Interaction between liquid droplets and membrane surfaces

Abstract

Multi-stage flue gas cleaning systems are used to reduce the pollutant emissions from fuel combustion. A variety of filters have been developed to capture soot particles in flue gases. Such filters are usually based on membranes. Another popular way of reducing the anthropogenic emissions in flue gases is by adding agents or water to fuels. Not much information is available on the impact of vapor produced by the combustion of such fuels on membrane permeability characteristics. Membrane permeability to gas flow should be studied with due consideration of membrane wettability and droplet agglomeration on it. This research focuses on identifying the main patterns of the interaction between liquid droplets and membranes of various types. Using the experimental findings, we have identified two droplet-membrane interaction regimes–spreading and breakup–as well as the interaction phases when each of these two regimes is observed. We have also established that the maximum spreading diameter remains relatively insensitive to the surface wettability at low Weber numbers. The analysis of the experimental findings has shown that an air pocket is formed under a droplet if its impact velocity exceeds 2.5 m/s. The impact with an air pocket triggers droplet breakup and reduces the maximum spreading diameter. This process is a decisive factor in favor of using membranes in flue gas cleaning systems. The findings of this paper can be used to extend the operating life of filtration membranes used in thermal power plants.