简述带式焙烧机的工艺气流循环系统。
参考答案：
带式焙烧机的工艺气流循环系统可采用鼓风式、抽风式或鼓风和抽风混合流程。
目前先鼓风后抽风干燥的方式已被广泛采用。沿焙烧机长度方向分为鼓风干燥、抽风干燥、预热、焙烧均热、鼓风冷却和抽风冷却等几段。各段之间通过管道、风机、阀门等组成一个气流循环系统。
各段的长度大致比例为：干燥带占总长度的18％~33％，预热、焙烧和均热段共占30％~35％，冷却段占33％~43％。
各段的温度：干燥段不高于800℃，预热段不超过1100℃，焙烧段为1250℃左右。带式焙烧机的气流循环方式、各段温度、气体流量和停留时间等参数，均可根据原料特性变更和调整。带式焙烧机冷却段多采用鼓风方式，可防止球团因骤冷而使强度降低，上部球团可受下部热气流的热处理使强度提高。
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