JP2002060208A - Sulfuric acid purifying device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sulfuric acid purifying device which is used for purifying industrial or recovered sulfuric acid and in which the service life of a distillation column is extremely prolonged by hardly causing a devitrifying phenomenon in the barrel part itself of the distillation column owing to the precipitation of impurities. SOLUTION: This sulfuric acid purifying device is provided with a concentrating or preheating column (1), the distillation column (2) and an optically controlling liquid level sensor (8) for externally detecting the boiling liquid level (L) of the sulfuric acid in the column (2) through the barrel part (2a) of the column (2). A quartz-made sleeve (2X) having the diameter smaller by one size than the inside diameter of the barrel part (2a) is inserted/disposed inside the zone where the liquid level (L) exists in the part (2a) of the column (2). A light transmitting hole (w) is preferably arranged for transmitting the light of the sensor (8).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sulfuric acid purifier for purifying industrial sulfuric acid or recovered sulfuric acid, and more particularly to an improvement in a structure of a sulfuric acid purifier in a portion of a distillation column around a boiling liquid level. .

[0002]

BACKGROUND ART <Sulfuric acid refining apparatus> A sulfuric acid refining apparatus for purifying industrial sulfuric acid or recovered sulfuric acid typically includes a sulfuric acid tank (surge tank), a concentration or preheating column, and a distillation column (reboiler column). Consists of The sulfuric acid supplied from the sulfuric acid tank to the concentration or preheating column is heated and concentrated or preheated in the concentration or preheating column, and then sent to the distillation column by overflow or the like to be distilled.

In a distillation column, control is performed by detecting a boiling liquid level with a liquid level sensor provided outside the column. Boiling is a phenomenon in which sulfuric acid blows up to a wave height in a column and moves up. The boiling liquid level has reached a position much higher than the liquid level at rest before distillation. As one of the liquid level sensors at this time, there is a type that uses an optical liquid level sensor (optical fiber type liquid level sensor) and arranges a light-emitting portion and a light-receiving portion of the sensor so as to face each other with a column interposed therebetween. Since the distillation column is made of quartz, such a light irradiation type sensor can be used as a liquid level sensor.

[0004] US Pat. No. 5,354,428 (JP-A-63-153825) discloses a continuous reprocessing method of ultrapure liquid used for cleaning semiconductor wafers. ing. A typical example of the target chemical substance is sulfuric acid. In FIG. 1, acid flows into a stripper (concentration column) 1 from a surge tank (sulfuric acid tank) 12 via a pump, and then a distillation column 2
Are shown. FIG. 2 shows the details of the stripper 1 and FIG. 3 shows the details of the distillation column 2. However, this publication does not describe a liquid level sensor used for controlling the liquid level of the distillation column 2.

[0005] Japanese Patent Application Laid-Open No. 10-29807 discloses a sulfuric acid refining apparatus for removing water and / or impurities from sulfuric acid by performing evaporation, distillation or rectification operations using two or more glass containers. There is shown a sulfuric acid refining apparatus in which a gas introduction pipe is connected to a communication pipe connecting between two or more glass containers. FIG. 4 of this publication shows an overall configuration diagram of a conventional sulfuric acid refining apparatus, in which a glass concentration vessel (concentration column) 1 → a glass distillation vessel (distillation column) 2 → glass The flow of sulfuric acid is shown through a sulfuric acid condenser (purified sulfuric acid condenser) 5 manufactured by the Company. The waste sulfuric acid introduction pipe 7 is shown, but the one corresponding to the sulfuric acid tank (surge tank) is not shown. The concentration vessel 1 is heated by a heater, the distillation vessel 2 is heated by a heater to perform distillation, and the sulfuric acid condenser 5 is condensed by cooling, whereby purified sulfuric acid is obtained. However, this publication does not describe a liquid level sensor of a distillation column (reboiler column).

[0006] Japanese Patent Application Laid-Open No. 10-330104 discloses a waste sulfuric acid continuous purification apparatus, a purification method, and a heater supporting structure in a glass heating apparatus. In the process, sulfuric acid is used for wafer cleaning and photoresist stripping, and the waste sulfuric acid used in such treatment is either neutralized and then discarded or sent to an industrial waste disposal company. It has been handed over or regenerated after concentration and distillation. "
There is a description. The statement at the last point of “regeneration by concentration and distillation” is common to the purpose of the operation by the sulfuric acid refining device of the present invention. FIG. 1 of this publication shows the flow of sulfuric acid from the raw material tank 16 to the product tank 17 through the heating can 1 for concentration, the heating can 7 for distillation, and the condenser 9 for distillation. However, the heating can 1 for concentration and the heating can 7 for distillation are of a horizontal type. This publication also refers to liquid level detectors 22, 27, 32, 37, and 39. In particular, paragraphs 0013 and 0016 refer to optical liquid level detectors using infrared rays. This is a liquid level sensor of the condensed liquid receiving tank 5 and has a different purpose from the light control type liquid level sensor (8) of the distillation column (2) of the present invention, which will be described in detail later.

[0007]

In a system in which an optical liquid level sensor (optical fiber type sensor) is used as a liquid level sensor in a distillation column (reboiler column), and a light emitting section and a light receiving section are arranged to face each other with the column interposed therebetween, There are the following problems. That is, during operation, impurities in sulfuric acid (mainly iron sulfate + SiO ₂ in the case of industrial sulfuric acid, mainly SiO _{2 in} the case of recovered sulfuric acid) precipitate and adhere to the inner surface of the column body near the boiling liquid level. As a result, a devitrification phenomenon is observed in the vicinity of the boiling liquid level on the inner surface of the transparent quartz glass constituting the column, and the light from the liquid level control sensor is hardly transmitted. Then, in such a case, the liquid level control in the relevant portion becomes impossible, so that the device is automatically stopped or
Prior to the automatic stop, a manual stop is performed.

[0008] Such a devitrification phenomenon in the vicinity of the boiling liquid level in the distillation column occurs approximately 3 to 6 months after the start of the operation, and therefore, conventionally, when the degree of devitrification exceeds an allowable limit, the distillation is performed. The operation of the column was stopped and the column was replaced.

<Object of the present invention> Under such a background, the present invention relates to a sulfuric acid refining apparatus for purifying industrial sulfuric acid or recovered sulfuric acid. It is an object of the present invention to provide a sulfuric acid refining apparatus capable of significantly improving the life of a distillation column by devising a device that hardly causes a permeability phenomenon.

[0010]

The sulfuric acid purifying apparatus of the present invention comprises a concentration or preheating column (1) and a distillation column (2), and the boiling liquid level (L) of sulfuric acid in the distillation column (2) is controlled. In a sulfuric acid refining apparatus of the type which is externally detected by a light-controllable liquid level sensor (8) through the body (2a) of the distillation column (2), the boiling liquid level of the body (2a) of the distillation column (2) is A quartz sleeve (2X) having a diameter slightly smaller than the inner diameter of the body (2a) is fitted inside the region where (L) is located.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

<Unit Apparatus> The sulfuric acid refining apparatus of the present invention is provided with a concentration or preheating column (1) and a distillation column (2) as shown in a schematic flow chart in FIG. These main units are made of quartz glass because they handle highly corrosive sulfuric acid. For pipes and the like, where there is no heating, polytetrafluoroethylene may be used in addition to quartz glass.

In FIG. 1, (6) is a sulfuric acid tank, and the sulfuric acid tank (6) is a tank for temporarily storing industrial sulfuric acid and recovered sulfuric acid. To transfer the liquid from the sulfuric acid tank (6) to the concentration or preheating column (1) described below, a pump is installed between the sulfuric acid tank (6) and the concentration or preheating column (1), or the gas is supplied to the sulfuric acid tank (6). This is done by applying pressure. In the case of a pump, the delivery amount is adjusted stepwise or steplessly. In the case of gas pressure, the flow rate is adjusted by opening and closing a valve provided in the pipe.
The adjustment of the flow rate in these cases is controlled in conjunction with the signal of the light control type liquid level sensor (8) described later.

The concentration or preheating column (1) is a heating vessel for concentration or preheating, and the sulfuric acid supplied from the sulfuric acid tank (6) is concentrated or preheated in the concentration or preheating column (1).

The distillation column (2) is a device for distilling sulfuric acid introduced from the concentration or preheating column (1) by overflow or the like. The distillation is often performed at normal pressure, but can be performed under increased or reduced pressure. During the operation, the boiling liquid level (L) will be located at the middle position of the distillation column (2).

In FIG. 1, (3) is a drain condenser, (4) is a sulfuric acid condenser, (5) waste sulfuric acid cooler, (6) is the sulfuric acid tank described above, and (7) is a purified sulfuric acid tank. is there. (9) is a heating furnace for concentration or preheating column, and (10) is a heating furnace for distillation column. The sulfuric acid tank (6) contains sulfuric acid such as industrial sulfuric acid and recovered sulfuric acid, and the purified sulfuric acid tank (7) contains purified sulfuric acid. When column (1) is a concentration column, a drain condenser
(3) is provided, but when the column (1) is a preheating column, it is not sufficient to provide the drain condenser (3).

<Light control type liquid level sensor (8)> Distillation column
In (2), sulfuric acid is in a boiling state, but light is emitted outside the body (2a) to detect the boiling liquid level (L) of the sulfuric acid through the body (2a) of the distillation column (2). Control type liquid level sensor (8)
Place. This sensor uses optical fiber,
It emits / receives light (it is preferable to use infrared rays having high transmittance even for contaminated glass).

More specifically, this light control type liquid level sensor (8) has a configuration in which a light emitting section and a light receiving section are arranged opposite to each other with the body section (2a) interposed therebetween, and is emitted from the light emitting section. Infrared light and the like pass through the quartz body (2a) on the near side, pass near the boiling liquid level (L) of sulfuric acid, pass through the opposite body (2a), and reach the light receiving unit. . At this time, there is a difference in the degree of attenuation due to absorption by sulfuric acid between the light passing through the sulfuric acid that has blown up to the wave height and the light that does not pass through the sulfuric acid because the blow-up stops for a moment. Is above or below the boiling liquid level (L). That is,
The number of times the light crosses the droplet can tell where the boiling liquid level (L) is, and the amount of sulfuric acid introduced into the distillation column (2) can be controlled accordingly.

However, when impurities in sulfuric acid precipitate on the inner surface of the body (2a) of the distillation column (2) and cause devitrification, the accuracy of detection of the boiling liquid level (L) by the liquid level sensor (8) is reduced. Becomes unstable, and further devitrification makes it impossible to detect the boiling liquid level (L) itself. The impurities causing devitrification are as follows:
In the case of industrial sulfuric acid, it is mainly iron sulfate + SiO ₂ , and in the case of recovered sulfuric acid, it is mainly SiO ₂ .

<Sleeve (2X)> Then, the distillation column (2)
In the present invention, in order to reduce the possibility of devitrification of the body (2a) of the distillation column (2a), the body (2a) of the distillation column (2) is provided with the body (2a) inside the region where the boiling liquid level (L) is located. A quartz sleeve (2X) having a diameter slightly smaller than the inner diameter of 2a) is fitted inside. This is the most important point of the present invention.

The sectional shape of the sleeve (2X) in the radial direction may be circular, or may be a shape such as a C-shape or a parenthesis in which a part of the circle is cut off. These cross-sectional shapes may be mixed above and below the sleeve (2X).

Since the outer diameter of the sleeve (2X) is designed to be slightly smaller than the inner diameter of the body (2a) of the distillation column (2), the outer wall of the sleeve (2X) -the body (2a) A slight gap (S) is formed between the inner peripheral walls. The gap (S) (clearance) is often set to, for example, 3 to 20 mm, preferably 5 to 15 mm from the viewpoint of devitrification suppression.

In order to fix the sleeve (2X) to the body (2a), for example, the lower side of the sleeve (2X) is partially or entirely welded to the body (2a) and the sleeve (2X) is welded. For example, measures are taken to support the upper side with a bar-like support.

The height of the sleeve (2X) is, for example, 150 to 300 in consideration of the fact that the boiling liquid level (L) jumps to the wave height.
mm, especially about 180 to 270 mm.
When the height of the sleeve (2X) is too low, the swing of the liquid level may be larger. On the other hand, there is no point in making the height of the sleeve (2X) unnecessarily high.

Sulfuric acid is introduced into the distillation column (2) from an inlet pipe (2b) provided through the body (2a).
Since the installation position of (2b) is usually the position of the installation position of the sleeve (2X), the sulfuric acid introduced from the introduction pipe (2b) is supplied to the sleeve (2X) and the body of the distillation column (2) ( Gap between 2a) (S)
Through the column.

<Light Passing Hole (w)> It is preferable to provide a light passing hole (w) through which light from the light control type liquid level sensor (8) passes through the peripheral wall of the sleeve (2X). With the light passage hole (w), even if the sleeve (2X) itself is devitrified, the light control type liquid level sensor will continue for a long period of time.
This is because control by (8) becomes possible.

The light passage hole (w) is a light control type liquid level sensor.
Since it is used as a hole for the light of (8) to pass through, one part on the lower half side of the sleeve (2X) and one on the opposite side
Usually, it is provided at a location. The width of the light passage hole (w) is 5
About 20 mm, especially about 7 to 15 mm is sufficient. The light passage hole (w) is preferably a vertically long hole so that the detection position by the light control type liquid level sensor (8) can be adjusted, and the length in the vertical direction at this time is, for example, 50 to 150 mm, particularly 80 mm.
Often 120 mm.

<Heater (2Y)> It is particularly preferable to install a heater (2Y) outside the body (2a) of the distillation column (2) at the position where the sleeve (2X) is installed. The heater (2Y) may be of any type, but a jacket type heater is preferred. Heater (2Y) is boiling liquid level (L)
It is particularly preferable that the body (2a) of the entire area of the sleeve (2X) installation area is heated so as to be heated in the vicinity and above the area.

When the heater (2Y) is installed, for example, a jacket-type heater (2Y) is provided so as not to hinder the emission / reception of infrared rays or the like by the light control type liquid level sensor (8).
Provide a window at a predetermined position in (Y), or make a contrivance so that a window-like area is opened when the heater (2Y) is installed.

Heater (2Y) and body (2a) of distillation column (2)
It is desirable to install a thermocouple between the two and heat the distillation column (2) to the target temperature while measuring the surface temperature of the distillation column (2), and to maintain the temperature substantially at that temperature.

<Target Sulfuric Acid, Installation Location> Examples of the sulfuric acid applied to the sulfuric acid refining apparatus of the present invention include industrial sulfuric acid (purification degree is not so high) and sulfuric acid recovered from a semiconductor manufacturing process.
The sulfuric acid refining device of the present invention is useful as an on-site device attached to a factory using sulfuric acid.

<Effect> The boiling of sulfuric acid in the distillation column (2) is that the sulfuric acid blows up to a wave height and moves. Therefore, the boiling liquid level (L) has reached a position much higher than the liquid level at rest before distillation. Distillation column
The inner peripheral wall of the trunk (2a) of (2) is splashed with boiling sulfuric acid with a high impurity concentration and wets or dries, and the outer peripheral wall of the trunk (2a) becomes lower due to the outside temperature. Therefore, impurities in the sulfuric acid easily precipitate on the inner peripheral wall of the body (2a) near the boiling liquid level (L), and as a result, the body (2a) is easily devitrified in a short period of time.

However, according to the present invention, a distillation column
When the inside of the body (2a) where the boiling liquid level (L) of the body (2a) is located, a quartz sleeve (2X) with a diameter slightly smaller than the inside diameter of the body (2a) is fitted. , Boiling sulfuric acid is a sleeve (2
X) Although it wets the inner wall, it hardly enters the gap (S) between the sleeve (2X) and the trunk (2a), so that precipitation of impurities on the inner peripheral wall of the trunk (2a) is largely suppressed. Also, sleeve (2X)
Is slightly smaller than the inner diameter of the body (2a) of the distillation column (2), so that the inner surface of the sleeve (2X) is not only at the same temperature as the boiling sulfuric acid but also not exposed to the outside air. As a result of the temperature of the outer surface of the sleeve (2X) also approaching the temperature of boiling sulfuric acid, it is possible to effectively prevent the impurities in the sulfuric acid from adhering to the sleeve (2X) due to cooling and devitrifying the sleeve (2X). As described above, the number of days required for the body (2a) to devitrify is greatly increased, and devitrification of the sleeve (2X) is unlikely to occur over a long period of time. The life is greatly improved.

If a light passing hole (w) is provided in the sleeve (2X) so that light from the light control type liquid level sensor (8) can pass therethrough, even if the sleeve (2X) itself is devitrified, Even then, control by the light control type liquid level sensor (8) can be continued for a long time.

In addition, the distillation column at the position where the sleeve (2X) is installed
When a heater (2Y) is installed outside the body (2a) of (2), preferably so that the entire area of the sleeve (2X) installation area is heated, the temperature of the body (2a) in that part is adjusted to the distillation column. Since the temperature is about the same as the boiling sulfuric acid in (2), the precipitation of impurities on the inner peripheral wall of the body (2a) due to cooling is suppressed. Similarly, the heater (2Y) installation is more positive in that the sleeve (2X) is hardly devitrified in order to maintain the inner and outer surfaces of the sleeve (2X) at almost the same temperature as the boiling sulfuric acid. Works.

[0036]

The present invention will be further described with reference to the following examples.

Example 1 FIG. 1 is a schematic flow chart of the sulfuric acid purifying apparatus of the present invention, as described above. FIG. 2 is an explanatory view of the distillation column (2) in which the sleeve (2X) and the heater (2Y) are installed. FIG. 3 is a plan view of the distillation column (2) of FIG.
In addition, (2b) in FIG. 2 is an introduction tube for introducing sulfuric acid into the distillation column (2).

As shown in FIG.
The sulfuric acid refining device of the present invention includes a concentration or preheating column (1) and a distillation column (2). These are all made of quartz glass. The column (1) is a preheated column when purifying industrial sulfuric acid, and a concentration column when purifying recovered sulfuric acid.

In FIG. 1, (3) is a waste water condenser, (4) is a sulfuric acid condenser, (5) waste sulfuric acid cooler, (6) is a sulfuric acid tank,
(7) is a purified sulfuric acid tank. (8) is a liquid level sensor. (9) is a heating furnace for concentration or preheating column, and (10) is a heating furnace for distillation column.

When the column (1) is a concentration column, a drain condenser (3) is provided as shown in FIG. When the column (1) is a preheating column, it is not necessary to provide the drain condenser (3). In addition, it is possible to substitute a concentration column as a preheating column.

Sulfuric acid such as industrial sulfuric acid or recovered sulfuric acid in the sulfuric acid tank (6) passes through a pipe provided by a pump provided in the middle of the pipe or gas pressure in the sulfuric acid tank (6) to concentrate or preheat the column (1). ).

The sulfuric acid introduced into the concentration or preheating column (1) is heated by a concentration or preheating column heating furnace (9). When the concentration is performed, the water containing sulfuric acid evaporates and the column (1) is heated. ) It is condensed by the drain condenser (3) provided at the top and discharged as waste water.

On the other hand, the sulfuric acid concentrated or preheated in the concentration or preheating column (1) is introduced into the middle stage of the distillation column (2) through a pipe (usually by overflow), and is heated by the distillation column heating furnace (10). It is heated and distilled (usually at normal pressure). Then, the sulfuric acid vapor evaporated in the distillation column (2) is condensed in a sulfuric acid condenser (4) provided at the upper part of the distillation column (2), passes through a pipe as purified sulfuric acid in a purified sulfuric acid tank (7). Is stored.

When industrial sulfuric acid or recovered sulfuric acid is concentrated or preheated by this method and then purified by distillation, the distillation column (2)
To control the amount of sulfuric acid evaporated in the furnace, adjust the output of the distillation column heating furnace (10) according to the amount of sulfuric acid introduced into the distillation column (2), or keep the output of the distillation column heating furnace (10) constant. The amount of sulfuric acid corresponding to the output is supplied to the distillation column (2).

As shown in FIGS. 1 and 2, the distillation column (2)
In order to detect the boiling liquid level (L) that fluctuates with the wave height of sulfuric acid in the body (2a) of the body (2a), an infrared A light control type liquid level sensor (8) for use is arranged.

As shown in FIGS. 2 and 3, the inside of the region where the boiling liquid level (L) of the body (2a) of the distillation column (2) is located is smaller than the inner diameter of the body (2a). A quartz sleeve (2X) with a small diameter is fitted inside. The cross-sectional shape of the sleeve (2X) in the radial direction is circular, but when a drain pipe for drainage is inserted, a part of the circular shape is C-shaped with a cutout in the vertical direction.

In this embodiment, the body (2) of the distillation column (2) is
The inner diameter of a) is 202mm and the outer diameter of the sleeve (2X) is 183mm
(The height of the sleeve (2X) is designed to be 225mm), so the gap between the inner peripheral wall of the body (2a) and the outer peripheral wall of the sleeve (2X)
(S) (clearance) is (202-183) / 2 = 9.5mm.

In this embodiment, the sleeve (2X) is fixed to the body (2a) by welding the lower side of the sleeve (2X) to the body (2a) and the upper side of the sleeve (2X) by a rod-shaped support. Is supported by welding.

On the peripheral wall of the lower half side of the sleeve (2X),
As shown in FIG. 2, the width is 10 mm and the height is 80 mm in order to allow the light of the light control type liquid level sensor (8) to pass therethrough.
The pair of light passing holes (w) and (w) are provided to face each other.

As shown in FIGS. 2 and 3, the sleeve (2
X) A jacket-type heater (2Y) is installed outside the body (2a) of the distillation column (2) at the installation position. The heater (2Y) heats the surface temperature of the body (2a) of the distillation column (2) to a target temperature of 320 ° C. and maintains the target temperature (the heater (2Y) and the distillation column (2)). Torso (2a)
A thermocouple (not shown) is installed between the two to control the temperature.) This jacket type heater
(2Y) is provided with a window as shown in FIG. 2 so as not to hinder the emission / reception of infrared light of the light control type liquid level sensor (8).

Using the sulfuric acid purifying apparatus of the above-described embodiment, a purification experiment of industrial sulfuric acid or recovered sulfuric acid was carried out, and a sleeve (2X) was obtained.
In comparison with the case where the conventional apparatus without the heater (2Y) is used, the number of days until it becomes difficult to control the boiling liquid level (L) due to devitrification is about 3 to
Although it was 6 months, especially 3 to 4 months, in the apparatus of Example 1, stable control was still possible after one and a half years had passed. When only the heater (2Y) was omitted, the stable control period was about one and a half years.

Example 2 Example 1 was repeated except that the installation of the slit holes (w), (w) in the sleeve (2X) was omitted. At this time, stable control was still possible after one year.

[0053]

According to the present invention, the following excellent effects can be obtained. 1. By providing the sleeve (2X) having a diameter slightly smaller than the inner diameter of the body (2a) of the distillation column (2), the degree of impurity precipitation on the inner peripheral wall of the body (2a) (that is, the degree of devitrification) Becomes much smaller. At the same time, it is also effectively prevented that impurities adhere to the sleeve (2X) and the sleeve (2X) is devitrified. As a result, the life of the distillation column (2) is greatly improved as compared with the conventional case. 2. If the sleeve (2X) is provided with a light passage hole (w) through which the light of the light control type liquid level sensor (8) passes, even if the sleeve (2X) itself has been devitrified, The control by the light control type liquid level sensor (8) becomes possible for a long time, and the life of the distillation column (2) is further improved. 3. Body (2a) of distillation column (2) where sleeve (2X) is installed
If a heater (2Y) is installed outside the body, the body of impurities (2a)
Precipitation on the inner peripheral wall is suppressed, and impurity sleeve (2X)
Precipitation is also suppressed, and the life of the distillation column (2) is further improved.

[Brief description of the drawings]

FIG. 1 is a schematic flow chart of a sulfuric acid purification apparatus of the present invention.

FIG. 2 is an explanatory view of a distillation column (2) in which a sleeve (2X) and a heater (2Y) are installed.

FIG. 3 is a plan view of the distillation column (2) of FIG.

[Explanation of symbols]

(1) ... concentration or preheating column, (2) ... distillation column, (2a) ... body, (2b) ... introduction tube, (2X) ... sleeve, (w) ... light passage hole, (2Y) ... heater, (L)… boiling liquid level, (S)… gap (between outer wall of sleeve (2X) and inner wall of body (2a)), (3)… drain condenser, (4)… sulfuric acid condenser, (5) )… Waste sulfuric acid cooler, (6)… Sulfuric acid tank, (7)… Purified sulfuric acid tank, (8)… Light control type liquid level sensor, (9)… Concentration or preheating column heating furnace, (10)… Distillation column heating furnace

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[Procedure amendment]

[Submission date] August 23, 2000 (2008.2
3)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction contents]

[0006] Japanese Patent Laid-Open No. 10-330104, and the heater supporting structure is illustrated in the waste sulfuric continuous refiner and purification methods, as well as glass heating apparatus, the section of the conventional <br/> technology described In the semiconductor manufacturing process, sulfuric acid is used for cleaning wafers and stripping photoresist. Waste sulfuric acid used for such processing is either neutralized and then discarded, or industrial waste is discharged. It is handed over to a material processing company or is regenerated by concentration and distillation. " The statement at the last point of “regeneration by concentration and distillation” is common to the purpose of the operation by the sulfuric acid refining device of the present invention. In FIG. 1 of this publication,
From the raw material tank 16, a heating can 1 for concentration, a heating can 7 for distillation,
The flow of sulfuric acid through the distillation condenser 9 to the product tank 17 is shown. However, the heating can 1 for concentration and the heating can 7 for distillation are of a horizontal type. This publication also refers to liquid level detectors 22, 27, 32, 37, and 39. In particular, paragraphs 0013 and 0016 refer to optical liquid level detectors using infrared rays. This is a liquid level sensor of the condensed liquid receiving tank 5 and has a different purpose from the light control type liquid level sensor (8) of the distillation column (2) of the present invention, which will be described in detail later.

[Procedure amendment 2]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

[Correction method] Change

[Correction contents]

FIG. 2

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kaoru Sakoda 1-1-8 Kubota, Yokkaichi-shi, Mie 201 Marvelous Kubota 201 (72) Inventor Yoshihiro Koyama 1-2-22 Ikeuracho, Izumiotsu-shi, Osaka F-term ( Reference) 4D076 AA06 AA16 AA22 BB03 BB30 CA02 CD50 EA15X EA35 JA06

Claims (3)

[Claims] 1. A boiling level of sulfuric acid in a distillation column (2) comprising a concentration or preheating column (1) and a distillation column (2).
(L) from the outside through the body (2a) of the distillation column (2) with a light-controllable liquid level sensor (8) for detecting sulfuric acid from the outside, the body (2a) of the distillation column (2) Characterized in that a quartz sleeve (2X) having a diameter slightly smaller than the inner diameter of the body (2a) is fitted inside the area where the boiling liquid level (L) of the sulfuric acid is located. apparatus. 2. The sulfuric acid according to claim 1, wherein a light passing hole (w) through which light from the light control type liquid level sensor (8) passes is provided on a peripheral wall of the sleeve (2X). Purification equipment. 3. The sulfuric acid refining apparatus according to claim 1, wherein a heater (2Y) is installed outside the body (2a) of the distillation column (2) at the position where the sleeve (2X) is installed.