Subtopic: Fluidization of granular solids – pneumatic, bucket, screw and belt conveying
Question Statement:
In pneumatic conveying, dilute phase conveying is distinguished from dense phase conveying by having:
Options:
(A) Higher superficial air velocities ($15\text{--}30\text{ m/s}$) and lower solid-to-air mass loading ratios (lt; 15\text{ kg solids/kg air}$)
(B) Lower superficial air velocities ($2\text{--}8\text{ m/s}$) and solid mass loading ratios exceeding $100\text{ kg/kg}$
(C) Operation strictly under high hydrostatic liquid head
(D) Plug-flow conveying with complete absence of air turbulence
Answer Key:
A
Step-by-Step Solution & Explanation
Dilute (lean) phase pneumatic conveying suspends individual particles in high-velocity air streams ($15-35\text{ m/s}$) at low solid-to-air mass ratios (lt; 10-15$). Dense phase utilizes low gas velocities with grains moving in dunes or plugs at high loading ratios.