Crystallization of calcium carbonate (CaCO3) in a flowing system: Influence of Cu2+ additives on induction time and crystalline phase transformation

Abstract

The Raman spectrum of CaCO 3 polymorphs calcite and aragonite: A combined experimental and computational study The Journal of Chemical Physics 140, 164509 (2014) Abstract. Scaling of calcium carbonate (CaCO 3 ) is commonly found in piping systems in oil, gas, desalination and other chemical processes. The scale may create technical problems, leading to the reduction of heat transfer, increase of energy consumption and unscheduled equipment shutdown. This paper presents crystallization scaling experiments and evaluation of the effect of Cu 2+ additives on the induction time and calcium carbonate transformation. The crystals precursors were prepared using equimolar of CaCl 2 and Na 2 CO 3 resulted in concentrations of 3000 ppm Ca 2+ in the solution. The Cu 2+ in amounts of 0, 1 and 10 ppm was separately added in the solution. The flow rates (20, 35, and 60 mL/min) and elevated temperatures (27, 35 and 45 0 C) were selected in the study. The induction time for crystallization of CaCO 3 was observed by measuring the solution conductivity over time, while the phase transformation of calcium carbonate was examined by XRD method and SEM/EDX. It was found that the conductivity remained steady for a certain period reflecting to the induction time of crystal formation, and then decreased sharply afterwards,. The induction time was increased from 34 and 48 minutes in the presence of Cu additives (1 and 10 ppm), depending on the flow rates and temperature observed. In all the experiments, the Cu 2+ addition leads to the reduction of mass of crystals. Apparently, the presence of Cu 2+ could inhibit the CaCO 3 crystallization. In the absence of Cu 2+ and at elevated temperature, the crystals obtained were a mixture of vaterite and calcite. In the presence of Cu 2+ and at elevated temperature, the crystals formed were aragonite and calcite. Here, the presence of Cu 2+ additives might have controlled the crystal transformation of CaCO 3 .

A Novel Approach To Quantify Scale Thickness and Distribution in Stirred Vessels

“…This challenge can be overcome by quantifying the scale thickness and its distribution on the surface of the reactor wall. A popular approach to quantifying scale thickness is to install a coupon on the surface of the studied vessel’s inner wall and measure its weight before and after scale deposition. − However, the coupon can become a barrier to fluid flow and influence the mass of the scale deposited on its surface. As a result, the data obtained using this technique are subject to errors and uncertainties.…”

CO2 Curing of Ca-Rich Fly Ashes to Produce Cement-Free Building Materials

“…This may show different thermal stability of the formation of new CaCO 3 phases at above room temperatures within the applied curing conditions. This can also be attributed to poor transformation of amorphous CaCO 3 into calcite, which generally has more stable formations at room temperature [42]. However, it is also known that the thermal stability of amorphous calcium carbonate could eventually increase and spontaneously crystallize.…”

Effects of the Produced Water from a Sour Oilfield in South Kuwait on the Production Tubing

“…A typical length of tubing used from the active production zone to the central process unit is in the range of 300 m -675 m, with a total tubing for the complete operation connected to one substation of about 40.000 m (Figure 2). The scale formation in pipe tubing in oil and gas fields is influenced by a number of factors such as the nature of the produced water, the temperature [17], pressure [18], pH [19], and flow velocity [20] [21]. Due to its high ion content, especially the high chloride [22], but also calcium content [23], produced water is corrosive to metals.…”