Particle size distributions from laboratory-scale biomass fires using fast response instruments

S Hosseini,A Miller,M Shrivastava,J W Miller,S Mahalingam,H Jung,D Cocker,M Princevac,D Weise,Q Li

doi:10.5194/acp-10-8065-2010

Abstract

Abstract. Particle size distribution from biomass combustion is an important parameter as it affects air quality, climate modelling and health effects. To date, particle size distributions reported from prior studies vary not only due to difference in fuels but also difference in experimental conditions. This study aims to report characteristics of particle size distributions in well controlled repeatable lab scale biomass fires for southwestern United States fuels with focus on chaparral. The combustion laboratory at the United States Department of Agriculture-Forest Service's Fire Science Laboratory (USDA-FSL), Missoula, MT provided a repeatable combustion and dilution environment ideal for measurements. For a variety of fuels tested the major mode of particle size distribution was in the range of 29 to 52 nm, which is attributable to dilution of the fresh smoke. Comparing mass size distribution from FMPS and APS measurement 51–68% of particle mass was attributable to the particles ranging from 0.5 to 10 μm for PM10. Geometric mean diameter rapidly increased during flaming and gradually decreased during mixed and smoldering phase combustion. Most fuels produced a unimodal distribution during flaming phase and strong biomodal distribution during smoldering phase. The mode of combustion (flaming, mixed and smoldering) could be better distinguished using the slopes in MCE (Modified Combustion Efficiency) vs. geometric mean diameter than only using MCE values.

Highlights

Biomass combustion encompasses a wide range of sources including wildland fires, prescribed burning, agricultural residue/waste burning, residential wood combustion, and power generation
The size distribution is averaged over the time from ignition to the end of sampling and over at least three burn replicates for each fuel type
The similarity of the size distribution among fuels tested can be attributable to the systematic burning and sampling method.The combustion facility in Missoula was designed to divert all the generated smoke into the chimney

Summary

Introduction

Biomass combustion encompasses a wide range of sources including wildland fires, prescribed burning, agricultural residue/waste burning, residential wood combustion, and power generation. In the United States, intentional biomass burning (prescribed burning) is regulated by the Clean Air Act. Prescribed burning is the planned use of fire under specified environmental and meteorological conditions to accomplish specific vegetation management objectives. In order to utilize prescribed burning, managers must provide estimates of the quantity of certain combustion products that will be produced before air quality regulators issue burn permits. These products of combustion include particulate matter (PM) released into the atmosphere (Chi, 1979; Levine, 1996; Goldammer, 2009). In the United States, the production of particles smaller than 2.5 μm is regulated due to the adverse impacts on human health and visibility

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Conclusion