Performance of ceramic microfiltration membranes for treating carbonated and filtered remelt syrup in sugar refinery

Abstract

The performance of a ceramic microfiltration membrane with 0.5 μm pore size in clarifying carbonated remelt syrup that was filtered by plate-and-frame filter press was investigated under different operating conditions. In total reflux experiments, using 0.5 μm ceramic membranes for treating carbonated, filtered remelt syrup at 80 °C produced steady-state fluxes of 328.4 and 293.1 L/(m2 h) at a cross-flow velocity of 5 m/s, and transmembrane pressures (TMPs) of 3.0 and 2.5 bar, respectively. Decreasing the temperature to 75 °C yielded a corresponding flux of 271.8 L/(m2 h) at a TMP of 3.0 bar. In concentration experiments, when treating 750 L of syrup, 96.7, 76.9 and 72.0 L/(m2 h) of average fluxes were obtained under three operating conditions mentioned above. All conditions produced high-quality filtered syrup. Research on membrane resistances indicated that TMP significantly affected irreversible cake resistance. The increase in cross-flow velocity decreased cake resistance but insignificantly affected pore blocking resistance. All component resistances were decreased with increasing temperature. Membrane fouling dynamics could be represented through a pseudo-first-order rate equation. Fluxes of fouled membranes were recovered by successive cleaning with de-ionized water, a 1% NaOH + 0.5% NaOCl mixed solution, and a 0.5% HNO3 solution.