Slurries

For the settlement in the North West province of South Africa, see Slurry, North West.

A slurry is a thin sloppy mud or cement or, in extended use, any fluid mixture of a pulverized solid with a liquid (usually water), often used as a convenient way of handling solids in bulk.[1] Slurries behave in some ways like thick fluids, flowing under gravity but are also capable of being pumped if not too thick.

Examples

Examples of slurries include:

  • Cement slurry, a mixture of cement, water, and assorted dry and liquid additives used in the petroleum and other industries[2]
  • Soil/cement slurry, also called Controlled Low-Strength Material (CLSM), flowable fill, controlled density fill, flowable mortar, plastic soil-cement, K-Krete, and other names[3]
  • A mixture of thickening agent, oxidizers, and water used to form a gel explosive
  • A mixture of pyroclastic material, rocky debris, and water produced in a volcanic eruption and known as a lahar
  • A mixture of bentonite and water used to make slurry walls
  • Coal slurry, a mixture of coal waste and water, or crushed coal and water[4]
  • A mixture of wood pulp and water used to make paper
  • A mixture of animal waste, organic matter, and sometimes water known simply as "slurry" in agricultural use, used as fertilizer after ageing in a slurry pit
  • Meat slurry, a mixture of finely ground meat and water, centrifugally dewatered and used as food
  • An abrasive substance used in chemical-mechanical polishing
  • Slurry ice, a mixture of ice crystals, freezing point depressant, and water
  • 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 bolus of chewed food mixed with saliva

Calculations

Determining solids fraction

To determine the percent solids (or solids fraction) of a slurry from the density of the slurry, solids and liquid[5]

\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 (state by volume)
\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

References

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