JP2005146409A - Adhesion-preventing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent ash such as coal ash or molten glass from adhering to a member made of a metal. <P>SOLUTION: This preventing method includes forming a coating layer 19 on the surface of a steam pipe 17 in a boiler by thermal spraying with the use of a material for thermal spraying. The material for thermal spraying includes a Ni-Cr-based alloy comprising, by wt.%, 21-25% Cr, 12-14% Mo, 6% or less Fe, 1-3% W, 2-9% Si, and the balance substantially Ni; a material comprising 2-9% Al as a substitute for Si; or a material comprising 4-9% mixture of Si and Al as a substitute for Si. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an adhesion prevention method, and more particularly to an ash adhesion prevention method for preventing coal ash and molten glass from adhering to a metal surface.

As a method for preventing the material from adhering to the surface, for example, a technique for preventing adhesion of ash such as coal ash to the furnace wall by forming a glass layer on the furnace wall of a coke oven such as brick is disclosed in Japanese Patent Laid-Open No. 8-12276 (Patent Document 1) and the like. However, a technique for preventing ash such as coal ash from adhering to a member made of a metal material such as a steam pipe (steam pipe in a boiler) disposed in a boiler used in a thermal power plant has been proposed. It wasn't.
JP-A-8-120276

  Therefore, when coal ash adheres to a member made of a metal material such as a steam pipe in a boiler, the heat transfer performance of the steam pipe is lowered, so that cleaning for removing coal ash periodically is not performed in a short period of time. The maintenance was troublesome. During the cleaning, the boiler operation had to be stopped.

  An object of the present invention is to provide an adhesion preventing method for preventing ash such as coal ash from adhering to a member made of a metal material such as a steam pipe in a boiler used in a thermal power plant or the like.

  Another object of the present invention is to provide an adhesion preventing method for preventing molten glass from adhering to a member made of a metal material.

  Still another object of the present invention is to provide a boiler that can prevent ash such as coal ash from adhering to the steam pipe in the boiler.

  Still another object of the present invention is to provide a thermal spray material capable of forming a coating layer capable of preventing coal ash and molten glass from adhering to a metal surface.

  The present invention aims to improve the adhesion prevention method. In the present invention, Cr: 21 to 25 wt%, Mo: 12 to 14 wt%, Fe: 6 wt% or less, W: 1 to 3 wt% on the surface of a member made of metal (hereinafter simply referred to as a metal member) , Si: 2 to 9% by weight, and a coating layer is formed of a Ni—Cr-based alloy consisting essentially of Ni to prevent ash made of unburned carbon from adhering to the metal member. Further, Al: 2 to 9% by weight can be used instead of Si. Further, a mixture of Si and Al: 4 to 9% by weight can be used instead of Si. Here, “metal” includes both a single metal and an alloy. Further, “the balance is substantially made of Ni” means that the balance except for substances such as inevitable impurities is made of Ni.

  Moreover, it can prevent that a molten glass adheres to a metal member by forming the coating layer of the said composition. Such an adhesion preventing method can be applied to prevent adhesion of molten glass to a mold or a metal tool used in the glass manufacturing process.

  When the coating layer is formed of a Ni—Cr based alloy as in the present invention, it is possible to effectively prevent ash or molten glass from adhering to the metal member surface. This is because the Ni-Cr-based alloy can prevent the oxidation of the surface of the metal member, so that the surface of the metal member becomes difficult to be uneven, and the adhesion of ash or molten glass can be prevented. Mo dissolves in the Ni—Cr base alloy, strengthens the base alloy, increases the high temperature strength, improves the passive characteristics, and plays a role of improving the corrosion resistance. Fe stabilizes the ground of the Ni—Cr base alloy and has an effect of improving the passive characteristics, and plays a role of improving the corrosion resistance. W has the same effect as Mo and plays the role of improving local corrosion resistance.

  In particular, in the present invention, since a predetermined amount of at least one of Si and Al is added, the oxidation resistance of the metal member can be effectively improved. If the amount of Si or Al is less than 2% by weight or the amount of the mixture of Si and Al is less than 4% by weight, sufficient oxidation resistance cannot be obtained. When the amount of Si, Al and the mixture of Si and Al exceeds 9% by weight, the coating layer becomes brittle.

  The adhesion preventing method of the present invention can be applied to preventing adhesion of various members. For example, it can be used to prevent adhesion of coal ash generated by burning coal to heat the steam pipe in the boiler to a metal member composed of the steam pipe in the boiler used in a thermal power plant or the like. In the adhesion preventing method of the present invention, since the heat transfer property of the coating layer is relatively high, even when the coating layer is used for a metal member composed of the steam pipe in the boiler, a decrease in heat transfer property due to the coating layer can be prevented. Further, in the adhesion preventing method of the present invention, a certain degree of adhesion preventing effect can be obtained even if the thickness of the coating layer is reduced, so that the thickness of the coating layer can be reduced. This also prevents a decrease in heat conductivity due to the coating layer.

  The coating layer can be formed by various methods. In particular, if the coating layer is formed by spraying a metal member, the coating layer can be formed easily and reliably in a short time.

  The coating layer is preferably flattened by polishing its surface. In this way, adhesion of ash or molten glass can be further reduced. Further, if the surface of the coating layer is polished and then the surface of the coating layer is heated to form a protective layer made of an oxide film on the surface, this protective layer can prevent the coating layer from proceeding with corrosion.

  The boiler to which the adhesion preventing method of the present invention is applied has a steam pipe in the boiler disposed therein, and generates steam in the steam pipe in the boiler. And the steam pipe in a boiler has Cr: 21-25 weight%, Mo: 12-14 weight%, Fe: 6 weight% or less, W: 1-3 weight%, Si: 2-9 weight% on the surface. The coating layer which consists of a Ni-Cr base alloy which consists of Ni and the remainder substantially consists of Ni is formed. Further, Al: 2 to 9% by weight is used instead of Si. Further, a mixture of Si and Al: 4 to 9% by weight is used instead of Si.

  The thermal spray material used for forming the coating layer used in the adhesion preventing method of the present invention is Cr: 21-25% by weight, Mo: 12-14% by weight, Fe: 6% by weight or less, W: 1-3% by weight, Si: 2 to 9% by weight, and the balance is made of a Ni—Cr base alloy substantially consisting of Ni. Further, Al: 2 to 9% by weight is used instead of Si. Further, a mixture of Si and Al: 4 to 9% by weight is used instead of Si. The thermal spray material may be a powder or a wire.

  According to the present invention, since the coating layer is formed of the Ni—Cr based alloy, it is possible to effectively prevent ash or molten glass from adhering to the surface of the metal member. Therefore, when it is used for preventing the adhesion of steam pipes in the boiler, the number of cleanings for removing coal ash can be reduced, and the number of times of shutdown of boilers and the like can also be reduced. Moreover, the heat transfer efficiency of a metal member can be improved by being able to prevent adhesion of ash. In particular, in the present invention, since a predetermined amount of at least one of Si and Al is added, the oxidation resistance of the metal member can be effectively improved.

  Hereinafter, the best mode for carrying out the present invention will be described. FIG. 1 schematically shows a boiler of a thermal power plant that implements the adhesion prevention method of this example. Here, the structure of the boiler will be briefly described. As shown in FIG. 1, the boiler includes a furnace body 1, a combustion burner 3, and first to third superheaters 5, 7, and 9. The furnace body 1 is connected in a horizontal direction by connecting the first and second cylindrical bodies 11 and 13 extending in the vertical direction and the first and second cylindrical bodies 11 and 13 communicating with each other in the upper direction. And a body 15. The combustion burner 3 is disposed below the first cylindrical body 11, and discharges a flame using coal as fuel into the first cylindrical body 11.

  The first to third superheaters 5, 7, 9 are all disposed in the connecting body 15. The structure of the superheater will be described by taking the first superheater 5 as an example. As shown in detail in FIG. 2, the superheater 5 is configured by combining a plurality of steam pipes 17 in the boiler. The steam pipe 17 in the boiler is composed of a pipe having a circular cross section made of heat-resistant cast steel or austenitic stainless steel, and extends in the vertical direction, the first and second pipe parts 17a and 17b, and the first and second pipe parts 17a. , 17b and a connecting pipe portion 17c extending in the lateral direction.

  In this boiler, when a flame is released from the combustion burner 3, heat is transferred from the first cylindrical body 11 to the connecting body 15 and the second cylindrical body 13 as shown by an arrow A in FIG. , Exhaust gas flows. Due to this heat, water in the steam pipes 17 in the boilers of the superheaters 5, 7, and 9 evaporates, and the evaporated steam rotates a power generation turbine (not shown) to generate power. However, if the coal ash, which is the ignited pulverized coal contained in the exhaust gas, adheres to the surface of the steam pipe 17 in the boiler, the thermal conductivity to the steam pipe 17 in the boiler is lowered. Therefore, in the ash adhesion preventing method of the present embodiment, as shown in FIGS. 2 and 3, 50 to 300 μm is formed on the surface of the steam pipe 17 in the boiler constituting the metal member by thermal spraying using a thermal spray material (wire material). A coating layer 19 having a thickness of 5 mm is formed. As a thermal spraying material, Cr: 21 to 25% by weight, Mo: 12 to 14% by weight, Fe: 6% by weight or less, W: 1 to 3% by weight, Si: 2 to 9% by weight, the balance being Thermal spraying material consisting essentially of a Ni—Cr based alloy consisting of Ni, or thermal spraying material using Al: 2-9 wt% instead of Si, or a mixture of Si and Al instead of Si: A thermal spraying material using 4 to 9% by weight is used. Next, after the surface of the coating layer 19 was polished, the surface of the coating layer 19 was heated at 500 ° C. for 120 minutes to form a protective layer made of an oxide film on the surface. In this example, the surface roughness was adjusted using a grindstone such as emery paper, green carbon, or zirconia. The final surface roughness was 10 to 30 μm in terms of 10-point average roughness.

Next, the test which confirms the effect of the ash adhesion removal by the composition of this coating layer was done. First, metal members made of cylindrical materials (thickness 2.3 mm, outer diameter 31.8 mm, length 120 mm) having the composition shown in Table 1 below were prepared. And as shown in FIG. 4, the cylindrical material 31 was attached to the probe 33 which can be water-cooled inside. And this was arrange | positioned in the pulverized coal combustion furnace 39 provided with the burner 35 and the pulverized coal feeder 37, the temperature in a furnace was adjusted to 1300 degreeC, and it combusted. Note that the distance L between the pulverized coal feeder 37 and the cylindrical material 31 is sufficiently long (1350 mm) in order to allow the molten ash to adhere under the condition that the combustion of the pulverized coal is completed. In addition, the code | symbol 33 is a water cooler and the internal diameter D of the combustion furnace 39 has a dimension of 120 mm. And the amount of coal ash adhesion for 10 minutes, 20 minutes, and 30 minutes after combustion was examined. The measurement results are also shown in Table 1.

  From Table 1, it can be seen that the cylindrical materials having the compositions of Examples 1 to 3 included in the composition of the present invention can reduce the adhesion amount of coal ash compared to the cylindrical materials having the compositions of Comparative Examples 1 to 10. In particular, the results of Comparative Examples 1 to 4 show that the amount of adhesion increases when the amount of at least one of Si and Al is small.

Next, as shown in FIG. 5, in each nitrogen atmosphere of 900 ° C. and 950 ° C., the metal plate 51 having the composition of Examples 1 to 3 and Comparative Examples 1 to 10 has a diameter of 2 mm at room temperature. The molten glass 53 was placed and the contact angle between the metal plate material 51 and the molten glass 53 was measured. The measurement results are shown in Table 2.

  From Table 2, it can be seen that the metal plate materials having the compositions of Examples 1 to 3 have a larger contact angle than the metal plate materials having the compositions of Comparative Examples 1 to 10. That is, it can be seen that the metal plate materials having the compositions of Examples 1 to 3 have lower wettability of the molten glass than the metal plate materials having the compositions of Comparative Examples 1 to 10, and the molten glass is difficult to adhere.

It is the schematic of the boiler of the thermal power plant which enforces the adhesion prevention method of embodiment of this invention. It is a top view of the superheater arrange | positioned in the boiler shown in FIG. It is sectional drawing of the board of the superheater shown in FIG. It is the schematic used in order to demonstrate the test which confirms the effect of ash adhesion removal. It is the schematic used in order to demonstrate the test which confirms the effect of adhesion removal of a molten glass.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Furnace 3 Combustion burner 5, 7, 9 1st-3rd superheater 17 Steam pipe in boiler 19 Coating layer

Claims (16)

  On the surface of the member made of metal, Cr: 21-25 wt%, Mo: 12-14 wt%, Fe: 6 wt% or less, W: 1-3 wt%, Si: 2-9 wt%, A method for preventing adhesion, wherein a coating layer is formed of a Ni—Cr base alloy, the balance of which is substantially made of Ni, to prevent ash made of unburned carbon from adhering to the member.   On the surface of the member made of metal, Cr: 21-25 wt%, Mo: 12-14 wt%, Fe: 6 wt% or less, W: 1-3 wt%, Al: 2-9 wt%, A method for preventing adhesion, wherein a coating layer is formed of a Ni—Cr base alloy, the balance of which is substantially made of Ni, to prevent ash made of unburned carbon from adhering to the member.   On the surface of the member made of metal, Cr: 21 to 25% by weight, Mo: 12 to 14% by weight, Fe: 6% by weight or less, W: 1 to 3% by weight, a mixture of Si and Al: 4 to 9% by weight %, A coating layer is formed of a Ni—Cr-based alloy consisting essentially of Ni, and an adhesion preventing method for preventing ash composed of unburned carbon from adhering to the member. The member consists of a steam pipe in the boiler,
The adhesion prevention method according to any one of claims 1 to 3, wherein the ash is coal ash generated by burning coal to heat the steam pipe in the boiler.   On the surface of the member made of metal, Cr: 21-25 wt%, Mo: 12-14 wt%, Fe: 6 wt% or less, W: 1-3 wt%, Si: 2-9 wt%, An adhesion prevention method for preventing a molten glass from adhering to the member by forming a coating layer of a Ni—Cr base alloy substantially comprising Ni as a balance.   On the surface of the member made of metal, Cr: 21-25 wt%, Mo: 12-14 wt%, Fe: 6 wt% or less, W: 1-3 wt%, Al: 2-9 wt%, An adhesion prevention method for preventing a molten glass from adhering to the member by forming a coating layer of a Ni—Cr base alloy substantially comprising Ni as a balance.   On the surface of the member made of metal, Cr: 21 to 25% by weight, Mo: 12 to 14% by weight, Fe: 6% by weight or less, W: 1 to 3% by weight, a mixture of Si and Al: 4 to 9% by weight %, A coating layer is formed of a Ni—Cr-based alloy consisting essentially of Ni and the adhesion preventing method for preventing molten glass from adhering to the member.   The adhesion preventing method according to claim 1, wherein the coating layer is formed by spraying the member.   The adhesion preventing method according to claim 1, wherein after the formation of the coating layer, the surface of the coating layer is polished to flatten the surface of the coating layer.   The adhesion preventing method according to claim 9, wherein after the surface of the coating layer is polished, the surface of the coating layer is heated to form a protective layer made of an oxide film on the surface. In the boiler that arranges the steam pipe in the boiler and generates steam in the steam pipe in the boiler,
The steam pipe in the boiler has Cr: 21 to 25% by weight, Mo: 12 to 14% by weight, Fe: 6% by weight or less, W: 1 to 3% by weight, Si: 2 to 9% by weight on the surface thereof. A boiler comprising: a coating layer made of a Ni—Cr based alloy containing Ni and the balance being substantially made of Ni. In the boiler that arranges the steam pipe in the boiler and generates steam in the steam pipe in the boiler,
The steam pipe in the boiler has Cr: 21 to 25% by weight, Mo: 12 to 14% by weight, Fe: 6% by weight or less, W: 1 to 3% by weight, Al: 2 to 9% by weight on the surface thereof. A boiler comprising: a coating layer made of a Ni—Cr based alloy containing Ni and the balance being substantially made of Ni. In the boiler that arranges the steam pipe in the boiler and generates steam in the steam pipe in the boiler,
The steam pipe in the boiler has Cr: 21 to 25% by weight, Mo: 12 to 14% by weight, Fe: 6% by weight or less, W: 1 to 3% by weight, a mixture of Si and Al: 4 A boiler comprising: a coating layer made of a Ni—Cr-based alloy containing ˜9% by weight and the balance being substantially made of Ni.   Cr: 21 to 25% by weight, Mo: 12 to 14% by weight, Fe: 6% by weight or less, W: 1 to 3% by weight, Si: 2 to 9% by weight, with the balance being substantially Ni Thermal spray material made of Ni-Cr base alloy.   Cr: 21 to 25% by weight, Mo: 12 to 14% by weight, Fe: 6% by weight or less, W: 1 to 3% by weight, Al: 2 to 9% by weight, with the balance being substantially Ni Thermal spray material made of Ni-Cr base alloy.   Cr: 21 to 25% by weight, Mo: 12 to 14% by weight, Fe: 6% by weight or less, W: 1 to 3% by weight, a mixture of Si and Al: 4 to 9% by weight, the balance being substantially A thermal spray material made of a Ni—Cr based alloy made of Ni.

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