Effects of Selective Catalytic Reduction on the Emissions of Persistent Organic Pollutants from a Heavy-Duty Diesel Engine

The effects of a zeolite urea-selective catalytic reduction aftertreatment system on a comprehensive spectrum of chemical species from diesel engine emissions were investigated in the present study. Representative samples were collected with a newly developed source dilution sampling system after an aging process designed to simulate atmospheric dilution and cooling conditions. Samples were analyzed with established procedures and compared between the measurements taken from a baseline heavy-duty diesel engine and also from the same engine equipped with the exhaust aftertreatment system. The results have shown significant reductions for nitrogen oxides, carbon monoxide, total hydrocarbons, polycyclic aromatic hydrocarbons, and organic carbon emissions. Additionally, less significant yet notable reductions were observed for particulate matter mass and metals emissions. Although two ionic compounds, sulfate and nitrate, displayed increased emission levels, the production of new species was not observed with the addition of the zeolite urea-selective catalytic reduction system joined with a downstream oxidation catalyst.

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Investigation of Urea Uniformity with Different Types of Urea Injectors in an SCR System

Catalysts ◽

10.3390/catal10111269 ◽

2020 ◽

Vol 10 (11) ◽

pp. 1269

Author(s):

Muhammad Khristamto Aditya Wardana ◽

Kwangchul Oh ◽

Ocktaeck Lim

Keyword(s):

Diesel Engine ◽

Catalytic Reduction ◽

Nox Reduction ◽

Heavy Duty ◽

Ammonia Gas ◽

Experimental Parameters ◽

Heavy Duty Diesel Engine ◽

Heavy Duty Diesel ◽

Scr System

Heavy-duty diesel engines in highway use account for more than 40% of total particulate and nitrogen oxide (NOx) emissions around the world. Selective catalytic reduction (SCR) is a method with effective results to reduce this problem. This research deals with problems in the urea evaporation process and ammonia gas distribution in an SCR system. The studied system used two types of urea injectors to elucidate the quality of ammonia uniformity in the SCR system, and a 12,000-cc heavy-duty diesel engine was used for experimentation to reduce NOx in the system. The uniformity of the generated quantities of ammonia was sampled at the catalyst inlet using a gas sensor. The ammonia samples from the two types of urea injectors were compared in experimental and simulation results, where the simulation conditions were based on experimental parameters and were performed using the commercial CFD (computational fluid dynamics) code of STAR-CCM+. This study produces temperatures of 371 to 374 °C to assist the vaporization phenomena of two injectors, the gas pattern informs the distributions of ammonia in the system, and the high ammonia quantity from the I-type urea injector and high quality of ammonia uniformity from the L-type urea injector can produce different results for NOx reduction efficiency quality after the catalyst process. The investigations showed the performance of two types of injectors and catalysts in the SCR system in a heavy-duty diesel engine.

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Urea injection control strategy in urea-selective catalytic reduction for heavy-duty diesel engine under transient process

International Journal of Engine Research ◽

10.1177/1468087419860633 ◽

2019 ◽

pp. 146808741986063

Author(s):

Binyang Wu ◽

Longfei Deng ◽

Yize Liu ◽

Dezeng Sun ◽

Wanhua Su

Keyword(s):

Selective Catalytic Reduction ◽

Transient Process ◽

Catalytic Reduction ◽

Heavy Duty ◽

Ammonia Slip ◽

Ammonia Storage ◽

Heavy Duty Diesel Engine ◽

Injection Control ◽

Storage Area ◽

Heavy Duty Diesel

A urea injection control strategy for urea-selective catalytic reduction under a transient process is investigated on a heavy-duty diesel engine test bench in this study. The aim is to improve NO x conversion efficiency and reduce ammonia slip. With the selective catalytic reduction system as the research object, an open thermodynamic conservation system is established. The conservation relationship in the process of urea injection, NO x reduction reaction, ammonia storage, and ammonia slip is investigated. The ideal target ammonia storage area and the ammonia storage characteristics during the transient process are studied. The ammonia storage area and boundary, which change with the transient temperature, are established. Correction of real-time ammonia injection is further deduced from the boundary of the area. The world harmonized transient cycle test cycle result showed that compared to feed-forward control, the NO x conversion efficiency increased by 16% and the NH3 slip decreased by 75% when using the proposed real-time ammonia storage-management control method.

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