Gas and liquid contact apparatus – Contact devices – Wet baffle
Patent
1988-01-22
1989-04-11
Miles, Tim
Gas and liquid contact apparatus
Contact devices
Wet baffle
261113, 55 87, 55178, B01F 304
Patent
active
048204560
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE ART
The invention relates to chemical and petroleum engineering and has specific reference to mass-transfer apparatus.
PRIOR ART
Known in the art is a mass-transfer apparatus for gas-to-liquid contact in the case whereof there are contained one perforated tray, or several such trays, and a sprayer (cf. Pozin M.E. "Pennye gazoochistiteli, teploobmenniki i absorbery", Leningrad, 1959, p. 51).
A liquid fed from the sprayer forms a layer of mobile froth on the tray to absorb certain gases or dust from the bulk gas flow.
The capacity of the known apparatus is low, for the flow rate of the gas through the net cross-sectional area thereof is slow, commonly not over 2 or 2.3 m/s, and the layer of froth on the tray is thin (around 100 mm).
Any attempt to boost the capacity gives rise to turbulence which leaves some portions of the tray uncovered with the froth, permitting some of the gas to pass through the tray unprocessed. This reduces the effectiveness of the apparatus.
Also known is a mass-transfer apparatus which, in addition to heat and mass transfer, can cope also with wet scrubbing of gases (cf. USSR Inventor's Certificate No. 434.969, Int. Cl.B01 d 47/04). The case of the known apparatus contains perforated trays each whereof is fitted with a contiguous froth retainer in the form of a grid made up of upright bars. The height of every bar is 0.2 to 0.6 times the thickness of the froth layer, and the net cross-sectional area of a grid is at least 0.8 time the net cross-sectional area of the apparatus. Perforations are provided in some of the bars of the froth retainer, next to the surface of the tray.
The main purpose the froth retainer is to set up on the tray a thick and homogenous layer of froth with fine cellular structure and to provide for a continuous flow of the phases at their interface without apparent fluctuations. In other words, the froth retainer eliminate turbulence and, consequently, increase the capacity of the apparatus.
However, the effectiveness of the process of heat and mass transfer taking place in the known apparatus at the gas flow rates over 2.6 to 3.0 m/s is low for the air-water system under the atmospheric conditions). Intermittent eddies brought at the top of the froth layer expel some of the liquid from grid cells along the axes thereof, rendering this portion ineffective as a medium for an active mass transfer or dust recovery. An accompanying splashing impairs the capacity of the apparatus and the effectiveness of mass transfer process.
The perforations in the lower portions of some bars of the froth retainer cannot provide for a uniform distribution of the liquid flow over the entire surface of the tray.
DISCLOSURE OF THE INVENTION
The main object of the invention is to provide in a mass-transfer apparatus a froth retainer designed so as to increase both the capacity and the effectiveness of the apparatus, uniformly distribute the liquid in the form of a froth with fine cellular structure over the entire surface of a tray and prevent splashing of the liquid along the axes of grid cells should the gas flow rate be speeded up.
The essence of the invention consists in that in a mass-transfer apparatus in the case whereof there are contained at least one horizontal perforated tray and a froth retainer in the form of a grid made up of upright bars which are fitted directly to the tray and form interconnected cells, according to the invention, the lower portions of the bars of the froth retainer are made solid and the cells of the grid communicate with one another by way of perforations in the upper portions of the bars of the froth retainer.
Such an arrangement ensures self-instituted distribution of the liquid on the tray thanks to overflow of froth from one cell to another through perforations of the bars of the froth retainer. The solid portions of the froth retainer bars serve to prevent undesired overflow of the liquids along the tray to depressions or obliquities of the tray, thereby ensuring uniform distribution of the liquid across the tray of relative
REFERENCES:
patent: 2875993 (1959-03-01), Marcy
patent: 2926754 (1960-03-01), Ragatz
patent: 4263021 (1981-04-01), Downs et al.
Pozin, M. E., "Pennye Gazoochistitel: Teploobmenniki i Absorbery", Lening, 1959, p. 51.
Miles Tim
Ukrainsky Nauchno-Issledovatelsky Institut Prirodnykh Gazov "Ukr
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