Experimental Study On Variable Frequency Electromagnetic Anti-fouling Mechanism For Industrial Circulating Water

In the long-term use of the circulating water,the solute concentration inevitably caused by the steam escaped,so that the scale is supersaturated in the circulating water,and precipitates on the tube wall.The adsorption of scale on the heat exchange surface not only sharp drop the heat exchange efficiency,increases the pressure drop in the heat exchange equipment,but also accelerates the corrosion of the equipment,and may even lead to safety accidents.Therefore,the industrial circulating cooling water must be treated.Electromagnetic anti-fouling technology has very good prospects due to its safety,harmlessness,short time,low energy consumption,and high efficiency.The process of scale formation includes three stages:crystal nucleation,crystal growth and crystal maturation.Supersaturation is not only the precondition of nucleation,but also has a great influence on the growth rate of crystal nucleus,and the electromagnetic field can reduce the concentration of scaling ions before entering the heat exchanges.This paper aimed to analyzes the anti-fouling mechanism of electromagnetic field.The rules of electromagnetic field intensity and distribution with the number of turns of winding coil,the material of pipe and the diameter of pipe are analyzed by ANSYS.Through comprehensive analysis of the magnetic field intensity and distribution in the treatment pipe,it is found that the number of turns of winding coil is 90 turns,the material of treatment pipe is PVC and the inner diameter of treatment pipe is 100 mm,which is the most suitable parameters for the pipe.The effects of material,electromagnetic field strength and frequency on the calcium carbonate crystals were experimentally studied,and it was found that the variable frequency electromagnetic field significantly promoted the nucleation and growth of calcium carbonate.The nucleation and particle size growth rate of calcium carbonate in the PVC treatment pipe solution is significantly greater than that in the carbon steel pipe under the same frequency,and the maximum scale inhibition rate is75.6%at 1-3khz.The greater the electromagnetic field strength,the greater the rate of nucleation and growth of calcium carbonate in the solution.When the frequency is1-3kHz,9-11kHz,19-21kHz,it is found that the frequency has a certain effect on the nucleation of calcium carbonate at the same electromagnetic field strength,9-11kHz is the best frequency.We built experiments to study the CaCl₂ solution and NaHCO₃ solution by variable frequency electromagnetic field separately treatment,the aim to investigated the effects of variable frequency electromagnetic field on Ca²⁺and HCO₃^-ions.We found that partially unstable water molecular group[Ca?H₂O?₆]²⁺convert to stable three-layered hydrated calcium ion cluster[Ca?H₂O?_n]²⁺?16-20,27?by the variable frequency electromagnetic field treatment.Its stable structure can hinder the nucleation and growth of calcium carbonate.After treatment of NaHCO₃ solution,it accelerates the nucleation and growth of calcium carbonate.