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）喷动床中固体循环机理的阐明和（2）流化床水泥生产过程放大方法的开发。(1)带有导流管的喷动床中颗粒循环特性拟议的流态化水泥生产工艺由两级流化床组成。一种是上部喷动床造粒，另一种是下部流化床煅烧。为了在1300 ℃下完成煅烧而不发生结块，必须在喷动床上部产生尺寸合适的颗粒，为此，在直径为0.205m的导向管喷动床上研究了气速对固体循环行为的影响。通过对压力脉动和光学信号的分析，发现固体颗粒在导流筒内周期性地从环形空间进入气体射流，形成团簇，并被向上携带。然而，在某一最大气体速度下，固体流变得均匀，并且向上输送而不形成团簇。(2)新型流化床水泥生产工艺的放大试验将日产20吨的中试装置放大为日产200吨的大型装置。在此放大过程中，主要设备的主要技术指标可在热平衡计算的基础上设计。造粒床和煅烧床都是通过二维扩大其直径来按比例放大的，但需要进行几次修改以实现平稳操作。

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.