链箅机回转窑球团热废气循环工艺及数值模拟研究

Recirculating process of pellet exhaust gas from grate-kiln and numerical simulation

针对链箅机回转窑环冷机生产过程中废气外排量大、余热利用率低的问题,在原有废气循环的基础上,提出了一种将过渡预热段的热废气循环到环冷机二段的废气循环工艺,并对新模式下的球团冷却过程进行模拟仿真研究。基于计算流体力学理论基础,结合局部非热力学平衡理论和磁铁矿氧化反应模型,采用CFD软件建立了数值仿真模型,揭示了废气循环对球团冷却的影响规律。研究结果表明,采用新的烟气循环系统之后,冷却二段的废气温度从511℃提高到523℃,提高了热利用效率。采用该废气循环模式,可减少废气排放11.5%,循环回收热量占球团生产热量总支出的3.45%。为球团生产进一步节能减排提供了新的方向,对于球团清洁生产具有重要意义。

Aiming at the problems of large exhaust gas discharge and low waste heat utilization rate of the grate-kiln ring cooler,a waste gas cycle technology that recycles the hot waste gas from the transitional preheating section to the second section of the circular cooling machine,was proposed.Then the pellet cooling process after using the waste gas cycle was simulated and studied.Based on the theory of computational fluid dynamics and combined with the local non-thermodynamic equilibrium theory and the magnetite oxidation reaction model,a numerical simulation model was established by CFD software to reveal the influence of exhaust gas cycle on pellet cooling.The results show that the exhaust gas temperature of the second cooling stage increases from 511℃to 523℃after adapting the flue gas circulation system,improving the heat utilization efficiency.The exhaust gas emission can be reduced by11.5%,and the energy occupying 3.45%of the total heat expenditure for pellet production can be recovered.This study provides a new direction for further energy saving and emission reduction in pellet production,which is of great significance for pellet cleaner production.