Trommel screens are one of the most commonly used screening equipment for solid waste treatment. The solid waste is classified by particle size using a cylindrical sieve body, and the cylindrical sieve body is installed obliquely during operation. The solid waste entering the drum screen spirals with the turning action of the sieve body. Under the action of gravity, the solid waste with a smaller particle size than the sieve hole is sieved through the sieve hole, and the solid waste larger than the sieve hole is in the sieve body. The bottom end is discharged.
1. Trommel screen screening principle The movement of materials in the drum screen presents three states, namely
1 Falling state: At this time, the rotation speed of the sieve is very low, the boring particles are brought up by the circular motion of the sieve, and then rolled onto the upward moving particles, the material mixing is insufficient, and it is difficult to make the intermediate fine material roll The mesh is touched to the edge and the screening efficiency is extremely low.
2 throwing state: When the rotating speed is high enough but lower than the critical speed, the material particles rise along the wall of the cylinder against gravity, until reaching the highest point of the drum, when the gravity exceeds the centrifugal force, the particles fall back along the parabolic trajectory Therefore, the tumbling degree of the material particles is the most severe, and the accumulation phenomenon rarely occurs, and the screening efficiency of the sieve is the highest.
3 Centrifugal state: When the rotational speed of the sieve is further increased, a certain critical speed is reached, and the material adheres to the wall of the cylinder due to centrifugation and cannot fall and roll, thereby causing a relatively low efficiency. The drum screen for sorting domestic garbage is to add some sorting or cleaning mechanism on the basis of the ordinary drum screen to make it more suitable for the screening of domestic garbage, mainly horizontal rotary drum screen, vertical drum screen and blade. Three types of drum screens. The movement of the refuse in the drum screen can be decomposed into a movement in the direction of the screen axis and a plane movement perpendicular to the plane of the screen axis. The linear motion along the axis of the screen is due to the inclined installation of the screen, the speed of which is the speed at which the refuse passes through the screen. The movement of the refuse in a plane perpendicular to the axis of the screen is closely related to the rotational speed of the screen. When the cylinder is always rotated at a lower critical speed, the garbage is brought to a certain height and then parabola falls. This movement is beneficial to the screening. Generally, the rotation speed of the trommel is 30%~60% of the critical speed, which is slightly lower than the rotation speed required for the maximum drop of the garbage material.