Mirror polishing technology for manufacturing acetylene mixer based on cracking device

Abstract

The invention discloses a mirror polishing technology for manufacturing an acetylene mixer based on a cracking device, and relates to the technical field of acetylene preparation and purification equipment, metal mirror polishing treatment is carried out on the surface, making contact with high-speed mixed gas, in a jet mixer of an acetylene cracking furnace; the mixer comprises a natural gas annular flow channel, a central oxygen nozzle, a mixing cavity and a diffusion section, the inner surface of the acetylene mixer of the cracking device is subjected to metal mirror polishing, and it is detected by a white light interferometer that the height of weld beading is gt; 1 mm is reduced to be less than or equal to 0.1 mm; the surface roughness is reduced to 0.08 to 0.16 [mu] m from 3.2 to 6.3 [mu] m; a friction energy test shows that the friction energy of the polished high-speed mixed gas flow is 0.08-0.09 mJ and is lower than the minimum ignition energy of an acetylene-oxygen mixture.

Description

Technical Field

[0001] The present invention relates to the technical field of acetylene preparation and purification equipment, and particularly to a mirror polishing technology based on the manufacture of an acetylene mixer for a cracking device. Background Art

[0002] The acetylene mixer of the cracking device is the core equipment of the acetylene cracking furnace. It adopts a jet structure (central oxygen nozzle + annular natural gas flow channel) and needs to achieve high-speed mixing of natural gas and oxygen (>50 m / s) at high temperature (600–650 °C) and medium pressure (0.135 MPa).

[0003] Due to weld beads (>1 mm), excessive weld reinforcement (>0.5 mm), oxidation of nickel-based welds, and rough inner surface (Ra≥3.2 μm) in the existing manufacturing technology, sparks are generated due to the friction of high-speed gas flow, leading to early ignition (interlock is triggered within 30 minutes after oxygen injection, and the longest operating time ≤2 hours). Traditional process adjustments cannot solve this problem, and the structural transformation has a long cycle.

[0004] Therefore, a mirror polishing technology based on the manufacture of an acetylene mixer for a cracking device is designed to solve the technical problems of quantifying weld bead, reinforcement, and roughness data. Summary of the Invention

[0005] In view of the deficiencies of the prior art, the present invention provides a mirror polishing technology based on the manufacture of an acetylene mixer for a cracking device, and solves the technical problems raised in the above background art.

[0006] To achieve the above objectives, the present invention is realized through the following technical solutions: A mirror polishing technology based on the manufacture of an acetylene mixer for a cracking device, which performs metal mirror polishing treatment on the surface inside the jet mixer of the acetylene cracking furnace that contacts the high-speed mixed gas; the mixer includes an annular natural gas flow channel, a central oxygen nozzle, a mixing chamber, and a diffusion section;

[0007] The objective of the metal mirror polishing treatment is to eliminate weld beads, weld reinforcement, local oxidation points, and surface roughness defects on the inner surface of the mixer, so that the surface roughness Ra of the polished inner surface ≤0.16 μm, in order to suppress the generation of sparks due to the friction of the high-temperature mixed gas of natural gas and oxygen flowing in the mixer with a flow rate greater than 50 m / s, thereby solving the problem of early ignition of the acetylene mixer.

[0008] Preferably, the area covered by the metal mirror polishing treatment includes the entire inner surface of the mixing chamber and the inner surface of the inlet area of the diffusion section.

[0009] Preferably, the metal mirror polishing treatment is preferentially applied to nickel-based alloy welds to ensure the elimination of excessive weld reinforcement and oxidation areas, and to achieve a smooth transition between the weld surface and the base metal surface.

[0010] Preferably, the mixer after the metal mirror polishing treatment is configured to:

[0011] Under the working condition that natural gas and oxygen are mixed at a pressure of 0.135 MPa and a temperature of 600 °C - 650 °C, and the mixing time is controlled within the flame induction period of 0.02 - 0.03 s, it can withstand continuous operation without causing interlock shutdown due to internal surface friction sparks.

[0012] Preferably, the working principle of the jet mixer is as follows: Oxygen is injected into the mixing chamber through the central nozzle, natural gas is input into the mixing chamber through the annular flow channel, and after the two are mixed in the mixing chamber, they are pressurized through the diffusion section and transported to the burner plate.

[0013] Beneficial effects

[0014] The present invention provides a mirror polishing technology based on the manufacture of an acetylene mixer for a cracking device. The present invention performs metal mirror polishing (surface roughness Ra ≤ 0.16 μm) on the inner surface of the acetylene mixer for the cracking device. After detection by a white light interferometer:

[0015] The height of the weld bead decreases from > 1 mm to ≤ 0.1 mm;

[0016] The surface roughness decreases from 3.2 - 6.3 μm to 0.08 - 0.16 μm;

[0017] Friction energy tests show that the friction energy of the high-speed mixed gas flow (52 - 55 m / s) after polishing is 0.08 - 0.09 mJ, which is lower than the minimum ignition energy of the acetylene-oxygen mixture (0.02 mJ).

[0018] Under the working conditions of 620 - 650 °C and 0.135 MPa:

[0019] The continuous operation time is increased from 1.8 ± 0.3 hours to continuous operation;

[0020] The number of early ignition times is reduced from 6 times per charge to 0 times;

[0021] The polishing cost is 4.7 - 5.1% of the equipment replacement cost, and the service life is extended from 3 months to 9.5 months. Description of the drawings

[0022] Figure 1 It is a schematic structural diagram before grinding of the mirror polishing technology based on the acetylene mixer for the cracking device described in the present invention.

[0023] Figure 2 Schematic diagram of the structure after grinding for a mirror polishing technology based on an acetylene mixer of a cracking device according to the present invention. Detailed implementation manners

[0024] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] Please refer to Figure 1-2 , the present invention provides a technical solution: a mirror polishing technology based on an acetylene mixer of a cracking device, and metal mirror polishing treatment is performed on the surface in contact with the high-speed mixed gas inside the jet mixer of the acetylene cracking furnace; the mixer includes a natural gas annular flow channel, a central oxygen nozzle, a mixing chamber, and a diffusion section;

[0026] The goal of the metal mirror polishing treatment is to eliminate the weld beads, weld reinforcement, local oxidation points, and surface roughness defects on the inner surface of the mixer, so that the surface roughness Ra of the polished inner surface is ≤ 0.16 μm, so as to suppress the generation of sparks due to friction with the surface of the natural gas and oxygen high-temperature mixed gas flowing in the mixer with a flow rate greater than 50 m / s, thereby solving the problem of early ignition of the acetylene mixer.

[0027] In this embodiment, it is further set that the area covered by the metal mirror polishing treatment includes the entire inner surface of the mixing chamber and the inner surface of the inlet area of the diffusion section.

[0028] In this embodiment, it is further set that the metal mirror polishing treatment is preferentially performed on nickel-based alloy welds to ensure the elimination of excessive weld reinforcement and oxidation areas and to achieve a smooth transition between the weld surface and the base metal surface.

[0029] In this embodiment, it is further set that the mixer after the metal mirror polishing treatment is configured to: be able to withstand continuous operation without causing interlock shutdown due to friction sparks on the inner surface under the condition that natural gas and oxygen are mixed at a pressure of 0.135 MPa and a temperature of 600 °C - 650 °C, and the mixing time is controlled within the flame induction period of 0.02 - 0.03 s.

[0030] In this embodiment, it is further set that the working principle of the jet mixer is: oxygen is injected into the mixing chamber through the central nozzle, natural gas is input into the mixing chamber through the annular flow channel, and after the two are mixed in the mixing chamber, they are pressurized through the diffusion section and delivered to the burner plate.

[0031] The detailed connection means are well-known techniques in the art. The following mainly introduces the working principle and process, and the specific work is as follows.

[0032] Example:

[0033] 1. Reproduction of technical problems

[0034] Scenario: In the first-phase project of the 800,000-ton functional new material project of Sichuan Yongying New Materials Co., Ltd., the acetylene cracking device is equipped with 6 jet-type acetylene mixers.

[0035] Fault phenomenon: The mixer catches fire frequently in the early stage within 30 minutes after oxygen injection during startup, triggering pressure interlock (alarm when ≥9.8 kPa), and the longest running time is less than 2 hours.

[0036] Root cause: Disassembling the faulty mixer reveals that:

[0037] There are weld beads (height > 1 mm) and excessive weld reinforcement ( > 0.5 mm) at the welds of the mixing chamber and the inlet of the diffuser section;

[0038] Local oxidation and discoloration of the nickel-based alloy weld;

[0039] The inner surface roughness is detected to be Ra ≈ 3.2–6.3 μm (far exceeding the safety threshold).

[0040] 2. Implementation of mirror polishing process

[0041] Step 1: Surface pretreatment

[0042] Use a belt grinding machine to remove the weld beads and excess height on the inner wall of the mixing chamber, ensure that the weld is flush with the base material (IncoI0y 800HT alloy), and eliminate the protruding structure.

[0043] Step 2: Gradient polishing

[0044] Rough polishing: Use 80#–120# diamond grinding wheels to grind and eliminate macroscopic defects;

[0045] Fine polishing: Replace with a fiber polishing wheel + diamond grinding paste (grain size W5–W1), and reciprocally polish the entire section of the mixing chamber and the inlet area of the diffuser section (high-risk friction area);

[0046] Final polishing: Use a wool wheel + mirror polishing paste (Cr2O3-based) to achieve a mirror finish with Ra ≤ 0.16 μm (measured Ra = 0.12–0.16 μm).

[0047] Step 3: Special treatment for welds

[0048] Perform laser remelting + manual fine polishing on the nickel-based alloy weld area to eliminate the oxide layer and ensure that the slope of the weld-base material transition zone < 0.05 mm (as Figure 2As shown, after polishing, the weld seam and the base metal present a continuous mirror surface).

[0049] 3. Verification of Polishing Effect

[0050] Comparison of Surface Topography (Explanation of Attached Drawings):

[0051] Figure 1 : On the inner surface of the mixing chamber before polishing, obvious weld beads and abrasion marks can be seen;

[0052] Roughness Detection:

[0053] Measured using a white light interferometer, the Ra value of the key area of the mixing chamber after polishing decreased from 3.2 μm to 0.16 μm (the decrease rate > 95%).

[0054] 4. Operation Test and Effect

[0055] Test Conditions:

[0056] Natural gas / oxygen preheated to 620°C ± 10°C, pressure 0.135 MPa;

[0057] Mixed gas flow rate 52–55 m / s, mixing time 0.025 s (within the flame induction period).

[0058] Results:

[0059] Continuous operation stability: 6 mixers continuously operated for ≥ 100 hours after the main oxygen was introduced, without triggering the pressure interlock (pressure fluctuation < 2 kPa);

[0060] Early ignition elimination: No frictional sparks were generated when the high-speed mixed gas passed through the polished surface, and the number of ignition times was zero;

[0061] Compensation for design defects: Without modifying the structure of the mixer, only through mirror polishing, the design working condition requirements are met.

[0062] 5. Summary of Technical Advantages

[0063]

[0064]

[0065] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

Claims

1. A mirror polishing technology based on the manufacture of an acetylene mixer for a cracking device, characterized in that, The surface of the internal part of the jet mixer of the acetylene cracking furnace that contacts the high-speed mixed gas is subjected to a metal mirror polishing treatment; the mixer includes a natural gas annular flow channel, a central oxygen nozzle, a mixing chamber and a diffusion section; The objective of the metal mirror polishing treatment is to eliminate the weld beads, weld reinforcement, local oxidation points and surface roughness defects on the inner surface of the mixer, so that the surface roughness Ra of the polished inner surface is ≤ 0.16 μm, in order to inhibit the natural gas and oxygen high-temperature mixed gas flowing in the mixer with a flow rate greater than 50 m / s from generating sparks due to friction with the surface, thereby solving the problem of early ignition of the acetylene mixer.

2. The mirror polishing technology based on the acetylene mixer of the cracking device according to claim 1, characterized in that , the area covered by the metal mirror polishing treatment includes the entire inner surface of the mixing chamber and the inner surface of the inlet area of the diffusion section.

3. A mirror polishing technique based on an acetylene mixer of a cracking device according to claim 1 or 2, characterized in that , the metal mirror polishing treatment is preferably carried out on nickel-based alloy welds to ensure the elimination of excessive weld reinforcement and oxidation areas and to achieve a smooth transition between the weld surface and the base metal surface.

4. A mirror polishing technique based on an acetylene mixer of a cracking device according to claim 1, characterized in that , the mixer after the metal mirror polishing treatment is configured as: Under the working conditions where natural gas and oxygen are mixed at a pressure of 0.135 MPa and a temperature of 600 °C - 650 °C, and the mixing time is controlled within the flame induction period of 0.02 - 0.03 s, it can withstand continuous operation without experiencing an interlock shutdown due to inner surface friction sparks.

5. A mirror polishing technique based on an acetylene mixer of a cracking device according to claim 1, characterized in that , the working principle of the jet mixer is as follows: oxygen is injected into the mixing chamber through the central nozzle, natural gas is input into the mixing chamber through the annular flow channel, and after the two are mixed in the mixing chamber, they are pressurized through the diffusion section and transported to the burner plate.

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