Potential and methods for increasing the flexibility and efficiency of the lignite fired power unit, using integrated lignite drying

Abstract

Present increase in the flexibility of coal power plants is a very important and complicated task. The paper discusses the problem of improving the flexibility and efficiency of the power unit on the example of a brown coal-fired unit including the option of low-temperature pre-drying of lignite. Drying technologies using low-temperature heat sources are analysed. Depending on the coal drying method, an up to 5% increase in power unit efficiency can be achieved. The possible actual increase in the efficiency of a specific power unit will result from the individual features and local conditions of the particular power plant. However, for hybrid systems with thermal energy accumulation system, the increase in efficiency depends on the selection of the energy charging system, type of accumulation system and working temperature range. In the authors’ opinion, the implementation of a drying technology for the needs of co-firing in power units should be based on rather the utilization of the internal heat sources of the given power unit with the possible additional use of “waste” or renewable energy sources. The proposed solutions are evaluated from the technical point of view and the expected increase in power unit efficiency is determined.