Concept of Vaporized Urea Dosing in Selective Catalytic Reduction

Sala, Rafal; Bielaczyc, Piotr; Brzeżański, Marek

doi:10.3390/catal7100307

Cited by 11 publications

(9 citation statements)

References 23 publications

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“…When the space for mixing is limited, then the spray properties become the key factor in determining the quality of the SCR system. Therefore, besides investigating alternative solutions [2], the urea-water sprays are more often studied than in the past-when the inline underfloor SCR systems were a standard solution.…”

Section: Introductionmentioning

confidence: 99%

Characteristics of Water and Urea–Water Solution Sprays

et al. 2019

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In spray studies related to selective catalytic reduction (SCR) systems a common approach is to replace the urea–water solution (UWS) with pure water, even though there is very limited detailed information on the spray properties for these two liquids obtained under the same conditions using the same experimental equipment. Neither is it known how the possible differences in spray properties influence computational fluid dynamics (CFD) simulations. In this study, besides the flow characteristics, we compare both global and local spray parameters measured for UWS and pure water in the same conditions. To our knowledge, this is the first study which examines the influence on the injection process of replacing UWS with water over such a wide range. Moreover, the influence of different spray properties on CFD simulations is also examined. The experimental studies showed differences in almost all considered spray parameters. Moreover, different spray behaviour was noticed in terms of primary break-up. One important finding is that water and UWS sprays do have a similar Sauter mean diameter, but at the same time the droplet size distribution is considerably different. The simulation results indicated noticeable differences in terms of wall film formation; nevertheless, the overall mixing performance was not significantly affected.

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Section: Introductionmentioning

confidence: 99%

Characteristics of Water and Urea–Water Solution Sprays

et al. 2019

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“…For safety and toxicological reasons, a urea water solution (UWS) is preferred instead of directly ammonia as a reducing agent. 5 The injected urea subjected to the exhaust high temperatures suffers from thermolysis ( eq 1 ) and the isocyanic acid (HNCO) undergoes hydrolysis ( eq 2 ) transforming into ammonia. 6 …”

Section: Introductionmentioning

confidence: 99%

Numerical Analysis of Urea to Ammonia Conversion in Automotive Selective Catalytic Reduction Realistic Conditions

Payri

Martí-Aldaraví

Marco-Gimeno

2021

Ind. Eng. Chem. Res.

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The selective catalytic reduction (SCR) is a technology employed for NO x reduction purposes which is based on the injection of an Urea Water Solution (UWS) into the exhaust line. Conversion of this injected urea into ammonia is a key step to ensure high SCR efficiency. In order to study this phenomenon, a three-dimensional model of the urea–water injection process has been created to recreate realistic conditions. A Lagrangian–Eulerian approach has been followed to model liquid and gas phases, respectively. Droplet evaporation as well as relevant chemical processes have been included to recreate the thermolysis and hydrolysis phenomena, and the results have been validated against literature data. Then, the validated model has been applied to recreate an in-house experimental facility that measured spray macroscopic and microscopic characteristics by means of diffused back illumination (DBI) visualization. Probability density functions of the UWS droplet sizes as well as the velocity distributions have been obtained at three different regions of interest to be compared with the experimental data set. Contours of isocyanic acid and ammonia mass fractions have been included to show the chemical transformation from urea into its products. The model accurately replicates the experimental results, and it stands as a good methodology to predict the main spray characteristics as well as the chemical processes that take place in actual SCR systems.

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“…The ammonia concentration distribution at the catalyst converter is a key parameter for best conversion performance [ 10 , 11 , 12 ]. Only a homogeneously- and uniformly-distributed ammonia concentration ensures the effective usage of the whole catalyst cross-section.…”

Section: Introductionmentioning

confidence: 99%

Ammonia Distribution Measurement on a Hot Gas Test Bench Applying Tomographical Optical Methods

Fischbacher¹,

Lechner²,

Brandstätter³

2019

Sensors

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Measuring the distribution of gas concentration is a very common problem in a variety of technological fields. Depending on the detectability of the gas, as well as the technological progress of the sector, different methods are used. In this paper, we present a device and methods to detect the ammonia concentration distribution in the exhaust system of diesel engines in order to increase the performance of the exhaust aftertreatment system. The device has been designed for usage on a hot gas test bench simulating exhaust gas conditions. It consists of multiple optical beams measuring ammonia line concentrations by applying nondispersive absorption spectroscopy in the deep ultraviolet region. The detectors consist of photodiodes allowing high sampling rates up to 3 kHz while providing a high signal-to-noise ratio. A detection limit of only 1 ppm has been achieved despite the short path length of only eight centimeters. The obtained line concentrations form an inverse problem. The methodology of the tomographic techniques is described in detail in order to best solve the inverse problem and obtain the ammonia concentration distribution images for each time step.

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Concept of Vaporized Urea Dosing in Selective Catalytic Reduction

Cited by 11 publications

References 23 publications

Characteristics of Water and Urea–Water Solution Sprays

Characteristics of Water and Urea–Water Solution Sprays

Numerical Analysis of Urea to Ammonia Conversion in Automotive Selective Catalytic Reduction Realistic Conditions

Ammonia Distribution Measurement on a Hot Gas Test Bench Applying Tomographical Optical Methods

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