What type of dryers use hot gases passed upward through wet solids at a velocity high enough to lift the solids and cause them to act like a fluid?
A. Flash dryers
B. Fluid bed dryers
C. Fixed bed dryers
D. Rotary dryers
A. Incorrect. Flash dryers are devices that force hot gas (usually air or nitrogen) through a vertical or horizontal flash tube, causing the moist solids to become suspended.
B. Correct. A fluid bed dryer uses hot gases (usually air) passed upward through wet solids at a velocity high enough to lift the solids and cause them to act like a fluid.
C. Incorrect. Fixed bed dryers are devices that use desiccants (substances that attract and adsorb moisture) to remove moisture from a process stream.
D. Incorrect. Rotary dryers are devices composed of large, rotating, cylindrical tubes that reduce the moisture content of a material by bringing it into direct contact with a heated gas.
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