Basic Separation Techniques and Sedimentation

Separation of solid particles suspended in a liquid using gravity.

The process of increasing the concentration of suspended solids in a liquid by sedimentation.

The process of removing suspended solids from a liquid to produce a clear effluent.

A zone in sedimentation where the concentration of suspended solids gradually increases.

The point in sedimentation where the settling rate decreases and both zones of constant and variable composition disappear.

A type of sedimentation where the solids are suspended at a constant concentration throughout the process.

A type of sedimentation where the solids are suspended at a varying concentration throughout the process.

The rate at which particles settle in a liquid during sedimentation.

The process of separating a mixture into its individual components, requiring energy input.

A natural process where chemical species combine without requiring energy.

Creating a second, immiscible phase to separate components based on differences in properties like boiling points (distillation) or melting points (crystallization).

Adding a fluid phase that selectively absorbs or extracts certain components, taking advantage of different solubilities (like liquid-liquid extraction or absorption).

Using a barrier, commonly a membrane, that allows selective passage of components based on their permeabilities (examples: osmosis, filtration, pervaporation).

Involving a solid agent, like porous particles, to separate components based on their adsorbability (examples: adsorption, chromatography, ion exchange).

Exploiting differences in volatility (e.g., vapor pressure) to separate components through evaporation and condensation.

Separating components based on differences in melting point. This involves crystallizing out a desired component from a liquid mixture.

A settling process where the interface between the clear liquid and suspension moves downwards at a constant rate, forming a layer of sediment at the bottom. The rate decreases as the interface approaches the sediment, reaching a critical settling point where the sediment and clear liquid directly interface. Further sedimentation occurs through sediment consolidation.

A settling process where the sedimentation rate decreases progressively throughout the operation. There is no zone of constant composition, and the zone of increasing concentration extends from the top interface to the sediment layer.

The speed at which individual particles settle in a suspension. This is affected by factors like particle size, density, and viscosity of the liquid.

Factors that influence the rate of sedimentation. These include the height of the suspension, diameter of the container, and volumetric concentration of solids.

The rate at which particles settle in a fluid is influenced by the concentration of particles in the suspension. In concentrated suspensions, particles interact with each other, affecting the settling rate.

In a concentrated suspension, larger particles settle faster than smaller ones, effectively increasing the density and viscosity of the fluid surrounding the smaller particles.

In a concentrated suspension, the fluid displacement caused by settling particles creates an upward flow that counteracts the downward settling velocity.

The flow patterns around settling particles in a concentrated suspension are altered due to the close proximity of particles, which affects the drag forces they experience.

The terminal velocity of a particle is the constant velocity reached when the gravitational force and drag force balance.

The drag force acting on a spherical particle is proportional to the projected area of the particle, the square of its velocity, and the fluid density. The drag coefficient accounts for the shape and size of the particle as well as the flow conditions around it.

The drag coefficient is a dimensionless parameter that relates the drag force to the projected area, velocity, and fluid density of the particle. It is influenced by factors such as the rotation of the particle, collisions with other particles, and Brownian motion.

The random motion of particles in a fluid, due to collisions with surrounding molecules, is called Brownian motion. It can affect the settling rate of very small particles.

A dimensionless number that describes the ratio of inertial forces to viscous forces in a fluid flow. It is widely used to predict flow patterns in different fluid flow situations, such as around a sphere or in a pipe.

A relationship that describes the drag force on a sphere moving through a viscous fluid at low Reynolds numbers. It states that the drag force is proportional to the velocity of the sphere, the viscosity of the fluid, and the diameter of the sphere.

A parameter used to categorize the different regimes of particle settling. It depends on the Reynolds number and the particle diameter.

The region where the drag coefficient is almost independent of the Reynolds number, meaning the drag force is primarily dependent on the particle's size and velocity.

The region where the drag coefficient is directly proportional to the Reynolds number, meaning the drag force increases linearly with the Reynolds number.

The region where the drag coefficient is more complex and changes with the Reynolds number, but is not directly proportional to it.

An empirical equation that combines the Reynolds number, particle size, and fluid properties to estimate the settling velocity in different flow regimes. It simplifies the calculations and provides a general criterion for determining the applicability of different settling equations.