Coal Quality Analysis
Coal is an important energy source, a significant raw material for many industries, and a major component of world industrial production. Consequently, there is a growing need for accurate and reliable coal quality analysis. This article examines the principles, techniques and terms used for a comprehensive coal quality analysis.
Coal is composed of a variety of organic and inorganic materials. The content of these organic and inorganic materials determine the properties of the coal and its usefulness. Coal quality analysis assesses the composition and properties of coal samples, enabling a measurement of the specific energy content and rank of the coal. These measurements determine the type of application for which the coal may be suited and the economic viability of using this coal.
The overall chemical composition of the sample and its physical properties, such as size and shape, are determined by a combination of mechanical and chemical methods. One of the primary methods is Proximate Analysis. This assessment utilizes mechanical methods, such as sieving and washing to separate the different components of the sample. These components consist of Volatile Matter, Fixed Carbon, Ash, and Moisture.
The Volatile Matter is the total amount of combustible material in the sample that is made up of several components, such as hydrocarbons and light hydrocarbons, caking index and calorific value. Large-scale combustion usually requires a maximum volatile matter content of 5-7%, while small-scale combustion requires a volatile matter content of up to 12-13%. The volatile matter content of the sample is determined by heating the sample to 800-900°C in an oxygen-free atmosphere.
The Fixed Carbon content of the sample is determined by subtracting the Volatile Matter content from the total moisture content of the sample. This is then calculated as a percentage of the total composition. Fixed Carbon is generally a solid material made up of carbon atoms bonded together in the sample. Examples of fixed carbon in coal samples include oils and fats, and it is the amount of fixed carbon present that determines the energy content of the sample.
The Ash content of the sample is determined by mechanically sieving the sample. This is then calculated as a percentage of the total composition. Ash is all of the noncombustible minerals, such as sand and other silicates, that are present in the sample.
The Moisture content of the sample is determined by drying the sample at a specific temperature. This is then calculated as a percentage of the total composition. Moisture content is an important factor in determining the calorific value and energy content of the coal; it may also indicate the suitability of the coal for specific applications.
In order to determine the rank of the coal, various tests such as Ultimate Analysis and Reactivity Tests are usually employed. Ultimate Analysis is a laboratory test that measures the amount of carbon, hydrogen, nitrogen, sulfur, oxygen, and other elements in the sample. Reactivity Tests measure the reactivity of the coal sample upon heating, which is then used to estimate the rank of the coal.
In addition to the aforementioned terms pertaining to coal quality analysis, there are two other terms commonly used to describe the properties of coal. These are Coal Index and Coal Grade. Coal Index is a numerical value that is calculated from the results of laboratory tests, such as Ultimate Analysis and Reactivity Tests. It is used as an overall way to quantify the quality of the coal. Coal Grade is a classification of coal based on its quality; it is typically determined from the Coal Index.
A comprehensive coal quality analysis requires an understanding of the different principles, techniques, and terms used. This article has examined the principles, techniques and terms used for coal quality analysis, as well as the components and properties of coal used to determine its suitability. It is important to have an understanding of these terms in order to accurately assess the quality of coal samples.
