TECHNOLOGICAL FIELD

The present disclosure concerns processes and systems for the manufacture of biodiesel, specifically enzymatic processes for manufacturing biodiesel from waste matter rich in free fatty acids (FFA).

BACKGROUND ART

References considered to be relevant as background to the presently disclosed subject matter are listed below:

- PCT patent application publication no. WO2011/107977

- PCT patent application publication no. W02013/030816

- PCT patent application publication no. W02012/130961

- PCT patent application publication no. WO2016/089443

- PCT patent application publication no. WO2018/191653

- PCT patent application publication no. WO2018/116297

Acknowledgement of the above references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter.

BACKGROUND

Finding renewable sources as alternatives for natural-oil based diesel has been a researching target in the past few decades. Fats and oil waste have been considered as a renewable source for various proposed manufacturing processes, recycling fat and oil waste into valuable products, one of which being biodiesel.

Common processes of transforming fats and oils into biodiesel are based on transesterification chemical processes, in which triglycerides in the oil or fat are reacted with alcohols, typically methanol, in order to obtain fatty acid methyl esters (FAME), which constitute the biodiesel. These processes are often carried out in the presence of various catalytic agents (alkalines, acids, transition metals/alloys, enzymes, etc.), and the biodiesel production yield typically heavily depends on the reaction conditions. One of the main difficulties in such processes is the presence of water and/or free fatty acids (FFA) in the oil/fat feed stream, as water and FFA often poison the catalysts utilized in the process. However, oil/fat waste products typically contain relatively high amounts of water and FFA, and hence are often more difficult and expensive to treat.

Thus, there is a need for biodiesel manufacturing processes that can utilize FFA- rich waste streams in a high yield and cost-effective manner.

GENERAL DESCRIPTION

The present disclosure concerns processes and systems for manufacturing of biodiesel from fat sources, e.g. waste fat or waste oils, that contain relatively high amounts of free fatty acids (FFA). The processes and systems of the present disclosure involve pre-treating the waste fats/oils in a sequence of processes steps, before carrying out an enzymatic-based transesterification/esterification processes, that enable utilizing the high content of the FFA in the feed stream to increase the yield of biodiesel manufacturing in a cost-effective manner. Hence, processes and systems disclosed herein are particularly suitable for treating fat/oil waste products that are relatively rich in FFA.

Further, it was surprisingly found that pre-treating the fat/oil waste feed as described herein, not only permits utilizing the high content of FFA in the waste feed, but also increase the active lifespan of the enzyme used for the transesterification/esterifi cation step in a continuous mode of operation.

In addition, as fat/oil waste can be obtained from various sources and with various contents of FFA, pre-treatment as described herein is utilized to obtain a more homogenous feedstock for the enzymatic-based transesterification/esterification stage, thereby enabling obtaining an effective continuous mode of operation.

Thus, by one of its aspects, the present disclosure provides a process for manufacturing biodiesel from a fat source that comprises glycerides and free fatty acids (FFA), the process comprising:

(a) heating the fat source to a temperature of at least 60 °C to obtain heated fat source;

(b) treating said heated fat source in one or more tricanters, to thereby separate the heated fat source into a solids stream, a water stream, and a crude oil stream; (c) contacting said crude oil stream with at least one aqueous acidic solution at a pH of at most about 3, to hydrate phosphatides in the crude oil stream, thereby obtaining gum residue and degummed crude oil;

(d) separating between said gum residue and said degummed crude oil to obtain a degummed crude oil stream;

(e) adding one or more aqueous basic solutions to the degummed crude oil until obtaining a pH of between about 6 and about 7.5, thereby obtaining neutral crude oil;

(f) transferring the neutral crude oil into one or more enzymatic reactors in the presence of at least one Ci-Ce alkyl alcohol, each of the one or more enzymatic reactors holding at least one immobilized enzyme, under conditions permitting concomitant enzymatic transesterification of said glycerides and esterification of said FFA in the neutral crude oil by reacting with said at least one Ci-Ce alkyl alcohol, to obtain a crude stream of fatty acid alkyl esters; and

(g) treating the crude stream of fatty acid alkyl esters to remove undesired contaminants therefrom, thereby obtaining said biodiesel.

In other words, the processes of this disclosure are based on a sequence of pretreatment steps that are carried out on the fat source prior to enzymatic reaction in order to obtain a relatively homogenous feed stream which comprises predominantly glycerides and FFA and significantly reduce the water content in the feed stream. The feed stream is then enzymatically treated under conditions permitting concomitant transesterification of the glycerides and esterification of the FFA, hence increasing the yield of fatty acid alkyl esters production, which constitutes the biodiesel, as will be further explained.

The term biodiesel means to denote a biofuel, i.e. a fuel derived from a biological source, such as animal fat or plant-originated oil. The biodiesel typically consists of long- chain fatty acid esters, which are the products of chemical reactions between fatty acids and, typically, short-chain alcohols.

In the process of the present disclosure, biodiesel is manufactured from one or more fat sources, which typically include animal-fats or plant-based oils, that comprise glycerides and free fatty acids (FFA). The fat source can be a native source, e.g. pure or refined plant oil or animal fat, or a processed fat/oil or fatty waste product, such as animal fat waste, cooking oil, frying oil, etc. Glycerides are types of carbonaceous esters, which include monoglycerides, diglycerides and triglycerides, together forming the main components in natural fats and oils. Triglycerides are structured out of a glycerol backbone substituted by three fatty acid groups.

Free fatty acids (or FFA) are fatty acids that are produced by hydrolysis of oils and fats. While typically found in higher amounts in processed fats and oils, FFA can be also found to some extent in unprocessed or native fats and oils. FFA encompass a carboxylic acid with an aliphatic tail (chain) of between about 2 to 30 carbon atoms, which is either saturated or unsaturated. The fatty acids can be short-chain fatty acids (1- 6 carbon atoms in the aliphatic tail), medium-chain fatty acids (6-14 carbon atoms), or long-chain fatty acids (above 14 carbon atoms). Non-limiting examples of medium-chain fatty acids include hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, undecanoic acid, dodecanoic acid, tridecanoic acid, tetradecanoic acid and their corresponding salts, such as sodium salts, etc.

By some embodiments, the fat source can comprise monoglycerides, diglycerides, triglycerides and FFA, their mixtures at any ratio, in the absence or presence of additional fatty acid derivatives such as phospholipids, wax esters, sterol esters, etc.

According to some embodiments, the fat source can be an edible fat/oil (or originating from an edible source) or a non-edible fat/oil (or originating from a non-edible source). According to other embodiments, the fat source comprises at least one oil selected from a vegetative source, animal fat, algal oil, fish oil, or any mixture or combination thereof. According to some other embodiments, the fat source comprises used cooking oil (UCO) and/or used frying oil (UFO). According to some further embodiments, the fat source can be waste cooking oil.

By some embodiments, the fat source can be selected from animal-derived fat, including lard, tallow, fish oil, chicken fat, yellow grease, brown grease, and any combination thereof.

By other embodiments, the fat source can be an oil from a vegetative source selected from soybean oil, canola oil (rapeseed oil), algae oil, olive oil, castor oil, palm oil, palm olein, palm stearin, grapeseed oil, hemp oil, sunflower oil, safflower oil, peanut oil, cotton seed oil, Jatropha oil, com oil, avocado oil, sesame oil, rice bran oil, coconut oil, mustard oil, flaxseed oil, jojoba oil, tall oil, oils derived from inedible plant sources, partial glycerides and free fatty acids derived oils, and mixtures and combinations thereof. As noted, the aim of the processes described herein is the production of biodiesel from fat sources that comprise both glycerides and FFA. According to some embodiments, the fat source comprises at least 5 wt% FFA. By other embodiments, the fat source comprises between about 5 and 100 wt% FFA. By some other embodiments, the fat source can comprise between about 20 and about 100 wt% FFA, between about 30 and about 100 wt% FFA, between about 40 and 100 wt% FFA, or even between about 50 and 100 wt% FFA. Without wishing to be bound by theory, the inventors have found that the higher the FFA in the feed stream fed into the enzymatic stage, the less glycerin by-product is produced during the enzymatic stage, thereby requiring less subsequent separation and treatment process steps.

In processes of this disclosure, the fat source is first heated to a temperature of at least about 60°C to obtain heated fat source. Without wishing to be bound by theory, the inventors have found that heating the fat source to a temperature of at least 60°C enables not only liquification of solid fats (fats having a relatively high melting temperature), but also assists in effective phase separation and preventing formation of emulsions (which are typically formed when handling and treating animal and vegetable fats/oils and are, therefore, harder to treat and separate).

By some embodiments, the fat source is heated to a temperature of between about 65°C and about 90°C.

The heated fat source is then treated in one or more tricanters to separate the heated fat source into a solids stream, a water stream, and a crude oil stream. The tricanter is a separation unit that permits solid-liquid-liquid separation in a continuous mode. Typically, the solids stream is collected as a slurry and separately processed or disposed; the water stream, typically comprising residual fatty components, is similarly separated and disposed. The utilization of tricanters also reduces process time, as separation of the fatty components from solids and water can be obtained in a single operational step.

By some embodiments, the heated fat source is treated in said one or more tricanters at a temperature of at least 75°C, at least 80°C, or even at least 90°C. The flow through the tricanter can, by some embodiments, be between about 5,000 and 25,000 kg/h.

The crude oil stream may, by some embodiments, comprise at least about 30 wt% FFA, typically between about 30 about 100 wt% FFA. According to some embodiments, the process may optionally comprise treating the heated fat source in one or more decanters arranged in a sequence prior to treatment in said one or more tri canters. Such decanting can be used in fat sources that are rich in FFA, e.g. fat sources with FFA content of at least 20 wt%. Treatment in the decanter(s) permits initial removal of solids and water from the heated fat source, increasing the efficiency of tricanting. By some embodiments, the heated fat source is decanted through 1, 2, 3, 4, 5, or even more decanters that are serially arranged. The decanters can be gravitational decanters, centrifugal decanters, gravitational separation tanks, etc.

According to some embodiments, the heated fat source is treated in said one or more decanters at a temperature of at least 60°C, e.g. at least 65°C, at least 70°C, at least 75°C, or even at least 80°C, before introduction into the tricanter(s).

Further, the combination of decanting and tricanting enables to work at higher flow rates, thereby reducing the overall time required for separating the fat source from water and solids compared to standard decanting processes.

By some other embodiments, the crude oil stream, after exiting the tricanter(s), is further treated to remove residual water and/or solids therefrom, e.g. by centrifugation, before transferring the stream into the next processing step (step (c)).

As noted, after tricanting, the crude oil stream is contacted with one or more acidic aqueous solutions, to react phosphatides present in the crude oil stream with the acid, thereby obtaining gum residue and degummed crude oil. This process is known as degumming. In this process step, the crude oil stream is typically mixed with an aqueous acidic solution, having a pH of at most about 3, e.g. between about 1.5 and about 2.5, thereby hydrating phosphatides present in the crude oil (such as phosphatidylcholine (lecithin), phosphatidylethanolamine (kephalin), phosphatidic acid, phosphatidylinositol, etc.) and increasing their hydrophilicity, thereby causing the hydrated phosphatides to be less soluble in the oil and sediment out of the mixture in the form of gum residue/sledge.

The aqueous acidic solution can comprise at least one acid which, by some embodiments, can be selected from phosphoric acid, citric acid, malic acid, or any mixture thereof. The aqueous acidic solution, by some embodiments, can comprise between about 50% and 85% of said acid (w/v).

Contacting between the aqueous acidic solution(s) and the crude oil stream is typically carried out at a temperature ranging between about 70°C and about 95°C. Contacting between the aqueous acidic solution(s) and the crude oil stream can be carried out by any suitable means, for example by mixing within a mixing tank/container, by co-current flow, counter-current flow, in-line mixer, or any other suitable mixing means. Preferably, the contacting is carried out within an in-line mixer followed by a holding/mixing tank/container.

The degummed crude oil is separated from the gum residue/ sludge by any suitable means, such as centrifugation, gravity separation, etc. Preferably, the degummed crude oil is separated from the gum residue/sludge by centrifugation.

By some embodiments, mechanical filtration can be carried out prior to of after degumming in order to further remove solids from the crude oil.

Following degumming, the degummed crude oil is neutralized, by adding one or more basic aqueous solutions in order to bring the pH of the degummed crude oil to a pH of between about 6 and about 7.5. The aqueous basic solution can comprise at least one base, which, by some embodiments, can be selected from sodium hydroxide, potassium hydroxide, or any mixture thereof. The aqueous basic solution, by some embodiments, can comprise between about 4% and 10% of said base (w/v).

Optionally, by some embodiments, water is separated from the neutral crude oil by any suitable means, such as centrifugation, before introducing the neutral crude oil into the next process step (step (f)).

The now pre-treated far source is ready for enzymatic treatment. Processes for enzymatic treatment are known, for example in WO2018/116297.

The neutral crude oil is transferred into one or more enzymatic reactors. The enzymatic reactors are configured to hold at least one immobilized enzyme, which is suitable to permit reaction between the glycerides and the FFA in the neutral crude oil and one or more alcohols, to thereby obtain fatty acid alkyl esters (i.e. the crude biodiesel). In the enzymatic reactor(s), the glycerides (at least the triglycerides) are transesterified while the FFA are esterified concomitantly in order to obtain the crude biodiesel. Hence, in the enzymatic reactor, the neutral crude oil and the alcohol undergo an enzyme-assisted chemical reaction.

The transesterification of triglycerides with methanol is shown in eq. 1, while the esterification of FFA with methanol is shown in eq. 2:

(Eq. 2)

In eqs. 1 and 2, R, Ri, R2 and R3 represent C1-C24 hydrocarbon chains, saturated or unsaturated, typically aliphatic, linear or branched. The triglycerides can be short chain triglycerides, medium chain triglycerides, long chain triglycerides, or any combination thereof.

By some embodiments, the alcohol is a Ci-Ce alkyl alcohol, preferably C1-C4 alkyl alcohol. By some embodiments, the Ci-Ce alkyl alcohol is selected from methanol, ethanol, propanol, isopropanol, butanol, and mixtures thereof. According to some preferred embodiments, the Ci-Ce alkyl alcohol is methanol or ethanol.

The reaction is assisted by one or more immobilized enzymes, which comprise at least one substrate associated with one or more suitable enzymes, e.g. one or more lipase enzymes. Commonly, enzymatic processes in the production of biodiesel are carried out by addition of the enzyme into the reaction vessel in a free form (i.e. mobile), and the enzyme is typically washed out during the process and needs to be continuously replenished. Contrary to these common methods, the transesterification/esterification reactions of this disclosure are carried out by utilizing an immobilized enzyme, that is physically and/or chemically associated with or fixated to a substrate, the substrate being in a form and/or size that prevents its unintended extraction from the reactor. Therefore, in the processes of this disclosure, the immobilized enzyme can be utilized for continuous production of biodiesel, without requiring frequent replenishment of enzyme.

The substrate can be of any suitable form, e.g. powder, agglomerated particles, flakes, discs, pellets, blocks, rods, etc. The enzyme is typically associated with or affixed to the surface of the substrate. The enzyme can be associated with one or more surface portions of the substrate or be associated substantially with the entire surface of the substate. In order to increase the surface available for enzymatic reaction, the substrate may be perforated or porous (for example having a surface area of at least 80 m ² /g or even at least 100 m ² /g).

When more than one enzyme is utilized, the substrate can be associated with one or more enzymes. Alternatively, a portion of the substrate can be associated with one of the enzymes, and another portion of the substrate can be associated with another one of the enzymes.

According to some embodiments, the substrate is a hydrophobic substrate, therefore being stable under the reaction conditions for a prolonged period of time. The substate may be made of or coated by one or more hydrophobic coatings. According to some embodiments, the substate can be made of or is coated by one or more hydrophobic polymers. The hydrophobic polymer(s) can be aliphatic or aromatic, linear or branched, thermoplastic or thermosetic.

According to some embodiments, the one or more enzymes is a lipase enzyme. By such embodiments, the lipase enzyme can be selected from lipases derived from Thermomyces lanuginosus, Rhizomucor miehei, Mucor miehei, Pseudomonas sp., Rhizopus sp., Mucor javanicus, Penicilhum roqueforli. Aspergillus niger. Chromobacterium viscosum, Acromobacter sp., Burkholderia sp., Candida antarctica A, Candida antarcticaH, Candida rugosa, Alcaligenes sp., Penicillium camem berth, papaya seeds, pancreatin or any other lipase source, and any mixture thereof.

The enzyme, according to some embodiments, is selected as to permit concomitant transesterification of the glycerides and esterification of the FFA, thereby permitting one-pot reaction. In the process described herein, the pre-treatment stages of the process prior to the enzymatic reaction are designed to increase the content of FFA in the crude oil (i.e. instead of other known processes which aim to remove FFA prior to transesterification), thereby enabling utilizing FFA as raw material for biodiesel production without requiring its separate treatment. This, in turn, increases the yield of biodiesel production, thereby obtaining a process yield of at least 75%, as well as reducing the production of glycerin by-products.

Process yield, in the context of this disclosure, means to refer to the amount of final product (i.e. biodiesel) divided by amount of neutral crude oil entering the enzymatic stage of the process. By some embodiments, the process yield is at least 76%, at least 77%, at least 78%, at least 79%, at least 80%, at least 81%, at least 82%, at least 83%, at least 84%, or even at least 85%.

In the enzymatic reactor, the neutral crude oil and alcohol are brought into contact in the presence of the immobilized enzyme under conditions permitting the concomitant enzymatic transesterification and esterification reactions. According to some embodiments, said conditions comprise carrying out the reaction at a temperature of between about 28°C and about 35°C. According to other embodiments, the conditions comprise maintaining the pH of the reaction at a value of between about 6 and 7.5.

According to some embodiments, the neutral crude oil is fed into the enzymatic reactor in excess with respect to the Ci-Ce alkyl alcohols. According to such embodiments, the ratio between the feed of neutral crude oil and the Ci-Ce alkyl alcohol (e.g. methanol) is between about 3 : 1 and 12: 1. According to some embodiments, the ratio between the feed of neutral crude oil and the Ci-Ce alkyl alcohol is between about 5: 1 and 10: 1.

According to some embodiments, the alcohol may be added into the enzymatic reactor continuously or in batches.

By some embodiments, the process comprises utilizing more than one enzymatic reactor, i.e. two or more enzymatic reactors arranged in sequence, e.g. 2, 3, 4, 5, or even more reactors.

As the transesterification/esterification also produces polyols as by-product (e.g. glycerol), the process can further comprise removal of polyol by-products and residual alcohols from the crude stream of fatty acid alkyl esters before further purification (step (g))-

Removal of the polyols can be continuous or batch wise. According to some embodiments, the removal of Ci-Ce alcohols and polyols by-products is carried out by treating the crude stream of fatty acid alkyl esters in one or more separation units, e.g. decanters and/or centrifuges, arranged in sequence. Alternatively, when more than one enzymatic reactor is used, each reactor can be followed by a decanter.

The polyol by-products can be subsequently separated for various industrial uses. Alternatively, in some embodiments, the polyols are returned into the fat source at step (a) for further treatment. The crude stream of fatty acid alkyl esters leaving the enzymatic reaction stage is then further treated to remove undesired contaminants therefrom and increase the purity level of the product, thereby obtaining the biodiesel.

In some embodiments, said further (purification) treatment comprises distilling the crude stream of fatty acid alkyl esters in one or more distillation columns arranged in sequence, to separate the biodiesel from undesired light fractions and heavy fractions. Unless otherwise specifically noted, the term light fractions refers to hydrocarbons having a boiling point of at most 200°C (measured according to ASTM D86), and heavy fractions mean to denote hydrocarbons having a boiling point of at least 340°C (according to ASTM D86).

Distillation can, by some embodiments, be carried out at a temperature of between about 110°C and 210°C (under vacuum of about 0.25 bar), e.g. at about 115°C and 180°C.

A further purification treatment, by some embodiments, is saponification of residual FFA that remain in the crude stream of fatty acid alkyl esters after enzymatic reaction (and, at times, after distillation). Thus, in some embodiments, the biodiesel can be further contacted with one or more bases to saponify the unreacted FFA. According to some embodiments, the biodiesel is contacted with sodium hydroxide and/or potassium hydroxide to saponify unreacted FFA in the biodiesel, followed by separation of the saponified FFA from the biodiesel. According to some embodiments, the sodium hydroxide is a sodium hydroxide solution (e.g. at least about 50% sodium hydroxide aqueous solution). Saponification can be carried out in one or more saponification tanks, typically at a temperature ranging between about 75°C and about 95°C.

After saponification, the saponified FFA are washed out of the biodiesel, and the biodiesel is neutralized by adding one or more acids (e.g. sulfuric acid solution or concentrated sulfuric acid). The biodiesel can then undergo further purification steps, as known per se, such as washing (e.g. with water, demineralized water, distilled water, etc.), vacuum drying, etc.

The saponified FFA can be disposed as waste. Alternatively, and preferably, the saponified FFA undergoes soap splitting to obtain de-saponified FFA (e.g. by contacting the saponified FFA with one or more acids, such as hydrochloric acid), the de-saponified FFA being returned into crude oil stream at step (c). Such soap-splitting step increases the overall yield of the process, as residual FFA which have not been esterified can be returned to the process for further esterification. By another aspect, the present disclosure provides a process for manufacturing biodiesel from a fat source that comprises glycerides and free fatty acids (FFA), the process comprising:

(a’) heating the fat source to a temperature of at least 60°C to obtain heated fat source;

(b’) treating said heated fat source in one or more decanters arranged in a sequence, followed by treating the heated fat source in one or more tricanters, to thereby separate the heated fat source into a solids stream, a water stream and a crude oil stream;

(c’) contacting said crude oil stream with aqueous acidic solution at a pH of at most about 3, to hydrate phosphatides in the crude oil stream, thereby obtaining gum residue and degummed crude oil;

(d’) separating between said gum residue and said degummed crude oil to obtain a degummed crude oil stream;

(e’) adding one or more aqueous basic solutions the degummed crude oil until obtaining a pH of between about 6 and about 7.5, thereby obtaining neutral crude oil;

(f ) transferring the neutral crude oil into one or more enzymatic reactors in the presence of at least one Ci-Ce alkyl alcohol, each of the one or more enzymatic reactors holding at least one immobilized enzyme, under conditions permitting concomitant enzymatic transesterification of said glycerides and esterification of said FFA in the neutral crude oil by reacting with said at least one Ci-Ce alkyl alcohol, to obtain a crude stream of fatty acid alkyl esters;

(g’) distilling the crude stream of fatty acid alkyl esters to separate biodiesel from light fractions and heavy fractions;

(h’) contacting the mid-fractions with one or more bases cause saponification of residual FFA, and separating saponified FFA from biodiesel; and

(i’) neutralizing the biodiesel by contacting with one or more concentrated acids, thereby obtaining biodiesel.

By yet another aspect, the present disclosure provides a process for manufacturing crude biodiesel from a fat source that comprises glycerides and free fatty acids (FFA), the process comprising: (a”) heating the fat source to a temperature of at least 60°C to obtain heated fat source;

(b”) treating said heated fat source in one or more decanters arranged in a sequence, followed by treating the heated fat source in one or more tricanters, to thereby separate the heated fat source into a solids stream, a water stream and a crude oil stream;

(c”) contacting said crude oil stream with aqueous acidic solutions at a pH of at most about 3, to hydrate phosphatides in the crude oil stream, thereby obtaining gum residue and degummed crude oil;

(d”) separating between said gum residue and said degummed crude oil to obtain a degummed crude oil stream;

(e”) adding one or more aqueous basic solutions to the degummed crude oil until obtaining a pH of between about 6 and about 7.5, thereby obtaining neutral crude oil; and (f ’) transferring the neutral crude oil into one or more enzymatic reactors in the presence of at least one Ci-Ce alkyl alcohol, each of the one or more enzymatic reactors holding at least one immobilized enzyme, under conditions permitting concomitant enzymatic transesterification of said glycerides and esterification of said FFA in the neutral crude oil by reacting with said at least one Ci-Ce alkyl alcohol, to obtain crude stream of fatty acid alkyl esters (crude biodiesel).

The present disclosure also provides a process for pre-treating a fat source that comprises glycerides and free fatty acids (FFA) to obtain crude oil basis, suitable for subsequent enzymatic treatment, the process comprising:

(A) heating the fat source to a temperature of at least 60°C to obtain heated fat source;

(B) treating said heated fat source in one or more decanters arranged in a sequence, followed by treating the heated fat source in one or more tricanters, to thereby separate the heated fat source into a solids stream, a water stream and a crude oil stream;

(C) contacting said crude oil stream with aqueous acidic solutions at a pH of at most about 3, to hydrate phosphatides in the crude oil stream, thereby obtaining gum residue and degummed crude oil;

(D) separating between said gum residue and said degummed crude oil to obtain a degummed crude oil stream; (E) adding one or more aqueous basic solutions to the degummed crude oil until obtaining a pH of between about 6 and about 7.5, thereby obtaining a neutral crude oil basis suitable for subsequent enzymatic treatment for obtaining biodiesel therefrom.

Processes described herein can be carried out in continuous mode, semi- continuous mode, or batch-wise.

According to another aspect of this disclosure, there is provided a system for manufacturing of biodiesel from a fat source comprising glycerides and free fatty acids (FFA), the system comprising: one or more heated containers for holding said fat source at a temperature of at least 60°C; one or more tricanters, in liquid communication with said one or more heated containers, configured for separating heated fat source received from the one or more heated containers into a solids stream, a water stream, and a crude oil stream; one or more degumming units, in liquid communication with said one or more tricanters, and configured for receiving said crude oil stream and one or more aqueous acidic solutions having a pH of at most about 3, to permit hydration of phosphatides in the crude oil stream, thereby obtaining gum residue and degummed crude oil; one or more separation units in liquid communication with said one or more degumming units, and configured for separating said gum residue for said degummed crude oil to obtain a degummed crude oil stream; one or more neutralizing containers, in liquid communication with said one or more separation units, configured for receiving said degummed crude oil stream and one or more aqueous basic solutions, to permit neutralization of said degummed crude oil to a pH of between about 6 and about 7.5, thereby obtaining neutral crude oil; one or more enzymatic reactors, in liquid communication with said one or more neutralizing containers, each of the one or more enzymatic reactors configured for holding at least one immobilized enzyme, and configured for receiving the neutral crude oil and at least one Ci-Ce alkyl alcohol, and operable under conditions permitting concomitant enzymatic transesterification of said glycerides and esterification of said FFA in the neutral crude oil by reaction with said at least one Ci-Ce alkyl alcohol, to obtain a crude stream of fatty acid alkyl esters; and one or more purification units, in liquid communication with said one or more enzymatic reactors, configured for treating the crude stream of fatty acid alkyl esters to remove undesired contaminants therefrom to obtain said biodiesel.

According to some embodiments, the system optionally comprises one or more fat source holding tanks, in liquid communication with the one or more heated containers, for receiving and holding said fat source prior to application of the processes of this disclosure.

By some embodiments, the system can optionally comprise one or more decanters arranged in a sequence, located between said heated containers and said tricanters, configured for initial removal of solids and water from said heated fat source.

By some other embodiments, the system can further comprise one or more first centrifuges, located between the tricanter(s) and the degumming unit(s), configured for removal of residual water and/or solids from the crude oil stream. According to some further embodiments, the one or more separation units comprise one or more second centrifuges.

The immobilized enzyme, by some embodiments, can comprise at least one substrate associated with one or more enzymes (e.g. lipase enzymes). The substrate can, by some embodiments, be is a hydrophobic substrate, i.e. made of or coated by one or more hydrophobic materials, for example one or more hydrophobic polymers.

According to some embodiments, the system optionally includes one or more secondary decanters and/or centrifuges, located between said enzymatic reactor(s) and said one or more purification units, and configured to receive said crude stream of fatty acid alkyl esters and remove Ci-Ce alcohols and polyols by-products therefrom.

The one or more purifications units can, by some embodiments, comprise at least one distillation module, downstream said one or more enzymatic reactors, configured to be operable under conditions permitting separation of said crude stream of fatty acid alkyl esters into crude biodiesel, light fractions, and heavy fractions. In such embodiments, the system can further comprise one or more saponification units, in liquid communication with said one or more distillation modules, and configured to receive said crude biodiesel and one or more aqueous basic solutions, to saponify unreacted FFA in the crude biodiesel, and separate the saponified FFA from said biodiesel. By another aspect, the disclosure provides a system for pre-treating a fat source that comprises glycerides and free fatty acids (FFA) to obtain crude oil basis, suitable for subsequent enzymatic treatment, the system comprising: one or more heated containers for holding said fat source at a temperature of at least 60°C; one or more tricanters, in liquid communication with said one or more heated containers, configured for separating heated fat source received from the one or more heated containers into a solids stream, a water stream and a crude oil stream; one or more degumming units, in liquid communication with said one or more tricanters, and configured for receiving said crude oil stream and one or more aqueous acidic solutions having a pH of at most about 3, to permit hydration of phosphatides in the crude oil stream, thereby obtaining gum residue and degummed crude oil; one or more separation units in liquid communication with said one or more degumming units, and configured for separating said gum residue for said degummed crude oil to obtain a degummed crude oil stream; and one or more neutralizing containers, in liquid communication with said one or more separation units, configured for receiving said degummed crude oil stream and one or more aqueous basic solutions, to permit neutralization of said degummed crude oil to a pH of between about 6 and about 7.5, thereby obtaining neutral crude oil basis suitable for subsequent enzymatic treatment for obtaining biodiesel therefrom.

As used herein, the term about is meant to encompass deviation of ±10% from the specifically mentioned value of a parameter, such as temperature, pressure, concentration, etc.

Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases “ranging ranges between" a first indicate number and a second indicate number and "ranging/ranges from" a first indicate number "to" a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

Generally it is noted that the term “ ...at least one... ” as applied to any component of the processes of systems of this disclosure should be read to encompass one, two, three, four, five, six, seven, eight, nine or ten different occurrences of said component in the processes or systems of this disclosure.

It is appreciated that certain features of this disclosure, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the disclosure, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable sub-combination or as suitable in any other described embodiment described herein. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

The processes of the present disclosure involve numerous process steps which may or may not be associated with other common physical-chemical processes so as to achieve the desired purity and form of each of the isolated components (e.g. biodiesel). Unless otherwise indicated, such process steps, if present, may be set in different sequences without affecting the workability of the process and its efficacy in achieving the desired end result. As a person skilled in the art would appreciate, a sequence of steps may be employed and changed depending on various economical aspects, material availability, raw materials, environmental considerations, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig- 1 is a block diagram of an exemplary process according to an embodiment of this disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

An exemplary process and system according to an embodiment of this disclosure will now be described. While the described process is typically continuous, it is contemplated that the processes, or stages thereof, can be carried out in a semi-continuous mode or batch-wise.

As used herein, the term container, tank, reactor (/'.< ., reaction vessels), or any alternative term used interchangeably, refers to a device for carrying a unit operation. Typically, such a device may be of any size, shape and constructed of any material suitable for the process step that is to be carried out within the device.

Depending on its operational requirements, each of the reaction vessels may comprise a temperature control unit, such as a heating/cooling unit or a heat exchanger, along with means for controlling said unit in response to autothermic or the absence of autothermic conditions within the reaction chamber; internal temperature gauges for monitoring the reaction's temperature; condensation units, scrubbing units and absorption columns, to afford treatment of gaseous reaction products and gaseous contaminants; baffles of various geometries for controlling the flow profile of substance within the reactor; a top plate that is movable with respect to an outer body of the reactor; a base plate that is movable with respect to an outer body of the reactor; reactants inlets at various angles; and products outlets at various angles.

Suitable pumps or gravity feeds and controllable valves may be provided for selectively transporting the respective materials between units of the system and a suitable controller monitors and controls operation of the system.

Turning to Fig. 1, schematically described is a process for manufacturing biodiesel from a fat source. Storage area 100 generally designates a tank farm, for temporarily storing the fat source(s), as well as products and/or by-products of the process.

Fat source, e.g. animal-fats and/or plant-based oils, that comprise glycerides and free fatty acids (FFA), are transferred from storage area 100 into waste processing area 200. The fat source can be a native source, e.g. pure or refined plant oil or animal fat, or a processed fat/oil or fatty waste product, such as brown grease, animal fat waste, cooking oil, frying oil, etc. As noted, the aim of the processes described herein is production of biodiesel from fat sources that comprise both glycerides and FFA, typically from fat sources that comprise at least 5 wt% FFA, preferably between about 30 and about 100 wt% FFA.

In the process described herein, the pre-treatment stages of the process prior to the enzymatic reaction are designed to increase the content of FFA in the crude oil (i.e. instead of other known processes which aim to remove FFA prior to transesterification), thereby enabling utilizing FFA as raw material for biodiesel production without requiring its separate treatment. This, in turn, increases the yield of biodiesel production, thereby obtaining a process yield of at least 75%, more typically in the range of 80-85%, and reduces the formation of glycerin as a by-product.

In waste processing area 200, the fat source is heated in one or more heating containers 202, in which the fat source to a temperature of at least 60°C, e.g. between 65°C and 90°C. Once heated, the heated fat source is optionally, but preferably, transferred to one or more decanters 204 that are arranged in a sequence for initial removal of water from the fat source. Such decanting can be used in fat sources that are rich in FFA, e.g. fat sources with FFA content of at least 30 wt%.

Following decanting, the fat source is transferred into one or more tricanters 206, separating the heated fat source into a solids stream, a water stream, and a crude oil stream. The tricanters are typically operated at a temperature of at least 75°C.

Treatment in the decanter(s) permits initial removal of solids and water from the heated fat source, increasing the efficiency of tricanting. Further, the combination of decanting and tricanting enables to work at higher flow rates, thereby reduce the overall time required for separating the fat source comparted to standard decanting processes.

The solids and water are collected as process waste and disposed (or returned to storage area 100 for storing until disposal or further treatment), while the crude oil stream is transferred to degumming unit 300, which is in liquid communication with tricanters 206.

In degumming unit 300, the crude oil stream is mixed in a degumming tank with an aqueous acidic solution at a pH of at most 3, to hydrate phosphatides in the crude oil stream, thereby obtaining gum residue and degummed crude oil. In this process step, decreasing the pH to, for example, between about 1.5 and about 2.5, hydrates phosphatides present in the crude oil (such as phosphatidylcholine (lecithin), phosphatidylethanolamine (kephalin), phosphatidic acid, phosphatidylinositol, etc.) and increasing their hydrophilicity, thereby causing the hydrated phosphatides to be less soluble in the oil and sediment out of the mixture in the form of gum residue/sledge.

An exemplary aqueous acidic solution for use in the degumming stage is a 75% phosphoric acid (H3PO4) solution. Degumming unit 300 further includes one or more separation units (not shown), e.g. a centrifuge, a sedimentation tank, etc., that are in liquid communication with the degumming tank, for separating the gum residue and undesired sludge from the degummed crude oil.

Additionally, degumming unit 300 comprises a neutralization container (not shown), that is in liquid communication with the separation unit, for contacting between the degummed crude oil stream and one or more aqueous basic solutions, e.g. sodium hydroxide (NaOH) solution, for example a solution containing 5-10% sodium hydroxide. The basic solution neutralizes the degummed crude oil to obtain a pH of between about 6 and about 7.5.

The neutral degummed crude oil is then enzymatically treated at area 400, in which the neutralized degummed crude oil is transferred into one or more enzymatic reactors 402 that hold one or more immobilized enzymes. A short-chain alcohol, in this example methanol, is fed into reactors 402 continuously or incrementally. Suitable conditions are then applied in reactor 402 to permit the glycerides (monoglycerides, diglycerides and triglycerides) and FFA to react with the methanol in, respective, transesterification and esterification processes, assisted by the enzyme. It is of note that while a single reactor 402 is shown in this example, this is done for convenience of view purposes, and any number of reactors can be used, in parallel, or preferably in sequence. It is also noted, as a person of the art may appreciate, that when two or more enzymatic reactors are used, the concentration (or amount) of components in each of the reactors can be the same or different.

Enzymatic reaction is typically carried out at a temperature of between about 28°C and 35°C.

The neutral crude oil is typically fed into the enzymatic reactor in excess with respect to the Ci-Ce alkyl alcohols; for example the ratio between the feed of neutral crude oil and the Ci-Ce alkyl alcohol (e.g. methanol) is between about 7 : 1 and 10: 1. According to a specific example, about 4000 kg/hr of neutral crude oil is added to about 1,000 kg/hr of Ci-Ce alkyl alcohols into the enzymatic reactor.

Also of note that while in the exemplified process the reagents are separately fed into enzymatic reactor 402, it is also contemplated that the neutralized degummed crude oil and methanol will be mixed prior to introduction into reactor 402.

The reactor 402 may further comprise one or more filtering elements, to permit filtering of the reaction products at the outlet of the reactor. Such filtering is typically utilized to prevent sweeping of immobilized enzyme particles from the reactor together with the products’ stream.

As noted, the reaction is assisted by one or more immobilized enzymes, which comprise at least one substrate associated with one or more suitable enzymes, e.g. one or more lipase enzymes. The immobilization of the enzyme permits carrying out a continuous process, without the need to replenish or continuously add enzyme into the reactor. Immobilization of the enzyme to a substrate prevents the enzyme to be washed out of the reactor, thereby enabling utilization of the enzyme for several cycles of production.

The substrate can be of any suitable form, e.g. powder, agglomerated particles, flakes, discs, pellets, blocks, rods, etc. The enzyme is typically associated with (chemically or physically) or affixed to the surface of the substrate. The enzyme can be associated with one or more surface portions of the substrate or be associated substantially with the entire surface of the substate. In order to increase the surface available for enzymatic reaction, the substrate may be perforated or porous (for example having a surface area of at least 80 m ² /g or even at least 100 m ² /g). The substrate is typically made of or coated by a hydrophobic material, e.g. one or more hydrophobic polymers.

The enzymatic reactor may be in the shape, e.g. a pipe or a tank, and can be selected from a fixed bed reactor (a reactor in which the immobilized enzyme is held in place and does not move with respect to a fixed reference frame, e.g. a packed bed), a moving bed, a fluidized bed reactor (FBR- a reactor device in which the streams of reactants are passed through the immobilized reactor at high enough velocities to suspend the immobilized enzyme and cause it to behave as though it were a fluid) and a circulating fluidized bed reactor.

Preferably, albeit not exclusively, the immobilized enzyme can be utilized in a packed-bed column constituting the enzymatic reactor.

The one or more enzymes are typically lipase enzymes. For example, the lipase enzyme can be selected from lipases derived from Thermomyces lanuginosus, Rhizomucor miehei, Mucor miehei, Pseudomonas sp., Rhizopus sp., Mucor javanicus, Penicilhum roqueforli. Aspergillus niger. Chromobacterium viscosum, Acromobacter sp., Burkholderia sp., Candida antarctica A, Candida antarctica B, Candida rugosa, Alcaligenes sp., Penicillium camemberlii, papaya seeds, pancreatin or any other lipase source, and any mixture thereof. The enzyme is selected to permit concomitant transesterification of the glycerides and esterification of the FFA, thereby permitting one-pot reaction.

Products of the reaction, which include at least fatty acid alkyl esters and polyols (e.g. glycerol) then need to be separated. Therefore, the reaction product stream is transferred into one or more secondary separation means 404, such as secondary decanters, centrifuges, settling tanks, etc., for separating a crude stream of fatty acid alkyl esters from a stream of methanol and polyols. The stream of methanol and polyols can be transferred into polyol and methanol recovery unit 800, in which the polyols are separated from the methanol (according to separation techniques known per-se). Recovered methanol can then be returned to the enzymatic reaction, while the polyols are separated and utilized as a stand-alone product or discarded.

The crude stream of fatty acid alkyl esters leaving the enzymatic reaction stage 400 is then further treated to remove undesired contaminants therefrom and increase the purity level of the product, thereby obtaining the biodiesel. In this example, the crude stream of fatty acid alkyl esters is transferred to one or more distillation columns 500, in which distillation is carried out at a temperature of between about 110°C and 210°C (under vacuum of about 0.25 bar), e.g. at about 115°C and 180°C. A specific example is distillation at a temperature range of between about 123°C and about 173°C (at vacuum of 0.25 bar), to separate a mid-fraction (i.e. the biodiesel) from lighter fractions and heavier fraction (such as biopitch).

The undesired fractions are stored in storage area until further treatment or disposal, while methanol can be further recovered at recovery unit 800 for further use.

The biodiesel stream (BioD) can then be transferred into one or more saponification units 600 (FFA recovery), in which the BioD stream is contacted with one or more bases, e.g. solution of 50 wt% sodium hydroxide, to saponify unreacted FFA that remain in the BioD. The saponified FFA is then washed out, and the de-saponified BioD is neutralized (e.g. by adding concentrated sulfuric acid), and transferred to finishing purification processes 700 (for example, washing followed by vacuum drying), to obtain the final biodiesel product.

The saponified FFA can be disposed as waste. Alternatively, and preferably, the saponified FFA undergoes soap splitting to obtain de-saponified FFA, the de-saponified FFA being returned into crude oil stream, e.g. into the degumming unit 300. Such soap- splitting step increases the overall yield of the process, as residual FFA which have not been esterified can be returned to the process for further esterification.