Characteristics of Waste Water Treatment Plant Sludge and Coal Co-Combustion

Wastewater Treatment Plant (WWTP) in electricity generation process produces sludges which are hazardous and toxic. As a consequence of clean production principle, the sludges were re-recombusted with coal in the boiler. Combination of coal co-combustion with household waste and biomass waste has been applied, but utilization of WW1P sludge co-combustion with coal was not found. As the WWTP sludge characteristics, chemical composition and ash fusion were unknown, phenomenon and effective combustion of coal-sludge co combustion were very interesting to be explored. This paper was aimed to study the sludge characteristics, to evaluate thermal energy of sludge combustion, to investigate the effect of sludge-coal co combustion on emissions and potential of boiler slagging. Experimental works comprised of coal characterization, proximate analysis of sludge-coal mixtures, ultimate analysis, chemical composition of ash as well as ash fusion temperature. Research found that the sludge had calorific value of 427.32 Kcal/kg, Sulphur content of 12.46% and CaO content of 34.11%. Based on boiler standard operation, ratios of coal-sludge for co combustion were 20:1 and 15:1. At those specific values, the calorific values were sufficient, slagging indexes were low and the generated emissions did not exceed the permitted standard.