Scottish Power Longannet Flue Gas Desulphurisation
In line with the Government’s regulations for large combustion plants (i.e. the Large Combustion Plant Directive), Scottish Power decided to fit Flue Gas Desulphurisation (FGD) plant to three of the four units, and in doing so secured the future of power generation at Longannet. The EPC contractor appointed to build the FGD plant was an alliance of Alstom Power and AMEC. This alliance was responsible for the design, construction and commissioning of the FGD project at Longannet.
As the FGD plant was to be fitted to an existing power plant, the process control had to interact with the existing boiler control systems. The challenge for Capula was to propose a suitable control system solution which would integrate into the existing system whilst giving Alstom Power a suitably powerful process control platform in which to install and commission the FGD plant. Additional demands were placed upon all parties to implement the flue gas path part of the works at an early stage to enable the generating plant to be brought back to commercial operation at the earliest time.
How we helped
Capula’s solution to Alstom and Scottish Power is based upon a Siemens Moore APACS system, which controls the flue gas path of the plant and integrates with the existing boiler control systems at Longannet, and a Rockwell Control Logix PLC platform to control the three FGD absorber plants. Both systems interface to the existing GE iFIX SCADA platform to enable process visualisation and supervisory control to be carried out by operators in the main control room. All systems incorporated a high level of component redundancy, so that the failure of a single item would not cause the system to become available.
As Longannet Power Station is situated on the Fife estuary, the most suitable method of FGD for this project was a sea-water scrubbing process. The process is capable of very high SO2 removal (upto 97-98%) and has been developed by Alstom Power Norway who have developed the technology to remove SO2 from flue gases by using sea water. Capula was awarded the contract to provide the process control platform for this project.
Our experience on previous FGD process plant at West Burton, Eggborough and Rugeley power stations was coupled with our knowledge of Longannet through extensive work previously on other projects such as the HP Heaters, BETTA Compliance and the LOMIS control refurbishment.