SU453162A1 - METHOD OF CARRYING OUT MASS TRANSFER - Google Patents

Description

The invention relates to mass transfer processes occurring in the foam layer, for example, in bubbling apparatus in a gas-liquid (vapor-liquid) system and in the particular case can be used in the purification of various liquids.

There is a known method of mass transfer in the foam layer by feeding gas through a liquid containing dissolved trace impurities.

This method can be carried out if one of the phases (liquid or gas) has a higher concentration of any component in its composition, since the difference in concentrations is the driving force for transferring mass from one phase to another.

The purpose of the invention is to intensify the process of mass transfer and purification of the liquid phase. This is achieved by separating the foam layer into fractions with different content of microimpurities, and the enriched fraction is removed from the system. It is advisable to supply the gas to the system at a rate that eliminates longitudinal mixing.

In contrast to the known methods of mass transfer, where the substance passes from one phase to another at the moment of contact between the liquid and gas phases, in the proposed method the gas is only a means of foaming and, not participating in mass transfer, promotes the redistribution of microimpurities along the height of the foam layer. Thus, mass transfer occurs only in the liquid phase. Selection

more or less liquid containing a certain amount of microimpurities, allows you to adjust the intensity of the process of mass transfer and to obtain a specified content of the substance in

fractions x.

When a gas bubble is formed in the liquid at the interface, due to the compensation of molecular forces, there is a layer of molecules that differs significantly in its properties from the internal layers of the adjacent phases. This is the so-called surface layer, the depth of which is close to the diameter of the sphere of action of the molecules, or a monomolecular layer.

With a highly developed coarse cellular structure of the foam layer, the process of redistribution of impurities occurs in thin films of liquid. Some impurities enter the gas phase due to molecular diffusion.

The process is conducted so as to avoid. strong foam turbulization, since during the turbulent regime there is a strong mixing and averaging of the impurity concentrations over the height of the foam layer. By

friction forces when gas bubbles rise, the diffusion layer moves from the upper (frontal) part of the gas bubble to the lower (rear) part. Traces accumulate in the lower part of the bubble, forming a saturated solution in a film of liquid separating two gas bubbles. As the foam layers are mixed on the plate, each upstream foam layer will be cleaner than the one below, as the liquid layer between the bubbles flows down, pitta the downstream foam layers. At the same time, a large number of trace impurities is contained in the flowing inter-step liquid layer, which respectively enrich the lower foam layers.

The described method is carried out in a plant designed to produce high purity nitric acid. During the cleaning process, acid streams from the upper and lower parts are separately removed from the apparatus.

foam layer Acid streams are analyzed by spectral and chemical methods to quantify trace amounts. The data obtained after repeated tests are in good agreement with each other and allow us to judge the degree of purification of the product as a whole.

Subject invention

Claims (2)

1. A method of mass transfer in the foam layer by supplying gas through a liquid containing dissolved trace impurities, characterized in that, in order to intensify the mass transfer, the foam layer is divided into fractions with different content of trace impurities, and the enriched fraction is removed from the system. 2. The method according to claim 1, about t and chajushchie and the fact that the gas is fed at a rate that excludes longitudinal mixing.