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 to perform a first reaction, obtaining a pretreated quench boiler; (2) contacting a low-oxygen partial pressure gas with the pretreated quench boiler to perform a second reaction, obtaining a quench boiler with an oxide film on the inner surface of the tubes that mitigates coking and carburization; wherein the oxygen content of the reducing gas is 0 ppm; and the dew point of the low-oxygen partial pressure gas is -20°C to 20°C. 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 reaction, and a pretreated quench boiler is obtained.

[0009] (2) The low oxygen partial pressure gas is brought into contact with the pretreated quench boiler to carry out a second reaction, resulting in a quench boiler with an oxide film on the inner surface of the tube side furnace tubes to slow down coking and carburizing.

[0010] The oxygen content of the reducing gas is 0 ppm; the dew point of the low oxygen partial pressure gas is -20°C to 20°C.

[0011] A second aspect of the present invention provides a quench boiler that slows down coking and carburization by the above method.

[0012] 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.

[0013] 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:

[0014] 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 described in 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

[0015] 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.

[0016] 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:

[0017] (1) The reducing gas is brought into contact with the tube side of the quench boiler to carry out the first reaction, and a pretreated quench boiler is obtained.

[0018] (2) The low oxygen partial pressure gas is brought into contact with the pretreated quench boiler to carry out a second reaction, resulting in a quench boiler with an oxide film on the inner surface of the tube side furnace tubes to slow down coking and carburizing.

[0019] The oxygen content of the reducing gas is 0 ppm; the dew point of the low oxygen partial pressure gas is -20°C to 20°C.

[0020] 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 combination of reducing gas and low oxygen partial pressure gas to generate an oxide film in situ on the inner surface of the tube side of the quench boiler. The resulting oxide film has strong adhesion to the substrate of the tube side of the quench boiler and is suitable for long-term use.

[0021] During the manufacturing process, quench boiler tubes inevitably retain residues on their inner surface. These residues not only affect the tubes' performance during service but also hinder the formation of an anti-coking oxide film on the inner surface during subsequent treatment. The high-temperature pretreatment of quench boiler tubes using the reducing gas of this invention thoroughly removes these residues and improves the dispersion of metals on the inner surface, facilitating the formation of a dense and stable anti-coking chromium-manganese spinel oxide film during the subsequent low-oxygen partial pressure gas treatment.

[0022] 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 capable of producing oxygen.

[0023] In this invention, the oxygen content of the reducing gas is measured using a trace oxygen analyzer.

[0024] According to the present invention, the reducing gas includes hydrogen and at least one gas selected from nitrogen, helium and argon.

[0025] According to the present invention, based on the total volume of the reducing gas, the hydrogen content is less than or equal to 80 vol%, preferably 60-80 vol%.

[0026] In this invention, by controlling the hydrogen content 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 formation of a dense and stable oxide film in subsequent low oxygen partial pressure atmosphere treatment.

[0027] In this invention, the low oxygen partial pressure gas with the aforementioned specific dew point results in a low oxygen partial pressure in the gas, thus the oxidation process is very slow, which is beneficial for forming a dense oxide film on the material surface. Oxygen partial pressure refers to the pressure occupied by oxygen in the atmosphere. Under a low oxygen partial pressure atmosphere, the oxygen in the atmosphere mainly comes from the oxygen produced by the decomposition of oxygen-containing compounds (such as H2O).

[0028] As those skilled in the art know, achieving a low-oxygen partial pressure atmosphere is extremely difficult, both in engineering and in the laboratory. Obtaining a stable low-oxygen partial pressure atmosphere through flow control devices is very challenging and difficult to achieve. Through theoretical analysis and numerous experiments, the inventors of this invention ingeniously discovered that controlling the dew point of the mixed gas can achieve accurate control of the low-oxygen partial pressure atmosphere. For example, controlling the dew point of the low-oxygen partial pressure gas to -20°C to 20°C allows for accurate control of the low-oxygen partial pressure atmosphere, thus providing an effective method for treating the tubes of a quench boiler with low oxygen partial pressure.

[0029] In this invention, the dew point refers to the temperature at which saturated water vapor in the air begins to condense and form dew. At 100% relative humidity, the temperature of the surrounding environment is the dew point temperature.

[0030] In this invention, the method further includes the step of determining the dew point of a low-oxygen partial pressure gas.

[0031] In this invention, the method further includes testing the dew point of the low-oxygen partial pressure gas (using a commercially available dew point meter) before treating the pre-treated quench boiler with the low-oxygen partial pressure gas, so that the low-oxygen partial pressure gas has the dew point defined by this invention.

[0032] Furthermore, the method also includes the step of monitoring the dew point of the low-oxygen partial pressure gas in real time using a commercially available dew point meter during the treatment reaction using the low-oxygen partial pressure gas.

[0033] Furthermore, the dew point of the low-oxygen partial pressure gas is -10°C to 10°C.

[0034] According to the present invention, the low-oxygen partial pressure gas is a gaseous mixture of water vapor, carbon monoxide and carbon dioxide.

[0035] In this invention, the volume ratio of carbon monoxide to carbon dioxide in the low oxygen partial pressure gas is 1:5-5:1.

[0036] According to the present invention, the oxide film comprises chromium manganese oxide and a metal element, wherein the metal element is iron.

[0037] 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.

[0038] According to the present invention, the dew point of the low-oxygen partial pressure gas and the content of metal elements in the oxide film on the inner surface of the tubes of the quench boiler satisfy the following relationship:

[0039] (W1-W2) / W1=aT 2 +bT+c Formula I;

[0040] In Equation I, -0.0005 ≤ a ≤ -0.0002, 0.0012 ≤ b ≤ 0.0021, 0.7346 ≤ c ≤ 0.7491, R 2 ≥0.9437;

[0041] Wherein, W1 is the content of metal elements in the tubes of the quench boiler before the first reaction, in wt%; W2 is the content of metal elements in the oxide film on the inner surface of the tubes of the quench boiler after the first reaction, in wt%; and T is the dew point of the low oxygen partial pressure gas, in °C.

[0042] In this invention, by using a reducing gas atmosphere and a low-oxygen partial pressure gas to process the gas stepwise and controlling the relationship between the dew point of the low-oxygen partial pressure gas and the content of metal elements in the oxide film on the inner surface of the tube side of the quench boiler, it is possible to further ensure that the inner surface of the tube side of the quench boiler forms a dense and stable oxide film through in-situ growth. The obtained oxide film is firmly bonded to the furnace 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.

[0043] In this invention, the content of metal elements in the tubes of the quench boiler before treatment and the content of metal elements in the oxide film on the inner surface of the tubes of the quench boiler after treatment are determined by X-ray energy dispersive spectroscopy (EDS).

[0044] 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%.

[0045] According to the present invention, the trace element is at least one selected from Al, Nb, Ti, W and rare earth elements.

[0046] According to the present invention, (W1-W2) / W1≥0.579.

[0047] In this invention, the 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.

[0048] Furthermore, (W1-W2) / W1≥0.663.

[0049] In one specific embodiment of the present invention, the dew point of the low oxygen partial pressure gas is -10°C to 10°C;

[0050] Based on the total volume of the reducing gas, the hydrogen content is 60-80 vol%.

[0051] The dew point of the low-oxygen partial pressure gas and the content of metal elements in the oxide film on the inner surface of the tubes of the quench boiler satisfy the following relationship:

[0052] (W1-W2) / W1=aT 2 +bT+c Formula I;

[0053] In Equation I, a = -0.0005, b = 0.0021, c = 0.7491, R2 =1.

[0054] In this invention, the processing 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.

[0055] According to the present invention, the conditions for the first reaction include: a processing temperature of 800-1000°C and a processing time of 10 hours or more.

[0056] Furthermore, the conditions for the first reaction include: a reaction temperature of 850-950℃ and a reaction time of 10-40h.

[0057] In this invention, in the first reaction, the flow rate of the reducing gas is 100-800 ml / min, preferably 200-600 ml / min.

[0058] 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 formation of a dense and stable oxide film in subsequent low oxygen partial pressure atmosphere treatment.

[0059] According to the present invention, the conditions for the second reaction include: a processing temperature of 800-1000°C and a processing time of 10 hours or more.

[0060] Furthermore, the conditions for the second reaction include: a reaction temperature preferably of 850-950℃ and a reaction time of 10-100h, preferably 10-50h.

[0061] In this invention, in the second reaction, the flow rate of the low oxygen partial pressure gas is 100-800 ml / min, preferably 200-600 ml / min.

[0062] In this invention, by controlling the flow rate of the low-oxygen partial pressure gas to meet the above-mentioned range, a dense and stable oxide film can be formed by low-oxygen partial pressure atmosphere treatment.

[0063] A second aspect of the present invention provides a quench boiler that slows down coking and carburization by the above method.

[0064] In this invention, the inner surface of the tube side of the quench boiler contains an oxide film.

[0065] In this invention, the oxide film is formed by in-situ growth.

[0066] 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 first treating the tubes of the quench boiler with reducing gas and then with a low-oxygen partial pressure atmosphere, an oxide film with strong adhesion to the tube substrate is generated in situ 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 in 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.

[0067] 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.

[0068] 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.

[0069] The present invention will be described in detail below through embodiments. In the following embodiments,

[0070] The elemental composition of the furnace tubes was determined using X-ray energy dispersive spectroscopy (EDS).

[0071] The dew point of the low oxygen partial pressure gas was measured using a commercially available dew point meter.

[0072] The oxygen content of the reducing gas was measured using a trace oxygen analyzer.

[0073] The amount of coke deposited on the furnace tubes was calculated by measuring the concentrations of CO and CO2 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.

[0074] The feedstock for cracking is naphtha, with the following properties: distillation range 33.4-162.8℃, specific gravity D. 20 : 0.7358g / ml.

[0075] Example 1

[0076] Seamless steel pipes made from 15CrMoG tubing are cold-drawn into... The small-scale test furnace tube has the following elemental 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 stepwise treatment with reducing gas and low-oxygen partial pressure gas:

[0077] (1) A gas mixture of H2 and N2 was used as the reducing gas. The oxygen content of the reducing gas was 0 ppm. The volume percentage of H2 was 70 vol%, and the remainder was N2. The flow rate of the mixed gas was 400 ml / min, the treatment temperature was 900 ℃, and the treatment time was 20 hours.

[0078] (2) A gas mixture of H2O, CO, and CO2 was used as the low oxygen partial pressure gas, wherein the volume ratio of CO to CO2 was 1:1, the dew point of the low oxygen partial pressure atmosphere was 0℃, the flow rate of the mixed gas was 400ml / min, the treatment temperature was 900℃, and the treatment time was 30 hours.

[0079] Through the stepwise treatment with reducing gas and low-oxygen partial pressure gas, an oxide film mainly composed of elements such as Cr, Mn, Fe, O, and Si was formed on the inner wall surface of the furnace tube. The chromium and manganese oxide in the oxide film is Mn2CrO4, and the iron content in the oxide film is 23.85 wt%. (W1-W2) / W1=0.749.

[0080] 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 quench boiler of the present invention was reduced by 90.21 wt% compared with the untreated quench boiler.

[0081] Example 2

[0082] The same small-scale furnace tube as in Example 1 was subjected to stepwise treatment with reducing gas and low-oxygen partial pressure gas. The difference was that the dew point of the low-oxygen partial pressure gas was 10°C, while other treatment conditions were the same as in Example 1. An oxide film mainly composed of Cr, Mn, Fe, O, and Si was formed on the inner wall surface of the furnace tube. The chromium and manganese oxide in the oxide film was Mn2CrO4, and the iron content in the oxide film was 26.55 wt%. (W1-W2) / W1 = 0.721.

[0083] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the quench boiler of the present invention was reduced by 85.34 wt% compared with that of the untreated quench boiler.

[0084] Example 3

[0085] The same small-scale furnace tube as in Example 1 was subjected to stepwise treatment with reducing gas and low-oxygen partial pressure gas. The difference was that the dew point of the low-oxygen partial pressure gas was -10℃, while other treatment conditions were the same as in Example 1. An oxide film mainly composed of Cr, Mn, Fe, O, and Si was formed on the inner wall surface of the furnace tube. The chromium and manganese oxide in the oxide film was Mn2CrO4, and the iron content in the oxide film was 30.47 wt%. (W1-W2) / W1 = 0.679.

[0086] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the quench boiler of the present invention was reduced by 80.15 wt% compared with that of the untreated quench boiler.

[0087] Example 4

[0088] The same small-scale furnace tube as in Example 1 was subjected to stepwise treatment with reducing gas and low-oxygen partial pressure gas. The difference was that the dew point of the low-oxygen partial pressure gas was 20°C, while other treatment conditions were the same as in Example 1. An oxide film mainly composed of Cr, Mn, Fe, O, and Si was formed on the inner wall surface of the furnace tube. The chromium and manganese oxide in the oxide film was Mn2CrO4, and the iron content in the oxide film was 32.53 wt%. (W1-W2) / W1 = 0.658.

[0089] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the quench boiler of the present invention was reduced by 55.58 wt% compared with that of the untreated quench boiler.

[0090] Example 5

[0091] The same small-scale furnace tube as in Example 1 was subjected to stepwise treatment with reducing gas and low-oxygen partial pressure gas. The difference was that the dew point of the low-oxygen partial pressure gas was -20°C, while other treatment conditions were the same as in Example 1. An oxide film mainly composed of Cr, Mn, Fe, O, and Si was formed on the inner wall surface of the furnace tube. The chromium and manganese oxide in the oxide film was Mn2CrO4, and the iron content in the oxide film was 36.29 wt%. (W1-W2) / W1 = 0.618.

[0092] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the quench boiler of the present invention was reduced by 45.64 wt% compared with that of the untreated quench boiler.

[0093] Example 6

[0094] The same small-scale test furnace tube as in Example 1 was subjected to stepwise treatment with reducing gas and low oxygen partial pressure gas. The difference was that the conditions for the reducing gas treatment were: a treatment temperature of 800°C and a treatment time of 30 hours. Other treatment conditions were the same as in Example 1.

[0095] Through stepwise heat treatment with reducing gas and low-oxygen partial pressure gas, an oxide film mainly composed of elements such as Cr, Mn, Fe, O, and Si was formed on the inner wall surface of the furnace tube. The chromium and manganese oxide in the oxide film is Mn2CrO4, and the iron content in the oxide film is 38.48 wt%. (W1-W2) / W1=0.595.

[0096] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the quench boiler of the present invention was reduced by 42.23 wt% compared with that of the untreated quench boiler.

[0097] Example 7

[0098] The same small-scale test furnace tube as in Example 1 was subjected to stepwise treatment with reducing gas and low oxygen partial pressure gas. The difference was that the conditions for the reducing gas treatment were: a treatment temperature of 1000°C and a treatment time of 15 hours. Other treatment conditions were the same as in Example 1.

[0099] Through stepwise heat treatment with reducing gas and low-oxygen partial pressure gas, an oxide film mainly composed of elements such as Cr, Mn, Fe, O, and Si was formed on the inner wall surface of the furnace tube. The chromium and manganese oxide in the oxide film is Mn2CrO4, and the iron content in the oxide film is 31.87 wt%. (W1-W2) / W1=0.665.

[0100] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the quench boiler of the present invention was reduced by 63.38 wt% compared with that of the untreated quench boiler.

[0101] Example 8

[0102] The same small-scale test furnace tube as in Example 1 was subjected to stepwise treatment with reducing gas and low oxygen partial pressure gas. The difference was that the conditions for the reducing gas treatment were: a treatment temperature of 750°C and a treatment time of 40 hours. Other treatment conditions were the same as in Example 1.

[0103] Through stepwise heat treatment with reducing gas and low-oxygen partial pressure gas, an oxide film mainly composed of elements such as Cr, Mn, Fe, O, and Si was formed on the inner wall surface of the furnace tube. The chromium and manganese oxide in the oxide film is Mn2CrO4, and the iron content in the oxide film is 48.97 wt%. (W1-W2) / W1=0.485.

[0104] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the quench boiler of the present invention was reduced by 23.45 wt% compared with that of the untreated quench boiler.

[0105] Comparative Example 1

[0106] The same small-scale furnace tube as in Example 1 was subjected to stepwise treatment with reducing gas and low-oxygen partial pressure gas. The difference was that the dew point of the low-oxygen partial pressure gas was 30°C, while other treatment conditions were the same as in Example 1. An oxide film mainly composed of Cr, Mn, Fe, O, and Si was formed on the inner wall surface of the furnace tube. The chromium-manganese oxide in the oxide film was Mn₂CrO₄, and the iron content in the oxide film was 45.88 wt%. (W₁-W₂) / W₁ = 0.517.

[0107] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after the stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the treated quench boiler was reduced by 26.73 wt% compared to the untreated quench boiler.

[0108] Comparative Example 2

[0109] The same small-scale furnace tube as in Example 1 was subjected to stepwise treatment with reducing gas and low-oxygen partial pressure gas. The difference was that the dew point of the low-oxygen partial pressure gas was -30°C, while other treatment conditions were the same as in Example 1. An oxide film mainly composed of Cr, Mn, Fe, O, and Si was formed on the inner wall surface of the furnace tube. The chromium and manganese oxide in the oxide film was Mn2CrO4, and the iron content in the oxide film was 50.38 wt%. (W1-W2) / W1 = 0.470.

[0110] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after the stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the treated quench boiler was reduced by 20.31 wt% compared to the untreated quench boiler.

[0111] Comparative Example 3

[0112] The same small-scale furnace tube as in Example 1 was used, except that only a low-oxygen partial pressure gas was used to treat the furnace tube. The treatment temperature was 900℃, and the treatment time was 50 hours. Other conditions were the same as in Example 1. An oxide film mainly composed of Cr, Mn, Fe, O, and Si was formed on the inner wall surface of the furnace tube. The chromium and manganese oxide in the oxide film was Mn2CrO4, and the iron content in the oxide film was 32.38 wt%. (W1-W2) / W1 = 0.659.

[0113] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after treatment with a low-oxygen partial pressure atmosphere. The cracking feedstock and cracking conditions were the same as in Example 1. The coking amount of the treated quench boiler was reduced by 62.31 wt% compared with the untreated quench boiler.

[0114] Comparative Example 4

[0115] The same small-scale furnace tube as in Example 1 was used, except that only reducing gas was used for treatment. All other conditions were the same as in Example 1. No chromium or manganese oxides were generated on the inner wall surface of the furnace tube after reducing gas treatment. The iron content on the inner surface of the furnace tube was 56.73 wt%. (W1-W2) / W1 = 0.403.

[0116] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after reducing gas treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the treated quench boiler was reduced by 8.69 wt% compared to the untreated quench boiler.

[0117] Comparative Example 5

[0118] The pilot-scale furnace tubes were the same as in Example 1, except that no treatment was performed. Hydrocarbon steam cracking was carried out in the pilot-scale furnace tubes, with the same cracking feedstock and conditions as in Example 1. The coking amount in the quench boiler was 100 wt%.

[0119] Comparative Example 6

[0120] The same small-scale reactor as in Example 1 was used, except that: first, a low-oxygen partial pressure gas was brought into contact with the reactor to carry out the first reaction, and then a reducing gas was brought into contact with the reactor after the above pre-reaction to carry out the second reaction. Other conditions were the same as in Example 1.

[0121] Through stepwise heat treatment with reducing gas and low-oxygen partial pressure gas, an oxide film mainly composed of elements such as Cr, Mn, Fe, O, and Si was formed on the inner wall surface of the furnace tube. The chromium and manganese oxide in the oxide film is Mn2CrO4, and the iron content in the oxide film is 42.16 wt%. (W1-W2) / W1=0.557.

[0122] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the quench boiler of the present invention was reduced by 28.57 wt% compared with that of the untreated quench boiler.

[0123] Comparative Example 7

[0124] The same small-scale reactor as in Example 1 was used, except that the oxygen content in the reducing gas was 10 ppm. All other conditions were the same as in Example 1.

[0125] Through stepwise heat treatment with reducing gas and low-oxygen partial pressure gas, an oxide film mainly composed of elements such as Cr, Mn, Fe, O, and Si was formed on the inner wall surface of the furnace tube. The iron content in the oxide film was 51.69 wt%. (W1-W2) / W1=0.456.

[0126] Hydrocarbon steam cracking was carried out in a pilot-scale furnace tube after stepwise treatment, with the same cracking feedstock and conditions as in Example 1. The coking amount of the quench boiler of the present invention was reduced by 11.85 wt% compared with that of the untreated quench boiler.

[0127] 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 reaction, and a pretreated quench boiler is obtained. (2) The low oxygen partial pressure gas is brought into contact with the pretreated quench boiler to carry out a second reaction, thereby obtaining a quench boiler with an oxide film on the inner surface of the tube side furnace tubes to slow down coking and carburizing. The oxygen content of the reducing gas is 0 ppm; the dew point of the low oxygen partial pressure gas is -20°C to 20°C. The dew point of the low-oxygen partial pressure gas and the content of metal elements in the oxide film on the inner surface of the tubes of the quench boiler satisfy the following relationship: (W1-W2) / W1 = aT 2 +bT+c Equation I; In formula I, -0.0005≤a≤-0.0002, 0.0012≤b≤0.0021, 0.7346≤c≤0.7491, R 2 ≥0.9437; R 2 is the goodness of fit of formula I; Wherein, W1 is the content of metal elements in the tubes of the quench boiler before the first reaction, wt%; W2 is the content of metal elements in the oxide film on the inner surface of the tubes of the quench boiler after the second reaction, wt%; T is the dew point of the low oxygen partial pressure gas, °C; (W1-W2) / W1≥0.

579. The oxide film comprises chromium manganese oxide and a metal element, wherein the metal element is iron. The low-oxygen partial pressure gas is a gaseous mixture of water vapor, carbon monoxide, and carbon dioxide; 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%.

2. The method according to claim 1, wherein, The reducing gas includes hydrogen and at least one gas selected from nitrogen, helium and argon.

3. The method according to claim 2, wherein, Based on the total volume of the reducing gas, the hydrogen content is less than or equal to 80 vol.

4. The method according to claim 3, wherein, Based on the total volume of the reducing gas, the hydrogen content is 60-80 vol.

5. The method according to claim 1 or 2, wherein, The composition of the chromium-manganese oxide is Mn x Cr 3-x O4, x having a value of 0.5-2.

6. The method according to claim 1 or 2, wherein, The trace element is at least one of Al, Nb, Ti, W and rare earth elements.

7. The method according to claim 2, wherein, The dew point of the low oxygen partial pressure gas is -10℃ to 10℃; Based on the total volume of the reducing gas, the hydrogen content is 60-80 vol%. The dew point of the low-oxygen partial pressure gas and the content of metal elements in the oxide film on the inner surface of the tubes of the quench boiler satisfy the following relationship: (W1-W2) / W1=aT 2 +bT+c formula I; In Equation I, a = -0.0005, b = 0.0021, c = 0.7491, R 2 =1; R 2 Let be the goodness of fit of Equation I.

8. The method according to claim 1 or 2, wherein, The conditions for the first reaction include: a processing temperature of 800-1000℃ and a processing time of more than 10 hours; And / or, the conditions for the second reaction include: a processing temperature of 800-1000°C and a processing time of more than 10 hours.

9. A quench boiler for slowing down coking and carburizing, prepared by the method according to any one of claims 1-8.

10. The application of the quench boiler for slowing coking and carburization as described in claim 9 in petroleum hydrocarbon thermal cracking.