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
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
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
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
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
Naphthenic Base Oil Refineries 2014 Capacities 25000 Lubes N Greases 2014 Guide to Global Base Oil Refining Barrels per Day 20000 15000 10000 5000 ERGON REFINING 8 th Largest Base Oil Refinery in the World, 4th Largest in US Independents and National Oil Companies 0 6
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
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
Chemical Structures Complex / Predictable PARAFFINIC Normal Paraffins (Wax) Isoparaffins NAPHTHENIC Cycloparaffins (Naphthenes) AROMATIC Monoaromatic Diaromatic 9 Polyaromatic
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
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
IEC 60296 Edition 4 Requirements! 3.4 - additive - chemical substance that is added to mineral insulating oil in order to improve certain characteristics.! 3.5 - 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.! 3.5.1 inhibitor antioxidant additives of the phenolic or amine-type, such as DBPC and DBP as described in IEC 60666. 12! 5.4 D The supplier shall declare the generic type of all additives, and their concentrations in the case of inhibitors and passivators.
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
Components Tested Neat Refinery Base Oils! Severely hydrotreated naphthenic! Extra severely hydrotreated naphthenic! Hydrocracked isoparaffin Additives! 2,6-Di-t-butyl-p-cresol (0.27-0.37%) 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
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
Hydroprocessing Differences (16 Hrs, µl/l) Hydroprocessed (ASTM) Hydroprocessed (IEC) ASTM Inhibited IEC Inhibited Isoparaffin 60* Solvent Neutral H 2 nd nd nd nd 34 99 CO nd nd nd nd 101 178 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 222 281 CO 2 nd nd nd nd 154 247 O 2 ~31,000 ~31,000 ~28,000 ~30,000 138 ~9300 TCG - Total Combustible Gases All Samples: C 2 H 2 not detected 16
ASTM Inhibited with Additives (16 Hrs, µl/l) ASTM Inhibited ASTM Inhibited + 100 ppm Irg 39 ASTM Inhibited + 100 ppm Irg 30 ASTM Inhibited + 0.4% Naphtha H 2 nd 420 545 10 CO nd 56 47 60 CH 4 nd nd nd nd C 2 H 6 nd nd nd nd C 2 H 4 nd nd nd nd TCG nd 476 592 70 CO 2 nd 415 101 84 O 2 ~28,000 ~24,000 ~21,000 ~22,000 17 TCG - Total Combustible Gases All Samples: C 2 H 2 not detected Irg 30 - Irgamet 30 Irg 39 - Irgamet 39
IEC Inhibited with Additives (16 Hrs, µl/l) IEC Inhibited IEC Inhibited + 100 ppm Irg 39 IEC Inhibited + 100 ppm Irg 30 IEC Inhibited + 0.4% Naphtha H 2 nd 350 555 9 CO nd 49 58 56 CH 4 nd nd nd nd C 2 H 6 nd nd nd nd C 2 H 4 nd nd nd nd TCG nd 399 613 65 CO 2 nd 107 113 63 O 2 ~30,000 ~22,000 ~23,000 ~22,000 18 TCG - Total Combustible Gases All Samples: C 2 H 2 not detected Irg 30 - Irgamet 30 Irg 39 - Irgamet 39
Isoparaffin 60 with Additives (16 Hrs, µl/l) Isoparaffin 60 Isoparaffin 60 + 0.37% BHT Isoparaffin 60 + 0.37% BHT + 100 ppm Irg 39 Isoparaffin 60 + 0.37% BHT + 3% Solvent Neutral H 2 34 nd 236 150 CO 101 54 35 nd CH 4 29 2 2 2 C 2 H 6 53 nd nd nd C 2 H 4 5 nd nd nd TCG 222 56 273 152 CO 2 154 83 109 148 O 2 138 ~29,000 ~28,000 ~29,000 19 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 + 0.4% Naphtha H 2 188 213 1079 2249 222 CO 157 296 200 161 168 CH 4 54 8 190 132 82 C 2 H 6 65 nd 190 134 96 C 2 H 4 65 55 32 30 54 TCG 529 572 1691 2706 622 CO 2 428 475 277 433 252 O 2 1667 7801 314 203 177 20 TCG - Total Combustible Gases All Samples: C 2 H 2 not detected Irg 30 - Irgamet 30 Irg 39 - Irgamet 39
100 ppm Irgamet 39 (16 Hrs, µl/l) ASTM Inhibited + Irg 39 IEC Inhibited + Irg 39 Isoparaffin 60 + 0.37% BHT + Irg 39 Uninhibited + Irg 39 H 2 420 350 236 1079 CO 56 49 35 200 CH 4 nd nd 2 190 C 2 H 6 nd nd nd 190 C 2 H 4 nd nd nd 32 TCG 476 399 273 1691 CO 2 415 107 109 277 O 2 ~24,000 ~22,000 ~28,000 314 21 TCG - Total Combustible Gases All Samples: C 2 H 2 not detected Irg 39 - Irgamet 39
100 ppm Irgamet 30 (16 Hrs, µl/l) ASTM Inhibited + Irg 30 IEC Inhibited + Irg 30 Uninhibited + Irg 30 H 2 545 555 2249 CO 47 58 161 CH 4 nd nd 132 C 2 H 6 nd nd 134 C 2 H 4 nd nd 30 TCG 592 613 2706 CO 2 101 113 433 O 2 ~21,000 ~23,000 203 22 TCG - Total Combustible Gases All Samples: C 2 H 2 not detected Irg 30 - Irgamet 30
0.4 % Naphtha (16 Hrs, µl/l) ASTM Inhibited + Naphtha IEC Inhibited + Naphtha Uninhibited + Naphtha H 2 10 9 222 CO 60 56 168 CH 4 nd nd 82 C 2 H 6 nd nd 96 C 2 H 4 nd nd 54 TCG 70 65 622 CO 2 84 63 252 O 2 ~22,000 ~22,000 177 TCG - Total Combustible Gases All Samples: C 2 H 2 not detected 23
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
Analysis Addition of Passivators! In the Inhibited Oils - the addition of 100 mg/kg of Irgamet 30 or 39 generated 250 550 ppm H 2 ; 35 60 ppm CO; 100 400 ppm CO 2! In the Uninhibited Oil the addition generated up to 2250 ppm H 2 ; 200 ppm CO; 300 400 ppm CO 2 ; 130 190 ppm CH 4 ; 30 ppm C 2 H 4 ; 130 190 ppm C 2 H 6 25
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
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
! 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
For further questions, technical or commercial, please contact us. North & South America Phone: +1 601 933 3000 ergonnsa.com Europe, Middle East & Africa Phone : +32 (0)2 351 23 75 ergoneurope.com Asia Phone : +32 (0)2 351 23 75 ergonasia.com Ergon North & South America Tel: 1 601 933 3000 Fax: 1 601 933 3361 2829 Lakeland Drive Jackson, MS 39232 Ergon Europe MEA Tel: +32 2 351 23 75 Fax: +32 2 351 15 24 161 Drève Richelle, Bat C 1410 Waterloo, Belgium 29