A Cement Rotary Kiln CFD simulation is a powerful computer model that allows engineers to see inside the heart of the cement-making process. These massive, rotating kilns are where raw materials are heated to extreme temperatures to create “clinker,” the main ingredient in cement. A Cement Rotary Kiln Simulation using ANSYS Fluent is essential because it can predict the complex interactions between the burning fuel, hot gases, and the solid particles.

This report details a Cement Rotary Kiln fluent analysis that uses two key modules. The Cement Rotary Kiln DPM fluent model (Discrete Phase Model) is used to track the path and temperature of every single raw material particle. At the same time, the Species Transport model is used to simulate the chemical reactions of the combustion process. By combining these, the simulation provides a complete picture of heat transfer and particle behavior. This allows designers and manufacturers to optimize fuel efficiency, control product quality, and reduce emissions without costly and difficult physical experiments. For more in-depth tutorials and simulations related to DPM, explore our resources at: https://cfdland.com/product-category/module/dpm-cfd-simulation/

• Reference [1]: Fardadi, Malahat. Modeling Dust Formation in Lime Kilns. University of Toronto (Canada), 2010.

Figure 1: A schematic of the Cement Rotary Kiln geometry

Simulation Process: Fluent-CFD Setup, A Coupled DPM, Species Transport, and Radiation Model

The simulation process for this Cement Rotary Kiln CFD analysis began with the cylindrical kiln geometry. Using ANSYS Fluent Meshing, a high-quality polyhedral mesh was created. This type of mesh is excellent for complex geometries and helps the solver to be both fast and accurate. Inside ANSYS Fluent, the physics was set up to model the real-world process as closely as possible. The Discrete Phase Model (DPM) was activated in a two-way coupled manner. The raw material particles (calcium carbonate) were injected from the feed end on the right. The Species Transport model was also enabled to simulate the combustion of the methane fuel with air, calculating the chemical reaction and the resulting heat release. Finally, because the flame is extremely hot, the P1 Radiation model was included. This is critical because, at these high temperatures, thermal radiation is a dominant mode of heat transfer inside the kiln.

Figure 2: The high-quality polyhedral mesh generated in Fluent Meshing for the rotary kiln CFD model.

Post-processing: CFD Analysis of Heat Transfer and Particle Journey

The simulation results are showing a clear cause-and-effect relationship between the burner’s flame and the heating of the raw material particles. The analysis starts with the source of all the energy: the flame. The gas temperature contour in Figure 4 shows the result of the methane combustion. An intense flame is clearly visible near the burner on the left, reaching a peak temperature of 1860K. This creates a powerful temperature gradient that drives the entire process, with the temperature gradually decreasing down the length of the kiln to 300K at the material inlet. This hot gas environment is what heats the solid particles. The DPM results in Figure 3 allow us to track the exact journey of these particles. We can see that the particles travel from the right inlet to the left outlet, and the color shows how long they have been inside the kiln. The simulation calculates a maximum residence time of 36.51 seconds. This is a critical design parameter because it tells us how long the material is exposed to the heat.

Figure 3: Particle residence time distribution colored by duration (0-36.51 seconds) showing material flow path and retention time through the rotary kiln from inlet to outlet.

Figure 4: Longitudinal static temperature contour in the cement rotary kiln displaying the flame region (1860K peak) and thermal gradient from methane combustion zone to material feed end (300K).

Figure 5: Particle temperature distribution colored by thermal state (299.93-803.28K) tracking solid material heating as particles travel through combustion zones in the rotating kiln CFD simulation.

The particle temperature contour in Figure 5 shows the direct result of this 36-second journey. The particles enter the kiln cold, at a temperature of 299.93K. As they travel through the hot gas, they absorb energy. The contour visualizes this heating process, with the particles turning green, yellow, and finally orange and red as their temperature rises to a maximum of 803.28K near the hot burner end. From an engineering viewpoint, this temperature rise is the entire purpose of the kiln. The simulation data confirms that the average outlet temperature of the material is 489.9K, proving that heat from the 1860K flame has been successfully transferred to the solid material bed.

The most important achievement of this simulation is the successful and quantitative linking of the combustion heat release to the particle’s thermal history. It provides a direct, visual connection between the flame, the particle residence time, and the final material temperature.

For a designer or manufacturer, this data is invaluable. It provides the kiln to:

1. Optimize Fuel Efficiency: The simulation shows the particles reach 803K. If the chemical process (calcination) only requires 750K, the manufacturer can use this model to test reducing the methane fuel flow, thereby saving significant energy and cost while still meeting the quality target.
2. Control Product Quality: The residence time of 36.51 seconds is now a known value. If the final clinker quality is poor, engineers can use this simulation to test if increasing the residence time (by slowing the kiln’s rotation) allows the particles to “cook” for longer and reach the required chemical conversion.
3. Prevent Damage: The gas temperature contour identifies the hottest part of the kiln (1860K). This information is given to mechanical engineers to ensure they use the correct heat-resistant refractory bricks in that specific area to prevent damage and extend the life of the kiln.