【Technical Field】
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims the benefit of priority
to Korean Patent Application No. 10-2021-0013214, filed on
January 29, 2021, the entire contents of which are
10 incorporated herein as a part of the specification.
Technical Field
The present invention relates to a method for
preparing synthesis gas, and more particularly, to a method
for preparing synthesis gas which allows pyrolyzed fuel oil
15 (PFO) in a naphtha cracking center (NCC) process to be used
as a raw material of a gasification process.
【Background Art】
Synthesis gas (syngas) is an artificially prepared gas,
20 unlike natural gas such as spontaneous gas, methane gas,
and ethane gas, which is released from land in oil fields
and coal mine areas, and is prepared by a gasification
process.
The gasification process is a process of converting a
2
hydrocarbon such as coal, petroleum, and biomass as a raw
material into synthesis gas mainly composed of hydrogen and
carbon monoxide by pyrolysis or a chemical reaction with a
gasifying agent such as oxygen, air, and water vapor. A
5 gasifying agent and a raw material are supplied to a
combustion chamber positioned at the foremost end of the
gasification process to produce synthesis gas by a
combustion process at a temperature of 700°C or higher, and
as a kinematic viscosity of the raw material supplied to
10 the combustion chamber is higher, a differential pressure
in the combustion chamber is increased or atomization is
not performed well, so that combustion performance is
deteriorated or a risk of explosion is increased due to
excessive oxygen.
15 Conventionally, as a raw material of a gasification
process for preparing synthesis gas using a liquid phase
hydrocarbon raw material, refinery residues, such as vacuum
residues (VR) and bunker-C oil, discharged from refinery
where crude oil is refined were mainly used. However,
20 since the refinery residue has a high kinematic viscosity,
a pretreatment such as a heat treatment, a diluent, or
water addition is required to be used as the raw material
of the gasification process, and since the refinery residue
has high contents of sulfur and nitrogen, production of
3
acidic gas such as hydrogen sulfide and ammonia is
increased during the gasification process, and thus, in
order to respond to tightened environmental regulations, a
need to replace the refinery residue with raw materials
5 having low contents of sulfur and nitrogen is raised.
Meanwhile, a pyrolysis fuel oil (PFO) which is a byproduct discharged from a naphtha cracking center (NCC)
process which is a process of preparing petrochemical basic
materials such as propylene is generally used as a fuel,
10 but since the sulfur content is a high level for using the
oil as a fuel without a pretreatment, the market is getting
smaller due to the environmental regulations and a
situation where sales are impossible in the future should
be prepared.
15 Accordingly, the present inventors completed the
present invention based on the idea that when the pyrolysis
fuel oil (PFO) of the naphtha cracking center (NCC) process
is used as the raw material of the gasification process,
greenhouse gas emissions may be reduced, operating costs of
20 the gasification process may be reduced, and process
efficiency may be improved, as compared with the case of
using the conventional refinery residue as a raw material.
【Disclosure】
4
【Technical Problem】
An object of the present invention is to provide a
method for preparing synthesis gas which may reduce
greenhouse gas emissions, reduce operating costs of a
5 gasification process, and improve process efficiency, as
compared with the case of a conventional refinery residue
as a raw material, by using the pyrolysis fuel oil (PFO) of
a naphtha cracking center (NCC) process as the raw material
of the gasification process.
10
【Technical Solution】
In one general aspect, a method for preparing
synthesis gas includes: supplying a PFO stream including a
pyrolysis fuel oil (PFO) and a PGO stream including a
15 pyrolysis gas oil (PGO) discharged from a naphtha cracking
center (NCC) process to a distillation column as a feed
stream (S10); and supplying a lower discharge stream from
the distillation column to a combustion chamber for a
gasification process (S20).
20
【Advantageous Effects】
According reducing a present invention, by using a
pyrolysis fuel oil (PFO) of the naphtha cracking center
(NCC) process as a raw material of a gasification process,
5
greenhouse gas emissions may be reduced, operating costs of
the gasification process may be reduced, and process
efficiency may be improved, as compared with the case of
using a conventional refinery residue as a raw material.
5
【Description of Drawings】
FIG. 1 is a process flow diagram for a method for
preparing synthesis gas according to an exemplary
embodiment of the present invention.
10 FIG. 2 is a process flow diagram for a method for
preparing synthesis gas according to Comparative Example 1
of the present invention.
FIG. 3 is a process flow diagram for a method for
preparing synthesis gas according to Comparative Example 2
15 of the present invention.
FIG. 4 is a process flow diagram for a method for
preparing synthesis gas according to Comparative Example 3
of the present invention.
20 【Best Mode】
The terms and words used in the description and claims
of the present invention are not to be construed limitedly
as having general or dictionary meanings but are to be
construed as having meanings and concepts meeting the
6
technical ideas of the present invention, based on a
principle that the inventors are able to appropriately
define the concepts of terms in order to describe their own
inventions in the best mode.
5 The term “stream” in the present invention may refer
to a fluid flow in a process, or may refer to a fluid
itself flowing in a pipe. Specifically, the “stream” may
refer to both a fluid itself flowing in a pipe connecting
each device and a fluid flow. In addition, the fluid may
10 refer to a gas or liquid, and a case in which a solid
substance is included in the fluid is not excluded.
In the present invention, the term “C#” in which “#”
is a positive integer represents all hydrocarbons having #
carbon atoms. Therefore, the term “C8” represents a
15 hydrocarbon compound having 8 carbon atoms. In addition,
the term “C#-” represents all hydrocarbon molecules having
# or less carbon atoms. Therefore, the term “C8-”
represents a mixture of hydrocarbons having 8 or less
carbon atoms. In addition, the term “C#+” represents all
20 hydrocarbon molecules having # or more carbon atoms.
Therefore, the term “C10+ hydrocarbon” represents a mixture
of hydrocarbons having 10 or more carbon atoms.
Hereinafter, the present invention will be described
in more detail with reference to the FIG. 1 for better
7
understanding of the present invention.
According to the present invention, a method for
preparing synthesis gas (syngas) is provided. Referring to
the following Table 1, the method for preparing synthesis
5 gas may include: supplying a PFO stream including a
pyrolysis fuel oil (PFO) and a PGO stream including a
pyrolysis gas oil (PGO) discharged from a naphtha cracking
center process (S1) to a distillation column 50 as a feed
stream (S10); and supplying a lower discharge stream from
10 the distillation column 50 to a combustion chamber for a
gasification process (S3) (S20).
The synthesis gas is an artificially prepared gas,
unlike natural gas such as spontaneous gas, methane gas,
and ethane gas, which is released from land in oil fields
15 and coal mine areas, and is prepared by a gasification
process.
The gasification process is a process of converting a
hydrocarbon such as coal, petroleum, and biomass as a raw
material into synthesis gas mainly composed of hydrogen and
20 carbon monoxide by pyrolysis or a chemical reaction with a
gasifying agent such as oxygen, air, and water vapor. A
gasifying agent and a raw material are supplied to a
combustion chamber positioned at the foremost end of the
gasification process to produce synthesis gas by a
8
combustion process at a temperature of 700°C or higher, and
as a kinematic viscosity of the raw material supplied to
the combustion chamber is higher, a differential pressure
in the combustion chamber is increased or atomization is
5 not performed well, so that combustion performance is
deteriorated or a risk of explosion is increased due to
excessive oxygen.
Conventionally, as a raw material of a gasification
process for preparing synthesis gas using a liquid phase
10 hydrocarbon raw material, refinery residues, such as vacuum
residues (VR) and bunker-C oil, discharged from refinery
where crude oil is refined were mainly used. However,
since the refinery residue has a high kinematic viscosity,
a pretreatment such as a heat treatment, a diluent, or
15 water addition is required to be used as the raw material
of the gasification process, and since the refinery residue
has high contents of sulfur and nitrogen, production of
acidic gas such as hydrogen sulfide and ammonia is
increased during the gasification process, and thus, in
20 order to respond to tightened environmental regulations, a
need to replace the refinery residue with raw materials
having low contents of sulfur and nitrogen is raised. For
example, among the refinery residues, a vacuum residue may
include about 3.5 wt％ of sulfur and about 3600 ppm of
9
nitrogen, and bunker C-oil may include about 4.5 wt％ of
sulfur.
Meanwhile, a pyrolysis fuel oil (PFO) discharged from
a naphtha cracking center process which is a process of
5 cracking naphtha to prepare petrochemical basic materials
such as ethylene and propylene is generally used as a fuel,
but since the sulfur content is a high level for using the
oil as a fuel without a pretreatment, the market is getting
smaller due to the environmental regulations and a
10 situation where sales are impossible in the future should
be prepared.
Therefore, in the present invention, it is intended
that greenhouse gas emissions may be reduced, operating
costs of a gasification process are reduced, and process
15 efficiency is improved, as compared with a case of using a
conventional refinery residue as a raw material, by using a
PFO stream including a pyrolysis fuel oil (PFO) discharged
from a naphtha cracking center process and a PGO stream
including a pyrolysis gas oil (PGO) as the raw material of
20 the gasification process.
According to an exemplary embodiment of the present
invention, the PFO stream including a pyrolysis fuel oil
(PFO) and the PGO stream including a pyrolysis gas oil
(PGO) may be discharged from a naphtha cracking center
10
process (S1).
Specifically, the naphtha cracking center process is a
process of cracking naphtha including paraffin, naphthene,
and aromatics to prepare olefins such as ethylene and
5 propylene used as a basic material for petrochemicals, and
may be largely composed of a cracking process, a quenching
process, a compression process, and a refining process.
The cracking process is a process of cracking naphtha
into hydrocarbons having fewer carbons in a cracking
10 furnace at 800°C or higher, and may discharge cracked gas
at a high temperature. Here, the naphtha may undergo a
preheating process from high pressure water vapor before
entering the cracking furnace, and then may be supplied to
the cracking furnace.
15 The quenching process is a process of cooling the
cracked gas at a high temperature, for suppressing a
polymerization reaction of a hydrocarbon in cracked gas at
a high temperature discharged from the cracking furnace,
and recovering waste heat and decreasing a heat load in a
20 subsequent process (compression process). Here, the
quenching process may include primary cooling of the
cracked gas at a high temperature with quench oil and
secondary cooling with quench water.
Specifically, after the primary cooling and before the
11
secondary cooling, the primarily cooled cracked gas may be
supplied to a gasoline fractionator to separate light oils
including hydrogen, methane, ethylene, propylene, and the
like, pyrolysis gasoline (PG), the pyrolysis fuel oil (PFO),
5 and the pyrolysis gas oil (PGO) therefrom. Thereafter, the
light oil may be transported to a subsequent compression
process.
The compression process may be a process of producing
compressed gas having a reduced volume by elevating
10 pressure of the light oil under high pressure for
economically separating and refining the light oil.
The refining process is a process of cooling the
compressed gas which is compressed with high pressure to a
cryogenic temperature and then separating the components in
15 stages by a boiling point difference, and may produce
hydrogen, ethylene, propylene, propane, C4 oils, pyrolysis
gasoline (PG), and the like.
As described above, from the quenching process of the
naphtha cracking center process (S1), a pyrolysis fuel oil
20 (PFO) and a pyrolysis gas oil (PGO) may be discharged. In
general, the pyrolysis fuel oil (PFO) includes about 0.1
wt％ of less of sulfur and about 20 ppm or less of nitrogen,
and when it is used as a fuel, sulfur oxides (Sox) and
nitrogen oxides (NOx) are discharged during a combustion
12
process, and thus, environmental issues may be raised.
Accordingly, in the present invention, the above
problems may be solved by pretreating a mixed oil stream in
which the pyrolysis fuel oil (PFO) and the pyrolysis gas
5 oil (PGO) are mixed and using the mixed oil stream as the
raw material of the gasification process, and furthermore,
greenhouse gas emissions may be reduced, operating costs of
the gasification process may be reduced, and process
efficiency may be improved, as compared with a case of
10 using a conventional refinery residue as the raw material
of the gasification process.
According to an exemplary embodiment of the present
invention, as described above, the PFO stream and the PGO
stream of the present invention may include the pyrolysis
15 fuel oil (PFO) and the pyrolysis gas oil (PGO) discharged
from the gasoline fractionator 10 of the naphtha cracking
center process (S1), respectively. As a specific example,
in the total number of stages of the gasoline fractionator
10 shown in FIG. 1, when a top stage is expressed as a
20 stage at 1％ and a bottom stage is expressed as a stage at
100％, the pyrolysis fuel oil (PFO) may be discharged from
a stage at 90％ or more, 95％ or more, or 95％ to 100％, and
the pyrolysis gas oil (PGO) may be discharged from a stage
at 10％ to 70％, 15％ to 65％, or 20％ to 60％, relative to
13
the total number of stages of the gasoline fractionator 10.
For example, when the total number of stages of the
gasoline fractionator 10 is 100, a top stage may be a first
stage and a bottom stage may be a 100th stage, and a stage
5 at 90％ or more of the total number of stages of the
gasoline fractionator 10 may refer to a 90th stage to a
100th stage of the gasoline fractionator 10.
According to an exemplary embodiment of the present
invention, as shown in FIG. 1, the PGO stream is discharged
10 from a side portion of the gasoline fractionator 10 of the
naphtha cracking center process (S1) and may be a lower
discharge stream which is discharged from a lower portion
of a first stripper 20 after supplying a side discharge
stream including the pyrolysis gas oil (PGO) to the first
15 stripper 20, and the PFO stream is discharged from a lower
portion of the gasoline fractionator 10 of the naphtha
cracking center process (S1) and may be a lower discharge
stream which is discharged from a lower portion of a second
stripper 30 after supplying a lower discharge stream
20 including the pyrolysis fuel oil (PFO) to the second
stripper 30.
The first stripper 20 and the second stripper 30 may
be devices in which a stripping process of separating and
removing gas or vapor dissolved in a liquid is performed,
14
and for example, may be performed by a method such as
direct contact, heating, and pressing by, for example,
steam, inert gas, or the like. As a specific example, the
side discharge stream from the gasoline fractionator 10 is
5 supplied to the first stripper 20, thereby refluxing an
upper discharge stream from the first stripper 20 including
a light fraction separated from the side discharge stream
from the gasoline fractionator 10 to the gasoline
fractionator 10. In addition, the lower discharge stream
10 from the gasoline fractionator 10 is supplied to the second
stripper 30, thereby refluxing an upper discharge stream
from the second stripper 30 including a light fraction
separated from the lower discharge stream from the gasoline
fractionator 10 to the gasoline fractionator 10.
15 According to an exemplary embodiment of the present
invention, the PGO stream may include 70 wt％ or more or 70
wt％ to 95 wt％ of C10 to C12 hydrocarbons, and the PFO
stream may include 70 wt％ or more or 70 wt％ to 98 wt％ of
C13+ hydrocarbons. For example, the PGO stream including
20 70 wt％ or more of C10 to C12 hydrocarbons may have a
kinematic viscosity at 40°C of 1 to 200 cSt and a flash
point of 10 to 50°C. In addition, for example, the PFO
stream including 70 wt％ or more of C13+ hydrocarbons may
have a kinematic viscosity at 40°C of 400 to 100,000 cSt
15
and a flash point of 70 to 200°C. As such, the PFO stream
including more heavy hydrocarbons than the PGO stream may
have a higher kinematic viscosity and a higher flash point
than the pyrolysis gas oil under the same temperature
5 conditions.
According to an exemplary embodiment of the present
invention, the PGO stream may have a boiling point of 200
to 288°C or 210 to 270°C, and the PFO stream may have a
boiling point of 289 to 550°C or 300 to 500°C.
10 The boiling points of the PGO stream and the PFO
stream may refer to the boiling points of the PGO stream
and the PFO stream in a bulk form, each composed of a
plurality of hydrocarbons. Here, the kind of hydrocarbons
included in the PGO stream and the kind of hydrocarbons
15 included in the PFO stream may be different from each other,
and some kinds may be the same. As a specific example, the
kind of hydrocarbons included in the PGO stream and the PFO
stream may be included as described above.
According to an exemplary embodiment of the present
20 invention, in step (S10), the PFO stream including a
pyrolysis fuel oil (PFO) discharged from the naphtha
cracking center process (S1) and the PGO stream including a
pyrolysis gas oil (PGO) may be supplied to a distillation
column 50 as a feed stream.
16
The feed stream supplied to the distillation column 50
includes both the PGO stream and the PFO stream, and may
include both heavies and lights. As such, the feed stream
including both the heavies and lights is supplied to the
5 distillation column 50, and by discharging an upper
discharge stream including lights from the upper portion of
the distillation column 50, a lower discharge stream having
a kinematic viscosity and a flash point which are adjusted
from the lower portion of the distillation column 50 may be
10 obtained. As a specific example, the PFO stream having a
higher content of heavies than the PGO stream may have
higher kinematic viscosity and flash point than the PGO
stream, and the PGO stream having a higher content of
lights than the PFO stream may have lower kinematic
15 viscosity and flash point than the PFO stream. In the feed
stream including both two conflicting streams, a stream
having desired kinematic viscosity and flash point may be
discharged from the lower portion of the distillation
column 50 by removing the lights, as described above.
20 According to an exemplary embodiment of the present
invention, a ratio of the flow rate of the upper discharge
stream from the distillation column 50 relative to the flow
rate of the feed stream supplied to the distillation column
50 (hereinafter, referred to as “distillation ratio of
17
distillation column 50”) may be 0.01 to 0.2, 0.01 to 0.15,
or 0.03 to 0.15. That is, in step (S10), the distillation
ratio of the distillation column 50 may be adjusted to 0.01
to 0.2, 0.01 to 0.15, or 0.03 to 0.15. Herein, the "flow
5 rate” may refer to a flow of a weight per unit hour. As a
specific example, the unit of the flow rate may be kg/h.
The distillation ratio of the distillation column 50
in the above range is adjusted by a flow rate adjustment
device (not shown) installed in a pipe in which the upper
10 discharge stream from the distillation column 50 is
transported, and the performance of the distillation column
50 may be performed by adjusting a reflux ratio of the
upper discharge stream of the distillation column 50, using
the distillation ratio and a second heat exchanger 51,
15 shown in the pretreatment process (S2) of FIG. 1. Here,
the reflux ratio may refer to a ratio of the flow rate of
the reflux stream to the flow rate of an outflow stream,
and as a specific example, the reflux ratio of the upper
discharge stream of the distillation column 50 may refer to,
20 when a part of the upper discharge stream from the
distillation column 50 is branched and refluxed to the
distillation column 50 as a reflux stream and the rest is
discharged as an outflow stream, a ratio of the flow rate
of the reflux stream to the flow rate of the outflow stream
18
(hereinafter, referred to as a “reflux ratio”). As a more
specific example, the reflux ratio may be 0.01 to 10, 0.1
to 7, or 0.15 to 5.
As described above, a gasifying agent and a raw
5 material are supplied to the combustion chamber (not shown)
positioned at the foremost end of the gasification process
(S3) to produce synthesis gas by a combustion process at a
temperature of 700°C or higher. Here, the reaction of
producing synthesis gas is performed under a high pressure
10 of 20 to 80 atm, and the raw material in the combustion
chamber should be moved at a high flow velocity of 2 to 40
m/s. Therefore, the raw material should be pumped at a
high flow velocity under a high pressure for the reaction
of producing synthesis gas, and when the kinematic
15 viscosity of the raw material supplied to the combustion
chamber is higher than an appropriate range, a high-priced
pump should be used due to reduced pumpability or costs are
increased due to increased energy consumption, and pumping
to desired conditions may be impossible.

【Claim 1】
A method for preparing synthesis gas, the method
comprising:
5 supplying a PFO stream including a pyrolysis fuel oil
(PFO) and a PGO stream including a pyrolysis gas oil (PGO)
discharged from a naphtha cracking center (NCC) process to
a distillation column as a feed stream (S10); and
supplying a lower discharge stream from the
10 distillation column to a combustion chamber for a
gasification process (S20).
【Claim 2】
The method for preparing synthesis gas of claim 1,
wherein a ratio of a flow rate of an upper discharge stream
15 from the distillation column to a flow rate of the feed
stream supplied to the distillation column is 0.01 to 0.2.
【Claim 3】
The method for preparing synthesis gas of claim 2,
wherein the ratio of the flow rate of the upper discharge
20 stream from the distillation column to the flow rate of the
feed stream supplied to the distillation column is 0.03 to
0.15.
【Claim 4】
The method for preparing synthesis gas of claim 1,
43
wherein the lower discharge stream from the
distillation column has a kinematic viscosity at the time
of supply to the combustion chamber of 300 cSt or less, and
the lower discharge stream has a flash point higher
5 than a temperature at the time of supply to the combustion
chamber by 25°C or more.
【Claim 5】
The method for preparing synthesis gas of claim 4,
wherein the lower discharge stream from the
10 distillation column has the kinematic viscosity at the time
of supply to the combustion chamber of 1 cSt to 300 cSt,
and
the lower discharge stream has the flash point higher
than the temperature at the time of supply to the
15 combustion chamber by 25°C to 150°C.
【Claim 6】
The method for preparing synthesis gas of claim 1,
wherein a temperature of the lower discharge stream from
the distillation column at the time of supply to the
20 combustion chamber is 20°C to 90°C.
【Claim 7】
The method for preparing synthesis gas of claim 1,
wherein the feed stream is a mixed oil stream in which the
PFO stream and the PGO stream are mixed.
44
【Claim 8】
The method for preparing synthesis gas of claim 7,
wherein the lower discharge stream from the distillation
column passes through a fourth heat exchanger before being
5 supplied to the combustion chamber.
【Claim 9】
The method for preparing synthesis gas of claim 7,
wherein the mixed oil stream is supplied to a stage at 10％
to 70％ relative to the total number of stages of the
10 distillation column.
【Claim 10】
The method for preparing synthesis gas of claim 1,
wherein the PGO stream includes 70 wt％ or more of C10
to C12 hydrocarbons, and
15 the PFO stream includes 70 wt％ or more of C13+
hydrocarbons.
【Claim 11】
The method for preparing synthesis gas of claim 1,
wherein the PGO stream has a flash point of 10 to 50°C,
20 and
the PFO stream has a flash point of 70 to 200°C.
【Claim 12】
The method for preparing synthesis gas of claim 1,
wherein the PGO stream has a kinematic viscosity at
45
40°C of 1 to 200 cSt, and
the PFO stream has a kinematic viscosity at 40°C of
400 to 100,000 cSt.
【Claim 13】
5 The method for preparing synthesis gas of claim 1,
wherein the PGO stream is a lower discharge stream
discharged from a lower portion of a first stripper after
supplying a side discharge stream discharged from a side
portion of a gasoline fractionator of the naphtha cracking
10 center process to the first stripper, and
the PFO stream is a lower discharge stream discharged
from a lower portion of a second stripper after supplying a
lower discharge stream discharged from a lower portion of
the gasoline fractionator of the naphtha cracking center
15 process to the second stripper.
【Claim 14】
The method for preparing synthesis gas of claim 13,
wherein the lower discharge stream from the gasoline
fractionator is discharged from a stage at 90％ or more
20 relative to the total number of stages of the gasoline
fractionator, and
the side discharge stream from the gasoline
fractionator is discharged from a stage at 10％ to 70％
relative to the total number of stages of the gasoline
46
fractionator.
【Claim 15】
The method for preparing synthetsis gas of claim 1,
wherein the upper discharge stream from the
5 distillation column has a content of C10+ hydrocarbons of
15 wt％ or less and a content of C8- hydrocarbons of 70
wt％ or more, and
the lower discharge stream from the distillation
column has a content of C10+ hydrocarbons of 80 wt％ or
10 more and a content of C8- hydrocarbons of 5 wt％ or less.
【Claim 16】
The method for preparing synthesis gas of claim 1,
wherein a part of the upper discharge stream from the
distillation column is branched and refluxed to the
15 distillation column as a reflux stream, and the rest is
discharged as an outflow stream, and
a ratio (reflux ratio) of a flow rate of the reflux
stream to a flow rate of the outflow stream is 0.01 to 10.
【Claim 17】
20 The method for preparing synthesis gas of claim 1,
wherein the synthesis gas includes carbon monoxide and
hydrogen.