Experimental study of the mixing kinetics of binary pharmaceutical powder mixtures in a laboratory hoop mixer

As increasingly commented by the literature during the last 5 years, estimating the homogeneity of a powder mixture and following powder mixing processes is not a simple task. In this paper, we present the development and statistical validation of a sampling methodology for defining the number of samples required to provide a reasonable estimation of the homogeneity attained in a laboratory scale tumbler mixer. This method is then used to follow the mixing kinetics of a dilute binary powder mixture in a hoop mixer. Special attention is paid to the statistical meaning of the values obtained and the influence of the physical characteristics such as particle size and shape. The role of the particle shape of the majority powder is particularly emphasised and it is quantitatively demonstrated that spherical particles are harder to mix and more ready to segregate than particles with irregular shapes. The different mixing mechanisms at play are identified; the practical limits of use of such tumbler mixers with pharmaceutical powders are discussed.     

Influence of stirrer type on mixture homogeneity in continuous powder mixing: A model case and a pharmaceutical case

Continuous powder mixers offer a viable alternative to batch processes, but have received very little attention in scientific literature and in the industrial world. Mixer design is still very empirical and is not based on assessed methodologies. In this paper, we report experiments that aimed to compare two very different types of stirrers for a pilot-scale continuous powder mixer, and for two types of mixtures: a model mixture and a real pharmaceutical mixture. The first stirrer A is of the frame type with inclined paddles and internal transporting screw, the other stirrer B is of the shaft type with paddles mounted on it. Results are first presented from the viewpoint of bulk powder flow by hold-up determination and correlation with operating conditions. General relationships are derived which show that the mobile B leads to higher hold-ups, which may be an important drawback. The study of mixture homogeneity globally confirms these findings, especially in a dense phase flow regime. In the fluidised regime, where the stirrer B can be used, attention is drawn to the negative effect of excessive rotational speeds on the quality of the mixtures.     

Development of a tribolelectric procedure for the measurement of mixing and drying in a vibrated fluidized bed

Fluidization of fine, pharmaceutical powders makes them easier to dry, coat and mix. Fine powders, however, are difficult to fluidize well with gas flow only. Vibration can often help achieve smooth fluidization at a lower gas flow. The objective of the present study was, thus, to develop reliable and quick experimental methods to characterize mixing and drying in vibrated fluidized beds of fine powders.Effective mixing is critical in many industrial applications and, in gas-solid fluidized beds, requires gas velocities greater than the minimum bubbling velocity (U_mb). There are a number of techniques available for determining U_mb. However, they often are impossible or impractical to use in an industrial application. A new measurement technique involving the use of triboelectric probes was developed. Signal characteristics obtained from sophisticated signal analysis were used to identify the minimum bubbling velocities. These predictions corresponded well with the values obtained from more traditional laboratory methods such as the bed pressure gradient.In a fluidized bed, particles hitting a metal probe will generate a small triboelectric current. Triboelectric probes are able to detect rapid changes in particle surface properties. Surface properties of the particles were modified by wetting the particles in a low shear mixer. This change was detected by triboelectric probes at various locations inserted throughout the bed. The water adsorbed on the particles will begin to evaporate when exposed to the gas stream and the surface properties of the particles will gradually return to their original dry state. The triboelectric probes were able to monitor this drying process. The effects of vibration amplitude on the mixing and drying rate of the bed were also determined.     

Clay and non-clay minerals in the pharmaceutical industry: Part I. Excipients and medical applications

Minerals are widely used in the pharmaceutical industry as lubricants, desiccants, disintegrants, diluents, binders, pigments and opacifiers, as well as emulsifying, thickening, isotonic agents, and anticaking agents, and flavour correctors and carriers of active ingredients.A variety of minerals are used as excipients in pharmaceutical preparations because they have certain desirable physical and physico-chemical properties, such as high adsorption capacity, specific surface area, swelling capacity, and reactivity to acids. Other important properties are water solubility and dispersivity, hygroscopicity, unctuosity, thixotropy, slightly alkaline reaction (pH), plasticity, opacity, and colour. Clearly such minerals must not be toxic to humans. The following minerals are commonly used as excipients: oxides (rutile, zincite, periclase, hematite, maghemite, magnetite), hydroxides (goethite), carbonates (calcite, magnesite), sulfates (gypsum, anhydrite), chlorides (halite, sylvite), phosphates (hydroxyapatite), and phyllosilicates (palygorskite, sepiolite, kaolinite, talc, montmorillonite, saponite and hectorite). More recently, some tectosilicates (zeolites) also feature in pharmaceutical preparations.Minerals also enjoy the following medical/health applications: a) contrast diagnostic techniques, b) production of dental cements and dental molds in odontology, c) immobilization of limbs and fractures or dental and craniofacial surgical procedures in traumatology, d) bone grafts or construction of orbital implants, and e) spas and aesthetic centers. Examples of such minerals are oxides (zincite, magnetite and maghemite), sulphates (gypsum and barite), phosphates (hydroxyapatite) and phyllosilicates (clay minerals).     

干混砂浆生产过程中几个问题的探讨

干混砂浆在与湿拌砂浆的竞争中出现一些制约行业发展的共性问题,诸如干混砂浆的离析,机制砂中石粉含量高,计量设备不完善,外加剂溶解性差,机制砂筛分系统的超径与逊径,干混砂浆搅拌的均匀性等。通过详细阐述这些影响干混砂浆快速发展的技术工艺因素,提出了干混砂浆设备供商应该努力研究的方向,同时也提供了干混砂浆生产企业可以采取的临时性措施的建议。只有这些行业共性问题的解决,才能迎来干混砂浆大面积的普及与应用,才能实现干混砂浆对湿拌砂浆的彻底取代与发展。     

Application of an immobilized microbial consortium for the treatment of pharmaceutical wastewater: Batch-wise and continuous studies

In the present investigation, a microbial consortium consisting of four bacterial strains was selected for the treatment of pharmaceutical industry wastewater. The consortium was immobilized on a natural support matrix-Luffa and used for the treatment of real-time pharmaceutical wastewater in batch and continuous processes. The batch process was carried out to optimize the culture conditions and monitor the enzymatic activity. An array of enzymes such as alcohol dehydrogenase, aldehyde dehydrogenase, monooxygenase, catechol 2,3-dioxygenase and hydroquinol 1,2-dioxygenase were produced by the consortium. The kinetics of the degradation in the batch process was analyzed and it was noted to be a first-order reaction. For the continuous study, an aerobic fixed-film bioreactor (AFFBR) was utilized for a period of 61 days with variable hydraulic retention time (HRT) and organic loading rate (OLR). The immobilized microbes treated the wastewater by reducing the COD, phenolic contaminants and suspended solids. The OLR ranged between (0.56 ± 0.05) kg COD·m^-3 d^-1 to 3.35 kg COD·m^-3·d^-1 and the system achieved an average reduction of 96.8% of COD, 92.6% of phenolic compounds and 95.2% of suspended solids. Kinetics of the continuous process was interpreted by three different models, where the modified Stover Kincannon model and the Grau second-order model proved to be best fit for the degradation reaction with the constant for saturation value, KL being 95.12 g·L^-1·d^-1, the constant for maximum utilization of the substrate U_max being 90.01 g·L^-1 d^-1 and substrate removal constant K_Y was 1.074 d^-1 for both the models. GC-MS analysis confirmed that most of the organic contaminants were degraded into innocuous metabolites.     

气流粉碎技术在尼莫地平微粉生产中的应用研究

介绍了气流粉碎机的结构，论述了气流粉碎技术的原理，以及气流粉碎技术在尼莫地平微粉制备中的研究应用，并讨论了影响粉碎效果的因素和该技术在医药生产中的应用，指出加快超细粉碎在制药工业中的应用，会使制药工业上一个新台阶。     

The use of two different models to describe the axial mixing of solids in fluidised beds

Two widely used models to describe axial solid mixing in fluidised beds (the dispersion model and the countercurrent backmixing (CCBM) model) are evaluated against identical sets of experimental data. Experimental work has been obtained at different conditions (gas velocity, particle properties and two column diameters) using an image analysis technique. Previously published data by other authors are also compiled to enlarge the experimental database for model development and validation. It is shown that both models are capable to fit the majority of experiments well, in agreement with a well-known relation between the models in some extreme conditions. This relation is further explored by incorporating independent measurements of the tracer rise velocities during the mixing experiments. It is concluded that, although a simple correlation for the solid dispersion coefficients compiled in this work is useful, the CCBM model is a much more reliable idealisation in describing and scaling up axial solid mixing in fluidised beds.     

硫酸生产用钒催化剂产品行业标准的使用现状和对策

与国外相比,我国硫酸生产用钒催化剂产品行业标准中活性试验的检验结果并不能准确客观地反映钒催化剂的真实质量,五氧化二钒含量的测定方法也存在一定的差距。另外,生产企业执行标准不够严格。因此,应尽快研究出一种能客观反应工业使用条件,准确评价该产品质量的方法,制定出科学的行业标准,以满足工业生产和应用的需要。     

自动仓储物流系统在轮胎行业应用的研究

根据轮胎行业的生产特点,分析了轮胎行业仓储物流系统应有的体系结构、功能架构。并指出此仓储物流的核心是物流能力规划、信息交互集成、库位分配设计。根据以上特点,对物流系统进行了计算仿真、最大八库量可达15000条／天。     

智能电力监控系统在电化学行业中的应用

详细介绍了几种智能电力监控系统及其在电化学行业中的应用情况。     

顶空气相色谱法在制药行业废水处理中的应用

苯系物、挥发性卤代烃、酯类对人体及水生生物都有不同程度的危害,在《污水综合排放标准》（GB8978－1996）中甲苯的最高允许排放质量浓度为0.5mg/L、氯仿质量浓度为1.0mg/L。利用固定液的优选原则,采用混合固定液以解决分离问题,采用顶空气相色谱法提高了方法的灵敏度,从而建立了简便、快速、准确的方法。     

Application of recurrent neural networks in batch reactors: Part I. NARMA modelling of the dynamic behaviour of the heat transfer fluid temperature

This paper is focused on the development of nonlinear models, using artificial neural networks, able to provide appropriate predictions when acting as process simulators. The dynamic behaviour of the heat transfer fluid temperature in a jacketed chemical reactor has been selected as a case study. Different structures of NARMA (Non-linear ARMA) models have been studied. The experimental results have allowed to carry out a comparison between the different neural approaches and a first-principles model. The best neural results are obtained using a parallel model structure based on a recurrent neural network architecture, which guarantees better dynamic approximations than currently employed neural models. The results suggest that parallel models built up with recurrent networks can be seen as an alternative to phenomenological models for simulating the dynamic behaviour of the heating/cooling circuits which change from batch installation to installation.     

Improvement of biodiesel production based on the application of ultrasound: Monitoring of the procedure by FTIR spectroscopy

A novel application of ultrasounds is presented for the improvement of the efficiency of the production of FAME (or biodiesel) from materials not used so far for this purpose, such as seed cakes. The novelty of this work is the introduction of in situ derivatization assisted by ultrasounds (ultrasonically assisted extraction transesterification) for biodiesel production. Thus, the TG contained in solid material are extracted and immediately transesterified in a methanolic solution of 1 M NaOH in an ultrasonic field. The total yield of FAME from seeds that contain TG is greatly increased in most instances. In the seeds use in this work yields were increased from 46 to 85.5% for cotton, 67.2 to 93% for sunflower, and 43.2 to 83.5% for sesame. An FTIR methodology was developed to determine the percentage of FAME in the n-hexane layer of the reaction and thus, to monitor the reaction process. Overall advantages of the proposed methodology include the elimination of saponification, low reaction time, milder reaction conditions, and higher FAME yields.     

The use of mixing-sensitive chemical reactions to study mixing in dispersed fibre systems: Adsorption of reactants and product dyes on the dispersed phase

Mixing-sensitive chemical reactions conducted under controlled conditions can be used to qualitatively and quantitatively assess mixing in aqueous systems. These reactions are typically competitive reactions where the distribution of products is used to quantify mixing. This technique is valuable for studying both mixing and local energy dissipation in dispersed systems where the opacity of the suspension prevents the use of other techniques. However, correct interpretation of the test results requires that adsorption of reactants and product dyes on the dispersed phase be known. The adsorption of the reactants and product dyes formed in the mixing-sensitive azo coupling between mixtures of 1- and 2- naphthol and diazotized sulfanilic acid was measured in aqueous suspensions of nylon, polyethylene, fibreglass and kraft pulp fibres. The polyethylene fibre did not adsorb the reactants or product dyes. The nylon, fibreglass and kraft fibres adsorbed both reactants and product dyes, with adsorption described by Langmuir isotherms. Accounting for the adsorption of dye on the dispersed phase allowed correct interpretation of mixing in the aqueous phase of the dispersions. This technique is evaluated for mixing assessment in suspensions of nylon fibre and fully bleached kraft (FBK) pulp in a medium-intensity mixer.     

创新和循环经济是磷化工发展的必由之路：Ⅰ.黄磷尾气的综合利用与粉状磷矿的烧结技术

阐述磷化工产业发展现状及方向;黄磷生产尾气的综合利用现状,净化CO应优先开发的产品;黄磷生产用矿现状及粉矿烧结技术。计算了全部用块矿、全部用磨粉烧结矿、块矿与烧结矿按一定比例搭配的原料矿成本。并介绍了伍德烧结技术的改进,可使原料矿的成本进一步降低。在磷矿资源日趋贫化、枯竭,矿、电价格不断上涨的今天,磷化工企业必须开发使用新烧结技术。     

Optimal design of reactive distillation systems: Application to the production of ethyl tert-butyl ether (ETBE)

This work addresses the design of reactive distillation columns to produce ETBE, based on a detailed first-principles model that considers equilibrium and kinetic information, rigorous physical property data, and catalyst deactivation. An evolutionary algorithm is used to generate a sequence of feasible designs with improved characteristics in a sequential solution/optimisation strategy, by specifying the design variables (both integer and continuous) that characterise a particular column configuration. Two classes of optimisation algorithms are compared: genetic algorithms and particle swarm optimisation. The objective function considered is the gross annual profit.The results demonstrate that both algorithms are adequate to solve this design problem. The effect of catalyst deactivation included in the design stage played a determinant role in the optimal column specification. A post-design sensitivity analysis is developed to assess the quality of the solutions obtained, together with the individual effects of each design variable in the optimal configuration identified.     

Concomitant use of liquid–liquid batch and continuous plug flow reactors for kinetic model discrimination. Application to the Rh/TPPTS catalysed reduction of the C–C double bond in dimethylitaconate

The biphasic catalytic reduction of the C–C double bond of dimethylitaconate with a water soluble rhodium/triphenylphosphinetrisulphonated sodium salt (TPPTS) complex is investigated. Kinetic studies in a well-mixed batch reactor provide kinetics parameters and an activation energy of 71 kJ mol⁻¹ but cannot discriminate between a first order or a complex kinetic model within the range of substrate concentration where the approximation of linear liquid/liquid partition is respected. Catalytic tests in the centrifugal partition chromatograph (CPC) reactor under steady-state operations in chemical regime and plug flow mode allow discriminating the kinetic models, the complex kinetic rate law being preferred.     

我国电镀行业节能减排的关键——促进中小电镀企业清洁生产实施的政策研究

大型电镀企业在节能减排方面能够很好地做到达标排放,但是中小电镀企业却一直负面地影响着整个电镀行业.本文针对现有政策之下,中小电镀企业与节能减排的关系,分析了中小电镀企业清洁生产实施中存在的问题,提出了促进中小电镀企业实现节能减排的政策建议,如给予中小企业特别的优惠等.