Dry residues of sewage - a promising energy fuel

From the profiles of the curves of differential scanning calorimetry, the maximum intensity of the heat flux, as well as the endothermic and exothermic effects of the combustion of wastewater residues (SWS) were determined. Sludge wastewater residues have a high ash content (more than 50 %), which reduces the value of the lower calorific value in the working state. The high content of volatile substances (more than 80 %) ensures early ignition at a temperature of 268 °C. Having a low ignition temperature, they can be a promising additional fuel to coal after enrichment in order to significantly reduce the ash content and increase the calorific value. The low value of the combustion index equal to 0.4×10-6 is due to the low value of the maximum reaction rate equal to 13 %/min and the high burnout temperature equal to 633 °C. The conducted studies have shown that the combustion of WWS does not lead to a deterioration in the operating conditions of the furnace screens in boiler furnaces due to the high content of minerals in the ash with a high melting point (iron and calcium phosphates). The high content of phosphorus in wastewater residues contributes to the immobilization of mobile iron into phosphates. Such a composition of WWS will help to reduce the mobility of heavy metals in slag and ash residues of co-combustion with coal during subsequent long-term storage. The results of this study should be used in the design of thermal power facilities.