Focused beam reflectant measurement as a tool to measure flocculation.

Application: The results from this study help further explain flocculation processes and can help obtain real-time flocculation data as a first step in controlling the flocculation process in a mill.

Flocculation is a complex phenomenon that is extremely important in papermaking. It is the intermediate state between the raw materials and the final product. Polymeric additives operate via different flocculation mechanisms. Depending on the required function of the additive it is often desirable for a given interaction to dominate.

We wanted to determine the "optimum flocculation" for good retention, drainage, and formation. This study involved monitoring particles of various pulp suspensions and furnish fractions under different conditions in order to understand the interactions between various polymeric additives and the different pulp fractions. We investigated the particles/polymer as a function of the process shear forces, time, and flocculant dosage, using non-imaging reflectance scanning laser microscopy (SLM) or focused beam reflectance measurement (FBRM).

FBRM helps us optimize polymer dosages and study floc characteristics, such as floc size and strength. The FBRM methodology provided a real-time in process monitor to establish the evolution of the resulting flocculation state and polymer efficiency under the influence of shear forces. The evaluation included a study of deflocculation and reflocculation processes occurring in the sample. Increasing use of recovered fiber and the closure of water systems present the problem of contaminants accumulation. FBRM also has been applied to identify dissolved and colloidal material agglomeration and to study its influence on polymer demand for a given furnish.

Blanco, Fuente, Negro, Monte, and Tijero are with the Chemical Engineering Department, Faculty of Chemistry, Complutense University of Madrid, 28040 Madrid, Spain. Contact Blanco by email at [e-mail]