ch18 - Exercise 18.1 Subject: Selection of dryer for...

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Unformatted text preview: Exercise 18.1 Subject: Selection of dryer for removal of surface moisture from 0.5 mm crystals of NaCl without breakage. Find: Suitable type continuous, direct-heat dryers. Highest gas feed temperature. Analysis: Applicable dryers are tunnel dryer or belt dryer . Inlet gas temperature can be high, to say 1400 o F, because of the high melting point of NaCl. Exercise 18.2 Subject: Batch drying of 100 kg/h of a toxic, temperature-sensitive material of 350 mm size. Find: Suitable dryers. Analysis: Select a rotating, double-cone vacuum dryer . Exercise 18.3 Subject: Drying of a thin, milk-like liquid to produce a powder Find: Suitable continuous, direct-heat dryer that will restrict temperature to less than 200 o F. Analysis: Select a spray dryer . Exercise 18.4 Subject: Selection of dryers from conditions of the feed, temperature sensitivity, and form of the dried product Find: Suitable batch or continuous dryers for different cases. Analysis: (a) A temperature-insensitive paste that must be maintained in slab form. Select a batch tray dryer or a continuous belt dryer. (b) A temperature-insensitive paste that can be extruded. Select a continuous through-circulation belt or band dryer, or a batch, agitated pan dryer. (c) A temperature-insensitive slurry. Select a continuous spray dryer. (d) A thin liquid from which flakes are to be produced. Select a continuous drum dryer . (e) Pieces of lumber. Select a batch closed container with wood stacked for good flow of air by kiln drying in a chamber with temperature and humidity control. (f) Pieces of pottery. Select a continuous tunnel dryer . (g) Temperature-insensitive inorganic crystals, where particle size is to be maintained and only surface moisture is to be removed. Select a tunnel dryer, a belt or band dryer, or an indirect-heat, steam-tube rotary dryer. (h) Orange juice to produce a powder. Select a batch freeze dryer. Exercise 18.5 Subject: Solar drying Find: Advantages and disadvantages of solar drying for organic materials. Other applicable dryers for organic materials and for continuously drying beans. Analysis: Advantage of solar drying is no cost for energy. Disadvantage of solar drying is long drying time, variability of weather, lack of control. Other dryers suitable for organic materials are tunnel dryer and belt or band dryer. For the continuous drying of beans, can use steam-tube rotary dryer, roto-louvre dryer, screw conveyor dryer, through-circulation or band dryer, and fluidized-bed dryer. Might also consider a column dryer with solids moving down by gravity with countercurrent flow of warm air. Exercise 18.6 Subject: Fluidized-bed dryer Find: Advantages of fluidized-bed dryer for vegetables, including potato granules, peas, diced carrots, and onion flakes....
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This note was uploaded on 04/27/2011 for the course CHEM 101 taught by Professor Suh during the Spring '11 term at University of Toronto- Toronto.

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ch18 - Exercise 18.1 Subject: Selection of dryer for...

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