KR20240155738A - Method and system for producing refined hydrocarbons from waste plastics - Google Patents

Abstract

The present disclosure relates to a method and a production system for producing purified hydrocarbons from waste plastic.
The method and system for producing refined hydrocarbons from waste plastic according to the present disclosure can minimize the generation of ammonium salts (NH ₄ Cl) in the process of refining waste plastic pyrolysis oil containing impurities including chlorine and nitrogen, and prevent the phenomenon of impurity particles being fixed within a reactor. In addition, the method and system for producing refined hydrocarbons according to the present disclosure have excellent refining efficiency because deactivation of a catalyst used in the process is prevented, long-term operation of the process is possible, and refined hydrocarbons and solid coke having low impurity content and low olefin content can be produced from waste plastic.

Description

Method and system for producing refined hydrocarbons from waste plastics

The present disclosure relates to a method and a production system for purified hydrocarbons from waste plastic.

Waste plastics are manufactured using petroleum as a raw material, and the recycling rate, such as energy recovery and mechanical recycling, is low, and a significant amount is simply incinerated or landfilled. Since these wastes take a long time to decompose in nature, they pollute the soil and cause serious environmental pollution. As a method for recycling waste plastics, there is a method of converting waste plastics into usable oil by thermal decomposition, and the oil produced by thermal decomposition of waste plastics in this way is called waste plastic pyrolysis oil.

However, pyrolysis oil obtained by pyrolyzing waste plastics has a higher content of impurities such as chlorine, nitrogen, and metals derived from waste materials compared to oil manufactured from crude oil using a general method. Therefore, there is a concern that it may emit air pollutants such as SOx and NOx when used as fuel, and only a limited amount can be blended with high value-added fuels such as gasoline and diesel.

In this way, as a purification method for removing impurities such as chlorine, nitrogen, oxygen, and metals contained in waste plastic pyrolysis oil, a method of reacting waste plastic pyrolysis oil with hydrogen in the presence of a hydrogenation catalyst to perform dechlorination/denitrogenation/deoxygenation, or a method of adsorbing and removing chlorine contained in waste plastic pyrolysis oil using a chlorine adsorbent, etc. are known.

Specifically, U.S. Patent Publication No. 3,935,295 discloses a technique for removing chloride contaminants from various hydrocarbon oils. The technique is a conventional technique in which oil is hydrogenated under a hydrogenation catalyst in a first reactor, a fluid containing hydrogen chloride (HCl) produced in the process and purified oil is introduced into a second reactor, and then the chlorine component contained in the fluid is removed by adsorption using an adsorbent.

However, as in the conventional technology described above, when reacting oil and hydrogen under a hydrogenation catalyst, chlorine compounds such as hydrogen chloride and nitrogen compounds generated together with the refined oil react to generate ammonium salts (NH ₄ Cl), and these ammonium salts cause various process problems. Specifically, the ammonium salts generated inside the reactor when the oil and hydrogen react not only cause corrosion of the reactor, reducing durability, but also cause many process problems such as differential pressure generation and reduced process efficiency due to this. In addition, when the process is operated for a long period of time, impurity particles in the waste plastic pyrolysis oil are fixed inside the reactor, similarly causing various process problems.

Therefore, there is a need to develop a method for producing refined hydrocarbons and solid coke from waste plastics while solving the process problems described above.

U.S. Patent Publication No. 3935295 (Registration Date: 1976.01.27)

The purpose of the present disclosure is to provide a method and a system for producing purified hydrocarbons from waste plastics, which minimize the production of ammonium salts (NH ₄ Cl) in a purification process of waste plastic pyrolysis oil containing impurities including chlorine and nitrogen.

Another object of the present disclosure is to provide a method and system for producing purified hydrocarbons from waste plastics, in which the activity of the catalyst is maintained for a long time, the purification efficiency is excellent, and long-term operation is possible.

Another object of the present disclosure is to provide a method and system for producing purified hydrocarbon from waste plastics, which can prevent the phenomenon of fixation of impurity particles.

Another object of the present disclosure is to provide a method and system capable of producing refined hydrocarbons and solid coke of high quality and having low content of impurities such as chlorine, nitrogen, oxygen, metals, and olefins from waste plastics.

In order to achieve the above object, in one aspect of the present disclosure, a method for producing refined hydrocarbons from waste plastic is provided, comprising: S1) a pyrolysis step of introducing waste plastic into a pyrolysis reactor to produce pyrolysis gas; S2) a step of introducing the pyrolysis gas into a hot filter filled with a neutralizing agent to produce waste plastic pyrolysis oil; S3) a step of dehydrating a first mixture comprising waste plastic pyrolysis oil, wash water, and a demulsifier by applying voltage; S4) a step of hydrogenating a second mixture comprising the first mixture dehydrated in step S3) and a sulfur source to produce refined oil from which impurities have been removed; and S5) a step of coking the refined oil from which the impurities have been removed.

In the step S3) according to an example of the present disclosure, the waste plastic pyrolysis oil can be mixed in a larger volume than the wash water.

In the step S3) according to an example of the present disclosure, the first mixture may be a mixture of waste plastic pyrolysis oil and washing water in a volume ratio of 1:0.001 to 0.5.

In the step S3) according to an example of the present disclosure, the first mixture may be a mixture of waste plastic pyrolysis oil and a demulsifier in a volume ratio of 1:0.000001 to 0.001.

The voltage according to an example of the present disclosure may be applied as an alternating current or a combination of alternating current and direct current.

According to one example of the present disclosure, the voltage may be applied through a vertical electrode.

A method for producing purified hydrocarbon from waste plastic according to an example of the present disclosure may further include, in step S3), a step of removing a rag layer from the first mixture after applying the voltage.

The step S3) according to an example of the present disclosure can be performed at a temperature condition of 20° C. to 300° C.

According to an example of the present disclosure, the ratio of the moisture content of the waste plastic pyrolysis oil and the moisture content of the first mixture dehydrated in step S3) may be 1:0.0001 to 0.9.

According to an example of the present disclosure, the step S3) may further dehydrate the dehydrated first mixture by coagulating the moisture.

According to an example of the present disclosure, the second mixture may have a weight ratio of nitrogen to chlorine of 1:1 to 10.

The sulfur source according to one example of the present disclosure may include a sulfur-containing oil.

According to an example of the present disclosure, the sulfur-containing oil may be included in an amount of less than 0.5 parts by weight based on 100 parts by weight of the first mixture dehydrated in step S3).

According to one example of the present disclosure, the sulfur source may include one or more sulfur-containing organic compounds selected from a disulfide compound, a sulfide compound, a sulfonate compound, and a sulfate compound.

The hydrogenation treatment according to an example of the present disclosure can be performed in the presence of a molybdenum-based hydrogenation catalyst.

The molybdenum-based hydrogenation catalyst according to one example of the present disclosure may be a catalyst in which a molybdenum-based metal or a metal including one or more selected from nickel, cobalt, and tungsten and the molybdenum-based metal are supported on a support.

The molybdenum-based hydrogenation catalyst according to one example of the present disclosure may include a molybdenum-based sulfide hydrogenation catalyst.

The hydrogenation treatment according to an example of the present disclosure can be performed under pressure conditions of 50 bar to 150 bar.

A method for producing refined hydrocarbons from waste plastic according to an example of the present disclosure may further include, after step S4), a step of washing a stream containing refined oil from which impurities have been removed by subjecting the stream to vapor-liquid separation.

The step S5) according to an example of the present disclosure may be coking the purified oil fraction separated by distillation of the purified oil from which the impurities have been removed.

The step S5) according to an example of the present disclosure may be coking a mixed oil in which the refined oil from which the impurities have been removed and the petroleum hydrocarbon are mixed.

The method and system for producing purified hydrocarbon from waste plastic according to the present disclosure can prevent the generation of ammonium salt (NH ₄ Cl) or minimize the generation thereof, and prevent the fixation phenomenon of impurity particles in the purification process of waste plastic pyrolysis oil containing impurities including chlorine and nitrogen.

The method and system for producing purified hydrocarbons from waste plastic according to the present disclosure have excellent purification efficiency and enable long-term operation of the process since catalyst deactivation due to moisture is prevented.

The method and system for producing purified hydrocarbon from waste plastic according to the present disclosure can provide purified hydrocarbon and coke having very low content of impurities such as chlorine, nitrogen, oxygen, metals, and olefins from waste plastic.

The method and system for producing refined hydrocarbons from waste plastics according to the present disclosure can be used in the production of environmentally friendly refined oil and petrochemical products using waste plastics.

FIG. 1 is a process diagram of a method for producing purified hydrocarbon from waste plastic according to one embodiment of the present disclosure.

The advantages and features of the present invention, and the method for achieving them, will become clear with reference to the embodiments described in detail below. However, the present invention is not limited to the embodiments disclosed below, but may be implemented in various different forms, and these embodiments are provided only to make the disclosure of the present invention complete and to fully inform a person having ordinary skill in the art to which the present invention belongs of the scope of the invention, and the present invention is defined only by the scope of the claims.

Unless otherwise defined, all terms (including technical and scientific terms) used in this specification may be used in a commonly understood meaning to a person of ordinary skill in the art to which the present invention belongs.

As used herein, the singular forms of terms are to be construed to include the plural forms as well, unless otherwise specified.

The numerical range used in this specification includes the lower and upper limits and all values within that range, increments logically derived from the shape and width of the defined range, all doubly defined values, and all possible combinations of the upper and lower limits of a numerical range defined in different shapes. Unless otherwise specifically defined in the specification of the present invention, values outside the numerical range that may arise due to experimental error or rounding of values are also included in the defined numerical range.

The term "includes" as used herein is an open-ended description that has the equivalent meaning of expressions such as "comprises," "contains," "has," and "is characterized by," and does not exclude additional elements, materials, or processes not listed herein.

The term 'reactor' used in this specification may mean a device that can be used in processes such as production, refining, classification, and mixing of waste plastic pyrolysis oil. For example, 'reactor' may be interpreted to mean devices such as a dehydrator, a coalescer, a hydrotreating reactor, and a separator used in a process of refining waste plastic pyrolysis oil.

As used herein, the term 'vertical electrode' may mean an electrode erected vertically with respect to the ground, and the term 'horizontal electrode' may mean an electrode laid horizontally with respect to the ground.

The method and system for producing refined hydrocarbons from waste plastic according to the present disclosure include a step of producing pyrolysis gas by pyrolyzing waste plastic, a step of producing waste plastic pyrolysis oil from the pyrolysis gas, and a dehydration step including washing, demulsification, and voltage application to reduce problems such as catalyst deactivation due to moisture dispersed in the waste plastic pyrolysis oil in the form of an emulsion, corrosion of a reactor due to chlorine contained in the moisture and low pH of the moisture, etc. In addition, the method includes a hydrogenation step capable of minimizing the generation of ammonium salts that cause various problems in a process of refining pyrolysis oil and in oil refining and petrochemical processes using refined oil as a raw material, and a coking step for coking refined oil from which impurities have been removed through the above steps. The method for producing refined hydrocarbons from waste plastic according to the present disclosure can stably produce refined hydrocarbons and solid coke with a low impurity content from waste plastic by organically combining the above series of sequential steps.

Below, a method and system for producing purified hydrocarbons from waste plastic are described in detail.

The present disclosure provides a method for producing refined hydrocarbons from waste plastic, comprising: S1) a pyrolysis step of introducing waste plastic into a pyrolysis reactor to produce pyrolysis gas; S2) a step of introducing the pyrolysis gas into a hot filter filled with a neutralizing agent to produce waste plastic pyrolysis oil; S3) a step of dehydrating a first mixture comprising waste plastic pyrolysis oil, wash water, and a demulsifier by applying voltage; S4) a step of hydrogenating a second mixture comprising the first mixture dehydrated in step S3) and a sulfur source to produce refined oil from which impurities have been removed; and S5) a step of coking the refined oil from which the impurities have been removed.

First, step S1) is a pyrolysis step that produces pyrolysis gas by feeding waste plastic into a pyrolysis reactor.

The above pyrolysis step is a step of introducing waste plastic into a pyrolysis reactor and heating it to produce pyrolysis gas. The pyrolysis step may be performed at a temperature of 400 to 550°C in a non-oxidizing atmosphere, and specifically, the non-oxidizing atmosphere is an atmosphere in which the waste plastic is not oxidized (burned), and may be, for example, an atmosphere in which the oxygen concentration is adjusted to 1% by volume or less, an atmosphere of an inert gas such as nitrogen, water vapor, carbon dioxide, and argon. When the pyrolysis temperature is 400°C or higher, fusion of chlorine-containing plastic can be prevented, and when the pyrolysis temperature is 550°C or lower, some of the chlorine in the waste plastic may remain in the pyrolysis residue (char).

The above pyrolysis step can produce a pyrolysis gas phase, a pyrolysis liquid phase including oil and wax, and a pyrolysis solid phase including pyrolysis residue.

The above waste plastic may include at least one selected from the group consisting of polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polystyrene (PS). The waste plastic may include organic chlorine (organic Cl) and inorganic chlorine (inorganic Cl). Waste oil generated through cracking and pyrolysis reactions of waste plastic, such as waste plastic pyrolysis oil, contains a large amount of impurities originating from the waste plastic. Therefore, there is a concern about the emission of air pollutants when the waste oil is utilized, and in particular, since organic chlorine and inorganic chlorine components are converted to HCl and emitted during the high-temperature treatment process, it is necessary to purify the waste oil to remove the impurities of the chlorine components.

In general, waste plastics can be divided into waste plastic waste from daily life and waste plastic waste from industrial life. Household waste plastic waste is a mixed plastic containing PVC, PS, PET, PBT, etc. other than PE and PP, and in the present invention, it can mean mixed waste plastic waste containing 3 wt% or more of PVC together with PE and PP, and the chlorine content of waste plastics is, for example, 5,000 ppm or more, 5,000 to 15,000 ppm, and is characterized by a relatively high chlorine content. Industrial waste plastic waste is mostly made up of PE/PP, and the chlorine content is 100 to 1,000 ppm, 500 to 1,000 ppm, or 700 to 1,000 ppm, and is characterized by a low chlorine content compared to daily waste plastics. However, it has a high organic Cl content caused by adhesive or dye components, and in particular, a high proportion of chlorine contained in an aromatic ring.

In particular, chlorine originating from PVC in household waste plastics is removed with HCl (hydrogen chloride elimination), whereas chlorine in PE and PP, which account for the majority of industrial waste plastics, originates from adhesive or dye components. In most cases, the proportion of organic chlorine originating from aromatic rings is higher than that of organic chlorine formed at the end of chain links, which poses a problem in that it is difficult to remove with general thermal decomposition or neutralizing agents.

The pyrolysis gas produced in the above pyrolysis step may contain 5 to 35 wt% of Naphtha (bp ~150℃), 10 to 60 wt% of Kero (bp 150~265℃), 20 to 40 wt% of LGO (bp 265~380℃), and 5 to 40 wt% of UCO-2/AR (bp 380℃) based on the total weight, and specifically 5 to 30 wt% of Naphtha (bp ~150℃), 15 to 50 wt% of Kero (bp 150~265℃), 20 to 35 wt% of LGO (bp 265~380℃), and 10 to 40 wt% of UCO-2/AR (bp 380℃), or 5 to 20 wt% of Naphtha (bp ~150℃), 15 to 35 wt% of Kero (bp 150~265℃). The pyrolysis gas may include a weight ratio of light oil (sum of naphtha and kero) to heavy oil (sum of LGO and UCO-2/AR) of 0.1 to 3, 0.1 to 2.0, or 0.2 to 1.0. When the pyrolysis gas having the above-described oil composition range is subsequently introduced into the high-temperature filter of the present disclosure, the hardening effect of the target pyrolysis oil and the impurity removal effect can be improved. Specifically, in the high-temperature filter, a pyrolysis reaction primarily occurs at high temperature, and additional chlorine dissociation and oil hardening simultaneously proceed, and secondarily, the dissociated chlorine comes into contact with a neutralizing agent (CaO) and is fixed in the form of a salt. In particular, the amount of HCl generated from pyrolysis oil derived from household waste plastics containing PVC is large, and it is analyzed that the HCl dissociated chlorine is not recombined with hydrocarbons but is fixed at a high rate to a neutralizing agent (CaO) in a high-temperature filter. Accordingly, the pyrolysis step of the present disclosure may have better chlorine removal efficiency when household waste plastic raw materials are used. However, in the case of industrial waste plastics, the chlorine removal efficiency may be somewhat lower than that of household waste plastics because the chlorine content itself in the raw materials is lower; however, the hardening effect can be significantly improved due to the difference in the composition of the waste plastics.

The above pyrolysis reactor can be carried out in a high-temperature and high-pressure reactor (autoclave reactor), a batch stirred reactor, a fluidised-bed reactor, a packed-bed reactor, etc., and specifically, can be applied to all reactors capable of stirring and temperature control, and in the present disclosure, can be carried out in a batch reactor.

Meanwhile, the pyrolysis step may further include a pyrolysis gas recovery step for recovering the pyrolysis gas phase and the pyrolysis liquid phase as gas, and a separation step for separating the pyrolysis solid phase (solid content) into fine particles and coarse particles.

In the above gas recovery step, the pyrolysis gas containing low-boiling-point hydrocarbon compounds such as methane (CH ₄ ), ethane (C ₂ H ₆ ), and propane (C ₃ H ₈ ) among the gaseous compounds generated in the pyrolysis step is recovered. The pyrolysis gas generally contains combustible substances such as hydrogen, carbon monoxide, and low-molecular-weight hydrocarbon compounds. Examples of the hydrocarbon compounds include methane, ethane, ethylene, propane, propene, butane, and butene. Since such pyrolysis gas contains combustible substances, it can be used as fuel.

In the above separation step, the solid phase produced in the pyrolysis step, for example, the solid matter, such as carbide, neutralizer, and/or copper compound, is separated into fine particles and coarse particles. Specifically, the solid matter produced in the pyrolysis step can be separated into fine particles and coarse particles by classifying using a sieve having a smaller average particle diameter than the chlorine-containing plastic and a larger average particle diameter than the neutralizer and the copper compound. In the above separation step, it is preferable to separate the solid matter into fine particles containing a relatively large amount of the chlorine-containing neutralizer and copper compound, and coarse particles containing a relatively large amount of carbide. The fine particles and carbide may be reprocessed as necessary, and may be reused, used as fuel, or discarded in the pyrolysis step, but the present disclosure is not limited thereto.

Next, the step S2) is a step of producing waste plastic pyrolysis oil by injecting the pyrolysis gas into a hot filter filled with a neutralizing agent.

In the above step S2), the production of waste plastic pyrolysis oil may be carried out at a temperature of 400 to 550° C. and a pressure of normal pressure to 0.5 bar in an oxygen-free atmosphere, and the oxygen-free atmosphere may be an inert gas atmosphere or a closed system atmosphere without oxygen. In the above temperature range, the hardening of the pyrolysis gas progresses well, thereby improving the clogging phenomenon caused by wax and the occurrence of differential pressure.

In addition, in the step S2), the production of waste plastic pyrolysis oil may be carried out under the condition that the gas volumetric flow rate (GHSV) is 0.3 to 1.2 /hr or 0.5 to 0.8 /hr. When this is satisfied, the waste plastic pyrolysis oil may be hardened and impurities in the pyrolysis oil may be reduced.

The neutralizing agent may be a metal oxide, hydroxide, carbonate or a combination thereof, and the metal may be calcium, aluminum, magnesium, zinc, iron, copper or a combination thereof. Specifically, the neutralizing agent may be aluminum oxide, calcium oxide, magnesium oxide, zinc oxide, iron oxide and/or copper oxide. In addition, the neutralizing agent may be a zeolite component such as a spent FCC catalyst (E-cat), and may further include a spent FCC catalyst in the metal oxide. The neutralizing agent may preferably be calcium oxide, a spent FCC catalyst, copper metal or copper oxide, or may be calcium oxide.

The neutralizing agent may have a particle size of 400 to 900 μm, or may have a particle size of 500 to 800 μm. By filling the neutralizing agent having the particle size described above into the high-temperature filter, not only can the residence time (GHSV) of the pyrolysis gas be controlled to achieve hardening of the pyrolysis oil, but also the generation of differential pressure in the high-temperature filter can be suppressed to improve the efficiency of process operation.

Meanwhile, the size of the neutralizing agent particles may refer to D50, and the D50 refers to the particle diameter when the cumulative volume from the smallest particle size becomes 50% in particle size distribution measurement by the laser scattering method. Here, D50 can be measured by collecting a sample according to the KS A ISO 13320-1 standard for the manufactured carbonaceous material and using Malvern's Mastersizer3000 to measure the particle size distribution. Specifically, ethanol can be used as a solvent and, if necessary, an ultrasonic disperser can be used for dispersion, and then the volume density can be measured.

In the relevant technical field, it is common for a high-temperature filter to separate gas (pyrolysis gas) and char from pyrolysis products. However, in the present disclosure, a high-temperature filter filled with a neutralizing agent was applied to reduce impurities while simultaneously hardening, and as described above, the operating conditions of the high-temperature filter, such as the temperature, and the particle size of the neutralizing agent were adjusted to a specific range.

The above step S2) may satisfy the following relations 1 and 2.

[Relationship 1]

50 < (A ₂ -A ₁ )/A ₁ (%) < 100

[Relationship 2]

-80 < (B ₂ -B ₁ /B ₁ ) (%) < -50

In the above relational expression 1, A ₁ is the total amount (weight %) of naphtha (bp ~150℃) and kero (bp 150~265℃) of the pyrolysis gas, A ₂ is the total amount (weight %) of naphtha (bp ~150℃) and kero (bp 150~265℃) of the pyrolysis oil, and in the above relational expression 2, B ₁ is the content (ppm) of chlorine of the pyrolysis gas, and B ₂ is the content (ppm) of chlorine of the pyrolysis oil.

Specifically, the above relations 1 and 2 may be 60 < (A ₂ -A ₁ )/A ₁ (%) < 90, 65 < (A ₂ -A ₁ )/A ₁ (%) < 85, or 70 < (A ₂ -A ₁ )/A ₁ (%) < 80, and -75 < (B ₂ -B ₁ /B ₁ ) (%) < -55, -70 < (B ₂ -B ₁ /B ₁ ) (%) < -55, or -65 < (B ₂ -B ₁ /B ₁ ) (%) < -55.

The above relational expressions 1 and 2 numerically represent the degree of hardening and heavyening of waste plastic pyrolysis oil by using the high-temperature filter filled with the neutralizing agent of the present disclosure. In the present disclosure, the degree of hardening of pyrolysis oil can be improved to a very high level by controlling the oil composition of pyrolysis gas fed into the high-temperature filter, the content of chlorine, and the organic/inorganic substances containing the chlorine.

The waste plastic pyrolysis oil manufactured in the above step S2) may contain 30 to 50 wt% of Naphtha (bp ~150℃), 30 to 50 wt% of Kero (bp 150 to 265℃), 10 to 30 wt% of LGO (bp 265 to 380℃), and 0 to 10 wt% of UCO-2/AR (bp 380℃~) based on the total weight, and specifically, 35 to 50 wt% of Naphtha (bp ~150℃), 35 to 50 wt% of Kero (bp 150 to 265℃), 10 to 30 wt% of LGO (bp 265 to 380℃), and 0 to 8 wt% of UCO-2/AR (bp 380℃~) or 35 to 45 wt% of Naphtha (bp ~150℃), Kero (bp The pyrolysis gas may contain 35 to 45 wt% of LGO (bp 265 to 380°C), 10 to 20 wt% of LGO, and 0 to 6 wt% of UCO-2/AR (bp 380°C~). In addition, the weight ratio of the light fraction (sum of naphtha and kero) to the heavy fraction (sum of LGO and UCO-2/AR) may be 2.5 to 5, 2.5 to 4, or 3 to 3.8.

In a method for producing purified hydrocarbon from waste plastic according to one embodiment of the present disclosure, steps S1) and S2) may satisfy the following relationship 3.

[Relationship 3]

0.7 < T ₂ /T ₁ < 1.3

In the above relational expression 3, T ₁ is the temperature at which waste plastic is thermally decomposed in the pyrolysis reactor in step S1), and T ₂ is the temperature at which waste plastic thermal decomposition oil is produced in the high-temperature filter in step S2).

When the above T ₂ /T ₁ value is 0.7 or less, the ratio of condensation in the high-temperature filter and circulation to the pyrolysis reactor may increase, which may cause the final boiling point of the pyrolysis oil to become excessively low. On the other hand, when the above T ₂ /T ₁ value is 1.3 or more, the ratio of loss in the gas phase may increase excessively, which may cause the yield of the pyrolysis oil to decrease.

Specifically, the T ₂ /T ₁ value may be 0.7 to 1.2, 0.8 to 1.2, 0.8 to 1.1, 0.9 to 1.1, or, for example, 1. Accordingly, the above-described effect can be further improved.

Step S3) is a step of dehydrating by applying voltage to a first mixture containing the waste plastic pyrolysis oil, washing water, and a demulsifier.

Waste plastic pyrolysis oil contains moisture, and problems such as deactivation of hydrogenation catalyst and corrosion of reactor may occur due to moisture in the pyrolysis oil, and water-soluble impurities are contained in the moisture, so it is necessary to remove moisture. By going through the above step S3), moisture existing in the form of an emulsion in the waste plastic pyrolysis oil can be easily removed.

The waste plastic pyrolysis oil according to one embodiment of the present disclosure may include impurities such as chlorine compounds, nitrogen compounds, oxygen compounds, metal compounds, particles derived from char, and may include impurities in the form of compounds in which chlorine, nitrogen, oxygen, or metals are combined within hydrocarbons, and may include hydrocarbons in the form of paraffins, olefins, naphthenes, or aromatics.

According to one embodiment of the present disclosure, the wash water can serve to increase the probability of contact between waste plastic pyrolysis oil and the water in the form of an emulsion. In addition, a basic compound can be added to the wash water so as to remove a water-soluble acidic substance contained in the water, and the basic compound can be sodium hydroxide (NaOH), but is not particularly limited. According to one embodiment of the present disclosure, the waste plastic pyrolysis oil can be mixed in a larger volume than the wash water, and specifically, the first mixed solution can be a mixture of waste plastic pyrolysis oil and wash water in a volume ratio of 1:0.001 to 0.5, more specifically in a volume ratio of 1:0.005 to 0.4, and most specifically in a volume ratio of 1:0.01 to 0.3. When the above range is satisfied, washing is sufficiently performed so that impurities in the pyrolysis oil can be significantly reduced, and the cost required for removing the mixed wash water can be minimized.

According to one embodiment of the present disclosure, the demulsifier may be one or a mixture of two or more selected from the group consisting of polyethylene glycol, tert-butanol, acetone, alkylnaphthalenesulfonate, alkylbenzenesulfonate, nonionic alkoxylated alkyl phenol resin, polyalkylene oxide, and polyoxyethylene sorbitan ester, but is not limited thereto.

According to one embodiment of the present disclosure, the first mixture may be a mixture of waste plastic pyrolysis oil and a demulsifier in a volume ratio of 1:0.000001 to 0.001, specifically, a volume ratio of 1:0.000002 to 0.0005, and more specifically, a volume ratio of 1:0.000003 to 0.0001. When the above range is satisfied, the emulsion can be decomposed while minimizing the impact on the quality of the pyrolysis oil.

According to one embodiment of the present disclosure, the emulsifier may have a weight average molecular weight of 200 to 2,000, specifically, a weight average molecular weight of 300 to 1,000, and more specifically, a weight average molecular weight of 400 to 800. When the above range is satisfied, mixing with waste plastic pyrolysis oil and washing water under conditions in which a dehydration process is performed is facilitated, thereby increasing the decomposition efficiency of the water emulsion.

The emulsion-type moisture contained in the first mixture containing the above-mentioned waste plastic pyrolysis oil, washing water, and demulsifier is still difficult to remove because it is stable. Therefore, the moisture can be easily removed by applying voltage to the first mixture.

According to one embodiment of the present disclosure, the voltage may be applied as an alternating current or a combination of an alternating current and a direct current. Some impurity particles contained in waste plastic pyrolysis oil exhibit polarity, and when a direct current voltage is applied, polar impurity particles may accumulate on a specific electrode, and when the process is performed for a long period of time, a phenomenon in which the impurities are fixed on the electrode may occur. However, when an alternating voltage is applied, the polarity of the electrode changes periodically, so that the fixation phenomenon of the impurity particles can be prevented. In addition, the frequency of the alternating current according to one embodiment of the present disclosure may be a single frequency or a combination of two or more frequencies. As a specific example, in the case of a single frequency, an alternating current having a frequency of 60 Hz may be applied, and in the case of a combination of two or more frequencies, an alternating current having frequencies of 50 Hz and 60 Hz may be applied alternately, but is not limited thereto.

According to one embodiment of the present disclosure, the voltage may be applied via a vertical electrode. If impurity particles accumulate on the electrode during the process of preparing the mixture or applying the voltage, if they are not artificially washed, the phenomenon of the impurity particles being fixed on the electrode may occur after a long period of time. However, if a vertical electrode is used, the impurity particles fall to the bottom of the reactor without being accumulated on the electrode due to gravity without performing a separate washing operation, so the phenomenon of the impurity particles being fixed can be prevented in advance.

The magnitude of the voltage according to one embodiment of the present disclosure may be, but is not limited to, 0.1 to 50 kV, specifically 1 to 30 kV, and more specifically 5 to 20 kV.

The dehydration according to one embodiment of the present disclosure may be performed by any method known in the art. As a non-limiting example, the water may be removed by following the separated water layer after voltage application. The water may also be removed in a gas-liquid separator.

Metal impurities in the waste plastic pyrolysis oil stabilize the emulsion, hindering the oil-water separation, and help form a stable emulsion layer, commonly called a rag layer. This rag layer can be formed between the demineralized oil layer on the upper side of the first mixture and the water layer below, and can gradually thicken during the continuous dehydration process. The excessively thick rag layer can be discharged to the hydrogenation treatment stage equipment together with the demineralized oil. This reduces the demineralization effect of the demineralized oil, thereby reducing the efficiency of the process. In addition, the rag layer can be discharged together with the water, causing problems in the wastewater treatment process. Therefore, it is desirable to remove the rag layer formed between the demineralized oil layer and the water layer.

Thus, the method for producing purified hydrocarbon from waste plastic according to one embodiment of the present disclosure may further include a step of removing a rag layer from the first mixture after applying voltage in step S3). The removal of the rag layer may be performed through a pipe that penetrates the wall of the dehydrator and is connected to the outside after measuring a change in the density of the mixture through a density meter in the dehydrator to determine the formation location and thickness of the rag layer, but is not necessarily limited thereto.

According to one embodiment of the present disclosure, the step S3) may be to dehydrate the first mixture, and then further dehydrate the dehydrated first mixture by coagulating the moisture.

According to one embodiment of the present disclosure, the additional dehydration may be performed by supplying the dehydrated first mixture to a coalescer. Specifically, the residual moisture contained in the dehydrated first mixture may be removed by being coagulated by a collection filter in the coalescer, but this is only a specific example and is not necessarily limited thereto. As the moisture content in the waste plastic pyrolysis oil is further reduced through the additional dehydration, the deactivation of the catalyst due to moisture is prevented, and the stability of the process and the quality of the refined oil can be improved.

According to one embodiment of the present disclosure, the ratio of the moisture content of the waste plastic pyrolysis oil and the moisture content of the dehydrated first mixture may be 1:0.0001 to 0.9, specifically 1:0.0005 to 0.5, and more specifically 1:0.001 to 0.1. When the above range is satisfied, the risk of trouble occurring in subsequent processes including hydrogenation treatment is significantly reduced, and high-quality refined oil satisfying the specifications as a raw material can be produced, but is not necessarily limited thereto.

The step S3) according to one embodiment of the present disclosure can be performed at a pressure of 50 bar or less. When performed at a pressure of 50 bar or less, moisture in the pyrolysis oil can be easily removed, and process stability can be secured. Specifically, it can be performed at a pressure of 30 bar or less, more specifically, it can be performed at a pressure of 20 bar or less, and, without limitation, it can be performed at a pressure of 5 bar or more.

The step S3) according to one embodiment of the present disclosure may be performed at a temperature of 20° C. to 300° C. When the above range is satisfied, emulsion decomposition and moisture coagulation may occur well, thereby improving dehydration efficiency. Specifically, it may be performed at a temperature of 50° C. to 250° C., and more specifically, 80° C. to 200° C.

In order to improve the dehydration efficiency in step S3) according to one embodiment of the present disclosure, one or more additional processes selected from the group consisting of centrifugation and distillation may be performed before and/or after dehydration. The above-described additional processes may be performed by methods known in the art and are not particularly limited.

Next, step S4) is a step of hydrogenating the first mixture dehydrated in step S3) and the second mixture mixed with a sulfur source to produce refined oil from which impurities have been removed.

The second mixture according to one embodiment of the present disclosure may have a concentration of chlorine (Cl) of 10 ppm or more, specifically 100 ppm or more, more specifically 200 ppm or more, and an upper limit may be, but is not limited to, 3000 ppm or less.

According to one embodiment of the present disclosure, the second mixture may have a weight ratio of nitrogen to chlorine of 1:0.1 to 10, specifically 1:0.5 to 5, and more specifically 1:1 to 2. However, the weight ratio is only a specific example that may be included in the waste plastic pyrolysis oil, and the composition of the waste plastic pyrolysis oil is not limited thereto.

The hydrogenation treatment according to one embodiment of the present disclosure can be performed under a condition where the ratio of hydrogen to the second mixture is 100 Nm ³ /Sm ³ to 5000 Nm ³ /Sm ³ , specifically 500 Nm ³ /Sm ³ to 3000 Nm ³ /Sm ³ , and more specifically 1000 Nm ³ /Sm ³ to 1500 Nm ³ /Sm ³ . When this is satisfied, impurities can be effectively removed, the activity of the hydrogenation catalyst can be maintained at a high level for a long period of time, and the process efficiency can be improved.

The above sulfur source refers to a sulfur source that can continuously supply sulfur components during the refining process.

The above step S4) can suppress deactivation of a molybdenum-based hydrogenation catalyst due to insufficient sulfur source and high-temperature operation during the purification process and maintain catalytic activity by producing a second mixture containing the sulfur source.

According to one embodiment of the present disclosure, the sulfur supply source may include a sulfur-containing oil fraction. The sulfur-containing oil fraction refers to an oil fraction composed of hydrocarbons containing sulfur obtained using crude oil as a raw material. There is no particular limitation on the sulfur-containing oil fraction, and examples thereof may include light gas oil, straight run naphtha, vacuum naphtha, thermal cracking naphtha, straight run kerosene, vacuum kerosene, thermal cracking kerosene, straight run light oil, vacuum kerosene, thermal cracking light oil, sulfur-containing waste tire oil, and the like, or any mixture thereof.

According to one embodiment of the present disclosure, by including waste tire oil as the sulfur-containing oil, the high content of sulfur contained in the waste tire is converted into oil together with hydrocarbons, so that it can preferably function as a sulfur source for waste plastic pyrolysis oil. In addition, by using waste tire oil as a sulfur source for waste plastic pyrolysis oil, it is advantageous in terms of reducing the environmental load due to recycling of waste tires and maintaining catalytic activity for a long period of time.

Specifically, the sulfur-containing fraction may be light gas oil (LGO) having a specific gravity of 0.7 to 1. When this is used, it can be uniformly mixed with the dehydrated first mixture, and has the advantage of high hydrogenation efficiency. Specifically, the specific gravity may be 0.75 to 0.95, and more specifically, may be 0.8 to 0.9. The sulfur-containing fraction may contain sulfur in an amount of 100 ppm or more. When the sulfur component is contained in an amount of 100 ppm or less, the content of the supplied sulfur component may be small, and the effect of preventing deactivation of the molybdenum-based hydrogenation catalyst may be minimal. Specifically, the sulfur component may be contained in an amount of 800 ppm or more, more specifically, 8,000 ppm or more, and, but not limited to, 200,000 ppm or less.

The second mixture according to one embodiment of the present disclosure may contain sulfur in an amount of 100 ppm or more. As in the case of the sulfur-containing oil, if the sulfur component in the second mixture is contained in an amount of 100 ppm or less, the content of the supplied sulfur component may be small, and thus the effect of preventing deactivation of the molybdenum-based hydrogenation catalyst may be minimal. Specifically, the sulfur component may be contained in an amount of 800 ppm or more, more specifically, in an amount of 8,000 ppm or more, and, without limitation, in an amount of 200,000 ppm or less.

According to one embodiment of the present disclosure, the sulfur-containing oil may be included in an amount of less than 0.5 parts by weight based on 100 parts by weight of the first mixture dehydrated in step S3). Specifically, the sulfur-containing oil may be included in an amount of less than 0.1 parts by weight, more specifically, less than 0.05 parts by weight, and, without limitation, more than 0.01 parts by weight. Since the sulfur-containing oil is included in an amount of less than 0.5 parts by weight, the concentration of chlorine (Cl) or nitrogen (N) included in the waste plastic pyrolysis oil is diluted, thereby controlling the production rate of ammonium salt (NH ₄ Cl) and improving process stability.

According to one embodiment of the present disclosure, the sulfur source may include one or more sulfur-containing organic compounds selected from a disulfide compound, a sulfide compound, a sulfonate compound, and a sulfate compound. Specifically, it may include one or a mixture of two or more selected from dimethyldisulfide, dimethylsulfide, polysulfide, dimethyl sulfoxide (DMSO), methyl methanesulfonate, ethyl methanesulfonate, propyl methanesulfonate, propenyl propenesulfonate, propenyl cyanoethansulfonate, ethylene sulfate, bicyclo glyoxal sulfate, and methyl sulfate, which is provided by way of example only and the present disclosure is not limited thereto.

According to one embodiment of the present disclosure, the sulfur-containing organic compound may be included in an amount of 0.01 to 0.1 parts by weight based on 100 parts by weight of the first mixture dehydrated in step S3). Specifically, it may be included in an amount of 0.02 to 0.08 parts by weight, and more specifically, it may be included in an amount of 0.03 to 0.06 parts by weight. If it is included in an amount of less than 0.01 parts by weight, the content of the supplied sulfur component may be low, and thus the effect of preventing deactivation of the molybdenum-based hydrogenation catalyst may be minimal.

The above hydrogenation treatment means a hydrogenation reaction in which a reaction gas containing hydrogen gas (H ₂ ) is added to a first mixture solution dehydrated in the step S3) and a second mixture solution containing a sulfur source under a molybdenum-based hydrogenation catalyst. Specifically, the hydrogenation treatment may mean a conventionally known hydrogenation treatment including a hydrodesulfurization reaction, a hydrocracking reaction, a hydrodechlorination reaction, a hydrodenitrogenation reaction, a hydrodeoxygenation reaction, and a hydrodemetallation reaction. Through the hydrogenation treatment, impurities including chlorine (Cl), nitrogen (N), and oxygen (O) and a portion of olefins are removed, and other metal impurities can also be removed, and by-products containing the above impurities are generated.

The above by-product is generated by the reaction of hydrogen gas (H ₂ ) with impurities contained in the waste plastic pyrolysis oil, such as chlorine (Cl), nitrogen (N), sulfur (S), or oxygen (O), and specifically, may include hydrogen sulfide gas (H ₂ S), hydrogen chloride (HCl), ammonia (NH ₃ ) or water vapor (H ₂ O), and in addition, may include unreacted hydrogen gas (H ₂ ), trace amounts of methane (CH ₄ ), ethane (C ₂ H ₆ ), propane (C ₃ H ₈ ) or butane (C ₄ H ₁₀ ).

The molybdenum-based hydrogenation catalyst according to one embodiment of the present disclosure may be a catalyst in which a molybdenum-based metal, or a metal including one or more selected from nickel, cobalt, and tungsten, and the molybdenum-based metal are supported on a support. The molybdenum-based hydrogenation catalyst has high catalytic activity during hydrogenation treatment, and may be used alone or, if necessary, in the form of a binary system catalyst combined with a metal such as nickel, cobalt, or tungsten.

According to one embodiment of the present disclosure, the support may be, but is not limited to, alumina, silica, silica-alumina, titanium oxide, molecular sieve, zirconia, aluminum phosphate, carbon, niobia or a mixture thereof.

The molybdenum-based hydrogenation catalyst according to one embodiment of the present disclosure may include a molybdenum-based sulfide hydrogenation catalyst. For example, it may include molybdenum sulfide (MoS) or molybdenum disulfide (MoS ₂ ), but is not limited thereto, and may include a known molybdenum-based sulfide hydrogenation catalyst.

The reaction gas according to one embodiment of the present disclosure may further include hydrogen sulfide gas (H ₂ S). The hydrogen sulfide gas (H ₂ S) included in the reaction gas may act as a sulfur source and regenerate the activity of a molybdenum-based hydrogenation catalyst that has been deactivated during a purification process, such as a sulfur source mixed with waste plastic pyrolysis oil.

The hydrogenation treatment according to one embodiment of the present disclosure can be performed at a pressure of 150 bar or less. Specifically, it can be performed at a pressure of 120 bar or less, more specifically, 100 bar or less, and, but not limited to, it can be performed at a pressure of 50 bar or more. When the hydrogenation treatment is performed under a pressure condition exceeding 150 bar, since ammonia and hydrogen chloride are generated in excess during the hydrogenation treatment, the ammonium salt formation temperature increases, which can easily cause a differential pressure within the process such as a reactor, and the process stability can be significantly reduced. By controlling the contents of nitrogen and chlorine in the waste plastic pyrolysis oil, the increase in the ammonium salt formation temperature can be partially suppressed even under a pressure condition exceeding 150 bar; however, in this case, the waste plastic that is the target of the manufacturing method according to the present disclosure can be extremely limited, which is not appropriate.

The hydrogenation treatment according to one embodiment of the present disclosure may be performed at a temperature of 150° C. to 500° C. When the above range is satisfied, the hydrogenation treatment efficiency may be improved. Specifically, it may be performed at a temperature of 200° C. to 400° C.

The hydrogenation treatment according to one embodiment of the present disclosure may be performed in multiple stages, and as a specific example, may be performed in two stages. When the hydrogenation treatment is performed in two stages, the first stage may be performed at a lower temperature than the second stage. In this case, the first stage may be performed at a temperature of 150° C. to 300° C., specifically 200° C. to 250° C., and the second stage may be performed at a temperature of 300° C. to 500° C., specifically 350° C. to 400° C., but is not limited thereto.

A method for producing purified hydrocarbon from waste plastic according to one embodiment of the present disclosure may further include, after step S4), a step of washing a stream containing purified oil from which impurities have been removed after gas-liquid separation.

The stream containing the refined oil from which the impurities have been removed according to one embodiment of the present disclosure may include the refined oil from which the impurities have been removed, discharged from the rear end of the reactor where the step S4) is performed, as well as hydrogen chloride, ammonia, and unreacted hydrogen gas.

According to one embodiment of the present disclosure, ammonia and hydrogen chloride generated by hydrogenation can be removed from a stream containing refined oil from which impurities have been removed through the gas-liquid separation, and unreacted hydrogen gas can be recovered.

The gas-liquid separation according to one embodiment of the present disclosure can be performed using a separator by a method known in the art and is not particularly limited.

According to one embodiment of the present disclosure, the gas-liquid separation may be performed 2 to 4 times, specifically 3 to 4 times, and more specifically 4 times. When the above range is satisfied, since the refined oil contains trace amounts of NH ₃ and HCl, the generation of ammonium salts may be minimized even under low-temperature conditions for oil-water separation. In addition, even without adding a separate salt remover to the refined oil in the future, oil refining and petrochemical processes using the refined oil as a raw material may be stably performed.

The gas stream generated as a result of the gas-liquid separation according to one embodiment of the present disclosure may include off-gas including light hydrocarbons, hydrogen sulfide, ammonia, or hydrogen chloride, and unreacted hydrogen gas. The off-gas and unreacted hydrogen gas are separated according to a method known in the art, and the unreacted hydrogen gas is recycled within the process, and the off-gas is treated through the steps described below and can be used as fuel or discharged into the atmosphere.

According to one embodiment of the present disclosure, the washing may be performed to dissolve and remove salts contained in the gas stream, or to dissolve gases capable of forming salts, thereby inhibiting salt formation. The washing may be performed by a method known in the art, and is not particularly limited.

The washing according to one embodiment of the present disclosure may be performed 2 to 4 times, specifically 2 to 3 times. When the above range is satisfied, the salt removal and salt formation inhibition effects are sufficiently exerted, so that high-quality refined oil can be obtained, and the stability of the process can be secured.

A method for producing refined hydrocarbon from waste plastic according to one embodiment of the present disclosure may further include, after the step of separating a stream containing refined oil from which impurities have been removed and then washing it, the step of combusting the separated off-gas; and the step of treating the uncombusted off-gas.

According to one embodiment of the present disclosure, the waste gas may include light hydrocarbons of C1-C4, hydrogen sulfide (H ₂ S), ammonia (NH ₃ ), etc. Therefore, in order to use the waste gas as fuel, it is necessary to remove hydrogen sulfide (H ₂ S), ammonia (NH ₃ ), etc. The exhaust gas containing sulfur dioxide (SO ₂ ), nitrogen dioxide (NO ₂ ), etc. generated by the combustion of the waste gas may be discharged into the atmosphere after performing caustic scrubbing to meet emission standards.

In addition, after the step of combusting the waste gas, the uncombusted waste gas can be discharged as waste water after being treated by sour water stripping, adsorption, biological treatment, oxidation, amine scrubbing, or caustic scrubbing.

Next, step S5) is a step of coking the refined oil from which the above impurities have been removed.

By including the above coking step, not only refined hydrocarbons but also solid coke can be obtained from waste plastics, thereby improving the economic efficiency of the process.

In the present disclosure, “coking” may mean a delayed coking process used to convert crude oil residues, such as atmospheric residue and vacuum residue, which are typically residues remaining at the bottom of a distillation tower during atmospheric and vacuum distillation of crude oil.

The coking step according to one embodiment of the present disclosure may be performed using one or more coking devices selected from the group consisting of a fired heater and a furnace.

The temperature at which the caulking according to one embodiment of the present disclosure is performed may be 425°C or higher, 450°C or higher, 470°C or higher, 700°C or lower, 650°C or lower, 600°C or lower, 550°C or lower, 500°C or lower, or a value between the above values, and specifically may be 425 to 700°C, and more specifically 450 to 550°C, but is not limited thereto.

The pressure at which the coking is performed according to one embodiment of the present disclosure may be in the range of 1 to 20 bar, specifically 1 to 10 bar, and more specifically 1 to 5 bar, but is not limited thereto.

The step S5) according to one embodiment of the present disclosure may be coking the purified oil fraction separated by distillation of the purified oil from which the impurities have been removed. The purified oil fraction according to one embodiment of the present disclosure may be, but is not limited to, atmospheric residue, vacuum residue, or a mixture thereof.

The step S5) according to one embodiment of the present disclosure may be coking a mixed oil in which the refined oil from which the impurities have been removed and the petroleum hydrocarbon are mixed. In addition, it goes without saying that the mixed oil in which the refined oil fraction and the petroleum hydrocarbon are mixed may be coked.

The above petroleum hydrocarbons collectively refer to a mixture of hydrocarbons that exist naturally or a compound separated from the mixture, and specifically, may be, but is not limited to, atmospheric residue, vacuum residue, or a mixture thereof derived from crude oil.

According to one embodiment of the present disclosure, the mixed oil may contain refined oil from which the impurities have been removed in an amount of 5 wt% or more, 10 wt% or more, 20 wt% or more, 40 wt% or more, or 50 wt% or more, based on the total weight of the mixed oil, and may have an upper limit of, but not limited to, 95 wt% or less. Although the present disclosure is not necessarily limited to the above range, generally, the lower the impurity content in the refined oil, the higher the proportion of refined oil that can be included in the mixed oil.

In addition, the present disclosure provides a system for producing refined hydrocarbons from waste plastic, including: a pyrolysis reactor for producing pyrolysis gas from waste plastic; a hot filter into which the pyrolysis gas is input to produce waste plastic pyrolysis oil; a dehydrator for performing dehydration by applying voltage to a first mixture in which the waste plastic pyrolysis oil, washing water, and a demulsifier are mixed; a hydrogenation reactor into which the first mixture dehydrated in the dehydrator and hydrogen gas are introduced and hydrogenated under a hydrogenation catalyst to produce refined oil from which impurities are removed; and a coking device for coking the refined oil from which the impurities are removed.

The description of the method for producing purified hydrocarbons from waste plastics can be equally applied to the description of the system for producing purified hydrocarbons from waste plastics, to the extent that there is overlap.

The dehydrator according to one embodiment of the present disclosure may be equipped with vertical electrodes. The number of vertical electrodes equipped in the dehydrator according to one embodiment of the present disclosure may be at least 2 or more, specifically 4 or more, more specifically 6 or more, and may be 20 or less as an upper limit, but is not necessarily limited thereto.

The dehydrator according to one embodiment of the present disclosure may include a coalescer therein. The coalescer is a device that collects fine droplets to form large droplets, and a device commonly used in the industry can be used, and is not particularly limited.

According to one embodiment of the present disclosure, the first mixture dehydrated in the dehydrator may be introduced into the coagulator to produce an additionally dehydrated first mixture. When a dehydrator including the coagulator is used, the additionally dehydrated first mixture is of course introduced into the hydrogenation reactor together with hydrogen gas.

The system for producing refined hydrocarbon from waste plastic according to one embodiment of the present disclosure may further include a separator for separating refined oil from which impurities have been removed, generated from the hydrogenation reactor, into gas and liquid.

The number of the separators according to one embodiment of the present disclosure may be 2 to 4, specifically 3 to 4, and more specifically 4. When the above range is satisfied, since the refined oil contains trace amounts of NH ₃ and HCl, the generation of ammonium salts can be minimized even under low-temperature conditions for oil-water separation. In addition, even without adding a separate salt remover to the refined oil in the future, oil refining and petrochemical processes using the refined oil as a raw material can be stably performed.

A system for producing purified hydrocarbons from waste plastics according to one embodiment of the present disclosure may further include a recycle gas compressor for recovering unreacted hydrogen gas from a gas stream separated from the separator and feeding it into a hydrogenation reactor.

Hereinafter, the method and system for producing purified hydrocarbons from waste plastic according to the present disclosure will be described in more detail through examples. However, the following examples are only one reference for describing the present disclosure in detail, and the present disclosure is not limited thereto, and may be implemented in various forms. In addition, unless otherwise defined, all technical terms and scientific terms have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure belongs. In addition, the terminology used in the description of the present disclosure is only for the purpose of effectively describing specific embodiments, and is not intended to limit the present disclosure.

[Example 1]

The waste plastics from daily life for use as feed contained 73.4 wt% PE, 10.4 wt% PP, 9.8 wt% PVC, 2.3 wt% PET, 2.1 wt% nylon, and 2.0 wt% PU.

The above 600g of waste plastic feed from the living world was fed into a batch pyrolysis reactor and pyrolysis was performed at 500°C. The produced pyrolysis gas was fed into a 500°C high-temperature filter filled with 20g of CaO having a particle size (D50) of 400 to 900 μm, collected in a condenser, and recovered as waste plastic pyrolysis oil in a recovery section.

Under the conditions of 150 ℃ and 10 bar, the waste plastic pyrolysis oil, washing water, and polyethylene glycol having a weight average molecular weight of 500 were introduced into a dehydrator in a volume ratio of 1:0.25:0.0001 and stirred to prepare a first mixture. The first mixture was separated into oil and water by applying an AC voltage of 15 kV through a vertical electrode, and then the water layer was removed to perform dehydration.

At this time, the waste plastic pyrolysis oil had a moisture content of about 5,000 ppm or more and contained high concentrations of impurities such as nitrogen (N) of 500 ppm or more, chlorine (Cl) of 200 ppm or more, and olefin of 20 volume% or more.

A second mixture was prepared by mixing 0.04 parts by weight of dimethyl disulfide with 100 parts by weight of the first mixture dehydrated in the above dehydrator, and then hydrogenation was performed under the conditions of 300°C and 70 bar to produce refined oil from which impurities were removed.

The refined oil from which the above impurities have been removed was distilled to separate the atmospheric residual oil and the atmospheric residual oil derived from crude oil having a boiling point of 380°C or higher were mixed in a weight ratio of 2 to 8, and the mixed oil was fed into a heating furnace and coked under the conditions of 480°C and 4 bar to obtain refined hydrocarbons and solid coke.

[Examples 2 and 3]

In Example 1, waste plastic pyrolysis oil, washing water, and polyethylene glycol were charged into a dehydrator in the volume ratios shown in Table 1 below, and the same conditions as in Example 1 were performed to obtain purified hydrocarbons and solid coke.

[Example 4]

Example 1 was performed under the same conditions as Example 1 except that a direct current voltage was applied through the horizontal electrode, to obtain refined hydrocarbon and solid coke.

[Example 5]

In Example 1, dehydration of the first mixture was performed under the same conditions as in Example 1, except that it was performed at a temperature of 120°C, to obtain purified hydrocarbon and solid coke.

[Example 6]

In Example 5, waste plastic pyrolysis oil and polyethylene glycol were introduced in a volume ratio of 1:0.00001, and the hydrogenation process was performed under the same conditions as Example 1, except that the pressure was 180 bar, to obtain refined hydrocarbons and solid coke.

[Example 7]

In Example 1, the same conditions as in Example 1 were performed except that additional dehydration was performed through a coagulant after dehydration of the first mixture, thereby obtaining purified hydrocarbon and solid coke.

[Comparative Example 1]

Example 1 was performed under the same conditions as Example 1 except that no wash water was added, thereby obtaining purified hydrocarbon and solid coke.

[Comparative Example 2]

Example 1 was performed under the same conditions as Example 1 except that polyethylene glycol was not added, thereby obtaining purified hydrocarbon and solid coke.

[Comparative Example 3]

Example 1 was performed under the same conditions as Example 1 except that no voltage was applied, to obtain purified hydrocarbon and solid coke.

[Comparative Example 4]

Example 1 was performed under the same conditions as Example 1, except that dimethyl disulfide was not mixed into the dehydrated first mixture, thereby obtaining purified hydrocarbon and solid coke.

Evaluation example

measurement method

The moisture and chlorine contents in the mixture obtained after the dehydration process and the chlorine content in the refined oil from which impurities were removed were measured and displayed using ICP and XRF analysis methods.

The catalytic activity retention time was measured in hours based on the point at which the nitrogen content in the refined oil exceeded 10 ppm through Total Nitrogen & Sulfur (TNS element) analysis on refined oil.

In addition, the processes of the above examples and comparative examples were operated for 3 months, and the particle fixation rate was measured according to Equation 1 below.

[Formula 1]

Particle fixation rate (%) = (amount of impurity particles fixed on the electrode/amount of impurity particles in the pyrolysis oil)*100

The above measurement results are shown in Table 1 below.

As shown in Table 1 above, Comparative Examples 1 to 3 showed low moisture and Cl removal effects by the dehydration step as a result of varying the presence or absence of wash water, presence or absence of demulsifier, and presence or absence of voltage application from the Examples, respectively. As the waste plastic pyrolysis oil containing many impurities was hydrogenated, the Cl content in the refined oil was high and the hydrogenation catalyst was deactivated relatively quickly. Although in Comparative Example 4, moisture and some impurities in the waste plastic pyrolysis oil were sufficiently removed in the dehydration step, the hydrogenation catalyst was deactivated in a short period of time due to the insufficient sulfur content, and if the process was maintained for a long time, the Cl content in the refined oil was high, as in the other Comparative Examples. Since a large amount of Cl included in the refined oil can cause corrosion of the coking device, it can be expected that the content of refined oil in the mixed oil cannot but be limited.

However, in Examples 1 to 7 according to the method for producing refined hydrocarbons from waste plastics of the present disclosure, a significant amount of moisture contained in the waste plastic pyrolysis oil was removed through the dehydration step, and a sulfur source was added, thereby significantly prolonging the activity of the hydrogenation catalyst. In addition, it was confirmed that a large amount of refined oil can be input into the coking step without performing additional impurity removal, since some water-soluble impurities are preemptively removed in the dehydration step and the content of impurities including Cl in the refined oil is low by hydrogenation treatment.

Meanwhile, when an AC voltage was applied using a vertical electrode, it was confirmed that the rate of fixation of impurity particles derived from char in the pyrolysis oil on the electrode surface was very low even after the process was conducted for more than 3 months. Through this, it was found that applying an AC voltage or using a vertical electrode can exhibit better process efficiency because there is no need to stop the process for cleaning the inside of the reactor.

In addition, in the case of Example 6, the dehydration result was poor compared to other examples, but since the hydrogenation treatment was performed under high pressure conditions, the Cl content of impurities in the refined oil was very low. However, since ammonia and hydrogen chloride are generated in excess due to the high pressure, it was confirmed that a relatively large amount of ammonium salts were generated even at the temperature at which the hydrogenation treatment was performed.

In Example 7, as additional dehydration was performed using a coagulant, the moisture and chlorine contents after dehydration were lower than in other examples. Therefore, it can be expected that the activation time of the catalyst, process stability, and refined oil quality are relatively better than in other examples.

In addition, it was confirmed that the economic feasibility of the process can be improved by obtaining solid coke that can be used as fuel and adding added value to refined hydrocarbons through the coking step.

While the exemplary embodiments of the present disclosure have been described above, the present disclosure is not limited thereto, and those skilled in the art will understand that various changes and modifications can be made thereto without departing from the concept and scope of the claims set forth below.

Claims (21)

S1) A pyrolysis step of producing pyrolysis gas by introducing waste plastic into a pyrolysis reactor;
S2) A step of producing waste plastic pyrolysis oil by injecting the above pyrolysis gas into a hot filter filled with a neutralizing agent;
S3) A step of dehydrating by applying voltage to a first mixture containing the waste plastic pyrolysis oil, washing water, and a demulsifier;
S4) a step of hydrogenating the first mixture dehydrated in step S3) and the second mixture mixed with a sulfur source to produce refined oil from which impurities have been removed; and
S5) A step of coking the refined oil from which the above impurities have been removed;
A method for producing purified hydrocarbons from waste plastics, comprising:
In the first paragraph,
In the above step S3),
A method for producing purified hydrocarbon from waste plastic, wherein the waste plastic pyrolysis oil is mixed in a larger volume than the wash water.
In the second paragraph,
In the above step S3),
A method for producing refined hydrocarbons from waste plastic, wherein the first mixture is a mixture of waste plastic pyrolysis oil and washing water in a volume ratio of 1:0.001 to 0.5.
In the first paragraph,
In the above step S3),
A method for producing refined hydrocarbons from waste plastic, wherein the first mixture is a mixture of waste plastic pyrolysis oil and a demulsifier in a volume ratio of 1:0.000001 to 0.001.
In the first paragraph,
A method for producing purified hydrocarbons from waste plastic, wherein the voltage is applied as an alternating current or a combination of alternating current and direct current.
In the first paragraph,
A method for producing purified hydrocarbons from waste plastic, wherein the voltage is applied through a vertical electrode.
In the first paragraph,
In the above step S3),
A step of removing a rag layer from the first mixture after applying the voltage;
A method for producing purified hydrocarbons from waste plastics, the method further comprising:
In the first paragraph,
A method for producing purified hydrocarbon from waste plastic, wherein the step S3) is performed at a temperature of 20° C. to 300° C.
In the first paragraph,
A method for producing refined hydrocarbons from waste plastic, wherein the ratio of the moisture content of the waste plastic pyrolysis oil and the moisture content of the first mixture dehydrated in step S3) is 1:0.0001 to 0.9.
In the first paragraph,
A method for producing purified hydrocarbon from waste plastic, wherein the step S3) comprises further dehydrating the dehydrated first mixture by coagulating moisture.
In the first paragraph,
A method for producing purified hydrocarbon from waste plastic, wherein the second mixture has a weight ratio of nitrogen to chlorine of 1:1 to 10.
In the first paragraph,
A method for producing refined hydrocarbons from waste plastic, wherein the sulfur source comprises a sulfur-containing oil.
In Article 12,
A method for producing refined hydrocarbon from waste plastic, wherein the sulfur-containing oil is contained in an amount of less than 0.5 parts by weight based on 100 parts by weight of the first mixture dehydrated in step S3).
In the first paragraph,
A method for producing purified hydrocarbon from waste plastic, wherein the sulfur source comprises one or more sulfur-containing organic compounds selected from disulfide compounds, sulfide compounds, sulfonate compounds, and sulfate compounds.
In the first paragraph,
A method for producing purified hydrocarbons from waste plastic, wherein the above hydrogenation treatment is performed in the presence of a molybdenum-based hydrogenation catalyst.
In Article 15,
A method for producing purified hydrocarbons from waste plastic, wherein the above molybdenum-based hydrogenation catalyst is a catalyst in which a molybdenum-based metal or a metal including one or more selected from nickel, cobalt and tungsten and the molybdenum-based metal are supported on a support.
In Article 15,
A method for producing purified hydrocarbons from waste plastic, wherein the above molybdenum-based hydrogenation catalyst comprises a molybdenum-based sulfide hydrogenation catalyst.
In the first paragraph,
A method for producing purified hydrocarbons from waste plastic, wherein the above hydrogenation treatment is performed under pressure conditions of 50 bar to 150 bar.
In the first paragraph,
After the above step S4),
A step of washing a stream containing refined oil from which the above impurities have been removed after gas-liquid separation;
A method for producing purified hydrocarbons from waste plastics, the method further comprising:
In the first paragraph,
The above step S5) is,
A method for producing refined hydrocarbons from waste plastic, comprising coking the refined oil fraction separated by distillation of refined oil from which the above impurities have been removed.
In the first paragraph,
The above step S5) is,
A method for producing refined hydrocarbons from waste plastic, comprising coking a mixed oil comprising refined oil from which the above impurities have been removed and petroleum hydrocarbons.