Experiments and modelling of carbon dioxide corrosion in sodium chloride solutions
Author(s)
Alsalem, Mustafa
Type
Thesis
Abstract
This work investigates carbon dioxide (CO2) corrosion in sodium chloride (NaCl) solutions to provide a mechanistic understanding of its processes. In particular, CO2 bulk reactions
(hydration and speciation), nucleation and growth of iron carbonate (FeCO3) crystals, and electrochemical reactions in the presence of NaCl salt are considered from thermodynamics
and kinetics perspectives. A dual approach where experiments and modelling are employed, is used to elucidate debated empirical observations. The outcomes of this study have
profound impacts on existing operations in the oil and gas industry, and are relevant to emerging CO2 capture processes, where CO2 corrosion attacks are expected. To reflect the effect of NaCl on CO2 species in solution, a CO2 speciation model, which estimated the activity instead of concentration, was developed and validated over a wide range of NaCl content (1 - 15 %) and temperatures (25 - 100 ◦C). Relying on this model, an improved solubility product of FeCO3 was derived to account for temperature and ionic strength (NaCl concentration). Collectively, this allowed for the development a revised FeCO3 precipitation expression for NaCl solutions. Moreover, employing a fractional factorial design provided an insight into how the interactions
between NaCl concentration, temperature, and pH shape FeCO3 layers and determine their protectiveness. Interestingly, a minor increase in NaCl concentration (from 1 to 3 % w/v) significantly impacted the characteristics of FeCO3 layers; it led to the formation of large crystals, while reducing their numbers...
(hydration and speciation), nucleation and growth of iron carbonate (FeCO3) crystals, and electrochemical reactions in the presence of NaCl salt are considered from thermodynamics
and kinetics perspectives. A dual approach where experiments and modelling are employed, is used to elucidate debated empirical observations. The outcomes of this study have
profound impacts on existing operations in the oil and gas industry, and are relevant to emerging CO2 capture processes, where CO2 corrosion attacks are expected. To reflect the effect of NaCl on CO2 species in solution, a CO2 speciation model, which estimated the activity instead of concentration, was developed and validated over a wide range of NaCl content (1 - 15 %) and temperatures (25 - 100 ◦C). Relying on this model, an improved solubility product of FeCO3 was derived to account for temperature and ionic strength (NaCl concentration). Collectively, this allowed for the development a revised FeCO3 precipitation expression for NaCl solutions. Moreover, employing a fractional factorial design provided an insight into how the interactions
between NaCl concentration, temperature, and pH shape FeCO3 layers and determine their protectiveness. Interestingly, a minor increase in NaCl concentration (from 1 to 3 % w/v) significantly impacted the characteristics of FeCO3 layers; it led to the formation of large crystals, while reducing their numbers...
Version
Open Access
Date Issued
2022-02-18
Date Awarded
01/12/2022
Copyright Statement
Creative Commons Attribution NonCommercial Licence
License URL
Advisor
Sedransk Campbell, Kyra
Ryan, Mary
Sponsor
Aramco
Publisher Department
Chemical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)