Bed Apparatus Research Articles

Effect of Rapid Preheating on the Caking Properties of Coals

In order to obtain fundamental data for rapid preheating process, the swelling and agglomerating behavior of coal particles and the thermoplastic behaviors of coal under various heating conditions were investigated with a fluidized bed apparatus and a rapid heating plastometer.Coal particles undergoing pyrolysis in N2 or CO2 atmosphere at a heating rate of 300°C/min were filmed using a high-speed camera. The swelling and agglomerating behavior of them were evaluated by image analysis. Coal particle started to increase its size slightly around 350°C and expanded dramatically. Then coal agglomeration occurred around 420°C. Coal swelling and agglomerating behavior was influenced by coal property and atmospheric condition. Especially CO2 atmosphere inhibited dilatation and agglomeration.As the plasticity behavior of coal, minimum apparent viscosity and all characteristic temperatures corresponding to softening, maximum fluidity and resolidification state same as Gieseler method were measured by a rapid-heating plastometer. Coal plasticity was strongly dependent upon the heating conditions. For example, it was clarified that there existed an optimum rapid preheating temperature and that temperature, which had to be less than the softening temperature of Gieseler test, was related to coal rank. Moreover it was suggested that rapid heating effect was improved with the increase of the H/C atomic ratio of raw coal.

Plastic particle separation via liquid‐fluidized bed classification

AbstractLiquid‐fluidized bed classification (LFBC) is being investigated as a potential process for the separation of complex waste plastic mixtures for recycling. Experiments were performed in a 10 cm diameter, fluidized bed apparatus that was designed to operate in both upflow and downflow modes, for the separation of “heavier‐than‐water” (HTW) and “lighter‐than‐water” (LTW) plastic particle species, respectively, using water as the fluidization medium. The investigations were primarily focused on binary plastic particle mixtures of the typical industrial plastics, PVC, PET, PS PC, HDPE, LDPE, and PP. Particle segregation was obtained for all the binary mixtures studied. The effects of particle size and superficial liquid velocity were examined. It was found that low fluidization velocities favored segregation performance by minimizing particle dispersion. A limited number of experiments with ternary plastic particle mixtures demonstrated that the behavior of more complex mixtures appears to be an extension of binary mixture behavior, and that multiple plastic particle mixtures can be separated in the same column. The novel technique of selective thermal modification of particle size/density by application of a step change in temperature of the fluidizing medium was demonstrated to improve separation performance for both HTW and LTW plastic sample mixtures. This behavior was attributed primarily to differences in the thermal diffusivities of plastic particle pairs. The experimental data and conclusions reported in the current work can serve as the basis for the development of LFBC systems for waste plastics separation. © 2005 American Institute of Chemical Engineers AIChE J, 2006

Batch Drying Kinetics in a Two-Zone Bubbling Fluidized Bed

This article deals with investigation and modeling of batch drying process of solids in fluidized bed apparatus. There has been used model of fluidized bed drying, which consists two zones: emulsion zone and bubbling zone with taking into consideration the presence of solid particles in the bubbles. The results of theoretical expectations that arise from simulation calculations have been verified with experimental data obtained with the use of fluidized bed dryer 0.225 m in diameter. A drying process of silica gel, sand, and ammonium sulfate has been tested. To verify the model, the concept of a generalized drying curve has also been employed.

New (oxy)nitride pearlescent pigments

Thin ( d = 60 nm/140 nm) nanocrystalline Ta 3N 5 and Zr 2ON 2 films were synthesized in a rotary kiln and in a fluidized bed apparatus. The control of the reaction was performed by optimizing the ammonia flow, the temperature and the reaction time. Using fluidized bed technology, the reaction times were significantly reduced compared to a stationary oven and to a rotary kiln. Movement of the particles in the gas phase favors gas–solid interaction that enhances gas diffusion in the pores. In addition, complete reactions and homogeneous products were obtained in the fluidized bed and not in a rotary kiln, which resulted in pigments having a stronger interference color.

Validation of fluid bed granulation utilizing artificial neural network

Three innovative components (an annular gap spray system, a booster bottom and an outlet filter) have been developed by Innojet Technologies to improve fluid bed technology and to reduce the common interference factors (clogging of nozzles and outlet filters, spray loss, spray drying and fluidized bed heterogeneity). In a fluid bed granulator, three conventional components have been replaced with these innovative components. Validation of the modified fluid bed granulator has been conducted using a generalized regression neural network (GRNN). Under different operating conditions (by variation of inlet air temperature, liquid-binder spray rate, atomizing air pressure, air velocity, amount and concentration of binder solution and batch size), sucrose was granulated and the properties of size, size distribution, flow rate, repose angle and bulk and tapped volumes of granules were measured. To confirm the method's validity, the trained network has been used to predict new granulation parameters as well as granule properties. These forecasts were then compared with the corresponding experimental results. Good correlation has been obtained between the predicted and the experimental data. From these findings, we conclude that the GRNN may serve as a reliable method to validate the modified fluid bed apparatus.

Enhancement of liquid-fluidized bed classification (LFBC) of plastic particle mixtures via selective thermal particle modification

A novel method, based on temperature programming of the fluidizing medium, is investigated to improve the separation of complex plastic mixtures via liquid-fluidized bed classification (LFBC). Experiments were performed in a liquid-fluidized bed apparatus that was designed to operate in both upflow and downflow modes, for “heavier-than-water” and “lighter-than-water” plastic particle species, respectively. Temperature programming was achieved by using heated or cooled fluidizing feed water from two different reservoirs controlled at the desired temperatures. Binary beds of plastic mixtures of typical consumer/industrial plastics (PVC, PET, PS PC, LDPE, HDPE, and PP) were used. Due to differences in the thermal properties of the various plastic types, namely thermal diffusivities and glass transition temperatures, the experimental results show that the separation performance of LFBC can be significantly improved by selective modification of particle size/density via temperature programming of the fluidizing medium, water.

Fluid Dynamics of Spouted Bed Apparatus with Two Fluid Inlets: An Experimental Study

AbstractSpouted bed apparatuses are already used in some technical areas for a variety of chemical and metallurgical operations. One of the advantages of spouted beds compared to the fluidized beds is the possibility of achieving better conditions for an intense heat and mass transfer. Spouted beds are characterized by a relatively simple construction and an easy design, which allows the scale‐up of the spouted bed apparatuses and the creation of industrial equipments.

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.

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.

Gas-flow bed apparatus for coal gasification with pressure control

Gas-flow bed apparatus for coal gasification with pressure control

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.

Unusual adsorber dynamics due to S-shaped equilibrium isotherm

A fixed bed adsorption study has been performed to investigate the effect of S-shaped (Type V) equilibrium isotherm on the breakthrough patterns. The adsorption breakthrough data of benzene vapours on dealuminated zeolite Y were collected by using a lab-scale fixed bed apparatus. It was found that the adsorption system, at influent concentrations from 100 to 5,000 ppm at 303 K, yields breakthrough curves of unusual shapes. A mathematical model was applied to predict the complex breakthrough patterns at various conditions. The experimental and modelling results suggest that the unusual breakthrough curve is due to the basic shape of the equilibrium isotherm.

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.