Energy & Fuels 1989,3,116-119
116
Art ic 1es Coprocessing Technology Development in Canada7 F. G. Boehm, R. D. Caron, and D. K. Banerjee" Canadian Energy Developments Inc., 4222 - 97 Street, Greystone Pavillion, Edmonton, Alberta, Canada T6E 529 Received July 28, 1988. Revised Manuscript Received September 16, 1988
The technical and economical viability of coprocessing technology is considered. Coprocessing involves simultaneous upgrading of heavy oil and subbituminous coal to synthetic fuels. Preliminary economic screening studies have shown that coprocessing offers economic advantages over conventional heavy oil upgrading. The capital costs are similar, but feedstock costs are lower because up to one-third of the heavy oil feedstock is replaced with low-cost coal. Two processing options seem most favorable: the CCLC process and the PYROSOL process. Both show considerable potential for the production of low-cost, high-quality synthetic crude from coprocessing. Overall distillate product yields of 70-78 wt % of the organic feed (containing 35% daf coal) have been achieved. Subbituminous coal and heavy oil show a synergistic effect in processing. Coprocessing technology may be an alternative technology for upgrading extensive contiguous deposits of coal and heavy oil in Alberta and in parts of the US.
Introduction The steady depletion of Canadian light crude resources since the early 1970s and the increase in energy consumption promoted the development of alternate technology for the production of synthetic liquid fuels from Canada's own resources. This led Canadian Energy Developments Inc. (CED) to evaluate direct coal liquefaction and heavy oil upgrading. From these investigations it became apparent that the simultaneous upgrading of coal and heavy oil-by using coprocessing technologyappeared to be a very attractive upgrading process. This process has a significant advantage over comparable heavy oil only upgrading processes, as up to one-third of the hydrocarbon feed stock for a coprocessing facility would consist of low-cost coal. As well, coprocessing offered a greater amount of coal-oil conversion with less than 50% of the capital required for a coal liquefaction plant. CED developed'* two coprocessing technologies, the PYROSOL process and the CCLC process, with the goal of commercializing one of the technologies by the 1990s. The choice of the technology will be based on project-specific criteria such as product quality, feed quality, and oil to coal ratio. Laboratory- and bench-scale programs have been completed to demonstrate the technical potential of the processes, and feasibility studies have been performed by Kilborn Energy6 to show their financial potential. CED has constructed and commissioned a fully automated 0.25 T P D pilot plant, to confirm the processes and to provide data for detailed feasibility studies and for process engineering of larger scale facilities. Presented a t the Symposium on Coal-Derived FuelsCoprocessing, 195th National Meeting of the American Chemical Society and 3rd Chemical Congress of North America, Toronto, Ontario, Canada, June 5-10, 1988.
0887-0624I89/ 2503-0116S01.50I O
Experimental Section The feed for all the initial test runs was composed of 39 wt % Alberta subbituminous coal, 59 wt % Cold Lake vacuum bottoms and 2 wt % "throwaway" catalyst. The CCLC process consists of two stages: the first step is coal solubilization into heavy oil. This is followed by the second step-hydrogenation. In the coal preparation section, run-of-mine coal is pulverized to below 200 mesh size. Then the coal is blended with vacuum bottoms and catalyst to form a slurry. The slurry is mixed with hydrogen in the preheating zone, and the mixture is fed to the bottom of the first reactor. The first reactor is maintained at 380-420 "C and 8-18 MPa pressare. The products from the first stage are then fed to the second reactor, where they are hydrogenated under moderately severe conditions of 440-460 "C and 14-18 MPa hydrogen pressure. The work was carried out in a continuous tubular reactor system of 2 kg f h capacity. The gaseous products and naphtha are separated by using a hot separator. The gaseous product is analyzed by on-line gas chromatography. The hot separator bottoms are then distilled to recover the distillate product (below 525 "C). The undistilled residue (525 "C+) is then further treated with THF (tetrahydrofuran)to determine the amounts of THF-soluble matter (residual oil) and THF-insoluble matter in the residue. The PYROSOL process was conceived by West Germany's Gesellschaftfur Kohleverfluessigung mbH (GfK) as an alternative to its more conventionalhigh-severitycoal liquefaction technology. (1) Boehm, F. G.; Liron, A. Presented at the 2nd Annual Pittsburgh Coal Conference Pittsburgh, PA, Sept. 1985. (2) Boehm, F. G.; St. Denis, E. Presented at the AOSTRA Conference on Upgrading Technology, Edmonton, Alberta, Canada, June 1987. (3) Boehm, F. G.; Caron, R. D. Presented at the 3rd Chemical Congress of North America, Toronto, Ontario, Canada, June 1988. (4) Banerjee, D. K.; Caron, R. D. Presented at the 38th Canadian Chemical Engineering Conference, Edmonton, Alberta, Canada, Oct 1988. (5) Banerjee, D. K.; Berger, D. J. Presented at the EPRI Conference on Upgrading Low-Rank Coals, Denver, CO, Oct 1988. (6) Boehm, F. G.; Caron, R. D.; Anderson, N. E. Presented at the 4th International Symposium on Heavy Crude and Tar Sand, Edmonton, Alberta, Canada, Aug 1988.
0 1989 American
Chemical Societv
Energy & Fuels, Vol. 3, No. 2, 1989 117
Coprocessing in Canada Product Stream
wT% DAF Fwd
AsRecrNad
DAF
CLVB
59
65
COAL
39
35 +REACTOR
CAT
88.1% Pitch Conv.
-
Naphtha-
26.5
-GOFRACTION2 ATOR
34.2
-
1a2
MOO-
-GO-
2
4.2
Total Diatillablr:
75.1
Hydrogen
-2.2
Figure 1. CCLC process. Key: CLVB, Cold Lake vacuum bottoms; LGO, light gas oil; MGO, medium gas oil; HGO, heavy gas oil; +525 Oil, THF-soluble 525 "C+ material; Solid, THF-insoluble organic material.
PYROSOL seeks to generate equally high yields, but employs milder process conditions with much less hydrogen consumption. This process also consists of two stages. A slurry of Cold Lake vacuum bottoms and coal is fed into the first-stage reactor at 380-420 OC and 8-10 MPa pressure. The product from the first stage is fed to a hot separator to remove lighter fractions and gaseous products. The hot separator bottoms stream, which is more than 65% of the feed stock, is then subjected to hydrocoking at 480-520 "C and 8-10 MPa pressure. Hydrocoking is a novel approach, which is carried out in the presence of pressurized hydrogen in a delayed coker system so that more oil and less coke are produced. The coker oil stream is collected and fractionated to determine the product quality. The coke is also analyzed in order to determine the elemental composition and volatile matter present. First-stage experiments of the PYROSOL process were done in a 2 kg/h capacity tubular reactor. The second stage was carried out in a 0.8-L delayed coker. The test was carried out batchwise. The gaseous products from both steps were analyzed by on-line gas chromatography. The overall mass balance was calculated by combining the two stages.
Results and Discussion In the CCLC process, the experiments were carried out under various conditions of temperature, pressure, and residence time. Results were interpreted on the basis of distillable oil yield (C5 to 525 "C). Results of a run at maximum distillable oil yield are shown in Figure 1. Conversion of pitch (525 OC+ organics) in the feed was 88.1 wt % and the total distillable oil yield was 75.1 wt %. The process produces 8.8 wt % hydrocarbon gases and 6.6 wt % other gases such as water vapor, H2S, NH4, and COX. On the basis of the amount of gas production, one can expect a maximum of 80 wt % of distillable oil yield for this pair of feed stocks. A barrel of coprocessed feed stock (35 wt % daf (dry ash-free) coal in vacuum bottoms) yields approximately 0.98 barrel of distillable oil. An average barrel of product consists of approximately 35 vol % naphtha, 45 vol % middle distillate, and 20 vol % of heavy oil. The naphtha is suitable for refining into high octane gasoline. This product is partially derived from coal, so it contains a higher percentage of aromatics than petroleum-derived naphtha. The middle distillate has potential for conversion to diesel or jet fuel. The heavier product needs further treatment before it can be converted into transportation
Table I. Properties of Liquid Product from the CCLC Process
C H N S H/C
below 380 "C 85.41 12.67 0.49
1.32 1.75
elem anal.. wt% 385-525 "C above 525 "C oil 86.76 87.32 9.16 5.86 1.16 2.08 1.85 1.96 1.26 0.80
fuel. Hydrogen consumption is about 2.2 wt % of the daf feed. Table I indicates the properties of the product obtained in the CCLC process. The lighter fraction (below 380 "C) has a H/C ratio of 1.75, which indicates that it has been significantly hydrogenated. As the boiling point range of the product increases, the H/C ratio decreases, and the product becomes more aromatic. Similarly, the amounts of nitrogen and sulfur in the product also increase with the boiling range. The product spectrum indicates that the CCLC process offers high conversion. Furthermore, the products would require only modest further upgrading. In the PYROSOL process, experiments were carried out under various conditions in the first and second stages to obtain a maximum oil yield with minimum hydrogen consumption. Because coking is a carbon rejection process, higher H/C ratio oil is obtained by rejecting carbon instead of consuming hydrogen. Figure 2 shows a typical product spectrum at maximum oil yield, obtained from the combination of hydrogenation and hydrocoking steps. After the first stage, 34.7 wt % of the feed goes into the overhead stream of the hot separator and 65.3 wt 90 goes into the bottom stream. Then 70.0 wt % of this stream is recovered as liquid in the coker. The overall liquid yield, combining the two stages, is 74.5 wt % of the daf feed stock. Overall hydrogen consumption is about 1 wt % of the daf feed stock. The synthetic oil produced contains about 15 vol % naphtha and 60 vol 70 middle distillate. The product spectrum is pointed toward the heavy end in the PYROSOL process as compared to the CCLC process. The middle distillate can be converted easily into transportation fuel.
118 Energy & Fuels, Vol. 3, No. 2, 1989
Boehm et al. Product Stream
IS1
STAGE REACTOR
4.1 1.5
b b
c1c4 c5c6
1,
-~~J-E$oE
HOT
sEw"oR
3.7 16.9 0.9
MGO
bker
Fnd
65.3
-
CLVB 59% COAL 39% CAT = 2%
1
6% .O*er G 3 0a -.v-r c1c4c5c6
Ir
COKER
-?O.O
0.4-
7.3
Na = -MGO LGO
-HGO
-
-1.1 8.2
35 -.
3.5 23.1 18 1-3.
2 169.-
8.4
1 6-.
9.4
3 3.8 i4.7 6.1
Figure 2. PYROSOL process. The abbreviations are the same as in Figure 1. The +525 oil in this case is distillable oil as it comes out of the overhead stream of the coker. The daf calculations are done on the basis of 10.2 wt % ash and moisture present in the
feedstock.
Table 11. Properties of the Products from the PYROSOL Process elem anal., wt % proximate anal. coker oil coke of coke 63.9 ash = 28.6% C 84.8 H 10.6 2.5 volatile matter = 9.4% N 0.4 1.7 fixed C = 61.7% S 2.2 5.6 caloric value = 15756 Btu/lb H/C 1.5 daf
The advantage of the coking step is that most of the undesirable products, such as heavy metals, high molecular weight sulfur and nitrogen compounds, ash, and other contaminants are concentrated into the coke and can be rejected easily. Table I1 shows the properties of the coker oil and coke. Coker oil has an H/C ratio of 1.5, indicating that the ratio has improved in the product not by consuming hydrogen but by rejecting carbon. The amounts of sulfur (2.2 w t 70) and nitrogen (0.5 wt 70) in the products need to be further reduced to produce transportation fuel. The coke produced contains more than 60 wt 70fixed carbon with a calorific value of about 16 000 Btu/lb daf. The thermal value of the coke can be recovered by producing excess heat and high-pressure steam in a fluidized-bed combustion unit and then producing electricity for internal plant use as well as for external markets. The CCLC and PYROSOL processes encompass the possibility of varying two-stage conditions: pressure, temperature, and residence time. That allows a broad range of conversion levels and final product compositions. Both processes are very flexible to feed stock pairs; the PYROSOL process can handle higher coal loading because of the coking step at the end. At present, CED is operating a 0.25 scale TPD pilot plant in coprocessing mode. These data are required to confirm the technologies as a first step scale up before a larger scale operation.
Economic Studies On the basis of the process development work completed over the last 5 years, CED initiated feasibility studies with
Table 111. Refinery Intearation Studv case B case C case A case D case E no HTb moderate HT syncrude syncrude oil only 10000 10000 loo00 16000 21000 ~~~
vacuum residue, bbl/day coal
~~
1371
1371
1371
2193
13060
13060
13060
20950
20160
capital cost 311.0 (1987)= product 31.3 price (1992), $ after tax 12.4 DCF -
385.6
416.0
539.2
505.0
33.3
35.3
35.3
35.3
11.4
11.8
14.4
8.4
9.3
8.9
7.0
12.5
(ROM),
ton/day liquid product,
bbl/day
ROE, % payback years
8.4
Model plant operation/330 days inflation oil price escalation vacuum residue price (1992) coal price ROM (1987) equity
25 years 4%
2% 70% of crude $16.00/ton 100%
"In millions of dollars. bHT = hydrotreatment. Kilborn Energy Inc. to examine the economics of a heavy oil upgrader using coprocessing technology as a means for converting heavy residues to acceptable refinery feedstocks. Table I11 gives the results of a refinery integration study. It was assumed that a coprocessing plant, with an input of 10000 bbl/day (1,600 m3/day) Cold Lake vacuum residues plus 1371 ton/day subbituminous coal, was integrated with the refinery operation. The following five cases were explored: Case A assumed maximum integration into the infrastructure of a refinery-i.e., the refinery is able to process the raw liquid products from the coprocessing plant without secondary hydrotreating in the coprocessing facility.
Coprocessing in Canada Case B assumed intermediate integration-i.e., the refinery was only capable of processing a moderately hydrotreated product from the coprocessing plant, and the coprocessing facility therefore included the capacity for upgrading high-sulfur naphtha as well as for fluid catalytic cracking of heavy oils. Case C considered minimum integration with the refinery, capable of accepting only secondary hydrotreated products of high-quality "synthetic crude" from the coprocessing plant. Case D, also based on minimum integration, assumed a larger coprocessing facility (16000 bbl/day or 2500 m3/day Cold Lake residues and 2193 ton f day of run-ofmine subbituminous coal) to assess the impact of plant size on capital and operating costs. Case E examined heavy oil only (no coal is used) upgrading by conventional hydrocracking in an ebullated bed and subsequent delayed coking. In cases C and D, the assumed plants produce 13 060 and 20950 bbl/day (2070 and 3340 m3/day), respectively, of distillable (C, to 525 "C) oil, and also furnished small amounts of C3/C4,sulfur and ammonia. Capital costs for the upgrader units, expressed in 1987 Canadian dollars, and including all off-site facilities and utilization systems as well as project contingencies, were $311, $385, $416, $539, and $505 million for cases A-E, respectively. The above case studies (Table 111) reached the following conclusions: (1) The after-tax, discounted cash flow (DCF) return on equity varies between 11 to 12% for cases A-C. If the product price differentials used in the study are correct, the return on investment is not substantially affected by the extent of hydrotreating required to be conducted in the upgrader.
Energy & Fuels, Vol. 3, No. 2, 1989 119 (2) The DCF increases from 11.8% to 14.4% with an increase in the plant capacity of 150% (cases C and D). (3) The DCF increases from 8.4% for a heavy oil only plant (case E) to 14.4% for a coprocessing plant (case D). A coprocessing plant can offer an acceptable rate of return if one-third of the heavy oil residues are replaced by coal. Such a plant is clearly more attractive than conventional heavy oil upgrading. There is also an advantage for a coprocessing plant compared to a coal liquefaction plant in the capital investment: a coprocessing plant is only marginally more expensive than a heavy oil only upgrader, while a coal liquefaction only plant is considerably more expensive than either, based on an independent study done internally for CED.
Conclusion Coprocessing-i.e., simultaneous upgrading of coal and heavy oil residues-is expected to play an increasingly important role in Canada's future energy supply. The six case studies show that coprocessing has a significant economic advantage over conventional heavy oil upgrading. Alberta's unique combination of an extensive reserve of highly reactive subbituminous coal, heavy oil, natural gas, and an established infrastructure provide an attractive method of producing high-quality "synthetic crude" through the use of state of the art coprocessing technology. The results obtained so far in terms of distillable oil yield and hydrogen consumptions have been most encouraging. Coprocessing is more economical compared to heavy oil upgrading in terms of feed stock cost. The technological risk involved with the coprocessing is not substantially greater than heavy oil upgrading as operating conditions are almost similar.
