Liquid-flow digester with a sealed flexible tank

Abstract

A liquid digester with a tank (C) comprising a closed liquid pumping circuit for agitating the liquid in the tank (C), a gas suction circuit (3) for the gas released by the digestion of the liquid in the tank (C), characterized in that the tank (C) is formed by the combination of an inverted pyramid-shaped excavation cut into the ground (S) which is fitted with a double-walled, leak-proof flexible casing (1) through which the gas suction and liquid pumping pipes (3, 6, 7) pass in a leak-proof manner, and a liquid leak detection system (2) between the two walls of the leak-proof flexible casing. Figure for the abstract: Fig. 2

Description

Title of the invention: Liquid digester with a sealed flexible tank

[0001] The present invention relates to a liquid digester with a sealed flexible tank.

[0002] By digester is meant a device for producing and recovering biogas from organic matter such as slurry or animal manure. By liquid is meant a material whose consistency is below 14% dry matter. Typically, this involves materials in the form of more or less liquid sludge. It is therefore understood that the liquid digester is a system for producing biogas from the digestion in the digester of liquid sludge from organic matter originating from the recovery and cleaning of agricultural operations.

[0003] Various liquid digesters are known.

[0004] The invention aims to improve so-called diamond-tip digesters, for example, that described in patent FR3067262 which involves the structural construction of a casing and a bell for storing the liquids in the process of methanization.

[0005] This construction of the tank with a concrete structural work presents defects which the present invention aims to resolve.

[0006] A first defect is that the sealing of the casing is uncertain in the sense that if a leak appeared, it would not be detectable. Sealing is linked to the quality of the structural work and this is very difficult to control. What is more, it can also appear after aging. What is more, the regulations governing the so-called methanization sector in which the present invention falls, require the implementation of leak control, which is extremely complicated and expensive to develop on a concrete tank.

[0007] A second drawback is that the work is expensive and requires difficult site interventions with pouring concrete on sloping ground.

[0008] A third defect is that the concrete structure must seal the joint between the dome added in a second construction stage and the casing constructed in a first construction stage. This sealing is difficult to achieve and leaks are also difficult to detect.

[0009] It is therefore understood that the solution currently developed in the prior art for a diamond-tipped liquid digester is expensive, difficult to achieve sealing, and cumbersome to manufacture and implement.

[0010] An object of the invention is to propose a solution with a sealing control system.

[0011] An object of the invention is to propose a solution which minimizes the structural work required to construct the installation.

[0012] An object of the invention is to provide an installation whose maintenance is easy and does not require fragile and expensive mechanical means.

[0013] An object of the invention is to propose an installation which optimizes the recovery of gas from organic matter, which minimizes the industrial investment for the operator and which maximizes the energy performance of the installation.

[0014] In a main aspect, the invention carries out specific earthworks to which various connections are added passing through a flexible watertight tank.

[0015] In a particular aspect the flexible tank is made by a particular combination with a separate double skin which cooperates with a pyramid-shaped earthwork dug into the ground.

[0016] In a particular aspect, the leak detection system detects liquid that would escape inside the double skin.

[0017] In a particular aspect, a machine room is arranged next to the methanization tank and comprises all of the electromechanical components for motorizing and controlling the various working functions of the tank.

[0018] The invention will be better understood from reading the attached figures which represent a particular embodiment of the invention in which

[0019] [Fig-1] represents an overview of the principle of the different organs of the digester

[0020] [Fig.2] represents an overall sectional view of the tank

[0021] [Fig.3] represents a detailed view of the sealing skin

[0022] [Fig.l] represents a principle overview of the various components of the digester which includes a digestion tank (C). Next to the digestion tank (C) is a technical room (20) which includes a liquid pump (40) which will circulate in a closed circuit the organic matter to be treated out of the tank (C) and then into the tank (C). The objective of this liquid pump (40) is to prevent the organic matter from forming a crust and from being stirred in order to optimize the gas recovery efficiency. More particularly, the liquid circuit will be described in the following figure. The recovered gases will be sent to a gas suction pump (50). Liquid leak detection will be done by means of a system described later with possibly a liquid detector (30) placed to detect the cleverly designed leak circuit and as described below.

[0023] [Fig.2] represents an overall sectional view of the tank (C) which is produced by the cooperation of a hollow earthwork made in the ground (S) and a flexible envelope (1) which fits the hollow of this earthwork. Typically the hollow is pyramidal in shape, in the form of an inverted pyramid. The envelope is sized to the format of the hollow made in the ground, and is blocked on the top by a flat part which fits the horizontality of the surrounding ground. In a way, except for the technical room which can resemble a house, the tank (C) does not block the view and does not deteriorate therefore not the landscape. Organic liquid is introduced into the tank by means of an inlet pipe (6) supplied by a circuit connected to the liquid pump (40). The inlet pipe (6) is arranged on the upper side of the casing (1). The liquid outlet pipe (7) which supplies the liquid pump (40) is positioned in the point at the bottom of the casing. By gravity the liquids flow downwards to return to the liquid pump (40) which makes it possible to create the closed circuit which rotates the liquid pump (40). The decomposition gases are recovered by drains (3), peripheral tubular systems which circulate at the top of the casing around its entire circumference. These gases are then directed through a pipe which crosses the casing (1) and sucked up by a gas suction pump (50) which directs them to a gas storage and / or recovery circuit.Obviously the connection between the gas outlet nozzle which passes through the casing (1) and the casing (1) is designed to be watertight to prevent any liquid or gas from escaping from the casing (1). A ballast (5) of density greater than that of the organic liquid is placed above the casing (1) so that the casing (1) hugs the surface of the liquid and limits the free volume of gas above the liquid between the casing and the surface of the liquid. In a way, the ballast (5) presses the upper surface of the casing against the surface of the liquid, regardless of the actual level of organic liquid in the tank (C). In the ground (S) near the tank (C) is the inlet of a plugged and sealed manhole (2), for example made with a network of tubes made of a so-called polymer material, which circulates to the bottom of the pyramid and passes through the casing (1) to collect any liquid that may be between the two walls (10a, 10b) of the casing (1). From the manhole (2), by visual inspection or by means of a liquid detector (20), it is inspected whether liquid is at the bottom of the manhole (2).In short, to detect if liquid could have leaked and crossed the inner wall of the envelope (1). This system therefore constitutes an unstoppable leak detection system which detects any possible source of liquid exiting from the envelope (1) which would not circulate through the liquid or gas pump networks of the technical room (20).

[0024] [Fig.3] represents a detailed view of the sealing skin of the envelope (1) which comprises two sealed walls (10a, 10b) with a so-called inner wall (10a) and an outer wall (10b), the two walls (10a, 10b) are finely separated by a flexible mesh (11) which maintains a slight distance between them which allows them to fit together but leaves room for a small flow of liquid which will make it possible to detect a possible leak between the two walls (10a, 10b).

[0025] The present invention therefore relates to a liquid digester with a tank (C) comprising a closed liquid pumping circuit (40, 6, 7) for agitating the liquid in the tank (C), a gas suction circuit (50, 3) released by the digestion of the liquid in the tank (C) characterized in that the tank (C) is produced by the cooperation of an inverted pyramid earthwork made hollow in the ground (S) which is matched by a flexible waterproof envelope (1) with double wall (10a, 10b) crossed in a sealed manner by the gas suction and liquid pumping pipes (3, 6, 7), and of a liquid leak inspection system (2) between the two walls (10a, 10b) of the flexible waterproof envelope.

[0026] The present invention therefore relates to a liquid digester with a sealed tank (C) characterized in that the two walls (10a, 10b) of the casing (1) are finely separated by a flexible mesh (11) which maintains a slight distance between them which allows them to fit together but leaves room for a small flow of liquid to detect a possible leak from the tank (C) between the two walls (10a, 10b).

[0027] The present invention therefore relates to a liquid digester with a sealed tank (C) characterized in that in the ground (S) near the tank (C) is positioned the inlet of a plugged and sealed inspection chamber (2) made with a network of sealed tubes which circulates to the bottom of the pyramid and passes through the casing (1) to collect any liquid which may be found between the two walls (10a, 10b) of the casing (1).

[0028] The present invention therefore relates to a liquid digester with a tank (C) characterized in that a ballast (5) of density greater than that of the organic liquid is placed above the casing (1) to immerse in the liquid and limit the free volume of air above the liquid between the casing and the surface of the liquid, the ballast (5) presses the upper surface of the casing against the surface of the liquid in the tank (C).

[0029] It is understood that it is possible to find variations to the present without departing from the scope of the present.

Claims

Claims

1. Liquid digester with tank (C) comprising a closed circuit for pumping a liquid (40, 6, 7) to agitate the liquid in a tank (C), a circuit for suctioning the gas (50, 3) released by the digestion of the liquid in the tank (C) characterized in that the tank (C) is produced by the cooperation of an inverted pyramid earthwork made hollow in a ground (S) which is matched by a flexible sealed envelope (1) with double wall (10a, 10b) crossed in a sealed manner by the gas suction and liquid pumping pipes (3, 6, 7), and a system for inspecting leakage (2) of liquid between the two walls (10a, 10b) of the flexible sealed envelope.

2. Liquid digester with tank (C) according to claim 1 characterized in that the two walls (10a, 10b) of the casing (1) are finely separated by a flexible mesh (11) which maintains a slight distance between them which allows them to fit together but leaves room for a small flow of liquid to detect a possible leak from the tank (C) between the two walls (10a, 10b).

3. Liquid digester with tank (C) according to claim 1 and 2 characterized in that in the ground (S) near the tank (C) is positioned the entrance of a plugged and sealed inspection chamber (2) made with a network of sealed tubes which circulates to the bottom of the pyramid and passes through the casing (1) to collect any liquid which may be found between the two walls (10a, 10b) of the casing (1).

4. Liquid digester with tank (C) according to claim 1 characterized in that a ballast (5) of density greater than that of the organic liquid is placed above the casing (1) to immerse in the liquid and limit the free volume of air above the liquid between the casing and the surface of the liquid, the ballast (5) presses the upper surface of the casing against the surface of the liquid in the tank (C).

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