Energy providers need to balance plant finely to maximise output while minimising emissions of sulphur dioxide (SO2), nitrous oxides (NOx) and particulates.
In January 2008, compliance with the European Large Combustion Plant Directive (LCPD) came into force. The directive, 2001/80/EC of October 23rd 2001, defines regulatory limits on these pollutants.
These regulations provide three options for generators to use:
ELV requirements set limits for the pollutant concentration per cubic metre of gas through the station chimneys. This was the option selected by EDF Energy.
In most cases, control automation and emission measurement systems were already in place to help balance commercial performance with regulatory compliance requirements, but overall information about environmental compliance from the existing system was only available on a monthly basis as offline reports. In order to keep emissions firmly in the forefront of operators’ minds, continuous real-time information was needed. However, to ensure that staff were responding appropriately to the emissions limits, these needed to be calculated in strict accordance with the regulators’ constraints. With continuous on-line information available, which stays in step with the regulatory reports, EDF Energy wanted to secure a definitive record of emissions from its power stations in Nottinghamshire.
A key objective was to provide more immediate and continuous real-time information about emissions, the aim being to change operational behaviours in order to optimise the plant environmental performance.
As a long-term partner of OSIsoft in Europe and with a wealth of PI application developments in the power generation industry, Capula was very well-placed to successfully execute this project. Capula installed and continue to support EDF Energy’s PI systems, and consequently understand the architecture.
Capula used OSIsoft solutions both to capture emissions data in realtime, and to analyse and present this to operators and their managers on a continuous basis. These mission critical solutions combine automation control, real-time data historians and business applications to provide integrated solutions that bridge the historic divide between engineering, commercial and regulatory activities.
Using the OSI PI Advanced Computing Engine (ACE), calculations are made on the data acquired from plant, and are presented to operators by PI Process Book graphics and trends showing current performance against the regulated hourly, 48-hourly and monthly targets.
Calculations are configured on a ‘per-chimney’ basis, the chimney being the output of a ‘Large Combustion Plant’. Emissions are also calculated on a ‘per unit’ basis. The information is presented on a moving average basis, so that operators can determine how emissions are changing with time. Emissions data is calculated for hourly, 48 hour and monthly averages, and rules are applied to ensure its validity, including looking at input signal health and the application of stack weightings. For instance, these rules account for whether an instrument is in calibration and/or fault mode or whether the unit is in start-up or shut-down mode.