212
edits
Difference between revisions of "Centrifugation"
Jump to navigation
Jump to search
→Solid bowl centrifugation
| Line 20: | Line 20: | ||
There is a correlation between the size and density of a particle and the speed at which the particle separates from a heterogeneous mixture, when the only force applied is gravity. The larger the size and the larger the density of the particles, the faster they separate from the mixture. By applying a larger effective gravitational force to the mixture, like a centrifuge does, the separation of the particles is accelerated. This way, in industrial and lab settings, particles that would naturally separate over a long period of time can be separated much faster. | There is a correlation between the size and density of a particle and the speed at which the particle separates from a heterogeneous mixture, when the only force applied is gravity. The larger the size and the larger the density of the particles, the faster they separate from the mixture. By applying a larger effective gravitational force to the mixture, like a centrifuge does, the separation of the particles is accelerated. This way, in industrial and lab settings, particles that would naturally separate over a long period of time can be separated much faster. | ||
The centrifugation speed is specified by the angular velocity, usually expressed as revolutions per minute (rpm), or acceleration expressed as ''g''. The conversion factor between rpm and ''g'' depends on the radius of the centrifuge rotor. The particles' settling velocity in centrifugation is a function of their size and shape, centrifugal acceleration, the volume fraction of solids present, the density difference between the particle and the liquid, and the viscosity. | The centrifugation speed is specified by the angular velocity, usually expressed as revolutions per minute (rpm), or acceleration expressed as ''g''. The conversion factor between rpm and ''g'' depends on the radius of the centrifuge rotor. The particles' settling velocity in centrifugation is a function of their size and shape, centrifugal acceleration, the volume fraction of solids present, the density difference between the particle and the liquid, and the viscosity. [[File:HD.16.088 (12523557255).jpg|alt=Picture showing basket centrifuge for the continuous collection of algae in 1966|thumb|Basket centrifuge for the continuous collection of algae in 1966]]The sedimentation of particles can be explained by Stoke's law. The equation can be used to calculate the velocity of sedimentation based on five parameters: | ||
The sedimentation of particles can be explained by Stoke's law. The equation can be used to calculate the velocity of sedimentation based on five parameters: | |||
[[File:Stokes-equation.jpg|center]] | [[File:Stokes-equation.jpg|center]] | ||
From the Stokes equation, five important behaviours of particles can be explained: | From the Stokes equation, five important behaviours of particles can be explained: | ||
| Line 33: | Line 31: | ||
=== Disc-stack centrifugation === | === Disc-stack centrifugation === | ||
Disc-stack centrifugation is used for removing suspended solids from a liquid having a lower specific gravity than the solids. The solids content of the feed is usually in the range of 0.1-10 V/V%. | Disc-stack centrifugation is used for removing suspended solids from a liquid having a lower specific gravity than the solids. The solids content of the feed is usually in the range of 0.1-10 V/V%. | ||
=== Basket centrifugation === | === Basket centrifugation === | ||