Experimental Study On CaCO₃ Fouling Characteristics Under Electric Field

CaCO₃ fouling,as a very common material in heat exchanger,has been the focus of industrial production and daily life due to its complex fouling mechanism,frequent cleaning cycle and hard to cure the harm.It is favored by people due to its no closed loop,the simple operation,the remarkable effect,the low running cost and so on.At present,most of the researchers focus on the anti-fouling effect of high voltage electric field on biofilm,but little on the fouling characteristics of heat transfer surface.The electric field was applied in the experimental section or before the experimental section plays the role of heat transfer surface fouling inhibition.However,whether there is a difference in the degree of fouling inhibition between them has not been revealed.There is no convincing and satisfactory explanation for the mechanism of fouling inhibition.The artificial CaCO₃solution is used to simulate the research object in this paper.The characteristics of Ca CO₃fouling on the surface of stainless steel have been experimentally studied by changing electric field intensity in the experiment section or before the experiment section.The results showed that:The fouling curves have no apparent induction period when the electric field acts on the experimental section.With the increasing of electric field intensity,the fouling rate and the asymptotic value of fouling resistance of Ca CO₃ decreases firstly and then increases,the optimum anti-fouling voltage is 3 000 V.The fouling resistance decreased 58.3%compared with that of without electric field.SEM pictures showed that,without electric field,the morphology of calcium carbonate fouling showed aragonite structure which irregular slender needle,cluster,aragonite structure with edges relatively clear.Under the action of electric field,calcium carbonate fouling exists in massive,granular and hexahedral shape,which showed the typical structure of calcite.The distribution of the fouling layer on the heat transfer surface is also different under various electric field intensities.Fouling layer is particularly dense without electric field,with the increasing of electric field intensity,the fouling layer from dense to sparse,then dense.The fouling curves have no apparent induction period when the electric field acts before the experimental section.With the increasing of electric field intensity,the fouling rate and the asymptotic value of fouling resistance of Ca CO₃ decreases firstly and then increases,the optimum anti-fouling voltage is 500 V.The fouling resistance decreased52.8%compared with that of without electric field.The SEM images of fouling deposits showed mainly aragonites with sharp and needle-like crystal structures.With the increasing of electric field intensity,the structure of Ca CO₃ fouling changed from aragonites to spherical vaterites.For the effect of electric field intensity on droplet characteristics,the surface tension and wall adhesion work of droplet do not change significantly with time without the electric field acts.With the increase of electric field intensity,the droplet surface tension and wall adhesion work decrease first and then increase,the optimum droplet surface tension and wall adhesion work are 100 V·cm^-1.