wood pellets: emission characterization and control -olga petrov.pdf · biomass pellet...

WOOD PELLETS: EMISSION CHARACTERIZATION AND

CONTROL Olga Petrov, PhD Candidate

Department of Chemical and Biological Engineering University of British Columbia

Biomass and Bioenergy Research Group [BBRG] Clean Energy Research Center

Bridge/CIHR Strategic Training Fellow

November 17, 2014 WPAC AGM 2014: Sustainable Growth, Vancouver, BC

UBC Wood Pellet Workshop

Outline

¨  Introduction ¨  Biomass Pellet Manufacturing Industry

¤ Pellet production process ¤ Process related emissions

¨  Wood pellet conversion for energy ¤ Point source emissions: Particulate matter and gaseous contaminants

¨  Pollution prevention and emission control ¨  Research directions

UBC Wood Pellet Workshop November 17, 2014

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Introduction

¨  Growing demand for biomass

¨  Paths towards sustainable development


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Source: Olsson & Kjällstrand, 2004

Introduction cont’d

¨  Biomass, wood

pellet market rapidly growing


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Source: NGO Briefing

Biomass Pellet Manufacturing Industry

¨  42 pellet plants (2012)

¨  3 million tonnes annual production capacity

¨  BC ~ 65% of Canadian capacity and production with 150,000 –

400,000 tonnes per plant annually

¨  Alberta, Quebec, New Brunswick, Nova Scotia, and Newfoundland

collectively ~ 35%

¨  Canadian exports mostly to Europe


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Source: WPAC

Biomass Pellet Manufacturing Industry cont’d

Pellet production process


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¨  Emissions associated with each step of pellet production including: ¤ Receiving and storage of the raw material (wood) ¤ Sizing the wood residue ¤ Drying ¤ Additional size reduction of the dried wood [hammer mills] ¤ Pelletizing – compressing the wood fines into pellets ¤ Cooling ¤ Storage, bagging

And ¨  Combustion of the process waste - heat for dryers


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Source: ESI, 2010


Process related emissions

¨  Point and volume source as well as fugitive emissions include: ¤ Particulate matter (PM), including condensable PM

¤ Total organic compounds (TOC)

¤ Carbon monoxide (CO) small amounts

¤ Oxides of nitrogen (NOx)

¤ Carbon dioxide (CO2) – close to neutral if biomass harvested sustainably


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¨  Particulate matter: ¤ Dryers are the main source of particles emissions ¤ Pelletizers and coolers are also significant sources unless collected

with cyclones ¤ Hammer mills - larger PM upstream of dryers than downstream ¤ Conveyors ¤ Sawdust piles sources of fugitive dust


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Average Permitted PM Emissions (kg/tonne) [Adopted from ESI, 2010]


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Note: values are based on wood pellet mills and similar facilities: 10 in US, 1 in Germany, 2 in Quebec and 8 in BC

PM emission limits for biomass power plants vs permitted wood mills emissions


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[Adopted from ESI, 2010]

¨  Volatile organic compounds (VOCs): ¤ Storage

¤ Handling of wood raw material

¤ Drying and pelletizing

¤ [Transport]


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¨ 


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Example of estimated VOCs (based on AP-42) from uncontrolled particleboard dryers

[Adopted from ESI, 2010]

¨  Experimental study Olsson & Kjällstrand, 2004 ¤ Higher with lower efficiency burners ¤ Benzene was the most noticeable aromatic hydrocarbon

Comparison of emissions from burning pellets in different combustors


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Wood pellet conversion for energy Point source emissions

Wood pellet conversion for energy cont’d


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¨  A LCA study Pa et al., 2011 ¤ Emission factors for pellet gasification

Wood pellet conversion for energy cont’d


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¨  Study by Ghafghazi et al., 2011

[Note: Partial table presented here]

Pollution prevention and emission control Fugitive emissions

q  Raw wood material (sawdust, shavings) handling and storage ¤ Fugitive dust (usually PM >10µm) as a function on plant location and layout due

to impacts of exposure to weather elements, pile dimensions, material characteristics etc.

¤ Prevention & control: use of logs or decreased material quantity at the site, enclosure and containment, wind barriers, dust suppressants, etc

q  Debarking, chipping: minor PM emissions, usually no emission controls q  Conveyors should be enclosed


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¨  Pollution prevention strategies: ¤ Homogenous and lower moisture (dry) content raw material where possible

¤ Maximize energy conservation and fibre recovery

¤ Efficient, low emissions, low inlet temperature dryers with recirculating airflow;

¤ Efficient combustion systems with low emissions.


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Pollution prevention and emission control Point source emissions

¨  Engineered controls: ¨  Cyclonic PM collectors – high efficiency for large PM, used as pre-

cleaners ¨  Fabric filters – high efficiency for fine PM, not appropriate for the

material with a high moisture content ¨  ESP, wet and dry – high efficiency for fine PM, not appropriate for

condensable PM ¨  High efficiency scrubbers – venturi type, high energy use ¨  Regenerative Thermal Oxidizers – for VOC control


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¨  Engineered controls costs: ¨  Variable based on parameters such as boiler capacity


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Pollution control Estimated costs (US $) Comment

cyclone 7-10K A multicyclone up to 16K

Fabric filter/baghouses 100K Additional ~10K maintenance costs

ESP (dry & wet) 1,000-5,000K Average maintenance ~5K

High efficiency scrubber (venturi) 100-800K -

¨  Direct industrial emission measurement instead of emission factors which could overestimate emissions

¨  Emission characterization of different wood raw material ¨  Emission characterization of pellet derived products – torrefied pellets ¨  Pollution prevention strategies should have priority over controls

¨  BACT


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Research directions


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References

ESI (Beauchemin, P.,Tampier, M). (2010). Emissions and Air Pollution Controls for the Biomass Pellet Manufacturing Industry. Professional Report prepared for The BC Ministry of the Environment

Ghafghazi, S., Sowlati, T., Sokhansanj, S., Bi, X., & Melin, S. (2011). Particulate matter emissions from combustion of wood in district heating applications. Renewable and Sustainable Energy Reviews, 15(6), 3019–3028. doi:10.1016/j.rser.2011.04.001

Johansson, L. S., Leckner, B., Gustavsson, L., Cooper, D., Tullin, C., & Potter, A. (2004). Emission characteristics of modern and old-type residential boilers fired with wood logs and wood pellets. Atmospheric Environment, 38(25), 4183–4195. doi:10.1016/j.atmosenv.2004.04.020

NGO briefing Sustainability issues for solid biomass in electricity, heating and cooling. (n.d.). Available at: http://www.birdlife.org/sites/default/files/attachments/EU-Joint-NGO-briefing-biomass-sustainability-energy-March2012.pdf Olsson, M., & Kjällstrand, J. (2004). Emissions from burning of softwood pellets. Biomass and Bioenergy, 27(6), 607–611. doi:10.1016/j.biombioe.2003.08.018

Pa, A., Bi, X. T., & Sokhansanj, S. (2011). A life cycle evaluation of wood pellet gasification for district heating in British Columbia. Bioresource Technology, 102(10), 6167–6177. doi:10.1016/j.biortech.2011.02.009

Sippula, O., Hokkinen, J., Puustinen, H., Yli-Pirila�, P., & Jokiniemi, J. (2009). Particle Emissions from Small Wood-fired District Heating Units. Energy Fuels, 23(6), 2974–2982. doi:10.1021/ef900098v

WPAC. Canadian wood pellet production. Available at: http://www.pellet.org/production/production

Thank you

[email protected]


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