Abstract: The dawncomer is the key component of a multi-stage fluidized bed. A pneumatically controlled downcomer has been devised, consisting of a fully fluidized dipleg followed by a conical spout for upward discharge in dense phase. Such a design has been found to insure against bridging of solids in descent and against spouting of solids from a lower layer caused by gas by passing. In experimental investigations, flow characteristics are measured including the pressure drops of the different fluidized beds and of the downcomers for various gas and solids flow rates as well as the solids residence time distribution, operating either with a multiplicity of gas sources for the various downcomers or with only two gas sources. In a particular design, a multi-stage fluidized bed with dual gas supply, in which one half is incorporated centrally in the other, has been tested on pilot scale for recovering solvents fromlow-concentration C2H4Cl2 streams of a plant waste gas. Main test results obtained were as follows: adsorption rate >97% concentration of waste gas <25mg/m3 active carbon loss <0.1% This kind of conical downcomer in which the solids are either transported from a high-to a low-pressure region, or from a low-to a high-pressure region, is also used to control the solids discharge of cyclone diplegs or the feeding and discharging in other solids circulation systems.

摘要： 溢流管是多层流化床的关键构件。本文设计的由下料料腿和锥斗组成的气控式锥形溢流管,由于物料在料腿中处于流态化状态,在锥斗中以气固顺流浓相向上输送,因此,这种溢流管可以防止物料在料腿中的架桥和喷料。 试验中测定了多气源和双气源两种气控式多层床的流动特性,包括各床层和溢流管压降以及固体停留时间分布。在回收低浓度二氯乙烷的中间工厂试验中,采用了具有同心圆的双气源多层流化床,获得以下主要结果: 吸附率>97%,排放气浓度<25mg/m~3,活性炭损失<0.1%。 这种能使固体物料由高压区输至低压区,或从低压区输至高压区的气控锥形溢流管结构,亦可用于旋风器料腿的返尘以及在循环系统中固体物料的连续加、排装置。