刚柔组合桨搅拌反应器强化锰矿浸出的中试试验研究

锰矿浸出搅拌反应器大多为刚性搅拌桨,其卷吸力较小,轴向输送能力较弱,容易形成对称性流场,固液两相悬浮程度较低,浸出时间较长、效率较低。提出了一种刚柔组合强化锰矿浸出的新方法,对比研究了刚性桨和刚柔组合对浸出时间及搅拌电耗的影响。结果表明:与刚性桨相比,刚柔组合桨能够缩短浸出时间近1h,增强了设备的生产能力。     

搅拌釜中自浮颗粒的三相搅拌混合问题

考察了釜径３８６ｍｍ的搅拌釜内５２种搅拌浆组合对自浮颗粒的气液固三相搅拌混合的功率消耗，气含率和釜底颗粒含量的影响，研究表明，自浮颗粒的悬浮行为与下沉颗粒有很大区别，有自浮颗粒三相体系的搅拌混合应采用多层浆，且上层最好用上推式浆，实验发现，当高径比为１．６时，三层桨的混合参数优于两层桨，确定了优异的搅拌桨型。f     

高固含固液搅拌槽内颗粒悬浮与混合特性

对高固含体系下Intermig桨搅拌槽内的桨叶搅拌性能以及颗粒的混合与悬浮特性进行实验研究.采用光导纤维技术对不同桨径、搅拌转速和桨叶离底距离下搅拌槽内底部以及轴向颗粒密度进行测量,同时对临界悬浮转速和搅拌功率进行测定.实验结果表明：对高固含液-固搅拌体系,所采用的Intermig搅拌桨具有很好的轴向混合特性,该桨适合在较大的桨径和较低的桨叶离底距离下应用,可在促进颗粒悬浮与均匀分布的同时,大大降低功率消耗.通过对实验结果的分析和拟合得出底部均匀度与搅拌槽内弗劳德数有关,Q=0.58Fr^-0.35,Intermig搅拌桨功率准数在0.2~0.3之间,且与雷诺数关系为N_P=2.1Re^-0.2.     

含钒页岩搅拌浸出槽结构优化的数值模拟

基于Fluent流体力学软件,采用标准k-ε湍流模型、欧拉-欧拉多相流模型、多重参考系稳态算法,通过改变搅拌槽内搅拌桨层数、桨叶层间距以及下层桨叶距底高度,对搅拌槽内固液两相流动过程进行优化与改进模拟研究。结果表明,增加搅拌桨层数能明显改善液面流速"死区"范围,整个槽内流体混合更加剧烈;桨叶层间距在0.33 D～0.53 D(D为搅拌槽内径)时,流体流型以合并流为主,能够加强固液之间的接触碰撞和两相间充分混合;下层桨叶距底高度为0.13 D～0.23 D时,可以有效缓解固体颗粒在槽底沉积问题,促进固体颗粒有效分散。     

搅拌槽形对含钒页岩固液混合特性的数值模拟

搅拌槽是湿法提钒工业应用的重要设备,但在实际应用中存在矿物混合不均匀、易沉积在搅拌槽底部的问题。运用计算流体动力学(CFD)FLUENT软件,采用多重参考系法（MRF）、标准的k-ε方程、欧拉—欧拉多相流模型,对不同底部形状搅拌槽进行固液流场数值模拟。研究表明,平底搅拌槽对大粒径颗粒易产生固相沉积,圆底搅拌槽能有效解决沉积问题且搅拌更加均匀,槽内搅拌死区大幅下降。对槽内不同位置流场进行考察,圆弧底搅拌槽的湍动能、速度均优于平底搅拌槽,有利于提高固液混合效率。     

DTB结晶器内草酸铈颗粒分散特性的数值模拟

为深入了解结晶器内复杂的流动情况及其对混合的影响,采用CFD(Computational Fluid Dynamics)软件模拟DTB结晶器内稳态单相流动过程和不同混合方式的多相流动过程。对不同搅拌桨在结晶器内单相流动作用时采用湍流模型中的标准k-ε双方程模型、MRF;在此基础上模拟4种不同混合方式对颗粒性质的影响时引入欧拉多相流模型,并分析其不同混合方式产生的不同剪切作用对颗粒粒度的影响,并分析产生影响的微观作用机理。结果表明,考虑颗粒在结晶器内所受剪切力的状况和悬浮状况有利于制备理想性质的颗粒。     

氟钽酸钾钠还原搅拌釜中的搅拌流场数值模拟

采用标准k-ε湍流模型、Eluer-Eluer双流体模型,结合滑移网格法,对氟钽酸钾钠还原搅拌釜中搅拌流场进行数值模拟,研究不同转速、搅拌桨叶类型对液钠-熔盐分散特性、流场的影响。结果表明,在两种桨叶模型下,液钠仅局部分布在混合熔盐表面;平直叶桨、折叶桨搅拌均在搅拌釜内形成四个循环流区域,且在搅拌轴附近区域存在搅拌死区;液钠在液面的分散面积均随着转速的增加而减小,沿搅拌轴进入熔盐的深度随转速的增加而增大;在折叶桨模型下,随着搅拌转速的增加,近液面处流场速度增大,速度沿X轴方向呈对称分布。     

新型侧搅拌流化床气-固流化质量的模拟

在流态化炼铁的过程中,由于气-固分布不均匀,导致节涌、沟流、气体利用率低、粘结失流等现象,甚至出现死床的状况.本实验建立新型侧搅拌流化床反应器的物理模型,研究了搅拌方式、空气体积流率、搅拌器转速、搅拌器倾斜角度四个因素对流化床内颗粒与气泡运动行为及压强变化规律的影响.结果表明:侧搅拌流化床的气-固流化质量优于垂直搅拌流...     

KR法脱硫搅拌桨叶几何结构优化

KR(kanbara reactor)法是铁水预处理阶段稳定深度脱硫的首选工艺，广泛应用于现代炼钢工业，其通过浸入铁水中的桨叶搅拌带动铁水与脱硫剂混合，因而具有良好的动力学特性。然而，搅拌过程中桨叶附近存在强制涡流区，脱硫剂在参与反应前大量凝并导致利用率较低。因此，设计了2种简便易行的新型搅拌桨(错位式搅拌桨、高低式搅拌桨),旨在通过相邻桨叶的高度差强化桨叶附近的轴向流动，破坏强制涡流区流动特征，增强铁水微元间的相对流动，进而减少强制涡流区对KR法脱硫混匀效果的不利影响，提高铁水与脱硫剂的混合效果。采用VOF(volume of fluid)和DPM(discrete phase model)建立了KR法搅拌过程的三维瞬态数学模型，对比分析了传统四叶桨及2种新型结构搅拌桨的铁水流动、颗粒分散程度、死区范围及液面以下颗粒比例等的影响。数值模拟结果表明，新型桨叶相比传统桨叶供给铁水更多的轴向速度。错位式桨叶和高低式桨叶强化了脱硫剂分散程度，其量化颗粒分散程度Sigma值分别低于传统四叶桨约9.49%、14.18%,脱硫后脱硫剂平均粒径相比传统桨叶工况分别降低约14.91%、13.38%。使...     

官地矿井下巷道喷射混凝土损伤力学数值模拟

利用PFC颗粒流离散单元法对矿井喷射混凝土支护进行了数值模拟分析,同时,通过实验室的混凝土单轴压缩试验得到了混凝土的单轴力学特性曲线。结合试件的单轴曲线,分析了试件在破坏过程中的裂隙演化规律,从宏观以及微观上详细地分析了混凝土的力学特性。模拟过程中关于离散单元的建立、颗粒平衡处理以及颗粒的剔除等方法和混凝土的力学参数可供实际工程参考。     

半圆管挡板搅拌槽内的固液悬浮

为了提高固液悬浮性能,设计了一种半圆管挡板搅拌槽。采用数值模拟和试验测试相结合的方法,研究了半圆管挡板Rushton桨搅拌槽内石英砂—水的混合特性,分析了固液悬浮特征、固相浓度分布和功率消耗情况,并与标准平直挡板搅拌槽内的悬浮性能进行了对比。结果表明,同一搅拌转速时,半圆管挡板能改善悬浮性能,低固含率(5%)时效果更好。整体而言,半圆管挡板搅拌时石英砂的浓度分布比标准平直挡板搅拌时均匀,而且功率准数低13%左右,节能效应明显。研究结果为半圆管挡板的工业应用奠定了基础。     

叶片形状对涡轮桨搅拌槽内尾涡特性的影响

Particle image velocimetry technique was used to analyze the trailing vortices and elucidate their relationship with turbulence properties in a stirred tank of 0.48 m diameter, agitated by four different disc turbines, including Rushton turbine, concaved blade disk turbine, half elliptical blade disk turbine, and parabofic blade diskturbine. Phase-averaged and phase-resolved flow fields near the impeller blades were measured and the structure of trailing vortices was studied in detail. The location, size and strength of vortices were determined by the simplified λ2-criterion and the results showed that the blade shape had great effect on the trailing vortex characteristics. The larger curvature resulted in longer residence time of the vortex at the impeller tip, bigger distance between the upper and lower vortices and longer vortex life, also leads to smaller and stronger vortices. In addition, the turbulent kinetic energy and turbulent energy dissipation in the discharge flow were determined and discussed. High turbulent kinetic energy and turbulent energy dissipation regions were located between the upper and lower vortices and moved along with them. Although restricted to single phase flow, the presented results are essential for reliable design and scale-up of stirred tank with disc turbines.     

桨叶结构对KR脱硫搅拌效果影响的数值模拟

摘要：相较于喷吹法,KR机械搅拌法在铁水脱硫稳定性方面具有显著优势。KR铁水脱硫采用的搅拌桨结构不同,其脱硫效果也不尽相同。基于多重参考系法（MRF）模型,对使用不同搅拌桨的流场进行数值模拟,模拟结果与水模型实验结果较为吻合,最大误差为9.20%。模拟研究了传统四叶桨、螺旋三叶桨,双层四叶桨,双层三叶桨叶对铁水及脱硫剂的搅拌效果。结果表明：使用单层三叶螺旋桨的铁水涡旋高度落差最大。使用双层三叶螺旋桨时的底部区域脱硫剂体积分数为7.89%,与传统桨叶和单层三叶螺旋桨相比,分别增加了175.87%和61.22%。在200t规模的铁水脱硫工业实验表明,与传统四叶桨相比,使用单层三叶桨在深脱硫后铁水中［S］无痕迹率提高10%。     

搅拌器参数对钒页岩浸出罐流场的影响优化

搅拌浸出罐是钒页岩湿法提钒浸出段主要操作单元,但在工业生产中因浸出罐流场状态的差异存在固相分布不均、罐底矿物易沉积等问题。通过改变桨叶层数、双层桨的层间距和下层桨距底高度等手段,结合计算流体力学软件FLUENT,模拟分析不同径向测点位置与轴向测点位置颗粒的速度场与浓度场分布特点。结果表明,增加桨叶层数能够有效降低浸出罐内存在的浓度梯度,促使固液两相充分混合;双层桨层间距的增大能够缓解浸出罐上方流体速度较小问题,以"合并流"为主的层间距在0.33D～0.53D时,更有利于加强桨叶间区域的固液两相接触碰撞和充分混合;双层桨的下层桨叶距底高度为0.13D～0.23D时,强化了罐底颗粒的轴向速度,有效缓解矿物颗粒在罐底沉积问题。     

Physical Modeling of Fluid Flow in Ladles of Aluminum Equipped with Impeller and Gas Purging For Degassing

In the current study a transparent water physical model was developed to study fluid flow and turbulent structure of aluminum ladles for degassing treatment with a rotating impeller and gas injection. Flow patterns and turbulent structure in the ladle were measured with the particle image velocimetry technique. The effects of process parameters such as rotor speed, gas flow rate, and type of rotor on the flow patterns and on the vortex formation were analyzed using this model, which control degassing kinetics. In addition, a comparison between two points of gas injection was performed: (a) conventional gas injection through the shaft and (b) a “novel” gas injection technique through the bottom of the ladle. Results show that the most significant process variable on the stirring degree of the bath was the angular speed of the impeller, which promotes better stirred baths with smaller and better distributed bubbles. A gas flow rate increment is detrimental to stirring. Finally, although the injection point was the less-significant variable, it was found that the “novel” injection from the bottom of the ladle improves the stirring in the ladle, promotes a better distribution of bubbles, and shows to be a promising alternative for gas injection.     

An Improved Model for the Flow in an Electromagnetically Stirred Melt during Solidification

A mathematical model for simulating the electromagnetic field and the evolution of the temperature and velocity fields during solidification of a molten metal subjected to a time-varying magnetic field is described. The model is based on the dual suspended particle and fixed particle region representation of the mushy zone. The key feature of the model is that it accounts for turbulent interactions with the solidified crystallites in the suspended particle region. An expression is presented for describing the turbulent damping force in terms of the turbulent kinetic energy, solid fraction, and final grain size. Calculations were performed for solidification of an electromagnetically stirred melt in a bottom chill mold. It was found that the damping force plays an important role in attenuating the intensity of both the flow and turbulent fields at the beginning of solidification, and strongly depends on the final grain size. It was also found that turbulence drops significantly near the solidification front, and the flow becomes laminarized for solid fraction around 0.3.     

Turbulence Dissipation in Stirred Jars

A two-compartment analytical model was developed to estimate the turbulent dissipation rates in a standard jar stirred by a radial impeller. A simple numerical simulation was also performed to support the analytical arguments. Results of the numerical model showed that away from the impeller, the turbulent dissipation rate rapidly decays proportionally with z?2, where z is the axial distance. The turbulent velocity away from the impeller region showed a decay proportional to z?0.5. Although the dissipation rates at the wall boundary layer were higher compared to those in the tank interior, the total energy dissipated in the boundary layer is smaller compared to that expended in the impeller zone.     

Numerical Simulation of Fluid Flow in Bath during Combined Top and Bottom Blowing VOD Refining Process of Stainless Steel

The fluid flow in a bath in combined top and bottom blowing vacuum‐oxygen decarburization (VOD) refining process of stainless steel has numerically been simulated. The three‐dimensional mathematical model used is essentially based on that proposed in our previous work for the flow in combined side and top blowing argon‐oxygen decarburization (AOD) process, but considering the influence of reduced ambient pressure. Applying it to the flow in the bath of a 120 t VOD vessel under the refining conditions, the results present that the model can fairly well simulate and estimate the flow phenomena. The flow pattern of molten steel in the bath with the combined blowing is a composite result under the common action of the jets from a three‐hole Laval top lance and gas bottom blowing streams. The jets have a leading role on it; the molten steel in the whole bath is in vigorous stirring and circulatory motion during the blowing process. The streams do not alter the basic features of the gas agitation and liquid flow, but can evidently change the local flow pattern of the liquid and increase its turbulent kinetic energy to a certain extent. The flow field and turbulent kinetic energy distribution in the combined blowing with three tuyeres are more uniform than those in the blowing with double tuyeres. Increasing properly the tuyere eccentricities is of advantage for improving the velocity and turbulent kinetic energy distributions, the stirring and mixing result in the practical VOD refining process.     

搅拌方式对多级钒页岩浸出槽内多相流行为的影响

钒页岩湿法提钒是一个多级浸出过程,现有的研究多将浸出槽视为单一的封闭容器,与现实情况不符,且作为新工艺的吹气搅拌机理和效果未有详细报道。采用数值模拟的方法,对比分析有无进出料口搅拌槽内流场与相分布,并研究搅拌方式对有进出料口搅拌槽内的多相流动行为的影响。结果表明：有无进出料口的搅拌浸出槽内流场有明显区别,同等机械搅拌条件下,有进出料口的近自由液面区域的死区由3.3%降低至1.8%,底部的死区则由1.07%降低至0.46%。当搅拌方式由仅吹气搅拌改变至仅机械搅拌时,顶层搅拌桨上部的区域流速由0.16 m/s增大至0.28 m/s,近自由液面的死区由8.5%降低至1.8%,底部死区的比例由2.68%降低至0.46%。而采用机械和吹气联合搅拌时,反而可能会削弱钒页岩的悬浮效果。