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Published on: January 16, 2011
Layer-by-Layer Crystallization Phenomena in Urea Solution: An Experimental Study
Liwei Mao1, Jialong Jiang1, Bingqi Tian2
1School of Mechanical Engineering, Shanghai Dianji University, shanghai 201306, China.
ACS Omega
|August 1, 2026
Summary
Urea deposits in heavy-duty diesel Selective Catalytic Reduction (SCR) systems form complex multilayer structures. A new method reveals these real-world urea crystals have different thermal properties and microstructures than lab samples.
Area of Science:
- Chemical Engineering
- Materials Science
- Environmental Science
Background:
- Urea deposits in heavy-duty diesel engine Selective Catalytic Reduction (SCR) systems exhibit complex structures under real operating conditions.
- Conventional laboratory methods fail to accurately replicate the morphology, composition, and structure of these stubborn deposits.
Purpose of the Study:
- To develop and utilize a novel multilayer liquid-film heating crystallization method.
- To investigate the fundamental differences between urea crystallization on pre-existing crystal layers versus static single-layer crystallization.
Main Methods:
- A multilayer liquid-film heating crystallization method was employed.
- Analysis of single-layer and multilayer urea crystals using thermogravimetric analysis (TGA), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM).
Main Results:
- Multilayer crystallization impedes heat transfer, favoring lower-temperature crystal components.
- Multilayer urea crystals exhibit higher thermal decomposition temperatures and greater crystal mass compared to single-layer crystals of equivalent thickness.
- Multilayer crystallization promotes ordered microstructures with cleaner surfaces due to secondary deposition and thermal history.
Conclusions:
- The proposed multilayer method better simulates real-world urea deposit formation in SCR systems.
- Understanding these crystallization differences is crucial for optimizing SCR system performance and preventing deposit-related issues.
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