Applicability assessment of functional adsorption zeolite materials in adsorption desalination cum cooling systems driven by low-grade heat source

Abstract

• Thermophysical properties of the FAM-Z series were evaluated using argon adsorption isotherms. • Modified Do–Do and hybrid Langmuir–Sips isotherm models were proposed. • AD cycle performance was evaluated in terms of SDWP, SCC, COP, and PR. • AFI-type zeolite has shown its applicability to residential and district cooling. • FAM-Z05 can be used for AD cycles driven by an extremely low-grade heat source (<55 °C). This study provides an in-depth analysis of the sequence of procedures required to evaluate the performance of adsorption desalination (AD) using functional adsorbent material zeolites (i.e., FAM-Z series with AFI and CHA types). The applicability of zeolite as an adsorbent for the AD cycle was also demonstrated by comparing it with the performance of AD using silica gel. The adsorption isotherm of the adsorbent, which is the most important parameter in the performance and design of the AD cycle, is recognized as a crucial parameter that significantly affects the AD performance. The thermophysical properties of the FAM-Z series were analyzed using argon adsorption and desorption isotherms at 87 K, followed by water vapor adsorption isotherms. Modified Do–Do and hybrid Langmuir–Sips isotherm models were proposed and are suitable for the anomalous stepwise isotherms of the FAM-Z series and the mesoporous adsorption characteristics of silica gel. The performance of the AD cycle was assessed in terms of the specific daily water production, specific cooling capacity, coefficient of performance, and performance ratio with respect to chilled and hot water temperatures and cycle times using a mathematical model of the AD cycle validated through a comparison with experimental data. AFI-type zeolites showed the applicability of residential (FAM-Z01) and district cooling (FAM-Z05), which have a low regeneration temperature of 55 ℃ owing to an unusual isotherm (i.e., sigmoid adsorption isotherm). In addition, FAM-Z05 exhibited considerable potential as an adsorbent for AD cycles driven by extremely low-grade heat sources (<55 °C) found in industrial plants and solar energy.