Development of fluidized-bed cement calcination process with energy conservation and low pollutant generatic

研究结果分为两个主题：(1)阐明喷流床中固体循环机理；(2)开发流化床水泥生产工艺的放大方法。(1)带导流管的喷流床内颗粒循环特性所提出的流化水泥生产工艺由两级流化床组成。：一为上喷床造粒，一为下流化床煅烧。为了在1300℃的温度下完成煅烧而不产生结块问题，必须在上部喷床上产生均匀的颗粒。在此基础上，采用直径为0.205m、带导流管的喷流床研究了气速对固体循环行为的影响。通过内窥镜目视观察、压力波动和光信号分析，发现固体颗粒周期性地从环空进入气体射流，并在尾水管中向上移动。然而，在一定的最大气速下，固体流动变得均匀，向上输送而不形成团簇。(2)创新的流化床水泥生产工艺的扩大一个日产量为20吨的中试工厂扩大到日产量为200吨的大型工厂。在此放大过程中，主要设备的主要规格可根据热平衡计算进行设计。造粒床和煅烧床都是通过扩大其二维直径来扩大规模的，但需要进行一些修改才能实现平稳运行。

Results are classified into two subjects : (1) elucidation of solids circulation mechanism in spouted beds and (2) development of a scale-up method for fluidiized-bed cement production process.(1) Characteristics of particle circulation in a spouted bed with a draft tubeThe proposed cement production process using fluidization consists of two-stage fluidized beds. : one is upper spouted bed for granulation and the other is lower fluidized bed for calcination. In order to complete the calcination at 1300ﾟC without agglomeration trouble it is essential to produce homogeneous-sized granulus at the upper spouted bed.With this view a spouted bed of 0.205m diameter with a draft tube has been used to study the effect of gas velocity on the behavior of solids circulation. Based on visual observation using a borescope and the analyzes of pressure fluctuation and optical signals it was found that solid particles move from annulus into gas jet to from clusters periodically and are carried upward in the draft tube. At a certain maximum gas velocity, however, solids flow becomes homogeneous and are transported upward without cluster formation.(2) Scale-up of an innovative fluidizd-bed cement production processA pilot-plant with 20 tons per day was scaled up to a larger plant having the capacity of 200 t/d. In this scale-up process the principal specifications of main equipments could be designed on the basis of heat-balance calculation. Both granulating and calcinating beds were scaled up by enlarging their diameters twodimensionally, but several modifications were needed to achieve smooth operation.