The high-performance scrubber REAplus
Ever since the 1980s, flue-gas desulphurisation (FGD, or its German equivalent REA) plants have been filtering sulphur dioxide (SO2) out of the flue gas from lignite-fired power stations. The scrubbing method, in which the SO2 is washed out using limestone slurry, has long since proved its worth. Today, more than 95% of the desulphurisation plants in power stations and industrial facilities worldwide are being reliably and successfully operated on the basis of this technology.
However, the high efficiency cy of the flue-gas scrubbing processes in use today is no reason for RWE Power to rest on its laurels. Its success is the spur that drives us on to develop new processes designed to make coal-based power generation even more environmentally compatible. This is where the REAplus concept comes in. This has been implemented in a pilot plant at the Coal Innovation Centre in collaboration with Andritz Energy & Environment (AE&E), a plant builder from Austria.
This concept optimises the chemical processes used in desulphurisation even further. The difference, compared with the previous method, lies in the staggered sequence of the scrubbing process and in improved contact between lime slurry and flue-gas SO2 by means of the “plus” module. The pilot scrubs 50,000 cubic metres of flue gas per hour from the BoA power plant. Trialling is focusing on the capture targets to be achieved and the suitability for continuous operation.
REAplus' highly efficient desulphurisation renders superfluous any pre-treatment of flue gases in the pilot CO2 scrubbing plant that is also linked to BoA 1. Combining REAplus and post-combustion capture creates conditions at Niederaussem that are unique worldwide for trialling modern, trail-blazing power plant engineering.
However, the technology is also of interest for existing REA absorbers: after a successful trial in the pilot plant, a “plus” module was installed in a large-scale REA absorber in Niederaussem power plant’s G unit. The data on the performance of the “plus” module collected over several months showed positive results. The module can reduce the REA’s power consumption at certain SO2 concentrations in the flue gas.