Dewatering zone

Screw press

The screw press thickens the pulp from 3% up to 35% consistency. As the pulp becomes thicker, it enters the heating zone with less water. Because of this, steam use drops, and the dispersing result improves. In the end, higher consistency means lower energy use and better pulp quality.

Heating zone

Plug screw

The plug screw seals the heating zone and keeps the temperature stable. As a result, the process uses less steam and allows flexible operation. At the same time, the plug screw creates gentle shear forces that start the pre-dispersing stage.

Shredder

Before heating begins, the shredder cuts the pulp into small and even pieces. This even size helps all fibers and particles heat up at the same rate. Therefore, the pulp reaches the right temperature in the pre-heater more quickly and evenly. In addition, this step improves the efficiency of the following stages.

Pre-heater

In the pre-heater, the pulp warms up to 90–120°C, depending on the raw material. At this point, wax, hot melts, and stickies melt and lose strength. As a result, these materials become softer and easier to remove during dispersing. This makes the process smoother and more efficient.

Dispersing zone

Infeeder

The infeeder moves the pulp from the pre-heater to the disperser. Its patented design prevents blocking and reduces energy use. Moreover, it ensures a steady flow for reliable operation.

Disperser

Inside the disperser, fibers pass through a narrow gap between rotating discs. Here, impurities break down into very small particles. The discs have a special devil-tooth pattern that is adjusted for each pulp type to protect the fibers. Furthermore, the operator can adjust the disc gap online with an accuracy of 0.01 mm for precise control.

Discharge plug screw (optional)

An optional discharge plug screw at the disperser outlet allows a high-consistency discharge of up to 35%. This feature helps when a thicker pulp output is needed.

Booster pump (optional)

The Grubbens booster pump fits directly after the disperser. It keeps the flow stable and works best with medium-consistency discharges between 8–12%. In short, it adds flexibility and consistency to the process.

Bleaching

Pre-bleaching (optional)

Pre-bleaching chemicals are added at the first plug screw. Because the pulp is under pressure and at high consistency, this step needs less energy and fewer chemicals. As a result, it offers an efficient and cost-saving bleaching process.

Post-bleaching (optional)

Post-bleaching takes place in the disperser. When both pre- and post-bleaching are used, operators can set different temperatures, consistencies, and chemical types. This flexible setup helps reach the target brightness while keeping energy use low. In addition, it improves the overall bleaching effect.