Aromatic Components on Larval Stages of the Dungeness Crab, Cancer Magister Dana”, in “Fate and Effects of Petroleum Hydrocarbons in Marine Ecosystems and Organisms”, pp 210-20, Pergamon, New York, N.Y., 1977. (16) Laflamme, R. E., Hites, R. A., Geochim. Cosmochim. Acta, 42, 289-303 (1978). (17) Button, D. K., ibid., 40,435-40 (1976). (18) Hoskin, C. M., Burrell, D. C., Freitag, G. R., Mar. Sci. Commun., 2,95-108 (1976).
(19) Shaw, D. G., Sci. Total Enuiron., 8,13-20 (1977).
Received for review January 27,1978. Accepted May 24,1978. Major financial support for this work provided by the Alyeska Pipeline Service Co. Acknowledgment is made to the donors of the Petroleum Res.earch Fund, administered by the American Chemical Society, for partial support of this work.
Incineration of Polychlorinated Biphenyls with Oxygen Burner Kogaku Komamiya and Shigeru Morisaki’ Research Institute of Industrial Safety, Ministry of Labour, 5-35-1, Shiba, Minato-ku, Tokyo, Japan
Polychlorinated biphenyls (PCB’s)were easily ignited and burned by atomizing with oxygen at the tip of an oxygen-PCB burner, giving a flame temperature over 2000 “C. The theoretical flame temperature of trichlorobiphenyl with oxygen was calculated to be 2921.3 “C. The capacity of the burner was about 2 L/h, and the furnace will keep its maximum temperature of around 1500 “C without auxiliary fuel. Retention time of the furnace was from 2 to 3 s. The quantity of undecomposed 4 C B was less than 0.1 mg/kg of PCB, indicating destruction efficiencies of over 99.99999%. The concentration of NO, exhausted was evaluated to be 10-30 ppm. Hydrogen chloride was eliminated by neutralization with sodium hydroxide.
PCB’s have been widely used as various electrical devices or heat transfer fluids because of their nonflammability and other prominent chemical and physical properties. The waste disposal of PCB’s has become one of the social problems in Japan since environmental contamination or PCB poisoning was confirmed. Since more than 20 000 tons of PCB liquids are assumed to be kept mainly in chemical and electrical machinery industries, the waste treatment of these PCB’s is an urgent assignment awaiting solution. PCB’s with four or more substituted chlorines per molecule are nonflammable. Most PCB’s as industrial products are slightly combustible in air because they contain appreciable nonflammable PCB’s. Therefore, PCB’s have a great defect from the standpoint of disposal by incineration. Some investigations have been undertaken for the destruction of PCB liquids. About 2 g of PCB in alkaline 2propanol solution, in which sodium hydroxide was dissolved, was irradiated with ultraviolet light under a nitrogen gas atmosphere ( I ) . The dechlorination was mostly completed within 30 min, giving a destruction efficiency of more than 99%. A small amount of 2-chlorobiphenyl, 2,2’-dichlorobiphenyl, and 2,6,2’-trichlorobiphenylremained in the solution. Irradiation with 6oCo y-rays was also carried out in an alkaline 2-propanol solution containing 0.3-1.P? PCB liquids (2). The major products in the solution after irradiation (total dose: 0.16-0.32 Mrad) were potassium chloride, acetone, lower chlorinated biphenyls, and biphenyls. There was no reference to the destruction efficiency of the PCB’s. Kawamura et al. ( 3 ) constructed an incinerator that consisted of three combustion furnaces for the destruction of PCB liquids. In the first furnace the mixtures of PCB and kerosine (PCB concentration: 5-70%) were injected at a rate of around 30 kg/h toward a sand bed located a t the bottom of the furnace. Auxiliary fuel from propane was fed at a rate of 5-6 kg/h in the first or the third furnace. Air was fed through the sand 0013-936X/78/0912-1205$01 .OO/O
bed at a rate of -130 m3/h, and about 255 m3/h of air was also supplied for the air-propane burners. The maximum temperatures of the incinerator ranged from 1288 to 1560 “C; the temperature tended to decrease as the PCB ratio to kerosine was increased. Overall retention time of the incineration system was from 1.5 to 2.0 s. While undecomposed PCB’s were scarcely found in the exhaust from the stack, the destruction efficiencies of PCB’s were not evaluated. Recently, incineration tests of PCB-containing capacitors were conducted by Ackerman et al. ( 4 ) . The incineration system consists of a rotary kiln and a liquid injection burner feeding a common afterburner. About 210 kg/h of hammermilled fluff of PCB-containing capacitors or 360 kg/h of whole PCB-containing capacitors was fed into the rotary kiln. The temperature in the rotary kiln was nominally 1300 “C and retention time of the incineration system was from 2 to 3 s. Fuel oil was used as auxiliary fuel. Analysis of the combustion gas sample indicated a destruction efficiency of over 99.999% for the waste constituent. The authors have confirmed that PCB’s burn immediately in oxygen gas atmospheres with white-orange flames by ignition with an electrical heater, and residue after combustion is less as the ambient gas pressure is increased (5). For example, about 20 mg of PCB (KC-300: average wt % of the chlorine is 42.4%), which was placed in a small cup at an atmospheric pressure of oxygen, was destroyed with a destruction efficiency of 88.5%. The destruction efficiency increased to 97.2% at an oxygen gas pressure of 5 kg/cm2. It may be expected that a nearly complete decomposition of PCB liquids will take place by atomizing PCB’s with oxygen. The present study was performed to determine the effectiveness of the oxidative destruction of PCB liquids by using an oxygen-PCB burner.
@ 1978 American Chemical Society
Experimental Test Sample. The sample used for the incineration test was KC-300, which was produced at Kanegafuchi Chemical Co., Japan. KC-300 has similar components to Aroclor 1242, produced at Monsanto Co. Incineration System. Figure 1 shows a flow sheet for the incineration of PCB. A furnace (200 X 1400 mm, 0.18 m3) in which 29 alumina pipes were inserted a t the center of the furnace to increase heat efficiency, as shown in Figure 2, was preheated up to 1000-1500 “C using an electrical heater and an oxygen-propane burner before the incineration. The temperature rises of the preheating are shown in Figure 3. KC-300, kept in a pressure vessel with argon gas at 7 kg/cm2, was mixed and atomized with oxygen a t the same pressure at the tip of the burner shown in Figure 4 to produce a flame. The pipe from the PCB tank to the burner was heated a t 150 “C to decrease the viscosity of the PCB. This oxygen burner, with a capacity of 2 L/h for KC-300, does not require auxiliary fuel, Volume 12, Number 10, October 1978
1205
Oxygen-Propane Burner
-,
(
Flgure 1. Flow sheet for incineration of KC-300
eook
0, 4 4 N m ' l H , Propan.
1
2
3
Oxygen-PC B Burner
15KgJH 1
4
(
5
0, 5 O N m 3 1 H , PCB I 9 l t n )
6
7
8
9
Time,(hour)
Figure 3. Temperature distribution in furnace 1400-
~
%
T -
Oxygen- P C L Burner
*w
W
Alukina Barrier
1I
,
W
Figure 2. Cross sections of furnace
and'kerosine (shown in Figure 1) is only used as a cleaning solution. Hence, KC-300 remaining in the pipe and burner at the end of the incineration test may be burned in the furnace with the kerosine. This incineration system is protected with fail-safe devices and alarms in the case of shutoff of the burner flame or water supply to the burner. KC-300 is easily ignited by atomizing in the preheated furnace a t about 1500 OC near the burner; then the oxygen may be turned on. The burning of PCB's a t the burner tip can be observed a t the rear of the furnace. As shown in Figure 3, the temperature of the furnace tended to increase as the PCB incineration proceeded. This increase of temperature may be natural since polychlorinated biphenyls have considerable heats of combustion of 3700-5500 cal/g. The waste gases, containing a good deal of hydrogen chloride and sucked by a blower, may be introduced directly into the base of a caustic scrubbing tower for neutralization. Mass Balance and Heat Balance. KC-300 is a mixture comprised of mainly di-, tri-, and tetrachlorobiphenyl, and the average number of substituted chlorines per molecule is calculated to be 3.14. The following chemical reaction was estimated for the combustion of KC-300 in oxygen a t 1 atm, assuming that KC-300 only consists of trichlorobiphenyl. C12H,C13 1206
+ 1302
+
12C02
+ 3HC1+ 2H20
Environmental Science 8 Technology
The heat of formation of trichlorobiphenyl was calculated to be +95.373 kcaljmol using the value 6f the heat of combustion of trichlorobiphenyl, 5.54 kcal/g (6). The components and their percentages of a stoichiometric trichlorobiphenyl/oxygen flame were estimated by a method developed by Zelezink and Gordon (7) and are shown with their dissociated products: C02: 17.89%, CO. 33.41%, H2O: 6.37%,OH: 5.53%,HC1: 5.14%, H2: 1.54%, 0 2 : 11.78%, Clz: 0.0034%, H: 3.4396, 0: 7.23%, C1: 7.68%, and C(g): -0%. The theoretical flame temperature of the trichlorobiphenyl-oxygen burner was also calculated to reach 2921.3 "C. The actual flame temperature, of course, will be appreciably low since there is heat loss by radiation, thermal conduction, or diffusion to the furnace wall. Though heat loss will vary from flame to flame, it may be possible to assume a heat loss of about 20% (8).For the analysis of heat balance, it was assumed that the temperatures of the formed gases of Con, H20, HC1, and 0 2 were 1600 "C, and the heat loss was 20% of the net calorific value of trichlorobiphenyl. Then, the sensible heat of those gases at 1600 "C and the net calorific value (4.974 kcal/g) were calculated. When trichlorobiphenyl is burnt at a rate of 2.6 k g h (2.0 L h ) with 1.2 times stoichiometric oxygen supply, the surplus heat of 6892.1 k c a l h may be produced in this incinerator. On the other hand, the volumetric release of those gases is 30.85 m 3 h , assuming the temperature of the furnace wall is 1500 "C. Analysis. An air pollutant concentrator (Nihon Denshi Co.) was used to determine the quantity of undecomposed PCB's in the waste gases. In this equipment one washing bottle with 40 mL water and two washing bottles with 150 mL n-hexane were installed. Thirty liters of waste gas, which was drawn through an alumina pipe inserted directly at the end of the furnace, passed through the three bottles at a rate of 1L/min.
% Flgure 4. Oxygen-PCB burner
Results and Discussion One of the main problems in this incineration system was keeping up the combustion of the PCB a t the burner tip. When oxygen was not gushed into the atomized PCB in an appropriate direction, the flame of the PCB-oxygen burner and the flow rate of the PCB became small as carbonized products stuck to the burner tip. Continuous incineration of KC-300 more than 5 h was feasible by rotating oxygen gas at the outside of the burner tip (Figure 4), where the carbonized products were blown off. Another difficulty was the exhaust of white mist that might be closely related to the evolution of sodium chloride. The elimination of this mist was possible by insertion of glass-wool filters near the blower since it could not be diminished by contact with water. The results of the analyses of the waste gases and the incineration conditions are summarized in Table I. The undecomposed PCB was detected in the exhausted gases from stack and the scrubbed solution. The values in the table show the total amount of undecomposed PCB during the iricineration by this system, since the undecomposed PCB was directly collected at the rear of the furnace. The ratio of the undecomposed PCB exhausted from the stack to that dissolved in the scrubbed solution is not known. In the scrubbed solution, the PCB content varied from 7 X 10-3 to 5 X 10-4 mg/L. The total amount of undecomposed KC-300 is 0.03-0.06 mg/kg of KC-300, which indicates that destruction efficiencies are over 99.99999%. The destruction efficiency may not be influenced by the stoichiometric ratio of oxygen to the PCB in the thermal oxidation process if the ratio exceeds approximately 1.The retention time ranges from 2 to 3 s. The maximum furnace temperature will rise over 1600 "C if the incineration of KC-300 is kept up for a few hours, and it tends to decrease the amount of undecomposed PCB. When KC-300 is subjected to incineration with the oxygen/PCB ratio less than about 1,the undecomposed PCB increases the quantity by about 10 times with production of soot and carbon monoxide. This is due to the low temperatures of the furnace followed by insufficient oxidative decomposition. It was possible to continue PCB incineration without the barrier of alumina pipes in the furnace, but the values of the destruction were measured to be 0.1-0.2 mg/kg of KC-300. NO, in the waste gases tended to increase as the furnace temperature was increased, but it had relatively low concentrations of 10-30 ppm. The amount of hydrogen chloride exhausted from the scrubbing tower was about 1 ppm, and chlorine could not be detected. The advantages of the PCB liquid incineration system using an oxygen burner are: the incinerator can be relatively small since auxiliary fuel is not required, and undecomposed PCB's are scarcely present; the facilities for treatment of waste gases may become small as the volume of the waste gases is greatly decreased; and carbonized products will not stick to the burner nozzle, and incineration operations may be easy. On consumption of oxygen, 1.2441 nm3 of oxygen is required for in-
KC-300
0
10
20
30
40
50
10
20
30
40
50
Retention T i m e , ( m i n 1
Figure 5. Gas chromatograms of KC-300and waste gas
After completion of the dissolution, the 300 mL of hexane and 40 mL of water were automatically collected in a flask with acetone and additional n-hexane for cleaning the bottles and pipes. This solution of about 500 mL was concentrated to one-tenth of the original volume after having washed the solution with l N sodium hydroxide. The wastewater of about 500 mL was collected from the bottom of the scrubbing tower and concentrated to about 3 mL by repeated extrption with n-hexane and decantation to eliminate solid materials in the solution. Those concentrated solutions were analyzed' with a gas chromatograph equipped with an elkctron-capture detector (63Ni)by injection of 3 pL. Glass columns (2.1 m X 3 mm i.d.) were packed with OV 1-2% Chromosorb W(AW-DMCS) 80-100 mesh. Nitrogen was used as a carrier gas at 1kg/cm2. The injection port, column, and detector were heated at 170 "C. The PCB's in the samples were identified by comparison with chromatographic traces of KC-300, and the quantities of PCB's in the waste gas or wastewater were determined from the integration of each peak height of the chromatograms as shown in Figure 5 . The minimum amount of detectable PCB's was less than 0.1 ng in a 1 pL injection. NO,, which was all converted to NOz, was determined with a chemiluminescent NO, analyzer (Therm0 Electron Co.), and the other gases were determined with a gas chromatograph. Hydrogen chloride was measured by an optical method.
Table 1. Analyses of Waste Gases and Incineration Conditions
-
incineration rate of PCB Wh)
consu mp tion rate 91 0 2 (nm /h)
1.95 1.95 1.70 1.70 2.20 1.70
4.0 3.5 2.7 3.5 5.5 2.4
analyses of waste gases 02/PCB ratio
1.4 1.2 1.1 1.4 1.7 0.96
incineration lime (min)
78 80 97 300 105 115
02
N2
(%I
( O h )
c02 (%)
20.8 21.2 8.0 15.8 38.6 0
1.3 4.6 1.8 6.3 0.9 3.1
77.8 74.2 90.1 77.9 60.4 69.8
co (%)
NOx (ppm)
PCB (mg/kg PCB)
PCB (mg/m3)
0.01> 10.7 2.0 X lop2 0.01> 12.8 2.4 X lop2 0.01> 20.6 4.5 X lo-' 0.01> 25.0 4.1 X lo-' 0.01> 30.4 2.5 X 26.0 9.7 0.5- 1.0
0.030 0.031 0.052 0.061 0.046 0.5- 1.0
furnace temp ( " C ) T-i T-2 T-3
1561 1416 883 1592 1450 908 1535 1398 916 1642 1498 929 1653 1530 1015 1478 1345 896
retention time
(f)
2.3 2.2 2.9 2.7 2.0 3.6
Volume 12,Number 10,October 1978
1207
cineration of 1 kg of trichlorobiphenyl (0&12H,C13 1.1).
T., Shimokawa, T., Shinozaki, Y., Bull. Chem. SOC.Jpn., 47 (a),
ratio:
Acknowledgment
The authors are greatly indebted to N. Kase and K. Seki, Nihon Sanso Co., Tokyo, for their help in the construction of the incineration plant and to H. Matsui for his help with the computer calculations. L i t e r a t u r e Cited (1) Nishiwaki, T., Ninomiya, J., Anda, K., Yamanaka, S., Nippon Kagaku Kaishi, 12,2225 (1972). (2) Swai, T., Shinozaki, Y., Chem. Lett., 1 (lo), 865 (1972); Sawai,
1889 (1974). (3) Kawamura, Y., Toba, Y., Oghisu, Y., Tanaka, Y., Kogai, 10 (2), 15 (1975). (4) Ackerman, D., Clausen, J., Johnson, R., Tobias, R., Zee, C., Adams, J., Harris, J., Levins, P., Stauffer, J., Thrun, K., Woodland, L., EPA Contract 68-01-2966, Facility Rep. No. 6 (PB-270 8971, 1977. (5) Morisaki, S., Komamiya, K., A n t e n Kogaku 15,8 (1976). (6) Akita, K., Ogiso, C., Kitagawa, T., ibid., 10,276 (1971). (7) Zelezink, F. J., Gordon, S., NASA T N D-1454, 1960. (8) Gaydon, A. G., Wolfhard, H. G., “Flames, Their Structure, Radiation, and Temperature”, p 289, Chapman and Hall, London, England, 1970.
Receiued for reuiew October 17,1977. Accepted May 31, 1978.
NOTES
Imaging and Analysis of Airborne Dust for Silica Frank H. Chung Sherwin-Williams Research Center, Chicago, 111. 60628
Chronic exposure to high concentrations of silica would cause lung damage (silicosis). Therefore, the amount of airborne silica in factories is regulated and monitored by OSHA. Among the six techniques available for the analysis of crystalline silica in airborne dust collected on membrane filters ( I ), chemical separation (colorimetric) and x-ray diffraction are most widely used. The advantages of the x-ray method over the chemical .method are simplicity and rapidity. However, these advantages are lost in NIOSH P&CAM Method No. 109 (x-ray diffraction) where an internal standard and a silver membrane are utilized to increase precision ( 2 , 3 ) .An in situ x-ray technique is more attractive when a large number of samples are to be screened and particularly when many of the samples contain little or no free silica. A crucial factor causing the spread of results of an in situ x-ray method is the distribution of dust particles on the filter. However, the dust distribution is generally invisible and hence overlooked.
by the developer, forming a transparent thin film. The dust particles are insoluble and thus are imbedded into the PVC film leaving a sharp image. The thin film dries in about a minute, giving a permanent sample or standard. Other than optimum solubility and fast drying, the developer system is chosen so that the filter retains its shape and the dust particles are not disturbed in the process of image development. Some typical examples are shown in Figure 1. A study of these developed images indicates that the distribution of dust particles on filters tends to be uneven when the dust level in a factory fluctuates, or when a short sampling period is necessary due to high dust levels. Uneven distributions are also likely to be found in standards made by using a wet suspension/filtration procedure. Generally speaking, neither aerosol nor suspensoid collected on a filter would produce a statistically uniform distribution of particles over the filter. Improperly collected, overloaded, or locally compacted samples may cause larger errors in subsequent analysis. The imaging technique can reveal the presence of these problems and warrant precautions or extra care. Besides image development, another application of this technique is the fixation and preservation of standards or samples in their undisturbed condition for shipping, stock, rescanning, or reference. By the same principle, for filters made of mixed esters of cellulose such as MF-Millipore, the image of dust particles can be developed with straight ethyl acetate or acetone in a similar manner.
Imaging t h e D u s t Particles
I n S i t u X - r a y Diffraction A n a l y s i s f o r Silica
Membrane filters used for airborne dust sampling are made of either polyvinyl chloride (PVC) or mixed esters of cellulose (nitrocellulose/cellulose acetate). PVC filters are recommended for free silica monitoring, while cellulose filters are routinely used for asbestos and heavy metals. A simple technique has been found to develop the image of dust particles collected on these membrane filters as described below. A developer is made of one part methylene chloride and five parts chloroform by volume. A few drops of this developer are spread on an aluminum disk about 45 mm in diameter (or square). Surface tension prevents the developer from spilling over the edge of the disk. The PVC filter is then carefully placed on the developer. The.filter is dissolved immediately
The quickest way to determine the quantity of free silica in airborne dust collected on a membrane filter is to measure the x-ray intensity of the characteristic silica peak from the filter as received without tedious sample preparation. The silica concentration is then read from a calibration curve previously prepared by use of external standards. Two conditions must be met to make this simplest scheme feasible: First, the matrix effect must be negligible; second, the sample composition must be uniform. In the case of a few milligrams of dust collected on a PVC filter, the matrix effect is indeed negligible ( 4 , 5 ) , but the dust particle distribution is far from uniform. Note that even though the dust distribution is uniform, the silica distribution might still not be uniform, espe-
A technique to develop the image of dust collected on membrane filters is reported. The developed images reveal that the dust particles from either aerosol or suspensoid are not uniformly distributed over the filter. This uneven distribution affects the precision of in situ x-ray diffraction analysis. To cope with this situation, a multiple-exposure x-ray diffraction method is developed and applied to free silica analysis. This method achieves substantial timesaving (15 min instead of 3 h/sample) and delivers reliable data.
1208 EnvironmentalScience 8. Technology
0013-936X/78/0912-1208$01.00/0 @ 1978 American Chemical Society
