| Ceramic microfiltration membranes was used to microfiltrate impure solvent naphtha 200 coming from aluminum pigment industry, and the effect of operating parameter, concentration experiment, membrane fouling mechanism, membrane flux recovery and the industrial design were investigated respectively. This work contributed to development of ceramic microfiltration membrane technology in the application of impure solvent naphtha.The microfiltration processes of solvent naphtha containing impurities were studied with 0.2μm, 0.5 and 0.8μm ceramic membranes. As for 0.2μm, two feeds were selected, one was the solvent naphtha without water, the other was the solvent naphtha with 0.5%(ω) water. The effects of operating time, trans-membrane pressure, cross-flow velocity, temperature and aluminum powder content on permeate flux and/or rejection were investigated, respectively. The results show that, permeate flux of the solvent naphtha without water was much higher than that of the solvent naphtha with 0.5%(ω) water. With increasing operating time, permeate flux decreased gradually to a steady value, and the rejection of aluminum powder increased rapidly to 100%. Steady-state flux enhanced with increasing trans-membrane pressure or temperature, and reached to a maximum value with the increase of cross-flow velocity. The higher the content of aluminum powder was, the higher the permeate flux was. Optimum operating parameters were trans-membrane pressure 0.16 MPa, cross-flow velocity 3.9 m/s and temperature 40℃. The similar results were obtained for 0.5μm and 0.8μm, the optimum trans-membrane pressures were 0.12 and 0.10 MPa respectively. In concentration experiments, with increasing volume concentration factor, permeate flux decreased more rapidly, then slowly, and finally rapidly again; rejection of aluminum powder was increased rapidly to 100%, and rejections of isostearic acid and linoleic acid were increased slightly, and purified solvent naphtha was transparent.The scanning electron microscope and energy dispersive spectrometer (SEM-EDS) were done. It indicates that the fouling on the membrane surface was an integrated effect of aluminum particles and organic matters, and it almost took place on the membrane surface. Further, various membrane resistances were calculated, the membrane fouling resistance (Rf) played an important role in flux decline. In the process of chemical cleaning, permeate flux could be recovered effectively to 94.9% new membrane flux for 0.2μm membrane by using 0.15%(ω) commercial detergent and 0.25%(ω) nitric acid, respectively. As for 0.5μm, when 0.15%(ω) commercial detergent, 0.25%(ω) nitric acid and 0.5%(ω) sodium hydroxide + 0.3%(ω) sodium hypochlorite cleaning stages were used, flux recovery can reach as high as 97.8%. Then, the backflushing can increase efficiently permeate flux, it is possible to recover over 94% of the original flux by a program of backflushing. A modificatory model for complete blocking model was built, and compared with other models on fitting the experimental data. It is found that the correlation coefficient for the modificatory model was higher than 0.99.Microfiltration process of solvent naphtha 200 containing impurities for industrial application was also investigated. It found that membrane pore size of 0.2μm and the membrane total area of 1.92 m2 can satisfy with the output of 1000 ton solvent naphtha per year. The flow diagram of serial and four parallel connection was designed, and it can make much profit. |
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