Tahir Furqan, Mabrouk Abdelnasser, Al-Ghamdi Sami G, Krupa Igor, Sedlacek Tomas, Abdala Ahmed, Koc Muammer
Division of Sustainable Development, College of Science and Engineering, Hamad Bin Khalifa University, Doha 34110, Qatar.
Water Center, Qatar Environment and Energy Research Institute, Hamad bin Khalifa University, Doha 34110, Qatar.
Polymers (Basel). 2021 Feb 24;13(5):681. doi: 10.3390/polym13050681.
Metal-alloys tubes are used in the falling-film evaporator of the multi-effect distillation (MED) that is the dominant and efficient thermal seawater desalination process. However, the harsh seawater environment (high salinity and high temperature) causes scale precipitation and corrosion of MED evaporators' metal tubes, presenting a serious technical challenge to the process. Therefore, the metal/metal alloys used as the material of the MED evaporators' tubes are expensive and require high energy and costly tube fabrication process. On the other hand, polymers are low-cost, easy to fabricate into tubes, and highly corrosion-resistant, but have low thermal conductivity. Nevertheless, thermally conductive fillers can enhance the thermal conductivity of polymers. In this article, we carried out a feasibility-study-based techno-economic and socioeconomic analysis, as well as a life-cycle assessment (LCA), of a conventional MED desalination plant that uses titanium tubes and a plant that used thermally enhanced polymer composites (i.e., polyethylene (PE)-expanded graphite (EG) composite) as the tubes' material. Two different polymer composites containing 30% and 40% filler (expanded graphite/graphene) are considered. Our results indicate that the MED plant based on polymer composite tubes has favored economic and carbon emission metrics with the potential to reduce the cost of the MED evaporator (shell and tubes) by 40% below the cost of the titanium evaporator. Moreover, the equivalent carbon emissions associated with the composite polymer tubes' evaporator is 35% lower than titanium tubes. On the other hand, the ozone depletion, acidification, and fossil fuel depletion for the polymer composite tubes are comparable with that of the titanium tubes. The recycling of thermally enhanced polymers is not considered in this LCA analysis; however, after the end of life, reusing the polymer material into other products would lower the overall environmental impacts. Moreover, the polymer composite tubes can be produced locally, which will not only reduce the environmental impacts due to transportation but also create jobs for local manufacturing.
金属合金管用于多效蒸馏（MED）的降膜蒸发器中，多效蒸馏是主要且高效的热法海水淡化工艺。然而，恶劣的海水环境（高盐度和高温）会导致MED蒸发器金属管结垢沉淀和腐蚀，给该工艺带来严峻的技术挑战。因此，用作MED蒸发器管材料的金属/金属合金价格昂贵，且需要高能量和昂贵的管材制造工艺。另一方面，聚合物成本低，易于制成管材，且具有高耐腐蚀性，但热导率低。尽管如此，导热填料可以提高聚合物的热导率。在本文中，我们对使用钛管的传统MED海水淡化厂和使用热增强聚合物复合材料（即聚乙烯（PE）-膨胀石墨（EG）复合材料）作为管材的工厂进行了基于可行性研究的技术经济和社会经济分析以及生命周期评估（LCA）。考虑了两种不同的含30%和40%填料（膨胀石墨/石墨烯）的聚合物复合材料。我们的结果表明，基于聚合物复合管的MED工厂在经济和碳排放指标方面具有优势，有可能将MED蒸发器（壳和管）的成本降低至比钛蒸发器成本低40%。此外，与复合聚合物管蒸发器相关的等效碳排放量比钛管低35%。另一方面，聚合物复合管的臭氧消耗、酸化和化石燃料消耗与钛管相当。本LCA分析未考虑热增强聚合物的回收利用；然而，在使用寿命结束后，将聚合物材料再用于其他产品将降低整体环境影响。此外，聚合物复合管可以在当地生产，这不仅将减少运输带来的环境影响，还将为当地制造业创造就业机会。
