硝基苯在湍动流化床加氢制取苯胺

初步研究了在内构件湍动流化床中硝基苯加氢制取苯胺特征,实验表明了在工业生产条件下,操作压降和氢气与硝基苯的比对硝基苯的转化率没有影响,而且已有的反应动力学完全满足工业设计。     

湍动流化床过渡段固含率分布特征的实验及数值模拟

在湍动流化床中,过渡段对于包括甲醇制烯烃在内的气固催化快反应有着重要的作用。采用PV6D反射型光纤探针对内径95 mm的湍动流化床内过渡段的固含率分布和脉动参数进行了测量,分别考察了表观气速和静床高的影响,并采用修正的基于颗粒动力学的三段曳力双流体模型进行模拟。实验表明,湍动流化床过渡段中固含率的轴向分布呈现S型和指数型两种类型,固含率轴向与径向分布都在过渡段内出现最大梯度,表明过渡段中固体浓度分布比稀相段和密相段更不均匀。表观气速和静床高的变化将导致S型和指数型分布的相互转变,并且对过渡段底部与壁面附近的固体高浓度区影响最为显著。局部固含率脉动概率密度分布表明,在静床高较小时,随着气速的增大,床层下部气含率最大值位置将从中心区移动至环隙区,呈现气含率的双峰型分布。本文提出的修正三段曳力模型考虑了颗粒团聚的影响,对过渡段中分布板影响区之外的固含率分布均能较好地模拟。     

液固导流管喷动流化床流型及流型转变的实验研究

以粒径为0.9mm的铜颗粒为流化颗粒,常温水为流化介质,在截面为59.2×15.6mm的矩形床中,对液固导流管喷动流化床的流型及流型转变进行实验了研究。通过对床层压降流量曲线的分析并结合实验观察,确定了液固导向管喷动流化床的流型及流型的划分,提出了流型图。研究结果对进一步开展导流管喷动流化床电极研究有重要的参考意义。     

两种新型流化床——高密度循环流化床和循环湍动流化床的对比分析

高密度循环流化床(HDCFB)和循环湍动流化床(CTFB)相比于传统循环流化床具有很多优点。从实验装置、原理、流动结构及其与不同流型之间的对比介绍了HDCFB和CTFB,得出以下结论:HDCFB和CTFB固体循环量大,固含率高,传热传质及气固接触效率高,固体返混少,具有较为均一的宏观流动结构。两者都可以满足现代工业高产率、高质量的发展需求。通过理论分析,CTFB相较于HDCFB具有更多优势,工业应用前景更好。     

两种新型流化床——高密度循环流化床和循环湍动流化床的对比分析

高密度循环流化床（HDCFB）和循环湍动流化床（CTFB）相比于传统循环流化床具有很多优点。从实验装置、原理、流动结构及其与不同流型之间的对比介绍了HDCFB和CTFB,得出以下结论：HDCFB和CTFB固体循环量大,固含率高,传热传质及气固接触效率高,固体返混少,具有较为均一的宏观流动结构。两者都可以满足现代工业高产率、高质量的发展需求。通过理论分析,CTFB相较于HDCFB具有更多优势,工业应用前景更好。     

气化剂预热温度对加压湍动循环流化床煤气化的影响

在实验室规模加压湍动循环流化床气化炉上,研究了气化剂预热温度对煤气化特性的影响。结果表明：气化介质温度从400℃提高到700℃后,煤气热值增加21%;煤气中可燃组分H₂和CO浓度分别从10.55%和9.57%提高到13.62%和13.12%;不可燃组分N₂和CO₂浓度分别从61.03%和16.14%降低到57.03% 和13.7%;甲烷含量变化较小;冷煤气效率由49.3%增加到56%。碳转化率和干煤气产率随气化剂预热温度的不同变化较小。实现了循环流化床提升段下部湍动流化、上部环核流动的特殊流场结构,与已有研究结果相比,煤气热值、煤气产率、冷煤气效率都略有提高,更加适合煤气化。     

湍动流化床醋酸乙烯合成反应器的工业试验

运用湍动流态化理论作指导，对醋酸乙烯合成反应器进行技术改造，在原有装置内设置复合内构件，增加颗粒回收系统降低催化剂平均粒径，使流化床操作状态由鼓泡流化转变为湍动流化，强化了气固接触，提高了产物的单程收率。     

方形气固流化床从鼓泡到湍动流态化转变速度预测模型

在368 mm×368 mm的方形气固流化床中对FCC颗粒进行了流态化实验,基于对床内总体压力脉动信号分析了从鼓泡流态化到湍动流态化的转变速度Uc与静床高度H0及床层面位置H的关系.结果表明,床层截面位置H较低或静床高度H0增加都使Uc增加,即鼓泡流态化到湍动流态化的流型转变是由床层上部逐渐向下扩展的递进行为.基于这一...     

湍动流化床中的颗粒减速现象

采用PV6D型光纤探针测量了直径为200 mm与95 mm的2套湍动流化床装置中的颗粒速度分布,据此将湍动床在轴向上分成6个区域,分析了上部出口减速区与下部过渡段减速区的产生机理,考察了流化段高度、静床高、表观气速对颗粒减速区的影响。结果表明:上部减速区是扩大段所产生的,下部减速区则是由于固含率急剧变化所引起的;随流化段高度减小,上部减速区下降,相邻的充分发展区与加速区缩短乃至消失;下部减速区的位置随静床高的增加而升高,随表观气速的增大而下移,与过渡段的变化趋势一致。     

TRANSITION OF FLOW REGIME IN FLUIDIZED BEDS WITH SLANTING BLADE BAFFLES

A flow model is proposed to investigate the transition of flow regime from bubbling to turbulent fluidization postulating that the flow in the emulsion phase follows the Richardson-Zaki equation.

Void fraction of the whole bed ε_f and the mean velocity of bubbles U_b were measured in fluidized beds of 0.3 and 0.5 m ID, in which slanting blade baffles were positioned. Mo-catalyst, silica gel, sand and glass beads with size between 135-443 μm were fluidized by air.

Void fraction of the emulsion phase ε _e was calculated on the basis of the above model. Correlating ε _e with superficial gas velocity U_ƒ, we found that ε _e was very close to ε _mƒ in the bubbling regime and that e, increased with increasing U_ƒ in the turbulent regime.

Calculated values of the volume fraction of bubble phase δ were correlated with U_ƒ, from which apparent transition point from bubbling to turbulent regime was estimated. Combining information obtained, transition of flow regime in the above type of fluidized beds is discussed     

气液固三相流化床流区及其过渡的混沌分析

运用确定性混沌分析技术、研究了气液固三相流化床内压力波动时间序列的混沌动力学行为,结果表明,非线性特征量最大Ｌｙａｐｕｎｏｖ指数可以用来定量表征三相流化床的流区及其过渡。并给出了以最大Ｌｙａｐｕｎｏｖ指数为基准的三相流区图,混沌分析还发现,三相流化床内存在着两混沌特性相差较大的塞状泡流区。     

气固流化床流型特性及其识别的复杂性研究

运用复杂性C2、涨落复杂性Cf及Lempel-Ziv复杂性C(n)等复杂性参数对气固流化床压力脉动信号进行分析,研究它们随流化床操作气速增大历经不同流型的变化趋势并将结果作了比较,进一步探讨了流化床流型特性的内在规律性,研究结果表明,在起始流化致鼓泡态转变的过程中,气－固体系会进行一种所谓的“重构”现象,并证实了气泡的存在是影响压力脉动信号复杂性的重要因素,同时实验显示复杂性参数能明确地指示固定床,鼓泡流化及湍动流化等不同流型之间的转变过程,为流型识别提供了新思路。     

CLUSTERS IN CIRCULATING FLUIDIZED BEDS: KINETIC THEORY APPROACH

The hydrodynamic behavior of particles in circulating fluidized beds has been studied by means of a Boltzmann-like kinetic model. Two main regimes of flow: a homogeneous and a heterogeneous regime have been delimited. In the homogeneous regime, for concentrations below a critical value, the flow consists of upward moving solids. Above the critical concentration, clusters appear. Particles velocity distribution at different values of the solid concentration and the ratio of particles being in clusters to those being in homogeneous flow are calculated for different solid mass fluxes, particle size distributions and superficial gas velocities. Slip factors and the effect of gas radial velocity profile have been predicted. Qualitative agreement with experimental data is obtained.     

GAS MIXING IN SLUGGING AND TURBULENT FLUIDIZED BEDS

The gas phase mixing in a fluidized bed of glass beads (d_p = 0.362 mm) in the slugging and turbulent flow regimes has been studied in a 0.1 m-ID × 3.0 m high Plexiglas column.

The gas dispersion in the downstream of the bed has been described by a diffusion process with the axial and radial dispersion coefficients. The radial dispersion coefficient of the gas phase is nearly constant with the variation of gas velocity in the slugging flow regime, but it increases with an increase in gas velocity in the turbulent flow regime.

Appreciable backmixing of the gas phase is pronounced in the slugging flow regime whereas the lower gas backmixing is produced in the turbulent flow regime. The gas backmixing coefficient increases with an increase in gas velocity in the slugging flow regime, but it decreases slightly with an increase in gas velocity in the turbulent flow regime.

The radial mixing and backmixing coefficients of the gas in terms of Peclet numbers have been correlated with the relevant dimensionless parameters (U_g/U_mf, p_s/p_g, d_p/D_t).

The gas flow pattern in the bed has been well represented by a simplified model based on the two gas phases in the dilute and dense phases which are percolating through the bed in plug flow. The present model can predict the gas exchange coefficient between the phases, the fractions of the dilute phase, the interstitial gas in the dense phase, and the interstitial gas velocity in the bed.     

气固流化床信息传输和流型识别

在互信息理论和涨落复杂性理论基础上,计算了压差、压力及光纤颗粒浓度3种不同传感器测量时间序列之间信息传递的复杂性测度,建立了多传感器信息传输矩阵ITM,并定义了矩阵平均值特征参数MITM.研究了矩阵平均值MITM在不同流化状态下的变化规律,结果表明MITM对不同流型的变化有明显的指示作用.     

FIBRE OPTIC AND CAPACITANCE PROBES IN TURBULENT FLUIDIZED BEDS

In the present study, local flow properties are investigated in pilot plant scale fluidized bed reactors using both fibre optic and capacitances probes. Measurements are conducted at ambient as well as at 150°C. The system used is air and spent FCC particles (mean particle diameter: 65pm). The static bed height is 1.6 m. Bubbling and turbulent regimes (V = 0.40 and 0.70 m/s) are investigated in two 0.3 and 0.5 m ID columns.

Bubble fraction under the bubbling regime and at room temperature, measured using fibre optic and capacitance probes, are in good agreement. However, in the turbulent regime, fibre optic probes are prone to underestimate the bubble fraction while capacitance sensors tend to overestimate it. These discrepancies between fibre optic and capacitance measurements increase with temperature.

Using capacitance probes, a prevalent flat bubble rise velocity profile is measured. This is assigned to the relatively slow response, to the size and to the geometry of the capacitance probes. Overall this gives an underestimation of the bubble frequency and an overestimation of the bubble contact time and the bubble contact length.

Due to the high fibre optic probe sensitivity, care should be taken in the interpretation of signals. Overestimation of bubble frequency leads to underestimation of both bubble contact times and bubble contact lengths.     

MASS TRANSFER AND PHASE HOLDUP CHARACTERISTICS IN THREE-PHASE FLUIDIZED BEDS

The effects of liquid surface tension (42.6 ∼ 72,4 mN/m) and viscosity (1 ∼214mPa • sⁿ), liquid (0.01 ∼0.12m/s) and gas (0.01 ∼0.20m/s) velocities and particle sizes (1 — 8 mm) on phase holdup and mass transfer coefficient ( k_La) have been determined in a 0.142 m-I.D. × 2.0 m-high Plexiglas column. The gas phase holdup increases with liquid velocity, and the rate of increase in gas phase holdup sharply increases with gas velocity in the bed of surfactant solutions. In the beds of 1.0 and 1.7 mm glass beads, the bed contraction occurs whereas in the beds of 2.3 mm glass beads the bed contraction does not occur with an aqueous soltuion of ethanol (σ = 50.4 mN/m). The value of k_La increases with decreasing surface tension (σ ) but it decreases exponentially with increasing liquid viscosity in continuous bubble columns and three-phase fluidized beds. In three-phase fluidized beds with surfactant solutions, k_La increases with gas and liquid velocities and particle size. In three-phase fluidized beds of viscous or surfactant soltuions, k_L,a can be estimated in terms of the energy dissipation rate based on the isotropic turbulence theory and a flow regime map is proposed based on the drift flux theory.     

多传感器数据融合在气固流化床流型识别中的应用

在模糊集理论的基础上给出了多传感器信息融合的一般化办法,并将这种办法用于气固流化床流型的识别中.以压差、压力信号的算法复杂性C(n)、涨落复杂性Cf作为特征参数,根据特征参数建立了单个传感器判别流型的隶属度函数.对多个传感器的识别结果进行数据融合,最后得到了多传感器对不同流型的识别结果.实验结果表明,应用多参数、多传感器数据融合能得到较好的识别结果.     

气固流化床中气泡流运动特征和空隙率径向分布

引言流态化技术在工业领域应用越来越广,但由于流态化行为复杂,许多内在规律还有待于进一步揭示．气固流化床中最基本的特征是颗粒聚集的乳化相与气体聚集的气泡相共存,它的复杂性就在于它的不均匀性和多态性．气固流化床中的不均匀性是由空隙率分布来描述的,然而空隙率的分布目前还未能从理论上得到定量的描述．气固流化床内的空隙率分布与气泡的运动密切相关,因此对床层空隙率的了解最终决定于对流化床气泡运动的研究．在此作者采用流体力学的方法从宏尺度和宇尺度范围来探讨气固流化床内气泡的运动规律,建立相应的多尺度、连续介质…