The screening process for banana screen is divided into two stages. The first is the layer of particles that can easily pass through the banana screen sieve and those that cannot pass through the sieve to reach the screen surface; Secondly, the particles that easily pass through the sieve are separated through the sieve. For these two stages to be possible, the material should have appropriate movement on the banana screen screen. On the one hand, the material on the screen surface is in a loose state, and the material produces granularity stratification, with large particles located in the upper layer and small particles located in the lower layer. On the other hand, the movement of the material and the sieve all promote the particles blocked on the sieve to leave the screen surface and enter the upper layer of the material.
banana screen screening efficiency Screening efficiency is an important indicator to evaluate the banana screen screening process and equipment performance, reflecting the extent of screening and product quality. The average screening efficiency of an industrial screen is 60% to 70%, and the screening efficiency of a banana screen can reach more than 95%.
Factors that affect the screening of banana screen
A Properties of the material
a Particle size composition
The more sieve particles contain, the easier the material is to screen; The more difficult to screen particles, the more difficult to screen the material size d = 1-1. 5a(a is
Sieve size) particles easily stuck in the banana screen sieve, called obstruction particles, affecting the material through the sieve. Therefore, the material contains difficult sieve particles, the more obstructing particles, the lower the screening efficiency.
b particle shape
Spherical particles easily pass through square and round hole banana screen, bar, sheet and polygonal materials are more difficult to pass through square and round hole screen, but easier to pass through rectangular hole banana screen.
c Water content
Dry screening, the material water and wettability and drilling adhesion better the material is easier to condense, caking, blocking the sieve,
The screening efficiency is greatly reduced.
d Packing density
In the case of material bulk density is relatively large, the screening capacity of banana screen is directly proportional to bulk density.
B Properties and motion of screen surface
a Opening rate
The ratio of the sifting area of a banana screen to the sifting surface area is called the opening ratio. The screen surface with large opening rate has high screening efficiency and large production capacity. But the screen surface has low strength and short life.
b Sieve shape
The ability of material to pass through varies greatly depending on the shape of the sieve. When choosing the banana screen sieve type, it should be suitable for the particle shape of the material, usually square sieve.
c Size of screen surface
When the length to width ratio of the screen surface is too large, the material layer is original; When the aspect ratio is too small, the screening time is short. Both of these conditions will make the screening
Less efficient. Therefore, the aspect ratio of the banana screen should be within the appropriate range, generally 2. 5 — 3.
d screen surface inclination
Too small inclination, low production capacity; Too large inclination Angle, low screening efficiency. Therefore, the Angle of screen surface should be selected appropriately, banana screen Angle is generally 0 to 25. , fixed screen Angle is generally 40 to 45.
e Motion condition
Different types of banana screen oil have different relative motion conditions between the material and the screen surface, and their screening efficiency is very different, as shown in Table 7. 6 as shown.
|
Table 7.6 Screening efficiency of different screening machines |
||||
|
Class type |
Fixed sieve | Rotary screen | Shaking sieve |
Vibrating screen |
| Sifting efficiency (%) | 50 ~ 60 | 60 | 70 ~ 80 |
90 + |
c Operating conditions
Screening efficiency.
