AU696266B2 - An apparatus and a method for mixing or dissolving a particulate solid in a liquid - Google Patents

Description

WO 95/103120 PCT/AU94/00422 AN APPARATUS AND A METHOD FOR MIXING OR DISSOLVING A PARTICULATE SOLID IN A LIQUID Field of the Invention The present invention relates to an apparatus and a method for mixing or dissolving a particulate solid in a liquid to form a solution and relates particularly, though not exclusively, to an apparatus and method .or mixing or dissolving particulate solid materials in water.

Background of the Invention Chemicals or fertilisers may be purchased in either the solid granular form or liquid form. The liquid form of these substances has inherent problems associated with handling and spillage which generally make the substance cumbersome and hazardous to work with. A safer alternative to liquid substances is the use of particulate solids whi.ch can be mixed or dissolved in a liquid to form a solution. The use of the particulate solid avoids the unnecessary hazards associated with spillage of liquid when decanting a liquid substance.

When mixing or dissolving a particulate solid in a liquid it is generally advantageous to form a solution of homogeneous concentration. The homogeneous concentration of the solution is important where a specific concentration of a liquid solution is required, as for example in chemical dosing for pH control in an effluent plant.

Furthermore where solids have coagulated or not dissolved this may result in blockage of downstream apparatus for example, spray nozzles in chemical applicators such as boom sprays, or filters.

Presently, solids are mixed or dissolved in liquids by adding the solid to the liquid and agitating the combined solution. This agitation may be performed by mechanical stirring or bubbling air through the solution.

In both instances it is difficult to ensure that there is a consistent level of agitation throughout the solution.

-2- Consequently the solid may settle to the bottom of a vessel without mixing or dissolving in the liquid and thereby coagulate to form a solid difficult to mix or dissolve.

Summary of the Invention The intention of the presenL invention is to provide an apparatus and a method for mixing or dissolving a particulate solid in a liquid that is relatively effective in mixing or dissolving the particulate solid, is safe to use, and requires relatively little maintenance.

According to one aspect of the present invention there is provided an apparatus for dissolving a particulate solid in a liquid to form a solution of substantially homogenous concentration, said apparatus comprising: a baffleless vessel for containing said liquid or said solution, said vessel comprising a substantially cylindrical portion having a smooth continuous inside surface and formed continuously with a lar'fe diameter end of a conical frustum portion, said conical frustum portion having an outlet at a small diameter end for discharge of 20 said liquid or said solution and at least one inlet in fluid communication with the outlet; .a pump for recirculating said liquid or said solution through saic vessel from said outlet to said at least one inlet to effect a flow of recirculated liquid or solution through the vessel; and, said at least one inlet of said vessel directing the recirculated liquid or solution to flow substantially parallel to an inside surface of the vessel so as to produce a substantially circular non turbulent flow of said recirculated liquid or solution in the vessel, said circular non turbulent flow being effected about a longitudinal axis of the vessel whereby, in use, the combined action of both said pump and said at least one inlet alone together create the substantially circular non turbulent flow of said recirculated liquid or solution which is effective in dissolving said particulate solid in -3said liquid to form said solution of substantially homogeneous concentration.

According to another aspect of the present invention there is provided a method for dissolving a particulate solid in a liquid for form a solution of substantially homogenous concentration, said method comprising the steps of: providing a baffleless vessel for producing a circular non turbulent flow of liquid about a longitudinal axis of the vessel, the vessel having a cylindrical portion provided with a smooth continuous inside surface formed continuously with a large diameter end of a conical frustum portion said conical frustum portion having an outlet at a small diameter r(nd for discharge of said liquid or ooo solution; is°: 1pouring said liquid into said vessel; recirculating said liquid through said vessel "'"between at least one inlet to the vessel and an outlet portion formed in said vessel; 20 disposing said at least one inlet for directing °said liquid or solution parallel co said smooth continuous inside surface to produce said substantially circular non turbulent flow of said liquid in said vessel; and adding particulate solid to said liquid or solution proximate said inside surface while maintaining said recirculating and said circular non turbulent flow, whereby, in use, the combined action of recirculating said liquid or solution and producing said circular non turbulent flow create a liquid or solution flow for dissolving said particulate solid in said liquid to form a solution of substantially homogeneous concentration.

WO 95/03120 PCTIAU94/00422 4

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Brief Description of the Drawings In order to facilitate a better understanding of the nature of the present invention a preferred embodiment of the apparatus and the method for mixing or dissolving a 20 particulate solid in a liquid will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 shows, in a schematic side elevational view, an apparatus according to the present invention for mixing or dissolving a particuiate solid in a liquid; and, Figure 2 shows a section A-A taken from the apparatus shown in Figure 1.

Detailed Description of the Preferred Embodiments As best shown in Figure 1 there is an apparatus 10 for mixing or dissolving a particulate solid such as a granular chemical 12 in a liquid such as water 14 to form a liquid solution 16 of substantially homogeneous concentration. The apparatus 10 comprises a vessel 18 for containing the water 14 or the solution 16. The vessel 18 has an outlet 32 for discharge of the water 14 or solution WO 95/03120 PCT/AU94/00422 5 16 and, in this embodiment, one inlet 34 in fluid communication with the outlet 32. A recirculating means shown generally as item 20 is provided for recirculating the water 14 or the solution 16 through the vessel 18 from the outlet 32 to the inlet 34. Static means shown generally as item 21 operatively cooperate with the veE*3el 18 to produce a substantially circular flow 36 of the water 14 or solution 16 in the vessel 18.

The vessel 18 substantially cylindrical in cross section is formed continuously with the largest diameter end of a conical frustum 24 at the outlet 32 of the vessel 18 with the smallest diameter end of the conical frustum 24 downstream of the largest diameter end of the conical frustum 24. The outlet 32 is defined by the largest diameter end of the conical frustum 24.

The recirculating means 20 comprises a suction line 26 connected upstream of a pump 28, and a discharge line 30 plumbed downstream from the pump 28. The suction line 26 is connected to the smallest diameter end cf the conical frustum 24 and the discharge line 30 is connected to the vessel 18 at the inlet 34.

The water 14 or solution 16 can be pumped from the outlet 32 through the conical frustum 24 and the suction line 26 by the pump 28 and discharged through the discharge line 30 to the inlet 34 and returned to the vessel 18 through a flow nozzle 22.

As best shown in Figure 2 the flow nozzle 22 comprises a tube formed in the shape of an elbow. One end of the flow nozzle 22 is connected to the vessel 18 at the inlet 34.

The flow nozzle 22 is shaped to direct the water 14 or solution 16 in a direction which is substantially parallel to an inside surface of the vessel 18 adjacent the inlet 34 such that the water 14 or solution 16 is given a substantially circular flow 36 (most clearly shown in Figure The circular flow 36 of the water 14 or WO 95/03120 PCTIAU94/00422 6 solution 16 moves in a downstream direction 38 in the vessel 18.

The mixing or dissolving apparatus 10 may additionally indorporate valving and plumbing for pumping the solution 16 to a holding tank (not shown) of, for example, a boom spray 40 following a mixing or dissolving process. In this instance a boom spray feed line 42 is connected to the holding tank of the boom spray 40 and at the opposite end is connected to the discharge line 30 at a T-piece 44. An isolating valve 46 on the boom spray feed line 42 is located between the discharge line 30 and the holding tank of the boom spray 40. A recirculating valve 48 is located downstream of the T-piece 44 on the discharge line A method for mixing or dissolving granular chemical 12 in water 14 using the apparatus 10 as described above will now be described in detail. The method is not, however, limited to this application of the apparatus and is merely illustrative of the inventive concept of the p:-ent invention.

The isolating valve 46 on the boom spray feed line 42 is closed and the recirculating valve 48 on the discharge line 30 is opened. A predetermined volume of water 14 is then poured into an open end of the vessel 18.

The predetermined volume of water 14 is such that the level of the water 14 is immediately above the flow nozzle 22 connected to the vessel 18. The pump 28 is then switched ON and the water 14 is sucked in the downstream direction 38 through the vessel 18, the conical frustum 24, and along the suction line 26. The pump 28 then discharges the water 14 through the discharge line 30 and returns the water 14 to the vessel 18 at the inlet 34. The substantially circular flow 36 is produced by the combined effect of the conical frustum 24 and the flow nozzle 22 which returns the water 14 to the vessel 18 in a direction substantially parallel to an inside surface of the vessel 18 adjacent the inlet 34. Once this circular flow 36 has been established WO 95/03120 PCT/AU94/00422 7 a predetermined mass of granular chemical 12 is added to the water 14 or the solution 16 through the open end of the vessel 18. Preferably, the granular chemical 12 is added to the surface* of the water 14 or solution 16 in a peripheral zone 52. In this way the retention time for the granular chemical 12 in the water 14 or solution 16 contained in the vessel 18 is maximised thereby promoting the mixing or dissolving of the granular chemical 12 in the water 14 or solution 16.

Once the granular chemical 12 is mixed or dissolved in the water 14 or solution 16, which time will be determined by trial and experiment, the recirculating valve 48 can be closed. A solution 16 of substantially homogenous concentration is now contained in the vessel 18.

The isolating valve 46 on the boom spray feed line 42 is then opened whereupon the substantially homogeneous solution 16 is sucked by the pump 28 through the conical frustum 24 along the suction line 26 and discharged by the pump 28 through the discharge line 30 and the boom spray feed line 42 to a holding tank (not shown) of the boom spray 40. When the spraying is complete, the pump 28 is turned OFF, the isolating valve 46 then closed and the recirculating valve 48 opened in preparation for mixing or dissolving another batch of granular chemical 12.

Now that a preferred embodiment of the mixing or dissolving apparatus and the method for mixing or dissolving a particulate solid in a liquid have been described in detail, it will be apparent to those skilled in the art that the apparatus and method described have a number of advantages over the prior art including: 1. the substantially homogeneous mixing or dissolving provided by the present invention as a result of the static means reduces the risk of blocking equipment downstream of the apparatus; 2. particulate solids are provided with more than a single pass through the mixing or dissolving apparatus by incorporating a recirculating means; and, WO 95103120 PCT/AU94/00422 8 3. moveable parts such as paddles or blade stirrers are eliminated thereby reducing maintenance and potential hazards associated with moving parts.

It will be apparent to persons skilled in the relevant arts that numerous variations and modifications can be made to the apparatus and method described in addition to those already mentioned above without departing from the basic inventive concepts of the present invention.

For example, the particulate solid may be injected into the recirculating means instead of adding the solid to the vessel, as was described in the above embodiment. The pump may also be configured to fill the vessel with a predetermined volume of liquid by incorporating the necessary valves and flow lines in the mixing or dissolving apparatus. While the use of the apparatus or method is described with reference to fertigation they could equally be used in other chemical applications such as mixing or dissolving granular caustic soda in water. Although in the preferred embodiment the static means for producing the circular flow is shown as a combination of the conical frustum and the flow nozzle the circular flow could in fact be achieved by either one of these devices. All such variations and modifications are to be considered within the scope of the present invention, the nature of which is to be determined from the foregoing description.

Claims (4)

1. An apparatus for dissolving a particulate solid in a liquid to form a solution of substantially homogenous concentration, said apparatus comprising: a baffleless vessel for containing said liquid or said solution, said vessel comprising a substantially cylindrical portion having a smooth continuous inside surface and formed continuously with a large diameter end of a conical frustum portion, said conical frustum portion having an outlet at a small diameter end for discharge of said liquid or said solution and at least one inlet in fluid communication with the outlet; so$: S* a pump for recirculating said liquid or said solution through said vessel from sa>- outlet to said at least one inlet to effect a flow of recirculated liquid or solution through the vessel; and, said at least one inlet of said vessel directing the recirculated liquid or solution to flow substantially parallel to an inside surface of the vessel so as to 50*8 '0 produce a substantially circular non turbulent flow of said recirculated liquid or solution in the vessel, said circular non turbulent flow being effected about a longitudinal axis of the vessel whereby, in use, the combined action of both said pump and said at least one inlet alone together create the substantially circular non turbulent flow of said recirculated liquid or solution which is effective in dissolving said particulate solid in said liquid to form said solution of substantially homogeneous concentration.

2. The apparatus according to claim 1 further including a separate elbow shaped tube connected to each of said inlets and extendciing into the vessel for directing said recirculated liquid or solution from said inlets to flow in a direction substantially parallel to said inside surface of said vessel. VS*A ~N

3. A method for dissolving a particulate solid in a liquid for form a solution of substantially homoyenous concentration, said method comprising the steps of: providing a baffleless vessel for producing a circular non turbulent flow of liquid about a longitudinal axis of the vessel, the vessel having a cylindrical portion provided with a smooth continuous inside surface formed continuously with a large diameter end of a conical frustum portion said conical frustum portion having an outlet at a small diameter end for discharge of said liquid or solution; pouring said liquid into said vessel; recirculating said liquid through said vessel 99*9 between at least one inlet to the vessel and an outlet 9996 o 1 5 portion formed in said vessel; disposing said at least one inlet for directing said liquid or solution parallel to said smooth continuous S"inside surface to produce said substantially circular non turbulent flow of said liquid in said vessel; and 20 adding particulate solid to said liquid or *999 solution proximate said inside surface while maintaining said recirculating and said circular non turbulent flow, whereby, in use, the combined action of recirculating said liquid or solution and producing said circular non turbulent flow create a liquid or solution flow for dissolving said particulate solid in said liquid to form a solution of substantially homogeneous concentration.

4. An apparatus for dissolving a particulate solid in a liquid substantially as herein described with reference to and as illustrated in the accompanying drawings. An method for dissolving a particulate solid in a liquid substantially as herein described with reference to and as illustrated in the accompanying drawings.