What limits the amount of coal that can be burned per square foot of grate surface?

The amount of combustion air delivered by the forced draft (FD) fan is crucial in determining how much coal can effectively be burned per square foot of grate surface. Combustion air is necessary for the chemical reaction of burning coal; without sufficient air, the burning process is incomplete, which leads to inefficiencies and excessive smoke production.

When more combustion air is delivered, it allows for larger amounts of coal to be burned efficiently. This is because the added oxygen supports the combustion process, enabling higher thermal output and better fuel utilization. Conversely, if the air supply is insufficient, it restricts the amount of coal that can burn effectively, potentially leading to unburned fuel and the formation of carbon monoxide and other pollutants.

While factors such as boiler pressure, coal moisture content, and grate design are important for overall boiler performance, they don't primarily dictate the quantity of coal that can burn per square foot of grate surface as directly as the amount of combustion air does. Boiler pressure can influence combustion efficiency under certain conditions but is not a limiting factor in the way combustion air is. Coal moisture content affects heating value and combustion efficiency but does not limit the physical amount of coal on the grate. Lastly, grate design can impact the burning characteristics but is secondary to the role