The present invention relates to a solid-liquid contacting device in which a particuiate solid is brought into contact with a fluid, and more particularly to such a device in which the solid and fluid move in counter current flow relative to one another.

It is well known in the food and other processing industries that counter current flows can be advantageously used for the continuous extraction into a fluid of diffusable material from a counter flowing stream of particuiate solids or the impregnation of a material from the fluid into the particuiate solids. The extraction of impregnation may, or may not, be associated with concommitant chemical reactions, physical change or microbiological activity. A variety of devices for carrying out such counter current extractions are known for carrying out such processes.

It is also known that solid and/or liquid materials may be blended together continuously in a V-blender. Such blenders comprise a V-shaped tubular member which is arranged to be rotated about an axis lying transversely of the bisector of the apex of the tubular member. A V-blender is an efficient device for the gentle batch mixing of two or more particuiate solids ur solids with liquids. A connected series of V-blenders rotated about a common axis can be used for the continuous co-current mixing of solids or solids and liquids. Such machines are sometimes known as zig-zag blenders. In such machines it is necessary for the axis of rotation to slope downwardly to achieve forward progression of solids from a common inlet end to a common outlet end of the tubular member. Liquids, if present, would also move in

the same direction as the solids under gravitational flow resulting in co-current contacting. Also if the V-shaped or zig-zag tubular member is stopped with the arms thereof each lying in a horizontal plane the liquids would drain from the solids under the influence of gravitational force in the same direction as the solids movement resulting in co-current contacting. Such known V-blenders and zig-zag blenders have not heretofore been able to carry out counter current extractions, impregnations including adsorptions, ion exchange or other reactions.

The present inventors have now realised that counter current contacting between fluids, particularly liquids, and particuiate solid streams can be achieved in V-blenders and zig-zag blenders by providing means to move the solid materials up the inclined axis of rotation while permitting the liquid or other fluid to flow down that incline under the influence of gravity.

The present invention consists in a counter current solid-fluid contacting device including a tubular member which includes at least one

V-shaped portion, the tubular member being rotatable about an axis lying transverse to a notional plane bisecting the apex of the said one v-shaped portion; particuiate solid material inlet means and fluid material outlet means at a first end of the tubular member, fluid material inlet means and particuiate solid material outlet means at the other end thereof; means to cause rotation of the tubular member, the axis of rotation of the tubular member being so inclined to the horizontal, at least some point in the rotation of the

tubular member, that upon rotation of the tubular member about its axis of rotation, fluid introduced into the tubular member will exhibit a nett flow from the said other end to the said first end; and means to cause distribution of the particuiate solid about . the apex of the V-shaped portion of the tubular member as it is rotated about its axis of rotation, the distribution means being such that the particuiate solids are moved from the said first end of the tubular member to the other end thereof.

It will be recognised that the fluid will normally be a liquid, however, there could be circumstances, such as the drying of grain, for instance, where it might be desirable to cause a gas to flow in counter current with a particuiate solid.

In a preferred embodiment of the invention the tubular member includes a plurality of V-shaped tubular segments, the segments being connected in end-to-end array with the longitudinal axis of each of the arms thereof lying in a common plane. The tubular member is preferably rotatable about a common axis lying at right angles to the planes bisecting the respective apices of the V-shaped tubular members as in a conventional zig-zag blender.

The fluid inlet is at the higher end of the tubular member so that it will have a nett forward flow therethrough as the tubular member is rotated, or if it is "parked" with the V-shaped segments lying in a substantially horizontal plane.

The means to cause a distribution of the particuiate solids about a, the, or each, apex of the tubular member

preferably includes distribution means positioned within the arm of the tubular member on the side of the apex proximal to the lower end of the axis of rotation of the tubular member (hereinafter called the downstream arm). The, or each, distribution means is so placed that as the apex is rotated rather than a greater amount of solid passing into the downstream arm than into the upstream arm, as would happen with a conventional zig-zag blender, an amount of solid is diverted from the downstream arm into the upstream arm such that there is a nett movement of solid in an upstream direction with each rotation of the tubular member. The distribution means may take the form of a scoop or baffle.

In another embodiment of the invention the objects of the invention may be achieved by inclining the V-shaped tubular member with the axis of rotation lying at an angle other than 90° to the planes bisecting the respective apices of the V-shaped tubular member provided at some point in each revolution of the tubular member there is an overall inclination from the first end to the other end of the tubular member (hereinafter called the "drain point"). In this embodiment of the invention there is no need for assymetric distribution of the particuiate solids provided that the tubular member is allowed to slow down or stop when it reaches the drain point in each revolution. The particuiate solids will be evenly divided by the apices of the tubular members as they are rotated. Thus, particuiate solids will be moved from the first end at which they are introduced to the other end at which they are removed and the liquid will have a nett flow from the other end to the first end due to the slowing down of the rotation of the tubular

members at the drain point.

In this second embodiment the axis of rotation of the V-shaped tubular member preferably lies in the plant thereof and passes through the longitudinal axis of the tubular member at its first end. The axis of rotation is preferably at a minimum angle of from approximately 85 to 55 tothe planes bisecting the apices.

It will be understood that means are provided to cause the tubular member to rotate about its axis of rotation however in the simplest form of the invention this could be manual means allowing manual rotation of the tubular member. The rotation of the tubular member may be continuous or intermittent.

The device according to the present invention could be used without a fluid merely to blend a plurality of particuiate solids. The real advantage of the device lies however in the capacity to move solid and fluid streams in counter current flow.

In operations of the device when a fluid stream is added at the upper end of the tubular member and the rotation thereof stopped with the V-shaped segment lying in a plane one axis of which is horizontal, the liquid will flow or drain under gravitational force in the opposite direction to that imparted on the solids stream by the rotation. If the plane of the V-shaped segments of the stopped tubular member lies at a slight angle to the horizontal fluid will be held up in each alternate apex of the tubular member while still permitting gravitational drainage. The proportionate flow will be determined by the inclination of the plane of the tubular member.

The mixing, or contacting, efficiency of the device will depend upon the rate of rotation of the tubular member provided centrifugal forces do not exceed gravitational forces. A rotational speed of from 1 to 10 r.p.m. is preferred.

The rate of solids progress through the tubular member will be dependent upon:

(a) the shape and design of the projections,

(b) the rate of rotation, (c) the time of rotation,

(d) the angle of the axis of rotation to the horizontal, and

(e) the bulk density of the solids.

The fluid flow through the tubular member depends upon:- (a) the angle of the axis of rotation to the horizontal,

(b) the time that the tubular member remains with the plane of the V*s sufficiently near to the horizontal for gravitational drainage to occur,

(c) the rate of rotation which will cause some fluid pumping up the incline.

The fluid held up and hence solid-fluid ratio within the tubular member will depend upon the three factors (a), (b) and (c) in the immediately foregoing paragraph and in the packing characteristics of the particuiate solids.

Suitable inlet and outlet peripheral equipment is preferably provided on the device. The solids feed or lower end should be provided with a drum containing a scoop to feed the solids into the tubular member and means for separating fluid containing dissolved solids at concentrations approximating those in the unextracted solids.

The upper end of the device preferably has attached a perforated drum or other means for draining extracting fluid from discharged extracted, or impregnated, solids.

If desired the tubular member may be jacketed to allow an appropriate extraction temperature to be maintained. Rotary unions or other means are preferably used for sealing the entry of heating or cooling media. The extracting fluid is preferably added at the upper end of the tubular member but could if desired by added at any point along the axis of rotation of the tubular member using a suitable rotary seal.

Hereinafter by way of example only is a preferred embodiment of the present invention described with reference to the accompanying drawings in which: Figure 1 is a partly cut away side elevational view of a counter current solid-liquid contacting device according to this invention;

Figure 2 is a detailed view of the apex of one of the V-shaped portions of the tubular member of the device of Figure 1;

Figure 3 is a view along the direction of arrow E of Figure 2; and

Figure 4 is a partly cut away side elevational view of another embodiment of a counter current solid-liquid contacting device according to this invention.

The counter current solid-liquid contacting device

10 in Figures 1 to 3 comprises essentially a tubular member

11 made up of five sections 12 each of which is inclined to the next to form four V-shaped portions 13. The tubular member 11 is mounted in bearings (not shown) and is rotated

by an electric motor (not shown) . The tubular member 11 is rotated about an axis which passes through a solids inlet aperture 14 and solids outlet aperture 15 in the tubular member 11. This axis is inclined upwardly from the aperture 14 to the aperture 15.

Coincident with the solids inlet aperture 14 of the tubular member 11 is a rotating drum 16 provided with a cylindrical sieve 17. Solids to be extracted are introduced into the drum 16 through a chute 18 in the direction of arrow A. Liquid introduced into the end of the tubular member 11 adjacent the solids outlet aperture 15, as hereinafter described, are drained from the incoming solids in the drum 16. The solids are retained in the drum by the screen 17 while the liquid drains through the screen 17 and exits the device 10 through funnel 19 in the direction of arrow B.

Adjacent the solids outlet aperture 14 means for discharging the solids from the device 10 through chute 21 in the direction of arrow C while preventing the flow of liquid therefrom. These means comprise an upwardly inclined tube 24 contiguous with the solids outlet aperture 14 of the tubular member 11 and adapted to rotate therewith. The inside surface of tube 24 is formed with a helical flight 25 adapted to convey solids upwardly from the tubular member 11 to the chute 21. The liquid is introduced into the solids outlet end of the tubular member 10 in the direction of arrow D along a pipe 22 and a nozzle 23. Each of the V-shaped portions of the tubular member 11 is formed with a baffle 26. A baffle 26 extends from the radially inner portion of the section 12 of the tubular member 11 forming the upstream one ^" of the sections making up each V-shaped portion of the

tubular member.

In use solids to be extracted are introduced into the device 10 through chute 18 as the tubular member 11 is rotated. Simultaneously extracting liquid is introduced into the other end of the tubular member 11 through nozzle 23. As the tubular member 11 rotates solids will flow into the first V-shaped portion 13, further rotation will cause the solids therein to be split by the baffle 26, part flowing back towards the inlet, and part flowing on to the second of the

0 V-shaped portions 13. The solids are thus gradually caused to flow upwardly from the solids inlet aperture 14 to the solids outlet aperture 15. The liquid will by contact flow gradually down the effective incline from the solids outlet 15 to the solids inlet 14 effecting a counter current 5 extraction of solubles therefrom.

The extraction device 50 of Figure 4 is essentially similar to the device 10 described above with the exception that the counter current flow is induced not by baffles in the tubular member 53 but by the expedient of causing the o tubular member to rotate about a slightly upwardly inclined axis X-X which is disposed at an angle to the axis Y-Y passing through the solids inlet and outlet apertures 51 and 52 and by causing the rotation of the tubular member 53 to slow down or stop when the plane containing the V-shaped 5 portions is substantially horizontal when the tubular member is viewed end on. In this position due to the slight inclination of axis X-X the liquid will drain towards the solids inlet aperture 14.

It will be recognised by persons skilled in the art _o that numerous variations and modifications may be made to the

invention as described above without departing from the spirit or scope of the invention as broadly described.