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A plate column (or tray column) is a
The feed to the column can be liquid, gas or gas and liquid at equilibrium. Inside the column there are always two phases: one gas phase and one liquid phase. The liquid phase flows downward through the column via gravity, while the gas phase flows upward. These two phases come in contact in correspondence of holes, valves or bubble caps that fill the area of the plates. Gas moves to the higher plate through these devices, while the liquid move to the lower plate through a downcomer.
The liquid is collected to the bottom of the column and it undergoes evaporation through a
chemical equipment
A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., with ...
used to carry out unit operations where it is necessary to transfer mass between a liquid phase and a gas phase. In other words, it is a particular gas-liquid contactor. The peculiarity of this gas-liquid contactor is that the gas comes in contact with liquid through different stages; each stage is delimited by two plates (except the stage at the top of the column and the stage at the bottom of the column).
Some common applications of plate columns are distillation, gas-liquid absorption and liquid-liquid extraction. In general, plate columns are suitable for both continuous and batch operations.
Fluid dynamics
The feed to the column can be liquid, gas or gas and liquid at equilibrium. Inside the column there are always two phases: one gas phase and one liquid phase. The liquid phase flows downward through the column via gravity, while the gas phase flows upward. These two phases come in contact in correspondence of holes, valves or bubble caps that fill the area of the plates. Gas moves to the higher plate through these devices, while the liquid move to the lower plate through a downcomer.
The liquid is collected to the bottom of the column and it undergoes evaporation through a reboiler Reboilers are heat exchangers typically used to provide heat to the bottom of industrial distillation columns. They boil the liquid from the bottom of a distillation column to generate vapors which are returned to the column to drive the distillatio ...
, while the gas is collected to the top and it undergoes condensation
Condensation is the change of the state of matter from the gas phase into the liquid phase, and is the reverse of vaporization. The word most often refers to the water cycle. It can also be defined as the change in the state of water vapor to ...
through a condenser. The liquid and gas produced at the top and at the bottom are in general recirculated.
In the simplest case, there are just one feed stream and two product streams. In the case of fractionating column
A fractionating column or fractional column is an essential item used in the distillation of liquid mixtures to separate the mixture into its component parts, or fractions, based on the differences in volatilities. Fractionating columns are used in ...
there are instead many product streams.
Notes
Bibliography
* Robert Perry, Don W. Green, Perry's Chemical Engineers' Handbook, 8th ed., McGraw-Hill, 2007. * *See also
{{commons category, Plate columns * Distillation * Packed bed *Fractionating column
A fractionating column or fractional column is an essential item used in the distillation of liquid mixtures to separate the mixture into its component parts, or fractions, based on the differences in volatilities. Fractionating columns are used in ...
Chemical equipment
Distillation