METHOD FOR PREPARING SYNTHESIS GAS

Abstract

A method for preparing synthesis gas is provided, and more particularly, a method for preparing synthesis gas comprising: supplying a cracked gas stream discharged from a cracking furnace of a naphtha cracking center (NCC) process to a gasoline fractionator, separating a side discharge stream from the gasoline fractionator using a first separator, and separating a bottom discharge stream from the gasoline fractionator using a second separator, wherein a mixed oil stream of a PGO stream and a PFO stream formed by controlling a flow rate of each stream are used.

Description

METHOD FOR PREPARING SYNTHESIS GAS [Technical Field] The present invention relates to a method for preparing synthesis gas, and more particularly, to a method for preparing synthesis gas that allows pyrolyzed fuel oil (PFO) from a naphtha cracking center (NCC) process to be used as a feedstock for a gasification process. [Precedent Technique] Synthesis gas (syngas) is an artificially prepared gas, distinct from natural gas such as spontaneous gas, methane gas, and ethane gas, which is released from the earth in oil fields and coal mining areas, and is prepared by a gasification process. The gasification process is a method for converting a hydrocarbon, such as coal, petroleum, or biomass, into synthesis gas, primarily composed of oxygen and carbon monoxide, through pyrolysis or a chemical reaction with a gasifying agent, such as oxygen, air, or steam. A gasifying agent and a feedstock are supplied to a combustion chamber located at the front end of the gasification process to produce synthesis gas through combustion at a temperature of 700°C or higher, and with a kinematic viscosity of the supplied feedstock σ. If the combustion chamber is too high, the differential pressure in the combustion chamber increases, or atomization is not performed well, combustion performance deteriorates, or the risk of explosion increases due to excessive oxygen. Conventionally, as a feedstock for a gasification process to prepare synthesis gas using a liquid-phase hydrocarbon feedstock, mainly refinery wastes, such as vacuum waste (VR) and bunker-C oil, discharged from the refinery where crude oil is refined, are used.However, since refinery residue has a high kinematic viscosity, pretreatment such as heat treatment, diluent, or water addition is required before it can be used as the feedstock for the gasification process. Furthermore, because refinery residue has high sulfur and nitrogen content, the production of acidic gases such as hydrogen sulfide and ammonia increases during the gasification process. Therefore, in order to meet stringent environmental regulations, there is a need to replace refinery residue with feedstocks that have low sulfur and nitrogen content. Meanwhile, pyrolysis fuel oil (PFO), a byproduct discharged from a naphtha cracking center (NCC) process for preparing petrochemical raw materials such as propylene, is commonly used as a fuel. However, because its sulfur content is too high for untreated fuel and its carbon dioxide (CO2) emission coefficient is too high, the market is shrinking due to environmental regulations, and preparations are underway for a future where sales are impossible. Thus, although a method was considered to replace the raw material of a gasification process with pyrolysis fuel oil, in order to replace the raw material of a gasification process with pyrolysis fuel oil, the pyrolysis fuel oil is heated to decrease a kinematic viscosity, but the kinematic viscosity of the pyrolysis fuel oil is high, so it was difficult to meet the kinematic viscosity conditions for use as the raw material of the gasification process at a flash point or lower. Accordingly, the present inventors completed the present invention based on the idea that when pyrolysis fuel oil (PFO) from the naphtha cracking center (NCC) process is used as the feedstock for the gasification process, greenhouse gas emissions can be reduced, the operating costs of the gasification process can be reduced, and the efficiency of the process can be improved, as compared to the case of using conventional refinery residue as a feedstock. [Description J] [Technical Problem] An objective of the present invention is to provide a method for preparing synthesis gas that can reduce greenhouse gas emissions, lower the operating costs of a gasification process, and improve process efficiency, as compared to using conventional refinery residue as a feedstock, by using pyrolysis fuel oil (PFO) from a naphtha cracking center (NCC) process as the feedstock for the gasification process. [Technical Solution] In a general aspect, a method for preparing synthesis gas includes: supplying a cracked gas stream discharged from a cracking furnace of a naphtha cracking center (NCC) process to a gasoline fractionator; supplying a side discharge stream from the gasoline fractionator to a first separator; operating the first separator under conditions in which a first steam stream is supplied; and separating a PGO stream that includes a pyrolysis gas oil (PGO) from a lower portion; σ a dividing a lower discharge stream from the gasoline fractionator into a reflux stream and a supply stream, supplying the supply stream to a second operator, and operating the second separator under conditions in which a second vapor stream is supplied, and separating a PFO stream that includes a pyrolysis fuel oil (PFO) from a lower portion; and supplying a mixed oil stream from the PFO stream and the PFO stream to a combustion chamber for a gasification process, wherein the following equations 1 and 2 are satisfied: [Equation 1] G > 0.5, G = GS / GF [Equation 2] F < 0.035, F = FS / FF where GF is the flow rate of the gasoline fractionator side discharge stream, GS is the flow rate of the first steam stream, FF is the flow rate of the supply stream, and FS is the flow rate of the second steam stream. [Advantageous Effects] According to the present invention, by using a pyrolysis fuel oil (PFO) from the naphtha cracking center (NCC) process as a feedstock for a gasification process, greenhouse gas emissions can be reduced, the operating costs of the gasification process can be reduced, and the efficiency of the process can be improved, as compared to the case of using a conventional refinery residue as a feedstock. [Description of the Drawings] FIG. 1 is a process flow diagram for a method for preparing synthesis gas according to an exemplary embodiment of the present invention. [Best Mode] The terms and words used in the description and claims of the present invention are not to be considered limited to having general or dictionary meanings, but are to be considered to have meanings and concepts that fulfill the technical ideas of the present invention, based on the principle that inventors are able to appropriately define the concepts of terms in order to best describe their own inventions. The term "stream" in the present invention may refer to a fluid flow in a process, or it may refer to a fluid that flows on its own in a tube. Specifically, "stream" may refer to both a fluid that flows on its own in a tube connecting each device and a fluid flow. Furthermore, "fluid" may refer to a gas or a liquid, and in one instance, a solid substance is included within the fluid. σ a In the present invention, the term C#, where C is a positive integer, represents all hydrocarbons having # carbon atoms. Therefore, the term C8 represents a hydrocarbon compound having 8 carbon atoms. Furthermore, the term C#- represents all hydrocarbon molecules having # or fewer carbon atoms. Therefore, the term C8- represents a mixture of hydrocarbons having 8 or fewer carbon atoms. Additionally, the term C#+ represents all hydrocarbon molecules having # or more carbon atoms. Therefore, the term C10+ represents a mixture of hydrocarbons having 10 or more carbon atoms. The present invention will then be described in more detail with reference to FIG. 1 for a better understanding of the present invention. According to the present invention, a method for preparing synthesis gas (syngas) is provided. The method for preparing synthesis gas may include: supplying a cracked gas stream discharged from a cracking furnace of a naphtha cracking center (SI) process to a gasoline fractionator 10; supplying a side discharge stream from the gasoline fractionator 10 to a first separator 20; operating the first separator under conditions in which a first vapor stream is supplied; and separating a PGO stream that includes a pyrolysis gas oil (PGO) from a lower portion.dividing a lower discharge stream from the gasoline fractionator 10 into a reflux stream and a supply stream, supplying the supply stream to a second separator 30, and operating the second separator 30 under conditions in which a second vapor stream is supplied, and separating a PFO stream that includes a pyrolysis fuel oil (PFO) from a lower portion; and supplying a mixed oil stream from the PFO stream and the PFO stream to a combustion chamber for a gasification process (S2). Synthetic gas is an artificially prepared gas, distinct from natural gas such as spontaneous gas, methane gas, and ethane gas, which is released from the earth in oil fields and coal mining areas, and is prepared by a gasification process. The gasification process is a process for converting a hydrocarbon, such as coal, petroleum, or biomass, into synthesis gas, which primarily consists of oxygen and carbon monoxide, through pyrolysis or a chemical reaction with a gasifying agent such as oxygen, air, or steam. Specifically, the synthesis gas in the present invention may include hydrogen and carbon monoxide.A gasifying agent and a feedstock are supplied to a combustion chamber positioned at the forward 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 feedstock supplied to the combustion chamber is higher, a differential pressure in the combustion chamber increases or atomization is not performed well, so that combustion performance deteriorates or a risk of explosion is increased due to excessive oxygen. Conventionally, as a feedstock for a gasification process to prepare synthesis gas using a liquid-phase hydrocarbon feedstock, mainly refinery waste, such as vacuum waste (VR) and bunker-C oil, discharged from the refinery where crude oil is refined, was used.However, because refinery residue has a high kinematic viscosity, pretreatment such as heat treatment, dilution, or water addition is required before it can be used as a feedstock in the gasification process. Furthermore, because refinery residue has high sulfur and nitrogen content, the production of acidic gases such as hydrogen sulfide and ammonia increases during gasification. Therefore, to meet stringent environmental regulations, there is a need to replace refinery residue with feedstocks that have low sulfur and nitrogen content. For example, among refinery residues, vacuum residue can contain approximately 3.5% sulfur and approximately 3600 ppm nitrogen, and bunker oil C can contain approximately 4.5% sulfur. Meanwhile, pyrolysis fuel oil (PFO) discharged from a naphtha cracking center process, which is a process for cracking naphtha to prepare basic petrochemical materials such as ethylene and propylene, is generally used as a fuel. However, since the sulfur content is too high to use the oil as a fuel without pretreatment, the market is shrinking due to environmental regulations, and a situation where sales are impossible in the future must be prepared. Thus, although a method was considered to replace the raw material of the gasification process with pyrolysis fuel oil, in order to use pyrolysis fuel oil as the raw material of the gasification process, the pyrolysis fuel oil is heated to decrease a kinematic viscosity, but the kinematic viscosity of pyrolysis fuel oil is high, so it was difficult to meet the kinematic viscosity conditions for use as the raw material of the gasification process at a flash point or lower. Therefore, in the present invention, it is proposed that greenhouse gas emissions can be reduced, the operating costs of a gasification process can be reduced, and the efficiency of the process can be improved, as compared to a case of using a conventional refinery residue as a feedstock, by developing a pretreatment process (S2) to use a PFO stream that includes a pyrolysis fuel oil (PFO) and a PGO stream that includes a pyrolysis gas oil (PGO) discharged from a naphtha cracking center process as the feedstock for 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) can be discharged from a naphtha cracking center (SI) process. Specifically, the naphtha cracking center process is a process for cracking naphtha, including paraffin, naphthenes, and aromatics, to prepare olefins such as ethylene and propylene used as a raw material for petrochemicals, and may be largely composed of a cracking process, a rapid cooling process, a compression process, and a refining process. The cracking process is a method for breaking down naphtha into hydrocarbons with lower carbon content in a cracking furnace at 800°C or higher, and it can discharge cracked gas at a high temperature. In this process, the naphtha may undergo a high-pressure steam preheating process before entering the cracking furnace, and then it can be fed into the furnace. The rapid cooling process is used to cool cracked gas at a high temperature to suppress the polymerization reaction of a hydrocarbon in the high-temperature cracked gas discharged from the cracking furnace, and to recover waste heat and reduce the heat load in a subsequent process (compression process). This rapid cooling process may include primary cooling of the high-temperature cracked gas with rapid cooling oil and secondary cooling with rapid cooling water. Specifically, in primary cooling, the cracked gas can be fed to a gasoline fractionator to separate light oils, including hydrogen, methane, ethylene, propylene, and the like, from crude pyrolysis gasoline (RPG), pyrolysis fuel oil (PFO), and pyrolysis gas oil (PGO). The light oil can then be conveyed in a subsequent compression process. The compression process can be a process to produce compressed gas that has a reduced volume by raising the pressure of light oil under high pressure to economically separate and refine the light oil. The refining process is a process to cool compressed gas that is compressed at high pressure to a cryogenic temperature and then separate the components in stages by a difference in boiling point, and can produce hydrogen, ethylene, propylene, propane, O4 oils, crude pyrolysis gasoline (RPG) and the like. As described above, the rapid cooling process of the naphtha cracking center (SI) can produce pyrolysis fuel oil (PFO) and pyrolysis gas oil (PGO). Pyrolysis fuel oil (PFO) generally contains approximately 0.1% by weight or less of sulfur and approximately 20 ppm or less of nitrogen. When used as a fuel, sulfur oxides (SOx) and nitrogen oxides (NOx) are released during combustion, potentially increasing environmental impact. However, when PFO is used as the feedstock for synthesis gas, the emission level is low. Therefore, in the present invention, the above problems can be solved by using the pyrolysis fuel oil (PFO) and pyrolysis gas oil (PGO) discharged while controlling the process conditions in the naphtha cracking center (SI) process as the feedstock for the gasification process to prepare synthesis gas, and furthermore, gas emissions can be reduced > you In greenhouse NCNN, the operating costs of the gasification process can be reduced and the efficiency of the process can be improved, as compared to a case of using conventional retinal waste as the raw material for 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 fuel oil (PFO) and the pyrolysis gas oil (PGO) discharged from the gasoline fractionator 10 of the naphtha cracking center process (SI), respectively. As a specific example, with respect to the total number of stages of gasoline fractionator 10, when an upper stage is expressed as a 1% stage and a bottom stage is expressed as a 100% stage, pyrolysis fuel oil (PFO) can be discharged from a 90% or higher stage, a 95% or higher stage, or a 95% to 100% stage relative to the total number of stages of gasoline fractionator 10. In addition, pyrolysis gas oil (PGO) can be discharged from a 10% to 70% stage, a 15% to 65% stage, or a 20% to 60% stage.For example, when the total number of stages of the gasoline fractionator 10 is 100, an upper stage may be a first stage and a bottom stage may be a 100th stage, and a stage of 90% or more of the total number of stages of the gasoline fractionator 10 may refer to. 90astage a 100astage of the gasoline fractionator 10. According to an exemplary embodiment of the present invention, the PGO stream is discharged from a side portion of the gasoline fractionator 10 of the naphtha cracking center (SI) process, and the side discharge stream, which includes the pyrolysis gas oil (PGO), is fed to a first separator 20 and then discharged from a lower portion of the first separator 20 as a bottom discharge stream. Herein, the temperature of the side discharge stream from the gasoline fractionator 10 can be 120°C to 180°C, 120°C to 175°C, or 130°C to 175°C. The operating temperature of the first separator 20 can be 110°C to 200°C, 115°C to 190°C, or 120°C to 185°C, and the operating pressure of the same can be 0.5 kg / cm2g to 3 kg / cm2g, 0.7 kg / cm2g to 2.5 kg / cm2g, or 0.8 kg / cm2g to 2 kg / cm2g. The first separator 20 can be operated under the conditions in which the first steam stream is supplied. For example, the pressure of the first steam stream can be 2 kg / cm² to 20 kg / cm², 2.5 kg / cm² to 18 kg / cm², or 3 kg / cm² to 16 kg / cm². When the first separator 20 is operated under the conditions described above, effective light oils from NCC, including RPG and similar oils, can be recovered, and light oils in the PGO stream can also be removed to increase the flash point of the PGO stream. Additionally, the PFO stream is discharged from a lower portion of the gasoline fractionator 10 of the naphtha cracking center process (SI), and the lower discharge stream which includes the pyrolysis fuel oil (PFO) is fed to a second separator 30 and then discharged from a lower portion of the second separator 30 as a lower discharge stream. The operating temperature of the second separator 30 can be 150°C to 350°C, 170°C to 330°C, or 180°C to 320°C, and the operating pressure of the same can be 0.6 kg / cm2g to 3.1 kg / cm2g, 0.8 kg / cm2g to 2.6 kg / cm2g, or 0.8 kg / cm2g to 2 kg / cm2g. The second separator 30 can be operated under the same conditions as the second steam stream. For example, the pressure of the second steam stream can be 2 kg / cm² to 20 kg / cm², 2.5 kg / cm² to 18 kg / cm², or 3 kg / cm² to 16 kg / cm². When the second separator 30 is operated under the conditions described above, effective light oils from NCC, including RPG and similar oils, can be recovered, and light oils from the PFO stream can also be removed to increase the flash point of the PFO stream. The first separator 20 and the second separator 30 can be devices in which a process is carried out to separate and remove gas or vapor dissolved in a liquid, and, for example, it can be done by a method such as σ through direct contact, heating, and pressure by means of, for example, steam, inert gas, cracked grease, or the like. For example, the side discharge stream from gasoline fractionator 10 is supplied to the first separator 20, thereby refluxing an upper discharge stream that includes light oil from the first separator 20 separated from the side discharge stream of gasoline fractionator 10 to gasoline fractionator 10, and discharging the PGO stream from the lower portion. In addition, the lower discharge stream from gasoline fractionator 10 is supplied to the second separator 30, thereby subjecting to reflux an upper discharge stream that includes light oil from the second separator 30 separated from the lower discharge stream of gasoline fractionator 10 to gasoline fractionator 10, and discharging the PFO stream from the lower portion. Here, the lower discharge stream from gasoline fractionator 10 can be divided into a reflux stream and a supply stream. The reflux stream can combine with the cracked gas stream and be supplied to gasoline fractionator 10, and the supply stream can be supplied to the second separator 30. Here, the temperature of the lower discharge stream from gasoline fractionator 10 can be 150°C to 300°C, 170°C to 270°C, or 180°C to 250°C. σ a For example, the ratio of the supply stream flow rate to the reflux stream and bottom discharge stream flow rate of the gasoline fractionator might be 0.0002 to 0.008, 0.0006 to 0.007, or 0.0014 to 0.006. Herein, flow rate may refer to a flow of one unit weight per hour. As a specific example, the unit of flow rate might be kg / h. According to an exemplary embodiment of the present invention, the method for preparing the synthesis gas can be operated such that the following Equations 1 and 2 are satisfied: [Equation 1] G > 0.5, G = GS / GF [Equation 2] F < 0.035, F = FS / FF where GF is a flow rate of the side discharge stream of the gasoline fractionator 10, GS is a flow rate of the first steam stream, FF is a flow rate of the supply stream, and FS is a flow rate of the second steam stream. Equation 1 can represent the ratio of the flow rate of the first vapor stream to the flow rate of the side discharge stream of the gasoline fractionator 10. For example, G can be 0.5 or more, 0.5 to 2, 0.5 to 1.5, or 0.5 to 1. When G is controlled within the range, σ The C6- hydrocarbon content included in the PGO stream can be controlled to 0.1% by weight or less. Specifically, C6- hydrocarbons are very light oils that are highly likely to be mixed into the PGO stream and have an extremely low flash point, thus lowering the flash point of the PGO stream. In this regard, in the present invention, G is controlled to 0.5 or more, thereby reducing the C6- hydrocarbon content in the PGO stream to 0.1% by weight or less, thereby raising the flash point of the PGO stream and further adjusting the flash point of the mixed oil stream, which is high. Equation 2 can represent the ratio of the flow rate of the second vapor stream to the flow rate of the feed stream supplied to the second separator 30 in the lower discharge stream of the gasoline fractionator 10. For example, F can be 0.035 or less, 0.001 to 0.035, 0.005 to 0.035, or 0.01 to 0.03. When F is controlled within the above range, the C8 and C9 hydrocarbon content included in the PFO stream can be controlled to 3 wt% or more. Specifically, C8 and C9 hydrocarbons, which have a relatively high flash point but low viscosity, can decrease the viscosity of the PFO stream and, furthermore, adjust the viscosity to be low while maintaining the flash point of the blended oil stream. As a specific example, the first separator 20 and the second separator 30 are operated under conditions that satisfy Equations 1 and 2, in order to control the compositions of the PGO stream and the PFO stream, and in this way, the flash point of the mixed oil stream of the PGO stream and the PFO stream can be raised and its viscosity can be decreased. When the mixed oil stream from the PGO and PFO streams is used as a simple fuel, as before, the operation is performed so that the effective NCC light oils in the PGO and PFO streams are recovered as much as possible, or the amount of energy used is minimized, and specifications such as flash point and kinematic viscosity must be met. Specifically, when the first separator 20 and the second separator 30 are operated so that the effective NCC light oils in the PGO and PFO streams are recovered as much as possible, both the flash point and kinematic viscosity of the mixed oil stream increase, and when the operation is performed so that the amount of energy used is minimized, both the flash point and kinematic viscosity decrease.As such, when the first separator 20 and the second separator 30 are operated under common operating conditions, the flash point and kinematic viscosity of the mixed oil stream are adjusted in the same direction, so that the kinematic viscosity and flash point conditions for the use of the synthesis gas feedstock are not implemented. In this respect, in the present invention, in order to use the mixed oil stream from the PGO and PFO streams as the feedstock for synthesis gas, the physical properties of kinematic viscosity and flash point become important. Specifically, a method for raising the flash point while lowering the kinematic viscosity of the mixed oil stream is provided. Specifically, the first separator 20 and the second separator 30 are operated under conditions that satisfy Equations 1 and 2. The light oil content in each of the PGO and PFO streams is adjusted to lower the kinematic viscosity of the mixed oil stream and also to raise the flash point, thereby controlling the kinematic viscosity and flash point to an appropriate level for use as the feedstock for the gasification process.According to an exemplary embodiment of the present invention, the PGO stream may include 0.1 wt.% or less, or 0 wt.% to 0.1 wt.% of C6- hydrocarbons and 72 wt.% or more, 72 wt.% to 96 wt.%, or 76 wt.% to 90 wt.% of C13+ hydrocarbons, and the PFO stream may include 3 wt.% or more, or 3 wt.% to 15 wt.% of C8 and C9 hydrocarbons and 67 wt.% or more, 67 wt.% to 93 wt.%, or 74 wt.% to 90 wt.% of C13+ hydrocarbons. For example, the PGO stream may have a kinematic viscosity at 40°C of 5 to 220 cSt and a flash point of 40 to 70°C. Furthermore, for example, the PFO stream may have a kinematic viscosity at 40°C of 250 to 70,000 cSt and a flash point of 65 to 190°C.As such, the PFO stream that includes heavier hydrocarbons than the PGO stream may have a higher kinematic viscosity and a higher flash point than pyrolysis gas oil under temperature conditions. For example, C6 hydrocarbons may include one or more selected from the group consisting of ethylene, propylene, butane, pentane, pentene, pentadiene, methylbutene, cyclopentane, cyclopentene, hexane, cyclohexane, and benzene. As a specific example, C6 hydrocarbons may include all the classes of C6 hydrocarbons described above, but are not limited to them. Furthermore, for example, C8 and C9 hydrocarbons may include one or more selected from the group consisting of n-octane, n-nonane, ethylbenzene, m-xylene, o-xylene, p-xylene, styrene, ethylcyclohexane, dimethylcyclohexane, dimethylcyclohexadiene, isopropylbenzene, n-propylbenzene, n-propylcyclohexane, indene, and indane. As a specific example, C8 and C9 hydrocarbons may include, but are not limited to, all the classes of C8 and C9 hydrocarbons described above. According to an exemplary embodiment of the present invention, the PGO stream can have a boiling point of 210°C to 300°C or 220°C to 290°C, and the PFO stream can have a boiling point of 270°C to 530°C or 275°C to 500°C. The boiling points of the PGO stream and the PFO stream can refer to the boiling points of the PGO and PFO streams in bulk form, each composed of a plurality of hydrocarbons. Here, the types of hydrocarbons included in the PGO stream and the types of hydrocarbons included in the PFO stream can be different, and some types can be the same. As a specific example, the types of hydrocarbons included in the PGO stream and the PFO stream can be as described above. According to an exemplary embodiment of the present invention, the mixed oil stream from the PGO stream and the PFO stream can be supplied to the combustion chamber for the gasification process (S2). As described above, a gasifying agent and a feedstock are supplied to the combustion chamber (not shown) located at the forward end of the gasification process (S2) to produce synthesis gas through combustion at a temperature of 700 °C or higher. Here, the reaction to produce synthesis gas is carried out under a high pressure of 20 to 80 atm, and the feedstock in the combustion chamber must be moved at a high flow rate of 2 to 40 m / s. Therefore, the feedstock must be pumped at a high flow rate under high pressure for the reaction to produce synthesis gas. When the kinematic viscosity of the feedstock supplied to the combustion chamber is higher than an appropriate range, a high-cost pump must be used due to the reduced pumpability, or costs increase due to increased energy consumption, and pumping to the desired conditions may become impossible.Furthermore, because the pumping is not performed correctly, the raw material cannot be supplied uniformly to the combustion chamber. Additionally, because a differential pressure in the combustion chamber increases, or because uniform atomization of the raw material is not achieved due to its small particle size, combustion performance can deteriorate, productivity can decrease, a large quantity of gasifying agent is required, and the risk of explosion increases due to excessive oxygen.Here, an appropriate range of kinematic viscosity may be a little different depending on the type of synthesis gas, the conditions of the combustion process carried out in the combustion chamber, and the like, but generally, a lower kinematic viscosity of the feedstock is better in terms of cost, productivity, and safety, at a given feedstock temperature at the time of delivery to the combustion chamber in the gasification process (S2), and it is preferred that the kinematic viscosity be in the range of 300 cSt or less and within the range, a rise in differential pressure in the combustion chamber is prevented, and atomization is well carried out to improve combustion performance. Furthermore, when the flash point of the raw material supplied to the combustion chamber is less than an appropriate range, flame may occur in a burner before the combustion reaction occurs, a risk of explosion is present due to a flashback fire phenomenon of the flame in the combustion chamber, and the refractories in the combustion chamber may be damaged.Here, an appropriate flash point range can be varied depending on the type of synthesis gas being synthesized, the combustion process conditions in the combustion chamber, and the like, but generally, it is preferred that the flash point of the feedstock be in a range of being higher than the temperature of the feedstock at the time of supply to the combustion chamber in the gasification process (S3) by 25°C or more, and within the range, a loss of feedstock, a risk of explosion, and damage to the refractories in the combustion chamber can be prevented. Accordingly, in the present invention, the operating conditions of the first separator 20 and the second separator 30 are controlled, in order to adjust the compositions of the PGO stream and the PFO stream to control the composition of the mixed oil stream from the PGO stream and the PFO stream and to use the mixed oil stream as the raw material supplied to the combustion chamber in the gasification process (S2), and in this way, the temperature of the mixed oil stream at the time of supply to the combustion chamber, the kinematic viscosity and the flash point of the mixed oil stream can be controlled at appropriate intervals. According to an exemplary embodiment of the present invention, the temperature of the mixed oil stream at the time of delivery to the combustion chamber may be lower than the flash point of the mixed oil stream at the time of delivery to the combustion chamber > you NCNN by 25°C or more and can be a temperature at which the kinematic viscosity is 300 cSt or less. That is, the mixed oil stream can have a kinematic viscosity at the time of delivery to the combustion chamber of 300 cSt or less, or 1 cSt to 300 cSt, and the flash point of the mixed oil stream can be higher than the temperature at the time of delivery to the combustion chamber by 25°C or more, or by 25°C to 150°C. Here, the temperature of the mixed oil stream at the time of delivery to the combustion chamber can be 20°C to 90°C or 30°C to 80°C.The kinematic viscosity of the mixed oil stream at the temperature at the time of supply to the combustion chamber within the range may be 300 cSt or less and may also be less than the flash point by 25°C or more, and in this way, it can satisfy the process operating conditions for use as a feedstock for the gasification process (S2). According to an exemplary embodiment of the present invention, a flow rate ratio of the PGO stream to the mixed oil stream (hereafter referred to as a PGO stream flow rate ratio) may be 0.35 to 0.7, 0.35 to 0.65, or 0.4 to 0.6. The mixed oil stream has controlled contents of low viscosity / low flash point material and low viscosity / high flash point material in the PGO stream flow rate ratio within the range, thereby satisfying the kinematic viscosity and flash point conditions for use as the feedstock for the gasification process (S2). According to an exemplary embodiment of the present invention, the blended oil stream may include 3% by weight or less, 0.1% to 2.5% by weight, or 0.001% by weight to 2% by weight of C7- hydrocarbons and 80% by weight or more, 80% by weight to 97% by weight, or 84% by weight to 95% by weight of C10+ hydrocarbons. For example, C7- hydrocarbons may include one or more selected from the group consisting of butane, pentane, pentene, pentadiene, methylbutene, cyclopentane, cyclopentene, hexane, cyclohexane, heptane, methylhexane, benzene, and toluene. As a specific example, C7- hydrocarbons may include all the classes of C7- hydrocarbons described above, but are not limited to them. Furthermore, for example, C10+ hydrocarbons may include one or more selected from the group consisting of dicyclopentadiene, naphthalene, methylnaphthalene, tetramethylbenzene, fluorene, and anthracene. As a specific example, C10+ hydrocarbons may include, but are not limited to, all the classes of C10+ hydrocarbons described above. According to an exemplary embodiment of the present invention, the boiling point of the mixed oil stream can be 180°C to 600°C, 190°C to 550°C, or 200°C to 500°C. The boiling point of the mixed oil stream can refer to the boiling point of the mixed oil stream in a bulk form composed of a plurality of hydrocarbons. Here, the class of hydrocarbons included in the mixed oil stream can include all C7- hydrocarbons and C10+ hydrocarbons, as described above. Meanwhile, the PGO stream discharged from a general naphtha cracking center (SI) process may include 70 wt% or more, or 70 wt% to 95 wt%, of C12 to C13 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 that includes 70 wt% or more of C12 to C13 hydrocarbons may have a kinematic viscosity at 40°C of 1 to 200 cSt and a flash point of 10 to 50°C. Furthermore, for example, a PFO stream containing 70 wt% or more C13+ hydrocarbons may have a kinematic viscosity at 40°C of 400 to 100,000 cSt and a flash point of 70 to 200°C. Therefore, a PFO stream containing heavier hydrocarbons than a PGO stream may have a higher kinematic viscosity σ. There is a higher flash point than pyrolysis gas oil under the same temperature conditions. Furthermore, the PGO stream can have a boiling point of 200 to 288°C or 210 to 279°C, and the PFO stream can have a boiling point of 289 to 550°C or 300 to 500°C. Here, when the PGO stream is supplied directly to the combustion chamber without a pretreatment process to control the composition of the PGO stream, the PFO stream is supplied directly to the combustion chamber without a pretreatment to control the composition of the PFO stream, or the oil stream mixed from the PGO and PFO streams, whose compositions are not controlled, is supplied directly to the combustion chamber, the temperature that satisfies both the kinematic viscosity and the flash point within the appropriate ranges described above cannot exist. As such, when the PFO stream, the PGO stream, or the mixed oil stream of the PFO stream and the PGO stream is supplied to the combustion chamber at a temperature that does not satisfy either the kinematic viscosity and flash point within the appropriate ranges, a differential pressure in the combustion chamber rises or atomization is not performed well, impairing combustion performance, and an explosion risk is increased due to excessive oxygen, or flame may occur in the burner before a combustion reaction occurs, and an explosion risk is present due to a flashback fire phenomenon of the flame in the combustion chamber, and the refractories in the combustion chamber may be damaged. Specifically, the PFO and PGO streams are the heaviest residues in the NCC process and have been used as a simple fuel. When used as such, their composition and physical properties do not need to be adjusted. However, as in the present invention, in order to use the stream as the feedstock for synthesis gas, specific physical properties, such as kinematic viscosity and flash point, must be met. Furthermore, since the PFO stream has a high heavy oil content, it has high viscosity. Therefore, its viscosity must be reduced by heating to use the PFO stream as the syngas feedstock. However, it presents a problem in controlling the kinematic viscosity at temperatures below the flash point within the appropriate range. Additionally, the PGO stream has a flash point at or below ambient temperature, so it cannot be used as the syngas feedstock. Moreover, the ratio of the PGO stream's flow rate to the combined flow rate of the PFO and PGO streams is approximately 0.35 to 0.7, and in that case too, both the kinematic viscosity and the flash point cannot be satisfied, and it is difficult to use the stream as the syngas feedstock. In this respect, in the present invention, the mixed oil stream from the PGO stream and the PFO stream discharged under the conditions in which the operating conditions of the first separator 20 and the second separator 30 are controlled are supplied to the combustion chamber as the feedstock for the gasification process (S2), whereby when the mixed oil stream is supplied to the combustion chamber, the flash point of the mixed oil stream can be controlled to a range higher than the temperature of the mixed oil stream at the time of supply by 25°C or more, and also the kinematic viscosity of the mixed oil stream can be controlled to a range of 300 cSt or less at the temperature of the mixed oil stream at the time of supply, and in this way, the conditions for using the stream as the feedstock for synthesis gas can be met. According to an exemplary embodiment of the present invention, the mixed oil stream can pass through a heat exchanger (not shown) before being supplied to the combustion chamber for the gasification process (S2). In this case, the temperature of the mixed oil stream at the time of supply to the gasification process (S2) is adjusted, and the sensible heat of the mixed oil stream that is discarded as waste heat is reused in the process using the heat exchanger, thereby reducing the process energy. According to an exemplary embodiment of the present invention, the combustion of the mixed oil stream supplied to the combustion chamber in the gasification process (S2) at a temperature of 700°C or higher, 700 to 2000°C, or 800 to 1800°C may also be included. Additionally, the mixed oil stream may be supplied to the combustion chamber together with the gasifying agent. Herein, the gasifying agent may include one or more selected from the group consisting of oxygen, air, and water vapor, and as a specific example, the gasifying agent may be oxygen or water vapor. As such, by burning the mixed oil stream at a high temperature in the presence of the gasifying agent, synthesis gas can be prepared. The synthesis gas prepared according to the preparation method of the present invention includes carbon monoxide and hydrogen and may further include one or more selected from the group consisting of carbon dioxide, ammonia, hydrogen sulfide, hydrogen cyanide, and carbonyl sulfide. According to an exemplary embodiment of the present invention, in the method for preparing synthesis gas, if necessary, devices such as a valve, a pump, a separator, and a mixer can also be installed. Previously herein, the method for preparing synthesis gas according to the present invention has been described and illustrated in the drawings, but the description and illustration in the drawings are the description and illustration of only core constitutions for the understanding of the present invention, and in addition to the process and devices described above and illustrated in the drawings, the process and devices not described and illustrated separately may be appropriately applied and used to carry out the method for preparing synthesis gas according to the present invention. The present invention will then be described in more detail by the Examples. However, the following Examples are provided to illustrate the present invention. It is evident to a person skilled in the art that various modifications and alterations can be made without departing from the scope and spirit of the present invention, and the scope of the present invention is not limited to them. Example Examples 1 to 4 According to the process flow diagram shown in FIG. 1, synthesis gas was prepared. Specifically, in the naphtha cracking center (SI) process, the cracked gras stream was supplied to the gasoline fractionator 10 and separated. A side discharge stream from a stage 40% relative to the total number of stages of the gasoline fractionator 10 was supplied to the first separator 20, and then the first separator was operated under the conditions in which the first vapor stream at a saturated pressure of 3.5 kg / cm2g is supplied to discharge a PGO stream that includes a pyrolysis gas oil from the lower portion of the first separator 20. At this time, the temperature of the side discharge stream from the gasoline fractionator 10 was 150°C, and the operating pressure of the first separator 20 was 1 kq / cm2g. Furthermore, a lower discharge stream from one stage, 100% relative to the total number of stages of the gasoline fractionator 10, was split into a reflux stream and a supply stream. The reflux stream was combined with a cracked gas stream and supplied to the gasoline fractionator 10. Additionally, the supply stream was fed to a second separator 30 and operated under conditions where a second stream at a saturated pressure of 3.5 kg / cm² is supplied to discharge a PFO stream, including pyrolysis fuel oil (PFO), from the lower portion of the second separator 30. At this time, the temperature of the lower discharge stream from the gasoline fractionator 10 was 210°C, and the operating pressure of the second separator 30 was 1.2 kg / cm². The PGO stream and the PFO stream were mixed to form a mixed oil stream, and then the mixed oil stream was supplied to a combustion chamber for a gasification process (S2). At this time, the flow rate ratio of the PGO stream to the mixed oil stream was 0.35. At this time, a flow rate (GF) from the side discharge stream of gasoline fractionator 10, a flow rate (FF) from a supply stream fed to the second separator in the lower discharge stream of gasoline fractionator 10, and each of a flow rate (GS) from the first vapor stream and a flow rate (FS) from a second vapor stream were controlled to control G(GS / GF) and F(FS / FF), which are shown in Table 1 below, and the composition and kinematic viscosity and flash point at 40°C of the PGO stream and the PFO stream are shown in Table 2 below. Furthermore, the temperature of the mixed oil stream at the time of delivery to the combustion chamber, as well as the flash point and kinematic viscosity of the mixed oil stream, were measured and are shown in Table 3 below. Additionally, compliance with process operating standards was verified based on the measured values. The delivery time of the mixed oil stream to the combustion chamber was adjusted to maintain a kinematic viscosity of 300 cSt using a heat exchanger. Specifically, to determine the temperature conditions for maintaining a kinematic viscosity of 300 cSt, the kinematic viscosity of the corresponding sample was measured at each temperature. A correlation between temperature and viscosity was then established, and the calculation was performed using interpolation. Kinematic viscosity and flash point were measured as follows, and applied to all examples and comparative examples. (1) Kinematic viscosity: A sample was obtained from the sample stream being measured and the measurement was performed based on ASTM D7042 using SVM 3001 available from Anton In addition, the temperature of each of the samples was kept at a temperature lower than a kinematic viscosity measurement temperature by 10°C, and the sample was stored in a closed container to prevent vaporization of light materials to minimize the occurrence of a gas base. (2) Flash point: A sample was obtained from the sample stream being measured, and the measurement was performed according to ASTM D93 using apm-8 available from Tanaka. Furthermore, the temperature of each sample was maintained 10°C below the expected flash point, and the sample was stored in a sealed container to prevent vaporization of light materials and minimize the occurrence of a gas phase. Comparative Example 1 The process was carried out in the same way as in Example 1, except that the PFO stream discharged from the lower portion of the second separator 30, instead of the mixed oil stream, was supplied to the combustion chamber for the gasification process. The temperature of the PFO stream at the time of delivery to the combustion chamber was measured and is shown in Table 3 below. Furthermore, it was confirmed whether the process operating standards were met based on the measurement results. At this point, the time during which the PFO stream was delivered to the combustion chamber was adjusted to maintain a kinematic viscosity of 300 cSt using a heat exchanger. Comparative Example 2 The process was carried out in the same way as in Example 1, except that the PGO stream discharged from the lower portion of the first separator 20, instead of the mixed oil stream, was supplied to the combustion chamber for the gasification process. The temperature of the PGO stream at the time of delivery to the combustion chamber was measured and is shown in Table 3 below. Furthermore, it was confirmed whether the process operating standards were met based on the measurement results. At this point, the time during which the PGO stream was delivered to the combustion chamber was adjusted to maintain the kinematic viscosity at 300 cSt using a heat exchanger. Comparative Examples 3 to 5 The process was carried out in the same way as in Example 1, except that the flow rate (GF) of the side discharge stream of the gasoline selector 10, the flow rate (FF) of the supplied supply stream > your NCNNC C σ a to the second separator in the inner discharge stream of the σ to gasoline fractionator 10, and each of the flow rate (GS) of the first vapor stream and the flow rate (FS) of the second vapor stream was controlled to control G(GS / GF) and F(FS / FF) as shown in Table 1 below. The 5 compositions and kinematic viscosity and flash point at 40°C of the PGO stream and the PFO stream are shown in Table 2 below. Furthermore, the temperature of the mixed oil stream at the time of delivery to the combustion chamber, as well as its flash point and kinematic viscosity, were measured and are shown in Table 3 below. Additionally, it was confirmed whether the process operating standards were met based on the measurement results. At this point, the time during which the mixed oil stream was delivered to the combustion chamber was adjusted to maintain the kinematic viscosity at 300 cSt using a heat exchanger. [Table 1] GF Example 1 0.6 0.03 Example 2 0.7 0.025 Example 3 0.8 0.02 Example 4 1 0.01 > your NCNNC C σ a Comparative Example 1 - 0.03 Comparative Example 2 0.6 - Comparative Example 3 0.3 0.07 Comparative Example 4 0.3 0.03 Comparative Example 5 0.6 0.07 [Table 2] PGO Stream PFO Stream C6 Content (% by weight) Flash Point (°C) Kinematic Viscosity (cSt@40°C) C8-9 Content (% by weight) Flash Point (°C) Kinematic Viscosity (cSt@40°C) Example 1 0.08 42 115 3.6 85 370 Example 2 0.04 45 115 4.1 85 360 Example 3 0.01 47.5 120 5.4 84.5 345 Example 4 0 51.5 125 8.2 84 310 Comparative Example 1 - - - 3.6 85 370 Comparative Example 2 0.08 42 115 - - - Comparative Example 3 1.6 25 110 1.7 87 425 Example Comparative 4 1.6 25 110 3.6 85 370 Comparative Example 5 0.08 42 115 1.7 87 428 [Table 3] Temperature at the time of delivery to the combustion chamber (°C) Flash Point (°C) Kinematic Viscosity (cSt) If the process operating standards were met Example 1 42.2 68 300 O Example 2 41.8 70 300 O Example 3 41.5 72.5 300 O Example 4 40.3 76 300 O Comparative Example 1 63 85 300 X Comparative Example 2 23.4 42 300 X Comparative Example 3 49 61.5 300 X Comparative Example 4 42.1 61 300 X Comparative Example 5 49.3 69 300 X In Table 3, regarding whether the σ are met to process operating standards, for the stream supplied to the combustion chamber in each of Examples 1 to 4 and Comparative Examples 1 to 5, if the temperature of the stream at the time of supply to the combustion chamber at which the kinematic viscosity of the stream at the time of supply to the combustion chamber is 300 cSt is less than the flash point by 25°C or more, it was expressed as O, and if not, it was expressed as X. With reference to Tables 1 and 3, in Examples 1 to 4 in which, according to the method for preparing synthesis gas of the present invention, the flow rate (GF) of the side discharge stream of the gasoline fractionator 10, the flow rate (FF) of the supply stream, the flow rate (GS) of the first steam stream, and the flow rate (FS) of the second steam stream were adjusted to control G and F to be within appropriate ranges, the kinematic viscosity and flash point of the blended oil stream were able to be adjusted. Specifically, in Examples 1 to 4 in which the mixed oil stream was supplied to the combustion chamber for the gasification process (S2) under conditions in which G is controlled to 0.5 or more, and F is controlled to 0.035 or less, it was confirmed that the C6- hydrocarbon content in the PGO stream was controlled to 0.The C8 and C9 hydrocarbon content in the PFO stream was controlled to 1% by weight or less, and the C8 and C9 hydrocarbon content in the PFO stream was controlled to 3% by weight or more, whereby when the mixed oil stream from the PGO and PFO streams was supplied to the combustion chamber, the flash point of the mixed oil stream was 25°C or more higher than the temperature of the mixed oil stream at the time of supply to the combustion chamber, and the kinematic viscosity of the mixed oil stream was within 300 cSt or less at the temperature of the mixed oil stream at the time of supply to the combustion chamber. Having both the flash point and kinematic viscosity within this range, the process operating conditions for use as the feedstock for the gasification process (S2) were met. However, in Comparative Example 1, where only the PFO stream was supplied to the combustion chamber instead of the mixed oil stream of the PFO and PGO streams of Example 1, or in Comparative Example 2, where only the PGO stream was supplied to the combustion chamber, it was confirmed that, although G or F were met as in the present invention, the temperature satisfying both the kinematic viscosity and the flash point within the appropriate range described above did not exist. Consequently, it was found that σ It is difficult to use the PGO stream or the PFO stream alone as the feedstock for synthesis gas. Furthermore, in Comparative Examples 3 through 5, where the mixed oil stream from the PGO and PFO streams was supplied to the combustion chamber as the feedstock for the gasification process (S2), but one or more of conditions G and F were not met as in the present invention, it was confirmed that the temperature satisfying both the kinematic viscosity and flash point within the appropriate range described above did not exist. Similarly, in Comparative Examples 1 through 5, where one or more of the kinematic viscosity and flash point were not met within the appropriate ranges, it was confirmed that the process operating conditions for use as the feedstock for the gasification process (S2) were not met. When the gasification process feedstock (S2) was supplied to the combustion chamber at a temperature that did not meet either the kinematic viscosity and flash point within the appropriate ranges, a differential pressure in the combustion chamber was raised, or atomization was not performed well, impairing combustion performance, and an explosion risk was increased due to excessive oxygen, or flame may occur in the burner before a combustion reaction occurs, and an explosion risk was present due to a flashback fire phenomenon of the flame in the combustion chamber, and the refractories in the combustion chamber may be damaged.

Claims

1. A method for preparing synthesis gas, the method characterized in that it comprises: supplying a cracked gas stream discharged from a cracking furnace of a naphtha cracking center (NCC) process to a gasoline fractionator; supplying a side discharge stream from the gasoline fractionator to a first separator, operating the first separator under conditions in which a first steam stream is supplied, and separating a PGO stream including a pyrolysis gas oil (PGO) from a lower portion; splitting a lower discharge stream from the gasoline fractionator into a reflux stream and a supply stream, supplying the supply stream to a second operator, and operating the second separator under conditions in which a second steam stream is supplied, and separating a PFO stream including a pyrolysis fuel oil (PFO) from a lower portion;and supplying a mixed oil stream from the PGO stream and the PFO stream to a combustion chamber for a gasification process, wherein the following equations 1 and 2 are satisfied: [Equation 1] G > 0.5, G = GS / GF [Equation 2] F < 0.035, F = FS / FF wherein GF is a flow rate of the side discharge stream of the gasoline fractionator, GS is a flow rate of the first steam stream, FF is a flow rate of the supply stream, and FS is a flow rate of the second steam stream.

2. The method for preparing synthesis gas according to claim 1, characterized in that G is 0.5 to 2.

3. The method for preparing synthesis gas according to claim 1, characterized in that F is 0.001 to 0.

035.

4. The method for preparing synthesis gas according to claim 1, characterized in that a temperature of the side discharge stream of the gasoline fractionator is 120°C to 180°C, and an operating pressure of the first separator is 0.5 kg / cm2g to 3 kg / cm2g.

5. The method for preparing synthesis gas according to claim 1, characterized in that a temperature of the lower discharge stream of the gasoline fractionator is 150°C to 300°C, and an operating pressure of the second separator is 0.6 kg / cm2g to 3.1 kg / cm2g.

6. The method for preparing synthesis gas of > your NCNNCC σ in accordance with claim 1, characterized in that each pressure of the first vapor stream and the second vapor stream is 2 kg / cm2g to 20 kg / cm2g.

7. The method for preparing synthesis gas according to claim 1, characterized in that the mixed oil stream has a kinematic viscosity at the time of delivery to the combustion chamber of 300 cSt or less, and the mixed oil stream has a flash point higher than a temperature at the time of delivery to the combustion chamber by 25°C or more.

8. The method for preparing synthesis gas according to claim 1, characterized in that the temperature of the mixed oil stream at the time of supply to the combustion chamber is 20°C to 90°C.

9. The method for preparing synthesis gas according to claim 1, characterized in that a C6- hydrocarbon content in the PGO stream is 0.1% by weight or less, and an O8 and O9 hydrocarbon content in the PFO stream is 3% by weight or more.

10. The method for preparing synthesis gas according to claim 1, characterized in that the PGO stream has a flash point of 40 to 70°C, and the PFO stream has a flash point of 65 to 190°C.

11. The method for preparing synthesis gas according to claim 1, characterized in that the PGO stream has a kinematic viscosity at 40°C of 5 to 220 cSt, and the PFO stream has a kinematic viscosity at 40°C of 250 to 70,000 cSt.

12. The method for preparing synthesis gas according to claim 1, characterized in that the bottom discharge stream of the gasoline fractionator is discharged from one stage at 90% or more relative to a total number of stages of the gasoline fractionator, and the side discharge stream of the gasoline fractionator is discharged from one stage at 10% to 70% relative to the total number of stages of the gasoline fractionator.

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