溶液pH值对碳酸钙结垢的影响

A experimental study of influence of pH on calcium carbonate crystallization fouling

换热表面上形成的污垢可使传热效率降低 ,流动阻力增大 ,严重妨碍换热设备的正常运行 ,造成能源浪费和经济损失。影响换热表面上污垢的主要成分碳酸钙结垢的因素除了热流密度、流体温度、换热面温度以及流速外 ,溶液的pH值也有着重要作用。从成垢溶液的离子平衡出发 ,得到了成垢指数与pH值的关系式。计算表明 ,总钙浓度一定时 ,pH值越高 ,成垢指数越大 ,结垢趋势越大。在pH值为 7～ 9和流速为 0 5～ 1 0m/s时进行了换热面上碳酸钙结垢的实验研究 ,结果表明 ,pH值越大 ,渐进污垢热阻越大 ,结垢诱导期越短。随着流速的增大 ,渐进污垢热阻减小。在实验范围内 ,流速对渐进污垢热阻的影响大于pH值的影响。

Fouling on heat transfer surfaces causes serious and economic problems in industry. In addition to physical factors such as fluid velocity, temperature, heat flux and surface temperature, thepH value of the salt solution has an important influence on the fouling behavior. Based on the reaction equations of the dissociation of CaCO 3,an expressionfor calculating saturation index with pH value is proposed.The calculation shows that ifpH value is higher,the saturation index is bigger and the crystallization trendis greater. Experiments have been carried out for the pH 7～9 and fluid velocity 0.5～1.0m/s. The asymptotic fouling resistance increases and the induction time reduces with the pH value. The asymptotic fouling resistance reduces with thefluid velocity.In the range this experiments, the influence of fluid velocity on crystallization fouling is greater than pH value's.