静电效应对有无埋管气固鼓泡床内气泡特性的影响分析

采用基于双流体模型(TFM)耦合静电模型的方法,研究颗粒的静电对有无埋管气固鼓泡床内气固流动特性和气泡特性的影响。首先在无静电场存在的条件下,利用双流体模型对自由鼓泡床和埋管鼓泡床内的流动情况进行模拟并与实验结果进行对比;进一步耦合静电模型,考察静电对自由鼓泡床和埋管鼓泡床内床层的整体性质和气泡特性的影响。研究结果表明,在无静电场条件下采用双流体模型能较好地预测自由鼓泡床和埋管鼓泡床内的气固流动状况以及气泡的平均直径和气泡的上升速度。埋管的存在使鼓泡床内气固流动发生强烈扰动,并使气泡的平均直径和气泡的上升速度均呈振荡分布。静电的存在对自由鼓泡床和埋管鼓泡床内床层的平均固含率影响不大,但对气泡分布规律影响较大,使得自由鼓泡床内气泡数目减少,而埋管鼓泡床下部区域的气泡分布比较集中,上部有大气泡出现。     

原料粒度分布对沸腾氯化工艺的影响

在沸腾氯化生产过程中,原料粒度、配碳比、反应温度和气流速度等是影响沸腾氯化效果的主要因素,而原料粒度及其分布是其中最重要的影响因素。原料的最小粒径应大于氯化过程中飘逸出炉体的最大颗粒粒径,最大粒径应小于现有载气压力能够浮起的最大颗粒粒径。从化学动力学和流体动力学两个角度计算气流速度和原料粒度匹配,并通过生产实践中的数据分析进行粒度范围修正,总结出与沸腾氯化设备结构相匹配的原料粒度分布范围。     

上扬子地块黔北坳陷及周缘水文地质-地球化学特征与油气保存

从地下水化学-动力学角度对上扬子地块黔北坳陷及周缘油气保存条件进行了研究。结果表明：黔北坳陷及周缘自震旦纪以来共经历了3次重要的水文地质旋回,即加里东期、海西期-印支期和燕山期-喜马拉雅期。黔北坳陷及周缘在加里东期和海西期-印支期是两次主要的油气成藏期,但加里东末期和燕山期-喜马拉雅期运动使得区内原已形成的油气藏几乎被破坏殆尽。多次构造运动和多期大气水下渗作用使得现今黔中隆起埋深小于2 500 m、黔北坳陷埋深小于3 000 m的地层水矿化度低,处于自由交替带且底界尚不清楚,油气保存条件较差;川南坳陷在埋深800 m的浅部地层已进入交替阻滞带,油气保存条件相对较好。     

气体分布器对浆态床环流反应器内流体流动特性影响的研究

基于一种浆态床环流反应器冷模试验装置,采用3种不同的气体分布器,考察了分布器结构对环流反应器流体力学特性的影响,为费托合成浆态床反应器及其内构件的设计和放大提供依据。试验结果表明:金属烧结板气体分布器的分布均匀性最好,但容易堵塞,不能满足长期稳定运行的要求。通过对不同开孔方向的两种双环管分布器进行比较,发现开孔向下时,总平均气含率高、气/液(浆)相界比表面积大,更适合应用于浆态床环流反应器。     

不同粒径固体颗粒的悬浮速度计算及测试

分析讨论了不同粒径固体颗粒群的料浆流体力学特性，并在模型反应器中对其悬浮速度进行了实验测量。结果表明，以粒径范围为判据判定颗粒周围流场的流态，可使悬浮速度的测量、研究变得更简单、准确。研究采用悬浮分级模型，提高了悬浮速度的分析计算精度     

Hydrodynamic Study of Gas–Solid Internally Circulating Fluidized Bed Using Multiphase CFD Model

In the present work, hydrodynamic study of gas and solid flow in an internally circulating fluidized bed (ICFB) was carried out using the CFD multiphase model. Two- (2D) and three-dimensional (3D) computational meshes were used to represent physical ICFB geometries of 0.186-m and 0.3-m diameter columns. The model approach uses the two-fluid Eulerian model with kinetic theory of granular flow options to account particle–particle and particle–wall interactions. The model also uses various drag laws to account the gas–solid phase interactions. The 2D simulation results by various drag laws show that the Arastoopour and Gibilaro drag models predict the fluidization dynamics in terms of flow patterns, void fractions, and axial velocity fields in close agreement with the Ahuja et al. (2008 Ahuja, G. N., and A. W. Patwardhan. 2008. CFD and experimental studies of solids hold-up distribution and circulation patterns in gas–solid fluidized beds. Chemical Engineering Journal 143:147–160.[Crossref], [Web of Science ®] , [Google Scholar]) experimental data. Three dimensional simulations were also carried out for a large-scale ICFB. The effects of superficial gas velocity and the presence of draft tube on solid holdup distribution, solid recirculation pattern, and gas bypassing dynamics for the 3D ICFB were investigated extensively. The mechanism governing the solid circulation and the pressure losses in an ICFB has been explained based on gas and solid dynamics obtained from these simulations. Predicted total granular temperature distributions in 3D ICFB draft tube and the annular zone are qualitatively in agreement with the experimental data. The total granular temperature tends to increase with the increase in solids concentration in the dilute region (? < 0.1) and decrease with an increase of solids concentration in the dense region (? > 0.1).     

Multiphase CFD-based models for chemical looping combustion process: Fuel reactor modeling

Chemical looping combustion (CLC) is a flameless two-step fuel combustion that produces a pure CO₂ stream, ready for compression and sequestration. The process is composed of two interconnected fluidized bed reactors. The air reactor which is a conventional circulating fluidized bed and the fuel reactor which is a bubbling fluidized bed. The basic principle is to avoid the direct contact of air and fuel during the combustion by introducing a highly-reactive metal particle, referred to as oxygen carrier, to transport oxygen from the air to the fuel. In the process, the products from combustion are kept separated from the rest of the flue gases namely nitrogen and excess oxygen. This process eliminates the energy intensive step to separate the CO₂ from nitrogen-rich flue gas that reduce the thermal efficiency.Fundamental knowledge of multiphase reactive fluid dynamic behavior of the gas-solid flow is essential for the optimization and operation of a chemical looping combustor.Our recent thorough literature review shows that multiphase CFD-based models have not been adapted to chemical looping combustion processes in the open literature. In this study, we have developed the reaction kinetics model of the fuel reactor and implemented the kinetic model into a multiphase hydrodynamic model, MFIX, developed earlier at the National Energy Technology Laboratory. Simulated fuel reactor flows revealed high weight fraction of unburned methane fuel in the flue gas along with CO₂ and H₂O. This behavior implies high fuel loss at the exit of the reactor and indicates the necessity to increase the residence time, say by decreasing the fuel flow rate, or to recirculate the unburned methane after condensing and removing CO₂.     

湍动浆态床流体力学研究（Ⅰ）气含率及其分布规律

对高气速、高固含率、大塔径条件下的湍动浆态床平均气含率和气含率径向分布进行了实验测定,结合工业实验数据,归纳出可用于工业条件的气含率计算关联式,给出了简化的流体力学模型用于气含率分布的模拟。结果表明,浆态床气含率将随塔径增加而降低,固含率与塔径之间存在交互影响;同时,气含率的径向分布也随气速和塔径的增大而改变,存在明显的放大效应,简化模型能够较好地模拟实验结果。     

倒锥型催化精馏构件的流体力学性能

为进一步提高催化精馏塔的性能,提出了一种新型倒锥型帽罩结构,针对帽罩结构参数进行实验研究。采用空气-水体系测定倒锥型塔构件不同参数下的塔板压降及液泛气速,并对其流体力学性能进行深入研究。实验结果表明,锥角对压降和液泛气速几乎没有影响。开孔比大于1时对压降无影响,开孔比小于1时压降随其值的增大而减小,液泛气速则略微增大。开孔孔径增大,则压降增大,而液泛气速减小。压降随锥体高度的增大而增大,但液泛气速与其并不呈线性变化。压降随堰高的增大而增大。催化剂装填量增大,压降增大,且液泛气速呈下降趋势。倒锥型催化精馏塔构件对其流体力学有显著影响,并在确定的条件下可选择较大的锥角,采用较小的开孔孔径和罩体高度。     

气-固循环流化床的流动特性

循环流化床是一种新型高效无气泡气-固反应器,应用广泛。文章首先介绍了气-固循环流化床的特点,总结了循环流化床上部区域的流动特性,并讨论了循环流化床底部区域的流动特性,最后展望了循环流化床流动特性研究的发展趋势。