Note: Descriptions are shown in the official language in which they were submitted.
-
-- 1 --
1146895
1 BACKGROUND OF THE INVENTION
2 This invention relates to an improved process
3 for converting coal or similar solid carbonaceous
4 materials. More particularly, this invention relates to
an improved process ~or liquefying coal and similar
6 carbonaceous substances.
~ As is well known, coal has long been used as a
8 fuel in many areas. For several reasons, coal has not been
9 a particularly desirable fuel from the ultimate consumers
point of view. As a result, oil and gas have enjoyed a
11 dominant position, from the standpoint of fuel sources,
12 throughout the world.
13 Several processes wherein coal is either liquefied
14 and/or gasified have been proposed heretofore. Of these,
the processes wherein coal is liquefied appear to be more
16 desirable since a broader range of products is produced and
17 these products are more readibly transported and stored.
1~ or the several ll~uefaction processes whlch have
1~ been heretorore proposed, th~se processes wherein coal ls
liquerled ln the presence Or a solvent or diluent, ~arti-
21 cularly a hydrogen donor solven~ or dl~uent, and a
22 hydrogen-containlng Fas appear to or~er the greater
23 advantages. In these processes, liouefactlon is accom-
2.~ pllshed at elévated temperatures and pressures and a broa~
2~ range or llquid and gaseous products are produced.
26 Moreover, a normally solid bottoms material remains arter
the liquid and gaseous products are separated. Generally,
.u th~s bottoms materlal will contain unconverted solid
29 carbonaceous products and may be burned directly to produce
30 steam. While direct co~bustion of the bottoms has been pre-
31 viously proposed, these proposals contemplate the direct com-
32 bustion in a conventional manner wherein steam is first
-- 2 --
1~46~3~5
1 produced and the steam then is used directly in the
2 process, or as a heat transfer media, or in the production
3 Or electrical power. When steam is used to provide process
4 ~.eat, thermal efriciency is lowered, and hence, cost Or
operatlon is agaln increased. Finally, gaseous or liquid
6 products can be burned ~or process heat but this is a
7 very expenslve energy source. Since the cost Or providing
8 process heat to a plant converting carbonaceous solids
9 to liquids and gas is substantial, the need remains for
.1~ a process wherein the heat is erriciently produced and
11 the overall operating cost reduced as much as possible.
12 It is an object of this invention to provide an
13 improved liquefaction process wherein the required conversion
14 and/or upgrading of the bottoms material is significantly
reduced and preferably wherein both process heat and/or power
16 requirements are provided in an economically attractive man-
17 ner. The foregoing and other objects and advantages will
18 become apparen~ from the description set forth hereinafter
19 and from the drawing appended thereto.
SUMMARY OF THE INVENTIO~
21 In accordance hith the present invention, the
22 roregoing and other ob~ects and advantages are accomplishcd
23 by liquerying coal in a conventional manner and then com-
24 bustlng at least a portlon Or the bottoms product dlrectly
ln either a llquld or solid state to produce both process
26 heat and steam which may then be used either in the
27 process directly and/or used to produce electrical power.
28 As indica~ed more fully hereinarter, this is accomplished
29 by combusting at least a Fortion Or the bottoms eithe~
alone or in combination with other ruels in a hybrid
31 boiler whereln steam is ~enerated in the radiant zone
32 and process heat produced in the convection zone. As
33 also indicated more rully hereinafter, process demands
34 may be met by cGmblning the bottoms material with one
or more other solid carbonaceous fuels or wlth any Or
36 the conventional llquid or g3seous ruels and efrecting
- 3 -
~6~395
1 combustion in the same boiler such that steam i5 produced
2 in the radiant zone and process heat produced in the
3 convection zone. Control ~ith respect to the amount Or
4 heat produced in each Or the radlant and convection
zones may be errected by conventlonal boiler control
6 technlques such as elther by bypassing all or a portion
7 Or the rlue gas or by controlllng the amount of excess
8 air used to rire the bottoms product.
g B~IEF DESCRIPTION OF THE DRAWINGS
The figure is a schematic flow diagram Or an
11 improved liquefaction process within the scope of the
12 present invention.
13 DETAILED DESCRIPTION OF THE INVENTION
1~ As indicated, supra, the present in~ention
15 relates to an improved process ror liquerying coal and
16 similar solld carbonaceous materials whereln at least a
17 portion Or the liqueraction bottoms ls subJected to direct
18 combustlon in a hybrid boller wherein steam is generated
19 in the radiant zone and process heat produced or trans-
rerred in the convection zone. When the amount Or
21 liqueraction bottoms available ror combustion is too low
22 to provide all or a signiricant portion Or the steam and
23 process heat requirements, the available bottoms may be
24 combined with a conventional ruel such as coal, fuel oil
2~ and natural gas such that the desired amount Or steam and
26 process heat ls produced within the hybrid boiler.
27 Altcrnatively, and particularly during startup when
2~ l~queraction bottoms will not generally be available,
29 alternate ruels, such as coal, ruel oil, and natural gas
30 could ~e combusted in the hybrid boiler to produce steam
31 and process heat. The steam may then be used to generate
_2 electricity or ror other purposes including the satis-
-,3 faction of steam require~r,ents-or a port~on tXereof for
-~4 the liqueraction process.
In general, the method Or the present invention
36 can be used to liquery any solid carbonaceous material
1~gl6~5
1 which can, efrectively, be hydrogenated. The method Or
2 this invention is particularly userul in the liqueraction
3 Or coal and may be used to liquery any Or the co~ls known
4 ln the prior art including anthracite, bltuminous coal,
subbltumlnous coal, llgnite, peat, brown coal and the
6 llke. Moreover, the method of thls lnventlon is parti-
7 cularly useful ln such llqueractlon processes wherein a
8 suitable solvent or diluent is employed as a carrler ror
9 the solld carbonaceous material.
In general, the solid carbonaceous material will
11 be ground to a finely divided state. The p~rticular si~e
12 or particle size range actually employed, however, is not
13 critical to this invention and, indeed, essentially any
14 particle size can be employed. Notwithstanding this,
generally, the solld carbonaceous material which is
16 llquerled in accordance with this invention will be ground
17 to a particle size of less than 1/4" and prèferably to a
18 siZe less than about 8 mesh (nbs sleve size). After the
19 solid carbonaceous material has been sized, the same will
then be slurried in a suitable solvent or diluent.
21 Normally, the ratio Or coal (on a moisture-free basis)
22 to solvent or dlluent in the slurry will be within the
23 range rrom about 1.0:1.0 to about 1.0:3.0, on a weight
24 basis.
Any Or the solvents or diluents known to be
26 useful in the prior art ror the liqueraction o~ solid
27 carbonaceous materials can be used in the improved lique-
28 raction process Or the present invention. Such solvents
29 or diluents include all types Or hydrocarbons and parti-
cularly those having the boiling point withln the range
31 from about 400F to about 1000F. The solvent or diluent
32 may be a straight or branched chain hydrocarbon, a cyclic
33 hydrocarbon, a naphthcnic or aromat~c hydrocarbon, a
34 phenol or substituted phenol, a hydroaromatic, a hetero-
3S cyclic compound which may contain oxygen, nitrogen or
36 sulfur or mixtures of any one or more Or these materi21s.
~1~6895
1 Moreover, the solvent or diluent may be inert at the
2 ligueraction conditions or the same may donate hydrogen
3 at these conditions. Particularly efrective solvents
4 include hydrogenated creosote oil and solvents derived
from the llqueraction Or coal, particularly those boiling
6 within the range rrom about 400~ to about 900F. Solvents
7 derived rrom the liquefaction of coal are particularly
a errectlve when the same are at least partially hydro-
g genated to produce a solvent containing hydrogen donor
s~ecies. Such species are bellevéd to be well ~nown in
11 the prior art and many are described in U.S. Patent
12 3,867,27~.
13 As previously indicated~ the method of this
14 invention may be used in combinatlon with any process
known to be erfecti~e ror the liquefaction Or coal or
16 other solid carbonaceous materials whereln a liquid
17 solvent or diluent is employed. In such processes,
18 liquefaction Or the coal or similar carbonaceous material
19 is errected by sub~ecting a mixture Or the coal or solid
carbonaceous material and the solvent to an elevated
21 temperature and pressure ror a period Or time sufricient
22 to permit at least partial liqueraction Or the coal. As
23 is well known, conversion Or the solid carbonaceous
24 materials to a li~uid required hydrogen and the hydrogen
25 may be provided via any method known to be effective
26 in the prior art ?ncludlng the use Or molecular hydrogen,
27 hydrogen donor solvents, other materials known to yield
28 hydroEen at liqueraction conditions and combinatlons Or
29 these. The liqueraction, which is efrectively, then, 2
hydro~enation operation, may ~e efrected either with or
31 w~thout an added catalyst.
32 In general, the liquefaction will be accomplished
33 at a temperature between the range rrom about 700F and
34 about 900F and at a pressure within the range from a~out
1000 psig to about 3000 pslg. Generally, the coal/sol~ent
36 slurry will be held at conditions within the arorcsaid
~689S
1 speciried ranges ror a nominal period Or time within the
2 range rrom about ~0 to about 200 minutes. As is well
3 known, the llqueraction may be accomplished in a plurality
4 Or stages and when multiple stages are employed, total
nomlnal holding times in excess Or 200 minutes may be
6 used.
7 In the improved method Or the present invention,
8 the heat required to errect liqueraction or at least 50
9 Or such heat requirement will be supplied by preheating
the slurry Or solid carbonaceous material to a temperature
11 within the range from about 700 to about 900F by passing
12 the same through the convection section Or a hybrid boiler.
13 As indicated more rully hereinarter, the hybrid boiler,
14 in its simplest form, will be a modification Or a conven-
tional boiler deslgn wherein steam ls produced ln the
16 radiant section and process heat supplied in the convection
17 section. The modiricatlon will, ~enerally, be nothing
18 more than a substitution Or tubes in the convection section
19 with tubes or coils designed for use in the preheatlng Or
a solid carbonaceous slurry and fashioned from a sultable
21 material of construction. As indicated previously, and
22 more ru ly hereinafter, heat in the convection section
23 will be transrerred rrom the rlue gas to the solid carbon-
24 aceous slurry material. The heat in the flue gas will
be produced by combustlon Or at least a portion of the
26 liqueractlon bottoms rrom the liqueraction process Or
27 this invention.
28 When molecular hydrogen is used in the lique-
29 faction reactor, the molecular hydro~en may also be
passed through the convection section Or the hybrid
31 boiler and preheated to the same temperature as the
32 solid carbonaceous material slurry. Alternatively,
33 mol.ecular hydrogen may be combined with the solld
34 carbonaceous material slurry prior to passlng the slurry
-35 through the convection sectlon Or the hybrid boiler.
36 Arter the solid carbonaceous material slurry
~46895
1 has been preheated, the same will then be passed to a
2 liquefaction zone wherein the same is sub~ected to
3 liquefaction conditions. In general, the liqueraction
4 wlll result in the production Or a gaseous product,
5 a liquids product and a normally solid bottoms product.
6 Arter liqueraction, these products may be separated into
7 respective phases using conventional techniques For
8 example, the gaseous product may be simply rlashed over-
9 head and the liquid and solids then separated using
filtratlon, centrirugation or distillation. or these,
11 distillation is most preferred since it a~rords the
12 cleanest and most controllable means Or separating
13 liquids and sollds. Arter separation, the gaseous
14 product may be burned to provide any energy ror the
liqueraction process which is not provided wlth the
16 hybrid boiler. Alternatively, a portion Or the gaseous
17 product could be burned as an auxilliary ruel in the
18 hybrid boiler. All, or a portlon, Or the gaseous product
19 may also be`rerormed to provide hydrogen rOr the lique-
raction process or sold as ruel. The liquid product may
21 be rractionated into a desired product distribution and/or22 a portion thereor may also be used directly as a ruei or
23 upgraded using conventional techniques. Slmilarly, a
24 portion Or the liquid product may be separated and used
as a solvent or diluent ln the liqueraction process Or
26 thls invention. In a prererred embodiment, such solvent
27 will be hydrogenzted to increase the amount Or donata~le
28 hydrogen therein prior to use as a solvent or a diluent.
29 Finally, and in accordance with the improvement Or this
invention, at least a portion Or the bottoms will be
31 withdrawn and sub~ected to direct combustion in the
32 hybrid boiler to produce at least a portion o~ the heat
33 required to er~ect li~uefaction. The remainder may then
34 be coked or gasiried to produce an intermediate BTU fuel
gas and/or hydrogen ror use in the liquefaction process.
36 In a most prererred embodiment, a sufficient portion Or
. 1~46~95
1 the bottoms product will be gasified to produce all Or the
2 hydrogen required ror liqueraction and the remainder will
3 be sub~ected to direct combustion ln the hybrld boiler.
4 In general, the bottoms which are sub,~ected to
direct combustion may be red to the hybrid boller either
6 as a liquid or as a solid. When red to the hybrid boiler
7 as a solid, heat may be recovered from cooling the bottoms
8 and used in the process, thereby reducing the amount Or
g heat required rrom the hybrid boiler. When the bottoms
are red to the hybrid boiler as a liquid, atomization
11 will, generally, be required and means known in the prior
12 art to be effective for the atomization Or a liquid ruel
13 containing relatively large amounts of solid residue may
14 be used.
The bottoms, in combination with any auxilliary
16 or alternate ~uel that may be required, wlll be combusted
17 in the combustion section of a hybrid boiler. Heat ln
18 the radiant section will be removed through the production
19 of steam. The steam will, generally, then be passed
through extraction/condensing steam turbines driving
21 generators to produce electrical power. The amount Or
22 steam required in the liquefaction process wlll be
23 extracted at appropriate pressure points along the
~4 steam turb~nes. The steam not required ln the lique-
raction process is condensed in the low pressure section
26 of the steam turbine, which generates additional
27 electrical power. The amount of steam actually produced
28 will determine the amount of heat available in the flue
29 ~as passing into the convection zone. Depend$ng upon
the amount o~ bottoms actually subJected to combustion
31 and the amount Or auxilliary fuel employed the amount of
32 steam actually produced may vary. In a preferred
33 embodiment, sufficient steam will be produced to supply
34 all process demands thereror. Any or all var~ations in
heat released in the boiler, or in process heat demand
36 in the convection sect~on, or in process steam demand
li~6~S
1 will r~sult in a variation in the amount of steam con-
2 densed, and thererore in the amount Or electrical po~'er
3 generated. Control Or the total operation may, therefore,
4 be obtained by varying the amount Or electricity -~--
purchased. Alternatively, when insufricient liqueraction
6 bottoms are available, control over the amount Or steam
7 actually produced and the amount Or electrlcity ac~ually
8 produced may be maintained by controlling the amount Or
9 auxilliary ~uel combusted in the hybrid boiler. In
general, the surface area for heat transrer ln the
11 convection section will be determined for any given
12 liqueract1on plant consistent with the amount of rlue
13 gas available ror heat transrer.
14 In general, from about 25 to about 100 wt %
Or the bottoms-material will be combusted in the hybrid
16 boiler and rrom about 0 to about 75 wt % thereof will be
17 either coked and ~asiried or gasiried. To insure that
18 the bottoms will be combustlble, it is important that
19 the liqueraction be controlled such that at least 50 wt
% carbon remains in the bottoms and preferably the
21 operation will be controlled that such rrom about 60 to
22 about 90 wt % carbon remains in the bsttoms product.
23 PREFERRED EMBODIMENT
24 In a preferred embodiment Or the present
25 invention, coal will be liqueried at a temperature rrom
26 wlthin the range rrom about 750 to about 950F, at a
27 pressure withln the range rrom about 1500 to about 3000
28 psig in the presence Or a coal derived hydrogen donor
29 solvent and in the presence Or molecular hydrogen. The
30 nominal holding time during llquefaction will be within
31 the range rrom about 25 to about 12~ minutes. Arter
32 lique~action, the liquid-solids mixture will be sub~ec ed
33 to both atmospheric and vacuum distillation such that .-,e
34 bottoms will be that material separated rrom the lique-
35 faction vessel havlng an initial boiling point within
36 the range from about 850 to about 1100F. When opera~ing
-- 10 --
11468~5
1 at these conditions, the bottoms will contain from abeu-
~2 60 to about 90 wt % carbon.
- 3 In a prererred embodin,ent from about 40 to about 100
4 wt % Or these bottoms will be sub~ected to direct com-
bustion in a hybrid ~oiler. The remaining bottoms will
6 be sub~ected to p~rtial oxidation to produce all or part
7 Or the hydrogen required to errect the liquefaction. The
8 bottoms which are sub~ected to direct combustion will be
g red either as a liquid or will be cooled and ~ed to the
hybrld boiler as solids. When additional fuel is required
11 to provide process heat, the solid or liquid bottoms will
12 be combusted with coal. Generally the same coal used in
13 the liqueraction process will be used to provide the
14 additional heat.
In the prererred embodlment, a surficient amount
16 Or bottoms or bottoms plus coal will be combusted to pro-
17 duce all Or ~he steam required in the liquefaction process
18 operation and to provide at least 60% Or all Or the
19 process heat required to errect liqueraction. Also in the
prererred embodiment, the amount Or bottoms or coal plus
21 bottoTns sub~ected to combustion will be sufficient to
22 produce enough steam to provide at least 50% Or the
23 electrical power required to operate the liqueractlon
24 'plant.
It is believed that the invention will be better
26 understood by rererence to the attached figure which
27 il~ustratcs a particularly prererred embodiment. Referrillg
28 then to the fi~ure, a finely divided coal or similar
29 solid carbonaceous material is introduced into mixing
vessel 10 through line 11 and slurried wlth a solvent or
31 diluent introduced through line 12. In a prererred
32 embodimcnt, the solvent will be derived from the solid
33 bcing subjected to liouefaction, will be hydro&enated to
34 produce hydrogen donor solvent species and will be recyc'Led
to the mixing vessel throu&h line 13. During start-up,
36 however, or when a recycle solvent is not employed, any
8~S
1 Or the known userul solvellts or diluents may be lntrodllced
2 into llne 12 through line 14. The coal or solid carbo..a-
3 ceous material slurry is withdrawn from mixing vessel
4 10 through line 15 and combined with hydrogen which is
lntroduced into line 15 through line 16. In the
6 preferred embodiment, the hydrogen will be produced
7 rrom li~ueractlon bottoms and red to line 16 through
8 line 17. Durlng start-up, however, or when the bottoms
g are not used to produce hydrogen, hydrogen from other
sources may be introduced into line 16 through line 18.
11 MoreoverJ while not illustrated, the hydrogen may be
12 lntroduced directly into the liqueraction vessel in which
13 case the same will, generally, be preheated via other
14 means or the same may be passed through a separate pre-
lS heatlng coil in the hybrid boiler. In any case, sufricient
16 hydrogen will be lntroduced to provide from about 2 to
17 about 8 wt % hydrogen based on dry, ash-rree coal.
18 In the embodiment illustrated, the combined
19 solid carbonaceous material slurry and the hydrogen is
then passed through a preheat coil 19 which is located
21 in the convection section 20 o~ hybrid boiler 21. In
22 the preheat coil, the slurry-hydrogen mixture will be
23 preheated to a temperature within the range rrom about
24 750 to about 900F.
In the convection section 20 Or hybrld boiler
26 21 heat is transrerred to the slurry-hvdrogen mixture
27 rrom the combustion rlue gas produced in combustion
28 section 22 Or the hybr~d boiler 21. Whilé not critical
29 to the present invention, the combustion flue gas will
rollow a path such as that represented by arrows 23-25
31 and will be withdrawn from the hybri~ boiler through
32 ~ine 26 arter normal practice Or passing through an
33 economl2er and air preheater section to improve overall
34 boiler ef~iciency.
The preheated slurry-hydroen mixture is with-
36 drawn rrom the preheat coil 19 through llne 28 and passed
6~95
l directly to liqueraction vcssel 29. In the liqueraction
2 vessel 29, the solid carbonaceous materlal is at least
3 part~ally liqueried and, generally, at least partially
4 gasif~ed. In general, the llquefaction vessel will be
sized so as to provide a nominal holding time within the
6 range rrom about 2~ to about 120 minutes and while a
7 single vessel has been illustrated, a plurality Or vessels
8 may be employed. Also, the temperature within the lique-
g faction zone wlll, generally, be within the range rrom
about 750 to about 900F and the liqueraction will be
ll accomplished at a pressure withln the range from about
12 1500 to about 3000 psig.
13 In the embodiment illustrated, the combined
14 product from the liquefaction vessel 29 is withdrawn
through line 30 and passed to separator 31. In the
16 embodiment illustrated, the separator may be a combined
17 atmospheric and vacuum distillation column wherein gaseous
18 products and products boiling below about 250F are with-
l9 drawn overhead through line 32 while unconverted solid
~arbonaceous material and mineral matter and converted
21 materials boiling at a temperature above about 850 to
22 about 1100F is withdrawn through line 33. ~he liquid
23 product is then fractionated into desired cuts and in
24 the embodiment illustrated, a naphtha product boiling
within the range rrom a~out 250F to about 400F is with-
26 drawn ~hrough line 34, a material boiling within the
27 range rrom about 400F to about 800F is withdrawn through
28 line 35 and a heavier fraction boiling from about 800F
29 to rrom about 8500F to about 1100~ ~s withdrawn through
line 36. In general, the overhead, gaseous material will
31 comprise &aseous and lower boiling hydrocarbons, steam,
32 acid ases such as SO2 and ~2S and any ammonia which may
33 h.~ve been produced during liquefaction. This stream may
34 be scrubbed and rurther divided to yield a high 3T~ gas
and lighter hydrocarbons. The naphtha stream may be
36 subjected to rurther upgrading to yield a good quality
- 13 -
11~68~5
l gasoline and the heavier stream withdrawn through line
2 3~ may be upgraded to produce a heavy fuel oil or
3 cracked and reformed to yield a gasoline bolllng
4 fractlon. Generally, ~he solvent boiling range material
or at least a portion thereor will be hydrogenated to
6 lncrease the concentration Or hydrogen donor specles
7 and recycled to mixin~ vessel lO as a solvent or dilueht.
8 As indlcated, supra, the particular separation
9 scheme employed is not critical to the present invention
and, indeed, any of the separation techniques known in
ll the prior art could be used to effect a separation of
12 the gaseous, liquld and solid products. In any case,
13 however, a bottoms product containing unreacted coal,
14 mineral matter and hlgh-boiling hydrocarbons will be
avallable ror subsequent processing in accordance with
16 the improved method Or this invent~on. Similarly, a
17 solvent bolling range material can be recovered for
18 recycle as the solvent or diluent.
l9 In the preferred embodiment, the solvent
fraction withdrawn through line 35 will be hydrogenated
21 before the same ls recycled to mixing vessel lO.
22 Preferably, the hydro~enation will be accomplished
23 catalytically at conditlons known to be errective ror
24 thls purpose ln the prlor art. In the embodlment lllus-
trated, the hydrogenation is accomplished in hydrogenation
26 vessel 37 wlth molecular hydrogen introduced through line
27 38 and produced by gasirication Or a portion of the
28 liquefactlon bottoms. ~uring start up, however, and
29 when surricient hydrogen ls not available rrom bottoms
gasirication, hydrogen rrom other sources may be intro-
31 duced into line 38 throu~h line 39. In the embodiment
32 illustrated, unreacted hydrogen and the gaseous products
33 of hydrogen are withdrawn through line 40. When desired,
34 this gaseous product may Le treated to recover recycle
hydrogén which may be recombined with hydrogen rrom
36 the gaslfication Or lique~action bottoms through line
114689S
1 41. Also in the embodiment illustrated, the hydrogenation
2 product ls withdrawn through line 42. In those cases
3 where the amount of liquid wlthdrawn through line 35
4 exceeds the amount of solvent required during liquefaction,
any excess may be withdrawn through line 43 and the
6 remainder recycled to mixing vessel 10 through lines 13
7 and 12.
8 Normally the hydrogenation will be accomplished
g at a temperature within the range from about 6500F to
about 8500F and at a pressure within the range rrom about
11 650 to 2000 psig. The hydrogen treat rate during the
12 hydrogenation generally will be within the range from
13 about 1000 to about 10,000 scf/bbl. Any of the known
14 hydrogenation catalyst may be employed but a nickel-moly
catalyst ls most prererred.
16 In accordance with the improved method Or the
17 present inventlon, the bottoms product withdrawn through
18 line 33 may be divided and a portion thereof gasified to
19 produce hydrogen and the remainder sub~ected to direct
combustion in hybrid boiler 21. In the embodiment illus-
21 trated, rrom about 0 to about 60% of the bottoms will be
2~ red through line 44 to gasirier 45. The remaining 40 to
23 about 100% will be red through lines 46-47 to the
24 combustlon section 22 of hybrid boiler 21.
In general, any gasirication technique known
26 in the prior art could be used to convert the bottoms to
27 hydrogen. In a preferred embodiment, however, an entrained
28 rlow ~asirier will be used to yield a synthesis gas via
29 combustion of the bottoms in the presence Or steam and
oxygen. ~he synthesis gas will then be upgraded in
31 accordance with conventional techniques to yield hydrogen.
32 In general, from about 0 to 1 pounds Or stcam and from
33 about 0.5 to about 1 pounds Or oxygen per pound of ~ottoms
34 will be used in the entrained rlow g2sirier and the
gasirication will be accomplishe~ at a temperature within
36 the ran~e rrom about 2000F to about 3000~F. In the
1 1~
11~689S
1 embodiment illustrated, hydrogen produced in the g25i~ ier
2 is withdrawn through line 46 and combined with any recycle
3 hydrogen that may be a~allable from the hydrogenation
4 and llque~action vessels. The comblned hydrogen then
passes through llne 47 and is then dlvided such that
6 h~drogen regulred for solvent hydrogenation is withdrawn
7 through line 48 and hydrogen required ror liquefactlon
8 wlthdrawn through llne 17. T~e ~Jydrogen withdrawn ror
g solvent hydrogenation is t~en combined with any makeup
hydrogen required and red to hydrogenation zone 37 through
11 line 38. Simllarly, hydrogen required for liqueraction
12 may be comblned with any ma~eup hydrogen required and
13 then combined with the solid carbonaceous material-solvent
14 slurry ln line 15. Residue rrom gasifier 45 is withdrawn
through line 49. -
16 In the embodiment illustrated, hydrogen is fed
17 separately to the liqueraction zone and the solvent
18 hydrogenation zone. As is well known in the prior art,
19 however, this is not critlcal to liqueraction and, indeed,
all Or the hydrogen produced in the gasirier could be
21 red first to the solvent hydrogenation zone and then to
22 the liqueraction zone or rirst to the liqueraction zone
23 and then to the solvent hydrogenation zone. Integrated
24 processes such as these are not, however, sub~ect to the
same de~ree o~ control as is available when hydrogen is
26 red separately to the two hydrogenation zones.
27 In the embodiment illustrated, from about 40
28 to about 100 wt Z of the bottoms is fed to combustion zone
29 22 Or hybrid boller 21 through line 47. During startup,
30 however, and when a sufrlcient quantity of bott~ms is not
31 available to produce the heat required in the hybrid
32 boiler, an alternate ruel such as a high BTU gas, oil or
33 coal will be introduced into combustion section 22 through
34 line 50. In the combustion section 22, then, the lique-
35 faction bottoms and any auxilliary ruel will be combusted
36 to produce heat and a heat containing flue gas. From
- 16 -
~46~5
l about ~0 to about 80~ Or the heat thus produced will be
2 used to produce steam in the radlant section 51 Or hybrid
3 boiler 21. The steam will be produced by passing
4 boller feed water introduced through lines 52 and 53
5 through steam coil 54. The amount of heat actually used
6 to produce steam may be controlled through the amount of
7 surrace area ~rovided ln steam coil 54. In general, the
8 steam produced will be withdrawn from the steam coils ~4
9 through line 56 at a temperature withln the range from
10 about 800F to about 1000F and at a pressure withln the
11 range rrom about lO00 to about 2000 psig. This steam ls
12 then passed to turbo generator 57 and used to produce
13 electricity. The electrlclty thus produced is trans-
14 rerred to electrlcal bus 58 through llne 59. Electrical
15 bus 58 which wlll, then, be used as a source ror some-
16 or all electrlcal power requlred ror the llqueractlon
17 operation and the same may be tied to commercially
18 available electrlclty or electriclty available rrom19 other sources through line 60 to provlde all Or the
20 electr~city requlred ln the llqueraction process. In
21 the embodlment lllustrated, all Or the steam thus pro-
22 duced will not be used to generate electricity and,
23 indeed, steam at almost any pressure may be wlthdrawn
24 for use ln the liqueractlon process. In the embodiment
25 illustrated, then, high pressure steam generally at a
26 pressure wlthln the range ~rom about 400 to about 800
27 psi may be ~ithdrawn through line 61 and a low pressure
28 steam generally at a pressure wlthi.n the range from about
29 15 to about 200 may be withdrawn through line 62.
30 Condensate rrom the turbo generator wlll be wlthdrawn
31 through line 55 and recycled to steam colls 54 through
32 line 53. At least a portion Or the ash rrom the lioue-
33 ~action bottoms combusted in combustion zone 22 and any
34 ash from the combustion Or auxilliary fuels introduced
35 through line 5~ will be withdrawn through line 63. ~he
36 remaining portlon may be withdrawn downstream wlth any
114689S
1 suitable means, not illustrated, such as electrostatic
2 preclpitators. ~
3 Having thus broadly described the present
4 lnvention and a prererred embodiment thereor, it is
bel~eved that the same will become more apparent by
6 rererence to the rollowing example. It will be appre-
7 ciated, however, that the example is presented solely
8 for purpose Or illustration and should not be construed
9 as limiting the invention.
EXAMPLE
11 Ir one were to liquery 24,000 tons Or an
12 Illlnois #6 coal ~dry base) per day in a process wherein
13 rinely divided coal is continuously slurried with a
14 400-800F solvent derived from Illinois #6 coal at a
solvent to coal ratio Or 1 . 2 and then liauefied at a
16 temperature Or 8400F, a pressure of 2000 psig at a
12- nominal holding time Or 40 minutes and in the presence
~18 Or molecular hydrogen at a rate Or 0.04 lbs H2/lb of
l9 coal, 12,000 tons Or 1000F plus bottoms would be
produced per day. The bottoms would contain 70 wt %
21 carbon. Ir ha1r Or these bottoms were then sub~ected
22 to gasirication in entrained bed gasifiers wherein gasi-
23 rication i8 accomplished in the presence Or 0.4 lb Or
24 steam per pound Or bottoms and o.8 lb Or 02/lb Or bottoms
at a temperature Or 2600F and a pressure Or lO00 psig>
26 surriclent hydrogen will be produced followlng water gas
27 shirt to errect both the liqueraction and solvent
hydrogenatton when unconverted hydrogen from both liaue-
29 ractlon and solvent hydrogenation are recovered and
recycled. The remaining 6000 tons per day of bottoms
31 can then be combusted in the combustion section Or
32 hybr~d boilers. The heat of combustion can then be
33 used to produce about 2,000,000 lb/hr Or 1500 psi/935F
34 steam. ~rocess steam requirements may then be met via
extraction Or steam at the desired pressure. Also, ste~m
36 turbine generators could be used to produce about 80S o~
17
- 18 -
1146895
1 the liquefaction plant electric power demands. The heat
2 remaining in the flue gas will then be sufricient to
3 supply 80% Or the liquefaction process heat requirements
4 in the convection section Or the hybrid boiler. ~ach
boller actually used would be desi~ned to combust 59
6 tons/hour Or vacuum bottoms produclng 1,430,000 BT~s/hour.
7 In normal operation 70% Or the heat produced would be used
8 to generate steam and the remaining 30~ to supply process
9 heat in the convection section. The hybrid boiler
operatlon may be controlled by recirculating rlue gas,
11 by bypassing rlue gas or by varying the quantity Or
12 excess air red to the combustion zone. During operation,
13 care will be e~ercised to maintain a temperature at the
14 bridge wall at or below 1900F to minimize or ellminate
ash fouling in the convection zone. It i8 anticlpated
16 that the process colls in the convection zone will
17 require decoking at about 6 month intervals.
lô From the foregoing it ls believed apparent
19 that the improved method Or the present invention ofrers
scveral advantages over prior art processes wherein pre-
21 heat rurnaces are employed to provide process heat and
22 coal is burned in orr-site coal boilers to raise steam.
23 For example, such preheat furnaces wlll no longer be
24 required thereby reducing the initial investment cost.
Moreover, proccssing steps such as coking and gasification
26 ~or producing a process fuel gas rrom vacuum bottoms are
27 no longer required thereby reducing initial investment
28 costs and increasing overall process thermal efriciency.
29 Alternatively, product ~ases produced in the liquefaction
step that might be burned as fuel ln such preheat furn2ces
31 can now be sold as substltute natural gas, which is a
32 product Or considerable value. In addition, since
33 considerable steam is produced in the combustion of
34 vacuum bottoms in a hybrid boiler, most or all Or the
3 coal-fired boilers which are often required in lique-
36 faction process to provide steam can be eliminated thereby
1:~ 46l8995
1 reducing the initial investment cost. Flnally, the on-site
2 generation Or a portion Or total electrical power demand
3 Or tbe liquefaction process reduces the cost of purchased
4 power and more impor~a~tly, provides a n,eans whereby the
operatlng rluctuat~ons in steam and process heat demand
6 which normally exist in all llqueractlon processes can
7 be accommodated by purchasing varylng amounts Or power
8 rrom a large electrical utility grld system thereby
9 reduclng initial investment cost for alternative on-site
methods required to provide this energy fluctuation
11 control mechanism.
12 While the present invention has been described
13 .and lllustrated by rererence to particular embodiments
14 thereof it wlll be appreciated by those Or ordinary skill
in the art that the same lends itselr to variations not
16 necessarily illustrated herein. For this reason, then,
17 rererence should be made solely to the appended claims
18 ror purposes Or determining the true scope Or the present
19 invention-
