CN113487120A - Method for establishing boiler flue corrosion prevention strategy and boiler flue corrosion prevention method - Google Patents
Method for establishing boiler flue corrosion prevention strategy and boiler flue corrosion prevention method Download PDFInfo
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- G06Q10/063—Operations research, analysis or management
- G06Q10/0633—Workflow analysis
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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
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- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
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Abstract
The invention relates to a method for establishing a boiler flue corrosion prevention strategy, which comprises the following steps: a, establishing an anticorrosive coating preparation comprehensive cost performance database; b, partitioning the internal area of the boiler flue and corroded metal parts contained in the internal area according to the sequence of the surface temperature of the heated surface in the boiler flue from small to large; c, sequencing each subarea of the boiler flue and metal parts contained in the subareas according to the sequence of the corrosion grades from small to large; and D, selecting corresponding anticorrosive coating materials, anticorrosive coating preparation methods, anticorrosive coating thickness and anticorrosive coating preparation cost from the comprehensive anticorrosive coating preparation cost performance database in the step A according to the sequence of the corrosion grades from small to large in the step C, and obtaining the boiler anticorrosive strategy. The method can provide a high-cost-performance equal-service-life corrosion protection strategy aiming at the specific boiler type accurate strategy, and meanwhile, the process realizability is kept.
Description
Technical Field
The invention belongs to the technical field of boiler flue corrosion prevention, and relates to a method for establishing a boiler flue corrosion prevention strategy and a boiler flue corrosion prevention method.
Background
Along with the improvement of domestic living standard, the classification of garbage sources is gradually improved, the heat value of garbage is gradually increased, the components of the garbage are gradually refined, and a high-parameter garbage incineration power generation boiler tends to be great. Under high temperature conditions, serious high-temperature corrosion caused by chlorides, sulfides, alkali metals, heavy metals and the like usually occurs on water-cooled walls, superheaters and the like of the waste incineration boilers. Particularly, in recent years, most waste incineration waste heat boilers are in an overload operation working environment, high-temperature corrosion is increased, and the pipe wall of a heating surface is quickly thinned until pipe explosion is frequent. The surface coating protection is the most common high-temperature corrosion protection method applied at present, and mainly aims at the tubular heating surfaces of boiler 'four tubes' such as a membrane water-cooled wall of a waste heat boiler, a superheater, a reheater, an economizer and the like, and the coating is prepared by adopting the protection methods such as surfacing welding, thermal spraying, remelting, surface cladding and the like so as to inhibit or delay corrosion and improve the corrosion resistance of the material.
However, at present, when the waste heat boilers of domestic garbage power stations (including various thermal power stations) are subjected to corrosion prevention by applying the various coating technologies, the preparation cost of the prepared coating per square meter is usually over ten thousand, the heating surface area of four pipes arranged in a flue (channel) in the boiler can reach nearly thousands to thousands of square meters, and at least two boilers of a common power station are used, so that the corrosion prevention cost of even one small power station can exceed ten million, and thus, a heavy economic burden is brought to enterprises.
Therefore, it is necessary to provide a set of coating protection schemes with the highest relative cost performance under the condition of not reducing the service life for specific boiler types.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for establishing a boiler flue corrosion prevention strategy aiming at the problems in the prior art, the method can provide a high-cost-performance equal-service-life corrosion prevention strategy aiming at the specific boiler type under the condition of not reducing the service life, and meanwhile, the process realizability is kept.
To this end, the invention provides a method for establishing a boiler flue corrosion prevention strategy in a first aspect. It includes:
step A, correlating an anticorrosive coating material, an anticorrosive coating preparation method, an anticorrosive coating thickness and anticorrosive coating preparation cost with the service life of an anticorrosive coating, sequencing the anticorrosive coating material, the anticorrosive coating preparation method, the anticorrosive coating thickness and the anticorrosive coating preparation cost in the order from small to large according to the service life of the anticorrosive coating, and establishing an anticorrosive coating preparation comprehensive cost performance database;
step B, correlating the internal area of the boiler flue and the corroded metal part thereof with the surface temperature of the heating surface inside the boiler flue, and partitioning the internal area of the boiler flue and the corroded metal part thereof according to the sequence from small to large of the surface temperature of the heating surface inside the boiler flue;
step C, analyzing the corrosion conditions of the surfaces of the metal parts in each partition of the boiler flue and the partitions, classifying the corrosion grades of the surfaces of the metal parts in each partition of the boiler flue, and sequencing each partition of the boiler flue and the metal parts in each partition of the boiler flue according to the sequence of the corrosion grades from small to large;
and D, selecting corresponding anticorrosive coating materials, anticorrosive coating preparation methods, anticorrosive coating thickness and anticorrosive coating preparation cost from the anticorrosive coating preparation comprehensive cost performance database established in the step A according to the sequence of the corrosion grades from small to large in the step C, and obtaining a boiler anticorrosive strategy.
According to the method, in the step C, the corrosion grade of the surfaces of the inner parts of each subarea of the boiler flue and the metal parts contained in the subareas of the boiler flue is divided according to the surface corrosion rate and/or the surface corrosion condition.
In some embodiments of the invention, the interior of each section of the boiler flue and the surfaces of the metal parts contained therein are classified into I-IV grade corrosions according to the corrosion rate of the surfaces, wherein the corrosion rate of the I-grade corrosion is less than or equal to 1 x 10-5mm/h，1×10-5The corrosion rate of the II-grade corrosion is more than mm/h and less than or equal to 3.5 multiplied by 10-5mm/h，3.5×10-5The corrosion rate of grade III corrosion is more than or equal to 5 multiplied by 10 when the thickness of the layer is more than mm/h- 5The corrosion rate of mm/h and IV grade corrosion is more than 5 multiplied by 10-5mm/h。
In other embodiments of the invention, the interior of each section of the boiler flue and the surface of the metal part contained in the section are divided into four levels of ultra-high temperature chemical corrosion, electrochemical corrosion/strong corrosion, electrochemical corrosion/weak corrosion and the like according to the surface corrosion condition, wherein the corrosion condition comprises one or more of corrosion type, corrosion thinning rule, tube explosion times, local bulging and dust deposition adhesion.
According to the method of the invention, in step A,
the anticorrosive coating material comprises glass fiber reinforced plastic, polyurethane, epoxy, polytetrafluoroethylene, NiCr/Cr3C2-NiCr, Ni-based self-fluxing alloy, NiCr-Cr for surface layer3C2、Inconel625；
The preparation method of the coating comprises spraying and/or brushing anti-corrosion paint and/or lacquer, plasma spraying, flame spraying and high-frequency remelting-supersonic plasma spraying, MIG/MAG surfacing and CMT;
the thickness of the coating is 0.1-1.5 mm;
the service life of the coating is 1-10 years;
the preparation cost of the coating is 50-12000 yuan/m2。
In some embodiments of the present invention, in step a, the comprehensive cost/performance ratio database for preparing the anticorrosive coating comprises:
(1) method for producing a coatingSpraying an anticorrosive paint; the coating material comprises one or more of glass fiber reinforced plastic, polyurethane, epoxy and polytetrafluoroethylene; the thickness of the coating is 0.1mm or 0.3 mm; the service life of the coating is 1-2 years or more than 2 years; the preparation cost of the coating is 50-100 yuan/m2；
(2) The preparation method of the coating is plasma spraying; the coating material comprises NiCr/Cr3C2-NiCr; the thickness of the coating is 0.5-0.8 mm; the service life of the coating is 3-5 years; the preparation cost of the coating is 500-800 yuan/m2；
(3) The preparation method of the coating comprises flame spraying and high-frequency remelting; the coating material is nickel-based self-fluxing alloy; the thickness of the coating is 0.5 mm; the service life of the coating is 6-10 years; the preparation cost of the coating is 5000-7000 yuan/m2；
(4) Economic: the preparation method of the coating comprises the steps of flame spraying, high-frequency remelting and supersonic plasma spraying; the coating material comprises nickel-based self-fluxing alloy used as a bottom layer and NiCr-Cr used as a surface layer3C2(ii) a The thickness of the coating comprises 0.5mm of the bottom layer and 0.2mm of the surface layer; the service life of the coating is 6-10 years; the preparation cost of the coating is 7000-2；
Or a conventional type: the preparation method of the coating is MIG/MAG surfacing; the coating material is Inconel 625; the thickness of the coating is 1.2 mm; the service life of the coating is 6-10 years; the preparation cost of the coating is 9000-10000 Yuan/m2。
(5) The preparation method of the coating is CMT; the coating material is Inconel 625; the thickness of the coating is 1.5 mm; the service life of the coating is 6-10 years; the preparation cost of the coating is 11000-12000 yuan/m2；
Or the coating preparation method comprises flame spraying and high-frequency remelting; the coating material is nickel-based self-fluxing alloy; the thickness of the coating is 0.5 mm; the service life of the coating is 6-10 years; the preparation cost of the coating is 5000-7000 yuan/m2。
According to the method of the invention, in the step B, the step of partitioning the inner area of the boiler flue and the corroded metal parts contained in the inner area of the boiler flue according to the sequence from small to large of the surface temperature of the heated surface inside the boiler flue comprises the following steps: a tail flue, a low-temperature area, 50-150 ℃; a middle temperature zone of 150-; a fourth flue at the temperature of 300-400 ℃; the third flue 400-500 ℃; a second flue at 600 ℃ in 500-; first flue, upper portion and ceiling: 600 ℃ and 700 ℃; middle and lower parts: 700 ℃ and 750 ℃.
In some embodiments of the invention, in step B, the metal part in each flue section comprises: a tail flue, a low-temperature area, a middle-temperature area, a heat exchanger and an induced draft fan; a fourth flue, an economizer and a convector tube bundle; a third flue, a membrane wall, a superheater and a reheater; second flue, first flue, upper portion and ceiling, middle and lower part: a membrane wall.
In some specific embodiments of the present invention, in step C, the corrosion grade of the surface of the metal part inside each section of the boiler flue and contained therein is divided into: tail flue, low temperature zone, electrochemical corrosion/strong corrosion; medium temperature zone, electrochemical corrosion/weak corrosion; a fourth flue, high-temperature chemical corrosion; high-temperature chemical corrosion of the third flue; a second flue, ultra-high temperature chemical etching; first flue, upper portion and ceiling: ultra-high temperature chemical corrosion; middle and lower parts: high-temperature chemical corrosion.
In some specific embodiments of the present invention, in step D, the coating material, the coating preparation method and the thickness of the interior of each section of each flue and the metal parts contained therein are determined, which comprises:
a tail flue: spraying anticorrosive paint, wherein the paint material comprises one or more of glass fiber reinforced plastic, polyurethane, epoxy and polytetrafluoroethylene, and the thickness of the paint coating is 0.1 +/-0.02 mm or 0.3 +/-0.02 mm;
a fourth flue: by adopting plasma spraying, the coating material comprises NiCr/Cr3C2-NiCr, coating thickness 0.8 mm;
a third flue: adopting flame spraying and high-frequency remelting, wherein the coating material comprises nickel-based self-fluxing alloy, and the thickness of the coating is 0.5 mm;
a second flue: the method is economical, and adopts flame spraying, high-frequency remelting and supersonic plasma spraying; coating material, nickel-based self-fluxing alloy for bottom layer and NiCr-Cr for surface layer3C2(ii) a Coating thickness: 0.5 plus or minus 0.02mm of the bottom layer and 0.2 plus or minus 0.02mm of the surface layer; or the traditional mode adopts MIG/MAG surfacing welding; coating material, Inconel 625; the thickness of the coating is 1.2 +/-0.02 mm;
a first flue: CMT is adopted for the upper part and the ceiling; the coating material is Inconel 625; the thickness of the coating is 1.5 +/-0.02 mm; flame spraying and high-frequency remelting are adopted on the middle part and the lower part; the coating material is nickel-based self-fluxing alloy; the thickness of the coating is 0.5 +/-0.02 mm.
The invention provides a boiler flue corrosion prevention method, which comprises the steps of establishing a boiler flue corrosion prevention strategy and constructing and manufacturing a boiler flue corrosion prevention strategy according to the boiler flue corrosion prevention strategy, wherein the step of establishing the boiler flue corrosion prevention strategy is carried out according to the method of the first aspect of the invention.
The invention provides an anti-corrosion boiler flue, which comprises a tail flue and first to fourth flues; wherein the content of the first and second substances,
a tail flue: the coating material comprises one or more of glass fiber reinforced plastic, polyurethane, epoxy and polytetrafluoroethylene, and the thickness of the coating is 0.1 +/-0.02 mm or 0.3 +/-0.02 mm;
a fourth flue: the coating material is NiCr/Cr3C2-NiCr, coating thickness 0.8 ± 0.02 mm;
a third flue: the coating material is nickel-based self-fluxing alloy, and the thickness of the coating is 0.5 +/-0.02 mm;
a second flue: economical, coating material, nickel-based self-fluxing alloy for bottom layer and NiCr-Cr for surface layer3C2(ii) a Coating thickness: 0.5 plus or minus 0.02mm of the bottom layer and 0.2 plus or minus 0.02mm of the surface layer; or the traditional type, the coating material is Inconel 625; the thickness of the coating is 1.2 +/-0.02 mm;
a first flue: the coating material of the upper part and the ceiling is Inconel 625; the thickness of the coating is 1.5 +/-0.02 mm; the coating materials of the middle and lower parts are nickel-based self-fluxing alloy; the thickness of the coating is 0.5 +/-0.02 mm.
The invention has the advantages that:
(1) cost-effective equal-life corrosion protection strategy
Because the temperature and the corrosion rate of different flues are different, even different parts of the same flue have larger difference, when designing an anti-corrosion scheme, a high-performance coating protection method and a coating material are selected as much as possible in areas and parts of the boiler with high wall temperature and high corrosion rate, and even the protection emphasis is strengthened in areas with the most serious corrosion, so that the thinnest and the weakest can be converted into the firmest; and on the contrary, the economical coating protection method and material are selected for the part with less corrosion. The equal-service-life strategy with high comprehensive cost performance of one strategy greatly reduces the burden of enterprises on the premise that the service life of four pipes of a boiler is not lower than that of the traditional method. From the overall view of the industry, the aims of saving energy and materials and reducing resource waste for the country are achieved.
(2) On the basis of counting, tracking and detecting failure data of a four-tube coating of the boiler, four-level regions, parts and distribution rules of the regions and the parts are divided, wherein the four-level regions, the parts and the distribution rules of the four-level regions are relatively serious, general, light and the like, so that the four-level regions, the parts and the distribution rules can be accurately protected by adopting a corresponding coating technology in advance, the times and the time of unplanned shutdown can be greatly reduced, and the operation cost of an enterprise is reduced to the maximum extent.
(3) Precise enforcement while maintaining process realizability
In formulating the protective solution, care is also taken to ensure that the coating preparation process should not become "trivial" due to careful considerations, yet maintain process feasibility.
(4) The protection strategy provided by the invention is more suitable for coating preparation enterprises with larger scale, and if the production batch is large to a certain extent, the same furnace type can be centralized and prepared in a classified manner, for example, one production line is specially used for preparing the coating of one flue, and four production lines are used for completing the coating preparation of the whole boiler. The large-scale and specialized classified production has wide development prospect for improving the efficiency and the quality of the coating.
Drawings
For the present invention to be readily understood, the following description is made with reference to the accompanying drawings. The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention.
FIG. 1 is a schematic structural view of a waste incineration exhaust-heat boiler according to the present invention;
FIG. 2 is a graph of the relationship between the wall temperature of the heated surface tube and the metal corrosion rate of a typical boiler in accordance with the present invention;
FIG. 3 is a schematic diagram of the "one strategy" corrosion prevention strategy of the present invention;
the reference numerals in fig. 3 are explained as follows:
a, flame spraying and high-frequency remelting;
B-CMT surfacing;
c, flame spraying, high-frequency remelting and supersonic plasma spraying;
D-MIG/MAG surfacing welding;
e, sealing holes by adding a hole sealing agent through plasma spraying;
f, spraying an anticorrosive paint.
Detailed Description
In order that the invention may be readily understood, a more particular description thereof will be rendered by reference to the appended drawings. However, before the invention is described in detail, it is to be understood that this invention is not limited to particular embodiments described. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting.
Where a range of values is provided, it is understood that each intervening value, to the extent that there is no stated or intervening value in that stated range, to the extent that there is no such intervening value, is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges, and are also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where a specified range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention.
Unless otherwise defined, all terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, the preferred methods and materials are now described.
I, embodiments
As mentioned above, when the existing coating technology is used for corrosion prevention in the waste heat boilers of domestic waste power stations (including various thermal power stations), the preparation cost of the prepared coating is usually over ten thousand yuan per square meter, the heating surface area of the four pipes arranged in the flue (channel) in the boiler can reach nearly thousands to thousands of square meters, and at least two boilers of a common power station are used, so that the corrosion prevention cost of even one small power station can be tens of millions, and thus, the heavy economic burden is brought to enterprises. Therefore, the problem exists at present that the research and development of the boiler flue corrosion prevention technology with long time and low cost are needed. In view of this, the present inventors have conducted extensive studies on the corrosion prevention technique for the boiler flue.
The inventor researches and discovers that all metal structures in the whole boiler are protected almost uniformly by the same method when the waste heat boiler of domestic garbage power stations (including various thermal power stations) applies various coating technologies for corrosion prevention. For example, when coating protection is performed on four pipes of a certain boiler, all heating surfaces of a pipeline, no matter a flue, no matter a part and the like, are provided with a protective layer by adopting a method of plasma surfacing Inconel 625. As mentioned above, the coating prepared by the method has a preparation cost of ten thousand yuan per square meter, the area of the heating surface of four pipes in a common boiler can reach nearly thousands to thousands of square meters, and at least two boilers in a common power station, so that the corrosion prevention cost of even one small power station needs tens of millions, thereby bringing heavy economic burden to enterprises.
Actually, the interior of the boiler is divided into four flues (channels), the temperature difference of each flue is large, the corrosion rates of high-temperature flue gas are different along with the temperature change, the highest corrosion rate and the lowest corrosion rate can be multiple times, and even the difference is large in the same flue, as shown in fig. 2 (see the research on high-temperature corrosion treatment of water-cooled walls of waste heat boilers in domestic garbage incineration plants, baixian, zhangyu, environmental sanitation engineering, volume 26, No. 3 in 2018, No. 26, and 68-74); on the other hand, according to the service life statistical results of the pipelines, the occurrence rate of the last pipe explosion of the corrosion-thinned pipeline is usually concentrated on the local parts with the highest high-temperature corrosion rate, the parts are required to be shut down for maintenance or cut off and replace the pipelines with the local pipe explosion, but other most parts of the pipelines can still be safely used for many years, and the service lives of all parts are quite different due to the fact that the other most parts of the pipelines are intact and undamaged after the pipelines are wholly scrapped. Therefore, it can be considered that all boilers use one standard for consistency protection, which not only burdens enterprises with heavy load, but also causes great waste of natural resources and energy.
Based on the analysis, the inventor researches and designs, and firstly proposes a concept of 'making an accurate protection strategy for the service life based on a high-temperature corrosion curve of a boiler flue', namely, based on the service life principle of a metal structure heating surface coating in the boiler, determining four-stage regions, parts and distribution rules of the four-stage regions, namely the heating surface corrosion is relatively severe (for example, ultrahigh-temperature chemical corrosion), severe (for example, high-temperature chemical corrosion), general (for example, electrochemical corrosion/strong corrosion), light (for example, electrochemical corrosion/weak corrosion), and the like, and accurately making the corrosion protection strategy and scheme according to the change rules of the actual temperature and corrosion rate of each channel in the boiler. Particularly, for areas and parts with high boiler wall temperature and high corrosion rate, a high-performance coating protection method and a coating material are selected as much as possible, and even the protection emphasis in the area with the most serious corrosion is strengthened, so that the weakest point is changed into the firmest point; on the contrary, economical coating protection methods and materials are selected for the parts with less corrosion. The method is characterized in that a fault probability distribution curve in normal distribution is converted into an average distribution rule, so that the times of irregular shutdown maintenance are greatly reduced, more importantly, according to the novel concept of equal-service-life protection, the corrosion is seriously close to the final service life of a slight part after accurate protection, the corrosion cost is greatly reduced, the burden of an enterprise is lightened, and meanwhile, energy, materials and resources are saved to the maximum extent on the premise that the service life of four pipes of a boiler is longer than that of a traditional method. In addition, in formulating a protective solution, care is also taken to ensure that the coating preparation process should not become "trivial" due to excessive considerations, and to maintain process feasibility.
Therefore, the technical solution for establishing the boiler flue corrosion prevention strategy according to the first aspect of the present invention is as follows:
firstly, establishing an anticorrosive coating preparation comprehensive cost performance database:
the existing selectively used anticorrosive coating material, anticorrosive coating preparation method, anticorrosive coating thickness, anticorrosive coating preparation cost and anticorrosive coating service life comprise:
(1) the anticorrosive coating material comprises glass fiber reinforced plastic, polyurethane, epoxy, polytetrafluoroethylene, NiCr/Cr3C2-NiCr, Ni-based self-fluxing alloy, NiCr-Cr for surface layer3C2、Inconel625；
(2) The preparation method of the coating comprises spraying and/or brushing anti-corrosion paint and/or lacquer, plasma spraying, flame spraying and high-frequency remelting-supersonic plasma spraying, MIG/MAG surfacing and CMT;
(3) the thickness of the coating is 0.1-1.5 mm;
(4) the service life of the coating is 1-10 years;
(5) the preparation cost of the coating is 50-12000 yuan/m2。
Correlating the anticorrosive coating material, the anticorrosive coating preparation method, the anticorrosive coating thickness and the anticorrosive coating preparation cost with the life of the anticorrosive coating, and sequencing the anticorrosive coating material, the anticorrosive coating preparation method, the anticorrosive coating thickness and the anticorrosive coating preparation cost in the order from small to large according to the life of the anticorrosive coating to form an anticorrosive coating preparation comprehensive cost performance database, wherein the anticorrosive coating preparation comprehensive cost performance database specifically comprises the following steps:
(1) the preparation method of the coating is spraying anticorrosive paint; the coating material comprises one or more of glass fiber reinforced plastic, polyurethane, epoxy and polytetrafluoroethylene; the thickness of the coating is 0.1mm or 0.3 mm; the service life of the coating is 1-2 years or more than 2 years; the preparation cost of the coating is 50-100 yuan/m2；
(2) The preparation method of the coating is plasma spraying; the coating material comprises NiCr/Cr3C2-NiCr; the thickness of the coating is 0.5-0.8 mm; the service life of the coating is 3-5 years; the preparation cost of the coating is 500-800 yuan/m2；
(3) The preparation method of the coating comprises flame spraying and high-frequency remelting; the coating material is nickel-based self-fluxing alloy; the thickness of the coating is 0.5 mm; the service life of the coating is 6-10 years; the preparation cost of the coating is 5000-7000 yuan/m2；
(4) Economic: the preparation method of the coating comprises the steps of flame spraying, high-frequency remelting and supersonic plasma spraying; the coating material comprises nickel-based self-fluxing alloy used as a bottom layer and NiCr-Cr used as a surface layer3C2(ii) a The thickness of the coating comprises 0.5mm of the bottom layer and 0.2mm of the surface layer; the service life of the coating is 6-10 years; the preparation cost of the coating is 7000-2；
Or a conventional type: the preparation method of the coating is MIG/MAG surfacing; the coating material is Inconel 625; the thickness of the coating is 1.2 mm; the service life of the coating is 6-10 years; the preparation cost of the coating is 9000-10000 Yuan/m2。
(5) The preparation method of the coating is CMT; the coating material is Inconel 625; the thickness of the coating is 1.5 mm; the service life of the coating is 6-10 years; the preparation cost of the coating is 11000-12000 yuan/m2；
Or the coating preparation method comprises flame spraying and high-frequency remelting; the coating material is nickel-based self-fluxing alloy; the thickness of the coating is 0.5 mm; the service life of the coating is 6-10 years; the preparation cost of the coating is 5000-7000 yuan/m2。
Partitioning the internal area of the boiler flue and the corroded metal parts contained in the internal area:
the structural characteristics of a general waste incineration waste heat boiler are analyzed, fig. 1 is a schematic diagram of the internal structure of a typical waste heat boiler which is widely applied to domestic waste incineration power generation (see 'design of a domestic waste incineration waste heat boiler', Zhao Ying, energy research and management, 2011(3), 45-47), and the boiler is in a structural form of natural circulation and vertical arrangement of a single boiler barrel. The heat absorption system is mainly formed by a structural mode that four vertical flues are vertically arranged, wherein the first flue, the second flue and the third flue are provided with membrane walls; the third flue is provided with a high-temperature superheater, a medium-temperature superheater, a low-temperature superheater, a reheater, an evaporator tube bundle and the like in addition to the membrane wall; the fourth flue is of a guard plate structure without a membrane wall, and a coal economizer tube bundle is arranged in the fourth flue. The first flue starts from the outlet of the incinerator, in order to protect the water-cooled wall and meet the requirement that the flue gas stays for more than 2s at 850 ℃, the middle lower part of the membrane wall is laid with refractory materials (castable), the temperature of the flue gas at the upper part and the top part is reduced, the membrane wall is not laid with the refractory materials any more, and similarly, the second flue membrane wall and the third flue membrane wall are not laid with the refractory materials. The tail flue is not shown in fig. 1, the tail flue is transversely arranged at the rear part of the third flue or the fourth flue, metal structures such as a heat exchanger, a preheater, an induced draft fan and the like are generally placed in the tail flue, and the wall temperature is below 300 ℃.
The internal area of the boiler flue and the corroded metal part thereof are related to the surface temperature of the heated surface in the boiler flue, and the internal area of the boiler flue and the corroded metal part thereof are partitioned according to the sequence from small to large of the surface temperature of the heated surface in the boiler flue, as shown in table 1.
As can be seen from table 1, partitioning the internal region of the boiler flue and the corroded metal parts contained in the internal region according to the sequence of the surface temperature of the heated surface inside the boiler flue from small to large includes: a tail flue, a low-temperature area, 50-150 ℃; a middle temperature zone of 150-; a fourth flue at the temperature of 300-400 ℃; the third flue 400-500 ℃; a second flue at 600 ℃ in 500-; first flue, upper portion and ceiling: 600 ℃ and 700 ℃; middle and lower parts: 700 ℃ and 750 ℃.
The metal parts in each flue segment include: a tail flue, a low-temperature area, a middle-temperature area, a heat exchanger and an induced draft fan; a fourth flue, an economizer and a convector tube bundle; a third flue, a membrane wall, a superheater and a reheater; second flue, first flue, upper portion and ceiling, middle and lower part: a membrane wall.
Thirdly, sequencing each subarea of the boiler flue and metal parts contained in each subarea according to the corrosion grade
Analyzing the surface corrosion conditions of the interior of each subarea of the boiler flue and metal parts contained in the interior of each subarea of the boiler flue, dividing the corrosion grades of the interior of each subarea of the boiler flue and the surfaces of the metal parts contained in the interior of each subarea of the boiler flue according to the surface corrosion rate and/or the surface corrosion condition, and sequencing each subarea of the boiler flue and the metal parts contained in the subarea of the boiler flue according to the sequence of the corrosion grades from small to large;
(1) according to the corrosion rate of the surfaceDividing the interior of each subarea of the boiler flue and the surface of a metal part contained in the interior of each subarea into I-IV-grade corrosion, wherein the corrosion rate of the I-grade corrosion is less than or equal to 1 multiplied by 10-5mm/h，1×10-5The corrosion rate of the II-grade corrosion is more than mm/h and less than or equal to 3.5 multiplied by 10-5mm/h，3.5×10-5The corrosion rate of grade III corrosion is more than or equal to 5 multiplied by 10 when the thickness of the layer is more than mm/h-5The corrosion rate of mm/h and IV grade corrosion is more than 5 multiplied by 10-5mm/h；
(2) Dividing the interior of each subarea of the boiler flue and the surface of a metal part contained in the interior of each subarea of the boiler flue into four grades such as ultrahigh-temperature chemical corrosion, high-temperature chemical corrosion, electrochemical corrosion/strong corrosion, electrochemical corrosion/weak corrosion and the like according to the surface corrosion condition, wherein the corrosion condition comprises one or more of corrosion type, corrosion thinning rule, tube explosion frequency, local bulging and dust deposition adhesion condition.
The results of sorting the sections of the boiler flue and the metal parts contained therein according to the corrosion levels are shown in table 1, and as can be seen from table 1, the corrosion levels of the interior of the sections of the boiler flue and the surfaces of the metal parts contained therein are classified according to the surface corrosion conditions into: tail flue, low temperature zone, electrochemical corrosion/strong corrosion; medium temperature zone, electrochemical corrosion/weak corrosion; a fourth flue, high-temperature chemical corrosion; high-temperature chemical corrosion of the third flue; a second flue, ultra-high temperature chemical etching; first flue, upper portion and ceiling: ultra-high temperature chemical corrosion; middle and lower parts: high-temperature chemical corrosion.
Fourthly, a high-temperature anticorrosion strategy is accurately carried out.
And (3) selecting corresponding anticorrosive coating materials, anticorrosive coating preparation methods, anticorrosive coating thickness and anticorrosive coating preparation cost from the comprehensive anticorrosive coating preparation cost performance database established in the step one according to the sequence of the corrosion grades from small to large in the step three, and obtaining the boiler anticorrosive strategy as shown in the table 1.
Fig. 2 shows a relationship curve between the wall temperature of the heated surface of the waste incineration power generation boiler and the metal corrosion rate, the protection method corresponds to each temperature interval of the abscissa in fig. 2, the corrosion rates of the flues are different as shown in fig. 1, and the corrosion prevention strategy is as follows:
1) first flue
The total wall temperature of the radiant membrane wall vertically arranged in the flue is 600-750 ℃. The device is divided into an upper part and a lower part: the middle and lower film walls of the flue have higher smoke temperature>900 ℃ and the pipe wall temperature (700-750 ℃) is 20G. However, because of the blocking of the castable, a large amount of high-concentration corrosive gas flows upwards rapidly along with high-temperature flue gas, and the concentration of the corrosive gas actually transmitted to the middle-lower membrane wall is low, so that the pipe wall is mainly corroded by high-temperature gas phase. The lower right broken line in FIG. 2 shows that if there is no high concentration corrosive gas generated by burning refuse, the high temperature oxidizing atmosphere alone corrodes, and the corrosion rate is significantly lower than that of the high concentration corrosive gas by only 3X 10-5mm/h. Aiming at the situation, the water-cooled wall of the first flue is in most of the length with the casting material, and the protection method recommends flame spraying and high-frequency remelting; while the upper portion of the flue and the ceiling membrane walls are directly exposed to high flue temperature gases and high concentrations of corrosive gases, the level of corrosion peaks very high as shown in figure 2, despite the wall temperatures of 600 c to 700 c being lower than the mid and lower portions: (>5×10-5mm/h), so the strongest corrosion resistant coating is adopted for protection, and flame spraying and high-frequency remelting-supersonic plasma spraying (economical) or CMT surfacing (traditional) are recommended.
2) Second flue
The wall temperature of the convection type water-cooling film type wall of the flue is 500-600 ℃, and the corrosion rate is 5 multiplied by 10 from the curve in figure 2-5mm/h rapidly decreases to 3.5X 10-5mm/h, although the corrosion rate is greatly changed, the protection method still keeps one in consideration of the coordination of the process. Flame spraying + high frequency remelting-supersonic plasma spraying (economy) or MIG/MAG surfacing (tradition) are recommended.
3) Third flue
The flue is internally provided with metals such as a convection diaphragm wall, a superheater, a reheater and the like, and the wall temperature of the metal structure is 400-500 ℃. The water-cooled wall material is 20G, the high-temperature superheater materials are mostly SA-213TP347H, SA-213TP347HFG, SUPER304H and the like, and the medium-low-temperature superheater and reheater materials are mostly 15CrMoG, 12Cr1MoVG and the likeThe change of the corrosion speed from 500 ℃ to 400 ℃ is reduced from 3.5 multiplied by 10 < -5 > mm/h to 2 multiplied by 10 < -5 > mm/h-5mm/h. The protection method recommends flame spraying and high-frequency remelting.
4) The fourth flue
The flue has a vertical direction and a horizontal direction. The common arrangement of economizer bank, convection bank, etc. has wall temperature of 300-400 deg.c and corrosion rate of 2X 10-5mm/h is reduced to 1 x 10-5mm/h or less. Because the corrosion rate is low, a method of plasma spraying NiCr, Cr3C2-NiCr hole sealing is recommended for protection.
5) Tail flue
The wall temperature of the heat exchanger, the preheater, the induced draft fan and other metal structures arranged in the tail flue is below 300 ℃, and the tail flue is divided into two parts according to the temperature: firstly, the chemical corrosion is slow in the temperature range of 150-300 ℃; secondly, at the temperature below 150 ℃, low-temperature chlorine and sulfur corrosion often occurs in the cold end of the air preheater, and particularly when the temperature of the heated surface is lower than the dew point of the flue gas, the sulfuric acid formed by combining the water vapor in the flue gas and sulfur trioxide generated after the combustion of the sulfur is condensed on the heated surface to form high-sulfur deposited ash to further corrode the heated surface. Below the dew point temperature the corrosion mechanism is dominated by electrochemical corrosion and therefore the corrosion rate rises sharply. The protection method recommends two schemes: firstly, protective coating (paint) is sprayed below 150 ℃, and protection can be selected not to be carried out at 150-300 ℃, because the corrosion is weak, and the service life of the used bare tube is basically equivalent to that of the used bare tube; and secondly, the two parts are sprayed with the same anticorrosive paint for protection, and only the thickness of the coating is different.
TABLE 1 Corrosion prevention method and evaluation for metal structural parts of each flue of boiler
As can be seen from table 1, the coating materials, the coating preparation methods and the thicknesses of the interior of each section of each flue and the metal components contained therein, which are determined by the precise high-temperature corrosion prevention strategy, include:
a tail flue: spraying anticorrosive paint, wherein the paint material comprises one or more of glass fiber reinforced plastic, polyurethane, epoxy and polytetrafluoroethylene, and the thickness of the paint coating is 0.1 +/-0.02 mm or 0.3 +/-0.02 mm;
a fourth flue: by adopting plasma spraying, the coating material comprises NiCr/Cr3C2-NiCr, coating thickness 0.8 mm;
a third flue: adopting flame spraying and high-frequency remelting, wherein the coating material comprises nickel-based self-fluxing alloy, and the thickness of the coating is 0.5 mm;
a second flue: the method is economical, and adopts flame spraying, high-frequency remelting and supersonic plasma spraying; coating material, nickel-based self-fluxing alloy for bottom layer and NiCr-Cr for surface layer3C2(ii) a Coating thickness: 0.5 plus or minus 0.02mm of the bottom layer and 0.2 plus or minus 0.02mm of the surface layer; or the traditional mode adopts MIG/MAG surfacing welding; coating material, Inconel 625; the thickness of the coating is 1.2 +/-0.02 mm;
a first flue: CMT is adopted for the upper part and the ceiling; the coating material is Inconel 625; the thickness of the coating is 1.5 +/-0.02 mm; flame spraying and high-frequency remelting are adopted on the middle part and the lower part; the coating material is nickel-based self-fluxing alloy; the thickness of the coating is 0.5 +/-0.02 mm.
It can also be seen from table 1 that, taking the first, second and third flues as examples, the preparation cost is 12000/m for example by uniformly adopting the traditional CMT surfacing method of Inconel6252(ii) a And if the protection strategy of the invention is adopted, under the condition of the same protection life, the average preparation cost is 7000 (economic type) -8000 (traditional type), and the cost is reduced by more than 30%, thus being very considerable.
It will be appreciated by those skilled in the art that the precise strategy employed in the present invention to determine the coating materials, coating preparation methods and thicknesses of the interior of each section of each flue and the metal components contained therein is actually to determine the coating materials, coating preparation methods and thicknesses of the metal components contained within each section of each flue.
Based on the above, it is understood that the term "high-frequency remelting" in the present invention means that the surface of the pipe in the flue is coated with a high-frequency induction remelting coating and then is mounted on the flue.
It will be understood by those skilled in the art that the term "same protective life" in the present invention refers to a comparison of coatings prepared by two methods under the same conditions, such as: the heating surface of the pipeline in the second flue adopts different processes of spraying a nickel-based self-fluxing alloy surface layer, and using NiCr-Cr3C2 or surfacing Inconel625, so that the protection life is the same.
The second aspect of the invention relates to a boiler flue corrosion prevention method, which comprises the steps of establishing a boiler flue corrosion prevention strategy and constructing and manufacturing the boiler flue corrosion prevention strategy according to the boiler flue corrosion prevention strategy, wherein the step of establishing the boiler flue corrosion prevention strategy is carried out according to the method of the first aspect of the invention.
A third aspect of the invention relates to an anti-corrosion boiler flue, based on the strategy established in the first aspect of the invention, and made by the method of the second aspect of the invention, comprising a back flue, and first to fourth flues; wherein the content of the first and second substances,
a tail flue: the coating material comprises one or more of glass fiber reinforced plastic, polyurethane, epoxy and polytetrafluoroethylene, and the thickness of the coating is 0.1 +/-0.02 mm or 0.3 +/-0.02 mm;
a fourth flue: the coating material is NiCr/Cr3C2-NiCr, coating thickness 0.8 ± 0.02 mm;
a third flue: the coating material is nickel-based self-fluxing alloy, and the thickness of the coating is 0.5 +/-0.02 mm;
a second flue: economical, coating material, nickel-based self-fluxing alloy for bottom layer and NiCr-Cr for surface layer3C2(ii) a Coating thickness: 0.5 plus or minus 0.02mm of the bottom layer and 0.2 plus or minus 0.02mm of the surface layer; or the traditional type, the coating material is Inconel 625; the thickness of the coating is 1.2 +/-0.02 mm;
a first flue: the coating material of the upper part and the ceiling is Inconel 625; the thickness of the coating is 1.5 +/-0.02 mm; the coating materials of the middle and lower parts are nickel-based self-fluxing alloy; the thickness of the coating is 0.5 +/-0.02 mm.
II example
In order that the invention may be more readily understood, the invention will now be described in further detail with reference to the accompanying drawings and examples, which are given by way of illustration only and are not limiting to the scope of the invention. The starting materials or components used in the present invention can be obtained commercially or by conventional methods unless otherwise specified.
Example 1:
(1) the method is characterized in that an actual boiler is used as a research object, the layout and the structural characteristics of a flue in the boiler are known, the rules of boiler parameters, maintenance records and the like are mastered, and the metal base material and the structural size which need to be protected by a coating are mainly investigated.
(2) The failure rule data of the four-tube coating of the boiler along the flue and the space position are statistically analyzed, the failure rule data comprise corrosion thinning rule, tube explosion times, local expansion, dust deposition adhesion and the like, and four-level regions and parts of the heating surface of each flue pipeline, such as relatively serious, common and light levels, and distribution rules of the four-level regions and the parts are determined according to the data.
(3) And establishing a coating preparation method and a coating material database for selection when establishing an anticorrosion strategy.
(4) And establishing a coating preparation process database for customers to call out after selecting the anticorrosion scheme.
(5) And (4) accounting the preparation cost of the coating, including materials, energy consumption, labor cost and the like, and sequencing the coatings according to the cost-performance comparison.
(6) A one-pass corrosion protection scheme is designed for the boiler required by the customer (see Table 1).
The general principle is to select high-performance coating protection methods and coating materials for pipe walls in areas and parts with high boiler wall temperature and high corrosion rate, and to select economical coating protection methods and materials for parts with slight corrosion.
Taking the typical boiler of FIG. 1 as an example:
1) flame spraying and high-frequency remelting are adopted for the middle lower part (part with castable) of the first flue; and CMT surfacing is adopted for the upper ceiling and the ceiling.
2) The second flue is selected from flame spraying and high-frequency remelting-supersonic plasma spraying (economical) or MIG/MAG surfacing (traditional).
3) And the third flue adopts flame spraying and high-frequency remelting.
4) And sealing the fourth flue by plasma spraying and adding a sealing agent.
5) And the tail flue adopts spraying anticorrosive paint.
(7) The designed corrosion protection solution is graphically and graphically represented as shown in fig. 3.
The anti-corrosion boiler flue manufactured based on the scheme is as follows:
a tail flue: the coating material comprises one or more of glass fiber reinforced plastic, polyurethane, epoxy and polytetrafluoroethylene, and the thickness of the coating is 0.1 +/-0.02 mm or 0.3 +/-0.02 mm;
a fourth flue: the coating material is NiCr/Cr3C2-NiCr, coating thickness 0.8 ± 0.02 mm;
a third flue: the coating material is nickel-based self-fluxing alloy, and the thickness of the coating is 0.5 +/-0.02 mm;
a second flue: economical, coating material, nickel-based self-fluxing alloy for bottom layer and NiCr-Cr for surface layer3C2(ii) a Coating thickness: 0.5 plus or minus 0.02mm of the bottom layer and 0.2 plus or minus 0.02mm of the surface layer; or the traditional type, the coating material is Inconel 625; the thickness of the coating is 1.2 +/-0.02 mm;
a first flue: the coating material of the upper part and the ceiling is Inconel 625; the thickness of the coating is 1.5 +/-0.02 mm; the coating materials of the middle and lower parts are nickel-based self-fluxing alloy; the thickness of the coating is 0.5 +/-0.02 mm.
It should be noted that the above-mentioned embodiments are only for explaining the present invention, and do not constitute any limitation to the present invention. The present invention has been described with reference to exemplary embodiments, but the words which have been used herein are words of description and illustration, rather than words of limitation. The invention can be modified, as prescribed, within the scope of the claims and without departing from the scope and spirit of the invention. Although the invention has been described herein with reference to particular methods, materials and embodiments, it is not intended that the invention be limited to the particulars disclosed herein, as the invention extends to all other methods and applications having the same functionality, such as thermal power boilers and the like.
Claims (10)
1. A method for establishing a boiler flue corrosion prevention strategy comprises the following steps:
step A, correlating an anticorrosive coating material, an anticorrosive coating preparation method, an anticorrosive coating thickness and anticorrosive coating preparation cost with the service life of an anticorrosive coating, sequencing the anticorrosive coating material, the anticorrosive coating preparation method, the anticorrosive coating thickness and the anticorrosive coating preparation cost in the order from small to large according to the service life of the anticorrosive coating, and establishing an anticorrosive coating preparation comprehensive cost performance database;
step B, correlating the internal area of the boiler flue and the corroded metal part thereof with the surface temperature of the heating surface inside the boiler flue, and partitioning the internal area of the boiler flue and the corroded metal part thereof according to the sequence from small to large of the surface temperature of the heating surface inside the boiler flue;
step C, analyzing the corrosion conditions of the surfaces of the metal parts in each partition of the boiler flue and the partitions, classifying the corrosion grades of the surfaces of the metal parts in each partition of the boiler flue, and sequencing each partition of the boiler flue and the metal parts in each partition of the boiler flue according to the sequence of the corrosion grades from small to large;
and D, selecting corresponding anticorrosive coating materials, anticorrosive coating preparation methods, anticorrosive coating thickness and anticorrosive coating preparation cost from the anticorrosive coating preparation comprehensive cost performance database established in the step A according to the sequence of the corrosion grades from small to large in the step C, and obtaining a boiler anticorrosive strategy.
2. The method according to claim 1, wherein in the step C, the corrosion grades of the surfaces of the inner parts of each subarea of the boiler flue and the metal parts contained in the inner parts are classified according to the surface corrosion rate and/or the surface corrosion condition; preferably, the inner part of each subarea of the boiler flue and the surface of the metal part contained in the subarea are divided into I-IV-grade corrosion according to the surface corrosion rate, wherein the corrosion rate of the I-grade corrosion is less than or equal to 1 x 10-5mm/h，1×10-5mm/h＜The corrosion rate of the II-grade corrosion is less than or equal to 3.5 multiplied by 10-5mm/h，3.5×10-5The corrosion rate of grade III corrosion is more than or equal to 5 multiplied by 10 when the thickness of the layer is more than mm/h-5The corrosion rate of mm/h and IV grade corrosion is more than 5 multiplied by 10-5mm/h; and/or dividing the interior of each partition of the boiler flue and the surface of a metal part contained in the interior of each partition of the boiler flue into four grades of ultrahigh-temperature chemical corrosion, high-temperature chemical corrosion, electrochemical corrosion/strong corrosion, electrochemical corrosion/weak corrosion and the like according to the surface corrosion condition, wherein the corrosion condition comprises one or more of corrosion type, corrosion thinning rule, tube bursting times, local bulging and dust deposition adhesion.
3. The method according to claim 1 or 2, characterized in that, in step A,
the anticorrosive coating material comprises glass fiber reinforced plastic, polyurethane, epoxy, polytetrafluoroethylene, NiCr/Cr3C2-NiCr, Ni-based self-fluxing alloy, NiCr-Cr for surface layer3C2、Inconel625；
The preparation method of the coating comprises spraying and/or brushing anti-corrosion paint and/or lacquer, plasma spraying, flame spraying and high-frequency remelting-supersonic plasma spraying, MIG/MAG surfacing and CMT;
the thickness of the coating is 0.1-1.5 mm;
the service life of the coating is 1-10 years;
the preparation cost of the coating is 50-12000 yuan/m2。
4. The method of claim 3, wherein in step A, the anticorrosion coating preparation comprehensive cost performance database comprises:
(1) the preparation method of the coating is spraying anticorrosive paint; the coating material comprises one or more of glass fiber reinforced plastic, polyurethane, epoxy and polytetrafluoroethylene; the thickness of the coating is 0.1mm or 0.3 mm; the service life of the coating is 1-2 years or more than 2 years; the preparation cost of the coating is 50-100 yuan/m2；
(2) The preparation method of the coating is plasma spraying; the coating material comprises NiCr/Cr3C2-NiCr; the thickness of the coating is 0.5-0.8 mm;the service life of the coating is 3-5 years; the preparation cost of the coating is 500-800 yuan/m2；
(3) The preparation method of the coating comprises flame spraying and high-frequency remelting; the coating material is nickel-based self-fluxing alloy; the thickness of the coating is 0.5 mm; the service life of the coating is 6-10 years; the preparation cost of the coating is 5000-7000 yuan/m2；
(4) Economic: the preparation method of the coating comprises the steps of flame spraying, high-frequency remelting and supersonic plasma spraying; the coating material comprises nickel-based self-fluxing alloy used as a bottom layer and NiCr-Cr used as a surface layer3C2(ii) a The thickness of the coating comprises 0.5mm of the bottom layer and 0.2mm of the surface layer; the service life of the coating is 6-10 years; the preparation cost of the coating is 7000-2；
Or a conventional type: the preparation method of the coating is MIG/MAG surfacing; the coating material is Inconel 625; the thickness of the coating is 1.2 mm; the service life of the coating is 6-10 years; the preparation cost of the coating is 9000-10000 Yuan/m2；
(5) The preparation method of the coating is CMT; the coating material is Inconel 625; the thickness of the coating is 1.5 mm; the service life of the coating is 6-10 years; the preparation cost of the coating is 11000-12000 yuan/m2；
Or the coating preparation method comprises flame spraying and high-frequency remelting; the coating material is nickel-based self-fluxing alloy; the thickness of the coating is 0.5 mm; the service life of the coating is 6-10 years; the preparation cost of the coating is 5000-7000 yuan/m2。
5. The method according to any one of claims 1 to 4, wherein in step B, the partitioning of the inner region of the boiler flue and the corroded metal parts contained in the inner region of the boiler flue according to the descending order of the surface temperature of the heated surface inside the boiler flue comprises: a tail flue, a low-temperature area, 50-150 ℃; a middle temperature zone of 150-; a fourth flue at the temperature of 300-400 ℃; the third flue 400-500 ℃; a second flue at 600 ℃ in 500-; first flue, upper portion and ceiling: 600 ℃ and 700 ℃; middle and lower parts: 700 ℃ and 750 ℃.
6. The method of claim 5, wherein in step B, the metal parts in each flue section comprise: a tail flue, a low-temperature area, a middle-temperature area, a heat exchanger and an induced draft fan; a fourth flue, an economizer and a convector tube bundle; a third flue, a membrane wall, a superheater and a reheater; second flue, first flue, upper portion and ceiling, middle and lower part: a membrane wall.
7. The method according to claim 5 or 6, wherein in step C, the corrosion grades of the surfaces of the inner part of each subarea of the boiler flue and the metal parts contained in the subarea are divided into: tail flue, low temperature zone, electrochemical corrosion/strong corrosion; medium temperature zone, electrochemical corrosion/weak corrosion; a fourth flue, high-temperature chemical corrosion; high-temperature chemical corrosion of the third flue; a second flue, ultra-high temperature chemical etching; first flue, upper portion and ceiling: ultra-high temperature chemical corrosion; middle and lower parts: high-temperature chemical corrosion.
8. The method of claim 7, wherein in step D, the coating material, the coating preparation method and the thickness of the interior of each section of each flue and the metal parts contained therein are determined, and the method comprises the following steps:
a tail flue: spraying anticorrosive paint, wherein the paint material comprises one or more of glass fiber reinforced plastic, polyurethane, epoxy and polytetrafluoroethylene, and the thickness of the paint coating is 0.1 +/-0.02 mm or 0.3 +/-0.02 mm;
a fourth flue: by adopting plasma spraying, the coating material comprises NiCr/Cr3C2-NiCr, coating thickness 0.8 mm;
a third flue: adopting flame spraying and high-frequency remelting, wherein the coating material comprises nickel-based self-fluxing alloy, and the thickness of the coating is 0.5 mm;
a second flue: the method is economical, and adopts flame spraying, high-frequency remelting and supersonic plasma spraying; coating material, nickel-based self-fluxing alloy for bottom layer and NiCr-Cr for surface layer3C2(ii) a Coating thickness: 0.5 plus or minus 0.02mm of the bottom layer and 0.2 plus or minus 0.02mm of the surface layer; or the traditional mode adopts MIG/MAG surfacing welding; coating material, Inconel 625; the thickness of the coating is 1.2 +/-0.02 mm;
a first flue: CMT is adopted for the upper part and the ceiling; the coating material is Inconel 625; the thickness of the coating is 1.5 +/-0.02 mm; flame spraying and high-frequency remelting are adopted on the middle part and the lower part; the coating material is nickel-based self-fluxing alloy; the thickness of the coating is 0.5 +/-0.02 mm.
9. A method for preventing corrosion of a boiler flue, comprising the steps of establishing a corrosion prevention strategy for the boiler flue and constructing and manufacturing the corrosion prevention flue of the boiler according to the corrosion prevention strategy for the boiler flue, wherein the step of establishing the corrosion prevention strategy for the boiler flue is carried out according to the method of any one of claims 1 to 8.
10. An anti-corrosion boiler flue comprises a tail flue and first to fourth flues; wherein the content of the first and second substances,
a tail flue: the coating material comprises one or more of glass fiber reinforced plastic, polyurethane, epoxy and polytetrafluoroethylene, and the thickness of the coating is 0.1 +/-0.02 mm or 0.3 +/-0.02 mm;
a fourth flue: the coating material is NiCr/Cr3C2-NiCr, coating thickness 0.8 ± 0.02 mm;
a third flue: the coating material is nickel-based self-fluxing alloy, and the thickness of the coating is 0.5 +/-0.02 mm;
a second flue: economical, coating material, nickel-based self-fluxing alloy for bottom layer and NiCr-Cr for surface layer3C2(ii) a Coating thickness: 0.5 plus or minus 0.02mm of the bottom layer and 0.2 plus or minus 0.02mm of the surface layer; or the traditional type, the coating material is Inconel 625; the thickness of the coating is 1.2 +/-0.02 mm;
a first flue: the coating material of the upper part and the ceiling is Inconel 625; the thickness of the coating is 1.5 +/-0.02 mm; the coating materials of the middle and lower parts are nickel-based self-fluxing alloy; the thickness of the coating is 0.5 +/-0.02 mm.
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