FR2912331A1 - METHOD OF EXTRACTING BIOGAS AND DEVICE THEREFOR - Google Patents

Abstract

The invention relates in particular to a method for controlling the extraction of biogas from an enclosure (50) equipped with at least one extraction assembly (31A, 31B) connected to a manifold (70A, 70B) via a control valve (10A, 10B), the method comprising the steps of: - supplying a respective predetermined collector pressure (Pr) to each manifold (70A, 70B), and - opening the control valve (10A, 10B) in a given position.The method is essentially characterized in that it further comprises the steps of: - measuring the value of a weather parameter external to the enclosure, - calculating a global setpoint (dPci) of position of the control valve (10A, 10B) according to the measured meteorological parameter value, and- open the control valve (10A, 10B) in a given position in response to the global setpoint (dPci).

Description

BIOGAS EXTRACTION METHOD AND CORRESPONDING DEVICE.

  The present invention relates to the field of biogas extraction.

  More specifically, according to a first aspect, the invention relates to a method for controlling the extraction of biogas from an enclosure (50) equipped with at least one extraction assembly (31A, 31B), each set of extraction being connected to a respective manifold (70A, 70B) via a respective control valve (10A,: L0B) and comprising at least one unitary extraction device (311A, 312A, 313A, 31B), the method comprising the steps of: - supplying a respective predetermined collector pressure (Pr) to each manifold (70A, 70B), and - opening the control valve (10A, 10B) in a given position. The extraction of biogas depends on internal parameters (type of waste, bacteria, amount of air / oxygen, age of waste), and parameters external to the enclosure. The distribution of production areas within a compound is heterogeneous. It is known to those skilled in the art to be prior art US 6169962. Biogas extraction is controlled well by well. The proposed system includes a sensor measurement device in each wellhead for measuring flow, vacuum, temperature, and O 2 / CH 4 / CO 2 content of the extracted gas. The measurement information is sent to a remote computer which, in return, by reference to a model, controls the respective opening / closing of a pneumatic control valve of each well, the pneumatic control valve allowing to adjust the flow of gas extracts 5 wells per well. However, such a system does not allow to take into account network disturbances or extraction disturbances due to atmospheric disturbances. It is also known to those skilled in the art the prior art document EP 1291093. The biogas extraction method proposed by this patent is based on a measurement of relative pressure between the atmospheric pressure and the pressure. of gas in the waste. The extraction of gas is based on a setpoint, dependent on weather forecasts, so that the setpoint is lowered in advance when weather forecasts provide for a drop in atmospheric pressure. However, such a solution does not allow optimal capture because it depends on a weather forecast, itself having a level of uncertainty more or mo = ins high in value, over time, and in space. The present invention aims to overcome these disadvantages by proposing a solution to capture the biogas optimally, that is to say, the captured flow is equal to the flow rate produced by the waste.

  With this objective in view, the device according to the invention, moreover, in accordance with the preamble cited above, is essentially characterized in that it further comprises the steps of

  measuring the value of a weather parameter external to the enclosure, calculating a global setpoint (dPci) of the position of the control valve (10A, 10B) in

  the value of the meteorological parameter measured, and

  - open the control valve (10A, 10B) in a given position in response to the global setpoint (dPci).

  In one embodiment, the method further comprises the steps of: - providing a first local instruction (dPcil) 15 by comparing the value of (the)

  meteorological parameter (s) measured at a

reference model,

  the step of calculating the global setpoint (dPci) being a function of said first local setpoint (dPcil).

  Thanks to this characteristic, it is possible to anticipate the effects related to climatic conditions on the quantity of biogas to be captured. Preferably, the measured external meteorological parameter is included in the set comprising the pressure

  atmospheric temperature, outdoor temperature and rainfall. In one embodiment, the method further comprises the steps of:

  Measuring the value of a physico-chemical parameter of internal regulation included in the set (content of O 2 / CH 4 / CO 2, temperature, pressure) at the level of at least one extraction unit; comparing the measured value to a reference value, and - to provide a second local instruction (dPci2) as a function of the result of the comparison, --the step of calculating the global setpoint (dPci) being a function of said second local instruction (dPci2).

  Preferably, the reference model is constructed by a preliminary learning step, in which the evolution of the internal pressure in the waste mass is measured as a function of the value of the external parameter (s) and / or internal (s) measured.

  In one embodiment, the method further comprises the steps of: - measuring the relative pressure (dPi) at at least one extraction unit, - comparing the measured relative pressure with a calculated target value ( dPci), and - change the position of the control valve according to the result of the comparison. Thanks to this characteristic, it is possible to anticipate the variations related to the operating conditions on a biogas extraction network. The relative pressure obtained at the extraction system is dependent on the relative pressure value imposed at the manifold by the biogas suction systems. In all cases the pressures (dPi, Pr, Pi) are differential pressure values with respect to the atmospheric pressure. For this reason, the notions of relative pressure and differential pressure will be used indistinctly. The invention also relates, in another of its aspects, to a device for controlling the extraction of biogas, capable of implementing the method according to the invention, the device comprising: an enclosure (50) equipped with at least one respective extraction extraction assembly with a collector (31A, 31B) each connected to a respective control valve (70A, 70B) (10A, 10B) and comprising at least one unitary extraction device (311A, 312A, 313A, 31B), - means for supplying a manifold pressure (Pr) to the respective manifold (70A, 70B), and means for opening the control valve (10A, 10B) in a given position. The device is essentially characterized in that it further comprises: - means for measuring the value of a weather parameter external to the enclosure, means for calculating a global setpoint (dPci) of the position of the control valve (10A, 10B) according to the value of the meteorological parameter measured, and - means for opening the control valve (10A, 10B) in a given position in response to the global setpoint (dPci). 6 2912331

  In one embodiment, the device further comprises - means for providing a first local setpoint (dPcil) by comparing the value of the meteorological parameter (s) measured with a model of reference, the step of calculating the global setpoint (dPci) being a function of said first local setpoint (dPcil). Preferably, the device according to the invention further comprises learning means, configured to measure the evolution of the internal pressure (Pi) as a function of the value of the external weather parameter (s). (s) measured, the reference model being constructed from the learning means. In one embodiment, the device further comprises: means for measuring the value of an internal physico-chemical parameter included in the set (O2 / CH4 / CO2 content) at at least one set of extraction, means for comparing the value. measured at a reference value, and means for supplying a second local setpoint (dPci2) as a function of the result of the comparison, the global setpoint (dPci) being a function of said second local setpoint (dPci2).

  In one embodiment, the device further comprises: means for measuring the differential pressure (dPi) at at least one extraction assembly; means for comparing the measured relative pressure with a value of setpoint (dPci), and - means for effecting a change of position of the control valve according to the result of the comparison. Thanks to the invention, the external (weather) disturbances can be taken into account. However, these external disturbances play a major role in the diffuse emissions, it is possible to extract some more biogas compared to the prior art. Likewise, thanks to the invention the internal disturbances can be compensated. The invention thus makes it possible to damp the variations in biogas production due to external parameters, as well as internal parameters due to the operation of a plurality of networked speakers. Thanks to the invention, it is possible to extract a determined quality of biogas, that is to say a biogas having a determined content of methane in a given range. The maintenance of a predetermined, constant quality makes it possible to optimize the recovery of the extracted biogas, in particular since the valorization systems do not accept significant variations in the methane content. The invention makes it possible to reduce the variations in quality of the biogas associated with atmospheric phenomena. Indeed, when we measure and control only the percentage of methane on a. Well, the resulting depression disturbances are only evaluated a few hours later. Thanks to the invention the depression can be adjusted at each well so that it can be adapted over time depending on the quality of methane and atmospheric variations, i.e. The vacuum applied by the model (dPcil) makes it possible to manage the imbalance associated with the change in atmospheric pressure, the variations in the quality of the biogas being lessened. Other characteristics and advantages of the present invention will emerge more clearly on reading the following description given by way of illustrative and nonlimiting example and with reference to the appended figures in which: FIG. 1 is a representation of an embodiment of the device according to the invention, and - Figure 2 is a block diagram of an embodiment of the method according to the invention. With reference to FIG. 1, the device according to the invention comprises an enclosure 50 equipped with a first assembly 31A of first unitary extraction devices, in this case wells 311A, 312A, 313A, connected to a collector 70A. through a control valve 10A. In addition, the device may comprise at least a second set 31B of second unitary extraction devices, in this case a second well 311B connected to a manifold 70B through a control valve 10B. Each set may therefore comprise a plurality of unitary extraction devices and the device 2912331 may include a plurality of networked assemblies as described later. Each unitary extraction device, hereinafter referred to as a well, comprises a suction head 41A, 42A, 43A, 41B for the collection of biogas within the enclosure 50, and each set comprises a wellhead, respectively 20A and 20B. The control valve 10A, 10B is mounted between the well heads 20A, 20B respectively and the respective primary collectors 70A, 70B. The manifolds 70A, 70B are connected to a main manifold 70 by a suitable pipe network, so that in other embodiments the manifolds 70A, 70B and 70 may be the same. The device comprises means, not shown, such as a constant or variable flow pump, to provide a collector pressure Pr, in the negative case, that is to say a depression dPci, at (x) 20 collector (s) 70A, 70B. The device also comprises means 60, 10 for automatically selectively opening the control valve 10A, 10B respectively in a given position. Preferably, these means comprise control means 60, in this case a computer or an automaton. The control means can directly control the control valve 10A, 10B. They comprise, or are coupled to, regulating means 10. Preferably, the regulating means comprise a first and a second regulator, they are configured to calculate and transmit a global control setpoint dPci of control valve 10A, 10B according to different parameters, as described later. The communication between the control means 60 and the control valve 10A, 10B can be done by any known means, with or without wire, the control means 60 can therefore be arranged remotely. The device according to the invention also comprises meteorological means 90 for measuring the value of at least one meteorological parameter external to the enclosure, in this case a pressure sensor for the atmospheric pressure, a thermometer for the temperature, and A rain gauge for rainfall is provided on the surface, preferably close to the enclosure 50. These meteorological means 90 communicate with the control means 60. The control means 60 advantageously comprise prediction means, in this case a reference model in software form for predicting the evolution of the internal pressure Pi at each extraction set as a function of the value of the meteorological parameter (s) measured. For this purpose, the value of the meteorological parameter (s) measured is compared with the reference model, so as to provide a first setpoint, said local, dPcil, by a regulator R "1 d A first control loop The first control loop is said to be slow in that it takes into account the changes due to the external diurnal / nocturnal conditions, the season, and other atmospheric effects. The constant quality of the extracted biogas as a function of the gas quality set point (ie substantially the methane content included in the biogas) is set by the operator. internal parameter setpoint, in another embodiment it can be the depression dPi, the gas temperature, the content of O2 or CO2, etc. Preferably, the reference model is constructed by a step prior learning. For example, training consists of measuring the evolution of the internal pressure Pi as a function of the meteorological parameter (s) measured. This evolution can be registered as a reference model in the control means 60. The model can be established beforehand, and possibly updated continuously, during the operation of the enclosure. At a given time, the measurement of a given meteorological parameter is compared to its nearest value in the model. The corresponding internal pressure is then estimated by the preliminary learning phase. With the reference model constructed with a learning step, it is possible to perform a step of predicting the evolution of the internal pressure Pi as a function of the meteorological parameter (s) measured, and provide an appropriate local dpci instruction. As a function of this prediction of the evolution of the internal pressure Pi, the control means 60 then issue a position change command of the control valve 10A, 10B. Thus, the detection of an external weather variation makes it possible to anticipate, to predict the variation of biogas production, and thus the internal pressure Pi to a set of wells. 12 2912331 The prediction is linked to the ideal gas law PV = nRT. If the pressure variation is known (measured pressure and temperature), then the variation in the volume of biogas produced in the chamber is known (calculated). In addition, an empirical delay factor, identified in situ, plus porosity coefficients of the medium, etc. allow to determine the variation of pressure on both sides of the control valve. As an illustration, if the atmospheric pressure is constant and the control valve is open, and the membrane is semi-permeable, air is drawn into the chamber and the methane is diluted, which is not not desirable. Thanks to the invention, even if the atmospheric pressure varies, the level of methane extracted from the biogas remains constant. The device according to the invention advantageously also comprises means for measuring the value of a physico-chemical parameter internal to the enclosure included in the set (content of O 2 / CH 4 / CO 2, quality of biogas, pressure , etc.) at at least one well, in this case suitable sensors. Measurements of at least one of the parameters included in the set are preferably made sequentially from one extraction head to another, and periodically. The measured content is compared with a reference value, for example by means of control means 60, which emit a second setpoint dPci2, called local, of a change of position of the control valve 10A, 10B as a function of the result of the comparison. the global setpoint dPci being a function of said second local setpoint dPci2. The second setpoint dPci2 is provided by a regulator R'l of the first regulation loop. Advantageously, the regulating means 10 comprise a feedback loop, linking the value of the comparison and the value of the opening / closing of the control valve, so as to obtain a precise open / close (position) gradual, and not an all-or-nothing opening / closing. In this embodiment, the global setpoint 10 dPci is a function of the two local setpoints dPcil, and dPci2. The first level of regulation therefore preferably comprises two regulators. Thus, the prediction made at the regulator R "1 is corrected by the measurement 15 made at the regulator R'l.This correction makes it possible at the same time to limit the introduction of air into the chamber, therefore of oxygen in the event of an increase in atmospheric pressure, and in the event of a drop in atmospheric pressure, the possible control valve position setpoint is calculated to always be at optimum. the atmospheric disturbances mentioned, the device according to the invention can also undergo internal disturbances In operation, a biogas extraction site is a system comprising a plurality of devices as described and connected to a main manifold 70 by The main collector is connected to means for treating the biogas (recovery, flare, etc.) If for various reasons one of the channels When the network is closed, the (constant) vacuum at the main header is distributed over the other pipes. Depression, therefore the capture flow increases, with the aforementioned risk of introduction of air into the enclosure.

  Thanks to the invention, this risk is eliminated by maintaining a fixed flow rate at each valve, or more accurately a maximum flow rate of biogas by maintaining a constant gas quality. Controlling the control valve position to measure the differential pressure defines a second regulation loop, implemented by a second regulator R2 of the regulation means 10. This second regulation loop makes it possible to configure the device in such a way that optimal for the instantaneous production of methane. It is said to be fast in that it allows adaptation to rapid changes in biogas production. For this purpose, the device according to the invention comprises means for measuring the differential pressure dPi at the level of at least one extraction assembly. The measured relative pressure dPi is compared with a setpoint value dPci and a change of position of the control valve is provided, according to the result of the comparison, by the regulator R1. That is to say that according to the setpoint dPci, the regulator R1 sends a control signal opening / closing of the control valve, defining a depression value to be applied at this valve. Thus, the regulator R1 has as input parameter at least the differential pressure, and possibly the local temperature, on either side of the valve considered, these variables being measured. The regulator 5 R1 has as its setpoint a determined differential pressure value dPci. If the measured differential pressure dPi is different from the setpoint value, the valve position is modified by regulation means 10, to obtain the differential pressure differential. The control means 60 are advantageously used as means for comparing the measured relative pressure with a reference value, and as means for supplying, via the regulating means 10, a first position change command of the control valve 15 in function. of the result of the comparison. Preferably, the setpoint dPci is fixed, predetermined for each of the extraction heads. In addition, this setpoint is advantageously determined as a function of the first control loop. The use of the differential pressure as a control variable makes it possible to eliminate the disturbances related to variations in the depression of the biogas extraction network, such as operating incident, sub-network isolation, change of the mode of operation. extractors. With regard to the external meteorological parameters measured. In one embodiment, the external parameter is the outside temperature, since the temperature influences the biological reactions and thus the biogas production (decrease of activity with a drop in temperature, for example in winter). However, the influence of the temperature remains lower than the influence of the following two parameters (rainfall and pressure). In one embodiment, the external parameter is rainfall. On the surface of an enclosure there is a zone known as a web beat. These zones have a thickness of the order of magnitude of a few meters, typically 4-5 m. Because of their geological situation, these zones are alternately aerobic and anaerobic as a function of rainfall, and therefore unusable for methanogenesis because they are not maintained under strict anaerobic conditions. It is common that these upper layers of the enclosure are clay (clay or other). In case of rain, the clay functions as an impermeable layer, and thus the capture flow can be increased. In the event of a rain storm, for example, there may be a rapid increase (within a few hours) in the quality of the biogas. Thanks to the invention, the thickness of the flapping zone is greatly reduced, or almost nil, by controlling the extraction of biogas. The invention advantageously anticipates the impact of rainfall on the extraction of biogas, since precipitation causes clogging of the clay cover. This favors a reduction of the air inlets and allows the increase of the depression to be supplied in the mass of waste to capture more biogas. In addition, a drought creates 30 cracks in the cover and creates emissive zones. The invention makes it possible to limit the inflow of air into the massive mass of waste, by regulating also the level of oxygen present in the biogas. In one embodiment, the external parameter is the atmospheric pressure. When the atmospheric pressure increases, the volume of biogas produced in the enclosure 50 decreases and the risk of capturing air increases (PV = constant). Conversely, as the atmospheric pressure decreases, the volume of biogas produced in enclosure 50 increases and the risk of leakage of biogas into the atmosphere increases. In addition, if the pressure for capturing Pi is too great, the risk of dilution increases (introduction of atmospheric air into the chamber), and if the pressure 15 Pi is too low, the risk is to increase the pressure in the chamber. the massive waste, thus losing biogas in the atmosphere and inhibiting the reactions of biogas production. The invention optimally captures the biogas, so as to avoid both the introduction of air and a methane emanation. For example, the surface of an enclosure may be of the order of magnitude of the hectare. For a volume of the enclosure of the order of one million m3, an atmospheric pressure variation of 2 mBar / h generates a change in volume of biogas of about 200 m 3 / h, after a certain lag time. (transmission / inertia time of the device). With respect to oxygen, it inhibits methanogenesis. In one embodiment, measurement means can be provided in the extraction heads and a set point relating to the oxygen content at the first regulation level, so that the extracted oxygen does not exceed a certain amount, therefore to maintain a certain quality of the biogas.

  Similarly, one can provide in another embodiment of the measurement means in the waste mass, which reflects a possible air inlet into the chamber. The measured value can then be used in the second control loop.

  Regarding the cover 110 (Figure 1), it is waterproof, or semi-permeable, according to local needs and regulations. Advantageously, a waterproof cover makes it possible to use a larger depression, and therefore to extract more biogas.

  Preferably, the depression of the collector Pr is greater than or equal to the internal depression Pi of the waste mass, which ensures that the methane is not released into the atmosphere. The invention can be implemented in particular according to two modes of operation. In a first mode of exploitation, one aims to valorize the biogas, that is to say to obtain a constant rate of methane in the extracted gas, and to obtain a flow (concentration x flow) maximum.

Advantageously, the extraction of biogas greatly limits the diffusion of methane in the surrounding lands. In a second mode of operation, for the end-of-life sites and including the enclosure or enclosures 30 according to the invention, it is possible to maximize the flow (content * flow) of methane extraction, in particular for safety reasons. , and greenhouse gases, while guaranteeing a minimum methane content necessary for the operation of a flare. Thanks to the invention, the set of control systems (control loops) that anticipate internal / external disturbances makes it possible to maintain a constant quality of biogas over time. Thanks to the invention, the flow of methane extracted from the biogas can be maintained a predetermined value.

Claims (4)

  1. A method for controlling the extraction of biogas from an enclosure (50) equipped with at least one extraction assembly (31A, 31B), each extraction assembly being connected to a respective manifold (70A, 70B) through a respective control valve (10A, 10B) and comprising at least one unitary extraction device (311A, 312A, 313A, 31B), the method comprising the steps of: - providing a manifold pressure predetermined (Pr) respective to each manifold (70A, 70B), and - open the control valve (10A, 10B) in a given position, characterized in that it further comprises the steps of - measuring the value of d a meteorological parameter external to the enclosure, -calculate a global setpoint (dPci) of the position of the control valve (10A, 10B) according to the value of the meteorological parameter measured, and - open the control valve (10A, 10B) in a given position in response to the global instruction (dPci) .   The method according to claim 1, further comprising a step of: - providing a first local instruction (dPcil) by comparing the value of the measured weather parameter (s) with a model reference, the step of calculating the global setpoint (dPci) is a function of said first local setpoint (dPcil).   The method of claim 2, wherein the measured external meteorological parameter is comprised in the set comprising atmospheric pressure, outdoor temperature, and rainfall.   The method according to any one of the preceding claims, further comprising the steps of: - measuring the value of an internal regulation parameter included in the set (content of O2 / CH4 / CO2, pressure, temperature) at at least one extraction unit, comparing the measured value with a reference value, and providing a second local instruction (dPci2) according to the result of the comparison, the step of calculating the global setpoint 20 (dPci) being a function of said second local setpoint (dPci2). 7. A method according to any one of claims 2 to 4, wherein the reference model is constructed by a prior learning step, wherein the evolution of the internal pressure of the waste mass is measured according to the value of external (s) and / or internal (s) parameter (s) measured. The method of any of the preceding claims, further comprising the steps of: - measuring the relative pressure (dPi) at at least one extraction assembly, - comparing the measured relative pressure with a value setpoint (dPci), and - change the position of the control valve according to the result of the comparison. 7. Device for controlling the extraction of biogas, capable of implementing the method according to any one of the preceding claims, the device comprising: an enclosure (50) equipped with at least one extraction assembly (31A , 31B), each extraction assembly being connected to a respective manifold (70A, 70B) via a respective control valve (10A, 10B) and comprising at least one unitary extraction device (311A, 312A). , 313A, 31B), - means for supplying manifold pressure (Pr) to respective manifold (s) (70A, 70B), and - means for opening the check valve (10A, 10B) ) in a given position, characterized in that it further comprises - means for measuring the value of a weather parameter external to the enclosure, - means for calculating a global setpoint (dPci) of the position of the control valve (10A, 10B) as a function of the measured meteorological parameter value, and 30 - means for opening the control valve (10A, 10B) in a given position in response to the global setpoint (dPci). 208. Device according to claim 7, further comprising: means for providing a first local instruction (dPcil) by comparing the value of the meteorological parameter (s) measured with a model of reference, the step of calculating the global setpoint (dPci) being a function of said first local setpoint (dPcil). 9. Device according to claim 8, further comprising learning means, configured to measure the evolution of the internal pressure (Pi) as a function of the value of the external weather parameter (s) (s). ) measured (s), the reference model being constructed from the learning means. 10. Device according to any one of claims 7 to 9, further comprising: - means for measuring the value of an internal physicochemical parameter included in the set (O2 / CH4 / CO2 content) at the level of at least one extraction unit, means for comparing the measured value with a reference value, and means for providing a second local instruction (dPci2) as a function of the result of the comparison, the global instruction (dPci) being a function of said second local instruction (dPci2). 11. Device according to any one of claims 7 to 10, further comprising: - means for measuring the differential pressure (dPi) at at least one extraction assembly, - means for comparing the measured relative pressure to a setpoint (dPci), and - means for effecting a change of position of the control valve according to the result of the comparison.