Simulating rotary calciners using new Rocky DEM heat transfer models

Heat transfer in particulate materials is a key phenomenon in a variety of industrial applications. Very often material is handled and stored in granular form and is need to be heated or cooled for a given process.

Rotary calciners are a common mixing device in metallurgical and catalyst industries. In general lines, they are long rotating drums with or without internal baffles. Their walls are heated and then the particles within them are heated and dried due to the heat transferred by conduction between the walls and the particles.

Since Rocky DEM software explicitly considers inter-particle and particle-to-boundary interactions, and with the latest 3.10 release now includes heat exchange, Rocky is a useful tool for studying heat transfer in granular materials in rotary calciners, helping engineers to design and optimize these equipments.

In the videos below, the particles and vessel temperatures are initially at 298K. Then, the curved wall is quickly heated up to 1298K and the evolution of the particles’ temperature is monitored over time. In the first video, the drum does not rotate while in the second video, the drum rotates at 30 RPM.


Video1 – Heat conduction within a stationary drum


Video 2 – Heat conduction within a rotating drum

Videos 1 and 2 show the influence of the drum speed on the averaged bed temperature, demonstrating that higher speed vessels lead to faster thermal uniformity.

Temperature evolution for different roational speeds

                 Figure 1 – Temperature evolution for different rotational speeds

 

The graph in Figure 1 shows that higher speed rotations results in higher average bed temperatures.

Drum views in Rocky showing how roational speed affects particle temperature over time

          Figure 2 – Drum views in Rocky showing how rotational speed affects particle temperature over time

 

The drum view matrix in Figure 2 demonstrates that regions with cold particles (dark blue) shrink faster for higher speed drums.

Using Rocky, the DEM evaluation of different geometries and operating conditions can be made quickly. Moreover, the Rocky-Fluent coupling capabilities now enables—in Rocky DEM release 3.10—users to account for the heat transfer between fluids and particles, enlarging the range of processes that can be modeled using DEM.

In an upcoming post, Rocky DEM coupling with ANSYS CFD will be presented.

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