气扫式膜蒸馏用于脱除水中氨的分离性能

针对气扫式膜蒸馏脱除水中氨的过程，以传质基本理论为依据，导出了考虑水中氨解离的总传质系数表达式，并建立了利用实验结果计算总传质系数和选择性系数的方程。在气扫式膜蒸馏实验中测定了各种操作条件下氨浓度和跨膜通量随时间的变化关系，并利用导出的方程、由实验结果得出了相应的总传质系数和选择性系数。研究结果表明，升高料液温度能够提高氨的总传质系数，但却使选择性系数下降；料液的流速对氨的总传质系数和选择性系数均无重要影响，但提高吹扫气速能使两者都明显上升；总传质系数和选择性系数随料液浓度的升高而略有下降；提高料液的初始pH值能同时明显地增大总传质系数和选择性系数。

Separation performance of sweep gas membrane distillation used in the removal of ammonia from water

The performance of sweep gas membrane distillation (SGMD) in the removal of ammonia from water has been evaluated. A mass transfer equation and equations for evaluating mass transfer coefficients and selectivity have been derived by taking into account the dissociation of ammonia in water. SGMD experiments were conducted under various operating conditions in order to measure the ammonia concentration and trans-membrane flux. The mass transfer coefficients and selectivity were calculated from the experimental data. Within the range of experimental parameters employed, mass transfer coefficients of up to 2.2×10^-5m/s and selectivities of up to 14 were obtained. It was found that high feed temperatures result in higher mass transfer coefficients, but lower selecitivity. The feed velocity has very little influence on either mass transfer coefficient or selectivity, but they both can be increased by increasing the velocity of the sweep gas. While mass transfer coefficient and selectivity decrease slightly with rising feed concentration, they can be greatly increased by increasing the feed pH.