CHEMICAL PROPERTIES OF MSW

Information on the chemical composition of the components that constitute MSW is important in evaluating alternative processing and recovery options. For example, the feasibility of combustion depends on the chemical composition of the solid wastes. Typically, wastes can be thought of as a combination of semimoist combustible and noncombustible materials. If solid wastes are to be used as fuel, the four most important properties to be known are:

1. Proximate analysis that includes the follow­ing tests:

a. Moisture (loss of moisture when heated to 105°C for 1 h)

b. Volatile combustible matter (additional loss of weight on ignition at 950°C in a covered crucible)

c. Fixed carbon (combustible residue left after volatile matter is removed)

d. Ash (weight of residue after combustion in an open crucible)

2. Fusing point of ash (i.e. temperature at which the ash resulting from the burning of waste will form a solid (clinker) by fusion and agglomeration. Typical fusing temperatures for the formation of clinker from solid waste range from 2000 to 2200°F (1100 to 1200°C)

3. Ultimate analysis (major elements) typically involves the determination of the percent C (carbon), H (hydrogen), O (oxygen), N (nitrogen), S (sulfur), and ash.

4. Energy content can be determined (a) by using a full scale boiler as a calorimeter, (b) by using a laboratory bomb calorime­ter, and (c) by calculation, if the elemental composition is known.

Where the organic fraction of MSW is to be composted or is to be used as feedstock for the production of other biological conversion products, not only will information on the major elements (ultimate analysis) that compose the waste be important, but also information will be required on the trace elements in the waste materials.

Date: 2014-12-28; view: 1414