WO2023235924A1

WO2023235924A1 - Pre-treatment of waste material for biofuel production

Info

Publication number: WO2023235924A1
Application number: PCT/AU2023/050496
Authority: WO
Inventors: Eduardo Andres RIVERA OLIVOS
Original assignee: Peerless Holdings Pty Limited
Priority date: 2022-06-09
Filing date: 2023-06-07
Publication date: 2023-12-14

Abstract

A process for the treatment of a raw fat, oil and grease (FOG) material to produce a refined FOG product comprising the steps of: i) acid degumming the raw FOG material to remove contaminants, ii) fat splitting the degummed raw FOG material to produce free fatty acids (FFA's) and glycerine; and iii) distilling the FFA's to produce a refined FOG product.

Description

Title of Invention

Pre-treatment of Waste Material for Biofuel Production.

Technical Field

[0001] The present invention relates to the recovery of useful materials from waste products that include fat, oil and grease (collectively known as FOGs). In particular, the present invention relates to a process for refining recovered raw FOG material to make it suitable for further processing. In a particular embodiment, the invention relates to the removal of contaminants from raw FOG material to produce a refined FOG material suitable for the production of biofuels.

Background of Invention

[0002] One source of FOGs is the biproduct of cooking with foods high in fat, such as butter, meat, sauces and cooking oil. In sewer lines, FOGs will mix with other wastes congealing into large masses that are able to clog wastewater pipe networks and, if not removed, cause raw sewage flooding.

[0003] The general authorities do impose particular requirements in order to reduce FOG discharge into the sewer system. These requirements may vary from location to location, but in general, grease traps are required for restaurants and small food services operations, while large industrial businesses such as food manufacturers, abattoirs and dairy producers may be required to install appropriate on-site treatment systems to continually remove FOGs before their effluent can be discharged to the sewer.

[0004] Requirements may vary, but there is a general requirement to reduce FOG discharge into waste-water systems.

[0005] The waste containing FOG that is prevented from entering the wastewater systems or sewer systems by grease traps and other systems, will quickly accumulate and will need to be disposed of in accordance with other local regulations. This can prove to be a costly and timely exercise. FOG recovery from waste materials is not a wide-spread practice and so there is the tendency for it to accumulate. Compositing is the main disposal method for waste containing FOGs. [0006] The lack of recovery methods for FOGs may be due to the many different forms of waste and the concentration and content of the FOGs do vary substantially. This makes recovery of FOGs difficult and difficult to process for other purposes. The quality of the FOGs recovered from waste sources is also generally quite poor. There is generally the presence of persistent contaminants such as phosphorous, sulphur and chlorine which limits the ability to use the material for other uses such as the production of sustainable fuel products.

[0007] There are a number of processes that do endeavour to produce biofuels from FOG’s recovered from waste materials. Such processes include, but not limited to, what may be broadly defined as a Hydrotreated Vegetable Oil (HVO) process and a Biodiesel process.

[0008] An HVO process converts FOG’s into hydrocarbons that can then be processed through existing petrochemical infrastructure into various selected fuels. The Biodiesel process converts triglycerides in a FOG product into a biodiesel product.

[0009] When used in an HVO process, it has also been found that as FOG’s include a large number of contaminants such sulphur, phosphorous, metals, nitrogen and organic chlorides, these contaminants can interfere with the performance of catalysts used in the HVO process.

[0010] The Biodiesel process converts triglycerides in a FOG product into a biodiesel product that is chemically similar to diesel. The free fatty acid (FFA) concentration of the feedstock has to be limited to less than 3% so as to avoid the formation of excessive soap and allow for the separation of biodiesel and glycerine. The FOG must be treated in a particular way to make it suitable for biodiesel processing.

[0011] US patent application 2020/0392426 to Neste Oyj relates to a process in the production of FFA’s, which may be used in the manufacture of renewable fuel by hydrotreating the FFA’s, where the feedstock includes algal oil or chlorophyll. The Neste process endeavoured to address this through a process of hydrolysing the feedstock to obtain an oily phase and distilling the oily phase to recover the free fatty acids for further processing. [0012] US patent 2,005,447 in the name of Wurster considerably predates the Neste application but looked at apparatus for splitting fats into fatty acids and glycerine. The fatty acids could then be used for other processing.

[0013] It is a desired feature of the present application to provide a process where FOGs may be recovered in a manner that allows for treatment to remove many of the contaminants to produce a refined FOG material and as part of a process to recover useful FFA materials from the FOG.

[0014] It is a further desired feature of the present invention to provide a process for the refining of a FOG material to remove contaminants such as such as sulphur, phosphorous, metals, nitrogen and organic chlorides prior to provide a FOG material suitable for the further processing for the production of biofuels.

[0015] It is a further desired feature to provide a process for the purification of a FOG material to provide a relatively pure free fatty acid product suitable for processing in an HVO process in the production of biofuels.

[0016] The discussion of documents, acts, materials, devices, articles and the like is included in this specification solely for the purpose of providing a context for the present invention. It is not suggested or represented that any or all of these matters formed part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

[0017] Where the terms "comprise", "comprises", "comprised" or "comprising" are used in this specification (including the claims) they are to be interpreted as specifying the presence of the stated features, integers, steps or components, but not precluding the presence of one or more other features, integers, steps or components, or group thereof.

Summary of Invention

[0018] The Applicants have developed a process to upgrade low value fats, oils and grease (FOGs) into high quality sustainable fuel feedstocks. The fuel feedstocks are a refined FOG that are useful for further processing into useful products such as biofuels. [0019] In one embodiment, the process of the invention relates to a process for the treatment of a raw fat, oil and grease (FOG) material to produce a refined FOG product comprising the steps of: i) acid degumming the raw FOG material to remove contaminants, ii) fat splitting the degummed raw FOG material to produce crude free fatty acids (FFA’s) and glycerol; and iii) distilling the FFA’s to produce a refined FOG product.

[0020] The raw FOG material is found as part of fatty waste material which is generally a biproduct of cooking with foods high in fat, such as butter, meat, sauces and cooking oil. Fatty waste material does come from a variety of sources such as commercial, domestic and industrial sources including grease traps, industrial effluents, sewage scum and oily sludges.

[0021] In a preferred embodiment, the process includes a step where the components of sourced fatty waste material have been separated into raw FOG, water and organic solid components following an extraction process. Generally, the extraction process may be a 3-phase decanter centrifuge process that is able to separate out the raw FOG in particular. The raw FOG is generally a single oil phase. The water carries contaminants which is in need of further treatment before it may be used. It is often referred to as effluent. The solids are often referred to as cake.

[0022] In a further preferred embodiment, the recovered raw FOG material is processed through an acid degumming step to remove impurities. The raw FOG material is treated with a mineral acid, preferably sulphuric, nitric or citric acid, to remove phospholipids, gums, proteins and metallic salts. The metals are generally precipitated as metallic salts. This produces a degummed raw FOG material.

[0023] The degummed raw FOG material will then undergo a fat splitting process. Preferably, this step involves feeding the degummed raw FOG material and water into a splitting column in a counter current process. In this process, water is fed from the top of the column and the degummed raw FOG material from the bottom. The water is added to hydrolyse the triglycerides in the raw FOG material to crude FFA’s and glycerine.

[0024] In the fat splitting step, the crude FFA’s rise to the top of the splitting column and pass the water injection point, the water and glycerine are flashed discharged from the bottom below the inlet of the degummed raw FOG (oil).

[0025] The water is added, preferably at a temperature of above 200°C, more preferably in the range of from 220°C to 280°C, but most preferably around 250°C under a pressure of preferably from 45 to 60 bar, but most preferably around 55 bar. The high pressure is to maintain the water in liquid state at the elevated temperature. At this temperature the solubility of oil in the water increases substantially and both liquids are able to mix. The water hydrolyses the degummed raw FOG releasing free fatty acids (FFA) and glycerine, but also the water has a washing effect over the oil dragging out pollutants as both liquids move counter current.

[0026] The fat splitting process removes further contaminants. Non-metallic impurities such as organic chlorides, phosphorous, sulphur, nitrogen and residual metals from the acid degumming step are removed through the fat splitting process. This is achieved through the contaminants being washed from the oil phase by contact with the water.

[0027] The crude FFA’s that have risen to the top of the splitting column are removed and distilled to form a refined FOG product. The distillation process is preferably conducted through vacuum distillation where the crude FFA’s are separated from non-volatile components, and through fractional distillation, different FFA chain lengths are obtained.

[0028] Low boiling impurities such as organic chlorides and residual sulphur are removed through vacuum distillation at 1 -10 mbar in a pre-cut column at a temperature of from 170°C to 230°C, but preferably around 200°C to produce a pretreated FFA product. The pre-treated FFA product is transferred to a main vacuum distillation column where the temperature is raised to around 200°C to 260°C, preferably around 240°C and the pressure maintained below 5 mbar, but preferably below 3 mbar to allow a refined FOG product to be removed leaving heavier residues of any remaining nitrogen, phosphorous and metals for removal at the base of the distillation column.

[0029] The refined FOG product is particularly suitable for use in a Hydrotreated Vegetable Oil (HVO) process to produce a biofuel product. The FFA content is generally above 95%, preferably above 98% and more preferably above 99% FFA which makes it particularly suitable feedstock for an HVO process. The refined FOG improves the HVO catalyst lifetime as essentially all contaminants are not present.

[0030] The HVO process may generally be described as comprising 4 reactions. Reaction 1 is first and reactions 2-3 occur in parallel. In reaction 1 hydrogen saturates any double bonds of the triglycerides followed by a cleavage to fatty acids and the hydrogenation (hydrogen removes the acid group oxygen as H₂O) of glycerol to propane (i.e. bie-LPG) and water. In reactions 2 to 4 the fatty acids undergo decarboxylation (the oxygen leaves as CO₂). By using refined FOG produced by the process described in the present application, an HVO producer is able to skip reaction 1 , which results in savings in hydrogen of around 25-30% and the absence of the byproduct propane, avoiding the need for further treatment.

Detailed Description

[0031] The process of the present application relates to a process to upgrade low value fats, oils and grease (FOGs) into a refined FOG product that is particularly suitable as a high-quality sustainable fuel feedstock. The fuel feedstocks are particularly suitable for further processing into useful products such as biofuels.

[0032] The process of the invention preferably includes the step of collecting fatty waste material from known sources. The fatty waste material for use in the process may be sourced from a variety of commercial, domestic and industrial sources including grease traps, industrial effluents, sewage scum or oily sludges.

Alternatively, they may be provided by fatty waste suppliers which will have obtained fatty waste from similar sources. This creates a fatty waste supply which is a mixture of organic solids and effluent and includes FOGs.

[0033] The fatty waste material includes raw FOG. The process of the invention involves the upgrading of raw FOG material to provide a refined FOG product that is suitable for biofuel production. The refined FOG product of the invention is particularly suitable for use in a Hydrotreated Vegetable Oil (HVO) process to produce biofuels but may also be useful in other processes for the production of industrial chemicals.

[0034] In a preferred embodiment of the invention, the process is a pre-treatment process to allow for ease of further processing of a FOG material. The process will generally involve first separating fatty waste material into separate components, namely organic solids that can be used for compost production, water and a raw FOG product. This separation step is preferably performed in a 3-phase centrifuge decanter process. The process then involves the pre-treatment of the recovered raw FOG material so that it becomes a useful feedstock for a process to manufacture biofuels.

[0035] This pre-treatment of the raw FOG may be considered to include three steps. The first step includes acid degumming of the raw FOG material. The second step involves a step of fat splitting, which is a hydrolysis process that removes glycerine and releases free fatty acids (FFA’s). The third step includes FFA distillation to produce a refined FOG product.

[0036] The raw FOG material includes a number of organic components or decomposition components such as free fatty acids, monoglycerides, diglycerides, unsaponifiables, tocopherols, chlorophylls, phospholipids and proteins. The raw FOG material will also include contaminants such as sulphur, phosphorous, metals, nitrogen, and organic chlorides which can interfere in the processing of the organic components. Catalysts used in an HVO process, are susceptible to poisoning and deactivation by the presence of such contaminants.

[0037] Certain contaminants like phospholipids, gums and proteins are soluble in oil in their anhydrous form, but insoluble once they have ben hydrated. The hydratable phospholipids maybe removed from the oil once hydrated. However, part of the contaminants such as gums and proteins and some phospholipids remain in the oil and may be treated with acid to remove them from the oil. In a first acid degumming step, the raw FOG material (oil) is treated with an acid, preferably a mineral acid is used such as sulphuric, nitric or citric acid, where the acid is able to wash the oil to remove contaminants such as gums and proteins. Metals are ionized by the addition of the acid and are generally precipitated as metallic salts.

[0038] The degummed raw FOG material is then subjected to fat splitting to produce FFA’s. In this step, triglycerides are hydrolysed to fatty acid chains and glycerine by adding water as the splitting agent. The water is preferably added at a temperature of from 220°C to 280°C, but most preferably around 250°C under a pressure of preferably from 45 to 60 bar, but most preferably around 55 bar. For the hydrolysis of triglycerides, water is decomposed to hydrogen cations (H⁺) and hydroxide ions (OH ) and these two ions break the ester bonds. The H⁺ ion is attached to the glycerol backbone to form glycerine and the OH’ ion is added on the three acyl groups to generate FFA’s.

[0039] A catalyst is generally not used in this step and splitting degrees can be as high as 99.5%. In a preferred process, the raw FOG material and water are fed into a splitting column in a counter current process, water from the top and the oil from the bottom. Crude FFA’s rise to the top of the splitting column and pass the water injection point. The water and glycerine are flashed discharged from the bottom below the inlet of the oil. The water may be recycled for use in the process and the glycerine may be recovered for use in other purposes. Crude FFA is then recovered from the fat splitting column.

[0040] The distillation process is conducted through vacuum distillation where the crude FFA’s are separated from non-volatile components. The fractional distillation at different temperatures and pressures is able to create FFA’s having different chain lengths. The fatty acids having different carbon chain lengths may be used for different purpose, for example some may be used as foaming agents while others are good emulsifiers.

[0041] Low boiling contaminants such as organic chlorides and residual sulphur are removed through vacuum distillation at 1 -10 mbar in a pre-cut column at a temperature of from 170°C to 230°C, but preferably around 200°C to produce a pretreated FFA product. The organic chlorides remain stubborn to remove but it has been found that if the temperature and pressure is controlled, then the organic chlorides can be removed. The pre-treated FFA product is transferred to a main vacuum distillation column where the temperature is raised to around 200 to 260°C, preferably around 240°C and the pressure maintained below 5 mbar, but preferably below 3 mbar. Under these conditions remaining heavier contaminants such as nitrogen, phosphorous and metals will not distil and be removed from the base of the distillation column as concentrated pitch. The refined FOG product may then be processed for the production of selected biofuels.

[0042] The advantages obtained by distillation of the FFA’s to produce a refined FOG product is that it will improve the HVO catalyst lifetime. There are also considerable savings in operational expenditure due to the reduced levels of hydrogen needed in the HVO process. The levels of hydrogen needed may be reduced by approximately 25-30%, for example there is no need to use hydrogen to saturate any double bonds of triglycerides or hydrogenation of glycerol to propane in the HVO process.

[0043] The HVO process is essentially the creation of biofuel made by the hydrocracking or hydrogenation of vegetable oil. The HVO process converts FOGs into hydrocarbons that can then be processed through existing petrochemical infrastructure into different fuels such as petrol (naphtha); jet fuel (kerosene) or diesel as illustrated in Figure 1 .

[0044] The presence of contaminants in the feedstock will affect the ability to make a useful biofuel product in the HVO process. It is difficult to make an effective biofuel product using the HVO process if the quality of the FOG material is of poor quality and includes many contaminants. The process of the present invention reduces the contaminants in a FOG supply allowing for an improved feedstock quality for the production of biofuels.

[0045] In the HVO process, the catalysts used in the process are susceptible to poisoning and deactivation by several contaminants such as sulphur, phosphorous, metals, nitrogen and organic chlorides. It is therefore preferred to pre-treat the feedstock for an HVO process to protect the catalysts and increase the useful life of the catalyst in the HVO process. The desired levels of contaminants for the HVO process, together with an alternative biodiesel process is shown in Table 1 . As the Biodiesel process looks to have an FFA level of less than 3%, the FOG material of the present application is not generally suitable for a biodiesel process.

Table 1

The process of the present application is outlined with reference to Figure 2.

Example 1

[0046] A process was run where raw FOG was treated in accordance with the process of the invention. The first step involved an acid degumming and washing step. In this step, phosphorous contaminants fell from 178ppm to 61 ppm, metals fell from 354ppm to 56ppm, nitrogen from 280ppm to 200ppm while organic chlorides remained around the same. The sulphur levels increased from 142ppm to 270ppm as sulphuric acid was used as the acid. The FFA levels also remained at around the same levels.

[0047] Following the hydrolysis or fat splitting step where triglycerides are converted to free fatty acids, the level of FFA’s increased from about 55.95% to 89.78%. The level of sulphur reduced to 38ppm while phosphorous reduced to 5.9ppm, metals to 7.1 ppm and nitrogen to 160pp. Organic chlorides reduced to 7ppm.

[0048] This is followed by a distillation step of the FFA’s to produce a refined FOG product that is suitable for processing to biofuels particularly in an HVO process. Following distillation, the refined FOG included 13 ppm sulphur, 1.1 ppm phosphorus, less than 1 ppm metals, 68ppm nitrogen and 3ppm organic chlorides. The FFA content had increase to 99.50% which is near a pure product. The moisture content had reduced through the process from 0.45% to 0.05%

[0049] This Example demonstrates the role of each step in the process to reduce the contaminants in the FOG material to produce a refined FOG product. These are levels of contaminants that will not have a significant detrimental effect on further processing of the product, particularly in an HVO process. Indeed, an HVO process calls for levels of contaminants, each of which are in excess of the levels obtained in this process.

Claims

1 . A process for the treatment of a raw fat, oil and grease (FOG) material to produce a refined FOG product comprising the steps of: i) acid degumming the raw FOG material to remove contaminants, ii) fat splitting the degummed raw FOG material to produce free fatty acids (FFA’s) and glycerine; and iii) distilling the FFA’s to produce a refined FOG product.

2. A process according to claim 1 wherein the raw FOG material is obtained from a fatty waste material that has been separated into raw FOG, water and organic solid components following an extraction process.

3. A process according to claim 2 wherein the extraction process is a 3-phase decanter centrifuge process.

4. A process according to claim 2 wherein the fatty waste material is sourced from a variety of commercial, domestic and industrial sources including grease traps, industrial effluents, sewage scum or oily sludges.

5. A process according to anyone of the preceding claims wherein the recovered oil phase of the raw FOG material is processed through an acid degumming step where the raw FOG material is treated with a mineral acid, preferably sulphuric, nitric or citric acid, to remove phospholipids, gums, proteins and metallic salts from the raw FOG material to produce a degummed raw FOG material.

6. A process according to claim 5 wherein the metals present are precipitated from the raw FOG material as metallic salts.

7. A process according to any one of the preceding claims wherein the degummed raw FOG material and water are fed into a splitting column in fat splitting step where water is fed from the top and the degummed raw FOG material from the bottom, the water is added to hydrolyse the triglycerides in the raw FOG material to crude FFA’s and glycerine. A process according to claim 7 wherein the fat splitting step is conduced as a counter-current process. A process according to claim 7 or 8 wherein the crude FFA’s rise to the top of the splitting column and pass the water injection point, the water and glycerine are flashed discharged from the bottom below the inlet of the raw FOG material. A process according to anyone of claims 7 to 9 wherein the water is added at a temperature of around temperature of from 220°C to 280°C, but most preferably around 250°C under a pressure of from 45 to 60 bar, but most preferably around 55 bar to maintain the water in a liquid phase. A process according to anyone of the preceding claims wherein non-metallic contaminants such as organic chlorides, phosphorous, sulphur, nitrogen and residual metals from the acid degumming step are removed through the fat splitting step. A process according to claim 11 wherein the crude FFA’s obtained from the splitting column are distilled to create a refined FOG product. A process according to claim 11 or 12 wherein the distillation process is conducted through vacuum distillation where the crude FFA’s are separated from non-volatile components, and through fractional distillation, different FFA chain lengths are obtained. A process according to anyone of claims 11 to 13 wherein low boiling pollutants such as organic chlorides and residual sulphur are removed through vacuum distillation at 1 -10 mbar in a pre-cut column at a temperature of from 170°C to 230°C, but preferably around 200°C to produce a pre-treated FFA product to produce a pre-treated FFA product. A process according to claim 14 wherein the pre-treated FFA product is transferred to a main vacuum distillation column where the temperature is raised to around 200 to 260°C, preferably around 240°C and the pressure maintained below 5 mbar, but preferably below 3 mbar to produce a refined FOG product leaving heavier residues of any remaining nitrogen phosphorous and metals for removal at the base of the distillation column. A process according to any one of the preceding claims wherein the refined FOG product is used in a Hydrotreated Vegetable Oil (HVO) process to produce a biofuel product. A process according to anyone of the preceding claims wherein the refined FOG improves the HVO catalyst lifetime and reduces the use of hydrogen in the HVO.