陶瓷喷雾干燥塔设计理论基础

陶瓷喷雾干燥塔是建筑陶瓷墙地砖生产过程中湿法制粉的关键设备。喷雾塔干燥技术自20世纪80年代研究开发成功以来,已经广泛应用于建筑陶瓷墙地砖生产过程中,喷雾干燥塔生产墙地砖成形颗粒粉料,仍然是目前大型自动化压机最理想的成形粉料。随着墙地砖生产装备技术的进一步发展,目前喷雾干燥塔已经进一步向大型化发展,以适应不断扩大的生产规模。     

喷雾干燥法制备固体粉末医药级磺丁基醚-β-环糊精

磺丁基醚-β-环糊精具有水溶性高、溶血作用小等优点,在医药中应用前景广泛。本文以β-环糊精与1,4-丁烷磺内酯在Na OH水溶液中反应,经纳滤提纯,喷雾干燥脱水制备了磺丁基醚-β-环糊精的固体粉末。喷雾干燥正交实验表明对产物含水量影响因素依次是进风温度物料浓度塔内压差雾化盘转速;对产物粉末堆密度影响因素依次是物料浓度雾化盘转速塔内压差进风温度,对进一步的制剂开发具有重要意义。     

甘露醇喷雾干燥过程中液滴粒度分布变化的群体粒数衡算模拟和实验研究

利用群体粒数衡算（population balance，PB）计算机模拟和实验研究了甘露醇水溶液的喷雾干燥过程中液滴的粒度分布的变化规律。液滴干燥过程中的颗粒粒度的萎缩速率，在群体粒数衡算模型中描述为液滴的逆（或负）生长项，通过单个液滴反应动力学方法（reaction engineering approach，REA）获得。基于单个液滴干燥的反应工程方法模型REA和群体粒数衡算模型PB集成建立了PBREA模型。PBREA 模型的求解是通过高分辨率数值方法。本文模拟研究了不同工况下，不同粒径液滴的干燥时间、液滴平均含湿量以及液滴粒度分布随时间的变化。结果显示，液滴粒径越大，干燥时间越长，模型预测的颗粒平均粒径为实验值的1.0~1.5倍，粒度分布跨度是实验值的0.61~0.89倍。模拟误差主要来源于液滴及颗粒粒径分布统计精度、单个静止液滴与群体运动液滴干燥的差异、热导率及扩散系数是经验值3个方面。在使用Buchi 290 小型喷雾干燥仪进行的实验中，使用了图像采集和分析方法得到了液滴及颗粒的数密度分布，并和模拟结果做了对比。结果表明该模型可以有效地预测喷雾干燥过程中干燥颗粒的平均粒度及分布跨度。     

喷雾干燥(一)

一、概述 采用雾化器将溶液分散为雾状液滴,在热风中干燥而获得粉状成品的过程,称为喷雾干燥。悬浮液或膏糊状物料也可以用喷雾干燥的方法获得成品,如果将一毫升的液体雾化为直径10微米的球形雾滴,其表面积将增大6000倍,这就显著地增大了水分的蒸发表面,从而缩短了干燥时间。     

干燥设备在纳米碳酸钙生产中的应用

纳米碳酸钙的生产过程中，干燥方式的选择是影响产品最终质量和成本的重要因素之一。简单介绍了纳米碳酸钙生产过程中的带式干燥、喷雾干燥和旋转闪蒸干燥等几种干燥方式，重点对桨叶一微粉干燥的工艺流程、设备选型、生产特点等进行了介绍，并对几种干燥方式所存在的优缺点进行了比较。     

并流垂直向上喷雾干燥进料装置的改进

在并流垂直向上喷雾干燥流程中物料雾化过程的送料方式阀改用压力罐反向送料方式，比传统的柱塞泵变速调控或螺旋泵返回阀调控均为优越，大大提高了对干燥产品的粒度分布和含量调控功能，消除了在连续生产过程中产品容易落塔和喷咀易堵塞烧结现象。     

离心喷雾干燥温度对FCC催化剂成型的影响

研究了离心喷雾干燥过程中干燥温度对催化裂化催化剂成型效果的影响。通过SEM、球形度及粒度测试结果,分析了干燥过程中干燥温度对浆液成型过程的影响以及不同形态不规则颗粒产生的原因。温度过低,水分难以挥发,造成颗粒含水量大,在塔内运动时,颗粒间易粘附且球形度差;温度过高,催化剂颗粒表层迅速变干,而内部水分汽化后需要冲破硬化干壳的束缚,造成颗粒表面形成裂纹或微裂纹。而在适宜的干燥温度340℃左右,液滴干燥有序进行,可获得颗粒圆整、具有良好球形度的催化剂产品。     

超声波在食品干燥中的应用

脱水食品的市场需求和质量要求越来越高,推动干燥新技术的发展。超声波干燥是一门新兴的干燥技术,可以在较低温度下更快地干燥食品,所以越来越受到人们的重视。文章首先介绍了超声波干燥的机理,然后论述了超声波预处理、超声热风干燥及超声喷雾干燥的研究现状、存在的问题和应用前景。     

喷雾干燥的节能、泵吸及理论计算的讨论

喷雾干燥是将溶液雾化成微滴经迅速干燥而成粉状产品的一个化工过程。由于受热时间短和产品粒度细等特点,使之适应于热敏性物质。在化工、轻工、食品等部门已广泛采用。林化工业中的栲胶、歧化松香、纸浆、酵母等物料的干燥均有采用。并且积累了丰富的经验。本文拟就喷雾干燥的节能、泵吸作用和计算液滴形成等方面的问题作下述探讨。     

二氧化硫还原喷雾干燥制碱式硫酸铬

详细描述了一种碱式硫酸铬制备方法，重铬酸钠溶液与二氧化硫气体在还原塔内进行氧化还原反应，经调整碱度后用离心雾化式喷雾干燥机干燥，得到优质碱式硫酸铬。该方法生产过程易于流态化、连续化、自动化，且产品溶解性和鞣革活性好。目前，中国二氧化硫塔式还原喷雾干燥法生产的碱式硫酸铬正逐步替代价格高的进口铬鞣剂，并有了出口。     

Drying of Probiotics: Optimization of Formulation and Process to Enhance Storage Survival

This work describes how probiotic bacteria can be dried at low temperature in two steps, combining spray drying and vacuum drying, in order to enhance their survival during storage. A sufficient number of dried probiotics survived storage for more than 3 months at 30°C, if an appropriate combination of protein and carbohydrate was selected as carrier and storage conditions were maintained optimal. The use of soy protein and maltodextrin or skim milk and arabic gum resulted in the best survival rates of probiotics during storage. No evident difference was found between different spray dryer configurations, although a cocurrent flow was preferred.     

Drying of Probiotics: Optimization of Formulation and Process to Enhance Storage Survival

This work describes how probiotic bacteria can be dried at low temperature in two steps, combining spray drying and vacuum drying, in order to enhance their survival during storage. A sufficient number of dried probiotics survived storage for more than 3 months at 30°C, if an appropriate combination of protein and carbohydrate was selected as carrier and storage conditions were maintained optimal. The use of soy protein and maltodextrin or skim milk and arabic gum resulted in the best survival rates of probiotics during storage. No evident difference was found between different spray dryer configurations, although a cocurrent flow was preferred.     

Effects of initial cell concentration,growth phase,and process parameters on the viability of Lactobacillus rhamnosus GG after spray drying

Abstract

During spray drying, probiotics encounter several stresses which can reduce their viability. To obtain powder with a sufficient amount of viable probiotics, we evaluated the effects of different process parameters, such as initial cell concentration and the bacterial growth phase, on the viability of the model probiotic Lactobacillus rhamnosus GG. Increasing the initial biomass did not positively impact bacterial viability after spray drying. For growth, we found that stationary grown bacterial cells were more resistant to the spray-drying process than mid-log grown cells, probably owing to an initiated stress response. Furthermore, a full factorial 3³ design was used to assess the influence of three different conditions of inlet temperature, feed rate, and atomizing air flow on the outlet temperature and bacterial viability after spray drying. As expected, inlet temperature had the largest influence on both outlet temperature and log-reduction in bacterial viability. An interaction effect was also observed between feed rate and inlet temperature. Considering the viability of L. rhamnosus GG, the optimal outlet temperature ranged between 50 and 60?°C for obtaining powders with the lowest log-reductions in viability.     

Dairy Milk Particles Made with a Mono-Disperse Droplet Spray Dryer (MDDSD) Investigated for the Effect of Fat

Mono-disperse droplet generation and subsequent drying in a spray-drying chamber, i.e., mono-disperse droplet spray dryer (MDDSD), provides a better-defined “flight experience” for liquid droplets. The related particle formation can be investigated more easily than that in the usual poly-disperse droplet spray dryer (PDDSD). Previously, skim milk, which is of high protein and high lactose content and is one of the two main dairy fluids that are processed into powder form for consumer markets, was subjected to this kind of investigation in Australia. Here, whole milk, which is the other main dairy fluid, has been spray-dried in a MDDSD set-up at Xiamen University (China). Because the initial droplet size is uniform, measurable, and the particle morphology after drying is consistent, it was possible to investigate the initial solids content effect upon shrinkage and inlet air temperature effect upon shrinkage. In contrast to what had been found for skim milk particles, the formation of the fat-containing (whole milk) particles does not follow the perfect shrinkage model as the skim milk does. This work has improved our quantitative understanding of the whole milk drying process. A fundamental analysis invoked with a modified one-dimensional modeling of spray drying has been given that has shown some further insight about the process.     

THE MORPHOLOGY OF SPRAY-DRIED PARTICLES A QUALITATIVE VIEW

ABSTRACT

Industrial and pilot plant spray-dried materials were obtained from various manufacturers and qualitatively examined in order to identify structural and morphological features. Three distinct categories of particle morphology were identified. Namely, crystalline, skin forming and agglomerate. A number of unusual morphological phenomena were also noted Selected properties such as powder flowability. particle size and particle friability, were found to be directly related to morphological structure. Single particles were also produced in a convective drying process analogous to spray drying, in which, different solids or mixtures of solids were dried from solutions, slurries or pastes as single suspended droplets. The localised chemical and physical structures were analysed, and the results related to experimental conditions viz. drying air temperature and initial solids concentration. There was a strong similarity between the industrial spray-dried material and those dried experimentally. The morphologies of multicomponent mixtures were found to be complex, with the respective migration rates of the solids being dependent on drying temperature. The results are of relevance to dryer optimisation and to the optimisation of product characteristics, They also go some way to validating the single droplet drying technique as a useful analytical tool in spray drying research, and possibly other particulate processing industries.     

Droplet–Droplet Interactions in Spray Drying by Using 2D Computational Fluid Dynamics

A 2D axisymmetric model of the spray drying process is presented. The two-phase flow theoretical model is based on a combined Eulerian-Lagrangian approach and takes binary interactions (coalescence or bouncing) between spray droplets into consideration. Validation of the model (incorporated in FLUENT 6.3.26) demonstrated good agreement and consistency with the literature data. The results of transient simulations showed that droplet–droplet interactions displace the region of heat and mass transfer from the central core toward the periphery of the drying chamber. It was also found that insulation of the spray dryer can substantially affect temperature and humidity patterns, whereas its influence on the velocity flow field is less marked.     

Design and Performance of a Laboratory Spray Dryer to Realize Evaporation-Induced Self-Assembly of Nanoparticles

This work discusses the design, development, and performance of an indigenous laboratory spray dryer with a relatively slow drying rate. The drying time of droplets of colloidal silica (5 wt%) and sodium chloride solution (20 wt%) in this spray dryer was nearly 10 s. The present system was composed of a four-jet compressed air nebulizer that generates a droplet size of 2–5 µm with a nebulization rate of nearly 60 mL/h. The generated powder can be collected using a cyclone or a wire mesh collector. Design and characterization of this system as well as characterization of the micrometric self-assembled powder grains obtained by this spray dryer are discussed.     

Establishing Guidelines to Retain Viability of Probiotics During Spray Drying

We present the application of a model-based approach to map processing conditions suitable to spray dry probiotics with minimal viability loss. The approach combines the drying history and bacterial inactivation kinetics to predict the retention of viability after drying. The approach was used to systematically assess the influence of operational co-current spray drying conditions on residual viability. Moreover, two promising alternative drying strategies for probiotics were evaluated involving encapsulation in a hollow particle and using an “ideal-mixed” dryer system. Finally, a graph was constructed with the model to provide visual guidelines to optimize spray dying for probiotics in terms of viability and drying efficiency.