• Contact Us
• Glossary
• Sitemap

• Five-year financial summary
• Shareholder profile
• Shareholder services and information
• Financial calendar
• Glossary
• Case studies
• Producing fresh water through desalination
• Reducing sulphur emissions
• Controlling dust emissions
• Wind generation

• Download Annual Report 2007
• Download sections of Annual Report
• Print Page
• Add to Print Basket
• Print Basket
• Email Page

Case study Reducing sulphur emissions

Coal contains sulphur in varying amounts, depending on the type, and region from which it is sourced. When burnt in the boilers of the power plant, the sulphur reacts with oxygen to form sulphur dioxide (SO₂) and sulphur trioxide (SO₃). Together these are generally known by the term SO_x which, when emitted by industry and transport, is a significant contributor to the production of acid rain.

Introduced across Europe on 1 January 2008, the LCPD aims at reducing SO_x emissions by giving coal fired plants two options. They can either agree to a very limited running regime with eventual closure by 2015, or install the equipment needed to remove SO_x from plant emissions. This equipment, known as FGD, is already installed at our Paiton plant in Indonesia and at International Power Opatovice in the Czech Republic. FGD equipment is currently being installed at our coal fired power plants at Pego in Portugal and Rugeley in the UK. Both FGD plants will become fully operational during 2008.

There are a number of competing FGD processes which can be used on power plants to remove the SO_x. The most common process is to pass flue gases through a slurry of limestone which reacts with SO_x to produce gypsum, a naturally occurring substance most commonly used in manufacturing plasterboard.

Raw limestone is crushed and mixed with water to produce the limestone slurry. This is then pumped into a large vessel, the absorber, installed between the boiler and the chimney. Within the absorber the slurry is sprayed over the exhaust gases in such a manner as to ensure over 90% of the SO_x reacts with the limestone to produce calcium sulphite. At the bottom of the absorber air is blown through the slurry to oxidize the calcium sulphite to form gypsum. The gypsum slurry is separated out from the limestone and stored ready for removal from the power plant. The remaining limestone slurry is recycled through the absorber to produce more gypsum.