Bituminous, brown or anthracite: what is the difference
All fossil coal is plant matter that has lain under pressure for millions of years. The longer and deeper, the more carbon it contains and the less volatile matter and moisture. Hence the three classes:
| Class | Grades | Calorific value, kcal/kg | How it burns |
|---|---|---|---|
| Brown coal | B | 2,500-4,500 | a lot of moisture and ash, burns out quickly; hardly sold for household use in Ukraine |
| Bituminous coal | D, DG, G (heating); Zh, K, OS, T (industry) | 5,000-6,500 | catches easily, long flame, burns without a fan |
| Anthracite | AO, AM, AS, AK | 6,500-7,500 | hard to light, burns long and hot, needs strong draught |
In other words, anthracite has more calories, but bituminous coal is more practical where there is no fan or the chimney draws poorly. A detailed comparison of burning time, smoke, ash and cost per kilowatt-hour is in the article "Anthracite or long-flame coal", and all the letters are explained in the article "Coal grades".
Bituminous coal grades for heating
- D: long-flame. The youngest bituminous coal: the most volatile matter, the easiest to light, the longest flame. Good for stoves and masonry heaters.
- DG: long-flame gas coal. An intermediate grade between D and G: slightly higher calorific value than D, catches just as easily and does not cake in the firebox. The most common household bituminous coal in Ukraine.
- G: gas coal. Higher in calories than D, but prone to caking: it can form a crust on the grate that has to be broken up. It more often goes to boiler houses with mechanised stokers.
The fraction is shown in the second part of the name: 50-100 mm is "slab" (DPK), 25-50 mm is "nut" (DO), 13-25 mm is "small" (DM). For a manually loaded boiler or a stove, the large 50-100 mm fraction is best: it burns longer and does not fall through the grate.
What bituminous coal is used for
- Stoves, masonry heaters, ranges and potbelly stoves: it burns on natural draught and needs no fan. More on the page coal for stoves and potbelly stoves.
- Solid fuel boilers without a fan and top-burning long-burn boilers.
- Lighting anthracite: a few shovels of DG under the anthracite help to start the boiler without firewood.
- Boiler houses with mechanised stokers: in bulk or in big bags on a schedule; terms are on the page fuel for boiler houses.
How to check bituminous coal on delivery
Bituminous coal is matte or has a dull sheen, is layered and soils your hands: that is normal (anthracite, by contrast, shines and hardly leaves a mark). Grey, brown and heavy lumps that do not burn are rock; good graded coal contains little of it. Dust and small pieces at the bottom of the bag are acceptable within 10%. Weigh any bag in front of the driver and ask for the test report: ash content for DG is usually up to 10-15%, moisture up to 10-14%. How to spot a dishonest seller is covered in the article about scammers, and how to burn coal without fumes or overuse in the article "How to burn coal".