Fluidizing Air Temperature Research Articles

Aerosol fluidized bed coating: Exploring the impact of process conditions on process yield, coating coverage and thickness

Aerosol droplets are used to coat fluidized particles in this work. Coating experiments utilizing aerosol droplets (with a mean diameter of around 1μm) were performed under different process conditions to explore their impact on process yield, as well as on coating coverage. Core materials were glass and porous γ-Al2O3, which had mean diameters of 653μm and 610μm, respectively. Sodium benzoate (NaB) solution and silicon dioxide (SiO2) nanosuspension were used as the coating liquid. After sampling, particle pictures were taken by a scanning electron microscope and analyzed using image processing to determine the coating coverage. To simulate the coating process and determine, for each experiment, a factor for preferential deposition on already occupied positions, Monte Carlo simulations were used. Also, some particles were cut in the middle to measure coating layer thickness. Intraparticle coating thickness distribution from Monte Carlo simulations coarsely matches the measured thickness from cut particles. Results show that the process yield, coating coverage, and preference factor are affected by experimental conditions such as expanded bed height, fluidization air temperature, atomizing pressure, the number of aerosol inlets, as well as the surface potential of core particles. This study is first to examine the impact of surface charge of different core materials on droplet deposition. In an experiment with SiO2 nanosuspension, γ-Al2O3 cores could be coated quite uniformly with SiO2 nanoparticles with a layer thickness of ca. 1.1μm. This shows the potential of aerosol droplet deposition as a novel semi-wet method for coating large particles with nanoparticles without using any binders.

Control of segregation by non-uniform aeration in a fluidized bed spray granulator

Controlling and influencing the rate of particle growth in spray granulators is key for consistent product quality and size, while reducing energy consumption and product re-circulation. To this end, we have implemented a new control device to actively change the fluidization topology of fluidized spray granulators and to influence the local particle segregation in the areas affected by the granulation, selectively growing fine particle fractions at will. Simulations using computational fluid dynamics coupled with the discrete element method (CFD-DEM) demonstrate how the different operational modes can be switched in a short period of time, resulting in full local segregation in less than 40 s, without changing the fluidization air or inlet temperature. It is shown how a central spout preferentially drags big particles to the top of the bed, while a side aeration system, where two smaller spouts are opened at the outermost sides of the bed, creates a concentration of fines in the spraying region. This process can be repeated as long as the fluidization velocity of all particle sizes in the bed can be attained and full fluidization is underway. The spout regime could be used to clean the distributor plate of undesired big or overgrown particles, and side aeration to preferentially grow finer particles, while homogeneous aeration should be the default operation mode when no anomalies are detected.

Drying Characteristics and Quality Attributes Affected by a Fluidized-Bed Drying Assisted with Swirling Compressed-Air for Preparing Instant Red Jasmine Rice

A new process for the production of instant red jasmine rice was investigated using fluidized bed drying with the aid of swirling compressed air. Drying characteristics were evaluated using the operating parameters of fluidizing air temperature (90–120 °C) and pressure of swirling compressed air (4–6 bar). Appropriate air pressure was determined based on the highest value of model parameters from the semi-empirical Page equation and effective diffusivity. Influences of supply time of swirling compressed air (2–10 min) and drying temperature of 90–120 °C were investigated and optimized based on the quality attributes using response surface methodology. Drying at 120 °C and compressed air pressure of 6 bar gave the highest rate constant and effective diffusion coefficient. Drying at 120 °C combined with injecting swirling air for 2 min was the most suitable approach, while drying at 90 °C and supplying compressed air for 10 min was the best choice to preserve antioxidant properties. Air temperature of 98.5 °C with 2 min supply of swirling compressed air suitably provided high physical and rehydration properties and retained high health benefits of antioxidant compounds. Finally, after rehydration in warm water at 70 °C for 10 min, the textural properties of the rehydrated rice sample were comparable to conventionally cooked rice.

A new approach to the mechanisms of agglomeration in fluidized beds based on Spatial Filter Velocimetry measurements

Spatial Filter Velocimetry (SFV) is a technique that has been used for agglomeration processes during the past few years as it can monitor, control, and understand granulation and its implications in particle size distribution. This work has considered and aimed to analyze the evolution of the process as time goes on and in real-time and the influence of operating conditions on the process. A Plackett-Burman design was proposed with seven factors and three replicates at the central point condition, using microcrystalline cellulose (CMC) as the raw material and a maltodextrin solution as a liquid binder. Binder concentration, binder flow rate, powder initial moisture content, and fluidizing air temperature were significant at a 90% confidence level. A new approach was proposed for delimiting the stages of the fluidized bed agglomeration process, based on particle size classes that were obtained from the SFV probe data.

Pea protein isolate fluid dynamics and characterization obtained by agglomeration in pulsed fluidized bed

The pea protein isolate (PPI) is characterized as a cohesive powder with crack and channeling formation during its fluidization. This work aimed to evaluate the fluid dynamic behavior of PPI during the agglomeration process and produce an instant product. The process was carried out in a pulsed fluidized bed and water was used as a liquid binder. The fluid dynamic behavior at four levels of sinusoidal pulsation was evaluated. Then, seven tests were performed according to a full-factorial design. Fluidizing air temperature (65–85 °C) and binder flow rate (2.4–3.8 mL/min) were the independent variables, and the responses analyzed were moisture content, process yield, and mean particle size. Size distribution, porosity, wetting time, flowability, and particle morphology were evaluated. Air pulsation promoted better fluid dynamics behavior at 4 Hz, with lower minimum fluidization velocity. Granules 3.9 times larger, 11.3% more porous and, at least, 10 sec of wetting time were obtained.

Fluidisation of lentil seeds during microwave drying and disinfection could prevent detrimental impacts on their chemical and biochemical characteristics

A microwave fluidized bed has proven to be substantially more efficient than a conventional fluidized bed dryer in food and agriculture. However, its effect on the quality attributes of the grains, have not yet been fully discovered. In the present study, the effect of microwave fluidized bed drying with the aim of pest and pathogen control, utilising microwave powers of 0, 300, 400, 500 W (0, 3.6, 4.8 and 6 W g−1 dry seeds, respectively) and fluidizing air temperature of 50 and 60°C, on the quality traits of lentil seeds were examined by measuring antioxidant enzyme activities, cooking quality and macronutrients analysis using Fourier transform infrared micro spectroscopy. A reduction in Peroxidase activity was observed at powers of 3.6 and 4.8 W g−1 and fluidizing air at 60 °C. The hardness of soaked and cooked seeds increased after drying at 6 W g−1 with both air temperatures and at 4.8 W g−1 with an air temperature of 60 °C. Based on the results of FTIR, no conformational changes in the protein secondary structure were observed at microwave powers of 0, 3.6, and 4.8 W g−1. Therefore, controlling microwave radiation utilising hot air for agitation could prevent any negative effect on the grain quality attributes.

Acacia gum fluidized bed agglomeration: Use of inulin as a binder and process parameters analysis

AbstractThis work aimed to investigate the use of inulin as an alternative binder in fluidized bed agglomeration to improve both acacia gum functional and handling properties. Acacia gum was agglomerated in fluidized bed with inulin solution (18.0% wt/wt) at two different fluidizing air temperature (65 and 85°C) and binder feed rate (1.5 ml/min and 3.0 ml/min). The granule growth kinetics and system stability were monitored by a spatial filter velocimetry probe. The influence of process parameters on process yields and product characteristics: final particle size, wettability, and flowability were also evaluated. We observed an increase in particle size and the agglomerated particles showed a short wetting time, indicating that inulin can be successfully used as an alternative binder adding both nutritional and functional value to the acacia gum. Low binder feed rate provided better system stability and larger particle size.Practical ApplicationsThis paper presents inulin as an alternative binder for application in powder food agglomeration processes. The use of inulin has provided improved flowability and wetting properties. Moreover, the inulin may also add functional value to agglomerated foods. Besides, it was possible to monitor particle growth and process stability through a relatively new technique that measures the particle size, spatial filter velocimetry. In this way, it is possible to establish which conditions of temperature and binder feed rate are the most suitable for the agglomeration process.

Production and Characterization of Controlled Release Urea Using Biopolymer and Geopolymer as Coating Materials.

Synthetic polymers-based controlled release urea (CRU) leaves non-biodegradable coating shells when applied in soil. Several alternative green materials are used to produce CRU, but most of these studies have issues pertaining to nitrogen release longevity, process viability, and the ease of application of the finished product. In this study, we utilized tapioca starch, modified by polyvinyl alcohol and citric acid, as coating material to produce controlled release coated urea granules in a rotary fluidized bed equipment. Response surface methodology is employed for studying the interactive effect of process parameters on urea release characteristics. Statistical analysis indicates that the fluidizing air temperature and spray rate are the most influential among all five process parameters studied. The optimum values of fluidizing air temperature (80 °C), spray rate (0.13 mL/s), atomizing pressure (3.98 bar), process time (110 min), and spray temperature (70 °C) were evaluated by multi-objective optimization while using genetic algorithms in MATLAB®. Urea coated by modified-starch was double coated by a geopolymer to enhance the controlled release characteristics that produced promising results with respect to the longevity of nitrogen release from the final product. This study provides leads for the design of a fluidized bed for the scaled-up production of CRU.

A Novel Process for Preparing Instant Riceberry Using Fluidized Bed Drying Assisted with Swirling Compressed-Air: Kinetic Aspects

Fluidized bed drying associated with pulsed swirling compressed-air was proposed as an alternative production method for instant riceberry to overcome surface stickiness and problematic preparation steps. Effects of fluidizing air temperature (70–90 °C) and compressed-air pressure (2–4 bar) were investigated by kinetic analysis. The Page model described drying kinetics associated with quadratic correlations between all model parameters and operating factors. Among different models, the Weibull equation suitably described rehydration behavior, and shape parameters quadratically correlated with drying parameters. Thermal degradation of anthocyanins was assessed using the first-order kinetics equation. Drying conditions influenced all kinetic parameters and physical properties. Optimal operation was determined as fluidizing air temperature at 90 °C with compressed-air pressure of 3.88 bar.

Valorization of anaerobic digestion liquid residue through the production of organic fertilizer by fluidized bed granulation

In this work the feasibility of developing a solid fertilizer by fluidized bed granulation, using digestate (liquid residue from anaerobic digestion) as binder and different minerals as seeds is analysed. Full characterization of the selected mineral particles and the liquid digestate was performed. Particularly, phosphorous and potassium content was assayed before and after granulation. Friability and breakage strength of product granules were tested as well. Also, the process operating conditions (bed temperature, fluidization air temperature and flowrate, digestate temperature and flowrate, etc.) that enable stable operation and the production of completely coated granules were successfully established for lab- and pilot-scale granulation units.

Wettability improvement of pea protein isolate agglomerated in pulsed fluid bed

The pea protein isolate (PPI) is characterized as a cohesive powder, presenting channeling formation during its fluidization (Geldart type A) and reduced dispersion in water. This work aimed at agglomerating the PPI for the production of an instant product. The process was carried out in a pulsed fluid bed and gum Arabic was used as a liquid binder. Seven tests were performed according to a full-factorial design, where the independent variables were fluidizing air temperature (65–85 °C) and binder flow rate (2.4–3.8 mL/min). Moisture content, process yield, and mean particle size were analyzed as responses. Furthermore, wetting time and flowability were compared before and after the agglomeration between raw and agglomerate PPI. Product transformations were also evaluated by analysis of size distribution, porosity, wetting time, flowability, and shape parameters. When compared to raw material, agglomerated particles had larger granules with a moisture content below 5.0% and process yield above 60.7%, as well as better flowability, a more regular shape, lower porosity, and a 99% reduction in wetting time.

Application of the Modified Tangential Spray-Fluidized Bed to Produce Nonpareils from Primary Crystals.

Coating of fine primary drug particles by a fluidized bed processor has been reported to be potentially challenging. This work aimed to develop a spray layering process to produce nonpareils by a side spray fluid bed with swirling air flow. The first part examined the effects of various parameters for producing lactose nonpareils by using Box-Behnken design. The factors considered were atomizing air pressure, spray rate, and fluidizing air temperature. This was followed by an in-depth investigation on the effects of inlet airflow rate, air temperature, and spray rate on properties of the product, in addition to process optimization. The results indicated a negative correlation between atomizing air pressure and D90 (particle size at 90th percentile in the cumulative undersize plot) as well as span (size distribution). Temperature had a positive correlation with D90 and span while spray rate affected span. Both atomizing air pressure and temperature correlated negatively with span. It was also found that spray rate negatively affected roundness at different coat weight gain levels across the study design space. Inlet airflow rate was found to correlate negatively with roundness at 15%, w/w coat weight gain. The mean useful yield of the optimized runs was about 91%. In the second part of this study, the metformin hydrochloride crystals as starter seeds were converted into nearly spherical shaped spheroids with 1:1 crystals to coat weight deposition over a processing time of about 3.5h. The processor studied shows promise for direct spheronization of crystals into spherical seeds.

Model Development and Validation of Fluid Bed Wet Granulation with Dry Binder Addition Using a Population Balance Model Methodology

An experimental study in industry was previously carried out on a batch fluid bed granulation system by varying the inlet fluidizing air temperature, binder liquid spray atomization pressure, the binder liquid spray rate and the disintegrant composition in the formulation. A population balance model framework integrated with heat transfer and moisture balance due to liquid addition and evaporation was developed to simulate the fluid bed granulation system. The model predictions were compared with the industry data, namely, the particle size distributions (PSDs) and geometric mean diameters (GMDs) at various time-points in the granulation process. The model also predicted the trends for binder particle dissolution in the wetting liquid and the temperatures of the bed particles in the fluid bed granulator. Lastly, various process parameters were varied and extended beyond the region studied in the aforementioned experimental study to identify optimal regimes for granulation.

Inline acoustic monitoring to determine fluidized bed performance during pharmaceutical coating

Fluidized beds are used by pharmaceutical manufacturers for multi-particulate drug coating. They provide effective mass and heat transfer; however, unit optimization can be difficult due to the multivariate nature of a fluidized bed system. This research explores the use of passive acoustic emissions monitoring as a method to improve temperature management during pellet coating. A piezoelectric microphone was placed inside the exhaust of a conical top spray fluidized bed. Spherical 1000 μm pellets were coated while recording acoustic emissions. Fluidization air temperature was adjusted between trials as a controlled variable to determine if pellet drying rate could be extracted from the data. During each trial, pellets became damp as the coating solution was applied. Drying stages were used to remove moisture whereby pellet fluidization continued without spraying. The moving standard deviation of the acoustic emissions increased by approximately 40 mV during each 2-min coating stage. The emissions then decreased during drying. This decrease was at a rate proportional to pellet drying independently measured at each controlled temperature. The overall coating-drying emissions profile was similar for trials using either sugar or Acryl-EZE® coating solutions. Passive acoustic emissions monitoring is non-invasive and provides reliable coating and drying information during fluidized bed operation.

Texture and Antioxidant Properties of Puffed Pounded-Unripe Rice Coated by Marigold Extract as Affected by Fluidized-Bed Coating Conditions

We investigated the effects of fluidized-bed coating parameters on texture and antioxidant properties of puffed pounded-unripe rice (PPUR) coated by marigold extract with variations of inlet air temperature of 50, 60 and 70°C and coating solution feed rate of 5, 7.5 and 10 ml/min. The results showed that increasing inlet air temperature tended to reduce the hardness of coated PPUR, while the adverse effect was found with increasing feed rate. Both parameters did not significantly affect the crispiness. We also found that fluidizing air temperature and feed rate significantly affect total phenolic content (TPC), total flavonoid content (TFC) and their antioxidant activities. Higher feed rate slightly increased TPC and antioxidant activities as determined by DPPH and FRAP assays, but not for TFC. As mostly found in medicinal plants, all antioxidant properties decreased when temperature increased. Based on the amount of TPC and TFC and their antioxidant activities, we recommend low inlet air temperature and high feed rate to improve health benefits of puffed pounded-unripe rice as a breakfast cereal. However, agglomeration must be concerned when using high feed rate.

Experimental Study on Combustion of Low Calorific Oil Shale Semicoke in Fluidized Bed System

Oil shale semicoke produced from the oil shale retorting process causes great hazards to the environment due to its high phenol and polycyclic aromatic hydrocarbons content. A good solution of the current of semicoke is to burn it as feedstock. In the present work, the extremely low calorific oil shale semicoke of 2384 kJ/kg was adopted, and a series of experimental investigations and computational analyses were carried out in bench-scale and pilot-scale bubbling fluidized bed combustors, to understand its combustion characteristics. Results indicated that by adopting effective technique means, the extremely low calorific oil shale semicoke could be directly burnt in the fluidized bed combustor, and the combustion was completely relying on its heat release. The main influence factors of combustion stability were combustion temperature, fluidization air temperature, and burnout rate. However, within the scope of test parameters, its combustion characteristics were mainly affected by dense-bed temperature, fluidization air velocity, and grain size, and less affected by static bed height. Furthermore, its comprehensive utilization system was put forward, and the general configuration and technical data of 35 t/h medium pressure fluidized bed boiler adopting the mixture of fine oil shale and extremely low calorific oil shale semicoke whose calorific value is 2876.2 kJ/kg were also given at the end of this article.

Drug loaded and ethylcellulose coated mesoporous silica for controlled drug release prepared using a pilot scale fluid bed system

The goal of this study was to test the feasibility to load non-ordered, non-spherical mesoporous silica with the model drug paracetamol, and subsequently coat the loaded particles using one single pilot scale fluid bed system equipped with a Wurster insert. Mesoporous silica particles (Davisil®) with a size ranging from 310 to 500μm and an average pore diameter of 15nm were loaded with paracetamol to 18.8% drug content. Subsequently, loaded cores were coated with ethylcellulose to obtain controlled drug release. Coating processing variables were varied following a full factorial design and their effect on drug release was assessed. Increasing coating solution feed rate and decreasing fluidizing air temperature were found to increase drug release rates. Increasing pore former level and decreasing coating level were found to increase drug release rates. The release medium’s osmolality was varied using different sodium chloride concentrations, which was found to affect drug release rates. The results of this study clearly indicate the potential of non-ordered, non-spherical mesoporous silica as a reservoir carrier for the controlled release of drugs. Although non-spherical, we were able to reproducibly coat this carrier using a bottom spray fluid bed system. However, a major hurdle that needs to be tackled is the attrition the material suffers from during fluid bed processing.

Fluidized bed drying characteristics and modeling of ginger (zingiber officinale) slices

In this study fluidized bed drying characteristics of ginger have been investigated. The effects of the fluidizing air temperature, velocity, humidity and bed height on the drying performance of ginger slices have been found. The experimental moisture loss data of ginger slices has been fitted to the eight thin layer drying models. Two-term model drying model has shown a better fit to the experimental data with R2 of 0.998 as compared to others.

Agglomeration of soy protein isolate in a pulsed fluidized bed: Experimental study and process optimization

The soy protein isolate contains a high amount of protein and small fractions of fat, carbohydrates, and fiber. The food industry often employs this isolate as an additive, despite its drawbacks: it is a cohesive powder; its fluidization culminates in cracks and channeling. In this paper we used the experimental design to establish the optimal operational conditions to produce agglomerated soy protein isolate in a pulsed fluidized bed. The bed operated with an air pulsation frequency of 600rpm; the liquid binder consisted of an aqueous carboxymethyl cellulose solution. We employed a 23 complete factorial design with three central points to evaluate how the variables fluidizing air temperature (60–80°C), fluidizing air velocity (0.51–0.67ms−1), and binder flow rate (1.2–2.0mLmin−1) affected the mean particle diameter, process yield, and moisture content. Surface response analysis pointed out the operational parameters that provided large granules with low moisture content and high process yield. Compared with the raw isolate, the agglomerated particles were more porous and irregular; they also presented good handling properties, reduced wetting time and cohesiveness, and improved free-flow. Moreover, agglomeration enhanced the functional properties of the powder such as water retention and foaming capacity.

Product design based on discrete particle modeling of a fluidized bed granulator

Fluidized bed agglomeration is a process commonly used to construct powdered food or pharmaceutical products to improve their instant properties. This works analyzes the influence of a wide range of operating parameters (i.e., fluidization air flow rate, temperature, and liquid injection rate) on growth rate, process stability, and product particle structure. Different granulator configurations (i.e., top spray, Wurster coater, spouted bed) are compared using identical process parameters. The impacts of both process variables and granulator geometry on the fluidization regime, the particle and collision dynamics, and the resulting product structure and corresponding properties are studied in detailed simulations using a discrete particle model (DPM) and lab-scale agglomeration experiments with amorphous dextrose syrup (DE21). The combination of numerical and experimental results allows to correlate the kinetics of micro-scale particle interactions and the final product properties (i.e., agglomerate structure and strength). In conclusion, detailed DPM simulations are proven as a valuable tool for knowledge-based product design.