The effect of operating and design parameter on bubble column performance: The LOPROX case study

It is known that the performances of multi-phase reactors depend on the operating parameters (the temperature and the pressure of the system), the phase properties, and the design parameters (the aspect ratio (AR), the bubble column diameter, and the gas sparger design). Hence, the precise design and the correct operation of multi-phase reactors depends on the understanding and prediction of the fluid dynamics parameters. This paper contributes to the existing discussion on the effect of operating and design parameter on multi-phase reactors and, in particular, it considers an industrial process (e.g., the LOPROX (low pressure oxidation) case study, which is typical example of two-phase bubble columns). Based on a previously-validated set of correlations, the influence of operating and design parameter on system performances is studied and critically analyzed. First, we studied the effects of the design parameter on the liquid–gas interfacial area, by keeping constant the fluid physical–chemical properties as well as the operating conditions; subsequently, we discussed for a fixed system design, the influence of the liquid phase properties and the operating pressure. In conclusion, this paper is intended to provide guidelines for the design and scale-up of multi-phase reactors.     

Influence of anode current density on carbon parasitic reactions during electrolysis

In the electro-deoxidation process, carbon parasitic reaction (CO₃^2- + 4e^-=C + 3O^2-) usually occurs when using carbon materials as the anode, which leads to increase of the carbon content in the final metal and decrease of the current efficiency of the process. The aim of this work is to reduce the negative effect of carbon parasitic reaction on the electrolysis process by adjusting anode current density. The results indicate that lower graphite anode area can achieve higher current density, which is helpful to increase the nucleation site of CO₂ bubbles. Most of CO₂ would be released from the anode instead of dissolution in the molten CaCl₂ and reacting with O^2- to form CO₃^2-, thus decreasing the carbon parasitic reaction of the process. Furthermore, the results of the compared experiments show that when the anode area decreases from 172.78 to 4.99 cm², CO₂ concentration in the released gases increases significantly, the carbon mass content in the final metal product decreased from 1.09% to 0.13%, and the current efficiency increased from 6.65% to 36.50%. This study determined a suitable anode current density range for reducing carbon parasitic reaction and provides a valuable reference for the selection of the anode in the electrolysis process.     

Material removal profile prediction and experimental validation for obliquely axial ultrasonic vibration-assisted polishing of K9 optical glass

K9 optical glass is one of the typical components in optical systems. However, because of its poor fracture resistance, it is difficult to polish it with ultra-precision and high-efficiency and without any surface damage simultaneously. The emergence of the obliquely axial ultrasonic vibration-assisted polishing (UVAP) method can solve this problem which encounters in polishing efficiency and shape accuracy. However, due to the unclear material removal profile (MRP) mechanism, obliquely axial UVAP is not widely used in the processing field. This paper introduces the obliquely axial UVAP method in research processes, mainly focusing on the fixed point MRP analysis of the obliquely axial UVAP. Based on Hertz's contact theory, polishing pressure, the length of the semi-long axis (LLA) and the length of the semi-short axis (LSA) of the contact area are calculated under ultrasonic vibration conditions. Meanwhile, the relative linear velocity distribution of the oblique polishing tool in the instantaneous contact area is modeled by mathematical geometry method. A novel model of the MRP distribution for obliquely axial UVAP is proposed following the Preston equation. Subsequently, a series of polishing experiments were carried out to verify this model. The results show that the numerical model has good agreement with the experimental results on MRP, LLA, LSA, material removal depth and material removal rate (MRR). In addition, the material removal capability can be significantly improved by larger ultrasonic amplitude and larger oblique angle. This model not only more clearly elucidates the processing mechanism of obliquely axial UVAP, but also provides theoretical support for the polishing of free-form optical lenses.     

小湾高拱坝坝基浅层松弛区超载屈服研究

通过对小湾高拱坝坝基浅层松弛区的弹塑性分析,采用数值计算方法,揭示超载过程中坝基屈服发展规律,并采用坝基整体超载安全系数等方法评价大坝局部安全性、整体安全性以及两者之间的关系。通过分析认为小湾坝基浅层松弛区发生屈服尚属于局部问题,坝基整体超载安全度仍可达3~3.5。     

区域水资源短缺的多目标风险决策模型研究

在水资源短缺风险分析和评价的基础上,构建了区域水资源短缺的多目标风险决策模型,并提出了求解方法.应用该模型对包括北京和天津在内的首都圈进行水资源短缺风险决策分析.结果表明,要解决首都圈的水资源短缺问题,南水北调的作用是不可忽视的,其它水资源管理措施的投入也应该掌握一定的规模,这样才能保证区域社会经济的可持续发展和区域水资源的可持续利用.     

广西沿海水功能区水污染状况与水环境保护

在分析了广西沿海主要水功能区水污染现状及河流纳污量、等标污染负荷评价和水功能区达标分析的基础上,提出水功能区管理和水环境保护措施,并依据沿海经济发展对水资源需求,提出对水功能区调整及补充建议。     

下福水利枢纽厂房整体稳定及地基应力计算

根据下福水电站厂房结构布置及其工程地质的实际情况,通过对下福水电站厂房整体稳定及应力计算,对厂房结构设计的安全可靠性进行评价,同时提出水电站厂房整体稳定及应力计算的计算过程和计算要点。     

河北平原井灌区冬小麦灌水定额的计算分析

根据华北半湿润偏旱井灌区节水农业综合技术示范区的建设实践,在河北平原三河井灌区,通过实时监测冬小麦田间土壤含水率,计算出其田间土壤含水量与田间持水量之差即为灌水定额;当实时监测的田间土壤含水率低于冬小麦适宜生长含水率高于凋谢系数时,便对监测地块进行灌溉。采用移动式管道喷灌或支管退行式畦灌模式进行冬小麦灌溉,使灌水定额控制在750m^3／hm^2以内,达到节水增产增收的目的,促进农业又好又快发展。     

淮河中游河道整治及其效果评价

淮河中游是淮河治理的重点和难点.由于受黄河夺淮和人口增加的影响,淮河中游河道淤积,大量的湖泊洼地被围垦成圩区,造成中游行洪不畅.1983年以来,采取了铲除、退建行蓄洪区堤防,切滩、疏浚河道,整治束水河段,调整设计水位等措施,扩大了河道行洪能力,工程措施在防御1991、2003年和2007年洪水中发挥了显著作用.在对25 a来工程措施进行研究、分析的基础上,对工程实施的效果进行了综合评价.     

高烈度区土(石)坝震损特征与成因初步研究

通过实地调查和收集“5·12”汶川8.0级地震后四川岷江、绵阳、安县等高烈度区（7°以上）大、中、小典型土（石）坝坝体变形、坝基地质条件、大坝几何参数等资料,对建筑物的震损裂缝分别进行相关分析,认为坝体裂缝成因除了与地震波直接有关外,其震损程度还与坝轴线的方向和区域应力方向关系密切;而裂缝的分布部位则与坝基覆盖层的分布范围、厚度、性状,坝体的材料、几何尺寸、风浪和动物活动掏蚀等有关,为我国西南水利水电工程建设、深覆盖层的利用、防渗材料的选择和抗震设计研究积累了难得的经验。