Explain the pulverizer does the powdering or the pulverizing.

Ch 13 + ch 14

n this reading assignment you will learn about the pulverization and the combustion of coal.

The basic requirement of coal combustion is that all the carbon particles in coal should get sufficient air to burn and release the heat. We discussed the idea of excess air.

Coal normally is available to power plants in large lumps ranging from 2 mm to 50 mm size. Coal is commercially available in different sizes known as “Run of Mine,” “stoker,” “slack,” etc. depending on their size.

Once coal was burned on grates without any change in size or pulverizing. Because of the large size of coal, some of the carbon particles do not come in contact with the air. These unburned carbon particles go out with ash. This is a loss and could be in the range of 5 % or greater in the older grate-fired combustion.

Modern boilers powder the coal to a very fine dust so that while burning, it is almost like a fluid stream. The size of the coal particles is in the range of 75 microns. This means every particle comes into contact with the air. The loss due to unburned carbon is only in the range of 0.5 % or less making the boilers very efficient.

The pulverizer does the powdering or the pulverizing. Pulverizers come in different models and are a very important auxiliary of a power plant.

You will also learn about NOx. Nitrogen Oxides are a family of reactive gases. These gases form when fuel is burned at high temperatures. NOx pollution is emitted by automobiles, trucks and various non-road vehicles (e.g., construction equipment, boats, etc.) as well as industrial sources such as power plants, industrial boilers, cement kilns, and turbines. NOx often appears as a brownish gas. It is a strong oxidizing agent and plays a major role in the atmospheric reactions with volatile organic compounds (VOC) that produce ozone (smog) on hot summer days.

The Clean Air Act Amendments of 1990 required major stationary sources of NOx like power plants to install and operate reasonably available control technology (RACT) by May 31, 1995. All of the New England States have developed and implemented NOx RACT regulations. Region-wide, these regulations have reduced NOx from stationary sources by more than 50% from 1990 levels.

In this assignment you will learn about the burner technology that can be used to reduce NOx production