FR3032777A1 - SYSTEM FOR COLLECTING BIOGAS PRODUCED BY AN UNIT OF METHANIZATION IMPLANTED IN AN AGRICULTURAL EXPLOITATION - Google Patents

Abstract

The invention relates to a biogas collection system produced by an anaerobic digestion unit (361; 371) located on a farm (36; 37) and purified. According to the invention, such a purified biogas collection system comprises: - a purified biogas storage station (34) connected to a natural gas distribution network; and at least one vehicle (38) for conveying said purified biogas from said anaerobic digestion unit (361; 371) to said storage station (34).

Description

BACKGROUND OF THE INVENTION Field of the Invention The field of the invention is that of energy.

More specifically, the invention relates to a system for the combined production of energy, and in particular electricity, gas and energy in the form of heat, from renewable raw materials and waste. 2. State of the art The increase in the price of fossil fuels and the need to fight against global warming by reducing the production of greenhouse gases encourages the development of alternative energy production techniques that respect the environment. There is a growing interest in the use of agricultural waste and waste from the agri-food industry, which is an available and renewable energy resource. For example, a slurry recovery technique is known in which the slurry is partially converted into biogas within a methanation unit. This technique is now widespread in farms in northern Europe.

A disadvantage of this technique is that it is necessary to connect the methanization unit to the natural gas network, which is often distant. This entails significant investment costs and requires obtaining administrative authorizations to proceed with the connection work, which is not without problems if the local population is reserved or hostile to the completion of this work. It has been suggested that a cogeneration unit be associated with an anaerobic digestion unit in order to produce electricity and heat from the biogas. A disadvantage of this known technique combining anaerobic digestion and cogeneration is that its overall energy efficiency is low.

Another disadvantage of an installation coupling a cogeneration unit to an anaerobic digestion unit is that excess biogas produced in a flare is burned to regulate electricity production as needed, which further deteriorates. the overall energy efficiency of the installation. Another disadvantage is that it is necessary to have near buildings or facilities to consume the electricity and the heat produced. 3. OBJECTIVES OF THE INVENTION The object of the invention is therefore in particular to overcome the disadvantages of the state of the art mentioned above. More specifically, the invention aims to provide a combined energy production technique that can substantially guarantee the energy independence of a territory of several square kilometers, including 15 of a community of municipalities. An object of the invention is also to provide a combined energy production technique that is respectful of the environment. Another object of the invention is to provide a reliable combined energy production technique.

The invention also aims to provide such a technique that is simple to implement and a reduced cost. Yet another object of the invention is to provide a combined energy production technique that is profitable to exploit in the medium and / or short term. 4. Objectives of the invention These objectives, as well as others which will appear later, are achieved by means of a system for the combined production of energies, particularly electricity, gas and energy. form of heat, especially from renewable raw materials and / or waste.

According to the invention, such a combined energy production system comprises: at least one methanisation unit fed with organic waste; At least one boiler, in particular a wood-burning boiler or a household waste boiler, suitable for heating the digesters of said methanisation unit and / or for sanitizing or drying at least part of the digestates from said anaerobic digestion unit; A cogeneration unit fed with biogas by said methanation unit, producing electricity and heat; a station for storing at least a portion of the biogas produced by said methanation unit and purified; and a control device controlling said anaerobic digestion unit, said cogeneration unit and said boiler, configured so as to optimize the production of the energies within said system. Thus, the invention proposes to combine, in a novel and particularly clever way, at least one boiler and a biomethane storage station with an anaerobic digestion unit and a cogeneration unit so as to be able to produce, in a combined and optimized manner, electricity, biomethane and heat from renewable raw materials and non-recovered waste. The invention thus provides a solution for producing different energies which has a high overall energy efficiency and the part of the different energies produced can be adapted in particular according to the evolution of the price of these energies. In addition, the invention is particularly respectful of the environment. It makes it possible to eliminate the organic waste generated by human consumption (fermentable fraction of household waste, sewage treatment plant sludge, industrial waste, on-farm waste, etc.), to reduce emissions. of greenhouse gases (CH4, CO2, N20) and to co-produce a digestate that can be used as an agricultural amendment, via anaerobic digestion, intended to replace chemical fertilizers. The integration of a boiler in this system is particularly clever. This boiler makes it possible in particular to ensure, via a hot water circuit connecting the digesters to the boiler, the heating of the digesters during the commissioning phase of the anaerobic digestion unit, for example following a shutdown of the boiler. methanization unit for maintenance reasons, so as to bring the temperature within the digesters to a required level in mesophilic regime or thermophilic regime. This boiler is advantageously a boiler using a renewable energy, namely wood, or a boiler for burning garbage. It should be noted that in the context of the invention, the purified biogas, or biomethane, can be stored in the storage station in a gaseous form and / or in a liquid form. The system according to the invention may also comprise several methanation units, boilers, cogeneration units or storage stations. Advantageously, such a combined energy production system 20 comprises a heat transport network produced by said cogeneration unit and / or said boiler. It may for example be a hot water system or a hot water system. steam network. Preferably, the combined energy production system as described above comprises a plurality of vehicles capable of using said biogas purified as fuel, intended to transport said renewable raw materials and / or said waste towards said methanation unit and / or or the digestates of said anaerobic digestion unit to a composting zone and / or a temporary storage zone before spreading.

According to an advantageous aspect of the invention, said control device comprises means for managing the amount of purified biogas stored in said biogas storage station. According to a particularly advantageous embodiment of the invention, said control device is configured so as to maintain the electricity production capacity of said cogeneration group between 70 and 100% of its maximum capacity. Preferably, the electrical efficiency on PCI of said cogeneration group is at least equal to 35%, preferably greater than or equal to 37% and even more preferably greater than or equal to 40%. Advantageously, said control device is configured in such a way as to optimize the production of the energies within said system as a function of the comparative rates of electricity and gas. Thus, the economic profitability of said system is improved.

In at least one particular embodiment of the invention, said purified biogas storage station, or biomethane, is connected to a natural gas distribution network. Preferably, said renewable raw materials and / or said waste comprise substances belonging to the group comprising at least: - slurry; - sewage sludge; - organic waste from the agri-food industry. According to a particular embodiment of the invention, such a system 25 comprises at least one additional methanization unit located in a farm and at least one vehicle capable of transporting biogas produced by said additional methanization unit and purified said farm agricultural to said storage station. Thus, it is not necessary to connect the additional methanation unit to the natural gas network.

Preferably, said vehicle or said farm comprises means for compressing said purified biogas at a pressure greater than or equal to 200 bars and preferably substantially equal to 300 bars. The invention also relates to a control device of a combined energy production system 5 as described above. 5. List of Figures Other features and advantages of the invention will appear more clearly on reading the following description of embodiments of the invention, given as simple illustrative and non-limiting examples, and the accompanying drawings. among which: Figure 1 is a schematic representation of a combined energy production system according to the invention, in a synoptic form; Figure 2 details the receipt and storage of organic waste feeding the methanization unit; FIG. 3 illustrates another exemplary embodiment of a combined energy production system according to the invention. 6. Detailed description of the invention 6.1. Example of embodiment of the invention The combined energy production system 10 according to the invention illustrated in FIG. 1 comprises a wood boiler 16 and an anaerobic digestion unit 11 composed of two digesters 12 and a post -digester 13, connected on the one hand to a cogeneration group 14 and on the other hand to a biomethane storage station for vehicle 15.

This combined electricity, biomethane and heat generating system 10 is sized to provide electric power, gas and heat production equivalent to the needs of a municipality of about 5,000 inhabitants. It is located on a unique site near this town.

The digesters 12 of the anaerobic digestion unit 11 are supplied with substrates via a preparation tank 17 in which slurry 19, sludge from a purification plant 110 and waste 18 from the industry have been mixed. food industry, including inert waste 181 category 3 which 5 were crushed and hygienized beforehand. As can be seen in FIG. 2, which is a schematic representation of the zone for receiving and storing organic waste intended to feed the anaerobic digestion unit, this waste is delivered by truck into the storage building 21 or conveyed by pipeline 22.

Each of these wastes is directed to a specific storage tank depending on its nature. Thus, in this particular embodiment of the invention, wet solid waste 23, pasty material 24, such as some sewage sludge 110, fat waste 25, liquid waste 26, such as manure 19 and category 3 waste from the agri-food industry 181 is stored in five respective tanks 27. In building 21, kept in a depression, dedicated receiving hoppers 28 and 29 are provided to receive category 3 waste from the industry respectively. The pasty materials 24 and a part of the greasy waste are discharged into the waste pits 210 and 211 each connected to the storage tank 27 intended to receive this substance. Liquid waste 26 conveyed by truck is directly dumped into the corresponding storage tank 27.

There is also provided in the building 21 a mill 213 and a sanitary waste cell 181 category 3. Liquid waste is taken from the storage tank of the waste by a conduit 212 to ensure a dilution of pasty substances. Dilution of category 3 wastes and wet solid wastes was performed using liquid digests 120.

The boiler of the wood boiler 16 makes it possible to heat and maintain the temperature in the digesters at 32 ° C. during the startup of the anaerobic digestion unit 11, via a network of steam pipes 111 connecting the boiler to the digesters 12.

Sanitation of category 3 waste is also carried out from the heat supplied by the wood boiler. The wood boiler 16 also ensures the drying and sanitization of part of the solid fraction 119 of the digestates in order to obtain approved fertilizer material (MF) 118. Another part of the digestate is recovered in the form of compost 112 10 or stored in liquid form on a storage area 113 to be spread on agricultural land of the municipality or neighboring municipalities. From 10 to 30% of the liquid fraction 120 of the digestates are directed to a buffer tank 126, where they are taken for the purpose of diluting the waste 18 from the food industry, the slurry 19 and the sludge 15 of the station. purification 110 or be eliminated in the purification plant of the town, after being burned in a thermal oxidizer 127. In a variant of this particular embodiment of the invention, it may be envisaged to use least part of the dried solid digestates obtained as biofuel, for example to supply the boiler of the energy production system and / or to substitute for fossil fuel. In addition, the boiler of this boiler room 16 delivers, if necessary, additional heating with hot water leaving the cogeneration unit 14 which supplies the heat network 115 of the municipality. It also allows for heating a building 114 housing the offices of the operating company of the production system 10 and a conference room. It should be noted that, in this embodiment of the invention, the wood used in the boiler of the boiler 16 is wood cut on the town. It can especially be pruning wood in the form of logs 30 or wood chips.

In variants of this embodiment of the invention, it may also be envisaged to feed the boiler with compacted granules formed in particular by-products of the wood processing, such as sawdust or chips.

The production system 10 has also been equipped with a biofilter 116 and two acidic chemical washers 117 which make it possible to treat the gases produced by the manure stock 19, the stock of sewage treatment plant sludge 110 and the storage stocks. waste 18 from the food industry, as well as the fermentable material obtained from digestates.

In this particular embodiment of the invention, at least 90% of the crude biogas extracted from the post-digester 13 is conditioned in a pre-conditioning unit 121, where it is desulfurized and where the water vapor it The excess crude biogas is burned in a flare 122. A portion 124 of the conditioned gas in the preconditioning unit 121 is purified during the operation of the engine of the cogeneration unit 14. transit through a treatment facility 123 to provide biomethane which is compressed in the storage station 15 for storage. The impurities 127 resulting from this treatment are reinjected into the post-digester 13. The storage station 15 makes it possible to refuel a GNV truck fleet transporting waste, slurry and sewage sludge, respectively. neighboring agri-food plant, farms and municipal wastewater treatment plant to site 25 of the combined energy production system 10. The surplus of stored biomethane is injected into the natural gas distribution network 125 , which increases the profitability of the system. The electricity produced by the cogeneration unit 14 is resold to an electricity distributor.

A control device (not shown in FIG. 1) controls the cogeneration group 14. It makes it possible to maintain the electricity production capacity of the cogeneration group 14 between 70 and 100% of its maximum capacity and the electrical efficiency. on PCI of cogeneration group 14 5 between 35% and 39%, in this embodiment of the invention. This centralized control device also controls the anaerobic digestion unit 11, the boiler of the wood-fired boiler 16 and the gas reserves of the storage station 15. It is configured so as to optimize the production of the energies within the system 10 according to the tariffs 10 compared electricity and gas and presents a module for managing the amount of biomethane stored in the storage station. Thus, for example, when the price of electricity remains stable and the price of gas falls, the control device favors a use of the biogas produced by the anaerobic digestion unit dedicated to electricity production and an excess biogas storage in the plant. limit of the capacity of the gas station. The production capacity of the cogeneration unit is then progressively increased, for example up to 90% of its maximum capacity, and the remaining purified biogas is compressed to be stored in the storage station, waiting to reinject it into the natural gas network, when the price of gas will increase again. 6.2. Another Exemplary Embodiment of the Invention Another example of a combined energy production system according to the invention is shown with reference to FIG. This combined energy production system 30 comprises a territorial energy center 35 equipped with a household waste boiler 31, an anaerobic digestion unit 32, a cogeneration unit 33 and a biomethane storage station. 34. It also includes two additional methanation units 361 and 371 and their 362 and 372 30 biomethane storage tanks located respectively on farms 36 and 37.

The biomethane produced by the anaerobic digestion units is stored under a relatively low pressure of about 10 millibars in the semispherical storage tanks 362 and 372. The biomethane contained in the storage tanks 362 and 372 is advantageously conveyed. to the station by a tanker truck 38 running on CNG. For this purpose, the tanker truck 38 is equipped with a 300 bar compressor enabling a substantial portion of the biomethane of the tanks 362 and 372 to be loaded into the tank of the truck 38 for transport to the storage station 34, where the biomethane contained in the tank tank is injected directly into the tanks of the storage station 34.

Claims (10)

REVENDICATIONS1. System for collecting biogas produced by an anaerobic digestion unit (361; 371) located on a farm (36; 37) and purified, characterized in that it comprises: - a purified biogas storage station (34) connected to a natural gas distribution network; and at least one vehicle (38) for conveying said purified biogas from said anaerobic digestion unit (361; 371) to said storage station (34). 2. biogas collection system according to claim 1, characterized in that said vehicle (38) is a tanker truck. 3. biogas collection system according to any one of claims 1 and 2, characterized in that said vehicle (38) is adapted to use said purified biogas as fuel. 4. biogas collection system according to any one of claims 1 to 3, characterized in that it comprises means for compressing said purified biogas at a pressure greater than or equal to 200 bar, equipping said vehicle (38) or said farming (36; 37). 5. biogas collection system according to claim 4, characterized in that said compression means of said purified biogas are able to compress said purified biogas at a pressure substantially equal to 300 bar. 6. biogas collection system according to any one of claims 4 and 5, characterized in that said compression means equipping said vehicle (38) are intended to compress a substantial portion of the biogas produced by said anaerobic digestion unit (361; 371) to transport it to said storage station (34) in a single path. 7. A biogas collection system according to any one of claims 1 to 6, characterized in that the purified biogas is stored in said storage station (34) in a liquid form. 3032777 13 8. biogas collection system according to any one of claims 1 to 6, characterized in that the purified biogas is stored in said storage station (34) in a gaseous form. The biogas collection system according to any one of claims 1-5, characterized in that said biogas storage station (34) is connected to a cogeneration unit (33). 10. Biogas collection system according to any one of claims 1 to 9, characterized in that it comprises means for managing the amount of purified biogas stored in said biogas storage station (34). 10