Rising of sewage sludge heating value by process integration with waste to energy power plant

Sewage sludge, at the outlet of waste water treatment plant, where a mechanical dewatering is made on by filter press, is still composed by 70 - 75% of intracellular water. Sewage sludge in this condition is not useful to produce power. Only by an effective thermal drying it is possible to obtain a refused derived fuel (RDF) with good thermal characteristics in terms of lower heating value (LHV). Sewage sludge thermal drying process needs a considerable amount of thermal power, but at a relatively low enthalpy value. It is not economically convenient if the power is fed by primary energy source. In this work, the two hundred thousand ton/year WTE (Waste To Energy) power plant, located close to Bologna, Italy, was chosen to show the advantages of the integration process using of waste energy from quenching system for gas cleaning. After a brief introduction to the main issues involved, the main plant sections are described and the process is shown. Due to the innovation process, several analysis were run on sludge, from municipal wastewater treatment plant of Bologna and mass and energy balances have been done, in order to examine main plant issues.