BE1023245B1 - Tank and bio-methanation plant - Google Patents

Abstract

The present invention relates to a concrete biogas tank having walls delimiting its internal volume and comprising: - a substance in carbonaceous material, - an outlet for a digestate obtained in said biogas tank following microbial degradation of said substance loaded with carbonaceous matter, and - an outlet for a biogas produced at the start of said substance loaded with carbonaceous matter following a microbial degradation of said substance loaded with carbonaceous matter, said walls delimiting the internal volume of said tank being walls in a concrete whose various composition parameters and whose physical characteristics meet at least the minimum values prescribed by standard NBN EN 206-1.

Description

Tank and bio-methanation plant

The present invention relates to a concrete biomethanization tank having walls defining its internal volume and comprising: - an inlet for a substance loaded with carbonaceous material, - an outlet for a digestate obtained in said biomethanisation tank following a microbial degradation of said substance loaded with carbonaceous material, and - an outlet for a biogas produced from said substance loaded with carbonaceous material following a microbial degradation of said substance charged with carbonaceous material.

Many bio-methanation tanks are known from the state of the art and are used to produce biogas from substances loaded with carbonaceous material, such as for example from wastewater (from waste from dairies, from breweries, slaughterhouses or sweets) but also from manure from farms.

Among these tanks, one essentially distinguishes those in steel and those in concrete. However, steel tanks are expensive and particularly sensitive to temperature variations to which they are subjected when they are exposed to outdoor temperature conditions. This has a direct impact on the performance of the biogas plant since the bacterial populations responsible for bio-methanisation have an optimum yield directly related to the working temperature. In addition, these steel tanks occupy a considerable volume, for example within a farm, and therefore results in a significant loss of space.

Concrete tanks, for their part, can be placed in the ground since they have external walls that can withstand the wet conditions encountered underground, this in contrast to steel tanks. Therefore, concrete tanks placed in the ground are less bulky and also significantly less subject to temperature variations.

As regards bio-methanisation, a first bio-methanisation technique relies on the use, in a tank such as that indicated above, of bacterial beds composed for example of slag or synthetic material serving as support elements for populations. bacterial. The presence of support elements for bacterial populations makes it possible to fix the latter, which makes it possible to increase the concentration thereof in the tanks used for the production of biogas from substances loaded with carbonaceous material. We then speak of digesters (reactors) fixed cultures or fixed beds.

A second technique is based on a continuous mixture of the substrate (substance loaded with carbonaceous material) with bacterial populations in the tank. These are referred to as "infinitely mixed" reactors (digesters) in which, in the presence of bacterial populations, the substrate (the material loaded with carbonaceous material) is continuously homogenized by mechanical stirring or by gas mixing. Generally, either of these two techniques is used, the tanks receiving the carbonaceous material loaded substances are part of an anaerobic treatment plant to produce both biogas but also to simultaneously purify said substance. As such, a non-limiting example is the purification of slaughterhouse water with a simultaneous production of biogas.

More particularly, a biogas production relies on bacterial degradation, generally by at least two main types of distinct bacterial populations, of the carbonaceous material present in a substance (in a fluid). It is in fact a methane fermentation that involves two successive phases of transformation of organic carbon first carbon dioxide (CO2) and then methane (CH4). The first phase is carried out under the action of acidogenic bacteria that degrade (hydrolyze) organic molecules to volatile fatty acids (VFA), mainly acetic acid and propionic acid, this first degradation being accompanied by a release of carbon dioxide. The second phase takes place under the action of methanogenic bacteria which transform the previously obtained AGV into methane and carbon dioxide.

However, there is a recurring problem associated with the fermentation process inherent in bio-methanization, which is known as a "biogenic attack". It is more specifically a phenomenon of biogenic "corrosion" due to the formation and the presence of sulfuric acid (H2SO4), which attacks and corrodes the walls of bio-methanation tanks, that they are steel or concrete. As a result, the walls of the tanks become porous and have cracks allowing the fluid (substance) loaded with organic material to flow out of the tanks.

This biogenic "corrosion" is directly related to the anaerobic microbial degradation of organic substances in the tanks of biogas plants. Indeed, this anaerobic microbial degradation releases not only the main components that are methane (CH4) and carbon dioxide (CO2) but also hydrogen sulphide (H2S) whose quantity produced depends, among other things, on the nature substrates employed and may vary from a few ppm to several thousand ppm (which is particularly the case during the fermentation of slurry, food waste and biological waste).

However, bacteria (thiobacilli), in the gas zone (that is to say in the upper part of the tank, above the part where the substance is loaded with carbonaceous material) and on the surface wet of the concrete building element, convert hydrogen sulphide (H2S) into sulfuric acid (H2SO4). This sulfuric acid reacts with the concrete components (mainly with calcium hydroxide to turn into gypsum) and as a result the concrete is altered and eroded by the streaming water. For example, in the space of a few years, it is estimated that layers of concrete of the order of 5 mm thick are removed in places exposed to such biogenic attacks.

From this problem related to biogenic attacks, it follows that the steel or concrete tanks, currently used for the production of biogas and / or the purification of substance (fluid) loaded with carbonaceous material, must be replaced punctually. This is particularly restrictive when it is necessary to stop the production of biogas, empty the tanks and reconnect new ones on the existing installation. In addition, for the vats that would be placed in the soil, it would be appropriate to unearthed them, which, again, is particularly binding. This relates more particularly to concrete tanks since the steel tanks are generally not placed underground for reasons of oxidation of the walls of the tank. To date, there is therefore a real need for concrete vats that can be placed in the soil in order to be less subject to temperature variations (that is to say buried tanks) and resistant to "biogenic attacks". ", That is to say resistant to the phenomenon of" corrosion "biogenic due to the formation and the presence of sulfuric acid (H2SO4). In this sense, the object of the invention is to overcome the drawbacks of the state of the art by providing a concrete vessel which is more resistant (that is to say which is more resistant) to the phenomenon of biogenic "corrosion" ("Biogenic attack").

To solve the known problems of the state of the art, according to the invention, there is provided a concrete vessel as indicated at the beginning, characterized in that said walls delimiting its internal volume are concrete walls of which the different composition parameters and whose physical characteristics meet at least the minimum values prescribed by the NBN EN 206-1 standard.

Advantageously, according to the invention, said concrete whose various composition parameters and whose physical characteristics meet at least the minimum values prescribed by the NBN EN 206-1 standard, is a concrete of composition C60 / 75 EE4 EA3 S4 D14 CEMI 52 , 5 R HES.

For the purposes of the present invention, the term "composition parameters" is intended to mean the type and quantity of cement and the size of the aggregates composing the concrete.

For the purposes of the present invention, the term "physical characteristics" particularly refers to the strength of the concrete, its consistency and the water / cement ratio by weight (W / C).

For the purposes of the present invention, concrete whose various composition parameters and whose physical characteristics meet at least the minimum values prescribed by the NBN EN 206-1 standard, is a concrete which can therefore either meet the minimum values defined by this invention. standard for the different composition parameters and for the physical characteristics, ie to present values higher than the minimum values of this standard for these same composition parameters and these same physical characteristics.

Against all expectations, while the concretes are all recognized as being particularly sensitive to biogenic attacks, it has been demonstrated, in the context of the present invention, that a tank according to the invention whose walls are formed of a concrete whose different compositional parameters and whose physical characteristics meet at least the minimum values prescribed by the NBN EN 206-1 standard is more effectively resistant to the phenomenon of biogenic "corrosion" due to formation and the presence of sulfuric acid (H2SO4). Indeed, it has been determined that the tanks according to the invention can be used for many years, that is to say for more than 10 years, without having to be replaced since their walls are not affected by the " biogenic attacks ". Therefore, tanks according to the invention can ensure that an installation will remain in place for many years without having to perform a one-time replacement of biogas tanks.

Advantageously, according to the invention, said concrete whose various composition parameters and whose physical characteristics meet at least the minimum values prescribed by the NBN EN 206-1 standard is a self-placing fiber-reinforced concrete comprising fibers. Such concrete allows, rather than pouring directly on site, to place preformed tanks in the ground.

Preferably, according to the invention, said self-placing fiber concrete comprises steel fibers. Such fibers are suitable for giving self-compacting fiber concrete sufficient resistance to the pressure exerted by the fluid (substance) loaded with organic material present in the tank.

Preferably, according to the invention, said fibers of self-placing fiber-reinforced concrete have a length of between 25 mm and 75 mm, preferably a length of between 50 mm and 60 mm.

Advantageously, according to the invention, said fibers of self-compacting fiber concrete have a diameter of between 0.5 mm and 1.3 mm, preferably a diameter of between 0.8 mm and 1 mm.

Fibers of self-compacting fiber concrete having such lengths and / or such diameters have been determined to be adequate so that the walls of the vessel according to the invention have sufficient strength.

Preferably, according to the invention, said walls of the tank are coated with a coating of an epoxy resin, a polyethylene coating or any other coating resistant to acid attacks. The presence of such a coating makes it possible to further ensure a resistance of the walls of the tank to the biogenic "corrosion" phenomenon due to the formation and the presence of sulfuric acid (H2SO4).

Advantageously, the concrete bio-methanation tank according to the invention further comprises a draining device. This system or emptying device makes it possible to empty the tank when, for example, it is necessary to carry out a repair or to clean them.

Preferably, the concrete bio-methanation tank according to the invention further comprises a heating device, for example a heating device in the form of a resistor. Such a heating device makes it possible to constantly maintain an adequate temperature within the tank, which enables the bacterial populations present to effectively degrade the carbonaceous material and thus to optimize the efficiency of the installation.

Advantageously, according to the invention, the concrete bio-methanization tank further comprises a sealed lid, for example a tight polyethylene lid.

Preferably, according to the invention, the concrete bi methanation tank further comprises at least one probe for measuring a parameter chosen from the group consisting of a temperature probe, a probe measuring the pressure in the tank and a probe measuring the pH of said substance loaded with carbonaceous material. All these measuring probes make it possible to control at any time the conditions prevailing in the biogas tank and, if necessary, to correct them, this always with the aim of optimizing the efficiency of the installation. For example, these probes can be at the level of the sealed lid of the tank.

Advantageously, the concrete bio-methanation tank according to the invention further comprises at least one bacterial carrier, for example a bacterial carrier in the form of a sphere containing fibers.

Preferably, according to the invention, said substance loaded with carbonaceous material is formed by wastewater, for example from dairies waste, breweries, slaughterhouses or even sweets, and slurry from farms and the like. Other embodiments of a concrete tank according to the invention are indicated in the appended claims.

The present invention also relates to a bio-methanisation plant comprising: - at least one bio-methanisation tank according to the invention, - at least one device for feeding a substance loaded with carbonaceous material into said at least one tank biomethanisation, - at least one device for collecting a biogas produced by biomethanization in said at least one biogas tank, and - at least one collection zone of a digestate obtained in said biogas tank following microbial degradation of said substance loaded with carbonaceous material.

Preferably, the bio-methanation plant according to the invention comprises a plurality of bio-methanization tanks placed in series and interconnected. In this case, the collection zone of a digestate is then connected to an outlet of the last tank of the plurality of tanks placed in series and the device for supplying a substance charged with carbonaceous material is connected to an inlet of the first tank of the plurality of tanks placed in series. Such a series placement of several biogas tanks according to the invention makes it possible to optimally exploit the substance loaded with carbonaceous material: the passage from tank to tank makes it possible to subject the digestate obtained at the start of a first tank to different bacterial populations contained in another tank placed downstream of the first tank. The different types of carbonaceous material initially present in the substance loaded with carbonaceous material can thus be exploited optimally, which contributes to the performance of a biogas plant.

Advantageously, the bio-methanization plant according to the invention further comprises a post-digestion device placed downstream of the outlet of said at least one biogas tank and upstream of said at least one collection zone. a digestate. It is in fact a device that still allows, after a tank or a series of bio-methanization tanks placed in series, to exploit the residual carbonaceous materials and possibly still produce the biogas before a rejection of the final digestate that would be obtained.

Preferably, the bio-methanisation plant according to the invention furthermore comprises a unit for producing electrical energy, for example a cogeneration unit, fed with the biogas produced in said at least one bio-methanation tank and collected at the same time. departure from the latter. Other embodiments of a biogas plant according to the invention are indicated in the appended claims.

The present invention also relates to a use of at least one concrete bio-methanation tank according to the invention for the production of biogas.

The present invention also relates to a use of at least one concrete bio-methanation tank according to the invention in a biogas plant according to the invention. Other forms of use of at least one biomethanisation tank according to the invention are indicated in the appended claims.

The present invention also relates to a use of a biogas plant according to the invention for energy production, for example for electricity production. Other forms of use of a biogas plant according to the invention are indicated in the appended claims. Other features, details and advantages of the invention will become apparent from the description given below, without limitation and with reference to the accompanying drawings.

Figure 1 is a sectional view of a biomethanization tank according to the invention.

Figure 2 is a sectional view of a biogas plant according to the invention comprising three biomethanization tanks in series according to the invention.

In the figures, identical or similar elements bear the same references.

FIG. 1 illustrates a bio-methanisation installation 1 comprising a tank 2 according to the invention. This tank 2 comprises high walls 3 and low 4 and side walls 5, 6 of a concrete whose different composition parameters and whose physical characteristics meet at least the minimum values prescribed by the NBN EN 206-1 to resist more effectively to the phenomenon of biogenic "corrosion" due to the presence of sulfuric acid. The tank 2 is also provided with a tight cover 7, for example polypropylene. As illustrated, the tank 2 furthermore has an inlet 8 for a substance loaded with carbonaceous matter, an outlet 9 for a digestate obtained in the biomethanisation vat 2 following a microbial degradation of the substance loaded with carbonaceous material, and an outlet 10 for a biogas produced from the substance loaded with carbonaceous material. A drain system 11 is also present and allows emptying the tank 2 if necessary.

In a zone A of the tank 2 which receives a substance loaded with carbonaceous material, there are (according to the nonlimiting embodiment illustrated) bacterial supports 12 in the form of spheres containing, for example, fibers to which bacterial populations responsible for the degradation of carbonaceous materials. Optionally, at the lower part of the zone A of the tank 2, is positioned a grating 13 kept at a distance from the bottom of the tank 2 by support elements 14. This grating 13 is intended for the supports 12 not to rest at bottom of the tank 2 where sediment particles present in the substance containing carbonaceous material. The tank 2 also comprises a heating element 15.

The degradation of the carbonaceous materials gives rise to the production of methane (biogas) and the production of other secondary substances including hydrogen sulphide converted into sulfuric acid by bacteria in the gas zone (zone B in Figure 1) . However, since the walls 3, 4, 5, 6 of the tank 2 are formed of a concrete whose different composition parameters and whose physical characteristics meet at least the minimum values prescribed by the NBN EN 206-1 standard, the presence of sulfuric acid alters weakly and the tank 2 remains waterproof for many years, that is to say beyond 10 years.

Of course, the inlet 8 for a carbonaceous material-laden substance is connected to a feed device (not illustrated) of a carbonaceous material-laden substance and the outlet 9 of a digestate obtained in the biotank 2 methanization (following a microbial degradation of the substance loaded with carbonaceous material) is connected to a collection zone (not shown) of the digestate. Furthermore, the outlet 10 of biogas can be connected to a storage device (not shown) of the biogas produced or be connected to a power generation unit (not shown), which is fed by the biogas produced in said at least one biogas tank 2 and collected from the latter.

FIG. 2 illustrates a bio-methanisation plant 1 comprising three tanks 2, 2 ', 2 "according to the invention. Each tank 2, 2 ', 2 "comprises the same elements as the tank has in Figure 1. However, as illustrated, the outlet 9 of the tank 2 is connected to the inlet 8' of the tank 2 'located downstream of the tank 2. Similarly, the outlet 9 'of the tank 2' is connected to the inlet 8 "of the tank 2" located downstream of the tank 2 '. In this embodiment, the substance loaded with carbonaceous material is fed via the inlet 8 of the tank 2 and the final digest obtained (after passing through the three tanks 2, 2 ', 2 ") will be evacuated through the outlet 9 "From tank 2" before reaching a collection area (not shown) of the final digestate.

As for the example illustrated in FIG. 1, for each of the tanks of FIG. 2, the biogas outlet 10 can be connected to a storage device (not shown) of the biogas produced or be connected to a production unit. electrical energy (not shown), which is fed by the biogas produced in said at least one tank 2, 2 ', 2 "bio-methanization and collected from the latter.

It is understood that the present invention is in no way limited to the embodiments described above and that many modifications can be made without departing from the scope of the appended claims.

Claims (20)

1. Concrete bio-methanization tank having walls defining its internal volume and comprising: - an inlet for a substance loaded with carbonaceous material, - an outlet for a digestate obtained in said biogas tank following a microbial degradation of said substance loaded with carbonaceous material, and - an outlet for a biogas produced from said substance charged with carbonaceous material following a microbial degradation of said substance charged with carbonaceous material, said tank being characterized in that said walls delimiting its internal volume are walls made of concrete with different composition parameters and whose physical characteristics meet at least the minimum values prescribed by the NBN EN 206-1 standard. 2. biogas tank concrete according to claim 1, characterized in that said concrete whose various composition parameters and whose physical characteristics meet at least the minimum values prescribed by the standard NBN EN 206-1, is a concrete of composition C60 / 75 EE4 EA3 S4 D14 CEMI 52.5 R HES. 3. Concrete bio-methanisation tank according to claim 1 or 2, characterized in that said concrete whose various composition parameters and whose physical characteristics meet at least the minimum values prescribed by the standard NBN EN 206-1 is a self-placing fibered concrete comprising fibers. 4. Concrete biomethanation tank according to claim 3, characterized in that said self-placing fiber concrete comprises steel fibers. 5. Concrete bio-methanisation tank according to claim 3 or 4, characterized in that said fibers have a length of between 25 mm and 75 mm, preferably a length of between 50 mm and 60 mm. 6. Concrete bio-methanation tank according to any one of claims 3 to 5, characterized in that said fibers have a diameter of between 0.5 mm and 1.3 mm, preferably a diameter between 0.8. mm and 1 mm. 7. biogas tank concrete according to any one of the preceding claims, characterized in that said walls are coated with a coating of an epoxy resin type, a polyethylene coating or other resistant coating to acid attacks. 8. biogas tank concrete according to any one of the preceding claims, characterized in that it further comprises a drain device. 9. A bio-methanisation concrete tank according to any one of the preceding claims, characterized in that it further comprises a heating device, for example a heating device in the form of a resistor. 10. A biogas tank concrete according to any one of the preceding claims, characterized in that it further comprises a sealed cover, for example a sealed polyethylene lid. 11. Concrete bio-methanation tank according to any one of the preceding claims, characterized in that it further comprises at least one probe for measuring a parameter chosen from the group consisting of a temperature probe, a a probe measuring the pressure in the tank and a probe measuring the pH of said substance loaded with carbonaceous material. 12. Concrete bio-methanisation tank according to any one of the preceding claims, characterized in that it further comprises at least one bacterial carrier, for example a bacterial carrier in the form of a sphere containing fibers. 13. Concrete bio-methanation tank according to any one of the preceding claims, characterized in that said substance loaded with carbonaceous material is formed by wastewater, for example from waste from dairies, breweries, slaughterhouses or more sweetmeats, and slurry from farms and the like. 14. Bio-methanisation plant comprising: - at least one concrete bio-methanation tank according to any one of claims 1 to 13, - at least one device for supplying a substance loaded with carbonaceous material in said at least one at least one biomethanisation tank, at least one device for collecting a biogas produced by biomethanization in said at least one biogas tank, and at least one collection zone for a digestate obtained in said biogas tank. methanization following microbial degradation of said carbonaceous substance. 15. Bio-methanation plant according to claim 14, characterized in that it comprises a plurality of biomethanisation tanks placed in series and interconnected. 16. bio-methanisation plant according to claim 14 or 15, characterized in that it further comprises a post-digestion device placed downstream of the outlet of said at least one biogas tank and upstream of said at least one collection area of a digestate. 17. bio-methanisation plant according to any one of claims 14 to 16, characterized in that it further comprises a power generation unit, for example a cogeneration unit, powered by the biogas produced in said at least one bio-methanation tank and collected at the start of the latter. 18. Use of at least one concrete bio-methanation tank according to any one of claims 1 to 13 for the production of biogas. 19. Use of at least one concrete biogas tank according to claim 18 in a biogas plant according to any one of claims 14 to 17. 20. Use of a biogas plant according to any one of claims 14 to 17 for energy production, for example for electricity production.