Nano-porous transport membrane condenser for flue gas water recovery: Modeling and parametric membrane design analysis

Water resources are becoming scarce and climate change is exacerbating the stress on traditional water supplies. Thus, it is important to identify viable solutions to resolve tensions in the water energy nexus. One example is the use of transport membrane condensers (TMCs) to recover water as well as waste heat from flue gases with the aim to improve economics and to reduce the environmental impact of the industrial sector. In this work, the authors present a detailed 1D+1D TMC model and investigate the impact of three key membrane design pa-rameters upon the water recovery rate. Sensitivity analyses of pore radius, membrane porosity and contact angle reveal that pore radii of smaller than 10 nm can substantially improve condensation rates due to the exponential vapor pressure dependency described by the Kelvin equation. Reducing the pore radius from 15 nm to 1 nm increases water recovery by over 74% in some of the study scenarios. Additionally, a higher membrane porosity is shown to increase water condensation rates. A higher porosity increases the number of pores on the surface, and thus, the driving force for mass transport. The results show an increase in water recovery of up to 7.7% per 10% porosity increase. The contact angle, which is related to the hydrophilicity of the membrane material, in-fluences the formation of the meniscus inside the pore. Changes in the contact angle from a flat surface (90 degrees) to 30 degrees are shown to have a strong impact upon the water condensation rate. Furthermore, condensation flux im-provements through the above-mentioned membrane design modifications are more pronounced in environ-ments with low mass transport driving force due to the nature of the suction effect, which is governed by diffusion and convection transport laws.

Automated summary

Water resources are scarce and climate change worsens the stress on traditional water supplies. Thus, it is important to find viable solutions to the water energy crisis. One possible solution is the use of transport membrane condensers (TMCs) to recover water and waste heat from flue gases in order to improve economics and reduce the environmental impact of the industrial sector.