Slurry

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.

Examples of slurries

Examples of slurries include:

• A mixture of cement and water to form concrete
• A mixture of thickening agent, oxidizers, and water used to form a gel explosive
• A mixture of pyroclastic rock and water known as a lahar
• A mixture of bentonite and water used to make slurry walls
• A mixture of coal waste and water known as coal slurry
• A mixture of wood pulp and water used to make paper
• A mixture of animal waste and water used as fertilizer
• A mixture of finely ground meat and water, centrifugally dewatered into meat slurry, a food product
• An abrasive substance used in chemical-mechanical polishing
• A mixture of ice crystals, freezing point depressant, and water called slurry ice
• A mixture of raw materials and water involved in the rawmill manufacture of Portland cement
• A mixture of minerals, water, and additives used in the manufacture of ceramics
• A mixture of water and food starch used to thicken puddings, sauces, and gravys.

The term slurry in farming parlance refers to a mixture of animal waste and organic matter, typically stored in a slurry pit, for a slow natural conversion into fertiliser.

Slurry calculations

Determining solids fraction

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

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

where

$\phi_{sl}$ is the solids fraction of the slurry

$\rho_{s}$ is the solids density

$\rho_{sl}$ is the slurry density

$\rho_{l}$ is the liquid density

In aqueous slurries, as is common in mineral processing, the specific gravity of the species is typically used, and since $SG_{water}$ 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.

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

$\phi_{sl}=\frac{M_{s}}{M_{sl}}$*100

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

$\phi_{sl}$ is the solids fraction of the slurry

$M_{s}$ is the mass or mass flow of solids in the sample or stream

$M_{sl}$ is the mass or mass flow of slurry in the sample or stream

$M_{l}$ is the mass or mass flow of liquid in the sample or stream

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

$\phi_{sl,v}$ is the solids fraction of the slurry on a volumetric basis

$\phi_{sl,m}$ is the solids fraction of the slurry on a mass basis

$M_{s}$ is the mass or mass flow of solids in the sample or stream

$M_{sl}$ is the mass or mass flow of slurry in the sample or stream

$M_{l}$ is the mass or mass flow of liquid in the sample or stream

$SG_{s}$ is the bulk specific gravity of the solids

See also

• Slurry pipeline
• Slurry Transport