Emulgieren im Rührapparat

Emulsifying by Stirring The emulsification of immiscible, liquid components by stirring requires a complex technical operation. Depending on the process flow a coarse pre‐emulsion or a stable emulsion with a narrow droplet‐size distribution is necessary. An optimal set‐up and running of the stirrer are required, whereby the characteristics of the mixture should be taken into account. The type and functionality of the used components (emulsifiers, stabilizers) as well as the flow properties of the different phases are the most important factors. Whereas Newtonian fluids have a constant viscosity, the flow dependence of non‐Newtonian fluids can present severe difficulties for the running of the stirrer. The emulsifying process and relevant mathematical models for the calculation of the particle size distribution are discussed.     

Microwave-hydrothermal synthesis of barium titanate under stirring condition

The role of in situ stirring under microwave-hydrothermal (M-H) conditions on the synthesis of barium titanate was investigated for the first time by powder X-ray diffraction and scanning and transmission electron microscopy. Stirring under M-H conditions in the temperature range of 150–200 °C led to enhanced crystallization of Ba titanate as revealed by yields compared to the static condition. In addition, stirring led to smaller and more uniform crystals under M-H conditions compared to those crystallized without stirring. Powder X-ray diffraction revealed the formation of only cubic polymorph of Ba titanate at or below 200 °C in 4 h with or without in situ stirring under M-H conditions. These results show that stirring is an important parameter during M-H synthesis of nanophase Ba titanate.     

Rühreinrichtungen in Schneckendosiergeräten — Wirkung und Auslegungsstrategie

Stirring Devices in Screw Metering Equipment – Action and Design Strategy. The accurarcy of metering by screw dosage equipment with or without gravimetric control depends primarily on the flow of material to the discharging screw. In the case of cohesive solids, stirring devices are generally required to prevent bridging. Experimental observations show that flow conditions correlate directly with the intensity of stirring. Mass flow in the metering container and hence optimum constancy of metering are attainable only from certain stirring efficiencies upwards. Cases of interference to metering due to poor flow of solids can be explained and overcome by modified dimensioning. The effects of the principal parameters – geometry and speed of rotation of the stirrer – are studied with the aid of two stirrer configurations – viz. overhead and concentric. Straightforward model calculations provide a mathematical method of estimation for optimum and reliable stirrer dimensioning also applicable to strongly cohesive solids.     

壳聚糖-铜(Ⅱ)的合成及在废水处理中的应用

用壳聚糖和氯化铜合成了壳聚糖-铜（Ⅱ）,并将其用于处理偶氮类废水的絮凝剂,考察了絮凝剂的用量,pH,搅拌时间,沉降时间等因素。确定了最佳反应条件为pH=8,快速搅拌3 min,慢速搅拌10 min,沉降30 min,絮凝剂用量为4 g/L。在此条件下壳聚糖-铜（Ⅱ）对此种废水的色度,浊度,COD的去除率在95%以上。     

半固态搅拌制SiC颗粒增强镁基复合材料过程的数值模拟

采用商用的计算流体动力学(CFD)计算软件Fluent对SiC颗粒增强镁基复合材料搅拌过程进行动态模拟,研究了不同搅拌速度、搅拌时间及温度对于SiCp/AZ91(SiC颗粒增强镁合金AZ91)组织的影响。研究结果表明,搅拌时间和搅拌速度对于SiCp/AZ91材料成品质量有显著的影响,搅拌速度的增加有助于SiC颗粒的分散,但速度过快导致液面起伏较大,大量气体进入镁液中,最终使成品中气孔较多。而在搅拌时间方面,当时间较短时,SiC颗粒未充分与合金液混合,因此出现大片SiC颗粒团聚现象。随着搅拌时间的延长,团聚的颗粒逐渐向镁合金液中均匀分散,当搅拌时间为15 min时,SiC固相颗粒与镁合金液所组成的混合相最为均匀,此时继续延长搅拌时间,其固相颗粒的宏观均匀性并未发生进一步变化。根据模拟和试验的结果得出最佳的搅拌时间为15 min,搅拌速度为300 r/min。     

Magnetic stirring assisted hydrothermal synthesis of Na3MnCO3PO4 cathode material for sodium-ion battery

Na₃MnCO₃PO₄ (NMCP) is considered one of the promising cathode materials for sodium-ion batteries due to its high theoretical capacity. The hydrothermal method is an efficient, environmental-friendly, and simple route with low instrument cost to prepare active cathode materials such as NMCP. In this research, magnetic stirring was applied to promote the hydrothermal synthesis, and NMCP was produced by controlling different stirring times. This method results in the formation of pure NMCP upon only 45 min processing time. According to the ICP results, the Na to Mn ratio in the NMCP approached the stoichiometric value of 3 by prolonging the stirring time. By analyzing the charge-discharge behavior of the NMCP materials synthesized through different reaction times, it was found that the NMCP produced at 120 ̊C for 480 min had the highest discharge capacity of 94 mAh g⁻¹, which was resulted from the increased Na to Mn ratio of 2.51. Besides, using Avrami's model, a kinetic equation was proposed for the particles' formation under the stirring hydrothermal process at 120 ̊C. Stirring the solution during the hydrothermal synthesis offers a fast, scalable and eco-friendly way of producing better performing NMCP cathodes with uniform morphological characteristics for sodium-ion batteries.     

Effect of stirring on the emulsion polymerization of styrene

The purpose of this paper is to clarify the effect of stirring on the course of emulsion polymerization of, for example, styrene. It establishes the existence of an optimum range of stirring speed and three important factors which must be considered in carrying out emulsion polymerization. (1) Stirring significantly affects the course of reaction in the presence of an imperfectly purified nitrogen atmosphere. Consequently, the number of polymer particles produced and the polymerization rate per particle will be affected. (2) At higher stirring speeds, polymer particles coagulate and coalesce. At lower stirring speeds, the reaction rate is controlled by the monomer transport rate from monomer droplets to the aqueous phase. (3) Stirring contributes to the reduction of the number of micelles because emulsifier molecules are adsorbed onto the surfaces of monomer droplets finely dispersed by the stirring. At low emulsifier concentrations near the critical micelle concentration, this effect cannot be neglected.     

Farbmeßgeräte für transparente Flüssigkeiten sichern die Qualität in der chemischen Industrie – Qualitätskontrolle an transparenten Flüssigkeiten

Colour Measuring Instruments for Transparent Liquids Safeguard the Quality in the Chemical Industry – Quality Control of Transparent Liquids In many areas of the chemical industry a complete product specification comprises – besides various other parameters – the colour characteristics as well. The colour of transparent liquids is still frequently determined by visual comparison of the product with e.g. iodine, Hazen- or Gardner colour standard solutions or appropriate colourfilter discs. In 1989 a new DIN 53995 standard for instrumental colour assessment of transparent liquids was introduced to replace the error-prone, subjective methods of visual comparisons. Dr. Lange GmbH, Düsseldorf, has developed the LICO 200 spectrophotometer under consideration of the new DIN 53995 for objective colour assessment in compliance with the iodine, Hazen and Gardner colour scales.     

Toxic gas and smoke measurement with the British Fire Propagation test. I: Test conditions

No standard method has been developed for measureing the evolution of specific toxic gases from building lings when involved in fire. The British Fire Propagation test (BS 476 Part 6) operated in an instrumented room has been proposed for this purpose previously but has not found general acceptance. It is considered further in this report, which investigates the movement and measurement of smoke and specific fire gases under different conditions of room stirring and the effect of the latter on fire propagation indexes. Stiring has been found to have no statistically significant effect on fire propagation indexes provided that the effects of this on calibration of the apparatus are taken into account. Stirring also had little effect upon smoke production per se. Under unstire conditions smoke and toxic gases stratify in the same layer early in the test, and measurement of their production at any single room location will be subject to the location, the way the room influences stratification and how the room is instrumentee, as well as by the prpduct performance. Under stirred room conditions smoke and toxic gases are evenly distributed and product performance can be assessed more simply from concurrent measurements of fire, smoke and toxic gas parameters. The latter procedure is proposed for obtaining relative data on building linings and for examination in further studies for correlation to room and corridor burns.     

Kinetic Investigation of Reaction Between Metallic Silver and Nitric Acid Solutions

In this study, the reaction kinetics between metallic silver and nitric acid solutions was investigated by taking into consideration the parameters of temperature, solid‐to‐liquid ratio, stirring speed, nitric acid concentration, particle size and addition of sodium nitrite. It was determined that the dissolution rate of the process increased with decreasing particle size and solid‐to‐liquid ratio, and increasing nitric acid concentration, reaction temperature and the amount of the sodium nitrite in the solution. In addition, it was observed that the stirring speed had more effect on the dissolution rate at low stirring speeds than at high stirring speeds. In the present study, the examination of shrinking core models of fluid‐solid systems showed that the dissolution of metallic silver in the nitric acid solutions was controlled by the reaction on the surface. A semiempirical model, which represented well the process, was developed by statistical methods. The activation energy of the process was found to be 57.66 kJ mol^–1.     

CAST工艺改良对系统强化除磷性能的影响

传统CAST工艺广泛应用于国内各种规模城镇污水处理厂,单凭生物法难以达到城市污水排放一级A标准。采用改良的CAST工艺,在传统CAST工艺基础上引入主反应区独立的搅拌时序,并在实际规模的污水处理厂进行工程示范。通过两阶段的试验,逐步缩短曝气时间延长缺氧搅拌时间,优化聚磷菌的代谢环境,增强聚磷菌的竞争优势。经过改良后的CAST工艺TP去除率达到89.1%,较传统CAST工艺提高了22%,出水TP稳定达到一级A标准。静态试验结果表明改良后的工艺反硝化聚磷菌的比例有所增加, 吸收相似文献   

搅拌混合中的循环与剪切

搅拌混合中的循环与剪切被定量化,搅拌功率分解为P=Q∑S_k,分解后的循环流量和总剪切强度,以及剪切强度在空间的分布应匹配．混合对偶合反应过程影响的实验结果表明,循环／剪切比适中的搅拌桨能较好地满足偶合反应工艺的需要,其分隔指数最小.用修正的拉格朗日法进行过程模拟,结果表明团块的循环经历影响其局部分隔指数,增大单位体积功耗、循环／剪切比以及循环区与桨叶区的能耗分配比能降低偶合反应的分隔指数．     

钛白粉生产中操作条件对水解过程的影响

水解过程是硫酸法钛白粉生产至关重要的一步。为了进一步探究水解过程的机理，选用工业中浓缩后的钛液为原料，通过响应面试验考察了4个操作条件，即搅拌速率、加料速率、加热时间、底水量对二氧化钛水解过程中水合二氧化钛粒子的粒径、过滤时间和水解率的影响，给出了各响应与4个操作条件的回归关系模型，并给出了最优的操作条件。该结果将用于指导工业生产。     

搅拌对氟硅酸钠氨化的作用

研究了氟硅酸钠晶体在溶液中产生氨化的搅拌工艺，研究表明：搅拌加速氨化反应，搅拌槽和搅拌器的转速、叶轮形式、规格是搅拌工艺的重要参数。     

Simulatoren zur Unterstützung der Prozeß- und Betriebsführung

Simulators for support of process and plant management. Process simulators are increasingly used for plant and process operation purposes. These simulators differ from those used in process design in the user interface, which is identical to the usual operator interface of distributed control systems. The progress of the numerical solution parallels the dynamic behaviour of the real process, and not that of the numerical procedure. The simulation-supported tasks of plant and process operation are: education of operators, training and instruction of operators, support of plant operation by interpretion of plant states and transitions and by helping to formulate operating instructions. These tasks, the available simulation concepts and examples are discussed in detail.     

The corrosion of iron in sulphate solutions at pH = 0–2

The effects of pH and stirring rate on the kinetics and mechanism of pure iron corrosion in deaerated, argon saturated solutions at 25°C have been studied. The entire concentration of sulphate ions in the tested solutions was 2.0 M. The increase of pH in the tested range causes the change of the anodic process mechanism, which is manifested in the decrease of the Tafel anodic straight line slope from 0.06 V (pH ～ 0) through 0.04 V (pH ～ 1) to 0.03 V (pH ～ 2) and the increase of the order of reaction with respect to OH^? ion, which is 0, 1 and 2 respectively. At adequately low potentials there occurs a change (to a small degree dependent on pH) of the anodic process mechanism which corresponds to the anodic straight line slope being 0.12 V. For the hydrogen evolution reaction the cathodic Tafel slope has been found to be ?0.12 V and the order of reaction with respect to OH^? ion to be ?1. Stirring of the solution has no practical effect on either the corrosion rate or the run of the polarization curves above pH = 1. For lower pH values, at the decrease of the stirring rate there occurs the increase of the corrosion rate and the increase of the anodic and cathodic process rate which is clearly visible below the corrosion potential. The cause of this phenomenon may be the catalyzing of both electrode processes by small quantities (～ 10^?7 Ml^?1) of the H₂SO₄ reduction products. The effect of pH on the corrosion potential and current has also been found.     

Integrated Modelling of Process Operation Systems Using the Agent‐Oriented Approach

For the past years, several software and computer tools have been developed to aid the chemical process operations including real‐time simulation, on‐line optimization, fault diagnosis, process monitoring, and many other functions. These tools were designed separately and did not collaborate efficiently, making it difficult to integrate different engineering tasks for the optimal process operation. In this paper, an agent‐oriented modelling approach is presented to address this problem. Elements in the process operation systems are divided into two classes. One class consists of equipment, units and processes, while the other class consists of production operation tasks. The two classes of elements are modelled as objects and agents, respectively. Then, three strategies are presented to implement the integration of the whole process operation system, which are integration of object models, integration of agent models and supervision of operator. Also presented is a case study of integration of process operation decision optimization and abnormal situation management using the proposed agent oriented approach for TE challenge problem.     

An empirical model for kinetics of boron removal from boron-containing wastewaters by ion exchange in a batch reactor

In this study, it was investigated boron removal from boron containing wastewaters prepared synthetically. The experiments in which Amberlite IRA 743, boron specific resin was used was carried out in a batch reactor. The ratio of resin/boron solution, boron concentration, stirring speed and temperature were selected as experimental parameters. The obtained experimental results showed that percent of boron removal increased with increasing ratio of resin/boron solution and with decreasing boron concentration in the solution. Stirring speed and temperature had not significant effects on the percent of total boron removal, but they increased the starting boron removal rate. As a result, it was seen that about 99 % of boron in the wastewater could be removed at optimum conditions. On the other hand, the process kinetics were predicted by using heterogeneous fluid-solid reaction models. It was seen statistically that the kinetics of this process agreed the pseudo- second order model, as follows: X_Bl(1−X_B) = 11,241.5[OH][C]^−1.76[S/L]^2.17exp(−19,57l.2/RT)t^1.24     

Die diskontinuierliche Zentrifuge als Betriebssystem in der Chemischen Industrie

Discontinuous centrifuges as operating systems in the chemical industry . Centrifuges are machines with rotors as working spaces in which the relative concentrations in mixtures of substances can be modified. Batch operating centrifuges are particularly suitable for this purpose when high demand on quality are made with regard to separation and purity of the substances separated or when the material parameters are subject to variation. The construction permits optimum adaptation to all operating parameters. The structural components for basic and additional functions have achieved a high standard of technical maturity and some have be specified in proven DIN standards. Centrifuges are particularly suitable for use as components of combined mechanical-thermal demoisturing plants. The technology of the drive systems of centrifuges and the control systems for conducting the process and for safety purposes utilize advanced hydraulics, pneumatics and electronics. Numerous materials of construction are available, including highly corrosion-resistant metals and alloys and those bearing a corrosion-resistant protective layer. The choice and utilization of a particular structural form are determined by the specific operational behaviour on filling, washing of the filter cake residual moisture content attainable, output of solids, demoisturizing capacity, industrial hygiene aspects of sealing during demoisturization and on output, optimum arrangement of the centrifuge in the overall plant, as well as costs of acquisition, installation and operation. Safety features are of particular importance in view of the large amount of energy stored and the possibility of operating with flammable liquids. On the basis of systematic analyses of the sources of danger, constructive measures and systems have been developed for the avoidance of explosion and fire which ensure safe operation of centrifuges.     

Zweiphasen-Titration von Aniontensiden mittels einer verbesserten Rührmethode

Two-Phase Titration of Anionic Surfactants Using an Improved Stirring Technique The construction of a simple stirred glass vessel in combination with modern metering devices permits two-phase titration of surfactants to be carried out more rapidly and conveniently than so far. Statistical comparisons, based on the mixed indicator titration of anionic tensides, show no differences between this “stirring” method and the established shaking method.