Properties Requirements of Metallurgical Coals

Parameters

Limits

Criteria

Total Moisture  (TM)

10% max as received

High moisture creates handling problem and lowers available carbon

Ash

10% max air dried

High ash reduces BF productivity and increases coke rate in BF

Volatile Matter

20-35% air dried

High VM reduces metallurgical coke yield, low VM causes high pressure on coke oven walls

Sulphur

0.6% max as dried

Part of sulphur goes to Hot Metal

Phosphorus

0.1% as dried

Phosphorus goes to Hot Metal creating difficulties in dephosphorization during steel making

Crucible Swelling Number

3 min. – 6 max.

Prime coking coal has higher CSN while soft coking coal has low CSN

Maximum Dilatation

55% min.

Depend on other components of coal blend

Maximum Fluidity

600 ddpm min.

Higher fluidity gives better flow in the coke ovens

Alkalis (Na2O, K2O)

2 % max. in ash

High alkalis are not desirable for BF refractory lining

Ash Fusion Temperature

1,450OC min.

AFT is to be higher than coking temperature

Gray King Coke type

G 5 min.

For soft coking coal the limit is G min

Mean Maximum Reflectance

0.85% – 1.35%

Soft coking coals have MMR in the lower range

Vitrinite

50% min.

For Soft coking coal the limit is 45%

Vitrinite Distribution (V9 – V 14)

70% min.

 

 

Metallurgical coal prices will continue to be determined in near future by the Chinese demand. However, the prices are not likely to increase to very high level since Australia has created additional mining capacity now. Only in case of natural calamity, prices may increase. And natural calamity in the mining area happens quite often in Australia.