Report on comparison among current industrial scale lignite drying technologies (A critical review of current technologies)

Abstract

Lignite constitutes a major energy source and has long been used for energy production despite its contribution in greenhouse gas (GHG) emissions, as a fossil fuel. For example, 27.4% of Germany’s electricity originates from lignite power plants, while in Greece more than 55% of its electric energy consumption is provided by lignite. 45% of the total global coal reserves consist of low-rank coals (LRCs) such as lignite. With this background, the utilization of lignite for energy production is expected to remain a common practice in the decades to come since the availability of lignite is considerable in many countries of Europe and the world (e.g. Germany, Poland, Greece, USA, and Australia). Therefore, problems regarding the combustion and use of lignite should be addressed in a more efficient and environmentally friendly way. One of the main existing problems is the high moisture contained in raw lignite as received from the mine. The high moisture content results in higher CO2 emissions per unit of energy produced and is responsible for high capital and transport costs as well as other technical problems such as reduction in coal friability and difficulties in its blending and pneumatic transportation. Therefore, processing of lignite through drying is considered of great interest in the implementation of energy production in lignite power plants. Taking into account the significance of the subject and the usefulness of such an attempt, an overview of the currently existing drying technologies, including both evaporative and non-evaporative drying methods is reported in the present paper.