Advances in emission control technologies have demanded development of new ceramic chemistries and improved microstructures in catalytic substrates and especially in diesel particulate filters. High porosity filters are desirable, as they decrease engine backpressure and enable application of advanced catalysts including, but not limited to, multi-functional filters (MFF).
A significant recent development has been in the use of ceramic fibers to create cross-linked microstructures in extruded honeycomb ceramics. This development allows high porosities to be attained while maintaining mechanical strength. However, according to the World Health Organization, certain classes of ceramic fibers are considered to have adverse health effects if released in air and inhaled. As a result, with fiber-based ceramic substrates and filters being introduced into the market, it becomes necessary to develop rigorous testing protocols for monitoring the release of fiber-fragments to qualify the substrates for regular operation.
A new preliminary set of methods and techniques were developed for verification of fiber-based filters under the Swiss VERT program. Details on the new testing protocols are provided. Mullite-fiber based Cross-Linked Microstructure (CLM™) honeycomb wall-flow filters from GEO2 Technologies were tested under the standard VERT protocols for criteria emissions and the preliminary protocols for secondary fiber emissions. With the uncatalyzed filter in a Fuel Borne Catalyst (FBC) configuration, results are reported for Particle Matter (PM) filtration efficiency, secondary emissions (e.g. NO2), and the release of fiber-fragments. Initial results indicate high filtration efficiency (>99.5%) for PM, an observed decrease in post-filter NO2 concentrations, and minimal to zero initial secondary fiber-fragment release.
From initial data, the newly developed VERT testing protocol for secondary fiber fragment release can be used in conjunction with the existing VERT protocols for evaluation of both fiber-release characteristics and filtration performance of fiber-based filters