Numerical analysis of ammonia homogenization for selective catalytic reduction application

Area of Science:

• Chemical Engineering
• Environmental Science
• Automotive Engineering

Background:

• Selective Catalytic Reduction (SCR) using urea water solution is vital for NOx abatement in mobile diesel engines.
• The SCR process involves urea injection, thermolysis into ammonia, and NOx reduction over a catalyst.
• Optimizing ammonia uniformity and minimizing ammonia slip are critical design challenges.

Purpose of the Study:

• To demonstrate a developed mathematical framework for simulating the SCR process.
• To analyze ammonia generation, NOx reduction, and ammonia slip in a real SCR reactor.
• To investigate the impact of injection direction and droplet size on SCR performance.

Main Methods:

• Implementation of a mathematical framework in AVL FIRE® CFD software.
• Simulation of physical processes including urea droplet heating, evaporation, and thermolysis.
• 3D modeling of a real SCR reactor to predict key performance indicators.

Main Results:

• The study highlights the significant influence of droplet size on SCR process efficiency.
• Counterflow injection of urea was found to be beneficial for minimizing ammonia slip.
• The CFD model successfully predicted ammonia generation, NOx reduction, and ammonia slip.

Conclusions:

• Droplet size is a critical parameter for optimizing SCR systems.
• Counterflow injection strategies enhance SCR performance by reducing environmental ammonia release.
• The developed CFD framework provides a valuable tool for designing efficient deNOx systems.