FR3035598A1 - METHOD AND SYSTEM FOR DIRECT INJECTION OF BIOMETHANE FROM BIOGAS WITHIN A DISTRIBUTION NETWORK. - Google Patents

Abstract

Installation for injecting gas from a renewable source into an injection station in a natural gas distribution and / or transmission network, comprising a main circuit including: a unit for continuously collecting the gas from the renewable source, - a gas purifier mounted downstream of the gas collection unit - a purified gas quality control instrument mounted at the outlet of the purifier to check its compliance with predetermined requirements, - an injection station within the distribution and / or transport network, the controlled gas conforming, mounted downstream of the purifier and the control instrument, a solenoid valve controlled according to the measurements delivered by the instrument of control preventing the introduction of improper gas into the injection station, the plant comprising, upstream of the injection station, a primary deflection circuit of the non-compliant gas within the main circuit to store the gas coming continuously from the collection unit, within the main circuit or in order to reprocess this gas within the main circuit.

Description

TECHNICAL FIELD OF THE INVENTION The technical field of the invention is that of renewable energies, and more particularly, that of injection molding. a purified gas from biogas produced by green waste, within a distribution network and / or gas transport.

Biogas is a gas produced by the fermentation of animal or vegetable organic matter in the absence of oxygen (anaerobic fermentation). A biogas typically comprises from 45% to 70% by volume of methane (CH4), from 30% to 50% by volume of carbon dioxide (CO2), it may also contain nitrogen (N2) as well as traces of other components such as sulphide, siloxane, VOC (volatile organic compound) in particular. It can be collected in landfill sites or obtained through an anaerobic digestion unit. Bio methane is a biogas that has undergone a thorough purification that gives it a composition comparable to that of natural gas, allowing it to be used instead of natural gas, and is also identified as a natural gas substitute. In other words, bio methane (bio methane) is a biogas purified to meet the specifications of the natural gas to which it will be substituted. It is then essentially to have a calorific value sufficient to be at least equivalent to the marketable natural gas to which it is substitutable. The standards vary according to the distribution networks, so the specifications imposed on bio methane can also vary according to the distributed natural gas to which it can be substituted. The purification of biogas in bio-methane essentially consists in eliminating CO2, in order to increase the methane content, but it must be accompanied by the elimination of the harmful elements present in the biogas, among which at least the sulfur-containing compounds. but also the siloxanes as well as the VOCs. Used as a natural gas substitute in distribution networks, bio methane can also be used as a substitute for natural gas to produce hydrogen. State of the art and its disadvantages Today, on a green waste recovery site, the biogas produced by this waste is converted into biomethane by facilities provided for this purpose. A major part of the biomethane produced is used on the site itself to supply energy to the various units of the installation, or other facilities present on the site. A minor or secondary portion of this biomethane is, after purification, odorization, control, counting, and a regulation of its pressure, likely to supply the distribution network and / or natural gas transport. Ideally, this part of biomethane could be introduced directly into the distribution and / or transport network. However, this portion of biomethane should then continuously meet all the quality criteria allowing its introduction into the network while it comes from a biogas source whose quality fluctuates by definition. And as soon as this is not the case, the injection should immediately be stopped in order to prevent its injection into the network. The immediate solution for treating this non-compliant biomethane would be to burn it with dry losses. If, on the contrary, the whole - and not a minor part - of the biogas production were to be devoted to the production of biomethane to be introduced directly into the distribution and / or transport network, these would be considerable quantities. of biomethane, which would then be totally lost. These losses would also become colossal in the particular case of an injection in the transport network since it requires considerable flow rates and pressures.

Thus, it has been retained in the prior art the solution of an indirect introduction of this biomethane. For example, in US Pat. No. 8,404,025, the solution adopted was to compress and store the biomethane produced in pressurized and transportable tanks, which are transported to the natural gas distribution sites, for example by truck, and only to inject it later. This solution thus presents not only an unsatisfactory carbon footprint and indirect injection into the distribution and / or transport network, the biomethane being stored within an intermediate reservoir.

Also, in the method for converting biogas to a renewable natural gas pipeline described in International Application WO 2008097304, the gas treated by the process is subsequently dried and compressed to be introduced into storage tanks.

Thus, in this example also, the injection of the biomethane into the distribution and / or transport network is carried out after having stored it in the tank. DESCRIPTION OF THE INVENTION The purpose of the present invention is to propose an installation capable of injecting biomethane from a biogas source directly into the natural gas distribution and / or transport network even when this biomethane represents a most or all of the biogas production, and is therefore produced in large quantities and with a high flow rate.

In this context, precautions must also be taken, always because of the large quantities or volumes of biomethane produced, when the latter does not fulfill, even at the end of purifier, the specifications authorizing its injection into the network, to avoid that these amounts of purified but non-compliant biomethane are also not released into the ambient air. The invention aims to solve this problem by proposing a facility for injecting gas from a renewable source into an injection station in a natural gas distribution and / or transport network, comprising a main circuit including: - a unit for the continuous collection of gas from the renewable source, - a gas purifier mounted downstream of the gas collection unit - a purified gas quality control instrument mounted at the outlet of the gas collection unit. purifier to verify compliance with predetermined requirements, - a purified gas compressor making it reach a pressure depending on that prevailing in the network into which this gas is injected 3035598 -4- - an injection station within the network of distribution and / or transport, of the controlled and compressed gas, mounted downstream of the purifier and the control instrument, a solenoid valve controlled according to the measurements delivered by the control instrument preventing the introduction of non-compliant gas into the injection station, the plant comprising, upstream of the injection station, a primary deflection circuit of the non-compliant gas comprising a portion of the main circuit excluding the substation; injection, to store the gas continuously from the collection unit, and / or to reprocess this gas within said portion of the main circuit.

The device according to the invention may furthermore have one and / or the other of the following characteristics: the primary deflection circuit of the non-compliant gas comprises a non-compliant gas deflection duct opening into the collection unit or in the scrubber. - The non-compliant gas diversion line further comprises a bypass line to a torch for burning the non-compliant gas and / or to a hydraulic guard for storing this non-compliant gas. The primary deflection circuit of the non-compliant gas comprises a pipe whose inlet is disposed between the purifier and the injection station. a compressor interposed between the purifier and the injection station, the inlet of the primary deflection duct being disposed between the purifier and the compressor or between the compressor and the injection station. - The input of the primary deflection pipe comprises a solenoid valve controlled by the quality control instruments of the gas leaving the purifier. - upstream of the purifier, are disposed a second instrument for analyzing the homogeneity of the gas flow from the collection unit, and a secondary deflection circuit of the non-homogeneous controlled gas by the second instrument, of which the inlet is interposed between the collection unit and the purifier of the main circuit and opening into the deflection circuit. The secondary deflection circuit comprises a secondary purifier. - At the input of the secondary deflection circuit, is disposed a secondary solenoid valve controlled by the second analysis instrument. The solenoid valve is controlled in such a way as to distribute the gas between the main circuit and the secondary deflection circuit in predetermined proportions. Presentation of the Figures Other data, characteristics and advantages of the present invention will appear on reading the description nonlimited which follows, with reference to: - Figure 1 attached schematically shows a biogas treatment injection plant for its introduction into an injection station of a distribution network and / or 1, which schematically represents a second embodiment of the plant according to the invention, and with reference to FIG. 3 illustrates by a graph, a principle of possible distribution of non-compliant gas between a main process circuit and a secondary deflection circuit.

DETAILED DESCRIPTION OF AN EMBODIMENT The invention as represented in FIG. 1 concerns a biogas injection plant 1 from a renewable source, within an injection station 2 in a distribution network. 25 and / or natural gas transport 3. This installation comprises, in a conventional manner, a main circuit has including: - a collection unit 4 of gasometer type 'continuous gas from the renewable source, - a gas scrubber 5 mounted downstream of the gas collection unit 4 - a control instrument or analyzer 6 of the purified gas quality mounted at the outlet of the purifier 5 to verify its compliance with predetermined requirements, - the position of injection 2 of the distribution network and / or transport 3, which allows the introduction of the controlled gas within the network, the injection station 2 being mounted downstream of the purifier 5 and the analyzer 6, a solenoid valve 7 piloted 3035598 -6- by the analyzer 6 preventing the introduction of improper gas into the injection station 2, - possibly, when the pressure in the distribution network and / or gas transport, is greater than that admitted by the gasometer 4 , the main circuit 5 comprises a compressor 8 disposed between the scrubber 5 and the injection station 2. - The various elements above the main circuit are successively connected in pairs by gas circulation pipes.

The quality of the biogas from the gas source does not allow its introduction into the network as such, this quality fluctuating further over time due to the inhomogeneity of the biogas produced by the source as a function of time. The term "biogas quality" means the conformity of its methane, CO2, N2, and other component traces, with predefined specific reference contents for each of its elements (specific biomethane contents). A maximum quality "n" is obtained when the contents of these elements fall within the ranges of values of the specific reference levels or reach specific reference levels. A lower quality "n-2%", "n-10%" ... "ni%" ... representing a range of biogas contents considered 20% i% on average with respect to the ranges of values of the specific contents reference. The aim of the gasometer is to store, by mixing it and thus homogenizing it by volume, a large quantity of biogas, so that at the outlet of the gasometer 4, the fluctuations in quality and flow of the biogas are less than in out of the biogas source. The gasometer 25 will for example be dimensioned in volume as a function of the flow rate of the biogas source, in order to ensure a buffer role of the fluctuation of the quality of the biogas, in order to reduce the output of the gasometer, with respect to the input, the deviations "i" between the contents of the biogas elements with respect to the specific reference levels. Also, the gasometer will be dimensioned to reduce the fluctuation amplitude of these differences between the output and the gasometer inlet. Thus, the gasometer may make it possible to pass from a biogas quality fluctuating between n-30% and n-10% (in arbitrary units) in the biogas coming from the source, to a biogas quality fluctuating between n15% and n -2% (in arbitrary units) in the biogas leaving the gasometer. In an installation of this type, in which the biogas produced by a source is introduced continuously into a circuit connected to the injection station of a distribution and / or transport network, it is necessary to provide different levels of safety to ensure that no molecule of gas that does not meet the requirements of the distribution and / or transport network is introduced. A first essential security level is to have before the entry of the injection station 2, a solenoid valve 7 whose closure will be controlled once the analyzer 6 has detected that the purified gas is in fact not in conformity. Of course, the positioning of the analyzer 6 and the solenoid valve 7 along the main circuit a will be studied (maximized taking into account the maximum flow rate of biogas for example), to ensure that no molecule of gas detected that does not comply with level of the analyzer 6, does not reach the injection station.

According to a first possible option for treating the non-compliant gas, this solenoid valve 7 can then be controlled to direct the non-compliant gas to a torch which will burn it as it is produced. However, this solution is not satisfactory since it leads to wastage at waste losses of the biogas introduced continuously into the main circuit, until the intervention of an operator who would put the circuit back into operation. The solution adopted by the invention is to recirculate this non-compliant gas, not to a unit that would waste it, but partly within the main purification circuit, via a deflection circuit (3. In accordance with FIG. 1, the input of this circuit (3 is arranged between the purifier 5 and the compressor 8 and a three-way solenoid valve VI is disposed at the input of this deflection circuit and on the main circuit A. It is controlled by the analyzer 6 of the quality of the gas leaving the purifier, in "all or nothing" operation that allows the passage of gas to the valve 7 and the injection station via the main circuit when the gas is analyzed in accordance (the valve 7 is then in the open position), and deviates the passage of the gas in the deflection circuit 25 when this is no longer the case, while the valve 7 is in the closed position.The deflection circuit (3 opens preferably at the within the gasometer 4 so that the gas not con form is diluted by the biogas entering the gasometer, and then purified with it in the purifier. The volume represented by the gasometer, the portion of the main circuit extending up to the inlet solenoid valve VI of the deflection circuit (3 and the deflection circuit (3 itself constitute a storage and recirculation volume the "buffer volume." It can be sized according to the maximum flow rate of the biogas source so that the equivalent of a biogas production can be stored for a specified period of time (a few hours, 3035598). a few days, a week, etc.) to treat this non-compliant gas and to delay (or make superfluous) any possible on-site intervention by an operator.An additional diversion conduit pl represented in dashed lines, makes it possible to recirculate the non-compliant gas directly into the scrubber 5.

It can be provided only a redirection of the non-compliant gas within the gasometer or only within the purifier, or on the contrary a distribution of this gas between the gasometer 4 and the purifier 5 by means of a solenoid valve three. The channels (not shown) disposed at the intersection of the two recirculation lines (3 and 31). In addition, still in this primary deflection circuit of the non-compliant gas, it is possible to direct part of this gas not only towards the gasometer 4 and / or the purifier 5 but also to a torch to be burnt, and / or to a hydraulic guard to be stored there.It may ideally be provided, upstream of the purifier 5, a second instrument A2 analysis which will study the homogeneity of the gas flow from the gasometer and the fluctuations of compositions / quality as a function of time, and a secondary circuit of deflection y of the "nonhomogeneous" controlled gas by the second analyzer A2, of which the 'Entrance is interposed between the gasometer 4 and the purifier 5 of the main circuit and opening into the deflection circuit downstream of the solenoid valve V1 controlled by the analyzer 6. This secondary deflection line may comprise a secondary purifier ensuring for example a purification less than the scrubber 5 of the main circuit, such as an activated carbon membrane or the like. A three-way solenoid valve V2, driven according to the measurements delivered by the second analyzer A2, will then be arranged at the intersection of the main circuit a and the secondary diversion line y. This solenoid valve will not necessarily be "all or nothing" but instead able to distribute the gas between the main circuit (to the purifier 5) and the secondary deflection circuit (to possibly purifier 2 or directly to the gasometer) in predetermined proportions. These proportions can be calculated to optimize the main circuit performance by maximizing the circulation time of the biogas within the main circuit and secondary circuit processing portion in the event of degradation of the biogas quality from the reactor. storage unit. This regulation process is illustrated in FIG. 3 in which: The curves in broken lines (quality of the biogas taken by the analyzer A2 between the gasometer and the scrubber E1, opening / closing of the valve V1) are curves obtained. to a decrease in the quality of the biogas at the outlet of the gasometer due, for example, to a decrease in that of the biogas produced by the source, and when the secondary purification loop y, (3 is not used (valve V2 closed) As soon as the quality of the biogas is less than n-10%, the valve V1 is closed to prevent injection into the network.These curves serve as a reference to illustrate the benefit of regulating the quality of biogas. The solid curves (scenario 1) are those obtained in the same context as the curve in broken lines (same profile of decrease of the quality of the biogas coming from the source) Secondary treatment y, (3 is used, with, as explained hereinafter, an efficiency allowing the quality of the biogas at the exit of the gasometer to remain greater than n-10%. The operation of the installation is then not interrupted, the valve V1 is kept open. The dotted line curves (scenario 2) are those obtained in the same context as the curve in broken lines (same profile of decrease of the quality of the biogas coming from the source) when however the secondary loop of purification is used, with 15 this time an efficiency does not prevent the quality of the biogas at the end of the gasometer to fall to n-10%, this moment however being delayed by the duration "Atl" thanks to the purification of the biogas within the secondary loop which This will have made it possible to increase the quantity of biogas injected into the network and to extend the operating time of the installation, as explained below.

Scenario 1: In nominal operation, the main circuit injects on the network a biogas of grade n, corresponding to the highest specifications achievable by the biogas generation process. When the gas quality at the outlet of the storage unit is greater than n-2%, the valve V2 is opened 100% towards the purifier and the valve V1 is opened 100% towards the compressor. When the gas quality decreases and falls below n-2%, the valve V2 will work to reduce the gas flow on the main line and thereby redistribute a portion of the flow in the secondary line to the storage unit. via the E2 scrubber that will treat this biogas. The percentage of opening of V1 and V2 towards the secondary network is inversely proportional to the quality of the gas. In other words, the lower the quality of the gas and the higher the flow to the secondary circuit (the opening percentage of V1 and V2 is regulated for this purpose).

Increasing the flow to the secondary circuit via the valve V2 will allow the scrubber E2 to increase the average gas quality of the secondary line and thus of the storage unit. Reducing the gas flow will increase the scrubbing rate of the exhaust gas El and thus maintain the continuous operation of the installation by guaranteeing continuous quality for variable flow.

5 Reference A: Quality correction by "learning" or "step by step": the opening of the valve V2 is a function of the biogas quality measured by the analyzer A2 and is thus all the higher as this quality is low Low gain: "default" programming Mark B: Quality correction by "anticipation": the opening of the V2 valve follows the 10 directives provided by an abacus to achieve a given quality regardless of the quality measured. The gains are associated with functions corresponding to scenarios of evolution of the quality of the biogas - this in order to correct as quickly / efficiently the quality before injection In scenario 1 illustrated, the action of the regulation of the opening of the valve V2 has allowed the quality of the biogas to remain higher than "n-10%" value at which the valve V1 is programmed to be closed. It will remain open throughout the process. The presence of the secondary circuit or purification loop has made it possible to avoid the closing of the valve V1 and the stoppage of the injection which occurred in the abovementioned reference case (broken line curves). The intervention of an operator is useless.

Scenario 2: In scenario 2 shown, the action of regulating the opening of the valve V2 did not allow the quality of the biogas to remain higher than "n-10%" value at which the valve V1 is programmed to be closed (due for example to a high flow rate or other or a regulation too "cautious"). When the quality of the biogas becomes less than "n-10%", the valve V1 is closed but thanks to the purification allowed by the secondary circuit, this moment is delayed by Atl which allows to increase the quantity of quality biogas greater than "n-10%" injected into the network, and the operating time of the installation, and thus delaying the possible intervention of an operator.

The additional deflection circuits (31, y, and / or the hydraulic guard can be taken into account for the calculation of the buffer volume and therefore for that of the on-site intervention time of an operator following the detection of a Figure 2 shows an alternative embodiment in which the primary deflection circuit (3) originates on the main circuit (a) between the compressor and the injection station, and this secondary deflection circuit (3035598) then comprises a nonconforming and compressed gas expansion valve before redirecting it towards the gasometer 4 and / or the scrubber E1. Another variant of embodiment not shown is in accordance with that of FIG. 2 with however the compressor 8 arranged upstream of the El purifier.

The installation as described above thus has the advantage of not leading to a waste of the biogas produced by the source as soon as the quality of the latter does not comply with the requirements, as is the case when this is flared, but allows on the contrary: a recirculation of this gas in the main processing circuit and in a primary deflection conduit, thus forming a recirculation loop whose internal volume may allow storage of this gas before the intervention of an operator even if "fresh biogas" continues to be injected into the main circuit (creation of a buffer volume), while allowing to continue to purify the gas mixture formed then between the non gas conform and the "fresh biogas" possibly until the mixture is again checked as compliant, and can be injected into the injection station, without requiring any intervention, obtaining pra immediately after the installation has returned to operation with a good quality of gas that can be injected due to the continuous treatment of the gas stored during the time of the stoppage of the injection 20, a start and a restart following an interruption of the facility facilitated and made quicker because of the presence of recirculation loops and gas purification noncompliance that allow to advance in time the possibility of injection of biomethane in the injection station compared to a installation without this type of recirculation loop 25 and non-compliant detected gas treatment.

Claims (10)

REVENDICATIONS1. Installation for injecting gas from a renewable source into an injection station in a natural gas distribution and / or transport network, comprising a main circuit 5 including: a continuous storage unit of the gas from the renewable source; - a gas purifier mounted downstream of the gas collection unit; - a purified gas quality control instrument mounted at the outlet of the purifier to check its compliance with predetermined requirements; A purified gas compressor causing it to reach a pressure that is a function of that prevailing in the network into which this gas is injected; an injection station within the distribution and / or transport network, the compliant and compressed controlled gas, mounted downstream of the purifier and the control instrument, a solenoid valve controlled according to the measurements delivered by the control instrument preventing the introduction of non-compliant gas into the injection station. ecti on, the installation comprising, upstream of the injection station, a primary deflection circuit of the non-compliant gas comprising a portion of the main circuit excluding the injection station, in order to store the gas coming continuously from the unit collection, and / or to reprocess this gas within said portion of the main circuit. 2. Installation according to claim 1, wherein the primary deflection circuit of the non-compliant gas comprises a deflection conduit of the non-compliant gas opening into the collection unit or within the purifier. 25 The plant of claim 2, wherein the non-compliant gas bypass line further comprises a bypass line to a torch for burning off the non-compliant gas and / or to a hydraulic guard for storing this non-compliant gas. 30 4. Installation according to one of the preceding claims, wherein the primary deflection circuit of the non-compliant gas comprises a pipe whose inlet is disposed between the scrubber and the injection station. 5. Installation according to claim 4, comprising a compressor interposed between the scrubber and the injection station, the inlet of the primary deflection conduit being disposed between the scrubber and the compressor. 6. Installation according to claim 4 or 5, wherein the inlet of the primary deflection pipe comprises a solenoid valve controlled by the quality control instruments of the gas leaving the purifier. 7. Installation according to one of the preceding claims, comprising, upstream of the purifier, a second instrument for analyzing the homogeneity of the gas flow from the collection unit, and a secondary deflection circuit of the gas controlled by the second instrument, whose input is interposed between the collection unit and the purifier of the main circuit and opening into the deflection circuit. 8. Installation according to claim 7, wherein the secondary deflection circuit comprises a secondary purifier. 15 9. Installation according to claim 7 or 8, comprising, at the input of the secondary deflection circuit, a solenoid valve controlled by the second analysis instrument. 10. Installation according to claim 9, wherein the solenoid valve is controlled so as to distribute the gas between the main circuit and the secondary deflection circuit in predetermined proportions. 25