Numerical simulation of low nitrogen oxides emissions through cement precalciner structure and parameter...

Area of Science:

• Combustion Engineering
• Environmental Engineering
• Chemical Engineering

Background:

• Nitrogen oxides (NOx) are major air pollutants contributing to environmental issues.
• Controlling NOx emissions from industrial combustion processes, like those in precalciners, is crucial.

Purpose of the Study:

• To optimize the structure and operational parameters of a 4500 t/d precalciner to minimize NOx emissions.
• To investigate the impact of raw material angle, tertiary air velocity, and temperature on NOx formation.

Main Methods:

• Utilized ANSYS FLUENT software (v14.5) to establish a precalciner model.
• Employed Box-Behnken design (BBD) and response surface methodology (RSM) to analyze parameter effects.
• Developed a two-order response model to predict NOx concentration.

Main Results:

• Simulated NOx concentration at the outlet was 526 ppm, with an acceptable error compared to monitoring data (496 ppm).
• Raw material angle significantly influenced NOx generation location and rate.
• Increased tertiary air velocity (22 to 38 m/s) raised NOx from 124 to 220 ppm.
• NOx peaked at 211 ppm when temperature reached 1123 K.
• Significant interactions were found between parameters (P < 0.05), except for tertiary air velocity and temperature.

Conclusions:

• A new response surface model accurately predicts NOx concentration.
• Optimal conditions for low NOx combustion were identified: 70° raw material angle, 26 m/s tertiary air velocity, and 1280 K tertiary air temperature.