强制对流换热器表面CaCO3附着垢方解石及文石晶体质量分数变化分析

利用工业循环冷却水动态模拟循环装置,对模拟换热器壁面CaCO3附着垢晶体进行了XRD衍射分析表明,CaCO3附着垢晶体主要由方解石和文石两相所组成。结合方解石和文石晶体物相含量的XRD定量分析,分析了随着循环水流速增大,两者的质量分数变化关系。研究表明,当水流速度从0.401 m·s-1升高至1.338 m·s-1时,CaCO3附着垢中方解石和文石的质量分数分别呈现降低和增加趋势,且附着垢中文石的质量分数明显比方解石的质量分数偏高。从CaCO3晶体的生长以及CaCO3晶粒所受的附着力与水流剪切应力角度分析了上述变化的原因。

Analysis on mass fraction change of calcite and aragonite crystals in CaCO3 adherent scale on surface of forced-convection heat exchanger

The CaCO3 adherent scale on the surface of simulation heat-exchange was obtained using a dynamic simulation device of industrial circulating cooling water.The XRD diffraction analysis of this scale revealed that the main phases present were aragonite and calcite.This study conducted XRD quantitative analysis of calcite and aragonite crystals to determine the change in the mass fraction on increasing the circulating water flow rate.An increase in the flow rate from 0.401 to 1.338 m·s-1 resulted in a decrease and increase in the mass fraction of calcite and aragonite,respectively,with a higher mass fraction of aragonite in the adherent scale.The cause of these changes was analyzed based on the growth of CaCO3 crystals and the adhesion with the flow shear stress from the perspective of CaCO3 crystals.