Page 126 - Materials Chemistry, Second Edition

CAT3525_C04.qxd 1/27/2005 11:12 AM Page 97
Characterization of Solid Waste 97

TABLE 4.23
Typical Particle Size Distribution of MSW

Component Size Range (mm) Typical (mm)
Food 0–200 100
Paper and cardboard 100–500 350
Plastics 0–400 200
Glass 0–200 100
Metals 0–200 100
Clothing and textiles 0–300 150
Ashes, dust 0–100 25
Source: Kiely, G., Environmental Engineering, McGraw-Hill,
New York, 1997. Reproduced with kind permission of
the McGraw-Hill Companies.

Using the five equations provided above, calculate the particle diameter D. What is the range of
variation in the calculated values?
D l 4
D ( l w h ) / 3 2.23
D (l w) / 2 2.6
D (lw) 1/2 2.19
D (lwh) 1/3 1.93

Particle diameters range from 1.93 to 4 units, i.e., by a factor of 2.1.
Obviously, MSW will contain particles having a wide range of individual sizes. Under such cir-
cumstances, the particle size is often expressed as mean particle diameter. A number of calculations
are possible. Some examples include:
D D D D ··· D
1
n
2
3
4
arithmetic mean D
n
geometric mean D (D D D D ··· D ) 1/n
1 2 3 4 n
W D W D W D W D ··· W D n
1
3
2
3
2
1
n
4
4
weighted mean D
W W W W ··· W n
2
1
4
3
M D M D M D M D ··· M D n
3
n
4
3
1
1
4
2
2
number mean D
M M M M ··· M
1 2 3 4 n
where W is the weight of material in each sieve size, M the total number of particles in each sieve
size and n the number of sieve sizes (diameters).
EXAMPLE 4.9
Given the data for the following waste sizes,
Sieve Size (mm)
Particle diameter (mm) 100 75 50 25 5
Weight of fraction (kg) 2 6 12 4 4
Number of particles 225 310 500 2000 5750