CA1250539A - Coprocessing of bitumen/coal slurries using hydrogen sulphide as promoter - Google Patents

Abstract

Abstract A process is described for coprocessing coal and a heavy hydrocarbon, such as bitumen from tar sands or heavy oil. A slurry of the heavy oil and coal is passed through a confined hydrocracking/hydrogenation zone in the presence of hydrogen sulphide as the sole catalyst.
The effluent emerging from the zone is separated into a gaseous stream containing a wide boiling range of mate-rial and a slurry stream containing heavy hydrocarbons and unreacted coal. This process permits maximum yields from both coal and bitumen, while suppressing coke for-mation during coprocessing.

Description

lZS6)539 Coprocessin~ Of Bitumen/Coal Slurries Using Hydro~en ~bL~

~ack round of the Invention q This invention relates to coprocessing and, more particularlyr to the simultaneous hydrocracking and hydrogenation of coal and a heavy hydrocarbon oil, such as bitumen from tar sands or heavy oil.
Hydrocracking and hydrogenation processes for the conversion of heavy hydrocarbon oils to light and inter-mediate naphthas of good quality for reforming feedstock,fuel oil and gas oil are well known. These heavy hydro-carbon oils can be such materials as petroluem crude oil, atmospheric tar bottoms products, vacuum tar bottoms pro-ducts~ heavy cycle oils, shale oils, coal derived fluids, crude oil re5iduum, topped crude oils and the heavy bi-tuminous oils extracted from tar sands. Of particular interest are the oils extracted from tar sands which contain wide boiling range materials from naphtha through kerosene, gas oil, pitch, etc., and which contain a large portion, usually more than 50 weight percent of material boiling above 525C, equivalent atmospheric boiling point~
The heavy hydrocarbon oils of the above type tend to contain nitrogeneous and sulphurous compounds in quite large concentrations. In addition, such heavy hydrocar-bon fractions frequently contain excessive quantities of

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organo-metallic contaminants which tend to be extremely detrimental to various catalytic processes that may sub-sequently be carried out, such as hydrofining. Of the metallic contaminants, those containing nickel and vana-dium are most common, although other metals are oftenpresent. These metallic contaminants, as well as others~
are usually present within the bituminous material as organo-metallic compounds of relatively high molecular weight. A considerable quantity of the organo-metallic complexes are linked with asphaltenic material and con-tain sulphur. Of course, in catalytic hydrocracking procedures, the presence of large quantitites of asphal-tenic material and organic-metallic compounds interferes considerably with the activity of the catalyst with res-pect to the destructive removal of nitrogeneous, sul-phurous and oxygenated compounds.
As the reserves of conventional crude oils decline, these heavy oils must be upgraded to meet demands. In this upgrading, the heavier material is converted to lighter fractions and most of the sulphur, nitrogen and metals must be removed. This is usually done by a cok-ing process such as delayed or fluidized coking or by a hydrogen addition process such as thermal or cataly-tic hydrocracking. The distillate yield from the coking process is about 70 weight percent and this process also yields about 23 wt. % coke as by product which cannot be used as fuel because of low hydrogen:carbon ratio, and high mineral and sulphur content. Depending on operat~
ing conditions, hydrogenation processes can give a dis-tillate yield of over 87 wt. %.
It has been shown in Ternan et al., Canadian PatentlrO73,389, issued March 11, 1980 and Ranganathan et al.
U.S. Patent 4,214,977, issued July 29, 1980 that ~he addition of coal or coal-based catalyst results in a reduction of coke deposition during hydrocracking and a

-3- lZS~539 generally improved operation. The coal additive acts as a "getter" for coke deposits and prevents accumulation of coke. It is also possible that coal mineral matter acts as a coke-preventing catalyst. In these previous proce-dures the hydrogenation of the coal represented only asecondary consideration. U.S. Patent 3t3Q3,126 describes a process for hydrorefining petroleum crude oils using a gaseous mixture of hydrogen and hydrogen sulphide, with no other catalyst.
In the liquefaction of coal, the hydrogen:coal pro-cess involves slurrying coal with a coal-derived oil and subsequent reaction with hydrogen at high temperatures and pressures in the presence of a catalyst. U.S. Patent

4,149,959 describes a coal liquefaction process in which a slurry of coal and a hydrogen donor diluent, such as hydrogenated creosote oil, is contacted under heat and pressure with hydrogen and hydrogen sulphide.
Not only the bitumen, but also the coal contains heavy asphaltenes and mineral matter which rapidly poison the catalyst. This results in excessive catalyst usage and high operating costs. For both bitumen and coal upgrad-ing processes, the fixed bed catalytic processes are not economical because o~ bed plugging resulting in costly shut-downs. An ebullated bed of catalyst is more suit-able for hydrocracking bitumen or coal. Both thehydrogen:coal and the hydrogen:oil processes use this mode of operation. In the ebullated bed, the upward passage of liquid and gaseous materials maintains the catalyst in a fluidized state~ Catalyst can be added and with-drawn continuously so that a constant activity can be maintained. However, the hydrogen:coal or hydrogen:oil processes use an expensive Co-Mo/alumina catalyst which deactivates rapidly at high conversions, resulting in excessive operating costs.
As has been shown in the above patents, the operat-~Z5~S3~

ing costs can be reduced by using cheap throw-away type catalysts and, for instance, U.S. Patent 4,214,977 des-cribes the use of a coal-iron catalyst which enables operation at lower pressures and at higher conversions.
The use of coal and Co, Mo and Al on coal catalysts are described in Canadian Patent 1,073,389.
It is the object of the present invention to take advantage of the solvent and hydrogen donor action of a bitumen feedstock as well as the catalytic action of coal mineral matter so as to provide a novel hydrocrack-ing process showing improved economics~

Summary of the Invention It has been discovered according to this invention that when a heavy hydrocarbon oil and coal are copro-cessed in the presence of hydrogen sulphide as the solecatalyst, quite surprisingly there is a large increase in distillate yield. This is believed to be the result of synergism between the hydrogen sulphide and coal dur-ing coprocessing. When a heavy hydrocarbon oil is hydro-cracked in the presence of hydrogen sulphide at 425C,there is only a slight increase in distillate yield.
Thus, the present invention relates to the coprocess-ing of a heavy hydrocarbon oil, a substantial portion of which boils above 525C, and coal. The process comprises-(a~ passing a slurry of said heavy hydrocarbon oil andfrom about 2 - 50 wt. % coal in the presence of hydrogen and hydrogen sulphide through a confined hydrocracking and hydrogenation zone, this zone being maintained at a temperature between about 375 and 500C, (b) removing from said hydrocracking ~one a mixed effluent containing a gaseous phase comprising hydrogen and vaporous hydro-carbons and a slurry phase comprising heavy hydrocarbons and unreacted coal, and (c) separating said effluent into a gaseous stream containing hydrogen and vaporous _5_ ~ 53~

hydrocarbons and a slurry stream containing heavy hydro-~
carbons and unreacted coal.
The heavy h,ydrocarbon oil is a pitch-like material and typically contains at least 50~ by weight of mate-

5 rial which boils above 525Co It may be a bitumen fromtar sands, a heavy oil, vacuum bottoms, etc.
The term "coal" is used herein to designate a nor-mally solid carbonaceous material including all ranks of coal, such as anthracite coal~ bituminous coalr semi-bituminous coal~ sub bituminous coal, lignite, peat andmixtures thereof. Preferably the coal has a high con-tent of volatile components, e.g. more than about 20% by weight of m.a.f, coal (moisture and ash-free coal). A
sub-bituminous type, such as Forestburg coal, is parti-cularly desirable.
The coal particles used should be small, e.g. lessthan 60 mesh (Canadian Standard Sieve) and it is parti-cularly preferred to use a material which will pass through a 100 mesh sieve~ The coal should be mixed with the bitumen in such a manner as to avoid formation of lumps and, if desired, additional homogeneous or heterogeneous catalysts may be mixed with the coal-hitumen slurry.
The hydrocracking process of this invention can be carried out in a variety of known reactors with either up or down flow. Thus, the hydrocracking reactor zone can be an empty tubular reactor, an ebullated bed re-actor or a fluidized bed reactor or stirred tank reactor.
The empty tubular reactor has been found to be parti-cularly convenient with the effluent from the top beingseparated in a hot separator and the gaseous stream from the hot separator being fed to a low temperature-high pressure separator where it i5 separated into a gaseous stream containing hydrogen and lesser amounts of gaseous hydrocarbons and a liquid product stream containing light

-6 :~L2~i~3539 oil products. It is also possible to have the reactors in stages where the first reactor is an empty tubular reactor and the second reactor contains an ebullated bed of catalyst extrudates.
The coprocessing is preferably carried out in the presence of about 14 - 1400 m3 of hydrogen per barrel of slurry feed. The hydrogen sulphide is preferably present in an amount of 3-8 wt%, ~based on m.a.f. slurry feed) or 2-6 vol. % of gas feed. The process preferably operates at a pressure of at least 1.4 MPa and a space velocity of up to 4 volumes of slurry feed per hour per volume of reactor zone capacity.
The simultaneous hydrogenation process produces pitch which contains asphaltenes, ash and residues from both bitumen and coal. Depending on the type of coal used, and the feedstock, the pitch properties vary. For example, low sulphur sub-bituminous coals obtained from Western Canada produce a low-sulphur pitch. This reduces the cost of stack gas cleanup, while increasing the ash content of the pitcho According to a preferred embodiment, the bitumen and coal are mixed in a feed tank and pumped with hydrogen and hydrogen sulphide through a vertical empty tubular reactor. The liquid-gas mixture from the top of the hydrocracking zone is separated in a hot separator main-tained at a temperature in the range of about 200 - 470C
and at the pressure of the hydrocracking zoneO The slurry product from the hot separator can be partially recycled to the hydrocracking zone or sent to secondary treatment.
The gaseous stream from the hot separator containing a mixture of hydrocarbon gases and hydrogen is further cooled and separated in a low temperature-high pressure separator. By using this type of separator, the outlet gaseous stream obtained contains mostly hydrogen with some hydrogen sulphide and light hydrocarbon gases. This

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gaseous stream is passed through a scrubber and the scrubbed hydrogen is recycled as part of the hydrogen feed to the hydrocracking process. The recycled hydro-gen gas purity is controlled by adjusting scrubbing conditions and by adding make-up hydrogen.
The li~uid stream from the low temperature-high pressure separator repres~nts the light hydrocarbon product of the present process and can be sent for secondary treatment.
Unreacted coal will be carried over with the heavy oil product from the hot separator and found in the 525C+ pi~ch fraction. This fraction can conveniently be burned or gasified.
For a better understanding of the invention, refer-ence is made to the accompanying drawing which illus-trates diagrammatically a preferred embodiment of the present invention.
Heavy hydrocarbon oil feed and coal are mixed together in a feed tank 10 to form a slurry. This slurry is pump-ed via feed pump 11 through i~let line 12 into the bottomof an empty tower 13. Recycled hydrogen and make up hy-drogen from line 30 is simultaneously fed into the tower 13 through line 12. A gas-slurry mixture is withdrawn from the top of the tower through line 14 and introduced into a hot separator 15. In the hot separator the efflu-ent from tower 13 is separated into a gaseous stream 18 and a slurry stream 16. The slurry stream 16 which contains heavy oil and coal is collected at 17.
The gaseous stream from hot separator 15 is carried by way of line 18 into a high pressure-low temperature separator 19. Within this separator the product is se-parated into a gaseous stream rich in hydrogen which is drawn off through line 22 and an oil product which is drawn off through line 20 and collected at 21.
The hydrogen rich stream 22, containing H2S, is lZ~S39 passed through a packed scrubbing tower 23 where it is scrubbed by means of a scrubbing liquid 24 which selec-tively removes gaseous hydrocarbons and Cx and is cycled through the tower by means of pump 25 and recycle S loop 26. This scrubbing system allows the H2S concen-tration to build up to the required amount. The scrubbed hydrogen rich stream containing H2S emerges from the scrubber via line 27 and is combined with fresh make up hydrogen added through line 28 and recycled through recycle gas pump 29 and line 30 back to tower 13.
Certain pre~erred embodiments of this invention will now be further illustrated by the following non-limitative examples.
Example 1 A sub-bituminous coal was obtained from the Forestburg coal mine and this coal had the followir.g properties: -M.F. As received Proximate analysis wt. % wt. %

Ash 8.2 6.58 Volatile matter 47.S 38.14 Fixed carbon 44.3 35.57 Moisture 19.70 M~A~Fo Ultimate analysis wt.

C 66.2 H 5.02 N 1.06 S 1.07 O (by diff~ 26.65 The above coal was crushed and screened to provide a 12~i()S3~
g 60 mesh material.
The heavy oil used was a Cold ~ake vacuum bottoms having the following properties:

General Specific gravity, 15/15C 1.038 Conradson carbon residue, wt. % 17.1 Pentane insoluble (asphaltenes), wt. %23.5 Benzene insoluble (preasphaltene), wt. % 0.2 Viscosity at 100C, poise 39.4 Aromaticity 34.5 Molecular weight (VOP), g/mol 820.8 Distillation (Spinning Band) IBP, ~C 420 Distillate (-525C), wt. % 16.8 Residue (+525CJ, wt. % 83.2 Blemental analysis (wt. ~) C 83.34 H 9.69 S 5.84 N 0.45 O (by diff) 0.68 Ash Metal content, ppm Ni 93 Fe 18 A blended slurry of the bitumen and 20% by weight of the coal was prepared. The mixture was gradually heated to about 105 - 110C with stirring to ensure that the slurry was homogeneous. The thus prepared slurry was used as a feedstock to a 2-litre stainless steel hot charge batch autoclave unit.
A series of tests were conducted in this autoclave unit using measured amounts of the slurry feed and measured amounts of a gas feed consist;ng of either hydrogen alone or hydrogen blended with hydrogen sulphide. When hydrogen ~LZ~i~539 sulphide was used, it was present in amounts of 10% by weight and 15~ by weight based on m.a.f. coal. Each autoclave task was conducted for a period of 60 minutes at the reaction temperature and a pressure of 17.2 MPa.
The results of the tests are shown in Table 1.

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~r Ln ~r o ~ ~ U~
o U~ o t`, ~ ~
O
v o o U~ C~ CO
+ ~

o ~ C E ~o E ~ E
U~ '~ U~ o C U~
~ +
v ~ ~ O
~1 ~ Q~ .. ,., s ~ ~ m Q t ~ ~ ~ ~U O ~ ~r/ ~ ~ 5 E~ m 3E~ V a -12- lZ~53~

Example 2 Using the same autoclave as was used in Example 1 with the bitumen and the same coal, a series of tests were conducted to compare the effects oE H2S on coke formation in the hydrocracking of bitumen only and in the coprocessing of coal and bitumen. Again the resi-dence time was 60 minutes at the reaction temperature and the pressure 17.2 MPa. The results are shown in Table 2.

Example 3 Again using the same autoclave as in the above Exam-ples, the same bitumen and same coal, tests were conduct-ed to compare the catalytic activity of hydrogen sulphide with the catalytic activity of an iron-coal catalyst such as that described in U.S. Patent 4,214,977. With the iron-- coal catalyst, iron was present in an amount of 0.48% by weight (on m~a.f. slurry feed) as FeSO4 - 7H2O.
These tests were conducted at an autoclave temperature of 40~C and a residence time of 60 minutes at a pressure of 17.2 MPa. The bitumen-coal slurry contained 20% by weight of coal.
The results obtained are shown in Table 3.

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~a $
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o o In o t~1 .

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O
U o U~ o :~
~J
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C U~ O O
O'1:1 v ~ ~ a~
O U~ U) Q Q
C) C) ~ d~ d~
. ~ O
_ O O ~ ~ ~
,~ o ~ )~) 3 3 _ . O
U~
Cq ~ ~ , a~ o E~ m E~

~14- 1~5~S39 Table 3.
catalyst distillate yield(2) pitch conversion(3) 15 wt % H2S(1) 39.3 35.~
0.48 wt % Fe as 29.3 25.5 FeSO4 - 7H20(2) (1) based on maf coal (2) wt %, based on maf slurry feed (3) maf(~525C)in - maf ~ 5~O out maf(~525C)in Example 4 Using the same bitumen and same coal as described in the above Examples, a slurry was prepared containing 30%
by weight of coal. This was used as the ~eedstock to a coprocessing pilot plant. The pilot plant used the re-action sequence shown in the attached drawing and was operated at a pressure of 13.9 MPa and a nominal liquid hourly space velocity (LHSV) of 1 kg/hr/L based on slurry feed.
Tests were conducted using hydrogen sulphide only and using an iron-coal catalyst only. When hydrogen sulphide only was used, this was present in an amount of 8% by weight based on the slurry feed and the iron-coal cata-lyst was used in an amount of 0.4-0.7% by weight iron as FeSO4-7H2O based on slurry feed.
The results are shown in Table 4.

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o U~ oct~ ~ O
o ~ ~ ~ ~ ~ a) ,1~ sr P:
,_ o o ~ ~ ~ Ut O ~ ~ ~u~ ,, I a~ o Q) O o tuU~
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::~ h L~ c:
~ 3 ~ + .,, ~ U~ ~ O --_~
3 ~ C) ta ~
w u E~ n i U7 O ~P +
_, O O ,t W
~ o 3 --~a ,~C o Ul ~ ~ O
~)O ~ ~C) o :~u) u o h aJ ~P Q Q Lt'\
a)~ ~ I ~

. C~ 0 3 ~ w ~r O _ -- ~1 0 0 ~ ~la ,~ o co o 3 3 E~
~ . _ ~ ._. s ~1 Q~ O ~ ~I C) ~ a) ~ aJ,, o ~1 ~ ~ ~ ~r In E~ ~ t~ h ~~.)P, ---- -- -- ---16- 1 Z ~ 5 3g Example 5 Using the same continuous reactor as in Example 4, further tests were conducted to measure the effect ~f the addition of hydrogen sulphide on the product distribution when coprocessing the same coal and bitumen as used in the above examples, also in the presence of the iron-coal catalyst. The reactor was operated at a pressure of 13.8 MPa and LHSV of 1 kg/hr/L. The slurry feed contained 30~
by weight of coal. Iron was present in an amount of 0.4 -0.7% by weight as FeS04 - 7H20 based on slurry feed and when H2S was used, this was present in an amount of 8% by weight based on slurry feed~
The results are shown in Table 5.

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Ln ~r >t O ~00 L Lt') ,i 1~

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r-l OLl~
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t') C L 1~ C

Lll ~Ll') O dPC ~ +

' + ~

- 18 ~ ~ ~S~ S ~'~

Example 6 In order to show a comparison between hydrocracking of heavy hydrocarbon oil, liquefaction of coal and copro-cessing, results were compared from tests conducted in the autoclave of Example 1. The same bitumen and coal were used as in Example 1 and for the coal liquefaction test the coal was formed into a slurry with anthracene oil. The processing conditions and results are shown in Table 6.
It will be seen from Table 6 that in the presence of H2S, coal conversion increased both in coal liquefaction and coprocessing. However, the increase in coal conver-sion due to the pressure of H2S did not result in an increase in distillate yield in the case of liquefaction.
Since there is only a slight increase in distillate yield in hydrocracking and a large increase in distillate yield in coprocessing due to the presence of H2S, it appears that there is a synergism between H2S and coal in copro-cessing, The ~eight percent distillates in Table 6 are also expressed in terms of percent increase in distillate yield due to the presence of H2S. Comparing these numbers, it is quite clear that the presence of H2S in coprocessing improves the distillate yield significantly relative to coal liquefaction.

lg~ 53~

Table 6 Comparision of processes Basis: 9/100 maf slurry feed _ _ Conditions Hydrocracking Liquefaction Coprocessing _ Atmosphere H~H2/H25 Hz H2/H25 H2 H2/H25 _ _ Coal concentration (maf) _ _ 20 20 20 20 _ Temperature9 C425 425 425 425 425 425 _ Residence time (min) 60 60 60 60 60 60 _ Pressure (MPa) 17.217~2 17.2 17.Z 17.2 17.2 H2S Concentration (based on maf aoal)10 10 10 10 10 10 . _ Solvent ColdCold Anthra- Anthra- ColdCold LakeLake cene cene Lake Lake Vacuum Vacuum Oil Oil Vacuum Vacuum Bottoms 80ttoms 80ttoms Bottoms _ _ Yields distillate 57.9 60.5 78.6 77.0 49.4 55.6 _ _ .
wt ~, increase due to the presence of _ 4.5 _ -2.0 _ 12.6 ~25 Conversion coal (wt ~') _ _ 60.5 90.0 55.6 71.4 _ ~

Claims (5)

Claims:

1. In the coprocessing of coal and a heavy hydro-carbon oil, a substantial portion of which boils above 525°C, which comprises:
(a) passing a slurry of said heavy oil and from about 2 - 50 wt. % coal in the presence of hydrogen through a confined hydrocracking/hydrogenation zone, said hydrocracking zone being maintained at a tempera-ture between about 375 and 500°C, (b) removing from said zone a mixed effluent con-taining a gaseous phase comprising hydrogen and vaporous hydrocarbons and a slurry phase comprising heavy hydro-carbons and unreacted coal, and (c) separating said effluent into a gaseous stream containing hydrogen and vaporous hydrocarbons and a slurry stream containing heavy hydrocarbons and unreacted coal, the improvement which comprises carrying out the above hydrocracking/hydrogenation process in the presence of added hydrogen sulphide as the sole catalyst.

2. A process according to claim 1, wherein the hydrogen sulphide is present in an amount of about 3 to 8 wt. % based on slurry feed.

3. A process according to claim 1, wherein the coal is -60 mesh (Canadian Sieve).

4. The process according to claim 3, wherein the coal is selected from sub-bituminous, bituminous, and lignite coal.

5. A process according to claims 1-3, wherein the feed slurry is moved upwardly through a tubular reactor.