JPH07139706A - High-temperature anticorrosion method of superheater for increasing temperature and pressure of boiler - Google Patents

Abstract

PURPOSE:To enhance against high-temperature corrosive gas and adhered ash without employing any expensive super-alloy material for all of superheating tubes. CONSTITUTION:In a superheater 1a for increasing the temperature and pressure of a boiler, high-temperature corrosion is prevented by a method wherein the banks of tubes of a primary superheater 1a, whose steam temperature is the lowest, is arranged at the inlet port side of combustion gas, then, the banks of tubes of tertiary superheater 1c and the banks of tubes of secondary superheater 1b are arranged sequentially on the downstream of the primary superheater 1a. A material, having the amount of corrosion lower than a set value, is selected for the banks of tubes of the primary superheater 11a based on a steam temperature therefor. Materials, having the amount of corrosion lower than a set value, are selected for the banks of tubes of secondary and tertiary superheaters 1b, 1c based on the heat flow fluxes therefor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing high temperature corrosion of a superheater when high temperature and high pressure is applied to a waste incineration boiler for the purpose of improving efficiency of power generation equipment by waste incineration.

[0002]

2. Description of the Related Art Power generation by a steam turbine is the most effective method for effectively utilizing waste incineration heat, and therefore high temperature and high pressure of the waste incineration boiler is being advanced. However, conventionally, in the refuse incineration boiler, in order to prevent high temperature corrosion due to hydrogen chloride gas in the combustion exhaust gas and low melting point ash, the superheated steam temperature is 300 ° C at the maximum, more specifically, the pipe wall temperature is Up to 320 ° C and steam pressure of 30
The power generation efficiency was 12 to 16%.

By the way, when the superheated steam temperature is set to 380 to 420 ° C. and the steam pressure is set to high temperature and pressure up to 40 ata as the above-mentioned steam conditions, the power generation efficiency is 20 to 25%.
This is about 1.5 times the current power generation efficiency. But,
Thus, a waste incineration boiler that exceeds the standard steam conditions described above, such as a steam temperature of 350 ° C. and a steam pressure of 24 ata
In the refuse incineration boiler, it is necessary to replace the superheater tube every year due to high temperature corrosion.

[0004]

In order to solve such problems, attempts have been made to develop a superalloy material capable of withstanding high temperature corrosive gas and adhered ash. It is practically impossible to make such a superalloy material because it is extremely expensive.

The present invention has been made in view of the above-mentioned conventional problems, and is capable of withstanding high temperature corrosive gas and adhered ash without using an expensive superalloy material for all superheater tubes. It is an object of the present invention to provide a method for preventing high-temperature corrosion of a boiler high-temperature and high-pressure superheater that can be performed.

[0006]

In order to achieve the above object, the present inventor conducted various experiments. First, size 2
After applying 50 mg of combustion ash from a refuse incinerator to a test piece of various materials of 0 mm × 15 mm × 3 mm per 1 cm ² of surface area, 8% CO ₂ + 8% O ₂ + 18% H ₂ O + 0.13%
Inserted in an annular electric furnace in a simulated gas stream of HCl + 65.87% N ₂ , 400 ° C, 450 ° C, 500 ° C, 550
The temperature was kept at 72 ° C and 600 ° C for 72 hours. The results are shown in Table 1 below. The temperatures and materials exhibiting an erosion degree of 0.5 mm or less per year are SUS347H, SUS309J ₂ , SUS310 with 450 ° C as the upper limit.
J ₁ , Incoloy 825 and Incoloy 800.

[0007]

[Table 1] (Unit: mm / year)

Next, four kinds of materials obtained by the above-described experiment are selected, superheater tubes are manufactured from these materials, and these superheater tube groups have steam temperatures of 370 to 42.
The test was carried out for 1 year by incorporating the device at 0 ° C. (tube wall temperature 410 to 450 ° C.) in the position shown in FIG. as a result,
It was found that the corrosion rate of each part on the tube surface is governed not only by the tube wall temperature but also by the heat flux, which is well consistent with the relationship with the heat flux.

FIG. 2 shows the effect of heat flux on the high temperature corrosion of the various materials used in the test. The results show that
When the practically applicable corrosion rate is 0.5 mm or less per year, the heat flux of Incoloy 825 is 1240 (kca).
1 / hm or less, 1180 (k in SUS310J ₁ )
cal / hm) or less, 1080 for SUS347H
(Kcal / hm) or less, 10 for SUS309J ₂
It can be seen that it may be set to 00 (kcal / hm) or less.

The method for preventing high temperature corrosion of the boiler high temperature and high pressure superheater of the present invention is based on the above-mentioned findings, and the primary superheater tube group having the lowest steam temperature is arranged on the combustion gas inlet side. After that, the secondary superheater tube group is sequentially arranged with the secondary superheater tube group, and the primary superheater tube group is based on the steam temperature, and the second and third superheater tube groups are based on the heat flux. The point is to select a material whose corrosion amount is less than the set value.

[0011]

According to the method for preventing high temperature corrosion of the boiler high temperature and high pressure superheater of the present invention, the primary superheater tube group having the lowest steam temperature is arranged on the combustion gas inlet side, and then the tertiary superheater tube group and the In addition to arranging with the secondary superheater tube group, the primary superheater tube group selects the material whose corrosion amount is less than the set value based on the steam temperature and the second and third superheater tube groups based on the heat flux. Therefore, high temperature corrosion of the boiler high temperature and high pressure superheater can be effectively suppressed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method for preventing high temperature corrosion of a boiler high temperature and high pressure superheater according to the present invention will be described below with reference to an embodiment shown in FIG. In Figure 3, the steam condition is 34.5t / h x 37ata x 3
It is explanatory drawing of the arrangement position of the 1st-3rd superheater tube group in a 80 degreeC boiler, (a) is a general view, (b) is a principal part enlarged view.

In FIG. 3, reference numeral 1 denotes a superheater which further superheats saturated steam generated in the boiler body 3 by combustion in the combustion chamber 2 to produce superheated steam, such as a primary superheater 1a and a secondary superheater. It is composed of a heater 1b and a tertiary superheater 1c. And these 1st-3rd superheaters 1a-1c are arrange | positioned from the inlet side (gas temperature: 650 degreeC) of combustion gas in order of the 1st superheater 1a, the 3rd superheater 1c, and the 2nd superheater 1b.

The steam condition in this boiler is, for example, 3
In the case of 4.5 t / h × 37ata × 380 ° C., the primary superheater 1a has a steam temperature of 255 ° C. on the inlet side and a steam temperature of 300 ° C. on the outlet side. It is made of existing carbon steel pipe for boiler (STB410).

The highest steam temperature (330 ° C. on the inlet side, 38 ° C. on the outlet side) is installed downstream of the primary superheater 1a.
The maximum heat flux of the third superheater 1c at 0 ° C is 1150k.
Since it also becomes cal / hm, from the relationship shown in FIG.
It is made with S310J ₁ .

The secondary superheater 1b, which is installed downstream of the tertiary superheater 1c and has a steam temperature of 300 ° C. on the inlet side and 340 ° C. on the outlet side, has a maximum heat flux of 800 kcal /
hm, so from the relationship shown in FIG. 2, SUS309J ₂
It is produced in.

That is, in the method for preventing high-temperature corrosion of the boiler high-temperature and high-pressure superheater according to the present invention, the primary superheater 1a having the lowest steam temperature is arranged on the combustion gas inlet side, and then the tertiary superheaters 1c, 2 are sequentially arranged. It is arranged with the secondary superheater 1b, of which the primary superheater 1a is based on the steam temperature, and the secondary superheater 1c.
For 1b, a material having an amount of corrosion, which has been measured in advance by experiments for each material based on the heat flux, is equal to or less than a set value is appropriately selected.

[0018]

As described above, according to the method for preventing high temperature corrosion of the boiler high temperature and high pressure superheater of the present invention, the primary superheater tube group having the lowest steam temperature is arranged on the combustion gas inlet side, and thereafter, sequentially. The secondary superheater tube group is arranged with a secondary superheater tube group, and the primary superheater tube group is based on the steam temperature, and
For the tertiary superheater tube group, materials whose corrosion amount is less than or equal to the set value are appropriately selected based on the heat flux, so that high temperature corrosion of the boiler high temperature / high pressure superheater can be effectively suppressed at a relatively low cost.

[Brief description of drawings]

Fig. 1 Superheater tubes were made from four kinds of materials obtained by high temperature corrosion experiments, and steam tubes with a steam temperature of 370 to 370 were produced.
It is explanatory drawing of the installation position of the superheater pipe | tube when it installs in the actual machine of 420 degreeC (tube wall temperature 410-450 degreeC), and implements a test for 1 year.

FIG. 2 is an experimental result diagram showing the effect of heat flux on high temperature corrosion.

[FIG. 3] Steam conditions are 34.5 t / h × 37 ata × 38
It is explanatory drawing of the arrangement position of the 1st-3rd superheater tube group in a 0 degreeC boiler, (a) is a general view, (b) is a principal part enlarged view.

[Explanation of symbols]

 1a 1st superheater 1b 2nd superheater 1c 3rd superheater 2 Combustion chamber

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazuhiro Toyama 5-3-2, Nishikujo 5-chome, Konohana-ku, Osaka City, Osaka Prefecture Hitachi Shipbuilding Co., Ltd.

Claims (1)

[Claims] 1. A method for preventing high-temperature corrosion in a boiler high-temperature and high-pressure superheater, wherein a primary superheater tube group having the lowest steam temperature is arranged on a combustion gas inlet side, and then a tertiary superheater tube is successively arranged. A secondary superheater tube group, the primary superheater tube group is based on the steam temperature, and the second and third superheater tube groups are based on the heat flux, and the amount of corrosion is less than a set value. Method for preventing high-temperature corrosion of boiler high-temperature and high-pressure superheater, characterized by selecting