Collection efficiencies and particle size distributions from sampling cyclones — comparison of recent theories with experimental data

The grade collection efficiencies and particle size distributions from Stairmand-type cyclones are compared with predictions from four theories, viz. the models of Leith and Licht (1972), Dietz (1981) Mothes and Loffler (1988) and Li and Wang (1989). It is shown that the theory of Mothes and Loffler, which recogizes different flow regions within a cyclone, coupled with a realistic estimate of the particles turbulent diffusivity, is capable of providing good estimates of both the grade-efficiency curves and particle size distributions of the cyclone catch and/or outlet dusts. The lack of adequate theories or empirical formulae to estimate the effective turbulent diffusivity under cyclone flow seems the major factor hindering the use of the Mothes and Loffler theory for predictive purposes. High loadings and agglomeration of fines, if present, are responsible for strong departures from theoretical predictions.     

应用CFD技术对工业结晶过程进行模拟和放大

Some empirical mixing models were used to describe the imperfect mixing in precipitation process.However, the models can not, in general, reflect the details of interactions between mixing and crystallization in a vessel. In this study, CFD (computational fluid dynamics) technique were developed by simulating the precipitation of barium sulphate in stirred tanks by integration of population balance equations with a CFD solver. Two typical impellers, Rushton and pitched blade turbines, were employed for agitation. The influence of feed concentration and position on crystal product properties was investigated by CFD simulation. The scale-up of these precipitators was systematically studied. Significant effect on the crystal properties was found for the scale-up under some conditions.Keywords simulation, scale up, precipitation, CFD(computational fluid dynamics)     

Fine particle capture in biomass boilers with recirculating gas cyclones: Theory and practice

This paper addresses the theoretical development and experimental validation of optimized recirculating reverse-flow gas cyclones. The simulation of these systems is based on the predictive properties of a finite diffusivity model, modified to include partial recirculation of the cyclones' emissions.Experimental validation was obtained at laboratory and pilot scales at low temperatures (up to 350 K) and for cork waste biomass boilers at higher temperatures (up to 600 K). Under certain circumstances, with recirculation, the proposed system showed a better performance than an online pulse jet bag filter, and substantially better than with multicyclone systems. The generally observed unexpected high collection of submicron particles, which occurs with inlet concentrations as low as 100 μg/m³, is attributed to turbulent dispersion, either by promoting fine particle capture by larger ones, much like what occurs in recirculating fluidized beds, or by bringing fine particles near the cyclone wall.The extremely fine particle size distributions exiting from the recirculation system, as measured off-line at laboratory, pilot and industrial scales, were confirmed at pilot scale using online measurements through a laser monitor.     

Design of parallel cyclones based on stability analysis

The uniform distribution of gas solids flow across parallel cyclones is required for high efficiency. In this study, we introduced mass flow rate ratio between solids and gas (C_T) to present multi‐phase interaction. And the direct Liapunov method is used to detect the instability of uniformity. Due to the special symmetry in this system, the criterion can be simplified into identifying the concavity (concave or convex) of pressure drop across a single cyclone with respect to C_T. Then, based on the stability analysis of uniformity, a novel design principle is provided to prevent non‐uniform distribution at dense phase. The effect of geometrical factor, i.e. dimensionless vortex finder diameter d_r, on the stability of uniformity has been further investigated. The phase diagram, illustrating the effects of both operational parameter (C_T) and geometrical parameter (d_r) on stability of uniformity is calculated to give a clue of designing a robust parallel cyclones system. © 2016 American Institute of Chemical Engineers AIChE J, 62: 4251–4258, 2016     

条形加氢处理催化剂的工业放大问题

本文论述了条形石油馏分加氢处理催化剂工业放大的某些问题,包括：（1） 目前存在的问题；（2）工业放大基本概念；（3）工业放大效应分析;(4）工业放大基本条件；（5）产品的物化性质指标的制定。     

Analytical Approach for Calculating the Separation Efficiency of Uniflow Cyclones

An approach for calculating the separation efficiency of uniflow cyclones for the separation of solid particles from gases is proposed. The analytical model is based on an equilibrium orbit concept, similar to that used in the Barth‐Muschelknautz model for conventional reverse‐flow cyclones, which has been proven to be successful for designing and calculating cyclones in a wide range of industrial applications. The proposed model takes into account the special flow pattern of uniflow cyclones, which differs substantially from that in reverse‐flow cyclones. The model provides correct dependencies of the separation efficiency on the main geometry and operation data of low‐loaded uniflow cyclones. Applying the calculation method to uniflow cyclones operated in test facilities indicates good agreement with experimental data.     

Challenges in the scale-up of particulate processes—an industrial perspective

Studies by the Rand Corporation in the 1980s identified substantial differences in the scale-up and start-up performance of plants processing particles versus those processing liquids or gases. These differences were inevitably unfavorable. Particulate process plants take longer to start up and are less likely to achieve desired production rates. Facility operators often underestimate the challenges involved. These problems generally relate to an inadequate understanding of the behavior of particle systems. Many of these behaviors are sensitive to process scale or process history in ways that would not be expected by engineers familiar only with liquid or gas systems. Empiricism must often substitute for first principles. Modeling provides some answers, but often not enough to eliminate the need to operate pilot plants. This paper reviews some of the unit operations involved in particle processing and highlights scale-up issues involved. The use of information from suppliers and other third parties is discussed, as well as scale-up strategies in competitive or regulated industries.     

HiGee strategy towards large-scale synthesis of soluble covalent organic frameworks

The scale-up synthesis of covalent organic frameworks (COFs) with uniform structure and properties is of great importance for their practical applications. Here, we proposed a facile way to massively produce phthalocyanine-like COFs (COF_BTC) via high-gravity intensified synthesis. Alcoholic solvent and basic catalyst were discovered synergically improved the formation of COF_BTC. High concentration and reaction temperature were beneficial for high production as well. The intensified mass and heat transfer at high-gravity promoted the scaling-up of COF_BTC with homogeneous structures and properties. A high space time yield of 305.9 kg∙(m³ D)⁻¹ was achieved for Fe-COF_BTC under optimized condition. The massively produced Fe-COF_BTC presented good solubility in alkaline and polar organic solvents, thus allow to process as homogeneous or heterogenous electrocatalyst for oxygen reduction reaction. The catalyst exhibited good performance of 0.79 V (vs. RHE, half-wave) and >95% recovery in homogeneous electroreduction of O₂ in 0.1 M KOH. A superior performance of 0.86 V was achieved by sol–gel-like processing of Fe-COF_BTC on carbon paper due to the enhanced conductivity. The scale-up soluble catalysts with uniform properties provide more opportunities for practical applications of COF_BTC.     

Scale-up study of supercritical fluid extraction process for clove and sugarcane residue

Many scale-up criteria for supercritical fluid extraction (SFE) can be found in literature. However, the studies are often divergent and inconclusive; therefore, more studies on this field are needed. The objective of the present work was to study the scale-up of SFE process focusing application to Brazilian raw materials. A laboratory scale equipment (290 mL extraction vessel) and a pilot scale equipment (5.15 L extraction vessel) were used to study scale-up of SFE for clove and sugarcane residue. The scale-up criterion adopted consisted in maintaining solvent mass to feed mass ratio constant. The criterion was successfully used for a 15-fold scale-up of overall extraction curves for both raw materials studied; yields in pilot scale were slightly higher than in laboratory scale. The criterion studied allows a rapid and simple scale-up procedure, which can be very useful for the purpose of developing SFE technology at industrial scale in developing countries where such technology is still not available at industrial level.     

有机颜料生产工艺放大的考虑

如何将一个有机颜料制造工艺成功地从实验室放大到工厂生产?为此,首先论述工艺放大的方法论、搅拌反应器放大准则、有机颜料工艺放大的困难等一些基本因素,接着分析有机颜料反应釜放大和沉淀釜的放大,最后提出有机颜料工艺放大应该遵守的准则。     

微生物燃料电池的研究应用进展

微生物燃料电池是利用微生物作为催化剂,氧化分解生物质同时输出电能的一种新装置,因其可将生物质中化学能直接转化为电能,可获得更高的能量转化效率,是未来缓解能源和环境问题的有效途径,引起了科研工作者的广泛关注。本文结合近几年微生物燃料电池的发展,综述了产电微生物种类、电池材料及其改性、反应器的放大以及微生物燃料电池应用方面的研究进展,分析了该领域未来发展的主要方向及面临的问题,指出筛选和诱导产电菌对不同有机底物的耐受性,开发高效价廉的电极材料以及构建易于放大的电池模式,是微生物燃料电池未来研究的重点。在此基础上,应该着重于反应器放大,深入研究其在废水处理、产氢、微生物电化学合成以及传感器方面的应用,确定其实际应用的相关参数和模型,为微生物燃料电池早日实际应用打下坚实基础。     

VAH型气相醛加氢催化剂的工艺研究

在试验室制备、评价所研制的醛加氢催化剂的基础上，进行了催化剂的工业放大生产和在化工二厂丁辛醇装置上的单管侧线放大试验，结果重复了实验室的小试水平，醛加氢催化剂各项性能优于进口的醛加氢催化剂G-66B-1，所研制的催化剂具有良好的活性、选择性和稳定性。具备了催化剂的国产化和工业应用的水平。     

黄磷脱砷生产技术工业性试验

工业黄磷经水相氧化法脱砷处理后,可使黄磷中杂质砷含量由0.015%降至0.002%以下,脱砷效果好,同时精制磷回收率高达92.71%,这表明“水相氧化法”脱砷技术经工业放大后,其放大效应是可靠的,工艺技术指标稳定,生产过程安全。此外,所采用装置的关键设备具有结构简单、易于操作等特点。     

Continuous-flow production of a pharmaceutical nanoemulsion by high-amplitude ultrasound: Process scale-up

High-pressure homogenization (HPH, including microfluidization) and high-amplitude ultrasonic processing are currently the leading two methods used to produce nanoemulsions of superior quality. Despite suffering from multiple important drawbacks, HPH is currently the technology of choice for the industrial manufacture of pharmaceutical nanoemulsions. The ultrasonic nanoemulsification technology is free from most of these drawbacks and frequently used in laboratory studies. The challenge for the ultrasonic method, however, has been bridging the gap between laboratory research and its industrial implementation. Due to limitations of conventional ultrasonic technology, scaling up has not been possible without a significant reduction in ultrasonic amplitudes, which compromises product quality. This limitation has been overcome by Barbell Horn Ultrasonic Technology (BHUT), which permits constructing bench and industrial-scale processors capable of operating at high ultrasonic amplitudes. In the present study, a high-quality MF59^®-analog pharmaceutical nanoemulsion has been successfully manufactured using laboratory, bench and industrial-scale high-amplitude ultrasonic processors. The overall laboratory-to-industrial scale-up factor achieved by using BHUT was approximately 55. The ultrasonic amplitude and the resulting product quality were maintained identical at all three scales. To our knowledge, this work is the first reported instance of a successful and systematic industrial scale-up of any high-amplitude ultrasonic process.     

塔板压力平衡的应用(Ⅱ)消除固舌催化分馏塔放大效应的新方法

针对工业催化裂化φ5 m的主分馏塔操作稳定性差、压降高等生产问题,利用FRI对网孔塔板试验现象观察结果,对催化分馏塔内固舌塔板的操作现象进行了类比,结果表明：催化分馏塔内的固舌塔板存在着严重的入口泄漏和出口喷射的分相流操作现象,表现出显著放大效应的特征。解决这一问题的关键是调控塔板上液层分布,为此提出了塔板上增设入口堰和出口堰,调控塔板上液层分布,消除放大效应,从而达到降低塔板压降,改善操作效果的目的。通过固舌塔板增堰的新方法并结合部分应用Super V1浮阀塔板,对装置进行了技术改造,结果表明：在140万吨/年加工能力的条件下,改造后的全塔压降由开车初期的28～34 kPa（国内设计经验值）降低到稳定的16 kPa,降低了约50％,该数值与设计计算的全塔压降18 kPa十分一致;汽柴油总收率由原来的68.13％提高到68.48％,轻收提高了0.35%,柴汽比由0.82提高到0.88;汽柴油产品由改造前重叠28℃降低到6℃,表明分离效率得到提高。在160万吨/年加工能力下,全塔压降仅为26 kPa,仍低于扩能前的压降,且操作平稳,产品质量完全合格。     

Applications of pressure balance in large scale distillation tower (Ⅱ) A new approach to solving scale up effects inside main fractionators equipped with jet trays in RFCC units

针对工业催化裂化φ5 m的主分馏塔操作稳定性差、压降高等生产问题,利用FRI对网孔塔板试验现象观察结果,对催化分馏塔内固舌塔板的操作现象进行了类比,结果表明：催化分馏塔内的固舌塔板存在着严重的入口泄漏和出口喷射的分相流操作现象,表现出显著放大效应的特征。解决这一问题的关键是调控塔板上液层分布,为此提出了塔板上增设入口堰和出口堰,调控塔板上液层分布,消除放大效应,从而达到降低塔板压降,改善操作效果的目的。通过固舌塔板增堰的新方法并结合部分应用Super V1浮阀塔板,对装置进行了技术改造,结果表明：在140万吨/年加工能力的条件下,改造后的全塔压降由开车初期的28～34 kPa（国内设计经验值）降低到稳定的16 kPa,降低了约50％,该数值与设计计算的全塔压降18 kPa十分一致;汽柴油总收率由原来的68.13％提高到68.48％,轻收提高了0.35%,柴汽比由0.82提高到0.88;汽柴油产品由改造前重叠28℃降低到6℃,表明分离效率得到提高。在160万吨/年加工能力下,全塔压降仅为26 kPa,仍低于扩能前的压降,且操作平稳,产品质量完全合格。     

Supercritical fluid extraction of peach (Prunus persica) almond oil: Kinetics, mathematical modeling and scale-up

Peach almonds contain oil with important therapeutic and nutritional properties due to the presence of unsaturated fatty acids, high content of oleic acid and other substances. In this study, peach almond oil was obtained by means of supercritical fluid extraction (SFE), with yield up to 24% w/w. The objective of this work was to evaluate the effect of the operation variables in the process kinetics in order to define scale-up parameters, like extractor volume and solvent flow rate. In spite of the importance for industrial application, the definition of a scale-up methodology is difficult. Therefore, the main goal of this work was to study the kinetic aspects of the SFE by modeling the extraction curves and, with these results, suggests a scale-up methodology. The parameters evaluated were extraction pressure, CO₂ flow rate and particle size. The mass transfer models used to describe the extraction curves were logistic model, diffusion model and Sovová model. Four scale-up methodologies, based on mass transfer mechanisms, were applied. The results indicate the best curve fitting by means of Sovová’s model, while the best scale-up criterion was maintaining the ratio Q_CO2/M (solvent flow rate/raw material mass) constant. This study also indicated the convection as the dominant mass transfer mechanism, while the diffusion was the limiting factor. Moreover, the SFE of peach almond oil could be predicted by the scale-up method used.     

Turbulent dispersion coefficients in cyclone flow: An empirical approach

Among the various theories available to predict cyclone collection efficiency, the finite diffusivity theory of Mothes and Loffler (1988) has been shown to give the best fit of the observed grade-efficiency curves. However, lack of knowledge on the dependence of the particles' turbulent dispersion coefficient with cyclone geometry, operating conditions and particle size has so far hindered the application of this theory for predictive purposes and for improved cyclone design. In this work, this theory is applied for predictive purposes, through the use of an empirical relation for the particles turbulent dispersion coefficient. The proposed relation is based on an analogy with turbulent dispersion in packed beds, and correlates the particle radial Peclet and Reynolds numbers. Laboratory-scale reverse-flow cyclones of previously unpublished geometries were built to test the applicability of the proposed relation. The Mothes and Loffler (1988) theory, when coupled with the proposed estimates of turbulent dispersion coefficients, is a powerful tool for predicting cyclone collection efficiency, short of using computational fluid dynamics tools.     

PILOT PLANT STUDIES AND MODELLING OF A SEMI-BATCH POLYESTERIFICATION PROCESS

A novel unsaturated polyester formulation was developed recently in our laboratories. The polyester resin, which was designed as a green-house glazing material, exhibited excellent optical properties and superior resistance to weathering conditions. This study describes the scale-up procedure followed in preparing the resin in a 200 L pilot plant reactor starting from its preparation in a 1 L reactor. The paper analyzes the major variables affecting the polyesterification process and presents a semi-empirical model capable of predicting the pilot plant kinetic data from laboratory reactor data. The model is based on a recently developed third order kinetic equation for the reaction of non-stoichiometric amounts of hydroxyl and carboxylic groups. The model quantifies the effects of reaction temperature and inert gas flow rate on reaction rate and provides a basis for the polyesterification process scale-up. The reaction temperature dependence is assumed Arrhenius, whereas the gas flow rate dependence is empirically determined as a function of the molar ratio of reactants to inert gas. Application of the model to commercial sized reactors will be highlighted.