Method for treating waste, such as biowaste, comprising non-synthetic biodegradable organic matter and solid impurities

Abstract

The invention relates to a method for treating waste, said waste comprising non-synthetic biodegradable organic matter and solid impurities, characterized in that said method comprises the following steps: - a) a step of biological treatment of said waste under anaerobic conditions, during which fluidized waste is produced; - b) a step of separating the solid impurities from said fluidized waste, during which purified waste is produced.

Description

Method for treating waste, such as biowaste, comprising biodegradable non-synthetic organic matter and solid impurities. Field of the invention

[0001] The present invention relates to a method for treating waste, in particular biowaste, comprising biodegradable non-synthetic organic matter and solid impurities. State of the art

[0002] A traditional waste treatment line by decomposition of organic matter under anaerobic conditions includes at least one preliminary waste preparation step (sorting, crushing, ...) followed by a liquid anaerobic digestion step.

[0003] Waste that can be treated by decomposition of organic matter under anaerobic conditions includes, in particular, biowaste from selective collections, pulp from industrial waste deconditioners, and mixtures of urban, agricultural and industrial organic waste.

[0004] The preliminary preparation stage, also called "deconditioning", usually includes the following treatments: - a grinding, - optionally, dilution with water, and - one or more mechanical separations.

[0005] Shredding makes the organic matter present in packaging accessible. It can utilize separator shredders (with integrated screens), possibly with the addition of water.

[0006] Mechanical separation processes remove some of the solid impurities present in waste, such as glass, plastics, and metals. Mechanical separation can involve screening (possibly integrated into the shredder), debarking, aeration, flotation, sedimentation, or centrifugation. The efficiency of the separation varies depending on the quality of the incoming waste.

[0007] Dilution with water helps to thin the waste stream and makes the organic matter more accessible. This organic matter can then be recovered. with better yield. However, dilution requires significant water consumption and an increase in the volume of flows to be treated in the various subsequent stages, which reduces the profitability of the treatment lines.

[0008] Furthermore, existing anaerobic digestion technologies require a trade-off between the concentration of biodegradable organic matter in the treated stream and the quality of the digestate exiting the digester in liquid form. Indeed, to improve digestate quality, the amount of solid impurities present downstream of the digester is reduced by performing one or more mechanical separations. However, these mechanical separations upstream of the digester also lead to a reduction in the amount of biodegradable organic matter in the waste, as some is removed along with the solid impurities.

[0009] The invention aims to remedy at least in part the disadvantages mentioned above, and in particular to propose a waste treatment process that increases the quantity of organic matter treated without degrading the quality of the residual products obtained by the process. Summary of the invention

[0010] To solve this problem, a waste treatment process is proposed, the waste comprising biodegradable non-synthetic organic matter and solid impurities. The process includes the following steps: - a) a biological treatment step under anaerobic conditions of said waste during which fluidized waste is produced; - b) a step of separating solid impurities from said fluidized waste during which purified waste is produced.

[0011] According to the invention, step a) of biological treatment makes the waste more fluid while converting the existing biodegradable organic matter. Indeed, during biological treatment, the biodegradable organic matter is broken down into smaller molecules, resulting in a reduction in the waste's viscosity. This fluidification of the waste thus facilitates the separation of solid impurities in the subsequent step b) while minimizing the loss of organic matter, since some of it will be converted during the biological treatment.

[0012] The purified waste produced during step b) is subjected to a methanation step d) in liquid phase during which biogas and digestate are produced.

[0013] According to an optional embodiment, the methanation step d) is carried out directly after step b). In other words, there is no intermediate step between step b) and the methanation step d).

[0014] Anaerobic digestion allows the remaining biodegradable organic matter to be broken down while producing valuable biogas.

[0015] The methanation in stage d) is carried out for a longer residence time and up to 5 times longer than the residence time in stage a).

[0016] Since the waste has previously undergone fluidization and separation of solid impurities, a less robust containment structure can be used in step d) than in step a). Furthermore, as most of the organic matter decomposition process takes place in step d), a smaller volume containment structure can be used for step a). However, since this containment structure, for example a plug flow digester, must be robust to process waste in solid form and is therefore expensive, reducing its volume reduces equipment costs.

[0017] Advantageously, part of the digestate exiting step d) is sent to the biological treatment step a).

[0018] The recirculation of digestate has the advantage of increasing the performance of the biological treatment stage a).

[0019] First, sending the digestate helps stabilize the pH in biological treatment step a). Indeed, it is important to control the pH during biological treatment step a) to maintain it within a slightly acidic to neutral range, typically between 6 and 8. A pH that is too low can indicate an excessive accumulation of volatile acids, which inhibits methanogenic bacteria and leads to an imbalance in the process. The digestate from step d) is generally alkaline. Thus, by sending the digestate with the waste to be treated in step a), the pH can be stabilized. preventing it from becoming too acidic. This therefore allows for a more efficient conversion of organic matter.

[0020] It should be noted that when there is a temperature difference between step a) and step d), the microorganisms involved in waste conversion are different. However, it has been discovered that, surprisingly, some of these microorganisms can adapt to the temperature difference. Thus, the inventors found that the microorganisms present in the digestate from step d) can also contribute to converting organic matter during step a) of biological treatment and thereby improve its performance.

[0021] Preferably, step a) of biological treatment includes partial anaerobic digestion, said step a) being carried out under operating conditions where only a portion of the hydrolyzed organic matter reaches methanogenesis.

[0022] Thus, partial anaerobic digestion hydrolyzes biodegradable organic matter, reducing the viscosity of waste.

[0023] Advantageously, prior to the biological treatment step a), said waste is subjected to a pretreatment step c) during which the waste is ground.

[0024] Such prior pretreatment of waste allows the waste to be prepared for further treatment, such as biological treatment.

[0025] Typically, separation step b) is chosen from at least (i) screw press separation, (ii) sieving separation, (iii) decantation separation, (iv) centrifugation separation, (v) screening separation and (vi) a combination of one of the preceding separations.

[0026] The invention also relates to a waste treatment plant, designed for the treatment of waste comprising biodegradable non-synthetic organic matter and solid impurities, and capable of implementing the process as described above. The plant comprises: - a biological treatment unit for treating waste under anaerobic conditions and producing fluidized waste, said biological treatment unit comprising a waste inlet and a fluidized waste outlet; - a separation unit for separating solid impurities from said fluidized waste, said separation unit comprising a fluidized waste inlet which is connected to the fluidized waste outlet of said biological treatment unit and said separation unit comprising a purified waste outlet.

[0027] The process according to the invention can in particular be implemented by the installation according to the invention.

[0028] The installation includes a digester capable of implementing anaerobic digestion of the treated waste to produce digestate and biogas, said digester comprising a treated waste inlet which is directly connected to the treated waste outlet of said separation unit, and said digester comprising a biogas outlet and a digestate outlet.

[0029] By directly connected we mean that no waste and / or organic matter treatment device is installed between the outlet of the separation unit and the inlet of the digester.

[0030] Advantageously, the installation includes a digestate outlet which is connected to a digestate inlet of the biological treatment unit.

[0031] Advantageously, the installation includes a pretreatment unit, said pretreatment unit comprising at least one shredder, a waste inlet and a pretreated waste outlet, said pretreated waste outlet being connected to the waste inlet of the biological treatment enclosure.

[0032] Advantageously, the separation unit is chosen from (I) a screw press, (II) a sieve, (III) a decanter, (IV) a centrifuge, (V) a screen and (VI) a combination of the preceding equipment. Detailed description of the invention

[0033] Definitions / Abbreviations

[0034] The dryness percentage represents the mass percentage of dry matter in a raw material.

[0035] Dry matter (DM) includes both suspended solids and dissolved salts. Dry matter content is expressed in g / L of sample and can be determined according to standard NF EN 12880- Nov 2000.

[0036] In what follows, the dryness percentage is expressed as a percentage. The dryness percentage corresponds to the ratio DM / MB of the mass of dry matter (DM) obtained after 24 hours of drying at 105°C to the raw matter (MB), which corresponds to the mass of raw matter before drying at 105°C.

[0037] Waste treated

[0038] The waste to be treated by the present invention consists of biowaste.

[0039] This includes biowaste collected from households, as well as biowaste from commercial or artisanal sources.

[0040] Biodegradable waste from household selective collection has the following characteristics:

[0041] - A dryness rate of 20 to 45%; - Organic matter / dry matter: 60 to 90%; - an undesirable content: from 2 to 10% by weight of the raw material, including solid impurities such as glass, metals, plastics, and textile fibers. Among the undesirable elements, glass represents approximately 5% by weight.

[0042] Furthermore, the waste treated by the present invention includes biodegradable organic matter. Typically, biodegradable organic matter is non-synthetic. The biowaste also exhibits anaerobic biodegradability of at least 50% of the non-synthetic organic matter. In other words, at least half of the natural organic matter present in this waste can be broken down by microorganisms in an oxygen-free environment, such as in an anaerobic digester.

[0043] Biodegradable waste also includes solid impurities, including synthetic impurities such as plastics.

[0044] Detailed description of the process

[0045] The process according to the invention is a waste treatment process that eliminates solid impurities that waste may contain, and in particular plastics, while maximizing the process yield, i.e. the quantity of biomethane produced per gross ton treated by the process. These advantages are obtained in particular through a biological treatment step followed by a step of separation of solid impurities.

[0046] Pretreatment step c) prior to the biological treatment step a)

[0047] Prior to the biological treatment step a), waste may be subjected to at least one pretreatment step c) so as to make biodegradable organic matter more accessible, particularly when packaged.

[0048] The pretreatment step c) involves grinding.

[0049] The pretreatment unit may include one or more crushers. These crushers may be separator crushers with integrated screens or screening systems to separate some of the impurities by particle size. These crushers may also include a metal removal system to separate and extract ferromagnetic impurities that may be present in the waste.

[0050] Step c) of pretreatment is advantageously carried out without the addition of water, which avoids the separation of impurities and part of the organic matter by flotation or sedimentation during the biological treatment step a).

[0051] Advantageously, the pre-treated waste has a particle size of 5 to 80 millimeters.

[0052] At the end of the pretreatment stage, the pretreated waste has a dryness level between 8 and 50%.

[0053] Biological processing step a)

[0054] The biological treatment step a) aims to make the waste, or optionally the pre-treated waste, more fluid.

[0055] To achieve this, the biological treatment step a) will hydrolyze some of the biodegradable organic matter present in the waste. Hydrolysis will thus modify the rheology of the waste by reducing its viscosity and making it more fluid.

[0056] The biological treatment step a) is implemented in a biological treatment chamber under anaerobic conditions.

[0057] The biological treatment unit may include one or more plug flow reactors or one or more batch reactors.

[0058] The biological treatment enclosure can also be a robust enclosure because the waste contains impurities that can damage it.

[0059] It may include recirculating some of the fluidized waste from the outlet to the inlet of the biological treatment unit by mixing it with the waste or pre-treated waste, which allows inoculation of the incoming stream.

[0060] Waste and / or pre-treated waste may also be preheated before the biological treatment step a) so that they have the temperature used during the biological treatment step a). Typically, they are preheated by a heat exchanger or other device capable of heating waste.

[0061] Step a) is a step of partial anaerobic digestion.

[0062] Anaerobic digestion corresponds to a cascade of well-known biochemical reactions that allow microorganisms to convert the organic matter present in a digester into biogas, namely: - hydrolysis, during which large organic molecules (such as proteins, fats, and carbohydrates) are broken down into simpler molecules, such as amino acids, fatty acids, and sugars; - Acidogenesis, which is a fermentation reaction in which simple molecules are converted into volatile fatty acids, alcohol, carbon dioxide, ammonia, and hydrogen by acidogenic bacteria; - Acetogenesis, which is a fermentation reaction in which volatile fatty acids are converted into acetate, hydrogen, and carbon dioxide; and - methanogenesis: during which microorganisms called methanogens transform acetate, hydrogen, and carbon dioxide into methane (CH4) and carbon dioxide (CO2).

[0063] In other words, partial digestion means that the conditions of the process, particularly the residence time, are such that only a proportion of the organic matter reaches methanogenesis.

[0064] In other words, the conditions of the partial anaerobic digestion process do not allow us to ensure that all of the hydrolyzed organic matter is converted into biogas.

[0065] Biogas can be utilized, possibly after treatment and purification. The remaining material is called digestate.

[0066] Biogas is a gaseous mixture generally saturated with water and typically composed of approximately 50% to 70% by volume methane (CH4), 30% to 50% by volume carbon dioxide (CO2), and some trace gases (H2, NH3, N2, H2S, etc.). Biogas is a renewable energy source that can be used for electricity and heat production and / or as a fuel.

[0067] If the residence time is short, the biogas produced will consist mainly of hydrogen and carbon dioxide.

[0068] For step a), anaerobic digestion is carried out at least partially so as to hydrolyze the waste, their residence time in the enclosure is therefore shorter than in a more complete anaerobic digestion where the aim is to optimize biogas production.

[0069] Anaerobic digestion can be carried out at a temperature of 15 to 75°C, and preferably between 25 and 60°C, under psychrotrophic, mesophilic, thermophilic or hyperthermophilic conditions with a residence time of between 3 and 20 days.

[0070] In the case where recirculation of fluidized waste is carried out, the recirculation rate can be between 1 and 300%, that is to say a volume of recirculated fluidized waste which is up to three times greater than the volume of incoming waste.

[0071] The residence time can also be reduced from 1 day to 7 days, to only carry out biological hydrolysis and acidogenesis, which are the first reactions of digestion.

[0072] The residence time can be determined and controlled to achieve a target chosen from (i) a rate of organic matter hydrolysis and / or (ii) a rate of methanogenic potential expression and / or (iii) a dryness level. This determination is based on the applied temperature as well as the characteristics of waste such as their hydrolysis kinetics, their nitrogen mineralization potential and the potential for volatile matter removal.

[0073] The temperature of the biological treatment can also be optimized, and additives such as biochar or trace metals can be added to further enhance the biological process. Trace elements, also known as micronutrients, are chemical elements present in small quantities in nutrients essential for the development of living organisms. These micronutrients include iron, nickel, cobalt, molybdenum, selenium, tungsten, zinc, and tin.

[0074] The digestate may include fermentative bacteria as well as hydrolytic enzymes capable of carrying out fermentation and accelerating the degradation of organic matter.

[0075] Separation step b)

[0076] The separation step b) aims to separate the solid impurities present in the said fluidized waste to produce purified waste.

[0077] The separation step b) is typically implemented in a separation unit equipped with an inlet for fluidized waste and an outlet for the purified waste produced.

[0078] The separation step b) is chosen from at least (i) separation by screw press, (ii) separation by sieving, (iii) separation by decantation, (iv) separation by centrifugation, (v) separation by screening and (vi) a combination of one of the preceding separations.

[0079] Screw press separation (i) is a separation method in which liquefied waste is compressed between a rotating helical screw and a filter wall. This compression separates a liquid fraction, corresponding to the treated waste, from a solid fraction containing impurities. The treated waste passes through the filter wall, while the impurities remain on the other side.

[0080] Separation by sieving (ii) is a separation in which the fluidized waste passes through a perforated support such as a sieve or a The perforated plate traps the solid fraction containing impurities, which is blocked by the perforated support. This step therefore does not use membranes that could clog and does not employ chemical separation aids.

[0081] Separation by sieving (ii) can be carried out using a device selected from a draining table, a sieve, a vibrating sieve, a rotary sieve or an ultrasonic sieve.

[0082] Gravity separation (iii) is a mechanism used to separate heavy solid impurities from the remaining liquefied waste by sedimentation and / or light solid impurities by flotation. Indeed, some solid impurities, such as metals, glass, and pebbles, can be denser than the other liquefied waste present, while some plastics are generally less dense. They can therefore be separated from the waste using a gravity-based principle. The gravity separation stage (iii) can be implemented in a gravity separation chamber. The gravity separation chamber may include one or more settling tanks and / or flotation chambers and / or one or more hydrocyclones. A portion of the solid impurities is then recovered from the bottom of the separation chamber (the densest impurities such as stones, pebbles, gravel, glass, metal, etc.).) and / or at the top of the enclosure on the surface of the waste (the less dense impurities, such as plastics). In general, a separation of at least some of the densest solid impurities is carried out first before a separation of at least some of the less dense solid impurities.

[0083] Centrifugal separation (iv) is a separation that uses centrifugal force to separate liquefied waste and impurities according to their density.

[0084] Centrifugation relies on the rapid rotation of a container or rotor, which pushes the dense parts of the liquefied waste outwards from the rotor or container, while the less dense parts of the liquefied waste remain close to the center of the rotor or container.

[0085] The separation unit then comprises one or more centrifuges.

[0086] Screening separation (v) is a mechanical separation in which fluidized waste passes through a screen or set of metal bars which retain large impurities while allowing smaller particles to pass through.

[0087] The combination (vi) of one of the separations described above may, for example, include separation by screw press or sieving followed by separation by centrifugation of the first purified fraction. Combining these separations allows for the initial separation of impurities and then the separation of phases to increase the dryness of the treated waste. Depending on the expected purification performance during the first separation, the second separation could produce a solid fraction that can be directly utilized, for example, by drying or composting.

[0088] The liquid portion recovered by certain separations can, in addition, be redirected to the biological treatment step (a), or it can be utilized by spreading, for example, or treated in other treatment units. It can also be treated before being directed to step (a) in order to (i) reduce the concentration of molecules that inhibit anaerobic digestion, such as ammonia, for example, or to (ii) recover molecules that promote anaerobic digestion, such as organic acids. For example, it can be treated by nitrogen stripping.

[0089] Depending on the configuration and quality of the solid fractions obtained, it is advantageous to recirculate them to the biological treatment stage a) either to increase the performance of organic recovery in case of malfunction in which organic matter is found in the solid fraction, or to provide microorganisms to accelerate the biological treatment stage a).

[0090] If necessary, water can be added to the fluidized waste in the separation chamber to further fluidize the fluidized waste and facilitate the separation of impurities.

[0091] Methanization stage d)

[0092] Once separated, the purified waste undergoes a liquid phase methanation stage to produce digestate and biogas.

[0093] Anaerobic digestion corresponds to the same biological process as anaerobic digestion. The use of this term emphasizes the final stage of anaerobic digestion, which leads to the production of biogas. Thus, it designates an anaerobic digestion process completed to its conclusion. In other words, the process conditions, particularly the residence time, are such that a high proportion of the organic matter reaches the point of methanogenesis. In other words, steps a) and d) together constitute complete anaerobic digestion, resulting in the production of biogas.

[0094] In general, methanation can be carried out at a temperature of 5 to 60°C, under psychrophilic, mesophilic or thermophilic conditions, preferably from 20 to 60°C. The residence time of step d) can be between 20 and 100 days.

[0095] The conditions for implementing this step, including temperature, pH and residence time, can be advantageously chosen to maximize biogas production.

[0096] The methanation stage d) is typically implemented in a digester.

[0097] For example, the digester can be an enclosure closed by a top wall, defining two volumes: a first volume containing the purified waste and the generated digestate, and a second volume between the first volume and the top wall, also called the gaseous head, and towards which the generated biogas rises.

[0098] The digester includes a treated waste inlet connected to the treated waste outlet of the separation chamber.

[0099] Since the treated waste contains virtually no impurities, the digester used can be a less robust one, which reduces the cost of the enclosure.

[0100] The digester can also consist of a liquid digester treating other organic matter in co-digestion that has not undergone the previous stages, for example sludge from wastewater treatment plants.

[0101] Alternatively, the liquid portion recovered by certain separations in step b) can also be partially or completely sent with the treated waste in digestion step d). Before being sent, the treated waste can be treated to (i) reduce the concentration of molecules that inhibit anaerobic digestion, such as ammonia, or (ii) recover molecules that promote anaerobic digestion, such as organic acids. For example, it can be treated by nitrogen stripping.

[0102] Heat recovery equipment can be used between step b) separation and step d) methanation. The recovered heat can then be used to heat the waste or pre-treated waste before step a) biological treatment.

[0103] The digestate from step d) can be used as fertilizer for spreading or it can be treated by an optional phase separation step or by an additional sanitization or sterilization step. The liquid and solid fractions can be treated with one of the separations proposed in separation step b). Residual impurities can thus be separated in this optional step. The solid or liquid fraction can then be sent to biological treatment step a).

[0104] The digestate a) can also be sent to the biological treatment stage a). The digestate recirculation rate can be between 1 and 300% of the waste treated by the biological treatment stage a), which may or may not be mixed with the recirculation of other streams intended for this purpose such as fluidized waste and / or treated waste.

[0105] The recirculation of digestate has the advantage of increasing the performance of the biological treatment stage a).

[0106] Finally, in the case where an additive such as biochar has been added upstream of step d) of methanization, it will also be sent with the digestate and it may accelerate the growth of microorganisms in step a) and thus improve its performance.

[0107] Optional process control

[0108] Optionally, process control is performed to optimize its yield. To this end, several operational parameters can be modified, with the parameters potentially differing depending on the process step to be influenced.

[0109] For example: - The control parameters of the optional pretreatment step c) may be the feed flow rate, the rotation speed, the particle size and / or any control parameter related to the typology of the specific equipment deployed; - The control parameters of the biological treatment step a) may be the feed flow rate, the withdrawal flow rate, the temperature, the pH, the passage time or residence time depending on the reactor, and the recirculation rate of the treated waste if recirculation is carried out; - the control parameters of step b) of separation may be the feed flow rate, the rotation speed if a mixing is carried out or for certain separations, the particle size and / or any control parameter related to the typology of the specific equipment used; - The control parameters of the optional step d) of methanization can be the feed flow rate, the digestate withdrawal flow rate, the temperature, the pH, the residence time and / or the digestate recirculation rate.

[0110] To control the process, it is also necessary to monitor one or more parameters to characterize the process and its execution. These parameters can be monitored continuously or periodically. They are commonly used parameters known to those skilled in the art.

[0111] The tracking parameter can be chosen from: - the parameter for characterizing the organic matter of waste by measuring the methanogenic potential or the hydrolysis constant. These parameters can be determined periodically in the laboratory, or by measurements made using an IR-SCAN device, as described in document FR3042596; - the biological health parameter of a biological reactor, either by determining the pH, volatile fatty acids, alkalinity, FOS / TAC ratio (ratio between volatile organic acids and buffering capacity), ammonia nitrogen, conductivity, or microbiological parameters. Biological health parameters can be determined by the SNAC device, as described in document FR3047562; - the biogas productivity parameter by determining the flow rate and methane composition of the biogas, whether or not related to the quantity of organic matter treated; - the microbiological parameter of methanation by determining the relative or absolute abundance of microorganisms of interest in the methanation process such as fermentative bacteria or methanogenic archaea. This parameter can be determined by PCR / qPCR which allows the initial quantity of DNA to be measured; - the microbiological parameter of health interest by determining the relative / absolute abundance of pathogenic microorganisms also determined by PCR / qPCR and / or determined by enumeration on a selective culture medium; - the rheological parameter by determining the dry matter content, density, shear stress, absolute viscosity, kinematic viscosity, viscosity profile, yield point, thixotropy, viscoelasticity, or rheological behavior. As a general rule, these parameters are determined on a spot basis in the laboratory or continuously for certain parameters such as dry matter content; - the hydraulic behavior parameter of a reactor by the residence time distribution, the passage time distribution (if it is a plug flow), the effective working volume, or the dead volume. These parameters are determined at specific points by a tracing campaign with the addition of tracer compounds such as lithium salts, and fluorescent molecules or devices such as RFID chips; - the impurity removal performance parameter, measured by the impurity removal rate between the inlet and outlet, or the impurity content of the treated waste or digestate; and / or, - the mechanical performance parameter of the equipment by measuring the torque of the shaft connecting the agitator blades of the reactor in stage a) of biological treatment. This measurement can be taken at the inlet and / or outlet of the shaft. It can also be a measurement of the torque gradient along the shaft or the measurement of the current intensity used by pumping systems to circulate waste.

[0112] Once the monitoring parameter(s) are determined, the process is controlled based on their values ​​to regulate the operational parameter(s). Depending on the observed monitoring parameter, the operator can decide at which stage of the process the operational parameter is controlled.

[0113] For example, if the tracking parameter is: - the organic matter characterization parameter, then step a) of biological treatment and / or step b) of separation will be controlled with one or more of the operational parameters mentioned above; - the biological health parameter monitored in step a) of biological treatment and / or step b) of separation then step a) of biological treatment and / or step b) of separation will be controlled with one or more of the operational parameters mentioned above such as temperature, passage time or residence time, and digestate recirculation rate; - the microbiological parameter of methanization followed in step a) of biological treatment and / or step b) of separation then step a) of biological treatment and / or step b) of separation will be controlled with one or more operational parameters mentioned above such as temperature, passage time and / or residence time and digestate recirculation rate; - the impurity removal performance parameter in step b) of separation or the rheological parameter will allow the control of one or more operational parameters of these steps to be determined; - the hydraulic behavior parameter monitored in step a) and / or step d) will allow the control of one or more operational parameters of this step or of steps a) and c) to be determined in order to ensure regulatory compliance from a health point of view; - the microbiological parameter of sanitary interest for the waste exiting stages a) and / or d) will allow the control of one or more operational parameters of these stages or of stage a) and c) so as also to ensure regulatory compliance from a sanitary point of view; and / or, - The mechanical performance parameter of the equipment provides an indication related to the evolution of rheological parameters and can also be used as indicators affecting the performance of impurity removal. Its evolution can allow an adjustment of the rheology of the treated waste at the outlet of step a) by adjusting the recirculation flow rate of the treated waste. Description of the drawings

[0114] The invention will be better understood with reference to Figures 1 and 2 representing a waste treatment installation according to two embodiments.

[0115] In the figure, the arrows represent the direction of waste flow within the facility. Waste flows between the different enclosures of the facility via pipes or conveyor belts, depending on the viscosity of the waste entering and exiting the enclosures.

[0116] With reference to Figure 1, the treatment installation 1 comprises a biological treatment chamber A connected to a waste inlet 3 and a fluidized waste outlet 4. A pump and / or a valve (not shown in the figure) may be provided to regulate the flow of waste feeding the waste inlet 3.

[0117] Waste inlet 3 can be located at any level within the biological treatment enclosure A.

[0118] Biological treatment unit A may include one or more plug flow reactors or one or more batch reactors. Biological treatment unit A is advantageously a robust unit because the waste contains impurities that could damage it.

[0119] The installation then includes a separation unit B to separate impurities from the fluidized waste.

[0120] Separation unit B is equipped with a fluidized waste inlet 2 connected to the fluidized waste outlet 4.

[0121] The separation unit B is also equipped with a purified waste outlet 10 and an impurity outlet 14.

[0122] The separation unit B can be at least (I) a screw press, (II) a sieve, (III) a decanter, (IV) a centrifuge, (V) a screen or (VI) a combination of the preceding units.

[0123] Figure 2 illustrates another embodiment of the invention.

[0124] It differs from the invention in that, prior to their entry into the biological treatment unit A, the waste is sent to a pretreatment unit C.

[0125] The pretreatment unit C then includes a waste inlet 5 and a pretreated waste outlet 9 which is connected to the waste inlet 3. Optionally, the pretreatment unit C includes a water inlet, if needed, not shown in the figure.

[0126] The pretreatment unit C may include one or more mills, possibly with water input. These mills may also be separator mills incorporating integrated screens to perform particle size separation. In this case, the pretreatment unit C is equipped with a ground impurity outlet 15.

[0127] Optionally, the pretreatment unit C is equipped with a grinding juice outlet 16 which can subsequently be returned to the biological treatment stage a) and to the methanation stage d).

[0128] Figure 2 also differs in that the biological treatment unit A is equipped with a recirculation line 8 for part of the fluidized waste, allowing fluidized waste to be collected from the outlet of fluidized waste 4 of the biological treatment unit A and conveyed to the inlet of waste 3 of the latter.

[0129] Optionally, the biological treatment unit A is equipped with a biogas outlet 17.

[0130] The separation unit B, illustrated in Figure 2, is divided into a combination of two pieces of equipment, B1 and B2. Equipment B1 is equipped with an intermediate outlet 18 connected to equipment B2 for transferring the waste exiting equipment B1. The intermediate outlet 18 includes the waste exiting equipment B1 and can also be connected to digester D. The intermediate outlet 18 can be connected to the biological treatment chamber A.

[0131] Equipment B2, for its part, is equipped with a purified waste outlet 10 which can include the liquid part of the separation implemented in equipment B2 and a purified solid outlet 11 which can be connected to the biological treatment chamber A.

[0132] A water inlet can also be added to the separation unit B (not shown in the figure).

[0133] The installation T illustrated in Figure 2 further includes an intermediate treatment unit E for treating waste in such a way as to (i) reduce the concentration of molecules that inhibit anaerobic digestion, such as ammonia, and / or (ii) recover value-added molecules, such as organic acids. The intermediate treatment unit E is equipped with a treated waste inlet 19 and a treated waste outlet 20.

[0134] The purified waste outlet 10 is also connected to the purified waste inlet 21 of the digester D and connected to the biological treatment unit A.

[0135] A heat recovery unit F is installed between the separation unit B and the intermediate treatment unit E. The heat recovery unit F comprises one or more heat exchangers which absorb heat from the flow circulating in the treated waste outlet 10 and transfer it to the pre-treated waste exiting the pre-treated waste outlet 9.

[0136] Installation T includes a digester D capable of implementing anaerobic digestion of treated waste to produce digestate and biogas.

[0137] The digester D has a purified waste inlet 21 which is connected to the purified waste outlet 10 and it includes a biogas outlet 12 and a digestate outlet 13.

[0138] The digestate outlet 13 can be connected to a digestate inlet 26 of the biological treatment unit A and to a digestate inlet 27 of the separation unit B.

[0139] Optionally, the T installation includes a phase separation unit G equipped with a digestate inlet 28 connected to the digestate outlet 13. The phase separation unit G is also equipped with a liquid fraction outlet 29, a solid fraction outlet 30 and an impurity outlet 31 (Depending on the technology applied, residual impurities can be separated). The solid fraction outlet 30 can be connected to the biological treatment chamber A. The liquid fraction outlet 29 can also be connected to an inlet 35 of the biological treatment chamber A.

[0140] The installation T ultimately includes a post-treatment unit H for the liquid fraction. This post-treatment unit can sterilize or sanitize the liquid fraction. It can also be used for the extraction of molecules of interest and / or the formulation of industrial or agricultural products. The post-treatment can be chemical (particularly strong acidification or alkalization) or thermal, such as evaporation and / or thermal drying.

[0141] Optionally, the post-treatment unit H can be installed just after the digester D to treat the digestate.

[0142] The post-treatment unit H is equipped with a liquid fraction inlet 32 ​​connected to the liquid fraction outlet 29, a treated liquid fraction outlet 33 and an impurity outlet 34.

[0143] Although the invention has been described in connection with several particular embodiments, it is clearly evident that it is by no means limited to them and that it includes all technical equivalents of the means described as well as their combinations if these fall within the scope of the invention, as defined by the claims.

[0144] The use of the verb "comporter", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or other steps than those stated in a claim.

[0145] In claims, any reference sign in parentheses shall not be interpreted as a limitation of the claim.

Claims

DEMANDS

1. A waste treatment process, said waste comprising biodegradable non-synthetic organic matter and solid impurities, said process comprising the following steps: - a) a biological treatment step under anaerobic conditions of said waste during which fluidized waste is produced; - b) a step of separating solid impurities from said fluidized waste during which purified waste is produced; characterized in that said purified waste, produced during step b), is subjected to a methanation step d) in liquid phase during which biogas and digestate are produced, the methanation step d) being carried out directly after the separation step b).

2. Processing method according to claim 1, characterized in that a portion of the digestate exiting step d) is sent to the biological treatment step a).

3. Processing method according to claim 1 or 2, characterized in that step a) of biological treatment comprises partial anaerobic digestion, said step being carried out under operating conditions where only a part of the hydrolyzed organic matter reaches methanogenesis.

4. A treatment process according to any one of claims 1 to 3, characterized in that, prior to the biological treatment step a), said waste is subjected to a pretreatment step c) during which the waste is ground.

5. Processing method according to any one of claims 1 to 4, characterized in that the separation step b) is selected from at least (i) separation by screw press, (ii) separation by sieving, (iii) separation by decantation, (iv) separation by centrifugation, (v) separation by screening and (vi) a combination of one of the preceding separations.

6. Waste treatment installation (1, T) intended for the treatment of waste comprising biodegradable non-synthetic organic matter and solid impurities, and capable of carrying out the process according to any one of the preceding claims, said Installation includes: - a biological treatment unit (A) for treating waste under anaerobic conditions and producing fluidized waste, said biological treatment unit (A) comprising a waste inlet (3) and a fluidized waste outlet (4); - a separation unit (B) for separating solid impurities from said fluidized waste, said separation unit (B) comprising a fluidized waste inlet (2) which is connected to the fluidized waste outlet (4) of said biological treatment unit (A) and said separation unit (B) comprising a purified waste outlet (10); characterized in that the installation (T) comprises a digester (D) capable of carrying out the anaerobic digestion of the purified waste to produce digestate and biogas, said digester (D) comprising a purified waste inlet (21) which is directly connected to the purified waste outlet (10) of said separation unit (B), and said digester (D) comprising a biogas outlet (12) and a digestate outlet (13).

7. Treatment plant (T) according to claim 6, characterized in that the plant (T) comprises a digestate outlet (13) which is connected to a digestate inlet (26) of the biological treatment unit (A).

8. Treatment installation (1, T) according to claim 6 or 7, characterized in that the installation (1') comprises a pretreatment unit (C), said pretreatment unit (C) comprising at least one grinder, a waste inlet (5) and a pretreated waste outlet (9), said pretreated waste outlet (9) being connected to the waste inlet (3) of the biological treatment enclosure (A).

9. Processing installation (1, T) according to any one of claims 6 to 8, characterized in that the separation unit (B) is selected from (I) a screw press, (II) a sieve, (III) a decanter, (IV) a centrifuge, (V) a screen and (VI) a combination of the preceding equipment.

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