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Ind. Eng. Chem. Process Des. Dev. 1083, 22, 144-149
Reaction Kinetics of Formatton of HCI in Municipal Refuse Incinerators Shlgeo UchMa' and Hlroshl Kamo Department of Chemical Englneedng, Shizwka University, 3-5- 1 Johoku, Harnamatsu 432, Japan
Hiroshl Kubota and Ken Kanaya Research Laboratory of Resources Utilization, Tokyo Instltute of Technology, 4259 Nagatsude-cho, M M - k u , Yokohama 227, Japan
The possibility of the production of HCI by reactions involving inorganic chlorides present in municipal incinerators has been suggested. I t was proved thermodynamically that the presence of SO2 in the gas phase and SO2and AI2O3in the s o l i phase could contribute to the production of HCI. Then, a series of experknents was performed in a fused alumina tube reactor under conditions sknilar to those in incinerators using Neck Si02, and AI& proved in this study to have strong potential for HCI production. The reaction kinetics of the HCI production in Incinerators has been also elucidated by the analysis of the experimental data obtained.
Introduction Flue gases from municipal refuse incinerators contain air pollutants such as hydrogen chloride (HCl), sulfur oxide (SO,), nitrogen oxides (NO,), and solid particles. Among these, HCl is one of the most troublesome materials from the point of view of the maintenance of equipment as well as an air pollutant. HCl emitted from incinerators has been considered to result mainly from the decomposition of organic chlorides, especially polyvinyl chloride (PVC), contained in solid refuse. Some municipalities have therefore been collecting plastic wastes separately from other plastic-free wastes. However, even when such plastic-free solid wastes have been incinerated, considerably high concentrations of HCl have been observed in flue gases. Although it is supposed to be produced from some inorganic chlorides such as NaC1, abundantly present in refuse, the mechanism of the formation of HC1 has not yet been fully understood. In this study, the kinetics of the conversion of inorganic chlorides to HC1 under the conditions of municipal refuse incinerators is elucidated from the thermodynamic point of view and it is experimentally proved. Previous Works Several experimental findings have been reported that in refuse incinerators HCl is formed not only from organic chlorides but also from inorganic chlorides. Kondo (1978) classified municipal refuse into six kinds and analyzed the produced gases after burning them. Paper and garbage produced a considerable amount of vaporized chlorine, most of which was considered to be HC1. Hiraoka et al. (1978) took a chlorine balance around a municipal incinerator under ita running condition by analyzing refuse charged and measuring HCl concentration in the flue gas for a week. They showed that 84% of the total chlorine in the refuse was combustible chlorine, which they define as the chlorine transferred to the gas phase when the refuse is burned in the laboratory electric &ace at 700 to 800 "C; it is considered to be the same as the vaporized chlorine mentioned above. The combustible chlorine was produced even when paper and garbage were burned; 50% of the total chlorine in the flue gas was reported to result from the burning of plastics. According 0196-4305f8311122-0 144$01.50/0
to their study, it was found that the combustible chlorine decreased when soluble salta such as NaCl were washed out of the refuse sample by water. This will be evidence of the HC1 production from inorganic chlorides. h u m a et al. (1978) and Hishida and Miyoshi (1979) also reported the emission of a considerable amount of HC1 even when plastic-free refuse was incinerated. The concentration of HCl in the flue gas from the incinerator not equipped with a water spray for flue gas cooling was between 190 and 730 ppm (average value was 400 ppm), and it often surpassed the upper limit of the concentration prescribed by the air pollution control regulation in Japan, which was 430 ppm. Iwasaki et al. (1975) performed a laboratory experiment of the reaction of NaCl with water under high-temperature conditions. In their experiment, 6 to 8 g of NaCl was held in a ceramic boat placed in a silica tube in an electric furnace and contacted with water vapor. They observed several hundreds ppm of HC1 at 800 "C and more than 1000 ppm a t 900 "C. Silica oxide @io2) in the boat and the reactor tube probably played a role in the formation of HCl in this case. Henriksson and Warnqvist (1979) recently reported a study on the kinetics of the formation of HCI by the reaction between NaCl and SO2, 02,and H20. They performed an experiment at 300 to 900"C using an AZO3 boat as a sample container. Although the rate equation was obtained, a question of the possibility of the reaction involving A1203 remained. Thermodynamics of HCl Formation As mentioned in the previous section, much experimental evidence of HCl production from other than organic chlorides contained in refuse has been reported. However, the equilibrium concentration of HCl for the reaction given by 2NaCl+ H20 e 2HC1+ Na20 (1) is less than 0.1 ppm at temperatures between 700 and 900 O C , and the reported HC1 Concentration higher than several hundred ppm cannot be explained by this reaction only. If the product of the above reaction, Na20,is consumed by some other reactions with components contained in refuse, reaction 1may shift to the right and HC1 is pro0 1982 American Chemical Society
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Table I. Equilibrium Constants Kp for Hargreaves Reaction, (Reaction 3), and Its Similar Reactions. NaCl in Reaction 3 is Replaceable by Other Alkali and Alkali Earth Metals temp, "C KP(NaC1) KPWCl) Kp(MgC1,) Kp(CaCl1)
300
500
700
800
900
3 x 1O'O 7 x 1O'O 2 x 10" 5 x 10'6
4 x 105 9 x 105 4 x 10'0
6 X 10' 1 x 103 5 x 106 1 x 106
5 x 10 1 x 102 2 x 105 5 x lo4
7 2 x 10
1
4 x 103
6
1 x 1O'O
1x
1000 5
lo4
1x 103 X
10'
Table 11. Percentages of Combustible S and Cl Contained in Public Refuse S 0.05-0.4% (av 0.1%) c1 0.1-1.0% (av 0.8%) Table 111. Concentration of SO, and HCl in Flue Gas From Municipal Incinerator SO1
HCl
16-85 ppm 330-1030 ppm
(av 35-45 ppm) (av 740-810 ppm)
duced. Such reactions coupled with the main reaction to reduce its product and to accelerate the reaction are called conjugate reactions. These reaction schemes are very common in biochemical reactions. The components possibly present in municipal refuse which react with Na20 and produce more stable products are discussed below. Conjugate Reactions with Gaseous Components. When SO2 is present in the gas phase, the conjugate reaction for reaction 1 is considered to be Na20 + SO2 + 1/202 + Na2S04
(2)
This reaction is combined to give the following overall reaction as
+ H 2 0 + Na2S04+ 2HC1 2NaC1+ SO2 + 1/202
(3)
This reaction, known as the Hargreaves reaction, was widely used in Europe since 1870 to produce Glauber's salt, Na2S04,which was the raw material for the Na2C03production in the Le Blanc process. The equilibrium constants for similar types of reactions to reaction 3 with some other chlorides in addition to that for NaCl are shown in Table I. It is seen that the values of the constants are quite large and that the chlorides are easily converted to HC1 under the conditions met in incinerators. The kinetics of reaction 3 has been reported by Henriksson and Warnqvist (1979). Tables I1 and I11 show the percentages of combustible sulfur (S) and chlorine (Cl), which were detected as SO2 and HC1 after combustion in refuse samples in the laboratory, obtained by Kakizaki (1978), and the measured concentrations of SO2 and HC1 in flue gas from a municipal incinerator by Ishiguro et al. (1974). Although these data were independently obtained, it is quite interesting to notice corresponding relations between them. As seen in these tables, the amount of S in the refuse is small and the concentration of SO2 in the flue gas is so low that the special control measure is not necessary for the SO2 emission at present. However, the amount of S in refuse convertible to SO2 might be larger than that of the corresponding S found in the flue gas. Under the conditions in incinerators, it is very possible that, once produced, SO2 is consumed to produce NaaO, and HC1 through reactions 2 and 3 and that the concentration of SO2observed in the flue gas is therefore lowered. According to Ishiguro et al. (1974), the concentration of SO2 in the incinerator decreased as the temperature rose. It is a trend similar to that of the equilibrium concentration of SO2 for reaction 3, as shown in Table I.
10-41
1000
1
1100 1200 Temperature, K
I
1300
Figure 1. Equilibrium HCl concentrations for reaction 1conjugated with different reactions under 10% initial water vapor at 1 atm and in the presence of a sufficient amount of solid Components.
Besides, in the gas phase, some other components such as NO, NO2, and C02 are present and the following conjugate reactions are considered. Na20 + 2N0 + 3/202 += 2NaN03 (4) Na20 + 2N02 + 1/202 + 2NaN03 (5) Na20 + C02 Na2C03 (6) However, as NaN03 decomposes under high-temperature conditions as in the incinerator, reactions 4 and 5 are not considered to occur. Since reaction 6 is not favorable from the thermodynamic point of view, SO2 is probably the only component in the gas phase to be the reactant to produce HC1 in incinerators. Conjugate Reactions with Solid Components. As a solid component corresponding to SOz in the gas phase, an acid oxide, Si02,is considered. Some other materials such as A1203and Fe203are also possible components to conjugate with reaction 1to produce HC1. In general, the overall reaction is represented as NaCl + H 2 0 (A) + (B) + 2HC1 (7) The equilibrium concentration of HC1 produced by reaction 7 in the presence of a sufficient amount of NaCl and each of the possible materials is calculated by using the free energy data (Barin, 1973,1977) for 10%-H20 initial concentration and shown in Figure 1. It should be mentioned that the HC1-producing reactions with solid components are favorable at higher temperature, while the reactions with SO2 are favorable at lower temperature. The solid components most commonly found in municipal incinerators are lined as follows in the order of calculated equilibrium concentrations of HC1 A1203 + nSi02 > mSiOz > A1203 > Fez03 (n = 4, 6; m = 1, 2) (8)
+
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Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 1, 1983
Table IV. Calculated Equilibrium HC1 Concentrations in ppm for Reaction: (Initial Mole Percentage of Water Is 10% a t 1atm) (XI
(B)
(A) 4Si0, Al,03 + 6Si0, SiO, A1,03 t 5/,SiO, SiO, 1/zAl,03+ 1/,SiO,
2KC1 2KC1 MEZClz MBCIz CaCl, CaC1,
(X)t H,O
t (A) 4
900 K
K,D4SiO, K,0.Al,03.6Si0, Mg 0.Si0, 1/z(2Mg0.Al,03.5Si0,) Ca 0.SiO, l/2(2Ca0.AlU,03.Si0,)
2.05 X 5.76 x 1.81 x 1.80 x 9.09 x 5.02 X
10 104 105
lo5 10, 10'
(B)+ 2HC1
1100 K
5.14 X 1.40 x 1.82 x 1.81 x 7.21 x 4.73 x
1300 K 4.68 x 1.65 x 1.82 x 1.82 x 2.35 X 1.73 x
10, 105 105
105 103 103
103 105 105 105
lo4 104
Table V. Analysis of Ashes Taken at an Incineration Plant in Tokyo ~
~
_
_
~~~
_
~
component to be analyzed c1 Na soluble Na insoluble Na total Na
~
~
~~
method of analysis
EP dust
residue
after extraction by water, use Mohr's method
12.3 wt %
1.3 wt %
5.3 wt % 1.6 wt % 6.9 wt %
0.5 wt % 1.1wt % 1.6 wt %
after extraction by water, use flame photometry total Na - soluble Na after decomposition by (HFt H,SO,) solution, use atomic absorption photometry
X-ray analysis
Silica mixed with A 1 2 0 3 gives the highest concentration of HC1. Inorganic chlorides other than NaC1, that is, such as KC1, MgC12, and CaC12 are also considered to become source materials for the HC1 formation in incinerators. The equilibrium concentrations of HCl produced from the reactions involving these chlorides are shown in Table IV. Analysis of Ashes. Samples of the residue in the incinerator and the dust collected by the electric precipitator (EP) of a municipal incineration plant in Tokyo, Japan, were analyzed to determine to what extent the inorganic materials in question are present in refuse. The results of the analysis are summarized in Table V. It is noticed that the weight percentage of the soluble Na in the EP duat is much higher than that in the residue in the incinerator. The soluble Na here is defined as the Na in the form of compounds of high solubilities in water such as NaCl and Na2SOl while the Na in the products such as Na&03 is considered as an insoluble Na. This difference is due to the fact that the water sprayed to prevent the scatter of the dust from the burned residue might wash out the soluble Na in the residue, and it proves that most of Na and C1 in the residue are still present in the form of soluble salta such as NaCl, KCl, and Na+304 rather than insoluble materials. These results agree with the data obtained by Takahashi (1980). He analyzed about 100 samples of the E P dust taken a t many municipal incineration plants. His data show that the average values of the total Na, K, and C1 are 6.5,7.1, and 12.9 wt %, respectively. The values of the total Na and C1 are approximately the same as those shown in Table V. He also confirmed that the average values of total SO2,Al2O3, and Fez03 were 19.9,11.2, and 3.4w t 70, reapectively. These data support the presence of sufficient inorganic materials for the HC1 production in ppm under concentration in municipal incinerators.
Experimental Apparatus and Procedure The possibility of the conversion of chlorides contained in municipal refuse into HCl through conjugate reactions with some other materials such as Si02, A1203, and SO2 has been proved from the point of view of thermodynamics and the conditions in incinerators. To confirm the fact, therefore, an experiment is performed on the reactions between NaCl and Si02/A1203which are considered to be present most commonly in municipal refuse. The experimental apparatus used in this study is shown in Figure 2. The main part of the reactor (5) is made of
detected NaCl, KCl
detected NaCl, KCl
0
J&C!
@ Compressor
0 2 Valve
I'
@ Manometer @ Humidifier @ Reoctor
@ Alumina boat @ Electric furnace @ HCI absorber @ pH. CI; No* electrodes @ Ion meter
Figure 2. Experimental apparatus.
a fused-alumina tube of 20 mm inner diameter and 700 mm length, placed in a temperature controlled electric furnace (7). A sample of a certain amount of NaCl and Si02/A1203is put in a fused-alumina boat of 15 mm width, 10 mm height, and 100 mm length. After the temperature of the reactor reaches the required value, the boat is first placed at a point 200 mm distant from the outlet point for 5 min. Then it is inserted in the center of the reactor and at the same time the air regulated by a value (2) and a manometer (3) passing through a humidifier (4) is introduced to the reactor. This moment is considered to be the initial time for each run of the experiment. The air contacted with the sample in the boat is then bubbled in an absorber (8) containing 1L of distilled and ion-exchanged water to catch all the HCl produced. The variations of the pH value and the concentration of C1- ion in the water with time are continuously measured by a Beckman-Toshiba SS-2 Type Expandomatic pH/ion meter. Some amount of NaCl may vaporize when the temperature is high. The concentration of Na* ion in the absorbing water is also measured a t the end of each experiment by the same pH/ion meter to see if the difference of the concentrations of H+ and C1- ions is due to the vaporized NaCl. Results and Discussion Determination of Moles of HCl Produced. The amount of HC1 produced is determined by the change in the pH value or C1- ion in the distilled water. Since HC1 is a strong acid, it will dissociate almost completely into H+ and Cl- ions in a dilute solution. If these two ions come only from the dissociation of HC1, their concentration should be nearly the same. If the vaporization of NaCl takes place, the concentration of Cl- ion will be higher than that of H+ ion and the difference is approximately equal
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 1, 1983
147
0 Time, min
Time, min.
Figure 3. Relation between H+and Cl- ion concentrationa and Na+ ion concentration at the end of experimental run (700,800, and 900
Figure 5. Effect of temperature on HCl production. I
0 0 .
"
"
I
I
0.31 4
250 250
Sample, mg
-1 E n
4-
Temp.. 800 ' G Fa = 9.9 cc/s pn ,=0.17atm
Temp.. 8OO'C
3c L C
.-
8
2-
+
I l-
I k*" O
Y
40
I20 I60 Time, min
00
200 210
Figure 6. Effect of partial pressure of water on HCL production. Time, min
Figure 4. Effect of sample composition on HC1 production.
to the concentration of Na'. In Figure 3, the variation in the concentration of these ions with time a t three different temperatures is shown. At 700 "C, the concentrations of H+ and Cl- ions are almost the same and the concentrations of Na+ is negligibly small. The vaporization of NaCl is considered to be negligible in this case while it becomes significant a t higher temperatures. The measured concentrations of Na+ ion were slightly higher than the difference of measured concentrations of H+ and C1- ions. Although the only source of Na+ ion to be considered in this experiment is the vaporization and dissolution of NaC1, some experimental error in measuring the concentration of Na+ ion might cause this discrepancy because of the lesser reliability of Na+ electrodes compared with the C1- electrodes. Therefore, the number of moles of HC1 produced is approximately equal to that of H+ and the increase in the H+ ion concentration in the absorbing water is used as the moles of HC1 produced in the following discussion. Effects of SiOz/Al2O3,Temperature, and Water. Figure 4 shows the effect of the amount of SiOz and A 1 2 0 3 added to NaCl in the boat on the rate of the HC1 production at 800 "C. Even when SiOz was not present, a small amount of HC1 was produced. This HC1 production may be caused by the reaction of vaporized NaCl with the
walls of the boat and the tube which are made of fused alumina. It is clearly shown that the coexistence of AlZO3 and SiOzpromotes HC1 production from NaCl as predicted from the calculated equilibrium concentration in Figure 1. The reaction continued even after 3 h passed and it could not go to completion since glass-like products covered the surface of the sample to prohibit the reaction as the reaction proceeded. The effect of A1203 is smaller than that of SiOz but recognizable. The effect of the temperature on the rate of the HC1 production reaction is shown in Figure 5: the higher the temperature, the faster the reaction rate. In the case of 900 "C, most of the reactants in the boat were consumed in 120 min and the rate of the HC1 production decreased. The rate of the HCl production also increased with the increase in the water vapor in the gas phase as shown in Figure 6. Analysis of Experimental Data. The maximum concentrations of HC1 in the exhaust gas from the tube reactor are calculated from the maximum slopes of the cummulative HC1 concentration curves as shown in Figures 3 through 6. In Figure 7, the effect of temperature on the maximum concentration of HC1 produced from the mixed samples of NaCl and Si02is shown. The equilibrium concentration of HCI for the reaction 2NaC1+ Si02 + HzO + NazO-SiOz+ 2HC1 (9)
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Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 1, 1983 -0002
I500
1
Fa
= 9.9 CC/S
2/
,
I 800 Temperature , "C
900
Figure 7. Effect of temperature on [HCl],, and comparison with equilibrium HC1 concentration for reaction 9.
Table VI. Analysia of Residue in the Boat
41 experimental run number 34 38 900 reaction temperature, "C 800 800 100 reaction time, min 180 180 9.9 dry air rate, Fa, cm3/s 9.9 9.9 0.17 vapor pressure of water, H, atm 0.16 0.17 4.3 moles of NaCl sample, mgmol 4.3 4.3 12.8 moles of SiO, sample, mg-mol 4.3 12.8 2.1 moles of Al,O, sample, mg-mol 2.1 2.1 C1 remaining in boat, mg-mol 0.2 0.0 0.0 soluble Na remaining in boat, 0.2 0.0 0.0 mgwl 2.0 total Na remaining in boat, 2.1 2.3 mg-mol 2.3 insoluble Na remaining in boat, 1.9 2.3 mg-mol 2.1 moles of HC1 produced, mg-mol 2.0 2.5 1900 [HCllma, P P ~ 560 1500
is given by a curve to compare with the experimental data. HCl in concentrations of 300 to 1100 ppm was produced from the mixed samples of NaCl and SiOzat temperatures similar to that in the incinerators (700 to 900 "C). As shown in Figure 4, the presence of A1203 increases the rate of the HCl production further. Therefore, a considerably large amount of HCl emitted from incinerators in practice may be due to the reactions between inorganic components such as NaC1, AlZ0,, and SiOz sufficiently contained in refuse. The increase in the rate of the HC1 production with temperature is seen from Figures 5 and 7. However, the difference between the maximum concentration of HCl experimentally obtained and the calculated equilibrium concentration increases as the temperatures becomes higher. One reason for this reduction of the HC1 production rate is that the silicate, one of the reaction products, covers the surface of the unreacted material to prohibit the reaction. The vaporization of NaCl at high temperature may be an another reason. As shown in Table VI, neither C1 nor soluble Na was detected in the residue in the boat. This means that there was no NaCl remaining in the boat at the end of the experiments at 800 and 900 "C. At 700 "C, the vaporization of NaCl is negligible and the silicate produced is a very small amount. The concentration of the produced HC1 in the leaving gas is close to the equilibrium concentration, and the resulting curve for the HC1 concentration vs. time becomes almost a straight line (Figure 3). On the other hand, at 800 and 900 OC, the effects of the vaporization of NaCl and the coverage of the silicate over the reactant are significant, and the rate of
6.10
0.20
0.30
0.40
pHz0 , a t m
Figure 8. Effect of partial pressure of water on [HCI],,.
the HC1 production decreases in a short time (see also Figure 3). The equilibrium concentration of HCl is, as seen from reactions 1 and 7,proportional to the square root of the partial pressure of water in the feed gas at a constant temperature. The maximum concentrations of HCl experimentally obtained show a similar trend to the calculated equilibrium concentrations as shown in Figure 8. The rate of HC1 production is, as mentioned before, accelerated by the presence of AlzO,. When only NaCl and SiOz are present, the reaction will be 2NaC1 + mSiOz + HzO + NazO-mSiOz+ 2HC1 (10) where the value of m is 1orland 2. If Alz03is added, in addition to the above reaction, the following reaction will occur 2NaCl+ nSiO, + Alz03+ HzO + Na20.A1,03.mSi0, + 2HC1 (11) where the value of n is either 4 or 6. If the reactanb consist of NaCl and Alz03,the reaction is given by 2NaC1 A1,03 + HzO + NaZ0.A1,O3 2HC1 (12) The equilibrium concentration of HC1 in this case agrees well with the experimental value. The comparison of the experimental data with the calculated values is shown in Figure 9. Analysis of Residue in the Boat. The present experiment and the analysis of the data show that HC1 is produced by reactions between inorganic materials poasibly present in incinerators. To confirm that HCl was really produced through reaction 7, it is necessary to show that the number of moles of insoluble Na (silicate in the present case) present in the residue in the boat after the experiment is equal to that of HCl produced. The relations among the number of moles of HC1 produced and the number of moles of C1, total Na, and soluble Na in the residue in the boat are given as follows [HCl produced] = [insoluble Na] = [total Na] - [soluble Na] (13) and [Cl in the residue] = [soluble Na] (14) The results of the analysis of the residues in the boat for three experimental runs are summarized in Table VI. The above relations hold approximately and the possibility
+
+
Ind. Eng. Chem. Process Des. Dev., Vol. 22, No. 1, 1983
149
experimental data obtained in this study. Acknowledgment
Fa= 9.9C C I S
- 1
g 1000 0
500 -
/
/
l o!
;
A
2 I Si02 /A1203 ,
-
5
6
+
B
Figure 9. Effect of mole ratio of SiOz/AlzOson [HCl],.
of the production of HC1 through reaction 7 is again supported by this result. Conclusions The following conclusions are drawn from this study. 1. The possibility of the production of HC1 by reactions involving inorganic solid materials present in incinerators has been confirmed from thermodynamic point of view. Some contribution of SO2gas to the HC1 production under the conditions in incinerators has also been shown. 2. A series of experiments has been performed in a fused-alumina tube reactor under the high-temperature conditions similar to those in incinerators using inorganic materials most generally contained in municipal refuse. A considerable amount of HC1 has been found to be produced by reactions between NaCl and Si02/A1203in the presence of water. 3. The reaction kinetics of the production of HC1 in incinerators has been elucidated by the analysis of the
The authors are grateful to Messrs. K. Takase, M. Nitta, T. Ohmura, B. Ikeda, and M. Masatoshi of The Association for Promotion of Plastic Waste Treatment and Utilization for helpful discussions during the course of this work. They would also like to thank Professor M. Ichikuni, Mr. M. Tsurumi, and Ms. N. Matsuzaki of Tokyo Institute of Technology and Department of Sewage Treatment of Machida-shi, Tokyo, for their help in the analysis of experimental samples. Mr. Miyaguchi’s contribution to the experimental work is also greatly appreciated. Nomenclature Fa = volume flow rate of dry feed air at 0 “C, 1 atm, cm3/s [HCl],, = maximum HC1 concentration at outlet point of reactor, ppm PHlo = equilibrium H2O partial pressure, atm Registry No. HCl, 7647-01-0;SiOp,7631-86-9;AZO3,1344-281; NaCl, 7647-14-5; SOz, 7446-09-5. Literature Cited Azuma, H.; Tahara, Y.; Kondo, K. K q i to Takeku 1078, 74, 1059. Barin, I.; Knacke, 0.; Kubaschewski, 0. “Thermochemical Properties of Inorganic Substances”; Sprlnger-Veriag, 1973; Supplement. 1977. Henriksson. M.; Warnquist, 6. Ind. Eng. Chem. Process Des. Dev. 1070, 18, 249. Hiraoka, M. Paper presented at 12th Fail Meeting of the Society of Chemical Engineering, Japan, Okayama, Japan, 1978. Hishida, K.; Miyoshi, Y. Paper presented at Congress for Waste Treatment and Utliizatlon, Tokyo, Japan, 1979. Ishiguro, T.; Iwasaki, Y.; Fukushima, Y.; Onozuka, H. Kogai to Talsaku 1074, 10. 421. Iwasaki, S.; Shkada, Y.; Noguchi, K. Report of Tokyo Metropolitan Cleansing Labcfatwy, 1975; p 61. Kakizakl, T. Paper presented at Hamamatsu Meeting of the Society of Chem lcai Engineering, Japan, Hamamatsu, Japan, 1978. Kondo, K. Kohl Helkbutsu 1078, No. 26, 30. Takahashi, A. Paper Presented at 1st Meeting of Japan Waste Management Association, Tokyo, Japan, 1980.
Received for review September 15, 1981 Accepted August 5, 1982
