Disc separator

Is a disk separator a type of centrifuge? study*……

The disc separator is a type of sedimentation centrifuge used to separate materials that are difficult to separate from each other (such as suspensions consisting of viscous liquids and fine solid particles, or emulsions made up of liquids with similar densities). The disc separator in separators is the most widely used type of sedimentation centrifuge. 　　The main operating parameters of a disc separator are: drum rotation speed, the position of the interface between the light liquid and the heavy liquid, and feeding speed. 　　The main structural parameters of a disc separator are: the inner diameter of the drum, the equivalent settling area, the size and total number of discs, as well as the slag discharge method and the slag discharge mechanism. Principle and structure of the disc separator: The disc separator is a vertical centrifuge, with the drum mounted at the upper end of a vertical shaft; it rotates at high speed driven by an electric motor through a transmission mechanism. Inside the drum, there is a set of disc-shaped components that are nested one inside another—discs. There is a very small gap between the discs. The suspension (or emulsion) is introduced into the drum through a feed pipe located at the center of the drum. As the suspension (or emulsion) flows through the gap between the discs, the solid particles (or liquid droplets) settle onto the discs under the action of centrifugal force, forming a sediment (or liquid layer). The sediment slides along the surface of the disc, detaches from it, and accumulates in the part of the drum with the largest diameter; the separated liquid is discharged from the drum through the outlet. The function of the discs is to reduce the settling distance of solid particles (or droplets) and increase the settling area of the drum; as a result of the installation of these discs, the production capacity of the separator is enhanced. The solids accumulated inside the drum are removed manually by disassembling the drum after the separator is stopped, or they are discharged from the drum through a slag discharge mechanism without shutting down the machine. 　　The disc separator can perform two types of operations: liquid-solid separation (that is, the separation of suspensions with a high solid concentration), known as clarification ； Liquid-liquid separation (or liquid-liquid-solid) separation (i.e., the separation of emulsions) is referred to as a separation operation.

A disc separator is a centrifugal separation device based on two media with different specific gravities that are immiscible with each other

The disk separator is a type of sedimentation centrifuge used to separate materials that are difficult to separate, such as suspensions consisting of viscous liquids and fine solid particles, or emulsions made up of liquids with similar densities. It utilizes the principle that light and heavy liquids with different densities, as well as solid phases present in a mixed liquid (turbid solution), acquire different sedimentation speeds in a centrifugal force field, thereby achieving separation and stratification or causing the solid particles in the liquid to settle. The disc separator in separators is the most widely used type of sedimentation centrifuge. The disk separator is a vertical centrifuge, with the drum mounted at the upper end of a vertical shaft and driven by an electric motor through a transmission mechanism to rotate at high speed. Inside the drum, there is a set of disc-shaped components that are nested one inside another–the discs ； There is a very small gap between the discs. The material to be separated is fed into the drum through a feed pipe located at the center of the drum. As the mixture (turbid fluid) flows through the gaps between the discs, the solid particles slide along the lower surface of the discs under the effect of centrifugal force, thereby separating from the discs and accumulating in the area with the largest diameter inside the drum to form a sludge layer, which is then removed from the drum via a sludge discharge mechanism (manual, continuous, or intermittent) ； The light-phase liquid moves along the upper surface of the disc toward the center of the drum, and is discharged from the upper outlet of the drum due to centrifugal force ； The heavy-phase liquid gathers in the middle area right next to the slag layer, and is discharged from the top outlet of the drum through specially designed heavy-phase fluid channels. The disk separator can perform two types of operations: liquid-solid separation (separation of suspensions), also known as clarification ； Liquid-liquid separation (or liquid-liquid-solid separation, which requires the two liquids to have different densities) is referred to as a separation process. Disk separators are widely used in the chemical, pharmaceutical, light industry, food, bioengineering, and transportation sectors due to their compact structure, small footprint, and high production capacity. The drum is equipped with a stack of conical disks used to separate the components of emulsions and low-concentration suspensions by centrifugal sedimentation. Disc separators can operate under conditions of closure, high temperature, low temperature, pressure, and vacuum. They are used to extract cream from milk, as well as for the purification of juices, beer, vegetable and animal oils, transformer oil, etc. They are also employed for yeast concentration and the extraction of serum from animal plasma. When separating the suspension, it enters the drum through the central feed pipe and flows from the outer edge of the disc bundle, through the gaps between the discs, toward the inner edge of those discs. Due to the effect of centrifugal force, solid particles settle onto the inner surface of each disc as they move with the liquid, then slide toward the outer edge of the discs, and finally deposit on the drum wall. The clarified liquid gathers toward the center of the drum and is discharged through an overflow port or a centrifugal pump. When separating the emulsion, it enters the gaps between the discs through the feed holes on the disc array; based on their density, it is divided into heavy liquid and light liquid. The heavy liquid flows along the inner surface of the discs toward the drum wall, while the light liquid flows toward the center, and both are discharged separately through the overflow port and the centrifugal pump. The feed hole should be located at the boundary between the heavy liquid layer and the light liquid layer. This is referred to as the neutral layer; its radius is given by the formula, where it represents the density ratio of the heavy fluid to the light fluid, and R1 and R2 are the outlet radii of the heavy fluid and the light fluid, respectively. When the feed hole does not coincide with the neutral layer, the discharged heavy or light liquid is not pure; in such cases, the radius of the outlet for the heavy or light liquid can be changed to adjust the position of the neutral layer. Since the liquid inside the drum is divided into many thin layers by the disk array, separation takes place within these thin layers; the distance for centrifugal sedimentation is very short, which significantly increases the separation speed. The efficiency of disc separators is high, ranging from 4000 to 10000, and the large number of discs inside the drum significantly increases the sedimentation area, resulting in high separation efficiency. A centrifugal pump features an impeller that is fixed in place within the casing; the outer edge of this impeller is submerged in a layer of separating fluid that rotates in sync with the drum. The separating fluid enters the arc-shaped flow channels at the outer edge of the impeller and then flows toward the discharge pipe at the center of the impeller for evacuation. The impeller converts the kinetic energy of the rotating liquid into static pressure, delivering the separated liquid discharged from the drum directly to a height of 10–20 meters. Disc separators are classified into three types based on the slag discharge method: manual slag discharge, nozzle-driven slag discharge, and valve-driven slag discharge. The manual slag discharge disc separator operates on a batch basis. It consists of a base, a transmission mechanism, a drum, and a casing; the entire unit is vertical, with the drum being supported from below. Near the main bearing of the drum, there is a shock-absorbing device composed of 6 springs (or rubber pads) arranged radially. The drive mechanism of the drum usually employs helical gear speed increase, while some use belt drives. The drum cover and the drum body are secured by a threaded locking ring, with a sealing ring to prevent leaks. The discs are conical in shape, with a half-cone angle that is greater than the friction angle between the solid particles and the surface of the discs; this angle is typically between 30° and 45°. The number of discs ranges from 50 to 180 ； The disc gap is 0.5 to 2 millimeters. After the separator has been in operation for a while, more sediment accumulates on the inner wall of the drum, and the clarity of the separated liquid decreases. When the clarity of the separated liquid no longer meets the requirements, the machine is stopped, the drum is disassembled, and the sediment inside it is removed manually. This separator can handle a throughput of up to 45 meters per hour, and is suitable for processing suspensions and emulsions with particle diameters ranging from 0.001 to 0.1 millimeters and a solid phase concentration of less than 1%. Nozzle slag discharge disc separator – continuous operation. The overall structure is similar to that of a manual slag discharge disc separator, but the inner cavity of the drum is biconical, which allows for the compression of the sludge and thus increases its concentration. The maximum inner diameter of the drum is 900 millimeters. There are 2 to 24 nozzles around the periphery of the drum for spraying slurry-like sediment, with the nozzle diameter ranging from 0.5 to 3.2 millimeters. The number and diameter of the nozzles are determined based on the properties of the suspension, the degree of concentration, and the processing volume. The sediment flow rate through the nozzle is very high; the nozzle is made of wear-resistant materials such as boron carbide and others. To increase the slag concentration, this separator also has a mechanism to send the discharged sediment back into the rotary drum for recycling. The solid phase concentration of the sludge can be increased by 5 to 20 times compared to that of the feed. This separator can handle up to 300 meters per hour; it is suitable for processing suspensions with solid particle diameters ranging from 0.1 to 100 microns, and a solid phase concentration typically below 10% (up to 25% at most). The valve-type slag discharge disc separator uses circular valves to open and close the slag discharge port for intermittent slag discharge; it is also known as an automatic slag discharge disc separator. The overall structure is similar to that of a manual slag discharge disc separator, and its feature is the presence of a valve-based slag discharge mechanism inside the drum, which allows the sediment in the drum to be removed without shutting down the machine. During operation, the suspension is fed in through the feed pipe at the center of the drum for separation; the total pressure of the sealing water below the valve is greater than the total pressure exerted by the suspension on the valve, causing the valve to stay in the upper position and thus closing the slag discharge outlet. During slag discharge, feeding is stopped and operating water is added from the bottom of the drum. The pressure relief valves for the sealing water surrounding the drum are opened to release this sealing water. The valve drops rapidly due to the hydraulic pressure of the suspension inside the drum, thereby opening the slag discharge port. After the sediment and liquid in the rotary drum have been drained, the supply of process water is stopped, the pressure relief valve closes, the sealing water pressure increases, and the valve rises to close the sediment discharge port, completing one working cycle. Methods for automatically controlling valve-based slag discharge include: ① Using a time relay to control slag discharge according to a predetermined operating cycle; ② Using a phototube to monitor the clarity of the separated liquid in order to control slag discharge; ③ Controlling slag discharge based on the degree of sediment accumulation in the drum, via pressure signals or slag level signals. The slag discharge time is generally 1 to 2 seconds. A drum with partial slag discharge allows for a shorter slag discharge time, as only a portion of the sludge within the drum is removed while no liquid is discharged. Feeding can continue without interruption during slag discharge, enabling continuous separation and thus improving processing capacity. This separator can handle a maximum volume of 60 meters per hour; it is suitable for processing suspensions and emulsions with solid particle diameters ranging from 0.001 to 0.5 millimeters, and a density difference between the solid and liquid phases of more than 0.01 kilograms per decimeter, provided that the solid phase concentration is less than 10%