Research On The Growth Inhibition Mechanism Of CaCO₃ Crystal In Circulating Cooling Water By Magnetic Field

Scale has always been an important factor affecting the recycling use of industrial circulating cooling water.The difference of scale because of the mineral content of water in different areas.Ca CO₃ is mainly the component of scale which is hard,dense and strong adhesion,even blockage of the flow channel,affecting the normal production.The magnetic treatment in the physical scale inhibition technology is a scale inhibition method of green,environmental protection and high repeatability,which is widely used to solve the scaling problem of industrial water.In this paper,the industrial circulating cooling water dynamic simulation test bench and magneto-electric co-scale inhibition device are used to apply the effects of constant magnetic field and pulsed magnetic field to the hard water with different calcium and magnesium ion concentration ratio to conduct the experimental study on the magnetic field scale inhibition of circulating cooling water.The main purpose is to explore the influence of magnetic field and calcium magnesium ion concentration ratio on calcium carbonate scale crystallization process and optimize the scale inhibition parameter design of the magnetic treatment system of circulating cooling water.Four kinds of hard water with different concentrations of calcium and magnesium ions are prepared,and constant magnetic field and pulsed magnetic field were applied to form 8 experimental groups and 4 control groups without magnetic fields.Firstly,at different times,testing water quality of the experimental group and the control group with the physical and chemical properties.The results showed that in thedue to the fast reaction rate of producing Ca CO₃ scale.The conductivity gradually increased in the experimental process.The viscosity of the experimental group is lower than the control group.Then,according to the collected experimental data,the fouling resistance value was calculated and drawn the fouling resistance curve.The results showed that:Under the effect of pulsed magnetic field,the average scale inhibition rate of all experiments is positive,one of the average scale inhibition rate is the largest when the concentration of magnesium ion is 2mmol/L,is 70.80%.Under the effect of constant magnetic field,the average scale inhibition rate showed great difference with the change of magnesium ion concentration,two groups are positive and two groups are negative,the average scale inhibition rate when the magnesium ion concentration is 0mmol/L is larger?21.64%?,meantime the average scale inhibition rate is the lowest?-53.69%?when the magnesium ion concentration is 2mmol/L.Finally,scale sample for X-ray diffraction?XRD?and scanning electron microscope?SEM?analysis,the results showed that the magnesium ion concentration of 0mmol/L,the non-adherent scale of the control group and experimental group are calcite,consistent with the SEM image analysis results,with the increase of the magnesium ion concentration,the pulse magnetic field of the non-adherent scale is still calcite and no aragonite structure.But the constant magnetic field and the control group appear aragonite crystals in the non-adherent scale,shows that the addition of magnesium ions can promote the growth of aragonite,however the pulse magnetic field can inhibit the aragonite.The results show that aragonite is more easily to adhere to the surface of the heat exchanger and increase the fouling resistance.In order to achieve better scale inhibition effect,restraining aragonite growth is necessary.The pulsed magnetic field has better scale inhibition effect on circulating cooling water than the constant magnetic field.In conclusion,the pulsed magnetic field can be used to treat the circulating cooling water and adjust the concentration ratio of calcium and magnesium ions in the water to achieve better scale inhibition effect,indicating that the pulsed magnetic field is a relatively effective physical scale inhibition method.