EP3666863B1 - Method for the purification of waste fats and oils containing plastic particles - Google Patents

Description

The project leading to this registration has received funding from the EU Horizon 2020 program for research and innovation under grant agreement No. 737802.

The invention relates to a method for cleaning waste fats and / or oils containing plastic particles, in particular animal fats.

Waste materials such as used cooking oils or animal fats have been increasingly used as raw materials for biodiesel production in recent years. Particularly in the case of animal fat, which comes from the recycling of residual and waste materials from the meat industry and subsequently comes from animal carcass recycling plants ("rendering"), a high proportion of plastic (polyethylene (PE) and related substances) can be used in addition to other solids such as bone meal Plastics). This plastic material, mostly in the form of microparticles, comes from, among other things, packaging that has not been completely separated.

If a starting material, e.g. animal fat, with a high plastic content (> 50 mg / kg) is processed in a further process, e.g. in biodiesel production, this can lead to massive clogging of pipelines and the associated failure of production facilities.

In order to be able to use raw materials such as animal fat for further processes, such as biodiesel production or soap production, it is therefore of great importance to reduce the proportion of plastic particles in the starting material as much as possible.

In order to remove plastic particles from animal fats that are used as raw materials for other applications, filtration with filter aids is usually carried out.

The publication Fats and Proteins Research Foundation, Inc., Director's Digest, No. 113 (November 1973) describes the separation of PE from sebum by means of filtration, the raw material being treated with filter aid and fuller's earth at a temperature of 200-250 ° F ( 93-121 ° C) and filtered at 190-250 ° F (88-121 ° C). As an alternative, treatment with aluminum hydroxide gel, lye or activated carbon is also mentioned.

According to the U.S. 4,159,992 the animal fat is adjusted to a temperature just above its solidification point and mixed with an organic solvent in which only the fat dissolves. The undissolved plastic particles are then removed from the solution by means of filtration.

The U.S. 3,758,533 teaches a method for cleaning fats containing plastic particles, in which the temperature of the fat is set in such a way that it is above the melting point of the starting material but below 95 ° C so as not to dissolve the polyethylene impurities in the fat, so that they can then be removed by filtration or Centrifugation can be separated. Before the separation, 0.5-2% by weight of a particulate material, for example Celite or fuller's earth, can be added as a filter aid.

Although the commonly used cleaning processes, which use filtering with filter aids, achieve a reduction in the content of plastic particles, on the one hand large amounts of filter aids are required for this and the water contained in the fat must be removed beforehand. Due to the different size distribution of the plastic particles, the filtration results achieved are usually difficult to reproduce.

In the known processes, precoat filtration is also often used, which is associated with high investment and operating costs.
The one in the U.S. 4,159,992 The method described in turn requires an organic solvent, which must be removed from the animal fat at the end of the process by means of energy-consuming distillation.

The invention attempts to overcome the above-mentioned disadvantages of the prior art, and has the object of providing a method for cleaning waste fats and / or oils containing plastic particles, in particular animal fats, which reduces the content of plastic particles without or achieved with lower amounts of filter aid than the known methods. In addition, it should also be possible to separate small particles from the animal fat which cannot be removed in a precoat filtration or which quickly lead to clogging of the filter cake.

• Erwärmen der Kunststoffpartikel enthaltenden Abfallfette und/oder -öle auf eine Temperatur über der Erweichungstemperatur des Kunststoffs der Kunststoffpartikel,
• Abkühlen der Abfallfette und/oder -öle auf eine Temperatur unter der Erweichungstemperatur des Kunststoffs der Kunststoffpartikel und
• Abtrennen der Kunststoffpartikel von den flüssigen Abfallfetten und/oder -ölen.

In a method for cleaning waste fats and / or oils containing plastic particles, this object is achieved according to the invention in that it comprises the following steps:

• Heating the waste fats and / or oils containing plastic particles to a temperature above the softening temperature of the plastic of the plastic particles,
• Cooling the waste fats and / or oils to a temperature below the softening temperature of the plastic of the plastic particles and
• Separating the plastic particles from the liquid waste fats and / or oils.

The softening temperature of the plastic is the Vicat softening temperature (VST) measured according to method A according to ISO 306, which was introduced as a substitute for the melting point of thermoplastics. It denotes the temperature at which a circular indenter with a 1 mm ² cross-section sinks exactly 1 mm into the test specimen under a standardized load of 10 N. The Vicat softening temperature is standardized in ISO 306 and ASTM D 1525, for example.

According to a particularly preferred embodiment, the method further comprises the step of adding filter aid to the waste fats and / or oils containing plastic particles, before or after the heating step, to produce a mixture of the waste fats and / or oils and the filter aid, wherein the filter aid is removed together with the plastic particles from the liquid waste fats and / or oils in the step of separation.

As already noted above, animal fat usually contains a proportion of solid impurities, namely the plastic particles that are to be removed or whose proportion is to be reduced by means of the method according to the invention, and other solid particles, such as bone fragments (in particular "bone meal"), protein residues , etc .. The proportion of these solid particles that are not plastic particles depends on the origin and processing of the starting material and is usually about 0.03% by weight or more, based on the raw material. In the process according to the invention, these solid particles can achieve the same effect as a filter aid.

In the inventive step of heating the waste fats and / or oils containing plastic particles to a temperature above the softening temperature of the plastic of the plastic particles, the plastic particles are deposited on solid particles that are not plastic particles, i.e. either those that are already present in the raw material or those of the admixed Filter aid, or both, deposited and fixed thereon by the subsequent step of cooling. The solid particles with the plastic fixed on them can then easily be separated from the liquid waste fats and / or oils.

In the case of some raw materials, the proportion of solid particles that are not plastic particles is too low to achieve the desired or even any cleaning effect. In this case, according to the invention, the step of admixing filter aids known to the person skilled in the art, such as bleaching earth, for example bentonite, is provided. This step can be done before or after the heating step. It is advantageous to ensure thorough mixing, for example by stirring, of waste fats and / or oils and filter aids containing plastic particles.

By heating the plastic particles contained in the waste fats and / or oils above the softening point of the plastic (if there are several plastics or different types of a plastic with different softening temperatures, the highest softening temperature is taken from these) and subsequent cooling below the softening point (if several plastics are present or different types of plastic with different softening temperatures, the lowest softening temperature is taken from these) it is possible to separate even small plastic particles which cannot be removed in a precoat filtration or which lead to clogging of the filter cake.

The step of adding filter aid preferably comprises adding filter aid in an amount of 0.1-1.0% by weight, based on the amount of waste fat and / or oil, such as 0.2% by weight, 0, 3% by weight, 0.4% by weight, 0.5% by weight, 0.6% by weight, 0.7% by weight, 0.8% by weight or 0.9% by weight. In comparison to conventional bleaching earth filtration, significantly smaller amounts of filter aid are advantageously required according to the invention.

According to a further preferred embodiment, the method according to the invention further comprises a step of holding the waste fats and / or oils containing plastic particles or the mixture of waste fats and / or oils and the filter aid, preferably for 10-25 min, at the temperature above the softening temperature of the plastic of the plastic particles before the step of cooling.

This makes it easier for the plasticized plastic particles to contact the solid particles (particles or filter aids already present in the waste fats and / or oils) and to settle or deposit on them, so that plastic particles can be fixed on them during the cooling step.

According to another preferred embodiment, the method according to the invention also comprises a step of holding the waste fats and / or oils containing plastic particles or the mixture of the waste fats and / or oils and the filter aid, preferably for 10-25 minutes, at the temperature below the softening temperature of the plastic of the plastic particles before the step of separating.

This step improves the adhesion of the plastic particles to the solids, as a result of which a higher proportion of plastic can be removed from the waste fats and / or oils.

In a preferred embodiment, the step of heating comprises heating to a temperature 130 ° C. In a further preferred embodiment, the step of cooling comprises cooling to a temperature <100.degree. This is particularly beneficial because the plastic most commonly found as a contaminant in animal fats is polyethylene, which, depending on the type, has a softening temperature of about 110 ° C to about 135 ° C.

The plastic of the plastic particles preferably comprises polyethylene, in particular it consists of it. "Polyethylene-type polymers" are defined according to analytical method ISO 6656 as impurities which are soluble in boiling perchlorethylene.

A preferred embodiment of the method is characterized in that the step of separation comprises centrifugation, in particular decanting centrifugation.

Surprisingly, it was also found that the type of fat preparation according to the invention not only cleans the waste fats and / or oils from plastic particles, but also removes substances that lead to phase separation difficulties in the further process.

The method advantageously further comprises the step of adding water or steam and acid after the step of cooling (or after the step of maintaining below the softening temperature), the acid preferably being selected from phosphoric acid, sulfuric acid, citric acid, methanesulfonic acid or any combination of these.

By adding water or steam and especially acid, the positive effect of removing substances that later lead to phase separation difficulties can be intensified. In particular, this dosage surprisingly results in a decrease in the water-insoluble unsaponifiables in animal fat. Unsaponifiable (lipids) are understood as meaning, in particular, sterols, hydrocarbons, carotenoids and tocopherols. These fat components have a disruptive effect on biodiesel production and should therefore be removed from the raw material as much as possible.

The addition step preferably comprises the addition of water or steam in an amount of 5-15% by weight or the addition of acid in an amount of 0.2-1.5% by weight, based in each case on the amount of waste fat and / or oil.

According to a preferred embodiment of the method, the step of separation comprises separation by means of a 3-phase decanter, an oil, a water and a solid phase being obtained.

Animal fat, for example for biodiesel production, is usually cleaned of solids and impurities by washing water at high temperature using a 3-phase decanter (three-phase separator). The method according to the invention can advantageously be carried out by decanting centrifugation in a 3-phase decanter. By adding and stirring in filter aid, if necessary, at temperatures above the softening point of the plastic of the plastic particles, these particles are brought onto the solid particles that are not plastic particles and / or the filter aid and are fixed on them by subsequent cooling below the softening temperature. The solid particles and / or the filter aid are then separated off with the three-phase separator required for the raw washing. In this way, the plastic particles can be removed without complex filtration equipment in a simultaneous washing step with a 3-phase decanter required for fat processing.

The invention is explained in more detail below with reference to examples and the drawing, wherein Fig. 1 shows a block diagram of an embodiment of the method according to the invention.

As in Fig. 1 As shown, waste fat and / or oil containing plastic particles, referred to as oil phase 1, is introduced into a tank 2. In the tank 2, the oil phase is heated to a temperature which is above the softening temperature of the plastic of the plastic particles. Before or after heating, a filter aid 3, for example bleaching earth, can be added to the oil phase 1 in order to produce a mixture of the oil phase 1 and the filter aid 3. The heated oil phase 1 or the mixture of the oil phase 1 and the filter aid 3 is advantageously kept in the tank 2 for 10-25 minutes at the temperature above the softening temperature of the plastic of the plastic particles. The oil phase 1 or the mixture of the oil phase 1 and the filter aid 3 is then conveyed into the tank 4, where it is cooled to a temperature below the softening temperature. The cooled oil phase 1 or the cooled mixture of the oil phase 1 and the filter aid 3 is preferably left to rest for a period of time, for example 10-25 minutes, before water / steam 5 and acid 6 are added. The mixture is then separated in a 3-phase decanter 7 into a purified oil phase 8, a water phase 9 and a solid phase 10 containing the plastic particles (optionally together with the filter aid) and other solid particles.

Examples Example 1:

1. (A) Der Rohstoff wurde auf ca. 130°C erwärmt und für 10 Minuten auf dieser Temperatur gehalten. Im Anschluss wurde er auf ca. 100°C abgekühlt. Nach 10 Minuten Verweilzeit wurde das Tierfett mit 10 Gew.% Wasser und 0,5 Gew.% Phosphorsäure, jeweils bezogen auf den Rohstoff, vermischt und anschließend über einen 3-Phasen-Dekanter aufgetrennt. Der PE-Gehalt wurde auf 182 ppm gesenkt.
2. (B) Dem Rohstoff wurden 0,25 Gew.% Filterhilfsmittel (Bentonit), bezogen auf den Rohstoff, zugegeben. Der Rohstoff wurde auf ca. 130°C erwärmt und für 10 Minuten auf dieser Temperatur gehalten. Im Anschluss wurde er auf ca. 100°C abgekühlt. Nach 10 Minuten Verweilzeit wurde das Tierfett mit 10 Gew.% Wasser und 0,5 Gew.% Phosphorsäure, jeweils bezogen auf den Rohstoff, vermischt und anschließend über einen 3-Phasen-Dekanter aufgetrennt. Der PE-Gehalt betrug nach der Abtrennung im 3-Phasen-Dekanter 51 ppm.

In the following tests, an animal fat with 290 ppm polyethylene (PE determined in accordance with ISO 6656) and a proportion of solids (which are not plastic particles) of 0.07%, based on the raw material, was used as the raw material.

1. (A) The raw material was heated to approx. 130 ° C. and kept at this temperature for 10 minutes. It was then cooled to approx. 100 ° C. After a residence time of 10 minutes, the animal fat was mixed with 10% by weight of water and 0.5% by weight of phosphoric acid, each based on the raw material, and then separated using a 3-phase decanter. The PE content was reduced to 182 ppm.
2. (B) 0.25% by weight of filter aid (bentonite), based on the raw material, was added to the raw material. The raw material was heated to approx. 130 ° C. and kept at this temperature for 10 minutes. It was then cooled to approx. 100 ° C. After a residence time of 10 minutes, the animal fat was mixed with 10% by weight of water and 0.5% by weight of phosphoric acid, each based on the raw material, and then separated using a 3-phase decanter. The PE content after the separation in the 3-phase decanter was 51 ppm.

Example 2:

1. (A) Der Rohstoff wurde auf ca. 130°C erwärmt, für 20 Minuten auf dieser Temperatur gehalten, nach dem Abkühlen auf 90°C und 10 Minuten Verweilzeit mit 10 Gew.% Wasser und 0,5 Gew.% Phosphorsäure, jeweils bezogen auf den Rohstoff, vermischt und anschließend über einen 3-Phasen-Dekanter aufgetrennt. Der PE-Gehalt betrug 139 ppm PE.
2. (B) Dem Rohstoff wurden 0,5 Gew.% Filterhilfsmittel (Bentonit), bezogen auf den Rohstoff, zugesetzt. Das Gemisch wurde auf ca. 130°C erwärmt und für 20 Minuten auf dieser Temperatur gehalten. Nach dem Abkühlen auf 90°C und einer Verweilzeit von 10 Minuten wurde das Tierfett mit 10 Gew.% Wasser und 0,5 Gew.% Phosphorsäure, jeweils bezogen auf den Rohstoff, vermischt und anschließend über einen 3-Phasen-Dekanter aufgetrennt. Die erhaltene Fettphase hatte einen Gehalt von 39 ppm PE.

In this example, an animal fat with 230 ppm PE and 0.05% by weight solid impurities (which are not plastic), based on the raw material, was used as the raw material.

1. (A) The raw material was heated to about 130.degree. C., kept at this temperature for 20 minutes, after cooling to 90.degree. C. and a residence time of 10 minutes, with 10% by weight of water and 0.5% by weight of phosphoric acid, each based on the raw material, mixed and then separated using a 3-phase decanter. The PE content was 139 ppm PE.
2. (B) 0.5% by weight of filter aid (bentonite), based on the raw material, was added to the raw material. The mixture was heated to about 130 ° C. and held at this temperature for 20 minutes. After cooling to 90 ° C. and a residence time of 10 minutes, the animal fat was mixed with 10% by weight of water and 0.5% by weight of phosphoric acid, each based on the raw material, and then separated using a 3-phase decanter. The fat phase obtained had a PE content of 39 ppm.

The results of Example 1 and Example 2 show that the content of plastic particles by means of the method according to the invention is clear even without the aid of filter aids can be reduced. The addition of filter aid leads to a further reduction, although a far smaller amount of filter aid is required for the end result compared to the known prior art.

Example 3:

An animal fat with 342 ppm PE (and 0.08% by weight of solid impurities that are not plastic, based on the animal fat) was mixed with 0.25% by weight of filter aid, based on the animal fat, heated to 130 ° C. and after different residence times (5, 10 and 20 minutes) cooled to 90 ° C. After a further residence time of 10 minutes, the mixture was mixed with 10% by weight of water and 0.5% by weight of phosphoric acid, each based on the fat, and the fat phase was then separated off using a three-phase decanter. The fat phases obtained had the following PE content: 5 minutes dwell time: 80 ppm PE (77% reduction) 10 minutes dwell time: 66 ppm PE (81% reduction) 20 minutes dwell time: 35 ppm PE (90% reduction)

These results show that the longer the step of holding the mixture of waste fats and / or oils and the filter aid at the temperature above the softening temperature of the plastic of the plastic particles, the more plastic particles can be separated. The same can be expected if no filter aid is added, but cleaning is carried out solely with the solid content already present in the animal fat.

Claims (15)

1. A method of cleaning waste fats and/or oils, in particular animal fats, containing plastic particles, characterized in that it comprises the following steps:

   - heating the waste fats and/or oils containing plastic particles to a temperature above the softening temperature of the plastic of the plastic particles,

   - cooling the waste fats and/or oils to a temperature below the softening temperature of the plastic of the plastic particles and

   - separating the plastic particles from the liquid waste fats and/or oils.
2. A method according to claim 1, characterized in that, furthermore, it comprises the step of admixing a filter aid to the waste fats and/or oils containing plastic particles before or after the heating step for producing a mixture of the waste fats and/or oils and the filter aid, with the filter aid being removed from the liquid waste fats and/or oils together with the plastic particles during the separating step.
3. A method according to claim 2, characterized in that the step of admixing a filter aid comprises the admixing of a filter aid in an amount of 0.1-1.0% by weight, based on the amount of waste fat and/or oil.
4. A method according to any of claims 1 to 3, characterized in that, furthermore, it comprises a step of keeping the waste fats and/or oils containing plastic particles or the mixture of the waste fats and/or oils and the filter aid, preferably from 10-25 min, at the temperature above the softening temperature of the plastic of the plastic particles before the cooling step.
5. A method according to any of claims 1 to 4, characterized in that, furthermore, it comprises a step of keeping the waste fats and/or oils containing plastic particles or the mixture of the waste fats and/or oils and the filter aid, preferably from 10-25 min, at the temperature below the softening temperature of the plastic of the plastic particles before the separating step.
6. A method according to any of claims 1 to 5, characterized in that the heating step comprises heating to a temperature of ≥ 130°C.
7. A method according to any of claims 1 to 6, characterized in that the cooling step comprises cooling to a temperature of < 100°C.
8. A method according to any of claims 1 to 7, characterized in that the plastic of the plastic particles comprises polyethylene.
9. A method according to claim 8, characterized in that the plastic of the plastic particles is made of polyethylene.
10. A method according to any of claims 1 to 9, characterized in that the separating step comprises a centrifugation, preferably a decanter centrifugation.
11. A method according to any of claims 1 to 10, characterized in that, furthermore, it comprises the step of adding water or vapour as well as acid after the cooling step.
12. A method according to claim 11, characterized in that the acid is selected from phosphoric acid, sulfuric acid, citric acid, methanesulfonic acid or any combination thereof.
13. A method according to claim 11 or 12, characterized in that the adding step comprises the adding of water or vapour in an amount of 5-15% by weight, based on the amount of waste fat and/or oil.
14. A method according to any of claims 11 to 13, characterized in that the adding step comprises the adding of acid in an amount of 0.2-1.5% by weight, based on the amount of waste fat and/or oil.
15. A method according to any of claims 11 to 14, characterized in that the separating step comprises the separation by means of a 3-phase decanter, whereby an oil, a water and a solid phase are obtained.

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