AU672665B2 - Procedure and apparatus for materials separation by pneumatic flotation - Google Patents

Description

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AUSTRALIA

Patents Act 1990 DANIEL ZYONIMIR URIZAR FUNES

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT 'b94 o 00 o *440 @44* 44 @04 0 00 04 4 @4 04 @0 4 o 4 @444 0 @44444 0 Invention Title: "Procedure and appAmL'atus for materials separation by pneumaitic flotation" The following statement is a full descfiption of this invention including the best method of performing it known to me:- F- I K.

This invention is related to procedures for the separation of materials suspended in liquid environments using flotation techniques in which hydrophobic particles are recovered from a pulp. The invention consists of a new collection and cleaning procedure and apparatus for carrying out the flotation technique.

DESCRIPTION OF THE RELATED ART There are several industrial applications of the flotation process that take advantage of the differences in the hydrophobicity of materials. Some of the typical applications include the benefaction of minerals and organic hydrophobic materials.

to The flotation process involves three phases: solid, liquid and gas. The solid phase 00 includes the hydrophobic material to be separa',d and the unwanted material (gangue). The liquid phase consists of water or another liquid which is associated with the solid in a naturali o. way or as the result of an industrial process. The gas phase consists of air or any gas inrt with respect to the solids involved in the separation. The gas is injected into the pul- to generate bubbles which collide with the hydrophobic particles forming a froth phase on the top of the pulp. The unwanted material or gangue, on the other hand, remains in the bulk.

There are several procedures afd apparatus that can carry out materials separation by the above mentioned flotation technique. The state-of-the-art flotation procedures can be divided into three main groups based on the type of operation and vessel desigh used in the T process.

oftedfeece ntehdohoiiyo aeias oeo hetpclapiatosicue; th beeato fmnrl n rgnchdoh cmtras I e flotation-- -r prcs novstrepae:sld iudadgs oi hs The first group of flotation procedures is based on mechanical operation arid Wrvolues eRi&ders feeding the pulp into an agitated vessel in order to maintain it well homogeneized.

The pulp is fed from the bottom while the gas is injected through the shaft of the agitator, either by pressure or self-induction. In order to increase bubble-particle collision cificiency, S baffles are installed to produce small bubbles. Tailings are removed frn- the bottom while the product is collected in a launder.

The apparatus used in this first group differ among themselves in design and size.

They vary in the agitation mechanisms and vessel shape. Their volume can reach 100 inr and their height over 2 m.

A second group of flotation procedures is based on pneumatic operation. This procedure considers conditioning the pulp with the appropriate reagents and feeding it into a vessel in which gas is injected by a device located outside the vessel. The device, an aerator, generates bubbles finely dispersed in the pulp. The collision-adhesion process takes places at the pulp feeding point located in the middle zone of the vessel. The product containing froth 15 overflows to launders while the tailings discharge from the bottom.

A third group of flotation procedures is also based on pneumatic operation. In this case the vessel is a column with a diameter much smaller than its height. In this kind of column, two zones are observed; a collection zone, the region between the gas injection point and the pulp-froth interface, and, a froth zone, bounded by the pulp zone interface D0 and the overflow point. The pulp is usually fed halfway the height of the column. Since gas injection takes place at the bottom of the column, bubble-particle adhesion occurs when rising bubbles collide with particles descending in the collection zone. In this way, collected particles rise to the froth zone and overflow at the top of the column.

Generally, column flotation cells require heights over 10 m in order to attain adequate 5 bubble-particle collision probabilities, and therefore, relatively high gas injection pressures are necessary. ie Ielbne J Mean residence time in any of thellotation proccduresiju' H niond..ug to exceed 5 min in order to achieve acceptable recoveries.

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3 Li The present invention seeks to provide an alternative method and apparatus, in which agitation is not required, Thus according to a first aspect of the present invention there is provided a froth flotation process for recovering hydrophobic particles from a pulp, comprising the steps of: a) providing a downwardly slanted first gas-permeable surface; b) feeding a thin layer of pulp onto the first gas-permeable surface, whereby the pulp flows downwardly along the first gas-permeable surface by gravity; c) supplying a low pressue gas homogeneously through the first gas-permeable surface thereby to generate bubbles that contact and collect hydrophobic materials in the pulp; d) discharging the aerated pulp into a downstream reservoir formed by a downwardly slanted second gas-permeable surface and a wall at the lower end of the second slanted gas-permeable surface; i supplying a low pressure gas homogeneously through the second Sgas-permeable surface thereby to separate a froth phase containing the hydrophobic material from the pulp, containing hydrophilic solids, flowing downwardly on the second gas-permeable surface; f) forcing the entire froth in the reservoir to flow underneath a liquid sprinkler by means of baffles disposed transversely to the froth flow and carried by the sprinkler, and washing the froth to cause drainage of the i[ hydrophilic material; g) discharging the froth accumulated in the reservoir to a launder by 25 permitting the froth to overflow the wall; h) evacuating the pulp continuously through a discharge means disposed in the lower part of the wall located at the downstream end of the second gas-permeable surface.

In a second aspect of the present invention there is provided a froth flotation process for recovering hydrophobic particles from a pulp, comprising the steps of: a) providing a lower downwardly slanted first gas-permeable surface and an upper downwardly slanted non-gas-permeable surface disposed over the first gas-permeable surface; -1 iRA ~r o I 4 b) feeding a thin layer of pulp onto the first gas-permeable surface and underneath the non-gas-permeable surface, whereby the pulp flows downwardly along the first gas-permeable surf-ace by gravity; c) supplying a low- pressure gas homogeneously through the first gas-permeable surface thereby to generate bubbles that contact and collect hydrophobic materials in the pulp; d) discharging the aerated pulp into a downstream open-topped reservoir formed by a downwardly slanted second gas-permeable surf-ace and a wall at the lower end of the second gas-permeable surface; e) supplying a low pressure gas-permeable homogeneously through the second gas-permeable surface thereby to separate the froth phase containing the hydrophobic material from the pulp, containing hydrophilic solids, flowing downwardly on the second gas-permneable surface; f) forcing the entire froth in the reservoir to flow underneath a liquid sprinkler by means of baffles disposed transversely to the froth flow, o arid washing the froth in the reservoir with the liquid sprinkler as the froth flwsiscr~ harin the froth accumulated in the reservoir to a launder by :00 erm-itting the froth to overflow the wall; 20 h1) evacuating the pulp continuously through a discharge means disposed in the lower part of the wall located at the downstream end of the second slanted gas-permeable surf-ace.

*000 In a third aspect of the present invention there is provided a froth :K.flotation apparatus for material separation, comprising; 0. 25 a) a downwardly slanted first gas-permeable surf-ace for receiving a thin layer of pulp from a pulp distributor, whereby the pulp flows downwardly along said first gas-peri-eable surf-ace by gravity;I 00040b) a first gas chamber disposed below said first gas-permeable surface for supplying low pressure gas through said first gas-permeable surface, thereby to generate bubbles that contact and collect hydrophobic materials in the pulp; a reservoir disposed downstream of said first gas-perineable surface, said resgrvoir having a second gas-permneable surf-ace, and a wall disposed downs ream of said second gas-permleable surface, said second gaspermeable surface being disposed to receive the aerated pulp fromn said first gas-permeable surface; d) a second gas chamber disposed below said second gas-permeable surface for supplying low pressure gas through said second gas-permeable surface, thereby to separate a froth phase containing the hydrophobic material from the pulp, containing hydrophilic solids, flowing downwardly on said second gas-permeable surface, whereby the froth accumulating in said reservoir is permitted to overflow said wall and discharge to a launder; e) a cleaning liquid sprinkler disposed above said reservoir for washing the froth thereby to cause the hydrophilic material to settle down; f) baffles disposed transverc2ly above said reservoir and carried by said sprinkler, said baffles being adapted to cause the entire froth to flow underneath said sprinkler; and g) a discharge disposed at a lower part of said wall for evacuating the pulp continuously from said reservoir.

In a fourth aspect of the present invention there is provided a froth flotation apparatus for material separation, comprising: Sa) a downwardly slanted first gas-permeable surface for receiving a thin layer of pulp from a pulp distributor, whereby the pulp flows downwardly t along said first gas-permeable surface by gravity; b) an upper downwardly slanted non-gas-permeable surface 20 disposed over said first gas-permeable surface; c) a first gas chamber disposed below said first gas-permeable surface for supplying low pressure gas through said first gas-permeable i esurface, thereby to generate bubbles that contact and collect hydrophobic materials in the pulp, whereby said non-gas-permeable surface causes a greater fraction of the gas to become part of a froth phase; d) an open-topped reservoir disposed downstream of said first gaspermeable surface, said reservoir having a downwardly slanted second gaspermeable surface and a wall disposed downstream of said second gaspermeable surface, said second gas-permeable surface being disposed to receive the aerated pulp from said first gas-permeable surface; e) a second gas chamber disposed below said second gas-permeable surface for supplying low pressure gas through said second gas-permeable sunfac thereby to separate the froth phase containing the hydrophobic material from the pulp, containing hydrophilic solids, flowing downwardly on said second gas-permeable slanted surface, whereby the froth accumulating in said reservoir is permitted to overflow said wall and discharge to a launder; RA 4d 'r 0 p.- 6 f) baffles disposed above said reservoir and carried by said sprinkler, said baffles being adapted to cause the entire froth to flow underneath said sprinkler; and g) a discharge disposed at a lower part of said wall for evacuating the pulp continuously from said reservoir, By utilising the process and apparatus of the present invention, flotation time and energy consumption are reduced while process efficiency increases, The principle of his invention consists of generating a thin layer of pulp over a gas-permeable slanted surface in which gas is injected, In this way intense and rapid collection of hydrophobic particles occurs as the pulp flows downward. The only force involved in the pulp transport is gravity.

The invention includes a cleaning zone downstream with a waterwashing system and baffle plates for modifying the cross section for the froth flow, i o' In order to better understand the invention, the procedure will be explained and two examples of the apparatus presented, BRIEF DESCIPTION OF THE DRAWINGS 20 Fig. 1 is a longitudinal view of the embodiment of the apparatus used i to carry out the procedure. The baffles and the gas-permeable plate are set in a first position, i Fig. 2 is a view similar to Fig, 1 but shiowing the baffles set in a second position, 44* 25 Fig. 3 is a view similar to Fig, 1 but showing the baffles set in a third position, Fig 4 is a view similar to Fig. 1 but showing the gas-permeable plate set in a second position.

Fig. 5 is a view similar to Fig. 1 but showing the gas-permeable plate set in a third position, Fig. 6 is a longitudinal view of a second embodiment of the apparatus used 'o carry out the procedure, The baffles and the gas-permeable plate are set in a first position, Fig, 7 is a view similar to Fig, 1 but showing the baffles set in a second position.

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i l 6/1 Fig. 8 is a view similar to Fig. 1 but showing the baffles set in a third position.

Fig. 9 is a view similar to Fig. 1 but showing the gas-permeable plate set in a second position.

Fig 10 is a view similar to Fig, 1 but showing the gas-permeable plate set in a third position.

DETAILED DESCRIPTION OF THE INVENTION J The procedure of the invention considers three basic steps in the apparatus used to perform such procedure and thus three zones associated to those steps can be distinguished.

The firs step, pulp feeding, consists in producing a thin layer of pulp on top of the slanted surface. The pulp, previously conditioned with the appropriate reagents is uniformly distributed in the upper side of the slanted surface and flows downward by gravity.

The second step, product collection, occurs as the bubbles formed at the gas permeable surface collide with the hydrophobic particles and produce a froth. The froth accumulates in a zone between the slanted surface and a wall at its lower end. The tailings are removed as a pulp through a gap at the i 0* 20 bottom of this zone.

The third step, a cleaning stage, removes hydrophilic particles collected in the froth by deflecting and controlling the cross section of the flow while water is added through a sprinkling system. The baffles force the froth to flow underneath the washing system, causing drainage of hydrophilic material.

The froth then flows through a smaller cross section and overflows to a launder.

*J C A first prototype of the apparatus has been built in order to obtain a better understanding of the flotation procedure and the modifications that can be introduced without changing the basic principles behind the invention.

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6/2 Fig. 1 shows a longitudinal (or radial) section of an apparatus for performing the procedure of the invention. The apparatus includes a gaspermeable slanted surface 1. Although an inclined plane is shown in Figure 1 variations are possible: the surface may be for example a convex mantle, or a conical concave mantle (inverted cone). The slope of the surface may be constant or variable. Moreover, the slope of this surface may vary continuously or have several discrete values over its length. In Figs. 1 through the gas-permeable slanted surface 1 is shown with a constant slope. This geometry may correspond to a simple inclined plane, a pyramidal face section or a conical surface section.

The pulp feeding system is located in the upper side of the gaspermeable slanted surface 1 and consists of a guide 2 that discharges onto an inclined tray 3 adjacent to the slanted surface 1. In order to make sure that the pulp is well distributed in the form of a thin layer flowing downstream across C 15 the gas-permeable surface, a barrier 4 is placed in between the tray 3 and the ii gas-permeable slanted surface 1, Grooves in the barrier facilitate the uniform distribution of the pulp across the gas-permeable slanted surface 1.

The gas-permeable slanted surface 1 is placed on top of one or more chambers that receive low pressure gas from a pipeline. Pressure regulators 4 and flow valves are included.

A vertical wall 8, that can alternatively be inclined, is located at the lower end of the gas-permeable slanted surface 1. This wall 8 and the lower part of the gas-permeable slanted surface 1 define a froth accumulation chamber 9. At the lower end of the gas-permeable slanted surface 1, a 25 discharge 10 is used to remove the flotation tailings.

Below the froth level of the accumulation chamber 9, a washing device 11 is set perpendicular to the froth flow with sprinlders 12 placed in its lower part. One or more baffles 13 pivoted on the upper part of the washing device 11 are used to change the depth and cross section of the froth downstream of the washing device 11, relative to the depth of froth upstream of the washing device 11.

The froth leaves the froth accumulation chamber 9 by overflowing a height adjustable lip 14 located at the upper end of the wall 8. i @1' 6/3 The baffles 13 force the froth to flow underneath the washing device 11 where the sprinklers 12 spray washing water onl it. When the baffles 13 are set in vertical position, as shown in Fig. 1, the froth flows through the maximum cross section available.

Fig. 2 and Fig. 3 show the baffles in alternative positions.

Fig. 2 depicts one of the baffles 13 in a vertical position that allows maxiimum froth depth/cross section upstream the washing device 11. The other baffle, on the other hand, is set in an inclined position which decreases the froth depth/cross section downstream the washing device 11. The reduction in cross section increases the process selectivity because the froth is forced to go through a narrow path where weakly attached particles are released. These particles do not have a -well defined hydro-affinity.

Fig. 3 depicts both baffles in an inclined position that decreases the P froth cross &ection in both sides of the washing device 11. In this condition, the selectivity of the process ismiaximisect (at least wihrgard tothcorl V. of the froth depth/cross section) due to the fact that the weakly attached particles are released from the froth and report to the tailings., Another way to control the selectivity-recovery relation consists of changing the depth of the froth accumulation chamnber 9 by moving the lower part of the gas-permieable slanted surf-ace 'I downwards. poeueo invention with the lower parnt of the gas-permeable slanted surface 1 displaced *to a lower position with the angle of the slope kept equal to that of the upper part of the slanted surface. In this way, the froth accumnulatio~n chamber 9 is deeper thnth n shown in Fg eutn nadee overflowing zone ia increases selectivity.

Onl the other hand, Fig. 5 shows anl apparatus with the lower part of the gas-permeable slanted surface 1 displaced in such a way that its angle of inclination is opposite to the inclination of the upper part of the gas-permeable slantedt surface 1. Therefore, the froth accumulation chamber 9, is deeper than the one shown in Fig. I but in this case the deepest 15 part is located upstream of washing device 11, The selectivity of this configuration is lower than in Fig.

4 but higher than the version shown in Fig. 1.

r1 7 Fig. 6 shows a longitudinal (or radial) section of o.

second &wapw-e apparatus for performing the procedure c? the invention.

In this apparatus the pulp is fed from a pipe or any other external device to a feeding line 1 located in the upper part of the equipment. The feeding line 1 discharges to feeding vessel 2. From this vessel 2, the pulp flows downward on the inclined plate 3. Above this plate 3, a cover 4 is used to define the maximum thickness (0 of the pulp layer entering the collection zone through distribution plate 5. This plate 5 is provided with evenly spaced orifices across the entire width of its lower end.

The collection zone is composed of two gas-permeable slanted surfaces. On top of the lower surface 6 the pulp flows downward by gravity with the maximum thickness of I oooo: the pulp layer determined by the upper surface 7. Through i both surfaces 6 and 7, low pressure gas is injected from chambers 8 and 9, respectively. The gas is produced SO and/or compressed externally and fed to chambers 8 and 9 through the respective lines 10 and 11, provided with "o valves and pressure regulators.

In the collection zone, the hydrophobic particles in the pulp adhere to the bubbles generated at the pores of .5 both surfaces 6 and 7.

Fig. 6 shows that the upper gas-permeable slanted surface 7 can be shorter than the lower surface 6 to facilitate the discharge of the aerated pulp to the froth areservoir 12 in the cleaning zone.

3o At the bottom of the froth reservoir 12 there is a gas-permeable surface 13 that is a continuation pf the lower gas-permeable surface 6 in the collection zone. The surface 13 sits on top of chamber 14 fed with gas produced and/or compressed externally through line 15 provided with its own valve and pressure regulators that allow gas flow L4 j) s s 8

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and pressure control independent of chambers 8 and 9 in the collection zone.

At the lower end of surface 13 the froth reservoir is limited by a wall 16 th( can be vertical or inclined.

This wall 16 permits froth acc,imulation and separation from the pulp carrying the hydrophilic particles not adhered to the bubbles. Froth overflows a height-adjustable plate 17 located at the upper end of wall 16 and is withdrawn from the apparatus through j (0 launder 18.

At the lower end of wall 16, the tailings discharge through orifice 19. The coarse material in the-tailings discharges through control valve 20 while the fines leave by overflowing the height-adjustable plate 21 to the duct 22. The fines in the tailings flow from the duct 22 and combine with the coarse material. By varying the height of plates 17 and 21 it is possible to control the •pulp level and froth height in the froth reservoir 12.

Below the froth level of the froth reservoir 12, a O washing device 23 is set perpendicular to the froth flow S. with sprinklers 24 placed in its lower part. Two baffles 25 and 26 pivoted on the upper part of the washing device 23 are used to change the froth cross section upstream and downstream the washing device 23.

55 The baffles 25 and 26 force the froth to flow underneath the washing device 23 where the sprinklers 24 spray washing water on it. When the baffles 25 and 26 are set in vertical position, as shown in Fig. 1, the froth iflows through the maximum cross section available.

Figs. 7 and 8 show some other positions of the baffles.

Fig. 7 depicts one o± zhe baffles 25 in a vertical position that allows maximum froth cross section upstream the washing device 23. The other baffle, on the other hand, is set in an inclined position which decreases the a Si froth cross section downstream the washing device 23. The reduction in cross section increases the process selectivity because the froth is forced to go through a narrow path where weakly attached particles are released.

These particles do not have a well defined hydro-affinity.

Fig. 8 depicts both baffles in an inclined position that decreases the froth cross section in both sides of the washing device 23. In this condition, the selectivity of the process is maximised (at least with regard to the (0 control of the froth cross section) due to the fact that the weakly attached particles are released from the froth and report to the tailings.

Another way to change the selectivity-recovery relation consists of changing the depth of the froth reservoir 12 I by relocating downward the lower part of the gas-permeable it surface 13.

Fig. 9 shows the apparatus used to carry out the procedure of the invention with the lower part of the S" gas-permeable slanted surface 6 displaced to a lower O position with the slope kept equal to that of the upper .part of the slanted surface. In this way, the froth reservoir 12 is deeper than the one shown in Fig. 6 resulting in a deeper overflowing zone that increases selectivity. 5 On the other hand, Fig. 5 shows an apparatus with the lower part of the gas-permeable slanted surface displaced in such a way that its inclination is opposite to the inclination of the upper part of the gas-permeable slanted 0:0l, surface. Therefore, the froth reservoir 12 is deeper than o 0 o0 the one shown in Fig. 6 but in this case the deepest part is located upstream the washing device 23. The.

*i r sele-tivity of this configuration is lower than in Fig. 4 but higher than the version shown in Fig. 6.

l The procedure and apparatus (flotation cell) 325 presented allows many obvious variations that can be Ii considered part of the invention.

An obvious variation is changing the shape of the slanted surface, which may include one or more inclined plates (pyramidal surfaces or pyramidal frustums (both convex or concave), conical surfaces or conical frustums (both convex or concave), etc. These different geometrks will affect the procedure selectivity. As a matter of fact, when o width of the slanted surface is increased downstream (such as in the case of a pyramidal, convex or 1) conical surfaces as well as trapezoidal planes with a wider lower part) froth depth diminishes so that the selectivity decreases and recovery increases. The opposite occurs when the gas permeable slanted surface 1 is reduced downstream such as in the case of pyramidal, conical or concave surfaces as well as trapezoidal planes with a smaller lower part.

SAnother obvious variation is the addition of grooves or ribs on the gas-permeable slanted surface 1 in order to obtain a uniform distribution of the pulp on the surface.

s The material and permeability of the gas-permeable slanted surface 1 of Figs 1-5 or 6,7 and 13 of Figs 6-10 can also be changed by using different materials such as cloth ceramics, or any gas-permeable material available. These materials can be natural or synthetic,hdowefr ont s- in_- eT- they must be inert to the wsubstances involved in the process.

A second example of the apparatus in which a better froth formation and fine particle collection can be obtained if the pulp is fed and flows between two pp 3 gas-permeable slanted surfaces with gas injection through IS* both surfaces.

The slope of the slanted gas-permeable slanted surface 1 of Figs 1-5 or 6,7 and 13 of Figs 6-10 can be h: aadjusted depending on the nature of the pulp to be treated.

o Also, the pulp feeding system can undergo some 3 ga-pereabe sante sufacs wih gs ijecf~oi thoug devices. These devices can be sliding cylinders, descending laminae, etc., set in an adjustable or fi-ed way.

Another go possible variationogser in the angle of the baffles in the washing zone that can be fixed or changeable.

Each step of the procedure and corresponding elements of the apparatus can be operated using manual, semi- or automatic control systems.

The economics of the procedure and apparatus of the invention compare favourably with other procedures and apparatus previously described because of nil energy consumption and small flotation cell size. Another advantage of the invention is the available number of options for controlling selectivity, such as the slope of the gas-permeable slanted surface 1, of Figs 1-5 or 6,7 S, and 13 of Figs 6-10, depth control of the froth accumulation chamber, and froth cross section adjustment .h using baffles.

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Claims (5)

1. A froth flotation process for recovering hydrophobic particles from a pulp, comprising the steps of: a) providing a downwardly slanted first gas-permeable surface; b) feeding a thin layer of pulp onto the first gas-permeable surface, whereby the pulp flows downwardly along the first gas-permeable surface by gravity; c) supplying a low pressure gas homogeneously through the first gas-permeable surface thereby to generate bubbles that contact and collect hydrophobic materials in the pulp; d) discharging the aerated pulp into a downstream reservoir formed by a downwardly slanted second gas-permeable surface and a wall at the lower end of the second slanted gas-permeable surface; supplying a low pressure gas homogeneously through the second gas-permneable surface thereby to separate a froth phase containing the hydrophobic material from the pulp, containing hydrophilic solids, flowing downwardly on the second gas-peri-eable surface; f) forcing the entire froth in the reservoir to flow underneath a liquid sprinkler by means of baffles disposed transversely to the froth flow and carried by the sprinkler, and washing the froth to cause drainage of the hydrophilic material; g) discharging the froth accumulated in the reservoir to a launder by permitting the froth to overflow the wall; h) evacuating the pulp continuously through a discharge means a 25 disposed in the lower part of the wall located at the downstream end of the second gas-permneable surface.

2. A froth flotation process for recovering hydrophobic particles from a pulp, comprising the steps of: a) providing a lower downwardly slanted first gas-permeable surface and an upper downwardly slanted non-gas-permeable surface disposed over the first gas-permneable surface; b) feeding a thin layer of pulp onto the first gas-perineable surface and underneath the non-gas-permeable surface, whereby the pulp flows downwardly along the first gas-perineable surface by gravity; 13 c) supplying a low pressure gas homogeneously through the first gas-permeable surface thereby to generate bubbles that contact and collect hydrophobic materials in the pulp; d) discharging the aerated pulp into a downstream open-topped reservoir formed by a downwardly slanted second gas-permeable surface and a wall at the lower end of the second gas-permeable surface; e) supplying a low pressure gas-permeable homogeneously through the second gas-permeable surface thereby to separate the froth phase containing the hydrophobic material from the pulp, containing hydrophilic solids, flowing downwardly on the second gas-permeable surface; f) forcing the entire froth in the reservoir to flow underneath a liquid sprinkler by means of baffles disposed transversely to the froth flow, and washing the froth in the reservoir with the liquid sprinkler as the froth flows underneath; g) discharging the froth accumulated in the reservoir to a launder by e; permitting the froth to overflow the wall; h) evacuating the pulp continuously through a discharge means disposed in the lower part of the wall located at the downstream end of the second slanted gas-permeable surface, 20 3, A froth flotation apparatus for material separation, comprising; a) a downwardly slanted first gas-permeable surface for receiving a thin layer of pulp from a pulp distributor, whereby the pulp flows downwardly along said first gas-permeable surface by gravity; j! b) a first gas chamber disposed below said first gas-permeable 25 surface for supplying low pressure gas through said first gas-permeable surface, thereby to generate bubbles that contact and collect hydrophobic materials in the pulp; c) a reservoir disposed downstream of said first gas-permeable surface, said reservoir having a second gas-permeable surface, and a wall disposed downstream of said second gas-permeable surface, said second gas- permeable surface being disposed to receive the aerated pulp from said first gas-permeable surface; d) a second gas chamber disposed below said second gas-permeable surface for supplying low pressure gas through said second gas-permeable surface, thereby to separate a froth phase containing the hydrophobic material j from the pulp, containing hydrophilic solids, flowing downwardly on said i^^a!Q T2 14 second gas-permeable surfAce, whereby the froth accumulating in said reservoir is permitted to overflow said wall and discharge to a launder; e) a cleaning liquid sprinkler disposed above said reservoir for washing the froth thereby to cause the hydrophilic material to settle down; f) baffles disposed transversely above said reservoir and carried by said sprinkler, said baffles being adapted to cause the entire froth to flow underneath said sprinkler; and g) a discharge disposed at a lower part of said wall for evacuatin~g the pulp continuiously from said reservoir.

4. An apparatus as claimed in claim 3, wherein: a) said baffles are inclination adjustable. Ani apparatus as claimed in claim 3 or claim 4, wherein: a) said wall is height adjustable. An apparatus as in claimed any one of claims 3 to 5, and further comprising: a) a duct connected to said discharge, said duct including a height- adjustable plate at its top for adjusting the overflow of the pulp. An apparatus as claimed in any one of claims 3 to 6, wherein; a) said discharge includes a valve. 20 81 A froth flotation apparatus for material separation, comprising: a a downwardly slanted first gas-permeable surface for receivinga thin layer of pulp from a pulp distributor, whereby the pulp flows downwardly along said first gas-permeable surface by gravity; anl upper downwardly slanted non-gas-perme able surf-ace disposed over said first gas-permeable surf-ace; a first gas chamber disposed below said first gas-permeable surf-ace for supplying low pressure gas through said first gas-permneable surface, thereby to generate bubbles that contact and collect hydrophobic materials in the pulp, whereby said nion-gas-peri-eable surface causes a greater fraction of the gas to become part of a froth phase; d) anl open-topped reservoir disposed downstream of said first gas- permeable surface, said reservoir having a downwardly slanted second gas- permeable surface and a wall disposed downstream of said second gas- permeable surface, said second gas-permneable surface being disposed to receive the aerated pulp froin said first gas-permneable surf-ace; *~RA4, As LUVr0 f lid e) a second gas chamber disposed below said second gas-permeable surface for supplying low pressure gas through said second gas-permeable surface, thereby to separate the froth phase containing the hydrophobic material from the pulp, containing hydrophilic solids, flowing downwardly on said second gas-permeable slanted surface, whereby the froth accumulating in said reservoir is permitted to overflow said wall and discharge to a launder; f) baffles disposed above said reservoir and carried by said sprinkler, said baffles being adapted to cause the entire froth to flow underneath said sprinkler; and g) a discharge disposed at a lower part of said wall for evacuating the pulp continuously from said reservoir.

9. An apparatus as claimed in claim 7, wherein: a) said baffles are inclination adjustable. An apparatus as claimed in claim 7 or claim 8 wherein: 15 a) said wall is height adjustable, .11 An apparatus as claimed in claim 7, 8 or 9 and further comprising: a) a duct connected to said discharge, said duct including a height- adjustable plate at its top for adjusting the overflow of the pulp.

12. A froth flotation process for receiving hydrophobic particles from a 20 pulp, substantially as hereinbefore described with reference to the drawings, "13. A froth flotation apparatus for material separation substantially as hereinbefore described with reference to and as shown in Figures 1 to 5 or Figures 6 to 10 of the drawings. *DATED this fifteenth day of August 1996 DANIEL ZVONIMIR URIZAR Patent Attorneys for the Applicant: F.B, RICE CO. I 1 J *r o $11~vT i P- tj ABSTRACT The invention is related to a procedure and an apparatus for the separation of hydrophobic substances and material by flotation have been developed. Basically, the invention consists of dripping pulp over a gas permeable slanted surface. Downstream of the gas permeable slanted surface froth product is collected and flotation tailings are removed. Baffles are used to selectivity and recovery control. As well, sprinkling means are used for the depletion of hydrophilic material presents in the froth zone. a. r a a ea *a a i r a J a m )i _I iY -I C