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Tuesday, January 10, 2012

What is incineration?

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Burning under controlled conditions is called as incineration.

Burning of waste under controlled conditions is a rather quick method of solid waste disposal especially in crowded cities. The heat so produced, may be utilized for some useful purposes. Ashes left after burning are hardly 8 to 10 percent of the total mass of the waste material.

Burning of waste may either be done in the presence of air or in its absence. Burning in the absence of air is called as Pyrolysis where as burning in the presence of air is just called as incineration.

An incinerator in its simplest form consists of a furnace which is provided for feeding the solid waste into the furnace. The burnt ash is taken out through the ash door.

Incineration is a preferred choice for the biomedical waste because it eliminates infectious organisms due to very high temperature ranging from 7500c to 980 0c. Secondly, it is very economic process due to the fact that a suitable landfill site for the disposal of biomedical waste is hard to find and it often takes a high charge in the transportation of these wastes.

There are two types of incinerators - Batch type, and Continuous feed type incinerators. The batch type incinerator is a simple device operated manually. A complete combustion in this type of incinerator does not take place and the temperature produced due to burning of waste does not remain in a uniform range.

Most of incinerators in use today are of continuous type. These incinerators are fitted with large storage bins, automatic feed hoppers, varied types of moving grates and ash discharge systems so that a uniform temperature of 750c to 980oc is maintained for combustion. These incinerators are fitted with pollution control devices such as gas scrubbers and electrostatic precipitators.

The use of water walls in the combustion chambers is a recent modification in incinerator. The water wall consists of vertically arranged boiler tubes of steel through which water is circulated. The water, heated in these ways is used in steam generation. At the same time water used in incinerator acts as a coolant. The heat produced through burning of wastes in incineration is also used for space heating, power generation, de-salination etc.

Incinerators of general type have many undesirable effects like release of particulate, smokes and gases like carbon dioxide. Most often many toxic substances like dioxins, heavy metals and compounds of chlorine etc. are also emitted out from incinerators.

Key Words:Pyrolysis,infectious, scrubbers, electrostatic precipitators, water walls, dioxins,

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