EP3666863A1 - Method for the purification of waste fats and oils containing plastic particles - Google Patents

Abstract

A method for cleaning waste fats and / or oils containing plastic particles comprises the steps 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, and cooling the waste fats and / or oils to a temperature below the softening temperature and the separation of the plastic particles from the liquid waste fats and / or oils. This process removes small plastic particles from them for further use in e.g. animal fats and used cooking oils intended for biodiesel production.

Description

The project leading to this application has received funding from the EU's 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 increasingly been used as raw materials for biodiesel production in recent years. Especially with animal fat, which originates from the recycling of residual and waste materials from the meat industry and subsequently comes from rendering plants ("rendering"), in addition to other solids, such as bone meal, a high proportion of plastic (polyethylene (PE) and related species) Plastics) may be included. This plastic material, mostly in the form of microparticles, comes from, among other things, packaging that has not been completely separated.

Is used in a further process, e.g. in biodiesel production, a raw material, e.g. Animal fat, processed with a high proportion of plastic (> 50 mg / kg), can lead to massive blockages of pipelines and the associated failure of production systems.

For raw materials, such as animal fat, for further processes, such as To be able to use biodiesel production or soap production, it is therefore very important 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 further 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 tallow by means of filtration, the raw material being treated with filter aids and bleaching earth at a temperature of 200-250 ° F ( 93-121 ° C) and filtered at 190-250 ° F (88-121 ° C). Treatment with aluminum hydroxide gel, lye or activated carbon is also mentioned as an alternative.

According to the US 4,159,992 the animal fat is set 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 filtration.

The US 3,758,533 teaches a process for cleaning greases containing plastic particles, in which the temperature of the grease is adjusted such that it is above the melting point of the starting material but below 95 ° C. in order not to dissolve the polyethylene impurities in the grease, so that these can subsequently be filtered or Centrifugation can be separated. Before separation, 0.5-2% by weight of a particulate material, for example Celite or bleaching earth, can be added as a filter aid.

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

In the known methods, precoat filtration is also frequently used, which is associated with high investment and operating costs.
The one in the US 4,159,992 The process 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-intensive distillation.

The invention attempts to overcome the above-mentioned disadvantages of the prior art, and has as its object to provide 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 smaller 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 clog 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.

This object is achieved according to the invention in a method for cleaning waste fats and / or oils containing plastic particles 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
• Separate 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 thermoplastic materials. It describes the temperature at which a circular indenter with a 1 mm ² cross-section sinks exactly 1 mm deep into the test specimen under a standardized load of 10 N. The Vicat softening temperature is standardized, for example, in ISO 306 and ASTM D 1525.

According to a particularly preferred embodiment, the method further comprises the step of adding filter aids 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 separating step.

As already noted above, animal fat usually contains a proportion of solid impurities, namely the plastic particles which 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 e.g. Bone fragments (especially "bone meal"), protein residues, etc. The proportion of these solid particles, which 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. These solid particles can achieve the same effect as a filter aid in the process according to the invention.

In the step according to the invention 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 become solid particles that are not plastic particles, i.e. either those that are already present in the raw material or those of the admixed one Filter aid or both, deposited and fixed on it by the subsequent step of cooling. The solid particles with the plastic fixed thereon can then be easily separated from the liquid waste fats and / or oils.

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

By heating above the softening point of the plastic of the plastic particles contained in the waste fats and / or oils (if several plastics or different types of plastic with different softening temperatures are present, the highest softening temperature is taken from them) and then 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 them), it is also possible to separate small plastic particles that cannot be removed in precoat filtration or lead to blockage of the filter cake.

The step of admixing filter aids preferably comprises admixing filter aids in an amount of 0.1-1.0% by weight, based on the amount of waste fat and / or oil, such as about 0.2% by weight. 3 wt%, 0.4 wt%, 0.5 wt%, 0.6 wt%, 0.7 wt%, 0.8 wt% or 0.9 wt%. Compared to conventional bleaching earth defiltration, significantly smaller amounts of filter aids are therefore 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 the waste fats and / or oils and the filter aid, preferably for 10-25 min, at the temperature above the softening temperature the plastic the plastic particles before the cooling step.

This makes it easier for the plasticized plastic particles to contact the solid particles (particles already present in the waste fats and / or oils or filter aids) and to settle on 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 min, at the temperature below the softening temperature the plastic 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 heating step comprises heating to a temperature 130 130 ° C. In a further preferred embodiment, the cooling step comprises cooling to a temperature <100 ° C. This is particularly favorable since the plastic most frequently present as an impurity in animal fats is polyethylene, which, depending on the type, has a softening temperature of approximately 110 ° C. to approximately 135 ° C.

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

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

It was also surprisingly found that not only the waste fats and / or oils are cleaned from plastic particles by the type of fat preparation according to the invention, but also substances are removed which lead to phase separation difficulties in the further process.

Advantageously, the method 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 increased. In particular, this dosage surprisingly results in a decrease in the non-water-soluble unsaponifiable matter in animal fat. Unsaponifiables (lipids) are understood to mean in particular sterols, hydrocarbons, carotenoids and tocopherols. These fat components interfere with biodiesel production and should therefore be removed as much as possible from the raw material.

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, in each case based on the amount of waste fat and / or oil.

According to a preferred embodiment of the method, the separation step comprises the separation using 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 water washing 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 aids, if necessary, at temperatures above the softening point of the plastic of the plastic particles, these particles are brought onto the solid particles, which are not plastic particles, and / or the filter aid and are fixed thereon by subsequent cooling below the softening temperature. The solid particles and / or the filter aid are then separated off using the three-phase separator required for the raw washing. The plastic particles can be removed in this way without complex filtration equipment in a simultaneous washing step with a 3-phase decanter required for fat preparation.

The invention is explained 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 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 the heating, a filter aid 3, for example bleaching earth, can be mixed into 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 at the temperature above the softening temperature of the plastic of the plastic particles for 10-25 min. 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 cools 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 stand for a time, for example 10-25 min, before water / water vapor 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 experiments, 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 approximately 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, in each case 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, in each case based on the raw material, and then separated using a 3-phase decanter. The PE content after 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, 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 approx. 130 ° C., kept at this temperature for 20 minutes, after cooling to 90 ° C. and a residence time of 10 minutes with 10% by weight of water and 0.5% by weight of phosphoric acid, based in each case 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 kept at this temperature for 20 minutes. After cooling to 90 ° C. and a dwell time of 10 minutes, the animal fat was mixed with 10% by weight of water and 0.5% by weight of phosphoric acid, in each case based on the raw material, and then separated using a 3-phase decanter. The fat phase obtained had a content of 39 ppm PE.

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 aids leads to a further reduction, but a much smaller amount of filter aids 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 solid impurities, which are not plastic, based on the animal fat) was mixed with 0.25% by weight 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, in each case based on the partial 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 off. The same can be expected if no filter aid is added, but the cleaning is carried out using only the solids content already present in the animal fat.

Claims (15)

Process for cleaning waste fats and / or oils containing plastic particles, in particular animal fats, 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. A method according to claim 1, characterized in that it further comprises the step of adding filter aids 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 comprises, wherein the filter aid is removed together with the plastic particles from the liquid waste fats and / or oils in the separating step. A method according to claim 2, characterized in that the step of admixing filter aids comprises admixing filter aids in an amount of 0.1-1.0% by weight, based on the amount of waste fat and / or oil. Method according to one of claims 1 to 3, characterized in that it further 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 from 10-25 min the temperature above the softening temperature of the plastic comprises the plastic particles before the cooling step. Method according to one of claims 1 to 4, characterized in that it further 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 from 10-25 min the temperature below the softening temperature of the plastic comprises the plastic particles before the separation step. Method according to one of claims 1 to 5, characterized in that the step of heating comprises heating to a temperature ≥ 130 ° C. Method according to one of claims 1 to 6, characterized in that the cooling step comprises cooling to a temperature <100 ° C. Method according to one of claims 1 to 7, characterized in that the plastic of the plastic particles comprises polyethylene. A method according to claim 8, characterized in that the plastic of the plastic particles consists of polyethylene. Method according to one of claims 1 to 9, characterized in that the step of separation comprises a centrifugation, preferably a decanting centrifugation. Method according to one of claims 1 to 10, characterized in that it further comprises the step of adding water or steam and acid after the step of cooling. 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. A method according to claim 11 or 12, characterized in that the adding step comprises adding water or steam in an amount of 5-15% by weight based on the amount of waste fat and / or oil. Method according to one of claims 11 to 13, characterized in that the step of adding comprises the addition of acid in an amount of 0.2-1.5% by weight, based on the amount of waste fat and / or oil. Method according to one of claims 11 to 14, characterized in that the separation step comprises the separation by means of a 3-phase decanter, an oil, a water and a solid phase being obtained.

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