Effect of Magnesium Ion Concentration on the Scale Inhibition of Heat Exchanger in Circulating Cooling Water under Alternating Electric Field

Abstract

This work investigated the effect of magnesium ion concentration on the formation of mineral scale in circulating cooling water under alternating electric field treatment (AEFT) by using a self-made power plant circulating cooling water simulator. In this experiment, the circulating cooling water used was artificial hard water. Three experimental groups with different magnesium ion concentrations and three corresponding control groups were studied. Scale inhibition rate, fouling resistance, calcium ion concentration, crystal phase, and crystal morphology were discussed. Results showed that 4 mmol/L magnesium chloride promoted the formation of scale on the copper tube wall, and the average scale inhibition rate was −107.86%. When the magnesium chloride concentration was 6 mmol/L, the situation was reversed, and the average scale inhibition rate reached 59.11%. The changes in calcium ion concentration supported the scale inhibition rate. Scanning electron microscope (SEM) photos showed the change in the composition of calcium carbonate crystals. The results showed that the effect of AEFT on fouling resistance is nonlinearly related to the concentration of magnesium ions in circulating cooling water.