气流粉碎对粉体颗粒形状的影响

用JFC气流粉碎分级设备对十几种物料进行了超细粉的制备 ,并用电子扫描电镜对这些超细粉体的颗粒形状进行了观察与分析 ,发现气流粉碎能够使大部分粉体保持原级颗粒的形状 ,从而可以充分发挥粉体的固有属性     

气流磨粉碎原理及在钛白粉生产中的应用

引言气流磨作为超细粉碎的一种重要设备,广泛应用于非金属矿物及化工原料的超细粉碎,产品粒度上限取决于混合气流中的固体含量,与单位能耗成反比。气流粉碎产品除粒度细以外,还具有粒度分布窄,颗粒表面光滑、颗粒形状规则,纯度高、活性大、分散性好等特点。由于粉碎过程中压缩气体绝热膨胀产生焦耳-汤姆逊降温效应,因而还适用于低熔点、热敏性物料的超细粉碎。下面就气流磨分类及粉碎原理作一介绍。1气流磨分类工业型气流粉碎自40年代问世以来发展很快,目前工业上应用的气流磨有以下五种类型:1.水平圆盘式(扁平式)气流磨2.循环管式气流磨3.靶式气流磨4.对喷式气流磨5.流化床对喷式气流磨2气流磨粉碎原理气流磨的一般原理:将干燥无油的压缩空气或过热蒸汽通过喷嘴高速喷出,高速射流带动物料作高速运动,使物料碰撞,摩擦而粉碎。被粉碎的物料随气流到达分级区,达到细度要求的物料,最终由收集器收集。没有达到要求的物料,再返回粉碎室继续粉碎,直到达到所需细度并被捕集为止。由于喷嘴附近速度梯度很高,因此绝大多数的粉碎作用发生在喷嘴附近。在粉碎室中,颗粒与颗粒间碰撞的频率远远高于颗粒与器壁的碰撞。也即气流磨中的主要粉碎作用是颗粒之间的冲击或摩擦。虽然气流...     

碳化硼超细微粉团聚及解决方法

对碳化硼超细微粉在干燥时的硬团聚现象进行了分析,并分别采用喷雾干燥和气流破碎两种方法对物料进行处理.喷雾干燥能避免硬团聚现象的发生,但其能耗要比厢式干燥器高,较细的颗粒需要回收.利用气流磨时干燥后的碳化硼超细粉进行解聚,有效地解决了颗粒在干燥过程中发生硬团聚的问题,物料收率高,分级轮的转速很低,几乎没有磨损.     

流化床对撞式气流磨对三七的超细粉碎

利用流化床对撞式气流磨对中药三七进行超细粉碎 ,然后分析粉体颗粒的微观形貌、粒度分布及表面积 ,结果表明 ;粉碎效果良好 ,达到了超细粉碎的目的 ,且粒度分布比较均匀     

超细粉体在液相中的分散

超细粉体材料合成与制备是当今科技界极引人注目的研究领域之一。性能不同形状各异的超细颗粒都可通过物理或化学等人工合成的方法制备出来。但是,由于超细粉体粒度小,极易产生自发凝并,表现出强烈的聚团特性,不论在空气中还是在液相中均易生成粒径较大的二次颗粒,聚团的结果导致超细粉体材料性能的严重劣化。另一方面,在复合材料的生产中,由于超细粉体的这种强烈聚团特性和它与复合基体材料的极性差异,超细粉体很难均匀地分散在基体材料中形成均质复合材料,使复合材料的性能难以达到人们预期的效果。可见,超细粉体的强烈的聚团特性严重制约着超细粉体材料的广泛而有效的应用,成为超微技术进一步发展的瓶颈。如何保证超细粉体在制备、贮存及随后的应用加工过程中保持分散而不聚团“长大”,以及超细粉体在复合材料中能充分分散成为超微技术,特别是纳米复合技术未来发展和应用的关键[1-7]。因此,超细粉体在液相中的抗聚团-分散技术对于拓宽超细粉体材料的应用领域,开发功能复合材料是十分有意义的。1超细粉体在液相中的分散原理从根本上说,超细粉体在液相中分散受液相介质对超细粉体的润湿作用和在液相中颗粒与颗粒的粒间相互作用两者所控制。1.1润湿超细粉体表面的润湿过程实际...     

中药三七的超细粉碎工艺与产品物性研究

以中药三七为研究对象 ,用高频振动磨进行干式超细粉碎 ,简要介绍了三七超细粉体的制备工艺过程和工艺特点 ,考察了超细粉碎过程中三七粉体的色泽变化。采用激光衍射法分析了粉体颗粒的粒度、粒度分布及比表面积的变化特征     

流化床气流磨粉碎制备超细SiC片晶的实验研究

超细SiC片晶由于其高强度、高弹性模量和导热系数已成为替代价值昂贵、制备技术复杂SiC晶须的理想的增韧材料。本文中通过对流化床气流磨粉碎机理,以及粉碎腔内工质压强与喷嘴个数对SiC颗粒形貌影响的研究,得出工质压强、喷嘴个数等参数对粉碎的颗粒形貌有很大的影响的结论,其中粉碎腔采用高的工质压强以增加粉碎强度。采用两喷嘴以增加颗粒互相撞击的几率是制备片状SiC粉的有效方法;采用流化床式气流磨加多级涡轮分级机的粉碎系统可以制备产品质量较好的多级别超细SiC片晶微粉。     

橡胶单颗粒低温冲击破碎的实验研究

单颗粒的破碎研究是粉碎技术发展的基础，对阐明物理过程、粒度变化和能量转换具有重要的意义，是材料研究与粉碎理论之间的桥梁。在分析了橡胶低温下破碎的影响因素后，选择其中的4个因素：破碎温度、速度、颗粒粒径和冲击角度进行变参数实验研究，自行设计了橡胶颗粒低温破碎实验系统，国内首次完成了橡胶单颗粒低温冲击破碎实验。通过对破碎产物粒度分布的分析，得到了这4个因素对粉碎结果的影响，为工程设计提供了第一手的资料。     

气流磨超细粉碎循环流化床锅炉脱硫灰的试验研究

为提高循环流化床燃煤锅炉脱硫灰在工程上的利用率,利用气流磨对循环流化床脱硫灰进行超细粉碎,通过调节分级机频率大小进行分组实验。结果表明:CaO和SO3组分含量在循环流化床脱硫灰中所占比例大,质量分数分别达26.84%和12.25%;采用气流磨粉碎循环流化床脱硫灰,有效地增大了CaO的比表面积,通过调节分级机的频率可获得窄粒度段分布的超细脱硫灰,获得的超细脱硫灰颗粒表面粗糙,凹凸不平,呈不规则形状。     

中药黄连超细粉碎工艺研究

为研究中药黄连超细粉碎后药材的利用率及最佳服用方式,通过振动粉碎制备中药黄连的超细粉体,利用激光粒度仪和电子显微镜对超细粉体进行粒度分析和微观表征,得出粉碎时间、填充率等主要因素与黄连粉碎效果的关系,对黄连超细粉体和粗粉的有效成分进行化学分析,同时将黄连传统饮片煎煮法与超微饮片浸泡法的效果进行比较。结果表明:在此工艺条件下,黄连超微中药饮片粒度小,药效成分含量显著提高。     

Physical Properties of Granules Containing Polysorbate 80

The friability and crushing load of granules containing polysorbate 80 were determined. It was found that while polysorbate 80 decreased granule hardness, as indicated by the load required to crush it, friability values increased to a maximum then decreasing at higher polysorbate 80 concentration. Thus the use of granule friability to measure granule strength may be erroneous unless good correlation between granule friability and direct crushing weight was obtained.

Direct measurement of granule strength tends to vary with granule shape and size giving a rather wide scatter of results. For overcoming this difficulty, tablet triturates could be prepared and the crushing strength determined. The crushing strength of the tablet triturates was found to be similar to that of granules but with a smaller scatter and more easily handled.

Studies of other physical properties of the granules containing polysorbate 80 were also made. Small amounts of the nonionic surfactant (0.002 - 0.2%) generally improved granule fluidity as characterised by the orifice flow velocity and the angle of repose of the granules.     

Physical Properties of Granules Containing Polysorbate 80

Abstract

The friability and crushing load of granules containing polysorbate 80 were determined. It was found that while polysorbate 80 decreased granule hardness, as indicated by the load required to crush it, friability values increased to a maximum then decreasing at higher polysorbate 80 concentration. Thus the use of granule friability to measure granule strength may be erroneous unless good correlation between granule friability and direct crushing weight was obtained.

Direct measurement of granule strength tends to vary with granule shape and size giving a rather wide scatter of results. For overcoming this difficulty, tablet triturates could be prepared and the crushing strength determined. The crushing strength of the tablet triturates was found to be similar to that of granules but with a smaller scatter and more easily handled.

Studies of other physical properties of the granules containing polysorbate 80 were also made. Small amounts of the nonionic surfactant (0.002 - 0.2%) generally improved granule fluidity as characterised by the orifice flow velocity and the angle of repose of the granules.     

Influence of granulating method on physical and mechanical properties, compression behavior, and compactibility of lactose and microcrystalline cellulose granules

The physical and mechanical properties of lactose (LC) and microcrystalline cellulose (MCC) granules prepared by various granulating methods were determined, and their effects on the compression and strength of the tablets were examined. From the force-displacement curve obtained in a crushing test on a single granule, all LC granules appeared brittle, and MCC granules were somewhat plastically deformable. Intergranular porosity ε_inter clearly decreased with greater spherical granule shape for both materials. Decrease in intragranular porosity ε_intra enhanced the crushing force of a single granule F_g. Agitating granulation brought about the most compactness and hardness of granules. In granule compression tests, the initial slope of Heckel plots K₁ appeared closely related to ease of filling voids in a granule bed by the slippage or rolling of granules. The reciprocal of the slope in the succeeding step 1/K₂ in compression of MCC granules indicated positive correlation to F_g, while in LC granules, no such obvious relation was evident. 1/K₂ differed only slightly among granulating methods. Tensile strength of tablets T_t obtained by compression of various LC granules was low as a whole and was little influenced by granulating method. For MCC granules, which are plastically deformable, tablet strength greatly depended on granulation. Granules prepared by extruding or dry granulation gave strong tablets. Tablets prepared from granules made by the agitating method showed particularly low T_t. From stereomicroscopic observation, the contact area between granule particles in a tablet appeared smaller; this would explain the decrease in intergranular bond formation.     

Influence of Granulating Method on Physical and Mechanical Properties,Compression Behavior,and Compactibility of Lactose and Microcrystalline Cellulose Granules

The physical and mechanical properties of lactose (LC) and microcrystalline cellulose (MCC) granules prepared by various granulating methods were determined, and their effects on the compression and strength of the tablets were examined. From the force-displacement curve obtained in a crushing test on a single granule, all LC granules appeared brittle, and MCC granules were somewhat plastically deformable. Intergranular porosity ε_inter clearly decreased with greater spherical granule shape for both materials. Decrease in intragranular porosity ε_intra enhanced the crushing force of a single granule F_g. Agitating granulation brought about the most compactness and hardness of granules. In granule compression tests, the initial slope of Heckel plots K₁ appeared closely related to ease of filling voids in a granule bed by the slippage or rolling of granules. The reciprocal of the slope in the succeeding step 1/K₂ in compression of MCC granules indicated positive correlation to F_g, while in LC granules, no such obvious relation was evident. 1/K₂ differed only slightly among granulating methods. Tensile strength of tablets T_t obtained by compression of various LC granules was low as a whole and was little influenced by granulating method. For MCC granules, which are plastically deformable, tablet strength greatly depended on granulation. Granules prepared by extruding or dry granulation gave strong tablets. Tablets prepared from granules made by the agitating method showed particularly low T_t. From stereomicroscopic observation, the contact area between granule particles in a tablet appeared smaller; this would explain the decrease in intergranular bond formation.     

快淬铜钴镍合金的晶体结构及其颗粒形貌研究

利用熔体快淬法制备了的铜钴镍合金材料Cu95-xCoxNi5（x=0,7,13,15,19,25,31）。利用场发射扫描电子显微镜及其X射线能谱附件研究了样品表面形貌以及颗粒和背景区域的Co／Ni／Cu含量比。利用X射线衍射研究了样品的晶体结构。发现样品具有面心立方结构,其晶格常数比Ni大,略小于Cu;样品表面存在着大量小颗粒,多数颗粒粒径分布在10-30nm之间,X射线能谱给出颗粒附近区域Co含量明显高于无颗粒区域。     

新型环形复合喷嘴的数值模拟分析与研究

为解决传统气流粉碎能量利用率不高、粉碎物料所需成本高、产量低、物料加工范围有限等问题,通过对气流粉碎中喷嘴结构的改进,开发设计了一种新型环形复合喷嘴,运用数值模拟的方法对常规喷嘴和新型环形复合喷嘴进行了模拟。模拟结果表明,这种新型环形复合喷嘴比常规喷嘴具有射流速度快、射流相对集中和射程远等优点。     

Evaluation of Binder Activities on the Physical Properties and Compression Characteristics of Granules Prepared by Two Different Modes

Abstract

The effects of various binders and binder concentrations in production of granules by two different granulation modes were first investigated on the basis of the granule size distribution. Increasing the amount of binder produced larger and less friable granules associated with a decrease in flow rate and an increase in angle of repose. The strength of granules prepared by either the wet conventional or the fluidized bed was a function of its mean particle diameter and of binder-content with the later factor being more predominant. The inclusion of paracetamol into the placebo formula decreased the granule crushing strength. The effect was more pronounced with smaller granules and decreased with increasing granule size.

The rank order of the paracetamol-PVP granules crushing strength was reversed for the tensile strength of their corresponding tablets, viz., the paracetamol-PVP tablets prepared from fluidized granulation exhibited a higher tensile strength than that compressed from wet granules. A new parameter index “ø_b index” which combines tablet characteristics is presented. The index proposed allowed an overall simpler quantitative evaluation of a binder activity. Incorporated into this index are four tablet parameters, viz., tensile strength, percent porosity, median dissolution time, and percent friability. A higher “ø_b, index” infers better physical properties of tablets. Binders used in this study are then classified according to this index: PVP > gelatin > PEG 6000.     

Ice crushing tests with variable structural flexibility

To learn more on ice crushing phenomena against a compliant stiffened plate structure, near full-scale ice crushing tests were conducted in Aker Arctic test basin with a 1:3 scaled model. The dimensions of the to be crushed ice sheet and the stiffened plate were chosen to present a full size ship or offshore structure steel plating which are designed to withstand the crushing loads of 60 cm thick level ice. A major difference to the crushing tests published earlier in literature was that the compliance of one stiffener could be adjusted. The instrumentation in the plate included both strain gauges for load paths from the plate to the stiffeners and a large tactile sensor for detailed direct crushing pressure distribution measurement. In order to have repeatable and homogeneous model ice properties the ice blocks were manufactured by snow ice technique with low salinity water impregnation under vacuum in the mould. Altogether 22 ice blocks were crushed with different ice velocities and plate compliancy. The well-known line like contact prevailed in continuous crushing. The test data indicates that the crushing load distribution is independent from the underlying plate stiffness distribution and no higher crushing pressure at the location of stiffeners was found.     

Influence of Metronidazole Particle Properties on Granules Prepared in a High-Shear Mixer-Granulator

ABSTRACT

Metronidazole is a good example of high-dose drug substance with poor granulating and tableting properties. Tablets are generally produced by liquid granulation; however, the technological process failure is quite frequent. In order to verify how the metronidazole particle characteristics can influence granule properties, three metronidazole batches differing for crystal habit, mean particle size, BET surface area and wettability were selected, primarily designed according to their different elongation ratio: needle-shaped, stick-shaped, and isodimensional. In the presence of lactose monohydrate and pregelatinized maize starch, respectively as diluent and binder, they were included in a formula for wet granulation in a high-shear mixer-granulator. In order to render the process comparable as far as possible, all parameters and experimental conditions were maintained constant. Four granule batches were obtained: granules from placebo (G-placebo), granules from needle-shaped crystals (G-needle-shaped), granules from stick-shaped crystals (G-stick-shaped), and granules from isodimensional crystals (G-isodimensional). Different granule properties were considered, in particular concerning porosity, friability, loss on drying (LOD), and flowability. In order to study their tabletability and compressibility, the different granules obtained were then compressed in a rotary press. The best tabletability was obtained with the isodimensional batch, while the poorest was exhibited by the stick-shaped one. Differences in tabletability are in good accordance with compressibility results: to a better tabletability corresponds an important granule ability to undergo a volume reduction as a result of an applied pressure. In particular, it was proposed that the greatest compressibility of the G-isodimensional must be related to the greatest granule porosity percentage.