Numerical simulation and reliability verification of pulverized coal combustion in rotary kiln and decomposing furnace under O 2 /CO 2 condition

Abstract

In order to study the feasibility of reducing CO2 and NOx emission by using O2/CO2 flue gas cycling calcinating cement technology, a numerical simulation method was used to study the pulverized coal combustion of the 2 500 t·d−1 rotary kiln and decomposing furnace models under 21%O2/79%CO2 combustion-supporting atmosphere. The simulations results of rotary kiln and decomposition furnace under O2/CO2 combustion-supporting conditions and air-supported combustion conditions were compared and analyzed. The reliability of numerical simulations was also verified by experiments test. The results showed that in comparison with the air-supported combustion conditions, the pulverized coal burnout rate of the rotary kiln and decomposing furnace under O2/CO2 combustion-supporting conditions were 92.41% and 91.15%, respectively, which decreased by 3.06% and 3.51%. The decomposition rate of raw materials at the exit of the decomposing furnace was 90.54%, which decreased by 2.90% and still basically met the production demand. Under O2/CO2 combustion-supporting conditions, NO emission of rotary kiln and decomposing furnace decreased significantly, and the denitrification rates were 74.47% and 11.80%, respectively. The CO2 volume fraction in flue gas increased from 32.23% to 95.35%, and the C capture could be achieved through simple treatment. This study provides a reference for the generalization and application of the O2/CO2 flue gas cycle calcinating cement technology.