Einfluss des Bindemittels und der Feuchtebeladung auf die Festigkeit von Zeolith 4A‐Granulaten

A comprehensive analysis of the material behavior and the strength of (temporary binder) binderless and binder containing zeolithic molecular sieves in granular form is presented. The material behavior has been studied using single granule uniaxial compression tests until primary fracture. The received force‐displacement curves have been approximated using the Hertz and the Tomas model, respectively. The rate independent micro‐mechanical properties and specific fracture characteristics are presented.     

Breakage in granulation: A review

The study of breakage in granulation is important from a process and from a product quality perspective. Breakage is considered an important rate process in granulation, and plays roles in granule homogeneity and strength. Understanding this rate process has important implications in the design and control of the granulation process. From a product perspective, the study of breakage has important implications for the subsequent processing, transport, handling and final use of granular products. Breakage behaviour of granules can be a strong signature of the consistency of properties between nominally identical granular products. This paper reviews the study of breakage from the process scale down to the single granule and sub-granule scale, discussing largely experimental results complemented with some modelling results.     

Effects of process parameters on granules properties produced in a high shear granulator

Results of a study on the influence of process parameters such as impeller speed, granulation time and binder viscosity on granule strength and properties are reported. A high shear granulator (Cyclomix manufactured by Hosokawa Micron B.V., The Netherlands) has been used to produce granules. Calcium carbonate (Durcal) was used as feed powder and aqueous polyethylene glycol (PEG) as the binder. The dried granules have been analysed for their strength, density and size distribution. The results show that increasing the granulation time has a great affect on granules strength, until an optimum time has been reached. The underlying cause is an increase in granule density. Granules are consolidated more at higher impeller speeds. Moreover, the granule size distribution seems not to be affected significantly by an increase in impeller speed. Granules produced with high binder viscosity have a considerably lower strength, wide strength distribution due to poor dispersion of binder on the powder bed. Binder addition methods have showed no considerable effect on granule strength or on granule size distribution.     

Failure mechanism determination for industrial granules using a repeated compression test

This work describes the development of a particle compression test that allows direct and repeated application of the stress. The test is designed to quickly reduce the load on a granule during its incipient failure. By so doing, the breakage can be arrested and thus the process can be studied in detail. Experimental tests have been made on samples of industrial enzyme granules, which have a complex layered structure, and reproducible results have been obtained. The contribution of the various layers to the strength of the granule has been investigated, showing that the use of coating materials results in improved granule strength. The microstructure of the granule determines the failure mode of the granule. It is concluded that the failure mechanisms can be defined from tests on only a few granules as can assessment of the relative contribution of the layers and of the granule core to its strength. A measurement of the distribution of strength requires a larger, statistically representative, sample.     

Length‐to‐Diameter Ratio of Extrudates in Catalyst Technology: III. Catalyst Breakage in a Fixed Bed

A correlation is demonstrated to predict the reduction in the mean length‐to‐diameter ratio of catalyst extrudates by breakage due to stress in a fixed bed. The stress can be caused either by the reactor load or it can be externally applied as in the bulk crush strength measurement. The strength characteristic of particular interest here is the extrudate bending strength characterized by the Euler‐Bernoulli modulus of rupture. The balance of the bending strength to the applied stress leads to a new dimensionless group. Extrudates in a fixed bed start to break above a specific critical stress, and their mean length‐to‐diameter ratio then becomes linearly proportional to this dimensionless group to the power one‐third.     

Simulation of the Spray Drying of Single Granules: The Correlation Between Microscopic Forces and Granule Morphology

In the ceramic industry, spray drying is an important process transforming fine primary powder into processable granular material. Granule formation at spray drying has been investigated in the past and plausible explanatory models have been established for the governing mechanisms of granule formation. In this study, we use numerical modeling via coupled discrete element method and computational fluid dynamics simulations to investigate this formation process. The focus lies on the evolution of the granule morphology during drying of single droplets. In addition to a demonstration, that the simulation results support the propositions made by the experimentally‐based models, a new correlation was found which leads to an extension of those models for granule formation in terms of the granule stability.     

Wet granule breakage in a breakage only high-hear mixer: Effect of formulation properties on breakage behaviour

Wet granule breakage can occur in the granulation process, particularly in granulators with high agitation forces, such as high-shear mixers. In this paper, the granule breakage is studied in a breakage only high-shear mixer. Granule pellets made from different formulations with precisely controlled porosity and binder saturation were placed in a high-shear mixer in which the bulk medium is a non-granulating cohesive sand mixture. After subjecting the pellets to different mixing time in the granulator, the numbers of whole pellets without breakage are counted and taken as a measure of granule breakage. The experimental results showed that binder saturation, binder viscosity and surface tension as well as the primary powder size have significant influence on granule breakage behaviour. It is postulated that granule breakage is closely related to the granule yield strength, which can be calculated from a simple equation which includes both the capillary and viscous force of the liquid bridges in the granule. The Stokes deformation number calculated from the impact velocity and the granule dynamic strength gives a good prediction of whether the granule of certain formulation will break or not. The model is completely based on the physical properties of the formulations such as binder viscosity, surface tension, binder saturation, granule porosity and particle size as well as particle shape.     

Mechanical and thermal properties of starch‐filled poly(D,L‐lactic acid)/poly(hydroxy ester ether) biodegradable blends

The mechanical, structural, and thermal properties of injection‐molded composites of granular cornstarch, poly(D ,L ‐lactic acid) (PDLLA), and poly(hydroxy ester ether) (PHEE) were investigated. These composites had high tensile strengths, ranging from 17 to 66 MPa, at starch loadings of 0–70 wt %. Scanning electron microscopy micrographs of fracture specimens revealed good adhesion between the starch granule and the polymer matrix, as evidenced by broken starch granules. The adhesion of the starch granules to the polymer matrix was the greatest when the matrix PDLLA/PHEE ratios ranged from zero to unity. At a PDLLA/PHEE ratio of less than unity, as the starch content increased in the composites, there was an increase in the tensile strength and modulus, with a concurrent decrease in elongation. The effects of starch on the mechanical properties of starch/PDLLA composites showed that as the starch content of the composite increased, the tensile strength and elongation to break decreased, whereas Young's modulus increased. In contrast, the tensile strength of starch/PHEE composites increased with increasing starch content. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1775–1786, 2003     

Mechanical,Water Absorption and Enzymatic Degradation Properties of Sago Starch Filled Linear Low Density Polyethylene

Abstract

Sago starch filled linear low density polyethylene (LLDPE) composites, have been prepared by melt mixing of the granular starch and LLDPE in a HAAKE internal mixer. The tensile, water absorption and enzymatic degradation properties of the composites have been determined. Incorporation of sago starch into LLDPE led to decrease in tensile strength and elongation at break of the composites. Up to 15 wt.% of sago starch could be added to LLDPE without adverse effects on the tensile properties. The water uptake increased with immersion time and the rate of absorption is strongly controlled by the immersion temperatures. Dramatic reduction in tensile properties were observed in the composites that were immersed in water at 90[ddot]C. The recovery of the tensile strength and elongation at break upon redrying is about 37.5 and 1.6% respectively. The permanent damage to the composites was attributed to severe hydrolysis of the starch particles. The enzymatic degradation study using oc-amylase revealed that both tensile strength and elongation at break reduced with time of treatment. Mode of failures of both LLDPE matrix and its sago starch filled composites, assessed by fracto-graphic analysis in a scanning electron microscope (SEM) are discussed.     

生产粒状NPK复合肥的改良美国TVA法

粒状 NPK复合肥美国 TVA法之改良系利用美国 TVA的连续式滚筒氨化粒化机 ,设计加装一特殊埋床式反应器进行一系列的化学反应 ,释出大量的化学反应热 ,融化及溶解部分固体原料 ,改变原料物化性能 ,提供各种有利的造粒条件 ,促使氨化粒化机内的各种原料在最少的水分下 ,紧密结成坚硬浑圆 ,易于流动、搬运、储存 ,不结块的颗粒状 NPK复合肥。台湾引进美国 30年经验所研发出来的 TVA改良法具有如下特色 :(1)建厂成本低 ;(2 )原料选用宽广灵活 ,以致原料成本低 ;(3)干燥成品耗用燃料少 ;(4 )回流比小 ,用电量少 ;(5 )颗粒强硬、耐水 ,养分缓释持久 ;(6 )可生产多种不同配方的复合肥 ;(7)配方更改容易、迅速 ,适合少量多批次之生产     

粘结剂对喷雾造粒ZrO2(Y2O3)粉末特性的影响

采用喷雾造粒工艺对及ZrO2(Y2O3)粉体进行造粒，研究喷雾造粒过程中粘结剂含量对粉料流动性、填充性、造粒团聚体强度的影响，并对坯体成形过程中团聚体的破碎行为进行了分析。结果表明：喷雾造粒过程中粘结剂含量较高时，造粒团聚体粒子具有良好的填充性，但粒子强度高，在成形过程中不易破碎，将阻碍致密化烧结。     

Strength and morphology of solid bridges in dry granules of pharmaceutical powders

This is an experimental study of the tensile strength of solid bridges between primary particles comprising granules of lactose or mannitol. We report on two systems: granules prepared with ethanol granulating solutions, in which the base powders were at most sparingly soluble, and aqueous granulating solutions, in which the base powder solubility was large. Both systems were studied with and without hydroxypropylcellulose (HPC) or polyvinylpyrrolidone (PVP) or surfactants (Triton-X100, sodium lauryl sulfate or polysorbate 80) added to the granulating solution. The interparticle bridge strength was determined from the granule crush strength with a simple model that assumes that solid bridges form by evaporation of solvent from liquid bridges that maintain their shape during drying.Lactose granules prepared with pure ethanol are very weak, with crush strength comparable to that predicted by JKR theory, consistent with its negligible solubility. Mannitol, which is sparingly soluble, forms granules with bridge strength similar to the theoretical (Griffith) strength of a pure mannitol. Addition of HPC or PVP to the granulating solution produces bridges with strength comparable to that of pure polymer films. In comparison, the behavior of granules prepared with aqueous granulating solutions was much more complex due to the high saturation concentration of base powder. Granules produced with pure water had bridge strength approximately 20% of the theoretical strength. Addition of HPC or PVP to lactose granules increased the bridge strength modestly, but the strength was much smaller than that of the corresponding pure polymer films. Addition of HPC to mannitol granules had little effect on bridge strength, while PVP reduced bridge strength by approximately 30%. Addition of surfactants to the granulating solution also reduced dry bridge strength. These results reflect the complex microstructure and resulting mechanical properties of dry bridges produced by coprecipitation of the sugars and polymers (or surfactants).     

Experimental and numerical analysis of the hydrodynamic behaviors of aerobic granules

Aerobic granular sludge has been recognized to be promising for wastewater treatment. Their hydrodynamic characteristics have a significant impact on the mass transfer process in reactors. In this study, the hydrodynamic characteristics of aerobic granules were studied using an experimental approach, and their fluid dynamic behaviors were analyzed using a numerical approach. Experimental results show that the aerobic granules are fractal‐like aggregates with porosity. Their porosity and permeability were found to increase with increasing granule size. The numerical model simulated the flow field surrounding a granule, which distinguished the flow behaviors of the granules with different permeability at different outflow Reynolds numbers. The velocity vectors colored by velocity magnitude in the granule internal depended significantly on the permeability of the granule and the Reynolds number. The results provided a helpful tool to investigate the hydrodynamic behavior of aerobic granules with a consideration of their porous structure characteristics. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

非晶颗粒态马铃薯淀粉结构特征

用扫描电子显微镜、偏光显微镜、X -射线衍射法等分析测试方法 ,以原淀粉为参照 ,对非晶颗粒态马铃薯淀粉的颗粒形貌、颗粒大小和结晶程度进行了详尽观察 ,结果发现 ,在非晶化处理过程中发生了从内向外爆裂式膨胀而形成大小、深度、位置不同的爆裂孔 ,并有少量的淀粉颗粒碎片粘附在颗粒的表面上 ,非晶颗粒态淀粉仍然能够保持颗粒外形 ,颗粒大小比原淀粉有所增加 ,不再具有原淀粉颗粒结晶性 ,整个颗粒呈现无定形结构     

Effect of Humidity on NPK Fertilizer Drying

The drying process within rotary coolers during the manufacture of granular NPK fertilizer plays an important role in the production of fertilizer granules possessing both a low moisture content and low caking propensity. A theory for fertilizer drying has been developed which takes into account the low critical relative humidity of complex fertilizer found at high temperature. The theory proposes that the gradient between the partial vapour pressure of moisture in the air and the vapour pressure moisture adjacent to the surface of the fertilizer granule, is the rate controlling stage in the drying of hot granular fertilizer rather than the internal diffusion of moisture within the particle.     

Modeling and simulation of the formation and utilization of microbial products in aerobic granular sludge

A mathematical model is established to simulate the formation of extracellular polymeric substances (EPS), soluble microbial products (SMP), and internal storage products (X_STO) in aerobic granular sludge. The sensitivity of these microbial products concentrations toward the key model parameters is analyzed. Independent experiments are conducted to find required parameter values and to test its predictive ability. The model is evaluated by using one‐cycle operating experimental results of a lab‐scale aerobic granule‐based sequencing batch reactor (SBR) and batch experimental results. Results show that the model is able to describe the microbial product dynamics in aerobic granules and provide further insights into a granule‐based SBR. The effect of the initial substrate and biomass concentrations on the formation of microbial products in aerobic granular sludge can therefore be analyzed by model simulation. A higher substrate concentration results in a greater concentration of EPS, SMP, and X_STO. An accumulation of biomass in the bioreactor leads to an increased production rate of EPS, SMP, and X_STO. © 2009 American Institute of Chemical Engineers AIChE J, 2010     

The S-statistic as an early warning of entrainment in a fluidized bed dryer containing pharmaceutical granule

The chaotic attractor comparison technique known as the S-statistic has been applied to pressure fluctuation data collected in a lab-scale fluidized bed dryer containing pharmaceutical granule. Along with pressure fluctuations, this unit has also been instrumented for measurements of bed temperature and fines entrainment. It has been determined that an increase in bed temperature, corresponding to the loss of granule surface moisture, occurs simultaneously with the onset of entrainment at a granule moisture content of approximately 11 wt.%. The S-statistic analysis is able to give an early warning of the undesirable hydrodynamic state where entrainment occurs provided an appropriate reference state is chosen. When a reference state of 10 wt.% moisture was chosen, a statistically similar hydrodynamic state was identified by the S-statistic occurring 8–9 min prior to the onset of entrainment, thus providing an early warning of this change. The monitoring of bed temperature alone provides no such early warning that entrainment is imminent. With further development, the S-statistic could become a valuable monitoring and control tool for the drying of granular material.     

Effect of Humidity on NPK Fertilizer Drying

ABSTRACT

The drying process within rotary coolers during the manufacture of granular NPK fertilizer plays an important role in the production of fertilizer granules possessing both a low moisture content and low caking propensity. A theory for fertilizer drying has been developed which takes into account the low critical relative humidity of complex fertilizer found at high temperature. The theory proposes that the gradient between the partial vapour pressure of moisture in the air and the vapour pressure moisture adjacent to the surface of the fertilizer granule, is the rate controlling stage in the drying of hot granular fertilizer rather than the internal diffusion of moisture within the particle.     

聚乙烯醇/淀粉共混体系的热塑性加工研究

讨论聚乙烯醇(PVAL)／淀粉体系在不同增塑剂增塑下的共混挤出工艺。研究了PVAL牌号、成型工艺、用量及水分对共混体系热塑性加工性能和拉伸性能的影响。研究表明,粒状PVAL17—88与淀粉的共混物加工性能较好;随PVAL用量的增加,共混体系的拉伸强度及断裂伸长率提高;将增塑剂与PVAL／淀粉直接干混挤出的工艺较为简便,并且效果良好;增塑剂甘油用量为40份时就能对共混体系起到较好的增塑作用;随水分含量的增加,共混体系的断裂伸长率提高,而拉伸强度降低。     

微生物颗粒在废水处理中的应用与研究

微生物颗粒是微生物在适当的环境条件下,相互聚集形成的自聚集体。由于微生物颗粒具有良好的生物活性、沉降速度快、无需载体、易于固液分离等许多优点,在废水处理中得到了广泛的研究与应用。微生物颗粒化是一个复杂的过程,受多种因素影响。作者对近些年来国内外的一些研究成果,从厌氧颗粒污泥、好氧颗粒污泥、菌丝球3个方面综述了微生物颗粒在废水处理中的研究进展,内容包括颗粒的基本特性、微生物相,主要影响因素及其颗粒化过程。