Grades of Coking Coal

GradeAsh Content
Steel Grade – INot exceeding 15%
Steel Grade -IIExceeding 15% but not exceeding 18%
Washery Grade -IExceeding 18% but not exceeding 21%
Washery Grade -IIExceeding 21% but not exceeding 24%
Washery Grade -IIIExceeding 24% but not exceeding 28%
Washery Grade -IVExceeding 28% but not exceeding 35%
Washery Grade – VExceeding 35% but not exceeding 42%
Washery Grade -VIExceeding 42% but not exceeding 49%

Grades of Semi-coking and Weakly Coking Coal

Semi Coking Grade -INot exceeding 19%
Semi Coking Grade -IIExceeding 19% but not exceeding 24%

Grades of Non-coking Coal

Exceeding 7000G-1
Exceeding 6700 and not exceeding 7000G-2
Exceeding 6400 and not exceeding 6700G-3
Exceeding 6100 and not exceeding 6400G-4
Exceeding 5800 and not exceeding 6100G-5
Exceeding 5500 and not exceeding 5800G-6
Exceeding 5200 and not exceeding 5500G-7
Exceeding 4900 and not exceeding 5200G-8
Exceeding 4600 and not exceeding 4900G-9
Exceeding 4300 and not exceeding 4600G-10
Exceeding 3700 and not exceeding 4000G-12
Exceeding 3400 and not exceeding 3700G-13
Exceeding 3100 and not exceeding 3400G-14
Exceeding 2800 and not exceeding 3100G-15
Exceeding 2500 and not exceeding 2800G-16
Exceeding 2200 and not exceeding 2500G-17

Coal Basics

What is coal?

Coal is a solid fossil hydrocarbon that represents the storage of solar energy from the past in the form of preserved plant material.  The plants during the preservation process have been broken down into organic matter that comprises moisture, ash, volatile matter (gases and liquids given off on heating) and fixed carbon.  The volatile matter and fixed carbon both contain energy and this is released on burning the coal.

In 2008 the world consumed some 4.76 billion tonnes of coal and this made up about 32.53% of all fossil fuel consumption in the world.

What are the types of coal?

There are four major types (or “ranks”) of coal. Rank refers to steps in a slow, natural process called “coalification,” during which buried plant matter changes into an ever denser, drier, more carbon rich, and harder material. The four ranks are:

  • Anthracite: The highest rank of coal. It is a hard, brittle, and black lustrous coal, often referred to as hard coal, containing a high percentage of fixed carbon and a low percentage of volatile matter.
  • Bituminous: Bituminous coal is a middle rank coal between subbituminous and anthracite. Bituminous usually has a high heating (Btu) value and is the most common type of coal used in electricity generation in the United States. Bituminous coal appears shiny and smooth when you first see it, but look closer and you may see it has layers.
  • Subbituminous: Subbituminous coal is black in color and dull (not shiny), and has a higher heating value than lignite.
  • Lignite: Lignite coal, aka brown coal, is the lowest grade coal with the least concentration of carbon.

Also, there is peat. Peat is not actually coal, but rather the precursor to coal. Peat is a soft organic material consisting of partly decayed plant and, in some cases, deposited mineral matter. When peat is placed under high pressure and heat, it becomes coal.

Coal Rank

Coal is made up plant material that has been initially broken down by bacteria and fungi in a peat swamp and then has been subjected to temperature for varying amount of time to produce a progression of coals Table 2.  In moving from peat through to anthracite the main driver is heat which is used for the coalification process.  This expels moisture, carboxyl groups (Carbon dioxide) and methane as rank increases.

Uses for Coal


  • Thermal Coal

Most coal is used for the energy content contained within the volatile matter and the fixed carbon.  These coals are generically termed thermal or steam coals.  These coals are mostly used for electricity generation.
A typical Australian thermal coal contains 6,080 kcal/kg of usable energy (net as-received energy) or 25.46 MegaJoules/kilogram (25.46 MJ/kg) of coal.  Electrical energy (power) is measured in Watts which are Joules per second, therefore 1 kilowatt hour of electricity (1 unit)converted from coal at 35% efficiency requires 10.286 MJ of coal energy every hour or 0.404 kg of coal.
Other thermal coal uses are the calcination (breakdown by heat) of limestone to form cement for construction industries or lime for agricultural purposes.
Hospitals and other institutions use coal for process heat as do meatworks, wool sours and timber drying processes.

  • Metallurgical Coal

Some special bituminous coals swell on heating above 350 degrees Celcius and release their volatile matter, leaving behind a hard porous carbon residue called coke. These coals are called coking coals and are limited in their occurrence around the world.  Coking coals are primarily used to make coke which under high temperatures reduces metal oxides to metals.  This process occurs when the coke is combined with the metal oxides at elevated temperatures.  The carbon from the coke combines with the oxygen from the metal oxides to produce carbon dioxide, liquid metal and residual ash (slag).

C (coke) + MO (metallic oxide)     Metal (liquid) + CO2 (gas) + slag (liquid)


Other coals used for the reduction of metallic oxides include non-coking coals that are used in direct reduction processes that rely on coal having very low ash contents and high reactivity of the carbon with carbon dioxide.  These processes are normally restricted to small electric arc furnaces or rotary kilns where no strength properties are required from the carbon.