Method for preparing pyrolytic oil from waste plastics

Abstract

The invention relates to a method for preparing pyrolytic oil from waste plastics. The method comprises the following steps: (A) preparing a waste plastic raw material; (B) supplying the waste plastic raw material through the lower part of a reaction distillation tower and pyrolyzing the waste plastic raw material to generate pyrolysis gas; (C) supplying a hydrogen donor stream through an upper portion of the reactive distillation column and reacting the hydrogen donor stream with the pyrolysis gas; and (D) discharging the pyrolysis gas reacting with the hydrogen donor stream through the upper part and condensing the discharged pyrolysis gas to obtain liquid oil.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0117692, filed on September 5, 2023, and Korean Patent Application No. 10-2024-0091880, filed on July 11, 2024, which are hereby incorporated by reference in their entirety. Technical Field

[0003] The present invention relates to a method for preparing pyrolysis oil from waste plastics, and more particularly to a method for preparing high-quality light hydrocarbon oil by reducing the amount of olefins in the pyrolysis oil of waste plastics. Background Art

[0004] Recently, the development and use of plastics with physical properties required for various applications and purposes has increased. Plastics require a lot of energy from crude oil extraction to production, and a large amount of carbon is emitted in the process. In addition, even when plastics used in various products are discarded, environmental pollution and huge disposal costs are generated, so the recycling of waste plastics has become an important social issue.

[0005] Generally, the methods of recycling waste plastics (resins) include mechanical recycling, chemical recycling and thermal recycling. Mechanical recycling is a method of crushing and selecting the collected waste plastics, separating the waste plastics by type, melting the waste plastics using an extruder, and mixing the waste plastics with new materials in a certain proportion or adding functional additives when granulating the waste plastics to produce resin products. Chemical recycling is a method of using various chemical means to extract only specific polymers, or to recycle and repolymerize pure single molecules. Thermal recycling is a method of burning waste plastics and recovering the waste plastics as heat energy.

[0006] In particular, chemical recycling can reduce greenhouse gases compared to incineration of waste plastics, and has recently received attention in alternative fuel development.

[0007] Specifically, for chemical recycling of waste plastics, a melt of waste plastics (WP) such as polyethylene or polypropylene is fed into a reactor and pyrolyzed at a certain temperature, and the pyrolysis product is fed into a separation tower and subjected to a refining process of separating the pyrolysis product according to boiling point, at which time C 5-12 Light oil (LO) is such as naphtha, long-chain heavy oil (HO) and high-boiling residual oil (RO). However, the light oil such as naphtha obtained by this method has the problem of high olefin content. The olefins contained in naphtha promote the generation of tar when introduced into the naphtha cracking center (NCC) process, thereby causing coking. Therefore, when the olefin content in naphtha is high, the product yield and quality may be reduced when introduced into NCC.

[0008] Therefore, a method of converting olefins into paraffins using hydrogen to reduce the amount of olefins has been proposed, but hydrogen is expensive and facilities for recycling unreacted hydrogen are also expensive, so this method is not economically feasible when applied to an actual process.

[0009] Therefore, when producing light hydrocarbon oil such as naphtha, a technology for reducing the amount of olefins is required. Summary of the invention

[0010] [Technical issues]

[0011] In order to solve the problems mentioned in the background technology, the purpose of the present invention is to prepare high-quality high-value-added light oil by reducing the amount of olefins in waste plastic pyrolysis oil.

[0012] However, the problem to be solved by the present application is not limited to the above-mentioned purpose, and other problems not described will be clearly understood by those skilled in the art from the following description.

[0013] [Technical solution]

[0014] In a general aspect, a method for preparing pyrolysis oil from waste plastics includes: preparing a waste plastic raw material; supplying the waste plastic raw material through a lower part of a reactive distillation tower and pyrolyzing it to generate a pyrolysis gas; supplying a hydrogen donor stream through an upper part of the reactive distillation tower and reacting the hydrogen donor stream with the pyrolysis gas; and discharging the pyrolysis gas that has reacted with the hydrogen donor stream through the upper part, and condensing the discharged pyrolysis gas to obtain liquid oil.

[0015] [Beneficial Effects]

[0016] The method for preparing pyrolysis oil from waste plastics of the present invention can reduce the amount of olefins in the pyrolysis oil by using cheap hydrogen donor compounds instead of expensive hydrogen (H2), thereby obtaining high-quality light hydrocarbon oil.

[0017] Furthermore, the amount of olefins in the pyrolysis oil is reduced, thereby preventing the production of tar that is promoted when light hydrocarbon oil is introduced into the NCC process.

[0018] Furthermore, a reactive distillation column is used, whereby a pyrolysis process of waste plastics and a refining process of gradually separating pyrolysis oil by boiling point difference can be performed in one device, and unreacted hydrogen donor compounds can be easily recycled, which can improve economic feasibility.

[0019] Effects that can be obtained by the present application are not limited to the above-described effects, and those skilled in the art to which the present invention pertains can clearly understand other effects not described above according to the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1The present invention is a flow chart of a method for preparing pyrolysis oil from waste plastics according to an embodiment.

[0021] Figure 2 The present invention is a flow chart of a method for preparing pyrolysis oil from waste plastics according to an embodiment. DETAILED DESCRIPTION

[0022] The terms and words used in the specification and claims of the present invention should not be limitedly interpreted as having conventional meanings or dictionary meanings, but should be interpreted as having meanings and concepts that satisfy the technical ideas of the present invention based on the principle that inventors can appropriately define the concepts of the terms in order to best describe their own inventions.

[0023] Regarding the description of the drawings, like reference numerals may be used to refer to like or related components.

[0024] Unless the relevant context clearly indicates otherwise, a singular form of a noun corresponding to an item may include more than one item.

[0025] In the present invention, phrases such as "A or B", "at least one of A and B", "at least one of A or B", "A, B or C", "at least one of A, B and C" and "at least one of A, B or C" may each include any or all possible combinations of the items listed together in one of the corresponding phrases.

[0026] The term "and / or" includes a combination of a plurality of related components or any one of the plurality of related components.

[0027] Terms such as “1st” and “2nd” or “first” and “second” may be used to simply distinguish a corresponding component from another component and do not limit the corresponding component in other aspects such as importance or order.

[0028] In addition, terms such as "front", "rear", "above", "below", "side", "left", "right", "upper" and "lower" used in the present application are defined based on the drawings, and the shapes and positions of the components are not limited by the terms.

[0029] The terms “comprising” or “having” specify the presence of features, numbers, steps, operations, components, parts or a combination thereof described in the present invention, but do not exclude the presence or addition of one or more other features, numbers, steps, operations, components, parts or a combination thereof.

[0030] When a component is referred to as being “connected,” “coupled,” “supported,” or “in contact with” another component, this includes not only the case where the components are directly connected, coupled, supported, or in contact with each other, but also the case where the components are indirectly connected, coupled, supported, or in contact with each other via a third component.

[0031] When a component is "on" another component, this includes not only a case where the component is in contact with the other component but also a case where the other component exists between the two components.

[0032] In addition, the terms "about" and "substantially" used in this application are used to refer to numerical values ​​or values ​​near the meaning when the inherent allowable errors of manufacturing and materials are proposed, and are used to prevent unintentional infringers from illegally using the exact or absolute numbers disclosed in the present invention to help understand the present invention.

[0033] The term "stream" used in this application may refer to a fluid stream in a process, and may also refer to the fluid itself flowing through a pipeline. Specifically, a stream may refer to both the fluid itself and the fluid stream flowing through a pipeline connecting corresponding devices to each other. In addition, a fluid may include any one or more components of a gas, a liquid, and a solid.

[0034] The term "C n ” refers to all hydrocarbons with n carbon atoms. For example, “C 5-12 ” refers to all hydrocarbon molecules with 5 to 12 carbon atoms, “C 13-22 ” refers to all hydrocarbon molecules having 13 to 22 carbon atoms, and “C 23-40 ” refers to all hydrocarbon molecules having from 23 to 40 carbon atoms.

[0035] The term "liquid oil" used in the present application refers to a product obtained by converting the gas stream obtained in the pyrolysis step into a liquid phase by condensation, and may also be referred to as "liquid distillate oil".

[0036] The "pressure" referred to in this application refers to the gauge pressure measured based on atmospheric pressure.

[0037] The "boiling point" referred to in this application refers to the boiling point at atmospheric pressure (1 bar).

[0038] The pyrolysis gas referred to in this application refers to gaseous pyrolysis oil.

[0039] The method for preparing pyrolysis oil from waste plastic according to an embodiment of the present invention comprises: (A) preparing a waste plastic raw material, (B) pyrolyzing the waste plastic raw material, (C) removing olefins by a hydrogen donor compound, and (D) obtaining liquid oil by condensation.

[0040] Hereinafter, each step of the method for preparing pyrolysis oil from waste plastics according to the present invention will be described in detail with reference to the accompanying drawings.

[0041] Figure 1 and Figure 2 is a flow chart of a method for preparing pyrolysis oil from waste plastics according to an embodiment.

[0042] First, a waste plastic raw material 1 (A) is prepared.

[0043] The waste plastic raw material 1 may contain natural polymers, synthetic polymers or mixtures thereof, and the synthetic polymers may include thermoplastic resins, such as polyethylene (PE), polypropylene (PP) and polystyrene. In addition, the thermoplastic resin may be a mixture with other types of resins, such as polyvinyl chloride (PVC) and polyethylene terephthalate (PET), thermosetting resins, etc.

[0044] After collection and selection, the waste plastic raw materials 1 such as these materials may be subjected to a pretreatment process including crushing, washing, drying and melting. The pretreatment process may be performed by conventional methods in the art.

[0045] For example, the size of the crushed waste plastic is not particularly limited, but the waste plastic raw material can generally be crushed into a size range of about 0.5 cm to 6.0 cm. Thereafter, the washed and dried waste plastic crushed material can be placed in a Figure 2 The incinerator 100 shown or a tubular melter such as an extruder is then melted. The extruder has an extrusion function through melting and kneading, and may be, for example, a twin-screw extruder.

[0046] When the waste plastic raw material 1 is a thermoplastic resin (e.g., polyethylene, polypropylene, or a mixture thereof), the melting temperature may be about 120° C. to 400° C., preferably about 320° C. to 380° C., but not limited thereto. The higher the melting temperature, the lower the viscosity of the molten waste plastic, which has the advantage of being able to transfer the fluid using a pump.

[0047] At the same time, refer to Figure 2 , the waste plastic melt may be heated by a heating device 110 disposed outside the reaction distillation tower 200, which will be described below, and then fed to the reaction distillation tower 200. The heating device 110 may be located upstream of the reaction distillation tower 200, and may be used as a heat source for the pyrolysis reaction of the waste plastic. For example, the heating device 110 may be an electric heater that transfers high-temperature heat to the waste plastic by passing high-temperature / high-pressure steam, hot water, a heat transfer fluid, etc. through a jacket, and there is no particular limitation on the heating device. For example, by the heating device 110, the waste plastic melt may be heated to a temperature higher than about 400° C. to 450° C., specifically about 420° C. to 430° C., for the pyrolysis reaction in the reaction distillation tower 200, which will be described below. At the same time, in order to maintain the temperature of the reaction distillation tower 200, a reboiler (not shown) may be additionally disposed outside the reaction distillation tower 200.

[0048] Subsequently, the waste plastic melt obtained through the pretreatment process is fed as a raw material through the lower portion of the reactive distillation tower 200 and then pyrolyzed to generate pyrolysis gas (B).

[0049] The reaction distillation tower 200 is a multistage distillation tower equipped with a plurality of trays (not shown), and in the storage tank area at the lower part of the reaction distillation tower 200, the pyrolysis reaction (B) of the waste plastic raw material 1 can be performed to produce pyrolysis gas, and the pyrolysis gas can be gradually separated into gas and liquid by boiling point difference. The number of stages and size of the reaction distillation tower are not particularly limited, and can be set based on the theoretical number of stages inferred from the distillation curve in consideration of the composition of the waste plastic raw material. Here, the "theoretical number of stages" refers to the number of virtual sections or stages in the reaction distillation tower in which two phases (e.g., gas phase and liquid phase) are balanced with each other. For example, the reaction distillation tower 200 may have a multistage structure including 20 to 50 stages. Since the temperature gradually decreases in the upper direction of the reaction distillation tower, the hydrocarbon component with a relatively high boiling point can be separated at the stage located at the lower part, and the hydrocarbon component with a relatively low boiling point can be separated at the stage located at the upper part.

[0050] Reference Figure 1 and Figure 2 , the waste plastic raw material 1 is fed into the storage tank at the lower part of the reaction distillation tower 200, and the pyrolysis reaction (B) of the waste plastic raw material 1 is performed in the storage tank to generate pyrolysis gas. Here, the storage tank may refer to an area containing liquid raw materials at the bottom below the lowermost tray of the reaction distillation tower 200. In addition, the waste plastic raw material 1 may be fed below the liquid level of the waste plastic raw material contained in the storage tank of the reaction distillation tower.

[0051] In the conventional waste plastic pyrolysis process, the waste plastic raw material is pyrolyzed in a reactor, and then the naphtha in the pyrolysis oil is separated in a distillation device. On the other hand, in the present invention, a reactive distillation tower 200 is used, so that an efficient process can be configured by integrating the facilities for the pyrolysis and separation processes of waste plastics. In addition, since the temperature at which the hydrogen donor compound described below reacts with the pyrolysis gas is about 200°C to less than 350°C, in the conventional method, a separate temperature control facility is required to react the pyrolysis gas with the hydrogen donor compound. On the other hand, when the reactive distillation tower 200 is used as described in the present invention, by introducing the hydrogen donor compound into the stage representing the above temperature range, the pyrolysis gas can be reacted with the hydrogen donor compound without a separate facility. In addition, when a conventional reactor is used, since the pyrolysis reaction continues to occur during the residence time of the waste plastic in the reactor, the naphtha produced in the reactor before the end of the residence time may be excessively decomposed, and therefore, the final naphtha yield may be reduced. On the other hand, when the reactive distillation column 200 is used as described in the present invention, the naphtha pyrolyzed in the storage tank undergoing the pyrolysis reaction is first immediately taken out and transferred to the upper distillation separation stage without additional pyrolysis, and therefore, the occurrence of excessive decomposition reaction can be suppressed, thereby improving the naphtha yield.

[0052] In one embodiment of the present invention, the pyrolysis reaction of the waste plastic melt may be carried out at a temperature higher than about 400°C to 450°C, specifically about 420°C to 430°C, but is not limited thereto. The waste plastic may be a mixture containing a thermoplastic resin, such as polyethylene, polypropylene, or a mixture thereof. For example, the waste plastic may be a mixture containing polyethylene having a number average molecular weight (Mn) of about 10,000 to 500,000 and / or polypropylene having a number average molecular weight of about 5,000 to 300,000, but is not limited thereto. Considering that the waste plastic is a thermoplastic resin, when the pyrolysis temperature is below 400°C, the pyrolysis rate may slow down, and when the pyrolysis temperature is higher than 450°C, the pyrolysis rate may speed up, but excessive solid carbides, such as coke, may be produced due to the high temperature.

[0053] In addition, considering the naphtha yield, the internal operating pressure of the reactive distillation tower 200 for the pyrolysis reaction may be adjusted to about 1 to 20 bar, specifically about 1 to 5 bar. When the above operating pressure is met, excessive pyrolysis of naphtha or failure to convert waste plastic into naphtha in the pyrolysis process may be minimized.

[0054] In one embodiment of the present invention, the pyrolysis product obtained by pyrolyzing the waste plastic melt may contain pyrolysis gas, and the pyrolysis gas contains non-condensable C 1-4 components, which can be converted into liquid oil by condensation 5-12 Light components (such as naphtha) and longer chain heavier hydrocarbon components, as well as high boiling point residues which are not completely decomposed and therefore do not vaporize.

[0055] In addition, the low molecular weight components produced by pyrolysis can include saturated hydrocarbons and unsaturated hydrocarbons. Here, the low molecular weight components can refer to light hydrocarbons with less than 12 carbon atoms, more specifically, the saturated hydrocarbons of the low molecular weight components can include naphtha, and the unsaturated hydrocarbons of the low molecular weight components can refer to olefins with less than 12 carbon atoms. For example, relative to the total volume of the low molecular weight components produced by pyrolysis, the low molecular weight components can include about 60 volume % to 90 volume % of light saturated hydrocarbons and about 10 volume % to 40 volume % of light unsaturated hydrocarbons, and preferably include about 80 volume % to 90 volume % of light saturated hydrocarbons and about 10 volume % to 20 volume % of light unsaturated hydrocarbons, but is not limited thereto.

[0056] Through the pyrolysis reaction (B), the pyrolysis gas may be generated in an amount of 20 to 90 wt %, or 25 to 80 wt %, of the total weight of the waste plastic raw material, and may migrate to the upper portion of the reaction distillation column 200, and the unvaporized high-boiling point residue may remain in the lower portion of the reaction distillation column 200. Specifically, the pyrolysis product in the pyrolysis step (B) may contain about 10 to 60 wt % of C 5-12Light hydrocarbons, 30 to 50 wt% C 13-40 Heavy hydrocarbons and 10 to 50 wt. % of hydrocarbons above C 40 of high boiling point residues.

[0057] More specifically, the pyrolysis gas may be a 1-4 Hydrocarbon, C 5-12 Light hydrocarbons, C 13-22 Medium hydrocarbons and C 23-40 A gas stream of heavy hydrocarbons. 1-4 Hydrocarbons (such as methane, ethane and propane) are separated by evaporation because they are not condensable, and the remaining hydrocarbons are condensed to obtain liquid distillate. At the same time, the unevaporated high-boiling residue can be discharged as the lower discharge stream 4 of the reactive distillation column 200.

[0058] Meanwhile, if necessary, the method may further include a process of separating and refining a part of the pyrolysis gas in any stage in the reactive distillation tower 200 before or after supplying the hydrogen donor stream 2 to be described below. Specifically, in the pyrolysis gas generated in the pyrolysis step (B), hydrocarbon components having a boiling point of about 200° C. or more may be separated and refined.

[0059] In one embodiment of the present invention, Figure 2 As shown, the method may further include the step of separating one or more hydrocarbon components selected from the group consisting of a hydrocarbon component 7 having a boiling point of 350°C to 570°C and a hydrocarbon component 8 having a boiling point of 200°C to less than 350°C from the pyrolysis gas generated in the pyrolysis step (B).

[0060] More specifically, the hydrocarbon component 7 having a boiling point of 350°C to 570°C may include C 23-40 Heavy oil (HO), and the hydrocarbon component 8 having a boiling point of 200°C to less than 350°C may contain C 13-22 Intermediate oil (MO).

[0061] Specifically, in order to separate the hydrocarbon component 7 having a boiling point of 350° C. to 570° C. from the pyrolysis gas, a process of separating and discharging the hydrocarbon component 7 upstream of the supply of the hydrogen donor stream 2 as described below is performed. 23-40 In order to separate the hydrocarbon component 8 having a boiling point of 200° C. to less than 350° C. from the pyrolysis gas, a process of separating and discharging the C 2 downstream of the supply of the hydrogen donor stream 2 described below is performed. 13-22 The process of intermediate oil can obtain hydrocarbon components with relatively low boiling points, but the present invention is not limited to this.

[0062] For example, refer to Figure 2In the case where the hydrocarbon component 8 having a boiling point of 200° C. to less than 350° C. and the hydrocarbon component 7 having a boiling point of 350° C. to 570° C. are all separated from the pyrolysis gas, while the pyrolysis gas generated in the lower part of the reactive distillation tower 200 migrates to the upper part, first, the hydrocarbon component 7 having a relatively high boiling point can be separated to obtain C 23-40 Heavy oil (HO) can then be separated into hydrocarbon components with relatively low boiling points 8 to obtain C 13-22 Intermediate Oil (MO). In addition, after the separation process, the remaining pyrolysis gas migrates to the top of the reactive distillation column 200 as a gas stream containing hydrocarbon components having a boiling point below about 200°C.

[0063] At the same time, refer to Figure 2 The high boiling point residue that is not gasified in the pyrolysis product can be discharged through the lower discharge stream 5 of the reactive distillation column using a liquid pump 400 due to its high viscosity. The high boiling point residue is not fully utilized because it causes process operation problems or deteriorates the quality of the final product.

[0064] More specifically, the lower discharge stream 5 of the reaction distillation tower 200 may be fractionated and discharged as a liquid stream containing a high-boiling residue 6, and the remaining liquid stream may be recycled to the reaction distillation tower 200. At the same time, the high-boiling residue 6 at the lower portion of the reaction distillation tower may be discharged in the form of a high-viscosity wax. Here, the recycling of the lower discharge stream of the reaction distillation tower 200 may be performed to ensure a sufficient flow rate to prevent scaling in the pipe due to coke. In addition, the lower discharge stream 5 may be connected to a reboiler (not shown) additionally provided outside the reaction distillation tower to reduce the generation of coke while maintaining the fluid temperature at the lower portion of the reaction distillation tower 200, but is not limited thereto.

[0065] Subsequently, the hydrogen donor stream 2 is fed through the upper portion of the reactive distillation column 200 and reacts with the pyrolysis gas (step C).

[0066] In one embodiment of the present invention, the hydrogen donor stream 2 contains a hydrogen donor compound. The hydrogen donor compound is a supply compound that provides hydrogen to olefins that are unsaturated hydrocarbons, plays a role in converting the double bonds of olefins in the pyrolysis gas into saturated bonds of alkanes by replacing the double bonds with hydrogen, and contains at least one compound other than hydrogen (H2). Specifically, the hydrogen donor compound may contain at least one functional group of a hydroxyl group (-OH) and a carboxyl group (-COOH), and may be a compound having a boiling point of about 30°C to 200°C. For example, the hydrogen donor compound may include one or more compounds selected from low molecular weight alcohols, ethylene glycol, and formic acid having 1 to 8 carbon atoms.

[0067] In the pyrolysis oil generated in the waste plastic pyrolysis process, the oil fraction evaporated into light hydrocarbons (such as naphtha) with a boiling point of 50°C to less than 200°C contains a large amount of olefins. When the pyrolysis oil with a high olefin content is used in the naphtha cracking center (NCC) process, there is a problem of causing the generation of tar. Therefore, in the present invention, Figure 1 As shown, the hydrogen donor stream 2 is fed to any stage at the upper part of the reactive distillation column 200 to react the olefins contained in the pyrolysis gas with the hydrogen donor compound (H donor), and through the reaction, the double bonds of the olefins as unsaturated hydrocarbons are substituted with hydrogen to convert the double bonds into paraffins, thereby reducing the amount of olefins in the pyrolysis gas. In this case, the paraffins produced by the hydrogen substitution reaction may be discharged together with the hydrocarbon component 8 having a boiling point of 200° C. to less than 350° C., or may be discharged together with the hydrocarbon component 4 having a boiling point of 50° C. to less than 200° C., but are not limited thereto.

[0068] According to one embodiment of the present invention, the hydrogen donor stream 2 may be fed to a stage corresponding to 15% to 60%, preferably 15% to 50%, and more preferably 15% to 40% of the theoretical number of stages from the upper portion of the reactive distillation column 200. For example, when the theoretical number of stages of the reactive distillation column is 100, the uppermost stage may be the 1st stage, the lowermost stage may be the 100th stage, and the stages corresponding to 50% or less of the theoretical number of stages may refer to the 1st to 50th stages of the reactive distillation column. When the hydrogen donor stream 2 is fed to a stage within the above range of the reactive distillation column 200, a condition of excellent reactivity between olefins and the hydrogen donor compound (H donor) may be satisfied, and thus the olefin removal rate may be improved.

[0069] More specifically, in the hydrogen donor stream supplying step (C), the hydrogen donor stream 2 may be introduced into a stage operating in a temperature range of 200° C. to 400° C., preferably 200° C. to 380° C., and more preferably 250° C. to 350° C. When the operating temperature of the stage where the hydrogen donor stream 2 is introduced is too low, the reaction between the olefins in the pyrolysis gas and the hydrogen donor compound (H donor) may not occur, resulting in reduced olefin removal performance. At the same time, the higher the operating temperature, the higher the reactivity between the olefins in the pyrolysis gas and the hydrogen donor compound (H donor). However, when the operating temperature of the stage where the hydrogen donor stream is introduced is too high, the hydrogen substitution reaction between the pyrolysis gas and the hydrogen donor compound may actually deteriorate.

[0070] As mentioned above, the pyrolysis oil comprising naphtha etc. generally has high olefin concentration and causes the generation of tar when being used as the feed of NCC process.Usually, consider using hydrogen (H2) to convert olefin into the method for paraffin.However, when using hydrogen (H2), due to the high cost of hydrogen and the high price of the condenser for hydrogen (H2) recycling, there is the problem of low economic feasibility.In order to solve the problem of related art, in the present invention, use is made of hydrogen donor compound as cheap hydrogen source (H-source), without using expensive hydrogen (H2) gas, in addition, when reusing hydrogen donor compound, conventional liquid pump can be used, which is conducive to disposing and running the process under the situation of having economic feasibility.

[0071] In the hydrogen donor stream supplying step (C), the ratio of the total weight of the waste plastic raw material 1 to the introduction flow rate of the hydrogen donor stream 2 can be 1:0.01 to 1:1, preferably 1:0.3 to 1:0.5, but is not limited thereto. When the amount of the introduced hydrogen donor stream 2 is too small, the amount of hydrogen provided to the olefins in the pyrolysis gas is insufficient, which may lead to the deterioration of the olefin removal performance, and when the amount of the introduced hydrogen donor stream 2 is too large, the hydrogen donor compound may generate oxides, which may lead to the problem of failing to meet the naphtha cracker specification.

[0072] In one embodiment of the present invention, Figure 2 As shown, in the case where hydrocarbon components having a boiling point of 200° C. or more are first separated and recovered, when the hydrogen donor stream 2 is fed, the pyrolysis gas may contain a high proportion of hydrocarbon components having a boiling point of less than 200° C.

[0073] At the same time, when the hydrogen donor stream 2 is fed, a reaction catalyst may also be introduced to improve the removal rate of olefins in the pyrolysis gas. Specifically, Figure 2 As shown, a catalyst layer 210 for supplying a reaction catalyst can be disposed above the position where the hydrogen donor stream 2 is fed. More specifically, a metal catalyst can be used as a reaction catalyst to promote the hydrogen substitution reaction between the hydrogen donor stream 2 and the olefins in the pyrolysis gas, and can include one or more metal components such as nickel (Ni), silicon (Si) and aluminum (Al), but is not limited thereto. More specifically, a catalyst in the form of Ni supported on a Si / Al carrier can be used as a metal catalyst, wherein the carrier can promote pyrolysis, and the carrier can promote the hydrogen supply reaction.

[0074] More specifically, the amount of the reaction catalyst introduced may be about 3 parts by weight or less, preferably 0.1 to 2 parts by weight, relative to 100 parts by weight of the amount of the hydrogen donor stream 2 introduced. By introducing the reaction catalyst, the olefin removal effect can be improved, but when the amount of the reaction catalyst introduced is too much, the problem of overreaction may occur.

[0075] Thereafter, the pyrolysis gas reacted with the hydrogen donor stream is discharged through the upper exhaust stream 3 and then condensed to obtain liquid oil 4 (step D).

[0076] The upper discharge stream 3 of the reactive distillation column 200 may be a gas stream containing light hydrocarbon components having a boiling point lower than 200° C. and unreacted hydrogen donor compounds, and more specifically, may contain non-condensable C 1-4 components, can be converted into liquid oil C by condensation 5-12 Light components (such as naphtha), and unreacted hydrogen donor compounds. In addition, the light components having 12 or less carbon atoms may include saturated hydrocarbon components (such as naphtha) and unsaturated hydrocarbon components (such as olefins).

[0077] The upper discharge stream 3 of the reactive distillation tower 200 can be obtained as liquid oil 4 through a condensation process after discharge. Condensation is a process of cooling the pyrolysis gas, thereby suppressing the polymerization reaction of hydrocarbons in the high-temperature pyrolysis gas discharged from the reactive distillation tower 200 and reducing the heat load of the subsequent process.

[0078] Reference Figure 1 The pyrolysis gas reacting with the hydrogen donor stream is discharged as the upper exhaust stream 3 through the upper part of the reactive distillation column 200 and fed to the condenser 300, and the upper exhaust stream 3 exchanges heat with the quench oil or quench water, and is cooled and condensed at this time, thereby obtaining liquid oil 4. Finally, phase separation with the unreacted hydrogen donor compound may occur in the condenser 300, thereby obtaining liquid oil 4. The cooling temperature by heat exchange may be about 0°C to 50°C, specifically about 20°C to 30°C.

[0079] Specifically, the liquid oil obtained in the condensation step (D) may contain C 5-12 More specifically, the liquid oil obtained in the condensation step (D) may contain 10 to 60 wt %, specifically 30 to 50 wt %, of C 2+ as a saturated hydrocarbon component, relative to the total weight of the liquid oil. 5-12 Light oil.

[0080] Meanwhile, the liquid oil obtained in the condensation step (D) may contain olefins as unsaturated hydrocarbon components in an amount of 25% by volume or less, specifically 1% to 20% by volume, and more specifically 10% to 20% by volume, relative to the total volume of the liquid oil. Since the amount of olefins in the liquid oil obtained in the condensation step (D) is low, a C olefin having a higher purity can be obtained. 5-12 Light saturated hydrocarbon oil (naphtha), and can minimize the tar formation that occurs when introduced into the NCC process. In addition, the liquid oil obtained in the condensation step (D) may also contain residual amounts of unreacted hydrogen donor compounds.

[0081] In one embodiment of the present invention, the upper effluent stream 3 of the reactive distillation column transferred to the condenser 300 may contain unreacted hydrogen donor compounds as polar components and C 5-12 Therefore, in the condensing step (D), the condensed unreacted hydrogen donor compound may be mixed with a C having a different polarity from that of the condensed unreacted hydrogen donor compound. 5-12 The light saturated hydrocarbon oil is separated into layers and can be discharged through the first lower discharge stream 9 of the condenser 300.

[0082] Reference Figure 2 , the first lower discharge stream 9 of the condenser 300 containing the unreacted hydrogen donor compound can be recycled as the hydrogen donor stream 2 in the hydrogen donor stream supplied in the step (C). More specifically, in the reactive distillation column 200, the unreacted hydrogen donor compound can be discharged together with the pyrolysis gas through the gaseous upper discharge stream 3 due to its low boiling point, and can be introduced into the condenser 300 and condensed, and in the condenser 300, the unreacted hydrogen donor compound as a polar component can be mixed with the C as a non-polar component. 5-12 The light saturated hydrocarbon oil layer is separated and can be discharged through the first lower discharge stream 9 of the condenser 300 to be reused as the hydrogen donor stream 2 of the reactive distillation column 200. The first lower discharge stream 9 of the condenser 300 is a liquid stream, and the unreacted hydrogen donor compound can be easily transferred at a low cost using a liquid pump, which is advantageous for economical reuse.

[0083] In addition, the second lower discharge stream of the condenser 300 containing naphtha may be refluxed to the upper portion of the reactive distillation column 200. The second lower discharge stream is a stream recycled in order to increase the purity of the upper discharge stream 3 separated and discharged through the upper portion of the reactive distillation column 200, and may be refluxed to the upper portion of the reactive distillation column 200 in a minimum amount to satisfy the target naphtha purity.

[0084] Meanwhile, in the condensation step (D), the uncondensed gas stream 10 can be recycled as a process gas in the raw material preparation step (A). Specifically, in the heat exchange in the condenser 300, the uncondensed gas components (e.g., C 1-4 The hydrocarbon gas) can be discharged through the upper discharge stream 10 of the condenser 300 and used as a process gas. Figure 2 , the upper exhaust stream 10 of the condenser 300 can be used as a fuel for the incinerator 100 in the melting process as a pre-processing process of the waste plastic raw material. As described above, the process gas 10 is reused and used as a fuel for the incinerator 100 without using additional external energy, thereby reducing energy use and improving process efficiency.

[0085] In the above, the method for preparing pyrolysis oil from waste plastics of the present invention has been described and explained with reference to the accompanying drawings. However, the description and explanation of the accompanying drawings are only used to illustrate the basic components of the present invention, and in addition to the processes and devices described and explained in the accompanying drawings, processes and devices that are not separately described and explained can be appropriately applied and used to implement the method for preparing pyrolysis oil from waste plastics of the present invention.

[0086] Hereinafter, the present invention will be described in more detail with reference to examples. However, the following examples are provided to illustrate the present invention. It will be apparent to those skilled in the art that various modifications and changes may be made without departing from the scope and spirit of the present invention, and the scope of the present invention is not limited thereto.

[0087] [Example]

[0088] Comparative Example 1

[0089] 300 parts by weight of a waste plastic melt including polyethylene (PE) and polypropylene (PP) in a weight ratio of 6:4 was put into a reactor and heated to 430° C. to perform a pyrolysis reaction, thereby obtaining pyrolysis oil.

[0090] Example 1

[0091] like Figure 1 As shown, 300 parts by weight of a waste plastic melt containing polyethylene (PE) and polypropylene (PP) in a weight ratio of 6:4 is heated to 430° C. using a heater, and then fed to a reaction distillation column 200, and subjected to a pyrolysis reaction. Subsequently, 100 parts by weight of formic acid is introduced from the upper portion of the reaction distillation column 200 into a stage corresponding to 15% of the theoretical stage number, and reacted at 200° C. That is, in Example 1, the flow ratio of the waste plastic melt to the formic acid is 3:1.

[0092] Example 2

[0093] The same method as in Example 1 was performed, except that 100 parts by weight of formic acid was introduced from the upper portion of the reactive distillation column 200 into a stage corresponding to 40% of the theoretical number of stages, and the reaction was performed at 350° C. That is, in Example 2, the flow ratio of the waste plastic melt to the formic acid was 3:1.

[0094] Example 3

[0095] The same method as in Example 1 was carried out, except that 150 parts by weight of methanol (MeOH) was introduced from the upper portion of the reaction distillation tower 200 into a stage corresponding to 40% of the theoretical number of stages, and the reaction was carried out at 350°C, i.e., in Example 3, the flow ratio of the waste plastic melt to methanol was 2:1.

[0096] Example 4

[0097] The same method as in Example 1 was performed, except that 150 parts by weight of methanol (MeOH) and 2.25 parts by weight of Ni / SiAl catalyst were introduced into the stage corresponding to 40% of the theoretical number of stages from the upper portion of the reactive distillation tower 200, and the reaction was performed at 350° C. That is, in Example 4, the flow ratio of the waste plastic melt, methanol, and catalyst was 2:1:0.015.

[0098] Example 5

[0099] The same method as in Example 1 was carried out, except that 150 parts by weight of methanol (MeOH) was introduced from the upper portion of the reaction distillation tower 200 into a stage corresponding to 60% of the theoretical number of stages, and the reaction was carried out at 400°C, i.e., in Example 3, the flow ratio of the waste plastic melt to methanol was 2:1.

[0100] Experimental example: Comparison of olefin amounts

[0101] In order to confirm the amount of olefins contained in the pyrolysis oil finally obtained from the waste plastic in each of Examples 1 to 5 and Comparative Example 1, the bromine number (BN) was measured according to the ASTM D1159 method, and the results are shown in Table 1.

[0102] Specifically, the bromine value (g / 100g) is a numerical value indicating unsaturated bonds, indicating the amount (g) of bromine substituted at the unsaturated component (ie, double bonds of olefins) in 100g of a sample. A lower bromine value indicates a lower olefin amount.

[0103] [Table 1]

[0104]

[0105] Referring to Table 1, it was confirmed that the bromine value of the pyrolysis oil of each of Examples 1 to 5 in which the waste plastic was reacted with formic acid or methanol as a hydrogen donor compound was reduced compared to Comparative Example 1 in which only the waste plastic was subjected to pyrolysis reaction. Thus, it was confirmed that the amount of olefins in the pyrolysis oil was reduced when reacting with the hydrogen donor compound.

[0106] More specifically, in Examples 1 and 2 and Examples 3 and 5, the amount and type of hydrogen donor compound are the same, and only the reaction temperature is different.

[0107] When comparing Examples 1 and 2, it was measured that the bromine value of Example 2, in which formic acid was fed from the upper part of the reactive distillation column 200 to a stage corresponding to 40% of the theoretical number of stages and the reaction was performed at a higher temperature of 350° C., was lower than that of Example 1, in which formic acid was fed from the upper part of the reactive distillation column 200 to a stage corresponding to 15% of the theoretical number of stages and the pyrolysis oil and the hydrogen donor compound were reacted at 200° C. This indicates that the higher the operating temperature at the position where the hydrogen donor compound is introduced in the reactive distillation column, the better the olefin removal effect.

[0108] However, when comparing Examples 3 and 5, the bromine value measured in the case of Example 5 in which methanol was fed from the upper portion of the reactive distillation column 200 into a stage corresponding to 60% of the theoretical number of stages and the pyrolysis oil and the hydrogen donor compound were reacted at 400° C. was lower than the bromine value in Example 3 in which methanol was fed from the upper portion of the reactive distillation column 200 into a stage corresponding to 40% of the theoretical number of stages and the reaction was performed at 350° C. This indicates that when the operating temperature at the position where the hydrogen donor compound is introduced in the reactive distillation column is too high, the olefin removal effect may actually be reduced.

[0109] Meanwhile, Example 4 is a case where only a reaction catalyst is further introduced when the hydrogen donor compound is introduced in Example 3. When Examples 3 and 4 are compared, the bromine value of Comparative Example 4 using the reaction catalyst is measured to be lower than that of Example 3 not using the reaction catalyst. Therefore, it is confirmed that when a reaction catalyst is introduced in the hydrogen substitution reaction of olefin with the hydrogen donor compound, the olefin removal performance is further improved.

[0110] Although exemplary embodiments of the present invention have been described, the present invention is not limited to these exemplary embodiments, and those skilled in the art will appreciate that various modifications and changes may be made without departing from the concept and scope of the following claims.

[0111] [reference numerals]

[0112] 1: Waste plastic raw materials

[0113] 2: Hydrogen donor flow

[0114] 3: Upper discharge flow of reactive distillation tower

[0115] 4: Hydrocarbon components with a boiling point of 50°C to below 200°C

[0116] 5: Bottom discharge flow of reactive distillation tower

[0117] 6: High boiling point residue

[0118] 7: Hydrocarbon components with boiling points of 350°C to 570°C

[0119] 8: Hydrocarbon components with a boiling point of 200°C to less than 350°C

[0120] 9: The first lower discharge flow of the condenser

[0121] 10: Upper discharge flow of condenser

[0122] 100: Incinerator

[0123] 110: Heating device

[0124] 200: Reaction distillation tower, 300: Condenser, 400: Pump

Claims

1. A method for preparing pyrolysis oil from waste plastics, the method comprising: (A) preparing waste plastic raw materials; (B) supplying the waste plastic raw material through the lower part of the reactive distillation tower and pyrolyzing it to generate pyrolysis gas; (C) supplying a hydrogen donor stream through an upper portion of the reactive distillation column and reacting the hydrogen donor stream with the pyrolysis gas; and (D) discharging the pyrolysis gas reacting with the hydrogen donor stream through the upper portion and condensing the discharged pyrolysis gas to obtain liquid oil.

2. The method of claim 1, wherein: The hydrogen donor stream comprises a compound selected from one or more of low molecular weight alcohols having 1 to 8 carbon atoms, ethylene glycol, and formic acid.

3. The method of claim 1, wherein: In step (C) the hydrogen donor stream is fed to a stage operating in a temperature range of 200°C to 400°C.

4. The method of claim 1, wherein: In step (C), the ratio of the total weight of the waste plastic raw materials to the supply flow rate of the hydrogen donor stream is 1:0.01 to 1:

1.

5. The method of claim 1, wherein: In step (C), a reaction catalyst is further introduced.

6. The method of claim 1, wherein: The liquid oil obtained in step (D) contains C 5-12 Light oil (LO).

7. The method of claim 6, wherein: The liquid oil obtained in step (D) contains olefins in an amount of 25% by volume or less relative to the total volume of the liquid oil.

8. The method according to claim 1, further comprising before step (C): separating one or more hydrocarbon components of hydrocarbons having a boiling point of 350° C. to 570° C. and hydrocarbons having a boiling point of 200° C. to less than 350° C. from the pyrolysis gas generated in the pyrolysis step (B), The hydrocarbons having a boiling point of 200°C to less than 350°C include C 13-22 intermediate oil (MO), and the hydrocarbons having a boiling point of 350°C to 570°C include C 23-40 Heavy oil (HO).

9. The method of claim 1, further comprising: In step (D), the unreacted hydrogen donor compound is phase-separated from the liquid oil, and the phase-separated unreacted hydrogen donor compound is recycled as the hydrogen donor stream in step (C).

10. The method of claim 1, wherein: The waste plastic raw material is a mixture containing polyethylene (PE) or polypropylene (PP).

11. The method of claim 1, wherein: The internal operating pressure of the reactive distillation column is 1 bar to 20 bar.

12. The method of claim 1, wherein: The reactive distillation column has a multi-stage structure including 20 to 50 stages.

13. The method of claim 1, wherein: A lower discharge stream containing a residue is discharged through the lower portion of the reactive distillation column, and a portion of the lower discharge stream is fractionated and refluxed to the reactive distillation column.

14. The method of claim 1, wherein: Step (A) comprises melting the waste plastic raw material, and The uncondensed gas stream in step (D) is used as fuel for melting the waste plastic raw material.

15. The method of claim 1, wherein: The hydrogen donor stream is fed from the upper portion of the reactive distillation column to a stage corresponding to 15% to 60% of the theoretical number of stages.

Images