U.S. patent application number 12/130020 was filed with the patent office on 2009-02-26 for method for producing feedstocks of high quality lube base oil from unconverted oil.
This patent application is currently assigned to SK Energy Co., Ltd.. Invention is credited to Chang Kuk Kim, Gyung Rok Kim, In Chan Kim, Sam Ryong Park, Jee Sun Shin.
Application Number | 20090050524 12/130020 |
Document ID | / |
Family ID | 40381166 |
Filed Date | 2009-02-26 |
United States Patent
Application |
20090050524 |
Kind Code |
A1 |
Kim; Gyung Rok ; et
al. |
February 26, 2009 |
METHOD FOR PRODUCING FEEDSTOCKS OF HIGH QUALITY LUBE BASE OIL FROM
UNCONVERTED OIL
Abstract
The present invention relates to a method of producing a
feedstock for high-quality lube base oil from unconverted oil (UCO)
obtained from fuel oil hydrocracking, and more particularly to a
method of producing a feedstock for high-quality lube base oil by
treating vacuum gas oil (VGO) or a mixture of vacuum gas oil (VGO)
with coker gas oil (CGO) or deasphalted oil (NAO) as a feedstock in
a hydrotreating unit and a first hydrocracking unit and recycling
the resulting unconverted oil (UCO) through a second hydrocracking
unit.
Inventors: |
Kim; Gyung Rok; (Daejeon,
KR) ; Kim; Chang Kuk; (Daejeon, KR) ; Kim; In
Chan; (Ulsan, KR) ; Shin; Jee Sun; (Seoul,
KR) ; Park; Sam Ryong; (Daejeon, KR) |
Correspondence
Address: |
DARBY & DARBY P.C.
P.O. BOX 770, Church Street Station
New York
NY
10008-0770
US
|
Assignee: |
SK Energy Co., Ltd.
Seoul
KR
|
Family ID: |
40381166 |
Appl. No.: |
12/130020 |
Filed: |
May 30, 2008 |
Current U.S.
Class: |
208/89 |
Current CPC
Class: |
C10G 2400/10 20130101;
C10G 65/12 20130101 |
Class at
Publication: |
208/89 |
International
Class: |
C10G 45/00 20060101
C10G045/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 22, 2007 |
KR |
10-2007-0084507 |
Claims
1. A method of producing a feedstock for high-quality lube base oil
from unconverted oil, the method comprising: distilling atmospheric
residue (AR) in a first vacuum distillation process (V1) to obtain
vacuum gas oil (VGO), and feeding the vacuum gas oil (VGO) into a
hydrotreating unit (HDT); removing impurities from the vacuum gas
oil through the hydrotreating unit (HDT); obtaining light and heavy
hydrocarbons from the vacuum gas oil through a first hydrocracking
unit (HDC1); feeding the light and heavy hydrocarbons into
fractionators (Fs) to separate the hydrocarbons into oil products
and unconverted oil; feeding a portion of the separated unconverted
oil into a second vacuum distillation unit (V2) to obtain a
feedstock for high-quality lube base oil, having a given viscosity
grade, and the remaining unconverted oil; feeding the remaining
unconverted oil separated from the fractionators (Fs) and the
unconverted oil obtained from the second vacuum distillation unit
(V2) into a second hydrocracking unit (HDC2); and recycling light
and heavy hydrocarbons, obtained through the second hydrocracking
process (HDC2), to the fractionators (Fs).
2. A method for producing a feedstock for high-quality lube base
oil from unconverted oil, the method comprising: distilling
atmospheric residue (AR) in a first vacuum distillation process
(V1) to separate it into vacuum gas oil (VGO) and vacuum residue
(VR) or a mixture of atmospheric residue (AR) with vacuum residue
(VR), feeding the vacuum gas oil (VGO) directly into a
hydrotreating (HDT) unit, feeding the vacuum residue (VR) or the
vacuum residue/atmospheric residue mixture (VR/AR) through
fractionators (Fs') to coker drums to subject it to a coking
process and passing the coked residue through fractionators (Fs')
to obtain coker gas oil, and feeding the obtained coker gas oil
together with the vacuum gas oil (VGO) into a hydrotreating (HDT)
unit; removing impurities from the vacuum gas oil and the coker gas
oil through the hydrotreating (HDT) unit; obtaining light and heavy
hydrocarbons from the vacuum gas oil through a first hydrocracking
(HDC1) unit; feeding the light and heavy hydrocarbons into
fractionators (Fs) to separate the hydrocarbons into oil products
and unconverted oil; feeding a portion of the unconverted oil to a
second vacuum distillation unit (V2) to obtain a feedstock for
high-quality lube base oil, having a given viscosity grade, and the
remaining unconverted oil; feeding the remaining unconverted oil,
separated from the fractionators, and the unconverted oil, obtained
from the second vacuum distillation unit (V2), into a second
hydrocracking unit (HDC2); and recycling light and heavy
hydrocarbons, obtained through the second hydrocracking unit
(HDC2), to the fractionators (Fs).
3. A feedstock of producing a feedstock for high-quality lube base
oil from unconverted oil, the method comprising: distilling
atmospheric residue in a first vacuum distillation unit (V1) to
separate it into vacuum gas oil (VGO) and vacuum residue (VR),
feeding the vacuum gas oil (VGO) directly into a hydrotreating unit
(HDT), feeding the vacuum residue into a solvent deasphalting unit
(SDA) to obtain deasphalted oil (DAO) from which asphalt and
impurities have been removed, and feeding the deasphalted oil (DAO)
together with the vacuum gas oil (VGO) into the hydrotreating unit
(HDT); removing impurities from the vacuum gas oil and the
deasphalted oil through the hydrotreating unit (HDT); obtaining
light and heavy hydrocarbons from the vacuum gas oil and the
deasphalted oil through a first hydrocracking unit (HDC1); feeding
the light and heavy hydrocarbons into fractionators (Fs) to
separate the hydrocarbons into oil products and unconverted oil;
feeding a portion of the separated unconverted oil into a second
vacuum distillation unit (V2) to obtain a feedstock for
high-quality lube base oil, having a given viscosity grade, and the
remaining unconverted oil; feeding the remaining unconverted oil,
separated from the fractionators, and the unconverted oil, obtained
from the second vacuum distillation unit (V2), into a second
hydrocracking unit (HDC2); and recycling light and heavy
hydrocarbons, obtained through the second hydrocracking unit
(HDC2), to the fractionators (Fs).
4. The method of claim 2, wherein the mixing volume ratio (VGO/CGO)
between the vacuum gas oil (VGO) and the coker gas oil (CGO), which
are fed into the hydrotreating unit (HDT), is 2-9.
5. The method of claim 3, wherein the mixing volume ratio (VGO/DAO)
between the vacuum gas oil (VGO) and the deasphalted oil (DAO),
which are fed into the hydrotreating unit (HDT), is 2-9.
6. The method of claim 1, wherein the ratio of the unconverted oil
fed into the second hydrocracking unit HDC2 to the unconverted oil
produced in the fractionators Fs is 1:2-1:5.
7. The method of claim 2, wherein the ratio of the unconverted oil
fed into the second hydrocracking unit HDC2 to the unconverted oil
produced in the fractionators Fs is 1:2-1:5.
8. The method of claim 3, wherein the ratio of the unconverted oil
fed into the second hydrocracking unit HDC2 to the unconverted oil
produced in the fractionators Fs is 1:2-1:5.
9. The method of claim 1, wherein the ratio of the unconverted oil
fed from the second vacuum distillation unit (V2) into the second
hydrocracking unit HDC2 to the unconverted oil fed into the second
vacuum distillation unit V2 is 1:1.2-1:1.5.
10. The method of claim 2, wherein the ratio of the unconverted oil
fed from the second vacuum distillation unit (V2) into the second
hydrocracking unit HDC2 to the unconverted oil fed into the second
vacuum distillation unit V2 is 1:1.2-1:1.5.
11. The method of claim 3, wherein the ratio of the unconverted oil
fed from the second vacuum distillation unit (V2) into the second
hydrocracking unit HDC2 to the unconverted oil fed into the second
vacuum distillation unit V2 is 1:1.2-1:1.5.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of Korean Patent
Application No. 10-2007-0084507, filed Aug. 22, 2007, entitled
"Method for producing feedstocks of high quality lube base oil from
unconverted oil", which is hereby incorporated by reference in its
entirety into this application.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a method of producing a
feedstock for high-quality lube base oil from unconverted oil (UCO)
obtained from fuel oil hydrocracking, and more particularly to a
method of producing a feedstock for high-quality lube base oil by
hydrotreating vacuum gas oil (VGO) or a mixture of vacuum gas oil
(VGO) with coker gas oil (CGO) or deasphalted oil (DAO) as a
feedstock in a hydrotreating unit and a first hydrocracking unit
and recycling the resulting unconverted oil (UCO) through a second
hydrocracking unit.
[0004] 2. Description of the Prior Art
[0005] A process of producing a feedstock for high-quality lube
base oil through a fuel oil hydrocracking process is a method of
using unconverted oil (UCO), which is generated during the
hydrocracking of vacuum gas oil (VGO) produced in a vacuum
distillation unit (V1). In this method, the VGO is first fed into a
hydrotreating (HDT) unit to remove sulfur, nitrogen, oxygen and
metals from the VGO, and then a significant amount of the
hydrotreated VGO is converted to light hydrocarbons through a
hydrocracking (HDC) process, which is a main reaction process. The
light hydrocarbons are passed through a series of fractionators
(Fs) to separate various oils and gases therefrom, thus producing
light oil products.
[0006] In the reaction, the pass conversion is generally designed
to be about 40%, and it is impossible in practice to accomplish a
pass conversion of 100%. For this reason, unconverted oil (UCO) is
always generated in the fractionators, and a portion of the
unconverted oil is drawn to the outside for use as a feedstock for
lube base oil, and the remaining unconverted oil is recycled to the
hydrocracking unit.
[0007] Aromatic compounds, sulfur compounds, oxygen compounds and
nitrogen compounds, which are contained in the vacuum gas oil (VGO)
feed in large amounts, are almost all saturated with hydrogen
through the hydrotreating process. For this reason, more than 90%
of the unconverted oil (UCO) byproducts are saturated hydrocarbons,
and thus have a high viscosity index, which is one of the most
important properties for lube base oil.
[0008] The applicant suggested an effective method of producing
feedstocks for fuel oil and high-quality lube base oil, in which
unconverted oil (UCO) is drawn out directly during the recycle mode
operation of the vacuum gas oil (VGO) hydrocracking unit to provide
a feedstock for producing lube base oil, such that the loads on a
first vacuum distillation unit (V1; a process for vacuum
distillation of atmospheric residue) and hydrotreating and
hydrocracking units (R1 and R2) are reduced without the need to
recycle the VGO to the first vacuum distillation process (V1)
(Korean Patent Publication No. 96-13606). In this method, 100N- and
150N-grade feedstocks for high-quality lube base oils could be
produced at greatly reduced inefficiency, but the method was
designed to use only vacuum gas oil (VGO), and did not consider
producing a feedstock for high-quality lube base oil in a more
economic manner by recycling unconverted oil (UCO) using, in
addition to vacuum gas oil, coker gas oil (CGO) or deasphalted oil
(DAO), which are inexpensive and, at the same time, have a high
concentration of impurities and low oxidation stability. Also, the
method had shortcomings in that, because the hydrocracking unit
consisted simply of a single stage, the size of the required
reactor was increased, and in addition, the operating cost was
increased due to the severity of operating conditions.
SUMMARY OF THE INVENTION
[0009] Accordingly, the applicant has conducted many studies to
maximize the efficiency and economy of the above-described method
for producing a feedstock for high-quality lube base oil and, as a
result, has developed a method capable of effectively producing a
feedstock for high-quality lube base oil by recycling unconverted
oil, generated from the hydrotreating and hydrocracking of either
vacuum gas oil or a mixture of vacuum gas oil with coker gas oil
(CGO) or deasphalted oil (DAO), through a second hydrocracking
process.
[0010] Therefore, the present invention provides a method for
producing a feedstock for high-quality lube base oil, which can
maximize efficiency by recycling unconverted oil (UCO) of an oil
hydrocracking unit through a second hydrocracking unit and, at the
same time, can remarkably improve economic efficiency by employing
coker gas oil (CGO) or deasphalted oil (DAO), which is otherwise
not very useful.
[0011] In one aspect, the present invention provides a method of
producing a feedstock for high-quality lube base oil from
unconverted oil, the method including: distilling atmospheric
residue (AR) in a first vacuum distillation unit (V1) to obtain
vacuum gas oil (VGO), and feeding the vacuum gas oil (VGO) into a
hydrotreating unit (HDT); removing impurities from the vacuum gas
oil through the hydrotreating unit (HDT); obtaining light and heavy
hydrocarbons from the vacuum gas oil through a first hydrocracking
unit (HDC1); feeding the light and heavy hydrocarbons into
fractionators (Fs) to separate the hydrocarbons into oil products
and unconverted oil; feeding a portion of the separated unconverted
oil into a second vacuum distillation unit (V2) to obtain a
feedstock for high-quality lube base oil, having a given viscosity
grade, and the remaining unconverted oil; feeding the remaining
unconverted oil, separated from the fractionators (Fs), and the
unconverted oil, obtained from the second vacuum distillation unit
(V2), into a second hydrocracking unit (HDC2); and recycling light
and heavy hydrocarbons, obtained through the second hydrocracking
process (HDC2), to the fractionators (Fs).
[0012] In another aspect, the present invention provides a method
of producing a feedstock for high-quality lube base oil from
unconverted oil, the method including: distilling atmospheric
residue (AR) in a first vacuum distillation unit (V1) to separate
it into vacuum gas oil (VGO) and vacuum residue (VR) or a mixture
of atmospheric residue (AR) with vacuum residue (VR), feeding the
vacuum gas oil (VGO) directly into a hydrotreating (HDT) unit,
feeding the vacuum residue (VR) or the vacuum residue/atmospheric
residue mixture (VR/AR) through fractionators (Fs) to coker drums
to subject it to a coking process and passing the coked residue
through fractionators (Fs') to obtain coker gas oil, and feeding
the obtained coker gas oil together with the vacuum gas oil (VGO)
into a hydrotreating (HDT) unit; removing impurities from the
vacuum gas oil and the coker gas oil through the hydrotreating
(HDT) unit; obtaining light and heavy hydrocarbons from the vacuum
gas oil through a first hydrocracking (HDC1) unit; feeding the
light and heavy hydrocarbons into fractionators (Fs) to separate
the hydrocarbons into oil products and unconverted oil; feeding a
portion of the unconverted oil to a second vacuum distillation unit
(V2) to obtain a feedstock for high-quality lube base oil, having a
given viscosity grade, and the remaining unconverted oil; feeding
the remaining unconverted oil, separated from the fractionators,
and the unconverted oil, obtained from the second vacuum
distillation unit (V2), into a second hydrocracking unit (HDC2);
and recycling light and heavy hydrocarbons, obtained through the
second hydrocracking unit (HDC2), to the fractionators.
[0013] In still another aspect, the present invention provides a
method of producing a feedstock for high-quality lube base oil from
unconverted oil, the method including: distilling atmospheric
residue in a first vacuum distillation unit (V1) to separate it
into vacuum gas oil (VGO) and vacuum residue (VR), feeding the
vacuum gas oil (VGO) directly into a hydrotreating unit (HDT),
feeding the vacuum residue into a solvent deasphalting unit (SDA)
to obtain deasphalted oil (DAO) from which asphalt and impurities
have been removed, and feeding the deasphalted oil (DAO) together
with the vacuum gas oil (VGO) into the hydrotreating unit (HDT);
removing impurities from the vacuum gas oil and the deasphalted oil
through the hydrotreating unit (HDT); obtaining light and heavy
hydrocarbons from the vacuum gas oil and the deasphalted oil
through a first hydrocracking unit (HDC1); feeding the light and
heavy hydrocarbons into fractionators (Fs) to separate the
hydrocarbons into oil products and unconverted oil; feeding a
portion of the separated unconverted oil to a second vacuum
distillation unit (V2) to obtain a feedstock for high-quality lube
base oil, having a given viscosity grade, and the remaining
unconverted oil; feeding the remaining unconverted oil, separated
from the fractionators, and the unconverted oil, obtained from the
second vacuum distillation unit (V2), into a second hydrocracking
unit (HDC2); and recycling light and heavy hydrocarbons, obtained
through the second hydrocracking unit (HDC2), to the fractionators
(Fs).
[0014] According to the present invention, the feedstock for
high-quality lube base oil can be produced in a more efficient
manner by carrying out the hydrotreating (HDT) process and the
first hydrocracking (HDC1) process using vacuum gas oil (VGO) or
the mixture of vacuum gas oil (VGO) with coker gas oil (CGO) or
deasphalted oil (DAO) as a feedstock, and recycling the unconverted
oil, obtained from the first hydrocracking unit, to the second
hydrocracking unit (HDC2). Also, a high-value-added feedstock for
high-quality lube base oil can be produced in a more economical
manner through the use of coker gas oil (CGO) and deasphalted oil
(DAO), which have a low grade and are difficult to treat.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The above and other objects, features and advantages of the
present invention will be more clearly understood from the
following detailed description taken in conjunction with the
accompanying drawings, in which:
[0016] FIG. 1 is a schematic process diagram of an embodiment of
the present invention, in which a feedstock for high-quality lube
base oil is produced in a fuel oil hydrocracking process in a
recycle-mode operation using vacuum gas oil as a feedstock;
[0017] FIG. 2 is a schematic process diagram of an embodiment of
the present invention, in which a feedstock for high-quality lube
base oil is produced in a fuel oil hydrocracking process in a
recycle-mode operation using a mixture of vacuum gas oil and coker
gas oil as a feedstock; and
[0018] FIG. 3 is a schematic process diagram of an embodiment of
the present invention, in which a feedstock for high-quality lube
base oil is produced in a fuel oil hydrocracking process in a
recycle-mode operation using a mixture of vacuum gas oil and
deasphalted oil as a feedstock.
DETAILED DESCRIPTION OF THE INVENTION
[0019] Hereinafter, the present invention will be described in
detail with reference to the accompanying drawings.
[0020] FIG. 1 is a schematic process diagram of an embodiment of
the present invention, in which a feedstock for high-quality lube
base oil is produced in a fuel oil hydrocracking process in a
recycle-mode operation using vacuum gas oil (VGO) as a feedstock.
As shown in FIG. 1, vacuum gas oil (VGO) produced from a first
vacuum distillation unit (V1) is fed into a hydrotreating unit
(HDT) to remove impurities, including sulfur, nitrogen, oxygen and
metal components, from the vacuum gas oil (VGO), and a light oil
fraction is produced from the hydrotreated vacuum gas oil through a
first hydrocracking unit (HDC1). Also, unconverted oil (UCO),
obtained from the first hydrocracking unit (HDC1), is fed into a
second hydrocracking unit (HDC2) and recycled, thus producing a
feedstock for high-quality lube base oil.
[0021] Unlike the prior single-stage hydrocracking process, in the
present invention, the unconverted oil, obtained by passing the
vacuum gas oil through the single-stage hydrotreating unit (HDT)
and the first hydrocracking unit (HDC) and then passing the
hydrocracked vacuum gas oil through fractionators (Fs), is fed into
a second vacuum distillation unit (V2) to obtain a feedstock for
high-quality lube base oil and the remaining amount of unconverted
oil. The remaining amount of unconverted oil, obtained from the
second vacuum distillation unit (V2), is introduced into a second
hydrocracking unit (HDC2) to additionally produce diesel and light
oil fractions, and then the produced diesel and light oil fractions
are recycled to the fractionators (Fs).
[0022] In the two-stage hydrocracking process (HDC1 and HDC2)
according to the present invention, hydrocracking is carried out in
two separate reactors, unlike the prior hydrocracking unit, which
consists only of a single stage. Thus, there are advantages in that
the size of the reactors can be reduced, severity of operating
conditions can be reduced, and the hydrocracking reaction can be
easily controlled so as to maximize the production of diesel
oil.
[0023] In general, because a one-through two-stage hydrocracking
process is operated at a low conversion rate, the content of
polycyclic aromatic components in the unconverted oil (UCO), which
is a bottom oil fraction, is high, and the quality of the
unconverted oil (UCO) is generally inferior to that in the case in
which the single-stage hydrocracking process is used. For this
reason, there is a problem in that the unconverted oil is difficult
to use as a feedstock for high-quality lube base oil. However, in
the present invention, the recovery of the required raw materials
can be maximized by recycling the unconverted oil (UCO) through the
two-stage hydrocracking process, and the reaction conversion rate
can be increased by recycling the remaining unconverted oil (UCO),
thus improving the quality of the feedstock for high-quality lube
base oil. Also, the production of the feedstock for high-quality
lube base oil can be increased.
[0024] The hydrotreating process (HDT) is a process of removing
sulfur, nitrogen, oxygen and metal components from the vacuum gas
oil as a feedstock, and the hydrotreated vacuum gas oil is
converted to light hydrocarbons through a hydrocracking process in
the first hydrocracking unit (HDC1).
[0025] The light and heavy hydrocarbons, produced through the first
hydrocracking unit (HDC1), are fed into fractionators Fs to
separate them into oil products and unconverted oil (UCO). A
portion of the separated unconverted oil (UCO) is fed into a second
vacuum distillation unit (V2) to separate a feedstock for
high-quality lube base oil, having a given viscosity grade,
therefrom, and to recover the remaining amount of unconverted oil
(UCO).
[0026] The remaining amount of unconverted oil from the second
vacuum distillation unit V2 is fed into a second hydrocracking unit
(HDC2) together with the remaining unconverted oil resulting from
the fractionators (Fs), and the light and heavy hydrocarbons
produced through the second hydrocracking unit (HDC2) are recycled
to the fractionators (Fs).
[0027] Herein, the ratio of the unconverted oil fed into the second
hydrocracking unit (HDC2) to the unconverted oil produced in the
fractionators Fs is preferably 1:2-1:5, and the ratio of the
unconverted oil fed from the second vacuum distillation unit (V2)
into the second hydrocracking unit (HDC2) to the unconverted oil
fed into the second vacuum distillation unit (V2) is preferably
1:1.2-1:1.5.
[0028] The second vacuum distillation unit (V2) is operated at a
bottom temperature of 320-350.degree. C., a bottom pressure of
140-160 mmHg, a top temperature of 75-95.degree. C. and a top
pressure of 60-80 mmHg. The feedstock for high-quality lube base
oil having a given viscosity grade, obtained in the second vacuum
distillation unit (V2), can further be subjected to a dewaxing
process and a stabilization process.
[0029] FIG. 2 is a schematic process diagram of an embodiment of
the present invention, in which a feedstock for high-quality lube
base oil is produced in a fuel oil hydrocracking process in a
recycle-mode operation using a mixture of vacuum gas oil and coker
gas oil as a feedstock. Referring to FIG. 2, in the present
invention, atmospheric residue (AR), separated from a crude
distillation unit (CDU), is distilled in a first distillation unit
V1 to separate it into vacuum gas oil and vacuum residue or a
mixture (VR/AR) of vacuum residue (VR) and atmospheric residue
(AR). The vacuum gas oil (VGO) is fed directly to a hydrotreating
unit HDT, and the vacuum residue (VR) or the atmospheric
residue/vacuum residue mixture (VR/AR) is passed through
fractionators (Fs'), subjected to a coking process in coker drums,
and then passed again through the fractionators Fs', thus obtaining
coker gas oil (CGO). The coker gas oil (CGO) thus obtained is fed
into a hydrocracking unit HDT together with the vacuum gas oil
(VGO), and the two-stage hydrocracking process according to the
present invention is carried out.
[0030] The process of producing the coker gas oil (CGO) will not be
described in further detail. The vacuum residue (VR) or the
atmospheric oil/vacuum residue mixture (VR/AR), separated from the
first distillation unit (V1), is passed through the fractionators
(Fs') to separate low-boiling-point components therefrom, and the
remaining oil fraction is fed into coker drums and heated in the
coker drums to a temperature sufficient for forming coke. At this
time, steam is also fed into the coker drums in order to maintain
the lowest speed and the shortest residence time in the heater
coils and to suppress the formation of coke in the heater coils.
Liquid remaining in the coker drums is converted to coke and light
hydrocarbon gases, and all of the gases are discharged through the
top of the coker drums. In order to carry out this process, at
least two coker drums are required. While coke is formed in one
drum, the flow of oil to the other drum is blocked, and coke is
removed from the other drum. The coker gas oil (CGO), produced
through this coking process, has poor color stability and a high
content of HPNA (heavy poly-nuclear aromatic hydrocarbons) (having
more than 7 aromatic rings), and for this reason, unconverted oil
(UCO), produced by feeding the coker gas oil to the hydrotreating
and hydrocracking units, is unsuitable for use as a feedstock for
high-quality lube base oil.
[0031] However, where unconverted oil (UCO) is recycled through the
second hydrocracking unit (HDC2) according to the method of the
present invention, it is possible to secure high-quality
unconverted oil (UCO) having a low HPNA content and ensured
stability, and the production of 100N- and 150N-grade feedstocks
for high-quality lube base oil can be maximized. In addition, coker
gas oil (CGO), which has been used as Bunker-C (B-C) oil or DSL
oil, can be used as a raw material for producing high-quality lube
base oil, and thus the added value of the product can be increased,
leading to an improvement in economic efficiency.
[0032] Specific conditions for the coking process in the method
according to the present invention are shown in Table 1 below.
TABLE-US-00001 TABLE 1 Operating conditions (unit) Range Heater
discharge temperature (.degree. C.) 480-500 Coker drum temperature
(.degree. C.) 500-600 Top-coker drum pressure (psig) 15-30
Recycling ratio, recycle volume/feed volume 0.05-0.2
[0033] The coker gas oil (CGO), produced from the coking process,
is mixed with vacuum gas oil and fed into the hydrotreating unit
HDT. When the content of the vacuum gas oil in the mixture of the
coker gas oil (CGO) with the vacuum gas oil (VGO) is increased, the
production of a feedstock for high-quality lube base oil will be
increased, but the production cost will be increased, and when the
content of the coker gas oil (CGO) is increased, the production
cost will be advantageously reduced. However, because the
properties of the coker gas oil (CGO) are inferior to those of the
vacuum gas oil (VGO), the mixing volume ratio (VGO/CGO) between the
vacuum gas oil (VGO) and the coker gas oil (CGO) is preferably
2-9.
[0034] The coker gas oil (CGO), extracted from the vacuum residue
(VR) or the atmospheric residue/vacuum residue mixture (VR/AR) in
an amount of about 20-50 vol %, can be mixed with the vacuum gas
oil (VGO) and can be used as a feedstock in the hydrotreating and
hydrocracking units (HDT and HDC). Thus, when the same amount of
atmospheric residue (AR) is fed into the first distillation unit
(V1), there is an advantage in that about 10-50% of the atmospheric
residue can be converted to high-value-added light oil and a
feedstock for high-quality lube base oil, unlike the case where
only vacuum gas oil (VGO) is used as the feedstock in the first
distillation unit (V1).
[0035] FIG. 3 is a schematic process diagram of an embodiment of
the present invention, in which a feedstock for high-quality lube
base oil is produced in a fuel oil hydrocracking process in a
recycle-mode operation using a mixture of vacuum gas oil and
deasphalted oil as a feedstock. Referring to FIG. 3, according to
the present invention, atmospheric residue (AR) is distilled in a
first vacuum distillation unit V1 to separate it into vacuum gas
oil (VGO) and vacuum residue (VR). The vacuum gas oil (VGO) is fed
directly to a hydrotreating unit HDT, and the vacuum residue (VR)
is fed into a solvent deasphalting unit (SDA) to obtain deasphalted
oil from which asphalt and impurities have been removed. The
deasphalted oil (DAO) thus obtained is fed into the hydrotreating
unit (HDT) together with the vacuum gas oil (VGO), and the
two-stage hydrocracking reaction is carried out in the same manner
as described above.
[0036] The process of producing the deasphalted oil (DAO) will now
be described in further detail. The deasphalted oil (DAO) is
produced by feeding the vacuum residue (VR), produced in the first
vacuum distillation unit (V1), as a feedstock to the solvent
deasphalting unit (SDA) so as to suitably remove asphalt and
impurities therefrom. As the solvent in the solvent deasphalting
unit (SDA), n- or iso-paraffin solvent having 3-6 carbon atoms is
mainly used. Specifically, the solvent is selected from the group
consisting of n-propane, n-butane, isobutene, n-pentane and
n-hexane. Also, the yield of the deasphalted oil (DAO) with respect
to the feedstock vacuum residue (VR) varies depending on the
operating conditions and the kind of solvent, shows a tendency to
increase with an increase in the carbon number of the solvent, and
is generally about 15-80%.
[0037] The deasphalted oil (DAO), produced in the solvent
deasphalting process, has low metal and residual carbon content,
but has a high aromatic content and contains an oil fraction having
a high boiling point, and thus it is difficult to use as a
feedstock for high-quality lube base oil.
[0038] However, when the unconverted oil (UCO) is fed into the
second hydrocracking unit (HDC2) and recycled according to the
method of the present invention, the aromatic content of the
deasphalted oil can be reduced, and it is possible to remove the
oil fraction having high boiling point, and thus the deasphalted
oil can be used as a feedstock for high-quality lube base oil. The
use of such deasphalted oil (DAO) allows restriction on a feedstock
for high-quality lube base oil to be relieved and the added value
of the product to be increased, leading to an improvement in
economic efficiency.
[0039] The deasphalted oil (DAO), extracted from the vacuum residue
(VR) or the atmospheric residue/vacuum residue mixture (VR/AR) in
an amount of about 20-50 vol %, can be mixed with the vacuum gas
oil (VGO) and can be used as a feedstock in the hydrotreating and
hydrocracking units (HDT and HDC). Thus, when the same amount of
atmospheric residue (AR) is fed into the first distillation unit
(V1), there is an advantage in that about 10-50% of the atmospheric
residue can be converted to high-valued-added light oil and a
feedstock for high-quality lube base oil, unlike the case where
only vacuum gas oil (VGO) is used as the feedstock in the first
distillation unit (V1).
[0040] When the content of the vacuum gas oil in the mixture of the
deasphalted oil (DAO) with the vacuum gas oil (VGO) is increased,
the production of high-quality lube base oil will be increased, but
the production cost will be increased, and when the content of the
deasphalted oil (DAO) is increased, the production cost will be
advantageously reduced. However, because the properties of the
deasphalted oil are inferior to those of the vacuum gas oil (VGO),
the mixing volume ratio (VGO/DAO) between the vacuum gas oil (VGO)
and the deasphalted oil (DAO) is preferably 2-9.
[0041] The typical properties of vacuum gas oil (VGO), coker gas
oil (CGO) and deasphalted oil (DAO), which are fed into the
hydrocracking unit (HDT) according to the present invention, are
shown in Table 2 below.
TABLE-US-00002 TABLE 2 Properties of feedstocks in hydrocracking
unit VGO CGO DAO Specific gravity 0.8660 0.8504 0.8686
Sulfur/nitrogen (wt ppm) 937/750 1137/1614 2200/600 C7 insoluble
substances (wt %) 0.35 0.05 0.01 Fe (wt ppm) 1.1 1.0 1.4 Ni + V (wt
ppm) 1.0 1.0 LT 1.0 Si (wt ppm) -- 3.5 LT 1.0 Distillation (ASTM
D-86) Initial boiling point 324.8 207.0 266 5% 354.3 249.2 33.9 10%
373.6 272.2 348 30% 412.0 314.5 438 50% 440.7 342.5 488 70% 474.5
370.8 539 90% 529.6 405.5 604 95% 546.8 422.0 633 Final boiling
point 586.0 452.0 699
[0042] Hereinafter, the present invention will be described in
further detail with reference to examples, but the scope of the
present invention is not limited thereto.
EXAMPLE 1
[0043] Vacuum gas oil (VGO), separated from atmospheric residue
(AR) as a feedstock in the first vacuum distillation unit (V1), had
the properties shown in Table 2 above, and was hydrotreated in the
hydrotreating unit (HDT) under conditions of an LHSV (Liquid Hourly
Space Velocity) of 3.881 hr.sup.-1, a pressure of 2417 psig, a
temperature of 389.degree. C. and a hydrogen feed rate of 1374
Nm.sup.3/m.sup.3 using KF-848 (Albemarle) as a catalyst. The
hydrotreated oil was treated in the first hydrocracking unit (HDC1)
under conditions of an LHSV of 1.068 hr.sup.-1, a pressure of 170
bar and a temperature of 395.degree. C. using DHC-8 (UOP) as a
catalyst at a hydrogen feed rate of 1050 nm.sup.3/m.sup.3, and was
then passed through a conventional separator and a plurality of
fractionators to recover some of the diesel and light oil products,
having a boiling point of less than 410.degree. C. Then, the
remaining oil was treated in the second hydrocracking unit (HDC2)
together with the recycled UCO, described below, under conditions
of an LHSV of 1.613 hr.sup.-1, a pressure of 170 bar and a
temperature of 403.degree. C. using a DHC-8 catalyst (UOP) at a
hydrogen feed rate of 1028 nm.sup.3/m.sup.3. Then, the hydrocracked
oil was passed through a conventional separator and a plurality of
fractionators to recover diesel and light oil products, having a
boiling point of 410.degree. C., thus obtaining unconverted oil
(UCO) having the properties shown in Table 2 above. The obtained
unconverted oil was subjected to vacuum distillation in a UCO
vacuum distillation unit (V2) under conditions of a top pressure of
75 mmHg, a top temperature of 80.degree. C., a bottom pressure of
150 mmHg and a bottom temperature of 325.degree. C., thus obtaining
20 LV % light distillate, a 32 LV % 100N distillate, 22 LV % middle
distillate, 4 LV % 150N distillate and 22 LV % bottom product,
shown in Table 3 below.
[0044] Among them, only the 100N and 150N distillates were drawn
out as intermediate products in an amount of 36% (100N: 32% and
150N: 4%) based on the feed amount (the amount of UCO fed into V2),
and the remaining distillates (64% of the feed amount) were
combined and recycled to the second hydrocracking unit (HDC2).
Thus, 100N- and 150N-grade feedstocks for high-quality lube base
oil, having a high viscosity index and 150N and low volatility, as
shown in Table 3 below, were produced. Also, because 36% of UCO was
drawn out, the accumulation of refractory components and
poly-nuclear aromatic components were prevented, while the reaction
conversion rate was increased, leading to an improvement in
quality. In addition, the spare capacities of V1 and R1 were
provided, and thus additional treatment capacity corresponding to
the production of the feedstock for lube base oil was provided, and
thus it was possible to use the system at very high efficiency.
TABLE-US-00003 TABLE 3 100N Middle 150N Bottom UCO Light distillate
distillate distillate distillate product Specific gravity 0.8289
0.7393 0.8223 0.8287 0.8349 0.8421 Distillation, ASTM D1160, @760
mmHg, .degree. C. Initial boiling point 220 227 368 387 406 412 5%
385 380 390 401 428 440 10% 404 395 402 421 440 465 30% 426 402 424
444 467 478 50% 450 410 438 459 482 496 70% 477 418 453 478 501 518
90% 535 426 471 503 521 541 95% 574 433 480 512 542 578 Final
boiling point 613 446 495 533 573 613 Viscosity, cSt @40.degree. C.
13.15 17.74 @ 100.degree. C. 3.493 2.968 4.226 5.065 6.653 7.523
Viscosity index 152 113 149 -- -- -- Flash point (COC) .degree. C.
146 230 243 266 289 Pour point 46 33 39 45 51
EXAMPLE 2
[0045] Vacuum residue (VR), separated from atmospheric residue (AR)
as a feedstock in the first vacuum distillation unit (V1), was
passed through the fractionators (Fs') to separate some components
having a low boiling point, and the remaining oil was heated to
500.degree. C. and fed into coker drums. In the coker drums, the
vacuum residue was heated under conditions of a temperature of
550.degree. C. and a top coker drum pressure of 25 psig, so that
liquid remaining in the drums was converted to coke and light
hydrocarbon gases, and all of the gases were passed through the
fractionators (Fs') to separate them into LPG, gas, naphtha and
coker gas oil (CGO).
[0046] The coker gas oil (CGO) and the vacuum gas oil (VGO) had the
properties shown in Table 2, below, and were hydrocracked in the
hydrocracking unit (HDT) under conditions of an LHSV of 3.56
hr.sup.-1, a pressure of 2417 psig, a temperature of 384.degree. C.
and a hydrogen feed rate of 962 Nm.sup.3/m.sup.3 using UF-210STARS
(UOP) as a catalyst. The hydrocracked oil was treated in the first
hydrocracking unit (HDC1) under conditions of an LHSV (Liquid
Hourly Space Velocity) of 1.246 hr.sup.-1, a pressure of 170 bar
and a temperature of 395.degree. C. using UF-210STARS/DHC-32 (UOP)
as a catalyst at a hydrogen feed rate of 1180 Nm.sup.3/m.sup.3, and
then was passed through a conventional separator and a plurality of
fractionators to recover some diesel and light oil products having
a boiling point lower than 370.degree. C. The hydrocracked oil was
treated in the second hydrocracking unit (HDC2) together with the
recycled UCO, described below, in conditions of an LHSV of 1.613
hr.sup.-1, a pressure of 170 bar and a temperature of 398.degree.
C. using a DHC-8 catalyst (UOP) at a hydrogen feed rate of 1028
Nm.sup.3/m.sup.3. Then, the hydrocracked oil was passed through a
conventional separator and a plurality of fractionators to recover
diesel and light oil products, having a boiling point lower than
370.degree. C., thus obtaining unconverted oil (UCO) shown in Table
4 below. The obtained UCO was subjected to vacuum distillation in
the second vacuum distillation unit (V2) under conditions of a top
pressure of 75 mmHg, a top temperature of 80.degree. C., a bottom
pressure of 148 mmHg and a bottom temperature of 330.degree. C.,
thus obtaining 30 LV % light distillate, 35 LV % 100N distillate,
18 LV % middle distillate, 4 LV % 150N distillate and 13 LV %
bottom product, as shown in Table 4 below.
[0047] Among them, only the 100N and 150N distillates were drawn
out as intermediate products in an amount of 39% (that is, 100N:
35% and 150N: 4%) based on the feed amount (the amount of UCO fed
into V2), and the remaining distillates (61%) were combined and
recycled to the second hydrocracking unit (HDC2). Thus, 100N- and
150N-grade feedstocks for high-quality lube base oil, having high
viscosity index and low volatility, as shown in Table 4, were
produced, and because 39% of the UCO was drawn out, high-quality
unconverted oil, having a low poly-nuclear aromatic component
content and ensured stability, could be secured. Also, because
additional treatment capacity corresponding to the production of
the feedstock for lube base oil was provided, the system could be
very efficiently utilized. In addition, because coker gas oil
(CGO), which has been used B-C oil or DSL oil, could be used as a
raw material for producing high-quality lube base oil, the added
value of the feedstock could be increased, leading to an
improvement in economic efficiency.
TABLE-US-00004 TABLE 4 Light 100N Middle 150N Bottom UCO distillate
distillate distillate distillate product Specific gravity 0.8250
0.7390 0.8223 0.8284 0.8348 0.8423 Distillation, ASTM D1160, @760
mmHg, .degree. C. Initial boiling point 225 227 365 381 403 410 5%
372 368 388 400 426 440 10% 395 384 400 421 438 465 30% 416 402 422
444 466 478 50% 442 408 436 456 482 498 70% 471 416 452 477 503 518
90% 530 424 470 498 521 539 95% 572 431 479 510 543 579 Final
boiling point 613 444 494 531 574 613 Viscosity, cSt @40.degree. C.
12.9 17.62 @ 100.degree. C. 3.432 2.932 4.21 5.060 6.652 7.526
Viscosity index 149 112 148 Flash point (COC) .degree. C. 142 222
240 264 286 Pour point 42 33 39 45 51
EXAMPLE 3
[0048] Vacuum residue (VR), separated from atmospheric residue (AR)
as a feedstock in the first vacuum distillation unit (V1), was fed
into the solvent deasphalting unit (SDA) to suitably remove asphalt
and impurities therefrom. Herein, as the deasphalting solvent,
n-propane (N-C3) was used, and the deasphalted oil (DAO) was
produced at a yield of 39% at a pressure of 45.7 kg/cm.sup.2g and
an asphaltene separation temperature of 83.degree. C. The vacuum
gas oil (VGO) and the deasphalted oil (DAO), having the properties
shown in Table 2 above, were fed into the hydrotreating unit (HDT)
at a mixing volume ratio (VGO/DAO) of 3-5 and hydrocracked therein
under conditions of an LHSV of 3.01 hr.sup.-1, a pressure of 2488
psig, a temperature of 395.degree. C. and a hydrogen feed rate of
1125 Nm.sup.3/m.sup.3 using UF-210STARS (UOP) as a catalyst. The
hydrotreated oil was treated in the first hydrocracking unit (HDC1)
under conditions of an LHSV (Liquid Hourly Space Velocity) of a
1.208 hr.sup.-1, pressure of a 170 bar and temperature of a
405.degree. C. using UF-210STARS/DHC-32 (UOP) as a catalyst at a
hydrogen feed rate of 1250 Nm.sup.3/m.sup.3, and then passed
through a conventional separator and a plurality of fractionators
to recover some of diesel and light oil products, having a boiling
temperature of 370.degree. C. The hydrocracked oil was treated in
the second hydrocracking unit (HDC2) together with the recycled
UCO, described below, under conditions of an LHSV of 1.405
hr.sup.-1, a pressure of 170 bar and a temperature of 403.degree.
C. using a HC-215 catalyst (UOP) at a hydrogen feed rate of 1200
Nm.sup.3/m.sup.3. Then, the hydrocracked oil was passed through a
conventional separator and a plurality of fractionators to recover
diesel and light oil products, having a boiling point lower than
370.degree. C., thus obtaining unconverted oil (UCO) having the
properties shown in Table 5 below. The unconverted oil was fed into
the vacuum distillation unit (V2), in which it was subjected to
vacuum distillation under conditions of a top pressure of 70 mmHg,
a top temperature of 80.degree. C., a bottom pressure of 150 mmHg
and a bottom temperature of 345.degree. C., thus obtaining 17 LV %
light distillate, 30 LV % 100N distillate, 20 LV % middle
distillate, 4 LV % 150N distillate and 29 LV % bottom product.
[0049] Among them, only the 100N and 150N distillates were drawn
out as intermediate products in an amount of 34% (that is, 100N:
30% and 150N: 4%) based on the feed amount (the amount of UCO fed
into V2), and the remaining distillates (66%) were combined and
recycled to the second hydrocracking unit (HDC2). Thus, the 100N-
and 150N-grade feedstocks for high-quality lube base oil, having
high viscosity index and low volatility, as shown in Table 5 below,
were produced. Also, because 34% of the UCO was drawn out, oil
fractions, having a low poly-nuclear aromatic component content and
a high boiling point, could be removed, so that high-quality
unconverted oil could be secured, and restriction on feedstock oil
was relieved, and thus the added value of the product could be
increased, leading to an improvement in economic efficiency.
TABLE-US-00005 TABLE 5 150N Bottom UCO Light distillate 100N
distillate Middle distillate distillate product Specific gravity
0.8340 0.7390 0.8223 0.8284 0.8348 0.8423 Distillation, ASTM D1160,
@760 mmHg, .degree. C. Initial boiling point 225 227 365 381 403
410 5% 372 368 388 400 427 450 10% 395 384 400 421 443 472 30% 416
402 422 443 470 494 50% 458 408 436 455 493 518 70% 529 413 452 476
510 549 90% 562 420 470 497 530 595 95% 598 428 479 508 558 613
Final boiling point 699 440 494 529 589 699 Viscosity, cSt
@40.degree. C. 12.9 17.62 @ 100.degree. C. 3.432 2.918 4.21 5.05
6.80 9.082 Viscosity index 149 109 146 -- -- -- Flash point (COC)
.degree. C. 142 220 239 264 301 Pour point 42 33 39 45 53
COMPARATIVE EXAMPLE
[0050] Vacuum gas oil (VGO), separated from atmospheric residue
(AR) as a feedstock in the first vacuum distillation unit and
having the properties shown in Table 2, was treated in a
hydrotreating unit under conditions of an LHSV (Liquid Hourly Space
Velocity) of 3.429 hr.sup.-1, a pressure of 2397 psig and a
temperature of 385.8.degree. C. using UF-210STARS (UOP) as a
catalyst at a hydrogen feed rate of 842 Nm.sup.3/m.sup.3. The
hydrotreated oil was treated in a hydrocracking unit together with
the recycled UCO, described below, under conditions of an LHSV of
1.241 hr.sup.-1, a pressure of 2397 psig and a temperature of
395.2.degree. C. using a UF-210/HC-115/UF-100 catalyst (UOP) at a
hydrogen feed rate of 1180 Nm.sup.3/m.sup.3.
[0051] Then, the hydrocracked oil was passed through a conventional
separator and a plurality of fractionators to recover diesel and
light oil products, having a boiling point lower than 350.degree.
C., thus obtaining unconverted oil (UCO) having the properties
shown in Table 6. The unconverted oil was fed into a second vacuum
distillation unit and subjected to vacuum distillation therein
under conditions of a top pressure of 75 mmHg, a top temperature of
80.degree. C., a bottom pressure of 150 mmHg and a bottom
temperature of 325.degree. C., thus obtaining 32.5 LV % light
distillate, 34.8 LV % 100N distillate, 14.6 LV % middle product
distillate and 18.1 LV % bottom product 150N distillate.
[0052] Among them, only the 100N and 150N distillates were drawn
out as intermediate products in an amount of 52.9% (that is, 100N:
34.8% and 150N: 18.1%) based on the feed amount (the amount of the
UCO fed into the second vacuum distillation unit), and the
remaining distillates (47.1% of the feed amount) were combined and
recycled to a hydrocracking process. Thus, the 100N- and 150N-grade
feedstocks for high-quality lube base oil, having high viscosity
indexes and low volatilities, as shown in Table 6 below, were
produced.
TABLE-US-00006 TABLE 6 Middle 150N UCO Light distillate 100N
distillate distillate distillate Specific gravity 0.8271 0.8374
0.8388 0.8418 0.8449 Distillation, ASTM D1160, @760 mmHg, .degree.
C. Initial boiling point 276 338 401 412 437 5% 368 358 410 428 449
10% 398 362 412 434 453 30% 432 376 418 443 461 50% 457 383 424 459
475 70% 485 392 432 478 496 90% 537 403 447 503 531 95% 567 406 456
532 552 Final boiling point 590 414 471 533 562 Viscosity, cSt
@40.degree. C. 20 19.39 @ 100.degree. C. 4.428 2.978 4.305 5.056
6.787 Viscosity index 136 113 132 -- -- Flash point (COC) .degree.
C. 212 250 Pour point 33 39
[0053] Although the preferred embodiment of the present invention
has been described for illustrative purposes, those skilled in the
art will appreciate that various modifications, additions and
substitutions are possible, without departing from the scope and
spirit of the invention as disclosed in the accompanying
claims.
* * * * *