Page 306 - Materials Chemistry, Second Edition

CAT3525_C09.qxd 2/8/2005 10:11 AM Page 277
Incineration of MSW 277
The total sulfur, nitrogen, and chlorine contents are a guide to possible gaseous emissions problems.
Similarly, the contents of heavy metals will help to predict the chemical properties of the resultant
ash. The total ash content will help direct ash handling protocols. It may also help to predict par-
ticulate generation rates. Moisture content provides an indication of burnability as well as ease of
handling and shipping. Variations in physical and chemical properties of RDF due to differing
sources, time of year, and methods of waste sorting make it difficult to present average analysis val-
ues; however, Table 9.8 provides a comparison between RDF and coal as fuels.
RDF has a calorific value of 50 to 60% and bulk density of 65 to 75% that of coal (Table 9.8).
As a result, considerably larger amounts of RDF must be burned to obtain performance similar to
that obtained with coal. Optimization of fuel feeding and firing parameters will also be necessary.
The higher ash content of RDF and lower ash fusion temperatures may require modifications to ash
storage and removal procedures.
The sulfur content of RDF is often significantly lower than that of coal; in some cases, total S of
RDF is less than 1/100 that of coal. Thus, there are obvious atmospheric benefits with co-combustion of
RDF with the latter fuel. On the other hand, the chlorine content of RDF is higher than that of typical

FIGURE 9.15 Two types of densified RDF, pellets and cubettes.

TABLE 9.8
Analysis of Fuel Used in Boiler Tests

RDF Bituminous
Pellets Coal
Calorific value (Btu/lb) 8,110 14,600
Moisture (%) 9.6 9.2
Ash (%) 8.1 6.2
Carbon (%) 45.6 69.0
Hydrogen (%) 6.3 4.8
Sulfur (%) 0.3 1.8
Chlorine (%) 1.8 0.02