Stripping (chemistry)

Stripping or the stripping is a physical separation method, wherein the substances are transferred from a liquid phase by desorption (using Henry's law ) in the gas phase. To the liquid phase is brought in countercurrent contact with a gas.

The term " stripping " is also erroneously used when materials are transferred into a phase of an emulsion or by shaking in a liquid phase (see liquid-liquid extraction).

Execution

Technically, the stripping is usually performed in packed columns. About a nozzle, the fluid pumped is finely distributed on the top of the column so that it trickles over the packing in the column into the swamp. Countercurrently stripping gas is fed through the column (such as air). The fillers are used to distribute the liquid fine and thus to maximize the phase interface. The cleaning performance is also determined by the gas / liquid ratio, the transfer of contamination from the liquid to the gas is described by the Henry's law constant of each material. The stripping is usually followed by a purification of the exhaust gas, for example by adsorption, or decomposition cooling.

The method can be adapted to the requirements within wide limits, so as to obtain the desired outlet concentration for a given inlet concentration of impurity in the liquid phase.

Several Stripptürme be realized in a multi-stage system, in order to achieve a desired cleaning efficiency. Theoretically, this approach of increasing the Füllkörperhöhe.

The variables determine the effectiveness of stripping:

• Diameter of column
• Füllkörperhöhe
• Füllkörpertyp
• Temperature
• Gas and liquid loading

For the liquid to be purified, an optimal amount of the column diameter can be calculated. A minimal amount of electricity means that the column has an infinite number of transfer units. The determination of the counter-current amount is an optimization process between column height and counter-current amount.

Application

Stripping is used in petroleum refining to purify the sidedraw product on a column of lighter components, such as kerosene from the lower-boiling gasoline.

In waste water treatment so that ammonia, hydrogen sulfide, mercaptans, phenols, organic halogen compounds and hydrocarbons can be removed.

In certain applications, sludge from precipitation reactions (iron, manganese) can clog the packing and reduce the cleaning performance of the procedure. In these cases, a prior iron removal is necessary.