10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
Abstract View
Investigating Catalytic Stripper Based System for Measurement of Sub-23 nm Particles from Vehicle Engine Exhaust
MOSTAFIZUR RAHMAN, Adam M Boies, University of Cambridge
Abstract Number: 1541 Working Group: Instrumentation
Abstract The European Union (EU) has included Gasoline Direct Injection (GDI) vehicles and non-road machinery engine into its Solid Particle Number (SPN) based Euro-VI emission standard. Diesel vehicles are complying with the SPN based standards from 2011 mainly by integrating Diesel Particulate Filter (DPF) in the exhaust system. Thanks to Particle Measurement Program (PMP) which paved the pathway to implementing the SPN based standard. However, there has been a widespread debate about the exclusion of sub-23 nm particles and semi-volatiles from PMP measurement protocol. Some studies found a high concentration of sub-23 nm particles in post DPF emissions, where other concluded it resulted measurement artifacts. Recently, this debate has got new momentum after the inclusion GDI vehicles into SPN based standard and subsequent introduction of Gasoline Particulate Filter (GPF) into the GDI vehicle exhaust system. Studies reported the consistent presence of 10-20 nm mode particles in GDI engine exhaust which are either elemental carbon or semi-volatiles (SV). The PMP system is yet to prove its robustness while measuring the sub-23 nm particles. Therefore there is a requirement for an even more robust measurement system to include sub- 23 particles into emission standards.
A measurement system employing catalytic stripper (CS) could be a potential solution to this problem. CS system removes volatile and semi-volatile particles by evaporating them upon heating at 350°C and subsequent oxidation. Therefore it eliminates the possibility of renucleation of those semi volatiles upon cooling down of the gas stream. This study under PEMs4Nano project is investigating the robustness of CS based measurement system in measuring sub 23 particles. We are testing a range of catalytic strippers for their SV and solid particle penetration efficiencies. The results suggest almost zero SV penetration efficiency and 50-60% solid particle penetration efficiency for 104 #/cm3 particles at 10 nm size. Further works are in progress to improve the solid particle penetration efficiency at 10 nm and beyond by optimizing the catalyst length, type, geometry and flow condition. Primary results of this study indicate that it is possible to reduce the cut-off point of SPN emissions from 23 nm to 10 nm, but a further comprehensive investigation is required to down size the cut point beyond 10 nm. The complete outcome of this project will help to implement 10 nm cut point in future EU emissions regulation.