JP2000308892A - Oxidation of metal in water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for oxidizing metallic ions and metallic compounds at a low running cost with good maintainability for treating waste water containing them. SOLUTION: Air and a bottom liquid are introduced to a pressure-reduced area generated at the rear side in the rotation direction of an impeller fixed to a drive shaft which rotates in water. Fine bubbles 37 of the air are generated by vortex caused by the rotation of the impeller and shearing force of the impeller to efficiently oxidize the metallic ions and metallic compounds in the waste water. As a result, a supply pressure of air can be made equivalent to only the liquid height (liquid pressure) so that the running cost can be reduced, and the maintenance and inspection can easily be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for efficiently oxidizing metal ions and metal compounds in wastewater containing metal ions and metal compounds.

[0002]

_2. Description of the Related Art In pickling of steel materials, pickling waste liquid containing ferrous ions (Fe ²⁺ ) and ferrous compounds (FeCl ₂ , FeSO ₄ ) is generated. As a method for treating the pickling waste liquid containing ferrous ions and a ferrous compound, waste hydrochloric acid treatment includes a roasting method (spray roasting, fluidized roasting), a heat evaporation method (substitution with sulfuric acid), and a neutralization treatment. Known methods of treating waste sulfuric acid include an iron sulfate crystal method and a neutralization treatment method.

[0003] Among the above, in the neutralization treatment method, wastewater is neutralized with an alkali agent to convert iron chloride or iron sulfate into ferrous ions and ferrous hydroxide, and then ferrous ions and ferrous hydroxide. Iron is forcibly oxidized with an oxidizing agent and recovered as ferric hydroxide. As the oxidizing agent in this case, there are air, pure oxygen, and ozone, and air is most commonly used.

[0004] Most of the oxidation of ferrous ions and ferrous hydroxide in wastewater using air is performed using a diffuser, and pressurized air generated by compressed air or a blower is used to remove pickling wastewater. Air is diffused from the bottom of the tank through the air diffuser through the air diffuser, oxidizing ferrous ions and ferrous hydroxide in the wastewater.

[0005] In the oxidation method using a diffuser tube, when the hole diameter of the diffuser nozzle is reduced, the problem of clogging of the diffuser nozzle occurs. Therefore, the size of bubbles blown out from the diffuser nozzle is limited, and inefficient gas-liquid contact occurs. It has become. For this reason, this method has a drawback that the efficiency of using oxygen in diffused air is low, a large amount of air is required, and the power applied to the compressed air, the blower and the like is large. Further, at the time of repairing the air diffuser nozzle, it is necessary to empty the pickling waste liquid tank, and there is a disadvantage that the maintenance property is poor.

[0006] Further, as another air diffusing device, a ventilation pipe having a gas inlet above and a plurality of gas ejection holes formed in a lower side portion, and a lower side of the ventilation pipe along the ventilation pipe. Gas-liquid mixing device having an impeller fixed to the section and a partition plate closing the lower opening of the ventilation pipe
No. 34436) has been proposed.

[0007]

The gas-liquid mixing device disclosed in Japanese Patent Publication No. 62-34436 discloses a rotary drive provided with a ventilation pipe, which also serves as a rotating shaft, extending from inside the liquid to outside the liquid. Since the apparatus is rotated by the machine, the size of the apparatus is increased according to the depth of the tank, and there is a problem that maintenance and inspection cannot be easily performed.

[0008] An object of the present invention is to solve the above-mentioned drawbacks of the prior art, and to provide an oxidizing method with low running cost and good maintainability in treating wastewater containing metal ions and metal compounds.

[0009]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for oxidizing a metal in water, comprising the steps of separating air and a liquid underneath into a negative pressure generated behind a rotating direction of an impeller fixed to a rotating shaft of a submerged rotary drive. The method is characterized in that vortices generated by the rotation of the impeller and the shear force of the impeller generate fine air bubbles to efficiently oxidize metal ions and metal compounds in wastewater.

As described above, the air and the lower liquid are introduced into the negative pressure generated on the rear side in the rotation direction of the impeller fixed to the rotation shaft of the submerged rotary drive, and the vortex generated by the rotation of the impeller is generated. By using an underwater air diffuser that generates fine air bubbles by the shearing force of the impeller, gas-liquid contact between the waste liquid and the air is enhanced, oxygen utilization efficiency is improved, and metal ions and metals in the waste water are improved. The compound can be oxidized efficiently. As a result, the air supply pressure is reduced to the liquid depth pressure of the wastewater treatment tank.
(Hydraulic pressure) only, and running costs can be reduced. In addition, since the main part is constituted by the submerged rotary drive and the impeller, maintenance and inspection can be easily performed.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the method for oxidizing a metal in water according to the present invention will be described with reference to FIG. The apparatus shown in FIG. 3 is an oxidation tank 31 for oxidizing wastewater mainly containing metal ions and metal compounds, a wastewater 32 in the oxidation tank 31,
It comprises a blower 33 for pressurizing air, and an air supply pipe 35 for guiding the air pressurized by the blower 33 to an underwater air diffuser 34.

For example, a pickling waste liquid obtained by pickling a steel material usually contains ferrous ions and ferrous ions at a level of several hundred ppm to several thousand ppm.
Iron compound is mixed. Such pickling waste liquid continuously flows into the oxidation tank 31 as raw water 36 after neutralization treatment with an alkali agent. On the other hand, the air pressurized by the blower 33 is continuously introduced into the air introduction pipe of the underwater air diffuser 34 via the air supply pipe 35. The pressure at which the air is introduced at this time is lower than the pressure corresponding to the water depth of the oxidation tank 31. If the pressure for introducing the air is higher than the pressure corresponding to the water depth, the action of the negative pressure generated in the liquid on the back side in the rotation direction of the impeller that rotates the underwater air diffuser 34 cannot be used.

[0013] The amount of air introduced at this time is determined by an underwater air diffuser.
It can be adjusted by 34 impeller dimensions and impeller rotation speed. When the underwater air diffuser 34 disposed at the bottom of the oxidation tank 31 is operated, air is continuously sucked into the waste liquid by the action of the negative pressure generated in the liquid on the back side in the rotation direction of the rotating impeller, and the blades Due to the vortex generated by the rotation of the car and the shearing force of the impeller, fine air bubbles 37 are generated, and the fine air bubbles 37 are ejected to the waste liquid 32. In the oxidation tank 31, gas-liquid contact between the waste liquid 32 and the air that has become the fine bubbles 37 occurs, and ferrous ions and ferrous compounds in the waste liquid 32 are efficiently oxidized by oxygen in the air. The oxidized treatment water 38 overflows from the oxidation tank 31 and is transported to a subsequent process.

The underwater air diffuser 34 used in the present invention includes:
The main part is composed of a submersible pump motor, an impeller, an air ejection path, a straightening plate, a suction hole, and an air supply pipe. The impeller is rotated by a motor for a submersible pump to cause the liquid to flow laterally from below. The air ejection path is provided, for example, in the impeller, and ejects air during negative pressure generated on the back surface in the rotation direction of the impeller. The current plate is located below the impeller, and guides liquid from the impeller to the side. The suction hole is provided in the current plate and guides the lower liquid to the impeller. The air supply pipe is provided on the current plate and supplies air from outside the liquid to the air ejection path.

[0015]

Example 1 An air diffusion tube shown in Table 1 or an underwater air diffuser shown in Table 1 was installed at the bottom of an oxidation tank having the specifications shown in Table 1, and neutralized with an alkaline agent as raw water. Ferrous ion and hydroxide
The pickling waste liquid containing iron is supplied, the air is supplied from the blower, and the air diffuser system of the conventional example that reduces ferrous ions and ferrous hydroxide in water, and the underwater air diffuser system of the present invention example An oxidation comparison test was performed. Table 2 shows the conditions and results of the oxidation test.
In addition, the ferrous iron concentration in water was measured using an atomic absorption spectrometer after the pretreatment.

As shown in FIG. 1, the air diffuser system of the comparative example has an air diffuser nozzle 2 having a hole diameter of 3 mm at the bottom of an oxidation tank 1, and supplies compressed air from outside the tank via a supply pipe 3 to the air diffuser nozzle. 2 and air was bubbled into the pickling waste liquid.

As shown in FIG. 2, the underwater air diffuser system according to the present invention employs a submersible pump motor 21, an impeller 22, an air
3, an underwater air diffuser 27, which is composed mainly of a current plate 24, a suction hole 25, and an air supply pipe 26, is installed at the bottom of the oxidation tank, and the submersible pump motor 21 is driven to rotate the impeller 22. At the same time, air is introduced into the air ejection passage 23 from outside the tank via the air supply pipe 26, and the air is continuously discharged into the waste liquid by the action of the negative pressure generated in the liquid on the back side in the rotation direction of the rotating impeller 22. The air was sucked into the nozzle, and the vortex generated by the rotation of the impeller and the shearing force of the impeller generated fine air bubbles, which were ejected into the waste liquid.

[0018]

【table 1】

[0019]

[Table 2]

[0020] As shown in Table 2, in the oxidation of the case 2 by the underwater aeration device system of the present invention, compared to the oxidation of the diffuser system of the comparative example of the case 1, the air flow rate was 1/3 or less. Ferrous iron is fully oxidized. The oxygen utilization rate was 15% in the diffusion tube type oxidation of the comparative example, whereas the oxygen utilization rate was 47% in the underwater diffusion apparatus type oxidation of the present invention example. In addition, the power consumption of the underwater air diffuser at the time of oxidation by the underwater air diffuser system of Case 2 of the present invention was very low power of 0.8 KW.

The method for oxidizing underwater metal according to the present invention can be judged to be extremely high in performance from the viewpoint of low running cost, when judged from the required air amount, oxygen utilization rate and power consumption of the underwater air diffuser.

[0022]

According to the method for oxidizing underwater metals of the present invention, an underwater air diffuser is disposed at the bottom of an oxidation tank, air is supplied to an air introduction pipe of the underwater air diffusion apparatus, and the underwater air diffusion is performed in the waste liquid of the oxidation tank. By operating the device, the air is continuously sucked into the waste liquid by the action of the negative pressure generated in the liquid behind the rotating impeller in the direction of rotation, and the vortex generated by the rotation of the impeller and the vortex Due to the shearing force, fine bubbles of air are generated, the gas-liquid contact between the waste liquid and the air is increased, and metal ions and metal compounds in the waste liquid can be efficiently oxidized by oxygen in the air. Therefore, as compared with the conventional method, it is possible to reduce the running cost and the like, and it is possible to improve the maintainability.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a diffuser system of a comparative example used in Examples.

FIG. 2 is a schematic explanatory view of an underwater air diffuser according to an example of the present invention used in an example.

FIG. 3 is a schematic explanatory view of a method for oxidizing a metal in water according to the present invention.

[Explanation of symbols]

 1, 31 Oxidation tank 2 Aeration nozzle 3 Supply pipe 21 Submersible pump motor 22 Impeller 23 Air ejection path 24 Rectifier plate 25 Suction hole 26, 35 Air supply pipe 27, 34 Underwater air diffuser 32 Wastewater 33 Blower 36 Raw water 37 Microbubbles 38 Treated water

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takanori Ueyama, 3rd, Oaza Hikari, Kashima City, Ibaraki Prefecture Sumitomo Metal Industries, Ltd. Kashima Works, Ltd. F-term in Kashima Works (reference) 4D050 AA13 AB52 AB55 BB01 BC10 BD02 BD03 BD06

Claims (1)

[Claims] 1. A method for oxidizing a metal in water in the treatment of wastewater containing metal ions and a metal compound, wherein air and air are mixed during a negative pressure generated on the back side in the rotation direction of an impeller fixed to a rotation shaft of a submerged rotary drive. Introduces liquid below and generates fine air bubbles by the vortex generated by the rotation of the impeller and the shearing force of the impeller, thereby efficiently oxidizing metal ions and metal compounds in wastewater. How to oxidize metals in water.