Factors affecting sieving performance

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Published:

2023-02-03

Screening performance is greatly influenced by equipment capacity, inclination and other factors, of which screening efficiency and product flow is an important indicator of screening performance.

Screening performance is greatly influenced by equipment capacity, inclination and other factors, of which screening efficiency and product flow rate are important indicators of screening performance.

Flux is defined as the amount of required composition (small size material) per unit area brought through the screening media from the feed each time. Sieving efficiency is expressed as the amount of material that actually passes through the aperture divided by the amount of feed material that should theoretically pass. Commercially perfect screening is considered to be 95% effective if the process is operated at the proper feed concentration and particle size. In general, the appropriate particle size difference between screening and feed should not exceed 30%. High screening efficiency increases mill capacity by reducing cycle loading and the qualified gain content of the screen.

Plant capacity is almost proportional to screen width. This means that by increasing the length, there will be more opportunity to pass and will generally result in increased transfer and efficiency. In general, the standard size of the screen length should be 2 to 3 times the width. However, certain special cases (such as space constraints) may require a different design.

The inclination angle can be designed according to the desired mineral particles. For example, the wet screen angle of a thickener is typically around 25 ± 2°. Increasing the tilt of the screen can effectively reduce the aperture of the cosine of the tilt angle. At the same time, the material moves faster across the screen, leading to more rapid stratification. However, because the deck slope is too large, most particles do not pass through the aperture but remain in the oversized airflow and tend to degrade in performance after a certain point, resulting in a lower flux.

The table below shows the relationship between the slope angle and the desired product flux and efficiency.

Inclined Angle (°)	Flow Rate/Flux (m/min)	Efficiency (%)
18	18.29	86.4
20	24.39	54.6
22	30.48	62.8
25	36.58	64.2
30	32.37	67.5