CO₂ capture technologies are expected to play an important role worldwide in carbon mitigation in fossil fuel power plants. The enabling technologies have to be technically and economically feasible for greenfield power plants and for retrofitting existing power plants. In general, there are three main technology options for CO₂ capture from power plants: Post-Combustion, Pre-Combustion and Oxyfuel. For the capture of CO₂ from the flue gases of coal-fired power plants post-combustion CO₂ capture influences the least the conventional steam power process, compared with the other alternative technologies.

On behalf of RWE Power, the ECO Scrub project investigates the CO₂ capture from dry lignite-fired power plants (retrofit) using post-combustion solvent scrubbing performed by the Institute of Energy Systems (IET). The basic idea of ECO Scrub is to reduce the energy demand of the downstream gas scrubbing by increasing the CO₂ concentration in the flue gas. The coal is combusted with oxygen-rich air, supplied with oxygen from a cryogenic air separation unit. Compared with conventional post-combustion CO₂ capture, the higher CO₂ partial pressure and the reduced volumetric flue gas flow here lead to a decreased heat demand for regenerating the solvent, a smaller cooling duty and a reduced power demand for the pumps and blowers. On the other hand, however, an additional power demand results from the need to supply oxygen to oxygenate the combustion air.

Main objective of the work performed by the IET is to model and evaluate the integration of the ECO Scrub scheme into a dry lignite-fired power plant. In the first step, a steam generator should be integrated into an existing model to analyse the changes imposed from the raising of the oxygen concentration. The influence on the flue gas and the boiler of different oxygen concentrations in the combustion air will be evaluated based on the modelled power plant. The achieved results will be used in other simulations to investigate the effects of a higher CO₂ partial pressure and a reduced volumetric flue gas flow on the electrical, heat and cooling requirements of a CO₂ flue gas scrubber. Finally the efficiency of the ECO Scrub concept will be compared with that of a conventional reference power plant process with no CO₂ capture. This comparison will be based on simulations of the entire plant process and will be accompanied by a first assessment of the resulting capital expenditures and operating costs.

The ECO Scrub project was funded by the European Commission under the Research Fund for Coal and Steel (Contract RFCR-CT-2007-00009).