JP6070009B2 - Chimney cylinder installation method - Google Patents

Description

  The present invention relates to a chimney cylinder installation method for renovating an existing chimney and a chimney modification cylinder.

  In a sinter factory, exhaust gas generated in the firing process of sinter is processed by a desulfurization facility and a denitration facility and then discharged from a steel chimney. The exhaust gas discharged from the steel chimney contains SOx, NOx, and HCl. This corrosive component condenses inside the chimney and corrodes the cylinder of the chimney. Conventionally, in order to protect the metal surface from corrosion, a treatment for applying a corrosion-resistant lining (such as an acid-resistant castable or a resin lining) to the inner surface of the cylinder has been performed.

  However, if the chimney is used over a long period of 30 years or more, the chimney lining is peeled off or dropped off, and the exhaust gas comes into contact with the iron skin of the chimney, and the corrosion and thinning of the iron skin proceeds. In addition, when the corrosion of the iron skin is severe, serious accidents such as deformation, buckling, and collapse of the cylinder occur, and the operation of the sintering plant stops.

  For this reason, when the chimney is corroded or thinned, it is dealt with by reinforcing the outer surface with a rib or a backing plate, or relining the lining.

  However, the work for renewing the lining requires a long-term stoppage of the chimney, and the production loss is very large. Specifically, it takes 3 months for acid-resistant castable renewal and 10 days or more for resin lining renewal.

  In addition, inspection and repair after renewing the lining must be done with a gondola inside the cylinder, which increases the maintenance cost. On the other hand, the reinforcement from the outer surface of the cylinder body by the ribs and the backing plate does not suppress the corrosion from the inner surface, and it is necessary to periodically reinforce, and this treatment also has a problem that the maintenance cost becomes high.

  In addition, there is a method to abolish the corroded and thinned tube, and to install a new one, but to construct a 200m class chimney, it will cost more than 4 billion yen and a space to construct a new chimney If there is not, it is necessary to stop the sintering factory during the construction of the chimney (1 year or more), which results in a great production loss.

  On the other hand, Patent Document 1 proposes a method of renovating a chimney without stopping the function of the chimney by installing a new cylinder on the outer periphery of the cylinder of the existing chimney.

  FIG. 11 is a conceptual diagram showing the chimney cylinder installation method disclosed in Patent Document 1, and is a diagram created by the present inventor for explanation. As shown in FIG. 11A, an arc-shaped divided new iron skin is combined with the outer circumference of the existing chimney 11 to form a new iron skin 12 concentric with the existing chimney 11. A gap is formed between the old iron skin and the new iron skin 12 of the existing chimney 11. As shown in FIG. 11 (b), a refractory 13 is injected into the gap between the existing chimney 11 and the new iron skin 12.

  Then, as shown in FIG. 11 (c), a new new iron skin 12 is formed on the new iron skin 12 injected with the refractory 13. And as shown in FIG.11 (d), the refractory 13 is further inject | poured between the old iron skin and the newly formed new iron skin 12. FIG.

  In this manner, the process of forming the new iron skin 12 around and injecting the refractory 13 between the old iron skin and the new iron skin 12 is repeated. Then, the new iron skin 12 is stacked up to the top of the chimney, and the refractory 13 is injected between the old iron skin and the new iron skin 12. Thereby, the chimney by a new iron skin is formed in the outer periphery of the existing chimney 11.

JP 54-73426 A

  However, in the chimney barrel installation method disclosed in Patent Document 1, every time the new iron skin 12 is formed, the refractory 13 must be injected between the old iron skin and the new iron skin 12, There is a problem of inefficiency.

  In addition, in the chimney tube body installation method disclosed in Patent Document 1, in order to stack new new iron skin from above, a large number of workplaces (scaffolds) used to stack new iron skin over the entire length of the chimney are installed. There is a problem that the construction cost becomes very expensive.

The present invention has the following features in order to solve the above problems.
[1] A first operation of installing a new iron skin by forming a plurality of arc-shaped iron skins on the outer periphery of an existing chimney;
A second operation of lifting up the new iron skin formed with go;
Below the lifted-up new iron skin, further, a third operation of forming a new new iron skin by surrounding the plurality of arc-shaped iron skins,
A fourth operation for lowering the lifted-up new iron skin onto the new new iron skin formed in the third operation;
A fifth operation for joining the new iron skin lowered in the fourth operation and the new new iron skin formed in the third operation;
A chimney cylinder installation method characterized in that a cylinder with a new iron skin is installed on the outer periphery of an existing chimney by repeating the first to fifth operations.
[2] Divide the work section into a plurality of sections in the height direction of the existing chimney,
In the first operation, on the new iron skin installed in the lower section, a plurality of arc-shaped iron skins are formed on the outer periphery of the existing chimney to install the new iron skin,
In the second operation, the new iron skin formed in the first operation is lifted up,
In the third operation, under the new iron skin that has been lifted up, further, the plurality of arc-shaped iron skins are formed to form the new new iron skin,
In the fourth operation, the new iron skin lifted up is lowered onto the new new iron skin installed in the third operation,
In the fifth operation, joining the new iron skin lowered in the fourth operation and the new new iron skin installed in the third operation,
By installing the new iron skin on the new iron skin installed in the lower section by repeating the first to fifth operations,
The chimney cylinder installation method according to [1], wherein the uppermost new iron skin installed in the lower section is joined to the lowermost new iron skin installed in the upper section.
[3] The chimney cylinder installation method according to [1] or [2], wherein the corrosion resistance of the steel material on the inner peripheral side of the new iron skin is higher than the corrosion resistance of the steel material of the existing chimney.
[4] The new iron skin is clad steel in which the corrosion resistance of the steel material on the inner peripheral side is higher than the corrosion resistance of the steel material on the outer peripheral side, [1] to [3] Chimney tube installation method.
[5] The chimney cylinder installation method according to [4], wherein the clad steel has an overall corrosion resistance index GI of 60 or more and a local corrosion resistance index CI of 47 or more.
[6] A chimney repair cylinder installed by any one of the chimney cylinder installation methods of [1] to [5].

  According to the chimney cylinder installation method and the chimney repair cylinder according to the present invention, the efficiency of the existing chimney repair work can be improved.

It is a figure which shows the outline | summary of the chimney cylinder installation method which concerns on embodiment of this invention. It is a figure which shows the structure of the new iron skin used for the chimney cylinder installation method which concerns on embodiment of this invention. It is a figure which shows the installation which repairs an existing chimney using the chimney cylinder installation method which concerns on embodiment of this invention. It is a figure which shows the chimney cylinder installation method of the 2nd or more work area in the chimney cylinder installation method which concerns on embodiment of this invention. It is a figure which shows the welding method of the new iron skin of the chimney cylinder body installation method which concerns on embodiment of this invention. It is a figure which shows the relationship between a current density and the polarization curve of each steel in a simulation solution. It is a figure which shows the relationship between a current density and the polarization curve of each steel in the simulation liquid for an acceleration test. It is a figure which shows the relationship between the current density and electric potential in each corrosion type. It is a figure which shows the general corrosion resistance performance and local corrosion performance of each steel. It is the figure which showed corrosion performance using both the general corrosion-resistant performance parameter | index and the local corrosion performance each steel parameter | index. It is a conceptual diagram of the chimney barrel installation method disclosed in Patent Document 1, and is a diagram created by the present inventor for the purpose of explanation.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

  FIG. 1 is a diagram showing an outline of a chimney cylinder installation method according to an embodiment of the present invention. First, as shown in FIG. 1A, a first-stage new iron skin 31 is formed around the outer periphery of the old iron skin of the existing chimney 1. The new iron skin 31 is obtained by joining a plurality of arc-shaped iron skins 3b that can be handled by welding in the vertical direction (see FIG. 2A). The new iron skin 31 to which a plurality of arc-shaped iron skins 3 b are joined is concentric with the existing chimney 1 and has an inner diameter larger than the outer diameter of the existing chimney 1. In other words, a gap is formed between the existing chimney 1 and the new iron skin 31.

  As shown in FIG. 1 (b), the first stage new iron skin 31 formed on the outer periphery of the old iron skin is lifted up by the winch 4. The lifted-up new iron skin is shown as 32. Then, a new new iron skin 31 is formed in the space below the lifted-up new iron skin 32 by the same method as in FIG. Thereafter, the lifted-up new iron skin 32 is lowered, and it is superimposed on the newly formed new iron skin 31 and joined in the circumferential direction by welding. As a result, the upper new iron skin 32 and the newly formed new iron skin 31 are integrated. The vertical seams of the divided new iron skins are arranged at different positions in the upper and lower stages.

  Then, as shown in FIG. 1 (c), while lifting up the already formed new iron skin 32, a new new iron skin 31 is formed at the bottom, and the new iron skin 32 listed above is lowered. Then, the operation of joining the circumferential direction after repeated is repeated, and as shown in FIG. 1 (e), a cylindrical body made of a new iron skin is formed to a predetermined height. In FIG. 1, a new iron skin newly formed at the lowermost stage is shown as 31, and a new iron skin already lifted up and formed as 32 is shown as 32. Further, the new iron skin 31 and the new iron skin 32 are collectively referred to as a new iron skin 3.

  The lift-up of the new iron skin may be performed by the jack 5, as shown in FIG. 1 (d). Whether the winch 4 or the jack 5 is used for lifting the new iron skin 32 depends on the working conditions. It may be arbitrarily selected depending on the situation.

  In addition, as shown in FIG.2 (b), the rib 1a which protruded to the outer periphery is provided in a part of old iron skin of the existing chimney 1. As shown in FIG. The new iron skin 3 may be provided with an engaging portion 3a at a position corresponding to the rib 1a, and the engaging portion 3a may be engaged with the rib 1a of the old iron skin.

  FIG. 3 is a diagram showing equipment for refurbishing an existing chimney using the chimney cylinder installation method according to the embodiment of the present invention. The existing chimney to be actually renovated is about 200m high. Therefore, in practice, a plurality of work sites (shaded portions) are installed in the height direction and divided into a plurality of sections to pile up the new iron skin. For example, from the ground to the first stage of work, a new iron skin is stacked with a crane, and from the first stage of work to the second stage of work, a new iron skin is stacked with a winch. Up to the work place, the new iron skin is piled up by the jack 1, and the new iron skin is piled up by the jack 2 from the third stage to the top.

  Stacking the new iron skin beyond the second section (workplace) is performed as shown in FIG. That is, as shown in FIG. 4 (a), a plurality of arc-shaped iron skins 3b that can be handled are joined on the new iron skins stacked in the lower section by welding in the vertical direction. Form. Next, as shown in FIG. 4 (b), only the formed one-stage new iron skin 31 is lifted up (note that the lifted-up new iron skin 31 is shown as 32).

  And as shown in FIG.4 (c), in the space under the new iron skin 32 lifted up, on the new iron skin piled up in the lower area, the new iron skin 31 for one step is newly provided. Form. As shown in FIG.4 (d), the new iron skin 32 which has lifted up is lowered | hung, and it overlaps on the newly formed new iron skin 31, and joins the circumferential direction by welding. Thereafter, the joined two-stage new iron skin is lifted up, and a new new iron skin is formed in the space below it (not shown). By repeating this work, a new new iron skin is stacked on the new iron skin stacked in the lower section.

  Then, the uppermost new iron skin in the lower section and the lowermost new iron skin in the upper section stacked as shown in FIG. 4 are joined. Thereby, the new iron skin of the lower section and the new iron skin of the upper section are integrated. Thereafter, similarly, on the integrated new iron skin, the new iron skin of the upper section is further stacked using the method of FIG. 4, and the new iron skin is stacked up to the uppermost stage.

  Here, as for the new iron skin 3 used by this Embodiment, it is preferable that the corrosion resistance of the steel material of an internal peripheral surface is higher than the corrosion resistance of the steel material of the existing cylinder body. More preferably, the new iron skin 3 is preferably clad steel in which super corrosion-resistant stainless steel having a thickness of about 2 mm is disposed on the inner peripheral surface. In the clad steel, the corrosion resistance of the steel material on the inner peripheral surface is higher than the corrosion resistance of the outer peripheral surface. Although it is preferable to use a high corrosion resistance steel for the new iron skin, since high corrosion resistance steel is expensive, by placing super corrosion-resistant super stainless steel only on the inner peripheral surface where more corrosion resistance is required, It is possible to achieve both functionality and economy.

  In addition, the arc-shaped iron skin and the upper and lower new steel skins are joined by welding. For welding, a backing metal is attached to the inner peripheral surface, and one-groove welding is performed from the outer peripheral surface. Thus, high-quality welding can be performed safely without an operator entering the chimney.

  Next, the effect of the chimney cylinder installation method according to the present embodiment will be described. In the chimney barrel installation method according to the present embodiment, the stacked new iron skin is lifted up, and a new new iron skin is formed under the lifted up new iron skin. Therefore, as shown in FIG. 3, the work place only needs to be installed in each section obtained by dividing the existing cylinder into a plurality of sections, and the number of work places can be reduced as compared with the prior art, thereby greatly reducing the construction cost. be able to.

  In the above description, every time a new iron skin is formed, the stacked new iron skin is lifted up. For example, the new iron skin is lifted up by two stages and then lifted up. May be configured to be repeated.

  As described above, in the chimney cylinder installation method according to the present embodiment, the corrosion resistance of the steel material on the inner peripheral surface of the new iron skin 3 is higher than the corrosion resistance of the steel material of the existing cylinder body. Therefore, unlike the prior art, it is not necessary to inject a refractory between the old iron skin and the new iron skin, and the working time can be shortened as compared with the prior art.

  In addition, for the stacking of the new iron skin 3 in the lower layer of each work section, a new new iron skin is stacked on the lower new iron skin as in the conventional method without using the method shown in FIG. May be.

In order to investigate the optimum conditions for welding clad steel, which is a steel material of the new iron skin, a test was conducted by combining the welding position, welding material and welding current. Super stainless steel (NAS254NM) and SM400A clad steel were used as objects to be welded.
(Invention Example 1) Hastelloy C276 welding material was used for welding the first layer on the old iron skin side. Inconel 625 welding material was used for the second and subsequent layers of welding. MAG welding was adopted as the welding method.
(Invention Example 2) In addition, Hastelloy C276 welding material was used for all layers as the welding material. MAG welding was adopted as the welding method.

  As a result, it has been found that both the inventive examples 1 and 2 can ensure sound welding quality in both vertical welding and horizontal welding.

  In order to investigate the optimum conditions for welding clad steel, which is a steel material of the new iron skin, a test was conducted by combining the welding position, welding material, and welding current. For the clad steel, SM400A (JIS G3106) having a base material of 9 mm in thickness was used, and NAS254NM (corrosion resistant super stainless steel (manufactured by Nippon Yakin Kagaku)) having a thickness of 2 mm was used for the laminated material. As the backing material, NAS254NM having a thickness of 6 mm was used. Table 1 shows the chemical composition of the clad steel and the backing material, and Table 2 shows the chemical composition of the welding material.

  Fig.5 (a) is a figure which shows the test material of a vertical welding attitude | position. Two clad steels were arranged in the horizontal direction with a gap (route interval) of 4 mm, and a backing material was arranged inside the gap (NAS254NM with a clad steel thickness of 2 mm). And the welding material of the 1st layer and the 2nd layer or more was welded from the outside. Each steel was welded under these test conditions. The specimens of each steel tested under the conditions of FIG. 5A are shown as test numbers AV1, BV1, and BV11 in Table 3.

  FIG.5 (b) is a figure which shows the test material of a vertical welding attitude | position. Two clad steels were arranged in a horizontal direction with a gap (route interval) of 10 mm, and a backing material was arranged inside the gap (clad steel 2 mm thick NAS254NM). Furthermore, a difference of 2 mm was provided in the horizontal direction on the clad steel disposed through the gap. And the welding material of the 1st layer and the 2nd layer or more was welded from the outside. Each steel was welded under these test conditions. The specimens of each steel tested under the conditions of FIG. 5B are shown as test numbers AV2 and BV2 in Table 3.

  FIG.5 (c) is a figure which shows the test material of a horizontal welding attitude | position. Two clad steels were arranged with a gap (route interval) of 10 mm in the vertical direction, and a backing material was arranged inside the gap (NAS254NM with a clad steel thickness of 2 mm). Furthermore, a difference of 2 mm was provided in the horizontal direction on the clad steel disposed through the gap. And the welding material of the 1st layer and the 2nd layer or more was welded from the outside. Each steel was welded under these test conditions. The specimens of the steels tested under the conditions of FIG. 5 (c) are shown as test numbers AH2 and BH2 in Table 3.

  FIG.5 (d) is a figure which shows the test material of a horizontal welding attitude | position. Two clad steels were arranged in a vertical direction with a gap of 4 mm (route interval), and a backing material was arranged inside the gap (clad steel 2 mm thick NAS254NM). And the welding material of the 1st layer and the 2nd layer or more was welded from the outside. Each steel was welded under these test conditions. The specimens of each steel tested under the conditions of FIG. 5D are shown as test numbers AH1, BH1, and BH11 in Table 3.

  Moreover, about each test body, the external appearance test | inspection, the cross-section macro defect inspection, the component analysis of the first layer weld metal, UT inspection, the joint tension test, and the surface bending test were done. The test results are shown in Table 4. As a result, it was found that no welding defect or the like was confirmed for any of the test bodies, and that any welding could be used for good welding.

  As the metal or welding material used as the new iron skin, it is preferable to use a metal having high corrosion resistance including Ni, Cr, Mo and the like. Here, the corrosion resistance of the welding material was examined using a plurality of metals. First, Table 5 shows chemical components of the weld metal. AV1, AV2, NAS254NM, and Hastelloy C276 are all metals having high corrosion resistance including Ni, Cr, Mo and the like.

  For these weld metals, the pitting corrosion resistance index PI and the overall corrosion resistance index ISC were calculated. Table 6 shows the pitting corrosion resistance index PI and the general corrosion resistance index ISC of NAS254NM. It was found that the weld metals AV1 and AV2 have a higher pitting corrosion resistance index PI and a general corrosion resistance index ISC than the metal (NAS254NM base material) used as the new iron skin, and are excellent in corrosion resistance.

The pitting corrosion resistance index PI and the general corrosion resistance index ISC are obtained by the following equations.
PI = Cr + 3.3Mo + 16N (1)
ISC = 0.6Cr + Ni + 1.5Mo + 7.5Cu + 122N (2)
The element symbol in the above formula indicates the mass of each element contained.

  Furthermore, a corrosion test was conducted using the corrosion products collected from the actual machine, and the corrosion resistance of the new iron skin and the welding material was evaluated. The clad steel used for the new iron skin is composed of SM400 having a thickness of 6 to 9 mm and NAS254NM having a thickness of 2 mm.

  Each steel was tested for corrosion using a simulated liquid containing corrosion products collected from the actual machine and an accelerated simulated liquid that accelerates corrosion. Table 7 shows the compositions of the simulated liquid and the accelerated simulated liquid.

The result of the corrosion test using the simulated liquid is shown in FIG. Moreover, the result of the corrosion test using an acceleration simulation liquid is shown in FIG. Table 8 summarizes the test results of FIGS. 6 and 7. The corrosion rate CR in the table was determined by the following formula.
CR [mm / year] = (i × t × M) / (z × F × ρ) (3)
i: current density [A / cm ² ], t: time [sec / year (Note: conversion from sec to year)], M: average atomic weight [g / mol], z: average valence, F: Faraday constant 96500 [C / mol], ρ: Density [g / cm ³ ]

  The corrosion pattern in Table 8 is as shown in FIG. When the relationship between the current density and the potential is the A pattern in FIG. 8A or the B pattern in FIG. 8B, there is a concern about overall corrosion, but for the C pattern in FIG. There is no concern about overall corrosion.

  From Table 8, the corrosion rate of NAS254NM was 0.02 mm / year for the base metal and 0.07 mm / year for the weld. Since the base material has a thickness of 2 mm, it has been found that a life of about 40 years can be expected with only the base material. As for the corrosion pattern, NAS254NM was a C pattern with no concern about the overall corrosion.

  FIG. 9 (a) is a diagram showing the general corrosion resistance and local corrosion performance of each steel. In FIG. 9A, the corrosion resistance performance of each steel type is shown by the overall corrosion resistance index GI. The overall corrosion resistance index GI is represented by the following formula. When the overall corrosion resistance index GI is 60 or more, sufficient overall corrosion resistance is obtained.

GI = −Cr + 3.6Ni + 4.7Mo + 11.5Cu (4)
Moreover, FIG.9 (b) is a figure which shows the local corrosion resistance performance of each steel type. In FIG. 9A, the corrosion resistance performance of each steel type is shown by the local corrosion resistance index CI. The local corrosion resistance index CI is expressed by the following equation. When the local corrosion resistance index CI is 47 or more, sufficient overall corrosion resistance is obtained.

CI = C + 0.4Ni + 2.7No + Cu + 18.7N (5)
FIG. 10 shows a summary of FIG. 9 (a) and FIG. 9 (b). NAS254NM is a steel having a general corrosion resistance index GI of 60 or more and a local corrosion resistance index CI of 47 or more, and has sufficient corrosion resistance even when employed as a material for a chimney cylinder. I found out.

  Using the method of Patent Document 1 as a comparative example, the effect of the chimney cylinder installation method of the present embodiment was verified. Specifically, in the method of Patent Document 1, the work of installing a work place for installing the chimney cylinder, the operation of installing the cylinder, and placing the refractory 13 between the old iron skin and the new iron skin Work is required (see FIG. 11). Then, the man-hour of each operation | work by the chimney cylinder installation method based on this invention when the man-hour of each operation | work of patent document 1 was set to 100 was investigated. As a result, the man-hours for each operation according to the method of the present invention are as shown in Table 9.

  Moreover, in patent document 1, when the man-hour of the whole operation | work is 100%, the operation | work which installs the work place for installing a chimney cylinder body, the operation | work which installs a cylinder body, between an old iron skin and a new iron skin The compositional ratios of the work of placing the refractory 13 on the top are 20%, 60% and 20%, respectively. Therefore, the number of man-hours for each work was multiplied by this component ratio to perform weighting, and the total man-hours of the method of the present invention for Patent Document 1 were calculated. As a result, when the total man-hour of the method of Patent Document 1 is 100, the total man-hour of the present invention is (20 × 20%) + (90 × 60%) + (0 × 20%) = 58. . Thus, it has been found that if the method according to the present invention is used, the number of steps can be reduced to about 60% of the conventional method.

DESCRIPTION OF SYMBOLS 1,11 Existing iron-skin chimney 1a Rib 3, 12, 31, 32 New iron-skin 3a Engagement part 3b Arc-shaped iron-skin 4 Winch 5 Jack 13 Refractory

Claims (5)

A first operation in which a plurality of arc-shaped iron skins are formed on the outer periphery of an existing chimney and a new iron skin is installed;
A second operation of lifting up the new iron skin formed with go;
Below the lifted-up new iron skin, further, a third operation of forming a new new iron skin by surrounding the plurality of arc-shaped iron skins,
A fourth operation for lowering the lifted-up new iron skin onto the new new iron skin formed in the third operation;
A fifth operation for joining the new iron skin lowered in the fourth operation and the new new iron skin formed in the third operation;
A chimney cylinder installation method characterized in that a cylinder with a new iron skin is installed on the outer periphery of an existing chimney by repeating the first to fifth operations. Dividing the work section into a plurality of sections in the height direction of the existing chimney, in the second or more section from the bottom,
In the first operation, on the new iron skin installed in the lower section, a plurality of arc-shaped iron skins are formed on the outer periphery of the existing chimney to install the new iron skin,
In the second operation, the new iron skin formed in the first operation is lifted up,
In the third operation, under the new iron skin that has been lifted up, further, the plurality of arc-shaped iron skins are formed to form the new new iron skin,
In the fourth operation, the new iron skin lifted up is lowered onto the new new iron skin installed in the third operation,
In the fifth operation, joining the new iron skin lowered in the fourth operation and the new new iron skin installed in the third operation,
By installing the new iron skin on the new iron skin installed in the lower section by repeating the first to fifth operations,
The chimney cylinder installation method according to claim 1, wherein the uppermost new iron skin installed in the lower section is joined to the lowermost new iron skin installed in the upper section.   The chimney cylinder installation method according to claim 1 or 2, wherein the corrosion resistance of the steel material on the inner peripheral side of the new iron skin is higher than the corrosion resistance of the steel material of the existing chimney.   The chimney cylinder installation method according to any one of claims 1 to 3, wherein the new iron skin is clad steel in which the corrosion resistance of the steel material on the inner circumferential side is higher than the corrosion resistance of the steel material on the outer circumferential side. . 5. The chimney cylinder installation method according to claim 4, wherein the clad steel has a general corrosion resistance index GI of 60 or more and a local corrosion resistance index CI of 47 or more .

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