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
  • B01F23/2335—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 direction of introduction of the gas relative to the stirrer
  • B01F23/23354—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 direction of introduction of the gas relative to the stirrer the gas being driven away from the rotating stirrer
• • 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
  • B01F23/2334—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements provided with stationary guiding means surrounding at least partially the stirrer
  • B01F23/23341—Mixing gases with liquids by introducing gases into liquid media, e.g. for producing aerated liquids using driven stirrers with completely immersed stirring elements provided with stationary guiding means surrounding at least partially the stirrer with tubes surrounding the stirrer
• • 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
  • B01F23/2336—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 location of the place of introduction of the gas relative to the stirrer
  • B01F23/23362—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 location of the place of introduction of the gas relative to the stirrer the gas being introduced under the stirrer
• • 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
  • B01F27/90—Mixers with rotary stirring devices in fixed receptacles; Kneaders with stirrers rotating about a substantially vertical axis with paddles or arms 
• • 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
  • B01F27/05—Stirrers
  • B01F27/11—Stirrers characterised by the configuration of the stirrers
  • B01F27/112—Stirrers characterised by the configuration of the stirrers with arms, paddles, vanes or blades
  • B01F27/1125—Stirrers characterised by the configuration of the stirrers with arms, paddles, vanes or blades with vanes or blades extending parallel or oblique to the stirrer axis
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
  • B01F33/00—Other mixers; Mixing plants; Combinations of mixers
  • B01F33/50—Movable or transportable mixing devices or plants
  • B01F33/503—Floating mixing devices

Definitions

• the present invention relates to a method for feeding gas or gas mixture into liquid, in which method a preferably vertical tube is arranged in a liquid contained in a tank or equivalent space, and the liquid is made to flow through the tube from top to bottom by means of a liquid transport device placed in the pipe and provided with an impeller, and gas is conducted into the liquid after the impeller, when seen in the flowing direction.
• the present invention also relates to an apparataus for feeding gas or gas mixture into liquid, the said apparatus comprising a tube which is installed preferably vertically in a liquid containing tank or equivalent, which tube is provided with a liquid inlet and a liquid outlet, and inside which tube there is arranged a liquid transport device provided with an impeller and a gas feeding device located in the tube below the impeller when seen in the flowing direction, through which gas feeding device gas is fed into the liquid flow, and which impeller makes the liquid and the liquid and gas mixture to flow through the tube downwards, i.e. from top to bottom.
• gas or gas mixture is blown onto the bottom of a liquid containing tank, wherefrom it rises in bubbles directly and rapidly to the surface of the liquid and is thereafter discharged into the environment. In this case only a small portion of the gas is transferred into the liquid, wherefore it is necessary to blow gas into the liquid continously and in large quantities. With this method, energy consumption tends to rise immoderately high while the gas transfer efficiency remains poor.
• gas or gas mixture is blown onto the bottom of a liquid containing tank, and the gas bubbles rising from the bottom are mixed into the liquid by means of a rapidly rotating flat blade turbine agitator.
• the Finnish Patent Publication No. 35233 introduces a method and apparatus for aerating liquid effluents in the process of biological treatment.
• water is made to flow within the tank at one or several spots through a cylindrical tube from top to bottom, essentially in vertical direction, first to the vicinity of the tank bottom and subsequently sideways.
• Air is mixed into the water flowing downwards in the tube so that the water and the air mixed therein both flow downwards together.
• the flowing of the water downwards in the tube and the mixing of the air therein are carried out by means of an impeller, pulsator or the like, and air is conducted through a tubular pipe either to above or below the impeller.
• the above described method is more advantageous than other prior art methods. It is not necessary to press air, or any gas, against a high liquid pressure down to the tank bottom, which procedure requires a lot of energy, but the mixture of air, water or gas and liquid is pumped deeper down by aid of the impeller, so that the energy consumption remains relatively low.
• the impeller, pulsator or the like also sets the surrounding water and/or air and water mixture in a turbulent motion while in operation.
• the air bubbles contained in the water or fed therein after the impeller may, as being lighter than water, be separated towards the vicinity of the centre axis of the tube and even be combined into large bubbles. Irrespective of the manner in which air is fed in, a homogeneous distribution of air into the water flowing in the tube is prevented. As a result, the air transfer efficiency in the liquid decreases.
• the said apparatus comprises an elongate chamber at the upper end of a tube, in which chamber there are arranged an impeller, a blade wheel or the like, air feeding means and baffle plates.
• the tube is narrower than the chamber and extends in the flow direction downwards, towards the bottom of the chamber. Air is admitted into the liquid effluent within the chamber, where the impeller agitates the water and the air, and pushes the mixture downwards into the subsequent tube.
• the impeller agitates the water and the air, and pushes the mixture downwards into the subsequent tube.
• planar baffle plates which are positioned parallel to the longitudinal axis of the pipe. The purpose of the said baffle plates is to prevent the air and water mixture agitated by the impeller from assuming turbulent motion and to convert its motion so that it is directed axially downwards.
• the object of the present invention is to realize an improved method and apparatus for feeding gas or gas mixture into liquid wherein the drawbacks of the above described methods and apparatuses are eliminated.
• the method of the invention is characterized in that the turbulent motion created by the impeller is attenuated so that the tube is provided with baffles which are installed radially in the tube after the impeller and in the vicinity thereof, mainly parallel to the tube, and that gas is fed into the liquid, when seen in the flowing direction, at the earliest stage only when the turbulent motion is attenuated and the liquid flows mainly in the tube direction.
• the apparatus of the invention it is characterized by the novel features mainly enlisted in the patent claim 7.
• the turbulent motion created by the impeller can be effectively attenuated.
• the kinetic energy bound in the turbulent motion of the liquid is converted into kinetic energy of the flow which is directed parallel to the tube axis.
• the impeller is fitted inside the tube so that the rotating area of the impeller covers at least 80 % of the cross-sectional area of the tube, and secondly, the baffles are fitted in the tube so that they extend, in the direction of the tube radius, advantageously over the whole rotating area of the impeller. If the first requirement is not fulfilled, liquid flows in the tube at an irregular velocity, and part of the large quantity of gas fed into the liquid may escape upwards through the annular aperture left between the tips of the impeller blades and the tube casing, which may critically disturb both the liquid transport and the feeding of gas into the liquid.
• the guide baffles advantegeousl y extend over the whole cross- sectional area of the tube, and their influence in the flowing liquid at each specific spot in the tube is equally strong. If the intake edges of the baffles extend near to the trailing edges of the impeller blades, the influence of the matching operation is most effective, and turbulent currents are not formed in the liquid.
• the feeding of gas into the flow can be carried out immediately after the liquid flow has been directed and the current flows mainly parallel to the tube. This may be realized for example so that gas is fed into the liquid within the area left between the guide baffles or their imaginable continuations, or so that gas is fed into the liquid through the very baffles.
• the gas flow is directed into the liquid mainly in the liquid flow direction, so that the kinetic energy of gas is utilized for maintaining the current, which arrangement reduces the total energy consumption.
• gas is fed into the liquid in the first described manner, i.e. into the area left between the baffles, a homogeneous distribution of gas into the liquid can be achieved. As for the latter method, it can be simply applied by utilizing the existing structures.
• Figure 1 is a schematical and partially cross-sectional illustration of a preferred embodiment of the invention for feeding gas into liquid
• Figure 2 is a schematical illustration of how the impeller blade and the baffle designed for directing the liquid flow are matched;
• Figure 3 shows the section A-A of the apparatus of figure
• FIG 1 is an illustration of the apparatus of the invention designed particularly for feeding air into water, but it is obvious that the apparatus is suited for feeding any gas or gas mixture into liquid.
• the pontoons 11 are arranged to support the apparatus in a water tank.
• the apparatus comprises the cylindrical tube 1, which is located advantageously vertically in the water tank.
• the tube is provided with at least one water inlet 2 and at least one water outlet 3.
• Inside the tube, on the axis D-D there is fitted the impeller 4 which makes the water flow through the tube 1 in the direction C from top to bottom, i.e. in through the inlet 2 and out through the outlet 3.
• the tube 1 comprises the guide baffles 5 and the gas feeding device 6.
• the guide baffles 5 are located radially and mainly parallel to the tube 1.
• the discharge openings of the gas feeding device 6 are connected to the inside of the tube, at the earliest stage with respect to the flowing direction on such a horizontal plane in the tube where the liquid already flows mainly in the tube direction D-D.
• the gas feeding device 6 is connected to the air blower 9.
• the feeding device 6 can, however, also be connected to an oxygen container or other vessel or device transferring or producing oxygen.
• the motor 8 On the raft 10, which floats in the water supported by the pontoons 11, there is installed the motor 8 and the air blower 9.
• the motor 8 is connected to the fulcrum 42 of the impeller 4 by means of the axis 7.
• the air blower 9 is connected by means of pipes 12 or hoses to the air feeding device 6 which is located in the tube 1.
• the impeller 4 is provided with two or more blades 41 , which are attached symmetrically around the fulcrum 42 of the impeller.
• the measures of the impeller 4 are arranged in a ry known fashion so that the difference in pressure over the impeller, at each separate spot thereof is equally great during operation.
• the impeller 4 is capable of pushing water n the tube 1 with equal power over the whole rotating area of the impeller.
• the rotating area of the impeller is defined as the area of the circle drawn by the tips of the impeller blades 41 while in rotation, the distance of the said tips from the centre axis being r-j .
• the form of the blade 41 of the impeller 4 is such that the angle oC between the tangent E of the trailing edge 41a of the blade (figure 2) and the rotating plane P-P of the impeller 41 changes as a function of the distance r (figure 1). This is due to the fact that while the impeller is in rotation, the circumferential speed at separate points of the trailing edge 41a of the blade 41 at the distance r changes: near the tip of the balde 41 the circumferential speed is high and the trailing angle o of the blade is small, whereas near the fulcrum 42 of the impeller the circumferential speed is low and the trailing angle oC is large.
• the angle oC of the trailing edge 41a of the blade 41 determines the angle at which the water leaves the blade 41.
• figure 2 which illustrates the cross-section of the blade 41 and the baffle 5 for instance at the distance r from the impeller axis in figure 1.
• the impeller rotating direction is marked P p and the direction of the impeller axis is marked P a , the latter being parallel to the axis D-D of the tube 1.
• the cicumferential speed vector of the impeller blade 41 is referred to as Vp, and V-
• the vector T is divided into two components, i.e. v- j parallel c to the tangent E of the blade 41 and v " ⁇ p parallel to the cicumferential speed vector of the impeller, and the cicumferential speed vector vV, of the impeller is taken into account
• the resulting vector is v ⁇ ? which approximately represents the speed and direction of the water flow leaving the blade 41.
• the angle of departure of the water flow, with respect to the rotating plane P-P, is marked with ⁇ .
• the impeller 4 and the baffles 5 are matched with each other so that the direction of the water flow leaving the blade 41 of the impeller 4, roughly parallel to the direction of the vector V , is equal to the direction F of the tangent of the intake edge 51a of the baffle 5.
• the baffles 5 are, at least at the end 51 which is first on the impeller side when seen in the tube direction D-D, members with an advantageously curved surface as is seen for example in figure 2.
• the tangent G of the trailing edge 52a of the baffle 5 is parallel to the tube axis D-D.
• the baffles 5 can also be realized as members parallel to the axis D-D, i.e. to the tube 1. This embodiment is illustrated by dotted lines in Figure 2. In this case the first end 51 ' of the baffle 5 at the impeller side is straight and parallel to the other end 52. While employing a baffle of this type, the liquid flow leaving the impeller blade 41 hits the baffle at a certain angle 90° - ⁇ with respect to the axis D-D, the size of which angle 90°- ⁇ also depends on each separate point on the blade and the baffle, i.e. it is a function of the distance r. This results in turbulent flows, and the turbulence does not attenuate as easily as in the case of the curved baffle described above.
• the impeller 4 is fitted within the tube 1 so that the ratio between the rotating area Hf r ⁇ of the impeller 4 and the cross-sectional area fT * R ⁇ of the tube, where R is the inner radius of the tube 1, is S, 0,8. This arrangement prevents back flows in the tube periphery and thus increases the efficiency.
• baffles 5 fulfil their function as well as possible, their vertical width is roughly equal to the tube radius R. Moreover, the greatest distance h-
• the gas feeding device 6 is formed of at least one member 61 with a blade-like profile. On the sides of this member, advantageously on its downwards curved parts and/or on its trailing edge, there are located discharge openings 62 at short intervals from each other.
• the device 6 is connected to the air blower 9 or equivalent by means of the pipe 12 or the like.
• At least one blade-like member 61 of the air feeding device 6 is placed at an interval from the baffles 5, when seen in the flow direction and advantageously so that the blade ⁇ like member 61 are located in between the imaginable continuations of the guide baffles 5 parallel to the tube axis, preferably in the middle of the said areas as is shown in figure 4.
• the blade-like members 61 also serve as members which stabilize the flow.
• the distance h of the blade-like members 61 of the air feeding device 6 from the baffles 5 in the direction D-D of the axis of the tube 1 is shorter than the length h s of the baffles 5 in the direction of the axis of the tube 1.
• the blade-like members 61 can also be postioned between the baffles 5.
• One viable solution is to leave out the blade-like members 61 and to feed the air into the water flow through the guide baffles 5.

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• Chemical & Material Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Structures Of Non-Positive Displacement Pumps (AREA)
• Aeration Devices For Treatment Of Activated Polluted Sludge (AREA)

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Publications (2)

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• 1985
  • 1985-03-07 FI FI850918A patent/FI74628C/fi not_active IP Right Cessation
  • 1985-09-30 AU AU49560/85A patent/AU4956085A/en not_active Abandoned
  • 1985-09-30 WO PCT/FI1985/000081 patent/WO1986005123A1/en not_active Ceased
  • 1985-09-30 DE DE8585904821T patent/DE3576464D1/de not_active Expired - Fee Related
  • 1985-09-30 EP EP85904821A patent/EP0252903B1/de not_active Expired
• 1986
  • 1986-03-06 DD DD86287637A patent/DD243434A5/de unknown
  • 1986-03-06 CN CN198686101405A patent/CN86101405A/zh active Pending

Non-Patent Citations (1)

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