阅读说明：本技术 处理烃类裂解炉管内表面的方法 (Method for treating inner surface of hydrocarbon cracking furnace tube ) 是由 王申祥 柳颖 郏景省 王红霞 王国清 张利军 于 2019-10-28 设计创作，主要内容包括：本发明涉及石油化工领域,公开了一种处理烃类裂解炉管内表面的方法,方法包括以下步骤：(1)对烃类裂解炉管内表面进行挤压研磨处理,得到预处理裂解炉管；(2)常压下,在H-2气氛中,对预处理裂解炉管进行热处理,得到热处理裂解炉管；(3)常压下,在处理气体存在下,对热处理裂解炉管的内表面进行氧化处理。该方法能够在烃类裂解炉管内表面形成致密地、厚度更薄且不易剥落的氧化物保护层,使得焦炭在裂管炉内表面的沉积显著减少,并且采用该方法处理得到的氧化物保护层的寿命更长,能够满足裂解炉管长期使用、反复升温等的需求。(The invention relates to the field of petrochemical industryA method for treating the inner surface of a hydrocarbon cracking furnace tube is disclosed, which comprises the following steps: (1) carrying out extrusion grinding treatment on the inner surface of the hydrocarbon cracking furnace tube to obtain a pretreated cracking furnace tube; (2) at normal pressure, in H 2 In the atmosphere, carrying out heat treatment on the pretreatment cracking furnace tube to obtain a heat treatment cracking furnace tube; (3) under normal pressure, the inner surface of the heat treatment cracking furnace tube is oxidized in the presence of treatment gas. The method can form a compact, thinner and difficult-to-peel oxide protective layer on the inner surface of the hydrocarbon cracking furnace tube, so that the deposition of coke on the inner surface of the cracking furnace tube is obviously reduced, the service life of the oxide protective layer obtained by the method is longer, and the requirements of long-term use, repeated temperature rise and the like of the cracking furnace tube can be met.)

1. A method of treating an interior surface of a hydrocarbon cracking furnace tube, wherein the method comprises the steps of:

(1) carrying out extrusion grinding treatment on the inner surface of the hydrocarbon cracking furnace tube to obtain a pretreated cracking furnace tube;

(2) at normal pressure, in H₂In the atmosphere, carrying out heat treatment on the pretreatment cracking furnace tube to obtain a heat treatment cracking furnace tube;

(3) under normal pressure, the inner surface of the heat treatment cracking furnace tube is oxidized in the presence of treatment gas.

2. The method of claim 1, wherein the elemental composition of the cracking furnace tubes comprises: 12-50 wt% of chromium, 20-50 wt% of nickel, 0.2-3 wt% of manganese, 0-3 wt% of silicon, 0.75 wt% of carbon, 0-5 wt% of trace elements and 0-67.05 wt% of iron;

preferably, the elemental composition of the cracking furnace tubes comprises: 15-40 wt% of chromium, 30-50 wt% of nickel, 0.3-2 wt% of manganese, 0-2.5 wt% of silicon, 0.60 wt% of carbon, 0.1-3 wt% of trace elements and 2.4-53.7 wt% of iron;

preferably, the trace element is selected from at least one of niobium, titanium, tungsten, aluminum, and rare earth elements;

preferably, the trace elements are sulphur or/and phosphorus.

3. The method according to claim 1 or 2, wherein the extrusion grinding process is carried out in the manner of: the grinding material is loaded into the cracking furnace tube, and under the action of pressure, the grinding material makes reciprocating motion in the furnace tube so as to realize the extrusion grinding of the inner surface of the cracking furnace tube.

4. The method of any of claims 1-3, wherein the extrusion milling conditions comprise: the pressure of extrusion grinding is 0.5-15MPa, preferably 1-12 MPa; the time for the extrusion-grinding is 5 to 3600 seconds, preferably 10 to 1800 seconds.

5. The method of claim 3 or 4, wherein the abrasive consists of abrasive particles and a liquid carrier;

preferably, the abrasive particles are used in an amount of 10 to 80 wt%, preferably 40 to 80 wt%, relative to the total weight of the abrasive; the amount of the liquid carrier is 20-90 wt%, preferably 20-60 wt%;

preferably, the abrasive grains are selected from at least one of tungsten oxide, cerium oxide, chromium oxide, aluminum oxide, silicon carbide, boron carbide, and diamond;

preferably, the grain size of the abrasive grains is 40-1000 meshes, preferably 200-1000 meshes;

preferably, the liquid carrier is selected from one or more of vaseline, paraffin, turpentine and oleic acid.

6. The method according to any one of claims 1 to 5, wherein the heat treatment step is performed by sequentially performing a first temperature raising treatment, a temperature lowering treatment, and a second temperature raising treatment;

preferably, the conditions of the first temperature raising process include: heating the pretreatment cracking furnace tube to 1100-1200 ℃ at the heating rate of 20-150 ℃/h; the cooling treatment conditions comprise: cooling the pretreatment cracking furnace tube to 300-500 ℃ at a cooling rate of 20-150 ℃/h; the conditions of the second temperature raising treatment include: heating the pretreatment cracking furnace tube to 800-1100 ℃ at the heating rate of 20-150 ℃/h;

more preferably, the conditions of the first temperature raising process include: heating the pretreatment cracking furnace tube to 1120-1170 ℃ at the temperature rise rate of 30-100 ℃/h; the cooling treatment conditions comprise: cooling the pretreatment cracking furnace tube to 400-500 ℃ at a cooling rate of 30-100 ℃/h; the conditions of the second temperature raising treatment include: the temperature of the pretreatment cracking furnace tube is raised to 850-1050 ℃ at the temperature raising rate of 30-100 ℃/h.

7. The method of any one of claims 1-6, wherein the treatment gas is a low oxygen partial pressure gas;

preferably, the low oxygen partial pressure gas comprises hydrogen and water vapor, optionally, the low oxygen partial pressure gas further comprises at least one of nitrogen, argon and helium.

8. The method according to any one of claims 1 to 7, wherein the oxidation treatment comprises a first oxidation treatment and a second oxidation treatment;

preferably, the conditions of the first oxidation treatment include: in the low oxygen partial pressure gas, H₂Molar ratio to water vapor 2X 10³-1×10⁷Preferably 4X 10³-1×10⁶(ii) a The first oxidation treatment temperature is 800-1100 ℃, and preferably 850-1050 ℃; the first oxidation treatment time is 5 to 50 hours, preferably 10 to 30 hours;

preferably, the conditions of the second oxidation treatment include: in the low oxygen partial pressure gas, H₂The molar ratio to the water vapor is 80-200, preferably 100-150; the second oxidation treatment temperature is 800-1100 ℃, and preferably 850-1050 ℃; the second oxidation treatment time is 5 to 50 hours, preferably 20 to 40 hours.

9. A hydrocarbon cracking furnace tube treated according to the method of any one of claims 1 to 8.

10. The hydrocarbon cracking furnace tube of claim 9, wherein an oxide protective layer is formed on the inner specific surface of the hydrocarbon cracking furnace tube;

preferably, the thickness of the protective layer is 0.1 to 10 μm, preferably 0.5 to 5 μm.

Technical Field

The invention relates to the field of petrochemical industry, in particular to a method for treating the inner surface of a hydrocarbon cracking furnace tube.

Background

Ethylene is one of the major products of the petrochemical industry, and trienes (ethylene, propylene, butylene) and triphenyl (benzene, toluene, xylene) produced by ethylene plants are the basic feedstocks of the petrochemical industry. The ethylene yield is a main mark for measuring the development level of the national petrochemical industry. The current method for producing ethylene is mainly based on the tubular furnace cracking technology, and is widely applied worldwide.

Coking of the radiant section furnace tube of the tube furnace cracking furnace is a main factor for limiting the production period of the tube furnace cracking furnace. When ethylene is produced by high-temperature thermal cracking of hydrocarbons, coke is formed along with the inner surface of the radiant section furnace tube of the tubular cracking furnace. The coke formed under the high-temperature condition is a poor thermal conductor, so that the heat transfer resistance of the furnace tube is increased, the inner diameter of the furnace tube is reduced, the surface temperature of the outer wall of the furnace tube is increased, the pressure drop of fluid in the furnace tube is increased, and even the pipeline is blocked, thereby influencing the operation. When the surface temperature of the furnace tube reaches the highest temperature which can be borne by the material of the furnace tube or the pressure drop reaches the maximum pressure drop of the cracking furnace, the cracking furnace must be decoked, and the coke in the tube can be removed before the production is carried out again. The increase in the number of decoking times brings unfavorable factors to the ethylene and byproduct yield, fuel consumption, furnace tube life, and the like.

At present, the anti-coking coating is mainly prepared at home and abroad by externally applying elements such as plasma spraying, sintering, magnetron sputtering, chemical (or physical) vapor deposition and the like, so as to inhibit coking of a furnace tube at a radiation section of a cracking furnace. However, under the cracking conditions of high temperature, high carbon potential and strong scouring, the service life of the coating cannot meet the requirement of long-term industrial use. Of course, a certain amount of aluminum element can be added into the furnace tube alloy, and then the furnace tube is oxidized in the air to form Al on the surface of the furnace tube in situ₂O₃Thin films, but the high temperature strength of the higher aluminum content furnace tubes is reduced.

From 1997 to 2006, Nova, canada, incorporated, disclosed a number of patents for pre-oxidizing the inside surface of cracking furnace tubes, e.g., US5630887A, US6824883B1, US7156979B2, US6436202B2, US2004265604a1, US2005077210a1, US2006086431a1, etc., disclose the formation of manganese chromium spinel MnCr on the inside surface of the tubes after pre-oxidation₂O₄And a protective layer.

CN101565807A discloses a method for treating a high-temperature alloy furnace tube, which comprises the following steps: controlling the pressure of low-oxygen partial pressure gas to be 0-3 atmospheric pressures, introducing the gas into an atmosphere furnace provided with a high-temperature alloy furnace tube, heating to 600-; wherein the low oxygen partial pressure gas comprises H₂And CO, and water vapor accounting for 0.17-2% of the volume fraction of the gas with low oxygen partial pressure. CN101565808A discloses a method for treating a high temperature alloy furnace tube, which comprises the following steps: controlling the pressure of the low-oxygen partial pressure gas to be 0-3 atmospheric pressures, passing through ammonia water, introducing into an atmosphere furnace provided with a high-temperature alloy furnace tube, heating to 600-And forming an oxidation protection layer on the surface of the gold furnace tube to obtain the treated high-temperature alloy furnace tube.

The above patents all obtain manganese chromium spinel by slowly oxidizing the inner wall of a new furnace tube by low-oxygen partial pressure gas formed by mixed gas of hydrogen and water vapor at high temperature, and they are different in that the low-oxygen partial pressure gas in Nova technology has lower water vapor content.

The method for forming the manganese-chromium spinel oxide layer covering Fe and Ni elements through low-oxygen partial pressure preoxidation is very suitable for the widely adopted radiation section furnace tube materials (such as HK40, HP40 and 3545) and cracking working conditions at present. However, the oxide layer has a short service life, and cannot completely meet the requirements of cracking conditions such as long-term use, repeated temperature rise and drop and the like.

Disclosure of Invention

The invention aims to overcome the problem of coking in a hydrocarbon cracking furnace tube in the prior art, and provides a method for treating the inner surface of the hydrocarbon cracking furnace tube, which can form a compact and thinner oxide protective layer which is difficult to peel off on the inner surface of the hydrocarbon cracking furnace tube, so that the deposition of coke on the inner surface of the cracking furnace tube is obviously reduced, and the oxide protective layer treated by the method has longer service life and can meet the requirements of long-term use, repeated temperature rise and the like of the cracking furnace tube.

To achieve the above object, a first aspect of the present invention provides a method for treating an inner surface of a hydrocarbon cracking furnace tube, wherein the method comprises the steps of:

(1) carrying out extrusion grinding treatment on the inner surface of the hydrocarbon cracking furnace tube to obtain a pretreated cracking furnace tube;

(2) at normal pressure, in H₂In the atmosphere, carrying out heat treatment on the pretreatment cracking furnace tube to obtain a heat treatment cracking furnace tube;

(3) under normal pressure, the inner surface of the heat treatment cracking furnace tube is oxidized in the presence of treatment gas.

In a second aspect, the invention provides a hydrocarbon cracking furnace tube treated by the method of the invention.

Through the technical scheme, the method for treating the inner surface of the hydrocarbon cracking furnace tube has the following beneficial effects:

according to the method, the step of extruding and grinding the cracking furnace tube is introduced before the oxidation treatment, so that a large number of brittle layers and microscopic defects on the inner surface of the furnace tube are removed, the organization structure of the inner surface of the furnace tube is more compact, the crystal grains are refined, the surface roughness can be greatly improved, and further, an oxide protective layer obtained by oxidation is more compact and difficult to peel off, and the anti-coking effect is better.

Further, the invention puts the pretreatment cracking furnace tube in H₂And carrying out heat treatment of secondary heating and primary cooling in the atmosphere, wherein Cr and Mn elements in the furnace tube alloy can absorb oxygen atoms more easily after the heat treatment, and the formed spinel protective layer is more uniform and compact.

Furthermore, the method adopts a mode of two times of oxidation treatment to carry out oxidation treatment on the cracking furnace tube, and the oxidation treatment is carried out in the presence of low-oxygen partial pressure treatment gas, so that the ratio of Mn/Cr in the formed manganese-chromium oxide is higher, a stable spinel structure is formed, Fe and Ni elements are more easily covered, and the anti-coking effect of the processed cracking furnace tube is further improved.

The method can be used for laboratory-scale cracking furnace tubes or industrial cracking furnace tubes, and has excellent effect. The method can reduce the coke deposited on the inner wall of the cracking furnace tube by more than 70 percent, and the formed oxide protective layer has lasting effect and can keep the anti-coking effect for a plurality of periods.

Detailed Description

The endpoints of the ranges and any values disclosed herein are not limited to the precise range or value, and such ranges or values should be understood to encompass values close to those ranges or values. For ranges of values, between the endpoints of each of the ranges and the individual points, and between the individual points may be combined with each other to give one or more new ranges of values, and these ranges of values should be considered as specifically disclosed herein.

In a first aspect, the present invention provides a method of treating an interior surface of a hydrocarbon cracking furnace tube, wherein the method comprises the steps of:

(1) carrying out extrusion grinding treatment on the inner surface of the hydrocarbon cracking furnace tube to obtain a pretreated cracking furnace tube;

(2) at normal pressure, in H₂In the atmosphere, carrying out heat treatment on the pretreatment cracking furnace tube to obtain a heat treatment cracking furnace tube;

(3) under normal pressure, the inner surface of the heat treatment cracking furnace tube is oxidized in the presence of treatment gas.

According to the invention, before the cracking furnace tube is oxidized, the cracking furnace tube is subjected to extrusion grinding treatment, under the action of the extrusion grinding, a large number of brittle layers and microscopic defects on the inner surface of the furnace tube are removed, so that the brittle layers and the microscopic defects on the inner surface of the furnace tube are removed, the tissue structure of the inner surface of the furnace tube is tighter, the crystal grains are refined, the surface roughness can be greatly improved, and further, an oxide protective layer obtained by oxidation is more compact and difficult to peel off, and the anti-coking effect is better.

Further, the invention puts the pretreatment cracking furnace tube in H₂And carrying out heat treatment of secondary heating and primary cooling in the atmosphere, wherein Cr and Mn elements in the furnace tube alloy can absorb oxygen atoms more easily after the heat treatment, and the formed spinel protective layer is more uniform and compact.

Furthermore, after the cracking furnace tube after extrusion grinding treatment and heat treatment is subjected to oxidation treatment, an oxide protective layer which is compact, thinner and not easy to peel can be obtained, the oxide protective layer can still maintain excellent bonding force with the inner surface of the furnace tube in the processes of long-term use, repeated temperature rise and the like of the cracking furnace tube, and the cracking furnace tube is ensured to still have excellent anti-coking capability in the processes of long-term use, repeated temperature rise and the like.

The method can be suitable for the currently adopted radiant section furnace pipe materials such as HK40, HP40 and 3545 and cracking working condition.

Specifically, the cracking furnace tube comprises the following element components: 12 to 50 weight percent of chromium, 20 to 50 weight percent of nickel, 0.2 to 3 weight percent of manganese, 0 to 3 weight percent of silicon, 0.75 weight percent of carbon, 0 to 5 weight percent of trace elements and trace elements, and 0 to 67.05 weight percent of iron.

Still further, the elemental composition of the cracking furnace tubes comprises: 15-40 wt% of chromium, 30-50 wt% of nickel, 0.3-2 wt% of manganese, 0-2.5 wt% of silicon, 0.60 wt% of carbon, 0.1-3 wt% of trace elements and 2.4-53.7 wt% of iron;

according to the invention, the trace elements are selected from at least one of niobium, titanium, tungsten, aluminium and rare earth elements.

According to the invention, the trace elements are sulphur or/and phosphorus.

According to the invention, the extrusion grinding process is carried out in the following manner: the grinding material is loaded into the cracking furnace tube, and under the action of pressure, the grinding material makes reciprocating motion in the furnace tube so as to realize the extrusion grinding of the inner surface of the cracking furnace tube.

In the invention, the extrusion grinding treatment comprises the following specific steps:

the grinding material is loaded in the furnace tube, the furnace tube is fixed on the machine tool, the upper grinding cylinder and the lower grinding cylinder are coaxially opposite, and the furnace tube is clamped between the upper cylinder body and the lower cylinder body by an oil pressure device. When the oil pressure piston of the lower cylinder body extrudes the grinding materials upwards, the grinding materials are forced to flow through the inner cavity of the furnace tube and enter the upper grinding cylinder. When the lower oil cylinder piston reaches the top dead center, the upper oil cylinder piston starts to downwards extrude the grinding materials, so that the grinding materials return to the lower grinding cylinder along the original channel. When the upper cylinder piston reaches the bottom dead center, the lower cylinder piston starts to move upwards again. The grinding material reciprocates in the channel and acts on the wall of the furnace tube under certain pressure, so that the grinding material can grind the inner wall of the furnace tube.

In the invention, the method further comprises the step of cleaning the pretreatment cracking furnace tube obtained by the extrusion grinding treatment.

The cleaning may be carried out in a manner conventional in the art, such as ultrasonic cleaning or the like. The solvent used for washing may be a solvent conventional in the art, such as water, ethanol, etc.

In the invention, the loading amount of the grinding material can be adjusted according to different furnace tubes.

According to the invention, the conditions of the extrusion grinding include: the pressure of extrusion grinding is 0.5-15MPa, and the time of extrusion grinding is 5-3600 seconds.

In the invention, in order to ensure the treatment effect on the inner surface of the cracking furnace tube, the inventor researches the conditions of extrusion grinding treatment, and the research shows that when the extrusion grinding pressure and time meet the requirements in the range, the extrusion grinding treatment can remove a large amount of brittle layers and micro defects on the inner surface of the furnace tube, the organization structure of the inner surface of the furnace tube becomes tighter, the crystal grains are refined, the surface roughness can be greatly improved, and the formation of a subsequent compact oxide protective layer is facilitated.

Furthermore, when the extrusion grinding pressure is 1-12MPa and the extrusion grinding time is 10-1800 seconds, the treatment effect on the inner surface of the cracking furnace tube is more excellent.

According to the invention, the abrasive consists of abrasive grains and a liquid carrier.

According to the invention, the abrasive grains are used in an amount of 10 to 80% by weight, preferably 40 to 80% by weight, relative to the total weight of the abrasive; the amount of the liquid carrier is 20 to 90 wt%, preferably 20 to 60 wt%.

According to the present invention, the abrasive grains are selected from at least one of tungsten oxide, cerium oxide, chromium oxide, aluminum oxide, silicon carbide, boron carbide, and diamond.

According to the invention, the grain size of the abrasive particles is 40-1000 meshes, preferably 200-1000 meshes.

According to the invention, the liquid carrier is selected from one or more of vaseline, paraffin, turpentine and oleic acid.

According to the present invention, the heat treatment step sequentially performs a first temperature increase treatment, a temperature decrease treatment, and a second temperature increase treatment.

In the present invention, the conditions of the first temperature raising process include: heating the pretreatment cracking furnace tube to 1100-1200 ℃ at the heating rate of 20-150 ℃/h; the cooling treatment conditions comprise: cooling the pretreatment cracking furnace tube to 300-500 ℃ at a cooling rate of 20-150 ℃/h; the conditions of the second temperature raising treatment include: heating the pretreatment cracking furnace tube to 800-1100 ℃ at the heating rate of 20-150 ℃/h;

the inventor researches and discovers that Cr and Mn elements in the cracking furnace tube alloy can more easily absorb oxygen atoms through heat treatment after the pretreatment cracking furnace tube is subjected to heat treatment by adopting the program, and a formed spinel protective layer is more uniform and compact.

More preferably, the conditions of the first temperature raising process include: heating the pretreatment cracking furnace tube to 1120-1170 ℃ at the temperature rise rate of 30-100 ℃/h; the cooling treatment conditions comprise: cooling the pretreatment cracking furnace tube to 400-500 ℃ at a cooling rate of 30-100 ℃/h; the conditions of the second temperature raising treatment include: the temperature of the pretreatment cracking furnace tube is raised to 850-1050 ℃ at the temperature raising rate of 30-100 ℃/h.

According to the invention, the treatment gas is a low oxygen partial pressure gas.

According to the present invention, the low oxygen partial pressure gas comprises hydrogen and water vapor, optionally, the low oxygen partial pressure gas further comprises at least one of nitrogen, argon and helium.

In the present invention, the low oxygen partial pressure gas is a gas containing a very small amount of oxygen, and the oxygen content in the low oxygen partial pressure gas is adjusted by the molar ratio of hydrogen to water vapor in the low oxygen partial pressure gas and the temperature of the low oxygen partial pressure gas.

According to the present invention, the oxidation treatment includes a first oxidation treatment and a second oxidation treatment.

In the invention, in order to further improve the anti-coking effect of the treated cracking furnace tube, the cracking furnace tube is subjected to oxidation treatment in a secondary oxidation treatment mode, and the oxidation treatment is carried out in the presence of low-oxygen partial-pressure treatment gas, so that the Mn/Cr ratio in the formed manganese-chromium oxide is higher, a stable spinel structure is formed, Fe and Ni elements are easier to cover, and the anti-coking effect of the treated cracking furnace tube is further improved.

The inventors have studied the conditions of the first oxidation treatment and the second oxidation treatment, and have found that, in the first oxidation treatment process: in the case of low oxygen partial pressure gas, H₂Molar ratio to water vapor 2X 10³-1×10⁷(ii) a First oxygenThe treatment temperature is 800-₂And MnO, wherein SiO₂Has the function of a diffusion barrier, can prevent Cr, Fe and Ni elements in the alloy from diffusing to the surface layer and oxygen elements in the atmosphere from diffusing inwards to a certain extent, and improves the anti-coking effect of the cracking furnace tube.

At the same time, in the second oxidation treatment, the low oxygen partial pressure gas contains H₂The molar ratio of the catalyst to the water vapor is 80-200, the second oxidation treatment temperature is 800-1100 ℃, and the second treatment temperature is 5-50 hours. At this time, under the oxygen partial pressure, the inventors found that spinel containing manganese and chromium and SiO grow on the inner surface of the furnace tube₂The inventors speculated that the reason for this is that the Cr element in the furnace tube can penetrate through the SiO layer under the second oxidation treatment condition₂The diffusion barrier is diffused to the surface layer to be oxidized to form Cr₂O₃。

Manganese chromium spinel and SiO generated on the inner surface of the furnace tube by the first oxidation treatment and the second oxidation treatment₂The main oxide protective layer covers Fe and Ni elements, so that catalytic coking in the hydrocarbon cracking process can be inhibited, and the spinel coating is very compact, so that carbon elements can be prevented from permeating into a furnace tube matrix, and the anti-coking effect of the cracking furnace tube is remarkably improved.

Further, in the first oxidation treatment, the oxygen partial pressure of the gas containing oxygen is low, H₂The molar ratio of the water vapor to the water vapor is 4X 10³-1×10⁶The first oxidation treatment temperature is 850-; in the second oxidation treatment, in a gas having a low oxygen partial pressure, H₂The mol ratio of the protective agent to water vapor is 100-150, the second oxidation treatment temperature is 850-1050 ℃, and the second oxidation treatment time is 20-40 hours, so that an oxide protective layer with a more compact structure and less possibility of falling off can be obtained, and further, cracking with an excellent anti-coking effect can be obtainedAnd (4) decomposing the furnace tube.

In a second aspect, the invention provides a hydrocarbon cracking furnace tube treated by the method of the invention.

According to the invention, an oxide protective layer is formed on the inner specific surface of the hydrocarbon cracking furnace tube.

According to the invention, the thickness of the protective layer is 0.1 to 10 μm, preferably 0.5 to 5 μm.

The present invention will be described in detail below by way of examples.

The composition of the inner surface of the cracking furnace tube is analyzed by an X-ray Energy Dispersive Spectrometer (EDS for short).

The thickness of the oxide protective layer can be determined by measuring the cross section of the inner surface of the cracking furnace by using an XL-30 field emission environment Scanning Electron Microscope (SEM) of FEI company, and the acceleration voltage is 15 kv.

The cracking material was an industrial naphtha, and its physical properties are shown in table 1;

examples and comparative examples all other materials were commercially available.

TABLE 1

Test example

The furnace tube is used for cracking coking evaluation test by taking naphtha as cracking raw material on a laboratory device with 200g/h feeding amount. After cracking, air is used for burning, and CO in the burnt gas are burnt₂The concentration is measured on line by an infrared instrument, the volume of the scorching gas is recorded on line by a wet flowmeter, and finally the carbon content in the scorching gas is calculated to be the coking content in the cracking process.

The cleavage assay conditions were as follows:

raw materials: industrial naphtha (physical properties are shown in Table 1)

Cracking time: 2 hours; temperature of the preheater: 600 ℃; temperature of the cracking furnace: 850 ℃; water-oil ratio: 0.5; residence time: 0.35 second.

Comparative example 1

By a dimension ofThe material is 3545 nickel-chromium alloy new furnace tube, and the furnace tube does not contain any coating. The inner surface of the furnace tube after mechanical processing is bright and has no oxide skin, the surface composition of the furnace tube is analyzed, and the results are shown in Table 2. The empty furnace tubes were subjected to 10 cycles of cracking and scorching according to the cracking conditions, and the coke amount for different cracking times is shown in Table 3.

Comparative example 2

Adopting a new furnace tube with the same size and material as the comparative example 1, preparing a spinel coating on the inner surface of the furnace tube according to the method of US6436202B2, and enabling the furnace tube to be coated with H with the water vapor volume percentage of 0.1%₂-H₂And keeping the temperature at 650 ℃ for 10 hours under the atmosphere of low oxygen partial pressure, then raising the temperature to 950 ℃, and keeping the temperature for 20 hours. After cooling, the composition of the inner surface of the furnace tube was analyzed and the thickness of the oxide layer on the inner surface was measured, the results are shown in Table 2.

The furnace tube was subjected to 10 cycles of cracking and scorching using the cracking conditions described in the test examples, and the coke quantities for different cracking times are shown in Table 3.

Comparative example 3

Adopting a new furnace tube with the same size and material as the comparative example 1, preparing a spinel coating on the inner surface of the furnace tube according to the method of CN101565807A, and leading the furnace tube to be coated with H with the water vapor volume percentage of 1.5 percent₂-H₂Keeping the temperature of 900 ℃ for 30 hours under the atmosphere of O low oxygen partial pressure. After cooling, the composition of the inner surface of the furnace tube was analyzed and the thickness of the oxide layer on the inner surface was measured, the results are shown in Table 2.

The furnace tube was subjected to 10 cycles of cracking and scorching using the cracking conditions described in the test examples, and the coke quantities for different cracking times are shown in Table 3.

Comparative example 4

A new furnace tube with the same size and material as the comparative example 1 was used, and extrusion-grinding was performed according to the following conditions: (1) abrasive formulation, 15% alumina (800 mesh) + 35% boron carbide (400 mesh) + 35% paraffin + 15% oleic acid; (2) extrusion grinding pressure, 5 MPa; (3) extrusion milling time, 60 seconds. The composition of the inner surface of the furnace tube was analyzed after extrusion grinding, and the thickness of the oxide layer on the inner surface was measured, the results are shown in Table 2. The furnace tube was subjected to 10 cycles of cracking and scorching using the cracking conditions described in the test examples, and the coke quantities for different cracking times are shown in Table 3.

Comparative example 5

A new furnace tube of the same size and material as in comparative example 1 was used and treated in a two-stage low oxygen partial pressure process. In the first stage, the furnace tube is in H₂H with a molar ratio to steam of 3000₂-H₂Keeping the temperature of 1000 ℃ for 10 hours under the atmosphere of O low oxygen partial pressure; the second stage, let the furnace tube in H₂H with a molar ratio to steam of 100₂-H₂O, keeping the temperature at 950 ℃ for 30 hours under the atmosphere of low oxygen partial pressure. After cooling, the composition of the inner surface of the furnace tube was analyzed and the thickness of the oxide layer on the inner surface was measured, the results are shown in Table 2.

The furnace tube was subjected to 10 cycles of cracking and scorching using the cracking conditions described in the test examples, and the coke quantities for different cracking times are shown in Table 3.

Comparative example 6

A new furnace tube of the same size and material as in comparative example 1 was used, and the coating was prepared according to the method of the invention. The tube was first extrusion milled as in comparative example 4 and then treated as a two stage low oxygen partial pressure process. In the first stage, the furnace tube is in H₂H with a molar ratio to steam of 4000₂-H₂Keeping the temperature of 1000 ℃ for 10 hours under the atmosphere of O low oxygen partial pressure; the second stage, let the furnace tube in H₂H with a molar ratio to steam of 100₂-H₂O, keeping the temperature at 950 ℃ for 30 hours under the atmosphere of low oxygen partial pressure. After cooling, the composition of the inner surface of the furnace tube was analyzed and the thickness of the oxide layer on the inner surface was measured, the results are shown in Table 2.

The furnace tube was subjected to 10 cycles of cracking and scorching using the cracking conditions described in the test examples, and the coke quantities for different cracking times are shown in Table 3.

Example 1

A new furnace tube of the same size and material as in comparative example 1 was used, and the coating was prepared according to the method of the invention. The tube was first extrusion-milled according to the method of comparative example 4, and thenThe furnace tube is in pure H₂Heating the cracking furnace tube to 1150 ℃ at the heating rate of 40 ℃/h in the atmosphere of normal pressure, and then cooling the furnace tube to 450 ℃ at the cooling rate of 40 ℃/h; then the temperature of the furnace tube is raised to 1000 ℃ at the heating rate of 60 ℃/h, and finally the furnace tube is treated according to a two-stage low oxygen partial pressure method. In the first stage, the furnace tube is in H₂H with a molar ratio to steam of 4000₂-H₂Keeping the temperature of 1000 ℃ for 10 hours under the atmosphere of O low oxygen partial pressure; the second stage, let the furnace tube in H₂H with a molar ratio to steam of 100₂-H₂O, keeping the temperature at 950 ℃ for 30 hours under the atmosphere of low oxygen partial pressure. After cooling, the composition of the inner surface of the furnace tube was analyzed and the thickness of the oxide layer on the inner surface was measured, the results are shown in Table 2.

The furnace tube was subjected to 10 cycles of cracking and scorching using the cracking conditions described in the test examples, and the coke quantities for different cracking times are shown in Table 3.

Example 2

A new furnace tube of the same size and material as in comparative example 1 was used, and the coating was prepared according to the method of the invention. Firstly, the furnace tube is extruded and ground according to the following conditions: (1) abrasive formulation, 83% silicon carbide (400 mesh) + 17% petrolatum; (2) extrusion grinding pressure is 2 MPa; (3) extrusion milling time, 500 seconds. Then let the furnace tube in pure H₂Heating the cracking furnace tube to 1120 ℃ at the heating rate of 60 ℃/h in the atmosphere of normal pressure, and then cooling the furnace tube to 400 ℃ at the cooling rate of 60 ℃/h; and then the temperature of the furnace tube is increased to 1050 ℃ at the heating rate of 50 ℃/h, and finally the furnace tube is treated according to a two-stage low oxygen partial pressure method. In the first stage, the furnace tube is in H₂H with a molar ratio to steam of 4000₂-H₂Keeping the temperature at 1050 ℃ for 20 hours under the atmosphere of O low oxygen partial pressure; the second stage, let the furnace tube in H₂H in a molar ratio of 120 with respect to water vapor₂-H₂O atmosphere of low oxygen partial pressure (nitrogen gas accounts for 60% of the total gas volume) at 900 ℃ for 40 hours. After cooling, the composition of the inner surface of the furnace tube was analyzed and the thickness of the oxide layer on the inner surface was measured, the results are shown in Table 2.

The furnace tube was subjected to 10 cycles of cracking and scorching using the cracking conditions described in the test examples, and the coke quantities for different cracking times are shown in Table 3.

Example 3

A new furnace tube of the same size and material as in comparative example 1 was used, and the coating was prepared according to the method of the invention. Firstly, the furnace tube is extruded and ground according to the following conditions: (1) abrasive formulation, 83% silicon carbide (400 mesh) + 17% petrolatum; (2) extrusion grinding pressure is 2 MPa; (3) extrusion milling time, 500 seconds. Then let the furnace tube in pure H₂Heating a cracking furnace tube to 1160 ℃ at a heating rate of 80 ℃/h in an atmosphere of normal pressure, and then cooling the furnace tube to 480 ℃ at a cooling rate of 100 ℃/h; then the temperature of the furnace tube is increased to 900 ℃ at the heating rate of 120 ℃/h, and the furnace tube is treated according to a two-stage low oxygen partial pressure method. In the first stage, the furnace tube is in H₂H with a molar ratio to steam of 5000₂-H₂Keeping the temperature of 900 ℃ for 10 hours under the atmosphere of O low oxygen partial pressure; the second stage, let the furnace tube in H₂H with a molar ratio to steam of 150₂-H₂O low oxygen partial pressure atmosphere (where helium is 50% of the total gas volume) at 1000 ℃ for 40 hours. After cooling, the composition of the inner surface of the furnace tube was analyzed and the thickness of the oxide layer on the inner surface was measured, the results are shown in Table 2.

The furnace tube was subjected to 10 cycles of cracking and scorching using the cracking conditions described in the test examples, and the coke quantities for different cracking times are shown in Table 3.

TABLE 2

TABLE 3

From table 2, we can find that the contents of Cr and Mn elements on the inner surfaces of the furnace tubes of the treated comparative examples and examples are significantly increased, while the contents of Fe and Ni elements having catalytic coking activity are greatly reduced, and are lower in the examples compared with the comparative examples.

From Table 3 we can see that the average coke charge for 10 cracks in comparative example 1 (blank value) is 1.53 grams; the coking amounts of the first times in the comparative examples 2, 3 and 5 are very low, but the coking amounts gradually increase along with the increase of the cracking and burning times; the coke amount in examples 1, 2 and 3 was low, and was reduced by 85% or more on average from the blank value, and the coke amount did not tend to increase significantly as the cracking and burning times increased.

Comparative example 7

The material of the furnace tube in the comparative example 1 was changed to HP40, the other conditions were unchanged, the composition of the surface of the furnace tube is shown in Table 4, and the amount of coking is shown in Table 5.

Comparative example 8

The material of the furnace tube in the comparative example 2 is changed into HP40, other conditions are not changed, the surface composition of the treated furnace tube is shown in Table 4, and the coking amount is shown in Table 5.

Comparative example 9

The material of the furnace tube in the comparative example 3 was changed to HP40, the other conditions were unchanged, the composition of the surface of the furnace tube is shown in Table 4, and the amount of coking is shown in Table 5.

Comparative example 10

The material of the furnace tube in the comparative example 4 was changed to HP40, the other conditions were unchanged, the composition of the surface of the furnace tube is shown in Table 4, and the amount of coking is shown in Table 5.

Comparative example 11

The material of the furnace tube in the comparative example 5 was changed to HP40, the other conditions were unchanged, the composition of the surface of the furnace tube is shown in Table 4, and the amount of coking is shown in Table 5.

Comparative example 12

The material of the furnace tube in the comparative example 6 was changed to HP40, the other conditions were unchanged, the composition of the surface of the furnace tube is shown in Table 4, and the amount of coking is shown in Table 5.

Example 4

The material of the furnace tube in example 1 was changed to HP40, the other conditions were unchanged, the composition of the treated furnace tube surface is shown in Table 4, and the amount of coking is shown in Table 5.

Example 5

The material of the furnace tube in example 2 was changed to HP40, the other conditions were unchanged, the composition of the treated furnace tube surface is shown in Table 4, and the coking amount is shown in Table 5.

Example 6

The material of the furnace tube in example 3 was changed to HP40, the other conditions were unchanged, the composition of the treated furnace tube surface is shown in Table 4, and the amount of coking is shown in Table 5.

TABLE 4

Elemental content (wt%)	Cr	Ni	Fe	Mn	Si	O	Others	Mn/Cr	Thickness of oxide layer
										Comparative example 7	24.91	35.29	35.15	1.13	1.21	0.76	1.55	0.05	0
Comparative example 8	58.25	2.88	5.65	10.33	0.54	21.59	0.76	0.18	12.2
										Comparative example 9	55.38	4.22	5.87	10.89	1.29	21.48	0.87	0.20	13.1
Comparative example 10	25.34	35.56	33.97	1.25	1.55	0.89	1.44	0.05	0
										Comparative example 11	52.25	3.31	4.07	16.24	1.02	22.24	0.87	0.31	14.5
Comparative example 12	57.23	0.92	1.88	16.77	1.33	21.78	0.09	0.29	6.8
										Example 4	56.87	0.71	0.64	17.33	1.32	22.61	0.52	0.30	6.2
Example 5	55.23	0.74	0.89	17.71	1.21	22.45	1.77	0.32	4.1
										Example 6	54.64	1.09	0.65	17.52	1.12	22.69	2.29	0.32	6.8

TABLE 5

From table 4, we can find that the contents of Cr and Mn elements on the inner surfaces of the furnace tubes of the treated comparative examples and examples are significantly increased, while the contents of Fe and Ni elements with catalytic coking activity are greatly reduced, and are lower in the examples compared with the comparative examples.

From Table 5 we can see that the average coke charge for 10 cracks in comparative example 7 (blank value) is 1.91 grams; the coking amounts of the first times in the comparative examples 8, 9 and 11 are very low, but the coking amounts gradually increase along with the increase of the cracking and burning times; the coke amount in examples 4, 5 and 6 was low, and was reduced by 86% or more on average from the blank value, and the coke amount did not increase significantly as the cracking and burning times increased.

The preferred embodiments of the present invention have been described above in detail, but the present invention is not limited thereto. Within the scope of the technical idea of the invention, many simple modifications can be made to the technical solution of the invention, including combinations of various technical features in any other suitable way, and these simple modifications and combinations should also be regarded as the disclosure of the invention, and all fall within the scope of the invention.