Evaluation of Sewage Sludge Co-incineration in the Existing Heating Plant or Power Plant from Emission Production Point of View

Abstract

Sewage sludge from wastewater treatment consists of inorganic elements (eg. nitrogen, phosphorus, potassium, calcium and magnesium) and organic elements. Up-to-date technologies allow a number of ways of sewage sludge treatment. Inorganic elements are good fertilizers and organic elements are used for regeneration of land – these are excellent features for fertilizing. But sewage sludge also contains large amounts of pollutants (e.g. heavy metals) which can contaminate agricultural land. This is the reason, why utilization for agricultural purposes is not allowed in several European countries and therefore other methods are preferred. These are landfilling, energy recovery (incineration, anaerobic digestion, pyrolysis, etc.) or mechanical and biological modifications to minimize the environmental impact. Incineration is an advantageous way of energy recovery. This process utilizes calorific value of sewage sludge and also minimizes the environmental impact. There are more options – incineration in new incineration units specialized on sewage sludge or co-incineration with another primary fuel (e.g. co-incineration with coal in heating or power plants). The objective of the paper is to create models (new sewage sludge incinerator and coal-fired power plant, where is incineration sludge with coal) to detection amount of emissions. Emissions are compared with European emission limits for waste incineration plants. The goal of the research is evaluation of the two mentioned ways of sewage sludge incineration from emission production point of view. Results are then compared with European limits on emissions from waste-to-energy plants. Further, modifications in flue gas cleaning system are proposed to meet the limits and costs on these modifications are performed.