Method and apparatus for producing nitrile with controlled input pressure of spraying liquid

Abstract

The present invention relates to a method for producing nitrile by controlling the input pressure of a spraying liquid and a production apparatus. The method can atomize the spraying liquid, increase the contact area with ammonia, and improve the mass transfer efficiency. The method for producing nitrile includes a step of producing a reaction product containing nitrile by subjecting a hydrocarbon raw material to an ammoxidation reaction (referred to as a reaction step), and a step of spraying a spraying liquid to the reaction product by a spraying device to cool the reaction product (referred to as a cooling step), wherein the spraying device includes a spraying liquid inlet, a first spraying pipe in fluid communication with the spraying liquid inlet, a plurality of second spraying pipes in fluid communication with the first spraying pipe and extending to both sides of the first spraying pipe perpendicularly thereto, a plurality of third spraying pipes in fluid communication with the second spraying pipes and extending to both sides of the second spraying pipes perpendicularly thereto, and a nozzle at the end of the third spraying pipes and in fluid communication therewith, and wherein the input pressure of the spraying liquid of the spraying liquid inlet is controlled to 0.06-1.00 MPaG in the cooling step.

Description

Technical Field

[0001] This invention relates to the field of gas absorption technology, and more specifically to a method and apparatus for manufacturing nitriles with controlled spray liquid input pressure. Background Technology

[0002] In ammoniation or ammoxidation processes to produce nitrile compounds, to maximize the conversion of hydrocarbon feedstock gases, ammonia is generally in excess in the feedstock gas, meaning the molar ratio of ammonia to hydrocarbons in the feedstock gas is greater than 1. For example, in propylene ammoxidation, the ammonia ratio (molar ratio of ammonia to propylene) is 1.10-1.35, and in aromatics ammoxidation, the ammonia ratio (molar ratio of ammonia to aromatics) is 4-8. Therefore, the reactor outlet gas will inevitably contain unreacted ammonia. On the one hand, in acrylonitrile production processes, acrylonitrile and other compounds in the reaction gas are prone to polymerization under alkaline conditions; on the other hand, even a small amount of unreacted ammonia escaping can easily cause environmental pollution. Therefore, in ammoniation or ammoxidation processes, it is essential to use an absorption device (generally called an ammonia absorption tower or quench tower) to remove unreacted ammonia from the gas phase using acid or water. This process is crucial.

[0003] With the development of production technology, production loads are constantly increasing, and the trend towards larger and more large-scale equipment is towards future development. The higher the equipment load, the larger the equipment, including the absorption unit, will be. It is known that in the absorption unit, the circulating liquid (spraying liquid) is dispersed into the absorption unit by a spraying device and comes into countercurrent contact with the ammonia-containing gas to absorb it, thereby achieving the purpose of removing residual ammonia from the gas phase.

[0004] Patent CN105425849 removes residual ammonia by adjusting the amount of acid added to the pH value of the effluent from the absorption device; patent CN1199940 improves the mass and heat transfer between the gas and liquid phases by adding internal components to the bottom of the absorption device, essentially solving the problem of uniform distribution of ammonia-containing gas phase. However, ammonia breakthrough still inevitably occurs in the absorption device, meaning that a small amount of ammonia still escapes, leading to product loss or environmental pollution in subsequent refining and separation units.

[0005] Because the circulating fluid contains a certain concentration of ammonium salts and polymers, these substances easily adhere to the walls of the spray pipes and the inner walls of the nozzles, resulting in insufficient pressure at the end of the spraying device and affecting the atomization effect. This is particularly noticeable at the nozzles furthest from the inlet of the spraying device. In existing devices, ammonia absorption is incomplete, and a small amount of ammonia still penetrates into subsequent equipment. Summary of the Invention

[0006] The inventors of this invention discovered that this problem can be solved by controlling the spray liquid input pressure at the spray liquid inlet within a specific numerical range. This invention is based on this discovery.

[0007] In a first embodiment, the present invention relates to a method for producing a nitrile, comprising a step of causing a hydrocarbon feedstock to undergo an ammonia oxidation reaction to produce a reaction product containing a nitrile (referred to as a reaction step), and a step of spraying a spraying liquid onto the reaction product via a spraying device to cool the reaction product (referred to as a cooling step), wherein the spraying device comprises a spraying liquid inlet, a first spray pipe in fluid communication with the spraying liquid inlet, a plurality of second spray pipes in fluid communication with the first spray pipe and extending to both sides therefrom perpendicular to the first spray pipe, a plurality of third spray pipes in fluid communication with the second spray pipes and extending to both sides therefrom perpendicular to the second spray pipes, and a nozzle located at the end of the third spray pipes and in fluid communication therewith, wherein in the cooling step, the spraying liquid input pressure at the spraying liquid inlet is controlled at 0.06-1.00 MPaG.

[0008] In a second embodiment, the present invention relates to an apparatus for producing nitrile, comprising a reactor, an absorption device, and a pressure controller, wherein the reactor is configured to produce a reaction product containing nitrile by ammonia oxidation of a hydrocarbon feedstock, and the absorption device is configured to cool the reaction product by spraying a spray liquid onto the reaction product through a plurality of spraying devices disposed therein, wherein each of the spraying devices independently comprises a spray liquid inlet, a first spray pipe in fluid communication with the spray liquid inlet, a plurality of second spray pipes in fluid communication with the first spray pipe and extending to both sides therefrom perpendicular to the first spray pipe, a plurality of third spray pipes in fluid communication with the second spray pipes and extending to both sides therefrom perpendicular to the second spray pipes, and a nozzle located at the end of the third spray pipe and in fluid communication therewith, and the pressure controller is configured to control the spray liquid input pressure at the spray liquid inlet of each of the spraying devices to be between 0.06 and 1.00 MPaG.

[0009] Technical effect

[0010] According to the spraying device of the present invention, the gas-liquid contact is more complete, and the ammonia absorption effect is better.

[0011] According to the spraying device of the present invention, the droplet size is more suitable for the operating conditions of the ammonia absorption tower.

[0012] The spraying device according to the present invention can maintain good ammonia absorption effect for a long period of time (such as continuous operation for 18 months or even longer) and reduce ammonia escape. Attached Figure Description

[0013] Figure 1 This is a front view schematic diagram of an existing ammonia absorption tower.

[0014] Figure 2 This is a front view schematic diagram of an existing ammonia absorption tower.

[0015] Figure 3a , Figure 3b This is a front view schematic diagram of the ammonia absorption tower of the present invention.

[0016] Figure 4 This is a front view schematic diagram of the ammonia absorption tower of the present invention.

[0017] Figure 5 This is a top view schematic diagram of the spraying device of the present invention.

[0018] Figure 6A , Figure 6B This is a top view schematic diagram of the spraying device of the present invention.

[0019] Explanation of reference numerals in the attached figures:

[0020] 1: Ammonia Absorption Tower

[0021] 2: Demister, an internal component of the ammonia absorption tower

[0022] 3: Spraying device for internal components of the ammonia absorption tower, 3a-3f are spraying devices.

[0023] 4: Gas distributor, an internal component of the ammonia absorption tower

[0024] 5: Spraying device for internal components of the ammonia absorption tower, 5a-5b are spraying devices.

[0025] 6: Upper section circulating pump

[0026] 7: Lower section circulating pump

[0027] 8: Ammonia-containing gas feed

[0028] 9: Ammonia absorption tower gas phase discharge

[0029] 10: Replenish water in the upper section

[0030] 11: Lower stage wastewater discharge

[0031] 12: Discharge of ammonium salt solution from the upper section

[0032] 13: Lower section circulating fluid

[0033] 14: Upper section circulating fluid

[0034] 15: Acidic solution

[0035] 16: Circulating fluid

[0036] 17: Circulation pump

[0037] 18: Spraying device inlet

[0038] 19: First spray pipe of the spraying device

[0039] 20a, 20b: Second spray pipe of the spraying device

[0040] 21: Third spray pipe of the spraying device

[0041] 22: Spraying device atomizing nozzle

[0042] P1, P2, P3, P4, P5, P6: Inlet pressure of the spraying liquid in the spraying device. Detailed Implementation

[0043] The specific embodiments of the present invention will be described in detail below. However, it should be noted that the scope of protection of the present invention is not limited to these specific embodiments, but is determined by the claims in the appendix.

[0044] All publications, patent applications, patents, and other references mentioned in this specification are incorporated herein by reference. Unless otherwise defined, all technical and scientific terms used in this specification have the meanings commonly understood by those skilled in the art. In case of conflict, the definitions in this specification shall prevail.

[0045] When this specification uses the prefixes “known to those skilled in the art,” “prior art,” or similar terms to derive materials, substances, methods, steps, apparatus, or components, the objects derived from such prefixes cover those commonly used in the art at the time of this application, but also include those that are not currently commonly used but will become generally recognized in the art as suitable for similar purposes.

[0046] In the context of this specification, "basically" means a deviation of no more than 20%, preferably no more than 10% or 5%.

[0047] Unless otherwise specified, all percentages, parts, ratios, etc. mentioned in this instruction manual are based on weight, and the pressure is gauge pressure.

[0048] In the context of this specification, any two or more embodiments of the present invention can be arbitrarily combined, and the resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0049] In the context of this specification, any technical details not mentioned herein shall be applied directly to information known in the art.

[0050] According to one embodiment of the present invention, a method for manufacturing a nitrile, particularly a method for manufacturing (meth)acrylonitrile, is provided.

[0051] According to one embodiment of the present invention, the method for producing the nitrile includes a step of causing a hydrocarbon feedstock to undergo an ammonia oxidation reaction to produce a reaction product containing nitrile (referred to as the reaction step), and a step of spraying the reaction product with a spraying liquid through a spraying device to cool the reaction product (referred to as the cooling step).

[0052] According to one embodiment of the present invention, the spraying device includes a spray liquid inlet, a first spray pipe in fluid communication with the spray liquid inlet, a plurality of (e.g., 10-26, preferably 12-22) second spray pipes in fluid communication with the first spray pipe and extending perpendicularly to both sides of the first spray pipe, a plurality of (e.g., 4-26, preferably 6-22) third spray pipes in fluid communication with the second spray pipes and extending perpendicularly to both sides of the second spray pipes, and a nozzle located at the end of the third spray pipes and in fluid communication therewith.

[0053] This invention does not specifically limit the connection methods between the spray pipes or between the third spray pipe and the nozzle; conventional connection methods in the art can be used. For example, a fixed connection or a detachable connection can be used, preferably a threaded connection, or other detachable connection methods; there are no specific limitations.

[0054] According to one embodiment of the present invention, the spraying liquid is water or an acidic aqueous solution. Preferably, ammonia-containing gas is brought into counter-current contact with the acidic aqueous solution as the spraying liquid from bottom to top, and the acidic H+ ions contained in the aqueous solution neutralize the ammonia, thereby removing the ammonia. Here, the acidic aqueous solution is an aqueous solution of an acidic substance. The acidic substance can be an inorganic acid, such as hydrochloric acid, sulfuric acid, or phosphoric acid; it can also be an organic acid, such as acrylic acid or acetic acid; or it can be an acidic salt, such as ammonium sulfate, without specific limitation.

[0055] According to the present invention, the droplet size of the spray liquid ejected from the nozzle is very small, typically only 50-5000 micrometers, which can effectively perform the gas absorption function, especially the ammonia removal function.

[0056] According to one embodiment of the present invention, in the cooling step, the spray liquid input pressure at the spray liquid inlet is controlled at 0.06-1.00 MPaG (preferably 0.12-0.90 MPaG, more preferably 0.18-0.80 MPaG). The inventors of this invention have discovered that the circulating liquid enters the spray device from the inlet, passes through the first spray pipe, the second spray pipe, and the third spray pipe, and is then transported to the absorption tower through the nozzle at the end of the third spray pipe. Since the pressure gradually decreases along the fluid travel direction, and the droplet size is inversely proportional to the pressure, the droplet size continuously increases along the circulating liquid travel direction. That is, the droplet size formed at the atomizing nozzle farther from the spray inlet in the fluid travel direction is larger than the droplet size formed at the atomizing nozzle closer to the spray inlet in the fluid travel direction. This results in the ammonia absorption efficiency at the farther end of the spray inlet in the fluid travel direction being lower than the ammonia absorption efficiency at the closer end. Maintaining the spray liquid input pressure at the spray liquid inlet within the aforementioned specified range is crucial to ensuring sufficient pressure at the distal nozzle and guaranteeing atomization. Furthermore, with prolonged operation, the viscous polymers generated during the reaction, mixed with ammonium salts from the circulating liquid, adhere to the spray pipe walls, causing a continuous increase in pipe resistance. This increase is particularly pronounced after 18 months of operation, further reducing the pressure at the distal nozzle and resulting in larger droplet size and poorer atomization. According to this invention, by controlling the spray liquid input pressure at the spray liquid inlet within the aforementioned specified range, sufficient pressure at the distal nozzle can be maintained even after long-term continuous operation, ensuring atomization.

[0057] According to one embodiment of the present invention, the plurality of second spray pipes extend substantially parallel to each other in a horizontal direction to their opposite sides, perpendicular to the first spray pipe.

[0058] According to one embodiment of the present invention, the plurality of third spray pipes extend substantially parallel to each other in a horizontal direction to their opposite sides, perpendicular to the second spray pipe.

[0059] According to one embodiment of the present invention, the inner diameter of the first spray pipe is 160-480mm (preferably 200-450mm), and the length is 4500-11500mm (preferably 4800-10500mm).

[0060] According to one embodiment of the present invention, the plurality of second spray pipes may be the same or different from each other, each having an inner diameter of 30-150 mm (preferably 40-120 mm) and a length of 1200-5750 mm (preferably 1800-5250 mm) independently.

[0061] According to one embodiment of the present invention, the plurality of third spray pipes may be the same or different from each other, each having an inner diameter of 10-60 mm (preferably 15-50 mm) and a length of 160-325 mm (preferably 175-300 mm) independently.

[0062] According to one embodiment of the invention, the nozzles may be identical or different from each other, each having an inner diameter (referring to the nozzle outlet) of 3-20 mm (preferably 6-14 mm), a diameter of 10.0-55.0 mm (preferably 13.0-45.0 mm), and a spray angle of 65-120° (preferably 70-100°). According to the invention, the rotating chamber can be of any structure known in the art, as long as it allows the sprayed liquid to exit the nozzle outlet in a rotating manner after passing through the rotating chamber; there are no particular limitations.

[0063] According to one embodiment of the present invention, on the first spray pipe, the horizontal distance between two adjacent second spray pipes is 640-1300 mm (preferably 700-1200 mm).

[0064] According to one embodiment of the present invention, on the same second spray pipe, the horizontal distance between two adjacent third spray pipes is 320-650mm (preferably 350-600mm).

[0065] According to one embodiment of the present invention, on two adjacent second spray pipes, the straight-line distance M between the end of any third spray pipe on one second spray pipe and the end of any third spray pipe on another adjacent second spray pipe (e.g., ...) Figure 6A , Figure 6B (As shown) The nozzle diameter should be no less than 320 mm, preferably no less than 350 mm. The inventors of this invention discovered that, in order to improve the absorption efficiency of ammonia, at any position on the cross-section of the tower, there should be at least two overlapping conical liquid surfaces centered on the nozzle, including at the tower wall. If the distance between the ends of the two spray pipes is too large, due to the limitations of the nozzle structure, it is difficult to ensure that the liquid surfaces sprayed from two or more nozzles overlap at any position on the tower wall, thus increasing the probability of ammonia escaping through the "gaps". If the distance between the ends of the two spray pipes is too small, in order to ensure the atomization quality of the sprayed liquid, the circulating liquid volume in the ammonia absorption tower will inevitably increase, i.e., the pump energy consumption will increase.

[0066] According to one embodiment of the present invention, the nozzles may be the same or different from each other, and the spraying rate of each nozzle is independently 0.5-7.5 t / h (preferably 0.9-6.5 t / h).

[0067] According to a preferred embodiment of the present invention, the nozzles may be identical or different from each other, and the spray pressure of the spray liquid at the nozzle outlet is independently 0.03-0.85 MPaG (preferably 0.04-0.65 MPaG). The inventors of this invention have discovered that for atomizing nozzles in ammonia absorption towers, pressure is one of the main factors promoting the formation of droplets. Within a certain pressure range, the droplet size increases as the pressure decreases. Smaller atomized droplets are generally considered to have better mass and heat transfer efficiency than larger droplets. When the spray pressure at the nozzle outlet is less than 0.03 MPaG, the atomization effect of the acidic circulating liquid after passing through the spraying device is poor, and the droplet size is large, meaning the contact with ammonia is insufficient. When the spray pressure at the nozzle outlet is greater than 0.85 MPaG, although the atomization effect of the acidic circulating liquid after passing through the spraying device is good, the droplet size is too small, making it easy for the liquid to be entrained by gas outside the ammonia absorption tower. The dissolved ammonium salts in the liquid cause unnecessary problems for subsequent processes. Furthermore, with prolonged operation, the viscous polymers generated during operation also adhere to the inner cavity of the nozzle, increasing resistance and causing a decrease in pressure at the nozzle outlet. For example, after 18 months of continuous operation, dirt accumulates inside the nozzle, altering the movement of the sprayed liquid within the nozzle. In particular, this increases the instability of atomization at the distal nozzle, and this instability becomes increasingly pronounced with prolonged operation. According to the present invention, by controlling the spray pressure at the nozzle outlet within the aforementioned specified range, even after long-term continuous operation, stable atomization at the distal nozzle can be ensured, guaranteeing the atomization effect.

[0068] According to one embodiment of the present invention, in the cooling step, the sprayed liquid and the reaction product are contacted in a countercurrent manner.

[0069] According to one embodiment of the present invention, in the cooling step, the flow rate ratio of the sprayed liquid to the reaction product is 15-25:1.

[0070] According to one embodiment of the invention, the cooling step is carried out in an absorption device (particularly an ammonia absorption tower or a quench tower), and multiple (e.g., 2-10, preferably 4-8) of the spraying devices are arranged in layers inside the absorption device at predetermined vertical intervals along the central axis of the absorption device.

[0071] According to one embodiment of the invention, when the absorption device is transversely cut in a direction perpendicular to the central axis of the absorption device to obtain a cross section, the projection of one of the plurality of spraying devices and at least one (preferably all) of another of the plurality of spraying devices selected from the first spray pipe, the second spray pipe and the third spray pipe on the cross section substantially coincides.

[0072] According to one embodiment of the invention, the projections of all the nozzles of the one spraying device and the other spraying device on the cross-section are substantially coincident.

[0073] According to one embodiment of the invention, two nozzles whose projections substantially overlap have the same spray diameter.

[0074] According to one embodiment of the present invention, the vertical distance between two adjacent spraying devices (based on the vertical distance between the spray liquid inlets of the spraying devices) is 650-1350 mm (preferably 750-1200 mm). The inventors of this invention have discovered that when the vertical distance between two adjacent spraying devices is less than 650 mm, for ammonia absorption towers with the same number of spraying devices, the contact time between the rising ammonia-containing gas and the descending circulating liquid is insufficient. As a result, some ammonia in the gas phase directly passes through the hollow conical liquid surface formed by the circulating liquid, leading to a decrease in ammonia absorption efficiency. Although sufficient gas-liquid contact time can be achieved by increasing the number of spraying devices to achieve complete absorption of ammonia in the gas phase, this increases the total amount of circulating liquid and the energy consumption of the pump, which is obviously uneconomical. When the vertical distance between two adjacent spraying devices is greater than 1350 mm, with the same number of spraying devices, the tower height increases, i.e., the equipment investment cost increases, and maintenance difficulty also increases.

[0075] According to one embodiment of the present invention, the difference (absolute value) in the spray liquid input pressure at the spray liquid inlet of any two of the spraying devices is less than 0.024 MPa (preferably less than 0.018 MPa, more preferably less than 0.012 MPa). The inventors of this invention have discovered that the size of the droplets after atomization of the circulating liquid is closely related to the pressure at the nozzle. Excessive or insufficient pressure is detrimental to the operation of the device. The nozzle pressure originates from the spray liquid input pressure at the spray liquid inlet. Theoretically, it is desirable for the spray liquid input pressures at the spray liquid inlets to be the same. However, in practice, because multi-layer spraying devices are arranged vertically, there is a pressure drop loss when the circulating pump delivers the circulating liquid to each layer of spraying devices. Therefore, the difference in spray liquid input pressure at the spray liquid inlet of any two spraying devices should be as low as possible to ensure that all nozzles of the uppermost and lowermost spraying devices meet the optimal pressure conditions.

[0076] According to one embodiment of the present invention, the inner diameter of the absorption device is 4.5-11.5m (preferably 4.8-10.5m).

[0077] According to one embodiment of the present invention, in the reaction step, the hydrocarbon feedstock is propylene, the molar ratio of propylene / ammonia / air (based on 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 catalyst weight hourly space velocity is 0.06-0.15 h⁻¹. -1Alternatively, the hydrocarbon feedstock is isobutylene, with a molar ratio of isobutylene / ammonia / air (based on molecular oxygen) of 1:1.3-1.6:2.2-2.8, a reaction temperature of 395-420℃, a reaction pressure (gauge pressure) of 0.03-0.14 MPa, and a catalyst weight hourly space velocity of 0.08-0.17 h⁻¹. -1 .

[0078] According to one embodiment of the present invention, in the cooling step, the sprayed liquid cools the temperature of the reaction product from 425-445°C (or 390-420°C) to 81-86°C (or 87-95°C).

[0079] According to one embodiment of the present invention, in the cooling step, the sprayed liquid reduces the ammonia content of the reaction product to below 150 ppm.

[0080] According to one embodiment of the present invention, an apparatus for manufacturing nitrile is also provided. According to the present invention, the apparatus for manufacturing nitrile is specifically designed for carrying out the aforementioned method for manufacturing nitrile. Therefore, for details not described in the section on the manufacturing apparatus, reference can be made directly to the relevant content described above regarding the manufacturing method.

[0081] According to one embodiment of the present invention, the nitrile manufacturing apparatus includes a reactor, an absorption device, and a pressure controller, wherein the reactor is configured to cause an ammonia oxidation reaction of a hydrocarbon feedstock to produce a reaction product containing nitrile, and the absorption device is configured to cool the reaction product by spraying a spray liquid onto the reaction product through a plurality of spraying devices disposed therein, wherein each of the spraying devices independently includes a spray liquid inlet, a first spray pipe in fluid communication with the spray liquid inlet, a plurality of second spray pipes in fluid communication with the first spray pipe and extending to both sides therefrom perpendicular to the first spray pipe, a plurality of third spray pipes in fluid communication with the second spray pipes and extending to both sides therefrom perpendicular to the second spray pipes, and a nozzle located at the end of the third spray pipe and in fluid communication therewith, and the pressure controller is configured to control the spray liquid input pressure at the spray liquid inlet of each of the spraying devices to be 0.06-1.00 MPaG (preferably 0.12-0.90 MPaG, more preferably 0.18-0.80 MPaG).

[0082] A specific embodiment of the present invention will now be described in detail by way of example, with reference to the accompanying drawings.

[0083] like Figure 4As shown, according to the present invention, the reactant gas at a temperature of 440°C and unreacted ammonia enter the ammonia absorption tower 1 from the ammonia-containing gas inlet 8. The circulating liquid is drawn from the bottom of the tower and sent to the spraying devices 3a-3f via the circulating pump 17. Spraying devices 3a, 3c, and 3e are on the same side, while spraying devices 3b, 3d, and 3f are on the opposite side to spraying devices 3a, 3c, and 3e. The spraying liquid input pressures at the spraying liquid inlets of spraying devices 3a, 3c, and 3e are 0.327 MPaG, 0.330 MPaG, and 0.334 MPaG, respectively. The spray liquid input pressures at the inlet of spray device 3e are 0.327 MPaG, 0.330 MPaG, and 0.334 MPaG, respectively. Sulfuric acid is added from the acid solution inlet 15 to the outlet pipeline of the circulating pump. The circulating liquid enters through the spray device 3 from the inlet 18, and flows along the fluid direction through the first spray pipe 19, the second spray pipe 20a (20b), and the third spray pipe 21 to the atomizing nozzle 22. The circulating liquid is sprayed out from the nozzle 22 to form an acid mist liquid layer in the ammonia absorption tower, absorbing gaseous ammonia from the gas inlet 8. The tail gas is discharged from the ammonia absorption tower from the gas phase outlet 9. The tail gas temperature at the top of the tower is 84℃. The projections of the ends of the third spray pipes of spray devices 3a-3f on the cross-section of the tower coincide, as shown in the figure. Figure 5 As shown.

[0084] Example

[0085] The present invention will be further described in detail below with reference to the embodiments, but the present invention is not limited to these embodiments.

[0086] Example 1

[0087] Ammonia absorption tower adopts Figure 3bThe absorption tower has a two-stage structure with an inner diameter of 7200mm. The acid added to the circulating liquid is sulfuric acid. The acid-containing circulating liquid is sent to the absorption tower through four spraying devices via an upper circulation pump. The fluid direction in the first spraying pipes of spraying devices 3a, 3c and 3b, 3d is opposite. The spraying liquid input pressures at the spraying liquid inlets of spraying devices 3a(b) and 3c(d) are 0.440MPaG and 0.446MPaG, respectively, and the spraying liquid discharge pressure is 0.051MPaG. The interval between two adjacent spraying devices is 1200mm. Each spraying device has 16 second spraying pipes, and each second spraying pipe is equipped with 11 to 18 third spraying pipes. The spraying system has a first spray pipe with an inner diameter of 250 mm and a length of 7000 mm; second spray pipes are spaced 820 mm apart, have an inner diameter of 100 mm, and a length ranging from 2100 mm to 3450 mm; third spray pipes are spaced 410 mm apart, have an inner diameter of 40 mm, and a length of 205 mm. The system has 960 nozzles, each with an outlet diameter of 11.5 mm, a rotating chamber diameter of 40 mm, a spray angle of 75°, and a spray rate of 4.8 t / h per nozzle. The weight ratio of spray liquid to gas entering through the gas inlet is 20. Initially, the residual ammonia concentration in the tail gas at the reaction outlet was 41 ppm. After 24 months of operation, the residual ammonia concentration in the tail gas at the reaction outlet was 52 ppm.

[0088] Example 2

[0089] Ammonia absorption tower adopts Figure 4 The absorption tower has a single-stage structure with an inner diameter of 7200 mm. The acid added to the circulating liquid is sulfuric acid. The acid-containing circulating liquid is pumped into the absorption tower through six spraying devices. The fluid direction in the first spray pipes of spraying devices 3a, 3c, 3e and 3b, 3d, 3f is opposite. The spraying liquid input pressures at the spraying liquid inlets of spraying devices 3a(b), 3c(d) and 3e(f) are 0.425 MPaG, 0.430 MPaG and 0.435 MPaG, respectively, and the spraying liquid discharge pressures are 0.055 MPaG. The vertical distance between two adjacent spraying devices is 880 mm. Each spraying device has 14 second spray pipes, and each second spray pipe is equipped with 6 to 14 third spray pipes. The first spray pipe of the spraying device has an inner diameter of 200mm and a length of 7000mm; the second spray pipes of the spraying device are spaced 1000mm apart, have an inner diameter of 100mm, and a length of 1850mm-3450mm; the third spray pipes of the spraying device are spaced 500mm apart, have an inner diameter of 40mm, and a length of 250mm. The projected ends of the third spray pipes of the spraying device overlap, and adjacent third spray pipes are arranged as follows: Figure 6AThe distance between the ends shown is 500 mm; the spraying device has a total of 912 nozzles, with a nozzle outlet diameter of 11.7 mm, a nozzle rotation chamber diameter of 36 mm, a spray angle of 80°, and a spray liquid output of 5.1 t / h per nozzle. The weight ratio of spray liquid to gas entering from the gas inlet is 20. In the initial stage of operation, the residual ammonia concentration in the tail gas at the reaction outlet was 27 ppm. After 24 months of operation, the residual ammonia concentration in the tail gas at the reaction outlet was 34 ppm.

[0090] Example 3

[0091] Similar to Example 2, the only difference is that the spray liquid input pressures at the spray liquid inlets of spray devices 3a(b), 3c(d), and 3e(f) are 0.098 MPaG, 0.103 MPaG, and 0.108 MPaG, respectively, and the spray liquid discharge pressures are 0.04 MPaG, respectively. The nozzle outlet diameter of the spray device is 12.3 mm. In the initial stage of device operation, the residual ammonia concentration in the tail gas at the reaction outlet is 85 ppm. After 24 months of device operation, the residual ammonia concentration in the tail gas at the reaction outlet is 108 ppm.

[0092] Example 4

[0093] Similar to Example 2, the only difference is that the spray liquid input pressures at the spray liquid inlets of spray devices 3a(b), 3c(d), and 3e(f) are 0.900 MPaG, 0.904 MPaG, and 0.909 MPaG, respectively, and the spray liquid discharge pressures are 0.42 MPaG, respectively. The nozzle outlet diameter of the spray device is 11.1 mm. In the initial stage of device operation, the residual ammonia concentration in the tail gas at the reaction outlet is 65 ppm. After 24 months of device operation, the residual ammonia concentration in the tail gas at the reaction outlet is 92 ppm.

[0094] Example 5

[0095] Similar to Example 2, the difference lies in that the vertical distance between two adjacent spraying devices is 1200mm, each spraying device has 24 second spray pipes, and each second spray pipe is equipped with 9 to 24 third spray pipes. The distance between the second spray pipes of the spraying device is 580mm, the inner diameter of the second spray pipe is 80mm, and the distance between two adjacent third spray pipes is as follows: Figure 6A The distance between the ends shown is 290 mm. The spraying device has a total of 2640 nozzles, with a nozzle outlet diameter of 9.1 mm, a nozzle rotation chamber diameter of 30 mm, a spray angle of 65°, and a spraying liquid output of 2.0 t / h per nozzle. Initially, the residual ammonia concentration in the tail gas at the reaction outlet was 106 ppm. After 24 months of operation, the residual ammonia concentration in the tail gas at the reaction outlet was 115 ppm.

[0096] Example 6

[0097] Similar to Example 2, the difference lies in that the spray liquid input pressures at the spray liquid inlets of spray devices 3a(b), 3c(d), and 3e(f) are 0.376 MPaG, 0.380 MPaG, and 0.385 MPaG, respectively; the spray liquid discharge pressures are 0.045 MPaG, respectively; the vertical distance between two adjacent spray devices is 550 mm; and the distance between two adjacent third spray pipes is as follows: Figure 6B The end distance shown is 707 mm. In the initial stage of unit operation, the residual ammonia concentration in the tail gas from the reaction outlet was 120 ppm. After 24 months of unit operation, the residual ammonia concentration in the tail gas from the reaction outlet was 132 ppm.

[0098] Example 7

[0099] Similar to Example 2, except that the vertical distance between two adjacent spraying devices is 1200mm, and the distance between two adjacent third spraying pipes is as follows: Figure 6B The distance between the ends shown is 707 mm. The nozzle outlet diameter of the spraying device is 11.8 mm, and the spraying liquid output of each nozzle is 5.8 t / h. In the initial stage of operation, the residual ammonia concentration in the tail gas from the reaction outlet is 98 ppm. After 24 months of operation, the residual ammonia concentration in the tail gas from the reaction outlet is 116 ppm.

[0100] Example 8

[0101] Similar to Example 2, the only difference is that the spray liquid input pressures at the spray liquid inlets of spray devices 3a(b), 3c(d) and 3e(f) are 0.405 MPaG, 0.0421 MPaG, and 0.435 MPaG, respectively. In the initial stage of device operation, the residual ammonia concentration in the tail gas at the reaction outlet is 65 ppm. After 24 months of device operation, the residual ammonia concentration in the tail gas at the reaction outlet is 89 ppm.

[0102] Example 9

[0103] Similar to Example 2, the only difference is that the spray liquid input pressures at the spray liquid inlets of spray devices 3a(b), 3c(d), and 3e(f) are 0.920 MPaG, 0.934 MPaG, and 0.959 MPaG, respectively, and the spray liquid discharge pressures are 0.88 MPaG, respectively. In the initial stage of device operation, the residual ammonia concentration in the tail gas at the reaction outlet is 112 ppm. After 24 months of device operation, the residual ammonia concentration in the tail gas at the reaction outlet is 145 ppm.

[0104] Comparative Example 1

[0105] Same as Example 1, except that the ammonia absorption tower uses... Figure 1The device has a two-stage structure. The spray liquid input pressures at the spray liquid inlets of spraying devices 3a, 3b, 3c, and 3d are 0.04 MPaG, 0.044 MPaG, 0.046 MPaG, and 0.051 MPaG, respectively. The spray liquid discharge pressure is 0.02 MPaG, and the nozzle outlet diameter is 14.2 mm. In the initial stage of operation, the residual ammonia concentration in the tail gas at the reaction outlet is 400 ppm. After 24 months of operation, the residual ammonia concentration in the tail gas at the reaction outlet is 529 ppm.

[0106] Comparative Example 2

[0107] Same as Example 2, except that the ammonia absorption tower uses... Figure 2 The unit has a single-stage structure with spraying devices 3a, 3b, 3c, 3d, 3e, and 3f. The spraying liquid input pressures at the inlet are 1.202 MPaG, 1.205 MPaG, 1.209 MPaG, 1.214 MPaG, 1.217 MPaG, and 1.220 MPaG, respectively, and the spraying liquid discharge pressure is 0.076 MPaG. In the initial stage of operation, the residual ammonia concentration in the tail gas at the reaction outlet is 85 ppm. After 24 months of operation, the residual ammonia concentration in the tail gas at the reaction outlet is 96 ppm. However, 1.5% ammonium sulfate was detected in the condensate of the tail gas at the outlet of the ammonia absorption tower.

Claims

1. A method for producing a nitrile, comprising a step of causing a hydrocarbon feedstock to undergo an ammoxidation reaction to produce a reaction product containing a nitrile, referred to as a reaction step, and a step of spraying a spraying liquid onto the reaction product via a spraying device to cool the reaction product, referred to as a cooling step, wherein the spraying device comprises a spraying liquid inlet, a first spray pipe in fluid communication with the spraying liquid inlet, a plurality of second spray pipes in fluid communication with the first spray pipe and extending to both sides therefrom perpendicular to the first spray pipe, a plurality of third spray pipes in fluid communication with the second spray pipes and extending to both sides therefrom perpendicular to the second spray pipes, and a nozzle located at the end of the third spray pipes and in fluid communication therewith, wherein in the cooling step... The spray liquid input pressure at the spray liquid inlet is controlled at 0.06-0.9 MPaG. The cooling step is carried out in the absorption device. Multiple spray devices are arranged in layers inside the absorption device at a predetermined vertical spacing along the central axis of the absorption device. The vertical spacing between two adjacent spray devices, based on the vertical spacing of the spray liquid inlet of the spray device, is 650-1350 mm. When the absorption device is transversely cut in a direction perpendicular to the central axis of the absorption device to obtain a cross-section, the projections of all nozzles of one of the multiple spray devices on the cross-section coincide with those of the other multiple spray devices.

2. The manufacturing method according to claim 1, wherein, The number of the second spray pipes is 10-26, and / or the number of the third spray pipes is 4-26, and / or, in the cooling step, the spray liquid input pressure at the spray liquid inlet is controlled at 0.12-0.90 MPaG.

3. The manufacturing method according to claim 1, wherein, The number of the second spray pipes is 12-22, and / or the number of the third spray pipes is 6-22, and / or, in the cooling step, the spray liquid input pressure at the spray liquid inlet is controlled at 0.18-0.80 MPaG.

4. The manufacturing method of claim 1, wherein the plurality of second spray pipes extend horizontally in parallel directions perpendicular to the first spray pipe to their opposite sides, and / or the plurality of third spray pipes extend horizontally in parallel directions perpendicular to the second spray pipe to their opposite sides.

5. The manufacturing method according to claim 1, wherein the inner diameter of the first spray pipe is 160-480 mm and the length is 4500-11500 mm, and / or, the plurality of second spray pipes are the same or different from each other, each having an independent inner diameter of 30-150 mm and an independent length of 1200-5750 mm, and / or, the plurality of third spray pipes are the same or different from each other, each having an independent inner diameter of 10-60 mm and an independent length of 160-325 mm.

6. The manufacturing method according to claim 1, wherein the inner diameter of the first spray pipe is 200-450 mm and the length is 4800-10500 mm, and / or, the plurality of second spray pipes are the same or different from each other, each having an independent inner diameter of 40-120 mm and an independent length of 1800-5250 mm, and / or, the plurality of third spray pipes are the same or different from each other, each having an independent inner diameter of 15-50 mm and an independent length of 175-300 mm.

7. The manufacturing method according to claim 1, wherein the nozzles are the same or different from each other, the inner diameter of the nozzle outlet is independently 3-20 mm, the diameter of the rotating chamber is independently 10.0-55.0 mm, and the spray angle is independently 65-120°.

8. The manufacturing method according to claim 1, wherein the nozzles are the same or different from each other, the inner diameter of the nozzle outlet is independently 6-14 mm, the diameter of the rotating chamber is independently 13.0-45.0 mm, and the spray angle is independently 70-100°.

9. The manufacturing method according to claim 1, wherein on the first spray pipe, the horizontal distance between two adjacent second spray pipes is 640-1300 mm, and / or, on the same second spray pipe, the horizontal distance between two adjacent third spray pipes is 320-650 mm, and / or, on two adjacent second spray pipes, the straight-line distance M between the end of any third spray pipe on one second spray pipe and the end of any third spray pipe on another adjacent second spray pipe is not less than 320 mm.

10. The manufacturing method according to claim 1, wherein on the first spray pipe, the horizontal distance between two adjacent second spray pipes is 700-1200 mm, and / or, on the same second spray pipe, the horizontal distance between two adjacent third spray pipes is 350-600 mm, and / or, on two adjacent second spray pipes, the straight-line distance M between the end of any third spray pipe on one second spray pipe and the end of any third spray pipe on another adjacent second spray pipe is not less than 350 mm.

11. The manufacturing method of claim 1, wherein the nozzles are the same or different from each other, the spray liquid output is independently 0.5-7.5 t / h, and / or the nozzles are the same or different from each other, and the spray liquid output pressure at the nozzle outlet is independently 0.03-0.85 MPaG.

12. The manufacturing method of claim 1, wherein the nozzles are the same or different from each other, the spray liquid output is independently 0.9-6.5 t / h, and / or the nozzles are the same or different from each other, and the spray liquid output pressure at the nozzle outlet is independently 0.04-0.65 MPaG.

13. The manufacturing method of claim 1, wherein in the cooling step, the sprayed liquid and the reaction product are contacted in a countercurrent manner.

14. The manufacturing method of claim 1, wherein in the cooling step, the flow rate ratio of the sprayed liquid to the reaction product is 15-25:

1.

15. The manufacturing method of claim 1, wherein the cooling step is performed in an absorption device, and 4-8 of the spraying devices are arranged in layers inside the absorption device at predetermined vertical intervals along the central axis of the absorption device.

16. The manufacturing method of claim 15, wherein the projection of one of the plurality of spraying devices onto the cross-section coincides with the projection of at least one of the plurality of spraying devices selected from the first spray pipe, the second spray pipe, and the third spray pipe.

17. The manufacturing method of claim 15, wherein the projection of one of the plurality of spraying devices onto the cross-section of all of the other of the plurality of spraying devices selected from the first spray pipe, the second spray pipe, and the third spray pipe coincides with that of the other of the plurality of spraying devices.

18. The manufacturing method of claim 16, wherein the two nozzles that project to overlap have the same spray diameter.

19. The manufacturing method of claim 15, wherein the vertical distance between two adjacent spraying devices, measured by the vertical distance between the spray liquid inlets of the spraying devices, is 750-1200 mm.

20. The manufacturing method of claim 15, wherein the absolute value of the difference in spray liquid input pressure at any two spray liquid inlets of the spraying devices is less than 0.024 MPa.

21. The manufacturing method of claim 15, wherein the absolute value of the difference in spray liquid input pressure at any two spray liquid inlets of the spraying devices is less than 0.018 MPa.

22. The manufacturing method of claim 15, wherein the absolute value of the difference in spray liquid input pressure at any two spray liquid inlets of the spraying devices is less than 0.012 MPa.

23. The manufacturing method of claim 15, wherein the inner diameter of the absorption device is 4.5-11.5 m.

24. The manufacturing method of claim 15, wherein the inner diameter of the absorption device is 4.8-10.5 m.

25. The manufacturing method according to claim 1, wherein in the reaction step, the hydrocarbon feedstock is propylene, the molar ratio of propylene / ammonia / air (based on 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 catalyst weight hourly space velocity is 0.06-0.15 h⁻¹. -1 Alternatively, the hydrocarbon feedstock is isobutylene, and the molar ratio of isobutylene / ammonia / air, calculated as molecular oxygen, is 1:1.3-1.6:2.2-2.8; the reaction temperature is 395-420℃; the reaction pressure (gauge pressure) is 0.03-0.14 MPa; and the catalyst weight hourly space velocity is 0.08-0.17 h⁻¹. -1 .

26. The manufacturing method of claim 1, wherein in the cooling step, the sprayed liquid cools the temperature of the reaction product from 425-445°C (or 390-420°C) to 81-86°C (or 87-95°C), and / or, in the cooling step, the sprayed liquid reduces the ammonia content of the reaction product to below 150 ppm.

27. The manufacturing method of claim 1, wherein in the cooling step, the sprayed liquid cools the temperature of the reaction product from 390-420°C to 87-95°C.

28. An apparatus for producing a nitrile, comprising a reactor, an absorption unit, and a pressure controller, wherein the reactor is configured to induce an ammoxidation reaction of a hydrocarbon feedstock to produce a reaction product containing a nitrile, and the absorption unit is configured to cool the reaction product by spraying a spray liquid onto the reaction product through a plurality of spraying devices disposed therein, wherein each of the spraying devices independently includes a spray liquid inlet, a first spray pipe in fluid communication with the spray liquid inlet, a plurality of second spray pipes in fluid communication with the first spray pipe and extending to both sides therefrom perpendicular to the first spray pipe, and a plurality of second spray pipes in fluid communication with the second spray pipes and extending to both sides therefrom perpendicular to the second spray pipes. The device comprises multiple third spray pipes and nozzles located at the ends of the third spray pipes and in fluid communication therewith. The pressure controller is configured to control the spray liquid input pressure at the spray liquid inlet of each of the spray devices to be between 0.06 and 0.9 PaG, wherein the vertical distance between two adjacent spray devices, measured by the vertical distance between the spray liquid inlets of the spray devices, is 650-1350 mm, wherein, when a cross-section is obtained by transecting the absorption device in a direction perpendicular to the central axis of the absorption device, the projections of all nozzles of one of the multiple spray devices on the cross-section coincide with those of the other spray device.

29. The manufacturing apparatus of claim 28, wherein, The pressure controller is configured to control the spray liquid input pressure at the spray liquid inlet of each of the spraying devices to be between 0.18 and 0.80 MPaG.

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