Page 113 - Materials Chemistry, Second Edition

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4.5.3 ENERGY CONTENT OF MSW
The energy content of the organic components of MSW can be determined by (1) combusting sam-
ples in a full-scale boiler and measuring steam output (Figure 4.6), (2) using a laboratory bomb
calorimeter (Figure 4.7), or (3) calculation from elemental composition (i.e., ultimate analysis). Most
data on the energy content of MSW are based on the results of bomb calorimeter tests. This test
measures the heat release at a constant temperature of 25°C (77°F) from the combustion of a dry
sample. The value of 25°C is used as a standard reference temperature for heat balance calculations.
The energy stored within the chemical bonds of a material is known as the heat of combustion.
This heat is released when the material is burned. The heat generated by the combustion of a mate-
rial in a calorimeter may be determined by measuring the temperature rise that occurs upon its com-
bustion:

U C ∆T / M (4.2)
V
where U is the heat value (cal/g) of the unknown material, ∆T the rise in temperature (°C) from ther-
mogram, M the mass (g) of the unknown material, and C the heat capacity (cal/°C) of the calorime-
V
ter (measured using a standardized material).

FIGURE 4.6 Chart showing steam production at a heating plant.