- 學位論文
非水相次微米粒子懸浮液之固液分離
Solid-Liquid Separation of Nonaqeous Submicron Particle Suspensions
摘要
本研究以大氣電漿熔射系統製備的氧化鋁管狀膜，表面具有高孔隙度之多孔結構，使其擁有較高純水透過量，並且利用平均粒徑0.18 μm二氧化矽粒子進行阻擋率測試，可獲得高於95%之粒子阻擋率。熔射於較大孔洞之基材，所得到的薄膜塗層平均孔徑也來的較大。電漿功率的增加會改變電漿射流的溫度與速度，在低電漿功率下，粒子受熱不足，熔融不完全；而電漿功率過高時，電漿溫度超過粒子沸點，使部分粒子氣化，不論是熔融不完全或是達其沸點都會造成塗層產生缺陷，而二次氣體的添加皆使電漿功率過高，研究發現熔射功率18 kW至21 kW為較佳的熔射功率。隨熔射趟數的增加使薄膜厚度增加，平均孔徑下降，但在溼式製程下，由於塗層孔隙度高，純水衰退量維持在20%左右，研究發現熔射5至7趟為較佳熔射趟數。隨熔射距離的拉長，飛行中熔融粒子溫度與速度受大氣環境影響提前固化，使塗層堆積效率不好，粒子阻擋率差，研究發現7至10公分為較佳熔射距離。隨著送粉速率的提升，氧化鋁粉體送入槍體中的量也隨著增加，但在相同功率下，電漿無法完全熔融所送入的粒子，造成塗層不完整，研究發現1至3 rpm為較佳送粉量。 將製備的陶瓷管狀膜應用於非水相次微米粒子懸浮液之固液分離上，研究發現在不同壓力操作下，隨壓力增加至3 bar後，受到濾餅緻密程度增加的影響，就不再呈線性增加，而次微米粒子的透過率受到濃度極化的影響，逆向擴散回進料液中，隨壓力增加而下降，在模組化擠壓過濾的操作下，逆洗流量與再生次數及陶瓷管狀膜的壽命為一重要參數，在此次微米粒子溶液裡，逆洗次數約為5次左右。
並列摘要
In this study, atmospheric plasma spray was used for making tubular aluminum oxide membranes. The membranes had porous structure in the surface and high flux for pure water permeation. Moreover, it had 95% rejection rate using average particle size 0.18 μm silica particle. As results, average pore size of the coating layer increased as substrates with larger pore sizes were utilized. Besides, for the plasma parameters, for example plasma power, spray times, spray distance and powder feed rate, changed for discussing the pure water permeation rate, particle rejection and surface structure of the sprayed membrane. At low plasma power, particles heated insufficiently, caused melt poorly. On the other hand, at high plasma power, the temperature of the plasma plume exceeded the particles boiling point, caused particles evaporated. No matter what kind of secondary gas injected into the plasma, the plasma power was so high that particles were evaporated. The optimum plasma power was 18 kW to 21 kW. As increasing the spray times, the thickness of the coating layer increased and the average pore size decreased. The optimum spray times were 5 times to 7 times in the wet process because the pure water declination rate kept at 20%. Increasing the spray distance resulted in decreasing particle rejection rate and coating efficiency due to the affecting of the ambient atmosphere on in-flight particles. Thus, the optimum spray distance was 7 cm to 10 cm. With the powder feed rate increased, the amount of injecting aluminum oxide particles increased. Plasma could not melt the particles totally, caused poor coating efficiency. The optimum powder feed rate was 1 rpm to 3 rpm. For the application of the membrane, nonaqeous submicron particle suspensions was used for studying the steady state flux and submicron particle rejection rate under different operating pressure and backwash times, With the pressure increased, steady state flux increased to 1 bar. After that, the denseness cake resulted in a decrease of the steady state flux. Moreover, submicron particle rejection rate increased with the pressure because of the concentration polarization phenomenon. As a result, the best operating pressure was 1 bar, which had higher steady state flux and submicron particle rejection rate. On the other hand, with the backwash times increased, the steady state flux increased because of higher amount of particles be washed from the membrane surface. But the effect on submicron particle rejection rate was not clear. The best backwash times was determined to be 5 times, which had higher steady state flux and submicron particle rejection rate.
參考文獻
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