Agitator Rotational Speed Research Articles

Development of Mechanized System for Production of Date-Palm Jaggery Granules

Making of date-palm jaggery (popularly known as khejur gur) with its characteristic aroma and flavor is very popular all over India for making various sweet dishes and confectionery products. It is available only for a short duration between middle of November and end of January. The production of solid jaggery includes sap collection (juice) by tapping, filtration, concentration by boiling, cooling of concentrated juice followed by moulding, drying, and storage. Making date-palm jaggery from the raw juice is an art and requires some skill to get the characteristic aroma bearing product with optimum stickiness and colour. Solid jaggery deteriorates rapidly and becomes liquid within 1 or 2 weeks due to its moisture content, invert sugar, and hygroscopic nature. Granular jaggery having low moisture content (1 - 2%d.b) is very popular, tenders several advantages, such as extended shelf-life, easy handling and distribution, high demand for domestic and international markets. It could be made from either solid jaggery or concentrated juice. Therefore, a manually-powered operated granulator (20 kg capacity) was designed, developed, and tested with 5 levels of moisture content (8.4 to 16.25 %db) and 5 levels of rotational speed (48 - 132 rpm) of blades for the production of desired size of jaggery granules. The mass mean diameter of the particles varied linearly with the moisture content of the feed, yielding particles having an average size of 656 µm (Dp) for feed containing 8.4 (%db) moisture. The mean particle size was as low as 700 µm when the machine was operated at 132 rpm with feed moisture content of 12 (%db). The average particle size of 1000 µm is obtained at feed moisture content of 9.0 (%db) and the agitator rotational speed of 76 rpm.

Influence of process variables on foaming ability of surfactants: Experimental study and dimensional analysis

By applying the dimensional analysis approach to a lab-scale stirred tank process, the influence of process parameters on the foamability of three model surfactants: SLES, Tween 20 and Brij L23 is investigated and modelled. For validation of process law, the theoretical approach is complemented with an experimental work varying process parameters such as agitator rotational speed rate (N), mixing time (tm) and bottom clearance (Cb). The foam rate of expansion of surfactant solutions is correlated with success to two dimensionless numbers: the Reynolds number and the mixing time number. Reynolds number is observed as mainly governing the amount of formed foam. A clear difference between the intermediate flow regime (Re<105) and the turbulent one (Re>105) is observed leading to a different process law for each regime. Master curves are finally drawn and can be used for helping to predict final foam volumes in the studied experimental domain according to both dimensionless numbers.

Heavy Fraction Separation From Used Lube Oil Using Thin Film Evaporator

Used lube oil is a dangerous waste that must be treated before disposed on the environment. Used lube oil treatment process consists of several stages, one of them is the separation of heavy fraction. Some equipment system can be used to complete this process, and thin film evaporator (TFE) is chosen for this research. The goal of this research is to understand the effect of temperature and rotor rotation on the heat transfer that happens in the distillation process using thin film evaporator. Simulation using Aspen Plus is used and is validated by manual calculation using Matlab. Temperature is varied between 250 – 330 °C and rotor rotation are varied between 0 – 60 rotations per minute (RPM) in a vacuum pressure of 2.53 kPa. From this research, the relation between operating temperature and rotor rotation in thin film evaporator to the vapor fraction produced is directly proportional. The optimum operating condition in this research was found at a temperature of 310 °C with the agitator rotational speed of 30 RPM.

Technological Progress in Biodiesel Production: An Overview on Different Types of Reactors

Nowadays, research on biodiesel focuses on enhancing the conversion and production yield to fulfill the demand. Utilization of new feedstocks, development of highly efficient catalysts, determination of effective and economical reaction approaches, and application of process system engineering tools are efforts for the optimization purposes. This paper reviews the technological progress of reactors used for biodiesel production. The first part gives an overview of previous findings available in the literature. Many factors affecting the production yield of biodiesel have been reviewed such as reaction time, agitator rotational speed, temperature, types of catalyst, catalyst concentration, the molar ratio of oil and alcohol, types of solvent, and types of feedstock. However, the review of different types of reactors used for the biodiesel production is still lacking. The appropriate selection of reactor type is necessary to enhance the product yield and the productivity. Thus, the second part of this paper aims at compiling the information on various reactors. The description of key operating conditions and process design, relevant integrated reaction and separation techniques, recent achievement and progress, and challenges for future development are highlighted. This review provides the basis for exploitation and selection of reactor to enhance optimization, scale-up development, and implementation in industrial-scale biodiesel production.

Numerical Modelling of the Molten Metal Flow in a Disk Agitator Mixer

Numerical modelling of the molten metal flow in a crucible under the action of stirred disk agitator is carried out. The influence of the agitator rotational speed on the molten metal flow field is investigated. Dependences of the turbulent diffusivity and the power number on the agitator rotational speed are obtained. The effect of the interaction between the molten metal-air interface and agitator elements on the flow field in a crucible is shown.

Feeding system for wood chips: A DEM study to improve equipment performance

Discrete element method (DEM) is useful for simulating the behavior of bulk solids and corresponding interaction with handling equipment. Although DEM is widely used for simulation of bulk solids, there are no applications involving biomass handling. This study presents the first published attempt at DEM modeling of wood chips in a feeding system. The DEM model of a wood chip feeding system was first validated with experimental data. Thereafter, the validated DEM model from this study was applied to study the effect of the mounting position as well as design aspects of a horizontal agitator within a wood chip feeding system. The validation outcome demonstrates that DEM is a suitable method to compute relevant values of a wood chip system and that it can be applied to predict trends with regard to more efficient operation of the system. Results show that a sensibly chosen agitator mounting position can decrease the mass-related energy consumption by as much as 30%. In terms of design aspects, the agitator's rotational speed and the blade design are the most influential factors governing the feeding system's mass-related energy consumption. Altering the number of agitator blades and blade design can also decrease energy use by 30%. In conclusion, even simple design changes can have considerable influence when feeding wood chips, while maintaining the system's mass flow. Besides, future studies could focus on more elaborate particle shape representation in the DEM model to enable to prediction of critical flow situations, such as blocking.

Segregation of multi-sized biomass particles in a horizontal stirred bed

A discrete element method (DEM) was used to numerically investigate the segregation of biomass particles (with multi-sized distribution) in a horizontal stirred bed. An analysis of the following factors was performed: agitator rotational speed, reactor diameter, weir height, particle size distribution on particle segregation, and residence time distribution. The results indicated that particle segregation increased with an increased reactor diameter, decreased weir height, and narrower particle size distribution. The influence of the agitator rotation rate was not as significant as the other three variables. When the ratio of the weir height to the reactor diameter was less than 1/2, then the smaller particles had a higher mean residence time than the larger particles; however, when the ratio was 2/3, the opposite result was obtained.

The effect of fluid rheology and medium on the performance of a helical ribbon mixer for concentrated manganese nodule slurry

ABSTRACTIn hydrometallurgical and mineral processing operations, slurries are often prepared at very small grind sizes and high solids concentrations. The presence of yield stress or flow limits results in flow anomalies as the slurry tends to stagnate close to vessel bottom, walls, and at any internal surface. The preparation of high-concentration slurries preferably in low shear rate ranges consuming less power is an integral part of high-concentration slurry transportation systems. Therefore, during mixing of such concentrated slurries, the selection of appropriate agitation equipment for preparation of a homogeneous suspension requires a thorough investigation. The rheological behavior of ground manganese nodule samples in solids concentration range of 55–65% by weight using both distilled water and sea water as mediums have been evaluated and the discrepancy in yield stress and plastic viscosity values affected by solids concentration and medium has been discussed and presented in the paper. The performance characteristics of a helical ribbon mixer influenced by fluid rheology, medium, and agitator rotational speed were evaluated. The appropriateness of the agitator for preparation of high-concentration manganese nodule slurry was further substantiated by comparing the experimental power consumption data with the theoretical power consumption values computed using Bakker and Gates correlations.

Application of DEM modified with enlarged particle model to simulation of bead motion in a bead mill

We applied the discrete element method (DEM) of simulation modified by an enlarged particle model to simulate bead motion in a large bead mill. The stainless-steel bead mill has inner diameter of 102mm and mill length of 198mm. The bead diameter and filling ratio were fixed respectively at 0.5mm and 85%. The agitator rotational speed was changed from 1863 to 3261rpm. The bead motion was monitored experimentally using a high-speed video camera through a transparent mill body. For the simulation, enlarged particle sizes were set as 3–6mm in diameter. With the DEM modified by the enlarged particle model, the motion of enlarged particles in a mill was simulated. The velocity data of the simulated enlarged particles were compared with those obtained in the experiment. The simulated velocity of the enlarged particles depends on the virtual frictional coefficient in the DEM model. The optimized value of the virtual frictional coefficient can be determined by considering the accumulated mean value. Results show that the velocity of the enlarged particles simulated increases with an increase in the optimum virtual frictional coefficient, but the simulated velocity agrees well with that determined experimentally by optimizing the virtual frictional coefficient in the simulation. The computing time in the simulation decreases with increased particle size.

Granulation of Core Particles Suitable for Film Coating by Agitation Fluidized Bed III. Effect of Scale, Agitator Rotational Speed and Blade Shape on Granule Properties and Development of a High Accuracy Scale-Up Theory

The preparation of core particles suitable for subsequent film coating was examined using different scales of agitation fluidized beds. Specifically, the effects of agitator rotational speed and agitator blade shape in different scales of granulators on granule properties such as mass median diameter, apparent density, friability and shape factor were studied. As the agitator rotational speed was increased or when the agitator blade height and angle were large, the mass median diameter and friability of the granules decreased, while the apparent density and shape factor increased, in a manner independent of the vessel size because the granules were subjected to greater compression, shearing and rolling effects. The same core particles could not be prepared using granulators with different vessel sizes by simply adopting a conventional scale-up theory(1,2)) based on kinetic energy similarity. Here, a novel scale-up theory that takes into account agitator blade shape factors is proposed.(3)) When the two scale-up theories were compared, our new theory was capable of predicting the granule properties more accurately than the conventional theory. By adopting this novel theory, the same core particles could be prepared under different operating conditions in any scale of granulator.

Numerical analysis of agitation torque and particle motion in a high shear mixer

Numerical simulation of particle motion in a high shear mixer was conducted using a three-dimensional discrete element method (DEM). Torque of an agitator blade, particle velocity profiles and forces acting on a particle were calculated under various agitator rotational speeds. The agitation torque showed a good correlation with the agitator rotational speed and reflected the particle motion in the mixer. The simulated results revealed that particles received greater forces near the bottom of the vessel, as compared to the upper or middle height in the mixer. The particle flow changed with the agitator rotational speed, as experimentally observed, and indicated different velocity profiles. Particle kinetic energy determined the agitation torque and the particle behavior, regardless of the complexity of the changes in the particle flow. A significance of monitoring of the agitation torque in the mixer is also discussed here from the perspective of the particle kinetic energy.

Heat Transfer and the Mechanism of Drying in Agitation Fluidized Bed.

This paper describes experimental and numerical analyses on the heat transfer between air and particles in an agitation fluidezed bed drying process. Spherical particles made of crystalline cellulose having been dampened to 15% were dried in an agitation fluidized bed. The effects of the operating variables such as air temperature, air velocity, agitator rotational speed and particle size on the heat transfer coefficient between air and particles were investigated experimentally. An empirical equation was then proposed to predict the heat transfer coefficient suder various operating variables and particle size. The empirical equation could predict the heat transfer coefficient very accurately.

Drying of Granules in Agitation Fluidized Bed.

This paper describes an experimental study on the drying of wet granules in an agitation fluidized bed. Wet granules composed of lactose and cornstarch were dried in an agitation fluidized bed under various air temperatures, air velocities and agitator rotational speeds. The effects of the conditions on the properties of granules such as mass median diameter, yield, shape and density of the granules are investigated. The relationships between the operating conditions and the drying rates were also examined. It is found that mass median diameter decreases with decreasing air temperature and velocity, and with an increase in agitator rotational speed, while the apparent density, shape factor and yield of fine granules increases. Granules are compressed by the tumbling and compaction effects due to the agitation rotation, which simultaneously diminishes the size of the granules by grinding them. It is also found that the drying rate over a constant drying period increases with air temperature and velocity, but decreases with agitator rotational speed. These results show that too much centrifugal force from agitator rotation forms condensed masses, leading to a decrease in the interfacial drying area.As a result, the mechanism of agitation fluidized bed drying is elucidated and optimal operating conditions are discussed from the view point of granule properties and drying rate.

Scale-Up of Agitation Fluidized Bed Granulation by Neural Network.

Scale-up of wet granulation by agitation fluidized bed was conducted using a hierarchy neural network with a back-propagation learning. Scale-up characteristics of agaitation fluidized bed granulation were self-learned using a developed neural network system, and properties of size, size distribution, apparent density and shape factor of granules prepared by the commercial scale under various operating conditions (moisture content, agitator rotational speed and fluidization air velocity) were predicted. To confirm the method's validity, the predicted properties were compared with the actual granulation data. Good correlation was obtained beteen the predicted and the experimental data of agitation fluidized bed granulation. It was found that the neural network could be a reliable tool to analyze the scale-up characteristics of granulation, and to predict granule properties being produced by the unknown larger scale granulator.

Measurement of Moisture Content by IR Sensor in Fluidized Bed Granulation. Effects of Operating Variables on the Relationship between Granule Moisture Content and Absorbance of IR Spectra.

In this study, the validity of moisture measurement by an IR sensor was investigated in fluidized bed granulation. The effects of operating variables on the relationship between granule moisture content and the absorbance of IR spectra were examined experimentally. It was found that the air flow rate of purge air used for preventing powder adhesion, fluidizing air velocity, agitator rotational speed and spray mist size had no effect on the relationship. However, if the dampening speed was extremely low, the effects of fluidization air temperature and liquid flow rate on the relationship could be recognized. This was because the surface drying due to the extremely low dampening speed caused water to transfer from the inside to the surface. As a result, it can be concluded that the measurement of moisture content by an IR moisture sensor can be conducted with high accuracy, free of operating conditions, unless the granulation is conducted under an extremely low dampening speed.

Modeling of Agitation Fluidized Bed Granulation by Random Coalescence Model.

Modeling of agitation fluidized bed granulation was conducted using a proposed random coalescence model, in which adhesion of two colliding particls was judged by the coherent strength of a liquid bridge formed between the particles and the separation force caused mainly by agitator rotation. Properties of coherent strangth and water absorbing characteristics of the starting materials, which were very important to determine granule growth, were also teken into consideration. Granule growth in various powder samples with different properties were simulated and the effects of moisture content and agitator rotational speed on this growth were numerically investigeted. The simulated results were in good agreement with the actual granulation data, and granule growth in various powder samples and operating conditions could be simulated with high accuracy. The mechanism of agitation fluidized bed granulation was also elucidated by the proposed model.

Scale-Up of Agitation Fluidized Bed Granulation. II. Effects of Scale, Air Flow Velocity and Agitator Rotational Speed on Granule Size, Size Distribution, Density and Shape.

Scale-up characteristics of agitation fluidized bed granulation using a pharmaceutical standard formulation was described. The effects of scale, air flow velocity and agitator rotational speed on granule properties such as granule mass median size, size distribution, apparent density and shape factor were investigated experimentally. Based on the results obtained, the effects of these parameters on granule growth and the mechanism of granule formation in different sized equipment were discussed.

Effects of agitator configuration and rotational speed on the production of extracellular polysaccharide by Xanthomonas cucurbitae PCSIR B-52

A strain of Xanthomonas cucurbitae PCSIR B-52, efficiently produced extracellular polysaccharide using partially deproteinized low-acid cheese whey without hydrolysis. The effects of the agitator configuration and rotational speed on the viscosity of the fermented broth and the productivity of extracellular polysaccharide based on bacterial growth were evaluated in a batch process. Agitation was performed by a six-bladed disc turbine impeller and by a similar agitator, equipped with six vertically attached stabilizing fins. Comparatively, the magnitude of the decrease in the DO tension resulting from increased viscosity of the broth was less with the stabilizing-fin agitator due to increased system damping. A drastic increase in the mechanical agitation speed after 30-h fermentation, however, increased the broth viscosity and the accumulation of polysaccharide. Moreover, the volume of the macromixing region decreased with increasing rotational speed of agitator.

Computer simulation of agitation fluidized bed granulation by a two-dimensional random addition model.

Computer simulation by a two-dimensional random addition model was proposed to elucidate the mechanisms of granule growth and compaction process of agitation fluidized bed granulation. In this paper, adhesion force by liquid bridge and separation force by agitator rotation were taken into consideration for adhesion probability of colliding granules. Effects of moisture content and agitator rotational speed on granule diameter, shape and internal structure were investigated theoretically. This simulation was applied to actual granulation, in which lactose and corn starch mixed in a weight ratio of 7:3 were granulated by an aqueous solution of hydroxypropylcellulose. Close agreement between simulated and experimental results was obtained.

Application of fuzzy logic to bed height control in agitation-fluidized bed granulation

Development of a new technique for producing spherical and well-compacted granules, and the application of fuzzy control to a fluidized bed granulation process are described. An agitation-fluidized bed, a type of fluidized bed equipped with an agitator blade, was used for granulation; bed height was controlled by fuzzy logic based on a linguistic algorithm employing IF—THEN rules, to maintain a constant bed height and impart effective agitation to the granules. It was shown that bed height control was effective in preventing defluidization and channeling, and was necessary for automatic operation. The effects of bed height and agitator rotational speed on granule properties, such as apparent density, and on granule shape were investigated. A new technique is proposed for utilizing bed height control to produce spherical and well-compacted granules, which cannot be done using conventional fluidized bed techniques.