Fluidized Bed Apparatus Research Articles

Preparation and characterization of chitosan based micro networks: Transposition to a prilling process

AbstractBeads of chitosan (CS) crosslinked network and of chitosan/poly(ethylene oxide) (CS/PEO) semi‐interpenetrating network (semi‐IPN) were prepared by a dropping technique and characterized. PEO content in the beads of semi‐IPN was determined by gel permeation chromatography. CS crosslinking ratio was evaluated qualitatively by ATR‐FTIR spectroscopy and quantitatively by UV spectrophotometry. After drying in a fluidized bed apparatus, a monodisperse population of well individualized, spherical, and smooth particles was obtained. It was shown that bead collapsus during the drying stage was avoided thanks to the chemical crosslinking of CS chains. By the prilling, or laminar jet break‐up technology, production at a larger scale was also achieved. This process allowed the formation of a row of well calibrated drops of polymer solution under the influence of a vibration. Polymer solution characteristics, particularly viscosity, constituted a critical factor in the feasibility of the prilling process. Transposition of the formulation was managed through the optimization of process parameters such as vibration frequency, amplitude, and flow rate. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2550–2558, 2004

Effect of ZSM-5 on the aromatization performance in cracking catalyst

Abstract Cracking of FCC naphtha has been investigated on the model catalysts containing ZSM-5 (Si/Al2=50, 500), Zn-ZSM-5 (Si/Al2=50) and USY. The presence of ZSM-5 and USY causes a tremendous decrease in olefins of gasoline fraction, leading to an enrichment of the aromatics in liquid product. It is evidently that aromatics are generated from lower olefins. The property of lower silica-to-alumina ratio of ZSM-5 and Zn modification enhance the aromatization process for higher cracking reactivity and dehydrogenation. The result of evaluation in confined fluid bed apparatus (CFBA) with the mixture of VGO and VTB as feed further confirms the aromatics generation in cracking reaction stimulated by ZSM-5 additive over base catalysts with different hydrogen transfer activity. Based on these results, relations between scission and aromatization in FCC catalyst containing ZSM-5 zeolite could be proposed. The suggested reaction path could better explain the reasons that effectiveness of ZSM-5 additive to lighter olefins is more profound in base catalyst of low hydrogen transfer activity and why so many researchers had not observed the aromatics generation motivated by ZSM-5 additive in catalytic cracking reaction.

Cofiring of Coal and Refuse-Derived Fuel in a New Type of Internally Circulating Fluidized Bed System

A new type of internally circulating fluidized bed (ICFB) was developed. The distributor plate of the fluidized bed was designed to give a nonuniform distribution of orifices; 2 areas on the distributor plate share the same wind-box. The characteristics of the distributor plate were studied in a transparent fluidized bed apparatus. The distributor plate was also applied in a bubbling fluidized bed combustor. The experimental results indicate that this kind of distributor plate is suitable for the cofiring of coal and refuse-derived fuel (RDF), and the emissions of SO2, CO, and HCl were lower than the bubbling fluidized bed.

Removal of Residual Monomers from Polymers in Fluidized Beds

We present a model for the removal of residual monomers or “purging” from polymers in fluidized beds. The purging is modeled as a diffusion-controlled process. To track the diffusion of the monomer from the polymer, the diffusion equation is solved by the method of lines coupled with the isothermal mass balance equations for either batch or continuously fed fluidized beds. The model accounts for particle size distribution in the fluidized bed. Bypassing of the gas in the form of bubbles is accounted for by using a simple model derived from the “two-phase” theory of fluidization. The diffusion coefficient of ethylidenenorbornene in granular EPDM (a polymer of ethylene copolymerized with propylene and the diene ethylidenenorbornene) is measured by carrying out separate experiments in a small fluidized-bed apparatus. Henry's law is used to represent the solubility of the monomer in the polymer. The model was validated with data from a 0.6-m-diameter experimental fluidized bed and is used to simulate a large-scale fluidized bed as an illustrative example. Simulations suggest that the bypassing of purge gas in the form of bubbles may reduce the purging efficiency significantly.

Statistical optimisation of diclofenac sustained release pellets coated with polymethacrylic films

The objective of the present study was to evaluate three formulation parameters for the application of polymethacrylic films from aqueous dispersions in order to obtain multiparticulate sustained release of diclofenac sodium. Film coating of pellet cores was performed in a laboratory fluid bed apparatus. The chosen independent variables, i.e. the concentration of plasticizer (triethyl citrate), methacrylate polymers ratio (Eudragit RS:Eudragit RL) and the quantity of coating dispersion were optimised with a three-factor, three-level Box-Behnken design. The chosen dependent variables were cumulative percentage values of diclofenac dissolved in 3, 4 and 6 h. Based on the experimental design, different diclofenac release profiles were obtained. Response surface plots were used to relate the dependent and the independent variables. The optimisation procedure generated an optimum of 40% release in 3 h. The levels of plasticizer concentration, quantity of coating dispersion and polymer to polymer ratio (Eudragit RS:Eudragit RL) were 25% w/w, 400 g and 3/1, respectively. The optimised formulation prepared according to computer-determined levels provided a release profile, which was close to the predicted values. We also studied thermal and surface characteristics of the polymethacrylic films to understand the influence of plasticizer concentration on the drug release from the pellets.

Jacobs secures Canadian Order

The relatively high sulphur content of coke produced during the upgrading of Athabasca bitumen, makes it environmentally unsuitable as a fuel. Using heavy oil or bitumen as a binder, attempts have been made to coagglomerate these cokes with sulphur dioxide capture agents, such as lime, hydrated lime and limestone, to reduce emissions during combustion. By providing an environment in which there is intimate contact between fuel and sorbent, it was hoped that greater utilization of the sorbent could be achieved, compared with the systems in which the sorbent is added separately to the combustion bed. Cokes from both Suncor and Syncrude operations were used in this investigation. The combustion tests on coke-sorbent agglomerates were carried out in a bench scale fluidized bed apparatus at 850 °C. Test results indicated sulphur capture of over 60 wt % for Syncrude coke and over 50 wt % for Suncor coke at a calcium to sulphur molar ratio of 1:1. The presence of moisture did not appear to have any significant effect on sulphur capture. Other variables investigated included: the role of binder, the effect of coke size and calcium to sulphur mole ratio. A comparison was made of the efficiency of the various sulphur sorbents in the reduction of sulphur dioxide emissions.

Batch and continuous fluid bed coating – review and state of the art

In this paper is presented a varied description of the fluid bed process for coating or air suspension coating with emphasis on the most efficient batch fluid bed apparatus (the wurster system) and the ideal continuous fluid bed. Phenomena involved in the process of coating fluidised solid particles are studied. The problem of the application of this technology to coat food particles, in terms of feasibility and profitability, is discussed. A comparison between the batch and the continuous systems will bring out the fact that the continuous fluid bed process is the economically suitable solution for coating food powders, but there are a number of problems that must be overcome to get the ideal or efficient continuous system, which does not exist yet. A short review of all these problems is presented.

Fluidized Bed-Steam Drying - Modeling and Experimental Studies

Fluidized bed-steam drying combines the energetic and operationally safe advantages of steam drying with the excellent heat and mass transfer conditions of fluidized bed technology. The existing moisture loading of the particles, as dependent variables in drying processes, is relatively difficult to determine through balancing the quantity of the escaping gas, since, in the case of the superheated steam drying observed in this paper, both the particle moisture and the drying medium are water. Temperature progressions however can be determined easily and without great demand on the apparatus. The experiments presented in this paper serve to establish a connection between the temperature and moisture progression, as well as between all other relevant drying parameters such as gas mass flow, gas temperature or particle mass. To do this, the components involved (fluidization gas, fluidized bed particles and apparatus wall) are balanced for mass and energy. With the help of modeling based on physical laws, the mechanism of fluidized bed drying with superheated steam as fluidizing and drying medium are resolved. The result is that any drying time progression can be simulated. Discontinuous fluidized bed drying in batches serves as the basis for the experiments. In order to use also the mathematical modeling of a discontinuous fluidized bed apparatus for continuously operated processes, a longitudinal mixture of the material being dried in a continuous drying apparatus, e.g. in a fluidized bed channel, must be suppressed or presumably disregarded. The local coordinate of the continuous fluidized bed apparatus and the time coordinate of the discontinuous fluidized bed apparatus are then connected to one another by the product velocity being set to a constant.

A novel pH- and time-based multi-unit potential colonic drug delivery system. II. Optimization of multiple response variables

The objective of this work was to optimize a novel potential colonic drug delivery system by using a statistical procedure. Pellets were prepared by powder layering of 5-aminosalicylic acid (5-ASA) on nonpareils (0.5–0.6 mm) in a coating pan. Drug-layered pellets were coated with an inner layer of a combination of Eudragit ® RL and RS and an outer layer of Eudragit FS in a fluidized-bed apparatus. Central composite design was used to study the effect of three independent variables. The proportion of the more hydrophilic polymer Eudragit RL had the most significant effect on drug release – higher proportion gave faster release; the amount of inner and outer coat did not have a significant effect on the rate of drug release at either 6 or 12 h in the range studied. A second order polynomial equation was fitted to the data, and the resulting equation was used to predict the responses in the optimal region. An optimized formulation was prepared and evaluated for individual responses. The experimental values of the response variables highly agreed with the predicted values. The results demonstrated the reliability of the model in the preparation of coated pellets having predictable drug release for colonic delivery of 5-ASA.

Modeling of Heat Transfer in a Three-Phase Fluidized-Bed Apparatus

A mathematical model is proposed for heat transfer in three-phase (gas–liquid–solid) fluidized-bed absorbers.

Studies of pectin HM/Eudragit® RL/Eudragit® NE film-coating formulations intended for colonic drug delivery

Theophylline pellets were coated with Eudragit® NE30D aqueous dispersions, containing various pectin HM/Eudragit® RL30D ionic complexes, using an Uni-Glatt fluidized-bed apparatus. Dissolution studies were then carried out on the coated pellets at pH 6.0, in absence and in presence of commercial pectinolytic enzymes. The theophylline release from the coated pellets, after an initial latency phase, occurred linearly as a function of time. The theophylline release rate was dependent on the pectin HM content of the complexes incorporated in the coatings. The lowest theophylline release from the coated pellets was obtained when the pectin HM content of the complexes was 20.0% w/w (related to Eudragit® RL), i.e. when the complexation between pectin HM and Eudragit® RL is optimal. The theophylline release from the coated pellets was slower in presence of the pectinolytic enzymes when the pectin content of complexes is higher than 20% w/w. On the other hand, the effect of the enzymes induced an increase of the theophylline release when the pectin HM content of the coatings ranged between 10.0 and 15.0% w/w (related to Eudragit® RL).

Drug Release from Film-Coated Chlorpheniramine Maleate Nonpareil Beads: Effect of Water-Soluble Polymer, Coating Level, and Soluble Core Material

The purpose of this research was to use a new drug release model to study the effects of formulation parameters on drug release from a film-coated chlorpheniramine (CPM) nonpareil system. The film-coated CPM nonpareils were prepared by using a fluid bed apparatus. A hydroxylpropylmethylcellulose (HPMC) solution was blended with an aqueous ethylcellulose dispersion (Surelease) to adjust the permeability of the film. The apparent permeability of samples was obtained from dissolution data using a previously reported drug release equation. The apparent permeability was plotted versus the film coating level or the HPMC concentration in the film. When the natural logarithm of the apparent permeability versus coating level was graphed, a biphasic plot was observed in the group without HPMC in the film, showing the occurrence of a critical coating level. It was suggested that a mechanically formed porous film (due to an incomplete coating) could change to a nonporous film after the bead was completely coated. However, in the group that contained 12% HPMC in the film, the critical coating level was not observed. A porous film, formed by the leaching out of the water-soluble polymer, would not change to a nonporous film even after the bead is completely coated. Through a mathematical derivation, the decrease of apparent permeability versus coating level was related to the reduction of the total hole area. The apparent permeability was found to increase with the HPMC concentration. After a critical concentration was reached, the further addition of HPMC into the film caused a rapid increase in apparent permeability. The critical HPMC concentration was related to a minimum domain formation concentration (MDFC). A rapid increase of the drug release was observed when the dissolution profile of a sample made from a regular sugar nonpareil core (soluble) was compared with the sample made from a precoated nonpareil core (insoluble), which suggests that the drug release can be enhanced by the dissolution of the core. A minimum concentration of the HPMC was required to effectively modify permeability of the film. The critical coating level and critical concentration of HPMC can be determined from the apparent permeability plot using a previously published equation. The dissolution of a soluble core can greatly enhance the release of the drug from the nonpareil system.

Surface treatment of dimenhydrinate crystals

Dimenhydrinate is a heat-sensitive antihistamine with a low melting point. The heat-sensitive feature is of importance if direct compression is used. Direct measurement of the heat originating in the texture of tablets during compression is very difficult. Thermoanalytical methods were used as indirect methods to describe the changes in material properties at high temperature: differential scanning calorimetry, thermomicroscopy and thermogravimetric analysis. Film coating method is widely used in pharmaceutical technology. A fluidized bed apparatus was applied to coat the crystals. The coating film forming agent was hydroxy-propyl-methylcellulose (HPMC), which is a gastric-soluble polymer. Thermoanalytical measurements reveal that dimenhydrinate crystals are sensitive to heat. Film coating method does not alter the shape of the DSC curve of dimenhydrinate, but increases the melting point. The presence of a macromolecular film reduces the thermal conductivity, because it separates the particles.

Hot-Melt Coating Technology. I. Influence of Compritol® 888 Ato and Granule Size on Theophylline Release

The aim of this work was to study the influence of theophylline granule size and the percentage of Compritol® 888 Ato on in vitro drug release from granules and tablets. The granules were coated in a fluidized bed apparatus. The dissolution profiles of these granules differed from those of granules coated with classical agents, and there were also differences between the various sieve fractions studied. Drug release was characterized by a rapid-release phase, followed by a slow-release phase. Results indicate that theophylline release can be controlled by controlling granule size. Inspection of the appearance of the tablets at the end of the dissolution test revealed that all tablets containing Compritol 888 Ato remained intact. This indicated that the Compritol 888 Ato used in the tablet formulation created an inert matrix through which the drug diffused. It was found that the Higuchi relationship of linear square root of time was the best model to describe the release kinetics of the drug from tablets. This also confirmed that a matrix diffusion-controlled mechanism was operative. Given the difference between the dissolution profiles of the granules and the tablets, it was concluded that this matrix is formed during compression.

Evaluation and Validation of a Fully Instrumented Hüttlin HKC 05-TJ Laboratory-Scale Fluidized Bed Granulator

The instrumentation and validation of a laboratory-scale fluidized bed apparatus is described. For continuous control of the process, the apparatus is instrumented with sensors for temperature, relative humidity (RH), and air velocity. Conditions of inlet air, fluidizing air, product, and exhaust air were determined. The temperature sensors were calibrated at temperatures of 0.0°C and 99.9°C. The calibration of the humidity sensors covered the range from 12% RH to 98% RH using saturated electrolyte solutions. The calibration of the anemometer took place in a wind tunnel at defined air velocities. The calibrations led to satisfying results concerning sensitivity and precision. To evaluate the reproducibility of the process, 15 granules were prepared under identical conditions. The influence of the type of pump used for delivering the granulating liquid was investigated. Particle size distribution, bulk density, and tapped density were determined. Granules were tableted on a rotary press at four different compression force levels, followed by determination of tablet properties such as weight, crushing strength, and disintegration time. The apparatus was found to produce granules with good reproducibility concerning the granule and tablet properties.

Drug Release from Film-Coated Chlorpheniramine Maleate Nonpareil Beads: Water Influx and Development of a New Drug Release Model

The purpose of this work was to investigate drug release from film-coated chlorpheniramine maleate (CPM) nonpareils (sugar spheres) and the effect of water influx on the drug release mechanism. The methods used in the study involved the layering of CPM onto nonpareil cores using a fluid-bed apparatus. These CPM cores were then coated with an aqueous ethylcellulose dispersion, which was blended with a solution of hydroxylpropylmethylcellulose (HPMC) at different concentrations. The net water influx was determined by measuring water uptake during dissolution. The film surface area was calculated from bead diameters measured with an optical microscope. Drug release profiles were measured using USP dissolution method I (basket). The results showed that significant water influx occurred, which produced an internal liquid phase ranging from 0 to 1.8 × 103 mm3/g of sample. As a result of the water uptake, an increase in bead size was observed. The bead surface area varied over the range of 40–80 × 103 mm2/g sample because of a combined effect of the water uptake and the release of the bead contents. A bead geometry parameter was proposed as the ratio of the bead surface area to the volume of the internal liquid phase. This bead geometry parameter was measured as a function of time and fit to an equation using a computer curve-fitting technique. This equation was substituted into an existing drug release model to give a more appropriate mathematical model describing drug release from this system. The conclusion drawn from these results is that the influx of water during drug dissolution creates a progressive increase in the liquid phase within the nonpareil bead; this causes a corresponding increase in the bead surface area which influences the drug release rate.

Design of a controlled release osmotic pump system of ibuprofen

Elementary osmotic pumps releasing solutions of active materials at a controlled rate have increased in popularity during the last two decades. In this study, the effect of the delivery orifices and the concentration of osmotic agents on the rate of release of the active material was investigated. For this purpose, ibuprofen tablets were prepared and sodium chloride and polyethylene glycol 6000 were used as osmotic agents. The tablets were coated with a mixture of cellulose acetate and polyethylene glycol 400 by the use of a modified fluidized bed apparatus. Delivery orifices on the coated tablets are produced using a microdrill. The tablets were tested for dissolution rate using the USP paddle method. Finally, it was observed that the release rate of ibuprofen was influenced by the concentration of osmotic agents sodium chloride and polyethylene glycol 6000.

97/03513 Fluidized-bed drying-classification apparatus and operation method

97/03513 Fluidized-bed drying-classification apparatus and operation method

Carbon Surface: Area, Porosity, Chemistry, and Energy

Data from the adsorption of nitrogen at 77 K are interpreted in terms of surface area and porosity, for a range of carbon blacks and two porous carbons, using the BET, αs, and Dubinin–Radushkevich methods. Heat of immersion (ΔHi) data, for nonpolar (n-heptane) and polar (water) liquids are correlated with surface structure and chemistry, respectively. An average value of ΔHi≈ 107 mJ m−2is obtained for the dispersion interaction of nonporous carbon blacks by immersion inton-heptane. Where nitrogen adsorption data indicate the presence of microporosity, higher values of ΔHiare observed which are thought to contain a contribution due to enhanced adsorption forces within pores. Data from samples of one specific black, which had been oxidized to varying levels using an oxygen/ozone fluidized bed apparatus, are presented showing a linear relationship between the surface oxygen levels and their polar interaction with water.

95/06323 Fluidized-bed apparatus for generating stream in coal combustion

95/06323 Fluidized-bed apparatus for generating stream in coal combustion