Emission regulations throughout the world continue to tighten, creating technical and economic challenges for various industries. The U.S. has proposed strict emissions limits that include mercury (Hg), particulate matter (PM) and a growing focus on NOx, while Europe is focusing more aggressively on reducing Nitrogen Oxides (NOx) and PM emissions first. Innovative new technologies are being developed and introduced to meet proposed emissions levels for industries such as waste to energy facilities, Cement clinker producers and Sintering processes.
Catalytically active ceramic or textile filter media have been applied over the past 15 years ensuring a simultaneous removal of PM, NOx and PCDD/F-compounds. A new textile filter type containing 2 filter bags (bag-over-bag) has recently been designed for such a multi-functional approach at elevated filter temperatures (T>170°C) where PMs are filtered on an ePTFE membrane (1st layer) and NOx is reduced by a catalytic reaction (2nd layer) with NH3 injected upstream. The separate bag construction enables the removal of the catalytic inner bag once it has been deactivated by ammonium-(bi)-sulphates. An appropriate regeneration process outside the bagfilter was developed for such new DeNOx system.
The implementation of this 2-layer filter bag concept into existing Air Pollution Control (APC) systems and the catalyst management has been demonstrated on full-scale at the waste to energy facility of Acegas APS Padova (Italy). Emissions of NOx (as NO2) < 70mg/Nm3 with NH3<3mg/Nm3 with PM<0,5mg/Nm3 can be constantly achieved.
The implementation of this filter bag system achieves highest energy efficiency, lowest costs for consumables when it is applied in dry sorption filters at elevated temperatures.
In U.S., the strong demand for lowest Hg emission promotes innovative solutions for efficient and reliable Hg removal. Hg can be efficiently captured in a new fixed sorbent bed technology which is installed downstream the baghouse.
This paper presents the innovative concepts for multi-functional filter as well as for Hg removal, showing also field data of both new technologies.