Mechanical milling for catalyst loading of polymer filters

This paper details results of an initial study into the feasibility of using the mechanical milling process as a means of embedding catalyst particles into fabric filters for improved pollution control. The specific combinations of catalysts and filters used in the study to demonstrate the method are currently being explored for use in the energy generation industry to help remove elemental mercury from flue gases. Circular fabric samples were placed in a hardened steel milling vial along with a number of PMMA milling balls. Catalyst powder and, in some cases, a solvent (water or 70% isopropyl alcohol) were added and the vial milled for 40 min. The fabric samples were then dried and subjected to airflow conditions typical for fabric filters in powerplant baghouses. Weight measurements were used to determine the amount of catalyst retained in the fabric at each stage. Results show that fabric type, number of milling balls used, catalyst powder/fabric mass ratio, particle size and the presence of a solvent can all affect the degree of catalyst loading. The embedded particles adhere well through a number of forward/backpulse cycles simulating airflow conditions in a powerplant baghouse. Modifications are needed to scale such a process to production levels but the current limitations are not insurmountable.