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Calcium carbonate precipitation in the presence of pollutants is a carrier of importance for their transport to the sediments and for their subsequent release depending on the local microenvironment conditions. Zinc is often present in industrial waters (heat exchangers and boilers) mainly for corrosion protection. Depending on the alkalinity and calcium concentration of waters used in water intensive processes, calcium carbonate fouling is common. Moreover, among other metals, is present in natural waters together with iron and copper, where the concentration of Zn(II) may reach at levels of several ppm.
The effect of the presence of Zn is solutions supersaturated with respect to calcium carbonate was investigated at 250C, pH 8.50. The stability domain of the calcium carbonate solutions was measured in the supersaturation ratio (SRcalcite) values between 20.89-32.36. Below the least SRcalcite value the solutions were stable. Above it, precipitation was spontaneous past induction time, inversely proportional to SRcalcite according to the classical nucleation theory (CNT). In the presence of 1.3 ppm of Zn in the supersaturated solutions, the stability domain was shifted to higher SRcalcite values (47.86<SRcalcite<112.2). The presence of Zn stabilized all three calcium carbonate polymorphs. In the absence of Zn only vaterite and calcite were identified in the precipitated. In all cases no Zn oxides were formed. The rate of spontaneous precipitation of calcium carbonate in the presence of Zn, was reduced by as much as 98% at the least SRcalcite values tested. Adsorption of Zn at the active sites of the supercritical nuclei of vaterite is responsible for the reduction of the rates of CaCO3 precipitation and for the delay of conversion of unstable polymorphs. Finally, induction times in the presence of Zn were significantly longer for the same SRcalcite values without Zn, suggesting that Zn is a nucleation inhibitor as well.
Potash is mined from deep underground deposits left by ancient inland seas or extracted from saltwater bodies. The typical composition of potash is 40% potassium chloride (KCl), 55% sodium chloride (NaCl) and 5% clay. About 95% of potash is used for fertilizer in agriculture; the remaining 5% is used in commercial and industrial products such as soap, water softeners, de-icers, drilling muds etc.
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Pulsed Eddy Current (PEC) technology is a widely accepted inspection method now covered by several industry standards such as ISO(1) 20669, API(2) RP 583, and the new ASME(3) Section V (BPVC for Boiler and Pressure Vessel Code), article 21. PEC is a versatile inspection technology which provides an average remaining wall thickness through insulation and coatings. The technique can also be used to safely assess the minimum remaining ligament under corrosion scabs or blisters without surface preparation. PEC is resilient to liftoff variations and provides volumetric measurements of remaining material. It is capable of both detecting and assessing general corrosion on the outer surface of the pipes such as scabs and blisters, and detecting erosion or Flow Accelerated Corrosion (FAC) on the inner surface.
Pipeline under, solids deposition deposit corrosion (UDC) is a localized corrosion phenomenon that develops beneath or around solid deposits, which settle at the bottom of low flow/intermittent flow pipelines. These deposits are complex mixtures of water, organic, inorganic, and biological materials, and their composition can vary significantly depending on the properties of the product being transported and the operating conditions in the pipeline.