Magnetic Fields Effects On The Calcium Carbonate Scale In Circulating Cooling Water

By using“the dual channel industrial circulating cooling water analysis test bench”and“Magnetic field industrial circulating cooling water scale inhibition treatment device”,the pulsed magnetic field scale inhibition experiments were made in the dynamic simulation condition of industrial circulating cooling water.The experimental platform has many functions such as water replenishing,automatic collection of experimental data,recording,image display,automatic operation and other functions.After the operation period of 24h,with 300 turns of coil,the flow rate is 1000L/h and pulsed voltage of 20V,the scale inhibition experiment were set to the constant magnetic field and the pulsed magnetic field which were repectively set to 50Hz?100Hz?150Hz?200Hz.The scale inhibition effect was evaluated by scale inhibition rate,the best scale inhibition parameters are determined,pulse frequency is 50Hz,the inhibition rate with fouling resistance law is 31.60%,and the inhibition rate with heat exchanger tubes weight is 49.79%,two methods of the scale inhibition rate are positive,at the constant magnetic field experiment group,the scale inhibition rate with fouling resistance law is-29.47%,and the inhibition rate with weight is-29.16%.At the pulsed magnetic field?f=50Hz?,the adherent scale quantity decreases with the value of 5.975g,the non-adherent scale quantity decreases with the value of 22.905g,compared with that of control group.This indicated that the pulsed magnetic field restrains the formation of the adherent scale.The scale crystal experiences was analyzed by scanning electron microscopy?SEM?and X-ray diffraction?XRD?,and the results show that,the scale is mostly composed by aragonite and calcite,the scale after processing by magnetic field,the amount of the calcite and aragonite content in adherent scale did not change significantly,the scale is mostly composed by aragonite,and the quantity fraction exceeds 95%,the grain size larger and looser.The calcite content in calcium carbonate crystals,the main components of scale,increases in different degrees,and the aragonite content reduces at different degree,the grain distribution is relatively loose.These indicate that magnetic field has little effect on the composition of adherent scale,though has obvious influence on that of non-adherent one.At the constant magnetic field,the adherent scale of aragonite content decreases with the value of 69.54%,the calcite content increases with the value of 30.12%,compared with that of control group.Scanning electron microscopy?SEM?shows clearly that the grain size is smaller and looser,while a large number of calcite appears.At the pulsed magnetic field,the amount of the calcite and aragonite content in non-adherent scale changed significantly,the aragonite content decreases with the value of 54.32%,the calcite content increases with the value of 45.68%,compared with that of control group,Scanning electron microscopy?SEM?shows clearly that the grain size is larger and more close.Finally,the crystallization process of Ca CO₃ in circulating cooling water was studied by analyzing the water quality indexes such as Ca²⁺,the hardness of water,alkalinity,the value of p H,water quality viscosity,Cl^-,SO₄^2-,and so on.Compared with other experiments,the pulse magnetic field is 50 Hz,the concentration of Ca²⁺and total hardness H increases,indicating that this process Ca CO₃ crystals is less and less in this process.Water viscosity decreased,indicating that the solution of Ca CO₃ decreased.In addition,p H value,alkalinity,Cl^-,SO₄^2-did not change significantly.At the same time,the amount of adherent is the least,and the non-adherent obviously decreased,indicating that the frequency of 50Hz pulse magnetic field can inhibit the formation of scale.