Slurry

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

A slurry is a mixture of solids denser than water suspended in liquid, usually water. The most common use of slurry is as a means of transporting solids, the liquid being a carrier that is pumped on a device such as a centrifugal pump. The size of solid particles may vary from 1 micron up to hundreds of millimeters. The particles may settle below a certain transport velocity and the mixture can behave as a Newtonian or non-Newtonian fluid. Depending on the mixture, the slurry may be abrasive and/or corrosive.

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

Potato starch slurry

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
• 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
• 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
• Slurry oil, the highest boiling fraction distilled from the effluent of an FCC unit in a oil refinery. It contains large amount of catalyst, in form of sediments hence the denomination of slurry.
• A mixture of wood pulp and water used to make paper
• Manure slurry, a mixture of animal waste, organic matter, and sometimes water often 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
• A mixture of epoxy glue and glass microspheres used as a filler compound around core materials in sandwich-structured composite airframes.

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 (state by mass)

$\rho _{s}$ 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 tonnes/m^3 (t/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

$\phi _{sl}={\frac {M_{s}}{M_{sl}}}$

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

• Grout
• Slurry pipeline
• Slurry transport
• Slurry wall

External links

• Bonapace, A.C. A General Theory of the Hydraulic Transport of Solids in Full Suspension
• Ravelet, F.; Bakir, F.; Khelladi, S.; Rey, R. (2013). "Experimental study of hydraulic transport of large particles in horizontal pipes" (PDF). Experimental Thermal and Fluid Science. 45: 187–197. doi:10.1016/j.expthermflusci.2012.11.003.
• Ming, G., Ruixiang, L., Fusheng, N., Liqun, X. (2007). Hydraulic Transport of Coarse Gravel—A Laboratory Investigation Into Flow Resistance.