The short version
“ROM”, “steam” and “slack” are not different minerals — they describe how the same thermal coal has been handled and sized after extraction. Choosing between them is mostly a question of how much sizing and consistency your process needs, and what you are willing to pay for it.
ROM coal (run-of-mine)
ROM is coal despatched broadly as it comes out of the mine, unsized, with a wide spread of lump sizes from fines up to large pieces. Because it skips screening and sizing, it is the most economical way to buy tonnage when your process can tolerate variability.
It suits buyers with their own crushing or who feed equipment that is indifferent to lump size — many cement kilns, sponge-iron units and captive power plants run comfortably on ROM.
- Unsized, mixed lump sizes
- Lowest handling premium
- Typical GCV 3,500–4,500 kcal/kg
Steam coal
Steam coal is the workhorse thermal grade, screened to more consistent size fractions and a more predictable calorific value. The tighter specification is what boilers and kilns want when combustion stability matters run to run.
It is the default choice for power, cement and steel buyers who value a repeatable burn over the lowest possible rupee-per-tonne.
- Sized fractions, more uniform
- Predictable combustion
- Typical GCV 4,000–5,000 kcal/kg
Slack coal
Slack is the fine fraction — small particles and fines, typically below ~20 mm. It is well suited to processes that need fine feed or that pulverise coal anyway, and to fluidised-bed combustion.
Because it is fine, slack handling, storage and dust management matter more; the upside is a grade that needs little or no further size reduction.
- Fines, typically 0–20 mm
- Good for FBC and pulverised feed
- Minimal further crushing
How to choose
Start from the equipment, not the price list. If your process pulverises or runs FBC, slack can remove a crushing step. If you crush on site or are size-indifferent, ROM is usually the most economical tonne. If combustion stability is the priority, sized steam coal earns its premium.
Whatever the grade, insist on a documented GCV for the consignment you are actually buying — sizing means little if the calorific value is not what was quoted. When you know what you need, request a quote and we'll price it against a verified spec.
Frequently asked
- Is steam coal better than ROM coal?
- Neither is universally better. Steam coal is sized and more consistent, which suits boilers that need a stable burn; ROM is unsized and more economical, which suits buyers who crush on site or are size-indifferent. The right choice depends on your equipment.
- What size is slack coal?
- Slack is the fine fraction, typically below about 20 mm. It suits pulverised and fluidised-bed combustion where fine feed is wanted.
- Which coal grade is cheapest?
- ROM coal usually carries the lowest handling premium because it skips screening and sizing. Total cost still depends on GCV, logistics and how much on-site processing you need.