Fluid Bed Granulation Articles

Tracking Individual Particles in a Fluidized Bed using a Medical PET-Camera

This paper describes a series of experiments tracing a single radioactive particle in a fluidized bed in an ECAT EXACT HR+ PET camera in order to obtain 3-D paths for an actual bed particle – i.e. a particle typical for the bed material – with a high spatial and temporal resolution. The paper describes how "lines of response" (LORs) were calculated from the binary list-mode files from the camera, and how particle positions (1 per ms) were computed from the LORs. It also gives a condensed account of how the data were analyzed further. The particle movement in the bed is shown graphically, and the findings interpreted in light of the theories o­n mechanisms behind particle movement in fluidized beds. Among other things the issue of fast, short-range movement of particles in fluidized beds is discussed. The findings are consistent with the notion of upward particle motion in the wakes of fluidization bubbles, and downward motion in the bulk.

Journal: 
3rd World Congress o­n Industrial Process Tomography, Banff, Canada .

Process Analysis of Fluidized Bed Granulation

This study assesses the fluidized bed granulation process for the optimization of a model formulation using in-line near-infrared (NIR) spectroscopy for moisture determination. The granulation process was analyzed using an automated granulator and optimization of the verapamil hydrochloride formulation was performed using a mixture design. The NIR setup with a fixed wavelength detector was applied for moisture measurement. Information from other process measurements, temperature difference between process inlet air and granules (Tdiff), and water content of process air (AH), was also analyzed. The application of in-line NIR provided information related to the amount of water throughout the whole granulation process. This information combined with trend charts of Tdiff and AH enabled the analysis of the different process phases. By this means, we can obtain in-line documentation from all the steps of the processing.

Journal: 
AAPS PharmSciTech. 2001; 2(4): article 21.

The Effect of Spray-Drying Feed Temperature and Subsequent Crystallization Condi

Spray-drying is known to produce predominantly amorphous material because of rapid solidification.1 The detection and control of the amorphous portion of powdered material is of utmost importance, as different physical forms of materials have different physicochemical properties that give rise to significant differences in functionality when used in dosage forms. The influence of spray-drier feed concentration o­n the degree of crystallinity and the crystal form of lactose (β-lactose, anhydrous α-lactose, α-lactose monohydrate) has been described previously.2It is known2 that the spray-drying process can be made to produce completely amorphous lactose particles. Furthermore, it is clear that the amorphous form is unstable and that it will revert to the crystalline form.

Journal: 
AAPS PharmSciTech. 2002; 3(4): article 37.

A New Method to Predict Flowability Using a Microscale Fluid Bed

Eetu Räsänen, Osmo Antikainen, Jouko Yliruusi
AAPS PharmSciTech. 2003; 4(4): article 53. The purpose of this research was to develop a new method to predict the flow behavior of pharmaceutical powders using a multichamber microscale fluid bed. Different amounts of poorly flowing paracetamol were added to various grades of microcrystalline celluloses and silicified microcrystalline cellulose powders. Magnesium stearate was used as a lubricant. Experimental minimum fluidization velocities (umf) were defined using 2 to 4 g (equal to 10 mL) of material (Video 1). The reference flowability of the powders was determined using a specific flow meter. Also, the weight variation of the compressed powders, using a single-punch press, was measured. When the amount of paracetamol in the excipients was increased, the experimental umf increased and the fluidization behavior grew worse (Video 2).

Journal: 
AAPS PharmSciTech. 2003; 4(4): article 53.

Manipulating fluidized beds by using internals: Fluidization with baffle

The fluidized bed is a process, which is difficult to manipulate: it either works or it doesn't. How it works has been the subject of much research, o­nly a few studies have considered how the operation of a fluidized process may be influenced. This article describes how fluidized beds can be manipulated to some extent by using internals: the natural tendency for particle segregation in the bed can be enhanced (e.g. for particle classification), and the application range of fluidization can be extended to finer or more sticky powders.


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Journal: 
Procestechnologie 7 No 2 (2000), 20-24.

The effect of adsorbed moisture on interparticle forces, investigated by means

A Molecular Dynamics (MD) simulation technique is used to investigate the effect of moisture o­n interparticle forces. This is carried out by simulating two opposing moist quartz surfaces at different separations. The spontaneous formation of a liquid bridge, was observed with o­nly three and a half monolayers o­n the surfaces, corresponding to a relative humidity of about 70% according to the BET-isotherm. In the article a brief account of the methodology is given. Results are shown in the form of snapshots of the position of the molecules at a given instant in time and mean forces between the quartz plates as a function of surface separation. The relation of the results to the macroscopic theory of liquid bridging is also mentioned, as are the density and diffusivity profiles of the adsorbed water layers.

Journal: 
Proceedings of the World Conference o­n Particle Technology 3, Brighton, UK, July 1998.

A stochastic modelling approach to particle residence time distribution

A stochastic model describing the axial particle transport and the particle residence time distribution (RTD) in continuous fluidized beds is presented. This model has the advantage of clarity and intuitive appeal. Moreover, the method of solution of the model is far simpler and more powerful than for the traditional modelling approach based o­n conservation equations. After presentation of the model and the method of solution, predictions for the transient axial distribution of tracer particles in a fluidized bed are shown graphically. Predicted RTD curves are also shown graphically and compared with experimental data from the literature. Agreement is good, although some discrepancy between prediction and experiment remains. A discussion is provided.


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Journal: 
Proceedings of the World Conference o­n Particle Technology 3, Brighton, UK, July 1998.

Experimental investigation of the behaviour of coarse particles in an interconne

With a view to investigating the potential of a four-compartment interconnected fluidized bed for the combustion of biomass, the motion of relatively large pellets in the bed has been examined. Different experimental techniques were used to look into the following aspects: the pellet distribution between the beds, the pellet circulation rate and the pattern of movement of individual pellets in the compartments. The results from the different types of experiments are shown and related to each other. Emphasis is laid o­n the quality and rate of pellet circulation and the dynamics and mode of transport of the individual pellets in the compartments. Pellet circulation was found to be unsatisfactory when the slow compartments were aerated at or above the rate required to fluidize the material. The pattern of axial movement is shown to be consistent with upwards motion mainly in the wakes of fluidization bubbles, and downwards motion in the bulk.

Journal: 
Proceedings of the World Conference on Particle Technology 3, Brighton, UK, July 1998.

Proceedings of the 3rd World Conference on Industrial Process Tomography

The movement of particles in fluidization processes in a model test reactor has been studied using an imaging technique from medical healthcare: Positron Emission Tomography (PET). With this noninvasive technique, tracer particles were followed o­n their way through the fluidized bed. Experiments were performed with pulses of tracer particles in different alignments. The results give a good impression of both axial and radial distribution of particles in fluidized bed. In this paper, the experimental results confirm the basic assumptions of the model. Our stochastic model captures the dynamic movement of particles qualitatively, but indications are that the system exhibits ‘gulfstreaming’, a feature which is not accounted for in the model, but is common in fluidized beds in practice.




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Journal: 
Proceedings of the 3rd World Conference o­n Industrial Process Tomography, Banff, Canada 2003.

Feasibility Study of Particle Classification in Fluidized Beds with Internal Baf

In a fluidized bed in which the particles vary in size or density segregation can occur.Including horizontal sieve-like baffles in the bed can greatly increase the tendency of powdersto segregate. This can make a fluidized bed particle classification process possible. In thisarticle a feasibility study of such a process is presented.Experiments were performed with a model system. It was found that the baffles increase thepurity of both the ‘flotsam’ and the ‘jetsam’ fractions. The capacity of a fluidized bed particleclassifier can be estimated using a mechanistic model, based o­n literature models. With sucha model we found that the baffles are most effective in systems that tend to segregate but doactually hardly segregate without baffles.

Journal: 
Proceedings WCPT4, the Fourth World Congress o n Particle Technology, Sydney, 2002.

Interparticle Forces for Granular Dynamics (or DEM ) by MD Simulations

One of the ingredients in Granular Dynamics (or DEM) is a description of interparticleforces. In this paper the effect of surface roughness o­n Hamaker and liquid bridgeinteractions is investigated. Three different models are used (excluded volume, stochasticroughness and explicit asperities). In general, the latter two give similar results. Roughnessdecreases interactions up to several orders of magnitude for rigid surfaces. To validate theanalytical results o­n liquid bridge interactions at low humidity, molecular dynamicssimulations were also performed o­n model systems.



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Journal: 
Proceedings WCPT4, the Fourth World Congress o­n Particle Technology, Sydney, 2002.

Airflow in Batch Fluid-Bed Processing

Dilip M. Parikh, Niro Inc Significant amounts of solid materials are processed using fluid-bed technology. Suspension and movement of particles in an airstream maximizes the exposure of particle surfaces to air or gas, producing efficient evaporation. The primary factor influencing a fluidized-bed process is airflow. To understand and manipulate processing in a fluid bed, it is important to learn how airflow is generated, conditioned, and distributed through the bed during drying, agglomerating, and coating. This article describes how uncommon pressure drops and related processing problems can be identified and rectified by studying the airflow of the system

Read more at
http://www.niroinc.com/html/pharma/pairflowarticle.html

Journal: 
Proceedings PARTEC 2001 International Congress for Particle Technology, Nürnberg, March 2001.

Fluid Bed Systems: Will they suit your requirements?

All the operations like formation of beads, layering of the beads, layering of the beads, agglomeration, enteric coating, tastemasking, drying are possible by the open system and fluid bed system. Fluid bed processing is being used in the pharmaceutical industry for the past three decades. The technology was originally developed specifically for rapid drying. Over the years, fluid bed processing has come into routine use for other applications such as particle coating, pellet coating, agglomerations, drug layering and pellet formation

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Journal: 
Pharma Technology Trends March 1, 2001.

Current issues and troubleshooting Fluid Bed Granulation

The granulation of powder to produce pharmaceutical solid dosage is an essential dosage form unit and the use of Fluid bed Technology provides a rapid and cost -effective means of drying the granules



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Journal: 
Pharmaceutical Technology Europe , May 1998.

Optimization of the Pelletization Process in a Fluid-Bed Rotor Granulator Using

This study examined the effect of rotor speed, amount of water sprayed, and atomizing air pressure o­n the geometric mean diameter and geometric standard deviation of pellets produced in a fluid-bed rotor granulator using a 23 factorial design and an optimization technique.

Pellets were prepared by wet granulation. Equal amounts of microcrystalline cellulose, α-lactose monohydrate, and distilled water were used as the granulation liquid. The size and the size distribution of the pellets were determined by sieve analysis.

The size of the pellets was found to be dependent o­n the amount of water added, while an increase in rotor speed decreased their size. Both factors were found to be statistically significant (P < .05). The effect of atomizing air pressure o­n pellet size was not statistically significant.

Journal: 
AAPS PharmSciTech. 2002; 1(4): article 35.

Next Generation Fluidized Bed Granulator Automation

A system for fluidized bed granulator automation with in-line multichannel near infrared (NIR) moisture measurement and a unique air flow rate measurement design was assembled, and the information gained was investigated. The multivariate process data collected was analyzed using principal component analysis (PCA). The test materials (theophylline and microcrystalline cellulose) were granulated and the calibration behavior of the multichannel NIR set-up was evaluated against full Fourier Transform (FT) NIR spectra. Accurate and reliable process air flow rate measurement proved critical in controlling the granulation process. The process data describing the state of the process was projected in two dimensions, and the information from various trend charts was outlined simultaneously. The absorbence of test material at correction wavelengths (NIR region) and the nature of material-water interactions affected the detected in-line NIR water signal.

Journal: 
AAPS PharmSciTech. 2000; 1(2): article 10.

Positron Emission Tomography (PET) for fluidization

In process engineering, fluidized beds have played an important role in the industry for quite a while already, and the rather complex motion of fluid and particles within such beds is of continued interest. Many measurement techniques have been used to study the distribution of particles and fluids ranging from simple to very complicated techniques, such as X-ray and radioactive tracing techniques. Some of the techniques used, for instance various types of probes are invasive and may disturb the movement of particles in the bed.


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Journal: 
Proceedings WCPT4, the Fourth World Congress o&shy;n Particle Technology, Sydney, 2002.