Date of Award

2016

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Mechanical Engineering (MS)

Administrative Home Department

Department of Mechanical Engineering-Engineering Mechanics

Advisor 1

Jeffrey Naber

Advisor 2

John Johnson

Committee Member 1

David Shonnard

Abstract

Abstract The heavy-duty diesel (HDD) engines use the diesel oxidation catalyst (DOC), catalyzed particulate filter (CPF) and urea injection based selective catalytic reduction (SCR) systems in sequential combination, to meet the US EPA 2010 PM and NOₓ emission standards. The SCR along with a NH₃ slip control catalyst (AMOX) offer NOₓ reduction >90 % with NH₃ slipHowever, there is a strong desire to further improve the NOₓ reduction performance of such systems, to meet the California Optional Low NOₓ Standard implemented since 2015. Integrating SCR functionality into a diesel particulate filter (DPF), by coating the SCR catalyst on the DPF, offers potential to reduce the system cost and packaging weight/ volume. It also provides opportunity to increases the SCR volume without affecting the overall packaging, to achieve NOₓ reduction efficiencies >95 %. xvii In this research, the NOₓ reduction and NH₃ storage performance of a Cu-zeolite SCR and Cu-zeolite SCR catalyst on DPF (SCRF®) were experimentally investigated based on the engine experimental data at steady state conditions. The experimental data for the production-2013-SCR and the SCRF® were collected (with and without PM loading in the SCRF®) on a Cummins ISB 2013 engine, at varying inlet temperatures, space velocities, inlet NOₓ concentrations and NO₂/NOₓ ratios, to evaluate the NOₓ reduction, NH₃ storage and NH₃ slip characteristics of the SCR catalyst. The SCRF® was loaded with 2 and 4 g/L of PM prior to the NOₓ reduction tests to study the effect of PM loading on the NOₓ reduction and NH₃ storage performance of the SCRF®. The experimental setup and test procedures for evaluation of NOₓ reduction performance of the SCRF®, with and without PM loading in the SCRF® are described. The 1-D SCR model developed at MTU was calibrated to the engine experimental data obtained from the seven NOₓ reduction tests conducted with the production-2013-SCR. The performance of the 1-D SCR model was validated by comparing the simulation and experimental data for NO, NO₂ and NH₃ concentrations at the outlet of the SCR. The NO and NO₂ concentrations were calibrated to ±20 ppm and NH₃ was calibrated to ±20 ppm. The experimental results for the production-2013-SCR indicate that the NOₓ reduction of 80 – 85% can be achieved for the inlet temperatures below 250°C and above 450°C and NOₓ reduction of 90 – 95% can be achieved for the inlet temperatures between 300 – 350°C, at ammonia to NOₓ ratio (ANR) 1.0, while the NH₃ slip out of the SCR wasConversely, the SCRF® showed 90 – 95 % NOₓ reduction at ANR of 1.0, while the NH₃ slip out of the SCRF® was >50 ppm, with and without PM loading in the SCRF®, for the inlet temperature range of 200 – 450 °C, space velocity in the range of 13 to 48 k/hr and inlet NO₂/NOₓ in the range of 0.2 to 0.5. The NOₓ reduction in the SCRF® increases to >98 % at ANR 1.2. However, the NH₃ slip out of the SCRF® increases significantly at ANR 1.2. xviii The effect of PM loading at 2 and 4 g/L on the NOₓ reduction performance of the SCRF® was negligible below 300 °C. However, with PM loading in the SCRF®, the NOₓ reduction decreased by 3 – 5% when compared to the clean SCRF®, for inlet temperature >350 °C. Experimental data were also collected by reference [1] to investigate the NO₂ assisted PM oxidation in the SCRF® for the inlet temperature range of 260 – 370 °C, with and without urea injection and thermal oxidation of PM in the SCRF® for the inlet temperature range of 500 – 600 °C, without urea injection by reference [1]. The experimental data obtained from this study and [1] will be used to develop and calibrate the SCR-F model at Michigan Tech. The NH₃ storage for the production-2013-SCR and the SCRF® (with and without PM loading) were determined from the steady state engine experimental data. The NH₃ storage for the production-2013-SCR and the SCRF® (without PM loading) were within ±5 gmol/m3 of the substrate, with maximum NH₃ storage of 75 – 80 gmol/m3 of the substrate, at the SCR/SCRF® inlet temperature of 200°C. The NH₃ storage in the SCRF®, with 2 g/L PM loading, decreased by 30%, when compared to the NH₃ storage in the SCRF®, without PM loading. The further increase in the PM loading in the SCRF®, from 2 to 4 g/L, had negligible effect on NH₃ storage.

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