What is the primary factor affecting the quality of coal in terms of burning?

The primary factor affecting the quality of coal during combustion is the presence of moisture. When coal contains moisture, it needs to be evaporated before the coal can burn effectively. This moisture not only reduces the calorific value of the coal but also can lead to difficulties in ignition and sustained burning. High moisture content means that more energy is required to vaporize the water, which ultimately decreases the amount of energy that can be extracted from the coal during combustion. As a result, the overall efficiency of the burning process is compromised.

In addition, moisture can also affect the handling and storage of coal, leading to issues such as clumping and a higher likelihood of mold growth, which can further degrade the coal. While ash content, fixed carbon, and volatile matter are also important factors that influence the combustion characteristics and efficiency of the coal, the presence of moisture has the most immediate and significant impact on the burning process.