LIME KILNS

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Temperature Distribution in a Lime Kiln Oxygen Distribution Effect of Excess Air and Burner Angle in a Lime Kiln
The function of the lime kiln is to convert CaCO3 back into CaO for reuse in the causticizing process. The lime kiln involves complicated processes, including flow, heat and mass transfer, combustion of fuel, drying of lime mud, and calcining of CaCO3. It is important to understand these processes to optimise the operation of the lime kiln, diagnose operational problems, improve energy consumption, increase production, lower emissions, increase refractory life, and reduce instabilities.

Process Model

The UBC modelling group in collaboration with PSL is currently working to complete a 3-D steady-state computational model to predict the flow and heat transfer in a lime kiln for application in the cement and pulp and paper industries. The model uses block-structure body-fitted coordinates with domain segmentation, models combustion and radiation, and incorporates the modelling of the non-Newtonian lime mud. Currently, the model includes radiation, combustion of natural gas and oil, buoyancy effects, and features complex geometry capability. Separate equations are solved for O2, N2, H2, CO, CO2, H2O and CH4. Previous applications include modelling the flow, heat transfer, and combustion in the lime kiln, and to analyze the influence on the flame of secondary flows from the hood and the primary air from the burner.

Issues Addressed by PSL

Advantage and Benefits

Model Predictions

Gas flow velocity fields Temperature distributions and heat transfer to wall surfaces and mud Gas species (H2, O2, N2, CO, CO2, H2O, CH4) distributions Pollutant emissions (NOx) Oil or solid fuel combustion and droplet trajectory.