Screening is a key step in the paper pulp preparation process. Main objective is to separate the unwanted components or pollutants from desirable fibres. This separation usually takes place by means of filter elements with holes or slots, and their sizes and designs can vary as per the requirements (coarse, fine screening, etc.). The fibres passing through the openings are called “accepted” and the larger and less flexible particles that cannot pass through the openings are caught or rejected and usually called “Rejects”.

 

This geometric selection is done physically by the baskets that are one of the key components for the effectiveness of the screening process; and one of the fundamental criteria of performance is the accuracy of the size and design of the openings. KADANT has developed a complete range of baskets with fine holes and slots in order to meet the specific requirements of pulp preparation and approach flow applications, and particularly with the FibreWALLTM baskets with a robustness and accurate geometry still unmatched (unequalled) today.

 

 

 

 

FiberWALL™ basket

 

 

The basket is always paired with a rotor equipped with deplugging elements that continuously clean or clear the openings of the basket plugged by particles larger than their sizes. This phenomenon is executed by local and periodic "suctions", which are known as micro pulses.

 

Different types of rotors

 

The performance of a screen depends on this basket – rotor pair, and is quantified by factors such as total solids rejects rate in weight, or volume, or Fibres reject rate in weight, the contaminants/pollutants removal efficiency, etc., and of course in addition to the paper making process performance, the specific energy required for its accomplishment.

 

The performance is intrinsically linked to this basket–rotor pair. The physical phenomena therefore depend on each other. For example, the natural thickening along the basket is due to the ability of water to pass more easily through the openings than the fibres and the accumulation of elements larger than the basket size.

 

This graph shows the effects of different deplugging depending on whether it is located at the basket’s middle section (red curve) or on the reject side (green curve)

 

 

KADANT has therefore developed BoosTEK® in order to increase the screening performances.

BoosTEK®, is creating macro-pulses of pressure, distantly and independently helps and maximises the positive effects of the rotor on the basket of the screen.

BoosTEK® can be easily installed at the accepts and / or rejects of all screens, without any initial impact on the Rotor–Basket pair that is already in place in the machine.

 

 

The applications are many and wherever a screen is installed, i.e. for virgin pulp, recycled pulp, plant fibres, non-woven, etc.

BoosTEK® consumes low power, from 0.37 to 2.2 kW, depending on the size.

As far as performance is concerned, BoosTEK® increases the capacity (by 10 to 25%), increases cleaning efficiency, and/or reduces fibrous and total losses (by -40 to -65%), and/or grants significant potential energy savings (30 to 50%).

 

“BoosTEK® is revolutioning the known principles of screening and expands the operational limits of screens and offers an innovative solution for significant qualitative and quantitative improvements, for optimizing operations of the pressure screens.”

 

Some industrial results:

 

BoosTEK® grants significant efficiency savings

 

Our installations with BoosTEK on screen rejects at the last stage have shown a significant reduction in the rejects from the screening process.

 

On an average, we recorded an overall increase in efficiency of 0.5 point with reduced fibrous losses of up to 55%

 

BoosTEK® helps to save fibres

 

The efficiency gains are obtained by the recovery of fibres, and therefore with high added value.

The contaminants are therefore more “pure”.

In the graph below, we have clearly a fibre saving.

 

 

BoosTEK® increases quality and/or capacity

 

Our experiences with BoosTEK® were able to show an increase in production of up to 25%, and/or a significant increase in quality especially at the level of the flexible contaminants such as stickies, with significant energy savings.

 

BoosTEK® saves energy

 

When installed, BoosTEK® reduces the specific energy by another method: by reducing the rotor speed.

Owing to its complementary nature with the rotor of the screen, BoosTEK® significantly reduces the rotation speed, while still retaining the same screening process parameters (dense and solid rejects). Reductions of up to 65% were obtained. 

Moreover, this reduction in speed allows for improved screening efficiency for flexible elements such as Stickies.