Multi-row radiant coil arrangement for cracking heaters used in olefin production

Abstract

A system for cracking hydrocarbons includes a flame heater having a radiant section and a convection section. A radiant coil is disposed within the radiant section of the heater, the radiant coil having three to seven rows of tubes, each row including two multi-pass tubes, and wherein the multi-pass tubes in the three to seven rows of tubes are arranged symmetrically or pseudo-symmetrically within the radiant section of the heater. The system also includes a transmission line exchanger fluidly connected to the outlet tube of each of the three to seven rows of tubes.

Description

Technical Field

[0001] The embodiments of this disclosure generally relate to heaters for hydrocarbon cracking. More specifically, the embodiments herein relate to the design of cracking heaters and the arrangement of radiant coils. Background Technology

[0002] Most cracking heaters used in ethylene production employ a single-row, in-line arrangement of radiant coils. In some cases, two rows are arranged in an offset or staggered configuration.

[0003] Figure 14 The diagram illustrates an example of a radiant coil. Feed is distributed via a venturi tube 2 to multiple inlet tubes 10 (e.g., ...). Figure 14 The coils shown are eight in number. Feed passes through the radiant zone of the heater, merges into manifold 4, and is then supplied through larger diameter outlet pipes 12 to transfer line exchangers (also known as in-line heat exchangers or oil-to-line heat exchangers) 14. As shown, each has two outlet pipes 10 (left and right sides of TLE 14), and thus this configuration has a total of four outlets. Figure 14 Only one side of TLE 14 is shown in the image.

[0004] Other short dwell time (SRT) coils are available from Lummus Technology LLC, including SRT-1 (typically an 8-pass (or channel) serpentine coil: denoted as 1-1-1-1-1-1-1-1) to SRT VII (typically with 32 inlet tubes and 4 outlet tubes); SRT II-VI have different designs. Two outlet tubes can be joined and connected to the TLE via a single wye fitting, or four outlet tubes can be directly connected to the TLE. Currently, a maximum of four outlet tubes can be connected to the TLE.

[0005] Similarly, US7964091 describes a three-row arrangement for 1-1 and 2-1 coils. A similar arrangement for six-pass coils is also described. Summary of the Invention

[0006] One or more embodiments disclosed herein relate to a system for cracking hydrocarbons, comprising a flame heater having a radiant section and a convection section. A radiant coil is disposed within the radiant section of the heater, the radiant coil having three to seven rows of tubes, each row comprising two multi-pass tubes, and wherein the multi-pass tubes in the three to seven rows of tubes are symmetrically or pseudo-symmetrically arranged together within the radiant section of the heater. The system also includes a transmission line exchanger fluidly connected to the outlet tube of each of the three to seven rows of tubes.

[0007] One or more embodiments disclosed herein relate to a system for cracking hydrocarbons, comprising a flame heater having a radiant section and a convection section. A radiant coil is disposed within the radiant section of the heater, the radiant coil having three to seven rows of tubes, wherein each row is symmetrically or pseudo-symmetrically disposed together within the radiant section of the heater. The system also includes a transmission line exchanger fluidly connected to the outlet pipe of each of the three to seven rows of tubes.

[0008] One or more embodiments disclosed herein relate to a method for cracking hydrocarbons. The method includes heating a hydrocarbon feedstock in one or more rows of tubes in the radiant section of a flame heater having a radiant section and a convection section. Each row of tubes includes two multi-pass tubes, wherein the multi-pass tubes in three to seven rows are symmetrically or pseudo-symmetrically arranged together within the radiant section of the heater. The method also includes cracking one or more hydrocarbons in the hydrocarbon feedstock in one or more rows of tubes, recovering the cracked hydrocarbon stream from an outlet tube on each of the one or more rows of tubes, and supplying the cracked hydrocarbons to a transfer line exchanger fluidly connected to the outlet tubes of each of the one or more rows of tubes.

[0009] Based on the following description, those skilled in the art will understand other embodiments disclosed herein. Attached Figure Description

[0010] In the accompanying drawings, where appropriate, the same reference numerals correspond to the same parts.

[0011] Figure 1 and 1A The illustration shows a radiant coil arrangement for use in a pyrolysis heater according to one or more embodiments disclosed herein.

[0012] Figure 2 The illustration shows a radiant coil arrangement for use in a pyrolysis heater according to one or more embodiments disclosed herein.

[0013] Figure 3A and Figure 3B The illustration shows an arrangement for connecting a coil to a transmission line switch according to one or more embodiments disclosed herein.

[0014] Figure 4 The illustration shows a radiant coil arrangement for use in a pyrolysis heater according to one or more embodiments disclosed herein.

[0015] Figure 5 The illustration shows a radiant coil arrangement for use in a pyrolysis heater according to one or more embodiments disclosed herein.

[0016] Figure 6 The illustration shows a radiant coil arrangement for use in a pyrolysis heater according to one or more embodiments disclosed herein.

[0017] Figure 7 The illustration shows a radiant coil arrangement for use in a pyrolysis heater according to one or more embodiments disclosed herein.

[0018] Figure 8 The illustration shows a radiant coil arrangement for use in a pyrolysis heater according to one or more embodiments disclosed herein.

[0019] Figure 9 The illustration shows a radiant coil arrangement for use in a pyrolysis heater according to one or more embodiments disclosed herein.

[0020] Figure 10 The illustration shows a radiant coil arrangement for use in a pyrolysis heater according to one or more embodiments disclosed herein.

[0021] Figure 11 The illustration shows a radiant coil arrangement for use in a pyrolysis heater according to one or more embodiments disclosed herein.

[0022] Figure 12 The illustration shows a radiant coil arrangement for use in a pyrolysis heater according to one or more embodiments disclosed herein.

[0023] Figure 13A and 13B The illustration shows a radiant coil arrangement for use in a pyrolysis heater according to one or more embodiments disclosed herein.

[0024] Figure 14 The diagram illustrates the coil configuration of the prior art. Detailed Implementation

[0025] As used herein, coil configurations can be referred to as having an xy arrangement, an xyz arrangement, an xyzw arrangement, or other arrangements, where x refers to the number of inlet tubes and y refers to the number of tubes in the next pass (whether the outlet pass (xy) or the second pass xyz), where z is the number of outlet passes. For example, see reference Figure 14 The arrangement is 4-1, in which four inlet pipes 10 supply one outlet pipe 12. Figure 14The coil arrangement comprises two rows of 10 tubes on each side, and can therefore be referred to as 16-4 (8-2 from the left as shown and 8-2 from the right as not shown); however, for simplicity, subgroups are usually referred to, each subgroup being 4-1. For other multi-pass arrangements, the number of tubes in each pass is defined, where 1-1-1-1-1-1-1-1 is an eight-pass serpentine coil, and a 4-2-1 coil has four inlet tubes connected to two tubes, such as to the second pass of the double-tube coil via Y-connectors, and then to a single outlet tube. As a general definition of “n” double-pass coils with “m” inlet tubes for each outlet tube, a single coil will have “m*2n–2n” arrangements for a single coil, where n refers to the number of rows (n = 1, 2, 3, also referred to as rows in this document). For simplicity, Figure 14 The diagram illustrates the cross-sectional line "XX". Figure 1 and Figure 4-12 The arrangement of coils in such a cross-section is shown. However, Figure 14 The diagram illustrates a 4-1 coil arrangement, while other diagrams show more or fewer inlet and outlet pipes, as well as different arrangements. The diagram illustrates... Figure 14 The prior art coil is provided for the purpose of better understanding the graphical illustration of the coil according to the embodiments disclosed herein.

[0026] The pyrolysis heater is designed to produce a specific amount of ethylene. Selectivity, i.e., the amount of ethylene converted per unit weight of feed, is important for economics in the industry. Therefore, multiple coils are used in a single heater, but each coil can be arranged in a near-linear manner to avoid coil bending. By providing multiple inlet tubes for each outlet tube, the fluid can be heated rapidly and thus pyrolysis can occur at high temperatures within a short residence time (almost entirely in the outlet tube). This results in high selectivity. Simultaneously, the outlet tube has a low surface area to volume ratio. Coke (a byproduct of the pyrolysis reaction) is a solid, and its yield is a strong function of heat transfer surface area and other transport parameters. Therefore, the coke deposition rate can be reduced using a split coil arrangement. Conventional tubes can have relatively small diameters throughout the process, and therefore many radiant coils (more than 8 coils, and sometimes up to 36 coils) must be combined to obtain an equivalent ethylene production capacity to the single split coil described herein.

[0027] Therefore, one or more embodiments of this paper relate to a cracking heater design. More specifically, embodiments of this paper relate to the coil arrangement within a cracking heater and with respect to a transmission line exchanger. By arranging the coil according to embodiments of this paper, it is possible to reduce heater costs for a given ethylene production capacity and to simplify operation, reduce coke formation, or both.

[0028] The cracking heater according to embodiments of this invention may include radiant coils arranged in multiple rows, said multiple rows having more than two rows of coils. The cracking heater according to embodiments of this invention may comprise multiple radiant coils. The coils can be used to crack hydrocarbons such as ethane, propane, butane, as well as heavier hydrocarbons and mixtures, including naphtha or other heavier hydrocarbons. Cracking can result in the formation of lighter hydrocarbon molecules, including olefins such as ethylene, propylene, and butene. Following the cracking reaction in the radiant coils, the reaction effluent is rapidly quenched in a transfer line heat exchanger (TLE), thereby generating, for example, steam. In some cases, the effluent can be quenched with water or oil, a process known as direct quenching. However, direct quenching can be inefficient, while indirect quenching with the generation of ultra-high temperature steam is the most economically attractive way to freeze or stop the reaction.

[0029] With a design utilizing multiple radiating coils, the coils cannot be individually connected to a transmission line switch (TLE) because this would be very expensive and require a significant amount of space. Therefore, in one or more embodiments described herein, multiple radiating coils are grouped and connected to a single TLE. For multi-pass coils, this requires all outlet coils to be very close together.

[0030] However, placing the outlet pipe very close together can cause problems when arranging multi-pass coils. For some arrangements, the shading effect or reduction in total heat exchange, convection, and radiation can be considerable due to the coil and its relative placement to the burner, and the radiant coil running length can be significantly reduced.

[0031] The embodiments described in this paper provide radiant coils arranged in multiple rows, which have shorter operating lengths while also enabling multiple outlet pipes to be connected to a single TLE. Therefore, one or more embodiments can increase heater capacity, reduce the number of TLEs, and simplify convection section design.

[0032] The coils according to the embodiments described herein can have multiple inlet and outlet pipes. The coils can also have multiple passes, such as two to twelve passes. For example, the embodiments described herein can relate to arrangements of multiple coils with 4-1 to 16-1 configurations. The embodiments described herein can also be extended beyond these configurations to include fewer or more coils and fewer or more passes. The embodiments described herein can also be used with two-pass coils, multi-pass coils, four-pass coils, six-pass coils, or serpentine coils (which can have 8 to 14 passes). Regardless of the configuration, the embodiments described herein can connect multiple coils to a single TLE. Therefore, the embodiments described herein can provide arrangements and effective quenching of systems with more than four outlet pipes (such as six, eight, ten, or twelve outlet pipes).

[0033] Because the embodiment described herein connects numerous coils to a single TLE, the ethylene production capacity per coil can be increased. The number of convection stages and convection tubes, based on the number of radiant coils, is also correspondingly reduced, as are the number of control valves, control loops, and radiant burners. This allows for the use of larger capacity heaters instead of a greater number of smaller capacity heaters. Currently, due to limitations in the number of convection stages, the ethylene production capacity per heater is approximately 200-300 kTA (thousand tons per year). Using the arrangement described in this embodiment, for the same number of convection stages, the capacity can be increased by 50% (i.e., each heater could potentially reach 300-450 kTA).

[0034] The coil and pipe arrangement according to the embodiments described herein can have multiple rows. The required number of rows can be arranged on both sides of the center of the arrangement, or they can be arranged along a center line. For simplicity, this is exemplified by... Figure 1 The diagram illustrates three rows A, B, and C. However, this can be extended to more than three rows, as illustrated with four rows A, B, C, and D. Figure 10 And the diagram shows five rows of A, B, C, D, and E. Figure 11 and 12 As shown. With more than five rows, the benefit may not be as high as with three rows. When using a linear TLE, multiple rows (more than three rows) may have more benefit. In one or more embodiments disclosed herein, any number of rows from three (3) to sixteen (16) may be used. For example, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or 16 rows may be used.

[0035] In one example, a typical three-row arrangement with 6-1 type coils can have a two-way coil, where there are six inlet pipes for each outlet pipe. Typically, the inlet pipe diameter is much smaller than the outlet pipe diameter. For example, for most two-way coils, the inlet pipe can be 1.25 inches inside diameter (ID) to 2.5 inches inside diameter. For multi-way coils, the inner diameter can be larger. For the outlet pipe, the diameter can be greater than 3 inches. The pipe spacing to outer diameter (OD) ratio can vary from 1.2 to 3.0, such as from 1.4 to 2.0. In an exemplary arrangement, six rows of 6-1 (6 inlet pipes, one outlet pipe, six rows of pipes) can be connected to a single TLE. The first 6-1 coil will be positioned south of the centerline. The second 6-1 will be positioned at the centerline of the radiating unit. The third 6-1 will be north of the centerline. The three outlets can be connected to a leg of a Y-connector via a three-way connector. The mirror image from the TLE centerline will be the other three coils. Therefore, there can be two three-way connectors that connect to a single inverted Y-connector, which in turn connects to the TLE. All six of these 6-1 tubes constitute a single coil. These six coils can be arranged in different ways, as further illustrated and described below.

[0036] To follow along with Figure 14 The diagram, showing cross-sectional sections similar to those in the XX section, illustrates many possible arrangements for multi-row implementations. The underlying principles are similar, for example, referring to a 24-6 coil or a six-row 4-1 type. In a given radiating unit, more than one 24-6 coil can exist to increase capacity. Anything described for one coil applies to all coils.

[0037] Now for reference Figure 1 Coil A can be on one side of the center row. Coil B can be located on the center row. Coil C can be on the other side of the center row. Four inlet pipes 10 in each row supply corresponding outlet pipes 12 in the same row. The three outlet pipes 12 can then be connected to a three-way connector (not shown). A Y-connector can be used to connect the outlet of the three-way connector to a TLE (not shown). Figure 1 A mirror image of the coil arrangement in the image, where the other side of TLE is connected to coils A', B', and C' in a similar manner, as shown below. Figure 1A As shown in the image.

[0038] In this way, six outlet pipes 12 can be connected to a single conventional TLE with an inlet nozzle. The inlet of the TLE can be an elliptical chamber. Figure 3A As shown, all six outlet pipes 12 can be connected to the elliptical chamber 20. Figure 3B The illustration shows an elliptical chamber 20 along a cross-section YY. Compared to a three-way connector and a Y-joint, as... Figure 3A and 3BThe direct connection shown allows for a low adiabatic volume. This reduces residence time and increases olefin selectivity. The elliptical chamber is internally profiled to enhance flow distribution to the TLE tube and minimize residence time. By eliminating all three-joints and Y-joints, the heater cost can be reduced compared to conventional tapered inlets.

[0039] Refer again Figure 1A There are multiple arrangements for these six rows of 4-1 type coils. Such an arrangement... Figure 4-12 The concept is shown and further described below. This design can be extended to more than three rows. In the case of four rows, two rows will be on one side of the centerline, and two rows will be on the other side. Instead of three-connectors, four-connectors can be used to bring outlet pipe 12 to the TLE. In some embodiments, two Y-connectors (often referred to as three-Y-connectors) connected to another Y-connector can also be used. In such an arrangement, a 4-1 type coil with eight such rows connected to a TLE is equivalent to a 32-8 type coil. In the case of a five-row 4-1 type, for example, it is equivalent to a 40-10 type supplying a TLE. For all these cases, a conventional TLE with a single inlet can be used, which requires multiple three / four / five-connectors connected to Y-connectors connected to a single TLE inlet.

[0040] like Figure 2 As shown, two three-way connectors 30 are connected to a Y-connector 32. Three outlet pipes 12 on the upper left side are connected to the three-way connectors 30, and then to one leg of the Y-connector 32. The other three outlet pipes 12 are connected to the second three-way connector 30, and then to the other leg of the Y-connector 32. The outlet of the Y-connector can be connected to a conventional TLE with a tapered inlet 34.

[0041] However, in some implementations, all outlet coils 12 can be directly connected to the elliptical chamber on the TLE, which eliminates the need for any three / four / five connectors and Y-joints, such as Figure 3A and 3B As shown in the diagram. When there are many outlet pipes (>4), a linear exchanger with two 4-1 coils or a single 4-1 coil can be connected to a dual-pipe exchanger (also known as a linear exchanger).

[0042] Although regarding the 4-1 type coil as a basic unit Figure 1While descriptions and explanations have been provided, the embodiments described herein are applicable to other types of coils, including, for example, type 1-1, type 2-1, type 3-1, type 5-1, and others up to type 16-1. The embodiments described herein are also applicable to other branch coils. For example, a coil can have a 4-2-1-1 arrangement (i.e., four inlet pipes connected to two pipes, which in turn connect to one pipe, and then to the outlet pipe via U-bends). Six such 4-2-1-1 coils can be similar to those described above for a type 4-1 coil. Figure 1 Arranged as discussed. More than three rows can also be considered using a 4-2-1-1 type coil. As an additional example, an 8-pass coil has eight tubes connected by U-bends to form a serpentine coil. In some embodiments, the diameter can be constant over the entire length of the serpentine coil, and in other embodiments, the diameter can vary from the inlet to the outlet along the entire serpentine coil.

[0043] Figure 4-12 Various arrangements of coils / rows are shown. Their coils are shown as two-pass coils. However, coils can also be four-pass, eight-pass, and other types of coils with any number of passes.

[0044] Refer again Figure 1 Only half of the six coils of the 4-1 type are shown. This would have a 24-6 arrangement, meaning 24 inlet pipes and 6 outlet pipes, with half of the inlet pipes and half of the outlet pipes arranged on each side, as shown. Figure 1A As shown in the diagram. The 4-1 coil can be arranged in three rows, A, B, and C. Four inlet pipes 10 connect to a single sub-manifold (such as manifold 4, e.g., ...). Figure 14 (as shown in the diagram), and then connected to outlet pipe 12. The length of the radiant coil can be, for example, 10 feet / pass to 50 feet / pass, or for a two-pass coil, 20 feet to 100 feet from inlet to outlet. For a multi-pass coil, the total length can be up to 400 feet, for example, 20 feet to 100 feet for each two passes.

[0045] All inlet pipes 10 in a row can be connected to a single bottom manifold and can be adjacent to each other in the same row. All manifolds can be placed in a slot, and movement can be guided by channels in the slot. Burners can be placed on the floor, on either side of the coil, or on both sides of the floor and the coil. Burners can be arranged symmetrically (as shown) or asymmetrically (not shown).

[0046] In some embodiments, such a coil can be connected to a conventional conical inlet shell-and-tube exchanger. In other embodiments, the coil can be connected to an elliptical inlet for TLE after a three-connector without a Y-connector. In still other embodiments, all six inlets can be directly connected to the elliptical inlet without any three-connectors or Y-connectors. In still other embodiments, the outlet coil can be connected to a linear exchanger or a twin-tube exchanger. In embodiments using twin-tube or linear exchangers, the outlet can be combined via a collector system or via a series of three / four / five-connectors (for rows 3, 4, and 5, respectively) and then combined into one or more Y-connectors. From the transfer line exchanger, such combined outlets can be further cooled in any type of secondary exchanger to generate steam, including ultra-high pressure steam. In some embodiments, instead of steam, other process fluids can be heated.

[0047] None of these options are explicitly shown in the figures, but are implied. Any options described with respect to one embodiment are also contemplated for use in all other types of arrangements according to the embodiments herein. For example, flow to each radiant coil inlet may be distributed via a critical flow venturi tube. Process fluid may be preheated in a convection section above the radiant section of the heater, and one or more coils may be supplied to a crossover manifold prior to distribution via the venturi tube. For the sake of brevity, not all common characteristics of radiant coils will be discussed here.

[0048] Now for reference Figure 4 This illustrates another embodiment of the arrangement of the coil according to the embodiments described herein. This arrangement may have a bottom manifold similar to the previously described manifold, which connects all first-pass inlet pipes to outlet pipes.

[0049] In such Figure 4 In the arrangement shown, all inlet pipes (four per group in this embodiment) are spaced apart. The pipe spacing to outer diameter ratio (TS / OD) is the ratio of the space between pipes in the same row to the pipe diameter. This ratio can range from 1.2 to 4.0, such as between 1.4 and 2.0. In this arrangement, TS / OD can be higher than [previous value]. Figure 1As shown in the diagram. When all inlet pipes are placed together (first, second, or third row), the TS / OD ratio can be low, and may be less than 1. For a TS / OD ratio greater than 1, no pipe blocks another pipe upstream or downstream. When the TS / OD is low, the peak-to-average flux ratio is high, and therefore the maximum temperature of the pipe metal is high. To minimize this effect, the ratio-based TS / OD can be kept to a minimum to reduce the total floor area of ​​the coils without blocking downstream pipes. However, with a lower TS / OD, more pipe can be packed into a given space, thus reducing heater costs. A TS / OD ratio of 1.4 to 1.8 allows for a greater amount of pipe packed into a given floor area than... Figure 1 More pipes are shown. For pipe repair and maintenance reasons, a minimum clearance may be required between two adjacent pipes. By alternating the inlet pipes on the manifold to different rows, pipes can be tightly packed into a single row without increasing the TS / OD ratio.

[0050] Figure 5 Another coil arrangement is illustrated. As shown, the 8-1 coil arrangement has a total of 48 inlet pipes 10 and 6 outlet pipes 12. The inlet pipes 10 can be arranged in three rows A, B, and C (8 inlet pipes 10 in each row) on one side, and the other inlet pipes 10 can be arranged in three rows A', B', and C' on the other side. The six outlet pipes 10 can be in the center, with rows A, B, C and A', B', and C' on any side. This arrangement corresponds to 4-1 or 8-1. Similar patterns can be followed for other arrangements.

[0051] Figure 6 The diagram illustrates another arrangement of the pipes (using a 4-1 coil as an example). For example... Figure 6 The arrangement shown can have in-line outlet pipes 12, while the inlet pipes 10 are staggered. In this way, only the inlet pipes are arranged in rows A, B, and C. All outlet pipes can be located at the centerline of the combustion chamber, or aligned with one of rows A, B, and C (as shown, aligned with row C). In this way, the maximum metal temperature of the outlet pipes 12 can be uniform and can be lower compared to other arrangements. Since the maximum metal temperature of the outlet pipes 12 can affect coking, keeping the outlet pipes aligned in a line can improve the heater operating length for the multi-row embodiments disclosed herein.

[0052] Figure 7 The diagram illustrates a straight-line arrangement of three 4-1 coils. In this manner, all pipes (inlet pipe 10 and outlet pipe 12) are in a single row along the centerline of the combustion chamber. The bottom manifold connecting the inlet and outlet pipes is placed in three rows. As discussed above, adjacent pipes can supply the same manifold or different manifolds. Closer spacing is possible when adjacent pipes supply different manifolds. Figure 7 As shown, every three inlet pipes 10 can be connected to different manifolds. Each manifold can be connected to a different outlet pipe 12. In this embodiment, the manifolds can be placed at relatively similar heights and respectively on one side of the centerline, the centerline, and the other side of the centerline.

[0053] Figure 8 The implementation plan is similar to Figure 7 In this implementation, the manifolds are also placed at the centerline of the radiation chamber. For this arrangement, the manifolds must be stacked one on top of the other. This means that all adjacent inlet pipes 10 (four in the illustrated implementation) will enter the same manifold. Each group of four manifolds will have slightly different lengths, allowing one manifold to be placed on top of the next. Thermal expansion can be considered when determining the location (length) of each inlet pipe 10 and outlet pipe 12. Because all pipes are inline, the peak-to-average flux ratio can be low, and therefore the maximum metal temperature can be low. Lower pipe metal temperatures can allow for longer operating lengths, greater throughput, or both. However, with this inline arrangement, more pipes cannot be packed into the heater as in other cases described herein.

[0054] For example Figure 8 In the embodiment shown, all inlet pipes 10 and outlet pipes 12 can be arranged vertically along the centerline. The four inner pipes can be slightly shorter than the four middle pipes, while the four outer pipes can be slightly longer than the four middle pipes. The manifolds connecting the inner and outer pipes can be stacked one on top of the other.

[0055] As discussed above, Figure 1A A symmetrical arrangement of the coils is provided. This symmetry can be applied to... Figure 4-8 Other configurations are shown. For example, in Figure 1A In the first half, rows A, B, and C are arranged in parallel. This results in the outlet pipe 12 being offset by one diameter length for each of rows A, B, and C. For rows A', B', and C' in the other half, the outlet pipe 12 is symmetrical (mirror image). For example, Figure 3B The outlet pipe 12 shown uses only pseudo-symmetry, thus allowing for closer spacing of the outlet pipes. However, for... Figure 3B The arrangement of outlet pipes 12 shown has a spacing of 2*W between adjacent internal outlet pipes when the distance between rows is W, while for other adjacent outlet pipes, the spacing between adjacent pipes is only W. Therefore, the shading effect of the internal outlet pipes 12 will be greater than that of the other pipes.

[0056] For example, Figure 9 The mirrored arrangement shown is used to minimize shadow effects. For example, for Figure 9As shown, the inlet pipes 10 and outlet pipes 12 for rows B and B' can be positioned closer to the centerline, while the inlet pipes 10 and outlet pipes 12 for rows A and A' can be placed further away from the centerline, resulting in a 1, 3, 2 arrangement, which gives a maximum distance of only W between two adjacent outlet pipes, instead of 2W. In some embodiments, the distance between two adjacent outlet pipes can be 1.5W or even 1.1W. This can reduce shading effects and improve process performance. This arrangement can also be applied to embodiments with more than three rows.

[0057] Figure 10 The illustration shows an embodiment with four rows of pipes A, B, C, and D. Any arrangement discussed for three rows can also be applied to an arrangement with four rows. The centerline of the radial section can, for example, be between rows B and C. Similar to other embodiments, only half of the total pipes is shown; the other half is arranged symmetrically or pseudo-symmetrically, similar to... Figure 1A , 5 And 9.

[0058] Figure 11 The illustration shows an implementation scheme with five rows of pipes. Any arrangement discussed above regarding three rows can also be applied to a five-row arrangement. Therefore, Figure 10 and 11 This illustrates how to expand three rows to four or five rows. For this implementation, the centerline of the radiation chamber can, for example, run along row C.

[0059] Figure 12 The diagram illustrates a structure similar to the one with five rows A, B, C, D, and E. Figure 11 One embodiment is shown. For example, outlet pipe 12 can be connected to a separate linear heat exchanger 16. With a linear heat exchanger, there are no three-joints or Y-joints. This can result in a low adiabatic residence time, but the cooling heat transfer rate for a linear heat exchanger may be lower, and a longer TLE (Time to Length Evaporation) is required. A second heat exchanger, such as a shell-and-tube heat exchanger, can be used after the linear heat exchanger for further cooling of the fluid. Other process fluids can also be used for heat transfer instead of generating steam. In other embodiments, a third heat exchanger can be dedicated to heating the process fluid, while the first two heat exchangers generate steam by cooling the effluent from outlet pipe 12. Other types of heat exchangers can also be used. As with other embodiments, only half of the pipe is shown.

[0060] In one or more embodiments described herein, the coil is free to move to accommodate thermal expansion. The coil can be guided by a pin or round stud attached to the manifold, which travels along the channel containing the coil. This reduces damage to the coil caused by contact during thermal expansion.

[0061] Figure 13A and 13BThe diagram shows a 4-2-1-1 type coil with three rows. Figure 13B The diagram shows... Figure 13A A top view of the coil arrangement. This is a 4-pass coil (passes 40, 41, 42, 43), in which four inlet pipes 10 are connected to outlet pipes 12 via Y-joints 32, which are connected to three-joints 30 and then to each row of pipes via U-bends. The three outlet pipes 12 on each side of the heater are joined by individual three-joints 30 and then connected to a leg of the Y-joint 32.

[0062] Such as having a four-stage system Figure 13A and 13B As shown, the multi-row arrangement according to the embodiments described herein can be extended to coils with multiple passes (4, 6, 8, 10, 12 passes, etc.), and is not limited to two-pass coils. According to the embodiments described herein, a variety of multi-pass coils can be arranged in configurations with more than two rows.

[0063] Example

[0064] Example 1: This concept has been applied to the design of a naphtha cracking heater. Performance is illustrated by an example. Full-range naphtha feed is cracked in any of the three-pass designs shown in the accompanying drawings and described above. Performance is compared to a prior art two-pass design. The same sub-groups (10-1 coil type) are used in both the three-pass and two-pass arrangements. The only difference between the two designs is the arrangement (how the coils are arranged). In other words, both the two-pass and three-pass configurations are based on the same 10-1 type two-pass coils.

[0065] Feed characteristics are provided in Table 1, and heater design and results are provided in Table 2.

[0066] Table 1. Characteristics of naphtha feedstock

[0067]

[0068] Table 2.

[0069] Feeding naphtha naphtha design 3-row design 2-row design Heater feed rate, T / h 71.952 71.952 Total 10-1 sets / heater 48 48 Number of radiant coils / heaters 8 12 TLE quantity / heater 8 12 Flow rate per coil, T / h / coil 8.994 5.996 Steam to oil ratio, w / w 0.5 0.5 Across temperature range, F 1175 1175 Coil outlet temperature, F 1600 1600 Machining depth, P / E, w / w 0.45 0.45 Ethylene yield, % by weight 34.0 34.0 Ethylene production, T / h / coil 3.058 2.039 Ethylene production, T / h / heater 24.464 24.464 Runtime, days 60 60

[0070] Example 2: This example is for ethane cracking. The ethane purity is 98.5%, and it is cracked in a 4-2-1-1 type coil. Six such coils are arranged in three rows. A total of 12 such coils are arranged in three or two rows. The heater design and results are provided in Table 3.

[0071] Table 3.

[0072] Feeding Ethane Ethane design 3-row design 2-row design Heater feed rate, T / h 47.0 47.0 Total SRT3 coils / heaters 12 12 Number of radiant coils / heaters 2 3 TLE quantity / heater 2 3 Flow rate per coil, T / h / coil 23.50 15.67 Steam to oil ratio, w / w 0.3 0.3 Across temperature range, F 1265 1265 Coil outlet temperature, F 1525 1525 Ethane conversion rate, % 65 65 Ethylene yield, % by weight 48.3 48.3 Ethylene production, T / h / coil 11.35 7.57 Ethylene production, T / h / heater 22.70 22.70 Run length, days 60 60

[0073] The above examples demonstrate that by filling each TLE with more coils, the same performance can be achieved with increased flow rates.

[0074] These arrangements can be used to crack any hydrocarbon feedstock (ethane, propane, C3 LPG, C4 LPG, naphtha, gas oil, hydrocracking vacuum gas oil, crude oil, oilfield condensate, stripping fluid, where such feedstocks can be introduced individually or in combination) to produce olefins. Coil outlet pressures can range from 15 psi to 95 psi, and are typically between 22 psi and 35 psi. The feedstock can be mixed with dilution steam or can be processed without dilution steam. Coil outlet temperatures can range from 700 to 1000 °C, such as 780 to 880 °C. Steam can be generated at any pressure level from 50 psi to 2000 psi, such as 1600–1800 psi.

[0075] Unless otherwise defined, all technical and scientific terms used have the same meaning as commonly understood by one of ordinary skill in the art to which these systems, devices, methods, processes and compositions belong.

[0076] Unless the context clearly indicates otherwise, the singular forms “a,” “an,” and “the” include plural references.

[0077] As used herein and in the appended claims, the terms “comprising,” “having,” and “including,” and all their grammatical variations, are intended to have an open, non-limiting meaning (not excluding additional elements or steps).

[0078] "Optional" means that the event or situation described below may or may not occur. The description includes both scenarios in which the event or situation occurs and scenarios in which the event or situation does not occur.

[0079] When the terms “approximately” or “about” are used, the term can mean a variation of up to ±10%, up to 5%, up to 2%, up to 1%, up to 0.5%, up to 0.1%, or up to 0.01%.

[0080] A range can be expressed as from about one particular value to about another particular value (inclusive). When expressing such a range, it should be understood that another implementation is from one particular value to another particular value, as well as all particular values ​​within that range and their combinations.

[0081] While this disclosure includes a limited number of embodiments, those skilled in the art who benefit from it will understand that other embodiments can be devised without departing from the scope of this disclosure. Therefore, the scope should be limited only by the appended claims.

Claims

1. A system for cracking hydrocarbons, comprising: A flame heater with a radiating section and a convection section; One or more radiant coils are disposed within the radiant section of the heater, each of the one or more radiant coils comprising three to seven rows of multi-pass tubes, wherein each row comprises an inlet tube and an outlet tube, and wherein each row of tubes in the three to seven rows of multi-pass tubes is arranged in parallel or in a straight line with each row of tubes in the other rows of the three to seven rows of multi-pass tubes. A single transmission line switch is fluidly connected to the outlet pipe of each row of multipass tubes in the three to seven rows of multipass tubes for each of the one or more radiant coils.

2. The system of claim 1, wherein for each of the one or more radiant coils, each of the three to seven rows of multi-pass tubes includes an inlet tube fluidly connected to an outlet tube, each row having 3 to 16 inlet tubes, and wherein at least three of the inlet tubes are fluidly connected to each corresponding outlet tube.

3. A method for cracking hydrocarbons, comprising: Hydrocarbon feedstock is heated in a radiant coil located in the radiant section of a flame heater having a radiant section and a convection section. The radiant coil includes three to seven rows of multi-pass tubes, each row of tubes includes two multi-pass tubes, and the multi-pass tubes in the three to seven rows of multi-pass tubes are arranged in the radiant section of the heater such that the tube spacing between the inlet tubes of each adjacent row is length W, and the tube spacing between each adjacent outlet tube is not greater than 2W. The hydrocarbons in the hydrocarbon feedstock are cracked in the radiant coil, and the cracked hydrocarbon stream is recovered from the outlet pipe on each of the rows of pipes; The cracked hydrocarbons are supplied to a transmission line exchanger that is fluidly connected to the outlet pipe of each of the one or more rows of pipes.

4. The method according to claim 3, further comprising preheating the hydrocarbon feedstock in a heating coil disposed in the convection section of the flame heater before heating the hydrocarbon feedstock in one or more rows of tubes in the radiant section of the flame heater.

5. A system for cracking hydrocarbons, comprising: A flame heater with a radiating section and a convection section; The radiant coil is disposed within the radiant section of the heater. The radiant coil includes three to seven rows of multi-pass tubes, wherein each row includes two multi-pass tubes, and the multi-pass tubes in the three to seven rows of multi-pass tubes are disposed together within the radiant section of the heater, such that the tube spacing between the inlet tubes of each adjacent row is length W, and the tube spacing between each adjacent outlet tube is not greater than 2W. The fluid is connected to the outlet pipe of each of the three to seven rows of multi-pass pipes.

6. The system of claim 5, wherein each of the three to seven rows of multi-pass tubes includes an inlet tube fluidly connected to an outlet tube, each row of tubes having 3 to 16 inlet tubes, and wherein at least three of the inlet tubes are fluidly connected to each corresponding outlet tube.

7. The system according to claim 5, wherein the three to seven rows of multi-pass tubes are two-pass tubes, four-pass tubes, six-pass tubes or eight-pass tubes.

8. The system according to claim 5, wherein the pipe spacing between the inlet pipes of each adjacent row is length W, and wherein the pipe spacing between each adjacent outlet pipe is not greater than 1.5W.

9. The system according to claim 5, wherein the pipe spacing between the inlet pipes of each adjacent row is length W, and wherein the pipe spacing between each adjacent outlet pipe is not greater than 1.1W.

10. The system of claim 5, further comprising a heating coil disposed in the convection section of the heater, the heating coil being fluidly connected to a feed distributor configured to distribute hydrocarbon streams to each inlet pipe of the radiant coil.

11. The system of claim 5, wherein the manifold fluidly connects the first set of inlet pipes to the outlet pipes, and wherein an outlet pipe is provided for every 3 to 14 sets of inlet pipes.

12. The system of claim 11, wherein the inlet pipes and outlet pipes of each row are arranged linearly.

13. The system of claim 11, wherein the inlet pipes of the three to seven rows of multi-pass pipes are arranged non-linearly relative to the outlet pipes.

14. The system of claim 11, wherein the outlet pipe is arranged linearly relative to the middle of the three to seven rows of multi-pass pipes.

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