Biogenic low viscosity insulating oil

Abstract

A method of producing a non-petroleum based electrical insulating oil, wherein the method can include providing a primary mixture of non-petroleum origin, containing isomerized straight chain hydrocarbons; performing a distillation and/or stripping of the primary mixture; collecting a paraffinic base oil as a product of the distillation and/or stripping, containing a mixture of isoalkanes and alkanes; and mixing the base oil with an antioxidant additive.

Claims

1. A method of producing a non-petroleum based electrical insulating oil, the method comprising: providing a primary mixture of non-petroleum origin, containing isomerized straight chain hydrocarbons in a range of C.sub.10-C.sub.20; performing a distillation and/or stripping of the primary mixture; collecting a paraffinic base oil as a product of the distillation and/or stripping, containing a mixture of isoalkanes and alkanes in a range of C.sub.14-C.sub.20; mixing the paraffinic base oil with an antioxidant additive; repeatedly taking a sample of a product of the distillation and/or stripping; and controlling collection of the paraffinic base oil in such a way that: collection of the product of distillation or stripping is started when a flash point of the sample is larger than 135° C. and lower than or equal to 160° C. measured by closed cup, Pensky-Marten; and the collection of the product of distillation or stripping is ended when a kinematic viscosity of the sample at 40° C. falls within a range of 3.4 to 4.5 mm.sup.2/s.

2. The method according to claim 1, wherein the said kinematic viscosity at 40° C. is selected to fall within a range of 3.6 to 3.9 mm.sup.2/s, or to be about 3.8 mm.sup.2/s.

3. The method according to claim 1, wherein the flash point is selected to be larger than 135° C. and lower than or equal to 155° C., or lower than or equal to 150° C., or lower than or equal to 145° C.

4. The method according to claim 1, wherein the primary mixture comprises: isomerized straight chain hydrocarbons selected to be in a range of at least one of C.sub.11-C.sub.20, C.sub.11-C.sub.19, C.sub.12-C.sub.19, or C.sub.12-C.sub.18.

5. The method according to claim 1, wherein the paraffinic base oil comprises: a mixture of isoalkanes and alkanes selected to be in a range of C.sub.15-C.sub.19 or C.sub.16-C.sub.18.

6. The method according to claim 1, wherein the antioxidant additive is selected to be in an amount of up to 0.4% by weight, up to 0.3% by weight, or up about to 0.24% by weight.

7. The method according to claim 1, wherein the antioxidant additive is butylated hydroxytoluene (BHT).

8. The method according to claim 1, comprising: mixing the paraffinic base oil with a gassing tendency lowering additive.

9. The method according to claim 1, wherein the primary mixture comprises: isomerised straight chain hydrocarbons of fatty acid origin.

10. A non-petroleum based electrical insulating oil manufactured according to the method according to claim 1.

11. The method according to claim 1, comprising: applying the a non-petroleum based electrical insulating oil for cooling of at least one electronic circuit, processor, electronic component, electric transformer, electric shunt reactor, or electric switch gear.

12. A method of producing a non-petroleum based electrical insulating oil, the method comprising: providing a primary mixture of non-petroleum origin, containing isomerized straight chain hydrocarbons in a range of C.sub.10-C.sub.20; performing a distillation of the primary mixture; collecting a paraffinic base oil as a product of the distillation, containing a mixture of isoalkanes and alkanes in a range of C.sub.14-C.sub.20; mixing the paraffinic base oil with an antioxidant additive; controlling collection of the paraffinic base oil in such a way that: an initial boiling point of a distillation cut is chosen so that a flash point is larger than 135° C. and lower than or equal to 160° C. measured by closed cup, Pensky-Marten; and a final boiling point of the distillation cut is chosen so that a kinematic viscosity of the paraffinic base oil at 40° C. falls within a range of 3.4 to 4.5 mm.sup.2/s.

13. The method according to claim 12, wherein the said kinematic viscosity at 40° C. is selected to fall within a range of 3.6 to 3.9 mm.sup.2/s, or to be about 3.8 mm.sup.2/s.

14. The method according to claim 12, wherein the flash point is selected to be larger than 135° C. and lower than or equal to 155° C., or lower than or equal to 150° C., or lower than or equal to 145° C.

15. The method according to claim 12, wherein the primary mixture comprises: isomerized straight chain hydrocarbons selected to be in a range of at least one of C.sub.11-C.sub.20, C.sub.11-C.sub.19, C.sub.12-C.sub.19, or C.sub.12-C.sub.18.

16. The method according to claim 12, wherein the paraffinic base oil comprises: a mixture of isoalkanes and alkanes selected to be in a range of C.sub.15-C.sub.19 or C.sub.16-C.sub.18.

17. The method according to claim 12, wherein the antioxidant additive is selected to be in an amount of up to 0.4% by weight, up to 0.3% by weight, or up about to 0.24% by weight.

18. The method according to claim 12, wherein the antioxidant additive is butylated hydroxytoluene (BHT).

19. The method according to claim 12, comprising: mixing the paraffinic base oil with a gassing tendency lowering additive.

20. The method according to claim 12, wherein the primary mixture comprises: isomerised straight chain hydrocarbons of fatty acid origin.

Description

DETAILED DESCRIPTION

(1) Embodiments described herein are to be regarded only as examples and are in no way to limit the scope of the protection provided by the patent claims.

(2) The electrical insulating oil comprises a paraffinic base oil and preferably one or more additives. The base oil is prepared preferably from a non-petroleum, biogenic feedstock.

(3) The isoalkanes of the feedstock may preferably originate from renewable fatty acids, or triglycerides processed by hydrodeoxygenation, i.e. the process for manufacturing of HVO, Hydrotreated Vegetable Oil, or from biogas (via the Fischer-Tropsch process followed by isomerization). Other potential original feedstocks are biooils from hydrothermal treatment of biomass, depolymerized lignin, or from biochemically available hydrocarbons such asfarnesene. In the latter cases, more elaborate hydrocarbon transformations are needed such as oligomerization, hydrotreatment, and hydrocracking.

(4) The paraffinic base oil of the present disclosure when produced from animal or plant fats is a result of hydrotreatment, leading to breaking of all carbon-oxygen bonds and saturation of all carbon-carbon double bonds, followed by hydroisomerization. The efficiency of the isomerization must be high enough to satisfy the demands on pour point of the final product and can be performed by proprietary or open methods.

(5) The base oil in the electrical insulating oil of the present disclosure was isolated by a process of, possibly fractional, distillation and/or by stripping of a feedstock as described above. During a distillation step, the collection of the paraffinic base oil (of the desired distillation cut) was controlled in such a way that the initial boiling point of the distillation cut was chosen so that the flash point requirement of the resulting oil fulfils the requirements of IEC 60296-2012 (>135° C. closed cup, Pensky-Marten) and/or ASTM D3487-2016 (145° C. Cleveland open cup). The final boiling point of the distillation cut was chosen so that the viscosity of the resulting oil fell within the range of 3.4 to 4.5 mm.sup.2/s at 40° C., or 1.3 to 1.6 cSt at 100° C.

(6) Feedstock example: isomerized saturated hydrocarbon mixture (C.sub.10-C.sub.20), having a boiling point range within 180-310° C., a kinematic viscosity at 40° C. of about 2.5-3.2 cSt, a flash point in the range of 100-120° C. (closed cup), and a pour point in the range of −60 to −40° C.

(7) The initial boiling point measured was in the range of 280-290° C., and the final boiling point in the range of 305-315° C. The possibly fractional distillation process is controlled by adjustment of the temperature and effective length of the distillation column by means of periodic measurement of the flash point and kinematic viscosity of the collected fraction. This gives a mixture comprising isoalkanes and alkanes in the range of C.sub.14-C.sub.20.

(8) Similarly, a separation of the desired paraffinic base oil from the isomerized saturated hydrocarbons can be achieved by regular stripping, employing known stripping agents such as inert gas, air, hydrocarbon gas, or steam. The regular control of the flash point and of the kinematic viscosity allow even in such case the controlled collection of desired product.

(9) Preferably, the collection of the product of distillation or stripping is started when the flash point of the sample is at a predetermined temperature which is larger than 135° C. and lower than or equal to 160° C. In some embodiments, the collection of the product of distillation or stripping is started when the flash point of the sample is just above 135° C. In other embodiments, the collection of the product of distillation or stripping is started when the flash point of the sample is 160° C.

(10) The electrical insulating oil of the present disclosure comprises the paraffinic base oil isolated as above, preferably also comprising an antioxidant additive. A surprisingly high responsiveness to the antioxidant BHT was observed, enabling the use of low quantities of additive while reaching excellent oxidation stability of the final product. Whereas the standards IEC 60296 and ASTM D3487 allow for 0.4 and 0.3% by weight of antioxidant respectively, the insulating oil of the present disclosure shows excellent oxidation stability with as little as 0.24% by weight of BHT. The physical properties of such an electrical insulating oil are listed in Table 2 below.

(11) The electrical insulating oil of the present disclosure shows a content of isoalkanes higher than 70% by mass, and a biogenic carbon content of more than 99.60% as measured by ASTM D6866.

(12) The electrical insulating oil of the present disclosure may optionally comprise even a gassing tendency lowering additive, giving limited gassing tendency or gas absorption properties. This can be an advantage is cases where evolution of hydrogen gas under partial electrical discharge is a concern.

(13) The electrical insulating oil of the present disclosure shows a surprisingly low viscosity. In fact, it has a much lower viscosity than previously commercially available insulating oils fulfilling either IEC 60296-2012 or ASTM D3487-2016. This means that any transformer designed for use of an oil fulfilling any of the two standards will function as per manufacturer's nameplate under normal circumstances when filled with oil in accordance with embodiments of the present disclosure. In addition, the low viscosity will give possibilities to handle over-load, and/or give the possibility to extend service life of the transformer because of improved cooling. The oil in accordance with the present disclosure gives the possibility to design a transformer in such a way that turbulent flow, which is more efficient for heat transfer than laminar flow, occurs both through the winding and through the cooling system. The former in not usually possible in the winding part because the overall flow speed cannot exceed a certain value, for example commonly 0.5 m/s, to avoid static electrification phenomena. This is the case for both natural convection (Oil Natural, ON) and when an external pump is used to force the oil flow through the system (Oil Forced, OF). In the latter case the lower viscosity of embodiments of the oil will give a decreased power consumption of the pump, or allow for a smaller, more energy efficient pump in the design. Another transformer design possibility is overall dimensional shrinkage, or the possibility to build a unit capable of higher output for the same ground footprint. The latter is of importance as transportation of transformer units from the site of production to the final point of use is a formidable hurdle because of the size of large power transformers. Additionally, the electrical insulating oil in accordance with embodiments herein will impregnate the solid insulation of a transformer faster in the production of the transformer.

(14) The term ‘isomerized saturated hydrocarbon mixture” refers herein to a mixture of oils containing a substantial amount of isoparaffinic compounds prepared by hydrotreating and isomerizing an oil derived from renewable or recycled raw materials.

(15) The renewable or recycled raw materials can be originated from plants or animals, such as vegetable oils, animal fats, fish oils and mixtures thereof. Examples of suitable renewable and recycled raw materials include, but are not limited to, rapeseed oil, canola oil, colza oil, tall oil, sunflower oil, soybean oil, hemp oil, olive oil, linseed oil, mustard oil, palm oil, arachis oil, castor oil, coconut oil, animal fats, such as suet, tallow, blubber. The renewable or recycled raw materials can also be produced by microbes such as algae and bacteria. Further, the renewable or recycled raw materials encompass condensation products, such as esters, and other derivates of the renewable or recycled raw materials.

(16) As renewable raw material we refer to any renewable raw material. For example, the renewable raw material may be a wax, a fat or an oil and may also be free fatty acid(s) (including salts thereof) or fatty acid ester(s).

(17) The renewable raw material is preferably a fat or an oil, more preferably a fat or an oil of plant origin (including algae and fungi), of animal origin (including fish) or of microbial origin, and in particular vegetable oil/fat, animal oil/fat, waste oil/fat from the food industry, algae oil/fat and/or microbial oil, such as palm oil, rapeseed oil, algae oil, jatropha oil, soybean oil, cooking oil, vegetable oil, animal fat and/or fish fat. The renewable raw material may be a mixture of compounds which is derived from a renewable source.

(18) Usually, the renewable raw material comprises heteroatoms (in addition to carbon atoms and hydrogen atoms), the renewable raw material may in particular comprise oxygen atoms. If the renewable raw material comprises heteroatoms, it is preferable that the hydrotreatment is carried out to remove the heteroatoms and to produce a hydrocarbon material, preferably n-paraffins or a mixture of n-paraffins and iso-paraffins. The hydrotreatment may also be carried out such that isomerisation is promoted so as to predominantly (more than 50 wt.-% of the hydrocarbon products) produce iso-paraffins.

(19) It is obvious to the person skilled in the art that isomerisation (a step of isomerising) can refer to any method which increases the degree of isomerisation, i.e. which increases the content of carbon chains having a high degree of branching relative to the content of carbon chains having a lower degree of branching. For example, isomerisation may include catalytic isomerisation in the presence of a catalyst and in the presence or absence of hydrogen and may also include cracking.

(20) Experimental Data

(21) 1. General Method:

(22) A feedstock example is an isomerized saturated hydrocarbon mixture (C10-C20), having a boiling point range within 180-310° C., a kinematic viscosity at 40° C. of about 2.5-3.2 cSt, a flash point in the range of 100-120° C. (closed cup), and a pour point in the range of −60 to −40° C.

(23) The initial boiling point measured was in the range of 280-290° C., and the final boiling point in the range of 305-315° C. The possibly fractional distillation process is controlled by adjustment of the temperature and effective length of the distillation column by means of periodic measurement of the flash point and kinematic viscosity of the collected fraction. This gives a mixture comprising isoalkanes and alkanes in the range of C.sub.14-C.sub.20.

(24) 2. Description of the Chemical Structure of the Preferred Biogenic Base Oil Composition.

(25) In one example, the carbon chain distribution of a base oil obtained by distillation contained C.sub.14-C.sub.18 carbon chain lengths, FP 151° C. (ENISO2719), and showed a viscosity of 3.8 mm.sup.2/s (EN ISO 3104) (see iTable 1, below). The distribution of n-paraffinic and iso-paraffinic component was identified by gas chromatography using FID detector. The utilized method was developed for carbon chain lengths of <C.sub.36. Area-% of hydrocarbons in the FID-chromatogram is equal to wt-% of the component. The components were identified based on model compound (normal-paraffins) chromatograms. The limit of quantitation for individual components is 0.01 wt-%.

(26) TABLE-US-00001 TABLE 1 Carbon chain distribution of the base oil (GC method). iso- normal- Carbon chain paraffins, paraffins, Sum, length wt % wt-% wt-% 2 0.0 0.0 0.0 3 0.0 0.0 0.0 4 0.0 0.0 0.0 5 0.0 0.0 0.0 6 0.0 0.0 0.0 7 0.0 0.0 0.0 8 0.0 0.0 0.0 9 0.0 0.0 0.0 10 0.0 0.0 0.0 11 0.0 0.0 0.0 12 0.0 0.0 0.0 13 0.0 0.0 0.0 14 0.0 0.0 0.0 15 0.1 0.0 0.1 16 1.8 0.3 2.0 17 7.3 5.2 12.4 18 79.3 2.6 81.9 19 1.3 0.0 1.3 20 1.1 0.0 1.1 21 0.2 0.0 0.2 22 0.2 0.0 0.2 23 0.2 0.0 0.2 24 0.2 0.0 0.2 25 0.0 0.0 0.0 >C36 0.0 0.0 0.0 C25-C29 0.2 0.0 0.2 C30-C36 0.0 0.0 0.0 Sum 91.8 8.2 100.0

(27) The content of iso-paraffins is 91 wt-% of which 57 wt % are di or poly methylated.

(28) 3. Another Example of the Detection of the Biogenic Content.

(29) Biogenic hydrocarbon content was detected by DIN51637. The 14C isotope content denotes to the biogenic content of the sample. Radioactive carbon isotope 14C beta decay can be detected by liquid scintillation counting. In fossil materials 14C is fully decayed whereas in biobased materials the 14C isotope is present in amount relative to the amount produced in the atmosphere.

INDUSTRIAL APPLICABILITY

(30) As illustrated in the examples above, but not restricted to solely these applications, the electrical insulating oil of the present disclosure is suitable for a wide variety of industrial applications.

(31) TABLE-US-00002 TABLE 2 Examples of properties of the electrical insulating oil of the present disclosure Property Method Typical Limit IEC 60296-2012 Unit Viscosity 40° C. ISO 3104 3.8 <12 mm.sup.2/s Viscosity −30° C. ISO 3104 50 <1800 mm.sup.2/s Pour point ISO 3016 −42 <−40 ° C. Water content IEC 60814 25 <30 (bulk), mg/kg <40 (drums/LBC) Breakdown voltage IEC 60156 80 >30 kV Density 20° C. ISO 3175 0.786 <0.895 g/ml DDF 90° C. IEC 60247 0.001 <0.005 Appearance Clear/bright Clear/bright Acidity IEC 62021 <0.01 <0.01 mg KOH/g Total sulphur ISO 14596 <1 <500 mg/kg Corrosive Sulphur (Ag) DIN 51353 Not corrosive Not corrosive Potentially corrosive IEC 62535 Not corrosive Not corrosive sulphur (Cu) DBDS IEC 62697-1 Not detectable Not detectable Inhibitor (BHT) IEC 60666 0.24 0.4 % Metal passivators IEC 60666 Not detectable Not detectable Furfural IEC 61198 Not detectable Not detectable Oxidation stability IEC 61125C TA 0.1 <0.3 mg KOH/g 500 h Sludge 0.02 <0.05 % DDF 0.01 <0.05 Flash point ISO 2719 145 >135 ° C. PCA IP 346 0 <3 % PCB IEC 61619 Not detectable Not detectable