CEMENT KILNS

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Temperature Distribution in a Kiln Oxygen Distribution Effect of Excess Air and Burner Angle in a Kiln
The function of the kiln in the cement industry is to first convert CaCO3 into CaO and then react Silica, Aluminum Oxide, Ferric Oxide, and Calcium Oxide with the free lime to form clinker compounds: C3S, C2S, C3A, and C4AF. The cement kiln uses higher temperatures to form the clinker. The process involves gas, liquid and solid flows with heat and mass transfer, combustion of fuel, reactions of clinker compounds and undesired chemical reactions that include sulphur, chlorine, and Alkalies. It is important to understand these processes to optimize the operation of the cement kiln, diagnose operational problems, increase production, improve energy consumption, lower emissions, and increase refractory life.

Process Model

PSL has developed a 3-D coupled computational model to predict the flow and heat transfer in cement kilns. The model is being extended to include the pre-calciner. The model uses block-structure body-fitted coordinates with domain segmentation, models combustion and radiation, and incorporates the modelling of the reactions occurring in the feed. The model includes radiation, combustion of coke and coal, buoyancy effects, and features complex geometry capability. Separate equations are solved for O2, N2, H2, CO, CO2, H2O CH4, HCN, NOx, and NH3.

Issues Addressed by PSL

Advantage and Benefits

Model Predictions

Gas flow velocity fields, temperature distributions, heat transfer to wall surfaces and feed, gas species (H2, O2, N2, CO, CO2, H2O, CH4, HCN, NOx, NH3) distributions, pollutant emissions, and droplet trajectory in the cooler, kiln hood, and kiln barrel.