CaCO_3结垢过程控制机理分析

An Analysis of the Mechanism Governing the Control of CaCO_3 Scale Formation Process

为了掌握结垢过程的控制机理,通过分析CaCO3在换热面上的结垢过程,得到了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,对流传质与表面反应共同控制的结垢过程可能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。

To gain an in-depth understanding of the mechanism involved in the control of a scale formation process, a resistance formula relating to the control of a scaling process has been identified through an analysis of CaCO3 scale formation on heat exchange surfaces. The calculation results show that the greater the flow velocity, the lower the supersaturation degree, and the easier the scale formation process will be controlled by a surface reaction. The slower the flow velocity, the greater the supersaturation degree, and the easier the scale formation process will be controlled by convection mass transfer. Moreover, the above process tends to occur under circumstances when liquid walls have a relatively big temperature difference and a relatively high temperature. During the scale-layer growing process and under the condition of the wall temperature being a constant, the scale formation process jointly controlled by the convection mass transfer and the surface reaction may shift to one controlled only by the surface reaction. The control mechanism will remain unchanged under the condition of a constant heat flux.