Note: Descriptions are shown in the official language in which they were submitted.
IMPROVED PROCESS FOR RECOVERING A
PREMIUM OIL FROM A SLURRY PRODUCED BY
HIGH TEMPERATURE EYDROGENATION OF
A SOLID, HYDROCARBONACEOUS FUEL
:
This invention relates to a process for sepa-
rating a slurry comprising fine solids, polar liquids and
premium oil, the slurry produced by high temperature hydro-
aenation of ~ solid ~ydrocarbonaceous fuel into a first
fraction comprising the premium oil and a second fraction
comprising the fine solids and polar liquids.
.~ :
The high temperature hydrogenation of solid,
hydro~arbonaceous fuels, such as the li~ue~action of
coal, produces a feed slurry, comprising not only pre-
mium liquid oil but also various solids, e.g., ash, inor-
ganic sulfur, and other liquids, e.g., polar liquids.Removal or separation of these materials, especially the
fine solids from the premium oil, is a major problem and
has been the subject of much research.
British Patent 312,657 discloses an apparatus
20~ and process ~or the separation from solid residues of oi].s
obtained in the destructive hydrogenation va.rieties of
coal, tars, mineral oi.ls and the like. The apparatus com-
prises a vertical column with a settling vessel attached
`
18,394A-F
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*o its top and a worm gear attached to its bottom. The
-process comprises introducing a slurry of solid residues
~d oils into the column at or near the column top and a
~olvent, typically benæene, into the column at or near
5 the column bottom such that the solvent, as it passes up
-~he col~mn, extracts from the slurry as it passes down
~he column, the oils. The solid residues are removed as
a powder from the bottom ~f the column by the worm gear
while the oils are remo~ed from the top of the column as
an overflow from the settling vessel.
~ err-McGee (USP 3,607,716 and 3,607,717)
teaches a gravity settling process comprising removing
~rom a coal liquefaction product fine solids using a
-solvent heated to a super-critical temperature. This
process differs from others in that the solids settle in
a dense phase gas (the solvent under super-critical con-
ditions). The fine solids are contained in the extrac-
tio~ residue.
he present invention is an improved process
for separating a feed slurry produced by high temperature
hydrogenation of a solid, hydrocarbonaceous fuel and com-
prising fine solids, polar liquids and premlum li~lid oil,
into a first fraction comprising the premium liquid oil
a~d a second fraction comprising the fine solids and polar
2~ liquids, characterized by
(a) mixing the feed slurry with a nonpolar
liquid solvent ~hich is a C5-Cg aliphatic or alic~I-
clic hydrocar~on or a naphthenic or paraffinic frac-
tion of a coal liquefaction product containing less
than 10 weight percerlt axomatic compounds, -the mixing
18,394A F
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~eing conducted in a vertical column comprising a
settling zone, a contacting zone and a collection
20ne, the settling and contacting zones operated at
a-temperature between 100C and 250C and at a pres-
sure sufficient to maintain both the slurry and sol-
Ye~t in a liquid state but less t~an 450 psi (317
-kg/cm2), the slurry being introduced into the column
at or near the top of ~he contacting zone and the
solvent being introduced into the column at or near
the bottom of the contacting zone, the sclvent and
slurry being mixed in a weight ratio of at least
0.5:1 and contacted in such a manner that the 501-
-vent:
: (1) passes up and through the column
while the slurry pas~es down and through the
~ol~mn;
: .(2) is in intimate contact with the
~ - slurry as the solvent and slurry simulta-
- . ~eously pass through the colum~; and
~0 (3) extracts from the slurry, as the
~olvent and slurry simultaneously pass through
the column, the premium liquld oil;
(b) recovering from the settling zone of the
column as an overflow the first frac-tion; and
: 25 ~c) recovexing from the collection zone of
the column, as a viscous slurry underflow, the
second fraction.
This process produces an essentiall~ solids-free over-
flow of premium oil and an under:1Ow con-tainlng a minimum
amount of pre~ium oil. Moreover, this process removes
o~her materials, such as uncon~er-ted fuel, polar mole-
cules rich in heteroatoms (o, N, S).
;~ .
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The slurry here used is a slurry generally
produced from the high temperature hydrogenation of any
solid, hydrocarbonaceous fuel. The slurry produced from
the liquefaction of coal is illustrative. The solids
portion of this slurry comprises fine solids (e.g., ash),
inorganic sulfur (e.g., pyrrhotite) and organic solids
(e.g., unreacted coal) while the liquid portion comprises
premium oil (e.g., hexane-soluble slurry components, such
~s paraffinic, naphthenic and aromatic hydrocarbons), and
polar liguids ~e.g., asphaltenes and toluene-insolubles,
both defined hereinafter). "Fine" here describes solids
or minute particles of about 0.1 -to 20 microns in size.
The solids content (weighk basis) of this slurry can vary
widely but is at least partially dependent upon the polar
liquid's content. Generally, the greater the ~uantity of
polar liguids present, the greater the solids content that
can be effectively processed. Specifically, a sufficient
guantity o~ polar llqulds must ~e lnsoluble ln the non-
polar solvent at column conditions such that the polar
liquids coalesce to form a separate, liguid continuum in
which the fine solids content can be dispersed. Although
guantitative parameters can and will vary with the par-
; ticular feed slurry, column conditions, solvent, etc., it
can be generally said that the resultant underflow should
comprise less than about 65 weight percen-t solids. Con-
~e~uently, a slurry compxising a solids content less than
about 25 weight percent is preferred and a slurry compris-
ing a solids content less than about 20 weight percent
more preferred.
In a specific embodiment of this invention
wherein hexane is the nonpolar solvent, an especially
~uited sluxry is produced by the liquefaction o a bitumi-
nous coal. This slurry can take many forms, such as the
~lurry as produced (ash content of about 3 to 8 weight
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pereent), the slurry after some solids removal, e.g.,
eentrifugation (ash content of about 0.5 to 5 weight per-
eent), or the slurry after a solids concentration proce-
dure, e.g., as the underflow from a hydrocyclone ~ash
5 eontent of about 10-15 weight percent). The solids con-
tent of each of these forms is less than about 25 weight
percent of the slurry.
The principle considerations in solvent selec-
tion are that the solvent selectively extracts the premium
oil and that the solvent and premium oil (extract) not
have significant overlap in their distillation ranges
(sinee such overlap can result in cross-contamination).
Sinee the components of the premium oil are generally
; nonpolar, a nonpolar solvent is used. The solvents are
preferably hydrocarbon and more preferably C5-Cg aliphatic
or alicyclic hvdrocarbon, such as ~entane, hexane heptane.
oetane, 3-methylpentane, cyclopentane, cyclohexane, etc.
Other suitable solvents inelude certain naphthenic or
paraffinic fractions of a coal liguefaction product, such
as a mixed C4-C5 portion or a paraffinic petroleum por-
tion, sueh fractions cont.aining less than about 10 weight
percent aromatic eompounds.
Column conditions (temperature and pressure)
ean and will vary with the solvent and khe eomposition
of the feed slurry. A minimum eolumn temperature is
required suf~icient to maintain the feed and residual
slurries in the li~uid state. The column temperature
eannot exceed the eritical temperature of the ~olvent.
A minimum p.ressure is reguired sufficient -to avoid vapor-
ization o both the solvent and the feed slurry. Practi-
eal eonsiderations, such as eguipment, economy, etc., are
~he only limitations upon the maximum pressure that can
be employed.
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As here used, "column t~mperature", "zone tem
perature", and similar terms mean the temperature of the
column wall or that portion of the column wall defining
a zone. The temperature of the slurry, solvent and sepa-
ration products of the slurry may or may not obtain the
same temperature of the column wall, depending upon the
flow rate of these materials. Generally, the greater the
flow rate, the less likely that these materials obtain
the temperature of the column wall. Of course, the mater-
ials obtain the heat of the column wall by conduction.
Although column pressure is generally uniform
~hroughout, column temperature generally varies from one
area or zone of the column to another. Since the residual
slurry is relatively high in solids and high molecular
. 15 weight polar materials content, it is the most viscous and
rec~ires the greater tem~erature. Thus, the zone wherein
this slurry collects is typically run at least about 20C
higher than the remainder of the column.
~ ~ .
Although quantitative temperature and pressure
ranges cannot be stated generically, by way of illustration
and with hexane as the solvent, a typical minimum column
tempe~ature (excluding the residual slurry collection zone)
is at least about 100C and preferably about 140C. The
corresponcling pressures are typically about 180 psi and
200 psi (12.7 and 14.1 kg/cm2). A typical maximum temper-
ature is about 225C and preferably about 200C with cor-
xesponding pressures of about 450 psi and about 325 psi
(31.8 and 23.0 kg/cm2). Although the residual slurry col-
lection zone temperatures are yenerally about 20C higher,
respectively, wi-th comparable pressures, p.referably the
r~sidual slurry collection zone is ma.intained at a temper-
atuxe of at least about 150C and most preferably at about
180~C.
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Premium oil extraction from the slurry is at
least partially dependent upon the solven-t:slurry weight
ratio fed to the vertical column. Generally the greater
the solids content of the slurry, the greater the sol-
vent:oil ratio used in the practice of this invention.
The use of a greater solvent:oil ratio under such circum-
stances leaves a greater amount of polar liquids in the
slurry and these polar liguids promote coalescence among
the solids and thus fluidity of the underflow. A -typical
minimum weight ratio of about 0.5:1 can be used although
a ratio of about 0.6:1 is preferred. Practical considera-
tions, such as energy efficiency, are the only limitations
upon the maximum weight ratio although a maximum weight
ratio of about 5:1, and preferably about 1:1, is typical.
A weight ratio of about 0.8:1 is especially preferred.
Generally, if the weight ratio is less than 0.5, i.e.,
less than 0.5:1, the recovered asphaltene has a reduced
viscositY wnich indicates Poor seParation from tne prod-
uct liquid. Moreover, detection of an interface between
the residual slurry and the solvent-slurry phases becomes
- difficult ,and the more difficult this becomes, the more
dificult is the selective removal of the residual slurry
from the vertical column. If the weight ratio is greater
than about 1.0, feed slurry throughput (volume per unit
time) is sacrificed and additional cost and utilities are
incurred.
;
Although the physical features (housing and
channel size and shape) of the vertical column here used
can be varied to choice, the column is typically a hol-
low, elongated cylinder or pipe-like structure with a
length over diameter (LOD) guotient between about 40 and
2 and preerably between about 20 and 5. The colurnn can
be made from any suitable material but materials, such as
~teel, known to perform well under elevated temperatures
,
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-and pressures are preferred. The column generally com-
prises three zones: a first or settling zone, a second
or contacting zone, and a third or collection zone.
~he first or settling zone is generally the
top portion of the column, equipped with a solvent-pre-
mium oil extract outlet, and commences abo~e an entry
port used for introducing th~ slurry into the second or
contacting zone. This first or settling zone collects
the solvent and premium oil flowing up from the second
or contacting zone for its ultimate removal from the
column. The function of this settling zone is to pro-
vide an area for the gravity separation of any fine solids
that may have been carried from the contacting zone by the
~olvent and premium oil. As such, it is desirable that
1~ the solvent and premium oil be quiescent, i.e., have little
~ or no convection currents, to encourage any fine solids to
- - settle ~ack lnto the contacting zone. On large scales,
~ertical baff-es or other design features may be useful in
-preventing such co~vection currents and resulting fine
solids presence in the column overflow.
The second or contacting zone is generally the
mid-portion, i.e., the portion between the first and third
zones, of ~he column and it generally is the largest (on
an overall length basis) portion of the column. Within
this zone, the slurry descends the column in a partially
back-mixed, partially countercurrent mode. Although the
solvent-premium oil phase is nearly completely back-mixed
in this second zone (due to both the density difference
between the premium oil and solvent and to convection cur-
rents), there is a net countercurrent flow of the residualslurr~ downward against the upflow of the solvent-premium
oil phase. This second zone is equipped with a slurry
entry port at or near its top and a solvent entry port at
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or near its bottom. Use of internals within this zone
may be useful, especially in large-scale operations, to
disrupt convection currents. Any such internals should
-~e designed to avoid the buildup of asphaltenic residue
with exposed surfaces generally no more than 30 degrees
off the vertical axis of the column.
The third or collection zone is generally the
bottom portion of the column and typically has an enlarged
; diameter relative to the first and second zones. This
æone collects ~he residual slurry, i.e., fine solids and
other materials comprising the slurry not soluble in the
nonpolar solvent, for their ultimate removal from the
column. The column wall defining this zone is generally
; maintained at a higher temperature than the wall defining
1~ the second zone because the residual slurry which is col-
-~; lected in the third zo~e has a greater viscosity than
, eit~er the slurry, premium oil or solvent and thus requires
a higher temperature to maintain its liquid state. Since
the third zone, like the first and second zones, is gen-
erally operated on a continuous basis, the temperature dif-
ferential exhibited between the wall defining the third
zone and the wall defining the second zone is not believed
paralleled by a similar temperature differential between
the contents o~ the second zone and the contents o the
third zone. Howevex, it is believed that the higher tem-
perature of the wall defining the third zone inhibits
accumulation of the solids-containing residual phase
along the interior of the wall and thus promotes a steady
~- and uninterrupted discharge of the residual slurry.
., .
The third zone is also equipped with a resi-
dual slurry outlet which can be located at any convenient
poin-t about the zone but is p~eferabl~ located at the
.
18,394A-F
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center of the bottom of the ~one. This avoids solvent
and premium oil escaping due to their bypassing the resi
dual slurry. The residual slurry outlet can be equipped
with any conventional means for facilitating the removal
of the residual slurry from the zone, such as a valve,
worm screw, or extruder.
In the accompanying drawings in which like
numerals are employed to desi~nate like parts through-
out the same:
Figure 1 is a preferred, specific embodirnent
of a vertical column;
Figure 2 is a schematic flow diagram illus-
trating the vertical column of Figure 1 in a specific
combination with conventional, downstream separation
1~ equipment, and
F~gure 3 is a schematic flow diagram illus-
~rati~g a variation of the combination shown in Figure Z.
'
~; Various items of equipment, such as valves,
; fittings, condensers, pumps, etc. have been omitted so
as to simplify the description. However, those sk1lled
in the ar-t will realize that such conventional e~uip-
ment can be, and is, employed as desired.
In Figure 1, a vertical column 10 consists of a
first or settling zone 11, a second or contacting zone 12,
and a third or collection zone 13. Zone 11 is equipped
with a solvent-premium oil outle-t 14 and a thermal jacket
lla. Zone 12 is equipped with a slurry inlet 16, a sol~
vent inlet 17 and a thermal jacket 12a. Zone 13 i'a
~quipped with a residual slurr~l outLet 19 and a thermal
jacket 13a.
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In Figure 2, column 10 is connected to an adi~
abatic flash drum 22 by conduits 21 and 23. A distilla-
tion unit 26 equipped with a removal conduit 28 is joined
both to flash 22 by conduit 24 and to column lO by con- ~:~
duits 27 and 23. Conduits 27 and 23 are mated with each
other. A separator 31 is connected to column 10 by con-
duit 29. A conduit 33 proceeds from separator 31 and a
conduit 32 joins separator 31 with a condenser 38 which
in turn is joined to column 10 by mated conduits 39 and
10 23~
In Figure 3, a separation unit 34 replaces
the adiabatic flash drum 22 and distillation unit 26
of Figure 2. Unit 34 is connected -to column 10 by con- :
duits 21 and 23 and is e~uipped with a removal conduit
37. Column 10 is e~uipped with removal conduit 29.
Having thus de-scribed the apparatus and refer-
ring now to Figure 1, a slurry is continuously charged to
~^~ column 10 through slurry inlet 16 while a nonpolar solvent
`, i5 simultaneously and continuously charged to column 10
~' 20 through solvent inlet 17. The solvent passes up and
~hrough zone 12 while the slurry simultaneously passes
down and through the same. During this continuous, simul-
; taneous passing, the solvent and slurry are in intimate
contact and the solvent extracts from the slurry the pre-
25 mium oil which is soluble in the solvent at the ~one 12
conditions, thus producing a first fraction comprising
the solvert and premium oil and a second fraction (resi~
dual slurry) comprising the fine solids and polar li~uids.
The solvent and premium oil are continuously transported
30 into zone 11 and removed therefrom through outlet 14. ~he
resldual slurry is continuously collected in zone 13 and
removed therefrom through residual slurry outLet 19.
.
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: . . .
- . .
.
. ~. .
. . . . . .
. . ~ . .
.
Referring now to Figure 2, the solvent-premium
oil mixture present in zone 11 of column 10 in the form of
a substantially quiescent pool is removed as an overflow
~nd is passed through conduit 21 to flash drum 22 where
some of the solvent is separated from the premium oil and
recycled to column 10 via conduit 23. The remaining sol-
vent~premium oil mixture is transferred to distillation
unit 26 where the remaining solvent is distilled overhead
and recycled to column 10 via conduits 27 and 23 while the
premium oil is removed as an underflow through removal out-
~; let 28.
The residual slurry collected in zone 13 ofcolumn 10 is removed as an underflow and is passed to
separator 31 via conduit 29. Separator 31 recovers any
solvent present in the residue and recycles it to column
10 via conduit 32, condenser 38, and conduits 39 and 23.
ne remaining resiaual slurry is removea as an underfiow
via conduit 33.
Referring now to Figure 3, the overflow from
column 10 can be transferred (via conduit 21) to a single-
-stage solvent removal (recovery) unit, such as separation
unit 34. Therein, the solvent is separated from the pre-
mium oil and recycled to column 10 via conduit 23 while
the extract is removed via conduit 37. The choice between
unit 34 and the combination of units 22 and 26 is governed
by the needs of the practitioner.
The recovered, high-solids content residual
slurry is suitable as a gasification feedstock. The
hydrogen:carbon ratio in this material is generally the
same as or lower than that of li.~uefaction eed coal.
Thus, if this material is used as uel, the expenditure
of hydrogen is minimi2ed. The premium oil is a desirable
18,394A-F
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recycle oil, a low-sulfur fuel or a feedstock for petro-
chemicals. This material is generally recovered as a bot
tom stream from a solvent distillation unit.
The process of this invention is particularly
well adapted for the separation of a slurry produced by
high temperature hydrogenation of coal into a first frac
tion of premium oil and a second fraction of fine solids
and polar liquids. The slurry differs from petroleum type
materials i~ several important aspects.
First, the slurries of this invention typi-
cally contain about 2 to 15 weight percent ash and about
8 percent unconverked organic solids.
.
Second, the softening temperature of the resi-
duai siurry c~nas co be ~vnsiu~ra~i~ higil~L tnall for pe~ro-
leum-derived asphaltenes. Consequently, while propane
`~ slurry separators (deasphalters) can operate at temperatures
below 100C with a fluid residual product, the viscosity of
the asphaltenic residue produced by this invention is typi-
cally between 100,000 and 200,000 cps at 200C.
Third, the coal-derived liquids of this inven-
tion tend to contain a larger fraction of solvent-insolu-
ble oil, i.e., polar liquids.
Fourth, due ko the highly aromatic nature of
~he coal-derived oil and the large amounts of heteroatom-
-containiny organics, particularly phenolics, the differ-
ence in interfacia]. tension bekween the premium oil and
~olvent tends to be greater for the coal-derived oil than
for the petroleum-derived oils. This latter difference is
believed to significantly effect the operation of the
invention here described. The Marangoni eect is directly
related to this interfacial tension difference.
18,394A-F
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,~ .
It is believed that the mechanism of extraction
occurring in the process of this invention is a manifesta-
tion of the Marangoni effect, a description of whlch fol-
lows. When an oil containing a mixture of polar and non-
polar species is contacted with a nonpolar solvent, inter-
facial tension forces tend to cause the nonpolar species
to concentrate at the oil surface. These nonpolar species
are rapidly extracted by the nonpolar solvent, leaving a
high concentration of polar species near the oil surface
with a relati~ely high interfacial tension - a thermody-
~amically unstable situation.
This thermodynamic driving force sets up circu-
lation patterns in the oil phase which transfer nonpolar
species rom the interior of -the oil phase to the inter-
face where they are extracted. ~hese circulation patternscause rapid movement at the interface and extremely high
; mass transfer rates. The interfacial tension forces which
drive the circulation patterns are opposed by the viscous
effects in the oil phase. Consequently, high viscosity
2~ near the oil sur~ace will dampen the circulation patterns.
When the solvent-oil interface is generated by
introducing oil into the solvent in the form of drops,
e.g., from a small tube, the Maran~oni instability leads
to a marked enhancement of the concomitant processes of
~5 dispersal and dissolution, i.e., to a rapid destruction
of the droplet into numerous smaller droplets with an
acco~panying extraction of the premium oil into the sol-
~ent. Other studies have sho~n that when a viscous oil
or polar solvents, like benzene or toluene, are used, the
raRid rate o destruction does not occur. This Marangoni
instability is believed to cccur under the operating con-
ditions of the instant invention. As a consequence, the
selection of solvent used in this invention preferably is
such that the Marangoni effect is promoted. Solvents that
18,39~A-F
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~do not promote this effect, such as benzene or toluene,
literally extract all the liquid from the slurry thus pro-
ducing powder for ultimate discharge as an underflow. As
~uch, polar liquids are not separated from the premium
oil but are carried into the settling zone and removed as
part of the overflow.
The Marangoni instability greatly enhances
liquid-liquid extraction by providing large interfacial
areas which thereby reduces the residence time required
in the extraction zone. This in turn permits the use
of e~uipment having smaller volume dimensions for a given
volume of slurry and solvent and simplifies the design of
the slurry inlet system, i.e., eliminates the need for
closely controlling the initial droplet size of the slurry
I5 previously necessary to obtain an extremely fine disper-
sion of slurry into the solvent. Thus, the essence of
this inven-tion lS the use of one o~ a specl~ic group of
solvents in combination with a temperature differential
`~ between various portions of the column wall to facilita-te
the handling of the residue as a viscous liquid slurry.
Such a combination not only easily renders the operation
of this invention, but it also promotes a desirable sepa-
ration of the premium oil from the polar li~uids and ~ine
solids.
The following examples illustrate this inven-
tion. Unless otherwise noted, all parts and percentages
are by weight.
~ .
~E~ ratus and Procedure
~ jacketed, vertical colu~m, 3 in. inner diam-
; 30 eter and 54 in. long ~7.G~ cm x 1.37 m) having a design
~imilar to that described by Fiyure 1 was employed. The
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first and second zones were operated at a temperature of
~bout 160C and a pressure of about 200 psig (14.1 kg/cmZ)
and the third zone was operated at a temperature of about
200C at a pressure of about 200 psig (14.1 kg/cm2). The
pressure in the column was controlled by a back pressure
~ontroller and a valve on the heated ~150C) solvent-pre-
mium oil outlet. This outlet fed into an adiabatic flash
drum. There the solvent was flashed, removed and subse-
guently condensed and recycled to a solvent feed tank.
Premium oil from the flash drum was stripped of any resi-
-dual solvent with a continuously fed distillation unit.
Residual slurry was removed from the column by
a control valve. A level controller capable of detecting
the interface between the residual slurry and solvent-
15 -premium oil phases was used to control the asphaltene
outlet valve.
~ exane was used as -the solvent and the column
was fed various slurries at the rate of about 45 lb/hour
(20.4 kg/hr). A hexane:slurry weight ratio of about 0.8:1
2Q was used.
Analytical Procedures
In the following examples, the analytical pro-
cedures employed were as follows:
.
Viscosity
Viscosikies of product li~uids were measured at
25C using a Brookfield Viscometer. Ash was not removed
from these li~uids prior to the measurement.
18,394A-F
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Toluene Insolubles
Product liquid (40 g) was shaken with toluene
(160 g) and subsequently centrifuged. The supernatant
li~uid was decanted and the remaining residue, toluene-
-insoluble hydrocarbons and ash, was vacuum-dried at 100C
and weighed. The ash content of the residue was deter-
mined by ANSI/ASTM D482-74.
~ Asphaltenes
; Product liquid (25 g) was.shaken wi-th n-hexane
~ 10 (100 g) and subsequently centrifuged. The supernatant
; liquid was decanted and the residue (a mixture of ash,
toluene insolubles, and toluene-soluble hydrocarbons which
are insoluble in n-hexane, i.e., asphaltenes) was vacuum-
-dried at lOO~C and weighed. The asphaltene content was
determined b~ s~lhtracti n~ t~ uene inso1llb1e~ and ash pre-
; viously determined from the total hexane insolubles.
~ ' ' ~' .
i~ Coal Analysis
,
The coal used to generate the various lique-
faction product liquids purified below was Pittsburg No. 8
Allison mine bituminous coal crushed, dried, pulverized
and classified such that 99.9 percent would pass through
a 120 mesh screen (U.S. Sieve Series). The sulfur content
was about 3.9 percent.
Examples 1-3:
In Tables I-III are listed data from three
operations employing different feed slurries, i.e., Table
I-Hydrocyclone Underflow (12.6 percent ash), Table II-
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-Liquefaction Product (5.2 percent ash) and Table III-
-Centrifuge Overhead (2.1 percent ash). ~eat of combus~
- tion (~Hc) was determined by ANSI/ASTM D2015-66 and Rams-
bottom Carbon was determined by ANSI/ASTM D524-76.
5TABLE I
IMPURITIES REMOVAL FROM A
HYDROCYCLONE UNDERFLOW SLURRY
Purified
Product Asphal-
10Feed Liquid tenes ~:
Amount, lb (kg) 51705 368.1 134.1
: (234~ (167)(60.8)
Amount, wt % 100.0 73.3 26.7 ~:
Analyses: .
Viscosity, cps, 25C 320 60
Toluene Insolubles, % 9.8 0.84
Asphait~n~ 0 2i.2 18.6
: Ash, % 12.4 0.33 41.2
Carbon, wt % - ~ 48.9
Hydrogen, wt % - - 3.19
Sulfur, wt % - - 4.1
~: Nitrogen Analysis, wt % - - 0.72
: ~Hc, BTU/lb (Kcal/g) - - 9,080
(2290)
Ramsbottom Carbon, wt % - l1.l 72.7
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TABLE II
IMPURITIES REMOVAL FROM A
LIQUEFACTION SLURRY
Purified
Product Asphal-
Feed Liquid tenes
: Amount, lb (kg)4066 0 3219 07 863)
Amount, wt % feed100.0 79.1717.67
Amount, wt % products - 81.76 18.24
Accountability = 96.8%
~nalyses 5C 632 . 152
;: Toluene Insolubles, % 113.41729 93
: 15 Asphaltenes, % ~ 02 u i228.i4
Carbon, wt % - - 61 63
Hydrogen, wt % 2 94
Sul~u~, wt % - - 10,880
~Hc, BTU/lb (Kcal/g) ~ ~ (2740)
.
~ 18,394A~F
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~ABLE III
IMPURITI ES REMGVAL FROM A
CENTRI FUGE OVERFLOW SLURRYl
Purified
5Product Asphal- :
Feed Liquid tenes
:: Amount, wt % 100.0 88.311.7
Analyses:
~ Viscosity, cps, 25C 670 83
- 10 Toluene Insolubles, % 9.1 2.4
: Asphaltenes, % 36 29
Ash, % 1.9 0.0917.7
Carbon, wt % - - 72.0
Hydrogen, wt % - - 4.2
: 15 Sulfur, wt % - - 1.7
~: Q~c' BTU/lb (Kcal/g) ~ ~13,200
~3330)
Ramsbottom Carbon, wt % - - 74
Represents average data based upon several runs made
with this type of feed slurry. As a result, informa-
tion on the total material fed and recovered and mater-
ial balance accountability is not available.
.,' :' These data demonstrate, over a wide array of
solid-containing slurries, the low residuum of ash in the
purified product li~uid (overflow) and the low residuum
of hexane-soluble hydrocarbon in the residual slurry.
Example 4:
~ series of experiments were conducted to
determine the degree of solub.ili~y of coal~der.ived oil
in pentane, hexane (a mixture of C6 paraf:~ins as con~
tained in commercial grade hexane solvents), cyclohexane,
n-decane and toluene, .respectively. For each solven-~ the
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oil solubility was measured for a series of solvent to
oil ratios. The oil solubility was determined by weigh-
ing the appropriate amount of solvent and oil into an 8
ounce (224 g) bottle, shaking the bottle mechanically
for at least 20 minutes to thoroughly m1x the two mater-
ials, contrifuging the bottles contai:ning the mixture
for at least 20 minutes to cause the insoluble phase to
collect in the bottom of the bottle, decantin~ the liquids
from the insoluble residue, vacuum-dryincJ the residue at
about 80C, determining the residue weight and finally
calculating the percent of the sample which was insoluble
(% soluble oil = 100% - % insoluble). The results are
reported in Table IV.
TABLE IV
% OF SAMPLE WHICH IS INSOLUBLE
Solvent
Solvent Wt. Cyclo-
Oil Wt. Pentane Hexane Hexane hexane Toluene
0.1 36.08 34.76 - - -
: 20 0.2 28.03 26.37 - - -
0.4 ~1.08 36.5419.8 25.8 9.~
0.8 44.4~ 39.9918.1 27.5 9.8
1.0 - 18.9 27.6 9.4
1.6 46.26 3g.26
3.2 43.21 36.71
; 6.4 43.36 30.20 - - -
Oil Sample A A B B B
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Oil Samples A and B are both samples of coal
liquefaction products with initial boiling points of about
150C which had been centrifuged prior to this experimen-
tation to remove all but a small frac-tion of the solids
present (less than about 2-3 percent of sample is fil-
terable solids).
Example 5:
~ series of experiments were performed as in
Example 4 using hexane and decane as solvents. The oil
used was the ash-rich fraction obtained by hydrocloning
the 150C+ product slurry from the liquefaction o Pitts-
burgh No. 8 coal. The results are reported in Table V.
TABLE V
% OF S~MPLE WHICH IS INSOLUBLE*
.
~ 15 Solvent Wt. Solvent
....
Oil Wt. Hexane Decane
0.1 19.79 21.14
0.3 .15.17 16.86
0.7 24.87 24.75
1.0 28.71 26.91
2.0 28.96 30.94
4.0 29.63 26.23
*Insolubles in the initial sample on an ash-free basis.
To assess the efEectiveness oE the solvent
precipitation, the ash levels in the decanted liquids
were determined for selected samples as shown below:
,
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TABLE VI
~ ASH IN DECANTED SOLVENT AND OIL
Solvent Wt. Solvent
Oil Wt. Hexane Decane
0.1 0.02 0.01
0.3 0.0 0.0
From the data presented in Tables IV-VI, several
conclusions appear. First, while the amount of insoluble
materials shows variations depending on the oil used and
the solvent:oil ratio, and to a lesser degree on experi-
mental uncertainty, there is a greater amount of insoluble
maierial recovered for a given soiven~:oii ra~io a~la a
given oil sample when pentane, hexane, cyclohexane or dec~
ane (all nonpolar solvents) is used thàn when the solvent
~; 15 is toluene (a polar solvent).
, .
Second, when the solvent is toluene, signifi-
cantly less insoluble material is obtained due to the
higher solubility of coal-derived oil in toluene than in
paraffinic hydrocarbons.
Third, even at very low solvent:oil ratios the
ash is very effectively removed from the soluble oil by
the practice of this invention. Centrifugation of whole
oil samples resul-ts in ash levels of 1-2 percent in the
decanted oil.
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Fourth, because of the increased solubility of
the oil in hydrocarbon solvents at elevated temperatures,
the operation of the deasphalter with an aromatic solvent
such as toluene can be expected to result in little non-
solid residue being separated as insoluble material. Resi-
due obtained under these circumstances is not a viscous
slurry but a powder wet with solvent. Problems with the
removal oE such a residue prevented extended operation
with toluene as a solvent. The xylenes, ethylbenzene and
other mono aromatics would be expected to perform in a
manner similar to toluene.
Example 6:
A room temperature study was conducted to
observe the effect of solvent on the occurrence of Maran-
goni instability. Hexane was placed in a glass vessel~iiled to a aep~n o~ a~out ~ incnes (~ cm). A coal-
-derived oil which contained about 0.1 percent ash, 1
percent toluene insolubles and 22 percent asphaltenes
was used as the test sample. When this oil was added
to the hexane dropwise from about 1 inch (2.54 cm) above
the hexane li~uid surface rapid drop dispersion was
observed. A photographic study of khe phenomena indi-
; cated droplet dispersion began before the oil had pene-
trated the hexane moxe than 1 inch. Secondary droplets
whose diameters were less than 1/20th that of the ini-
tial oil droplet were formed within one second and before
the oil had penetrated the hexane more than 2 inches (5.1
cm). Simultaneously a clouding of the solvent in the
vicinity indicated that extraction of a portion o:E the
oil had occurred.
18,394A-F
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When the identical experimer.t was performed
u~ing toluene in place of hexane as the solvent, no drop
dispersion occurred. The oil drop settled through the
~olvent and rested on the bottom of the vessel with mini-
~al extraction having occurred. The toluene solvent wasonly slightly discolored by the passage of the oil drop
~hrough it.
This data supports the importance of the Maran-
goni effect in the rapid and effective ex-traction of the
deasphalter ~eed slurry. The choice of solvenks which are
less polar than mono aromatics, for example, C5-Cg paraf-
~ins, is thus essential to obkain proper operation of the
prozess.
EXample 7:
Using the apparatus and procedure of Examples
1-3, an extraction experiment was conducted in which coal-
-derived product oil with the below-described composition
was processed. Oil feed rate was about 48.6 pounds (2.20
~g) per hour and hexane feed rate was about 36.5 pounds
(16.6 kg) per hour. Fox this experiment the column extrac-
tion zone temperature was about 190C. The residue collec~
tion zone was hotter, i.e., the wa].l temperatures were
204C and 207C at the middle and bottom of the collection
zone, respectively. The temperature in the center of the
third zone was 195C. Operations under these conditions
; resulted in the by-passing of significant amounts of hex-
ane and hexane-soluble oil through the residue outlet line.
About lS weight percent o~ the material in the residue col-
lection vessel was a low viscosity hexane~-oil mixture
ra~her than the desired viscous slurry. A sample of the
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oil was analyzed after decanting a5 indicated below. A
hexane material balance indicated that much more than the
usual amount of hPxane had escaped through the third zone
outlet.
TABLE VII
~NALYSES
Feed Product Decanted Total
Oil Oil Oil* Residue
Viscosity @ 25C375 95 3000
~sh % ~.14 0.002 14.22 30.54
% Toluene Insolubles 9.78 0.83 17.26
% Asphaltenes21.12 17.17 25.80
*Decanted from material in residue collection vessel.
:
Example 8:
As a continuation of the operation described
in Example 7, the extraction process was kept in opera-
tion while the temperature of the wall of the third zone
was increased. After reaching steady state the following
te~perature profile was recorded: Zone 2, 190C; wall
20 temperature at the middle and bottom of Zone 3, 225C and .
255C; temperature in the center of Zone 3, 212C. At
these operating conditions no decantable oil was obser~ed
in the residue collection zone. Product quality was as
~ollows:
.
18,394A-F
-27~
TABLE VIII
ANALYSES
Feed Oil Product Oil Residue
Viscosity @ 25C 375 62
5 Ash % 8.14 0.004 35.15
% Toluene Insolubles 9.78 0.88
: % Asphaltenes 21.12 17.08
. ~
A comparison of the data presented in Tables
VII and VIII support the need for maintaining the wall
temperature of the third zone at a temperature of about
: 20C higher than the wall temperature of the rest of the
column if a viscous residual slurry is to be recovered
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