Dialysis
For continuous removal of the hemi-cellulose content of the steeping lye.
Features
- Highly effective membranes
- With several years life
- Reliable and stable operation
- High availability
In Detail
During the mixing of cellulose with soda-lye, the hemicellulose contained in the cells is dissolved in the soda-lye. As a result, the soda-lye (lye solution) has a stable hemi content which must be remain below a certain level due to the requirements of quality, production, technology, and environmental protection.
Dialysis is a physical procedure for the separation of low-molecular weight substances (e.g. NaOH) and macro-molecular substances (e.g. hemicellulose).
The procedure is based on the fact that low-molecular weight solutes are light, whereas macro-molecular solutes or colloids are very heavy in comparison and cannot penetrate semipermeable membranes. Dialysis takes place in a dialysator (1), which consists of two chambers separated by a semipermeable membrane (2). One of these chambers contains a solvent (water) (3) while the other one contains a solution (press-lye) (4).
The low-molecular weight substances will then diffuse through the semipermeable membrane into the solvent, while the macro-molecular or colloid substances remain. This process is known as osmosis. The hydrostatic overpressure on the side of the solution which is in the process of being diluted, whereby it remains at a stronger concentration, is called "osmotic pressure".
For optimum performance of the Cerini-apparatus the solution (press-lye) and the solvent (water) are driven by reverse current. This means the press-lye flows from the bottom up, while the water flows from the top down.
