Chemical makeup and physical characterization of a synthetic fuel and methods of heat content evaluation for studies on MSW incineration

A well-characterized synthetic fuel is often needed for research related to the efficiency or completeness of combustion and emissions from municipal solid waste incinerators. Knowledge of the chemical makeup, physical characteristics and heat content of such a synthetic fuel is important to establish accurate baseline operating conditions for experiments and to provide a mechanism for verification of data. A synthetic fuel was formulated to be representative of municipal solid waste (MSW) found in the US waste-stream, after some recycling. A majority of the fuel consists of cellulose in the form of paper and wood. Low-density polyethylene is chosen to represent the plastic polymer content, and iron represents the metal content. The waste food organic content is simulated by animal feed. Water and the inert component silica make up the rest of the fuel. The fuel is fabricated in three stages: (i) mixing the components, (ii) size reduction by shredding and (iii) compaction into cylindrical pellets of 2.5 cm diameter and approximate length 5 cm. Chemical analysis of the fuel includes testing its chlorine, nitrogen and sulfur content. The physical characterization includes tests for fixed carbon, ash, volatile matter and moisture content of the fuel. The heat content of the synthetic fuel is determined by three different methods. The first method to determine the heat content is the standard bomb calorimeter method, in which a powdered sample of fuel is burned with excess oxygen in an adiabatic calorimeter. The second method, also experimental in nature, is to apply calorimetry on the individual components of the synthetic fuel. The third method is to investigate literature values for the heat content of the individual fuel components and then multiply them by their mass fractions and sum to find the total heat content. These three values for the heat content are compared, and close agreement is found. The value determined by all three methods is the 'higher heating value' (HHV), that is, it includes the latent heat of condensation of water vapor, which is formed during combustion. Thus, in all three methods, among the final combustion products the water content is taken to be condensed (liquid). The data show that any one of the three methods can accurately determine the heat content of a synthetic fuel. (C) 2001 Elsevier Science Ltd. All rights reserved.