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

研究结果分为两个方面：(1)喷动床内固体循环机理的阐明和(2)流态化水泥生产过程放大方法的发展：(1)导流管喷动床内颗粒循环特性研究提出的流态化水泥生产工艺由两段流态化组成。一种是用于造粒的上部喷动床，另一种是用于焙烧的下部沸腾床。为了在1300ﾟC下完成焙烧而不出现团聚问题，在上部喷动床上生成尺寸均匀的颗粒是必不可少的。基于这一观点，利用直径为0.205m的导流管喷动床研究了气速对固体循环行为的影响。通过孔径显微镜的目测、压力脉动和光学信号的分析，发现固体颗粒在导流管中周期性地从环空进入气体射流，形成团簇，并向上携带。然而，在一定的最大气速下，固体流动变得均匀，向上输送，没有形成团簇。(2)创新的流态化水泥生产工艺的放大由20吨/天的中试装置扩大到200吨/天的较大装置。在这个放大过程中，主要设备的主要规格可以根据热平衡计算进行设计。造粒床和焙烧床都是通过二维扩大直径来放大的，但需要进行几次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.