Electrically Enhanced Particulate Matter Reduction of Flue Gas Scrubbers and Cyclones in Small Biomass-fired Boilers

Transcription

1 Electrically Enhanced Particulate Matter Reduction of Flue Gas Scrubbers and Cyclones in Small Biomass-fired Boilers H. Suhonen 1, A. Laitinen 2, M. Kortelainen 1, A. Mesceriakovas 1, H. Koponen 1, P. Tiitta 1, P. Yli-Pirilä 1, J. Jokiniemi 1 and O. Sippula 1 1 Fine Particle and Aerosol Technology Laboratory, Department of Environmental and Biological Sciences, University of Eastern Finland, P.O Box 1627, FI-70211, Kuopio, Finland 2 Aerosol Physics Laboratory, Department of Physics, Tampere University of Technology, Tampere, Finland

2 Background There is an obvious need to develop cost-efficient particle emission reduction technologies for small biofuel-fired boilers to reduce adverse health and environmental effects of fine particulate matter and to comply the small boilers with the forthcoming EU emission regulation (e.g. Ecodesign directive (<1000 kw), MCP-directive (1-50 MW) In this collaborative work of UEF&TUT, we demonstrate a novel system for reduction of particle emissions which is based on high-temperature electrical charging of particles and subsequent collection of particles in a scrubber or a cyclone

3 PM (mg/nm 3, 6% O 2 ) 300 PARTICLE EMISSION LIMIT VALUES PIPO Existing boilers Ecodesign 2015/1189 ( ) Review (tighter values for < 1 MW boilers) Ecodesign 2015/1185 ( ) Stoves 75 mg/nm3 Pellet boilers 38 mg/nm3 PIPO moving of act 2016 (biomass) PIPO New boilers ? PIPO Existing boilers SUPO Existing boilers PIPO New boilers MCP (new) ->2030 MCP (new) ->2030 MCP (new) ->2030 SUPO new boilers kw, MNL kw, AUT MW after MW 5-10 MW MW MW

4 Electrical condensing heat exchanger / scrubber (echx) The method combines effective particle separation and heat energy recovery (if needed) High particle separation efficiency by combining four phenomena: Electrophoretic deposition due to charging of particles Thermophoretic deposition based on high thermal gradient Diffusiophoretic deposition due to water condensation Brownian diffusion (only very small particles affected) H2O Condense water film prevents fouling of the heat exchanger Additional water spraying system upstream of heat exchanger for moisturing the flue gas More information on the CHX Grigonyte, J., Nuutinen, I., Koponen T., Lamberg, H., Tissari, J., Jokiniemi, J. and Sippula, O. (2014) Energy Fuels 28,

5 Design of the Shielded Corona Charger In an earlier work a long version with multiple corona needles of the Shielded Corona Charger (SCC) was used. Part of the dust is collected too early to the walls of the reactor, outside of CHX cleaning influence. A short version with only one corona needle was developed Better design together with the CHX Less sheath air needed The principles of the shielded corona charger (SCC) are presented in Laitinen A., Keskinen J. J Electrostat 2016; 83, ; 83, 1-6

6 Assembly of the electrical charging system upstream of the condensing heat exchanger

7 Laboratory pilot-experiments at 40 kw grate reactor fueled with wood chips

8 Reduction efficiency [%] Reduction efficiencies of different SCC- CHX setups SCC (long version) only SCC (long version) - CHX SCC - CHX (optimized settings) SCC - CHX (long time experiment) CHX only SCC CHX

9 Long time experiment including startup of the reactor Mass concentration [mg/m3] Erotustehokkuus [%] Fluctuation during ignition phase Charger off briefly Time SCC on SCCoff Reduction Efficiency Corona voltage had to be reduced due to contamination in the beginning Still over 80 % reduction efficiency with stable voltage

10 Mass concentration [mg/m3] Reduction efficiencies of different measurement devices in the long time experiment 35,00 30,00 25,00 77 % 20,00 15,00 79 % 77 % 10,00 82 % 5,00 0,00 TSP PM1 Filter SMPS ELPI SCC on SCC off

11 Reduction Efficiency [%] Particle Number Concentration [dn/dlogdp] Number size distribution 120 6,00E ,00E ,00E ,00E ,00E ,00E Particle Diameter [nm] 0,00E+00 Reduction Efficiency per sized SCC On SCC Off Usage of the SCC creates a nucleation mode of very small particles

12 (A) (B) Particle morphology and composition (C) (D)

13 CXH replaced by a cyclone

14 Mass Concentration [mg/m3] CHX replaced by a cyclone 45,00 40,00 35,00 30,00 25,00 TSP filter with cyclone TSP filter without cyclone 20,00 15,00 80 % 47 % 75 % 10,00 Cyclone removes the large particles that are re-entrained to the flue gas flow 5,00 0,00 SCC + cyclone Cyclone only SCC only No particle reduction mechanism

15 Condense water chemistry Condensing heat exchanger produces waste water what is the composition and is it harmful?

16 Concentration [mg/l] Elemental concentrations compared with limit values ,1 0,01 0,001 SCC on (long version) Flushing Long Term Experiment, Afternoon, SCC on Long Term Experiment, Afternoon, SCC off SCC off (long version) Long Term Experiment, morning, SCC on Long Term Experiment, Morning, SCC off Legislative limit

17 Conclusions The results indicate that a simple corona charger can enhance the particle filtration of 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 up-scaled by increasing the number of corona chargers.

18 Acknowledgements This work was supported by the European Regional Development Fund, Fortum Power and Heat, Savon Voima, Ramboll and Tassu ESP Ltd. under the Pyreus-project (Grant A70994).