CaSO_4于换热面上结垢过程的控制机理分析

Analysis of Mechanism Controlling Calcium Sulphate Scale Formation on Heated Surface

为了掌握结垢过程的控制机理,通过分析CasO4在换热面上的结垢过程,得到控制结垢过程的阻力关系式．计算结果表明,流速越大,过饱和度越小,结垢过程越易为表面反应所控制．流速越小,过饱和度越大,结垢过程越易为对流传质所控制,且往往发生在液壁温差较大,壁温较高的情况下．垢层生长过程中,在恒壁温条件下,由对流传质与表面反应共同控制的结垢过程转变为只由表面反应控制结垢过程．在恒热流条件下,控制机理没有变化．

In order to investigate the mechanism of how to control scale formation, a formula of resistance force to control scale formation process was proposed through analyzing the calcium sulphate scale over heated face. The higher velocity of slow and the lower super saturation, the more easily the surface reaction tends to dominate the whole process. The lower velocity and the higher super saturation, the more easily mass transfer tends to dominate the process, especially under the condition of higher temperature difference in liquid-wall and with high wall temperature. During the period of scale growth controlled by convection of mass transfer and surface reaction together, surface reaction would become to control the process only when the wall temperature were steady, but the control mechanism would last without change when the heat flux was constant.