柑桔汁陶瓷膜微滤澄清和污染阻力试验

    Experiments on clarification of orange juice and fouling resistances by using ceramic microfiltration membrane

    • 摘要: 为了探讨柑桔汁微滤澄清技术及微滤膜污染阻力,建立膜清洗方法,研究以0.2 mm陶瓷膜微滤柑桔汁时膜通量变化及处理效果,结果表明:当温度30℃、压差0.16 MPa及膜面流速4 m/s时,全循环模式下稳定膜通量为22.4 L/(m2·h),浓缩模式下体积浓缩因子为12时,膜通量为10.6 L/(m2·h),澄清汁得率达91.67%;澄清汁浊度仅为0.62 NTU,澄清度高达99.93%,且各主要营养成分变化不大。通过建立膜污染阻力模型,考察操作参数对各分解阻力的影响,进而研究膜污染动力学后发现:压差对不可逆极化层阻力影响最为明显;增大膜面流速显著降低各极化层阻力,但对不可逆污染阻力作用不大;升高温度使得各阻力下降;膜污染可用拟二级速率方程描述。研究污染膜清洗过程,结果表明采用去离子水、1% NaOH和0.5% NaClO混合液、0.2% HNO3溶液依次清洗膜,膜通量可迅速恢复。

       

      Abstract: The purpose of this work was to study the clarification of orange juice, membrane fouling resistances and cleaning methods by microfiltration. Ceramic membranes with a pore diameter of 0.2 mm were employed. The changes of permeate flux and the efficiency of retention were investigated during the clarification process. It was found that, at temperature 30℃, transmembrane pressure 0.16 MPa and cross-flow velocity 4 m/s, the steady-state permeate flux reached 22.4 L/(m2·h) in the total recirculation experiment, however the permeate flux was only 10.6 L/(m2·h) in the concentration experiment, which corresponded to the volume concentration factor of 12 and the percentage yield of 91.67% for the clarified juice. The turbidity of clarified juice was 0.62 NTU, the percentage of clarification reached as high as 99.93%, and the main nutrition elements of clarified juice change insignificantly. On the basis of the fouling resistance model, the effects of operating parameters on various resistances and the kinetics of membrane fouling were studied in detail. The results indicate that transmembrane pressure affects significantly the reversible polarized layer resistance; the increase of cross-flow velocity decreases various polarized layer resistances, but affects insignificantly the irreversible fouling resistance; the various resistances decrease with increasing temperature; the fouling kinetics can be describe by a pseudo-second-order equation. The cleaning procedures for fouled membranes were investigated. The results show that permeate fluxes are recovered rapidly by using deionized water, the mixed solution containing 1% NaOH and 0.5% NaClO, 0.2% HNO3 solution to clean the membranes in turn.

       

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