FR3038323A1 - PROCESS FOR THE PREPARATION OF A COMBUSTIBLE ACID OIL RESULTING FROM THE ACIDIFICATION OF A NEUTRALIZATION PULP OF VEGETABLE AND / OR ANIMAL ORIGIN. - Google Patents

Abstract

The present invention relates to a process for preparing a combustible acid oil derived from biomass, in particular resulting from the acidification of a neutralization paste obtained by a process for refining a vegetable and / or animal oil. The method according to the invention makes it possible to obtain a fuel acid oil with a low content of water, ash, sulfur, calcium, phosphorus, sodium, and possibly alkali metals other than sodium, suitable for being burned in industrial combustion plants.

Description

PROCESS FOR THE PREPARATION OF A COMBUSTIBLE ACID OIL RESULTING FROM THE ACIDIFICATION OF A NEUTRALIZATION PULP OF VEGETABLE AND / OR ANIMAL ORIGIN

TECHNICAL AREA

The present invention relates to a process for preparing a combustible acid oil derived from biomass, in particular resulting from the acidification of a neutralization paste obtained by a process for refining a vegetable and / or animal oil. The invention also relates to a fuel acid oil and the use of this oil. The fuel acid oil of the present invention is more particularly adapted for use in combustion plants consuming exclusively, alone or as a mixture, natural gas, liquefied petroleum gases, heating oil, coal, heavy fuel oils, biomass.

In particular, the combustible acid oil of the present invention can be used in combustion plants classified under heading 2910 A (and a fortiori 2910 B and 2910 C) of the nomenclature of classified installations for the protection of the environment (nomenclature ICPE) defined in Decree No. 2013-814 of 11 September 2013, published in the Official Journal of the French Republic of 13 September 2013.

PRIOR ART The petroleum refining industry, at least in Western Europe, tends to decrease the production of heavy fuel oil, because of the drop in demand. This decline is related to the switch to alternative sources of energy by customers, including natural gas, as well as environmental constraints that tend to limit the amount of NOx, SO2 and dust emitted into the atmosphere. In order to comply with the most stringent regulatory requirements, high-power combustion plants should use oil that is free from nitrogen, sulfur and ash or smoke treatment techniques, which is not economically viable. compared to other energies, such as natural gas for example.

In addition, the heavy fuel oil generally needs to be stored at a temperature of 50 ° C to make it pumpable and to be sprayed at a temperature between 85 and 130 ° C according to burner technology, in connection with the viscosity of the product. These heating steps represent a significant energy consumption.

In addition, the flash point of heavy fuel oil (typically between 70 and 120 ° C) close to its implementation temperature, may cause additional constraints in terms of safety (explosive atmospheres).

There is therefore a need for a fuel substitute for heavy fuel which is less restrictive when it is implemented and which makes it possible to meet the higher and higher requirements relating to atmospheric emissions resulting from its combustion.

There are fuel compositions based on heavy fuel oil and products made from biomass, such as, for example, the fuel compositions prepared by the applicant and described in documents WO2013 / 098524 and WO2014 / 102492. The fuel compositions described in WO2013 / 098524 are a mixture of heavy fuel oil and a tall oil or a neutralization oil (composition of acidic acids neutralized with a base and then acidified), tall oil and the neutralization oil for stabilizing the fuel composition. The compositions described in WO2014 / 102492 are mixtures of a neutralization paste and a heavy fuel of petroleum origin. These different fuel compositions are however not entirely derived from biomass.

There is a need for a fuel substitute for heavy fuel oil which is less restrictive during its implementation, which makes it possible to meet the higher and higher requirements relating to atmospheric emissions resulting from its combustion and which is entirely derived from the biomass.

BRIEF SUMMARY OF THE INVENTION

The Applicant proposes a process for preparing a fuel, in particular a liquid fuel, derived from biomass that can be substituted for an oil, in particular for being burned in an industrial boiler or an industrial oven instead of an oil .

A first subject of the invention thus relates to a process for preparing a fuel derived from biomass comprising: a) a step of supplying an acidic oil resulting from the refining of one or more oils chosen from an oil plant and / or an animal oil, the acidic oil having a water content less than or equal to 1% by weight, or even less than or equal to 0.8% by weight, in particular from 0.1% to 0.7% by weight b) a step of reducing the ash, sulfur, phosphorus, calcium and sodium contents of the acidic oil obtained in step a), this reduction step comprising one or more sub-steps chosen from a filtration; and precipitation, carried out under conditions effective to obtain a fuel acid oil comprising an ash content of less than or equal to 0.1% wt, ideally less than 0.05 wt%, sulfur less than or equal to 150 mg / kg, preferably less than 100 mg / kg, • inferior calcium less than or equal to 5 mg / kg, preferably less than 1 mg / kg, • phosphorus less than or equal to 150 mg / kg, • sodium less than or equal to 10 mg / kg, preferably less than 1 mg / kg.

Advantageously, step b) may also make it possible to reduce also the content of alkali metals other than sodium, especially at a value of less than or equal to 1 mg / kg. The acidic oil supplied in step a) can be defined as resulting from the acidification of a neutralization paste.

Acidic oils thus naturally have low but variable levels of sulfur and nitrogen, so that their combustion produces low SO2 and NOx emissions. However, it is necessary to reduce the sulphate content (so sulfur) to limit particulate emissions. However, their water and ash content is important and leads, on the one hand, to a reduction in combustion efficiency and, on the other hand, to particulate emissions that do not meet environmental requirements.

The method according to the invention makes it possible to obtain a combustible acid oil, constituting the fuel derived from the biomass of the present invention, having a good calorific value and which can be burned by producing low emissions of atmospheric pollutants. It can thus substitute for a heavy fuel type fuel. The invention thus makes it possible to obtain a fuel derived solely from biomass, namely neutralization pastes, the emissions of which respect high environmental constraints.

In addition, despite varying compositions of the acid oils according to their origin (in particular depending on the nature of the vegetable and / or animal oil from which they are derived and the quality of this oil), the process according to the present invention allows to obtain a fuel with constant characteristics in terms of emissions of atmospheric pollutants, guaranteeing the use of fuel in combustion plants usually using heavy fuel oil or the other types of fuel mentioned above (in particular installations classified according to types 291 OA, 2910B, 291 OC ICPE nomenclature).

Another subject of the invention relates to a fuel acid oil, in particular derived from the acidification of a neutralization paste obtained by a process for refining a vegetable and / or animal oil, comprising contents of: • lower ash or 0.1% wt%, ideally less than 0.05 wt%, • sulfur less than or equal to 150 mg / kg, preferably less than 100 mg / kg, • calcium less than or equal to 5 mg / kg, preferably less than 1 mg / kg, • phosphorus less than or equal to 150 mg / kg, • sodium less than or equal to 10 mg / kg, preferably less than 1 mg / kg.

According to advantageous forms, the ash content may be less than or equal to 0.04% by weight.

Advantageously, the fuel acid oil according to the invention may further comprise an alkali metal content other than sodium less than or equal to 1 mg / kg.

Advantageously, the fuel acid oil according to the invention has a water content less than or equal to 1% by weight, or even less than or equal to 0.8% by weight, in particular from 0.1% to 0.7% by weight.

Advantageously, the fuel acid oil according to the invention may have a flash point greater than or equal to 200 ° C. (measured according to standard NF EN ISO 2719 by means of a so-called Pensky Martens device). A high flash point makes it possible to reduce storage safety constraints compared to a heavy fuel oil with a lower flash point. This results in lower implementation costs and easier implementation.

Such a combustible acid oil can be directly obtained by the process according to the invention.

Another subject of the invention relates to a method of combustion of a fuel in a combustion plant, in particular of type 2910A or 2910B or 2910C according to the ICPE nomenclature, in which a fuel acid fuel directly obtained by the process according to the invention or a combustible acid oil according to the invention. DETAILED DESCRIPTION OF THE INVENTION Step a) supplying an acidic oil The acidic oil supplied in step a) is obtained by refining one or more oils chosen from a vegetable oil and / or an oil animal.

It is in particular an oil resulting from the acidification of a neutralization paste, this neutralization paste being derived from the refining of one or more oils chosen from a vegetable oil and / or an animal oil.

An acidic oil can be defined as base-neutralized fatty acid compositions and then acidified.

The fatty acids advantageously come directly from the saponification of a vegetable and / or animal oil, such that, without being limiting, sunflower, soybean, rapeseed, palm, coconut, peanut, olive oil. , a fish oil, and typically comprising in the great majority of saturated or unsaturated C 16 -C 18 carbon chains, of which, for example, unsaturated carbon chains of C 18. Vegetable oils usually include palmitic, oleic, linoleic acid and other acids in smaller amounts. The base neutralized fatty acid compositions are typically neutralization pastes.

Typically, an acidic oil contains from 30 to 70% by weight of fatty acids. The acidic oil provided in step a) advantageously has a water content less than or equal to 1% by weight, or even less than or equal to 0.8% by weight, in particular from 0.1% to 0.7% by weight. . Stage a) can in particular comprise the supply of an acid oil resulting from the refining of one or more oils chosen from a vegetable oil and / or an animal oil having a water content of less than or equal to 3 % wt, followed by a centrifugation step making it possible to obtain a water content less than or equal to 1% by weight, or even less than or equal to 0.8% by weight, in particular from 0.1% to 0.7% by weight. wt. Step a) of supplying an acidic oil may advantageously comprise: a) a step of extracting the fatty acids present in a neutralization paste resulting from the refining of one or more oils chosen from a vegetable oil and or an animal oil, this extraction step being carried out in an acidic medium under conditions that are effective for forming an aqueous phase and an organic phase comprising said fatty acids, a2) a separation step during which said organic phase is separated beforehand. formed and recovered.

The organic phase recovered in step a2) constitutes an acidic oil generally having a water content of less than or equal to 3% by weight. Neutralization paste used in step a1)

The neutralization paste treated in step a1) may be a mixture of neutralization pastes obtained from the refining of different oils or may be a neutralization paste resulting from the refining of a single oil.

Such neutralization pastes come in particular directly from the saponification of a vegetable oil and / or an animal oil. In general, this saponification is carried out by adding a base, usually sodium hydroxide, and eliminates the free fatty acids present in the oil, which are found in the soapstock. form of alkaline salts of fatty acids. Before this saponification, the vegetable and / or animal oil may undergo a degumming or degumming operation to eliminate phospholipids, lecithins, sugar complexes and other impurities. The separation of the oil and the neutralization paste resulting from the saponification can be carried out by centrifugation.

The neutralization pastes thus essentially comprise base neutralized fatty acids. They typically comprise from 30 to 70% by weight of fatty acids.

In addition to the base-neutralized fatty acids, the neutralization pastes may contain, depending on their origin and the quality of the saponification, unreacted phospholipids or mono-, di- or tri-glycerides. Usually, the fatty acids have C12-C24 carbon chains, preferably C16-C20 or better C16-C18.

A neutralization paste is therefore a product derived from biomass. Advantages associated with such neutralization pastes reside, on the one hand, in their low cost of implementation, and, on the other hand, in the absence of undesirable toxic substances, such as pesticides, garlic toxins, heavy metals, precursors of dioxins and furans, PCBs and nitrites.

However, the water content of these neutralization pastes is prohibitive as to their use alone as a fuel. Indeed, such pastes may contain significant proportions of water from the saponification reaction or addition of water for the fluidification in the industrial process. Typically, the aqueous phase represents at least 50% of the mass of the neutralization paste. Another difficulty is related to the fact that it is emulsion cases, which should be treated specifically. The use as a fuel therefore requires the implementation of methods of removing this water and other unwanted solids or viscous liquid residues.

Step a1) Extraction The extraction step a1) of the process according to the invention has the function of extracting the fatty acids contained in the neutralization paste. This extraction is carried out in an acidic medium under conditions that are effective for forming an aqueous phase and an organic phase comprising the fatty acids initially contained in the neutralization paste.

This organic phase comprising the fatty acids is generally called "acid oil" or "neutralizing oil". The acid used to extract the fatty acids present in the neutralization paste in the form of salts is generally an inorganic acid, such as, for example, sulfuric acid, phosphoric acid or hydrochloric acid. Sulfuric acid is however preferred because it allows better extraction of fatty acids at a favorable economic cost. The extraction is generally carried out under heating, at a temperature between 70 and 100 ° C (inclusive), preferably between 80 and 90 ° C (inclusive).

In order to obtain a good extraction of the fatty acids, an acidic pH is preferably maintained during the reaction time, for example a pH of less than or equal to 6, preferably less than or equal to 4.

The reaction time is chosen to allow extraction of all the fatty acids. It is for example from 1 hour to 12 hours, depending on the geometry of the reactor, the nature and composition of the charge to be treated. The extraction is preferably carried out with stirring.

The formation of an aqueous phase and an organic phase containing the fatty acids are thus obtained.

Step a2) of separation

During this step, the organic phase formed during step a1) of the aqueous phase is separated off. In other words, the acidic oil which will subsequently be subjected to step b) of the process according to the invention is isolated, optionally after a centrifugation step a3 when its water content is greater than 1% but less than or equal to 3%. .

This separation can be carried out by distillation, decantation or even centrifugation. This step can be implemented by any appropriate device known and commercially available.

Advantageously, this separation is carried out by decantation, followed by removal of the aqueous phase. Decantation depends on the difference in density of the liquids and their viscosity, parameters which can be modified in a manner known to those skilled in the art to promote separation if necessary.

Advantageously, filtration can be carried out at 150 gm of the acidic oil before any subsequent step.

Centrifugation step

When the water content of the acidic oil is less than or equal to 3% by weight but greater than 1% by weight, the acidic oil may advantageously be subjected to centrifugation prior to step b). An objective of this centrifugation is to lower the water content of the acidic oil.

Centrifugation is advantageously carried out on an acidic oil obtained by steps a1) and a2) previously described.

This centrifugation operation makes it possible to obtain an acidic oil having very advantageously a water content of less than or equal to 1% by weight, or even less than or equal to 0.8% by weight, in particular from 0.1% to 0.7% by weight. % in weight.

In addition to the removal of water, recovered in an aqueous phase, the centrifugation also allows the removal of some of the solid residues in suspension. The centrifugation step has the advantage of simplified implementation, avoiding resorting to complex chemical separation methods, such as distillation, which can be restrictive in terms of unwanted precautions and corrosion, and expensive. The centrifugation step may advantageously be a triphasic centrifugation,

However, the centrifugation step may itself be a combination of steps, in particular comprising a first diphasic type centrifugation step, which makes it possible to separate the suspended solids in the form of sludge, coupled with a second centrifugation step. triphasic, which separates the organic phase, the purified aqueous phase and the residual suspended solids from the first centrifugation. This step can be implemented by any appropriate device known and commercially available.

Conventionally, the centrifugation can be implemented with speeds of 4000 - 6000 rpm.

The duration of the centrifugation depends on the nature of the species to be separated, their partition coefficient, the difference in density between the aqueous phase, the oily organic phase and the particles, the particle size, the surface tension of the particles. species to be separated, temperature, centrifugation rate. The separation time (called residence time) is therefore adapted case by case by those skilled in the art by conventional means of measurement and control.

Step b) reduction of the ash, sulfur, calcium, phosphorus, sodium and optionally alkali metal content other than sodium

During this step b), the content of ash, sulfur, calcium, phosphorus, sodium, and optionally of alkali metals other than sodium, of the acid oil supplied in step a) is reduced by means of a or several sub-stages of filtration and / or precipitation.

This step b) can be implemented by any appropriate devices known and commercially available.

Filtration can thus be carried out by means of a filter press, or a filter cartridge, or a filter membrane or be an ultra filtration, nano filtration or reverse osmosis filtration. Step b) may advantageously comprise at least one filtration step carried out using at least one passage through a cellulose filter. Such a cellulose filter can improve the efficiency of filtration by avoiding clogging. The precipitation step can advantageously be carried out under conditions that are effective for precipitating the sulphates present in the acidic oil. These sulphates may come from the saponification of the oil and / or the acid extraction of the fatty acids.

Without wishing to be bound by theory, the precipitation of sulphates seems to be associated with the precipitation of calcium, phosphorus, sodium, and possibly alkali metals other than sodium, which has the effect of reducing the ash content of the product. .

In general, the conditions for carrying out the precipitation will be determined by those skilled in the art by conventional means depending on the species to be precipitated.

The precipitation of the sulphates may in particular be carried out by addition of Ca 2+ ions, for example in the form of CaCb (calcium chloride).

The choice and the number of these sub-steps can easily be determined by those skilled in the art by controlling the content of ash, sulfur, calcium, phosphorus and sodium of the final organic phase, constituting the fuel acid oil according to the invention. .

In one embodiment, step b) may comprise at least two successive filtration steps with increasingly weak mesh filters. By way of example, the filtrations can be carried out by means of a first filter of 20 to 30 gm and a second filter of 0.5 to 1.5 gm.

In another embodiment, step b) may comprise a filtration step followed by a precipitation step, in particular sulphates.

Optionally, these filtration and precipitation steps may be preceded or followed by one or more other filtration steps, or even one or more precipitation steps. Advantageously, the last step may be a filtration step.

The method may comprise a succession of filtrations by means of decreasing mesh filters to reach the final target, for example from 200 gm up to 25 gm. Advantageously, the last filtration step is then performed by means of a filter having a mesh of 0.5 to 1.5 gm.

With this step b), it is possible to obtain an acidic oil constituting a final combustible acid oil having very advantageously contents of: • ash less than or equal to 0.1%, ideally less than 0.05% by weight, • sulfur less than or equal to 150 mg / kg, preferably less than 100 mg / kg, • calcium less than or equal to 5 mg / kg, preferably less than 1 mg / kg, • phosphorus less than or equal to 150 mg / kg, • sodium less than or equal to 10 mg / kg, preferably less than 1 mg / kg, and optionally an alkali metal content other than sodium less than or equal to 1 mg / kg.

The ash content can be measured according to standard NF EN ISO 6245.

The sulfur content can be measured according to standard NF EN ISO 20846.

The calcium content can be measured according to standard NF T 60106.

The phosphorus content can be measured according to standard NF T 60106.

The sodium content may be measured according to standard NF T 60106.

The alkali metal content other than sodium may be measured according to standard NF T 60106.

It will be noted that the process according to the invention can make it possible to obtain oils whose contents in ash, sulfur, calcium, phosphorus, sodium and possibly in alkali metals other than sodium are much lower than the aforementioned thresholds, or even zero or almost zero. and undetectable by the usual quantization means.

In addition, the final fuel acid oil advantageously has a water content less than or equal to 1%, or even less than or equal to 0.8%, in particular from 0.1% to 0.7% by weight. EXAMPLES Example 1

Table 1 summarizes some physicochemical characteristics typical of an acidic oil and a heavy fuel oil SULV (Very Low Sulfur Content) (non additive heavy fuel oil), as well as the specifications imposed by the CSR 500 for a heavy fuel oil. These specifications are established by the Chambre Syndicale du Raffinage in France. Step a) of the process according to the invention may in particular provide an acidic oil having characteristics such as those shown in Table 1. It will be noted that a typical acidic oil complies with CSR 500 specifications.

Table 1

Example 2: pilot combustion test

This pilot test is carried out on a decanted oil, but which has not undergone centrifugation or filtration / precipitation. In other words, the oil tested corresponds to an acidic oil having a water content less than or equal to 3% by weight.

Obtaining the acidic oil

A neutralization paste has undergone the following treatment: al) injection of 1201 of 97% sulfuric acid in a reactor containing 4000 kg of neutralization paste, where the temperature is 80 to 90 ° C. The reaction time is 24 hours, under continuous control of the pH to maintain the pH at a value below 4, a2) decantation of the aqueous phase and the organic phase formed during step a1) and elimination the aqueous phase,

An acidic oil (Sample A) is obtained which has not undergone any subsequent treatment such as centrifugation, precipitation / filtration.

Table 2 presents the characteristics of this acidic oil (Sample A) in comparison with those of a heavy fuel oil SULV (Very Low Sulfur Content) (Sample B, non-additive heavy fuel oil STEL).

Table 2: ____

(*) Measurement carried out according to the method of the Union Française des Industries Pétrolière (U FI P) and the Association Technique Energie Environnement (ATEE).

Combustion test

Each fuel (samples A and B) is burned separately in a 1 MW flue gas boiler, 1 unattended mechanical spray burner. The fumes are analyzed via analyzers placed continuously in the combustion fumes.

Table 3 below summarizes the combustion conditions of this test as well as the measured emissions.

Table 3

m3 (n): normal cubic meters, measured at P = 101.3kPa and T = 273K)

It will be noted that the combustion yields of the sample A and the heavy fuel oil are substantially equivalent, showing that an acid oil can be substituted for a heavy fuel oil in a combustion plant. In addition, the spraying temperature and the booster temperature are lower for the acidic oil, so that the total energy consumption of the plant is reduced compared to the combustion of a heavy fuel oil. The implementation of the acidic oil is also simpler.

Due to the nature of an acidic oil, NOx and SO2 emissions are zero or very low. On the other hand, the emission of dust from an acidic oil is greater than for a heavy fuel oil and does not make it possible to comply with the regulatory constraints relating to the emissions from combustion plants (Exposure Limit Value (TLV) for dust between 20 and 50 mg / m3).

Example 3: Industrial Combustion Test Fuel Analysis

The physico-chemical characteristics of the fuels tested are shown in Table 4.

In contrast to the pilot test, heavy fuel oil (Sample C) is a heavy-duty SIDS fuel oil supplemented with a combustion additive that reduces dust emissions.

Table 4:

(*) Measurement carried out according to the method of the Union Française des Industries Pétrolière (U FI P) and the Association Technique Energie Environnement (ATEE).

Industrial combustion test

Each fuel tested (samples A and C) is burned in a 39 MW water tube boiler, including 3 mechanical and steam assisted burners.

The fuels have been burned between other fuels: the fouling of the boiler before each of the combustion tests may therefore be different.

Combustion conditions and measured emissions are collated in Table 5.

Table 5____

m3 (n): normal cubic meters, measured at P = 101.3 kPa and T = 273K (*) NF EN 14385

Although the yields are not directly comparable because of a potentially different fouling of the boiler before the combustion of Samples A and C, an acceptable combustion efficiency for the acid oil is observed, for a very lower injection temperature. compared to heavy fuel oil.

It should be noted that heavy fuel oil does not comply with the NOx Emission Limit Value: 450 mg / m3 (n) imposed by the regulations.

The dust emissions of the acid oil are very important and do not respect the limits of the different legislations. In particular, dust emissions are much higher than the TLV of 50 mg / m3. In order to burn an acid oil of this type, the combustion plant should be equipped with a flue gas treatment, such as an electro-filter.

Without wishing to be bound by theory, it is assumed that dust emissions are due to the high levels of acid oil in ash, calcium, sodium, and possibly phosphorus.

Example 4 Characteristics of a Liquid Fuel Obtained According to the Process According to the Invention

Obtaining liquid fuel

A neutralization paste has undergone the following treatment: al) injection of 1201 of 97% sulfuric acid in a reactor containing 4000 kg of neutralization paste, where the temperature is 80 to 90 ° C. The reaction time, with stirring to ensure a homogeneous mixture, is 24 hours, under continuous pH control in order to maintain the pH at a value below 4, a2) decantation of the aqueous phase and the organic phase formed at during step a1) and then removal of the aqueous phase, a3) centrifugation at 5000 rpm for 5 minutes using an Alpha Laval® centrifuge, then removal of the aqueous phase, b) first filtration on a 25 μm paper filter followed by a second filtration on 0.9 μm cellulose filter, the two filtrations being carried out in series with a speed of one ton / hour.

The characteristics of the fuel thus obtained are collated in Table 6.

(*) Measurement carried out according to the method of the Union Française des Industries Pétrolière (U FI P) and the Association Technique Energie Environnement (ATEE).

Physico-Chemical Characteristics of the Liquid Fuel Table 7 shows the evolution of the characteristics affecting the dust emissions during the fuel fabrication process as described in the present invention.

Table 7 summarizes the physico-chemical characteristics of an acid oil stored in a tank (Sample No. 1). This acidic oil corresponds to an acidic oil having a water content greater than 1% by weight. The acid oil stored in the tank then undergoes a stirring and a centrifugation step (5000 rpm in an Alpha Laval® apparatus) until sample No. 2 is obtained. Sample No. 2 thus corresponds to an acidic oil as provided in step a) of the process according to the present invention, with a water content of less than 1% by weight. Sample No. 3 results from the filtration of sample No. 2 through a 25 micron filter followed by a 0.9 micron filter. Sample No. 3 corresponds to a combustible acid oil as obtained in step b) of the process according to the present invention.

In view of these characteristics, it is noted that the centrifugation makes it possible to significantly reduce the ash content and the sodium content (see Sample No. 2). There is also a decrease in the water content as well as in the calcium and phosphorus content. This centrifugation step can thus be used to reduce the water content but also to reduce the ash content insofar as the centrifugation also seems to reduce the phospholipid content, which is the source of phosphorus, and the content made of metals (see Table 7).

Each of the subsequent filtrations makes it possible to lower these contents even further (see Sample No. 3).

It is also noted that each of the samples No. 2 and No. 3 has contents of water, ash, calcium, phosphorus and sodium lower than those of the sample A and the contents of water, ash, calcium and sodium of the same order of the sample C of Example 3. It is therefore expected that the combustion of these samples will meet the requirements for emissions, particularly dust.

The process according to the invention thus makes it possible to produce a fuel acid oil having a reduced water and ash content.

Claims (13)

A process for the preparation of a fuel derived from biomass comprising: a) a step of supplying an acidic oil resulting from the refining of one or more oils chosen from a vegetable oil and / or an animal oil, the acidic oil having a water content less than or equal to 1% by weight, or even less than or equal to 0.8% by weight, in particular from 0.1% to 0.7% by weight, b) a reduction step of the ash, sulfur, phosphorus, calcium and sodium content of the acidic oil obtained in step a), this reduction step comprising one or more sub-steps chosen from filtration and precipitation, carried out under conditions effective to obtain a fuel acid oil comprising an ash content of less than or equal to 0.1%, ideally less than 0.05% by weight, sulfur less than or equal to 150 mg / kg, preferably less than 100 mg / kg, • calcium less than or equal to 5 mg / kg, preferably lower than at 1 mg / kg, phosphorus less than or equal to 150 mg / kg, sodium less than or equal to 10 mg / kg, preferably less than 1 mg / kg. 2. The method of claim 1, wherein the fuel acid oil obtained in step b) further comprises an alkali metal content other than sodium less than or equal to 1 mg / kg. The process according to claim 1 or 2, wherein step a) comprises providing an acidic oil derived from the refining of one or more oils selected from a vegetable oil and / or an animal oil having a water content less than or equal to 3% by weight, followed by a centrifugation step making it possible to obtain a water content less than or equal to 1% by weight, or even less than or equal to 0.8% by weight, in particular from 0, 1% to 0.7% in weight. 4. The method of claim 3, wherein the step a) of providing an acidic oil comprises: a) a step of extracting the fatty acids present in a neutralization paste resulting from the refining of one or more oils selected (s) from a vegetable oil and / or an animal oil, this extraction step being carried out in an acid medium under conditions that are effective for forming an aqueous phase and an organic phase comprising said fatty acids, a2) a separation step during from which said previously formed organic phase is separated and recovered, the organic phase recovered in step a2) constituting an acidic oil having a water content less than or equal to 3% by weight. 5. Method according to any one of claims 1 to 4, wherein step b) comprises at least two successive filtration steps with mesh filters increasingly low. The process of any one of claims 1 to 5, wherein step b) comprises a filtration step followed by a precipitation step. The process of any one of claims 1 to 6, wherein step b) comprises at least one filtration step performed with at least one passage through a cellulose filter. 8. Process according to any one of claims 1 to 7, in which step b) comprises at least one precipitation step carried out under conditions that are effective for precipitating sulphates present in the acidic oil obtained in step a). . 9. Combustible acid oil, especially resulting from the acidification of a neutralization paste obtained by a process for refining a vegetable and / or animal oil, said fuel acid oil being capable of being obtained by the implementation of the Process according to one of Claims 1 to 8, comprising an ash content of less than or equal to 0.1%, ideally less than 0.05% by weight, and sulfur of less than or equal to 150 mg / kg, preferably less than or equal to 150 mg / kg. at 100 mg / kg, • calcium less than or equal to 5 mg / kg, preferably less than 1 mg / kg, • phosphorus less than or equal to 150 mg / kg, • sodium less than or equal to 10 mg / kg, preferably lower at 1 mg / kg. 10. Combustible acid oil according to claim 9, having an alkali metal content other than sodium less than or equal to 1 mg / kg. Combustible acid oil according to claim 9 or 10, having a flash point greater than or equal to 200 ° C. 12. Fuel acid oil according to any one of claims 9 to 11, comprising a water content less than or equal to 1% by weight, or even less than or equal to 0.8% by weight, in particular from 0.1% to 0, 7% in weight. 13. A method of combustion of a fuel in a combustion plant, in particular of type 2910A or 2910B or 2910C according to the ICPE nomenclature, in which a fuel consisting of a fuel directly obtained by the process according to any one of the claims is burned. 1 to 8 or a combustible acid oil according to any one of claims 9 to 12.