Prevention of corrosion by improved incineration quality

Rising heating values of the refuses resulted in a spontaneous worsening of the heating surface corrosion. Consequently, before the construction of our new boilers substantial new studies and tests on combustion control were carried out between 1977 and 1979. Now on the basis of around 60 000 operating hours in 8 years, i.e. approximately 85% availability, the new boiler concept has proved to be exceptionally good. With combustion chamber temperatures between 900 and 1100°C and oxygen contents of between 7 and 9% the unburned carbon compounds in the flue gas are very low and no 2,3,7,8 dioxine components have been detected in the ashes. In total the measures described result in combustion with low pollutants but naturally do not alone enable adherence to the modern clean gas specifications. Stadtwerke Düsseldorf AG has also here in good time developed an advanced quasi‐dry flue gas cleaning concept that produce no waste water. Approximately 97% of the particulate and up to approximately 98,5% of the gaseous heavy metals are precipitated by this quasi‐dry absorption. A waste‐water free process has also been pursued for more extensive removal of gaseous residuals (i.e. mercury). In this case the selection fell to the coke filter technique, whereby, however, on account of costs it was necessary to abandon the regeneration of the coke, so that only the use of more economical lignite coke was considered.