Performance evaluation and feasibility study of a cooling tower model for zero liquid discharge-desalination processes

The growing freshwater demand in arid and semi-arid regions has necessitated the desalination of seawater and groundwater. To address the generated reject brine from this process, a zero-liquid discharge approach was proposed, utilizing an induced draft crossflow cooling tower technology. With this aim, a model was developed by using TRNSYS 18 to assess the cooling tower's operation under different locations and meteorological conditions. The model includes a brine tank, biomass boiler, heat exchanger, and recirculation and boiler pumps. Experimental data of brine temperature, air temperature, air velocity, fan speed, and brine evaporation were used to validate the simulation's reliability. Furthermore, the potential implementation of this zero liquid discharge cooling tower technology in various Mediterranean basin locations, considering environmental parameters, was explored. Results indicate that the induced draft cooling tower used in this study can evaporate up to 177 l/h of the liquid fraction of brine at a brine temperature of 23 degrees C. The entire set of experimental data was utilized to validate the model. A correlation coefficient higher than 0.91 was determined for parameters such as dry and wet bulb temperature, humidity ratio, and evaporated mass. The model was then suitable to predict the performance of an evaporative brine cooling tower system and assess its potential installation under different locations, with emphasis in arid and semi-arid regions. From the results, in locations such as Kuwait and Abu Dhabi, and considering annual environmental values of air temperature and humidity as input parameters, over 400 l/h of brine evaporation could be achieved. These findings indicate that the cooling tower system offers a sustainable and efficient solution to treat reject brine from desalination processes in water-stressed regions, presenting an effective method for brine management in such areas.