EP-4741040-A1 - ABSORPTION DEVICE HAVING OPPOSITE SPRAY LIQUID INLETS AND MANUFACTURING METHOD FOR NITRILE

EP4741040A1EP 4741040 A1EP4741040 A1EP 4741040A1EP-4741040-A1

Abstract

The present invention relates to an absorption device with opposing-placed spraying liquid inlets and a process for producing nitrile. The absorption device can maximize the ammonia absorption rate and reduce ammonia breakthrough. The absorption device of the present invention comprises a shell and a plurality of spraying devices arranged in layers along the central axis direction of the absorption device at predetermined vertical spacings, wherein each of the spraying devices independently 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, perpendicularly to the first spraying pipe, arranged along both sides thereof, a plurality of third spraying pipes in fluid communication with the second spraying pipes and, perpendicularly to the second spraying pipes, arranged along both sides thereof, and nozzles located at the ends of the third spraying pipes and in fluid communication therewith, 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 selected from the group consisting of the first spraying pipe, the second spraying pipes, and the third spraying pipes of one of the plurality of spraying devices and at least one selected from the group consisting of the first spraying pipe, the second spraying pipes, and the third spraying pipes of another of the plurality of spraying devices substantially coincide in terms of the projection on the cross-section, and the angle between the projections of the spraying liquid inlet of the one spraying device and the spraying liquid inlet of the another spraying device on the cross-section is 180°.

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 (14)

An absorption device, comprising a shell and a plurality of spraying devices arranged in layers along the central axis direction of the absorption device at predetermined vertical spacings, wherein each of the spraying devices independently 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, perpendicularly to the first spraying pipe, arranged along both sides thereof, a plurality of third spraying pipes in fluid communication with the second spraying pipes and, perpendicularly to the second spraying pipes, arranged along both sides thereof, and nozzles located at the ends of the third spraying pipes and in fluid communication therewith, 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 group consisting of the first spraying pipe, the second spraying pipes, and the third spraying pipes of one of the plurality of spraying devices and at least one (preferably all) selected from the group consisting of the first spraying pipe, the second spraying pipes, and the third spraying pipes of another of the plurality of spraying devices substantially coincide in terms of the projection on the cross-section, and the angle between the projection on the cross-section of the spraying liquid inlet of the one spraying device and the projection on the cross-section of the spraying liquid inlet of the another spraying device is 180°.
The absorption device according to claim 1, wherein on the first spraying pipe, the horizontal spacing between two adjacent second spraying pipes is 640-1300 mm (preferably 700-1200 mm), and/or, on a same second spraying pipe, the horizontal spacing between two adjacent third spraying pipes is 320-650 mm (preferably 350-600 mm), and/or, on two adjacent second spraying pipes, the linear distance M between the end of any one third spraying pipe on one second spraying pipe and the end of any one third spraying pipe on another adjacent second spraying pipe is not less than 320 mm (preferably not less than 350 mm).
The absorption device according to claim 1, wherein the nozzles are the same 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).
The absorption device according to claim 1, wherein among all the spraying devices, the angle between the projections on the cross-section of the spraying liquid inlets of any two odd-numbered spraying devices is 0°, the angle between the projections on the cross-section of the spraying liquid inlets of any two even-numbered spraying devices is 0°, and the angle between the projection on the cross-section of the spraying liquid inlet of any odd-numbered spraying device and that of the spraying liquid inlet of any even-numbered spraying device is 180°.
The absorption device according to claim 1, wherein all of the nozzles of the one spraying device and all of the nozzles of the another spraying device substantially coincide in terms of the projection on the cross-section, and/or, two nozzles with the substantially coinciding projections have the same spray diameter.
The absorption device according to claim 1, wherein the nozzle comprises a nozzle inlet, a rotating chamber, and a nozzle outlet, wherein the rotating chamber is configured such that the spraying liquid fed in through the nozzle inlet leaves the nozzle outlet in a rotating manner after passing through the rotating chamber.
The absorption device according to claim 6, wherein the rotating chambers each independently have a diameter of 10.0-55.0 mm (preferably 13.0-45.0 mm), and/or, two nozzles with the substantially coinciding projections have the same rotating direction.
The absorption device according to claim 1, wherein on at least one (preferably all) of the second spraying pipes, two adjacent (preferably all) nozzles located on the same side of the second spraying pipe are configured such that the spraying liquid is ejected out with the same rotating direction.
The absorption device according to claim 8, wherein all nozzles on the facing sides of two side-by-side adjacent second spraying pipes are configured such that the spraying liquid is ejected out with the opposite rotating directions.
The absorption device according to claim 8, wherein on at least one (preferably all) of the second spraying pipes, at least one (preferably all) nozzle located on one side of the second spraying pipe is configured such that the spraying liquid is ejected out with a rotating direction A, while at least one (preferably all) nozzle located on the opposite side of the second spraying pipe is configured such that the spraying liquid is ejected out with a rotating direction B, wherein the rotating direction A is opposite to the rotating direction B.
The absorption device according to claim 10, wherein among all the nozzles of the spraying device, the number of nozzles ejecting the spraying liquid with the rotating direction A is equal or substantially equal to the number of nozzles ejecting the spraying liquid with the rotating direction B.
The absorption device according to claim 1, wherein the vertical spacing between two adjacent spraying devices (calculated as the vertical spacing of the spraying liquid inlets of the spraying devices) is 650-1350 mm (preferably 750-1200 mm).
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 the reaction step), and a step of spraying a spraying liquid to the reaction product to cool the reaction product (called as the cooling step), wherein the spraying liquid is sprayed to the reaction product in an absorption device according to claim 1.
The process according to claim 13, wherein in the cooling step, the flow ratio of the spraying liquid to the reaction product is 15-25:1.

Description

TECHNICAL FIELD The present invention relates to the technical field of gas absorption, and more particularly, to an absorption device with opposing-placed spraying liquid inlets and a process for producing nitrile. BACKGROUND In the process route for producing corresponding nitriles by ammoniation 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 spraying liquid inlets of existing devices are generally arranged on the same side, after long operation cycles, solid impurities or other viscous heavy components and other deposition-prone substances accumulate in the circulating spraying liquid, which adhere to the inner walls of the spraying pipelines and nozzles of the spraying device, causing the fluid flow resistance to continuously increase, resulting in insufficient nozzle pressure and poor atomization effect. The farther the distance away from the spraying liquid inlet, the more severe the accumulation problem. After long-term operation, the degree of accumulation at different positions of the spraying device varies, leading to different atomization degrees of the spraying liquid from different nozzles. In regions with poor atomization, ammonia escape becomes significant. 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 the complementarity between regions with different atomization degrees (different degrees of deterioration) of different spraying devices, have discovered that by arranging a plurality of layers of spraying devices and making the vertical projections of different spraying devices overlap and the spraying liquid inlets opposing-placed to each other, regions with different atomization degrees can correspond to and compensate for each other, achieving overall uniform atomization degree. The inventors of the present invention have also found that, as the spraying liquid in the prior art is ejected with the same rotating direction, during the downward movement of the spraying liquid, droplets formed by one spraying liquid are contacted with droplets formed by another spraying liquid, causing the droplet size to increase, which reduces the effective area for gas-liquid contact, leading to lower acid utilization efficiency, accompanied by more ammoni