Method for manufacturing open rack gasifier component, and open rack gasifier component

Abstract

The present invention is a method for manufacturing an open rack vaporizer component in which an Al powder or an Al alloy powder and an Al2O3 powder are introduced into a high-speed flame to form a spray coating film on the surface of a substrate comprising Al or an Al alloy.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an open rack vaporizer component and an open rack vaporizer component. In particular, it relates to a method for manufacturing an open rack vaporizer component using a substance containing corrosive components such as seawater as a refrigerant, and an open rack vaporizer component. Background Art

[0002] An open rack vaporizer is a device that exchanges heat between a cryogenic liquid state liquefied gas (such as LNG) using a refrigerant (such as seawater) to vaporize the liquefied gas. Figure 7 And Figure 8 is a partial schematic diagram of an enlarged part of the open rack vaporizer, Figure 7 is a perspective view, Figure 8 is a side view. As Figure 7 , Figure 8 shown, in the open rack vaporizer, a lower header pipe 102 and an upper header pipe 104 are arranged at a distance in the vertical direction. LNG flows through a heat transfer pipe 103 connecting the lower header pipe 102 and the upper header pipe 104. The refrigerant overflowing from the refrigerant spraying tank 106 flows along the outside of the heat transfer pipe 103. Then, the LNG inside the heat transfer pipe 103 exchanges heat with the refrigerant outside the heat transfer pipe 103. Thus, the LNG is vaporized into a gas.

[0003] Vaporizer components such as the heat transfer pipe 103, header pipes 102 and 104 mounted on the heat exchange panel of the open rack vaporizer are made of Al alloys (3000 series, 5000 series, 6000 series, etc.) with high thermal conductivity to facilitate heat absorption from seawater. However, as described above, such vaporizer components have a risk of corrosion when used in an environment exposed to seawater. Therefore, it is preferable to perform an anti-corrosion treatment on the vaporizer components.

[0004] Conventionally, as an anti-corrosion treatment for vaporizer components, for example, in Patent Document 1, a method of forming a sacrificial anode layer on the outer surface of an Al alloy substrate by fuse-type flame spraying of an Al-2 mass% Zn alloy is described. Prior Art Documents Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2011-112294 Summary of the Invention -Problems to be Solved by the Invention-

[0006] However, the present inventors have found that the corrosion resistance and adhesion to the Al alloy substrate of the sprayed film described in Patent Document 1 are insufficient and there is room for improvement.

[0007] The present invention provides a method for manufacturing an open rack vaporizer component having a sprayed film with excellent corrosion resistance and adhesion to a substrate, and an open rack vaporizer component having a sprayed film with excellent corrosion resistance and adhesion to a substrate. - Solution to the problem -

[0008] The method for manufacturing an open rack vaporizer component of the present invention is characterized in that an Al powder or an Al alloy powder and an Al2O3 powder are introduced into a high-speed flame to form a sprayed film on the surface of a substrate made of Al or an Al alloy.

[0009] As a more preferable feature of the method for manufacturing an open rack vaporizer component of the present invention, it can be cited that the volume ratio of the Al powder or Al alloy powder (A) to the Al2O3 powder (B) is 0.1 ≤ (B) / (A) ≤ 3.5.

[0010] In addition, the open rack vaporizer component of the present invention is characterized in that the open rack vaporizer component includes a substrate made of Al or an Al alloy and a sprayed film formed on the surface of the substrate, and the sprayed film includes a main phase made of Al or an Al alloy and Al2O3 particles dispersed in the main phase.

[0011] As more preferable features of the open rack vaporizer component of the present invention, the following three points can be cited. (1) The Al2O3 content of the sprayed film is greater than or equal to 10% and less than 30%. (2) The porosity of the sprayed film is less than 4%. (3) The adhesion force between the sprayed film and the substrate is 25 MPa or more. - Effects of the invention -

[0012] According to the present invention, an open rack vaporizer component having a sprayed film with excellent corrosion resistance and adhesion to a substrate can be provided. Description of the drawings

[0013] Figure 1 is a perspective schematic view showing an example of an open rack vaporizer. Figure 2 is Figure 1 a partially enlarged perspective schematic view of the open rack vaporizer of Figure 3 is a graph showing the relationship between the volume ratio of the material powders (Al2O3 / A1) in the test pieces of Examples 1 to 7 and the Al2O3 content in the film. Figure 4 is a graph showing the relationship between the volume ratio of the material powders (Al2O3 / A1) in the test pieces of Examples 1 to 7 and the porosity in the film. Figure 5 It is a partial cross-sectional view of a sprayed film formed by the method of Example 3. Figure 6 It is a partial cross-sectional view of a sprayed film formed by the method of Comparative Example 1. Figure 7 It is a partially enlarged three-dimensional schematic view of an open rack vaporizer. Figure 8 It is a partially enlarged side view schematic of an open rack vaporizer. Detailed Embodiment

[0014] Hereinafter, an embodiment of the open rack vaporizer component of the present invention will be described with reference to the accompanying drawings.

[0015] Figure 1 It is a three-dimensional schematic view showing an example of an open rack vaporizer. Additionally, Figure 2 is Figure 1 a partially enlarged three-dimensional schematic view of the open rack vaporizer. As Figure 1 , Figure 2 shown, the open rack vaporizer 1 includes, for example: a lower header 2, heat transfer tubes 3, an upper header 4, a refrigerant supply component 5, a refrigerant spray tank 6, and a liquefied gas supply component 7. The liquefied gas flows into the lower header 2. The gas formed by vaporizing the liquefied gas flows out from the upper header 4. The heat transfer tubes 3 connect the lower header 2 and the upper header 4. In the heat transfer tubes 3, the liquefied gas flowing in from the lower header 2 is vaporized by the heat from the external refrigerant as it flows upward. Then, the vaporized gas flows from the heat transfer tubes 3 into the upper header 4. The refrigerant supply component 5 supplies a refrigerant for heat exchange with the liquefied gas to the outside of the heat transfer tubes 3 to vaporize the liquefied gas. The liquefied gas supply component 7 supplies the vaporized liquefied gas.

[0016] In the open rack vaporizer 1, a plurality of lower headers 2 and upper headers 4 are respectively provided, and the lower headers 2 and the upper headers 4 extend along a direction parallel to the surface on which the open rack vaporizer 1 is installed. The heat transfer tubes 3 extend along a direction perpendicular to the extension direction of the lower headers 2 and the upper headers 4. Additionally, in order to increase the surface area where the refrigerant and the liquefied gas can perform heat exchange, a plurality of heat transfer tubes 3 are gathered to form a plate. The refrigerant supply component 5 includes a portion that extends parallel to the upper header 4. The refrigerant spray tank 6 extends in a curved manner parallel to the upper header 4 such that it has an opening at the upper side. The refrigerant spray tank 6 is provided near the connection portion between the upper header 4 and the heat transfer tubes 3. The refrigerant supply component 5 is connected to the refrigerant spray tank 6.

[0017] In this embodiment, LNG is used as the liquefied gas, and seawater is used as the refrigerant. It should be noted that the refrigerant is not limited to seawater, and for example, fresh water can also be used. The base materials of the lower header 2, the heat transfer tubes 3, and the upper header 4 are made of Al or an Al alloy with high thermal conductivity. Here, the Al alloy refers to an alloy in which the ratio of Al is the highest among the elements constituting the alloy. At this time, the content of Al in the Al alloy is preferably 80% by mass or more, more preferably 90% by mass or more. The type of the Al alloy is not particularly limited, and for example, an Al-Mn series alloy, an Al-Si series alloy, an Al-Mg series alloy, an Al-Cu series alloy, an Al-Zn series alloy, an Al-Mg-Si series alloy, an Al-Mg-Cu series alloy, an Al-Zn-Mg series alloy, etc. can be used.

[0018] Next, an embodiment of the manufacturing method of the open rack vaporizer components of the present invention will be described.

[0019] As described above, since seawater is supplied to the vaporizer components made of Al or an Al alloy such as the lower header 2, the heat transfer tubes 3, and the upper header 4, there is a risk of corrosion. Therefore, a sprayed film having an anti-corrosion effect is formed on the surface of the vaporizer components.

[0020] The sprayed film of this embodiment is a sprayed film formed on the surface of the base material of the open rack vaporizer component mainly composed of Al or an Al alloy by simultaneously injecting Al powder or Al alloy powder and Al2O3 powder into a high-speed flame. In this embodiment, a film-forming method of supplying Al powder or Al alloy powder and Al2O3 powder to the same high-speed flame is adopted. Thus, an Al film or an Al alloy film can be formed on the surface of the base material, and the unmolten Al2O3 particles impact the surface of the just-formed Al film or Al alloy film at high speed, and can destroy the pores formed during film formation. By repeating this process, the entire area of the film is densified, and a sprayed film with excellent corrosion resistance without through pores is formed. In particular, when the film near the base material interface is pressed into the base material surface and undergoes plastic deformation, the contact area between the base material and the film increases. As a result, due to the improvement of the anchoring effect, a sprayed film with excellent adhesion to the base material can be formed compared with the conventional film-forming methods. The high-speed flame can be generated by a commercially available high-speed flame spraying device. When the unmolten Al2O3 particles impact the surface of the Al alloy film, a part of them is incorporated into the Al alloy film to form a film. For example, as Figure 5 shown in the cross-sectional photograph, the sprayed film formed in this embodiment is formed in a state including a main phase composed of Al or an Al alloy and unmolten Al2O3 particles dispersed in the main phase. It should be noted that in this specification, when observing the cross section of the sprayed film, a phase with an area ratio of 50% or more of the components in the sprayed film is called the main phase.

[0021] In this embodiment, the material powders introduced into the high-speed flame are Al powder or Al alloy powder, and Al2O3 powder. Al and Al alloys have high thermal conductivity and easily function as sacrificial anti-corrosion layers. Examples of the types of Al alloy powders that can be used include Al-Mn series alloys, Al-Si series alloys, Al-Mg series alloys, Al-Cu series alloys, Al-Zn series alloys, Al-Mg-Si series alloys, Al-Mg-Cu series alloys, Al-Zn-Mg series alloys, etc. In addition, the average particle size of the Al powder or Al alloy powder is preferably 20 to 100 μm, and the average particle size of the Al2O3 powder is preferably 8 to 450 μm. It should be noted that in this specification, the "average particle size" is defined as the particle size (median particle size) at which the cumulative value is 50% when measuring the particle size distribution using the laser diffraction-scattering method (micro-track method).

[0022] In this embodiment, the volume ratio of the Al powder or Al alloy powder (A) to the Al2O3 powder (B) is preferably 0.1 ≤ ((B) / (A)), more preferably 1.0 ≤ ((B) / (A)). In addition, the volume ratio of the Al powder or Al alloy powder (A) to the Al2O3 powder (B) is preferably ((B) / (A)) ≤ 3.5. If the volume ratio is in such a relationship, the adhesion of the sprayed film to the substrate is further improved, and the porosity can be further reduced. If the porosity in the sprayed film is high, the possibility of generating through-holes in the sprayed film increases. If there are through-holes, seawater may invade from the surface of the sprayed film to reach the interface with the substrate. If seawater invades the interface between the sprayed film and the substrate, the corrosion deteriorates. Therefore, in order to suppress the deterioration of corrosion, the porosity in the sprayed film is preferably less than 4%, more preferably 2.5% or less. In addition, if the content of Al2O3 particles in the Al or Al alloy film is too large, the original properties of Al or Al alloy may be damaged. On the other hand, if the Al2O3 content in the sprayed film is less than 30%, a sufficient anti-corrosion effect can be obtained. From the viewpoints of improving adhesion and reducing porosity, the content of Al2O3 particles is preferably 10% or more. Therefore, the Al2O3 content in the sprayed film is preferably 10% or more and preferably less than 30%. In addition, from the viewpoint of the Al or Al alloy being the main phase in the sprayed film, the content of Al or Al alloy in the sprayed film is preferably 70% or more and preferably less than 90%. The porosity of the sprayed film and the content of the components constituting the sprayed film can be obtained by appropriately processing the cross-section of the film obtained by cutting the vaporizer component, such as mirror polishing, and observing with a microscope. For example, it can be determined by image analysis of a photograph taken at 100 times magnification with a scanning electron microscope and calculating the area ratio of each part.

[0023] As described above, in this embodiment, the sprayed film is formed by high-speed impact of unmelted Al2O3 particles on the surface of the just-formed Al film (Al alloy film) and repeating this process, so that the entire film area is densified. Thus, by densifying the entire film area, a film with few through-holes can be formed, and the corrosion resistance is further improved. In addition, near the substrate interface of the sprayed film, the anchoring effect is improved due to the increased contact area between the substrate and the film, so that a film with high adhesion to the substrate can be formed.

[0024] In this embodiment, the adhesion between the sprayed film and the substrate is preferably 25 MPa or more. As described above, an open rack vaporizer is a device that exchanges heat between cryogenic liquefied gas inside the vaporizer component and a refrigerant outside the vaporizer component, so the temperature gradient between the inner surface and the outer surface of the vaporizer component is very large. Therefore, due to the temperature difference between the substrate on the inner surface of the vaporizer component and the sprayed film on the outer surface of the vaporizer component, the thermal expansion difference between the substrate and the sprayed film increases, and as a result, the sprayed film may peel off. In addition, since the open rack vaporizer is repeatedly started and stopped, the vaporizer component is exposed to thermal cycling, and the sprayed film may peel off. In response, by making the adhesion between the sprayed film and the substrate 25 MPa or more, peeling of the sprayed film can be suppressed.

[0025] It should be noted that the components to which the sprayed film in this embodiment is applicable are not limited to heat transfer tubes, upper headers, and lower headers, and can also be applied to other components. [Examples]

[0026] Hereinafter, examples applying the present invention will be described. These examples are illustrative of the present invention and do not limit the scope of the invention.

[0027] [Example 1] As the substrate, an A5052 alloy (Al-Mg alloy) with dimensions of 50×50×5 mmt was prepared. Next, the substrate was roughened by sandblasting with WA (white alumina) F60 abrasive at a spraying pressure of 0.3 MPa. Next, a test piece was formed by forming a film on the roughened substrate according to the following points. Film forming method: The powder mixture of Material 1 and Material 2 was introduced into the high-speed flame generated by a high-velocity oxy-fuel spraying device Material 1: Al powder (average particle size: 38 μm) Material 2: Al2O3 powder (average particle size: 108 μm) Volume ratio (Al2O3 powder / Al powder): 0.18

[0028] [Example 2] The volume ratio of the material powders (Al2O3 powder / Al powder) was 0.65, and a test piece was produced in the same manner as in Example 1 except for this.

[0029] [Example 3] The volume ratio of the material powders (Al2O3 powder / Al powder) was 1.05, and a test piece was produced in the same manner as in Example 1 except for this.

[0030] [Example 4] The volume ratio of the material powders (Al2O3 powder / Al powder) was 1.31, and a test piece was produced in the same manner as in Example 1 except for this.

[0031] [Example 5] The volume ratio of the material powders (Al2O3 powder / Al powder) was 1.98, and a test piece was produced in the same manner as in Example 1 except for this.

[0032] [Example 6] The volume ratio of the material powders (Al2O3 powder / Al powder) was 2.52, and a test piece was produced in the same manner as in Example 1 except for this.

[0033] [Example 7] The volume ratio of the material powders (Al2O3 powder / Al powder) was 3.31, and a test piece was produced in the same manner as in Example 1 except for this.

[0034] [Example 8] The base material used was A5083 (A1-Mg alloy), Material 1 used Al-3% Zn powder, and the volume ratio (Al2O3 powder / Al powder) was 1.05. A test piece was produced in the same manner as in Example 1 except for this.

[0035] [Example 9] The base material used was A5083 (A1-Mg alloy), Material 1 used Al-5% Mg powder, and the volume ratio (A12O3 powder / Al powder) was 1.05. A test piece was produced in the same manner as in Example 1 except for this.

[0036] [Comparative Example 1] The base material used was A5083 (A1-Mg alloy), and film formation was carried out according to the following points. A test piece was produced in the same manner as in Example 1 except for this. Film formation method: The following materials were put into the flame generated by a fuse-type flame spraying device Materials: Al wire

[0037] [Comparative Example 2] The test pieces were produced in the same manner as in Example 1, except that only Al powder was used as the material.

[0038] Test pieces were produced using the methods of Examples 1 to 9 and the methods of Comparative Examples 1 and 2, and then the following measurements were performed on each test piece.

[0039] [Al2O3 content] Each test piece was cut perpendicular to the surface on which the film was formed, the cut piece was embedded in resin, the cross-section produced by the cutting was polished, and then an image of the film cross-section was taken with a scanning electron microscope (JSM-IT300LA, manufactured by JEOL Ltd.). Next, the cross-sectional image was binarized using image analysis software (WinROOF2018, manufactured by MITANI CORPORATION.) to identify Al2O3 particles, and the proportion of the area of the Al2O3 particles in the cross-section of the sprayed film was calculated.

[0040] [Porosity] Each test piece was cut perpendicular to the surface on which the film was formed, the cut piece was embedded in resin, the cross-section produced by the cutting was polished, and then an image of the film cross-section was taken with a scanning electron microscope (JSM-IT300LA, manufactured by JEOL Ltd.). Next, the cross-sectional image was binarized using image analysis software (WinROOF2018, manufactured by MITANI CORPORATION.) to identify pores, and the proportion of the area of the pore part in the cross-section of the sprayed film was calculated.

[0041] Test pieces were produced using the methods of Examples 1 to 9 and the methods of Comparative Examples 1 and 2, and then the following tests were performed on each test piece.

[0042] [Adhesion test] The adhesion test was carried out in accordance with the method of Japanese Industrial Standard JIS H 8402, and the adhesion between the substrate and the sprayed film was evaluated based on the fracture surface pressure (MPa).

[0043] [Salt spray test] The salt spray test was carried out for 300 hours in accordance with the method of Japanese Industrial Standard JIS Z2371:2015. Then, cross-sectional observation was performed, and the corrosion resistance was evaluated by confirming the presence or absence of corrosion products at the interface between the film and the substrate. The meanings of the evaluation indexes for corrosion resistance are as follows. ○: No corrosion products appeared after 300 hours. ×: Corrosion products appeared after 300 hours.

[0044] Table 1 is a summary table of the results of the above measurements and tests on the test pieces of Examples 1 to 9 and Comparative Examples 1 and 2. In addition, Figure 3It is a graph showing the relationship between the volume ratio (Al2O3 powder / Al powder) in each test piece of Examples 1 to 7 and the Al2O3 content in the film. Figure 4 It is a graph showing the relationship between the volume ratio (Al2O3 powder / Al powder) in each test piece of Examples 1 to 7 and the porosity in the film.

[0045] [Table 1]

[0046] In the adhesion item in Table 1, none of the test pieces broke between the substrate and the sprayed film, and breakage occurred between the sprayed film and the adhesive layer at a stress of less than 25 MPa. Therefore, at least the minimum adhesion size confirmed was recorded in the table. It can be seen that the sprayed films of Examples 1 to 9 all have an adhesion of 25 MPa or more. From this, it can be known that in terms of adhesion, compared with the sprayed films formed by the conventional fuse-type flame spraying, at least a three-fold or more improvement effect can be confirmed.

[0047] As shown in Table 1, it can be seen that the test pieces of Examples 1 to 9 obtained good results in terms of porosity, adhesion, and corrosion resistance compared with Comparative Example 1.

[0048] A photograph of a partial cross-sectional view of the film formed by the method of Example 3 is shown in Figure 5 and a photograph of a partial cross-sectional view of the film formed by the method of Comparative Example 1 is shown in Figure 6 . It can be seen that the sprayed film of Example 3 forms a dense structure in the entire film area, while the sprayed film of Comparative Example 1 forms a structure with many pores. It should be noted that although not shown, the films of Examples 1 to 9 are all films that are dense in the entire film area as Figure 5 shown. From this, it is speculated that the test pieces of Examples 1 to 9 obtained good results in terms of porosity, adhesion, and corrosion resistance compared with the test pieces of Comparative Example 1 because the entire area is a dense film structure.

[0049] In addition, as shown in Figure 3 and Figure 4 , it can be seen that the Al2O3 content of the test pieces of Examples 3 to 7 is greater than that of Examples 1 and 2, and the porosity of the test pieces of Examples 3 to 7 is less than that of Examples 1 and 2. That is, it can be known that if the Al2O3 content in the material powder or the film increases to a certain value or more, the porosity is significantly reduced. -Industrial Applicability-

[0050] The open-type vaporizer component described in the present invention can be used as, for example, a heat transfer tube, an upper header, and a lower header. -Symbol Explanation-

[0051] 1: Open rack vaporizer 2: Lower header 3: Heat transfer tube 4: Upper header 5: Refrigerant supply component 6: Refrigerant spray tank 7: LPG supply component 102: Lower header 103: Heat transfer tube 104: Upper header 106: Refrigerant spray tank

Claims

1. A manufacturing method of an open rack vaporizer component, characterized in that, the manufacturing method of the open rack vaporizer component forms a sprayed coating on the surface of a substrate made of Al or an Al alloy by putting Al powder or Al alloy powder and Al2O3 powder into a high-speed flame.

2. The manufacturing method of the open rack vaporizer component according to claim 1, characterized in that, the volume ratio of the Al powder or Al alloy powder (A) to the Al2O3 powder (B) is 0.1 ≤ (B) / (A) ≤ 3.

5.

3. An open rack vaporizer component, characterized in that, the open rack vaporizer component includes a substrate made of Al or an Al alloy and a sprayed coating formed on the surface of the substrate, the sprayed coating contains a main phase made of Al or an Al alloy and Al2O3 particles dispersed in the main phase.

4. The open rack vaporizer component according to claim 3, characterized in that, the Al2O3 content of the sprayed coating is greater than or equal to 10% and less than 30%.

5. The open rack vaporizer component according to claim 3, characterized in that, the porosity of the sprayed coating is less than 4%.

6. The open rack vaporizer component according to claim 3, characterized in that, the adhesion force between the sprayed coating and the substrate is 25 MPa or more.

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