Numerical Simulation of Rice Husk as an Alternative Fuel in a Precalciner

To tackle the issues of high energy consumption, substantial carbon emission intensity in the cement industry, as well as under-utilization of agricultural waste, this study took an 8000 t/d cement production line at a plant in Indonesia as the research object. Using a Computational Fluid Dynamics (CFD)-based numerical method, the co-firing of pulverized coal with rice husk was simulated in both In-Line Calciner (ILC) and Separate-Line Calciner (SLC) precalciners. Four rice husk replacement levels (10%, 20%, 30%, and 40%) were evaluated in terms of temperature distribution, species concentration, raw meal calcination, and pollutant formation. The results indicate that increasing the rice husk ratio reduces the high-temperature region, lowers the peak temperature, and decreases overall thermal levels. The decomposition rate of CaCO3 at the outlet of the ILC-type precalciner decreased from 81.11% to 75.32%, while that of the SLC-type precalciner fell from 93.27% to 88.50%. CO2 and NOX emissions were remarkably reduced, with the emission reduction effect positively correlated with the rice husk substitution ratio. Taking into account both decomposition rate requirements and emission reduction targets, it is recommended that the blending ratio of rice husk in ILC precalciners should be controlled at 10%, while for SLC precalciners, it can be increased to 40%. This provides a technical reference for low-carbon transformation and biomass resource utilization in the cement industry.