8 Production of Low Sulfur Fuel Oils from Utah Coals S. A. QADER and G. R. HILL Department of Mining, Metallurgical and Fuels Engineering, University of Utah, Salt Lake City, Utah 84112 Low sulfur fuel oils were prepared from a high volatile bituminous coal by hydrogenation under high temperatures and pressures. At a coal conversion of 80%, the ratio of oil-to-gasyields was about three, and 23% of the coal sulfur was contained in the oil. Sulfur content of the oil, however, remained the same at different coal conversion levels. The data obtained in the semi-continuous, dilute phase hydrogenation system showed that the whole oil can be directly used as a fuel oil where 1% sulfur is tolerated. Fuel oils containing 0.5 and 0.25% sulfur were produced by desulfurization of the whole oil. A preliminary economic evaluation indicated that low sulfur fuel oils can be produced from coal by hydrogenation at a manufacturing cost of about $5-6 per barrel.
/ ^ o a l can be converted to a synthetic crude oil by hydrogenation under ^ high temperatures and pressures. The synthetic crude can be subsequently converted to a low sulfur fuel oil by desulfurization. Four different approaches may be used in the hydrogenation of coal to liquid fuels. In the German process (I), a paste of coal, oil, and catalyst is hydrogenated under high pressures of 5000-10,000 psi. The H-coal process (2) uses an ebullating bed of catalyst to hydrogenate a mixture of coal and oil under medium pressure conditions of 2000-4000 psi. Fixed beds (3) of catalyst are used by the Bureau of Mines for the hydrogenation of coal and oil mixtures under conditions of high turbulence and high hydrogen flow. Coals impregnated with catalysts are hydrogenated in dilute phase, free fall reactors under medium pressures of 2000-3000 psi to produce synthetic oil at the University of Utah (4). In the present investigation, coal was hydrogenated in batch and dilute phase systems 91
92
POLLUTION CONTROL AND ENERGY NEEDS
to produce crude oil. The crude oil was then desulfurized in fixed and ebullating bed reactor systems to produce low sulfur fuel oils. The economics of producing fuel oils containing 0.5 and 0.25% sulfur are presented Experimental High volatile sub-bituminous coals from Utah were used in this work. The coal was ground to less than 200 mesh and impregnated with 10 wt % of zinc chloride. The hydrogenation experiments were performed 9
1. Heating jacket
9. Pressure gage
2. Thermowell
10. Pressure recorder
3. Magnetic drive assembly
11. Temperature recorder
4. Cooling coil
12. Hydrogen tank
5. Liquid sampling line
13. Vacuum pump
6. Gas sampling line
14. Stirrer controller
7 Flow meter
15. Moter
8. Gas chromatograph
l€L Temperature controller
Figure 1.
Batch stirred tank reactor
8.
QADER AND HILL
93
LOW Sulfur Fuel Oils
in batch (Figure 1) and semi-continuous (Figure 2) reactor systems. The coal oil produced in the semi-continuous system was desulfurized in fixed and ebullating bed reactor systems using a commercial desulfurization catalyst containing sulfides of nickel and tungsten supported on alumina. Product evaluations were done by standard methods. i
n _
1. COMPRESSOR 2. P R E H E A T E R 3. REACTOR 4. COAL HOPPER 5. SEPARATOR
-OIL, GAS
Figure 2.
Coal hydrogenation system (bench scale)
Table I. Sulfur Distribution in Products (Sulfur Content of Coal = 1.31 % ) Reaction Coal Time, Conversion rain wt% 20 30 40 50 60
41 52 61 73 81
Product Yield, wt % ! L__ Oil Gas Char 36 43 51 57 61
5 9 10 16 20
59 48 39 27 19
Sulfur Distribution, wt % _ : Char Gas Oil 16 18 20 22 23
9 10 13 16 17
75 72 67 62 60
Results and Discussion The product distributions obtained in the batch work are given in Table I. Hydrogenation was performed at 500°C and initial hydrogen pressure of 2000 psi. The results show that, at a coal conversion of about 80%, the ratio of oil-to-gas yields will be about three, and 23% of the coal sulfur will be contained in the oil. The data given in Table II indicate that the sulfur content of the oil remains almost the same at different coal conversion levels and probably depends upon the organic
POLLUTION CONTROL AND ENERGY NEEDS
Table II.
Sulfur Distribution in Oil
Coal Conversion, wt. %
Sulfur Content of Oil, wt. %
41 52 61 73 81
0.53 0.54 0.52 0.51 0.52
Table III.
Analysis of Coal Oil and Its Fractions
(Sulfur Content of Coal — 2.5% ) Property
Whole Oil
Distribution, vol. % Sulfur, wt % Nitrogen, wt % Oxygen, wt % H / C (atomic) Asphaltene, vol %
100.0 1.01 1.22 5.65 1.09 26.5
-300°C Fraction 42.0 0.49 0.65 4.54 1.25 10.5
+300*0 Fraction 58.0 1.53 1.31 6.57 0.96 39.6
20 - . — | — . — | — - — | — i — | — - — | — (+300°C OIL) 18 16 O -300°C FRACTION, VOL % 14 • COKE.WT % 12 h A GAS, VOL % 10 8 6 4 2 0.9
0.8
0.7
SULFUR
0.6
0.5
0.4
0.3
CONTENT, WT
%
20 - . — | — i — | — i — | — . — | — i — | — 18 (WHOLE OIL) 16 O-200°C FRACTION, VOL % 14 • C0KE.WT % 12 10 A GAS, VOL % 8 6 4 2
T
0.9
0.2
0.8 0.7 0.6 0.5 0.4 0.3 0.2 SULFUR CONTENT, WT %
Figure 3. Influence of desJfunzation on product distribution (fixed bed)
8.
QADER AND HILL
LOW Sulfur Fuel Oils
95
sulfur content of the coal. The data given in Tables I and II were obtained from a coal containing about 0.6-0.7% organic sulfur. The properties of the oil obtained in the semi-continuous, dilute phase hydrogenation system (4) are given in Table III. These oils were prepared from a coal containing about 2.5% total sulfur. The data show that the whole oil can be directly used as a fuel oil where 1% sulfur is tolerated. A 0.5% sulfur oil can be produced by desulfurization of either whole oil or the + 3 0 0 ° C fraction. If a fuel oil of less than 0.5% sulfur is desired, it may be necessary to desulfurize the whole oil. The whole oil and + 3 0 0 ° C fraction were desulfurized in benchscale, fixed and ebullating bed reactor systems, and the product distributions obtained are shown in Figures 3 and 4. The data show that fuel oils
containing about 0.2% sulfur can be obtained by desulfurization of either the whole oil or the + 3 0 0 ° C fraction. As the sulfur content of the product oil decreases, there will be an increase in the yields of low boiling oil, gas, and coke. A comparison of the data indicates that the fixed bed system
96
POLLUTION CONTROL AND ENERGY NEEDS
produces more gas and coke than the ebullating bed system, irrespective of the type of feed oil used. A conceptual material balance of a refinery producing 100,000 bbl/ day of fuel oil from coal was calculated (Table IV) based on the benchscale data obtained by the authors and the published data available. In this projection, a coal containing 7.5% moisture, 10% ash, and 2.5% total sulfur is used as the feed. The hydrogenation can be performed in any type of reactor system in the ranges of 5 0 0 ° - 5 5 0 ° C and 2000-3000 psi. The process conditions will be optimized for a coal conversion of about 80%. The hydrocarbon gases produced in the process will be used Table IV.
Material Balance
(Capacity: 100,000 bbl/day of Fuel Oil) Sulfur Content of Fuel Oil, wt % Materials Raw Materials Coal, tons Hydrogen, M M SCF Catalyst, tons Products d-C4 gases, M M SCF Naphtha, bbl Fuel oil, bbl Char, tons Sulfur, tons Ammonia, tons Water, M M gal. Table V .
0.50
0.25
39,500 1,073 732
43,500 1,275 800
271 36.280 100,000 8,052 175 350 1.1
317 49,000 100,000 8.800 175 350 1.
Economic Summary
(Capacity: 100,000 bbl/day of Fuel Oil) Sulfur content, wt % Parameter Fixed capital, $ M M Working capital, $ M M Total Revenue, $ M M Fuel oil price: $5/bbl $6/bbl S7/bbl Total operating cost, $ M M Rate of Return, % Fuel Oil Price: $5/bbl $6/bbl $7/bbl
0.50
0.25
312 31
344 34
238 271 304 194
261 294 327 327
6.9 12.2 17.5
5.4 10.2 15.0
8.
QADER AND HELL
< ill >ZD
o >< Q.
97
LOW Sulfur Fuel OUs
. ( S I
'
1
'
I
"
1 '
1 •
-
~ A F U E L OIL, 0 . 5 % S ^ < > . O FUEL OIL, 0 . 2 5 % S 5
6
'
1
7
1
1
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1
1
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Figure 5.
8
9 10 RETURN
1
1 •
1
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1
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12
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RETURN
Variation of return and payout time with fuel oil price
for making process hydrogen. The residual char will be used as a fuel. Based on the conceptual data, we made a preliminary economic evaluation of the process for making fuel oils of 0.50 and 0.25% sulfur (Table V ) . The calculations were based on approximate energy and material balances and estimated equipment costs. The data indicate that fuel oils can be produced from coal by hydrogenation at a manufacturing cost of about $5-6 per barrel. The data (Figure 5) also show that the cost of reducing the sulfur content of fuel oil from 0.5 to 0.25% will be about 30-40^ per barrel. Literature Cited 1. Gordonk, K., "Report on the Petroleum and Synthetic Fuel Oil Industry of Germany," Ministry of Fuel and Power, Her Majesty's Stationary Office, London, 1947. 2. Alpert, S. B., Johanson, E. S., Schuman, S. C., Chem. Eng. Prog. (1964) 60, 35. 3. Aktar, S., Friedman, S., Yavorsky, P. M., Bureau of Mines Technical Progress Report 35, July 1971. 4. Qader, S. A., Haddadin, R. A., Anderson, L. L., Hill, G. R., Hydrocarbon Process. (1969) 48, 147. 5. Qader, S. A., Hill, G. R., Hydrocarbon Process. (1969) 48, 141. 6. Qader, S. A., Wiser, W. H., Hill, G. R., Erdoel und Kohle, Erdgas, Petrochem. (1970) 12, 801. RECEIVED February 15, 1973. Work supported by Office of Coal Research and University of Utah.
