成型过程对加氢催化剂载体孔结构的影响

采用挤出成型法制备加氢催化剂载体,研究载体制备过程中捏合工艺、水粉比及不同挤出设备对载体孔结构的影响。结果表明,缩短捏合时间有利于载体孔结构向较大孔区域集中;提高水粉比有利于提高载体的总孔容;与螺杆挤条机相比,柱塞式挤条机生产的载体总孔容较大,且孔径更趋向(6～10) nm集中。采用优化的工艺条件,制备的载体满足产品质量要求,催化剂活性相对较高。     

正交试验在优化Φ600mmUHP石墨电极挤压成型工艺中的应用

通过对Φ600mmUHP石墨电极挤压成型工艺生产资料的分析,针对成型工艺实际情况,选取了挤压压力、捣固压力、保压时间、下料温度、糊缸温度、变径段温度、真空度等7个成品率影响参数编制了正交试验方案,对生坯成品率影响因素进行了正交分析,得到了不同参数对成品率影响的主次关系。探讨了正交试验用于压型工艺优化的合理性及试验结果的可靠性。     

Box-Behnken效应面法优化Ni/ZnO-SiO_2复合氧化物制备工艺及其吸附脱硫性能研究

利用响应曲面法对影响Ni/ZnO-SiO_2复合氧化物制备工艺的主要因素:活性金属组分比例、成胶pH值、老化时间进行试验设计。以Ni/ZnO-SiO_2复合氧化物用于低硫石脑油吸附脱硫处理中,产物硫含量为响应函数,建立相应的数学模型,优化试验方法。得到的最佳试验条件为:活性金属组分比例(Ni/Zn)为1.09、成胶pH值为5、老化时间为5h。此时Ni/ZnO-SiO_2复合氧化物对低硫石脑油的吸附脱硫性能为最优。Box-Behnke实验设计法用于Ni/ZnO-SiO_2复合氧化物制备工艺优化筛选是可行的,数学模型的预测值与实验观察值相符。     

加氢催化剂载体粒度控制技术研究

加氢催化剂主要通过螺杆挤条机挤条成型,成型后的载体湿条经干燥、断条、焙烧后得到催化剂载体成品,传统的粒度控制方法是采用机械切粒后进行筛分。制备过程工艺繁琐,工业生产过程中物耗、能耗较大,对产品质量及成本影响很大。随着催化剂成本市场竞争的日益激烈及环保要求的提高,不断寻找新的技术,简化催化剂生产流程,减少产品质量波动,降低催化剂成本,满足日益提高的环保要求,已成为催化剂制备企业愈来愈迫切的需求。     

影响重油加氢催化剂强度因素的探讨

考察在制备重油加氢催化剂时,挤条成型过程中各因素对重油加氢催化剂强度的影响。结果表明,物料中水粉比过高或过低均使催化剂强度下降,催化剂强度随着胶溶剂添加量增大而减小;随着混捏时间延长,挤条压力增大,催化剂强度提高。采用适宜条件制备的重油加氢催化剂,并进行小型加氢装置评价,结果表明,在水粉比为(0.35~0.45) mL·g^-1、胶溶剂与拟薄水铝石质量比为0.90~0.95、扩孔剂与拟薄水铝石质量比为0.05~0.1、助挤剂田菁粉与拟薄水铝石质量比为0.05~0.10、焙烧温度为（550~600） ℃、延长混捏时间和提高挤条压力条件下,制备的重油加氢催化剂加氢脱硫率为89%,加氢脱氮率为35%。     

塑料三通挤胀成型过程的有限元模拟

塑料挤胀成型是一种新的塑料固态成型方法,目前还没有关于塑料挤胀成型方法系统的研究报道。通过对塑料三通挤胀成型过程进行有限元分析,研究了轴向压缩、胀形压力、过渡圆角和平衡压力等工艺参数对硬质聚氯乙烯管材挤胀成型三通的影响。研究表明,采用有限元分析能够确定合理的胀形压力区间和平衡压力大小,能够预测不同轴向压缩作用和不同模具过渡圆角条件下管坯的变形情况,从而为优化挤胀成型工艺和设计合理的挤胀成型模具及设备参数提供了可靠的依据。     

基于神经网络和遗传算法的注射成型工艺优化

论述人工神经网络和遗传算法在塑料注射成型工艺优化中的应用,首先利用人工神经网络建立注射成型工艺参数与塑件翘曲量之间关系的数学模型,然后用遗传算法对工艺参数优化.其中由正交法设计得到实验样本,由数值模拟软件计算得到塑件翘曲量,将其作为优化目标.按优化后的工艺参数进行实验,获得较高质量的塑料制品,从而为建立和控制注射模工艺参数提供一种行之有效的途径.     

塑料三通挤胀成型过程的有限元模拟

塑料挤胀成型是一种新的塑料固态成型方法，目前还没有关于塑料挤胀成型方法的系统的研究报道。本文通过对塑料三通挤胀成型过程进行有限元分析，研究了轴向压缩、胀形压力、过渡圆角和平衡压力等工艺参数对硬质聚氯乙烯管材挤胀成型三通的影响。研究表明，采用有限元分析能够确定合理的胀形压力区间和平衡压力大不，能够预测不同轴向压缩作用和不同模具过渡圆角条件下管坯的变形情况，从而为优化挤胀成型工艺和设计合理的挤胀成型模具和设备参数提供了可靠的依据。     

用于催化剂成型的前挤式双螺杆挤条机

介绍了催化剂成型设备———前挤式双螺杆挤条机的工作原理及在催化剂成型生产中的应用试验。     

分子筛成型技术研究进展

综述目前分子筛制备催化剂成型技术研究进展,重点介绍工业上应用广泛的挤条法和喷雾干燥法分子筛成型技术,并从成型助剂(黏结剂、胶溶剂、助挤剂、扩孔剂、水)及配比、工艺条件等阐述对催化剂的机械强度和催化性能的影响,分析两种成型技术在应用上的优势与不足。在此基础上,从科学研究角度,认为建立微观、直接的表征方法和构建数学模型等提高理论指导水平是该技术发展的方向;从工业应用角度,认为创新优化工艺并综合考虑成本因素,开发低成本的高活性催化剂工程化制备技术仍是今后的研究方向。     

橡胶冷喂料挤出机螺杆造型及工艺参数与挤出温度的数学模型

研究了螺杆造型（长径比，螺旋升角，螺槽深度，螺杆几何压缩比），挤出工艺（螺杆转速，机头口型）和胶料种类对橡胶冷喂料挤出机挤出温度的影响，并对各实验因素及实验结果做了统计分析，得出了他们之间的定量数学模型。     

双螺杆挤出过程数值模拟研究进展

在聚合物的双螺杆挤出过程的研究中,采用数值模拟的方法可以克服传统实验方法的局限,可为挤出机的设计加工提供参考。回顾了近年来国内外对双螺杆挤出过程数值模拟的研究成果,介绍了一维数学模型和三维数学模型对挤出过程进行数学描述的优缺点,从双螺杆挤出机内部的流场特性、瞬态混合性能、停留时间分布以及反应挤出等方面综述了相关研究进展,并对双螺杆挤出过程数值模拟的今后发展方向进行了展望。     

A study on the performance of the maddock mixing head in plasticating single-screw extrusion

An experimental and theoretical study was conducted on the performance of the Maddock mixing head in plasticating single-screw extrusion. For the experimental study, a low-density polyethylene was extruded in an extruder that had nine pressure transducers mounted, almost equally spaced along the extruder axis, on the wall of the extruder barrel. Two screws with the Maddock mixing head were used, namely: one screw to measure the pressure difference between the entrance and the exit of the mixing head in the down-channel direction, and the other screw to measure pressure variations in the cross-channel direction in the middle of the mixing head. Our experimental results showed both pressure decrease and pressure increase in the down-channel direction of the mixing head, depending upon the extrusion conditions employed. Using the flow analysis network (FAN) method, we predicted pressure variations in both the downchannel and cross-channel directions of the Maddock mixing head, which agree with experimental results.     

A study on the reactive extrusion process of polyurethane

An engineering analysis of the reactive extrusion process of a thermoplastic polyurethane was made through numerical simulation and actual experiment. The reactants used in this system were 4,4′diphenylmethane diisocyanate, polycaprolactone diol (M.W., 824), and 1,4-bu-tanediol with equivalent weight ratio of 2:1:1. As a catalyst, dibutyltin dilaurate was used. The reaction kinetics and the viscosity function were obtained through experiments, and the mathematical model which includes the conservation equations of mass, momentum, energy, and chemical species was solved numerically to obtain the velocity, concentration, temperature, viscosity, and pressure profiles. The actual experiments were performed in the laboratory scale extruder to compare the experimental results with those of the numerical simulation.     

Solid-State Extrusion of Isotactic Polypropylene Through a Tapered Die. I. Phenomenological Analysis

Abstract

The solid state extrusion of isotactic polypropylene through a tapered die was conducted under various extrusion conditions using a piston-cylinder type extruder. The equation for evaluating the extrusion pressure was derived based on the plasticity theory as a function of die geometry and frictional coefficient between die wall and material. The integrand of the equation includes the yield stress as a function of true strain, which was given by the tensile properties of the same polymer. The data of lower degree of processing were fairly well described by the equation, but the estimation was not so accurate at high extrusion ratio. The molecular weight dependence of extrusion pressure was very small in solid state extrusion compared with the case of melt viscosity. This fact showed that the local inter-molecular interaction is a predominant factor in solid state extrusion. The effect of frictional resistance on a cylinder part was found to be negligible in our experimental conditions.     

渣油加氢脱硫催化剂载体堆积密度的精确控制

采用挤出成型法制备氧化铝载体,考察挤出成型工艺条件、切粒频率、焙烧温度和焙烧气氛对渣油加氢脱硫催化剂载体堆积密度及物化性能的影响。结果表明,酸粉比（A+0.5） mL·g^-1、水粉比（B+0.10） mL·g^-1和混捏时间（t+5） min制备的载体堆积密度合适,物化性能优良;切粒整形频率为40 Hz时,载体条长分布中,（3~8） mm条占87.14%;随着焙烧温度的升高,载体比表面积减少,孔径分布中小于6 nm孔减少,堆积密度减小;随着焙烧气量的减少,载体比表面积降低,孔体积增加,堆积密度减小,孔径分布中小于6 nm孔减少,（6~20） nm孔增加。精确控制载体焙烧温度和气量,可制备出比表面积合适、堆积密度稳定、孔径分布集中和满足固定床渣油加氢脱硫要求的工业氧化铝载体。     

Entrance pressure drop studies of corn meal dough during extrusion cooking

The entrance pressure drop during extrusion cooking of corn grits was measured using a cylindrical die viscometer attached to a single screw extruder and compared with results obtained using low-density polyethylene (LDPE). The cylindrical die viscometer had a length to diameter ratio of 40 with half-entry angles of 30, 37.5, 45 and 90° with the horizontal. The entrance pressure drop at the die was measured as a function of extrusion temperature, product moisture content and the die entry angle. Results indicate that the flow behavior of corn grits and the entrance pressure drop were affected by product moisture content, process temperature and the shear history in the extruder. Entrance pressure drop also increased with wall shear stress for plastic melt, but for food biopolymer, the increase was observed provided shear history effects were minimized. Entrance correction increased with apparent shear rate for LDPE, but the reverse was true for corn meal. Using Cogswell's analysis, corn grits exhibit severe extension thinning behavior in entry flow.     

Application of ultrasound and neural networks in the determination of filler dispersion during polymer extrusion processes

Mineral filler dispersion is important information for the production of mineral‐charged polymers. In order to achieve timely control of product quality, a technique capable of providing real‐time information on filler dispersion is highly desirable. In this work, ultrasound, temperature, and pressure sensors as well as an amperemeter of the extruder motor drive were used to monitor the extrusion of mineral‐filled polymers under various experimental conditions in terms of filler type, filler concentration, feeding rate, screw rotation speed, and barrel temperature. Then, neural network relationships were established among the filler dispersion index and three categories of variables, namely, control variables of the extruder, extruder‐dependent measured variables, and extruder‐independent measured variables (based on ultrasonic measurement). Of the three categories of variables, the process control variables and extruder‐independent ultrasonically measured variables performed best in inferring the dispersion index through a neural network model. While the neural network model based on control variables could help determine the optimal experimental conditions to achieve a dispersion index, the extruder‐independent network model based on ultrasonic measurement is suitable for in‐line measurement of the quality of dispersion. This study has demonstrated the feasibility of using ultrasound and neural networks for in‐line monitoring of dispersion during extrusion processes of mineral‐charged polymers. POLYM. ENG. SCI., 45:764–772, 2005. © 2005 Society of Plastics Engineers     

Extrusion of alumina and cordierite-based tubes containing Al-rich anodising sludge

An Al-rich anodising sludge has been used as the feedstock to produce alumina and cordierite-based tubes produced by extrusion. The extrudability is strongly dependent on the materials composition and on the resultant plasticity of the pastes. For the process to be successful, the design and operating conditions need to be considered in detail.In this work, the effect of die design, ram speed and pressure was evaluated using the Benbow–Bridgwater model of paste extrusion. In general, predicted and measured values were in good agreement. This approach revealed differences in the flow between the two ceramic formulations and it was possible to relate the rheological observations during extrusion to the quality of the final product.     

国产电极挤压机抽真空改造的生产实践

对国产25MN挤压机进行了改造，经过生产实践，安装的抽真空系统和同步剪切装置应用效果较好。用真空成型和同步剪切技术压制的电极，其性能和质量指标发生了许多变化：生电极回涨减少，各工序电极体积密度、强度提高，孔度减少，电极成品率、出口电极挑料比提高，成品电极单重提高。