JP5954530B2 - Sulfuric acid waste liquid treatment apparatus and sulfuric acid waste liquid treatment method - Google Patents

Description

  The present invention relates to a sulfuric acid waste liquid treatment apparatus and a sulfuric acid waste liquid treatment method for treating a sulfuric acid waste liquid containing hydrogen peroxide used as a cleaning liquid in a semiconductor manufacturing process.

  In a batch-type cleaning process in a semiconductor manufacturing process, SPM (Sulfuric acid Hydrogen Peroxide Mixture), which is a mixed liquid of sulfuric acid and hydrogen peroxide, is used as a cleaning liquid. In the batch-type cleaning process, after the SPM is used for cleaning, it is often circulated, hydrogen peroxide is added to the SPM to regenerate the oxidizing power, and it is often used again as a cleaning liquid. However, the SPM that is regenerated and used for cleaning while circulating increases the content of water derived from hydrogen peroxide over time, the sulfuric acid concentration decreases, and the cleaning power decreases. There is a need to do. The SPM waste liquid discharged from the system during the liquid exchange has a sulfuric acid concentration of about 70% by mass. When a sulfuric acid solution having such a sulfuric acid concentration is discarded as industrial waste, generally, the salt obtained by neutralizing the sulfuric acid waste liquid with an alkaline chemical and then concentrating it is recovered to form solid waste. . In this method, there is a problem that a drug cost for neutralization increases.

  In addition, the SPM used as a cleaning liquid in the semiconductor manufacturing process may have a hydrogen peroxide concentration of 2% by mass or more, and such an SPM waste liquid increases the danger when mixed with other waste liquids. There arises a problem that it cannot be processed as waste and there is no pick-up company.

  On the other hand, a distillation method has been conventionally used to concentrate a sulfuric acid solution. However, the general properties of the waste liquid of SPM are a sulfuric acid concentration of about 70% by mass and a hydrogen peroxide concentration of about 2% by mass. When this is subjected to distillation, there is a problem that hydrogen peroxide is decomposed to generate oxygen gas or ozone gas, which foams inside the distillation tower and hinders the distillation operation.

In order to avoid the above problems, a method that also serves as gas-liquid separation in a hydrogen peroxide decomposition reactor covered with a mantle heater (see Patent Document 1) or a method that uses a gas separation membrane made of Teflon (registered trademark) (Patent Document) 2) has been proposed.
Patent Document 1 describes a waste sulfuric acid refining device in which a distillation section is provided with a degassing tower for containing waste sulfuric acid containing hydrogen peroxide and heating to decompose the contained hydrogen peroxide. In the purification apparatus, before distilling the waste sulfuric acid in the distillation section, the waste sulfuric acid is heated in a deaeration tower with a mantle heater or the like to decompose hydrogen peroxide contained in the waste sulfuric acid. In the distillation section, the waste sulfuric acid after deaeration is purified by distillation by a conventional method.

  In addition, Patent Document 2 discloses a sulfuric acid waste liquid purification provided with a filter having a hydrophobic membrane for separating hydrogen peroxide and oxygen from a heated sulfuric acid waste liquid before supplying the sulfuric acid waste liquid to a concentration tower for distilling the sulfuric acid waste liquid. An apparatus is described. In the refining apparatus, sulfuric acid waste liquid before distillation is used as a cooling medium for the condenser provided at the top of the concentration tower. In the condenser, the sulfuric acid waste liquid before distillation is heat-exchanged with steam in the concentrating tower and heated, and hydrogen peroxide contained in the sulfuric acid waste liquid is vaporized or decomposed into water and oxygen. Vaporized hydrogen peroxide and oxygen generated by decomposition of hydrogen peroxide are separated from the sulfuric acid waste solution supplied to the concentration tower by a filter having a hydrophobic membrane.

JP-A-8-175810 JP-A-10-231107

  However, the techniques described in Patent Documents 1 and 2 are suitable for extremely small-scale waste liquid treatment, and have various problems when applied to industrial-scale waste liquid treatment. For example, a mantle heater is used to heat an object to be heated in a laboratory flask. However, when the scale is increased, the heat transfer area is small instead of the capacity, and it is difficult to obtain a sufficient heat transfer rate. In addition, the technique using a filter having a hydrophobic membrane is difficult to apply to a large apparatus, and is not suitable for continuous operation over a long period of time such as 24 hours due to filter clogging. There's a problem.

  The present invention has been made against the background of the above circumstances, and provides a sulfuric acid waste liquid treatment apparatus and a sulfuric acid waste liquid treatment method capable of treating sulfuric acid waste liquid containing hydrogen peroxide continuously for a long time on an industrial scale. Objective.

Among the sulfuric acid waste liquid treatment apparatuses of the present invention, the first present invention includes a thermal decomposition heating section for heating the sulfuric acid waste liquid containing hydrogen peroxide, and is included in the sulfuric acid waste liquid by heating by the thermal decomposition heating section. A thermal decomposition gas-liquid separation unit for thermally decomposing the hydrogen peroxide and separating a gas containing a decomposition gas generated by the thermal decomposition from the sulfuric acid waste liquid;
A distillation unit for heating the sulfuric acid waste liquid separated in the pyrolysis gas-liquid separation unit to heat the sulfuric acid waste liquid, and distilling the sulfuric acid waste liquid heated by the distillation heating unit under reduced pressure; Have
The heating section for thermal decomposition heats the sulfuric acid waste liquid containing hydrogen peroxide to a temperature not boiling and to a temperature of 150 ° C. or higher.
The pyrolysis gas-liquid separation unit separates the gas without reducing pressure,
The pyrolysis gas-liquid separation unit has a pyrolysis gas-liquid separation unit main body in which the sulfuric acid waste liquid stays and gas-liquid separation is performed, and a part of the sulfuric acid waste liquid in the pyrolysis gas-liquid separation unit main body And having a heating circulation line for thermal decomposition that returns to the main body of the thermal decomposition gas-liquid separation part after heating,
The pyrolysis heating section is interposed in the pyrolysis heating circulation line.

  In the sulfuric acid waste liquid treatment apparatus of the second aspect of the present invention, in any one of the first aspects of the present invention, a gas-liquid separation condenser is connected to a gas discharge side of the pyrolysis gas-liquid separation unit. A condensate circulating line for circulating the condensate of the condenser to the pyrolysis gas-liquid separator is provided.

  In the sulfuric acid waste liquid treatment apparatus of the third aspect of the present invention, in any one of the first or second aspects of the present invention, the distillation section includes a distillation section main body in which the sulfuric acid waste liquid is evaporated, and the inside of the distillation section main body. It has a decompression part which decompresses, and a condensation part which condenses the vapor evaporated in the distillation part main part.

  The sulfuric acid waste liquid treatment apparatus of the fourth aspect of the present invention is characterized in that, in the third aspect of the present invention, the distillation section main body has a shelf.

  In the sulfuric acid waste liquid treatment apparatus of the fifth aspect of the present invention, in any one of the first to fourth aspects of the present invention, the distillation section adiabatically compresses steam generated by heating the sulfuric acid waste liquid by the heating section for distillation. The distillation heating unit obtains condensate, and the heating unit for distillation uses sensible heat of the condensate as a part or all of a heat source.

  A sulfuric acid waste liquid treatment apparatus according to a sixth aspect of the present invention is the pyrolysis gas-liquid separation unit according to any one of the first to fifth aspects of the present invention, wherein the sulfuric acid waste liquid concentrated by the distillation unit is pyrolyzed by the pyrolysis gas-liquid separation unit. And a preheating unit for preheating the sulfuric acid waste liquid.

  A sulfuric acid waste liquid treatment apparatus according to a seventh aspect of the present invention is the liquid waste separation apparatus according to any one of the first to sixth aspects of the present invention, wherein the pyrolysis gas-liquid separation unit is gas-liquid separated and discharged from the pyrolysis gas-liquid separation unit It has a gas dilution part which mixes air with the gas and dilutes the gas.

  The sulfuric acid waste liquid treatment apparatus of the eighth aspect of the present invention is the apparatus according to any one of the first to seventh aspects of the present invention, wherein the distillation section is provided in multiple stages, and the concentration of sulfuric acid vapor in the gas phase is increased by distillation at the distillation section on the preceding stage. The reduced sulfuric acid waste liquid is distilled in a later distillation section to obtain a further concentrated sulfuric acid waste liquid.

  In the sulfuric acid waste liquid treatment method of the ninth aspect of the present invention, the sulfuric acid waste liquid containing hydrogen peroxide is heated to a temperature of 150 ° C. or higher without boiling, and the thermal decomposition of the hydrogen peroxide in the sulfuric acid waste liquid is performed. A pyrolysis gas-liquid separation step of gas-liquid separation from the sulfuric acid waste liquid without depressurizing the gas containing the cracked gas generated by the decomposition, and heating and distilling the sulfuric acid waste liquid from which the gas has been separated, under reduced pressure, A distillation step of concentrating the sulfuric acid waste liquid, and in the pyrolysis gas-liquid separation step, the sulfuric acid waste liquid stays and gas-liquid separation is performed, and further, the sulfuric acid in the main body of the pyrolysis gas-liquid separation unit A part of the waste liquid is taken out, and after heating, returned to the pyrolysis gas-liquid separation unit main body.

  The sulfuric acid waste liquid treatment method according to a tenth aspect of the present invention is characterized in that, in any of the ninth aspects of the present invention, in the distillation step, the distillation is performed under a reduced pressure of 250 to 350 Torr.

  The sulfuric acid waste liquid treatment method of the eleventh aspect of the present invention is the method of concentrating the sulfuric acid waste liquid to a sulfuric acid concentration of 80% by mass or more and 96% by mass or less in the distillation process according to any of the ninth or tenth aspects of the present invention. Features.

That is, according to the present invention, the sulfuric acid waste solution containing hydrogen peroxide is heated, and the hydrogen peroxide in the sulfuric acid waste solution is thermally decomposed. The cracked gas produced by the thermal decomposition is separated into gas and liquid, while the sulfuric acid waste liquid from which the gas has been separated is distilled under reduced pressure to concentrate the sulfuric acid waste liquid.
Since the cracked gas is separated from the sulfuric acid waste solution prior to the distillation of the sulfuric acid waste solution, the distillation operation is not hindered by the foaming of the gas, and since the distillation is performed under reduced pressure, sulfuric acid is concentrated at a relatively low distillation temperature. It can be concentrated.

  The sulfuric acid waste liquid to be treated by the present invention is not particularly limited as long as it is a sulfuric acid waste liquid containing hydrogen peroxide. For example, as the sulfuric acid waste liquid to be treated, an SPM waste liquid that is a mixed liquid of sulfuric acid and hydrogen peroxide solution after being used in a batch cleaning step and other cleaning steps in a semiconductor manufacturing process can be exemplified. If SC1 cleaning waste liquid (ammonia + hydrogen peroxide) and SC2 cleaning waste liquid (hydrochloric acid + hydrogen peroxide) are mixed, ammonia and chlorine volatilize with thermal decomposition, so it is safe to use SPM waste liquid alone. is there.

  The sulfuric acid waste liquid treatment apparatus of the present invention has a thermal decomposition gas-liquid separation part provided with a heating part for thermal decomposition for heating the sulfuric acid waste liquid containing hydrogen peroxide in order to realize the separation of the cracked gas. In addition, oxygen gas and ozone gas are mentioned as decomposition gas generated by thermal decomposition of hydrogen peroxide contained in sulfuric acid waste liquid.

  The pyrolysis gas-liquid separation unit is preferably one that performs gas separation without reducing pressure. When gas containing cracked gas is separated under reduced pressure, large bubbles are generated by the cracked gas, and the liquid level may become unstable. In such a state, there is a problem that sulfuric acid mist is generated or gas-liquid separation trouble occurs. By performing gas-liquid separation without reducing the pressure, the generation of bubbles due to the decomposition gas can be suppressed. Higher pressure results in smaller bubbles and less foaming. The atmospheric pressure may be normal pressure.

Moreover, it is preferable that the pyrolysis heating part provided in the pyrolysis gas-liquid separation part heats the sulfuric acid waste liquid to a temperature that does not boil. When the sulfuric acid waste liquid is boiled, the amount of gas generated increases, increasing the energy required for heating and cooling and making gas-liquid separation more difficult. The upper limit temperature at which the sulfuric acid waste liquid is not boiled is lower than the boiling point of the sulfuric acid waste liquid, but the boiling point of the sulfuric acid waste liquid is preferably −10 ° C. or lower.
Furthermore, the heating temperature of the sulfuric acid waste liquid is preferably 150 ° C. or higher. When the temperature is lower than 150 ° C., the reaction rate of thermal decomposition of hydrogen peroxide is low, so the reaction volume needs to be increased.

The sulfuric acid waste liquid is preferably retained in the pyrolysis gas-liquid separation section for thermal decomposition and gas-liquid separation of hydrogen peroxide.
For example, an SPM waste liquid having a sulfuric acid concentration of 70 mass% and a hydrogen peroxide concentration of 2 mass% is assumed as a sulfuric acid waste liquid containing hydrogen peroxide. When this waste liquid of SPM is heated to 150 ° C., hydrogen peroxide is thermally decomposed according to the following formula.
H ₂ O ₂ → H ₂ O + (1/2) O ₂
Since the half-life of hydrogen peroxide is 1 minute or less at 150 ° C., if the residence time of the residence is 10 minutes, the hydrogen peroxide concentration becomes (1/2) ¹⁰ <(1/1000), It is thought that it will fall to about 0.002 mass%.
Accordingly, the heating temperature of the sulfuric acid waste liquid in the heating section for thermal decomposition is preferably 150 ° C. or higher. Further, the residence time during which the sulfuric acid waste liquid stays in the pyrolysis gas-liquid separation unit is sufficient if it is 5 minutes or more, but 10 minutes or more is preferable.

  The reaction heat of thermal decomposition of hydrogen peroxide is 98.05 kJ / mol. For example, if the total amount of 2 mass% hydrogen peroxide contained in the waste liquid of SPM is thermally decomposed, the amount of heat at that time corresponds to the amount of heat that raises the liquid temperature of the waste liquid of SPM by 30 ° C. Using this heat, the sulfuric acid waste liquid can be further heated.

  The installation location and heating method of the thermal decomposition heating section are not limited to specific ones in the present invention. A part of sulfuric acid waste liquid is removed from the main body of the pyrolysis gas-liquid separation part where the sulfuric acid waste liquid stays and gas-liquid separation is performed. The sulfuric acid waste liquid may be heated by providing a thermal decomposition heating section in the thermal decomposition heating circulation line. According to this configuration, the sulfuric acid waste liquid can be maintained at a high temperature, and the temperature can be equalized and the efficiency of gas separation can be improved by circulation.

  In addition, a gas-liquid separation condenser is connected to the gas discharge side of the pyrolysis gas-liquid separation section, and a condensate circulation line for circulating the condensate of the gas-liquid separation condenser to the pyrolysis gas-liquid separation section is provided. May be. The gas discharged from the pyrolysis gas-liquid separation unit contains not only a decomposition gas generated by thermal decomposition of hydrogen peroxide but also steam. The gas discharged from the pyrolysis gas-liquid separation unit is condensed by the gas-liquid separation condenser, and the condensate is circulated to the pyrolysis gas-liquid separation unit through the condensate circulation line to be discharged from the pyrolysis gas-liquid separation unit. The vapor component contained in the gas can be recovered.

  Further, the sulfuric acid waste liquid treatment apparatus of the present invention may be provided with a gas dilution section that separates the gas by mixing it with the gas separated by the pyrolysis gas-liquid separation section and discharged from the pyrolysis gas-liquid separation section. . The gas discharged from the pyrolysis gas-liquid separation part contains oxygen gas and ozone gas generated by the decomposition of hydrogen peroxide. Oxygen has the property of promoting combustion and explosion. Moreover, ozone has a strong oxidizing power and shows toxicity at a high concentration. Safety can be improved by mixing air with the exhaust gas to dilute and cool the gas.

Moreover, the sulfuric acid waste liquid which isolate | separated gas in the pyrolysis gas-liquid separation part is distilled under pressure reduction in a distillation part. At this time, the sulfuric acid waste liquid is heated in the heating section for distillation.
The said distillation part can be comprised by what has a distillation part main body in which sulfuric acid waste liquid is evaporated, a pressure reduction part which decompresses the inside of a distillation part main body, and a condensation part which condenses the vapor | steam evaporated in the distillation part main body.
The structure of the distillation unit body is not limited to a specific structure, but the distillation unit body preferably has a shelf from the viewpoint of sulfuric acid recovery efficiency and ease of condensate treatment. By distilling the sulfuric acid waste liquid in the main body of the distillation part while reducing the pressure by the pressure reducing part, the sulfuric acid waste liquid concentration is increased at a relatively low temperature to improve the sulfuric acid recovery efficiency, and the condensate sulfuric acid concentration is lowered. Thus, the condensate can be easily treated.

  Moreover, it is desirable to set the pressure when performing distillation in the distillation section to 250 to 350 Torr. If the pressure is reduced to this level, the sulfuric acid waste liquor can be concentrated to 80% by mass or more at a distillation temperature that is easily realized, for example, at 170 to 180 ° C.

  Moreover, it is preferable that a distillation part concentrates a sulfuric acid waste liquid to 80 mass% or more of sulfuric acid concentration from a viewpoint which enables reuse of a concentrate.

  The distillation section may have an adiabatic compression section that adiabatically compresses steam generated by heating the sulfuric acid waste liquid by the distillation heating section to obtain a condensate. In this case, the distillation heating unit can use the sensible heat of the condensate obtained by the adiabatic compression unit as a part or all of the heat source for heating the sulfuric acid waste liquid. By using the sensible heat of the condensate as part or all of the heat source for heating the sulfuric acid waste liquid, the sulfuric acid waste liquid can be treated with high energy efficiency, and energy saving can be achieved.

  Moreover, the sulfuric acid waste liquid treatment apparatus of the present invention may include a preheating unit for preheating the sulfuric acid waste liquid heated in the pyrolysis gas-liquid separation unit by sensible heat of the sulfuric acid waste liquid concentrated by the distillation unit. Since the sulfuric acid waste liquid concentrated in the distillation section has a high temperature according to the distillation temperature, the sulfuric acid waste liquid can be preheated using the sensible heat as a heat source.

  In addition, the distillation section is provided in multiple stages, the sulfuric acid concentration in the gas phase is lowered by lowering the sulfuric acid concentration in the condensate in the distillation section on the front side, and the sulfuric acid concentration in the liquid phase is increased in the upstream side on the rear stage side. Thus, a concentrated sulfuric acid waste solution can also be obtained. Thereby, high purity sulfuric acid can be recovered as a condensate.

  As described above, according to the present invention, the sulfuric acid waste liquid containing hydrogen peroxide can be continuously processed on an industrial scale for a long time.

It is the schematic which shows the sulfuric acid waste liquid processing apparatus of one Embodiment of this invention. Similarly, it is the schematic which shows the sulfuric acid waste liquid processing apparatus of other embodiment. Similarly, it is the schematic which shows the sulfuric acid waste liquid processing apparatus of other embodiment. Similarly, it is the schematic which shows the processing system which has a sulfuric acid waste liquid processing apparatus of one Embodiment. FIG. 2 is a schematic view showing a pyrolysis gas-liquid separation unit used in Example 1.

(Embodiment 1)
Hereinafter, a sulfuric acid waste liquid treatment apparatus according to an embodiment of the present invention will be described with reference to FIG.
The sulfuric acid waste liquid treatment apparatus has a pyrolysis gas-liquid separation unit 1 and a distillation unit 2, and the sulfuric acid waste liquid treated by the pyrolysis gas-liquid separation unit 1 can be introduced into the distillation unit 2.
The pyrolysis gas / liquid separation unit 1 includes a pyrolysis gas / liquid separation unit main body 10 in the shape of a sealed container that contains sulfuric acid waste liquid, and the sulfuric acid waste liquid in the pyrolysis gas / liquid separation unit main body 10 of the pyrolysis gas / liquid separation unit main body 10. A thermal decomposition heating circulation line 11 that is taken out from the bottom side and returned to the central portion of the pyrolysis gas-liquid separation unit main body 10 to circulate the sulfuric acid waste liquid, and a thermal decomposition heating circulation line 11 is provided. And a reboiler 12 for heating the sulfuric acid waste liquid flowing in the line 11. The reboiler 12 corresponds to the thermal decomposition heating section of the present invention.

A spray nozzle 15 is installed on the upper side in the pyrolysis gas / liquid separation unit main body 10, and a waste liquid supply line 13 for supplying sulfuric acid waste liquid from the outside of the pyrolysis gas / liquid separation unit main body 10 to the spray nozzle 15 is provided. It is connected. A valve 14 is interposed in the waste liquid supply line 13, and a flow rate instruction controller 16 that detects the flow rate of sulfuric acid waste liquid flowing through the waste liquid supply line 13 and adjusts the opening degree of the valve 14 is provided downstream of the valve 14. It has been.
A mist separation plate 17 is provided on the upper side of the spray nozzle 15 in the pyrolysis gas-liquid separation unit main body 10. The mist separating plate 17 can be constituted by a perforated plate or a net.

  In the thermal decomposition heating circulation line 11, a circulation pump 20 is interposed on the upstream side of the reboiler 12. The reboiler 12 heats the sulfuric acid waste liquid in the heating circulation line 11 for thermal decomposition through heat exchange after the heating medium is introduced. In this embodiment, steam is used as the heating medium. A steam supply line 21 to which steam is supplied is connected to the reboiler 12 so that heat can be exchanged. A valve 22 is interposed in the steam supply line 21 on the upstream side of the reboiler 12. In addition, a temperature indication controller 23 that detects the temperature of the sulfuric acid waste liquid in the pyrolysis gas-liquid separator main body 10 and adjusts the opening degree of the valve 22 is provided at the liquid storage position of the pyrolysis gas-liquid separator main body 10. It is connected.

  A gas discharge line 24 is connected to the top of the pyrolysis gas-liquid separation unit main body 10, and a condenser 25 is connected to the gas discharge line 24. The condenser 25 corresponds to the gas-liquid separation condenser of the present invention, and cools the exhaust gas by heat exchange with the cooling liquid to obtain a condensate. A condensate reflux line 26 and a gas discharge line 28 are connected to the condensate discharge side of the condenser 25. The condensate reflux line 26 extends downward and is arranged in a U shape, and is connected to the upper side of the pyrolysis gas-liquid separation unit main body 10 by changing the direction on the lower end side of the U shape. . Further, the pressure equalization line that extends upward and is connected to the vicinity of the upstream end of the gas discharge line 24 is located at a position where the condensate recirculation line 26 changes its direction so as to be connected to the pyrolysis gas-liquid separation unit main body 10. 27 is branched.

  The gas discharge line 28 extends upward, and the air supply line 29 joins. The air supply line 29 constitutes a gas dilution part of the present invention. An ozonolysis reactor 30 for decomposing ozone is interposed in the gas discharge line 28 on the downstream side of the junction.

In the thermal decomposition heating circulation line 11, the sulfuric acid waste liquid transfer line 3 branches on the upstream side of the circulation pump 20, and the downstream side of the sulfuric acid waste liquid transfer line 3 is connected to the distillation unit 2 side. Therefore, the upstream side of the thermal decomposition heating circulation line 11 is also used as the sulfuric acid waste liquid transfer line. The sulfuric acid waste liquid transfer line may be directly connected to the pyrolysis gas-liquid separation unit main body 10 without using part of the thermal decomposition heating circulation line 11.
A valve 5 is interposed in the sulfuric acid waste liquid transfer line 3, and the liquid level of the sulfuric acid waste liquid in the pyrolysis gas-liquid separation body 10 is detected at the liquid storage position of the pyrolysis gas-liquid separation body 10. A liquid level indicating controller 4 is provided for adjusting the opening degree of the valve 5.

  The distillation unit 2 includes a tower-shaped distillation unit main body 31 that stores the sulfuric acid waste liquid supplied from the sulfuric acid waste liquid transfer line 3, and the sulfuric acid waste liquid in the distillation unit main body 31 is taken out from the bottom side of the distillation unit main body 31 to be a distillation unit. A distillation heating circulation line 32 for returning the sulfuric acid waste liquid to the lower part of the main body 31, a reboiler 33 for heating the sulfuric acid waste liquid flowing in the distillation heating circulation line 32 interposed in the distillation heating circulation line 32, and distillation A condenser 34 that cools and condenses the vapor discharged from the main part 31 and a vacuum pump 35 that decompresses the inside of the distillation part main body 31 are provided. The reboiler 33 corresponds to the heating section for distillation of the present invention, the condenser 34 corresponds to the condensing section of the present invention, and the vacuum pump 35 corresponds to the decompression section of the present invention.

A downstream end of the sulfuric acid waste liquid transfer line 3 is connected to the middle stage of the distillation section main body 31, and a plurality of theoretical shelves 36 (shelf stages + reboiler stages) are arranged inside the distillation section main body 31. . A circulation pump 41 is interposed on the upstream side of the reboiler 33 in the distillation heating circulation line 32. The reboiler 33 heats the sulfuric acid waste liquid in the heating circulation line 32 for distillation by introducing a heating medium and exchanging heat. In this embodiment, steam is used as the heating medium. A steam supply line 42 to which steam is supplied is connected to the reboiler 32 so that heat can be exchanged, and a valve 43 is interposed in the steam supply line 42.
Connected to the liquid storage position of the distillation unit body 31 is a temperature indicating controller 44 that detects the temperature of the sulfuric acid waste liquid in the distillation unit body 31 and adjusts the opening of the valve 43.

  A steam discharge line 45 is connected to the top of the distillation section main body 31, and the other end of the steam discharge line 45 is connected to the condenser 34. A vacuum pump 35 is connected to the condenser 34 via an exhaust line 46 extending upward. The condenser 34 exchanges heat between the coolant and steam to obtain a condensate. A condensate discharge line 47 is connected to the drain side of the condenser 34, and the condensate discharge line 47 extends outside the system.

In the heating circulation line 32 for distillation, a concentrated liquid transfer line 37 is branched upstream of the circulation pump 41. Therefore, the upstream side of the distillation heating circulation line 32 is also used as the concentrate transfer line. In addition, you may connect a concentrate transfer line directly to the distillation part main body 31, without using a part of heating circulation line 32 for distillation.
The concentrated liquid transfer line 37 is provided with a transfer pump 38 and a valve 39 in this order from the upstream side to the downstream side. The liquid storage position of the distillation unit main body 31 has a liquid waste solution of sulfuric acid in the distillation unit main body 31. A liquid level indicating controller 40 for detecting the surface and adjusting the opening degree of the valve 39 is provided.

Next, the operation of the sulfuric acid waste liquid treatment apparatus will be described.
For example, an SPM waste liquid used in a batch cleaning process in a semiconductor manufacturing process is used as a processing target. However, the source of sulfuric acid waste liquid containing persulfuric acid is not particularly limited in the present invention.
In the pyrolysis gas-liquid separator 1, SPM waste liquid (hereinafter referred to as sulfuric acid waste liquid) is supplied through the waste liquid supply line 13, and is sprayed into the pyrolysis gas-liquid separator 1 by the spray nozzle 15. At this time, the flow rate of the sulfuric acid waste liquid flowing through the waste liquid supply line 13 is detected by the flow rate indicating controller 16, and the flow rate indicating controller 16 performs control to adjust the opening degree of the valve 14 so as to become a predetermined flow rate.

  The interior of the pyrolysis gas-liquid separation unit main body 10 is initially at normal pressure without being depressurized, and the sulfuric acid waste liquid stored in the pyrolysis gas-liquid separation unit main body 10 by the circulation pump 20 is passed through the thermal decomposition heating circulation line 11. Circulate. The SPM waste liquid flowing through the thermal decomposition heating circulation line 11 is heated by the reboiler 12 to a temperature at which it does not boil, for example, 150 ° C. or higher. The temperature of the sulfuric acid waste liquid is detected by the temperature indicating controller 23, and the amount of steam supplied from the steam supply line 21 to the reboiler 12 is determined by the opening degree of the valve 22 so that the temperature indicating controller 23 reaches a predetermined liquid temperature. Control to adjust. As the predetermined liquid temperature, a temperature of 150 ° C. to 180 ° C. and 10 ° C. lower than the boiling point of the sulfuric acid waste liquid is preferable.

When the sulfuric acid waste liquid in the pyrolysis gas-liquid separation unit main body 10 is heated, hydrogen peroxide contained in the sulfuric acid waste liquid is thermally decomposed, and oxygen gas and ozone gas are generated as decomposition gases. The generated gas containing the cracked gas is released from the liquid sulfuric acid waste liquid into the gas phase and separated in the pyrolysis gas-liquid separation unit main body 10.
On the other hand, the opening degree of the valve 5 is controlled by the liquid level indicating controller 4, and the liquid level of the sulfuric acid waste liquid in the pyrolysis gas-liquid separation unit main body 10 is maintained constant. By adjusting the liquid level, it is desirable that the liquid depth in the pyrolysis gas-liquid separation unit main body 10 is 0.7 or more, and more preferably 1.0 or more. The liquid depth can be adjusted by adjusting the liquid level by the liquid level indicating controller 18. Here, the liquid depth means the liquid depth (L) in the pyrolysis gas-liquid separator main body 10 / the inner diameter (d) of the pyrolysis gas-liquid separator main body 10.

In the pyrolysis gas-liquid separation unit body 10, the gas superficial velocity in the gas phase in the pyrolysis gas-liquid separation unit main body 10 is preferably 7 mm / second or less, and the liquid superficial velocity in the liquid phase is It is preferable that it is 5.5 mm / second or less. These can be adjusted by the supply flow rate of the sulfuric acid waste liquid from the waste liquid supply line 13, the heating temperature by the reboiler 12, the liquid level adjustment by the liquid level indicating controller 4, and the like.
Further, it is desirable that the sulfuric acid waste liquid stays in the pyrolysis gas-liquid separation unit main body 10 for preferably 5 minutes or longer, more preferably 10 minutes or longer. The residence time can be adjusted by the supply flow rate of the sulfuric acid waste solution from the waste solution supply line 13 and the waste solution flow rate in the valve 5 by the liquid level indicating controller 4.

The gas containing the cracked gas separated from the sulfuric acid waste liquid is separated from the entrained mist as much as possible by the mist separation plate 17, and is discharged out of the pyrolysis gas-liquid separation unit main body 10 through the gas discharge line 24. be introduced. In the condenser 25, the introduced gas is cooled to obtain a condensate. The condensate is returned to the pyrolysis gas-liquid separation unit main body 10 through the condensate circulation line 26.
The gas separated and cooled by the condenser 25 is discharged through the gas discharge line 28, and the air supplied from the air supply line 29 is mixed and diluted and cooled. Thereafter, ozone contained in the gas is decomposed in the ozone decomposition reactor 30 and discharged into the atmosphere.

The sulfuric acid waste liquid from which the gas containing the cracked gas has been separated has a hydrogen peroxide concentration of, for example, 0.002% by mass or less, and is extremely low, and the distillation part main body 31 of the distillation part 2 is passed through the sulfuric acid waste liquid transfer line 3. Continuously supplied.
The inside of the distillation unit main body 31 is depressurized by the vacuum pump 35 to, for example, 250 to 350 Torr.

In the distillation unit main body 31 to which the sulfuric acid waste liquid is supplied, the sulfuric acid waste liquid that accumulates in the tower bottom as the tower bottom liquid is circulated through the heating heating circulation line 32 for distillation by the circulation pump 41. The sulfuric acid waste liquid flowing through the distillation heating circulation line 32 is heated to a temperature at which the reboiler 33 can be distilled. The liquid temperature of the sulfuric acid waste liquid is detected by the temperature indicating controller 44, and the temperature indicating controller 44 adjusts the amount of steam supplied from the steam supply line 42 to the reboiler 33 by the valve 43 so as to obtain a predetermined liquid temperature. To control. As the predetermined liquid temperature, a temperature of 170 to 180 ° C. is suitable.
Note that the sulfuric acid waste liquid supplied from the pyrolysis gas-liquid separation unit 1 to the distillation unit main body 31 has a high temperature of, for example, about 180 ° C. due to the heat of reaction of thermal decomposition of hydrogen peroxide contained in the sulfuric acid waste liquid. Thus, the energy required for heating the sulfuric acid waste liquid can be reduced.

In the distillation unit main body 31, the sulfuric acid waste liquid is distilled while being heated by the reboiler 33.
In the sulfuric acid waste liquid, the cracked gas is sufficiently separated in the pyrolysis gas-liquid separation unit 1, and it is possible to avoid the distillation rate from being lowered due to the vacuum degree in the distillation unit main body 31 being lowered by the cracked gas or the like.

  The steam generated in the distillation unit main body 31 is discharged from the steam discharge line 45 and introduced into the condenser 34. In the condenser 34, the introduced steam is cooled by heat exchange with the cooling water to obtain a condensate. The condensate obtained in the condenser 34 is discharged from a condensate discharge line 47. The condensate is mainly composed of water, and its sulfuric acid concentration is low. For this reason, the condensate can be easily drained. Other gas components are exhausted by the vacuum pump 35 through the exhaust line 46.

  The column bottom liquid collected at the column bottom of the distillation unit main body 31 is concentrated with sulfuric acid as the distillation progresses, for example, with a sulfuric acid concentration of 80% by mass or more. The liquid level of the concentrated liquid is detected by the liquid level indicating controller 40, and the liquid level indicating controller 40 performs control to adjust the opening degree of the valve 39 so as to be a predetermined liquid level. The concentrate is transferred by the transfer pump 38 through the concentrate transfer line 37 and can be discarded or reused.

(Embodiment 2)
Next, a sulfuric acid waste liquid treatment apparatus according to another embodiment of the present invention will be described with reference to FIG.
The sulfuric acid waste liquid treatment apparatus of the present embodiment is obtained by preheating the sulfuric acid waste liquid supplied to the pyrolysis gas-liquid separation part by sensible heat of the concentrated liquid obtained in the distillation part and adiabatically compressing the vapor in the distillation part. The sensible heat of the condensate is used as a heat source for heating the sulfuric acid waste liquid of the distillation section main body to save energy in the entire apparatus. Other configurations are the same as those of the first embodiment, and will be described briefly.

  The pyrolysis gas-liquid separation unit 1a of this embodiment is a hermetic container-like pyrolysis gas-liquid separation unit main body 48 that contains sulfuric acid waste liquid, and heating that heats the sulfuric acid waste liquid supplied to the pyrolysis gas-liquid separation unit main body 48. Instrument 49. The heater 49 corresponds to the heating section for thermal decomposition of the present invention.

A waste liquid supply line 50 is connected to the sulfuric acid waste liquid introduction side of the pyrolysis gas-liquid separation unit main body 48, and the waste liquid supply line 50 is connected to the liquid feed pump 51, the preheater 52, and the heater 49 from the upstream side to the downstream side. Is installed. The preheater 52 corresponds to the preheating unit of the present invention.
The heater 49 heats the sulfuric acid waste liquid flowing through the waste liquid supply line 50 by heat exchange using steam as a heat source. The heater 49 detects the temperature of the sulfuric acid waste liquid flowing through the waste liquid supply line 50 on the downstream side of the heater 49 and adjusts the amount of steam supplied to the heater 49 to feedback control the heating temperature of the sulfuric acid waste liquid. May be.

A sulfuric acid waste liquid transfer line 3a is connected to the sulfuric acid waste liquid discharge side of the pyrolysis gas-liquid separator main body 48, and a distillation section 2a is connected to the transfer side of the sulfuric acid waste liquid transfer line 3a.
It should be noted that the liquid level in the pyrolysis gas-liquid separation unit main body 48 is detected, and the flow rate of the sulfuric acid waste liquid transferred in the waste liquid waste liquid transfer line 3a is controlled by a valve or the like so that the liquid level becomes a certain level. It may be.

  A gas discharge line 59 is connected to the top of the pyrolysis gas-liquid separation unit main body 48, and the gas discharge line 59 is connected to the condenser 60. The condenser 60 corresponds to the gas-liquid separation condenser of the present invention. A condensate discharge line 61 is connected to the condensate discharge side of the condenser 60, and a gas discharge line 62 is connected to the gas discharge side of the condenser 60. An air supply line 63 constituting a part of the gas dilution section of the present invention is joined to the gas discharge line 62.

  The distillation section 2a includes a tower-shaped distillation section main body 64 to which the sulfuric acid waste liquid transfer line 3a is connected, a reboiler 65 for heating the sulfuric acid waste liquid taken out from the distillation section main body 64, and vapor compression connected to the distillation section main body 64. Machine 66. The distillation part main body 64 corresponds to the distillation part main body of the present invention. The reboiler 65 corresponds to the heating section for distillation of the present invention. The vapor compressor 66 corresponds to the adiabatic compression part and the decompression part of the present invention.

The distillation section main body 64 may have a shelf. A column bottom liquid discharge line 68 having a liquid feed pump 69 interposed is connected to the column bottom of the distillation section main body 64. The liquid level in the distillation unit main body 64 is detected, and the flow rate of the sulfuric acid waste liquid transferred through the tower bottom liquid discharge line 68 is controlled by a valve or the like so that the liquid level becomes a certain level. Good.
The column bottom liquid discharge line 68 is connected to the preheater 52 on the downstream side of the liquid feed pump 69 so that heat exchange is possible, and the concentrated liquid is discharged out of the system on the downstream side.

  One end of a column bottom liquid circulation line 72 for taking out the column bottom liquid in the distillation unit main body 64 is connected to the column bottom of the distillation unit main body 64, and the column in the column bottom liquid circulation line 72 is connected to the side wall of the distillation unit main body 64. The other end of the tower bottom liquid circulation line 72 for returning the bottom liquid into the distillation section main body 64 is connected. A circulation pump 73 and a reboiler 65 are interposed in the tower bottom liquid circulation line 72.

A steam discharge line 74 is connected to the top of the distillation section main body 64, and the downstream end of the steam discharge line 74 is connected to the steam introduction side of the steam compressor 66.
A compressed steam discharge line 75 is connected to the compressed steam discharge side of the steam compressor 66, and a reboiler 65 is interposed in the compressed steam discharge line 75 so as to be able to exchange heat. In addition, the liquid temperature of the sulfuric acid waste liquid in the distillation part main body 64 is detected, the amount of compressed steam supplied to the reboiler 65 through the compressed steam discharge line 75 is adjusted so that the liquid temperature becomes a set value, and the distillation part main body 64 is adjusted. The liquid temperature inside may be controlled.

Next, the operation of the sulfuric acid waste liquid treatment apparatus will be described.
The sulfuric acid waste liquid containing hydrogen peroxide is fed through the waste liquid supply line 50 by the liquid feed pump 51, and after preheating by the preheater 52 and heating by the heater 49, the pyrolysis gas-liquid separation section of the pyrolysis gas-liquid separation section 1a. It is supplied to the main body 48.

In the preheater 52, the sulfuric acid waste liquid flowing in the waste liquid supply line 50 is preheated by exchanging heat with the concentrated liquid flowing in the tower bottom liquid discharge line 68. In the heater 49, the sulfuric acid waste liquid flowing through the waste liquid supply line 50 is heated by heat exchange with steam or the like.
By the heating by the preheater 52 and the heater 49, the sulfuric acid waste liquid is heated to a temperature at which it does not boil, for example, 150 ° C. to 180 ° C. and below the boiling point (for example, a temperature that is 10 ° C. or more lower than the boiling point). Since the preheater 52 uses the sensible heat of the concentrated liquid in the distillation unit main body 64, energy efficiency can be increased.

In the pyrolysis gas-liquid separation unit main body 48, hydrogen peroxide contained in the supplied sulfuric acid waste liquid is thermally decomposed to generate oxygen gas and ozone gas as decomposition gases. The generated gas containing the cracked gas is released into the gas phase from the liquid sulfuric acid waste liquid and separated in the pyrolysis gas-liquid separation unit main body 48.
In order to sufficiently perform the pyrolysis and gas separation, the gas superficial velocity in the gas phase in the pyrolysis gas-liquid separation section main body 48 is 7 mm / second or less, as in the first embodiment. The liquid superficial velocity in the liquid phase is preferably 5.5 mm / second or less. Further, the ratio L / d between the depth L of the sulfuric acid waste liquid in the pyrolysis gas-liquid separator main body 48 and the diameter d of the cross section of the pyrolysis gas-liquid separator main body 48 is preferably 0.7 or more. 1.0 or more is more preferable.

  The gas containing cracked gas and steam separated from the sulfuric acid waste liquid is discharged from the gas discharge line 59 and introduced into the gas introduction side of the condenser 60, cooled with cooling water or the like, and condensed with the steam. The condensed water is generated and discharged out of the system through the condensate discharge line 61. The gas from which the vapor is removed by the condensation is discharged through the gas discharge line 62, and the air supplied from the air supply line 63 is mixed, diluted, cooled, and released to the atmosphere.

The sulfuric acid waste liquid from which the gas has been separated in the pyrolysis gas-liquid separation part main body 48 is supplied to the distillation part main body 64 through the sulfuric acid waste liquid transfer line 3a.
Note that the flow rate of the sulfuric acid waste liquid transferred from the sulfuric acid waste liquid transfer line 3a is adjusted so that the sulfuric acid waste liquid stays in the pyrolysis gas-liquid separation unit main body 48 preferably for 5 minutes or more, more preferably for 10 minutes or more.

The inside of the distillation section main body 64 is decompressed by the vapor compressor 66 that also serves as the decompression section of the present invention, and is maintained in a decompressed state of, for example, 250 to 350 Torr.
In the distillation unit main body 64, the supplied sulfuric acid waste liquid is circulated through the tower bottom liquid circulation line 72 by the circulation pump 73 and heated by the reboiler 65.
In the distillation part main body 64, a part of sulfuric acid waste liquid evaporates by the heating by the reboiler 65, a vapor | steam is discharged | emitted through the vapor | steam discharge line 74, is suck | inhaled by the vapor | steam compressor 66, and is adiabatically compressed. In the steam compressor 66, high-temperature compressed steam is generated by adiabatic compression, supplied to the reboiler 65 through the compressed steam discharge line 75, and discharged as a condensate after heat exchange with the sulfuric acid waste liquid.
The sulfuric acid waste liquid in the distillation unit main body 64 is heated to 170 to 180 ° C. by the reboiler 65, and the sensible heat of the condensate obtained by adiabatic compression in the vapor compressor 66 is used as a heat source. Efficiency can be increased.

  The column bottom liquid collected at the column bottom of the distillation unit main body 64 is concentrated with sulfuric acid as the distillation progresses, for example, with a sulfuric acid concentration of 80% by mass or more. The concentrated liquid has a very low hydrogen peroxide concentration of, for example, 0.002% by mass or less. For this reason, it can be discarded at low cost as industrial waste.

(Embodiment 3)
Next, a sulfuric acid waste liquid treatment apparatus according to still another embodiment of the present invention will be described with reference to FIG.
In addition, about the structure similar to the said Embodiment 1, the same code | symbol is attached | subjected and description is abbreviate | omitted or simplified.
The sulfuric acid waste liquid treatment apparatus of this embodiment is provided with a plurality of stages of distillation sections after the pyrolysis gas-liquid separation section.

The sulfuric acid waste liquid treatment apparatus of the present embodiment has the same pyrolysis gas-liquid separation unit 1 as that of the first embodiment.
That is, the pyrolysis gas / liquid separation unit main body 10 provided in the pyrolysis gas / liquid separation unit 1 is supplied with SPM waste liquid (hereinafter referred to as sulfuric acid waste liquid) through a waste liquid supply line 13 and is sprayed by a spray nozzle 15 to generate a pyrolysis gas / liquid separation unit main body. 10 is sprayed. The inside of the pyrolysis gas-liquid separation unit main body 10 is not depressurized, and the sulfuric acid waste liquid is circulated in the heating circulation line 19 and is not boiled by the reboiler 12, for example, 150 ° C. to 180 ° C. Temperature lower than ℃).

Hydrogen peroxide is thermally decomposed in the pyrolysis gas-liquid separation unit main body 10, and the decomposition gas is gas-liquid separated. The liquid depth in the pyrolysis gas-liquid separation unit main body 10 is desirably 0.7 or more, and more desirably 1.0 or more.
In the pyrolysis gas-liquid separation unit main body 10, the gas superficial velocity is preferably 7 mm / second or less, and the liquid superficial velocity is preferably 5.5 mm / second or less.

The gas containing the cracked gas separated from the sulfuric acid waste liquid is discharged to the outside of the pyrolysis gas-liquid separator main body 10 through the gas discharge line 24 and cooled by the condenser 25 to obtain a condensed liquid. The condensate is returned to the pyrolysis gas-liquid separation unit main body 10 through the condensate circulation line 26.
The gas cooled by the condenser 25 is discharged through the gas discharge line 28, and the air supplied from the air supply line 29 is mixed and diluted and cooled, and the ozone contained in the gas is decomposed by the ozone decomposition reactor 30. Discharged into the atmosphere.

The sulfuric acid waste liquid obtained by thermally decomposing hydrogen peroxide and separating the cracked gas is introduced into the first distillation section 2-1 provided at the subsequent stage of the pyrolysis gas-liquid separation section 1.
The first distillation unit 2-1 includes a vacuum distillation unit main body 31a having a theoretical shelf 36a (shelf + reboiler).
The pressure in the vacuum distillation unit main body 31a is adjusted to a reduced pressure of 350 Torr by the vacuum pump 35a. The sulfuric acid waste liquid in the vacuum distillation unit main body 31a is circulated through the distillation heating circulation line 32a by the circulation pump 41a, and heated to 180 ° C., which is the temperature at which the reboiler 33a can be distilled. The steam generated in the distillation unit main body 31a is introduced into the condenser 34a through the steam discharge line 45a to obtain a condensate. The condensate is discharged from the condensate discharge line 47a, and other gas components are exhausted by the vacuum pump 35a through the exhaust line 46a.

  In the column bottom liquid of the distillation unit main body 31a, sulfuric acid is concentrated as the distillation proceeds, and the sulfuric acid concentration is concentrated to 80% by mass. The concentrated concentrate is transferred by the transfer pump 38a through the concentrate transfer line 37a while the transfer amount is adjusted by the valve 39a. The concentrated sulfuric acid solution can be discarded as industrial waste unless further concentration or the like is required at a later stage. Further, a part of the concentrated sulfuric acid solution may be discarded. Further, the sulfuric acid waste liquid to be concentrated is transferred to the subsequent distillation section.

A second distillation unit 2-2 having a shelf 36b (shelf + reboiler) is connected to the subsequent stage of the first distillation unit 2-1.
The pressure in the vacuum distillation unit main body 31b is reduced to 25 Torr by the vacuum pump 35b. The sulfuric acid waste liquid in the vacuum distillation section main body 31b is circulated through the distillation heating circulation line 32b by the circulation pump 41b and heated to 200 ° C., which is the temperature at which the reboiler 33b can be distilled. The sulfuric acid waste liquid is concentrated in the first distillation part 2-1, and a higher distillation temperature is selected.
The steam generated in the distillation section main body 31b is introduced into the condenser 34b through the steam discharge line 45b to obtain a condensate. The condensate is discharged from the condensate discharge line 47b, and other gas components are exhausted by the vacuum pump 35b through the exhaust line 46b.

The bottom liquid of the distillation unit main body 31b is concentrated with sulfuric acid as the distillation proceeds, and is concentrated to a sulfuric acid concentration of 96% by mass. If the sulfuric acid waste liquid contains a substance having a high boiling point other than sulfuric acid and hydrogen peroxide, it remains as an impurity in the concentrated liquid. Examples of the high boiling point substance remaining as impurities include resist residues and dopants.
The concentrated concentrate is transferred by the transfer pump 38b through the concentrate transfer line 37b while the transfer amount is adjusted by the valve 39b. In addition, if it is a use which can use low-purity sulfuric acid, the concentrated sulfuric acid solution can be reused as it is. A part of the concentrated sulfuric acid solution may be reused. Sulfuric acid waste liquor requiring high purity is transferred to a subsequent distillation section.

The third distillation unit 2-3 is connected to the subsequent stage of the second distillation unit 2-2.
The pressure in the vacuum distillation unit main body 31c is reduced to 25 Torr by the vacuum pump 35c. The sulfuric acid waste liquid in the vacuum distillation unit main body 31c is heated to 230 ° C., which is a temperature at which sulfuric acid can be distilled, by the heating unit 33c.
The steam generated in the distillation section main body 31c is introduced into the condenser 34c through the steam discharge line 45c to obtain a condensate. The condensate is discharged from the condensate discharge line 47c, and the other gas components are exhausted by the vacuum pump 35c through the exhaust line 46c. The condensate is a condensation of sulfuric acid evaporated by distillation, and has a sulfuric acid concentration of 96% by mass. Moreover, the high boiling point impurity substance remains in the column bottom liquid in the distillation part main body 31b, and the condensate becomes a high-purity sulfuric acid solution. Therefore, the condensate can be reused as a high-purity sulfuric acid solution.
The remaining tower bottom liquid (residue) is transferred through the waste liquid transfer line 37c and discarded. The amount is small and can be easily disposed of.

(Embodiment 4)
Next, the whole processing system provided with the pyrolysis gas-liquid separation part 100 and the distillation part 200 is demonstrated based on FIG.
The treatment system has a waste liquid tank 110 into which SPM waste liquid (hereinafter referred to as sulfuric acid waste liquid) is introduced, and the other end of the waste liquid supply line 111 connected to one end of the waste liquid tank 110 is the thermal decomposition of the pyrolysis gas-liquid separation unit 100. The gas-liquid separator main body 101 is connected. In the waste liquid supply line 111, a liquid feed pump 112, a valve 113, and a heater 114 are interposed in this order from the upstream side to the downstream side. The heater 114 is supplied with steam and exchanges heat between the steam and the sulfuric acid waste liquid.
The waste liquid supply line 111 is provided with a flow rate indicating controller 115 that detects the flow rate of the sulfuric acid waste liquid flowing through the waste liquid supply line 111 and controls the opening degree of the valve 113. Further, the waste liquid supply line 111 detects the temperature of the sulfuric acid waste liquid flowing through the waste liquid supply line 111 on the downstream side of the heater 114 and adjusts the opening degree of the valve 116 for adjusting the flow rate of steam supplied to the heater 114. A temperature indicating controller 117 to be controlled is provided.

A gas discharge line 120 provided with a valve 121 is connected to the top of the pyrolysis gas-liquid separation unit main body 101, and a condenser 123 is connected to the other end of the gas discharge line 120. The pyrolysis gas-liquid separation unit main body 101 is provided with a pressure indicating controller 122 that measures the pressure inside the pyrolysis gas-liquid separation unit main body 101 and adjusts the opening degree of the valve 121.
In the condenser 123, heat exchange is performed between the cooling water (CW) and the gas. A condensate discharge line 124 and a separated exhaust gas line 125 are connected to the condenser 123. The condensate discharge line 124 is connected to the condensate tank 240, and the separation exhaust gas line 125 is connected to the mixed gas exhaust line 127 by joining the air supply line 126, and the mixed gas is discharged through the mixed gas exhaust line 127. Release into the atmosphere (vent).

A waste liquid discharge line 102 provided with a valve 103 is connected to the pyrolysis gas-liquid separation unit main body 101, and the other end of the waste liquid discharge line 102 is connected to the distillation unit 200 side.
The pyrolysis gas-liquid separation unit main body 101 is provided with a liquid level indicating controller 104 that detects the liquid level of the sulfuric acid waste liquid inside and adjusts the opening degree of the valve 103.
The thermal decomposition gas-liquid separation part 100 is comprised by each said structure.

The distillation unit 200 includes a distillation unit main body 201 having a shelf 202, and a waste liquid discharge line 102 is connected thereto.
One end of a heating circulation line 203 for distillation is connected to the tower bottom of the distillation section main body 202, and the other end is connected to a lower portion of the distillation section main body 202. The distillation heating circulation line 203 is provided with a circulation pump (not shown) and a reboiler 204 in this order from the upstream side to the downstream side. A steam supply line to which steam is supplied is connected to the reboiler 204 so that heat can be exchanged, and a valve 205 is interposed in the steam supply line.
Connected to the liquid storage position of the distillation unit main body 201 is a temperature indicating controller 206 that detects the temperature of the sulfuric acid waste liquid in the distillation unit main body 201 and adjusts the opening of the valve 205.

  A steam discharge line 210 is connected to the top of the distillation unit main body 201, and the other end of the steam discharge line 210 is connected to a condenser 211. A vacuum pump 214 is connected to the condenser 211 via an exhaust line 213 extending upward. The condenser 211 obtains a condensate by exchanging heat between the coolant (CW) and the steam. A condensate discharge line 212 is connected to the drain side of the condenser 211, and a condensate tank 240 is connected to the condensate discharge line 212. A condensate drain line 241 is connected to the condensate tank 240 via a pump 242, and the condensate in the condensate tank 240 is drained out of the system through the condensate drain line 241 by the pump 242. Is done. The exhaust line 213 joins the mixed gas exhaust line 127 on the downstream side of the vacuum pump 214.

A concentrated liquid transfer line 220 is connected to the bottom of the distillation section main body 202. The concentrate transfer line 220 is provided with a transfer pump 221, a valve 222, and a cooler 224 in this order from the upstream side to the downstream side. The downstream end of the concentrate transfer line 220 is connected to the concentrate tank 230. ing. A concentrated liquid drain line 231 is connected to the concentrated liquid tank 230 via a pump 232.
In addition, a liquid level indicating controller 223 that detects the level of sulfuric acid waste liquid in the distillation unit main body 202 and adjusts the opening degree of the valve 222 is provided at the liquid storage position of the distillation unit main body 202.

Next, the operation of the sulfuric acid waste liquid treatment apparatus will be described.
SPM waste liquid (hereinafter referred to as sulfuric acid waste liquid) is introduced into a waste liquid tank 110 and supplied to a pyrolysis gas-liquid separation unit main body 101 through a waste liquid supply line 111 by a liquid feed pump 112. At this time, the flow rate of the sulfuric acid waste liquid flowing through the waste liquid supply line 111 is detected by the flow rate indicating controller 115, and the flow rate indicating controller 115 performs control to adjust the opening of the valve 113 so that a predetermined flow rate is obtained. Further, the sulfuric acid waste liquid flowing through the waste liquid supply line 111 is heated by the heater 114, and the temperature of the heated sulfuric acid waste liquid is detected by the temperature indicating controller 117. The temperature indicating controller 117 performs control to adjust the flow rate of steam supplied to the heater 114 according to the opening degree of the valve 116 so that the sulfuric acid waste liquid heated by the heater 114 has a predetermined liquid temperature. By this heating, the sulfuric acid waste liquid becomes a temperature of 150 ° C. to 180 ° C. and lower than the boiling point (for example, a temperature lower than the boiling point by 10 ° C. or more).

  The heated sulfuric acid waste liquid is introduced into the pyrolysis gas-liquid separation unit main body 101. In the pyrolysis gas-liquid separation unit main body 101, hydrogen peroxide is thermally decomposed, and the decomposition gas is gas-liquid separated. The liquid depth in the pyrolysis gas-liquid separation unit main body 101 is desirably 0.7 or more, and more desirably 1.0 or more. In the pyrolysis gas-liquid separation part main body 101, the gas superficial velocity is preferably 7 mm / second or less, and the liquid superficial velocity is preferably 5.5 mm / second or less.

The gas containing the cracked gas separated from the sulfuric acid waste liquid is discharged through the gas discharge line 120 and cooled by the condenser 123 to obtain a condensed liquid.
At this time, the pressure of the pyrolysis gas-liquid separation unit main body 101 is detected by the pressure indicating controller 122, and the opening degree of the valve 121 is adjusted so that the inside of the pyrolysis gas-liquid separation unit main body 101 is maintained at a predetermined pressure. Control to adjust. The predetermined pressure is preferably set to 0.2 MPa or less.
The condensate is stored in the condensate tank 240 through the condensate circulation line 124.
The gas cooled by the condenser 123 is discharged through the gas discharge line 125, the air supplied from the air supply line 126 is mixed and diluted and cooled, and is discharged (vented) into the atmosphere through the mixed gas exhaust line 127. The

  The sulfuric acid waste liquid obtained by thermally decomposing hydrogen peroxide and separating the decomposition gas is introduced to the distillation unit 200 side through the waste liquid discharge line 102. At this time, the liquid level in the pyrolysis gas-liquid separation unit main body 101 is detected by the liquid level indicating controller 104, and the liquid level indicating controller 104 controls the valve 103 so that the sulfuric acid waste liquid becomes a predetermined liquid level. The control which adjusts the opening degree of is performed.

The sulfuric acid waste liquid is supplied to the distillation section main body 201 of the distillation section 200 through the waste liquid discharge line 102. The distillation unit main body 201 is decompressed to 100 to 350 Torr by the vacuum pump 214. The sulfuric acid waste liquid in the vacuum distillation unit main body 201 is circulated through the distillation heating circulation line 203 and heated to 180 ° C. or higher, which is a temperature at which the reboiler 204 can be distilled. At this time, the temperature of the sulfuric acid waste liquid in the distillation unit main body 201 is detected by the temperature indicating controller 206, and the temperature indicating controller 206 supplies steam to the reboiler 204 so that the liquid temperature becomes a predetermined temperature. The control which adjusts the opening degree of the valve | bulb 205 to perform is performed.
The steam generated in the distillation unit main body 201 is introduced into the condenser 211 through the steam discharge line 210 to obtain a condensate. The condensate is discharged from the condensate discharge line 212 and stored in the condensate tank 240. Other gas components are sent to the mixed gas exhaust line 127 by the vacuum pump 214 through the exhaust line 213 and vented.

In the column bottom liquid of the distillation unit main body 201, sulfuric acid is concentrated as the distillation proceeds, and the sulfuric acid concentration is concentrated to 80% by mass or more. The concentrated concentrate is transferred through the concentrate transfer line 220 by the transfer pump 221. At this time, the liquid level of the distillation unit main body 201 is detected by the liquid level indicating controller 223, and the liquid level indicating controller 223 performs control for adjusting the opening degree of the valve 222 so that the liquid level becomes a predetermined level. Do.
The concentrated liquid transferred through the concentrated liquid transfer line 220 is cooled by cooling water (CW) in the cooler 224 and is stored in the concentrated liquid tank 230. Thereafter, the concentrate in the concentrate tank 230 is drained out of the system through the concentrate drain line 231 by the pump 232 as necessary.

  As described above, the present invention has been described based on the above embodiments, but the present invention is not limited to the contents of the above embodiments, and appropriate modifications can be made without departing from the scope of the present invention. is there.

Next, examples of the present invention will be described in comparison with comparative examples.
[Example 1]
An SPM waste liquid having a sulfuric acid concentration of 70% by mass and a hydrogen peroxide concentration of 2.0% by mass was treated continuously for 24 hours at a flow rate of 60 m ³ / day using the pyrolysis gas-liquid separation unit shown in FIG.
The pyrolysis gas-liquid separation part has a hollow pyrolysis gas-liquid separation part main body in which the tower top and the tower bottom are each formed into an outwardly convex curved surface, and between them is a cylindrical part. The inner diameter of the cylindrical part of the pyrolysis gas-liquid separation part main body is 1600 mm, the height of the cylindrical part is 3360 mm, of which the liquid phase depth in the cylindrical part filled with the waste liquid of SPM is 1120 mm, and the gas phase part in the cylindrical part Is 2240 mm in height.
The operating temperature was 150 ° C., and the pressure in the pyrolysis gas-liquid separation unit main body was normal pressure.

The flow rate of oxygen gas generated by the thermal decomposition of hydrogen peroxide is 26.4 Nm ³ / h, the gas superficial velocity is 5.6 mm / sec, which is a preferable upper limit of the gas superficial velocity of 7 mm / About 80% of the second.
If the number of circulation times of the waste liquid by the reboiler is five, the liquid superficial velocity of the waste liquid is 2.2 mm / second, which is about 40 of 5.5 mm / second, which is a preferable upper limit of the liquid superficial velocity. %Met.
The residence time of the waste liquid in the pyrolysis gas-liquid separation part main body was 54 minutes, and the decomposition rate of hydrogen peroxide was 100%. Further, there was almost no gas accompanying the waste liquid side, and the gas separation efficiency was almost 100%.

[Comparative Example 1]
After heating the SPM waste liquid having the same composition as in Example 1 to 150 ° C., gas-liquid separation was performed using a gas-liquid separation membrane made of Teflon (registered trademark). The flow rate of the waste liquid when supplying to the gas-liquid separation membrane was 1 L / min. As a result, the gas separation efficiency was 95%. In addition, it was found that the area of the gas-liquid separation membrane required for treating the waste liquid at a flow rate of 2.5 m ³ / hour is excessive, so that it is not practical as an apparatus for processing on an industrial scale.

(Example 2)
In the embodiment shown in FIG. 1, the process calculation was performed by changing the operation pressure in the distillation unit main body 31. The results are shown in Table 1.
It can be seen that if the operating pressure is 350 torr or less, the sulfuric acid concentration can be concentrated to 80% by mass or more.

Example 3
The following SPM waste liquid was treated using the system shown in FIG.
Composition of SPM waste liquid: sulfuric acid concentration 70 mass%, hydrogen peroxide concentration 2.0 mass%
Waste liquid temperature: 25 ° C
Waste liquid flow rate: 40 L / min (2.4 m ³ / hr)
Thermal decomposition gas-liquid decomposition part temperature 150 ℃
Distillation section: temperature 180 ° C, pressure 350 torr

  As a result, a liquid containing no hydrogen peroxide and having a sulfuric acid concentration of 80% by mass or more can be obtained from the bottom of the distillation section main body, and the industrial waste contractor can easily take it up.

(Comparative Example 2)
About the SPM waste liquid similar to Example 3, neutralization with the caustic soda aqueous solution was performed, and the normal waste liquid process diluted with industrial water was performed subsequently. As a result, while neutralizing with 35% by weight aqueous sodium hydroxide solution and reducing the hydrogen peroxide concentration to 0.2% by weight or less, it was diluted 10 times with industrial water, so the amount of waste liquid increased to 10 times the amount of the stock solution. .

DESCRIPTION OF SYMBOLS 1 Thermal decomposition gas-liquid separation part 1a Thermal decomposition gas-liquid separation part 2 Distillation part 2a Distillation part 2-1 1st distillation part 2-2 2nd distillation part 2-3 3rd distillation part 10 Pyrolysis gas-liquid separation part main body 11 Thermal decomposition heating circulation line 12 Reboiler 29 Air supply line 30 Ozone decomposition reactor 31 Distillation unit body 32 Distillation heating circulation line 33 Reboiler 34 Condenser 35 Vacuum pump 48 Pyrolysis gas-liquid separation unit main body 49 Heater 52 Preheater 63 Air supply line 64 Distillation unit body 66 Steam compressor 100 Pyrolysis gas-liquid separation unit 101 Pyrolysis gas-liquid separation unit body 114 Heater 200 Distillation unit 201 Distillation unit body 203 Distillation heating circulation line 204 Reboiler 214 Condenser

Claims (11)

A thermal decomposition heating unit that heats the sulfuric acid waste liquid containing hydrogen peroxide is decomposed, and the hydrogen peroxide contained in the sulfuric acid waste liquid is thermally decomposed by heating by the thermal decomposition heating unit. A pyrolysis gas-liquid separation unit for separating a gas-containing gas from the sulfuric acid waste liquid;
A distillation unit for heating the sulfuric acid waste liquid separated in the pyrolysis gas-liquid separation unit to heat the sulfuric acid waste liquid, and distilling the sulfuric acid waste liquid heated by the distillation heating unit under reduced pressure; Have
The heating section for thermal decomposition heats the sulfuric acid waste liquid containing hydrogen peroxide to a temperature not boiling and to a temperature of 150 ° C. or higher.
The pyrolysis gas-liquid separation unit separates the gas without reducing pressure,
The pyrolysis gas-liquid separation unit has a pyrolysis gas-liquid separation unit main body in which the sulfuric acid waste liquid stays and gas-liquid separation is performed, and a part of the sulfuric acid waste liquid in the pyrolysis gas-liquid separation unit main body And having a heating circulation line for thermal decomposition that returns to the main body of the thermal decomposition gas-liquid separation part after heating,
The sulfuric acid waste liquid treatment apparatus, wherein the thermal decomposition heating section is interposed in the thermal decomposition heating circulation line.   A gas-liquid separation condenser is connected to the gas discharge side of the pyrolysis gas-liquid separation section, and a condensate circulation line for circulating the condensate of the gas-liquid separation condenser to the pyrolysis gas-liquid separation section is provided. The sulfuric acid waste liquid treatment apparatus according to claim 1.   The distillation section has a distillation section main body in which the sulfuric acid waste liquid is evaporated, a decompression section for decompressing the inside of the distillation section main body, and a condensing section for condensing vapor evaporated in the distillation section main body. The sulfuric acid waste liquid treatment apparatus according to claim 1 or 2.   4. The sulfuric acid waste liquid treatment apparatus according to claim 3, wherein the distillation section main body has a shelf. The distillation section has an adiabatic compression section that adiabatically compresses steam generated by heating the sulfuric acid waste liquid by the distillation heating section to obtain a condensate,
The sulfuric acid waste liquid treatment apparatus according to any one of claims 1 to 4, wherein the heating unit for distillation uses sensible heat of the condensate as a part or all of a heat source.   The preheating part which preheats the said sulfuric acid waste liquid heated by the said pyrolysis gas-liquid separation part by the sensible heat of the sulfuric acid waste liquid concentrated by the said distillation part is provided in any one of Claims 1-5 characterized by the above-mentioned. The sulfuric acid waste liquid treatment apparatus as described.   7. A gas dilution part for diluting the gas by mixing air with the gas separated by the pyrolysis gas-liquid separation part and discharged from the pyrolysis gas-liquid separation part. The sulfuric acid waste liquid processing apparatus of any one of these.   The distillation section is provided in multiple stages, and the sulfuric acid waste liquid in which the concentration of sulfuric acid vapor in the gas phase is reduced by distillation in the distillation section on the front stage side is distilled in the distillation section on the rear stage side to obtain the concentrated sulfuric acid waste liquid. The sulfuric acid waste liquid treatment apparatus according to any one of claims 1 to 7. Without boiling the sulfuric acid waste solution containing hydrogen peroxide, heat the hydrogen peroxide in the sulfuric acid waste solution by heating to a temperature of 150 ° C. or higher, and decompress the gas containing the decomposition gas generated by the thermal decomposition. A pyrolysis gas-liquid separation step for gas-liquid separation from the sulfuric acid waste liquid without
The sulfuric acid waste liquid from which the gas has been separated is heated and distilled under reduced pressure, and the sulfuric acid waste liquid is concentrated.
In the pyrolysis gas-liquid separation step, the sulfuric acid waste liquid stays and gas-liquid separation is performed. Further, a part of the sulfuric acid waste liquid in the main body of the pyrolysis gas-liquid separation unit is taken out, heated, and then decomposed. A method for treating a sulfuric acid waste liquid, wherein the sulfuric acid waste liquid is returned to the body of the gas-liquid separator.   The sulfuric acid waste liquid treatment method according to claim 9, wherein in the distillation step, the distillation is performed under a reduced pressure of 250 to 350 Torr.   11. The sulfuric acid waste liquid treatment method according to claim 9, wherein the sulfuric acid waste liquid is concentrated to a sulfuric acid concentration of 80% by mass or more and 96% by mass or less by the distillation step.

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