[Azeotrope (point)] [Azeotropic distillation] [Azeotropic mixture] [Biazeotropicmixture] [Batch distillation boundary] [Batch distillation region] [Composition space] [Composition trajectory] [Condensate curve] [Condensation curve] [Distillate curve] [Distillation] [Distillation boundary] [Distillation line] [Distillation line map] [Distillation region] [Distribution coefficient] [Entrainer] [Equilibrium vector] [Equilibrium staged distillation ] [Extractive distillation] [Heteroazeotrope] [Heteroazeotropic distillation] [Heterogeneous mixture] [Homoazeotrope] [Homoazeotropic distillation] [Homogeneous mixture] [Ideal mixture] [Isodistribution line] [Isotherm] [Isotherm map] [Isovolatility line] [K-value] [Monoazeotropic mixture] [Node] [Nonideal mixture] [Ockham’s Razor] [Open condensation] [Open distillation] [Open evaporation] [Open evaporation distillate curve] [Pressure sensitive azeotrope] [Pressure swing distillation] [Rayligh distillation] [Relative volatility] [Residue curve] [Residue curve map] [Residue curve region] [Saddle] [Separatrix] [Simple distillation] [Simple distillation region] [Simple distillation residue curve] [Simple equilibrium phase transformation] [Singular point] [Still-path] [Tie-line] [Tie-line] [Unidistribution line] [Unity lines] [Univolatility line] [VLE] [VLE manifold] [VLE diagram] [Zeotropic mixture]
These definitions based on Hilmen (2000).
Azeotrope (point/composition) - that composition, where equilibrium vapor and liquid (brutto) compositions are equal at the given system temperature and pressure.
Azeotropic distillation - distillation that involves azeotropic mixtures. Note that this is a much broader definition than traditionally used in the distillation literature where the term is frequently used as an abbreviation of heteroazeotropic distillation.
Azeotropic mixture - mixture taht forms one or several azeotrope(s). The azeotrope can be homoazeotrope, when one liquid and one vapour phases are in equilibrium and it can be heteroazeotrope, when two liquid and one vapour phases are in equilibrium.
Biazeotropicmixture - mixture that forms two binary azeotropes for a binary pair or two ternary azeotropes.
Composition space - for an n-component mixture the composition space contains all the n-dimensional vectors of Rn where the elements sum to unity.
Composition trajectory - the steady state or instantaneous composition profile of a distillation column, or the trajectory of composition change during batch distillation.
Condensate curve - open condensation liquid composition trajectory.
Condensation curve - open condensation vapor composition trajectory.
Distillate curve - composition trajectory of the vapor during open evaporation.
Distillation - the process of separating a liquid mixture by successive evaporation and condensation.
Distillation boundary - locus of compositions that cannot be crossed by the given distillation process. The existence and location of such boundaries depend critically on the type of distillation in question. Distillation boundaries are thermodynamic barriers for multicomponent distillations in the same way that azeotropes are barriers to binary distillation. They split the composition space into distillation regions.
Distillation line - the set of points x for which the vapor composition in equilibrium y also lies on the same line in the composition space (Zharov and Serafimov, 1975). A discrete distillation line is drawn as a piecewise linear curve through a sequence of conjugated vapor-liquid equilibrium vectors in the composition space. Continuous distillation lines interpolate the same sequence of equilibrium points and are not mathematically unique.
Distillation line map - diagram that shows distillation lines for different initial conditions for a given mixture in the composition space.
Distillation region - a subspace of the composition space defined by a family of distillation trajectories that join a stable and unstable node.
Distribution coefficient - ratio of mole fractions in vapor and liquid phase for the given species. Commonly referred to as vapor-liquid equilibrium ratio or K-value.
Entrainer - material that helps to separate azeotropes.
Equilibrium vector - composition vector between two phases in equilibrium, also named tieline.
Equilibrium staged distillation - staged distillation column where vapor-liquid equilibrium is assumed between the phases on all trays.
Extractiv distillation - orginally this term was used for that special distillation method, when an additional component helps the separation of the azeotropes. This additional component has a boiling-point that is substantiallay higher thatn the original mixture components and is selective to one of the components. Nowadays the "extractive distillation" is used for other special distillation method also.
Heteroazeotrope - azeotrope where the vapor phase coexists with two liquid phases.
Heteroazeotropic distillation - special distillation method for the separation of the azeotropes, when an additional component (entrainer) helps the separation. The entrainer forms heteroazeotrope with at least one of the original mixture components.
Heterogeneous mixture - mixture with more than one liquid phase.
Homoazeotrope - azeotrope where the vapor phase coexists with one liquid phase.
Homoazeotropic distillation - special distillation method for the separation of the azeotropes, when an additional component (entrainer) helps the separation. The entrainer may form homoazeotropes with the original components.
Homogeneous mixture - mixture with a single liquid (and vapor) phase.
Ideal mixture - mixture that obeys Raoult’s law (or Henry’s law), i.e., the activity coefficients for all components of the liquid are equal to unity. Ideal mixtures are a special case of zeotropic mixtures.
Isodistribution line - locus of points in the composition space where the distribution coefficient for a particular component is constant.
Isotherm - locus of points in the composition space where the temperature for a given mixture at vapor-liquid equilibrium is constant. Liquid isotherms are lines of constant value of the boiling temperature and vapor isotherms are lines of constant value of the condensation temperature.
Isotherm map - diagram that shows isotherms for a given mixture in the composition space. Contour plot of one or both of the vapor-liquid equilibriumtemperature surfaces for a given mixture.
Isovolatility line - locus of points in the composition space where the relative volatility of a pair of components is constant.
K-value - see distribution coefficient.
Monoazeotropic mixture - mixture that forms only one azeotrope at each element of the composition simplex (only one binary azeotrope for each binary pair in an azeotropic mixture).
Node (mathematically) - critical point with all paths either approaching (stable) or departing (unstable).
Nonideal mixture - mixture that exhibits deviations from Raoult’s law (or Henry’s law). Nonideal mixtures may be zeotropic or azeotropic.
Ockham’s Razor - principle stated by English philosopherWilliam of Ockham (1285-1347/49) that the simplest of competing theories should be preferred to the more complex, and that entities are not to be multiplied beyond necessity.
Open condensation - condensation of a vapor phase where the liquid formed is removed continuously.
Open distillation - distillation with input and/or output mass streams.
Open evaporation - evaporation of a liquid phase where the vapor formed is removed continuously. Also referred to as simple distillation or Rayleigh distillation.
Open evaporation distillate curve - see distillate curve.
Pressure sensitive azeotrope - Many mixtures contain azeotrope whose position can be shifted substantially by changing system pressure. These azeotropes are named pressure sensitive azeotropes.
Pressure swing distillation (PSD)- Distillation process for the separation of the azeotropes, where the property of the pressure sensitive helps to separate the azeotropes.
Rayligh distillation - see the open evaporation.
Relative volatility - the ratio of distribution coefficients for pair of components in a mixture.
Residue curve - composition trajectory of the residue liquid in the still during open equilibrium evaporation. Sometimes referred to as “distillation line” in Russian and old Germanlanguage literature. (See more)
Residue curve map - diagram that shows residue curves for different initial still compositions for a given mixture in the composition space. (See more)
Residue curve region - set of liquid compositions in the composition space that belong to a family of residue curves with common initial and final points. (See more)
Saddle (mathematically) - singular point with finitely many paths both approaching and departing. Only separatrices extends or terminate in the saddle point. All other paths have a hyperbolic course in the vicinity of the singular point.
Separatrix - locus of bifurcation points of differential equations, i.e., points at which an in-finitesimal perturbation causes at least one of the integration endpoints to change. A separatrix may be stable or unstable dependent on whether solutions in its vicinity approach or depart as the value of the independent (integration) parameter goes to infinity.
Simple distillation - see open evaporation.
Simple distillation region - see residue curve region.
Simple distillation residue curve - see residue curve.
Simple equilibrium phase transformation- process where the composition of one phase changes according to its phases equilibrium and where the other phase is continuously removed. Open evaporation and open condensation are such processes.
Singular point- root to the first order derivative of a function.
Tie-line- see equilibrium vector.
Tie-line curve - sequence of conjugated vapor-liquid equilibrium vectors (tie-lines) in the composition space. Here referred to as a discrete distillation line,see distillation line.
Unidistribution line - locus of points in the composition space where the distribution coeffi-cient of the given component equals unity. At each point along the unidistribution line of component i, the equilibrium vector in the composition space has a direction normal to the component i vertex of the composition simplex.
Unity lines - collective term for unidistribution and univolatility lines.
Univolatility line - locus of points in the composition space where the relative volatility of pair of components equals unity. In ternary systems, a univolatility line of the components i and j is the locus where the equilibrium vectors in the composition space point directly at the third component h vertex.
VLE - vapor-liquid equilibrium.
VLE manifold - union of all possible vapor-liquid equilibrium pairs in a mixture.
VLE diagram - graphical presentation of the vapor-liquid equilibrium functions of a mixture like isotherm maps, residue curve maps and distillation lines maps.
Zeotropic mixture - mixture that does not form azeotropes. A mixture may be zeotropic, but still nonideal.
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