Three-dimensional Cathode For Electrochemical Descaling System: Mechanism And Process Optimization

As an important part of industrial production,industrial circulating cooling water system is of great significance for the rational utilization of water resources.However,the fouling problem of concentrated industrial circulating cooling water on the wall of heat exchanger will not only reduce the heat transfer efficiency,but also lead to corrosion under fouling and even unplanned shutdown,which brings potential safety hazards for industrial production.In recent years,electrochemical descaling is known as environmentally friendly technology because it can directly remove scale ions from circulating water,effectively improve the concentration ratio and reduce emissions.Although electrochemical descaling technology has irreplaceable advantages,low descaling rate,high energy consumption and difficult cathode cleaning and regeneration limit its application.In this paper,the performance of three-dimensional cathode enhanced electrochemical descaling device is systematically studied.Firstly,a serrated cathode was invented to solve the problem of energy consumption and cathode deactivation due to the adhesion of the scale layer in the electrochemical descaling process.When the serrated length is 20 mm,the angle is 60°,the cathode and anode spacing is 15 mm,and the current is 0.3 A,the cathode descaling rate is high and the energy consumption is low.The cathode descaling rate of the new descaling device was 15.2 g/m²·h,and the energy consumption was reduced to 5.27 k W·h/kg Ca CO₃,which was more than three times lower than that of the published literature at home and abroad.On this basis,the scale removal rate was further improved by changing the three-dimensional structure of the cathode and adding ion exchange membrane.The low descaling energy consumption mechanism of saw-tooth mesh cathode was explained by morphology characterization and COMSOL Multiphysics software simulation.Due to the tip effect,this structure greatly increases the local alkalinity and the deposition rate of scale,and promotes the continuous renewal of the cathode surface.The flat part can also be covered by the fouling layer at the tip,providing a place for the subsequent cathode reaction.At the same time,the sawtooth form effectively increases the cathode area,and promotes the cathode surface renewal through the synergy of the tip area and the flat area,which greatly reduces the energy consumption of the electrochemical descaling system.Subsequently,the electrochemical descaling device with sawtooth mesh electrode was used for descaling experiments.In order to solve the problem of scale removal after electrochemical descaling,a method of rotating descaling and pre-deposition of magnesium hydroxide in high-speed mixer matching with sawtooth mesh cathode was proposed.The parameters of rotating descaling and pre-depositing magnesium hydroxide of high-speed mixer were optimized from the aspect of process conditions.The experimental results show that in a certain range,the higher the concentration of pre-deposited magnesium hydroxide,the longer the time and the greater the current density,the higher the cathodic descaling rate and the higher the descaling rate.The descaling rate can be increased by 28.4%to 27.02 g/m²·h and the descaling rate can be increased by 15%±5%At the same time,the cathodic potential in the electrochemical descaling process is monitored after pre-deposited magnesium hydroxide,and the self-cleaning phenomenon of the cathode can be observed obviously,which is beneficial to the renewal of the cathode surface and the reduction of the descaling energy consumption.