In the drive to protect the environment, reducing the concentrations of harmful chemicals that are released into the atmosphere has become a priority for industries. One key example is the removal of sulphur dioxide (SO2) from flue gas, which can be formed as a by-product of processing of raw materials, for example. In order to achieve this, a filtering procedure needs to be implemented. However, most existing methods, such as "gas scrubbing", require high input power and a specifically suited operation site. This can be expensive and time-consuming for companies to implement.
We have worked with W.L. Gore and Associates, famous for their waterproof clothing GORE-Tex, on a more desirable and cost-effective method of removal of SO2. In their Gore Mercury Control System pictured above, flue gas flows through stacks of parallel open channels and diffuses into their porous surface, which consists of a fibrous matrix with multiple microscopic catalytic pellets, where a chemical reaction takes place and converts SO2 into liquid sulphuric acid. This method requires very low input power, does not need a special operation site, and also generates sulphuric acid "for free". However, these filters exhibit one main problem: as liquid sulphuric acid accumulates, it gradually blocks the filter and limits its subsequent efficiency.
We have developed a multi-scale mathematical model that couples an understanding of how liquid sulphuric acid evolves on the microscale with a device-scale model to predict the global filter properties such as its efficiency over time. Our modelling framework comprises three core components: