BE1024199B1 - Tank and bio-methanation plant - Google Patents

Abstract

The present invention relates to a 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 bio-methanation 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, said walls delimiting the internal volume of said tank being walls formed of a concrete comprising or not aggregates and / or aggregates, said concrete comprising: at least 95% by weight of Portland cement with respect to the total weight of said concrete, at least one superplasticizer, at least one formaldehyde resin, hydroxyethylcellulose and / or hydroxyalkylcellulose, and metal fibers, example of steel fibers.

Description

Tank and bio-methanation plant

The present invention relates to a biomethanization tank made of a concrete, comprising or not aggregates and / or aggregates, said tank having walls delimiting its internal volume and comprising: - an inlet for a substance loaded with carbonaceous material, - an outlet for a digestate obtained in said biomethanization tank following a microbial degradation of said carbonaceous material-loaded substance, and - an outlet for a biogas produced from said carbonaceous material-laden substance following a microbial degradation of said material-laden substance. carbon.

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, there are essentially those of steel and those of a concrete with or without aggregates and / or aggregates. 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 with or without aggregates and / or aggregates, for their part, can be placed in the soil since they have external walls that can withstand the wet conditions encountered underground, unlike steel tanks. Consequently, tanks made of a concrete with or without aggregates and / or aggregates placed in the ground are less bulky and also much 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 materials 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 in a concrete with or without aggregates and / or aggregates. 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 building element into a concrete with or without aggregates and / or aggregates, convert hydrogen sulfide (H2S) to 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 (whether or not containing aggregates and / or aggregates) is altered and eroded by the water runny condensation. 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 steel or concrete tanks (with or without aggregates and / or aggregates) currently used for the production of biogas and / or the purification of substance (fluid) charged in 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 tanks that would be placed in the ground, they should be dug, which, again, is particularly restrictive. 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.

Moreover, unfortunately, with the present concrete tanks (concrete including or not aggregates and / or aggregates), it is observed that the resistance of the walls of the tanks is low in the face of the pressure exerted by the fluid (substance) loaded in organic matter being contained therein. To date, there is therefore a real need for concrete tanks (whether or not including aggregates and / or aggregates) that can be placed in the soil in order to be less subject to temperature variations (ie ie buried tanks) and resistant to "biogenic attacks", that is to say, resistant to the phenomenon of biogenic "corrosion" due to the formation and the presence of sulfuric acid (H2SO4). In addition, there is also a need to provide tanks that are more resistant to the pressure exerted on their walls by the fluid (substance) loaded with organic matter contained therein.

In this sense, the object of the invention is to overcome the drawbacks of the state of the art by providing a tank made of a concrete with or without aggregates and / or aggregates which is more resistant (that is to say which resists better) to the phenomenon of biogenic "corrosion" ("biogenic attack") and which has an optimal resistance to the pressure exerted on their walls by the fluid (substance) loaded with organic matter contained therein.

To solve the known problems of the state of the art, according to the invention, there is provided a concrete tank with or without aggregates and / or aggregates as indicated at the beginning, characterized in that said walls defining its internal volume are walls formed of a concrete comprising: at least 95% by weight of Portland cement relative to the total weight of said concrete, at least one superplasticizing agent, at least one formaldehyde resin, hydroxyethylcellulose and / or hydroxyalkylcellulose, and - metal fibers, for example steel fibers.

Advantageously, according to the invention, said concrete has physical characteristics that meet at least the minimum values prescribed by the NBN EN 206-1 standard. More particularly, according to the invention, the concrete is a concrete corresponding to the name CEM I, in particular to the name C60 / 75 EE4 EA3 S4 D14 CEM I 52.5 R HES which further comprises other constituents: superplasticizer, formaldehyde resin, hydroxyethylcellulose and / or hydroxyalkylcellulose, and metal fibers.

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, the concrete 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 standard for the physical characteristics, or present values higher than the minimum values of this standard for these same physical characteristics.

Against all expectations, whereas concretes comprising or not aggregates and / or aggregates are all recognized as being particularly sensitive to biogenic attacks, it has been demonstrated, in the context of the present invention, that a vessel according to the invention whose walls are formed of a concrete comprising at least 95% by weight of Portland cement relative to the total weight of said concrete, at least one superplasticizer, at least one formaldehyde resin, hydroxyethylcellulose and / or hydroxyalkylcellulose, and metal fibers, for example steel fibers, more effectively withstand 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.

Furthermore, according to the invention, in order to ensure that the tanks have optimum strength, the concrete forming the walls comprises metal fibers, in particular steel fibers. However, it is recognized that the steel fibers placed in conventional concretes known in the state of the art are particularly sensitive to corrosion, all the more so when they are present in a concrete which is itself in contact. a fluid (substance) loaded with organic matter as is the case in the biomethanisation tanks. However, surprisingly, in the context of the present invention, it has been determined that a concrete comprising at least 95% by weight of Portland cement relative to the total weight of said concrete, at least one superplasticizer, at least one resin formaldehyde, hydroxyethylcellulose and / or hydroxyalkylcellulose makes it possible to avoid or at least significantly minimize the corrosion of metal fibers, in particular steel fibers. Indeed, it has been observed that the metal fibers present (included) in a concrete according to the invention corrode significantly less or not at all.

In addition, it has also been demonstrated, in the context of the present invention, that a concrete according to the invention makes it possible to ensure that the metal fibers, in particular the steel fibers, do not settle during casting and of the formation of the vats in molds. This results in a very homogeneous distribution of the metal fibers in the concrete according to the invention, which contributes on the one hand to the optimization of the resistance of the walls of the tanks to pressure and, on the other hand, to the obtaining vats formed in a self-placing concrete. For the purposes of the present invention, the term "self-placing concrete" means a concrete for which it is not necessary to proceed to a specific step, for example to a vibration step carried out via needles, when pouring so that it is evenly distributed.

Advantageously, according to the invention, the concrete forming the walls of the tank comprises said at least one superplasticizer at a rate of 0.8 to 1.9% by weight relative to the total weight of said concrete.

For the purposes of the present invention, the term "superplasticizer" means a (synthetic) polymer for example chosen from one of the following five families of superplasticizers: (1) the sulphonated salts of polycondensates of naphthalene and of formaldehyde commonly called polynaphthalenesulphonates or naphthalene superplasticizers; (2) sulfonated salts of polycondensates of melamine and formaldehyde, commonly referred to as melamine superplasticizers; (3) lignosulphonates having very low sugar contents; (4) polyacrylates and (5) products based on polycarboxylic acids.

Preferably, according to the invention, the concrete forming the walls of the tank comprises said at least one formaldehyde resin in a proportion of 0.01 to 0.035% by weight relative to the total weight of said concrete.

Preferably, according to the invention, the concrete forming the walls of the tank comprises said hydroxyethylcellulose and / or said hydroxyalkylcellulose at a rate of 0.05 to 0.15% by weight relative to the total weight of said concrete.

Advantageously, according to the invention, the concrete forming the walls of the tank comprises said metal fibers, for example steel fibers, in a proportion of 0.5 to 1% by weight relative to the total weight of said concrete.

Preferably, according to the invention, said metal fibers, for example steel, 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 metal fibers, for example steel, have a diameter of between 0.5 mm and 1.3 mm, preferably a diameter of between 0.8 mm and 1 mm.

Such fibers 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 biogas 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 biogas 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 bio-methanation tank further comprises a sealed lid, for example a tight polyethylene lid.

Preferably, according to the invention, the bio-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 of 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 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 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 biogas tank according to the invention for the production of biogas.

The present invention also relates to a use of at least one biogas 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 comprising at least 95% by weight of Portland cement relative to the total weight of said concrete, at least one superplasticizer, at least one formaldehyde resin , such as hydroxyethylcellulose and / or hydroxyalkylcellulose, and metal fibers, for example steel fibers. Such walls made of such a concrete make it possible to resist more effectively the phenomenon of biogenic "corrosion" due to the presence of sulfuric acid but also ensure optimal resistance of the tank 2 to the pressure exerted by the fluid (substance) loaded organic matter contained therein, this without the metal fibers (for example steel) corrodes, the distribution of these fibers is also homogeneous in the walls 3, 4, 5, 6 of the vessel 2. The vessel 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 comprising at least 95% by weight of Portland cement with respect to the total weight of said concrete, at least one superplasticizer, at least one formaldehyde resin, hydroxyethylcellulose and / or hydroxyalkylcellulose, and metal fibers, for example steel fibers, the presence of sulfuric acid weakly alters them and the tank 2 nevertheless remains tight 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.

2 illustrates a bio-methanisation plant 1 comprising three tanks 2, 2 ', 2 "according to the invention, each tank 2, 2', 2" comprising the same elements as those that the vessel has in FIG. However, as illustrated, the outlet 9 of the vessel 2 is connected to the inlet 8 'of the vessel 2' located downstream of the vessel 2. Similarly, the outlet 9 'of the vessel 2' is connected to the 8 "of the tank 2" located downstream of the tank 2 'In this embodiment, the carbonaceous material-loaded substance is fed via the inlet 8 of the tank 2 and the final digest obtained (after passing through three tanks 2, 2 ', 2 ") will be evacuated through the outlet 9" of the 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 (19)

1. Bio-methanization tank made of a concrete comprising or not aggregates and / or aggregates, said 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 biomethanization 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 carbonaceous material-laden substance, said tank being characterized in that said walls defining its internal volume are walls formed of a concrete comprising: at least 95% by weight of Portland cement relative to the total weight of said concrete, at least one superplasticizer, at least one formaldehyde resin, - hydroxyethylcellulose and / or hydroxyalkylcellulose, and - metal fibers, for example, steel fibers. 2. bio-methanation tank according to claim 1, characterized in that said concrete forming said walls of said vessel comprises said at least one superplasticizer at a rate of 0.8 to 1.9% by weight relative to the total weight of said concrete. 3. A bio-methanation tank according to claim 1 or 2, characterized in that said concrete forming said walls of said tank comprises said at least one formaldehyde resin in a proportion of 0.01 to 0.035% by weight relative to the total weight of said concrete. 4. bio-methanation tank according to any one of the preceding claims, characterized in that said concrete forming said walls of said vessel comprises said hydroxyethylcellulose and / or said hydroxyalkylcellulose at a rate of 0.05 to 0.15% by weight per relative to the total weight of said concrete. 5. Bio-methanation tank according to any one of the preceding claims, characterized in that said concrete forming said walls of said vessel comprises said metal fibers, for example steel fibers, at 0.5 to 1% by weight. weight relative to the total weight of said concrete. 6. Bio-methanation tank according to any one of the preceding claims, characterized in that said metal fibers, for example steel, have a length of between 25 mm and 75 mm, preferably a length of between 50 mm and 60 mm. mm. 7. bio-methanation tank according to any one of the preceding claims, characterized in that said metal fibers, for example steel, have a diameter of between 0.5 mm and 1.3 mm, preferably a diameter between 0.8 mm and 1 mm. 8. bio-methanation tank according to any one of the preceding claims, characterized in that said walls of the tank are coated with a coating of an epoxy resin or a polyethylene coating. 9. Bio-methanation tank according to any one of the preceding claims, characterized in that it further comprises a drain device. 10. bio-methanation 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. 11. biogas tank according to any one of the preceding claims, characterized in that it further comprises a sealed lid, for example a tight polyethylene lid. 12. 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 selected 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. 13. Biogas 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. 14. Bio-methanisation plant comprising: at least one bio-methanation tank according to any one of claims 1 to 13, at least one device for feeding a substance loaded with carbonaceous material into said 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 biomethanisation tank. microbial degradation of said carbonaceous material-laden 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 any one of claims 14 or 15, 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. 17. Use of at least one bio-methanation tank according to any one of claims 1 to 13 for the production of biogas. 18. Use of at least one bio-methanation tank according to claim 17 in a bio-methanation plant according to any one of claims 14 to 16. 19. Use of a biogas plant according to any one of claims 14 to 16 for energy production, for example for electricity production.