流经床造粒影响因素及层式成长模型的研究

将流态化技术应用于粉体物料的造粒过程,在我国还是一项亟待研究开发的课题。本文对流化床造粒进行了实验研究,着重讨论了流化气速,粘合剂种类、浓度、流率,原料初始粒度、喷嘴位置等因素对颗粒成长速率及机理的影响。在此基础上,建立了粒子层式成长模型,并与实验数据进行了比较。     

振动流化床喷雾造粒颗粒成长特性实验研究

在振动流化床中以平均粒径为1.88mm的油菜籽为晶种,用质量百分率为44%的尿素水溶液进行喷雾造粒实验,研究了振动频率、振幅对颗粒成长速率和颗粒结块率的影响。结果表明:与普通流化床相比,振动强化了颗粒的流化效果,提高了颗粒成长速率;颗粒成长前期,大振幅和低振动频率有利于颗粒成长;在造粒后期,小振幅和高振动频率有利于颗粒成长;振动强度大,能有效抑制造粒过程颗粒结块。     

新型流化床造粒器的研究

本文对新型流化床造粒器进行了研究。通过对尿素、氯化钙等物料进行了冷态和热态涂敷造粒实验，确定了适合于涂敷造粒的流化床和分布板的形式，并成功地进行了造粒中试实验。对尿素、氯化钙等物料，单喷嘴产量达到９０ｋｇ／ｈ。     

搅拌流化床喷雾造粒过程实验研究

在实验室规模的搅拌流化床干燥器中 ,对苯甲酸钠和聚丙烯酰胺为粘合剂的造粒过程进行了实验研究 ,分析了料液流率、过剩气体速度、雾化空气流率以及喷嘴高度对颗粒成长速率的影响 ,实验结果表明 ,苯甲酸钠明显以分层生长为主 ,聚丙烯酰胺则是团聚生长。这一结果对指导工业操作具有现实的意义     

流化床喷雾造粒的研究进展

对流化床喷雾造粒技术进行了简述,对其颗粒成长机理、造粒影响因素和造成聚变失稳因素进行了归纳,并就其发展前景作了展望。     

喷雾流化床造粒的层式生长模型试验

本文对喷雾流化床造粒过程中颗粒的层式生长进行了理论分析研究,得出了造粒层式生长模式下颗粒质量随操作时间变化的线性增长模型,并通过喷雾流化床对玻璃球的包衣试验对此进行了验证。试验表明,颗粒相对质量的增长速率大小可用来初步判断造粒过程颗粒的成长方式。     

封接玻璃密度与粘结剂含量对造粒粉性能的影响

选用不同种类玻璃粉末进行喷雾造粒实验,研究了密度与粘结剂含量对玻璃造粒性能与烧结性能的影响。结果表明,相同工艺条件下,玻璃粉密度增大,所得造粒粉平均粒径增加、球形度降低,保持相同流动性需要更高的粘结剂含量;造粒粉中的粘结剂含量影响封接玻璃的排胶温度与保温时间,对封接性能无明显影响。     

喷动流化床造粒实验研究

喷动流化床用于粉体造粒，是一种新型的造粒方法。与其它几种造粒方法相比．具有设备投资省、能耗低、设备结构简单等优点。作者经过实验发现，气流雾化器安装于底部或侧部，或是二者结合。可实现对多种粉体的造粒和包衣。气流雾化喷嘴是喷动流化造粒装置的主要部件。为此对气流雾化喷嘴作了一些实验研究。     

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     

陶瓷干法造粒过程温度场对造粒效果的研究

针对陶瓷干法造粒机造粒过程温度场对造粒效果的影响,结合实验与数值模拟对比分析造粒过程温度场对造粒效果的影响.基于CFD方法建立模拟造粒过程温度场的数学模型,模拟造粒过程中温度场随时间变化情况,并实验测得造粒室温度值、造粒成品率随时间变化情况.仿真结果与实验数据对比表明:当造粒时间为7 min时,仿真结果显示造粒室内的温度值都低于80℃,实验测得颗粒成品率占整体颗粒质量的56％;当造粒时间为9 min时,仿真结果显示造粒室内温度值高于80 ℃的区域占造粒体积3％,实验测得颗粒成品率占整体颗粒质量的72％;当造粒时间为11 min时,仿真结果显示造粒室内温度值高于80℃的区域占造粒体积21％,实验测得颗粒成品率占整体颗粒质量的61％.仿真结果与实验数据对比分析说明:当造粒室内温度值高于80℃时,将在一定程度上降低造粒的成品率.     

Particle growth mechanisms in fluidised bed granulation—II: Comparison of experimental data with growth models

Growth data from batch granulation experiments have been fitted to simple geometrical models. Layered granule growth approximates to concentric coating of core particles with binder, although the actual mechanism of growth is different. In the case of agglomeration, a relationship is established betwee mean granule size and binder content.     

The effect of powder size on induction behaviour and binder distribution during high shear melt agglomeration of calcium carbonate

Growth mechanisms in high shear mixer granulation were observed over a wide range of particle size and liquid-to-solid (L/S) ratio. The materials used were calcium carbonate (CaCO₃; size fractions in the range 1.5 to 85 μm) with a binder of polyethylene glycol 6000 (PEG 6k). The binder, solid at room temperature, was added by the “melt-in” method. A 10 L vertical-axis granulator was used, with a chopper and a four-bladed impeller.

The mean granule size and granule size distribution were measured at regular intervals during the agglomeration process by careful sampling and sieving. The uniformity of binder distribution among the granules was also measured.

The growth behaviours of each grade of primary particles were classified and compared. An induction type mechanism was observed with an initial period of slow growth in mean particle size that lasted 2 to 3 min (the induction period). This was followed by a short rapid growth phase lasting 1 to 2 min. The final stage was a plateau of more or less zero growth. Interestingly, the end of the induction period and the onset of rapid growth corresponded to a change in the granule size distribution from bimodal to monomodal and a similar change in the distribution of binder. Induction period growth rate tended to be lower for granules of finer particles, but these grew more rapidly during the rapid growth stage and produced larger granules than the coarser primary particles.

The liquid-to-solid (L/S) ratio had a significant effect on the growth rate during the rapid growth stage but a minor effect on the granule size distribution and binder distribution. Primary particle size had a significant effect on the final average size of granules, the growth rate during the rapid growth stage and the distribution of granule size and binder.     

Binder Distribution in Ceramic Greenware During Thermolysis

Capillary forces were shown to influence the distribution of polymer-plasicizer mixtures within ceramic green bodies during binder thermolysis. Isothermal thermogravimetric analysis was performed on tape-cast sheets of an aluminapoly(vinyl butyrall-dibutyl phthalate composite and direct observations were made of the binder distribution and pore growth after partial pyrolysis. This led to the investigation of a model system, an alumina-eicosane composite, by similar experimental techniques. The early stage of binder removal was found to be similar to the drying of particle beds in which capillary forces draw liquid into the smaller pores at the surface. The morphology of the binder distribution produced by these processes dictates which mass-transfer resistances may be controlling in binder burnout. A model is described that determines the length scale over which capillarity acts based on measurable physical parameters of the binder system and the packing of the ceramic particles.     

Effect of process parameters on the melt granulation of pharmaceutical powders

Co-melt granulation of lactose and PEG was investigated in a fluidised bed granulator. The effect of process parameters such as binder content and binder viscosity were correlated to granulation time and particle size distribution. The experimental data indicated that after initial nucleation the granulation mechanism was dependent upon binder content and binder viscosity. When the binder content was increased above 18% (w/w) de-fluidisation of the bed occurred and granulation moved to the slurry regime. As the process involved the melt granulation of relatively high molecular weight (6-20 k) and thus high viscosity PEG (500-19000 mPa s), it was found that binder viscosity had a significant affect on the granule growth mechanism. Granulation with a binder viscosity of 500 mPa s resulted in granule growth by coalescence, however, an increase in binder viscosity resulted in less coalescence and a lower granule growth rate. Furthermore, the granulation data were characterised by Stokes number analysis.     

Hot-Stage Study of Bubble Formation During Binder Burnout

A technique for observing bubble formation during binder burnout in ceramics processing has been developed using the hot-stage microscope. Four sets of samples were designed to meet different objectives of the study. Bubble nucleation, growth, and shrinkage were observed. Influencing factors, such as initially trapped gas bubbles, amount of residual solvent, ceramic powder surface, and heating rate were studied.     

The relationship between surface properties and binder performance in granulation

A crucial stage in the granulation of pharmaceutical products is the selection of the most appropriate formulation of drug/excipient/binder. The binder must not only wet both solid species sufficiently to form (liquid) bridges to hold them together so that granules can then proceed to grow, but also must distribute homogeneously amongst the particles in the mixture to ensure a uniform distribution of each species in the resultant granules.This paper reports a micro-scale study to elucidate the wetting behaviour of binder solutions on paracetamol crystals in order to provide a low-cost and effective selection procedure for the optimal binder solution. A previous study has determined the spreading behaviour of two commonly used binders, hydroxypropyl methylcellulose (HPMC) and polyvinylpyrrolidone (PVP), on paracetamol crystals. This study is focussed on the additional use of wetting agents, namely sodium lauryl sulphate and sodium docusate, to improve the wetting behaviour and distribution of the binders on the particles. The balance between binder adhesion (with the solid surfaces) and cohesion (for itself) in relation to granule growth is inferred from the interaction forces and the binder wetting behaviour.     

Computer simulation of granule microstructure formation

The diagenesis (porous microstructure evolution) of granules formed by a layering growth mechanism in a wet granulation process has been modelled. The model includes the packing of primary particles with a given size and shape distribution, and the deposition, spreading, and solidification of binder droplets within the growing granule. The dependence of granule porosity on the binder/solids ratio, primary particle size and morphology, and the rates of binder spreading and solidification has been investigated. The results are presented in the form of structure maps relating volume-averaged microstructure parameters with dimensionless groups including the ratio of droplet spreading and solidification times and the mean time between particle collisions. These graphs can guide the selection of process operating conditions or formulation ingredient properties required to obtain a particular granule microstructure.     

Agglomeration modeling of small and large particles by a diffusion theory approach

The interaction particle‐binder during the wet granulation process plays a major role in the agglomeration of particles. This interaction has been modeled by a force balance acting on the particle where the binder's viscous force increases the strength of liquid bridge and facilitates the particle agglomeration. In this work, agglomeration kernels based on Brownian movement approach of small particles in the binder layer, the size ratio between particles (monodispersed and polydispersed), and binder's viscous forces were considered to model the wet granulation process of pharmaceutical powders in a laboratory‐scale high shear mixer. The assumptions of no‐stationary and pseudostationary behavior were suitable to describe the growth kinetics of the two stages (fast and slow) observed. A volume ratio of 150 between large and small particles produces the most effective granulation growth. The developed kernels were tested simulating experimental data obtained from a high shear mixer. © 2009 American Institute of Chemical Engineers AIChE J, 2009     

用CMC作为生物质型煤粘结剂的试验研讨

用CMC作为生物质型煤粘结剂与黄泥生物质型煤进行比较试验表明 ,CMC生物质型煤在防水性 ,防振性能 ,抗压性方面远远优于黄泥生物质型煤 ,燃烧强度相差不明显 ,固硫效率有所提高 ,且可以大大降低粉尘污染。CMC是一种清洁、有效的型煤粘结剂     

煤沥青与橡胶改质筑路油族组成分析

利用石油道路沥青 ４ 组分分离方法,测定了石油沥青、石油道路沥青以及煤沥青的族组成。利用该测定结果指导煤沥青橡胶改质筑路油的开发和橡胶改质的机理研究,并在此基础上成功地开发出高质量的煤沥青筑路油新产品。建立了能关联煤沥青组成与软化点之间关系的方程。