10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
A Corona Charger System for Improving Particle Filtration Efficiency of Flue Gas Scrubbers and Cyclones in Small Biomass-fired Boilers
HEIKKI SUHONEN, Ari Laitinen, Miika Kortelainen, Arunas Mesceriakovas, Hanna Koponen, Petri Tiitta, Pasi Yli-Pirilä, Jorma Jokiniemi, Olli Sippula, University of Eastern Finland, Kuopio, Finland
Abstract Number: 724 Working Group: Control and Mitigation
Abstract New flue gas particulate matter filtering technologies are needed due to upcoming new regulations for small and medium -scale biomass combustion appliances in Europe. The Ecodesign directive will affect combustion appliances with a rated heat output of 500 kW or less and the Medium Combustion Plant (MCP) directive boilers of 1-50 MW output. Existing commercial flue gas cleaning techniques are often either too expensive compared to the total costs of small boilers, provide too much pressure loss and maintenance, or are not efficient enough to meet the new regulations. Therefore, new methods for cost-efficient particulate filtering need to be developed. For existing boiler units the utilization of electrical charging of flue gas particles upstream of heat exchangers or in front of existing particulate filters is an interesting low-cost approach to improve the filtration efficiency of particles.
A single needle corona charger (Laitinen et al. 2016), was used together with a pilot-scale condensing heat exchanger (CHX) (Grigonyte et al. 2014) and a cyclone, which were installed into a wood chip fired combustion reactor simulating automatic grate boilers. The single needle corona charger is mechanically simple and can be introduced into the flue gas in existing devices and shielded against contamination, while the CHX and cyclone provide the collection surface and additional cleaning mechanism. The effects of charging temperature and different combustion conditions on the charger performance were investigated by changing the charger position in the combustion reactor and using it with different fuel qualities.
Total particle mass emissions were reduced by >80 % with the combination of charger and CHX while the combination of the charger and cyclone setup was slightly less efficient. Particle number reduction efficiency varied between 30 % and 70 %, because the usage of the corona charger produced a nucleation mode below particle size of 30 nm that was highly dependent on the charging temperature and voltage. Particle mass was measured also from between the charger and CHX, for estimating the reduction efficiency of the CHX alone. PM1 emissions were reduced in the CHX by 30-40 % when particles were not charged and 60-70 % when particles were charged before the CHX. Chemical analysis of the condense water from the CHX support the results as enhanced concentrations of typical components of wood combustion fly ash were also found in the water.
The results indicate that a simple corona charger system can provide a feasible particle filtration system together with a condensing heat exchanger, wet scrubber and/or a cyclone to achieve the upcoming new regulations. The system is best suited for small-scale boilers but can be upscaled by increasing the number of corona chargers.
This work was funded by the European Regional Development Fund, within the Pyreus project.
[1] Grigonyte, J., Nuutinen, I. Koponen T., Lamberg H.,Tissari, J., Jokiniemi, J. and Sippula O. (2014) Energy Fuels 28, 6058-6065. [2] Laitinen, A., Keskinen, J. (2016) J Electrostat 83, 1-6.