JPH08120377A - Heat transfer pipe of waste heat boiler utilizing garbage burning exhaust gas excellent in high temperature corrosion resistance - Google Patents

Abstract

PURPOSE: To produce the heat transfer pipe of a waste heat boiler utilizing a garbage burning exhaust gas having high temp. corrosion resistance. CONSTITUTION: This heat transfer pipe is constituted of an Ni-base alloy having a compsn. contg., by weight, 23 to 27% Cr, 7 to 10% Mo, 0.5 to 5% Nb, 0.01 to 7% Fe, <=0.05% C, <=0.1% Si, <=0.03% P and <=0.03% S, and the balance Ni with other impurities, and furthermore contg., at need, one >= two kinds selected from among 0.1 to 2% W, 0.001 to 0.1% rare earth elemensts, 0.001 to 0.1% Y, 0.001 to 0.1% Zr, 0.001 to 0.1% Hf and 0.001 to 0.01% B.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat transfer tube material for a waste heat boiler using waste incineration exhaust gas, which is highly corrosive and exhibits excellent high-temperature corrosion resistance against high temperature waste incineration exhaust gas.

[0002]

2. Description of the Related Art Generally, a waste heat boiler is installed in a refuse incineration facility in order to utilize high temperature latent heat of exhaust gas. The heat transfer tube material, which is a structural member of the waste heat boiler, is made of highly corrosive HCl or SO ₂ gas, molten sulfate such as Na ₂ SO ₄ or Ca ₂ SO ₄ , and further NaCl or KC.
Since it is exposed to high-temperature exhaust gas containing corrosive products such as molten chloride such as 1 and is in an environment in which the above-mentioned sulfates and chlorides are deposited on the surface, Various excellent materials are used.

[0003]

On the other hand, due to the urgent energy situation in recent years, the steam condition of the waste heat boiler tends to be high temperature and high pressure in order to maximize the use of waste heat from incineration of waste. Along with this, the temperature of the heat transfer tube wall will rise further, and the corrosiveness of the exhaust gas will become even more severe due to the high calorie content of waste and the increase in plastics. Although much higher temperature corrosion resistance is strongly required for pipe materials, the various conventional heat transfer pipe materials described above cannot satisfy these requirements at present due to insufficient high temperature corrosion resistance. is there.

[0004]

Therefore, the present inventors have
From the above viewpoints, as a result of conducting research to develop a heat transfer tube material for a waste heat boiler using waste incineration exhaust gas, which has further excellent high temperature corrosion resistance,
(Hereinafter,% means% by weight), Cr: 23 to 27%,
Mo: 7-10%, Nb: 0.5-5
%, Fe: 0.01 to 7%, C: 0.
05% or less, Si: 0.1% or less,
P: 0.03% or less, S: 0.03%
The following are contained, and (a) W:
0.1-2%, (b) rare earth element: 0.001-0.
1%, Y: 0.001-0.1%, Zr:
0.001-0.1%, Hf: 0.001-0.1%,
B: 0.001 to 0.01%, one or two or more of them, containing at least (a) and / or (b), and the balance being Ni and other impurities. According to the above, the research results show that the resulting Ni-based alloy heat transfer tube material exhibits excellent corrosion resistance under extremely severe high temperature corrosive environment.

The present invention was made based on the above-mentioned research results, and the Ni constituting the heat transfer tube material will be described below.
The reason why the component composition of the base alloy is limited as described above will be described. (A) Cr and Mo These components have the effect of improving high-temperature corrosion resistance and high-temperature oxidation resistance to high-temperature waste incineration exhaust gas in the coexisting state, but when the content is either Cr or Mo, Cr: If it is less than 23% and Mo: less than 7%, the desired effect cannot be obtained, while the content is C.
Even if it exceeds r: 27% and Mo: 10%, the effect of further improving the high temperature corrosion resistance does not appear. Therefore, the content of Cr: 23 to 27%, preferably 24 to 26%, M
o: 7 to 10%, preferably 8.5 to 10%.

(B) Nb The Nb component has the function of improving the corrosion resistance to the corrosive products such as sulfates and chlorides in the high temperature exhaust gas, but if the content is less than 0.5%, The desired effect of improving the high-temperature corrosion resistance cannot be obtained, and if the content exceeds 5%, the bending workability will decrease. Therefore, the content is 0.5 to 5%, preferably 0.5. It was set at ~ 2%.

(C) Fe Fe component has an action of improving hot workability, but if the content of Fe is less than 0.01%, the desired hot workability cannot be ensured. If the amount exceeds 7%, the toughness will decrease, so the content should be 0.0
It was set to 1 to 7%, preferably 1 to 5%.

(D) When the content of the C component as the C impurity exceeds 0.05%, the amount of carbides existing at the grain boundaries is increased, especially the molten chloride contained in the high temperature exhaust gas. Since the progress of intergranular corrosion due to the above is promoted, the content thereof is set to 0.05% or less.

(E) Si Since the Si component has a deoxidizing action, it may be used for deoxidizing a molten metal, but even in this case, if the content exceeds 0.1%, the toughness deteriorates. Therefore, the content is determined to be 0.1% or less.

(F) P and S: P and 0.03% of these components as impurities, respectively.
And, if S: 0.03% is exceeded, segregation occurs at the grain boundaries, which deteriorates hot workability and also decreases high temperature corrosion resistance. Therefore, the content of P: 0.03%
Below and S: 0.03% or less.

(G) The W W component has a function of further improving the high temperature corrosion resistance, and thus it is contained as necessary, but the content thereof is 0.
If it is less than 1%, the desired improving effect on the above-mentioned action cannot be obtained, while if it exceeds 2%, the bending workability is deteriorated. Therefore, the content is defined as 0.1 to 2%. It was

(H) Rare earth element, Y, Zr, Hf, and B All of these components have the action of improving the adhesion of the protective scale formed on the surface of the pipe material, and thus contributing to the improvement of high temperature corrosion resistance. Therefore, it is contained as necessary, but
If the content is less than 0.001%, the desired effect is not obtained on the other hand. On the other hand, if the content is 0.1% except B, and B exceeds 0.01%, hot work is not achieved. Since the workability is lowered, the content of each of the elements other than B is 0.001 to 0.1%, and the content of B is 0.001 to 0.1%.
It was set at 0.1%.

(I) Other Impurities Mn, Ti, and Al may be contained as other impurities, but the content of each of these components is 0.4.
%, The bending workability will be impaired, so the content of each must be 0.4% or less.

[0014]

EXAMPLES Next, the heat transfer tube material of the present invention will be specifically described by way of examples. Using a normal high frequency melting furnace, Table 1
~ 3 to prepare a Ni-based alloy melt having the composition of the composition, cast into an ingot, 1000 ~
Hot forging is performed at a predetermined temperature within the range of 1250 ° C. to form a round bar material having a diameter of 55 mm, and then the diameter of the round bar material is:
50 mm x wall thickness: The heat transfer tube materials 1-28 of the present invention and the comparative heat transfer tube materials 1-4 were manufactured by cutting into a size of 6 mm. In addition, in the comparative heat transfer tube materials 1 to 4, among the constituent components of the Ni-based alloy constituting the comparative heat transfer tube materials, any one of the components that affect the high temperature corrosion resistance and the high temperature strength (Table 3
Are marked with *) are outside the scope of this invention.

Next, various heat transfer tube materials obtained as a result are incorporated into a waste heat boiler, and the waste heat boiler has a treatment capacity:
It was installed in a refuse incineration facility of 150 tons / day, operated for 1000 hours under the conditions of the surface temperature of the heat transfer tube: 450 ° C and the exhaust gas temperature: 700 ° C, and after the operation was completed, the heat transfer tube was taken out and attached to the surface The wall thickness in the circumferential direction was measured with ash and scales removed to determine the maximum amount of wall thinning, and the microstructure of the cross section of the surface was observed to measure the maximum intergranular corrosion length. The measurement results are shown in Tables 4 and 5.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

[Table 3]

[0019]

[Table 4]

[0020]

[Table 5]

[0021]

From the results shown in Tables 1 to 5, the heat transfer tube materials 1 to 28 of the present invention all show excellent high temperature corrosion resistance in the high temperature refuse incineration exhaust gas atmosphere, while the heat transfer tube materials 1 to 4 of the comparative example are shown. As can be seen, if the content of any one of Cr, Mo, and Nb in the Ni-based alloy constituting the same falls outside the range of the present invention, the desired high temperature corrosion resistance cannot be secured. Is clear. As described above, the heat transfer tube material of the present invention exhibits excellent high-temperature corrosion resistance against high-temperature waste incineration exhaust gas, and therefore can sufficiently cope with the increase in size of waste incineration facility and improvement in treatment capacity. Of.

Claims (4)

[Claims] 1. By weight%, Cr: 23-27%, Mo: 7-10
%, Nb: 0.5 to 5%, Fe: 0.01
~ 7%, C: 0.05% or less, Si: 0.1%
Below, P: 0.03% or less, S: 0.03%
A heat transfer tube material for a waste heat boiler using a waste incineration exhaust gas with excellent high temperature corrosion resistance, characterized in that it is composed of a Ni-based alloy having the following composition and the balance consisting of Ni and other impurities. 2. By weight%, Cr: 23-27%, Mo: 7-10
%, Nb: 0.5 to 5%, Fe: 0.01
~ 7%, C: 0.05% or less, Si: 0.1%
Below, P: 0.03% or less, S: 0.03%
The following is included, and further, W: 0.1 to 2% is contained, and the remainder is composed of a Ni-based alloy having a composition of Ni and other impurities. Heat transfer tube material for waste heat boiler using incineration exhaust gas. 3. By weight%, Cr: 23-27%, Mo: 7-10
%, Nb: 0.5 to 5%, Fe: 0.01
~ 7%, C: 0.05% or less, Si: 0.1%
Below, P: 0.03% or less, S: 0.03%
The following are contained, and further, rare earth element: 0.001 to 0.1%, Y: 0.001
~ 0.1%, Zr: 0.001-0.1%, Hf: 0.00
1 to 0.1%, B: 0.001 to 0.01%, one or more of them, and the balance is composed of a Ni-based alloy having a composition of Ni and other impurities. A heat transfer tube material for a waste heat boiler using waste incineration flue gas with excellent high temperature corrosion resistance. 4. By weight%, Cr: 23-27%, Mo: 7-10
%, Nb: 0.5 to 5%, Fe: 0.01
~ 7%, C: 0.05% or less, Si: 0.1%
Below, P: 0.03% or less, S: 0.03%
The following are contained: W: 0.1 to 2% are contained, and further, a rare earth element: 0.001 to 0.1%, Y: 0.001
~ 0.1%, Zr: 0.001-0.1%, Hf: 0.00
1 to 0.1%, B: 0.001 to 0.01%, one or more of them, and the balance is composed of a Ni-based alloy having a composition of Ni and other impurities. A heat transfer tube material for a waste heat boiler using waste incineration flue gas with excellent high temperature corrosion resistance.