Ore dressing: crushing, sintering, concentrating
Getting the ore ready for the furnace
1. Iron ores and extraction of iron
2. Straight from the mine
Ore comes out of the mine as big rocks, mixed with impurities. It cannot go straight into the furnace.
Pick the right answer
Predict: why are the rocks crushed first?
- A. To get pieces of a suitable size, so the ore is easily reduced
- B. Crushing turns the iron oxide into iron
- C. Crushing removes all the impurities
Explanation
Crushing breaks the rocks into pieces of a suitable size, so the ore is easily reduced. Breaking the rock does not remove the impurities or turn the iron oxide into iron.
3. What ore dressing does
Ore dressing
The processes that prepare iron ore for reduction, by improving its physical, mechanical and chemical properties.
- Ore dressing → 1- Physical and mechanical properties
- 1- Physical and mechanical properties → a- Crushing
- a- Crushing → b- Sintering
- b- Sintering → c- Concentrating
- Ore dressing → 2- Chemical properties
- 2- Chemical properties → Roasting (next lesson)
This lesson covers the three processes of part 1.
4. a- Crushing
Crushing gives the ore a suitable size, so it is easily reduced.
Pieces along each edge of the rock 1
Pieces 1
Surface exposed 1 × the whole rock
Smaller pieces expose more surface to the substance that reduces them.
5. b- Sintering
Crushing and cleaning the furnace leave a huge amount of fine particles. They cannot be used directly in the blast furnace (where the ore is reduced).
Sintering
Treating the fine ore particles to collect them into larger lumps that are similar and homogeneous.
True or false?
Sintering means melting the ore.
Explanation
Sintering collects the fine ore particles into larger lumps that are similar and homogeneous; the ore is not melted.
6. c- Concentrating
Concentrating
Increasing the percentage of iron in the ore by removing most of the impurities, which are chemically combined or mixed with the ore.
Impurities mixed with the ore are separated by surface tension, magnetic or electric separation.
Made-up sample: 100 kg of ore holding 50 kg of iron. Remove impurities and watch.
Impurities removed 0 kg
Iron in the sample 50 kg
Iron % 50 %
7. Which process?
Sort into groups
Each ore sample has one problem. Which process fixes it?
Big rocks, too large to be easily reducedFine dust collected while cleaning the furnaceFine particles left over from crushingOre with a lot of sand mixed in
8. Apply: concentrate it
Pick the right answer
Crushed magnetite ore is mixed with sand. Which method best concentrates it?
- A. Magnetic separation
- B. Sintering
- C. Melting the ore
Explanation
Magnetite has magnetic properties and sand does not, so magnetic separation removes the mixed sand and concentrates the ore. Sintering joins fine particles into lumps without removing the sand, and melting does not sort the sand out.
True or false?
Concentrating an ore by magnetic separation changes the iron oxide into a new substance.
Explanation
The iron oxide itself does not change: the impurities mixed with the ore are separated physically.
9. Summary
- Crushing: gives a suitable size, so the ore is easily reduced.
- Sintering: collects fine particles into larger, similar, homogeneous lumps. No melting.
- Concentrating: raises the iron % by removing most of the impurities. Mixed impurities go by surface tension, magnetic or electric separation.
| Process | Problem it fixes | Result |
|---|---|---|
| Crushing | Big rocks | A suitable size, easily reduced |
| Sintering | Fine particles from crushing and cleaning the furnace | Larger, similar, homogeneous lumps |
| Concentrating | Impurities chemically combined or mixed with the ore | A higher iron % |
Can you explain why both crushing and sintering are needed?