Method of manufacturing cracking reactor fuel

Abstract

The present invention provides a method for producing a cracking furnace fuel, the method including the steps of preparing a first methane off-gas stream derived from a liquid-phase cracking furnace and a second methane off-gas stream derived from a gas-phase cracking furnace; branching a part of the first methane off-gas stream as a methane off-gas export stream and obtaining a first fuel gas stream from the remainder; obtaining a second fuel gas stream from the second methane off-gas stream; mixing the first and second fuel gas streams to prepare a mixed fuel gas stream; and mixing a hydrogen gas stream with the mixed fuel gas stream.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0131809 filed on October 13, 2022, and all the contents disclosed in the document of the corresponding Korean patent application are incorporated herein by reference as part of this specification.

[0002] The present invention relates to a method for producing cracking furnace fuel for use in naphtha cracking facilities.

Background Art

[0003] Naphtha is a fraction obtained by distilling crude oil and is used as a material for producing ethylene, propylene, benzene, etc., which are basic raw materials of petrochemistry, through thermal cracking. The production of products by thermal cracking of naphtha is usually carried out by heating hydrocarbon compounds such as naphtha in a cracking furnace for thermal cracking, and then cooling, compressing and purifying the thermal cracking products.

[0004] The conventional thermal cracking process of hydrocarbons such as naphtha is accompanied by the problem that a considerable amount of carbon dioxide is generated by the combustion of fuel required for thermal cracking. That is, methane off-gas (MOG) produced in the naphtha cracking process is mainly used as the fuel for the cracking furnace. Since methane off-gas contains methane as the main component, when methane off-gas is used as the fuel for the cracking furnace, a problem of a large amount of carbon dioxide being discharged occurs. The amount of carbon dioxide emissions generated in the thermal cracking process accounts for more than 90% of the carbon dioxide emissions generated in a series of naphtha processes related to naphtha. Therefore, in order to respond to the issue of environmental regulations that have recently been discussed, it is necessary to reduce the amount of carbon dioxide emissions generated in the naphtha process. As part of this, since hydrogen does not emit carbon dioxide during combustion, attempts have been made to increase the hydrogen content in the cracking furnace fuel, that is, to replace a part of the methane off-gas with hydrogen as the cracking furnace fuel.

[0005] However, in order to raise the hydrogen content in the fuel above a certain level, it is necessary to purchase and apply high-purity hydrogen gas from outside the naphtha cracking reactor facility, which could reduce the overall economic efficiency of the process due to the purchase of hydrogen. Therefore, there is a need for a method that can minimize the amount of high-purity hydrogen introduced from outside while maximizing the hydrogen content in the cracking reactor fuel.

[0006] Furthermore, since methane off-gas, while containing hydrogen, has value as a fuel, methods for economically utilizing methane off-gas that would otherwise be replaced by hydrogen must also be developed. [Overview of the project] [Problems that the invention aims to solve]

[0007] The problem that this invention aims to solve is to provide a method for producing cracking furnace fuel that can reduce carbon dioxide emissions during combustion by maintaining a high hydrogen content in the fuel when producing fuel for a cracking furnace necessary for a petrochemical process involving pyrolysis, in order to solve the problems mentioned in the background art of the invention described above. Furthermore, the invention aims to provide a method for producing cracking furnace fuel that can improve economic efficiency by efficiently utilizing the hydrogen generated as a by-product in the process, thereby reducing the amount of hydrogen that must be further introduced from an external source.

[0008] Furthermore, while methane off gas (MOG), which is used as a cracking reactor fuel and replaced with hydrogen, is generally sold or transported to downstream processes for use, the objective is to provide a method for producing cracking reactor fuel that can minimize hydrogen loss due to hydrogen contained in the methane off gas being transported externally in this manner. [Means for solving the problem]

[0009] According to one embodiment of the present invention for solving the above problems, a method for producing cracking reactor fuel is provided, which includes the steps of: preparing a first methane off-gas stream originating from a liquid-phase cracking furnace and a second methane off-gas stream originating from a gas-phase cracking furnace; branching off a portion of the first methane off-gas stream as a methane off-gas discharge stream and obtaining a first fuel gas stream from the remainder; obtaining a second fuel gas stream from the second methane off-gas stream; mixing the first and second fuel gas streams to prepare a mixed fuel gas stream; and mixing a hydrogen gas stream into the mixed fuel gas stream. [Effects of the Invention]

[0010] When using the method for producing cracking furnace fuel according to the present invention, the amount of carbon dioxide emitted from the cracking furnace can be reduced by increasing the hydrogen content of the fuel supplied to the cracking furnace. This makes the petrochemical process and the products produced therefrom more eco-friendly.

[0011] On the other hand, this method provides a method for manufacturing cracked reactor fuel that minimizes the loss of hydrogen that may be leaked by methane off-gas used in downstream processes of the naphtha cracking process or that has its own independent marketability, and furthermore, by increasing the efficiency of the naphtha cracking process itself and making maximum use of hydrogen generated or produced as a by-product within the process, the amount of hydrogen further introduced from outside can be minimized, thereby reducing costs during the production of cracked reactor fuel. [Brief explanation of the drawing]

[0012] [Figure 1] This is a process flowchart of a method for manufacturing cracked reactor fuel according to one embodiment of the present invention. [Figure 2] This is a process flowchart of a method for producing cracked reactor fuel, using comparative examples to be compared with the embodiments of the present invention. [Figure 3]This is a process flowchart of a method for producing cracked reactor fuel, using comparative examples to be compared with the embodiments of the present invention. [Modes for carrying out the invention]

[0013] The terms and words used in the description and claims of this invention should not be interpreted in a manner limited to their ordinary or dictionary meanings, but rather should be interpreted in a manner consistent with the technical idea of ​​this invention, in accordance with the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0014] In this invention, the term "stream" may mean the flow of fluid within a process, or the fluid itself flowing within a pipe. Specifically, "stream" may simultaneously mean the fluid itself and the flow of fluid within the pipes connecting each device. Furthermore, the fluid may mean gas or liquid.

[0015] To facilitate understanding of the present invention, the present invention will be described in more detail below with reference to Figure 1.

[0016] A method for producing cracking reactor fuel according to one embodiment of the present invention involves a first methane off-gas stream (MOG) derived from a liquid-phase cracking reactor. L and the second methane off-gas stream MOG derived from the gas phase decomposition reactor. G This could include a step to prepare it.

[0017] The liquid cracking furnace is a cracking furnace in which a liquid phase feedstock is supplied and thermally decomposed, and the gas cracking furnace is a cracking furnace in which a gas phase feedstock is supplied and thermally decomposed. On the other hand, the thermal decomposition process carried out in the liquid cracking furnace and the gas cracking furnace is a process for obtaining thermal decomposition products from the feedstock, and can be divided into a liquid cracking furnace and a gas cracking furnace depending on the phase of the feedstock.

[0018] In other words, the thermal decomposition process according to one embodiment of the present invention can be carried out by separating the decomposition process of the liquid phase component, which uses naphtha as the raw material, from the decomposition process of the liquid phase component, which uses hydrocarbon compounds with 2 to 4 carbon atoms, such as ethane and propane, as the raw material, in order to increase the production of products such as ethylene.

[0019] Specifically, the feedstock supplied to the liquid-phase cracking furnace may include a mixture of hydrocarbon compounds supplied in liquid form. A concrete example is a feedstock containing naphtha, and a more concrete example is naphtha itself. The naphtha may be derived from a gasoline fraction obtained from a crude oil distillation unit.

[0020] The thermal decomposition temperature of the liquid phase decomposition furnace can be 500°C to 1,000°C, 750°C to 875°C, or 800°C to 850°C, and within this range, there is an excellent effect in achieving a high thermal decomposition yield of the feed material supplied to the liquid phase decomposition furnace.

[0021] Furthermore, the gas-phase decomposition furnace may be a decomposition furnace for thermally decomposing a feed material supplied in the gas phase. The feed material for the gas-phase decomposition furnace may be a gas-phase feed material containing a hydrocarbon compound having 2 to 4 carbon atoms. Here, the hydrocarbon compound having 2 to 4 carbon atoms may include one or more selected from the group consisting of recycled C2, recycled C3 hydrocarbon compounds, propane, and butane, which are separated and recycled in subsequent processes.

[0022] On the other hand, one type of gas phase decomposition furnace can be used, and according to one embodiment of the present invention, two or more types of gas phase decomposition furnaces can be used depending on the gas phase raw materials supplied in the gas phase. That is, depending on the supplied raw materials, the gas phase decomposition furnace may include a first gas phase decomposition furnace for thermally decomposing recirculated C2 and C3 hydrocarbon compounds, and a second gas phase decomposition furnace for thermally decomposing one or more of propane and butane, which are supplied separately from the recirculated C2 and C3 hydrocarbon compounds. The first and second gas phase decomposition furnaces can be connected in parallel to each other.

[0023] The recirculated C2 hydrocarbon compound and the recirculated C3 hydrocarbon compound supplied to the first gas-phase decomposition furnace may be C2 hydrocarbon compounds and C3 hydrocarbon compounds that are purified in a subsequent purification step and then recycled. Specifically, the recirculated C2 hydrocarbon compound may be ethane that is purified in a purification step (S4) described later and then recycled, and the recirculated C3 hydrocarbon compound may be propane that is purified in a purification step (S4) described later and then recycled.

[0024] The feedstock supplied to the second gas-phase decomposition furnace is a hydrocarbon compound having 2 to 4 carbon atoms, supplied separately from the recirculated C2 hydrocarbon compound and the C3 hydrocarbon compound, and may include one or more selected from the group consisting of propane and butane, and more specifically, may be derived from liquefied petroleum gas (LPG). On the other hand, the liquefied petroleum gas can be vaporized and supplied to the second gas-phase decomposition furnace. The cost of the feedstock supplied to the second gas-phase decomposition furnace is relatively low and it is easy to supply from external sources, which has the effect of reducing production costs and increasing the amount of pyrolysis products produced.

[0025] The thermal decomposition temperature of the gas phase decomposition furnace can be 500°C to 1,000°C, 750°C to 900°C, or 825°C to 875°C, and within this range, there is an excellent effect in the thermal decomposition yield of the feed material supplied to the gas phase decomposition furnace.

[0026] The first and second methane off-gas streams MOG according to an embodiment of the present invention L 、MOG G can each be derived from the liquid-phase cracking furnace and the gas-phase cracking furnace, respectively.

[0027] Specifically, the first and second methane off-gas streams MOG L 、MOG G can be prepared by a process including the steps of: supplying the above-described feedstock to respective pyrolysis furnaces for pyrolysis (step S1); cooling the pyrolysis gas containing hydrogen, C1, C2, and hydrocarbons having three or more carbon atoms by cooling in a cooling tower after pyrolysis (step S2); compressing the cooled pyrolysis gas with two or more compressors (step S3); and purifying the pyrolysis compression stream (step S4).

[0028] That is, the first methane off-gas stream MOG derived from the liquid-phase cracking furnace L can be a stream produced after the liquid-phase feedstock is supplied to the liquid-phase cracking furnace and then through the steps S1 to S4, and the second methane off-gas stream MOG derived from the gas-phase cracking furnace G can be a stream produced after the gas-phase feedstock is supplied to the gas-phase cracking furnace and then through the steps S1 to S4. Also, the steps S1 to S4 for producing the first and second methane off-gas streams MOG L 、MOG G can be performed via separate lines, respectively.

[0029] On the other hand, according to an embodiment of the present invention, the step of obtaining the first and second methane off-gas streams MOG L 、MOG G by purifying the pyrolysis compression stream (step S4) can be performed by a device including a demethanizer and a cold box (CB).

[0030] Specifically, the pyrolysis compression stream can be supplied to a demethanizer, and optionally, if the pyrolysis compression stream passes through a gas-liquid separator, the lower discharge stream from the gas-liquid separator can be supplied to the demethanizer. The demethanizer is a device for distilling the pyrolysis compression stream containing hydrogen, C1 hydrocarbon compounds, and C2 hydrocarbon compounds to separate the upper discharge stream containing hydrogen and C1 hydrocarbon compounds from the lower discharge stream containing C2 hydrocarbon compounds.

[0031] Next, the upper discharge stream of the demethane tower containing hydrogen and C1 hydrocarbon compounds, or optionally, if the gas-liquid separator is in operation, the upper discharge stream of the gas-liquid separator and the upper discharge stream of the demethane tower, can be supplied to and circulated in a cooling circulation area. This allows for the separation and production of a hydrogen-rich stream and a methane-rich stream.

[0032] Here, the first and second methane off-gas streams MOG L MOG G This can be a methane-rich stream produced as a result of the separation and purification processes carried out in the demethane tower and cooling circulation zones of each line.

[0033] On the other hand, according to one embodiment of the present invention, the first methane off-gas stream MOG L The hydrogen content can be 10% to 25% by volume, and the methane content can be 75% to 90% by volume. The remaining components may include, for example, 0.1% or less by volume of carbon monoxide, 0.3% or less by volume of ethylene, and 0.002% or less by volume of ethane.

[0034] The second methane off-gas stream MOG GThe hydrogen content can be 67% to 77% by volume, and the methane content can be 23% to 33% by volume. The remaining components may include 0.05% or less of carbon monoxide and 0.1% or less of ethylene.

[0035] Second methane off gas originating from the aforementioned gas phase cracking reactor discharge stream stream MOG G The hydrogen content contained in is derived from the first methane off-gas stream MOG from the liquid phase cracking reactor discharge stream. L The hydrogen content is higher than that contained in the gas phase decomposition furnace. This is because, compared to when naphtha, the raw material for the liquid phase decomposition furnace, is thermally decomposed, when ethane and propane, the raw materials for the gas phase decomposition furnace, are thermally decomposed, the hydrogen content in the decomposition furnace discharge stream itself is higher, the purification process to obtain methane off gas from the gas phase decomposition furnace discharge stream is relatively simple, and most of the hydrogen in the gas phase decomposition furnace discharge stream is methane off gas in the MOG G This is because it can be included in the first methane off-gas stream (MOG). In addition, in the case of a purification process associated with the cracking reactor discharge stream, a condensation process using cryogenic ethylene refrigerant is performed on the upper discharge stream of the demethane tower in order to minimize the outflow of C2 hydrocarbon compounds to the upper part of the demethane tower. However, because the condensation temperature during the condensation process associated with the liquid phase cracking reactor is lower than the condensation temperature during the condensation process associated with the gas phase cracking reactor, the first methane off-gas stream (MOG) L The hydrogen content contained in the second methane off gas stream MOG G The hydrogen content will be lower than that contained in [the substance].

[0036] Typically, methane-off gas derived from cracking furnaces contains a large amount of methane and can therefore be used as fuel for furnaces. That is, because methane-off gas is economically viable, it can be recycled and used as fuel for furnaces installed within the naphtha process, such as cracking furnaces, or it can be discharged outside the naphtha process system and sold. However, when methane-off gas is recycled and used as fuel for cracking furnaces, the combustion of hydrocarbon compounds contained in the methane-off gas generates and emits carbon dioxide, which can cause environmental pollution or lead to restrictions due to environmental regulations. Furthermore, as mentioned above, methane-off gas contains a certain amount of hydrogen, but when it is discharged outside the system and sold, the hydrogen contained in the sold methane-off gas is also exported, potentially causing a hydrogen leak. Hydrogen does not produce carbon dioxide when burned and has a relatively high combustion value, making it highly valuable from both an economic and environmental perspective. Therefore, from an economic standpoint, it is necessary to improve process efficiency to minimize the leakage of hydrogen contained in methane off-gas and to minimize the supply of hydrogen imported from external sources. Furthermore, from an environmental standpoint, it is necessary to increase the hydrogen content within the cracking reactor fuel.

[0037] From this viewpoint, a method for producing cracking reactor fuel according to one embodiment of the present invention may include the step of branching off a portion of the first methane off gas stream as a methane off gas export stream from the first and second methane off gas streams prepared as described above, and obtaining a first fuel gas stream F1 from the remainder.

[0038] As described above, the second methane off-gas stream MOG originates from the gas phase decomposition furnace. G The first methane off-gas stream MOG originates from the liquid phase cracking furnace. L In contrast to the first methane off-gas stream MOG, the hydrogen content is higher. LThe flow rate is the second methane off-gas stream MOG G It is larger compared to the flow rate. Specifically, the first methane off-gas stream MOG L The mass flow rate is the second methane off-gas stream MOG G The mass flow rate can be 3 to 10 times the normal rate. This can be controlled by the amount of raw materials introduced into the liquid-phase and gas-phase decomposition furnaces, and it is generally preferable to operate at the aforementioned mass flow rate ratio from the standpoint of utilizing naphtha, which is the main raw material, and from the economic standpoint of process operation.

[0039] Therefore, the second methane off-gas stream MOG G Compared to the first methane off-gas stream (MOG), it has a lower hydrogen content, but a higher flow rate. L It is preferable to branch off a portion of the stream to export the methane off-gas, as this minimizes hydrogen leakage without significantly changing the flow rate of the methane off-gas produced. The flow rate of the methane off-gas export stream is controlled by the hydrogen gas stream F introduced from the outside. H It can increase as the flow rate increases. On the other hand, the hydrogen content in the methane off-gas discharge stream MOGex can be 15% to 25% by volume.

[0040] First Methane Off-Gas Stream MOG L The first methane off-gas stream MOG can be supplied to drum D1, and after the liquid-phase hydrocarbons have been removed, it can be discharged from drum D1. L A portion of it is branched off and discharged as the methane off-gas discharge stream MOGex, and the remainder can be used to obtain the first fuel gas stream F1. The first fuel gas stream F1 and the second fuel gas stream F2 can be mixed in the header. That is, the methane off-gas discharge stream MOGex is used before the first fuel gas stream F1 is mixed with the second fuel gas stream F2. L This could mean a stream that branches off and is exported from another source.

[0041] According to one embodiment of the present invention, the second methane off-gas stream MOG G The first methane off-gas stream MOG L Because it has a higher hydrogen content compared to the second methane off-gas stream MOG G It is mixed with the first fuel gas stream F1 by itself and mixed fuel gas stream F mixed This can be a second fuel gas stream F2 that forms a second fuel gas stream F2. Thus, the present invention reduces the amount of carbon dioxide that can be generated during the combustion of cracking reactor fuel by introducing hydrogen F from an external source into the cracking reactor fuel. H When including hydrogen, by limiting the points where the methane off-gas discharge stream MOGex is branched to streams with relatively high methane content, it is possible to minimize hydrogen leakage to the outside and thereby maximize economic efficiency.

[0042] On the other hand, according to another embodiment of the present invention, the second methane off-gas stream MOG G A second fuel gas stream F2 can be formed by mixing it with a recirculated hydrogen gas stream. Here, the recirculated hydrogen gas stream is a stream that is separated and circulated in a subsequent process within the system and is rich in hydrogen, and the hydrogen content in the recirculated hydrogen gas stream can be higher than the hydrogen content in the second methane off gas stream. This allows the hydrogen gas stream F2 introduced from the outside to be formed. H This allows for a reduction in the flow rate, while also increasing the hydrogen content within the cracking reactor fuel.

[0043] More specifically, the recirculated hydrogen gas stream can be the ejected gas from the pressure swing adsorption process. That is, the second methane off-gas stream MOG G This is the reject gas F by the pressure swing adsorption process PSA. PSA It can be mixed with this to form a second fuel gas stream F2.

[0044] The pressure swing adsorption process is performed in conjunction with the thermal decomposition process of naphtha to obtain a high-purity hydrogen stream, and the reject gas F of the pressure swing adsorption process PSA is used. PSA This may refer to low-purity hydrogen streams with a low hydrogen content, other than the high-purity hydrogen streams obtained by the pressure swing adsorption process (PSA).

[0045] The inflow introduced into the pressure swing adsorption process or the upstream or downstream processes of the pressure swing adsorption process are not particularly limited, but as an example, a hydrogen-rich stream can be introduced into the pressure swing adsorption process as a stream discharged from the cooling circulation area, and a high-purity hydrogen stream can be produced by the pressure swing adsorption process, with the remaining stream being the pressure swing adsorption process PSA reject gas F PSA It can be discharged as such.

[0046] The aforementioned eject gas F PSA The ejected gas is the gas discharged by the pressure swing adsorption process (PSA), and the hydrogen content in the ejected gas can be 60% to 80% by volume, specifically 70% to 80% by volume. On the other hand, the methane content in the ejected gas can be 20% to 40% by volume, or 20% to 30% by volume.

[0047] In other words, since the reject gas from the pressure swing adsorption process (PSA) has a higher hydrogen content than the first and second methane off-gas streams, utilizing the reject gas from the pressure swing adsorption process as fuel for the decomposition furnace can reduce the amount of carbon dioxide emitted during combustion. Furthermore, by utilizing the reject gas rather than the high-purity hydrogen gas produced by the pressure swing adsorption process (PSA), the overall economic efficiency of the process can be improved.

[0048] As described above, the reject gas of the pressure swing adsorption process PSA is the second methane off-gas stream MOG.G It can be mixed with the first methane off-gas stream MOG. L It has a relatively low hydrogen content, and therefore, the first methane off-gas stream MOG L A portion of it is diverted as an export stream and used for the production of methane off-gas, therefore, for the production of cracking reactor fuel with a high hydrogen content, the aforementioned reject gas is used in the second methane off-gas stream MOG G Mixing with the other gas is preferable from the viewpoint of preventing hydrogen leakage. From this standpoint, the flow rate of the ejected gas in the pressure swing process can be 5% to 15% by weight relative to the flow rate of the second methane off-gas stream.

[0049] On the other hand, the second methane off-gas stream MOG is mixed with the reject gas from the pressure swing adsorption process PSA. G This is supplied to drum D2, and after the liquid-phase hydrocarbons in the stream are removed, it is discharged from drum D2 to form a second fuel gas stream F2.

[0050] According to a method for producing cracking reactor fuel according to one embodiment of the present invention, the first and second fuel gas streams F1 and F2 are mixed to produce a mixed fuel gas stream F mixed The steps of preparing the mixed fuel gas stream F mixed Hydrogen gas stream F H This may include a step of mixing the ingredients.

[0051] In other words, the first and second fuel gas streams F1 and F2 produced in the above process are mixed to make them suitable for supply as cracking reactor fuel to create a mixed fuel gas stream F mixed Forms the mixed fuel gas stream F mixed To maintain the hydrogen content within at the desired level, further hydrogen gas stream F H The mixed fuel gas stream F mixed Decomposition reactor fuel can be manufactured by mixing it with other materials.

[0052] First, it is preferable that the hydrogen content in the cracking reactor fuel be controlled to between 50% and 90% by volume. If the hydrogen content in the cracking reactor fuel is less than 50% by volume, the amount of carbon dioxide emitted during combustion increases, which is undesirable from an environmental standpoint. Also, if the hydrogen content in the cracking reactor fuel exceeds 90% by volume, a hydrogen gas stream F must be added to the fuel. H An increase in the amount of fuel reduces economic viability, and when such fuel is burned in a decomposition furnace burner, safety problems can arise due to backfire, and nitrogen oxides (NOx) are produced during combustion. x This can result in excessive production, which is undesirable from an environmental standpoint.

[0053] The mixed fuel gas stream F mixed The hydrogen gas stream F H By adding further components, the hydrogen content in the final cracking reactor fuel can be controlled to between 50% and 90% by volume.

[0054] Generally imported hydrogen gas stream F H The cost per kg is for the first methane off-gas stream MOG L Because it is more expensive per kilogram than the methane off-gas stream discharged from the reactor, an additional hydrogen gas stream F is introduced to control the hydrogen content in the cracking reactor fuel to the desired level. H It is important to minimize the flow rate. Therefore, according to the present invention, a recirculated hydrogen gas stream, for example, the reject gas from the pressure swing adsorption process, is mixed with a second methane off gas stream originating from the gas phase decomposition furnace, and a methane off gas output stream for methane off gas production is branched from the first methane off gas stream, thereby introducing a hydrogen gas stream F that is further needed to produce decomposition furnace fuel having the desired hydrogen content. H It is possible to minimize the flow rate. This makes it possible to economically produce eco-friendly cracking reactor fuel.

[0055] On the other hand, the fuel produced by the method for producing cracking reactor fuel of the present invention can be used as fuel for one or more cracking reactors, including liquid-phase cracking reactors and gas-phase cracking reactors.

[0056] The present invention will be described in more detail below with reference to examples. However, the following examples are for illustrative purposes only, and it will be obvious to an ordinary person that various changes and modifications are possible within the scope of the present invention and the technical concept, and the scope of the present invention is not limited to these examples alone.

[0057] Examples and Comparative Examples Comparative Example 1 The process flowchart shown in Figure 3 was simulated using the Aspen Plus simulator from AspenTech.

[0058] First, naphtha is fed into a liquid-phase decomposition furnace for thermal decomposition, and then the thermal decomposition products are sequentially cooled, compressed, and purified to produce the first methane off-gas stream MOG with a hydrogen content of 18% by volume. L Here, the first methane off-gas stream MOG was prepared. L The flow rate was 49.8 tons / hr. Meanwhile, recirculated C2 and C3 hydrocarbon compounds and propane were supplied to a gas-phase decomposition furnace for thermal decomposition, after which the thermal decomposition products were sequentially cooled, compressed, and purified to produce a second methane off-gas stream MOG with a hydrogen content of 67 volume%. G We prepared the following: Here, the second methane off-gas stream MOG G The flow rate was 7.8 tons / hr.

[0059] The first and second methane-off gas streams prepared in this manner were not mixed with the recirculated hydrogen gas stream, but instead became the first and second fuel gas streams F1 and F2, respectively. These were then mixed to form the mixed fuel gas stream F mixed This was used as the fuel for the cracking reactor, without being mixed with another hydrogen gas stream. The hydrogen content in the cracking reactor fuel was 29.7% by volume.

[0060] Example 1 The process flowchart shown in Figure 1 was simulated using the Aspen Plus simulator from AspenTech.

[0061] A first methane off-gas stream (flow rate: 49.8 ton / hr; hydrogen content: 18 vol%) and a second methane off-gas stream (flow rate: 7.8 ton / hr; hydrogen content: 67 vol%) were prepared as in Comparative Example 1.

[0062] On the other hand, a pressure swing adsorption process (PSA) is performed on the stream discharged from the cooling circulation area during the purification of the pyrolysis products, resulting in the rejection of gas F. PSA to the second methane off-gas stream MOG G It was mixed with the aforementioned Rejet gas F. PSA The hydrogen content inside was 77% by volume, and the flow rate was 0.6 tons / hr.

[0063] The first methane off-gas stream MOG L and second methane off-gas stream MOG mixed with eject gas G These were supplied to drums D1 and D2 respectively, and each stream was discharged at the same flow rate as the flow rate supplied to drums D1 and D2.

[0064] The first methane off gas stream MOG discharged from the drum D1 L A portion of the gas was branched off as the methane off-gas discharge stream MOGex, and the remainder was used to obtain the first fuel gas stream F1. Here, the hydrogen content in the discharge stream MOGex was 18% by volume and the flow rate was 32.8 ton / hr, while the hydrogen content in the first fuel gas stream F1 was 18% by volume and the flow rate was 17.0 ton / hr. Meanwhile, the second methane off-gas stream MOG was mixed with the ejected gas discharged from drum D2. G This was changed to the second fuel gas stream F2 (flow rate: 8.4 tons / hr).

[0065] Next, the first and second fuel gas streams F1 and F2 are mixed to form a mixed fuel gas stream F mixed Obtaining a mixed fuel gas stream F mixed The hydrogen content inside was 43% by volume, and the flow rate was 25.4 tons / hr.

[0066] Mixed fuel gas stream F mixed To adjust the hydrogen content inside to 85% by volume, 100% pure hydrogen gas stream F H The final decomposition reactor fuel (hydrogen content: 85% by volume, flow rate: 39.6 tons / hr) was produced by mixing the materials at a rate of 14.2 tons / hr.

[0067] Comparative Example 2 The process flowchart shown in Figure 2 was simulated using the Aspen Plus simulator from AspenTech.

[0068] First and second methane off-gas streams (MOG) with the same hydrogen content and flow rate as in Example 1. L MOG G And a reject gas (hydrogen content: 77% by volume; flow rate: 0.6 tons / hr) was prepared.

[0069] Next, the ejected gas is directed to the second methane off-gas stream MOG. G Without mixing, the first methane off-gas stream MOG L Mix with the methane off-gas output stream MOGex and the first methane off-gas stream MOG L Without branching, the first and second fuel gas streams F1 and F2 are mixed into a single fuel gas stream F mixed It was branched off from there. Here, the hydrogen content of the methane off-gas discharge stream MOGex was 31% by volume, and the flow rate was 33.7 tons / hr.

[0070] On the other hand, the mixed fuel gas stream F according to Comparative Example 2 mixed The hydrogen content inside was 31% by volume, and the flow rate was 24.5 tons / hr.

[0071] For the rest, it was carried out in the same manner as in Example 1, and the hydrogen content in the mixed fuel gas stream F mixed was adjusted to 85% by volume in the same manner as in Example 1. To achieve this, a hydrogen gas stream F H with a purity of 100% was mixed at 15.1 ton / hr to produce the final decomposer fuel (hydrogen content: 85% by volume, flow rate: 39.6 ton / hr).

[0072] Examples 2 to 5 For the process flowchart shown in FIG. 1, the process was simulated using the Aspen Plus simulator manufactured by AspenTech.

[0073] In Examples 2 to 5, to adjust the hydrogen content in the decomposer fuel as shown in Table 1, the introduction amount of the hydrogen gas stream F H and the discharge amount of the methane off-gas removal stream MOGex branched from and discharged from the first methane off-gas stream were controlled as shown in Table 1. Except for this, the decomposer fuel was produced in the same process flow as in Example 1.

[0074] Comparative Examples 3 to 6 For the process flowchart shown in FIG. 2, the process was simulated using the Aspen Plus simulator manufactured by AspenTech.

[0075] In Comparitive Examples 3 to 6, to adjust the hydrogen content in the decomposer fuel as shown in Table 2, the introduction amount of the hydrogen gas stream F H and the discharge amount of the methane off-gas removal stream MOGex branched from and discharged from the first methane off-gas stream were controlled as shown in Table 2. Except for this, the decomposer fuel was produced in the same process flow as in Comparitive Example 2.

[0076] In Tables 1 and 2 below, the reduction of carbon dioxide means the amount reduced annually compared to Comparitive Example 1.<着

[0077]

Table 1

[0078] [Table 2]

[0079] The results from Examples 1-5 and Comparative Examples 2-6 showed that the effect of reducing carbon dioxide emissions from the cracking reactor increased as the hydrogen content in the cracking reactor fuel increased.

[0080] Furthermore, in Examples 1 to 5, where a recirculated hydrogen gas stream, specifically the reject gas from the pressure swing adsorption process, is mixed with a second methane off-gas stream originating from the gas-phase decomposition furnace, and the methane off-gas (MOG) discharge stream is discharged from a first methane off-gas stream originating from the liquid-phase decomposition furnace, it can be confirmed that the amount of hydrogen discharged along with the methane off-gas discharge stream is reduced to approximately half or more compared to the comparative example without this method, and that the flow rate of the hydrogen gas stream that must be further introduced from an external source is reduced. In other words, even when achieving the same hydrogen content in the decomposition furnace fuel, the examples of the present invention can improve profitability by reducing the amount of hydrogen that must be introduced from an external source.

Claims

1. The steps include preparing a first methane off-gas stream originating from a liquid-phase decomposition furnace and a second methane off-gas stream originating from a gas-phase decomposition furnace, The steps include: branching off a portion of the first methane off-gas stream as a methane off-gas discharge stream and obtaining a first fuel gas stream from the remainder; The steps include obtaining a second fuel gas stream from the second methane off-gas stream, The steps include: preparing a mixed fuel gas stream by mixing the first fuel gas stream and the second fuel gas stream; The step includes mixing a hydrogen gas stream with the aforementioned mixed fuel gas stream, The hydrogen content in the first methane off-gas stream is 10% to 20% by volume, and the methane content is 75% to 90% by volume. The hydrogen content in the aforementioned second methane off-gas stream is 67% to 77% by volume, and the methane content is 23% to 33% by volume. The feedstock for the aforementioned liquid-phase decomposition furnace includes naphtha, The feedstock for the aforementioned gas phase decomposition furnace contains hydrocarbon compounds having 2 to 4 carbon atoms. The thermal decomposition temperature of the liquid phase decomposition furnace is 500°C to 1,000°C. A method for producing decomposition furnace fuel, wherein the thermal decomposition temperature of the gas phase decomposition furnace is 500°C to 1,000°C.

2. The method for producing cracking reactor fuel according to claim 1, wherein the hydrocarbon compound having 2 to 4 carbon atoms, which is the raw material supplied to the gas phase cracking reactor, includes one or more selected from the group consisting of recycled C2 hydrocarbon compounds, recycled C3 hydrocarbon compounds, propane, and butane.

3. The second fuel gas stream is a mixture of the second methane off gas stream and a recirculated hydrogen gas stream. The method for producing cracking reactor fuel according to claim 1, wherein the hydrogen content in the recirculated hydrogen gas stream is higher than the hydrogen content in the second methane off gas stream.

4. The method for producing cracking reactor fuel according to claim 3, wherein the recirculated hydrogen gas stream is a reject gas produced by a pressure swing adsorption step.

5. The method for producing cracking furnace fuel according to claim 4, wherein the flow rate of the reject gas produced by the pressure swing adsorption step is 5% to 15% by weight relative to the flow rate of the second methane off gas stream.

6. The method for producing cracking reactor fuel according to claim 1, wherein the hydrogen content in the methane off-gas discharge stream is 15% to 25% by volume.

7. The method for producing cracked reactor fuel according to claim 1, wherein the hydrogen content in the cracked reactor fuel is 50% by volume to 90% by volume.

8. The aforementioned gas phase decomposition furnace includes a first gas phase decomposition furnace and a second gas phase decomposition furnace. The method for producing cracking reactor fuel according to claim 1, wherein the second methane off-gas stream is derived from a mixed stream of the discharge streams of the first and second gas-phase cracking reactors.

9. The first methane off-gas stream and the second methane off-gas stream are The steps include supplying the raw material to a liquid-phase decomposition furnace or a gas-phase decomposition furnace for thermal decomposition, The steps include: cooling the pyrolysis gas containing hydrogen, C1, C2, and C3 or higher hydrocarbon compounds, which are pyrolysis products, in a cooling tower; The steps include compressing the cooled pyrolysis gas with a compressor, A method for producing cracking reactor fuel according to claim 1, comprising the steps of preparing the fuel by a process including purifying the pyrolysis compression stream discharged from the compressor.

10. A step of preparing a first methane off-gas stream originating from a liquid-phase decomposition furnace and a second methane off-gas stream originating from a gas-phase decomposition furnace, The steps include: branching off a portion of the first methane off-gas stream as a methane off-gas discharge stream and obtaining a first fuel gas stream from the remainder; The steps include obtaining a second fuel gas stream from the second methane off-gas stream, The steps include: preparing a mixed fuel gas stream by mixing the first fuel gas stream and the second fuel gas stream; The steps include: preparing cracking reactor fuel by mixing a hydrogen gas stream with the aforementioned mixed fuel gas stream; The step includes using the aforementioned cracking reactor fuel as fuel for one or more cracking reactors, which are liquid-phase cracking reactors and gas-phase cracking reactors. The hydrogen content in the first methane off-gas stream is 10% to 20% by volume, and the methane content is 75% to 90% by volume. The hydrogen content in the aforementioned second methane off-gas stream is 67% to 77% by volume, and the methane content is 23% to 33% by volume. The feedstock for the aforementioned liquid-phase decomposition furnace includes naphtha, The feedstock for the aforementioned gas phase decomposition furnace contains hydrocarbon compounds having 2 to 4 carbon atoms. The thermal decomposition temperature of the liquid phase decomposition furnace is 500°C to 1,000°C. The decomposition method is such that the thermal decomposition temperature of the gas phase decomposition furnace is 500°C to 1,000°C.

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