Abstract View
Design and Characterization of an Advanced Thermal Denuder
MARTIN IRWIN, Jacob Swanson, Adam M Boies, Catalytic Instruments
Abstract Number: 96
Working Group: Instrumentation and Methods
Abstract
Aerosols are comprised of solid and semi-volatile particles suspended in a gas. The semi-volatile fraction comprises tens of thousands of organic compounds. By precisely changing the temperature of an aerosol sample, semi-volatile constituents can be selectively partitions based on their volatility, which is the basis of the thermal denuder. In this device, particles typically pass through a heated section of tube wherein semi-volatile material evaporates. The “dried” particles and evaporated vapor then pass into a cooled section where the vapor adsorbs to activated carbon. The “dried” particles pass out the device to be measured.
One issue with this technique is the transition from the hot section to the cooled section typically creates two undesired effects: 1) the vapors nucleate and form additional particles rather than adsorb to the activated or 2) the vapors adsorb to the existing particles rather than the activated carbon. One solution to these problems can be found in addressing the heating and/or cooling rates, transitions, etc. Secondary to these problems of a fundamental nature is that the geometry described typically results in a “large” device. Due to the size (and thermal mass) of the device, the temperature cannot be changed rapidly, which limits the number of temperature setpoints typically achievable.
In the Advanced Thermal Denuder, the problematic transition from the heating section to the cooled section has been eliminated because there is just a single section that is heated. Energy flows from the inside to the outside. This results in the adsorption section being cooler than the aerosol heating section. The direction of heat flow maximizes adsorption capacity near the exterior of the device where the adsorbent is located. We present data characterizing the design and performance of this new Adavanced Thermal Denuder operating at 1 LPM in the temperature range of 20ºC to 400ºC.