Conference Paper

Monitoring of Powder Homogeneity During Double-Cone Blending

  • Thermal Analysis Labs
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A challenge central to the Powder Metallurgy (PM) process is achieving consistent and uniform products. A crucial step in reaching this goal, is ensuring powder blending sufficiently homogenizes a mix. A challenge to powder and parts producers is creating a process that both achieves homogeneity and operates efficiently. C-Therm’s ESP technology offers a window into the blender by measuring the thermal properties of powder during processing. Powder chemistry and density have a significant impact on the thermal properties and measuring thermal effusivity repeatedly throughout processing can indicate once a stable, homogenous blend has been achieved. The authors seek to establish the usability and accuracy of measuring effusivity by monitoring multiple blend conditions and comparing results to standard industry methods such as thief sampling.

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Mixing is probably the most widely performed unit operation in pharmaceutical manufacturing, in fact, it is difficult to find a product where mixing is not involved in some stage of the process It is difficult to determine, what degree of mixing is required in particular circumstances and ways to assess the same. Blending operation could be affected by the physical properties of the materials to be mixed, blending time, rotation speed and percentage of blender capacity. Poor uniformity of the blend is obtained especially during the mixing of low dose drug with large amount of excipient. Chlorpheniramine maleate is example of one such drug. Optimization of the mixing procedure in a double cone blender for a potent drug like Chlorpheniramine maleate was carried out. For uniform mixing of the blend following parameters were optimized blending time, rotational speed and fill volume. Statistical techniques like Analysis of Variance also known as ANOVA was applied to designed experiments to determine variations within a batch, within equipment or even due to operators. It proved to be a valuable tool in maintaining product and process uniformity by comparing two or more groups. This method can be employed in pharmaceutical industry for optimization of equipments for higher production output and uniform mixing of low dose drug.
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This paper intends to review the basic theory of Near Infrared (NIR) Spectroscopy and its applications in the field of Analytical Science. It is addressed to the reader who does not have a profound knowledge of vibrational spectroscopy but wants to be introduced to the analytical potentialities of this fascinating technique and, at same time, be conscious of its limitations. Essential theory background, an outline of modern instrument design, practical aspects, and applications in a number of different fields are presented. This work does not intend to supply an intensive bibliography but refers to the most recent, significant and representative material found in the technical literature. Because this paper has been produced as consequence of the First Workshop on Near Infrared Spectroscopy, whose venue was Campinas - Brazil, as a pre-conference activity of the XI National Meeting on Analytical Chemistry (ENQA), it also depicts the state of the art of NIR spectroscopy in Brazil, pointing out the current achievements and the need to take the technology to a level consistent with this country's economical activities.
Numerical simulations of granular flow in a cylindrical vessel agitated by a four-blade impeller were performed using the discrete element method. Velocity, density, and stress profiles within the mixer displayed a periodic behavior with a fluctuation frequency equal to that of the blade rotation. Blade orientation was found to affect flow patterns and mixing kinetics. For an obtuse blade pitch orientation, a three-dimensional recirculation zone develops in-front of the blade due to formation of heaps where the blades are present. This flow pattern promotes vertical and radial mixing. No recirculation zone was observed when the blade orientation was changed to an acute blade pitch. The system's frictional characteristics are shown to strongly influence the granular behavior within the mixer. At low friction coefficients, the 3-D recirculation in front of the obtuse blade is not present reducing convective mixing. Higher friction coefficients lead to an increase in granular temperature which is associated with an increase in diffusive mixing. Normal and shear stresses were found to vary with mixer height with maximum values near the bottom plate. Additionally, a strong dependence between the magnitude of the shear stresses and the friction coefficient of the particles was found. The stress tensor characteristics indicate that the granular flow in our simulations occurs in the quasi-static regime. At the same time, the averaged pressure was found to vary linearly with bed height and could be predicted by a simple hydrostatic approximation. © 2009 American Institute of Chemical Engineers AIChE J, 2009
Granular mixing is a vital operation in food, chemical, and pharmaceutical industries. Although the tumbling blender is by far the most common device used to mix grains, surprisingly little is known about mixing or segregation in these devices. In this paper, we report the first fully three-dimensional (3D) particle dynamics simulations of granular dynamics in two standard industrial tumbling blender geometries: the double-cone and the V-blender. Simulations for both monodisperse and bidisperse (segregating) grain sizes are performed and compared with experiment. Mixing and transport patterns are studied, and we find in both tumblers that the dominant mixing mechanism, azimuthal convection, contends against the dominant bottleneck, axial dispersion. The dynamics of blending, on the other hand, differs dramatically between the two tumblers: flow in the double-cone is nearly continuous and steady, while flow in the V-blender is intermittent and consists of two very distinct processes.
Blending and Premixing of Metal Powders and Binders
  • T Chirkot
T. Chirkot, "Blending and Premixing of Metal Powders and Binders", ASM Handbook, Vol.7. pp.103-105.
Handbook of Powder Metallurgy
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H.H. Hausner, Handbook of Powder Metallurgy, Chemical Publishing Corporation, 1973, pp.68-81.
Monitoring Blending of Pharmaceutical Powders with Multipoint NIR Spectroscopy
  • O Scheilholbofer
O. Scheilholbofer at al., "Monitoring Blending of Pharmaceutical Powders with Multipoint NIR Spectroscopy," AAPS PharmSciTech, March 2013, no. 1, pp.234-244.
Effusivity Sensor Package (ESP) System for Process Monitoring and Control
  • M Emanuel
Emanuel, M., "Effusivity Sensor Package (ESP) System for Process Monitoring and Control," THERMAL CONDUCTIVITY, Vol, 28, 2006, p. 256.