Heat exchanger having powder coated elements
View Patent ↗Powder coated heat exchange elements for a heat exchanger. Powder coating provides improved protective coating on surfaces of heat exchange elements. In many applications, the heat exchange elements are subjected to harsh operating conditions that promote corrosion. Traditional enamel coating tends to fracture when subjected to mechanical stresses thereby allowing corrosion inducing agents to penetrate and corrode the underlying surfaces. Powder coating reduces breaches in the protective layer. Powder coating may be adapted to withstand high temperatures so as to make them suitable for use in harsh operating environments. One such environment can be found in the processing of flue gas from fossil burning power generators, where the flue gas has a relatively high temperature and high sulfur content.
1. A method of fabricating a heat exchanger having a heat exchange body and a plurality of seals disposed between a heat exchange body and a housing, the method comprising:
preparing a surface of the heat exchanger that is susceptible to pitting and structural deterioration when exposed to a corrosive environment, the heat exchanger adapted for use in reducing a temperature of a flue gas emitted from a coal burning power generator prior to said gas being released into the environment; and
powder coating the surface, the powder coating being a resilient coating robustly adhered to the surface and having a high acid resistivity and configured to inhibit the adherence of, and decrease the accumulation of, sulfur-based particles to the powder coated surface, thereby forming a barrier that resists corrosion inducing agents created by the coal burning power generation process from contacting the surface,
wherein the coating is a uniform coating with an area density of between about 1.55 g/cm 2 and about 6 g/cm 2 .
2. The method of claim 1 , further comprising assembling the heat exchanger after powder coating the surface.
3. The method of claim 1 , wherein preparing the surface further comprises forming a line grain on the surface to provide a textured finish with a porous structure to the surface to facilitate adhesion of the powder coating to the surface.
4. The method of claim 3 , wherein the line grain is formed in a generally linear direction to provide a brushed finish.
5. The method of claim 1 , further comprising cleaning the surface.
6. The method of claim 5 , wherein cleaning the surface includes applying an Iron phosphate wash to the surface.
7. The method of claim 6 , wherein the Iron phosphate wash is applied at an area density of between about 300 and about 900 mg/m 2 .
8. The method of claim 5 , wherein cleaning the surface includes rinsing the surface.
9. The method of claim 8 , wherein the surface is rinsed with de-ionized water.
10. The method of claim 8 , further comprising heating the surface to a temperature of about 400 deg. F for a period of about 20 minutes to remove moisture from the surface.
11. The method of claim 1 , wherein the coating has a thickness of between about 3 mils and bout 5 mils.
12. The method of claim 1 , wherein the coating has an area density of between about 1.55 g/cm 2 and about 1.8 g/cm 2 .
13. The method of claim 1 , further comprising curing the surface for a period of between about 5 minutes and about two hours at a temperature of between about 50 deg. F. and about 1000 deg. F.
14. The method of claim 1 , further comprising curing the surface for a period of between about 20 minutes and thirty minutes at a temperature of about 400 deg. F.
15. The method of claim 13 , wherein said curing results in a coating hardness of between about HB and about 5H in an ASTM Method D3363 pencil hardness standard.
16. The method of claim 1 , wherein the powder coating has a thickness of between about 0.0015 inches and 0.0025 inches.
17. The method of claim 1 , wherein the powder coating has a thickness of between about 0.002 inches and about 0.004 inches.
18. The method of claim 1 , wherein the powder coating comprises an epoxy resin.
19. The method of claim 4 , further comprising sandblasting the surface.
20. The method of claim 1 , wherein powder coating the surface comprises:
spraying a layer of electrostatically charged powder particles to the surface; and
fusing the layer of electrostatically charged powder particles to the surface.
21. The method of claim 20 , wherein fusing the layer includes curing the powder particles on the surface without oxidizing or corroding the surface.
22. The method of claim 21 , wherein curing comprises curing the layer of powder particles at a temperature of between about 400° F. and 450° F. for a period of about 15 minutes.
23. The method of claim 21 , wherein curing comprises curing the layer of powder particles at a temperature of about 400° F. for a period of about 60 minutes.
24. The method of claim 1 , wherein the powder coating is configured to withstand an operating temperature of about 975° F.
25. A method of fabricating a heat exchanger having a heat exchange body and a plurality of seals disposed between a heat exchange body and a housing, the method comprising:
preparing a surface of the heat exchanger that is susceptible to pitting and structural deterioration when exposed to a corrosive environment, the heat exchanger adapted for use in reducing a temperature of a flue gas emitted from a coal burning power generator prior to said gas being released into the environment;
spraying a layer of electrostatically charged powder particles onto the surface, where the surface has been electrically grounded; and
curing the layer of powder particles onto the surface to form a resilient powder coating fused to the surface, the powder coating having a high acid resistivity and configured to inhibit the adherence of, and decrease the accumulation of, sulfur-based particles to the powder coated surface, thereby forming a barrier that resists corrosion inducing agents created by the coal burning power generation process from contacting the surface,
wherein the coating is a uniform coating with an area density of between about 1.55 g/cm 2 and about 2.5 g/cm 2 .
26. The method of claim 25 , wherein curing comprises curing the layer of powder particles at a temperature of between about 400° F. and 450° F. for a period of about 15 minutes.
27. The method of claim 25 , wherein curing comprises curing the layer of powder particles at a temperature of about 400° F. for a period of about 60 minutes.
28. The method of claim 25 , wherein the cured powder coating is configured to withstand an operating temperature of about 975° F.
29. The method of claim 25 , wherein the powder coating has a thickness of between about 0.0015 inches and 0.0025 inches.
30. The method of claim 25 , wherein the powder coating comprises an epoxy resin.
31. The method of claim 25 , wherein the coating has an area density of between about 1.55 g/cm 2 and about 1.8 g/cm 2 .
32. The method of claim 25 , wherein said curing results in a coating hardness of between about HB and about 5H in an ASTM Method D3363 pencil hardness standard.
33. The method of claim 25 , further comprising cleaning the surface.
34. The method of claim 33 , wherein cleaning the surface includes applying an Iron phosphate wash to the surface.
35. The method of claim 34 , wherein the Iron phosphate wash is applied at a density of between about 300 and about 900 mg/m 2 .