Quenching boiler for retarding coking and carburization and its preparation method and application

Abstract

This invention relates to the field of petroleum hydrocarbon pyrolysis, and discloses a quench boiler that mitigates coking and carburization, its preparation method, and its application. The method includes: (1) contacting a reducing gas with the tubes of the quench boiler for a first heat treatment reaction to obtain a pretreated quench boiler; (2) contacting an oxidizing gas with the pretreated quench boiler for a second heat treatment reaction to obtain a quench boiler with a double-layer oxide film on the inner surface of the tubes; (3) contacting the reducing gas with the quench boiler with the double-layer oxide film on the inner surface of the tubes for a third heat treatment reaction to obtain a quench boiler with a double-layer anti-coking oxide film on the inner surface of the tubes; wherein the oxygen content in the reducing gas is 0 ppm; and the oxygen volume fraction in the oxidizing gas is 6-22%. The preparation process of this quench boiler is simple, and it can significantly reduce coking and carburization in the quench boiler, extending its operating cycle.

Description

Technical Field

[0001] This invention relates to the field of petroleum hydrocarbon thermal cracking, specifically to a quench boiler for slowing down coking and carburization, its preparation method, and its application. Background Technology

[0002] Ethylene is a fundamental raw material for the petrochemical industry. Ethylene production volume, scale, and technology indicate a country's level of petrochemical development. Currently, the main method for ethylene production is tubular furnace petroleum hydrocarbon steam cracking technology. Statistics show that approximately 99% of the world's ethylene and over 50% of its propylene are produced using this method. During the tubular furnace petroleum hydrocarbon steam cracking process for ethylene and propylene, the high-temperature cracked gas, while recovering heat through the quench boiler, will coke on the inner wall of the quench boiler's tube side. Prolonged operation under coking conditions may cause carburization on the inner wall of the quench boiler's tube side. Coking and carburization reduce the heat transfer efficiency of the quench boiler and may affect its online time. Insufficiently short online time for the quench boiler and frequent hydraulic or mechanical decoking increase labor costs, consume large amounts of energy, reduce effective production time, and shorten equipment lifespan.

[0003] The tubes of the quench boiler are mainly made of 15Mo3 material, which is primarily composed of metallic elements such as Fe and Cr. At high temperatures, petroleum hydrocarbons interact with the iron in the quench boiler tube metal, resulting in dehydrogenation and carbon deposition. In other words, iron has a significant catalytic effect on coking on the inner surface of the quench boiler tubes. As the temperature decreases (below 500℃), low-temperature condensation coking, based on catalytic coking, begins to dominate.

[0004] Currently, two main methods are used to mitigate coking and carburizing in quench boilers: adding coking inhibitors to the pyrolysis feedstock and applying an anti-coking coating to the inner surface of the tubes in the quench boiler tube side. Adding coking inhibitors to passivate the inner surface of the tubes or to gasify the coke not only pollutes downstream products but also requires specialized injection equipment, and this method is less effective for low-temperature coking. The method of applying an anti-coking coating to the inner surface of the tubes aims to form a protective coating with excellent mechanical properties and thermal stability, isolating petroleum hydrocarbons from the metal elements on the inner surface of the tubes, thereby reducing the catalytic coking activity of the metal elements on the inner surface of the tubes and slowing down the entire coking process in the quench boiler. There are two different preparation methods for furnace tubes with anti-scorching coatings. One method involves forming a protective layer of metal or non-metal oxides such as chromium oxide, silicon oxide, aluminum oxide, and titanium oxide on the inner surface of the furnace tube through means such as plasma spraying, thermal sputtering, high-temperature sintering, and chemical vapor deposition. The disadvantage of this method is that the protective layer is not firmly bonded to the furnace tube substrate and is prone to peeling off. The other method involves treating the furnace tube in a specific atmosphere at a certain temperature to form an oxide protective layer on the inner surface of the furnace tube in situ. The advantage of this method is that the protective layer has a strong bond with the furnace tube substrate and is not prone to peeling off.

[0005] NOVA Chemicals of Canada proposed a technical solution to obtain a chromium-manganese spinel oxide film on the inner surface of pyrolysis furnace tubes under low oxygen partial pressure using a mixture of hydrogen and water vapor as the treatment atmosphere. They have applied for a number of patents based on this solution, including US5630887A, US6436202B1, US6824883B1, US7156979B2, and US7488392B2. However, this technical solution cannot effectively solve the current problems of coking and carburization in quench boilers. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of coking and carburization in existing quench boilers, and to provide a quench boiler that reduces coking and carburization, as well as its preparation method and application. The preparation process of this quench boiler is simple, and it can significantly reduce coking and carburization in quench boilers and extend the operating cycle.

[0007] To achieve the above objectives, a first aspect of the present invention provides a method for preparing a quench boiler that slows down coking and carburization, characterized in that the method comprises:

[0008] (1) The reducing gas is brought into contact with the tube side of the quench boiler to carry out the first heat treatment reaction, and a pretreated quench boiler is obtained.

[0009] (2) The oxidizing gas is brought into contact with the pretreated quench boiler to carry out a second heat treatment reaction, so as to obtain a quench boiler with a double oxide film on the inner surface of the tube side furnace tubes.

[0010] (3) The reducing gas is brought into contact with the quench boiler with a double-layer oxide film on the inner surface of the tubes of the tube-pass furnace to carry out a third heat treatment reaction, so as to obtain a quench boiler with a double-layer anti-coking oxide film on the inner surface of the tubes of the tube-pass furnace.

[0011] The reducing gas contains 0 ppm of oxygen; the oxidizing gas contains 6-22% oxygen by volume.

[0012] A second aspect of the present invention provides a quench boiler that slows down coking and carburization by the above method.

[0013] The third aspect of the present invention provides the application of the above-mentioned rapid cooling boiler for mitigating coking and carburization in petroleum hydrocarbon cracking.

[0014] Through the above technical solutions, the rapid cooling boiler for slowing down coking and carburization, its preparation method, and its application provided by the present invention achieve the following beneficial effects:

[0015] The preparation process of the quench boiler that mitigates coking and carburization provided by this invention is simple and easy to implement. The quench boiler prepared by the method of this invention can inhibit catalytic coking, condensation coking, and the entire coking process in the tube side of the quench boiler, and effectively improves the anti-carburization performance of the tube side tubes, thereby extending the online time and service life of the quench boiler. Detailed Implementation

[0016] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] The first aspect of this invention provides a method for preparing a quench boiler that slows down coking and carburization, characterized in that the method comprises:

[0018] (1) The reducing gas is brought into contact with the tube side of the quench boiler to carry out the first heat treatment reaction, and a pretreated quench boiler is obtained.

[0019] (2) The oxidizing gas is brought into contact with the pretreated quench boiler to carry out a second heat treatment reaction, so as to obtain a quench boiler with a double oxide film on the inner surface of the tube side furnace tubes.

[0020] (3) The reducing gas is brought into contact with the quench boiler with a double-layer oxide film on the inner surface of the tubes of the tube-pass furnace to carry out a third heat treatment reaction, so as to obtain a quench boiler with a double-layer anti-coking oxide film on the inner surface of the tubes of the tube-pass furnace.

[0021] The reducing gas contains 0 ppm of oxygen; the oxidizing gas contains 6-22% oxygen by volume.

[0022] This invention solves the coking and carburizing problems of quench boilers by forming an oxide film on the inner surface of the tube side of the quench boiler. Specifically, it uses a stepwise heat treatment method with reducing gas, oxidizing gas, and reducing gas to generate a double-layer anti-coking oxide film on the inner surface of the tube side of the quench boiler in situ. The obtained double-layer anti-coking oxide film has strong adhesion to the substrate of the tube side of the quench boiler and is suitable for long-term use.

[0023] During the manufacturing process of quenched boiler tubes, residues inevitably remain on the inner surface of the tubes. These residues not only affect the performance of the tubes during service but also hinder the formation of an anti-coking oxide film on the inner surface during subsequent processing. The high-temperature pretreatment of the quenched boiler tubes using the reducing gas of this invention thoroughly removes these residues and improves the dispersion of the metal on the inner surface, facilitating the formation of a double-layer oxide film during subsequent oxidizing gas heat treatment. Further cooling the alloy tubes with the double-layer oxide film to room temperature using the reducing gas further promotes the formation of a dense and stable double-layer anti-coking oxide film, consisting of a chromium oxide lower layer and a chromium-manganese oxide upper layer.

[0024] Furthermore, by controlling the oxygen content in the reducing gas to 0 ppm and the oxygen volume fraction in the oxidizing gas to 6-22%, a dense and stable anti-coking oxide film can be formed on the inner surface of the furnace tube.

[0025] In this invention, the oxygen content of the reducing gas being 0 ppm means that the reducing gas does not contain oxygen or is a gas that can produce oxygen.

[0026] In this invention, the oxygen content in the reducing gas and the oxidizing gas is measured using a trace oxygen analyzer and a constant oxygen analyzer, respectively.

[0027] Furthermore, the volume fraction of oxygen in the oxidizing gas is 13-22%.

[0028] According to the present invention, the oxidizing gas includes air and at least one gas selected from nitrogen, helium and argon.

[0029] According to the present invention, the reducing gas includes carbon monoxide, hydrogen, and at least one gas selected from nitrogen, helium, and argon.

[0030] According to the present invention, based on the total volume of the reducing gas, the content of carbon monoxide and hydrogen is less than or equal to 80 vol%, preferably 60-80 vol%.

[0031] In this invention, the volume ratio of carbon monoxide to hydrogen is 1:0.2-5.

[0032] In this invention, by controlling the content of carbon monoxide and hydrogen in the reducing gas to meet the above-mentioned range, it is possible to completely remove the residues on the inner surface of the tubes in the quench boiler tube side, improve the dispersion performance of the metal on the inner surface of the tubes, and facilitate the subsequent reprocessing of oxidizing and reducing gases to form a dense, stable, and anti-coking oxide film.

[0033] According to the present invention, the conditions for the first heat treatment reaction include: heating from room temperature to 800-1000°C at a heating rate of less than or equal to 150°C / h, and holding at that temperature for more than 10 hours.

[0034] In this invention, when the conditions of the first heat treatment are controlled to meet the above-mentioned range, it is possible to completely remove the residues on the inner surface of the furnace tube, improve the dispersion performance of the metal on the inner surface of the furnace tube, and facilitate the formation of a dense and stable oxide film by subsequent treatment with oxidizing and reducing gases.

[0035] Furthermore, the conditions for the first heat treatment include: heating from room temperature to 850-950°C at a heating rate of less than or equal to 100°C / h, and treating for 10-40 hours.

[0036] In this invention, in the first heat treatment reaction, the flow rate of the reducing gas is 100-800 mL / min, preferably 200-600 mL / min.

[0037] In this invention, by controlling the flow rate of the reducing gas to meet the above-mentioned range, it is possible to thoroughly remove the residues on the inner surface of the tubes in the quenched boiler tube side, improve the dispersion performance of the metal on the inner surface of the tubes, and facilitate the subsequent reprocessing of the oxidizing and reducing gases to form a dense and stable oxide film.

[0038] According to the present invention, the conditions for the second heat treatment reaction include: a treatment temperature of 800-1000°C and a treatment time of 10 hours or more.

[0039] In this invention, when the conditions for controlling the second heat treatment reaction meet the above-mentioned range, it is possible to form a double oxide film on the inner surface of the furnace tube, with a chromium oxide lower layer and a chromium-manganese oxide upper layer.

[0040] Furthermore, the conditions for the second heat treatment reaction include: a reaction temperature of 850-950℃ and a reaction time of 10-100h, preferably 10-50h.

[0041] In this invention, in the second heat treatment reaction, the flow rate of the oxidizing gas is 100-800 mL / min, preferably 200-600 mL / min.

[0042] In this invention, by controlling the flow rate of the oxidizing gas to meet the above-mentioned range, the oxidizing gas can be made to fully contact the pretreated alloy furnace tube, thereby forming a double-layer anti-coking oxide film on the inner wall of the alloy furnace tube.

[0043] According to the present invention, the conditions for the third heat treatment reaction include cooling from 800-1000°C to room temperature at a cooling rate of less than or equal to 100°C / h.

[0044] In this invention, controlling the third heat treatment reaction to meet the above-mentioned range can make the double-layer anti-coking oxide film formed on the inner surface of the final alloy furnace tube more dense and stable.

[0045] Furthermore, the conditions for the third heat treatment reaction include cooling from 850-950°C to room temperature at a cooling rate of less than or equal to 50°C / h.

[0046] In this invention, in the third cooling heat treatment reaction, the flow rate of the reducing gas is 20-200 mL / min, preferably 50-100 mL / min.

[0047] In this invention, by controlling the flow rate of the reducing gas to meet the above-mentioned range, it is possible to obtain the effect of forming a dense and stable double-layer anti-coking oxide film through reducing gas treatment.

[0048] According to the present invention, the double-layer anti-coking oxide film comprises a chromium oxide layer in the lower layer and a chromium-manganese oxide film in the upper layer.

[0049] In this invention, the lower layer refers to the portion close to the inner wall of the alloy furnace tube, while the surface layer refers to the portion away from the inner wall of the alloy furnace tube.

[0050] According to the present invention, the chromium-manganese oxide film comprises chromium-manganese oxide and metal elements.

[0051] According to the present invention, the composition of the chromium manganese oxide is Mn x Cr 3-x O4, x value is 0.5-2.

[0052] In this invention, by sequentially heat-treating the tubes of the quench boiler with reducing gas, oxidizing gas, and reducing gas, it is possible to ensure that a dense and stable double-layer anti-coking oxide film is formed on the inner surface of the tubes through in-situ growth. The obtained double-layer anti-coking oxide film is firmly bonded to the tube substrate, which can significantly inhibit or reduce catalytic coking, reduce the degree of carburization in the quench boiler, and extend the service life of the quench boiler.

[0053] Furthermore, in this invention, the surface oxide film on the inner surface of the tube side of the quench boiler obtained by the above method has a low iron content, which can inhibit catalytic coking in the hydrocarbon cracking process, extend the operating cycle of the quench boiler, and meet the requirements for long-term use of the quench boiler.

[0054] Specifically, the iron content is less than or equal to 40 wt% relative to the total weight of the chromium-manganese oxide film.

[0055] In this invention, the content of metal elements on the inner surface of the tubes of the quenched boiler before treatment and the content of metal elements in the oxide film on the inner surface of the tubes of the quenched boiler after treatment are determined by X-ray energy dispersive spectroscopy (EDS).

[0056] According to the present invention, the alloy composition of the tube side of the quench boiler includes: Cr: 1.0-20wt%, Mo: 0.2-0.6wt%, Mn: 0.3-0.8wt%, Si: 0.3-2wt%, C: 0.1-0.2wt%, O: <5wt%, Fe: 76.4-98wt%, and trace elements: 0-1wt%.

[0057] According to the present invention, the trace element is at least one selected from Al, Nb, Ti, W and rare earth elements.

[0058] In this invention, the first heat treatment reaction, the second heat treatment reaction, and the third heat treatment reaction can be carried out in conventional equipment capable of maintaining a certain atmosphere, for example, the reaction can be carried out in at least one of a tube furnace, a pit furnace, and an atmosphere box furnace.

[0059] A second aspect of the present invention provides a quench boiler that slows down coking and carburization by the above method.

[0060] In this invention, the inner surface of the tubes in the quench boiler contains a double-layer anti-coking oxide film. The double-layer anti-coking oxide film comprises a chromium oxide layer at the bottom and a chromium-manganese oxide layer at the top.

[0061] In this invention, the double-layer anti-coking oxide film is formed by in-situ growth.

[0062] In this invention, the inventors discovered that the reason why the quench boiler described in this invention can slow down coking and carburization is that, by employing the technical solution described in this invention, the tubes of the quench boiler are first subjected to reducing gas heat treatment, and then further subjected to stepwise oxidizing gas and reducing gas heat treatment. This results in the in-situ formation of a double-layer anti-coking oxide film with strong adhesion to the tube substrate on the inner surface of the tubes, shielding the iron elements in the tube section. When the cracked gas recovers heat through the quench boiler, the oxide film on the inner wall of the tubes can isolate the cracked gas from contact with the iron elements on its inner surface, thereby inhibiting catalytic coking, condensation coking, and the entire coking process within the tube section, and effectively improving the anti-carburization performance of the tube section, thus extending the online time and service life of the quench boiler.

[0063] The third aspect of the present invention provides the application of the above-mentioned rapid cooling boiler for mitigating coking and carburization in petroleum hydrocarbon thermal cracking.

[0064] In this invention, the cracking reaction can be carried out according to the conventional naphtha cracking process in the prior art. Specifically, the cracking temperature is 830-850℃, and the water-oil ratio is 0.5-0.55.

[0065] Unless otherwise specified, room temperature in this invention refers to 25°C.

[0066] The present invention will be described in detail below through embodiments. The following embodiments include:

[0067] 15CrMoG tubing is a commonly used material for tubes in quench boilers.

[0068] The elemental composition of the furnace tube alloy and the elemental content in the oxide film on the inner surface of the furnace tube after treatment were determined by X-ray energy dispersive spectroscopy (EDS).

[0069] The oxygen content of reducing gases was measured using a trace oxygen analyzer;

[0070] The oxygen content in the oxidizing gases was measured using a constant oxygen analyzer.

[0071] The amount of coke deposited on the furnace tubes was calculated by measuring the concentrations of CO and H2 in the coking gas online using an infrared instrument and by measuring the volume of the coking gas online using a wet gas flow meter.

[0072] The feedstock for cracking is naphtha, with the following properties: distillation range 33.4-162.8℃, specific gravity D. 20 : 0.7358g / mL.

[0073] Example 1

[0074] Seamless steel pipes made from 15CrMoG tubing are cold-drawn into... The small-scale test furnace tube has the following alloy element composition (wt%): Cr: 1.03, Mo: 0.47, Mn: 0.58, Si: 0.32, C: 0.16, O: 2.13, Fe: 95.07, and others 0.24%. The small-scale test furnace tube undergoes step-by-step heat treatment:

[0075] (1) A gas mixture of CO, H2 and N2 was used as a reducing gas to perform the first heat treatment on the furnace tube to obtain a pretreated small-scale furnace tube. The oxygen content in the reducing gas was 0 ppm, the volume ratio of CO to H2 was 1:1, the volume percentage of CO and H2 was 70 vol%, and the remainder was N2. The flow rate of the reducing gas was 400 mL / min, the heating rate was 80 ℃ / h, the treatment temperature was 900 ℃, and the treatment time was 15 hours.

[0076] (2) The pretreatment small test furnace tube was subjected to a second heat treatment using an oxidizing gas composed of air and N2, wherein the volume fraction of O2 was 16%, the flow rate of the oxidizing gas was 400 mL / min, and the conditions for the second heat treatment were: treatment temperature of 900℃ and treatment time of 15 hours.

[0077] (3) Using the same CO, H2 and N2 gas mixture as in step (1) as the reducing gas, the furnace tube is subjected to a third cooling heat treatment to room temperature. The difference is that the flow rate of the reducing gas is 80 mL / min, and the conditions for the third cooling heat treatment are: the cooling rate is 40 °C / h, and the temperature is reduced from 900 °C to room temperature.

[0078] Through stepwise heat treatment with reducing gas, oxidizing gas, and reducing gas again, a double-layer anti-coking oxide film was formed on the inner wall surface of the small-scale furnace tube. The lower layer is chromium oxide, and the upper layer is a chromium-manganese oxide film. The upper chromium-manganese oxide film contains chromium-manganese oxide (Mn2CrO4) and iron. The iron content in the chromium-manganese oxide film is 20.68 wt% relative to the total weight of the chromium-manganese oxide film.

[0079] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after stepwise treatment. The cracking conditions were: cracking temperature 845℃ and water-oil ratio 0.5. Experimental results showed that the coking amount of the pilot-scale furnace tube of the present invention was reduced by 92.12 wt% compared with the untreated pilot-scale furnace tube.

[0080] Example 2

[0081] The same small-scale furnace tube as in Example 1 was subjected to stepwise heat treatment with reducing gas, oxidizing gas, and reducing gas. The difference was that the conditions for the first heat treatment with reducing gas were: a treatment temperature of 800°C and a treatment time of 20 hours; the conditions for the second heat treatment with oxidizing gas were: a treatment temperature of 800°C and a treatment time of 20 hours; and the conditions for the third cooling heat treatment with reducing gas were: a treatment temperature of 800°C to room temperature. Other treatment conditions were the same as in Example 1.

[0082] Through stepwise heat treatment with reducing gas, oxidizing gas, and reducing gas again, a double-layer anti-coking oxide film was formed on the inner wall surface of the small-scale furnace tube. The lower layer is chromium oxide, and the upper layer is a chromium-manganese oxide film. The upper chromium-manganese oxide film contains chromium-manganese oxide (Mn2CrO4) and iron. The iron content in the chromium-manganese oxide film is 36.38 wt% relative to the total weight of the chromium-manganese oxide film.

[0083] Hydrocarbon steam cracking was carried out in the pilot-scale furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the pilot-scale furnace tube of the present invention was reduced by 45.12 wt% compared with that of the untreated pilot-scale furnace tube.

[0084] Example 3

[0085] The same small-scale furnace tube as in Example 1 was subjected to stepwise heat treatment with reducing gas, oxidizing gas, and reducing gas. The difference was that the conditions for the first heat treatment with reducing gas were: a treatment temperature of 1000°C and a treatment time of 10 hours; the conditions for the second heat treatment with oxidizing gas were: a treatment temperature of 1000°C and a treatment time of 10 hours; and the conditions for the third heat treatment with reducing gas were: a treatment temperature of 1000°C to room temperature. Other treatment conditions were the same as in Example 1.

[0086] Through stepwise heat treatment with reducing gas, oxidizing gas, and reducing gas again, a double-layer anti-coking oxide film was formed on the inner wall surface of the small-scale furnace tube. The lower layer is chromium oxide, and the upper layer is a chromium-manganese oxide film. The upper chromium-manganese oxide film contains chromium-manganese oxide (Mn2CrO4) and iron. The iron content in the chromium-manganese oxide film is 28.89 wt% relative to the total weight of the chromium-manganese oxide film.

[0087] Hydrocarbon steam cracking was carried out in the pilot-scale furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the pilot-scale furnace tube of the present invention was reduced by 65.28 wt% compared with that of the untreated pilot-scale furnace tube.

[0088] Example 4

[0089] The same small-scale test furnace tube as in Example 1 was subjected to stepwise heat treatment with reducing gas, oxidizing gas, and reducing gas, with the difference being:

[0090] (1) A gas mixture of CO, H2 and N2 was used as the reducing gas to perform the first heat treatment on the furnace tube to obtain a pretreated small-scale furnace tube. The oxygen content in the reducing gas was 0 ppm, the volume ratio of CO to H2 was 1:0.3, the volume percentage of CO and H2 was 50 vol%, and the remainder was N2. The flow rate of the reducing gas was 150 mL / min, the heating rate was 110 ℃ / h, the treatment temperature was 800 ℃, and the treatment time was 42 hours.

[0091] (2) The pretreatment small test furnace tube was subjected to a second heat treatment using an oxidizing gas composed of air and N2, wherein the volume fraction of O2 was 10%, the flow rate of the oxidizing gas was 150 mL / min, and the conditions for the second heat treatment were: treatment temperature of 800℃ and treatment time of 42 hours.

[0092] (3) Using the same CO, H2 and N2 gas mixture as in step (1) as the reducing gas, the furnace tube is subjected to a third cooling heat treatment to room temperature. The difference is that the flow rate of the reducing gas is 40 mL / min, and the conditions for the third cooling heat treatment are: the cooling rate is 70 °C / h, and the temperature is reduced from 800 °C to room temperature.

[0093] Through stepwise heat treatment with reducing gas, oxidizing gas, and reducing gas again, a double-layer anti-coking oxide film was formed on the inner wall surface of the small-scale furnace tube. The lower layer is chromium oxide, and the upper layer is a chromium-manganese oxide film. The upper chromium-manganese oxide film contains chromium-manganese oxide (Mn2CrO4) and iron. The iron content in the chromium-manganese oxide film is 39.25 wt% relative to the total weight of the chromium-manganese oxide film.

[0094] Hydrocarbon steam cracking was carried out in the pilot-scale furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the pilot-scale furnace tube of the present invention was reduced by 40.84 wt% compared with that of the untreated pilot-scale furnace tube.

[0095] Example 5

[0096] The same small-scale test furnace tube as in Example 1 was subjected to stepwise heat treatment with reducing gas, oxidizing gas, and reducing gas, with the difference being:

[0097] (1) A gas mixture of CO, H2 and N2 was used as the reducing gas to perform the first heat treatment on the furnace tube to obtain a pretreated small-scale furnace tube. The oxygen content in the reducing gas was 0 ppm, the volume ratio of CO to H2 was 1:6, the volume percentage of CO and H2 was 85 vol%, and the remainder was N2. The flow rate of the reducing gas was 80 mL / min, the heating rate was 160 ℃ / h, the treatment temperature was 750 ℃, and the treatment time was 8 hours.

[0098] (2) The pretreatment small test furnace tube was subjected to a second heat treatment using an oxidizing gas composed of air and N2, wherein the volume fraction of O2 was 5%, the flow rate of the oxidizing gas was 80 mL / min, and the conditions for the second heat treatment were: treatment temperature of 750℃ and treatment time of 8 hours.

[0099] (3) Using the same CO, H2 and N2 gas mixture as in step (1) as the reducing gas, the furnace tube is subjected to a third cooling heat treatment to room temperature. The difference is that the flow rate of the reducing gas is 15 mL / min, and the conditions for the third cooling heat treatment are: the cooling rate is 110℃ / h, and the temperature is reduced from 750℃ to room temperature.

[0100] Through stepwise heat treatment with reducing gas, oxidizing gas, and reducing gas again, a double-layer anti-coking oxide film was formed on the inner wall surface of the small-scale furnace tube. The lower layer is chromium oxide, and the upper layer is a chromium-manganese oxide film. The upper chromium-manganese oxide film contains chromium-manganese oxide (Mn2CrO4) and iron. The iron content in the chromium-manganese oxide film is 45.88 wt% relative to the total weight of the chromium-manganese oxide film.

[0101] Hydrocarbon steam cracking was carried out in the pilot furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the pilot furnace tube of the present invention was reduced by 31.56 wt% compared with that of the untreated pilot furnace tube.

[0102] Example 6

[0103] The same small-scale furnace tube as in Example 1 was subjected to stepwise heat treatment with reducing gas, oxidizing gas, and reducing gas. The difference was that the conditions for the first heat treatment with reducing gas were: a treatment temperature of 700°C and a treatment time of 25 hours; the conditions for the second heat treatment were: a treatment temperature of 700°C and a treatment time of 25 hours; and the conditions for the third heat treatment were: a treatment temperature of 700°C to room temperature. Other treatment conditions were the same as in Example 1.

[0104] Through stepwise heat treatment with reducing gas, oxidizing gas, and reducing gas again, a double-layer anti-coking oxide film was formed on the inner wall surface of the small-scale furnace tube. The lower layer is chromium oxide, and the upper layer is a chromium-manganese oxide film. The upper chromium-manganese oxide film contains chromium-manganese oxide (Mn2CrO4) and iron. The iron content in the chromium-manganese oxide film is 42.47 wt% relative to the total weight of the chromium-manganese oxide film.

[0105] Hydrocarbon steam cracking was carried out in the pilot-scale furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The amount of coke deposited in the pilot-scale furnace tube was reduced by 36.39 wt% compared to the untreated pilot-scale furnace tube.

[0106] Comparative Example 1

[0107] The same pilot furnace tube as in Example 1 was used, except that the second heat treatment was performed on the pilot furnace tube using only an oxidizing gas. The volume fraction of O2 in the oxidizing gas was 16%, the treatment temperature was 900°C, and the treatment time was 55 hours. Other conditions were the same as in Example 1. An oxide film was formed on the inner wall surface of the pilot furnace tube, containing chromium oxide and iron. The iron content in the oxide film on the inner surface of the furnace tube was 50.45 wt% relative to the total weight of the oxide film.

[0108] Hydrocarbon steam cracking was carried out in a pilot furnace tube after treatment with oxidizing gas. The cracking feedstock and cracking conditions were the same as in Example 1. The amount of coke in the treated pilot furnace tube was reduced by 17.37 wt% compared with that in the untreated pilot furnace tube.

[0109] Comparative Example 2

[0110] The same pilot furnace tube as in Example 1 was used, except that only reducing gas was used for the first and third heat treatments. Other conditions were the same as in Example 1. After the reducing gas treatment, no chromium oxide or chromium-manganese oxides were generated on the inner wall surface of the furnace tube. The iron content on the inner surface of the furnace tube was 53.63 wt%.

[0111] Hydrocarbon steam cracking was carried out in a pilot furnace tube after treatment with reducing gas. The cracking feedstock and cracking conditions were the same as in Example 1. The amount of coke deposited in the treated pilot furnace tube was reduced by 9.78 wt% compared with that in the untreated pilot furnace tube.

[0112] Comparative Example 3

[0113] The pilot furnace tube was the same as in Example 1, except that it was not treated in any way. Hydrocarbon steam cracking was carried out in the pilot furnace tube, with the same feedstock and cracking conditions as in Example 1. The coking amount in the pilot furnace tube was 100 wt%.

[0114] Comparative Example 4

[0115] The same pilot furnace tube as in Example 1 was used, except that step (3) was omitted, while other conditions remained the same as in Example 1. A double-layer anti-coking oxide film was formed on the inner wall surface of the furnace tube, consisting of a chromium oxide lower layer and a chromium-manganese oxide film upper layer. The upper chromium-manganese oxide film contained chromium-manganese oxide (Mn2CrO4) and iron, with the iron content in the chromium-manganese oxide film being 48.38 wt% relative to the total weight of the chromium-manganese oxide film.

[0116] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after stepwise treatment. The cracking conditions were: cracking temperature 845℃ and water-oil ratio 0.5. The experimental results showed that the coking amount in the pilot-scale furnace tube was reduced by 26.52 wt% compared with that in the untreated pilot-scale furnace tube.

[0117] Comparative Example 5

[0118] The same pilot furnace tube as in Example 1 was used, except that the oxygen content in the reducing gas was controlled at 10 ppm, while other conditions remained the same as in Example 1. A double-layer anti-coking oxide film was formed on the inner wall surface of the pilot furnace tube, consisting of a chromium oxide lower layer and a chromium-manganese oxide film upper layer. The upper chromium-manganese oxide film contained chromium manganese oxide (Mn₂CrO₄) and iron, with the iron content in the chromium-manganese oxide film being 49.27 wt% relative to the total weight of the chromium-manganese oxide film.

[0119] Hydrocarbon steam cracking was carried out in the pilot-scale furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the pilot-scale furnace tube of the present invention was reduced by 20.18 wt% compared with that of the untreated pilot-scale furnace tube.

[0120] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a quench boiler that slows down coking and carburization, characterized in that, The method includes: (1) The reducing gas is brought into contact with the tube side of the quench boiler to carry out the first heat treatment reaction, and a pretreated quench boiler is obtained. (2) The oxidizing gas is brought into contact with the pretreated quench boiler to carry out a second heat treatment reaction, so as to obtain a quench boiler with a double oxide film on the inner surface of the tube side furnace tubes. (3) The reducing gas is brought into contact with the quench boiler with a double oxide film on the inner surface of the tubes of the tube-pass furnace to carry out the third heat treatment reaction, so as to obtain a quench boiler with a double anti-coking oxide film on the inner surface of the tubes of the tube-pass furnace. The reducing gas contains 0 ppm of oxygen, and the oxidizing gas contains 6-22% oxygen by volume. The conditions for the first heat treatment reaction include: heating from room temperature to 800-1000℃ at a heating rate of less than or equal to 150℃ / h, and holding the temperature for more than 10 hours. The conditions for the second heat treatment reaction include: a treatment temperature of 800-1000℃ and a treatment time of more than 10 hours; The conditions for the third heat treatment reaction include cooling from 800-1000℃ to room temperature at a cooling rate of less than or equal to 100℃ / h.

2. The method according to claim 1, wherein, The volume fraction of oxygen in the oxidizing gas is 13-22%.

3. The method according to claim 2, wherein, The oxidizing gas is air and at least one gas selected from nitrogen, helium and argon.

4. The method according to claim 1, wherein, The reducing gas is carbon monoxide and hydrogen, and at least one gas selected from nitrogen, helium, and argon.

5. The method according to claim 4, wherein, Based on the total volume of the reducing gas, the total content of the carbon monoxide and the hydrogen is less than or equal to 80 vol.

6. The method according to claim 5, wherein the total content of the carbon monoxide and the hydrogen is 60-80 vol.

7. The method according to claim 1, wherein, The double-layer anti-coking oxide film includes a chromium oxide layer in the lower layer and a chromium-manganese oxide film in the upper layer.

8. The method according to claim 7, wherein, The chromium-manganese oxide film comprises chromium-manganese oxide and metallic elements.

9. The method according to claim 8, wherein, The composition of the chromium manganese oxide is Mn x Cr 3-x O4, x value is 0.5-2.

10. The method according to claim 8, wherein, The metallic element is iron.

11. The method according to claim 10, wherein, The iron content is less than or equal to 40 wt% relative to the total weight of the chromium-manganese oxide film.

12. The method according to claim 1, wherein, The alloy composition of the tube side of the quench boiler includes: Cr: 1.0-20wt%, Mo: 0.2-0.6wt%, Mn: 0.3-0.8wt%, Si: 0.3-2wt%, C: 0.1-0.2wt%, O: <5wt%, Fe: 76.4-98wt%, and trace elements: 0-1wt%.

13. The method according to claim 12, wherein, The trace element is at least one of Al, Nb, Ti, W and rare earth elements.

14. The application of the quench boiler for slowing coking and carburization, prepared by the method of any one of claims 1-13, in the thermal cracking of petroleum hydrocarbons.