Improved process for pretreating raw renewable feedstocks intended for transformation processes into biofuels

Abstract

A method for pretreating and purifying raw bio-feedstocks intended for transformation processes into biofuels is described, said method being characterised in that said raw bio-feedstock is subjected, in the form of an aqueous emulsion, to a heat treatment by passing through a reactor at a temperature of 230-260°C for a contact / residence time of 1-5 minutes, the effluent leaving said reactor being subsequently subjected to at least one non-absorbent physical separation to separate said bio-feedstock from said metallic contaminants including phosphorus.

Description

[0001] IMPROVED PROCESS FOR PRETREATING RAW RENEWABLE FEEDSTOCKS

[0002] INTENDED FOR TRANSFORMATION PROCESSES INTO BIOFUELS

[0003] The present invention relates to an improved purification pretreatment of edible or non-edible raw renewable feedstocks (hereinafter also referred to as raw "bio- feedstocks" for the sake of simplicity) , which makes them suitable for the production of biofuels by hydrodeoxygenation and subsequent isomerisation (e.g. Ecofining process™) and / or suitable to be subjected to upgrading processes such as co-feeding in gasoil desulphurisation units, hydrocracking, fluid catalytic cracking (FCC) .

[0004] More particularly, the present invention relates to a pretreatment process as defined above wherein raw biofeedstocks such as, for example, vegetable oils, animal fats, derivatives thereof including Used Cooking Oil (UCO) and by- products / scraps obtained from the processing thereof, are subjected to a fast non-catalytic heat treatment and to a subsequent non-absorbent physical separation of metallic contaminants so as to enhance the purified renewable feedstock .

[0005] More particularly, the present invention relates to a process of purification from metal contaminants / pollutants (i.e. alkali metals, alkaline earth metals, heavy metals including transition metals) and phosphorus (i.e. from phospholipids) carried out in a single step with a demetallation (defined as a percentage decrease in the metal and phosphorus content of the purified renewable feedstock in relation to their content in the raw renewable feedstock) of at least 94%, achieved in a residence time of 5 minutes or less.

[0006] It is known in the art that catalytic processes of transforming renewable feedstocks into biofuels, such as upgrading and / or Ecofining™ processes, require the aforementioned feedstocks to be substantially free of compounds contaminating the catalysts such as, for example, metal pollutants and phosphorous (present in oils in the form of phospholipids) in order to preserve catalytic activity .

[0007] For example, in Ecofining™ processes, the total content of metal pollutants (e.g. Ca, K, Fe, Mg) and phosphorus in the renewable feedstock being supplied to the process is required to be, as a battery limit, less than lOppm, while, in the raw renewable feedstocks, such as a vegetable oil, the total content of metal pollutants is around 100-200 ppm and the phosphorus content is around 20-30 ppm. These metal and phosphorous contents can reach values even higher than 500 ppm in case of waste raw materials such as animal fats and oils from vegetable residues.

[0008] At present, different industrial pretreatment processes are used depending on the type of raw renewable feedstock, its metal pollutant and phosphorus content, and the type of transformation into biofuels.

[0009] The main pretreatment technologies can be summarised as follows :

[0010] • Degumming (and neutralization with caustic substances)

[0011] • Bleaching

[0012] • Deodorizing

[0013] • Catalytic hydrogenation (the purpose of which is only to remove contaminants, including metals, and possibly make a mild hydrogenation of the double bonds) .

[0014] In order to bring the raw renewable feedstock to specification for its transformation into biofuel, the aforementioned processes are generally used in series, as each of the aforementioned technologies is specific for the removal of certain impurities present in the renewable feedstock .

[0015] Typically, the DEGUMMING and BLEACHING processes are used in series as they allow the removal of phosphorus and alkali metals, alkaline earth metals and heavy metals, reaching a phosphorus content less than or equal to 3 ppm.

[0016] In particular, the DEGUMMING process makes it possible to lower the phosphorus content linked to the presence of phospholipids, and the content of Ca, Mg, which are responsible for the ageing and the deactivation of upgrading catalysts, but not the content of other types of contaminants, e.g. Iron, K. In this type of pretreatment, vegetable oils, waste oils and animal fats are washed under heat (75-100°C) , at atmospheric pressure, with an aqueous acid solution (of different nature, the acid concentration being such that it has a pH of about 5) and subjected to strong mechanical stirring in order to hydrate the nonhydratable phospholipids, and then these oils are neutralized with NaOH to neutralize the excess acid. The gums formed are then separated from the oily phase by various techniques including filtration and ion exchange resins. The product obtained is called degummed oil and the waste products are gums and lecithins. The main acids used are citric acid, oxalic acid, amidosulphonic acid, polycarboxylic acids (ethylenediaminetetraacetic acid EDTA) and phosphoric acid. An example of such a process may be the one described in W02012 / 004810. In some cases, enzymatic degumming is performed using enzymes instead of acids to hydrate non-hydratable phospholipids. See for example the process described in US7494676.

[0017] The BLEACHING process is a process for the physical removal of impurities (oxidation products) , metals not removed by degumming such as alkali metals, e.g. K, transition metals, e.g. Fe, pigments (e.g. carotenoids and chlorophylls) , and phosphorus by adsorption on materials called bleaching earths (such as bentonites) or clays, operating at temperatures around 75-100°C and pressures below 3 barg. Typically, such adsorption materials are activated by a dilute acid solution (e.g. citric CgHgO? or phosphoric acid) for the hydration of non-hydratable phospholipids. Typically, the oils that are subjected to bleaching pretreatment are oils with reduced amounts of phosphorus such as, for example, degummed oils, or other impurities. The product obtained is called bleached product, and the waste products are the spent earths containing the phospholipids and the adsorbed metals. See for example the process described in US6027755.

[0018] The DEODORAZING process is a process that is limited to lowering the amount of free fatty acids (FEA) , present or formed, by stripping with superheated vapor, in a vacuum column (<5mbar) , at temperatures of approximately 230-275°C: it is carried out to prevent a high content of these acids from causing corrosion in the metallurgy of the upgrading plant. See for example the process described in US4072482.

[0019] The HYDROTREATING process is a process for saturating the double bonds of vegetable oil that occurs by using nickel-based catalysts: the high content of double bonds would in fact lead to a considerable increase in the reaction exotherm in the subsequent deoxygenation processes with hydrogen. See for example what is described in US2007 / 0010682 .

[0020] At present, there are a number of widely used alternative industrial processes in which the aforementioned pretreatment processes are carried out in the same plant in different combinations with one another, depending on the content and type of pollutants, which can be identified in the following processes:

[0021] • Palm Oil Treatment (POT) ;

[0022] • Biomass Treatment Unit (BTU) ;

[0023] • Splitting process - Hydrolysis (for high pollutant feedstocks in the order of a few % by weight) ;

[0024] • Continuous Standard Oil&Fat Pretreatment;

[0025] • Continuous High Fatty Acid Feedstock Pretreatment;

[0026] • Double Pass bleaching;

[0027] • Pretreatment System for Biodiesel.

[0028] The "Palm Oil Treatment (POT)" process involves using a Degumming section, a Bleaching section and a Deodorizing section .

[0029] The process referred to as "Biomass Treatment Unit (BTU)" allows for the pretreatment and purification of Used Cooking Oil (UCO) and animal fats that have a content of pollutants generally not exceeding 500 ppm, and employs a plant with functions very similar to those of the POT but with some differences in configuration compared to the POT. In fact, there are two degumming sections in parallel instead of one: one dedicated to the acid pretreatment of UCOs and the other for tallow (animal fats) . The bleaching section is similar to that of the POT process, but it is supplied with degummed product and a mixture of palm oil and PFAD (Palm Fatty Acid

[0030] Distillate) . The process for "Splitting" vegetable oils, which is a process of hydrolysis of triglycerides, makes it possible to obtain fatty acids free of impurities in a simple way. The raw bio-feedstock, consisting of oils, fats or a mixture thereof, is introduced, at a temperature of 80-120°C, into a reactive splitter with feedstocks, together with water at 40-60°C and high-pressure vapor (70 bar) , which also provides the heat for the feedstock. The hydrolysis reaction of triglycerides takes place at high temperature and high pressure, at 250-260°C and 60 bar, respectively. The reaction product consisting essentially of stripped fatty acids is taken from the head of the stripping column. The fatty acids obtained are completely free of impurities and constitute a bio-feedstock ready to be subjected to upgrading processes. However, a mixed phase of water, glycerine and contaminants present in the starting raw feedstock exits from the bottom of the column. The yield of the process in terms of fatty acids is about 72%.

[0031] This SPLITTING process allows an almost complete removal of the pollutants (metals and phosphorus are eliminated) that make up the incoming feedstock but it changes the chemical nature of the product (mixture of free fatty acids) compared to the incoming oil, producing as a co-product about 9% glycerine, which can be valorised and sold in the reference markets. The disadvantage of this process is the high investment costs compared to those of the POT / BTU for the same processed flow rate.

[0032] Furthermore, as the product obtained is a mixture of free fatty acids (and not oil) , this requires plants with highly acid-resistant metallurgy to be further processed.

[0033] The pretreatment system called "Continuous Standard Oil&Fat Pretreatment" is suitable for the pretreatment of feedstocks with a high phosphorus content (generally around 0.5% by weight of phosphorus or less) and with a low free fatty acid (FFA) content (less than 5% by weight) . This system includes a degumming and neutralisation section (with caustic substances) and a bleaching section with silica.

[0034] The "Continuous High Fatty Acid Feedstock Pretreatment" process, which is suitable for the treatment of feedstocks with high FFA content (> 5% by weight) and high phosphorus content, provides for three stages: a degumming / neutralization section (which aims at neutralizing the acidity introduced by the acid used for degumming) , a bleaching section and a deodorizing section. The removal of fatty acids takes place in the deodorizing section by means of high-temperature vacuum stripping with vapor.

[0035] The "Double Pass Bleaching" process essentially consists of a pretreatment with silica of an already degummed / neutralized bio-feedstock which is mixed with silica to absorb the gums, which essentially consist of soaps and phospholipids.

[0036] The "Pretreatment System for Biodiesel" is a process involving a series of stages and equipment as follows :

[0037] • Acid degumming;

[0038] • Centri fuge operating at high speed for the separation by precipitation of gums ;

[0039] • Bleaching with bleaching earths and / or activated charcoals .

[0040] I f the bio- feedstocks are particularly rich in contaminants ( around 0 . 5% by weight or less ) , the process involves a more complex treatment methodology that involves the following four or five steps :

[0041] • Degumming (not only acid but with water or enzymatic ) ;

[0042] • Chemical neutrali zation with soda ;

[0043] • Bleaching with bleaching earths and / or activated charcoals ;

[0044] • Dewaxing for those bio- feedstocks containing waxes ;

[0045] • Deodori zing ( through the addition of soda or a stripping column) .

[0046] CA 3 212 084 Al in the name of the Applicant discloses a method of processing palm oil by thermally treating it with water or citric acid, wherein the contact time during the thermal treating is 10- 15 minutes . The use of waste water separated from the oil phase is not disclosed .

[0047] It is therefore an obj ect of the present invention to provide a simpli fied industrial process capable of lowering the total content of impurities in the treated renewable feedstock, in particular capable of lowering the total content of metal pollutants (alkali metals, alkaline earth metals, heavy metals and transition metals such as Ca, K, Fe, Mg) and phosphorus to below 10 ppm (by weight) , regardless of their initial total content.

[0048] A further object of the present invention is to provide such a process or method for pre-treating and purifying raw bio-feedstocks as defined above, which employs fewer chemicals such as acids, bases and absorbent materials, and in low quantities, so as to have lower operating costs.

[0049] Another object of the present invention is to provide a method for pre-treating and purifying the aforementioned raw bio-feedstocks that exhibits a substantial decrease in or absence of industrial by-products to be disposed of as waste, e.g. waste water, so as to make the purification process more environmentally sustainable.

[0050] A further object of the present invention is to provide a method that can purify raw bio-feedstocks having a high total amount of metal contaminants (alkali metals, alkaline earth metals and heavy metals such as Ca, K, Fe, Mg) above 100 ppm up to values in the order of some % by weight, without transforming the renewable bio-feedstock into a product of a different chemical nature.

[0051] Another object of the present invention is to provide a process that allows to obtain in a short time, e.g. equal to or less than 5 minutes, and with less energy consumption, a purified renewable feedstock having a demetallation degree of at least 94%, with a lower increase in TAN and with less degradation of the processed feedstock, e.g. less than 0.5%, preferably less than 0.1% evaluated as CO2 yield (%wt / raw feedstock weight) .

[0052] In accordance with these objects, the present invention relates to a simplified industrial process for pre-treating and purifying raw, edible or non-edible bio-feedstocks, such as vegetable oils, animal fats, derivatives thereof, including Used Cooking oil and by-products / scraps obtained from their processing and the like, intended for transformation processes into biofuels, as defined in the appended claim 1.

[0053] Preferred aspects and features of the invention are defined in the dependent claims.

[0054] The Applicant has in fact unexpectedly found that by subjecting an acidic aqueous emulsion of a raw bio-feedstock to a non-catalytic heat treatment operating under specific conditions of temperature, pressure and residence time in the thermal reactor, it is possible to obtain an efficient decrease in the content of metallic contaminants / pollutants such as alkali metals, alkaline earth metals, heavy metals including transition metals, and a decrease in phosphorus content obtaining a purified bio-feedstock having a total content of these metal contaminants of less than 10 ppm (overall) and / or a total phosphorus content of less than 3 ppm, values achievable in the prior art by a degumming process followed by a bleaching process.

[0055] Therefore, a first object of the present invention is a pretreatment process for purifying raw bio-feedstocks, intended for transformation processes into biofuels, in order to decrease the content of metal contaminants and phosphorous deriving from phospholipids, said method comprising the following steps

[0056] (a) contacting said raw bio-feedstock with acidulous water to form an aqueous emulsion;

[0057] (b) subjecting said acidulous aqueous emulsion to a heat treatment, in a heat treatment reactor, at a temperature ranging from 230°C to 260°C, at a pressure ranging from 40 to 65 barg, preferably from 45 to 55 barg, and for a contact time ranging from 1 minute to 5 minutes (extremes included) , preferably from 1.5 minutes to 4.5 minutes, obtaining an effluent;

[0058] (c) subjecting said effluent to at least one non-absorbent physical separation to separate said heat-treated biofeedstock from said phosphorus, metal contaminants and acidulous water.

[0059] The "contact time" (hereinafter also referred to as "residence time") is intended to identify the ratio between the volume of the heat treatment reactor, expressed in m3, and the volumetric flow rate, expressed in m3 / h, of the acidulous aqueous emulsion containing the raw bio-feedstock that is supplied into the reactor. The density of the raw feedstock generally used to calculate the aforementioned volume flow rate of the aqueous emulsion is preferably the one measured at the temperature at which step a) is carried out, e.g. T ranging from 40 to 80°C, generally 80°C, although this is not binding for the purposes of the present invention.

[0060] It is also possible to refer to the "contact time" or "residence time" calculated on the volumetric flow rate of the bio-feedstock alone, in which case it will be expressly specified in this description.

[0061] Raw bio-feedstocks that can be used in the process of the present invention may be edible or non-edible, of renewable origin such as, for example, vegetable oils, animal fats, derivatives of vegetable oils and / or animal fats, including Used Cooking Oil, and by-products / scraps obtained from the processing thereof, e.g. husk oil, and the like.

[0062] Other examples of bio-feedstocks are tobacco oil, palm oil, used cooking oil (UCO) , raw soybean oil, CAT 1, 2 and 3 animal fats, acid oils, Crude Palm Oil Mill Effluent and their by-products.

[0063] The invention will hereinafter be described in detail referring, for the sake of simplicity, only to "oil" as a renewable feedstock, but is intended to be applicable to any renewable feedstock or bio-feedstocks as set forth above and detailed below, even those with a high contaminant content, without thereby departing from the scope of the present invention .

[0064] The aforementioned purification treatment takes place in a single stage, without supplying vapor from outside.

[0065] After step (c) , a step (d) is advantageously provided to purify said acidulous water separated in step (c) to obtain purified acidulous water that is reused in said step (a) , as will be explained in detail hereinafter.

[0066] The heat treatment of step (b) makes it possible to transform, in the aforementioned contact time range and at the aforementioned temperatures and pressures, the raw renewable feedstock into an effluent comprising a gaseous phase, a liquid phase and a solid phase, i.e. at least a three-phase effluent, obtaining a demetallation of at least 94% at pressures below 65 barg and at temperatures below 260°C, with considerable energy and economic savings compared to other processes known in the art.

[0067] The pressure of step (b) can be selected within the aforementioned range so as to keep the acidulous water in the liquid phase at the selected working temperature (singlephase liquid system) or so that the acidulous water partially vaporises .

[0068] In one embodiment, the pressure of step (b) can be selected within the aforementioned range so as to keep the water in the liquid phase at the selected working temperature .

[0069] Alternatively or in addition to the above, in one embodiment, the process is carried out under conditions of temperature, pressure, and possibly residence time, such that there is a CO2 yield greater than 0 but less than 0.5 % evaluated as CO2 %weight / raw feedstock weight.

[0070] The liquid phase included in the effluent comprises:

[0071] • Purified oil to be sent to downstream conversion processes (lipid phase or otherwise referred to as oily phase) ;

[0072] • Acidulous water (waste water) containing some of the contaminants initially present in the raw feedstock, e.g. metals and phosphorus in the form of water-soluble substances, and to a much lesser extent lipid phase entrainments .

[0073] The solid phase included in the effluent comprises:

[0074] • Solids wherein phosphorus is present, in the form of inorganic phosphates, and the remaining metal contaminants in the raw feedstock (i.e. non-water-soluble metal contaminants) .

[0075] The fact that most of the metal and phosphorous contaminants initially present in the raw bio-feedstock result in a solid phase is one of the advantages of this process, as they can be more easily separated from both the treated oil and the aqueous phase, which will be more easily processed in the appropriate purification treatments.

[0076] The amount of solids produced by the process of the invention varies depending on whether the raw renewable feedstock contains a high or low total amount of pollutants as defined above. These solids consist of metals such as, for example, potassium, calcium and magnesium, and the phosphorous originally present in the oil, and which, following treatment at the temperatures, pressures and residence times defined above for step (b) , form a third phase as such. In particular, in the solid phase included in the effluent, phosphorus is found in the form of inorganic phosphates. Given its composition, this solid material can be used directly in agriculture.

[0077] Therefore, the metal contaminants and phosphorous initially present in the raw bio-feedstock are present in said effluent as solid residues that can be separated from the purified bio-feedstock by a simple non-absorbent separation, e.g. gas-liquid separation + centrifugation or three-phase separation in a three-phase separator, as will be explained in detail below.

[0078] The purified oil obtained from this purification process generally has a total contaminant content of less than 10 ppm and / or a phosphorous content of less than 3 ppm.

[0079] The water used to form the acidulous water to be used in step (a) is advantageously demineralised water, distilled water, industrial water, with a low salt content, although the Applicant has unexpectedly found that even waste water obtained from effluent separation can be reused to form the aforementioned emulsion, if it has previously undergone membrane puri fication .

[0080] In fact , it was found that in step ( a ) of the present heat treatment process , it is possible to reuse the acidulous water separated from the ef fluent (waste water ) , after membrane filtration, without substantially modi fying the pollutant removal performance of the raw feedstock obtainable in step (b ) .

[0081] The membrane puri fication of waste water can be carried out by conventional nanofiltration or reverse osmosis processes used to treat liquids with solids in low concentrations , so that a puri fied but still acidulous waste water is obtained, without thereby departing from the scope of the present invention .

[0082] With the nanofiltration and reverse osmosis processes o f the prior art , residual contaminants are removed from the process waste water, in addition to traces of organic compounds of the feedstock that were entrained in the aqueous phase .

[0083] This recovery and subsequent recycling of the puri fied waste water advantageously results in acid savings , in addition to avoiding the disposal of this still acidulous waste water in a special waste water treatment system (WWT ) that does not always exist within industrial plants .

[0084] The possibility of reintroducing waste water as a supply to the process of the invention makes it advantageously possible to install the heat treatment process of the invention even in industrial sites not provided with WWT .

[0085] In addition, the reuse of acidulous waste water in the process of the invention makes it possible to limit the consumption of volumes of demineralised water, distilled water, industrial water, with less dependence on supply sources and environmental benefits as well.

[0086] In practice, the pretreatment and purification process of the present invention can advantageously provide to carry out, after step (c) , a step (d) of purification of said acidulous water separated in step (c) resulting in a purified acidulous water to be recycled in said step (a) .

[0087] The heat treatment reactor (herein defined also as "thermal reactor") in which step (b) of the present process takes place may be a helical coil, or a tube, or a conventional tubular reactor, without thereby departing from the scope of the present invention.

[0088] The coil, tube or tubular reactor is usually heated from the outside along its entire length, evenly and uniformly, e.g. by contact with thermostatic hot-oil or a thermostatically controlled heating device, e.g. electric heating means, resulting in an isothermal tube or coil.

[0089] The heat treatment reactor contains no catalyst.

[0090] External heating of the tube, coil or reactor in general ensures that the heat treatment temperature of the mixture inside the reactor is essentially equal to the selected temperature as defined above. It is understood that the reactor may include not only one tube but also a plurality of parallel tubes , heated from outside , without thereby departing from the scope of the present invention .

[0091] Hereinafter, any reference to "tube" is to be understood as extended and also applicable also to "tubes" without thereby departing from the scope of the present invention .

[0092] In the present heat pretreatment and puri fication process , it was observed that the hydrolysis of triglycerides leading to the formation of free fatty acids is negligible , thus not changing the chemical nature of the puri fied biofeedstock compared to the one to be puri fied .

[0093] The pretreatment and puri fication process in accordance with the present invention therefore makes it possible to ef fectively and simply remove , in a single stage , all the metal pollutants / contaminants such as alkali metals , alkaline earth metals and heavy metals , ( e . g . Ca, K, Fe , Mg ) and the phosphorous deriving from the phospholipids present in the raw bio- feedstock, without having to resort to the use of bases and / or absorbent materials , achieving an overall content of impurities in terms of metallic pollutants such as , for example , Ca, K, Fe, Mg, P, Na, Al , Sn, Zn, less than or equal to 10 ppm (by weight ) and a phosphorous content of less than 3 ppm, preferably also less than 1 ppm .

[0094] The pre-treatment and puri fication process in accordance with the invention is suitable to be applied to any bio- feedstock that can be used to obtain biofuels, such as vegetable oils, animal fats, but also to derivatives thereof including, for example Used Cooking oil and by- products / scraps , obtained from processing thereof, which also contain mixtures of free fatty acids.

[0095] A first embodiment of the invention will now be described by referring to a "raw oil" as a renewable feedstock for the sake of simplicity.

[0096] The raw oil, generally contained in a first tank, is preferably heated in said tank and sent by means of a pump to a mixer.

[0097] This preheating of the raw oil is preferably done under stirring .

[0098] The temperature of the raw oil, heated in the first tank, can generally range from 30°C to 90°C, preferably from 40°C to 80°C, more preferably from 40°C to 50°C.

[0099] In the mixer, said heated oil is placed in contact with acidulous water, preferably hot, e.g. having a temperature ranging from 80°C to 160°C, so as to create a water in oil emulsion .

[0100] The acidulous water can

[0101] - come from a second tank; or

[0102] - be formed in situ by injecting acid into the water line entering the mixer; or

[0103] - be formed ex situ by mixing acid and water in a special tank, then sending the resulting acidulous water to the mixer .

[0104] Acids that can be used to form acidulous water include , for example , citric acid or other acids such as those used in the degumming process such as oxalic acid, or amidosulphonic acid, polycarboxylic acids ethylenediaminetetraacetic acid, phosphoric acid .

[0105] In a preferred embodiment , the acid is citric acid .

[0106] The acid can be used in quantities such that the acid content is between 0 . 5-7 % , preferably between 1-5% by weight of the acidulous water .

[0107] The amount of acidulous water to be used to form the emulsion is such as to have the volumetric oil / acidulous water ratio ranging from 1 to 20 , preferably less than 6 .

[0108] This ratio is generally calculated by considering the density of water and feedstock at the temperature at which step ( a ) is carried out, e . g . T ranging from 40 to 80 ° C .

[0109] The mixer of acidulous water and oil can be a static mixer, or a mechanical mixer with a stirrer capable of producing a water-oil emulsion .

[0110] In a preferred embodiment , the mixer is a static mixer .

[0111] The water-oil emulsion formed in the mixer is then supplied to the reactor, optionally in combination with a flow of nitrogen gas or other inert gas such as Ar, He , to prevent heat decomposition and / or polymerisation phenomena of the triglyceride structures in the raw oil .

[0112] The supply of nitrogen flow or other inert gas can take place

[0113] - in the mixer when mixing oil / water; or

[0114] - in the water-oil emulsion supply line entering the heat treatment reactor; or

[0115] - at both of the aforementioned points (in the mixer and in the line entering the reactor) , without thereby departing from the scope of the present invention .

[0116] In one embodiment, inert gas is supplied into the line supplying the water-oil emulsion to the reactor so as to increase the pressure in the heat-treatment reactor to the predetermined working pressure (the one which keeps the water in the liquid phase at the selected working temperature) .

[0117] The flow of inert gas, preferably nitrogen, can range from 245 — 1600 Nl / lraw feedstock *

[0118] Without an inert gas supply, the working pressure is regulated by means of other devices of the prior art (e.g. control valves on the liquid line) .

[0119] In case the oily phase of the effluent, i.e. the treated bio-feedstock, does not meet the requirements in terms of contaminant content, it is possible to supply the effluent back into the reactor for a second pass through the heat treatment reactor.

[0120] The effluent exiting the reactor may optionally be added with a de-emulsif ying additive (e.g. dmo86596 marketed by the Baker Hughes company) and / or anti-foaming additive conventionally used in the art , before being subj ected to step ( c ) of non-absorbent physical separation in a nonabsorbent physical separation system .

[0121] The separation of said heat-treated bio- feedstock from said metal contaminants and said phosphorus provided for in step ( c ) of the process of the invention can also be carried out by performing several stages of non-adsorbent physical separations .

[0122] In one embodiment , the step ( c ) of the process of the invention is carried out by subj ecting said ef fluent to an initial gas-liquid separation so as to separate the ef fluent into at least two phases represented by a liquid phase (water + oil ) also containing residues from impurities and a vapour phase (water vapour ) and / or gas phase ( the latter containing the reaction products such as a mixture of CO / CO2 and possibly the inert gas ) .

[0123] Said first gas-liquid separation can be carried out in a non-adsorbent physical separation system comprising at least one high-pressure separator .

[0124] The high pressure separator may be any two-phase gasliquid separator known in the art , particularly known in the Oil & Gas industry .

[0125] In this case , the liquid phase exiting said two-phase separator containing purified oil , acidulous water and the residues resulting from the impurities can advantageously be subj ected to a second non-absorbent physical separation step, e.g. by centrifugation in one or more centrifuges, in order to separate an aqueous phase containing the residues of the initial impurities, also in the form of solids (e.g. gums, solubilised pollutants, e.g. contaminating metals) from the oily phase formed by the purified oil.

[0126] The purified oil leaving the centrifuge is therefore already to specification as it has a total metal and phosphorous content of less than 10 ppm.

[0127] This purified oil exiting the centrifuge may optionally be subjected to an optional filtration in order to eliminate any dispersed solids, if still present, without thereby departing from the scope of the present invention.

[0128] The aqueous phase which contains the solid residues (including metal contaminants) and which has been separated from the oily phase in the centrifuge will then advantageously be subjected to a non-absorbent separation step, e.g. centrifugation, filtration, to remove said solid residues (e.g. gums, solids which may contain metal contaminants and any other residues) from said aqueous phase.

[0129] The aqueous phase separated from the solid residues can then be

[0130] - sent to a treatment step to allow the proper disposal of said aqueous phase (waste water that is still acidulous) in an appropriate waste water treatment (WWT) system; or subjected to membrane purification so that it can be reused in step (a) of the process of the invention.

[0131] In another embodiment, the non-absorbent physical separation of step (c) can be carried out by means of at least a three-phase separation, by sending the three-phase effluent leaving the heat treatment reactor to a three-phase separator so as to obtain three distinct phases represented by an oily phase, an aqueous phase with the aforementioned dispersed residues / solids , and a gas phase.

[0132] The three-phase separator may be any three-phase separator known in the art, for example a three-phase separator used in the Oil & Gas industry (e.g. three-phase centrifuge) .

[0133] Alternatively, the three-phase separator may be a gaswater-oil separator.

[0134] The purified oil leaving the three-phase separator therefore meets the specification as it has a total metal pollutant and phosphorous content of less than 10 ppm.

[0135] This purified oil exiting the three-phase centrifuge may optionally be subjected to an optional filtration in order to remove any dispersed solids, if still present, without thereby departing from the scope of the present invention.

[0136] Even in the case of the three-phase separator, the aqueous phase containing the solid residues (including metal pollutants) , also referred to as "waste water", can then be - sent to a treatment step to allow the proper disposal of said aqueous phase (waste water that is still acidulous) in an appropriate waste water treatment (WWT) system; or

[0137] - subjected to membrane purification so that it can be reused in step (a) of the process of the invention.

[0138] In a preferred embodiment, the step (c) of the process of the invention is carried out by means of a first nonabsorbent gas-liquid physical separation and a second nonadsorbent aqueous phase-oily phase physical separation to be carried out in a non-adsorbent physical separation system comprising a three-phase separator (e.g., a three-phase centrifuge) and, downstream thereof, possibly a filter system.

[0139] The process according to the present invention can thus be carried out in a plant comprising the following sections: raw oil supply; acidulous water supply; raw oil / acidulous water mixing; heat treatment comprising a heat treatment reactor; separation of the aqueous phase and solid residues from the oily phase in a physical separator (e.g. biphasic) ; centrifugation of the oily phase to remove any solid residues ; separation of acidulous water from solid residues.

[0140] The defects of the prior art are therefore overcome by the method in accordance with the invention, which achieves in particular the following advantages: substantial reduction in total content of metal pollutants (<10 ppm) , particularly of phospholipids ( < 3ppm, preferably less than Ippm) , with a reduced process and plant complexity; fewer chemicals used as bases and absorbent materials and used in low quantities ;

[0141] - a substantial absence of industrial by-products to be disposed of as waste , thus making the process and the plant more environmentally sustainable ;

[0142] - greater ease of use and lower running costs .

[0143] - The method according to the present invention may be carried out in a plant comprising a heat treatment reactor ;

[0144] - a non-adsorbent physical separation unit comprising at least a filter and / or centri fuge , preferably a centri fuge , for the separation of the bio- feedstock from said metal contaminants including phosphorus in the form of solid residues and possibly a gas / liquid separator, located upstream of said filter or centrifuge , to separate a gas and / or vapor phase from the remaining liquid-solid phase , where said separation section is located downstream o f said reactor .

[0145] The thermal treatment reactor is configured to receive an acidulous aqueous emulsion containing a raw bio- feedstock and an acidulous water, in particular from a mixing section . The reactor is also configured to produce an ef fluent by thermal reaction, preferably an ef fluent comprising a gaseous phase , a liquid phase and a solid phase .

[0146] In addition, upstream of said reactor, said plant al so advantageously includes one or more of the following sections :

[0147] - a storage section of the raw bio- feedstock to be treated comprising a heated tank;

[0148] - a water and / or purified waste water storage section located upstream of said reactor ; wherein said sections are in fluid communication with each other by means of fluid lines such as conduits .

[0149] Moreover, said plant comprises a mixing section located downstream of said storage section and upstream of said reactor .

[0150] The mixing section comprises a mixer configured to receive said acidulous water and said raw feedstock to form said acidulous aqueous emulsion .

[0151] Said mixer is thus capable o f mixing an acidulous water and at least one raw feedstock thus forming the acidulous aqueous emulsion containing the raw bio- feedstock and the acidulous water .

[0152] The mixer is in fluid communication with said reactor .

[0153] The mixer of acidulous water and raw feedstock has a liquid outlet of said formed acidulous aqueous emul sion connected to a liquid inlet of the reactor for supplying said formed acidulous aqueous emulsion to said reactor .

[0154] The heat treatment reactor has a liquid inlet for receiving said formed acidulous aqueous emulsion and an outlet for discharging the ef fluent of the heat treatment reaction .

[0155] The mixer and the heat treatment reactor are thus in fluid communication by means of the formed acidulous aqueous emulsion and they are linked by a line for the passage of said the formed acidulous aqueous emulsion from the liquid outlet of the mixer to the liquid inlet of the heat treatment reactor .

[0156] Some illustrative but not limiting examples of the present invention follow .

[0157] EXAMPLES

[0158] Characterization

[0159] - POLLUTANT CONTENT DETERMINATION

[0160] It was obtained by elemental analysis (by TCP technique ) using the Thermo ICAP 6500 DUO TCP instrument from Thermo Fisher Scienti fic to quanti fy residual contaminants .

[0161] PURIFICATION OF ANIMAL FAT : EXAMPLES 1-2 AND COMPARATIVE EXAMPLES

[0162] Example 1

[0163] An animal fat ( indicated in the table as "Animal fa t 2022") was used, the characterisation of which in terms o f metals and phosphorus is indicated in Table 1 .

[0164] This fat had Density at 80°C : 0.8695 g / ml.

[0165] Viscosity at 80°C : 11.38 mm2 / s.

[0166] FFA (free fatty acid) : 16% by weight.

[0167] The fat was mixed with acidulous demi-water containing 0.5%wt of citric acid to the total weight of acidulous water and in such quantities that the f at / acidulous water volume ratio was 5 (vol / vol) .

[0168] Mixing took place at a temperature of about 80°C.

[0169] The acidulous water-oil emulsion thus obtained by mixing was subjected to heat treatment at 240°C and 45 bar, in a heat treatment reactor, for a residence time, indicated by the term "tau" in the table, of 1 minute.

[0170] The reactor used is in the form of a coil (coil volume of 15 ml) heated by means of an electric oven.

[0171] The effluent obtained was then subjected to separation at high pressure (corresponding to heat treatment pressure) wherein the gaseous phase (consisting of CO / CO2) is separated from the liquid phase (aqueous phase + oily phase) containing solids .

[0172] The liquid phase is collected in a dedicated tank: a physical separation of the oil from the aqueous phase is carried out by centrifugation and ends with the filtration of the oily phase obtained by centrifugation in order to remove any dispersed solids which include the metals and phosphorous removed from the raw feedstock.

[0173] The percentage decrease in the metal and phosphorus content of the treated feedstock compared to their quantity in the starting feedstock (also referred to as "demetallation") is reported in Table 1.

[0174] Example la (comparative) Example 1 was repeated with the exception that the residence time was set at 0.5 minutes.

[0175] The percentage decrease in the metal and phosphorus content of the treated feedstock compared to their quantity in the starting feedstock is reported in Table 1.

[0176] Table 1 As it can be seen from Table 1, carrying out the process of the invention with a residence time of at least 1 minute makes it possible to obtain a demetallation greater than 95% .

[0177] Example 2

[0178] The same animal fat as in Example 1 and in Example la (comparative) was subjected to the pre-treatment and purification process of the invention, using longer residence times.

[0179] This fat was mixed with acidulous water containing 1% citric acid by weight and in such quantities that the volumetric f at / acidulous water ratio was 2.4 (vol / vol) , i.e. about half of the ratio used in Examples 1 and la (comparative) .

[0180] The aqueous emulsion thus obtained by mixing was subjected to heat treatment at 240°C and 45 bar, in the heat treatment reactor of Example 1, for a residence time, indicated in the table as "tau", of 5 minutes.

[0181] The effluent obtained was then subjected to separation at high pressure (corresponding to heat treatment pressure) wherein the gaseous phase (consisting of CO / CO2) is separated from the liquid phase (aqueous phase + oil phase) containing solids .

[0182] The liquid phase is collected in a dedicated tank: a physical separation of the oil from the aqueous phase is performed by centrifugation, and the oily phase obtained by centrifugation is then filtered to remove the dispersed solids, which comprise the metals and phosphorous removed from the raw feedstock.

[0183] The percentage decrease in the metal and phosphorus content of the treated feedstock compared to their quantity in the starting feedstock (also referred to as "demetallation") is shown in Table 2.

[0184] Example 2a ( comparative )

[0185] Example 2 was repeated with the exception that the residence time was almost doubled, setting it at 8 minutes, and the volumetric oil / acid water ratio was halved (1.2 vol / vol) .

[0186] The percentage decrease in the metal and phosphorus content of the treated feedstock compared to their quantity in the starting feedstock is shown in Table 2.

[0187] Table 2

[0188] As it can be seen from Table 2, carrying out the process of the invention with a residence time of 5 minutes (7.5 minutes referred to oil) guarantees an almost complete purification from metals and phosphorous at a nearly 99%. The increase of the residence time to 8 minutes (which corresponds to a residence time of 15 minutes when referring only to the feedstock) results in a doubling of the TAN compared to the initial one without any significant improvement in terms of demetallation.

[0189] In addition, the longer contact time caused a greater degradation of the processed feedstock, by at least 1 order of magnitude, as it can be seen from the higher CO2 yield.

[0190] PURIFICATION OF SOYA OIL AT VARIOUS TEMPERATURES: EXAMPLE 3 AND COMPARATIVE EXAMPLES

[0191] Example 3

[0192] A soybean oil was used, the characterisation of which in terms of metals and phosphorus is indicated in Table 3.

[0193] This soya oil had

[0194] Density at 80°C : 0.8791 g / ml.

[0195] Viscosity at 80°C : 11.43 mm2 / s.

[0196] FEA (free fatty acid) : 1% by weight.

[0197] Soybean oil was mixed with acidulous water containing 1% citric acid by weight and in such quantities that the volumetric oil / acidulous water ratio was 2.4 (vol / vol) .

[0198] Mixing took place at a temperature of about 80°C.

[0199] The aqueous emulsion thus obtained from mixing was subjected to heat treatment at 250°C and 55 bar, in the heat treatment reactor of Example 1, for a residence time, indicated in the table by the term "tau", of 5 minutes

[0200] (corresponding to 7 minutes if referring to oil only) . The effluent obtained was then subjected to separation at high pressure (corresponding to the heat treatment pressure) wherein the gaseous phase (consisting of CO / CO2) is separated from the liquid phase (aqueous phase + oil phase) containing solids.

[0201] The liquid phase is collected in a dedicated tank: a physical separation of the oil from the aqueous phase is performed by centrifugation, and the oily phase obtained by centrifugation is then filtered to remove the dispersed solids which include the metals and phosphorous removed from the raw feedstock.

[0202] The percentage decrease in the metal and phosphorus content of the treated feedstock compared to their quantity in the starting feedstock (also referred to as "demetallation") is shown in Table 3.

[0203] Example 3a (comparative)

[0204] Example 3 was repeated with the exception that the working temperature was set at 150°C and the working pressure at 5 barg.

[0205] The percentage decrease in the metal and phosphorus content of the treated feedstock compared to their quantity in the starting feedstock is shown in Table 3.

[0206] Example 3b (comparative)

[0207] Example 3 was repeated with the exception that the working temperature was set at 300°C and the working pressure at 90 barg. The percentage decrease in the metal and phosphorus content of the treated feedstock compared to their quantity in the starting feedstock is shown in Table 3.

[0208] Table 3

[0209] Table 3 shows the advantage of carrying out the process at temperatures around 250°C. In fact, at an operating temperature of 150°C, demetallation is limited to 76%. By increasing the temperature to 250°C, almost complete demetallation is achieved, settling at over 98%, reaching the specifications required for downstream hydrogenation processes. Further raising the operating temperature to 300°C does not lead to significant improvements.

[0210] In fact, although demetallation reaches 99.5%, this is also accompanied by an increased degradation of the feedstock, as it can be seen by the significant increase in the acidity number value which goes from 4.5 mgKOH / g to over 21 mgKOH / g.

[0211] Higher temperatures also increase the energy costs of the process and the risk of undesired reactions, such as oligomerisation .

[0212] WASTE WATER RECYCLING

[0213] EXAMPLE 4

[0214] Example 2 was repeated with the exception that a different fat was used, the composition of which is reported in Table 4.

[0215] The percentage decrease in the metal and phosphorus content of the treated feedstock compared to their quantity in the starting feedstock is shown in Table 4.

[0216] EXAMPLE 5

[0217] Example 4 was repeated with the exception that purified waste water was used, instead of demi-water, which was obtained by the separation of the aqueous phase from the ef fluent obtained from Example 4 by nanofi ltration separation .

[0218] The percentage decrease in the metal and phosphorus content of the treated feedstock compared to their quantity in the starting feedstock is shown in Table 4 .

[0219] EXAMPLE 6

[0220] Example 4 was repeated with the exception that puri fied waste water was used, instead of demi-water, which was obtained by the separation of the aqueous phase from the ef fluent obtained from Example 4 by reverse osmosi s separation .

[0221] Residual contaminants initially present in the oil , as well as organic traces entrained in the aqueous phase , are removed from the process waste water by prior art puri fication processes known as nanofiltration and reverse osmosis .

[0222] The percentage decrease in the metal and phosphorus content of the treated feedstock compared to their quantity in the starting feedstock is shown in Table 4 .

[0223] Table 4

[0224] As it can be seen from the results reported in Table 4 the use of waste water obtained from the ef fluent of the process of the present invention and puri fied does not impair the puri fication performance o f the treated feedstock and at the same time allows to obtain a product with a degree of demetallation comparable to that given by the use of demiwater . In addition, the membrane puri fication tests carried out , have not only made it possible to puri fy water and recycle it as a supply, but have also limited the reintegration of acid at the beginning of the process .

[0225] In fact , the processes adopted do not involve the total removal of the acid present in the waste water, which i s then recycled back to the process along with water, making it possible to lower the costs associated with the process .

Claims

CLAIMS1. Method for pre-treating and purifying raw biofeedstocks, intended for transformation processes into biofuels, to reduce the content of metal contaminants and phosphorus deriving from phospholipids, said method comprising the following steps(a) contacting said raw bio-feedstock with acidulous water to form an acidulous aqueous emulsion;(b) subjecting said acidulous aqueous emulsion to a heat treatment, in a heat treatment reactor, at a temperature ranging from 230°C to 260°C, at a pressure ranging from 40 to 65 barg, preferably from 45 to 55 barg and for a contact time ranging from 1 minute to 5 minutes (extremes included) , preferably from 1.5 minutes to 4.5 minutes, obtaining an effluent, preferably an effluent comprising a gaseous phase, a liquid phase and a solid phase;(c) subjecting said effluent to at least one non-adsorbent physical separation to separate said heat-treated biofeedstock from said phosphorus, metal contaminants and said acidulous water.

2. Method according to claim 1, wherein the raw biofeedstock is edible or non-edible, preferably selected from vegetable oils, animal fats, derivatives of vegetable oils and / or animal fats, including Used Cooking Oil and by- products / waste obtained from the processing of the same,e.g. HUSK oil, and the like.

3. Method according to claim 1 or 2, wherein said biofeedstock is selected from tobacco oil, palm oil, Used Cooking Oil (UCO) , crude soybean oil, animal fats CAT 1, 2 and 3, acid oils, Crude Palm Oil Mill Effluent and any byproducts thereof.

4. Method according to any one of the preceding claims 1 to 3, wherein after step (c) a step (d) of purification of said acidulous water separated in step (c) is provided, obtaining a purified acidulous water which is recycled in said step (a) .

5. Method according to any one of the preceding claims 1-4, wherein said non-absorbent physical separation of said effluent carried out in said step (c) comprises- subjecting said effluent to a first separation in a high-pressure separator to separate said effluent into a gas and / or vapour phase and a liquid phase containing purified oil, acidulated water and residues deriving from impurities; and subjecting said liquid phase to a further nonabsorbent physical separation step, preferably by centrifugation, to separate an aqueous phase containing residues of impurities from the oily phase formed by the purified bio-feedstock.

6. Method according to any one of the preceding claims1-5, wherein the quantity of water to be used to form theemulsion is such as to have a volumetric ratio of oil / acidulous water ranging from 1 to 20, preferably less than 6.

7. Method according to any one of the preceding claims 1-6, wherein said acidulous water has an acid content of between 0.5-7%, preferably between 1-5% by weight with respect to the weight of the acidulous water.

8. Method according to claim 7, wherein the acid is citric acid.

9. Method according to any one of the preceding claims 1-8, wherein said crude bio-feedstock in the form of an aqueous emulsion is prepared by hot mixing of said biofeedstock with acidulous water.

10. Plant for pre-treating and purifying raw biofeedstocks intended for transformation processes into biofuels to remove phospholipids and metal contaminants from said bio-feedstocks by the method as defined in claims 1-9, said plant comprising a thermal treatment reactor configured to receive an acidulous aqueous emulsion containing a raw bio-feedstock and an acidulous water; a non-adsorbent physical separation unit comprising- at least one filter and / or centrifuge, preferably a centrifuge, for the separation of the heat-treated bio-feedstock from said metal contaminants including phosphorus, and optionallyat least one gas / liquid separator placed upstream of said fi lter or centri fuge , for separating a gas and / or vapor phase from the remaining liquid-sol id phase said separation section being arranged downstream of said reactor .11 . Plant according to claim 10 , further comprising, upstream of said reactor, a storage section of the raw bio- feedstock to be treated comprising a heated tank; a mixing section located downstream of said storage section and upstream of said reactor, said mixing section comprising a mixer configured to receive said acidulous water and said raw feedstock to form said acidulous aqueous emulsion, an acidulous water supply section, said sections being in fluid communication with each other by means of fluid lines (pipes ) , said mixer having a liquid outlet of formed acidulous aqueous emulsion connected to a liquid inlet of the reactor for supplying said formed acidulous aqueous emulsion to said reactor .

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