Encyclopedia of Environmental Science and Engineering, Volume I and II

MANAGEMENT OF SOLID WASTE 653

This is equivalent to 500 to 1000 ppm of NO x in the off-

gas depending on the refuse composition and the amount

of excess air. Other trace components can be found in the

off-gas and air summarized in Table 18. Their presence or

absence is very much dependent on the type of refuse incin-

erated and the operating conditions.

Particulate matter is also present in the stack gas and is

removed by the usual techniques discussed in the section on

Air Pollution. Particulate loadings of 3 to 25 pounds per tonne

of refuse burned have been reported. 21,22 Typically, particles

range from 5 to 350 microns in size with 30% by weight

under 10 microns and 75% less than 200 microns in size.

Solids residue from incinerators will vary widely with the

type of feed and incinerator operating conditions. Typical resi-

dues have been examined by the Bureau of Mines. The results

of this work are summarized in Table 19. A typical ash and

slag chemical analysis may be found in Table 20. This residue

can be utilized in road fill or separated (see Reclamation).

Incineration can effectively be divided into local, onsite

and central methods. The basic principles are the same but

the applications vary considerably. Central incineration facil-

ities handle refuse from many sources and a wide variety of

feeds. Local incinerators handle either special feeds, onsite,

such as industrial or hospital wastes, or serve a particular

small location such as an apartment house. Size is not nec-

essarily a criterion although generally central incineration

facilities have capacities in excess of 100 tons per day.

At the present time there are about 200 central incin-

eration facilities in use (making this type of waste reduction

facility the most prevalent one). Central incineration handled

about 15 million tons of waste annually and is concentrated

in the northeastern part of the United States. It is also widely

practiced in Europe. The practice of incineration of wastes

was growing as land for fill, particularly in urban areas,

becomes scarcer and technological improvements provide

more efficient and cleaner systems.

A typical incineration facility will have a capacity rang-

ing from 100 to 1200 tons per day with individual furnaces

usually limited to a 300 ton per day rating. Most large incin-

erators today are continuous-feed rather than batch design

because operation is more controlled and easier. In addition

the absence of the heating and cooling cycle results in lower

maintenance and a higher capacity per investment dollar. Air

pollution control is improved significantly in continuous-feed

incinerators are compared to batch plants.

A large central incineration facility is schematically

shown in Figure 3. It can be divided into five areas: (1) the

receiving section which includes the weight station, storage

hopper and bucket crane; (2) the furnace—which includes

the charging hopper, stokers, furnace chamber and air feed

system; (3) the effluent gas treating facilities; (4) the ash

handling system; and (5) the cooling water system. The par-

ticular system shown does not have provision for waste-heat

recovery; only a few systems incorporate this at present.

For mixed refuse, a typical refractory-wall incinerator

will have 12.7 cubic feet in the primary furnace chamber and

18.5 cubic feet in the secondary chamber per ton of refuse per

24 hours with a grate loading of 77 pounds per square foot

per hour. Volume and loading requirements will vary with the

type of feed as well as furnace configuration. Typically the

values quoted correspond to a 12,500 Btu per hour per cubic

foot heat release. A detailed discussion of furnace design is

TABLE 12

Generation by type of solid wastes from the mineral and fossil and fuel industries (1965)

Industry Mine waste Mill tailings

Washing

plant rejects Slag

Processing plant

wastes

Total

(thousands

of tons)

Copper 286,600 170,500 — 5,200 — 466,700

Iron and steel 117,599 100,579 — 14,689 1,000 233,877

Bituminous coal 12,800 — 86,800 — — 99,600

Phosphate rock 72 — 54,823 4,030 9,383 68,308

Lead-zinc 2,500 17,811 970 — — 20,311

Aluminum — — — — 5,350 2,350

Anthracite coal — — 2,000 — — 2,000

Coal ash — — — — 24,500 24,500

Other — — — — — 229,284

Total 419,571 288,900 144,593 23,919 40,233 1,146,500

TABLE 11

Unit generation rates

Animal Waste (tons unit yr)

Cattle 12.0

Cows, milk 10.6

Hogs 8.0

Sheep 3.0

Chicken, broilers 0.0045

Turkeys 0.025

Chicken, layers 0.047

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