Abstract
 
The range of fuels fed to waste incineration plants extends from well-sorted domestic refuse through mixed waste fractions to fuel mixtures that may additionally contain various types of hazardous waste and biomass. This diversity results in a great number of fuel and ash compositions. Among these are fuels with high as well as low calorific values and simple fuel ashes just as highly problematic fuel ashes. The latter can lead to increased slagging in the furnace and massive fouling in the convective passes of the boiler as well as accelerated corrosion. The plant operator is consequently faced with considerable challenges associated with unscheduled boiler downtime and production losses.
 

Conclusion and outlook

A novel, fully automatic, highly efficient and precise on-load boiler cleaning system to control fouling in the superheater area of a boiler has been introduced. The novelty of this system is the cleaning medium, which is water instead of the usually used steam. Furthermore, the advanced positioning system of the blowing nozzle is a key feature. Water cleaning allows to significantly intensify cleaning efficiency and therefore to control heat transfer and flue gas temperatures over long periods in the convective part of a boiler.

A new Go-Stop-Clean-Go approach is described. This approach provides the targeted positioning of the water jet, so that only the required areas at the right time are cleaned.

The combination of the above mentioned two factors allows effective and selective onload cleaning of the convective heat exchanger surfaces of waste incinerators and RDF- and biomass fired boilers. Plant availability can be prolonged radically towards several thousand hours per year by avoiding uncontrolled fouling in the convective part and the resulting unplanned outages. Long term stabilization of the flue gas temperature was observed as well.