Calcium looping for CO2 capture from a lignite fired power plant

Abstract

Calcium looping (CaL) process is considered as a competitive technology for the capture of CO2 emitted from fossil fuel power plants. In this process two fluidized bed reactors are coupled. In the first reactor, i.e. carbonator, CO2 is absorbed by CaO and CaCO3 is produced, while in the second one, referred as calciner, fuel is oxy – fired, so that calcium particles, already having absorbed CO2 in the carbonator in order to produce CO2-rich flue gases, are regenerated. Numerous studies have focused so far on the implementation of this process in coal fired plants. However, little work has been performed in terms of lignite fired plants. Thus here, the knowledge gaps are filled by means of a thorough investigation of the particular technology using a thermodynamic approach. It is worthwhile noticing, that the analysis is conducted on an existing lignite power plant, which is already operating and is located at the wider area of Meliti, Greece (330MWe lignite fired power plant). For a more profound work, a series of parametric scenarios are investigated, for their optimum coupling setup, which subsequently lead to the conclusion that the energy penalty for the sorbent regeneration in cases of lignite combustion is higher than in cases of coal combustion. This is due to the higher moisture content and lower calorific value of lignite compared with coal. Finally, in order to achieve a lower energy penalty, several configurations are presented, resulting that the optimum is to burn pre-dried fuel, utilize solid heat exchanger and insert the fresh limestone inside the calciner instead of the carbonator. All configurations are evaluated in terms of CO2 capture and net efficiency.