Co-incineration of dried sewage sludge in coal-fired power plants: a case study

With the ongoing investment in sewage treatment capacity in Flanders (Belgium), a new challenge is the management of the rising amount of sludge. Since sludge disposal to agriculture and landfill is regularly becoming very difficult, alternative thermal disposal routes become more important. This paper presents the results of the various co-incineration tests with dried sludge in coal-fired power plants. The aim of this project was to investigate whether adding dried sludge to the combustion process is technically possible, whether the emissions remain below the permitted levels, and whether the quality of residual products remains acceptable. It is concluded that the co-incineration of dried sludge is a valuable and responsible sludge disposal option because it can be carried out in the existing units with a high electrical efficiency. Also, sludge disposal is achieved with a limited influence on emissions and residual ashes, without creating additional waste streams. The main points of attentionare a limitation of the co-incineration rate and the total input of sulphur, chloride and (earth) alkali elements to avoid corrosion and fouling problems.