Wikipedia
Plate column
A plate column (or tray column) is a chemical equipment 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.