Heat removal tube assembly, reaction charge increase method and unsaturated nitrile production method

Abstract

The present application relates to a heat removal tube assembly, a method for increasing the reaction load using a heat removal tube assembly and its use in the production of unsaturated nitrile. The heat removal tube assembly includes at least 10 heat removal tubes and in at least one and at most 88% of all heat removal tubes of the heat removal tube assembly, an angle between a line drawn through the centerline at at least one of the joints and a line drawn through the centerline of the other joints is formed that is greater than 0 degrees and less than 180 degrees. By installing such a set of heat removal tubes, the heat removal capability and fluidization efficiency of the fluidized bed reactor are improved, so that the need for increasing the reaction load can be fully met.

Description

Heat removal tube assembly, reaction load increase method and unsaturated nitrile production method Technical background The present application relates to a heat removal tube assembly which is particularly suitable for use in a fluidized bed reactor. The present application further relates to a method for increasing the reaction load using the heat removal tube assembly and its use in the production of unsaturated nitriles. Background knowledge Acrylonitrile is an important chemical raw material for the petrochemical industry. A single-step method for producing acrylonitrile by ammoxidation of propylene is commonly used in various countries in the world, that is, under the influence of a fluidized bed ammoxidation catalyst and under a certain reaction temperature and pressure, propylene is subjected to ammoxidation to produce acrylonitrile, and at the same time by-products such as acetonitrile, hydrocyanic acid and the like are produced, and deep oxidation products such as CO, CO2 are also produced. This reaction is highly exothermic and is accompanied by the generation of a large amount of heat. The inside of the acrylonitrile fluidized bed reactor consists of a propylene-ammonia distributor, an air distribution plate, a heat removal pipe (also known as a cooling coil) and a cyclone separator, in which the heat removal pipe and the cyclone separator plug are placed in the catalyst bed as vertical components of the fluidized bed. The heat removal pipe can remove a large amount of the generated reaction heat from the reaction system in time and keep the reaction temperature stable, and the cyclone separator captures the catalyst carried by the gas moving upwards and returns the catalyst to the catalyst bed through the diplog so that the catalyst loss is reduced. Figure 1 shows an acrylonitrile fluidized bed reactor, the internal parts of which mainly include: an oxygen-containing gas distribution plate, a propylene-ammonia distributor, a heat removal tube, and a cyclone separator. In an existing acrylonitrile reactor shown in Figure 1, 85% or more of the total heat removal tubes are in operation, that is, those heat removal tubes are filled with a heat removal medium colder than the reaction temperature, and the reaction temperature is kept constant by heat exchange with the heat removal medium. The improvement of the ammoxidation catalyst performance allows the fluidized bed reactor to operate with a higher reaction load (e.g. 50% more) at the same size, that is, the feed amount of propylene raw materials, ammonia and oxygen-containing gas is increased by 50%, which results in a 50% increase in the released heat of reaction. Although part of the heat removal pipes in the existing fluidized bed reactor are in an idle state, the excess heat of reaction cannot be removed sufficiently, which leads to a decrease in the reaction temperature, or due to the lack of sufficient heat removal pipes for alternative use, although the reaction temperature can be kept constant in the initial stage of equipment operation, the molybdenum scale on the surfaces of the heat removal pipes increases, the heat conduction efficiency decreases, and as the operating period of the equipment increases, more heat removal pipes are put into operation. Finally, there is no idle heat removal pipe available for switching, and the stable control of the reaction temperature cannot be maintained, so that the requirement for long-term stable operation of the equipment cannot be met.On the other hand, since the initial bubbles generated when the raw materials exit the gas distribution / distributor plate become larger, and therefore, in the case of the existing fluidized bed reactor, the bubbles also become relatively larger throughout the bed, so that the acrylonitrile efficiency and propylene conversion are reduced, which is detrimental to equipment savings. Existing fluidized bed reactors are limited in heat removal capacity and fluidization efficiency, and therefore cannot meet the need for increasing the reaction load. Disclosure of the invention In the acrylonitrile fluidized bed reactor of the present application, the heat removal tubes are arranged parallel to each other at equal or perpendicular distances to each other, and a service passage is provided in the distance between the straight tubes of two adjacent heat removal tubes.Conventional heat removal pipes are characterized in that the upper connecting clamps, lower connecting clamps and the straight pipe of the heat removal pipe are arranged on the same straight line on the reactor cross section, and the upper connecting clamps and the lower connecting clamps are arranged at an angle of 180 degrees; while the profile heat removal pipes are characterized in that at least one of the upper connecting clamps forms a certain angle with the lower connecting clamps, and the protrusions of the straight pipes in fluid communication on the reactor cross section along the flow direction of the main fluid body are two straight lines close to each other; since the profile heat removal pipes are more closely connected than the conventional heat removal pipes, the heat removal capacity is continuously improved with the increase in the number of conventional heat removal pipes replaced by the profile heat removal pipes, which is also more conducive to breaking large bubbles. Meanwhile, sufficient space is still reserved between the heat removal pipes for equipment maintenance and repair.The present application is based on this finding and is carried out by changing the configuration and number of heat removal tubes in a fluidized bed reactor to increase the heat removal capability and fluidization efficiency of the fluidized bed reactor. Conventional heat removal tubes and profile heat removal tubes are configured in a predetermined ratio according to the performance of the ammoxidation catalyst and the reaction load, so that stable, high-efficiency and long-term operation of the equipment can be realized. Specifically, the present declaration relates to technical solutions in the following aspects. 1. A set of heat removal tubes (in particular a set of heat removal water tubes) characterized in that it is configured to be arranged in a heat removal section of a fluidized bed reactor, said set of heat removal tubes comprising at least 10 heat removal tubes (preferably 10 to 100, preferably 20 to 80), said heat removal tubes comprising N (N is equal to or greater than 3, preferably N is equal to 3 to 30, preferably N is equal to 3 to 20) straight tubes and N-1 connecting joints for connecting any two adjacent straight tubes in series and establishing fluid communication therebetween, Where the length of the heat removal section along the central axis of the fluidized bed reactor is determined to be H (in meters), a cross-section of the heat removal section (referred to as section A) is obtained by cutting along a direction perpendicular to the central axis of the fluidized bed reactor at a position in the entire region of the length H of the heat removal section (preferably in a region from 49% H above to 49% H below the center point of the reaction heat removal section, preferably in a region from 45% H above to 38% H below the center point of the reaction heat removal section, preferably in a region from 40% H above to 8% H below the center point of the heat removal section), For at least one of (preferably 1, 2 or 3, or at least 20%, at least 50% or at least 65% of the total) heat removal pipes (as profiled heat removal pipes) of the heat removal pipe assembly and up to 88% (preferably 75% or 70%) of the total heat removal pipes of the heat removal pipe assembly, an angle between a line extended from the central axis of the projection of at least one (preferably at least 2, 3 or 4, and at most 80%, 90% or 100% of the total) of the profiled heat removal pipe connection fasteners (preferably excluding the first profiled heat removal pipe connection fasteners) in cross section A and a line extended from the central axis of the projection of at least one of the other connection fasteners (preferably other connection fasteners on the profiled heat removal pipe in a position immediately above and in fluid communication with said connection fasteners) on cross section A is greater than 0 degrees and less than 180 degrees (Preferably 30-150 degrees and preferably 60-120 degrees and most preferably about 90 degrees). 2. The heat removal pipe assembly as described in any of the preceding or following aspects, wherein the cross-sectional area A is set to S1 (in m2), and the sum of the outer perimeters of the cross-sectional areas of all the straight pipes from the heat removal pipe on the cross-sectional area A is set to L1 (in m), L1 / S1 is 1.0 to 6.0 m-1 (preferably 2.4 to 5.6 m-1, preferably 2.9 to 5.3 m-1), and / or the area S1 is 20 to 700 m2 (preferably 35 to 350 m2) and / or L1 is 20 to 4200 m2, preferably 5.87 to 1225 m2. 3. The heat removal tube assembly as described in any of the preceding or following aspects, wherein the total number of straight tubes in the heat removal tube assembly is set to Nt, the number of straight tubes per unit cross-sectional area A, i.e. Nt / S1, is 4-16 / m2 (preferably 5-14 / m2, and preferably 7-13 / m2), and / or the cross-sectional shape of A is circular, oval, and preferably circular or substantially circular, and / or the internal shape and external contours of the cross-sectional shape of the straight tube are circular, oval, and preferably circular or substantially circular. 4. The heat removal tube assembly as described in any of the preceding or following aspects, characterized in that the heat removal tube assembly is capable of recovering 1-10 MPa saturated steam (preferably 2-8 MPa saturated steam, preferably 3-5 MPa saturated steam) and / or has a heat removal capacity of 0.5-3.0 t saturated steam per unit cross-sectional area (m2) per hour, preferably 1.0-2.8 t saturated steam per unit cross-sectional area (m2) per hour, preferably 1.2-2.4 t saturated steam per unit cross-sectional area (m2) per hour, when recovered as 4.5 MPa saturated steam, wherein the unit cross-sectional area refers to the unit cross-sectional area A. 5. A heat removal tube assembly as described in any of the preceding or following aspects, wherein for heat removal tube(s) of said heat removal tube assembly other than a profiled heat removal tube, an angle between a line drawn from the central axis of the projection of each connecting connection on cross section A and a line drawn from the central axis of the projection of other connecting connections on said heat removal tube at a position immediately above or below and in fluid communication with said connecting connections on said intersection A is 180 degrees, and / or said heat removal tube comprises a cooling water inlet, and a number of cooling water inlets from (preferably 2-8, 2-6 or 2-4) of said heat removal tubes merge into a cooling water inlet header in said heat removal section, and / or where said heat removal tube comprises a cooling water outlet, and a number of cooling water outlets (preferably 2-8, 2-6 or 2-4) of said heat removal tubes In a header, the cooling water outlet is integrated into the heat removal section. 6. Heat removal pipe assembly As described in any of the previous or subsequent aspects, it is specified that the outer diameter of the straight pipes is respectively 80-180 mm, preferably 90-170 mm, and / or the inner diameter of the straight pipes is respectively 150-60 mm, preferably 70-140 mm, and / or the length of the straight pipes is respectively 4-13 m, preferably 5-12.0 m, and / or the distance between two adjacent straight pipes in each heat removal pipe is 100-700 mm, preferably 150-300 mm, and / or the length H of the heat removal section is 4-13 m (preferably 5-12 m). 7. A heat removal tube assembly as described in any one of the preceding or following aspects, wherein it is specified that (1) The full propylene treatment capacity of the fluidized bed reactor per hour is 140-290 kg propylene / m2 of section A, except for the end point 290, L1 / S1 is 1.0-2.5 m-1 (except for the end point 2.5), preferably 1.4-2.2 m-1, or, (2) The full propylene treatment capacity of the fluidized bed reactor per hour is 200-370 kg propylene / m2 of cross section A, L1 / S1 is 1.8-4.6 m-1, preferably 2.0-4.1 m-1, or (3) The full propylene purification capacity of the fluidized bed reactor per hour is 290-445 kg propylene / m2 of cross section A, L1 / S1 is 2.5-6.0 m-1, preferably 2.9-5.3 m-1, 8. A fluidized bed reactor, characterized in that it comprises a header, a dilute phase zone, a heat removal section, a pre-reaction section and a cone from top to bottom, in which a heat removal tube assembly according to any one of the previous or subsequent aspects is located in the heat removal section. 9. A method for producing an unsaturated nitrile, comprising the step of subjecting an olefin (such as propylene) to an ammoxidation reaction in a fluidized bed reactor, as described in any of the preceding or following aspects to obtain an unsaturated nitrile (such as acrylonitrile). 10. A method for increasing the load of a fluidized bed reactor, wherein the full propylene treatment capacity per hour in the fluidized bed reactor is 140-290 kg propylene / m2 of cross section A (excluding the end point 290) and L1 / S1 is 1.0-2.5 m-1 (excluding the end point 2.5), the method comprising increasing L1 / S1 to 2.5-6.0 m-1, preferably to 2.9-5.3 m-1, while increasing the full propylene treatment capacity per fluidized bed reactor to 290-445 kg propylene / m2 of cross section A. 11. A method for producing an unsaturated nitrile, comprising the step of subjecting an olefin (such as propylene) to an ammoxidation reaction in a fluidized bed reactor to obtain an unsaturated nitrile (such as acrylonitrile), wherein the load of the fluidized bed reactor is increased according to the load increase method as described in any of the preceding or following aspects. 12. The method as described in any one of the preceding or following aspects, wherein the molar ratio of propylene / ammonia / air (calculated as molecular oxygen) is 1:1.1-1.3:1.8-2.0, the reaction temperature is 420-440℃, the reaction pressure (gauge pressure) is 0.03-0.14 MPa, and the hourly space velocity of the catalyst weight is 0.06-0.15 h-1. Brief description of the maps Figure 1 is a schematic view of the front of an existing fluidized bed reactor. Figure 2 is a schematic top view of an existing reaction heat removal tube assembly for a fluidized bed. Figure 3 is a schematic top view of a reaction heat removal tube assembly for a fluidized bed in accordance with the present application. Figures 4A-4B are schematic views of the heat removal tube arrangement of a heat removal tube assembly in accordance with the present disclosure. Figure 5 is a graph of the pressure pulse intensity. Figures 6 and 7 are schematic views of the heat removal tube header layout of the present application. Explanation of reference numbers: 1: Fluidized bed reactor wall 2: Heat removal pipe 3: Cooling water inlet heat removal pipe 4: Cooling water outlet heat removal pipe 5: Lower connection clamps of heat removal pipe 6: Upper connection clamps of heat removal pipe 7: Oxygen-containing gas distribution plate 8: Propylene-ammonia distributor 9: High efficiency cyclone separator Technical effects By using the heat removal tube assembly and fluidized bed reactor according to the present disclosure, the production capacity of the desired product of the equipment can be improved, the need for improving the reaction load can be fully met, and the operating cost of the equipment can be reduced. In the heat removal tube assembly according to the present disclosure, a closer arrangement can be realized, that is, more straight tubes can be arranged per unit cross-sectional area of ​​the reactor, thereby increasing the heat removal capability. By using the heat removal tube assembly and fluidized bed reactor according to the present application, the change of flow pattern in the fluidized bed can be accelerated and the mass transfer efficiency can be improved. By using the heat removal tube assembly and fluidized bed reactor according to the present disclosure, the growth of bubbles can be effectively inhibited, so that the feed gas conversion rate can be improved and the yield of the target reaction product can be increased. By using the heat removal tube assembly and fluidized bed reactor according to the present application, the degree of re-mixing of the gas and solid phases can be reduced and the production of deep oxidation products can be reduced. By using the heat removal tube assembly and fluidized bed reactor according to the present application, the heat transfer efficiency can be improved and the operation period of the equipment can be prolonged. Detailed description of the invention The present disclosure is illustrated in detail below with reference to its embodiments, but it should be noted that the scope of the present disclosure is not limited by those embodiments, but rather is defined by the appended claims. All advertisements, patent applications, patents, and other references cited herein are hereby incorporated by reference in their entirety. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as is commonly understood by those skilled in the art. In the event of a conflict, the material described herein, including the definitions, shall control. Where a material, method, component, apparatus or equipment is described herein as "known to those skilled in the art," "commonly known in the art," or the like, it is to be understood that it covers not only those materials, methods, components, apparatus or equipment in use in the art at the time of filing of the present application, but also those not currently in use, but commonly known in the art as suitable for similar purposes. In the context of the present disclosure, the term "substantially" means that a deviation acceptable or reasonable by those skilled in the art may exist, such as a deviation within ±10%, within ±5%, within ±1% within ±0.5% or within ±0.1%. In the context of this declaration, unless specifically stated otherwise, all percentages, parts, ratios, etc., are expressed by weight and all pressures given are gauge pressures. In the context of the present disclosure, any two or more embodiments of the present disclosure may be optionally combined, and the resulting technical solution forms part of the primary disclosure of the present disclosure and falls within the scope of the present disclosure. According to one embodiment, the present disclosure relates to a heat removal tube assembly, particularly a heat removal water tube assembly. According to the present disclosure, a "heat removal tube assembly" and "heat removal tube" may be used to remove excess heat from a reactor in which an exothermic reaction (or some exothermic reaction step) is being carried out, to maintain the reaction within a certain temperature range. Examples of the reactor include a fluidized bed reactor, and in particular a fluidized bed reactor for the production of acrylonitrile. According to an embodiment of the present disclosure, the heat removal tube assembly includes at least 10 (preferably 10 to 100, more preferably 20 to 80) heat removal tubes. Typically, the heat removal tubes include a cooling water inlet, straight tubes, and a cooling water outlet, and connection clamps for connecting these tubes in a fluid communication manner. Preferably, the heat removal pipe comprises N (N is equal to or greater than 3, preferably N is equal to 3 to 30, and preferably N is equal to 3 to 20) straight pipes and N-1 connecting fittings for connecting two adjacent straight pipes in series and establishing fluid communication therebetween. As shown in FIG. 3 , each heat removal pipe 2 comprises: a cooling water inlet 3 , a cooling water outlet 4 , at least 3 adjacent straight pipes and connecting fittings for connecting two adjacent straight pipes in series and establishing fluid communication therebetween. As shown in FIG. 4 , where a fitting for connecting two straight pipes is located below the straight pipes (hereinafter, sometimes simply referred to as "lower connecting fittings 5"), another connecting fitting is located adjacent to it above the straight pipes (hereinafter, sometimes referred to as "lower connecting fittings 6"). In the context of the present application, the straight pipe near the cooling water inlet of a heat removal pipe is referred to as the first connection fittings. In addition, in a heat removal pipe, each straight pipe shows an upper-lower positional relationship along the cooling water flow direction. In the present application, the position adjacent and above is referred to as the upper position, and the position adjacent and below is referred to as the lower position. According to an embodiment of the present disclosure, a heat removal tube assembly is configured to be located in a heat removal section of a fluidized bed reactor. It is understood that the heat removal tube is also configured to be located in the heat removal section of the fluidized bed reactor. In particular, the straight tubes of the heat removal tubes are located substantially in the dense phase region of the fluidized bed reactor and are used to remove the heat of reaction from the system in a timely manner and maintain stable operation of the system. For this reason, within the framework of the present specification, the "heat removal section" refers to the region of the fluidized bed reactor in which the heat removal tubes are located, in particular the region of the fluidized bed reactor in which the straight tubes from the heat removal tubes are located, in particular the region in the dense phase region of the fluidized bed reactor in which the straight tubes from the heat removal tubes are located. In the prior art, the heat removal tube sets in the heat removal section are usually arranged in the manner shown in Figure 2, that is, the heat removal tubes are arranged in a straight line. On the other hand, as shown in Figure 1, other internal components such as the Cyclone Diplog 9 are also included in the heat removal section of the fluidized bed reactor. For this reason, in order to further improve the fluidization conditions and the high capacity of the equipment required, the existing heat removal tube sets may not be sufficient to enable the normal operation of the equipment. According to the embodiment of the present disclosure, in which the length of the heat removal section along the central axis of the fluidized bed reactor is designated as H (in meters), a cross section of the heat removal section (referred to as cross section A) is obtained by cutting along a direction perpendicular to the central axis of the fluidized bed reactor at a position in the entire length H area of ​​the heat removal section. Here, the cross section of the heat removal section refers to the cross section of the internal lines of the fluidized bed reactor in the heat removal section. This region is preferably within a region of 49% H above to 49% H below the center point of the reaction heat removal section, preferably within a region of 45% H above to 38% H below the center point of the reaction heat removal section, and preferably within a region of 40% H above to 8% H below the center point of the reaction heat removal section. According to an embodiment of the present disclosure, the heat removal tube assembly comprises a profiled heat removal tube. Here, the number of profiled heat removal tubes in the heat removal tube assembly is at least 1, preferably 1, 2 or 3 or at least 20%, at least 50% or at least 65% of the total heat removal tubes of the heat removal tube assembly. In addition, in terms of optimally achieving the technical effects of the present disclosure, the number of profiled heat removal tubes is up to 88%, preferably 75% or 70% of the total heat removal tubes in the heat removal tube assembly. Theoretically, in order to maintain the stability of the radial reaction temperature, it is desirable that the heat removal straight tubes are uniformly distributed over the cross-section of the reactor during operation. However, in reality, the heat of the reaction changes with the change of the feed gas feed amount, and for the heat removal straight tubes fixed in the reactor bed layer, the heat removal straight tubes in operation cannot be completely uniformly distributed, but it is preferable that the heat removal straight tubes are distributed as uniformly as possible, so that the radial reaction temperature difference is as small as possible, for example, within 3 ℃. The heat emitted by the chemical reaction can be estimated, and the required heat removal straight tubes can also be calculated in advance. Since the heat removal capacity in the area where the profile heat removal pipe is placed is greatly increased, the distance between adjacent profile heat removal pipes at the operating site is increased, and although the heat transfer efficiency of the fluidized bed is high, there is a risk that the reaction heat cannot be removed in time from the area between the two profile heat removal pipes. If all (100%) of the heat removal pipes in the heat removal pipe assembly are profile heat removal pipes, the technical effect intended by the present disclosure cannot be effectively achieved. According to an embodiment of the present application, a profiled heat removal pipe refers to a heat removal pipe in which an angle (i.e., angle A) is formed between a line extended from the central axis of the protrusion of at least one of the connection fasteners (referred to as special connection fasteners) on cross section A and a line drawn from the central axis of the protrusion of at least one other connection fastener on cross section A, which is greater than 0 degrees and less than 180 degrees. The angle A is preferably 30-150 degrees, and preferably 60-120 degrees. From the perspective of realizing the technical effect of the present application, the angle A is preferably about 90 degrees, so that close arrangement of straight heat removal pipes can be realized. In addition, the number of special connection fasteners in a profile heat removal pipe is preferably at least 2, 3 or 4 and at most 80, 90% or 100% of the total connection fasteners in the profile heat removal pipe. From the perspective of realizing an optimal technical effect, the number of special connection fasteners is preferably 100% of the total connection fasteners in the profile heat removal pipes, so that the heat removal pipes are arranged parallel to each other at the same distance while maintaining sufficient service paths in the equipment. According to an embodiment of the present disclosure, as at least one of the other connection fasteners is said, further connection fasteners are preferably provided on the profiled heat removal pipe in a position immediately above and in fluid communication with the connection fasteners. Furthermore, the first connection fasteners of the profiled heat removal pipe are usually excluded, given the situation that they are not immediately above the first connection fasteners. However, the angle (i.e., angle A1) formed between a line extending from the centerline of the first sealing connection on the cross section A and a line extending from the centerline of the cooling water inlet on the cross section of the section A may be any value, for example 30-180 degrees, 60-180 degrees, 90 degrees or 180 degrees. For the same reason explained above, angle A1 is also preferably 90 degrees. Specifically, in the projection on the cross section, the straight pipes and connecting clamps of the same heat removal pipe 2 may be arranged in the manner shown in Figures 4A to 4D. According to an embodiment of the present disclosure, the straight pipes of the heat removal pipe 2 in the heat removal pipe assembly have circular cross-sectional outer lines with an outer perimeter of 3.14 × D. Here, D is the diameter of the straight pipe outer lines. Therefore, in the cross-section of the heat removal section shown in FIG. 3, the sum L1 of the cross-section outer lines of all the straight pipes of the heat removal pipe assembly is the sum of the outer perimeters of all the straight pipes in the cross-section of the heat removal section. According to the embodiment of the present disclosure, in which the cross-sectional area A is set to S1 (in m2) and the sum of the outer perimeters of the cross-sectional areas of all the straight pipes of the heat removal pipe assembly in the cross-section A is set to L1 (in m), L1 / S1 is 1.0 to 6.0 m-1 (preferably 2.4 to 5.6 m-1, more preferably 2.9 to 5.3 m-1). Here, L1 / S1 represents the distribution density of all the heat removal pipes (or straight pipes) in the cross-section A, which is an optimal range for achieving the technical effect of the present disclosure. When the distribution density L1 / S1 is less than 1.0, the operating reaction load of the equipment is low, so that the production cost is high and the economy is poor for enterprises, and when the distribution density L1 / S1 is greater than 6.0, the equipment can operate with a large reaction load, so that the need for more reaction heat removal can be met, the number of profiled heat removal pipes in the reactor can be increased, and the stability of the reaction temperature may be damaged in the operation process or the storage space may be compressed. According to one embodiment, the present disclosure relates to a heat removal tube assembly, characterized in that the heat removal tube assembly is located in a heat removal section of a fluidized bed reactor, the heat removal tube assembly comprises at least one (preferably 10 to 100 and more preferably 20 to 80) heat removal tubes, the heat removal tubes comprise N (N) greater than or equal to 3, preferably N is 3 to 30 and more preferably N is 3 to 20) heat removal tubes, and N-1 connecting clamps are provided for connecting two adjacent straight tubes therein in series and providing a fluidic connection therebetween, wherein the length of the heat removal section along the central axis of the fluidized bed reactor is set to H (in m) and the cross-sectional area of ​​the heat removal section is obtained by cutting along a direction perpendicular to the central axis of the fluidized bed reactor at a position in the entire region of the length H of the heat removal section (preferably within a region from 49% above H to 49% below the central point of the section) Heat of reaction removal, preferably in the region from 45% H above to 38% H below the center point of the section Heat of reaction removal, preferably in the region from 40% H above to 8% H below the center point of the sectionreaction heat removal) is set as S1 (in m2), in the heat removal pipe, an angle is formed between a line drawn from the central axis of the protrusion of at least one of the connection fasteners on the cross-sectional surface and a line drawn from the central axis of the protrusion of at least one other connection fastener on the cross-sectional surface, which is greater than 0 degrees and less than 180 degrees (preferably 30-150 degrees, preferably 60-120 degrees, preferably 90 degrees), and in the cross-section, the sum of the outer perimeters of the cross-sectional areas of all the straight pipes of the heat removal pipe assembly is set as L1 (in m), L1 / S1 is equal to 1.0-6.0 m-1 (preferably 2.0-4.0 m-1, preferably 2.5-3.5 m-1). According to an embodiment of the present disclosure, said area S1 is between 20 and 700 m2 (preferably between 35 and 350 m2). According to an embodiment of the present disclosure, L1 is equal to 20 to 4200 m, preferably 87.5 to 1225 m. According to an embodiment of the present disclosure, in which the total number of straight pipes in the heat removal pipe assembly is set to Nt, the number of straight pipes per unit cross-sectional area A, that is, Nt / S1, is 4-16 / m2 (preferably 5-14 / m2, and more preferably 13-7 / m2). Here, Nt / S1 also represents the distribution density of heat removal pipes (or straight pipes) over the cross-sectional area A, which has an optimal range for achieving the technical effect of the present disclosure. When the distribution density Nt / S1 is less than 4, the bubble collapse is not beneficial to the fluidized bed, so that more feed gas is discharged from the reactor along with the gas without participating in the reaction, and the reaction is affected; and when the distribution density Nt / S1 is more than 16, the high-load reaction operation can be satisfied, but there is a risk of instability of the reaction temperature during the operation process and the space for storage is compressed due to the increase of profiled heat removal pipes. According to an embodiment of the present disclosure, the cross-sectional shape of A is circular, oval or, preferably, circular or approximately circular. According to an embodiment of the present disclosure, the inner and outer contours of the cross-sectional area of ​​the straight tube are circular, oval, preferably circular or nearly circular. According to an embodiment of the present disclosure, the heat removal tube assembly is capable of recovering 1 to 10 MPa of saturated steam, preferably 2 to 8 MPa of saturated steam, preferably 3 to 5 MPa of saturated steam. In particular, the heat removal capacity of the heat removal tube assembly, when 4.5 MPa saturated steam is recovered, is 0.5 to 3.0 t of saturated steam per unit cross-sectional area (m2) per hour, preferably 1.0 to 2.8 t of saturated steam per unit cross-sectional area (m2) per hour, preferably 1.2 to 2.4 t of saturated steam per unit cross-sectional area (m2) per hour, where the unit cross-sectional area refers to the unit cross-sectional area A. Compared with the prior art, the heat removal tube assembly can recover more saturated steam, thereby exhibiting a stronger heat removal capacity and meeting the requirement of high reaction load. According to an embodiment of the present disclosure, the heat removal pipe assembly further includes a conventional heat removal pipe, and the conventional heat removal pipes and the profiled heat removal pipes together constitute the heat removal pipe assembly. Here, in a conventional heat removal pipe, an angle is formed between a line drawn from the central axis of the protrusion of each of the connection clamps on cross section A and a line drawn from the central axis of the protrusion of the other connection clamps on the heat removal pipe at a position exactly above or below and in fluid communication with the connection clamps on cross section A, which is 180 degrees. In short, like a conventional heat removal pipe, all the straight pipes lie in one plane. In the context of the present application, a heat removal pipe includes a profile heat removal pipe and a conventional heat removal pipe, unless expressly stated otherwise. According to an embodiment of the present disclosure, a number (preferably 2-8, 2-6 or 2-4) of the cooling water inlets of the heat removal tubes are combined into a cooling water inlet header in the heat removal section. In other words, a plurality of the heat removal tubes share a common cooling water inlet. According to the present disclosure, the cooling water inlet header is in fluid communication with an external cooling water supply source through the wall of the fluidized bed reactor, whereby cooling water is supplied to each heat removal tube through the cooling water inlet header. The heat removal tube herein (referred to as a heat removal branch tube) may be a conventional heat removal tube, a profiled heat removal tube, or any combination thereof, and is not particularly limited. According to an embodiment of the present disclosure, a plurality (preferably 2-8, 2-6 or 2-4) of the cooling water outlets of the heat removal tubes are integrated into a cooling water outlet header in the heat removal section. In other words, a plurality of the heat removal tubes share a common cooling water outlet. According to the present disclosure, the cooling water outlet header is in fluid communication with an external cooling water receiving means through the wall of the fluidized bed reactor, so that the cooling water (usually containing more steam) is discharged to the external environment through the cooling water outlet header after heat removal from the heat removal tubes. The heat removal tube herein (referred to as a heat removal branch tube) may be a conventional heat removal tube, a profiled heat removal tube or any combination thereof, and is not particularly limited. Figures 6 and 7 are schematic views of the heat removal tube header layout of the present application. As can be seen from the figures, the cooling water inlets / outlets of many heat removal tubes are integrated into one header. According to an embodiment of the present disclosure, the ratio of the cross-sectional area of ​​a header (such as a cooling water inlet header or a cooling water outlet header) to the total cross-sectional area of ​​a plurality of heat removal branch pipes (usually calculated based on the cooling water inlets or cooling water outlets of a plurality of heat removal branch pipes) corresponding thereto is 0.5 to 1, preferably 0.55 to 0.95, and preferably 0.6 to 0.9. According to an embodiment of the present disclosure, the inner diameter of the straight pipes is each independently 60-150 mm, preferably 70-140 mm. According to an embodiment of the present application, the length of the straight pipes is each independently 4 to 13 m, preferably 5 to 12.0 m. According to an embodiment of the present disclosure, the distance between two adjacent straight pipes in each heat removal pipe is 100-700 mm, preferably 150-300 mm. According to an embodiment of the present disclosure, the length H of the heat removal section is 4-13 m (preferably 5-12 m). According to the embodiment of the present disclosure, in which the total propylene treatment capacity per hour of the fluidized bed reactor is 140-290 kg propylene / m2 of cross section A (excluding the end point 290), L1 / S1 is equal to 1.0-2.5 m-1 (excluding the end point 2.5), preferably 1.4-2.2 m-1. This situation shows the performance of the fluidized bed reactor at a lower operating load. According to the embodiment of the present disclosure, in which the total propylene treatment capacity per hour in the fluidized bed reactor is 200-370 kg propylene / m2 of cross section A, L1 / S1 is 1.84-4.6 m-1, preferably 2.0-4.1 m-1. This represents the operating condition of the fluidized bed reactor at an average operating load. According to the embodiment of the present disclosure, in which the total propylene treatment capacity per hour in the fluidized bed reactor is 290-445 kg propylene / m2 of cross section A, L1 / S1 is 2.5-6.0 m-1, preferably 2.9-5.3 m-1. This condition represents the operation of the fluidized bed reactor at a higher operating load and is the most preferred operating condition of the present disclosure. According to one embodiment, the present disclosure also relates to a fluidized bed reactor. The reactor sequentially comprises a header, a dilute phase zone, a heat removal section, a pre-reaction section, and a cone from top to bottom, wherein a heat removal tube assembly as described in any of the preceding embodiments is disposed in the heat removal section. According to one embodiment, the present disclosure also relates to a method for producing an unsaturated nitrile, in particular a method for producing acrylonitrile. The method comprises the step of subjecting an olefin (such as propylene) to an ammoxidation reaction in a fluidized bed reactor as described in any of the preceding embodiments to obtain an unsaturated nitrile (such as acrylonitrile). According to one embodiment, the present disclosure also relates to a method for increasing the reaction load of a fluidized bed reactor. Here, as the initial reaction load of the circulating fluidized bed reactor, the total propylene treatment capacity per hour in the circulating fluidized bed reactor is 140-290 kg propylene / m2 of cross section A (excluding the end point 290), the initial value of L1 / S1 of the fluidized bed reactor is 1.0-2.5 m-1 (excluding the end point 2.5). In order to achieve the increased reaction load, the method includes increasing the total propylene treatment capacity of the fluidized bed reactor from the initial reaction load to 290-445 kg propylene / m2 of cross section A per hour, and in order to accommodate this increase in reaction load to ensure that the reaction can proceed smoothly, it is necessary to increase L1 / S1 from the initial value to 2.5-6.0 m-1, preferably to 2.9-5.3 m-1.According to one embodiment, the present disclosure also relates to a method for producing an unsaturated nitrile comprising the step of subjecting an olefin (such as propylene) to an ammoxidation reaction in a fluidized bed reactor to obtain an unsaturated nitrile (such as acrylonitrile), wherein the fluidized bed reactor load is increased according to the load increase method as described in any of the previous embodiments described in the present specification. According to an embodiment of the present disclosure, the ammoxidation reaction may be carried out in any manner and by any method known in the art, and such information is known to those skilled in the art and will not be described in detail herein. However, for the ammoxidation reaction conditions, specific examples thereof include those in which the molar ratio of propylene / ammonia / air (calculated as molecular oxygen) is 1:1.1-1.3:1.8-2.0, the reaction temperature is 420-440 ℃, the reaction pressure (gauge pressure) is 0.03-0.14 Mpa, and the weight hourly space velocity of the catalyst is 0.06-0.15 h-1. Examples The present disclosure will be explained in more detail with reference to the following examples and comparative examples, but the present disclosure is not limited to those examples. In the following examples and comparative examples, acrylonitrile yield and propylene conversion can be calculated based on the following equations: Acrylonitrile yield: AN%=CAN / ΣC*100 Propylene conversion: Cc3%= (1-Cc3out / Cc3in)*100 Where: CAN: The molar amount (mol) of carbon present in AN in the gas at the reactor outlet. ΣC: Total molar amount (mol) of carbon present in the gas at the reactor outlet. Cc3out: The molar amount (mol) of carbon present in C3 in the gas at the reactor outlet. Cc3in: The molar amount (mol) of carbon present in C3 in the reactor inlet gas. It is known in the art that the quality of fluidization can be well evaluated if the pressure pulse intensity of the fluidized bed has the characteristic of “low amplitude with high frequency” as shown in Figure 5. In all the following examples, the pressure pulse intensity from the fluidized bed was similar to Figure 5. In the following examples and comparative examples, the heat removal tubes that are not specifically arranged are conventional heat removal tubes. Example 1 The fluidized bed reactor had a diameter of 9 m, which was filled with 180 tons of SANC series acrylonitrile catalyst of Sinopec Shanghai Petrochemical Research Institute Co., Ltd., 480 straight tubes with the same height were arranged in the reactor, which were divided into 44 heat removal tubes, 12 heat removal tubes were arranged in the manner shown in Figure 4A, the number of straight tubes per unit cross-sectional area of ​​the heat removal section at its central point was 7.6 / m2, the outer diameter of the heat removal tubes was 89 mm, and L1 / S1 was 2.1 / m. The propylene feed rate was 7700 NM3 / h, the full propylene purification capacity at this time was 227 kg propylene / h / m2 of section A, the reaction temperature was 430 ℃, the reaction pressure was 0.04MPa, the ratio of propylene: ammonia: air was 1: 1.2: 9.6, the reaction could be carried out stably for a long time (such as 10,000 hours), and the amount of heat removed per hour was 1.24 tons of 4.5 MPa saturated steam / m2. Example 2 The fluidized bed reactor had a diameter of 9 m, and 180 tons of SANC series acrylonitrile catalyst of Sinopec Shanghai Petrochemical Research Institute Co., Ltd. were filled into it. 572 straight tubes with the same height were arranged in the reactor, which were divided into 56 heat removal tubes. 36 heat removal tubes were arranged in the manner shown in Figure 4A. The number of straight tubes per unit cross-sectional area of ​​the heat removal section at its center point was 9.0 / m2. Each group was formed by connecting 6, 10, and 12 straight tubes of the heat removal tube in series through straight tube connecting clamps. The outer diameter of each heat removal tube was 140 mm and L1 / S1 was 4.0. The propylene feed rate was 11800 NM3 / h, the full propylene purification capacity at this time was 349 kg propylene / h / m2 of section A, the reaction temperature was 430 ℃, the reaction pressure was 0.04MPa, and the ratio of propylene: ammonia: air was 1:1.2:9.6, the reaction could be carried out stably for a long time (such as 10000 hours), and the amount of heat removed per hour was 1.98 tons of 4.5 MPa steam / m2. Example 3 The fluidized bed reactor had a diameter of 9 meters, and 180 tons of SANC series acrylonitrile catalyst of Sinopec Shanghai Petrochemical Research Institute Co., Ltd. were filled into it. 732 straight tubes with the same height were arranged in the reactor, which were divided into 70 heat removal tubes. 42 heat removal tubes were arranged in the manner shown in Figure 4A. The number of straight tubes per unit cross-sectional area of ​​the heat removal section at its center point was 11.5 / m2. Each group was formed by connecting 6, 10, and 12 straight tubes of the heat removal tube in series through straight tube connecting clamps. The outer diameter of each heat removal tube was 114 mm and L1 / S1 was 4.1. The propylene feed rate was 11800 NM3 / h, the full propylene purification capacity at this time was 349 kg propylene / h / m2 of section A, the reaction temperature was 430 ℃, the reaction pressure was 0.04MPa, and the ratio of propylene: ammonia: air was 1:1.2:9.6, the reaction could be carried out stably for a long time (such as 10000 hours), and the amount of heat removed per hour was 2.01 tons of 4.5 MPa steam / m2. Example 4 The fluidized bed reactor had a diameter of 9 m, and 180 tons of SANC series acrylonitrile catalyst of Sinopec Shanghai Petrochemical Research Institute Co., Ltd. were filled into it. 584 straight tubes with the same height were arranged in the reactor, which were divided into 58 heat removal tubes. 36 heat removal tubes were arranged in the manner shown in Figure 4B. The number of straight tubes per unit cross-sectional area of ​​the heat removal section at its center point was 9.18 / m2. Each group was formed by connecting 6, 10, and 12 straight tubes of the heat removal tube in series through straight tube connecting clamps. The outer diameter of each heat removal tube was 114 mm and L1 / S1 was 3.3. The propylene feed rate was 11800 NM3 / h, the full propylene purification capacity at this time was 349 kg propylene / h / m2 of section A, the reaction temperature was 430 ℃, the reaction pressure was 0.04MPa, and the ratio of propylene: ammonia: air was 1:1.2:9.6, the reaction could be carried out stably for a long time (such as 10000 hours), and the amount of heat removed per hour was 1.98 tons of 4.5 MPa steam / m2. Example 5 The fluidized bed reactor had a diameter of 9 meters, and 180 tons of SANC series acrylonitrile catalyst of Sinopec Shanghai Petrochemical Research Institute Co., Ltd. were filled into it. 732 straight tubes with the same height were arranged in the reactor, which were divided into 72 heat removal tubes. 52 heat removal tubes were arranged in the manner shown in Figure 4A. The number of straight tubes per unit cross-sectional area of ​​the heat removal section at its center point was 11.5 / m2. Each group was formed by connecting 6, 10, and 12 straight tubes of the heat removal tube in series through straight tube connecting clamps. The outer diameter of each heat removal tube was 140 mm and L1 / S1 was 5.1. The propylene feed rate was 14400 NM3 / h, the full propylene purification capacity at this time was 425 kg propylene / h / m2 of section A, the reaction temperature was 430 ℃, the reaction pressure was 0.04MPa, and the ratio of propylene: ammonia: air was 1:1.2:9.6, the reaction could be carried out stably for a long time (such as 10000 hours), and the amount of heat removed per hour was 2.40 tons of 4.5 MPa steam / m2. Example 6 The fluidized bed reactor had a diameter of 9 meters, and 180 tons of SANC series acrylonitrile catalyst of Sinopec Shanghai Petrochemical Research Institute Co., Ltd. were filled into it. 584 straight tubes with the same height were arranged in the reactor, which were divided into 56 heat removal tubes. 32 heat removal tubes were arranged in the manner shown in Figure 4C. The number of straight tubes per unit cross-sectional area of ​​the heat removal section at its center point was 9.18 / m2. Each group was formed by connecting 6, 10, and 12 straight tubes of the heat removal tube in series through straight tube connecting clamps. The outer diameter of each heat removal tube was 140 mm and L1 / S1 was 4.04 / m. The propylene feed rate was 11800 NM3 / h, the full propylene purification capacity at this time was 349 kg propylene / h / m2 of section A, the reaction temperature was 430 ℃, the reaction pressure was 0.04MPa, and the ratio of propylene: ammonia: air was 1:1.2:9.6, the reaction could be carried out stably for a long time (such as 10000 hours), and the amount of heat removed per hour was 1.93 tons of 4.5 MPa steam / m2. Example 7 The fluidized bed reactor had a diameter of 9 meters, and 180 tons of SANC series acrylonitrile catalyst of Sinopec Shanghai Petrochemical Research Institute Co., Ltd. were filled into it. 584 straight tubes with the same height were arranged in the reactor, which were divided into 56 heat removal tubes. 32 heat removal tubes were arranged in the manner shown in Figure 4D. The number of straight tubes per unit cross-sectional area of ​​the heat removal section at its center point was 9.18 / m2. Each group was formed by connecting 6, 10, and 12 straight tubes of the heat removal tube in series through straight tube connecting clamps. The outer diameter of each heat removal tube was 140 mm and L1 / S1 was 4.04 / m. The propylene feed rate was 11800 NM3 / h, the full propylene purification capacity at this time was 349 kg propylene / h / m2 of section A, the reaction temperature was 430 ℃, the reaction pressure was 0.04MPa, and the ratio of propylene: ammonia: air was 1:1.2:9.6, the reaction could be carried out stably for a long time (such as 10000 hours), and the amount of heat removed per hour was 1.94 tons of 4.5 MPa steam / m2. Example 8 The fluidized bed reactor had a diameter of 9 meters, and 180 tons of SANC series acrylonitrile catalyst of Sinopec Shanghai Petrochemical Research Institute Co., Ltd. were filled into it. 584 straight tubes with the same height were arranged in the reactor, which were divided into 56 heat removal tubes. 48 heat removal tubes were arranged in the manner shown in Figure 4A. The number of straight tubes per unit cross-sectional area of ​​the heat removal section at its center point was 9.18 / m2. Each group was formed by connecting 6, 10, and 12 straight tubes of the heat removal tube in series through straight tube connecting clamps. The outer diameter of each heat removal tube was 140 mm and L1 / S1 was 4.04. The propylene feed rate was 11800 NM3 / h, the full propylene purification capacity at this time was 349 kg propylene / h / m2 of section A, the reaction temperature was 430 ℃, the reaction pressure was 0.04MPa, and the ratio of propylene: ammonia: air was 1:1.2:9.6, the reaction could be carried out stably for a long time (such as 10000 hours), and the amount of heat removed per hour was 1.98 tons of 4.5 MPa steam / m2. Comparative Example 1 The fluidized bed reactor had a diameter of 9 meters, and 180 tons of SANC series acrylonitrile catalyst of Sinopec Shanghai Petrochemical Research Institute Co., Ltd. were filled into it. 380 straight tubes with the same height were arranged in the reactor, which were divided into 36 heat removal tubes and arranged in the heat removal tube method shown in Figure 2. The number of straight tubes per unit cross-sectional area of ​​the heat removal section at its central point was 6.0 / m2, the outer diameter of each heat removal tube was 89 mm, and L1 / S1 was 1.67 / m. The propylene feed rate was 11800 NM3 / h, the full propylene purification capacity at this time was 349 kg propylene / h / m2 of section A, the reaction temperature was 430 ℃, the reaction pressure was 0.04MPa, and the ratio of propylene: ammonia: air was 1:1.2:9.6. During the operation process of the equipment, the reaction temperature could not be stably controlled by the heat removal tube assembly, and due to the insufficient amount of heat removal tubes, the long-term stable operation of the equipment could not be achieved. Comparative Example 2 The fluidized bed reactor had a diameter of 9 meters, and 180 tons of SANC series acrylonitrile catalyst of Sinopec Shanghai Petrochemical Research Institute Co., Ltd. were filled into it. 584 straight tubes with the same height were arranged in the reactor, which were divided into 56 heat removal tubes and arranged in the heat removal tube method shown in Figure 2. The number of straight tubes per unit cross-sectional area of ​​the heat removal section at its center point was 9.18 / m2. Each group was formed by connecting 6, 10, and 12 straight tubes of heat removal tubes in series through straight tube connecting clamps. The outer diameter of each heat removal tube was 140 mm and L1 / S1 was 4.04 / m. The propylene feed rate was 11800 NM3 / h, the full propylene purification capacity at this time was 349 kg propylene / h / m2 from section A, the reaction temperature was 430 ℃, the reaction pressure was 0.04MPa, and the ratio of propylene: ammonia: air was 1:1.2:9.6, and the amount of heat removed was 1.98 tons of steam / m2. Although normal operation of the equipment can be achieved, the maintenance of internal components cannot be met when the equipment is stopped. Comparative Example 3 The fluidized bed reactor had a diameter of 9 meters, and 180 tons of SANC series acrylonitrile catalyst of Sinopec Shanghai Petrochemical Research Institute Co., Ltd. were filled into it. 532 straight tubes with the same height were arranged in the reactor, which were divided into 46 heat removal tubes. All the heat removal tubes were arranged as shown in Figure 4A. The number of straight tubes per unit cross-sectional area of ​​the heat removal section at its center point was 8.37 / m2. Each group was formed by connecting 6, 10, and 12 straight tubes of heat removal tubes in series through straight tube connecting clamps. The outer diameter of each heat removal tube was 89 mm and L1 / S1 was 2.34. The propylene feed rate was 11800 NM3 / h, the full propylene purification capacity at this time was 349 kg propylene / h / m2 of section A, the reaction temperature was 430 ℃, the reaction pressure was 0.04MPa, and the ratio of propylene: ammonia: air was 1:1.2:9.6, the reaction could be carried out stably for a long time (such as 10000 hours), and the amount of heat removed per hour was 1.88 tons of 4.5 MPa steam / m2. Compared with Example 2, the fluidization quality was lower, which led to a decrease in propylene conversion and a decrease in the yield of the reaction product, and thus a decrease in the exothermic heat of the reaction. Example 8 The fluidized bed reactor had a diameter of 9 meters, and 180 tons of SANC series acrylonitrile catalyst of Sinopec Shanghai Petrochemical Research Institute Co., Ltd. were filled in it. 732 straight tubes with the same height were arranged in the reactor, which were divided into 70 heat removal tubes. 4 groups were formed by connecting 3 sets of heat removal tubes in parallel. The outer diameter of an inlet header of each heat removal tube was 140 mm. The outer diameter of an outlet header of each heat removal tube was 150 mm. The number of straight tubes per unit cross-sectional area of ​​each heat removal section at its center point was 11.5 / m2. Each heat removal tube was formed by connecting 6, 10, and 12 straight tubes of the heat removal tube in series through straight tube connecting clamps. The outer diameter of each heat removal tube was 89 mm, L1 / S1 was 3.2, the ratio of the cross-sectional area of ​​the inlet header to the total cross-sectional area of ​​the heat removal branch tubes was 0.82, and the ratio of the cross-sectional area of ​​the heat removal tube to the total cross-sectional area of ​​the heat removal branch tubes was 0.82. The outlet header to the total cross-sectional area of ​​the heat removal branch pipes was 0.95. The propylene feed rate was 11800 NM3 / h, the full propylene purification capacity at this time was 349 kg propylene / h / m2 of section A, the reaction temperature was 430 ℃, the reaction pressure was 0.04MPa, and the ratio of propylene: ammonia: air was 1:1.2:9.6, the reaction could be carried out stably for a long time (such as 10000 hours), and the amount of heat removed per hour was 1.98 tons of 4.5 MPa steam / m2. Example 9 The fluidized bed reactor had a diameter of 9 meters, and 180 tons of SANC series acrylonitrile catalyst of Sinopec Shanghai Petrochemical Research Institute Co., Ltd. were filled in it. 732 straight tubes with the same height were arranged in the reactor, which were divided into 70 heat removal tubes. 10 groups were formed by connecting 2 sets of heat removal tubes in parallel. The outer diameter of an inlet header of each heat removal tube was 180 mm. The outer diameter of an outlet header of each heat removal tube was 180 mm. The number of straight tubes per unit cross-sectional area of ​​each heat removal section at its center point was 11.5 / m2. Each heat removal tube was formed by connecting 6, 10, and 12 straight tubes of heat removal tubes in series through straight tube connecting clamps. The outer diameter of each heat removal tube was 140 mm. L1 / S1 was 5.1. The ratio of the cross-sectional area of ​​the inlet header to the total cross-sectional area of ​​the heat removal branch pipes was 0.83, and the ratio of the cross-sectional area of ​​the outlet header to the total cross-sectional area of ​​the heat removal branch pipes was 0.83. The propylene feed rate was 11800 NM3 / h, the full propylene purification capacity at this time was 425 kg propylene / h / m2 of section A, the reaction temperature was 430 ℃, the reaction pressure was 0.04MPa, and the ratio of propylene: ammonia: air was 1:1.2:9.6, the reaction could be carried out stably for a long time (such as 10000 hours), and the amount of heat removed per hour was 2.40 tons of 4.5 MPa steam / m2.

Claims

Claims 1. A set of heat removal tubes, wherein it is specified that it is configured to be located in a heat removal section of a fluidized bed reactor, the set of heat removal tubes includes at least 10 heat removal tubes, said heat removal tubes include N straight tubes and N-1 connecting clamps for connecting two adjacent straight tubes in series and establishing fluid communication therebetween, wherein N is equal to or greater than 3, the length of the heat removal section along the central axis of the fluidized bed reactor is determined by H in m, a cross-section of the heat removal section, referred to as cross-section A, is obtained by cutting along a direction perpendicular to the central axis of the fluidized bed reactor at a position in the entire area of ​​the length H of the heat removal section, for at least one of the heat removal tubes of the set of heat removal tubes and up to 88% of the total heat removal tubes of the set of heat removal tubes, referred to as profiled heat removal tubes, an angle between a line drawn from the central axis of the protrusion on the cross-section A of at least one of the clamps Profiled heat removal pipe connection and line drawn from the axisThe center of the protrusion on the cross section A is 30-150 degrees from at least one of the other connecting fasteners.

2. The heat removal tube assembly according to claim 1, wherein the heat removal tube assembly is a heat removal tube assembly, and / or said heat removal tube assembly comprises 10 to 100 or 20 to 80 heat removal tubes, and / or N is 3 to 30 or 3 to 20, and / or, the heat removal cross-section is obtained by cutting along a direction perpendicular to the central axis of the fluidized bed reactor at a position in a region of 49% H above to 49% H below the central region of the reaction heat removal section, or in a region of 45% H above to 38% H below the central region of the reaction heat removal section, or in a region of 40% H above to 8% H below the central region of the reaction heat removal section, and / or, for at least one of the heat removal tubes of the heat removal tube assembly and up to 88% of the total heat removal tubes of the heat removal tube assembly, referred to as profiled heat removal tubes, an angle between a line drawn from the central axis The projection on the cross section A of at least one of the connecting clamps of the profile heat removal pipe and the line drawn from the central axis of the projection on the cross section A of at least one of the other connecting clamps is 60-120 degrees or about 90 degrees.and / or wherein the cross-sectional area A is designated as S1 in m2, and wherein the sum of the outer perimeters of the cross-sectional lines of all the straight pipes of the heat removal pipe assembly in cross-section A is designated as L1 in m, L1 / S1 is 1.0 to 6.0 m-1 and / or the area S1 is 20 to 700 m2 and / or L1 is 20 to 4200 m.

3. The heat removal pipe assembly according to claim 1, wherein L1 / S1 is 2.4 to 5.6 m-1 or 2.9 to 5.3 m-1, and / or the area S1 is 35 to 350 m2, and / or L1 is 87.5 to 1225 m, and / or at least 20%, at least 50% or at least 65% of the total heat removal pipes of the heat removal pipe assembly and up to 75% or 70% of the total heat removal pipes of the profiled heat removal pipe assembly are profiled heat removal pipes, and / or the angle formed between a line drawn from the central axis of the protrusion on the cross section A of at least 2, 3 or 4 and up to 80%, 90% or 100% of the total profiled heat removal pipe connection fasteners, excluding the first profiled heat removal pipe connection fastener, and a line drawn from the central axis of the protrusion on the cross section A of at least one Other connection joints are 60-120 degrees or about 90 degrees.

4. The heat removal pipe assembly according to claim 1, wherein at least one further connection fastener is a connection fastener on the profiled heat removal pipe in a position directly above and in fluid communication with the connection fastener and / or the total number of straight pipes in the heat removal pipe assembly in the cross-section A is determined as Nt, the number of straight pipes per unit cross-sectional area A, i.e. Nt / S1 is equal to 4-16 / m2 and / or the cross-sectional shape of the cross-section A is circular, oval or almond-shaped and / or the inner shape and outer contours of the cross-section of the straight pipe are circular, oval or almond-shaped.

5. The heat removal tube assembly according to claim 4, wherein Nt / S1 is 5-14 / m2 or 7-13 / m2, and / or the cross-sectional profile A is circular or substantially circular, and / or the inner shape and outer circumference of the straight tube cross-section are circular or nearly circular.

6. The heat removal tube assembly according to claim 1, wherein the heat removal tube assembly is capable of recovering saturated steam of 1-10 MPa, and / or has a saturated steam heat removal capacity of 0.5-3.0 t per unit cross-sectional area per hour, the cross-sectional area being in m2, when recovered as saturated steam of 4.5 MPa, wherein the cross-sectional area refers to the cross-sectional area A.

7. The heat removal tube assembly according to claim 6, wherein the heat removal tube assembly is capable of recovering 2-8 MPa or 3-5 MPa saturated steam and / or has a heat removal capacity of 1.0-2.8 t or 1.2-2.4 t saturated steam per unit cross-sectional area per hour, the unit cross-sectional area being in m2, when evaluated as 4.5 MPa saturated steam recovered.

8. The heat removal tube assembly according to claim 1, wherein for the heat removal tube(s) of said heat removal tube assembly other than said profiled heat removal tube, an angle between a line drawn from the central axis of the projection of each of the connecting clamps on said cross-section A and a line drawn from the central axis of the projection of another connecting clamp on said heat removal tube at a position above or below and in fluid communication with said connecting clamp on said cross-section A is formed to be 180 degrees, and / or wherein said heat removal tube includes a cooling water inlet and the cooling water inlets of a plurality of heat removal tubes merge into a cooling water inlet header in said heat removal section, and / or said heat removal tube includes a cooling water outlet, and the cooling water outlets of a plurality of heat removal tubes merge into a cooling water outlet header in said heat removal section.

9. The heat removal tube assembly according to claim 8, wherein the cooling water inlets 2-8, 2-6 or 2-4 of said heat removal tubes are merged into a cooling water inlet header in said heat removal section and / or the cooling water outlets 2-8, 2-6 or 2-4 of said heat removal tubes are merged into a cooling water outlet header in said heat removal section.

10. The heat removal pipe assembly according to claim 1, wherein the outer diameter of the straight pipes is 80-180 mm, and / or the inner diameter of the straight pipes is 60-150 mm, and / or the length of the straight pipes is 4-13 m, and / or the distance between two adjacent straight pipes on each heat removal pipe is 100-700 mm, and / or the length H of the heat removal section is 4-13 m.

11. The heat removal tube assembly according to claim 10, wherein the outer diameter of the straight tubes is 90-170 mm, and / or the inner diameter of the straight tubes is 70-140 mm, and / or the length of the straight tubes is 5-12.0 m, and / or the distance between two adjacent straight tubes on each heat removal tube is 150-300 mm, and / or the length H of the heat removal section is 5-12 m.

12. The heat removal tube assembly of claim 1, wherein it is specified that, (1) the full propylene treatment capacity per hour in the fluidized bed reactor is 140-290 kg propylene per m2 of cross-section A, excluding the end point 290, L1 / S1 is 1.0-2.5 m-1 excluding the end point 2.5, or (2) the full propylene treatment capacity per hour of the fluidized bed reactor is 200-370 kg propylene per m2 of cross-section A, L1 / S1 is 1.8-4.6 m-1, or (3) the full propylene treatment capacity per hour of the fluidized bed reactor is 290-445 kg propylene per m2 of cross-section A, L1 / S1 is 2.5-6.0 m-1.

13. The heat removal tube assembly of claim 12, wherein (1) the total propylene treatment capacity per hour in the fluidized bed reactor is 140-290 kg propylene per m2 of cross-section A, excluding the end point 290, L1 / S1 is 1.4-2.2 m-1 excluding the end point 2.5, or (2) the total propylene treatment capacity per hour of the fluidized bed reactor is 200-370 kg propylene per m2 of cross-section A, L1 / S1 is 2.0-4.16 m-1, or (3) the total propylene treatment capacity per hour of the fluidized bed reactor is 290-445 kg propylene per m2 of cross-section A, L1 / S1 is 2.9-5.3 m-1.

14. A fluidized bed reactor, wherein it is specified that it comprises a header, a dilute phase zone, a heat removal section, a pre-reaction section and a cone from top to bottom in sequence, wherein a heat removal tube assembly according to claim 1 is disposed in the heat removal section.

15. A method for producing an unsaturated nitrile, comprising the step of subjecting an olefin to an ammoxidation reaction in a fluidized bed reactor according to claim 14 to obtain an unsaturated nitrile.

16. A method for increasing the load of a fluidized bed reactor according to claim 14, wherein the full propylene treatment capacity per hour in the fluidized bed reactor is 140-290 kg propylene per m2 of cross section A except for the end point 290 and L1 / S1 is 1.0-2.5 m-1 except for the end point 2.5, the method comprising increasing L1 / S1 to 2.5-6.0 m-1, while the full propylene treatment capacity per hour in the fluidized bed reactor is increased to 290-445 kg propylene per m2 of cross section A.

17. The method according to claim 16, wherein the method comprises increasing L1 / S1 to 2.9-5.3 m-1, while increasing the total propylene treatment capacity per hour in the fluidized bed reactor to 290-445 kg propylene per m2 of cross section A.

18. A method for producing an unsaturated nitrile, comprising the step of subjecting an olefin to an ammoxidation reaction in a fluidized bed reactor to obtain an unsaturated nitrile, wherein the load of the fluidized bed reactor is increased according to the load increasing method described in claim 16.

19. The method according to claim 15 or 18, wherein the molar ratio of propylene / ammonia / air calculated as molecular oxygen is 1 : 1.1-1.3 : 1.8-2.0, the reaction temperature is 420-440 ℃, the reaction pressure is gauge pressure 0.03-0.14 Mpa, and the weight hourly space velocity of the catalyst is 0.06-0.15 h-1.

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