Effect of Dissolved Oxygen, Sodium Bisulfite, and Oxygen Scavengers

Apr 16, 2018 - WA School of Mines: Minerals, Energy, and Chemical Engineering, Curtin University, Bentley , Western Australia 6102 , Australia. ‡ Pe...
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Cite This: J. Chem. Eng. Data XXXX, XXX, XXX−XXX

Effect of Dissolved Oxygen, Sodium Bisulfite, and Oxygen Scavengers on Methane Hydrate Inhibition Khalid Alef,*,† Stefan Iglauer,‡ and Ahmed Barifcani† †

WA School of Mines: Minerals, Energy, and Chemical Engineering, Curtin University, Bentley, Western Australia 6102, Australia Petroleum Engineering Department, Edith Cowan University, Joondalup, Western Australia 6027, Australia

‡

ABSTRACT: Numerous chemical additives are added to monoethylene glycol (MEG) injection streams to maintain and protect assets as well as to ensure steady production of hydrocarbons. Oxygen scavengers are injected for the purpose of lowering dissolved oxygen to levels that do not pose the risk of corrosion. In this study, the effect of dissolved oxygen and some oxygen scavengers on gas hydrate inhibition was investigated. Results reveal that high levels of dissolved oxygen may promote the formation of hydrates due to the reaction of dissolved oxygen with impurity components such as iron carbonate that may exist in the MEG solution, thus decreasing overall MEG quality. Sodium bisulfite had negligible effect on hydrate inhibition at low concentrations but showed greater inhibition performance at higher concentrations due to the electrostatic attraction between ions and water molecules. A proprietary oxygen scavenger showed hydrate promotion effect, which suggests that proprietary chemical additives should undergo extensive compatibility and risk analysis. An erythorbic acid-based oxygen scavenger showed minor inhibition performance albeit at small concentration, possibly due to hydrogen bonding between hydroxyl groups of its components with water molecules.

1.0. INTRODUCTION Gas hydrate formation and corrosion are flow assurance issues which adversely affect gas processing and transportation. Chemical additives such as hydrate inhibitors are commonly injected to shift hydrate formation conditions so that pipeline operating conditions are within the hydrate-safe region, or to postpone hydrate nucleation, or to prevent the agglomeration of hydrate particles thus preventing hydrate plugging.1−3 Monoethylene glycol (MEG) is a popular thermodynamic hydrate inhibitor due to its recoverability using close-loop MEG regeneration and reclamation facilities.4 Preventing or lowering the risk of corrosion in gas pipelines is commonly achieved by pH stabilization or the injection of film forming corrosion inhibitors.5,6 The pH stabilization method requires that pH is adjusted using an amine to precipitate a stable protective iron carbonate film.7,8 However, dissolved oxygen (DO) even in small concentrations within lean-MEG injection lines, gas pipelines, downstream and well-head equipment, and MEG regeneration facilities also poses serious corrosion and operational risks.9−14 Dissolved oxygen can cause serious pitting corrosion to carbon steel and certain corrosion resistant alloy (CRA) pipelines especially in the presence of MEG.6,10 Dissolved oxygen also increases the rate of carbon dioxide corrosion of carbon steel.15−17 Furthermore, DO may hinder the effectivity of film forming corrosion inhibitors as well as the stability of iron carbonate films on the inner walls of pipelines.17,18 © XXXX American Chemical Society

Oxygen ingress is typically addressed by either purging using an inert gas for the removal of dissolved oxygen or the injection of specific chemicals known as oxygen scavengers (typically sulfites) to react with dissolved oxygen, lowering levels to 3%).6 A combined approach where nitrogen purging in storage vessels alongside the injection of oxygen scavengers is commonly implemented to not only reduce the dissolved oxygen concentration but to do so in a short duration of time.19 Even small amounts of dissolved oxygen over an extended period could result in nucleation of corrosion pits and consequent autocatalytic propagation.12 In terms of gas hydrate inhibition, it is important to understand how the added chemicals or oxygen scavengers will affect the hydrate inhibition performance of MEG. These chemicals must be assessed to ensure there are no opposing effects on the desired hydrate inhibition performance owing to dissociation products, byproducts of side-reactions, impedance to MEG’s inhibition kinetics, and incompatibilities. The tendency for these side-reactions to occur are further enhanced Received: February 20, 2018 Accepted: April 11, 2018

A

DOI: 10.1021/acs.jced.8b00150 J. Chem. Eng. Data XXXX, XXX, XXX−XXX

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oxygen scavenger, and the dosages used in the test solutions are reported in Table 2 and 3.

by the high operational temperatures applied in MEG close loops, and thus buildup of byproducts and chemical additives in the MEG close loop may play a role in hydrate inhibition. In this study, the methane hydrate inhibition performance of MEG combined with various oxygen scavengers was investigated. Oxygen scavengers are required in large concentrations to have an effective result.6 Optimally, oxygen scavengers should be nonvolatile, allowing for removal with salts during the reclamation process, preventing unnecessary build-up and fouling of the MEG close loop.6 However, MEG operations may not have a reclamation stage, or may have slip-stream reclamation depending on the allowable salt tolerance in the final lean-MEG solution to be injected at the well head, so oxygen scavengers may not be removed at all, or are removed from only a portion of the MEG inventory. Thus, knowing whether they perform as hydrate promoters or inhibitors is crucial to a successful hydrate flow assurance program.

Table 3. Oxygen Scavenger Dosage in Each Test Solution test solution blank blank sodium bisulfite (NaHSO3)

purity (mol %)

supplier

monoethylene glycol methane nitrogen sodium bisulfite

C2H6O2 CH4 N2 NaHSO3

99.477 99.995 99.9959 >99.5

Chem-Supply BOC NGP10+ Sigma-Aldrich

0.01 (100 ppm) 0.1 1 10 0.01 (100 ppm) 0.1 1 10 0.025 (250 ppm) 0.01 (100 ppm)

OS-P

20

IFEox2

20

catalyst (ppm)

dissolved oxygen (ppb)

1

7500 80 wt %). This hydrate promotion may be overlooked, but due to the small dosage of the chemical as well as the various other proprietary chemical additives used in the industry may result in detrimental effects. We conclude that

Figure 4. Hydrate phase boundaries for aqueous NaHSO3 solutions.

Figure 5. Hydrate phase boundaries for aqueous NaHSO3 + MEG solutions.

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the remaining hydroxyl groups of erythorbic acid, DEAE, and erythorbate salt. Erythorbate salt is a result of the postneutralization reaction by DEAE with erythorbic acid (Figure 8).

4.0. CONCLUSIONS The influence of dissolved oxygen and various oxygen scavengers on gas hydrate formation was studied. Gas hydrates can cause dangerous consequences, and thus, it is important to understand how the various chemical additives that are injected alongside MEG behave and distort the hydrate inhibition performance. The study produced new hydrate equilibria data for sodium bisulfite solutions (0.01−10 wt %) with and without the presence of MEG. Results show greater inhibition at higher concentrations as opposed to commonly used dosages for oxygen scavenging applications. However, a proprietary oxygen scavenger promoted hydrate formation, which suggests that chemical additives should be thoroughly assessed for compatibility with other chemicals as well as tested to determine any potential negative consequences. A nonsulfite oxygen scavenger showed inhibition performance but may not surmount to any benefit due to the small dosages required. Furthermore, the study has revealed that dissolved oxygen, while it already negatively affects corrosion risk, may have a hydrate promotion effect as well, which increases the risk of gas hydrate formation. Clearly, dissolved oxygen levels should be kept to a minimum.

Figure 6. Hydrate phase boundary of proprietary oxygen scavenger, OS-P (0.025 wt %) in 20 wt % MEG solution.

proprietary chemical additives designed and created for specific purposes may have negative consequences on other flow assurance issues. 3.4. Effect of Nonsulfite-Based Oxygen Scavenger (IFEox2). The nonsulfite oxygen scavenger (IFEox2) developed by Kundu and Seiersten was investigated in this study which comprises erythorbic acid, diethylaminoethanol (DEAE), and a manganese catalyst. It was tested to realize its influence on gas hydrate formation in the presence of 20 wt % MEG solution. The measured hydrate phase boundary is plotted in Figure 7. The results show that the phase boundary has shifted

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AUTHOR INFORMATION

Corresponding Author

*E-mail: [email protected], Alef.Khalid@ gmail.com; Phone: +61 412 875 860. ORCID

Khalid Alef: 0000-0003-1751-5636 Stefan Iglauer: 0000-0002-8080-1590 Notes

The authors declare no competing financial interest.

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ACKNOWLEDGMENTS The authors would like to acknowledge the contribution of an Australian Government Research Training Program Scholarship in supporting this research.

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Figure 7. Hydrate phase boundary of IFEox2 (0.01 wt %) in 20 wt % MEG solution.

ABBREVIATIONS MEG, monoethylene glycol; NaHSO3, sodium bisulfite; OS-P, proprietary oxygen scavenger; IFEox2, nonsulfite oxygen scavenger developed by Kundu and Seiersten; DEAE, diethylaminoethanol; AARE, absolute average relative error; DI, deionized water

to the left by ∼0.1 °C, suggesting this oxygen scavenger acted as a hydrate inhibitor. This slight inhibition performance could be related to hydrogen bonding of some water molecules with

Figure 8. Conversion of erythorbic acid to erythorbate salt by neutralization reaction by DEAE. E

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(21) Kundu, S. S.; Seiersten, M. Development of a non-sulphite oxygen scavenger for monoethylene glycol (MEG) used as gas hydrate inhibitor. J. Pet. Sci. Eng. 2017, 158, 120−128. (22) Podkrajšek, B.; Berčič, G.; Turšič, J.; Grgić, I. Aqueous oxidation of sulfur (IV) catalyzed by manganese (II): a generalized simple kinetic model. J. Atmos. Chem. 2004, 47, 287−303. (23) Sloan, E. D.; Koh, C. A. Clathrate hydrates of natural gases, 3rd ed.; CRC Press, Taylor and Francis Group: Boca Raton, FL, 2008. (24) Alef, K.; Smith, C.; Iglauer, S.; Gubner, R.; Barifcani, A. The effect of regenerated MEG on hydrate inhibition performance over multiple regeneration cycles. Fuel 2018, 222, 638−647. (25) Smith, C.; Barifcani, A.; Pack, D. Gas hydrate formation and dissociation numerical modelling with nitrogen and carbon dioxide. J. Nat. Gas Sci. Eng. 2015, 27, 1118−1128. (26) Smith, C.; Barifcani, A.; Pack, D. Helium substitution of natural gas hydrocarbons in the analysis of their hydrate. J. Nat. Gas Sci. Eng. 2016, 35, 1293−1300. (27) Eichholz, C.; Majumdar, A.; Clarke, M.; Oellrich, L.; Bishnoi, P. Experimental investigation and calculation of methane hydrate formation conditions in the presence of ethylene glycol and sodium chloride. J. Chem. Eng. Data 2004, 49, 847−851. (28) Haghighi, H.; Chapoy, A.; Burgess, R.; Tohidi, B. Experimental and thermodynamic modelling of systems containing water and ethylene glycol: Application to flow assurance and gas processing. Fluid Phase Equilib. 2009, 276, 24−30. (29) AspenTech. Aspen HYSYS (Version 9). Aspen Technology, Inc.: Calgary, 2016. (30) Rock, A. Experimentelle und theoretische Untersuchung zur Hydratbildung aus Gasgemischen in inhibitorhaltigen wassrigen Losungen. FORTSCHRITT BERICHTE-VDI REIHE 3 VERFAHRENSTECHNIK 2003.1 (31) Rossiter, W. J.; Godette, M.; Brown, P. W.; Galuk, K. G. An investigation of the degradation of aqueous ethylene glycol and propylene glycol solutions using ion chromatography. Sol. Energy Mater. 1985, 11, 455−467. (32) Bamford, C. H.; Compton, R.; Tipper, C. Liquid-Phase Oxidation. Elsevier: Amsterdam, 1980. (33) AlHarooni, K.; Barifcani, A.; Pack, D.; Gubner, R.; Ghodkay, V. Inhibition effects of thermally degraded MEG on hydrate formation for gas systems. J. Pet. Sci. Eng. 2015, 135, 608−617. (34) Madera, M.; Höflinger, W.; Kadnar, R. Ion chromatographic identification and quantification of glycol degradation products. J. Chromatogr. A 2003, 997, 279−284. (35) Tohidi, B.; Burgass, R.; Danesh, A.; Østergaard, K.; Todd, A. Improving the accuracy of gas hydrate dissociation point measurements. Ann. N. Y. Acad. Sci. 2000, 912, 924−931. (36) Nguyen, N. N.; Nguyen, A. V. The dual effect of sodium halides on the formation of methane gas hydrate. Fuel 2015, 156, 87−95. (37) Sun, Q.; Chen, B.; Li, X.; Guo, X.; Yang, L. The investigation of phase equilibria and kinetics of CH4 hydrate in the presence of bioadditives. Fluid Phase Equilib. 2017, 452, 143−147. (38) Cha, M.; Hu, Y.; Sum, A. K. Methane hydrate phase equilibria for systems containing NaCl, KCl, and NH4Cl. Fluid Phase Equilib. 2016, 413, 2−9. (39) Lv, Q.; Zang, X.; Li, X.; Li, G. Effect of seawater ions on cyclopentane-methane hydrate phase equilibrium. Fluid Phase Equilib. 2018, 458, 272−277.

REFERENCES

(1) Cha, M.; Shin, K.; Kim, J.; Chang, D.; Seo, Y.; Lee, H.; Kang, S.P. Thermodynamic and kinetic hydrate inhibition performance of aqueous ethylene glycol solutions for natural gas. Chem. Eng. Sci. 2013, 99, 184−190. (2) Kelland, M. A. History of the development of low dosage hydrate inhibitors. Energy Fuels 2006, 20, 825−847. (3) Sloan, E. Clathrate Hydrates of Natural Gases; Marcel Deckker Inc.: New York, 1998. (4) Brustad, S.; Løken, K.-P.; Waalmann, J. G. Hydrate Prevention using MEG instead of MeOH: Impact of experience from major Norwegian developments on technology selection for injection and recovery of MEG; Offshore Technology Conference: Houston, TX, 2005. (5) Latta, T. M.; Seiersten, M. E.; Bufton, S. A. Flow assurance impacts on lean/rich MEG circuit chemistry and MEG regenerator/reclaimer design; Offshore Technology Conference: Houston, TX, 2013. (6) Lehmann, M.; Lamm, A.; Nguyen, H.; Bowman, C.; Mok, W.; Salasi, M.; Gubner, R. Corrosion Inhibitor and Oxygen Scavenger for use as MEG Additives in the Inhibition of Wet Gas Pipelines; Offshore Technology Conference: Kuala Lumpur, Malaysia, 2014. (7) Dugstad, A.; Seiersten, M. pH-stabilisation, a reliable method for corrosion control of wet gas pipelines. In SPE International Symposium on Oilfield Corrosion; Society of Petroleum Engineers: Aberdeen, United Kingdom, 2004. (8) Halvorsen, A. M. K.; Andersen, T. R.; Halvorsen, E. N.; Kojen, G. P.; Skar, J. I.; Biørnstad, C.; Fitje, H. The Relationship Between Internal Corrosion Control Method, Scale Control And Meg Handling Of A Multiphase Carbon Steel Pipeline Carrying Wet Gas With CO2 and Cetic Acid; In Corrosion; NACE International: Nashville, Tennessee, 2007. (9) Ivonye, I.; Wang, C.; Neville, A. The Corrosion of Carbon Steel in the Presence of Monoethylene Glycol (MEG)−Assessing the Influence of an Iron Carbonate Scale. In Corrosion; NACE International: Orlando, Florida, 2013. (10) Joosten, M. W.; Tier, B.; Seiersten, M.; Wintermark, C. Materials Considerations for MEG (Mono Ethylene Glycol) Reclamation Systems. In Corrosion; NACE International: Nashville, Tennessee, 2007. (11) Kvarekval, J.; Olsen, S.; Skjerve, S. The effect of O2 on CO2 corrosion in pH stabilized gas/condensate pipelines. In Corrosion; NACE International: Houston, Texas, 2005. (12) Salasi, M.; Pojtanabuntoeng, T.; Wong, S.; Lehmann, M. Efficacy of Bisulfite Ions as an Oxygen Scavenger in Monoethylene Glycol (At Least 20 wt%)/Water Mixtures. SPE J. 2017, 22, 1467. (13) Wang, C.; Hu, X.; Ivonye, I.; Neville, A. Corrosion Study of Carbon Steel in the Presence of Monoethylene Glycol (MEG) and Corrosion Inhibitors in Acid. In Corrosion; NACE International: Orlando, Florida, 2013. (14) Wang, H.; Wylde, J. Corrosion Inhibitor Development For Slight Sour Environment With Oxygen Intrusion Issue. In Corrosion; NACE International: San Antonio, Texas, 2010. (15) John, D.; Kinsella, B.; Bailey, S.; De Marco, R. Flow dependence of carbon dioxide corrosion using short electrodes by jet impingement. Corros. Sci. 2009, 65, 771−777. (16) Martin, R. L. Corrosion consequences of oxygen entry into sweet oilfield fluids. In SPE Annual Technical Conference and Exhibition; Society of Petroleum Engineers: New Orleans, Louisiana, 2001. (17) Xiang, Y.; Choi, Y.-S.; Yang, Y.; Nešić, S. Corrosion of carbon steel in MDEA-based CO2 capture plants under regenerator conditions: effects of O2 and heat-stable salts. Corros. Sci. 2014, 71, 30−37. (18) Gulbrandsen, E.; Kvarekvål, J.; Miland, H. Effect of Oxygen contamination on inhibition studies in carbon dioxide corrosion. Corros. Sci. 2005, 61, 1086−1097. (19) Braga, T. Effects of Commonly, Used Oilfield Chemicals on the Rate of Oxygen Scavenging by Sulfite/Bisulfite. SPE Prod. Eng. 1987, 2, 137−142. (20) Kelland, M. A. Production Chemicals for the Oil and Gas Industry. Chromatographia 2009, 72, 199−199. F

DOI: 10.1021/acs.jced.8b00150 J. Chem. Eng. Data XXXX, XXX, XXX−XXX