51316-7455-Calcium Carbonate Scale Formation and Prevention in Aqueous Solutions and Mixed Solvents

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Product Number: 51316-7455-SG

ISBN: 7455 2016 CP

Author: Petros Koutsoukos

Publication Date: 2016

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The formation of calcium carbonate scale deposits formation causes serious problems in water desalination CO2 sequestration in subsoil wells in geothermal systems and in heat exchangers because of the low thermal coefficient of the salt. In a number of instances including oil production water miscible and immiscible hydrocarbons are present and the concomitant changes of the dielectric constant of the fluid phase has serious impact in the kinetics of calcium carbonate precipitation which remains largely unknown. The problem becomes even more complicated if polymorphism exhibited by calcium carbonate is also taken into consideration. In the present work the stability of aqueous solutions supersaturated with respect to all calcium carbonate polymorphs and the subsequent kinetics of calcium carbonate precipitation were measured. The measurements included aqueous solutions and solutions in the presence of water miscible (ethylene glycol MEG) and water immiscible organics (n-dodecane). Initially the metastable zone width (MZW) was determined from measurements of the effect of the solution supersaturation on the induction time preceding the onset of precipitation at free-drift conditions. The rates of crystal growth were measured as a function of the solution supersaturation using the highly accurate and reproducible methodology of constant supersaturation. The dependence of the rates of crystal growth on supersaturation suggested surface diffusion controlled mechanism. Polyacrylic acid polymers and co-polymers have been tested and the inhibition effects in aqueous and mixed solvents was investigated. In all cases and depending on the solution supersaturation vaterite formed first from solutions of high supersaturation while at low supersaturations calcite formed exclusively. The presence of dodecane reduced the stability of the supersaturated solutions with the crystals forming at the oil-water interface. The presence of ethylene glycol (concentrations between 10-80%) also affected the stability and the kinetics of calcium carbonate precipitation. The morphology of the formed crystals showed habit modifications: Spherical formations consisting of aggregated nanocrystals and calcite crystals with profound pits on the faces was the characteristic feature in the presence of dodecane.ACKNOWLEGMENTThis research was partially funded by the European Union (European Social Fund-ESF) and Greek National Funds through the Operational program Education and Lifelong Learning’ under the action Aristeia II( Code No 4420).