RU2553861C1 - Hydrodynamic mixer - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: mixer comprises a casing with axial and radial branch pipes for component supply, mixing elements. The axial inlet branch pipe can move back-and-forth and is made as a conical-cylindrical nozzle. A mixing element consists of a conical insert with circular grooves on its surface. The insert is located in the conical part of the mixing element casing. A deflector in the form of an indentation is provided at the end face of the insert opposite the conical-cylindrical nozzle in the centre. The mixing element casing is fitted by through channels set on concentrical circumferences. The circular grooves are connected to the first mixing chamber by channels. There shall be at least two mixing elements. The total area of the channels connecting the circular grooves to the mixing chamber amounts to (5-20)% of the area of the cross section of the circular radial gap at the inlet to the mixing element. Diameters of the concentrical circumferences on which centres of the channels provided on the end face surface of the conical insert greater base are located, are determined according to a mathematical expression.

EFFECT: intensified hydrodynamic, physical-chemical and heat-and-mass exchange processes.

4 cl, 3 dwg

Description

The invention relates to devices for mixing, emulsification, homogenization of liquid media and can be used to conduct and intensify various physicochemical, heat and mass transfer processes in the liquid-liquid and liquid-gas systems.

Known gas-liquid mixer (RU 2336940 IPC B01F 5/06, publ. 27.10.2008) containing a housing with transverse diaphragms, a pipeline for supplying gas with a nozzle, and the diaphragms are made with the possibility of longitudinal movement and equipped with a Central slotted hole. Each opening of the subsequent diaphragm is offset by a slight angle. The intensification of the mixing process is carried out due to the turbulization of the flow of the processed medium.

The disadvantages of the mixer are the absence of acoustic vibrations and cavitation, which reduces the quality of the resulting gas-liquid emulsion and the intensity of mixing.

The closest in technical essence and the achieved result is a cavitation type mixer (RU 2158627 IPC B01F 5/08, publ. 10.11.2000) containing a cylindrical working chamber with a coaxial inlet in the form of a diffuser pipe, mixing elements and a pipe for supplying an additional component of the mixture, and mixing elements are made in the form of a multi-jet nozzle. Mixing is carried out due to hydrodynamic cavitation.

The disadvantage of the mixer is the absence of acoustic oscillations of significant amplitude in the medium being processed at a certain frequency, because the acoustic radiation caused by the collapse and pulsation of cavitation bubbles is insignificant and has a continuous spectrum from hundreds of Hz to tens of thousands of Hz. (Ultrasound. Little Encyclopedia. Head. Ed. IP Galyamin. - M.: Soviet Encyclopedia. 1979, p. 161).

The technical task of the invention is the intensification of hydrodynamic, physico-chemical and heat and mass transfer processes.

The stated technical problem is achieved in that in a hydrodynamic mixer containing a cylindrical housing with axial and radial nozzles for introducing components, the mixing elements, the axial inlet pipe has the possibility of reciprocating movement and is made in the form of a conical-cylindrical nozzle, and the mixing element is a conical insert , on the surface of which at least two annular grooves are made, and fixed in the housing of the mixing element having an internal conical surface ited on the end face of the larger base of the conical insert opposite the exit cone and a cylindrical nozzle is a concave reflector in the form of wells; in the end wall of the housing of the mixing element, where the conical insert is fixed, through channels are made located on concentric circles, and on the end surface of the larger base of the conical insert of the mixing element there are channels located on concentric circles connected to the annular grooves.

The number of mixing elements is at least two.

The total area of the channels made on the end surface of the larger base of the conical insert of the mixing element is (5 ... 20)% of the cross-sectional area of the annular radial clearance at the entrance to the mixing element.

The diameters of the concentric circles D _qi , on which the centers of the channels located on the end surface of the larger base of the conical insert of the mixing element are located, are determined from the expression

where D _Vpi - the diameter of the hollows of the annular grooves;

D _height - the smallest diameter of the protrusion of the annular groove;

i = 1, 2, 3 ... n - number in the order of grooves;

n is the number of annular grooves on the conical insert of the mixing element.

In Fig 1. schematically shows a hydrodynamic mixer, a longitudinal section. In Fig 2. shows a section aa in Fig 1. Ha Fig 3. shows a view of B in Fig 1.

The hydrodynamic mixer contains a housing 1 with a radial nozzle for the input of the additional component 2, a cover 3 with a nozzle for the axial inlet of the main component 4, spacer sleeves 5, at least two mixing elements 6, each consisting of a housing 7 with an internal conical surface and through channels 8 fixed in a conical insert 9 with annular grooves 10 and annular protrusions 11, with through channels 12, a first mixing chamber 13 formed by a cover 3, a spacer sleeve 5 and the end face of the conical insert 9 of the first mixture solid element; reflector 14, an annular radial clearance 15, formed by the conical outer surface of the annular protrusions 11 and the inner conical surface of the housing of the mixing element 7, the second mixing chamber 16 located in the housing of the mixing element 7, the third mixing chamber 17, formed by the end face of the housing of the first mixing element, the end of the conical the insertion of the second mixing element and the spacer sleeve 5, the chamber 18 formed by the end face of the previous mixing element 6, the spacer sleeve 5, the cover 19, the output second port 20.

The mixer operates as follows: the main liquid component under pressure enters through the inlet axial nozzle 4 into the first mixing chamber 13 and enters the reflector 14, at the same time the second component is pressurized through the radial nozzle 2 into the chamber 13, then the pre-mixed components through the annular radial clearance 15 , the annular grooves 10 enter the second mixing chamber 16, while part of the medium being processed from the chamber 13 passes directly through the channels 12 located in the conical insert 9, in annular grooves 10. Then, the medium to be processed through the channels 8 passes to the next mixing chamber 17. The movement in the following mixing elements proceeds in the same way as in the first mixing element, except that the cavitation reflector 14 does not generate oscillations after exiting the last mixing element the medium enters the chamber 18 and is discharged from the outlet pipe 20.

The main component of the medium being processed, passing the central inlet nozzle, made in the form of a confuser-cylindrical nozzle, significantly increases the speed of movement and, falling on the reflector located on the end surface of the conical insert of the mixing element, forms a cavitation cavity between the nozzle exit and the reflector. The cavitation cavity pulsates with a certain frequency and intensity, determined by the relations between the diameter of the nozzle and the diameter of the reflector with a certain shape of the reflector. The most economically advantageous concave shape of the reflector in the form of a hole. (Ultrasound. The Little Encyclopedia. Ed. By I.P. Galyamin. - M .: Soviet Encyclopedia, 1979 p. 80). Thus, in the first mixing chamber, intense cavitation and medium vibrations occur. The cavitation intensity is controlled by changes in the distance between the nozzle exit and the reflector using the axial movement of the central pipe. At the same time, the second medium component is fed into the mixing chamber through a radial nozzle. Thus, in the mixing chamber due to intense vibrations and cavitation, preliminary mixing of the components is carried out. Further mixing is carried out in the mixing elements.

The medium being processed, passing through an annular radial clearance formed by conical surfaces, the inner - the housing of the mixing element and the outer - annular protrusions, is subjected to significant shear stresses. The annular radial clearance in the longitudinal section is a series of successive narrowings and extensions, causing intense vortex formation in the extensions, in our case, in circular grooves. With a sudden expansion, energy losses are spent mainly on vortex formation, i.e. to maintain the rotational movement of the fluid and their constant exchange. With a sudden narrowing, the vortex formation is smaller and the annular space around the narrowed part of the flow is filled with a sedentary swirl fluid (V.V. Bogdanov, E.I. Khristovorov, B.A. Klotsung. Effective low-volume mixers. L .: Chemistry, 1989, p. 47- 48). To eliminate stagnation of swirling fluid in the annular grooves, channels 12 are provided connecting the mixing chamber 13 and the cavity of the annular grooves. It was empirically established that the total area of the channels connecting the mixing chamber and the annular groove cavities, depending on the flow rate of the liquid medium and the geometric dimensions of the mixer, should be (5 ... 20)% of the cross-sectional area of the annular radial clearance at the entrance to the mixing element. Thus, there is an optimal ratio of areas. With a ratio of less than optimal flow rate of the processed medium through the channels 12 does not eliminate stagnation in the cavities of the annular grooves. When the ratio is more than optimal, a significant part of the flow enters the cavity of the annular grooves, without being processed in the radial clearance between the conical surfaces: the inner - the housing of the mixing element and the outer - protrusions of the conical insert. In addition, with large ratios of areas and, accordingly, costs, vortex movement may not occur in the cavities of the grooves. Therefore, in these cases, the efficiency of the mixing element is reduced.

The cross-sectional area of the annular stepped radial clearance in the direction of motion of the medium being processed decreases, while the flow rate increases, therefore, the efficiency of mixing, dispersion, etc.

A special role in the intensification of the processes occurring in the mixing element is played by the superposition on the flow of oscillations generated by the cavitation region in the first mixing chamber and the first mixing element. It is known that the imposition of vibrations on the processed medium intensifies various hydromechanical, heat and mass transfer and physicochemical processes.

A further effect on the medium to be treated is in the second mixing chamber 16, in which, upon sharp expansion, vortex processes occur that contribute to an additional improvement in the quality of the mixture. Then, from the mixing chamber 16, through the channels 8, the medium enters the next mixing chamber, formed by the ends of the mixing elements 6 and spacer sleeves 5. Once in the mixing chamber, the jets of the medium being processed begin to diverge fan-shaped at a certain distance from the nozzle, with the jets actively colliding, which contributes to an additional increase in the efficiency of mixing, dispersion, etc. Obviously, in the second and other sequentially installed mixing elements, there are no sound vibrations emitted by a pulsating cavitation cavity. They are installed if one mixing element does not provide the required quality of the mixture or other result, for example, the required dispersion of the emulsion.

It should be noted that at certain flow rates of the medium in the mixing elements, when the flow is interrupted, the radial clearance suddenly expands in the region of the annular grooves, intense hydrodynamic cavitation occurs.

In the proposed construction, due to exposure to cavitation medium, turbulent pulsations, shear stresses, shock, dispersion of immiscible media is especially effective, for example, if the dispersion medium is water and the dispersed phase is oil. Thus, mixing and dispersing processes occur simultaneously in the device, which is necessary to obtain, for example, finely dispersed emulsions with a long separation time of the resulting product.

The proposed mixer design can be used to obtain a gas-liquid emulsion. In this case, it is necessary to supply gas to the radial pipe 2, made, for example, in the form of nozzles or another device for uniform distribution and crushing of the gas stream.

To confirm the effectiveness of the proposed device, preliminary experiments were conducted to obtain a cutting fluid with a 10% content of emulsol. The effectiveness of the mixer was evaluated by the time it takes to delaminate the emulsion, i.e. achieve a certain layer thickness of the oil film. A series of experiments was conducted when the water flow rate varied in the range (0.05 ... 1) m ³ / h, the supply pressure of the main water component (0.2 ... 0.4) MPa, the temperature of the initial mixture changed slightly (22 ... 25) ° C. In the first series, the inlet pipe was replaced by a cylindrical one. In the second, a conical-cylindrical one was installed. In the first and second series, two mixing elements were used. In the third series - a cylindrical pipe. In the fourth series - conical-cylindrical pipe. In the third and fourth, one mixing element was used. Preliminary results showed that the proposed design used in the second series is most effective. The delamination time in the first series decreased by 41%, in the third - by 56%, in the fourth - by 12%. It was found that the use of a movable conical-cylindrical pipe allows one to determine its optimal position from the point of view of the most developed cavitation. Note that in the second and fourth series in the chamber 13, sound vibrations with increased amplitude at a certain frequency were observed. In the tested design, the fundamental frequency was approximately 2.5 kHz, with harmonics up to 50 kHz being observed. The intensity of vibrations and cavitation was determined using a hydrophone from barium titanate with a head diameter of ≈3.5 mm.

Thus, preliminary experiments have confirmed the high efficiency of the proposed mixer design.

Claims (4)

1. A hydrodynamic mixer comprising a cylindrical body with an axial and radial nozzle for introducing components, mixing elements, characterized in that the axial inlet nozzle has the possibility of reciprocating movement and is made in the form of a conical-cylindrical nozzle, and the mixing element is a conical insert, on the surface of which is made of at least two annular grooves, and fixed in the housing of the mixing element having an internal conical surface, on the end face of a larger base Nia conical insert opposite the exit cone and a cylindrical nozzle is a concave reflector in the form of wells; in the end wall of the housing of the mixing element, where the conical insert is fixed, through channels are made located on concentric circles, and on the end surface of the larger base of the conical insert of the mixing element there are channels located on concentric circles connected to the annular grooves. 2. The hydrodynamic mixer according to claim 1, characterized in that the number of mixing elements is at least two. 3. The hydrodynamic mixer according to claim 1, characterized in that the total area of the channels made on the end surface of the larger base of the conical insert of the mixing element is (5 ... 20)% of the cross-sectional area of the annular radial clearance at the entrance to the mixing element. 4. The hydrodynamic mixer according to claim 1, characterized in that the diameters of the concentric circles D _qi, on which the centers of the channels located on the end surface of the larger base of the conical insert of the mixing element are located, are determined from the expression

,
where D _Vpi - the diameter of the hollows of the annular grooves;
D _height - the smallest diameter of the protrusion of the annular groove;
i = 1, 2, 3 ... n - number in the order of grooves;
n is the number of annular grooves on the conical insert of the mixing element.

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