JP2535534Y2 - Corrosion protection structure in chloride treatment container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to an anticorrosion coating structure in a chloride treatment vessel such as a multitubular heat exchanger used in a titanium tetrachloride concentration and purification process.

[Conventional technology]

In an industrial titanium tetrachloride production process, chlorine gas is blown in from a furnace bottom while simultaneously heating synthetic rutile and natural rutile mainly composed of TiO ₂ and coke in a fluidized-chlorination furnace, thereby obtaining crude TiCl _4. To manufacture. This crude TiCl ₄ contains, in addition to TiCl ₄ , FeCl ₃ , AlCl ₃ , VOCl ₃ (panadium oxychloride), a TiO ₂ raw material as a carryover, coke, and the like. Therefore, TiCl ₄ is vaporized and separated using a distillation method in order to purify the crude TiCl ₄ . The heating means at that time multitubular heat exchanger is used to flow the crude TiCl ₄ in the inner tube, the crude TiCl ₄ is heated by passing steam to the tube outside as a heating source, other and TiCl ₄ Separate from high boilers.

[Problems to be solved by the invention]

However, the boiling point of VOCl ₃ contained in crude TiCl ₄
Since there is almost no difference from the boiling point of TiCl ₄ , it is difficult to separate by vaporization. Then, to remove VOCl ₃ , the crude oil was
The mineral oil is dripping on the iCl ₄ , causing the heat exchanger to corrode.

In addition, when cleaning the heat exchanger, lime water is usually used as a cleaning liquid, but strong hydrochloric acid is generated by reaction with chloride, which is also a cause of premature corrosion of the heat exchanger. .

If the corrosion is left undisturbed, steam penetrates into the tube from the corroded portion and generates hydrochloric acid to accelerate the corrosion rapidly. Corrosion is particularly remarkable in the vicinity of the welded portion between the tube 3 and the tube sheet 2 as shown in FIG. 3, and when the inside and outside of the tube sheet 2 are microscopically communicated due to corrosion, the periphery is accelerated. Corrosion and forced repairs. Also,
The increase in deposits due to corrosion causes clogging in the tubes of the heat exchanger, which also reduces the capacity of the circulation pump.

In some cases, TiO ₂
However, since the sprayed layer of TiO ₂ alone is inferior in the corrosion resistance to acid, the sprayed layer peels off when used for a long time. In addition, when cleaning the heat exchanger, there is a high risk that cracks and spalling may occur due to the impact of the tube cleaner. As a result, corrosion may rapidly progress at the time of re-use after cleaning. To prevent this, thermal spraying must be performed each time cleaning is performed, which is not a practical measure.

The present invention has been made in view of such circumstances,
In chloride treatment vessels such as heat exchangers for Cl ₄ concentration and purification,
It is an object of the present invention to provide an anticorrosion structure capable of greatly suppressing the progress of corrosion without taking time.

[Means for solving the problem]

The anti-corrosion structure of the present invention consists of a multi-layer coating layer in which a corrosion-resistant Ni alloy sprayed layer, a sealing agent coating layer, and a ceramic adhesive coating layer are combined. The coating agent layer is an intermediate layer, and the ceramic adhesive coating layer is an outer layer. Here, the corrosion-resistant Ni alloy is Ni known as Hastelloy (registered trademark of INCO).
This high alloy is referred to as Hastelloy in the following description.

[Action]

Hastelloy itself, which forms the inner layer, exhibits excellent resistance to chloride-induced corrosion. However, the thermal sprayed layer becomes porous due to the gas involved during thermal spraying, and cannot prevent chlorides and the resulting acids from penetrating through the pores. The sealing agent coating layer, which is an intermediate layer, seals the pores and imparts an excellent corrosion protection function to the inner Hastelloy sprayed layer. The ceramic adhesive layer, which is the outer layer, protects the intermediate layer, prevents liquid penetration in the intermediate layer, and maximizes the anti-corrosion effect of Hastelloy.

〔Example〕

 Hereinafter, embodiments of the present invention will be described.

FIG. 2 shows a chloride treatment container provided with the anticorrosion structure of the present invention. The processing vessel is a well-known multi-tube heat exchanger and includes a cylindrical shell 1. The shell 1 has an inlet pipe 11 and an outlet pipe 12 for the heating medium, and both ends are closed by tube sheets 2, 2 '. A large number of tubes 3 are mounted in parallel between the tube sheets 2, 2 ', and both are connected by welding. Both ends of shell 1 are also hemispherical cups 4,
The cup 4 'is closed at 4'. One of the cups 4 'is divided into two upper and lower chambers by a partition plate 41, and a lower chamber is provided with an inflow pipe 42 for the medium to be heated and an upper chamber is provided with a discharge pipe 43.

When distilling crude TiCl ₄ in the heat exchanger, shell 1
Steam is injected from the inflow pipe 11 into the inside, and crude TiCl ₄ is injected from the inflow pipe 42 into the tube 3. Coarse T in tube 3
iCl ₄ is heated by steam to evaporate TiCl ₄ .
The evaporated TiCl ₄ is taken out through the discharge pipe 43, and the steam after the heat exchange is discharged out of the shell 1 through the discharge pipe 12. In this case, particularly significant corrosion occurs in the vicinity of the weld between the tube 3 and the tube sheets 2, 2 '.

As shown in Fig. 1, the anticorrosion structure of the present invention is composed of this tube 3 and tube sheets 2, 2 '(only 2 is shown in the figure, the same applies hereinafter)
Is provided around the welded portion. The tube 3 is joined at its tube end to the tube sheets 2, 2 'by a weld 31.

In the anti-corrosion structure of the present invention, 80Ni-20Cr is applied to the range from the inner surface of the tube end of the tube 3 to the outer surface of the tube sheet 2, 2 'through the tube end surface.
After spraying the alloy, a Hastelloy sprayed layer 5 is formed thereon. The spraying of the 80Ni-20Cr alloy was performed to improve the adhesion of the Hastelloy sprayed layer 5 to the coating. As for Hastelloy, Hastelloy B, which has excellent resistance to chlorides, is preferred.
It is performed by a conventional method, and the thickness is suitably about 0.2 mm to 0.4 mm.

On the Hastelloy sprayed layer 5, a sealing agent coating layer 6 is formed so as to completely cover the Hastelloy sprayed layer 5. The sealing agent is mainly composed of an SiO ₂ -based material, and is applied once or plural times after the application of the primer, and is dried by heating to form a coating layer having a required strength. Generally, a commercially available sealing agent is used, so that the thickness of the coating layer 6 may be appropriately selected based on a usage manual. The pores generated in the Hastelloy sprayed layer 5 are closed by the sealing agent coating layer 6.

A ceramic adhesive layer 7 is further formed on the sealing agent coating layer 6. The ceramic adhesive coating layer 7 is also provided so as to completely cover the sealing agent coating layer 6. The ceramic adhesive is mainly composed of ceramics such as alumina, silica, and zirconia. The coating layer 7 has excellent durability by itself, and effectively protects the sealing agent coating layer 6. Generally, a commercially available ceramic adhesive is used, and thus the thickness of the coating layer 7 may be appropriately selected based on a manual for use.

When such a heat exchanger having corrosion structure was used to concentrate and purify the crude TiCl ₄ showed excellent resistance ceramics adhesive coating layer 7 with respect to the flow resistance of the crude TiCl _4, a sealing treatment agent In addition to preventing peeling of the coating layer 6 and the like, TiCl ₄ is prevented from penetrating into the sealing agent coating layer 6. As a result, the ceramic sprayed layer 5 via the sealing agent coating layer 6
Chloride and the resulting acid permeation into the cell are eliminated.
Thereby, the coating portion of the Hastelloy sprayed layer 5 is
Is effectively protected from corrosion caused by TiCl ₄ . Needless to say, this anticorrosion effect is maintained even when the heat exchanger is washed. If the ceramic adhesive coating layer 7 or the sealing agent coating layer 6 is damaged by mechanical shock caused by a tube cleaner during cleaning of the heat exchanger, these are formed again as appropriate. In this case, since the lower Hastelloy sprayed layer 5 is not damaged, the heat exchanger can be reused only by reforming the ceramic adhesive coating layer 7 and the sealing agent coating layer 6.

With the adoption of the anticorrosion structure of the present invention, the tube replacement work that has been performed about once in the past three years can be reduced to about once in six years, as estimated from the wear situation after applying the present invention. Is expected. Here, Hastelloy B (manufactured by INCO) is used as Hastelloy. Santomo DH-X (silica type, manufactured by Santomo) is used for the sealing agent, and Aron Ceramic D (manufactured by Toa Gosei Chemical) is used for the ceramic adhesive, and the thickness is determined based on the respective manuals. Have been.

In the above embodiment, the heat exchanger for concentration and purification of TiCl ₄ is described, but the anticorrosion structure of the present invention is not limited to this, and the same anticorrosion effect can be obtained by applying it to other chloride treatment containers. It goes without saying that it can be done.

[Effect of the invention]

By applying the anticorrosion structure of the present invention to a portion of the chloride treatment container where corrosion is remarkable, the progress of corrosion can be largely suppressed by the high anticorrosion ability inherent to Hastelloy. In addition, it is strong against the shock at the time of cleaning the container, and even if it is damaged by the shock, the outer layer and the intermediate layer are restored to a predetermined performance only by repairing the outer layer and the intermediate layer. Therefore, the working life of the chloride treatment container is significantly extended without adding labor and cost, and the economic effect is great.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an example of the anticorrosion structure of the present invention, FIG. 2 is a cross-sectional view of a multi-tube heat exchanger illustrating an application of the present invention, and FIG. 3 is corrosion in the multi-tube heat exchanger. It is sectional drawing which shows a situation. In the figure, 2,2 ': tube sheet, 3: tube, 5: corrosion-resistant Ni alloy (Hastelloy) spray layer (inner layer), 6: sealing agent coating layer (intermediate layer), 7: ceramic adhesive coating layer (Outer layer).

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Keisuke Suzuki 1-9-1, Jokoji, Amagasaki City, Hyogo Prefecture Inside Osaka Fuji Industrial Co., Ltd. (56) References JP-A-64-25960 (JP, A) JP-A 60-59059 (JP, A) JP-A 64-4464 (JP, A) JP-A-59-145776 (JP, A) Yoshio Ogouchi, Dictionary of Metallic Materials, 9th Edition (53.2.20, 1953) Engineering Book Publishing Co., Ltd. 142−143

Claims (1)

(57) [Scope of request for utility model registration] The present invention comprises a coating layer having a multilayer structure in which a corrosion resistant Ni alloy sprayed layer, a sealing agent coating layer, and a ceramic adhesive coating layer are combined, wherein the corrosion resistant Ni alloy sprayed layer is an inner layer, a sealing agent coating layer. Anti-corrosion structure in chloride treatment container where the layer is the middle layer and the ceramic adhesive coating layer is the outer layer.