Greenhouse Desalination by Humidification–Dehumidification Using a Novel Green Packing Material

Abstract

Humidification–dehumidification (HD) is a non-traditional desalination process in which water evaporates from a saline liquid stream and the vapour condenses into purified water. In nature, seawater is heated by solar radiation and evaporates from the air that moistens it. This is known as the rainy cycle. The artificial version of this cycle is called the HD desalination cycle. The latter has received a lot of attention in recent years, and many researchers have studied the complexities of the technology. In the present work, experimental work with a simple configuration was developed and built, consisting of a humidification column followed by a condenser, in which the humidified air is dehumidified to produce fresh water. A novel and unique packaging material was used in the humidifier, consisting of a cellulose plant grown on the banks of the River Nile. In all previous work, the main problem was the type of packaging material that could ensure intimate contact and uniformity between aqueous flow and airflow. Consequently, this new filler material proved extremely suitable in terms of hydrophilicity and interconnectivity. Several variables, including the packing mass of each stage, the number of stages, the flow of air and saltwater, the concentration of saltwater, and the inlet temperature of saltwater and condensation temperature, were examined to determine their influence on the production of fresh water and its salinity. The best results arrived at in this study were wet packing conditions, 0.5 m/s air flowrate, 26 g packing for each of the 6-stage columns, and 500 mL/min water flow rate at 70 °C. It was found that this present setup, which can be coupled with solar heating to make the greenhouse desalination process cost-effective, could produce a high production of fresh water and be competitive compared with other commercial applications.