Session: 3.2 - Computational Turbulent Combustion

Paper Number: 158133

158133 - Computational Fluid Dynamics Modeling of Turbulent Combustion and Heat Transfer in Cement Rotary Kilns 

Abstract: 

Cement manufacturing is one of the most carbon and energy-intensive industries in the world. Emissions from cement production come mostly from the calcination of limestone with the remaining resulting from the fossil fuel combustion required to reach the temperature required for the clinker production. Cement kilns operate at high temperatures to convert raw materials into cement clinker. The process consumes a large amount of fuel and generates substantial emissions, resulting in a negative impact on the environment. It is important to investigate the high-temperature process that happens inside the cement rotary kiln. Understanding the turbulent combustion and heat transfer processes inside the cement rotary kiln is essential for improving energy efficiency and reducing pollution, particularly NO_x and CO, which are major contributors to climate change and air quality degradation. Conducting physical tests to investigate the high-temperature process inside the cement rotary kiln under various scenarios requires substantial energy resources, time, and labor. To address the challenge, computational fluid dynamics (CFD) offers a robust and efficient alternative for analyzing the complex high-temperature combustion process. The CFD model provides the capability to consider various parameters including the operational conditions of the cement kiln without the need of extensive experimental trial and error. In this paper, we develop a three-dimensional (3D) CFD model of turbulent combustion to simulate the high-temperature process inside the cement rotary kiln using Ansys Fluent 2024 R1. We utilize the Realizable k-epsilon (k-) turbulence model to characterize turbulent flow, and the eddy-dissipation combustion model (EDM) to model the combustion process. The temperature distribution and energy flux profiles will be generated from the turbulent combustion model. A parametric study is performed to investigate the effect of key operational parameters, including the air-to-fuel ratio, air preheating temperature, and kiln rotation speed, on critical performance metrics such as temperature profiles, combustion efficiency, and pollutant emissions. The interaction between heat transfer mechanisms and operational condition parameters is analyzed to understand their combined impact on energy consumption and pollutant reduction. Additionally, this paper further explores the relationship between turbulent mixing intensity and pollutant formation to identify optimal operational strategies for reducing emissions without compromising thermal efficiency. The utilization of the presented method also allows for the assessment of heat recovery potential within the kiln system, providing additional insights into energy conservation processes and supporting the development of innovative, sustainable kiln designs. This research contributes to the understanding of rotary kiln operations and provides sustainable strategies for low-carbon, low-energy, and low-cost cement manufacturing practices, aligning with the net zero emissions goal by 2050 in the cement industry.

Presenting Author: Rongze Hu Purdue University

Presenting Author Biography: Rongze is a Ph.D. student in the School of Construction Management Technology at Purdue University. She received her master's degree in Power Engineering and Engineering Thermophysics from Tongji University. Her research is on thermodynamics and energy modeling.