WO2010004103A2

WO2010004103A2 - Sludge diffusion device and method for a sludge bed digester, and corresponding sludge bed digester

Info

Publication number: WO2010004103A2
Application number: PCT/FR2009/000671
Authority: WO
Inventors: Pierre Lemaire
Original assignee: Societe Civile Dlmr
Priority date: 2008-06-12
Filing date: 2009-06-08
Publication date: 2010-01-14
Also published as: FR2932469A1; WO2010004103A3; FR2932469B1

Abstract

The invention relates to a sludge diffusion device or diffuser (10) for a sludge bed digester, particularly one having a large diameter. According to the invention, the digester comprises: a) a bottom (11) formed from a solid wall (12) turned up on its outer perimeter (13); b) a cover (14) formed from a wall (15) drilled with holes (16) distributed so as to allow a diffusion area of between 15% and 45%, preferably between 25% and 35% and very preferably 30% of the surface of the wall; and c) a feed (17) for the diffuser, placed at the centre of the cover (14) and opening into the space provided when the bottom (11) is joined to the cover (14) of the diffuser, the cover/bottom assembly constituting a hermetically sealed assembly, the distance between the bottom (11) and the cover (14) being at least between 5 and 15 cm, preferably 10 cm.

Description

Device and method for sludge diffusion for a sludge bed digester, and corresponding sludge bed digester.

The present invention relates to the treatment of wastewater. The invention is in the field of purification plants, particularly sludge bed digesters, very particularly large mud bed digesters.

More particularly, the invention relates to a sludge diffusion device for sludge bed digesters which are used in anaerobic digestion processes for treating sludge from domestic wastewater. Anaerobic digestion is a microbiological process in which organic matter is decomposed by the action of microorganisms in the absence of oxygen.

Anaerobic microorganisms reduce the amount of organic material present in biologically activated sludge while releasing gases, mainly methane. Anaerobic digestion of municipal wastewater sludges and agri-food industries generally requires the use of large holding tanks large enough to hold sludge for the entire retention time required, which may exceed 21 days.

These tanks require a permanent agitation or sludge diffusion system, so that the sludge is permanently suspended for better efficiency of anaerobic digestion.

Currently, sludge bed digesters operate in upflow, fresh sludge is diffused into the bottom of the digester through a perforated sheet covering the entire bottom surface of the digester. For example, reference may be made to the documents WO-98/19971 A and FR-2 877 322 A1. The sludge is incorporated under this perforated plate by a pipe fed by a single pump in the center, and they are diffused through the perforations of the sheet and through the sludge bed which is maintained above the perforated sheet. This diffusion is random and preferential near the center, where is placed the delivery pipe of the pump. To complete the technological background, reference may also be made to US-4,592,845 A and AU-584,228 B2.

There is therefore a need for improvement of sludge diffusion systems in the digesters to always improve their setting in motion for better efficiency of said digester. The present invention relates to a major innovation of diffusion systems and sludge distribution in large diameter digesters.

Thus, the subject of the invention is a device for diffusing sludge or diffuser for sludge bed digester, particularly of large diameter, generally comprising: a. a bottom consisting of a solid wall raised on its outer circumference; b. a cover consisting of a wall perforated with holes; vs. a supply of the diffuser placed in the center of the cover and opening inside the space provided by the meeting of the bottom and the cover of the diffuser, the cover / bottom assembly constituting a closed and hermetic assembly. The diffusion device according to the invention constitutes an independent unit, which makes it possible to put the sludge arriving in the digester permanently suspended in said digester under the effect of the pressure exerted by the flow of sludge carried in the device by the supply in the internal volume of said device according to the invention.

By "closed and hermetic" is meant according to the invention that the lid / bottom assembly delimits a volume without any opening to the outside that the holes in the lid. It is therefore understood that the lid and the bottom are in contact by their circumferences and that said contact is hermetic.

But according to the invention, the lid of said device is pierced with holes through which, under the effect of the pressure induced by the feed, the sludge will diffuse.

A great advantage of the invention lies in the fact that the device according to the invention can take all the desired dimensions. Thus, the skilled person will adapt the outer dimensions of the device according to the invention depending on the size of the digester.

Indeed, if it is readily conceivable that one can use a device according to the invention for a digester, it is actually much more efficient to multiply the number of devices according to the invention in the same digester. Indeed, the sludge being routed to the center of each of the devices positioned in the digester, the diffusion of these is then much more effective and better distributed in the overall volume of the digester than if one used only one device.

According to the invention, the lid of the device is pierced with holes distributed so as to leave an optimal passage of diffusion of the sludge. To be effective said sludge diffusion passage is between 15% and 45% of the surface of the lid, preferably between 25% and 35%, very preferably 30%.

Those skilled in the art will be able to adapt the dimensions of the holes of the lid as a function of the flow rate and / or the pressure of the sludge feed, as well as the sludge diffusion rate in the digester that it wishes to obtain.

The holes of the lid of said device may in particular have a diameter of between 1 cm and 5 cm, preferably between 2 cm and 4 cm, very preferably 3 cm.

According to the invention, for maximum efficiency, the internal distance between the bottom and the cover of said device is at least between 5 and 15 cm, preferably 10 cm.

The skilled person will adapt the shape of the device according to the invention according to the needs dictated by the digester in which he wants to install said device according to the invention. Thus said device may be triangular, square, rectangular, parallelepipedal with n sides, or circular. Preferably according to the invention, the device is circular in shape.

Of course, the skilled person will know how to use the appropriate materials to achieve the walls of the bottom and the lid of the device according to the invention. It will preferentially use materials generally used in the field of wastewater treatment plants, if only to ensure that the device according to the invention withstands the stresses imposed on it by its function (resistance to pressure, corrosion, corrosion). oxidation, etc.).

Thus according to the invention, the walls of the bottom and the lid, simultaneously and / or independently, are made of stainless steel.

As regards the sampling of the materials used, those skilled in the art will again be able to determine without difficulty the thickness of the walls constituting the bottom and the lid according to their respective dimensions and the constraints that they will have to undergo. According to the invention, the bottom of the device takes the form of a box if it is of parallelepipedal shape, or a saucer if it is circular in shape, whose outer circumference is raised with respect to its own bottom. Thus according to the invention the outer periphery raised from the bottom can rise to a height of between 10 cm and 30 cm, preferably 20 cm, with respect to the inner bottom of the diffuser. According to the invention the conveyance of the sludge in the diffuser is ensured by a feed which may comprise a pipe with a diameter of between 8 cm and 12 cm, preferably 10 cm, said pipe opening inside the internal space diffuser by an orifice preferably placed in the center of the cover of said diffuser. The flow of sludge to the diffuser can be provided by any means allowing the flow of mud flow in the diffuser. This may be by simple gravity, but preferably, according to the invention, the sludge will be conveyed forcibly, for example by means of a pump pushing the sludge in an associated pipe towards the interior of the diffuser. It is understood that there is according to the invention a power supply provided with a pump for each individual diffuser.

It is understood that, the flow of mud arriving continuously in the diffuser due to the pressure induced by the pump, said sludge will be rejected outside said diffuser through the holes in the lid, so from the top of the diffuser, in the overall internal volume of the digester, according to an upward movement.

According to the invention, the diffusion device can also be provided with all the known means for regulating and / or measuring the flow rate of the sludge arriving in the diffuser, the pressure of said sludge in the supply system and / or in the diffuser , such as one or more valves, mechanical or pneumatic, one or more pressure indicators such as manometers, one or more flow meters.

According to the invention, the sludge feed circuit may be further provided with any purge means and / or any means of expansion common in this type of installation. The sludge feed of the digester can be carried out by any means already known.

The fresh sludge is diffused into the bottom of the digester through a perforated sheet covering the entire surface of the bottom of the digester. The sludge is incorporated under this perforated plate by a pipe, fed by a single pump, in the center, and they are diffused through the perforations and pass through the sludge bed which is maintained above the perforated sheet. This diffusion is random and preferential near the center, where is placed the delivery pipe of the pump.

The invention further relates to a sludge bed digester comprising at least one sludge diffusion device as described above, said at least one sludge diffusion device possibly being connected to a specific sludge feed device.

According to the invention, a preferred means of supplying said sludge digester is carried out through a sludge injection means to be incorporated in the digester, which may comprise d.) A receptacle formed by a reservoir, placed under the surface of the liquid level of said digester; e.) a tube immersed under the liquid level inside said receptacle; f.) a sludge inlet pipe to be incorporated, immersed in said submerged pipe inside said receptacle; g.) at least one sludge suction pipe to be incorporated opening at the bottom of said receptacle, said suction pipe being connected to the supply of at least one sludge diffusion device or diffuser, said supply being placed in the center the cover of said diffuser.

According to the invention, said reservoir of the receptacle is of any imaginable form, preferably of circular shape, having a diameter which may be between 1 m and 3 m, preferably 2 m.

According to the invention, said reservoir of the receptacle can be immersed under the surface of the liquid level of the digester. Preferably, said receptacle is placed at a distance _r

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between 10 cm and 30 cm, preferably 20 cm, below the surface of the liquid level of the digester.

According to the invention, said tube immersed under the level of the liquid inside said receptacle may have a diameter of between 20 and 70 cm, preferably between 35 and 45 cm, very preferably 40 cm, and it may be immersed in water. interior of said receptacle at a depth of between 1, 50 and 2 m, preferably at 1.70 m, below the level of the liquid inside said receptacle.

According to the invention, said inlet pipe of the sludge to be incorporated, immersed in said submerged tube inside the reservoir of said receptacle, can be positioned at a distance of between 10 and 30 cm, preferably 20 cm, above the level. liquid from the digester.

Incidentally, said sludge inlet pipe to be incorporated may be fed by a feed pump outside the digester.

The invention further relates to a sludge diffusion process inside a sludge bed digester as described above, characterized in that a. the sludge to be incorporated into said digester is injected through the sludge injection means to be incorporated; b. said sludge is sucked inside said receptacle of said injection means, through at least one sludge suction pipe to be incorporated opening at the bottom of said receptacle, said suction pipe being connected to a diffusion pump; vs. the sucked sludge is pumped by means of said pump into the feed pipe of said at least one sludge diffusion device, said sludge penetrating into said diffuser under the effect of the pressure induced by said pump, and leaving said diffuser, still under the effect of the pressure induced by said pump, through the holes in the cover of said diffusion device to the sludge bed digester.

Preferably, according to the invention, the sludge diffusion process is characterized in that the suction and discharge flow rate of said diffusion pump is greater than the feed rate of the sludge in said sludge injection means. to incorporate.

In fact, the presence of valve sets on the supply and / or arrival of the sludge circuits makes it possible to adjust the sludge flow rate independently in each of the diffusers, it being understood that, preferentially according to the invention, the sludge flow rate in each of the diffusers is identical regardless of the distance between the pump and the diffuser. This may be important particularly for keeping the rate of rise of the flow constant through the sludge bed in the digester. According to the invention when the digester comprises more than one diffuser, therefore more than one pump, each pump can operate independently of the other pumps, but preferably according to the invention, all the pumps operate simultaneously.

Other advantages, aims and features of the present invention will emerge from the description which follows, made for an explanatory and non-limiting purpose, with reference to the appended drawings, in which: FIG. 1 shows a sectional view of the diffusion device sludge or diffuser according to the invention; FIG. 2 shows a top view of a mud bed digester comprising a set of seven sludge or diffuser diffusion devices according to the invention; FIG. 3 shows at A a representation of the seven sludge feed / discharge pumps each connected to a diffuser according to the invention, and to B a detail of one of these pumps; Figure 4 shows a section of a digester provided with a diffuser according to the invention, and a sludge feed means which is connected to the supply means of the diffuser; and Figure 5 shows at A a section of the sludge feed means of the digester of Figure 4, and at B a top view of the same sludge feed means of the digester. Thus, with reference to the figures, FIG. 1 shows a sectional view of the diffusion device (10) for sludge, or diffuser, according to the invention, comprising a bottom (11) consisting of a solid wall (12) raised. on its outer periphery (13), a cover (14) consisting of a wall (15) perforated with holes (16), a supply (17) of the diffuser opening through the center of the cover (14) inside the space provided by the meeting of the bottom (11) and the cover (14) of the diffuser.

The diffuser (10) of the mixing circuit is intended to be placed on the bottom of a digester, and it is circular in shape built in two parts, with a solid bottom sheet raised on its outer circumference, and at the top a sheet perforated holes, for example 30 mm in diameter, distributed so as to leave a diffusion passage equal to 30% of the surface of said sheet. This perforated plate is placed 10 cm above the bottom sheet to maintain a steady pressure of the rising mud flow.

In digesters large diameter, the bottom of the digester is equipped with seven diffusers distributed on the surface of the bottom of the digester, spaces that can be voluntarily arranged for reasons that do not fall within the scope of the invention. FIG. 2 shows an upper view of a mud bed digester comprising a receptacle formed by a reservoir (28), and a set of seven sludge or diffuser diffusion devices (a, b, c, d, e , f and g) of circular shape, each of these diffusers having a feed (27) in the center of its lid, which is connected to a pipe (215), said pipe being itself connected to an associated pump supply / discharge (P1, P2, P3, P4, P5, P6 and P7) located outside the digester.

The seven pumps (P1 to P7), whose flow rate is adapted to the flow of sludge, thus independently feed each diffusion cone, these seven pumps operating simultaneously.

FIG. 3 shows a representation of a group of seven sludge feed / discharge pumps (P1, P2, P3, P4, P5, P6 and P7) or (38) each connected to a diffuser according to the invention via an associated supply line (315 in B), and receiving the sludge through an associated sludge conveying channel (39). Pumps and associated lines are marked by the presence of a flow meter (310), butterfly valves (311), a bleed valve (312), and expansion flanges (313). In B, the detail of one of the pumps and pipes connected to it is represented from another angle. Each pump is equipped with a flowmeter (310). The flow is adjustable using a set of valves, so the flow rate is the same for each pump regardless of the distance between the pump and the diffuser. This makes it possible to keep the rate of rise of the flow constant through the sludge bed. This speed is known to those skilled in the art. FIG. 4 shows a side section of a mud bed digester (414) equipped with a diffusion or diffuser device (40) according to the invention (the section makes it appear only a), said diffusion device (40) being of the aforementioned type and having a supply (47) connected by a pipe (415) to a pump (48) or P (x) supply / discharge, said pump being itself even connected to a sludge injection means (416) in the digester via an associated pipe (49), a portion of said sludge injection means (416) being below the level of the liquid contained in the digester (417) the other part emerging above said liquid. It is still noted in this figure the presence of a flow meter (410), valves (411), and an expansion flange (413). The aforementioned means for injecting the sludge to be incorporated into the digester is shown in greater detail in FIG. 5, said means, then noted (516), comprising a receptacle formed by a cylindrical reservoir (518) 2 m in diameter, of which the upper edge is placed at a distance of 20 cm below the surface of the liquid level (517) of the digester. This tank (518) allows to receive the sludge to be incorporated, this via a submerged tube (519) 50 cm in diameter. This tube (519) is immersed to a depth of 1.70 m below the level of the liquid (517) within the receptacle. The sludge to be incorporated is fed into this tube (519) via a pipe (520) which is powered by a feed pump (not shown). The sludge is discharged into the tube (519) at a distance of 20 cm above the liquid level (517) of the digester. Seven pipes (59), that is to say one per pump, suck the bottom of the receptacle (518) continuously. The suction flow of the diffusion pumps is greater than the flow rate of the feed pump, in order to prevent overflow of the fresh sludge above the wall of the receptacle. There are thus seven pipes (59) each connecting the bottom of the receptacle (518) of the sludge feed means (516) to a pump (not shown). Here again the presence of the reservoir (518) forming the receptacle of said sludge feed means (516), the tube (519) immersed under the liquid level (517) inside said receptacle, the pipe of arrival of the sludge to be incorporated (520), immersed in said submerged tube (519) within said receptacle. It will also be noted that said pipe (520) stops above the level (517) of the liquid contained in the digester.

On view B of FIG. 5, there is also the circular arrangement of the orifices (521) of the seven pipes (59) each connecting the bottom of the receptacle (518) of said sludge feed means (516) to a pump ( not shown).

Claims

1.) sludge diffusion device or diffuser (10, 40) for sludge bed digester, particularly of large diameter, characterized in that it comprises: a. a bottom (11) consisting of a solid wall (12) raised on its outer circumference (13); b. a cover (14) consisting of a wall (15) perforated with holes (16) distributed so as to leave a diffusion passage comprised between 15% and 45% of the surface of the wall, preferably between 25% and 35%, very preferably 30%; vs. a supply (17, 47) of the diffuser placed in the center of the cover (14) and opening inside the space provided by the meeting of the bottom (11) and the cover (14) of the diffuser, the cover assembly / background constituting a closed and hermetic assembly, the distance between the bottom (11) and the cover (14) being at least between 5 and 15 cm, preferably 10 cm.

2.) diffusion device (10, 40) according to claim 1, characterized in that it is circular in shape.

3.) A diffusion device according to any one of claims 1 or 2, characterized in that the walls of the bottom (11) and the cover (14), simultaneously and / or independently, are stainless steel.

4.) A diffusion device according to any one of claims 1 to 3, characterized in that the outer periphery raised bottom (11) amounts to a height of between 10 cm and 30 cm, preferably 20 cm, compared at the bottom of the diffuser.

5.) Diffuser device according to any one of claims 1 to 4, characterized in that the bottom (11) takes the form of a flat-bottomed circular saucer with raised edges.

6.) A diffusion device according to any one of claims 1 to 5, characterized in that the supply of the diffuser comprises a pipe (215) with a diameter of between 8 cm and 12 cm, preferably 8 cm.

7.) A diffusion device according to any one of claims 1 to 6, characterized in that the holes of the lid (14) have a diameter between 1cm and 5cm, preferably between 2 cm and 4 cm, very preferably 3 cm.

8.) A diffusion device according to any one of claims 1 to 7, characterized in that the supply of the diffuser is connected to a pump (38, 48) pushing the sludge in an associated pipe (315, 415) to the inside the diffuser.

9.) A diffusion device according to claim 8, characterized in that the power supply of the diffuser is provided with a set of valves (311, 411) for adjusting the flow of sludge in the diffuser.

10.) A diffusion device according to any one of claims 8 or 9, characterized in that the supply of the diffuser is provided with a flow meter (310, 410).

11.) Digester with mud bed (414) of large diameter, characterized in that it is provided with at least one sludge diffusion device (10, 40) as defined in any one of claims 1 to 10.

12.) digester mud bed according to claim 11, characterized in that it is further provided with means (416, 516) for injecting sludge to be incorporated in the digester.

13.) Mud bed digester according to claim 12, characterized in that the means (416, 516) for injecting the sludge to be incorporated is constituted by d. a receptacle (518) formed by a reservoir, located below the surface of the liquid level (417, 517) of the digester; e. a tube (519) immersed under the liquid level inside said receptacle; f. a pipe (520) for introducing the sludge to be incorporated, immersed in said tube (519) immersed inside said receptacle; boy Wut. at least one aspiration pipe (49, 59) for incorporating sludge opening at the bottom of said receptacle (518), said suction pipe being connected to the supply of at least one sludge diffusion device (40), said feed being placed in the center of the lid of said at least one sludge dispensing device.

14.) Mud bed digester according to claim 13, characterized in that said reservoir (518) of the receptacle is circular in shape.

15.) Mud bed digester according to claim 14, characterized in that said circular reservoir (518) of the receptacle has a diameter between 1m and 3 m, preferably 2 m.

16.) Mud bed digester according to any one of claims 13 to 15, characterized in that said reservoir (518) of the receptacle is placed at a distance between 10 cm and 30 cm, preferably 20 cm, below the surface the liquid level (417, 517) of the digester.

17.) Mud bed digester according to any one of claims 13 to 16, characterized in that said submerged tube (519) has a diameter of between 20 and 70 cm, preferably between 35 and 45 cm, very preferably 40 cm .

18.) Mud bed digester according to claim 17, characterized in that said submerged tube (519) is immersed inside the reservoir (518) of said receptacle at a depth of between 1, 50 and 2 m, preferably at 1.70 m, below the level (417, 517) of the liquid inside said receptacle.

19.) Mud bed digester according to any one of claims 13 to 18, characterized in that said pipe (520) for arrival of the sludge to be incorporated, immersed in said tube (519) immersed inside the tank (518) of said receptacle, is fed by a feed pump external to the digester.

20.) Mud bed digester according to any one of claims 13 to 19, characterized in that said pipe (520) for arrival of the sludge to be incorporated is positioned at a distance of between 10 and 30 cm, preferably 20 cm. above the liquid level (517) of the digester.

Sludge diffusion process within a sludge bed digester (414) according to claims 11 and 12, and any one of claims 13 to 20, characterized in that a. the sludge to be incorporated into said digester (414) is injected through the means

(416, 516) injection of the sludge to be incorporated; b. said sludge is sucked inside said receptacle (518) of said injection means, through at least one aspiration pipe (49, 59) for incorporating sludge opening at the bottom of said receptacle, said suction pipe (49, 59) being connected to a diffusion pump (48); vs. the sludge sucked by said pump (48) is forced back into the supply pipe (415) of the at least one sludge diffusion device (10, 40), said sludge penetrating into said diffuser under the effect of the pressure induced by said pump, and out of said diffuser, still under the effect of the pressure induced by said pump, through the holes in the cover of said diffusion device to the sludge bed digester.

22. Sludge diffusion method according to claim 21, characterized in that the suction and discharge flow rate of said diffusion pump (48) is greater than the feed rate of the sludge in said means (416, 516). ) injection sludge to incorporate.