EP4359489A1 - Process for conversion of waste plastics into hydrocarbons - Google Patents
Process for conversion of waste plastics into hydrocarbonsInfo
- Publication number
- EP4359489A1 EP4359489A1 EP22734936.2A EP22734936A EP4359489A1 EP 4359489 A1 EP4359489 A1 EP 4359489A1 EP 22734936 A EP22734936 A EP 22734936A EP 4359489 A1 EP4359489 A1 EP 4359489A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- stream
- reactor
- process according
- furnace
- supplied
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 239000004033 plastic Substances 0.000 title claims abstract description 51
- 229920003023 plastic Polymers 0.000 title claims abstract description 51
- 238000000034 method Methods 0.000 title claims abstract description 44
- 239000002699 waste material Substances 0.000 title claims abstract description 39
- 238000006243 chemical reaction Methods 0.000 title claims abstract description 15
- 229930195733 hydrocarbon Natural products 0.000 title abstract description 12
- 150000002430 hydrocarbons Chemical class 0.000 title abstract description 12
- 239000000571 coke Substances 0.000 claims abstract description 32
- 238000005194 fractionation Methods 0.000 claims abstract description 26
- 239000000126 substance Substances 0.000 claims abstract description 12
- 238000004519 manufacturing process Methods 0.000 claims abstract description 11
- 239000003921 oil Substances 0.000 claims description 22
- 239000000155 melt Substances 0.000 claims description 13
- 229920000642 polymer Polymers 0.000 claims description 13
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 9
- 229910052801 chlorine Inorganic materials 0.000 claims description 9
- 239000000460 chlorine Substances 0.000 claims description 9
- ZAMOUSCENKQFHK-UHFFFAOYSA-N Chlorine atom Chemical compound [Cl] ZAMOUSCENKQFHK-UHFFFAOYSA-N 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 7
- 239000010779 crude oil Substances 0.000 claims description 5
- 238000010438 heat treatment Methods 0.000 claims description 5
- 239000010812 mixed waste Substances 0.000 claims description 5
- 229920000098 polyolefin Polymers 0.000 claims description 5
- 239000004800 polyvinyl chloride Substances 0.000 claims description 5
- 238000009835 boiling Methods 0.000 claims description 3
- 238000004821 distillation Methods 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims description 3
- 238000005292 vacuum distillation Methods 0.000 claims description 3
- 125000001309 chloro group Chemical group Cl* 0.000 claims 2
- 238000000354 decomposition reaction Methods 0.000 claims 2
- 239000004215 Carbon black (E152) Substances 0.000 abstract description 6
- 229920001169 thermoplastic Polymers 0.000 abstract description 2
- 239000000463 material Substances 0.000 description 17
- 239000007789 gas Substances 0.000 description 6
- 230000004992 fission Effects 0.000 description 4
- 239000002994 raw material Substances 0.000 description 4
- 206010011906 Death Diseases 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000004939 coking Methods 0.000 description 2
- 230000003111 delayed effect Effects 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000001125 extrusion Methods 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 229920000915 polyvinyl chloride Polymers 0.000 description 2
- 230000015556 catabolic process Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000002440 industrial waste Substances 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 239000003345 natural gas Substances 0.000 description 1
- 239000013502 plastic waste Substances 0.000 description 1
- 239000002861 polymer material Substances 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 239000002910 solid waste Substances 0.000 description 1
- 239000004416 thermosoftening plastic Substances 0.000 description 1
- 238000004056 waste incineration Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
- C10B55/00—Coking mineral oils, bitumen, tar, and the like or mixtures thereof with solid carbonaceous material
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
- C10B53/00—Destructive distillation, specially adapted for particular solid raw materials or solid raw materials in special form
- C10B53/07—Destructive distillation, specially adapted for particular solid raw materials or solid raw materials in special form of solid raw materials consisting of synthetic polymeric materials, e.g. tyres
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
- C10B57/00—Other carbonising or coking processes; Features of destructive distillation processes in general
- C10B57/08—Non-mechanical pretreatment of the charge, e.g. desulfurization
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
- C10G1/002—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal in combination with oil conversion- or refining processes
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G1/00—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal
- C10G1/10—Production of liquid hydrocarbon mixtures from oil-shale, oil-sand, or non-melting solid carbonaceous or similar materials, e.g. wood, coal from rubber or rubber waste
Definitions
- the present invention relates to a process for conversion of waste plastics into hydrocarbons, such as hydrocarbon that may be used to form new plastics.
- the invention relates to a process for conversion of waste plastics into hydrocarbons via delayed coking.
- waste plastics streams can be obtained from consumer waste collection, from industrial waste collection, of by collection of waste as littered in the environment, either as aquatic littering or as land-based littering.
- waste plastics streams are mixtures of various types and qualities of plastics.
- sorting certain streams may be obtained that qualify for re-use as thermoplastics, either by directly subjecting them to thermal shaping processes or via blending them with high-quality virgin-type plastic materials to compensate for loss of properties.
- Such way of re-use of material however is only appropriate for a limited fraction of waste plastics that can be sorted out of the mixed waste streams as provided from waste collection so that the obtained stream has high uniformity of material composition.
- Such chemical conversion processes provide certain benefits, amongst others in that they may be operated using waste plastic compositions of varying nature, including waste plastic compositions that show particularly large variation in batch-to- batch composition.
- a process for production of chemical feedstocks from waste plastics comprising providing a process configuration comprising a fractionation tower (1), a furnace (2), one or more coke drum(s) (3), and a pre-reactor (4), configured so that a bottoms stream (A) from the fractionation tower is mixed with a stream originating from waste plastics (L), and supplied to the furnace, the product stream from the furnace (C) is supplied to a coke drum, and an overhead stream (D) from the coke drum is supplied back to the fractionation tower; wherein the stream (L) is obtained as product stream from conversion of a waste plastics stream (B) in the pre-reactor; wherein the stream (L) is supplied in molten condition; and preferably wherein stream (L) has a weight average molecular weight of less than 100,000 g/mol; more preferably wherein the stream (L) is an oligomeric stream having a weight average molecular weight of between
- Such process allows for the conversion of a wide variety of waste plastics into valuable chemical products. Furthermore, such process allows for the increase in production of naphtha- range hydrocarbon products that may be used for production of for example new polymer products via conversion in steam cracker facilities.
- the process in accordance with the present invention is further elucidated by the Figure 1.
- the unit (1) represents the fractionation tower.
- the furnace is represented by unit (2).
- the coke drum(s) are represented by units (3).
- a pre-reactor is represented by unit (4).
- This configuration presents a representative embodiment of the invention, but does not limit the invention thereto.
- the process according to the present invention may comprise one single coke drum (3), or multiple coke drums.
- Figure 1 presents a particular embodiment of the invention, wherein two coke drums are present. Such configuration allows for switching operations between the coke drums so that one drum can be used in operation whilst the other drum can be cleaned out.
- a bottoms stream (A) is provided to feed the furnace.
- the bottoms stream (A) may for example be supplied at a temperature of 3 300 and £ 400 °C.
- a furnace product stream (C) is provided to coke drum(s).
- Feed (B) is a waste plastics stream, which may be first reacted in the pre-reactor (4) to reduce the molecular weight and by so form an oligomer (L) which is then mixed with the bottoms stream (A) and fed into the furnace.
- a cracked overhead product (D) is obtained that is to be supplied to the fractionation tower for fractionation, with a fraction residual oil (K), into typically a top gaseous stream (F), a naphtha-range stream (G), a light gas oil stream (J), a heavy gas oil stream (H), and a bottoms stream (A).
- a coke stream (E) is obtained, which accumulates in the drum, to be evacuated therefrom upon discontinuation of the operation of that drum.
- the furnace (2) that may be used in the process according to the present invention may for example be a furnace in which multiple feed tubes are passed through a heating chamber, also referred to as a firebox, so that the feed is heated by external heating.
- the tubes may be passed through the firebox multiple times, for example two or four times.
- the heat may for example be provided by burners placed below the tubes. The burners may be controlled in such way to provide the required heating of the feed in the tubes to obtain the desired temperature of the feed exiting the furnace.
- the mass velocity of the feed through the furnace is preferably greater than 1800 kg/s/m 2 .
- a quantity of steam may be added to the feed tubes, such as for example between 0.1 and 2.0 wt% of steam with regard to the total weight of the feed. Such addition of steam contributes to increase of velocity in the tubes.
- the combined feed (A) and (B) may be heated in the furnace by passing the feed through heating tubes and subjecting it to external heat energy to obtain a furnace product stream (C) having a temperature of 3 450°C and £ 550°C, preferably of 3 475°C and £ 500°C.
- the feed exits the furnace at a temperature of preferably 3 450°C and £ 550°C, more preferably of 3 475°C and £ 500°C.
- the heated furnace product stream (C) is transported via a transfer line into a coke drum. It is desirable that the residence time in the transfer line is kept as short as possible, to avoid occurrence of coking prior to reaching the coke drum. Accordingly, it is desirable to keep the transfer line as short as possible.
- a switch valve may be present in the transfer line, to allow directing the feed to a desired coke drum.
- a typical coke drum that may be used in the process according to the present invention may have a diameter of between 4 and 9 m., and a length of between 20 and 30 m.
- the drum typically is positioned vertically.
- the drum may be operated at a pressure of between 100 and 600 kPa, such as between 200 and 300 kPa.
- a typical configuration may involve two or more, often two, coke drums, so that one drum may be in operation whilst the other drum(s) may be subjected to coke removal and cleaning before switching back in operation again.
- the drum needs to be evacuated from time to time in a batch operation.
- a cracking process occurs that in the coke drum results in a top product that is continuously removed from the drum as overhead stream (D), and a bottoms product, being the coke, that is removed as stream (E) when the feed to the drum is discontinued.
- the overhead stream (D) may be removed from the drum at a temperature of below 500°C, such as between 475°C and 500°C, to avoid coke formation in the transport line.
- the overhead stream (D) is supplied to the fractionation tower (1).
- a separation process is performed so that a gaseous stream (F), a naphtha-range stream (G), a light gas-oil stream (J), and a heavy gas-oil steam (H) are obtained.
- a bottoms steam (A) is obtained that is recycled to the furnace (2).
- the fractionation tower is further fed with fresh residual oil (K), which preferably is fed to the bottom part of the fractionation tower to avoid condensation of vapours in the upper parts of the tower.
- the fractionation tower may for example be operated so that the temperature in the bottom section of the tower is between 340°C and 385°C.
- a fractionation of a mixture comprising the overhead stream (D) and a residual oil (K) is performed to result in a gaseous output stream (F) obtained as overhead stream from the fractionation tower, a naphtha-range stream (G), a light gas oil stream (J), a heavy gas oil stream (H), and a bottoms stream (A).
- a residual oil stream obtained from refinery operations may be used.
- the residual oil may be a residual oil from atmospheric distillation (ADR), or may be a residual oil from vacuum distillation in a refinery (VDR).
- ADR is to be understood to be the fraction of crude oil having an initial boiling point of above 340 °C.
- VDR is to be understood to be the fraction of crude oil having an initial boiling point of above 535°C.
- the stream (L) may for example be provided at a temperature of 3 300 and £ 450°C, preferably of 3 300 and £ 400°C.
- the stream (L) may be prepared by converting solid waste plastics into a molten stream via one of more melt extruder(s) as unit (4).
- the waste plastics stream may for example by supplied by a melt extruder that is connected to the feed line to the furnace.
- the pre-reactor (4) preferably being a melt extruder, is operated under such conditions that the oligomer stream (L) has a weight average molecular weight of less than 100,000 g/mol, preferably between 5,000 and 50,000 g/mol, more preferably between 5,000 and 10,000 g/mol.
- the waste plastic material may be subjected to each or both of high temperature and high shear which result in chain fission.
- Such chain fission leads to reduction of the weight average molecular weight of the plastic material, such that the oligomer stream (L) that, upon exiting the melt extruder, is supplied as feed to the furnace (2) has a reduced weight average molecular weight, such as a weight average molecular weight of less than 100,000 g/mol, preferably between 5,000 and 50,000 g/mol, more preferably between 5,000 and 10,000 g/mol.
- the weight average molecular weight of the stream (L) may for example be determined according to the method of ASTM D6474-12.
- the pre-reactor (4) may be operated at a temperature of 3 350 and £ 450 °C.
- the pre-reactor (4) preferably a melt extruder, is operated at a temperature of 3 400 and £ 450°C.
- the waste plastic is subjected to a certain lengthy residence time in the pre-reactor (4).
- the waste plastic may be subjected to a residence time of 3 10 min, preferably of 3 10 and £ 30 min.
- the pre-reactor (4) which may for example be a melt extruder such as a twin-strew melt extruder, is operated under such conditions as to effect the removal of chlorine from the waste plastics stream (B).
- the solid mixed waste plastics stream (B) which may for example comprise 80-90 wt% of polyolefins, and 1-5 wt% of chlorine-containing polymers such as polyvinylchloride (PVC), is heated to such temperature where the PVC is molten and decomposes to form a gaseous HCI product that is removed as stream (M).
- PVC polyvinylchloride
- Stream (M) may further be contacted with an aqueous stream (R) containing a base such as NaOH to neutralise the HCI and thereby produce an aqueous stream (S) containing NaCI.
- the removal of the gaseous HCI stream (M) from the pre-reactor (4) may be further enhanced by applying a vacuum to the pre-reactor (4), or by use of an inert sweep gas that may be injected to pre-reactor (4) as stream (N).
- the contact time in the pre-reactor (4) preferably is sufficient to remove > 95%, preferably > 99%, of the chlorine from stream (L).
- the pre-reactor (4) comprises a first pre-reactor (4A) and a second pre-reactor (4B).
- the first pre-reactor (4A) which may for example be a melt extruder such as a twin-screw melt extruder
- the solid mixed waste plastics stream (B) which may for example comprise 80-90 wt% of polyolefins, and 1-5 wt% of chlorine-containing polymers such as polyvinylchloride (PVC)
- PVC polyvinylchloride
- Stream (M) may further be contacted with an aqueous stream (R) containing a base such as NaOH to neutralise the HCI and thereby produce an aqueous stream (S) containing NaCI.
- the removal of the gaseous HCI stream (M) from the first pre-reactor (4A) may be further enhanced by applying a vacuum to the first pre-reactor (4A), or by use of an inert sweep gas that may be injected to first pre-reactor (4A) as stream (N).
- the contact time in the first pre-reactor (4A) preferably is sufficient to remove > 95%, preferably > 99%, of the chlorine, to form a molten plastic stream (B’).
- Stream (B’) may then be supplied to a second pre-reactor (4B), which may for example be a melt extruder such as a twin-screw melt extruder, wherein stream (B’) is processed at a temperature of 3 350 and £ 450 °C, preferably 3 400 and £ 450°C, during a residence time of 3 10 min, preferably of 3 10 and £ 30 min, to form the oligomeric stream (L). Under such conditions, the chain fission process may be adequately performed.
- a melt extruder such as a twin-screw melt extruder
- the waste plastics stream (B) that is subjected to the process of the present invention preferably comprises a major quantity of polyolefin plastics.
- the waste plastics stream may comprise 3 60.0 wt% of polyolefin plastics, preferably 3 75.0 wt%.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Oil, Petroleum & Natural Gas (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Chemical Kinetics & Catalysis (AREA)
- General Chemical & Material Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Wood Science & Technology (AREA)
- Separation, Recovery Or Treatment Of Waste Materials Containing Plastics (AREA)
- Production Of Liquid Hydrocarbon Mixture For Refining Petroleum (AREA)
Abstract
The present invention relates to a process for production of chemical feedstocks from waste plastics, the process comprising providing a process configuration comprising a fractionation tower (1), a furnace (2), one or more coke drum(s) (3), and a pre-reactor (4), configured so that a bottoms stream (A) from the fractionation tower is mixed with an oligomeric stream (L) and supplied to the furnace, the product stream from the furnace (C) is supplied to a coke drum, and an overhead stream (D) from the coke drum is supplied back to the fractionation tower; wherein the oligomeric stream (L) is obtained as product stream from conversion of a waste plastics stream (B) in the pre-reactor, and has a weight average molecular weight of between 5,000 and 10,000 g/mol. Such process allows for the conversion of a wide variety of waste plastics into valuable chemical products. Furthermore, such process allows for the increase in production of naphtha-range hydrocarbon products that may be used for production of for example new thermoplastic polymer product via conversion in steam cracker facilities.
Description
Process for conversion of waste plastics into hydrocarbons.
[0001] The present invention relates to a process for conversion of waste plastics into hydrocarbons, such as hydrocarbon that may be used to form new plastics. In particular, the invention relates to a process for conversion of waste plastics into hydrocarbons via delayed coking.
[0002] To the background of the present global developments to reduce energy and material footprint in amongst others the manufacturing of materials such as polymers and chemicals, there is a clear driver to seek reduction of energy and raw materials that are used in manufacturing of such materials. Particularly, there is a driver to enhance circularity of use of materials, after having arrived at end-of-life for a certain application, thereby reducing the use of virgin raw materials in the manufacturing of polymers and chemicals, which typically are fossil- feed based raw materials, obtained from crude oil or natural gas feedstocks. By increasing the circularity, the use of virgin raw materials is reduced, and thereby the materials footprint associated with the manufacturing of polymers and chemicals.
[0003] A promising way of increasing the circularity is by re-using end-of-life plastics, collected and made available as waste plastics streams. Such waste plastics streams can be obtained from consumer waste collection, from industrial waste collection, of by collection of waste as littered in the environment, either as aquatic littering or as land-based littering. Typically, such waste plastics streams are mixtures of various types and qualities of plastics. Through sorting, certain streams may be obtained that qualify for re-use as thermoplastics, either by directly subjecting them to thermal shaping processes or via blending them with high-quality virgin-type plastic materials to compensate for loss of properties. Such way of re-use of material however is only appropriate for a limited fraction of waste plastics that can be sorted out of the mixed waste streams as provided from waste collection so that the obtained stream has high uniformity of material composition.
[0004] Still, typically a significant portion of the waste plastics as provided by collection, if not a major portion, is not suitable for such direct re-use as polymer. Such mixed plastic waste commonly is discarded of by processes like waste incineration. In order to increase material circularity, there is a desire to develop alternative processing methods for such mixed waste plastic streams. One route for doing so is by means of chemical recycling, wherein the polymer
materials that constitute the waste plastics streams are depolymerised to provide hydrocarbon materials that, directly or indirectly, can by once again be converted into polymers through polymerisation processes.
[0005] Such chemical conversion processes provide certain benefits, amongst others in that they may be operated using waste plastic compositions of varying nature, including waste plastic compositions that show particularly large variation in batch-to- batch composition.
[0006] It is particularly desirable for one to be able to utilise existing chemical conversion process technologies for the purpose of converting waste plastic streams into valuable hydrocarbon materials. Therefore, where a technology would be made available via which existing petrochemical assets would be rendered suitable for use in conversion of waste plastics streams into hydrocarbons, such would be broadly desirable.
[0007] One such opportunity now is presented by certain refinery assets. In view of reduced hydrocarbon consumption for energy and transport, which is a current and expectedly further developing trend, a certain fraction of the ubiquitously present refinery assets may well become underutilised or even idled, and therefore available for alternative uses. One such use may well be the conversion of waste plastics into hydrocarbons that can serve as feedstocks for making chemical and/or polymer products, thereby creating a circular economy of plastics materials and reducing the material footprint.
[0008] In accordance with the present invention, this has now been provided by a process for production of chemical feedstocks from waste plastics, the process comprising providing a process configuration comprising a fractionation tower (1), a furnace (2), one or more coke drum(s) (3), and a pre-reactor (4), configured so that a bottoms stream (A) from the fractionation tower is mixed with a stream originating from waste plastics (L), and supplied to the furnace, the product stream from the furnace (C) is supplied to a coke drum, and an overhead stream (D) from the coke drum is supplied back to the fractionation tower; wherein the stream (L) is obtained as product stream from conversion of a waste plastics stream (B) in the pre-reactor; wherein the stream (L) is supplied in molten condition; and preferably wherein stream (L) has a weight average molecular weight of less than 100,000 g/mol; more preferably wherein the stream (L) is an oligomeric stream having a weight average molecular weight of between 5,000 and 50,000 g/mol, even more preferably between 5,000 and 10,000 g/mol.
[0009] Such process allows for the conversion of a wide variety of waste plastics into valuable chemical products. Furthermore, such process allows for the increase in production of naphtha- range hydrocarbon products that may be used for production of for example new polymer products via conversion in steam cracker facilities.
[0010] The process in accordance with the present invention is further elucidated by the Figure 1. In Figure 1, the unit (1) represents the fractionation tower. The furnace is represented by unit (2). The coke drum(s) are represented by units (3). A pre-reactor is represented by unit (4). This configuration presents a representative embodiment of the invention, but does not limit the invention thereto. The process according to the present invention may comprise one single coke drum (3), or multiple coke drums. Figure 1 presents a particular embodiment of the invention, wherein two coke drums are present. Such configuration allows for switching operations between the coke drums so that one drum can be used in operation whilst the other drum can be cleaned out. From the fractionation tower, a bottoms stream (A) is provided to feed the furnace. The bottoms stream (A) may for example be supplied at a temperature of ³ 300 and £ 400 °C. Out of the furnace, a furnace product stream (C) is provided to coke drum(s). Feed (B) is a waste plastics stream, which may be first reacted in the pre-reactor (4) to reduce the molecular weight and by so form an oligomer (L) which is then mixed with the bottoms stream (A) and fed into the furnace. Out of the coke drums, a cracked overhead product (D) is obtained that is to be supplied to the fractionation tower for fractionation, with a fraction residual oil (K), into typically a top gaseous stream (F), a naphtha-range stream (G), a light gas oil stream (J), a heavy gas oil stream (H), and a bottoms stream (A). Further, out of the coke drums, a coke stream (E) is obtained, which accumulates in the drum, to be evacuated therefrom upon discontinuation of the operation of that drum.
[0011] The furnace (2) that may be used in the process according to the present invention may for example be a furnace in which multiple feed tubes are passed through a heating chamber, also referred to as a firebox, so that the feed is heated by external heating. The tubes may be passed through the firebox multiple times, for example two or four times. The heat may for example be provided by burners placed below the tubes. The burners may be controlled in such way to provide the required heating of the feed in the tubes to obtain the desired temperature of the feed exiting the furnace. In order to ensure that the coke formation of the feed does not occur in the furnace tubes, but is delayed until the feed materials reach the coke drum, the mass velocity of the feed through the furnace is preferably greater than 1800 kg/s/m2. A quantity
of steam may be added to the feed tubes, such as for example between 0.1 and 2.0 wt% of steam with regard to the total weight of the feed. Such addition of steam contributes to increase of velocity in the tubes. The combined feed (A) and (B) may be heated in the furnace by passing the feed through heating tubes and subjecting it to external heat energy to obtain a furnace product stream (C) having a temperature of ³ 450°C and £ 550°C, preferably of ³ 475°C and £ 500°C.
[0012] The feed exits the furnace at a temperature of preferably ³ 450°C and £ 550°C, more preferably of ³ 475°C and £ 500°C. Upon exiting the furnace, the heated furnace product stream (C) is transported via a transfer line into a coke drum. It is desirable that the residence time in the transfer line is kept as short as possible, to avoid occurrence of coking prior to reaching the coke drum. Accordingly, it is desirable to keep the transfer line as short as possible.
Furthermore, as typically a furnace is connected to multiple coke drums to ensure continuous operations, a switch valve may be present in the transfer line, to allow directing the feed to a desired coke drum.
[0013] A typical coke drum that may be used in the process according to the present invention may have a diameter of between 4 and 9 m., and a length of between 20 and 30 m. The drum typically is positioned vertically. The drum may be operated at a pressure of between 100 and 600 kPa, such as between 200 and 300 kPa.
[0014] A typical configuration may involve two or more, often two, coke drums, so that one drum may be in operation whilst the other drum(s) may be subjected to coke removal and cleaning before switching back in operation again. As coke is deposited into the drum, the drum needs to be evacuated from time to time in a batch operation.
[0015] As a result of the temperature in the product exiting the furnace, a cracking process occurs that in the coke drum results in a top product that is continuously removed from the drum as overhead stream (D), and a bottoms product, being the coke, that is removed as stream (E) when the feed to the drum is discontinued. The overhead stream (D) may be removed from the drum at a temperature of below 500°C, such as between 475°C and 500°C, to avoid coke formation in the transport line.
[0016] The overhead stream (D) is supplied to the fractionation tower (1). In the fractionation tower, a separation process is performed so that a gaseous stream (F), a naphtha-range stream
(G), a light gas-oil stream (J), and a heavy gas-oil steam (H) are obtained. Furthermore, a bottoms steam (A) is obtained that is recycled to the furnace (2). The fractionation tower is further fed with fresh residual oil (K), which preferably is fed to the bottom part of the fractionation tower to avoid condensation of vapours in the upper parts of the tower. The fractionation tower may for example be operated so that the temperature in the bottom section of the tower is between 340°C and 385°C.
[0017] In an embodiment according to the invention, in the fractionation tower a fractionation of a mixture comprising the overhead stream (D) and a residual oil (K) is performed to result in a gaseous output stream (F) obtained as overhead stream from the fractionation tower, a naphtha-range stream (G), a light gas oil stream (J), a heavy gas oil stream (H), and a bottoms stream (A).
[0018] As feed (K) to the fractionation tower, a residual oil stream obtained from refinery operations may be used. The residual oil may be a residual oil from atmospheric distillation (ADR), or may be a residual oil from vacuum distillation in a refinery (VDR). Preferably, the residual oil is a residual oil from vacuum distillation. In the context of the present invention, ADR is to be understood to be the fraction of crude oil having an initial boiling point of above 340 °C. In the context of the present invention, VDR is to be understood to be the fraction of crude oil having an initial boiling point of above 535°C.
[0019] The stream (L) may for example be provided at a temperature of ³ 300 and £ 450°C, preferably of ³ 300 and £ 400°C. The stream (L) may be prepared by converting solid waste plastics into a molten stream via one of more melt extruder(s) as unit (4). The waste plastics stream may for example by supplied by a melt extruder that is connected to the feed line to the furnace.
[0020] In certain embodiments of the invention, the pre-reactor (4), preferably being a melt extruder, is operated under such conditions that the oligomer stream (L) has a weight average molecular weight of less than 100,000 g/mol, preferably between 5,000 and 50,000 g/mol, more preferably between 5,000 and 10,000 g/mol. This involves operating the pre-reactor, preferably being a melt extruder, under such conditions that certain degradation of the waste plastic material that is supplied to the extruder occurs during the melt extrusion operation. During the melt extrusion operation, in such circumstances, the waste plastic material may be subjected to each or both of high temperature and high shear which result in chain fission. Such chain fission
leads to reduction of the weight average molecular weight of the plastic material, such that the oligomer stream (L) that, upon exiting the melt extruder, is supplied as feed to the furnace (2) has a reduced weight average molecular weight, such as a weight average molecular weight of less than 100,000 g/mol, preferably between 5,000 and 50,000 g/mol, more preferably between 5,000 and 10,000 g/mol. In the context of the present invention, the weight average molecular weight of the stream (L) may for example be determined according to the method of ASTM D6474-12.
[0021] For example, the pre-reactor (4) may be operated at a temperature of ³ 350 and £ 450 °C. Preferably, the pre-reactor (4), preferably a melt extruder, is operated at a temperature of ³ 400 and £ 450°C. In order to adequately perform the chain fission process, it is desirable that the waste plastic is subjected to a certain lengthy residence time in the pre-reactor (4). For example, the waste plastic may be subjected to a residence time of ³ 10 min, preferably of ³ 10 and £ 30 min.
[0022] In one embodiment of the invention, as shown in Figure 1 , the pre-reactor (4), which may for example be a melt extruder such as a twin-strew melt extruder, is operated under such conditions as to effect the removal of chlorine from the waste plastics stream (B). In this operation, the solid mixed waste plastics stream (B), which may for example comprise 80-90 wt% of polyolefins, and 1-5 wt% of chlorine-containing polymers such as polyvinylchloride (PVC), is heated to such temperature where the PVC is molten and decomposes to form a gaseous HCI product that is removed as stream (M). Stream (M) may further be contacted with an aqueous stream (R) containing a base such as NaOH to neutralise the HCI and thereby produce an aqueous stream (S) containing NaCI. The removal of the gaseous HCI stream (M) from the pre-reactor (4) may be further enhanced by applying a vacuum to the pre-reactor (4), or by use of an inert sweep gas that may be injected to pre-reactor (4) as stream (N). The contact time in the pre-reactor (4) preferably is sufficient to remove > 95%, preferably > 99%, of the chlorine from stream (L).
[0023] In another embodiment of the invention, as shown in figure 2, the pre-reactor (4) comprises a first pre-reactor (4A) and a second pre-reactor (4B). In the first pre-reactor (4A), which may for example be a melt extruder such as a twin-screw melt extruder, the solid mixed waste plastics stream (B), which may for example comprise 80-90 wt% of polyolefins, and 1-5 wt% of chlorine-containing polymers such as polyvinylchloride (PVC), is heated to such temperature, preferably ³ 300°C and £ 350°C, where the PVC is molten and decomposes to
form a gaseous HCI product that is removed as stream (M). Stream (M) may further be contacted with an aqueous stream (R) containing a base such as NaOH to neutralise the HCI and thereby produce an aqueous stream (S) containing NaCI. The removal of the gaseous HCI stream (M) from the first pre-reactor (4A) may be further enhanced by applying a vacuum to the first pre-reactor (4A), or by use of an inert sweep gas that may be injected to first pre-reactor (4A) as stream (N). The contact time in the first pre-reactor (4A) preferably is sufficient to remove > 95%, preferably > 99%, of the chlorine, to form a molten plastic stream (B’). Stream (B’) may then be supplied to a second pre-reactor (4B), which may for example be a melt extruder such as a twin-screw melt extruder, wherein stream (B’) is processed at a temperature of ³ 350 and £ 450 °C, preferably ³ 400 and £ 450°C, during a residence time of ³ 10 min, preferably of ³ 10 and £ 30 min, to form the oligomeric stream (L). Under such conditions, the chain fission process may be adequately performed.
[0024] The waste plastics stream (B) that is subjected to the process of the present invention preferably comprises a major quantity of polyolefin plastics. For example, the waste plastics stream may comprise ³ 60.0 wt% of polyolefin plastics, preferably ³ 75.0 wt%.
Claims
1. Process for production of chemical feedstocks from waste plastics, the process comprising providing a process configuration comprising a fractionation tower (1), a furnace (2), one or more coke drum(s) (3), and a pre-reactor (4), configured so that a bottoms stream (A) from the fractionation tower is mixed with a stream originating from waste plastics (L), and supplied to the furnace, the product stream from the furnace (C) is supplied to a coke drum, and an overhead stream (D) from the coke drum is supplied back to the fractionation tower; wherein the stream (L) is obtained as product stream from conversion of a waste plastics stream (B) in the pre-reactor; wherein the stream (L) is supplied in molten condition; and preferably wherein stream (L) has a weight average molecular weight of less than 100,000 g/mol; more preferably wherein the stream (L) is an oligomeric stream having a weight average molecular weight of between 5,000 and 50,000 g/mol, even more preferably between 5,000 and 10,000 g/mol.
2. Process according to claim 1, wherein in the fractionation tower a fractionation of a mixture comprising the overhead stream (D) and a residual oil (K) is performed to result in a gaseous output stream (F) obtained as overhead stream from the fractionation tower, a naphtha-range stream (G), a light gas oil stream (J), a heavy gas oil stream (H), and a bottoms stream (A).
3. Process according to any of claims 1-2, wherein the stream (L) is supplied at a temperature of ³ 300 and £ 450°C.
4. Process according to any of claims 1-3, wherein the bottoms stream (A) is supplied at a temperature of ³ 300 and £ 400 °C.
5. Process according to any of claims 1-4, wherein the combined feed (A) and (B) are heated in the furnace by passing the feed through heating tubes and subjecting it to external heat energy to obtain a furnace product stream (C) having a temperature of ³ 450°C and £ 550°C, preferably of ³ 475°C and £ 500°C.
6. Process according to any of claims 1-5, wherein the bottoms stream (A) has a boiling point of ³ 400°C.
7. Process according to any of claims 1-6, wherein the pre-reactor (4) is a melt extruder.
8. Process according to any one of claims 1-7, wherein the pre-reactor (4) is operated at a temperature of ³ 350 and £ 450 °C, and/or wherein the waste plastic is subjected to a residence time in the pre-reactor of ³ 10 min., preferably ³ 10 and £ 15 min.
9. Process according to any of claims 2-8, wherein the residual oil (K) is a residual oil obtained from atmospheric distillation of crude oil, or a residual oil obtained from vacuum distillation of the residual oil obtained from atmospheric distillation of crude oil.
10. Process according to any of claims 1-9, wherein the coke drum is operated at a pressure of between 100 and 600 kPa.
11. Process according to any of claims 1-10, wherein the fractionation tower operated so that the temperature in the bottom section of the tower is between 340°C and 385°C.
12. Process according to any of claims 1-11, wherein the furnace product stream (C) comprises ³ 0.1 and £ 50.0 wt% of the stream (L), with regard to the total weight of the stream (C), preferably ³ 5.0 and £ 30.0 wt%, more preferably ³ 5.0 and £ 20.0 wt%.
13. Process according to any one of claims 1-12, wherein a gaseous stream (M) comprising HCI that is formed from decomposition of chlorine-containing polymers, is removed from the pre-reactor (4), wherein the pre-reactor (4) is operated at a temperature where decomposition of the chlorine-containing polymers that are present in the waste plastics stream (B) occurs.
14. Process according to any one of claims 1-13, wherein the pre-reactor (4) comprises a first pre-reactor (4A) and a second pre-reactor (4B), wherein in the first pre-reactor (4A), which may for example be a melt extruder such as a twin-screw melt extruder, the solid mixed waste plastics stream (B), which may for example comprise 80-90 wt% of polyolefins, and 1-5 wt% of chlorine-containing polymers such as polyvinylchloride (PVC), is heated to
such temperature, preferably ³ 300°C and £ 350°C, where the chlorine-containing polymers are molten and decompose to form a gaseous HCI product that is removed as stream (M), so that a molten, dechlorinated plastic stream (B’) is formed, which then is supplied to a second pre-reactor (4B), which may for example be a melt extruder such as a twin-screw melt extruder, wherein stream (B’) is processed at a temperature of ³ 350 and £ 450 °C, preferably ³ 400 and £ 450°C, during a residence time of ³ 10 min, preferably of ³ 10 and £ 30 min, to form the oligomeric stream (L).
15. Process according to any one of claims 13-14, wherein the stream (M) is further contacted with an aqueous stream (R) containing a base, preferably NaOH, to neutralise the HCI and thereby produce an aqueous stream (S), preferably containing NaCI.
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PCT/EP2022/066603 WO2022268663A1 (en) | 2021-06-22 | 2022-06-17 | Process for conversion of waste plastics into hydrocarbons |
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JP6952105B2 (en) * | 2016-08-01 | 2021-10-20 | サビック グローバル テクノロジーズ ベスローテン フェンノートシャップ | Dechlorination of mixed plastic pyrolysis oil using devolatile extrusion and chloride sweeping agent |
RU2721849C1 (en) * | 2019-12-26 | 2020-05-25 | Общество с ограниченной ответственностью "ЛУКОЙЛ-Нижегородниинефтепроект" | Method of processing polymer wastes at delayed coking plants |
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