JPH08175810A - Purification apparatus for waste sulfuric acid - Google Patents

Abstract

PURPOSE: To provide a purification apparatus for waste sulfuric acid free from the exhaust of toxic gas when distilling a waste sulfuric acid containing hydrogen peroxide and enabling the stabilization of the degree of vacuum during distillation and the reduction of distillation time in a purification apparatus for waste sulfuric acid of a reduced pressure distillation-type. CONSTITUTION: This purification apparatus for waste sulfuric acid 12 is provided with a distillation tower 2 for receiving a waste sulfuric acid, a heating means 3 for heating the waste sulfuric acid received in the distillation tower 2 and a condenser 4 for cooling and condensing each fraction of vapors derived from the distillation tower 2. The distillation tower 2 is attached with a degasifier 14 composed of a degasifying column 46 which receives a waste sulfuric acid containing hydrogen peroxide and decomposing the hydrogen peroxide under the heating of the waste sulfuric acid and a toxicant-decomposing column 48 for decomposing ozone which is produced by the decomposition of the hydrogen peroxide.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for recovering and refining used spent sulfuric acid solution, and more particularly to an apparatus for refining spent sulfuric acid capable of safely recovering and refining spent sulfuric acid containing hydrogen peroxide.

[0002]

2. Description of the Related Art In recent years, a large amount of sulfuric acid has been used in a semiconductor factory for a wafer cleaning process, an etching process, and a photoresist stripping process. Here, it is desired to purify spent sulfuric acid after use to produce high-purity sulfuric acid that can be reused in a semiconductor manufacturing process, and a method by distillation is adopted as a method therefor.

In many cases, the waste sulfuric acid generated in these steps is either disposed of after being treated in a neutralization tank or is handed over to an industrial waste treatment company for treatment. It caused many problems in terms of impact and economy.
Therefore, in recent years, a method by distillation as shown in FIG. 4 has been adopted as a refining device for collecting, refining and reusing waste sulfuric acid that has been used in a manufacturing process such as a semiconductor factory.

This waste sulfuric acid refining apparatus 1 is equipped with a distillation column 2 for containing a waste sulfuric acid solution, heating means 3 provided below the bottom of the distillation column body, and cooling the sulfuric acid vapor derived from the distillation column body. It comprises a condenser 4 for condensing and liquefying, a condensate distribution device 5 connected to the condenser 4, and an exhaust device 6 connected to the condenser 4 for exhausting the inside of the distillation system.

The waste sulfuric acid refining apparatus 1 is operated as follows. A desired amount of the waste sulfuric acid solution containing a trace amount of metal components as impurities is introduced into the distillation column 2 through the waste sulfuric acid solution supply port 7. Then, the vacuum evacuation device 8 is driven to reduce the pressure of the entire system of the waste sulfuric acid purification device 1 to about 10 TORR, and the heater 9 is operated while maintaining this pressure to start heating the waste sulfuric acid solution in the distillation column 2.

When the waste sulfuric acid solution is heated up to about 130 ° C., the water content in the waste sulfuric acid solution evaporates violently, and the evaporated water vapor is cooled by the condenser 4 and discharged to the drain tank 10.

Further, the temperature of the waste sulfuric acid solution in the distillation column 2 is gradually raised to about 190.degree. Therefore, impurities lower than the boiling point of sulfuric acid in the waste sulfuric acid are vaporized, introduced into the condenser 4, condensed there, and further discharged to the drain tank 10.
Further, the temperature of the waste sulfuric acid solution is heated to 200 ° C. to 210 ° C., and as a result, the vaporization of sulfuric acid starts and is introduced into the condenser 4 to be condensed and become a high purity (96% by weight or more) sulfuric acid liquid. After the time condenser 4 is cleaned, it is collected and stored in the product tank 11.

In this way, the distillation treatment is continued and the distillation column 2
When the amount of the waste sulfuric acid solution in the inside is exhausted, a waste sulfuric acid solution to be purified is reintroduced and the above-mentioned distillation treatment step is repeated. When metal components and the like are accumulated as a residue at the bottom of the distillation column 2, they are discharged from the bottom of the distillation column 2. Then, the sulfuric acid in the product tank 11 is supplied again to the semiconductor factory for reuse.

On the other hand, recently, an SPM cleaning method in which hydrogen peroxide is added to concentrated sulfuric acid and treated with a sulfuric acid solution heated to a high temperature of 100 ° C. or higher in order to remove organic substances in a wafer cleaning process or a photoresist stripping process. Is used. The concentration of waste sulfuric acid after used in this SPM cleaning method is 60-
It is a mixed solution of 80%, hydrogen peroxide 0.1 to 5%, and water.

[0010]

When such waste sulfuric acid containing hydrogen peroxide is distilled by the above-mentioned conventional waste sulfuric acid refining apparatus, the liquid temperature of the waste sulfuric acid to be treated in the distillation column and the top of the tower. The results of measuring the temperature and the degree of vacuum in the tower are shown in FIG. Figure 5
The solid line indicates the degree of vacuum in the distillation column, the one-dot chain line indicates the liquid temperature in the distillation column, and the two-dot chain line indicates the column top temperature in the distillation column.
In FIG. 5, waste sulfuric acid is sequentially heated in a distillation column maintaining a vacuum degree of 15 TORR, and when the liquid temperature of the waste sulfuric acid reaches about 100 ° C., the vacuum degree in the column is lowered, and the liquid temperature is 140 ° C. 160 ° C
At the liquid temperature of, the degree of vacuum in the tower is temporarily 53 to 55 TO.
It deteriorates to RR. Such a decrease in the degree of vacuum is due to a large amount of oxygen containing ozone, which is a harmful gas, generated by the decomposition of hydrogen peroxide.

Such a decrease in the degree of vacuum in the column results in a decrease in the evaporation action of waste sulfuric acid and a reduction in the distillation rate.
Further, when degassing the waste sulfuric acid solution at a temperature around 100 ° C., decomposition of hydrogen peroxide in the solution causes the liquid surface to violently vibrate and bumping occurs. Therefore, the heater output must be reduced for safety reasons. Will decrease. Further, since the degree of vacuum is disturbed due to such bumping, it is difficult to accurately control the sulfuric acid concentration, which causes an error in the operation of the apparatus, and there is a risk of damage to the apparatus.

Further, as described above, ozone is generated by the decomposition of hydrogen peroxide, but the concentration thereof reaches a harmful concentration of 0.01 to 0.1 ppm, and as it is, there is a problem in operational safety.

The present invention has been made in view of the above circumstances, and in a distillation-type waste sulfuric acid refining apparatus, when the waste sulfuric acid containing hydrogen peroxide is distilled, no harmful gas is discharged,
In addition, it is an object of the present invention to provide a waste sulfuric acid refining apparatus of the vacuum distillation system, which can stabilize the degree of vacuum during distillation and shorten the distillation time.

[0014]

In the waste sulfuric acid refining apparatus of the present invention, a distillation column for containing waste sulfuric acid, a heating means for heating the waste sulfuric acid contained in the distillation column, and a derivation unit from the distillation column And a condenser for cooling and condensing the vapor of each component, the waste sulfuric acid refining apparatus stores waste sulfuric acid containing hydrogen peroxide in the distillation column, and heats the waste sulfuric acid to decompose the contained hydrogen peroxide. The provision of a deaerator equipped with a deaeration tower and a detoxification tower for decomposing ozone generated by the decomposition of hydrogen peroxide was provided as a means for solving the above problems.

It is preferable to dispose a catalyst for reducing the ozone in the detoxification tower. Further, it is preferable to connect a cooling condenser to the degassing tower or the detoxification tower. Further, a vacuum exhaust device for reducing the pressure inside the degassing tower and the inside of the condenser can be provided.

[0016]

Before the waste sulfuric acid is distilled, the waste sulfuric acid is placed in a degassing tower and subjected to heat treatment to decompose the hydrogen peroxide contained in the waste sulfuric acid solution. Oxygen gas containing ozone is generated here,
While degassing the generated gas, the ozone contained is decomposed in the detoxification tower to completely detoxify the generated gas. Waste sulfuric acid after degassing is distilled and purified by a conventional method.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a waste sulfuric acid refining apparatus according to the present invention. This waste sulfuric acid refining apparatus 12 is a distillation apparatus 13
And a deaeration device 14. The distillation apparatus 12 has the same structure as the conventional waste sulfuric acid refining apparatus 1 shown in FIG. 4, and includes a distillation column 2, a condenser 4 connected to the distillation column 2, and a condenser 4 connected to the condenser 4. Condensate distributor 5
And an exhaust device 6 connected to the condenser 4 for exhausting the inside of the distillation system.

The distillation column 2 is a container made of a material that is unlikely to be corroded by waste sulfuric acid and sulfuric acid vapor generated during distillation, and has a pressure resistance capable of being operated in a depressurized state, and preferably a thick glass. A container made of ceramics, more preferably quartz glass or borosilicate glass is used. A heater 6 is provided at the bottom of the distillation column 2. As the heater 6, for example, a mantle heater is preferably used.

A pressure gauge 15 for measuring the pressure and a thermometer 16 for measuring the temperature of the solution in the distillation column 2 are provided in the distillation column 2. A packing layer 17 filled with a packing material such as Raschig ring for improving the separation of the low boiling point component (mainly water) vapor generated in the initial stage of distillation from the sulfuric acid vapor is provided in the upper part of the distillation column 2. There is.

The distillation column 2 is provided with a waste sulfuric acid supply pipe 18 for introducing waste sulfuric acid into the column, and a drain pipe 19 for discharging the waste sulfuric acid from the bottom of the distillation column 2. The waste sulfuric acid supply pipe 18 and the drain pipe 19 are provided with valves 20, 2 respectively.
1 is interposed.

At the upper part of the distillation column 2, there is provided a pipe 22 for guiding the vapor generated in the column into the condenser 4. Condenser 4
Is a container made of a material that is unlikely to be corroded by sulfuric acid vapor and having pressure resistance capable of being operated in a reduced pressure state inside, preferably thick glass or ceramics, more preferably quartz glass or borosilicate glass. It is a container made of.

Inside the condenser 4, there is provided a cooling flexible pipe 23 for circulating cooling water to cool, condense and liquefy the steam introduced into the condenser 4. At the bottom of the condenser 4, a pipe 24 for leading the condensed liquid from the inside of the condenser 4 to the condensed liquid distribution device 5 and a pipe 25 connected to the exhaust device 5 are attached.

The condensate distributor 5 is provided with a product tank 11
, A drain tank 10, a pipe 24 connecting the condenser 4 and the product tank 11, a first switching valve 26 interposed in the pipe 24, a first switching valve 26 of the pipe 24 and the condenser 4 A pipe 24a which is branched between and connected to the drain tank 10.
And a second switching valve 27 interposed in the pipe 24a. A valve 28 is provided at the bottom of the product tank 11.
A product sulfuric acid extraction pipe 29 having a valve is attached, and a drain pipe 31 having a valve 30 is attached to the bottom of the drain tank 10.

In the condensate distribution device 5, the condensate drawn out from the bottom of the condenser 4 through the pipe 24 by the opening / closing switching operation of the first and second switching valves 26, 27 is drain tank 10 and product tank 11. It is possible to switch the supply direction of the condensate to be introduced into either of the above.

The exhaust device 6 is a vacuum exhaust device 8 and a pipe 25 arranged between the vacuum exhaust device 8 and the condenser 4.
Mist separator 32 and sulfuric acid removal cylinder 33 interposed in
It is comprised including. The mist separator 32 is filled with a filter made of a material resistant to concentrated sulfuric acid such as glass wool, and a cooling pipe 3 for cooling the gas phase introduced through the pipe 25 again and liquefying the low boiling point component in the gas phase.
4 are provided. The sulfuric acid removing cylinder 33 is filled with an alkaline absorbent such as soda lime. Further, at the bottom of the mist separator 32, a discharge pipe 36 having a valve 35 for discharging the liquid accumulated inside is attached.

The product tank 11 is provided with a pipe 38 connected to the mist separator 32 via a valve 37, and the drain tank 10 is joined to the pipe 38 via a valve 39 to join the mist separator 32. A connected tube 40 is provided. And product tank 11 and drain tank 10
Is connected to the mist separator 32 through these valves 37 and 39 and pipes 38 and 40 so that the same reduced pressure state as the inside of the condenser 4 and the distillation column 2 which are also connected to the mist separator 32 by the pipe 25 can be achieved. It has become.

In the present embodiment, the product sulfuric acid can be withdrawn from the product tank 11 or the low boiling point condensate can be withdrawn from the drain tank 10 while the pressure inside the distillation column 2 and the condenser 4 is reduced. In this way, the pipe 38 that connects the product tank 11 and the mist separator 32 is branched,
A pipe 43 that opens to the atmosphere through a valve 41 and a filter 42 is provided, and a pipe 40 that connects the drain tank 10 and the mist separator 32 is branched and joined to the pipe 43 through a valve 44 to reach the filter 42. A tube 45 is provided.

The waste sulfuric acid refining apparatus according to the present invention is characterized in that the degassing apparatus 14 is connected to the distillation column 2 of the distillation apparatus having the above-mentioned configuration via the waste sulfuric acid supply pipe 18. There is. The deaerator 14 is connected to the deaeration tower 46 connected to the waste sulfuric acid supply port 7 of the distillation tower 2, a cooling condenser 47 connected to the deaeration tower 46, and a cooling condenser 47. Detoxification tower 48 and vacuum exhaust device 4 connected to detoxification tower 48
9 is provided.

The degassing tower 46 is a container made of a material that is not easily corroded by waste sulfuric acid and sulfuric acid vapor generated during distillation, and has a pressure resistance capable of being operated in a depressurized state inside. Containers made of glass or ceramics, more preferably quartz glass or borosilicate glass are used. A pipe 18 is connected to the bottom of the degassing tower 46, and a waste sulfuric acid supply port 51 equipped with a valve 50 and a vaporized gas outlet 52 are provided at the top.

A heater 53 for heating is provided at the bottom of the distillation column 2.
Is provided. As the heater 53 for heating, for example, a mantle heater is preferably used. Degassing tower 4 above
A pressure gauge 54 for measuring the pressure and a thermometer 55 for measuring the temperature of the solution in the tower are provided inside 6.

Vaporized gas outlet 5 in the upper part of the degassing tower 46
2 is provided with a pipe 50 for guiding the vapor generated in the tower into the cooling condenser 47. The cooling condenser 47 is a container that is made of a material that is unlikely to be corroded by sulfuric acid vapor and has pressure resistance capable of being operated in a decompressed state inside, preferably thick glass or ceramics, more preferably quartz glass or It is a container made of borosilicate glass. Inside this cooling condenser 47, there is provided a cooling flexible pipe 56 for circulating cooling water to cool, condense and liquefy the steam introduced into the cooling condenser 47. At the bottom of the cooling condenser 47, a pipe 57 and a valve 58 for discharging the liquid accumulated inside from the inside of the cooling condenser 47 are attached. A gas outlet 59 is provided above the cooling condenser 47.

A pipe 60 is connected to the gas outlet 59, and the abatement tower 48 is connected to the other end of the pipe 6. The detoxification tower 48 is a device for decomposing ozone generated in the degassing tower. The ozone decomposition method may be any conventionally known method, for example, a thermal decomposition method,
A chemical cleaning method, a sodium sulfite method, a sodium thiosulfate method, an activated carbon method, a catalytic method using manganese (IV) oxide, lead (IV) oxide, platinum powder, or the like can be used, but a catalytic method is preferable, and a catalytic method is more preferable. A reduction catalyst method using manganese oxide can be used.

When a catalytic method is used as the ozone decomposing method, a desired catalyst is filled in the detoxifying tower 48, and the gas discharged from the cooling condenser passes therethrough. Good.

A vacuum exhaust device 49 is connected to the upper part of the abatement tower 48 via a pipe 61.

The operation method of the above-mentioned waste sulfuric acid refining apparatus will be described below by exemplifying the case of purifying a waste sulfuric acid aqueous solution containing a sulfuric acid concentration of 88% by weight, hydrogen peroxide of 3% by weight, and a trace amount of metal.

First, the valve 20 which connects the distillation apparatus 13 and the degassing apparatus 14 to each other is closed to cut off the flow of these, and the distillation apparatus 13 and the degassing apparatus 14 are individually operated by the vacuum devices 8 and 19 for the entire system. Evacuate to about 10 TORR and continue. Then, a waste sulfuric acid solution (W) containing 3% by weight of hydrogen peroxide and 88% by weight of sulfuric acid is supplied into the degassing tower 46 through the valve 50. Then, the pressure in the degassing tower 46 is set to about 10 TOR.
While maintaining at R, the heating device 53 heats the waste sulfuric acid solution (W) to 160 ° C. When the temperature of the waste sulfuric acid solution (W) in the degassing tower 46 exceeds 100 ° C., the hydrogen peroxide in the waste sulfuric acid solution (W) is decomposed, and gas such as oxygen and ozone starts to be generated. When the temperature of W) is around 150 ° C, the gas is most intensely generated. The oxygen and ozone generated at this time and a small amount of water vapor pass through the cooling condenser 47 and the detoxification tower 48 to remove water vapor and harmful ozone, and the residual gas is exhausted to the outside by the vacuum exhaust device 49. During this time, the degree of vacuum in the degassing tower 46 deteriorates to about 50 TORR, and the generation of gas decreases with time, and the degree of vacuum in the degassing tower 46 returns to the initial state of 10 TORR.

A certain amount of the waste sulfuric acid solution (W ') thus deaerated is introduced into the distillation column 2 from the waste sulfuric acid supply port 7 by opening the valve 20.

The waste sulfuric acid solution (W ') in the distillation column 2 has already been heated to 150 ° C. or higher in the degassing column 46, and the distillation column 2
Since the inside is depressurized to 10 TORR in advance, evaporation of water begins as soon as it is supplied into the distillation column 2. Further, the heater output of the heating device 3 is kept constant and the waste sulfuric acid solution (W ′) is gradually heated.

When the waste sulfuric acid solution (W ′) reaches 195 ° C., low-boiling substances in the solution (W ′) start to evaporate, and this vaporized gas is filled with a packing material such as Raschig ring in the upper part of the distillation column 2. It passes through the packed bed 17 and moves to the condenser 4.

In the meantime, in the condenser 4, the component having a lower boiling point than sulfuric acid is condensed, and thus this is discharged to the drain tank 10 by opening the valve 27. At this time, the valve 26 to the product tank 11 is closed.

While the sulfuric acid concentration of the degassed waste sulfuric acid solution (W ') in the distillation column 2 is 96% by weight or less, the condensed low boiling point substances are drained with the valve 27 opened. It is discharged to 10.

In this way, the waste sulfuric acid solution (W ') is condensed when the temperature reaches 200 to 210 ° C, and the concentration of the solution (W') exceeds 96% by weight. There is. When the concentration of the waste sulfuric acid solution (W ') exceeds 96% by weight, the sulfuric acid component of the solution (W') becomes vaporized,
The sulfuric acid vapor passes through the packed bed 17, moves to the condenser 4 and is condensed, and high-purity sulfuric acid is stored in the inner bottom of the condenser 4. Therefore, the valve 27 is closed and the drain tank 10 is discharged. Stop and open the valve 26 to collect the product sulfuric acid in the product tank 11.

The degassed waste sulfuric acid solution (W ') thus introduced into the distillation column 2 is heated and vaporized for purification. On the other hand, during this period, in the deaerator 14, the waste sulfuric acid solution (W ') is deaerated by the above-described operation. Therefore, when the remaining amount of the charged degassed waste sulfuric acid solution (W ′) in the distillation column 2 becomes small in the distillation process in the distillation apparatus 13, the valve 20 is opened to remove the degassed waste sulfuric acid solution (W ′). The desired amount is introduced into the distillation column 2 from the degassing column 46, and thereafter, such operation is repeated to continuously operate.

When supplying the product sulfuric acid stored in the product tank 11, the valves 26 and 37 are closed and the valve 4 is closed.
1 is opened and the inside of the product tank 11 is temporarily returned to the atmospheric pressure through the filter 42, and then the valve 28 is opened and the product is supplied. Also, when waste such as water stored in the drain tank 10 is discharged to the outside, the valve 27 is closed and the valve 44 is opened to introduce the atmosphere into the drain tank 10 through the filter 42 to temporarily. After setting to atmospheric pressure, the valve 30 is opened to release.

The mist separator 32 is filled with a filter material such as glass wool, and the sulfuric acid removing cylinder 33 is filled with an alkaline absorbent such as soda lime to prevent the harmful substances from entering the vacuum exhaust device 8. There is.

In the above embodiment, the vacuum evacuation system of the deaerator 14, that is, the cooling condenser 47, the detoxification tower 48, and the vacuum evacuation system of the vacuum evacuation device 49 and the distillation device 13, that is, the mist separator 32, the sulfuric acid removal cylinder 33, the vacuum Although an example in which the exhaust devices 8 are separately provided has been illustrated, the vacuum exhaust system connected to the degassing tower 46 of the degassing device 14 as shown in FIG. 2 in order to downsize the device. The distillation apparatus 101
A pipe 62 connecting the degassing tower 46 to the vacuum exhaust system via a valve 63 so that the mist separator 32, the sulfuric acid removing cylinder 33 of the vacuum exhaust system of the distillation apparatus 13 can be shared.
It may be connected to the vacuum exhaust device 8.

In this case, the cooling condenser and the vacuum evacuation device provided in the deaerator 14 can be omitted.

In order to verify the operation and effect of the apparatus of the present invention, the case where the apparatus of the present invention is used for purification (Example) and the case of the conventional apparatus used for purification (Conventional example) are compared below.

A waste sulfuric acid solution having a sulfuric acid concentration of 88% by weight and a hydrogen peroxide of 3% by weight was purified in each of the apparatus of the present invention and a conventionally used apparatus. The outline specifications of the device used are as follows.

Distillation column, degassing column Material: Quartz glass Boiler capacity: 10 l Vacuum exhaust device Dry pump Ultimate vacuum: 10 TORR Equipment material (other than distillation column) Pyrex product Sulfuric acid treatment rate 50 ML / min Recovery rate 95% Sulfuric acid concentration Inlet: 90% by weight Outlet: 96% by weight

(Example-Case of purification treatment by the apparatus of the present invention) Treatment was performed by using the waste sulfuric acid purification apparatus of the present invention shown in FIG. The waste sulfuric acid solution (W) was supplied into the degassing tower 46, and the solution was heated to about 150 ° C. by the heating device 53 to remove oxygen and ozone generated here. About 55 for this degassing process
It took time. The degassed waste sulfuric acid solution (W ′) that has been degassed is introduced into the distillation column 2, and the solution (W ′) is gradually raised to about 195 ° C. to 198 ° C. by a heating device to perform distillation. It was

FIG. 3 shows the distillation data in the distillation column 2. In FIG. 3, the solid line indicates the degree of vacuum in the distillation column, the one-dot chain line indicates the liquid temperature in the distillation column, and the two-dot chain line indicates the column top temperature in the distillation column. At the start of distillation, evaporation of water occurs, so that the degree of vacuum rises to 21 TORR and the heater output of the heating device is 60%. Vacuum degree is 13 TORR
The heater output of the heating device 6 was able to be increased to 70% at the time when the temperature fell down to 70%. It took 55 minutes from the evaporation of water from the waste sulfuric acid solution in the distillation column to the steady state. During this time, the liquid condensed in the condenser 4 was sent to and stored in the drain tank via the valve 27.

After confirming that the sulfuric acid concentration of the degassed waste sulfuric acid solution in the distillation column 2 reached 96% by weight, the liquid temperature was 205 ° C.
A steady state with a vacuum degree of 10 TORR was maintained. During this time, the liquid condensed in the condenser was stored in the product tank 11 as product sulfuric acid by opening the valve 26 and closing the valve 27. It took 55 minutes to manufacture 5 kg of the product sulfuric acid in this manner.

(Conventional Example-When Using Conventional Waste Sulfuric Acid Purification Device) A waste sulfuric acid solution containing hydrogen peroxide was supplied to the distillation column 2 of the conventional device shown in FIG. 4 and gradually heated by the heating device 6. Heated. The state change in the distillation column 2 will be described below with reference to FIG.

When the waste sulfuric acid solution (W) exceeded 100 ° C., oxygen and ozone began to be generated and the degree of vacuum in the distillation column 2 deteriorated. When the liquid temperature reached 150 ° C., the vacuum degree in the distillation column 2 reached 54 TORR. It took about 50 minutes from the introduction of waste sulfuric acid into the distillation column 2 until the complete degassing treatment was completed. Since the liquid level of the sulfuric acid solution in the distillation column 2 fluctuates or bumps occur, this is prevented, and the heater output of the heating device 6 of the device is 40% for the safety maintenance of the device. The maximum concentration of ozone generated was 0.1 ppm when the degree of vacuum was 54 TORR.

After that, the degree of vacuum gradually began to recover, and after the deaeration from the waste sulfuric acid solution was completed, steam started to be generated.
During this time, the degassed gas is sucked by a vacuum exhaust device, harmful substances are captured by a mist separator and a sulfuric acid removal cylinder, and the condenser 4
The liquid condensed in (1) is discharged to the drain tank 10 via the valve 27.

At this time, the degree of vacuum in the distillation column 2 is temporarily set to 1
Although it recovered to 6 TORR, when the liquid temperature reached 195 to 198 ° C., the degree of vacuum in the distillation column 2 again decreased to 20 TORR due to water evaporation. Thereafter, the heater output of the heating device 3 was set to 60% and heating was continued until it reached 14 TORR. After that, the steady state (about 10 TORR)
The heater output of the heating device 3 was increased to 70% until the temperature reached.
At a liquid temperature of 150 ° C, the degree of vacuum is 10T after water begins to evaporate
It took 65 minutes for the ORR to reach a steady state. During this time, the water condensed in the condenser 4 opens the valve 27 and the drain tank 1
It was discharged to 0. This stable steady state is 10 TOR
The sulfuric acid concentration of the waste sulfuric acid solution that has reached the vacuum degree of R is 96% by weight
Even after confirming that, heating was continued while maintaining the vacuum degree 10 TORR in the distillation column 2. Liquid temperature is 20
When the temperature reached 6 ° C., the vaporized sulfuric acid mist was condensed in the condenser 4 and started to be stored in the product tank 11 through the valve 26.
It took about 55 minutes to produce 5 kg of this product sulfuric acid.

Comparing the above-mentioned example with the conventional example, in the case of the conventional example using the conventional waste sulfuric acid refining device without the deaerator, when the waste sulfuric acid solution containing hydrogen peroxide was purified by distillation, , The liquid surface violently fluctuates during heating for distillation, and there is a risk of bumping, so the heater output of the heating device must be set low at the beginning for the safety of the device, degassing is completed, and the vacuum level drops to the specified level. Could not concentrate the waste sulfuric acid.

Further, since the heater output of the heating device is gradually increased in accordance with the fluctuation of the degree of vacuum in the distillation column, the purification processing time of the waste sulfuric acid solution per unit is the waste sulfuric acid refining device of the present invention. Needed more than if.

On the other hand, in the case of the embodiment using the waste sulfuric acid refining apparatus utilizing the apparatus of the present invention, the process is carried out in a stable state without liquid pulsation or bumping in the distillation column in the above conventional apparatus. As a result, the driving operation could be performed reliably and safely.
Moreover, the processing time can be shortened by 37% compared with the conventional method.

In the apparatus of the present invention, deaeration treatment is performed in advance to remove gases such as oxygen and ozone, so that the degree of vacuum in the distillation column does not become unbalanced, so that the heater output of the heating apparatus can be increased as compared with the conventional apparatus. did it. Further, since the waste sulfuric acid solution which has been degassed is already heated to 150 ° C., the distillation is started at the same time when it is introduced into the distillation column 2 and the distillation time is shortened significantly.

In the above examples, the case of the vacuum distillation treatment was described as an example, but the present invention is not limited to this, and it goes without saying that it can be applied to atmospheric distillation or pressure distillation. The evacuation device may be omitted.

[0063]

Industrial Applicability The waste sulfuric acid refining apparatus of the present invention comprises a distillation column containing waste sulfuric acid, a heating means for heating the waste sulfuric acid contained in the distillation column, and a vapor of each component derived from the distillation column. In a waste sulfuric acid purifying apparatus comprising a condenser for cooling and condensing, the distillation column contains a waste sulfuric acid containing hydrogen peroxide, and a degassing column for heating the waste sulfuric acid to decompose the contained hydrogen peroxide,
The degassing device is provided with a detoxification tower for decomposing ozone generated by decomposition of the hydrogen peroxide.

Therefore, ozone generated at the time of degassing can be made harmless and safety can be improved. Further, since the waste sulfuric acid solution is heated when it is introduced into the distillation column, the sulfuric acid purification time can be significantly shortened.

Further, by providing a vacuum exhaust device for reducing the pressure inside the distillation column and the inside of the condenser, waste sulfuric acid introduced into the distillation column does not bump or the liquid level does not move suddenly.
A depressurized waste sulfuric acid refining device having a stable vacuum degree in the distillation column can be obtained. In such a waste sulfuric acid refining apparatus, the distillation temperature is not raised more than necessary, and the distillation rate is not lowered due to the deterioration of the vacuum degree. In addition, since the degree of vacuum is stable, it is possible to control the quality of the product sulfuric acid to be constant due to the poor conversion of the concentration by the vapor-liquid equilibrium calculation. Further, since the waste sulfuric acid solution degassed as described above is supplied to the distillation column, the heater output of the heating device of the distillation column can be set higher than before.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a waste sulfuric acid refining apparatus of the present invention.

FIG. 2 is a configuration diagram showing another embodiment of the waste sulfuric acid refining apparatus of the present invention.

FIG. 3 is a diagram showing a state change of vacuum distillation of waste sulfuric acid by the waste sulfuric acid refining apparatus of the present invention.

FIG. 4 is a configuration diagram showing an example of a conventional waste sulfuric acid refining apparatus.

FIG. 5 is a diagram showing a state change in vacuum distillation of waste sulfuric acid by a conventional waste sulfuric acid refining apparatus.

[Explanation of symbols]

2 ... Distillation tower, 4 ... Condenser, 3 ... Heating means, 46 ...
… Deaeration tower, 12 …… Waste sulfuric acid refining equipment, 14 …… Deaeration equipment, 48 …… Detoxification tower, 47 …… Cooling condenser, 49 …… Vacuum exhaust equipment, 53 …… Heating equipment

Claims (5)

[Claims] 1. A distillation column containing waste sulfuric acid, a heating means for heating the waste sulfuric acid contained in the distillation column, and a condenser for cooling and condensing the vapor of each component derived from the distillation column. In the waste sulfuric acid refining apparatus, a degassing column for accommodating waste sulfuric acid containing hydrogen peroxide in the distillation column and heating the waste sulfuric acid to decompose the contained hydrogen peroxide, and ozone generated by the decomposition of the hydrogen peroxide An apparatus for purifying waste sulfuric acid, comprising a deaerator equipped with a detoxification tower for decomposing sewage. 2. The waste sulfuric acid refining apparatus according to claim 1, wherein a catalyst for reducing the ozone is arranged in the detoxification tower. 3. A waste sulfuric acid refining apparatus according to claim 1, wherein a cooling condenser is connected to the degassing tower or the detoxification tower. 4. The waste sulfuric acid purification device according to claim 3, further comprising a vacuum exhaust device for reducing the pressure inside the degassing tower and the cooling condenser. 5. The waste sulfuric acid refining apparatus according to claim 1, further comprising a vacuum exhaust device for reducing the pressure inside the distillation column and the inside of the condenser.