GB1569020A - Continuous decantation clarifier - Google Patents

Description

(54) CONTINUOUS DECANTATION CLARIFIER , 1, Lolz ANTONIO CERVEIRA DE MELO RIBEIRO PINTS, a Brazilian Citizen, of 384 Banderantes Avenue, 14100 Ribeirao llreto, Sao Paulo, Brazil, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to a continuous decantation clarifier which operates to provide efficient and very fast clarification of sugar juices, such as are employed in the production of sugar, although it can be utilized for treating other liquids containing suspended decantable solids.

The principle of the clarifier of the invention does not follow the classical concept of multiple trays decanters, wherein liquid to be decanted is fed continuously from above down through a central shaft, in the interior of a single cylinder from which it flows radially outwardly to chambers of frusto-conical form, commonly called "trays", and wherein the solids are deposited by simple decantation, the solids being swept along the bottoms of the trays by mechanical action and being returned to the central shaft through which they descend to the bottom where they form a thick mud or sludge which, in turn, is also removed continuously through the bottom of the device, the clean juices being collected in the upper periphery of each tray.

The clarifier of the invention comprises: means defining a vertically-extending first zone and adapted for liquid to be clarified to pass downwards therethrough so that the liquid is subjected to flocculation; means defining a vertically-extending second zone adjacent to said first zone for receiving the liquid from the lower end of said first zone and for directing said liquid in a vertically upward direction, said second zone being arranged adjacent to a third zone for receiving solid particles separated from the liquid in said third zone, which solid particles sink in the second zone to collide and coalesce with flakes and solids in suspension in the liquid in said second zone, so that said flakes and solids will precipitate towards the bottom of the clarifier, and means for defining said third zone comprising at least one frusto-conical surface or frusto-conical tray arranged adjacent to said second zone so as to receive the liquid from the second zone and direct it radially outwardly and upwardly and scraper means for scraping the or each said frusto-conical surface or frusto-conical tray so as to displace therefrom solid particles precipitated in said third zone and to cause them also to sink into said second zone to collide and coalesce with flakes and solids in suspension in the liquid in the second zone, and collectors disposed to enable clarified liquid to be collected close to the outer periphery of the or each said frusto-conical surface or frusto-conical tray.

The clarifier of the invention carries out decantation on trays by intense coalescence of the decantable solid particles, which coalescence is attained by upward movement of the liquid to be decanted through a cloud of solid particles suspended in the liquid, these particles being in slow upward movement. Such system provides for very effective juice clarification wherein the smaller solid particles which, due to their high specific surface areas, are entrained by the upward movement of the juice, pass through the cloud of precipitated particles already in downward movement by virtue of the smaller specific surface areas thereof, and collide with the former and adhere to them by coalescence increasing the size of the precipitated particles and thereby accelerating progressively their downward speed.

This provides for quick and perfect clarification, resulting in cleaner and clearer juice in a considerably reduced total period of time as compared with prior known processes, which is a very important factor in sugar production.

For a better understanding of the invention, it will be described further, by way of example, with reference to the accompanying drawings, wherein: Fig. 1 is a diagrammatic sectional elevation of a preferred embodiment of the con tintlous clarificr of the invention; this figure illustrating in its right hand half and by means of long arrows, the movement direction of clean juices and, in its left hand half and by means of short arrows, the paths of the solids in their decantation movement; and Fig. 2 is a view similar to Fig. 1, but illustrating the continuous clarifier in more detail.

As shown in the drawings, the illustrated embodiment of the continuous decantation clarifier in accordance with the invention basically comprises an internal small-diameter cylinder 3, mounted vertically by a support 18 at the centre of a cone frustum assembly formed by an intermediate-diameter cylinder 11, of diameter larger than the internal cylinder 3, having a frusto-conical bottom and supporting, above its upper part, a series of conical surfaces or tilted trays 5 of annular shape equally spaced in the vertical direction.

These trays have internal diameters which diminish progessively, the higher the tray 5, the smaller the internal diameteer of the tray 5, the smallest of these internal diameters still being larger than the external diameter of the internal cylinder 3 and terminating at their external peripheries at an external large-diameter vertical cylinder 13 whose diameter is larger than the diameters of the cylinders 3 and 11. Upon the external cylinder 13, there is a coneshaped lid supporting a central mechanism ]0 for rotating mechanical means 9 comprising a central vertical axle 15, radial arms and supports connected to rotary scrapers overlying the trays 5, and to a mud stirrer 17, to scrape the upper surfaces of the respective trays 5, and the bottom of the device.

Sugar juice, coming from a flash reservoir 1, is fed to the device through a radial distributor 2, disposed in a central position in the internal cylinder 3 and projecting downwards below the normal surface of liquid within the cylinder 3 when the apparatus is in use, the lower end of the internal cylinder 3 being masked by a screen or punched plate 4.

The apparatus further includes an upper gas outlet 14, a lower central outlet 8, at the bottom of the cylinder 11, for removal of mud or sludge, a collecting box 12 on the upper part of the internal cylinder 3 and at least one lower foam collecting gutter 16 for receiving foam collected by said box 12.

At the outer peripheries of the trays 5, and at the respective levels thereof, means are provided for removing cleaned juice through respective adjustable overflow pipes or collectors 6 that conduct the cleaned juice to a clean juice collecting box 7.

In the above-described construction in the apparatus of the present invention, three different zones are defined, which zones are slowly and methodically traversed by the juices to be clarified. These zones are: a vertically-extending first or flocculation zone Zl; a vertically extending second or filtration and coalesence zone Z2, and a third or decantation zone 23.

The first or flocculation zone Z1 is defined by the central internal cylinder 3. The juices from the distributor pass downwards through this zone Z1, at the same time being subject to mixing which eliminates any small differences of temperature and density, and flocculation. In this stage or step, the process which takes place in the apparatus, precipitation of solid flakes just commences, while any high density particles (sand, for example) quickly gravitate toward the bottom. At the outlet of this zone Z1, the juice is uniformly distributed in radial sense, with a small pressure loss created by the screen or plate 4.

The second or coalescence zone Z2, which is external and concentric to the flocculation zone Z1 is defined by the space limited by the internal cylinder 3 and by the lower or intermediate cylinder 11. In such zone Z2, the juice reverses its direction of movement and starts flowing upwards during which, it passes through a "cloud" of solid particles suspended in the liquid and in descending movement of decantation. In its descent, the small flakes collide, coalescence and precipitate, increasing their dimensions and speed of precipitation as they get lower and lower.

The third or final decantation zone Z3 is constituted by the trays 5, arranged above and concentrically to the filtration and coalescence zone Z2. In this zone Z3, final clarification of the juice occurs in that the particles, still entrained by the upward movement of the juices, are separated through decantation when the juice is flowing radially, the particles being deposited upon the trays 5. The solid material on the trays 5 is mechanically swept by means of scrapers 9 toward the centre of the device, and falls gravitationally and uniformly into the coalescence zone Z2, already in the form of large coalescend particles. The clean juice is then removed adjacent the upper external peripheries of the trays 5 by means of the adjustable overflow pipes or collectors 6 and is collected in the clean juice collecting box 7.

The apparatus further has a fourth zone Z4, located at the bottom thereof, where solid particles gather and concentrate, being swept to the central round outlet 8 by the mechanical means 9, the particles being continuously removed in concentrated form.

WHAT I CLAIM IS: 1. A continuous decantation clarifier comprising: means defining a verticallyextending first zone and adapted for liquid to be clarified to pass downwards therethrough so that the liquid is subjected to flocculation; means defining a vertically extending second zone adjacent to said first zone for receiving the liquid from the lower end of said first zone and for directing said liquid in a vertically upward direction, said second zone being arranged adjacent to a third zone for receiving solid particles separated from the liquid in said third zone, which solid particles sink in the second zone to collide and coalesce with flakes and solids in suspension in the liquid in said second zone, so that said flakes and solids will precipitate toward the bottom of the clarifier, and means for defining said third zone comprising at least one frustoconical surface or frusto-conical tray ar ranged adjacent to said second zone so as to receive the liquid from the second zone and direct it radially outwardly and upwardly scraper means for scraping the or each said frusto-conical surface or frusto-conical tray so as to displace therefrom solid particles precipitated in said third zone and to cause them also to sink into said second zone to collide and coalesce with flakes and solids in suspension in the liquid in the second zone, and collectors disposed to enable carified liquid to be collected close to the outer periphery of the or each said frusto-conical surface or frusto-conical tray.

2. A clarifier as claimed in claim 1, wherein said first, second and third zones are substantially concentric, the first zone being centrad, the second zone being external to the first zone and the third zone being arranged above and externally of said second zone.

3. A clarifier as claimed in claim 1 or 2 which further includes a fourth zone at the bottom of the second zone substantially not traversed by the liquid to be clarified, but provided with a lower central outlet for removal of solid particles accumulating in said fourth zone.

4. A clarifier as claimed in claim 1, 2 or 3 wherein a radial distributor is provided in an upper central position in the first zone so as to protrude below the surface of liquid in said zone, and a screen or punched plate is provided at the lower end of said zone.

5. A clarifier as claimed in claim 3 and which comprises an internal cylinder defining said first zone and vertically suspended at the centre of a frusto-conical assembly formed by an intermediate cylinder defining said second zone and having a diameter larger than that of the internal cylinder and having a conical bottom and having in its upper part a series of vertically-spaced frusto-conical trays, having internal diameters which decrease the higher the tray and which are larger than the external diameter of the internal cylinder and terminate at external peripheries at an external cylinder, of a diameter larger than the diameters of the internal and intermediate cylinders, defining said third zone, the assembly of cylinders being closed in the upward direction by a conical lid and said fourth zone being defined by the conical bottom of the intermediate cylinder.

6. A clarifier as claimed in claim 5 which includes rotary scrapers to scrape the bottom of the intermediate cylinder.

7. A clarifier as claimed in claim 5 or 6, which further includes means permitting removal of clean juice through adjustable overflow pipes arranged adjacent the peripheries of the trays, and gutters for collecting surface foam from the liquid in the interior of said first zone.

8. A continuous decantation clarifier substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. swept to the central round outlet 8 by the mechanical means 9, the particles being continuously removed in concentrated form. WHAT I CLAIM IS:

1. A continuous decantation clarifier comprising: means defining a verticallyextending first zone and adapted for liquid to be clarified to pass downwards therethrough so that the liquid is subjected to flocculation; means defining a vertically extending second zone adjacent to said first zone for receiving the liquid from the lower end of said first zone and for directing said liquid in a vertically upward direction, said second zone being arranged adjacent to a third zone for receiving solid particles separated from the liquid in said third zone, which solid particles sink in the second zone to collide and coalesce with flakes and solids in suspension in the liquid in said second zone, so that said flakes and solids will precipitate toward the bottom of the clarifier, and means for defining said third zone comprising at least one frustoconical surface or frusto-conical tray ar ranged adjacent to said second zone so as to receive the liquid from the second zone and direct it radially outwardly and upwardly scraper means for scraping the or each said frusto-conical surface or frusto-conical tray so as to displace therefrom solid particles precipitated in said third zone and to cause them also to sink into said second zone to collide and coalesce with flakes and solids in suspension in the liquid in the second zone, and collectors disposed to enable carified liquid to be collected close to the outer periphery of the or each said frusto-conical surface or frusto-conical tray.

2. A clarifier as claimed in claim 1, wherein said first, second and third zones are substantially concentric, the first zone being centrad, the second zone being external to the first zone and the third zone being arranged above and externally of said second zone.

3. A clarifier as claimed in claim 1 or 2 which further includes a fourth zone at the bottom of the second zone substantially not traversed by the liquid to be clarified, but provided with a lower central outlet for removal of solid particles accumulating in said fourth zone.

4. A clarifier as claimed in claim 1, 2 or 3 wherein a radial distributor is provided in an upper central position in the first zone so as to protrude below the surface of liquid in said zone, and a screen or punched plate is provided at the lower end of said zone.

5. A clarifier as claimed in claim 3 and which comprises an internal cylinder defining said first zone and vertically suspended at the centre of a frusto-conical assembly formed by an intermediate cylinder defining said second zone and having a diameter larger than that of the internal cylinder and having a conical bottom and having in its upper part a series of vertically-spaced frusto-conical trays, having internal diameters which decrease the higher the tray and which are larger than the external diameter of the internal cylinder and terminate at external peripheries at an external cylinder, of a diameter larger than the diameters of the internal and intermediate cylinders, defining said third zone, the assembly of cylinders being closed in the upward direction by a conical lid and said fourth zone being defined by the conical bottom of the intermediate cylinder.

6. A clarifier as claimed in claim 5 which includes rotary scrapers to scrape the bottom of the intermediate cylinder.

7. A clarifier as claimed in claim 5 or 6, which further includes means permitting removal of clean juice through adjustable overflow pipes arranged adjacent the peripheries of the trays, and gutters for collecting surface foam from the liquid in the interior of said first zone.

8. A continuous decantation clarifier substantially as hereinbefore described, with reference to and as illustrated in the accompanying drawings.