Dynamic Numerical Simulation Of Aerosol A Mmonia Accumulation In Air Preheater

After the SCR denitrification reform of the power station boiler,the ammonium sulphate?NH₄HSO₄,ABS for short?ash is introduced from the downstream air preheater.This ash is different from ordinary loose ash,has strong viscosity and is difficult to remove.However,the current prediction method for ABS ash still uses the traditional loose ash calculation method,and the traditional ash model rarely considers the influence of the dynamic change of the ash layer on the flue gas flow rate.Therefore,this paper takes ABS cohesive ash as the research object,constructs a dynamic calculation model of ash layer which can predict ABS cohesive ash and loose ash,and analyzes the heat storage in the air preheater of a 600 MW denitrification unit.The dynamic ash deposition process and characteristics between the plates were studied.The effects of different plate types and loads on ABS ash and loose ash accumulation were studied.An air pre-block ash monitoring system was developed according to the characteristics of ABS ash,which can be ABS.The study of cohesive ash deposition and the provision of air preheater soot provide theoretical guidance.In this paper,the ABS cohesive ash calculation model which can describe the dynamic growth process of gray scale layer is constructed.The ABS cohesive ash model was established by writing the deposition criterion of ABS cohesive ash.The dynamic mesh technique was used to realize the dynamic product of collision,adhesion,growth and peeling of soot particles and corrugated board wall.Gray simulation;and through the comparison with experimental data,the accuracy and reliability of the model were verified.Secondly,using the dynamic ash model built,the three corrugated plates of a 600 MW boiler air preheater?HS type before control,HC type control and HCP after modification?were simulated and analyzed,and a rotation period of the air preheater was analyzed.The distribution of ash accumulation in aerodynamic field and ash deposition intensity,ash accumulation thickness,and ash accumulation probability in 80 s),and the influence of the slab deposition characteristics on the ash accumulation characteristics in the air preheater.The results show that the dynamic ash model constructed in this paper can describe the gray scale shape growth process and the change of flue pressure drop,and improve the calculation accuracy.The ash accumulation probability of ABS cohesive ash deposit area is more than 80%?with The particle size is irrelevant?,and the ash accumulation probability of the loose ash accumulation area is less than 30%,and it is negatively correlated with the fly ash particle size;the ash deposition strength of the ABS cohesive ash accumulation area is 5 times that of the loose ash accumulation area and Above;the anti-blocking ability of the three types of plates is HCP plate type>HC plate type>HS plate type;the combination of herringbone corrugation and bow-shaped corrugation in HCP plate type can effectively reduce the amount of cohesive ash accumulation at the cold end ABS The amount of ash accumulation is only 50%of the HS type corrugated board,and the selection of the heat storage board after the transformation has certain rationality.Thirdly,the flow field and ash deposition characteristics of HCP type heat storage plates with 50%,60%,70%,80%,90%and 100%BMCR were calculated,and the air pressure of different heat storage plates was analyzed.The distribution of ash accumulation in the dynamic field and ash accumulation strength,ash accumulation thickness,and ash accumulation probability.The results show that for every10%increase in load,the total resistance pressure drop increases by 60 Pa,the speed attenuation increases by 0.14 m/s,and the ABS liquefaction temperature range moves to the cold end of the air preheater by 1.4cm.The ash strength of loose ash accumulation With an increase of 2.15?g/mm2,the ABS cohesive ash strength increased by 9.90?g/mm2.In addition,the relationship between the load and the ash accumulation probability is related to the area where the ash is located.In the loose ash deposit area,when the particle size is constant,the ash accumulation probability of the same particle size increases by about1.4%for each 10%increase in load,while in the ABS cohesive ash deposit area,the ash accumulation probability is always greater than 80%.The calculation result of the ash accumulation characteristic under different loads provides a database of the ash accumulation characteristics under various working conditions for the design of the rotary air pre-monitoring system.Finally,based on the built dynamic empty gray model of the rotary air preheater,the Python language is used as the development script to construct the rotary air pre-blocking ash monitoring system.The system can reflect the ash distribution in the rotary air preheater in real time and intuitively,enhance the understanding of the operation personnel of the power plant on the accumulation of ash and ash in the air preheater,and give an alarm prompt when the ash accumulation is serious.The pre-operation is safe to operate.