Facilitating removal efficiency of electrochemical descaling system using confined crystallization membranes

Abstract

As an environmentally friendly technology, electrochemical descaling has received extensive attention and research. In the traditional electrochemical descaling system, the precipitated scale is affected by several factors and only a portion of these ions can crystallize and grow into the scale layer on the cathode surface. In addition, the alkalinity ions are severely depleted by neutralization reactions, resulting in a decrease in pH value and unfavorable for the crystallization of scale. A confined crystallization membrane (CCM) for inducing scale crystallization is set to the traditional electrochemical descaling system in this paper, which weakens the negative effect of concentration polarization on mass transfer, providing an environment with high pH and low water flow interference for the crystallization of scale. Cyclic electrolysis experiments show that the addition of CCM greatly increases the amount of scale deposition, with a maximum of 60.26 g·h−1·m−2. The scale consumption per unit weight is saved by more than 50 % after adding the CCM, the values of Ryznar Stability Index (RSI) and Langelier Saturation Index (LSI) of the solution can reach the ideal range in a shorter time. The cleaning cycle of CCM is about 144 h, and the scale can be removed by pickling, thus restoring the enhanced descaling function of CCM.