HEAT-TRANSFER AND PRESSURE-DROP CONSIDERATIONS IN THE DESIGN OF SIROSMELT LANCES

The Sirosmelt submerged combustion smelting process utilizes top injec tion lances to deliver fuel and air into a metallurgical melt. Helical vanes are used within the annular lance to impart swirl to the flowin g air and enhance heat transfer from the lance wall to the air. To imp rove the understanding of transport phenomena within the lance, a deta iled study of the fluid-flow and heat-transfer characteristics of deca ying swirling flow in a heated annulus has been performed. Swirl stren gth and type were varied, the outer wall of the test section was heate d uniformly, and Reynolds numbers ranged from 85,000 to 175,000. The s wirl decay characteristics, heat-transfer coefficient, pressure losses , and heat transfer per unit pumping power were determined, and heat-t ransfer mechanisms were identified. It was found that the entrance pre ssure losses associated with the helical vane swirlers contributed up to 80 pet of the total pressure loss, indicating that improved swirler entrance design could significantly reduce operation costs. Recommend ations are made for optimizing the shape of the swirler by using varia ble pitch/variable span swirlers and optimizing swirler position by al igning the entrance of the swirlers with the local flow angle. These c hanges will significantly improve the heat transfer per unit pumping p ower within a Sirosmelt lance.