Techno‐Economic Evaluation of Cyclopentane Hydrate‐Based Desalination with Liquefied Natural Gas Cold Energy Utilization

Abstract

The clathrate hydrate‐based desalination process coupled with liquefied natural gas (LNG) cold energy (ColdEn‐HyDesal) strengthens energy–water nexus by integrating two energy‐intensive processes into one. A typical HyDesal process that uses a gas as a hydrate former requires elevated pressure for hydrate formation that results in a higher specific energy consumption (SEC). The efficiency of the process improves by adopting hydrate formers with a milder hydrate formation condition, such as cyclopentane (CP). In this study, the ColdEn‐HyDesal process using CP as the hydrate former is modeled and investigated. The results show that the SEC of the ColdEn‐HyDesal process using CP is 0.35 kWh m−3. The effects of water recovery rate, hydrate formation temperature and heating seawater pressure on SEC, volumetric flow rate, exergy efficiency, and fixed capital investment (FCI) are investigated. The water recovery rate is found to have a significant effect on the SEC, volumetric flow rate, exergy efficiency, and FCI, whereas, hydrate formation temperature has a pronounced impact on FCI, while small impacts on SEC, volumetric flow rate, and exergy efficiency. With a lower operating pressure and the elimination of compressor for recycle, the ColdEn‐HyDesal process using CP as the hydrate former further reduces SEC by 58% when compared with gas such as propane as a hydrate‐forming guest.

Cyclopentane hydrates – A candidate for desalination?

“…Two thermodynamic parameters including heat of formation and heat capacity have been well reported in literature [60,78,130,186,187]. These two parameters are crucial for the design and optimization of CPH-based desalination [186].…”

“…5.098 [186]; 6.786 [78]. The CPH heat capacity was firstly approximated from the heat capacities of THF and propane hydrate according to He el al.…”

“…Recently, the use of CPH for desalination has been investigated at both laboratory and pilot scales [42,43,69,119,124,186,188,[196][197][198] considering three main concerns: yield of dissociated water from CPH, water conversion to hydrate, and salt removal efficiency. The effects of mentioned considerations on CPH-based desalination process are detailed in Table 8.…”

“…When compared to MSF, RO, and freezing techniques, Babu et al [229] demonstrated that this technology (the HyDesal process) can be economically attractive. As shown in [186] stated that the escalation of the water recovery rate of the CPH can lead to a decline in the SEC and FCI, and to a rise in the pure water flow rate and exergy efficiency. Consequently, improving the water recovery rate of CPH is crucial to enable fresh water production from this technique.…”

“…Utilizing LNG cold energy during the regasification process in the LNG regasification terminals for CPH-based desalination is one of the promising approaches to minimize the energy consumption and hence Strengthen Energy-Water Nexus [186]. Of course, this technique requires more experimental explorations before commercial readily-available in the freshwater production industry.…”