contact with the material must be thoroughly cleaned to ensure that no foreign matter remains. By manually turning the rotor, you can initially check whether the rotation of the rotor is flexible and whether there is any stagnation phenomenon. Check the tension of the narrow V-belt. The proper tension of the V-belt ensures the effective transmission of power and avoids slippage. Adjust the tension of the V-belt according to the machine instructions so that it is in the right range. Check whether the hydraulic oil reaches 2/3 of the level gauge to ensure that the oil is sufficient. At the same time, observe the colour and transparency of the hydraulic oil to determine whether it has deteriorated. If the hydraulic oil becomes dark, cloudy or has a strange smell, it means that the hydraulic oil has deteriorated and needs to be replaced in time. Finally, it is necessary to check whether the rotation direction of the oil pump and motor is correct.
2.Code of practice for start-up and operation
In the start-up, the first step is to start the oil pump motor, so that the oil pump began to work. After the oil pump motor is started, it is necessary to wait for about 1 minute, so that the oil pump will deliver hydraulic oil to the various parts of the work, to ensure that the pushing mechanism is fully lubricated and power support. The main motor can be started only after the pushing mechanism works normally. When the main motor starts, pay attention to the starting current value. The starting current is usually higher than the normal running current. The feeding operation can only be carried out when the main motor reaches the working speed. When feeding, open the feeding valve, gradually increase the feeding rate, and closely observe the working status of the centrifuge. The adjustment of the feeding rate should be determined according to the model of the centrifuge, the material characteristics and the requirements of the production process.
Motor current is an important parameter reflecting the load of the centrifuge. Under normal operation, the motor current should be kept within a certain range. If the motor current suddenly increases, it may be caused by excessive feed volume, increased material viscosity, filter cake clogging and other reasons.
Oil pressure is also one of the parameters that need close attention. The stability of oil pressure is the key to ensure the normal operation of the pushing mechanism. During operation, make sure the oil pressure is within the specified range. If the oil pressure is too high, it may be caused by the clogging of the hydraulic system, the failure of the relief valve, etc. Excessive oil pressure will cause damage to the components of the hydraulic system, and it is necessary to investigate and solve the problem in time.
In addition, it is necessary to pay close attention to the discharge of the centrifuge. Observe the speed, humidity, particle size and other indicators of the discharge to determine whether the separation effect of the centrifuge is normal.
3.Shutdown and cleaning processes
When the pusher centrifuge completes the work task or needs maintenance, the first thing to do is to stop feeding. Close the feed valve to cut off the passage of material into the centrifuge. After stopping the feed, the drum should be cleaned. First open the cleaning tube inside the cleaning drum to clean the residual material inside the drum. When cleaning, make sure that the cleaning liquid can fully cover all parts of the drum, and completely remove the materials attached to the inner wall of the drum, the screen and the pushing disc and other parts. Then open all the cleaning tube, the drum, the shell inside and outside and the feed pipe for a comprehensive cleaning. Cleaning time is generally about 5 – 10 minutes, the specific time can be adjusted according to the degree of pollution and cleaning effect of the equipment. During the cleaning process, pay attention to observe the discharge of cleaning fluid to ensure that the cleaning fluid can be discharged smoothly, to avoid the accumulation of cleaning fluid inside the equipment.
After the cleaning is completed, stop the main motor. Press the stop button of the main motor to gradually decelerate the main motor until it stops rotating. In the process of stopping the main motor, pay close attention to the speed change of the motor and the operating status of the equipment to ensure that the motor stops smoothly. If abnormal vibration, noise or other faults occur during the stopping process of the main motor, timely measures should be taken to deal with them to avoid equipment damage.
Wait until the drum completely stops rotating, and then stop the oil pump motor. This is because when the drum is rotating, the pushing mechanism needs the support of hydraulic oil to keep working properly. If the oil pump motor is stopped before the drum stops rotating, it will result in a loss of power to the pushing mechanism, which may cause the filter cake to build up inside the drum, affecting the normal shutdown and next start-up of the equipment. Therefore, it is necessary to wait until the drum stops rotating completely before stopping the oil pump motor to ensure the safe shutdown of the equipment.
