Potential for energy recovery from maltese MSW: a thermodynamic analysis

Abstract

An investigation of the Maltese Municipal Solid Waste (MSW) potential for energy recovery is carried in this work. In a first step, MSW composition data was collected to evaluate the waste combustion enthalpy by a weighted average of each fraction, using the corresponding Low Heat Value (LHV). Results indicate that each kilogram of Maltese MSW releases circa 8,726 kJ of energy when combusted. Data from 1997 to 2009 allowed the conclusion that an incinerator with a capacity of 32.5 tonnes per hour can treat the waste expectably generated in Malta during the plant life span. In a second step, MSW elemental analysis was used to evaluate (i) the necessary stoichiometric air (152.4%) and (ii) the temperature of the flue gas (915.5 ºC), respecting the 6% ratio (voxygen/vfluegas) imposed by EU regulations. Finally, the thermodynamics of the steam cycle was applied to study the possible contribution of energy recovery for electrical power generation (PG) and co-generation (CHP). The thermal energy was analyzed assuming its use in desalination (multi effect distillation, MED), by means of the so-called gain output ratio (GOR) index. The final results lead to a potential power of 10 MW (PG) or a minimum of 7.25 and 4.85 millions m3/year of desalinated water MW (CHP).