以矽油加水在旋轉填充床吸收甲苯之研究

Abstract

本研究為錯流式旋轉填充床內吸收甲苯的質傳程序，分別以水、矽油以及矽油加水為吸收劑去吸收甲苯。由於甲苯為疏水性有機揮發物，利用水去吸收甲苯實驗中，其最佳吸收分率為0.12，可見水並非一個適當的吸收劑。在以疏水性之吸收劑矽油吸收甲苯實驗中，其最佳吸收分率可達0.9，可見矽油對於甲苯的吸收是不錯的吸收劑。 接著，利用矽油加水吸收甲苯實驗中發現，在固定矽油流量下，加水對於吸收程序有正向幫助。如在氣體流量為21.3L/min，甲苯濃度為1400ppmV，轉速為500rpm，矽油流量為0.1L/min下，水量由0.01L/min增加至0.6L/min，吸收分率由0.37增加至0.74。由先前實驗得知，水並不是一個好的吸收劑，但在矽油加水吸收甲苯實驗中發現，加水後對於吸收分率有很大的提升，可見水不再只是扮演單純的吸收劑，而是扮演著幫助矽油吸收甲苯的角色。在低矽油流量(0.1L/min)下，水主要是扮演增加總液體流量的角色，使得矽油在床內分佈更均勻，進而提高吸收效果。在高矽油流量(0.5L/min)下，水主要是扮演被矽油包覆的角色，藉由矽油包覆水來使得矽油有效接觸面積上升，進而提升吸收效果。在矽油加水實驗中，其最佳之吸收分率為0.96，達到可以直接排放之標準。

This work presented a mass transfer process of absorbing toluene in a cross-flow rotating packed bed. Water, silicone oil, and silicone oil with water were used as absorbents in the experiments to absorb toluene, respectively. The best absorption fraction for water was 0.12. This showed that water was not an appropriate absorbent for toluene, owing to that toluene is hydrophobic VOC. On the contrary, the best absorption fraction for hydrophobic silicone oil was 0.9, showing that it was a good absorbent in this process. Using silicone oil with water as absorbent in the experiments, changing water flow rate that would enhance the absorption efficiency obviously at constant silicone oil flow rate. For example, at gas flow rate 21.3L/min, toluene concentration 1400ppmV, rotor speed 500rpm, oil flow rate 0.1L/min, water flow rate changing from 0.01L/min to 0.6L/min, the absorption fraction varied from 0.37 to 0.74. However, in the previous study, it showed that water was not a good absorbent. It was thus clear that water did not act as an absorbent. Actually, it played a role of assisting silicone oil to absorb toluene. At low oil flow rate (0.1L/min), water played a role of increasing the total liquid flow rate that led the silicone oil well distribution. Thus, the silicone oil effective gas-liquid interfacial area would increase. Then the absorption efficiency increased. At high oil flow rate (0.5L/min), water played a role of inserting into silicone oil that would enhance the effective gas-liquid contact area of oil, thus increase the absorption efficiency. In the silicone oil with water as absorbent to absorb toluene experiments, the best absorption fraction was 0.96, satisfying of emission regulation.