高温流化床结焦特性

分析了近年来高温流化床结焦研究的状况,总结了流化床结焦现象及其影响因素、流化床结焦时的最小流化速度及影响因素、流化床结焦机理,并分析了研究中存在的问题,探讨了高温流化床结焦特性研究的方向。     

高温流化床中IHI灰样的临界流化速度研究

在D82的不锈钢高温流化床实验台中,以IHI灰样作为实验物料,研究了高温流化床的临界流化速度,结果表明,对于属于B类粒子的IHI灰样,温度由常温升高于1000℃时,雷诺数小于40,流化床运动处于层流运动区范围,随着床层温度升高,物料颗粒的最小流化速度减小,根据实验结果提出了预测不同温度下的该灰样题粒最小流化速度式。     

CHARACTERIZATION OF AXIAL NONUNIFORMITY IN FLUIDIZED BED BY THE AMPLITUDE OF LOCAL PRESSURE DROP FLUCTUATIONS

The amplitude of local pressure drop fluctuations was used to characterize the axial stability of a freely bubbling fluidized bed. The experiments were carried out in a bed of 0.318 m dia at normal and elevated temperatures. It was found that the transition between a freely bubbling zone, consisting of small bubbles distributed uniformly across the bed, and a zone of incipient slugging occurs if bubble to bed diameter ratio is about 0.15. The amplitude of local pressure drop fluctuations was found to be a linear function of gas velocity in a broad range of temperatures if measured in the freely bubbling zone     

INVESTIGATIONS OF THE BUBBLE PHASE BEHAVIOR IN A HIGH TEMPERATURE FLUIDIZED BED REACTOR WITH COALCOMBUSTION

The properties of bubbles in a bench-scale fluidized bed reactor, 30 cm in diameter, during coal combustion were determined by means of a newly developed cooled bubble probe and a data processing system at temperatures up to 850°C and fluidization indexes up to 10 in axial and radial positions in the bed. The fluidization index above 4 and the temperature have only slight effect on the bubble properties. Their variation along the height above the gas distributor is dominant.

Oxygen and Co₂-concentration profiles were measured in the bed and in the freeboard, and the o₂-profiles were calculated by means of measured bubble data and bubble models. A comparison of measured and calculated o₂-profiles indicates that the mass transfer rates between the emulsion and bubble phases are larger than the ones calculated by the models.     

振动流化床双组分颗粒的混合与分离

研究了振动流化床中颗粒的轴向浓度分布及最小流化速度,根据不同操作条件下最小流化速度的实验值,定义了最小流化速度的计算式;同时考察双组分颗粒混合与分离情况,根据实验结果,修正了Ｎｉｅｎｏｗ定义的双组分颗粒的转变气速,并与实验值相符。     

STOCHASTIC BEHAVIOR OF FLUIDIZED PARTICLES IN A LIQUID-SOLID FLUIDIZED BED

In a liquid-solid fluidized bed, the apparently irregular or stochastic behavior of particles gives rise to various flow regimes depending on parameters such as the particle size, liquid flow rate, static bed height and axial position in the bed. It is highly plausible that this irregular behavior manifests itself as pressure fluctuations; thus, the effects of these parameters on the particle behavior or the particle flow regime were investigated through measurement and spectral analysis of the pressure fluctuations. The results indicate that the amplitude of pressure fluctuations exhibits a maximum and that the decay constant in the autocorrelation function attains its minimum at the intermediate liquid flow rate where the particle flow regime undergoes transition from the cluster circulation to the individual quasi random motion. The model composed of the periodic and stochastic components of pressure fluctuations, is in good accord with the experimental results in terms of both the autocorrelation and power spectral density functions.     

ATTRITION IN THE BUBBLING ZONE OF A STEADY-STATE FLUIDIZED BED

This paper describes the kinetics of attrition in the bubbling zone of a fluidized bed and focuses on the development of an equation for attrition in continuous fluidized beds operating at steady state.

Laboratory data describing batch attrition of a limestone sorbent are applied to the integrated equations to describe overall attrition rate in a full-scale continuous system.     

FCC细颗粒湍流流化床流体力学性能研究

ＦＣＣ细颗粒湍流流化床流体力学性能研究李俊，张蕴璧，闫遂宁（西安石油学院，西安７１００６１）（西北大学）（洛阳石化公司）关键词：流化床，湍流，气泡，空隙率１前言湍流流化床有着广泛的工业背景。湍流流化床反应器存在着物质空间分布的不均匀现象，这种分布对湍...     

EFFECT OF HIGH VOIDAGE ON MASS TRANSFER COEFFICIENT IN A FLUIDIZED BED

Experiments were carried out to determine the gas-solid mass transfer coefficient for the air-naphthalene system under fast-fluidized conditions. The data were obtained under conditions of high voidage (as high as 98%) and high gas velocities (0·5 m/s-2·2 m/s). The results indicate that the correlation for the mass-transfer coefficient in a gas-solid fluidized bed under low voidage conditions established by previous investigators can be extended to the fast fluidization regime. Significantly lower mass transfer coefficients were, however, obtained under high voidage compared to low voidage conditions.     

流化床连续聚合反应器出料状态分析

研究了粗颗粒树脂加压流态化时气固混和物自由出料过程的物理模型，建立了出料气含率与流化床结构参数、操作条件之间的关系。计算表明出料气含率的理论预测值和测量值一致。运用此结论进一步计算了流化床乙烯聚合反应生产聚乙烯工业过程中乙烯的原料单耗值，为工业生产指标的分析计算提供了理论依据     

STUDIES OF STEAM DRYING IN A FLUIDIZED BED

In general, drying processes are described by the quantity of air humidity of the exiting gases. This approach is not possible however by the drying medium of water in steam drying, since the air humidity naturally possesses a constant value of 100%. This paper presents a model which represents the drying processes on the basis of the observation of temperature profiles of the material and energetic balancing of all components involved as well as the wall of the apparatus. The modeling differentiates three intervals: the condensation phase, the 1st drying period and the 2nd drying period. In addition, a validation of the model on the basis of experiments in an experimental plant DN100 belonging to the university is dealt with. The satisfying concurrence of the theoretical and practical results shows that, with the help of the theoretical model, discontinuous steam drying processes can be theoretically described with sufficient accuracy.     

PARTICLE GROWTH IN A CONTINUOUSLY OPERATED FLUIDIZED BED GRANULATOR

Fluidized bed spray granulation offers several advantages compared to commonly used drying processes as spray drying, e.g. free flowing dust free coarse particles with a narrow particle size distribution can be produced in a single processing step. Especially for large production units a continuous operation is desirable. Unfortunately, there is still a lack of understanding concerning the mechanisms of particle formation and growth leading to difficulties in planning and operating such continuous granulators. Hence, experiments were performed to investigate the influence of process parameters on the growth process in a continuously operated fluidized bed granulator. Furthermore, a model was developed taking into consideration the particle exchange between nozzle jet and fluidized bed as well as the wetting and drying processes. The processes inside the jet are modeled in analogy to a wet scrubber. This modeling approach predicts an increase of growth rate with particle size. The prediction is in good agreement with experimental findings.     

PARTICLE GROWTH IN A CONTINUOUSLY OPERATED FLUIDIZED BED GRANULATOR

Fluidized bed spray granulation offers several advantages compared to commonly used drying processes as spray drying, e.g. free flowing dust free coarse particles with a narrow particle size distribution can be produced in a single processing step. Especially for large production units a continuous operation is desirable. Unfortunately, there is still a lack of understanding concerning the mechanisms of particle formation and growth leading to difficulties in planning and operating such continuous granulators. Hence, experiments were performed to investigate the influence of process parameters on the growth process in a continuously operated fluidized bed granulator. Furthermore, a model was developed taking into consideration the particle exchange between nozzle jet and fluidized bed as well as the wetting and drying processes. The processes inside the jet are modeled in analogy to a wet scrubber. This modeling approach predicts an increase of growth rate with particle size. The prediction is in good agreement with experimental findings.     

流化床中侧向射流穿透深度的研究

流化床中侧向射流穿透深度的研究李海滨，王洋，张海生（中国科学院山西煤炭化学研究所，太原０３０００１）关键词：流化床，侧向射流，穿透深度１前言气固流化床反应器中，分布板起着气体分布和支持床层物料的作用，分布板区是气体与所处理固体接触最强的区域，在氧化反...     

流化床造粒影响因素及层式成长模型的研究

将流态化技术应用于粉体物料的造粒过程,在我国还是一项亟待研究开发的课题。本文对流化床造粒进行了实验研究,着重探讨了流化气速,粘合剂种类、浓度、流率,原料初始粒度,喷嘴位置等因素对颗粒成长速率及机理的影响。在此基础上,建立了粒子层式成长模型,并与实验数据进行了比较。     

BUBBLE MOTION IN A THREE-PHASE LIQUID FLUIDIZED BED

This paper presents results for the rise velocities of air bubbles in liquids and liquid-solid fluidized beds. The bubble sizes ranged from approximately 0.03 to 0.45 cm radius. Tap water and distilled water were used as the fluidizing liquids. The solid phase consisted of low density alginate gel beads of mean radius 0.04 cm. The gel beads were translucent which permitted observation of bubbles inside the bed even at large solids volume fractions. Experiments were conducted for solids volume fractions ranging from 15% to 52% and in clear liquids. The goal of the experiments was to determine rise velocities of bubbles and to develop and evaluate correlations of bubble rise velocity based on bubble size, solids volume fraction and liquid properties. It was determined that, for moderate solids fractions (ranging from 28% to 45% solids), a semi-empirical correlation that treated the fluidized bed as a pure liquid with a higher viscosity than the liquid phase could be used to represent the data. The Thomas effective viscosity model was used to predict the viscosity. Provided that one restricts attention to a water fluidized bed, a second empirical correlation can be used to represent the data over a broader range of solids fractions.     

快速流化床内颗粒速度的关联

颗粒速度是快速流化床内重要的流体力学参数,直接测定是困难的,一般都是通过测定其他参数,来计算颗粒的速度。本研究在内径6.6cm 和9.7cm,高3m 的快速流化床内测定颗粒的轴向滞留量分布及压头损失,分析床层内颗粒速度及其影响因素,对三种不同颗粒进行测定,将实验数据进行关联,得出颗粒速度的关联式:适用范围:气体流速:1.4～6.0m/s颗粒循环速度:30～130kg/m~2·s颗粒终端速度:0.133～0.880m/s将实验值与计算的结果比较,基本一致。故可认为该式在实验范围内,可用于推算快速流化床内的颗粒速度。     

MODELING OF ETHANOL BIOPRODUCTION IN THREE-PHASE FLUIDIZED BED REACTORS

A time dependent and one-dimensional model is developed to analyze the performance of three-phase fluidized reactors and is applied to the fermentation of glucose to ethanol. The reactor model takes into consideration the presence of three different phases; the yeast (solid) which is continuously fluidized by the liquid stream, the gas bubbles which greatly enhance mixing and the wake phase which follows the tracks of the gas bubbles. The reactor performance is analyzed as a function of major operating conditions. The analysis includes variations in dispersion of glucose and yeast inside the reactor, the concentration of glucose in feed, and of the yeast mass inside the reactor, reaction temperature, velocities of gas and liquid feeds, and reactor aspect ratio. Computed glucose conversion is presented as a function of reactor length and time. The results indicate that high glucose conversions can be obtained at high gas velocities, low liquid flow rates, large aspect ratios, high yeast concentration, and an optimum operating temperature of 36°C,     

义马煤灰高温下矿物质变化

煤灰在高温下的热行为对气化过程有很大的影响.利用热重-差示扫描量热(TG-DSC)、X-射线衍射(XRD)和扫描电镜(SEM)研究了义马煤中矿物质在高温氧化气氛下的热行为及矿物质演变.结果表明,矿物质组分随温度的升高发生了转变,主要由硅铝酸盐控制,这种改变会对灰熔融特性产生影响;矿物质形貌和分布状态随温度的升高也发生了变化.     

THE TEMPERATURE OF BURNING CARBON PARTICLES IN A FAST FLUIDIZED BED OF FINE PARTICLES

The temperature of coarse (6–8 mm) carbon particles burning in a fast fluidized bed was measured. The burning carbon particle was found to be 50–70^°C hotter than the bed solids. The convective heat transfer coefficient on the particle was also measured in a separate experiment to help predict the temperature of the carbon particle using a mathematical model which considered both combustion kinetics and heat transfer on the particle. A good agreement between the predicted and measured values of temperature was found.