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research-article

RAPIDLY PULSED REDUCTANTS FOR DIESEL NOX REDUCTION WITH LEAN NOX TRAPS: COMPARISON OF ALKANES AND ALKENES AS THE REDUCING AGENT

[+] Author and Article Information
Amin Reihani

Department of Mechanical Engineering, University of Michigan G.G. Brown Laboratory, 2350 Hayward, Ann Arbor MI 48109
areihani@umich.edu

Brent Patterson

Department of Chemical Engineering, University of Michigan 3074 H.H. Dow 2300, Hayward Street, Ann Arbor, MI 48109-2136
patbre@umich.edu

John Hoard

Department of Mechanical Engineering, University of Michigan 1231 Beal Ave, 1012 Lay Autolab, Ann Arbor, MI 48109
hoardjw@umich.edu

Galen B. Fisher

Department of Chemical Engineering, University of Michigan 3170 H.H. Dow 2300, Hayward Street, Ann Arbor, MI 48109-2136
gbfisher@umich.edu

Joseph R. Theis

Ford Motor Company 2101 Village Rd, Dearborn, MI 48124
jtheis@ford.com

Christine K. Lambert

Ford Motor Company 2101 Village Rd, Dearborn, MI 48124
clamber9@ford.com

1Corresponding author.

ASME doi:10.1115/1.4036295 History: Received February 16, 2017; Revised February 27, 2017

Abstract

Lean NOx Traps (LNTs) are often used to reduce NOx on smaller diesel passenger cars where urea-based Selective Catalytic Reduction (SCR) systems may be difficult to package. However, the performance of LNTs at temperatures above 400°C needs to be improved. Rapidly Pulsed Reductants (RPR) is a process in which hydrocarbons are injected in rapid pulses ahead of the LNT in to improve its performance at higher temperatures and space velocities. This approach was developed by Toyota and was originally called Di-Air [1]. Four important parameters were identified to maximize NOx conversion while minimizing fuel penalty associated with hydrocarbon injections in RPR operation: (1) flow field and reductant mixing uniformity; (2) pulsing parameters including the pulse frequency, duty cycle, and magnitude; (3) reductant type; (4) catalyst composition, including the type and loading of precious metal and NOx storage material, and the amount of oxygen storage capacity (OSC). In this study, RPR performance was assessed between 150°C and 650°C with several reductants including dodecane, propane, ethylene, propylene, H2, and CO. Under RPR conditions, H2, CO, C12H26, and C2H4 provided approximately 80% NOx conversion at 500°C; however, at 600°C the conversions were significantly lower. The NOx conversion with C3H8 was low across the entire temperature range. In contrast, C3H6 provided greater than 90% NOx conversion over a broad range of 280°C to 630°C. This suggested that the high temperature NOx conversion with RPR improves as the reactivity of the hydrocarbon increases.

Copyright (c) 2017 by ASME
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