气—固流化床颗粒的内循环流动

从多尺度范围考察了气－固流化床内尾涡颗粒流和乳化相颗粒流的运动规律，将分散的尾涡颗粒流和乳化相颗粒流连续介质化，从流变学角度定义了颗粒洗粘度，用流体力学方法建立了内循环流动结构的多尺度，连续介质流模型，较好地揭示了颗粒循环循环流动的规律。实验观测支持模型预测结果。     

内循环快速流化床流动特性研究

建立了一种新型的内循环流化床并实现了快速流态化运转，根据轴向和径向颗粒浓度的测定结果，分析了气固环隙流动和圆管流的差异，经实验数据关联，得到了曳力系数比值Ｃ＿ｄ／Ｃ＿（ｄｓ）随浓稀相极限颗粒浓度的变化趋势；实验中还考察了颗粒浓度受操作条件及物性参数的影响结果，并与传统空管快速床进行了比较。     

不均匀布风的内循环流化床特性研究

开发了一种新型的内旋流流化床气体分布板 ,像传统内循环流化床气体分布板一样 ,该分布板也有两个区域 ,但产生内循环的机理不同 ,其内循环不是由两个区域的不同气体流速产生 ,而是由两个区域的不同气体通量控制 ,中部为低开孔率区 ,运行时呈移动床状态 ,周围为高开孔率区 ,运行时呈流态化状态 ,两种状态共同作用 ,实现物料在床的内部循环     

内循环微型流化床流动特性

针对开发适用于化学气相沉积反应动力学研究的微型流化床反应分析仪的应用需求,研究了外径为30 mm的内循环微型流化床中气固流动特性,具体考察了中心射流管伸入高度、内导流管直径和颗粒装载量对实现固体物料内循环的最小操作气速和导流管与环隙区间窜气的影响。结果表明,随着射流管伸入高度的增大,实现颗粒内循环流动的最小操作气速变大;存在最优的导流管直径(20 mm),使得实现颗粒环流的最小操作气速较小;增大颗粒装载量有利于降低颗粒内循环的最小操作气速。通过检测示踪气体在环隙区内的质谱信号,发现在所考察的参数范围内,反应器底部不存在导流管区向环隙区的窜气;在反应器上部,由于颗粒对气体的夹带,环隙区上部总能检测到示踪气体,且窜气特性随操作气速的增大而增强。研究结果可为设计适用于化学气相沉积反应的内循环微型流化床反应器提供参考。     

超细粉在内循环流化床中的流态化特性

在内径120 mm的半圆柱形内循环流化床中,以平均粒径387 nm的Ti O2为原料,考察了单独通入流化气、射流气和同时通入流化气和射流气三种流化方式下超细粉的流化特性以及射流气速对超细粉聚团尺寸的影响。结果表明:同时通入流化气和射流气时,流化气能促进粉体循环,消除环隙死区;高速射流能有效破碎聚团,显著减小聚团尺寸,从而使超细粉在环隙区与导流管之间形成稳定循环,小聚团在环隙区实现平稳流态化。随着射流气速的增大,聚团尺寸减小,粒度分布变窄,在射流气速分别为60,90,120,150 m/s的条件下,聚团平均直径分别为194,158,147,135μm。     

气-固流化床中颗粒的内循环流动

从多尺度范围考察了气－固流化床内尾涡颗粒流和乳化相颗粒流的运动规律,将分散的尾涡颗粒流和乳化相颗粒流连续介质化,从流变学角度定义了颗粒流粘度,用流体力学方法建立了内循环流动结构的多尺度、连续介质流模型,较好地揭示了颗粒循环流动的规律。实验观测支持模型预测结果。     

内循环流化床固体循环速率的研究

研究一种加料不独立的垂直气力输送装置，并以流化床作为料仓和混合区，两者构成固体循环系统。由于系统特性，加料喷嘴的插入高度与加料结构将会直接影响操作的稳定性，从力的平衡出发导出临界结构为ｈｅ／Ｄｅ＜ｆＨＬ／Ｒ，其中ｆ是颗粒特性的函数。     

漏斗型导流内构件对内循环三相流化床流体力学与传质特性的影响

通过增加新型内构件来改善内循环三相流化床的流体力学与传质特性,以实现化工、环保领导中追求高氧利用率的过程。针对此过程设计了3种不同结构参数的漏斗型导流内件并设置于导流筒顶端,分别测定反应器内气含率、液相混合时间、液体循环速度、体积氧传质系数的数据并分析其变化规律,以解析内件的作用机制。实验在有效体积39L,以空气为气相、水为液相、多孔泡沫颗粒为固相的反应器中进行,研究发现：漏斗型导流内件的设置使升流区气含率平均增大10%,体积氧传质系数kLa提高了15%,液相混合时间下降10%-25%;内件的设置可以改变液体循环速度,当表观气速<0.5cm/s时,液体循环速度加快,当表观气速>0.5 cm/s时,液体循环速度下降;此外,漏斗型导流内件的结构参数变化对流化床流体力学与传质特性有较大影响。结果表明,流化床内增加新型内构件并合理设置能够实现反应器效能的提高。     

三相内循环生物流化床内循环时间的研究

采用脉冲示踪法测定了三相内循环生物流化床反应器在不同进气量Q_g、固含率ε_s和升降流区截面积比条件下的循环时间T_C,对反应器的内循环特征和混合情况进行了系统的研究。结果表明：进气量Q_g、固含率ε_s和升降流区截面积比A_r/A_d共同影响了反应器的内循环时间T_C,进气量能在较大范围内调控反应器的循环时间T_C。循环时间T_C随进气量Q_g呈指数衰减,随ε_s的增加而增大,并且最小进气量Q_g,min也随ε_s的增加而升高;随A_r/A_d的增大,T_C总体也呈增大趋势。Q_g为96 L/h时T_C 随ε_s变化的转折点,当Q_g大于96 L/h时,T_C随ε_s的增加显著增大;并进一步讨论了进气量和固含率对反应器的生物处理效率和效果的影响,为反应器的改进、放大和运行提供了可靠的依据。     

三相内循环生物流化床处理废水的研究

以活性碳和陶瓷颗粒为载体粒子,采用快速排泥挂膜法启动实验,在反应器的运行过程中逐渐加大进气量及进水量,直至出水COD浓度达到一个较低水平.分别考虑了进水COD浓度、空气流量、废水流量、容积负荷四个因素对COD去除率的影响.结果表明:当系统运行到第13 d时,COD的去除率达到了一个较大值,并趋于稳定.     

Hydrodynamics of circulating fluidized bed risers: A review

Any vessel in which solids are transported upward by a gas stream and then recycled to the bottom may be classified as a Circulating Fluidized Bed (CFB). We describe possible CFB operating regimes in the context of this broad classification and highlight commercial processes that employ CFB technology and potential applications. Process design and development require a fundamental understanding of gas and solids hydrodynamics — solids hold-up, mixing and velocity distribution. We discuss techniques used to measure solids mass flux, which is a critical parameter for both design and control. In the last decade, significant research efforts have been devoted to new experimental techniques to measure both gas and solids spatial and temporal distribution. We list these techniques and detail the different modelling approaches that have emerged based on the new data. Characterization of the data is still incomplete and the available models require further refinement to reliably predict the effect of scale, operating conditions and particle characteristics on hydrodynamics.     

Hydrodynamics of erosion of heat exchanger tubes in fluidized bed combustors

The hydrodynamics of fluidization for two thin “two-dimensional” fluidized beds, one containing a centrally located rectangular obstacle and the other containing three square tubes roughly approximating a portion of a fluidized bed combustor (FBC), was solved using the FLUFIX/MOD2 computer program. The monolayer energy dissipation erosion model extended to include solids viscous stress was compared with the Finnie erosion model. The material properties of the eroding surface are introduced through the hardness for both erosion models. Hydrodynamic and erosion convergence studies were performed for the first bed. Computed erosion rates from the monolayer energy dissipation erosion model compare more favorably for both beds with available erosion data than those from the Finnie erosion model.     

Effect of temperature on gas bypassing and solids circulation rate in an internally circulating fluidized bed

The effect of bed temperature in the annulus region on gas bypassing from annulus to riser and solids circulation rate has been determined in an internally circulating fluidized bed. The bed voidage in the annulus region increases with increasing temperature. The average fractions of gas bypassing of annulus gas are 59.4% and 87% at room temperature and high temperature (400°C to 800°C), respectively. Solids circulation rate increases with increasing annulus gas velocity, but is nearly independent of riser velocity. Solids circulation rate increases with increasing temperature.     

Solid circulation and gas bypassing characteristics in a square internally circulating fluidized bed with draft tube

The effects of gas velocities to draft tube (26.64–52.54 cm/s) and to annulus section (8.14–11.84 cm/s) on solid circulation rate and gas bypassing fractions were determined in a square internally circulating fluidized bed reactor with an orifice-type square draft tube. The solid circulation rate and gas bypassing fraction from the annulus section to the draft tube increase but gas bypassing fraction from the draft tube to the annulus section decreases with increasing gas velocity to the draft tube. With increasing gas velocity to the annulus section, the solid circulation rate and gas bypassing fraction from the draft tube to the annulus section increase but, gas bypassing fraction from the annulus section to the draft tube decreases. The solids circulation rate was correlated with the pressure drop across the orifice and the opening area ratio based on the orifice theory. The gas bypassing fraction was correlated with gas velocities to the fluidized and the moving beds. Based on the gas bypassing fraction data, the gas flow rates across the orifice were correlated with gas velocities to the fluidized and the moving beds, opening area ratio, particle size and solids height in the bed.     

循环流化床锅炉的清洗

介绍了循环流化床锅炉的特点及其构造、流程.通过某自备电厂的220t/h循环流化床锅炉EDTA清洗实例,讨论了化学清洗的范围、清洗工艺和参数等.分析总结了清洗中应注意的事项.     

流化床化学气相沉积多晶硅的技术进步与挑战

Various methods for production of polysilicon have been proposed for lowering the production cost and energy consumption, and enhancing productivity, which are critical for industrial applications. The fluidized bed chemical vapor deposition (FBCVD) method is a most promising alternative to conventional ones, but the homogeneous reaction of silane in FBCVD results in unwanted formation of fines, which will affect the product quality and output. There are some other problems, such as heating degeneration due to undesired polysilicon deposition on the walls of the reactor and the heater. This article mainly reviews the technological develop-ment on FBCVD of polycrystalline silicon and the research status for solving the above problems. It also identifies a number of chal-lenges to tackle and principles should be followed in the design of a FBCVD reactor.     

隔板式内循环流化床压力脉动信号递归分析

隔板式内循环流化床中流化态及颗粒循环特性对压力脉动信号特征具有重要影响,其作用机制尚未完全清楚。测量了隔板式内循环流化床在不同气速比条件下的压力脉动信号,通过时域及递归分析,获得了压力脉动信号的标准差、递归率、确定性及香农熵等特征参数。结果表明,随着表观气速比的增加,内循环中颗粒循环状态存在未循环、鼓泡循环、过渡循环和湍动循环四个阶段;通过压力脉动信号的标准差、递归图黑白结构占比和递归特征参数可识别这四种循环状态,递归特征参数在不同循环区域内显示出良好的线性关系,可用于识别隔板式内循环流化床系统的循环状态。     

内循环流化床烟气脱硫装置研究

开发研究了一种内循环流化床烟气脱硫装置,用40—80目河沙做粗颗粒床料,可实现固体颗粒在脱硫塔内的内循环,床内物料浓度高于传统结构的流化床烟气脱硫反应器,强化热质传递的同时可克服粘壁现象。通过热态烟气脱硫试验表明,系统能在接近绝热饱和温度的条件下连续稳定运行,在钙硫摩尔比x=1.3,粗颗粒质量浓度ρs=10 kg/m3,趋近绝热饱和温度Δt=8—10℃的条件下,脱硫效率达90%。     

低固含率气-液-固循环流化床流动特性

应用基于互补金属氧化物半导体(complementary metal oxide semiconductor,CMOS)传感器的高速图像采集和处理技术,实验研究了低固含率条件下,低密度大孔吸附树脂固体颗粒气-液-固三相循环流化床的流体力学行为,分析了操作条件、液相物性、颗粒性质等对床内的固体颗粒循环速率、相含率、气泡运动等特性的影响,得到了具有合理物理解释的实验数据和结果。