Page 17 - mobile Workbook-chapter 2

There are three groups of models based on analysis. The amount of the lower heat value (LHV)

- Hn (Kcal/kg) can be estimated by compositional analysis, proximate analysis, and ultimate
analysis [3].

Physical Composition Proximate Analysis Ultimate Analysis

Conventional equation: Traditional equation: Dulong's equation:
Hn = 88.2R + 40.5(G + P) - 6W Hn = 45B - 6W Hn = 81C + 342.5(H - O/8) +

Bento's equation: 22.5S - 6(9H + W)

Hn = 44.75B - 5.85W + 21.2 Steuer's equation:
Hn = 81(C - 3×O/8) +

57×3×0/8 + 345(H - O/16) +

25S - 6(9H + W)
Scheurer-Kestner's equation:

Hn = 81 (C - 3×O/4) + 342.5H +

22.5S + 57×3×0/4 - 6(9H + W)
Heat values for the individual waste materials can be approximated by using the equation

known as the modified Dulong formula:

E (kJ/kg) = 337C + 1419(H – 0.125O) + 93S + 23N
%weight on dry basis, where:

R: Plastics C = Carbon
G: Garbage H = Hydrogen

P: Paper 0 = Oxygen
W: Water S = Sulfur

B: Combustible volatile matter

Note: % weight on dry basis = mdry weight/msample
Using a more direct approach, Khan et al. estimated the energy content from MSW with the

equation: E = 0.051[F + 3.6CP] × 0.352PLR

where E is the energy content in MJ/kg, F the percent by weight food in the waste, CP the
percent cardboard and paper and PLR the percent plastic and rubber.

Refuse can be characterized as being made up of organic materials, inorganic materials, and

water. Moisture and inorganics (e.g., ash) will diminish the heat of combustion in a sample. Thus,
the energy content of MSW on dry weight of sample (after drying) is the higher heat value (HHV).

In treatment engineering, LHV is more important than HHV although LHV is lower than HHV

Moisture - free (dry basis): HHV = LHV (as discarded) × 100%/(100% - %moisture)
Dry ash - free dry basis: HHV = LHV (as discarded) × 100%/(100% - %moisture - %ash )

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