Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1989-02-06
1990-05-08
Sever, Frank
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
55 16, 55158, 210791, 21032169, 210409, B01D 4100
Patent
active
049236148
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method of and a device for the widespread, finely-bubbled aeration of liquids with a porous or perforated, thin hose- or cushion-like resilient membrane which is clamped at at least two opposite sides and to which a gas is supplied, which passes out from the membrane and into the liquid.
A method and a device of the above type are known from German Patent Number 2,942,607, in which a perforated air distribution sheet is clamped at its edges in a closed frame and is arranged over an unperforated sheet, which is likewise clamped in the frame, so that the perforated sheet, when an air supply is lacking or is low, lies fully against the unperforated sheet. There are arranged both beneath the unperforated sheet and above the perforated sheet crosspieces which are offset from one another and which give the sheets stability. Additionally, the perforated air distributor sheet can be provided at its side facing the unperforated sheet with a glass fiber re-inforced layer as a support member, which gives the perforated support sheet a special stiffness, so that a strong curvature of the perforated air distribution sheet by the air pressure between the crosspieces arranged above the unperforated sheet is also avoided.
In a normal utilization of the prior device for the fine-bubble aeration of water in regeneration ponds of biological filtration plants or for the supply of oxygen in fish breeding ponds or the like, however, problems occur with respect to the uniform gas distribution and a blockage of the perforation openings from the liquid side. A uniform gas distribution depends both on the sizes of the individual through-openings and also on the differential pressure between the interior and the exterior of the air distribution sheet. Due to the dust content of the compressed gas employed, but to a special extent to the blockage of the openings from the liquid side during continuous operation, unavoidable impairments occur with this device and with other devices which, in the course of time, lead to nonuniform bubble formation and/or to an increased pressure loss.
The unavoidable blockages during operation are overcome in the prior devices only to an incomplete extent, so that an increase of the pressure loss, a nonuniform bubble formation or an at least partial interruption of the course of operation for removal and cleaning of the device always has to be taken into account.
With a fine-bubble distribution of the gas in the relevant liquid, a gas distribution which is as uniform as possible with respect to the ground area of the liquid receptacle or parts thereof is additionally desired. If, for this purpose, vent pipes, plates or hoses are arranged at a spacing from one another of a few decimeters, then during operation there results, above the aeration locations, an often undesired fast upstream flow of the liquid-gas bubble mixture, which causes a reduction in the time for which the gas remains in the liquid and also, e.g. during the entry of oxygen from air into water, has as a consequence a substantial reduction of efficiency. The greater the specific charging of the vent device with gas, the lower is the efficiency of the solution of the gas into the respective liquid.
From German Publication (OLS) 3,318,412, there is known a device for applying a gas to a liquid, and in particular to waste water which is to be treated, in which elastomeric, hose-shaped membranes are employed, the walls of which have perforations, through which the gas supplied passes from the interior to the exterior and reaches the surrounding liquid in the form of bubbles. The perforations provided in the walls of the membrane comprise, in that case, transverse slots arranged along the longitudinal axis of the membrane. The hose-shaped membranes were provided on support members.
From German Publication (OLS) 2,757,255 there is known a method of finely distributing liquid substances in gases and/or of gases in liquids in which the substance which is to be finely distributed is supplied under superatmospher
REFERENCES:
patent: 4622148 (1986-11-01), Willinger
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