What is Pressure Screen Rotor

Base Structure of Pressure Screen

Pressure screen is a device that separates impurities based on the difference in morphology between impurities and good pulp fibers. Its typical structure is shown in the rotary pressure screen, which mainly includes foil rotor, screen basket, pulp inlet pipe, rejects pipe, and rejects pipe. The design of the screen rotor is ingenious, including a mounting surface connected to the shaft, a thrust surface at the front, and a suction surface at the tail, which are connected to form an outward convex arc shape, aiming to optimize the efficiency of pulp processing.

Working Principle of Pressure Screen Rotor

The working process of the rotary pressure screen is as follows: the pulp enters the interior of the screen basket through the pulp inlet pipe under a specific pressure, the good pulp passes through the holes on the screen basket under the pressure difference, and the heavier pulp slag moves from top to bottom towards the slag discharge pipe. It is worth mentioning that the gap between the pressure screen rotor and the screen basket is controlled quite finely. At the front of the rotor, as the gap between the propeller surface and the sieve plate gradually narrows, the pressure on the pulp gradually increases, which helps the good pulp fibers to pass smoothly through the screen basket; At the tail of the rotor, the gradual increase in the gap between the suction surface and the screen basket leads to a gradual decrease in pressure and the generation of negative pressure. This design has a recoil effect on the slurry attached to the screen basket, effectively preventing blockage of the screen basket.

The Normal Problem of Screen Rotor

When pulp flows through the working surface of the screen rotor, strong vortex effects are generated due to the interaction between vortices and the working surface of the screen rotor, as well as the mutual influence between vortices. These vortices will quickly spray outward and interact with the vortices inside the screen, exchanging momentum, resulting in an increase in the instantaneous velocity and momentum of the ejected vortices. However, this type of vortex injection will increase the drag of the screen rotor blades, and at the same time, the increase in vortex momentum will also increase the ineffective power during the screening process, thereby reducing the overall efficiency of the screening. Therefore, designing a new type of pressure screen rotor is particularly important, aimed at reducing resistance during operation, improving screening efficiency, and achieving energy conservation and consumption reduction.

The Improvement and New Design of Screen Rotor

The installation surface and propeller surface design of the new pressure screen rotor continue the classic structure of traditional pressure screen. However, the core improvement lies in the suction surface of the screen rotor, where several rows of parallel grooves are cleverly designed, arranged in the same direction as the rotor's running direction. Combining tradition with innovation, the new design continues the classic structure and adds parallel grooves on the suction surface to reduce vortex momentum and resistance.

The cross-sectional shape and size of each row of grooves are carefully designed to maintain consistent height and achieve continuous distribution on the suction surface. The optional cross-sectional shapes include rectangular, V-shaped, and U-shaped, with rectangular shape being the most preferred.

We follow a series of principles in the selection of groove size. The cross-sectional depth of the groove should be controlled between 0.5-3mm and not exceed 1/4 of the maximum thickness of the screen rotor. At the same time, the maximum width of the groove section is set to 0.5-5mm, and the spacing between adjacent grooves is 1.1-2 times the maximum width of the groove section. The longer and higher the concentration of the screened pulp fibers, the larger the corresponding groove size. The specific groove size needs to be carefully determined based on experimental and practical operating conditions, but it must be ensured that the length of the groove does not exceed the length of the suction surface and is consistent with the length of the suction surface.

The working principle of this design is to reduce the lateral flow of vortices on the rotor surface by machining several rows of grooves on the working surface (i.e. suction surface) of the screen rotor that are consistent with the direction of rotor operation, thereby reducing the frequency of momentum exchange between vortices and the instantaneous velocity of surface vortices. This design not only reduces the momentum of surface eddies, but also effectively reduces the surface drag coefficient of the rotor, thereby saving screening energy and improving screening efficiency.

In addition, this design also brings multiple beneficial effects. Firstly, by machining grooves on the suction surface of the screen rotor, the resistance during the screening process can be effectively reduced, thereby improving the screening efficiency. Secondly, the design of these grooves not only reduces the weight of the screen rotor and further lowers screening energy consumption, but also helps to save materials and lower manufacturing costs. Furthermore, these parallel grooves on the suction surface have directional and dispersing effects on the pulp fibers, which helps to maintain consistency in fiber arrangement and reduces fiber flocculation, making it easier for fibers to pass through the sieve holes on the sieve plate, thereby further improving screening efficiency.

Ultimately, this design provides users with a pressure screen rotor solution that runs smoothly, efficiently, and consumes low energy.