Techniques for processing pyrolysis feedstock using boiling point adjustments

Abstract

Disclosed is a process that includes flowing a hydrocarbon material through a first tube bank disposed in a convection section of a pyrolysis furnace along a flow path of a flue gas generated in a radiant section of the pyrolysis furnace. The process further includes flowing the hydrocarbon material through a second tube bank disposed upstream of the first tube bank along the flow path of the flue gas. Then, the process include flowing the hydrocarbon material through a third tube bank disposed downstream of the second tube bank along the flow path of the flue gas. Flowing the hydrocarbon material through the second tube bank before the third tube bank may prevent coke deposition in areas of the convection where it is difficult to remove coke deposits.

Description

TECHNIQUES FOR PROCESSING PYROLYSIS FEEDSTOCK USING BOILING POINT ADJUSTMENTSCROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority to and the benefit of U.S. Provisional Application No. 63 / 678,295 having a filing date of August 01, 2024, the disclosure of which is incorporated herein by reference in its entirety.FIELD

[0002] This disclosure relates to pyrolysis furnaces and processing of hydrocarbon material with pyrolysis furnaces. In particular, this disclosure relates to processes and pyrolysis furnaces for processing hydrocarbon materials that include contaminants which may otherwise result in fouling in pyrolysis furnaces. The devices and processes of this disclosure are especially useful for reducing fouling and removing molecules, such as coke, tar, asphaltenes, ash, char, and the like, from a convection section of a steam cracking furnace.BACKGROUND

[0003] Crude oils and fractions thereof are typically processed first by fractionating in a refinery and then by cracking, such as in a pyrolysis furnace, to yield various products including light olefins, such as ethylene, propylene, and butylene.

[0004] Conventional steam cracking utilizes a pyrolysis furnace, which has two main sections: a convection section and a radiation section. In operation, the feedstock enters the convection section of the furnace where it is heated and, in the instance of a liquid feedstock, vaporized by indirect contact with hot flue gas from the radiant section before or after combination with steam. The vaporized feedstock and steam mixture is then introduced into the radiant section where the cracking takes place. The resulting products, including the valuable light olefins (e.g., ethylene, propylene, and butylene), leave the pyrolysis furnace for further downstream processing, including a combination of quenching, separations, fractionation, reaction, or other processes using one or more fractionating columns or towers.

[0005] The feedstock(s) is generally selected such that fouling of the convection section does not occur. As referred to herein, “fouling” refers to the formation of deposits within the convection section that negatively affect the pyrolysis furnace performance due to increased pressure drop, reduced heat transfer and plugging, and other problems in tube banks of the convection section. The deposits may include non-volatile material or heavy molecules, such as coke, tar, asphaltenes, polyaromatic hydrocarbons (PAHs), solids entrained in the feed, and several other sources, including ash and char.

[0006] In general, hydrocarbon materials that include asphaltenes and other heavy molecules (e.g., high final boiling point (FBP) materials or materials contaminated with PAHs, ash, char, or other solids or semi-solids) are not desirable feedstock, because the asphaltenes and / or other heavy molecules become convection section fouling precursors. For example, materials derived from plastic waste may contain contaminants, such as ash, char, coke, PAHs, asphaltenes, long polymer chains, or other solids or semi solids, that can foul the convection section. Further, materials such as condensates and naphtha may be contaminated by molecules including but not limited to asphaltenic molecules and / or PAHs, which may have a high FBP or may not otherwise vaporize within a steam cracking furnace convection section. For instance, condensates and naphtha are often transported in containers, such as ships, which may have previously contained crude oil, heavy gas oil, residual oils (e.g., resids and / or residuum), and the like, having FBP greater than 950°F (510°C) and / or small but significant amounts of material having FBP of 1200°F (650°C) and higher. Condensates and other crude-derived oils or fractions thereof may also be obtained from the gas fields contaminated with these high FBP molecules and / or otherwise non-volatile materials. Once contaminated, these materials have decreased value as pyrolysis furnace feeds, because they may result in fouling and / or coking within the convection section. In any case, many potential hydrocarbon materials derived from crude oils or condensates and materials derived from plastic waste may be undesirable for processing within a steam cracking furnace, or, if used, may increase the rate at which the convection section must be cleaned or otherwise maintained.

[0007] References of interest include U.S. Patent Nos. 7,297,833 and 7,625,480.SUMMARY

[0008] This disclosure relates to a process that includes (I) providing a first pyrolysis feed material having a first end boiling point. The first pyrolysis feed material comprises at least a fraction of a plastic-derived component, a biological-material-derived component, and / or a reactive component. The process also includes (II) adding a second pyrolysis feed material to the first pyrolysis feed material to obtain a first pyrolysis feed mixture. The second pyrolysis feed material has a second end boiling point higher than the first end boiling point. Further, the process includes (III) adding water and / or steam to the first pyrolysis feed mixture to obtain a second pyrolysis feed mixture. Further, the process includes (IV) heating the second pyrolysis feed mixture in a tube bank located in a convection section of a pyrolysis furnace by flowing the second pyrolysis feed mixture in the tube bank and contacting the tube bank with a flue gas in the pyrolysis furnace to obtain a heated second pyrolysis feed mixture. Further still, the process includes (V) after step (IV), flowing at least a portion of the heated second pyrolysis feed mixture through aradiant tube located in a radiant section of the pyrolysis furnace to produce a steam cracked effluent exiting the radiant section.

[0009] The disclosure also relates to a process that includes (I) providing a first pyrolysis feed material having a first final boiling point Tbpl. The first pyrolysis feed material comprises at least at least a fraction of one of the following: a plastic-derived component, a biological-material- derived component, and a reactive component. The process also includes (II) adding a second pyrolysis feed material to the first pyrolysis feed material to obtain a first pyrolysis feed mixture, wherein the second pyrolysis feed material has a second final boiling point Tbp2, wherein 0 °C < Tbp2 - Tbpl < 400°C. Further, the process includes (III) adding water and / or steam to the first pyrolysis feed mixture to obtain a second pyrolysis feed mixture. Further still, the process includes (IV) heating the second pyrolysis feed mixture in a tube bank located in a convection section of a pyrolysis furnace by flowing the second pyrolysis feed mixture in the tube bank and contacting the tube bank with a flue gas in the pyrolysis furnace to obtain a heated second pyrolysis feed mixture. Further still, the process includes (V) after step (IV), flowing at least a portion of the heated second pyrolysis feed mixture through a radiant tube located in a radiant section of the pyrolysis furnace to produce a steam cracked effluent exiting the radiant section.

[0010] These and other features and attributes of the disclosed pyrolysis furnace and convection section of the present disclosure and their advantageous applications and / or uses will be apparent from the detailed description which follows.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] 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:

[0012] FIG. 1 is a schematic diagram of a pyrolysis furnace that includes a convection section and a radiant section, in accordance with an aspect of the present disclosure;

[0013] FIG. 2 is a schematic diagram of a first example of the convection section of the pyrolysis furnace of FIG. 1, in accordance with an aspect of the present disclosure;

[0014] FIG. 3 is a schematic diagram of a second example of the convection section of the pyrolysis furnace of FIG. 1, in accordance with an aspect of the present disclosure; and

[0015] FIG. 4 is a schematic diagram of a third example of the convection section of the pyrolysis furnace of FIG. 1, in accordance with an aspect of the present disclosure.DETAILED DESCRIPTION

[0016] One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in thedevelopment of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers’ specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

[0017] When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. All numerical values within the detailed description herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art. For example, “about” or “approximately” may indicate that an amount may be ± 0.5%, ±1 %, ± 2%, ± 5%, or ± 10% the amount.

[0018] In this disclosure, a process is described as including at least one “step.” It should be understood that each step is an action or operation that may be carried out once or multiple times in the process, in a continuous or discontinuous fashion. Unless specified to the contrary or the context clearly indicates otherwise, multiple steps in a process may be conducted sequentially in the order as they are listed, with or without overlapping with one or more other steps, or in any other order, as the case may be. In addition, one or more or even all steps may be conducted simultaneously with regard to the same or different batch of material. For example, in a continuous process, while a first step in a process is being conducted with respect to a raw material just fed into the beginning of the process, a second step may be carried out simultaneously with respect to an intermediate material resulting from treating the raw materials fed into the process at an earlier time in the first step. Preferably, the steps are conducted in the order described.

[0019] The term “hydrocarbon” as used herein means (i) any compound consisting of hydrogen and carbon atoms or (ii) any mixture of two or more such compounds in (i). The term “Cn hydrocarbon,” where n is a positive integer, means (i) any hydrocarbon compound comprising carbon atom(s) in its molecule at the total number of n, or (ii) any mixture of two or more such hydrocarbon compounds in (i). Thus, a C2 hydrocarbon can be ethane, ethylene, acetylene, or mixtures of at least two of these compounds at any proportion. A “Cm to Cn hydrocarbon” or “Cm-Cn hydrocarbon,” where m and n are positive integers and m < n, means any of Cm, Cm+1, Cm+2, ..., Cn-1, Cn hydrocarbons, or any mixtures of two or more thereof. Thus, a “C2 to C3 hydrocarbon” or “C2-C3 hydrocarbon” can be any of ethane, ethylene, acetylene, propane,propene, propyne, propadiene, cyclopropane, and any mixtures of two or more thereof at any proportion between and among the components. A “saturated C2-C3 hydrocarbon” can be ethane, propane, cyclopropane, or any mixture thereof of two or more thereof at any proportion. A “Cn+ hydrocarbon” means (i) any hydrocarbon compound comprising carbon atom(s) in its molecule at the total number of at least n, or (ii) any mixture of two or more such hydrocarbon compounds in (i). A “Cn- hydrocarbon” means (i) any hydrocarbon compound comprising carbon atoms in its molecule at the total number of at most n, or (ii) any mixture of two or more such hydrocarbon compounds in (i). A “Cm hydrocarbon stream” means a hydrocarbon stream consisting essentially of Cm hydrocarbon(s). A “Cm-Cn hydrocarbon stream” means a hydrocarbon stream consisting essentially of Cm-Cn hydrocarbon(s).

[0020] The term “resid” or “residuum” refers to a bottoms cut of a crude distillation process that contains non-volatile components. Resids are complex mixtures of heavy petroleum compounds otherwise known in the art as residuum or residual or pitch. Atmospheric resid is the bottoms product produced from atmospheric distillation of crude where a typical endpoint of the heaviest distilled product is nominally 343°C, and is referred to as 343°C resid. The term “nominally”, as used herein, means that reasonable experts may disagree on the exact cut point for these terms, but by no more than + / - 55.6°C preferably no more than + / - 27.8°C. Vacuum resid is the bottoms product from a distillation column operated under vacuum where the heaviest distilled product can be nominally 566°C, and is referred to as 566°C resid.

[0021] The term “hydrocarbon feed” or “hydrocarbon material” refers to a composition that includes one or more hydrocarbons. Illustrative hydrocarbon feeds can be or can include, but are not limited to, crude, gas oils, heating oil, jet fuel, diesel, kerosene, gasoline, coker naphtha, steam cracked naphtha, catalytically cracked naphtha, hydrocrackate, reformate, raffinate reformate, Fischer-Tropsch liquids and / or gases, natural gasoline, distillate, virgin naphtha, atmospheric pipestill bottoms, vacuum pipestill streams such as vacuum pipestill bottoms and wide boiling range vacuum pipestill naphtha to gas oil condensates, non-virgin hydrocarbons from refineries, vacuum gas oils, heavy gas oil, naphtha contaminated with crude, atmospheric residue, heavy residue, a C residue admixture, naphtha / residue admixture, hydrocarbon gases / residue admixture, hydrogen / residue admixtures, waxy residues, gas oil / residue admixture, relatively light alkanes, e.g., ethane, propane, butane, and / or pentane, recycle streams that can include ethane, propane, ethylene, propylene, butadiene, or a mixture thereof, one or more condensates, fractions thereof, or any mixture thereof.

[0022] The term “coke” refers to the solid or semi-solid product that can be produced during the steam cracking of hydrocarbons that includes carbon and high carbon-content organic molecules,whether produced within the convection section, radiant section, transfer lines therebetween, or within transfer lines and other equipment, e.g., a transfer line heat exchanger, downstream of the radiant section.

[0023] As referred to herein, a “naphtha” refers to a material obtainable as a distillate of petroleum with a boiling range of approximately 70 to 400°F (20 to 205°C).

[0024] The term “asphaltene” refers to a material obtainable from crude oil or other sources and having an initial boiling point above 650°C and which is insoluble in a paraffinic solvent. At least in some instances, asphaltenes may include waxes, heavy oils, and resins, which may be measured using ASTM D3279 Asphaltene Content & Heptane Insolubles.

[0025] It is noted that some types of plastic material 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 plastic material of a pre- or postconsumer plastic feedstock material can correspond to bio-derived material. Such bio-derived material can also potentially contribute to the nitrogen content and / or oxygen content of a plastic material. The plastic material, in addition to the one or more polymers, can also include any additives, modifiers, packaging dyes, and / or other components typically added to a polymer during and / or after formulation. The plastic material can also further include any components typically found in polymer waste. In some embodiments, the plastic material may include a liquid material.

[0026] A "polymer" has two or more of the same or different repeating units / mer units or simply units. A "homopolymer" is a polymer having repeating units that are the same. A "copolymer" is a polymer having two or more repeating units that are different from each other. As such, the term “copolymer” includes terpolymers (a polymer having three units that are different from each other), tetrapolymers (a polymer having four units that are different from each other), and so on. The term "different" as used to refer to units indicates that the units differ from each other by at least one atom and / or are different isomerically.

[0027] In some embodiments, the polymer can be or can include, but is not limited to, a nitrogen-containing polymer, a chlorine-containing polymer, a bromine-containing polymer, a fluorine-containing polymer, an oxygen-containing polymer, a polyethylene polymer, a polypropylene polymer, a polystyrene polymer, a butadiene polymer, an isoprene polymer, an isobutylene polymer, or any mixture thereof. In some embodiments, the oxygen-containing polymer can be or can include a polyterephthalate polymer, an ethylene vinyl acetate polymer, a polycarbonate polymer, a polylactic acid polymer, an acrylate polymer, a polyoxymethylene polymer, a polyester polymer, a polyoxybenzylmethylenglycolanhydride polymer, a polyepoxidepolymer, or any mixture thereof. In some embodiments, the nitrogen-containing polymer can be or can include one or more polyamide polymers, e.g., nylon; one or more polynitrile polymers, e.g., poly(acrylonitrile) and / or poly(methacrylonitrile); one or more aramids, one or more polyurethane polymers, or any mixture thereof.

[0028] In this disclosure, 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 plastic feedstock. In some embodiments, the chlorine-containing polymers can be or can include, but are not limited to, polyvinyl chloride (PVC) and / or polyvinylidene chloride (PVDC). A polymer can be naturally occurring, modified naturally occurring, and / or synthetic.

[0028] The plastic material alone, the plastic material that has been processed, through chemical reactions, solvation, or other processes, or the plastic material mixed, blended, or otherwise combined with an optional carrier liquid is also referred to as a “heavy feed.” Although the heavy feed may have a similar or identical composition as the hydrocarbon feed, preferably the heavy feed differs from the hydrocarbon feed. Although the hydrocarbon feed may contain a plastic material, e.g., the same or different plastic material contained in the heavy feed, preferably the hydrocarbon feed is substantially free, or completely free of a plastic material. Preferably, the hydrocarbon feed is derived from a petroleum source substantially free or completely free of a plastic material.

[0029] The terms “char” and “ash” interchangeably refer to the solid, solid / liquid mixture, or semisolid produced during the pyrolysis of an optionally contaminated plastic material and deposited on the inner surface of a conduit or vessel, which can include organic molecules having long carbon chains and / or high boiling points such as asphaltenes, coke, organometallic compounds, inorganic materials such as metals, metallic oxides, and salts, organometallic molecules, and mixtures thereof. Char and ash may be produced from the chemical reactions of the various components of a plastic material and / or introduced directly from the plastic feed material.

[0030] An "olefin" is a linear, branched, and / or cyclic compound (e.g., certain cyclic molecules are branched) of carbon and hydrogen having at least one double bond. The term “olefin product” as used herein means a product that includes an olefin, preferably a product consisting essentially of or consisting of an olefin. An olefin product in the meaning of this disclosure can be, e.g., an ethylene stream, a propylene stream, a butylene stream, an ethylene / propylene mixture stream, and the like.

[0031] The term “aromatic” as used herein is to be understood in accordance with its art- recognized scope which includes alkyl substituted and unsubstituted mono- and poly-nuclear compounds.

[0032] The term “ppm” refers to parts per million, which is the number of units of mass of a material (e.g., a contaminant) per million units of total mass. For example, 1 ppm equals 1 mg of substance per kg of solid (mg / kg). The term “ppb” refers to parts per billion. In a generally similar manner as described with respect to ppm, ppb refers to the number of units of mass of a material (e.g., a contaminant) per billion units of total mass.

[0033] All ranges expressed herein should include both end points as two specific embodiments unless specified or indicated to the contrary.

[0034] As discussed above, many hydrocarbon materials may include contaminants, including but not limited to at least a portion of asphaltenes, condensates, naphtha, ash, char, relatively large molecules (e.g., long polymer chains), PAHs and other materials that may foul the convection section of the pyrolysis furnace. Fouling potential for heavy liquid feeds is typically quantified through the CCR (Conradson Carbon Residue) test and through the analysis of the feed’s color (API color). High (>0.1 wt%, >0.2 wt%, and >0.3 wt%) CCR values may correspond with potential for convection section fouling. Similarly, darker relative color readings may correlate with higher potential for convection section fouling. In some embodiments, liquids or other heavy feeds derived at least in part from plastic-containing feedstocks may have a relatively low CCR (<0.1 wt%) with very dark color, which may indicate the presence of some asphaltenic materials but to a lower extent than liquids feeds contaminated with condensate and / or crude oil contamination. However, feeds derived from plastic waste contain different contaminants than traditional steam-cracker liquid feeds. Feeds derived from plastic waste may or may not contain asphaltenic material. As such, it may be advantageous to develop techniques for reducing the likelihood of forming non-volatilizing material deposits in regions of the convection section that are difficult to de-coke or otherwise remove. For example, and as discussed in more detail herein, it may be advantageous to add an amount of a boiling point elevation material to a hydrocarbon material to increase the boiling point, final boiling point, or end boiling point of the resulting mixture, such that any non-volatilizing material deposits in a lower portion (e.g., downstream segments) of the convection section.

[0035] Accordingly, the present disclosure is directed to techniques for processing a variety of hydrocarbon materials by selectively depositing coke and other non-volatilizing materials in particular locations within the pyrolysis furnace. In general, the techniques include directing or providing a first pyrolysis feed material having a first end boiling point, and adding a secondpyrolysis feed material to the first pyrolysis feed material. It is presently recognized that it may be advantageous that the second pyrolysis feed material has a second end boiling point that is higher than the first end boiling point. As referred to herein, the “end boiling point” of a material refers to the weight-average boiling point of the 10 wt% components having the highest boiling points, based on the total weight of the material. The end boiling point can be determined from the boiling point distribution curve obtained by using ASTM2887 or its equivalent. The first pyrolysis feed material may be a plastic-derived component, a biological-material-derived component, and / or a reactive component. In any case, it is presently recognized that heating a hydrocarbon material such that it vaporizes and forms a coke deposit within a lower portion of the convection section (e.g., less than about 50%, 40%, 30%, 20%, or 10% of the length of the convection section, or between about 50% and 20%, between 40% and 20%, between 30% and 10% of the length of the convection section) will enable a broader range of acceptable feedstock to be used in pyrolysis furnace.

[0036] Reference is now made to the embodiments illustrated in FIGS. 1-4 wherein like numerals are used to designate like parts throughout.

[0037] FIG. 1 shows a schematic diagram of an embodiment of a pyrolysis furnace 10 (e.g., steam cracking furnace) in accordance with the present disclosure. As shown, the pyrolysis furnace 10 includes a convection section 12 and a radiant section 14. The convection section 12 generally receives a hydrocarbon material 15 (e.g., a feedstock, or first pyrolysis feed material) in accordance with aspects of the present disclosure) and, while within the convection section 12 (e.g., one or more tube banks within the convection section 12), the hydrocarbon material 15 is mixed with a boiling point elevation material 16 (e.g., a second pyrolysis feed material) to form a mixture 17 (e.g., first pyrolysis feed mixture). In general, the mixture 17 has a higher end boiling point or higher final boiling point as compared to the hydrocarbon material 15. As described in further detail herein, the relatively higher boiling point of the mixture 17 may cause any nonvolatilizing deposits to form in relatively lower sections of the convection section 12 that are easier to de-coke. In some embodiments, the boiling point elevation material 16 may be added to one or more of the tube banks insides of the convection section 12 (e.g., the first tube bank, the second tube bank, the third tube bank, or a combination thereof).

[0038] The hydrocarbon material 15 and the boiling point elevation material 16 are heated and vaporized by indirect contact with a hot flue gas 18 emitted by or generated in a combustion zone 19 in the radiant section 14 (e.g., via one or more burners). Water and / or steam 21 is added to the mixture (e.g., hydrocarbon material 15 and the boiling point elevation material 16) and the vaporized hydrocarbon material 15 is ultimately directed into the radiant section 14. In someembodiments, the water and / or steam 21 may be preheated using at least one steam preheating tube bank described herein.

[0039] As shown in the illustrated embodiment, the convection section 12 includes a first tube bank 22, a second tube bank 24, and a third tube bank 26. However, in some embodiments, the convection section 12 may only include two tube banks (e.g., the first tube bank 22 and the second tube bank 24). The first tube bank 22, the second tube bank 24, and the third tube bank 26 are arranged along the longitudinal axis 28 of the pyrolysis furnace 10. Put differently, the first tube bank 22, the second tube bank 24, and the third tube bank 26 are located at different longitudinal positions along the section height 30 of the convection section 12. Each tube bank 22, 24, and 26 includes one or more tubes (e.g., fluid conduits) extending through the interior of the pyrolysis furnace 10 across a flow path of the hot flue gas 18. In general, each tube bank 22, 24, and 26 may include any number of tubes (e.g., 2, 3, 4, 5, 6, or more than 6) and having any suitable size. Moreover, each tube bank 22, 24, and 26 may include any suitable heat transfer profiling (e.g., ability to transfer heat from the flue gas 18). Further, while the illustrated embodiment shows the tubes of the tube banks 22, 24, and 26 running down the section height 30 and along a width of the convection section 12, it should be noted that the tubes of the tube banks 22, 24, and 26 may also extend along a depth (into the page) of the convection section 12.

[0040] The hot flue gas 18 contacts an exterior of the one or more tubes of each tube bank 22, 24, and 26, whereas the hydrocarbon material 15 contacts and flows within an interior (e.g., internal flow path) of the one or more tubes of each tube bank 22, 24, and 26. The one or more tubes of each tube bank 22, 24, and 26 may wind back and forth across the flow path of the hot flue gas 18 to improve heat transfer between the hot flue gas 18 and the hydrocarbon material 15. For example, the tubes of each tube bank 22, 24, and 26 may wind back and forth in a crosswise (e.g., perpendicular) direction relative to the longitudinal axis 28. Accordingly, the tubes form rows that extend crosswise to the longitudinal axis 28. Thus, each tube bank 22, 24, and 26 may include a plurality or bundle of tubes that are parallel to one another in the crosswise direction (e.g., crosswise tube bundle). Each tube bank 22, 24, and 26 may include a single tube that winds back and forth defining the parallel tubes, or a plurality of tubes that independently wind back and forth defining the parallel tubes.

[0041] In some embodiments, the pyrolysis furnace 10 may include a transfer line exchanger (TLE) used to quench the furnace effluent (hereinafter "TLE furnace"). In such embodiments, the steam cracked effluent leaving the radiant section 14 may be cooled by the TLE. In turn, the heat exchange between the steam cracked effluent and the TLE may be used to generate steam (e.g., high-pressure steam and / or super-high-pressure steam). In some embodiments steam generatedin the TLE may be used as the feed for the steam preheating tube bank 32, but is not preferred. The high-pressure (HP) steam may have a pressure greater than 150 psia.

[0042] The mixture 17 may be mixed with the water and / or steam 21 form a mixture 27 that is ultimately heated by subsequent tube banks (e.g., the second tube bank 24 and the third tube bank 26). In operation, the mixture 27 flows into the first tube bank 22 (e.g., via an inlet 22a of the first tube bank 22). Within the first tube bank 22, the mixture 27 is heated to a first temperature via heat exchange between the flue gas 18 and the first tube bank 22. As discussed in more detail below, the first temperature may be within a threshold range below the dewpoint (e.g., no greater than about 60°C, 50°C, 40°C, 30°C, 20°C, 15°C, 10°C, 5°C, 2°C, or 1°C below the dewpoint) of the mixture 27 including hydrocarbon material 15, the boiling point elevation material 16, and the water and / or steam 21. For example, the mixture 27 may be heated to a first temperature, Tl, where Td - 60°C < Tl < Td, and where Td is the dewpoint of the mixture 27 (e.g., at the inlet 26b of the third tube bank 26 or otherwise an entry to a tube bank) in an embodiment where the threshold range is no greater than 60°C below the dewpoint of the mixture 27.

[0043] In a preferred embodiment, the mixture 27 exiting the outlet of the second bank 24 is heated to the first temperature, such that any vaporization happens in the third tube bank 26 (closest to the radiant section). The first tube bank 22 is fluidly coupled to the second tube bank 24 (e.g., via a fluid conduit connecting an outlet 22b of the first tube bank 22 and an inlet 24a of the second tube bank 24). As such, during operation, the mixture 17 that may include hydrocarbon material 15 flows from the first tube bank 22 to the second tube bank 24. Within the second tube bank 24, the mixture 17 and the water and / or steam 21 (e.g., combined to form the mixture 27) is heated to a second temperature via heat exchange between the flue gas 18 and the second tube bank 24. As discussed in more detail below, the second temperature may be a temperature sufficient to vaporize at least a portion of the mixture 27. In some embodiments, the mixture 27 may be transmitted to a flash drum and the heated vapor phase (e.g., produced via the flash drum) may be returned to the convection section 12 before, ultimately, being provided to the radiant section 14. For example, the heated mixture 27 may be transmitted to a flash drum where the mixture 27 is separated to obtain a vapor phase and a liquid phase. Then, the vapor phase may be returned to the convection section 12 and heated in the third tube bank 26 by contacting the second tube bank with the flue gas to obtain a heated vapor phase. In such embodiments, at least a portion of the heated vapor phase may be supplied to the radiant section 14.

[0044] In some embodiments, the hydrocarbon material 15 may include hydrocarbon and contaminants. In some embodiments, the hydrocarbon material 15 is at least partially derived from plastic. For example, at least 10%, at least 20%, at least 30%, at least 40%, at least 50%, atleast 60%, at least 70%, at least 80%, at least 90%, at least 95%, or at least 99% of the hydrocarbon material may be derived from plastic based on the total weight of the hydrocarbon material 15. In some embodiments, the hydrocarbon material 15 includes naphtha and / or gasoils. As referred to herein, a “naphtha” refers to a material obtainable as a distillate of petroleum with a boiling range of approximately 70 to 400°F (20 to 205°C). In some embodiments, the hydrocarbon material 15 may include contaminants such as asphaltenes.

[0045] In some embodiments, the hydrocarbon material 15 may include asphaltenes at a total concentration, based on the total weight of the hydrocarbon material 15 (e.g., first pyrolysis material), from a lower value of about 1 ppb, 2 ppb, 4 ppb, 5 ppb, 6 ppb, 8 ppb, or 10 ppb, to an upper value of about 20 ppb, 40 ppb, 50 ppb, 60 ppb, 80 ppb, or 100 ppb, or to an upper value of about 200 ppb, 400 ppb, 500 ppb, 600 ppb, 800 ppb, or 1000 ppb, or to an upper value of about 2 ppm, 4 ppm, 5 ppm, 6 ppm, 8 ppm, 10 ppm, or to an upper value of about 20 ppm, 40 ppm, 50 ppm, 60 ppm, 80 ppm, 100 ppm, or to an upper value of 200 ppm, 400 ppm, 500 ppm, 600 ppm, 800 ppm, 1000 ppm, or to an upper value of about 2000 ppm, 4000 ppm, 5000 ppm, 6000 ppm, 8000 ppm, or to an upper value of about 1 wt%, 2 wt%, 4 wt%, 5 wt%.

[0046] In some embodiments, the hydrocarbon material 15 may include inorganic material at a total concentration, based on the total weight of the hydrocarbon material 15 (e.g., first pyrolysis material), from a lower value of about 1 ppb, 2 ppb, 4 ppb, 5 ppb, 6 ppb, 8 ppb, or 10 ppb, to an upper value of about 20 ppb, 40 ppb, 50 ppb, 60 ppb, 80 ppb, or 100 ppb, or to an upper value of about 200 ppb, 400 ppb, 500 ppb, 600 ppb, 800 ppb, or 1000 ppb, or to an upper value of about 2 ppm, 4 ppm, 5 ppm, 6 ppm, 8 ppm, 10 ppm, or to an upper value of about 20 ppm, 40 ppm, 50 ppm, 60 ppm, 80 ppm, 100 ppm, or to an upper value of about 200 ppm, 400 ppm, 500 ppm, 600 ppm, 800 ppm, 1000 ppm, or to an upper value of about 2000 ppm, 4000 ppm, 5000 ppm, 6000 ppm, 8000 ppm, or to an upper value of about 1 wt%, 2 wt%, 4 wt%, 5 wt%.

[0047] In some embodiments, the hydrocarbon material 15 may include a plastic-derived component, a biological-material-derived component, a reactive component, or a combination thereof. In embodiments where the hydrocarbon material 15 includes a plastic-derived component and / or a biological material-derived component, the plastic-derived component and / or biological material -derived component can include a non-volatilizing material. As referred to herein, a “nonvolatilizing material” refers to a material that is not fully (>99.9%) vaporized by the heat transferred in the convection section 12. The non-volatizing material can cause pre-mature coking or fouling in an upper, non-decokable segment of the heating tube in the convective section 12. In any case, the hydrocarbon material 15 may include the plastic-derived component at a concentration, based on the total weight of the hydrocarbon material 15 (e.g., first pyrolysis feedmaterial), of from, e.g., 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, 50 wt%, to 55 wt%, 60 wt%, 65 wt%, 70 wt%, 75 wt%, 80 wt%, to 85 wt%, 90 wt%, 95 wt%, 100 wt%.

[0048] The non-volatilizing material (e.g., of the hydrocarbon material 15) may result from one or more of the sources described below. For example, the non-volatilizing material may originate from a source such as any hydrocarbon stream containing non-volatile components, which may comprise any of ash, char, coke, asphaltenes, PAHs, etc. Example hydrocarbon streams include but are not limited to crude oil and its fractions, gasoils, condensates, resid or residuum, wherein the contamination with nonvolatile material may be inherent to the feed or induced by transportation or storage in contaminated vessels. As another non-limiting example, the nonvolatilizing material may originate from a source such as any stream derived at least in part or derived wholly from plastic, where that plastic may comprise any plastic or plastic waste, pre- or post-consumer, from industrial or non-industrial sources. Example streams derived at least in part from plastic waste include oil derived from plastic pyrolysis (i.e., “pyoil”), or oils derived from catalytic or other treatment of plastic waste. As another non-limiting example, the non-volatilizing material may originate from a source such as any stream derived at least in part from bio-based materials, including cooking oils or other plant-based oils, which may or may not have been subject to use in culinary applications (i.e., used cooking oils). These may also include refinery fractions derived at least in part or derived wholly from bio-based sources (i.e., bio-diesel).

[0049] As described above, in some embodiments, the hydrocarbon material 15 may include a reactive component (e.g., one or more reactive components). As referred to herein, a “reactive component” refers to a material or component that is capable of undergoing a chemical reaction (e.g., polymerization) to form a heavy species when heated in the convection section 12. In some embodiments, the reactive component may be an "aliphatic mono-olefin." As referred to herein, an “aliphatic mono-olefin” refers to an aliphatic, cyclic or non-cyclic, hydrocarbon compound comprising one C=C double bond in its molecular structure, preferably, C2 - C10; more preferably C2 - C5. Examples include: ethylene, propylene, butenes, pentenes, cyclopentene, cyclohexene, and the like.

[0050] In some embodiments, the reactive component (e.g., the hydrocarbon material 15) may be an "aromatic mono-olefin." As referred to herein, an “aromatic mono-olefin” refers to an aromatic hydrocarbon comprising one C=C bond that is not included in an aromatic ring in its molecular structure, such as styrene; prop-l-en-ylbenzene; and the like. In some embodiments, the reactive component may be an "aromatic multi-olefin.” As referred to herein, the “aromatic multi-olefin” refers to an aromatic hydrocarbon compound comprising two or more C=C bondsthat are not included in any aromatic ring in its molecular structure, such as 4-phenyl-l,3- butadiene.

[0051] In some embodiments, the reactive component (e.g., the hydrocarbon material 15) may be an “aliphatic multi-olefin”. As referred to herein, an “aliphatic multi-olefin” refers to an aliphatic, cyclic or non-cyclic, hydrocarbon compound comprising two or more C=C bonds in its molecular structure, such as butadiene; isoprene; 1,3 -pentadiene; 1,4-pentadiene; cyclopentadiene; cyclohexa-l,3-diene; cyclohexa- 1,4-diene; and the like.

[0052] In some embodiments, the reactive component (e.g., the hydrocarbon material 15) may include a C2-C20 linear or branched non-cyclic aliphatic mono-olefin, a C5-C20 cyclic mono-olefin, a C4-C20 linear or branched non-cyclic aliphatic di-olefin, a C5-C20 cyclic aliphatic di -olefin; a Cs- C20 aromatic mono-olefin; a C8-C20 aromatic di -olefin, or mixtures and combinations thereof.

[0053] In some embodiments, the reactive component (e.g., the hydrocarbon material 15) may include a peroxide. As referred to herein, a "peroxide" refers to a compound having a -O-O- moiety in its molecular structure, such as t-butyl hydroperoxide; dicumyl peroxide; t- butylperoxybenzoate; dibenzoyl peroxide; and the like. In any case, the reactive component may include one or more of an aliphatic mono-olefin, an aromatic mono-olefin, an aliphatic multiolefin, an aromatic multi-olefin, or a peroxide (e.g., mixtures and combinations thereof).

[0054] In some embodiments, the hydrocarbon material 15 may include a plastic-derived component, such as a pyoil, bio-derived components, and other plastic materials as described herein.

[0055] As described herein, it is presently recognized that it may be advantageous to add a higher boiling point material to the hydrocarbon material 15 to reduce a likelihood of fouling or coking within the convection section 12. In particular, adding the higher boiling point material (e.g., the boiling point elevation material 16) causes deposits (e.g., non-volatile material) of heavy molecules, such as coke, tar, asphaltenes, PAHs, solids entrained in the feed, and several other sources, including ash and char, to form in lower sections of the convection section 12. It should be noted that it is relatively easier to de-coke (e.g., remove coking and / or other fouling form) a tube bank when the deposit forms in a tube bank within the lower portion of the convection section 12.

[0056] Accordingly, the boiling point elevation material 16 (e.g., the second pyrolysis feed material) includes an end boiling point that is higher than the end boiling point of the hydrocarbon material 15. That is, a first end boiling of the hydrocarbon material 15 is less than a second end boiling point of the boiling point elevation material 16. In some embodiments, the second end boiling point Te(2) is higher than the first end boiling point Te(l). As such, Te(2) - Te(l) canrange from, e.g., 0, 1, 2, 4, 5, 6, 8, 10, to 20, 25, 30, 35, 40, 45, 50, to 55, 60, 65, 70, 75, 80, to 85, 90, 95, 100, to 120, 140, 150, 160, 180, 200, 300, 400°C. For example, the second end boiling point is at least 10 °C higher than the first end boiling point. In some embodiments, the hydrocarbon material 15 has a first final boiling point Tbpl, and the boiling point elevation material 16 has a second final boiling point Tbp2, and 0 °C < Tbp2 - Tbpl < 400°C or 10 °C < Tbp2 - Tbpl < 200°C.

[0057] Accordingly, the mixture 17 of the boiling point elevation material 16 and the hydrocarbon material 15 may have a relatively higher end boiling point than the hydrocarbon material 15. For example, the mixture 17 may include a third end boiling point that may be as high as the boiling point of the material 16 depending on the quantity of material 16 added. For example, the third end boiling point may be at least 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, or 15 °C higher than the first end boiling point (e.g., corresponding to the hydrocarbon material 15), or at least 0.1%, 0.5%, 1%, 2%, 3%, 4%, or 5% higher than the first end boiling point. Accordingly, by adding the boiling point elevation material 16 to the hydrocarbon material 15, thereby forming the mixture 17 having a higher end boiling point than the hydrocarbon material 15, any deposits formed due to contaminants in the hydrocarbon material 15 form at a relatively lower section within the convection section 12. In particular, it may be easier to remove deposits in the lower section via decoking interval or decoking operation, as described below.

[0058] In some embodiments, the pyrolysis furnace 10 may be operated in a decoking interval. As referred to herein, a “decoking interval” or a “decoking operation” refers to an operation of the pyrolysis furnace 10 where the pyrolysis furnace 10 is heated to a temperature and / or fluids (e.g., steam, oxidizers, air, or a combination thereof) are provided to the tube banks to oxidize and remove any deposits (e.g., of cokes or other organic materials as discussed herein) and remove some portion of any non-organic deposits. At least in some instances, decoking may occur in the convection section 12. Further, “online decoking” refers to steam-only decoking, and “offline decoking” refers to steam-air decoking. Both methods of decoking (e.g., online and offline) may clean the convection section 12 when the deposits form in the lower section 29, as described herein, and reduce or eliminate the need of mechanical cleaning of the convection section 12. At least in some instances, during a decoking operation, the air / steam decoking mixture is hot enough to bum the deposits, thereby removing the deposits from the convection section 12. As described herein, the disclosed embodiments may promote cokes and other deposits to deposit in the third tube bank 26. The third tube bank 26 may receive the flue gas 18 at a relatively higher temperature (e.g., as compared to the second tube bank 24 or other tube banks upstream of the third tube bank26 along the flow of the flue gas 18), which may facilitate the decoking operation because the temperature in the lower section may have a sufficiently high temperature for removing deposits.

[0059] In any case, the boiling point elevation material 16 may include any liquid hydrocarbon feed, inclusive of crude oil and its fractions and refined petroleum fractions, inclusive of condensates, residuum, resid, naphtha, diesels, kerosene, gas oils, vacuum gas oils, treated oils or oil fractions, etc. For example, the boiling point elevation material 16 may include a waxy basestock, a hydrocrackate, an atmospheric gas oil, a hydrotreated gas oil, a vacuum gas oil, or mixtures or combinations thereof.

[0060] The illustrated embodiment of the convection section 12 also includes a steam preheating tube bank 32 and an auxiliary tube bank 34. In general, the steam preheating tube bank 32 may preheat the steam and / or water 20. For example, steam 21 may be superheated (e.g., thereby forming a superheated steam stream) before injecting the steam 21 into the mixture 17 to form the mixture 27. Alternatively, any water may be heated to form steam 21, before the fluid (e.g., water, steam, water and steam, or only water) is injected into the hydrocarbon material 15. The temperature of the steam 21 and hydrocarbon material 15 may be between approximately 100 to approximately 340 °C). To illustrate this, FIG. 2 is a schematic diagram of a first example of the convection section 12 in accordance with certain embodiments of the present disclosure. As shown, the convection section 12 includes the first tube bank 22, the second tube bank 24, and the steam preheating tube bank 32 arranged along the section height 30. As illustrated, the steam preheating tube bank 32 is disposed upstream of the second tube bank 24 and downstream of the first tube bank 22 along the longitudinal axis 28. However, it should be noted that the steam preheating tube bank 32 may be disposed in any suitable location within in the convection section 12. In general, the mixture 17 (e.g., the hydrocarbon material 15 and the boiling point elevation material 16) moves sequentially through the first tube bank 22 and the second tube bank 24. The water and / or steam 21 may be added to the mixture 17 in the second tube bank 24 to form the mixture 27. The flue gas 18 sequentially contacts the second tube bank 24, the steam preheating tube bank 32, and the first tube bank 22. Accordingly, the temperature of the flue gas 18 may decrease sequentially from the second tube bank 24, to the steam preheating tube bank 32, and to the first tube bank 22. In any case, after leaving the radiant section 14, the cracked hydrocarbon material 15 may be sent to a downstream processing system 37, as shown in FIG. 1.

[0061] As described herein, the steam preheating tube bank 32 may preheat the steam and / or water 20. For example, steam 21 may be superheated before injecting the steam 21 into the hydrocarbon material 15. Alternatively, any water may be heated to form steam 21, before the fluid (e.g., water, steam, water and steam, or only water) is injected into the hydrocarbon material15. The temperature of the steam 21 and hydrocarbon material 15 may be between approximately 100 to approximately 340°C.

[0062] As shown in the illustrated embodiment, the water and / or steam 21 is added to the hydrocarbon material 15 upstream of the second tube bank 24 or before the hydrocarbon material 15 flows into the second tube bank 24. However, in some embodiments, the water and / or steam 21 is added to the hydrocarbon material 15 after the hydrocarbon material 15 flows into the second tube bank 24.

[0063] In the illustrated embodiment of FIG. 2, the boiling point elevation material 16 is mixed with the hydrocarbon material 15. In some embodiments, the boiling point elevation material 16 may include a boiling point exceeding 350°C. For example, in a preferred embodiment, the hydrocarbon material that is asphaltene-free. The amount of boiling point elevation material 16 may be a suitable amount to raise the boiling point of the hydrocarbon material to greater than 350°C, greater than 360°C, greater than 370°C, greater than 380°C, greater than 390°C, greater than 400°C, greater than 410°C, greater than 420°C, greater than 450°C, greater than 480°C, or greater than 500°C. In general, the boiling point elevation material 16 may be a high boiling point hydrocarbon that has a higher end or final boiling point than a boiling point or average boiling point of the hydrocarbon material 15. As such, the boiling point elevation material 16 may reduce the possibility of deposits forming at higher sections within the convection section 12. The quantity of boiling point elevation material 16 to be added will be an amount sufficient to raise the final boiling point of the hydrocarbon material 15, which can be determined by routine experimentation, modeling, or other physical and / or analytical means by one of ordinary skill in the art in possession of the present disclosure. The final boiling point (FBP) of the mixture 17 may be defined utilizing the terminology for FBP from ASTM methods D2887, D7096, D7169 as the point at which 99.5% of the cumulative area and / or volume count is eluted from the chromatogram or alternatively utilizing a) the definition in D86 as the maximum corrected thermometer reading obtained during the test or b) the definition from DI 160 as the maximum vapor temperature reached during the test. This may be further aided by vapor / liquid simulations using commercially available software, including but not limited to AVEVA PR0 / II™ that is now available from AVEVA, previously available from Schneider Electric and Simulation Sciences Inc.

[0064] In some embodiments, the convection section 12 may include one or more auxiliary tube banks 34, such as a boiler water preheat tube bank, a high-pressure steam bank, or both). To illustrate this, FIG. 3 is a schematic diagram of a second example of the convection section 12 in accordance with certain embodiments of the present disclosure. As shown, the convection section 12 includes the first tube bank 22, the second tube bank 24, the third tube bank 26, the steampreheating tube bank 32, and an auxiliary tube bank 34 arranged along the section height 30. As illustrated, the auxiliary tube bank 34 is disposed downstream of the first tube bank 22. Accordingly, the auxiliary tube bank 34 may be heated by a flue gas 18 that has a relatively higher temperature than the first tube bank 22 in this embodiment.

[0065] As described herein, the steam preheating tube bank 32 may preheat the water and / or steam 21. For example, steam 21 may be superheated before injecting the steam 21 into the hydrocarbon material 15 or mixture 17. Alternatively, any water may be heated to form steam 21, before the fluid (e.g., water, steam, water and steam, or only water) is injected into the hydrocarbon material 15 or mixture 17. The temperature of the steam 21 and hydrocarbon material 15 or mixture 17 may be between approximately 100 to approximately 350°C (e.g. a temperature sufficient to vaporize the mixture 17.

[0066] In some embodiments, the auxiliary tube bank 34 include a boiler water preheat tube bank (e.g., an economizer) or a steam bank, which may include high- or super-high-pressure steam. High pressure steam may have a pressure between 225-600 psig, and super-high-pressure steam may have a pressure between 600-2000 psig. In general, the auxiliary tube bank 34 may receive water 36 and preheat it for use with at least one of a transfer line exchanger and / or steam drum or other component that utilizes steam or water. For example, the auxiliary tube bank 34 may superheat steam to form a high-pressure steam 38. In some embodiments, the auxiliary tube bank 34 may be a boiler feedwater tube bank. As shown, the auxiliary tube bank 34 is downstream of the first tube bank 22 along the flow path of the flue gas 18 (e.g., substantially parallel to the longitudinal axis 28). However, it should be noted that the auxiliary tube bank 34 may be disposed in other suitable positions within the convection section 12, such as upstream of the first tube bank 22, and such as between the first tube bank and the steam preheating tube bank 32, and / or between the second tube bank 24 and / or the steam preheating tube bank 32, the third tube bank 26 and / or the steam preheating tube bank 32, and so on.

[0067] In some embodiments, the convection section 12 may include a selective catalytic reduction (SCR) unit. In general, the SCR unit may be capable of reducing nitrogen oxides (NOx) in the flue gas using a selective catalytic reduction (SCR) unit located in the convection section 12 along the flow path of the flue gas 18. To illustrate an arrangement of the SCR unit, FIG. 4 is a schematic diagram of a second example of the convection section 12 in accordance with certain embodiments of the present disclosure. As shown, the convection section 12 includes the first tube bank 22, the second tube bank 24, the third tube bank 26, the steam preheating tube bank 32, the auxiliary tube bank 34, and the SCR unit 40 arranged along the section height 30. As illustrated, the SCR unit 40 is disposed upstream of the first tube bank 22 relative to the flue gasflow. As such, the SCR unit 40 may be heated by a flue gas 18 that has a relatively higher temperature than the flue gas 18 heating the first tube bank 22 in this embodiment. The SCR unit 40 may also include an ammonia injection system, which may be located anywhere upstream of the SCR unit 40 relative to the flue gas flow.

[0068] As described herein, it may be advantageous to add an amount of the boiling point elevation material 16 to the hydrocarbon material 15 such that the mixture 17 has a higher end boiling point or higher final boiling point. In this way, a non-volatilizing material deposit may form in a relatively lower section or segment of the convection section 12. As shown, the SCR unit 40 generally divides the flow path of the mixture 17 from the first tube bank 22, the second tube bank 24, and the third tube bank 26 into two segments, namely, a first segment 42 and a second segment 44 (e.g., including the second tube bank 24 and the third tube bank 26). As shown, the SCR unit 40 is located downstream of the second segment 44 in the flow path of the flue gas 18. However, it should be noted that the SCR unit 40 may be located in any suitable positions, such as downstream of the second segment 44 in the flow path of the flue gas 18. For example, it should be noted that, depending on the SCR catalyst used and its preferred operation temperature, the SCR unit and associated ammonia injection (e.g., as described above) can be located anywhere in the convection section 12. In any case, the disclosed techniques include adding an amount of the boiling point elevation material 16 such that essentially no non-volatilizing material deposits in the first segment 42. Instead, the non-volatilizing material (e.g., coke or other deposits) may deposit along the second segment 44. For example, the non-volatilizing material may deposit along the last 50%, 40%, 30%, 20%, or 10% or rows of the second segment 44.

[0069] As shown, the steam preheating tube bank 32 is located downstream of the second segment 44 in the flow path of the flue gas 18. However, it should be noted that the steam preheating tube bank 32 may be located in any suitable positions, such as downstream or upstream of the second segment 44 in the flow path of the flue gas 18. As shown, the auxiliary tube bank 34 is disposed between the second tube bank 24 and the third tube bank 26 along the second segment 44 of the flow path of the flue gas 18. However, it should be noted that the auxiliary tube bank 34 may be located in any suitable positions, such as downstream or upstream of the second segment 44 in the flow path of the flue gas 18. Several examples are described below with respect to Table 1.

[0070] Although described with respect to FIG. 4, it should be noted that the discussion of the first segment 42 and the second segment 44 may generally apply to FIGS. 2 and 3. For example, with respect to FIG. 1, the second segment 44 may include only the second tube bank 24. In a generally similar manner as described in FIG. 3, the auxiliary tube bank 34 may receive water 36and preheat it for use with a steam drum or other component that utilizes steam or water. For example, the auxiliary tube bank 34 may superheat steam to form a high-pressure steam 38. Although the first tube bank 22, the second tube bank 24, and the third tube bank 26 are described separately. It should be noted that the first tube bank 22, the second tube bank 24, and the third tube bank 26 may be a single tube bank. As such, the single tube bank may be described as having a first segment 42 and a second segment 44.

[0071] It should be noted that the example convection sections 12 described in FIGS. 2-4 are meant to be non-limiting. That is, the convection sections 12 may include any arrangement of one or more steam preheating tube banks 32, auxiliary tube banks 34, SCR units 40, and tube banks (e.g., the first tube bank 22, the second tube bank 24, and the third tube bank 26). Several example convection section 12 arrangements are depicted in Table 1.Table 1- Relative arrangements of different sections within the convection section.

[0072] In general, “A” and “C” (e.g., “Cl” and “C2”) refer to tube banks, such as the first tube bank 22, the second tube bank 24, and the third tube bank 26. “B” refers to the steam preheating tube bank 32. “D” (e.g., “DI” and “D2”) refers to auxiliary tube bank 34. “SCR” refers to the SCR unit 40. Accordingly, example 1 (e.g., “Ex 1”) depicted in Table 1 represents an example convection section 12 having an SCR unit 40 (e.g., “SCR”), a first tube bank 22 (e.g., “A”), a steam pre-heating tube bank (e.g., “B”), a second tube bank 24 (e.g., “Cl”), an auxiliary tube bank 34 (e.g., “D”), and a third tube bank 26 (e.g., “C2”) arranged sequentially from a top portion 46 to a bottom portion 48 of the convection section 12. In some embodiments, the SCR unit 40 may be surrounded or otherwise embedded by other tube banks. In Table 1, the SCR unit 40 embedded by a tube bank is depicted by (SCR). As such, the SCR unit 40 embedded by the first tube bank 22 is depicted as A(SCR) in Table 1. Although the above descriptions relate to the SCR unit 40, it should be noted that the above descriptions may also refer to the SCR unit 40 and associated chemical injection, as described herein.

[0073] Accordingly, the present disclosure is directed to techniques for treating a hydrocarbon material 15, such that a deposit preferentially forms in a lower section or downstream (e.g., downstream relative to the direction of flow of the hydrocarbon material 15) segment (e.g., thesecond segment 44) of the convection section 12 of a pyrolysis furnace 10 where it may be relatively easier to de-coke. In general, the techniques include adding the boiling point elevation material 16 that has a higher end boiling point and / or final boiling point than the hydrocarbon material 15. Technical effects of the present disclosure include reducing the likelihood of fouling by increasing the end boiling point and / or final boiling point of material flowing within the convection section 12. The amount of the boiling point elevation material 16 may be sufficient such that the end boiling point or final boiling point of the mixture 17 is at least 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 20, 25, 50, 100°C higher, or higher than 100°C, than the hydrocarbon material 15. In this way, the disclosed techniques (e.g., the addition of the boiling point elevation material) may cause any non-volatile materials to deposit in regions of the convection section 12 that are exposed to higher temperatures, thereby presenting an advantage over convention furnaces where non-volatile material may deposit higher in the convection section.

[0074] This written description uses embodiments / examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other embodiments / examples that occur to those skilled in the art. Such other embodiments / examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. 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.

Claims

1. CLAIMS:

1. A process, comprising:(I) providing a first pyrolysis feed material having a first end boiling point, wherein the first pyrolysis feed material comprises a plastic-derived component, a biological-material- derived component, and / or a reactive component;(II) adding a second pyrolysis feed material to the first pyrolysis feed material to obtain a first pyrolysis feed mixture, wherein the second pyrolysis feed material has a second end boiling point higher than the first end boiling point;(III) adding water and / or steam to the first pyrolysis feed mixture to obtain a second pyrolysis feed mixture;(IV) heating the second pyrolysis feed mixture in a tube bank located in a convection section of a pyrolysis furnace by flowing the second pyrolysis feed mixture in the tube bank and contacting the tube bank with a flue gas in the pyrolysis furnace to obtain a heated second pyrolysis feed mixture; and(V) after step (IV), flowing at least a portion of the heated second pyrolysis feed mixture through a radiant tube located in a radiant section of the pyrolysis furnace to produce a steam cracked effluent exiting the radiant section.

2. The process of claim 1, wherein the reactive component comprises one or more of the following: an aliphatic mono-olefin; an aromatic mono-olefin; an aliphatic multi-olefin; an aromatic multi-olefin; a peroxide; and mixtures and combinations thereof.

3. The process of claim 2, wherein the first pyrolysis feed comprises at least one of the following: a C2-C20 linear or branched non-cyclic aliphatic mono-olefin; a C5-C20 cyclic mono-olefin; a C4-C20 linear or branched non-cyclic aliphatic di-olefin; a C5-C20 cyclic aliphatic di-olefin; a C8-C20 aromatic mono-olefin; a C8-C20 aromatic di-olefin; and mixtures and combinations thereof.

4. The process of any of claims 1 to 3, wherein the second end boiling point is at least 10 °C higher than the first end boiling point.

5. The process of claim 4, wherein the first pyrolysis feed mixture has a third end boiling point, and the third end boiling point is at least 10°C higher than the first end boiling point.

6. The process of any of claims 1 to 5, wherein the first pyrolysis feed material has a first final boiling point Tbpl, and the second pyrolysis feed material has a second final boiling point Tbp2, and wherein Tbp2 - Tbpl is greater than or equal to 1°C.

7. The process of any of claims 1 to 6, wherein the second pyrolysis feed material is selected from a waxy basestock, a hydrocrackate, an atmospheric gas oil, a hydrotreated gas oil, a vacuum gas oil, and mixtures thereof.

8. The process of any of claims 1 to 7, wherein the plastic-derived component comprises a pyoil.

9. The process of any of claims 1 to 8, wherein: in step (IV), the tube bank comprises a first segment and a second segment downstream of the first segment in the flow path of the second pyrolysis feed mixture, the first segment is not decokable in a decoking interval, and the second segment is decokable in the decoking interval; and in step (IV), depositing coke in the second segment.

10. The process of claim 9, wherein the step (IV), essentially no coke is deposited in the first segment.

11. The process of claim 9 or claim 10, further comprising:(VI) during a decoking interval, removing at least a portion of the coke deposited in the second segment.

12. The process of any of claims 1 to 11, wherein the first pyrolysis feed material comprises asphaltenes at a total concentration of at least 1 ppb by weight, based on the total weight of the first pyrolysis feed material.

13. The process of any of claims 1 to 12, wherein the first pyrolysis feed material comprises inorganic material at a total concentration of at least 1 ppb by weight, based on the total weight of the first pyrolysis feed material.

14. The process of any of claims 1 to 13, wherein the first pyrolysis feed material comprises at least 10 wt% of the plastic-derived component, based on the total weight of the first pyrolysis feed material.

15. The process of any of claims 1 to 14, wherein the first pyrolysis feed material comprises a component originated from crude oil, condensate, or a combination thereof.

16. The process of any of claims 1 to 15, further comprising flowing a boiler feedwater in a boiler feedwater tube bank located in the convection section, wherein the boiler feedwater tube bank is located downstream of the second segment portion along the flow path of the flue gas.

17. The process of any of claims 1 to 16, further comprising:(VII) reducing nitrogen oxides (NOX) in the flue gas using a selective catalytic reduction (SCR) unit located in the convection section along the flow path of the flue gas.

18. The process of claim 17, wherein the SCR unit is located upstream of the second segment in the flow path of the flue gas.

19. The process of claim 18, wherein the SCR unit is located downstream of the second segment in the flow path of the flue gas.

20. The process of any of claims 1 to 19, further comprising, after step (IV) and before step (V):(VIII) separating the heated second pyrolysis feed mixture in a flash drum to obtain a vapor phase and a liquid phase;(IX) heating the vapor phase in a second tube bank located in the convection section by contacting the second tube bank with the flue gas to obtain a heated vapor phase; and(X) supplying at least a portion of the heated vapor phase as the at least a portion of the heated second pyrolysis feed mixture in step (V).

21. The process of any of claims 1 to 20, further comprising:(XI) heating a steam stream in a superheating tube bank located in the convection section to obtain a superheated steam stream, wherein the superheating tube bank is located upstream of the tube bank in the flow path of the flue gas.

22. The process of claim 21, further comprising:(XII) cooling the steam cracked effluent in a transfer line exchanger (“TLE”) and producing a high-pressure steam from the TLE; and(XIII) supplying the high-pressure steam as at least a portion of the steam stream to step (XI).

23. A process, comprising:(I) providing a first pyrolysis feed material having a first final boiling point Tbpl, wherein the first pyrolysis feed material comprises at least one of the following: a plastic- derived component, a biological-material-derived component, and a reactive component;(II) adding a second pyrolysis feed material to the first pyrolysis feed material to obtain a first pyrolysis feed mixture, wherein the second pyrolysis feed material has a second final boiling point Tbp2, wherein 0 °C < Tbp2 - Tbpl < 400°C;(III) adding water and / or steam to the first pyrolysis feed mixture to obtain a second pyrolysis feed mixture;(IV) heating the second pyrolysis feed mixture in a tube bank located in a convection section of a pyrolysis furnace by flowing the second pyrolysis feed mixture in the tube bank and contacting the tube bank with a flue gas in the pyrolysis furnace to obtain a heated second pyrolysis feed mixture; and(V) after step (IV), flowing at least a portion of the heated second pyrolysis feed mixture through a radiant tube located in a radiant section of the pyrolysis furnace to produce a steam cracked effluent exiting the radiant section.

24. The process of claim 23, wherein 10 °C < Tbp2 - Tbpl < 200°C.

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