INDUSTRIAL AND ENGINEERING CHEMISTRY
2388
establishment and generous support by this company of its Laboratory for Agricultural Research near Salt Lake City were equally important. For over three decades this research group has not only kept the company fully advised on atmospheric pollution and remedial measures a t its many plants over the country, but has published many papers, covering research in plant fumigation and the development of procedures of the highest accuracy in experimental work in that field. The recorder, developed by Thomas ( I S ) of that group, is now widely employed in sulfur dioxide determinations. This remarkable analytical robot makes a determination of sulfur dioxide and records it, automatically, every 20 minutes with an accuracy of a fraction of a part in a million parts of air, and requires servicing only once aweek for replenishing solutions and exchanging recording charts. Later designs (15, 16) record a determination every 10 or 15 seconds and are adapted also to the estimation of total gaseous sulfur compounds in the air. The fifth decade of the half-century or so since the smoke problem came across the Atlantic to plague us is fully covered b y the ensuing papers in this symposium. Research in our universities, research institutes, and industrial research laboratories is finding more lines of approach, more tools to work with, more ideas, than ever before. Most of our large cities are attempting t o work out sound measures of inspection and control. I n the West, especially, there is a rapid increase in the use of hydroelectric power in private homes and industry, and the use of natural gas, rapidly becoming nationwide, is a big step forward. Thus there is promise that the pendulum will soon be swinging toward less polluted atmospheres in iimerica. Coal smoke and slums have much in common. Both promote squalor, cut out the
Vol. 41, No. in
sunshine, cultivate gloom and uncleanlniess, and set up conditions which in general are bad. There i s n o aubsfitute for clean air in any human environment.
LITERATURE CITED Cohen, J. B., and Rushton, A, G,,Smoke, A Study of Town 2nd ed., London, E. Arnold & Co., 1925. Dean, R. S.,and Svain, R. ElsI C.7- S . Bur. Mines, Bull. 453 (1944).
Harkins, W. D., andswainsR,. E,, .Ic Am, Chem. SOC.,29,970--98 (1907) Ibid., 30,928-46 (1908) e
~
Haselhoff, E., and Lindau, G., ””DieBeschadigung der Vegetatioa, durch Rauch,’nBerlin, Bosntriiger, 1903, Hewson, E. W., IND.EKG.CHERI.,36, 195-201 (1944). Holmes, J. A., Franklin, E. C., and Gould, R. A,, U.S.B~rut.. M i n e s , Bull. 98 (1915).
Meller, H. B., IND. EXG.CHEM.,27, 949 (1935). Meller, H. B., and Sisson, L. B., Ibid., 27, 1309 (1935). National Research Council of Canada, Ottawa, Associate Co~rrmittee, “’Effect of Sulfur Dioxide on Vegetation,” 1939. O’Gara, P. J., and Fleming, E. P.,J. IND.ENG.CHEM.,14, 744 (1922). Swain, R.E., and Harkins, 11‘.J - ) ~ .lo , A m , Chem. Soc., 30, 915--2in (1908) * Thomas, &I. D., I X D . ER’G.C H E M , , B K a L . E D . , 4,253-6 (1932). Thomas, M. D., and Hill, G . R.. Jr., Plant Phys., 10, 291-302 (1935) Thomas, M. D., Ivie, J. O., Abersolde, J. N., and Hendricks, 11, I N D . EXG.CEEM., ) \ N I L . ED., 15, 28‘7-90 (1943). Thomas, D., Ivie, J, O., and Fitt, T. C., Ibid., 18, 383-95 (1946). Wells, A. E., J. IKD. ENG.CHEM.,9,640-59 (1917). Weler, 4.,“Cntersuchungeu uber die Einwirkung schwofligoSaure auf die PflanzenPs’Revlin, Rorutrager, 1905. e
w.,
K c c ~ n - mMarch 7, 1040.
Dust and Fume Stand LOUIS C. MCCABE, A. H. ROSE, W. 9. HAMMING,
AND
F. H. WETS
2.0s Angeles County Air Pollution Control D i s t r i c t , Los Angeles, Calif.
T
HE meteor ologicalfactors
T h e average weight of the hourly charge of materials Atmospheric contamiriainfluencing air pollution used in a process determines the amount of solids (dusts tion may be caused by liquids, ( g ) , the technical aspects of and fumes) that may be released from stacks in Los Ansolids, or gases, but the standgeles County. Data from nonferrous, steel, gray iron, and ards discussed here are cont h e smog problem ( 3 ) , and electric iron industries were used in developing the “masscerned only with solids, which the nature of industrial dusts and fumes in the Los Anpeles rate” standard which has been in use since March 1949, are further classified as dusts area ( 4 ) have been discussed and fumes. They are definrd in the regulations as folloa i: by others. These studies Fumes (1)are solid particles commonly generated by the condemonstrate the necessity for limiting the amount of pollution densation of vapors of solid matter after volatilization from the entering the atmosphere from industrial and other sources. Durmolten state. They may be generated by sublimation, distill%ing t h e past year, the Los Angeles County Air Pollution Control tion, calcination, or chemical reaction, whenever such procehscw District and the industries that release dust and fumes in their create air-borne particles. stack effluents have studied the nature and quantity of the mateDusts (1) are solid particles released to the air by natural rials t h a t contribute to air contamination. The development of forces, or generated by mechanioal processes such as crushings thc dust and fume standards discussed herein is based largely on grinding, milling, drilling, demolition, bagging, sweeping, and these tests. shoveling. More than half of the 100 tons of industrial dusts released to Over a period of several months, dust and fume data from furthe atmosphere daily is of submicron size. Below one micron, nace operations were collected, tabulated, and analyzed (Table l the particles are most effective in scattering light and, therefore, They represent the various metallurgical installations in the Los o n t r i b u t e to low visibility. They do not settle unless washed Angeles area, correlate well, and are of sufficient accuracy for use out by rain and there is normally no effective removal in this manin dust and fume standards. ner except in the winter and early spring months. Temperature Initially, attempts were made to develop standards of emission inversion, the low average wind velocity, and the topography of based on the opacity of the stack effluent or on the total process the area prevent easy dispersion and removal from the basin. As enthalpy. These were of little practical value, but the concept the natural agencies hinder thorough cleansing of the atmosphere, of total process enthalpy led t o the use of total process weight as a the standards described here have been incorporated in the rules basis for establishing the weight of solids that may be released t o and regulations of the Los Angeles Air Pollution Control District the atmosphere. This ignores the relationship between the volto cause the maximum collection of dust and fumes a t the source, ume of effluent gases and the weight of solids discharged from a consistent with the availability of equipment for the purpose.
>.
November 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
2389
and electric iron industries. In presenting them graphically, process weight per hour was plotted K as the abscissa and per cent of process weight a R B Red brass per hour as the ordinate (Figure 1). The experi0 mental data from each furnace established a point s m on each of two curves. The values of maximum g20 hourly discharge formed one curve and the values 8 a of average discharge formed another. + z V The third curve was developed t o show the a. w maximum discharge, expressed as a percentage d10 2 of process weight, permitted in any hour. Several L 0 steps are involved in its development. Maximum .x stack losses, as indicated by the maximum m W hourly discharge curve for given process weights, z were reduced by known efficiencies of collect2 0 a PROCESS WEIGHT PER HOUR, THOUSANDS OF POUNDS ing equipment t o establish a set of new points. The collecting efficiencies used were those t h a t jFigure 1. Derivation Curve of Actual 'and Allowable Fume and Dust Discharges can be obtained with commercial equipment t h a t is within economic reach of industry. Large 0 industrial units constitute a greater point source of atmospheric contamination, and can usually handle high efficiency collection more economically than small units. These considerations are reflected in t h e Los Angeles District regulations and are illustrated by the allowable discharge curve. T h e average collecting efficiency required of small industrial units is approximately 80%; of large industrial plants, approximately 90%. The formula for the allowable discharge curve was determined using a n asymptote and two points on a curve because the d a t a when plotted approximate a portion of an equilateral hyperbola. The asymptote was calculated t o be 0.06% of the process weight. This was done by using a loss of 3% of the process weight and applying t o this loss a collection equipment efficiency of 98% (see data curve 1). Efficiencies of this order or better are obtainable PROCESS WEIGHT PER HOUR, P W N D S with a t least two types of equipment. Thus, only the largest process unit having a 3% loss Figure 2. Derivation Curve of Allowable Discharge would be required t o collect 98% of its stack discharge. stack. However, i t simply and effectively limits the amount of The two points chosin for the curve to pass through were: (1) solids discharged, and makes it unnecessary to consider dilution that representing the small industries operating at a process in control standards. weight of 250 pounds per hour; and (2) that representing the Certain variables considered in the study and used in the regulations are defined as follows: Table I. Summary of Data on Dust and Fume Losses from Metallurgical Industries Process weight is the total weight Effluent of all materials used in the process, to Stack Loading Max. excluding air, gas, and oil, but including Process process G./Cu. Feet at StaAdard Rate of Discharge solid fuels. Type of Height Time, Max./ Cu. Feet at Hourly, Av., Effluent gas-process weight ratio is Process Lb./Ho;r Min. Av. hour Standard 5% the volume of efRuent gas, in cubic Red brass 500 72 0.250 0.393 273 1.53 0.97 feet a t standard conditions, per pound 435 84 0.254 0 395 289 1.63 1.04 152 1,500 0.320 of material processed. 0.559 172 1.38 0.79 1,620 130 0.595 0.903 147 1.92 1.26 Maximum hourly discharge is the 470 Yellow brass 102 0.410 0.780 231 2.57 1.35 maximum mass rate of discharge of 535 0.452 90 2.15 0.762 197 1.27 Brass smelting 2,000 25 hours 2.11solid material in a single hour dur... 0.390 226 1.26 630 95 0.985 282 3.95 ing the process cycle. It is expressed 5,000 Lead smelting 24 hours 0 385 355 3.01" 1:io as a percentage of the process weight Steel, open hearth 14,500 8 hours 0:%3 2.000 56.6 0.63 1.58 10,200 per hour. 10 hours 0.863 1.720 53.1 1.31 0.65 Gray iron 9,250 1.604 80 1.604 32.5 0.75 0.75 Average discharge is the average mass 13,450 1.110 156 1.110 81.5 1.45 1.45 rate of discharge for the process cycle. 18,900 320 0.798 0.56 0.798 49.5 0.56 8,350 It is expressed as a percentage of the Data by outside laboratory 1.07 1.07 process weight per hour. Gray iron discharges constant throughout melt cycle. Average and hourly rate of discharge equal K
$30
yl$J:
...
T h e data (Table I) are representative of the nonferrous, steel, gray iron,
...
3,325 130 0.306 1.17 Steel, electric a % calculated, based on average increase found in nonferrous industry.
1.02
0.29
INDUSTRIAL AND ENGINEERING CHEMISTRY
2390 Table 11.
Vol. 41, No. 18.
relatively large industries operating a t 2500 pounds per hour. At these hourlv process weights, the average maximum loss is 2.02 and 1.8570, respectively, as shown by the average discharge curve. Applying 80% collecting efficiency for small industries to the 2.0270 loss, an allowable loss of 0.404% is derived as one point on the allowable discharge curve. Applying 90% collecting cficiency for large industries to the 1.85% loss, a second point is derived having a value of 0.1S570. Using these two points, the asymptote as calculated above, and the formula for a hyperbola, the constants in the equation v e r e calculated. This curve is (z 1000) (y - 0.06) = 440 (Figure 1). An additional curve, expressing the allowable discharge in pounds per hour. rather than in per cent, was derived from the original equation (Figures 2 and 3). This curve enables the allowable discharge t o be read directly in pounds per hour rather than in per cent of process weight.
Maximum Allowable Discharge per Hour
Process Alloxable Allowable Process AllowabIe Allowable Process Process Discharge Weight Discharge Weight Discharge Disoharge Weight Weight per per per per per per per per Hour, Lb. Hour, Lb. Hour, Lb. Hour, Lb. Hour, Lb. Hour, Lb. Hour, Lb. Hour, Lb. 9.03 1300 3.26 3500 5.52 8,500 0.24 50 9.36 1400 3.40 3600 5.61 9,000 0.46 100 3700 9.67 1500 3.54 5.69 9,500 0.66 I50 10.0 3800 5.77 10,000 1600 3.66 0.852 200 3900 1700 3.79 6.85 10.63 11,000 250 1 03 4000 5.93 11.28 12 000 1800 3.91 1.20 300 4100 6.01 11.89 13:OOO 1900 4.03 1.35 350 4200 12.50 2000 4.14 6.08 14,000 400 1.50 4300 13.13 4.24 6.15 15,000 2100 1 63 450 4400 13.74 2200 4.34 6.22 16,000 1.77 500 4500 14.36 4.44 6.30 17,000 2300 1.89 550 4600 14.97 6.37 18,000 4.55 2400 2.01 600 4700 15.58 6.45 19,000 4.64 2500 2 12 650 4800 16.19 6.52 20,000 2600 4.74 2 24 700 22.22 6.60 30,000 4900 2700 4.84 2.34 750 5000 28.3 6.67 40,000 4.92 2.43 2800 800 84.3 5500 5.02 7.03 50,000 2900 2 53 850 6000 7.37 5.10 3000 2 62 900 6500 7.71 2.72 3100 ;.18 950 7000 8.05 ~ . 2 7 3200 2.80 1000 7500 8.39 3300 5.36 2.97 1100 8000 8.71 5 . 4 4 3.12 3400 1200 Where process weight falls between figures stated, values of allowable disoharge per hour are interpolated. I n no case is particulate matter in excess of 4 0 pounds per hour allowed t o emit from a n y one source. Process weight is defined as total weight of ram materials o r materials entering process (not weight of finished product). Solid fuels charged are considered as part of process weight b u t liquid a n d gaseous fuels a n d combustion air are not. I n continuous operation average rate of feed is used. I n batch operation total batch weight, divided by operating time of a batch cycle determines process weight per hour.
+
Pounds of allowable discharge per hour = process weight per hour (pounds)
100 b.06
440 - ___process weight per hour
X
(pounds)
- 1000
No set colIecting efficiencies are required by the regulations, but the weight of material discharged must be below a stated number of pounds per hour. Inasmuch as a curve for allowable discharge is not easily incorporated into regulations, t h e maximum allowable discharge, expressed in pounds per hour for selected weights, is presented in Table 11. A further restriction was made on the allowablc discharge in t h a t it becomes constant when 40 pounds per hour are reached, regardless of the process weight involved.
LITERATURE CITED Ani. SOC. Heating Ventilating Engrs., “Heating, Ventilating, and Air-Conditioning Guide,” Chap. 10, p. 184, 1946. (2) Beet, G. P., and Leopold, L. B., Trans. Am. Geophys. Union, 28, No. 2, 173 (April 1947). ( 3 ) Johnstone, H. F., J. fnd. Hug. Tosicol., 30, No. 6, 358 (No(lj
0
vember 1948). (4) McCabe, L. C., et al., Ivn. EN%CHEM.,41, 2486 (1949),
PROCESS WEIGHT PER HOUR POUNDS
Figure 3. Derivation Curve of Allowable Discharge
RECEIVEDMarch
26, 1949.
