过程所与流态化-庆祝过程工程研究所建所60周年

中国科学院过程工程研究所自1958年创建以来已经走过60年一个甲子的历程. 该所坚持面向科学前沿、面向国家重大需求、面向国民经济主战场的中国科学院办院方针,在应用基础研究和工业应用两方面均取得了一系列重要成果,在流态化科学与技术领域尤为突出. 在已故所长郭慕孙院士的领导下,过程所在流态化科学与技术领域长期处于世界领先地位. 本文回顾和概述了该所在流态化理论与工业应用两方面所取得的一系列重要成果. 理论方面包括诸如广义流态化理论、无气泡气固接触理论、气固流态化的散式化理论、流化床结构?传递关系理论、EMMS理论与介科学、微型流化床的提出及定义等;工业应用方面涉及诸如贫铁矿的流态化磁化焙烧、煤的流态化热解、锰矿的流态化还原、高湿高氮燃料的低NOx双流化床解耦燃烧、低焦油流化床两段气化、中石化MIP(Maximizing Iso-Paraffins)循环流化床技术的计算机模拟放大等. 仅以此文作为献给过程所创建60周年的生日礼物,以此激励我们继承与发扬老一辈科学家的求真务实爱国敬业精神,在科研工作中取得更大的成就.     

循环流态化（Ⅰ）

循环流态化是近年来化学工程中最活跃的研究领域之一,是既具有重大的工业应用背景,又具有重要学术理论价值的研究课题。为了有利于我国对这一技术的研究与应用,本文试图较全面地介绍:一、循环流态化技术的发展及工业应用二、循环流态化的存在区域三、循环流态化气、固流动规律四、循环流态化气、固流动模型五、循环流态化气、固混合及传递规律六、循环流化床反应器及其数学模型七、循环流化床反应器设计及放大文中将充分介绍我国在循环流态化基础研究与应用方面的成果,同时努力体现循环流态化技术研究的前沿。     

2万吨／年硝基苯加氢流化床反应器设计

本文主要介绍流化床反应器设计中的工程放大技术。其特点是抓住工程放大的核心——克服放大效应,即如何控制气泡直径和防止气体返混这两个基本要点。流化床反应器放大时在以下三方面作了改正:1.气、固分离散术;2.反应热回收技术;3.密相床气泡控制技术。这项设计的技术水平属国内领先、并达到国外同类流化床反应器的生产水平。     

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…     

华南理工大学环境科学与工程学院

研究方向 废水生物处理新型反应器及其理论 以生物三相流化床为典型代表，分别研究射流曝气厌氧流化床、污泥自吸内回流好氧流化床、各种床型结构反应器的流体力学、工业有机废水处理的生物学与工程学。     

华南理工大学环境科学与工程学院

韦朝海教授，研究方向：废水生物处理新型反应器及其理论以生物三相流化床为典型代表，分别研究射流曝气厌氧流化床、污泥白吸内回流好氧流化床、各种床型结构反应器的流体力学、工业有机废水处理的生物学与工程学。     

沸腾转化催化剂床内气泡特性研究与工业反应器的模拟和优化

在直径190mm的有机玻璃塔内,对填装0.27～0.79mm的以球形硅胶为载体的钒催化剂(B类粒子)流化床进行了实验研究。用直射式光纤探头连接微机采样和分析。结果表明,气泡直径和上升速度与A类粒子流化床获得的关联式基本相符。但气泡分率随床高增加而明显增加。根据实验结果,确定了B类粒子流化床反应器的模型参数。用两相平推流模型与本研究所获得的气泡参数及反应动力学方程相结合,对直径为1500mm的工业反应器进行了模拟,得到令人满意的结果,并进一步优化了工业操作条件。     

乙炔加氢制乙烯浆态床反应器的CFD模拟

对浆态床反应器中乙炔加氢制乙烯过程进行了模拟研究，采用TFM-PBM耦合方法描述浆态床内气相与浆态相的流动，并耦合乙炔加氢反应动力学建立流动-反应综合模型。通过小试实验对该模型进行验证，并将验证后的模型应用于浆态床中试装置中内构件作用机制与操作条件影响的模拟分析。结果表明，在浆态床反应器放大时，可通过设置竖管内构件，以破碎气泡，抑制气相径向运动，使乙炔加氢过程均匀、充分地进行。乙炔加氢制乙烯过程与气相停留时间和反应温度密切相关，在反应器放大中需严格控制温度，并可通过改变反应器内液位高度实现对气相停留时间的调控，从而可在保证乙炔充分转化的同时获得更高的乙烯选择性。     

乙炔加氢制乙烯浆态床反应器的CFD模拟

对浆态床反应器中乙炔加氢制乙烯过程进行了模拟研究,采用TFM-PBM耦合方法描述浆态床内气相与浆态相的流动,并耦合乙炔加氢反应动力学建立流动-反应综合模型。通过小试实验对该模型进行验证,并将验证后的模型应用于浆态床中试装置中内构件作用机制与操作条件影响的模拟分析。结果表明,在浆态床反应器放大时,可通过设置竖管内构件,以破碎气泡,抑制气相径向运动,使乙炔加氢过程均匀、充分地进行。乙炔加氢制乙烯过程与气相停留时间和反应温度密切相关,在反应器放大中需严格控制温度,并可通过改变反应器内液位高度实现对气相停留时间的调控,从而可在保证乙炔充分转化的同时获得更高的乙烯选择性。     

新型循环流化床反应器研究进展

开发新型循环流化床反应器始终是流态化领域研究的热点。本文首先简介了循环流态化的基本原理以及床层内部流体动力学特性,然后从装置构型、操作工况、流动特性以及应用前景等方面综述了近年来新型循环流化床反应器技术的研究进展,并对其进行了系统分类:高密度循环流化床和循环湍动流化床在实现提升管增浓的基础上,极大地改善了流化床体系中明显的不均匀时空流动结构,但是各有弊端,例如高密度循环流化床(HDCFB)中颗粒沿径向混合有很大的梯度,循环湍动流化床(CTFB)中存在强烈的轴向返混以及颗粒停留时间较长,且两者整体偏低的颗粒浓度进一步限制了其在两段提升管催化裂解多产丙烯(TMP)等生产低碳烯烃工艺的应用;变径提升管反应器、内循环型提升管反应器以及多流型提升管反应器等新型反应器将提升管高效的气力输送特性与密相床内较高的颗粒浓度、高效的热质传递等优点相互耦合,在提升管内既能实现高密度输送又能形成均匀的流动结构,消除反应环境对产品分布的影响。最后指出,新型循环流化床的研究应从改善流动结构、发展优化组合技术以及建立统一流动模型3个方面着手。     

Deterministic chaos: a new tool in fluidized bed design and operation

Deterministic chaos theory offers new and useful quantitative tools to characterize the non-linear dynamic behaviour of fluidized beds. The dimension and entropy of the fluidized bed's strange attractor can be used for various purposes, such as the classification of fluidization regimes or fluidized bed scale-up. This is illustrated by experimental and model simulation examples of deterministic chaotic behaviour in ambient gas-solids fluidized beds of Geldart B particles. It is shown that the Kolmogorov entropy is dependent on, amongst other parameters, the gas velocity and the bed aspect ratio. In dimensionless scaling of fluidized bed reactors this type of relationship can probably be of use in establishing full dynamic similarity.     

气固流化系统多尺度跨流域EMMS建模

气固流化床反应器是典型的具有多尺度非均匀动态结构的复杂系统。实现对该类反应器定量描述和定向调控的关键是深入了解系统内介尺度结构的形成和演化特征。能量最小多尺度（EMMS）方法为气固非均匀系统的量化表征提供了一种通用的建模思路。首先回顾了EMMS理论在构建曳力本构关系方面的应用,重点介绍了本课题组在EMMS曳力模型普适化方面所做的部分工作;随后对介尺度结构时空动态演化行为的群平衡建模方法进行了论述,并给出了群平衡和结构曳力模型相耦合的连续介质模拟框架;最后讨论了EMMS原理在预测反应器宏尺度动力学方面的应用,包括模型在不同流域的拓展、操作相图的绘制以及循环流化床的全回路稳态建模方法等。     

3D simulation of effect of geometry on minimum fluidization velocity and flow regimes in a spout-fluidized bed

Spout–fluid beds are used for a variety of processes involving particulate solids, like coating, drying, granulation and etc. The spout–fluidized bed combines a number of favorable properties of both spouted and fluidized beds. In this study, the Granular Eulerian model is used in 3-D hydrodynamic simulation of spout fluidized bed for calculation of minimum fluidization velocity. The results of simulation were compared with experimental data and good agreement was obtained. Then the effect of geometry on minimum fluidization velocity was studied. Also a review of flow regimes in different spout fluidized bed geometries was studied.     

流态化模拟:基于介尺度结构的多尺度CFD

介尺度结构是研究气固流态化多尺度行为的关键。传统的基于平均化处理方式的双流体模拟不能准确描述流化床中的多尺度流动和传递行为。相较而言,基于能量最小多尺度(EMMS)方法的结构多流体模型(SFM)基于局部空间(网格)内的非均匀介尺度结构流动特征,其宏观预测结果与网格分辨率基本无关,因而可以大幅降低模拟计算量。基于SFM模拟得到的流动结构,EMMS多尺度传质模型进一步成功解释了传统传质文献中的数据差异。集成上述模型,形成了一整套模拟流化床流动-传递-反应耦合过程的多尺度计算流体力学(CFD)方法,并将其应用于预测循环流化床中典型的S型轴向分布、揭示噎塞转变的机理以及流化床放大困难的原因。多尺度CFD使工业规模循环床的三维、全系统、动态流动-反应耦合过程的准确模拟成为可能,并为实现从模拟向实时虚拟过程转变的目标打下基础。     

粘附性颗粒流态化研究进展

主要阐述了粘附性颗粒流态化特性（初始流化速度、床膨胀、塌落）及聚团流化过程,提出了粘附性颗粒流态化的机理是聚团流化．并对近年来国内外在预测聚团大小、床层结构模型、改善粘附性颗粒流化性能方面的研究进展进行了总结．     

Prediction of critical fluidization velocity and maximum bed pressure drop for binary mixture of regular particles in gas–solid tapered fluidized beds

The problems associated with conventional (cylindrical) fluidized beds, viz., fluidization of wider size range of particles, entrainment of particles and limitation of fluidization velocity could be overcome by using tapered fluidized beds. Limited work has been carried out to study the hydrodynamics of single materials with uniform size particles in tapered beds. In the present work, an attempt has been made to study the hydrodynamic characteristics of binary mixtures of homogeneous and heterogeneous regular particles (glass bead and sago) in tapered fluidized beds having different tapered angles. Correlations have been developed for critical fluidization velocity and maximum bed pressure drop for gas–solid tapered fluidized beds for binary mixtures of regular particles. Model predictions were compared with experimental data, which were in good agreement.     

Numerical investigation for the suitable choice of bubble diameter correlation for EMMS/bubbling drag model

Mesoscale bubbles exist inherently in bubbling fluidized beds and hence should be considered in the constitutive modeling of the drag force. The energy minimization multiscale bubbling (EMMS/bubbling) drag model takes the effects of mesoscale structures (i.e., bubbles) into the modeling of drag coefficient and thus improves the coarse-grid simulation of bubbling and turbulent fluidized beds. However, its dependence on the bubble diameter correlation has not been thoroughly investigated. The hydrodynamic disparity between homogeneous and heterogeneous fluidization is accounted for by the heterogeneity index,H_d, which can be affected by choice of bubble diameter correlation. How this choice of bubble diameter correlation influences the model prediction calls for further fundamental research. This article incorporated seven different bubble diameter correlations into EMMS/bubbling drag model and studied their effects onH_d. The performance of these correlations has been compared with the correlation used previously by EMMS/bubbling drag model. We found that some of the correlations predicted lower H_d by order of a magnitude than the correlation used by the original EMMS/bubbling drag. Based on such analysis, we proposed a modification in the EMMS drag model for bubbling and turbulent fluidized beds. A computational fluid dynamics (CFD) simulation using two-fluid model with the modified EMMS/bubbling drag model was performed for two bubbling and one turbulent fluidized beds. Voidage distribution, time averaged solid concentration and axial solid concentration profiles were studied and compared with the previous version of the EMMS/bubbling drag model and experimental data. We found that the right choice of bubble diameter correlations can significantly improve the results for CFD simulations.     

Models for prediction of hydrodynamic characteristics of gas–solid tapered and mini-tapered fluidized beds

Prediction of hydrodynamic characteristics is a prerequisite in the design and operation of tapered and mini-tapered fluidized beds. This paper has been focused on the development of generalized models for prediction of minimum fluidization velocity and maximum pressure drop in gas–solid tapered and mini-tapered fluidized beds. The empirical correlations were developed based on dimensionless analysis of empirical data. These correlations have the ability to predict the minimum fluidization velocity and maximum pressure drop in both tapered and cylindrical beds (the beds with tapered angle of zero). The empirical data were collected from tapered beds with different cone angles for various particles. The predicting capability of correlations has been discussed. Predicted values of minimum fluidization velocity and maximum pressure drop by the proposed models compared well with the empirical data. The effects of tapered angle are also discussed.     

A consolidated flow regime map of upward gas fluidization

A new flow regime map, resulting from more fundamental studies on the hydrodynamics and new flow regimes, is proposed in response to more practical reclassifications of the existing regimes with the development of upward gas-solids fluidization systems. The previously reported flow regime maps and flow structures of some widely used fluidized beds are carefully examined. To better reflect the industrial applications, the fast fluidization regime is reclassified as high-density and low-density circulating fluidization regimes. A consolidated flow regime map is then proposed where the flow regimes of upward fluidization expand to include new types of fluidized beds such as circulating turbulent fluidized bed and high-density circulating fluidized bed. The proposed flow regime map consists of six flow regimes: bubbling, turbulent, circulating turbulent, high-density circulating and low-density circulating fluidization, and pneumatic transport. The transitions between the regimes are discussed with new correlations proposed for fluid catalytic cracking type particles. Analysis on the dominating phase in the different types of fluidized beds reveals the dynamic changeover from solids phase continuous in conventional low-velocity batch/“fixed” fluidization operations to gas phase continuous in high-velocity continuous/“moving” fluidization operations and provides more insights to the transitions between the flow regimes for industrial design and practice.