Simulation on coal combustion and calcium carbonate decomposition in a 5500 t/d full scale cement calciner

With the continuous growth of global cement production, the increasing coal consumption in the cement industry has been drawing great attention, thus adopting advanced technologies to reduce energy consumption has become an important issue. To address this problem, this study carried out 3D Eulerian-Lagrangian simulations of the coupling process of pulverized coal combustion and CaCO3 decomposition in a 5500 t/d full-scale cement calciner. On the basis of the multiphase particle-in-cell (MP-PIC) approach, reaction models including devolatilization, combustion of char and volatiles, and CaCO3 decomposition are incorporated into the scheme. Detailed combustion characteristics including temperature distribution, carbon exhaust rate, and gas emission characteristics, as well as decomposition characteristics are comprehensively analyzed. Besides, effects of different operating performances including O2 content in bottom flue gas on carbon exhaust rate, CaCO3 decomposition rate, and NOx emission are also investigated. Results show that under the typical working condition with O2 concentration in the flue gas of 1.7 %, the CaCO3 decomposition rate can reach around 96.42 %, the carbon conversion rate is up to 98.65 %, and the NOx can be controlled at around 105 ppm. The increase of O2 content promotes higher carbon conversion rates with excessive O2 leading to higher NOx emission. Appropriately increasing the proportion of raw material flow rate in upper tubes can facilitate a more complete CaCO3 decomposition.