1993 Volume 47 Issue 7 Pages 837-844
A number of factors affect flocculation. The influences on flocculation by these factors have been estimated by the coefficient of variation of the transmitted light intensity or gray level and the distribution of floc size. These factors affect not only the floc size distribution but also the shape of flocs. It was found that the fractal dimension can express the floc shape of areas which vary from 1 mm2 to 300 mm2.
The energy given to a pulp slurry on a paper machine can be divided into two processes : one used to weaken and/or activate the network and rupture the flocs, the others used to build-up the flocs. As the floc formation proceeds, the shape of flocs tends to become simpler. On the other hand, as the dispersion proceeds, the shape of flocs tends to be more complicated. The shape of flocs is a result of the equilibrium of the forming and dispersion processes. When we compare single and dual system in retention aid, the flocs in dual system have simpler shape and smaller average floc size than single system at the same level of coefficient of variation. The difference in behavior of floc size distribution and floc shape against the shear force may be caused by the difference in the mechanism of flocculation. The shape of the floc is a good index to describe the conditions of the slurry such as the distribution of floc size and the coefficient of variation.
