Because of these mechanical limitations, a 45 pitched blade turbine may be a more costeffective, better alternative to a hydrofoil impeller in. The impeller which is employed in mixing of the dry powder and spreading of the granulating fluid in highshear granulator normally rotates at a speed ranging from 100rpm to 500rpm. The doubledischarge volute casing is a structural constraint and is maintained for its shape. Impact of impeller design on highshear wetgranulation request. The redesign effort was geared towards meeting the design volute exit pressure while reducing the power required to operate the fan. Design of large scale mixer settlers in sx solvent. Effect of chopper presence, design and impeller speed. Less temperature increase during granulation for the twoblade impeller. The analysis of impeller shape performance was carried out with the sst shear stress transport model coupled with the streamline curvature turbulence model. The particle trajectories are nontrivial due to recirculation regions resulting from the use of mixing impellers. Rushton impellers come in four or six blade configurations and are ideal for high intensity mixing applications in which gas dispersion or solids suspension is required. We offer the widest selection of impeller designs in sizes from 2 to 36 in diameter.
Impeller design for mixing of suspensions tomas jirout, frantisek rieger czech technical university in prague, faculty of mechanical engineering, department of process engineering, technicka 4, 166 07 prague 6, czech republic abstract this paper deals with effect of impeller type on offbottom particle suspension. Introduction fluid mixer design is often thought of as the application of two engineering disciplines in sequence. Laser velocimeter taking velocity measurements of a mixing impeller. Effect of impeller design on power characteristics and. Blend times are somewhat longer than helical ribbon type impellers. Chopper presence and then chopper speed was varied during wet high shear granulation of a placebo formulation using a pma1 granulator while also varying the impeller speed. Wet granulation in laboratoryscale high shear mixers. Outlet velocity of main velocity component versus time for a310, a200, and r100 impellers. Axial flow impeller effective for low shear mixing. The rotosolver high shear mixer is a recognized industry leader, offering processors excellent performance and efficiency. Effect of impeller design on homogeneity, size and.
Chapter 5 centrifugal pump impeller vane profile the concept of impeller design and the application of inverse design for the vane profile construction are discussed in this chapter. The aim of this paper is to evaluate the 69 performance of the other impellers in high shear wet granulation in terms of extent of mixing, 70 strength of the granules formed and the size distributions. Saw tooth impeller generates heavy turbulence in the area around the impeller. Given the high performance of the baseline impeller, the redesign adopted a high. So, axial flow pump type that is high specific speed pump is chosen in this study. Morehousecowles impellers are also available for dissolvers made by other manufacturers. Tackling difficult mixing problems impeller selection this is the third article in a threepart series.
Some designs have been developed specifically to perform well in laminar flow applications and even in high shear mass transfer processes. The number of blades, and tip chord angle can be varied to meet your process requirements. A larger impeller is more efficient and this definition of hydraulic efficiency does not take this into. Fluid enters the rapidly rotating impeller along its axis and is cast out by centrifugal force along its circumference through the impeller s vane tips.
Effect of impeller speed on mechanical and dissolution properties of high shear granules article pdf available in chemical engineering journal 1642. A more detailed analysis of the effect of turbulence, distribution of shear rates in particular points of the impeller, and effects of throttling to the shear rate are under investigation lutz et at. Impact of impeller design on high shear wet granulation. A novel approach to protein recovery a high shear impeller is used for stirring and critical values for the impeller speed must be exceeded to create these stable gas liquid dispersions typically 5000 rpm.
After spraying, the mixture was wet massed for a period defined by the experimental design. Accept nothing less than genuine morehousecowles impellers. The vane profile plays a vital role to develop the streamlined flow. Request pdf impact of impeller design on highshear wetgranulation in recent decades, threeblade impellers have been wellestablished. Interchangeable stators enable precise high shear mixing according. Innovative design combines the shearing capabilities of a. Powder flow in vertical high shear mixer granulators uq espace. Close clearance agitator high speed impeller design layout of agitators. Design of a low shear hydrofoil through the use of. Defining scaling criteria in high shear granulation.
Impact of impeller design on highshear wetgranulation. Pdf effect of impeller speed on mechanical and dissolution. Obviously flow for larger crystals, shear for smaller impeller type. If a best impeller design ever exists, it must be an optimum based on impeller performance within the limits of mechanical design for impeller diameter, impeller weight mass, and critical speed. The chopper forms part of highshear granulator and is used to break down the wet lump to produce granules. Recent research indicates that hydrofoils may produce very.
It is the easiest high viscosity impeller onto which scrapers can be mounted for very difficult heat transfer applications. Conclusions electrodiffusion technique of shear rate determination can be applied even for the measurement of high shear rates. The problem of high shear in the mixer also causing the formation of very small droplets and resulting in high solvent losses was one of the most important factors affecting the choice of impeller. The impeller is a timing belt connected to the motor shaft. Impact of impeller design on highshear wet granulation. The previous articles offered guidance on impeller selection. Outlet velocity of perpendicular component versus time for a310, a200, and r100 impellers. In this design, calculated value of specific speed based on required head and capacity is 877 rpm and it is within the range of high specific speed pump that is 400 and 1200. The high solidity design is also optimum for gashandling applications.
In our article on 4 impeller types and their applications, we provided an overview on the most common types of impellers used in industrial mixing. Now well go into more detail about each impeller type and their influences on the mixing process. The first step is process design from a chemical perspective and involves the specification of the impeller configuration, speed, temperature, and pressure. The purpose of this chapter is to provide practical information about the mechanical design of mixing equipment. Pitched blade turbine curved blade turbine sometimes termed an axial flow impeller, the pitched.
A highshear mixer uses a rotating impeller or high speed rotor, or a series of such impellers or inline rotors, usually powered by an electric motor, to work the fluid, creating flow and shear. Effect of impeller design on homogeneity, size and strength. For low shear, high toptobottom pumping capacity with high gas injection. High shear impellers high shear cowles high shear statorrotor gas induction disperser parabolic disc turbine vineet. Start shape impeller is used in polymerization reactor. Advanced mixing technologies high shear mixing equipment. Closing the gap in series scale up of high shear wet granulation process using impeller power and blade design. At dispersion speeds 4,000 6,000 fpm the impeller imparts high velocity. Suggested design changes for a centrifugal pump impeller handling dredged mud a report for c. Fluid undergoes shear when one area of fluid travels with a different velocity relative to an adjacent area. Then water was sprayed onto the powder bed at 27 gmin, with the impeller and chopper speeds set at 688 and 3000 rpm, respectively. The effect of the chopper on granules from wet highshear.
Mixerdirect uses three grades for its highshear blades. The scope of this work is the comparison of a novel twoblade impeller design against a traditional threeblade impeller in high shear wet granulation. Provides equal flow at half the power of common pitched blade turbines. Hyf518 the wide blade hyflo high efficiency hydrofoil is best used on medium viscosity nre. A method is presented for redesigning a centrifugal impeller and its inlet duct. Pdf design of experimental high shear granulator for the. The granules were extensively analyzed for differences due to the chopper. Impact of impeller design on highshear wetgranulation article in powder technology 295. Agitation and mixing of fluids purpose of agitation. Impellers for every mixing process philadelphia mixing. Shear rate on centrifugal pump impeller pdf free download. Main street, palmyra, pa 17078, usa abstract hydrofoil impellers are considered to be low shear devices.
Radial flow impellers, including the rushton turbine and curved blade turbine product lines. Low shear mixing with a novel impeller design chris hibshman. Cowless high shear disc impeller designed for high speed operation creates high shear to prevent clumping, wet out powders, reduce particle size, and emulsify can be used in conjunction with an axial impeller to provide tank circulation and high shear. Oct 18, 2011 chopper presence and then chopper speed was varied during wet high shear granulation of a placebo formulation using a pma1 granulator while also varying the impeller speed. A centrifugal pump is a mechanical device designed to move a fluid by means of the transfer of rotational energy from one or more driven rotors, called impellers. Screw auger impeller a screw impeller produces effective high viscosity blending of shear sensitive polymers. For this reason, high shear impellers operated at high speed are used, yielding a high energy consumption. A number of plants operating in the metallurgical field were known to have relatively high solvent losses and an effort was made to design a mixer. Can be used in conjunction with an axial impeller to provide tank circulation and high shear. Determination of impeller hubratio and blade number.
However, if the rotational speed of the impeller is sufficiently high. Their unique design significantly reduces dissolving time. Vessel baffling may be required for optimum performance. Sc3 high efficiency impeller high efficient, low shear impeller with laser designed curved blades providing high strength and low weight which is ideal for long overhung shaft applications deep tank mixing applications require long agitator shaft extensions, as well as lower rotational speeds to avoid critical speed problems. High shear impellers are operated at high speeds and are generally used for addition of the second phase. Therefore, descriptions, equations, and nomenclature will be given in both u.
The target in the development of the twoblade impeller was to improve process robustness. The difference in efficiency within a class of impellers is a result of the impeller to tank diameter ratio. Rapid hydraulic attrition is accomplished in this zone, utilizing shear and impact energy. Impeller design of a centrifugal fan with blade optimization. Mixing impeller designed to efficiently apply all energy to produce optimal shear and direct product flow. The high shear disperser impeller is the least efficient, with a hydraulic efficiency of less than 1%. Star shaped impeller having tapered blades provides intermediate shear levels. Provides good batch movement and high shear mixing. At dispersion speeds 4,000 6,000 fpm the impeller imparts high velocity to the material.
187 1429 252 708 1039 1355 1122 1193 904 696 817 970 643 70 353 220 667 581 1140 680 1019 331 1170 153 834 613 66 1153 446 1126 430 676 818 217 627 1058 611 1232 1426