ARTICLE pubs.acs.org/EF
Direct Thermal and Catalytic Treatment of Paraffinic Crude Oils and Heavy Fractions Robert L. Krumm,*,† Milind Deo,† and Mike Petrick‡ †
Department of Chemical Engineering, University of Utah, Room 3290, 50 South Central Campus Drive, Salt Lake City, Utah 84112, United States ‡ Argonne National Laboratory, 9700 South Cass Avenue, Argonne, Illinois 60439, United States ABSTRACT: With the continuously decreasing quality of crude oils, issues may arise with refining and transporting such oils. New technology must be developed to address these issues. Coupling a thermal cracker with a catalytic cracker in series was investigated as a possible method of directly treating heavy fractions as well as paraffinic whole crude oils. A potential application of this cracker configuration would be upstream treatment of high pour point crudes to improve flowability. The idea was to deposit a fraction of the coke on the thermal medium that would otherwise be deposited on the catalyst, thereby extending the life of the catalyst. This concept was tested using two transport reactors, one with sand and the other with catalyst, and with three feedstocks, atmospheric residuals, fluid catalytic cracker feed, and a waxy crude oil. Product distributions were determined for variations in thermal and catalytic cracker residence times, cracker temperatures, feedstock type, and catalyst/oil ratios. The data gathered show that coupling a thermal and a catalytic cracker may provide some definite advantages. The typical liquid yields for the combined thermal and catalytic cracker ranged from around 50 to 75%. One of the experiments produced a bimodal distribution of hydrocarbons in the liquid products, with the first distribution being olefinic and the second distribution being paraffinic, with a 68.4% liquid yield. Promising results were obtained with a waxy crude oil, wherein 34.6% by weight of the liquid products was naphtha.
’ INTRODUCTION Petroleum refining comprises 7.4% of the U.S. energy use.1 One of the most important processes in petroleum refining is cracking. Cracking is used to upgrade heavy oil feedstocks into lighter and more profitable distillate fractions. Thermal cracking involves heating oil in the absence of oxygen to break long and heavy molecular chains into lighter chains. Thermal cracking units were introduced into the refining process in 1913 to produce products such as gasoline.2 Thermal cracking in the form of visbreaking is used in modern refining processes to reduce the viscosity of residual oils.3 Coking is another form of thermal cracking being used by refineries. Coking is used to upgrade residual oil and remove contaminants from process streams that would not otherwise be suitable for a catalytic cracker.2,4 Linden and Peck5 were able to show that coke production in thermal cracking increases with heavier feedstocks. More than 50 years have passed since Linden and Peck’s research, and with the trend in oil production toward heavier crudes,6 thermal cracking remains an important refining process. The chemistry of thermal cracking is breaking molecular bonds to form free radicals, which continue to react and form more free radicals.7 Thermal cracking of long paraffinic chains yields αolefins from primary cracking, ethylene and propylene from secondary cracking, methane and ethane from free-radical elimination,8 and coke. Thermal cracking is not selective and produces more methane than catalytic cracking. Commercial catalytic cracking technology began in the 1920s with Eugene Houdry. The first commercial fluid catalytic cracking (FCC) unit began operation in 1942.2,4 Fluid catalytic cracking is one of the most important refinery operations, with many improvements since its introduction. The typical FCC comprises two major units, the reactor and the regenerator. In the reactor, hot catalyst vaporizes oil and initiates cracking. As the catalyst promotes reaction, coke deposition on the catalyst reduces its activity. The regenerator r 2011 American Chemical Society
Figure 1. Schematic for the combined thermal and catalytic crackers: (1) nitrogen tank, (2) oil storage bucket, (3) sand storage hopper, (4) thermal cracker mixer, (5) risers, (6) cyclones, (7) thermal solids collection, (8) catalyst storage hopper, (9) catalytic cracker mixer, (10) catalytic solids collection, (11) exhaust, (12) Allihn condenser, (13) coil condenser, (14) filter, (15) pump, (16) dry gas flow meter, and (17) bag for gas samples.
combusts the coke on the catalyst to restore activity while supplying energy to the FCC process. Innovative FCC reactor/regenerator configurations have resulted in better yields and operation.9 Developments in catalysts Special Issue: 12th International Conference on Petroleum Phase Behavior and Fouling Received: September 15, 2011 Revised: November 21, 2011 Published: November 22, 2011 2663
dx.doi.org/10.1021/ef2013985 | Energy Fuels 2012, 26, 2663–2671
Energy & Fuels
ARTICLE
have had a great impact on FCC operation and yields. One of the greatest advancements in catalyst technology was the introduction of zeolite-Y in the 1960s.10 Zeolite-Y has greater gasoline selection than previous catalysts, and its implementation improved FCC profitability. Mobil developed the ZSM-5 catalyst to improve gasoline octane rating and olefin production.11 The current state of the art in catalyst development is finding catalysts that are resistant to metal (e.g., Ni) poisoning and catalysts suitable for residual oils.10 With the continuously decreasing quality of crude oils, issues may arise with refining and transporting such oils. New technology must be developed to address these issues. The intent of this study was to determine if combining a thermal cracker and a FCC into one unit is a feasible method for directly treating heavy fractions and whole paraffinic crudes. Having the thermal cracker before the catalytic cracker allows for the cracking of large molecules as well as removing coke. The catalytic cracker further upgrades the products from the thermal cracker. An argument that combining both processes could work is that thermal cracking and catalytic cracking occur simultaneously in every FCC and that the smaller molecules and free radicals from thermal cracking can be acted upon by a catalyst.12 Thermal preprocessing is not commonly used in most refineries. Thermal processing in the form of coking is the main Table 1. Summary of the Simulated Distillation of the Feedstocks Useda feedstock
waxy crude
atmospheric residuals
FCC feed
0.001
distillation mass fraction
a
naphtha (38204 °C)
0.101
0.001
middle distillate (204343 °C)
0.191
0.062
0.074
fuel oil (343566 °C)
0.411
0.581
0.888
residuals (566+ °C)
0.138
0.160
0.012
undetected
0.159
0.196
0.013
Values are reported as mass fractions. The waxy crude contained the largest amount of the residual fraction as well as a high amount of undetectable hydrocarbons. The FCC feed contained the lowest amount of residuals and undetectable hydrocarbons.
component of most schemes for the upgrading of heavy and ultraheavy oils (bitumen). The purpose of this work was to improve the overall operability in typical refining/processing. Two possible applications of a hybrid thermal/catalytic system would be as follows: (1) The treatment of highly asphaltenic oils, wherein the thermal process would be used to deposit coke on the sand, extending the life of the catalyst and the efficiency of the catalytic treatment process in the subsequent step. (2) Treatment of a whole crude oil prior to distillation, thus reducing overall process energy requirements. In addition to determining if combining thermal and catalytic crackers is feasible, this study investigated the effect of the temperature, residence time, catalyst/oil ratio, and feedstock on liquid yields and product slates.
’ EXPERIMENTAL SECTION The apparatus in the experiments consisted of two crackers in series. The configuration of the apparatus was intended to reach a pseudo-steady state. The crackers used in these experiments were similar in design to a reactor used by Zhang et al.13 for fast pyrolysis of biomass. Each cracker consisted of a mixer, a riser, and a cyclone. The apparatus also had two hoppers for heating and storing solids, a reservoir for heating and containing oil, and a sample collection system. A flowchart for the entire system is represented in Figure 1. The mixers used in the experiments were fabricated out of stainless steel. The mixers consisted of two separate parts, a body and a distributor plate. The mixer body was a 76.2 mm diameter cylinder with a reducer at the top, choking the diameters down to 25.4 mm. The distributor plate was perforated with approximately 30, 1.6 mm holes through which air or nitrogen would enter the mixer. Tape heaters and cartridge heaters were used to heat the mixers. Two identical stainless-steel risers were used in this experiment. The risers measured 1.2 m in length and 25.4 mm in diameter. Cyclones were used to remove solids from the mixture exiting the risers. A slipstream collection system was used to condense part of the product stream. The slipstream collection system sampled a fraction of the products and was tapped into the exhaust line. The collection system consisted of one Allihn condenser, one coil condenser, a pump, a filter, and a dry gas meter. Liquid samples were collected from the condensers, and gas samples were taken in bags. Gas samples were analyzed on a Hewlett-Packard 6890 gas chromatograph fitted with an Agilent GS-GasPro column with a flame ionization detector (FID). The FID operated at a temperature of 300 °C with
Figure 2. Simulated distillation of the feedstocks used. The atmospheric residue and the waxy crude had components in the higher SCN range. The atmospheric residuals had the largest amounts of residual hydrocarbons and undetected sample. The catalytic cracker feedstock had the least amounts of residuals and undetected hydrocarbons. 2664
dx.doi.org/10.1021/ef2013985 |Energy Fuels 2012, 26, 2663–2671
Energy & Fuels 400 mL/min of air and 42 mL/min of hydrogen. The gas makeup for the FID was 50 mL/min of helium. Liquid samples were analyzed using American Society for Testing and Materials (ASTM) D5703-97 simulated distillation.14 The simulated distillation was performed on a Hewlett-Packard 6890 gas chromatograph with a MXT-1 column. The carrier gas in the column was helium and flowed at a constant 1.0 mL/min. A FID was used to detect components as they eluted from the column. The FID operated at 450 °C with a zero air flow rate of 400 mL/min and a hydrogen flow rate of 40 mL/min. Determination of coke production was performed by thermogravimetric analysis using a TA Instruments Q500. The mass of coke on the sample was determined by the weight difference. The mass balances are reported as fractions of the oil fed into the system and are comprised of four segments, gas, liquid, coke, and non-reacted oil. Liquid was defined as any component heavier than ethylene. The total amount of gas produced is the remaining mass after the masses of the liquids, coke, and non-reacted oil are subtracted from the mass of the oil fed. The residence times for the vapor stream depended upon the riser temperature, the nitrogen flow rate, and the amount of solids being fed into the system. The calculations for the residence times assume a fast
Figure 3. Mass balances for thermal cracker experiment T2 and catalytic cracker experiments C3 and C4. The mass balances are reported as percentages of the mass of feedstock oil fed into the system. The mass balances consist of gas, liquid, and coke fractions. Gas and liquid samples were analyzed using gas chromatography and simulated distillation. Coke was determined by gravimetric analysis. The gas fraction of the mass balance was calculated as the remainder of the mass of the oil fed subtracting the masses of liquid and coke. Experimental conditions can be found in Table A1 in Appendix A.
ARTICLE
fluidization regime and that the reactors are well-mixed. The residence times reported were calculated using eq 115 τ¼
εVR νmix
ð1Þ
where τ is the residence time, ε is the void fraction, νmix is the volumetric flow rate, and VR is the volume of the reactor.
’ RESULTS AND DISCUSSION Feedstock Analysis. Three different feedstocks were examined in this study, atmospheric residuals, FCC feed, and a waxy crude oil. Simulated distillation was performed on the feedstocks, and the results of the analysis are reported in Table 1. The atmospheric residue had more components tailing off into the higher single carbon number (SCN) range (Figure 2). The atmospheric residuals had the highest percentage of residuals and undetected hydrocarbons. The FCC feedstock contained the smallest percentages of residuals. Summary of Experiments. A total of 11 experiments will be discussed in this paper: 1 thermal cracker experiment, 2 catalytic cracker experiments, and 8 combined thermal cracker and catalytic cracker experiments. A summary of the experiments performed and the results of the experiments are reported in Table A1 in Appendix A. Thermal Cracker Only Experiment. Experiment T2 was two thermal crackers in series with solids being added in each mixer and solids removed in each cyclone. This was performed by reconfiguring the catalytic cracker for thermal cracking. This configuration was chosen to provide the highest possible amount of thermal cracking. The feed for experiment T2 was atmospheric residual, as seen in Figure 3. In experiment T2, the amount of coke from the first thermal cracker was measured to be 0.13% of the total mass of solids collected, while the amount of coke collected from the second thermal cracker was 0.04%. Even though the residence times for both risers were not identical, the residence time for the second riser was very close to the catalytic cracker residence times for some of the combined thermal/ catalytic experiments. This is important because it shows that the majority of the catalyst deactivating coke can be removed by the frontend thermal cracker. The liquid product samples for experiment T2 were analyzed using pseudo-single instruction multiple data (SIMD), and residuals were not determined. Thermal cracking caused a shift in the products
Figure 4. Boiling point fractions from hydrocarbon products produced by the thermal cracker experiment and the catalytic cracker experiments. The values presented relate the mass of the boiling point fraction to the total amount of feedstock fed into the system. The products are shown alongside the fractions of the atmospheric residual feedstock. The fractions are broken down into categories based on boiling point ranges and the amount of sample that was undetected. Samples were analyzed using gas chromatography for the vapor samples and simulated distillation (ASTM 5703-97) for the liquid samples. The amount of undetected hydrocarbons was not determined for experiment T2. The amount of residuals and undetected fraction from the catalytic cracker experiments was very small. 2665
dx.doi.org/10.1021/ef2013985 |Energy Fuels 2012, 26, 2663–2671
Energy & Fuels
ARTICLE
Figure 5. Mass balances for selected experiments using combined thermal and catalytic crackers. The mass balances are reported as percentages of the mass of feedstock oil fed into the system. The mass balances consist of five categories: gas, liquid (defined as hydrocarbons with molecular weights greater than or equal to that of propane), thermal coke, catalytic coke, and residuum left in the reactors after the experiment was completed. Gas and liquid samples were analyzed using gas chromatography and simulated distillation. Thermal coke and catalytic coke were analyzed using gravimetric analysis. The gas fraction of the mass balance was calculated as the remainder of the mass of the oil fed subtracting the amounts of liquids, coke, and residuum. Experimental conditions are reported in Table A1 in Appendix A.
toward naphtha and the middle distillate fractions and a reduction in the fuel oil fraction. It is difficult to make a comparison between literature values for the expected yields of fluidized thermal crackers and fluidized catalytic crackers and the experimental values because of differences in operational conditions and feedstock compositions.
Literature values for expected refinery yields for fluidized thermal cracking of feedstocks similar to those used in these experiments range in coke yields from 12 to 21 wt %, liquid yields ranging from 71 to 81 wt %, and gas yields ranging from about 8 to 15 wt %.16,17 Catalytic Cracker Only Experiments. The main difference between the catalytic cracker experiments C3 and C4 was the 2666
dx.doi.org/10.1021/ef2013985 |Energy Fuels 2012, 26, 2663–2671
Energy & Fuels
ARTICLE
Figure 6. Boiling point distribution of the liquid hydrocarbon products from experiments using both the thermal and catalytic crackers. The values presented relate the mass of the boiling point fraction to the total amount of feedstock fed into the system. Products are compared to the respective feedstock used for the experiment. Samples were analyzed using gas chromatography for the vapor samples and simulated distillation (ASTM 5703-97) for the liquid samples. All experiments showed some degree of conversion of the higher molecular-weight hydrocarbons and an increase in the naphtha and middle distillate fractions.
catalyst/oil ratio. The catalyst/oil ratio for experiment C3 was 15:1, and the catalyst/oil ratio for experiment C4 was 5:1. This compares to commercial catalyst/oil ratios ranging from 5.7:1 to 9.5:1.18
The higher amount of liquid product obtained with the catalytic cracker experiments compared to that of the thermal cracker experiment is due to catalytic cracking producing less gas 2667
dx.doi.org/10.1021/ef2013985 |Energy Fuels 2012, 26, 2663–2671
Energy & Fuels
ARTICLE
Figure 7. Simulated distillation SCN distributions for experiment TC14. The simulated distillation of products from experiment TC14 has two overlapping Gaussian peaks. The first peak in the distribution for experiment TC14 consists mostly of olefin compounds, and the second peak is mostly paraffinic. Naphtha is considered to be compounds ranging from SCN 5 to SCN 12 based on the boiling point. A sizable part of the olefinic compounds produced for TC14 fall within the naptha fraction. The presence of a discernible olefin peak with experiment TC14 suggests that the conditions used were favorable for olefin production.
per extent of conversion. This is consistent with data presented by Avidan et al.12 The mass balances also show that the amount of coke formed is greater with higher catalyst/oil ratios. The higher amount of gas present in experiment C4 may be the result of more thermal cracking occurring alongside catalytic cracking. The products from the catalytic cracker experiments have greater fractions of naphtha and middle distillates than the thermal cracking experiment. The catalytic cracker experiments produced small residual fractions, as seen in Figure 4. Literature values for refinery FCC yields vary: coke yields range from 2 to 8 wt %; gas yields range from 1 to 10 wt %; and liquid yields range up to 90 wt %.16,17 Thermal and Catalytic Crackers in Series Experiments. Dependence upon the Riser Temperature. Experiments TC5 and TC9 illustrate the dependence of the products upon the temperatures of the crackers. Experiment TC5 had a thermal cracker riser temperature of 587 °C, while experiment TC9 had a thermal riser temperature of 377 °C. Experiment TC5 also had a higher catalyst riser temperature. The solids recovered from the thermal cracker on experiment TC5 contained 0.07% coke, while the solids collected from the thermal cracker for TC9 were 0.06% coke. Increases in the temperature have been shown to increase the rate of paraffin cracking.19 The difference in the amounts of coke produced suggests that more thermal cracking occurred with the higher thermal riser temperature. Mass balances for experiments TC5 and TC9 can be found in Figure 5. There may have been gas production from coking in the catalytic cracker for experiment TC9. Jacob et al.20 postulated that the ratio of coke produced per amount cracked is greater at lower temperatures. More coke at lower temperatures is due to the lower activation energy for coking compared to cracking.21 More coking on the catalyst with lower temperatures can be evidenced by the catalytic cracker solids from TC9 being 0.82% mass coke compared to 0.60% for experiment TC5. As shown in Figure 6, the product slates for TC5 and TC9 show that the conditions used for TC5 produced lighter distillate fractions than its colder counterpart, especially in the middle
distillate range. The conversion of the heavier fractions was also greater with the hotter risers used in experiment TC5. Dependence upon the Catalytic Cracker Residence Time. The experiments TC10 and TC11 show the variation in products because of differences in the catalytic cracker residence time. Experiment TC10 had a catalytic cracker gas residence time of 0.32 s, while experiment TC11 had a residence time of 0.23 s. As shown in Figure 5, the coke yield was higher and the liquid yield was lower with TC11 compared to TC10. The higher amount of gas products from experiment TC11 is suggestive of more thermal cracking, possibly because of the sand feed temperature of 771 °C compared to 672 °C for TC10. The conversion of molecules with a boiling point greater than 566 °C was greater for TC10 than TC11 (Figure 6). The difference in this conversion may be the result of the different residence times in the catalytic cracker. Voorhies21 had shown that the extent of cracking increases with residence time. This suggests that certain catalytic cracker residence times may provide greater amounts of naphtha and middle distillate fractions. Experiments with a Higher Catalyst/Oil Ratio. Two experiments, TC12 and TC13, were performed with a catalyst/oil ratio of 18:1. The catalyst/oil ratio of 18:1 corresponds to the maximum catalyst feed rate for the apparatus used. A catalyst/oil ratio of 18:1, with somewhat similar conditions to experiments with catalyst/oil ratios of 10:1, provided higher amounts of liquid products. This suggests that more catalyst in the reactor can reduce the effects of thermal cracking in a catalytic reactor. Dependence upon the Feedstock. A different feedstock was used for two experiments to determine the effect of the feedstock on conversion and product slates. In experiment TC8, a FCC feedstock was used, while in experiment TC15, a waxy crude oil (whole oil) was used. The amount of coke formed in experiment TC8 was less than in a similar experiment conducted with atmospheric residuals, TC10. This difference in the amount of coke produced suggests that coke production is directly related to the feedstock characteristics. The production of gas products was also greater for TC8 than TC10. The greatest reduction with the FCC feedstock 2668
dx.doi.org/10.1021/ef2013985 |Energy Fuels 2012, 26, 2663–2671
Energy & Fuels
ARTICLE
was in the fuel oil fraction. There was more naphtha production with the FCC feedstock than the atmospheric residuum. There was good production of liquid products for experiment TC15 with the waxy crude oil. The comparison of simulated distillation of the products of experiment TC15 and the waxy crude feedstock can be found in Figure 6. The simulated distillation of the highly paraffinic crude used showed that 13.8% mass of the sample had a boiling point above 566 °C and 15.9% of the crude did not elute from the gas chromatography column. This contrasts with the cracked products, where only 2% of the sample has a boiling point greater than 566 °C and less than 1% of the sample did not elute from the column. The most notable differences between the simulated distillations of the product and the feedstock are the reduction residual fraction and increase in the naphtha fraction. There was a 24.5% mass increase in the naphtha fraction between the waxy crude feedstock and the product. The data presented in the product analysis for experiment TC15 suggest that the conditions and feedstock used were favorable toward naphtha production. Presence of Olefinic Products. Experiment TC14 was conducted with the goal of maximizing cracking. The main difference between experiment TC14 and most of the other experiments (with the exception of experiment TC15) is that experiment TC14 had exceptionally long residence times in both crackers. Experiment TC14 had a liquid yield of 68.4%. While the liquid yields were less than some of the other thermal and catalytic cracker experiments, the product slate for experiment TC14 shows a good conversion of the residual and the fuel oil fractions. The simulated distillation of the products from experiment TC14 shows two overlapping peaks. The simulated distillation distributions can be seen in Figure 7. The first peak for TC14 is mostly olefinic, and the second peak is mostly paraffinic. A sizable portion of the olefinic peak falls
within the naphtha fraction boiling point range (SCN < 12). The presence of a discernible olefin peak with experiment TC14 suggests that the conditions used were favorable for olefin production.
’ CONCLUSION We were successful in showing that combining a thermal cracker and a catalytic cracker into one continuous process is a feasible means for directly upgrading heavy fractions as well as waxy crude oil. We were also able to show how product quality and the type of products depend upon a number of variables, including the riser temperature, residence time, and feedstock. Experiment TC14 showed good production of light olefins using both a thermal cracker and a catalytic cracker. The results of experiment TC14 are particularly important for a few reasons. The first reason is that the condensate simulated distillation distribution had two peaks, the first being olefinic and the second being paraffinic. The second reason that this experiment was important is that it shows selectivity for naphtha production. The third reason is that the liquid yields were comparable to the catalytic cracker only experiments when the gas products were reduced. Experiment TC15, which used waxy crude as the feedstock, had the highest amount of naphtha in the products stream, 34.6%. This hints at the possibility of using this technology for upstream treatment of certain crudes to improve flowability. ’ APPENDIX A Summary of the conditions and products for each experiment (Table A1) and computer-aided design (CAD) drawing for the combined thermal and catalytic cracker apparatus (Figure A1).
Table A1. Summary of the Conditions and Products for Each Experimenta experiment
T2
feedstock
C3
C4
atmospheric; residuals
sand/ oil
15:l
catalyst/oil
15:1b
TC7
TC8
FCC feed
TC15
TC5
TC9
new field
TC11
TC14
TC12
TC13
atmospheric; residuals
n/a 15:1
TC10
15:1 5:1
10:l
18:1
thermal side temperature (°C)
726
432
443
504
587
377
466
499
489
532
488
τ residence (s)
0.84
0.89
0.876
0.965
0.54
0.558
0.85
0.887
0.984
0.78
0.477
N2 flow (L/h) catalytic side
2124
2265
2265
1982
2832
3398
2265
2124
3398
2265
3398
temperature (°C) τ residence (s)
682c 0.33
651 1.44
702 1.44
510 0.315
488 0.324
431 0.58
482 0.32
454 0.27
510 0.315
538 0.234
510 0.522
621 0.256
510 0.251
N2 flow (L/h)
2124
1416
1416
2265
2265
1133
1699
1982
2265
3398
1982
2265
1982
mass fractions (wt % of feed) gas
328
8.5
17.8
32.0
25.2
19.6
21.2
28.8
15.5
27.3
8.5
15.6
15.7
liquid coke
64.6 2.6
80.3 11.2
76.8 5.4
63.1 4.9
68.2 6.6
71.5 8.9
68.2 10.6
61.2 10.0
70.9 13.5
57.6 15.1
68.4 23.0
72.7 11.7
74.0 10.3
reactor residua
0.0
0.0
0.0
0.0
0.0
0.6
0.0
2.9
4.1
0.0
3.0
4.7
4.3
gas products (HC % mass in gas sample) methane
7.2
4.8
6.6
1.2
3.8
3.7
6.8
6.1
3.6
7.1
23
2.8
1.7
ethane
2.7
1.6
23
0.5
1.5
1.5
3.9
1.7
1.3
1.6
1.2
1.0
0.8
ethene
31.8
5.4
14.4
5.1
16.3
13.6
21.3
30.8
16.8
30.1
7.8
14.1
7.1
propanes propenes
1.1 18.8
27 20.7
1.4 19.4
0.2 7.3
0.6 11.8
1.3 14.8
1.2 18.7
1.0 16.1
0.6 13.2
2.9 13.8
0.6 9.5
0.7 17.8
0.6 10.2
butanes butenes pentanes
0.6 9.3 10.7
22.5 5.6 34.4
13.0 6.3 31.5
2.3 2.5 12.1
1.8 4.0 13.2
8.9 5.0 27.1
4.0 7.5 18.9
0.8 6.1 11.3
1.7 5.6 13.0
0.9 6.2 10.4
4.1 3.2 13.4
1.4 7.0 19.5
3.3 3.9 14.8
pentenes
3.7
1.2
2.2
1.5
1.5
2.4
4.2
2.1
3.1
2.5
1.9
2.4
2.5
2669
dx.doi.org/10.1021/ef2013985 |Energy Fuels 2012, 26, 2663–2671
Energy & Fuels
ARTICLE
Table A1. Continued experiment
T2
C3
C4
TC7
TC8
TC15
TC5
TC9
TC10
TC11
TC14
TC12
TC13
hexanes hexenes
0.1 5.2
0.5 0.3
0.6 1.0
12.3 4.9
10.1 2.6
2.0 2.4
0.3 5.4
7.0 3.7
11.8 5.2
7.2 4.3
12.2 3.2
11.0 4.2
13.6 4.1
>C6
6.9
0.2
0.8
19.5
11.3
11.0
6.3
10.6
19.0
10.2
37.2
13.7
27.2 10.8
product slates (mass %) naphtha (38204 °C)
11.6
23.5
25.6
16.8
14.4
34.6
16.7
13.5
13.0
120
16.6
15.2
middle distillate (204343 °C)
16.1
36.8
34.0
12.7
14.0
23.6
26.7
14.9
16.7
10.9
19.8
20.6
14.2
fuel oil (343566 °C)
45.5
18.9
20.0
39.6
48.3
20.0
24.7
38.1
428
33.7
34.7
39.7
50.3
residuals (566+ °C)
n/a
0.5
0.5
0.2
0.2
1.7
0.8
2.6
3.5
4.8
22
2.8
6.8
1.9
2.1
0.4
2.3
2.6
1.3
3.7
3.9
13.4
1.9
1.6
0.13
0.05
0.02
0.08
0.07
0.06
0.25
0.25
0.69
0.09
0.13
solid products thermal coke (wt % of feed) (wt % of solids) catalytic coke (wt % of feed) (wt % of solids)
0.7b
11.2
5.4
2.8
6.1
6.6
8.0
8.7
9.9
11.1
9.6
9.8
8.7
0.04b
0.87
1.24
0.15
0.42
0.52
0.60
0.82
0.93
0.95
0.62
0.62
0.61
a
Experiments starting with T represent a thermal cracking only. Experiments starting with C represent catalytic cracking only. Experiments starting with TC represent thermal and catalytic crackers in series. The residence times in Table 1 were calculated using eq 1. Hydrocarbons at least as heavy as propane are considered liquid products. The gas fraction in the mass balance is the remainder after subtracting the masses of coke, liquid products, and reactor residua from the mass fed. Gas chromatography was used to determine the vapor compositions. Liquid products were quantified using ASTM 5703-97 simulated distillation. The fractions of undetectable hydrocarbons from simulated distillation were lumped with the residuals reaction. Solid product masses were determined by combusting coke on sand or catalyst. b Sand fed instead of catalyst. c Runs performed using risers from both thermal and catalytic crackers.
’ AUTHOR INFORMATION Corresponding Author
*E-mail:
[email protected].
’ ACKNOWLEDGMENT We gratefully recognize those who helped with this research: Reza Sadeghbeigi, Lamont Tyler, Vince Memmott, Jim Vemich, Dave Wagner, Ryan Okerlund, Kohle Hansen, Nick Dahdah, and Pankaj Tiwari. We also thank Argonne National Laboratory and the Department of Energy for their financial support. ’ REFERENCES
Figure A1. CAD drawing for the combined thermal and catalytic cracker apparatus. The two crackers consisted of a mixer, a riser, and a cyclone. The mixers were 3 in. in diameter and had a distributor plate for nitrogen. The risers measured 1.22 m in length and 25.4 mm in diameter. Stainless steel was used for all plumbing applications. Not shown are the heaters, the oil feeding system, and the condensers.
(1) United States Energy Information Administration (U.S. EIA). DOE/EIA Monthy Energy Review (Preliminary) and Extrapolates from MECS; U.S. EIA: Washington, D.C., 2004. (2) Speight, J. G. Petroleum refinery processes. In KirkOthmer Encyclopedia of Chemical Technology; Wiley: Hoboken, NJ, 2007; Vol. 1, pp 291333. (3) Salazar, J. R. Handbook of Petroleum Refining Processes; McGrawHill: New York, 1986. (4) Sadeghbeigi, R. Fluid Catalytic Cracking Handbook; Gulf Publishing Co.: Houston, TX, 1995. (5) Linden, H. R.; Peck, R. E. Gasous product distribution in hydrocarbon pyrolysis. Ind. Eng. Chem. 1955, 2470–2474. (6) Swain, E. J. Sulfur, coke, and crude quality—Conclusion: US crude slate continues to get heavier, higher in sulfur. Oil Gas J. 1995, 93:2, 37–42. (7) Kossiakoff, A.; Rice, F. O. Thermal decomposition of hydrocarbons, resonance stabilization and isomerization of free radicals. J. Am. Chem. Soc. 1943, 65 (4), 590–595. (8) Voge, H. H.; Good, G. M. Thermal cracking of higher paraffins. J. Am. Chem. Soc. 1949, 71 (2), 593–597. (9) Wilson, J. W. Fluid Catalytic Cracking Technology and Operations; PennWell: Tulsa, OK, 1997. (10) Harding, R. H.; Peters, A. W.; Nee, J. R. D. New developments in FCC catalyst technology. Appl. Catal., A 2001, 221 (12), 389–396. 2670
dx.doi.org/10.1021/ef2013985 |Energy Fuels 2012, 26, 2663–2671
Energy & Fuels
ARTICLE
(11) Degnan, T. F.; Chitnis, G. K.; Schipper, P. H. History of ZSM-5 fluid catalytic cracking additive development at Mobil. Microporous Mesoporous Mater. 2000, 3536, 245–252. (12) Avidan, A. A.; Shinnar, R. Development of catalytic cracking technology. A lesson in chemical reactor design. Ind. Eng. Chem. 1990, 29, 931–942. (13) Zhang, H.; Xiao, R.; Huang, H.; Xiao, G. Comparison of noncatalytic and catalytic fast pyrolysis of corncob in a fluidized bed reactor. Bioresour. Technol. 2009, 1428–1434. (14) American Society for Testing and Materials (ASTM). ASTM D5703-97, Standard Test Method for Determination of Boiling Range Distribution of Crude Petroleum by Gas Chromatography; ASTM International: West Conshohocken, PA, 2002. (15) Schmidt, L. D. The Engineering of Chemical Reactions; Oxford Universitty Press: New York, 2005. (16) Maples, R. E. Petroleum Refinery Process Economics; PenWell Corporation: Tulsa, OK, 2000. (17) Raseev, S. Thermal and Catalytic Processes in Petroleum Refining; Marcel Dekker, Inc.: New York, 2003. (18) Gray, M. R. Upgrading Petroleum Residues and Heavy Oils; Marcel Dekker, Inc.: New York, 1994. (19) Bragg, L. B. Rate of cracking of paraffin wax. Ind. Eng. Chem. 1941, 376–380. (20) Jacob, S. M.; Gross, B.; Voltz, S. E.; Weekman, V. W. J. A lumping and reaction scheme for catalytic cracking. AIChE J. 1976, 701–713. (21) Voorhies, A. J. Carbon formation in catalytic cracking. Ind. Eng. Chem. 1945, 318–322.
2671
dx.doi.org/10.1021/ef2013985 |Energy Fuels 2012, 26, 2663–2671
