循环流化床中C类颗粒的干燥

为将循环流化床(CFB)技术应用于C类颗粒(＜30μm)的干燥,在自建的循环流化床(内径0.104 m×高2.35 m)内,以玉米淀粉(dp=8 μm,ρp=800 kg/m3)为研究对象,考察了不同操作参数对其干燥特性及干湿分离情况的影响.结果表明:循环流化床适用于C类颗粒的干燥;干燥速率随气速及进风温度的增大而增大...     

循环流化床中C类颗粒连续干燥的研究

循环流化床(CFB)作为一种新兴反应器,其结构简单、气固接触效率高、处理量大,成为气固二相干燥应用研究的新方向.文中在自建的循环流化床(内径0.104 m×高2.35 m)内,以玉米淀粉(dp=8 μm,ρp=800 kg/m3)为C类颗粒,进行了连续干燥.实验初步研究了进料速率、进风温度及气速等操作参数对淀粉平均停留...     

离心流化床中的干燥特性的实验研究

报道了多种不同形状的萝卜、韭菜等蔬菜及粮食种子在离心流化 中干燥特性的实验结果,得出了恒速干燥阶段的传热准数关联式,并找出了影响整个干燥过程干燥速率的因素,同时讨论了不同操作条件对干燥速率的影响。     

循环流化床流体特性研究

在 D2 0 0 mm× 2 560 mm自制循环流化床上利用生石灰进行了流体特性研究 .实验结果表明 :固体颗粒循环速率和表观气速是影响压力分布的两个重要因素 .降低气速、提高颗粒循环速率 ,可以提高床内颗粒浓度 ,增加颗粒停留时间 .最后经无因次分析和实验数据拟合 ,分别得到了循环流化床压降和颗粒浓度沿床轴向分布经验关联式 .     

振动流化床干燥装置干燥特性计算方法研究

通过对振动流化床（ＶＦＢ） 干燥装置中传热与传质过程的分析,建立了物料在其中的干燥特性模型, 得到了振动流化床干燥装置物料出口含湿量与温度的计算公式。     

循环流化床流体动力特性研究

循环流化床的设计和放大需要对其流动特性进行细致地研究,文章采用RSM模型对新型的双外循环流化床流场进行了三维的数值模拟,得到了在不同入射速度下的流化床主、副床的三维的速度分布、压强分布及湍流强度分布等,给出了主床在典型位置x方向的上分布图,并与实验结果进行了对比。结果表明,在不同入射速度下RSM模型数值模拟结果与实验结果符合均较好,模拟计算可以很好地反映流化床中真实的流动状况,可以用于反应过程的性能评价,为设备优化设计和相似放大提供依据。     

循环流化床回流物料循环的特性

为了研究循环物料在流化床内回流并参与循环的过程,进一步揭示流化床内物料的循环特性,文中搭建了冷态循环流化床顶部回流试验台。利用激光多普勒粒子动态分析仪(PDA)对塔内颗粒回流时床内气固二相流场和颗粒浓度分布进行了测量。同时对物料回流量和床内表观气速等操作条件对回流过程的影响进行了考察。研究表明,回流颗粒在流化床内的返混可以分为3个区域:回流区、返混加速区和主流区,回流颗粒造成床内流场的不均匀性。回流长度主要受物料回流量和床内表观气速影响。     

循环流化床置换燃烧机理介绍及流动特性研究

介绍了一种基于循环流化床的动力系统方案——循环流化床置换燃烧。这种燃烧系统能在没有能量损失的前提下,将CO2从燃烧产物中分离出来。本文设计建立了一套燃煤循环流化床置换燃烧冷态实验系统,以此为研究对象,选择具有代表性的实验物料,利用测试系统取得多种信号参数,获得反应装置之间的气固流动特性,总结出一定的规律,为以后的热态实验以及进一步探索奠定基础。     

循环流化床置换燃烧机理介绍及流动特性研究

介绍了一种基于循环流化床的动力系统方案———循环流化床置换燃烧。这种燃烧系统能在没有能量损失的前提下,将CO2从燃烧产物中分离出来。本文设计建立了一套燃煤循环流化床置换燃烧冷态实验系统,以此为研究对象,选择具有代表性的实验物料,利用测试系统取得多种信号参数,获得反应装置之间的气固流动特性,总结出一定的规律,为以后的热态实验以及进一步探索奠定基础。     

硼砂在内热式振动流化床中的干燥特性研究

采用内热式振动流化床对硼砂进行了干燥实验,考察了流化气速、进气温度和振动频率对硼砂干燥特性的影响,分析了硼砂湿含量、含水分子个数和干燥速率的变化规律。结果表明,干燥速率随着流化气速和进气温度的增加而增加,随着振动频率增加变化不大。通过实验数据得到了计算干燥速率的关联式,计算值与实验值吻合较好,误差在±20%范围内。结果可为内热式振动流化床的设计和研究提供参考。     

煤粉惰化设计回转式干燥工艺的研究与应用

介绍了一种煤粉的惰化干燥处理工艺研究。采用加压或抽真空惰化情况下惰化次数的计算方法和采用通流惰化情况下惰化时间的计算公式,提出了一种惰化设计干燥工艺,用氮气作为载湿气体在煤粉干燥中能最大限度地避免易燃爆炸的发生。同时,实践也证明此种回转干燥工艺简单,运转稳定,适合干燥煤粉。     

Measurement of constant drying rate of wet material placed in a fluidized bed of inert particles under reduced pressure

The objective of this study is to estimate the drying characteristics of a relatively large material immersed in a fluidized bed under reduced pressure by measuring the constant drying rate. The constant drying-rate period in a fluidized bed under reduced pressure is difficult to measure because it is extremely short. To maintain the constant drying-rate period, distilled water is directly supplied to the drying material. Through our experiment, the heat transfer coefficient of the material surface was also determined. The results were compared with data on hot air drying. The constant drying rate is higher for fluidized bed drying than for hot air drying. It suggests that the heat transfer coefficient on the surface of the drying material is much larger for fluidized bed drying than for hot air drying. For fluidized bed drying, the effect of pressure in the drying chamber on the heat transfer coefficient is slight at the same normalized mass velocity of dry air (G/G_mf). The temperature difference between the inside of the drying chamber and the drying material is much smaller for fluidized bed drying than for hot air drying. The constant drying rate increases as the pressure in the drying chamber decreases.     

聚合物干燥技术进展

根据不同的聚合工艺和聚合反应,聚合物有多种多样的干燥方法。介绍了聚合物滤饼、聚合物分散体、溶液物料及脱除挥发性有机化合物的干燥工艺和干燥技术,对典型的干燥设备操作系统进行了综述。     

纺织印染废水活性污泥干燥器设计计算探讨

污泥作为再生资源加以有效利用是世界各国共同的课题.理论研究表明,脱水污泥含有一定量的有机物质,可以用作燃料.然而由于脱水泥饼含水率过高,污泥燃烧产生的热能不足于抵消水分蒸发所需的热能.因此,寻找可以利用的废热源来干燥脱水污泥成为污泥有效利用的重要一环.本文为电厂烟道气用于干燥纺织印染活性污泥的案例,文中结合其他作者的研...     

高颗粒通量循环流化床的构型作用

In order to achieve high solids circulation rate (G_s),an idea of coupling a moving bed to the bottom section of the riser of a circulating fluidized bed (CFB) was proposed and tested.The results from the preliminary study demonstrated that the solids circulation rate in the new-structure bed approached 370 kg·m^-2·s^-1 at superficial gas velocities around 10.5 m·s^-1 for sand particles with an average Sauter mean size of 378 μm.This study was devoted to further justifying the effects of the coupled moving bed by performing comparative studies in two CFBs with conventional configurations.It was shown that the pressure at the riser bottom and the realized solid circulation rate were only about 15 kPa and 230 kg·m^-2·s^-1 in the two conventionally configured CFBs,obviously lower than 25 kPa and 370 kg·m^-2·s^-1 in the moving bed coupled CFB.These verified that the coupled moving bed increased the force driving particles form the particle recycling side into the riser.The study further tested the effect of a few specially designed riser exit configurations,revealing that a smooth riser exit could facilitate solids circulation to increase the solids circulation rate.     

Residence time distribution in spouted bed drying of maltodextrin solutions on a bed of inert particles

Residence time distributions (RTD) for aqueous maltodextrin solutions were determined in two kinds of spouted bed dryers: (1) conventional spouted bed (CSB) 0.305 m diameter with a bed of polypropylene beads and (2) spout‐fluid bed 0.143 m diameter with draft tube submerged in a bed of FEP® pellets (S‐FBDT). RTD, mean residence time t_m, and spread of the distribution σ², were determined at different drying temperatures, spouting velocities, bed depths, spraying pressures, and feed concentrations. Average values of t_m and σ² were 6.5 min and 26.6 min² for the CSB and 6.9 min and 36 min² for the S‐FBDT, respectively, for all operating conditions except spraying pressure. RTD curves were well represented by the response of an ideal stirred tank with a superimposed bypass of 15% on average for the CSB and 7% on average for the S‐FBDT dryer for all operating conditions. Increase in spraying pressure produced a reduction of t_m and an increase in the bypass fraction of the product in both dryers. © 2011 Canadian Society for Chemical Engineering