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

Abstract

The invention relates to a waste treatment process, the waste comprising biodegradable non-synthetic organic matter and solid impurities, characterized in that the process comprises the following steps: - a) a biological treatment step under anaerobic conditions of the waste, during which fluidized waste is produced; - b) a separation step of the solid impurities from the fluidized waste, during which purified waste is produced. Abstract figure: Fig. 1

Description

Title of the invention: 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, grinding, etc.) 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] Grinding makes the organic matter present in packaging accessible. It can utilize separator grinders (with integrated screen), possibly with the addition of water.

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

[0007] Dilution with water makes the waste stream more fluid and the organic matter more accessible. This allows for better recovery. However, dilution requires significant water consumption and increases the volume of waste streams to be treated in the subsequent stages, thus reducing the profitability of the treatment lines.

[0008] Furthermore, existing anaerobic digestion technologies require a compromise between the concentration of biodegradable organic matter in the stream The treated and the quality of the digestate exiting the digester in liquid form are improved. Indeed, to improve digestate quality, the quantity 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 quantity of biodegradable organic matter in the waste, as some of it is eliminated 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] In order to solve this problem, a waste treatment process is proposed, said waste comprising biodegradable non-synthetic organic matter and solid impurities. The process comprises 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 viscosity of the waste. 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] Preferably, the treated waste produced during step b) is subjected to a methanation step d) in liquid phase during which biogas and digestate are produced.

[0013] Methanization will allow the remaining biodegradable organic matter to be degraded while producing valuable biogas.

[0014] The methanation in step d) is carried out for a longer residence time and up to 5 times longer than the residence time of step a).

[0015] Since the waste has previously undergone fluidization and separation of solid impurities, a less robust enclosure 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 enclosure can be used for step a). However, as This enclosure, for example a plug flow digester, must be robust to treat waste in solid state and therefore expensive; reducing its volume helps to reduce equipment costs.

[0016] Advantageously, part of the digestate exiting step d) is sent to the biological treatment step a).

[0017] Recirculating the digestate has the advantage of increasing the performance of the biological treatment step a).

[0018] First, sending the digestate helps stabilize the pH of the biological treatment step a). Indeed, it is important to control the pH during biological treatment step a) so that it is maintained within a range of slightly acidic to neutral, 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 exiting 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 more efficient conversion of organic matter.

[0019] 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.

[0020] Preferably, step a) of biological treatment includes partial anaerobic digestion.

[0021] Partial anaerobic digestion hydrolyzes biodegradable organic matter, reducing the viscosity of waste.

[0022] Advantageously, prior to the biological treatment step a), said waste is subjected to a pretreatment step c) during which the waste is ground.

[0023] Such prior pretreatment of waste makes it possible to prepare the waste for its treatment such as biological treatment.

[0024] Typically, 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.

[0025] The invention also relates to a waste treatment plant, intended for the treatment of waste comprising non-synthetic organic matter biodegradable and free of solid impurities, and capable of carrying out the process according to any one of the preceding claims. The installation 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 and said separation unit comprising a purified waste outlet.

[0026] The method according to the invention can in particular be implemented by the installation according to the invention.

[0027] Advantageously, 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 connected to the treated waste outlet, and said digester comprising a biogas outlet and a digestate outlet.

[0028] Advantageously, the installation includes a digestate outlet which is connected to a digestate inlet of the biological treatment unit.

[0029] Advantageously, the installation includes a pretreatment unit, said pretreatment unit comprising at least one grinder, a waste inlet and a pretreated waste outlet, said pretreated waste outlet being connected to the waste inlet of the biological treatment enclosure.

[0030] 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

[0031] Definitions / abbreviations

[0032] The dryness percentage represents the mass percentage of dry matter in a raw material.

[0033] Dry matter (denoted DM) includes both suspended solids and dissolved salts. The dry matter content is expressed in g / L of sample and can be determined according to standard NF EN 12880- Nov 2000.

[0034] 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.

[0035] Treated waste

[0036] The waste to be treated by the present invention consists of biowaste.

[0037] This refers to biowaste collected from households, as well as biowaste of commercial or artisanal origin.

[0038] Biowaste from household selective collection has the following characteristics:

[0039] - 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.

[0040] Furthermore, the waste treated by the present invention comprises 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 degraded by microorganisms in an oxygen-free environment, such as in an anaerobic digester.

[0041] Biowaste also includes solid impurities, including synthetic impurities such as plastics.

[0042] Detailed description of the process

[0043] The process according to the invention is a waste treatment process that removes solid impurities it may contain, particularly plastics, while maximizing process efficiency, i.e., the amount of biomethane produced per ton of raw material treated by the process. These advantages are achieved in particular through a biological treatment step followed by a solid impurity separation step.

[0044] Pretreatment step c) - prior to the biological treatment step a)

[0045] Prior to the biological treatment step a), the waste may be subjected at least one pretreatment step c) so as to make biodegradable organic matter more accessible, especially when packaged.

[0046] The pretreatment step c) includes grinding.

[0047] The pretreatment unit may include one or more crushers. These crushers may be separator crushers comprising integrated screens or screening systems to achieve particle size separation of some of the impurities. These crushers may also include a metal removal system to separate and extract ferromagnetic impurities that may be present in the waste.

[0048] The pretreatment step c) 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).

[0049] Advantageously, the pre-treated waste has a particle size of 5 to 80 millimeters.

[0050] At the end of the pretreatment stage, the pretreated waste has a dryness rate between 8 and 50%.

[0051] Biological treatment step a)

[0052] The biological treatment step a) aims to make the waste more fluid or, optionally, the pre-treated waste.

[0053] To achieve this, the biological treatment step a) will hydrolyze a portion of the biodegradable organic matter present in the waste. Hydrolysis will thus modify the rheology of the waste by reducing its viscosity and thereby making it more fluid.

[0054] The biological treatment step a) is carried out in a biological treatment chamber under anaerobic conditions.

[0055] The biological treatment unit may include one or more plug flow reactors or one or more batch reactors.

[0056] The biological treatment enclosure can also be a robust enclosure because the waste contains impurities that can damage it.

[0057] It may include a recirculation of part 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.

[0058] The waste and / or pre-treated waste can 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 any other device for heating waste.

[0059] Step a) is a partial anaerobic digestion step.

[0060] Anaerobic digestion corresponds to a cascade of well-known biochemical reactions enabling 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).

[0061] In other words, partial digestion means that the conditions of the process, in particular the residence time, are such that only a proportion of the organic matter reaches methanogenesis.

[0062] Biogas can be used, possibly after treatment and purification. The remaining material is called digestate.

[0063] Biogas is a gaseous mixture generally saturated with water and typically composed of approximately 50% to 70% by volume of methane (CH4), 30% to 50% by volume of carbon dioxide (CO2), and some trace gases (H2, NH3, N2, H2S, etc.). Biogas is a renewable energy source that can be used for the production of electricity and heat and / or as a fuel.

[0064] If the residence time is short, the biogas produced will consist mainly of hydrogen and carbon dioxide.

[0065] 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 lower than in a more complete anaerobic digestion in which the aim is to optimize biogas production.

[0066] 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.

[0067] 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.

[0068] The residence time can also be reduced from 1 day to 7 days, to carry out only the biological hydrolysis and acidogenesis which are the first reactions of digestion.

[0069] The residence time can be determined and controlled to achieve a target chosen from (i) a rate of hydrolysis of organic matter and / or (ii) a rate of expression of the methanogenic potential and / or (iii) a dryness level. This determination is made based on the applied temperature as well as the characteristics of the waste, such as its hydrolysis kinetics, its nitrogen mineralization potential, and its volatile matter removal potential.

[0070] The temperature of the biological treatment can, moreover, be optimized and additives such as biochar or trace metals can be added to optimize the biological treatment. Trace elements are also called oligos Trace elements are chemical elements present in small quantities in nutrients essential for the development of living organisms. Trace elements are notably chosen from among Iron, Nickel, Cobalt, Molybdenum, Selenium, Tungsten, Zinc, and Tin.

[0071] The digestate may include fermentative bacteria as well as hydrolytic enzymes capable of carrying out fermentation and accelerating the degradation of organic matter.

[0072] Separation step b)

[0073] The separation step b) aims to separate the solid impurities present in said fluidized waste to produce purified waste.

[0074] 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.

[0075] 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.

[0076] Screw press separation (i) is a separation method in which the liquefied waste is compressed between a rotating helical screw and a filter wall. This compression separates a liquid fraction corresponding to the purified waste from a solid fraction containing the impurities. The purified waste thus passes through the filter wall while the impurities remain on the other side.

[0077] Separation by sieving (ii) is a separation in which the liquefied waste passes through a perforated support such as a sieve or a perforated plate, while the solid fraction containing impurities is blocked by the perforated support. This step therefore does not involve membranes that could become clogged and does not use chemical separation aids.

[0078] Separation by sieving (ii) can be implemented using a device selected from a draining table, a sieve, a vibrating sieve, a rotary sieve or an ultrasonic sieve.

[0079] Gravity separations (iii) are mechanisms that allow the separation of so-called "heavy" solid impurities from the remaining liquefied waste by sedimentation and / or so-called "light" solid impurities by flotation. Indeed, some solid impurities such as metals, glass, and pebbles can be denser than the rest of the liquefied waste present, while some plastics are generally less dense than the rest of the waste. They can therefore be separated from the waste using a gravity principle. The gravity separation step (iii) can be implemented in a gravity separation chamber. The gravity separation chamber can include one or more settling tanks and / or flotation chambers and / or one or Several hydrocyclones are used. Some of the solid impurities are then collected at the bottom of the separation chamber (the densest impurities such as stones, pebbles, gravel, glass, metal, etc.) and / or at the top of the chamber on the surface of the waste (the less dense impurities, such as plastics). Generally, at least some of the densest solid impurities are separated before at least some of the less dense solid impurities are separated.

[0080] Centrifugal separation (iv) is a separation that exploits centrifugal force to separate liquefied waste and impurities according to their density.

[0081] Centrifugation is based on the rapid rotation of a container or rotor which will push the dense parts of the fluidized waste towards the outside of the rotor or container while the less dense parts of the fluidized waste remain close to the center of the rotor or container.

[0082] The separation unit then comprises one or more centrifuges.

[0083] Screening separation (v) is a mechanical separation in which fluidized waste passes through a screen or a set of metal bars which retain large impurities while allowing smaller particles to pass through.

[0084] 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. The combination of these separations makes it possible to separate the impurities first and then separate the phases to increase the dryness of the purified waste. Depending on the expected purification performance during the first separation, the second separation could produce a solid fraction that can be directly recovered, for example, by drying or composting.

[0085] 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) so as 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. By way of example, it can be treated by nitrogen stripping.

[0086] Depending on the configuration and quality of the solid fractions obtained, it is advantageous to recirculate them to the biological treatment step a) either to increase the performance of organic recovery in the event of a malfunction in which organic matter is found in the solid fraction, or to introduce microorganisms to accelerate the biological treatment step a).

[0087] If necessary, water can be added to the fluidized waste in the separation chamber so as to further fluidize the fluidized waste and facilitate the separation of impurities.

[0088] Methanization stage d)

[0089] Once separated, the purified waste is subjected to a liquid phase methanation stage to produce digestate and biogas.

[0090] Methanization corresponds to the same biological process as anaerobic digestion. The use of this term emphasizes the final stage of anaerobic digestion that enables 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 methanogenesis. In other words, steps a) and d) together constitute complete anaerobic digestion, enabling the production of biogas.

[0091] Generally, 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.

[0092] The conditions for carrying out this step, in particular the temperature, pH and residence time, can advantageously be chosen in order to maximize biogas production.

[0093] The methanization step d) is typically implemented in a digester.

[0094] For example, the digester can be an enclosure closed by an upper wall, defining two volumes: a first volume containing the purified waste and the digestate generated, and a second volume between the first volume and the upper wall, also called the gaseous head, and towards which the generated biogas rises.

[0095] The digester includes a purified waste inlet connected to the purified waste outlet of the separation chamber.

[0096] Since the treated waste contains virtually no impurities, the digester used can be a less robust digester, which reduces the cost of the enclosure.

[0097] The digester may also consist of a liquid-phase digester treating other organic matter in co-digestion that has not undergone the previous stages, for example, sewage treatment plant sludge.

[0098] Alternatively, the liquid portion recovered by certain separations during step b) may, in addition, be partially or totally sent with the treated waste in step d) of digestion. Before being sent, the treated waste may be treated so as to (i) reduce the concentration of molecules that inhibit anaerobic digestion, such as ammonia, for example, or to (ii) recover molecules that promote the Anaerobic digestion of substances such as organic acids. For example, they can be treated by nitrogen stripping.

[0099] 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.

[0100] 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 be sent to the biological treatment step a).

[0101] The digestate a) can also be sent to the biological treatment stage a). The recirculation rate of the digestate 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 purified waste.

[0102] Recirculating the digestate has the advantage of increasing the performance of the biological treatment step a).

[0103] 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.

[0104] Optional process control

[0105] Optionally, process control is carried out to optimize its yield. For this purpose, several operational parameters can be modified, the parameters possibly differing depending on the process step that one wishes to influence.

[0106] By way of example: - the control parameters of the optional pretreatment step c) can be the feed 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 step a) of biological treatment can 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 for step b) of separation may be the feed rate, the rotation speed if mixing is carried out, or for certain separations, 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.

[0107] To control the process, it is also necessary to monitor one or more monitoring parameters to characterize the process and its execution. These parameters can be monitored continuously or periodically. They are parameters that are commonly used and known to those skilled in the art.

[0108] 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 buffer capacity), ammonia nitrogen, conductivity or microbiological parameters. These biological health parameters can be determined by the SNAC apparatus, 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 volume effective, or dead volume. These parameters are determined on an ad hoc basis 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 is measured 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 a measurement of the current intensity used by the pumping systems to circulate the waste.

[0109] Once the monitoring parameter(s) are determined, the process is controlled based on their values ​​to monitor the operational parameter(s). Depending on the monitored parameter observed, the operator can decide at which stage of the process the operational parameter is controlled.

[0110] 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 waste exiting stages a) and / or d) will allow the control of one or more operational parameters to be determined. of these steps or of step a) and c) so as also to ensure regulatory compliance from a health perspective; 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 an indicator affecting the impurity removal performance. Its evolution can allow for 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

[0111] The invention will be better understood with reference to Figures 1 and 2 representing a waste treatment plant according to two embodiments.

[0112] In the figure, the arrows represent the direction of waste flow within the installation. The waste flows between the different enclosures of the installation via pipes or conveyor belts, depending on the viscosity of the waste entering and exiting the enclosures of the installation.

[0113] With reference to [Fig. 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.

[0114] The waste inlet 3 can be located at any level in the biological treatment enclosure A.

[0115] The biological treatment unit A may include one or more plug flow reactors or one or more batch reactors. The biological treatment unit A is advantageously a robust unit because the waste contains impurities that could damage it.

[0116] The installation then includes a separation unit B for separating impurities from fluidized waste.

[0117] The separation unit B is equipped with a fluidized waste inlet 2 connected to the fluidized waste outlet 4.

[0118] The separation unit B is further equipped with a purified waste outlet 10 and an impurity outlet 14.

[0119] 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 enclosures.

[0120] Figure [Fig. 2] illustrates another embodiment of the invention.

[0121] 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.

[0122] 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.

[0123] The pretreatment unit C may include one or more mills, optionally with water input. These mills may also be separator mills comprising integrated screens to perform separation by particle size. In this case, the pretreatment unit C is equipped with a ground impurity outlet 15.

[0124] Optionally, the pretreatment unit C is equipped with an outlet for a grinding juice 16 which can subsequently be returned to the biological treatment step a) and to the methanation step d).

[0125] The [Fig.2] also differs in that the biological treatment unit A is equipped with a recirculation line 8 for a portion 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.

[0126] Optionally, the biological treatment unit A is equipped with a biogas outlet 17.

[0127] The separation unit B, illustrated in [Fig. 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.

[0128] Equipment B2 is, for its part, 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 enclosure A.

[0129] A water inlet can also be added to the separation unit B (not shown in the figure).

[0130] The installation 1' illustrated in [Fig. 2] further comprises an intermediate treatment unit E for treating the waste so as to (i) reduce the concentration of molecules that inhibit anaerobic digestion, such as ammonia, for example, and / or to (ii) recover value-added molecules, such as organic acids. The intermediate treatment unit E is equipped with a purified waste inlet 19 and a treated purified waste outlet 20.

[0131] The outlet of the treated waste 10 is, in addition, connected to the inlet of the treated waste 21 of the digester D and connected to the biological treatment unit A.

[0132] 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.

[0133] Installation 1' includes a digester D suitable for carrying out anaerobic digestion of treated waste to produce digestate and biogas.

[0134] 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.

[0135] 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.

[0136] Optionally, the installation 1' 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.

[0137] Installation 1' ultimately comprises a post-treatment unit H for the liquid fraction. The post-treatment unit can sterilize or sanitize the liquid fraction. The post-treatment unit can be used for the extraction of molecules of interest and / or the formulation of industrial or agricultural products. The post-treatment can be chemical (in particular, strong acidification or strong alkalinization) or thermal, such as evaporation-concentration and / or thermal drying.

[0138] Optionally, the post-treatment unit H can be installed just after the digester D to treat the digestate.

[0139] 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.

[0140] 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.

[0141] The use of the verb "comprise", "comprendre" or "include" and its conjugated forms does not exclude the presence of other elements or steps than those stated in a claim.

[0142] In the 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, characterized in that said process comprises the following steps: - a) a biological treatment step under anaerobic conditions of said waste during which fluidized waste is produced; - b) a separation step of solid impurities from said fluidized waste during which purified waste is produced.

2. A treatment process according to claim 1, 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.

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

4. Processing method according to any one of claims 1 to 3, characterized in that step a) of biological treatment comprises partial anaerobic digestion.

5. A treatment process according to any one of claims 1 to 4, 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.

6. Processing method according to any one of claims 1 to 5, 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.

7. Waste treatment installation (1, 1') 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, characterized in that said installation comprises: - a biological treatment chamber (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) and said separation unit (B) comprising a purified waste outlet (10).

8. Treatment plant (T) according to claim 7, characterized in that the plant (1') comprises a digester (D) capable of carrying out the anaerobic digestion of the treated waste to produce digestate and biogas, said digester (D) comprising a treated waste inlet (21) which is connected to the treated waste outlet (10), and said digester (D) comprising a biogas outlet (12) and a digestate outlet (13).

9. Treatment plant (T) according to claim 8, characterized in that the plant (1') comprises a digestate outlet (13) which is connected to a digestate inlet (26) of the biological treatment unit (A).

10. Treatment plant (1, 1') according to any one of claims 7 to 9, characterized in that the plant (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).

11. Processing installation (1, 1') according to any one of claims 7 to 10, 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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