膜极距离子膜电解槽垫片粘贴的重要性

烧碱生产用离子膜价格昂贵,离子膜的运行寿命直接关系到烧碱的运行成本。电解槽垫片粘贴不当,会使单台电解槽大部分离子膜出现针孔。分析不同离子膜泄漏情况及阴阳极垫片粘贴情况,找到离子膜出现针孔的原因:如果阳极垫片部分粘贴靠下,堵塞了气液出口,就会使氯气滞留在阳极部分并渗透;如果阴极垫片粘贴位置偏上,使阴极垫片的下端橡胶部分裸露在易腐蚀部位,阴极垫片出现溶解。给出阴阳极垫片的正确粘贴顺序。采用该法粘贴垫片后,可以有效防止因氯气滞留、阴极垫片腐蚀而导致的离子膜针孔。     

关于德山曹达(株)离子膜法制烧碱技术的探讨

本文就引进日本德山曹达株式会社离子膜法生产技术中砂滤器,Ca~(++)在线分析仪器、零极距、活性阴极复极式电槽、用检查离子膜针孔检查机和热压式膜修补机的使用情况作一介绍,同时还提出了电槽停电时保护活性阴极的措施。     

阴极液中氯酸钠成因分析及预防探讨

在离子膜烧碱法生产过程中,氯酸盐的产生离不开迁移到阳极室的碱,离子膜上的针孔或破损为阴极室碱向阳极室渗透提供了通道。作者通过对氯酸盐产生的原因和机理进行分析,同时结合生产经验,提供了控制系统内氯酸盐含量的方法和措施。     

某次阴极电泳出现针孔原因分析及其解决方案

针对某次阴极电泳生产线发生的车身后侧围外表面和尾门外表面针孔问题,采用显微分析法探讨了阴极电泳膜层针孔发生的原因,并提出了相应的解决方案。     

离子膜电解槽阴、阳极极片涂层调研

分析活性阴极失活原因及阳极涂层寿命的主要因素，提出离子膜电解槽对阳极、阳极涂层、阴极、阴极涂层的技术要求，结合天津化工厂2.5万t/a离子膜生产实际，对国内重涂电极与国外离子膜阴极涂层国内运行1年后阴极的槽压数据进行了对比。采用国内离子膜电解槽极片重涂技术，每年可节约电费约90万元。     

离子膜针孔和起泡原因分析及处理措施

分析离子膜边缘区域和膜上部30cm区域产生针孔及起泡的原因为气泡效应、电流密度分布不均等，并找出相应的措施：在修槽时仔细检查和处理毛刺和单元进料管、停车时严格进行阳极液置换及保证操作条件平稳等措施，使自贡鸿鹤化工股份公司氯碱厂的离子膜装置运行29个月后，电流密度升至4．5kA/m^2，其阴极电流效率达到94．69％，平均单元槽压为3．28V，直流电耗为2378kW．h／(t．NaOH)。     

造成离子膜出现针孔和阴极起泡的原因分析及预防措施探讨

介绍了离子膜的特性,分析了造成离子膜起泡和出现针孔的原因并提出了相应的解决方法。     

离子膜使用过程中起泡的原因及危害

分析并列举了离子交换膜在使用过程中鼓泡的原因，阳极液质量浓度；pH值；阴极液质量浓度；电流密度；开停车及盐水质量等因素都可以造成膜鼓泡，形成针孔。提出了相应的预防措施。     

电解槽阴极改造前后运行对比

电解槽运行中离子膜针孔率较高,气液分离盒泄漏较多。通过取消镍带焊接,改为折边工艺等技术改进,并对改造前后的折标电压、电流效率、针孔率等进行对比,各项指标均好于改造前,尤其是离子膜针孔率大大降低。     

离子膜稳定运行的影响因素分析

分析盐水质量、阴极液NaOH浓度、阳极液NaCl浓度、电流密度、阳极液pH值、电解液温度和流量、电解槽压力和压差、开停车及伴生水摩尔量不符合运行指标时,会造成离子膜起泡、针孔,阴、阳极涂层损坏。结合济宁中银电化有限公司的运行实际,强调分析化验的重要性。     

分子筛碳膜的制备

以含六次甲基四胺的热塑性酚醛树脂的乙醇溶液为涂膜液,采用浸渍法在支撑体原膜上涂膜,干燥后一步碳化制备了分子筛碳膜,有效地解决了碳膜制备中分离层易产生针眼﹑裂纹的问题,扫描电镜显示分离层与支撑体结合良好,膜表面光滑无缺陷,所制碳膜H2/CH4的分离系数达到171, H2/N2的分离系数达到74. 实验发现,涂膜液性质、支撑体的孔径以及表面粗糙度、浸渍时间对碳膜的性能有显著影响. 碳膜分离气体的机理主要为分子筛分.     

High velocity sand impact damage on CVD diamond

This paper describes a recent study of the damage mechanisms generated by high velocity-sand impact on diamond coatings deposited on tungsten substrates by chemical vapour deposition (CVD). The coatings were erosion tested using 90–355-μm diameter sand at a velocity of 268 m s⁻¹ and the eroded coatings examined by scanning electron and acoustic microscopy. The images indicate that the circumferential cracks and pinholes are the main erosion features and are only located on debonded areas of the coating. This suggests that they could be formed by stress waves reflected from the coating–substrate interface, which interact with surface waves to generate circumferential cracks, the precursor to pinholes. The high spatial resolution of scanning acoustic microscopy enables the resolution of individual pinholes, thus, providing important evidence for identifying the mechanism responsible for the formation of circumferential cracks, the precursor to the pinholes. However, the acoustic images must be interpreted with care; in particular, it is important to compare microstructural features observed by acoustic microscopy with other techniques.     

A reactor–separator incorporating porous and dense membrane systems

This study employs mathematical models to compare and assess the relative performance of various composite membranes incorporated in a high-temperature membrane reactor. Two categories (porous and dense) and five types of composite membrane systems (Pd/Ag, polyimide, silica, inert porous and Ru-dispersed porous) have been considered. Also included in the study is the special case of the Pd/Ag composite system having imperfections (pinholes and cracks). Ethylbenzene dehydrogenation over promoted iron oxide catalyst has been studied as the model reaction. Overall, the dense systems show higher performance levels at lower membrane thicknesses. However, the porous composite systems, especially those in which active metal particles have been incorporated within the micropores, can be very useful due to their significantly higher contact surface to volume ratio. The study has also confirmed that high hydrogen perm-selectivity is a key factor in determining reactor performance in terms of con-version enhancement. ©1997 SCI     

二次生长法合成SAPO-34沸石膜及其气体渗透性能

以四乙基氢氧化铵(TEAOH)为模板剂,采用二次生长法在α-Al_2O_3多孔陶瓷管上合成了SAPO-34沸石膜.利用X射线衍射(XRD)、扫描电镜(SEM)以及气体渗透对合成的膜进行了表征.XRD结果表明合成的膜具有典型的CHA型沸石特征峰,无其它杂相存在.SEM显示膜厚大约为5 μm,膜表面晶粒交织共生完好,且连续、致密,没有发现明显的针孔和裂纹.室温下, 当膜两侧压降为0.1 MPa时,CO_2/CH_4的理想选择性和混合气体分离选择性分别为7和40.     

Effects of Poly(Vinyl Alcohol) Content and Calcination Temperature on the Characteristics of Unsupported Alumina Membrane

Abstract

Nonsupported alumina porous membranes without pinholes or cracks were prepared by the sol-gel process using aluminum sec-butoxide as the starting material. The effects of using different PVA contents at various calcination temperatures on the characteristics of the membrane were investigated by scanning electron microscopy and nitrogen sorption porosimetry. The results after calcining at 450°C for 5 hours showed that the range of pore size distributions increases with increasing PVA concentration. The active nucleus numbers of phase transition to α-alumina decreased as the content of PVA increased at about 1050°C. The morphology of unsupported alumina membranes was affected by the PVA concentration and calcination temperature.     

Electropolymerised polyaniline films on AA 7075 alloy and its corrosion protection performance

Polyaniline has been electrodeposited on AA 7075 alloy and its corrosion protection ability has been studied by Tafel and impedance techniques in 1% NaCl. Pure polyaniline film is not found to protect the aluminium alloy due to galvanic interaction of polyaniline and aluminium surface exposed through pinholes and cracks. However, it is found that the corrosion resistance property of the polyaniline film can be substantially increased by post-treatment in cerium salt solution.     

Preparation and characterization of Al3+-doped TiO2 tight ultrafiltration membrane for efficient dye removal

Al³⁺-doped TiO₂ (AT) tight ultrafiltration membrane with stable anatase phase was prepared by a modified sol-gel process using butyl titanate and aluminum chloride as the precursor and aluminum source respectively. The removal of Alizarin red-S was investigated by filtration experiment. A dip-coating process on homemade flat Al₂O₃ intermediate layer by TiO₂ sol followed by heat treatment was adopted to obtain the desired AT membrane. The addition of Al³⁺ inhibits the phase transformation of nanosized TiO₂ from anatase to rutile and restrains the growth of crystallite, resulting in the pore size of the separation layer reducing to 3.5 nm. The prepared AT1-500 membrane exhibits enhanced hydrophilicity with no cracks or pinholes, and shows a water permeability of 9.6 L m^-2 h⁻¹ bar⁻¹ and cut-off molecular weight (MWCO) of 4650 Da. The membrane demonstrated a retention rate of 96.9% for Alizarin Red-S (250 ppm) and maintained almost constant under repeated using.     

FM21型离子膜电解槽问题分析

针对FM21型离子膜电解槽运行中离子膜穿孔、进槽盐水供应故障,检修后送电前盐水杂质含量多,停槽时阳极液中有效氯含量多、碱液中铁和盐含量高等问题,提出了应对措施。     

复合陶瓷料浆分散剂在电瓷干法生产中的应用

分析了瓷绝缘子的等静压干法生产中回料循环使用后,分散剂引入的氧化钠的增长趋势;试验了复合分散剂对泥浆性能的影响,考虑了生产成本等因素,确定了复合分散剂的组成并应用于生产,解决了产品拉伸、针孔、开裂、掉头等缺陷,大幅度提高了产品合格率并稳定在较高的水平,探讨了复合分散剂对坯料性能的影响。     

Titania ultrafiltration membrane: Preparation,characterization and photocatalytic activity

A mesoporous photocatalytic titania (TiO₂) membrane on alumina support is successfully fabricated via the sol–gel processing method. Several techniques such as dynamic light scattering, X-ray diffraction (XRD), TGA, N₂-sorption, and SEM are utilized to investigate the optimized processing parameters and their influence on the final properties of the developed membrane. The prepared titania sol containing organic additives (HPC and PVA) has an average particle size of 55.6 nm with a narrow distribution. The resulting TiO₂ membrane with thickness of 1 μm exhibits homogeneity with no cracks or pinholes. It also maintains small pore size (4.7 nm), large specific surface area (75 m²/g), and small crystallite size (8.3 nm).The permeability and photocatalytic properties of the titania membrane were measured. The permeability coefficient of the fabricated membrane is 30.09 cm³ min^?1 bar^?1 cm^?2. These measurements indicate an optimum processing condition for the preparation of the membrane. The prepared titania membrane has a great potential in developing high efficient water treatment and reuse systems because of its multifunctional capability such as decomposition of organic pollutants and physical separation of contaminants.