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Using Combustion and Thermogravimetric Analyzers from ELTRA

Coal is one of the most important fossil fuels. In 2012, the global stone coal output was about 6.6 billion metric tons [1]. A huge amount of the worldwide traded stone coal is mined in China, USA, Russia and India. Compared to the large amount of mined coal the required sample volume for the characterization of coal, varying from a few mg up to 1 gram, seems unbelievably small. The characterization of coal is important for its quality assessment and further use. Depending on the product quality, coal is suitable for coking, steel production or electrical power generation. This article takes a look at the chemical background of proximate and ultimate coal analysis and how these parameters are measured with ELTRA’s combustion and thermogravimetric analyzers. The most common types of coal (lignite, bituminous and anthracite) can be distinguished by their different chemical and physical properties. The elements carbon (C ), hydrogen (H), nitrogen (N), sulfur (S) and oxygen (O) are the most frequently measured elements. Additionally, the mineral content of the ash (esp. silica, alumina, ferric oxide etc.) is determined. Coal is characterized by more or less physically determined parameters such as moisture, volatile and ash content, and also calorific value and ash fusion temperature.

1. Proximate coal analysis (physical testing)

Given the variety of parameters which influence the quality of coal, it seems rather ambitious to name one parameter which best describes the coal quality. Due to the fact that coal is mostly used as fuel the calorific value is suitable to give a first impression of the product quality. For a first (“proximate”) analysis of coal the calorific value, the moisture, ash, and volatile content are measured. From these data the so called fixed carbon content is calculated.

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