AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Parametric Study of Secondary Air Injection to Reduce Particulate Emissions from Biomass Cookstoves
JULIEN CAUBEL, Vi Rapp, Sharon Chen, Ashok Gadgil, Lawrence Berkeley National Laboratory
Abstract Number: 256 Working Group: Combustion
Abstract Nearly half of the world relies on biomass stoves for their daily cooking needs. Exposure to indoor combustion pollution from these biomass fires is the world’s greatest environmental health risk, causing about 4 million premature deaths annually. Consequently, researchers have designed biomass cookstoves that aim to reduce harmful pollutant emissions, primarily focusing on particulate matter (PM). Previous research demonstrates that secondary air injection into the combustion zone increases turbulent mixing that can dramatically reduce PM emissions. However, the air injection design parameters driving emission reductions are not well characterized. Therefore, we designed and built a modular wood-fueled cookstove to parametrically investigate critical forced-air injection design parameters that reduce PM emissions. For our parametric study, the cookstove design was methodically adjusted and evaluated using repeated water-boiling experiments. During each experiment, total PM emissions were measured gravimetrically, while size resolved PM measurements from 5 nm to 2.5 μm were collected using a TSI Fast Mobility Particle Sizer and a TSI Aerodynamic Particle Sizer.
Our parametric testing results show that secondary air injection flow rate and velocity are the primary design parameters that impact PM emissions. By experimentally optimizing these two design parameters, we reduce the total mass of PM emitted during the water-boiling test by nearly 90% relative to a traditional biomass fire. However, results show that secondary air injection can increase the emission of ultrafine particles (<100 nm in diameter), which may have greater adverse health effects. Overall, this study demonstrates that secondary air injection can practically achieve significant PM mass emission reductions in biomass cookstoves that operate continuously with unprocessed wood fuels, but further work is needed to achieve emission reductions throughout the particle size range.