Abstract: Pressure and carryover leakages are inherent in operation of rotary air preheater due to regenerative heat transfer mode. 18 leakage flows take place in multiple sites, including peripheral and axial pressure leakages interacted with each other, which formulate a complex network of gas flow in tri-sectional rotary air preheater. The objective of this paper is to provide a comprehensive modeling for leakages calculation in the design of the preheater. It is based on the leakage mass flow rates governed by the matrix rotation and pressure drops across the seals, together with mass and energy balance equations in mixing processes. Air and flue gas temperature and pressure inlet/outlet the preheater, primary and secondary air mass flow rates outlet the preheater, flue gas mass flow rates inlet the preheater, as well as seal clearance are considered as known in the model, the leakage mass flow rates and directions, and actual gas flow rates through the matrix are determined by solving pressure leakage and mixing equations. For a tri-sectional rotary air preheater of a 600 MW boiler, pressure and carryover leakages are simulated in various seal settings, the results clearly show that primary air leakage accounts for about 75% of the amount of air leakage, the actual primary flow through the matrix accounts for 72% to 86% of the inlet flow, changes in seal settings have more impact on primary air system than secondary air system, ignore of flue gas carryover leakage, done as in National standards, can cause the measured air leakage rate 0.85% lower than the actual value.

Key words: Leakages, Regenerative heat transfer, Rotary air preheaters, Sealing, Tri-sectional