US2658861A - Process for the hydrogenation of coal - Google Patents

Description

NOV- 10, 1953 E. F. PEVERE Er A1.

PROCESS FOR THE HYDROGENATION OF COAL Filed Nov. 19, 194e Patented Nov. 10, 1953 UNI-TE D STATES offre-free;

PR OCES SfFOR lRO'GETN`- Ernest Ft Pevereand Howard V. Hess, Beacon,

and' George? B; Arnold,.Glenhan1,-z N; Y., lassignors toThe Texas Company,Newllorkyllflila` a; corpora'tioxrofl Delawarev Application.' November 19, 1918"; Serial l`-'No.=- 61,012T

This invention relatesto,aprcee'ssl for the hydrogenation of co'a1.' The process ofthisinvention is particularly applicable to the treatment of bituminous coals. r.

In the conventional coal-'hydrogenation processes, suchoas practiced inG'ermanythe coal is dried, pulverized, and made intooa paste.v Heavir oil derived from the process is admixedlwith the powdered coal in approximately equalproportions by Weight to formthe'paste. Ahydrogenation catalyst, e. g., iron sulfate' in an amount equivalent to aboutV 1 per cent by Weight,.is incorporated'in thejpaste.' The paste is mixed with hydrogen, preheated to. the operating temperatures, generally about 850`F.', and' passed into convertersunder a pressure of from about4,0'00 to about` 10,000 pounds per square inch. Thisst'ep is called thev liquid'phasehydrogenation stepof the process; Vapo'rs arek separated" from. there'- sidual solids and liquid'A at the operating pressure and temperature. nreact'ed hydrogen and most of the oil are removed as vapors; Thetvapors are cooledtocondense theoil, andV and the hydrogen isrecycled. Heavy" oil is separated from' theresidualI solids. The heavy oil' is' used for preparing thepaste, while residua-l solids are used' asfuel'. The light oils are subjected to' vapor phasehydrogenationfor conversion'togasoline. In this step, oil vapors andhydrogen are passed: over a=cata1ys't,.e;.g.., tungsten sulfide, at a pressurey of about`4,500 pounds perf square inch: Oils` boiling above the"V motorv fuelY boiling'v range arerecycledto the process;

An important element of cost in conventional coal liquefactionV processes is in the preparation ofl the coal` for hydrogena'tion". In the process of the present invention it. is not necessary tofpul- Verize thecoal'feed or to'prepare a paste in conventional manner. Elimination of the pulveriz'- ing and conventional pasting steps resultsin a substantial` saving in operating costs;

A11-object of this-inventionfisI toiprovde animproved process for the hydrogenationfof coal.

Another Objectis to provide animproved'process for the production of oil from coa-lby-liquid phase reaction of coal with hydrogen;

Other objects and advantageswill be apparent to those skilled in theart from the following detailed descriptionv of the invention;

In accordancel with the' process! of this'l inven'- tion, coal is liquefied, theli'uueed coal isatuI-i'ill` ized, and subjected to hydrogenation' in a dls" persed condition' at anA elevated temperature: andi pressure, Y

Coal may be rendered plasticby heating; The

plastic point varies with different lcoals. Gren'L erallyV -coal'l becomes plastic.y or: liqueiiesat f a temperature-Withinthe range` of `fromifabout. '550 to about- 7 00 'F'. When coall is. heated-"in" the.I presience of a: mineral-oil, the? coaland. oil` become miscible and: may be mixed: to-form'. aI substanitially homogeneousl `viscous'sliquid. Somerhydroy carbon oils;` Vespecially hydroaromatics; suoli as tetralin, decalin, and heavy oils obtained by hydrogenation: ofcoal,v actas: solventsA arid aid'V in the. liquefaction the coal; At" temperatures above about 700 F., there'isa' condensationr of free radicals? or. unsaturated: compounds (generiated by thermal-decomposition of coal substance) into materialsV more 'stab-le; than theoriginallcoal substances. At temperatures above* about? 825 E., the ratecfv precipitatio-nof insolublepolymer may exceedthefrate cffi'liquefaetion; Thecoal should be kept at: av temperature: as;y lowaspos'- sibledur-ing; liquefaction. andisubsequent': handlingfin theliquidistate?tc'preventexcessive precipitation'- off the' solid: polymer; The optimum temperature.. for liquefactionf isf dependent Y upon the. type and source# off. the: coal an'dthe"v length off time/'in whichthefcoali niust bekeptin lliquid state' prior to hydrogenation' andi isi best` determined by trial-for anygiven coal;

When tlfxeiA coal.- isiliquefied'witli the oil with mechanical mixing.; d aA substantially homogeneous liquidf'mixturermay bei' obtained; Finely divided solid particles may lierpresent. in` the mixture. This mixture may beatomizedswtliout further treatment. Oni the otherhand"1 when' the par'-r ticles-ofv coal are extractedI Withr oil'without agi-- tation.abouty 65v` per; cent biyweight'of the coal is-ftak"en:.into solution. .in the oiI leaving' a1 porous riabler residue; The liquefied. coal or' extract ob-v tained'. '.by` this'v method iis substantially free' from ash: The undissolve'cl portioniofthecoalissuitable for reaction,.inrsituftoiproduce carbon mon-y oxideA and l.hydrogexr by. reactiomwitli steamV or with-fa; mixture of steamkandoxygen; Witheith'er methodo liquefaetionthe residual solids :may be used for thefgeneratiorrof syntiiesis-ga'sesorfor' production. of: hydrogen. for the process InA accordancefwth:preferred: practice of` this invention; ccal= and o'I are` admixed toform a'- liduia atatemperatureWithin@therangerof about 550 to 850 F. and the resulting li'quiisatomized." intol at hydrogenatiort-'reaotor' operated-fat a temperature-zwithin. the range off from about '750 to about 850 F. and a pressureA aboveabout 1000. pounds. per suda-ref inch-1 gauge. Hydrogen is=.pref'erab1y-usecias adi'spersing rrieui'uiii for" atomzation of thercoal r"llieividalmay lbe liql-f fed at a temperature of 550 to '700 F. and the resulting liquid heated to a temperature within the range of from about 750 to about 850 F. prior to hydrogenation.

The quantity of liquid admixed with the coal to form a liquid stream which may be atomized with conventional equipment may vary considerably depending upon the type of coal and oil' used in the preparation step. Generally, a quantity of oil equivalent to about 50 per cent by Weight based on the weight of the coal is sufficient to provide a fluid feed stream which may be atomized.

The particle size of the coal fed to the process is not of particular importance. The smaller particles are more quickly liquefied. 'Ihe particles should be of such size that substantially complete liquefaction takes place in a reasonable period of time. Generally it is desirable to use particles ranging from about x/z-inch in average diameter to powder.

With the present process it is not necessary to resort to fine grinding or pulverization of the coal prior to preparation of the feed as in conventional hydrogenation processes. It is contemplated that in most applications of the process, the coal will be reduced only to a particle size such that the largest particles are dissolved prior to discharge of the liquid from the liquefaction vessel. Coal may be crushed mechanically to a particle size of 1/g-inch to 1/il-inch in average diameter with a relatively small expenditure of power. Further reduction in size becomes progressively more expensive, pulverization by rnechanical means requiring large expenditures of power. The process of the present invention represents a considerable saving in power requirements for the preparation of the feed over conventional methods of preparation.

The atomized coal maybe hydrogenated under conditions satisfactory for conventional liquid phase hydrogenation of coal. Liquid phase coal hydrogenation is a well-known procedure. In atomized form, the liqueed coal is more reactive than in conventional paste form, hence the time required to effect a given percentage of conversion is somewhat less than for conventional procedures. The pressure under which the coal is hydrogenated may range from 1,000 to 10,000 pounds per square inch gauge or higher, and the temperature from 600 to 900 F.

In a preferred embodiment, the liquefied coal is atomized and suspended in hydrogen. rIhe suspension is introduced into a uidized bed of residual solid material resulting from the coal hydrogenation reaction. The solid residual particles are entrained in the product stream and are separated from the oil in subsequent separation steps of conventional design. The residual solid material contains unreacted carbon as well as ash from the coal and may be used as fuel or reacted with steam or with steam and oxygen to produce a mixture of carbon monoxide and hydrogen. About '70 per cent by weight of the coal charged to the process may be converted to Iiuid products by hydrogenation, the hydrogen consumption generally ranging from about 1.5 to about 3 per cent by weight based on the Weight of the dry coal.

The invention will be more readily understood from the following detailed description and the accompanying drawing.

The gure is a diagrammatic elevational view illustrating a preferred inode of carrying out the process of the present invention.

With reference to the drawing, coal of a suitable particle size is supplied to a hopper 5 through a conduit 6. From the hopper the coal may be fed through conduit 'I into liquefaction vessel 8 or through conduit 9 into liquefaction vessel I0. Any number of such vessels may be employed. With two vessels, as illustratedone of the vessels is charged with coal and cil to prepare a liquefied coal feed stream for hydrogenation While the other is being discharged to the hydrogenation reactor. When a vessel has been filled with coal from the hopper, inert gas from line I2 may be admitted to the vessel to purge it of air. Valve I3, associated with vessel 8, and valve I4, associated with vessel I0, are provided for this purpose. Air and other gases may be vented from the vessels to line I5. Gases from vessel 8 are vented to line I5 through valve I6; those from vessel I0, through valve II.

Preheated oil from line IB may be admitted to vessel 8 through valve I9 and to vessel I0 through valve 2G. When a vessel is lled with coal and oil the valves are closed and the coal particles at least partially liqueed due to the combined effect of heating and the solvent or plasticizing action of the hot oil. A substantially homogeneous liquid mixture of coal substance and oil is thus obtained.

Mechanical mixers, not illustrated in the drawing, may be supplied to insure complete disintegration of the coal, if desired.

As illustrated in the drawing; the coal is subjected to intimate contact with hot oil without agitation, effecting solution of a part of the coal in the oil and leaving a porous friable residue in the liquefaction vessels 8 and I0. The resulting liquid, comprising liquefied coal and oil, is discharged from vessel 8 through valve 23 and from vessel I0 through valve 24 to a charge pump 25 as feed for the hydrogenation step..

Inert gas from line I2 may be admitted to the vessel during the period of discharge to the feed pump. Gas from line I2 may be supplied under pressure to build up a pressure Within the vessel and aid in the removal of liquid from the residual solid. This gas may be heated if desired to an elevated temperature. This porous friable residue remaining in the liquefaction vessel is in a state nearly ideal for gasification, A mixture of steam and oxygen may be supplied to the liquefaction of vessels through line 21. The ow of gas from line 21 is controlled by valves 28 and 29, associated with vessels 8 and I0, respectively. The resulting products of gasification may be discharged into line I5 for further use as desired.

Catalyst may be admitted through line 30 into admixture with the stream of liquefied coal and oil.

From the charge pump 25 the liqueed coal and oil stream is passed through a heating coil 32 and charged through line 33 into an atomizer 34 associated' with a hydrcgenation reactor 35. The coal feed stream may be fed directly from the charge pump 25 to the atomizer 34 through line 36 as controlled by valve 37. Since it is generally desirable to carry out the hydrogenation reaction at a pressure above about 1,000 pounds per square inch gauge and often not desirable to subject the heating coil 32 to excessive pressure, a second charge pump 38 may optionally be provided to increase the pressure of the hot charge stream immediately prior to introduction of the stream to the atomizer 34.

Hydrogen is admitted to the system through line 49. Fresh and recycled hydrogen are pumped by a pump 4l through line 42 into the atomizer 34. In the atomizer 34, which may be of any conventional type, the liquefied coal feed stream is broken up into small droplets and dispersed in the stream of hydrogen from line 42. From the atomizer, the dispersion of liquefied coal and hydrogen is discharged directly into the hydrogenation zone 35. In the dispersed state, the hydrogenation reaction proceeds rather rapidly.

Somewhat more hydrogen is usually required for atomization and dispersion of the atomized coal stream than is required in the conventional liquid phase hydrogenation. This merely results in a higher recycle rate, since hydrogen consumption, for a given percentage conversion, is not appreciably affected.

The hydrogenation reaction results in precipitation of ash and the more difcultly hydrogenatable fraction of the coal substance as solids. These solids are entrained in the eilluent stream discharged from the hydrogenation zone 35 through line 4l'. The hydrogenation eiliuent is passed to a separation system 48 wherein it is separated into various fractions. Any of several known conventional methods of separation may be employed. A gaseous fraction is recycled to the hydrogenation reactor through line 4Q to pump 4 I. A portion of the gaseous fraction may be purged from the system through line 5|. A light oil fraction is taken from the separation system through line 52 and a middle oil fraction through line 53 for further processing. In accordance with general conventional practice, the middle oil stream is subjected to further hydrogenation in vapor phase to produce motor fuels. Residual solids separated from the oils in the separation system 49 are discharged through line 54.

Heavy oil is discharged from the separation system through line 56 as a recycle stream to the liquefaction vesels 8 and I0. A portion of the heavy oil may be withdrawn for other uses through line 57. Other oils may be supplied if desired to the heavy oil recycle stream through line 58. The heavy oil stream is heated in a heating coil 50 to the desired temperature prior to `admission to the liquefaction vessels 6 and I0 through line i8. All of the heat required for the process may be supplied by the hot oil stream.

It will be understood by those skilled in the art that various alternatives are available in the way of equipment and methods of handling the various streams and utilizing the heat contents to maximum advantage. In the interest of simplicity, various conventional pieces of apparatus such as control valves, heat exchangers, and the like, have been omitted.

In a typical operation of la process such as illustrated in the drawing, Pittsburgh Bed coal containing about 2 per cent water, 31 percent volatile matter, 58 per cent fixed carbon, and 9 per cent ash, as received, is subjected to hydrogenation. The coal is charged to a liquefaction vessel in the form of lumps about 1/2 to 1A inch in average diameter. This coal is mixed with heavy oil obtained from the hydrogenation of coal in an amount approximately equal in weight to the weight of the coal. The oil is preheated to a temperature of about 850 F. before admixture with the coal, resulting in a temperature of about 750 F. in the liquefaction vessel. About 6 65 per cent by Weight of the coal is liquefied or extracted by the liquid oil without agitation, leaving a rporous friable carbonaceous residue.

The resulting liquid comprising liquefied coal is atomized with hydrogen into a reactor at about 750 F. and about 1,000 pounds per square inch gauge.

Obviously many modifications and variations of the invention as hereinabove set forth may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

We claim:

1. A process for the hydrogenation of fusible coal which comprises contacting particles of said coal having an average diameter smaller than about l inch with a hydroaromatic oil at a temperature Within the range of from about 550 to about 850 F. and above the plastic point of said coal, mixing the coal and oil at said temperature for a period of time sumcient to form a substantially homogeneous liquid mixture, contacting said liquid mixture with hydrogen in a hydrogenation zone at a temperature within the range of from about 600 to about 900 F'. and a pressure within the range of from about 1,000 to about 10,000 pounds per square inch gauge whereby hydrogenation of said liquid takes place With the formation of particulate solid residue, maintaining a fluidized bed of said particulate solid residue Within said hydrogenation zone, discharging resulting Huid products of hydrogenation and solid residue from said hydrogenation zone, and recovering said fluid products.

2. A process for the hydrogenation of fusible coal which comprises contacting particles oi said coal having an average diameter within the range of from about 1/4 inch to about 1/2 inch with a hydroaromatic oil at a temperature within the range of from about 550 to about 350 F. and above the plastic point of said coal, mixing the coal and oil at said temperature for a period of time sucient to form a homogeneous liquid mixture, atomizing said liquid mixture, suspending the atomized liquid in hydrogen at a ternpertaure within the range of from about 600 to about 900 F. and a pressure within the range of from about 1,000 to about 10,000 pounds per square inch gauge whereby hydrogenation of said liquid takes place with the formation of particulate solid residue, introducing said suspension at said hydrogenation temperature and pressure into a uidized bed of particulate residual solid material resulting from the hydrogenation reaction, discharging the resulting fluid products of hydrogenation and solid residue from said hydrogenation zone, and recovering said fluid products.

ERNEST F. PEVERE. HOWARD V. HESS. GEORGE B. ARNOLD.

References Cited in the le of this patent UNITED STATES PATENTS Number Name Date 1,864,496 Pier et al June 2l, 1932 1,390,435 v Krauch et al Dec. 6, 1932 2,215,190 Pier et al Sept. 17, 1940 2,436,938 Scharmann et al. Mar. 2, 1948 2,464,271 Storch etal Mar. 15, 1949 2,476,999 Orchin July 26, 1949

Claims (1)

1. A PROCESS FOR THE HYDROGENATION OF FUSIBLE COAL WHICH COMPRISES CONTACTING PARTICLES OF SAID COAL HAVING AN AVERAGE DIAMETER SMALLER THAN ABOUT 1/2 INCH WITH A HYDROAROMATIC OIL AT A TEMPPERATURE WITHIN THE RANGE OF FROM ABOUT 550 TO ABOUT 850* F. AND ABOVE THE PLASTIC POINT OF SAID COAL, MIXING THE COAL AND OIL AT SAID TEMPERATURE FOR A PERIOD OF TIME SUFFICIENT TO FORM A SUBSTAN TIALLY HOMOGENEOUS LIQUID MIXTURE, CONTACTING SAID LIQUID MIXTURE WITH HYDROGEN IN A HYDROGENATION ZONE AT A TEMPERATURE WHITHIN THE RANGE OF FROM ABOUT 600 TO ABOUT 900* F. AND A PRESSURE WITHIN THE RANGE OF FROM ABOUT 1,000 TO ABOUT 10,000 POUNDS PER SQUARE INCH GAUGE WHEREBY HYDROGENATION OF SAID LIQUID TAKES PLACE WITH THE FORMATION OF PARTICULATED SOLID RESIDUE, MAINTAIN-

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