Abstract

Ash deposition in flue gas heat exchanger affects its heat transfer performance and lifecycle, which becomes a crucial factor restricting the efficient recovery and utilization of flue gas waste heat. In this paper, a numerical method was established to investigate the characteristics of ash deposition in tube bundle heat exchangers. An integrated fouling model including transport, rebound, deposition, and removal of particles was employed to predict the behaviour of particles. Then, the effects of particle diameter and flue gas velocity on collision mass, deposition mass, absolute deposition ratio, and relative deposition ratio were studied. At last, the thermal–hydraulic and ash deposition characteristics of three different tube shapes were compared. The results showed that the low-velocity regions on the circumference were the primary locations of particle deposition, and the medium-diameter particles were the main deposition components. With the increase in flue gas velocity, the deposition mass of large-diameter particles decreased, and that of small-diameter particles increased. The use of an elliptical tube and flattened round tube with an apex angle of 60°had also excellent thermal–hydraulic and anti-fouling performances. Consequently, the ash deposition and wear can be reduced by increasing flue gas velocity, filtering medium and large-diameter particles, and using elliptical and flattened round tubes.

Graphic abstract

中文翻译：

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减少烟气换热器积灰的机理与策略

摘要

烟气换热器中的积灰影响其传热性能和生命周期，成为制约烟气余热高效回收利用的关键因素。本文建立了一种数值方法来研究管束式换热器中积灰的特性。采用包括颗粒的传输、回弹、沉积和去除的综合污染模型来预测颗粒的行为。然后，研究了颗粒直径和烟气流速对碰撞质量、沉积质量、绝对沉积比和相对沉积比的影响。最后，比较了三种不同管形的热工水力和积灰特性。结果表明，圆周上的低速区域是颗粒沉积的主要位置，中径颗粒是主要的沉积成分。随着烟气流速的增加，大直径颗粒的沉积量减少，小直径颗粒的沉积量增加。椭圆管和顶角为60°的扁平圆管的使用也具有优异的热工水力和防污性能。因此，可以通过提高烟气流速、过滤介质和大直径颗粒、使用椭圆和扁平圆管来减少积灰和磨损。大直径颗粒的沉积量减少，小直径颗粒的沉积量增加。椭圆管和顶角为60°的扁平圆管的使用也具有优异的热工水力和防污性能。因此，可以通过提高烟气流速、过滤介质和大直径颗粒、使用椭圆和扁平圆管来减少积灰和磨损。大直径颗粒的沉积量减少，小直径颗粒的沉积量增加。椭圆管和顶角为60°的扁平圆管的使用也具有优异的热工水力和防污性能。因此，可以通过提高烟气流速、过滤介质和大直径颗粒、使用椭圆和扁平圆管来减少积灰和磨损。

图形摘要