Breakage of protein precipitates flowing through orifices

The effect of orifice diameter and orifice length on the breakage of flowing protein precipitates was evaluated. These orifices were intended to mimic the flow intensity present in certain valves, pumps, flow meters and centrifuges that might be present in the transportation of precipitates. Different orifice contraction ratios (0.12-0.36), orifice lengths (0.3, 1.0 and 3.5 mm) and flow rates (6.0-9.0 g s(-1)) were studied. The extent, rate and mechanism of precipitate disruption were significantly affected by all these variables. The energy dissipation rate (F) within each flow geometry was computed using CFD. A wide range of F values (3.4 x 10(2) to 1.4 x 10(6) m(2) s(-3)) was generated and at least two different breakage mechanisms were observed. The first mechanism dominates at high F and is characterized by significant production of submicron particles; the other one dominates at low E: with negligible production of fines. Both the breakage rate and mechanism were modelled as continuous functions of c. The proposed breakage model predicts that significant precipitate disruption will occur according to the former breakage mechanism in certain post-formation processing equipment. (c) 2007 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.