Corrosion prevention and control device and method for cracking gas compressor sections of ethylene plant

Abstract

The present invention discloses a corrosion prevention and control device and method for use between cracking gas compressor sections of an ethylene device. The corrosion prevention and control device is specifically a corrosion inhibitor injection device, which includes a corrosion inhibitor storage tank, a pressure pump, a mass flow meter, an electromagnetic control valve, and a corrosion inhibitor injection pipe that are sequentially connected through pipelines, and the corrosion inhibitor injection pipe is installed on the compressor outlet pipeline between the cracking gas compressor of the ethylene device and the compressor outlet heat exchanger. The present invention can alleviate or inhibit the corrosion of steel equipment / pipelines between the cracking gas compressor sections of an ethylene device under multiple media. The core of the present invention is the corrosion inhibitor injection pipe and its nozzle structure and injection method, which enable the corrosion inhibitor to quickly and efficiently perform corrosion inhibition, while avoiding the problem of uneven dispersion of the corrosion inhibitor under high-flux cracking gas and accumulation and erosion of the wall surface that affects safe production. It has the advantages of high efficiency, stability, safety and environmental protection, and greatly improves the long-term safe operation period of the device.

Description

Technical Field

[0001] The invention relates to a corrosion prevention and control device and a method for a cracking gas compressor section of an ethylene device, belonging to the technical field of petrochemical corrosion protection. Background Art

[0002] In the steam cracking process for ethylene production, naphtha, hydrotreated diesel and other raw materials are cracked at high temperatures to produce H2 and mixed hydrocarbon gas products mainly composed of C1 to C4, accompanied by the production of some acidic gases, mainly CO2, H2S, HCl, organic acids (such as CH3COOH), and some organic sulfur (COS). These acidic gases enter the olefin separation process together with the cracking gas. The equipment and pipelines between the cracking gas compressor sections before the alkali washing tower often corrode. The corrosion forms often exist in the coupling of multiple media and multiple mechanisms such as CO2-H2S-HCl-(R-COOH)-COS-H2O, making corrosion prevention and control difficult.

[0003] In order to reduce the corrosiveness of the acidic gas in the cracking gas, the process of injecting neutralizing corrosion inhibitors is generally added between the sections of the cracking gas compressor. The injection pipe is mostly inserted vertically into the center of the main pipe in order to facilitate the uniform dispersion of the corrosion inhibitor in the cracking gas. The end of the injection pipe is set to a horizontal structure with the main pipe, and an atomizing nozzle is installed. In recent years, through investigations on many domestic ethylene plants, it was found that although the vertical injection method has a good corrosion inhibition effect, the pipeline located in a range downstream of the corrosion inhibitor injection port still has serious corrosion. This is because the vertical insertion method will cause the tail of the injection pipe to deviate from the center of the main pipe under the action of the cracking gas field force, and the accuracy of the injection position cannot be guaranteed, which is not conducive to the formation of a uniform and effective protective film on the pipeline surface. In addition, the larger the contact area between the corrosion inhibitor and the cracking gas, the smaller the ratio of the corrosion inhibitor injection flow rate to the cracking gas flow rate, which is more conducive to improving the uniformity of the dispersion of the corrosion inhibitor in the cracking gas. However, the existing atomizing nozzles do not fully consider this characteristic when using the injection pipe, and mostly use atomizing nozzles with the same diameter as the injection pipe.

[0004] Therefore, the present invention proposes a corrosion prevention and control method for the cracking gas compressor sections of an ethylene plant, which comprehensively considers aspects such as corrosion inhibitor screening, dosage, injection method, and injection form to achieve accurate and stable injection of corrosion inhibitors. The corrosion inhibitor can be quickly and evenly dispersed to the surface of the downstream pipeline of the injection pipe inlet to form a uniform and effective protective film, thereby improving the corrosion inhibition effect. Summary of the invention

[0005] The purpose of the present invention is to provide a corrosion prevention and control device and method for use between sections of cracking gas compressors of an ethylene device, which can alleviate or inhibit the corrosion of steel equipment / pipelines between sections of cracking gas compressors of an ethylene device under multiple media such as CO2-H2S-HCl-(R-COOH)-COS-H2O. The core of the device is a corrosion inhibitor injection pipe and its nozzle structure and injection method, which enable the corrosion inhibitor to quickly and efficiently perform corrosion inhibition, while avoiding the problem of uneven dispersion of the corrosion inhibitor under high-flux cracking gas and accumulation and erosion of the wall surface affecting safe production. The device has the advantages of high efficiency, stability, safety and environmental protection, and greatly improves the long-term safe operation period of the device.

[0006] In order to achieve the above object, the present invention adopts the following technical means:

[0007] The present invention provides a corrosion prevention and control device for use between cracking gas compressor sections of an ethylene device, specifically a corrosion inhibitor injection device, the corrosion inhibitor injection device comprising a corrosion inhibitor storage tank, a pressure pump, a mass flow meter, an electromagnetic control valve and a corrosion inhibitor injection pipe which are sequentially connected through pipelines, and the corrosion inhibitor injection pipe is installed on a compressor outlet pipeline between the cracking gas compressor of the ethylene device and a compressor outlet heat exchanger.

[0008] Preferably, an emergency shut-off valve is provided on the pipeline from the corrosion inhibitor storage tank to the booster pump, which cooperates with the mass flow meter to accurately control the flow to ensure safety.

[0009] Preferably, the corrosion inhibitor injection pipe is installed in a straight pipe section with stable flow on the compressor outlet pipeline, avoiding a high-speed spiral flow area, and at a distance of not less than 3 times the pipe diameter from upstream and downstream elbows.

[0010] Preferably, the corrosion inhibitor injection pipe is installed in a downstream oblique insertion manner according to the pipeline space layout of the compressor outlet pipeline, the angle between it and the pipe wall of the compressor outlet pipeline is between 10° and 80°, and the insertion length is between 1 / 5 and 1 / 2 of the pipe diameter.

[0011] Preferably, the nozzle of the corrosion inhibitor injection tube is elliptical, rectangular or hole-shaped, and its nozzle cross-sectional area is adjusted according to the cracking gas flow rate and the viscosity of the corrosion inhibitor. The contact area between the corrosion inhibitor and the cracking gas is as large as possible, and the ratio of the corrosion inhibitor injection flow rate to the cracking gas flow rate is as small as possible; more preferably, for corrosion inhibitors with low viscosity, the nozzle of the corrosion inhibitor injection tube adopts an elliptical or rectangular shape, and for corrosion inhibitors with high viscosity, the nozzle of the corrosion inhibitor injection tube adopts a hole-shaped type with an expansion section, and its opening rate needs to be controlled between 30 and 80%, and the diameter after expansion is less than 1.5 times the original diameter.

[0012] The present invention also provides a method for preventing and controlling corrosion between sections of cracked gas compressors of an ethylene plant using the above device, comprising the following steps:

[0013] (1) Screening corrosion inhibitors suitable for multi-media and multi-mechanism corrosion environments such as CO2-H2S-HCl-(R-COOH)-COS-H2O and steel used in equipment / pipelines, as well as appropriate injection amounts;

[0014] (2) Install the corrosion inhibitor injection pipe on the compressor outlet pipeline between the cracked gas compressor and the compressor outlet heat exchanger of the ethylene unit. The appropriate installation position, angle and nozzle type should be selected according to the site conditions;

[0015] (3) The prepared corrosion inhibitor is sent to a corrosion inhibitor storage tank for storage. The corrosion inhibitor flow is pressurized by a pressure pump. The mass flow rate of the corrosion inhibitor injection is accurately controlled through a feedback regulation loop between a mass flow meter and an electromagnetic control valve. The corrosion inhibitor is injected into the compressor outlet pipeline through a corrosion inhibitor injection pipe. The corrosion inhibitor is quickly torn into pieces by the high-flux cracking gas and evenly dispersed into the cracking gas, thereby playing a dual protective role of neutralizing the acid gas and forming a protective film on the metal surface, thereby achieving corrosion prevention and control.

[0016] Preferably, the corrosion inhibitor is selected from 2-aminoethanol, 3-methoxypropylamine, imidazoline, imidazoline amide, Mannich base quaternary ammonium salt, sodium molybdate or a combination thereof; the internal polar groups (such as amino, methoxy, hydroxyl, molybdate) of the corrosion inhibitor coordinate with the empty electron orbits on the metal surface to form an adsorption film, or with the Fe 2+ The reaction generates a precipitation film, which simultaneously alleviates / inhibits the corrosion of the CO2-H2S-HCl-(R-COOH)-COS-H2O corrosive medium, is environmentally friendly, and does not affect the quality and yield of the target product.

[0017] Preferably, the corrosion inhibitor is a combination of 2-aminoethanol and 3-methoxypropylamine, which can achieve a high corrosion inhibition efficiency with a small injection amount, and the corrosion inhibition effect is not less than 90%.

[0018] Preferably, the injection amount of the corrosion inhibitor needs to be adjusted according to the steel used for the equipment / pipeline, the concentration of each corrosive medium and the iron ion content in the subsequent equipment / pipeline after on-site sampling and analysis.

[0019] Preferably, an emergency shut-off valve is provided on the pipeline from the corrosion inhibitor storage tank to the booster pump, which cooperates with the mass flow meter to accurately control the flow to ensure safety.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] (1) The corrosion prevention and control device and method of the present invention have strong adaptability, and can alleviate or inhibit the corrosion of steel equipment / pipelines between sections of the cracking gas compressor of the ethylene plant under multiple media such as CO2-H2S-HCl-(R-COOH)-COS-H2O, and the injection of the corrosion inhibitor is accurate and stable, which can improve the protection effect of the downstream pipeline of the injection pipe inlet;

[0022] (2) The corrosion inhibitor injection method of the present invention can make the corrosion inhibitor more fully and evenly dispersed in the cracking gas, which can improve the corrosion inhibition effect and avoid the problem of uneven dispersion of the corrosion inhibitor and accumulation of erosion wall surface under high-flux cracking gas, affecting safe production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a process diagram of corrosion prevention and control between cracking gas compressor sections of an ethylene plant according to the present invention;

[0024] Explanation of symbols: 1. Cracking gas compressor of ethylene unit (ethylene cracking gas compressor sections I to IV); 2. Compressor outlet pipeline; 3. Corrosion inhibitor injection pipe; 4. Compressor outlet heat exchanger; 5. Alkali washing tower; 6. Corrosion inhibitor storage tank; 7. Emergency shut-off valve; 8. Pressure pump; 9. Mass flow meter; 10. Solenoid control valve.

[0025] Figure 2 It is a layout diagram of the corrosion inhibitor injection pipe under the pipeline space layout of different compressor outlet pipelines of the present invention;

[0026] Explanation of symbols: 1. Corrosion inhibitor injection pipe; 2. Corrosion inhibitor injection pipe nozzle; 3. Compressor outlet pipeline wall.

[0027] Figure 3 It is a design drawing of a nozzle of a corrosion inhibitor injection pipe of the present invention;

[0028] Explanation of symbols: 1. Corrosion inhibitor injection pipe cross section; 2. Corrosion inhibitor injection pipe nozzle cross section; 3. Corrosion inhibitor injection pipe nozzle expansion section.

[0029] Figure 4 It is the distribution condition of corrosion inhibitor under inappropriate corrosion inhibitor injection method.

[0030] Figure 5 This is the corrosion inhibitor distribution condition under the corrosion inhibitor injection method of the present invention. DETAILED DESCRIPTION

[0031] The present invention will be further described below in conjunction with specific embodiments, and the advantages and features of the present invention will become clearer as the description proceeds. However, these embodiments are exemplary only and do not constitute any limitation to the scope of the present invention. It should be understood by those skilled in the art that the details and forms of the technical solution of the present invention may be modified or replaced without departing from the spirit and scope of the present invention, but these modifications and replacements all fall within the scope of protection of the present invention.

[0032] Example 1

[0033] See also Figure 1 As shown, this embodiment provides a corrosion prevention and control device for use between cracking gas compressor sections of an ethylene device, specifically a corrosion inhibitor injection device, the corrosion inhibitor injection device includes a corrosion inhibitor storage tank 6, a pressure pump 8, a mass flow meter 9, an electromagnetic control valve 10 and a corrosion inhibitor injection pipe 3 connected in sequence through pipelines, and the corrosion inhibitor injection pipe 3 is installed on the compressor outlet pipeline 2 between the cracking gas compressor 1 and the compressor outlet heat exchanger 4 of the ethylene device.

[0034] Among them, an emergency shut-off valve 7 is provided on the pipeline between the corrosion inhibitor storage tank 6 and the pressure pump 8, which cooperates with the mass flow meter 9 to accurately control the flow to ensure safety.

[0035] The installation position of the corrosion inhibitor injection pipe 3 is located on the straight pipe section with stable flow on the compressor outlet pipeline 2, avoiding the high-speed spiral flow area, and the distance from the upstream and downstream elbows is not less than 3 times the pipe diameter.

[0036] The corrosion inhibitor injection pipe 3 is installed in a downstream oblique insertion manner according to the pipeline space layout of the compressor outlet pipeline 2 (such as Figure 2 As shown), the included angle α between it and the pipe wall of the compressor outlet pipeline 2 is between 10° and 80°, and the insertion length h is between 1 / 5 and 1 / 2 of the pipe diameter.

[0037] The nozzle of the corrosion inhibitor injection pipe 3 is elliptical, rectangular or hole-shaped (such as Figure 3 As shown), the cross-sectional area of ​​the nozzle is adjusted according to the cracking gas flow rate and the viscosity of the corrosion inhibitor, the contact area between the corrosion inhibitor and the cracking gas is as large as possible, and the ratio of the corrosion inhibitor injection flow rate to the cracking gas flow rate is as small as possible; for corrosion inhibitors with low viscosity, the nozzle of the corrosion inhibitor injection pipe adopts an elliptical or rectangular type, and for corrosion inhibitors with high viscosity, the nozzle of the corrosion inhibitor injection pipe adopts a hole-shaped type with an expansion section, and its opening rate needs to be controlled between 30 and 80%, and the diameter after expansion is less than 1.5 times the original diameter.

[0038] Example 2

[0039] See also Figure 1As shown, this embodiment provides a corrosion prevention and control method for the cracking gas compressor section of an ethylene device using the device of Example 1, comprising the following steps:

[0040] (1) Screening corrosion inhibitors suitable for multi-media and multi-mechanism corrosion environments such as CO2-H2S-HCl-(R-COOH)-COS-H2O and steel used in equipment / pipelines, as well as appropriate injection amounts;

[0041] (2) installing the corrosion inhibitor injection pipe 3 on the compressor outlet pipeline 2 between the cracked gas compressor 1 and the compressor outlet heat exchanger 4 of the ethylene device, and the appropriate installation position, angle and nozzle type should be selected according to the site conditions, as described in Example 1;

[0042] (3) The prepared corrosion inhibitor is sent to the corrosion inhibitor storage tank 6 for storage, and the corrosion inhibitor flow is pressurized by the pressure pump 8. The mass flow rate of the corrosion inhibitor injection is accurately controlled through the feedback regulation loop between the mass flow meter 9 and the electromagnetic control valve 10. The corrosion inhibitor is injected into the compressor outlet pipeline 2 through the corrosion inhibitor injection pipe 3, and is quickly torn into pieces by the high-flux cracking gas and evenly dispersed into the cracking gas, playing a dual protective role of neutralizing the acid gas and forming a protective film on the metal surface, thereby achieving corrosion prevention and control.

[0043] The corrosion inhibitor is selected from 2-aminoethanol, 3-methoxypropylamine, imidazoline, imidazoline amide, Mannich base quaternary ammonium salt, sodium molybdate or a combination thereof; the internal polar groups (such as amino, methoxy, hydroxyl, molybdate) of the corrosion inhibitor coordinate with the empty electron orbits on the metal surface to form an adsorption film, or with the Fe 2+ The reaction generates a precipitation film, which simultaneously alleviates / inhibits the corrosion of the CO2-H2S-HCl-(R-COOH)-COS-H2O corrosive medium, is environmentally friendly, and does not affect the quality and yield of the target product.

[0044] Furthermore, the corrosion inhibitor is a combination of 2-aminoethanol and 3-methoxypropylamine, which can achieve a high corrosion inhibition efficiency with a very small injection amount, and the corrosion inhibition effect is not less than 90%.

[0045] The injection amount of the corrosion inhibitor needs to be adjusted according to the steel used for the equipment / pipeline, the concentration of each corrosive medium and the iron ion content in the subsequent equipment / pipeline after on-site sampling and analysis.

[0046] Among them, an emergency shut-off valve 7 is provided on the pipeline between the corrosion inhibitor storage tank 6 and the pressure pump 8, which cooperates with the mass flow meter 9 to accurately control the flow to ensure safety.

[0047] Example 3

[0048] See also Figure 1As shown, this embodiment adopts the device of Example 1 and the method of Example 2, and takes the corrosion prevention and control of equipment and pipelines from section I to VI 1 of the cracking gas compressor to the alkali washing tower 5 of a 1.2 million tons / year naphtha cracking and ethylene production unit as an example. The main corrosive medium of the cracking gas is CO2-H2S-HCl-CH3COOH-COS-H2O, etc. The tube bundle materials of the compressor outlet pipeline 2 and the compressor outlet heat exchanger 4 are API-5L-B and 10# steel, respectively, and the corrosion mechanism is mainly dew point corrosion and acidic water corrosion.

[0049] The selected corrosion inhibitor is a compound of 2-aminoethanol and 3-methoxypropylamine in a mass ratio of 1:1, with a pH of 9. The initial injection amount is 500 ppm relative to the amount of the corrosion solution. A protective film is formed quickly at a higher rate, and the subsequent injection amount is 50 ppm relative to the amount of the corrosion solution.

[0050] The installation position of the corrosion inhibitor injection pipe is selected from the straight pipe section with stable flow on each section of the compressor outlet pipeline 2, avoiding the high-speed spiral flow area, and the distance from the upstream and downstream elbows is not less than 3 times the pipe diameter; the corrosion inhibitor is accurately controlled by the feedback regulation loop between the mass flow meter 9 and the electromagnetic control valve 10 to achieve stable injection; the corrosion inhibitor injection pipe 3 is installed in a downstream oblique insertion manner, and the angle between it and the pipe wall of the compressor outlet pipeline 2 is 50°, the insertion length is 1 / 3 of the pipe diameter, and the nozzle adopts a hole-shaped nozzle with an opening rate of 40%. The diameter after expansion is 1.2 times the original diameter, so as to maximize the contact area between the corrosion inhibitor and the cracking gas and minimize the ratio of the corrosion inhibitor injection flow rate to the cracking gas flow rate.

[0051] Compared with other corrosion inhibitor injection methods, the injection method of the present invention greatly alleviates the corrosion of equipment and pipelines between sections I to VI of the cracking gas compressor and the alkali washing tower, reduces the average corrosion rate by more than 30%, and reduces the corrosion of the compressor outlet pipe section and the heat exchanger tube bundle by more than 90%.

[0052] Compared with injection into the wall of the unstable section of the compressor outlet pipeline or the center of the pipe, the injection method of the present invention can reduce the amount of corrosion inhibitor used by more than 10% on the one hand, and on the other hand, the corrosion inhibition effect is stable and efficient, and the problem of uneven dispersion of corrosion inhibitor and accumulation and erosion of the wall under high-flux cracking gas, which affects safe production, can be avoided. Figure 4 The corrosion inhibitor distribution status of the outlet pipe of the actual ethylene compressor section III under the improper corrosion inhibitor injection method (the color indicates the concentration of the corrosion inhibitor phase) is shown. The corrosion inhibitor is concentrated near the side wall of the nozzle, which actually causes the pipe wall to be eroded, thinned and cracked. Figure 5 Demonstrates the same pipeline using the present invention Figure 2 (a) and (c) The distribution of the corrosion inhibitor after the corrosion inhibitor injection method. The corrosion inhibitor is evenly dispersed inside the pipe, and there is no corrosion inhibitor aggregation and erosion corrosion on the pipe wall. The erosion and thinning of the pipe wall on site is significantly alleviated.

Claims

1. A corrosion prevention and control device for cracking gas compressor sections of an ethylene plant, specifically a corrosion inhibitor injection device, characterized in that: The corrosion inhibitor injection device comprises a corrosion inhibitor storage tank, a pressure pump, a mass flow meter, an electromagnetic control valve and a corrosion inhibitor injection pipe which are sequentially connected through pipelines, and the corrosion inhibitor injection pipe is installed on the compressor outlet pipeline between the cracked gas compressor of the ethylene device and the compressor outlet heat exchanger; Among them, an emergency shut-off valve is provided on the pipeline between the corrosion inhibitor storage tank and the pressure pump, which cooperates with the mass flow meter to accurately control the flow to ensure safety; The installation position of the corrosion inhibitor injection pipe is located on the straight pipe section with stable flow on the compressor outlet pipeline, avoiding the high-speed spiral flow area, and the distance from the upstream and downstream elbows is not less than 3 times the pipe diameter; Among them, the corrosion inhibitor injection pipe is installed in a downstream oblique insertion manner according to the pipeline space layout of the compressor outlet pipeline. The angle between it and the pipe wall of the compressor outlet pipeline is between 10° and 80°, and the insertion length is between 1 / 5 and 1 / 2 of the pipe diameter.

2. The corrosion prevention and control device according to claim 1, characterized in that: The nozzle of the corrosion inhibitor injection pipe is elliptical, rectangular or hole-shaped, and its nozzle cross-sectional area is adjusted according to the cracking gas flow rate and the viscosity of the corrosion inhibitor. For corrosion inhibitors with low viscosity, the nozzle of the corrosion inhibitor injection pipe adopts an elliptical or rectangular shape. For corrosion inhibitors with high viscosity, the nozzle of the corrosion inhibitor injection pipe adopts a hole-shaped type with an expansion section, and its opening rate needs to be controlled between 30% and 80%, and the diameter after expansion is less than 1.5 times the original diameter.

3. A method for corrosion prevention and control of cracking gas compressor sections of an ethylene plant using the corrosion prevention and control device according to any one of claims 1 to 2, characterized in that: The following steps are involved: (1) Screening corrosion inhibitors suitable for the multi-media and multi-mechanism corrosion environment of CO2-H2S-HCl-(R-COOH)-COS-H2O and steel used in equipment / pipelines, as well as the appropriate injection amount; (2) Install the corrosion inhibitor injection pipe on the compressor outlet pipeline between the cracking gas compressor of the ethylene unit and the compressor outlet heat exchanger. The appropriate installation position, angle and nozzle type should be selected according to the site conditions; (3) The prepared corrosion inhibitor is sent to the corrosion inhibitor storage tank for storage. The corrosion inhibitor flow is pressurized by a pressure pump. The mass flow rate of the corrosion inhibitor injection is accurately controlled through a feedback regulation loop between a mass flow meter and an electromagnetic control valve. The corrosion inhibitor is injected into the compressor outlet pipeline through a corrosion inhibitor injection pipe. The corrosion inhibitor is quickly torn into pieces by the high-flux cracking gas and evenly dispersed into the cracking gas, thereby playing a dual protective role of neutralizing the acid gas and forming a protective film on the metal surface, thereby achieving corrosion prevention and control.

4. The corrosion prevention and control method according to claim 3, characterized in that: The corrosion inhibitor is selected from 2-aminoethanol, 3-methoxypropylamine, imidazoline, imidazoline amide, Mannich base quaternary ammonium salt, sodium molybdate or a combination thereof.

5. The corrosion prevention and control method according to claim 3, characterized in that: The corrosion inhibitor is a combination of 2-aminoethanol and 3-methoxypropylamine.

6. The corrosion prevention and control method according to claim 3, characterized in that: The injection amount of the corrosion inhibitor needs to be adjusted according to the steel used for the equipment / pipeline, the concentration of each corrosive medium and the iron ion content in the subsequent equipment / pipeline after on-site sampling and analysis.

7. The corrosion prevention and control method according to claim 3, characterized in that: An emergency shut-off valve is provided on the pipeline from the corrosion inhibitor storage tank to the booster pump, which cooperates with the mass flow meter to accurately control the flow to ensure safety.

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