Note: Descriptions are shown in the official language in which they were submitted.
v
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TS 8514 CAN
PROCESS FOR THE CONVERSION OF A RESIDUAL
HYDROCARBON OIL
The present invention relates to a process for the
conversion of a residual hydrocarbon oil.
Thermal cracking is a widely and commonly applied
route for converting residual hydrocarbon oils into
lighter products. It usually involves preheating the
feedstock to the appropriate temperature, thermally
cracking the preheated feedstock and fractionating the
effluent, which often is quenched prior to fractionation
in order to stop the cracking reactions. Fractionation
l0 may for instance be conducted by atmospheric distillation
solely or by a combination of atmospheric and vacuum
distillation.
One of the undesired phenomena occurring in thermal
cracking of residual oil feedstocks at high conversion
levels is the formation of insoluble material limiting
the production of distillates. This formation of
insoluble material mainly originates from heavy
asphaltenic components and to some extent from larger
aromatic components present in the feedstocks.
2o Additionally, insoluble material is produced from
synthetic asphaltenes formed in condensation reactions
occurring in the thermal cracking process. Particularly
at severe cracking conditions, formation of insoluble
material is known to occur. However, thermal cracking is
a relatively simple process requiring a relatively low
capital investment and having relatively low operating
costs. This makes thermal cracking an attractive option
from both a manufacturing and an economic point of view.
For this reason there is a continuous effort for further
improving the efficiency of thermal cracking. In the
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past, several methods have been proposed for achieving
this goal.
In NL-A-8400074, for instance, a process for
producing hydrocarbon mixtures from an oil residue is
disclosed, wherein the oil residue is first deasphalted,
after which the deasphalted oil is subjected to a
cracking process, eventually producing one or more
distillate fractions. The asphaltic bitumen fraction is
partially oxidised using oxygen to produce a gasmixture
containing carbon monoxide and hydrogen, which gasmixture
is subsequently used in a catalytic hydrocarbon synthesis
to produce synthetic hydrocarbons. These synthetic
hydrocarbons are then mixed, suitably after having been
separated by atmospheric distillation, with at least a
part of the said distillate fractions produced in the
cracking of the deasphalted oil. The cracking process, to
which the deasphalted oil is subjected, most suitably is
a catalytic cracking process, because the quality of the
light naphtha produced by catalytic cracking is stated to
be excellent. A light naphtha produced by thermal
cracking, on the other hand, has to be subjected to an
additional hydrogenation step for converting dimes into
olefins in order to obtain a light naphtha having the
desired quality.
In EP-A-0,372,652 as a disadvantage of the type of
process according to NL-A-8400074 is mentioned that the
asphaltenes removed from the residual oil in the
deasphalting step can no longer contribute to the
production of distillates and the yield of distillates is
consequently not optimal. Accordingly, the process
disclosed in EP-A-0,372,652 for converting a heavy
hydrocarbonaceous feedstock, such as the vacuum residue
of a crude oil, into lighter products involves first
preheating the heavy feedstock, after which the preheated
feedstock is passed through a thermal cracking zone under
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such conditions that a conversion of at least 35~ by
weight, suitably up to 70~ by weight, of hydrocarbons
having a boiling point of 520 °C or higher is
accomplished. The effluent from the cracking zone is
subsequently separated into one or more distillate
fractions -to be recovered as products- and a residual
fraction, which is deasphalted to obtain an asphalt and a
deasphalted oil. This deasphalted oil can be further
treated, e.g. by catalytic cracking, hydrotreatment,
l0 hydrocracking or thermal cracking, thus yielding more
useful distillate fractions. Basically, the process
disclosed involves thermal cracking under relatively
severe conditions followed by deasphalting of the
residual fraction. However, this process is again
confronted with the fact that the asphaltenes present in
the feedstock for thermal cracking limit the final yield
of distillate fractions due to the formation of insoluble
and/or coke material, despite the relatively severe
cracking conditions. Additionally, the deasphalted oil
fraction obtained from the deasphalting treatment of the
thermally cracked residual oil fraction still needs
further upgrading in additional conversion process units
in order to attain conversion into useful distillate
products.
Hence, there is still room for improvement of the
efficiency of a conversion process involving thermal
cracking of residual hydrocarbon oils. It is therefore an
object of the present invention to provide a process for
converting a residual hydrocarbon oil into lighter
products of excellent quality at a high efficiency, both
costwise and yieldwise. Regarding the cost-efficiency, it
is an object to use as little equipment as possible
without affecting the product yield and the quality of
the final products. Of course, the process should also
meet the appropriate safety and environmental
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requirements. It is a further object of the present
invention to provide a process, which can be suitably
integrated in various refinery configurations, such as
e.g. a thermal cracker refinery, a catalytic cracker
refinery, a hydrocracker refinery or a refinery which is
a combination of two or more of the before-mentioned
refinery configurations.
Accordingly, the present invention relates to a
process for the conversion of a residual hydrocarbon oil
comprising the steps of:
(a) deasphalting the residual hydrocarbon oil to obtain
(i) a deasphalted oil (DAO) at a yield of at least
50~ by weight, preferably from 60 to 90~ by
weight, more preferably from 65 to 85$ by
weight, based on total weight of residual
hydrocarbon oil; and
(ii) an asphaltene fractions and
(b) passing part or all of the DAO through a thermal
cracking zone so that a 520 °C+ conversion of at
least 60~ by weight, preferably from 70 to 90$ by
weight, based on the total weight of material boiling
above 520 °C present in the DAO before thermal
cracking, is obtained.
The process of the present invention thus basically
involves severe thermal cracking of a deasphalted oil
obtained at high yield from a residual hydrocarbon oil.
With the expression "520 °C+ conversion" as used
throughout this specification is meant the conversion of
the hydrocarbons having a boiling point of 520 °C and
higher present in the thermal cracking feedstock. The
520 °C+ conversion is conveniently expressed in a weight
percentage based on thermal cracking feedstock, i.e. DAO,
and is determined as follows:
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520 °C+ conversion =
520 °C+ in feed - 520 °C+ in effluent * 100$
520 °C+ in feed
It will be evident that "520 °C+" refers to the amount of
hydrocarbons having a boiling point of 520 °C or higher.
An immediate advantage of the process according to
the present invention is the fact that the formation of
insoluble material during thermal cracking is greatly
reduced due to the removal of the heavier asphaltenes
from the residual hydrocarbon oil prior to thermal
cracking by the deasphalting treatment. As a result, the
maximum achievable conversion level is now primarily
determined by the production of synthetic asphaltenic
components formed in condensation reactions occurring
during thermal cracking instead of by the asphaltenic
components present in the residual hydrocarbon oil prior
to deasphalting. This implies that higher conversion
levels with higher distillate productions can be achieved
according to the process of the present invention than is
the case with severe thermal cracking of residual oils
without prior deasphalting this residual oil.
Another advantage of the process according to the
present invention is that the quality of the distillate
fractions from the thermal cracking zone is very good:
the distillate fractions have an excellent H/C ratio and
a low content of sulphur- and nitrogen-containing
contaminants. Such contaminants, which are present in the
residual hydrocarbon oil feedstock, were found to mainly
concentrate in the asphalt phase produced in the
deasphalting treatment rather than in the DAO. Therefore,
the said contaminants, concentrated in the asphalt phase,
can no longer end up in the distillate fractions produced
in the thermal cracking of the DAO.
Furthermore, the process has an excellent synergy
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potential when included in a thermal cracker refinery, a
hydrocracker refinery or a catalytic cracker refinery,
while incorporation in a refinery which is a combination
of two or more of such refinery configurations may offer
an even higher synergy potential. For the individual
refinery configurations, this will be discussed and
illustrated in greater detail below by figures 2, 3 and
4.
The residual hydrocarbon oil used as the feedstock
for the process of the present invention in principle may
be any residual fraction resulting from a fractionation
treatment. Consequently, the residual hydrocarbon oil in
any event has a relatively high content of asphaltenes.
Preferably, the residual hydrocarbon oil is a heavy
asphaltenes-containing hydrocarbonaceous feedstock
comprising at least 35~ by weight, preferably at least
75~ by weight and more preferably at least 90$ by weight,
of hydrocarbons having a boiling point of 520 °C or
higher. A particularly suitable hydrocarbonaceous
feedstock meeting this requirement is a vacuum residue of
a crude oil, also commonly referred to as a short
residue.
The deasphalting of the residual hydrocarbon oil
prior to thermal cracking may be carried out in any
conventional manner, such as by physical separation using
membranes or by adsorption techniques. However, for the
purpose of the present invention it is preferred to use
the well known solvent deasphalting method. In this
method the residual hydrocarbon oil to be deasphalted is
treated countercurrently with an extracting medium which
is usually a light hydrocarbon solvent containing
paraffinic compounds. Commonly applied paraffinic
compounds include C3_g paraffinic hydrocarbons, suitably
C3-C5 paraffinic hydrocarbons, such as propane, butane,
isobutane, pentane, isopentane or mixtures of two or more
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of these. For the purpose of the present invention
however, it is preferred that butane, pentane or a
mixture thereof is used as the extracting solvent,
whereby the use of pentane is most preferred. In general,
the extraction depth increases at increasing number of
carbon atoms of the extracting solvent. In this
connection it is noted that at increasing extraction
depth, the total amount of heavy hydrocarbons being
extracted together with the lighter hydrocarbons from the
residual hydrocarbon oil increases as well, while the
asphaltene fraction is smaller but heavier and hence more
viscous. Accordingly, the extraction depth cannot be too
high as this would result in a very viscous, very heavy
asphaltene raction, which can hardly be processed any
further.
In the solvent deasphalting process a rotating disc
contactor or a plate column can be used with the residual
hydrocarbon oil entering at the top and the extracting
solvent entering at the bottom. The lighter hydrocarbons
with an overall paraffinic solvency behaviour present in
the residual hydrocarbon oil dissolve in the extracting
solvent and are withdrawn at the top of the apparatus.
The asphaltenic components which are insoluble in the
extracting solvent are withdrawn at the bottom of the
apparatus. The conditions under which deasphalting takes
place are known in the art. Suitably, deasphalting is
carried out at a total extracting solvent to residual
hydrocarbon oil ratio of 1.5 to 8 wt/wt, a pressure of
from 1 to 50 bar and a temperature of from 40 to 230 °C.
As already described hereinbefore, for the purpose of the
present invention, the deasphalting of the residual
hydrocarbon oil is carried out such that a DAO is
obtained at an extraction depth of at least 50~ by
weight, preferably from 60 to 90$ by weight, more
preferably 65 to 85$ by weight, the balance up to 100$ by
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_8_
weight being formed by the asphalt fraction. The
expression "extraction depth" indicates the yield of DAO
after deasphalting by solvent extraction and is expressed
in a weight percentage based on total weight of the
initial residual hydrocarbon oil prior to deasphalting.
The thermal cracking of the DAO in accordance with
the present invention can be carried out by the
conventional thermal cracking processes. The exact
conditions under which the thermal cracking is carried
l0 out can be varied and the pexson skilled in the art will
be able to select the temperature, the pressure and the
residence time in such way that the desired conversion
occurs. It will be understood that the same conversion
can be obtained at a high temperature and a short
residence time on the one hand and a lower temperature
but longer residence time on the other hand. In order to
achieve a 520 °C+ conversion of at least 60$ wt on DAO,
as is required in accordance with the present invention,
the thermal cracking of the deasphalted oil in the
thermal cracking zone is suitably conducted at a
temperature of from 350 to 600 °C, a pressure of from 1
to 100 bar and average residence time of from 0.5 to
60 minutes. This residence time relates to the cold
feedstock, i.e. the cold oil feedstock at ambient
temperature.
The effluent from the thermal cracking zone may be
quenched prior to its separation into one or more
distillate fractions and a cracked residual fraction.
Quenching may for instance be effected by contacting the
effluent with a colder quench fluid. Suitable quench
fluids include relatively light hydrocarbon oils, such as
gasoline or a recycled cool residual fraction obtained
from the effluent. After the optional quench, the
effluent is suitably fractionated into one or more
distillate fractions and a cracked residual fraction, for
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instance by atmospheric and/or vacuum distillation. This
cracked residual fraction is rather viscous due to the
presence of heavy asphaltenic components, but is
considerably less viscous than the heavy asphalt phase
separated from the residual hydrocarbon oil in the
deasphalting step.
It is also an aspect of the present invention that
the said cracked residual fraction is, in part or in
total, recycled to the residual oil feedstock and/or to
the DAO in order to maximise the use of plant capacity
and to optimise the distillate production.
In another aspect of the present invention, the
cracked residual fraction is blended with the more
viscous asphalt fraction from the deasphalting treatment
and the resulting blendstream is subsequently subjected
to partial oxidation (gasification). The blending ratio
should be adjusted such that the viscosity of the
blendstream meets the viscosity specification of the
gasification equipment. The production of a cracked
residue, which is available as diluent for the more
viscous asphalt fraction in the gasifier feedstock,
offers the possibility to produce an asphalt in the
deasphalting treatment with a viscosity exceeding the
gasifier feedstock viscosity specification. This implies
that a DAO can be produced at higher yield on residual
hydrocarbon oil feed and consequently, the final
production of distillates in the thermal cracking step is
higher.
Gasification is suitably carried out using any well
known partial oxidation process, wherein a heavy
hydrocarbonaceous feedstock is partially oxidised using
oxygen in the presence of steam, usually high pressure
steam, thus resulting in clean gas after gas treatment.
This clean gas, in return, can be applied as clean fuel
gas in the refinery or for cogeneration of power and
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steam, hydrogen manufacture and hydrocarbon synthesis
processes.
Figure 1 depicts a typical line up of the process of
the present invention.
Figure 2 depicts a line up of a thermal cracking
refinery. .
Figure 3 depicts a line up of a catalytic cracker
refinery.
Figure 4 depicts a line up of a hydrocracker
refinery.
According to figure 1 residual hydrocarbon oil (106),
preferably a short residue, is passed into deasphalting
zone (101), resulting in a DAO (107) and an asphalt
fraction (119), which is further referred to as "pentane-
asphalt". The DAO (107) is led into thermal cracking zone
(102), where it is heated and where the cracking
reactions take place. The reaction zone (102) may
suitably consist of a furnace alone or of a combination
of a furnace plus one or more soaker vessels. Upon
leaving the reaction zone (102), the "cracked DAO" (108)
is passed into cyclone (103), where it is quenched and
separated into a cracked residue fraction (110) and a
lighter fraction (109). This lighter fraction (109) is
separated in atmospheric fractionator (104) into a
naphtha minus fraction (111), kerosine fraction (112),
gasoil fraction (113) and bottom fraction (114). This
bottom fraction (114) is blended with the before-
mentioned cracked residue fraction (110) and the
resulting blend stream is fed into vacuum distillation
unit (105), where fractionation takes place into a vacuum
gas oil fraction (115), a light flashed distillate (116),
a heavy flashed distillate (117) and a vacuum flashed
cracked residue (118). The flashed distillates (116) and
(117) can be recovered as a product component or can be
further upgraded, e.g. by further thermal cracking, by
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hydrocracking or by catalytic cracking, optionally
followed by hydrotreatment. As already mentioned before,
the cracked residue (118) may be partially or totally
recycled to residual hydrocarbon oil feed (106) and/or to
DAO (107) in order to maximise the use of plant capacity
and to optimise distillate production. These options are
reflected by the dotted lines in figure 1.
In figure 2 crude oil (211) is passed into
atmospheric distillation unit (201) and separated into
to one or more distillate fractions (212), covering all
fractions ranging from naphtha minus to heavy gasoil, and
long residue (213). This long residue (213) is further
separated in (high) vacuum distillation unit (202) in
vacuum gasoil (214), light flashed distillate (215),
heavy flashed distillate (216) and short residue (217).
Flashed distillates (215) and (216) are combined and
passed into distillate cracking unit (207). Short residue
(217) is deasphalted in deasphalting zone (203),
resulting in DAO (219) and pentane-asphalt (218). DAO
(219) is subsequently subjected to severe thermal
cracking (TC) in TC-zone (206) producing -after
separation (distillation)- distillate fractions (220),
which are passed into distillate cracking unit (207), and
bottom product (221), which is subsequently passed into
vacuum flashing unit (208) together with the bottom
product (222) produced in the distillate cracking unit
(207). In this vacuum flashing unit (208) separation into
thermally cracked flashed distillates (223) and vacuum
flashed cracked residue (224) takes place. The thermally
cracked flashed distillate fraction (223) is routed to
distillate cracking unit (207) and the vacuum flashed
cracked residue (224) is added as a diluent to the
pentane-asphalt (218), so that the resulting blendstream
meets the viscosity specification of gasification unit
(204). In the distillate cracking unit (207) there are
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further produced naphtha minus fraction (225) and gasoil
fraction (226), which -after hydrodesulphurization in
hydrodesulphurization unit (209)- is recovered as
valuable automotive gasoil and industrial gasoil
components (227). Gasification of the before-mentioned
blendstream (218/224). takes place by passing this
blendstream as well as oxygen (228) and steam (229) into
gasification unit (204), where partial oxidation of the
heavy hydrocarbons present in the said blendstream takes
l0 place to produce a gas mixture (230) mainly consisting of
carbon monoxide and hydrogen, which mixture is
subsequently purified in gas treatment unit (205). The
purified gas (231) can be partially or totally recovered
as clean fuel gas in the refinery or can be applied for
the cogeneration of power and steam, hydrogen manufacture
and/or hydrocarbon synthesis processes.
Compared with a thermal conversion refinery wherein
the short residue is thermally cracked without prior
deasphalting, the thermal conversion refinery according
to figure 2 produces more distillates and less vacuum
flashed cracked residue. When deasphalting the short
residue at a high extraction depth by using pentane as
the extracting solvent, the production of pentane-asphalt
is also relatively low. The low production of both vacuum
flashed cracked reside and pentane-asphalt means that
less gasification capacity is required than with straight
severe thermal cracking of short residues, which is
attractive from both refinery margin and capital
investment point of view.
In the catalytic cracker refinery according to
figure 3, a crude oil (310) is separated in atmospheric
distillation unit (301) into one or more distillate
fractions (311), covering all fractions ranging from
naphtha minus to heavy gasoil, and long residue (312),
which is further separated in (high) vacuum distillation
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unit (302) into vacuum gasoil (313), light flashed
distillate (314), heavy flashed distillate (315) and
short residue (316). Short residue (316) is then
deasphalted in deasphalting unit (303), resulting in
pentane-asphalt (317) and DAO (318), which is passed to
TC-zone (306) where thermal cracking reactions occur
producing (after separation) naphtha minus (319), gasoil
fraction (320) and bottom product (321). Bottom product
(321) is separated in vacuum flashing unit (307) into
to thermally cracked flashed distillate fraction (322) and
vacuum flashed cracked residue fraction (323). Thermally
cracked flashed distillate fraction (322) and light and
heavy flashed distillates (314) and (315) are passed into
catalytic cracking zone (309), where tops (324), naphtha
(325), kerosine (326), light cycle oil (327) and heavy
cycle oil/clarified slurry oil (328) are produced. The
light cycle oil (327) and gasoil fraction (320) are both
passed through hydrodesulphurization unit (308) resulting
in valuable automotive and industrial gasoil components
(329). Heavy cycle oil/clarified slurry oil (328),
pentane-asphalt (317) and vacuum flashed cracked residue
fraction (323) are blended, so that the resulting
blendstream meets the viscosity specification of gasifier
(304). The blendstream, oxygen (330) and steam (331) are
passed into the gasifier (304) where the heavy
hydrocarbons are partially oxidised to produce a gas
mixture (332) mainly consisting of carbon monoxide and
hydrogen, which gas mixture is subsequently purified in
gas treatment unit (305). The purified gas (333) can be
partially or totally recovered as clean fuel gas in the
refinery or can be applied for the cogeneration of power
and steam, hydrogen manufacture and/or hydrocarbon
synthesis processes.
Compared with a long residue fluid catalytic cracker
(LRFCC) refinery, a refinery with a flashed distillate
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fluid catalytic cracker (FDFCC) and severe thermal
cracking of DAO -as illustrated by figure 3- has the
advantage that no catalyst cooling capacity is required
on the FDFCC, which means a significant cost saving.
Additionally, contrary to an LRFCC refinery, metals
present in the crude_oil no longer end up on the FCC
catalyst in the FDFCC refinery, thus reducing costs for
FCC catalyst replacement and spent catalyst disposal or
rejuvenation. Another advantage is the fact that SOx
l0 emissions are strongly reduced in the FDFCC refinery,
since the major part of the sulphur present in the long
residue ends up in the pentane-asphalt after
deasphalting. Sulphur removal in this case takes place in
the gasifier gas treating step after partial oxidation of
the gasifier feedstock mixture.
In the line up of the complex hydrocracker refinery
according to figure 4 all reference numbers (401) to
(433) have the same meaning as the corresponding
reference numbers (201) to (233) in figure 2. The line up
according to figure 4 only differs from that according to
figure 2 in that flashed distillates (415) and (416) are
passed into hydrocracking zone (434) instead of being
passed into distillate cracking unit (407) as is the case
in figure 2, where flashed distillates (215) and (216)
are passed into distillate cracking unit (207). In this
hydrocracking zone (434) the flashed distillates (415)
and (416) are upgraded, i.e. cracked and hydrotreated,
into tops (435), naphtha (436), kerosine (437), gasoil
(438) and hydrowax (439). This hydrowax (439) can
3o suitably be used as a feedstock for a chemical complex,
e.g. for producing lower olefins. It is also noted that
the thermally cracked flashed distillate (423) may also
be partially or totally used as a feed for the
hydrocracking zone (434) instead of being passed into
distillate cracking zone (407).
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Compared with a refinery with a hydrocracker unit
(HCU) on a feedstock consisting of a mixture of flashed
distillates and DAO (FD/DAO HCU), the flashed distillate
hydrocracker refinery with severe thermal cracking of DAO
(FD/HCU+DAO/TC refinery) according to figure 4 has the
advantage that a smaller hydraulic capacity of the
expensive high pressure HCU is required and that due to
the absence of the DAO feed it can be operated at a lower
combined feedratio, which in return results in a lower
reactor volume and hence lower capital investment and
operating costs. Moreover, no expensive high pressure
guard bed reactor is required to protect the hydrocracker
from metal contaminants and high Conradson Carbon Residue
material present in the DAO feedstock. Another important
advantage of the FD/HCU+DAO/TC refinery according to
figure 4 is that due to the upgrading of the DAO via
severe thermal cracking, the optimum DAO yield on short
residue is mainly determined by the blending of the
pentane-asphalt with the vacuum flashed cracked residue
to meet the maximum viscosity specification of the
gasifier feedstock. This optimum DAO yield is higher than
the optimum DAO yield on short residue in the case of the
FD/DAO HCU, the latter being predominantly determined by
the maximum guard bed reactor Conradson Carbon Residue
specification. Therefore, with the HCU refinery including
the severe thermal cracking of DAO more DAO is available
for upgrading into valuable distillates, resulting in a
lower asphalt production, a lower capacity requirement
for the gasifier unit and hence lower capital investment
and operating costs.
The invention is further illustrated by the following
examples.
Example 1
Arabian Heavy Short Residue (AHSR) was deasphalted
using pentane as the extracting solvent, yielding 70$ by
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weight on AHSR of DAO (AHSR C5-DAO). The extraction was
carried out at a total solvent/feed ratio of 2.0 (wt/wt)
and a feedstock predilution of 0.5 (wt/wt) at 193 °C and
40 bar pressure. The AHSR C5-DAO was subsequently
subjected to severe thermal cracking at a pressure of
5.0 bar and at outlet temperatures of 470, 480, 490 and
500 °C.
Comparative Example 1
The same AHSR as used in Example 1 was subjected to
l0 thermal cracking at a pressure of 5.0 bar. Outlet
temperatures were 460, 465, 470, 475 and 481 °C.
The analytical data regarding AHSR C5-DAO and AHSR
are listed in Table I. The following abbreviations are
used: "$w" means percent by weight and "CSt" means
centistokes.
The results of the thermal cracking of AHSR C5-DAO
and AHSR at the different outlet temperatures are listed
in Tables II and III respectively.
TABLE I Data regarding AHSR C5-DAO and AHSR
AHSR C5-DAO AHSR
TBP/GLC
165 - 350 C ($w) 1.2 0
350 - 520 C ($w) 13.3 7.0
520 C+ ($w) 85.5 93.0
Density 15/4 0.98 1.03
Viscosity at 100 C (CSt) 143 2351
at 150 C (CSt) 24 154
Sulphur ( $w) 4 . 1 5 . 3
Carbon ($w) 84.4 84.0
Hydrogen ($w) 11.0 10.2
C5 asphaltenes ($w) 1.9 19.9
C7 asphaltenes ($w) 0.1 12.3
Conradson Carbon ($w) 10.2 21.7
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TABLE II Thermal cracking of AHSR C5-DAO
Experiment No. 1 2 3 4
Outlet temp. (C) 470 480 490 500
Product distribution:
C4- ( $w) 2 . 3 . 3 . 5 .
0 0 9 4
C5 - 165 C ($w) 4.8 7.7 10.3 16.3
165 - 350 C ($w) 10.0 16.5 21.2 26.6
350 - 520 C (~w) 27.7 30.1 31.8 28.3
520 C+ (~w) 55.6 42.7 32.8 23.3
520 C+ conversion
on AHSR C5-DAO ($w) 35.0 50.0 61.6 72.7
520 C+ conversion
on AHSR feed (~w) 24.5 35.0 43.1 50.9
Properties of 350 C+
residual fraction: 1.01 1.01 1.03 1.04
Density 15/4
Viscosity at 100 C (CSt) 79 62 51 57
at 150 C (CSt) 16 14 12 13
Sulphur (~w) 4.7 4.8 4.8 5.1
Carbon (~w) 84.4 84.6 84.7 84.9
Hydrogen ($w) 10.3 10.0 9.7 9.2
C5 asphaltenes (~w) 4.8 9.2 13.9 20.3
C7 asphaltenes ($w) 2.7 4.3 8.1 15.7
Conradson Carbon (~w) 11.4 13.1 15.3 18.4
Insolubles(~w) 0.01 0.01 0.01 0.03
520 C+ content (~w) I 65.5 156.0 I 47.0141.4
~~4~oso
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TABLE III Thermal cracking of AHSR
Experiment No. 1 2 3 4 5
Outlet temp. (C) 460 465 470 475 481
Product distribution:
C4- (~w) 2.1 2.6 3.1 2.9 3.7
C5 - 165 C (~w) 3.7 5.1 6.1 6.7 7.5
165 - 350 C ($w) 9.0 12.7 15.7 16.5 16.4
350 - 520 C (~w) 21.5 22.2 22.7 22.4 22.8
520 C+ (~w) 63.8 57.4 52.4 51.7 49.8
520 C+ conversion
on AHSR feed (~w) 31.5 38.2 43.7 44.4 46.5
Properties of 350 C+
residual fraction: 1.05 1.06 1.01 1.07 1.08
Density 15/4
Viscosity at 100 C (CSt) 1390 1376 1754 1322 1754
at 150 C (CSt) 109 108 127 106 127
Sulphur ($w) 5.50 5.60 - 5.60 -
Carbon (~w) 84.3 83.3 84.6 84.5 84.6
Hydrogen ($w) 9.7 9.4 9.2 9.1 9.0
C5 asphaltenes ($w) 26.0 27.8 29.3 31.8 31.5
C7 asphaltenes (~w) 21.3 22.9 25.0 25.3 25.1
Conradson Carbon (~w) 20.4 28.2 28.4 28.5 29.6
Insolubles (~w) 0.13 0.52 0.39 0.54 0.48
520 C+ content (~w) 73.9 _ _ 167.7 66.3
70.2 r67.5
At an insolubles content exceeding about 0.5 $w the
thermal cracking pilot plant was found to block due to
deposition of insoluble material. As a result, further
cracking at higher conversion levels was not feasible.
Using the DAO-TC route according to example 1, on the
other hand, resulted in a 350 °C+ residual fraction
having an insolubles content of only 0.03 ~w at an outlet
temperature as high as 500 °C, thus still having
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potential for further cracking at higher conversion
levels without blocking of the pilot plant due to the
deposition of insoluble material. In addition hereto, it
is also evident from comparing the 520 °C+ conversion
levels relative to the AHSR feed given in tables II and
III, that the process according to the present invention
as illustrated by example 1 allows a higher conversion
and hence a higher distillate yield without blocking of
the thermal cracking unit by insolubles formed.
