The Optimization Design And Corrosion Inhibition And Scale Inhibition Mechanism Of Circulating Water System In Natural Gas Treatment Plant

A LNG plant put into production in less than a year later, the heat exchanger in plant has the serious corrosion perforation. The analysis found that this is because the heat exchanger in circulating cooling water system fouling caused serious corrosion under the scale, eventually led to the heat exchanger perforated and scraped. Therefore, this paper aims to study the mechanism of corrosion and scale inhibitor, and also choose the best scale inhibitor in order to control the scaling and corrosion of the heat exchanger.This paper determined the water quality by the Ryznar stability index method and found the R.S.I value is 6.74. So the source water of the LNG plant belong to corrosive water. The scale inhibition mechanism of QD-681 A was researched by calcium carbonate deposition method. The experimental process shows that the scale inhibition mechanism of the polyacrylic acid scale inhibitor are in accordance with the lattice distortion theory and the theory of removing film by regeneration and self decomposition.The inhibition performance of four scale inhibitors including QD-681 A, QD-632 A, QD-631-5A and QD-655 were evaluated by calcium carbonate deposition method. The experimental results show that the inhibition efficiency of QD-655 is the highest and the inhibition efficiency of QD-681 A is the lowest when scale inhibitor is single-use. The inhibition efficiency of QD-632 A and QD-631-5A in 4:1 ratio is the highest when scale inhibitors are mixed-use. With the increased mass concentration, the inhibition performance of QD-681 A is enhanced, and the inhibition performance of QD-655 decrease slightly. As the temperature increases, the inhibition efficiency of scale inhibitors decreases. With the increased concentration of Ca2+, the inhibition efficiency of QD-681 A increases first and then decreases, and the inhibition efficiency of QD-655 decreases. As the concentration of HCO3-increases, the inhibition efficiency of scale inhibitors decreases. As the p H value increases, the inhibition efficiency of the two scale inhibitors decreases.