Study On The Growth Regularity Of Calcium Carbonate Scale And The Effect Of Scale Inhibitor On EQCM

In industrial production, especially in the process of producing oil and gas, scaling not only could lead to the efficiency reducing of equipment and oil tubing, but also accelerates the corrosion under the scaled position. It was a great significance for improving production efficiency to delay and reduce the fields scaling. Among the constituent of scale, CaCO3is the most harmful and common. In existing works, adding the scale inhibitor is usually used to decrease the scaling.This paper was carried out to investigate the accelerated calcium carbonate scaling behaviors by cathodic polarization under several factors which may promote the generation of CaCO3using electrochemical quartz crystal microbalance technique(EQCM). The performance of several scale inhibitors (e.g. the organic phosphonic, polymer carboxylic and inorganic phosphorus series) is researched. Moreover, the efficiency of each scale inhibitor is timely monitored, meanwhile, the scale inhibitor efficiency of thydrolyzed polyacryamidehe (HPAM) and the cooperation with different scale inhibitors are both researched. Based on those, the kinetics of the process CaCO3scaling is analyzed and compared in dynamic or static solution system whether adding inhibitor or not, also the effect on the growth kinetics under different flow rates. Scaling of the mechanism of the three types of scale inhibitors are given by X-ray diffraction, Scanning electron microscopy, Energy dispersive spectroscopy and cathodic polarization curves.The detailed research results are shown as follows:1) Cathodic polarized potential, temperature, the concentration of calcium ions and liquid velocity are all affected the scale mass of CaCO3:polarization potential has remarkable impact on the morphologies of CaCO3crystal and liquid velocity has remarkable impact on the scaling rate of CaCO3.2) The optimal concentration of1-Hydroxyethylidene-1,1-diphosphonic acid(HEDP), Copolymer of Phosphono and carboxylic Acid(POCA), Amino Trimethylene Phosphonic Acid (ATMP) and Sodium Hexametaphosphate (SHMP) are obtained at the temperature of50℃in static solution system. Both evaluated under molar concentration or mass concentration, the four kinds inhibitor make the scale mass from high to low order in SHMP, HEDP, ATMP and POCA when the concentrations are same.3) The inhibitor performance of polymer HPAM is proved. And its synergistic effect with four inhibitor is also presented. The best synergistic effect is with organic phosphine series inhibitor.4) As injecting scale inhibitor into solution, the relationship between the amount of scaling and time in static solution could be described as three stages:scaling, diffusion and unstable affection of scale inhibitor, stable affection of scale inhibitor. But in dynamic solution, it only consisted in two stages:scaling and stable affection of scale inhibitor. The curve of two stable sedimentary processes and the amount of scaling is linear, and it conformed to the linear equation:y=yo+kx, the value of slope k could quantify the growth kinetics. Because of the difference of the mechanism of scaling inhibitor, the effect of the flow velocity to performance of scaling inhibitor was different.5) The size of CaCO3particle and crystalline grain is obviously decreased after adding ATMP and HEDP. In addition, POCA not only can reduce the size at a certain degree, but also makes particle and crystalline grain decreased, but the CaCO3particle hollows. And the SHMP effect of morphology of CaCO3is little.6) ATMP can inhibit the process of the electrochemical reaction to some extent when CaCO3deposited onto the gold surface and the four scale inhibitor added to a certain extent, inhibit the concentration polarization process.