(736d) Exploring the Contribution of Liquid in the Pore Network of Sorbent Polymer Composite Materials on Hg Removal from Flue Gas

Emissions of mercury, a toxic substance, from industrial flue gas stacks are regulated in many countries around the world. Several technologies are being developed to address the decreasing emission limits. W.L. Gore & Associates Inc. has developed an innovative technology, called the GOREâ„¢ Mercury Control System (GMCS) [1], for addressing this need. The GMCS is a unique fixed sorbent system that also provides SO₂ removal as a co-benefit. It is based on discrete stackable modules comprised of Sorbent Polymer Composite (SPC) materials with an open channel geometry. Hg is chemisorbed from the flue gas and bound into the SPC. On the other hand, SO₂ is converted to sulfuric acid filling a fraction of the SPC pores. However, due to the hydrophobic nature of the SPC, the liquid acid is expelled preventing the flooding of the entire pore network with liquid, which would have an adverse effect on Hg capture rates.

In this talk, a short description of the transport processes that take place during Hg capture in GMCS will initially be presented, and the importance of knowing the fraction of liquid into the SPC tape pores will be highlighted. Characterizing the pore network of the SPC tapes is a challenging task not only because the pore sizes span several orders in magnitude, but also because measurements need to happen at dry and 100% relative humidity conditions. Emphasis will be placed on how we combined a set of complimentary techniques (Hg intrusion, N₂ & H₂O physisorption, and X-ray computed tomography) to obtain a 3-D reconstruction of the dry and wet SPC pore network, and how this reconstruction was analyzed using diffusion calculations to get information about the porosity and tortuosity of wet and dry SPC tapes. Finally, we will show an example of how we used this information as input in a reactor model that captures the effects of kinetics and mass transport to quantify the impact of liquid on Hg removal rate.

[1] https://www.gore.com/products/gore-mercury-control-systems