Storage of Solids in Silos and Bins

2. topic: storage of particulate solid’s:
 Presented by :
Muhammad Haris Minhas
12063123-037
University Of Gujrat Chemical
Engineering Department
Waseem Ahmad
12063123-001
 Presented to:
Engr. Waqas Qamar

3. Storage of Solids
There are two types of storage
 Outdoor storage
 Confined storage

4. Outdoor storage:
 Coarse solid are stored outside in large piles ,when hundred or
thousand of ton of material are involved.
 Out storage can be effected by environmental problem such as
dusting or leaching of soluble material from the piles.
 Dusting is control by covering the piles
 Leaching can be control by covering or by locating it in a shallow
basin .

5. Outdoor storage:
Coal storage Gravel storage

6. Confined storage.
 Solids that are valuable and can be effected by the environment in
out door piles are stored in Bin’s, Hopper and Silo’s
Silo’s Bin

7. Silos
 Silo is a storage structure for storing
bulk materials like storage of
grain, coal, cement, food products
etc
 Silo is tall and relatively small in
diameter which is used for bin
storage.

8. TYPES OF SILO
 Cement storage silos
 Tower silo
 Low-oxygen tower silos
 Bag silos

9. Cement storage silos
 There are different types of cement silos such as the low-level mobile
silo and the static upright cement silo.
 The low-level silos are fully mobile with capacities from 10 to 75 tons.
 The static upright silos have capacities from 20 to 80 tons.
 These are considered a low-maintenance option .

10. Fig …
Low level mobile
silo’s
Static upright
cement silo’s

11. Tower silo
 Tower silos are cylindrical structures, typically
10 to 90 ft in diameter and 30 to 275 ft in
height.
 Silos can be loaded and unloaded by using
rail cars or conveyors.
 Silos storing grain, cement and woodchips.

12. Bag silos
 Bag silos are heavy plastic tubes, usually around 8 to 12 ft in diameter,
and of variable length as required for the amount of material to be
stored.
 They can be used as a temporary measure when growth or harvest
conditions require more space

13. Low-oxygen tower silos
 Low-oxygen silos are designed to keep the
contents in a low-oxygen atmosphere at all
times, to keep the fermented contents in a
high quality state, and to prevent mold and
decay.
 Low-oxygen silos are only opened directly to
the atmosphere during the loading.

14. Bin Storage:
 A bin is typically much shorter than a silo, and is typically used
for holding dry matter such as concrete or grain.
 Bins may be round or square,
 Round bins tend to empty more easily due to lake of corners,
 The stored material may be powdered, as seed kernels, or as
cob corn.

15. Fig:
Square Bins. Round Bins

16. Hoppers
 Hopper is small vessel with a sloping bottom for a temporary
storage before feeding solids to a process.
 It is filled at the top and Discharge is from the base,
 Hopper can be vibrated externally to encourage flow
 Angle of sloping sides  angle of repose.
Pile of bulk
solids


17. Fig of Hopper:

18. Mass and Core flow from a Hopper
 Core flow occurs
when only material in
the centre flows from
the hopper
All the powder in the
hopper is in motion
with Mass flow

19. Intermediate Bulk Container
 An IBC is a mobile hopper moved by pallet/fork truck
 Volume usually about 1m3, stainless steel
 Can store material that is waiting for further processing
 Filled at top and placed on an IBC discharge station for
emptying.

20. Pressure in bins & silos:
 The pressure of solid exerted on the wall at any point is less than predicted
from head of material above that point.
 The effect of friction force.
 The actual pressure of the solid depends on
value of K
coefficient of friction
way the solid are placed in the vessel.
 Effect of height of solid
 Arch breaker

21. Flow out of Bins:
 Flow through a side
 Flow through a bottom
Factor affecting the flow:
 Steepness of the wall
 Coefficient friction between solid and wall.
 Discharge opening
 Property of solid

22. KVJ
Flow Modes
 Mass Flow:
All the material is in motion, but not necessarily at the same
velocity
 Tunnel Flow :
Centrally moving core, dead or non-moving annular
region

23. KVJ
Mass Flow
Material in
motion
along the walls
Does not imply plug
flow with equal
velocity

24. Mass Flow Advantages:
 Flow is more consistent
 Stress field is more predictable
 Full bin capacity is utilized
 First in/first out principle

25. Mass flow disadvantages:
 wall wear is higher (esp. for abrasives)
 Higher stresses on walls
 More height is required

26. Tunnel Flow
“Dead” or non-flowing
region
KVJ 3/17/00

27. Tunnel flow Disadvantage:
 Speed of Flow
 Flushing
 Inadequate Emptying
Time Consolidation - Caking
Flushing: Uncontrolled flow from a hopper due to powder being in
an aerated state. Occurs only in fine solids.

28. Inadequate emptying
Usually occurs in funnel flow where the
cone angle is insufficient to allow self
draining of the bulk solid.
Remaining bulk solid

29. Time Consolidation - Caking
 Many powders will tend to cake as a function of time, humidity,
pressure, temperature.
 Particularly a problem for funnel flow which are infrequently
emptied completely.

30. What about angle of repose?

Pile of bulk solids

 Do not use angle of repose to design the angle on a
hopper

31. Characteristics to be considered before selection
 Wall Friction Testing
 Powder Shear Testing - measures both powder internal friction and
cohesion
 Compressibility/Permeability

32. Testing Considerations
Must consider the following variables
 time
 Temperature
 Humidity
 process conditions