OCR Text |
Show Table 5 Comparison of limestone and sea-water methods of flue gas desulphurisation 1. 2. 3. 4. A. Limestone method Relatively low desulphurisation efficiency (generally 80 to 90%) Expenses and environmental problems associated with quarrying and transport of limestone, preparation of scrubbing liquor and disposal of spent slurry Plugging of scrubbers Production of carbon dioxide B. Sea-water method 1. High desulphurisation efficiency (> 99%) 2. Simple 3. Economical 4. Environmentally compatible Desulphurisation of flue gases by means of sea-water scrubbing offers several advantages over the currently popular lime/limestone methods as indicated in Table 5. The lime/limestone methods require the quarrying, preparation and transport of the reagent to the plant, preparation of the scrubbing slurries and transport and disposal of the spent slurry. Furthermore, problems due to plugging are common in many lime/limestone systems. As many power stations are located on the coast in order to obtain water for cooling of the condensers, sea-water scrubbing is a cost-effective method for reducing pollutant emissions. The use of sea-water for cooling and scrubbin~ would also help to relieve the strain on the valuable fresh water resources. The pOSSIbility of piping sea-water to plants located some distance from the coast could also be considered. Salt -waters other than sea-water could also be employed for scrubbing flue gases. Preli~nary studies of the effect of sea-water scrubbing on marine chemistry and ecosystems suggest minimal effects (12,13). Nevertheless, more detailed investigations are necessary, in particular with regard to toxic metal pollution. The effects of thermal pollution also need to be assessed. 9 |