Ultimate analysis

1. Ultimate analysis is useful during mass balance calculations for a chemical or thermal process. Ultimate analysis of waste is carried out to determine the proportions of carbon, hydrogen, oxygen, nitrogen and sulphur.
2. The ash fraction should also be determined because of its potentially-harmful environmental effects, brought about by the presence of toxic metals-cadmium, chromium, mercury, nickel, lead, tin and zinc.
3. Other metals, such as iron, manganese, calcium, magnesium and sodium are also present but because they are not toxic, they do not present a serious problem.

Proximate analysis

1. Proximate analysis is important in evaluating the combustion properties of waste or waste derived fuel. The fractions of greatest interest are: moisture content, ash, volatile matter and fixed carbon
2. Moisture adds weight to the waste fuel without increasing its heating value and the evaporation of water reduces the heat released from the fuel. Ash also adds weight without releasing any heat during combustion.
3. Volatile matter is that portion of the waste that is converted to gas before and during combustion and fixed carbon represents the carbon remaining on the surface of grates as char. High proportion of fixed carbon requires longer retention time to achieve complete combustion.