A mathematical model of a twin-shaft parallel flow regenerative lime kiln

ABSTRACT

Lime is an important flux used in the iron and steel-making processes. Tata Steel Jamshedpur uses a twin-shaft Parallel Flow Regenerative type kiln to calcine limestone. Previously, the kiln was operated based on the temperature measurement at only three locations. This led to suboptimal kiln performance and difficulty in maintaining lime quality. A thermal digital twin was developed using first principles to address these issues. A set of unsteady-state partial-differential equations representing the thermophysical phenomena is solved numerically using the finite volume method. The model was validated with the measured flue gas temperature and lime temperatures. The model is implemented online with the real-time operating parameters to estimate the temperature profile of solid and gas and the degree of conversion of limestone. This real-time visibility enables the operators to optimize the process and achieve lime conversion up to 94%, resulting in energy savings of 31.8 GJ/day and stable lime quality.

KEYWORDS:

• Steel-making
• lime kiln
• twin shaft parallel flow regenerative (PFR) lime kiln
• lime calcination
• thermal digital twin
• numerical simulation
• heat transfer model
• lime dissociation

Acknowledgements

The authors hereby express their gratitude to the software support team for their involvement in the development of the visualisation tool. Assistance provided by the lime plant operation team is also greatly appreciated. Authors are also thankful to the Tata Steel Management for allowing the authors to publish the work.

Disclosure statement

No potential conflict of interest was reported by the author(s).