FR2721226A1 - Separation of animal slurry into liquid and solid phases - Google Patents

Abstract

The solid and liquid phases of an effluent, such as an animal slurry, are separated in a device with three coaxial chambers. Slurry is fed (11) into the first, or entrance, chamber (10) then carried by Archimedes screw (40) into the second, or separation chamber (20). Liquid is removed (21) and solids pushed into the third, or compression chamber (30). The thread of the Archimedes screw is interrupted in this chamber and solids are compressed by the force of more solids behind them. When a pre-determined pressure is reached the end cover of the chamber (50) is pushed open and a lump of solids discharged. The end cover is then returned (60a) to the closed position.

Description

 The present invention relates to an apparatus for separating the liquid and solid phases of an effluent, such as slurry, an apparatus which is intended to be normally used in effluent treatment installations, in particular pig slurry.

 In certain pig breeding units, to treat the slurry and to degrade it, a bacteriological process is implemented in a station which requires a relatively homogeneous medium at the input to function properly. Furthermore, this process of degradation by bacteria is all the more effective as the slurry to be treated contains particles of smaller dimensions.

Consequently, in the breeding units for which such a process is implemented, an apparatus for separating the liquid and solid phases of the slurry is used which is placed upstream of the bacteriological station and which essentially serves to separate the particles of which the average dimensions are between 100 and 700 microns.

 Such a separation device is in particular described in patent document US-A-5,009,795. It essentially consists of three coaxial chambers: an inlet chamber provided with an inlet mouth for the introduction of the slurry to be treated, a separation chamber provided with an outlet orifice for the evacuation of the liquid phase from the treated slurry and a compression chamber open, in its front part, by a mouth for the evacuation of the solid phase from the treated slurry. The three chambers are crossed by an Archimedes screw whose external edge of the thread is, in the separation chamber, in contact with play, with a filtration element. This filtration element, known per se, consists of 'A plurality of lamellae mounted side by side on generators of a cylinder and spaced from each other by a distance between, depending on the filter element, between 100 and 700 microns. The thread of the Archimedes screw is interrupted to the right of the compression chamber.

 The slurry is introduced into the entry chamber and it is entrained, by the Archimedes screw, towards the separation chamber. There, the liquid phase is filtered by the filter element while the solid phase is entrained in the compression chamber. This solid phase is then compressed and forms a plug which, little by little, goes towards the mouth where it is extracted. Compression of the plug results in increased separation of the liquid phase from the solid phase. It is the length of the compression chamber which, for a given viscosity of the slurry introduced, determines the compression rate of the plug and therefore the humidity rate of the solid phase extracted.

 In practice, such a liquid and solid phase separation device is entirely satisfactory for separating bovine excrement which is very thick, but it poses problems for the separation of the liquid and solid phases from pig manure.

This is indeed more liquid and therefore does not require the use of the separation device with much lower flow rates, especially for the formation and conservation of the plug.

 In addition, pig manure is less homogeneous than cattle excrement. It follows that the plug which is formed in the compression chamber can suddenly disintegrate when the slurry introduced becomes more liquid. The liquid is then directed directly to the mouth where it sprinkles the solid phase already extracted. The whole operation is then to be started again.

 The object of the invention is therefore to propose an apparatus for separating the liquid and solid effluent phases which makes it possible to work at relatively high flow rates, of the order of 50 m 3 per day, and which avoids the disintegration of the plug in the compression chamber when the slurry introduced becomes more liquid.

 To this end, an apparatus according to the invention comprises a valve which can take either a closed position in which it seals the mouth of the compression chamber or an open position where it releases said mouth, said valve being subjected to the action of a return mechanism which keeps it in its closed position with a predetermined force.

 When the valve is in its closed position, the solid phase plug can form and compress, even if the slurry suddenly becomes more liquid. As soon as the compression force of the plug has reached a given threshold, threshold determined by the return mechanism, the valve takes its open position in which the plug is evacuated.

 Advantageously, to take one or the other of said two positions, said valve can slide parallel to the axis of the Archimedes screw.

 According to an advantageous embodiment, said Archimedes screw consists of a shaft which carries the thread of said screw, said shaft extending beyond said compression chamber to be guided in a bearing mounted on the chassis of said device . In this case, it is possible to provide for said valve to be guided, in its sliding movement, over the part of the shaft of the Archimedes screw which is beyond the compression chamber.

 To allow an easy and rapid change of the bearing which is highly stressed and subjected to a corrosive medium, said bearing consists of a centering pin which is integral with said chassis and which is intended to penetrate a blind hole drilled axially at the end of the screw shaft. Advantageously, in said blind hole, there is mounted a socket made of self-lubricating material.

 To seal the closure of the valve on the mouth of the compression chamber, the mouth side of said valve is covered with a layer of a flexible material, such as rubber. A ring has also been provided on the tree, in line with the mouth.

 In a preferred embodiment of the invention, said return mechanism is designed to maintain a return force of constant intensity on the valve regardless of the position of said valve. This mechanism can consist of at least one cylinder, the rod of which is connected to said valve, said cylinder being supplied at constant and adjustable pressure.

 In the case of devices intended for large flows, said valve advantageously consists of two half-shells, each of them being subjected to the action of a jack supplied with constant and adjustable pressure. The force of action of each cylinder is transmitted to the corresponding half-shell by means of a pivoting link.

 According to another characteristic of the invention, the said jack (s) are of the double-acting type, the other supply orifice of the said jack (s) being connected to a security system.

The characteristics of the invention mentioned above, as well as others, will appear more clearly on reading the following description of an exemplary embodiment, said description being made in relation to the accompanying drawings, among which:
Fig. 1 is a sectional view along a median vertical plane of an apparatus according to the invention,
Fig. 2 is a partial top view of an apparatus according to the invention in a first embodiment, and
Fig. 3 is a partial top view of an apparatus in a second embodiment of the invention.

 The separation apparatus shown in FIG. 1 comprises, mounted on a frame 1, essentially three coaxial chambers: an inlet chamber 10 which is provided with an inlet mouth 11 through which the slurry to be treated can be introduced into the separation apparatus, a separation 20 which is provided with an outlet orifice 21 through which the liquid phase of the treated slurry is discharged and a compression chamber 30 the front part of which is open according to a cylindrical mouth 31 provided to allow the evacuation of the solid phase from the treated slurry.

 The chambers 10, 20 and 30 have essentially a cylindrical shape with a horizontal axis. They are crossed axially by an Archimedes screw 40 consisting of a thread 41 carried by a shaft 42. While the thread 41 is present in the inlet chamber 10 as well as in the separation chamber 20, it is interrupted at right of the compression chamber 30.

 It will be noted that the length of the compression chamber 30, that is to say the distance which separates the mouth 31 from the front end of the thread 41, is critical for the operation of the apparatus and that a length of 8 cm was entirely satisfactory.

The end of the shaft 42 is provided with a blind hole 42a in which a bushing 43 is mounted. A centering pin 44 is mounted on the bore 45a of a frame 45 integral with the chassis 1. The axis of centering 44 is rotatably mounted in the bushing 43. The latter is self-lubricating and is, for example, made of Teflon (R)
Note that the sleeve 43 could also consist of a ball bearing. The assembly formed by the bush 43 and the centering pin 44 constitutes a bearing for the shaft 42.

 The Archimedes screw is rotated by a geared motor group 46 mounted on the chassis 1.

 The separation chamber 20 consists of a cylindrical filter element 22 and a cylindrical side wall 23 coaxial with the filter element 22 and of larger diameter than the latter. The chamber 20 is closed at its two ends by flanges 24 and 25. The filtration element 22 and the side wall 23 delimit an annular space around the screw 40 which is opened, in its lower part, by the orifice of outlet 21. The filter element 22 consists of a plurality of lamellae mounted side by side on generators of a cylinder and spaced from each other by a distance comprised, depending on the filter element, between 100 and 700 microns. The cylinder formed by the filter element 22 has a diameter which is such that the external edge 41a of the thread 41 is in contact, apart from play, with the internal wall of the filter element 22.

On the part of the shaft 42 beyond the mouth 31, is mounted a valve 50 provided for sliding axially under the action of two jacks 60 and 61. In FIG. 1, only the end of the rod 60a of the concealed jack 60 is shown, this in order not to weigh down the
Fig. 1. The two cylinders 60 and 61 are visible in FIG. 2.

 The rear face of the valve 50 is covered with a layer 51 of a flexible material, such as rubber. On the circumference of the shaft 42 is welded, in line with the mouth 31, a ring 46.

 When the valve 50 is in the extreme retracted position, the layer 51 is in contact with the circumferential edge of the mouth 31 but also with the advanced surface of the ring 46. Thus, the chamber 30 has its front part which is closed , and with sealing in particular against liquids.

 In Fig. 2, we see the two cylinders 60 and 61 whose barrels 60b and 61b are respectively mounted on the sides of the frame 45 and whose ends of the rods 60a and 61a are respectively mounted, by means of articulations 62 and 63 on the front face of the valve 50. The cylinders 60 and 61, of the pneumatic type, are respectively supplied with air by pipes 64 and 65 so that the valve 50 closes the mouth 31. The air introduced is under a predetermined pressure and adjustable so that the closing force of the valve 50 on the mouth 31 is of predetermined and adjustable intensity.

 It will be noted that the jacks 60 and 61 described here as pneumatic jacks could also be hydraulic jacks, or the like.

 Advantageously, the jacks 60 and 61 are of the double-acting type. Lines 66 and 67 are provided to supply them with air so as to be able to release the valve 50 from the mouth 31, if necessary, in particular when great forces are exerted on the screw 40. To this end, the lines 66 and 67 are for example connected to a security system.

 It will be noted that the two jacks 60 and 61 constitute a mechanism which maintains a constant axial force on the valve 50, whatever its position on the shaft 42. Other systems ensuring the same function as that which is represented and described here might be fine.

 There is shown in FIG. 3, an alternative embodiment of the control for sliding the valve 50. This variant is suitable for large flow rates of slurry.

 According to this variant, the valve 50 is formed by two half-shells 50a and 50b which, like the valve 50, have their rear faces covered with a layer of flexible material 51a and 51b. The half shells are designed to be able to slide on the shaft 42.

 Two cylinders 70 and 71 have their barrels 70a and 71a which are respectively mounted, by joints 72 and 73, on the chassis 1, while their rods 70b and 71b are respectively connected, by joints 74 and 75, at the end of rods 76 and 77 which can pivot about axes substantially perpendicular to the direction of sliding of the half-shells 50a and 50b. The other ends of the links 76 and 77 rest on the front faces of the half-shells 50a and 50b. The links 76 and 77 ensure the transmission of the force exerted by the jacks 70 and 71 to the half shells 50a and 50b. The intensity of this effort is, as in the previous embodiment, adjustable and is constant whatever the position of the half-shells on the shaft 42.

 The operation of the apparatus according to the invention is as follows.

 The slurry is introduced into the inlet chamber 10 through the inlet mouth 11 and is entrained by the thread 41 of the Archimedes screw 40 towards the separation chamber 20. The liquid phase of the slurry flows through the filter element 22 and is discharged through the outlet orifice 21. The largest particles of slurry are entrained by the net 41 in the compression chamber 30 where they form a plug against the rear face of the valve 50. This plug is strongly compressed as the product arrives, which results in increased elimination of the liquid phase.

 When the pressure exerted by the plug on the valve 50 is greater than the pressure exerted by the jacks 60 and 61, the valve 50 by sliding forward releases the mouth 31. The plug is then evacuated through the mouth 31. Submitted when the jacks 60 and 61 act, the valve 50 then closes on the mouth 31.

 It is understood that the valve 50 plays a self-regulating role in the sense that the solid particles are only extracted after the compression pressure has reached a predetermined value by the jacks 60 and 61. Thus, by adjusting the air pressure admitted into the cylinders 60 and 61, the compression pressure of the solid particles is determined.

 The mounting of the end of the shaft 42 described above has the advantage that it is easily interchangeable, which is advantageous insofar as the forces exerted on the shaft 42, in particular by the plugs formed in the compression chamber 30, are of relatively high intensity and where the device works in a very corrosive environment.

 In addition, the centering thus carried out is precise and avoids, by the play which it could take, the deterioration of the filtration element 22 by the external edge 41a of the thread 41 of the screw 40.

 The apparatus of the invention is entirely suitable for treating slurry, the composition of which is not always homogeneous.

Unlike the apparatuses of the prior art, the compression pressure of the solid materials in the compression chamber 30 is substantially constant, whatever the composition and the viscosity of the slurry introduced.

 In addition, it has been noted that the particles of small size, of the order of 100 microns, which would normally have to be filtered by the filter element 22 are in reality entrained by the particles of larger size and are trapped in the chamber. compression 30. Thus, surprisingly, the liquid leaving the orifice 21 contains only a few particles larger than 100 microns in size. With an apparatus according to the invention, humidity levels were measured not exceeding 20% for the product leaving the mouth 31.

Claims (13)

 1) Apparatus for separating the liquid and solid phases of an effluent, such as slurry, of the type comprising three coaxial chambers, an inlet chamber (10) provided with an inlet mouth (11) for the introduction of the slurry to be treated, a separation chamber (20) provided with an outlet orifice (21) for the evacuation of the liquid phase of the treated slurry and a compression chamber (30) open, in its front part, by a mouth (31) for evacuating the solid phase from the treated slurry, said chambers (10, 20, 30) being traversed by an Archimedes screw (40) whose external edge (41a) of the thread (41) is , in the separation chamber (20), in close contact with a filtration element (22), said thread (41) being interrupted in line with the compression chamber (30), characterized in that it comprises a valve (50) which can take either a closed position in which it seals the mouth (31) of the compression chamber sion (30) is an open position where it releases said mouth (31), said valve (50) being subjected to the action of a return mechanism (60 to 67; 70 to 77) which keeps it in its closed position with a predetermined force.  2) apparatus for separating the liquid and solid phases according to claim 1, characterized in that, to take one or the other of said two positions, said valve (50) can slide parallel to the axis of the screw Archimedes (40).  3) Separation device according to claim 1 or 2, characterized in that said Archimedes screw (40) consists of a shaft (42) which carries the thread (41) of said screw (40), said shaft ( 42) extending beyond said compression chamber (30) to be guided in a bearing (43, 44, 45) mounted on the chassis (1) of said device.  4) Separation device according to claim 3 when it is according to claim 2, characterized in that said valve (50) is guided, in its sliding movement, on the part of the shaft (42) of the screw Archimedes (40) which is located beyond the compression chamber (30).  5) Separation device according to claim 3 or 4, characterized in that said bearing consists of a centering pin (44) which is integral with said frame (1) and which is intended to penetrate a blind hole (42a) drilled axially at the end of the shaft <42) of the Archimedes screw (40).  6) Separation device according to claim 5, characterized in that, in said blind hole (42a), is mounted a sleeve (43) of self-lubricating material.  7) Separation device according to one of the preceding claims, characterized in that the mouth side face of the compression chamber of said valve (50) is covered with a layer (51) of a flexible material, such as rubber.  8) Separation device according to claim 4, characterized in that the mouth side face of said valve is covered with a layer (51) of a flexible material, such as rubber, and in that, on the shaft ( 42), at the level of the mouth (31) is provided a ring (46).  9) Separation device according to one of the preceding claims, characterized in that said return mechanism (60 to 67; 70 to 77) is provided to maintain on the valve (50) a return force of constant intensity whatever the position of said valve (50).  10) A separation device according to claim 9, characterized in that said mechanism consists of at least one jack (60, 61) whose rod (60b, 61b) is connected to said valve (50), said jack (60, 61) being supplied at constant and adjustable pressure.  11) Separation device according to claim 9, characterized in that said valve (50) consists of two half-shells (50a and 50b), each of them being subjected to the action of a jack (70, 71 ) supplied at constant and adjustable pressure.  12) Separation device according to claim 11, characterized in that the force of action of each jack (70, 71) is transmitted to the corresponding half-shell (50a, 50b) by means of a pivoting link ( 76, 77).  13) Separation device according to claim 13, characterized in that the said cylinder (s) (60, 61; 70, 71) are of the double-acting type, the other supply orifice of the said cylinder or cylinders being connected to a system of security.