[0001] The present invention relates to a process for the conversion of a residual hydrocarbon
oil.
[0002] 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 may for instance be conducted by atmospheric distillation solely or
by a combination of atmospheric and vacuum distillation.
[0003] 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. 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 past, several methods have been proposed for achieving this goal.
[0004] 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 dienes into olefins in order to
obtain a light naphtha having the desired quality.
[0005] 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
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, 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.
[0006] 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 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.
[0007] 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 fraction; 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.
[0008] 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:

It will be evident that "520 °C+" refers to the amount of hydrocarbons having a boiling
point of 520 °C or higher.
[0009] 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.
[0010] 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.
[0011] Furthermore, the process has an excellent synergy 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.
[0012] 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.
[0013] 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
₋₈ paraffinic hydrocarbons, suitably C₃-C₅ paraffinic hydrocarbons, such as propane,
butane, isobutane, pentane, isopentane or mixtures of two or more 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.
[0014] 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 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.
[0015] 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 out can be varied and the person 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.
[0016] 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 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.
[0017] 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.
[0018] 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.
[0019] 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 steam, hydrogen manufacture and hydrocarbon
synthesis processes.
[0020] Figure 1 depicts a typical line up of the process of the present invention.
[0021] Figure 2 depicts a line up of a thermal cracking refinery.
[0022] Figure 3 depicts a line up of a catalytic cracker refinery.
[0023] Figure 4 depicts a line up of a hydrocracker refinery.
[0024] 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 beforementioned 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 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.
[0025] In figure 2 crude oil (211) is passed into atmospheric distillation unit (201) and
separated into 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 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 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.
[0026] 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.
[0027] 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 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 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.
[0028] Compared with a long residue fluid catalytic cracker (LRFCC) refinery, a refinery
with a flashed distillate 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 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.
[0029] 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 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).
[0030] 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 (

) 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

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.
[0031] The invention is further illustrated by the following examples.
Example 1
[0032] Arabian Heavy Short Residue (AHSR) was deasphalted using pentane as the extracting
solvent, yielding 70% by 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
[0033] The same AHSR as used in Example 1 was subjected to thermal cracking at a pressure
of 5.0 bar. Outlet temperatures were 460, 465, 470, 475 and 481 °C.
[0034] 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.
[0035] 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 |
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) |
2.0 |
3.0 |
3.9 |
5.4 |
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: |
|
|
|
|
Density 15/4 |
1.01 |
1.01 |
1.03 |
1.04 |
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) |
65.5 |
56.0 |
47.0 |
41.4 |
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: |
|
|
|
|
|
Density 15/4 |
1.05 |
1.06 |
1.01 |
1.07 |
1.08 |
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 |
70.2 |
67.5 |
67.7 |
66.3 |
[0036] 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
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.
1. 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 fraction; 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.
2. A process according to claim 1, wherein the residual hydrocarbon oil is a heavy asphalthenes-containing
hydrocarbonaceous feedstock comprising at least 75% by weight of hydrocarbons having
a boiling point of 520 °C or higher.
3. A process according to claim 2, wherein the heavy asphalthenes-containing hydrocarbonaceous
feedstock is a vacuum residue of a crude oil.
4. A process according to any one of the preceding claims, wherein the deasphalting is
carried out by solvent extraction using butane, pentane or a mixture thereof as the
extracting solvent.
5. A process according to claim 4, wherein pentane is used as the extracting solvent.
6. A process according to any one of the preceding claims, wherein the 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 160 to 230 °C.
7. A process according to any one of the preceding claims, wherein thermal cracking of
the DAO in the thermal cracking zone is 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.
8. A process according to any one of the preceding claims, wherein the cracked residue
finally obtained from the thermal cracking zone is partially or totally recycled to
the residual hydrocarbon oil feed for the deasphalting treatment and/or to the DAO.
9. A process according to any one of the preceding claims, wherein at least a part of
the cracked residue finally obtained from the thermal cracking zone and the asphaltene
fraction from the deasphalting treatment are blended and the resulting blendstream
is subsequently subjected to gasification.
10. A thermal conversion refinery wherein the process according to any one of claims 1
to 9 has been integrated.
11. A catalytic cracker refinery wherein the process according to any one of claims 1
to 9 has been integrated.
12. A hydrocracker refinery wherein the process according to any one of claims 1 to 9
has been integrated.
13. A refinery comprising a combination two or more of the refinery configurations as
claimed in claims 10 to 12.