Method for producing ethylene and / or propylene and apparatus for producing ethylene and / or propylene

Abstract

To provide ethylene and / or propylene efficiently with high quality by employing, as a feedstock for a production process of ethylene and / or propylene, a pyrolysis gas derived from waste plastic in place of hydrocarbon oil.SOLUTION: There are provided a method for producing ethylene and / or propylene, and an apparatus for producing ethylene and / or propylene, the method comprising a pyrolysis step of pyrolyzing waste plastic, and a washing step of washing a pyrolysis gas obtained in the pyrolysis step, wherein the washing step is performed by bringing the pyrolysis gas into contact with water, and a ratio (QW / QG) of a supply amount QW (kg / h) of the water to a supply amount QG (kg / h) of the pyrolysis gas is 25.0 or more and 65.0 or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method and apparatus for producing ethylene and / or propylene. [Background technology]

[0002] In ethylene production equipment, hydrocarbon oils such as naphtha are commonly used as a feedstock, and the hydrocarbon oils are thermally cracked to produce cracked gases such as methane, ethane, ethylene, and propylene. Ethylene and propylene are then produced through a quenching process for cooling the cracked gases, a compression process for pressurizing the cooled cracked gases, and an acidic component removal process for removing acidic components (e.g., carbon dioxide, hydrogen sulfide, etc.) contained in the cracked gases (see, for example, Patent Document 1). Patent Document 2 discloses a recycling method in which carbon components in a feedstock such as waste plastics are selectively combusted, the combustion heat in the combustion process is used as a heat source to thermally decompose and gasify the feedstock, and the resulting pyrolysis products are supplied to at least one of an oil refining process and a petrochemical process. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-172887 [Patent Document 2] Special Publication No. 2007-504292 Summary of the Invention [Problem to be solved by the invention]

[0004] In recent years, with the growing interest in reducing environmental loads, waste plastics have been attracting attention as a raw material that can replace hydrocarbon oils. Because waste plastics are poorly degradable, discarded waste plastics are a cause of, for example, marine pollution, and therefore reducing the amount of waste plastics discarded directly leads to reducing the environmental load.

[0005] Since waste plastics can be converted into pyrolysis gas, as described in Patent Document 2, for example, recycling waste plastics as pyrolysis gas can be an effective means of reducing the amount of waste plastics disposed of. However, because waste plastics are waste, the pyrolysis gas obtained by pyrolyzing them contains impurities derived from the various additives contained in the waste plastics, as well as impurities derived from the type of waste plastic and the manufacturing process (hereinafter, these impurities may be collectively referred to as "impurities derived from additives, etc."). Therefore, it has become clear that pyrolysis gas obtained from waste plastics cannot be immediately used as a raw material for petrochemical processes, etc. For example, in the production process of ethylene and / or propylene, if pyrolysis gas containing impurities is used as a raw material, it is difficult to produce high-quality ethylene and propylene, and there is a risk of malfunctioning of equipment related to the production process.

[0006] However, Patent Document 2 does not acknowledge that impurities derived from various additives contained in waste plastics are contained in the pyrolysis gas, and that pyrolysis gas containing such impurities cannot be used as a raw material in petrochemical processes, particularly processes for producing ethylene and / or propylene, etc. Therefore, there is no sufficient consideration given to removing the impurities contained in the pyrolysis gas.

[0007] Thus, although pyrolysis gas obtained from waste plastics is expected to be a substitute for hydrocarbon oils as a feedstock for petrochemical processes such as the production process of ethylene and / or propylene, a pyrolysis gas that meets the properties required for a feedstock has not yet been obtained. Therefore, a challenge is to produce a pyrolysis gas obtained from waste plastics that meets the properties required for a feedstock for petrochemical processes such as the production process of ethylene and / or propylene.

[0008] The present invention has been made in view of the above circumstances, and has an object to efficiently provide high-quality ethylene and / or propylene by using a pyrolysis gas obtained from waste plastics as a substitute for hydrocarbon oil as a raw material in a production process of ethylene and / or propylene. [Means for solving the problem]

[0009] The present inventors have conducted extensive research in light of the above problems and have found that the following invention can solve the problems. That is, the present invention provides a method and an apparatus for producing ethylene and / or propylene having the following configurations.

[0010] [1] A thermal decomposition process for thermally decomposing waste plastics and a cleaning process for the thermal decomposition gas obtained in the thermal decomposition process, The cleaning step is carried out by contacting the pyrolysis gas with water, and the supply amount Q of the pyrolysis gas is G (kg / h) of the water supply Q W (kg / h) ratio (Q W / Q G ) is between 25.0 and 65.0, A method for producing ethylene and / or propylene. [2] The method for producing ethylene and / or propylene according to the above [1], wherein the contact is carried out using a wet scrubber. [3] The method for producing ethylene and / or propylene according to the above [1] or [2], wherein the contact is carried out by circulating the water. [4] The method for producing ethylene and / or propylene according to any one of the above [1] to [3], wherein the temperature of the pyrolysis gas after the contact is 10°C or higher and 100°C or lower. [5] A waste plastics thermal decomposition facility and a cleaning facility for cleaning the thermal decomposition gas obtained in the thermal decomposition facility by contacting the thermal decomposition gas with water, The cleaning equipment supplies the pyrolysis gas with a supply amount Q G (kg / h) of the water supply Q W (kg / h) ratio (Q W / Q GA supply device for supplying the pyrolysis gas and the water so that the temperature is 25.0 or more and 65.0 or less. Ethylene and / or propylene production equipment. [6] The ethylene and / or propylene production apparatus according to the above [5], further comprising a compression facility and a purification facility in this order following the washing facility. [Effects of the Invention]

[0011] According to the present invention, high-quality ethylene and / or propylene can be efficiently provided by using pyrolysis gas obtained from waste plastics as a substitute for hydrocarbon oil as a raw material in the production process of ethylene and / or propylene. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, a method and apparatus for producing ethylene and / or propylene according to an embodiment of the present invention (hereinafter, sometimes simply referred to as "the present embodiment") will be specifically described. In this specification, the terms "less than," "greater than," and "to" used in describing a range of values ​​are values ​​that can be arbitrarily combined. For example, when a certain range of values ​​is described as "A to B" or "C to D," the ranges of "A to D" and "C to B" are also included. Furthermore, the numerical values ​​in the examples are values ​​that can be used as upper or lower limits.

[0013] [Method for producing ethylene and / or propylene] The method for producing ethylene and / or propylene of the present embodiment includes: A pyrolysis process for thermally decomposing waste plastics; and a cleaning step of the pyrolysis gas obtained in the pyrolysis step, The cleaning step is carried out by contacting the pyrolysis gas with water, and the supply amount Q of the pyrolysis gas is G (kg / h) of the water supply Q W (kg / h) ratio (Q W / Q G ) is between 25.0 and 65.0.

[0014] As mentioned above, the challenge is to produce pyrolysis gas from waste plastics that meets the required properties as a feedstock for petrochemical processes, such as the production of ethylene and / or propylene. Under these circumstances, the inventors discovered that the impurities contained in pyrolysis gas from waste plastics are compounds derived from various additives contained in the waste plastics, and that most of these impurities can be removed with water. Water is inexpensive, and contacting pyrolysis gas with water is relatively easy. Thus, the inventors have made it possible to easily remove impurities from pyrolysis gas from waste plastics and use it as a substitute for hydrocarbon oils, which have been used as feedstock for petrochemical processes, particularly the production of ethylene and / or propylene. As a secondary effect, this is expected to contribute to a reduction in the amount of waste plastics disposed of and to a reduction in the consumption of hydrocarbon oils.

[0015] The production method of this embodiment is a method for producing ethylene and / or propylene, and according to the production method of this embodiment, ethylene, propylene, or ethylene and propylene can be produced.

[0016] [Pyrolysis process] The production method of this embodiment includes a pyrolysis step in which waste plastics are thermally decomposed. The pyrolysis gas obtained in the pyrolysis step is used as a raw material for ethylene and / or propylene. However, as described above, the pyrolysis gas obtained in the pyrolysis step contains impurities derived from additives contained in the waste plastics. Therefore, the production method of this embodiment includes a cleaning step, which will be described later, and by removing the impurities in the cleaning step, it is possible to produce high-quality ethylene and / or propylene with extremely low impurity content or no impurities at all.

[0017] (Waste plastic) The waste plastics to be pyrolyzed in the pyrolysis step can be any waste plastic, without any particular limitation, and typical examples include materials constituting various materials such as containers such as food and drink bottles, packaging supplies such as shopping bags, food trays, and packaging films, interior and exterior parts for housing construction materials, interior parts for automobiles, and exterior parts for electrical appliances, construction materials such as PVC pipes, etc. Typical examples of materials constituting these various materials include various resins such as acrylic resin, styrene resin, polyester resin, polyamide resin, PVC resin, polyolefin resin such as polyethylene and polypropylene, and mixtures of these resins.

[0018] These waste plastics are generally treated with additives depending on their intended use, and therefore, as mentioned above, the pyrolysis gas obtained from the waste plastics contains impurities derived from the additives contained in the waste plastics, impurities derived from the materials themselves that make up the waste plastics, and impurities contained in the materials themselves that make up the waste plastics during the production process of the waste plastics.

[0019] Representative examples of additives include plasticizers such as esters of various organic acids such as phthalic acid, adipic acid, and trimellitic acid; lubricants such as fatty acid alcohols and aliphatic amides; antioxidants such as phenols, amines, and thioethers; flame retardants such as bromine-based flame retardants such as brominated diphenyl ether; ultraviolet absorbers such as benzophenones and triazines; surfactants such as perfluoroalkyl compounds, perfluorocarboxylic acids, and perfluorosulfonic acids; colorants such as azo compounds and phthalocyanines; etc. Impurities derived from these additives, impurities derived from the materials themselves of the waste plastics, and impurities contained in the materials themselves that constitute the waste plastics during the production process of the waste plastics will be described later.

[0020] (Thermal decomposition of waste plastics) The method for pyrolyzing waste plastics is not particularly limited as long as pyrolysis gas is obtained, and may be carried out according to a conventionally known method, for example, by pyrolysis in a pyrolysis furnace. The pyrolysis temperature in the pyrolysis furnace is preferably 550°C or higher, more preferably 565°C or higher, and even more preferably 580°C or higher, and the upper limit is preferably 700°C or lower, more preferably 690°C or lower, and even more preferably 680°C or lower.

[0021] The pyrolysis gas obtained by the pyrolysis treatment in the pyrolysis furnace may be cooled using a cooling device such as a quencher, if necessary, before undergoing the cleaning treatment described below. By lowering the temperature of the pyrolysis gas, more efficient contact between the pyrolysis gas and water can be achieved. As the quencher, any device that can cool the pyrolysis gas can be used without particular limitation, and for example, a general-purpose device such as a shell-and-tube heat exchanger or a plate-type heat exchanger may be used. The cooling temperature of the pyrolysis gas by a cooling device such as a quencher (i.e., the temperature at which the pyrolysis gas is supplied to the gas-liquid contactor in the cleaning step described below) is preferably 150°C or lower, more preferably 125°C or lower, and even more preferably 110°C or lower, with a lower limit of 80°C or higher. By cooling the pyrolysis gas by a cooling device to within the above temperature range, the pyrolysis gas can be more efficiently contacted with water in the cleaning step.

[0022] (Properties of pyrolysis gas) The pyrolysis gas obtained by the pyrolysis step contains components corresponding to the various resins that are the materials constituting the waste plastics, as well as impurities derived from additives contained in the waste plastics.

[0023] Representative examples of components suitable for the various resins include hydrocarbons such as alkanes having 1 to 6 carbon atoms, such as methane, ethane, propane, butane, pentane, and hexane; alkenes having 1 to 6 carbon atoms, such as ethylene, propylene, butene, pentene, and hexene; and dienes having 3 to 6 carbon atoms, such as propadiene, butadiene, pentadiene, and hexadiene; and also carbon monoxide, carbon dioxide, hydrogen, and water vapor.

[0024] The content of components corresponding to these various resins in the total amount of pyrolysis gas (which can also be said to be the content of components excluding impurities, which will be described later) cannot be generalized because it varies depending on the blend of various resins contained in the waste plastic, but is 75% by mass or more, 80% by mass or more, or 85% by mass or more, with an upper limit of 98% by mass or less or 95% by mass or less.The content of components corresponding to these various resins in the pyrolysis gas (total amount of dry gas) excluding water vapor (which can also be said to be the content of components excluding impurities, which will be described later, on a dry gas basis) is 65% by mass or more, 70% by mass or more, or 75% by mass or more, with an upper limit of 90% by mass or less or 85% by mass or less. Furthermore, among the above hydrocarbons contained in the total amount of pyrolysis gas, the total content of ethylene and propylene is 5% by mass or more, 7.5% by mass or more, or 10% by mass or more, with no particular upper limit, and typically 30% by mass or less.

[0025] (Impurities contained in pyrolysis gas) The pyrolysis gas obtained by the thermal decomposition step contains impurities derived from the additives used in the waste plastics. The impurities derived from the additives are compounds generated when the additives are heated during the thermal decomposition of the waste plastics (usually by heating to 550 to 700°C), and include various compounds containing atoms contained in the additives, such as nitrogen atoms, oxygen atoms, sulfur atoms, and halogen atoms such as fluorine atoms, chlorine atoms, and bromine atoms. This is because atoms other than hydrogen atoms and carbon atoms contained in these various compounds constitute impurities in ethylene and propylene.

[0026] Of the various compounds described above, typical examples of compounds containing a nitrogen atom include ammonia; amines such as aliphatic amines such as trimethylamine and aromatic amines such as aniline; saturated or unsaturated aliphatic nitriles such as methanenitrile, acetonitrile, acrylonitrile, propionitrile, and isobutyronitrile; and aliphatic amides such as dimethylformamide.

[0027] Representative examples of compounds containing an oxygen atom include alcohols such as saturated or unsaturated aliphatic alcohols such as methanol, ethanol, and allyl alcohol, and aromatic alcohols such as phenol; saturated or unsaturated aliphatic aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and isobutyraldehyde; saturated or unsaturated ketones such as acetone and methyl ethyl ketone; saturated or unsaturated carboxylic acids such as formic acid, acetic acid, benzoic acid, and acrylic acid; various ethers such as aliphatic ethers such as dimethyl ether, methyl ethyl ether, and diethyl ether, cyclic ethers such as tetrahydrofuran, and aromatic ethers such as diphenyl ether; and saturated or unsaturated carboxylic acid esters such as methyl formate, ethyl formate, methyl (meth)acrylate, and methyl isobutyrate.

[0028] Typical examples of compounds containing a sulfur atom include hydrogen sulfide; sulfur oxides such as sulfur dioxide and sulfur trioxide; carbon disulfide; and carbonyl sulfide.

[0029] Representative examples of compounds containing a halogen atom include hydrogen halides such as hydrogen fluoride, hydrogen chloride, and hydrogen bromide; and saturated or unsaturated halogenated aliphatic hydrocarbons such as perfluoroethane, hexafluoropropylene, decafluorodecane, vinyl fluoride, ethyl chloride, bromomethyl, dibromomethane, and tribromomethane.

[0030] In addition, the pyrolysis gas obtained from waste plastics may contain impurities derived from the waste plastics themselves in addition to the impurities derived from the additives. For example, when the waste plastic contains chlorine, such as in vinyl chloride resins (polyvinyl chloride, etc.), when it contains nitrogen, such as in polyamide resins, or when it contains fluorine, such as in fluororesins such as PTFE (polytetrafluoroethylene) and PFA (perfluoroalkoxy fluororesin), compounds containing atoms derived from the chlorine, nitrogen, fluorine, and other atoms contained in the waste plastics themselves may be contained as impurities. Representative examples of impurities derived from atoms such as chlorine, nitrogen, and fluorine contained in the waste plastics themselves include the compounds exemplified as compounds containing chlorine, nitrogen, and fluorine atoms among the impurities derived from the additives.

[0031] The pyrolysis gas obtained from waste plastics may also contain impurities contained in the materials that make up the waste plastics during the production process of the waste plastics. These impurities other than those derived from the additives can also be removed in the cleaning process described below, similar to the impurities derived from the additives. As such, according to the manufacturing method of this embodiment, it is possible to widely handle any pyrolysis gas of waste plastic, without being limited to the additives contained in the waste plastic or the type of waste plastic.

[0032] [Cleaning process] The production method of this embodiment includes a step of purifying the pyrolysis gas obtained in the pyrolysis step. As described above, the pyrolysis gas obtained from waste plastic contains impurities derived from additives contained in the waste plastic. If the pyrolysis gas obtained from waste plastic is used as is, these impurities will cause a deterioration in the quality of the polyethylene and polypropylene, making it difficult to use it as a substitute for hydrocarbon oil. According to the production method of this embodiment, by including a step of purifying the pyrolysis gas, it is possible to suppress the deterioration in the quality of the polyethylene and polypropylene due to the impurities, and to produce polyethylene and polypropylene of higher quality.

[0033] In the manufacturing method of this embodiment, the cleaning step must be carried out by contacting the pyrolysis gas with water. By using water in the cleaning step, it is possible to remove most of the above-mentioned impurities. The advantages of being able to remove impurities by the simple method of simply contacting the pyrolysis gas with water, as well as the advantage of being able to use a versatile cleaning medium such as water and remove most of the impurities, are extremely significant.

[0034] (Method of contacting pyrolysis gas with water) The method for contacting the pyrolysis gas with water is not particularly limited, and any method can be used as long as it can bring the pyrolysis gas and water into contact. For example, it is preferable to use a gas-liquid contactor. The gas-liquid contactor is usually also called a scrubber, and a wet scrubber that can bring the pyrolysis gas and water into contact is preferably used. The type of wet scrubber is not particularly limited, and it is preferable to use a wet scrubber that can bring the pyrolysis gas and water into contact. Preferred examples of wet scrubbers include devices that are generally included in wet scrubbers, such as a scrubbing tower where the contact occurs; a tank for storing water; a pump for supplying water; and, if necessary, a supply fan and an exhaust fan; and devices that are equipped with piping that connects these devices.

[0035] The scrubber is preferably a type in which water can be supplied from the top of the scrubber and pyrolysis gas can be supplied from the bottom. Furthermore, the scrubber is preferably a type equipped with a spray nozzle (also called a shower nozzle) so that water can be supplied in a spray form to more efficiently contact the pyrolysis gas, i.e., a spray tower scrubber.

[0036] The contact of the pyrolysis gas with water is preferably carried out by circulating the water. There are no particular limitations on the method of circulating the water, as long as the water that has come into contact with the pyrolysis gas is used again for contact with the pyrolysis gas. For example, when a wet scrubber is used, water can be circulated by contacting the pyrolysis gas with the water supplied from the top of the scrubbing tower with the water, discharging the water from the bottom of the scrubbing tower into a tank for storing water, and storing the water in the tank. The water stored in the tank is then pumped from the top of the scrubbing tower to supply the water to the scrubbing tower.

[0037] The water that can be used in the production method of this embodiment may be various types of water, such as industrial water, ion-exchanged water, boiler feed water, etc. From the viewpoint of further reducing impurities, ion-exchanged water is preferably used. Furthermore, as the water, water containing, for example, an inorganic acid such as hydrochloric acid or sulfuric acid, or an alkali such as an organic amine or an alkali metal hydroxide may be used as needed for pH adjustment or the like.

[0038] In the manufacturing method of this embodiment, the supply amount Q of pyrolysis gas G Water supply rate Q (kg / h) W (kg / h) ratio (Q W / Q G ) must be between 25.0 and 65.0. W / Q G If the ratio (Q) is less than 25.0, impurities contained in the pyrolysis gas may not be completely removed. W / Q G ) exceeding 65.0 does not improve the effect of removing impurities, and therefore it may not be possible to say that the impurities can be removed efficiently. From the viewpoint of more efficient impurity removal, the above ratio (Q W / Q G ) is preferably 27.5 or more, more preferably 30.0 or more, and the upper limit is preferably 62.5 or less, more preferably 60.0 or less.

[0039] In the production method of this embodiment, the temperature of the pyrolysis gas after contact with water in the washing step is preferably 10°C or higher, more preferably 15°C or higher, with the upper limit being preferably 100°C or lower, more preferably 75°C or lower, even more preferably 50°C or lower, and even more preferably 45°C or lower. By contacting the pyrolysis gas with water to achieve such a temperature, it becomes possible to more efficiently and reliably remove impurities contained in the pyrolysis gas. The temperature of the pyrolysis gas after contact with water is determined by the amount of water used to contact the pyrolysis gas (i.e., the above ratio (Q W / Q G )), the temperature of the pyrolysis gas before contacting with water, the temperature of the water to be brought into contact with the pyrolysis gas, etc. can also be adjusted.

[0040] The production method of this embodiment can use, as a raw material, pyrolysis gas obtained by the thermal decomposition of the above-mentioned waste plastics. It is also possible to use pyrolysis gases other than the pyrolysis gas, such as various fractions obtained by distilling crude oil, generally referred to as naphtha fraction, kerosene fraction, light oil fraction, heavy oil fraction, etc., or pyrolysis gas obtained by thermally decomposing hydrocarbon oils such as bio-oil.

[0041] (Other processes) The method for producing ethylene and / or propylene according to the present embodiment may include the above-described thermal decomposition step and washing step, and preferably includes at least one step selected from the following steps in order as a step other than these steps: (i) Compression process (ii) Purification process

[0042] The (i) compression step is a step of pressure-feeding the pyrolysis gas to the (ii) purification step described below. Pressure-feeding enables cryogenic separation in the purification step, making it possible to more efficiently produce high-quality ethylene and / or propylene. The compression of the pyrolysis gas in the (i) compression step can be carried out using a compressor, and the compression pressure is preferably 3 MPa or more, more preferably 3.5 MPa or more, with the upper limit usually being 5 MPa or less.

[0043] The (ii) purification step is a step for purifying the pyrolysis gas compressed and sent in the (i) compression step to obtain highly pure ethylene and / or propylene. Representative preferred examples of the purification step include impurity removal steps using distillation columns such as a demethanization step, deethaneization step, and depropanization step, and rectification columns such as an ethylene rectification column and a propylene rectification column; and reaction steps using a catalyst such as an acetylene hydrogenation column that hydrogenates acetylene contained in the cracked gas to ethylene, and a MAPD hydrogenation column that hydrogenates methylacetylene and propadiene (MAPD). These purification steps may be carried out in accordance with methods conventionally employed in ethylene and / or propylene production methods.

[0044] The purification step may be appropriately selected depending on the properties of the pyrolysis gas, the required performance of the resulting ethylene and propylene, and the like. Typically, ethylene and propylene can be produced by the steps of (i) a step in which the pyrolysis gas pumped from the compression step is passed through a demethanizer, a deethanizer, an acetylene hydrogenation tower, and an ethylene fractionator to obtain ethylene; and a step in which the bottom product of the deethanizer is passed through a MAPD hydrogenation tower and a propylene fractionator to obtain propylene.

[0045] Furthermore, as a process other than the (i) compression process and the (ii) purification process, it is preferable to provide, for example, an acidic component removal process for removing acidic components contained in the pyrolysis gas before supplying it to the (ii) purification process. Depending on the properties of the waste plastic, the pyrolysis gas may contain acidic components such as carbon dioxide and hydrogen sulfide. When a column equipped with a catalyst is used in the (ii) purification process, it is preferable to remove these acidic components in advance in the acidic component removal process to prevent poisoning of the catalyst.

[0046] When the acidic component removal step is employed, the concentrations of carbon dioxide and hydrogen sulfide contained in the pyrolysis gas after the acidic components have been removed are preferably 5 mol ppm or less, and more preferably 3 mol ppm or less, from the viewpoint of more efficiently extending the catalyst life.

[0047] Similarly to the above-mentioned (ii) purification step, the acidic component removal step may be carried out in accordance with a method conventionally employed in the production of ethylene and / or propylene, and a representative preferred example thereof is a method comprising an absorption step using an aqueous amine solution such as monoethanolamine as a solution for removing acidic components, and a regeneration step.

[0048] [Ethylene and / or propylene production apparatus] The ethylene and / or propylene production apparatus of this embodiment includes: The present invention comprises a thermal decomposition facility for waste plastics and a cleaning facility for cleaning the thermal decomposition gas obtained in the thermal decomposition facility by contacting the thermal decomposition gas with water, The cleaning equipment supplies the pyrolysis gas with a supply amount Q G (kg / h) of the water supply Q W (kg / h) ratio (Q W / Q G A supply device for supplying the pyrolysis gas and the water so that the temperature is 25.0 or more and 65.0 or less. The method for producing ethylene and / or propylene of the present embodiment can be easily carried out by the production apparatus of the present embodiment described above.

[0049] Furthermore, the production apparatus of this embodiment preferably further includes a compression facility and a purification facility in this order after the washing facility, and more preferably includes a compression facility, an acidic component removal facility, and a purification facility in this order. By including these facilities, ethylene and / or propylene with higher purity can be produced.

[0050] The pyrolysis equipment and washing equipment are as described in the ethylene and / or propylene production method of the present embodiment. Regarding the supply equipment for supplying pyrolysis gas and water possessed by the washing equipment, the supply equipment for supplying pyrolysis gas includes, for example, the supply fan and exhaust fan for the pyrolysis gas, and the supply equipment for supplying water includes, for example, a tank for storing the water, a pump for supplying water, and a spray nozzle (also referred to as a shower nozzle) for supplying water in a spray form into the washing tower.

[0051] The compression equipment preferably provided in the production apparatus of this embodiment is equipment that compresses the pyrolysis gas obtained in the washing equipment and pressure-feeds it to the purification equipment, and the purification equipment is equipment that purifies the pyrolysis gas pressure-feed by the compression equipment. The acidic component removal equipment more preferably provided in the production apparatus of this embodiment is equipment for removing acidic components contained in the pyrolysis gas before it is supplied to the purification equipment. Details of these equipment are also as described above in the production method for ethylene and / or propylene of this embodiment. Furthermore, a cooling device such as a quencher may be provided before the pyrolysis gas obtained in the pyrolysis equipment is supplied to the cleaning equipment, as described above in the production method for ethylene and / or propylene of this embodiment. [Example]

[0052] Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to these examples in any way.

[0053] Example 1 A simulated sample of pyrolysis gas from waste plastic was prepared, with the composition shown in Table 1. The nitrogen-atom-containing compounds, oxygen-atom-containing compounds, sulfur-atom-containing compounds, fluorine-atom-containing compounds, chlorine-atom-containing compounds, and bromine-atom-containing compounds in Table 1 correspond to impurities derived from additives contained in the waste plastic. The pyrolysis gas had a flow rate of 4,900 kg / h and was contacted with 161,000 kg / h of water. The contact between the pyrolysis gas and water was carried out using a wet scrubber equipped with a scrubbing tower where the contact took place, a water storage tank for storing water, a water supply pump for supplying water from the tank to the scrubbing tower, and piping connecting these devices. The scrubbing tower was equipped with a gas inlet for supplying pyrolysis gas obtained in the pyrolysis equipment from the bottom, a gas outlet for discharging pyrolysis gas from the top of the tower, a water inlet for supplying water from the top, a spray nozzle for supplying water in a spray form into the scrubbing tower, and a water outlet for discharging water from the bottom (tower bottom). The water discharged from the outlet was drained into a water storage tank and circulated by being supplied to the scrubbing tower by the water supply pump. The composition of the pyrolysis gas after contact with water in the scrubbing tower was analyzed, and the impurity contents are shown in Table 2.

[0054] Example 2 The pyrolysis gas was contacted with water in the same manner as in Example 1, except that the water supply rate was changed to 284,000 kg / h. The composition of the pyrolysis gas after contact with water in the scrubbing tower was analyzed, and the impurity contents are shown in Table 2.

[0055] (Comparative Example 1) The pyrolysis gas was contacted with water in the same manner as in Example 1, except that water was not supplied. The composition of the pyrolysis gas after contact with water in the scrubbing tower was analyzed, and the impurity contents are shown in Table 2.

[0056] (Comparative Example 2) The pyrolysis gas was contacted with water in the same manner as in Example 1, except that the water supply rate was changed to 95,000 kg / h. The composition of the pyrolysis gas after contact with water in the scrubbing tower was analyzed, and the impurity contents are shown in Table 2.

[0057] [Table 1] *In Table 1, the total content of nitrogen-containing compounds is the sum of the contents of ammonia; amines such as trimethylamine and aniline; nitriles such as methanenitrile, acetonitrile, acrylonitrile, propionitrile, and isobutyronitrile; and aliphatic amides such as dimethylformamide.

[0058] The total content of oxygen atom-containing compounds is mainly the sum of the contents of alcohols such as methanol, ethanol, and allyl alcohol; phenols; aldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and isobutyraldehyde; ketones such as acetone and methyl ethyl ketone; ethers such as dimethyl ether, methyl ethyl ether, diethyl ether, tetrahydrofuran, and diphenyl ether; carboxylic acids such as formic acid, acetic acid, benzoic acid, and acrylic acid; and carboxylic acid esters such as methyl formate, ethyl formate, methyl (meth)acrylate, and methyl isobutyrate.

[0059] The total content of sulfur atom-containing compounds is mainly the sum of the contents of hydrogen sulfide; sulfur oxides such as sulfur dioxide and sulfur trioxide; carbon disulfide; and carbonyl sulfide.

[0060] The total content of fluorine atom-containing compounds that are halogen atom-containing compounds is mainly the sum of the contents of hydrogen fluoride, perfluoroethane, hexafluoropropylene, decafluorodecane, vinyl fluoride, etc., the total content of chlorine atom-containing compounds is mainly the sum of the contents of hydrogen chloride, ethyl chloride, etc., and the total content of bromine atom-containing compounds is mainly the sum of the contents of hydrogen bromide, bromomethyl, dibromomethane, tribromomethane, etc.

[0061] [Table 2]

[0062] In Examples 1 and 2, the supply amount Q of pyrolysis gas in the cleaning process G Water supply rate Q (kg / h) W (kg / h) ratio (Q W / QG It has been confirmed that by setting the RI* value between 25.0 and 65.0, the contents of impurities resulting from additives, etc. (which correspond to nitrogen-containing compounds, oxygen-containing compounds, sulfur-containing compounds, fluorine-containing compounds, chlorine-containing compounds, and bromine-containing compounds in Table 2) can all be kept below the target values. The target values ​​in Table 2 are those when using pyrolysis gas from hydrocarbon oils that are already in operation, and it has been confirmed that if the pyrolysis gas is below the target values, catalyst poisoning in the refining process can be suppressed and high-quality ethylene and / or propylene can be produced. Therefore, it was confirmed that high-quality ethylene and / or propylene can be produced by using the pyrolysis gases obtained in Examples 1 and 2.

[0063] On the other hand, when the pyrolysis gas of Comparative Example 1 was not cleaned, the target values ​​for fluorine atom-containing compounds were achieved, but the target values ​​for other compounds were not achieved. Also, in Comparative Example 2, it was confirmed that the target values ​​for sulfur atom-containing compounds and chlorine atom-containing compounds could not be achieved. Therefore, in the cases of Comparative Examples 1 and 2, it is expected that the catalyst will be poisoned in the refining step and the quality of the ethylene and / or propylene produced will be reduced. [Industrial Applicability]

[0064] According to the method for producing ethylene and / or propylene of the present embodiment, a pyrolysis gas obtained from waste plastics is used as a raw material for the ethylene and / or propylene production process as an alternative to hydrocarbon oil, and high-quality ethylene and / or propylene can be efficiently provided. Therefore, the method is suitable for use as an industrial production method for ethylene and / or propylene.

Claims

1. The method comprises a pyrolysis step of pyrolyzing waste plastics and a cleaning step of pyrolysis gas obtained in the pyrolysis step, The cleaning step is carried out by contacting the pyrolysis gas with water, and the supply amount Q of the pyrolysis gas is Ｇ The water supply amount Q relative to (kg / h) Ｗ (kg / h) ratio (Q Ｗ / Q Ｇ ) is 25.0 or more and 65.0 or less, A method for producing ethylene and / or propylene.

2. 2. The method for producing ethylene and / or propylene according to claim 1, wherein the contacting is carried out by a wet scrubber.

3. 3. The method for producing ethylene and / or propylene according to claim 1 or 2, wherein the contact is carried out by circulating the water.

4. 3. The method for producing ethylene and / or propylene according to claim 1 or 2, wherein the temperature of the pyrolysis gas after the contact is 10°C or higher and 100°C or lower.

5. The present invention comprises a thermal decomposition facility for waste plastics and a cleaning facility for cleaning the thermal decomposition gas obtained in the thermal decomposition facility by contacting the thermal decomposition gas with water, The cleaning equipment supplies the pyrolysis gas with a supply amount Q Ｇ The water supply amount Q relative to (kg / h) Ｗ (kg / h) ratio (Q Ｗ / Q Ｇ a supply device for supplying the pyrolysis gas and the water so that the temperature difference (Tc) is 25.0 or more and 65.0 or less; Ethylene and / or propylene production equipment.

6. The ethylene and / or propylene production apparatus according to claim 5, further comprising a compression facility and a purification facility in this order following the washing facility.

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