阅读说明：本技术 导热炉管及制备方法和在裂解炉中的应用 (Heat-conducting furnace tube, preparation method and application in cracking furnace ) 是由 刘俊杰 杨士芳 王国清 张利军 周丛 张兆斌 杜志国 李晓锋 杨沙沙 郭莹 于 2019-10-29 设计创作，主要内容包括：本发明涉及用于乙烯裂解炉的导热炉管领域,公开了一种导热炉管及制备方法和其在裂解炉中的应用。该导热炉管包括炉管主体,所述炉管主体的内侧壁设置沿炉管主体的长度方向依次重复设置多组导热构件；所述导热构件包括多条沿炉管主体内壁横截面环绕一周形成的第一导热件和沿炉管主体的轴向呈螺旋设置的第二导热件。导热构件主要应用于裂解炉管的前1/3处。该导热炉管具有良好的传热效果,显著提高传热炉管的传热强化综合因子,同时能够有效降低传热炉管的结焦量和渗碳现象。(The invention relates to the field of heat-conducting furnace tubes for ethylene cracking furnaces, and discloses a heat-conducting furnace tube, a preparation method and application thereof in a cracking furnace. The heat conduction furnace tube comprises a furnace tube main body, wherein a plurality of groups of heat conduction components are sequentially and repeatedly arranged on the inner side wall of the furnace tube main body along the length direction of the furnace tube main body; the heat conducting component comprises a plurality of first heat conducting pieces formed by surrounding a circle along the cross section of the inner wall of the furnace tube main body and second heat conducting pieces arranged spirally along the axial direction of the furnace tube main body. The heat conducting member is mainly applied to the front 1/3 of the cracking furnace tube. The heat-conducting furnace tube has good heat transfer effect, remarkably improves the heat transfer strengthening comprehensive factor of the heat-transferring furnace tube, and can effectively reduce the coking amount and the carburization phenomenon of the heat-transferring furnace tube.)

1. A heat conduction furnace tube is characterized in that: the heat conduction furnace tube comprises a furnace tube main body, and a plurality of groups of heat conduction components are arranged on the inner side wall of the furnace tube main body from the feeding hole along the length direction of the furnace tube main body; the group of heat conducting components consists of a plurality of first heat conducting pieces and a second heat conducting piece, the first heat conducting pieces surround a circle along the cross section of the inner side wall of the furnace tube main body and protrude towards the inside of the furnace tube main body, and the second heat conducting pieces are spirally arranged along the axial direction of the furnace tube main body.

2. The thermally conductive furnace tube of claim 1, wherein an inner wall of the thermally conductive furnace tube is coated with a thermal barrier coating.

3. The heat conducting furnace tube according to claim 1 or 2, wherein the portion of the heat conducting furnace tube where the heat conducting member is not disposed is provided with second heat conducting members at intervals.

4. The thermally conductive furnace tube of claim 3, wherein the thermal barrier coating comprises a thermally conductive layer comprising 30-40 wt.% Cr, 2.5-6 wt.% Ni, 3-9 wt.% Fe, 8-13 wt.% Mn, 0-0.5 wt.% C, 35-40 wt.% O, 1.5-20 wt.% of at least one element selected from the group consisting of Al, Zr, Nb, and Mo, based on the total amount of the thermally conductive layer;

preferably, the thickness of the heat conducting layer is 0.1-5 μm.

5. The heat conductive furnace tube of claim 3, wherein the interior side of the heat conductive furnace tube further comprises a reinforcement coating over the thermally conductive layer, the reinforcement coating comprising SiO in weight percent based on the total amount of reinforcement coating₂45-80% by weight, K₂O 10-25 wt.% of Al₂O₃0-10 wt%, MgO 0-10 wt%, ZnO 0-20 wt%, Co₃O₄0-5 wt%, Na₂0-10 wt% of O;

preferably, the thickness of the reinforcement coating is 5-10 μm.

6. The heat conduction furnace tube of any one of claims 1 to 5, wherein the extension length H of the multiple groups of heat conduction members along the axial direction of the furnace tube main body satisfies the following condition: h is not less than 1/4L and not more than 1/3L; wherein L is the length of the furnace tube main body.

7. The heat conduction furnace tube of any one of claims 1 to 5, wherein the diameter of the inner ring of the first heat conduction member is D, D satisfies the condition that D/D is 0.1-0.9, and D is the inner diameter of the furnace tube main body; preferably, 0.4. ltoreq. D/D. ltoreq.0.7.

8. The heat conducting furnace tube according to any one of claims 1 to 5, wherein the rotation angle of the spiral in the second heat conducting member is 90 ° to 1080 °, preferably 120 ° to 360 °; the extension length H1 of the second heat-conducting piece along the axial direction of the furnace tube main body meets the following conditions: h1 is more than or equal to 2D and less than or equal to 8D, and D is the inner diameter of the furnace tube main body; the ratio of the area of the middle opening of the second heat conduction piece to the cross section area of the furnace tube is 0.05-0.95:1, and preferably 0.6-0.8: 1.

9. The heat conducting furnace tube according to any one of claims 1 to 5, wherein the axial distance between adjacent first heat conducting members in a group of heat conducting members is 0.01D-2.5D, preferably 0.3D-1.0D.

10. The thermally conductive furnace tube of claims 1-6, wherein the ratio of the axial length of a set of thermally conductive members to the inside diameter of the furnace tube body is from 8 to 12, preferably from 9 to 10.

11. A method for manufacturing the heat conducting furnace tube according to any one of claims 1 to 10, comprising heating the heat conducting furnace tube under an atmosphere of low oxygen partial pressure to form a heat conducting layer on the surface.

12. The production method according to claim 11, wherein the conditions of the low oxygen partial pressure atmosphere include: the gas providing the low oxygen partial pressure atmosphere comprises CO₂、CO、H₂And water vapor, the oxygen partial pressure is less than or equal to 10^-16Pa; the conditions of the heat treatment include: the temperature of the heating treatment is 400-1100 ℃, and preferably 800-1000 ℃; the time of the heat treatment is 5 to 200 hours, preferably 10 to 100 hours.

13. The method of claim 11, further comprising spraying a reinforcement coating on the surface of the thermally conductive layer;

preferably, the preparation method of the reinforced coating comprises the following steps: mixing the raw materials with water to form slurry, spraying the slurry on the surface of the heat-conducting layer, and sintering at the temperature of 1000-1100 ℃ to form a reinforced coating;

the reinforced coating comprises SiO in percentage by weight based on the total amount of the reinforced coating₂45-80% by weight, K₂10-25% by weight of O, Al₂O₃0-10 wt%, MgO 0-10 wt%, ZnO 0-20 wt%, Co₃O₄0-5 wt%, Na₂0 to 10 weight percent of O.

14. Use of the heat conducting furnace tube of any one of claims 1-13 in a pyrolysis furnace.

15. A pyrolysis furnace radiant section tube comprising the thermally conductive tube of any one of claims 1-10;

preferably, the radiant section furnace tube of the cracking furnace is U-shaped, and the heat conduction furnace tube is arranged at two vertical parts of the radiant section furnace tube of the cracking furnace.

Technical Field

The invention relates to the field of heat-conducting furnace tubes for ethylene cracking furnaces, in particular to a heat-conducting furnace tube, a preparation method and application in a cracking furnace.

Background

The cracking furnace is an important device in petrochemical industry, is mainly used for heating cracking raw materials to realize cracking reaction, and is beneficial to primary reaction of target products such as ethylene generated by cracking through high temperature, short retention time and low hydrocarbon partial pressure according to the analysis of cracking principle.

For shortening the retention time of the cracking raw material in the cracking furnace tube, the method of increasing the treatment capacity of the furnace tube, reducing the tube diameter of the furnace tube and reducing the tube length can be adopted. However, the first two methods also result in a corresponding increase in pressure drop, thus partially offsetting the effect of the reduction in residence time, and are rarely used alone because of the reduced selectivity of cracking that results from the increased pressure drop. The preferred option for reducing the residence time is to reduce the tube length, so that for a single pass cracking furnace tube, the residence time of the cracking feedstock in the tube can be below 0.1 s. Therefore, for a furnace tube having a small tube length, it is necessary to improve the heat transfer performance of the furnace tube in a short time.

In the prior art, the furnace tubes of cracking furnaces commonly used in the petrochemical industry generally have the following structure:

(1) one or more ribs on the inner surface of the tube wall of one or more regions or all regions are arranged in the cracking furnace tube from the inlet end to the outlet end of the furnace tube along the axial direction of the furnace tube, and the ribs extend spirally on the inner surface of the tube wall along the axial direction of the furnace tube. For example, the reinforced heat transfer tube disclosed in CN2144807Y includes a tube body, in which single-blade rotating fins are fixed, and although the fins can achieve the purpose of stirring the fluid to reduce the thickness of the boundary layer as much as possible, as the service time of the furnace tube increases, the coking on the inner surface of the furnace tube will make the fins have weaker functions, and the function of reducing the boundary layer will also be reduced correspondingly.

(2) The fins, which are discretely disposed on the inner surface of the furnace tube, also reduce the boundary layer thickness, but also play a smaller and smaller role as the amount of coking on the inner surface of the furnace tube increases.

(3) The cracking furnace tube is additionally provided with a twisted piece reinforced heat transfer tube, such as the heat transfer tube disclosed in CN104560111A, the twisted piece extends spirally along the axial direction of the heat transfer tube, although the twisted piece reinforced heat transfer tube has good effects of reinforcing heat transfer and inhibiting coking, in the long-time operation process, because the tube is often over-temperature in the operation process, and because the cracking furnace tube inevitably generates phenomena such as carburization in the use process, the twisted piece reinforced heat transfer tube cracks, and the twisted piece reinforced heat transfer tube fails.

Therefore, the problem to be solved in the field is how to further slow down coking and carburization in the heat transfer pipe while ensuring the heat transfer effect of the heat transfer pipe, and to increase the temperature of the cracking material in a short time.

Disclosure of Invention

The invention aims to solve the problems that the inner wall of a heat transfer furnace tube in the prior art is easy to coke and carburize and has poor heat transfer effect, and provides a heat conduction furnace tube, a preparation method and application thereof in a cracking furnace.

In order to achieve the above object, a first aspect of the present invention provides a heat conducting furnace tube, which includes a furnace tube main body, wherein a plurality of groups of heat conducting members are arranged on an inner side wall of the furnace tube main body along a length direction of the furnace tube main body from a feeding port; the group of heat conducting components consists of a plurality of first heat conducting pieces and a second heat conducting piece, the first heat conducting pieces surround a circle along the cross section of the inner side wall of the furnace tube main body and protrude towards the inside of the furnace tube main body, and the second heat conducting pieces are spirally arranged along the axial direction of the furnace tube main body.

A second aspect of the present invention provides a method for manufacturing the heat conducting furnace tube of the first aspect, including heating the heat conducting furnace tube in an atmosphere with a low oxygen partial pressure to form a heat conducting layer on the surface of the heat conducting furnace tube.

In a third aspect, the invention provides a use of the heat conducting furnace tube of the first aspect in a cracking furnace.

The invention provides a cracking furnace radiation section furnace tube in a fourth aspect, which comprises the heat conducting furnace tube in the first aspect.

The heat-conducting furnace tube prepared by the invention is matched with the coating thermal barrier coating through the heat-conducting component, so that the heat transfer performance of the heat-conducting furnace tube can be effectively improved, the heat-conducting furnace tube can reach the high temperature required by the cracking reaction in a short time, the coking amount in the heat-conducting furnace tube prepared by the invention is greatly reduced, and the service life of the heat-conducting furnace tube is prolonged; and the carburization phenomenon of the heat conduction furnace tube can be reduced.

Drawings

Fig. 1 is a schematic structural view of a heat conductive member according to the present invention;

FIG. 2 is a schematic structural diagram of a heat transfer furnace tube in example 1;

FIG. 3 is a schematic view showing the structure of a type 1-1 furnace tube for a cracking furnace in example 2;

FIG. 4 is a schematic view showing the structure of a 2-1 type furnace tube for a cracking furnace in example 3.

Wherein, 1-the first heat conducting piece, 2-the second heat conducting piece, 3-the heat conducting furnace tube, 4-the first pass furnace tube, and 5-the second pass furnace tube.

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.

The first aspect of the invention provides a heat-conducting furnace tube, wherein the heat-conducting furnace tube 3 comprises a furnace tube main body, and a plurality of groups of heat-conducting components are arranged on the inner side wall of the furnace tube main body from a feeding hole along the length direction of the furnace tube main body; the group of heat conducting components consists of a plurality of first heat conducting pieces 1 and a second heat conducting piece 2, the first heat conducting pieces 1 are formed by surrounding a circle along the cross section of the inner side wall of the furnace tube main body and protruding towards the inside of the furnace tube main body, and the second heat conducting pieces 2 are spirally arranged along the axial direction of the furnace tube main body.

According to the invention, the heat conduction member formed by the first heat conduction piece 1 and the second heat conduction piece 2 is arranged in the furnace tube main body, so that the tangential speed of fluid is improved, the boundary layer near the wall surface of the furnace tube is damaged, the heat transfer effect is improved, the coking phenomenon on the inner wall of the furnace tube is reduced, and the decoking period and the service life of the furnace tube are effectively prolonged. In the invention, the heat conduction components are arranged at the feed inlet of the heat conduction furnace tube, a plurality of groups of heat conduction components are arranged from the feed inlet, and the heat conduction components are arranged in a mode that the first heat conduction piece is close to the feed inlet and the second heat conduction piece is close to the discharge outlet.

The heat conducting furnace tube 3 can be a nickel-chromium furnace tube, and the composition of the nickel-chromium furnace tube comprises Cr, Ni, Fe, Mn, C and at least one element selected from Al, Zr, Nb and Mo.

In order to further improve the heat transfer performance of the heat conduction furnace tube and reduce the coking phenomenon of the inner wall of the heat conduction furnace tube, the inner wall of the heat conduction furnace tube 3 is coated with a thermal barrier coating. Preferably, the second heat-conducting members are arranged at intervals in the part, where the heat-conducting member is not arranged, of the heat-conducting furnace. That is, in the invention, the heat conducting furnace tube is provided with a plurality of groups of heat conducting components and second heat conducting pieces arranged at intervals in sequence from the feeding hole, and the inner wall of the heat conducting furnace tube is coated with a thermal barrier coating.

Further preferably, the thermal barrier coating comprises a thermally conductive layer comprising 30-40 wt% Cr, 2.5-6 wt% Ni, 3-9 wt% Fe, 8-13 wt% Mn, 0-0.5 wt% C, 35-40 wt% O, 1.5-20 wt% of at least one element selected from the group consisting of Al, Zr, Nb and Mo, based on the total weight of the thermally conductive layer.

In the invention, the heat conduction layer is arranged in the heat conduction furnace tube, and the heat conduction layer and the heat conduction component are matched with each other, so that the heat transfer performance and the wear resistance of the heat conduction furnace tube can be effectively improved, the coking phenomenon of the inner wall of the heat conduction furnace tube can be effectively inhibited, the anti-permeability performance of the heat conduction furnace tube is improved, the decoking period of the heat conduction furnace tube is prolonged, and the service life of the heat conduction furnace tube is prolonged.

Preferably, the thickness of the heat conducting layer is 0.1-5 μm. The heat conduction layer is within the thickness range, the coking amount of the heat conduction furnace tube can be effectively reduced, and the heat transfer performance of the heat conduction furnace tube cannot be influenced.

Preferably, the inner side of the heat conducting furnace tube 3 further comprises a strengthening coating positioned above the heat conducting layer, and the strengthening coating comprises SiO in percentage by weight based on the total amount of the strengthening coating₂45-80% by weight, K₂10-25% by weight of O, Al₂O₃0-10 wt%, MgO 0-10 wt%, ZnO 0-20 wt%, Co₃O₄0-5 wt%, Na₂0 to 10 weight percent of O.

According to the invention, the reinforcing coating, the heat conduction layer and the heat conduction member arranged on the inner wall of the heat conduction furnace tube are matched with each other, so that the coking phenomenon of the inner wall of the heat conduction furnace tube can be further inhibited, and the service life of the furnace tube is prolonged.

Preferably, the thickness of the reinforcement coating is 5-10 μm. In the invention, the reinforced coating is in the thickness range, so that the coking amount of the heat-conducting furnace tube can be effectively inhibited, the carburization phenomenon of the heat-conducting furnace tube is reduced, and the service life and the heat transfer efficiency of the heat-conducting furnace tube are improved. The reinforced coating and the heat conduction layer are mutually matched, so that the strong impact effect of air flow on the heating furnace tube in the decoking process can be effectively reduced, and the service life and the decoking period of the furnace tube can be further prolonged.

In order to further improve the heat transfer performance of the heat-conducting furnace tube, preferably, the extension length H of the multiple groups of heat-conducting members along the axial direction of the furnace tube main body satisfies: h is not less than 1/4L and not more than 1/3L; wherein L is the length of the furnace tube main body.

The extension length H of the heat conduction member along the axial direction of the furnace tube main body in the invention refers to the extension length of the heat conduction member composed of the first heat conduction piece 1 and the second heat conduction piece 2 along the axial direction of the furnace tube main body. The heat conduction members can be arranged in multiple groups according to actual conditions, and if the heat conduction members are arranged in multiple groups, H refers to the total extension length of the heat conduction members in the axial direction of the furnace tube main body.

The ethylene cracking reaction usually needs a very short time to reach the cracking high temperature, and the heat conducting components of the heat conducting furnace tube are arranged according to the structure, so that the heat transfer performance of the heat conducting furnace tube is further improved.

In order to further improve the heat transfer effect and simultaneously reduce the coking amount of the furnace tube, the diameter of an inner ring of the first heat conducting piece 1 is D, D satisfies D/D is more than or equal to 0.1 and less than or equal to 0.9, and D is the inner diameter of the main body of the furnace tube; preferably, 0.4. ltoreq. D/D. ltoreq.0.7.

In the invention, the inner diameters of the furnace tube main bodies are all diameters.

Preferably, the rotation angle of the spiral in the second heat-conducting member 2 is 90 ° to 1080 °, preferably 120 ° to 360 °; the extension length H1 of the second heat conduction member 2 along the axial direction of the furnace tube main body satisfies the following conditions: h1 is more than or equal to 2D and less than or equal to 8D, and D is the inner diameter of the furnace tube main body. The extension length H1 of the second heat conduction member 2 along the axial direction of the furnace tube main body is only the extension length of one second heat conduction member 2 in a spiral shape along the axial direction of the furnace tube main body. The ratio of the area of the middle opening of the second heat conduction member 2 to the cross section area of the furnace tube is 0.05-0.95:1, preferably 0.6-0.8: 1.

In the invention, one group of heat conducting members consists of a plurality of parallel first heat conducting pieces 1 and one second heat conducting piece 2, and the ratio of the axial length of the group of heat conducting members to the inner diameter of the furnace tube main body is 8-12, preferably 9-10, and more preferably 10. The diameter D of the inner ring of the first heat conducting piece 1 is the diameter of the inner ring formed by the highest point of the first heat conducting piece 1 protruding out of the inner side of the furnace tube main body, and the axial distance between adjacent first heat conducting pieces 1 in one group of heat conducting components is 0.01D-2.5D, preferably 0.3D-1D, and more preferably 0.5D. The inner spiral of the second heat conduction member 2 can rotate clockwise or counterclockwise, and the spiral directions of the second heat conduction member 2 can be the same or opposite.

The first heat conducting piece 1 and the second heat conducting piece 2 are arranged according to the structure, and particularly under the condition that the first heat conducting piece 1 and the second heat conducting piece 2 are matched with the thermal barrier coating, the heat transfer effect of the heat conducting furnace tube can be greatly improved, the flow resistance of fluid in the heat conducting furnace tube is reduced, and the coking phenomenon of the inner wall of the heat conducting furnace tube is reduced.

In the invention, after the heat-conducting component and the second heat-conducting piece are arranged in the heat-conducting furnace tube under the actual use condition, the surface of the inner wall of the heat-conducting furnace tube is coated with the thermal barrier coating.

A second aspect of the present invention provides a method for manufacturing the heat conducting furnace tube of the first aspect, including heating the heat conducting furnace tube in an atmosphere with a low oxygen partial pressure to form a heat conducting layer on the surface of the heat conducting furnace tube.

In the process of preparing the heat-conducting furnace tube, at least one metal selected from Al, Zr, Nb and Mo is added into the nickel-chromium alloy containing Cr, Ni, Fe, Mn and C elements according to the conventional manufacturing process of the cracking furnace tube (such as a centrifugal casting method, the temperature is 900-1000 ℃, the rotating speed is 1000-1300r/min, and the forming time is 3-4h) to prepare the tube, and then the tube is heated under the environment of low oxygen partial pressure to form a heat-conducting layer on the surface of the tube. The heat conductive layer comprises 30-40 wt% of Cr, 2.5-6 wt% of Ni, 3-9 wt% of Fe, 8-13 wt% of Mn, 0-0.5 wt% of C, 35-40 wt% of O, and 1.5-20 wt% of at least one element selected from the group consisting of Al, Zr, Nb and Mo, based on the total weight of the heat conductive layer. The method is more convenient to form the heat conduction layer on the surface of the heat conduction furnace tube, reduces the thermal interface between the heat conduction furnace tube and the heat conduction layer, and improves the heat conduction performance of the heat conduction furnace tube.

In order to further improve the heat conductivity of the heat conducting furnace tube, the conditions of the low oxygen partial pressure atmosphere comprise: the gas providing the low oxygen partial pressure atmosphere comprises CO₂、CO、H₂And water vapor, the oxygen partial pressure is less than or equal to 10^-16Pa; the conditions of the heat treatment include: the temperature of the heating treatment is 400-1100 ℃, and preferably 800-1000 ℃; the time of the heat treatment is 5 to 200 hours, preferably 10 to 100 hours.

Preferably, the gas providing the low oxygen partial pressure atmosphere comprises CO₂Gas mixture with CO, gas mixture of water vapor and CO, H₂And water vapor.

The heat conduction layer formed on the surface of the heat conduction furnace tube by the method has a stable structure and excellent heat transfer performance, and can reduce the coking amount of the inner wall of the heat conduction furnace tube.

In order to further improve the anti-coking performance of the heat conduction furnace tube and prolong the service life of the heat conduction furnace tube, the method also comprises the step of spraying a reinforcing coating on the surface of the heat conduction layer.

Preferably, the preparation method of the reinforced coating comprises the following steps: mixing the raw materials with water to form slurry, spraying the slurry on the surface of the heat-conducting layer, and sintering at the temperature of 1000-1100 ℃ to form a reinforced coating;

the reinforced coating comprises SiO in percentage by weight based on the total weight of the reinforced coating₂45-80% by weight, K₂10-25% by weight of O, Al₂O₃0-10 wt%, MgO 0-10 wt%, ZnO 0-20 wt%, Co₃O₄0-5 wt%, Na₂0 to 10 weight percent of O.

The reinforced coating is arranged on the surface of the heat conducting layer according to the method, so that the interface thermal resistance between the heat conducting layer and the reinforced coating is reduced, the heat transfer performance of the heat conducting furnace tube is improved, and the coking amount of the inner wall of the heat conducting furnace tube is effectively reduced.

In a third aspect, the invention provides use of the thermally conductive furnace tube of the first aspect in a pyrolysis furnace. Preferably used in the radiant section furnace tube of the cracking furnace.

The invention provides a cracking furnace radiation section furnace tube in a fourth aspect, which comprises the heat conducting furnace tube in the first aspect; preferably, the radiant section furnace tube of the cracking furnace is U-shaped, and the heat conduction furnace tube is arranged at two vertical parts of the radiant section furnace tube of the cracking furnace. Wherein, the radiant section furnace tube of the cracking furnace can be a 1-1 type furnace tube or a 2-1 type furnace tube. If the furnace tube is a 1-1 type furnace tube, as shown in fig. 3, the structure is U-shaped, and heat conducting furnace tubes are respectively disposed at two vertical portions of the U-shape. In the case of the 2-1 type furnace tube, as shown in FIG. 4, the structure is to add a single-pass furnace tube on the basis of the 1-1 type furnace tube, and the installation position of the heat conduction furnace tube is the same as that of the 1-1 type furnace tube.

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

In the following examples and comparative examples,

the heat transfer enhancement integration factor is defined as follows:

wherein, Nu_sNu represents the Nussel number of the untreated smooth heat transfer furnace tube and the high-performance heat transfer furnace tube added with the inner member, f_sF represents the resistance coefficient of the untreated smooth heat transfer furnace tube and the high-performance heat transfer furnace tube added with the inner member, d represents the inner diameter of the furnace tube, Δ p represents the pressure drop of the furnace tube, L represents the length of the furnace tube, ρ represents the density of fluid in the tube, and u represents the flow velocity of the fluid in the tube. In the above, the untreated smooth heat transfer furnace tube means that the heat conducting member, the heat conducting layer and the reinforcing coating are not arranged in the heat transfer furnace tube.

The untreated smooth heat transfer furnace tube means that the heat transfer furnace tube is internally provided with no heat conducting component, no heat conducting layer and no reinforcing coating.

The variation of the heat transfer enhancement factor in the examples and the comparative examples was determined by measuring the heat transfer enhancement factor η 1 of the heat conductive furnace tubes, the heat transfer enhancement factor η 0 of the untreated smooth heat transfer furnace tubes, and the variation of the heat transfer enhancement factor ═ η 1- η 0)/η 0 × 100% in one operating cycle.

The variation of the coking amount is detected in one operation cycle, the coking thickness h1 of the inner wall of the heat-conducting furnace tube in the following examples and comparative examples, the coking thickness h0 of the heat-conducting furnace tube without the heat-conducting component, the heat-conducting layer and the reinforcing coating inside, and the variation of the coking amount is (h0-h1)/h0 x 100%. Wherein, the operation periods of different heat conduction furnace tubes are not necessarily the same.

Example 1

The present embodiment is used to provide a heat conducting furnace tube, as shown in fig. 2, which is a single-pass furnace tube in a radiant section furnace tube of a cracking furnace.

The heat conducting furnace tube 3 includes a furnace tube main body, a plurality of sets of heat conducting members are fixed on the inner side wall of the furnace tube main body, as shown in fig. 1, the portion of the furnace tube main body where the heat conducting members are arranged includes a first heat conducting piece 1 and a second heat conducting piece 2 which are alternately fixed along the length direction of the furnace tube main body, and the portion where the heat conducting members are not arranged has the second heat conducting piece 2 fixed at intervals. The inner side wall of the heat conduction furnace tube 3 is coated with a thermal barrier coating, and the thermal barrier coating comprises a heat conduction layer and a reinforcing coating which are sequentially fixed from the inner wall of the heat conduction furnace tube.

The inner diameter D of the furnace tube main body is 25mm, the length L of the furnace tube main body is 13m, 16 groups of heat conduction members are uniformly arranged along the axial direction of the furnace tube, and the extension length H of the 16 groups of heat conduction members along the axial direction of the furnace tube main body is 4 m. One set of heat conducting members comprises 15 first heat conducting members 1 and 1 second heat conducting member 2.

The first heat conducting piece 1 is a circular ring formed by surrounding a circle along the cross section of the inner wall of the furnace tube main body, the diameter d of the inner ring of the first heat conducting piece 1 is 12.5mm, and the axial distance between the adjacent first heat conducting pieces 1 is 12.5 mm.

The second heat conducting pieces 2 are arranged in parallel along the axial direction of the furnace tube main body, the rotating angle of the second heat conducting pieces 2 along the spiral of the inner wall of the furnace tube main body is 180 degrees, and the two second heat conducting pieces 2 are spiral along the clockwise direction. The length H1 of the second heat conduction member 2 extending along the length direction of the furnace tube main body is 62.5mm, and the ratio of the area of the middle opening of the second heat conduction member 2 to the cross-sectional area of the furnace tube is 0.65: 1.

And the second heat-conducting pieces 2 are only arranged at intervals at the position where the axial length of the furnace tube main body is 4-13 m.

The preparation method of the heat conduction furnace tube 3 comprises the following steps:

(1) and carrying out low-oxygen partial pressure gas atmosphere treatment on the nickel-chromium furnace tube. The method comprises the steps of treating a nickel-chromium furnace tube containing Cr, Ni, Fe, Mn, C and Zr for 3 hours at the temperature of 900 ℃ and the rotating speed of 1300r/min by adopting a centrifugal casting method, and then carrying out heat treatment under low oxygen partial pressure to form a heat conduction layer on the surface of the nickel-chromium furnace tube.

The low oxygen partial pressure gas used in the low oxygen partial pressure condition is H₂And water vapor, the water vapor accounts for 10% of the gas mixture by volume, the oxygen partial pressure is less than or equal to 10^-16Pa. The heating temperature is 1000 ℃, the heating treatment time is 50h, and the heat conduction layer with the thickness of 3 μm is formed on the surface of the nickel-chromium furnace tube by the treatment of the method. Carrying out energy spectrum analysis on the heat conduction layer, and taking the total amount of the heat conduction layer as a reference, wherein the heat conduction layer comprises the following components in percentage by weight: 40 wt% of Cr, 5 wt% of Ni, 5 wt% of Fe, 10 wt% of Mn, 0.5 wt% of C, 35 wt% of O, and 4.5 wt% of Zr.

(2) And coating a reinforced coating on the surface of the heat-conducting furnace tube 3. Mixing SiO₂、K₂O、Al₂O₃MgO and water are uniformly mixed to form slurry, the slurry is uniformly sprayed on the surface of the heat conduction layer and is sintered at the temperature of 1100 ℃ to form a reinforced coating with the thickness of 8 mu m, so that in the reinforced coating, the reinforced coating comprises the following components in percentage by weight based on the total amount of the reinforced coating: SiO 2₂75% by weight, K₂O10 wt%, Al₂O₃5 wt% and MgO 10 wt%.

The heat-conducting furnace tube 3 manufactured by the method is tested, the heat-conducting furnace tube 3 is used in a cracking furnace, the operation period is 35 days, and the heat-conducting furnace tube 3 can be normally used in the whole operation period. The coking amount of the heat-conducting furnace tube 3 is reduced by 30 percent, and the heat transfer enhancement comprehensive factor eta is improved by 26 percent.

Example 2

The present embodiment is used to provide a heat conducting furnace tube, as shown in fig. 3, which is a 1-1 type furnace tube in a radiant section furnace tube of a cracking furnace.

The 1-1 type furnace tube is U-shaped, the two vertical parts of the U-shaped furnace tube are heat conduction furnace tubes with the structure similar to that of the embodiment 1, and the lower ends of the two heat conduction furnace tubes are connected by a section of arc-shaped tube. The heat conducting furnace tube 3 in this embodiment includes a furnace tube main body, a plurality of sets of heat conducting members are fixed on an inner side wall of the furnace tube main body, a portion of the furnace tube main body where the heat conducting members are disposed includes first heat conducting pieces 1 and second heat conducting pieces 2 that are alternately fixed along a length direction of the furnace tube main body, and a portion where the heat conducting members are not disposed fixes the second heat conducting pieces 2 at intervals. The inner side wall of the heat conduction furnace tube 3 is coated with a thermal barrier coating, and the thermal barrier coating comprises a heat conduction layer and a reinforcing coating which are sequentially fixed from the inner wall of the heat conduction furnace tube.

The inner diameter D of the furnace tube main body is 50mm, the length L of the furnace tube main body is 13m, 8 groups of heat conducting members are uniformly arranged along the axial direction of the furnace tube, and the extension length H of the 8 groups of heat conducting members along the axial direction of the furnace tube main body is 4 m. One set of heat conducting members comprises 15 first heat conducting members 1 and 1 second heat conducting member 2.

The first heat conducting piece 1 is a circular ring formed by surrounding a circle along the cross section of the inner wall of the furnace tube main body, the diameter d of the inner ring of the first heat conducting piece 1 is 12.5mm, and the axial distance between every two adjacent first heat conducting pieces 1 is 25 mm.

The second heat conducting pieces 2 are arranged in parallel along the axial direction of the furnace tube main body, the rotating angle of the second heat conducting pieces 2 along the spiral of the inner wall of the furnace tube main body is 180 degrees, and the two second heat conducting pieces 2 are spiral along the clockwise direction. The length H1 of the second heat conduction member 2 extending along the length direction of the furnace tube main body is 125mm, and the ratio of the area of the middle opening of the second heat conduction member 2 to the cross-sectional area of the furnace tube is 0.65: 1.

And the second heat-conducting pieces 2 are only arranged at intervals at the position where the axial length of the furnace tube main body is 4-13 m.

The preparation method of the heat conduction furnace tube 3 comprises the following steps:

(1) and carrying out low-oxygen partial pressure gas atmosphere treatment on the nickel-chromium furnace tube. The method comprises the steps of treating a nickel-chromium furnace tube containing Cr, Ni, Fe, Mn, C and Nb for 4 hours at the temperature of 1000 ℃ and the rotating speed of 1000r/min by adopting a centrifugal casting method, and then carrying out heat treatment under low oxygen partial pressure to form a heat conduction layer on the surface of the nickel-chromium furnace tube.

The low oxygen partial pressure gas used in the low oxygen partial pressure condition is H₂And water vapor, the water vapor accounts for 10% of the gas mixture by volume, the oxygen partial pressure is less than or equal to 10^-16Pa. The heating temperature is 800 ℃, the heating treatment time is 100h, and the heat conduction layer with the thickness of 5 μm is formed on the surface of the nickel-chromium furnace tube by the treatment of the method. The heat conductive layer was analyzed by energy spectroscopy and comprised, in weight percent, 30% Cr, 3% Ni, 3% Fe, 8% Mn, 0.3% C, 38% O, and 17.7% Nb, based on the total weight of the heat conductive layer.

(2) And coating a reinforced coating on the surface of the heat-conducting furnace tube 3. Mixing SiO₂、K₂O、Al₂O₃、MgO、Co₃O₄、Na₂Mixing O and water uniformly to form slurry, spraying the slurry on the surface of the heat-conducting layer uniformly, and sintering at the temperature of 1000 ℃ to form a reinforcing coating with the thickness of 10 mu m, so that the reinforcing coating comprises the following components in percentage by weight based on the total amount of the reinforcing coating: SiO 2₂70% by weight, K₂O10 wt%, Al₂O₃5 wt%, MgO5 wt%, Co₃O₄5% by weight and Na₂O5 wt.%.

The heat-conducting furnace tube 3 manufactured by the method is tested, the heat-conducting furnace tube 3 is used in a cracking furnace, the operation period is 110 days, and the heat-conducting furnace tube 3 can be normally used in the whole operation period. The coking amount of the heat-conducting furnace tube 3 is reduced by 28 percent, and the heat transfer enhancement comprehensive factor eta is improved by 25 percent.

Example 3

The present embodiment is used to provide a heat conducting furnace tube, as shown in fig. 4, which is a two-pass radiant-section cracking furnace tube, i.e. a 2-1 type furnace tube, and includes a first-pass furnace tube 4 and a second-pass furnace tube 5.

The 2-1 type furnace tube is formed by adding a one-way furnace tube on the basis of the 1-1 type furnace tube, and the one-way furnace tube is connected with the arc tube of the 1-1 type furnace tube through a section of arc tube. The arrangement positions of the heat conduction furnace tubes are the same as those in embodiment 2, and the heat conduction furnace tubes are both arranged at two vertical parts of the U-shaped structure. The heat conducting furnace tube 3 in this embodiment includes a furnace tube main body, a plurality of sets of heat conducting members are fixed on an inner side wall of the furnace tube main body, a portion of the furnace tube main body where the heat conducting members are disposed includes first heat conducting pieces 1 and second heat conducting pieces 2 that are alternately fixed along a length direction of the furnace tube main body, and a portion where the heat conducting members are not disposed fixes the second heat conducting pieces 2 at intervals. The inner side wall of the heat conduction furnace tube 3 is coated with a thermal barrier coating, and the thermal barrier coating comprises a heat conduction layer and a reinforcing coating which are sequentially fixed from the inner wall of the heat conduction furnace tube.

The inner diameter D of the furnace tube main body is 50mm, the length L of the furnace tube main body is 13m, 8 groups of heat conducting members are uniformly arranged along the axial direction of the furnace tube, and the extension length H of the 8 groups of heat conducting members along the axial direction of the furnace tube main body is 4 m. One set of heat conducting members comprises 15 first heat conducting members 1 and 1 second heat conducting member 2.

The first heat conducting piece 1 is a circular ring formed by surrounding a circle along the cross section of the inner wall of the furnace tube main body, the diameter d of the inner ring of the first heat conducting piece 1 is 12.5mm, and the axial distance between every two adjacent first heat conducting pieces 1 is 25 mm.

The second heat conducting pieces 2 are arranged in parallel along the axial direction of the furnace tube main body, the rotating angle of the second heat conducting pieces 2 along the spiral of the inner wall of the furnace tube main body is 180 degrees, and the two second heat conducting pieces 2 are spiral along the clockwise direction. The length H1 of the second heat conduction member 2 extending along the length direction of the furnace tube main body is 125mm, and the ratio of the area of the middle opening of the second heat conduction member 2 to the cross-sectional area of the furnace tube is 0.65: 1.

The second heat conducting pieces 2 are only arranged at intervals at the position where the axial length of the furnace tube main body is H-4 m-13m and the position of the second-stroke furnace tube 5.

The preparation method of the heat conduction furnace tube 3 comprises the following steps:

(1) and carrying out low-oxygen partial pressure gas atmosphere treatment on the nickel-chromium furnace tube. The method comprises the steps of treating a nickel-chromium furnace tube containing Cr, Ni, Fe, Mn, C and Mo for 3 hours at 950 ℃ and 1200r/min by adopting a centrifugal casting method, and then carrying out heat treatment under low oxygen partial pressure to form a heat conduction layer on the surface of the nickel-chromium furnace tube.

The low oxygen partial pressure gas used in the low oxygen partial pressure condition is CO₂And CO in an amount of 20% by volume of the gas mixture, the partial pressure of oxygen being less than or equal to 10^-16Pa. The heating temperature is 800 ℃, the heating treatment time is 200h, and the heat conduction layer with the thickness of 1 μm is formed on the surface of the nickel-chromium furnace tube by the treatment of the method. Carrying out energy spectrum analysis on the heat conduction layer, and taking the total amount of the heat conduction layer as a reference, wherein the heat conduction layer comprises the following components in percentage by weight: 30% by weight of Cr, 4% by weight of Ni, 6% by weight of Fe, 9.5% by weight of Mn, 0.5% by weight of C, 40% by weight of O, and 10% by weight of Mo.

(2) And coating a reinforced coating on the surface of the heat-conducting furnace tube 3. Mixing SiO₂、K₂O、Al₂O₃MgO, ZnO and water are uniformly mixed to form slurry, the slurry is uniformly sprayed on the surface of the heat conduction layer and is sintered at the temperature of 1100 ℃ to form a reinforced coating with the thickness of 5 mu m, so that the reinforced coating comprises the following components in percentage by weight based on the total amount of the reinforced coating: SiO 2₂70% by weight, K₂O10 wt%, Al₂O₃7 wt%, MgO5 wt% and ZnO8 wt%.

The heat-conducting furnace tube 3 manufactured by the method is tested, the heat-conducting furnace tube 3 is used in a cracking furnace, the operation period is 110 days, and the heat-conducting furnace tube 3 can be normally used in the whole operation period. The coking amount of the heat-conducting furnace tube 3 is reduced by 28 percent, and the heat transfer enhancement comprehensive factor eta is improved by 20 percent.

Example 4

This embodiment provides a heat conduction furnace tube, which has the same structure as the heat conduction furnace tube in embodiment 1, and the difference is that: the heat conducting furnace tube is not provided with a thermal barrier coating. The heat-conducting furnace tube is used in a cracking furnace, the operation period is 30 days, and the heat-conducting furnace tube can be normally used in the whole operation period. The heat transfer strengthening comprehensive factor eta of the heat conduction furnace tube 3 is improved by 23 percent.

Comparative example 1

This comparative example provides a single pass heat transfer tube having the same structure as the heat transfer tubes of example 1, except that: the heat conducting component is not arranged in the single-pass heat transfer pipe, and the thermal barrier coating is not arranged in the single-pass heat transfer pipe. The single pass heat transfer tube was used in a cracking furnace with a 15 day operating cycle. After 15 days, the coke inside the coke oven is serious, and the coke oven cannot be normally used, so that the coke oven needs to be cleaned.

Comparative example 2

This comparative example provides a 1-1 type pyrolysis furnace heat transfer tube, the same in construction as the heat transfer tube of example 2, except that: the heat transfer tube of type 1-1 is not provided with a heat conductive member inside, nor with a thermal barrier coating. The 1-1 type heat transfer tube was used in a cracking furnace and operated for a period of 60 days. After more than 60 days, the coke inside the coke oven is serious, and the coke oven cannot be normally used, so that the coke oven needs to be cleaned.

Comparative example 3

This comparative example provides a two-pass heat transfer tube having the same structure as the heat transfer tube of example 1, except that: the heat conducting component is not arranged in the two-stroke heat transfer pipe, and the thermal barrier coating is not arranged in the two-stroke heat transfer pipe. The two-pass heat transfer tube is used for a cracking furnace, and the operation period is 60 days. After more than 60 days, the coke inside the coke oven is serious, and the coke oven cannot be normally used, so that the coke oven needs to be cleaned.

Comparative example 4

This comparative example provides a single pass heat transfer tube having the same structure as the heat transfer tubes of example 1, except that: the heat conducting member inside the single pass heat transfer tube includes only the first heat conducting member. The single pass heat transfer tube was used in a cracking furnace with a 28 day operating cycle. After 28 days, the coke inside the coke oven is serious, and the coke oven cannot be normally used, so that the coke oven needs to be cleaned. The heat transfer enhancement comprehensive factor eta is improved by 9 percent.

Comparative example 5

This comparative example provides a single pass heat transfer tube having the same structure as the heat transfer tubes of example 1, except that: the heat conducting member inside the single pass heat transfer tube includes only the second heat conducting member. The single pass heat transfer tube was used in a cracking furnace with a 30 day run cycle. After more than 30 days, the coke inside the coke oven is serious, and the coke oven cannot be normally used, so that the coke oven needs to be cleaned. The heat transfer enhancement comprehensive factor eta is improved by 12 percent.

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.