FR2719507A1 - Clarification of wine must or fruit juice by froth flotation - Google Patents

Abstract

Liq. foodstuffs such as wine musts and fruit juices etc. are clarified by froth flotation. The flotation cell (11) is a semi-circular vessel, open at the top and divided into three chambers for clarification (13), decantation (14) and collection (15). Liq. for clarification, at least partially supersaturated with gas, is fed (16) into the base of the clarification chamber. A deflector (19) directs the flow up the sides of the chamber, along all of its length. The collectors of froth (21) and clarified liq. (25) are situated longitudinally in the centre of the chamber. The liq. collector has openings just above the inlet deflector and leads to the decantation chamber. The froth collector is open at the top, near the free surface of the liq., and leads to a discharge outlet.

Description

FLOATING CLARIFICATION DEVICE
The present invention relates to a flotation clarification device.

 The flotation clarification device according to the invention is advantageously used, although not exclusively, for treating food liquids such as wine must or fruit juices.

 The process for clarifying a food liquid by flotation is known, which consists in letting spread inside a container containing the liquid to be clarified in which there are solid particles, a gas which saturates said liquid and determines the formation of bubbles of small dimensions in its mass.

 If the gas is properly dispersed, gas-solid aggregates are formed which have the desired density and which, therefore, are flush with the free surface of the liquid, from which they are then removed.

 Chemical co-adjuvants, called flocculants, and coagulants, which destabilize colloids, can be used, allowing particles to come together to improve the efficiency of the process.

 Flotation clarification installations include a flotation cell which is continuously traversed by the fluid to be treated. The flotation cells can be supplied with a stream of raw edible liquid to be treated, which is supersaturated and then allowed to spread in the flotation cell.

 According to other embodiments, the flotation cells are supplied by a pre-mixed stream, consisting of a portion of the clarified edible liquid by supersaturated flotation and by a stream of raw edible liquid to be treated.

 Known flotation cells are mainly of two types, depending on the flow which must be treated and, more precisely, cells with a rectangular plane and cells with a circular plane. For low flows, of the order of 50 to 70 quintals / hour, the flotation cells used are those with a rectangular plane in which the cell, of parallelepiped shape, is crossed by the fluid in the longitudinal direction.

 In this type of cell, the clarified liquid is discharged by means of a weir blade, which extends over the entire transverse dimension of the cell.

 The reduced size of the overflow blade implies a high speed of overflow flow, which creates turbulence, which recirculates the material which had concentrated on the free surface of the liquid, thereby reducing the system efficiency.

 For a question related to the distribution of fluxes inside the cell, the rectangular-shaped cell has dimensional limits which require the use of several flotation cells in parallel when the flows involved are high.

 This fact considerably increases the installation and operating costs of the installation, since all the devices associated with the flotation cell must be multiplied, which makes this solution economically disadvantageous.

 For large flows, we therefore prefer the flotation cells in the form of a circular plane in which the fluid to be clarified is introduced in the center while the clarified liquid is collected at the periphery.

 The circular shape generally ensures better distribution of the flows and therefore makes it possible to achieve more effective clarification.

 In addition, the control of the removal of the foam layer and the manner in which this removal is carried out are important for the purposes of clarification.

 Indeed, the controlled removal of the foam layer influences the content of dry substances present in the foam and the efficiency of the clarification operation in terms of the degree of clarification that can be obtained for the liquid. food.

 In cells with a rectangular plane shape, the scum removal device is generally constituted by a scraper blade system, which is set in longitudinal movement in the opposite direction to the clarified liquid food.

 In cells in the form of a circular plane, the collecting device is generally produced by means of a rotating radial arm with a central axis on which the collecting elements are distributed.

 Said collecting elements are constituted by suction mouths or by pallets oriented so as to transport the foam to the center of the flotation cell, in which a collecting duct is present.

 To overcome the drawbacks of the known technique and to obtain other and new advantages, the applicant has studied, tested and carried out the present invention.

 The invention relates to a flotation clarification device, used for clarifying edible liquids such as wine must, fruit juices, etc., comprising a flotation cell which is supplied with a stream of liquid at least partially supersaturated with gas and which has, at the top, means for collecting and discharging the floating foam, characterized in that the flotation cell has substantially the shape of a half-cylinder open at the top, which comprises a first clarification chamber and a second settling chamber, said first clarification chamber being equipped with means for feeding the liquid to be clarified placed at the bottom, said clarification chamber having means for distributing the flow of incoming food liquid, which distribute the food liquid on two parallel fronts , one of which extends over the entire length of the clarification chamber, of the first means collect eurs of clarified liquid and of the second foam collecting means, said first collecting means and said second collecting means extending in the longitudinal direction of said clarification chamber, said first collecting means having an inlet mouth placed near said means distributors and said second collecting means having an inlet mouth placed near the upper free surface, said first collecting means being connected to said second settling chamber and said second collecting means being connected to a scum discharge mouth.

 The object of the invention is to provide a flotation clarification device used for the clarification of edible liquids such as wine must or fruit juice.

 The flotation clarification device according to the invention has, at equal flow rate of treated fluid, a more compact shape and reduced overall dimensions, compared to the flotation cells already known in the form of a rectangular plane or in the form of a circular plane. .

 To optimize the flotation process, one of the critical parameters to which the Applicant has focused its attention is the configuration of the flotation cell, since the degree of clarification achieved depends notably on the regime of the liquid-gas-solid flows.

 Another important parameter is the system for collecting and removing the foam which forms on the free surface of the liquid.

 The clarification device according to the invention comprises a flotation cell having a semicylindrical shape open at the top, in which the supply flow of the liquid to be treated is orthogonal to the longitudinal axis of the cell.

 More particularly, in the flotation cell according to the invention, the liquid to be treated is introduced from below on two parallel fronts each of which extends over the entire length of the flotation cell, which makes it possible to have a speed d very low entry of the liquid to be treated, which is favorable for flotation.

 The flotation cell according to the invention makes it possible to ensure a very high clarification efficiency.

 In the flotation cell according to the invention, the line for collecting the clarified liquid and the line for collecting the scum both extend over a length substantially equal to or twice the length of the flotation cell.

 This significant extension of the collection line and the configuration of the variable-section collection channel make it possible to have very low and substantially constant collection speeds along the entire axis of the cell.

 Said very low and substantially constant speeds do not create turbulence or preferential passages and thus make it possible to obtain a very high clarification efficiency.

 The flotation clarification device according to the invention can be supplied with a stream of raw edible liquid to be treated, which is supersaturated with gas under pressure and which is thus caused to expand in the flotation cell.

 According to an advantageous embodiment, the flotation clarification device according to the invention is supplied by a premixed stream consisting of a portion of the clarified edible liquid by supersaturated flotation with pressurized gas and a stream of raw edible liquid to be treated.

 The flotation cell according to the invention advantageously cooperates with a device for supersaturation of the liquid placed upstream, in which the gas is continuously introduced into a static mixer under pressure, in which said gas is brought into contact with the food liquid to be supersaturated .

 By acting in this way, the discontinuity in the supply of the liquid-gas mixture is avoided, which would periodically disturb the fluid-dynamic regime in the flotation cell, resulting in a reduction in the clarification efficiency of the flotation cell.

 The flotation cell according to the invention is divided longitudinally into a first clarification chamber and a second decantation chamber, which are contiguous, and which are successively crossed by the liquid to be treated.

 The flotation cell according to the invention has at least one feed mouth placed on the bottom, through which the stream of raw food liquid and the supersaturated clarified food liquid are introduced, suitably mixed, in a mixing device placed upstream.

 In the case of cells having large dimensions, it can be provided several supply vents present on the bottom of the cell.

 The clarification chamber has means for distributing the liquid food liquid introduced, which constrains the incoming liquid food to be divided into two streams substantially orthogonal to the longitudinal axis of the flotation cell.

 In the device according to the invention, said distributing means comprise a double bottom associated with the clarification chamber and which extends transversely, symmetrically over an arc defined by an angle a between 900 and 150, advantageously equal to 1200.

 Said double bottom is substantially parallel to the bottom itself of the clarification chamber, but suitably spaced from this bottom to define a transport channel, which distributes the food liquid introduced and forces it to lick the longitudinal side walls of the clarification chamber.

 The food liquid therefore firstly describes an ascending trajectory near the side walls and then collects towards the substantially longitudinal lower longitudinal zone.

 In the flotation cell according to the invention, the stream of food liquid to be treated is thus distributed into two substantially equal and symmetrical streams, having a very wide cross section and an even lower speed, thereby promoting the flotation process .

 In the flotation cell according to the invention, the collection and the evacuation of the clarified liquid food as well as the collection and the evacuation of the foam which floats on the free surface of the water occur in a direction orthogonal to the longitudinal axis of the flotation cell.

 More particularly, the flotation cell has an axial scum collecting channel, open at the top and extending longitudinally, advantageously over the entire clarification chamber.

 Said scum collecting channel is positioned in the central part of the flotation cell and extends over the entire length of said flotation cell.

 The unloading of the floating foam is carried out by touching in the transverse direction along the upper edge of the two longitudinal walls which define said foam collecting channel.

 Said scum collecting channel advantageously has an inclined bottom to form a chute on which the discharged scum descends by gravity and collects at the lowest point of the scum collecting channel, in which a discharge discharge mouth is previously disposed. scum.

 The flotation cell has a substantially axial clarified liquid food collection channel, open at the bottom and extending longitudinally at least over a large part of the clarification chamber.

 Said clarified liquid food collecting channel is positioned under the scum collecting channel and is defined by the same side walls which extend longitudinally.

 Said clarified liquid food collecting channel has an inlet mouth placed near the distributing means.

 More particularly, the passage of the clarified food liquid inside said collecting channel of clarified food liquid is carried out from the bottom in the direction orthogonal to said longitudinal walls defining said collecting channel of clarified food liquid.

 Said clarified liquid food channel advantageously has a cross section with variable shape along its length. More particularly, the cross section of the collecting channel for clarified liquid food gradually increases as one goes towards the settling chamber, so as to ensure that the clarified liquid movement in the longitudinal direction at a substantially constant and uniform speed.

 The low speed of reception of the clarified food liquid prevents the creation of preferential high-speed currents, which could resuspend the flocculated substances, with consequent reduction in the efficiency of the clarification device.

 The channel for receiving the clarified liquid then opens into the settling chamber, in which the suspended solids of high specific gravity possibly present can settle and be evacuated from the bottom, while the clarified liquid food is collected and, by pouring over the beyond an overflow blade, goes to the following operations.

 According to a variant, said overflow blade of the clarified food liquid is advantageously movable, to allow the level of the free surface of the food liquid to be adjusted inside the flotation cell according to the invention.

 The flotation cell according to the invention also has a foam collecting device which sends the foam which is flush with the free surface of the liquid in the foam collecting channel.

 The scum collecting device according to the invention comprises two scraper means extending longitudinally over the entire length of the clarification chamber and arranged on both sides of the scum collecting channel.

 Each scraper comprises motorized chain means, closed in a ring, on which are mounted a plurality of pallets, said pallets being partially immersed in the layer of foam which floats.

 The setting in motion of said chains causes the plurality of pallets in translation in the transverse direction, from the outside towards the central collecting channel of the foam, in which this foam is discharged.

 The collecting device, which extends over a length equal to twice the length of the clarification chamber, makes it possible to circulate the pallets in translation at a very reduced speed, thereby avoiding possible flake breaks and re-mixing of the liquid. clarified, which would lower the performance of the clarification process.

 The accompanying drawings are given by way of non-limiting example and illustrate a preferred embodiment of the invention.

On these drawings
- Figure 1 shows, in perspective view, the flotation clarification device according to the invention
- Figure 2 shows the device of Figure 1 in longitudinal section along the line AA
- Figure 3 shows the device of Figure 2 in cross section along the line BB.

 In the accompanying drawings, the reference number 10 as a whole designates the flotation clarification device according to the invention.

 The flotation clarification device 10 according to the invention is advantageously used, although not exclusively, for clarifying food liquids such as wine must, fruit juices, etc.

 The flotation clarification device 10 according to the invention comprises a flotation cell 11 having, in the high position, scraping and collecting means 12 of the material collected or scum, present on the free surface of the liquid food.

 The flotation cell 11 according to the invention has a semi-cylindrical shape open at the top and, in the case under consideration, it is divided longitudinally into three chambers.

 More particularly, the flotation cell 11 according to the invention has a first clarification chamber 13, a second decantation chamber 14 and a third chamber for collecting and discharging the clarified liquid 15, said chambers 13, 14 and 15 being traversed successively by the liquid to be treated.

 The flotation cell 11 according to the invention has at least one supply mouth 16 placed on the bottom and through which the liquid to be treated is introduced.

 In the case under consideration, there are two supply outlets 16 placed in line with the clarification chamber 13, and along its longitudinal axis.

 The flotation cell 11 according to the invention can be supplied, as well with the food liquid to be treated, supersaturated with gas, as with a mixed stream composed of raw food liquid to be treated and clarified liquid supersaturated with gas.

 The operation of supersaturation of the liquid to be introduced is advantageously carried out in a device placed upstream and not shown here, in which the gas is introduced continuously by bringing it into contact with the liquid in a static mixer under pressure.

 This thus minimizes the disturbances of the fluid-dynamic regime in the first clarification chamber 13 of the flotation cell according to the invention, with consequent increase in the clarification efficiency.

 In the case under consideration, there is associated with each supply mouth 16 a mixing device 17, having an inlet conduit 18a for the raw liquid to be treated, an inlet conduit 18b for the clarified supersaturated liquid and a drainage conduit 18c for emptying the flotation cell.

 The first clarification chamber 13 has means for distributing feed flows containing a double bottom 19 which extends symmetrically over an angle a between 900 and 1500, advantageously equal to 1200, at a desired and constant distance from the bottom of the flotation cell 11, to define two channels 20 for transporting the liquid to be treated.

 Said transport channels 20 give a very wide passage section for the liquid to be treated, with a liquid entry speed reduced accordingly, to improve the flotation process.

 The incoming liquid to be treated is therefore forced to lick the longitudinal walls of the clarification chamber 13 in the upward direction to then describe a movement directed substantially downwards in the central zone of the clarification chamber 13.

 The Applicant has discovered that both the reduced speed and the route thus defined improve the flotation process by promoting the floating of the foam.

 The clarification chamber 13 has in the central position a scum collecting channel 21 open at the top and extending over the entire length of said clarification chamber 13.

 The said scum collecting channel 21 is defined by two lateral walls 22 extending over the entire length of the clarification chamber 13 and having the bottom wall 23 inclined downwards in the opposite direction to the settling chamber 14.

 The flotation cell 11 has a froth for discharging froth 24 at the lowest point of said froth collecting channel 21.

 The side walls 22 extend downwards until defining a collecting channel for the clarified liquid 25 open at the bottom.

 Said collecting channel for the clarified liquid 25 has, in the case under consideration, an upper wall 26 inclined and having a height which increases towards the settling chamber 14.

 The clarified liquid passes from the clarified liquid collecting channel 25 into the decantation chamber 14, in which any suspended solids settle out and settle on the bottom in order to be evacuated through a conduit 27 for discharging the decanted material which is specially provided.

 The clarified liquid, by pouring over the transverse wall 28 which separates the collecting and discharge chamber of the clarified liquid 15, is collected and sent to successive treatments by a conduit for transporting the clarified liquid 29.

 According to a variant which is not shown here, said transverse wall 28 which separates the collecting and discharge chamber of the clarified liquid 15 is advantageously of the height adjustable type.

 In the flotation cell 11 according to the invention, the means 12 for scraping and collecting the foam which floats on the clarified liquid present in the clarification chamber 13 comprise two scrapers 30, extending longitudinally over the entire length of the clarification chamber 13 and arranged on both sides of the foam collecting channel 21.

 Each scraper 30 comprises means 31 forming motorized chains, closed in a loop, on which is mounted a plurality of pallets 32, said pallets 32 being partially immersed in the layer of foam which floats.

 On part of their course, said chain-forming means 31 are positioned facing the free surface of the clarified liquid on which the foam to be discharged floats and parallel to this surface.

 The setting in motion of said chain means 31 causes the plurality of pallets 32 to move in translation in the transverse direction, from the outside towards the central foam collecting channel 21, in which this foam is discharged.

 To prevent the clarified liquid from being able to pour into the scum collecting channel 21, the side walls 22 extend upwards to a dimension greater than the dimension of the transverse overflow wall 18.

 In the case under consideration, the transverse walls 22 have at the top a segment 33 having the shape of an ascending chute, and with which the pallets 32 come to cooperate by turning.

 Of course, the invention is not limited to the embodiments described above and shown, from which other embodiments can be provided, without going beyond the ambit of the invention.

Claims (10)

 1. Flotation clarification device, used for clarifying edible liquids such as wine must, fruit juices, etc., comprising a flotation cell which is supplied with a stream of liquid at least partially supersaturated with gas and which has, in the high position, means for collecting and discharging the floating foam, characterized in that the flotation cell (11) has substantially the shape of a half-cylinder open at the top, which comprises a first chamber clarification chamber (13) and a second settling chamber (14), said first clarification chamber (13) being equipped with means (16) for supplying the liquid to be clarified placed at the bottom, said clarification chamber (13) having means (19) for distributing incoming food liquid which distribute the food liquid on two parallel fronts, one of which extends over the entire length of the clarification chamber (13), first clarified liquid collecting means (25) and second scum collecting means (21), said first collecting means (25) and said second collecting means (21) extending in the longitudinal direction of said clarification chamber ( 13), said first collecting means (25) having an inlet mouth placed near said distributing means (19) and said second collecting means (21) having an inlet mouth placed near the upper free surface, said first collecting means (25) being connected to said second settling chamber (14) and said second collecting means (21) being connected to a scum discharge mouth (24).  2. clarification device by flotation according to claim 1, characterized in that the second collecting means (21) have a bottom (23) inclined towards the discharge mouth of foam (24).  3. Flotation clarification device according to claim 1 or 2, characterized in that with the free surface, scraping means (30) cooperate acting in the radial direction directed towards the central longitudinal axis of the clarification chamber (13 ).  4. Flotation clarification device according to either of the preceding claims, characterized in that the first clarified liquid collecting means (25) have their ceiling (26) inclined towards the second settling chamber (14).  5. Flotation clarification device according to either of the preceding claims, characterized in that the means for introducing the food liquid to be treated comprise at least partial supersaturation means (17) using gas .  6. Clarification device by flotation according to either of the preceding claims, characterized in that the liquid flow distributing means comprise a double bottom (19) which extends over an arc of a circle to define with the bottom from the clarification chamber (13) a channel (20) for transporting the liquid to be clarified.  7. Flotation clarification device according to claim 6, characterized in that the double bottom (19) extends symmetrically with respect to the longitudinal axis of the flotation cell (11) on an arc defined by an angle included between 900 and 1500, and advantageously equal to 1200.  8. Clarification device by flotation according to either of the preceding claims, characterized in that it comprises a third collecting and discharging chamber for the clarified liquid (15) placed longitudinally in series with the settling chamber ( 14).  9. Flotation clarification device according to either of the preceding claims, characterized in that the scraper means (30) of the foam which floats on the clarified liquid associated with the clarification chamber (13) comprise two or more than two pigs (30) extending longitudinally over the entire length of the clarification chamber (13) and arranged on both sides of the second scum collecting means (21).  10. Flotation clarification device according to either of the preceding claims, characterized in that it is associated with a supersaturation device placed upstream, in which the gas is introduced continuously by bringing it into contact with liquid food in a static pressure mixer.