Pulp and wood pulp production

Bleaching process

Depending on the pulp density, the chemical pulp is transported via pumps, a flow distributor, or conveying spirals to the bleaching tower. The bleaching process then runs continuously at temperatures up to 95°C (203°F), with bleaching chemicals such as oxygen, ozone, or peroxide being added. The bleached pulp is discharged via feed screws. Similar processes are used for wood pulp bleaching and waste paper deinking.

Level measurement with VEGAPULS 68 and VEGABAR 54

A constant level in the bleaching tower is important for the quality of the bleaching process. To ensure this, a continuous level measurement works in conjunction with a discharge control. The powerful radar sensor VEGAPULS 68 has special dynamics that ensure reliable measuring results even under the difficult conditions in the bleaching tower. The pressure transmitter VEGABAR 54 with ceramic CERTEC measuring cell is integrated in a ball valve fitting to carry out the required measurement in the discharge area.

Overfill protection with VEGACAP 64

The capacitive level switch VEGACAP 64 is used as an additional protective measure to avoid overfilling the bleaching tower. The level switch prevents any spillages or blockages and the continuity of the process is ensured.

Chip storage

Chips are the raw material for refined lignin and pulp. They are made from debarked logs or bought as waste from sawmills. They are transported via conveyor belts to large silos with a height of up to 25 m (82 ft) and, after screening, to a digester or a TMP plant (Thermo Mechanical Pulp). During storage, oxygen is consumed in the silo; the temperature then rises due to the exothermal reaction.

Level measurement with VEGAPULS 68

Chip silos must be filled and emptied in batches. During filling a material cone is formed, large amounts of dust are generated, and material bridges collapse during emptying. The optimum solution for level measurement is the radar sensor VEGAPULS 68 for bulk solids. VEGAPULS 68 is so powerful and has such a high dynamic range compared with conventional radar sensors, that measurement works reliably even during filling. Continuous recording, as well as reliable logistics planning are thus possible. Further application sites for VEGAPULS 68 are the bark silos as well as the aeration tanks following the digester.

Indication and adjustment with VEGADIS 61

VEGADIS 61 enables reliable and convenient indication and adjustment on site or remotely up to 25 m (82 ft) away.

VEGAPULS 68

- non-contact, maintenance free measurement
- safe function even in case of high stock consistency
- unaffected by steam and build-up

VEGACAP 64

- insensitive to adhesion
- rugged and maintenance free

VEGABAR 54

- front flush installation into ball vave fitting
- mounting and dismounting of the pressure transmitter without emptying the bleaching tower

VEGADIS 61

- separate mounting up to 25 m (82 ft) away
- no additional power supply necessary

VEGAPULS 68

- optimal alignment acc. to vessel geometry and material cone
- reliable function during filling