A Heated AdBlue/DEF Mixer for High Efficiency NOx Reduction in Low Temperature Drive Cycles, RDE and City Driving

Abstract

An electrically heated mixer (EHM™) has been developed. It enables injecting urea-water solution in low temperature Diesel exhaust operations, such as in low-load cycles, real-driving-emissions (RDE), stop-and-go, city driving and local delivery cycles, enabling high efficiency (SCR) selective catalytic reduction of NOx in challenging operations. In low temperature exhaust, EHM frees the injected droplets from relying on the heat of the exhaust. It provides thermal energy to swiftly heat and evaporate the droplets, accelerating their thermolysis and hydrolysis reactions. Designed to be compact, low cost and robust, EHM forms plenty of reductants (ammonia, isocyanic acid) while mitigating the deposit risks. It has been tested on an engine in highly transient, low-load cycles exhibiting robust SCR of NOx well below 200 °C in long cycles with urea injection starting in as low as 130 °C. The mixer has been evaluated on a light duty Diesel engine using a purged (no-ammonia-stored) SCR catalyst simulating extended stop-and-go operations, demonstrating 99–100% NOx reduction efficiency during “stops” (idling) at 180 °C, and 80 to 95% during fast transients at 160 °C, while inhibiting deposit formation. These results were achieved without any engine or system calibration. EHM needs less than 200 W to operate on a light duty Diesel engine, and about 500 W on a heavy-duty engine. Given its thermal energy, it can be also used during cold-starts or cold-cycles for rapid-heatup of the SCR catalyst(s). EHM can also enable high engine-out NOx strategy so for fuel economy and reduced CO2.

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Topics in Catalysis (2023) 66:771–776
https://doi.org/10.1007/s11244-022-01714-2
ORIGINAL PAPER
A Heated AdBlue/DEF Mixer forHigh Efficiency NOx Reduction inLow
Temperature Drive Cycles, RDE andCity Driving
M.Masoudi1 · N.Poliakov1· S.Noorfeshan1· J.Hensel1· E.Tegeler1
Accepted: 10 October 2022 / Published online: 31 October 2022
© The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2022
Abstract
An electrically heated mixer (EHM™) has been developed. It enables injecting urea-water solution in low temperature Diesel
exhaust operations, such as in low-load cycles, real-driving-emissions (RDE), stop-and-go, city driving and local delivery
cycles, enabling high efficiency (SCR) selective catalytic reduction of NOx in challenging operations. In low temperature
exhaust, EHM frees the injected droplets from relying on the heat of the exhaust. It provides thermal energy to swiftly heat
and evaporate the droplets, accelerating their thermolysis and hydrolysis reactions. Designed to be compact, low cost and
robust, EHM forms plenty of reductants (ammonia, isocyanic acid) while mitigating the deposit risks. It has been tested on an
engine in highly transient, low-load cycles exhibiting robust SCR of NOx well below 200°C in long cycles with urea injection
starting in as low as 130°C. The mixer has been evaluated on a light duty Diesel engine using a purged (no-ammonia-stored)
SCR catalyst simulating extended stop-and-go operations, demonstrating 99–100% NOx reduction efficiency during “stops”
(idling) at 180°C, and 80 to 95% during fast transients at 160°C, while inhibiting deposit formation. These results were
achieved without any engine or system calibration. EHM needs less than 200W to operate on a light duty Diesel engine, and
about 500W on a heavy-duty engine. Given its thermal energy, it can be also used during cold-starts or cold-cycles for rapid-
heatup of the SCR catalyst(s). EHM can also enable high engine-out NOx strategy so for fuel economy and reduced CO2.
Keywords Deposit· NOx· SCR· Ammonia· Mixer· Low-load
1 Introduction
Selective catalytic reduction (SCR) of NOx is a robust tech-
nology for NOx mitigation in Diesel exhaust [1] and much
literature has been published on the technology and appli-
cation of SCR catalysts and systems [2–7]. SCR operations
require injecting urea-water-solution (here called ‘urea’ for
simplicity) known as AdBlue™, Diesel exhaust fluid™ or
by other names around the world. In general, injecting urea
below 200°C specially for longer durations can form a non-
negligible amount of urea deposits (crystals) n the emission
control system [8–11], an unwanted by-product created due
to incomplete evaporation of urea. Deposits can damage
exhaust components, yield large ammonia slips and possi-
bly increase N2O emission, amongst other adverse impacts.
As a result, in general urea is not widely injected in Diesel
exhaust in temperatures below 200°C. This allows Diesel
NOx to leave the tailpipe largely unabated, ensuing major
health, environmental and regulatory concerns. To make up
for this shortcoming, evaporation of injected urea spray and
formation of gaseous reductants are typically assisted via
adding a heat source, such as exhaust heaters [12], electri-
cally heated catalysts (EHCs) [13], burners [14] or post-
injection of fuel [15]. Other techniques have included inject-
ing gaseous ammonia [16] or using an electrically heated
urea doser (injector) [17]. Each approach has pros and cons
on cost, complexity, maturity, durability, fuel penalty, CO2,
regulatory concerns or a mix. Here, we discuss a newly-
developed electrically heated mixer (EHM™) providing a
low-energy, low-cost, compact, easy-to-integrate and dura-
ble solution forming plenty of gaseous reductants in low
exhaust temperature operations while simultaneously hin-
dering urea deposit formation. It is shown that EHM enables
highly efficient SCR of NOx in challenging low-load Diesel
engine operations and fast transients well below 200°C.
EHM could be also used to heat the exhaust components/
catalysts during cold start for rapid heatup. EHM draws its
* M. Masoudi
mansour.masoudi@emissol.com
1 Emissol LLC, MillCreek, WA, USA
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