JP2014168767A - Sulfide treatment apparatus within an alkaline region - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform a sulfide treatment within an alkaline region in acknowledgment of facts that, at times of sulfide treatments for executing sulfide addition controls by sensing generated hydrogen sulfide gases, sulfide reactions are induced at pH=7.0 or below for almost all metals, that, in cases of Co, Ni, and Mn, however, the metals are not completely removed even at pH=8.0, that the quantity of generated hydrogen sulfide diminishes as the reaction pH becomes higher, that, as Figure 1 demonstrates, S becomes HSat pH=9.0 or above and cannot be gasified, and that the sulfide treatment via the hydrogen sulfide gas control accordingly becomes impossible.SOLUTION: A portion of a solution within a reaction tank is proportionately fed into a hydrogen sulfide generator and then adjusted, by adding thereto an acid, at a fixed acidity in terms of the pH thereof measured via a pH meter. The concomitantly generated hydrogen sulfide gas is sensed by a hydrogen sulfide gas sensor, whereas a sulfurizing agent (NaHS, NaS, or HS gas) is added into the reaction tank so as to induce a gas-controlled sulfide reaction even within an alkaline region.

Description

The present invention relates to a sulfide treatment apparatus for detecting hydrogen sulfide in an alkaline region.

As a waste liquid treatment technique, a hydroxide method in which lime or sodium hydroxide is added is widely used. However, since the water content of the generated sludge is high and the metal content is low, it is often dumped in a landfill. Moreover, since the solubility product of metal hydroxide is relatively large, the metal concentration in the treated water does not decrease sufficiently. In particular, when a complexing agent (organic acid, ammonia, EDTA, etc.) coexists, advanced treatment is difficult. Therefore, it is widely practiced to add a polyvalent metal such as aluminum or ferric chloride to reduce the metal concentration in the treated water by coprecipitation. The sulfide method can be considered as an alternative to the hydroxide method, but this method is used only in part due to the bad smell of hydrogen sulfide and colloidalization. Recently, hydrogen sulfide gas sensor controlled sulfides have been developed (hereinafter referred to as NS method) and have been implemented on an industrial scale. In this method, hydrogen sulfide is basically not generated until the precipitation reaction of the metal sulfide is completed. After the reaction is completed, hydrogen sulfide is generated by the reaction between excess sulfur ions and hydrogen ions in the liquid. Is continuously detected by a gas sensor, and the signal is fed back to control the sulfidizing agent pump. However, when the liquid is alkaline, hydrogen sulfide gas is not generated, and thus this method cannot control the reaction. Development of a method capable of performing the NS method even on the alkali side is desired.

Table 03/020647

In the NS method, which detects the hydrogen sulfide gas generated and controls the addition of the sulfiding agent, the sulfide reaction is carried out at pH = 7.0 or less for most metals, but the NS method is almost applicable to Co, Ni and Mn. metal even pH = 8.0 which can not be completely removed, the presence form of S at pH = 9.0 or more as the reaction pH the less the amount of generated becomes higher with hydrogen sulfide to Figure 1 HS ^-, and the gas The sulfide treatment by hydrogen sulfide gas control is impossible. Development of a technique capable of performing the NS method in an alkaline region is a problem to be solved by the present invention.

A small portion of the solution in the reaction vessel is quantitatively sent to a hydrogen sulfide generator (hereinafter referred to as a vaporizer), acid is added, and the pH is adjusted to a constant acidity with a pH meter and stirred. As a stirring method, aeration or a stirrer may be used. The generated hydrogen sulfide gas is detected by a hydrogen sulfide gas sensor, and the addition pump or the actuator valve of the sulfiding agent (NaHS, Na ₂ S, H ₂ S gas) is controlled to add the sulfiding agent to the reaction tank. Thus, sulfide reaction is performed by gas control even in the alkaline region, and the concentration of treated water of the metal that reacts in the alkaline region such as Ni is reduced. In addition, the sulfide treatment can be performed without changing the pH of the solution.

  In the "sulfide treatment equipment using hydrogen sulfide generator" developed this time from the sulfide treatment flow sheet shown in Fig. 1, the solution containing metal from the T-1 raw water tank is sent to the T-2 reaction tank by the P1 raw water pump. The caustic soda is fed with a P2 caustic soda pump to a constant pH with a pH meter.

  A small portion of the reaction solution in the T2 reaction tank is quantitatively sent to the T3 vaporizer using the P4 sample pump, and the sulfuric acid is sent to the pH with the pH meter using the P3 sulfuric acid pump. And

  The reaction liquid acidified by the T-3 vaporizer is aerated and stirred by a circulating P5 air pump or agitated by a stirrer, and excess sulfide ions are gasified and sent to a hydrogen sulfide detection / control device through a pipe.

A P6 sulfiding agent pump is used to send the sulfiding agent to the reaction vessel so that the hydrogen sulfide detecting / controlling device has a constant concentration of hydrogen sulfide, thereby causing a reaction between the metal ions and the sulfiding agent. While reacting with the metal, basically no surplus S ²⁻ is present, and surplus S ²⁻ is generated from the end of the reaction. Therefore, by using a T3 vaporizer, the metal can be recovered even in the alkaline region. The NS method can be used for removal.

  Until now, in the NS method, hydrogen sulfide is not generated at all when the pH is 9 or more, and it has been impossible to perform treatment without changing the pH of the metal solution that reacts with sulfide in the alkaline region. Therefore, a small part of the reaction vessel solution is quantitatively sent to the vaporizer, acid is added to generate hydrogen sulfide gas at a constant pH (8 or less), and addition control of the sulfurizing agent is performed by the hydrogen sulfide gas detection control device. As a result, a metal solution such as Ni and Mn that causes a sulfide reaction mainly in the alkaline region can be NS-treated, and metal recovery and advanced treatment of Ni and Mn can be performed.

Form of S by pH Sulfide treatment flow sheet in alkaline region Relationship between vaporization liquid pH and vaporization rate Relationship between the amount of sulfiding agent added and hydrogen sulfide gas concentration Relationship between reaction pH, generated hydrogen sulfide gas concentration and residual Ni concentration

According to FIG. 1 showing the existence form of S due to pH, all forms of S become H ₂ S when pH is 5 or less, and HS ⁻ form when pH is 9 or more. Therefore, in order to cause a sulfide reaction at a concentration of hydrogen sulfide gas, the reaction pH must be 9 or less. In this case, there is a problem in recovering and removing the metal that reacts in the alkaline region.

FIG. 3 shows the relationship between the pH and the evaporation rate when changing the pH from 0.85 to 7.53 with a 20 mL / L vaporizer solution as S ²⁻ at a flow rate of 10 mL / min in a 100 mL vaporizer. Indicated. The relationship between pH and vaporization rate is negative, and the vaporization rate increases as pH decreases.
Therefore, it is necessary to keep the pH of the vaporized liquid constant. From the viewpoint of the vaporization rate, the vaporized liquid pH is preferably 5 or less.

FIG. 4 shows the relationship between the amount of sulfiding agent and the amount of generated hydrogen sulfide gas when the pH of the vaporized liquid is set to 2 in a 100 mL vaporizer at a flow rate of 10 mL / min and the S2 ^- concentration is changed. FIG. 4 reveals that there is a clear positive correlation between the amount of sulfiding agent and the amount of generated sulfurized water gas, and it is found that the amount of sulfiding agent added can be controlled by measuring the concentration of generated hydrogen sulfide.

  In FIG. 5, the initial Ni concentration was set to 1000 mg / L, the pH of the reaction vessel was changed from 9 to 11, and the sulfide reaction was made to have a reaction time of 1 hour. This is the relationship between the generated hydrogen sulfide gas concentration and the residual Ni concentration. From FIG. 5, when the reaction pH in the reaction tank is 9, the residual Ni concentration remains 2 mg / L. However, when the reaction pH is 10 or more, the minimum is 0.4 mg / L or less when the generated gas concentration is 7 ppm.

Claims (2)

  Sulfide treatment with vaporizer (hydrogen sulfide generator) for sulfide treatment in the alkaline region   The apparatus according to claim 1, wherein a pH meter is provided in the hydrogen sulfide generator in order to make the hydrogen sulfide generation reaction constant.

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