A two-stage injection combustible gas and oxygen mixer

Abstract

The application discloses a two-stage injection combustible gas and oxygen mixer, which comprises a mixer main pipe for a combustible gas channel and an oxygen injection pipe for an oxygen channel. The combustible gas enters the mixer main pipe, flows through the oxygen injection ring, mixes with the oxygen in the main pipe, and then flows to the downstream; the oxygen injection pipe comprises an oxygen main pipe, an oxygen branch pipe, an oxygen injection ring and an oxygen flow control valve, wherein the oxygen main pipe is arranged outside the mixer main pipe, the oxygen branch pipe is connected with the oxygen main pipe through the wall of the mixer main pipe and is arranged inside the mixer main pipe and the oxygen injection ring, the oxygen injection ring is a two-stage channel structure, each stage channel surface is provided with uniformly distributed injection holes with the same injection direction as the combustible gas flow direction, and the oxygen flow control valve is arranged on the oxygen branch pipe to control the oxygen flow entering the oxygen injection ring. The mixer can quickly and uniformly mix the combustible gas and the oxygen, and solves the combustion or explosion accidents caused by the local high concentration in the mixing process.

Description

Technical Field

[0001] This invention relates to a mixer for combustible gas and oxygen, and more particularly to a mixer for alkane or olefin and oxygen, which can be used for the oxidative dehydrogenation of ethane to ethylene or the catalytic oxidation of ethylene to ethylene oxide. Background Technology

[0002] Ethylene is a basic raw material for petrochemicals, and its output is an important indicator of a country's chemical industry development level. There are many methods for its production, including high-temperature cracking of ethane and catalytic oxidative dehydrogenation. The former is a strongly endothermic process, which is limited by thermodynamic equilibrium, resulting in high energy consumption, low equilibrium conversion rate, and problems such as coking of the reaction equipment. The latter introduces gaseous oxygen into the ethane cracking feed gas, making the reaction to produce ethylene an exothermic process. In principle, low temperature is conducive to the reaction, saving energy and improving energy efficiency. Therefore, the method of oxidative dehydrogenation of ethane to produce ethylene is receiving increasing attention.

[0003] Ethylene oxide is a crucial downstream chemical product of the ethylene industry, second only to polyethylene. It is mainly used to produce nonionic surfactants, ethanolamines, ethylene glycol ethers, choline chloride, and pharmaceuticals, among other fine chemical products. The main preparation methods are the chloroethanol process and the direct oxidation of ethylene. The direct oxidation of ethylene is further divided into air oxidation and oxygen oxidation. Compared with air oxidation, oxygen oxidation has significant advantages, such as lower production costs, shorter process flow, lower reaction temperature, and higher catalyst selectivity. Therefore, oxygen oxidation is currently the most common method used in ethylene oxide plants worldwide.

[0004] Whether it's the oxidative dehydrogenation of ethane to ethylene or the oxygen oxidation of ethylene to ethylene oxide, both processes require mixing combustible gas and oxygen before the reaction. The resulting mixture is highly explosive, with a wide explosive limit. Improper control can easily lead to combustion and explosion accidents. Therefore, it is crucial to ensure that the concentration of the mixed combustible gas and oxygen is far from the explosive range, while simultaneously ensuring as uniform a mixing process as possible and minimizing the flammable zone. Currently, rapid mixing of combustible gas and oxygen in production facilities typically employs porous jet mixers. These mixers inject oxygen into the combustible gas through small orifices of a specific size, quickly pushing it past the explosive limit. However, even these methods can still result in less than ideal mixing effects.

[0005] Patent CN 105214528A discloses a mixer for mixing olefins and oxygen. This mixer mainly consists of several oxygen dispersion tubes symmetrically arranged at the end of an oxygen pipeline. Each oxygen dispersion tube has several oxygen dispersion holes evenly distributed on it, and the oxygen pipeline is connected to a mixing chamber through these holes. However, looking at the cross-section of the olefin pipeline, the oxygen dispersion holes are denser at the center and sparser near the wall. During mixing, the oxygen concentration at the center of the main pipe is higher than near the wall, affecting the mixing effect. Summary of the Invention

[0006] The technical problem solved by this application is to overcome the shortcomings of the prior art and provide a two-stage injection combustible gas and oxygen mixer, which solves the problem of unsatisfactory mixing effect of combustible gas and oxygen.

[0007] The technical solution provided in this application is as follows:

[0008] A two-stage combustible gas and oxygen mixer includes a mixer main pipe, a large-ring oxygen branch pipe, a small-ring oxygen branch pipe, a large oxygen injection ring, and a small oxygen injection ring. The large-ring oxygen injection ring has a larger diameter than the small-ring oxygen injection ring. The large-ring oxygen injection ring and the small-ring oxygen injection ring are sequentially installed inside the mixer main pipe along the combustible gas flow direction. One end of the large-ring oxygen branch pipe is connected to the large-ring oxygen injection ring, and the other end extends to the outside of the mixer main pipe. One end of the small-ring oxygen branch pipe is connected to the small-ring oxygen injection ring, and the other end extends to the outside of the mixer main pipe. The large-ring oxygen branch pipe and the small-ring oxygen branch pipe are used for oxygen injection. Injection holes aligned with the combustible gas flow direction are opened on the surface of the large-ring oxygen injection ring and the small-ring oxygen injection ring.

[0009] A combustible gas and oxygen mixer includes a main mixer pipe for the combustible gas passage and an oxygen main pipe for the oxygen passage. The combustible gas enters through the main mixer pipe, flows through an oxygen injection ring, mixes with oxygen in the main pipe, and then flows downstream. The oxygen injection pipe includes an oxygen main pipe, an oxygen branch pipe, and an oxygen injection ring. The oxygen main pipe is located outside the main mixer pipe, and the oxygen branch pipe passes through the wall of the main mixer pipe and connects the oxygen main pipe to the oxygen injection ring located inside the main mixer pipe. The oxygen injection ring has a two-stage channel structure, and each stage channel surface is provided with evenly distributed injection holes whose injection direction is consistent with the combustible gas flow direction. An oxygen flow control valve is located on the oxygen branch pipe to control the oxygen flow rate entering the oxygen injection ring.

[0010] Preferably, there are two oxygen injection rings, namely a large oxygen injection ring and a small oxygen injection ring, and the oxygen flow rate inside the oxygen injection ring is 10-30 m / s.

[0011] Preferably, the centers of all oxygen injection rings are located on the main axis of the mixer.

[0012] Preferably, the ratio of the inner diameter of the mixer main pipe, the diameter of the large oxygen injection ring, and the diameter of the small oxygen injection ring is approximately 1:(0.5-0.6):(0.3-0.4).

[0013] Preferably, the large oxygen injection ring is provided with a large annular primary oxygen channel, a large annular secondary oxygen channel, a large annular primary injection hole, and a large annular secondary injection hole. The large annular primary oxygen channel and the large annular secondary oxygen channel are two annular channels arranged sequentially along the combustible gas flow direction in the main mixer pipe. The axis of the annular channel is coaxial with the main mixer pipe. The large annular primary injection hole connects the large annular primary oxygen channel and the large annular secondary oxygen channel. The large annular oxygen branch pipe is connected to the large annular primary oxygen channel. The large annular secondary injection hole connects the large annular secondary oxygen channel and the internal space of the main mixer pipe. The small oxygen injection ring is provided with a small annular primary oxygen channel, a small annular secondary oxygen channel, a small annular primary injection hole, and a small annular secondary injection hole. The small annular primary oxygen channel and the small annular secondary oxygen channel are two annular channels arranged sequentially along the combustible gas flow direction in the main mixer pipe. The axis of the annular channel is coaxial with the main mixer pipe. The small annular primary injection hole connects the small annular primary oxygen channel and the small annular secondary oxygen channel. The small annular oxygen branch pipe is connected to the small annular primary oxygen channel. The small annular secondary injection hole connects the small annular secondary oxygen channel and the internal space of the main mixer pipe.

[0014] Preferably, the distance between the two oxygen injection rings is 90-110 times the diameter of the large ring secondary injection hole; the distance between the pitch circle of the small ring oxygen primary channel and the outlet end of the mixer main pipe is 8-10 times the inner diameter of the mixer main pipe.

[0015] Preferably, the side of the inner wall of the large annular oxygen secondary channel facing the large annular primary injection hole is a planar side, which is perpendicular to the axis of the large annular primary injection hole; the distance between the planar side of the large annular oxygen secondary channel and the end of the large annular primary injection hole near the planar side is the height direction of the large annular oxygen secondary channel, and the height of the large annular oxygen secondary channel is 4-6mm; the height of the small annular oxygen secondary channel is 4-6mm.

[0016] Preferably, the diameter of the large ring primary injection hole is 4-5 mm, the diameter of the large ring secondary injection hole is 5-6 mm, the diameter of the small ring primary injection hole is 3-4 mm, the diameter of the small ring secondary injection hole is 4-5 mm, and the oxygen injection velocity at the outlet of the secondary injection hole is 85-110 m / s.

[0017] Preferably, the spacing between the injection holes on the same ring is 10-30 times the diameter of the injection hole.

[0018] Preferably, the primary injection holes on the same ring are evenly distributed, and the secondary injection holes are evenly distributed with offsets from the primary injection holes.

[0019] Preferably, the opening direction of the oxygen injection hole is consistent with the flow direction of the combustible gas.

[0020] Preferably, each oxygen branch pipe is equipped with an oxygen flow control valve.

[0021] In summary, this application includes at least the following beneficial technical effects:

[0022] Oxygen flows with varying mass within the primary channel of the oxygen injection ring. The oxygen flow rate is highest at the injection hole closest to the oxygen branch pipe and lowest at the injection hole furthest from the branch pipe. This results in uneven oxygen flow rate and velocity distribution across the primary injection hole cross-section of the entire injection ring, affecting the free development and diffusion distance of oxygen exiting the injection hole. The combined effect of these two factors makes it difficult to guarantee rapid and uniform mixing within the main mixer pipe. This invention designs a two-stage injection combustible gas and oxygen mixer. Oxygen is injected from the primary channel of the injection ring into the secondary channel, where it undergoes secondary flow distribution before being injected into the main mixer pipe through the secondary injection holes. The oxygen flow rate and velocity at the outlet of the secondary injection holes are significantly improved, enabling rapid, uniform, and accurate mixing of combustible gas and oxygen within the main mixer pipe. This minimizes the explosion zone during mixing and ensures that the composition of the mixed gas is far from the explosive range.

[0023] This invention incorporates an oxygen flow control valve on the oxygen branch pipe, enabling the mixer to have a wider range of oxygen flow regulation. When the flow rate in the main oxygen pipe deviates from normal operating conditions, the flow rate entering the two oxygen injection rings is controlled by adjusting the opening of the oxygen flow control valve. If necessary, the oxygen supply to one of the oxygen branch pipes can be directly cut off, ensuring that the oxygen velocity at the oxygen injection orifice is within a suitable range, which is beneficial to both the mixing effect and the structural safety of the equipment.

[0024] The present invention has a simple structure, can significantly reduce the number of welds in the mixing equipment, is easy to install and implement. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of a two-stage injection combustible gas and oxygen mixer.

[0026] Figure 2 This is a schematic diagram of the large ring of the oxygen injection ring and the two-stage injection holes.

[0027] Figure 3 for Figure 2 AA cross-section view.

[0028] Explanation of reference numerals in the attached diagram: 1. Combustible gas inlet pipe; 2. Inlet transition pipe; 3. Mixer main pipe; 4. Outlet transition pipe; 5. Mixed gas outlet pipe; 6. Oxygen main pipe; 7. Large ring oxygen branch pipe; 8. Large ring oxygen flow control valve; 9. Small ring oxygen branch pipe; 10. Small ring oxygen flow control valve; 11. Large ring oxygen primary channel; 12. Large ring oxygen secondary channel; 13. Large ring primary injection port; 14. Large ring secondary injection port; 15. Small ring oxygen primary channel; 16. Small ring oxygen secondary channel; 17. Small ring primary injection port; 18. Small ring secondary injection port. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments disclosed in the present invention will be described in further detail below with reference to the accompanying drawings.

[0030] Figure 1 This is a schematic structural diagram of a two-stage injection combustible gas and oxygen mixer provided in an embodiment of the present invention. This application discloses a combustible gas and oxygen mixer, such as… Figure 1 As shown, it includes a combustible gas inlet pipe 1, an inlet transition pipe 2, a mixer main pipe 3, an outlet transition pipe 4, and a mixed gas outlet pipe 5 connected in sequence. The mixer main pipe 3 is connected to upstream and downstream main pipes of different diameters through the combustible gas inlet pipe 1, the inlet transition pipe 2, the outlet transition pipe 4, and the mixed gas outlet pipe 5. The connection method can be flange connection or welding.

[0031] In some embodiments provided by the present invention, the front section of the mixer is a flow channel for combustible gas. The cross-sectional area of ​​the flow channel can be determined according to the flow velocity of the combustible gas, which is usually between 6 and 12 m / s.

[0032] An oxygen injection ring is provided inside the mixer main pipe 3. The oxygen injection ring includes a large oxygen injection ring and a small oxygen injection ring. Along the direction of combustible gas flow in the mixer main pipe 3, the large oxygen injection ring and the small oxygen injection ring are installed in sequence inside the mixer main pipe 3. The central axis of the large oxygen injection ring and the small oxygen injection ring is located on the axis of the mixer main pipe 3.

[0033] The oxygen main pipe 6 is welded with oxygen branch pipes, the other end of which is connected to the oxygen injection ring. Specifically, the oxygen branch pipes include a large ring oxygen branch pipe 7 and a small ring oxygen branch pipe 9. One end of the large ring oxygen branch pipe 7 is located outside the mixer main pipe 3, and the other end extends into the mixer main pipe 3 and is connected to the large oxygen injection ring. One end of the small ring oxygen branch pipe 9 is located outside the mixer main pipe 3, and the other end extends into the mixer main pipe 3 and is connected to the small oxygen injection ring. These two branch pipes penetrate the wall of the mixer main pipe 3 to deliver oxygen into the two oxygen injection rings located inside the mixer main pipe 3.

[0034] like Figure 2 and Figure 3 As shown, the oxygen injection ring is provided with a large annular oxygen primary channel 11, a large annular oxygen secondary channel 12, a large annular primary injection hole 13, and a large annular secondary injection hole 14. The large annular oxygen primary channel 11 and the large annular oxygen secondary channel 12 are two annular channels arranged sequentially along the combustible gas flow direction in the mixer main pipe 3. The axis of the annular channel is coaxial with the mixer main pipe 3. The large annular primary injection hole 13 connects the large annular oxygen primary channel 11 and the large annular oxygen secondary channel 12. The large annular oxygen branch pipe 7 is connected to the large annular oxygen primary channel 11. The large annular secondary injection hole 14 connects the large annular oxygen secondary channel 12 and the internal space of the mixer main pipe 3. The oxygen injection ring is equipped with a small ring oxygen primary channel 15, a small ring oxygen secondary channel 16, a small ring primary injection hole 17, and a small ring secondary injection hole 18. The small ring oxygen primary channel 15 and the small ring oxygen secondary channel 16 are two annular channels arranged sequentially along the combustible gas flow direction in the mixer main pipe 3. The axis of the annular channel is coaxial with the mixer main pipe 3. The small ring primary injection hole 17 connects the small ring oxygen primary channel 15 and the small ring oxygen secondary channel 16. The small ring oxygen branch pipe 9 connects to the small ring oxygen primary channel 15. The small ring secondary injection hole 18 connects the small ring oxygen secondary channel 16 and the internal space of the mixer main pipe 3.

[0035] Oxygen undergoes variable mass flow within the large annular oxygen primary channel 11 and the small annular oxygen primary channel 15. The oxygen flow rate and velocity through the large annular primary injection hole 13 and the small annular primary injection hole 17 gradually decrease as the distance from the large annular oxygen branch pipe 7 and the small annular oxygen branch pipe 9 increases.

[0036] The large-ring primary injection holes 13 are evenly distributed around the circumference of the large oxygen injection ring, and the large-ring secondary injection holes 14 are evenly distributed with offsets from the large-ring primary injection holes 13; the air outlet of the large-ring oxygen branch pipe 7 is staggered with the large-ring primary injection holes 13. Similarly, the small-ring primary injection holes 17 are evenly distributed around the circumference of the small oxygen injection ring, and the small-ring secondary injection holes 18 are evenly distributed with offsets from the small-ring primary injection holes 17; the air outlet of the small-ring oxygen branch pipe 9 is staggered with the small-ring primary injection holes 17.

[0037] Oxygen is injected from the large ring primary injection hole 13 and the small ring primary injection hole 17 into the large ring secondary oxygen channel 12 and the small ring secondary oxygen channel 16. The cross-sections of the large ring secondary oxygen channel 12 and the small ring secondary oxygen channel 16 are approximately rectangular. After being ejected from the primary injection hole, the oxygen impacts the inner wall of the secondary channel directly opposite it and then disperses to both sides, undergoing mass distribution within the secondary channel. Finally, it is injected from the large ring secondary injection hole 14 and the small ring secondary injection hole 18 into the mixer main pipe 3 to mix with the combustible gas.

[0038] In some embodiments provided by the present invention, the cross-sectional area of ​​the secondary channel of the oxygen injection ring can be determined based on the cross-sectional area of ​​the primary channel. Generally, the cross-sectional area of ​​the secondary channel is about 10%-15% of the cross-sectional area of ​​the primary channel.

[0039] In some embodiments provided by the present invention, such as Figure 2 As shown, the outlet of the large-ring oxygen branch pipe 7 is connected to a centerline position of the large oxygen injection ring. The primary injection holes 13 on the large-ring oxygen injection ring are evenly distributed across the centerline, ensuring that the outlet of the large-ring oxygen branch pipe 7 is not directly aligned with the primary injection holes 13. The secondary injection holes 14 are evenly distributed with a staggered arrangement compared to the primary injection holes 13. The total area of ​​the secondary injection holes 14 is determined by the total oxygen flow rate, ensuring that the oxygen velocity at the outlet of the secondary injection holes 14 is 85-110 m / s. After determining the total area, the number of openings in the secondary injection holes 14 is matched with the diameter of each hole, ensuring that the spacing between adjacent secondary injection holes 14 is 10-30 times the diameter of the secondary injection hole 14. After determining the secondary injection holes 14, the number of primary injection holes 13 is the same as the number of secondary injection holes 14, but the diameter of each hole is 0.5-1 mm smaller.

[0040] Similarly, the total area of ​​the small-ring secondary injection orifice 18 is determined by the total oxygen flow rate, ensuring that the oxygen velocity at the outlet of the small-ring secondary injection orifice 18 is 85-110 m / s. After determining the total area, the number of openings in the small-ring secondary injection orifice 18 is matched with the diameter of each orifice, such that the distance between two adjacent small-ring secondary injection orifices 18 is 10-30 times their diameter. Following the small-ring secondary injection orifices 18, the number of small-ring primary injection orifices 17 is the same as the number of small-ring secondary injection orifices 18, but their diameters are 0.5-1 mm smaller.

[0041] exist Figure 1 In the illustrated embodiment, the centers of the two oxygen injection rings are located on the axis of the mixer main pipe 3. The ratio of the inner diameter of the mixer main pipe 3 to the diameter of the two oxygen injection rings is approximately 1:(0.5-0.6):(0.3-0.4), ensuring sufficient space for the injected oxygen to develop in the radial direction. The distance between the pitch circle of the large annular oxygen primary channel 11 and the pitch circle of the small annular oxygen primary channel 15 is typically 90-110 times the diameter of the large annular secondary injection hole 14, while the distance between the pitch circle of the small annular oxygen primary channel 15 and the outlet of the mixer main pipe 3 is typically 8-10 times the inner diameter of the mixer main pipe 3. These two distances ensure that the oxygen can diffuse freely in the axial direction and mix thoroughly with the combustible gas.

[0042] exist Figure 1In the illustrated embodiment, a large-ring oxygen flow control valve 8 is installed on the large-ring oxygen branch pipe 7 outside the mixer main pipe 3, and a small-ring oxygen flow control valve 10 is installed on the small-ring oxygen branch pipe 9. Under normal oxygen flow conditions, both the large-ring oxygen flow control valve 8 and the small-ring oxygen flow control valve 10 are fully open. Under conditions of reduced oxygen flow, the opening of these two valves is adjusted, or even one of the valves is closed, to ensure that the oxygen velocity at the injection orifice outlet is within a suitable range. This is beneficial for both mixing effect and equipment structural safety, thereby giving the mixer a wider oxygen flow adjustment range.

[0043] The contents not described in detail in this application specification are common knowledge to those skilled in the art.

[0044] The present application has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present application. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and implementation methods of the present application without departing from the spirit and scope of the present application, and all such modifications and improvements fall within the scope of the present application. The scope of protection of the present application is determined by the appended claims.

Claims

1. A two-stage injection combustible gas and oxygen mixer, characterized in that: It includes the mixer main pipe (3), the large ring oxygen branch pipe (7), the small ring oxygen branch pipe (9), the oxygen injection large ring and the oxygen injection small ring, and the large ring of the oxygen injection ring has a larger circle diameter than the small ring of the oxygen injection ring. Along the direction of combustible gas flow inside the main mixer pipe (3), the large oxygen injection ring and the small oxygen injection ring are installed sequentially inside the main mixer pipe (3). One end of the large ring oxygen branch pipe (7) is connected to the large oxygen injection ring and the other end extends to the outside of the main mixer pipe (3). One end of the small ring oxygen branch pipe (9) is connected to the small oxygen injection ring and the other end extends to the outside of the main mixer pipe (3). The large ring oxygen branch pipe (7) and the small ring oxygen branch pipe (9) are used for oxygen injection. The surfaces of the large oxygen injection ring and the small oxygen injection ring are provided with injection holes that are consistent with the direction of combustible gas flow. The oxygen injection ring is provided with a large ring oxygen primary channel (11), a large ring oxygen secondary channel (12), a large ring primary injection hole (13), and a large ring secondary injection hole (14). The large ring oxygen primary channel (11) and the large ring oxygen secondary channel (12) are two annular channels arranged sequentially along the combustible gas flow direction in the mixer main pipe (3). The axis of the annular channel is coaxial with the mixer main pipe (3). The large ring primary injection hole (13) connects the large ring oxygen primary channel (11) and the large ring oxygen secondary channel (12). The large ring oxygen branch pipe (7) is connected to the large ring oxygen primary channel (11). The large ring secondary injection hole (14) connects the large ring oxygen secondary channel (12) and the internal space of the mixer main pipe (3). The oxygen injection ring is provided with a small ring oxygen primary channel (15), a small ring oxygen secondary channel (16), a small ring primary injection hole (17), and a small ring secondary injection hole (18). The small ring oxygen primary channel (15) and the small ring oxygen secondary channel (16) are two annular channels arranged sequentially along the combustible gas flow direction in the mixer main pipe (3). The axis of the annular channel is coaxial with the mixer main pipe (3). The small ring primary injection hole (17) connects the small ring oxygen primary channel (15) and the small ring oxygen secondary channel (16). The small ring oxygen branch pipe (9) is connected to the small ring oxygen primary channel (15). The small ring secondary injection hole (18) connects the small ring oxygen secondary channel (16) and the internal space of the mixer main pipe (3).

2. The two-stage injection combustible gas and oxygen mixer according to claim 1, characterized in that: The centers of the large and small oxygen injection rings are located on the axis of the mixer main pipe (3).

3. The two-stage injection combustible gas and oxygen mixer according to claim 1, characterized in that: The primary injection holes (13) of the large ring are evenly distributed around the oxygen injection ring, and the secondary injection holes (14) of the large ring are evenly distributed with the primary injection holes (13) of the large ring offset. The air outlet of the large ring oxygen branch pipe (7) is intersected with the large ring primary injection hole (13).

4. A two-stage injection combustible gas and oxygen mixer according to claim 1, characterized in that: The cross-sectional area of ​​the macrocyclic oxygen secondary channel (12) is 10%-15% of the cross-sectional area of ​​the macrocyclic oxygen primary channel (11); The inner wall of the large annular oxygen secondary channel (12) facing the large annular primary injection hole (13) is a planar side, which is perpendicular to the axis of the large annular primary injection hole (13). The distance between the planar side of the large annular oxygen secondary channel (12) and the end of the large annular primary injection hole (13) near the planar side is defined as the height of the large annular oxygen secondary channel (12), which is 4-6 mm.

5. A two-stage injection combustible gas and oxygen mixer according to claim 1, characterized in that: The total area of ​​the large annular secondary injection orifice (14) is determined according to the total oxygen flow rate. After the total area of ​​the large annular secondary injection orifice (14) is determined, the number of openings of the large annular secondary injection orifice (14) is matched with the diameter of a single orifice so that the distance between two adjacent large annular secondary injection orifices (14) is 10-30 times the diameter of the large annular secondary injection orifice (14). The number of large annular primary injection orifices (13) and large annular secondary injection orifices (14) are equal, and the diameter of the large annular primary injection orifice (13) is 0.5-1 mm smaller than the diameter of the large annular secondary injection orifice (14). The oxygen injection velocity of the large annular secondary injection hole (14) is 85-110 m / s.

6. A two-stage injection combustible gas and oxygen mixer according to claim 1, characterized in that: The distance between the pitch circle of the large annular oxygen primary channel (11) and the pitch circle of the small annular oxygen primary channel (15) is 90-110 times the diameter of the large annular secondary injection hole (14); the distance between the pitch circle of the small annular oxygen primary channel (15) and the outlet end of the mixer main pipe (3) is 8-10 times the inner diameter of the mixer main pipe (3).

7. A two-stage injection combustible gas and oxygen mixer according to claim 1, characterized in that: The ratio of the inner diameter of the main pipe (3) of the mixer, the diameter of the large oxygen injection ring, and the diameter of the small oxygen injection ring is 1:(0.5~0.6):(0.3~0.4).

8. A two-stage injection combustible gas and oxygen mixer according to claim 1, characterized in that: It also includes an oxygen main pipe (6) located outside the mixer main pipe (3), which is connected to both the large ring oxygen branch pipe (7) and the small ring oxygen branch pipe (9) so as to inject oxygen into the large ring oxygen branch pipe (7) and the small ring oxygen branch pipe (9) through the oxygen main pipe (6).

9. A two-stage injection combustible gas and oxygen mixer according to claim 1, characterized in that: The large ring oxygen branch pipe (7) is equipped with a large ring oxygen flow control valve (8) to control the oxygen flow rate entering the oxygen injection large ring; the small ring oxygen branch pipe (9) is equipped with a small ring oxygen flow control valve (10) to control the oxygen flow rate entering the oxygen injection small ring.

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