Gas-Enhanced Ultra-High Shear Mixing: A Concept and Applications
- PDF / 2,177,984 Bytes
- 10 Pages / 593.972 x 792 pts Page_size
- 17 Downloads / 221 Views
N
THE physical treatment of liquids and liquid-based dispersions is widely used across processing industries, including chemical, cosmetic, food, pharmaceutical, adhesives, and plastics, where homogenous liquids or dispersions of solid particles are commonly needed during manufacturing of various products, such as paint, ink, coatings, shampoo, beverages, or polishing media. Thus, the processing cycle requires steps of homogenization, blending, dissolving, emulsification, deagglomeration, and particle refining.[1] In metallurgy, external stress applied to a molten metal initiates flow within it resulting in macroscopic and microscopic mass transport that assists a distribution of heat and chemical constituents, therefore affecting solidification. While the conventional treatments were limited to melt degassing and purification, the novel approach, being recently of great interest, includes a variety of physical often combined with chemical treatments of molten or semi-molten metallic alloys influencing their solidification and improving properties of castings.[2] The engineering applications include control of casting integrity, grain refinement, refining coarse intermetallic compounds, generation thixotropic morphologies for semisolid processing, mixing immiscible metals, or creating metal matrix composites.[3]
The attraction forces of physical and chemical nature that held individual particles together have to be overcome during separation. Therefore, to create stable emulsions and fine dispersions, a very intensive shear is required, especially for higher viscosity liquids, such as polymers or resins. Different technologies are commonly used for liquid mixing and dispersing of powders into liquids including high-pressure homogenizers, agitator bead mills, impinging jet mills, and rotor–stator mixers.[4] For high-viscosity fluids, the co-axial or multi-shaft agitators are recommended with stator–rotor and often pumps enhancing flow through inline homogenizers. Although it is generally believed that all molten metals behave as Newtonian liquids, due to their high melting temperature and corrosive nature, not all designs used by other industries are transferable to metallurgical applications. The subject of this paper is the novel concept of treatment of liquids or liquid–solid mixtures, exploring a combination of gas injection with an ultra-high shear mixing. In addition to background information, design details, and a prototype apparatus description, major benefits of synergy between gas injection and ultra-high shearing are provided through experiments with water– air system.
II. FRANK CZERWINSKI and GABRIEL BIRSAN are with the CanmetMATERIALS, Natural Resources Canada, 183 Longwood Road South, Hamilton, ON L8P 0A1, Canada. Contact e-mail: [email protected] Manuscript submitted August 30, 2016. Article published online December 27, 2016. METALLURGICAL AND MATERIALS TRANSACTIONS B
ROTOR–STATOR TECHNOLOGY FOR HIGH-SPEED HIGH SHEAR MIXING
The ultra-high shear mixers are designed for applications that are beyond capabi
Data Loading...
