Numerical Investigation on the Low Temperature Corrosion Characteristics of Flue Gas Heat Exchanger
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TECHNICAL ARTICLE—PEER-REVIEWED
Numerical Investigation on the Low Temperature Corrosion Characteristics of Flue Gas Heat Exchanger Lei Fu . Pengfei Liu . Guojun Li
Submitted: 4 August 2017 / Published online: 13 September 2017 Ó ASM International 2017
Abstract Low temperature corrosion characteristics on flue gas heat exchanger surfaces are crucial for reliability of equipment operation. Reasonable fin structure and accurate prediction of sulfuric acid vapor can understand corrosion characteristics and enhance performance. In this paper, a coupling numerical model is adopted to predict the condition of sulfuric acid vapor on heat exchanger surfaces. A rectangular type finned tube is employed to analyze the effect of operating parameters on sulfuric acid condensation and corrosion. The results show that fin regions with higher temperature have higher acid solution concentration. Although the increases of water vapor concentration could result in increase of deposition, the increase of flue gas temperature will reduce corrosion risk. The important is the rectangular fin can avoid high corrosion risk on its leading edge. Therefore, rectangular fin may be considered as an alternative scheme without reducing heat transfer performance and elongating the lifespan of individual fin. Keywords Low temperature corrosion Condensation Heat exchanger Heat transfer
Introduction Flue gas heat exchanger is a kind of typical gas heat exchanger for waste heat recovery from industrial flue gas. Heat exchangers such as the preheater and the economizer have got widely used as critical equipment in industry.
L. Fu (&) P. Liu G. Li Key Laboratory of Thermo-Fluid Science and Engineering of MOE, School of Energy & Power Engineering, Xi’an Jiaotong University, Xi’an 710049, China e-mail: [email protected]
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Certain elements in the flue gas would condense when the temperature on the heat exchanger surface is below the dew point of the flue gas. The condensate like the sulfuric acid solution could lead to operating failure of equipment. The corrosion degree for equipment can be largely predicted by examining the acid condensation rate and the acid concentration. Consequently, reasonable prediction of acid condensation rate and acid concentration would precisely guide the design of heat exchangers. Condensation of acid vapor and water vapor is complex due to the existence of non-condensable gases and particulates in the flue gas. Thus, condensation in the large space inside heat exchanger and the effect of particulate on condensation was ignored in the present investigation. Much research has been performed on the concurrent condensation and heat transfer of sulfuric acid vapor and water vapor with the existence of non-condensable gases. Abel [1] derived for the first time the fugacity equation for the possible prediction of water partial pressure from the acid solution concentration. However, acid partial pressure is highly overestimated in their model. Considering the decomposition of H2SO4 into SO3 and H2O, Gmitro et a
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