Modeling of product variability in fluidized bed coating equipment

Particle coating in fluidized bed equipment is common practice for improving the properties of solid products, particularly in the pharmaceutical, food and agricultural industries. In this thesis, the application of particle coating to pharmaceutical products utilizing the Wurster-column coating process is addressed. This technique is extensively used in the pharmaceutical industry for precision drug coating and modified release coating of tablets and pellets.;The simulation of particle movement in fluidized beds has been successfully developed using Monte Carlo simulation. Raw velocity and voidage data for each region of a semicircular fluidized bed, obtained by Subramanian (2001), are used in the simulation. The average velocities in the x- and y-directions, the average voidage, and the standard deviations of the velocities in each region were calculated and used as input data for the model. Random numbers generated from a unit normal distribution were used to determine the starting position of the particle as well as the movement of the particles within the bed. The simulation results show that the pattern of particle movement is similar to the velocity profile of the original data and voidage profile agrees with the original data.;A simple experiment in an empty (without particles) fluidizing bed shows that the spray material moves vertically through the draft tube and out of the top of the bed. In addition, the spray material was found to vary radially from the spray nozzle and form a non-symmetric spray distribution. The simulation results, which are verified with pulse test experiments, show that the spray distribution and the spray shape at the bottom of the bed varied with different bed conditions, particularly with and without the presence of a particle deflector. Comparison of simulated results with pulse test experiments showed that the distribution of spray material and shape of the spray play important roles in the prediction of the mass coating distributions per-tablet-per-pass through the spray zone

An Algorithmic Framework for Multiobjective Optimization

Multiobjective (MO) optimization is an emerging field which is increasingly being encountered in many fields globally. Various metaheuristic techniques such as differential evolution (DE), genetic algorithm (GA), gravitational search algorithm (GSA), and particle swarm optimization (PSO) have been used in conjunction with scalarization techniques such as weighted sum approach and the normal-boundary intersection (NBI) method to solve MO problems. Nevertheless, many challenges still arise especially when dealing with problems with multiple objectives (especially in cases more than two). In addition, problems with extensive computational overhead emerge when dealing with hybrid algorithms. This paper discusses these issues by proposing an alternative framework that utilizes algorithmic concepts related to the problem structure for generating efficient and effective algorithms. This paper proposes a framework to generate new high-performance algorithms with minimal computational overhead for MO optimization

Investigation of Vortex Clouds and Droplet Sizes in Heated Water Spray Patterns Generated by Axisymmetric Full Cone Nozzles

The hot water sprays are an important part of many industrial processes, where the detailed knowledge of physical phenomena involved in jet transportation, interaction, secondary breakup, evaporation, and coalescence of droplets is important to reach more efficient processes. The objective of the work was to study the water spray jet breakup dynamics, vortex cloud formation, and droplet size distribution under varying temperature and load pressure. Using a high speed camera, the spray patterns generated by axisymmetric full cone nozzles were visualized as a function water temperature and load pressure. The image analysis confirmed that the spray cone angle and width do not vary significantly with increasing Reynolds and Weber numbers at early injection phases leading to increased macroscopic spray propagation. The formation and decay of semitorus like vortex clouds were also noticed in spray structures generated at near water boiling point temperature. For the nozzle with smallest orifice diameter (1.19 mm), these vortex clouds were very clear at 90°C heating temperature and 1 bar water load pressure. In addition, the sauter mean diameter (SMD) of the spray droplets was also measured by using Phase Doppler Anemometry (PDA) at different locations downstream of the nozzle exit. It was noticed that SMD varies slightly w.r.t. position when measured at room temperature whereas at higher temperature values, it became almost constant at distance of 55 mm downstream of the nozzle exit

Coating uniformity on a pharmaceutical tablet: An experimental study and finite volume modeling of droplet impact behavior.

The behavior of a single liquid droplet impacting a solid surface is a complex phenomenon and is a basic component of various industrial processes. One such process is the film coating process in the pharmaceutical industry, where coating uniformity is important especially if the coating is for functional purposes. Coating variability on a tablet could be affected by several factors, one of which is the impingement of droplets on its surface. The spreading behavior of a droplet on a solid surface was reported to be affected by the surface properties, particularly the surface roughness. To understand these phenomena completely, a series of experiments were conducted to investigate the impact behavior of a droplet on tablet surface with different roughnesses. These studies were considered in two stages; namely, a short-term phenomenon and long-term phenomenon. A 2-mm droplet was used in the short-term phenomenon study since for a micro-droplet this event occurs in a micro-second time scale, which is too fast for our high-speed camera that has a maximum framing rate of 2000 per second. However, a 60-μm droplet was used to study the long-term phenomenon, in which penetration and recoiling of droplet were observed. The results from the short-term phenomenon study showed that the initial spreading behavior of a droplet on tablets and stainless steel surfaces were similar, which suggests that penetration is negligible during this period. Droplets were found to spread less and bounce higher on a rougher surface. The results of the long-term phenomenon study showed that the bigger droplet (2-mm) took a longer time to penetrate compared to the smaller droplet (60-μm). The penetration rate was also affected by the tablet hardness; the harder the tablet the longer the penetration rate. The long-term phenomenon was also performed on tablet edge with different curvature; namely, ‘sharp’ and ‘round’. The results showed that on the round edge of a tablet, the spreading and penetration rates were found to be similar to the rate on the flat surface. However, on the sharp edge of a tablet, the penetration rate was found to be much faster than the spreading rate. This is due to the non-homogeneous packing of granules at the sharp edge giving rise to a porous region around the edge. On the other hand, the packing of granules is more homogeneous on the round edge and surface of a tablet. A multiphase volume-of-fluid (VOF) model was developed to predict the short term spreading phenomenon of a droplet, which also indicates the maximum spreading diameter resulting from the impact. The results from the 2-mm droplet were used to verify the model and a good agreement was obtained between simulations and experiments. The same variables and computational schemes were used in modeling a 60-μm droplet on different surface roughnesses. The 60-μm model developed in this work is useful to the spray coating processes to predict the maximum coating coverage following the droplet impact

Crude Oil Fouling in Heat Exchangers: A Study on Effects of Influencing Forces

One of the major concerns in petroleum refinery preheat trains is identified as fouling. Fouling impacts the refinery economics and environment heavily. Various approaches to mitigate fouling have not yielded the desired results. This is due to lack of understanding on the effect of influencing forces on crude oil fouling in heat exchangers. Therefore, this study attempts to investigate the effects of various forces such as gravity, Saffman Lift, drag and thermophoretic on crude oil fouling in heat exchangers through Computational Fluid Dynamics (CFD) simulations. From the simulations, it is observed that the higher particle size and particle concentration resulted in higher deposition of particles. Deposition velocities increase for larger sized particles and decrease for small and medium sized particles. The Increased flow velocities and surface roughness increases wall shear and mitigate fouling. Lower temperature gradients at the heat exchanger surface decreases deposition rates due to high thermophoretic forces. The mass deposition rate is reduced by 10.3 and 16.9% with 0.03 and 0.05 Pa, respectively, for 0.14 m/s flow velocity. Also, the mass deposition rate is reduced by 15.6 and 25.1% with 0.03 and 0.05 Pa, respectively, for 0.47 m/s flow velocity. With increased surface roughness from 0.03 to 0.05 mm, the mass deposition rate is reduced by 11.48 and 19.18%, respectively, for 0.14 m/s flow velocity. Also, for 0.47 m/s flow velocity, the mass deposition rate is reduced by 18.84 and 32.92% for 0.03- and 0.05-mm surface roughness, respectively

Estimating Young’s Modulus of Single-Walled Zirconia Nanotubes Using Nonlinear Finite Element Modeling

The single-walled zirconia nanotube is structurally modeled and its Young’s modulus is valued by using the finite element approach. The nanotube was assumed to be a frame-like structure with bonds between atoms regarded as beam elements. The properties of the beam required for input into the finite element analysis were computed by connecting energy equivalence between molecular and continuum mechanics. Simulation was conducted by applying axial tensile strain on one end of the nanotube while the other end was fixed and the corresponding reaction force recorded to compute Young’s modulus. It was found out that Young’s modulus of zirconia nanotubes is significantly affected by some geometrical parameters such as chirality, diameter, thickness, and length. The obtained values of Young’s modulus for a certain range of diameters are in agreement with what was obtained in the few experiments that have been conducted so far. This study was conducted on the cubic phase of zirconia having armchair and zigzag configuration. The optimal diameter and thickness were obtained, which will assist in designing and fabricating bulk nanostructured components containing zirconia nanotubes for various applications

Characterization of Modified Tapioca Starch Solutions and Their Sprays for High Temperature Coating Applications

The objective of the research was to understand and improve the unusual physical and atomization properties of the complexes/adhesives derived from the tapioca starch by addition of borate and urea. The characterization of physical properties of the synthesized adhesives was carried out by determining the effect of temperature, shear rate, and mass concentration of thickener/stabilizer on the complex viscosity, density, and surface tension. In later stage, phenomenological analyses of spray jet breakup of heated complexes were performed in still air. Using a high speed digital camera, the jet breakup dynamics were visualized as a function of the system input parameters. The further analysis of the grabbed images confirmed the strong influence of the input processing parameters on full cone spray patternation. It was also predicted that the heated starch adhesive solutions generate a dispersed spray pattern by utilizing the partial evaporation of the spraying medium. Below 40°C of heating temperature, the radial spray cone width and angle did not vary significantly with increasing Reynolds and Weber numbers at early injection phases leading to increased macroscopic spray propagation. The discharge coefficient, mean flow rate, and mean flow velocity were significantly influenced by the load pressure but less affected by the temperature

Coupling of subcritical methanol with acidic ionic liquids for the acidity reduction of naphthenic acids

The presence of naphthenic acids (NAs) in crude oil is the major cause of corrosion in the refineries and its processing equipment. The goal of this study is to reduce the total acid number (TAN) of NAs by treating them with subcritical methanol in the presence of acidic ionic liquid (AIL) catalysts. Experiments were carried out in an autoclave batch reactor and the effect of different reaction parameters was investigated. It was observed that TAN reduction was positively dependent on the temperature and concentration of the AIL whereas excess of methanol has a negative effect. Approximately 90% TAN reduction was achieved under the optimized reaction conditions using [BMIM]HSO4 as catalyst. It was also perceived from the experimental results that the AILs with longer alkyl chain exhibited higher catalytic activity. The activity and stability of AIL showed that they can be promising catalyst to esterify NAs under subcritical methanol