About the project
In 1988 National Power undertook an eight year project to install a flue gas desulphurisation plant (FGD) at Europe's largest coal-fired power station in Drax, North Yorkshire. This would neutralise over 250,000te of annual sulphur emissions from the boilers; vital in reducing Britain's contribution to the effects of acid rain.
The Drax 400MW power station has six large boilers and generates one tenth of Britain's total energy demand. The FGD plant diverts the flue gases from each pair of boilers through a large cylindrical tower where they are scrubbed with a limestone slurry: most of the sulphur dioxide is removed, thus cleaning the flue gases and producing high quality gypsum. Every week at full load, the power station imports 10,000te of crushed limestone and produces 15,000te of gypsum that goes for manufacture into plasterboard. To support the new flue gas ductwork and piping, and provide the frames for the absorber towers and the buildings for limestone and gypsum, over 23,000te of diverse structural steelwork was required. Cleveland Bridge was awarded the sub-contract to detail, supply and erect this steelwork over a three year period on site.
The new plant had to be installed without interrupting the power output from the station and each pair of boilers could only be shut down for a fourteen week "outage" every three years. The design and construction of the FGD plant was dominated by this constraint – this applied equally in the steelwork erection. The most difficult challenge lay in working around the existing buildings and live ducts and services. Redesign of works to overcome these problems for the plant increased the steel requirement to 27,000te as well as the numbers of pieces to be erected – with no increase in the time for erection. At one stage, 10,000te of steel were put up in just 10 months. The 60m high absorber buildings contained twice the tonnage originally envisaged and required 50% more lifts. The new plant was complete in 1996.