Skip to main content
SpringerLink
Log in

Handling of Powders

  • Chapter
The Dynamics of Fine Powders

Part of the book series: Elsevier Handling and Processing of Solids Series ((HPSS))

  • 162 Accesses

Abstract

In Chapter 1 it was mentioned that during handling of fine powders their mobility is increased by reshuffling so that extra gas is encapsulated and the powder can expand. The increased mobility of the powder strongly favours the desired action of the processing such as mixing and milling of the powder. In most cases the encapsulation of gas is caused by mechanical stirring of the powder in the process apparatus. As a consequence of the continuous action of gravity a pressure gradient arises which forces the entrapped gas to escape. Hence, the degree of expansion obtained depends strongly on the permeability of the powder and on the gas viscosity. In order to show the effect of the entrapped gas on the powder behaviour we did some experiments, described below.

This is a preview of subscription content, log in via an institution to check access.

Access this chapter

Log in via an institution
Chapter
USD 29.95
Price excludes VAT (USA)
  • Available as PDF
  • Read on any device
  • Instant download
  • Own it forever
eBook
USD 79.99
Price excludes VAT (USA)
  • Available as PDF
  • Read on any device
  • Instant download
  • Own it forever
Hardcover Book
USD 99.99
Price excludes VAT (USA)
  • Durable hardcover edition
  • Dispatched in 3 to 5 business days
  • Free shipping worldwide - see info

Tax calculation will be finalised at checkout

Purchases are for personal use only

Institutional subscriptions

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

Abbreviations

bij :

Portion of the jth interval which falls by milling in the ith interval (—)

c1 :

Dimensionless constant (—)

C:

Composition of powder mix (—)

dp :

Particle size (m)

D:

Dispersion coefficient (m2 s −1)

E:

Elasticity modulus (N m −2)

Fo:

Fourier number (—)

g:

Gravitational constant (m s −2)

g*:

Resultant of gravitation and centrifugal acceleration (m s −2)

l:

Thickness of powder layer in the drum (m)

L:

Part of the wall of the mill covered by powder, or length of the mixing drum (m)

n:

Rotation speed (rpm) (s −1)

N:

Number of balls inside the drum (—)

NF :

Fluidization number (—)

Ng :

Particle-gas interaction number (—)

p:

Pressure of gas (N m −2)

qci :

Amount of powder of the ith interval milled by one cascading ball collision (—)

qfi :

Amount of powder of the ith interval milled by one falling ball collision (—)

Q:

Amount of powder inside the drum (—)

R:

Radius of the ball mill (m)

Rk :

Radius of the milling balls (m)

s:

Spread of the slip velocity of balls

Si :

Specific rate of breakage of powder of the ith interval (s −1)

t:

Mixing time (s)

td :

Time to discharge the upper hopper of the sand-glass (s)

Uc :

Velocity of a continuity wave (m s −1)

vs :

Slip velocity of powder with gas (m s −1)

Va :

Circumferential velocity of the mill (m s −1)

Vs :

Slip velocity of balls (m s −1)

wi :

Weight fraction in the ith interval (—)

x:

Length coordinate (m)

α:

Dynamic angle of repose (—)

ε:

Porosity (—)

µ:

Gas viscosity (N s m −2)

ρd :

Density of the solids (kg m −3)

σci :

= qci/Qwi(—)

σfi :

= qfi/Qwi(—)

References

  • Austin, L.G. (1971). A review. Introduction to the mathematical description of grinding as a rate process. Powder Team., 5, 1.

    Article  Google Scholar 

  • Austin, L.G. (1973). Understanding ball mill sizing. Ind. Eng. Chem. Process Design and Fundamentals, 12, 121.

    Article  CAS  Google Scholar 

  • Austin, L.G. & Bagga, P. (1981). An analysis of fine dry grinding in ball mills. Powder Techn., 28, 83.

    Article  Google Scholar 

  • Cottaar, W. & Rietema, K. (1984). The effect of interstitial gas on milling. Part I. Powder Techn., 38, 183.

    Article  CAS  Google Scholar 

  • Cottaar, W. & Rietema, K. (1985). The effect of interstitial gas on milling. Part II. Powder Techn., 43, 189.

    Article  CAS  Google Scholar 

  • Cottaar, W. & Rietema, K. (1986). The effect of interstitial gas on milling. Part III. Correlation between ball and powder behaviour and the milling characteristics. Powder Techn., 46, 89.

    Article  CAS  Google Scholar 

  • Cottaar, W., Heynen, A. & Rietema, K. (1987). The effect of interstitial gas on mixing of fine powders. Powder Techn., 46, 219.

    Article  Google Scholar 

  • Gupta, V.K., Zouiet, H. & Hodouin, D. (1985). The effect of ball and mill diameters on grinding rate parameters in dry grinding operation. Powder Techn., 42, 199.

    Article  Google Scholar 

  • Rietema, K. & Cottaar, W. (1987). The effect of interstitial and circumambient gas in fine powders on the scaling up of powder handling apparatus as illustrated by ball mill operation. Powder Techn., 50, 147.

    Article  CAS  Google Scholar 

Download references

Author information

Authors and Affiliations

  1. Europlaan 16, 5691, En Son, The Netherlands

    K. Rietema

Authors
  1. K. Rietema
    View author publications

    You can also search for this author in PubMed Google Scholar

Rights and permissions

Reprints and permissions

Copyright information

© 1991 Elsevier Science Publishers Ltd

About this chapter

Cite this chapter

Rietema, K. (1991). Handling of Powders. In: The Dynamics of Fine Powders. Elsevier Handling and Processing of Solids Series. Springer, Dordrecht. https://doi.org/10.1007/978-94-011-3672-3_11

Download citation

  • DOI: https://doi.org/10.1007/978-94-011-3672-3_11

  • Publisher Name: Springer, Dordrecht

  • Print ISBN: 978-1-85166-594-5

  • Online ISBN: 978-94-011-3672-3

  • eBook Packages: Springer Book Archive

Publish with us

Policies and ethics

Search

Navigation