WO1982002152A1

WO1982002152A1 - Liquid mixer

Info

Publication number: WO1982002152A1
Application number: PCT/US1981/001719
Authority: WO
Inventors: Systems Inc Komax; Tony L King
Original assignee: Systems Inc Komax
Priority date: 1980-12-22
Filing date: 1981-12-22
Publication date: 1982-07-08
Also published as: EP0067218A4; EP0067218A1

Abstract

A device for the mixing of materials which comprises a mixing tank (1) having a substantially circular cross-section, a fluid inlet pipe (7) having at least one inlet (8) located below the intended level of the fluid to be mixed within the mixing tank, a fluid exit pipe (10) having at least one fluid outlet (11) below the intended level of the fluid to be mixed within the mixing tank, wherein the fluid exit is substantially tangential to the side wall of the mixing tank. The fluid inlet pipe (7) and exit pipe (10) are intended to be connected through a fluid pump (19) and, as a preferred embodiment, an inline motionless mixer (12) is placed downstream of the pump (9).

Description

LIQUID MIXER -

Background of the Invention _ It has long been known that efficient fluid

5 mixing is enhanced through the formation of a vortex within the mixing tank or vessel. This is illustrated in Fig. 1A wherein a two-component mixture, for example, water 2 and oil 3 have been allowed to settle within mixing tank 1. 10 In Fig. 1B- stirring has begun as shown by arrow 4 and the resultant force exerted upon the fluids exhibits itself particularly at the surface of fluid 3 and at the interface between fluids 2 and 3. This phenomenon is further accentuated as stirring continues 15 as seen in Fig. 1C. As vortex formation becomes more acute- the top surface of fluid 3 becomes markedly depressed at 6 while a significant segment of fluid 2 rises at the center of the vortex so that areas 5 and 6 approach each other and, under intense mixing, touch. 20 Vortex formation, such as described above and illustrated in Fig. 1, results in a most advantageous condition for the mechanical mixing of two or more non-miscible fluids. As one would probably imagine, a most ideal mixing system would be one which establishes 25 vortex formation while minimizing the disturbance of the natural upper and lower vortices (see elements 5 and 6 of Fig. IC) . Unfortunately, conventional mixing systems have presented a substantial inhibition to vortex formation. J- 30 Conventional mixing paddles have proven to be

__r a major problem. Basically, the conventional mixing paddle is comprised of a shaft, mixing blades and boss which connects the blades to the shaft. The shaft and boss actually interfere with the generation of natural mixing vortices that lift heavier material from the bottom of the mixing tank and suppress or drive light material downwards.

Prior art mixing tanks have attempted to minimize disruptions in natural vortex formation by selectively placing baffles against the vertical side walls of the mixing tank. The baffles act to induce the fluid materials to move vertically and mini¬ mize stratification within the tank. However, the baffles act as a resistance to fluid movement within the tank and greatly increase the power requirements necessary to establish and maintain acceptable fluid mixing.

-It is thus an object of the present invention to teach a device to maximize fluid mixing.

It is yet another object of the present invention to teach a device to optimize vortex formation in fluids held within a mixing tank to maximize fluid mixing. It is still another object of the present invention to teach a device for maximizing fluid mixing through the expenditure of a minimum of energy.

Brief Description of the Drawing

These and other objects will be further described and understood by reference to the following drawings in which:

Fig. 2 is a cross-sectional schematic of one embodiment of the present invention;

Fig. 3 is a cross-sectional schematic of a preferred embodiment of the present invention; and

Fig. 4 is a cross-sectional schematic of an even more preferred embodiment of the present invention.

Summary of the Invention

A device for the mixing of materials, such as two or more immiscible fluids, is taught. The device comprises a mixing tank 1 having a substantially circular cross-section. Within mixing tank 1 is a fluid inlet pipe 7 having at least one inlet 8 located , below the intended level of the fluid to be mixed 5 within the mixing tank. The tank also embraces a fluid exit pipe 10 having at least one fluid outlet 11 below the intended level of the fluid to be mixed within the tank. Fluid exit 11 is positioned so that the fluid being discharged from pipe 10 moves substan- 10 tially tangentially to the side wall of the mixing tank. Inlet pipe 7 and exit pipe 10 are connected to an inline motionless mixer, such as a Komax mixer, which provides the fluid flow within the mixing tank. The arrangement described above mixes the 15 fluids within tank 1 by drawing fluid into inlet 8 and expelling the fluid through outlet 11. Pump 9 acts to draw and push the fluid as described previously and vortex formation is established quite readily without the necessity for the baffles of the prior art. To 20 further enhance mixing, the inline motionless mixer 12, as recited above, is inserted downstream of pump 9.

Although the mixing device as shown in Fig. 2 adequately performs the intended function of the present invention, the device shown in Fig. 3 provides 25 for improved results. More specifically, it has been found to be advantageous to place the pump below the mixing tank rather than in the position shown in Fig. 2 for not all pumps are self-priming.

It has also been determined that providing a 30 plurality of inlets 8 and outlets^'11 in the fluid inlet and exit pipes 7 and 10, respectively, is advantageous > in controlling stratification effects. It was found that when rather large density differences exist between various components being mixed, top to bottom 35 density variations in the final product can be virtually eliminated. - -

Yet another advantage in the device depicted in Figs. 3 and 4 is that inlet pipe 7 is opened at its top 13, which allows for the addition of concentrated components to be mixed. There are instances wherein it 5 would not be advantageous to mix two components by crudely dumping a first fluid within the body of a second fluid contained within mixing tank 1. This is particularly the case when there are significant density differences between the first and second

10 fluids. By introducing the concentrated fluid to the system through open end 13 of inlet pipe 7, it is caused to be premixed with the bulk fluid being drawn into inlet pipe 7 through top 13 as well as through inlet 8. These components are then premixed by virtue

15 of the action of pump 9 as well as optional inline motionless mixer 12. A concentrated solution of the fluid is then introduced to the main fluid body via outlet ports 11.

Fig. 4 illustrates yet another improved

20 embodiment of the present invention. More specifically, inlet pipe 7 has been moved proximate the side wall of tank 1 ideally diametrically opposite to the position of inlet pipe 10. Having the inlet ports 8 tangentially positioned as are the exit ports 11, it has been

25 determined that vortex formation is further enhanced. As in the embodiment shown in Fig. 3, premixing can again be accomplished by introducing fresh components to the top of inlet pipe 7 at 13, the premixing being done in pump 9 as well as in inline motionless mixer

30 12.

As a further optional embodiment, inlet 14 is provided downstream of pump 9 for the introduction of air or any other suitable gas to aerate the fluid within the mixer. Furthermore, valve 15 can be located

35 as shown in Fig. 4 to transfer fluid to a downstream processing station. By placing exit 16 for with-

OMPI drawing fluid as shown in Fig. 4, pump 9 acts as a transfer pump to encourage the passage of fluid through valve 15. It should be noted that with such an arrange¬ ment, the fluid can continue to be mixed while transferring fluid to the next processing station. Although the present invention was described as a device which enhances vortex formation and thus results in more efficient mixing, other advantages inherent in practicing the present invention would clearly be obvious to those skilled in this art. For example, often times when a mixing operation is shut down, a heavy slurry will settle at the bottom of the mixer and form a dense region of high resistance. In a conventional mixing tank, the mixing blades are caused to begin turning when embedded in such a thick slurry, and it is often difficult if not impossible to commence fluid movement within the mixing tank. High resistance to flow during initial start-up is also the cause of motor burn out as well as a diminished life expectancy for the paddle and associated parts. By contrast, the present invention experiences no problem in start-up operations. When confronted with this type of situa¬ tion, the pump first feeds on light fluid at the top of the tank resulting in the commencement of stirring by injecting the light fluid out of the exit ports, which eventually begins moving the heavier slurry. In a very short period of time, the entire mixture becomes quite homogeneous.

In practicing the present invention, very little pumping capacity is required. For example, when using a 5-gallon test tank, it was found that a pump operating at merely 2 gallons per minute could completely disperse particulate material, namely, yellow cornmeal, within an aqueous medium in less than 20 seconds. While particular preferred embodiments of the invention have been shown and described and various modifications thereof suggested, it will be understood that the true spirit and scope of the invention is set forth in the appended claims, which embrace other modifications and embodiments which will occur to those of ordinary skill in the art.

Claims

1. A device for the mixing of material comprising a mixing tank having a substantially circular cross-section, a fluid inlet pipe having at least one inlet located below the intended level of fluid to be mixed within the mixing tank, a fluid exit pipe having at least one fluid outlet below the intended level of fluid to be mixed within the mixing tank, said fluid exit being substantially tangential to the side wall of the mixing tank, and wherein said fluid inlet pipe and exit pipe are connected through a fluid pump.

2. The device of claim 1 which further comprises an inline motionless mixer located between the fluid pump and fluid exit pipe.

3. The device of claim 1 wherein said fluid pump is located above the mixing tank.

4. The device of claim 1 wherein said fluid pump is located below the mixing tank.

5. The device of claim 4 wherein the fluid inlet pipe is open above the intended level of fluid to be mixed.

6. The device of claim 1 wherein the fluid inlet pipe is located proximate the side wall of the mixing tank.

7. The device of claims 1 or 6 wherein the inlet and exit pipes are proximate the vertical side walls of the mixing tank such that the fluid being mixed is tangentially drawn from the mixing tank by the inlet pipe and tangentially fed to the mixing tank by the exit pipe.

8. The device of claim 1 wherein the mixing tank has located therein, two fluid inlet pipes, the first being proximate the side wall of the mixing tank and the second being proximate the geometric center of the mixing tank.

9. The device of claim 1 which further comprises a fluid inlet downstream of the fluid pump.

10. The device of claim 2 which further comprises a valve downstream of the inline motionless mixer and upstream of the exit pipe to selectively remove fluid from the mixing tank.

11. The device of claim 1 wherein the inlet pipe has inlet orifices located repeatedly along substantially the entire length of the pipe.

12. The device of claim 1 wherein the exit pipe has exit orifices located repeatedly along substan¬ tially the entire length of the pipe.