Dephosphorization of ferromanganese using BaCO 3 -based fluxes by submerged injection of powders: A preliminary kinetic
- PDF / 136,256 Bytes
- 4 Pages / 612 x 792 pts (letter) Page_size
- 65 Downloads / 160 Views
G. ROY, Assistant Professor, is with the Department of Metallurgy and Materials Engineering, 11T Kharagpur, Kharagpur, 721 302 India. P.N. CHAUDHARY and R.K. MINJ, Scientists, and R.P. GOEL, Deputy Director, are with the National Metallurgical Laboratory, Jamshedpur 831 007, India. Manuscript submitted May 26, 2000. 558—VOLUME 32B, JUNE 2001
contact reaction is rather harmful, when the transitory reaction is also high, because uneconomically excess species transport beyond the equilibrium value takes place to the slag phase, which later reverts back to the metal phase. However, an increase in permanent contact reaction, at a comparatively lower rate of transitory reaction, was found to be beneficial. Based on their laboratory scale experiments on desulfurization of liquid iron at 4-kg scale laboratory setup, they observed that the relative contributions of transitory and permanent contact reactions were almost equal. However, for a system with different equilibrium partition ratios and different gas and powder flow rates, the depths of the injection-relative contribution may be different. In view of the preceding discussion, the present article seeks to calculate the relative contribution of the permanent and transitory contact reactions for the present dephosphorization study, which might subsequently help in selecting the design parameters that could be of importance for efficient phosphorus removal. Injection involves initial transportation followed by discharge of compressible fluid–mixed particles as a submerged jet in the liquid metal. The process demands injection of powder using a minimum amount of carrier gas. The carrier gas stream mixed with powder overcomes the resistance due to the hydrostatic head, and upon leaving the outlet dipped in the liquid metal, develops a reverse motion due to buoyancy and breaks into bubbles due to the hydrostatic head, surface tension, and drag forces. The bubble size increases with the decrease of hydrostatic head and bubbling improves the kinetics of treatment of liquid metal. The amount of solid particles that can be conveyed with the carrier gas depends on the loading ratio. For those particles that have poor air/ gas holding capacities, the loading ratio can be maintained only up to 20:1. For BaCO3, which was injected in the present investigation, the loading ratio was kept at 15:1, considering its hygroscopic nature. In order to achieve efficient conveying through ducting, uses of sudden enlargement, contraction, bends, and joints should be reduced to a minimum limit. The dephosphorization was carried out in an induction furnace, and the experimental setup using an injector is shown in Figure 1. A graphite crucible of 9-cm internal diameter and 25-cm height was used to melt the high carbon ferromanganese. Seven-kilogram metal weight was considered appropriate so that there is enough space over the liquid alloy in the furnace for flux addition. Argon gas was used as a carrier gas and an on-line rotameter was attached for regulating the flow of gas. A 700-g flux mixture
Data Loading...
