堆积法制造青瓷用胎体陶瓷粉料体制备及表征

针对堆积法制造龙泉青瓷,采用水基料浆与流态化喷雾造粒相结合制备青瓷胎体陶瓷粉料,研究了水基料浆的分散稳定机制及其喷雾造粒行为,分析了固相含量对料浆流变性能、造粒粉粒径分布及成型性能的影响机制。研究表明:水基料浆具有宾汉型流体特性,固相含量为40%的料浆具有较低粘度和剪切应力,而固相含量为50%的料浆的稳定性和分散性更好;喷雾造粒后,固相含量为50%料浆喷雾造粒颗粒呈规则球形,粒径分布较宽,具有较好的填充性能和成型性能。     

流化床喷雾造粒颗粒包覆过程的因素研究

以玻璃珠为原始晶种分别在流化床喷雾造粒器中进行碳酸钾涂布造粒,考察了床层温度、料液流率、料液浓度和流化气速对颗粒粒径和体积增长的影响;结果表明,料液浓度越高。流化气速越低,其生长速率越大,而床层温度则呈现一定的非单调性。     

底部进料流化床喷雾造粒器内尿素造粒过程

在下端直径２００ｍｍ、上端直径３９０ｍｍ、高１０００ｍｍ的圆锥形流化床喷雾造粒器内，研究了尿素颗粒的生长规律和机理．料液从底部喷入床层，颗粒生长完全由分层生长控制，增大料液流量和降低床层温度，颗粒的粒径生长速率增大．床层内的温度分布类似于开口向上的抛物线，径向上温度差别大，轴向上温度差别小，中心轴线上温度最低，温度随径向距离的增大而升高．产品颗粒与塔式造粒产品颗粒相比，抗压强度明显提高．     

第六届全国流态化会议在武汉召开

由中国颗粒学会流态化专业委员会委托华中理工大学煤燃烧国家重点实验室和科学技术协会筹备的第六届全国流态化会议,于1993年10月6日至9日在武汉华中理工大学召开。出席会议的有来自国内外的71个研究院校、设计单位和工厂企业的代表144位(包括5位国外代表).其中工厂企业代表占近一半,会上共宣读学术论文121篇,其中3篇为大会报告.其他论文则分为气—固流态化及其他、液固两相流态化及气液固三相流态化和传热与分离器及料腿、流态化燃烧技术及其他3个专题小组进行宣读和讨论。     

浅析影响大颗粒尿素造粒的因素

介绍了大型尿素流化床造粒装置流态化造粒过程的基本机理;分析了大颗粒尿素造粒的影响因素。结果表明:造粒系统的床层高度、床层温度、流化风量、喷射风量、喷嘴尿液压力以及蒸发系统中的尿液浓度、缩二脲含量、甲醛加入量均对大颗粒尿素的造粒产生影响。     

有关氯化铵结晶造粒沉降动力学的研究

固体颗粒在液体中沉降速率的计算直接关系反应器的选型和尺寸的确定。关于氯化铵颗粒悬浮在饱和液中的沉降动力学目前国内外并没有人进行深入探讨,而这对于氯化铵造粒结晶器的设计是不利的。本研究以此为出发点,通过氯化铵颗粒的悬浮流态化试验测定氯化铵颗粒的表观沉降速度,并由此得出氯化铵颗粒的沉降动力学特性,以供工程设计者参考。     

流化床涂敷造粒生产大颗粒尿素

本文对流化床涂敷造粒工艺进行研究,得到粒径＞６ｍｍ的大颗粒尿素,并对流化气速、保护气流量和料液浓度对涂敷造粒的影响进行了讨论。     

射流喷动流化床实验研究

射流喷动流化床 ,是在喷动床的基础上 ,通入流化气 ,降低喷动床柱体部分的高度 ,提高喷动速度的方法得到 ;作为一种新型流态化装置 ,可用于颗粒物料的干燥和包衣 ,粉状物料的造粒 ;同时可用于悬浮液的干燥。通过射流喷动流化床用于颗粒物料涂敷造粒的试验 ,对射流喷动流化床流型、压降及其影响因素进行了研究     

AZF工艺返料质量对造粒的影响

返料是参与喷浆造粒工艺生产NPK复合肥造粒环节不可缺少的一部分。分析和讨论返料粒度分布、返料湿度和温度对造粒液固质量比、成粒率及造粒稳定性的影响。     

硝铵磷铵混肥振动流化床喷雾造粒实验研究

以油菜籽为模型晶种 ,进行硝铵磷铵混合液的流态化喷雾造粒实验 ,比较了固定流化床和振动流化床两种喷雾造粒工艺。实验结果表明 :振动流化床造粒产品粒径均匀 ,表面平整 ,颗粒强度高。建立了振动流化床造粒产品粒径简化模型 ,并与实验数据进行比较 ,验证了模型的正确性     

Granulation time in fluidized bed granulators

Size enlargement of particles in fluidized bed granulation involves mixing of particles with a binder liquid to form larger wet granules and drying them to form dry granules. Identification of the time for completion of granulation process is critical as further fluidization of dry granules is providing extra energy for their attrition. Monitoring the bed pressure drop and bed temperature of a batch fluidized bed granulator with time can provide information on the time for completion of the granulation process. Experimental observations on granulation time and size of granules in a lab-scale batch fluidized bed granulator are presented. Model based equations are developed for the estimation of granulation time and size of granules.     

Characterisation of spouting behaviour of coal ash with thermo-mechanical analysis

Bed material agglomeration and loss of fluidization present a major problem in fluidized bed combustion or gasification of low rank coals. Ash particles start to agglomerate and fluidization becomes unstable at temperatures well below the ash softening point measured by the ASTM methods. Attempts have been made to develop a method to determine this characteristic temperature. This paper presents results from an investigation into thermo-mechanical analysis (TMA) as a potential technique. It is shown that, when applied to the coating materials at a heating rate of less than 5°C/min under a force of 0.5 N, the technique can successfully detect the point at which the particles change its spouting or fluidization characteristics.     

搅拌流化床中超细氧化铁粉流态化及还原实验研究

在内径50 mm的搅拌流化床内进行了平均粒径239 nm的氧化铁粉的流态化及氢气还原实验. 结果表明,床中氧化铁颗粒以聚团鼓泡形式实现完全流化,最小流化速度为0.025 m/s,最大床层膨胀比为2.0. 在500℃下用氢气还原该氧化铁粉的反应过程为：Fe2O3?Fe3O4?Fe,Fe颗粒的粒径比Fe2O3小,有颗粒烧结现象,由Fe引起的颗粒烧结和粘结作用可能导致失流. 与普通流化床相比,搅拌能使流化时间由3 min延长至15 min,使失流时样品的金属化率由15%提高至76%.     

Improvement of the Fluidizability of Cohesive Powders through Mixing with Small Proportions of Group A Particles

The gas fluidization behaviour of fine cohesive powders, classified as Geldart group C, is known to be characterized by cracks and channels leading to severe non‐homogeneities in the bed. Geldart group A particles, on the other hand, are known to show more homogeneous and regular fluidization behaviour. This paper studies the effects of the addition of small proportions of group A on the fluidization behaviour of a group C powder. Differential pressure fluctuations data at a sampling frequency of 200 Hz were recorded for two cases. In the first case, the bed contained only group C powder while in the second case small amounts of group A particles were added to the existing group C powder. Visual/image observations coupled with time series analysis showed that the addition of small proportions of group A particles substantially improved the fluidization behaviour of the bed even at low superficial gas velocities, leading to a more uniform fluidization. Evaluation of mean and standard deviations has shown the advantage of mixing the two powders as it allowed larger pressure fluctuations and smaller standard deviations. Power spectra, on the other hand, showed that unlike group C, for which fluctuations were small in magnitude and broadband in structure, the mixture showed stronger periodic behaviour as result of the attenuation of the small and rapid fluctuations caused by the flow of gas in the cracks and channels. Advanced methods such as the principal component analysis of the embedded trajectories allowed a quantitative comparison between the fluidization behaviour of the two systems.     

Process intensification in particle technology: Characteristics of powder coatings produced by nonisothermal flow‐induced phase inversion

The characteristics of powder coatings manufactured through a novel processing technique based on nonisothermal Nlow‐induced phase inversion granulation enhanced by fluid injection to promote phase inversion and particle formation from melt state is summarized. Experiments were carried out in a purpose‐built granulator, which operates in a parallel disk rotor‐stator arrangement, so that the mechanism of granulation could be studied. The product of this intensive granulation was compared with that of the conventional powder coating manufacturing process. Understanding the mechanism of intensive granulation helped to redesign the equipment that resulted in smaller particles. Pigment dispersion characteristics were improved by intensive granulation. Also, the particle size span can be significantly reduced by dry granulation and gas‐phase granulation, and the flowability can be improved by wet granulation. Chemical analysis of particles by Fourier transform infrared spectroscopic analysis showed that the injection of coolant fluid had no effect on the chemical composition. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Drop penetration time in heterogeneous powder beds

Wet granulation is a technique in which enlarged particles or ‘granules’ are produced from the coalescence of fine particles, with the intention of improving the powder properties. High shear granulators are often used to carry out the granulation process where the powder mass is agitated in a vessel by mechanical means while liquid is sprayed from above onto the powder bed surface. When the binder droplets impact the powder surface, the drop penetration time of the droplet into the powder is important for uniform binder dispersion and the prediction of the formation of granule nuclei from the nucleation map, which depends on the dimensionless spray flux. Previous studies on the drop penetration time were carried out on predominantly hydrophilic powder beds. Although this gives a good prediction of the nucleation behaviour in granulation, it does not reflect the condition where hydrophobic drugs are used in the formulation without surfactants. This paper aims to look at the effects of powder bed hydrophobicity on the drop penetration time.Single drop nucleation experiments using a syringe and a small powder bed were carried out on varying ratios of salicylic acid and lactose powders to study the kinetic of drop penetration. As expected, the drop penetration time increased as the proportion of hydrophobic component increased in the powder mixture. However, long drop penetration times were observed for low degrees of drug loading, showing that hydrophobicity strongly influences the drop penetration time. The wettability of the powder mixture also has a pronounced affect on the granule properties in which the hydrophobicity of the powder mixture is proportional to the granule strength and inversely proportional to the granule size. These findings have important implications in terms of the design of the granulation process where conditions of minimum spray flux or efficient mechanical forces are recommended to produce a more uniform granulation batch.     

Real-Time Monitoring of Gas–Solid Fluidized-Bed Granulation and Coating Process: Evolution of Particle Size,Fluidization Regime Transitions,and Psychometric Parameters

Moisture content and particle size are critical parameters in fluidized-bed granulation and coating. In this study, microcrystalline cellulose was granulated and coated. The particle size was monitored in real time by a Parsum IPP70 probe. The fluidization regime was assessed by Gaussian spectral analysis. The bed temperature and gas humidity profile were monitored to evaluate the drying efficiency. The defluidization phase was detected in the early stages with frequencies below 6.0 Hz. The Parsum probe showed the growth of the particles due to agglomeration. The psychometric parameters indicated the lower potential energy for drying. Therefore, monitoring in real time is important to detect failures.     

细颗粒的团聚流态化及其判定

本文在考查了不同细颗粒的流态化过程及物料的气动特性与粘附力关系的基础上，提出了当量流态化的概念；实验发现聚团密度的减小是改善细颗粒流化性能的一种有效途径；根据气动情况下不同的成团结果，把细颗粒的聚团流态化分成了三类：沟流；似A类聚团流态化；似B／D类聚团流态化；同时，结合实验结果，给出了不同细颗粒聚团流态化类型的定量判据     

TEC大颗粒装置在越南金瓯化肥厂的应用

通过TEC大颗粒尿素造粒装置在越南金瓯化肥厂的试车到平稳运行的实际操作,得出了甲醛加入点为尿液泵P106入口是比较理想的位置;造粒机多孔板孔径偏大时需要加快颗粒在造粒机内的水平运动,防止颗粒滞留时间过长产生包裹式结块;在空气湿度较大的地区应用时流化风温度需提高,但第一室流化风温度不宜超过90℃。     

非磁性粘性颗粒在添加磁性大颗粒磁场流化床中的流化性能

通过添加磁性大颗粒，破碎活塞及沟流，显著改善了非磁性粘性颗粒在磁场流化床中的流化性能。为了评价非磁性粘性颗粒在磁场流化床中的流化性能，测量了最小流化速度、床层压力降和床膨胀高度。实验结果表明，非磁性粘性颗粒的最小流化速度，由于添加磁性大颗粒，而显著降低。磁性大颗粒添加量对非磁性粘性颗粒的最小流化速度有较大影响，随磁性大颗粒添加量的增加，最小流化速度降低，但当磁性大颗粒添加量增大到40％后，非磁性粘性颗粒和磁性大颗粒的混合物的最小流化速度就不再降低。