Investigation of clarification control based on secondary juice mud solids

Flocculants are used to improve the efficiency of clarification, a key process in the production of quality sugar. The flocculant requirement might be expected to be dependent on the mud solids content of juice. Therefore, control of the flocculant addition rate based on a measurement of mud solids could provide optimisation of its usage and achieve better overall clarifier performance. An Amdel Model 870 Percent Solids Gauge that measures the gamma radiation emitted by mud solids was installed at Tully Sugar Limited in 1997 for the purpose of controlling the flocculant rate. Following calibration trials that proved a strong relationship between the counts per second of gamma radiation and percent mud solids, the instrument output was incorporated into the mill's flocculant control system. For control purposes, in an evaluation of the effectiveness of the system it could not be demonstrated that there is a direct relationship between flocculant requirement and the percent mud solids as determined by its natural gamma radiation. It appears that unknown properties of juice have a greater effect on the amount of flocculant required than percent mud solids. A baseline flocculant rate in excess of any possible minimum is required to maintain stability in clarifiers.