JP7722407B2 - Sulfuric acid storage tank - Google Patents

Description

The present invention relates to a sulfuric acid storage tank.

In various industrial facilities, steel tanks are widely used as tanks for storing concentrated sulfuric acid (98% by mass sulfuric acid) (hereinafter referred to as "sulfuric acid tanks" in this specification). These tanks exhibit corrosion resistance due to the formation of a protective precipitate film of iron sulfate on the steel surface (Patent Document 1).

It has long been known that in sulfuric acid storage tanks, concentrated sulfuric acid absorbs moisture from the air and becomes diluted with sulfuric acid, particularly near the liquid surface (waterline) in the tank, posing a risk of early corrosion of the tank walls. To reduce this risk, conventional sulfuric acid storage tanks have been designed with various measures to prevent localized dilution of sulfuric acid near the liquid surface.

Patent Document 1 discloses a sulfuric acid storage tank in which a portion of the sulfuric acid is repeatedly returned to the tank when it is extracted, and the water vapor in the air that flows into the tank is absorbed by the repeatedly returning sulfuric acid. Furthermore, Patent Document 2 discloses a sulfuric acid tank that prevents localized dilution of the sulfuric acid by injecting air into the tank from near the bottom of the tank below the liquid level (waterline).

However, in "sulfuric acid storage tanks," not only does sulfuric acid dilute near the liquid surface (waterline) within the tank as described above, but droplets of concentrated sulfuric acid splash irregularly in various directions on the liquid surface when the sulfuric acid is fed, and these droplets adhere to various locations within the tank, diluting the sulfuric acid and causing rapid localized corrosion in various locations within the tank. The risk of corrosion progressing in this way is difficult to sufficiently reduce using the conventional methods described above, and it is also impossible to identify areas with a high risk of corrosion progressing, making it difficult to implement effective countermeasures.

Japanese Utility Model Application Publication No. 57-18646 Japanese Patent Application Laid-Open No. 2003-64491

The purpose of this invention is to prevent the progression of corrosion inside a sulfuric acid storage tank that stores concentrated sulfuric acid, caused by sulfuric acid splashing on the liquid surface as it is pumped into the tank.

The inventors of the present invention came up with the idea that the above-mentioned problems could be solved by spraying the sulfuric acid in the sulfuric acid storage tank toward the side panel so that it does not fall directly onto the liquid surface, and by further installing a corrosion-resistant protective plate between the side panel and the nozzle to catch the sprayed sulfuric acid, and thus completed the present invention. Specifically, the present invention provides the following:

(1) A sulfuric acid storage tank comprising a tank body for storing sulfuric acid and a feed pipe for feeding sulfuric acid into the tank body, wherein the feed pipe has a nozzle for spraying sulfuric acid above the gas-liquid interface inside the tank body, the nozzle is oriented so that the sulfuric acid is sprayed toward the side plate of the tank body, and a corrosion-resistant protective plate is disposed inside the tank body between the side plate and the nozzle.

In the sulfuric acid storage tank (1), the sulfuric acid being pumped into the tank does not splash irregularly on the liquid surface, and the placement of a corrosion-resistant protective plate also avoids the risk of corroding the side plate in the direction from which the sulfuric acid is sprayed, thereby effectively preventing the progression of corrosion inside the tank caused by sulfuric acid splashing on the liquid surface.

(2) The sulfuric acid storage tank described in (1), wherein the corrosion-resistant protective plate is suspended from the top plate of the tank body via a fixing portion that detachably joins the top plate and the corrosion-resistant protective plate.

With the sulfuric acid storage tank of (2), the corrosion-resistant protective plate can be replaced in a short amount of time with simple work. Therefore, by focusing on the progression of corrosion of the corrosion-resistant protective plate and repeatedly replacing the corrosion-resistant protective plate as necessary, the above-mentioned effects of the sulfuric acid storage tank of (1) can be enjoyed over a long period of time at low cost.

(3) A sulfuric acid storage tank according to (1) or (2), wherein the corrosion-resistant protective plate is suspended at a distance of no more than 0.3 m from the side plate, and the distance between the nozzle and the corrosion-resistant protective plate is no more than 0.3 m.

The sulfuric acid storage tank of (3) more reliably prevents droplets of concentrated sulfuric acid being pumped into the tank from adhering to areas other than the corrosion-resistant protective plate, further improving the reliability of the effects achieved by the sulfuric acid storage tank of (1) or (2).

(4) A sulfuric acid storage tank according to (1) or (2), in which the inlet pipe is joined to the top plate of the tank body via an inlet pipe fixing part that detachably joins the inlet pipe to the top plate.

According to the sulfuric acid storage tank (4), in the sulfuric acid storage tank described in (1) or (2), if corrosion of the inlet pipe progresses due to concentrated sulfuric acid being fed into the tank remaining in the inlet pipe or traces of sulfuric acid splashing off the corrosion-resistant protective plate and adhering to the inlet pipe, the inlet pipe can be easily replaced in a short time. Therefore, by repeatedly replacing the inlet pipe as needed, the above-mentioned effects of the sulfuric acid storage tank described in (1) or (2) can be enjoyed over a longer period of time at low cost.

This invention makes it possible to prevent the progression of corrosion inside a sulfuric acid storage tank that stores concentrated sulfuric acid, which is caused by sulfuric acid splashing on the liquid surface as it is pumped into the tank.

FIG. 1 is a perspective view schematically illustrating the configuration of a sulfuric acid storage tank of the present invention. FIG. 1 is a side view (cross-sectional view) schematically showing the configuration of a sulfuric acid storage tank of the present invention.

Embodiments of the present invention are described below. However, the present invention is not limited to the embodiments described below.

<Sulfuric acid storage tank>
The "sulfuric acid storage tank" of the present invention is an industrial storage tank for storing concentrated sulfuric acid (98% by mass sulfuric acid) and is installed alongside various industrial facilities. FIG. 1 is a diagram schematically illustrating the overall configuration of a sulfuric acid storage tank 100, an example of an embodiment of the present invention. As shown in the figure, the sulfuric acid storage tank 100 is primarily characterized by including at least a tank body 1 for storing sulfuric acid, an inlet pipe 2 for feeding sulfuric acid into the tank body 1 from the direction of a top plate 12, and a corrosion-resistant protective plate 3 disposed inside the tank body 1 and toward which sulfuric acid is sprayed. While not shown in the drawings, the "sulfuric acid storage tank" of the present invention may further include various other components that can be disposed in an industrial sulfuric acid storage tank, such as a mechanism for removing sulfuric acid, a mechanism for introducing or removing liquids or gases other than sulfuric acid, or a mechanism for agitating the liquid in the tank, as long as it includes these characteristic components.

[Tank body]
The tank body 1 is, for example, a sealed tank made of steel that exhibits corrosion resistance by forming a protective precipitated film of iron sulfate on the steel surface. It may also be made of various other corrosion-resistant metals, or may be coated with PTFE or the like. Furthermore, the tank body 1 is provided with a top plate 12 that seals the upper part (top surface side), and the overall shape is not particularly limited as long as it has a structure that provides a predetermined level of airtightness. The tank having a roughly rectangular prism shape as shown in FIG. 1 is merely an example.

[Feed pipe]
The feed pipe 2 is a pipe for feeding concentrated sulfuric acid into the inside of the tank body 1, and is preferably made of a metal having the same corrosion resistance as the tank body 1.

As shown in Figures 1 and 2, the supply pipe 2 is joined to the top plate 12 and passes through the top plate 12 to be inserted into the tank body 1. There are no particular limitations on the installation (insertion) position of the supply pipe 2 on the top plate 12, but it is preferable that it be installed not in the center but in the vicinity of the side plate 11; specifically, it is preferable that the distance from the outlet 24 at the end of the supply pipe 2 to the inner surface of the side plate 11 be within 0.8 m.

The vertical positioning of the feed pipe 2 is such that the nozzle 24 at its end is positioned so that it can spray sulfuric acid above the gas-liquid interface inside the tank body 1. The feed pipe 2 is inserted through the top plate 12 (more specifically, through a hole drilled in the top plate 12) and extends vertically downward inside the tank body 1, where it is bent at a bent section 23 toward the side plate 11. Due to this bending, when sulfuric acid is supplied into the tank body 1, the direction in which sulfuric acid is sprayed from the nozzle 24 at the end of the feed pipe 2 is toward the side plate 11 of the tank body 1.

Regarding the direction of sulfuric acid ejection from the nozzle 24, the aforementioned "direction toward the side plate" does not necessarily have to be the shortest path connecting the nozzle 24 and the side plate, nor does it have to be horizontal or normal to the side plate. Furthermore, this direction does not have to be a straight path, nor does it have to be maintained in the same direction at all times. By appropriately varying the direction of sulfuric acid ejection from the nozzle 24 from vertically downward toward the side plate, it is sufficient that most, and preferably all, of the ejected sulfuric acid can reach the opposing corrosion-resistant protective plate 3 without falling directly onto the liquid surface. Specifically, although this depends on factors such as the distance between the nozzle 24 and the corrosion-resistant protective plate 3, the height of the nozzle 24 from the gas-liquid interface, and the sulfuric acid jetting pressure, as a guideline, if the distance between the nozzle 24 and the corrosion-resistant protective plate 3 is approximately 0.15 m, the direction of sulfuric acid jetting from the nozzle 24, i.e., the bending angle of the bent portion, is preferably 30° to 60°, where 0° is the vertical downward direction and 90° is the horizontal direction. Setting the sulfuric acid jetting direction to 30° or more in this sense provides the sulfuric acid with horizontal kinetic energy, sufficiently enabling most of the sulfuric acid to reach the surface of the corrosion-resistant protective plate 3 directly. Furthermore, setting this direction to 60° or less makes it difficult for the sulfuric acid that has reached the corrosion-resistant protective plate 3 to scatter in the normal direction from the surface of the corrosion-resistant protective plate 3, and it is more likely to flow downward quickly along the surface.

In the sulfuric acid storage tank 100 shown in Figures 1 and 2, the direction of sulfuric acid spray from the nozzle 24 is set to a pre-determined optimal angle by setting the bending angle of the bent section 23 of the inlet pipe 2. However, the sulfuric acid storage tank of the present invention can also be configured so that the direction of sulfuric acid spray from the nozzle 24 is "towards the side panel" by, for example, attaching an angle-variable nozzle to the nozzle 24 that can control the direction of sulfuric acid spray.

The inlet pipe 2 can also be welded to the tank body 1, but to facilitate easy replacement, it is preferable that it be indirectly fixed to the top plate 12 of the tank body 1 in a detachable manner via an inlet pipe fixing part 22 or the like. Specifically, as shown in FIG. 2, the inlet pipe 2 has a fixing flange 21, and is preferably joined to the inlet pipe fixing part 22, which also has a flange and is stably installed on the top surface of the top plate 12, by a detachable joining method such as bolting them together. By attaching a height adjuster that can control the insertion depth of the inlet pipe 2 into the tank body 1, the direction of sulfuric acid spray from the spray outlet 24 can be adjusted "toward the side plate."

[Corrosion-resistant protective plate]
The corrosion-resistant protective plate 3 is a plate-shaped member made of a corrosion-resistant material that is installed to receive the sulfuric acid sprayed from the nozzle 24 of the feed pipe 2 toward the side plate 11 and allow it to fall downward. A steel plate having the same corrosion resistance as the tank body 1 can be used, or a structure in which a wear-resistant material is attached to the surface of a support material can also be used.

As shown in Figures 1 and 2, the corrosion-resistant protective plate 3 is joined to the top plate 12 and is suspended inside the tank body 1, penetrating the top plate 12. The installation (insertion) position of the corrosion-resistant protective plate 3 on the top plate 12 is not particularly limited as long as it is located between the side plate 11 inside the tank body 1 and the outlet 24 of the feed pipe 2. However, it is preferable to install the corrosion-resistant protective plate 3 in the vicinity of the side plate 11, specifically within a distance of 0.3 m from the inner surface of the side plate 11. Furthermore, in terms of its relative position with the feed pipe 2, it is preferable that the distance between the corrosion-resistant protective plate 3 and the outlet 24 of the feed pipe 2 is within 0.3 m.

The widthwise length of the corrosion-resistant protective plate 3 should be long enough to prevent the sulfuric acid from reaching the side plate 11, taking into account the diffusion angle of the sulfuric acid sprayed from the nozzle 24 of the feed pipe 2. Furthermore, the heightwise length of the corrosion-resistant protective plate 3 is preferably long enough to position a portion of the lower end of the corrosion-resistant protective plate 3 below the gas-liquid interface, i.e., to be immersed in the sulfuric acid solution.

More preferably, the shape of the lower end of the corrosion-resistant protective plate 3 is bent toward the center of the tank at a position higher than the expected height of the gas-liquid interface, forming an inclined surface. In this case, the bending angle of the lower end of the corrosion-resistant protective plate 3 is preferably between 10° and 30°, with 0° being the vertically downward position. By arranging the corrosion-resistant protective plate 3 in this manner, the inflow velocity of the liquid (more specifically, the vertical component of this velocity) as the sulfuric acid flows along the surface of the corrosion-resistant protective plate 3 into the gas-liquid interface can be attenuated, more reliably preventing splashing at the gas-liquid interface.

The corrosion-resistant protective plate 3 can also be welded to the tank body 1, but to facilitate easy replacement, it is preferable that it be indirectly fixed to the top plate 12 of the tank body 1 in a detachable manner via a corrosion-resistant protective plate fixing portion 32 or the like. Specifically, as an example, as shown in Figure 2, the corrosion-resistant protective plate 3 has a fixing flange 31, and is preferably joined to a corrosion-resistant protective plate fixing portion 32, also having a flange, that is stably installed on the top surface of the top plate 12 using a detachable joining method, such as by bolting them together.

1 Tank body 100 Sulfuric acid storage tank 11 Side plate 12 Top plate 2 Inlet pipe 21 Fixed flange 22 Inlet pipe fixing part 23 Bent part 24 Spout 3 Corrosion-resistant protection plate 31 Fixed flange 32 Corrosion-resistant protection plate fixing part

Claims (4)

a tank body for storing sulfuric acid;
an inlet pipe for injecting sulfuric acid into the tank body;
Equipped with
A sulfuric acid storage tank,
the feed pipe has an ejection port for ejecting sulfuric acid above the gas-liquid interface inside the tank body,
The ejection port is oriented so that the ejection direction of the sulfuric acid is directed toward a side plate of the tank body, and an angle-variable nozzle having a movable range for directing the ejection direction of the sulfuric acid toward the side plate can be attached to the ejection port,
a corrosion-resistant protective plate is disposed inside the tank body between the side plate and the ejection port;
The corrosion-resistant protective plate has a lower end formed with an inclined surface for preventing sulfuric acid from scattering at the gas-liquid interface, the inclined surface being disposed below the jet outlet and above the gas-liquid interface, and bending toward the center of the inside of the tank body at a bending angle of 10° to 30° when the vertical downward direction is defined as 0°.
Sulfuric acid storage tank. The corrosion-resistant protective plate is suspended from the top plate of the tank body via a fixing portion that detachably joins the top plate and the corrosion-resistant protective plate.
The sulfuric acid storage tank according to claim 1. the corrosion-resistant protective plate is suspended at a position within 0.3 m from the side plate,
The distance between the nozzle and the corrosion-resistant protective plate is within 0.3 m.
The sulfuric acid storage tank according to claim 1 or 2. The inlet pipe is joined to the top plate of the tank body via an inlet pipe fixing part that detachably joins the top plate of the tank body and the inlet pipe.
The sulfuric acid storage tank according to claim 1 or 2.