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EP-4741039-A1 - METHOD AND APPARATUS FOR MANUFACTURING NITRILE USING CONTROLLED SPRAY LIQUID INPUT PRESSURE

EP4741039A1EP 4741039 A1EP4741039 A1EP 4741039A1EP-4741039-A1

Abstract

The present invention relates to a process and device for producing nitrile with controlled input pressure of spray liquid. The producing process can atomize the spray liquid, increase the contact area with ammonia, and improve mass transfer efficiency. The process for producing the nitrile comprises: a step of subjecting a hydrocarbon feedstock to ammoxidation reaction to produce a reaction product containing nitrile, and a step of spraying a spraying liquid onto the reaction product through a spraying device to cool the reaction product, wherein the spraying device comprises 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 perpendicularly to the first spraying pipe toward both sides thereof, a plurality of third spraying pipes in fluid communication with the second spraying pipes and extending perpendicularly to the second spraying pipes toward both sides thereof, and nozzles located at the ends of the third spraying pipes and in fluid communication therewith, wherein in the cooling step, the spraying liquid input pressure at the spraying liquid inlet is controlled to be 0.06-1.00 MPaG.

Inventors

  • ZHAO, Le
  • WU, LIANGHUA

Assignees

  • China Petroleum & Chemical Corporation
  • Sinopec (Shangai) Research Institute of Petrochemical Technology Co., Ltd.

Dates

Publication Date
20260513
Application Date
20240508

Claims (12)

  1. A process for producing a nitrile, comprising a step of subjecting a hydrocarbon feedstock to an ammoxidation reaction to produce a reaction product containing the nitrile (called as a reaction step), and a step of spraying a spraying liquid to the reaction product through a spraying device to cool the reaction product (called as a cooling step), wherein the spraying device comprises 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 perpendicularly to the first spraying pipe toward both sides thereof, a plurality of third spraying pipes in fluid communication with the second spraying pipes and extending perpendicularly to the second spraying pipes toward both sides thereof, and nozzles located at the ends of the third spraying pipes and in fluid communication therewith, wherein in the cooling step, the spraying liquid input pressure at the spraying liquid inlet is controlled to be 0.06-1.00 MPaG (preferably 0.12-0.90 MPaG, more preferably 0.18-0.80 MPaG).
  2. The producing process according to claim 1, wherein on two adjacent second spraying pipes, the linear distance, M, between the end of an arbitrary third spraying pipe on one second spraying pipe and the end of an arbitrary third spraying pipe on the other adjacent second spraying pipe is not less than 320 mm (preferably not less than 350 mm), and/or, the nozzles are the same as or different from each other, each independently having a spraying liquid ejection rate of 0.5-7.5 t/h (preferably 0.9-6.5 t/h), and/or, the nozzles are the same as or different from each other, each independently having a spraying liquid ejection pressure at the nozzle outlet of 0.03-0.85 MPaG (preferably 0.04-0.65 MPaG), and/or, in the cooling step, the flow ratio of the spraying liquid to the reaction product is 15-25:1.
  3. The producing process according to claim 1, wherein the cooling step is carried out in an absorption device, and a plurality of (e.g., 2-10, preferably 4-8) the spraying devices are arranged in layers inside the absorption device along the central axis direction of the absorption device at a predetermined vertical interval.
  4. The producing process according to claim 3, wherein when a cross-section is obtained by cutting the absorption device at a direction perpendicular to the central axis of the absorption device, at least one (preferably all) selected from the first spraying pipe, the second spraying pipes and the third spraying pipes on one of the plurality of spraying devices and at least one (preferably all) selected from the first spraying pipe, the second spraying pipes, and the third spraying pipes on any other of the plurality of spraying devices substantially coincide in terms of the projection on the cross-section.
  5. The producing process according to claim 4, wherein all nozzles of said one spraying device and those of said any other spraying device substantially coincide in terms of the projection on the cross-section, and/or, two nozzles whose projections substantially coincide have the same spray diameter.
  6. The producing process according to claim 3, wherein the vertical spacing between two adjacent spraying devices (calculated as the vertical spacing between the spraying liquid inlets of the two spraying devices) is 650-1350 mm (preferably 750-1200 mm).
  7. The producing process according to claim 3, wherein the difference (absolute value) in the spraying liquid input pressures at the spraying liquid inlets of any two spraying devices is less than 0.024 MPa (preferably less than 0.018 MPa, more preferably less than 0.012 MPa).
  8. The producing process according to claim 3, wherein the absorption device further comprises a shell and a gas inlet, wherein the reaction product is fed into the absorption device through the gas inlet, and the gas inlet is located below the spraying device along the central axis direction of the absorption device.
  9. The producing process according to claim 8, wherein the vertical distance between the gas inlet and the spraying liquid inlet of the spraying device (when more than one spraying devices are present, referring to the spraying device closest to the gas inlet) is 800-6000 mm (preferably 1000-5000 mm), and/or, the gas inlet has an inner diameter of 800-1900 mm (preferably 900-1700 mm), and/or, the linear velocity of the gas inside the shell is 0.6-1.5 m/s (preferably 0.7-1.3 m/s).
  10. The process according to claim 8, wherein in the internal space of the absorption device between the gas inlet and the spraying device (when more than one spraying devices are present, referring to the spraying device closest to the gas inlet), no mechanical component which may substantially affect the gas flow is arranged.
  11. A device for producing nitrile, comprising a reactor, an absorption device, and a pressure controller, wherein the reactor is configured to subject a hydrocarbon feedstock to an ammoxidation reaction to produce a reaction product containing the nitrile, the absorption device is configured to spray a spraying liquid to the reaction product through a plurality of spraying devices arranged therein to cool the reaction product, wherein the spraying devices each independently comprise 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 perpendicularly to the first spraying pipe toward both sides thereof, a plurality of third spraying pipes in fluid communication with the second spraying pipes and extending perpendicularly to the second spraying pipes toward both sides thereof, and nozzles located at the ends of the third spraying pipes and in fluid communication therewith, and the pressure controller is configured to control the spraying liquid input pressure at the spraying liquid inlet of each spraying device to be 0.06-1.00 MPaG (preferably 0.12-0.90 MPaG, more preferably 0.18-0.80 MPaG).
  12. The device according to claim 11, wherein the absorption device further comprises a shell and a gas inlet, wherein the gas inlet is located below the spraying device along the central axis direction of the absorption device, and the vertical distance between the gas inlet and the spraying liquid inlet of the spraying device (when more than one spraying devices are present, referring to the spraying device closest to the gas inlet) is 800-6000 mm (preferably 1000-5000 mm).

Description

Technical Field The present invention relates to the technical field of gas absorption, and more particularly, to a process and device for producing nitrile with controlled input pressure of spraying liquid. Background In the process route for producing corresponding nitriles by ammonification or ammoxidation, in order to maximize the conversion of feedstock gases such as hydrocarbons, the feedstock gas ammonia is generally used in an excess amount, i.e., the molar ratio of ammonia to hydrocarbon feedstock gas being greater than 1. For example, in ammoxidation of propylene, the ammonia ratio (molar ratio of ammonia to propylene) is 1.10-1.35, and in ammoxidation of aromatic hydrocarbons, the ammonia ratio (molar ratio of ammonia to aromatic hydrocarbons) is 4-8. Therefore, the reactor outlet tail gas necessarily contains unreacted ammonia. On one hand, as in acrylonitrile production processes, reaction gases such as acrylonitrile are prone to polymerization under alkaline conditions. On the other hand, the escape of even a small amount of unreacted ammonia can easily cause environmental pollution. Therefore, in ammonification or ammoxidation processes, it is desired to use an absorption device (generally called as an ammonia absorption column or quench column) to remove unreacted ammonia from the gas phase using acid or water, which process is very necessary. With the development of production technology, production loads are continuously increasing, and the trend towards large-scale of devices represents the future development direction. The higher the device load, the larger the equipment, including the absorption device. It is known that in the absorption device, the circulating liquid (spraying liquid) is distributed within the absorption device via a spraying device and contacted countercurrently with the ammonia-containing gas to be absorbed, achieving the purpose of removing residual ammonia from the gas phase. CN105425849 teaches removal of residual ammonia by adjusting the amount of acid added based on the pH value of the effluent from the absorption device. CN1199940 teaches to improve the mass transfer and heat transfer effect between gas and liquid phases by adding internal components at the bottom of the absorption device, which in fact addresses the issue of uniform distribution of the ammonia-containing gas phase. However, the absorption device is still inevitably subjected to ammonia breakthrough, i.e., a small amount of ammonia escape still existing, leading to product loss in subsequent refining and separation units or causing environmental pollution. In the ammonia absorption methods of the prior art, after long-term operation of the absorption device, the ammonia content in the absorption tail gas increases significantly compared with the initial period of the operation. Summary of the Invention The inventors of the present invention have found that as the circulating liquid contains a certain concentration of easily deposition-prone substances such as ammonium salts and polymers, after long operation cycles, these easily deposition-prone substances tend to adhere to the inner walls of the spraying pipes and nozzles of the spraying device, resulting in insufficient nozzle pressure of the spraying device and affecting the atomization effect. Furthermore, the farther from the spraying liquid inlet, the more severe this accumulation problem becomes. After long-term operation, the accumulation degrees at different positions of the spraying device varies, leading to different spraying liquid atomization degrees at different nozzles. In areas with poor atomization, ammonia escape becomes more significant. In existing devices, the problem of insufficient pressure at the nozzle farthest from the spraying device inlet is particularly obvious. Ammonia absorption is not complete, and a small amount of ammonia still breaks through to subsequent equipment. The inventors of the present invention, by analyzing the accumulation degrees of easily deposition-prone substances at various parts of the spraying device as the operation cycle continues and its impact on the atomization effect, and comprehensively considering factors such as the overall uneven accumulation degrees of the spraying device and the pressure drop along the pipe course, have found that by setting the spraying liquid input pressure at the spraying liquid inlet of the spraying device to a specific value, the uneven accumulation phenomenon at different positions of the spraying device after long-term operation can be reduced or eliminated, thereby achieving overall uniform atomization degree. The inventors of the present invention have also found that in a single-stage ammonia absorption column, the ammonia-containing gas is fed into the column along the inlet semicircular pipeline, wherein the gas is delivered from bottom to top, contacting countercurrently with the acidic circulating liquid, during which process, gaseous ammonia is neu