On the technical and economic issues involved in the co-firing of coal and waste in a conventional pf-fired power station

The introduction of co-firing schemes to large-scale utility plant has to date been limited in the UK. The need to conform to ever more stringent emissions legislation, reduced levels of carbon dioxide (CO2), and the recently introduced Renewables Obligations Certificates (ROCs) means that conventional power stations are having to change their operating philosophy and encompass new technologies and operating techniques. rrent paper describes some of the key work associated with the feasibility, design, and construction stages of a 100,000 tonne/annum dried sewage sludge co-firing facility attached to an existing 2,400 MWe pf-fired power station. The scheme is one of the first of its type and the largest in the UK, and represents an important milestone in the complex progress of integrating a biomass fuel with a conventional boiler process. al steps in the initial feasibility phase of the design process are described, such as the detailed evaluation of the raw materials suitability for co-firing in terms of the chemical and physical properties of the waste fuel. The resultant raw material properties are presented as input data to a detailed computer model developed by Sinclair Knight Merz (Europe) Ltd, the output of which indicates the co-firing potential of the composite fuel with respect to its impact on plant efficiency, thermal balance, flue gas characteristics, system performance (throughput, materials and maintenance) and potential for environmental impact. Specific areas of interest are highlighted such as fuel volatility, emission levels, trace element partitioning, ash composition and behaviour, fouling and slagging mechanisms and predicted erosion and corrosion levels. ting requirements of the co-firing schemes have also been considered, with the Integrated Pollution Control (IPC), Integrated Pollution Prevention and Control (IPPC), Town and Country Planning and the Electricity Act (Section 36 Consent) being examined.