Fluid flow and heat transfer with nail dipping method in mould during continuous casting process

ABSTRACT

The character and cause of sliver defect on IF steel sheet surface are studied by means of SEM, unstable flow in mould could induce surface velocity and level fluctuations, leading to surface defects during continuous casting of steel. The nozzle clogging is a serious problem during the continuous casting of steel, due to its influence on the casting operations and products quality. In this study, the nail dipping method for measuring surface velocity and flow direction in molten steel were employed. The fluid flow in mould of whole casting sequence was investigated, especially during the nozzle clogging conditions. The results showed that when nozzle clogging occurred in the 7th heat, the flow velocities on R and L side of nozzle were 0.280 and 0.402?m/s, respectively. The surface defect ratio of hot-rolled and cold-rolled plates increases with the increase of heat flux deviation on both sides of the mould copper. The different clogging per cent on both sides of the nozzle will lead to asymmetry flow, the surface velocity is higher with the small clogging per cent side compared to that of relatively large per cent clogging side.     

浅谈地下水人工补给问题

列举了因地下水开采过量而引起的环境问题，介绍了地下水人工补给的方式及目的，简单阐述了人工补给地下水的水质保护问题，最后总结了注水井堵塞的主要原因和相应的解决措施。     

含钛夹杂物对连铸保护渣性能的影响

含钛钢连铸过程中析出氮化钛夹杂,并参与渣-金界面反应,严重恶化传统含钛钢连铸保护渣的理化性能。研究了不同含量的TiN和TiO₂对不同碱度保护渣的熔点、黏度、结晶比例以及凝固温度等性能的影响规律。测试结果表明,TiN对CaO-SiO₂基保护渣的性能影响最大,随着渣中TiN含量的升高,保护渣的黏度、结晶比例和凝固温度大幅度升高;当TiN质量分数大于5%时,熔点大幅升高。TiO₂对CaO-Al₂O₃基保护渣的性能影响最大,当TiO₂质量分数小于4%时,可小幅度降低保护渣的黏度和凝固温度;当TiO₂质量分数大于10%时,渣中钙钛矿成为主要析出物相,熔渣的性能严重恶化,影响对坯壳的润滑作用。通过对比3种不同碱度的基础渣发现,CaO-SiO₂-Al₂O₃基保护渣具有较好吸收含钛夹杂物的能力。     

煤矿黏土注浆管路淤堵软化实验与应用

为了解决煤矿黏土注浆管路淤堵问题,开展黏土注浆管路淤堵软化实验和应用研究。在黏土注浆管路淤堵特征剖析的基础上,通过软化剂作用下黏土崩解实验开展相关研究。结果表明:强氧化类的软化剂与黏土试样反应最为激烈,碱性软化剂与黏土试样反应最慢,酸性软化剂与黏土试样反应速度适中。以0.1 mol/L氨基磺酸溶液或0.25 mol/L醋酸溶液作为黏土淤堵软化剂最优。实践证明,采用管路涂抹环氧树脂,重点部位压力监测,淤堵管路浸泡软化剂等手段可以有效防治黏土灌浆管路淤堵问题。     

细粒尾矿库中土工织物反滤设计初探

围绕尾矿库排渗设施运行中淤堵的难题,在总结分析国内外淤堵机理研究的基础上,本文认为应从反滤材料选择、设置粗砂垫层、优化排渗位置及形式等三个方面开展探索研究,提出了一种坝前真空席垫排渗方法并开展现场试验。试验结果表明,该方法能有效诱发细颗粒排出,隔绝空气与排渗管的接触,具备良好的防物理化学淤堵性能。该成果对于今后细粒尾矿坝排渗系统的设计、建造以及运行管理等具有指导意义。     

Modeling simultaneous biological clogging and physical plugging in trickle-bed bioreactors for wastewater treatment

A major drawback limiting the use of trickle-bed bioreactors for biological wastewater treatment is ascribed to the concomitant biological clogging and physical plugging phenomena induced, respectively, by the formation of an excessive amount of biomass and the retention of inert suspended fine particles advected in the liquid influent stream. Biomass growth and fine particles deposition permanently reshape the bed pore structure and narrow the free interstitial space left to the fluids flow thus occasioning progressive bed obstruction often accompanied with pressure drop build-up for the cocurrent gas-liquid flows taking place in trickle-bed biofilters. In these circumstances, for maintaining acceptable operating cycles, the unit must be backwashed and/or shutdown regularly for removing the excess biomass and for cleaning from the specific solid deposit. A predictive two-dimensional dynamic model linking the two-phase flow hydrodynamics to the space-time distribution of bioclogging/biokinetics and of inert fine particles deposition via deep-bed filtration in trickle-bed bioreactors for wastewater treatment was developed. The model was based on the volume-average mass and momentum balance equations for the gas and liquid phases and continuity equation for the solid phase, the volume-average species balance for the fine particles, simultaneous transport and consumption of substrate (pollutant) and oxygen within the biofilm and collecting solid particle, and the volume-average species balance equations in the liquid and gas phases. Phenol biodegradation by Pseudomonas putida as the predominant species immobilized on activated carbon was chosen as a case study to illustrate the incidence of biomass accumulation on trickle-bed bioreactor hydrodynamics.     

Vortex characteristics due to nozzle clogging in water caster mould: modelling and validation

In continuous slab casting, clogging in the submerged entry nozzle (SEN) ports leads to flow asymmetry and vortex formation in the mould. Knowledge of vortexing and its influence on product quality is fundamental for defect-free production. In this study, the interconnected effects of nozzle clogging and SEN submergence depth, variation on flow asymmetry and vortex characteristics in a 0.4 scale water caster have been characterised by CFD investigation and validated with experimental results from the authors’ previous work. Mean flow velocities at the sub-meniscus and near the port exit predicted by the computational model are compared with the time-averaged values of the impeller probe velocity measurements and found to be in reasonable agreement. Three different clogging conditions (0, 33 and 66% in the left port of the SEN) for SEN submergence depth of 60?mm are studied and the 66% clogging produced vortices having largest diameter, which is consistent with the experimental observations. The effects of SEN submergence depth on flow asymmetry and vortexing are investigated with three different conditions – 40, 60 and 80?mm. It is found that the shallow SEN submergence depth (40?mm) produces vortices of largest diameter and the flow is most stable for a SEN submergence depth of 60?mm among the three cases. Vortex bending towards the SEN as noticed in the experimental observations is also observed in the computational study. This work illustrates the possibility of capturing features of vortexing using validated CFD model.     

微灌用砂过滤器堵塞与反冲洗效果研究

分析了过滤与堵塞的规律，即过滤时表层堵塞比下层严重．随着过滤运行时间的延续．滤层堵塞由表层逐渐向下层推移；根据反冲洗试验结果，提出了最佳反冲洗强度和最佳膨胀率，并对反冲洗效果进行了实际验证，为正确设计农用砂过滤器提供了设计依据．     

连铸浸入式水口结瘤现象的研究现状及发展

 水口结瘤是影响铸坯质量的重要因素，阐述了浸入式水口结瘤现象的研究现状，并概述了水口结瘤的机理，总结了目前防止结瘤的一些措施，提出从动力学角度研究水口结瘤的思路。     

Fe-WC料浆浇注过程中颗粒偏析的研究

粉浆浇注过程中颗粒偏析现象是由细颗粒的堵塞效应和重力场的沉降作用共同决定的.通过深入分析粉浆浇注过程颗粒沉降运动规律,研究了颗粒偏析的本质.分析表明:粉浆浇注过程中的颗粒偏析与粉浆粘度η,液体介质流速υ0、综合沉降因子r2ρ有关;提高粉浆粘度可以有效抑制颗粒偏析;降低液体介质流速可以抑制细颗粒堵塞效应.粉末装载量和石膏...