Factors affecting energy efficiency of waste to energy plants

Abstract

Improvement of the energy efficiency of waste to energy (WtE) plants demands closer attention to detail in order plant integrity is not compromised. Availability for operation of WtE plants of .90% is a basic requirement to ensure the continuous supply of waste can be managed without the need for excessive storage or unnecessary transport. The drive to increase energy efficiency comes from the need of plant operators to maximise economic income, but also from European targets to meet the challenges of climate change and security of energy supply. Energy efficiency in WtE plants is reviewed based on experiences in Europe. While in the 1990s the emphasis for WtE operators was reducing emissions, more recently major efforts have been made to increase the export of energy. In the main, this has been approached by increasing steam temperature. However, the subsequent rate of corrosion can be catastrophically high and there is thus a need to improve corrosion resistance of heat exchange components to achieve acceptable service lifetimes. Trials have been conducted using more corrosion resistant boiler steels, but the preference is now for use of corrosion resistant coatings and claddings (e.g. alloy 625) to ensure plant reliability. Spray coating and weld cladding techniques are described. Other energy efficiency improvement methods described include online boiler cleaning, inhibiting fouling, achieving complete combustion and optimising flue gas cleaning (to reduce plant internal energy consumption). From what was until recently considered a good net efficiency of electricity production of 18%, measures being taken aim to achieve 30% in the most optimistic case.