Encyclopedia of Environmental Science and Engineering, Volume I and II

MANAGEMENT OF SOLID WASTE 651

Japanese have been leaders in this area using high pressure

presses to provide solid cubes suitable for use in building new

land in tidal areas. A facility is being successfully operated

in New Jersey. More details may be found in the discussion

of compaction.

Incineration

Incineration is essentially a method for reducing waste volume

and at the same time producing an inert, essentially inor-

ganic, solid effluent from material which is largely organic.

Typical feed analyses are shown in Table 4. In addition to the

solid product a gas is produced consisting mainly of CO 2 , H 2 ,

O 2 and N 2 but containing other gaseous components in tract

quantities depending on the type of material burned and the

operating conditions. Incineration is not an ultimate disposal

method in that the solid residue which is primarily an ash

containing some metal must still be disposed of, usually as

landfill. The primary advantage is that it reduces the volume

to be disposed of and results in a “clean” inert fill. For every

100 tons of material fed to the incinerator approximately

20 tons of residue result. The volume reduction is even more

significant, often resulting in a 90% lower solids volume for

organic materials.

The theory of incinerator operation is very simple. A unit

is designed to expose combustible material to sufficient air at

high temperature to achieve complete combustion. Combustion

is usually carried out in fuel beds to ensure good contact of air

and refuse. Several types of configurations are used to achieve

contact; these include concurrent flow of fuel and air-underfire,

countercurrent flow of fuel and air-overfire, flow of fuel and

air at an angle to each other—crossfeed; and combinations of

these. The combustion is basically the same for all methods

in that at the ignition front oxygen is rapidly consumed in the

reaction O 2 
 C → CO 2 and if oxygen is depleted CO 2 
 C →

2CO. Therefore, sufficient oxygen must be available to obtain

complete combustion; usually this is provided by adding addi-

tional air in the chamber above the fuel. Incinerators are typi-

cally operated with about 50 to 150% excess air in order that

the gas temperatures do not drop below that required for good

odor-free combustion; this is usually in the 1700–2300°F range.

Recent trends have been to go to the higher part of this range

while old units often operate at 1600°F or below. The effect of

excess air on gas composition is summarized in Table 17 for

a typical refuse. A detailed discussion of typical air require-

ments and their effect on the thermal balance may be found in

Principles and Practices of Incineration.^18

Trace components in the incinerator-start gas include

some SO 2 and NO x. The former depends on the sulfur in the

refuse and is typically around 0.01 to 0.02%. Nitrogen oxide

is generally formed in combustion processes and depends on

the amount of excess air and to some degree the operating

temperature of the incinerator. Typical values of two pounds

of equivalent NO 2 per ton of refuse have been reported. 19,20

FIGURE 2 Sanitary land fill operations: Credit: US Public Health Service.

C013_002_r03.indd 651C013_002_r03.indd 651 11/18/2005 2:27:19 PM11/18/2005 2:27:19 PM