科研之友
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摘要
Forward osmosis processes are an emerging set of technologies that show promise in the treatment of complex and impaired water streams (e.g., those encountered in industrial wastewater treatment and the extraction of unconventional oil resources). The effective operation of these systems requires that the operating conditions be chosen wisely based on the membrane to be used and the streams to be treated. In this work, to aid in the design of these systems, an analytical model was developed that describes the module-level performance (i.e., water recovery rate and separation factors of the feed and draw solutes) for cocurrent and countercurrent forward osmosis systems in the thermodynamic limit of osmotic equilibrium. In the limit of osmotic equilibrium, the model expresses the recovery rate and separation factors in terms of the operating conditions (e.g., the flow rates and concentrations of the feed and draw solutions) and the characteristic membrane transport properties (e.g., the hydraulic and solute permeability coefficients). The model was validated by comparing its predictions with numerical simulations of the full system of governing equations: strong agreement between the model predictions and numerical simulations was observed. Analysis of the model demonstrates that the reverse flux selectivity, the ratio of the forward water flux to the reverse draw solute flux, is a key parameter in the design of forward osmosis systems that controls the maximum solute rejection that the systems can achieve at osmotic equilibrium. Further analysis shows that the flow ratio, the ratio of the inlet flow rate of the draw solution to the inlet flow rate of the feed solution, is an important design parameter. Specifically, in countercurrent operation, a critical value of the flow ratio that maximizes the recovery rate was identified.
- 出版日期2015-1-14
