FR2669018A1 - Anaerobic digester with a turbulent stationary bed - Google Patents

Abstract

Digester consisting of an insulated tank heated by a heating floor 3. A slowly rotating movable fitting 80 carries a group of members which make it possible to introduce the products to be purified uniformly over the whole surface near the bottom of the digester and to recover them uniformly at the top of the digester over the whole surface; it also carries sheets of vertically stretched fabrics which occupy most of the volume of the digester and which, owing to the effect of the slow rotation, come into contact with the products.

Description

PATENT APPLICATION
- The present invention relates to devices intended for the continuous purification by the anaerobic route of liquid effluents containing a maximum of 4 to 5% of dry matter. It relates more precisely to fixed bed digesters.

- the patent application is entitled: DIGESTEUR
TURBULENT FIXED BED ANAEROBIC.

STATE OF. L.! \ .TE &# I.QQE
- The anaerobic route is a very effective purification means for liquids moderately and heavily loaded with organic matter.

 - In particular for the effluents moderately loaded with organic matter which are generally those of the food industry presents in many cases a decisive advantage compared to the aerobic way but it is then essential to reduce residence times as much as possible in the digester.

 - To achieve this result, if you want to have devices of an acceptable volume taking into account the daily volumes to be treated which are generally important, try to keep the maximum of active methanogenic bacteria in the digester.

 - Methanogenic bacteria reproducing very slowly (average doubling time of 10 days), we tried to maintain the maximum of bacteria in digesters mainly by the fixed bed technique where we exploit the property that methanogenic bacteria have of fixing themselves on solid supports. The main fixing materials used so far are gravel, coke, plastic materials, more rarely plastic films.

 - But these digesters traditionally have problems with clogging and preferential circuits, they can therefore only treat effluents very lightly loaded with suspended matter or effluents removed when possible from their suspended matter by sieving. They are therefore ultimately specialized in very specific types of effluents.

PRESENTATION OF CHARACTERISTICS
- The present invention aims to remedy the drawbacks of the prior art and proposes a digester consisting of a cylindrical tank whose diameter is greater than the height.

 - The lower part of this tank is mainly constituted by a heating floor 3 resting on an incompressible insulator 2. Because the sludge from the bottom of the digester is stirred slowly as will be mentioned below, the heat exchanges take place normally and allow the products to be maintained at the desired temperature which avoids the external exchangers and all their drawbacks.

 - The insulation of the side walls 5 in reinforced concrete of the tank is ensured by an external insulator 6 put in place by pouring and kept in place by a cladding 7.

 The upper part of the digester is horizontal and is constituted by an insulated fixed cover supported by radiating beams 11 which bear in the center on a central pillar 8 via a support plate 9.

 - This assembly leaves a completely free space below it so as to allow the movement, in slow rotation in the clockwise direction, of a mobile assembly 80 which scans the entire base surface of the digester and which is guided and supported by a rail 78 fixed on the upper face of the side walls 5 of the tank.

 - The moving part 80 which supports almost all of the elements located under the cover, and all of the elements present inside the tank is set in slow discontinuous rotation in the direction of clockwise by the action simultaneous and combined 2 hydraulic cylinders 81 - 82 each fixed at the end of a diameter and which bear successively on all the fixed elements 84 fixed to the upper part of the side walls 5 of the tank.

 - The continuity of the connection for the transfer of incoming or outgoing fluids between the fixed pipe 14 which brings the effluent to be treated, the fixed pipe 60 which discharges the purified effluent, the fixed pipe 65 which discharges the biogas produced and the pipes corresponding supported by the moving part 80 is ensured by 3 concentric troughs 66, 67, 68, and which are integral with the moving moving part 80.

 - The effluents to be purified arrive via the fixed pipe 14, they fall by gravity into the mobile chute 67 from where they flow by gravity thanks to the pipe 16. This same chute can also ensure the recycling of sludge from the bottom or floats arriving via line 27.

- The rotating mobile chute 66 collects
- the purified liquids brought in by the pipeline
45
- bottom sludge brought in by the pipeline
27
- the floats brought in by line 53
- All these products are taken up by the fixed pump 59 which rejects them to the outside thanks to the fixed pipe 60.

 - The biogas produced arrives through the pipe 63 which opens under the bell 71 whose edges plunge into a liquid 69 contained in the movable central chute 68. The seal is ensured by the hydraulic seal 70. The biogas is evacuated to the outside by the fixed channel 65. Most of the volume of the digester, with the exception of a lower cylindrical volume of 0.2 meters high located at the bottom of the digester and an upper cylindrical volume of 1 meter high located immediately below the free surface of the products being digested, is occupied pr sheets 76 of fabrics stretched vertically at regular intervals.

 - These layers form hexagonal structures nested regularly and at regular intervals in each other.

 - All of these layers of fabrics are animated by two movements: a slow and discontinuous circular movement and slow alternating rectilinear vertical movements. The first of these movements is communicated by the moving element 80, the second movement is communicated by the lifting cylinders 77. These layers of tissue ensure the attachment of bacteria. Their arrangement in parallel vertical layers, the intervals between two successive layers, and the movements communicated to them, ensure maximum contact with the products being digested and the absence of clogging.

 - The maximum contact between the sheets of fabric and the liquids to be cleaned is further facilitated by the fact that the products to be cleaned are introduced as we will see later in the description in quantity dosed between each sheet of fabric. The interval between each sheet of fabric forms chimneys in which the products to be purified rise slowly, undergoing regular and maximum contact with the tissues and therefore with the bacteria which are fixed there.

 - The effluent to be treated is brought into the constant level tank 17.It is taken up by cups 18 of different volumes which ensure the metering of the incoming products and their introduction. For this a device 20 and a connecting pin 19 integral with all the cups 18 allow these to be filled in the storage tank before introduction 17 and their emptying into the introduction pipes 21.

 - The introduction pipes 21 are arranged on a radius of the tank; between each sheet of fabrics 76 there is an introduction pipe 21 which descends vertically and which opens about 20 centimeters above the base of the sheets of fabrics, each pipe 21 corresponds to a cup 18, the volume of which is proportional to the quantity of products comprised between two successive sheets of contiguous tissue, these volumes are obviously increasing as one goes towards the outside of the digester.

- Liquid or solid outgoing products are located in 3 areas of the digester:
- At the bottom, the sludge which sediments.

 - On the surface the floats.

- Immediately below the floats the
purified liquids.

 - The mixing of the bottom sludge and its recovery are ensured by a pipe, the end 24 of which sweeps the entire surface located immediately above the heating floor by means of a device 25 which prints the circular pipe 22 with alternating circular movements of rotation .

 - The pump 26 ensures the recovery of the sludge. The purified liquids are taken up approximately 20 cm below the free surface of the floats by a recovery tube 29 protected against the rising of sludge by a deflector 28. They arrive in a tank compartmentalized recovery 30.

 - They are then taken up by buckets of different volumes 31 which by rotation about an axis 32 empty their content into a tank 33 for discharging the purified liquids.

 - The volumes of the wells 31 increase as one goes towards the periphery of the digester so that for each sampling area the samples are a function of the quantities introduced into these same areas in the lower part of the digester.

 - The aim is that by metering the quantities of effluents to be purified introduced to the bottom and the quantities of purified liquids collected in the upper part, the ascent of the liquids takes place almost vertically in the digester and the ascending speeds are appreciably equal throughout the volume of the digester.

 - The transit of purified liquids is facilitated by an archimedes screw 34 it is then carried out towards the tank 38 for secondary recovery of purified liquids. From there the liquids are evacuated by a pump 44. In this tank 38 the levels are regulated between a minimum level 40 and a maximum level 41 by 2 probes 42 and 43.

 - The possible layer of floats (the importance of this depends on the effluent treated) is degassed and disintegrated by the action of a mechanical crust breaker 85. The place 86 of movement of its active part in contact with the floats corresponds to almost all of the free surface of the products being digested.

 - The control device 87 is designed so as to measure the resistance opposed by the layer of floats to the action of the active part of the crust breaker. This resistance makes it possible to determine and therefore indirectly control the thickness of the layer of floats.

 - The action of the crust breaker 85 is made possible by the action of an anti-rotation blade which prevents the layer of floats from rotating by floating above the liquids. This blade is periodically in a working position 89 and then in a displacement position 88 before occupying a new working position 89. The blade is guided by a tube 91 which slides around the central pillar 8.

 - The surface layer of floats which has been disintegrated by the mechanical action of the crust breaker is, as necessary, removed periodically by the buckets 46.

The volume of each bucket 46 varies according to its geographic position, the volume of each bucket is such that all the samples are taken homogeneously over the entire surface of the floats.

 - The content of the buckets 46 is poured into a tank 47 for dumping the floats by simultaneous tilting of all the buckets around the axis 49.

 - An archimedean screw 48 then assists in their evacuation to the tank 54 for taking up the floats from where a pump 52 evacuates them. Two probes 55 and 56 make it possible to regulate the level of the products between a high level and a low level.

 - The biogas produced by methanogenic fermentation is collected by a flexible cover 64 secured to the mobile assembly, the edges of which plunge into a fixed chute 61 with rectangular section.

 - The chute is fixed to the upper internal part of the tank. It is filled with water and thus ensures a seal by hydraulic seal.

ORIGINAL POINTS OF OUR TECHNOLOGY
- Our invention eliminates the traditional problems of clogging and preferential circuits of fixed bed digesters which by accelerating the speed of the products in certain zones cause partial leaching in these zones. It avoids treating only effluents very lightly loaded with matter suspension or effluents removed when possible from their suspended matter by sieving. Our fixed bed digesters are therefore no longer specialized on very specific types of effluents
- Due to the design, we permanently have the maximum number of active bacteria in the fermenter by achieving maximum and homogeneous contact between the methanogenic bacteria and the effluent to be treated. The productivity of a digester being directly dependent of this number of active bacteria we will have the maximum efficiency of the digester, ie a maximum of kg of COD destroyed per cubic meter of digester and per day.

ESQNRE FROM FI-GUsRlER
- Figure 1 shows a vertical section through the axis of the digester.

 - Figure 2 shows a top view of the digester, the upper cover being removed.

 - Figure 3 shows a schematic vertical section showing the introduction devices, on the one hand, and on the other hand the devices for discharging purified liquids and floats.

 - Figure 4 is a vertical schematic section showing the main elements involved in the disposal of purified liquids.

 - Figure 5 shows a schematic vertical section through the fixed pipes and mobile pipes and shows the connecting device between these two types of pipes.

 - Figure 6 shows the arrangement of the introduction buckets of the effluents to be purified.

 - Figure 7 shows the anti-rotation paddle and its annexes.

 - Figure 8 is a schematic top view showing the arrangement of the webs of fabrics.

 - Figure 9 is a perspective view showing the interweaving of the webs of fabrics with respect to each other.

(# E ## RI # T I. QN j) #TA ILLEE
- In Figure 1 we first see the lower structures of the tank, namely: the concrete slab 1 which is surmounted by an incompressible insulator 2 itself surmounted by the heating floor 3 traversed by the heating tubes
The lateral structures include, from the inside to the outside, the side walls 5 of reinforced concrete, an insulator 6 put in place by pouring and finally A cladding 7; in the center of the digester there is a central pillar 8 surmounted by a support plate 9 .

 - The upper structures include horizontal radiating beams 11 which are supported on the one hand on the support plate 9 and on the other hand on the lateral supports 10. They are surmounted by a horizontal insulator 12 and a horizontal seal 13 .

 - The entry of the products is provided by the fixed pipe 14 the outlet of the bottom sludge is provided by a pipe which has a vertical part 22, a horizontal part 23 which ends in one end 24. In addition, there is a device 25 for alternating rotation of this pipe, a recovery pump 26 and a connecting pipe 27.

 - The level of the products in the digester is shown at 35. The purified liquids are evacuated by the spill tank for purified liquids 33 then by the secondary recovery tank for purified liquids 38 then by the pump 44 for recovering liquids which discharge into a connecting pipe 45.

 - All of the outgoing product is evacuated by the pump 59 and the fixed evacuation pipe 60.

 The evacuation of the biogas uses the peripheral chute 61 a hydraulic seal 62, a recovery tank 64, the connection pipe 63 and the fixed evacuation pipe 65.

 - The connecting elements comprise the external concentric crown 66, the central concentric crown 67 and finally the internal concentric crown 68 which includes the concentric bell 71.

 - In this figure is shown the area 72 occupied by the sheets of fabrics, these are limited in the lower part at 73, at the upper part in 74, all of the sheets of fabrics are connected to the jack 77, for lifting the assembly by the link arms 75.

 - The moving part 80 is supported and guided by the rail 78 via the rollers 79. This moving part is set in discontinuous circular motion thanks to the 2 jacks 81 and 82 located at the end of the same diameter of the tank.

 - SIb LI: L! are shown the side walls 5, the central pillar 8, the product introduction pipes 21, the vertical part 22, of the bottom sludge pipe.

 - With regard to the outlet of purified liquids, there is a tube 29 for the recovery of purified liquids below the floats, the compartment 30 for primary compartmentalized recovery, the buckets 31 for discharging the liquids, their pivot axis 32, the tank 33 for discharging purified liquids; the archimedes screw 34 which facilitates their evacuation and the pump 44 for taking up these same liquids; finally there are the devices 36 for tilting the buckets and the device 37 for controlling the rotation of the archimedean screw.

 - With regard to the recovery of the floats, we can see in this same figure the buckets 46 for evacuating the floats which are discharged by a device 50 by tilting around an axis 49 in a tank 47 for discharging the floats a screw d archimede 48 driven by a device 51 leads them to a tank 54 for recovering the floats from which they are extracted by a recovery pump 52. Finally, are shown a probe 55 for high level control and a probe 56 for control of low level.

 - Against the side wall 5 is shown the peripheral chute 61.

 - In this same figure is shown the metal frame 83 in the form of a cross for the moving assembly. The cylinders 81 and 82 which bear on the support points 84 fixed to the upper part of the side wall 5.

 - The crust breaker 85 as well as the place 86 for movement of this same crust breaker also appear.

 - Su # fiqXufire, 3 are shown the tray 17 for storing products before introduction, an introduction bucket 18 which rotates around the tilting axis 19 to pour its contents into a pipe 21 of introduction.

 - Concerning the outlet of the purified liquids are represented the deflector 28 against the rising of sludge, the tube 29 for the recovery of the purified liquids below the floats, the tank 30 for compartmentalized primary recovery, a bucket 31 for evacuation of the liquids which switches around from its axis 32, the tank 33 for discharging purified liquids, the archimedes screw 34 and the level 35 of the products in the digester.

 - Concerning the evacuation of the floats are shown a bucket 46 of evacuation which rocks around the axis 49, the spill tank 47 and the archimedes screw 48. In this same figure is identified the position of the tarpaulin 64 of biogas recovery.

 - Is also shown the upper 73 and lower 74 of the area occupied by the sheets of fabrics.

 Finally, the crust breaker 85 and its control device 87 are shown, the direction of movement of the moving assembly is represented by the arrow 94.

 4. On ~ l. & fi # urg #. 4 are shown concerning the evacuation of purified liquids the spill tank 33 for purified liquids, the archimedean screw 34 as well as its control device 37, the tank 38 for secondary recovery of purified liquids, the agitator 39, the levels mini 40 and maxi 41 controlled by the minimum level detection probe 42 and the maximum level detection probe 43. The pump 44 for taking up these liquids and its connecting pipe 45.

 - In FIG. 5 are shown the radiating beams 11 which rest on the support plate 9.

 - The fixed pipe 14 for supplying the effluent and the intermediate pipe 16, the connection pipe 27 for removing sludge from the bottom, the connection pipe 45 for discharging purified liquids, the connection pipe 53 elimination of the floats, the valve 57 controlling the rejection of the products, the valve 58 controlling the recycling of the floats or bottom sludge, the pump 59 for recovering the outgoing products which flow into the fixed evacuation pipe 60. The connection pipe 63 for evacuating biogas and the fixed pipe 65 for evacuating this same biogas.

 - The external concentric crown 66, the central concentric crown 67 and the internal concentric crown 68 are also represented. The latter is filled with a liquid 69 which provides a hydraulic seal 70. It also comprises a concentric bell 71.

 - ## r la. ~ figuy # # are shown concerning the entry of the intermediate la-pipe 16 products which allows to bring the products into the storage bin 17 before introduction, the introduction buckets 18 which tilt thanks to the device 20 for tilting the buckets around the axis 18 to supply the vertical introduction pipes 21.

 - In Figure 7 is shown the central pillar 8, the level 35 of the products in the digester as well as the position 64 of the biogas recovery tank and 74 of the upper area occupied by the layers of tissue.

 - With regard to the anti-rotation blade, its displacement position 88, its working position 89, the link arm 90, the sliding tube 91, the counterweight 92 and the control device 93 are shown.

 - In FIG. 8 are represented the central pillar 8, the vertical introduction pipes 21 and the sheets of fabrics 76. Finally, the peripheral chute 61 is represented.

 - In Figure 9 are shown the arrangement of the layers of fabrics relative to each other which form hexagonal structures nested one inside the other

Claims (1)

 CLAIM 1.  - Turbulent fixed bed anaerobic digester characterized  - In that it is mainly composed of a cylindrical tank insulated from the outside, the diameter of which is greater than the height.  - In that the upper part of the tank is surmounted by a metal frame made up of radiating beams 11 which bear at the center on the central pillar 8 the whole being designed so as to delimit an underlying volume which is entirely free except of the axial part occupied by the upper part of the central pillar 8 so as to allow the circular movement in one direction of a movable assembly sweeping the entire internal surface of the tank.  - In that it comprises a movable assembly 80 set in motion by jacks and which supports all of the elements located inside the tank and most of the elements located at the top of the tank under the radiant beams 11.  - In that the passage of the products coming from the fixed pipes and going towards the pipes supported by the mobile equipment and vice versa is ensured by a device mainly comprising 3 concentric troughs 66, 67, 68 with the vertical axis of the central pillar 8  - In that the greater part of the volume of the tank is with the exception of a lower cylindrical volume, and a higher cylindrical volume occupied by vertical sheets of fabrics separated by regular intervals which form nested hexagonal structures into each other.  - In that the effluent is introduced by vertical pipes 21 which open between each sheet of tissue.  - In that it comprises a device carrying out the slow mixing of the sludge situated between the heating floor 3 and the lower zone 73 of the sheets of fabrics as well as the evacuation of the excess quantities of these same sludges  - In that the purified liquids are collected at the top of the digester under the floats about 30 centimeters below the free surface of the products being digested. And that these same purified liquids are taken homogeneously in a cylindrical volume located above the upper zone 74 of the layers of tissue, and the base surface of which is equal to the internal base surface of the digester tank.  - In that the surface part of the floating layer is collected in a homogeneous way with a view to its evacuation over the entire free surface of the products being digested. And that the layer of floats is homogenized and degassed mechanically by the crust breaker 85 at the same time as the displacement in rotation of the entire layer of floats is avoided by an anti-rotation blade 89.  - In that the digestion gases are collected by a flexible cover 64 having the general shape of a cylindrical bell, integral with the mobile assembly  REYENDICATJS? ### ..  - Apparatus according to claim 1 comprising a cylindrical tank characterized:  - In that its lower structures are formed from bottom to top by a concrete slab 1 surmounted by a continuous layer of incomprehensible insulator 2, surmounted by a heating floor 3, traversed by heating tubes 4, and that the upper face of the heated floor 3, in contact with the products being digested is horizontal.  - In that the lateral structures are made up from the inside towards the outside of a vertical wall 5 of reinforced concrete, of an insulation 6 put in place by pouring and finally of an external cladding 7.  - In that the central structures are constituted by a vertical pillar 8 whose longitudinal axis of symmetry merges with the axis of symmetry of the digester tank. And that this pillar rests at its lower part on the heating floor 3 and that it is surmounted at its upper part by a support plate 9.  - In that the tank is surmounted by upper structures constituted by horizontal radiating beams 11 which bear on the one hand on the support plate 9 and on the other hand on side supports 10 fixed to the upper part of the side walls 5 of the tank. And that the radiating beams 11 are surmounted by a continuous horizontal layer of insulation 12 and a horizontal seal 13.  REYE.NDICATION 3.i ~  - Apparatus according to claim 1 comprising a mobile assembly 80 characterized:  - In that it is mainly composed of a metal frame in the shape of a cross which bears at its ends on a rail 78 by means of rollers 79. The elements 83 of this metal frame are arranged in such a way that the attachment points 95, 96, 97, 98, 99, and 100 of the six cylinders 77 for lifting the sheets of fabric form a regular hexagon.  - In that it supports all of the elements present inside the tank, and all of the equipment in the upper part of the digester located below the radiating beams 11 with the exception of the fixed pipe 14 d arrival of the effluent to be treated, of the recovery pump 59 rigidly linked to the fixed pipe 60 for discharging the purified effluents, and of the bell 71 rigidly linked to the fixed pipe 65 for discharging the biogas.  - In that the moving element is set in discontinuous circular motion in one direction, by the simultaneous and repeated actions of the 2 jacks 81 and 82 each mounted at the end of the same horizontal diameter and which bear simultaneously on elements 84 fixed at regular intervals around the periphery of the upper face of the side walls 5 of the tank.  REY.EN # i: t # .C & I.QN #. '  - Apparatus according to claim 1 comprising connecting equipment between the fixed pipes and the mobile pipes characterized  - In that the internal concentric chute 68 allows passage to the fixed biogas evacuation pipe 65 of the biogas supplied by the mobile pipe 63 coming from the recovery tank 64. And that this passage is carried out thanks to the concentric bell 71 which plunges into a liquid 69 while ensuring a hydraulic seal 70.  - In that the central concentric chute 67 allows the passage of the products to be purified brought by the fixed pipe 14 to the mobile pipe 16 which transports them into the storage bin 17 before introduction, and that this same concentric chute 67 also allows recycling possible thanks to the action of the recycling valve 58 of the floats brought by the pipe 53 and the bottom sludge brought by the movable pipe 27.  - In that the external concentric chute 66 allows passage to the fixed pipe 60 for evacuating outgoing products and @eci thanks to the pump 59 for taking up outgoing products either purified liquids brought in by mobile pipe 45 or also thanks to the action of the rejection valve 57 of the floats brought in by the movable pipe 53 or else sludge from the bottom brought in by the movable pipe 27.  R # VENQIgATION 5.  - Apparatus according to claim 1 comprising a volume occupied by layers of characterized fabrics  - In that these layers occupy the entire volume 72 of the digester from a lower horizontal plane 73 located about 20 centimeters above the heating floor 3 to an upper horizontal plane 74 located about one meter above the free surface of the products being digested.  - In that these sheets of fabric are stretched vertically in parallel planes about 15 centimeters apart and that a section of the volume occupied by the sheets of fabric using a horizontal plane shows that the sheets of fabric form hexagonal structures nested one inside the other and that the peripheral structures form hexagonal structures with an incomplete perimeter and that the axis of symmetry of all of its structures is the axis of symmetry of the digester tank.  - In that all of the fabrics 76 are subjected to slow rectilinear and reciprocating vertical movements of amplitude about 20 centimeters by 6 jacks 77 and that the connection between the jacks 77 and all of the fabrics 76 made by link arms 75.  - CLAIM 6  - Apparatus according to claim 1 comprising a device for introducing the liquids to be purified, characterized  - In that the products to be purified are brought through a connecting pipe 16 to a storage tank 17 before introduction and that this tank is at constant level, and occupies most of a radius of the tank.  - In that the products to be purified are taken up in the tank 17 by cups 18 arranged on almost all of a radius of the tank and that the unit capacity of these cups increases as one moves away from the center of the digester so that after each revolution of the moving equipment each square meter of base surface of the tank has received the same volume of incoming products.  - In that after tilting around an axis 19 by means of a device 20 each bucket 18 pours its content into a vertical introduction pipe 21, the end of which opens about 20 centimeters above the lower part of the sheets tissue, and that the pipes 21 are arranged along a radius and that on this radius there is an introduction pipe 21 for each volume determined by two sheets of parallel and contiguous fabrics.  - In that the introduction of the products to be digested is therefore carried out near the bottom of the tank over the entire internal base surface of the digester tank.  RE.VENDI.C.A.TI.O.N .7  - Apparatus according to claim 1 comprising a device for mixing and extracting the sludge from the bottom characterized  - In that it is mainly composed of a device 25 which communicates to a pipe comprising a vertical part 22 and a horizontal part 23 of slow reciprocating circular movements of variable amplitude so that the end 24 of the pipe sweeps homogeneously the bottom of the tank by performing, as necessary, the slow mixing of the sludge located in this zone or their extraction when they are in excess, they are then discharged by the pump 26 and the connecting pipe 27.  EBESERU  - Apparatus according to claim 1 comprising a device for discharging purified liquids, characterized:  - In that the purified liquids are taken up under the layer of possible floats by tubes 29 whose entry is protected by deflectors 28 and which are arranged on a radius of the tank at distances of approximately 45 centimeters which correspond to three intervals between two successive layers of fabric.  - In that in each compartment of the primary recovery tank 30 a bucket 31 allows the evacuation of purified liquids. The liquids are collected over a whole radius located in a plane very close to the plane where the radius materialized by the vertical pipes 21 of introduction is located. The quantities of purified liquids withdrawn for their evacuation increase as one moves away from the axis of the tank, they are such that in each vertical elementary volume the displacement of the products being digested takes place practically vertically.  - In that all the buckets 31 are integral with an axis 32, that a device 36 causes the tilting of all of the buckets and their emptying into a discharge tank 33, and that the evacuation of the products towards the tank secondary recovery 38 is facilitated by an archimedean screw 34 controlled by a device 37.  - In that the level of the liquids in the secondary recovery tank 38 is regulated between a maximum level 41 and a minimum level 40 by a device mainly comprising two level detection probes 42 and 43 and a pump 44 for discharging the liquids .  REYE # D.LC) ki: I.ON -9.  - Apparatus according to claim 1 comprising a device for taking up floats characterized by:  - In that the floats are homogenized and mechanically degassed by a crust breaker 85 made of slow alternating circular movements of variable amplitude so that the active part of the crust breaker in contact with the floats uniformly sweeps the entire surface of the tank. And that the control device 87 of the crust breaker measures at the same time the mechanical resistance opposed by the floats to the action of the crust breaker so as to indirectly determine their thickness and control their evacuation.  - In that the rotation of the entire floating layer is prevented by the action of an anti-rotation blade which has two positions: a high displacement position 88 and a low position 89 for blocking the rotation of the layer floats, and that the blade is balanced by a counterweight 92, the assembly being guided by a sliding tube 91 centered on the central pillar 8 and which a control device 93 successively ensures as and as required by the rotation of the moving element: first the release then the lifting of the assembly to pass from the working position 89 to the displacement position 88 then a rotation of 90 degrees then the lowering of the assembly to pass from the displacement position 88 to a new working position 89 and finally the re-locking of the assembly in rotation.  - In that the upper part of the float layer is taken almost homogeneously by buckets 46 located on a radius of the tank and whose unit volume increases as one moves towards the periphery of the digester so to carry out a homogeneous sampling.  - In that the set of buckets 46 is secured to an axis 49 and that the action of the device 50 causes the buckets 46 to be emptied into the spill tank 47.  - In that the passage of the floats from the discharge tank 47 to the recovery tank 54 is facilitated by an archimedean screw 48 controlled by a device 51 and that the evacuation of the floats from the recovery tank 54 is ensured by a float recovery pump 52 which regulates the level in the recovery tank 54 between a high level and a low level thanks to two level probes 55 and 56.  - In that the rotation of the moving assembly is done in a clockwise direction and that at the same point we first observe the passage of the floating recovery system, then the passage of the recovery system purified liquids.  CLAIM 10  - Apparatus according to claim 1 comprising a biogas recovery device characterized:  - In that the biogas is collected by a recovery tank 64 secured to the mobile assembly and the edges of which plunge into a fixed peripheral chute 61 located at the upper internal part of the side walls of the tank and that the edges of the tank plunge into this peripheral chute filled with water ensuring the sealing by a hydraulic seal 62.