Doctoral Dissertations

Keywords and Phrases

After-Treatment System; Diesel Engine; NOx Emissions; Selective Catalytic Reduction; Urea Decomposition; Urea Deposits


“Urea-selective catalytic reduction (SCR) system has proved to be an effective solution to reduce NOx emissions in commercial vehicle (CV) diesel engines. A significant challenge in urea injection is to comprehend its decomposition chemistry that leads to formation of undesired deposits in the exhaust system unit. Due to complex interaction of multi-phase fluid flow and transport processes, significant uncertainty is associated with the identification of interacting factors that control the deposit initiation and its growth. To meet the future ultra-low NOx emissions and to deliver ammonia without deposit formation, there is an imminent need to develop the urea-SCR technology.

The overall objective is to guide new product development and design a better exhaust mixer that would minimize deposits.

A systematic investigation into the mechanism of deposit formation was conducted through numerous experiments and deposits were characterized to measure their chemical composition. Effect of pressure on urea deposits was investigated for the first time by heating aqueous urea solution in a closed system maintained between 30-200psia. The deposit forming temperatures and phase change compositions were identified in both open and closed system. Based on this understanding, deposit test was conducted on a hot gas test setup with a typical after-treatment system layout. Deposit initiating temperatures were identified, and the effect of gas flow rate was studied. The chemical characterization procedure was carried out using different analytical techniques such as thermogravimetric analysis (TGA), electrospray ionization (ESI) and liquid chromatography (LC)”--Abstract, page iii.


Smith, Joseph D.

Committee Member(s)

Rownaghi, Ali A.
Mooney, Brian
Ludlow, Douglas K.
Dogan, Fatih


Chemical and Biochemical Engineering

Degree Name

Ph. D. in Chemical Engineering


The author is grateful to Faurecia Clean Mobility for funding his research.


Missouri University of Science and Technology

Publication Date

Fall 2020


xiv, 113 pages

Note about bibliography

Includes bibliographic references (pages 106-112).


© 2020 Anand Alembath, All rights reserved.

Document Type

Dissertation - Open Access

File Type




Thesis Number

T 11994