Systems and methods for measuring carburization of an electrified cracking coil

Abstract

A system for measuring carburization may comprise an electrified cracking electrified by a electric current; and first and second thermocouples separated by a length along the electrified cracking coil. Each thermocouple may comprise a first wire, a second wire, wherein the first wire and the second wire are joined at a junction proximate the electrified cracking coil, an electrically conductive sheath surrounding the first and second wires, wherein the electrically conductive sheath is in contact with the electrified cracking coil, a thermocouple sensor coupled to the first wire and the second wire opposite the junction, the thermocouple sensor configured to determine a temperature from a voltage difference between the first wire and the second wire, and a voltmeter electrically coupled to the electrically conductive sheath and configured to determine a voltage of the electrified cracking coil at a contact point between the electrically conductive sheath and the electrified cracking coil.

Description

Atorney Docket No.: 85999-WO-PCT / DOW 85999 WO1SYSTEMS AND METHODS FOR MEASURING CARBURIZATION OF AN EEECTRIFIED CRACKING COIEFIELD

[0001] Embodiments of the present disclosure generally relate to the field of refining and upgrading hydrocarbons, and pertain particularly to systems and methods for determining the degree of carburization of an electrified cracking coil.BACKGROUND

[0002] Ethylene is widely used as an intermediate in the petrochemical industry and its production exceeds that of any other organic compound. Much of ethylene production goes to the manufacture of ethylene oxide, ethylene dichloride and polyethylene, which are precursors to a multitude of everyday consumer products. Despite various improvements over the years in thermal efficiency, reliability and safety, steam cracking furnaces used to upgrade hydrocarbons and other feedstocks into products such as ethylene remain heavily reliant on combustion of fossil fuels to provide process heat leading to greenhouse gas emissions.

[0003] The steam cracking process to produce ethylene requires roughly half the energy required of competing processes (e.g., direct Ci conversion technologies) and is projected to remain as the most energy efficient process. CO2 emissions from steam cracking of ethane can reach the level of 1 ton-CCL per ton-ethylene produced and is lower than steam cracking of naphtha and alternates Ci-based routes to ethylene.

[0004] Accordingly, the growth and availability of renewable electricity creates an opportunity to use renewable energy in the upgrading of hydrocarbons and other feedstocks into products such as ethylene, eliminating the need to burn fossil fuels and lower CO2 emissions.SUMMARY

[0005] However, regardless of the energy medium used, carburization of the coils used to upgrade the feedstocks remains a concern. Carburization is a phenomenon where petroleum coke, formed as a byproduct of the reactions within the coil, reacts with the metals in the alloy matrix ofAtorney Docket No.: 85999-WO-PCT / DOW 85999 WO2the coil, forming coarse metal carbides. These metal carbides, when present in a sufficient amount, render the coil brittle and susceptible to rupture, reducing the useable lifetime of the coils and increasing the occurrence of unplanned re-coiling. Further, as carburization gradually increases, process parameters and / or current applied to the coils may need to correspondingly increase to sufficiently heat the feedstock through the carburization and / or coke and maintain the desired product yield.

[0006] Accordingly, methods by which the relative degree of carburization can be measured are continually desired, so as to better inform when the coils need to be replaced, the process parameters need to be altered, and / or when the coils need to be decoked.

[0007] One common method of determining the carburization degree of a coil is by utilizing eddy currents. However, the eddy current method requires that the coil be electrically deenergized, and the inspection devices operate at room temperature conditions, such that the underlying upgrading process is disturbed. Another common method is by utilizing the tube metal temperature measurement (temperature of coil’s outer wall) as an estimation of the degree of coking of the coil, which in turn can be utilized to estimate the carburization. However, this method is an estimation of an estimation, thereby being subject to potential error in measurement.

[0008] Accordingly, the presently understood methods of carburization measurement come with noticeable drawbacks. However, the use of electrified cracking coils presents a unique opportunity to use the electric current and resistivity properties of the coil as a means of determining the degree of carburization of the coil, even while concurrently upgrading the hydrocarbons. This presents a noticeable advantage over the prior methods.

[0009] Particularly, by arranging a system with at least two thermocouples in contact with the electrified cracking coil, the thermocouples may be utilized both as a temperature sensor and a voltmeter, such that a determination of temperature and voltage may be determined at two discrete points in the electrified cracking coil. The voltages may in turn be converted to an observed resistance by calculating the voltage loss between the two points and dividing by the electric current through the coil. The observed resistance may then be converted into a coil resistivity utilizing the cross-section area of the coil and the length separating the thermocouples.

[0010] Finally, this coil resistivity can be plotted on a carburization plot vs. a matched average temperature curve. The carburization plot contains historical data of relative carburization (carbonAtorney Docket No.: 85999-WO-PCT / DOW 85999 WO3content) vs. resistivity for various surface temperatures of a material (expressed as a plurality of curves), such that a relative degree of carburization may be determined.

[0011] All of the above may be conducted while the coil remains in operation, such that realtime determinations of carburization can be estimated and intelligent decisions regarding decoking or coil replacement can be made.

[0012] According to one embodiment, a system for measuring carburization of an electrified cracking coil may comprise the electrified cracking coil, wherein the electrified cracking coil is electrified by electric current; and first and second thermocouples separated by a length along the electrified cracking coil, each thermocouple comprising: a first wire, a second wire, wherein the first wire and the second wire are joined at a junction proximate the electrified cracking coil, an electrically conductive sheath surrounding the first and second wires, wherein the electrically conductive sheath is in contact with the electrified cracking coil, a thermocouple sensor coupled to the first wire and the second wire opposite the junction, the thermocouple sensor configured to determine a temperature from a voltage difference between the first wire and the second wire, and a voltmeter electrically coupled to the electrically conductive sheath and configured to determine a voltage of the electrified cracking coil at a contact point between the electrically conductive sheath and the electrified cracking coil.

[0013] Another embodiment may include at least the previous embodiment, and may further comprise a method for measuring carburization of an electrified cracking coil comprising determining the temperature of the electrified cracking coil at the junctions of the first and second thermocouples; determining an average temperature between the first and second thermocouples based on the temperatures at the junctions of the first and second thermocouples; determining the voltage of the electrified cracking coil at the contact points of the first and second thermocouples; determining a voltage loss across the first and second thermocouples; converting the voltage loss into a resistance by dividing by the electric current to the electrified cracking coil; converting the RAresistance into a coil resistivity according to the formula p = — , wherein p is the coil resistivity,R is the resistance, A is the average cross-sectional area of the electrified cracking coil, and d is the length; and determining a relative degree of carburization of the electrified cracking coil basedAtorney Docket No.: 85999-WO-PCT / DOW 85999 WO4on interpolation of a data set comprising the average temperature, the coil resistivity, and varying carburization percentage for a electrified cracking coil composition.

[0014] Yet another embodiment may include at least the previous embodiment, and may further comprise adjusting a current to or replacing the electrified cracking coil based on the relative degree of carburization.

[0015] Additional features and advantages of the embodiments described herein will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the embodiments described, including the detailed description and the claims which are provided infra.BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The following detailed description of specific embodiments of the present disclosure can be best understood when read in conjunction with the following drawings in which:

[0017] FIG. 1 illustrates a system for measuring carburization of an electrified cracking coil in accordance with embodiments described herein;

[0018] FIG. 2 illustrates an exemplary carburization plot with carburization percentage on the x-axis, resistivity on the y-axis, and temperature as a plurality of curves, for a chromium, nickel, niobium, aluminum, and iron alloy coil, in accordance with embodiments described herein, and

[0019] FIG. 3 illustrates another exemplary carburization plot with carburization percentage on the x-axis, resistivity on the y-axis, and temperature as a plurality of curves, for a silicon, manganese, chromium, nickel, niobium, and titanium alloy coil, in accordance with embodiments described herein;

[0020] FIG. 4 illustrates the exemplary carburization plot of FIG. 3 with an exemplary demonstration of at least one manner in which the relative carburization may be determined;

[0021] FIG. 5 illustrates another version of the exemplary carburization plot of FIG. 2, with temperature on the x-axis, resistivity on the y-axis, and the carburization percentage as a plurality of curves;

[0022] FIG. 6 illustrates another version of the exemplary carburization plot of FIG. 3, with temperature on the x-axis, resistivity on the y-axis, and the carburization percentage as a plurality of curves; andAtorney Docket No.: 85999-WO-PCT / DOW 85999 WO5

[0023] FIG. 7 illustrates the exemplary carburization plot of FIG. 6 with an exemplary demonstration of at least one manner in which the relative carburization may be determined.

[0024] These and other aspects of the present systems and methods are described in further detail below with reference to the accompanying figures, in which one or more illustrated embodiments and / or arrangements of the systems and methods are shown. In the description of the embodiments that follows, like numerals denote like components across the various figures. The systems and methods of the present application are not limited in any way to the illustrated embodiments and / or arrangements. It should be understood that the systems and methods as shown in the accompanying figures are merely exemplary of the systems and methods of the present application, which can be embodied in various forms as appreciated by one skilled in the art. Therefore, it is to be understood that any structural and functional details disclosed herein are not to be interpreted as limiting the present systems and methods, but rather are provided as a representative embodiment and / or arrangement for teaching one skilled in the art one or more ways to implement the present systems and methods.DETAILED DESCRIPTION

[0025] Embodiments of the present disclosure generally relate to the field of refining and upgrading hydrocarbons, and pertain particularly to systems and methods for determining the degree of carburization of an electrified cracking coil.

[0026] For the purpose of describing the simplified schematic illustrations and descriptions of the relevant figures, the numerous temperature sensors, electronic controllers, lead lines and the like that may be employed and well known to those of ordinary skill in the art of certain chemical processing operations may not be included. However, it should be understood that these components are within the spirit and scope of the present embodiments disclosed. However, operational components, such as those described in the present disclosure, may be added to the embodiments described in this disclosure.

[0027] Additional features and advantages of the described embodiments, some embodiments of which are illustrated in the accompanying drawings, will be set forth in the detailed description, which follows, and in part will be readily apparent to those skilled in the art from that descriptionAtorney Docket No.: 85999-WO-PCT / DOW 85999 WO6or recognized by practicing the described embodiments, including the detailed description, which follows, as well as the claims.

[0028] Now referring to FIG. 1, illustrated is a system 100 for determining the carburization of a cracking coil 104. As shown in FIG. 1, the system 100 may comprise the cracking coil 104, a power source 112, a first thermocouple 120a, and a second thermocouple 120b. Although not illustrated, embodiments herein may comprise any number of electrified cracking coils 104 and any number of thermocouples greater than or equal to 2. For example, and without being limited by theory, it may be desired to measure the carburization of an extended length of the electrified cracking coil 104, such that there may be three thermocouples, the third thermocouple of which may be similarly positioned and configured as the first and second thermocouples 120a / 120b. Each of the thermocouples may also be spaced along the electrified cracking coil 104 by a distance “d”, which may vary between the specific thermocouples chosen.

[0029] In embodiments, the power source 112 may be configured to provide electric current to the cracking coil 104. Accordingly, in at least some embodiments, the cracking coil 104 may be regarded as an electrified cracking coil 104. In at least some embodiments, the power source 112 may be configured to supply an electric current to the electrified cracking coil 104, such that determinations of the carburization can be made, as explained in further detail herein. Further, the electric current may operate to heat the cracking coil 104, such that a feedstock 101, such as a hydrocarbon or hydrocarbon / steam mixture, transported within an internal channel 108 of the electrified cracking coil 104 is cracked and forms an upgraded product, such as ethylene. In embodiments, the feedstock 101 may comprise naphtha, gas oil, pyrolysis gasoline, Fischer -Tropsch derivatives, natural gas condensates, C1-C4 hydrocarbons, or combinations thereof. Additionally, the feedstock 101 may comprise steam.

[0030] The electrified cracking coil 104 may in turn comprise electrically conductive materials, such as alloys of transition metals, post-transition metals, metalloids, non-metals, or combinations thereof, such as, but not limited to, alloys of two or more of carbon, silicon, manganese, chromium, nickel, niobium, titanium, iron, or aluminum. For example, the electrified cracking coil 104 may comprise an alloy rich in (i.e. majority being) nickel and chromium (FIGS. 2 and 3). In embodiments, a surface temperature and / or internal temperature of the electrified cracking coil 104 in the operative system 100 may be from 25 °C to 1200 °C, such as from 25 °C to 100°C, fromAtorney Docket No.: 85999-WO-PCT / DOW 85999 WO7100 °C to 200 °C, from 200 °C to 600 °C, from 600 °C to 800 °C, from 800 °C to 900 °C, from 900 °C to 1100°C, from 1100 °C to 1200 °C, or combinations of the previous ranges or smaller ranges therein, such as from 200 °C to 900 °C. In at least some embodiments of the system 100, the electrified cracking coil 104 may be at least partially carburized and / or coked.

[0031] In embodiments, the electrified cracking coil 104 may have a circular, semi-circular, triangular, or polygonal cross-section, or frusto-variations thereof, with the same possibilities for the internal channel.

[0032] Still referring to FIG. 1, each of the thermocouples 120a / 120b may comprise similar or identical sub-components, designated 124a in the drawings with an “a” or “b” as appropriate. For example, and in embodiments, the thermocouples 120a / 120b may be N-type thermocouples, and may comprise a first wire 124 and a second wire 128, designated 124a and 128a for the first thermocouple 120a, and 124b and 128b for the second thermocouple 120b. In embodiments, the first wire 124 and the second wire 128 may be formed of two different electrically conductive materials, such as nicrosil and nisil. The first and second wires 124 / 128 may be joined at a junction 132, which may be proximate the electrified cracking coil 104, but may not be in direct contact with the same, as explained in further detail herein. The thermocouples 120a / 120b may also comprise a thermocouple sensor 140, which may be coupled to the first and second wires 124 / 128 opposite the junction 132. The thermocouple sensor 140 may be configured to determine a temperature from a voltage difference between the first wire 124 and the second wire 128.

[0033] In embodiments, the first and second wires 124 / 128 may comprise metal and / or semiconductor materials, such as but not limited to platinum with rhodium, chromel, iron, chromel, nicrosil, constantan, alumel, and nisil.

[0034] As shown in FIG. 1, each of the thermocouples 120a / 120b may further comprise an electrically conductive sheath 136. The electrically conductive sheath 136 may surround the first and second wires 124 / 128, such that the first and second wires 124 / 128 do not contact the electrified cracking coil 104. Further, the electrically conductive sheath 136 is in contact with the electrified cracking coil 104, such that at least a portion of the electric current from the electrified cracking coil 104 is transmitted through the electrically conductive sheath 136. The electrically conductive sheath 136 may in turn be electrically coupled to a voltmeter 144. As shown in at least FIG. 1, the voltmeter may comprise a resistor 145 having a known resistivity, such as from 10Atorney Docket No.: 85999-WO-PCT / DOW 85999 WO8MegaOhms to 1000 MegaOhms. Accordingly, the voltmeter 144 may be configured to determine a voltage of the electrified cracking coil 104 at the contact point between the electrically conductive sheath 136 and the electrified cracking coil 104.

[0035] In embodiments, the electrically conductive sheath 136 may comprise any electrically conductive metallic material, similar to the first and second wires 124 / 128, such as any electrically conductive metallic capable of withstanding temperatures greater than 1300 °C, such as from 1300 °C to 2,000, for example. In at least one embodiment, the sheath may comprise Alloy 600 (Ni-Cr) or alloy 304 (Fe-Ni-Cr) (stainless steel).

[0036] Still referring to FIG. 1, the first and second thermocouples 120a / 120b may further comprise an electrically insulating medium positioned between the electrically conductive sheath 136 and the first and second wires 124 / 128, such that the first and second wires 124 / 128 and junction 132 are not in electric contact with the electrically conductive sheath 136. In embodiments, the electrically insulating medium may comprise air, or any solid or liquid non-conductive medium, such as, but not limited to silicon and / or ceramics such as silicon carbide or magnesium oxide.

[0037] In at least some embodiments, the electrically insulating medium may be chosen such that it has a high thermal conductivity (i.e. is thermally conductive) in addition to its electrical insulation qualities. Without being limited by theory, choosing an electrically insulating medium with a high thermal conductivity may be of benefit in reducing any potential error induced by the electrically insulated medium shielding the first and second wires 124 / 128 from the heat of the electrified cracking coil 104.

[0038] Still referring to FIG. 1, the system 100 may further comprise a thermally insulated enclosure 148. As shown in FIG. 1, the thermally insulated enclosure 148 may surround at least a portion of the electrified cracking coil 104 as well as the first and second thermocouples 120a / 120b. However, in at least some embodiments the thermocouple sensor 140 and the voltmeter 144 may be positioned outside of the thermally insulated enclosure 148.

[0039] As also shown in FIG. 1, the system 100 may further comprise one or more grounds due to the system 100 being electrified. For example, and as shown, the system 100 may comprise a ground 116 connected to the thermally insulated enclosure 148, as well as supplemental grounds 118a / 118b for the first and second thermocouples 120a / 120b. As shown in FIG. 1, theAtorney Docket No.: 85999-WO-PCT / DOW 85999 WO9supplemental grounds may be connected down-current of each of the voltmeters, respectively. The thermally insulated enclosure 148 may also be generally electrically insulated from the electrified cracking coil 104 and the first and second thermocouples 120a / 120b, and particularly the electrically conductive sheaths 136a / 136b.

[0040] As previously stated, embodiments herein may also be directed to methods for measuring carburization of an electrified cracking coil 104. The methods may utilize any of the systems 100 previously described. Particularly, the method may initially comprise determining the temperature of the electrified cracking coil 104 at the junctions 132a / 132b of the first and second thermocouples 120a / 120b, such as by utilizing the thermocouple sensors 140a / 140b. The method may also comprise determining an average temperature between the first and second thermocouples 120a / 120b based on the temperatures at the junctions 132a / 132b of the first and second thermocouples 120a / 120b. Further, the method may comprise determining the voltage of the electrified cracking coil 104 at the contact points of the first and second thermocouples 120a / 120b, such as by utilizing the voltmeters 144a / 144b, and determining a voltage loss across the first and second thermocouples 120a / 120b.

[0041] The method may then further comprise converting the voltage loss into a resistance by dividing the electric current supplied to the electrified cracking coil 104, as previously explained.RAThe resistance may then be converted into a coil resistivity according to the formula p = — ,wherein p is the coil resistivity, R is the resistance, A is the average cross-sectional area of the electrified cracking coil 104, and d is the length separating the first and second thermocouples 120a / 120b.

[0042] The relative degree of carburization may then be determined based on interpolation of a data set comprising average temperatures, resistivities, and varying carburizations based on the composition of the electrified cracking coil being tested. For instance, experimental data may be collected wherein a slice, coupon, or sample of a used electrified cracking coil is subjected to various electrical currents. The subsequent resistivity and temperature in response to the current may then be recorded, along with a degree of carburization determined utilizing a scanning electron microscope or otherwise. This data can then be compiled with other coil slices, coupons, or samples of varying degrees of carburization to fill out the data set including averageAttorney Docket No.: 85999-WO-PCT / DOW 85999 WO10temperatures, resistivities, and carburizations. This is shown below for example in Tables 1 and 2, which illustrate temperature and resistivity data for coils having no carburization (fresh) 2% carburization (mid-life), and 4% carburization (end of life).

[0043] Table 1 : Cr-Ni-Nb-Al-Fe Alloy Coil Carburization Data

[0044] Table 2: Si-Mn-Cr-Ni-Nb-Ti-Fe Alloy Coil Carburization Data

[0045] For example, and in embodiments, the measured average temperature and the resistivity may be used to interpolate a relative degree of carburization based on the data set, such as the dataAtorney Docket No.: 85999-WO-PCT / DOW 85999 WO11sets provided in Table 1 and Table 2 above. For instance, an average temperature of around 1000 °C and average resistivity of around 5* 1 O'7utilizing the data set of Table 2 would indicate a relative degree of carburization between 2% (mid-life) and 4% (end-of-life). Without being limited by theory, increasingly accurate interpolations may be made a larger number of data sets, which is contemplated in embodiments herein and is only not included for brevity and conciseness of the present embodiments.

[0046] Further, without being limited by theory, while the above tables are expressed in terms of temperature and resistivity for varying degrees of carburization, it is contemplated that the three variables may be rearranged for generating other transformations of the data set. For example, and in embodiments, the data set may be expressed as carburization percentage vs. resistivity for varying temperatures. This may be of benefit when utilizing the carburization plot, which is at least one option for the interpolation of the data set, as explained in further detail herein with regards to FIGS. 2-7.

[0047] Particularly, as shown in FIGS. 2-7, and in embodiments of the method herein, determining a relative degree of carburization of the electrified cracking coil based on interpolation of a data set of the average temperature, the coil resistivity, and varying carburization percentage for a electrified cracking coil composition may comprise mapping the coil resistivity, the average temperature, and the varying carburization percentage to a carburization plot.

[0048] For example, and in embodiments, data associated with one of the average temperature, the coil resistivity, or the varying carburization percentage may be fixed to an x-axis of the carburization plot. Data associated with another of the average temperature, the coil resistivity, or the varying carburization percentage may be fixed to a y-axis of the carburization plot. Finally, the remaining data of the average temperature, the coil resistivity, or the varying carburization percentage may be ploted as a plurality of curves as a function of the data affixed to the x-axis and the y-axis.

[0049] As shown in FIGS. 2 and 3, one version of the carburization plot maps a carburization percentage (x-axis) vs. resistivity (y-axis) for a coil of composition at varying tube metal temperatures, expressed as a plurality of (surface temperature) curves. Accordingly, by matching the average temperature to one of the surface temperature curves, and by mapping the coilAtorney Docket No.: 85999-WO-PCT / DOW 85999 WO12resistivity to the y-axis of the carburization plot, the relative degree of carburization of the cracking coil may be deduced by a relative position within the plot.

[0050] In the event that the average temperature does not directly match one of the plurality of temperature curves, a relative position between the two nearest curves above and below the average temperature may be estimated. This relative position may then be intersected with the resistivity to deduce the relative degree of carburization of the electrified cracking coil 104. This may be shown for example in FIG. 4 for an average temperature of 1000 °C as compared to the measured resistivity of 5 *10'7ohm*meters (dashed line), for an estimated carburization of 3.1%.

[0051] Alternatively FIGS. 5 and 6 illustrate another version of the carburization plot mapping temperature (x-axis) vs. resistivity (y-axis) for a coil of composition at varying carburization percentages, expressed as a plurality of (carburization) curves. Accordingly, by determining a relative proximity of the mapped coil resistivity and average temperature to one of the curves, a determination of the relative degree of carburization may be made. This may be shown for example in FIG. 4 for an average temperature of 1000 °C as compared to the measured resistivity of 5 *10’7ohm*meters (dashed line), for an estimated carburization of between 3% to 3.5%.

[0052] Further, as shown in FIGS. 5-7, it is contemplated there may be certain areas in which the carburization plot curves converge or diverge from each other. Accordingly, it may be appreciated that selecting an x-axis range (average temperature, resistivity, or carburization percentage) within the diverging curve range may allow more accurate determinations of the relative degree of carburization vs. a selection of the converging areas.

[0053] For example, and in embodiments, the method may further comprise altering the electric current to the system such that the average temperature is within the range at which the curves most diverge from each other. In at least some embodiments, the electric current may be altered such that the average temperature between the first and second thermocouples is from 25 °C to 900 °C, such as from 25 to 100 °C, from 100 to 200 °C, from 200 to 300 °C, from 300 to 400 °C, from 400 to 500 °C, from 500 to 600 °C, from 600 to 700 °C, from 700 to 800 °C, from 800 to 900 °C, or any combinations of the previous ranges or smaller ranges therein, such as from 500 °C to 700 °C, which may also be the temperature range at which the curves most diverge from each other in at least some embodiments.Atorney Docket No.: 85999-WO-PCT / DOW 85999 WO13

[0054] Further, if it is determined that the degree of carburization exceeds a predetermined threshold based on the experience of field personnel and / or the specs of the coil, one or more operations to remove the coke and / or remediate the carburization may be taken. For example, and without being limited by theory, these operations may include adjusting a current to the electrified cracking coil 104, conducting a decoking cycle in the electrified cracking coil 104, or replacing the electrified cracking coil 104.

[0055] With regards to the adjustment of current, it is contemplated that the degree of carburization may be related to the degree of coke layering in the internal channel 108 of the coil. This coke may act as a barrier to the transfer of heat to the feedstock 101, and correspondingly may operate to decrease the desired yields of the upgrading process. Accordingly, by making an informed adjustment to the current supplied to the coil based on the relative degree of carburization determined in real-time, desired yields of the process may be optimized over the entire lifetime of the coil.

[0056] With regards to the decoking cycle, it is contemplated that there may be a point in which it no longer makes sense to increase the current to the coils to counteract the coke layering, and / or the degree of carburization is approaching a level at which coil structural integrity is at risk. Accordingly, real-time determinations of the resistance and the average temperature, such as through embodiments herein, may allow informed implementation of a decoking cycle to remove the layered coke and / or proactively remove the layered coke before substantial carburization takes place. As compared to eddy-current carburization measurement, the present embodiments may be of particular benefit in not requiring that the upgrading process be halted to assess the coils. Instead, the process may progress continuously or almost continuously from upgrading to decoking.

[0057] With regards to FIGS. 3-7, the composition of the electrified cracking coils 104 were as follows in Table 1.

[0058] Table 1 : Composition of Cracking Coils in FIGS. 3-7&Atorney Docket No.: 85999-WO-PCT / DOW 85999 WO14&

[0059] As used herein, “decoking” generally refers to a process in which steam and / or air instead of the feedstock 101 is introduced at high temperature into a coked cracking coil 104, which operates to combust and gasify the layered coke within the coil.

[0060] The present disclosure may include one or more aspects. Particularly, according to a first aspect, a system for measuring carburization of an electrified cracking coil may comprise the electrified cracking coil, wherein the electrified cracking coil is electrified by a electric current; and first and second thermocouples separated by a length along the electrified cracking coil, each thermocouple comprising: a first wire, a second wire, wherein the first wire and the second wire are joined at a junction proximate the electrified cracking coil, an electrically conductive sheath surrounding the first and second wires, wherein the electrically conductive sheath is in contact with the electrified cracking coil, a thermocouple sensor coupled to the first wire and the second wire opposite the junction, the thermocouple sensor configured to determine a temperature from a voltage difference between the first wire and the second wire, and a voltmeter electrically coupled to the electrically conductive sheath and configured to determine a voltage of the electrified cracking coil at a contact point between the electrically conductive sheath and the electrified cracking coil.

[0061] A second aspect may comprise the first aspect, wherein the first and second thermocouples further comprise an electrically insulating substance positioned between the electrically conductive sheath and the first and second wires.

[0062] A third aspect may comprise either the first aspect or the second aspect, wherein the electrically insulating substance is a ceramic.

[0063] A fourth aspect may comprise any previous aspect, wherein the electrified cracking coil is configured to transport a gas within an internal channel of the electrified cracking coil.

[0064] A fifth aspect may comprise any previous aspect, further comprising a thermally insulated enclosure surrounding at least a portion of the electrified cracking coil, the first thermocouple, the second thermocouple, or combinations thereof.Atorney Docket No.: 85999-WO-PCT / DOW 85999 WO15

[0065] A sixth aspect may comprise any previous aspect, wherein the thermocouple sensor and the voltmeter are positioned outside of the thermally insulated enclosure.

[0066] A seventh aspect may comprise any previous aspect, wherein the electrified cracking coil comprises alloys of transition metals, post-transition metals, metalloids, non-metals, or combinations thereof.

[0067] An eighth aspect may comprise any previous aspect, wherein the electrified cracking coil is at least partially carburized.

[0068] A ninth aspect may comprise any previous aspect, wherein the electrically conductive sheath is metallic.

[0069] A tenth aspect may comprise any previous aspect, wherein a surface temperature, an internal temperature, or both, of the electrified cracking coil is between 25 °C and 1200 °C.

[0070] An eleventh aspect may comprise any previous aspect, and may further comprise a method for measuring carburization of an electrified cracking coil, the method comprising: determining the temperature of the electrified cracking coil at the junctions of the first and second thermocouples; determining an average temperature between the first and second thermocouples based on the temperatures at the junctions of the first and second thermocouples; determining the voltage of the electrified cracking coil at the contact points of the first and second thermocouples; determining a voltage loss across the first and second thermocouples; converting the voltage loss into a resistance by dividing by the electric current to the electrified cracking coil; converting the RAresistance into a coil resistivity according to the formula p = — , wherein p is the coil resistivity, R is the resistance, A is the average cross-sectional area of the electrified cracking coil, and d is the length; determining a relative degree of carburization of the electrified cracking coil based on interpolation of a data set comprising the average temperature, the coil resistivity, and varying carburization percentage for a electrified cracking coil composition; and adjusting a current to or replacing the electrified cracking coil based on the relative degree of carburization.

[0071] A twelfth aspect may comprise the eleventh aspect, further comprising altering the electric current to the system such that the average temperature between the first and second thermocouples is from 25 °C to 900 °C.Atorney Docket No.: 85999-WO-PCT / DOW 85999 WO16

[0072] A thirteenth aspect may comprise either the tenth or eleventh aspects, wherein the average surface temperature of the electrified cracking coil is from 200 °C to 1100 °C.

[0073] A fourteenth aspect may comprise any of the tenth through thirteenth aspects, further comprising passing a feedstock through an internal channel of the electrified cracking coil concurrently with determining the temperatures, determining the average temperature, determining the voltages, determining the voltage loss, converting the voltage loss into the resistance, and converting the resistance into a coil resistivity.

[0074] A fifteenth aspect may comprise any of the tenth through fourteenth aspects, wherein determining a relative degree of carburization of the electrified cracking coil based on interpolation of the data set comprises: obtaining a plot, wherein: data associated with one of the average temperature, the coil resistivity, or the varying carburization percentage is fixed to an x-axis of a carburization plot, data associated with another of the average temperature, the coil resistivity, or the varying carburization percentage is fixed to a y-axis of the carburization plot, and the remaining data of the average temperature, the coil resistivity, or the varying carburization percentage is plotted as a plurality of curves as a function of the data affixed to the x-axis and the y-axis; and determining the relative degree of carburization of the electrified cracking coil by a relative position within the plot.

[0075] It is noted that recitations in the present disclosure of a component of the present disclosure being “operable” or “sufficient” in a particular way, to embody a particular property, or to function in a particular manner, are structural recitations, as opposed to recitations of intended use. More specifically, the references in the present disclosure to the manner in which a component is “operable” or “sufficient” denotes an existing physical condition of the component and, as such, is to be taken as a definite recitation of the structural characteristics of the component.

[0076] The singular forms “a,” “an” and “the” include plural referents, unless the context clearly dictates otherwise.

[0077] Throughout this disclosure ranges are provided. It is envisioned that each discrete value encompassed by the ranges are also included. Additionally, the ranges which may be formed by each discrete value encompassed by the explicitly disclosed ranges are equally envisioned.Atorney Docket No.: 85999-WO-PCT / DOW 85999 WO17

[0078] As used in this disclosure and in the appended claims, the words “comprise,” “has,” and “include” and all grammatical variations thereof are each intended to have an open, non-limiting meaning that does not exclude additional elements or steps.

[0079] As used in this disclosure, terms such as “first”, “second”, “third”, etc. are arbitrarily assigned and are merely intended to differentiate between two or more instances or components. It is to be understood that the words “first”, “second”, “third”, etc. serve no other purpose and are not part of the name or description of the component, nor do they necessarily define a relative location, position, or order of the component. Furthermore, it is to be understood that the mere use of the term “first”, “second”, or “third” does not require that there be any “fourth” component, although that possibility is contemplated under the scope of the present disclosure.

[0080] For the purposes of describing and defining the present embodiments it is noted that the terms “substantially” and “approximately” are utilized herein to represent the inherent degree of uncertainty that may be attributed to any quantitative comparison, value, measurement, or other representation. The terms “substantially” and “approximately” are also utilized herein to represent the degree by which a quantitative representation may vary from a stated reference without resulting in a change in the basic function of the subject matter at issue.

[0081] Having described the subject mater of the present disclosure in detail and by reference to specific embodiments, it is noted that the various details disclosed in the present disclosure should not be taken to imply that these details relate to elements that are essential components of the various embodiments described in the present disclosure. Further, it will be apparent that modifications and variations are possible without departing from the scope of the present disclosure, including, but not limited to, embodiments defined in the appended claims.

Claims

Atorney Docket No.: 85999-WO-PCT / DOW 85999 WO18CLAIMS1. A system for measuring carburization of an electrified cracking coil comprising:the electrified cracking coil, wherein the electrified cracking coil is electrified by an electric current; andfirst and second thermocouples separated by a length along the electrified cracking coil, each thermocouple comprising:a first wire,a second wire, wherein the first wire and the second wire are joined at a junction proximate the electrified cracking coil,an electrically conductive sheath surrounding the first and second wires, wherein the electrically conductive sheath is in contact with the electrified cracking coil, a thermocouple sensor coupled to the first wire and the second wire opposite the junction, the thermocouple sensor configured to determine a temperature from a voltage difference between the first wire and the second wire, and a voltmeter electrically coupled to the electrically conductive sheath and configured to determine a voltage of the electrified cracking coil at a contact point between the electrically conductive sheath and the electrified cracking coil.

2. The system of claim 1, wherein the first and second thermocouples further comprise an electrically insulating substance positioned between the electrically conductive sheath and the first and second wires.

3. The system of claim 2, wherein the electrically insulating substance is a ceramic.

4. The system of any previous claim, wherein the electrified cracking coil is configured to transport a gas within an internal channel of the electrified cracking coil.Atorney Docket No.: 85999-WO-PCT / DOW 85999 WO195. The system of any previous claim, further comprising a thermally insulated enclosure surrounding at least a portion of the electrified cracking coil, the first thermocouple, the second thermocouple, or combinations thereof.

6. The system of claim 5, wherein the thermocouple sensor and the voltmeter are positioned outside of the thermally insulated enclosure.

7. The system of any previous claim, wherein the electrified cracking coil comprises alloys of transition metals, post-transition metals, metalloids, non-metals, or combinations thereof.

8. The system of any previous claim, wherein the electrified cracking coil is at least partially carburized.

9. The system of any previous claim, wherein the electrically conductive sheath is metallic.

10. The system of any previous claim, wherein a surface temperature, an internal temperature, or both, of the electrified cracking coil is between 25 °C and 1200 °C.

11. A method for measuring carburization of an electrified cracking coil utilizing the system of any previous claim, the method comprising:determining the temperature of the electrified cracking coil at the junctions of the first and second thermocouples;determining an average temperature between the first and second thermocouples based on the temperatures at the junctions of the first and second thermocouples;determining the voltage of the electrified cracking coil at the contact points of the first and second thermocouples;determining a voltage loss across the first and second thermocouples;converting the voltage loss into a resistance by dividing by the electric current to the electrified cracking coil;Atorney Docket No.: 85999-WO-PCT / DOW 85999 WO20converting the resistance into a coil resistivity according to the formula p = — wherein pis the coil resistivity, R is the resistance, A is the average cross-sectional area of the electrified cracking coil, and d is the length;determining a relative degree of carburization of the electrified cracking coil based on interpolation of a data set comprising the average temperature, the coil resistivity, and varying carburization percentage for a given electrified cracking coil composition; andadjusting a current to or replacing the electrified cracking coil based on the relative degree of carburization.

12. The method of claim 11, further comprising altering the electric current to the system such that the average temperature between the first and second thermocouples is from 25 °C to 900 °C.

13. The method of claim 11, wherein the average surface temperature of the electrified cracking coil is from 200 °C to 1100 °C.

14. The method of either claim 11 or 12, further comprising passing a feedstock through an internal channel of the electrified cracking coil concurrently with determining the temperatures, determining the average temperature, determining the voltages, determining the voltage loss, converting the voltage loss into the resistance, and converting the resistance into a coil resistivity.

15. The method of any of claims 12-14, wherein determining a relative degree of carburization of the electrified cracking coil based on interpolation of the data set comprises:obtaining a plot, wherein:data associated with one of the average temperature, the coil resistivity, or the varying carburization percentage is fixed to an x-axis of a carburization plot, data associated with another of the average temperature, the coil resistivity, or the varying carburization percentage is fixed to a y-axis of the carburization plot, andAttorney Docket No.: 85999-WO-PCT / DOW 85999 WO21the remaining data of the average temperature, the coil resistivity, or the varying carburization percentage is plotted as a plurality of curves as a function of the data affixed to the x-axis and the y-axis; anddetermining the relative degree of carburization of the electrified cracking coil by finding a relative position within the plot based on the data in the x-axis and the data in the y-axis of the plot.

Images