A wear-resistant and corrosion-resistant heat pipe heat exchanger and its preparation method

Abstract

The present invention provides a wear-resistant and corrosion-resistant heat pipe heat exchanger and a preparation method thereof. The preparation method of the present invention includes: S1: soaking the heat pipe in an anti-corrosion solution containing β-cyclodextrin, gluconic acid and a catalyst, and drying; S2: soaking the heat pipe in a sodium silicate solution, and drying; S3: soaking the heat pipe in a solution containing PDMS and a supporting curing agent, and curing to obtain a wear-resistant and corrosion-resistant heat pipe heat exchanger. The present invention uses sodium silicate and gluconic acid to form films on the metal surface of the heat pipe respectively to form a double-film synergistic anti-corrosion effect. At the same time, cyclodextrin combines with gluconic acid to increase the thermal stability of the material to adapt to a higher flue gas temperature; in addition, PDMS and the supporting curing agent not only form a hydrophobic structure to isolate the influence of corrosive media, but also increase the viscosity of the double film, making the film not easy to fall off, while sodium silicate has good strength, hardness and smoothness after curing, and can cope with the flue gas conditions with more dust.

Description

Technical Field

[0001] The present invention relates to the technical field of heat pipe heat exchangers, and in particular to a wear-resistant and corrosion-resistant heat pipe heat exchanger and a preparation method thereof. Background Art

[0002] In order to recover the heat loss caused by flue gas emissions, a large number of low-temperature economizers are usually installed at the tail of the boiler. The low-temperature economizer is generally arranged between the air preheater and the electrostatic precipitator. The dust concentration of the flue gas at this position is relatively high, generally between 20 - 50 g / Nm 3 . The flue gas with this dust concentration causes relatively serious erosion and wear to the heat exchange tubes of the economizer; at the same time, the acidic gas in the flue gas has a corrosive effect on the heat exchange tubes. The heat exchanger is easily perforated when it is in an environment of erosion and wear for a long time. After perforation, the cooling water inside the tube will leak to the flue gas side, causing the mixture of moisture and flue gas dust to deposit and harden at the bottom of the flue, and will cause the entire serpentine heat exchange tube to lose its heat exchange capacity. It is necessary to stop and isolate the entire heat exchange module to prevent the cooling water inside the module from entering the flue, which seriously affects the operation reliability of the unit.

[0003] To solve the above problems, the current common solution is to use vacuum heat pipes with fins on the flue gas side. The vacuum heat pipe heat exchanger avoids the problem of water continuously entering the flue due to wear of the heat exchange tubes. However, since the low-temperature economizer is arranged in a high-dust environment and the dust concentration of the flue gas is relatively high, the flue gas erodes the finned vacuum heat pipes severely. The external fins of the vacuum heat pipes are severely worn under the erosion of high-dust flue gas for a long time, and the wear of the fins greatly reduces the heat exchange effect of the heat exchanger.

[0004] In view of this, the present invention is specifically proposed. Summary of the Invention

[0005] The purpose of the present invention is to provide a wear-resistant and corrosion-resistant heat pipe heat exchanger and a preparation method thereof, which are used to overcome the problems of corrosion and wear of traditional low-temperature economizers, so as to ensure the safe, stable and reliable operation of the heat pipe heat exchanger.

[0006] The present invention provides a preparation method of a wear-resistant and corrosion-resistant heat pipe heat exchanger, including the following steps carried out in sequence:

[0007] S1: Immerse the heat pipe in an anti-corrosion solution containing β-cyclodextrin, gluconic acid and a catalyst, and then dry it;

[0008] S2: Immerse the heat pipe in a sodium silicate solution, and then dry it;

[0009] S3: Immerse the heat pipe in a solution containing PDMS and its supporting curing agent, and after curing, a wear-resistant and corrosion-resistant heat pipe heat exchanger is obtained.

[0010] Specifically, in step S1, the mass content of gluconic acid in the anti-corrosion solution is 20 - 30%, and the mass content of β-cyclodextrin is 10 - 20%; the catalyst is sodium dihydrogen phosphate, and the mass content of sodium dihydrogen phosphate in the anti-corrosion solution is 1 - 5%.

[0011] In particular, the preparation method of the anti-corrosion solution includes: adding β-cyclodextrin and a catalyst to a gluconic acid solution, stirring evenly, and then heating at 120 - 180°C for 10 - 300 min.

[0012] In addition, in step S1, the soaking time is 10 - 15 h; the drying temperature is 70 - 90°C, and the drying time is 4 - 6 h.

[0013] In the above step S1, gluconic acid can complex with metal ions on the surface of the heat pipe metal to form an anti-corrosion film, thereby preventing the continuous corrosion of the heat pipe metal; the intervention of β-cyclodextrin can increase the thermal stability of the anti-corrosion film formed by gluconic acid to adapt to a higher flue gas temperature.

[0014] In step S2, the mass content of the sodium silicate solution is 15 - 20%; in addition, the soaking time is 20 - 30 h.

[0015] In the above step S2, sodium silicate can form a passivation film with the heat pipe metal, and cooperate with the anti-corrosion film formed by gluconic acid to jointly form a good anti-corrosion effect.

[0016] In step S3, the mass content of PDMS in the solution is 10 - 20%, the mass content of the curing agent is 1 - 2%, and the solvent of the solution is n-hexane; in addition, the soaking time is 8 - 12 min; the curing time is 22 - 26 h.

[0017] In the above step S3, PDMS can form a lotus effect hydrophobic layer to prevent corrosive media such as moisture in the flue gas from contacting the heat pipe wall. While PDMS and the supporting curing agent form a hydrophobic structure to isolate the influence of corrosive media, they can also increase the viscosity of the anti-corrosion film formed by gluconic acid and the passivation film formed by sodium silicate, making the double-layer film not easy to fall off; at the same time, the cured sodium silicate has good strength, hardness and smoothness, and can cope with the flue gas conditions with more dust; in particular, PDMS can form a covalent bond bridge with the hydroxyl groups in the inner anti-corrosion film and the outer passivation film, improving the thermal stability and viscosity of the anti-corrosion film and the passivation film.

[0018] The present invention also provides a wear-resistant and corrosion-resistant heat pipe heat exchanger prepared according to the above preparation method.

[0019] The implementation of the present invention has at least the following advantages:

[0020] 1. In the present invention, sodium silicate and gluconic acid are respectively used to form an inner anti-corrosion film and an outer passivation film with the heat pipe metal. The two films act synergistically to improve the anti-corrosion effect;

[0021] 2. In the present invention, β-cyclodextrin and gluconic acid are combined through an esterification reaction, which increases the thermal stability of the material and enables it to adapt to higher flue gas temperatures;

[0022] 3. After curing, the sodium silicate in the present invention has good strength, hardness and smoothness, and can withstand the erosion of flue gas dust;

[0023] 4. The present invention also uses PDMS and its supporting curing agent. It can not only form a hydrophobic structure to isolate the influence of corrosive media, but also increase the viscosity of the anti-corrosion film and the passivation film, making the anti-corrosion film and the passivation film not easy to fall off;

[0024] 5. The PDMS in the present invention can form a covalent bond bridging between the inner anti-corrosion film and the outer passivation film, overcoming the capillary action of water and thus improving the stability of the anti-corrosion film and the passivation film;

[0025] 6. The modification cost of the present invention is low, the loss is small, the maintenance cost is less, and the maintenance and flushing are convenient. When regularly inspected, the heat pipe wall can be made brand new by flushing with circulating water, adapting to various flue gas conditions, and can well meet the actual application requirements. Detailed Embodiments

[0026] It should be noted that the following detailed description is illustrative and is intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs.

[0027] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form also includes the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0028] The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the protection scope of the present invention.

[0029] Example 1

[0030] The preparation method of the wear-resistant and corrosion-resistant heat pipe heat exchanger in this embodiment is as follows:

[0031] 1) Prepare a 20wt% gluconic acid solution. Then, add sodium dihydrogen phosphate to the gluconic acid solution at 1wt%, stir well to dissolve, and then add β-cyclodextrin at 10wt%. After stirring evenly, heat at 120°C for 4h to obtain a corrosion prevention solution.

[0032] 2) Immerse the heat pipe to be modified in the corrosion prevention solution of step 1) for 12h, then take it out and dry it at 80°C for 5h.

[0033] 3) Prepare a 15wt% sodium silicate solution. Place the heat pipe modified in step 2) into the sodium silicate solution for 24h, then take it out and dry it with a blower.

[0034] 4) Add PDMS to n-hexane at 10wt% and add a supporting curing agent at 1wt%, stir well to dissolve, and obtain a wear-resistant solution.

[0035] 5) Place the heat pipe modified in step 3) into the wear-resistant solution, soak it for 10min and then take it out, and cure it naturally for 24h to obtain a wear-resistant and corrosion-resistant heat pipe heat exchanger.

[0036] Example 2

[0037] The preparation method of the wear-resistant and corrosion-resistant heat pipe heat exchanger in this embodiment is as follows:

[0038] 1) Prepare a 25wt% gluconic acid solution. Then, add sodium dihydrogen phosphate to the gluconic acid solution at 3wt%, stir well to dissolve, and then add β-cyclodextrin at 15wt%. After stirring evenly, heat at 150°C for 2h to obtain a corrosion prevention solution.

[0039] 2) Immerse the heat pipe to be modified in the corrosion prevention solution of step 1) for 10h, then take it out and dry it at 70°C for 6h.

[0040] 3) Prepare a 20wt% sodium silicate solution. Place the heat pipe modified in step 2) into the sodium silicate solution for 20h, then take it out and dry it with a blower.

[0041] 4) Add PDMS to n-hexane at 15wt% and add a supporting curing agent at 2wt%, stir well to dissolve, and obtain a wear-resistant solution.

[0042] 5) Place the heat pipe modified in step 3) into the wear-resistant solution, soak it for 8min and then take it out, and cure it naturally for 22h to obtain a wear-resistant and corrosion-resistant heat pipe heat exchanger.

[0043] Example 3

[0044] The preparation method of the wear-resistant and corrosion-resistant heat pipe heat exchanger in this embodiment is as follows:

[0045] 1) Prepare a 30 wt% gluconic acid solution. Subsequently, add sodium dihydrogen phosphate to the gluconic acid solution at 5 wt%, stir well to dissolve, then add β-cyclodextrin at 20 wt%. After stirring evenly, heat at 180 °C for 1 h to obtain an anti-corrosion solution.

[0046] 2) Immerse the heat pipe to be modified in the anti-corrosion solution prepared in step 1) for 15 h, then take it out and dry it at 90 °C for 4 h.

[0047] 3) Prepare an 18 wt% sodium silicate solution. Place the heat pipe modified in step 2) into the sodium silicate solution for 30 h, then take it out and dry it with blowing.

[0048] 4) Add PDMS to n-hexane at 20 wt% and add the supporting curing agent at 2 wt%, stir well to dissolve to obtain an abrasion-resistant solution.

[0049] 5) Place the heat pipe modified in step 3) into the abrasion-resistant solution, soak for 12 min and then take it out, and let it cure naturally for 26 h to obtain an abrasion-resistant and corrosion-resistant heat pipe heat exchanger.

[0050] Control Example 1

[0051] Except that gluconic acid is not added to the anti-corrosion solution in step 1), the rest is basically the same as in Example 1.

[0052] Control Example 2

[0053] Except that step 3) is not carried out (i.e., not treated with sodium silicate solution), the rest is basically the same as in Example 1.

[0054] Control Example 3

[0055] Except that β-cyclodextrin is not added to the anti-corrosion solution in step 1), the rest is basically the same as in Example 1.

[0056] Control Example 4

[0057] Except that steps 4) and 5) are not carried out (i.e., not treated with PDMS and the supporting curing agent), the rest is basically the same as in Example 1.

[0058] Test Example 1

[0059] Use an adhesive strength tester, sand falling method, simulate an acidic environment, etc. to detect the coating strength, abrasion resistance, and corrosion resistance of the heat pipe heat exchangers of each example and control example. The specific results are shown in Table 1 and Table 2 respectively.

[0060] Table 1 Detection results of the heat pipe heat exchangers of each example

[0061] Test Items Example 1 Example 2 Example 3 Coating Strength MPa 10 14 12 Abrasion Resistance L / um 12.6 17.1 16.8 High Temperature Resistance at 200°C for 1000 h No Change No Change No Change Resistance to 5% Sulfuric Acid for 10000 h No Change No Change No Change Resistance to 50% Sulfuric Acid for 5000 h No Change No Change No Change

[0062] Test Results of Heat Pipe Heat Exchangers in Each Control Example in Table 2

[0063] Test Items Control Example 1 Control Example 2 Control Example 3 Control Example 4 Coating Strength MPa 9 5 10 7 Abrasion Resistance L / um 11.3 5.4 12.7 8.9 High Temperature Resistance at 200°C for 1000 h Bubbling No Change Bubbling No Change Resistance to 5% Sulfuric Acid for 10000 h Slight Bubbling Slight Bubbling No Change No Change Resistance to 50% Sulfuric Acid for 5000 h Bubbling Bubbling No Change Slight Bubbling

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a wear-resistant and corrosion-resistant heat pipe exchanger, characterized in that: The steps include the following steps in order: S1: immersing the heat pipe in an anti-corrosion solution containing β-cyclodextrin, gluconic acid and a catalyst, and drying; S2: immersing the heat pipe in a sodium silicate solution and drying; S3: Immersing the heat pipe in a solution containing PDMS and a curing agent, and obtaining a wear-resistant and corrosion-resistant heat pipe exchanger after curing.

2. The preparation method according to claim 1, characterized in that: The mass content of gluconic acid in the anti-corrosion solution is 20-30%, and the mass content of beta-cyclodextrin is 10-20%.

3. The preparation method according to claim 1, characterized in that: The catalyst is sodium dihydrogen phosphate, and the mass content of the sodium dihydrogen phosphate in the anti-corrosion solution is 1-5%.

4. The preparation method according to claim 1, characterized in that: The preparation method of the anti-corrosion solution comprises: adding beta-cyclodextrin and a catalyst into a gluconic acid solution, stirring evenly, and heating at 120-180° C. for 10-300 minutes.

5. The preparation method according to claim 1, characterized in that: In step S1, the soaking time is 10-15 hours; the drying temperature is 70-90° C., and the drying time is 4-6 hours.

6. The preparation method according to claim 1, characterized in that: The mass content of the sodium silicate solution is 15-20%.

7. The preparation method according to claim 1, characterized in that: In step S2, the soaking time is 20-30 hours.

8. The preparation method according to claim 1, characterized in that: The mass content of PDMS is 10-20%, and the mass content of its matching curing agent is 1-2%.

9. The preparation method according to claim 1, characterized in that: In step S3, the soaking time is 8-12 minutes; and the curing time is 22-26 hours.

10. A wear-resistant and corrosion-resistant heat pipe heat exchanger, characterized in that: Prepared according to any one of the preparation methods of claims 1-9.