CH466818A - Process for treating a liquid by means of a gaseous fluid and installation for carrying out this process - Google Patents

Description

Process for treating a liquid by means of a gaseous fluid and installation for carrying out this process In various industries and, in particular, in the field of water treatment, it is often necessary to gasify a liquid to obtain specific chemical or biological reactions, to saturate the liquid with a gas, or even to eliminate suspended matter. towards the surface of the liquid by flotai sol, etc.

Generally, this gasification is carried out by insufflation of gas under pressure in the liquid mass or by projection of the liquid in a gaseous atmosphere or even using rotary agitators in combination with an insufflation of gas under pressure below the blades of the agitator.

The subject of the present invention is a process for treating a liquid by means of a gaseous fluid characterized in that the gaseous fluid is diffused directly into a reduced volume of the liquid mass to be treated and in that this is propelled reduced volume of treated liquid in the rest of the gross liquid mass.

The invention also relates to an installation for the implementation of the method indicated above, installation comprising a basin intended to contain the liquid to be treated, a pipe for supplying the raw liquid to the basin and a pipe for discharging the treated liquid, a centrifugal rotary pump for dispersing the gaseous fluid in the liquid, a propeller-shaped stirring member arranged under the pump and driven by the same shaft from the same motor, the gaseous fluid supply pipe to the pump forming a guide tube around the shaft dipping into the liquid. The installation according to the invention is characterized in that it comprises a ferrule surrounding the pump with clearance and of which a downward tubular extension surrounds the brewing member, this ferrule being entirely embedded in the basin, the whole being arranged so that the pump directly injects gaseous fluid only into a reduced volume of the liquid to be treated, limited by the shell, this reduced volume then being propelled by the propeller into the rest of the basin.

The accompanying drawing represents, schematically and by way of example, one embodiment of the installation according to the invention.

The single figure in this drawing shows the installation in an axial section view.

With reference to the drawing, this installation comprises a basin, or tank, 1 intended to contain the liquid 2 to be treated. This tank 1 is preferably of circular section. In the center of the tank 1 is arranged a shell 3 open at its upper part and whose edge 4 is below the constant level 5 of the liquid 2. The bottom 6 of the shell 3 is of frustoconical shape and ends in its center at a tubular extension 7 directed towards the bottom 8 of the tank 1 which is in the form of a hopper, also frustoconical in the embodiment shown. The ferrule 3 which can, for example, be constructed of sheet metal or a cement element or other material, is concentric with a guide tube 9 arranged in the axis of the basin 1. The ferrule 3 is raised to the guide tube 9 by supports 10. Inside the guide tube 9 is housed a shaft 11 intended to be driven by an electric motor 12 carried by the upper end of the tube 9. The guide tube 9 is provided with an opening 13 d gas suction located above the level 5 of the liquid 2. At its lower part, the guide tube 9 has a flange 14 carrying at its periphery a number of ribs 15 intended to constitute the diffuser of a centrifugal pump whose the impeller 16 is part by the shaft 11. This collar 14 and the diffuser 15 constitute, in fact, a pump half-body. The wheel 16 is in the form of a disc provided on its upper face with radial ribs 17. At the end of the shaft 11, below the wheel 16, is disposed a propeller 18 constituting a member for mixing or propelling the liquid.

The liquid to be treated is brought into the basin 1 by a pipe 19 opening inside the shell 3.

An evacuation pipe 20 for the treated liquid is connected to the lower part of the tank 1, that is to say close to the bottom 8 of the latter. The height of the overflow 21 formed by this discharge pipe 20 determines the level 5 of the liquid 2 in the basin 1.

The ferrule 3, the guide tube 9 and the motor 12 driving the shaft 11, the wheel 16 and the propeller 18, are supported at the center of the basin 1 by spacers, or support rails, 23 arranged diametrically above pool 1.

The operation of the installation described above is as follows: the liquid to be gasified flows through the pipe 19 inside the shroud 3. The level 5 of the liquid 2 to be treated corresponds to the height of the overflow 21. The gas to be introduced into the liquid 2 is brought to the suction opening 13 provided in the tube 9. When the motor 12 rotates, it rotates the pump wheel 16, on the one hand, and the propeller 18, on the other hand. According to the direction of rotation of the motor 12, the liquid is discharged from the bottom of the basin 1 towards the inside of the ferrule 3 through the tubular extension 7 surrounding the propeller 18 (in the direction indicated by the solid line arrows represented on the left half of the figure). The liquid thus passes through a reduced space 22 surrounding the diffuser 15. During this passage through this reduced space 22, the gas projected by the pump wheel 16 and its fins 17 through the diffuser 15, is finely dispersed in the space. 22 in which the liquid to be treated is forced to pass. This therefore results in an intimate mixture of the gas and the liquid, a mixture which rises inside the shroud 3. The gas not dissolved in the liquid then escapes to the surface 5 of the liquid. The gas-liquid contact time thus depends on the distance between the space 22 and the surface 5 of the liquid 2. if it is desired to extend the gas-liquid contact time, the motor 12 is operated in the opposite direction as shown on the right side of the figure (dotted arrows). The direction of the current resulting from the propulsion of the propeller 18 is then reversed. The liquid enters through the top of the shroud 3, passes into the reduced space 22 to be gasified, the gas-liquid mixture then being pushed back by the propeller 18 towards the bottom 8 of the basin 1. It is thus noted that more the tubular extension 7 will be long and the bottom 8 of the basin 1 at a greater distance from the space 22, the greater will be the duration of contact of the gas-liquid mixture. Indeed, the gas not dissolved in the liquid must rise between the shell 3 and the basin 1 before reaching the surface 5 where it can escape.

It is obvious that by varying the speed of rotation of the motor 12, it is possible to adjust the volume of introduction of gas and the flow rate of mixing of the liquid.

The basin, or tank, 1 can be closed at its upper part if the nature of the gases to be introduced into the liquid mass so requires. This may be the case, for example, if the gas is a toxic gas, a rare gas or an explosive gas to be recovered and circulated in a closed circuit inside the installation. On the other hand, if the installation is only used for a simple aeration of a liquid mass, the basin 1 can be open.

The advantage of the method described above resides in particular in the fact that the liquid to be treated is forced to circulate and pass in direct proximity to the gas injection, thus ensuring uniform gasification of the liquid mass, without creating preferential gasification zones, as is the case with conventional processes. This advantage is all the more marked in that only a reduced volume of the liquid mass 2 is treated at a time by gas diffusion, that is to say only the volume contained inside the shroud 3. The treatment continues of course with the propulsion of this treated primary liquid mass in the secondary liquid mass 2 still in its raw state.

In addition, depending on the direction of circulation of the liquid propelled by the propeller 18, it is possible, depending on the desired treatment conditions, to shorten or prolong the duration of contact between the liquid and the gas, this simply by causing the liquid to circulate in the direction amount or in the downward direction inside the ferrule 3. Of course, the electric motor 12 must be provided to be able to operate in both directions of rotation and, possibly, at different rotation speeds depending on the degree of gas diffusion that we want to obtain.

CLAIMS I. Process for treating a liquid by means of a gaseous fluid, characterized in that the gaseous fluid is diffused directly into a reduced volume of the liquid mass (2) to be treated and in that this is propelled reduced volume of treated liquid in the rest of the gross liquid mass.

II. Installation for carrying out the method according to claim I, comprising a basin (1) intended to contain the liquid to be treated, a pipe for supplying the crude liquid to the basin (1) and a pipe (20) for discharging the treated liquid, a rotary centrifugal pump (16) for dispersing the gaseous fluid in the liquid (2), a stirring member (18) in the form of a propeller disposed under the pump (16) and driven by the same shaft (11) from the same motor (12), the pipe for supplying gaseous fluid to the pump (16) forming a guide tube (9) around the shaft (11) immersed in the liquid, characterized in that it comprises a shroud (3) surrounding the pump (16) with clearance and of which a downward tubular extension (7) surrounds the stirring member (18), this shroud (3) being entirely embedded in the basin (1), the whole being arranged so that the pump (16) directly injects gaseous fluid only into a reduced volume of the liquid to be treated (2), limited by the shroud (3), this reduced volume then being propelled by the propeller (18) in the rest of the basin (1).

SUB-CLAIMS 1. Installation according to claim II, characterized in that the motor (12) is capable of driving the pump (16) and the propeller (18) in both directions, the choice of a direction of rotation allowing a setting in contact of the reduced volume deals with the raw liquid (2) over a longer path than in the opposite direction.

2. Installation according to claim II and sub-claim 1, characterized in that the pipe (19) for supplying the raw liquid (2) opens inside the shell (3), the pipe (20) d evacuation having its entry near the bottom (8) of the basin (1).

**WARNUNG** Ende DESC Feld konnte Anfang CLMS uberlappen**.

Claims (5)

WARNUNG* Anfang CLMS Feld konnte Ende DESC uberlappen *. has a propeller 18 constituting a liquid stirring or propulsion member. The liquid to be treated is brought into the basin 1 by a pipe 19 opening inside the shell 3. An evacuation pipe 20 for the treated liquid is connected to the lower part of the tank 1, that is to say close to the bottom 8 of the latter. The height of the overflow 21 formed by this discharge pipe 20 determines the level 5 of the liquid 2 in the basin 1. The ferrule 3, the guide tube 9 and the motor 12 driving the shaft 11, the wheel 16 and the propeller 18, are supported at the center of the basin 1 by spacers, or support rails, 23 arranged diametrically above basin 1. The operation of the installation described above is as follows: the liquid to be gasified flows through the pipe 19 inside the shroud 3. The level 5 of the liquid 2 to be treated corresponds to the height of the overflow 21. The gas to be introduced into the liquid 2 is brought to the suction opening 13 provided in the tube 9. When the motor 12 rotates, it rotates the pump wheel 16, on the one hand, and the propeller 18, on the other hand. According to the direction of rotation of the motor 12, the liquid is discharged from the bottom of the basin 1 towards the inside of the ferrule 3 through the tubular extension 7 surrounding the propeller 18 (in the direction indicated by the solid line arrows represented on the left half of the figure). The liquid thus passes through a reduced space 22 surrounding the diffuser 15. During this passage through this reduced space 22, the gas projected by the pump wheel 16 and its fins 17 through the diffuser 15, is finely dispersed in the space. 22 in which the liquid to be treated is forced to pass. This therefore results in an intimate mixture of the gas and the liquid, a mixture which rises inside the shroud 3. The gas not dissolved in the liquid then escapes to the surface 5 of the liquid. The gas-liquid contact time thus depends on the distance between the space 22 and the surface 5 of the liquid 2. if it is desired to extend the gas-liquid contact time, the motor 12 is operated in the opposite direction as shown on the right side of the figure (dotted arrows). The direction of the current resulting from the propulsion of the propeller 18 is then reversed. The liquid enters through the top of the shroud 3, passes into the reduced space 22 to be gasified, the gas-liquid mixture then being pushed back by the propeller 18 towards the bottom 8 of the basin 1. It is thus noted that more the tubular extension 7 will be long and the bottom 8 of the basin 1 at a greater distance from the space 22, the greater will be the duration of contact of the gas-liquid mixture. Indeed, the gas not dissolved in the liquid must rise between the shell 3 and the basin 1 before reaching the surface 5 where it can escape. It is obvious that by varying the speed of rotation of the motor 12, it is possible to adjust the volume of introduction of gas and the flow rate of mixing of the liquid. The basin, or tank, 1 can be closed at its upper part if the nature of the gases to be introduced into the liquid mass so requires. This may be the case, for example, if the gas is a toxic gas, a rare gas or an explosive gas to be recovered and circulated in a closed circuit inside the installation. On the other hand, if the installation is only used for a simple aeration of a liquid mass, the basin 1 can be open. The advantage of the method described above resides in particular in the fact that the liquid to be treated is forced to circulate and pass in direct proximity to the gas injection, thus ensuring uniform gasification of the liquid mass, without creating preferential gasification zones, as is the case with conventional processes. This advantage is all the more marked in that only a reduced volume of the liquid mass 2 is treated at a time by gas diffusion, that is to say only the volume contained inside the shroud 3. The treatment continues of course with the propulsion of this treated primary liquid mass in the secondary liquid mass 2 still in its raw state. In addition, depending on the direction of circulation of the liquid propelled by the propeller 18, it is possible, depending on the desired treatment conditions, to shorten or prolong the duration of contact between the liquid and the gas, this simply by causing the liquid to circulate in the direction amount or in the downward direction inside the ferrule 3. Of course, the electric motor 12 must be provided to be able to operate in both directions of rotation and, possibly, at different rotation speeds depending on the degree of gas diffusion that we want to obtain. CLAIMS I. Process for treating a liquid by means of a gaseous fluid, characterized in that the gaseous fluid is diffused directly into a reduced volume of the liquid mass (2) to be treated and in that this is propelled reduced volume of treated liquid in the rest of the gross liquid mass. II. Installation for carrying out the method according to claim I, comprising a basin (1) intended to contain the liquid to be treated, a pipe for supplying the crude liquid to the basin (1) and a pipe (20) for discharging the treated liquid, a rotary centrifugal pump (16) for dispersing the gaseous fluid in the liquid (2), a stirring member (18) in the form of a propeller disposed under the pump (16) and driven by the same shaft (11) from the same motor (12), the pipe for supplying gaseous fluid to the pump (16) forming a guide tube (9) around the shaft (11) immersed in the liquid, characterized in that it comprises a shroud (3) surrounding the pump (16) with clearance and of which a downward tubular extension (7) surrounds the stirring member (18), this shroud (3) being entirely embedded in the basin (1), the whole being arranged so that the pump (16) directly injects gaseous fluid only into a reduced volume of the liquid to be treated (2), limited by the shroud (3), this reduced volume then being propelled by the propeller (18) in the rest of the basin (1). SUB-CLAIMS 1. Installation according to claim II, characterized in that the motor (12) is capable of driving the pump (16) and the propeller (18) in both directions, the choice of a direction of rotation allowing a setting in contact of the reduced volume deals with the raw liquid (2) over a longer path than in the opposite direction. 2. Installation according to claim II and sub-claim 1, characterized in that the pipe (19) for supplying the raw liquid (2) opens inside the shell (3), the pipe (20) d evacuation having its entry near the bottom (8) of the basin (1). 3. Installation according to claim II and subclaims 1 and 2, characterized in that the lower end of the tube (9) for guiding the shaft (11) carries a flared collar (14) constituting a pump half-body above the pump wheel (16), this adhesive rette (14) being provided with radial ribs (15) forming a diffuser around the pump wheel (16). 4. Installation according to claim II and subclaims 1 to 3, characterized in that the main part of the shell (3), which is in the general shape of a vertical cylinder, is connected to its tubular extension (7) surrounding the propeller (18) by a frustoconical part (6). 5. Installation according to claim II and sub-claims 1 to 4, characterized in that the bottom (8) of the basin (1) is in the form of a hopper, the lower zone of which is opposite the said cylindrical extension (7).