GB2245190A

GB2245190A - Mixing a liquid and solids

Info

Publication number: GB2245190A
Application number: GB9110005A
Authority: GB
Inventors: Paul Fallows; Alan Nigel Greenwood
Original assignee: UK Atomic Energy Authority
Current assignee: UK Atomic Energy Authority
Priority date: 1990-06-06
Filing date: 1991-05-09
Publication date: 1992-01-02
Also published as: GB9012605D0; CA2042122A1; EP0460804A1; JPH04227836A; AU7812591A; GB9110005D0

Description

j 1 A Method of Mixing a Liquid and Solids and Apparatus Therefor This

invention relates to a method and apparatus for mixing a liquid and solids and more particularly but not exclusively to the continuous mixing of a liquid and solids in powder form.

According to one aspect of the present invention, there is provided a method of mixing a liquid and solids, -the method comprising feeding the solids into the liquid whilst the liquid is swirling about the surface of a chamber which is converging downwardly towards an outlet, the chamber comprising at least two frusto-conical portions thereof disposed one above the other, the upper said portion having a substantially larger included angle than that of the lower said portion.

According to a second aspect of the invention, there is provided apparatus for the mixing of a liquid and solids by the method of the first aspect of the invention, the apparatus comprising a chamber having a plurality of inlets for the liquid aligned so as to induce swirling of the liquid at an upper end of the chamber and an outlet at the lower end of the chamber, and means for feeding the solids into the upper end of the chamber, the chamber comprising at least two frusto-conical portions thereof disposed one above the other, the upper said portion having a substantially larger included angle than thaL of the lo,,7er said portion.

2 Preferably, the liquid flows in turbulent flow about the portions. Desirably, the included angles of the portions are such as to maintain the tangential component of flow of the liquid thereon above a predetermined 5 velocity. In one form of the invention, the solids may comprise powder having an average particle size between and 5OOpm, for example micronised powder having an average particle size of between 5 and 10pm. The invention will now be further described by way of example only and with reference to the accompanying drawings in which: Figure 1 shows a schematic representation of a liquid/solids mixing apparatus; Figure 2 shows to an enlarged scale a fragmentary portion of Figure 1; Figure 3 shows to an enlarged scale a sectional view on the line III-III of Figure 1; Figure 4 shows a sectional view on the line IV-IV of Figure 3, and Figure 5 shows to an enlarged scale a fragmentary view on the line V-V of Figure 1. Referring to Figure 1 a liquid/solids mixing apparatus 10 is shown and comprises an inlet head assembly 12, and a collecting vessel 14. A powder feed 16 is aranged to drop powder through the inle"C head assembly 12 into a converging chamber 18. The chamber 18 3 as shown more clearly in Figure 2 has an upper frusto-conical portion 20 joined to a lower frusto-conical portion 22 having an outlet 24 to the collecting yessel 14. An inlet 26 for liquid discharges into the inlet head assembly 12. The collecting vessel 14 discharges through an outlet 28 into a pipeline 30 connected to a pump 32. The pump 32 has a product discharge line 34 with a branch line 35 for recycling, when desired, mixed liquid and solids to the chamber 18.

In more detail and referring now to Figures 3 and 4, the inlet head assembly 12 comprises parallel circular flanges 36, 38 respectively having between them a body member 40 defining an annular plenum chamber 42 into which the inlet 26 discharges. A plurality of nozzles 44 (ten are shown) from the plenum chamber 42 are aligned substantially tangentially to a cylindrical inlet chamber 46 to connect the plenum chamber 42 thereto. The upper portion 20 is joined to the flange 38 below the inlet chamber, and a tube 48 from the powder feed 16 (not shown in Figures 2 and 3) extends through the inlet chamber 46 to discharge into the upper portion 20- At the outlet 28 of Figure 1, a vortex breaker 50 as shown in Figure 5 eliminates air flow associated with swirling liquid, the vortex breaker 50 comprising a circular plate 52 having several (three are shown) holes 54 therethrough for liquid flow.

In operation, liquid is injected throug'ii the inlet 4 26 into the plenum chamber 42 and is discharged through the nozzles 44 into the inlet chamber 46 at an angle thereto so as to set up a swirling motion. From the inlet chamber 46 the liquid falls onto the upper portion 20, and because of the relatively large angle defined by the upper portion 20 the downward liquid flow is retarded which ensures that the entire surface of the upper portion 20 is wetted by the liquid. From the upper portion 20 the swirling liquid falls into the lower portion 22, and then whilst still swirling falls through the outlet 24 into the collecting vessel 14. Powder fed from the powder feed 16 and through the tube 48 falls onto the wetted surface of the upper portion 20 and the lower portion 22, where it is entrained in the liquid thereon. The effect of the angular shape of the upper portion 20 and the lower portion 22 is to overcome frictional effects and maintain the tangential component of flow of the liquid as it falls in the chamber 18. Hence the swirling motion of the liquid is maintained as it falls in the chamber 18 into the vessel 14. The mixed liquid/powder is then discharged through the outlet 28 and the pipe 30 to the pump 32.

The rate of flow of the liquid is arranged to ensure that there are no dry areas on the upper portion 20 and the lower portion 22 on which powder could collect. The flow is also arranged to be turbulent in the 18 to enhance entrainment of the powder by the 'L-Lqu.-c-. A typical liquid flow velocity of about 6.5 m/sec at a pressure of 3 x 10 5 Nm 2 has been suitable for some applications, in which the upper portion 20 defines an angle from the vertical of 300 (ie 600 included angle) and the lower portion 22 an angle from the vertical of between 7 to 100 (14'- 200 included angle).

The liquid may be organic, for example an organic solvent, or aqueous, for example an acid or alkali solution. The powder may have an average particle size between 5 and 500pm, for example micronised powder having an average particle size of between 5 and 10 pm.

One advantage of the invention is that continuous mixing of the liquid and solids occurs, and the absence of dry areas on the mixing surfaces inhibits the local build-up of solids. If necessary the mixed liquid and solids may be recycled through the apparatus via the branch line 35. A conventional screw.feeder device (not shown) may be used to feed powder to the powder feed 16. EXAMPLES EXAMPLE I

Mixing kieselguhr powder with water as follows:- a) powder feed @ 90t/hr =- 18kg/hr 420t/hr water b) as (a) but with 48t/hr water powder feed @ 200z/hr =- 40kg/hr 420t/hr water d) as (c) but 195/,-li..,ater c) 6 EXAMPLE II Pharmaceutical powders: a) base powder at 22-44kg/hr organic solvent mix @ 120424OL/hr b) base powder @ 22-44kg/hr organic solvent @ 170434OZ/hr EXAMPLE III Flocculent Dispersal Aid: granules @ 0. 3 to 1.2kg/hr water @ 195-390z/hr r.

The liquids and solids of the above EXAMPLES were successfully mixed using the apparatus of Figures 1 to 5.

14698AnS 7

Claims

Claims

1) A method of mixing a liquid and solids, the method comprising feeding the solids into the liquid whilst the liquid is swirling about the surface of a chamber which is converging downwardly towards an outlet, the chamber comprising at least two frusto-conical portions thereof positioned one above the other, the upper said portion having a substantially larger included angle than the included angle of the lower said portion.

2) A method as claimed in Claim 1, wherein the liquid flows in turbulent flow about the portions.

3) A method as claimed in Claim 1 or Claim 2, wherein the included angles of the portions are such as to maintain the tangential component of flow of the liquid thereon above a predetermined velocity.

4) A method as claimed in any one of the preceding Claims, wherein the liquid has a flow velocity of about 6.5m/sec.

5) A method as claimed in any one of the preceding Claims, wherein the liquid is injected into the upper portion at a pressure of about 3x105NM2.

6) A method as claimed in any one of the preceding Claims, wherein the solids comprise powder having an average particle size of between 5 and 500pm.

7) A method as claimed in Claim 6, where-'Ln the powder has an average particle size of between 5 and lopm.

8 8) A method as claimed in any one of the preceding Claims, wherein the solids comprise kieselguhr or a flocculent dispersal aid.

9) A,method as claimed in Claim 8, wherein the liquid comprises water.

10) A method as claimed in any one of Claims 1 to 7, wherein the solids comprise a pharmaceutical compound.

11) A method as claimed in Claim 10, wherein the liquid comprises an organic liquid.

12) A method as claimed in Claim 11, wherein the organic liquid has a flow rate between 170 and 340Z/hr.

13) A method as claimed in any one of the preceding Claims, wherein mixed liquid and solids from the outlet are recycled through the chamber.

14) Apparatus for the mixing of a liquid and solids by the method as claimed in Claim 1, the apparatus comprising a chamber having a plurality of inlets for the liquid aligned so as to induce swirling of the liquid at an upper end of the chamber and an outlet at the lower end of the chamber, and means for feeding the solids into the upper end of the chamber, the chamber comprising at least two frusto-conical portions thereof disposed one above the other, the upper said portion having a substantially larger included angle than that lower said portion.

15) An apparatus as claimed in Claim l4k, wharein the inlets are arranged to be supplied from an annular plenum disposed about the chamber.

1 9 16) An apparatus as claimed in Claim 14 or Claim 15, wherein the outlet is connectable to an inlet of a vessel for collecting solids and liquid mixed in the chamber.

17) An apparatus as claimed in Claim 16, wherein a vortex breaking means is disposed at an outlet from the vessel.

18) An apparatus as claimed in any one of Claims 14 to 17, wherein the solids feeding means extends to below the inlets but terminates above the upper portion.

19) An apparatus as claimed in any one of Claims 14 to 18, wherein the upper portion has an included angle of about 600.

20) An apparatus as claimed in any one of Claims 14 to 19, wherein the lower portion has an included angle of between 140 and 200. 21) An apparatus as claimed in any one of Claims 14 to 20, wherein the inlets are aligned so as to be substantially tangential to the upper end of the chamber. 20 22) An apparatus as claimed in any one of Claims 14 to 21, wherein pump means are connectable with the vessel outlet so as to extract mixed liquid and solids from the vessel. 23) Apparatus as claimed in Claim 22, wherein the pump means is arranged to discharge through discharge duct means, and branch duct means are connectable to the discharge duct means for recycling mixed ligu'l-d and solids to the chamber.

1 24) A method of mixing a liquid and solids, substantially as hereinbefore described with reference to Figures 1 to 5 of the accompanying drawings.

25) An apparatus for mixing a liquid and solids, substantially as hereinbefore described with reference to Figures 1 to 5 of the accompanying drawings.

14698AnS Published 1991 at The Patent Office. Concept Houm Cardiff Road. Newport. Gwent NP9 I RH- Furthereopic, rnavb, obtained from Sales Branch. Unit 6. Nine Mile Point. Cwmfehnfach. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex I,:- S' Marv Cray. Kent.