Research On Deposition Characteristics Of A New Type Heat Storage Plate Of Rotary Air Preheater

Rotary air preheater is an important waste heat recovery facility in the tail flue of boiler.Its low heat transfer efficiency and ash on the wall of heat storage elements are common problems in the operation of air preheater.The reason is that ammonium bisulfate is produced by the reaction between left NH₃ after SCR denitrification and SO₃in flue gas.When the temperature is low,ammonium bisulfate liquefies and condenses,and the fly ash adhering to the wall of the heat storage element of air preheater,which results in the blockage of ash accumulation and the decrease of heat transfer efficiency of air preheater.In order to study the ash accumulation characteristics of the heat storage element of rotary air preheater after SCR denitrification,the temperature field model of the rotary air preheater was established,and the whole three-dimensional temperature field was simulated.The effects of rotor speed,material of the heat storage element and air inlet temperature of the air preheater on the thermal performance of the air preheater were studied.The conclusions are as follows:（1）Along the rotating direction of the rotor,the flue gas temperature increases and the air temperature decreases.Along the rotating direction,the temperature of the heating surface firstly rises and then decreases,and the decreasing range of the secondary air zone is larger than that of the primary air zone.（2）The low temperature corrosion risk areas are mainly in the cold section while the ABS deposition risk areas are mainly at the junction of the cold section and the hot section.（3）The increase of rotor speed of air preheater will enhance the average temperature and heat transfer efficiency of air outlet and decrease the average temperature of flue gas outlet to a certain extent.Different materials of heat storage elements have little effect on heat transfer efficiency of air preheater.The change of inlet temperature of primary and secondary air has little effect on the outlet temperature of air preheater,and it has much greater effect on the outlet temperature of flue gas.A new type of heat storage element of rotary air preheater is proposed,and the ash accumulation model of heat storage element is established.The heat transfer,resistance and ash accumulation characteristics of new heat storage element and traditional heat storage element are compared and analyzed.Finally,the influence of flue gas parameters on ash accumulation characteristics of heat storage element is studied.The conclusions are as follows:（1）Under the same Reynolds number,the new heat storage element increases by about 2 and the resistance coefficient decreases by about 0.005 compared with the corrugated plate;under the same conditions,the average ash accumulation strength and probability of corrugated plate in common ash accumulation area are 17.5ug/mm 2 and 2.43%higher than that of the new plate,and the anti-ash performance of the new heat storage plate is slightly worse than that of the plate.There is no obvious difference in NH₄HSO₄ depositional area.（2）When the inlet temperature of flue gas changes,there is no significant influence on the ash accumulation intensity and probability of heat storage elements.When the flue gas velocity increases,the ash accumulation intensity and probability of heat storage elements decrease.When the mass flow rate of flue gas fly ash increases,the ash accumulation intensity increases and the ash accumulation probability basically remains unchanged.