Pyrometallurgy 3 (Terms) Flashcards
- the oldest type of furnace
- the crucible is heated by the flame and radiation from the sidewalls, and transfers the heat to the bath
- the charge is isolated from external heat source
Oil/Coke-fired Crucible Furnaces
- Uses heating coils
- Indirect heating of charge
Induction Furnace
- the flame heats the bath both directly and by radiation from the roof
- considerable length is required to attain proper heat transfer from the long flame
Hearth Furnaces
- electrodes deliver the electrical energy
- Electric arc + slag resistance provides heating
- advantages include
◦ high degree of
temperature control,
◦ flexibility of operation,
◦ cleanliness of melt
Electric Arc Furnace
- used for continuous melting
processes; - solid charge flows down under gravity and product collected at the bath
- Hot gases rise to heat / react with charge
Vertical Shaft Furnace
recovery of volatile products
Retorts
high temperature vessels in which gas is blown through liquid metal
Converters
- Liquid product with the lowest specific gravity
- Generally the waste product
- Major components are oxides, fluorides, silicates, phosphates, borates, etc., but they lose their individual identities in the slag
- Complex, but single phase solutions
Slag
Properties of Pyromet Phases
inherent porosities
Solid Metals
Properties of Pyromet Phases
volatilize as mono-atomic gases; obey the IDEAL GAS EQUATION
Gaseous Metals
Properties of Pyromet Phases
low viscosity, high surface tension, good solubility with other metals of similar characteristics
- Liquid Metals
As the outlet of unwanted charge components, it must collect and dissolve the maximum possible amounts
◦ On the converse, it should carry the minimum amount of wanted component
- Metallurgical Requirements
Fluxes are cost centers
◦ Sensible heat in slag
◦ Physical entrainment in slag
- Minimum Cost
◦ Should not be too thick
o to resist flow out of the furnace
o to cause suspension of metallic phase
- Viscosity and Fluidity
◦ The critical temperature of smelting systems are dictated by the temperature at which the slag forms and freely flows
◦ Presence of fluxes significantly lowers the melting temperatures of charge
- Formation and Free-Running Temperature
◦ Should be compatible with the refractory of the furnace
◦ Acidic vs. basic slags
Corrosiveness
◦ Should be significantly lighter than the metallic phase for ease of stratification
Specific Gravity
Balance between the amounts of silica, magnesia, quicklime, alumina, etc.
◦ E.g. steel refining – removal of sulfur and phosphorus
Acidic vs Basic Slag
Basic slag tend to be ___
lumpy
Acidic slag tend to be ___
viscous
____Fe only exist when the sulfur is in excess relative to copper (stage converting of copper)
Fe
Property of Matte
When a metal forms more than one sulfide, the higher sulfide tends to ____ before melting, forming a lower sulfide and sulfur gas
decompose
Liquid solutions of sulfides
Principal metallic products of copper and nickel smelting
Matte
property of matte
At melting temp, the matte tends to volatilize ____
sulfur
Liquid solutions of arsenides and antimonides
Hard to separate from the metal layer when formed
Remedied by pre-roast / calcine prior to smelting
Speiss
Mixture of precipitated solid and liquid components
Skimmed from the top of the metallic layer
◦ E.g. lead smelting
Dross
