(142g) Process Design of a LiBr Absorption Chiller Integrated Hdh-Mee-Mvr System for Zero Liquid Discharge Seawater Desalination

The world is facing a major challenge in providing access to clean water, with almost 70% of the population expected to face water scarcity by 2025 [1]. Desalination is a solution for producing potable water on a global scale [2,3], and among various thermal desalination techniques, humidification-dehumidification (HDH) is particularly suitable for small-scale desalination applications. However, to adapt this technology for large-scale production, the integration of HDH with other desalination technologies such as multi-effect evaporation (MEE) is necessary [3]. While this can increase the processing capacity, it can also increase energy consumption and CO₂ emissions. Several studies have also aimed to reduce the energy consumption of seawater desalination by integrating heat pumps, mechanical vapor recompression (MVR), and lithium bromide (LiBr) chillers [4,5]. Other studies have focused on reducing brine discharge or achieving zero liquid discharge (ZLD) [6]. However, there is a lack of a holistic study that simultaneously addresses these two critical environmental issues.

In this work, we design a multipurpose seawater desalination process that integrates a LiBr absorption chiller, HDH, MEE, and MVR to improve the energy effectiveness of conventional desalination processes [7]. This process not only decreases energy consumption but also aims to turn the desalination into a multipurpose unit by providing air conditioning, reducing the brine discharge, and preparing it for the ZLD process. The LiBr absorption chiller cycle preheats the seawater prior to the steam generation in the MEEs, while the MVR system activates the LiBr cycle. The integrated HDH system further recovers the excess water in the process stream and concentrates the brine effluent for ZLD processing. We comparatively study a stand-alone HDH desalination with our integrated system, quantify their performances over several metrics, perform a technoeconomic analysis to assess the economic feasibility, and carry out a sensitivity analysis to observe the effects of changing process variables on the overall performance of the integrated system. The results show that our proposed process design achieves several times higher gain-output ratio compared to a conventional HDH system of equal capacity, with a levelized water production cost of $8.4/m³ and 6 kW of cooling capacity that can be used for air conditioning.

References

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[2] Panagopoulos, A., 2021. Water-energy nexus: desalination technologies and renewable energy sources. Environmental Science and Pollution Research, 28(17), pp.21009-21022.

[3] Lawal, D.U., Antar, M.A. and Khalifa, A.E., 2021. Integration of a MSF desalination system with a HDH system for brine recovery. Sustainability, 13(6), p.3506.

[4] Lawal, D.U., Antar, M.A., Khalifa, A., Zubair, S.M. and Al-Sulaiman, F., 2020. Experimental investigation of heat pump driven humidification-dehumidification desalination system for water desalination and space conditioning. Desalination, 475, p.114199.

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[6] Tahir, F. and Al-Ghamdi, S.G., 2022. Integrated MED and HDH desalination systems for an energy-efficient zero liquid discharge (ZLD) system. Energy Reports, 8, pp.29-34.

[7] Nikkhah, H. and Beykal, B., 2023. Process Design and Technoeconomic Analysis for Zero Liquid Discharge Desalination via LiBr Absorption Chiller Integrated HDH-MEE-MVR System. Desalination (Under Review).