Patent Application
20240084095
Systems and methods are provided for integration of polymeric waste co-processing in cokers to produce circular chemical products from coker naphtha.
Processing of polymeric waste is a subject of increasing importance. It is desirable to have a processing pathway that allows for production of circular chemical products. Specifically, it is desirable to produce circular chemical products through a processing pathway that includes polymeric waste recycling. Although dedicated processing systems could be used for polymeric waste recycling, such dedicated systems require substantial initial capital costs and a constant supply of waste feedstock. Thus, it is desirable to leverage an existing processing unit to be able to co-process polymeric waste into feedstock for production of circular chemical products.
Disclosed herein is an example method of producing circular chemical products comprising: providing a coker naphtha that is at least partially derived from polymeric waste, wherein the coker naphtha has a total halide content of about 1 wppm to about 0.5 wt %, a 2-3 ring aromatic content of about 0 wt % to about 5 wt %, and a sulfur content of about 750 ppm to about 2 wt %; and converting the coker naphtha into at least a polymer.
Further disclosed herein is an example a method of producing circular chemical products comprising: cracking at least a coker naphtha to form at least a cracking effluent, wherein the coker naphtha is at least partially derived from polymeric waste, wherein the coker naphtha has a total halide content of about 1 wppm to about 0.5 wt %, a 2-3 ring aromatic content of about 0 wt % to about 5 wt %, and a sulfur content of about 750 ppm to about 2 wt %; recovering olefins from the cracking effluent; and polymerizing at least a portion of the olefins to form at least a polyolefin.
These and other features and attributes of the disclosed methods and systems of the present disclosure and their advantageous applications and/or uses will be apparent from the detailed description which follows.
To assist those of ordinary skill in the relevant art in making and using the subject matter hereof, reference is made to the appended drawings, wherein:
In various embodiments, systems and methods are provided for chemical recycling of polymeric waste, such as plastic waste. In some embodiments, the polymeric waste is co-processed in a coker to produce coker products, including coker naphtha. Example embodiments further include includes production of circular chemical products from the coker naphtha that is at least partially derived from polymeric waste. In some embodiments, the circular products comprise circular olefins, which can be further processed to produce circular polyolefins.
Circular chemical products are chemical products derived from polymeric waste wherein the molecules of the chemical product can be attributed to the polymers in the polymeric waste, such as by crediting, allocating offsetting for other hydrocarbons, and/or substituting for other hydrocarbons in a mass or energy balance for a system. Circular chemical products include circular monomers, circular aromatics, and circular polymers, among others. Polymers that are certified for their circularity by third party certification may be referred to as certified circular. One example of such a certification is the mass balance chain of custody method set forth by the International Sustainability and Carbon Certification.
Coker naphtha is a liquid coker effluent fraction that is formed in the coker with a T10 distillation point of 30° C. or higher and a T90 distillation point of 220° C. or less. In some embodiments, the coker naphtha has a T10 distillation point of 30° C. or higher and a T90 distillation point of 177° C. or less. As used herein, the distillations points are determined in accordance with ASTM D86. In the event that ASTM D86 is unsuitable for characterization of a sample, ASTM 2887 may be used instead. Coker naphtha is a mixture of many different hydrocarbons, including paraffins, naphthenes, olefins, and aromatics. Coker naphthas can comprise hydrocarbons ranging from 5 carbon atoms to 12 carbon atoms.
Naphtha typically has a number of uses, including as a petrochemical feedstock, a gasoline blendstock, or feedstock to a reformer for making reformate for gasoline blending. However, while naphtha can be used as a steam cracker feedstock, coker naphtha presents challenges making it use as a steam cracker feedstock undesirable. For example, coker naphtha typically contains levels of sulfur that results in poor quality of resultant chemical products as well as posing challenges with process reliability. In addition, aromatic and olefin content of the coker naphtha relative to paraffins also poses challenges to process reliability while also making chemical production less cost effective.
In one or more embodiments, the coker naphtha is at least partially derived from polymeric waste. In some embodiments, the coker naphtha is produced by co-processing of polymeric waste with a conventional coker feedstock. By co-processing of the polymeric waste, the coker naphtha should have reduced aromatic content with corresponding increase in paraffin and olefin content. For example, the coker naphtha that is at least partially derived can have an aromatic content that is reduced by 10% to 40% as compared to coker naphtha from hydrocarbon feedstocks. In addition, the co-processing of the polymeric waste should also provide coker naphtha with reduced sulfur content. Advantageously, the reduction in aromatic and sulfur content from co-processing of polymeric waste should increase the value of coker naphtha for subsequent chemical production.
Accordingly, present embodiments utilize the coker naphtha that is at least partially derived from polymeric waste as a feedstock for chemical production. This integration of a coker with chemical production allows the polymeric waste to be chemically recycled into chemical products, such as monomers (e.g., olefins), aromatics, polymers, synthetic elastomers and rubbers, plastic additives, epoxies, and resins, and specialty fluids, such as isopropyl alcohol, oxo-alcohols, detergents, and lubricants.
In
The coker naphtha fraction 116 comprising coker naphtha that is at least partially derived from polymeric waste can then be passed into the cracking stage 104. Cracking stage 104 corresponds to any suitable process for cracking saturated hydrocarbons into smaller hydrocarbons, including olefins such as ethylene, propylene, butylene (e.g., isobutylene), and butadiene, among others. Examples of suitable techniques include steam cracking and fluid catalytic cracking, among others. Feeding the coker naphtha fraction 116 to the cracking stage 104 may allow the unit to run with lower severity, for example, due to the increased olefin content. In addition, with the coker naphtha fraction 116 feed the unit may include increased caustic and water rates. In the example shown in
After the cracking stage 104, the cracking effluent 122 can be passed to an olefins recovery stage 106. In the olefins recovery stage 106, olefins are separated from the cracking effluent to form at least an olefins stream 124 and an additional product stream 126. It should be understood that separation of the olefins from the cracking effluent 122 can occur in one or more vessels and/or one or more different operations. For example, the cracking effluent 122 can be fractionated or otherwise separated to form at least the olefins stream 124 and additional products stream 126. At least a portion of the olefins separated from the cracking effluent include circular olefins, such as circular ethylene, circular propylene, and circular butylene (e.g., circular butylene), and circular butadiene, among others. Circular olefins can be attributed, for example, to polymers in the polymeric waste. In some embodiments, the olefins stream 124 can be separated into one or more additional fractions, such as an ethylene fraction comprising circular ethylene, a butylene fraction comprising circular butylene, a propylene fraction comprising circular propylene, and/or a butadiene fraction comprising circular butadiene, among others. As used herein, separated fractions do not necessarily contain 100% of the indicated species, but typically primarily comprise the indicated species, for example, containing at least 50 wt %, 80 wt %, 90 wt %, 95 wt %, 98 wt %, or more of the indicated species. At least a portion of the products in the additional product stream 126 include circular products, such as aromatics, including benzene, toluene, xylene, and styrene. Additional circular products include, for example, cyclohexane, cyclopentadiene, and dicyclopentadiene. In some embodiments, the additional product stream 126 is separated into one or more fractions, such as an aromatics stream.
The olefins stream 124 from the cracking stage 104 can then be passed to a polymerization stage 108 for production of chemical products, such as polymer products 128. For example, an ethylene fraction, propylene fraction, and/or butylene fraction can be separately passed to a polymerization stage. Polymerization stage 108 corresponds to any suitable polymerization process for bonding two or more olefins, including chain growth propagation, step-growth, and condensation polymerization. The polymerization processes may be in the solution, slurry, or gas-phase, among others. In some embodiments, the polymer products 128 include polyolefins. At least a portion of the polymer products 128 produced in the polymerization stage include circular polymers, such as circular polyethylene, circular polypropylene, circular polybutylene (e.g., circular polyisobutylene), circular polybutadiene, circular polyethylene terephthalate, circular polystyrene, circular polycarbonate, and circular polycaprolactam, among others. Circular polymers can be attributed, for example, to polymers in the polymeric waste. In the example shown in
In
The coker naphtha fraction 216 that is at least partially derived from polymeric waste can then be passed into the hydroprocessing stage 203. Hydroprocessing stage 203 corresponds to any suitable process for hydroprocessing the naphtha, including hydrotreatment, hydrocracking, catalytic dewaxing and/or hydroisomerization, aromatic saturation. In the example shown in
The hydroprocessing effluent 221 that is at least partially derived from polymeric waste can then be passed into the cracking stage 204. Cracking stage 204 corresponds to any suitable process for cracking saturated hydrocarbons into small hydrocarbons, including olefins such as ethylene, propylene, butylene (e.g., isobutylene), and butadiene, among others. For example. In the example shown in
After the cracking stage 204, the cracking effluent 222 can be passed to an olefins recovery stage 206. In the olefins recovery stage 206, olefins are separated from the cracking effluent to form at least an olefins stream 224 and an additional product stream 226. It should be understood that separation of the olefins from the cracking effluent 222 can occur in one or more vessels and/or one or more different operations. For example, the cracking effluent 222 can be fractionated or otherwise separated to form at least the olefins stream 224 and additional products stream 226. At least a portion of the olefins separated from the cracking effluent include circular olefins, such as circular ethylene, circular propylene, and circular butylene (e.g., circular butylene), and circular butadiene, among others. Circular olefins can be attributed, for example, to polymers in the polymeric waste. In some embodiments, the olefins stream 224 can be separated into one or more additional fractions, such as an ethylene fraction comprising circular ethylene, a butylene fraction comprising circular butylene, a propylene fraction comprising circular propylene, and/or a butadiene fraction comprising circular butadiene, among others. At least a portion of the products in the additional product stream 226 include circular products, such as aromatics, including benzene, toluene, xylene, and styrene. Additional circular products include, for example, cyclohexane, cyclopentadiene, and dicyclopentadiene. In some embodiments, the additional product stream 226 is separated into one or more fractions, such as an aromatics stream.
The olefins stream 224 from the cracking stage 204 can then be passed to a polymerization stage 208 for production of chemical products, such as polymer products 228. For example, an ethylene fraction, propylene fraction, and/or butylene fraction can be separately passed to a polymerization stage. Polymerization stage 208 corresponds to any suitable polymerization process for bonding two or more olefins, including chain growth propagation, step-growth, and condensation polymerization. The polymerization processes may be in the solution, slurry, or gas-phase, among others. In some embodiments, the polymer products 228 include polyolefins. At least a portion of the polymer products 228 produced in the polymerization stage include circular polymers, such as circular polyethylene, circular polypropylene, circular polybutylene (e.g., circular polyisobutylene), circular polybutadiene, circular polyethylene terephthalate, circular polystyrene, circular polycarbonate, and circular poly caprolactam, among others. Circular polymers can be attributed, for example, to polymers in the polymeric waste. In the example shown in
In
The coker naphtha fraction 316 that is at least partially derived from polymeric waste can then be passed into the hydroprocessing stage 303. Hydroprocessing stage 303 corresponds to any suitable process for hydroprocessing the naphtha, including hydrotreatment, hydrocracking, catalytic dewaxing and/or hydroisomerization, aromatic saturation. In the example shown in
The hydroprocessing effluent 321 that is at least partially derived from polymeric waste can then be passed into the reforming stage 328. Reforming stages corresponds to any suitable process for catalytic reforming of hydrocarbons into branched paraffins and aromatics. In the example shown in
After the reforming stage 328, the reformate stream 332 can be passed to an aromatics recovery stage 330. In the aromatics recovery stage 330, aromatics are separated from the reformate stream 332 to form at least a C6-C8 aromatic stream 334 and an additional product stream 336. It should be understood that separation of the C6-C8 aromatics from the reformate stream 332 can occur in one or more vessels and/or one or more different operations. For example, the reformate stream 332 can be fractionated or otherwise separated to form at least the C6-C8 aromatic stream 334 and additional product stream 336. At least a portion of the C6-C8 aromatics separated from the reformatted stream 332 include circular aromatics, such as circular benzene, circular ethylbenzene, circular toluene, circular o-xylene, circular p-xylene, circular m-xylene, and circular cyclohexane. Circular aromatics can be attributed to polymers in the polymeric waste feedstock. In some embodiments, the aromatics can be separated into one or more additional fractions, such as a benzene fraction comprising circular benzene fraction, a toluene fraction comprising circular toluene, a mixed C6 fraction comprising circular p-xylene, circular m-xylene, circular o-xylene, and circular cyclohexane fraction. At least a portion of the products in the additional product stream 226 include C9+ aromatics and other hydrocarbons, such as paraffins. In some embodiments, the additional product stream 226 is separated into one or more fractions, such as a C9+ aromatic stream and/or a paraffin stream. While not shown, downstream processing of the C6-C8 aromatic stream 334, additional product stream 336, or a portion thereof can product polymers.
In accordance with present embodiments, coking can be used to process a waste feedstock to produce coking products. In some embodiments, the waste feedstock is co-processed with a conventional coking feedstock.
The waste feedstock for coking can include or consist essentially of one or more types of polymers, such as polymers corresponding to plastic waste. The systems and methods described herein can be suitable for processing polymeric waste corresponding to a single type of polymer and/or polymeric waste corresponding to a plurality of polymers. In aspects where the waste feedstock consists essentially of polymers, the feedstock can include one or more types of polymers as well as any additives, modifiers, packaging dyes, and/or other components typically added to a polymer during and/or after formulation. The waste feedstock can further include components (e.g., paper) typically found in polymeric waste.
In some embodiments, the waste feedstock includes polymeric waste obtained from any source including, but not limited to, municipal, industrial, commercial or consumer sources. In some embodiments, the waste feedstock includes post-consumer use plastics. The polymeric waste further may include plastics obtained from a common source or from mixed sources, including mixed plastic waste obtained from municipal or regional sources and/or from waste streams of PET, HDPE, LDPE, LLDPE, polypropylene, and/or polystyrene. Furthermore, the waste feedstock may include thermoplastic elastomers and thermoset rubbers, such as from tires and other articles made from natural rubber, polybutadiene, styrene-butadiene, butyl rubber and EPDM.
Even further, examples of suitable waste feedstocks may include any of various used polymeric articles without limitation. Some examples of the many types of polymeric articles may include: films (including cast, blown, and otherwise), sheets, fibers, woven and nonwoven fabrics, furniture (e.g., garden furniture), sporting equipment, bottles, food and/or liquid storage containers, transparent and semi-transparent articles, toys, tubing and pipes, sheets, packaging, bags, sacks, coatings, caps, closures, crates, pallets, cups, non-food containers, pails, insulation, and/or medical devices. Further examples include industrial waste streams, such as linear alpha olefins and polypropylene heavy streams (e.g., >50 wt %). Further examples include automotive, aviation, boat and/or watercraft components (e.g., bumpers, grills, trim parts, dashboards, instrument panels and the like), wire and cable jacketing, agricultural films, geomembranes, playground equipment, and other such articles, whether blow molded, roto-molded, injection-molded, or the like. Any of the foregoing may include mixtures of polymeric and non-polymeric items (e.g., packaging or other articles may include inks, paperboards, papers, metal deposition layers, and the like). The ordinarily skilled artisan will appreciate that such polymeric articles may be made from any of various polymer and/or non-polymer materials, and that the polymer materials may vary widely (e.g., ethylene-based, propylene-based, butyl-based polymers, and/or polymers based on any C2 to C40 or even higher olefins, and further including polymers based on any one or more types of monomers, e.g., C2 to C40 α-olefin, di-olefin, cyclic olefin, etc. monomers). Common examples include ethylene, propylene, butylene, pentene, hexene, heptene, octene, and styrene; as well as multi-olefinic (including cyclic olefin) monomers such as ethylidene norbornene (ENB) and vinylidene norbomene (VNB) (including, e.g., when such cyclic olefins are used as comonomers, e.g., with ethylene monomers).
In various embodiments, the waste feedstock can include one or more nitrogen-containing polymers. Examples of nitrogen-containing polymers include polyamides (such as Nylon 6), polyurethanes, and polynitriles. The nitrogen-containing polymers can correspond to 0.1 wt % to 25 wt % of the waste feedstock (relative to the weight of the waste feedstock), or 1.0 wt % to 25 wt %, or 5.0 wt % to 25 wt %, or 10 wt % to 25 wt %, or 1.0 wt % to 15 wt %, or 5.0 wt % to 15 wt %, or 1.0 wt % to 10 wt %. For example, nitrogen-containing polymers may be in the waste feedstock in an amount of 25 wt % or less, 10 wt % or less, 5 wt % or less, 1 wt % or less, or 0.1 wt % or less.
In some embodiments, the waste feedstock can include one or more chlorine-containing polymers. Examples of chlorine-containing polymers including PVC (polyvinyl chloride) and PVDC (polyvinylidene chloride). In some aspects, the chlorine-containing polymers can correspond to as 0.001 wt % to 15 wt % of the waste feedstock (relative to the weight of the waste feedstock), or 0.1 wt % to 15 wt %, or 1.0 wt % to 15 wt %, or 0.001 wt % to 10 wt %, or 0.1 wt % to 10 wt %, or 1.0 wt % to 10 wt %, or 0.001 wt % to 5.0 wt %, or 0.001 wt % to 1.0 wt %. For example, the chlorine-containing polymers may be in the waste feedstock in an amount of about 15 wt % or less, 10 wt % or less, 5 wt % or less, 1 wt % or less, or 0.1 wt % or less.
In some embodiments, the waste feedstock can include at least one of polyethylene and polypropylene. The polyethylene can correspond to any convenient type of polyethylene, such as high density or low-density versions of polyethylene. Similarly, any convenient type of polypropylene can be used. Additionally or alternately, the waste feedstock can include one or more of polystyrene, polyamide (e.g., nylon), polyethylene terephthalate, and ethylene vinyl acetate. Still other polyolefins can correspond to polymers (including co-polymers) of butadiene, isoprene, and isobutylene. In some embodiments, the polyethylene and polypropylene can be present in the mixture as a co-polymer of ethylene and propylene. More generally, the polyolefins can include co-polymers of various olefins, such as ethylene, propylene, butenes, hexenes, and/or any other olefins suitable for polymerization.
In this discussion, unless otherwise specified, weights of polymers in a feedstock correspond to weights relative to the total polymer content in the feedstock. Any additives and/or modifiers and/or other components included in a formulated polymer are included in this weight. However, the weight percentages described herein exclude any solvents or carriers that might optionally be used to facilitate transport of the polymer into the coker.
In some embodiments, the waste feedstock includes 0.01 wt % to 35 wt % of polystyrene, or 0.1 wt % to 35 wt %, or 1 wt % to 35 wt %, or 0.01 wt % to 20 wt %, or 0.1 wt % to 20 wt %, or 1 wt % to 20 wt %, or 10 wt % to 35 wt %, or 5 wt % to 20 wt %, or 0.01 wt % to 10 wt %, or 0.01 wt % to 1 wt %. In some embodiments, the waste feedstock can also include oxygen-containing polymers, such as polyterephthalates. It is noted that polyamides also contain oxygen as part of the polymer structure. In this discussion, a polymer that includes both oxygen and nitrogen as part of the repeat unit for forming the polymer is defined as a nitrogen-containing polymer for purposes of characterizing the waste feedstock.
In addition to polymers, a waste feedstock can include a variety of other components. Such other components can include additives, modifiers, packaging dyes, and/or other components typically added to a polymer during and/or after formulation. The waste feedstock can further include any components typically found in polymeric waste. Finally, the feedstock can further include a carrier fluid so that the waste feedstock to the cracking process corresponds to a solution or slurry of the polymeric waste.
In embodiments where the waste feedstock is introduced into the coking environment at least partially as solids, having a small particle size can facilitate transport of the solids and/or reduce the likelihood of incomplete conversion. In some embodiments, the waste feedstock includes polymeric waste having a median particle size to 0.01 mm to 50 mm, 0.01 to 25 mm, 0.01 to 10 mm, 1 mm to 50 mm, 1 mm to 25 mm, 1 mm to 10 mm, 5 mm, or 0.1 mm to 5 mm, or 0.01 mm to 3 mm, or 0.1 mm to 3 mm, or 0.01 mm to 3 mm, or 0.1 mm to 3 mm, or 1 mm to 5 mm, or 1 mm to 3 mm. For determining a median particle size, the particle size is defined as the diameter of the smallest bounding sphere that contains the particle. Additionally or alternately, the polymeric waste in the waste feedstock can be melted and/or pelletized to improve the uniformity of the particle size of the plastic particles. In some embodiments, the polymeric waste has a maximum particles size of 10 mm or less, or 5 mm or less. Additionally or alternately, the polymeric waste can be provided in waste bail. In some embodiments, the waste bale is a composite bale.
It is noted that some types of polymeric waste can also include bio-derived components. For example, some types of plastic labels can include biogenic waste in the form of paper compounds. In some embodiments, 1 wt % to 25 wt % of the waste feedstock can correspond to bio-derived material. Such bio-derived material can also potentially contribute to the nitrogen and/or oxygen content of a waste feedstock.
Optionally, a carrier fluid can also be included in the waste feedstock to assist with introducing the polymeric waste into the cracking environment. For introduction into a cracking environment, it can be convenient for the feedstock to be in the form of a slurry. If a carrier fluid is used for transporting the waste feedstock, any suitable fluid can be used. Examples of suitable carrier fluids can include (but are not limited to) a wide range of petroleum or petrochemical products. For example, some suitable carrier fluids include crude oil, naphtha, kerosene, diesel, light or heavy cycle oils, catalytic slurry oil, and gas-oils. Other potential carrier fluids can correspond to naphthenic and/or aromatics solvents, such as toluene, benzene, methylnaphthalene, cyclohexane, methylcyclohexane, and mineral oil. Still other carrier fluids can correspond to refinery fractions, such as a gas oil fraction or naphtha fraction from a coker. As yet another example, a distillate and/or gas oil boiling range fraction can be used that generated by cracking of the waste feedstock, either alone or with an additional feedstock.
In various embodiments, coking is used to co-process a combined feedstock corresponding to a mixture of a conventional coking feedstock and a waste feedstock. In some embodiments, the conventional coking feedstock is used as the carrier fluid for the waste feedstock. The conventional coking feedstock can correspond to one or more types of petroleum and/or renewable feeds with a suitable boiling range for cracking, such as processing in a coker. The amount of waste feedstock in the combined feedstock can correspond to 1 wt % to 50 wt %, 3 wt % to 50 wt %, 10 wt % to 50 wt %, 25 wt % to 50 wt %, 1 wt % to 25 wt %, 1 wt % to 10 wt %, 1 wt % to 5%, 1 wt % to 3 wt %, 3 wt % to 25 wt %, 10 wt % to 25 wt %, 3 wt % to 15 wt % by weight of the combined feedstock. The conventional coking feedstock can correspond to 50% to 99% by weight of the combined feedstock to the coker.
In some embodiments, the coking feedstock for co-processing with the waste feedstock can correspond to a conventional petroleum feedstock having a relatively high boiling fraction, such as a heavy oil feed. For example, the coking feedstock portion of the feed can have a T10 distillation point of 343° C. or more, or 371° C. or more. In some embodiments, the coking feedstock has a T10 distillation point of 343° C. to 650° C. Examples of suitable heavy oils for inclusion in the coking feedstock include reduced petroleum crude; petroleum atmospheric distillation bottoms; petroleum vacuum distillation bottoms, or residuum; pitch; asphalt; bitumen; other heavy hydrocarbon residues; tar sand oil; shale oil; or even a coal slurry or coal liquefaction product such as coal liquefaction bottoms. Such feeds will typically have a Conradson Carbon Residue (ASTM D189-165) of at least 5 wt %, generally from 5 wt % to 50 wt %. In some embodiments, the coking feedstock comprises a petroleum vacuum residuum.
Some examples of conventional petroleum feedstock suitable for processing in a delayed coker or fluidized bed coker can have a composition and properties within the ranges set forth below in Table 1.
In addition to petroleum feedstocks, renewable feedstocks derived from biomass having a suitable boiling range can also be used as part of the cracking feed. Such renewable feedstocks include feedstocks with a T10 boiling point of 340° C. or more and a T90 boiling point of 600° C. or less. An example of a suitable renewable feedstock derived from biomass can be a cracking oil feedstock derived at least in part from biomass.
In some particular embodiments, the waste feedstock and the conventional coking feedstock (e.g., coker feedstock) are mixed to form a combined feedstock prior to entering the coking environment. In other embodiments, the waste feedstock and the conventional coking feedstock are separately introduced into the coking environment. More generally, however, any convenient method for introducing both the waste feedstock and the coking feedstock into the coking environment can be used.
Prior to being introduced into the coking environment, the feedstocks (optionally in the form of a combined feedstock) are pre-heated in accordance with one or more embodiments. Pre-heating the feedstocks in one or more heating stages can increase the temperature of the feedstocks to a mixing and storage temperature, to a temperature related to the cracking temperature, or to another convenient temperature.
In some embodiments, a portion of the pre-heating of a waste feedstock can be performed by mixing the waste feedstock with a coking feedstock in a mixing tank and heating the mixture in the mixing tank. For example, a waste feedstock and a coking feedstock can be mixed in a heated stirred tank for storage operating at 200° C. to 325° C., or 275° C. to 325° C. In some embodiments, tank agitation aids in uniform dispersal of the waste feedstock into resid and maintains slurry suspension. Heating in a mixing tank provides heat to the combined feedstock prior to introducing the combined feedstock into the cracking reaction environment. This can reduce or minimize additional cracking heat duty that would otherwise be required to heat the waste feedstock to thermal cracking temperatures. The mixed feedstock may be further heated and/or physically processed for particle size reduction prior to injection into the cracking reactor. The combined feedstock may be sized to provide particles with a maximum particle size, for example, of 5 mm or less, 2 mm or less, or 1 mm or less. In some embodiments, the particles are sized with milling equipment, such as a roller mill. In addition to heating, stripping of the combined waste feedstock and coking feedstock using a stripping gas can be performed in a mixing tank. Passing a stripping gas through the combined feedstock can assist with removing gases that are entrained in the combined feedstock.
In some embodiments, the waste feedstock is melted, for example, in an extruder. After extruding, the waste feedstock comprising melted polymeric waste can either be directly mixed with a conventional coking feedstock and/or a solvent, or the extruded plastic can be pelletized to form a desired particle size for the waste feedstock.
Still another option can be to mix the waste feedstock with the coking feedstock after the pre-heater furnace for the coker, in accordance with certain embodiments. In these embodiments, the coking feedstock can be heated to a higher temperature in the pre-heater, and then the waste feedstock can be added to the pre-heated coking feedstock to heat the waste feedstock.
In accordance with one or more embodiments, the waste feedstock is pyrolyzed to generate a pyrolysis oil that is then fed to the coking environment. In some embodiments, the waste feedstock is pyrolyzed with one or more additional feedstocks, such as rubber-containing feedstocks. In some embodiments, the pyrolysis oil at least partially derived from polymeric waste is co-processed in the coking environment with a conventional coking feedstock.
Pyrolysis is a technique of chemical recycling that includes thermal degradation of the pyrolysis feedstock to produce gas and liquid products, referred to as pyrolysis oil and a pyrolysis gas. Waste plastic pyrolysis units are distinct from coker units that have been specially designed to handle heavier feeds. In some embodiments, the waste feedstock may be heated in an environment free (or substantially free) of oxygen. For example, the pyrolysis may occur in an environment that includes about 5 weight percent oxygen or less, about 3 weight percent oxygen or less, about 1 weight percent oxygen or less, or about 0.5 weight percent oxygen or less. The pyrolysis products may depend on a number of factors, including, but not limited to, pyrolysis reactor temperature, pyrolysis reactor pressure, reactor residence time, feed type, feed quality, and process configuration.
A specific pyrolysis technique will now be described in more detail. In an example embodiment, a pyrolysis feedstock (e.g., a waste feedstock) may be provided, for example, in a granular, flake, or pellet form, and fed to a pyrolysis unit. In the pyrolysis unit, the waste feedstock may be melted to produce a molten liquid (e.g., molten plastic). For example, the polymeric waste may be melted in an extruder to a temperature of about 300° C. to about 320° C. The molten liquid may then be pyrolyzed in an environment free (or substantially free) of oxygen to produce pyrolysis gases. For example, the molten liquid may be heated in pyrolysis chamber to a higher temperature, such as 390° C. to about 550° C., while agitating. Long chain hydrocarbons (e.g., approximately 30 carbon atoms or longer) in the produced pyrolysis gases may then be condensed and further pyrolyzed for further thermal degradation while shorter chain hydrocarbons may exit in gaseous form. For example, the produced pyrolysis gases may be directed to a contactor for contact with a bank of condenser elements (e.g., plates) upon which the long chain hydrocarbons may condense. The long chain hydrocarbons may flow from the condenser back to the pyrolysis chamber. The pyrolysis gases including the shorter chain hydrocarbons may be distilled in a distillation column to provide pyrolysis gas and pyrolysis oil.
The pyrolysis oil 408 that is at least partially derived from polymeric waste is then passed into coking stage 412. Coking stage 412 corresponds to any suitable coking for coking the pyrolysis oil, including a delayed coker, a fluidized coker, or a combination thereof. As illustrated, a conventional coking feedstock 410 can also be fed into the coking stage 412 in accordance with one or more embodiments. In the coking stage 412, the combined feedstock of the pyrolysis oil 408 and the conventional coking feedstock 410 are processed to form at least a coking effluent. In the example shown in
In accordance with one or more embodiments, the waste feedstock is coked, either alone or with a conventional coking feedstock, to produce more valuable coking products. In various aspects, co-processing can be performed by exposing the combined feedstock of waste feedstock and conventional coking feedstock to coking conditions.
Coking is a refining process that includes thermal cracking of longer chain molecules into shorter chain molecules with excess carbon left behind in the form of coke. Coking processes in modem refinery settings can typically be categorized as delayed coking or fluidized bed coking. In both processes, the feedstock is cracked to produce gas and liquid products, leaving behind coke. In delayed coking, the feedstock is heated and fed to a coking reactor (commonly referred to as a “coke drum”) where the cracking takes place. To remove the coke, alternating drums can be used. In fluidized coking, the feedstock is head to the coking reactor where cracking takes place with coke transferred from the coking reactor to a heater as a fluidized solid.
The coking products produced from coking include a cracking effluent, which may include a gas, a liquid, or a mixture thereof. The cracking effluent can be fractionated or otherwise separated to form desirable product streams, such as coker gas (e.g., C4 and lighter hydrocarbons), coker naphtha, and coker gas oil.
Coker gas is a coker effluent fraction that is formed in tie coker with a T90 distillation point of 40° C. or less. Coker gas is a mixture of many different hydrocarbons, including paraffins, olefins, and aromatics. Coker gas can comprise hydrocarbons ranging from 1 carbon atom to 5 carbon atoms. Coker gas can additionally comprise trace amounts of higher hydrocarbons (e.g., C6), including benzene in gas. While coker gas is referred to a gas, it should be understood that the coker gas can be in liquid form, for example, depending on temperature and pressure, so long as the coker gas has a final boiling point of 100° C. or less.
Coker gas oil is a coker effluent fraction that is formed in the coker with a T10 distillation point of 225° C. or higher and a T90 distillation point of 650° C. or less. Coker gas oil is a mixture of many different hydrocarbons, including paraffins, olefins, and aromatics. Coker gas oil can comprise hydrocarbons ranging from 8 carbon atoms to 70 carbon atoms.
Coker naphtha is a liquid coker effluent fraction that is formed in the coker with a T10 distillation point of 30° C. or higher and a T90 distillation point of 220° C. or less. Coker naphtha is a mixture of many different hydrocarbons, including paraffins, napthenes, olefins, and aromatics. Coker naphthas can comprise hydrocarbons ranging from 4 carbon atoms to 12 carbon atoms.
The coker naphtha at least partially derived from polymeric waste can have desirable reductions in certain components as compared to from a conventional hydrocarbon feedstock, such as decreases in aromatic and sulfur content. For example, the aromatic content of coker naphtha derived from a conventional hydrocarbon feedstock can range from roughly 15 wt % to 25 wt % while coker naphtha that is at least partially derived from polymeric waste can have an aromatic content can of 10 wt % to 20 wt %, or 10 wt % to 15 wt %, or 15 wt % to 20 wt %. Coker naphtha also shows decreases in 2-3 ring aromatics. For example, the coker naphtha that is at least partially derived from polymeric waste can have a 2-3 ring aromatic content or 0 wt % to 5 wt % or 1 wt % to 3 wt %. By way of further example, the sulfur content of coker naphtha derived from a conventional hydrocarbon feedstock can range from roughly 0.5 wt % to 5 wt % while coker naphtha that is at least partially derived from polymeric waste can have a lower sulfur content, for example, about 0.1 wt % or less.
In addition to a desirable decrease in aromatics and sulfur, the coker naphtha that is at least partially derived from polymeric waste can have increased levels of other components that can complicate subsequent chemical processing. Such components include organic halides and basic nitrogen, for example. The specific type and amount of these components depends, for example, on the particular polymeric waste used in forming the coker naphtha. For example, the coker naphtha at least partially derived from polymeric waste can have a total halide content, such as chlorine, fluorine, and bromine, in amounts, for example, ranging from 1 wppm to 0.5 wt %, 10 wppm to 0.5 wt %, or 10 wppm to 0.1 wt %, while coker naphtha derived from a conventional hydrocarbon feedstock can include organic contaminants at levels below 1 wppm. By way of further example, the coker naphtha at least partially derived from polymeric waste can include basic nitrogen at levels of 100 wppm to 5000 wppm while coker naphtha from conventional hydrocarbon feedstock can include basic nitrogen at levels from 10 wppm to 50 wppm.
As used herein, the basic nitrogen content of a feed, fraction, or product can be determined according to the following method by performing measurements on two samples of the feed, fraction, or product. First, the total nitrogen of a sample is characterized according to ASTM D4629. Next, a sample can be acid washed by adding 1 ml of 1 N sulfuric acid to a 10 ml sample. This mixture can be formed in a suitable vessel, such as a 20 ml vial. The mixture of the sample and the sulfur acid is shaken vigorously, and then allowed to settle for 5 minutes. After settling, the sulfuric acid should be at the bottom of the vessel. The acid washed sample is removed from the top of the vessel, such as by using a pipette to remove the acid washed sample while not including any of the sulfuric acid. The acid washed sample can then be characterized according to ASTM D4629. The difference in nitrogen content between the untreated sample and the acid washed sample corresponds to the nitrogen that is removed by acid treatment. In this discussion, the nitrogen removed by acid treatment is defined as the basic nitrogen content. Amides and amines present in a sample correspond to basic nitrogen, so the presence of excess amides and amines in a sample due to decomposition of nitrogen-containing polymers will result in a corresponding increase in the basic nitrogen content of a sample.
The coking products further include coke. Because many polymeric wastes have relatively low sulfur content (as compared to a conventional coking feedstock), the cracking products have reduced sulfur content, in some embodiments, thus reducing the needed severity for any subsequent sulfur removal processes, such as hydroprocessing. Coke produced in a coking process is typically a carbonaceous solid material of which a majority is carbon. Since the coke is produced from the co-processing of a conventional coking feedstock in the coker, it can also be referred to as petroleum coke or petcoke, in accordance with one or more embodiments. The coke yield typically is 20 wt % to 40 wt % of the combined coker feedstock. However, since polymeric wastes can have substantially higher atomic ratio of hydrogen to carbon, coking with a waste feedstock can produce a reduced or minimized amount of coke. The particular composition of the coke depends on a number of factors, including the particular coking process, such as a delayed coker or fluidized coker. Additional components in the coke include hydrogen, nitrogen, sulfur, and heavy metals, such as aluminum, boron, calcium, chromium cobalt, iron, manganese, magnesium, molybdenum, nickel, potassium, phosphorous, silicon, sodium, titanium, and/or vanadium. In some embodiments, the coke can include phosphorous in amount of 0 wppm to 1,000 wppm, 10 wppm to 1,000 wppm, or 100 wppm to 300 wppm.
In accordance with one or more embodiments, polymeric waste can be processed in a fluidized coker. In some embodiments, the plastic waste is co-processed with a conventional coking feedstock. In various aspects, co-processing can be performed by exposing the combined feedstock of waste feedstock and conventional coking feedstock to fluidized coking conditions.
Fluidized coking is a petroleum refining process in which heavy petroleum feeds, typically the non-distillable residues (resids) from the fractionation of heavy oils are converted to lighter, more useful products by thermal decomposition (coking) at elevated reaction temperatures, typically 480° C. to 590° C., and in most cases from 500° C. to 550° C. Example heavy oils suitable for processing by the fluidized coking process include heavy atmospheric resids, petroleum vacuum distillation bottoms, aromatic extracts, asphalts, and bitumens from tar sands, tar pits and pitch lakes. In accordance with present embodiments, the plastic waste is processed in the fluidized coker either alone or in combination with a conventional coker feedstock.
Fluidized coking is carried out in a unit with a large reactor containing hot coke particles which are maintained in the fluidized condition at the required reaction temperature with steam injected at the bottom of the vessel with the average direction of movement of the coke particles being downwards through the bed. In particular embodiments, the combined feedstock is heated to a pumpable temperature, typically in the range of 350° C. to 400° C., mixed with atomizing steam, and fed through multiple feed nozzles arranged at several successive levels in the reactor. Steam is injected into a stripping section at the bottom of the reactor and passes upwards through the coke particles descending through the dense phase of the fluid bed in the main part of the reactor above the stripping section. Part of the feed liquid coats the coke particles in the fluidized bed and is subsequently cracked into layers of solid coke and lighter products which evolve as gas or vaporized liquid. The residence time of the feed in the coking zone (where temperatures are suitable for thermal cracking) is on the order of 1 second to 30 seconds. Reactor pressure is relatively low in order to favor vaporization of the hydrocarbon vapors which pass upwards from dense phase into dilute phase of the fluid bed in the coking zone and into cyclones at the top of the coking zone where most of the entrained solids are separated from the gas phase by centrifugal force in one or more cyclones and returned to the dense fluidized bed by gravity through the cyclone diplegs. The mixture of steam and hydrocarbon vapors from the reactor is subsequently discharged from the cyclone gas outlets into a scrubber section in a plenum located above the coking zone and separated from it by a partition. It is quenched in the scrubber section by contact with liquid descending over sheds. A pump-around loop circulates condensed liquid to an external cooler and back to the top shed row of the scrubber section to provide cooling for the quench and condensation of the heaviest fraction of the liquid product. This heavy fraction is typically recycled to extinction by feeding back to the coking zone in the reactor.
During a fluidized coking process, the coking feedstock, pre-heated to a temperature at which it is flowable and pumpable, is introduced into the coking reactor towards the top of the reactor vessel through injection nozzles which are constructed to produce a spray of the feed into the bed of fluidized coke particles in the vessel. Temperatures in the coking zone of the reactor are typically in the range of 450° C. to 650° C. and pressures are kept at a relatively low level, typically in the range of 0 kPag to 700 kPag, and most usually from 35 kPag to 320 kPag, in order to facilitate fast drying of the coke particles, preventing the formation of sticky, adherent high molecular weight hydrocarbon deposits on the particles which could lead to reactor fouling. In some embodiments, the temperature in the coking zone can be 450° C. to 600° C., or 450° C. to 550° C. The conditions can be selected so that a desired amount of conversion of the feedstock occurs in the fluidized bed reactor. For example, the conditions can be selected to achieve at least 10 wt % conversion relative to 343° C. (or 371° C.), or at least 20 wt % conversion relative 343° C. (or 371° C.), or at least 40 wt % conversion relative to 343° C. (or 371° C.), such as up to 80 wt % conversion or possibly still higher. The light hydrocarbon products of the coking (thermal cracking) reactions vaporize, mix with the fluidizing steam and pass upwardly through the dense phase of the fluidized bed into a dilute phase zone above the dense fluidized bed of coke particles. This mixture of vaporized hydrocarbon products formed in the coking reactions flows upwardly through the dilute phase with the steam at superficial velocities of roughly 1 to 2 meters per second (˜3 to 6 feet per second), entraining some fine solid particles of coke which are separated from the cracking vapors in the reactor cyclones as described above. In embodiments where steam is used as the fluidizing agent, the weight of steam introduced into the reactor can be selected relative to the weight of feedstock introduced into the reactor. For example, the mass flow rate of steam into the reactor can correspond to 6.0% of the mass flow rate of feedstock, or 8.0% or more, such as up to 10% or possibly still higher. The amount of steam can potentially be reduced if an activated light hydrocarbon stream is used as part of the stripping and/or fluidizing gas in the reactor. In such embodiments, the mass flow rate of steam can correspond to 6.0% of the mass flow rate of feedstock or less, or 5.0% or less, or 4.0% or less, or 3.0% or less. Optionally, in some embodiments, the mass flow rate of steam can be still lower, such as corresponding to 1.0% of the mass flow rate of feedstock or less, or 0.8% or less, or 0.6% or less, such as down to substantially all of the steam being replaced by the activated light hydrocarbon stream. The cracked hydrocarbon vapors pass out of the cyclones into the scrubbing section of the reactor and then to product fractionation and recovery.
In a general fluidized coking process, the coke particles formed in the coking zone pass downwards in the reactor and leave the bottom of the reactor vessel through a stripper section where they are exposed to steam in order to remove occluded hydrocarbons. The solid coke from the reactor, consisting mainly of carbon with lesser amounts of hydrogen, sulfur, nitrogen, and traces of vanadium, nickel, iron, and other elements derived from the feed, passes through the stripper and out of the reactor vessel to a burner or heater where it is partly burned in a fluidized bed with air to raise its temperature from 480° C. to 700° C. to supply the heat required for the endothermic coking reactions, after which a portion of the hot coke particles is recirculated to the fluidized bed reaction zone to transfer the heat to the reactor and to act as nuclei for the coke formation. The balance is withdrawn as coke product. The net coke yield is only 65 percent of that produced by delayed coking.
For a coking process that includes a gasification zone, the cracking process proceeds in the reactor, the coke particles pass downwardly through the coking zone, through the stripping zone, where occluded hydrocarbons are stripped off by the ascending current of fluidizing gas (steam). They then exit the coking reactor and pass to the gasification reactor (gasifier) which contains a fluidized bed of solid particles and which operates at a temperature higher than that of the reactor coking zone. In the gasifier, the coke particles are converted by reaction at the elevated temperature with steam and an oxygen-containing gas into a fuel gas comprising carbon monoxide and hydrogen.
The gasification zone is typically maintained at a high temperature ranging from 850° C. to 1,000° C. and a pressure ranging from 0 kPag to 1000 kPag, preferably from 200 kPag to 400 kPag. Steam and an oxygen-containing gas are introduced to provide fluidization and an oxygen source for gasification. In some embodiments, the oxygen-containing gas can be air. In other embodiments, the oxygen-containing gas can have a low nitrogen content, such as oxygen from an air separation unit or another oxygen stream including 95 vol % or more of oxygen, or 98 vol % or more, are passed into the gasifier for reaction with the solid particles comprising coke deposited on them in the coking zone. In embodiments where the oxygen-containing gas has a low nitrogen content, a separate diluent stream, such as a recycled CO2 or H2S stream derived from the fuel gas produced by the gasifier, can also be passed into the gasifier.
In the gasification zone the reaction between the coke and the steam and the oxygen-containing gas produces a hydrogen and carbon monoxide-containing fuel gas and a partially gasified residual coke product. Conditions in the gasifier are selected accordingly to generate these products. Steam and oxygen rates (as well as any optional CO2 rates) will depend upon the rate at which cold coke enters from the reactor and to a lesser extent upon the composition of the coke which, in turn will vary according to the composition of the heavy oil feed and the severity of the cracking conditions in the reactor with these being selected according to the feed and the range of liquid products which is required. In some embodiments, the fuel gas product from the gasifier contains entrained coke solids and these are removed by cyclones or other separation techniques in the gasifier section of the unit. Suitable cyclones include internal cyclones in the main gasifier vessel itself or external in a separate, smaller vessel as described below. The fuel gas product is taken out as overhead from the gasifier cyclones. The resulting partly gasified solids are removed from the gasifier and introduced directly into the coking zone of the coking reactor at a level in the dilute phase above the lower dense phase.
In some embodiments, the coking conditions can be selected to provide a desired amount of conversion relative to 343° C. Typically, a desired amount of conversion can correspond to 10 wt % or more, or 50 wt % or more, or 80 wt % or more, such as up to substantially complete conversion of the feedstock relative to 343° C.
The volatile products from the coke drum are conducted away from the process for further processing. For example, volatiles can be conducted to a coker fractionator for distillation and recovery of coker gases, coker naphtha, light gas oil, and heavy gas oil. Such fractions can be used, usually, but not always, following upgrading, in the blending of fuel and lubricating oil products such as motor gasoline, motor diesel oil, fuel oil, and lubricating oil. Upgrading can include separations, heteroatom removal via hydrotreating and non-hydrotreating processes, de-aromatization, solvent extraction, and the like. The process is compatible with processes where at least a portion of the heavy coker gas oil present in the product stream introduced into the coker fractionator is captured for recycle and combined with the fresh feed (coker feed component), thereby forming the coker heater or coker furnace charge. The combined feedstock ratio (“CFR”) is the volumetric ratio of furnace charge (fresh feed plus recycle oil) to fresh feed to the continuous fluidized coker operation. Fluidized coking operations typically employ recycles of 5 vol % to 35 vol % (CFRs of 1.05 to 1.35). In some embodiments, there can be no recycle and sometimes in special applications recycle can be up to 200%.
The Flexicoking™ process, developed by Exxon Research and Engineering Company, is a type of fluidized coking process that is operated in a unit including a reactor and a heater, but also including a gasifier for gasifying the coke product by reaction with an air/steam mixture to form a low heating value fuel gas. A stream of coke passes from the heater to the gasifier where all but a small fraction of the coke is gasified to a low-BTU gas (˜120 BTU/standard cubic feet) by the addition of steam and air in a fluidized bed in an oxygen-deficient environment to form fuel gas comprising carbon monoxide and hydrogen. In a conventional Flexicoking™ configuration, the fuel gas product from the gasifier, containing entrained coke particles, is returned to the heater to provide most of the heat required for thermal cracking in the reactor with the balance of the reactor heat requirement supplied by combustion in the heater. A small amount of net coke (1 percent of feed) is withdrawn from the heater to purge the system of metals and ash. The liquid yield and properties are comparable to those from fluidized coking. The fuel gas product is withdrawn from the heater following separation in internal cyclones which return coke particles through their diplegs.
In this description, the term “Flexicoking” (trademark of ExxonMobil Research and Engineering Company) is used to designate a fluidized coking process in which heavy petroleum feeds are subjected to thermal cracking in a fluidized bed of heated solid particles to produce hydrocarbons of lower molecular weight and boiling point along with coke as a by-product which is deposited on the solid particles in the fluidized bed. References to fluidized cokers are intended to include conventional fluidized cokers as well as flexicokers. The resulting coke can then be converted to a fuel gas by contact at elevated temperature with steam and an oxygen-containing gas in a gasification reactor (gasifier). This type of configuration can more generally be referred to as an integration of fluidized bed coking with gasification.
It is noted that in some optional embodiments, heater cyclone system 532 can be located in a separate vessel (not shown) rather than in heater 504. In such aspects, line 530 can withdraw the fuel gas from the separate vessel, and the line 522 for purging excess coke can correspond to a line transporting coke fines away from the separate vessel. These coke fines and/or other partially gasified coke particles that are vented from the heater (or the gasifier) can have an increased content of metals relative to the feedstock. For example, the weight percentage of metals in the coke particles vented from the system (relative to the weight of the vented particles) can be greater than the weight percent of metals in the feedstock (relative to the weight of the feedstock). In other words, the metals from the feedstock are concentrated in the vented coke particles. Since the gasifier conditions do not create slag, the vented coke particles correspond to the mechanism for removal of metals from the coker/gasifier environment. In some embodiments, the metals can correspond to a combination of nickel, vanadium, and/or iron. Additionally, or alternately, the gasifier conditions can cause substantially no deposition of metal oxides on the interior walls of the gasifier, such as deposition of less than 0.1% by weight of the metals present in the feedstock introduced into the coker/gasifier system, or less than 0.01% by weight.
In configurations such as
As an alternative, integration of a fluidized bed coker with a gasifier can also be accomplished without the use of an intermediate heater. In such alternative aspects, the cold coke from the reactor can be transferred directly to the gasifier. This transfer, in almost all cases, will be unequivocally direct with one end of the tubular transfer line connected to the coke outlet of the reactor and its other end connected to the coke inlet of the gasifier with no intervening reaction vessel, i.e., heater. The presence of devices other than the heater is not however to be excluded, e.g., inlets for lift gas etc. Similarly, while the hot, partly gasified coke particles from the gasifier are returned directly from the gasifier to the reactor this signifies only that there is to be no intervening heater as in the conventional three-vessel Flexicoker™ but that other devices may be present between the gasifier and the reactor, e.g., gas lift inlets and outlets.
In the configuration shown in
The coker and gasifier can be operated according to the parameters necessary for the required coking processes. Thus, the heavy oil feed in the coking feedstock will typically be a heavy (high boiling) reduced petroleum crude; petroleum atmospheric distillation bottoms; petroleum vacuum distillation bottoms, or residuum; pitch; asphalt; bitumen; other heavy hydrocarbon residues; tar sand oil; shale oil; or even a coal slurry or coal liquefaction product such as coal liquefaction bottoms. Such feeds will typically have a Conradson Carbon Residue (ASTM D189-165) of at least 5 wt %, generally from 5 wt % to 50 wt %. In some embodiments, the coking feedstock is a petroleum vacuum residuum.
In particular embodiments, delayed coking is performed on a waste feedstock optionally combined with a conventional coking feedstock to produce liquid and vapor hydrocarbon products and coke. In various embodiments, the waste feedstock and optional conventional coking feedstock are exposed to delayed coking conditions.
Delayed coking is another coking process for the thermal conversion of heavy oils such as petroleum residua (also referred to as “resid”) to produce liquid and vapor hydrocarbon products and coke. In some embodiments, the conventional hydrocarbon feedstock includes resids from heavy and/or sour (high sulfur) crude oils. Delayed coking of the feedstock is carried out by converting part of the feedstock to more valuable hydrocarbon products. The resulting coke has value, depending on its grade, as a fuel (fuel grade coke), electrodes for aluminum manufacture (anode grade coke), etc.
Generally, a feedstock is pumped to a pre-heater where it is pre-heated, such as to a temperature from 480° C. to 520° C. The pre-heated feed is conducted to a coking reactor, typically a vertically oriented, insulated coker vessel, e.g., drum, through an inlet at the base of the drum. Pressure in the drum is usually relatively low, such as 100 kPa-g to 550 kPa-g, or 100 kPa-g to 240 kPa-g to allow volatiles to be removed overhead. Typical operating temperatures of the drum will be between roughly 400° C. to 445° C., but can be as high as 475° C. The hot feed thermally cracks over a period of time (the “coking time”) in the coke drum, liberating volatiles composed primarily of hydrocarbon products that continuously rise through the coke bed, which consists of channels, pores and pathways, and are collected overhead. The volatile products are conducted to a coker fractionator for distillation and recovery of coker gases, gasoline boiling range material such as coker naphtha, light gas oil, and heavy gas oil. In an embodiment, a portion of the heavy coker gas oil present in the product stream introduced into the coker fractionator can be captured for recycle and combined with the fresh feed (coker feed component), thereby forming the coker heater or coker furnace charge. In addition to the volatile products, the process also results in the accumulation of coke in the drum. When the coke drum is full of coke, the heated feed is switched to another drum and hydrocarbon vapors are purged from the coke drum with steam. The drum is then quenched with water to lower the temperature down to 95° C. to 150° C., after which the water is drained. When the draining step is complete, the drum is opened, and the coke is removed by drilling and/or cutting using high velocity waterjets (“hydraulic decoking”).
In various embodiments, at least a portion of a coker naphtha can be exposed to hydroprocessing conditions to reduce or minimize certain components, such as metals, organohalides, olefins, and/or sulfur-, nitrogen-, and oxygen-containing species, in the feed to subsequent chemical processing. In accordance with present embodiments, the coker naphtha is at least partially derived from plastic water. Such hydroprocessing can include, but is not limited to, hydrotreatment, hydrocracking, catalytic dewaxing and/or hydroisomerization, aromatic saturation.
In this discussion, hydroprocessing is defined as exposing an input flow to a hydroprocessing stage to a partial pressure of H2 of 50 kPa or more (such as 3000 kPa) in the presence of a catalyst at a temperature of 150° C. to 450° C. Temperatures below 150° C. result in de minimis hydroprocessing activity, while temperatures greater than 450° C. primarily result in thermal cracking of hydrocarbon-like feeds.
Hydroprocessing (such as hydrotreating) is carried out in the presence of hydrogen. Hydrogen, contained in a hydrogen “treat gas,” is provided to the reaction zone. For example, a hydrogen-containing stream is fed, injected, or otherwise introduced into a vessel, reaction zone, or hydroprocessing zone corresponding to the location of a hydroprocessing catalyst. Treat gas, as referred to herein, can be either pure hydrogen or a hydrogen-containing gas stream containing hydrogen in an amount that is sufficient for the intended reaction(s). Treat gas can optionally include one or more other gasses (e.g., nitrogen and light hydrocarbons such as methane) that do not adversely interfere with or affect either the reactions or the products. Impurities, such as H2S and NH3 are undesirable and can typically be removed from the treat gas to a sufficiently low level before conducting the treat gas to the reactor. In aspects where the treat gas stream can differ from a stream that substantially consists of hydrogen (i.e., at least 99 vol % hydrogen), the treat gas stream introduced into a reaction stage can contain at least 50 vol %, or at least 75 vol % hydrogen, or at least 90 vol % hydrogen.
During hydrotreatment, the coker naphtha can be contacted with a hydrotreating catalyst under effective hydrotreating conditions which can include temperatures in the range of 230° C. to 430° C.), or 285° C. to 400° C.); pressures in the range of 1.5 MPag to 20.8 MPag, or 2.9 MPag to 13.9 MPag; a liquid hourly space velocity (LHSV) of from 0.1 to 10 hr−1, or 0.1 to 5 hr−1; and a hydrogen treat gas rate of from 430 to 2600 Nm3/m3, or 850 to 1700 Nm3/m3. In some embodiments, hydrotreatment of coker naphtha can be performed at temperatures in the range of 230° C. to 375° C.), or 230° C. to 345° C.); pressures in the range of 1.5 MPag to 10.4 MPag, or 2.9 MPag to 6.9 MPag; a liquid hourly space velocity (LHSV) of from 0.1 to 10 hr−1, or 0.1 to 5 hr−1; and a hydrogen treat gas rate of from 430 to 2600 Nm3/m3, or 850 to 1700 Nm3/m3.
Any convenient type of hydrotreating catalyst may be used, such as hydrotreating catalysts for naphtha hydrotreating, and/or for catalysts for hydrotreatment of wide cut fractions. The above hydrotreatment conditions cover a wide range of severities.
The catalyst in a hydrotreatment stage can be a conventional hydrotreating catalyst, such as a catalyst composed of a Group VIB metal and/or a Group VIII metal on a support. Suitable metals include cobalt, nickel, molybdenum, tungsten, or combinations thereof. Preferred combinations of metals include nickel and molybdenum or nickel, cobalt, and molybdenum. Suitable supports include silica, silica-alumina, alumina, and titania.
Another hydroprocessing option is to expose coker naphtha (or at least a portion thereof) to catalytic dewaxing conditions. Exposing coker naphtha to catalytic dewaxing can be performed after hydrotreatment of the coker naphtha in a hydroprocessing stage, or the catalytic dewaxing can correspond to the first (and possibly only) type of hydroprocessing in a hydroprocessing stage. It is noted that many types of dewaxing catalysts involve noble metal catalysts. For such types of catalysts, performing hydrotreatment prior to dewaxing may be beneficial for improving the activity and/or operating lifetime of the dewaxing catalyst. For dewaxing catalysts that include non-noble metals and/or that are based primarily on cracking rather than isomerization, the dewaxing catalyst may be able to tolerate higher levels of sulfur and/or nitrogen while still providing dewaxing activity.
Process conditions in a catalytic dewaxing zone (in the presence of a dewaxing catalyst) can include a temperature of from 200° C. to 450° C., or 270° C. to 400° C., a hydrogen partial pressure of from 1.8 MPag to 34.6 MPag, or 4.8 MPag to 20.7 MPag, and a hydrogen treat gas rate of from 35.6 m3/m3 to 1781 m3/m3, or 178 m3/m3 to 890.6 m3/m3. The liquid hourly space velocity (LHSV) can be from 0.2 h−1 to 10 h−1, such as from 0.5 h−1 to 5 h−1 and/or from 1 h−1 to 4 h−1.
Still another hydroprocessing option can be to expose coker naphtha to a catalyst under aromatic saturation conditions/hydrofinishing conditions. Aromatic saturation conditions can include temperatures from 125° C. to 425° C., preferably 180° C. to 280° C., a hydrogen partial pressure from 3.4 MPa to 21 MPa), or 10 MPa to 17.5 MPa, and liquid hourly space velocity from 0.1 hr−1 to 5 hr−1 LHSV, preferably 0.5 hr−1 to 2.0 hr−1.
In accordance with one or more embodiments, the processing of the polymeric waste results in the production or recovery of chemical products. For example, coker naphtha from coking of polymeric waste can be processed to form chemical products. By way of further example, coker naphtha from coking of pyrolysis oil that is at least partially derived from polymeric waste can be processed to form chemical products.
In some embodiments, the coker naphtha includes one or more components that need to be removed and/or reduced in concentration prior to subsequent processing. For example, embodiments include treating the coker naphtha to remove at least a portion of contaminants, including halides, acids, and sulfur species. Any of a variety of techniques may be used for treatment of the coker naphtha, including absorption, adsorption, hydroprocessing, filtration, and fractionation. Adsorption can be used for removal of specific contaminants, such as mercury. Examples of specific adsorption techniques include treatment beds, such as mercury beds. Absorption includes solid and liquid contacting methods such as water washing, amine gas treating, caustic treatment. Water washing includes, for example, contacting the coker naphtha with a water stream. Example hydroprocessing techniques include hydrogenation and hydrotreating. Embodiments of hydroprocessing also may convert organic halides in the coker naphtha to inorganic acid. Neutralizing additives can then be added to the hydroprocessing effluent for neutralization of the produced inorganic acids. Mercury is removed, in some embodiments, for example, with mercaptan oxidation. Filtration is used, for example, to remove solid particulates.
The chemical products produced from integration of co-processing of polymeric waste includes a variety of chemical products, including olefins (e.g., alpha-olefins), aromatics, oligomers, and polymers. A “polymer” has one or more repeating units that are the same or different. The term “polymer” as used herein includes oligomers (up to 75 repeating units) and larger polymers (greater than 75 repeating units). “Homopolymer” is a polymer having the same repeating unit. A “copolymer” is a polymer having t wo or more repeating units different from each other, A “terpolymer” is a polymer having two or more repeating units different from each other. “Different” is used to mean that the repeating units differ from each other by at least one atom or isomer. Therefore, the definition of the copolymer used herein includes a terpolymer and the like. The chemical products include or can be processed to form a number of desirable products, including: olefins, such as ethylene, propylene, butylene, butadiene, pentenes, C5 olefins, and C5 di-olefins, as well as longer olefins, such as hexene, nonene, and tetramer; aromatics, such as benzene, styrene, and toluene; cyclohexane; polymers, such as polyethylene, polypropylene, polystyrene, polyesters, poly-vinyl chloride; and di-vinyl chloride; synthetic elastomers and rubbers, such as styrene-butadiene rubber, ethylene-propylene-diene-rubbers, butyl rubbers, and halobutyl rubbers; plastic additives and modifiers, such as plasticizers; epoxies resins; and fluids with multiple applications, such as isopropyl alcohol, oxo-alcohols, glycols, detergents, and lubricants.
At least a portion of these chemical products may be circular chemical products that are attributable to the polymeric waste, such as determined by crediting, allocating, and/or offsetting or substituting for other hydrocarbons in a mass or energy balance for a system, such as in accordance with a third-party certification relating to circularity. At least a portion of these chemical products may be certified circular chemical products that are certified for their circularity by third party certification may be referred to as certified circular.
Various processes may be employed to integrate chemical production with coking. For example, coker naphtha received from coking may be converted in one or more of the following unites: hydroprocessing units, such as hydrocracking and hydrotreating units; fluid catalytic cracking units; steam cracking units; catalytic reforming units; partial oxidation to synthetic gas; and/or isomerization. The chemical products may be directly produced by such processes or may be obtained by further processing, such as separation, treating, and/or cracking of an effluent of such processes. As an example, the chemical products may be obtained by processing of coker naphtha at least partially derived from polymeric waste. In addition, co-processing of polymeric waste as a feed or co-feed into delayed or fluidized coking units (including FLEXICOKING™ units), may result in the attribution of the polymeric waste to chemical products (including olefins, polymers, or aromatics), such as determined by crediting, allocating, and/or offsetting or substituting for other hydrocarbons in a mass or energy balance for a system, such as in accordance with a third-party certification relating to circularity.
Accordingly, processes per various embodiments herein may further include obtaining olefins that have been produced or recovered from the processing of polymeric waste or olefins to which the processing of polymeric waste has been attributed, e.g., for employment in polymerization processes; and polymers of various embodiments described herein may comprise olefins that have been produced or recovered from the processing of polymeric waste or olefins to which the processing of polymeric waste has been attributed. As an example, at least a portion of the olefin content (e.g., employed in processes and/or included in compositions as described herein) may be from olefins that are produced or recovered directly from the processing of polymeric waste. Similarly, the processing of polymeric waste may be attributed to at least a portion the olefins (e.g., employed in processes and/or included in compositions as described herein).
Accordingly, the present disclosure may provide for the integration of polymeric waste co-processing in cokers to produce circular chemical products from coker naphtha. The methods and systems may include any of the various features disclosed herein, including one or more of the following statements.
Embodiment 1. A method of producing circular chemical products comprising: providing a coker naphtha that is at least partially derived from polymeric waste, wherein the coker naphtha has a total halide content of about 1 wppm to about 0.5 wt %, a 2-3 ring aromatic content of about 0 wt % to about 5 wt %, and a sulfur content of about 750 ppm to about 2 wt %; and converting the coker naphtha into at least a polymer.
Embodiment 2. The method of Embodiment 1, wherein the coker naphtha is derived from co-processing of polymeric waste and a heavy oil with a T10 distillation point of about 343° C. to about 575° C.
Embodiment 3. The method of Embodiment 1 or Embodiment 2, wherein providing the coker naphtha comprises: coking a feedstock comprising the polymeric waste and a heavy oil with a T10 distillation point of about 343° C. to about 575° C. to form at least a coker effluent and coke; and separating the coker naphtha from the coker effluent.
Embodiment 4. The method of Embodiment 3, wherein the polymeric waste comprises plastic waste.
Embodiment 5. The method of Embodiment 3 or Embodiment 4, wherein the heavy oil comprises petroleum vacuum resid.
Embodiment 6. The method of any of Embodiments 3 to 5, wherein the feedstock comprises the polymeric waste in an amount of about 0.1 wt % to about 25 wt %.
Embodiment 7. The method of Embodiments 3 to 6, wherein the coking comprises exposing the feedstock to delayed coking conditions.
Embodiment 8. The method of any of Embodiments 1 to 7, wherein providing the coker naphtha comprises pyrolyzing the polymeric waste to produce at least a pyrolysis oil and then coking at least the pyrolysis oil and a heavy oil with a T10 distillation point of about 343° C. to about 575° C.
Embodiment 9. The method of any of Embodiments 1 of 8, wherein the coker naphtha comprises basic nitrogen in an amount of about 100 wppm to about 5000 wppm.
Embodiment 10. The method of any of Embodiments 1 to 9, wherein the polymeric waste comprises plastic waste.
Embodiment 11. The method of any of Embodiments 1 to 10, wherein at least a portion of the polymer is attributable to one or more polymers in the polymeric waste.
Embodiment 12. The method of any of Embodiments 1 to 11, wherein the polymer comprises a circular polymer.
Embodiment 13. The method of any of Embodiments 1 to 12, wherein at least a portion of the polymer is certified circular.
Embodiment 14. The method of any of Embodiments 1 to 12, wherein at least a portion of the polymer is certified circular in accordance with International Sustainability and Carbon Certification.
Embodiment 15. The method of any of Embodiments 1 to 14, wherein the coker naphtha is further converted into at least one chemical product selected from the group consisting of a monomer, an aromatic, a synthetic elastomer, a synthetic rubber, an epoxy, a resin, isopropyl alcohol, an oxo-alcohol, and combinations thereof.
Embodiment 16. The method of any of Embodiments 1 to 15, wherein converting the coker naphtha into at least the polymer comprises cracking at least a portion of the coker naphtha to form at least a cracking effluent, recovering olefins from the cracking effluent; and polymerizing at least a portion of the olefins to form at least a polyolefin.
Embodiment 17. The method of any of Embodiments 1 to 15, wherein converting the coker naphtha into at least the polymer comprises hydroprocessing at least a portion of the coker naphtha to form at least a hydroprocessed naphtha; cracking at least a portion of the hydroprocessed naphtha to form at least a cracking effluent; recovering olefins from the cracking effluent; and polymerizing at least a portion of the olefins to form at least a polyolefin.
Embodiment 18. The method of any of Embodiments 1 to 15, wherein converting the coker naphtha into at least the polymer comprises hydroprocessing at least a portion of the coker naphtha to form at least a hydroprocessed naphtha; catalytically reforming at least a portion of the hydroprocessed naphtha to form a reformate; and recovering aromatics from at least a portion of the reformate.
Embodiment 19. A method of producing circular chemical products comprising: cracking at least a coker naphtha to form at least a cracking effluent, wherein the coker naphtha is at least partially derived from polymeric waste, wherein the coker naphtha has a total halide content of about 1 wppm to about 0.5 wt %, a 2-3 ring aromatic content of about 0 wt % to about 5 wt %, and a sulfur content of about 750 ppm to about 2 wt %; recovering olefins from the cracking effluent; and polymerizing at least a portion of the olefins to form at least a polyolefin.
Embodiment 20. The method of Embodiment 19, further comprising coking a feedstock comprising the polymeric waste and a heavy oil with a T10 distillation point of about 343° C. to about 575° C. to form at least a coker effluent and coke; and separating the coker naphtha from the coker effluent.
Embodiment 21. The method of Embodiment 19 or Embodiment 20, wherein the coker naphtha comprises basic nitrogen in an amount of about 100 wppm to about 5000 wppm.
Embodiment 22. The method of any of Embodiments 19 to 21, wherein the polyolefin comprises a circular polyolefin.
To facilitate a better understanding of the present invention, the following examples of certain aspects of some embodiments are given. In no way should the following examples be read to limit, or define, the entire scope of the disclosure.
In this example, a plastic feedstock and a petroleum vacuum resid were co-processed in a pilot-scale coking unit. Six different plastic feedstocks were tested, identified as Plastic Feed A, Plastic Feed B, Plastic Feed C, Plastic Feed D, Plastic Feed E, and Plastic Feed F. Plastic Feed A was 100% linear low density polyethylene. Plastic Feed B was 100% polypropylene. Plastic Feed C was 100% high density polyethylene. Plastic Feed D was a plastic waste that included 12 wt % of polyvinylidene chloride with the remainder being polyethylene and ethyl vinyl acetate. Plastic Feed E was a plastic waste that included 10 wt % polyamide or nylon with the remainder being polyethylene, ethyl vinyl alcohol, and polyethylene terephthalate. Plastic Feed F was a plastic waste that included pellets of 100% low density polyethylene. The plastic feedstocks were provided in various forms including small granules, shreds (about 1-2 inches in length) or shreds with about 0.25 inches per side. The plastic feedstocks were processed into smaller grounds due to the size requirements and mixing capabilities if the pilot scale coking unit. The plastic feedstocks were fed into the pilot scale coking unit as a homogenous mixture with the petroleum vacuum resid after the plastic feedstock had been melted.
The pilot scale coking unit had the following operating conditions: (1) Pressure=15 psig; (2) Inlet Temperature=930° F. (500° C.); (3) Outlet Temperature=844° F. (avg) (450° C.); (4) Residence Time=5 hours). The compositional data for liquid product (coker effluent) from the pilot-scale coking unit for each test are provided below.
Table 1 provides the results for the comparative test with only petroleum vacuum resid and no plastic feed, as well as Plastic Feeds A-C while Table 2 provides the results for Plastic Feeds D-F.
The coker effluent was fractionated to provide various fractions, including a coker naphtha fraction. The comparative data for Test 1 shows that the separated fraction has a higher T90 distillation point than would be considered naphtha. The higher T90 distillation point is likely due to the tests being performed in a pilot scale plant. The compositional data for the coker naphtha is provided in the tables below.
The following summary table is provided to summarize the results from Tables 4 and 5. In the following tables, the co-processing results for Tests 2-10 are averaged for 5 wt % and 10 wt % plastic.
The above table illustrates that coker naphtha at least partially derived from polymers, including plastic waste, has a different composition than conventional coker naphtha. As shown, the sulfur content in the coker naphtha from co-processing includes significantly less sulfur than Test 1 with no polymeric waste. In addition, the coker naphtha from co-processing of the polymers, including plastic waste, also includes significantly less 2-ring and 3+-ring aromatics, as well as having an increase in hydrogen concentration. The co-processed naphtha also includes an increase in chlorine and fluorine, with chlorine having a substantial increase from <1 ppm to 76 and 320 wppm, respectively.
While the disclosure has been described with respect to a number of embodiments and examples, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments can be devised which do not depart from the scope and spirit of the disclosure as disclosed herein. Although individual embodiments are discussed, the present disclosure covers all combinations of all those embodiments.
While compositions, methods, and processes are described herein in terms of “comprising,” “containing,” “having,” or “including” various components or steps, the compositions and methods can also “consist essentially of” or “consist of” the various components and steps. The phrases, unless otherwise specified, “consists essentially of” and “consisting essentially of” do not exclude the presence of other steps, elements, or materials, whether or not, specifically mentioned in this specification, so long as such steps, elements, or materials, do not affect the basic and novel characteristics of the disclosure, additionally, they do not exclude impurities and variances normally associated with the elements and materials used.
All numerical values within the detailed description are modified by “about” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.
Many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description without departing from the spirit or scope of the present disclosure and that when numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.
This application claims the benefit of and priority to U.S. Provisional Application No. 63/374,943 filed Sep. 8, 2022, the disclosure of which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 63374943 | Sep 2022 | US |
