LIQUID AND SLURRY MIXERS

A mixing vessel comprises a top portion (12) on an inverted conical middle portion (14) and a mixing chamber (16) below the middle portion. A launder (28) surrounds the upper part of the top portion. Solution from the launder is led to a vertical pipe (46) including a motor driven impeller (42) down to the level of the mixing chamber. Two vertically spaced feed pipes (46, 48) lead from the vertical pipe to enter the mixing chamber tangentially in opposite directions.

This invention relates to liquid and slurry mixers.

According to the invention there is provided a mixer comprising a vessel having a base plate and a launder at its upper end,a frame mounted on the side and upper end of the vessel,a motor, preferably a variable speed motor, carried by the frame,a vertical pipe underneath the launder and extending to the lower end of the vessel,a pump within the pipe and connected to the motor to be driven thereby, andtwo feed pipes tangentially entering into the bottom portion of the vessel and extending from the lower end of the pipe.

The upper end of the pipe is located, in use, somewhat lower than the level of the solution in the vessel. The liquid thus enters the upper end of the pipe and is driven downwardly by the pump to the two feed pipes in the bottom chamber of the vessel which directs the flow tangentially in opposite directions, causing very good mixing. Means are provided projecting into the lower portion of the vessel and inhibiting the upward movement of the liquid/slurry before moving inwardly beyond the said means whereafter the liquid/slurry is permitted to pass upwardly above the said means so that the liquid/slurry that has been passed down the pipe will mix well with the material in the vessel below and above the said means. Thus, the liquid that has been passed down the pipe will mix well with the material in the vessel below and above the said means which are often called “shoulder rings”. The pump and motor frame are preferably removably connected to the vessel so that it can be easily removed therefrom for repair or replacement.

Each “shoulder ring” preferably comprises an outer wall mounted ring that could divided into a number of segments with slots or holes. The shoulder rings improve the turbulence in the bottom mixing chamber as well as ensuring even upflow distribution in the upper part of the vessel.

The pump preferably comprises a helical impeller mounted on the motor drive shaft. A stator surrounds the shaft preferably below the helical impeller to provide support for the shaft and to break the swirl effect. A second stator can be added above the impeller to minimise air intake into the solution/slurry.

The mixer can be used as a single unit or part of a group of mixers.

An embodiment of the invention will now be described by way of example with reference to the accompanying drawings.

Referring now to the drawings there is shown a mixer10. The mixer10comprises an upper cylindrical vessel tank section12on a conical tank section14which rests on a bottom mixing chamber16. The bottom mixing chamber16is divided by a “bottom shoulder ring” or shelf18into upper and lower parts20and22. There is an upper “shoulder ring”24at the top of the mixing chamber16and this has an inclined ring26running from the inner edge of the upper shoulder ring24to the top edge of the mixing chamber16. The upper edge of the upper cylindrical tank section12has an overflow launder28.

Mounted on the top portion of the tank12, the launder28carries a removable frame30. The frame30carries at its centre a platform32on which is vertically mounted a variable speed drive motor34. The motor34has a vertical motor driveshaft36rotatably mounted in bearings38and40carried on upper and under platforms42and44on the frame30. Below the platform32is a vertical pipe46. The driveshaft36is contained within the vertical pipe48and extends to the bottom of the mixer12. The pipe48and the mixer10are mounted on ground engaging carriers50.

Within the lower part of the pipe38and within the pipe is a pump40in the form of a helical impeller42. Below the impellor42is a stator44to remove or minimise the swirl in solution being driven by the impellor42.

At the bottom end of the pipe28are two distribution pipes46and48that enter respectively the upper and lower parts of the mixing chamber16in a tangential direction so that the water from the upper distribution pipe46enters the mixing chamber16clockwise and the lower distribution pipe46guides the solution into the lower part of the mixing chamber16in a counter-clockwise direction. The upper edge of the pipe is slightly below the lower part of the launder28and in use the solution/slurry enters the pipe and then is forced down the pipe by the impeller to the mixing chamber16. The solution mixes tangentially and counter currently and passed the shoulder rings18and24so that the solution/slurry moves upwardly in the vessel and causes the solution/slurry to mix with the material and maintain suspension.

Reference is made toFIG.5where the direction of movement of the solution is given by arrows as can be seen in which the water moves over the top edge of the upper tank section12and down into the launder28. Then the water runs down the base of the launder28and into the pipe48.

In a typical use of the vessel10it serves to mix solution and particles (solids for either the leaching process or for an absorption process). The mixer can be used to mix any solution, reagent or slurry as an example. The vessel can also be used for flotation and as a jig (particle separation).

It will be seen that the vessel10with the pump40as described above is more efficient than the agitator/mixer units used currently. By having a variable speed drive motor20it is possible to avoid the necessity of using gearboxes as is required in apparatus used heretofore. The variable speed drives give full flow control for mixing and suspending the materials. The embodiments above-described provides extremely good mixing of, for example, any solution and solids. It will further be seen that the pump/mixer unit is easy to maintain as it can be taken out of the tank even when there is solution and/or solids in the tank and then repaired or replaced with a new pump/mixer unit.

It also be seen that the pump/mixer unit10draws solution from the top of the tank or vessel12and transfers it through the pipe via the impeller to the bottom of the vessel and thereafter the flow of the solution is upward in the direction that the particle suspension is required this provides more efficient mixing compared to conventional mixer/agitators. We have also found that this arrangement enables much better absorption apparatus than currently in use of which we are aware.

The mixing vessel can be used as a single unit. It can also be used with others to form a carousel as shown inFIG.8. The mixers are placed into lines of three and the mixers are in pairs. Running down the middle of the two lines of mixers is a tails slurry manifold ending in a downpipe leading to the tail slurry. Two parallel tank drainpipes join near one end connected to the six mixers then there is a feed slurry manifold leading to the six mixers and then leads to a bypass to the tails manifold near the end thereof.

Valves are provided so that the connections to and from the six mixers to the slurry feed; connections from the mixers to the tails manifold; and from the other six mixers to the tank drain can be varied so that the order in which the mixers are connected to the manifolds can be altered as desired.

The invention is not limited to the precise constructional details hereinbefore described and illustrated in the drawings. For example, there may be two pumps each connected to a downpipe forcing the solution downwards and respectively to the two distribution pipes. The numbers of mixers may be increased or decreased in the carousel.