RU2800956C1 - Anti-coke equipment, method of manufacture and use thereof - Google Patents

Abstract

FIELD: pyrolysis of petroleum hydrocarbons; aromatization of light hydrocarbons.

SUBSTANCE: invention relates to a coke-preventing device and a method for its production and its use. The manufacturing method includes: bringing a gas with a low partial pressure of oxygen into contact with a reaction device to obtain an anti-coking device containing an oxide film on the inner surface; while the dew point of a gas with a low partial pressure of oxygen is in the range from -40°C to 40°C.

EFFECT: technical result of the invention is to suppress or slow down the process of catalytic coke formation, reduce the level of carburization of the device and extend the service life of the device due to the formation of a dense and stable oxide film on the inner surface of equipment manufactured by this method.

19 cl, 44 ex

Description

Cross-reference to related applications

The application claims priority by the filing date of Chinese patent applications Nos. 202010582151.8, 202010582144.8, 202010582969.X and 202010582183.8, filed on June 23, 2020, which are incorporated herein in their entirety by reference.

Technical field

The present invention relates to the technical field of devices for the pyrolysis of petroleum hydrocarbons and devices for the aromatization of light hydrocarbons, and in particular to an anti-coke device and a method for producing the same, and its use.

State of the art

Cracking furnaces, transfer line heat exchangers (abbreviated TLT) and hydrocarbon aromatization reactors are widely used devices in the petrochemical industry, each of which is one of the important devices used in the pyrolysis of hydrocarbons to produce ethylene or in the aromatization reaction of light hydrocarbons. In order to ensure the high-temperature strength of the above devices during operation, the materials used in cracking furnaces, CLTs and aromatization reactors mainly contain Fe, Cr, Ni, etc., while under the operating conditions of cracking furnaces, TLTs and aromatization reactors, elements Fe and/or Ni in devices can cause catalytic coking, carburization and other phenomena on the inner wall of said devices, which ultimately leads to significant carbon deposits on the inner walls of devices such as cracker tubes, TLT flue tubes and aromatization reactors. light hydrocarbons, and the pressure drop in the bed increases, the devices cannot be operated for a long time. In addition, heavy hydrocarbon feedstock is accompanied by a large amount of free radical coking and polycondensation coking during the pyrolysis process.

Currently, two main approaches are used to mitigate coking and carburization processes, namely: adding coke inhibitors to the pyrolysis feedstock and applying an anti-coke coating to the internal surface of these reactors. However, the method of adding coke formation inhibitors to passivate the inner surface of said reactors or evaporate coke not only leads to contamination of the subsequent product, but also requires replenishment of specialized injection equipment, the method is ineffective for low-temperature coking. The main line of current research is to provide an inert coating on the inner surface of these reactors, which can reduce the contact of hydrocarbons with the active Fe and/or Ni metal particles on the inner surface of the tubes of the cracking furnace, thereby reducing catalytic coking caused by the active Fe and/or Ni metal particles. Ni. On the other hand, researchers are also taking measures such as adding components to the reactors, reducing the pressure in the reactors, reducing the residence time, lowering the pyrolysis temperature, optimizing the pyrolysis feedstock to reduce free apical coking holes and polycondensation coking in the pyrolysis process.

Methods for forming a protective layer on the inner surface of the reactor have two different approaches, one approach is to form a protective layer on the inner surface of the reactor through thermal spraying, thermal spraying, high temperature sintering, chemical thermal treatment, chemical vapor deposition, and the like; the disadvantage of this method is that the protective layer is not firmly bonded to the base of the reactor, and the protective layer can be easily peeled off; another approach is to form an oxide protective layer on the inner surface of the reactor in-situ by processing in a certain atmosphere at a certain temperature. The method has the advantage that the protective layer adheres strongly to the base of the chimney and the protective layer cannot be easily separated.

The Canadian Chemical Corporation NOVA discloses a series of patents for treating the inner surface of a cracking furnace tube in an atmosphere with low partial pressure of oxygen to obtain an oxide film of chromium-manganese spinel, which include US 5630887 A, US 6436202 B1, US 6824883 B1, US 7156979 B2, US 7488392 B2 . It can be seen from the disclosed materials that the technology has the desired effect of suppressing coking in a gas cracking furnace using ethane, propane and other light hydrocarbons as feedstock, but the technology has a poor effect of preventing coking in a liquid feedstock cracking process. Since the coking of said gas cracking furnace is dominated by catalytic coking, the oxide film isolates the elements Fe, Ni having catalytic coking activity in the chimney from the source of hydrocarbon coking. In the case of a liquid cracking furnace fed with naphtha, diesel fuel, etc., although coking is also based on catalytic coking, polycondensation coking accounts for more than 50% of the total coking amount, and the coke formed during polycondensation can completely cover the oxide film. Therefore, the oxide film in the tube of the liquid cracking furnace is only effective for suppressing coking at the initial stage of operation of said furnace tube, because at this time the oxide film is not covered with coke formed by polycondensation; during the operation of the cracking furnace in the middle and late periods, the oxide film cannot exert its effect.

CN 105506713 A describes a method for forming a chromium-based coating on a component, which includes: immersing the component and counter electrode in an electrolyte solution containing trivalent chromium salt and nanosized ceramic particles, applying current to the component and counter electrode, and electrodepositing a chromium-based coating layer containing chromium and nanoscale ceramic particles, on the component. The method serves to form a chromium coating by electrodeposition for coating Fe, Ni elements.

CN 103374705 A describes a magnetron sputtering apparatus including a reaction chamber, cartridge and target materials. The chuck is located at the bottom of the reaction chamber and is used to hold workpieces being processed. Target materials are located at the top of the reaction chamber. Edge magnets are located outside the side wall of the reaction chamber. The edge magnets are located above the cartridge, while the auxiliary magnets are located on the edge of the cartridge. The magnetic pole of the auxiliary magnets and the magnetic pole of the edge magnets are located in the same direction. Auxiliary magnets and edge magnets form a magnetic loop. Through a magnetic loop, metal ions in the plasma move to the edge zone of the reaction chamber in order to increase the amount of deposited particles of the target material on the edge zone of the workpieces. An inert coating is formed using a magnetron sputtering device.

However, inert coatings formed by deposition of foreign elements are short-lived in practical industrial applications, and the coatings peel off to a large extent after several cycles, so these coatings have not found wide application in industry.

Brief description of the invention

The present invention serves to overcome the existing problems of the prior art related to coking and carburization on the inner wall of the device, as well as difficulties in obtaining an oxide film on the inner surface of the device, and provides an anti-coking device, and a method for producing the same, and its use. By adjusting the dew point of the gas with low oxygen partial pressure and the ratio between the content of metal elements Fe and/or Ni in the device before and after processing, a dense and stable oxide film can be formed on the inner surface of the device obtained by this method, which suppresses or slows down the process. catalytic coking, reduces the level of carburization of the device and prolongs the service life of the device.

In order to achieve the above object, in the first aspect of the present invention, there is provided a method for manufacturing an anti-coking device, comprising reacting a gas with a low oxygen partial pressure and the device to obtain an anti-coking device having an oxide film on an inner surface;

while the dew point of a gas with a low partial pressure of oxygen is in the range from -40°C to 40°C.

In a second aspect of the present invention, there is provided an anti-coke device manufactured using the above manufacturing method.

In a third aspect, the present invention provides for the use of an anti-coke device in at least one of a cracker, a TLT, and an aromatization reactor.

Owing to the above-described technical scheme, the anti-coking device of the present invention, its production method and its use provide the following beneficial effects:

the present invention can ensure that a dense and stable oxide film is formed on the inner surface of the device, which suppresses or slows down the catalytic coking process, reduces the carburization rate of the device, and prolongs the service life of the device, by adjusting the dew point of a gas with a low oxygen partial pressure, and in particular by adjusting the relationship between the dew point of a low oxygen partial pressure gas and the content of the metal element in the oxide film of the anti-coking device.

In addition, the inner surface of the anti-coke device provided by the present invention contains an oxide film formed by the in-situ growth method, the obtained oxide film has a strong adhesion force to the base of the device, so that the device can be used for a long time, solving the problem of coking and carburization. devices.

Detailed description of the invention

The endpoints and any values of the ranges disclosed herein are not limited to precise ranges or values, such ranges or values should be understood to include values close to those ranges or values. For numerical ranges, the end values of each range, the end values of each range, and individual point values, as well as individual point values, may be combined to form one or more new numerical ranges, and these numerical ranges should be considered as specifically disclosed herein.

In a first aspect, the present invention provides a method for manufacturing an anti-coke device, comprising contacting a low oxygen partial pressure gas and the device to form an anti-coke device having an oxide film on an inner surface;

while the dew point of a gas with a low partial pressure of oxygen is from -40°C to 40°C.

As used herein, a low oxygen partial pressure atmosphere refers to a reducing atmosphere in which the oxygen partial pressure is low so that the oxidation process is very slow, which promotes the formation of a dense oxide film on the surface of the material. Oxygen partial pressure means the pressure exerted by oxygen gas present in the atmosphere, and the oxygen in the atmosphere is mainly formed from oxygen generated by the decomposition of an oxygen-containing compound (for example, H ₂ O) in an atmosphere with a low oxygen partial pressure.

In engineering or in the laboratory, it is difficult to obtain a low oxygen partial pressure atmosphere, and it is very difficult and unattainable to obtain a stable low oxygen partial pressure atmosphere with a flow control device.

It has been unexpectedly found through theoretical analysis and a large number of experiments that a dense and stable oxide film can be formed on the inner surface of the device by adjusting the dew point of the gas mixture, for example, adjusting the dew point of a gas with a low partial pressure of oxygen in the range from -40 ° C to 40°C, thereby significantly suppressing or slowing down the process of catalytic coking, reducing the level of carburization of the device and prolonging the service life of the device.

As used herein, 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 ambient temperature exactly corresponds to the dew point.

In the present invention, the method further includes the step of measuring the dew point of a low oxygen partial pressure gas.

In the present invention, the method further includes measuring the dew point of the low oxygen partial pressure gas (using a commercially available dew point meter) prior to the contact reaction between the low oxygen partial pressure gas and the device, such that the low oxygen partial pressure gas contacting the device , has a dew point defined by the present invention.

In addition, the method may also include the step of monitoring the dew point of the low oxygen partial pressure gas in the contact reaction in real time using a commercially available contact dew point meter.

According to the present invention, the device materials contain an iron element and/or a nickel element.

According to the present invention, the oxide film contains chromium manganese oxide and metal elements, the metal elements being an iron element and/or a nickel element.

In the present invention, the oxide of chromium and manganese has the composition Mn _x Cr _3-x O ₄ where x has a numerical value of 0.5-2.

In the present invention, the content of metal elements in said device before the contact reaction and the content of metal elements in the oxide film of the anti-coke device after the contact reaction are measured using energy dispersive X-ray spectrometry (EDS).

According to the present invention, the dew point of the low oxygen partial pressure gas and the content of metallic elements in the oxide film of the anti-coke device satisfy the following relationship:

in formula I -0.0039≤a≤-0.0001, 0.001≤b≤0.0294, 0.7269≤c≤0.8577, R ² ≥0.879;

where W1 denotes the content of metal elements in the device before the contact reaction, wt. %; W2 denotes the content of metal elements in the oxide film of the device after the contact reaction, wt. %; T is the dew point of a low oxygen partial pressure gas, °C.

The present invention can further ensure the formation of a dense and stable oxide film on the inner surface of the device, suppress or slow down the process of catalytic coking, reduce the carburization rate of the device, and prolong the service life of the device by controlling the ratio between the dew point of a low oxygen partial pressure gas and the content of metal elements in the oxide layer. a film of an anti-coking device that satisfies the above ratio.

In a specific embodiment of the present invention in formula I -0.0005≤a≤-0.0001, 0.001≤b≤0.0035, 0.7355≤c≤0.8577, R ² ≥0.9463.

In a specific embodiment of the present invention in formula I, a=-0.0003, b=0.0035, c=0.7882, R ² =0.9463.

In a specific embodiment of the present invention in formula I, a=-0.0001, b=0.002, c=0.8577, R ² =0.9785.

In a specific embodiment of the present invention in formula I, a=-0.0003, b=0.001, c=0.7355, R ² =0.9867.

In a specific embodiment of the present invention in formula I, a=-0.0005, b=0.0022, c=0.7678, R ² =0.98.

According to the present invention in formula I (W1-W2)/W1≥0.281, preferably (W1-W2)/W1≥0.583.

In a specific embodiment of the present invention (W1-W2)/W1≥0.791, preferably (W1-W2)/W1≥0.861.

In a specific embodiment of the present invention (W1-W2)/W1≥0.587, preferably (W1-W2)/W1≥0.690.

In a specific embodiment of the present invention (W1-W2)/W1≥0.594, preferably (W1-W2)/W1≥0.797.

According to the present invention, the device is at least one device selected from the group consisting of an alloy chimney, a TLT, and a light hydrocarbon aromatization reactor.

In the present description, the alloy stove pipe may be a nickel-chromium alloy pipe commonly used in the prior art.

In accordance with the present invention, when the device is an alloy stovepipe, the total content of metal elements in the alloy stovepipe before the contact reaction is 25-90 wt. %.

In particular, the metal elements include 20-50 wt. % nickel element and 5-40 wt. % iron element in the alloy chimney, and the alloy chimney further contains 12-50 wt. % chromium element, 0.2-3 wt. % manganese element, 1-3 wt. % silicon element, 0.1-0.75 wt. % element carbon, 0-5 wt. % trace elements and trace elements, in addition to the elements iron and nickel.

In addition, the total content of these metal elements in the alloy chimney is 37-83 wt. %; in particular, the metal elements contain 25-48 wt. % nickel element and 12-35 wt. % iron element; alloy furnace tube additionally contains 20-38 wt. % element chromium, 1-2.5 wt. % manganese element, 1-2 wt. % silicon element, 0.1-0.6 wt. % element carbon, 0-3 wt. % trace elements and trace elements, in addition to the above elements iron and nickel.

In the present invention, trace elements are one or more elements selected from the group consisting of niobium, titanium, tungsten, aluminum and rare earth elements, and trace elements are selected from sulfur and/or phosphorus.

According to the present invention, when the device is a TLT, the total content of metal elements in the chimneys of the TLT pipe passage before the contact reaction is 76.4-98 wt. %.

In the present invention, the metal element in the chimneys of the TLT pipe passage is iron, and the alloy of the chimneys of the TLT pipe passage additionally contains 1.5-20 wt. % chromium element, 0.2-0.6 wt. % element molybdenum, 0.3-0.8 wt. % manganese element, 0.4-2 wt. % silicon element, 0.1-0.2 wt. % element carbon, less than 5 wt. % element oxygen and 0-1 wt. % trace elements, in addition to the iron element.

In the present invention, the trace elements in the chimneys of the TLT pipe passage are at least one element selected from the group consisting of Al, Nb, Ti, W, and rare earth elements.

In the present invention, the TLT may be a conventional prior art TLT, it may be manufactured using conventional prior art manufacturing techniques. In the present invention, the TLT pipe section is machined so that its inner surface is shiny and scale-free, and the oxygen content is less than 5 wt. %.

In addition, when the device is a TLT, the total content of the metal element (iron element) in the chimneys of the TLT pipe passage before the contact reaction is 80-97 wt. %, the chimneys of the TLT pipe passage additionally contain 2-15 wt. % element chromium, 0.25-0.35 wt. % element molybdenum, 0.55-0.65 wt. % manganese element, 0.5-1.9 wt. % silicon element, 0.14-0.17 wt. % element carbon, less than 3 wt. % element oxygen and 0.15-0.65 wt. % trace elements, in addition to the metal element (iron element).

In the present invention, the TLT flue pipe alloy may be a conventional alloy known in the art, such as 15Mo3.

According to the present invention, the aromatization reactor alloy material is at least one material selected from the group consisting of 304, 316, and 321 stainless steel, more preferably, the aromatization reactor alloy material is 304 stainless steel, and the metallic element content of the aromatization reactor before contact reaction is 68-81 mass. %.

In the present invention, the aromatization reactor may be a conventional prior art aromatization reactor or an aromatization reactor manufactured using conventional prior art manufacturing techniques.

In a specific embodiment of the present invention, the dew point of a gas with a low partial pressure of oxygen is in the range from -30°C to 30°C; in formula I -0.0005≤a≤-0.0003, 0.001≤b≤0.0092, 0.7355≤c≤0.8308, R ² ≥0.9539.

In a specific embodiment of the present invention, the dew point of the low oxygen partial pressure gas is in the range of -20°C to 20°C; in formula I -0.0006≤a≤-0.0003, 0.001≤b≤0.0092, 0.7269≤c≤0.8308, R ² ≥0.879.

In a specific embodiment of the present invention, the dew point of a gas with a low partial pressure of oxygen is in the range from -15°C to 15°C; in formula I -0.0006≤a≤-0.0005, 0.0021≤b≤0.0049, 0.7419≤c≤0.8109, R ² ≥0.879.

In a specific embodiment of the present invention, the dew point of a gas with a low partial pressure of oxygen is in the range from -15°C to 10°C; in formula I -0.0005≤a≤-0.0003, 0.0021≤b≤0.0053, 0.7419≤c≤0.8138, R ² ≥0.8943.

In a specific embodiment of the present invention, the dew point of a gas with a low partial pressure of oxygen is in the range from -10°C to 10°C; in formula I a=-0.0005, b=0.0021, c=0.7419, R ² =1.

In a specific embodiment of the present invention, the dew point of a gas with a low partial pressure of oxygen is in the range from -5°C to 5°C; in formula I a=-0.0039, b=0.0041, c=0.8333, R ² =1.

In a specific embodiment of the present invention, the dew point of a gas with a low partial pressure of oxygen is in the range from 0°C to 20°C, in the formula I a=-0.0004, b=0.0092, c=0.8308, R ² = 1.

In a specific embodiment of the present invention, the dew point of the low oxygen partial pressure gas is in the range of 0°C to 10°C; in formula I a=-0.0022, b=0.0238, c=0.7787, R ² =0.9887.

In a specific embodiment of the present invention, the dew point of the low oxygen partial pressure gas is in the range of 2°C to 8°C; in formula I a=-0.0028, b=0.0294, c=0.7678, R2=0.9995.

In accordance with the present invention, the low oxygen partial pressure gas is a gas mixture consisting of CO ₂ and/or H ₂ O and at least one gas selected from the group consisting of CO, CH ₄ , C ₂ H ₆ , C ₃ H ₈ , NH ₃ , H ₂ , N ₂ , Ar, He, air and pyrolysis gas.

Preferably, the low oxygen partial pressure gas is at least a gas selected from the group consisting of CH ₄ and H ₂ O gas mixture, CO ₂ and CO gas mixture, H ₂ O and CO gas mixture, and H ₂ O gas mixture, and H ₂ .

Preferably, the method further comprises the step of measuring the dew point of the low oxygen partial pressure gas.

According to the present invention, the contact reaction conditions include: reaction temperature 400-1100°C, preferably 600-1100°C; reaction time 5-100 hours, preferably 5-72 hours.

In one embodiment of the present invention, the contact reaction conditions include: a reaction temperature of 750-1000° C. and a reaction time of 20-50 hours.

In one embodiment of the present invention, the contact reaction conditions include: reaction temperature 700-950° C. and reaction time 10-80 hours.

In one embodiment of the present invention, the contact reaction conditions include: a reaction temperature of 750-950° C. and a reaction time of 20-60 hours.

In one embodiment of the present invention, the contact reaction conditions include: reaction temperature 800-1050° C. and reaction time 30-60 hours.

In the present invention, the flow rate of the low oxygen partial pressure gas is 100-500 ml/min, preferably 200-400 ml/min.

In the present invention, the contact reaction can be carried out in a device capable of maintaining a certain atmosphere and commonly used in the art, for example, the contact reaction can be carried out in at least one device selected from the group consisting of a tube furnace, a shaft furnace and an atmospheric chamber furnace.

According to the present invention, the apparatus is an alloy stove pipe used in a cracking furnace.

In addition, the alloy stovepipe includes a heat transfer enhancement element fixed in the stovepipe.

In the course of research, it has been found that by providing a heat transfer enhanced element inside a chimney, the heat transfer enhanced element changes the state of the low oxygen partial pressure gas flow during the contact reaction between the chimney and the low oxygen partial pressure gas, a trace amount of O ₂ in gas with a low oxygen partial pressure can be brought into sufficient contact with the pipe wall so that the pipe wall is completely oxidized and the content of metal elements in the formed oxide film is further reduced.

On the contrary, when the furnace pipe without the heat transfer element is subjected to gas treatment with low oxygen partial pressure, the gas contacts the pipe wall in a laminar state, O ₂ in the middle of the gas flow hardly participates in the pipe wall oxidation reaction, the pipe wall cannot be completely oxidized. , so the resulting oxide film has a high content of metallic elements.

In addition, with the heat transfer element, after the heat transfer element changes the state of the pyrolysis gas flow at the pipe wall from laminar to turbulent flow during the pyrolysis process, the condensation formed coke on the inner surface of the chimney is easily washed away by the pyrolysis gas flow, the reason for which may be that the coke formed as a result of the condensation is usually a relatively loose coke and has a relatively weak adhesion to the inner wall of the chimney. Therefore, the coke adhering to the inner wall of the chimney containing the heat transfer enhancement element is mainly composed of catalytic formed coke, so that the oxide film formed by the low oxygen partial pressure treatment can sufficiently exhibit its effect, thereby significantly prolonging operating cycle of the cracking furnace.

In the present invention, the heat transfer enhancement element may be a common prior art component capable of changing the state of the fluid flow and increasing the heat transfer coefficient, for example, the heat transfer enhancement element is preferably at least one element selected from the group consisting of a swirling radiant tube. element (abbreviated as SERT), pipes with internal slats and pipes with internal ribs.

In the present invention, a cracking furnace alloy stove pipe provided with a heat transfer enhancement element is manufactured by a conventional method known in the art. For example, a cracking furnace alloy stovepipe is generally manufactured by centrifugal casting, while a stovepipe having a heat transfer enhancement member inside can be manufactured in various shapes. For example, a stovepipe having a SERT or a tube with internal ribs is usually made by casting in one block by static casting, and a stovepipe having an inner lath is made by welding the lath inside the stovepipe.

In addition, alloy furnace tubes used for the cracking furnace equipped with an improved heat transfer element are also commercially available, such as Kellogg Corporation's Plum Blossom tubes, Kubota Corporation's MERT tubes. and SERT pipes (pipes provided with inside twisted plates) of China Petroleum & Chemical Corporation (Sinopec).

In accordance with the present invention, pipes with an improved heat transfer element have a length of 20-80 cm, the number of said pipes is 1-200, and the pipes are distributed in various pipe passages of the entire chimney.

In a second aspect, the present invention provides an anti-coke device manufactured using the above manufacturing method.

In the present invention, the inner surface of the anti-coking device contains an oxide film including chromium and manganese oxide and metal elements.

In the course of research, it has been found that the anti-coke device of the present invention can reduce or suppress the coking and carburization phenomena in the device at high temperature, the reasons for which may be that after contacting the device with a gas with a low oxygen partial pressure, when using the solution according to of the present invention, the Cr element and the Mn element in the device have a higher activity of interacting with oxygen to form oxides than the Fe element and/or the Ni element, so the chromium and manganese elements on the inner surface of the device are slowly oxidized under conditions of low oxygen partial pressure, while the iron element and/or the nickel element are not substantially oxidized; In addition, the partial pressure of oxygen in the atmosphere is low, so the oxidation process is very slow, so that a dense oxide film is formed on the inner surface of the device in-situ, which has a strong adhesion force to the base of the device, the oxide film covers Fe and Ni elements, which have a catalytic effect on coking of said device, so that the content of iron element and/or nickel element on the inner wall of said device is reduced, coking and carburization phenomena of the apparatus are reduced or suppressed, the working cycle of the device is prolonged.

According to the present invention, the total content of the Fe element and/or the Ni element in the oxide film on the inner surface of the device treated by the above method is low, so that the device can suppress catalytic coking in the hydrocarbon cracking process or the aromatization process, prolonging the cycle time of the device, thereby meeting the requirements for long-term operation of the device.

In a third aspect, the present invention provides for the use of the aforementioned anti-coke device in at least one of a cracker, a TLT, and an aromatization reactor.

In the present invention, the pyrolysis feedstock may be gaseous hydrocarbons or liquid hydrocarbons. In particular, gaseous hydrocarbons are at least one hydrocarbon selected from the group consisting of ethane, propane, butane and liquefied petroleum gas; liquid hydrocarbons are at least one hydrocarbon selected from the group consisting of naphtha, gas condensate, hydrocracking tail oil and diesel fuel.

In the present invention, the cracking reaction can be carried out in accordance with the conventional cracking method of the prior art. For example, the cracking temperature is 770-880°C, the ratio of water to oil is 0.3-0.8. Preferably, the naphtha cracking temperature is 830-850°C and the ratio of water to oil is 0.5-0.55.

In the present invention, the aromatization reaction of light hydrocarbons can be carried out in accordance with conventional aromatization reaction conditions of the prior art. Specifically, the reaction temperature is 280-530° C. and the reaction pressure is 0.3 MPa.

The present invention is described below with reference to examples. In the following examples:

the elemental composition of the device was measured by X-ray energy dispersive spectrometry (EDS);

the dew point of the low oxygen partial pressure gas was determined using a detection method using a commercially available dew point meter;

the amount of coke on the device was calculated after the on-line measurement of the concentration of CO and CO ₂ in the decoke gas with an infrared meter and the measurement of the volume of the decoke gas on-line with a wet gas flow meter;

the raw material for pyrolysis was naphtha, which has the following physical properties: distillation interval 32.8-173.8°C and density D ₂₀ 0.7058 g/ml.

In the following examples and comparative examples:

on a self-made laboratory installation, the tube of a small-sized experimental cracking furnace or imitation of the TLT chimney was treated in an atmosphere of low partial pressure of oxygen, as well as evaluation tests of coke formation during the production of ethylene by cracking naphtha at a flow rate of 200 g/h.

The aromatization reaction of light hydrocarbons was carried out in a small-sized experimental reactor treated with an atmosphere with a low partial pressure of oxygen, the HZSM-5 catalyst was used, the feedstock was n-hexane, the aromatization reaction conditions included: volumetric hourly space velocity of the reaction 1 h ^-1 , reaction temperature 500 ° C, hydrogen to oil volume ratio 400:1, reaction pressure 0.3 MPa, reaction time 20 hours.

Example 1

The chimneys of the radiant section of an industrial cracking furnace made of 35Cr45Ni chimney material were subjected to treatment in a low oxygen partial pressure gas atmosphere. The elemental composition (wt. %) of the chimney alloy includes: 32.55 wt. % Cr, 42.60 wt. % Ni, 21.12 wt. % Fe, 0.98 wt. % Mn, 1.41 wt. % Si, 0.64 wt. % Nb, 0.53 wt. % C and 0.17 wt. % other items. Tubes with twisted plates, made as a whole with chimneys, were located axially in the radiation section of the chimneys of the cracking furnace at a distance from each other, the axial length of the twisted plates, twisted by 180°, was a step, the distance between two adjacent twisted plates was 15 steps , the spun plate pipes were 35 cm long, 100 spun plate pipes were distributed in different pipe runs of all the chimneys. The low oxygen partial pressure gas used was a gas mixture of CO and steam, where the dew point of the gas mixture was 5° C., the treatment temperature was 900° C., and the treatment time was 50 hours; an oxide film containing such elements as Cr, Mn, Ni, Fe, O and Si was formed on the inner surface of the walls of the chimneys of the radiation section. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ and the total content of iron and nickel elements was 9.93 wt. % relative to the total weight of the oxide film.

After treatment in a gas atmosphere with a low oxygen partial pressure in the above industrial cracking furnace, a steam cracking reaction of hydrocarbons was carried out. The raw material for cracking was naphtha, which has the following physical properties: distillation interval 32.8-173.8°C and density D ₂₀ 0.7058 g/ml. Cracking conditions were as follows: coil outlet temperature 830° C., water to oil ratio 0.55. The cracking furnace had a run of 230 days.

Example 2

An HP40(Cr25Ni35) tube of a small-sized experimental furnace containing 1 tube with twisted plates was subjected to pre-oxidation at a low partial pressure of oxygen; elemental composition (wt. %) of the chimney alloy included: 25.1 wt. % Cr, 35.2 wt. % Ni, 1.0 wt. % Mn, 1.5 wt. % Si, 0.4 wt. % C, less than 0.03 wt. % P, less than 0.03 wt. % S, the rest Fe (wt %).

As the treatment gas of the low oxygen partial pressure gas atmosphere, a gas mixture of CO and water vapor was used, while the dew point of the gas mixture was 5°C, the flow rate of the low oxygen partial pressure gas was 400 ml/min, the treatment temperature was 950°C, the treatment time was 30 hours; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the furnace tube wall. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ , and the total content of iron and nickel elements was 11.27 wt. % relative to the total weight of the oxide film.

In a tube of a small-scale experimental furnace subjected to the above-described treatment in an atmosphere with a low partial pressure of oxygen, a steam cracking reaction of hydrocarbons was carried out. The cracking feedstock was naphtha with physical properties including a distillation range of 32.8-173.8°C and a D ₂₀ density of 0.7058 g/ml. The cracking conditions were as follows: the cracking temperature was 845°C, the ratio of water to oil was 0.5. The amount of coke in the chimney according to the present invention was reduced by 95.21% compared to the amount of coke in the prior art HP40(Cr25Ni35) chimney that did not contain the heat transfer element and did not undergo low oxygen partial pressure treatment. .

Example 3

The same pipe of the small experimental furnace as in Example 2 was subjected to a pre-oxidation treatment at a low oxygen partial pressure, but the dew point of the gas mixture of CO and steam was 8° C., other treatment conditions were the same as in Example 2; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ and the total content of iron and nickel elements was 12.88 wt. % relative to the total weight of the oxide film.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 2. The amount of coke in the furnace tube in the present invention was reduced by 90, 15% compared to the amount of coke in a prior art HP40(Cr25Ni35) chimney that did not contain an improved heat transfer element and did not undergo a low oxygen partial pressure treatment.

Example 4

The same pipe of the small-scale experimental furnace as in Example 2 was subjected to a pre-oxidation treatment at a low oxygen partial pressure, but the dew point of the gas mixture of CO and steam was 2° C., other treatment conditions were the same as in Example 2; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ and the total content of iron and nickel elements was 13.29 wt. % relative to the total weight of the oxide film.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 2. The amount of coke in the furnace tube in the present description was reduced by 86, 38% compared to the amount of coke in the prior art HP40(Cr25Ni35) chimney that did not contain the heat transfer element and did not undergo low oxygen partial pressure treatment.

Example 5

The same pipe of the small experimental furnace as in Example 2 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the dew point of the gas mixture of CO and steam was 10° C., other treatment conditions were the same as in Example 2; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ and the total content of iron and nickel elements was 14.80 wt. % relative to the total weight of the oxide film.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 2. The amount of coke in the furnace tube in the present description was reduced by 81. 46% compared to the amount of coke in a prior art HP40(Cr25Ni35) chimney that did not contain an improved heat transfer element and did not undergo a low oxygen partial pressure treatment.

Example 6

The same pipe of the small-scale experimental furnace as in Example 2 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the dew point of the gas mixture of CO and steam was 0°C, other treatment conditions were the same as in Example 2; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ and the total content of iron and nickel elements was 15.89 wt. % relative to the total weight of the oxide film.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 2. The amount of coke in the furnace tube in the present description was reduced by 75, 69% compared to the amount of coke in the prior art HP40(Cr25Ni35) chimney that did not contain the heat transfer element and did not undergo low oxygen partial pressure treatment.

Comparative Example 1

The chimneys of the radiant section of an industrial cracking furnace having the same furnace profiles as in Example 1 were used, except that the chimneys were not treated with a low oxygen partial pressure atmosphere. In an industrial cracking furnace, a steam cracking reaction of hydrocarbons was carried out, the cracking feedstock and cracking conditions were the same as in Example 1. The cracking furnace had a duty cycle of 100 days.

Comparative Example 2

Used chimneys of the radiant section of an industrial cracking furnace having the same furnace profiles as in example 1, except that the chimneys of the radiant section did not contain twisted plates and they were not processed in a gas atmosphere with a low partial pressure of oxygen; the cracking furnace had a duty cycle of 55 days.

Example 7

The same pipe of the small experimental furnace as in Example 2 was subjected to a pre-oxidation treatment at a low oxygen partial pressure, but the dew point of the gas mixture of CO and steam was 20° C., other treatment conditions were the same as in Example 2; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ and the total content of iron and nickel elements was 17.62 wt. % relative to the total weight of the oxide film.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 2. The amount of coke in the furnace tube in the present invention was reduced by 33, 90% compared to the amount of coke in a prior art HP40(Cr25Ni35) chimney that did not contain a twisted plate and was not subjected to a low oxygen partial pressure treatment.

Example 8

The same tube of the small experimental furnace as in Example 2 was subjected to a pre-oxidation treatment at a low partial pressure of oxygen, but the dew point of the gas mixture of CO and steam was −10° C., other treatment conditions were the same as in Example 2; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ , and the total content of iron and nickel elements was 19.01 wt. % relative to the total weight of the oxide film.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 2. The amount of coke in the furnace tube in the present invention was reduced by 24, 55% compared to the amount of coke in a prior art HP40(Cr25Ni35) chimney that did not contain a twisted plate and was not subjected to a low oxygen partial pressure treatment.

Example 9

The same tube of the small experimental furnace as in Example 2 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the dew point of the gas mixture of CO and steam was −30° C., other treatment conditions were the same as in Example 2; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ and the total content of iron and nickel elements was 42.39 wt. % relative to the total weight of the oxide film.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 2. The amount of coke in the furnace tube in the present description was reduced by 17, 15% compared to the amount of coke in a prior art HP40(Cr25Ni35) chimney that did not contain a twisted plate and was not subjected to a low oxygen partial pressure treatment.

Example 10

The same pipe of the small experimental furnace as in Example 2 was subjected to a pre-oxidation treatment at a low oxygen partial pressure, but the dew point of the gas mixture of CO and steam was −40° C., other treatment conditions were the same as in Example 2; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ and the total content of iron and nickel elements was 51.72 wt. % relative to the total weight of the oxide film.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 2. The amount of coke in the furnace tube in the present description was reduced by 13, 09% compared to the amount of coke in the prior art HP40(Cr25Ni35) chimney that did not contain a twisted plate and was not subjected to a low oxygen partial pressure treatment.

Example 11

The same pipe of the small experimental furnace as in Example 2 was subjected to a pre-oxidation treatment at a low oxygen partial pressure, but the dew point of the gas mixture of CO and steam was −20° C., other treatment conditions were the same as in Example 2; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ and the total content of iron and nickel elements was 34.96 wt. % relative to the total weight of the oxide film.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 2. The amount of coke in the furnace tube in the present description was reduced by 18, 64% compared to the amount of coke in a prior art HP40(Cr25Ni35) chimney that did not contain a twisted plate and was not subjected to a low oxygen partial pressure treatment.

Example 12

The same pipe of the small experimental furnace as in Example 2 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the dew point of the gas mixture of CO and steam was −15° C., other treatment conditions were the same as in Example 2; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ , and the total content of iron and nickel elements was 26.98 wt. % relative to the total weight of the oxide film.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 2. The amount of coke in the furnace tube in the present description was reduced by 20, 73% compared to the amount of coke in the prior art HP40(Cr25Ni35) chimney that did not contain a twisted plate and did not undergo a low oxygen partial pressure treatment.

Example 13

The same tube of the small experimental furnace as in Example 2 was subjected to a pre-oxidation treatment at a low partial pressure of oxygen, but the dew point of the gas mixture of CO and steam was 15° C., other treatment conditions were the same as in Example 2; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ and the total content of iron and nickel elements was 15.4 wt. % relative to the total weight of the oxide film.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 2. The amount of coke in the furnace tube in the present description was reduced by 65, 88% compared to the amount of coke in a prior art HP40(Cr25Ni35) chimney that did not contain a twisted plate and was not subjected to a low oxygen partial pressure treatment.

Example 14

The same tube of the small experimental furnace as in Example 2 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the dew point of the gas mixture of CO and steam was 30° C., other treatment conditions were the same as in Example 2; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ and the total content of iron and nickel elements was 27.94 wt. % relative to the total weight of the oxide film.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 2. The amount of coke in the furnace tube in the present description was reduced by 30, 23% compared to the amount of coke in the prior art HP40(Cr25Ni35) chimney that did not contain a twisted plate and did not undergo a low oxygen partial pressure treatment.

Example 15

The same pipe of the small experimental furnace as in Example 2 was subjected to a pre-oxidation treatment at a low oxygen partial pressure, but the dew point of the gas mixture of CO and steam was 40° C., other treatment conditions were the same as in Example 2; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ and the total content of iron and nickel elements was 37.41 wt. % relative to the total weight of the oxide film.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 2. The amount of coke in the furnace tube in the present description was reduced by 28, 56% compared to the amount of coke in the prior art HP40(Cr25Ni35) chimney that did not contain a twisted plate and was not subjected to a low oxygen partial pressure treatment.

Comparative Example 3

The same tube of the small experimental furnace as in Example 2 was used, except that the furnace tube did not contain a twisted plate and was not subjected to a low partial pressure treatment; in the pipe of the small experimental furnace, a steam cracking reaction of hydrocarbons was carried out, the cracking feedstock and the cracking conditions were the same as in Example 2. The amount of coke in the pipe of the small experimental furnace was 100%.

Example 16

The pipe of a small-sized experimental furnace was subjected to a pre-oxidation treatment at a low oxygen partial pressure, the elemental composition (wt.%) of the sintered pipe alloy included: 25.1 wt. % Cr, 35.2 wt. % Ni, 1.0 wt. % Mn, 1.5 wt. % Si, 0.4 wt. % C, less than 0.03 wt. % P, less than 0.03 wt. % S and the rest was Fe (wt %).

A gas mixture of H ₂ and H ₂ O was used as the treatment gas of the gas atmosphere with low oxygen partial pressure, while the dew point of the gas mixture was 10°C, the gas flow rate with low oxygen partial pressure was 400 ml/min, the treatment temperature was 950° C, the treatment time was 30 hours; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was MnCr ₂ O ₄ , the content of the iron element and the nickel element in the oxide film was respectively 3.76 wt. % and 4.58 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere, a steam cracking reaction of hydrocarbons was carried out in a tube of a small experimental furnace. The cracking feedstock was a naphtha having physical properties including a distillation range of 32.8-173.8° C. and a D ₂₀ density of 0.7058 g/ml. The cracking conditions were as follows: the cracking temperature was 845° C. and the ratio of water to oil was 0.5. The amount of stovepipe coke in the present specification was reduced by 91.85% compared to the amount of prior art HP40(Cr25Ni35) stovepipe coke that was not subjected to the low oxygen partial pressure treatment.

Example 17

The same pipe of the small experimental furnace as in Example 16 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the dew point of the H ₂ and H ₂ O gas mixture was 20° C., other treatment conditions were the same as in Example 16 ; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The chromium manganese oxide in the oxide film was MnCr ₂ O ₄ , and the contents of the iron element and the nickel element in the oxide film were respectively 5.23 wt. % and 4.87 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 16. The amount of coke in the furnace tube in the present description was reduced by 87, 65% compared to the amount of prior art HP40(Cr25Ni35) stovepipe coke that was not subjected to low oxygen partial pressure treatment.

Example 18

The same pipe of the small experimental furnace as in Example 16 was subjected to pre-oxidation treatment at low oxygen partial pressure, but the dew point of the gas mixture of H ₂ and H ₂ O was 0°C, other treatment conditions were the same as in Example 16 ; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The chromium manganese oxide in the oxide film was MnCr ₂ O ₄ , and the contents of the iron element and the nickel element in the oxide film were respectively 6.48 wt. % and 5.69 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 16. The amount of coke in the furnace tube in the present description was reduced by 80, 65% compared to the amount of prior art HP40(Cr25Ni35) stovepipe coke that was not subjected to low oxygen partial pressure treatment.

Example 19

The same tube of the small experimental furnace as in Example 16 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the dew point of the H ₂ and H ₂ O gas mixture was 40° C., other treatment conditions were the same as in Example 16 ; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The chromium manganese oxide in the oxide film was MnCr ₂ O ₄ , and the contents of the iron element and the nickel element in the oxide film were respectively 11.02 wt. % and 8.28 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 16. The amount of coke in the furnace tube in the present description was reduced by 51, 87% compared to the amount of prior art HP40(Cr25Ni35) stovepipe coke that was not subjected to low oxygen partial pressure treatment.

Example 20

The same pipe of the small-scale experimental furnace as in Example 16 was subjected to a pre-oxidation treatment at a low oxygen partial pressure, but the dew point of the H ₂ and H ₂ O gas mixture was −40° C., other treatment conditions were the same as in Example 16; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The chromium manganese oxide in the oxide film was MnCr ₂ O ₄ , and the contents of the iron element and the nickel element in the oxide film were respectively 15.89 wt. % and 13.95 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 16. The amount of coke in the furnace tube in the present description was reduced by 32, 58% compared to the amount of prior art HP40(Cr25Ni35) stovepipe coke that was not subjected to low oxygen partial pressure treatment.

Comparative Example 4

The same pipe of the small-scale experimental furnace as in Example 16 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the dew point of the H ₂ and H ₂ O gas mixture was 50° C., other treatment conditions were the same as in Example 16 ; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The chromium-manganese oxide in the oxide film was MnCr ₂ O ₄ , and the contents of the iron element and the nickel element in the oxide film were respectively 20.13 wt. % and 19.78 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 16. The amount of coke in the furnace tube in the present description was reduced by 19, 69% compared to the amount of prior art HP40(Cr25Ni35) stovepipe coke that was not subjected to low oxygen partial pressure treatment.

Comparative Example 5

The same pipe of the small-scale experimental furnace as in Example 16 was subjected to a pre-oxidation treatment at a low oxygen partial pressure, but the dew point of the H ₂ and H ₂ O gas mixture was −50° C., other treatment conditions were the same as in Example 16; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The chromium manganese oxide in the oxide film was MnCr ₂ O ₄ , and the contents of the iron element and the nickel element in the oxide film were respectively 25.09 wt. % and 24.95 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 16. The amount of coke in the furnace tube in the present description was reduced by 13, 48% compared to the amount of prior art HP40(Cr25Ni35) stovepipe coke that was not subjected to low oxygen partial pressure treatment.

Comparative Example 6

The same small experimental furnace tube as in Example 16 was used, except that the furnace tube was not subjected to low oxygen partial pressure treatment; in the pipe of the small experimental furnace, a steam cracking reaction of hydrocarbons was carried out, the cracking feedstock and the cracking conditions were the same as in Example 16. The amount of coke in the pipe of the small experimental furnace was 100%.

Example 21

A seamless steel pipe made of 15CrMoG pipe material was cold drawn to form a ϕ14×2 small experimental furnace pipe (i.e., 14mm outer diameter and 2mm wall thickness), the inner surface of the pipe after the machining process was shiny and did not contain oxide scale, the elemental composition (wt.%) of the chimney alloy included: 1.03 wt. % Cr, 0.47 wt. % Mo, 0.58 wt. % Mn, 0.32 wt. % Si, 0.16 wt. % C, 2.13 wt. % O, 96.87 wt. % Fe and 0.24 wt. % other items.

As the treatment gas of the low oxygen partial pressure gas atmosphere, a gas mixture of CO ₂ and CO was used, while the dew point of the gas mixture was 0°C, the flow rate of the low oxygen partial pressure gas was 400 ml/min, the treatment temperature was 900°C, the treatment time was 35 hours; an oxide film containing elements such as Cr, Mn, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn ₂ CrO ₄ , the content of the iron element in the oxide film was 25 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere, a steam cracking reaction of hydrocarbons was carried out in a tube of a small experimental furnace. The cracking conditions were as follows: the cracking temperature was 845° C. and the ratio of water to oil was 0.5. The experimental results showed that the amount of coke in the TLT in the present invention was reduced by 88% compared to the amount of coke in the untreated TLT.

Example 22

The same pipe of the small experimental furnace as in Example 21 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the dew point of the CO ₂ and CO gas mixture was 10° C., other treatment conditions were the same as in Example 21; an oxide film containing elements such as Cr, Mn, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn ₂ CrO ₄ , the content of the iron element in the oxide film was 28 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere in the tubes of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 21. The amount of coke in the TLT in the present invention was reduced by 82% by compared with the amount of coke in the untreated TLT.

Example 23

The same tube of the small experimental furnace as in Example 21 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the dew point of the CO ₂ CO gas mixture was −10° C., other treatment conditions were the same as in Example 21; an oxide film containing elements such as Cr, Mn, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn ₂ CrO ₄ , the content of the iron element in the oxide film was 32 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 21. The amount of coke in the TLT in the present description was reduced by 78% by compared with the amount of coke in the untreated TLT.

Example 24

The same pipe of the small experimental furnace as in Example 21 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the dew point of the CO ₂ and CO gas mixture was 20° C., other treatment conditions were the same as in Example 21; an oxide film containing elements such as Cr, Mn, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn ₂ CrO ₄ , the content of the iron element in the oxide film was 35 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-sized experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 21. The amount of coke in the TLT in the present description was reduced by 51% by compared with the amount of coke in the untreated TLT.

Example 25

The same small experimental furnace tube as in Example 21 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the dew point of the CO ₂ CO gas mixture was −20° C., other treatment conditions were the same as in Example 21; an oxide film containing elements such as Cr, Mn, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn ₂ CrO ₄ , the content of the iron element in the oxide film was 38 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-scale experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 21. The amount of coke in the TLT in the present description was reduced by 40% by compared with the amount of coke in the untreated TLT.

Example 26

The same pipe of the small experimental furnace as in Example 21 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the dew point of the CO ₂ and CO gas mixture was 30° C., other treatment conditions were the same as in Example 21; an oxide film containing elements such as Cr, Mn, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn ₂ CrO ₄ , the content of the iron element in the oxide film was 51 wt. %.

After the above treatment in a low oxygen partial pressure atmosphere in a tube of a small experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 21. The amount of coke in the TLT in the present description was reduced by 21% by compared with the amount of coke in the untreated TLT.

Example 27

The same pipe of the small experimental furnace as in Example 21 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the dew point of the CO ₂ CO gas mixture was −30° C., other treatment conditions were the same as in Example 21; an oxide film containing elements such as Cr, Mn, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn ₂ CrO ₄ , the content of the iron element in the oxide film was 57 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere in a tube of a small-sized experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 21. The amount of coke in the TLT in the present description was reduced by 15% by compared with the amount of coke in the untreated TLT.

Comparative Example 7 The same chimney of a small experimental furnace as that of Example 21 was used, except that the chimney was not subjected to a low oxygen partial pressure treatment; in a tube of a small experimental furnace, a hydrocarbon steam cracking reaction was carried out, the cracking feedstock and cracking conditions were the same as in Example 21. The amount of coke in the TLT was 100%.

Example 28

Treatment of the aromatization reactor with an atmosphere with a low oxygen partial pressure and an evaluation test of the aromatization reaction of light hydrocarbons were carried out on a small-sized experimental reactor with dimensions ϕ35×9 made of 304 stainless steel. The inner surface of the reactor after the mechanical treatment was shiny and did not contain oxide scale (wt %) of the reactor alloy included: 18.05 wt. % Cr, 7.71 wt. % Ni, 1.43 wt. % Mn, 1.34 wt. % Si, 1.91 wt. % C, 2.78 wt. % O, 0.64 wt. % Al and 66.14 wt. % Fe.

The gas mixture of CH ₄ and H ₂ O was used as the treatment gas of the gas atmosphere with low oxygen partial pressure, while the dew point of the gas mixture was 3°C, the gas flow rate with low oxygen partial pressure was 400 ml/min, the treatment temperature was 900° C, the treatment time was 30 hours; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si formed on the inner surface of the reactor wall. The oxide of chromium and manganese in the oxide film was Mn _0.5 Cr _2.5 O ₄ , the total content of the iron element and the nickel element in the oxide film was 14 wt. %.

The experimental results showed that the amount of coke in the aromatization reactor of the present invention was reduced by 86% compared to the untreated aromatization reactor.

Example 29

The same small-sized experimental reactor as in Example 28 was subjected to a pre-oxidation treatment at a low partial pressure of oxygen, but the dew point of the gas mixture of CH ₄ and H ₂ O was 5°C, other treatment conditions were the same as in Example 28; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si formed on the inner surface of the reactor wall. The oxide of chromium and manganese in the oxide film was Mn _0.5 Cr _2.5 O ₄ , the total content of the iron element and the nickel element in the oxide film was 18 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere, in a small-sized experimental reactor, an aromatization reaction of light hydrocarbons was carried out, the reaction feedstock and reaction conditions were the same as in Example 28. The amount of coke in the aromatization reactor in the present description was reduced by 80% by compared to the amount of coke in the untreated aromatization reactor.

Example 30

The same small-sized experimental reactor as in Example 28 was subjected to a pre-oxidation treatment at a low partial pressure of oxygen, but the dew point of the gas mixture of CH ₄ and H ₂ O was -5°C, other treatment conditions were the same as in Example 28 ; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si formed on the inner surface of the reactor wall. The oxide of chromium and manganese in the oxide film was Mn _0.5 Cr _2.5 O ₄ , the total content of the iron element and the nickel element in the oxide film was 21 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere, in a small-sized experimental reactor, an aromatization reaction of light hydrocarbons was carried out, the reaction feedstock and reaction conditions were the same as in Example 28. The amount of coke in the aromatization reactor in the present description was reduced by 76% by compared to the amount of coke in the untreated aromatization reactor.

Example 31

The same small-sized experimental reactor as in Example 28 was subjected to a pre-oxidation treatment at a low partial pressure of oxygen, but the dew point of the gas mixture of CH ₄ and H ₂ O was 15°C, other treatment conditions were the same as in Example 28; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si formed on the inner surface of the reactor wall. The oxide of chromium and manganese in the oxide film was Mn _0.5 Cr _2.5 O ₄ , the total content of the iron element and the nickel element in the oxide film was 24 wt. %.

After the above-described treatment under a low oxygen partial pressure atmosphere, in a small-sized experimental reactor, the aromatization reaction of light hydrocarbons was carried out, the reaction feedstock and reaction conditions were the same as in Example 28. The amount of coke in the aromatization reactor in the present description was reduced by 50% by compared to the amount of coke in the untreated aromatization reactor.

Example 32

The same small-scale experimental reactor as in Example 28 was subjected to a pre-oxidation treatment at a low partial pressure of oxygen, but the dew point of the gas mixture of CH ₄ and H ₂ O was -15°C, other treatment conditions were the same as in Example 28 ; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si formed on the inner surface of the reactor wall. The oxide of chromium and manganese in the oxide film was Mn _0.5 Cr _2.5 O ₄ , the total content of the iron element and the nickel element in the oxide film was 28 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere, a light hydrocarbon aromatization reaction was carried out in a small-scale experimental reactor, the reaction feedstock and reaction conditions were the same as in Example 28. The amount of coke in the aromatization reactor in the present description was reduced by 39% by compared to the amount of coke in the untreated aromatization reactor.

Example 33

The same small experimental reactor as in Example 28 was subjected to a low oxygen partial pressure pre-oxidation treatment, but the CH ₄ and H ₂ O gas mixture dew point was 25° C., other treatment conditions were the same as in Example 28; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si formed on the inner surface of the reactor wall. The oxide of chromium and manganese in the oxide film was Mn _0.5 Cr _2.5 O ₄ , the total content of the iron element and the nickel element in the oxide film was 37 wt. %.

After the above-described treatment under a low oxygen partial pressure atmosphere, in a small-sized experimental reactor, an aromatization reaction of light hydrocarbons was carried out, the reaction feedstock and reaction conditions were the same as in Example 28. The amount of coke in the aromatization reactor in the present description was reduced by 20% by compared to the amount of coke in the untreated aromatization reactor.

Example 34

The same small experimental reactor as in Example 28 was subjected to a pre-oxidation treatment at a low partial pressure of oxygen, but the dew point of the gas mixture of CH ₄ and H ₂ O was -25°C, other treatment conditions were the same as in Example 28 ; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si formed on the inner surface of the reactor wall. The oxide of chromium and manganese in the oxide film was Mn _0.5 Cr _2.5 O ₄ , the total content of the iron element and the nickel element in the oxide film was 45 wt. %.

After the above-described treatment under a low oxygen partial pressure atmosphere, in a small-sized experimental reactor, the aromatization reaction of light hydrocarbons was carried out, the reaction feedstock and reaction conditions were the same as in Example 28. The amount of coke in the aromatization reactor in the present description was reduced by 14% by compared to the amount of coke in the untreated aromatization reactor.

Comparative Example 8

The same small experimental reactor as in Example 28 was used, except that the small experimental reactor was not subjected to the low partial pressure treatment; in a small-sized experimental reactor, an aromatization reaction of light hydrocarbons was carried out, the catalyst used, the reaction raw material, and the reaction conditions were the same as in Example 28. The amount of coke in the aromatization reactor was 100%.

Comparative Example 9

The same small furnace tube as in Example 2 was subjected to a low oxygen partial pressure pre-oxidation treatment, except that the volume percentage of water vapor in the low oxygen partial pressure gas was adjusted to 7.5% (corresponding to the point dew 41°C), other processing conditions were the same as in example 2; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ , the total content of the iron element and the nickel element in the oxide film was 52.85 wt. %.

After the above treatment in a low oxygen partial pressure atmosphere, a steam cracking reaction was carried out in a tube of a small experimental furnace, the cracking feedstock and cracking conditions were the same as in Example 2. The amount of coke in the furnace tube in the present description was reduced by 12.32% by compared with the prior art HP40(Cr25Ni35) chimney that did not contain the heat transfer enhancement element and was not subjected to low oxygen partial pressure treatment.

Comparative Example 10

The same small furnace tube as in Example 14 was subjected to a low oxygen partial pressure pre-oxidation treatment, except that the volume percentage of water vapor in the low oxygen partial pressure gas was adjusted to 4.2% (corresponding to the point dew 30°C), other processing conditions were the same as in example 14; an oxide film containing elements such as Cr, Mn, Ni, Fe, O, and Si was formed on the inner surface of the wall of the chimney. The oxide of chromium and manganese in the oxide film was Mn _1.5 Cr _1.5 O ₄ , the total content of the iron element and the nickel element in the oxide film was 38.08 wt. %.

After the above-described treatment in a low oxygen partial pressure atmosphere, a steam cracking reaction was carried out in a tube of a small experimental furnace, the cracking feedstock and cracking conditions were the same as in Example 14. The amount of coke in the furnace tube in the present invention was reduced by 25.45% by compared with the prior art HP40(Cr25Ni35) chimney that did not contain the heat transfer enhancement element and was not subjected to low oxygen partial pressure treatment.

Claims (32)

1. A method for manufacturing an anti-coke device, comprising contacting a gas with a low partial pressure of oxygen and the device to obtain an anti-coke device having an oxide film on an inner surface; while the dew point of a gas with a low partial pressure of oxygen is in the range from -40°C to 40°C. 2. The method according to claim 1, wherein the device materials comprise an iron element and/or a nickel element, preferably the oxide film comprises chromium manganese oxide and metallic elements which are an iron element and/or a nickel element. 3. The method of claim 2, wherein the dew point of the low oxygen partial pressure gas and the content of metal elements in the oxide film of the anti-coke device satisfy the following relationship: in formula I -0.0039≤a≤-0.0001, 0.001≤b≤0.0294, 0.7269≤c≤0.8577, R ² ≥0.879; where W1 denotes the content of metal elements in the device before the contact reaction, wt. %; W2 denotes the content of metal elements in the oxide film of the device after the contact reaction, wt. %; T is the dew point of a low oxygen partial pressure gas, °C. 4. The method according to any one of paragraphs. 1-3, in which the device is at least one device selected from the group consisting of an alloy chimney, a transfer line heat exchanger - TLT, and a light hydrocarbon aromatization reactor; and/or when the device is an alloy chimney, the total content of metal elements in the alloy chimney before the contact reaction is 25-90 wt. %; and/or when the device is a TLT, the total content of metal elements in the chimneys of the TLT pipe passage before the contact reaction is 76.4-98 wt. %; and/or the aromatization reactor alloy material is at least one material selected from the group consisting of 304, 316, and 321 stainless steel, more preferably the aromatization reactor alloy material is 304 stainless steel, and the total metal content of the aromatization reactor before contact reaction is 68-81 mass. %. 5. The method according to claim 3 or 4, wherein (W1-W2)/W1≥0.281. 6. The method according to claim 3 or 4, wherein (W1-W2)/W1 ≥ 0.583. 7. The method according to any one of paragraphs. 3-6, wherein the dew point of the low oxygen partial pressure gas is in the range of −30° C. to 30° C.; in formula I -0.0005≤a≤-0.0003, 0.001≤b≤0.0092, 0.7355≤c≤0.8308, R ² ≥0.9539. 8. The method according to any one of paragraphs. 3-6, wherein the dew point of the low oxygen partial pressure gas is in the range of −20° C. to 20° C.; in formula I -0.0006≤a≤-0.0003, 0.001≤b≤0.0092, 0.7269≤c≤0.8308, R ² ≥0.879. 9. The method according to any one of paragraphs. 3-6, wherein the dew point of the low oxygen partial pressure gas is in the range of −15° C. to 15° C.; in formula I -0.0006≤a≤-0.0005, 0.0021≤b≤0.0049, 0.7419≤c≤0.8109, R ² ≥0.879. 10. The method according to any one of paragraphs. 3-6, wherein the dew point of the low oxygen partial pressure gas is in the range of −15° C. to 10° C.; in formula I -0.0005≤a≤-0.0003, 0.0021≤b≤0.0053, 0.7419≤c≤0.8138, R ² ≥0.8943. 11. The method according to any one of paragraphs. 3-6, wherein the dew point of the low oxygen partial pressure gas is in the range of 0°C to 10°C; in formula I a=-0.0022, b=0.0238, c=0.7787, R ² =0.9887. 12. The method according to any one of paragraphs. 1-11, wherein the low oxygen partial pressure gas is a gas mixture consisting of CO ₂ and/or H ₂ O and at least one gas selected from the group consisting of CO, CH ₄ , C ₂ H ₆ , C ₃ H ₈ , NH ₃ , H ₂ , N ₂ , Ar, He, air and pyrolysis gas; and/or the low oxygen partial pressure gas is at least one gas mixture selected from a gas mixture of CH ₄ and H ₂ O, a gas mixture of CO ₂ and CO, a gas mixture of H ₂ O and CO, and a gas mixture of H ₂ O, and H ₂ ; and/or the method further includes the step of measuring the dew point of the low oxygen partial pressure gas. 13. The method according to any one of paragraphs. 1-12, wherein the contact reaction conditions include: reaction temperature 400-1100°C; reaction time 5-100 h. 14. The method according to any one of paragraphs. 1-12, wherein the contact reaction conditions include: reaction temperature 600-1100°C; reaction time 5-72 hours. 15. The method according to any one of paragraphs. 1-14, wherein the device is an alloy chimney; and/or the alloy chimney includes an improved heat transfer element fixed in the chimney. 16. The method of claim. 15, wherein the element with improved heat transfer is at least one element selected from the group consisting of a twisted plate, an inner bar and an inner rib. 17. The method according to claim 15 or 16, wherein the pipes with the heat transfer element have a length of 20-80 cm, the number of said pipes is 1-200, and the pipes are distributed in different pipe passages throughout the chimney. 18. Preventing coking device manufactured by the method according to any one of paragraphs. 1-17. 19. Use of the anti-coke device according to claim 18 in at least one of the cracker, the heat exchanger of the conveyance lines, and the aromatization reactor.