Anthracite Coal

Overview

Engineering reference data for Anthracite Coal in combustion engineering.

Key Formulas

Heat Release

$Q = \dot{m} \cdot HV$

Fuel energy release rate.

Air-Fuel Ratio

$AF = \frac{m_{air}}{m_{fuel}}$

Mass of air per mass of fuel.

Excess Air

$EA = \frac{O_2}{21 - O_2} \times 100\%$

From flue gas oxygen measurement.

Variables

Symbol	Description	Unit
$Q$	Heat release rate	W
$\dot{m}$	Mass flow rate	kg/s
$HV$	Heating value	J/kg
$AF$	Air-fuel ratio	—

References

• Original Source

## Grades of Anthracite Coal

Anthracite coal is available in several grades or sizes, each suited for specific applications and firepot configurations. The primary grades are:

| Grade     | Primary Application | Typical Firepot/Bed Specifications |
|-----------|---------------------|------------------------------------|
| Buckwheat | Automatic coal firing burners in domestic, commercial, and industrial stokers | Not specified |
| Egg       | Large firepots      | Beds typically more than 16 inches deep |
| Stove     | Heating buildings   | (Largely replaced by gas or oil systems) |
| Chestnut  | Medium firepots     | Beds typically ranging 10–15 inches deep |

Additional grades mentioned include *pea* and *broken*, though their specific applications are not detailed in the source material. The selection of coal size is primarily determined by the physical dimensions of the grate and firepot.

## Applications by Grade

The following table details common applications and requirements for each anthracite coal size.



## Size and Application Engineering Notes

The suitability of anthracite coal grades is directly tied to combustion equipment design. Key engineering considerations include:

- **Grate Compatibility**: Coal particle size must align with grate opening dimensions to maintain adequate airflow and prevent fines from falling through or blocking air passages.

- **Bed Depth Optimization**: 
  - **Egg-sized coal** requires deep beds (>16 inches) to achieve stable combustion zones and prevent channeling.
  - **Chestnut-sized coal** operates efficiently with moderate bed depths (10–15 inches), balancing air distribution and heat output.

- **Feeding Mechanisms**: 
  - **Buckwheat grade** is specifically engineered for automatic stokers, as its small, uniform size allows consistent feeding and metering.
  - **Pea and broken grades** may be used in specialized systems where feed rate control or grate design differs.

- **Modern Replacements**: Note that stove-sized coal, while historically common for building heating, has largely been supplanted by natural gas and oil systems due to handling convenience and automation.