99E-5 |
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S.-Q. LI and Q. H. Zhang. Dept. of Food Science and Technology, Ohio State Univ., 2015 Fyffe Ct., 110 Parker Food Science Bldg., Columbus, OH 43210-1007 Pulsed Electric Field (PEF) processing is an emerging nonthermal technology for reducing microbial load in many biological systems, including pumpable food, wastewater and sludge. PEF chambers provide treatment zones where pulsed electric energy is delivered to the treatment fluid. Erosion of the electrodes is a critical factor determining life expectation of PEF treatment chambers. The objectives of this study were to evaluate the incidents of electrodes erosion under high intensity PEF and to investigate the correlation between erosion and critical operation parameters. An OSU-5B PEF unit with co-field flow chambers provided selected treatments. Treatment fluid was semi-liquid sludge in middle Ohio with electric conductivity varying ranging from 0.14 to 0.21S/m at room temperature. The treatment fluid passed through the treatment chambers once only. The erosion was quantified by measuring both the loss of weight and changes in geometry of the borate carbide electrodes (two catheti of the erosion triangle) before and after PEF operation. Significant erosion (p<0.01) of the tested borate carbide electrodes was observed at 25-30kV/cm after PEF operation. The amount of 0.26g of electrode material was leached into the treatment fluid and the inner diameter of the opening of the electrodes was increased by 3.5mm after 100h operation at 28kV/cm-58.8μs using bipolar square pulses with pulse-width of 4μs. At 28kV/cm, both loss of weight and changes in geometry in either axial or radial direction showed close correlation assuming a linear relation with operation time. However, the hypotenuse of the erosion triangle was not a straight line, but a pseudo-exponential curve. This study provides useful information to facilitate the fundamental understanding of electrode erosion under high intensity PEF operation and engineering design of treatment chambers.
Session 99E, Nonthermal Processing: General II
2005 IFT Annual Meeting, July 15-20 - New Orleans, Louisiana |