{"id":6903,"date":"2017-08-11T12:17:19","date_gmt":"2017-08-11T18:17:19","guid":{"rendered":"https:\/\/www.ulprospector.com\/knowledge\/?p=6903"},"modified":"2018-07-11T12:16:04","modified_gmt":"2018-07-11T18:16:04","slug":"pe-ross-agitated-vacuum-systems-drying-plastics","status":"publish","type":"post","link":"https:\/\/ulprospector.ul.com\/6903\/pe-ross-agitated-vacuum-systems-drying-plastics\/","title":{"rendered":"Equipment Feature: Ross Agitated Vacuum Systems for Drying Plastics"},"content":{"rendered":"
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Paid Content by Charles Ross & Son Company<\/h2>\n

Introduction<\/h3>\n

Agitated vacuum drying is an efficient method for removing volatile components from plastics, ceramics, metals, specialty chemicals and other products. Due to the reduced pressure within the dryer, the liquid\u2019s boiling point is lower than in atmospheric conditions and drying can proceed at lower temperatures. Vacuum drying is therefore ideal for processing heat-sensitive materials without risk of thermal degradation. It also allows manufacturers to recover costly solvents or safely dispose of any harmful volatiles removed from the closed system.<\/p>\n

The combination of deep vacuum, gentle heat and agitation achieves significantly shorter drying times compared to high heat alone. It is not uncommon for atmospheric oven and tray drying operations to run for many hours, sometimes overnight, in order to reach very low moisture levels. The impact on energy costs and production rates is tremendous.<\/p>\n

Vacuum ovens and tray dryers offer better drying rates than their atmospheric counterparts but agitated vacuum dryers are even more effective. In these systems, materials in direct contact with the dryer\u2019s heated surfaces are continuously renewed, ensuring that drying is not only fast but also uniform.<\/p>\n

Another advantage of agitated vacuum dryers is the wide range of feed forms that they can accommodate \u2013 from slurries and pastes, to granules, pellets and powders. A liquid feed material, for example, may undergo a series of relatively swift changes in physical state \u2013 from slurry to a viscous paste, and from a paste to a dry powder.<\/p>\n

The characteristics of the feed, intermediate and final dried product are all important considerations when selecting the right equipment for a particular application. Process engineers are faced with many options in today\u2019s market but the three most common and superior technologies are the Vertical Blender\/Dryer, Cylindrical Blender\/Dryer and Double Planetary Mixer<\/strong>.<\/p>\n

Vertical Blender\/Dryers<\/h3>\n

\"RossVertical Blender<\/a>\/Dryers feature a slow-turning auger screw which orbits around a conical vessel. The screw gently lifts material upward as it advances along the vessel walls. At the same time, materials at the upper most level of the batch cascade slowly back down into regions opposite the moving auger screw. The constant exchange of materials between the heated sidewalls and center of the blender accelerates the drying process.<\/p>\n

A main issue with agitated dryers is the risk of product attrition or generation of fines. This concern is well minimized on a Vertical Blender\/Dryer. The blending action it imparts is very thorough but gentle enough even for the most delicate of applications.<\/p>\n

The low impact agitation of this dryer is also ideal for highly abrasive materials which would quickly abrade horizontal systems like ribbon or paddle-type blender\/dryers. On the other hand, shear input can be increased in a Vertical Blender\/Dryer when necessary. For instance, products that contain undesired lumps benefit from the addition of a high-speed chopper assembly.<\/p>\n

During the drying cycle, hot water, oil or steam is recirculated through the vessel jacket. Due to the lower processing temperatures made possible by the vacuum environment, there is a reduced risk of creating hot spots on the vessel walls where product could bake.<\/p>\n

\"Anatomy<\/p>\n

\"Ross<\/p>\n

Advantages of Vacuum Drying
\nin a Ross Vertical Blender<\/h3>\n