| These years,the demand for single and poly crystal silicon has been soaring since the solar cell and electronic industries are developing rapidly.As the essential raw material,the consumption of lubricating liquid for wire-slicing silicon is also increasing rapidly.Because of the exhausted lubricating and spent abrasive grains,the manufacturing process produces a great amount of waste which is difficult to be disposed of.Nowadays,some processes have been developed aimed at the waste treatment,while there exists the drawbacks for these processes,such as high energy consumption,complicated procedures.In order to solve the problems,Microfiltration(MF) or Ultrafiltration(UF) membrane method has been proposed as an alternative to recover the lubricating liquid. Although MF or UF membrane has already been applied in various kinds of water treatment processes,it has rarely been reported to recover highly viscous liquid.Therefore,it is worthwhile to study the highly viscous liquid recovering process,which would help broaden the application area of MF or UF membrane.In this thesis,the contact angles between lubricating liquid and membranes prepared with different materials have been measured,and the contact angle between PAN membrane and liquid is the smallest,which shows PAN is an appropriate material for preparing high permeation flux membrane.The home-prepared PAN UF membrane with molecular weight cut-off(MWCO) 67,000Da is used to study the effects of temperature,solid content, trans-membrane pressure(TMP) and crossflow velocity(CFV) on the permeation flux. Because of the relationship of temperature and viscosity,the viscosity decreases as temperature increases,and the corresponding permeation flux would increase.Under the operating condition,the temperature of 60℃,solid content of 229.6mg/L,TMP of 0.1MPa and CFV of 0.05m/s,the steady permeation flux of 7.68L·m-2·h-1 has been obtained.In addition,taking into account the packing capacity and washing characteristic,the tubular and hollow fiber membranes have been also used in the experiment.The permeation flux recovering ratio for tubular MF membrane is satisfactory under the operating condition of back washing pressure of 0.08MPa and back washing time of 5 minutes.Under the same operating condition the hollow fiber membrane with MWCO of 45,000 Da exhibit the tendency of slowest permeation flux decline.After the treatment of MF or UF membrane,the permeate is transparent without solid particles and shows yellow color.The color magnitude for the permeates is identical,85 by color comparing method.The color change and red sediment after adding sodium hydroxide could verify the existence of ferric ions.The model for predicting permeation flux decline has been established under the condition of low shear stress,and it shows good agreement with the experimental results, which could validate the precision of the model.The common crossflow model has also been established by combining the calculation of forces acting on single particle and the model of low shear stress.After comparing the calculating results of model and experimental results, the accuracy of model has been verified.Finally,based on the experimental results and model, the UF membrane process for recovering the lubricating liquid from the exhausted slurry has been designed for an enterprise.
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