Metal/Slag Separation in Iron Nugget Production

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The separation of liquid metal and molten slag from each other is expected to be controlled by two factors: (1) Fluid viscosity, which controls the speed with which metal droplets and molten slag droplets move past each other so that they can coalesce and separate from each other, and (2) Surface tension of the metal and of the slag, which determines how completely the two phases will separate from each other. The important information needed in order to properly design and control iron nugget production facilities are:

1. What are the effects of temperature and composition on the viscous and surface tension effects during nugget formation? These will be examined by determining the morphology and microstructure of iron nuggets and slag and comparing with known microstructures.
2. How do fluxes interact with slag compounds and metals to control nugget and slag properties? Studies are needed to determine how this impacts slag separation and removal, thermal requirements, and the mechanisms of generation of airborne particulates or other pollutants by this process

Project Objectives: The objective is to determine how the slag viscosity and slag/metal surface tension is related to the composition and temperature of the slag and metal, and to measure how variations in these properties alters the rate and completeness of the separation of metallic droplets from the slag.

Proposed Deliverables: A model of the separation of slag and metal from each other as a function of composition, temperature, and time.

Proposed Methodology: Surface tensions will be calculated based on microscopic measurements of the air/slag/metal interfaces in specified configurations, where the geometry can be used to determine how the surface tensions are related. Viscosities will be calculated based on the flow of slag. Modeling will be carried out using the FEMLAB multiphysics software, with capability for modeling fluid flow.

Milestones and Time to Completion: The overall project is expected to require 3 years to complete. The major milestones will be: (a) Production and analysis of iron nugget/slag assemblages suitable for analysis to determine ranges of slag chemistry and geometry of slag/metal contact – 3 months; (b) Determination of slag viscosity as a function of temperature and composition – 8 months; (c) Determination of slag/metal interfacial tension by microscopic geometrical measurements of metallographic samples – 10 months; (d) Development and validation of mathematical model to predict slag/metal separation behavior based on slag chemistry, time, and temperature – 15 months.