Diffusion Driven Desalination for Simultaneous Fresh Water Production and Desulfurization

The diffusion driven desalination (DDD) process has been previously introduced as a process for distilling water using low-grade waste heat. Here, a configuration of the DDD process is introduced for simultaneously distilling water and scrubbing sulfur dioxide $(SO2)$ out of heated air streams, which is also known as flue gas desulfurization (FGD). This novel DDD/FGD process utilizes the low-grade waste heat carried in industrial discharge air streams. There are many applications, where the industrial air discharge also contains $SO2$⁠, and in order to utilize the waste heat for the DDD process, the $SO2$ must be scrubbed out of the air stream. The two major components of the DDD process are the diffusion tower and the direct contact condenser. In the present work, a thermal fluid transport model for the DDD/FGD process, that includes $SO2$ scrubbing, is developed. It is an extension of the heat and mass transport model previously reported for the DDD process. An existing laboratory scale DDD facility was modified and tested with $SO2$ in the air stream and with seawater as the feed water to the diffusion tower. The experimental investigation has been completed to evaluate the fresh water production and $SO2$ scrubbing potential for the DDD/FGD process. The experimental results compare favorably with the model predictions. Chemical analysis on the condenser water demonstrates the capability of the DDD/FGD process to produce high quality fresh water using seawater as the input feed water to the process.