JP3284794B2 - Heat transfer tubing for waste heat boilers utilizing refuse incineration exhaust gas with excellent high temperature corrosion resistance - Google Patents

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 for a waste heat boiler utilizing refuse 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 plant for the purpose of utilizing high-temperature latent heat of exhaust gas. The heat transfer tube, 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 , NaCl or KC.
1) are exposed to high-temperature exhaust gas containing corrosive products such as molten chloride such as l, and are placed in an environment where the sulfates and chlorides are deposited on the surface. Various excellent materials are used.

[0003]

On the other hand, due to the urgent situation of energy in recent years, the steam condition of a waste heat boiler tends to be high temperature and high pressure in order to make maximum use of waste heat generated by incineration of waste. Along with this, the wall temperature of the heat transfer tubes further rises, and the corrosiveness of the exhaust gas is further increased due to the increase in the amount of calories and the amount of plastics in the garbage. Further high-temperature corrosion resistance is strongly demanded of pipe materials, but at present, the above-mentioned various conventional heat transfer tubes cannot satisfy these requirements satisfactorily due to insufficient high-temperature corrosion resistance. is there.

[0004]

Means for Solving the Problems Accordingly, the present inventors have
From the above-mentioned viewpoint, as a result of conducting research to develop a heat transfer tube for a waste heat boiler utilizing refuse incineration exhaust gas which has much higher high temperature corrosion resistance, the heat transfer tube was
(% Indicates weight% (mass%)), Cr: 23 to 27%, Mo: 7 to 10%, Nb: 0.5 to 5%, Fe: 0.01 to 7 %, C: 0.05% or less, Si: 0.1% or less, P: 0.03% or less, S: 0.03% or less, and W: 0.1 to 2%. Rare earth elements: 0.001 to 0.1%, Y: 0.001 to 0.1%, Zr: 0.001 to 0.1%, Hf: 0.001 to 0.1%, B: 0.001 to 0.01%, and the remainder is composed of a Ni-based alloy having a composition composed of Ni and other impurities. Research has shown that heat pipes exhibit excellent corrosion resistance in extremely harsh high-temperature corrosive environments.

[0005] The present invention has been made based on the above research results.
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 an effect of improving high-temperature corrosion resistance and high-temperature oxidation resistance against high-temperature waste incineration exhaust gas in a coexisting state, and even if the content is either Cr or Mo, Cr: If the content is less than 23% and Mo: less than 7%, the desired effect cannot be obtained for the above-mentioned action, while the content is C
Even if r exceeds 27% and Mo exceeds 10%, no further improvement effect is exhibited by high-temperature corrosion resistance. Therefore, the content is set to Cr: 23 to 27%, desirably 24 to 26%, M
o: 7 to 10%, preferably 8.5 to 10%.

(B) Nb The Nb component has an effect of improving corrosion resistance to sulfates, chlorides, and the like, which are corrosive products in high-temperature exhaust gas. The desired effect of improving the high-temperature corrosion resistance cannot be obtained. On the other hand, if the content exceeds 5%, the bending workability decreases, so that the content is 0.5 to 5%, preferably 0.5 to 0.5%. ２2%.

(C) Fe The Fe component has an effect of improving hot workability, but if its content is less than 0.01%, desired hot workability cannot be ensured. If the amount exceeds 7%, the toughness will decrease.
1-7%, preferably 1-5%.

(D) When the content of the C component as the C impurity exceeds 0.05%, the amount of carbide present at the grain boundaries increases, and particularly the molten chloride contained in the high-temperature exhaust gas. Therefore, the content is determined to be 0.05% or less.

(E) Si Since the Si component has a deoxidizing effect, it may be used for deoxidizing the molten metal. Even in this case, if the content exceeds 0.1%, the toughness decreases. Therefore, the content was determined to be 0.1% or less.

(F) P and S These components as impurities are each P: 0.03%
And S: more than 0.03%, segregates at the grain boundaries, lowers hot workability, and also lowers high temperature corrosion resistance. Therefore, the content of P is set to 0.03%.
And S: 0.03% or less.

(G) W The W component has a function of further improving the high-temperature corrosion resistance. However, if its content is less than 0.1%, a desired improvement effect cannot be obtained in the above-mentioned effect. Exceeds 2%, the bending workability deteriorates, so the content was determined to be 0.1 to 2%.

(H) Rare earth elements, Y, Zr, Hf, and B These components all have the effect of improving the adhesion of the protective scale formed on the surface of the pipe material and contributing to the improvement of high-temperature corrosion resistance. However, the content is 0.0
If it is less than 01%, a desired effect cannot be obtained in the above-mentioned action.
If the content exceeds 1%, the hot workability is reduced, so that the content is 0.001 to 0.
1% and B were determined to be 0.001 to 0.1%.

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

[0014]

Next, the heat transfer tube of the present invention will be described in detail with reference to examples. Using a normal high-frequency melting furnace, Table 1
Prepare a Ni-base alloy melt having the component composition shown in
Cast into ingots and add 1000 to 12
Hot forging is performed at a predetermined temperature within the range of 50 ° C., and the diameter is 5
5mm round bar, then 50mm in diameter from this bar
× Wall thickness: Heat transfer tubes 1 to 5 of the present invention were manufactured by cutting to a size of 6 mm.

Then, the heat transfer tube obtained as a result is incorporated into a waste heat boiler, and the waste heat boiler is processed at a processing capacity of 150.
ton / day in a garbage incineration facility, where the surface temperature of the heat transfer tube is 450 ° C and the exhaust gas temperature is 100 ° C under the condition of 700 ° C.
After operating for 0 hours, take out the heat transfer tube after the operation is completed, measure the wall thickness in the circumferential direction with the ash attached to the surface and the generated scale removed, find the maximum wall thickness reduction, and cut the surface section The microstructure was observed and the maximum intergranular corrosion length was measured. Table 2 shows the results of these measurements.

[0016]

[Table 1]

[0017]

[Table 2]

[0018]

From the results shown in Tables 1 and 2, it is clear that the heat transfer tubes 1 to 5 of the present invention all show excellent high-temperature corrosion resistance in a high-temperature incineration exhaust gas atmosphere. As described above, since the heat transfer tube material of the present invention exhibits excellent high-temperature corrosion resistance against high-temperature waste incineration exhaust gas, it can sufficiently respond to an increase in the size of a waste incineration facility and an improvement in processing capacity. It is.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-62-188765 (JP, A) JP-A-64-15353 (JP, A) JP-A-57-203740 (JP, A) JP-A 60-88 131958 (JP, A) JP-A-63-213633 (JP, A) JP-A-5-59475 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 19/05

Claims (1)

(57) [Claims] 1. In weight% (mass%), Cr: 23 to 27%, Mo: 7 to 10%, Nb: 0.5 to 5%, Fe: 0.01 to 7%, C: 0.05 %, Si: 0.1% or less, P: 0.03% or less, S: 0.03% or less, W: 0.1 to 2%, and Rare earth element: 0 0.001 to 0.1%, Y: 0.001 to 0.1%, Zr: 0.001 to 0.1%, Hf: 0.001 to 0.1%, B: 0.001 to 0.01 % Or more of the following, and the remainder is composed of a Ni-based alloy having a composition consisting of Ni and other impurities. Heat transfer tube for boiler.