• 281-282-9200
  • This email address is being protected from spambots. You need JavaScript enabled to view it.

Calciner conjugate heat transfer 191118

When You Can’t Tell How Hot It Is

Lime production relies on a continuous smooth operation of the calciners. Calciners are basically massive cylindrical furnaces divided into multiple hearths. Insulation and thermal performance of the calciner is a key component of their successful operation. Having a CFD examination of what is happening inside the calciner helps to determine local fluid and solid temperatures that otherwise cannot be measured.

Conjugate Heat Transfer inside a Calciner

KHE was contracted to investigate the root cause of a refractory roof collapse inside a calciner. It was suspected that the recent increase in product throughput had caused over heating in the refractory bricks. However, thermal measurements inside the calciner were not feasible, and the complex physics governing the problem prevented us from doing accurate hand calcs. KHE quickly developed a CFD model of the collapsed hearth, capturing the interaction of combustion, convection, radiation and buoyancy effects. Accurate brick temperature distributions were obtained through coupling the solid and fluid heat transfer solutions. This Conjugate Heat Transfer approach finds the local maximum temperature, whereas the uncoupled FEA heat transfer predictions are highly sensitive to the assumptions made by the analyst (these assumptions are often too many, and average global rather than maximum local).
A sensitivity analysis can further help to pin down the problematic conditions. Once a CFD model is set up, tweaking parameters such as the process gas flow rate or air-fuel-ratio gives a clear picture of the brick temperature sensitivity to any of these parameters. In this case, the thermal gradients across the roof were excessive and the burner flame caused overheating. Both problems can be solved either by switching to a more conductive and reflective refractory material to retain less heat while maintaining the same product throughput, or by reducing the gas injection rate, which the temperature has the most sensitivity to.

Specialists in Design, Failure Analysis and Troubleshooting of Static and Rotating Equipment


  • Failure Investigation
  • Field Service
  • Rotordynamics
  • Rotating Equipment Analysis
  • Vibration Analysis
  • Computational Fluid Dynamics (CFD)
  • Finite Element Analysis (FEA)
  • Acoustic Analysis
  • Stress Analysis
  • Metallurgical and Metrology Lab
  • Fit for Service Analysis
  • Expert Witness