Incineration is a modern combustion technology where harmful wastes are transformed into gases and incombustible solid waste (Hester & Harrison, 1994). It is commonly used in burning municipal and industrial wastes. During incineration, there are factors that affect the quantities and composition of gases emitted. In considering the incinerator design, operation, and waster properties, the factors are (Rand et al., 2000): physical and chemical properties of waste; Combustion efficiency; and residency time.
Physical and chemical properties of waste determine the composition of gases emitted in the sense that if sulphur was a constituent in the waste, then the expected emissions after combustion will be Sulphur dioxide. On quantity of gases produced, presence of inhibitors in the waste could alter the amount of gases produced (Woodard, 2001). For instance, the presence of iron in the waste containing sulphur during combustion would alter the quantities of sulphur dioxide produced as some sulphur would react with iron to form iron sulphide.
The combustion efficiency determines the composition and quantities of gas emissions. For example, high efficiency combustion ensures that nearly all methane is converted to carbon dioxide and water vapour and less efficiency results to considerable emission of methane in addition to water vapour and carbon dioxide (Hester & Harrison, 1994). In considering residency time, waste should be exposed to the combustion temperatures for a specified time or else gasses emitted will be different from what could have been emitted if the residency time was inadequate.
The factors that influence the amount of solid residues in waste during incineration are temperatures, the nature and size of particles, and energy content of the waste (Rand et al., 2000). Higher temperatures in combustion of wastes results in complete volatilisation of most solid wastes hence less solid residues compared to if lower combustion temperatures are used. Furthermore, the nature of waste determines the amount of residue where inorganic or metallic wastes form more solid residues than organic wastes which form more gaseous emissions. Wastes that have higher energy contents are seen to have more solid residues than those that have lower energy content. This factor is considered in designing an incinerator that would incorporate the energy contents of wastes.
Hester, R., E. & Harrison, R., M. (eds). (1994). Waste Incineration and the Environment. Manchester: Royal Society of Chemistry. Pp. 53-67
Rand, T., Haukohl, J. & Marxen, U. (2000). Municipal Solid Waste Incineration: requirements for a successful project. Washington D.C: World Bank. Pp. 4-10
Woodard, F., (2001). Industrial Waste Treatment Handbook. Boston: Butterworth-Heinemman. Pp.78-98