Pre-dried lignite technology implementation in partial load/low demand cases for flexibility enhancement

•Lignite drying & use depending on certain periods of the day, when the power load of the plant varies.•Thermodynamic analysis: mass & energy balance at full & partial loads using raw & raw/dried lignite.•The use of the drying system when the plant operates in partial load is the suggested mode.•The increase in the income from the electricity can be more than 3.5–4.0%.

The contribution of Renewable Energy Sources to the electricity production is gradually increasing, and due to the stochastic fluctuations of their load curve, the necessity for flexible operation in the fossil fuel power plants is boosted. The present study examines various scenarios of lignite drying and utilization depending on power load variation of the plant during certain periods of the day, in order to simultaneously increase the plant efficiency and reduce the electricity cost. The main goal is to evaluate the economic feasibility of the concepts, the reduction in the cost of electricity and the CO2 emissions avoidance. The thermodynamic analysis of a lignite power plant includes the mass and energy balance calculations at full and partial loads using either raw or raw/dried lignite mixture. The operation of the drying system in periods when the plant operates in partial load turned out to be the most suitable mode. Economic analysis revealed that employing the proposed scenario, the increase in the income from electricity can be more than 3.5–4.0%. The annual CO2 emissions savings can reach 130,000 tn. The dryer cost, the fuel price and the CO2 emissions allowances affect significantly the profit from the electricity sales.