Gas and liquid contact apparatus – Contact devices – Rotating
Reexamination Certificate
1999-10-05
2001-08-07
Bushey, C. Scott (Department: 1724)
Gas and liquid contact apparatus
Contact devices
Rotating
C261S093000
Reexamination Certificate
active
06270061
ABSTRACT:
This application claims priority under 35 U.S.C. §§119 and/or 365 to 98 12696 filed in France on Oct. 9, 1998; the entire content of which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The subject of the present invention is a device for agitating a liquid in a reactor and for injecting a gas into this liquid, comprising a drive device arranged above the reactor, provided with a vertical output shaft equipped at its end with at least one axial-flow mobile assembly immersed in the liquid.
2. Description of the Related Art
The gas injected into the liquid can be either an oxygenated gas with a proportion of oxygen varying from 20 to 100%, or carbon dioxide, or an ozonized gas, or a biogas etc. The liquid into which the gas is to be injected is arranged in reactors used in particular for the biological treatment of industrial effluents and whose height generally varies from 2 to 10 meters in depth.
In what follows “reactor” signifies both a natural “basin” (lagoon, pond, lake etc.) and also an enclosed or open headspace “tank” whose walls may be relatively close together or far apart. The reactors into which these systems enable gases to be injected generally contain activated sludges. These reactors may therefore be either natural basins, or open headspace reactors with closely spaced walls, or enclosed reactors, which may or may not be pressurized.
In the field of the biological treatment of water, various types of systems are known depending on whether the gas is injected at the surface, or at the bottom of the basin. For example, there are surface turbines, brushes enabling air to be transferred into the liquid by creating agitation. Such devices can only be used for small heights of water and have limited oxygenation capacities.
Thus Patent EP-0 583 509 from PRAXAIR Technology Inc. describes a system characterized chiefly by a propeller situated in a hollow shaft and entraining, during its rotation and by vortex effect from the surface of the liquid, gas and liquid located under an immersed cover. The gas/liquid mixture thus formed is propelled downwards. The gas bubbles being undissolved rise within a radius of action corresponding overall to that of the cover where they are collected so as to be reinjected again. The inputting of feed gas and venting, as well as the optimal level of the liquid in the cover, are regulated by the pressure prevailing under the cover.
Although the stated transfer efficiencies are very good, the limits of this system are chiefly:
the zone of action limited to a radius much like that of the cover and to a relatively small depth of water,
the enrichment of the gaseous phase with CO2, N2 and other gases arising from the biological activity, in the case of activated sludge applications, and the need to carry out venting causing losses of O2,
the complexity of the pressure regulation under the cover,
use of a gas at high pressure: need to use a booster following a VSA or MPSA (on-site production unit operating by adsorption under pressure or with vacuum regeneration).
Porous “bottom” systems with injection of gas and agitation means are also known. These systems have a fixed and limited oxygenation capacity, and tend to clog. Finally, there are other “bottom” devices comprising jets or the device known by the brand name “Ventoxal” with injection of gas (oxygen-enriched air, or pure oxygen). The “Ventoxal” system developed by the applicant consists of a pump, a Venturi type injection system, a flow distributor and an ejector
ozzle pair, for which the gas injection pressure depends on the height of water and remains chiefly greater than 1.5 bar absolute. The agitation obtained is satisfactory in the bottom of the basin but may be average in the remainder of the volume.
SUMMARY OF THE INVENTION
The purpose of the invention is to propose a device for agitating a liquid and for injecting a gas into this liquid, of the type mentioned above, making it possible efficiently to transfer a gas into a liquid and to ensure agitation enabling particles to be placed in suspension and held there.
In accordance with the invention, the output shaft of the drive device also carries an auto-suction turbine immersed in the liquid and drivable by the output shaft, and the latter is enveloped coaxially by a cylinder linked at its upper end to the drive device and whose lower end opens out into the turbine; in the upper end of the cylinder is drilled an aperture for injecting a gas into an annular gap delimited by the shaft and the cylinder.
The output shaft of the drive device drives the turbine and the propeller at the same speed.
The rotation of the turbine causes gas to be sucked through the hollow cylinder enveloping the output shaft of the drive device. This turbine propels the gas/liquid dispersion radially.
The device comprises means for directing towards the propeller the gas/liquid dispersion expelled radially by the turbine.
According to one embodiment of the invention, the said means comprise an annular box forming a deflector, enveloping the turbine and profiled so as to direct towards the propeller the stream issuing radially from the turbine, and a set of substantially vertical plates forming counter-blades, arranged radially and fixed to the deflector.
Advantageously, the said means may comprise an additional agitation mobile assembly preferably driven in rotation by the output shaft, or any other means, preferably at the same speed of rotation as the shaft.
The deflector which envelopes the turbine pushes the gas/liquid dispersion down towards the propeller which propels gas bubbles towards the bottom, and creates a stream of pumping liquid allowing agitation of the basin. The counter-blades make it possible to direct the various liquid and gaseous streams so as to maximize the performance in terms of transfer and agitation.
REFERENCES:
patent: 2875897 (1959-03-01), Booth
patent: 2928661 (1960-03-01), MaClaren
patent: 3092678 (1963-06-01), Braun
patent: 3650950 (1972-03-01), White
patent: 3776531 (1973-12-01), Ebner et al.
patent: 3972815 (1976-08-01), O'Cheskey et al.
patent: 4290885 (1981-09-01), Kwak
patent: 4297214 (1981-10-01), Guarnaschelli
patent: 5795504 (1998-08-01), Berchotteau
patent: 6109449 (2000-08-01), Howk et al.
patent: 0 446 192 (1991-09-01), None
patent: 0 583 509 (1994-02-01), None
patent: 0 593 074 (1994-04-01), None
patent: 7304539 (1974-10-01), None
Bouquet Florent
Ferrand Frédérique
Gouhinec Florence
Burns Doane Swecker & Mathis L.L.P.
Bushey C. Scott
L'Air Liquide, Societe Anonyme pour l'Etude et l'
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