Research Article
Effect of Natural Organic Matter on Scale reduction in Cooling Water Circuits: A Comprehensive assessment based on Empirical Characterization and Theoretical PHREEQCI Model computations
G.O Bosire1 and J.C. Ngila1,2
1Department of Applied Chemistry, University of Johannesburg, PO Box 17011, Doornfontein 2028 Johannesburg, South Africa
2Kenya Pipeline Company Morendat Institute of Oil &Gas, Kenpipe Plaza, Sekondi Road Off Nainyuki Road, Industrial Area, Nairobi, Kenya
Submitted: September 11, 2017; Accepted: December 15, 2017
Abstract
This study examined a comprehensive semi-empirical approach assessing the influence of natural organic matter (NOM) on scale forming mineral phases in cooling water circuitry. Higher molecular weight NOM fractions were efficiently characterized and quantified using a combination of three techniques; viz the GC x GC-TOFMS (gas x gas chromatography with time-of-flight mass spectrometer) and LC-OCD (liquid chromatography-organic carbon detection) fluorescence emission excitation matrices (FEEM), the latter being a useful technique in confirming the type of humic substance in samples. Using the GC x GC-TOFMS, 80 low molecular weight organic compounds were determined in cooling water. The simulated scaling capacities due to interactions of metal ions and humics complemented experimental data favourably. Accurate speciation and simulative model computations were generated by the PHREEQC code, which suggested that Ca, Mg, Cu and Fe-based mineral phases potentially precipitate. Through unique speciation, complexation and saturation index profiles of these metals with fulvic acid in the modified Tipping and Hurley (T_H) database, their corresponding fulvate species such as CaFulvate, BaFulvate, MgFulvate, ZnFulvate, CuFulvate and FeFulvate+ were formed, which were found to influence saturation indices of mineral phases responsible for scaling in pipes.
Keywords
Complexation; fulvate; speciation and simulative models.
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