摘要
不锈钢304和316是冷却塔、板式热交换器等换热设备的常用材料,为研究CaCO3析晶污垢在不锈钢304和316表面的生长特性,在35℃下1.0mmol/L的CaCO3溶液中,通过静态反应,采用称重法获得不同浸入时间的结垢重量,并采用扫描电子显微镜(SEM)获得不同浸入时间污垢的微观形貌。结果表明:相同条件下不锈钢304比316更易结垢;pH升高不仅促进新晶核形成而且促进四方形文石和方解石的形成,并且四方形文石逐步重结晶形成热力学最稳定晶型(方解石);pH升高使本体溶液中均相成核率和金属表面异相成核率均增加,且均相成核率增加更多,因此在高过饱和度下,pH较高时表面结垢量反比pH较低时少;污垢在材料表面能较高区域先生长再向四周扩散,通过数量增多和单个晶体不断长大并互相连接最终形成覆盖表面的污垢层。
Stainless steel 304 and 316 are widely used in heat exchangers, and get the precipitation characteristic of CaCO3 is the first step to research anti-fouling technology. CaCO3 precipitated on stainless steel 304 and 316 coupons from 1.0mmol/1 CaCO3 solution at 35℃. By weighing the coupon before and after experiment and using scanning electron microscope （SEM）, the amount of fouling and the morphology can be obtained. The results show that at the same conditions there are more fouling on stainless steel 304 than 316; high pH not only makes more new crystal nucleation but also promotes square aragonite and calcite, and recrystallization of square aragonite into calcite, the most thermodynamically steady crystal type; high pH makes both homogeneous and heterogeneous nucleation rate increasing, but the former increases more, which results in more fouling at low pH under high supersaturation degree; fouling first grows at the place with high surface energy and then extend to more place, and when the number increases and crystal grows to connect each other, fouling layer is formed.
出处
《制冷学报》
CAS
CSCD
北大核心
2013年第1期89-93,共5页
Journal of Refrigeration
基金
上海市研究生创新基金项目(JWCXSL1101)
上海市重点学科建设项目(S30503)资助~~
关键词
CaCO3析晶污垢
挂片实验
生长特性
晶体形貌
晶体尺寸分布
CaCO3 crystallization fouling
coupon test
precipiation characteristics
crystal morphology
crystal size distribution
