CN112342545B - Thermal spraying glass layer hole sealing preparation method - Google Patents
Thermal spraying glass layer hole sealing preparation method Download PDFInfo
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- CN112342545B CN112342545B CN202011038811.2A CN202011038811A CN112342545B CN 112342545 B CN112342545 B CN 112342545B CN 202011038811 A CN202011038811 A CN 202011038811A CN 112342545 B CN112342545 B CN 112342545B
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23D—ENAMELLING OF, OR APPLYING A VITREOUS LAYER TO, METALS
- C23D5/00—Coating with enamels or vitreous layers
- C23D5/04—Coating with enamels or vitreous layers by dry methods
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- C—CHEMISTRY; METALLURGY
- C03—GLASS; MINERAL OR SLAG WOOL
- C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
- C03C8/00—Enamels; Glazes; Fusion seal compositions being frit compositions having non-frit additions
- C03C8/14—Glass frit mixtures having non-frit additions, e.g. opacifiers, colorants, mill-additions
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- Coating By Spraying Or Casting (AREA)
Abstract
The invention provides a method for preparing a hole sealing by thermally spraying a glass layer, which comprises the following steps: firstly, preparing a binder, then mixing the binder, glass powder and wollastonite into slurry, spraying the prepared slurry on the surface of an electric arc spraying layer, drying to obtain a slurry layer, heating the slurry layer to melt the glass powder in the slurry, and cooling to form a compact glass layer; the invention has the beneficial effects that: after the glass layer compounded on the surface of the electric arc spraying layer is subjected to hot melting treatment to form a compact glass layer, the average porosity of the composite layer can be greatly reduced, the adhesion capability of the composite layer is obviously improved, the phenomenon that the glass layer falls off in later use to reduce the corrosion resistance is avoided, and the service life is prolonged; the higher the binder proportion, the higher the adhesion to the composite layer, but the lower the average porosity; the adhesive capacity is improved, the falling off in later use is prevented, the service life is prolonged, the corrosion resistance is reduced, and the coating is suitable for being used in high-impact low-corrosion environments.
Description
Technical Field
The invention relates to the technical field of boiler corrosion prevention, in particular to a method for preparing a hole sealing of a thermal spraying glass layer.
Background
The high-temperature heating surface of a heat exchanger of a thermal power plant often fails early due to high-temperature oxidation and corrosion. With the application of a large-capacity and high-parameter boiler, the high-temperature corrosion phenomenon is more obvious, the safe operation of a power plant is seriously influenced, and the high-temperature corrosion phenomenon is an important factor for causing abnormal shutdown of a unit. The high-temperature corrosion phenomenon exists on unit boilers with different capacities, steam parameters comprise sub-high temperature and high pressure, ultra-high temperature and high pressure and subcritical pressure, fuels used comprise anthracite, semi-anthracite and meager coal, and similar conditions also exist in units using lignite abroad.
The process of high-temperature corrosion of the heat exchanger is complex, and the occurrence of the high-temperature corrosion is generally considered to be related to the following factors: the sulfur content of the coal is high; the smoke temperature of the heating surface area is high; the heat exchanger is often in a reducing atmosphere; the material of the heating surface is not resistant to high temperature corrosion; the pulverized coal flame containing combustible materials directly rushes to a heat exchanger and the like.
At high coal sulfur levels, the chemical makeup of the deposits on the exterior of the heat exchanger tends to contribute to high temperature corrosion. If the exterior of the heat exchanger is constantly subjected to a flame containing a large amount of unburned coal dust, iron disulfide (FeS) is produced 2 ) The atoms S and SO formed by the catalysis in the furnace along with the adhesion of the coal dust particles or ash on the tube wall 3 The water-cooled wall can be corroded at high temperature; in the absence of oxygen if the reducing gas H is near the water-cooled wall 2 High S and CO contents also cause high temperature corrosion of the heat exchanger.
1) During the combustion process of the coal, pyrite (the main component is FeS) in the coal 2 And SiO 2 ) The following reaction will occur to form free sulfur, forming a sulfiding atmosphere.
FeS 2 →FeS+S (1)
It is known that alloys in oxidizing, sulfidizing atmospheres have a critical oxygen partial pressure value above which a continuous, oxidizing protective film is formed on the surface of the alloy for a given ambient partial pressure, or that sulfur must be below a critical oxygen partial pressure value for the surface of the alloy to form a protective film. As the problems of boiler structure parameters, operation conditions, coal types and the like can form reducing atmosphere around the heat exchanger, the protective oxide film cannot be generated or is unstable. In this case, the main corrosion reaction of steel is shown in the formulas (2) to (4), and the gas component contains a large amount of H 2 、CO、CO 2 、H 2 O、H 2 S (H in flue gas) 2 S、SO 2 S) can be further generated to cause corrosionThe process is further complicated.
Fe+S→FeS (2)
Fe+H 2 S→FeS+H 2 (3)
FeO+H 2 S→FeS+H 2 O (4)
2) During the combustion process of the boiler, most of sulfur in the fuel is oxidized into SO 2 Wherein about 0.5% to about 5% of the oxygen is oxidized to SO 3 ，SO 2 、SO 3 Is in a gaseous state at high temperature, SO 3 Combined with water to generate H with corrosive action on the heated surface 2 SO 4 。
3) The coal powder contains a small amount of metal oxide Na 2 O、K 2 O, etc. will sublimate with SO in the flue gas at high temperature (848 deg.C) 3 The reaction produces sulfate which is deposited on the tube wall:
Na 2 O+SO 3 →Na 2 SO 4 (5)
K 2 O+SO 3 →K 2 SO 4 (6)
these sulfates destroy the protective film of the heat exchanger to produce complex sulfates.
3K 2 SO 4 +Fe 2 O 3 +3SO 3 →2K 3 Fe(SO 4 ) 3 (7)
3Na 2 SO 4 +Fe2O 3 +3SO 3 →2Na 3 Fe(SO 4 ) 3 (8)
A large amount of unburned coke residues are deposited on the heat exchanger, and the main component is FeS 2 ，FeS 2 Slow oxidation to FeS and Fe occurs 3 O 4 Formation of SO in the vicinity of the heat exchanger 3 So that the above reaction is accelerated.
In the low-temperature section of the heat exchanger, the compound sulfates are in a solid state and have the tendency of reducing corrosion; however, in the high-temperature section, these complex sulfates are in liquid form and directly cause corrosion to the heat exchanger:
when the ratio of potassium to sodium in the ash deposit is high, the mixture of SO3 and alkali sulfates forms liquid coke-state sulfates, accelerating the corrosion reaction.
3K 2 S 2 O 7 +Fe 2 O 3 →2K 3 Fe(SO 4 ) 3 (11)
3Na 2 S 2 O 7 +Fe 2 O 3 →2Na 3 Fe(SO 4 ) 3 (12)
The ash falls off due to excessive thickness of ash or ash during operation, so that K is removed 3 Fe(SO 4 ) 3 And Na 3 Fe(SO 4 ) 3 Exposure to flame high temperature radiation produces the following reactions:
2K 3 Fe(SO 4 ) 3 →3K 2 SO 4 +3SO 3 +Fe 2 O 3 (13)
2Na 3 Fe(SO 4 ) 3 →3Na 2 SO 4 +3SO 3 +Fe 2 O 3 (14)
formation of a new alkali metal sulfate layer in SO 3 The tube wall is continuously corroded under the action of the corrosion inhibitor.
The failure modes of the high-temperature sulfidation corrosion described above mainly occur in the region where the reducing atmosphere inside the boiler is concentrated, mainly in the region where oxygen is deficient near the burner, i.e., mainly on the heat exchanger near the burner.
Although the surface of the heat exchanger adopts the arc spraying anti-corrosion layer, the heat exchanger has certain effect, and the hole of the arc spraying layer is higher, so that corrosive media permeate to form corrosion under the pattern layer; therefore, it is necessary to perform a sealing treatment of the arc layer.
Disclosure of Invention
The invention provides a method for preparing a hole sealing of a thermal spraying glass layer aiming at the defects of the prior art.
The invention solves the technical problems through the following technical means:
a method for preparing a thermal spraying glass layer hole sealing comprises the following steps: preparing a binder, mixing the binder, glass powder and wollastonite into slurry, spraying the prepared slurry on the surface of an electric arc spraying layer, drying to obtain a slurry layer, heating the slurry layer to melt the glass powder in the slurry, and cooling to form a compact glass layer.
As an improvement of the above technical solution, the formula of the binder is as follows: 83-88 parts of silica sol, 0.5-1 part of cerium oxide, 10-15 parts of organic epoxy resin and 0.5-1 part of dispersing agent.
As an improvement of the technical scheme, the preparation process of the adhesive is as follows, the components are added into a disperser in proportion and stirred at the rotating speed of 1200r/min for 30min.
As an improvement of the above technical scheme, the formula of the slurry is as follows: 30-40 parts of binder, 55-70 parts of glass powder and 5-8 parts of wollastonite.
As an improvement of the technical scheme, the melting point of the glass powder is 750 ℃.
As an improvement of the technical scheme, the slurry layer is heated by adopting oxy-acetylene flame.
The invention has the beneficial effects that: after the glass layer compounded on the surface of the electric arc spraying layer is subjected to hot melting treatment to form a compact glass layer, the average porosity of the composite layer can be greatly reduced, the adhesion capability of the composite layer is obviously improved, the phenomenon that the glass layer falls off in later use to reduce the corrosion resistance is avoided, and the service life of the glass layer is prolonged.
The higher the proportion of the binder is, the higher the adhesion capability of the composite layer is improved, but the average porosity is lower; the adhesive capacity is improved, the falling off in later use is prevented, the service life is prolonged, the corrosion resistance is reduced, and the coating is suitable for being used in high-impact low-corrosion environments.
Drawings
FIG. 1 is an electron microscope scan of the composite layer in example 1 of the present invention;
FIG. 2 is an electron microscope scan of the composite layer in example 2 of the present invention;
FIG. 3 is an electron micrograph of an unmelted composite layer of a comparative example of the present invention;
FIG. 4 is a scanning electron microscope image of the electric arc sprayed coating of the original example of the present invention;
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It will be understood that when an element is referred to as being "secured to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.
Example 1
The method for preparing the hole sealing of the thermal spraying glass layer comprises the following steps: firstly, preparing a binder, namely adding 83 parts of silica sol, 1 part of cerium oxide, 15 parts of organic epoxy resin and 1 part of dispersing agent into a disperser, and stirring at the rotating speed of 1200r/min for 30min; then 40 parts of binder, 55 parts of glass powder with the melting point of 750 ℃ and 8 parts of wollastonite are mixed to form slurry, the prepared slurry is sprayed on the surface of an electric arc spraying layer and dried to obtain a slurry layer, oxygen-acetylene flame is adopted to heat the slurry layer to melt the glass powder in the slurry, and a compact glass layer is formed after cooling.
The average porosity of a composite layer of the composite glass layer on the surface of the electric arc spraying layer is 0.33 percent; the electron microscope scanning image of the composite layer after the corrosion test is shown in FIG. 1; the adhesion capability of the composite layer was measured by a tensile method, and the bond strength was 78MPa.
Example 2
The method for preparing the thermal spraying glass layer hole sealing comprises the following steps: firstly, preparing a binder, adding 88 parts of silica sol, 0.5 part of cerium oxide, 10 parts of organic epoxy resin and 0.5 part of dispersing agent into a disperser, and stirring at the rotating speed of 1200r/min for 30min; then, 30 parts of binder, 70 parts of glass powder with the melting point of 750 ℃ and 5 parts of wollastonite are mixed to form slurry, the prepared slurry is sprayed on the surface of an electric arc spraying layer and dried to obtain a slurry layer, oxygen-acetylene flame is adopted to heat the slurry layer to melt the glass powder in the slurry, and a compact glass layer is formed after cooling.
The average porosity of a composite layer of the composite glass layer on the surface of the electric arc spraying layer is 0.2 percent; the electron microscope scanning image of the composite layer after the corrosion test is shown in FIG. 3; the adhesion capability of the composite layer was measured by a tensile method, and the bond strength was 65MPa.
Comparative example
The method for preparing the thermal spraying glass layer hole sealing comprises the following steps: firstly, preparing a binder, namely adding 88 parts of silica sol, 0.5 part of cerium oxide, 10 parts of organic epoxy resin and 0.5 part of dispersing agent into a disperser, and stirring at the rotating speed of 1200r/min for 30min; then, 30 parts of binder, 70 parts of glass powder with the melting point of 750 ℃ and 5 parts of wollastonite are mixed into slurry, the prepared slurry is sprayed on the surface of the electric arc spraying layer, and the slurry layer is obtained after drying.
The average porosity of a composite layer of the composite glass layer on the surface of the electric arc spraying layer is 0.56 percent; the electron microscope scanning image of the composite layer after the corrosion test is shown in FIG. 3; the adhesion capability of the composite layer was measured by a tensile method, and the bond strength was 28MPa.
Original example
Only an electric arc spraying layer is made for corrosion prevention, and hole sealing is not performed; the average porosity of the arc sprayed layer was 1.2%; an electron micrograph of the arc sprayed coating after the corrosion test is shown in FIG. 4.
By comparing the examples 1 and 2 and the comparative example with the original example, the average porosity of the anti-corrosion layer can be reduced by compounding a glass layer on the surface of the electric arc spraying layer, and the electric arc spraying layer and the glass layer can generate a synergistic effect, so that the generated anti-corrosion effect is far greater than that of the electric arc spraying layer; the glass layer is compounded on the surface of the electric arc spraying layer, so that the adhesion capability of the anticorrosive layer can be improved, the anticorrosive performance is prevented from being reduced due to falling off in later use, and the service life is prolonged.
Comparing examples 1 and 2 with the comparative example, it can be seen that after the glass layer compounded on the surface of the arc spraying layer is subjected to hot melting treatment to form a compact glass layer, the average porosity of the composite layer can be greatly reduced, the adhesion capability of the composite layer is remarkably improved, and the corrosion resistance and the service life are prevented from being reduced due to falling off in later use.
Comparing example 1 with example 2, it can be seen that the higher the binder content, the higher the adhesion to the composite layer, but the lower the average porosity; the adhesive capacity is improved, the falling-off in later use is prevented, the service life is prolonged, the corrosion resistance is reduced, and the paint is suitable for being used in high-impact low-corrosivity environments.
It is noted that, in this document, relational terms such as first and second, and the like, if any, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrases "comprising a," "8230," "8230," or "comprising" does not exclude the presence of additional like elements in a process, method, article, or apparatus that comprises the element.
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (4)
1. A method for preparing a hole sealing of a thermal spraying glass layer is characterized by comprising the following steps: firstly, preparing a binder, then mixing the binder, glass powder and wollastonite into slurry, spraying the prepared slurry on the surface of an electric arc spraying layer, drying to obtain a slurry layer, heating the slurry layer to melt the glass powder in the slurry, and cooling to form a compact glass layer;
the formula of the binder is as follows: 83-88 parts of silica sol, 0.5-1 part of cerium oxide, 10-15 parts of organic epoxy resin and 0.5-1 part of dispersing agent;
the formula of the slurry is as follows: 30-40 parts of binder, 55-70 parts of glass powder and 5-8 parts of wollastonite.
2. The method for preparing the hole sealing of the thermal spraying glass layer according to claim 1, wherein: the preparation process of the adhesive is as follows, the components are added into a disperser according to the proportion and stirred at the rotating speed of 1200r/min for 30min.
3. The method for preparing the hole sealing of the thermal spraying glass layer according to claim 1, wherein: the melting point of the glass powder is 750 ℃.
4. The method for preparing the hole sealing of the thermal spraying glass layer according to claim 1, wherein: the slurry layer is heated using an oxygen-acetylene flame.
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| CN104498856B (en) * | 2013-05-20 | 2017-03-29 | 河北工程大学 | A kind of high pure spelter coating hole sealing agent of anti-rotten electric arc spraying and preparation technology and its application |
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