GATE Metallurgical Engineering Mineral Processing and Extractive Metallurgy Syllabus

Mineral Processing and Extractive Metallurgy syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Mineral Processing and Extractive Metallurgy in GATE Metallurgical Engineering, not a summary of it.

1. 1

   Comminution techniques

   1 topic

   • Size classification
2. 2

   Flotation

   overview

   Examined as a single unit within Mineral Processing and Extractive Metallurgy — no further topic split in the official outline.

3. 3

   Gravity and other methods of mineral beneficiation

   overview

   Examined as a single unit within Mineral Processing and Extractive Metallurgy — no further topic split in the official outline.

4. 4

   Agglomeration

   3 topics

   • Sintering
   • Pelletizing
   • Briquetting
5. 5

   Material and Energy balances in metallurgical processes

   overview

   Examined as a single unit within Mineral Processing and Extractive Metallurgy — no further topic split in the official outline.

6. 6

   Principles and processes for the extraction of non-ferrous metals

   3 topics

   • Aluminium
   • Copper
   • Titanium
7. 7

   Iron and steel making

   8 topics

   • Material and heat balance in blast furnace
   • Structure and properties of slags and molten salts
     • Basicity of slags
     • Sulphide and phosphate capacity of slags
   • Production of metallurgical coke
   • Other methods of iron making
     • COREX
     • MIDRE
   • Primary steel making
     • Basic oxygen furnace
     • Process dynamics
     • Oxidation reactions
     • Electric arc furnace
   • Secondary steel making
     • Ladle process
     • Principles of degassing methods
   • Basics of stainless steel manufacturing
   • Continuous Casting
     • Fluid flow in the tundish and mould
     • Heat transfer in the mould
     • Segregation
     • Inclusion control

Mineral Processing and Extractive Metallurgy flashcards for GATE Metallurgical Engineering

22 of 63 cards from the Mineral Processing and Extractive Metallurgy deck — real questions with worked answers.

1. What is size classification in mineral processing, and on what principle does it separate particles?

   Size classification is the separation of a mixture of mineral particles into fractions based on size, exploiting differences in the settling velocity of particles in a fluid (water or air). Coarse, heavy particles settle faster while fine, light particles remain suspended.

2. State Stokes' law for the terminal settling velocity of a small spherical particle in a fluid, and its size range of validity.

   For fine particles (laminar regime, $Re < 1$): $$v_{t} = \frac{g\,d^{2}(\rho_{s}-\rho_{f})}{18\,\mu}$$ where $d$ is particle diameter, $\rho_{s}$ and $\rho_{f}$ are solid and fluid densities, and $\mu$ is fluid viscosity. Valid for particles roughly below $50\,\mu m$.

3. State Newton's law for the terminal settling velocity of a coarse particle in the turbulent regime.

   For coarse particles (turbulent regime, $Re > 1000$): $$v_{t} = \sqrt{\frac{3g\,d(\rho_{s}-\rho_{f})}{\rho_{f}}}\times k$$ commonly written $v_{t}=1.74\sqrt{\dfrac{g\,d(\rho_{s}-\rho_{f})}{\rho_{f}}}$. Terminal velocity is independent of fluid viscosity here.

4. Distinguish free settling from hindered settling in classification.

   Free settling occurs in dilute suspensions where particles settle independently without interference. Hindered settling occurs in concentrated suspensions where particle crowding and upward fluid displacement reduce settling velocity, enhancing separation by density over separation by size.

5. Define equal-settling particles and the settling ratio for free settling under Stokes' law.

   Equal-settling particles have the same terminal velocity despite different sizes/densities. For two minerals under Stokes' law: $$\frac{d_{1}}{d_{2}}=\left(\frac{\rho_{2}-\rho_{f}}{\rho_{1}-\rho_{f}}\right)^{1/2}$$ and under Newton's law the exponent becomes $1$.

6. What is sintering in iron ore agglomeration, and what feed size does it agglomerate?

   Sintering is the agglomeration of fine iron ore particles (typically $-10\,mm$, mainly $0.5$–$8\,mm$ fines) into a porous, hard, lumpy mass by incipient fusion. Heat from combustion of coke breeze partially melts particle surfaces, bonding them into sinter suitable for the blast furnace.

7. In the Dwight–Lloyd sintering machine, how is the sinter bed ignited and how does combustion proceed?

   The Dwight–Lloyd machine is a continuous travelling grate. The top of the bed is ignited by a gas/oil ignition hood, and air is drawn downward by suction (downdraught). The combustion (flame) front of coke breeze travels downward through the bed as the strand moves, sintering the charge.

8. What is the role of coke breeze and basic flux (limestone) in the sinter mix?

   Coke breeze ($\sim 4$–$6\%$) is the internal fuel that supplies heat for partial fusion. Limestone/dolomite ($\ce{CaCO3}$) acts as flux, raising sinter basicity, improving reducibility and strength; this produces self-fluxing or super-fluxed sinter that reduces blast-furnace flux load.

9. Define the basicity of sinter and a typical target value for self-fluxing sinter.

   Sinter basicity is the mass ratio $B=\dfrac{\%\ce{CaO}}{\%\ce{SiO2}}$ (sometimes $\dfrac{\ce{CaO}+\ce{MgO}}{\ce{SiO2}+\ce{Al2O3}}$). Self-fluxing sinter typically targets $B\approx 1.0$–$2.0$, with optimum strength/reducibility around $1.4$–$1.6$.

10. What is pelletizing, and what feed size and product does it produce?

    Pelletizing agglomerates very fine iron ore concentrate (typically $-45\,\mu m$, i.e. finer than sinter feed) into uniform spherical green balls of $\sim 9$–$16\,mm$, which are then hardened (indurated) at $\sim 1250$–$1350^{\circ}C$ to produce fired pellets with high strength and reducibility.

11. What is a binder in pelletizing and name the most common one?

    A binder promotes cohesion of green pellets and improves green/dry strength. The most common is bentonite clay (added $\sim 0.5$–$1\%$); organic binders and hydrated lime are alternatives. Moisture (capillary forces) also provides green strength.

12. Compare balling discs and balling drums for green-pellet formation.

    A balling disc (inclined rotating pan) gives a self-classifying action, discharging only sized pellets, with good control of pellet size. A balling drum (rotating cylinder) has higher capacity but no inherent size classification, so it requires external screening and recycle of undersize.

13. List the three thermal stages a green pellet passes through in the induration (firing) process.

    1. Drying — removal of moisture (avoid spalling from rapid steam generation). 2. Preheating — decomposition of carbonates/hydrates and oxidation of magnetite to hematite. 3. Firing/induration — high-temperature bonding by recrystallization and slag bonding, followed by cooling.

14. What is briquetting, and how does its bonding mechanism differ from sintering/pelletizing?

    Briquetting compacts fine particles (ore, coal, sponge iron fines) into dense blocks/briquettes by applying high mechanical pressure, with or without a binder, usually without high-temperature fusion. Unlike sintering/pelletizing, bonding is primarily by pressure and binder adhesion rather than thermal fusion.

15. Name the principal industrial process for primary aluminium extraction and the cell type used.

    Primary aluminium is produced by the Hall–Héroult process: electrolytic reduction of alumina ($\ce{Al2O3}$) dissolved in molten cryolite ($\ce{Na3AlF6}$) at $\sim 950$–$980^{\circ}C$ in a carbon-lined electrolytic cell with consumable carbon anodes.

16. Why is alumina dissolved in molten cryolite rather than melted directly in the Hall–Héroult process?

    Pure $\ce{Al2O3}$ melts at $\sim 2050^{\circ}C$, which is impractical. Cryolite ($\ce{Na3AlF6}$) dissolves alumina and lowers the operating temperature to $\sim 950$–$980^{\circ}C$, providing an electrically conductive molten bath for electrolysis.

17. Write the overall cell reaction of the Hall–Héroult process including anode consumption.

    $$\ce{2Al2O3 + 3C -> 4Al + 3CO2}$$ Aluminium is deposited at the cathode (cell bottom) while the carbon anode is consumed, evolving $\ce{CO2}$ (and some $\ce{CO}$).

18. What is the Bayer process and what is its role relative to the Hall–Héroult process?

    The Bayer process refines bauxite into pure alumina ($\ce{Al2O3}$) by leaching with hot caustic soda ($\ce{NaOH}$), precipitating $\ce{Al(OH)3}$, and calcining. It supplies the alumina feed for the Hall–Héroult smelting cell.

19. Outline the pyrometallurgical route for copper extraction from sulphide concentrate up to blister copper.

    1. Roasting/drying of $\ce{CuFeS2}$ concentrate. 2. Smelting in a furnace to form matte ($\ce{Cu2S\text{-}FeS}$) and slag. 3. Converting (Pierce–Smith): slagging FeS off, then blowing $\ce{Cu2S}$ to blister copper ($\sim 98$–$99\%\,\ce{Cu}$).

20. What is copper matte and what determines its grade?

    Matte is a molten mixture of $\ce{Cu2S}$ and $\ce{FeS}$ formed during smelting that collects copper and separates from slag. Its grade is the $\%\ce{Cu}$, controlled by the degree of iron/sulphur removal during smelting; modern flash smelters make high-grade matte ($60$–$70\%\,\ce{Cu}$).

21. Write the two main reactions of the converting (slag-blow and copper-blow) stages in copper making.

    Slag-forming (FeS removal): $$\ce{2FeS + 3O2 + SiO2 -> 2FeO\cdot SiO2 + 2SO2}$$ Copper-making blow: $$\ce{Cu2S + O2 -> 2Cu + SO2}$$ producing blister copper.

22. How is blister copper refined to high-purity copper, and why is electrolytic refining important?

    Blister copper is fire-refined then electrorefined: impure copper anodes dissolve in $\ce{CuSO4}\text{-}\ce{H2SO4}$ electrolyte and pure copper deposits on cathodes. This achieves $\geq 99.99\%$ purity and recovers valuable anode-slime metals (Au, Ag, Pt-group).

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