Page 13 - mobile Workbook-chapter 2

2.8 Chemical properties

According to G. Tchobanoglous,the information on the chemical composition that constitute

MSW is important in evaluating alternative processing, and recovery options [1]. The three most
important properties to be known are:

• Proximate analysis

• Ultimate analysis
• Fusing point of ash

2.8.1 Proximate analysis for the combustible components of MSW

Proximate analysis is done in order to estimate the heating value of municipal solid waste fuel
and it includes the following test:

• Moisture (ASTM E1756-01)
• Volatile combustible matter (ASTM E-872)

• Ash (ASTM D1102)
• Fixed carbon

Volatile combustible matter is vapor released when the solid fuel is heated at 950 C for two
o
hour. It is important to note that the test used to determine volatile combustible matter in a

proximate analysis is different from the volatile solids test used in biological determinations.

o
Ash is the inorganic solid residue left after the fuel is completely burned at 575 C for an hour.
Fixed carbon represents the solid carbon in the municiple solid waste that remains in the char

after devolatilization process. Fixed carbon is the combustible residue left after volatile matter is
removed; ignition at 600 to 900°C

%fixed carbon = 100% - %moisture - %ash - %volatile matter

2.8.2 Ultimate analysis

Ultimate analysis (elemental analysis) is done to identify the major atoms in sample (C, H, O,
N, S and ash) even the weight. Based on that, chemical formula of waste can be estimate.

Five materials tend to predominate in the organic portion of MSW: cellulose, lignins, fats,
proteins and hydrocarbon polymers. Cellulose accounts for the majority of the dry weight of MSW

and is the predominant compound in paper, wood, food waste, and yard waste. Sulfur is not a

component of any solid waste category, except perhaps building materials (gypsum panels) or
yard waste. Nitrogen occurs mainly in food waste, grass clippings, and textiles (e.g., wool and

nylon) [3]. Chlorine occurs in the organic form as polyvinyl chloride (PVC) and vinyl, and paper
products bleached with chlorine. Chlorine may also occur in the inorganic form as sodium chloride

and other simple salts. The ash fraction is the residual remaining after combustion and is primarily
inorganic although some organics may remain as well. Ash can impart significant environmental

and public health effects if improperly managed. Ash may exit an incinerator and enter the

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