关键词: 水泥回转窑, 烟气再循环技术, 烟气再循环率, 加热过程, 数值模拟

Abstract: In order to reduce the emission of CO2 and NOx during the heating process of cement rotary kiln, flue gas recirculation technology was introduced as a clean combustion technology. A physical and mathematical model of a 2500 t/d cement rotary kiln was established, and the numerical simulation of heating process in the rotary kiln by using CFD software. The effects of conventional air combustion and flue gas recirculation combustion on the temperature field, flow field, concentration field, NOx emission and raw meal decomposition rate in the kiln were compared and analyzed. The results showed that the flue gas recirculation technology can reduce the maximum temperature in the kiln, and the maximum reduction was 13.6%. With the increase of flue gas recirculation rate, the area of the high temperature zone in the kiln gradually decreased, but the average temperature was almost unchanged, which indicated that the flue gas recirculation technology can still make the average temperature in the kiln met the temperature requirements of cement production while reducing the local high temperature area. The CO2 concentration at the flue gas outlet increased by 45.4%, which was conducive to the capture and utilization of CO2. The NOx concentration at the flue gas outlet decreased from 235.7 mg/m3 to 39.4 mg/m3, and the NOx emission decreased by 83.3%, indicating that this technology was not only conducive to the capture and utilization of CO2, but also can effectively reduce the NOx emission in the cement industry. Although the decomposition rate of raw meal reduced by 8%, but remained above 90%, which still met the output requirements of cement production.

Key words: cement rotary kiln, flue gas recirculation technology, flue gas recirculation rate, heating process, numerical simulation