Tubular Membrane Liquid-solid Two-phase Flow Cleaning System

Concentration polarization and membrane fouling in membrane process severally limit its application and development. The paper is aimed to clean the fouled tubular membrane with rubber sponge balls in order to solve the problem which is not able to do with some traditional cleaning methods.First, rubber sponge balls are mainly synthesized with silicone rubber. In addition, tubular membrane is dominatingly made of polyvinylidene fluoride(PVDF) with the integrated production technology and the membrane is tested with self-made leak hunting device. In succession, we manufacture the solid-liquid two phase cleaning system, in which the shooting liquid device, phase break device and tubular membrane bracket are the key factors.Second, "mixed flow" is proposed for the first time as a method in membrane field. Three models are proposed as follows by applying the model of "mixed flow" : the stress of increasing fluid on fouling, collision between solid particles and fouling, and solid particles movement velocity; the effects of operating parameters, properties of particles, and the volume fraction of particles on stress in solid-liquid two phase flow, collision stress between solid particles and fouling, maximal contacting area between solid particles and fouling and maximal contacting time between solid particles and fouling are investigated systematically by calculating and theoretical analysis.Third, according to the water flux and the rejection ratio of original sample, the fouled sample and the washed sample with rubber sponge balls, we know that the same change current of the three samples. Moreover, some effect factors to water flux are discussed as follow: the operation pressure, the number and diameter of rubber sponge ball, the soluble-starch concentration, and so on. In order to study solid-liquid two phase washing system further,we compare that method with traditional mass water washing method and get the over 10% recovery ratio of the former than the latter. In addition, we test the rejection ratio of very sample and get the result of the rubber sponge ball no damnification to the membrane.Fourth, the advanced surface analysis technique -X ray photoelectron spectrum is employed to study the adsorption of soluble-starch on the PVDF membrane. Then we test by using XPS combined with SEM the original sample, the fouled sample and the washed sample with rubber sponge balls. According to the analysis of the fitting spectrum of carbon and oxygen, the result indicates that soluble-starch is adsorbed much on the membrane, but it physically deposits on the membrane. Also, the washing effect of rubber sponge balls is better.