Development and Validation of an Extractive Dilution System for In-situ Measurement of Residential Wood Heating Appliance PM Emissions Using a TEOM
GEORGE ALLEN, Mark Champion, NESCAUM
Abstract Number: 30
Working Group: Instrumentation and Methods
Abstract
Measurements of in-situ residential wood heater PM emissions are needed for updated emission inventories and to assess the efficacy of state wood stove changeout programs. Certification testing of wood heater PM emissions to demonstrate compliance with US EPA standards is done using a dilution tunnel under tightly controlled laboratory conditions that may not reflect the installation, operating and fueling conditions of real-world use. To assess this difference, we developed an extractive dilution system that completely mixes the sample and matches the key dilution tunnel characteristics of dilution factor (DF), residence time and temperature to ensure that the condensation dynamics of semi-volatile organics in the tunnel and diluter are similar. Commercial dilution systems were evaluated but did not condense semi-volatiles and had issues with inlet clogging when sampling high-emitting devices. This diluter system uses 1-minute PM measurements from a Thermo Scientific TEOM concurrent with measurement of stack flow using a vane anemometer to provide temporally detailed emissions data and to resolve issues with proportional sampling when using integrated PM measurements. A modular diluter design allows DF from 5 to 50 and residence times from 0.5 to 5 seconds. A short straight-through sample inlet line minimizes particle losses and avoids water vapor condensation in the sample stream without an external heater; the inlet line is easily cleaned or replaced. The simple design eliminates the need for validation of DF using inert tracer gases. Performance was assessed by direct comparison to laboratory dilution tunnel PM emission rate measurements using a TEOM. Field performance was evaluated by testing three stoves first in the laboratory and then in a home using the same operating and fueling protocol.