JPH10153312A - Air nozzle in recovery boiler and its forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent corrosion at an air nozzle of a recovery boiler caused by smelt produced from black liquor in a paper making process. SOLUTION: An air nozzle 4 is formed of a material comprising 0.080wt.% or less of C, 35.0 to 60.0wt.% of Cr, 10.0wt.% or less of Fe, balance of Ni and unavoidable impurities in view of its chemical composition; or material having 5.0 to 18.0wt.% of Mo added to the aforesaid chemical composition; or material having 0.5 to 4.0wt.% of Mn added to the aforesaid chemical composition. In addition, powder of the aforesaid chemical composition produced by an atomizing method is injected against the surface of a base material by a plasma spraying process to form the air nozzle 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an air port nozzle of a recovery boiler.

[0002]

2. Description of the Related Art A recovery boiler is used in a paper making process or the like. As shown in FIG.
, A heat exchanger 3 composed of a superheater tube and the like provided in the upper part of the furnace 1, an air nozzle 4 provided on a side wall of the furnace 1 for introducing combustion air 9, 1
Is formed by a smelt spout 5 provided at the lower part of the side wall of the smelt tank and communicating with the dissolving tank 6.

The role of the above-mentioned recovery boiler in the papermaking process is as follows.
And from the smelt 8 discharged to the dissolving tank 6 via the smelt spout 5,
The required Na is recovered in the papermaking process.

In the air nozzle 4 used in a conventional recovery boiler, ferrite stainless steel such as SUS430 containing about 17% by weight of Cr,
SUS3 containing about 18% and about 25% Cr
Austenitic stainless steels (0% Mo) such as 04 and SUS310 were used.

[0005]

The air port nozzle of the conventional recovery boiler has been formed of ferritic stainless steel or austenitic stainless steel as described above.

In recent years, it has been desired to improve the energy efficiency of the recovery boiler. Attempts to increase the temperature and pressure of steam conditions and the concentration of black liquor as fuel have been studied and implemented, and the heat load of the furnace has increased. The environment tends to be harsh.

The smelt produced from the above black liquor is in a molten state at a temperature of about 800 ° C. or higher and contains a large amount of Na ₂ S, so that it is a very corrosive substance. It is desirable to avoid this in order to ensure the safety of the recovery boiler. In addition, as a place where leakage of smelt may occur, an air port nozzle for introducing combustion air into a furnace is given.

The corrosion of the conventional air port nozzle is shown in FIG.
As shown in Fig. 5, the solidified smelt 8a and the environmental gas (a mixture of the introduced combustion air and the gas in the furnace) were used. The average temperature of the air port nozzle was about 350 ° C. due to cooling by combustion air, and the melting point of the smelt was about 700 ° C. or more, so that the smelt attached to the air port nozzle was solidified.

However, due to the recent increase in heat load, the possibility that the smelt in a molten state directly contacts the air nozzle is increased. That is, the air port nozzle is
It is necessary to periodically clean the adhered smelt to secure the flow path of combustion air, but after cleaning, the smelt in the molten state contacts the air port nozzle until the solidified smelt adheres again. More likely.

[0010] Corrosion due to smelt in the molten state is significantly greater than corrosion due to solidified smelt and environmental gas, and the effective material components for preventing this corrosion are different. It was found that it was desired to improve the corrosion resistance of the air port nozzle.

The conventional air port nozzle is formed by casting or by forging and heat treatment after casting. If the air port nozzle is corroded, it needs to be replaced. If such a method is costly, it may not be possible to replace it in practice, and it is desired to establish a simple method of forming an air port nozzle that can repair that part if it is corroded. Was rare.

In order to solve the above-mentioned problems, the present invention has sufficient corrosion resistance to smelt in a molten state, and has sufficient resistance to periodic cleaning (hitting solidified smelt with a steel rod). An object of the present invention is to provide an air port nozzle having high toughness and a simple method of forming the air port nozzle capable of repairing a part of the nozzle.

[0013]

[Means for Solving the Problems]

(1) The air port nozzle of the recovery boiler according to the first aspect of the present invention is characterized in that the chemical component is 0.080% or less by weight of carbon (hereinafter referred to as C) and 35.0 to 60.0% of chromium. (Hereinafter referred to as Cr), and is characterized by being formed of a material comprising 10.0% or less of iron (hereinafter referred to as Fe) and the balance being nickel (hereinafter referred to as Ni) and an unavoidable impurity.

In the present invention, the reason why the materials containing C, Cr and Fe are used as the material of the air port nozzle and the ranges of the respective components are limited will be described below in detail.

C is Cr, which is a component for improving corrosion resistance.
To form carbides, thereby reducing corrosion resistance and toughness. Therefore, the content is desirably small, and the upper limit is set to 0.080%. When repair welding or the like is considered to be performed after long-time use, 0.040% or less is particularly desirable.

Cr is a component that improves corrosion resistance.
In particular, considering corrosion due to smelt in the molten state,
The effect appears at 35.0% or more. However, if added in a large amount, the toughness deteriorates, so the upper limit is made 60.0%.

Since the air nozzle is preferably small in view of securing a heat transfer area of the furnace and improving reliability against leakage, it is formed of a relatively thin material. Since it is advantageous to use a forged or rolled material that can be easily secured, a range of 35.0 to 50.0% that can be easily forged or rolled is particularly desirable.

Fe is a component that improves forgeability and the like, but is a component that reduces corrosion resistance. It is desirable that the Fe content be small, and the upper limit is 10.0%.

By the above, it is possible to form an air port nozzle which is excellent in corrosion resistance, can secure a predetermined toughness and can be easily processed, and can realize a recovery boiler which is excellent in reliability and high in energy efficiency. Become.

(2) The air port nozzle of the recovery boiler according to the second aspect of the present invention has a chemical component containing 0.080% by weight of a chemical component.
% C, 35.0 to 60.0% Cr, 10.0%
The following Fe, molybdenum of 5.0 to 18.0% (hereinafter M
o), and the remainder is formed of a material comprising Ni and unavoidable impurities.

In the present invention, as a material for forming the air port nozzle, the material according to the above invention (1) is made of Mo.
Is added by 5.0 to 18.0% by weight. This Mo is a component for improving corrosion resistance, and is 5.0% in consideration of corrosion due to smelt in a molten state.
As described above, a clear effect appears. However, if added in a large amount, the toughness deteriorates, so the upper limit is set to 18.0%.

In the case of the present invention, Mo is set to 5.0 to 18.0%.
Therefore, the corrosion resistance is further improved as compared with the above invention (1), and a predetermined toughness can be ensured similarly to the above invention (1), and it is possible to realize an air port nozzle that can be easily processed. Become.

(3) The air port nozzle of the recovery boiler according to the third aspect of the present invention has a chemical component containing 0.080% by weight of a chemical component.
% C, 35.0 to 60.0% Cr, 10.0%
It is characterized by being formed of the following Fe, 0.5 to 4.0% of manganese (hereinafter referred to as Mn), and the balance being made of a material comprising Ni and unavoidable impurities.

In the present invention, as a material for forming the air port nozzle, Mn is added to the material according to the above invention (1).
Is added in an amount of 0.5 to 4.0% by weight. This Mn improves the flowability of the molten metal during welding, thereby improving the toughness. However, this effect is not observed at 0.5% or less, and the addition of a large amount deteriorates the corrosion resistance. 0%.

In the case of the present invention, since Mn is added in the range of 0.5 to 4.0%, the flowability of the molten metal at the time of welding is improved as compared with the above invention (1), processing becomes easy, and toughness is improved. As in the above invention (1), it is possible to realize an air port nozzle which is excellent in corrosion resistance, more excellent in toughness than the above invention (1), and easy to process.

(4) The method for forming an air port nozzle of a recovery boiler according to the invention described in claim (4) is characterized in that the material of the chemical component described in the inventions (1), (2) and (3) is respectively A powder is formed by an atomizing method, and an air port nozzle is formed by a plasma spraying method using each powder.

In the present invention, a powder containing a predetermined chemical component at a predetermined content by an atomizing method is produced,
The powder is fed into a plasma arc generated by supplying a gas to the arc, and is sprayed on the surface of the base material, thereby forming a sprayed coating of a predetermined component on the surface of the base material.

This method of forming by plasma spraying can be applied to only a part of the air nozzle when corrosion occurs, and the air nozzle can be partially repaired. , The service life can be extended, and the cost can be greatly reduced.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An air nozzle of a recovery boiler according to a first embodiment of the present invention will be described. The air port nozzle according to this embodiment has a chemical component of 0.080% by weight.
% C, 35.0 to 60.0% Cr, 10.0%
The following Fe and the remainder are formed of a material comprising Ni and unavoidable impurities.

With respect to the above-mentioned materials, test materials are manufactured and tested for the purpose of evaluating the characteristics thereof, and the contents will be described below. As the specimen, a material obtained by melting a material having a component constitution shown in Table 1 by vacuum melting was used. In Table 1, the material of the present invention is a material in which each component is in the above component range, and the comparative material is a material having a conventional component configuration.

[0031]

[Table 1]

Each specimen was subjected to an aging treatment at 700 ° C. for 300 hours in consideration of long-term use, and then subjected to the following corrosion test and Charpy impact test for the evaluation of toughness.

In the corrosion test, as shown in FIG. 1A, a test material 11 was partially immersed in a smelt 8 in a crucible 12 for 5 hours, and the temperature was set to 800 ° C. in the atmosphere. Smelt 8 emits gas such as H ₂ S and deteriorates.
Updated every hour.

The dimensions of the test material 11 are 5 mm × 5 mm × 6.
The reference thickness was set to 0 mm, 11 reference points were set at a pitch of 5 mm in the longitudinal direction (60 mm), and the thickness at each reference point was measured. Incidentally, to determine the reference point of the measurement, one end of the sample materials 11 AI ₂ O
Protected by a ceramic coating 13 containing ₃ as a main component.

The results of this test are indicated by open circles in FIG. 2, and in the case of the material of the present invention, 0 is the reference value of the corrosion thinning amount of the material that can be used for the air port nozzle of the recovery boiler. .1 mm (indicated by a broken line in the figure), which proved to be sufficient for the corrosion thinning amount.

In the Charpy impact test, the test material was tested as shown in FIG.
A test piece 14 having the shape shown in FIG.
Performed at room temperature according to The results of this test are shown in FIG. 3, and all of the materials of the present invention exceeded the reference value of the impact value of 0.5 kgf · m / cm ^{2 and} were sufficiently usable for impact. I found it to be.

Next, an air port nozzle of a recovery boiler according to a second embodiment of the present invention will be described. The air port nozzle according to the present embodiment has a chemical component of 0.080% by weight%.
The following C, 35.0 to 60.0% Cr, 10.0% or less iron, 5.0 to 18.0% Mo, and the balance is made of a material including Ni and unavoidable impurities.

With respect to the above-mentioned materials, specimens having the components shown in Table 2 were manufactured and subjected to a corrosion test and a Charpy impact test in the same manner as in the first embodiment to evaluate the characteristics.

[0039]

[Table 2]

The results of the corrosion test and the Charpy impact test are shown in FIG. 4 (indicated by white circles) and FIG. 5, respectively. Below, the standard value of impact value 0.5kgf
-It was more than m / cm ^2, and it was found that it can be sufficiently used as a material for the air port nozzle of the recovery boiler as in the case of the first embodiment.

Next, an air port nozzle of a recovery boiler according to a third embodiment of the present invention will be described. The air port nozzle according to the present embodiment has a chemical component of 0.080% by weight%.
It is made of a material comprising the following C, 35.0 to 60.0% Cr, 10.0% or less iron, 0.5 to 4.0% Mn, and the balance being Ni and unavoidable impurities.

With respect to the above materials, a specimen having the composition shown in Table 3 was manufactured, and a corrosion test and a Charpy impact test were conducted in the same manner as in the first and second embodiments to evaluate the characteristics. .

[0043]

[Table 3]

The results of the corrosion test and the Charpy impact test are shown in FIG. 6 (indicated by white circles) and FIG. 7, respectively. Under 0.1mm, standard value of impact value 0.5kg
f · m / cm ² , which indicates that it can be sufficiently used as a material for the air port nozzle of the recovery boiler as in the case of the first and second embodiments.

Next, a method of forming an air port nozzle of a recovery boiler according to a fourth embodiment of the present invention will be described. In the method of forming the air port nozzle according to the present embodiment, first, the materials of the chemical components used in the first, second, and third embodiments are each made into a powder by an atomizing method.

Next, each of the powders was mixed with a SUS310 base under the conditions that the plasma gas was Ar 45 L / min + H ₂ 4 L / min, the plasma arc current was 600 A, the plasma voltage was 60 V, and the spraying distance was 100 to 150 mm. An air port nozzle is formed by plasma spraying on the surface of the material.

In the above description, the atomizing method is shown in FIG.
As shown in (a), after a material of a predetermined component is melted in a vacuum induction furnace 20, a spray gas 22 is sprayed into the powder in a sprayer 21 to obtain a powder, and a powder having a predetermined particle size is obtained by a cyclone 23. is there.

In the plasma spraying, as shown in FIG. 8B, an arc 27 is formed using a copper nozzle 25 as an anode and a tungsten electrode 26 as a cathode, and a gas is supplied to the arc 27 to form a plasma. An arc is generated, and the powder is fed into the plasma arc and sprayed onto the surface of the base material 28 to obtain a thermal spray coating 29.

In the present embodiment, unlike the conventional method in which a predetermined component is formed by casting or the like, the powder of the predetermined component is formed by plasma spraying. If
Since that part can be repaired by plasma spraying, the life of the recovery boiler can be extended, and the cost can be significantly reduced.

Also in this embodiment, in order to confirm the performance of the air port nozzle formed by this forming method,
As in the second and third embodiments, a test is performed, and the contents and results will be described below. In addition, in the case of the formation method by plasma spraying, since the influence of aging embrittlement was small, only the corrosion test was performed without performing the Charpy impact test.

In this corrosion test, a specimen was formed by subjecting a powder of a predetermined component produced by an atomizing method to a base material of SUS310 having a length of 5 mm × a width of 5 mm × a length of 60 mm by plasma spraying under the above conditions. The test was performed in the same manner as in the first, second, and third embodiments.

The results are shown in FIGS. 2, 4 and 6, respectively.
The results are almost the same as those in the first, second and third embodiments, and are shown to be sufficiently usable.

[0053]

The air inlet nozzle of the recovery boiler of the present invention is
C of less than 0.080% by weight of a chemical component, 35.0 to 35.0%
60.0% Cr, 10.0% or less Fe, the balance being Ni
And, by being formed of a material consisting of unavoidable impurities, it is possible to form an air port nozzle having excellent corrosion resistance to smelt, having a predetermined toughness, and being easily processed, and having high reliability and good energy efficiency. A recovery boiler can be realized, and the above chemical components are 5.0 to 18.0%
By adding Mo, it is possible to realize an air port nozzle having more excellent corrosion resistance, and 0.5 to 0.5%
By adding 4.0% Mn, it is possible to realize an air port nozzle that is easier to process and has excellent toughness.

Further, by forming powders of the above-mentioned chemical components by an atomizing method and spraying these powders on the surface of a base material by plasma spraying to form a sprayed film, an air port nozzle is formed, whereby air Since the corrosion generated in a part of the mouth nozzle can be repaired, the life of the recovery boiler can be extended, and the cost can be significantly reduced.

[Brief description of the drawings]

FIGS. 1A and 1B are explanatory diagrams of a characteristic test according to first, second, and third embodiments of the present invention, wherein FIG. 1A illustrates a corrosion test procedure and FIG. 1B illustrates a test piece used in a Charpy test; FIG.

FIGS. 2A and 2B are explanatory diagrams of a corrosion test result according to the first embodiment of the present invention, in which FIG. 2A shows the content of C on the horizontal axis, FIG. 2B shows the content of Cr, and FIG. 2C shows the content of Fe. FIG. 7 is an explanatory diagram in the case where the amount is set.

FIGS. 3A and 3B are explanatory diagrams of the results of the Charpy test according to the first embodiment, in which FIG. 3A is a diagram illustrating a case where the horizontal axis represents the content of C and FIG.

4A and 4B are explanatory diagrams of a corrosion test result according to the second embodiment of the present invention, in which (a) is the content of Cr on the horizontal axis, (b) is the content of C, and (c) is the content of Fe. (D) is an explanatory diagram when the content of Mo is assumed.

FIGS. 5A and 5B are explanatory diagrams of Charpy test results according to the second embodiment, in which FIG. 5A shows the Cr content on the horizontal axis, C shows the C content, and FIG. 5C shows the Mo content. It is an explanatory view of a case.

FIG. 6 is an explanatory diagram of a corrosion test result according to the third embodiment of the present invention (the horizontal axis is the Mn content).

FIG. 7 is an explanatory diagram of a Charpy test result according to the third embodiment (the abscissa is the Mn content).

8A and 8B are explanatory diagrams of a method of forming an air port nozzle according to a fourth embodiment of the present invention, wherein FIG. 8A is an explanatory diagram of an atomizing method, and FIG. 8B is an explanatory diagram of a plasma spraying method.

9A and 9B are explanatory views of an air port nozzle provided in a recovery boiler, where FIG. 9A is an overall side view, FIG. 9B is a detailed side view, and FIG.
FIG. 3 is a view taken along the line AA in FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Furnace 2 Evaporation tube 3 Heat exchanger 4 Air nozzle 5 Smelt spout 6 Dissolving tank 8 Smelt 8a Solidified smelt

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kazuo Hiromatsu 5-7-17-1 Fukabori-cho, Nagasaki-shi Mitsubishi Heavy Industries, Ltd. Nagasaki Research Institute Co., Ltd. (72) Inventor Yasuko Takano 1-1-1, Akunoura-cho, Nagasaki-shi Mitsubishi Heavy Industries Inside Nagasaki Shipyard Co., Ltd. (72) Inventor Yuichi Doi 5-717-1 Fukahoricho, Nagasaki City, Nagaishi Engineering Co., Ltd.

Claims (4)

[Claims] 1. A material whose chemical composition is composed of carbon of 0.080% or less by weight, chromium of 35.0 to 60.0%, iron of 10.0% or less, and a balance of nickel and unavoidable impurities. An air outlet nozzle of a recovery boiler, characterized in that it has been manufactured. 2. The chemical composition in which the chemical composition is 0.080% or less by weight of carbon, 35.0 to 60.0% of chromium, 10.0% or less of iron, 5.0 to 18.0% of molybdenum, and the balance. Is formed of a material comprising nickel and unavoidable impurities. 3. The chemical composition of the carbon component is 0.080% or less by weight, 35.0 to 60.0% of chromium, 10.0% or less of iron, 0.5 to 4.0% of manganese, with the balance being the balance. Is formed of a material comprising nickel and unavoidable impurities. 4. A recovery boiler characterized in that the material of the chemical component according to claim 1, 2, or 3 is formed into a powder by an atomizing method, and an air port nozzle is formed by a plasma spraying method using each powder. Method of forming an air port nozzle.