Page 255 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Mechanical Separations 225

Table 4-1 Table 4-3
Sizes of Common Dusts and Mists Dry Particle Screen Sizes
Average Particle Diameter, W. S. Tyler Screen
Dust or Mist Microns Scale Micron (approximate)
Human Hair (for comparison) .... 50-200 80 · · · · · · · · · · · - · · · · ·. · · - 174
Limit of visibility with naked eye .. 10-40 100 .................................. 146
Dusts 115 .................................. 123
Atmospheric dust . 0.5 150 .............................•.... 104
Aluminum . 2.2 170 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
Anthracite Coal Mining 200 . . . . . . . . . . . . . . . . . . . . . . . . . . . • . . . . . . 74
Breaker air . 1.0 250 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
Mine Air . 0.9 270 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Coal Drilling . 1.0 325 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Coal loading . 0.8
Rock drilling . 1.0
Alkali fume . 1-5
Ammonium Chloride fume . 0.05-0.1-1 Table 44
Catalyst (reformer) . 0.5-50
Cement . 0.5-40-55 Approximate Particle Sizes From Liquid Full Cone
Coal . 5-10 Spray Nozzles*
Ferro-manganese, or silicon . 0.1-1
Foundry air . 1.2 Liquid: Water
Flour-mill . 15
Fly Ash (Boiler Flue gas) . 0.1-3
Iron (Gray Iron Cupola) . 0.1-10 Operating Pressure, Approx. Mean Particle
Iron oxide (steel open hearth) .. 0.5-2 Nozzle Size, In. Psig Size, Microns
Lime (Lime Kiln) . 1-50 ---y;----:-:-:-: . . . . . . . . . . . 15 . . . . . . . . . . . . . . . . 1200
Marble cutting . 1.5 60 . . . . . . . . . . . . . . . 750
Pigments . 0.2-2 % 10 1600
Sandblasting . 1.4 40 1000
Silica . 1-10 ............... 15 1750
Smelter . 0.1-100 40 1250
Taconite Iron ore lYz 15 2300
(Crushing & Screening) . 0.5-100 60 .........•...... 1800
Talc · ·. 10 3 . . . . . . . . . . . . . . . 10 5300
Talc Milling . l.5 30 .........•...... 4300
Tobacco smoke . 0.2
Zinc oxide fume . 0.05
Zinc (sprayed) . 15 *Private communication, Spraying Systems Co., Bellwood, Ill.
Zinc (condensed) . 2
Mists
Atmospheric fog . 2-15 Example 4-1: Basic Separator Type Selection [2, 17]
Sulfuric acid . 0.5-15
Compiled from References 1, 13, and 15. A suitable collector will be selected for a lime kiln Lo
illustrate the use of the Sylvan Chart (Figure 4-3). Refer-
ring to the chart, the concentration and mean particle
Table 4-2 size of the material leaving the kiln can vary between 3
Typical Dust Size Analysis-IC· and 10 grains/ cu ft with 5 to 10 microns range of mass
mean particle size. Assume an inlet concentration of 7.5
DUST grains/ cu ft and inlet mean particle size of 9 microns.
Cement ----- Projection of this point vertically downward Lo the collec-
Kiln Foundry
Rock Exhaust Sand Limestone tion efficiency portion of the chart will indicate that a low
-�--
Sp. Gravity 2.63 2.76 2.243 2.64 resistance cyclone will be less than 50% efficient; a high
Apbarent we, efficiency centrifugal will be between 60 and 80% effi-
1 s./cu.ft. . .... 61.3 52.0 45.9 72.0
Screen Analysis cient, and a wet collector, fabric arrester and electro-stat-
( Percent passed) ic precipitator will be 97%-plus efficient. The last three
100 Mesh 98.8 99.6 91.2 85.6
200 Mesh ..... 92.8 92.2 78.4 76.4 collectors are often preceded by a precleaner so a high
325 Mesh ..... 79.6 80.8 67.6 66.4 efficiency centrifugal will be selected. Using the average
400 Mesh ..... 70.8 73.2 64.4 63.2
Elutriation Analysis: line of this group, the efficiency will be 70%. Therefore,
Percent Under the effluent from this collector will have a concentration
Terminal Velocity of 7.5(1.00 - 0.70) = 2.25 grains/cu ft.
320 In./min. 75.8 78.0 64.2 70.5
80 In./min. .. 37.0 61.0 53.9 52.0
20 In./min . . . 17.5 40.8 42.0 33.0 Draw a line through the initial point with a slope par-
5 In./min . . . 8.9 23.0 32.0 18.0 allel to the lines marked "industrial dust." Where devia-
-�------ tion is not known, the average of this group of lines will
*Compiled from Bulletin No. 1128, American Blower Corp.,
Detroit, Michigan. normally be sufficiently accurate to predict the mean par-