Investigation on regenerative heat exchanger with novel low-leakage system for flue gas denitration in steel industry

Abstract

In order to counter the excessive NOx emissions caused by the leakage of regenerative rotary gas-to-gas heater (GGH) in the denitration system of steel industry, a new low-leakage system was proposed. An analytical model based on local thermal non-equilibrium was developed and the corresponding calculation program was built to analyze and compare the characteristics of the GGHs with and without the low-leakage system. As circulated flue gas mass flow rate increases, the increasing rate of the scavenge flow is far greater than that of the purge flow, due to the much higher resistance of the purge flow. The temperature distributions of matrix and flue gas were obtained for the GGH with and without the low-leakage system. The scavenge flows can greatly affect the flue gas temperature distribution but has little effect on that of matrix temperature. The effects of matrix height, hydraulic diameter, porosity and rotating speed on the leakage rate and thermal efficiency were examined. The low-leakage system can greatly reduce the leakage rate by up to 66.5% and save up to 12.26 kW fan power in operation, though it could also cause a reduction of the heat exchanger effectiveness of GGH by less than 2.2%. The circulated mass flowrate should not be too large, otherwise the leakage rate cannot be further decreased and the saved fan power would even be reduced.