Electric Double Layer

An electric double layer around suspended particles exists due to the fact that the particle surfaces carry an electric charge. To this surface adheres a respectively opposing, loaded ion layer (Stern layer), compensating particle charge extensively but not totally. Complete neutralization is achieved through a diffuse, further liquid layer, displaying a slight excess of the respective counter-ions. Only outside of this „double layer" are the charges in the suspension balanced again.


Process for agglomeration of fine particles that carry a surface charge in liquids and therefore form at first a stable suspension. By application of an electrical field the particles are moved respective to their charge to the opposing electrode, where they are discharged and subsequently are capable of agglomerating due to Van-der-Waals forces. The process is especially of interest when additional substances, such as flocculation agents, are disallowed in the system.


includes as a collective term various electro-kinetic effects that are produced when a suspension is exposed to an electrical field. lf charged solids particles move in a suspension, then it is called electrophoresis. The movement of liquid inside of a solids structure under influence of an electrical field is called electroosmosis.


is the decomposing of electrically conductive liquids (electrolyte) by current flow into their constituents.


Term for liquids, which are conductive due to molecules dissociated into ions.


Electro-kinetic phenomenon by which water can be removed from a porous solids system, if this is in contact with an electrical field. A mechanism for the liquid transport derives from the fact that the ions contained in the liquid, can form hydrate shells and in this manner carry water to the electrode during their migration. Electroosmotic effects have been or are currently applied in the desalinization of water, demoisturing of peat, pigments, or colloids (e.g. latex, glue), for the cleaning of clay, silicic acid, or for the desiccation of moist brick walls.


Process, at which molecular disperse or colloid disperse particles of a solution migrate in an electrical field, i.e. respective to their charge to the cathode (cataphoresis) or to the anode (anaphoresis). This way, they are separated from each other.

Electrostatic Repulsion

If suspended solid particles carry an electrical charge then the particles, often charged with the same polarity, will repel each other. Therewith the electrical potential shields oft so effectively the Van-der-Waals forces originating from the particles, that the moving particles are prevented from adhering to each other and the suspension remains stable.


Safety switch installed in the working area of an operator for activating an immediate stand still (shut down) of the apparatus in the case of emergency.

Empty Pipe Velocity

Flow velocity of a fluid, establishing before and behind a bulk, if one assumes the cross-sectional area as being perpendicular to the flow direction. The mean flow velocity in the bulk is enlarged by the contraction of the cross sectional area and can be found by dividing the empty pipe velocity by the bulk porosity.


Dispersion made of two immiscible liquids, where one is distributed in form of small, stable drops in the other liquid.

Service Life
Entry Cross Section

Area in the feeding device of a separation apparatus that is perpendicular to the flow direction of the suspension.

Equilibrium Load
Equilibrium Moisture
Equilibrium Moisture

An equilibrium moisture of a filter cake or of a sediment is established when, following the completion of the demoisturing kinetics, the driving potential such as a gas difference or a centrifugal pressure is in equilibrium with the opposing potential, i.e. the capillary pressure or the solids pressure. The equilibrium moisture represents for a given demoisturing potential the physically minimally reachable moisture of a product. Respectively to the definition of the moisture degree in the bulk one talks either about equilibrium residual moisture, equilibrium saturation, or equilibrium load. In the course of a technical demoisturing process there is generally not enough time available to reach this equilibrium. The equilibrium moisture, however, that is determined in the laboratory indicates the physically possible demoisturing potential at a certain pressure.

Equilibrium Residual Moisture
Equilibrium Moisture
Equilibrium Saturation
Equilibrium Moisture
Equivalent Cake Thickness

Term originating from cake filtration. The equivalent cake hce height characterizes the applied filter medium with a cake layer of the same flow resistance. lt is calculated, respectively, as the product of the specific cake permeability Pc and the filter medium resistance Rm, or as the quotient of filter medium resistance Rm and specific cake resistance rc:

Equivalent Clarifying Area

Term applied in sedimentation centrifuge technology. The equivalent clarifying area L of a sedimentation centrifuge indicates how many m2 clarifying area A in the earth's gravitational field can be substituted by it, if one applies Stokes' law for expressing the settling velocity of the particles:


C is herein the C-value, indicating the multiple of the earth's acceleration g, which can be realized inside the centrifuge in question.

Equivalent Diameter

The equivalent diameter of a particle or a pore is a measure of a particle or a pore with defined geometrical shape (e.g. circle} with the same characteristic property (e.g. area) as the observed characteristic of the investigated particle or pore. The settling velocity equivalent diameter of a particle of any shape velocity for example corresponds to the diameter of a sphere with the same settling velocity.

Excess Pressure

In extraction selectively enriched component from a suspension in a dissolution process with an extraction agent that is not miscible with the suspension liquid.


Process for complete or partial separation of a liquid or solid substance mixture by means of a solvent or extraction agent that is not miscible with the suspension liquid. The components of the substance mixture to be removed must have different solubilities in the solvent and the extraction agent. Extraction is a selective pro­cess, i.e. the extraction agent has the capability to accept only certain preferred substances.

Extraction Agent

A liquid capable of incorporating certain substances selectively by solution during extraction.

Extraction Decanter

A Three Phase Decanter for extracting a substance out of a slurry or solution by an immiscible extraction agent. The extraction agent is dosed to the material to be extracted and fed into a three phase decanter. During feeding and acceleration an intensive mixing process takes place. Solid particles and the two liquids are then separated due to their density difference. The separated liquids are drained oft with different discharge systems. There is an option to discharge one of the components with and the other without pressure. The position of the separation line between the liquids can be adjusted with a height-variable peeling disc

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