| As a heat transfer equipment in a tail flue of a utility boiler,the rotary air preheater plays a key role in a utility boiler.Its waste heat recovery efficiency is closely related to the efficiency of the boiler.The heavy use of selec tive catalytic reduction(SCR)denitrification equipment leads to frequent plugging of the power plant's rotary air preheater.In order to ensure the operation of the power plant boiler,it is crucial to prevent and control the dust accumulation of air preheater.Aiming at preventing and controlling dust accumulation,this paper analyzes comprehensively the causes of dust accumulation in rotary air preheater firstly,mainly including coal quality,the shape of heat storage element plate,soot washing and washing operation,operating condition and SCR system.The heat storage element should not only have good anti ash characteristics,but also need to consider the heat transfer and resistance characteristics.To determine the breakthrough point of the study,a new type of regenerator for the rotary air preheater is proposed in this paper.This paper established a new type heat storage element and two kinds of commonly used 3D model of the heat storage element and simulated the gas flow in the heat storage element in different type with ANSYS FLUENT.What's more,the comparative analysis of different kinds of regenerators on flow characteristics and heat transfer characteristics and dust accumulation characteristics under various operation conditions.The main conclusions are as follows:1)Under the same conditions,the results of comparison analysis of three kinds of heat storage element and their temperature and velocity of the outlet flue are that the outlet temperature of corrugated plate heat storage element is the lowest,its hea t transfer performance is the best of all,its export speed is lower than others and it have high flow resistance while the plain plate have low flow resistance and the plain plate worsen its heat transfer characteristics.The new plate heat storage eleme nt increases the pits and bumps in the flat on the surface,its increased flow resistance is low and its heat transfer performance is obviously improved.2)Different flue gas flow velocity is simulated,and the calculated results are postprocessed in this paper and the corresponding curves of heat transfer and flow resistance characteristics are obtained.It is found that the improved new plate has better comprehensive performance of heat transfer and flow.3)The ash accumulation characteristics of the three kinds of thermal storage elements are analyzed and compared.The ash accumulation performance of the new heat storage element is slightly worse than that of the flat plate,and the probability of ash accumulation and deposition probability of the corrugated plate heat storage element are obviously higher than that of the other type of plate.4)Fouling characteristics of different storage conditions are obtained by changing the boundary conditions and numerical simulation.The results shows that when the gas velocity increases,the ash fouling intensity and the probability of fly ash decreases and while flue gas mass flow increases,the ash deposition strength increases.It is conducive to reduce the fly ash deposition rate and weaken the ash accumulation when the particle size of fly ash increases.5)In order to prevent ash accumulation blocking in thermal storage unit,the frequency of high ash blowing should be raised properly when the ash accumulation intensity is getting large in that ash particle size is smaller or coal ash is higher.6)With the ash accumulation characteristics stays the same,the new heat storage plate performance in heat transfer has improved than before,which can shorten the length of the heat storage element,reduce pressure drop,helps ash blowing and water cleaning. |
PDF Full Text Request