WO2022036117A1

WO2022036117A1 - Versatile oil recovery process from spent oily solid material

Info

Publication number: WO2022036117A1
Application number: PCT/US2021/045772
Authority: WO
Inventors: Matthias ZICK; Marc Kellens; John Weston
Original assignee: Zick Matthias; Marc Kellens; John Weston
Priority date: 2020-08-12
Filing date: 2021-08-12
Publication date: 2022-02-17

Abstract

A process for the treatment of oily hazardous solid materials, such as, for example, spent bleaching earths, active carbon, silicas or filter aids resulting from some refining step(s) of glyceridic materials such as vegetable or animal oils and fats, used cooking oils or other waste fat streams, and containing typically 25 to 35% of residual oil or fat. The process allows a safe and economical recovery of typically about 85% to 95% of the residual oil contained in those hazardous solid materials and transforms those ones into inert materials safe to transport, store, dispose of, or even makes them valuable for some applications. The recovered oil can be used for various oleochemical applications.

Description

VERSATILE OIL RECOVERY PROCESS FROM SPENT OILY SOLID MATERIAL CROSS-REFERENCE TO RELATED APPLICATION [0001] This application claims priority to U.S. Provisional Patent Application Serial No. 63/064,513, filed on August 12, 2020, and titled VERSATILE OIL RECOVERY PROCESS FROM SPENT OILY SOLID MATERIAL, which is herein incorporated by reference in its entirety. FIELD OF INVENTION [0002] The disclosed technology generally relates to a process for the treatment of oily hazardous solid materials (collectively designated “SBE”), such as, for example, spent bleaching earths, active carbon, silicas or filter aids resulting from some refining step(s) of glyceridic materials, such as, but not limited to, vegetable or animal oils and fats, used cooking oils or other waste fat streams, and containing typically about 25 to 35% of residual oil or fat. More particularly, the disclosed technology allows a safe and economical recovery of typically about 85% to 95% of the residual oil contained in said oily hazardous solid materials, and transforms those ones into inert materials easy to transport, store, dispose of, or even makes them valuable for some applications. The recovered oil can be used for various oleochemical applications. BACKGROUND OF THE INVENTION [0003] Powdery, solid adsorbents are intensively used in one or more steps of the refining of vegetable and animal oils and fats, collectively designated as “glyceridic oil” or “oil”. Adsorbents are contacted with oil to remove various unwanted impurities and then separated from the treated oil usually by filtration with, for example, vertical leaf filters. The most widespread adsorbents used in the refining of oil are bleaching earths (also designated as bleaching clays), which are able to remove pigments and many other impurities from said oil. Several grades of bleaching earths are available and depending on the exact application, one or some of those grades are preferred. [0004] During a bleaching step, along with the impurities that are desired to be removed from the oil, a significant amount of oil will be adsorbed by the bleaching earth as well, even after a careful filtration. Consequently, after the bleaching operations, the spent bleaching earth (SBE), contains all the removed pigments and impurities, but also about 25 to 35% of oil. This oil adsorption on the SBE represents a substantial material loss, and furthermore complicates their disposal. Indeed, the presence of oil in the SBE makes them prone to auto-ignition and therefore they are considered hazardous waste, requiring regulated costly disposal procedures. Furthermore, for the same reason, their storage and transportation are also problematic. [0005] Consequently, several processes to extract the residual oil contained in SBE have been proposed. [0006] The most obvious process to extract the residual oil from the SBE consists in utilizing a percolation solvent extractor similar to the one used for the solvent extraction of oleaginous materials. However, this approach is not cost effective because the solvent percolation through SBE is unsatisfactory. Indeed, bleaching earths, as well as other adsorbents in general, are purposely made of a very fine powder in order to increase their specific surface, and, hence optimizing their adsorptive properties. Consequently, the particles of SBE, when soaked with oil, is generally a compact material. Therefore, the solvent percolation through such compact material is poor and reduces greatly the capacity of a percolation solvent extractor. Indeed, sufficient percolation is only attainable with a very thin bed of SBE laying on the moving belt of the solvent extractor, which consequently, reduces considerably its capacity. Therefore, this approach turns to be cost prohibitive because it will require an over-sized solvent extractor. [0007] The extraction of the residual oil contained in the SBE has been attempted when said SBE is contained in vertical leaf or even candle filters. The extraction is realized by introducing a flow of solvent, such as hexane, in those filters to wash away the residual oil contained in the SBE. However, such procedure is highly hazardous and inefficient. Indeed, the hermeticity of those filters is only satisfactory when those ones are fully loaded with SBE containing residual oil which is a compact and relatively sticky material. When the residual oil is progressively washed away and replaced by solvent, the SBE become lose and less sticky. Consequently, the uniformity in cake distribution and hence cake thickness in these filters is not properly maintained. Furthermore, hermiticity of these filters is not well maintained and as they operate under pressure, the risk of substantial leakage of solvent is real, which is particularly hazardous. Furthermore, the partially washed SBE (becoming less compact and less sticky) may drop, hence they will not fill completely and homogeneously the filters. Consequently, washing solvent will preferably flow though voids progressively appearing in the SBE and hence an inefficient washing is observed. The desolventizing of the deoiled cakes inside the filter by steam blowing is also questionable as the steam distribution through the cake will not be uniform and hence less efficient. For those reasons, this process is particularly deficient. [0008] Accordingly, it is preferred to realize the extraction of the residual oil contained in the SBE by mixing them with an extraction solvent to produce a slurry, and let the residual oil dissolve in the solvent, in particular, non-polar solvent, such as hexane. This approach is exemplified by US 6,780,321 B2. This invention discloses a process to extract oil from SBE recovered from vegetable oil refining process. The process involves three sub-processes comprising of reacting the SBE with a solvent selected from a group consisting of toluene, acetone, xylene, isopropyl alcohol or n- hexane at a temperature between 35°C. to 50°C.; separating the solids and liquid from the slurry formed in the previous step; and extracting oil from the liquid fraction obtained in the previous step. The separation of the solids and the liquid from the slurry can be formed in two steps. The slurry mixture of solids and liquid is first separated into a solid fraction and a liquid fraction. The solid fraction so separated still contains a significant portion of oil. Therefore, the solid fraction is reacted with some solvent. The next slurry of solids and liquids is again separated into a solid fraction and a liquid fraction. Thus, in this process, two slurry extractions in series are necessary to sufficiently reduce the SBE residual oil content which in practice also require two phase separations, hence increasing the complexity and the cost of the process. Indeed, the filtration of the slurry is realized on a vacuum belt filter which means that the cake resulting from the filtration must be handled to produce the second slurry. This handling is complex because the cake contains flammable and explosive solvent such as hexane. Another disadvantage of US 6,780,321 B2 process is the absolute necessity to prepare the slurries in a regulated area with explosion proof pieces of equipment and specific strict working procedures which incurs substantial additional installation and running cost. Even so, adding flammable and explosive solvent to SBE, which is a self-igniting material, remains particularly hazardous. Furthermore, vacuum belt filters are very bulky and energy demanding pieces of equipment since the vacuum must be constantly maintained in a large volume. Washing the cake in a vacuum belt filter is possible but often not optimal due to a tendency of the cake to form cracks. The washing solvent flows preferably though those cracks which results in sub-optimal washing action. This results in a large volume of washing solvent resulting in diluted full miscella requiring more energy for its distillation. [0009] Thus, what is needed in the art is a process allowing the recovery of the residual oil contained in SBE in a more safe and economical manner, in particular, a process for which only one slurry preparation step is sufficient to reduce significantly the residual oil content of the SBE. There is also a need for a process allowing the production of a slurry with non-flammable and non-explosive liquid, and thus, allowing the preparation of said slurry in non-regulated area and with non-explosion proof pieces of equipment and decreasing considerably the risk of fire and/or explosion during the slurry preparation. There is also a need for a process for which the cake handling is reduced compared to existing processes, in particular, when the cake is in presence of, or contains flammable and/or explosive non-polar solvent, which represents a particularly hazardous circumstance. OBJECT OF THE INVENTION [0010] It is an object of the invention to disclose a process for the recovery of the oil contained in SBE requiring the preparation of only one slurry. [0011] It is an additional object of the invention to disclose a process allowing the preparation of said slurry with non-flammable and non-explosive liquid, and thus, making possible the preparation of said slurry in non-regulated area, in particular, the area where SBE is produced (i.e. for example, the area corresponding to the oil bleaching step in the oil refining facility), in particular, the direct vicinity of the leaf- filters from which SBE are discharged. [0012] It is an additional object of the invention to disclose a process wherein the cake handling is significantly reduced compared to existing processes, in particular, when said cake contains flammable and/or explosive solvent. [0013] It is an additional object of the invention to disclose a process reducing significantly fire and explosion hazards compared to existing processes. SUMMARY OF THE INVENTION [0014] In one aspect of the disclosed technology, the technology generally provides for a process for the recovery of the oil contained in SBE comprising the steps of: (a) producing a slurry by mixing said SBE with a liquid, (b) transporting and feeding said slurry to at least one centrifuge separator, (c) spinning said at least one centrifuge separator to obtain a SBE cake remaining into said at least one centrifuge separator and a liquid removed from said at least one centrifuge separator, (d) washing said SBE cake remaining into said at least one centrifuge separator to yield a fully washed cake and several miscellas of various strengths, (e) discharging said fully washed cake from the said at least one centrifuge separator, (f) recovering the oil originally contained in SBE from the full miscella, said full miscella being the liquid obtained in step c) or the miscella having the highest strength of step d), characterized in that the washing of step d) is realized with one or more washing liquid(s), to produce a fully washed cake substantially de-oiled, said cake remaining constantly into said at least one centrifuge separator during the washing, and to produce one or more miscellas of different strengths that are removed from said at least one centrifuge separator. [0015] In some embodiments, the oil originally contained in the SBE is reduced by said process to low level, typical to a level lower than 2 weight% (calculated on the dry basis). [0016] In some embodiments, the liquid of step a) used to produce the slurry can be glyceridic oil. [0017] In some embodiments, the liquid of step a) used to produce the slurry is non-polar solvent selected from the group consisting in hexane, toluene, xylene, ethanol, petroleum diesel and renewable diesel or miscella containing a non-polar solvent of the same group of solvents. [0018] In some embodiments, the fully washed cake obtained in step d) is desolventized by further washing said fully washed cake with hot water, said fully washed cake remaining in the one or more centrifuge separator during said further washing with hot water. [0019] In some embodiments, the discharged fully washed cake is thermally desolventized. [0020] In some embodiments, said liquid of step a) used to produce the slurry is glyceridic oil and said step a) is located in a non-regulated area and steps b), c), d), e) and f) is located, at least partially, in one or more regulated area. [0021] In some embodiments, said SBE may contain water, and said water is optionally decanted from any liquids removed from said centrifuge separator. [0022] In some embodiments, said liquid of step a) used to produce the slurry is glyceridic oil and additional non-polar solvent or miscella can be added to said slurry during its transportation or before the feeding of said slurry to the one or more centrifuge separator. [0023] In some embodiments, the strongest miscella produced is step d) is used at least partially in step a) as liquid to produce the slurry. [0024] In some embodiments, said liquid of step a) used to produce the slurry is glyceridic oil and the liquid obtained in step c) is recycled, at least partially, in step a) as liquid to produce the slurry. [0025] In some embodiments, said liquid used to produce the slurry is hexane and/or a miscella containing hexane and the liquid obtained in step c) is the full miscella. [0026] In some embodiments, said liquid used to produce the slurry is renewable diesel or a miscella containing renewable diesel, and the liquid obtained in step c) is the full miscella, said full miscella being used as feedstock for an hydrotreatment process of the glyceridic oil contained in said full miscella. [0027] In some embodiments, said cake washing of step d) is realized counter- currently. [0028] In some embodiments, the liquid to SBE ratio of step a) preferably ranges from 1:10 to 10:1, and even more preferably ranges from 1:1 to 3:1. [0029] In some embodiments, the SBE of step a) includes oily solids particulate materials used during the refining of glyceridic oil and contains adsorbed residual oil after their usage during any step of the glyceridic oil refining, such as, spent bleaching earths, spent clays, spent filter aids, spent silicas, spent active carbons, or any blends thereof. BRIEF DESCRIPTION OF THE DRAWINGS [0030] Figure 1 is schematic diagram depicting several embodiments of the process according to the present technology. DEFINITIONS [0031] SBE: In the context of the presently disclosed technology, the term “SBE” stands for “Spent Bleaching Earths” and refers to any solid material used for the refining of glyceridic oils. By extension, the term “SBE” also includes materials such as spent clays, spent filter aids, spent silicas, spent active carbons or any spent solid particulate material used during the refining of glyceridic oil and containing adsorbed residual oil after their usage during any step of the glyceridic oil refining, or any blends thereof. In the presently disclosed technology, the term “SBE” is also used when said SBE have been partially and/or totally extracted. SBE can be singular or plural depending on the context. [0032] Slurry: In the context of the presently disclosed technology, the term “slurry” refers to the suspension of a particulate solid material, in particular SBE, in a liquid medium. Adequate liquid mediums are for example non-polar solvent such as hexane, renewable diesel, but also their miscellas containing the same non-polar solvent (or blends thereof), or liquid that are not solvents, in particular glyceridic oil. [0033] Miscella: In the context of the presently disclosed technology, the term “miscella” refers to a solution and/or a suspension of glyceridic oil in a non-polar solvent, such as, but not limited to, hexane or renewable diesel. Thus, a miscella usually contains highly flammable and explosive non-polar solvent and glyceridic oil. In the process according to the present technology, miscellas of various strengths (of various concentrations in glyceridic oil) are found. The miscella having the highest strength is called the “full miscella” and all the other miscellas are collectively called “miscellas of intermediate strength” or “weak/weaker miscellas”. The full miscella is sent to a distillation unit to separate the oil extracted from the SBE and the non-polar solvent which is recycled in the process. In the process according to the present technology, the intermediate weaker miscella(s) (i.e. miscella having a lower concentration of oil than the full miscella) is/are used as washing liquid in a counter-current mode of washing the SBE, in particular, for the washing of cake of SBE, said cake still laying in the centrifuge separator. [0034] Cake: In the context of the presently disclosed technology, the terms “cake”, or “SBE cake” refer to the deposit of solid SBE accumulated in the basket of a centrifuge separator. The cake can be washed one or several time(s) with fresh solvent and with miscellas of intermediate strengths. The cake containing the least residual oil is called the “fully washed cake”, and by definition, has been washed at least with fresh solvent. In the present technology, the cake remains in place during all the washing steps, hence only necessitating the handling of solid fully washed and de-oiled SBE cake when this one is discharged from the centrifuge separator after the last washing (with fresh solvent), or according to some embodiments, when the residual solvent has been eliminated, at least partially, with hot water. [0035] Washing: In the context of the presently disclosed technology, the term “washing” refers to the spraying of washing liquids, such as, but not limited to, non- polar solvent or miscellas of intermediate strength (that are, by definition, miscellas less concentrated than the full miscella) on the SBE cake while said cake still remains in the basket of a centrifuge separator, and the washing also includes the spinning of the centrifuge subsequently to the spraying. The spraying of the washing liquids is preferably realized when the centrifuge is rotating at moderate rpm, while the spinning is preferably realized at higher rpm. Conventionally, several counter-current washings are successively realized in order to extract enough residual oil from the SBE and obtain de-oiled SBE having a low residual oil content (ROC) of about 2%. Because the process according to the present technology is realized counter-currently, each washing results in a new miscella having a higher strength than the miscella that was used to perform said washing. Each washing includes the spinning of the centrifuge separator, in absence of any spraying, to recover the maximal amount of new and stronger miscella and to simultaneously remove most of the residual miscella and/or residual oil from the cake. Washing liquids include all the miscellas of various strengths, at the exception of the full miscella, and also includes pure non-polar solvent. In the presently disclosed technology, the washing realized with intermediate miscellas and non-polar solvent can optionally be followed by the spraying of water, preferably hot water of 50°C to 95°C, on the fully washed cake while this one is still laying inside the centrifuge separator. Such spraying with water is followed by a spinning as well. Thus, this optional washing with hot water leads to the at least partial desolventization of the fully washed cake (i.e. to the at least partial removal of the non-polar solvent contained in said fully washed cake), the non-polar solvent being replaced by water. Any liquids resulting from the washing of the fully washed cake with water are not mixed with any miscellas, but are collected specifically, cooled, and decanted to separate the water from the non-polar solvent. [0036] Glyceridic Oil: In the context of the presently disclosed technology, the term “glyceridic oil” refers to oils and fats, or blends thereof, containing tri- and partial glycerides and optionally FFA and/or the typical various impurities contained in natural or recycled oils and fats. Glyceridic oil may be of animal or vegetal origin, may be edible or non-edible, may be crude, partially refined or fully refined, may be modified by processes such as interesterification, fractionation, hydrogenation, or may be obtained from the collection of waste oils and fats of various origins. [0037] Non-polar solvents: In the context of the presently disclosed technology, the term “non-polar solvents” refer to solvents able to solubilize and extract the residual oil contained in SBE, such as, but not limited to, xylene, toluene, hexane, renewable diesel, or absolute ethanol. Non-polar solvents are usually highly flammable and explosive liquid. Some halogenated solvents are both non-polar and not flammable and not explosive. Those solvents are not excluded from the present technology. However, halogenated solvents are usually avoided or even forbidden in some jurisdictions due to their toxicity and their adverse effects on the environment. Halogenated solvents are also usually considerably more expensive than hexane for example. [0038] Non-polar liquid: In the context of the presently disclosed technology, the term “non-polar liquid” encompasses non-polar solvents, such as, but not limited to, hexane, renewable diesel, and non-flammable and non-explosive liquids, such as, but not limited to, glyceridic oils. [0039] Non-flammable and non-explosive liquid: In the context of the presently disclosed technology, the term “non-flammable and non-explosive liquid” designate a liquid that is not more flammable and not more explosive that the typical glyceridic oil (such as soybean oil or palm oil for example) when such glyceridic oil undergone a bleaching refining step. Thus, the safety measures in place to handle such typical glyceridic oil will also be satisfactory if similar glyceridic oils are used to produce the slurry according to the present technology, particularly if the temperature of said glyceridic oil ranges from 60°C to 130°C, which is the maximal bleaching temperature range, 90°C to 100°C being the most usual and preferred bleaching temperature range. [0040] Renewable diesel: In the context of the presently disclosed technology, the term “renewable diesel” refers to a fuel produced by the hydrotreatment of glyceridic oil (i.e. the reduction of glyceridic oil in presence of hydrogen and catalyst). Renewable diesel, which is very similar to standard diesel, is a mixture of linear and branched alkanes. Renewable diesel is technically advantageous over FAME biodiesel. Its production process is described in JP2009138144 and a full review of their properties is available in: “Hydrotreated vegetable oil (HVO) – premium renewable biofuel for diesel engines, Neste oil Proprietary publication for public use, February 2014”. [0041] Regulated area: In the context of the presently disclosed technology, the term “regulated area” indicates that highly flammable and/or explosive substances are used. Typically, costly explosion proof equipment and very strict and constringent working procedures must be used in such regulated area implying both higher investment and operating costs. [0042] Non-regulated area: In the context of the presently disclosed technology, the term “non-regulated area” indicates that no flammable and no explosive substances are used. Typically, standard equipment and working procedures can be used in such area. Glyceridic oil bleaching is usually realized in a non-regulated area since bleaching, which is a standard refining step, does not involve flammable or explosive substances. DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS [0043] The disclosed technology is particularly advantageous to provide for a process for the recovery of the oil contained in SBE requiring the preparation of only one slurry. [0044] The present technology provides a process that allows for the preparation of said slurry with non-flammable and non-explosive liquid, and thus, making possible to prepare said slurry in non-regulated area, such as, for example, the oil refining area, in particular, the area where the oil is bleached. Consequently, the slurry can be prepared directly after the SBE has been produced, and thus, the disclosed technology suppresses the need to store and/or transport the hazardous SBE from their production area to their extraction area, which reduces considerably the hazards, the investment and operative costs as compared to current technologies. [0045] The present technology also provides the additional advantage of providing a process wherein the cake handling is significantly reduced compared to existing process, in particular, when said cake contains flammable and/or explosive solvent. [0046] The present technology also provides the additional advantage of providing a process that significantly reduces fire and explosion hazards compared to existing processes. Further advantages of the present technology will become apparent from the detailed description. [0047] It was surprisingly observed that the residual oil contained in SBE can be recovered in a process comprising the steps of: (a) producing a slurry by mixing said SBE with a liquid, (b) transporting and feeding said slurry to at least one centrifuge separator, (c) spinning said at least one centrifuge separator to obtain an SBE cake remaining into said at least one centrifuge separator and a liquid removed from said at least one centrifuge separator, (d) washing said SBE cake remaining into said at least one centrifuge separator to yield a fully washed cake and several miscellas of various strengths, (e) discharging said fully washed cake from the said at least one centrifuge separator, (f) recovering the oil originally contained in SBE from the full miscella, said full miscella being the liquid obtained in step c) or the miscella having the highest strength of step d), characterized in that the washing of step d) is realized with one or more washing liquid(s), to produce a fully washed cake substantially de-oiled, said cake remaining constantly into said at least one centrifuge separator during the washing, and to produce several miscellas of different strengths that are removed from said at least one centrifuge separator. [0048] The present technology will be disclosed in detail with the help of Figure 1. However, the present technology is limited by the claims and not by Figure 1. [0049] Figure 1 represents schematically various embodiments according to the present technology. In Figure 1, SBE (1), typically the residue obtained from bleaching operations in the field of oils and fats refining, is introduced in a slurry tank (2) and mixed with a liquid. The liquid is, for example, non-polar solvent (3) originating from any source, and/or miscella (4), preferably the penultimate strongest miscella (i.e. the strongest miscella but that is still not the full miscella), which also contains a substantial fraction of the same non-polar solvent, or glyceridic oil (5) such as the glyceridic oil recovered from the SBE (6) or the glyceridic oil that is refined and bleached in an neighboring glyceridic oil refining installation (not shown), and introduced via line (7) for example. Typically, the temperature of the non-polar solvent will be well below its boiling point to avoid any pressure build-up in the slurry tank, for example, at least 5°C to 20°C below its boiling point, and e.g. below 130°C when glyceridic oil is used to produce the slurry. Preferably, the slurry tank is constructed hermetically and provided with mixing means. Typical residence time of the slurry is about 10 to 30 minutes. Typically, the liquid to SBE ratio of the slurry is comprised between 1:10 to 10:1, but preferably comprised between 1:1 to 3:1. [0050] It was surprisingly observed that when glyceridic oil is used to produce the slurry, this ratio can in some cases be reduced because the purpose of using glyceridic oil is simply to produce a pumpable non-flammable and non-explosive slurry. Usually, adding the minimal amount of glyceridic oil to the SBE resulting in a fluid and pumpable slurry is preferred. Rising the temperature of the glyceridic oil used to produce the slurry can further reduce the viscosity of said slurry, which may be useful for some types of SBE. For example, the temperature of the glyceridic oil used to produce the slurry can be in the range of the temperature of the SBE resulting from the leaf-filters that are used in the bleaching operations, i.e. about 70°C to 130°C, most usually about 90°C to 100°C. However, care should be taken not to raise said temperature in excess of about 130°C in order to maintain the low flammability of glyceridic oil. [0051] Realizing the slurry with glyceridic oil is highly advantageous from a safety point of view. Indeed, in that case, the slurry preparation can be located in a non- regulated area, such as, for example, the direct vicinity of the oil refining installations, in particular the bleaching step where the SBE is produced. Consequently, the SBE must not be transported and stored, prior to their subsequent treatment, but can be directly transformed in a non-explosive slurry that can be easily pumped, typically in an agitated day tank to be treated by the next steps of the process according to the present technology, said next steps making use of flammable non-polar solvent, and which, thus require special explosion-proof pieces of equipment. Thus, producing the slurry of SBE with glyceridic oil which is a non-flammable and non-explosive liquid in the condition of temperature selected i.e. max 130°C, an even preferably max 100°C, save considerable expenditure, is safer and permits much more flexibility in particular when retrofitting existing installations. It must be noted that mixing SBE with flammable solvent is a hazardous operation even if performed in a regulated area. Indeed, SBE are notorious for their self-igniting tendency. To reduce this risk, they are often sprayed with water. However, the presence of water usually complicates the extraction of the oil contained in SBE. [0052] Thus, in a preferred embodiment, the slurry preparation is realized by mixing SBE with glyceridic oil in a non-regulated part of a glyceridic oil refining facility. This preferred slurry preparation mode is represented in Figure 1 with dashed lines by adding glyceridic oil (5) to the SBE (1), and said slurry is pumped and conveyed through a pipe (8) or any adequate transportation mean to a regulated part of the refining facility where the centrifuge separator(s) (9) is/are installed. The slurry is fed to the one or more centrifuge separator(s), which proceed firstly to a spinning resulting in the phase separation of said slurry into an essentially solid cake of SBE remaining in the centrifuge separator(s) and liquid glyceridic oil expelled (10) form the centrifuge separator(s), and secondly, to several washings of said cake with one or more intermediate miscellas and pure non-polar solvent until a fully washed cake is obtained and discharged from said centrifuge separator into typically a hopper (11). The liquid glyceridic oil firstly expelled from the centrifuge separator can be stored (12) and used for its own merits and/or recycled at least partially as liquid for the slurry preparation via line (13). The fully washed cake is conducted typically with a conveyor (14) from the hopper (11) to a desolventizer (15) yielding de-oiled and desolventized SBE (16) and solvent vapours (17) which are, after condensation in a condenser-decanter (18), stored in solvent tank (19) and recycled in the process as washing solvent, in the centrifuge separator(s) via line (20). [0053] It must be noted that the solvent could optionally be added via line (21) to the slurry tank when the said slurry is prepared with a liquid containing non-polar solvent. However, pure solvent is preferably used as washing liquid. The washing of the cake obtained directly after the feeding of the slurry and the first spinning of the centrifuge separator(s) is preferably realized counter-currently. For example, pure non- polar solvent is used to wash the cake that contains low amount of residual oil. Thus, pure solvent, conducted to the centrifuge separator (9) from the solvent tank (19) via line (20) will be sprayed on a cake that has been already washed previously with, for example, three miscellas of intermediate strengths and consequently said cake only contains a low amount of residual oil, and therefore, this last washing with pure solvent will result in the fully washed cake, thus a cake containing even less residual oil, and a weak miscella expelled from centrifuge separator(s) during the washing, that is stored in miscella collection tank (22) via line (23). This weak miscella is then pumped from miscella collection tank (22) via line (24) to be used as washing liquid for a cake laying in the centrifuge separator(s) and containing a medium amount of residual oil, because said cake has been previously washed only twice with intermediate miscellas. This will result in the cake containing the low amount of residual oil and into a miscella of medium strength that is expelled from the centrifuge separator and stored in miscella collection tank (25) via line (26). This weak miscella is then pumped from miscella collection tank (25) via line (27) to be used as washing liquid for a cake laying in the centrifuge separator(s) and still containing a relatively high amount of residual oil, because said cake has been washed only once with a miscella of intermediate strengths. This will result in the cake containing the medium amount of residual oil and into a miscella of higher strength that is expelled from the centrifuge separator and stored in miscella collection tank (28) via line (29). In fact, this miscella of higher strength can be pumped from miscella collection tank (28) via lines (30) and (31) and used as washing liquid to wash the cake obtained directly after the first spinning of the centrifuge separator subsequent to the slurry feeding into said centrifuge separator. This will result in the cake containing the relatively high amount of residual oil and into the full miscella (i.e. the miscella of the highest strength) that is expelled from the centrifuge separator and stored in miscella collection tank (32) via line (33). [0054] In the process according to the present technology, the washing of the cake is realized when this one stays static inside the centrifuge separator(s). Hence, any cake handling is superfluous during the washing, which is highly advantageous and safer over current practices. Furthermore, centrifuge separators are compact and can be made highly hermitical, which is essential and advantageous from a safety point of view. [0055] In Figure 1, the process according to the present technology is represented including three washing steps of miscellas of intermediate strengths and one washing with pure non-polar solvent. However, the present process is not limited to this precise number of washing steps. Advantageous and satisfactory extraction of the residual oil contained in SBE can be achieved with less or more washing steps. The number of washing steps will depend on the type of SBE, the level of the residual oil initially contained in the SBE and of the level of the residual oil targeted in the de-oiled SBE. However, it is expected that two to three counter-current washing steps with intermediate miscellas combined to one washing step with pure solvent will reduce the residual oil of the most common SBE to less than 2%. [0056] In some embodiments, the full-miscella is conducted from the miscella collection tank (32) via line (35) to a distillation unit (36) yielding the recovered oil from the SBE which may, at least partially, be recycled to prepared the slurry via lines (37) and (6) or stored and used for its own merits via lines (37) and (38). The repartition of the recovered oil used to prepare the slurry and the oil stored and used for its own merits is regulated via a three-way valve for example (39), or similar adequate mean. The distillation unit (36) yields also the non-polar solvent vapours conducted by line (40), to a condenser-decanter (18) to produce pure solvent stored in solvent tank (19) via line (22) and recycled in the process as washing liquid via line (20) or as liquid to prepare the slurry via line (21). Indeed, it must be noted that if the slurry is not prepared with glyceridic oil, then the penultimate miscella is preferably used to prepare said slurry and the three-way valve (34) is positioned to conduct the penultimate miscella from miscella collection tank (28) to slurry tank (2) via line (30) and line (4). In that case, line (31) is not used. [0057] In some embodiments, the fraction of the residual oil recovered from the SBE that is not recycled, but used for its own merits is useful, for example, but not limited to, as feedstock for biodiesel, for renewable diesel or for other oleochemical applications. This residual oil, even if surprisingly free of contaminations is to be considered non-edible. [0058] In some embodiments, the de-oiled SBE typically contains about 2% or less of residual oil and such low amount has been proven to present no safety issue. Thus, the de-oiled SBE can be safely stored, transported, disposed of in landfill or recycled in application such as garden amendment for moisture retainer. [0059] In the process according to the present technology, the cake remains static in the centrifuge separator(s) during all the washing steps. It is only discharged from the centrifuge separator when the removal of its residual oil is completed, thus, typically when pure solvent has been used for an ultimate cake washing and thus the cake that is discharged from the centrifuge separator is loaded with flammable non- polar solvent such as hexane for example. Typically, in some embodiments, the fully washed cake contains about 15% to about 25% of non-polar solvent. Thus, even if the handling of the cake is reduced compared to other existing processes, the remaining handling of the fully washed deoiled cake loaded with flammable solvent remains hazardous and requires drastic safety precautions. [0060] Furthermore, the desolventization of the cake with non-polar solvent requires an energy intensive desolventization step in a desolventizer (15), which is also a relatively expensive piece of equipment. However, it has been surprisingly observed that with the process according to the present technology, making use of centrifuge separator(s), permits to suppress the need to use a desolventizer and suppress the need to discharge a fully washed cake loaded with flammable non-polar solvent. Indeed, optionally, after the ultimate washing with pure non-polar solvent, a washing with hot water can be realized while the cake still lays static in the centrifuge separator. The combination of the spraying of water which washes away the non-polar solvent, and of the higher temperature, which evaporates at least a part of the non-polar solvent is very efficient to remove a large fraction of the non-polar solvent initially present in the fully- washed cake. Hence, the cake discharge from the centrifuge separator(s) is greatly simplified and safer. Such a cake can be directly disposed of, or used in any applications. Indeed, the cake contains water, but this one is not problematic, since SBE are mineral materials not prone to fermentation and this water tends to evaporate naturally. [0061] Turning to Figure 1, this optional embodiment can be put in place by conducting hot water from hot-water tank (41) to the centrifuge separator(s) via line (42). The mixture of water, non-polar solvent and vapours resulting from the washing of the cake with hot water and expelled from the centrifuge separator(s) is conducted via line (43) to collecting tank (44). This mixture is conducted via line (45) to a condenser-decanter (18) to yield water recycled to the hot-water tank (41) via line (46) and non-polar solvent, which is also recycled in the process by conducting it to the solvent tank (19) via line (22). A small quantity of water must be regularly topped to the hot-water tank (41) via line (47). This topped water corresponds to the water remaining in the cake when discharged from the centrifuge separator. The fully washed and desolventized cake is thus directly discharged from the centrifuge separator (9) into hopper (11) and conducted via a conveyor (14) to an intermediate storage location that can be situated in a non-regulated area (48). The cake can optionally pass over a belt dryer to further cool down the cake an remove any residual solvent left behind. Thus, in some embodiments, desolventizer (15) and the related downstream elements (16), (17) are superfluous. Consequently, in such embodiments, the hazardous handling of a material loaded with flammable solvent is reduced and the need of an energy intensive desolventization is suppressed. Therefore, such embodiments are particularly and considerably safer and more economical than standard practices. [0062] In some embodiments, a decanter (49), or any adequate phase separator, can be installed in line (35) in order to allow the phase separation and removal of any aqueous phase possibly presents in the full miscella. Indeed, SBE is sometimes sprayed with water during storage and/or transportation to reduce its self-ignition tendency. This removed aqueous phase can even be optionally recycled in the hot-water tank (41) via line (50). If no aqueous phase is present in the full miscella, the decanter is simply by-passed by line (51). [0063] In other embodiments, similar decanter, or any adequate phase separator, can advantageously be installed on-line (10) in order to allow the phase separation and removal of any aqueous phase possibly presents in the glyceridic oil expelled from the centrifuge separator when the slurry is prepared with glyceridic oil. In other embodiments, similar decanters, or any adequate phase separators can be installed on the lines (23) and/or (26) and/or (29) transporting the intermediate miscellas. Indeed, when the SBE contains water, it is possible that part of this water is progressively released during the successive washing steps. (Those last embodiments are not shown in Figure 1 to not obscure it.) [0064] Even if it may seem counter-productive to realize said slurry with glyceridic oil, since the goal of the process is to extract glyceridic oil from the SBE, this mode of preparation of the slurry, according to one of the preferred embodiments of the present technology, is advantageous in many aspects. If the slurry is prepared with non- polar solvent, such as, but not limited to, hexane or renewable diesel, the slurry tank and all other equipment must be explosion proof and placed in a regulated area. And even in such regulated area, mixing potentially self-igniting SBE with flammable solvent remains highly hazardous. Therefore, preparing the slurry with glyceridic oil is the safest and best mode of the present technology when said slurry must be prepared in a non-regulated area. Nitrogen blanketing of the slurry tank can further reduce any hazard when preparing the slurry with glyceridic oil. Said slurry is sufficiently fluid to be pumped over a long distance to a regulated area where flammable solvents are used. Regulation often impose minimal distance of 50 meters or more between such regulated area and non-regulated area. The present technology permits easy and safe transportation of the slurry containing the SBE over such long distance and an efficient and safe connection between non-regulated and regulated areas. [0065] In some embodiments, some miscella or non-polar solvent can be blended with a slurry initially prepared with glyceridic oil before being introduced into one or more centrifuge separator(s). In its most simple execution, the blending can be realized in-line using a feeding pump to introduce an intermediate miscella or the non- polar solvent in the slurry pipe. In some embodiments, a static mixer is installed in said pipe down-stream said feeding pump. Alternatively, a small agitated tank can be used to realize such blending. However, the size of such agitating tank will remain very limited since the residence time is also very limited. [0066] In such embodiments, the blending must be accomplished in a regulated area (typically the area where the centrifuge separator(s) are located, and all the pieces of equipment used to realize such blending will be explosion proof. The advantage of blending some intermediate miscella or non-polar solvent in a slurry composed of glyceridic oil and SBE is the possibility to further reduce its viscosity which will, in case of very viscous slurry, ease its feeding to the centrifuge separator, and also, in some cases, accelerate the initial phase separation upon the first spinning of the slurry after its feeding to the centrifuge separator. Since the addition of non-polar solvent or intermediate miscella to a slurry prepared with glyceridic oil will be realized in the regulated area where the centrifuge separator(s) are installed, the slurry preparation per se can still be realized in a non-regulated area which is advantageous. It must be noted that this optional embodiment is considerably less hazardous than mixing directly flammable non-polar solvent (or intermediate miscellas containing the same) to SBE. Indeed, the addition can be realised in-line in total absence of oxygen. Furthermore, SBE slurry based on glyceride oil is not self-igniting anymore. However, this embodiment has the disadvantage of increasing slightly the needed investments and the complexity. [0067] In some embodiments, the process according to the present technology is equally suitable for treating SBE produced remotely in one or more refining facilities and transported by truck loads for example to a centralized SBE treatment facility preferably fully located in a regulated area. Indeed, in such embodiments, the SBE are often sprayed with water to reduce the risk of self-ignition. In such embodiments, since the risk of self-ignition of the SBE is reduced, it may be advantageous to prepare the slurry with solvent or miscella of intermediate strengths. In such embodiments, a significant fraction of the oil contained in the SBE is already extracted during the slurry preparation, which may reduce the number of washing steps necessary to realize the complete extraction of said oil contained in the SBE. [0068] Thus, for various reasons, in some circumstances, it may be preferred to realize the slurry with non-polar-solvent or even preferably their corresponding miscellas. This embodiment is also exemplified in Figure 1. Non-polar solvent (3) such as, for example, hexane or miscella, preferably the penultimate strongest miscella (i.e. the miscella containing the highest amount of oil but that is still not the full miscella), is used as liquid to prepare the slurry and is mixed with SBE (1) in the slurry tank (2). This penultimate miscella is fed to the slurry tank via lines (30) and (4). The three-way valve (34) is positioned to prevent the recycling of the penultimate miscella to the centrifuge separator. Thus, line (31) is not used when the slurry is not prepared with glyceridic oil. Similarly, the dashed lines (5), (6), (7), (10), (12) and (13) are not used when the slurry is not prepared with glyceridic oil. Preferentially, the totality of the penultimate miscella will be recycled as liquid to produce the slurry. The slurry, after being conducted via pipe (8), and fed to the centrifuge separator (9) is spun and yield a cake remaining in the centrifuge separator and a liquid corresponding to the full miscella conducted via line (33) to the full miscella collecting tank (32). This full miscella will be treated as previously described. The cake remaining in the centrifuge separator is washed as previously described to yield a fully washed cake which will be treated as previously described as well. [0069] Thus, in any embodiment of the process according to the present technology, the slurry is conducted to one or more centrifuge separator(s), preferably one or more basket centrifuge(s) to realize or continue the extraction of the residual oil contained in the SBE. If the slurry has been prepared with non-polar solvent (or miscella containing the same non-polar solvent), the extraction taking place in the one or more centrifuge separator(s), also involves at least the same non-polar solvent. If the slurry has been prepared with glyceridic oil, then the extraction, taking place in one or more centrifuge separator(s), involves a different liquid: non-polar solvent, preferably hexane or renewable diesel and/or their corresponding intermediate miscellas. [0070] Accordingly, the slurry is conveyed to at least one centrifuge separator. This one will sequentially operates three distinct steps: 1) a slurry feeding and spinning step, leading to the separation of said slurry into a cake remaining in the centrifuge and a liquid expelled from the centrifuge, 2) one or more cake washing cycle(s) consisting in the spraying of solvent or weak miscella on the cake, each washing cycle including, after the spraying, a spinning, to yield a washed cake remaining in the centrifuge and one or more less weaker miscella(s) of various strengths expelled from the centrifuge and collected in dedicated miscella tanks, and 3) the discharge step of the fully washed cake. The washing cycles are preferably realized counter-currently. [0071] Optionally the fully washed cake is further washed with hot water to remove the non-polar solvent contained in said fully washed cake. All those steps can be automated and realized without or with limited operator intervention. The first liquid expelled from the centrifuge after the slurry feeding step is the full miscella when the penultimate miscella was used to produce said slurry. However, when glyceridic oil is used to produce the slurry, the first liquid expelled from the centrifuge after the slurry feeding step will be glyceridic oil, the full-miscella will be obtained from the washing of this resulting cake with the penultimate strongest miscella (the ultimate one being the full miscella). [0072] In a preferred embodiment, the process according to the present technology concerns the de-oiling of the SBE obtained from the refining, and in particular the bleaching, of waste oils and animal fats to obtain a suitable feedstock for the production of renewable diesel. Such renewable diesel is produced by the reduction of glyceridic oil in presence of hydrogen and catalyst. Renewable diesel, which is very similar to standard diesel, is a mixture of linear and branched alkanes. Waste oils and animal fats are usually highly degraded material containing notably high concentration of Phosphorus notably in the form of phospholipids and metals such as Fe, Na, Ca, K, Mg that are removed by several bleaching steps. Therefore, the refining of such type of glyceridic oil generates a rather high quantity of SBE, generally in the range of 5 to 25 kg per ton of refined oil, and therefore, the removal of the residual oil from said SBE is particularly primordial. [0073] It has been surprisingly observed that the renewable diesel can be advantageously used as non-polar liquid to prepare the slurry. The same renewable diesel or miscella based on renewable diesel can be used as washing liquid in the one or more downstream centrifuge separator(s). The advantage is that the preparation of the slurry as well as the centrifugation separation can be realized according to the safety standard applied for the production of renewable diesel by hydrotreatment, and will therefore benefit of an economy of scale if the installation for the treatment of the SBE is located on a site producing renewable diesel. [0074] Another surprising advantage is that renewable diesel extracts selectively the glyceride oil contained in the SBE but not the various contaminants adsorbed on said SBE. Consequently, the recovered oil can usually be advantageously directly used as feedstock for the production of renewable diesel by hydrotreatment of glyceridic oil. Even more advantageously, the full miscella containing the SBE recovered glyceridic oil and the renewable diesel that was used as non-polar solvent, can be directly conducted and processed by the hydrotreatment unit since the presence of renewable diesel has no deleterious effect on the hydrotreatment process. Indeed, renewable diesel is fully saturated and will not compete in the hydrogenation reaction. However, when the full miscella is not processed by a hydrotreatment unit and consequently, the renewable diesel must be thermally removed from said full miscella, it is much more economical to realize the extraction with a more volatile solvent, such as hexane. [0075] However, in some embodiments, when the slurry must be prepared in a non-regulated area, the slurry is preferably produced by mixing glyceridic oil to SBE. The slurry is prepared in an agitated tank located in non-regulated area of the refining facility, preferably in the direct vicinity of the vertical leaf-filters typically used after the bleaching of the oil and from which said SBE is discharged. Therefore, the SBE discharged by those leaf-filters does not have to be stored and/or transported but can directly be transformed into a slurry with non-explosive liquid, typically the same glyceridic oil that is refined, or the glyceridic oil that is recovered from the same SBE, or any blend thereof. The slurry is then pumped from the slurry tank and transported, preferably by a properly sized pipe, to an regulated area of the refining facility and is further introduced in centrifuge separator(s) and subjected to at least one centrifugation to recover the glyceridic oil that was added to the SBE to produce the slurry. At least a part of this glyceridic oil can optionally be recirculated to the slurry tank. Consequently, said glyceridic oil may be circulated in closed circuit and does not increase the filtrate volume during the distillation of the solvent. Thus, in some embodiments, only one slurry is produced, and furthermore, glyceridic oil is used to produce said slurry. In such embodiments, it is particularly preferred for treating directly the SBE produced locally in a refining facility since in that case the slurry can be prepared in a non-regulated area, typically in the direct vicinity of the bleaching installations of said refining facility. The slurry can be easily transported to a small regulated area where the centrifuge separator(s) are installed and where flammable and explosive solvent such as hexane or renewable diesel is used. [0076] Moreover, the process according to the present technology is prone to automatization and does not require the attention of numerous operators. Indeed, the loading of the slurry tank with SBE and the selected liquid (non-polar solvent and/or miscella or glyceridic oil) is automatically realized via conveyors and dosing pumps and appropriate piping. The one or more centrifuge separator(s) can be designed to operate the feeding, washing and discharge steps automatically without or with limited operator intervention. [0077] Accordingly, the process according to the present technology can be operated in continuous mode even if an individual centrifuge separator is operated in a discontinuous mode. For example, three centrifuge separators can operate in parallel and, at a given time, each one of them realizing a different step in a way of being able to deliver, globally, a nearly continuous flow of fully washed cake and full-miscella. In some embodiments, preferred centrifuge separators are basket centrifuges, such as, pusher centrifuges or peeler centrifuges, the last one being more preferred. Preferably, in some embodiments, the three centrifuge separators cycle (feeding, washing and cake discharge) can be automatized and coordinated so that at any given time, one of the separator operates a feeding cycle, another separator operates one or more washing cycle(s), and another separator operates a fully washed cake discharge. [0078] In some embodiments, the centrifuge separators are working in parallel and not in series and may be coordinated and set so that the first peeler centrifuge is fed with slurry that is separated into a cake and a full miscella, while the second peeler centrifuge is washing, and spinning, and the third peeler centrifuge is discharging a fully washed cake. Then, the first peeler centrifuge will be washing the cake and spinning, the second peeler centrifuge will discharge a fully washed cake, and the third peeler centrifuge will be fed with new slurry and separating it into a cake and a full miscella. Then the first peeler centrifuge will be discharging the fully washed cake, the second one will be feed with a new slurry and will separate it into a cake and full miscella, and the third one will be washing and spinning. This sequence is then repeated continuously. This set up is particularly advantageous because it will allow a continuous operation of the slurry tank, of the desolventizer, and of the distillation unit provided that buffer tanks, piping and valves are in place. EXAMPLES [0079] The present technology will be further described in the following examples, which should be viewed as being illustrative and should not be construed to narrow the scope of the disclosed technology or limit the scope to any particular embodiments. Slurry preparation. [0080] In the process according to the present technology, the primary function of producing the slurry is to transform the solid SBE into a liquid of adequate viscosity able to be pumped, transported by pipe, and feed to at least one centrifuge separator. The slurry preparation consists in mixing SBE with liquids such as glyceridic oil, or with non-polar and flammable solvents such as hexane, renewable diesel and/or their corresponding miscellas (or blends thereof). The slurry is preferably maintained in an agitated reactor for about 15 to 30 minutes. [0081] The advantage of using glyceridic oil instead of highly flammable and explosive non-polar solvent or miscella, is that the slurry preparation can be realized in a non-regulated area since glyceridic oils (at the temperature selected in the present process) are not flammable and not explosive and thus this slurry preparation can be done in the direct vicinity of for example the leaf-filters of a vegetable oil refining facility where the SBE are usually produced. Using a non-polar solvent such as hexane which is highly flammable and explosive, would require that all the slurry preparation area must be regulated which considerably increases both investment and operation cost. Furthermore, mixing SBE, known for its self-igniting tendency, with flammable solvent remains hazardous even in a regulated area. Thus, the process according to the present technology, for which the slurry can be prepared with glyceridic oil, is highly advantageous, particularly for vegetable oil refining facilities treating their own SBE, because only a limited area must be regulated, and furthermore, this regulated area can be located at distance of the refining area since the slurry prepared with glyceridic oil is safely transportable and storable without using explosion-proof pieces of equipment. Glyceridic oil cannot be considered as a non-polar solvent since its boiling point is excessively high (above 300°C) and even if contacting SBE with glyceridic oil will most likely displace some of the oil adsorbed in said SBE, it will not result in a net extraction of the oil contained in the SBE since the displaced adsorbed oil will be replaced by the glyceridic oil that was used to produce the slurry. [0082] Another suitable non-polar liquid to produce the slurry is hexane (or miscella containing hexane), typically of the same quality than the one used in the solvent extraction of edible oil and fat. Hexane has the advantage of being economically distilled and evaporated. The disadvantage of hexane, beside its flammability, is that this non-polar solvent will evaporate if in contact with hot SBE discharged from the leaf-filters used in the oil bleaching operations. Indeed, usually those SBE are at a temperature of about 90°C to 100°C which is much higher than the boiling point of hexane. Therefore, the SBE discharged from the leaf filter must be cooled to about 50°C to 60°C before being mixed with hexane (or its corresponding miscella). This issue is solved by the utilization of renewable diesel (or miscella containing renewable diesel) as liquid to produce the slurry since its boiling point is substantially superior to 90°C or by the utilization of glyceridic oil to produce the slurry. Then, the slurry is even preferably produced directly after the discharge of the SBE from the leaf filter, when the SBE are still at a temperature of about 90°C to 100°C. [0083] Care shall be taken to produce a pumpable slurry to convey this one readily from the slurry tank to the centrifuge separator. To this end, it has been found that preferably, a slurry prepared with hexane or renewable diesel (or their corresponding blends) contains about 10% to 50% (by weight) of spent blenching earth. With such content of SBE in the slurry, not only the pumpability of the last one is assured but its feeding to the centrifuge separator is facilitated. Producing a slurry fluid enough to be pumped over a long distance is important when the slurry is produced in a non-regulated area far away of the regulated area where the centrifuge separator(s) is/are installed. It is expected that the content of SBE in the slurry may be adapted to the specific characteristic of the bleaching earths such as its average size, its size distribution, its morphology, its type (acid activated or neutral bleaching earth). Another aspect needing attention is the sedimentation during transportation from the slurry tank to the centrifuge separator. It has been observed a marked tendency of sedimentation for some SBE when agitation of the slurry is stopped. Therefore, preferably only agitated buffer tank will be placed between the slurry tank and the centrifuge separator. [0084] Preferably, the SBE and the liquid are continuously added to the slurry tank while an equivalent fraction of the slurry is continuous pumped and conveyed to the one or more centrifuge separator(s). The slurry is preferably pumped from the bottom of the slurry tank in order to avoid any accumulation of sediment that may occur even with agitation. Non-polar solvent for the extraction taking place in the centrifuge separator(s) [0085] The non-polar solvent should be able to selectively dissolve and extract the residual oil contained in the SBE. Furthermore, its boiling point should be preferably relatively low to minimize the energy needed for its distillation. Its cost and toxicity should be minimal. It should be immiscible with water to facilitate the decantation of water in the case SBE are contaminated with water. From all those considerations, hexane is the non-polar solvent of choice for the present technology. In contrast, renewable diesel has a boiling point considerably superior to hexane and hence its distillation will require considerably higher energy input. However, its distillation can be totally avoided. Indeed, renewable diesel may be advantageous if the miscella recovered from the SBE is directly used in a glyceridic oils hydrotreatment process. This miscella contains a mixture of renewable diesel and glyceridic oil. As a matter of fact, only the glyceridic part of this mixture will be reduced by the hydrotreatment process and the renewable diesel will have a simple role of solvent and thus will not interfere with said hydrotreatment process and will notably not consume any hydrogen since renewable diesel is made exclusively of alkanes (already totally reduced). Therefore, it that option, the miscella does not need to be distilled. [0086] The exhausted SBE still containing the renewable diesel can be advantageously extracted with a low melting point solvent such as hexane. As a matter of fact, this second extraction can be realized in the same centrifuge separator that was used to extract the SBE residual oil with renewable diesel. This second extraction requires only a few washing cycles, again preferably realized counter-currently with a volatile solvent such as hexane that will result in mixture of renewable diesel dissolved in hexane and exhausted SBE containing about 15% to 25% of residual hexane. Thus, the final exhausted SBE will contain residual hexane which is easily evaporated in conventional desolventizer. The renewable diesel that has been extracted from the de- oiled SBE is therefore solubilized in hexane. This hexane is again easily recovered by evaporation to yield renewable diesel, and after condensation of said hexane, both solvents are preferably recycled in the process. Thus, with this strategy, no more energy is required for the evaporation of solvent compared to the direct slurry preparation and extraction with hexane or miscella containing hexane. The usage of renewable diesel as non-polar solvent is particularly advantageous for integrated facilities where the treatment of SBE is integrated to the production of renewable diesel by the hydrotreatment process, and even more particularly more advantageous when renewable diesel shows less propension to extract the contaminations present in the SBE than hexane. Results show that it is the case for the SBE that was evaluated. However, the justification of this observation is currently not fully understood since, to our knowledge, both solvents are similarly non-polar and should have, therefore, a similar extraction performance and selectivity. Nevertheless, usually, hexane is far more economical to use than renewable diesel. Centrifuge separators and cake washings [0087] Good results have been obtained with basket centrifuges, in particular with peeler centrifuges. Basket centrifuges are advantageous because they permit a washing of the cake with fresh solvent and weak miscella(s) containing the same solvent in a counter-current mode thus allowing to obtain a low residual oil content in the de-oiled SBE with a minimal consumption of solvent. Furthermore, said cake washing is realized while the cake remains in place in the centrifuge, thus reducing considerably the SBE handling. However, it is expected that other type of basket centrifuges such as pusher centrifuge could be adequate provided they permit the washing of the cake in a counter-current mode and permit, as well the automatization of the various steps of the process according to the present technology. Several manufacturers commercialize basket centrifuge separators. It is of course mandatory to select explosion proof centrifuge separator. Separation of the slurry into a miscella and a cake is very efficient and fast and need no more than a few minutes. Miscellas of various strength are collected into dedicated miscella tanks and recycled as washing liquid in a counter-current mode. The full miscella, i.e. the miscella containing the highest concentration of recovered glyceridic oil is not recycled as washing liquid, but sent to a distillation installation to recover the solvent and the extracted oil. [0088] In the counter-current mode of operation, the cake is successively washed with various miscella of decreasing strengths and finally with fresh solvent. The fresh solvent is sprayed onto the cake and is therefore able to displace the miscella still entrapped in the cake. A relatively limited quantity of washing liquids (solvent and/or weak miscellas) is sufficient to realize such washing and typically the weight of washing liquid will be similar to the weight of the cake. This washing is also very rapid and realized in a few minutes. After the spraying of the washing liquid onto the cake, the centrifuge is spun at high rotational speed for about 1 to 3 minutes to further eliminate the maximal amount of residual miscella (hence residual oil as well) from the cake. The last cake washing is realized with pure solvent and results in the fully washed cake which may be discharged from the centrifuge separator. Another advantage of the process according to the present technology is the low concentration of residual solvent in the fully washed cake. It has been observed that only about 15 to 25% of solvent remained in the washed cake. This is considerably lower than the residual solvent of a washed cake produced with a vacuum belt filter for example. This is advantageous because less energy will be necessary to desolventize the cake produced by the process according to the present technology compared to currently available technology. Furthermore, optionally, the residual solvent present in the fully washed cake can be removed while said fully washed cake still lays in the centrifuge separator(s) by washing it with hot water. This will reduce furthermore the energy requirements and the investments needed for the removal of the solvent from the fully washed cake. [0089] Another advantage of the process according to the present technology, is that those successive washings are realized without having to handle the SBE since this one stays static in the form of cake inside the centrifuge separator. Each washing is systematically followed by the spinning of the centrifuge separator to expel the maximal amount of new and stronger miscella out of the cake of the SBE. Those successive washing and spinning cycles are preferably realized counter-currently meaning that the fresh solvent is used to extract the cake of SBE containing the lowest amount of oil and that stronger miscella (but that is yet not the full miscella) can be used as washing medium for the cake of SBE containing the higher concentration of oil, such washing resulting in an even stronger miscella. The full miscella is obtained from the spinning or from the washing of the slurry. The full miscella is not used to wash any cake. [0090] The counter-current mode of operation is advantageous because it will require less solvent to extract a given quantity of oil from the SBE. Thus, the washing, as performed in the process according to the present technology, does not require the handling of solid SBE, because the SBE cake stays constantly in the centrifuge. When an adequate number of counter-current washing cycles are completed, a fully washed cake is obtained. The fully washed cake usually contains no more than 2% of residual oil (expressed on dry basis). Therefore, the deoiled cake can be discharged from the centrifuge separator. This discharge can be automatic in the case of basket centrifuges such as peeler centrifuges or pusher centrifuges. At this stage, a new load of slurry is introduced again in the centrifuge separator and the preferably counter-current washing cycle is initiated again. The washing/spinning cycles can be automated. The one or more washing/spinning cycle(s) can be realized with one or several centrifuge separators working in parallel provided proper piping, pumps, valves, and tanks for the holding of the miscellas of different strengths are adequately connected. Such connection is within the reach of the skilled artisan, in particular the artisan knowledgeable in the solvent extraction of oleaginous vegetable materials since said solvent extraction in also preferably realized in a counter-current mode. [0091] It must be noted that centrifuge separators are compact and in particular much more compact than vacuum belt filters or leaf filters used in current processes. Therefore, the process according to the present technology is advantageous since it requires a limited footprint compared to current technologies. Centrifuge separators are less demanding in electrical power than vacuum belt filters. Indeed, in vacuum belt filters, the vacuum must be maintained constantly in a large volume which is particularly energy demanding. [0092] In contrast, centrifuge separator will mostly consume energy in the accelerating phase of the spinning, but globally, for a given quantity of treated material, the energy demand will be lower than the energy consumed by a vacuum belt filter. Furthermore, since a fully washed cake resulting from a centrifuge separator contains substantially less solvent than a washed cake resulting from a vacuum belt filter, the energy to evaporate the said solvent will be also substantially lower for the present technology compared to current technology. Consequently, the process according to the present technology is substantially less energy demanding than currently available technologies. Furthermore, it has been observed that the cake laying in basket centrifuge does not crack and stays compact during the washing steps and this is highly advantageous over current technologies where the cake shows a market tendency to form cracks and voids when washed. This induces an inefficient washing and over- consumption of washing liquids since this one will flow preferentially through the voids and cracks. Miscellas handling [0093] Miscellas are always resulting from a phase separation occurring in at least one centrifuge separator, for example, during the washing of SBE cake with non- polar solvent or with a weaker miscella or resulting of from the spinning systematically realized after each washing. Miscellas of various concentrations in oil are found in the process according to the present technology. Since the washing of the SBE is preferably realized in a counter-current mode, the weakest miscella is obtained from the washing of the most exhausted cake with fresh solvent. This weakest miscella is then used to wash a less exhausted cake to obtain a stronger miscella. This stronger miscella is then used to wash an even less exhausted cake to obtain an even stronger miscella. [0094] This counter-current mode of washing is continued until a full miscella is obtained. When the slurry is prepared with glyceridic oil, the full miscella is obtained after the washing of the cake containing the highest concentration of residual oil. However, when the slurry is prepared with a liquid containing highly flammable and explosive non-polar solvent, the penultimate miscella, i.e. the stronger miscella that is still not the full miscella is advantageously, at least partially, used to produce the slurry. In that case the full-miscella is recovered directly after the slurry has been spin once subsequently to its introduction in the centrifuge separator. It is primordial that each miscella is segregated in function of its strength and collected in a dedicated holding tank in order to be used counter-currently as cake washing medium. [0095] Full-miscella contains usually about 20 to 40% of recovered oil. Its distillation can be realized in equipment similar to one used in the field of the solvent extraction of edible oil. However, dedicated equipment is preferred to avoid any mixing of the recovered oil from SBE with edible oil. The recovered oil, even if not edible, can be used as feedstock for the production of biodiesel or renewable diesel or other oleochemical applications such as the production of FFA. Fully washed-cake handling [0096] The fully washed cake is usually directly conveyed to a desolventizer for the evaporative removal of the remaining solvent which is then condensed, decanted to remove water, and recycled in the slurry tank and used as washing liquid. It has been found that a vertical desolventizer made of several staked compartments similar to the ones used for the desolventization of the extracted meal obtained in the solvent oil extraction of oleaginous material, is very efficient. Typically, a de-oiled SBE containing less than 2% of residual oil and less than 500 ppm of solvent will exit such desolventizer. It is thus safely storable, transportable and safe enough to be disposed of in landfills. As a matter of fact, the de-oiled SBE can be used for soil amendment, for example as a moisture retainer. [0097] Alternatively, the residual solvent present in the fully washed cake can be removed while said fully washed cake still lays in the centrifuge separator(s) by washing it with hot water. This will reduce furthermore the energy requirements and the investments needed for the removal of the solvent from the fully washed cake. Indeed, a desolventizer is a relatively expensive piece of equipment and SBE, particularly when de-oiled, are abrasive materials that will erode over time the surface of said desolventizer even more so that in a desolventizer, the material is stirred and constantly moves from the top compartment to the bottom compartment. This will generate high maintenance cost. In contrast, when the residual solvent contained in the fully washed cake is removed while this one still lays in the centrifuge separator(s) by washing it with hot water, the SBE cake remains constantly static and hence, the abrasive nature of SBE is not problematic. [0098] Thus, the process according to the present technology is able to transform a problematic waste into valuable products while necessitating a minimal energy input and limited investments and footprint. It is particularly surprising that satisfactory de-oiling of the SBE can be realized safely with only one slurry step and thus more rapidly, with less equipment, less handling, less solvent and less energy consumption compared to existing processes. [0099] Without willing to be bound to any theory, it is believed that what makes the process more economical and more efficient is the ability of the centrifuge separator, in particular the peeler centrifuge, to remove a superior fraction of miscella from the slurry. It is believed that the washing steps realized in the centrifuge separator(s) not only remove the remaining miscella still entrapped in the cake but is also operating as a real oil extraction and this despite the known poor solvent percolation of SBE cake. This oil extraction realized by the centrifuge separator(s) is particularly demonstrated when the slurry is prepared with glyceridic oil since in that case the role of the slurry is simply to transform the solid SBE into a pumpable and transportable liquid but not to perform any oil extraction. The reasons of this considerably better separation and extraction occurring in centrifuge separator are not fully understood even if it is suspected that the high g-force occurring in said centrifuge separator is the main contributor to this observation. The washing of the cake according to the present technology is efficient because the cake shows much less tendency to form cracks and/or voids compared to current technologies. However, this observation is totally unexpected and not understood. [00100] It must be pointed out that the process according to the present technology is highly advantageous over current practices. Indeed, most surprisingly, the process according to the present technology is able to deliver de-oiled SBE having sufficiently reduced residual oil content with only one slurry production step, said slurry being produced with non-polar solvent or miscella or blends thereof, or with glyceridic oil. Furthermore, the one or more washing and spinning cycles of the cake delivers a fully washed cake containing a limited amount of residual non-polar solvent, compared to prior technology, which is also advantageous, since the desolventization of said fully washed cake requires less energy and a desolventizer of reduced size. Thus, compared to current technologies, the present technology requires less investment, less footprint and less energy input and is also considerably less hazardous since it allows to safely handle SBE particularly when the slurry is prepared with glyceridic oil and/or when the fully washed cake is desolventized with hot water while this one still lays static in the centrifuge separator. [00101] While embodiments of the disclosed technology have been described, it should be understood that the present disclosure is not so limited and modifications may be made without departing from the disclosed technology. The scope of the disclosed technology is defined by the appended claims, and all devices, processes, and methods that come within the meaning of the claims, either literally or by equivalence, are intended to be embraced therein.

Claims

CLAIMS 1. A process for the recovery of the oil contained in SBE comprising the steps of: a) producing a slurry by mixing said SBE with a liquid, b) transporting and feeding said slurry to at least one centrifuge separator, c) spinning said at least one centrifuge separator to obtain a SBE cake remaining into said at least one centrifuge separator and a liquid removed from said at least one centrifuge separator, d) washing said SBE cake remaining into said at least one centrifuge separator to yield a fully washed cake and several miscellas of various strengths, e) discharging said fully washed cake from the said at least one centrifuge separator, f) recovering the oil originally contained in SBE from the full miscella, said full miscella being the liquid obtained in step c) or the miscella having the highest strength of step d), characterized in that the washing of step d) is realised with one or more washing liquid(s), to produce a fully washed cake substantially de-oiled, said cake remaining constantly into said at least one centrifuge separator during the washing, and to produce one or more miscellas of different strengths that are removed from said at least one centrifuge separator.

2. The process according to claim 1, wherein said substantially de-oiled cake contains less than 2 weight % of residual oil on a dry basis.

3. The process according to claim 1, wherein said liquid of step a) used to produce the slurry is glyceridic oil.

4. The process according to claim 1, wherein said liquid of step a) used to produce the slurry is a non-polar solvent selected from the group consisting of hexane, toluene, xylene, ethanol, petroleum diesel and renewable diesel, or miscella containing a non- polar solvent of the same group of non-polar solvents.

5. The process according to claim 1, wherein the fully washed cake obtained in step d) is desolventized by further washing said fully washed cake with hot water, said fully washed cake remaining in the one or more centrifuge separator during said further washing with hot water.

6. The process according to claim 1, wherein the discharged fully washed cake is thermally desolventized.

7. The process according to claim 1, wherein said liquid of step a) used to produce the slurry is glyceridic oil, and wherein said step a) is located in a non-regulated area, and steps b), c), d), e) and f) are located at least partially in one or more regulated area(s).

8. The process according to claim 1, wherein said SBE contains water, said water being optionally decanted from any liquids removed from said centrifuge separator.

9. The process according to claim 1, wherein said liquid of step a) used to produce the slurry is glyceridic oil, and wherein additional non-polar solvent or miscella is added to said slurry during its transportation or before the feeding of said slurry to the one or more centrifuge separator(s).

10. The process according to claim 1, wherein the strongest miscella produced is step d) is used at least partially in step a) as liquid to produce the slurry.

11. The process according to claim 1, wherein said liquid of step a) used to produce the slurry is glyceridic oil, and wherein the liquid obtained in step c) is recycled, at least partially, in step a) as liquid to produce the slurry.

12. The process according to claim 1, wherein said liquid used to produce the slurry is hexane and/or a miscella containing hexane, and the liquid obtained of step c) is the full miscella.

13. The process according to claim 1, wherein said liquid used to produce the slurry is renewable diesel or a miscella containing renewable diesel, and the liquid obtained in step c) is the full miscella, said full miscella being used as feedstock for an hydrotreatment process of glyceridic oil contained in said miscella.

14. The process according to claim 1, wherein said cake washing of step d) is realized counter-currently.

15. The process according to claim 1, wherein the liquid to SBE ratio of step a) preferably ranges from 1:10 to 10:1, and even more preferably ranges from 1:1 to 3:1.

16. The process according to claim 1, wherein the SBE of step a) includes spent bleaching earths, spent clays, spent filter aids, spent silicas, spent active carbons or any spent solid particulate materials, or any blends thereof, used during the refining of glyceridic oil and containing adsorbed residual oil after their usage during any step of the refining of glyceridic oil.