Furnace and endothermic process with improved burner arrangement

Abstract

The invention relates to a furnace for performing an endothermic process, the furnace comprising: a plurality of process tubes comprising a catalyst for converting a gaseous feed, wherein the process tubes are arranged in rows within the furnace, each row of process tubes thereby defining a row of process tubes; a plurality of inner burners arranged in rows, each row of inner burners being arranged between and parallel to the rows of process tubes, thereby defining a row of inner burners; and a plurality of outer burners arranged in rows, each row of outer burners being arranged between and parallel to a row of process tubes and a furnace wall, thereby defining a row of outer burners. The invention is characterized in that the number of burners of a row of outer burners is smaller than the number of burners of a row of inner burners. The invention also relates to a method for operating a furnace for performing an endothermic process, and to the use of a furnace according to the invention in steam methane reforming or steam cracking of hydrocarbons.

Description

Technical Field

[0001] This invention relates to a furnace for performing endothermic processes. In particular, it relates to a furnace for steam methane reforming (SMR) and other endothermic reactions (such as hydrocarbon feedstock cracking in an externally heated reactor). The invention further relates to a method for operating a furnace for performing endothermic processes. Background Technology

[0002] SMR processes are primarily based on the reforming of light hydrocarbon gases (such as methane), which, in the presence of water vapor, produce a mixture of hydrogen (H2) and carbon monoxide (CO). The reaction is highly endothermic and slow, requiring additional heat input and a catalyst. SMR reactor performance is typically limited by heat transfer rather than by the kinetics of the chemical reaction.

[0003] In industrial practice, an SMR reactor comprises multiple process tubes packed with catalyst placed within a furnace. The catalyst medium used to fill the process tubes includes granular and structured catalysts. The process tubes are fed a process gas mixture comprising methane and water vapor. The process tubes are heated by multiple burners placed adjacent to the process tubes.

[0004] Several burner configurations are known in the prior art, including bottom-burning (also known as "top-burning") burners, top-burning (also known as "bottom-burning") burners, side-burning burners, and stepped-wall-arranged burners.

[0005] Downfire technology is the most common and has been proposed by several technology providers. Downfire furnaces are typically constructed with a refractory-lined furnace chamber containing several rows of catalyst-filled process tubes. The heat required for the endothermic reaction is provided by burners mounted at the top of the furnace chamber. These burners are arranged in rows between the process tubes and additionally in rows along the furnace walls on the sides. The combustion products of the burners are typically blown vertically downwards, so that the upper portions of the process tubes face the flame. Flue gas collectors are located at the level of the furnace bottom plate.

[0006] Top-firing technology is less common. Here, the burners are arranged in rows on the bottom plate of the furnace, burning vertically upwards. Similarly, the burners are arranged in rows between the process tubes, and additionally in rows along the furnace walls on the sides.

[0007] The goal of furnace design is to optimize heat transfer from the burner to the process piping. Heat is transferred from the burner flame, furnace walls, and hot flue gas. In this regard, the maximum piping operating temperature (MOT) must be considered. MOT varies with several factors, and in particular with variations in the pipe mechanical load (i.e., feed gas pressure), the mechanical properties of the alloys used to manufacture the process pipes, and the expected lifespan of the process pipes exposed to creep and thermal aging.

[0008] Uneven heat distribution within the furnace will cause some tubes to be hotter than others, thus limiting furnace performance to the temperature of the hottest tube. The hottest tube should not exceed its MOT (Mean Time To Temperature). However, the process performance (productivity, conversion efficiency, among other things) depends on the average process tube heat flux and temperature. The smaller the difference between the hottest process tube temperature and the average process tube temperature, the better the furnace's process performance. Therefore, the goal is to achieve the most uniform heat distribution within the furnace possible.

[0009] The following explanation pertains to bottom-fired furnaces, but also applies to top-fired furnaces. In a typical bottom-fired furnace, burners arranged in rows between process tube banks have process tubes on both sides. Burners arranged between process tube banks and the furnace wall have process tubes only on one side. Therefore, the heat transfer requirement in the burner row between process tubes is twice that in the burner row between process tubes and the furnace refractory wall. Thus, burners arranged between process tube banks and the furnace wall (also called "external burners," "external exhaust burners," "OR burners," or "ORB") theoretically require only 50% of the required combustion rate compared to burners arranged between two process tube banks (also called "internal burners," "internal exhaust burners," "IR burners," or "IRB"). Including heat losses from the furnace wall, the required combustion rate of an OR burner is approximately 52% of that required for an IR burner arranged between process tube banks. The same consideration applies to the mass flow rate Q, which is directly related to the combustion rate and is defined as...

[0010] Q = ρSu

[0011] Where ρ is the mass density of the fluid injected into the burner, S is the cross-sectional surface area of ​​the burner, and u is the average velocity of the air / fuel mixture injected through (multiple) burner nozzles.

[0012] Given the lower combustion rate (and therefore lower mass flow rate) of the OR burner, its power can be reduced, for example, by using an OR burner design that is the same as or at least similar to that of the IR burner, and by throttling the amount of combustion air and / or fuel supplied to the OR burner. The final difference in mass flow rate between the “OR” burner and the “IR” burner is expressed by the following equation.

[0013] Q ORB =αQ IRB

[0014] Among them, Q ORB Q is the mass flow rate of the exhaust burner. IRB α is the mass flow rate of the internal exhaust burner, and α is the flow ratio between the external exhaust burner and the internal exhaust burner, where 0 < α < 1.

[0015] Therefore, for the "ideal" combustion rate of 52% of the combustion rate of the OR burner relative to the IR burner, and assuming that the mass density of the fluid and the cross-sectional surface area of ​​the burner are equal, the velocity of the flow (combustion air and fuel) at the nozzle of the OR burner is also only 52% of the velocity of the flow in the IR burner, as expressed by the following equation:

[0016] u ORB =αu IRB

[0017] Among them, u ORB It is the average velocity of the air / fuel mixture injected through the exhaust burner nozzle, and u IRB It is the average velocity of the air / fuel mixture injected through the nozzle of the internal exhaust burner.

[0018] The parallel jet behavior of the burner flame is largely influenced by its relative momentum flux J, which is defined by the following equation:

[0019] J = ρSu 2

[0020] As a result, due to the lower velocity at the burner nozzle of the OR burner compared to the IR burner, the momentum flux of the combustion product stream in the OR burner will also be significantly lower than that in the IR burner. However, a jet with a higher momentum flux will attract a jet with a lower momentum flux, resulting in the IR burner's flame jet attracting the OR burner's flame jet. This is because the higher momentum flux of the IR burner will create a lower static pressure zone in the burner exhaust area near the top of the IR burner than it does at the top of the OR burner. This static pressure difference causes the combustion products from the OR burner to flow towards the center of the furnace, a phenomenon known as "flame bending" in both IR and OR burner flames. As heat is thus transferred towards the center of the furnace, the outer exhaust pipes, i.e., the pipes closest to the furnace wall, find themselves heated relative to the inner exhaust pipes. To compensate for the heat transferred towards the inner exhaust pipes, the OR burner typically operates at a combustion rate higher than 52%, typically 60% to 80% of the combustion rate of the IR burner. However, when this interaction occurs between flames, it is difficult to balance the heat load between process tube banks, regardless of the load level.

[0021] The solution to the aforementioned problem is to use an OR burner (S) with a smaller outlet size. ORB IRB ), and simultaneously increase the speed of the exhaust burner (u ORB >u IRB This generates a uniform momentum flux (J) for both the internal and external exhaust burners. ORB ​=J IRB Therefore, US 2015 / 0239736 A1 teaches to modify the OR burner's exhaust velocity to be higher than that of the IR burner. The exhaust velocity of the "OR" burner is increased by reducing the area used to restrict the burner exhaust flow for the "OR" burner. The reduced flow area will increase the required combustion air pressure in the OR burner relative to the IR burner, which can be achieved by modifying the furnace's combustion air supply system. Alternatively, the necessity of a combustion air pressure difference between the OR and IR burners can be eliminated by modifying the design of the IR burner. Therefore, the solution proposed in US 2015 / 0239736A1 requires either modification of the furnace's combustion air supply system or a design modification of the IR burner.

[0022] US 7,686,611 B2 discloses a method and apparatus for generating a direct flame in a furnace. The method and corresponding apparatus include adding an oxidizer conduit to direct the oxidizer to the fuel.

[0023] US 5,795,148 sought to address the problem of unstable flame patterns and found that external winds were a contributing factor. Therefore, US 5,795,148 teaches a device for controlling the amount of air received by the furnace burner and providing uniform air pressure toward the burner.

[0024] According to EP 2 369 229, multiple oxidizer and fuel conduits are added to the burner in order to modify the behavior of the flame.

[0025] EP 2 708 812 A1 proposes a solution for an upfire reformer, wherein the OR burner should be positioned close to the furnace wall to prevent the OR burner flame from bending toward the IR burner flame. The ORB should be positioned close enough to the adjacent wall that the Coanda effect forces overcome the OR burner jet entrained by the IR burner jet.

[0026] All proposed solutions require significant modifications to the combustion system, either to the burner itself or to the burner distribution manifold. Further drawbacks include the need for different burner types, the requirement to test at least two different burners before commissioning, difficulties in pressure drop control when using different burners, and challenges in designing the burner flow distribution system. Summary of the Invention

[0027] Therefore, the object of the present invention is to provide a furnace for performing an endothermic process that overcomes or at least mitigates the problems mentioned above.

[0028] Another object of the present invention is to provide a furnace for performing an endothermic process that eliminates or at least reduces flame bending between burner rows, particularly without requiring significant structural changes to the burner.

[0029] Another object of the present invention is to provide a furnace with improved heat distribution uniformity, in particular without requiring significant structural changes to the burner.

[0030] Another object of the present invention is to provide a furnace with improved performance, particularly in terms of productivity and conversion efficiency, without requiring significant structural changes to the burner.

[0031] Another object of the present invention is to provide a furnace that is easier to design with respect to the common system of combustion air and fuel flow, thereby providing the same range of operating loads for all burners.

[0032] Another object of the present invention is to provide a process for operating a furnace for performing an endothermic process, which overcomes or at least mitigates the problems mentioned above and solves the aforementioned objects.

[0033] This is achieved through the subject matter of the independent claims. Further embodiments are described in the dependent claims.

[0034] Typically, a furnace used to perform an endothermic process includes multiple process tubes containing a catalyst for converting the gaseous feed, wherein...

[0035] The process tubes are arranged in rows within the furnace, each row defining a process tube row; multiple internal burners are arranged in rows, each row of internal burners being arranged between and parallel to these process tube rows, thereby defining an internal burner row; and multiple external burners are arranged in rows, each row of external burners being arranged between and parallel to the process tube rows, thereby defining an external burner row.

[0036] Its characteristic is that the number of burners in the outer burner row is less than the number of burners in the inner burner row.

[0037] The furnace according to the invention comprises a multi-row burner having at least one inner burner row arranged between two adjacent process tube rows and at least two outer burner rows, each of the outer burner rows being arranged between the process tube row and the furnace wall. According to the invention, the number of burners in the outer burner rows is reduced relative to the number of burners in the inner burner rows. This burner configuration eliminates or at least significantly reduces flame jet bending between the inner and outer burners. Furthermore, differences in heat transfer between process tubes are avoided.

[0038] According to the invention, a "row" means a defined number of elements arranged in a specified direction and in a continuous manner, specifically without any additional elements inserted into the row of continuous elements. For example, a "burner row" according to the invention means a number of burners arranged in a continuous manner without any additional elements arranged between two consecutive burners in the burner row. Such additional elements could be, for example, process tubes. For example, the same consideration applies to a "process tube row".

[0039] The external burner array is arranged between and parallel to the process tube bank and the furnace wall. The "furnace wall" parallel to the burner array and / or process tube bank can also be referred to as a "side-parallel" wall. Typically, but not necessarily, the furnace according to the invention comprises two facing side-parallel walls. The furnace wall arranged perpendicular to the burners and process tube bank can also be referred to as a "side-vertical" wall. Typically, but not necessarily, the furnace according to the invention comprises two facing side-vertical walls.

[0040] According to an embodiment, the number of burners in the outer burner row is less than the number of burners in the adjacent inner burner row. Flame bending primarily occurs between the outer burners of the outer burner row and the inner burners of the inner burner row adjacent to the aforementioned outer burner row. Therefore, it is preferable to reduce the number of burners in the outer burner row relative to the number of burners in the inner burner row adjacent to the outer burner row.

[0041] According to an embodiment, the ratio of the number of burners in the outer burner row to the number of burners in the inner burner row is in the range of 0.25 to 0.75, preferably in the range of 0.4 to 0.6, and more preferably in the range of 0.45 to 0.55. More preferably, the ratio of the number of burners in the outer burner row to the number of burners in the inner burner row is 0.5. Because the burners in the outer burner row are arranged between the process tube bank and the furnace wall, those burners will only have process tubes on one side of the burner row. Therefore, ideally, the heat transfer requirement in the burner row arranged between the process tube bank and the refractory wall of the furnace wall is half of the heat transfer requirement in the inner burner row arranged between two process tube banks. For this ideal case, the number of burners in the outer burner row should be half of the number of burners in the inner burner row, and particularly half of the number of burners in the inner burner row adjacent to the outer burner row. For furnaces with an uneven number of burners per row, especially per inner burner row, the ideal situation cannot be achieved, and the ratio of the number of burners in the outer burner rows to the number of burners in the inner burner rows will deviate from 0.5. Furthermore, the ratio of the number of burners in the outer burner rows to the number of burners in the inner burner rows must be adapted to accommodate local characteristics of the furnace, such as the greater distances between burners belonging to different sections of the furnace and / or between process tubes.

[0042] According to an embodiment, each inner burner row of the furnace includes the same number of burners and / or each outer burner row of the furnace includes the same number of burners. To further reduce flame merging and further reduce the tube temperature range along the tube rows, the furnace layout should be as uniform and / or symmetrical as possible in terms of burner arrangement, taking into account the reduced number of burners in the outer burner rows.

[0043] According to embodiments, these outer burners are configured to operate at a combustion rate in the range of 85% to 115% of the combustion rate of these inner burners, preferably in the range of 90% to 110% of the combustion rate of these inner burners, and more preferably in the range of 95% to 105% of the combustion rate of these inner burners. A key advantage of the invention is that by reducing the number of outer burners relative to the number of inner burners per row, the inner and outer burners can operate at the same or at least similar combustion rates. Therefore, the inner and outer burners will also have the same or at least similar mass flow rates (Q). ORB =Q IRB Or Q ORB ≈Q ORB And the same or at least similar momentum flux J. Under the condition of the same or at least similar combustion rate, mass flow rate and momentum flux, not only is flame bending eliminated or at least reduced, but the same burner with no or at least minimal structural differences can be applied.

[0044] Therefore, according to another embodiment, these external burners and these internal burners are configured to operate at equal nominal combustion rates. In this case, "equal nominal combustion rates" means that the expected or target value of the parameter "combustion rate" is equal for each burner, and in particular for both the internal and external burners. In practice, the measured combustion rate may deviate from the nominal combustion rate set for each of the burners in the furnace.

[0045] According to embodiments, these internal and external exhaust burners are constructed identically. Preferably, the same burners are used for both the internal and external exhaust burners, for example, to ensure the same momentum flux J of the combustion products discharged from the burner nozzles. Since the number of burners in the external burner rows is reduced compared to the number of burners in the internal burner rows, less heat will be supplied to the process tube rows or rows adjacent to the external burner rows. When the ratio of the number of burners in the external burner rows to the number of burners in the internal burner rows is 0.5 or in the range of around and including 0.5, for example, 0.45 to 0.55, the same or at least nearly the same amount of heat will be supplied to each process tube row. Since the internal and external exhaust burners will have the same pressure drop, the inlet manifolds for the air and fuel flows will be easier to design. Furthermore, the internal and external exhaust burners will have the same response to load changes with respect to air and / or fuel load, and the furnace can operate at lower loads when needed. In general, the use of burners with the same structure as the entire furnace simplifies the furnace design.

[0046] According to an embodiment, the outer burners of the outer burner rows are at least partially aligned with the inner burners of the inner burner rows along the direction of these burner rows. In this respect, "aligned with the inner burners of the inner burner rows along the direction of the burner rows" means the following: Assuming an imaginary line arranged perpendicular to (side-parallel to) the furnace wall passes through the center of the inner burner rows of the inner burner rows, the same line will not pass through the center of the outer burner rows of the outer burner rows because the corresponding outer burners are arranged to deviate from the line passing through the center of the inner burner rows. The outer burners of the outer burner rows may be aligned with the inner burners of the inner burner rows adjacent to the outer burner rows and / or with additional inner burners of inner burner rows not adjacent to the outer burner rows.

[0047] In another preferred embodiment, the outer burners of the outer burner row are at least partially offset from the alignment of the inner burners of the inner burner row along the direction of the burner row, such that the outer burners are arranged in the middle between the two inner burners of the inner burner row, preferably in the middle between the two burners of the inner burner row adjacent to the outer burner row. In this respect, "middle" means the following. Assume two imaginary lines (each arranged perpendicular to the (side-parallel) furnace wall) pass through the centers of the two inner burners of the inner burner row respectively. The two inner burners are arranged adjacent to each other within the inner burner row. In order to be arranged "middle" between the two inner burners of the inner burner row, the outer burners are arranged such that the distance from the center of the outer burner to each of the two lines is equal or at least substantially equal.

[0048] According to an embodiment, the distance between two inner burners in an inner burner row is IB2IB, and the distance between two outer burners in an outer burner row is OB2OB. The inner and outer burners in these rows are arranged such that the ratio of IB2IB to OB2OB is 0.3 to 0.81, preferably 0.4 to 0.71, and more preferably 0.5 to 0.61. The distance between outer burners is increased compared to the distance between inner burners by reducing the number of burners in each outer burner row. By reducing the number of outer burners in each outer burner row and simultaneously increasing the distance, the heat distribution in the furnace is improved in terms of uniformity. That is, a more uniform heat distribution is achieved throughout the furnace.

[0049] According to an embodiment, the inner burner rows, the outer burner rows, and the process pipe rows are terminated by vertical walls perpendicular to the sides of the inner burner rows, the outer burner rows, and the process pipe rows, and wherein the inner burner rows, the outer burner rows, and the process pipe rows are divided into multiple sections, wherein the distance from the end inner burner or the end outer burner to the vertical wall is B2W, the distance between two adjacent inner burners or outer burners in the section is B2B, and half the distance between two sections is B2S, wherein the inner burners and outer burners in these rows are arranged in such a way that the ratios B2B / B2W and B2B / B2S are greater than 1.3, preferably greater than 1.6, and more preferably greater than 1.8. As explained in detail in European patent application EP 3 182 003 A1 (which is incorporated herein by reference in its entirety), this arrangement further avoids flame merging within the rows and significantly reduces the mean square value of the pipe temperature distribution.

[0050] According to an embodiment, these burner rows and process tube rows terminate with vertical walls perpendicular to the sides of the burner rows and process tube rows, and wherein these burner rows and process tube rows are divided into multiple sections, wherein on each row of process tubes, the distance from the wall-end process tube to the vertical wall is T2W, the distance between two adjacent internal process tubes in a section is T2T, and the distance between two symmetrical end process tubes in two adjacent sections is T2S, wherein the process tubes in these rows are arranged such that the ratios T2T / T2W and T2T / T2S are greater than 0.5 and less than 2, preferably greater than 0.75 and less than 1.75. This arrangement further avoids the thermal differences of the end tubes in the cross-section as explained in detail in European patent application EP 3 279 561 A1 (which is incorporated herein by reference in its entirety).

[0051] According to an embodiment, these external burners are positioned such that the distance from the central axis of these external burners to the furnace wall is less than 25% of the distance between the outermost tube and the furnace wall, preferably less than 10%, more preferably less than 5%, and most preferably less than 2%. By placing the external burners close to the furnace wall, the problems of flame merging and overheating of the process tubes are further reduced, as explained in detail in European patent application EP2 708 812A1 (which is incorporated herein by reference in its entirety).

[0052] According to embodiments, these burners are mounted to the furnace top configured for a bottom-fired arrangement, or to the furnace bottom plate configured for an top-fired arrangement. Flame bending is most successfully avoided in both bottom-fired and top-fired arrangements by reducing the number of outer burners per row compared to the number of inner burners per row.

[0053] According to an embodiment, the furnace according to the invention is a steam methane reforming furnace. The furnace according to the invention is preferably used, but not limited to, steam methane reforming processes. In steam methane reforming, natural gas containing methane as a major component reacts with steam to obtain syngas, i.e., a gas mixture containing at least hydrogen and carbon monoxide. The furnace according to the invention can be used in similar processes in which carbonaceous feedstocks (with or without a catalyst) are converted into a gas mixture by heat input.

[0054] Typically, a process for operating a furnace for performing an endothermic process using multiple process tubes containing catalysts for converting gaseous feed includes: the process tubes being arranged in rows within the furnace, each row of process tubes thereby defining a process tube row; multiple internal burners being arranged in rows within the furnace, each row of internal burners being arranged between and parallel to the process tube rows, thereby defining an internal burner row; and multiple external burners being arranged in rows within the furnace, each row of external burners being arranged between and parallel to the process tube rows and the furnace wall, thereby defining an external burner row, wherein the burners of the external burner rows heat at least one row of adjacent process tubes, and the burners of the internal burner rows heat at least two rows of adjacent process tubes, characterized in that the external burners operate at a combustion rate in the range of 85% to 115% of the combustion rate of the internal burners. Internal and external burners operating at the same or at least similar combustion rates are less affected by flame merging, resulting in a more uniform heat distribution within the furnace compared to processes where the internal and external burners operate at more different combustion rates. The result of equal or at least similar combustion rates for the internal and external burners is a mass flow rate Q. ORB and Q IRBThey are also equal or at least similar. This will result in equal or at least similar momentum fluxes for the internal and external burners, and avoid flame bending. In order to operate these external burners at combustion rates in the range of 85% to 115% of the combustion rate of these internal burners, the number of burners in the external burner row is less than the number of burners in the internal burner row.

[0055] Therefore, an alternative general process for operating a furnace for performing an endothermic process using multiple process tubes containing catalysts for converting gaseous feedstocks may include: the process tubes being arranged in rows within the furnace, each row of process tubes thereby defining a process tube row; multiple internal burners being arranged in rows within the furnace, each row of internal burners being arranged between and parallel to the process tube rows, thereby defining an internal burner row; and multiple external burners being arranged in rows within the furnace, each row of external burners being arranged between and parallel to the process tube rows and the furnace wall, thereby defining an external burner row.

[0056] The burners in the outer burner row heat at least one row of adjacent process tubes, and the burners in the inner burner row heat at least two rows of adjacent process tubes, characterized in that the number of burners in the outer burner row is less than the number of burners in the inner burner row.

[0057] The following explanation of the embodiments may refer to the above-described general process, alternative general processes, or combinations thereof.

[0058] According to embodiments, these external burners operate at a combustion rate in the range of 90% to 110% of the combustion rate of these internal burners, preferably in the range of 95% to 105% of the combustion rate of these internal burners. More preferably, these external burners and internal burners operate at equal nominal combustion rates. In this case, "equal nominal combustion rates" means that the expected or target value of the parameter "combustion rate" is equal for each burner, particularly for the internal and external exhaust burners. In practice, the measured combustion rate may deviate from the nominal combustion rate set for each of the burners in the furnace.

[0059] According to embodiments, these internal burners burn gas at a burner exhaust velocity of μm / s, and wherein the external burners burn gas at a burner exhaust velocity of 0.85 to 1.15 μm / s, preferably 0.90 to 1.10 μm / s, more preferably 0.95 to 1.05 μm / s. The parameter "u" is the average velocity of the air / fuel mixture injected through the burner nozzles. According to the foregoing embodiments, the average velocity u of the air / fuel mixture injected through the (multiple) external burner nozzles... ORB Equal to or at least similar to the average velocity U of the air / fuel mixture injected through the nozzles of (multiple) internal exhaust burners.IRB By applying equal or similar average velocities u ORB and u IRB This avoids low static pressure zones in the central section of the furnace, and conversely, avoids high static pressure zones in the outer sections. Therefore, flame bending is also avoided. In another preferred embodiment, these inner and outer burners operate at the same nominal burner emission rate of μm / s. In this case, the "nominal" burner emission rate means that the expected or target value of the parameter "burner emission rate" u is equal for each burner, particularly for both the inner and outer exhaust burners. In practice, the measured burner emission rate may deviate from the nominal burner emission rate set for each of the burners in the furnace.

[0060] According to an embodiment, the endothermic process is a steam methane reforming process. The method according to the invention for operating a furnace for performing an endothermic process is preferably used, but not limited to, a steam methane reforming process. In a steam methane reforming process, natural gas containing methane as a major component reacts with steam to obtain syngas, i.e., a gas mixture containing at least hydrogen and carbon monoxide. The process according to the invention can be used in similar processes in which a carbonaceous feedstock (with or without a catalyst) is converted into a gas mixture by heat input.

[0061] Furthermore, the problems faced by the present invention are at least partially solved by using the furnace according to the invention in the steam methane reforming (SMR) process and / or in the hydrocarbon steam cracking process. Brief description of the attached diagram

[0062] The present invention will now be described in detail with reference to the accompanying drawings and exemplary embodiments.

[0063] In the attached diagram:

[0064] Figure 1 A perspective view of a typical furnace 100 for performing an endothermic reaction according to the prior art is depicted;

[0065] Figure 2a A top view depicting the burner arrangement of a furnace 200 according to the prior art;

[0066] Figure 2b A top view depicting the burner arrangement of a furnace 210 according to an embodiment of the present invention is shown;

[0067] Figure 3a The flame shape profile obtained from the burner arrangement of a furnace according to the prior art is depicted;

[0068] Figure 3bA flame shape profile obtained from the burner arrangement of a furnace according to an embodiment of the present invention is depicted;

[0069] Figure 4a The temperature distribution of process tubes in a furnace with burner arrangement according to the prior art is depicted;

[0070] Figure 4b The temperature distribution of process tubes in a furnace with a burner arrangement according to an embodiment of the present invention is depicted. Detailed Implementation

[0071] Figure 1 A typical prior art arrangement for a top-fired (bottom-fired) furnace 100 for obtaining syngas from a feed containing, for example, methane and steam is shown. The furnace includes a facing furnace wall 102a formed by planes in the xz direction and a facing furnace wall 102b formed by planes in the yz direction. All furnace walls 102a and 102b have refractory linings on their inner sides.

[0072] The catalyst-filled process tubes 101 are arranged in four rows 101a and 101b, with thirty process tubes in each row, each row of process tubes 101 thus defining a process tube row. Two process tube rows 101a are arranged between and parallel to the furnace wall 102a and the process tube rows 101b, thus defining an outer process tube row. Two process tube rows 101b are each arranged between two process tube rows, thus defining an inner process tube row. The process tubes arranged adjacent to the furnace wall 102b are called end tubes. Each process tube row 101a, 101b includes two end process tubes, and the furnace as a whole thus includes eight end process tubes.

[0073] Burners 103 are arranged in five rows 103a and 103b, with eight burners in each row, thus defining a burner row. Two burner rows 103a are arranged between and parallel to the furnace wall 102a and the process tube row 101a, thus defining an outer burner row 103a. Two burner rows 103b are arranged between and parallel to the process tube rows (101b, or 101a and 101b), thus defining an inner burner row. Burners arranged adjacent to the furnace wall 102b are referred to as end burners. Each burner row 103a, 103b includes two end burners. Therefore, according to Figure 1 The example of ten burners can be referred to as end burners.

[0074] Methane and steam are supplied from top to bottom through process pipe 101, from which the resulting products, such as synthesis gas containing hydrogen, carbon monoxide, and residues, are discharged. Combustion is carried out vertically downwards from the top in burner 103. The resulting flue gas is discharged through exhaust passage 104.

[0075] Figure 2aand Figure 2b A top view of a bottom-fired furnace is depicted, in which... Figure 2a This indicates the burner arrangement of the furnace 200 according to existing technology, and Figure 2b This illustrates the burner arrangement of a furnace 210 according to an embodiment of the present invention. The rows of burners 203 and process tubes 201 extend in the x-direction (similar to...). Figure 1 (Description).

[0076] like Figure 2a The depicted furnace comprises five burner rows 203a and 203b, each burner row comprising eight burners 203, each burner represented by a square dot. The furnace further comprises four process tube rows 201a and 201b, each process tube row comprising thirty process tubes 201, each process tube represented by a dot with a circular shape. The burners 203 and process tubes 201 are enclosed by furnace walls 202a and 202b, each furnace wall having its inner side lined with refractory material.

[0077] Burner row 203a is arranged between and parallel to process tube row 201a and furnace wall 202a, thus defining the outer burner row 203a. The furnace wall (multiple) 202a can also be referred to as a "side-parallel" wall. Burner row 203b is arranged between and parallel to two process tube rows (one on each side), thus defining the inner burner row 203b. The burners of the outer burner row 203a heat one side of process tube row 201a and furnace wall 202a. The burners of the inner burner row 203b heat either process tube rows 201a or 201b and both sides of 201b. Because the burners of the outer burner row 203a only heat one side of the process tube row, these burners operate at only 78% of the combustion rate of the burners of the inner burner row 203b. This 78% combustion rate value is significantly higher than the theoretical value of 52% to compensate for heat loss due to flame bending effects, as described in detail above. However, the flame bending problem persists, and due to the increased combustion rate, it is difficult to balance the heat load between process tube banks regardless of the load level.

[0078] like Figure 2a The furnace depicted is a completely symmetrical furnace. Burner rows 203a and 203b and process tube rows 201a and 201b are organized into two sections. Because only a limited number of burners and / or process tubes can be fixed to a single suspension system, the process tube rows and burner rows must be separated into multiple sections. Figure 2aFor example, burner rows 203a and 203b are separated into two sections, each with four burners. Process tube rows 201a and 201b are separated into two sections, each with 15 process tubes. The left and right sections of the furnace, thus defined, are separated by a plane of symmetry indicated by a dashed line passing through the center of the furnace. For structural reasons, the distance between burners and / or process tubes between sections is generally greater than the distance between burners within a section. As depicted, the distance between burners within a section of the furnace is called the "B2B" distance, and half the distance between two adjacent burners between two sections is called the "B2S" distance. Additionally, the distance between the burners and the furnace wall 202b is called "B2W". The furnace wall 202b can also be referred to as the "side-vertical" wall. The same considerations apply to the distances between process tubes (not shown), referred to as "T2T" (distance between tubes within a section), "T2W" (distance from tube to wall 202b), and "T2S" (half the distance between tubes between adjacent sections).

[0079] Figure 2b The furnace depicted represents a furnace having a burner arrangement according to the invention.

[0080] like Figure 2b The depicted furnace comprises five burner rows 213a and 213b. The outer burner row 213a comprises only four burners 213, while each of the inner burner rows 213b comprises eight burners 213. Similarly, a single burner 213 is represented by a square dot. The furnace further comprises four process tube rows 211a and 211b, each comprising thirty process tubes 211, each process tube represented by a dot with a circular shape. The burners 213 and process tubes 211 are enclosed by furnace walls 212a and 212b, each furnace wall having its inner side lined with refractory material. The furnace walls 212a may also be referred to as "parallel-sided" furnace walls, while the furnace walls 212b may also be referred to as "vertical-sided" furnace walls.

[0081] Burner row 213a is arranged between and parallel to process tube row 211a and furnace wall 212a, thus defining outer burner row 213a. Burner row 213b is arranged between and parallel to two process tube rows (one on each side), thus defining inner burner row 213b. The burners of outer burner row 213b heat one side of process tube row 211a and furnace wall 212a. The burners of inner burner row 213b heat process tube rows 211a and 211b, or both sides of 211b.

[0082] According to the present invention, the number of burners 213 in the outer burner row 213a is less than the number of burners 213 in the inner burner row 213b. Figure 2bThe number of burners 213 in the outer burner row 213a is half the number of burners 213 in the inner burner row 213b. This applies to all burner rows; that is, the two outer burner rows 213a contain only half the number of burners compared to the inner burner row 213b. Therefore, the ratio of the number of burners in the outer burner row 213a to the number of burners in the inner burner row is 0.5. The outer burner row 213a, with its reduced number of burners, is further adjacent to the inner burner row 213b, which has a "standard" number of burners. Figure 2b For example, each inner burner row 213b further includes the same number of burners, and each outer burner row 213a includes the same number of burners. The outer burners 213 of row 213a are arranged offset from the inner burners 213 of row 213b, i.e., the outer burners are not arranged "at the same x-coordinate" as the inner burners. This offset arrangement provides further benefits in terms of the uniformity of heat distribution throughout the furnace, and thus provides uniformity of heat distribution in the process tubes.

[0083] and Figure 2a The comparison examples are the opposite, according to Figure 2b The burner of the outer burner row 213a in the invention example is configured to operate at 100% of the combustion rate of the burner of the inner burner row 213b. In other words, the outer burner of row 213a and the inner burner of row 213b are configured to operate at equal nominal combustion rates. Therefore, as another advantage of the invention, the outer and inner burners are constructed identically, so that only one type of burner is needed for the entire furnace. Since all burners are constructed identically, it is easier to operate all burners at equal burner exhaust rates, which will further reduce or even eliminate flame bending effects. In other words, the inner burner of row 213b and the outer burner of row 213a can be operated in such a way that they burn gas at nearly equal or even equal burner exhaust rates u.

[0084] like Figure 2b As further described, the distance between two adjacent burners in the inner burner row 213b is referred to as "IB2IB", and the distance between two adjacent burners in the outer burner row 213a is referred to as "OB2OB". Figure 2b For example, IB2B is approximately half the size of OB2OB. This applies to adjacent burners within a section (“intra-section” burners) and adjacent burners between two sections (“inter-section” burners).

[0085] by Figure 3a and 3b The quantitative method shown in the figure further demonstrates the advantages of the present invention through computational simulation.

[0086] Figure 3a Depicting according to Figure 2a A side view of a comparative example (i.e., involving the same burner arrangement). Figure 3a (and Figure 3b The graphic elements shown in the diagram represent the flame shape calculated through simulation. In the x-direction, a single flame in the flame "pile" represents a single burner 203 in the burner row. A flame pile referred to as 303a represents... Figure 2a External burner row 203a. According to Figure 2a Flame stack 303b represents two external burner rows 203b. For symmetry reasons, only half of the furnace has been simulated, as... Figure 2a As shown in the shaded area. Therefore, Figure 3a The outer right flame pile (in the y direction) only indicates Figure 2a The center burner row 203b is "half" of the center burner. Generally speaking, Figure 3a The left part represents the outer area of ​​the furnace, and the central area of ​​the furnace is reached by moving from left to right in the y direction.

[0087] The flame shape of the outer burners in burner rows 202a, and particularly the flame shape of 303a, illustrates a typical flame curvature of a symmetrical top-fired furnace according to the prior art. The combustion rate of the burners in the outer burner rows is only 78% of that in the inner burner rows, resulting in lower momentum for the outer burners. Consequently, the hot combustion gases released from the outer burners are deflected towards the center of the furnace (especially in the y-direction).

[0088] Figure 3b Depicting according to Figure 2b A transverse view of an embodiment of the invention (i.e., relating to the same burner arrangement). Similarly, Figure 3b The graphic elements shown represent flame shapes calculated through simulation. In the x-direction, a single flame in a flame "pile" represents a single burner 213 in a burner row. A flame pile referred to as 313a represents a flame pile according to... Figure 2b External burner row 213a. According to Figure 2b Flame stack 313b represents two external burner rows 213b. For symmetry reasons, only half of the furnace has been simulated, as shown... Figure 2b As shown in the shaded area. Therefore, Figure 3b The outer right flame pile (in the y direction) only indicates Figure 2b The center burner row 213b is "half" of the center burner. Generally speaking, Figure 3b The left part represents the outer area of ​​the furnace, and the central area of ​​the furnace is reached by moving from left to right in the y direction.

[0089] according to Figure 3bThe flame shape demonstrates that the flame of the outer burner (represented by the flame shape of 313a) is prevented from bending towards the center of the furnace. Since the combustion rates of the outer burner (represented by flame shape 313a) and the inner burner (represented by flame shape 313b) are the same, the combustion gases from both burners are discharged with substantially uniform or identical momentum. Therefore, no or at least significantly less flame bending occurs. As a result of the invention, the flame, particularly the flame of 313a representing the outer burner 213a, is substantially straight.

[0090] The improved burner arrangement according to the invention also results in significantly better uniformity in temperature distribution at the reformer scale. This is achieved by adapting the prior art ( Figure 2a and Figure 3a ) and according to the present invention ( Figure 2b and Figure 3b The simulated temperature distribution obtained from the burner arrangement is used to demonstrate this. Figure 4a The temperature distribution of the process tube is shown as a comparative example, and according to... Figure 4b The temperature distribution of the process tube is shown in an embodiment of the present invention.

[0091] like Figure 4a As shown, there is a significant temperature difference between the process tubes near the outer burner row (outer tubes represented by dots = ORB) and the tubes between the inner burner rows (inner tubes represented by square dots = IRB). Due to the flame bending effect, i.e., the flame bends towards the center of the furnace, the inner tubes exhibit a significantly higher average temperature. Therefore, there is a significant temperature difference between the inner and outer process tubes, also known as "temperature deviation".

[0092] By applying the burner arrangement according to the invention, this undesirable temperature deviation is significantly reduced, such as Figure 4b The diagram shows that the basic sections of the inner and outer process tubes even exhibit the same or at least substantially the same temperature.

[0093] It should be noted that embodiments of the present invention are described with reference to different subject matter. In particular, some embodiments are described with reference to method-type claims, while other embodiments are described with reference to apparatus-type claims. However, those skilled in the art will understand from the above and below description that, unless otherwise notified, any combination of features related to different subject matter, in addition to any combination of features belonging to one type of subject matter, is also considered to be disclosed with this application. However, all features can be combined to provide synergies that are not merely a simple summation of features.

[0094] Although the invention has been shown and described in detail in the accompanying drawings and the foregoing description, such showing and description is to be considered illustrative or exemplary, and not restrictive. The invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments will be understood and implemented by those skilled in the art in practicing the claimed invention through a study of the drawings, disclosure, and dependent claims.

[0095] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite articles "a" or "an" do not exclude a plurality. A single processor or other unit can perform the function of several items recited in the claims. The fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used advantageously. Any reference numerals in the claims should not be construed as limiting the scope.

[0096] List of reference numerals

[0097] 100 furnaces

[0098] 101 process tube

[0099] 101a (External) Process Pipeline

[0100] 101b (Internal) Process Pipeline

[0101] 102a (parallel side) furnace wall

[0102] 102b (vertical side) furnace wall

[0103] 103 Burner

[0104] 103a (external) burner exhaust

[0105] 103b (internal) burner row

[0106] 104 Exhaust passage

[0107] 200 furnaces

[0108] 201 Process Pipe

[0109] 201a (External) Process Pipeline

[0110] 201a (internal) process pipe bank

[0111] 202a (parallel side) furnace wall

[0112] 202b (vertical side) furnace wall

[0113] 203 Burner

[0114] 203a (external) burner exhaust

[0115] 210 Stove

[0116] 211 Process Pipe

[0117] 211a (External) Process Pipeline

[0118] 211a (internal) process pipe bank

[0119] 212a (parallel side) furnace wall

[0120] 212b (vertical side) furnace wall

[0121] 213 Burner

[0122] 213a (external) burner exhaust

[0123] Flame shape of the 303a external burner

[0124] Flame shape of the 303b internal burner

[0125] Flame shape of the 313a external burner

[0126] Flame shape of 313b internal burner

Claims

1. A furnace for performing an endothermic process, comprising: Multiple process tubes containing catalyst for converting gaseous feed, wherein The process tubes are arranged in rows within the furnace, and each row of process tubes defines a process tube row. Multiple internal burners are arranged in rows, each row of internal burners being positioned between and parallel to the process tube banks, thereby defining an internal burner row. Multiple external burners are arranged in rows, with each row of external burners positioned between and parallel to the process tube bank and the furnace wall, thus defining the external burner row. Its features are, The number of burners in the outer burner row is less than the number of burners in the inner burner row.

2. The furnace as claimed in claim 1, wherein, The number of burners in the outer burner row is less than the number of burners in the inner burner row adjacent to the outer burner row.

3. The furnace as described in claim 1 or 2, wherein, The ratio of the number of burners in the outer burner row to the number of burners in the inner burner row is in the range of 0.25 to 0.

75.

4. The furnace as described in claim 3, wherein, The ratio of the number of burners in the outer burner row to the number of burners in the inner burner row is in the range of 0.4 to 0.

6.

5. The furnace as described in claim 3, wherein, The ratio of the number of burners in the outer burner row to the number of burners in the inner burner row is in the range of 0.45 to 0.

55.

6. The furnace as claimed in claim 3, wherein, The ratio of the number of burners in the outer burner row to the number of burners in the inner burner row is 0.

5.

7. The furnace as described in claim 1 or 2, wherein, Each inner burner row of the furnace includes the same number of burners and / or each outer burner row of the furnace includes the same number of burners.

8. The furnace as claimed in claim 1 or 2, wherein, These external burners are configured to operate at a combustion rate in the range of 85% to 115% of the combustion rate of these internal burners.

9. The furnace as claimed in claim 8, wherein, These external burners are configured to operate at a combustion rate in the range of 90% to 110% of the combustion rate of these internal burners.

10. The furnace as claimed in claim 8, wherein, These external burners are configured to operate at a combustion rate in the range of 95% to 105% of the combustion rate of these internal burners.

11. The furnace as claimed in claim 1 or 2, wherein, These external burners and these internal burners are configured to operate at equal nominal combustion rates.

12. The furnace as claimed in claim 1 or 2, wherein, These internal exhaust burners and these external exhaust burners are constructed in the same way.

13. The furnace as claimed in claim 1 or 2, wherein, The outer burners of the outer burner rows are aligned with the inner burners of the inner burner rows along the direction of these burner rows.

14. The furnace as claimed in claim 1 or 2, wherein, The distance between two internal burners in an internal burner row is IB2IB, and the distance between two external burners in an external burner row is OB2OB, wherein the internal and external burners in these rows are arranged such that the ratio of IB2IB to OB2OB is 0.3 to 0.

81.

15. The furnace as claimed in claim 14, wherein, The ratio of IB2IB to OB2OB is 0.4 to 0.

71.

16. The furnace as claimed in claim 14, wherein, The ratio of IB2IB to OB2OB is 0.5 to 0.

61.

17. The furnace as claimed in claim 1 or 2, wherein, These internal burner rows, these external burner rows, and these process pipe rows are terminated by vertical walls perpendicular to the sides of the internal burner rows, these external burner rows, and these process pipe rows, and are divided into multiple sections, wherein the distance from the end internal burner or end external burner to the vertical wall is B2W, the distance between two adjacent internal burners or external burners in the section is B2B, and half the distance between two sections is B2S, wherein the internal burners and external burners in these rows are arranged in such a way that the ratios B2B / B2W and B2B / B2S are greater than 1.

3.

18. The furnace as claimed in claim 17, wherein, The ratios B2B / B2W and B2B / B2S are greater than 1.

6.

19. The furnace as claimed in claim 17, wherein, The ratios B2B / B2W and B2B / B2S are greater than 1.

8.

20. The furnace as claimed in claim 1 or 2, wherein, These burner rows and process tube rows are terminated by vertical walls perpendicular to the sides of the burner rows and process tube rows, and are divided into multiple sections. In each row of process tubes, the distance from the wall-end process tube to the vertical wall is T2W, the distance between two adjacent internal process tubes in the section is T2T, and the distance between two symmetrical end process tubes in two adjacent sections is T2S. The process tubes in these rows are arranged such that the ratios T2T / T2W and T2T / T2S are greater than 0.5 and less than 2.

21. The furnace as claimed in claim 20, wherein, The ratios T2T / T2W and T2T / T2S are greater than 0.75 and less than 1.

75.

22. The furnace as claimed in claim 1 or 2, wherein, These external burners are positioned such that the distance from the central axis of these external burners to the furnace wall is less than 25% of the distance between the outermost tube and the furnace wall.

23. The furnace as claimed in claim 22, wherein, These external burners are positioned such that the distance from the central axis of these external burners to the furnace wall is less than 10% of the distance between the outermost tube and the furnace wall.

24. The furnace as claimed in claim 22, wherein, These external burners are positioned such that the distance from the central axis of these external burners to the furnace wall is less than 5% of the distance between the outermost tube and the furnace wall.

25. The furnace as claimed in claim 22, wherein, These external burners are positioned such that the distance from the central axis of these external burners to the furnace wall is less than 2% of the distance between the outermost tube and the furnace wall.

26. The furnace as claimed in claim 1 or 2, wherein, These burners are mounted on the furnace top, which is configured for a bottom-fired arrangement, or on the furnace bottom plate, which is configured for an top-fired arrangement.

27. The furnace as described in claim 1 or 2, wherein the furnace is a steam methane reforming furnace.

28. A method for operating a furnace for performing an endothermic process using a plurality of process tubes containing catalysts for converting gaseous feed, wherein... The process tubes are arranged in rows within the furnace, and each row of process tubes defines a process tube row. Multiple internal burners are arranged in rows within the furnace, with each row of internal burners positioned between and parallel to the process tube rows, thus defining the internal burner rows. Multiple external burners are arranged in rows within the furnace. Each row of external burners is positioned between and parallel to the process tube bank and the furnace wall, thus defining the external burner row. These burners in the external burner row heat at least one row of adjacent process tubes, and These burners in the internal burner row heat at least two adjacent rows of process tubes. Its features are, These external burners operate at a combustion rate in the range of 85% to 115% of that of the internal burners. The number of burners in the outer burner row is less than the number of burners in the inner burner row.

29. The method of claim 28, wherein, These external burners operate at a combustion rate in the range of 90% to 110% of the combustion rate of these internal burners.

30. The method of claim 29, wherein, These external burners operate at a combustion rate in the range of 95% to 105% of the combustion rate of these internal burners.

31. The method according to any one of claims 28 to 30, wherein, These external burners and these internal burners operate at the same nominal combustion rate.

32. The method of any one of claims 28 to 30, wherein the internal burners burn gas at a burner exhaust rate of μm / s, and wherein the external burners burn gas at a burner exhaust rate of 0.85 to 1.15 μm / s.

33. The method of claim 32, wherein these external burners burn gas at a burner exhaust rate of 0.90 to 1.10 μm / s.

34. The method of claim 32, wherein the external burners burn the gas at a burner exhaust rate of 0.95 to 1.05 μm / s.

35. The method of any one of claims 28 to 30, wherein the internal and external burners operate at the same nominal burner emission rate of μm / s.

36. The method of any one of claims 28 to 30, wherein the endothermic process is a steam methane reforming process.

37. Use of a furnace as described in any one of claims 1 to 27 in a steam methane reforming process.

38. Use of a furnace as described in any one of claims 1 to 27 in a hydrocarbon steam cracking process.

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