urea-SCR Aftertreatment System Research Articles

Demonstration of 2027 Emissions Standards Compliance Using Heavy-Duty Gasoline Compression Ignition with P1 Hybridization

<div>Heavy-duty on-road engines are expected to conform to an ultralow NO<sub>x</sub> (ULNO<sub>x</sub>) standard of 0.027 g/kWh over the composite US heavy-duty transient federal test procedure (HD-FTP) cycle by 2031, a 90% reduction compared to 2010 emissions standards. Additionally, these engines are expected to conform to Phase 2 greenhouse gas regulations, which require tailpipe CO<sub>2</sub> emissions under 579 g/kWh. This study experimentally demonstrates the ability of high fuel stratification gasoline compression ignition (HFS-GCI) to satisfy these emissions standards. Steady-state and transient tests are conducted on a prototype multi-cylinder heavy-duty GCI engine based on a 2010-compliant Cummins ISX15 diesel engine with a urea-SCR aftertreatment system (ATS). Steady-state calibration exercises are undertaken to develop highly fuel-efficient GCI calibration maps at both cold-start and warmed up conditions. A P1 hybrid architecture is proposed to enable the use of an integrated starter generator (ISG) capable of spinning the engine up to idle speeds and an electrically heated ATS for fast heat-up and better thermal management. The combined solution is shown to satisfy the aforementioned ULNO<sub>x</sub> standard across the composite HD-FTP while decreasing the CO<sub>2</sub> emissions compared to the 2013 baseline values, cementing the credentials of low-cetane fuels as viable, near-term alternatives to diesel fuel in heavy-duty on-road engines.</div>

Urea-SCR System Development in the Mitigation of NOx Emissions from Diesel Engines – A Review Study

Introduction: Due to energy demand concerns, diesel engines have gained much attraction recently compared to petrol engines because of their higher thermal efficiencies. However, they emit a larger amount of NOx emissions into the atmosphere. Objective: Nitrogen oxides are known as important ambient air pollutants that are responsible for health problems, forest damage, and buildings corrosion. Therefore, using emissions control strategies for diesel engines is required in order to have a cleaner environment. Urea-SCR (selective catalytic reduction of NOx by urea) after-treatment system is considered as one of the most efficient techniques available to reduce engine-out NOx emissions sufficiently. Conclusion: This review article discusses all the methods suggested to diminish nitrogen oxides emissions and then presents a comprehensive survey on developing urea-SCR unit -whether from catalyst development aspect or from injection system modification point of view- in diesel engines to meet strict emissions regulations.

Experimental investigation of the distinct effects of nanoparticles addition and urea-SCR after-treatment system on NOx emissions in a blended-biodiesel fueled internal combustion engine

The present study reports an investigation about the distinct effects of nanoparticles addition and urea-SCR system on NOx emissions. Also nano-additives influence on pollutants (NOx and CO) reduction performance of a urea-SCR system is investigated. B20 blended biodiesel which contains of 20% waste frying oil biodiesel and 80% diesel has been used as the base fuel in this work. Manganese oxide and cobalt oxide nanoparticles with the mass fractions of 25 and 50 ppm were dispersed in the base fuel as nano-fuel additives. The findings showed that both studied nano-additives reduce NOx emissions. However, the reduction level is lower compared to urea-SCR system. As well as, the results revealed that the pollutants reduction efficiency of the urea-SCR system was appreciably enhanced due to nanoparticles addition.

Measurement of diesel exhaust fluid concentration in urea-SCR after-treatment system

In an effort to meet the established emission standards Selective Catalytic Reduction (SCR) is used to reduce NOx emissions with diesel exhaust fluid (DEF) as additive in the exhaust of diesel engines. ISO 22241-1:2006 specifies the quality characteristics of DEF in order to maintain efficiency and hence, it is essential that the concentration of urea in DEF is accurately monitored. In this paper, a measurement system is designed, developed and tested for measuring the concentration of urea in DEF. The design involves piezoelectric ultrasound transmitter and receiver with associated electronics operating at a frequency of 4 MHz. The concentration of urea in DEF is measured (i) by measuring the time of flight of ultrasound waves between transmitter and receiver (ii) by measuring the amplitude of received signal in terms of frequency using voltage-to-frequency converter. The measurement system is modeled using two-port network model for piezoelectric transmitter/receiver and transmission line model for DEF medium. The prototype of measurement system is fabricated with all associated electronics and tested for variation in concentration of urea in DEF. The results from prototype are in close agreement with the results obtained from analytical model. The measurement system is tested for repeatability and sensitivity to temperature.

LPG 증기보일러의 배기 배출물에 미치는 요소-SCR 후처리 시스템의 영향에 관한 연구

The aim of this study is to investigate the effect of SCR reactor on the exhaust emissions characteristics in order to develop a urea-SCR aftertreatment system for reducing <TEX>$NO_x$</TEX> emissions. The experiments are conducted by using a flue tube LPG steam boiler with the urea-SCR aftertreatment system. The urea-SCR aftertreatment system utilizes the ammonia converted from 17% aqueous urea solution injected in front of SCR catalyst as a reducing agent for reducing <TEX>$NO_x$</TEX> emissions. The equivalence ratio, urea injection amount, ammonia slip and <TEX>$NO_x$</TEX> conversion efficiency relative to boiler load are applied to discuss the experimental results. In this experiment, the average equivalence ratio is calculated by changing only the fuel consumption rate while the intake air amount is constantly fixed at <TEX>$25,957.11cm^3/sec$</TEX>. The average equivalence ratios are 1.38, 1.11, 0.81 and 0.57 when boiler loads are 100, 80, 60 and 40%. The <TEX>$NO_x$</TEX> conversion efficiency is raised with increasing urea injection amount, and <TEX>$NH_3$</TEX> slip is also boosted at the same time. Consequently, the <TEX>$NO_x$</TEX> conversion efficiency relative to boiler load should be examined in combination with urea injection amount and <TEX>$NH_3$</TEX> slip. The results are calculated by 89, 85, 77 and 79% for the boiler loads of 100, 80, 60 and 40%. The appropriate amount of urea injection for the respective boiler load can be not discussed by only <TEX>$NO_x$</TEX> emissions, and should be determined by considering the <TEX>$NO_x$</TEX> conversion efficiency, <TEX>$NH_3$</TEX> slip and reactive activation temperature simultaneously. In this study, the urea amounts of 230, 235, 233 and 231 mg/min are injected at the boiler loads of 100, 80, 60 and 40%, and the final <TEX>$NH_3$</TEX> slips are measured by 8.48, 5.58, 11.97 and 11.34 ppm at the same conditions. THC emission is affected by the SCR reactor under other experimental conditions except 100% engine load, and CO emission at only 40% engine load. The rest of exhaust emissions are not affected by the SCR reactor under all experimental conditions.

Demonstration and evaluation of a retrofit urea-SCR after-treatment system for NOx reduction in marine diesels

A stand-alone retrofit urea-SCR after-treatment system has been developed employing a pre-SCR NOx sensor, exhaust flow measurement, wire mesh mixer, clean-up catalyst, open-loop feed-forward control and stoichiometric NOx reduction logic. Demonstration of the urea-SCR system on a 1991 Detroit Diesel Corporation 12L engine in a West Virginia University (WVU) transient test cell achieved a 50% weighted NOx reduction and zero ammonia slip over the ICOMIA E5 marine cycle. The cost-effectiveness of the urea-SCR system was determined, including a $50 000 capital cost and $2705/t NOx reduced annually, which is consistent with Carl Moyer program estimates.

Model-based control system design in a urea-SCR aftertreatment system based on NH3 sensor feedback

This paper presents preliminary control system simulation results in a urea-selective catalytic reduction (SCR) aftertreatment system based on NH3 sensor feedback. A four-state control-oriented lumped parameter model is used to analyze the controllability and observability properties of the urea-SCR plant. A model-based estimator is designed via simulation and a control system is developed with design based on a sliding mode control framework. The control system based on NH3 sensor feedback is analyzed via simulation by comparing it to a control system developed based on NOx sensor feedback. Simulation results show that the NH3 sensor-based strategy performs very similarly in comparison to a NOx sensor-based strategy. The control system performance metrics for NOx index, urea index, urea usage, and NH3 slip suggest that the NOx sensor can be a potential alternative to a NOx sensor for urea-SCR control applications.