Revisiting Coiled Flocculator Performance for Particle Aggregation.

  This work summarizes recent studies evaluating the torsion and curvature parameters in flocculation efficiency using a hydraulic plug flow flocculator known as a Flocs Generator Reactor (FGR). Colloidal Fe(OH)3 and coal particles were used as suspension models and a cationic polyacrylamide was used for the flocculation. The effectiveness of the aggregation process (in the distinct curvature and torsion parameters, and hydrodynamic conditions) was evaluated by the settling rate of the Fe(OH)3 flocs, and flocs size by photographic analysis. As a result of curvature, a secondary flow is induced and the profiles of the flow quantities differ from those for a straight pipe. Results showed that the differences in the flocculator design influences the Fe(OH)3 flocs size and settling rates, reaching values of about 13 and 4 m/h, for the coiled and straight pipes respectively. Coal flocs generation was also shown to be dependent on the flocculator design and shear rate. Results showed that turbulent kinetic energy increases because of curvature when the torsion parameter is kept constant (pitch close to zero), enhancing the flocs formation.