I d . Eng. Chem. Process Des. Dev. 1984, 23,641-640
and lowering of hydroxypropanone and furfurylic alcohol; caustic soda gives more hydroxypropanone and less furaldehyde. These results do agree with the ionic mechanism of pyrolytic reactions proposed for cellulose by Byrne et al. (1966). An acid catalyst promotes dehydration and furaldehyde formation (Shafizadeh, 1968). Basic catalyst favors gasification and charring. Influence of the Sweeping Gas Flow. The flow of nitrogen affects the residence time of the vapor phase produced by pyrolysis. Different flow values were used under similar conditions of operation (flash pyrolysis at 350 “C) so that the residence time would vary from a few seconds to more than 1 min (Table V). The overall yields of char, oil, and gas are not significantly affected, but the amount of water increases considerably when the sweeping flow is decreased. Unstable organics undergo secondary dehydration when the rapid extraction and dilution by sweeping is not achieved. This is of particular relevance for process design of extractive pyrolysis for chemicals recovery. Influence of Chemical Nature of the Sweeping Gas. The experimental setting makes sweeping possible not only by a permanent gas, but also by condensable vapor of a solvent. Three solvents were tested: methanol, 2-methylpropanol, and ethylglycol (C2HSOCH2CH20H). All three are good solvents of the prolytic oil. When using this procedure, the solvent is collected and condensed with the pyrolytic oil. The considerable complication of oil analysis explains why these experiments could not be performed extensively. The results, presented in Table VI, show very little difference between nitrogen and helium. Use of a vapor slightly modifies yields expecially on acetic acid, but no modification in qualitative composition is noted so that a chemical reaction with the solvent is excluded and the thermal nature of pyrolysis is confirmed. Conclusions The comprehensive results of this study lead to an evaluation of the significance of each parameter of wood pyrolysis. The major influence of temperature and rate
841
of heating is clearly established. The particle size has an influence on the overall yield of char, oil, and gas, but does not modify the qualitative Composition of oil. In addition, this influence is explained by the relation between particle size and heat transfer. Influence of moisture is interpreted in the same way: effective pyrolysis temperature is shifted by the heat requirement of moisture vaporization. Pyrolysis carried out with different sweeping gases shows that pyrolysis reactions are not changed. Wood pyrolysis appears as a thermal phenomenon only. Variations of sweepinggas rate have, on the contrary, great significance;they modify the residence time of vapors in the hot zone and their evolution after the pyrolysis. Finally, the significant influence of catalysts confirms the ionic nature of pyrolytic mechanisms. The results also show the influence of the reactor design on the pyrolysis reactions. The extraction procedure used here characterized by the flash effect and the rapid withdrawing of pyrolytic vapors out of the hot zone leads to original results. In the perspective of an industrial application, reactor design and operating conditions should be adapted to the desired product of pyrolysis charcoal, gas, or instable chemicals. The study presented here provides some of the necessary information. Registry No. FeClS,7705-08-0; NaOH, 1310-73-2;methanol, 67-56-1; ethyl glycol, 110-80-5;2-methylpropanol, 78-83-1; acetaldehyde, 75-07-0; acetone, 67-64-1; formic acid, 64-18-6; acetic acid, 64-19-7; propionic acid, 79-09-4; 1-hydroxypropane,116-09-6; l-hydroxy-2-butanone,5077-67-8; 2-furaldehyde,98-01-1;furfuryl alcohol, 98-00-0.
Literature Cited Byne, 0. A.; Gardlner, D.; Holmes, F. H. J . Appl. Chsm. 1988, 76, 81. Jecko, G.; Reynaud. B. Association Technique de la SWrurgle Francgise (Commission des Ing6nleurs de Laboratolre), Paris, France, 1967. Knight J. A. Symposium on “Thermal Uses and Properles of Carbohydrates and Llgnlns”; Shafizadeh, Ed.. Academlc Press: New York, 1976. Petroff, G.; Doat, J. Bois Fw. Trop. 1978, 177, 51. Rollln T h h CNAM, Unlversk6 de Nancy I, Nancy, France, 1981. Shadzadeh. F. A&. Carbohydr. Chem. 1968, 23, 419. Shwenker, R. F.; Beck, L. R. J . Powm. Sci., Pari C 1983, 2 331.
Received for review March 4, 1982 Revised manuscript received August 4, 1983 Accepted September 23,1983
Upgrading of Heavy Oils by Asphaltenic Bottom Cracking Jlro Sudoh,’ Yorhlmi Shlroto, Yoshlo Fukul, and Chlsato Takeuchl C h w h Chemlcai Engineering & Construction Co.,Ltd., 3-13, Moriya-cho, Kanagawa-ku, Yokohema 221, Japan
Asphaltenk Bottom Cracking (ABC) is a catalytic hydrotreating process for heavy asphaitenic petroleum ends. ABC in combination with solvent deasphalting (SDA) is an effective way to completely convert and upgrade asphaltenic bottoms. This paper presents various correlations in SDA operations for yleids and properties of deasphaked oils (DAO) and asphalts obtained from KhafJivacuum residua under different hydrotreating conditions. By using a mathematical model of the combined process of ABC and SDA, the quantitative reiatlonship between the recycle rate of SDA asphatt and the ABC conditlons in the extinction and partial recycle operations is discussed.
Introduction Technologies such as upgrading of heavy petroleum ends and converting them into high quality lighter stocks have become more desirable due to the recent growing demand for lighter oil products. On the other hand, since the supply of crude is likely to consist more of heavy oils, 0196-4305/8411123-0641$01.50/0
research and development of conversion technologies have been actively carried out worldwide. The Asphaltenic Bottom Cracking (ABC) process under development by Chiyoda is a catalytic hydrotreating process for residua containing large quantities of metals and asphaltenes. This process upgrades the residua by selectively cracking as@ 1984 American Chemical Society
842
Ind. Eng. Chem. Process Des. Dev., Vol. 23,No. 4, 1984
Solvent Deasphdting Section Figure 1. Simplified diagram of pilot plant.
phaltenes through the removal of metals and sulfur, resulting in a reduction of Conradson carbon residue (CCR) (Takeuchi et al., 1983; Asaoka et al., 1983). It is also possible to completely convert such asphaltenic bottoms to deasphalted oil (DAO) and lighter fractions by combining ABC with solvent deasphalting (SDA). The test results of the residua from various ultraheavy crudes produced in Venezuela were reported at the second UNITAR conference (Takeuchi et al., 1982). The DAO obtained from the ABC/SDA combination process contains only minute amounts of metals and asphaltenes and can be further processed and converted to lighter oils by conventional means such as hydrocracking and FCC. The purpose of this paper is to present: First, test results using the ABC/SDA pilot plant for Khafji vacuum residue (VR); second, the correlations in SDA operation for DAO and asphalt obtained from Khafji VR under various hydrotreating conditions; and third, the quantitative relation between the recycle rate of SDA asphalt and the ABC condition in extinction and partial recycle operations using a mathematical model of the ABC/SDA process. Experimental Section Feedstock. Khafji VR, a typical heavy residue produced from Middle East Crude, was used as the feedstock for the experiments. Properties of the Khafji VR are shown in Table I. Catalyst. In the experiments, the ABC catalyst used is proprietary. The chemical composition of the catalyst, the physical structure of its pores, the chemical properties of the active surface, the mechanical properties, and the size and shape are specially designed for catalytic hydrotreating of heavy oils. The activity and stability of the
Table I. Insmction of Khafii VR yield on crude vol % specific gravity d,,/4 "C viscosity at 100 "C CP Conradson carbon residue wt % asphaltenes wt % sulfur wt % nitrogen wt % carbon wt % hydrogen wt 5% vanadium wt, ppm nickel wt, PPm
30.5 1.023 1,662 21.2 11.4 4.96 0.40 84.18 10.28 130 41
ABC catalyst have already been described in previous papers (Takeuchi et al., 1979; Takeuchi et al., 1983). Although the catalyst employed in the present experiment was speciallyprepared in Chiyoda's R & D center, it is also being produced on a commerical scale. Equipment. In the pilot plant used for the experiment, the catalytic hydrotreating section, with a fixed bed, high pressure catalytic reaction unit (37 mm in inner diameter and 3320 mm in length), is connected with the SDA section, which includes a column (27 mm in inner diameter, 1190 mm in length, and 102 18-mm diameter disks). The asphalt from the extractor bottom cannot only be withdrawn from the system but it can also be totally or partially recycled into the catalytic hydrotreating section. A simplified flow diagram of the pilot plant is shown in Figure 1, but details of operation are reported elsewhere (Takeuchi et al., 1983). The range of the operating conditions is as follows. Hydrotreating section: pressure, up to 140 kg/cm2g;temperature, up to 410 "C; LHSV, up to 1.0 h-l; HP/oil,lo00 NL/L. SDA section: solvent, butane, pentane; solvent ratio, up to 9 v/v; pressure, 40 kg/cm2g; temperature, up to 190 "C.
Ind. Eng. Chem. Process Des. Dev., Vol. 23, No. 4, 1984 643
I
No.
Operationhlode
I
SDA
8C %
s 2
6C
B d P
4c
a
ASPHALT +b
2c C
I
I
500
1,OOO
I
1,500
I
I
2 Po0
2,500
-
3 00
Roearr Time, hr
Figure 2. Typical pilot test results for Khafji VR. Table 11. Yields and Qualities of DAO and Asphalt from ABC/SDA Combination Test for Khafji VR butane pentane SDA solvent ABClSDA ABClSDA ABClSDA ABClSDA operation mode SDA once through recycle SDA once through recycle DAO asphalt
38.1 61.9
specific gravity, d,,/4 "C vificosity at 5 0 OC, CP pour point, "C CCR, wt % sulfur, wt % nitrogen, wt % asphaltenes, wt % vanadium, wt, ppm nickel, wt, ppm
0.951 982 52.5 3.9 3.39 0.13 0.02 3.2 1.1
specific gravity, d,J4 "C softening point, "C CCR, wt % sulfur, wt % nitrogen, wt % asphaltenes, wt % vanadium. wt, ppm nickel. wt. ppm
1.104 100 36.8 6.44 0.80 25.8 27 0 a2
Yield, wt % on Fresh Feed 75.8 94.7 0 21.8 DAO Inspections 0.935 0.941 123 155 12.5 20.0 4.3 4.6 1.36 1.63 0.24 0.26 0.02 0.02 0.2 0.2 0.3 0.3 Asphalt or Recycle Inspections 1.138 1.150 134 , 136 51.2 51.5 3.24 3.70 0.78 0.96 22.0 25.8 32 58 51 60
Analytical. The determination of physicochemical properties, i.e., specific gravity, viscosity, CCR, pour point, softening point, and elemental analyses were all carried out by routine methods. The heptane insolubles (asphaltenes) were analyzed with UOP614. Results and Discussion Typical Pilot Plant Test Results of ABC/SDA Combination Operation. Typical results of the pilot plant test for the conversion of asphaltenes by the combination of ABC and SDA for Khafji VR are shown in Figure 2. It shows the operation of about 3OOO h, including the test for the complete conversion of asphaltenes, by flow rates of streams in relation to operating hours. In Figure 2, the circled numbers 4 and 5 indicate the results of tests in which butane and pentane were used as deasphalting
61.1 38.9
86.3 10.7
95.5 0
0.966 2,000 70.0 8.60 3.86 0.21 0.1 16.4 4.4
0.952 2i6 10.0 8.1 2.50 0.25 0.04 16 1.7
0.962 199 21 .o 8.2 2.42 0.30 0.07 1.2 1.8
1.136 148 50.0 6.68 0.60 36.4 309 113
1.166 175 58.3 4 47 0.74 57.2 135 112
1.172 185 65.6 3.81 1.00 64.8 137 131
solvents, and all of the SDA asphalt was recycled for complete conversion of the asphaltenes. It is noted that in both cases, the reaction reached a steady level. The results of the repeated operation shown at 2 and 4 indicate that the activity of the catalyst did not show any appreciable degradation despite the extinction recycling of the SDA asphalt. As is apparent from the test results, DAO not containing asphaltenes can be obtained at high yield by the ABC/SDA combination process. Yields and properties of product DAO and asphalt from Khafji VR are shown in Table 11. When butane is used as a deaaphalting solvent, a comparison of the DAO obtained by SDA to the DAO obtained by the ABC/SDA once-through operation reveals that DAO yield increases approximately twofold, and the DAO is of high quality; i.e., it has no appreciable amounts of asphaltenes and
644
Ind. Eng. Chem. Process Des. Dev., Vol, 23,No. 4, 1984 IW \
CorrelationC u m for ABC-Treated Oil of Khafji VR
9
i $
90
loo*
lG
\
90-
85
0
A
Arabian tight VR Cach Saran VR
A Uoydminster VR 75
0
2
4
6
8
10
Aaphdtme Content of SDA Feedstock, wtX
Figure 3. DAO and asphalt yield of ABC-treated Khafji VR under various ABC conditions.
metals, and lower sulfur content and viscosity due to the effect of ABC treatment. The fact that the asphalt obtained by the ABC/SDA once-through operation has considerablyless yield and remarkably reduced metal and sulfur contents in contrast to the asphalt obtained only by SDA indicates that the ABC catalyst decomposes heavier fractions more selectively. By comparing the DAO obtained by the extinction recycle operation to the DAO obtained by the once-through operation, there is no appreciable difference in quality despite the DAO yield which reaches up to ca. 95 wt %. This shows that the extinction recycle of the SDA asphalt hardly affecta the DAO quality. Yet, when pentane is used instead as a deasphalting solvent, ABC treatment and the recycle of SDA asphalt have the same effect on product yield, and quality shows the same trend as for butane. Although asphaltenes and metals are hardly present in the DAO, as is the case for butane, the quality of both DAO and asphalt is slightly lower than that obtained by butane solvent; that is, higher gravity and viscosity, and greater quantities of sulfur and CCR are present. Pentane solvent, however, makes it possible to reduce SDA asphalt drastically.
Correlation in SDA Operation for Product Yield and Quality at Different ABC Conditions Effect of ABC Conditions on DAO Yield. When ABC-treated oils are separated by SDA in the ABC/SDA combination process, yields of DAO or asphalt vary depending on the difference in ABC conditions because of the asphaltenes cracking reaction occurring in the ABC section, even if the same solvent is used under a constant SDA condition. Therefore, yields of DAO and asphalt obtained from SDA feedstocks have been investigated in relation to the asphaltenes content of the SDA feedstock. SDA feedstocks are oils from Khafji VR treated at various ABC conditions by using pentane under constant SDA conditions such as a 40 kg/cm2g pressure, a 3 v/v solvent to oil ratio, and a 180 OC extractor bottom temperature (the column top temperature being higher than the bottom by 10 "C). Figure 3 shows that the yields of DAO and asphalt correlate well to the asphaltenes contents of SDA feedstocks. As the result of similar investigations made for other various feedstocks, it was recognized that the correlation obtained from Khafji VR could be practically applied to other feedstocks as shown in Figure 4. Therefore, the yields of ABC-treated oils are determined under the SDA conditionsmentioned above, provided that ABC conditions are fixed, since asphaltenes cracking reaction in ABC treatment is expressed by reaction kinetics,
75
0
2
4
6
8
1
kphdtenes Content of SDA Fedstock. wt%
Figure 4. DAO yield for various ABC-treated oil.
Figure 5. Effect of solvent ratio on DAO yield for ABC-treated Khafji VR.
which will be described later. Effect of SDA Conditions on DAO Yield. Although DAO and asphalt yields produced in the ABC/SDA combination process vary according to ABC conditions as mentioned before, they are also influenced by SDA conditions. The SDA operating conditions which govern the DAO yield consist mainly of two factors: the solvent to oil ratio and the extraction temperature in case the same solvent is employed as a deasphalting agent. An attempt has been made to express the effect of these two factors on a DAO yield by the relative DAO yield, i.e., the ratio of DAO yield obtained at various SDA conditions to the DAO yield defined at the following standard SDA conditions solvent solvent ratio extractor bottom temperature
butane 3 v/v 125 "C
pentane 3 vlv 180 "C
where the extractor top temperature is higher than the bottom by 10 "C. The results of an investigation of various ABC-treated oils from Khafji VR in both butane and pentane are shown in Figure 5. In this study both solvents show a similar tendency as the relative DAO yield increases when the solvent to oil ratio for various ABC-treated oils containing different amounts of asphaltenes is reduced. From the point of view that the curves in Figure 5, obtained at different extractor temperatures, are approximately parallel, the effect of the solvent to oil ratio can be expected to be almost the same at any extraction temperature, and it is also apparent that the effect of the solvent to oil ratio on a DAO yield is greater with butane than with pentane. The effect of extraction temperature with respect to butane and pentane is shown in Figure 6. The lower the temperature, the more the DAO yield, and the tendency is more marked in butane than in pentane. As a result, the lighter the solvent is as a deasphalting agent, the more the operating conditions will affect at SDA. It is clear that the degree of the effect of the SDA conditions on the DAO yield can be quantitatively correlated to any ABC-treated oil of Khafji VR by the relative value
Ind. Eng. Chem. Process Des. Dev., Vol. 23, No. 4, 1984
645
._ soivsnt Butane Solvent Ratio 5 v/b
Solvent Ratio J vlv
2
d
08
10s
115
0
12s
160
EXIm.ClOrBottom
Temperature 'C
8 170 ExtractorBottom Tcmpnturr. 'C
I80
1
Figure 6. Effect of extractor temperature on DAO yield for ABCtreated Khafji VR.
1 Rehtivr SPEC velocity
Figure 9. Second-order plot for asphaltenes cracking reaction.
51
10 Khafii VR
KhifJ SDA A s p M t
Solvent 0
Solvent 0 Butane A Pentane
Butane
0
3:
E
:: 33
o,
0.2
0.4
0.6
0.8
I Relative Space Vcleeity
--P--i
10
0.4
0.6
08
1.0
I Relative S p e e Veloeity
Figure 10. Second-order plot for asphalt cracking reaction.
== 0 0
99
'0
0.2
00,
quality of DAO obtained from the ABC/SDA combination process for Khafji VR can be found for various ABC conditions. Recycle Model of ABC/SDA Combination Process ABC Reaction Kinetics. Asphaltenes in heavy residua are cracked and reduced considerably during hydrotreating by the ABC catalyst. The apparent rate of the asphaltenea cracking reaction is expressed by the second order kinetics as illustrated in Figure 9 for Khafji VR. Figure 9 suggests that other solvent insolubles or SDA asphalt may be handled in the same way as asphaltenes. Therefore, conversion to DAO by ABC treatment of SDA asphalt contained in the feedstock and defined by using a solvent of butane or pentane for SDA has been investigated to determine whether or not it is fit for the second-order kinetics. The results shown on the left side of Figure 10 are for Khafji VR and those on the right side are for Khafji SDA asphalt, which is produced from Khafji VR by SDA using butane. Figure 10 indicates that conversion of SDA asphalt to DAO by ABC treatment can also be predicted fairly accurately by the second-order kinetics. The activation energy for conversionof these asphaltenic bottoms is about 26 kcal/mol K. Recycle Model. Since it was found that the conversion of SDA asphalt to DAO by ABC treatment can be expressed by the second-order kinetics, the model shown in Figure 11can be conceived for the ABC/SDA combination process wherein unreacted SDA asphalts are in turn recycled to the ABC section,provided those asphalts can also be expressed by the second-order kinetics. The symbols in Figure 11are interpreted as follows: F is the flow rate of the feedstock (fresh feed); D1and B1 indicates the rates of DAO and the asphalt obtained from F, respectively; R , is the total amount of the recycled asphalt; D, and B, indicates the rates of DAO and the
Ro. c o
do
k0
I
I I
1
Scheme I DI
I
1-
81
RI
81
W
Subatituting eq 8 and 9 for eq 12, the following equation can be derived
I
B1 = F
X (a0 X
ko/LHSV
+ c[')-'
(14)
where CY,, means the dilution rate for the fresh feed and is expressed as
Bn
Rn
Figure 11. Recycle model for ABC/SDA combination process.
asphalt obtained from R , respectively; Ro and Ri represent the rates of the asphalt contained in the fresh feed and the ith recycle stream, respectively; Bi+l and Di+l indicate the rates of DAO and the asphalt obtained from Ri; ko and ki are the rate constants of the fresh feed and the ith recycle stream, respectively; cf is the asphalt content of the fresh feed, co and do represent the asphalt contents of the fresh feed before and after the reaction, respectively; and ci and di represent the asphalt contents of the recycle stream before and after the reaction, respectively. If the mass change before and after ABC treatment is neglected, the material balance for the fresh feed will be as shown in Figure 11 F = D 1 + B1 (1) and the material balance for the ith recycle stream is (2) Ri = Di+l + Bi+l R, = D , + B, (3)
(YO
= F/(Rn + F)
(15)
Similarly for the ith recycle streams
Bi+l = Ri
X (ai X
kj/LHSV
+ l.O)-'
(16)
where ai indicates the dilution rate of the ith recycle stream and is expressed as ai
= Ri/(R,
+ F)
(17)
For the s u m of recycle streams
and by rearranging
where m
R, = C R i i=l
i=l m
B, = C B i + l is1
The asphalt content of each stream before and after the reaction is expressed as follows for the fresh feed co = Ro/(Rn + F) (7) Since
Ro = F CO
X cy
= F X c,/(R,
+ F)
(8)
do = Bl/(Rn + F)
(9) and the asphalt contents of the recycle streams are expressed as ci = R i / ( R , + F) (10) di = Bi+l/(Rn + F) The kinetic equation for the fresh feed is do-' - cO-' = ko/LHSV
and for the ith recycle stream is d;' - c;' = ki/LHSV
(11)
(12) (13)
In the case of ABC/SDA extinction recycle operation for Khafji VR using butane solvent at SDA, the change in flow ratio of recycle to fresh feed (recycle ratio), R,/F in relation to the operation time, and the change in both the rate constant of the recycled SDA asphalt and the value indicated by the parenthesis in eq 19 in relation to recycle times are shown in Figure 12. Here, the recycle times are estimated by the residence time in the unit. The lower side in Figure 12 indicates that ki and the value in the parenthesis in eq 19 decrease gradually with recycle times due to a greater difficulty to crack the recycled asphaltenea and become almost constant at the 13th recycle. When both of these become constant, the recycle ratio, RJF, is ale0 observed to become constant at about 500 h in Figure 12, and the reaction reaches a stationary state. The fact that the value in the parenthesis in eq 19 becomes constant suggests the possibility that the recycle stream is regarded as a single component. Therefore, the model in which the recycle stream is considered as a component for the recycle process containing partial withdrawal was investigated. This inventigation is illustrated in Scheme I, where c, and d, indicate the asphalt contents of the recycle stream before and aftsr the reaction, respectively. W expressee the withdrawal rate, and k, repreaenta the rate cbnstant of the asphalt contained in the recycle stream. The other symbols mean the same 88 described before. In this model, the material balance for the recycle stream is written as
R, = B1+ B , - W
(20)
Ind. Eng. Chem. Process Des. Dev., Vol. 23,No. 4, 1984 647
RnidmecThe: 16hr
i.th Recycle Stream
I
j
Relative Space Velocity at ABC Section
1
Figure 13. Confirmation of recycle model in extinction recycle operation for Khafji VR: (0)experimental data; (-) calculated results from recycle model.
O’I
0.01 5
10
Recycle Times
Figure 12. Change of recycle ratio and relative rate constants. Table IlI. Calculation Formula for Recycle Ratio
Wuhthdnvml to Fresh Feed b h o . w/w
Fieum 14. Effect of withdrawal rate on recycle ratio: (0) experimental data; (-) calculated results from recycle model.
I
OperationMode
Extinction Recycle
1
Calculation Formula
F
1
cfxLHSVx(kn t LHSV) knx(cFko+LHSV)
Partial Recycle
The asphalt contenta of each stream before and after the reaction are expressed as eq 21 and 22 for the recycle stream, respectively. Cn Rn/(Rn + F) (21) d n = Bn/(Rn + F) (22) The rate equation for the fresh feed is expressed as eq 14 and eq 23 is for the recycle stream. d,-’ - c,-’ = k,/LHSV (23) Substituting eq 21 and eq 22 for eq 23, eq 24 can be derived for the recycle stream B, = R, X (anX k,/LHSV + l.O)-l (24)
where anindicates the dilution rate for the recycle stream, i.e. an = Rn/(Rn+ F) (25) Finally, by substituting eq 14 and eq 24 for eq 20, the recycle ratio can be simply expressed by the equations of Table 111. Confirmationof Model. Extinction recycle tests have been carried out under several kinds of LHSV in order to confiim the recycle model, and the recycle ratio obtained from the test was compared with those calculated from the model. As shown in Figure 13, the model conforms with the teat. Furthermore, Figure 14 indicates that the model is also fit for the results of the test performed to withdraw the recycle stream partially. It has also been proved that the recycle ratio decreases linearly with the withdrawal rate. Although the model is very simple and convenient, the use of the model is limited by the reaction conditioQ, particularly low hydrogen pressure such as less than 90 kg/cm2. Conclusion The following are concluded by various ABC/SDA
640
~ n dEng. . Chem. process Des. Dev. 1904, 23,648-854
combination tests for Khafji VR. (1)Features of the ABC/SDA combination process become clear by product yields and qualities obtained from the three kinds of tests,i.e., conventional SDA, ABC/SDA once-through operation, and ABC/SDA extinction recycle operation. (2) Correlations related to product yield and quality are obtained for SDA operation of various ABC treated oils. (3) By modeling the ABC/SDA combination process including the recycle of SDA asphalt, the relation between the ABC condition and the recycle rate can be expressed quantitatively. Literature Cited Asaoka, S.; Nakata, S.; Shkoto, Y.; Takeuchi, C. Znd. fng. Chem. Process Des. Dev. 1983, 22, 248.
Ditman, J. G. w&oarbon Process. 1973, 52, 110. Flinn, R. A.; Beuther, H.;Schmld, B. K. Pet. Reflner 1961. 4 0 , 139. Takeuchl. C.; Nakamwa, M.; Shkoto, Y. Paper presented at the 62nd Canadian Chemical Conference & Exhibition, Sect. Novel Chem. Processes, Vancouver, June 6, 1970. Takeuchi. C.; Komatsu, S.; Kashlwara, H. Paper presented at the United Netlons Instttute for Trainlng and Research, Second International Conference on Heavy Crude and Tar Sand, Caracas, Feb 7, 1982. Takeuchl, C.; Nakamwa, M.; Shiroto, Y. I d . fng. Cbem. Process D e s . Dev. 1983, 22, 236.
Received for review May 24, 1983 Accepted October 31, 1983 This work was presented in part at the 185th National Meeting of the American Chemical Society, Division of Petroleum Chemistry, Symposium on Processing Heavy Oils and Residua, Seattle, WA, March 22, 1983.
Polymer Waste Reclamation by Pyrolysis in Molten Salts Carey Chambers, John W. L a w n , ' Walter Li, and Bob Wlesen Depsrtmnt of Chemistty, University of Tennessee, Knoxville, Tennessee 379 16
The rubber-rich organic fraction from an automobile shredder has been pyrolyzed in a variety of molten salts at temperahre6 between 380 and 570 'C. The reactkns are very rapid. As the temperahre is increased, the amount of methane increases, whk the C4 gases decrease. Gas production was higher [30% (wt/feed)] with more acidii melts such as NaCI/AICi,. Production of lower boiling oils is favored by longer residence times in the reactor. Hydrogen is the limiting factor in the reactions, the residue being a carbon char. Most efficient conversion of hydrogen in the feed to useful products was obtained usJng a KCIIUCI melt containing 10 % CuCI. Both the nature of the products and the amount of hydrogen retained in the product char depend on the molten salt used as the pyrolysis medium.
Introduction A study of the utility of several molten salts as pyrolysis media in the reclamation of automobile shredder wastes has been made. Ford Motor Company Research estimates that in 1978, the average junked car contained 80 kg of plastic and non-tire rubber (Mahoney et al., 1979). The amount is expected to increase at a rate of 4% per year. About 30% of the plastics and 70% of the rubber are collected as part of the nonmagnetic fraction of the junk car shredder output. After separation of the nonferrous metals from this fraction, the remaining rubber and plastic is land-filled. It is eetimated that by 1990 a nonferrous metal processor handling the nonmagnetic fraction obtained from two million shredded automobiles will process -200 million kilograms of plastic and rubber waste. Disposal of such quantities of material in landfills, which is the current practice, is costly as well as a waste of a petroleum-based resource. This investigation is a further development of earlier work (Larsen and Chang, 1976) on the recovery of valuable products from old tires by pyrolysis in molten salts. Any useful products of the pyrolysis of this scrap will have a higher H/C ratio than that of the scrap ( 1)and so the efficient recovery of the hydrogen contained in the scrap is an important goal. The second goal is to produce pyrolysis products of maximum value. The third goal is to
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*Address inquiries to this author at Department of Chemistry, Lehigh University, Bethlehem, PA 18015. 0196-4305/84/1123-0648$01.50/0
achieve rapid pyrolyses; thus molten salts with their excellent heat transfer properties are interesting media. Early results showed that the reactions in most salts are quite rapid, at least 90% (vol) of the gasses produced appearing during the first 400 s reaction at 450 "C (Chambers et al., 1981). The principal questions addressed here are the dependencies of the efficiency of hydrogen utilization and of the nature of the products on the molten salt used in the pyrolysis. It was necessary to establish early in this investigation whether the hydrogen utilization and product slate depended significantly on the nature of the salt used as the pyrolysis medium and, if so, which salts would lead to the most efficient use of hydrogen to form the most valuable products. This portion of the investigation is reported here. A subsequent paper will deal with reaction kinetics and a more complete study of the most interesting systems. To determine conditions that give the most favorable product yields from the shredder waste, catalytic and noncatalytic melts were examined. Molten salt systems studied included a tetrachloroaluminate melt, several cuprous chloride-containing melts, zinc chloride and zinc chloride eutectics, and a lithium chloride-potassium chloride eutectic. Ford Motor Company Research is concurrently investigating an inert gas pyrolysis reclamation process on the same batches of shredder material. The yield and composition of oil and gas products obtained from the two different processes will be compared, with the aim of deciding which process holds greater promise for further development work. The yields of oil and gas obtained when molten salts are used as the pyrolysis me@ 1984 American Chemical Society
