Gravity Conveyor With Air Fluidize

Gravity Conveyor with Air Fluidize Sometime we called “Air Slide” or “Air Activated Gravity Conveyor” that solid will be transferred under the effect of fluid means the solid become like a fluid (fluidize).

 ρ  p = Particle density (kg/m3)  ρ  f  = Fluid density, gas density (kg/m3)

d = Average particle size ( μ m ) A Type when material is not C type

22500

d  =

 ρ  p

The flow inside duct is just only some part, it was not fully which can be applied the design concept of flow in open channel. The properly material which can be applied with gravity conveyor is material type B or A base on Geldart’s concept.

−  ρ  f 

μ m

B Type when material is not C or A

d  < 2

10 9  ρ  p

−  ρ  f 

(μ m )2

D Type when material is not C, A and B

Geldart’s concept (Fluidization)

d  > 2

Geldart separate material 4 type depend on size and density.

 ρ  p

A Type (Aeration) like dust, low density, <1400 kg/m3 B Type (Sandy) a bit volume expansion (but lower than A type) C Type (Cohesive) material can stick itself, when material moving may possible make the vertical channel (Square  Nose Bubble) D Type (Spoutable Powder) big size and high density

Determine type of solid C Type when  ρ  p

− ρ  f  > 1000kg / m 3

or   ρ  p Where

and d  < 20 μ m

− ρ  f  > 1000kg / m 3

and d  <

20000  ρ  p

−  ρ  f 

10 9

μ m

−  ρ  f 

(μ m )2

Properly velocity of fluid (for fluidized) Generally, for design, fluid velocity should around 1.5-5 times of minimum velocity which can handle solid like a fluid (fluidized).

v = 1.5U mf  Where Umf  = minimum fluidized velocity (mm/sec) −4

U mf  = 8 x10  x

2

d v g η 

x( ρ  p − ρ  f  )

Where dv = Average particle size (m) 2 g = Specific gravity (9.81 m/s ) η = fluid viscosity (Pa.sec)

Width of transportation equipment Width of equipment is the major factor for transportation.

⎛ m s  ⎞ ⎟ b ≈ 1.6⎜ ⎜  ρ  ⎟ ⎝   p  ⎠

0.5

Where ms = Mass Flow Rate (kg/sec)  b = The width of transportation equipment

Height of fluid which ready to be fluidize  Normally, it was very difficult to estimate this value  because it depends so many factor such solid flow rate, angle, air flow e.g.

 H  =

ms

(0.5 ρ  bg ) ) 0.5

 B

Where ρB= fluidized density (kg/m3) B

 B

ε

=

 p

(1 − ε  )

= Void of air 

Pressure drop across bed Pressure drop across bed while fluid is following.

ΔPbed  =

 B

gH 

Overall pressure drop of fluid which use for transportation The estimation of overall pressure drop of air which use for fluidization is;

ΔP ≈ 1.5 ρ  B gH