US 3117921 A
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E. GORIN Jan. 14, 1964 PRODUCTION 0F HYDROGEN-ENRICHED LIQUID FUELS FROM COAL Filed Jan. 21, 1963 mZON mzON
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Rm ah mm ma n V ...u N mE R R 0 E T v T E United dtates Patent 3,117,921 PRQUQHGN @il lYDRGEN-ENRCHED MQW@ EL LS BRGM @GAL Everett (Gerin, lishurgh, Pa., assigner to Consolidation Coal Company, ittshurgli, Pa., a corporation of Pennsylvania Filed Een. 2l, i963, Ser. No. 252,222 S Claims. (Cl. 208-8) The present invention relates to a process for the production of hydrogen-enriched liquid Jfuels from coal.
This application is a continuation-in-part of my cepending application Serial No. 144,428, filed October ll, 196l, now abandoned, which is assigned to the assignee of the present application.
Hydrogen-enriched liquid fuels such as gasoline, diese oils, fuel oils, kerosene, and the lure represent more than one-third or the total annual United States natural energy production, and from all indications, die demand for such lio-.uid fuels will increase in the years to come. At the present time the principal source of such liquid fuels is petroleum; however, for many years researchers have 'een atternp 'ng to design economic processes of cotA merfiai utility for producing such liquid fuels from solid materials such as coal.
One approach to the production of synthetic hydrogenenriched liquid fuels from coal involves coal solvent extraction wherein the coal is extracted to yield coal extract wh ch thereafter is hydrogenated to yield tre desired liquid fuels. Heretofore, all of the resulting extract was completely converted via hydrogenation to the desired fuels one or more stages at elevated temperatures and pres4 .Ires in the presence or" a catalyst. I have now found that coal extract varies in its reactivity to hydrogenation and conseouently it is desirable, economically, to convert vis. hydrogenation only a portion or" the coal extract to the desired liquid tu s. For exanple, at a given set of hydrogenation conditions a portion oi ti e extract will be ferted to the desired lfuiid fuels. ln order to conhe remaining unconver ed extract to the same lit1 iid more severe hydrogen tion conditions are required, which in most instances substantially increase the cost of the over-all cool conversion process.
r" fnary object of the present invention is to pro- A oved process for Foducing hydrogen-enriched liquid iusls such as gaso e from coal.
ln accordance with my invention, coal is subiected to solvent extr:w under cond ions to dissolve up to 8G weight percent or the coal (on a moisture-tree and ad" free basis). The coal extraction product, which como coal extract and undissolved coal residue, is then treated, for example, in a filtration zone, to separately recover coal extract. This extract, whic1 's a solid at room teinperature and wl ch is substantially free of hydrocarbons boilgig below C., is composed almost entirely of `e, molecular weight poly/cyclic aromatica. These poiycyclic aromatics differ substantially in their r spouse to hydrogenation treatment at elevated temperatures. i have observed that the hydrogenation conditions are dictated by the more refractory components of the extract, then an inordinate amont of coke and gas is produced. Accordingly, in rny improved process the extract is subjected to a preh fdrogenatiorr treatment which only partial conversion of the extract to a distilla- -L boiling below 325 C. in general, the prehydrogenation conducted at a temperture between 490 and 470 C. and at a A ressure between 500 and 5,05) psig. However, the conditions may fall somewhat outside th se ranges depending on the nature of the extract or on the selection of catalyst, ir" any. A higher boiling or so-called bottoms portion of the prehydrogenated extract is subjected to carbonization, i.e. coking, at 425 to 760 C., to
' Contact wit referred Embodz'ment Referring to the drawing, coal, preferably high volatile bituminous coal, is introduced into a stirred solvent extraction zone lil concurrently with 0.5 to lf3 parts oy weight of a coal extraction solvent. The extraction zone lil is adapted to coniine the coal and tire solvent for a esidenc-e period from about five minutes to four nours at elevated pressures and temperatures. Tire residence period and temperatures are determined by the specific rhe solvent and the desired depth of coal extraction. pressure is preferably that required to maintain the solvent as a liquid at the selected temperature, generally in the range of l to 6560 psig.
Suitable solvents for the coal in the extraction step are those which are predomins'rly poiycyclic, aromatic hydrocarbons, preferably partially or completely hydrogenated arornatics, including comp' ely saturated naphthenic hydrocarbons which are liq 'd under the temperature and pressure of extraction. Mixtures or" these hydrocarbons may be used and are preferably derived from inteifnediate or nal steps oi' he process of this invention. those hydrocarbons or mixtures thereof boiling between about Z50 and 425 C. are especially preferred. Examples of suitable solvents are tetrahydronaphthalene, decalin, biphenyl, methylnaphtbalene, and dimethylnaphthalene. Other types of coal solvent may be added to the abovementioned types for special reasons, but the resulting mixre should be predon. antly of the types mentioned. s of additive solvents are the phenolic compounds Such as phenol, cresols, and xylenols.
rhe coal ard 'the solve' t are maintained in intimate .c extracti n Zone it? un the solvent has dissolved, ie., converted the desired amount of coal. Preferably up to 3G weight percent o the MAF (MAF signiies moisture-free and ash-free) coal is dissolved, as it has been found that the cost of converting more than 89 wei ht percent of the coal becomes economically prohioitive il. terms of the amount or hydrogen translC r that is needed. ln addition, as the depth o coal extraction is increased, each addi" r' l increment of coal extract contains a higher proportion of benze e-insduble material which correspondingly maires the resu ig coal extract more dicult to hydrogcnate. l desired, however, any depth of coal conversion may be used. fact, ir more than S0 weight percent coal conversion is used, the process of present invention becomes even more desirable. have fou that it particule v preferred to conduct th sol' nt v:attract und-ci condi ns to yield an extract arnounmfby to less than 6G weight percent of the MAF coal.
The temperature of the extraction zone should be an elevated temperature bete/een about and 560 C., but preferably not high enough to cause appreciable colte formation. In some instances it may be desirable to conduct the coal extraction in stages at successively higher temperatures until the desired depth of extraction is attained. Instead of a batch system, a continuous or a countercurrent system may be employed. The particular system used is not material to the practice of my invention.
Following extraction, the mixture of solvent, extract,
and residue is conveyed through a conduit 12 to a conventional type separation zone 14 such as a Altration zone, sedimentation zone, or centrifugation zone. The extract, which is usually a solid at room temperature and generally contains less than weight percent hydrocarbons boiling below 400 C., is therein separated from the residue. If desired, a portion of the coal extract may be separated `with the residue and processed therewith. For example, in my US. Patent No. 3,013,241, it is shown that the extract may be cooled or treated l'with a paratiinic solvent such as hexane to separate the extract into a benzene-soluble rich extract fraction and a benzene-insoluble rich extract fraction. The latter extract fraction may be coked alone or in combination with the residue.
The residue, alone or in combination with a precipitated benzene-insoluble rich extract fraction, is conveyed via a conduit 16 to a drying zone '18 wherein a recycle gas stream entering through a conduit 20 is used to strip any retained solvent therefrom. The efuent stream from the drying zone 1S is passed through a conduit 22 to a pair of cyclone separators 2d and 25 which separate the vapors from the solids. rlhe solids drop into a conduit where they are picked up by a carrier gas and introduced into a carbonization zone Z8.
rlhe carbonization zone 2% may be any one of the wel-iknown systems for carbonizing carbonaceous solids at low temperatures, i.e. 425 to 760 C. For example, solids may be maintained in the Zone in a fluidized bed by means of the above-mentioned carrier gas. The temperature of the carbonization zone may be maintained by any suitable means, for example, by preheating the carrier gas to the appropriate high temperature or by burning a portion of the carbonized residue, i.e., char, produced in the carbonization zone 2S. This latter method is accomplished by withdrawing char from the carbonization Zone 28 through a conduit 3d, and conveying the withdrawn char by means of an inert gas such as recycle gas entering through a conduit 32, into a char devolatilization zone 34S. The char is preferably maintained in a iluidized bed in the zone 34 at a temperature between about 645 and 945 C. The devolatilization temperature must be higher than any processing temperature to which the solids have been previously exposed. The volatile content of the solids will be driven olf as a hydrogen-rich gas which can be recovered through a conduit 36.
' A portion of the devolatilized char is withdrawn from the devolatilization zone 34 through a conduit 3d, picked up by air entering through a conduit 4%, and lifted through a combustion leg 42. The temperature of the char as a I result of the combustion is raised to that sufficient to maintain the temperature in the devola-tilization zone 34 when returned through a cyclone separator 44 and a conduit 4d to that zone. Elue gas is removed from the cyclone separator 44 through a conduit 48. Hot char from the devolatilization zone 34 is transferred by a conduit 50 back to the carbonization zone 23 by means of recycle gas from the conduit 35i. Net char produced in the carbonization zone 21S is discharged through a conduit 52.
The hydrogen-rich gas from the char devolatilization zone 34 is conducted via the conduit 36 to a conversion zone 54 wherein substantially pure hydrogen is produced by techniques well known in the art, as is fur-ther er;- plained in my copending application Serial No. 144,423, iled October 1l, 1961, and assigned to the assignee of this invention. The resulting hydrogen may be used, for example, in the subsequent hydrogenation of the extract.
Returning to the carbonization zone 23, the eliluent tar vapors are circulated through cyclone separators 56 and 53, which return iinely divided solids to the carbonization zone 2S. rfhe distillate tar vapors are withdrawn from the carbonization zone via a conduit ou and subsequently fractionated, as more fully explained hereinafter.
Returning now to the coal extract which is separated from the residue in the separation zone i4, the extract is conducted through a conduit 62 to a llash tower 64 wherein at least some of the solvent is flashed off through a conduit 56. The solvent vapors are commingled with solvent vapors from the afore-rnentioned residue drying zone 13 in a conduit 63 which carries the solvent vapors to a condenser 7i?. Any noncondensable gas is discharged through a conduit 72 While the condensed solvent is returned to the extraction zone i0' via a conduit 74.
The extract is conveyed from the flash tower 64.- through a conduit 76 to a preheater '7S which serves to raise the temperature of the extract to about 426 to 468 C. The preheated extract is passed through a mild prehydrogenation zone 80 which serves to add about 0.5 to 2.0 pounds of hydrogen per 100' pounds of feed. The operating conditions are as follows:
Temperature 425 to 470 C. Pressure 500 to 2500 p.s.i.g. Residence time 5 to 60 minutes, preferred l0 to 30 minutes.
Hydrogen input to the prehydrogenator Si) may be by means of hydrogen transfer from hydrogenated oil derived from a final step of the present process. Free hydrogen gas may also be added to aid hydrogenation. The prehydrogenation operation is preferably conducted substantially noncatalytically, or 'with relatively small amounts of homogeneous catalysts, i.e., 0.05 to 1.0 .weight percent of a hydrogen halide or its corresponding ammonium salt, i.e., NHiCl, NHBr, or NH4I. lInexpensive catalysts such as red mud may also be used if desired. The hydrogenated oil is used in amounts between 1 and 3 parts per part of extract, preferably mixed with solvent from the flash tower 64.
The mildly prehydrogenated extract is discharged through a conduit 82 into a fractionation zone 84 which preferably separates the prehydrogenated 'extract products into a +325 C. and a 325 C. fraction. The latter fraction is withdrawn through a conduit 85 and subsequently hydrogenated. The +325 C. bottoms fraction which still contains nondistillable hydrocarbons is conveyed through a conduit 35 into a conduit S8 to a preheater 9b, and thence through a conduit 92 to a coking zone 94- operating at 425 to 760 C. Ash-free coke is discharged through a conduit 96. Coker distillate is withdrawn from the coking zone $4 via a conduit 98 and is commingled with the distillate tar vapors Withdrawn from the carbonizer 2S via a conduit el?. The distillate mixture is introduced into a fractionation zone 100. A 300 C. fraction is recovered through a conduit 102 for further reiining, if desired, to yield chemicals and low boiling solvents. A 300 to 425 C. fraction is sent through a conduit 104 to a preheater 106. The preheated fraction is withdrawn via a conduit il and thence admixed in the conduit 85 with the 325 C. fraction of the prehydrogenated extract. The mixture is then introduced into a hydrogenation zone 10. The portion of the distillates boiling above 425 C. is withdrawn from the fractionation zone .itl-0 via a conduit 1&9 and recycled to the coking zone 94.
In the hydrogenation zone 110, the prehydrogenated extract and tar are contacted with hydrogen, preferably in the presence of a hydrogenation catalyst, Hydrogenation of the extract and tar may be conducted at pressures of 1000 to 10,000 p.s.i.g., preferably about 2000 to 3500 psig., a range well below lthat normally required for direct hydrogenation of coal. The hydrogenation temperature range is about 400 to 600 C., preferably about 410 to 455 C. The hydrogenation catalyst should be sulfur-resistant, eg., molybdenum or tungsten oxides or suldes impregnated on a refractory support to permit catalyst regeneration. The support usually will be an alumina-rich material such as purey gamma alumina or alumina composited with other oxides such as silica. Other metals such as nickel or cobalt may be added as catalyst promoters.
The products of hydrogenation are discharged from the hydrogenation zone 110 through a conduit 112, cooled, and passed into a fractionation zone 114 wherein the products are separated into any desired fractions. A preferred separation is to fractionate the hydrogenation product into a fraction boiling above 360 C. and a fraction boiling below 360 C. The latter fraction is passed through a conduit 116 to further refining and hydrogenation operations for conversion to gasoline. The former fraction is passed through a conduit 118 and may be reintroduced into the hydrogenation zone 119 or into the coking zone 94. If desired, portions of both fractions may be introduced into the solvent extraction zone as a part of the solvent therein.
According to the provisions of the patent statutes, I have explained the principle, preferred construction, and mode of operation of my invention and have illustrated and described what I now considere to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specically illustrated and described.
1. A combination process for the production of hydrogen-enriched liquid fuels from coal, which comprises (a) subjecting the coal to solvent extraction to yield a mixture of extract and undissolved coal residue,
(b) recovering from said mixture at least a portion of said extract which is substantially free of hydrocarbons boiling below 400 C.,
(c) subjecting said extract portion to prehydrogenation to effect only partial conversion thereof to a distillable fraction boiling below 325 C.,
(d) subjecting at least a portion of the +325 C. product from step (c) to carbonization to yield a liquid distillate,
(e) combining at least a portion of said liquid distillate of carbonization and a lower boiling portion of the product from step (c), and
() thereafter hydrogenating the resulting mixture to yield hydrogen-enriched liquid fuels.
2. A combination process for the production of hydrogen-enriched liquid fuels from coal, which comprises (a) subjecting the coal to solvent extraction to yield a mixture of extract and undissolved coal residue,
(b) separating at least a portion of said extract from said residue,
(c) subjecting the extract to mild prehydrogenation at a temperature between 425 and 470 C. and at a pressure between 500 and 2500 p.s.i.g. to yield prehydrogenated extract,
(d) subjecting a higher boiling fraction of said prehydrogenated extract products to carbonization at 425 to 760 C. to yield a liquid distillate,
(e) combining at least a portion of said liquid distillate of carbonization and a lower boiling fraction of said prehydrogenated extract products, and
(f) thereafter hydrogenating the resulting mixture to yield said hydrogen-enriched liquid fuels.
The process of claim 2 wherein said undissolved coal residue is subjected to carbonization in a fluidized low temperature carbonization Zone at a temperature between 425 and 760 C. to yield a liquid distillate, at least a portion of which is subjected to hydrogenation in step (f).
4. The process of claim 2 wherein said coal is subjected to solvent extraction under conditions to dissolve less than weight percent of the moisture-free and ashfree coal, whereby a mixture of extract and undissolved coal residue is obtained.
5. A combination process for the production of hydroenriched liquid fuels from :coal which comprises (a) subjecting the coal to solvent extraction under conditions to yield an extract amounting to less than 60 percent by weight of the moisture-free and ashfree coal and containing both benzene-soluble and benzene-insoluble material,
(b) separating the extract from the undissolved coal residue,
(c) subjecting said residue to carbonization under conditions yielding a liquid distillate,
(d) subjecting the extract to mild prehydrogenation under substantially noncatalytic conditions at 425 to 470 C. and 500 to 2500 p.s.i.g. until about 0.5 to 2.0 pounds of hydrogen per pounds of extract have been added to said extract,
(e) subjecting at least a higher boiling portion of said prehydrogenated extract to carbonization at 425 to 760 C. to yield a liquid distillate,
(f) combining said liquid distillates of carbonization,
(g) subjecting the resulting mixture to hydrogenation under catalytic conditions at 400 to 600 C. and 1000 to 10,000 p.s.i.g., and
(h) recovering the hydrogenated products.
No references cited.