Stray Gassing of Transformer. Streams and Addi;ves. Ed Casserly, Ph.D. Director - Reﬁnery R&D Ergon Reﬁning, Inc.

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1 Stray Gassing of Transformer Oils Eﬀects of Reﬁnery Streams and Addi;ves Ed Casserly, Ph.D. Director - Reﬁnery R&D Ergon Reﬁning, Inc. Presented at My Transfo 2014

2 Outline! Definition and Issue of Stray Gassing! Naphthenic Mineral Oil! Base Oil Types Refinery Processes! Additives Tested! Testing Procedure for Stray Gassing! Results! Conclusions 2

3 Definition of Stray Gassing! CIGRE Brochure 296 the formation of gases from insulating mineral oils heated at relatively low temperatures (90 to 200 C).! ASTM D7150 the low temperature (120 C) gassing characteristics of insulating liquids specifically and without the influence of other electrical apparatus materials or electrical stresses. 3

4 Issue of Stray Gassing! This occurs before a transformer is energized. The primary gas generated is hydrogen but other gases are also produced.! Potential issues with Dissolved Gas Analysis (DGA).! Some prior reports have implicated the refining process, specifically severe hydrotreatment, while other reports have implicated additives. 4

5 Naphthenic Crude/Refining Locations Naphthenic crudes (5% of world s crude) are located across the globe. Some of the 16 naphthenic refineries also include networks of terminals for local sourcing. 5

6 Naphthenic Base Oil Refineries 2014 Capacities Lubes N Greases 2014 Guide to Global Base Oil Refining Barrels per Day ERGON REFINING 8 th Largest Base Oil Refinery in the World, 4th Largest in US Independents and National Oil Companies 0 6

7 Refinery Processes! Solvent Extraction Historical Refining Process! An equilibrium process used to remove aromatics and polar compounds.! Hydroprocessing State-of-the-Art Process! A kinetic process used to saturate olefins and aromatics and to eliminate heteroatoms, S, N, O.! Uses catalysts, hydrogen pressure, and temperature. 7

8 Processing Comparison Solvent Extraction! A polar solvent is used to physically remove unwanted polar compounds in the oil, reactive compounds remain reactive! Relies on differential solubilities and extraction efficiencies! Variables solvent/oil ratio, temperature, time, solvent type Severe Hydrotreating! Reactive compounds chemically react with hydrogen on a catalytic metal surface! Reactive compounds are converted to stable, nonreactive compounds or broken apart into smaller compounds and removed! Variables temperature, hydrogen pressure, time, catalyst type 8

9 Chemical Structures Complex / Predictable PARAFFINIC Normal Paraffins (Wax) Isoparaffins NAPHTHENIC Cycloparaffins (Naphthenes) AROMATIC Monoaromatic Diaromatic 9 Polyaromatic

10 Sulfur Containing Compounds R-S-H R-S-R Mercaptan Thio-ether Dibenzyl disulfide (DBDS) REACTIVE SULFUR Synthetic chemical used in industrial oil formulations to improve oxidation stability and anti-wear properties. It is not found in crude oil nor formed during the refining process. US Patent 7,846,882 Dec 7, 2010 to Shell Oil Co. Benzothiophene Dibenzothiophene 10 HINDERED SULFUR IN RING STRUCTURES

11 Transformer Oil Properties Good Elimination of Corrosive Sulfur Response to Inhibitor Electrical Properties Health & Safety For Sulfur to be Corrosive, it needs to be Reactive As such, it s easy to remove in the refining process! Gas Absorption Poor CORROSIVE! = Premium Uninhibited Transformer Oil = Premium Inhibited Transformer Oil = Poorly Refined Corrosive Transformer Oil Oxidation Stability of neat oil Severity of Refining Cleaning of the Oil 11

12 IEC Edition 4 Requirements! additive - chemical substance that is added to mineral insulating oil in order to improve certain characteristics.! antioxidant additive - additive incorporated in mineral insulating oil that improves oxidation stability.! NOTE: A large number of additives which improve oxidation stability, including inhibitors, peroxide decomposers, metal passivators and metal deactivators, are available and may be used if declared.! inhibitor antioxidant additives of the phenolic or amine-type, such as DBPC and DBP as described in IEC ! 5.4 D The supplier shall declare the generic type of all additives, and their concentrations in the case of inhibitors and passivators.

13 Additives! Some additives are chemically inert and only affect physical properties such as viscosity or pour point.! Some additives are REACTIVE and affect the chemistry present in the oil. Antioxidants Passivators 13

14 Components Tested Neat Refinery Base Oils! Severely hydrotreated naphthenic! Extra severely hydrotreated naphthenic! Hydrocracked isoparaffin Additives! 2,6-Di-t-butyl-p-cresol ( %) BHT, DBPC (antioxidant)! Irgamet 39 (100 mg/kg) Passivator/Deactivator! Irgamet 30 (100 mg/kg) Passivator/Deactivator Refinery Blend Components! Aromatic naphtha (0.4%) Negative gassing ingredient! Solvent extracted neutral (3%) Non-hydrotreated base oil Commercial Products! IEC Un-inhibited! ASTM Type II Inhibited! IEC Inhibited Special Applications 14

15 Testing! The initial Stray Gassing was tested* after 16 hours as outlined in CIGRE Brochure 296.! Samples were degassed under vacuum, saturated with air then placed in a 30 ml syringe.! The syringe was incubated for 16 hours at 120 C.! DGA pre-incubation and post heat treatment. Pre-incubation results were nd. ** * Independent European Laboratory ** Several samples: 2 ppm CH 4 15

16 Hydroprocessing Differences (16 Hrs, µl/l) Hydroprocessed (ASTM) Hydroprocessed (IEC) ASTM Inhibited IEC Inhibited Isoparaffin 60* Solvent Neutral H 2 nd nd nd nd CO nd nd nd nd CH 4 nd nd nd nd 29 2 C 2 H 6 nd nd nd nd 53 nd C 2 H 4 nd nd nd nd 5 2 TCG nd nd nd nd CO 2 nd nd nd nd O 2 ~31,000 ~31,000 ~28,000 ~30, ~9300 TCG - Total Combustible Gases All Samples: C 2 H 2 not detected 16

17 ASTM Inhibited with Additives (16 Hrs, µl/l) ASTM Inhibited ASTM Inhibited ppm Irg 39 ASTM Inhibited ppm Irg 30 ASTM Inhibited + 0.4% Naphtha H 2 nd CO nd CH 4 nd nd nd nd C 2 H 6 nd nd nd nd C 2 H 4 nd nd nd nd TCG nd CO 2 nd O 2 ~28,000 ~24,000 ~21,000 ~22, TCG - Total Combustible Gases All Samples: C 2 H 2 not detected Irg 30 - Irgamet 30 Irg 39 - Irgamet 39

18 IEC Inhibited with Additives (16 Hrs, µl/l) IEC Inhibited IEC Inhibited ppm Irg 39 IEC Inhibited ppm Irg 30 IEC Inhibited + 0.4% Naphtha H 2 nd CO nd CH 4 nd nd nd nd C 2 H 6 nd nd nd nd C 2 H 4 nd nd nd nd TCG nd CO 2 nd O 2 ~30,000 ~22,000 ~23,000 ~22, TCG - Total Combustible Gases All Samples: C 2 H 2 not detected Irg 30 - Irgamet 30 Irg 39 - Irgamet 39

19 Isoparaffin 60 with Additives (16 Hrs, µl/l) Isoparaffin 60 Isoparaffin % BHT Isoparaffin % BHT ppm Irg 39 Isoparaffin % BHT + 3% Solvent Neutral H 2 34 nd CO nd CH C 2 H 6 53 nd nd nd C 2 H 4 5 nd nd nd TCG CO O ~29,000 ~28,000 ~29, TCG - Total Combustible Gases All Samples: C 2 H 2 not detected Irg 39 - Irgamet 39

Uninhibited with Additives (16 Hrs, µl/l) Uninhibited Uninhibited + 0.27% BHT Uninhibited + 100 ppm Irg 39 Uninhibited + 100 ppm Irg 30 Uninhibited + 0.

20 Uninhibited with Additives (16 Hrs, µl/l) Uninhibited Uninhibited % BHT Uninhibited ppm Irg 39 Uninhibited ppm Irg 30 Uninhibited + 0.4% Naphtha H CO CH C 2 H 6 65 nd C 2 H TCG CO O TCG - Total Combustible Gases All Samples: C 2 H 2 not detected Irg 30 - Irgamet 30 Irg 39 - Irgamet 39

21 100 ppm Irgamet 39 (16 Hrs, µl/l) ASTM Inhibited + Irg 39 IEC Inhibited + Irg 39 Isoparaffin % BHT + Irg 39 Uninhibited + Irg 39 H CO CH 4 nd nd C 2 H 6 nd nd nd 190 C 2 H 4 nd nd nd 32 TCG CO O 2 ~24,000 ~22,000 ~28, TCG - Total Combustible Gases All Samples: C 2 H 2 not detected Irg 39 - Irgamet 39

22 100 ppm Irgamet 30 (16 Hrs, µl/l) ASTM Inhibited + Irg 30 IEC Inhibited + Irg 30 Uninhibited + Irg 30 H CO CH 4 nd nd 132 C 2 H 6 nd nd 134 C 2 H 4 nd nd 30 TCG CO O 2 ~21,000 ~23, TCG - Total Combustible Gases All Samples: C 2 H 2 not detected Irg 30 - Irgamet 30

23 0.4 % Naphtha (16 Hrs, µl/l) ASTM Inhibited + Naphtha IEC Inhibited + Naphtha Uninhibited + Naphtha H CO CH 4 nd nd 82 C 2 H 6 nd nd 96 C 2 H 4 nd nd 54 TCG CO O 2 ~22,000 ~22, TCG - Total Combustible Gases All Samples: C 2 H 2 not detected 23

24 Analysis Hydrotreating Severity! Neat hydrotreated base oils and hydrotreated inhibited transformer oils showed NO stray gassing.! Hydrocracked isoparaffin had some stray gassing (inadvertent contamination?).! Non-hydrotreated solvent neutral had some stray gassing as well.! Uninhibited transformer oil had some stray gassing. 24

25 Analysis Addition of Passivators! In the Inhibited Oils - the addition of 100 mg/kg of Irgamet 30 or 39 generated ppm H 2 ; ppm CO; ppm CO 2! In the Uninhibited Oil the addition generated up to 2250 ppm H 2 ; 200 ppm CO; ppm CO 2 ; ppm CH 4 ; 30 ppm C 2 H 4 ; ppm C 2 H 6 25

26 Role of Oxidation! The level of oxygen decreased with the formation of stray gasses.! Oxidation is a complex free radical process.! Generated free radicals can react with the more reactive molecules, especially the reactive additives.! Passivators are thought to degrade via a free radical process, generating stray gasses. 26

27 Conclusions - 1! Hydroprocessing Severity NO EFFECT! Hydroprocessed base oils and inhibited transformer oils generated NO STRAY GASSING.! Solvent Extraction! Non-hydroprocessed, solvent extracted base oils generated some stray gassing.! Refinery Blend Components! Other blend components generated some stray gassing. 27

28 ! Additives - Passivators Conclusions - 2! Passivators had the greatest impact on stray gassing, generating up to 2,200 ppm of H 2 after 16 hours.! Passivation induced stray gassing Scatiggio, Pompili, Bartnikas, 2011! A properly refined naphthenic mineral oil does not need the addition of non-inhibitor additives which could have unintended consequences. 28

29 For further questions, technical or commercial, please contact us. North & South America Phone: ergonnsa.com Europe, Middle East & Africa Phone : +32 (0) ergoneurope.com Asia Phone : +32 (0) ergonasia.com Ergon North & South America Tel: Fax: Lakeland Drive Jackson, MS Ergon Europe MEA Tel: Fax: Drève Richelle, Bat C 1410 Waterloo, Belgium 29

Transformer oils - Production, performance and in-service behaviour

Transformer oils - Production, performance and in-service behaviour Johan Grövik Nynas AB TRANSFORM Partner Nynas Nynas AB founded 1928 Swedish based company Approximately 850 employees Turnover 2 billion