Scouring-resistant elbow for furnace

Abstract

The utility model discloses a scour-resistant elbow for a furnace, which comprises an elbow inner wall inner cambered surface, an elbow inner wall outer cambered surface and a step-shaped tooth-shaped step arranged on the elbow inner wall outer cambered surface on an elbow medium inlet side, and the tooth surface of the step-shaped tooth-shaped step forms an included angle of 90 degrees. Wherein one tooth surface of the step-shaped tooth-shaped step is perpendicular to the flowing direction of a medium entering the elbow, the other tooth surface of the step-shaped tooth-shaped step is parallel to the flowing direction of the medium entering the elbow, and the tooth-shaped step is in a crescent shape in the circumferential direction of the pipe wall of the elbow. The sizes of the tooth-shaped steps are in smooth transition from small to large and then from large to small on the circumference of the pipe wall of the elbow within the range of 0-180 degrees, the size of the tooth-shaped steps is the largest when the angle is 90 degrees, and the effective wall thickness of the pipe wall outside the stepped tooth-shaped steps on the inner wall of the elbow is larger than or equal to the design wall thickness of the elbow. The effective thickness of the elbow is prevented from being thinned, the thinning rate of the effective thickness of the elbow by a medium can be effectively reduced, and the service life of the elbow is prolonged.

Description

Technical Field

[0001] The utility model belongs to the technical field of metal pipe fittings, and in particular relates to an elbow for a scour-resistant furnace. Background Art

[0002] 180° or 90° elbows are often used to connect furnace tubes in petrochemical industry, such as atmospheric and vacuum furnaces, coking furnaces, and ethylene cracking furnaces. However, due to the erosion and corrosion of high-speed media in the tubes, the elbows are the weakest part of the entire heating furnace pipe system structure. Elbows often need to be replaced before reaching their expected service life due to local thinning, which not only causes direct economic losses, but also brings safety hazards such as fire and explosion.

[0003] Document 1, "Analysis of the Cause of the Crack of the Elbow of the HP Ethylene Cracking Furnace Tube" (Wang Lai, Yu Yongsi, Wang Fugang, etc., Journal of Dalian University of Technology. 1990(04):443-448), describes that the elbow of the cracking furnace of a certain ethylene unit was cast from HP high alloy material. After 63,000 hours of operation, a penetrating crack occurred at the outer arc of the inner wall of the elbow (about 45° cross-section position). The document analysis believes that the thinning of the inner wall is caused by the scouring and chemical corrosion of the high-speed airflow in the furnace tube.

[0004] Document 2, "Design of Radiant Coils for Ethylene Cracking Furnaces" (Hu Ming, Petrochemical Equipment Technology, 1997(02):32-38), states that the high-speed flow of high-temperature cracking gas in the radiant coils and the hard coke particles produced during coke cleaning make a sharp turn at the elbow, which causes a great deal of erosion to the inner wall. After a certain period of time, this may cause local thinning, penetration or cracking.

[0005] Document 3 "Analysis of the Causes of Perforation of the Elbow at the Radiation Outlet of the Coking Furnace of the Delayed Coking Unit" (Wang Jun, Huang Wei, Sun Depei, etc., Corrosion Science and Protection Technology, 2005, 17(004): 279-281) introduces that during the steam coking process of the coking furnace of a delayed coking unit, the 90° elbow at the radiation outlet was perforated, and there were obvious scouring marks on the inner wall of the outer arc surface of the elbow. The document analysis believes that since the elbow changes the flow direction of the residual oil, the high-speed moving residual oil impurities and the detached solid corrosion product particles strongly scour the inner surface of the elbow, and the corrosive media such as sulfur and oxygen in the residual oil corrode the elbow at high temperature all the time. The corrosion products peel off due to scouring. The greater the scouring force, the faster the peeling, and the exposed fresh metal active surface produces new corrosion products. This cycle causes the elbow to be continuously corroded and thinned until it is perforated.

[0006] Chinese patent CN 206861133 U proposes an eccentric cast elbow. It is characterized in that a wear-resistant structure is provided on the elbow body, the wear-resistant structure is provided in the upper part of the curved flow channel, and the wear-resistant structure is eccentrically arranged between the curved flow channel to form a thick wall. Compared with the traditional structure, this patent is provided with a wear-resistant structure, the thickness of the wear-resistant structure is thicker than other parts of the elbow body, and a wear-resistant layer is provided to improve the wear resistance. Chinese patent CN217762574U proposes an elbow for furnace use that is resistant to erosion and corrosion. It is characterized in that the wall thickness of the thinning part of the elbow that is prone to erosion is increased, the wall thickness of the outer arc top of the outer arc surface of the elbow is 1.5 to 3 times the wall thickness of the straight section, and the wall thickness at the elbow is consistent, so as to increase the erosion resistance time of the elbow and improve the service life of the elbow.

[0007] In summary, the prior art petrochemical furnace elbows mainly extend the service life of the elbows by increasing the wall thickness of the elbows' easily eroded parts, but do not consider reducing the erosion and thinning rate of the elbows' easily eroded and thinned parts from the erosion mechanism to extend the service life of the elbows, and are unable to fundamentally solve the erosion resistance problem of the elbows. Utility Model Content

[0008] In order to solve the technical problems of excessive wall thickness, large material consumption and high scouring and thinning rate in the prior art, the utility model provides a scouring-resistant furnace elbow.

[0009] The utility model provides an elbow for a scour-resistant furnace, comprising an inner arc surface of an inner wall of the elbow, an outer arc surface of the inner wall of the elbow, and a stepped toothed step on the outer arc surface of the inner wall of the elbow at the medium inlet side of the elbow, the tooth surface of the stepped toothed step forms an angle of 90 degrees, wherein one tooth surface of the stepped toothed step is perpendicular to the flow direction of the medium when entering the elbow, the other tooth surface of the stepped toothed step is parallel to the flow direction of the medium when entering the elbow, the stepped toothed step is crescent-shaped along the circumferential direction of the elbow pipe wall, the size of the stepped toothed step in the range of 0 degrees to 180 degrees on the circumference of the elbow pipe wall first transitions smoothly from small to large and then from large to small, the size of the stepped toothed step is the largest at 90 degrees, and the effective wall thickness of the pipe wall outside the stepped toothed step on the inner wall of the elbow is greater than or equal to the designed wall thickness of the elbow.

[0010] The erosion-resistant furnace elbow is preferably a 90° elbow or a 180° elbow.

[0011] The number of the stepped tooth-shaped steps is one or more.

[0012] The effective wall thickness of the tube wall outside the stepped toothed steps on the inner wall of the elbow is preferably equal to the designed wall thickness of the elbow.

[0013] The utility model has the following beneficial effects:

[0014] The stepped toothed steps of the utility model enable the medium to be in vertical contact with the easily scourable part of the elbow inside the elbow, thereby avoiding the formation of a shear force due to a certain angle formed between the medium and the contact surface. In addition, the toothed steps enable the scouring and thinning of the part to first occur at the steps, thereby avoiding the thinning of the effective thickness of the elbow, and can effectively reduce the thinning rate of the effective thickness of the elbow caused by the medium, thereby extending the service life of the elbow. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a structural schematic diagram of a scour-resistant furnace elbow of the utility model;

[0016] Figure 2 for Figure 1 Schematic diagram of the cross-sectional structure along the AA direction.

[0017] In the figure: 1-inner arc surface of the inner wall of the elbow, 2-outer arc surface of the inner wall of the elbow, 3-step-shaped toothed step, 4-elbow medium inlet, 5-tooth surface, 6-tooth surface;

[0018] B-effective wall thickness, C-medium flow direction. DETAILED DESCRIPTION

[0019] The present invention will be described in more detail below with reference to the accompanying drawings. Although preferred embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0020] Figures 1-2 A structural schematic diagram of the utility model is given. As shown in the figure, the erosion-resistant furnace elbow of the utility model is a 90° elbow, including an inner arc surface 1 of the inner wall of the elbow, an outer arc surface 2 of the inner wall of the elbow and a stepped toothed step 3, wherein the stepped toothed step 3 is arranged on the outer arc surface of the inner wall of the elbow on the side of the medium inlet 4 of the elbow. The tooth surface of the stepped toothed step 3 forms a 90° angle, wherein the tooth surface 5 of the stepped toothed step 3 is perpendicular to the medium flow direction C when the medium enters the elbow, and the tooth surface 6 of the stepped toothed step 3 is parallel to the medium flow direction C when the medium enters the elbow, and the stepped toothed step 3 is crescent-shaped along the circumferential direction of the elbow pipe wall, and the size of the stepped toothed step in the range of 0° to 180° on the circumference of the elbow pipe wall first transitions smoothly from small to large and then from large to small (see Figure 2 ), when the angle is 90°, the size of the stepped toothed step 3 is the largest, and the effective wall thickness B of the tube wall outside the stepped toothed step 3 on the inner wall of the elbow is equal to the designed wall thickness of the elbow.

[0021] The parts of the utility model that are not described in detail are prior art. Although the utility model is demonstrated and introduced in conjunction with specific implementation methods, there are still many ways to implement the technical solution. Technical personnel in the relevant field should understand that various adjustments can be made to the form and details of the utility model without departing from the spirit and scope of the utility model defined by the attached claims, all of which are within the scope of protection of the utility model.

Claims

1. A scour-resistant furnace elbow, characterized in that: It includes an inner arc surface of the inner wall of the elbow, an outer arc surface of the inner wall of the elbow, and a stepped tooth-shaped step on the outer arc surface of the inner wall of the elbow on the medium inlet side of the elbow. The tooth surface of the stepped tooth-shaped step forms a 90° angle, wherein one tooth surface of the stepped tooth-shaped step is perpendicular to the flow direction of the medium when entering the elbow, and the other tooth surface of the stepped tooth-shaped step is parallel to the flow direction of the medium when entering the elbow. The stepped tooth-shaped step is crescent-shaped along the circumferential direction of the elbow pipe wall. The size of the stepped tooth-shaped step in the range of 0° to 180° on the circumference of the elbow pipe wall first transitions smoothly from small to large and then from large to small. The size of the stepped tooth-shaped step is the largest at 90°, and the effective wall thickness of the pipe wall outside the stepped tooth-shaped step on the inner wall of the elbow is greater than or equal to the designed wall thickness of the elbow.

2. The erosion-resistant furnace elbow according to claim 1, characterized in that: The scour-resistant furnace elbow is a 90° elbow or a 180° elbow.

3. The erosion-resistant furnace elbow according to claim 1, characterized in that: The number of the stepped tooth-shaped steps is multiple.

4. The erosion-resistant furnace elbow according to claim 1, characterized in that: The effective wall thickness of the pipe wall outside the stepped tooth-shaped steps on the inner wall of the elbow is equal to the designed wall thickness of the elbow.

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