This study delves into the realm of water treatment by conducting a comprehensive techno-economic evaluation of direct contact membrane distillation (DCMD) and nanofiltration (NF) processes. While previous research has explored the technical aspects of membrane distillation (MD) and nanofiltration, there remains a notable gap in economic analyses. Our research aims to bridge this gap by assessing the financial feasibility of employing MD and NF technologies for water desalination. Specifically, we scrutinize the performance of hydrophobic microporous flat sheet membranes crafted from polytetrafluoroethylene (PTFE) supported by non-woven polypropylene (PP) in desalinating brackish water through DCMD and NF processes. By varying operating conditions such as flow rate and feed temperature, we evaluate the membrane's efficacy. Employing an analytical model based on heat and mass transfer equations, we predict process performance across diverse scenarios. Our model demonstrates a high level of accuracy, with flux predictions deviating by less than 10% when utilizing the Knudsen-molecular mechanism model. Furthermore, through a detailed design and economic analysis of industrial-scale units for both processes, we reveal that the cost of permeated water is lower with NF compared to DCMD. Specifically, our calculations indicate a water cost of 1.34 USD/m³ for DCMD at a feed temperature of 65 °C with an 80% recovery rate, positioning it as a competitive option among conventional desalination methods. Notably, our financial assessment highlights that steam cost constitutes the primary expense in DCMD operations, contingent upon heating value and fuel prices. Noteworthy findings suggest that natural gas emerges as the most cost-effective fuel for steam production in a DCMD plant. This study underscores the economic viability and potential cost efficiencies associated with NF over DCMD in water treatment applications.

本研究通过对直接接触膜蒸馏（DCMD）和纳滤（NF）工艺进行全面的技术经济评估，深入研究水处理领域。虽然之前的研究已经探讨了膜蒸馏（MD）和纳滤的技术方面，但在经济分析方面仍然存在显着差距。我们的研究旨在通过评估采用 MD 和 NF 技术进行海水淡化的财务可行性来弥补这一差距。具体来说，我们仔细研究了由无纺聚丙烯 (PP) 支撑的聚四氟乙烯 (PTFE) 制成的疏水性微孔平板膜在通过 DCMD 和 NF 工艺淡化苦咸水时的性能。通过改变流速和进料温度等操作条件，我们评估膜的功效。我们采用基于传热传质方程的分析模型，预测不同场景下的过程性能。我们的模型表现出很高的准确性，利用 Knudsen 分子机制模型时，通量预测偏差小于 10%。此外，通过对两种工艺的工业规模装置的详细设计和经济分析，我们发现，与 DCMD 相比，NF 的渗透水成本更低。具体来说，我们的计算表明，在进水温度为 65 °C 的情况下，DCMD 的水成本为 1.34 美元/m ³，回收率为 80%，使其成为传统海水淡化方法中具有竞争力的选择。值得注意的是，我们的财务评估强调，蒸汽成本构成 DCMD 运营的主要支出，具体取决于热值和燃料价格。值得注意的发现表明，天然气成为 DCMD 工厂蒸汽生产最具成本效益的燃料。这项研究强调了在水处理应用中 NF 相对于 DCMD 的经济可行性和潜在成本效率。