JPS632149Y2 - - Google Patents

Description

[Detailed description of the invention] [Field to which the invention pertains] This invention relates to a treatment device for dithionic acid-containing wastewater such as blowdown water of a wet exhaust gas desulfurization equipment and regenerated concentrated wastewater generated during its ion exchange treatment. This invention relates to a treatment device that adds sulfuric acid to wastewater containing COD components mainly composed of dithionic acid and decomposes it by heating.

[Prior art]

Conventional JP-A-52-146962, JP-A-56-50637, etc., which mainly contain dithionic acid from blowdown water discharged from wet exhaust gas desulfurization equipment and recycled concentrated wastewater of ion exchange resin generated during ion exchange treatment. Add sulfuric acid to wastewater containing COD components to
1.5 or less, and heated at a temperature of 60 to 100℃.
A treatment method is disclosed in which COD components are decomposed and the generated sulfur dioxide gas is absorbed and removed using an alkaline agent.

Conventional thermal decomposition tanks are open to the atmosphere in order to perform thermal decomposition at temperatures below 100°C, so the decomposition rate is approximately 65-90%, and the exhaust gas mainly composed of sulfur dioxide gas SO ₂ generated during the decomposition reaction. It was necessary to process.

One method for treating exhaust gas is to send it back to the wet flue gas desulfurization equipment using a blower for reprocessing, but this method requires a long, corrosion-resistant duct and is limited by the operating time of the wet flue gas desulfurization equipment. There were some shortcomings.

[Purpose of invention]

The purpose of this invention is to provide a treatment device for dithionate-containing wastewater that eliminates the drawbacks of the prior art, improves the decomposition rate of dithionate ions, and eliminates the need for exhaust gas treatment.

[Key points of the idea]

This idea was developed by adding sulfuric acid to wastewater containing dithionate ions at a temperature of 100℃ or higher and at a temperature of 1.15 to 1.15℃.
A closed thermal decomposition tank that thermally decomposes at a pressure of 1.20Kg/cm ² , a neutralization absorption tank that absorbs the generated sulfite gas SO ₂ with an alkaline agent, and an oxidizing agent that uses the generated sulfite ion SO ₃ ^2- . The sulfuric acid ion is thus oxidized into a stable sulfate ion SO ₄ ^2- , and an oxidation tank.

[Example of idea]

FIG. 1 shows a sectional view of one embodiment of the dithionic acid-containing wastewater treatment apparatus according to this invention.

A wastewater supply pipe 2 is connected to the lower part of the closed type thermal decomposition tank 1, and a steam supply pipe 3 and a sulfuric acid supply pipe 4 for heating are connected to the wastewater supply pipe 2. Thermal decomposition tank 1
Several cutting boards 5 are provided inside. A treated water discharge pipe 6 is connected to the upper part of the thermal decomposition tank 1, and a pressure regulating valve 7 is provided in the middle to connect it to a neutralization absorption tank 8. The neutralization absorption tank 8 is provided with an alkali agent supply facility consisting of an alkali agent supply pipe 9, a PH controller 10, an alkali agent supply pump 11, and an alkali agent tank 12. The neutralization absorption tank 8 and the oxidation tank 14 are connected via an absorption treatment water pipe 14, and the oxidation tank 14 is connected to an air supply pipe 15.

Next, this effect will be explained.

Wastewater containing dithionic acid (S ₂ O ₆ ^2- ) is introduced into the lower part of the thermal decomposition tank 1 from the wastewater supply pipe 2.
Steam and sulfuric acid are added through the steam supply pipe 3 and the sulfuric acid supply pipe 4 in the introduction path. The wastewater rises in the thermal decomposition tank 1 in a flow indicated by a dotted line. At this time, the flow of wastewater flows upward from a macroscopic perspective, and since this flow is heated by steam, it naturally rises due to the difference in specific gravity. The decomposition reaction of dithionic acid (S ₂ O ₆ ^2- ) in the thermal decomposition tank 1 is shown as S ₂ O ₆ ^2- →SO ₄ ^2- +SO ₂ ↑ −(1), and this reaction depends on the amount of sulfuric acid added, The higher the temperature and pressure, the faster the process progresses. In this example, the amount of sulfuric acid added was 3.5v/v%, the temperature was 105°C, and the pressure was 1.15 to 1.20.
Kg/ ^cm2 .

The dithionic acid is decomposed, and the wastewater containing sulfuric acid ions SO ₄ ^2- and sulfur dioxide gas SO ₂ is discharged from the upper part of the thermal decomposition tank 1 through the treated water discharge pipe 6, and the pressure is reduced by the pressure regulating valve 7 to atmospheric pressure. Neutralization absorption tank 8
supplied to In the neutralization absorption tank 8, the PH in the tank is detected by the PH controller 10, and the supply pump 11 is operated so that the PH is maintained at 7 to 10. 9 and is supplied to the neutralization absorption tank 8. In the neutralization absorption tank 8, the wastewater containing sulfur dioxide gas SO ₂ reacts with an alkaline agent to become SO ₂ +2OH ^- →SO ₃ ^2- +H ₂ O -(2) as shown in the following equation, and sulfur dioxide gas SO ₂ becomes sulfite ion SO ₃ ^2- and is fixed in the liquid.

The treated water containing sulfite ions SO ₃ ^2- is introduced into the oxidation tank 14 through the absorption treatment water pipe 13 . Since air was used as the oxidizing agent in this embodiment, air bubbles were dispersed in the liquid through an air supply pipe 15 and an aeration nozzle. The reaction between sulfite ion SO ₃ ^2- and air is SO ₃ ^2- + 1/2O ₂ →SO ₄ ^2- −(3), and sulfite ion SO ₃ ^2- becomes a stable sulfate ion SO ₄ ² that does not undergo oxidation. -Changes ^to .

In this example, dithionic acid S ₂ O ₆ concentration 30000
CODMn50 of the treated water
mg/ or less, the decomposition rate was 99.8% and stable processing was possible.

[Variations and application examples of the idea]

In this embodiment, steam was used as a heating source for wastewater and was supplied directly to the wastewater supply pipe 2, but it may also be supplied to the lower part of the thermal decomposition tank 1. Further, as a heating source other than steam, for example, a heater may be wound around the outer periphery of the thermal decomposition tank 1, and the heating method is not limited. Further, the oxidizing agent used in the oxidizing tank 14 is not limited to air, and hydrogen peroxide, ozone, etc. can also be used.

[Effect of idea]

The dithionic acid-containing wastewater treatment device according to this invention has a closed thermal decomposition tank, so the heating temperature can be controlled.
At 100°C or higher, the decomposition rate can be improved, the reaction time can be shortened, the capacity of the thermal decomposition tank can be reduced, the amount of sulfuric acid consumed can be reduced, and sulfur dioxide gas is not released, making it possible to eliminate the need for an exhaust gas treatment device.

Furthermore, since a neutralization absorption tank and an oxidation tank are installed, stable sulfate ions can be produced.

[Brief explanation of the drawing]

FIG. 1 shows a cross-sectional view of one embodiment of the dithionic acid-containing wastewater according to this invention. 1... Thermal decomposition tank, 2... Waste water supply pipe, 3...
Steam supply pipe, 4... Sulfuric acid supply pipe, 5... Stainless steel board, 6... Treated water discharge pipe, 7... Pressure adjustment valve,
8... Neutralization absorption tank, 9... Alkali agent supply pipe, 1
0...PH controller, 11...Supply pump, 12...
Alkaline agent tank, 13... Absorption treatment water pipe, 14...
Oxidation tank, 15...Air supply pipe.

Claims (1)

[Scope of utility model registration request] In a treatment device for dithionic acid-containing wastewater that adds sulfuric acid to dithionic acid-containing wastewater and thermally decomposes it, sulfuric acid is added to the wastewater and the temperature is 100°C or higher and the pressure is
A closed thermal decomposition tank that maintains 1.15 to 1.20 Kg/ ^cm2 , a pressure regulating valve attached to the outlet of this closed thermal decomposition tank, and an alkali agent supply device connected to the closed thermal decomposition tank were attached. A treatment device for wastewater containing dithionic acid, comprising a neutralization absorption tank and an oxidation tank connected to the neutralization absorption tank and equipped with an oxidizing agent injection device.