EXPERIMENT 1.3 : POWDER FLOW - HOPPER

OBJECTIVE:

To evaluate the powder flow of various sand with different particles size using hoppers with different dimension with different orifices. 

INTRODUCTION:

Powder that discharges freely from the hopper is said to undergo mass flow. This means that particles that first in will be the first to come out from the hopper. Powder that do not discharged freely, due to high adhesion or cohesion or hopper angles that are too shallow may undergo funnel flow. Particles which the last enter the hopper are the first to leave hopper forming ‘pipe’, ‘rat-hole’ or ‘funnel’.

In general, most powders will discharge by mass flow from hoppers with θ angles of about 20˚ , and by funnel flow from hoppers with angles of approximately 50˚.

METHODOLOGY:

i) Apparatus and Materials 

1. hopper with different sizes
2. stopwatch
3. different sand samples

ii) Procedures

       I.          Four to five of different sizes of hopper were prepared.

     II.         Various particle sizes of sand samples were prepared.

   III.         The hopper’s orifice was closed and 100g (or any suitable weights) of sand was placed inside
the hopper.

  IV.         The orifice was opened and the sand was allowed to flow out.

    V.          The time required for all the sand to flow out of the hopper completely was measured. The  hopper should not be shaken or tapped. The flow of sand was allowed to happen naturally.

  VI.         The above steps were repeated with different sand or hopper sizes.

RESULTS:

QUESTIONS:

1) What are the factors that influence the flow of a powder?

Factors that influence powder flow are particle shape or texture which need to be spherical. The surface texture must be smooth as rough texture will be more cohesive. Next is surface forces which is reduce the electrostatic forces by altering process condition that will reduce surface friction. Furthermore, moisture content also need to be low as moisture will increase bulk density and reduce porosity. Addition of glidants as flow activator also will influence powder flow as it will reduces adhesion and cohesion. Lastly, process condition of powder flow also influence powder flow.

2) Based on the experiment, which sand and hopper size resulted in the best powder flow?

Based on the experiment,  sand with 850 micrometer with hopper size of 16 mm resulted in best powder flow. This is because, bigger size of sand will show better flow rate than smaller size of sand

CONCLUSION:

The larger the diameter, the faster the powder will flow

Small size powder will have higher cohesion

The bigger the opening of hopper, the more easier the powder flow.

REFERENCES:

1. http://www.wiley.com/legacy/wileychi/rhodestechnology2e/hopper_flow.html

2. http://www.chemicalprocessing.com/assets/Media/MediaManager/fine-powder-flow.pdf