Method for separating oily sludge by thermo-mechanical filtration

Abstract

The present invention relates to a method for extracting fatty substances contained in oily sludge, in particular oily sludge from cleaning wastewater works and sanitation networks, comprising the following steps: (a) thermo-mechanically filtering the oily sludge, without any organic solvent, so as to separate the oily sludge into a solid fraction and a liquid fraction, the liquid fraction comprising the fatty substances; (b) collecting the liquid fraction comprising the fatty substances.

Description

[0001] Process for separating fatty sludge by thermomechanical filtration

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a method for extracting fatty substances contained in fatty sludge, in particular in the cleaning sludge from wastewater treatment works and networks.

[0004] TECHNOLOGICAL BACKGROUND

[0005] The drastic increase in the amount of greenhouse gases in our atmosphere is resulting in global warming of our planet. Reducing the carbon footprint of human activity in general (transport, energy production, industry) is a priority for the scientific community and the socio-economic world as a whole.

[0006] Improving the carbon lifecycle by recycling industrial carbon into a reusable product is of prime importance. This will prevent CO2 emissions into the atmosphere during waste incineration and will replace the use of environmentally harmful fossil carbon.

[0007] From an energy production perspective, the establishment of a virtuous "mix" including renewable energies, nuclear power, and hydrogen is essential. This will contribute positively to achieving the 2050 decarbonization objectives and, consequently, to maintaining global temperatures below +1.5 degrees above pre-industrial levels, set by the Paris Agreement of December 12, 2015.

[0008] The use of non-fossil and renewable carbon, derived from the recycling of industrial waste and / or biomass, to power energy, chemicals, transport and pharmaceuticals will help achieve the net zero carbon emissions targets planned for 2050.

[0009] Liquid biofuels such as first-generation biodiesel are mainly derived from vegetable oils from oilseed plants such as rapeseed, sunflower, wheat, soybean, and oil palm, which are mainly composed of a mixture of triglycerides of fatty organic acids. Ranges of biodiesels have been developed from these oils, notably by transforming them into fatty acid methyl and ethyl esters (FAME and EEAG). These biodiesels are contained at a rate of 7 to 10% in commercial diesel fuels (B7 and B10). More recently, vegetable oils as well as hydrotreated fatty acid esters (HVO and HEFA), which are more stable and 100% substitutable for petrodiesel, without impact on engines ("drop-in" fuels), are produced in the latest generation of biorefineries.These HVO and HEFA exhibit better stability over time and at high and low temperatures, and are further tested for the design of new sustainable jet fuels.

[0010] The disadvantages of using raw materials from agriculture are, on the one hand, direct competition with human and animal food and, on the other, a concern for the preservation of agricultural land. Today, only 6% of the global biodiesel market is supplied by the use of fats other than those from agriculture. These so-called "second-generation" biofuels are derived from various waste products (animal oil, agricultural waste, used frying oil) and constitute one of the components of the virtuous energy "mix", provided they are produced locally.

[0011] Alternatives based on renewable and local waste are therefore being sought to produce these biofuels. Furthermore, since the global resource of fossil and agricultural carbon is limited, obtaining bio-sourced carbon from waste recycling is an ecological, economic, and societal challenge. The use of this source of recycled and / or bio-sourced carbon cannot be limited to second-generation biofuels, but rather to the supply of renewable carbon as a whole for the production of biofuels, lubricants, solvents, synthons for chemistry, waxes, etc.

[0012] Thus, a need remains for the provision of a process for accessing fatty acids and their derivatives that can be used for the preparation of fatty acid esters, hydrotreated fatty acid esters (HEFAs) or for the aforementioned applications from a new local source of renewable waste. Advantageously, the proposed process should be simple to implement, respectful of the environment and human health and inexpensive in terms of energy and raw materials.

[0013] BRIEF DESCRIPTION OF THE INVENTION

[0014] The present invention relates to a method for extracting fatty substances contained in fatty sludge, in particular sludge from cleaning works and sanitation networks. It comprises the following steps:

[0015] (a) thermo-mechanical filtration of the fatty sludge, in the absence of organic solvent, so as to separate the fatty sludge into a solid fraction and a liquid fraction, the liquid fraction comprising the fatty substances; (b) collection of the liquid fraction comprising the fatty substances.

[0016] Other aspects of the invention are as described in the claims and hereinafter.

[0017] FIGURES

[0018] Figure 1 illustrates an example of a thermo-mechanical filtration device (1) for implementing the method of the present invention.

[0019] Figure 2 illustrates an example of a thermo-mechanical filtration device (1) for implementing the method of the present invention as well as its heating system in the form of a steam generator.

[0020] DETAILED DESCRIPTION OF THE INVENTION

[0021] The proposed process meets the expressed needs. The proposed process makes it possible to extract the fatty substances contained in greasy sludge, particularly in the sewage sludge from sanitation structures and networks, at a lower cost. Furthermore, the proposed process is environmentally friendly because it does not require the use of organic solvents. In addition, the process can be applied in discontinuous mode (commonly referred to as "batch") or can be adapted to continuous operation. Finally, the process is easily industrializable: scaling up is possible through the use of correctly sized equipment.

[0022] The proposed process for extracting fatty substances contained in greasy sludge, particularly in sewage system cleaning sludge, comprises the following steps:

[0023] (a) thermo-mechanical filtration of the fatty sludge, in the absence of organic solvent, so as to separate the fatty sludge into a solid fraction and a liquid fraction, typically two-phase, the liquid fraction comprising the fatty substances;

[0024] (b) collection of the liquid fraction comprising the fatty substances.

[0025] The term "thermo-mechanical filtration" refers to filtration carried out by the supply of thermal and mechanical energy. The thermal and mechanical energy are supplied concomitantly (i.e., not sequentially). The conditions for implementing thermo-mechanical filtration and examples of thermo-mechanical filtration are as described in detail below. Fatty sludge

[0026] The term "greasy sludge" refers to sludge rich in fatty substances (greasy waste) resulting from human activities (e.g. industrial installations, food processing, catering, sanitation networks, etc.). Greasy sludge is made up of liquid (water and oily organic matter) and solid matter (organic matter, mineral matter or their mixtures). Greasy sludge generally has a dryness rate (% by weight of dry matter relative to the total weight of greasy sludge) greater than 5%, typically ranging from 5% to 98%. Greasy sludge generally has a content of hexane extractable substances of at least 5% by weight relative to the total weight of greasy sludge. Hexane extractable substances refer to fatty substances.

[0027] The term "fatty substances" means: fatty acids from biomass as well as triglycerides and their corresponding partially hydrolyzed derivatives (di- and mono-glycerides); or a mixture of hydrocarbons (for example from an industrial activity); or a mixture of these two categories.

[0028] Fats can be in the form of a solid or liquid mixture or a heterogeneous solid-liquid mixture. The constituents of fats (fatty acids, triglycerides and their partially hydrolyzed derivatives or a mixture of hydrocarbons) depend on the origin of the fatty sludge.

[0029] Typically, the greasy sludge used is sludge from sewerage networks, sludge collected from grease traps in wastewater treatment plants (WWTP), machining or grinding sludge, refinery sludge pellets, rolling mill sludge, sludge from ship bilges or sludge from grease pits or grease traps, in particular grease traps leaving central kitchens and food industries. Preferably, the greasy sludge is sludge from sewerage networks or sludge from grease traps leaving central kitchens and food industries. The role of the sewerage networks, located upstream of urban wastewater treatment plants, is to convey domestic wastewater, effluent from communities and / or industries, and periodically rainwater to these treatment plants.These waters and effluents are loaded with fats mainly resulting from human consumption of lipids, particularly through food and cooking (domestic and catering). These lipids, originally triglycerides of fatty acids from edible oils (olive, rapeseed, sunflower, palm, and peanut) and animal fats, are, from partially to completely, hydrolyzed into fatty acids via digestion on the one hand and natural hydrolysis generated by the mixing of materials in the effluent path in contact with water, air and time spent in the networks. These fats accumulate in the form of a surface crust in grease traps or agglomerate and clog the pipes and, in particular, the pumping stations of these networks, requiring operators to periodically clean the networks and these various stations upstream of urban treatment plants.

[0030] Sewage sludge from sanitation works and networks refers to the sludge collected during the cleaning and pumping operations of sanitation works and pipes, i.e. the sludge collected upstream of wastewater treatment plants (WWTP). This may include sludge collected at pumping stations (PLP), in pipes as well as in various structures: pits and grease traps, particularly at the outlet of kitchens, meat cutting workshops, slaughterhouses and other agri-food activities generating fats (dairies, cheese factories, bakeries, etc.). This sewage sludge, rich in fats, is currently little recovered: it is typically either incinerated (co-generation), or mixed with other waste and methanized or lyophilized then spread. Sewage sludge typically has a dryness rate ranging from 5 to 10%.

[0031] Thermo-mechanical filtration of fatty sludge

[0032] Thermomechanical filtration of greasy sludge allows the separation of greasy sludge into a solid fraction and a liquid fraction.

[0033] Thermomechanical sludge filtration is typically carried out at high temperature, i.e. carried out at a temperature ranging from 50 to 150°C, preferably from 60 to 120°C or from 85 to 100°C, even more preferably around 95°C.

[0034] In some embodiments, the thermomechanical filtration is carried out at atmospheric pressure at a temperature ranging from 50 to 150°C, preferably from 60 to 120°C or from 85 to 100°C, even more preferably around 95°C. Such temperatures will be achieved by any suitable heating means.

[0035] Most preferably, the thermomechanical filtration is carried out at atmospheric pressure at a temperature of, or close to, 100°C. In such embodiments, the thermomechanical filtration includes the diffusion of water vapor within the fatty sludge. In other words, the thermomechanical filtration includes a thermal input by diffusion of water vapor within the fatty sludge. The water vapor, diffusing within the sludge, would break the emulsion and allow the separation / release of the liquid fraction (comprising the fatty substances) from the solid fraction, and this particularly when the water vapor is combined with the input of mechanical energy in the form of agitation / stirring, for example slow stirring of the materials by mechanical energy.

[0036] Thermomechanical filtration is typically carried out in a heating chamber. The mechanical energy input during thermomechanical filtration typically takes the form of stirring / agitation of the sludge.

[0037] Thermomechanical filtration, in particular the supply of mechanical energy, can be implemented by vibration of a filter grid on which the sludge rests, by mixing the sludge placed on a filter grid or by means of a device as described in detail in the section "Specific embodiment". In this last embodiment, the mixing can be carried out by slow rotation of a cylinder (see below).

[0038] The sludge is therefore typically agitated during thermomechanical filtration (by stirring, agitation). Agitation / stirring particularly helps to establish good contact between the sludge and the water vapor. The mechanical energy helps to aerate the sludge and prevents its compression, which is not desired in the context of the present invention.

[0039] In some embodiments, the thermomechanical filtration includes a thermal input by diffusion of water vapor within the fatty sludge and a mechanical energy input by mixing the fatty sludge.

[0040] For energy saving reasons, the sludge subjected to the thermomechanical filtration step may be partially dehydrated beforehand, for example to achieve a dryness level greater than or equal to 30%, preferably greater than 40%, even more preferably greater than or equal to 50%, or even greater than or equal to 70%. The sludge subjected to the thermomechanical filtration step then has a dryness greater than that of the sludge from the collection, i.e. a dryness greater than that of the sludge collected at the collection point. In other words, the sludge subjected to the thermomechanical filtration step has a water content lower than that of the sludge collected at the collection point.

[0041] Thus, in certain embodiments, before the thermo-mechanical filtration step, the sludge may have undergone or may undergo a thickening and / or dehydration step aimed at removing part of the water contained therein. The removal of part of the water may be carried out according to conventional methods known to those skilled in the art such as thickening by gravity or dynamic settling, cold gravity drainage, centrifugation, pressing for example by means of a screw press or by cold filtration or the combination of these methods. For example, the removal of part of the water may be carried out by means of the device allowing thermo-mechanical filtration without input of thermal energy, i.e. at ambient temperature (20 - 25 °C).

[0042] Thus, in certain embodiments, the method of the present invention has, before the thermo-mechanical filtration step, a step of partial dehydration of the sludge, preferably so as to produce sludge having a dryness level greater than or equal to 30%, preferably greater than 40%, even more preferably greater than or equal to 50%, or even greater than or equal to 70%. Such a step is particularly implemented when the fatty sludge is sewage sludge, the sewage sludge having a low dryness.

[0043] It should be noted that before being subjected to the possible partial dehydration stage and the thermo-mechanical filtration stage, the sludge may have previously undergone one or more pre-treatments intended to make the process more efficient. The sludge may be screened to eliminate large solid waste, acidified and / or oxidized as a pre-treatment to "break" the soaps present or even pre-heated to facilitate their transfer.

[0044] Collection of the liquid fraction

[0045] Thermomechanical sludge filtration separates the sludge into a solid fraction and a liquid fraction; the liquid fraction is typically two-phase. The liquid fraction includes fatty substances. The liquid fraction is collected. The process may further include a step of drying the collected liquid fraction.

[0046] It will be easily understood that depending on the water / dryness content of the sludge subjected to the thermomechanical filtration step and / or depending on the heating means (e.g.: water vapor introduced into the heating chamber as detailed below), the liquid fraction may be two-phase. The two-phase liquid fraction then consists of an aqueous phase and an organic phase comprising the fatty substances. The aqueous phase and the organic phase of the two-phase liquid fraction are collected and separated. The separation may be carried out by decanting the collected two-phase liquid fraction followed by separation of the two phases. The addition of salts may be considered to facilitate decantation. Any other method of separating an aqueous and organic phase known to those skilled in the art may be used (centrifugation, overflow, etc.). In certain embodiments, the organic phase may be withdrawn continuously.

[0047] The process may further comprise a step of drying and / or filtering the organic phase.

[0048] In some embodiments, the method may be carried out in continuous mode, for example via the use of a "conveyor belt" or a conveyor tunnel conveying the sludge from a dewatering stage, for example dewatering, to the thermo-mechanical filtration stage.

[0049] The process of the present invention makes it possible to achieve mass extraction yields of fatty substances of the order of 20 to 85% or 20 to 50% relative to the initial mass of fatty sludge, i.e. at the inlet of the thermo-mechanical filtration process.

[0050] Special embodiment

[0051] The method for extracting fatty substances contained in fatty sludge, in particular in sewage sludge, can be implemented in a thermomechanical filtration device. The thermomechanical filtration device can be as shown in Figure 1. The thermomechanical filtration device (1) comprises: a heating enclosure (2); a static collector (3) arranged inside the heating enclosure (2); a perforated cylinder (4) arranged inside the static collector (3), the perforated cylinder being configured to receive the sludge, in particular sewage sludge, and to be driven in rotation; the static collector (3) being configured to receive a liquid (or liquids) ejected from the perforated cylinder during rotation of the perforated cylinder (4).

[0052] The extraction process then includes the following steps:

[0053] (a') introduction of fatty sludge, in particular cleaning sludge, into the perforated cylinder (4);

[0054] (b') thermo-mechanical filtration of the fatty sludge at a temperature ranging from 50 to 150°C by rotating the perforated cylinder (4); and

[0055] (c') collection of a liquid fraction, typically two-phase, ejected from the perforated cylinder into the static collector (3).

[0056] The heating enclosure (2) may incorporate heating elements (e.g. circulation of a heat transfer fluid in a double jacket or the presence of an electrical resistor) or be configured to allow the introduction of heat, for example to allow the introduction of water vapor and maintain the required temperature. Preferably, the heating enclosure comprises means allowing the introduction of water vapor into the enclosure and preferably means for maintaining a temperature of or close to 100°C. The introduction of water vapor may be carried out continuously. The heating enclosure may be thermostatically controlled.

[0057] The static collector (3) shown in Figure 1 is cylindrical in shape. Those skilled in the art will recognize that it can be of any suitable shape. The static collector is intended to receive liquids, it is therefore made of a material suitable for collecting liquids (e.g. any fatty substance and water). In certain embodiments, the static collector is made of glass.

[0058] The perforated cylinder (4) is configured to receive the sludge and to be driven in rotation. It is therefore a rotating perforated cylinder. In certain embodiments the perforated cylinder is suspended from a rotation shaft (5). In certain embodiments, a collection volume is present under the perforated cylinder.

[0059] The rotating perforated cylinder is made of a material suitable for containing greasy sludge, particularly sewage sludge. In some embodiments, the rotating perforated cylinder is made of steel.

[0060] The holes (7) of the rotating perforated cylinder (4) are configured to allow the ejection of liquids during the rotation of the rotating perforated cylinder (e.g.: any fatty substance and water) and to retain solid matter.

[0061] The diameter of the holes generally varies from 1 pm to 1000 pm, preferably from 1 pm to 500 pm or from 5 pm to 500 pm or from 10 pm to 500 pm, or from 5 pm to 300 pm or from 10 pm to 300 pm or from 50 pm to 300 pm or from 10 pm to 100 pm. Such diameters make it possible to retain the solid materials within the perforated cylinder and to allow only the liquid fraction, typically two-phase, to pass through.

[0062] In some embodiments, the holed cylinder is a perforated cylinder. In other embodiments, the holed cylinder is made of metal micromeshes (e.g., metal micromeshes with a passage size of 1 μm to 1000 μm, preferably 1 μm to 500 μm or 5 μm to 500 μm or 10 μm to 500 μm, or 5 μm to 300 μm or 10 μm to 300 μm or 50 μm to 300 μm or 10 μm to 100 μm).

[0063] In some embodiments, the diameter of the holes in the cylinder may be greater than the diameters previously described. Indeed, in some embodiments, the rotating perforated cylinder may be lined, preferably internally, with a microperforated membrane. The holes / perforations in the microperforated membrane typically have a diameter ranging from 1 μm to 1000 μm, or preferably from 1 μm to 500 μm or from 5 μm to 500 μm or from 10 μm to 500 μm, or from 5 μm to 300 μm or from 10 μm to 300 μm or from 50 μm to 300 μm or from 10 μm to 100 μm. The use of a microperforated membrane therefore makes it possible to consider the use of a rotating perforated cylinder whose holes have a diameter greater than 1 mm (typically up to several mm, for example from 1 to 5 mm). The microperforated membrane can be a polypropylene, nylon or PTFE membrane.

[0064] In some embodiments, the microperforated membrane only allows hydrophobic substances to pass through.

[0065] In this particular embodiment implementing a thermo-mechanical filtration device as shown in figure 1, the fatty sludge, in particular the cleaning sludge, is introduced into the rotating perforated cylinder.

[0066] As indicated above, the greasy sludge may have previously undergone one or more pre-treatments intended to make the process more efficient. The sludge may be screened to remove large solid waste, acidified and / or oxidized as a pre-treatment to "break" the soaps present, or pre-heated to facilitate their transfer.

[0067] In particular, before introduction into the cylinder, the fatty sludge may have been dehydrated, for example according to one of the methods described above, to remove part of the water contained therein. In certain embodiments, the partial dehydration of the fatty sludge may be carried out within the present device before implementing the thermomechanical filtration. The dehydration is then carried out by filtration at ambient temperature, that is to say by rotating the perforated cylinder without inputting thermal energy. The filtration at ambient temperature is typically carried out at a rotation speed of the perforated cylinder ranging from 30 to 1000 rpm, preferably ranging from 200 to 500 rpm. The filtration at ambient temperature is typically carried out for a period ranging from 5 to 30 minutes, preferably ranging from 5 to 10 minutes. The filtration at ambient temperature is typically carried out at atmospheric pressure.Water extracted from the sludge during filtration at room temperature and collected in the static collector can be removed before implementing thermomechanical filtration.

[0068] The thermomechanical filtration is typically carried out at a temperature ranging from 50 to 150°C, preferably ranging from 60 to 120°C, preferably ranging from 85 to 100°C, even more preferably around 95°C. A temperature of 50 to 150°C can be reached by means of a heat transfer liquid, typically an oil, circulating in a double jacket of the heating enclosure, by means of an electrical resistance or by means of the introduction of water vapor into the heating enclosure (2). Preferably, the temperature ranging from 50 to 150°C in the heating enclosure is reached by introducing water vapor therein. In some embodiments, the thermomechanical filtration is carried out at atmospheric pressure at a temperature ranging from 50 to 150°C, preferably from 60 to 120°C or from 85 to 100°C, even more preferably around 95°C.

[0069] In certain particularly preferred embodiments, the thermomechanical filtration is carried out at atmospheric pressure at a temperature of, or close to, 100°C. The thermomechanical filtration, more precisely the heat input, is then carried out by diffusion of water vapor within the fatty sludge in the cylinder. The water vapor diffusing within the sludge would break the emulsion and allow the separation / release of the liquid fraction (comprising the fatty substances) from the solid fraction.

[0070] The thermomechanical filtration is carried out by rotating the perforated cylinder (4). The thermomechanical filtration is typically carried out at a rotation speed of the cylinder ranging from 30 to 1000 rpm or from 30 to 500 rpm, preferably ranging from 200 to 500 rpm or from 200 to 300 rpm. The rotation speed is therefore significantly lower than that used during centrifugation. The thermomechanical filtration is typically carried out for a period ranging from a few minutes (for example ranging from 5 minutes, or 10 minutes, or 20 minutes, or 30 minutes) to 120 minutes, preferably ranging from 45 to 75 min. In continuous embodiments, the thermomechanical filtration is typically carried out for short times, for example for a period of a few minutes, for example 5 minutes.Typically, thermomechanical filtration is carried out at a cylinder rotation speed ranging from 30 to 1000 rpm, preferably ranging from 200 to 500 rpm, for a duration ranging from a few minutes (for example ranging from 5 minutes, or 10 minutes, or 20 minutes, or 30 minutes) to 120 minutes, preferably ranging from 45 to 75 min.

[0071] Thermomechanical filtration is typically performed at atmospheric pressure.

[0072] The liquid ejected during rotation of the perforated cylinder (4) during thermomechanical filtration is collected in the static collector (3). This liquid includes the fatty substances. In certain embodiments, the liquid containing the fatty substances collected in the static collector can be continuously withdrawn. In certain embodiments, the liquid fraction can be dried.

[0073] As indicated previously, depending on the water content of the sludge subjected to the thermomechanical filtration step and / or depending on the heating means (e.g.: water vapor introduced into the heating chamber), the liquid is possibly a two-phase liquid comprising an aqueous phase and an organic phase comprising the fatty substances. Thus, the fatty substances and the water contained in the sludge, in particular in the cleaning sludge, and extracted by thermomechanical filtration are collected hot in the static collector (3).

[0074] The static collector (3) may also contain water from filtration at room temperature if this step has been implemented and if the extracted and collected water has not been eliminated.

[0075] In some embodiments, the aqueous phase collected in the static collector may be continuously withdrawn.

[0076] In some embodiments, the aqueous phase and the organic phase containing the fatty substances collected in the static collector can be continuously withdrawn.

[0077] When the liquid fraction is two-phase, the method implemented in this device typically comprises a step (d') of decanting the two-phase liquid collected in step (c') and separating the phases to isolate the organic phase. The organic phase containing the fatty substances is collected. The method may further comprise a step of drying and / or filtering the organic phase.

[0078] In this particular embodiment, mass extraction yields of fatty substances of the order of 20 to 75% or 20 to 50% relative to the initial fatty sludge mass can be obtained.

[0079] In this particular embodiment, the proposed process can be implemented in batch or continuous mode. For example, the use of a filtering (vibrating) conveyor belt or a conveyor tunnel conveying the sludge through a heated enclosure equipped with a collection gutter allows for continuous collection of the liquid, allowing the process to be implemented continuously.

[0080] Valorization of collected fats

[0081] The collected fats consist of an acidic oil (AI generally between 160 and 200 mg KOH / g). This oil, which can be solid, liquid and / or a heterogeneous solid / liquid mixture at room temperature, contains a significant proportion of fatty acids from biomass (human food) as well as triglycerides and their corresponding partially hydrolyzed derivatives (di- and monoglycerides). The fatty acids were characterized by gas chromatography coupled with mass spectrometry. Stearic, palmitic, linoleic and oleic acids constitute the largest fraction of the detected fatty acids. Myristic and linolenic acids may also be present. Hydrocarbons may also be present.

[0082] These fatty acids and their derivatives can be used directly as biofuels, for example for industrial furnaces and boilers.

[0083] Alternatively, the collected fatty acids can be modified by methods well known to those skilled in the art.

[0084] For example, these fatty acids can be hydrogenated into HEFA (Hydroprocessed esters and fatty acids) or HVO (Hydrotreated Vegetable Oil) to make biodiesel.

[0085] For example, fatty acids can be esterified. For example, they can be esterified into methyl or ethyl esters of fatty acids. The transformation can be done in two ways: by direct esterification in an acidic catalytic medium and in the presence of an alcohol, preferably bio-sourced, by prior refining of the fatty acids after extraction and then an esterification / transesterification sequence.

[0086] These fatty acid esters can find outlets as biodiesel, lubricants / cleaning solvents (in particular for cleaning metal parts, cleaning in printing, as a release agent for concrete), fluidizer for bitumen, solvents for chemistry, synthons for chemistry.

[0087] The following examples are given for illustrative purposes, but should in no way be considered as limiting the present invention.

[0088] EXAMPLES

[0089] Materials and methods

[0090] Mass spectrometry: Mass analyses were performed on a spectrometer equipped with an ion trap (amaZon SL, Bruker) and an electrospray ion (ESI) source operating in positive or negative mode.

[0091] Settings:

[0092] - capillary voltage: ± 4500 V

[0093] - end plate offset: ± 500 V

[0094] - nebulizer gas pressure: 0.3 bar

[0095] - dry gas pressure: 4.0 L / min

[0096] - dry gas temperature: 200°C

[0097] - scanning range 50-1000 m / z

[0098] Sample preparation and introduction: Typically, samples are diluted 100-fold in a solvent consisting of 46.1% methanol, 38.4% dichloromethane, 15.4% milliQ water, and 0.1% formic acid (% by volume). The diluted sample is then introduced directly into the source using a syringe pump at a flow rate of 10 pL / min.

[0099] • Measurement of the dryness rate of the sludge

[0100] The dry matter content is expressed as a percentage of the sample weight. The measurement method consists of placing a sludge sample in an oven at 105°C until a constant mass is obtained. Let r be the mass of the wet sample and m2 its mass after treatment in an oven at 105°C. x 100 -

[0101] «h

[0102] • Analysis of acid and saponification indices:

[0103] Acidity index measurement

[0104] Principle:

[0105] Dosage of free acids with alcoholic potash. Since the value varies greatly, tests must be carried out to find the appropriate concentration of alcoholic potash. The neutrality of the solvent used must first be checked. Method

[0106] Solvent acidity measurement: 25 mL of 95% ethanol and 25 mL of toluene are introduced into a flask in the presence of phenolphthalein (10 drops). The solution is measured with 0.005 M alcoholic potash.

[0107] 25 mL of 95% ethanol and 25 mL of toluene are introduced into a flask. Weigh 1.0 g of fat. Dissolve the sample and measure (very quickly - with moderate stirring) the acidity using alcoholic potash of concentration x M.

[0108] The dosage is monitored by colorimetry and / or pH-metry.

[0109] Result :

[0110] Let V2, V1 ml be the volume required for the determination of the fatty substance and the solvent mixture respectively, y the molar concentration of the potash solution, M the molar mass of the potash and mg the mass of the test sample.

[0111] Measurement of the saponification index

[0112] The fatty substances will be treated with a large excess of alcoholic potash and hot. The excess potash is then measured with hydrochloric acid.

[0113] Fashion

[0114] For the sample, isolate directly in a 100mL flask, m grams of fatty substance which is dissolved in 20mL of toluene. Add 25mL of alcoholic potash of concentration x M. Make a control under the same conditions.

[0115] The two flasks equipped with a condenser are brought to a gentle boil in a sand bath for 1 hour 30 minutes.

[0116] Remove the flasks from the sand bath and let them cool to room temperature, then under a stream of cold water. Rinse the cooling rods with 5 mL of ethanol to collect any splashes. Measure the excess potassium hydroxide with hydrochloric acid of concentration y M in the presence of phenolphthalein. Colorimetric and / or pH-metric monitoring.

[0117] Results :

[0118] Let V2, V1 ml be the volume required for the determination of the sample and the control respectively, y the molar concentration of the hydrochloric acid solution, M the molar mass of the potash and mg the mass of the test sample.

[0119] • Method for determining the mass percentage of fatty substances in fatty sludge

[0120] The mass percentage of fatty substances in the fatty sludge is determined by solid-liquid extraction with hexane:

[0121] In a filter cartridge, weigh approximately exactly 20g of greasy sludge to be extracted (rriboue). The RS-CAR252780 filter cartridge is introduced into a “Soxlhet” type assembly topped with a condenser. In the previously tared receiving flask, introduce 120 mL of hexane and three grains of pumice stone. Bring to reflux then allow solid-liquid extraction cycles to operate for 20 hours. Cool and recover the residual organic phase in the cartridge. Combine the organic juices then evaporate the hexane under reduced pressure. The residue at the bottom of the flask is weighed (m gr as) and corresponds to fatty substances extracted in the form of an oil which solidifies completely or partially at room temperature.

[0122] The mass percentage of fat is expressed as:

[0123] Sewage sludge

[0124] The sewage sludge used comes from samples taken from the walls of a pumping station in a sanitation network. In the example used, 3 kg of sludge (references BAL0522A) were taken from a pumping station on 04 / 05 / 2022, coordinates of the pumping station: GPS point 45.926247005143246, 4.652735136978171), the sludge is stored by freezing at -18°C. Composition of sewage sludge

[0125] After collection, the sludge was homogenized by mechanical stirring for 3 hours at room temperature. The amount of fat in this sludge was calculated from the average of two hot solvent (hexane) extraction experiments using the Soxhlet method as described above (reflux for 24 hours, 6 cycles per hour). The measured amount of fat is 63.5% by weight for this sludge (see Table 1).

[0126] Table 1: Results of solid-liquid extractions by the Soxhlet method on BAL0522A sludge

[0127] Thermo-mechanical filtration device

[0128] The thermo-mechanical filtration device (1) is as illustrated in Figure 2.

[0129] In this embodiment, the enclosure (2) is heated by introducing water vapor from a vapor generator (8) as shown.

[0130] This steam generator (8) consists of a Pyrex three-necked flask (4 L) (9) placed in a heating mantle (10) topped with a 100 mL dropping funnel (11) and a pressure balancing tube (12) (length (L) of 45 cm, external diameter (0) of 0.7 cm and internal diameter (0) of 0.4 cm).

[0131] The filtration system includes a heating enclosure (2) (0inteme=15 cm, 0 exteme=19 cm and H=27 cm) also serving as collector (3), a perforated cylinder (4) (0=10 cm and height (H) of 15 cm and holes (7) of diameter of 0.3 cm) lined with a membrane inside, a rotation shaft (5) (L=46 cm, 0=0.8 cm) and a cooling tube (13). The collected two-phase liquid comprises an aqueous phase (14) and an oily phase (15) which are subsequently separated at the collector outlet. The heating chamber is connected to the steam generator by a glass cannula (16) (L=45 cm, 0 e xteme=19 cm, H=27 cm). A thermometer (17) is also present in the heating chamber to measure the temperature. Extraction of fatty substances from sludge BAL0522A

[0132] 513 g of BAL0522A sludge are introduced into the perforated cylinder (4) lined inside with a porous polypropylene membrane of type BP-3472035-X3 (200-300 microns) of the Toucan brand. The lined perforated cylinder (4) is closed by a cover then positioned in the heating chamber (2). The rotation shaft is fixed to the motor. First, a static draining (10 min.), then a spin by rotating the perforated cylinder (4) (200 rpm, duration 5 min) is carried out. 104.5 g of water are recovered then drawn off from the collector (3) after this draining / spinning operation. Still rotating at 200 rpm, the steam generator as described in Figure 1 is then started at a heating power of 66%. 25 minutes are needed to obtain the first vapors in the heating chamber (2).By condensation, water runs down the walls of the heating chamber (2) and accumulates at the bottom of the collector (3), this water is not drawn off at this stage of the operation. From a temperature of 41.2°C in the atmosphere of the heating chamber (2) i.e. 8 minutes after the first vapors, the first drops of fat run down the walls of the collector (3) then form a dark immiscible supernatant layer on the much lighter aqueous phase at the bottom of the collector. After the temperature of the atmosphere of the heating chamber has stagnated at 62°C, the heating power is increased to 80% to reach a plateau of around 95°C in the atmosphere of the heating chamber (2) after 15 minutes. The aqueous and oily phases gradually increase in volume, the aqueous (lower) phase is drawn off, collected and measured as it progresses.As the volume of the oily phase increases less rapidly visually, the rotation speed is then increased to 260 then 330, then 400 rpm for a total of 15 minutes to complete the thermomechanical filtration operation. The steam supply is stopped, and, during cooling, the aqueous phase then the oily phase are withdrawn one after the other, then stored separately. The GAL0722VC1 fatty substance is packaged then stored at 4°C. The experimental values ​​are reported in Table 2.

[0133] The solid residues in the membrane are weighed, the oily phase (extracted fatty substances) is weighed, the results are presented in Table 3. The extracted fatty substance GAL0722VC1 was analyzed by: mass spectrometry (Table 4), Acidity index = 172 mg KOH / g, saponification index = 181 mg KOH / g, water content = 2.2%.

[0134]

[0135] Table 2

[0136] Table 3

[0137] Analysis of the GAL0722VC1 body by mass spectrometry revealed that it comprises the compounds shown in Table 4.

[0138] Table 4

[0139] Note: "Dimeric" species of fatty acids are observed, notably the dimer of 10 OH-Stearic (2x(Cis, 1 OH)), MH + = 601.5, Molecular formula = C36H72O6 Example 2: Transformation of the collected fatty substance into EMAG

[0140] The collected fatty substance GAL0722VC1 is esterified by methanol in an acid catalytic medium (H2SO4) to obtain the EMAG referenced GN0722MeOH.

[0141] In a laboratory setup of the single-necked flask type topped with a straight condenser, suitable for heating and equipped with a silicone oil bath, a heating and magnetic plate for stirring by a magnetic "olive", 40.7 g of fatty substance referenced GAL0722VC1, then 17.2 g of anhydrous methanol, then 0.546 g of 96% sulfuric acid are introduced. The reaction mixture is brought to reflux with stirring for 2 hours 45 minutes. After returning to room temperature, the mixture is transferred to a separating funnel, then the phases are left to stand for 15 hours until decantation. The lower phase, containing the unreacted alcohol and the acidic aqueous fractions, is withdrawn. Two water washes (2 x 25 mL) are carried out on the upper phase containing the FAME and the unreacted fatty substance. In order to optimize the conversion of the fatty substance into EMAG, the phase containing the EMAG and the unreacted fatty substance is re-reacted for 1 hour 30 minutes at reflux with 17g of methanol and 0.4 g of sulfuric acid according to the same procedure as before. After stopping the heating, the reaction medium is decanted for 15 hours, then washed with water (2x25 mL), then filtered on anhydrous MgSC to remove the residual water. 29.3 g of a translucent golden yellow liquid corresponding to the EMAG referenced GN0722MeOH are obtained. Mass spectrometry (Table 5); Acidity index = 0.56 mg KOH / g, saponification index = 177.6 mg KOH / g, water content = 2.2%.

[0142] Table 5

[0143] Note: "Dimeric" species of FAME are observed, including the FAME 10 OH-Stearic dimer (2x(Cis, 1 OH)), MNa + = 629.4, Molecular formula = CssH / eOe Example 3: Transformation of the collected fatty substance into EMAG

[0144] A collected fatty substance GCCMIX290923 obtained by the process described in example 1 is esterified by methanol in an acid catalytic medium (APTS) to produce the EMAG referenced EMAGCCMIX271123.

[0145] In a laboratory setup of the hoop reactor type surmounted by a straight condenser, suitable for heating, equipped with a double jacket and an oil heating circulator and a mechanical stirrer, 504.3 g of fatty substance referenced GCCMIX290923, then 75.1 g of anhydrous methanol and 88.1 g of APTS previously dissolved in methanol, are introduced. The reaction mixture is brought to reflux with stirring for 5h30. After returning to room temperature, the mixture is left to settle in the reactor. The lower phase, containing the unreacted alcohol and the acidic aqueous fractions, is withdrawn. Three water washes (3 x 250 mL) are carried out on the upper phase containing the FAME and the unreacted fatty substance. The upper phase containing the EMAG and the unreacted fatty substance is then left to stand overnight on anhydrous Na2SO4 to remove the residual water. Finally, the mixture is filtered under vacuum through celite and then silica.

[0146] 339.1 g of a translucent golden yellow liquid corresponding to the EMAG referenced EMAGCCMIX271123 are obtained. The analyses are in accordance with the EMAG referenced GN0722MeOH (example 2).

Claims

CLAIMS 1. Process for extracting fatty substances contained in fatty sludge comprising the following steps: (a) thermo-mechanical filtration of the fatty sludge, in the absence of organic solvent, so as to separate the fatty sludge into a solid fraction and a liquid fraction, the liquid fraction comprising the fatty substances; (b) collection of the liquid fraction comprising the fatty substances.

2. Method according to claim 1 in which the greasy sludge is sludge from cleaning out sanitation networks, sludge collected from grease traps in wastewater treatment plants (WWTP), machining or grinding sludge, refinery sludge residues, rolling mill sludge, sludge from the bilges of ships or sludge from grease pits or grease traps, preferably sludge from cleaning out structures and sanitation networks.

3. Method according to claim 1 or 2 in which the thermo-mechanical filtration of the fatty sludge is carried out at a temperature of, or close to, 100°C, at atmospheric pressure.

4. Method according to any one of claims 1 to 3 in which the thermomechanical filtration includes a thermal input by diffusion of water vapor within the fatty sludge.

5. Method according to any one of claims 1 to 4 comprising, before step a), a step of partial dehydration of the fatty sludge, preferably by draining and / or spinning.

6. Method according to any one of claims 1 to 5 in which the fatty sludge subjected to step (a) has a dryness rate of at least 30%, preferably at least 40%.

7. A method according to any one of claims 1 to 6 wherein the liquid fraction is a two-phase liquid fraction comprising an aqueous phase and an organic phase and further comprising a separation of the organic and aqueous phases of the two-phase liquid fraction, preferably by decanting the two-phase liquid fraction and then separating the phases.

8. Method according to any one of claims 1 to 7 in which the thermo-mechanical filtration includes a supply of mechanical energy by stirring.

9. Method according to any one of claims 1 to 7 in which the thermomechanical filtration of the sludge is carried out in a thermomechanical filtration device (1) comprising: - a heating enclosure (2); - a static collector (3) arranged inside the heating enclosure (2); - a perforated cylinder (4) arranged inside the static collector (3), the perforated cylinder being configured to receive the cleaning sludge and to be driven in rotation; the static collector (3) being configured to receive a liquid ejected from the perforated cylinder during rotation of the perforated cylinder (4).

10. Method according to claim 9 in which the perforated cylinder has holes whose diameter varies from 1 pm to 500 pm, preferably from 50 pm to 100 pm.

11. Method according to claim 9 or 10 in which the perforated cylinder is coated with a microperforated membrane, preferably a microperforated membrane whose perforations have a diameter ranging from 1 μm to 500 μm.

12. Method according to any one of claims 9 to 11 in which the thermo-mechanical filtration of step (b) is carried out by rotating the perforated cylinder (4) at a speed ranging from 30 to 500 rpm, preferably ranging from 200 to 300 rpm.

13. Method according to any one of claims 9 to 12 in which the thermo-mechanical filtration of step (b) is carried out by rotating the perforated cylinder (4) for a period ranging from 30 to 120 minutes, preferably ranging from 45 to 75 min.

14. A method according to any one of claims 9 to 13 wherein a temperature of, or close to, 100°C in the heating enclosure is reached by introducing water vapor into the heating enclosure.

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