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Low Cost, Retrofit FGD Systems

AUTHOR: Kazunori Fukasawa
DATE: September 1997

There is considerable demand for retrofitting FGD on coal-fired plants, not only in OECD but also in non-OECD countries. A low capital cost option for SO2 emission control is the most important requirement for plants with a limited remaining life. One low cost option is to use a simple FGD process, even if this means sacrificing the sulphur retention to some extent. A variety of such technologies have recently been developed. This report focuses on the development of sorbent injection systems as prime candidates for SO2 control in older plants. Sorbent injection processes are compared with spray dry scrubbers and wet scrubbers. The process characteristics are discussed especially with respect to SO2 removal performance, operating parameters and experience.

With respect to environmental impacts, sorbent injection as well as spray dry scrubber processes have the advantage of not requiring wastewater treatment, while wet scrubber processes do. On the other hand, wet lime/limestone FGD systems have the advantage of procuring gypsum as a saleable by-product, whereas sorbent injection processes generally produce residues which have to be disposed of because the utilisation of their by-products still has limitations.

Development of methods to improve by-product utilisation from sorbent injection systems, would be a major factor in reducing the cost of SO2 emissions control and would promote the worldwide market share of sorbent injection technology. In the final chapter, the costs of specific processes are compared.