Urea-SCR: a promising technique to reduce NOx emissions from automotive diesel engines

Koebel, Manfred; Elsener, Martin; Kleemann, M.

doi:10.1016/s0920-5861(00)00299-6

Cited by 988 publications

(563 citation statements)

References 5 publications

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“…It was found that only the Ti/(Pt-Ir) and Ti/(Ta 2 O 5 -IrO 2 ) electrodes were sufficiently active to decompose urea to nontoxic products (N 2 and CO 2 ). There have also been reports of BiO x /TiO 2 electrodes used in urea electro-oxidation [58], which yielded N 2 and CO 2 gases and a small amount of NO 3 -ions as the products. Hernlem et al [47] studied industrially oriented, dimensionally stable electrodes (DSA Ò ) coated with RuO 2 .…”

Section: Anode Materialsmentioning

confidence: 99%

“…Hernlem et al [47] studied industrially oriented, dimensionally stable electrodes (DSA Ò ) coated with RuO 2 . The concentration of urea in the solution used in this study was up to 750 ppm, the concentration of chloride ranged from 100 to 400 ppm with addition of 2000 ppm NaHCO 3 . The efficiency of urea decomposition was found to be increasing with temperature and initial urea and chloride concentrations.…”

Section: Anode Materialsmentioning

confidence: 99%

“…Urea derivatives are used in pharmaceuticals production and as bioactive compounds in cosmetics and dermatology as well as herbicides and insecticides [2]. Urea is an excellent reducing agent in the selective catalytic reduction (SCR) reaction of nitrogen oxides (NO x ) from exhaust gases in internal combustion engines, especially heavy-duty diesel engines [3].…”

Section: Introductionmentioning

confidence: 99%

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Urea removal from aqueous solutions—a review

2016

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The abundance of urea in the natural environment is dictated by the fact that it is one of the major products of mammalian protein metabolism. Due to the extensive use of urea in many branches of industry, it is produced in large quantities. Urea enters into the environment not only with wastewater from the production plants but also by leaching from the fields, agro-breeding farms, and the effluents from the plants using it as a raw material. There are many methods of urea removal, but most of them are still being developed or are very new. The methods themselves differ in terms of physicochemical nature and technological ingenuity. Many wastewater treatment methods include processes such as hydrolysis, enzymatic hydrolysis, decomposition in the biological bed, decomposition by strong oxidants, adsorption, catalytic decomposition, and electrochemical oxidation. In this work, methods of urea removal from aqueous solutions have been reviewed. Particular attention was paid to electrochemical methods.

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Section: Anode Materialsmentioning

confidence: 99%

Section: Anode Materialsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Urea removal from aqueous solutions—a review

2016

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“…The diesel engine was run on a dynamometer produced by the SIEMENS Company. The selective reducing agent adapted was urea because of its safety and low toxicity characteristics [6]. In automotive applications, Urea (AdBlue)-based SCR is a promising method for the control of NOx emissions [7].…”

Section: Engine and Catalystsmentioning

confidence: 99%

Urea-SCR Temperature Investigation for NOx Control of Diesel Engine

Asif

Zhang

Lin

2015

MATEC Web of Conferences

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Abstract. SCR (selective catalytic reduction) system is continuously being analyzed by many researchers worldwide on various concerns due to the stringent nitrogen oxides (NOx) emissions legislation for heavy-duty diesel engines. Urea-SCR includes AdBlue as urea source, which subsequently decomposes to NH3 (ammonia) being the reducing agent. Reaction temperature is a key factor for the performance of urea-SCR system, as urea decomposition rate is sensitive to a specific temperature range. This particular study was directed to investigate the temperature of the SCR system in diesel engine with the objective to confirm that whether the appropriate temperature is attained for occurrence of urea based catalytic reduction or otherwise and how the system performs on the prescribed temperature range. Diesel engine fitted with urea-SCR exhaust system has been operated on European standard cycle for emission testing to monitor the temperature and corresponding nitrogen oxides (NOx) values on specified points. Moreover, mathematical expressions for approximation of reaction temperature are also proposed which are derived by applying energy conservation principal and gas laws. Results of the investigation have shown that during the whole testing cycle system temperature has remained in the range where urea-SCR can take place with best optimum rate and the system performance on account of NOx reduction was exemplary as excellent NOx conversion rate is achieved. It has also been confirmed that selective catalytic reduction (SCR) is the best suitable technology for automotive engine-out NOx control.

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“…As soon as the urea-water solution is injected into the exhaust tailpipe, water will evaporate to leave a trail of solid molten urea, which will convert into gaseous ammonia. This conversion of molten urea into ammonia can occur by two steps, namely, thermolysis and further hydrolysis 12 Hydrolysis of iso-cyanic acid into NH3 HNCO (g) + H2O (g) → NH3 (g) + CO2 (g) Decomposition of the injected urea is initiated at 133 o C for a very short residence time of 0.1 s 13 and goes to completion at 350°C. 14 To achieve this condition, positioning of the urea injection is crucial; if this position is not proper incomplete urea decomposition may happen.…”

Section: Introductionmentioning

confidence: 99%

Investigation of Urea Decomposition and Uniform Concentration of Urea Water Solution in SCR System for Diesel Engine Exhaust Using CFD

2017

Rasayan J Chem

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Urea-SCR has received worldwide attention for reducing the harmful NOx emission from present diesel engines. But this faces lot of challenges such as complete decomposition of reducing agent urea and its deposition at the bottom of exhaust tail pipe, lack of uniform distribution of the urea-decomposed ammonia during the continuous running of the engine. This study is involved with CFD evaluation of urea decomposition rate by adopting different urea injection angles and nozzle positions. Also, urea atomization and evaporation/decomposition to ammonia and ammonia distribution on tail pipe cross-sectional area are investigated. Exhaust tail pipe is fitted with guided pipe at different angles. Also, urea and air are injected at different pressures respectively, in the twin-flow nozzle. The CFD analysis indicated that, the ammonia conversion rate is well improved using guided pipe fitted at 30 o inclination with exhaust tail pipe. The CFD analysis is validated by engine experiments. It was proven that, the conversion increased for the 5bar urea and 1bar air.

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Urea-SCR: a promising technique to reduce NOx emissions from automotive diesel engines

Cited by 988 publications

References 5 publications

Urea removal from aqueous solutions—a review

Urea removal from aqueous solutions—a review

Urea-SCR Temperature Investigation for NOx Control of Diesel Engine

Investigation of Urea Decomposition and Uniform Concentration of Urea Water Solution in SCR System for Diesel Engine Exhaust Using CFD

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