FLUIDISED BED DRYER SCALE-UP

Abstract

Design methods for fluidised bed dryers have developed to the point where reliable scale-up is now possible for most applications. The model underlying the methods is described in terms of its constituent parts, namely a material model and an equipment model. The material model utilises drying data from laboratory tests together with scientifically based rules for predicting the effect of changes in operating conditions and the main design parameters on performance. The equipment model describes the residence time distribution for the system. This paper focuses on continuous well mixed and plug flow units.

There are a number of factors which must be considered in scale-up beyond the basic design method. In particular, the feed system, distributor, plenum and freeboard regions can introduce operational differences between the laboratory and full scale units which may adversely affect performance. Guidance is given on these practical considerations.     

Design of Crystallizers

It is shown how to design a crystallizer starting with data which must be determined in laboratory crystallizers and other measuring equipment. A survey on kinetic data of a large number of systems is given in order to show the range of parameters involved in crystallization.

The paper deals with the scale-up problems of crystallizers which are important when laboratory data are transferred to large-scale crystallizers.     

Predicting cone-in-cone blender efficiencies from key material properties

Blending of powders and granular materials is a critical unit operation in many industries, yet the ability to predict blending effectiveness lags well behind our ability to create new and novel blenders. As a result of this, production plants must rely on vendor blending tests conducted on small scale model blenders to determine if their specific material will work in the proposed blender design. Once these blending tests are conducted, engineers must then use past experience and conservative design practices to scale-up to full scale units at process flow rates.The difficulty in predicting blending efficiencies arises from the fact that blending performance depends on basic material properties, blender geometry, blender flow rates, and blender operation parameters. These effects are convoluted during blending operation. Successful scale-up would require understanding how to separate the influence of these four effects. If this could be accomplished, blender performance could be determined by measuring simple material properties, predicting blender velocity profiles, and computing blender efficiencies from predicted velocity patterns. This method would allow separation of factors affecting blender performance and provide a means of reliable scale-up using simple material properties and specified blenders geometries.This paper presents a methodology of predicting blender performance in simple in-bin blenders using easily measured material properties. It discusses blender optimization and determines the influence of gas pressure gradients on blender flow and operation. The specific blender analyzed is the cone-in-cone blender and the analysis suggests that blender performance depends on wall friction parameters for conditions where input concentration fluctuations occupy much of the blender volume. However, blending action appears to be independent of friction angle for conditions where there are many concentration fluctuations within a blender volume. The analysis also shows that gas pressure gradients can lead to stagnant region formation.     

Methoden und derzeitiger Kenntnisstand für Auslegungen beim Mischen von Feststoffen

Mixing of solids: present methods and current state of knowledge in design of equipment. In the design of mixing processes involving solids, power requirements and mixing time are of primary interest. Frictional forces, which are responsible for the resistance to mixing tools, depend on such parameters as fineness and roughness of the material. In addition, the state of compression of the material and geometric considerations exert their influence. Fundamental investigations which involve scale-up are extremely laborious and hence insufficiently available at present. For this reason, design depends mainly on the body of experience available to manufacturers. This paper reviews our present knowledge as illustrated by several well known mixing processes.     

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.     

Scale-up and design of a continuous microwave treatment system for the processing of oil-contaminated drill cuttings

A continuous microwave treatment system has been developed for the remediation of contaminated drill cuttings at pilot scale. Using the mechanisms of oil removal as a basis, a design was produced using electromagnetic simulations to find the optimum microwave applicator geometry which yielded the most favourable power density distribution. Bulk materials handling and process engineering principles were systematically integrated with the electromagnetic design to produce a system capable of treating 500 kg/h of material. The effects of the key design parameters are simulated, and a number of the simulations are verified with experimental data. It is shown that the environmental discharge threshold of 1% oil can be achieved in continuous operation, and the sensitivity of the system to changing feedstock properties is also highlighted. The parity between the simulations and experimental results in this paper highlights the necessity of electromagnetic modelling in the design and scale-up microwave processing equipment.     

Modellübertragung in der Verfahrenstechnik

Model scale-up in chemical engineering . Similarity theory and the theory of models based thereon are working tools which permit reasonable planning of experiments, their execution with a minimum of effort, and their evaluation in such a way as to provide reliable information about the design and the operating conditions of the technical plant – provided these methods are used in good time and in the proper manner. A brief introduction to the problems involved and to the methodology of similarity theory is provided by the introductory section and the first example. Four more problems and their solutions according to similarity theory serve to answer questions concerning the size of the experimental scale, the choice of material system used in the experiment, and the problem of scale-up under conditions of partial similarity. Two of these examples clearly illustrate that an inadequate knowledge of the material parameters (e. g. for foams and slurries) necessitates model measurements on the technical system with a change of scale.     

Scale-up of fluidized-bed hydrodynamics

The scale-up of fluidized beds is not an exact science. However, using proven techniques based on experience and mathematical and/or design models can minimize risk and uncertainty when scaling up fluidized beds. Scaling, which maintains that certain dimensionless groups be matched in different sized units for hydrodynamic similarity to be achieved, is different than scale-up, and generally can not be applied to pilot plants used for scale-up. Scaling is typically more useful to be applied to cold model studies that can be used to improve the operation of an existing plant. Deep fluidized beds of Group A materials can cause significant gas bypassing leading to poor gas-solids contacting. Because commercial beds are generally deeper than beds used in pilot plants, care must be taken to ensure that beds that do not exhibit gas bypassing in smaller units, do not have gas bypassing in commercial systems.     

环氧乙烷氨化制乙醇胺ZSM-5沸石催化剂扩试研究

以特定无定形氧化硅小球为前体,优化沸石分子筛晶化工艺条件,成功用5 m~3晶化釜完成无定形氧化硅小球向ZSM-5分子筛整体转晶的扩试放大研究,再经氨交换及焙烧等过程制备环氧乙烷氨化制乙醇胺催化剂。XRD、SEM、低温N_2吸附-脱附等表征结果显示扩试催化剂的物化数据与小试催化剂基本一致。考察n(NH_3)∶n(环氧乙烷)对吨级扩试催化剂性能的影响,并进行1 000 h稳定性实验,在设计工艺条件下,吨级扩试催化剂性能可达到小试催化剂水平,且稳定性良好。     

生物柴油超临界甲醇法生产工艺全流程模拟与经济分析

基于小试结果放大,应用SuperPro Designer?仿真软件,设计模拟超临界甲醇法年产5万t生物柴油的工艺流程,并进行了经济成本核算. 模拟结果表明,主要过程数据符合实验结果,工艺设计合理;经济分析显示,高温高压设备占设备成本较大比例,原料成本占生产成本70%以上,项目总投资约7272万元,税后净利润约2704万元/a. 该工艺具有较好的可行性.     

Scale-up of single screw extruders

Scale-up from small laboratory size extruders to large production size extruders is a procedure of great practical importance. Many scale-up rules and theories have been proposed in the past, however it is not always clear how the different scale-up methods will affect extruder performance. A basic analysis of scale-up in plasticating single screw extruders is developed from which the effect of a certain scale-up strategy on extrusion performance can be evaluated in terms of solids conveying, melting, melt conveying, mixing, residence time, heat transfer, power consumption, and specific energy consumption. Various existing scale-up theories are evaluated and compared using the basic analysis. A number of existing scale-up theories have some significant drawbacks, in particular with non-constant specific energy consumption and imbalance between melting rate and pumping rate. Conditions that are desirable to achieve in scale-up are enumerated and ranked in terms of importance. This leads to two new scale-up methods that result in constant mechanical specific energy consumption and high throughput rates. The first scale-up method keeps the specific surface area constant. This scale-up should work well for high values of the Brinkman number. However, at low values of the Brinkman number, the melting rate may be insufficient. The second scale-up method keeps the melting rate at low Brinkman number equal to the pumping rate and, thus, should be useful in cases where the first scale-up method cannot be used.     

Pipeline scale-up in drag reducing turbulent flow

Models available in literature for predicting drag reduction scale-up are inadequate as they have been successful only over a narrow range of diameters. A new scale-up model is presented which equates dampening of turbulent velocity fluctuations by drag reducing additives to a reduction in the Prandtl mixing length. Flow and pressure drop data from a laboratory scale pipe along with shear viscosity measurements are sufficient to predict drag reduction scale-up in bigger diameter pipes. Using this approach, scale-up was successfully predicted over a diameter range of 7 to 154 mm for a surfactant-water system and 26.6 to 1194 mm for a polymer-oil system.     

Scale-up in the 4th dimension in the field of granulation and drying or how to avoid classical scale-up

In the pharmaceutical industry, the production of granules is based on a batch concept. This concept offers many advantages, as a batch can be accepted or rejected. However, the scale-up of the batch size may lead to problems. The variety of the equipment involved does not facilitate the scale-up process and the capital invested in space and equipment is high. An alternative approach is the use of a continuous process. However, continuous processes have the disadvantage among others that the batch size is not well defined. Thus, a special quasi-continuous production concept was developed, taking into account the advantages of a batch type and a continuous process. This concept was developed in cooperation with the Institute of Pharmaceutical Technology of the University of Basel, Glatt CH-4133 Pratteln and F. Hoffmann-La Roche, CH-4070 Basel. The equipment allows to implement a “Just in Time Production Concept” as a large batch B consists of n subunit (SU) batches b, i.e. B=nb. The subunit batch b corresponds to, e.g. 7-kg material for the production of pharmaceutical granules for further processing such as tabletting. At the Roche production site, this novel process equipment was used to manufacture batch sizes B with n=10, n=100 and so far up to n=600 subunits. This leads to an optimal use of capital invested in GMP space and equipment. The difference to the classical scale-up is the following: with classical scale-up, the dimensions of the equipment x, y, z is enlarged and the process time is more or less kept constant. With this novel concept, the dimension x, y, z of the equipment is kept constant and the process is repeated in the 4th dimension “n times”. Thus, for the scale-up in the 4th dimension, i.e. in the time, the equipment needs to show a “self-cleaning” property and appropriate formulations. The novel concept is of special interest, as the quality of the product is not changed during scale-up.     

SCALE-UP OF CONTACT DRYERS

The scale-up of contact dryers is still based on experimental drying curves. In order to keep the effort to a minimum the drying curve is determined using a small laboratory or pilot dryer of similar geometry to the production dryer.

This paper introduces a new scale -up method for contact dryers. The new scale-up method is based on the assumption that heat transfer is the controlling mechanism. The scale-up method is derived from the material balance, the energy balance, the kinetic equation of heat transfer and thermodynamic equilibrium. The scale up method can be used to convert the drying time required to achieve a certain residual moisture content from the laboratory or pilot dryer to the production dryer and/or different drying conditions.

The scale-up method was verified by drying test with four different products in conical mixer dryers of 1, 60, 250, 1000 I volume. Two products were free flowing and two products were non free flowing in the wet state. The products can be considered non-hygroscopic in the moisture range investigated.     

化学产品过程开发实验平台--公斤实验室的建设和应用

以化工产品设计和过程开发为导向,建立了一个化工产品过程开发实验平台--化工产品公斤实验室Kilo-lab.该公斤规模试验装置可进行反应、结晶、分离、提纯等系列产品的开发过程,研究了流程装置集成和柔性生产系统的规律和特征,为小批量、多品种、高附加值化学产品快速响应市场的变化和需求,以及过程开发的工业化放大提供理论和实验依据.     

Modelling and design of thin-film slurry photocatalytic reactors for water purification

Photocatalytic oxidation processes are highly effective clean technologies for the degradation and mineralization of a wide variety of priority pollutants in water and wastewater. However, the application of heterogeneous photocatalysis for wastewater treatment on an industrial scale has been impeded by a lack of mathematical models that can be readily applied to reactor design and scale-up. As a results current photocatalytic reactors in research and development have been designed by empirical or semi-empirical methods only.In this paper, a simple and generic mathematical model for steady-state, continuous flow, thin-film, slurry (TFS) photocatalytic reactors for water purification using solar and UV lamps is presented. The model developed is applicable to TFS flat plate and annular photoreactors of (a) falling film design or (b) double-skin design, operating with three ideal flow conditions: (1) falling film laminar flow, (2) plug flow and (3) slit flow. The model is expressed in dimensionless form and scale-up of TFS photocatalytic reactors can be carried out by dimensional analysis. In addition, the model parameters can be estimated easily from real systems and model solutions can be obtained with little computational effort.Comparison of a number of ideal flow systems shows that both falling film laminar flow and plug flow operation modes give higher performance than the slit flow system. Slit flow operation mode results in lower conversions due to the non-correspondence of fluid-residence time and the transversal radiation field. The effect of optical thickness, on reactor performance and the evolution of radial profiles of a model pollutant with photoreactor length are presented for each of the operation modes. The falling film laminar flow system was found to be more efficient than the plug flow system when the reactor conversion is above 80%. For lower reactor conversion the plug flow system was found to be marginally more efficient than the falling film laminar flow system. A methodology for the optimal geometrical design of a highly efficient configuration of TFS photocatalytic reactors is also presented. The mathematical models presented may be used as a tool for the design, scale-up and optimization of these types of photocatalytic reactors.     

橙色PE100级管材专用树脂的中试放大研究

在前期橙色PE100级管材专用树脂小试配方实验的基础上,进行了中试放大研究,评价2544或2029B色母粒的性能及专用树脂体系的最佳加工方式.结果表明:2544色母粒在承压环境下的表现更好,2029B色母粒适合在各种老化条件(如光照和热氧)的环境中使用,综合分散差异、老化和静液压等性能,经二次造粒得到的专用树脂的整体性...     

Scale-up of binder agglomeration processes

This review article describes scale-up of batch and continuous granulation processes where liquid binder is added to fine powder in order to form a granular product. The technical goal of scale-up is to maintain similarity of critical product attributes as the production scale and/or throughput of a manufacturing process is increased. This paper provides a framework for scaling-up that considers critical process transformations in relation to the desired product attributes. A similar approach can be taken in developing process control strategies. In any agglomeration process, transformations can be used to describe how raw materials (typically fine powders and liquid binders) are converted into a granular product. Often the critical product attributes are characterized on the scale of individual granules (e.g., size, shape, porosity, mechanical strength, etc.). On the other hand, industrial scale-up requires predictive relations for the sizing, design and operation of process equipment. Considering scale-up on the basis of transformations is one way to link the macro-scale equipment decisions with micro-scale product attributes. This approach can be applied to the scale-up of batch and/or continuous granulation processes as well as transitioning from small batch prototypes to continuous production circuits.     

Commercial Development of Oil Palm Clones

The laboratory techniques for clonal propagation of oil palms by tissue culture have been available for the past 10 years. Production of commercially useful oil palm clones which can be propagated economically requires integrated programs of factory development and of palm breeding and selection. The laboratory techniques require optimization and scale-up to enable cost effective production of uniform good quality plants. Successful clones depend on selection of the best genetic material from current breeding programs. Since genetic and environmentally induced variation both contribute to individual palm performance, each clone must be field tested over several years in different environments before final clone selections are made and they enter commercial production. A number of clones in current commercial trial show promissing yield increases compared with seedling palms. Several clones subjected to large-scale production are producing abnormal flowers resulting in bunch failure. Current research is concentrated on discovering the cause of the abnormality and providing quality control and cultural methods to avoid its induction and to guarantee production of normal palms.