Browse Topic: Selective catalytic reduction (SCR)
This paper is to introduce a new catalyst family in gasoline aftertreatment. The very well-known three-way catalysts effectively reduce the main emission components resulting from the combustion process in the engine, namely THC, CO, and NOx. The reduction of these harmful emissions is the main goal of emission legislation such as Bharat VI to increase air quality significantly, especially in urban areas. Indeed, it has been shown that under certain operating conditions, three-way catalysts may produce toxic NH3 and the greenhouse gas N2O, which are both very unwanted emissions. In a self-committed approach, OEMs could want to minimize these noxious pollutants, especially if this can be done with no architecture change, namely without additional underfloor catalyst. In most Bharat VI gasoline aftertreatment system architectures, significant amounts of NH3 occur in two phases of vehicle driving: situations with the catalyst temperature below light-off, which appear after cold start or
After the implementation of BS-VI emission standards, effective exhaust after-treatment has become critical in minimizing harmful emissions from diesel engines. One significant challenge is the accumulation of hydrocarbons (HC) in the Diesel Oxidation Catalyst (DOC). Certain hydrocarbons may adsorb onto the catalyst surface yet remain unreactive, leading to potential operational inefficiencies. This phenomenon necessitates the desorption of unreactive hydrocarbons to allow space for more reactive species, thereby enhancing oxidation efficiency and overall catalyst performance. The process of desorption (DeSorb) is vital to maintaining the balance of reactive hydrocarbons within the DOC. When a vehicle is idling, unburnt fuel produces hydrocarbons that accumulate in the DOC. Upon acceleration, these hydrocarbons can lead to an uncontrolled rise in temperature, resulting in DOC push-out, catalyst damage, and downstream impacts on the Diesel Particulate Filter (DPF). To mitigate these
The study emphasizes on development of Diesel Exhaust Fluid (DEF) dosing system specifically used in Selective Catalytic Reduction (SCR) of diesel engine for emission control, where a low pressure pumpless DEF dosing system is developed, utilizing compressed air for pressurizing the DEF tank and discharging DEF through air assisted DEF injection nozzle. SCR systems utilize Diesel Exhaust Fluid (DEF) to convert harmful NOx emissions from diesel engines into harmless nitrogen and water vapor. Factors such as improper storage, handling, or refilling practices can lead to DEF contamination which pose significant operational challenges for SCR systems. Traditional piston-type, diaphragm-type, or gear-type pumps in DEF dosing systems are prone to mechanical failures leading to frequent maintenance, repairs, and costly downtimes for vehicles. To overcome the existing challenges and to create a more reliable and simple DEF delivery mechanism the pumpless DEF Dosing system is developed. The
Cu/zeolite selective catalytic reduction (SCR) catalysts are used globally to reduce NOx emissions from diesel engines. These catalysts can achieve high NOx conversion efficiency, and they are hydrothermally durable under real world diesel exhaust environments. However, Cu/zeolite catalysts are susceptible to sulfur poisoning and require some type of sulfur management even when used with ultra-low sulfur diesel (ULSD). In the present study, the authors seek to better illuminate the chemical processes responsible for ammonium sulfate formation and decomposition occurring in Cu/zeolite SCR catalysts. Reactor-based experiments are first conducted with a real-world concentration of SO2 (0.5 ppmv) and a typical diesel exhaust water vapor concentration (7 vol.%) to quantify progressive effects of ammonium sulfate formation. A second group of experiments probe the chemical decomposition of ammonium sulfate via NO titration. The “movement” of sulfate species during this process is monitored
Hydrogen internal combustion engines (H2-ICE) do not emit any fuel-borne carbon emission species. Nitrogen oxides are the remaining raw emission species at significant levels. However, the exhaust aftertreatment system is exposed to a different exhaust matrix, including unburned hydrogen. This raises the question of the role of hydrogen emissions for the aftertreatment system. Extensive synthetic gas bench (SGB) test campaigns address the role of hydrogen in several production catalyst components. Starting with selective catalytic reduction (SCR) systems, a systematic variation of the hydrogen concentration shows rather small effects on the NOX reduction performance. A change in selectivity results in increased secondary N2O emissions for a copper-zeolite system, whereas a vanadium-based SCR catalyst is unaffected. However, both SCR types are highly sensitive to the NO2/NOX ratio in the raw emission. Therefore, an upstream oxidation catalyst remains important for low temperature
This paper investigates heated and cold Diesel Exhaust Fluid (DEF) sprays with the aim of establishing the effect of temperature on the resulting spray characteristics. The work is motivated by the need to optimize active Selective Catalytic Reduction (SCR) systems to meet more stringent nitrogen oxide (NOx) emission regulations for internal combustion engines. Pre-heating DEF has the potential to improve evaporation of the injected fluid, increasing the NOx conversion efficiency of the SCR at low exhaust temperatures. Experiments are carried out using the MAHLE SmartHeat fluid heater and mounted atop a DEF injector, with an incorporated thermocouple for fluid temperature. The fluid temperature established by the heater in this configuration was about 130 °C. The fluid is injected into an atmospheric environment and Schlieren imaging is used to visualize the spray evolution. CFD simulations are also carried out to validate the experimental observations and further shed light on the
Selective Catalytic Reduction (SCR) is an optimized technology developed to encounter current BS6 Emission Regulations. AdBlue is the reductant used in the SCR Dosing system to eliminate NOx in the Exhaust gas. In order to ensure engine emissions compliance, insufficient or improper reductant in tank required to be detected. The right AdBlue concentration of 32.5% is highly necessary to attain the higher NOX conversion efficiency. Low concentration of the reductant will drastically reduce the NOx conversion in the system. Hence monitoring the AdBlue concentration in the tank itself is more important as per the OBD legislation. This implies on a physical quality sensor in the tank for detecting the reductant concentration. The functionalities of the quality sensor can also be instituted via a virtual software modelling called Improper Reductant Detection (IRD). IRD logic is highly robust and work competently to meet the BS6 stage 2 legislation’s NOx target. The reductant is suspected
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