径向流反应器流场分布的数值模拟分析

径向流反应器是一种高效节能反应器。为了深入研究四种不同流动类型的径向流反应器的流场分布特征,在验证模拟可行性的基础上,引入多孔介质模型,运用FLUENT软件对不同类型的径向流反应器内的流场进行数值模拟。在边界条件设置一定时,模拟分析四种类型径向流反应器内分流流道与集流流道间的压降沿轴向的变化程度,结果说明:离心流动的流体分布均匀度优于向心流动,П型离心的径向流反应器内部流场分布最均匀,其次是Z型离心流动、П型向心流动、Z型向心流动。     

大型乙苯脱氢轴径向反应器的研究与开发(Ⅰ) 流体力学特性

乙苯脱氢轴径向反应器是一种催化床上部采用催化剂自封结构的新颖径向反应器 ,其催化床中的流体流动是复杂的二维流动 .在催化床的表征体积元上应用连续性方程和Ergen方程描述了其流动 ,应用有限差分法通过数学模拟得出了轴径向反应器流场 ,其结果在Φ30 0 0× 10 0 0 0的冷模装置得到了验证 .以大型乙苯脱氢轴径向反应器为背景 ,讨论了流向和触媒封高对流场的影响 ,得出径向段主要以径向流动为主 ,在催化剂封区以轴向、径向二维流动为主 ;催化剂封高是影响流场的主要因素 ,对于向心流动δ在 0 .7附近是Q_a/Q与Q_r/Q相同的等比流量点 ,对于离心流动在δ为 1.1处 ,是Q_a/Q和Q_r/Q相同的等比流量点 .δ小于此值 ,是以轴向流动为主径向流动为次的二维流动区 ;δ大于此值 ,是轴向流动为次径向流动为主的二维流动区 ;与离心流动型相比 ,向心流动型轴径向床有明显的限流作用     

离心型径向固定床分气流道内局部动量交换系数

针对离心型径向固定床气体流道内变质量流动特点，在一套冷模实验装置上，分别采取Π型和Z型操作模式，测量并分析了两气流道内压力分布，发现分气流道内的压力沿气体轴向流动方向呈增加趋势，集气流道与之相反。根据颗粒床层压降分布不均匀度和采用Ergun方程求得的径向气速轴向分布，发现离心Π型均略优于离心Z型。通过对气流道内微元控制体进行流量和动量衡算，由颗粒床层径向气速轴向分布可依次得到分气和集气流道内气速、局部动量交换系数计算方程。相较于集气流道，分气流道内动量交换系数对压力测量误差的敏感度较小。分气流道中，整体动量系数几乎不随操作模式、气体流量和轴向位置发生变化；而局部动量交换系数仅是流速比u/u0的函数，随流速比增大先降低后保持稳定。根据实验结果，回归得到的分气流道局部动量交换系数计算方程的误差在11%以内，有望为气流道内局部压力计算和结构优化设计提供参考。     

移动床径向反应器中气体离心流动对颗粒移动状况的影响

对于催化剂不断失活但可再生的工业过程,广泛采用移动床径向反应器在较低的系统压降下进行连续操作.此时存在由贴壁和空腔现象所决定的径向气体流量的上限值.本文分析了有径向离心气体流动时颗粒层中的应力分布,应用散料力学理论建立了计算床中初始形成空腔时无因次床层总压降的理论模型,模型预测值与实验值符合很好.同时测定了不同条件下空腔界面的形状.     

径向流动反应器流体力学特性研究

本文提出了表征径向流动反应器内流体流动规律的数学模型.该模型为一特殊的二阶微分方程的边值问题.对于Ⅱ型流动:Au′u″+Bu′u+Cu~2=0对于Z型流动:Au′u″+Bu′u+Cu′+Eu~2+F(1-u)~2=0边界条件为y=0,u=1;y=1,u=0式中模型参数A、B、C、E、F决定于径向反应器分布流道结构尺寸、穿孔阻力系数和径向床层特性等因素.为简化Ⅱ型径向反应器边值问题的求解过程,本文推荐一种解析求解方法.该模型应用于径向氨氧化炉操作工况和径向氨合成塔设计工况的模拟,揭示了径向流动反应器内的流体力学特性.     

绝热固定床反应器的研究——(Ⅲ)径向反应器着火规律和温度分布

由丁径向反应器内气体流道面积的变化,其着火和熄火规律与轴向床有所不同.本文研究了向心和离心两种流型的径向反应器的着火规律及床内定态温度分布,并就一个实例作了模拟计算.     

径向流动反应器工艺设计要点

径向流动反应器具有流道短、阻力小、可使用小颗粒催化剂、空速大等优点 ,已在石油与化学工业中推广应用。讨论了径向流动反应器工艺设计中的几个关键问题 :①两种流体流动型式 (Π型与Ζ型 )的选择原则 ;②为防止流体短路而设置“催化剂封” ;③防止催化剂细粒吹入分流与集流流道的措施 ;④移走反应热效应的方法 ;⑤流体均布的设计 ;⑥径向流动反应器的工艺设计模型。     

BCL407型高压离心式压缩机轴向推力的计算

详细分析了离心叶轮外侧间隙内泄漏气体的流动规律和离心式压缩机轴向推力的组成。建立了离心叶轮盘、盖外侧间隙内泄漏气体流动的计算模型,采用了低Ｒｅ数κ ε紊流模型,并用ＳＩＭＰＬＥＣ方法求解控制方程。分别计算了离心叶轮盘、盖两侧不同间隙宽度及不同泄漏流量大小时的压力沿径向的分布。对一台化工用ＢＣＬ４０７型高压离心式压缩机高压缸的轴向推力进行了计算,结果令人满意。     

多床层径向反应器中床层的流场行为

在直径3m、高5m的大型多床层径向反应器冷模装置上,通过测定流体在流道和各分床层内的静压分布,考察了各分床层的流体流动行为和特征.结果表明,当流道静压差的均方根偏差小于1%时,各分床层静压差的均方根偏差小于5%,流体在各分床层的径向流速沿轴向分布均匀,流速最大偏差小于5%;当流道静压差沿轴向的差别大于10%时,则其沿轴向分布显著不均匀,且靠近流道静压变化梯度大的分床层的径向流速均匀性最差,床层上下端流速偏差达70%.Π型流动形式是动量交换型径向反应器的最佳选择,适宜的两流道静压差设计可实现径向流速沿床层轴向完全均匀分布。     

循环流化床下料管中气固流动模型的研究

本文在下料管（内径100mm）的循环流化床内研究了气固流动规律。通过测定颗粒速度、颗粒浓度以及气体速度，进一步描述了气固相对速度与颗粒浓度的变化关系，在对气固相互作用分析的基础上，得到了描述气固下行流动的R－Z方程。     

Investigations on hydrodynamics of radial flow moving bed reactors

Distributions of pressure and velocity in the main channels were studied in a radial flow cold model of a moving bed reactor, 500 mm in diameter, in four different gas flow modes, inward Z gas flow, inward Π gas flow, outward Z gas flow, outward Π gas flow. It has been found that, in outward Π gas flow mode, the axial non-uniformity of the gas is at a minimum. The following correlations are proposed for the momentum recovery factors K_a and K_b: K_a = 0.684 + 0.0128 (du/dx)/u, K_b = 1.135 + 0.0158 (du/dx)/u. Pressure distributions in the main channels can be accurately predicted using K_a and K_b.     

The formation and growth of bubbles at a submerged orifice

A model has been developed to describe the formation of single bubbles at a submerged orifice. The model is based on a modified Rayleigh equation for bubble growth and describes the effect of gas momentum by assuming that the flow field inside the growing bubble is in the form of a circulating toroidal vortex. The equations describing the bubbling system are solved numerically using an explicit finite-difference technique. The model shows that bubble growth is characterised by an initial outward movement of the base of the bubble along the plate floor followed by an inward movement back towards the orifice which leads to a severing of the bubble from the orifice and termination of the growth cycle.Computed bubble growth rates, formation times and chamber pressure fluctuations are shown to be in good agreement with available experimental data for a wide range of system pressure (0–1.37 MN/m²) and computed bubble shapes are similar to those observed experimentally.     

喷射引流式BOG回收装置的研究

利用喷射泵原理设计了一种BOG气体回收装置,这是首次将喷射引流技术应用于LNG接收站BOG气体的回收,利用较高的外输压力作为喷射气体,可以实现LNG接收站外输流量较低或者BOG再冷凝系统检修时BOG气体的回收。采用气体动力函数法对混合室动量方程进行求解,利用Matlab编制喷射器尺寸设计程序。为将吸入流体增压到下游管网压力以实现外输,采用牺牲吸入量与多级喷射增压技术相结合的方式。多级增压级间压力可由气体动力函数法求解喷射系数而算得,经过计算,外输3Mm~3的工况下,装置每天可回收7.374Mm~3 BOG气体。     

Analysis of centrifugal annular reactor with radial flow

A model for centrifugal annular catalytic reactor is presented. The gas flows radially through the annulus while the inner cylinder is rotated to produce the centrifugal effect. A catalytic consecutive reaction takes place at the external surface of the annulus. The reactor is aimed to utilize the fact that heavier substances concentrate on the external walls of rotating reactors more than the lighter ones, so as to improve the conversion and yield of the desired intermediate product in consecutive reactions.The reaction performance is examined for various reaction kinetics, angular velocity and gas flow rate. The gas flow direction (inward or outward) is aIt is shown that for a given reaction and reactor geometry, an optimal angular velocity exists, where the reaction conversion is maximum. It is also sh     

柱塞气固两相流输送特性

为了研究柱塞式气力输送气固两相流的输送特性,对实际的工业气力输送系统进行1∶1试验台改造,首先进行了粉煤灰在输送管内的流动模式试验;然后进行粉煤灰输送压力、输送质量流量特性试验;最后考察了主进气流量、补气流量、助吹气流量对粉煤灰输送量、固气比的影响。研究表明,柱塞式气力输送流动模式以密相栓柱流为主,其灰栓长度为0.8～2.3 m,移动速度约为2.8～11.3 m·s^-1;输送压力与输送流量呈双曲线特性,且随着气量的增加输送量增大;主进气流量起主导作用并与输送粉煤灰质量流量呈单调上升抛物线关系,与固气比呈上凸抛物线关系即先增大后减小。研究结果对柱塞式气力输送系统的工程设计、运行和理论研究提供依据并具有指导作用。     

Pattern formation in drying of particle-laden sessile drops of polymer solutions on solid substrates

The drying of particle-laden sessile drops of water or polymer solutions was investigated experimentally. The contact angle of water on the solid surface was 45°. Particles used in the experiment were polystyrene particles of 1 and 6 μm and hollow glass spheres of 9–13 μm. As the polymers polyethylene oxide of 200 and 900 kDa and xanthan gum were used. Depending on particle size and fluid viscosity, the drying pattern varied and there was a competition of the inward movement due to the capillary and/or buoyant force acting on the particles trapped at the liquid interface and the outward movement due to the Deegan flow. The typical ‘coffee ring’ of colloidal particles was not always observed. Either inward or outward motion was observed depending on low shear viscosity. Elasticity does not appear to change the Deegan flow qualitatively. However, elasticity appears to change the pinning characteristics of the contact line.     

Electrocatalytic hydrogenation of soybean oil in a radial flow-through Raney nickel powder reactor

Soybean oil has been hydrogenated electrocatalytically on Raney nickel powder catalyst at atmospheric pressure and moderate temperatures in a novel undivided packed bed radial flow-through reactor. The reactor consisted of a single anode/cathode tubular element, where Raney nickel catalyst powder was contained in the annular space between two concentric porous ceramic tubes and the flow of the reaction medium (a dispersion of oil in a water/t-butanol/tetraethylammonium p-toluenesulfonate electrolyte) was either in the inward or outward radial direction. The innovative design of this reactor allows for a thin nickel bed and a high anode/cathode interfacial area without the normal problems associated with electrolyte flow distribution. The total size of the reactor can be increased without changing the relative anode/cathode position and the electrolyte flow pattern by simply increasing the length and/or number of anode/cathode elements in a single common shell (similar to a shell-and-tube heat exchanger). For the brush hydrogenation of soybean oil, current efficiencies of 90–100% were achieved with a single element reactor when the electrolyte oil content was 10 or 25 wt/vol %, the apparent current density was 10 or 15 mA cm^–2, the temperature was 75 °C, and the electrolyte flowed in the inward radial direction. The electrohydrogenated oil product was characterized by a high stearic acid content and low concentrations of linolenic acid and trans fatty acid isomers, as compared to the traditional high temperature chemical catalytic oil hydrogenation route with hydrogen gas.     

锥芯可调型引射技术变工况适应性实验研究

随着天然气井开发时间的推移，井口压力逐渐降低，低压井口的增压集输成为研究热点。目前，常用的天然气引射技术由于结构尺寸固定，对气井的压力和流量的变化适应性差，使其运行效率普遍较低。据此，设计加工了一台锥芯可调型引射器装置，并对其变工况性能进行了实验研究。结果表明随着可调锥的深入，高压口流量减小，可实现70%左右的流量调节，而且调节过程中低压口流量几乎保持不变，从而使得装置引射率ξ提高，可见该引射技术具有很强的抗流量波动能力。随着可调锥的深入，装置对应的最佳膨胀比增大，从而提高了装置对大膨胀比工况的适应性。同样压缩比下，装置引射效率会随着可调锥的深入而提高，但会降低装置有效引射的压缩比范围。     

Hydrodynamic behaviour of a draft tube gas-liquid-solid spouted bed

Experiments were conducted using various types of solid particles to investigate the hydrodynamic properties of a gas-liquid-solid spouted bed with a draft tube. The hydrodynamic properties under study include flow modes, pressure profile and pressure drop, bubble penetration depth, overall gas holdup, apparent liquid circulation rate and bubble size distribution. Three flow modes were classified: a packed bed mode, a fluidized bed mode and a circulated bed mode. It was found that the friction factor accounting for the friction loss in the bed varies linearly on a logarithmic scale with the Reynolds number defined based on the apparent liquid circulation rate. The bubble penetration depth in the annular region, overall gas holdup and apparent liquid circulation rate increase with an increase in gas or liquid velocity. At high gas flow conditions an optimal solids loading exists which yields a maximum apparent liquid circulation rate. A model was proposed to describe the liquid circulation behaviour in the draft tube three-phas spouted bed. The average bubble size in the draft tube region is higher than that in the annular region for both the dispersed bubble regime and the coalesced bubble regime in the draft tube region.