PBS_Powder & Bulk Solids

Powder & Bulk Solids, May 2014

Issue link: http://dc.cn.ubm-us.com/i/301026

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Powder & Bulk Solids 32 TechnicalExclusive M a y 2 0 1 4 properties, such as specific grav- ity. However, we are grinding to a much higher fineness than this in steam. How then can we con- trol the classification process to produce a finer product? The solution again lies in the actual grinding medium - steam. There are two forces acting on particles in a classifier field (see figure on page 29). These are mass force and drag force. Mass force - which in the case of a dynamic classifier is a result of centrifugal force - tends to move particles to the coarse fraction – away from the classifier field and back into the grinding process. Drag force – which is a result of the fluid medium transporting the particles - tends to move particles through the classifier field to the fines fraction where they are dis- charged with the fluid medium. The gas properties of steam allow for finer particle sizes to be pro- duced by influencing these forces. As mentioned above, steam has a much lower dynamic viscosity and density than air and a higher speed of sound than air. The higher speed of sound in steam results in a significantly higher peripheral velocity of the gas flow within the classifier (at the same classifier speed). This increases the acceleration of the particles in the classifier field. For example, if the peripheral velocity increases from 200 to 300 m/s, the equivalent effect of the mass force on the particles is a relationship of the square of the difference. Therefore in this example the mass force on the particles is increased by a factor of 2.25, moving the cut size to a finer range by that same factor. The reduced dynamic viscos- ity reduces the drag force on the particle. Drag force tends to move the particle to the fines fraction. Reducing the drag force lessens the tendency to drag coarser par- ticles to the fine fraction, also moving the cut size to the finer range. Combined, these two fac- tors reduce the median particle size of the product by a factor of 0.3 times finer or more. This means – if your air jet mill is ca- pable of making your product to a fineness of 1.0 µm, it is now pos- sible to make that same product to a fineness of 0.3 µm or even finer using a steam fluidized bed jet mill. The forces acting on the particles are really quite simple – but the result is dramatic. The use of dry grinding technology to reach particle sizes below 200 nm opens a whole new world of op- portunities for businesses seeking to expand their product offerings. Steam Jet Milling Is Greener Steam is the oldest utilization of thermal energy known to hu- mankind, and is the driving force of almost all energy production worldwide. In 2012, about 87% of the electrical energy in the U.S. was generated by large power plants (coal, gas, and nuclear). Large power plants operate on average with a degree of primary energy efficiency of around 40%. Transformation and line losses cause an additional loss of about 10%. Therefore when the electric- ity arrives at the plant, it has a degree of efficiency (compared to the primary energy) of about 36%. When you factor in com- pressor efficiency, which is about 45%, the overall energy is only about 16% from primary energy Your Answer To Successful Solids Processing Eagle Group LTD, Greenville Michigan (616) 754-7777 www.eagle group ltd.com Eagle Group LTD Mention This Ad For New Customer Discount Contact Eagle Contract Installation Division for all Process Equipment and Storage Tank Applications. Contract Installation Service for All Your Needs Bulk Bag Unloading Complete dust free bag discharge to down stream process equipment. Container Dischargers s 'AYLORD "OX AND $RUM $UMPERS s )NNOVATIVE DESIGNS TO TRANSFER MATERIALS from containers to process equipment Mixing & Blending -IXINGWEIGHINGOFDRYBULKPOWDERSANDGRANUALS Storage Tanks, Surge Bins & Portable Hoppers $ESIGNMANUFACTUREANDINSTALLATIONOFDRYBULKMATERIALSTORAGETANKS Accurate Inventory Control s4ANKSANDBINSMOUNTED on weigh scale modules s%XISTINGTANKSRETROlTTED on Eagle Load Ring ™ WEIGHTECHNOLOGY , Blending Silo 85,000 lbs DustTight Hi-Lift and Seal Dumper Side Load Hi-Lift Dumper Lift and Seal Dumper 20,000 lbs Magnum Mixer Vertical Ribbon Blender Field Welded Tanks Bolted Tanks Shop Welded Tanks From Concept to Completion Cyclonaire gives you experienced system design – using unequalled equipment backed by exceptional personal service. We engineer and manufacture material handling systems specializing in pneumatic conveying. Cyclonaire provides expert start-up assistance plus ongoing maintenance support. ©2007B Cyclonaire Corporation CYCA-2374 ® 888-593-6247 Multiple patents issued and pending Conveying Solutions – contact us for information on these and other Cyclonaire components. Bulk Bag Unloader VibraPad™ Aerator Rotary Airlock Feeder Diverter Valve CB Series Blender CycloLift™ Line Injector Visit us at the Powder Show booth #2506 ES426755_PB1405_032.pgs 04.22.2014 05:06 UBM black yellow magenta cyan

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