Slurry

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A slurry composed of glass beads in silicone oil flowing down an inclined plane.

A slurry is, in general, a thick suspension of solids in a liquid.

Contents

[edit] Examples of slurries

Examples of slurries include:

  • A mixture of water and cement to form concrete
  • A mixture of water, gelling agent, and oxidizers used as an explosive
  • A mixture of water and bentonite used to make slurry walls
  • A mixture of wood pulp and water used to make paper
  • A mixture of water and animal waste used as fertilizer
  • Meat slurry, a food product
  • An abrasive substance used in chemical-mechanical polishing, a semiconductor manufacturing process
  • A mixture of ice crystals, water and freezing point depressant, called slurry ice
  • A wet-process cement rawmix
  • A mixture of water, ceramic powder and various additives (e.g., dispersant) used in the processing of ceramics.
  • A mixture of water and a starch (normally corn starch) used to thicken liquids to make a culinary sauce; usually for a clear sauce, as the product will be translucent. It is comparable to and often the same as a gravy.

[edit] Slurry calculations

[edit] Determining solids fraction

To determine the percent solids (or solids fraction) of a slurry from the density of the slurry, solids and liquid[1]

\phi_{sl}=\frac{\rho_{s}(\rho_{sl} - \rho_{l})}{\rho_{sl}(\rho_{s} - \rho_{l})}

where

φsl is the solids fraction of the slurry
ρs is the solids density
ρsl is the slurry density
ρl is the liquid density

In aqueous slurries, as is common in mineral processing, the specific gravity of the species is typically used, and since SGwater is taken to be 1, this relation is typically written:

\phi_{sl}=\frac{\rho_{s}(\rho_{sl} - 1)}{\rho_{sl}(\rho_{s} - 1)}

even though specific gravity with units tons/m^3 is used instead of the SI density unit, kg/m^3.

[edit] Liquid mass from mass fraction of solids

To determine the mass of liquid in a sample given the mass of solids and the mass fraction: By definition

\phi_{sl}=\frac{M_{s}}{M_{sl}}

therefore

M_{sl}=\frac{M_{s}}{\phi_{sl}}

and

M_{s}+M_{l}=\frac{M_{s}}{\phi_{sl}}

then

M_{l}=\frac{M_{s}}{\phi_{sl}}-M_{s}

and therefore

M_{l}=\frac{1-\phi_{sl}}{\phi_{sl}}M_{s}

where

φsl is the solids fraction of the slurry
Ms is the mass or mass flow of solids in the sample or stream
Msl is the mass or mass flow of slurry in the sample or stream
Ml is the mass or mass flow of liquid in the sample or stream

[edit] Volumetric fraction from mass fraction

\phi_{sl,m}=\frac{M_{s}}{M_{sl}}

Equivalently

\phi_{sl,v}=\frac{V_{s}}{V_{sl}}

and in a minerals processing context where the specific gravity of the liquid (water) is taken to be one:

\phi_{sl,v}=\frac{\frac{M_{s}}{SG_{s}}}{\frac{M_{s}}{SG_{s}}+\frac{M_{l}}{1}}

So

\phi_{sl,v}=\frac{M_{s}}{M_{s}+M_{l}SG_{s}}

and

\phi_{sl,v}=\frac{1}{1+\frac{M_{l}SG_{s}}{M_{s}}}

Then combining with the first equation:

\phi_{sl,v}=\frac{1}{1+\frac{M_{l}SG_{s}}{\phi_{sl,m}M_{s}}\frac{M_{s}}{M_{s}+M_{l}}}

So

\phi_{sl,v}=\frac{1}{1+\frac{SG_{s}}{\phi_{sl,m}}\frac{M_{l}}{M_{s}+M_{l}}}

Then since

\phi_{sl,m}=\frac{M_{s}}{M_{s}+M_{l}}=1-\frac{M_{l}}{M_{s}+M_{l}}

we conclude that

\phi_{sl,v}=\frac{1}{1+SG_{s}(\frac{1}{\phi_{sl,m}}-1)}

where

φsl,v is the solids fraction of the slurry on a volumetric basis
φsl,m is the solids fraction of the slurry on a mass basis
Ms is the mass or mass flow of solids in the sample or stream
Msl is the mass or mass flow of slurry in the sample or stream
Ml is the mass or mass flow of liquid in the sample or stream
SGs is the bulk specific gravity of the solids

[edit] See also

Search Wiktionary Look up slurry in Wiktionary, the free dictionary.

[edit] References

  1. ^ Wills, B.A. and Napier-Munn, T.J, Wills' Mineral Processing Technology: an introduction to the practical aspects of ore treatment and mineral recovery, ISBN 978-0-7506-4450-1, Seventh Edition (2006), Elsevier, Great Britain
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