A central jet mixer for ethylene oxide production

Abstract

This invention provides a central jet mixer for ethylene oxide production, belonging to the technical field of gas mixers. It solves the problems of suboptimal mixing of ethylene and oxygen and the long mixing time in existing technologies, which leads to prolonged exposure to the explosion limits. The mixer includes a housing, within which a central jet assembly for outputting ethylene circulating gas is vertically arranged. A distributor is fitted around the outer side of the central jet assembly to divide the housing into two regions, and several nozzles are horizontally arranged on the distributor. The distributor ejects oxygen through the nozzles, while the central jet assembly ejects a high-speed circulating ethylene gas stream. Compared to the circulating ethylene flow rate, the oxygen is essentially stationary. When the rapidly moving circulating ethylene gas stream enters the relatively stationary oxygen fluid, a velocity difference is created at the jet boundary, achieving the effect of mixing and agitation between the two fluids, thereby achieving rapid mixing and moving them away from their explosion limits.

Description

Technical Field

[0001] This invention belongs to the field of gas mixer technology, specifically to a center jet mixer for ethylene oxide production. Background Technology

[0002] Ethylene oxide is an important derivative of ethylene and is widely used in ethylene glycol ethers, nonionic surfactants, ethylene glycol, polyoxyethylene alkyl ethers, and other fields. It can also be used in plasticizers, lubricants, plastics, and rubber. Ethylene oxide production processes include the chloroethanol method and the direct oxidation method of ethylene. Depending on the oxidant used, the direct oxidation method of ethylene is further divided into air oxidation and pure oxygen oxidation. Although the chloroethanol method has a simple process flow, it has been replaced by the direct oxidation method because it requires highly toxic chlorine gas as a raw material and involves numerous side reactions. The main disadvantages of the air oxidation method are the high silver content requirement of the catalyst, low selectivity, large catalyst loading for the same processing scale, and high ethylene consumption; in addition, an air purification system is required.

[0003] The pure oxygen oxidation method has advantages such as a short process flow, low silver content in the catalyst, high selectivity, mild reaction conditions, and low ethylene consumption. In particular, the production cost of the pure oxygen oxidation method is 10% lower than that of the air oxidation method. Therefore, the pure oxygen oxidation process for ethylene production is now widely used in industrial production. Major pure oxygen oxidation process routes are used by Shell, Scientific Design Corporation (SD), and Dow Chemical Company.

[0004] The pure oxygen oxidation method uses pure oxygen and ethylene as raw materials. Before entering the high-temperature reactor, the two need to be thoroughly mixed in an ethylene-oxygen mixer. However, the mixture of ethylene and oxygen is a flammable and explosive gas, with ethylene having an explosion limit of 2.7%–36%, a relatively wide range. Therefore, the mixer design needs to ensure that the oxygen concentration decreases rapidly when mixed with ethylene, which places high demands on the ethylene-oxygen mixer.

[0005] Common mixing methods in industrial applications include stirring and static mixing. Stirring is generally suitable for liquid-liquid mixing but not for gas-gas mixing of pure oxygen and ethylene. Static mixing typically involves using baffles or other structures in the mixer to alter fluid flow and increase turbulence. The time from mixing to homogenization is relatively long. Because ethylene and oxygen have a wide explosion limit range, during static mixing, there is a process where the ethylene concentration decreases from within the explosion limit range to outside it. From an intrinsic safety perspective, the shorter this process time, the better. Static mixing, due to its longer time from mixing to homogenization, results in a longer period of inherent unsafety, increasing uncontrollable factors.

[0006] Patent CN 108310989 B discloses a rapid mixing device for ethylene and oxygen, including an ethylene main pipeline and a mixing chamber. The end of the ethylene main pipeline connects to the mixing chamber, and several oxygen spiral distribution pipes are arranged inside the mixing chamber. The plane of the spiral distribution pipes is perpendicular to the ethylene flow direction. Several oxygen nozzles are evenly distributed on each spiral distribution pipe, and the nozzles are oriented in the same direction as the ethylene flow direction. The oxygen feed pipe splits into several branch distribution pipes in the main pipeline and enters the main ethylene pipeline, so that the ethylene entering from the main pipeline and the oxygen sprayed from the nozzles of the spiral distribution pipes are rapidly mixed in the mixing zone. However, because the oxygen feed pipe splits into several branch distribution pipes in the main pipeline and enters the main ethylene pipeline, the oxygen in each oxygen branch pipe may be different, which will lead to uneven mixing of oxygen in the mixing zone, affecting the mixing effect and easily causing safety accidents.

[0007] Patent CN 104084065 B describes a method of mixing ethylene entering from the main channel with oxygen entering through a radially arranged oxygen distributor in a mixer. The oxygen distributor includes a central main pipe and at least one branch pipe. The central main pipe and the branch pipe are perpendicularly connected, and the branch pipes are symmetrically arranged on both sides of the central main pipe, with centrally symmetrically distributed small holes on the branch pipes. Similar to the aforementioned patent, the oxygen in this multi-branch oxygen pipe may be different, which will lead to uneven mixing of oxygen in the mixing zone and affect the mixing effect.

[0008] Patent CN 108295689 A discloses a static mixer for ethylene and oxygen. This static mixer includes an ethylene main pipeline, the end of which connects to a mixing chamber. Several oxygen spiral distribution pipes are arranged within the mixing chamber. Oxygen pipes enter the center of the ethylene main pipeline from the side and then enter the oxygen distributor. Oxygen passes through the distributor and enters the spiral distribution pipes. The plane of the spiral distribution pipes is perpendicular to the ethylene flow direction, and several oxygen nozzles are evenly distributed on each spiral distribution pipe. This structure is a static mixer; the time from the start of mixing to uniform mixing of ethylene and oxygen is relatively long, and the time both remain within the explosive limits is prolonged, posing a significant safety risk.

[0009] In summary, the existing technology in the current ethylene epoxidation production process has several drawbacks: the mixing of ethylene and oxygen is not ideal and is uneven; the time required for ethylene and oxygen to mix evenly is relatively long, resulting in a longer period within the explosion limit range, which poses a safety risk. Summary of the Invention

[0010] To address the aforementioned problems, the present invention aims to provide a central jet mixer for ethylene oxide production. The distributor ejects oxygen through nozzles, while the central jet assembly ejects a high-speed circulating ethylene gas stream. Compared to the circulating ethylene flow rate, the oxygen is essentially stationary. When the rapidly moving circulating ethylene gas stream enters the relatively stationary oxygen fluid, a velocity difference is created at the jet boundary, achieving the mixing and disturbance of the two fluids. This results in rapid mixing and keeps the mixture away from the explosive limits of both fluids.

[0011] The technical solution adopted in this invention is as follows:

[0012] A center-jet mixer for ethylene oxide production includes a housing, in which a center-jet pipe assembly for outputting ethylene circulating gas into the housing is vertically arranged. A distributor for dividing the housing into two regions is sleeved on the outside of the center-jet pipe assembly, and several nozzles are horizontally arranged on the distributor. An oxygen inlet is connected to the housing below the distributor. A mixed gas outlet is provided at the top of the housing. An acceleration flow assembly for increasing the gas flow rate is provided above the center-jet pipe assembly in the housing.

[0013] Preferably, the central jet assembly includes at least one jet pipe, the lower end of which extends through the housing and is provided with a gas inlet.

[0014] Preferably, the central jet pipe assembly includes at least two spaced-apart jet pipes, with the upper outlet of the inner jet pipe protruding beyond the upper outlet of the outer jet pipe, and an annular guide vane provided on the upper outer wall of each jet pipe.

[0015] Preferably, the distributor has an inverted conical structure that is wider at the top and narrower at the bottom.

[0016] Preferably, the horizontal angle of the distributor is 30 to 60°.

[0017] Preferably, the accelerated flow component includes several baffles spaced apart, each baffle having through holes and the through holes of two adjacent baffles being staggered.

[0018] Preferably, the through-holes on the lowest baffle plate are not aligned with the central jet assembly.

[0019] Preferably, the spacing between two adjacent baffles is 100-200 mm.

[0020] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0021] The distributor sprays oxygen through nozzles, and the central jet assembly sprays high-speed circulating ethylene gas. Compared with the circulating ethylene gas, the oxygen is essentially stationary. When the rapidly moving circulating ethylene gas enters the relatively stationary oxygen fluid, a velocity difference is formed at the jet boundary, achieving the effect of mixing and disturbing the two fluids, thereby achieving rapid mixing and moving away from the explosion limits of both. Attached Figure Description

[0022] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 This is a cross-sectional structural schematic diagram provided for an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the central jet pipe assembly structure provided in an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of the accelerated flow component structure provided in an embodiment of the present invention.

[0026] Figure Descriptions: 1-Shell; 2-Oxygen Chamber; 3-Third Jetting Mixing Zone; 4-Mixing Buffer Zone; 5-Accelerating Flow Assembly; 501-Baffle Plate; 502-Through Hole; 6-Mixed Gas Outlet; 7-Oxygen Inlet; 8-Central Jetting Pipe Assembly; 801-First Gas Inlet; 802-Second Gas Inlet; 803-Third Gas Inlet; 804-First Central Injection Pipe; 805-Second Central Injection Pipe; 806-Third Central Injection Pipe; 807-Annular Guide Vane; 808-Support Bar; 9-Distributor; 10-Third Nozzle Opening Zone; 11-Second Nozzle Opening Zone; 12-First Nozzle Opening Zone; 13-Second Jetting Mixing Zone; 14-First Jetting Mixing Zone. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0028] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0029] In the description of this invention, it should be noted that if terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product is in use, they are only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0030] The following is combined Figures 1-3 The present invention will be described in detail below.

[0031] Example

[0032] A center-jet mixer for ethylene oxide production, such as Figure 1 As shown, the device includes a housing 1, in which a central jet pipe assembly 8 for outputting ethylene circulating gas into the housing 1 is vertically arranged. A distributor 9 for dividing the housing 1 into two regions is sleeved on the outside of the central jet pipe assembly 8, and several nozzles are horizontally arranged on the distributor 9.

[0033] Below the distributor 9 is the oxygen chamber 2. The housing 1 is connected to the oxygen inlet 7 located below the distributor 9. The oxygen inlet 7 supplies oxygen to the oxygen chamber 2, which serves as a storage and buffer. The area between the distributor 9 and the outlet of the central jet pipe assembly 8 is the jet mixing zone. After the oxygen and the circulating ethylene gas are mixed evenly, they are discharged from the housing 1 through the mixed gas outlet 6 at the top of the housing 1.

[0034] The nozzle is cylindrical with a diameter of Φ4 to Φ10 mm, preferably Φ6 to Φ8 mm. The length of the cylindrical nozzle ranges from 20 to 60 mm, the vertical distance between two cylindrical nozzles is 60 to 120 mm, and the center-to-center distance between nozzles on the same annular surface is 50 to 200 mm.

[0035] The central nozzle assembly 8 includes at least one injection pipe, the lower end of which extends through the housing 1 and is provided with a gas inlet. When the central nozzle assembly 8 is provided with only one injection pipe, the ejected ethylene circulating gas has a high velocity, which can generate large longitudinal and lateral disturbance forces, causing the fluid in the area to quickly backmix and mix, greatly reducing the time that ethylene and oxygen are within the explosion limit range, thus achieving intrinsic safety.

[0036] The central jet assembly 8 includes at least two spaced-apart jets, with the upper outlet of the inner jet protruding beyond that of the outer jet. Each jet has an annular guide vane 807 on its upper outer wall. When the central jet assembly 8 has two or more jets, they are arranged in a nested configuration, and the outlets of the jets are vertically staggered. Combined with the horizontal airflow guidance provided by the annular guide vane 807, this allows for multi-zone mixing of the ethylene circulating gas. This multi-zone mixing design can handle the high flow rates of ethylene and oxygen, significantly increasing the processing capacity of a single unit. The annular guide vane 807 also reduces backmixing in the various jet mixing zones.

[0037] In this embodiment, as Figure 2 As shown, three injection pipes are arranged: a first central injection pipe 804, a second central injection pipe 805, and a third central injection pipe 806. The first central injection pipe 804 is connected to a first gas inlet 801; the second central injection pipe 805 is connected to a second gas inlet 802, and the second gas inlet 802 is fixedly inserted through the side wall of the first central injection pipe 804; the outer wall of the second central injection pipe 805 is provided with a support bar 808 fixedly connected to the first central injection pipe 804; the third central injection pipe 806 is connected to a third gas inlet 803, and the third gas inlet 803 is fixedly inserted through the side walls of the first central injection pipe 804 and the second central injection pipe 805; the outer wall of the third central injection pipe 806 is provided with a support bar 808 fixedly connected to the second central injection pipe 805. The third central injection pipe 806 is a straight pipe with an inner diameter preferably of 300–700 mm. This channel handles 30–60% of the ethylene circulating gas flow rate. The gap between the first central injection pipe 804 and the second central injection pipe 805 is 100–200 mm, and the gap between the second central injection pipe 805 and the third central injection pipe 806 is 200–300 mm. The gas velocity of the ethylene circulating gas in the first central injection pipe 804, the second central injection pipe 805, and the third central injection pipe 806 is adjusted by the annular gap distance to achieve the effect of jet-fluidized mixing. The gas velocity of the ethylene circulating gas in the injection pipes can reach 80–120 m / s.

[0038] Correspondingly, the jet mixing zone is also divided into three areas: the first jet mixing zone 14, the second jet mixing zone 13, and the third jet mixing zone 3. The first jet mixing zone 14 is mainly for mixing the circulating ethylene gas ejected from the first central injection pipe 804, the second jet mixing zone 13 is mainly for mixing the circulating ethylene gas ejected from the second central injection pipe 805, and the third jet mixing zone 3 is mainly for mixing the circulating ethylene gas ejected from the third central injection pipe 806.

[0039] Correspondingly, the nozzle orifice area on the distributor 9 is also divided into three regions: the first nozzle orifice area 12, the second nozzle orifice area 11, and the third nozzle orifice area 10. The nozzles on the first nozzle orifice area 12, the second nozzle orifice area 11, and the third nozzle orifice area 10 have different diameters to facilitate adjustment of the material flow rates in the first jet mixing zone 14, the second jet mixing zone 13, and the third jet mixing zone 3. The oxygen flow velocity ejected from the nozzle is 50–100 m / s. Since the unfolded area of ​​the distributor 9 is relatively large compared to the nozzle orifice area, the apparent gas velocity of the oxygen on the upper surface of the distributor 9 after passing through the nozzle rapidly decreases to 0.05–0.2 m / s.

[0040] Each jet mixing zone adjusts the ratio of oxygen to ethylene circulating gas to expand the mixing space and mix in batches, thereby greatly reducing the risk of uneven mixing and long mixing time of large flow rates of oxygen and ethylene circulating gas in a limited area, and thus enabling the mixture to quickly pass through the explosion limit range.

[0041] The distributor 9 has an inverted conical structure that is wider at the top and narrower at the bottom. The inverted conical structure makes it easy to divide the housing 1 into two areas. The horizontal angle of the distributor 9 is 30-60°, preferably 45°, to ensure the mixing effect of oxygen and circulating ethylene gas.

[0042] An accelerating flow assembly 5 is installed in the housing 1 above the central jet pipe assembly 8 to increase the airflow velocity. Due to the large cross-sectional area of ​​the jet mixing zone, the apparent velocity of the mixed gas drops to 1-3 m / s, and the time for the mixed gas to exit the housing 1 is longer, increasing the safety risk. Therefore, the accelerating flow assembly 5 is installed to separate the housing 1. The area where the accelerating flow assembly 5 is located is the mixing buffer zone 4. The mixing buffer zone 4 allows the ethylene recycle gas and oxygen after rapid jet mixing to be further mixed and leave the mixer more quickly, thereby reducing the safety risk.

[0043] like Figure 3 As shown, the accelerated flow assembly 5 includes several spaced-apart baffles 501. Each baffle 501 has through holes 502, and the through holes 502 of two adjacent baffles 501 are staggered. The distance between two adjacent baffles 501 is 100–200 mm. The baffles 501 serve to guide the flow, making the mixing of ethylene and oxygen more uniform and preventing dead zones. Another function is to reduce the cross-sectional area of ​​the mixing buffer zone 4, increasing the apparent flow velocity of the mixture and allowing the material to leave the mixer more quickly.

[0044] The through hole 502 on the bottom baffle 501 is not aligned with the central jet assembly 8 to prevent the ethylene circulating gas ejected from the third central jet pipe 806 from entering the mixing buffer 4 without being fully mixed.

[0045] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A central jet mixer for ethylene oxide production comprising a housing (1), characterized in that The housing (1) is vertically provided with a central jet pipe assembly (8) for outputting ethylene circulating gas into the housing (1). A distributor (9) for dividing the housing (1) into two regions is sleeved on the outside of the central jet pipe assembly (8), and several nozzles are horizontally arranged on the distributor (9). The housing (1) is connected to an oxygen inlet (7) located below the distributor (9). A mixed gas outlet (6) is provided at the top of the housing (1). An acceleration flow assembly (5) for increasing the airflow velocity is provided above the central jet pipe assembly (8) in the housing (1). The central jet pipe assembly (8) includes at least two spaced jet pipes. The upper end outlet of the inner jet pipe protrudes from the upper end outlet of the outer jet pipe. An annular guide vane (807) is provided on the upper outer wall of each jet pipe. The lower end of the jet pipe passes through the housing (1) and is provided with a gas inlet.

2. The center-jet mixer for ethylene oxide production according to claim 1, characterized in that, The distributor (9) is an inverted cone-shaped structure that is wider at the top and narrower at the bottom.

3. A center-jet mixer for ethylene oxide production according to claim 2, characterized in that, The horizontal angle of the distributor (9) is 30~60°.

4. A center-jet mixer for ethylene oxide production according to claim 1, characterized in that, The accelerated flow component (5) includes several baffles (501) spaced apart. The baffles (501) have through holes (502) and the through holes (502) of two adjacent baffles (501) are staggered.

5. A center-jet mixer for ethylene oxide production according to claim 4, characterized in that, The through hole (502) on the bottommost baffle plate (501) is not aligned with the central jet pipe assembly (8).

6. A center-jet mixer for ethylene oxide production according to claim 4, characterized in that, The distance between two adjacent baffles (501) is 100~200mm.

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