Assessing the degree of plug flow in oxidation flow reactors (OFRs): a study on a potential aerosol mass (PAM) reactor

Abstract

Abstract. Oxidation flow reactors (OFRs) have been developed to achieve high degrees of oxidant exposures over relatively short space times (defined as the ratio of reactor volume to the volumetric flow rate). While, due to their increased use, attention has been paid to their ability to replicate realistic tropospheric reactions by modeling the chemistry inside the reactor, there is a desire to customize flow patterns. This work demonstrates the importance of decoupling tracer signal of the reactor from that of the tubing when experimentally obtaining these flow patterns. We modeled the residence time distributions (RTDs) inside the Washington University Potential Aerosol Mass (WU-PAM) reactor, an OFR, for a simple set of configurations by applying the tankin-series (TIS) model, a one-parameter model, to a deconvolution algorithm. The value of the parameter, N, is close to unity for every case except one having the highest space time. Combined, the results suggest that volumetric flow rate affects mixing patterns more than use of our internals. We selected results from the simplest case, at 78 s space time with one inlet and one outlet, absent of baffles and spargers, and compared the experimental F curve to that of a computational fluid dynamics (CFD) simulation. The F curves, which represent the cumulative time spent in the reactor by flowing material, match reasonably well. We value that the use of a small aspect ratio reactor such as the WU-PAM reduces wall interactions; however sudden apertures introduce disturbances in the flow, and suggest applying the methodology of tracer testing described in this work to investigate RTDs in OFRs to observe the effect of modified inlets, outlets and use of internals prior to application (e.g., field deployment vs. laboratory study).

Secondary organic aerosol formation from α-pinene, alkanes and oil sands related precursors in a new oxidation flow reactor

“…CC BY 4.0 License. establishment of jetting and recirculation in the OFR (Huang et al, 2017), which were noted for straight OFR inlets (Huang et al, 2017;Mitroo et al, 2018). There are seven openings at the output end of the ECCC-OFR; six of them (I.D.=0.25") are equally spaced around the perimeter to provide side flow as exhaust with a distance to the walls of 2.5 cm, intended to reduce the impact of gas and particle wall losses on sampling.…”

“…Conversely, the Ptrans of the TPOT (Toronto Photo-Oxidation Tube), PAM (Potential Aerosol Mass) reactor (Lambe et al, 2011) and CPOT (Caltech Photooxidation Flow Tube) (Huang et al, 2017) are 15-85%, 20-60% and 20-45% lower respectively than the ECCC-OFR across a range of particle sizes. Potential causes of these discrepancies include recirculation and turbulence induced by a straight inlet and/or output sampling end (Lambe et al, 2011), noncenterline sampling (Huang et al, 2017) and longer residence times (Huang et al, 2017) in the other OFRs (see Supporting Information), which have been noted as potential factors previously (Lambe et al, 2011;Simonen et al, 2017;Mitroo et al, 2018).…”

Secondary organic aerosol production from local emissions dominates the organic aerosol budget over Seoul, South Korea, during KORUS-AQ

“…In 2007, the human population living in urban areas had increased to over 50 % (making it the first time in human history that more people reside in urban than rural areas), and it is predicted that nearly two-thirds of the human population will be living in urban areas by 2050 (Monks et al, 2009;UNDESA, 2015;Baklanov et al, 2016). Urban areas are large sources of anthropogenic emissions to the atmosphere (from sources including transportation, industry, cooking, personal care products, and power produced from fossil fuels), and these emissions have important impacts on local, regional, and global air pollution, climate, and human and ecological health (Hallquist et al, 2009;Monks et al, 2009;Myhre et al, 2013;Baklanov et al, 2016;WHO, 2016;Cohen et al, 2017;Landrigan et al, 2018;McDonald et al, 2018). Effects from urban emissions are strongly modulated by the chemical evolution of the primary emissions (e.g., nitrogen oxides, hydrocarbons, and primary organic aerosols, POAs) to secondary pollutants, including secondary organic aerosols (SOAs, produced from atmospheric reactions) and other aerosols (Monks et al, 2009).…”

“…Urban areas are large sources of anthropogenic emissions to the atmosphere (from sources including transportation, industry, cooking, personal care products, and power produced from fossil fuels), and these emissions have important impacts on local, regional, and global air pollution, climate, and human and ecological health (Hallquist et al, 2009;Monks et al, 2009;Myhre et al, 2013;Baklanov et al, 2016;WHO, 2016;Cohen et al, 2017;Landrigan et al, 2018;McDonald et al, 2018). Effects from urban emissions are strongly modulated by the chemical evolution of the primary emissions (e.g., nitrogen oxides, hydrocarbons, and primary organic aerosols, POAs) to secondary pollutants, including secondary organic aerosols (SOAs, produced from atmospheric reactions) and other aerosols (Monks et al, 2009). These emissions and their chemical by-products significantly influence hemispheric climate and air quality.…”

Secondary organic aerosol formation from <i>α</i>-pinene, alkanes, and oil-sands-related precursors in a new oxidation flow reactor

“…Over the last several decades, oil production from unconventional sources has increased significantly and is expected to continue to increase into the future due to its abundant reserves, particularly in North America (Alboudwarej et al, 2006;Mohr and Evans, 2010;Owen et al, 2010). The Alberta oil sands (OS) are a large unconventional crude oil deposit, which are extracted through both open-pit mining and in situ steam-assisted techniques.…”