醋酸洗涤塔塔盘脱落原因分析及应对措施

结合醋酸洗涤塔内部检查情况及出现塔盘脱落的问题,分析了可能引起塔盘脱落的几种原因,并提出了应对措施,对比了整改措施实施前后的运行效果。实践证明:整改措施实施后,醋酸洗涤塔运行稳定,出塔物料结构与设计相符,装置得以长周期、满负荷运行。     

15万吨/年气体分馏装置的优化设计

从工艺流程模拟、进料罐液面控制方案、原料与重组分的合理换热、高效塔盘的采用及安全设计等方面,介绍了15万吨/年气体分馏装置的设计特点。     

PET酯化工艺塔塔盘开裂分析及应对措施

针对酯化工艺塔塔盘使用寿命短(2年),从设计、加工、操作等方面加以分析,找出原因。塔盘稳定性差,操作时,产生冲击振动,且处于腐蚀介质中;介质的腐蚀作用与材料的疲劳相互促进,导致塔盘的早期失效。通过一些结构上的改进,强化氯离子管控,提升了塔盘使用寿命。     

甲醇羰基合成醋酸成品塔使用情况

甲醇羰基合成醋酸中成品塔为板式ADV浮阀塔,在投产后会出现塔盘坍塌,塔板及浮阀腐蚀减薄,紧固件脱落现象,导致工艺操作不平稳,并致使醋酸成品质量不合格。本公司在实际生产过程中,对成品塔塔盘进行改造及升级,以满足实际生产需求。现将成品塔使用及改造情况介绍,供同行参考。     

塔的计算机辅助设计

介绍计算机辅助设计（ＣＡＤ）技术在塔盘设计中的应用。采用ＡＵＴＯＣＡＤ内嵌的ＡＵＴＯＬＩＳＰ语言编写板式塔塔盘工艺参数计算程序和塔盘绘图程序。使用该程序进行塔盘设计，可以节约大量时间，并获得满意的设计效果。     

燃料油汽提塔塔盘结焦原因分析及解决方法

介绍了中国石油独山子石化分公司乙烯厂乙烯装置10-C-102塔（燃料油汽提塔）的工艺流程以及运行过程中发生的塔盘结焦甚至脱落的原因。在原因分析、日常操作、实验总结的基础上提出优化操作的方案。     

六溢流塔盘工艺计算优化

六溢流塔盘主要应用于大直径且高液汽比的塔器中。与四溢流塔盘相比,其结构与四溢流类似,且两者均要求气液相在各鼓泡区上均匀分布。但六溢流塔盘结构更复杂,且具有更高的液相处理能力。通过介绍六溢流塔盘的主要结构,将水力学平衡用于六溢流塔盘设计中,并建立不带气相连通管和带气相连通管两种六溢流水力学平衡方程。同时,提出六溢流塔盘各鼓泡区气液相分配合理性的判定标准,为六溢流塔盘的优化设计提供参考。最后,举例说明合理的六溢流塔盘设计应在正常工况、操作上限和操作下限同时满足水力学平衡和各鼓泡区液气比偏差要求。     

大型平口塔盘在锌精馏炉的应用及改进实践

锌精馏炉常用碳化硅塔盘,它是以人造碳化硅(金刚砂)为原料,加入软质耐火粘土结合剂,成型后经1450 ℃煅烧而成的.碳化硅塔盘制品中SiC含量＞90%(特级).目前某厂生产的碳化硅塔盘制品有三种型号:990 mm×457 mm的小型塔盘,1260 mm×620 mm的中型塔盘和1372 mm×762 mm的大型塔盘.锌精馏炉常用的是大中型塔盘,每座塔由50～60块塔盘组成,塔盘的结构根据在塔内的作用,其形状各异,主要是由呈W形的蒸发盘和呈U形的回流盘来组合.另外,还有加料盘、底盘、大檐盘、导气盘、锌封盘和反扣盘等.     

尿素塔节能高效塔盘的运行总结

介绍了尿素塔高效塔盘的应用情况,高效塔盘安装投运后,尿素转化率有了较大的提高,蒸汽消耗远低于设计值,达到了预期的目的。     

立式换热器支座及膨胀节设置问题探讨

针对某公司1台塔和换热器合为一体的汽化塔因换热器换热管泄漏严重而需更换换热器的情况,分析塔和换热器一体化设计存在的问题,进而讨论立式换热设备支座和膨胀节的选择及设置应注意的问题。     

尿素合成塔塔板改造后对工艺系统的影响

采用新型高效节能塔板对尿素合成塔传统塔板进行更新改造,改善塔内物料的传质传热过程,并利用塔底部原有空间增加塔板,提高了尿素合成转化率,降低了尿素生产的氨耗和蒸汽消耗。     

尿素合成塔塔板技术改造总结

对传统的普通平筛板塔板进行改造,采用高效波形塔板,加强了塔内的传热与传质,利用原合成塔下部空间,增加了塔板数目,使物料在全塔的停留时间分布更理想,反应更充分,提高了合成塔的生产效率.     

The second law optimal state of a diabatic binary tray distillation column

A new numerical procedure to minimize the entropy production in diabatic tray distillation columns has been developed. The method was based on a least square regression of the entropy production at each tray. A diabatic column is a column with heat exchangers on all trays. The method was demonstrated on a distillation column separating propylene from propane. The entropy production included contributions from the heat transfer in the heat exchangers and the mass and heat transfer between liquid and vapor inside the distillation column. It was minimized for a number of binary tray distillation columns with fixed heat transfer area, number of trays, and feed stream temperature and composition. For the first time, the areas of heat exchange were used as variables in the optimization. An analytical result is that the entropy production due to heat transfer is proportional to the area of each heat exchanger in the optimal state. For many distillation columns, this is equivalent to a constant driving force for heat transfer. The entropy production was reduced with up to 30% in the cases with large heat transfer area and many trays. In large process facilities, this reduction would ideally lead to 1-2 GWh of saved exergy per year. The most important variable in obtaining these reductions is the total heat transfer area. The investigation was done with a perspective to later include the column as a part in an optimization of a larger process. We found that the entropy production of the column behaved almost as a quadratic function when the composition of the feed stream changed. This means that the feed composition is a natural, easy variable for a second law optimization when the distillation column is a part of a process. The entropy production was insensitive to variations in the feed temperature.     

Heat transfer modelling of sieve trays

A heat transfer model that accounts for both gas and liquid phase resistance was developed for sieve trays where the overall heat transfer coefficient is expressed as a function of Sauter-mean bubble diameter. These diameters, obtained from pilot plant data, were correlated and used to predict point efficiencies on production plant trays. Applying the appropriate liquid flow distribution model allows the prediction of overall tray efficiencies. Predicted temperature profiles have agreed well with measured plant profiles and tray changes at the production plant have resulted in steam savings that were adequately predicted by the model.     

Hydraulic,mass transfer and heat transfer performance comparison between ordered bed packing and sieve trays

The Girdler–Sulfide (GS) heavy water production process has traditionally used tray columns because of their large size. In recent years, the chemical industry has extended the use of packing to larger columns because of economic and performance advantages. A pilot scale study was thus initiated to compare the hydraulic, mass transfer and heat transfer performance of an ordered bed packing (Mellapak) with sieve trays operating under GS process conditions. Mellapak offered lower pressure drops, higher throughputs and improved heat transfer over sieve trays. However, benefits to deuterium mass transfer were only marginal in large diameter columns.     

EXPERIMENTAL STUDY OF CASSAVA SUN DRYING

Experiments were carried out in Davis, California, USA to compare sun drying of a bed of cassava chips placed in wire mesh trays with those placed in trays made of sheet metal. The wire mesh permitted wind to blow easily through the bed of chips, while the sheet metal constrained the wind to flow across the top of the bed, Drying was faster in the wire mesh trays; the chips reached a moisture content for safe storage after 27 hours of drying, while those in the sheet metal trays took 35 hours. The uniformity of drying was also markedly better in the wire mesh trays. Higher temperatures were attained in the chips contained in the sheet metal trays due to contact heat transfer between the trays and the chips. However the restricted air flow around the chips in the sheet metal trays led them to dry slower than those in the wire mesh trays.     

液体并流塔板技术进展

液体并流塔板,即相邻2层塔板上液体流动方向相同,能有效提高塔板效率。文中介绍了国内外并流塔板的板效率模型的发展状况,对国内外开发的各种并流塔板结构及性能进行了分析,并考察了立体传质塔板的性能及工业应用情况。为了开发适合大塔径的高效塔板,基于液体并流板型能提高板效率的机理,结合性能优良的立体传质塔板,采用特殊的降液结构,提出了一种新型液体并流复合塔板的结构型式。新型塔板具有气、液体处理量大、传质效率高、操作弹性大的特点,而且有效避免了普通逆流板型的液体滞留区的产生。     

EXPERIMENTAL STUDY OF CASSAVA SUN DRYING

ABSTRACT

Experiments were carried out in Davis, California, USA to compare sun drying of a bed of cassava chips placed in wire mesh trays with those placed in trays made of sheet metal. The wire mesh permitted wind to blow easily through the bed of chips, while the sheet metal constrained the wind to flow across the top of the bed, Drying was faster in the wire mesh trays; the chips reached a moisture content for safe storage after 27 hours of drying, while those in the sheet metal trays took 35 hours. The uniformity of drying was also markedly better in the wire mesh trays. Higher temperatures were attained in the chips contained in the sheet metal trays due to contact heat transfer between the trays and the chips. However the restricted air flow around the chips in the sheet metal trays led them to dry slower than those in the wire mesh trays.     

Trays for gas-liquid contacting

A type of tray for gas-liquid contacting is described, in which the free area for gas flow through the tray is variable with and controlled by the gas flowrate. The property through which control of the free area is effected is the surface tension of the liquid phase. The advantages are the same as those of ballast and valve trays; namely, reduced pressure drop at high gas rates resulting in increased column capacity, and reduced free space at lower gas rates resulting in high mass transfer efficiency at low and medium vapor loadings as well. Tooling and production costs for the trays of the present investigation, however, are considerably lower than for ballast or valve trays or any other types which require machining operations in their fabrication, and are as low or lower than for sieve trays. Initial experimental comparisons with conventional trays demonstrated that the trays of the present investigation, although designed primarily for operation at high vapor loadings, were indeed capable of yielding high mass transfer efficiencies in the low-to-medium range of vapor loading     

Efficiencies of Sieve Tray Distillation Columns by CFD Simulation

A 3‐D two‐fluid CFD model in the Eulerian‐Eulerian framework was developed to predict the hydrodynamics and heat and mass transfer of sieve trays. Interaction between the two phases occurs via interphase momentum and heat and mass transfer. The tray geometries are based on the large rectangular tray of Dribika and Biddulph and FRI commercial‐scale sieve tray of Yanagi and Sakata. In this work a CFD simulation is developed to give predictions of the fluid flow patterns, hydraulics, and mass transfer efficiency of distillation sieve trays including a downcomer. The main objective has been to find the extent to which CFD can be used as a design and prediction tool for real behavior, concentration and temperature distributions, and efficiencies of industrial trays. Despite the use of simple correlations for closure models, the efficiencies obtained are very close to experimental data. The results show that values of point efficiency vary with position on the tray because of variation of affecting parameters, such as velocities, temperature and concentration gradients, and interfacial area. The simulation results show that CFD can be used as a powerful tool in tray design and analysis, and can be considered as a new approach for efficiency calculations and as a new tool for testing mixing models in both phases. CFD can be used as a “virtual experiment” to simulate tray behavior under operating conditions.