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Vacuum membrane distillation multi-component numerical model for ammonia recovery from liquid streams
Journal of Membrane Science ( IF 9.5 ) Pub Date : 2020-11-01 , DOI: 10.1016/j.memsci.2020.118399
D.M. Scheepers , A.J. Tahir , C. Brunner , E. Guillen-Burrieza

Abstract In this work, a modelling research on the separation of ammonia gas from liquid streams via vacuum membrane distillation (VMD) is conducted. An experimentally validated multi-component simulation model of a flat sheet VMD module is developed by implementing heat and mass balances through the feed, membrane and permeate channels. Continuous removal of the gases transferred through the membrane at a constant pressure in the permeate channel is assumed. The transport mechanisms through the pores under VMD conditions for both volatiles are discussed. Under studied VMD conditions and the typical concentration range in waste waters (i.e. 1-10 g TAN l-1), it is observed that none of the two volatile components (ammonia and water) is preferentially transported. The resulting VMD performance is simulated and evaluated in terms of total transmembrane flux, ammonia flux, ammonia selectivity and thermal energy consumption. The model was validated experimentally and showed good agreement, with an average relative error J N H 3 ) and selectivity ( S N H 3 ) of ammonia. Increasing feed temperature and decreasing vacuum pressure results in higher J N H 3 but lower S N H 3 . Moreover, those parameters that enhance the heat transfer through the membrane (i.e. feed temperature, pore size, porosity, vacuum pressure, etc.) promote the water flux over ammonia. While those parameters that enhance mixing and the ammonia mass transfer in the feed (i.e. feed velocity, spacer geometry, pH, ammonia feed concentration, etc.) promote the ammonia flux over water. The only operating parameter which enhances simultaneously the J N H 3 and S N H 3 is the feed velocity, indicating that the spacer geometry can play an important role in designing VMD modules for ammonia separation. VMD can extract and concentrate ammonia on the permeate side at a low specific thermal energy consumption. However, the J N H 3 is greatly limited by the feed ammonia concentration which will ultimately determine the cost-effectiveness of the recovery. The trends described by the model are in agreement with other authors’ observations and give insight into the mechanisms dominating ammonia separation via VMD and its performance limits.

中文翻译:

从液流中回收氨的真空膜蒸馏多组分数值模型

摘要 在这项工作中,对通过真空膜蒸馏 (VMD) 从液体流中分离氨气进行了建模研究。通过通过进料、膜和渗透通道实现热量和质量平衡,开发了一种经过实验验证的平板 VMD 模块的多组件模拟模型。假设在渗透通道中以恒定压力连续去除通过膜转移的气体。讨论了两种挥发物在 VMD 条件下通过孔的传输机制。在研究的 VMD 条件和废水中的典型浓度范围(即 1-10 克 TAN l-1)下,观察到两种挥发性成分(氨和水)都没有优先传输。根据总跨膜通量、氨通量、氨选择性和热能消耗来模拟和评估由此产生的 VMD 性能。该模型经过实验验证并显示出良好的一致性,平均相对误差 JNH 3 ) 和氨的选择性 ( SNH 3 )。提高进料温度和降低真空压力导致更高的 JNH 3 但更低的 SNH 3 。此外,增强通过膜的传热的那些参数(即进料温度、孔径、孔隙率、真空压力等)促进氨上的水通量。而那些增强混合和进料中氨质量传递的参数(即进料速度、间隔几何形状、pH、氨进料浓度等)促进了氨在水中的通量。同时提高 JNH 3 和 SNH 3 的唯一操作参数是进料速度,这表明隔板几何形状可以在设计用于氨分离的 VMD 模块中发挥重要作用。VMD 可以以较低的比热能消耗在渗透侧提取和浓缩氨。然而,JNH 3 受到进料氨浓度的极大限制,这将最终决定回收的成本效益。该模型描述的趋势与其他作者的观察一致,并深入了解了通过 VMD 进行氨分离的主要机制及其性能限制。VMD 可以以较低的比热能消耗在渗透侧提取和浓缩氨。然而,JNH 3 受到进料氨浓度的极大限制,这将最终决定回收的成本效益。该模型描述的趋势与其他作者的观察一致,并深入了解了通过 VMD 进行氨分离的主要机制及其性能限制。VMD 可以以较低的比热能消耗在渗透侧提取和浓缩氨。然而,JNH 3 受到进料氨浓度的极大限制,这将最终决定回收的成本效益。该模型描述的趋势与其他作者的观察一致,并深入了解了通过 VMD 进行氨分离的主要机制及其性能限制。
更新日期:2020-11-01
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