Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F23/00—Mixing according to the phases to be mixed, e.g. dispersing or emulsifying
  • B01F23/20—Mixing gases with liquids
  • B01F23/23—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids
  • B01F23/233—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements
  • B01F23/2331—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements characterised by the introduction of the gas along the axis of the stirrer or along the stirrer elements
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
  • B01F27/80—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a substantially vertical axis

Definitions

• the present invention relates to a device for injecting a gas into a liquid.
• the invention finds a particularly advantageous application in the field of biological treatment of industrial effluents.
• the gas injected into the liquid can be either an oxygenated gas with an oxygen proportion varying from 20 to 100%, or carbon dioxide, or an ozone gas, or a biogas.
• the liquid into which the gas must be injected is placed in reactors used in particular for the biological treatment of industrial effluents and whose height generally varies from 2 to 10 meters in depth.
• reactor means natural "basin” (lagoon, pond, lake.) As well as “reservoir” with more or less close walls and with open or closed sky.
• Reactors in which gas injection systems allow gas to be injected generally contain activated sludge. These reactors can therefore be either natural basins, or surface reactors with close walls, or closed reactors, under pressure or not.
• different types of devices are known depending on the injection of gas either at the surface or at the bottom of the basin. For example, there are surface turbines, brushes used to transfer air into the liquid by creating agitation. Such devices can only be used for low water heights and have limited oxygenation capacities.
• European Patent No. 0 583 509 describes a system characterized mainly by a propeller located in a hollow shaft and causing, during its rotation and by vortex effect from the surface of the liquid, the gas and the liquid being under a submerged cover.
• the gas-liquid mixture thus formed is propelled downwards.
• the gas bubbles which have not dissolved go up in a radius of action corresponding overall to that of the cover where they are recovered to be reinjected again.
• the contribution make-up gas and the purge, as well as the optimal level of liquid in the cover, are regulated by the pressure prevailing under the cover.
• the limits of this system are mainly: - the action area limited to a radius close to that of the cover and to a relatively shallow depth of water,
• a device for stirring a liquid in a reactor and for injecting a gas in this liquid comprising a drive motor disposed at the - above the reactor and provided with a vertical output shaft.
• a drive motor disposed at the - above the reactor and provided with a vertical output shaft.
• One end of this output shaft is equipped with an axial flow mobile, such as a propeller.
• the output shaft of the drive motor also carries, above the axial flow mobile, a self-aspirating turbine immersed in the reactor and capable of being driven by the output shaft at the same time as the axial flow mobile .
• the output shaft is wrapped coaxially by a cylinder linked at its upper end to the drive device and whose lower end opens into the turbine.
• a gas injection opening in an annular interval delimited by the shaft and the cylinder.
• the rotation of the turbine causes the gas to be drawn through the hollow cylinder enveloping the output shaft of the drive device.
• the turbine also allows the suction of the liquid through an annular space placed between the turbine and the cylinder, which creates, with the gas, a gas-liquid dispersion. This turbine propels the gas-liquid dispersion radially.
• This known device also comprises means for directing the gas-liquid dispersion expelled radially by the turbine towards the propeller.
• These means essentially comprise an annular box forming a deflector, enveloping the turbine and profiled in order to direct the flow coming radially from the turbine towards the propeller, and a set of substantially vertical plates forming counter-blades, arranged radially and fixed to the deflector.
• the deflector that envelops the turbine folds the gas-liquid dispersion towards the propeller which propels gas bubbles towards the bottom, and creates a liquid pumping flow allowing the agitation of the basin.
• the counter-blades make it possible to direct the various liquid and gas flows: them in order to maximize performance in terms of transfer and agitation.
• the device which has just been described with reference to European patent application No. 0 995485 has the following drawbacks, however: - low oxygenation capacity.
• the gas suction capacity is in fact limited by the congestion phenomenon of the deflector box / turbine assembly.
• the blockage is mainly due to the deflector which does not allow satisfactory evacuation of the two-phase mixture beyond a certain gas / liquid ratio, - unstable operation since in order to make the best use of the device, it works at a rate close to congestion.
• Costly safety devices must be added to detect the untimely crossing of the bottleneck and restart the device, - a high manufacturing cost.
• the technical problem to be solved by the object of the present invention is to propose a device for injecting a gas into a liquid, comprising a self-aspirating turbine capable of producing a gas-liquid dispersion, a flow mobile axial resumption of said dispersion, and means for directing the gas-liquid dispersion towards said mobile axial flow, which would offer a lower cost of oxygenation and a limited congestion phenomenon.
• the solution to the technical problem posed consists, according to the present invention, in that said means comprise deflection means integrated into the self-aspirating turbine.
• the deflection function of the device according to the invention is ensured by the single turbine. It is therefore not necessary to have recourse to additional members such as the deflector box of European patent application No. 0 995485. This results in the following advantages: - an increase in the gas suction capacity and therefore the suction capacity of the device,
• said deflection means consist of an upper element, called deflector element, of the self-aspirating turbine, having a diameter greater than the diameter of a lower element of said turbine and a profile capable of deflecting said dispersion towards the mobile with axial flow. It is thus understood that a feature of the invention is to implement a turbine which, unlike the turbines usually used, has upper and lower elements which are not parallel or of the same diameter.
• Figure 1 is a sectional view of a first embodiment of a gas injection device in a liquid according to the invention.
• Figure 2 is a sectional view of a second embodiment of a gas injection device in a liquid according to the invention.
• Figure 3 is a half side view of an upper element of a turbine of an alternative embodiment of the device of Figure 2.
• Figure 4 is a side half view of an upper element of a turbine of a third embodiment of a device according to the invention.
• the device shown in Figures 1 and 2 is intended to allow the injection of a gas into a liquid L, this gas being preferably, but not exclusively, oxygenated.
• This device comprises a drive means 1, for example a motor, disposed above the surface of the liquid L, and provided with a rotary outlet shaft 2 extending vertically and partially immersed in the liquid L.
• the shaft 2 outlet is equipped at its lower end 3 with a mobile 4 axial flow, here a propeller immersed in the liquid L.
• the shaft 2 also carries, disposed between the propeller 4 and the surface of the liquid L, a turbine self-aspirating 5 which is therefore immersed in the reactor and can be driven by the output shaft 2 at the same speed as the propeller 4.
• the output shaft 2 is coaxially wrapped by a cylinder 6 linked at its end upper by means 1 of drive, with the interposition of a sealing device 7 known per se, and the lower end 6a of which opens into the turbine 5 coaxially with the shaft 2.
• a sealing device 7 known per se
• the gas injection system in the orifice 14 is known per se and not shown.
• the self-aspirating turbine 5 consists, on the one hand, of two superimposed elements, namely, an upper element 8, 8 'and a lower element 9 in the form of a disc, placed horizontally and, on the other hand, a set of radial vanes 11 placed between the upper 8, 8 'and lower 9 elements and fixed thereto.
• an upper element 8, 8 ′ is arranged a central hole 12 delimited by a projecting collar, into which penetrates the lower end 6a of the cylinder 6, which thus delimits with the edge of said hole 12 an annular space 13.
• the shaft 2 outlet axially passes through the elements 8, 8 'and 9 while being fixed to the lower disc 9, so that when the drive motor 1 is actuated, the shaft 2 drives the turbine 5 and the propeller 4 in rotation at the same speed.
• the rotation of the turbine 5 creates the suction of the gas arriving through the orifice 14, via the cylinder 6, as well as the suction of a part of the liquid which is introduced through the annular gap 13 left free between the turbine 5 and the cylinder 6.
• This gas-liquid dispersion results in a population of bubbles the size of which is mainly between 10 000 ⁇ m and 2 mm.
• the device of FIGS. 1 and 2 also comprises means for directing towards the propeller 4 the gas-liquid dispersion expelled radially by the turbine 5 between its blades 11.
• these means include deflection means integrated into the turbine 5 itself since they are constituted by the upper element 8, 8 ′, called the deflector element, which has a diameter greater than the diameter of the lower disc 9 and a profile capable of deflecting the gas-liquid dispersion towards the mobile 4 axial flow.
• the deflector element 8 has a conical profile, in the form of a roof.
• the conical profile makes an angle between 306 140 ° with the horizontal plane.
• the deflector element 8 ′ has a section 8 ′ a in the form of a horizontal disc and an annular flap 8 ′ b of frustoconical shape.
• the annular flap 8 "b has a rounded profile, the central section 8" a of the deflector element 8 "having, as in FIG. 2, the shape of a horizontal disc.
• FIG. 4 represents a deflector element 8 '"with a curved profile, more especially an elliptical profile.
• the means for directing the liquid gas dispersion towards the propeller 4 also comprise a set of substantially vertical plates 19, forming counter-blades, arranged radially around the turbine 5 and the propeller 4 in suitable numbers at intervals. determined angles.
• each counter blade 19 In the inner edge of each counter blade 19 is formed, at the level of the turbine 5, an upper notch 21a into which the deflector element 8, 8 ′ can penetrate, and, at the level of the propeller 4, a lower notch 21b into which the ends of the propeller blades can penetrate 4.
• the counter-blades 19 extend vertically from a level corresponding substantially to that of the liquid L, over a total height H of between 0.7 and 12 times the diameter d of the turbine 5.
• the device for injecting gas into a liquid which has just been described operates as follows. Once the drive means 1 started, the output shaft 2 rotates at the same speed the self-aspirating turbine 5 and the propeller terminal 4.
• the gas is injected or sucked through the opening 14 in the annular gap 15 from where it is sucked towards the turbine 5, as well as part of the liquid L in the annular gap 13 between the element upper 8, 8 'and cylinder 6 (as indicated by the arrow in Figure 1).
• At least 90% of the dispersion of bubbles is taken up thanks to the presence of the counter-blades 19 and of the deflector element 8, 8 'which directs the flow towards the propeller 4, as indicated by the two lateral deflections in the figures. 1 and 2.
• the propeller 4, consisting of at least two blades 4a, propels the dispersion of the bubbles at a speed of, for example, between 1 and 5 m / second towards the bottom of the basin.
• the dimensioning and the operating conditions applied can make it possible to propel the bubbles up to 10 meters deep while maintaining a horizontal speed at the raft sufficient (that is to say greater than 0.1 m / s) to prevent or prevent the formation of zones of deposits or solid particles at the bottom of the basin.
• the bubbles projected at the bottom of the tank then rise at the periphery of the assembly (4, 5) around the central axis 2.
• the travel time of the gas bubbles in the liquid is sufficient to ensure the transfer of oxygen from the gas phase (if the injected gas is oxygenated) to the liquid phase. Oxygen can thus be used for the respiration needs of the biomass or for the oxidation of certain compounds.
• the pumping flow rate induced by the presence of the recovery propeller 4 and the counter blades 19 ensures mixing of the liquid volume within a radius which depends on the power dissipated by the propeller 4 (power between 40 and 90% of the power applied to the motor shaft 2). This mixing allows the sludge and / or solid particles to be suspended in order to ensure the homogenization of the sludge and / or particle concentration in all of the volumes stirred by the propeller 4.
• the gas injected by the orifice 14 is oxygenated, the device described above makes it possible to carry out biological treatments of industrial or urban effluents, by transferring the oxygen into the activated sludge and by agitating the biomass in order to homogenize the sludge concentration.
• the deflector element 8, 8 ′ which envelops the turbine 5 folds the gas-liquid dispersion towards the propeller 4 which propels the gas bubbles towards the bottom of the reactor, and creates a liquid pumping rate allowing the reactor to be agitated.
• the counter blades 19 make it possible to direct the various liquid and gaseous flows in order to maximize the performance in terms of transfer and agitation.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Mixers Of The Rotary Stirring Type (AREA)

Applications Claiming Priority (2)

Publications (1)

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Country Status (5)

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• 2004
  • 2004-04-02 FR FR0450660A patent/FR2868335B1/fr not_active Expired - Fee Related
• 2005
  • 2005-03-22 EP EP05739371A patent/EP1750831A1/de not_active Withdrawn
  • 2005-03-22 CA CA002561426A patent/CA2561426A1/fr not_active Abandoned
  • 2005-03-22 WO PCT/FR2005/050184 patent/WO2005099880A1/fr active Application Filing
  • 2005-03-23 US US10/599,573 patent/US20070290380A1/en not_active Abandoned

Non-Patent Citations (1)

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