Performance control on adsorption desalination using initial time lag (ITL) of individual beds

Abstract

This paper introduces a novel time-scheduling scheme for adsorption desalination (AD). Mathematically, a critical bed pressure of the Toth isotherm is defined as the pressure above which the uptake ratio scarcely changes. Heat balance equations of sorption beds for precooling, adsorption, preheating, and desorption are unified into a single equation. This general governing equation is used to model AD systems, which consists of an arbitrary number of bed pairs with specifically preset initial thermal phases. A theoretical minimum of switching interval is derived as a function of thermal properties,of reaction beds and heat exchangers. In the new time scheduling scheme, no bed pairs are in an identical process schedule, because each bed has its initial time lag (ITL) when the operation starts. We found that specific AD performances vary noticeably depending on the ITL values, the number of beds, and more importantly, the number of beds in a time-lag group. There must be an optimal ITL for given operational parameters, which can distinctly increase the water production rate without using extra heat sources. This can dynamically optimize the relative performance of desalination rates and cooling capacities of AD processes. (C) 2016 Elsevier B.V. All rights reserved.