JP2018012860A - Method and facility for removing impurities in organic solvent - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and a facility for removing impurities in an organic solvent capable of efficiently and stably separating the organic solvent and the impurities.SOLUTION: There is provided a method for removing impurities in an organic solvent, which comprises: a neutralization step of supplying an organic solvent and a neutralizer to a neutralization tank 11: an oil-water separation step of oil-water separating a liquid discharged from the neutralization step into a heavy liquid and a light liquid; an acid dissolution step of supplying the heavy liquid and an acidic aqueous solution to a dissolution tank 13; and a step of temporarily storing an overflow liquid from the dissolution tank 13 in a relay tank 14 and then feeding the overflow liquid to the neutralization tank 11 with a pump 16, wherein the pump 16 is intermittently operated. The overflow liquid is hardly separated into an organic solvent and water and only a water component can be suppressed from being fed to the neutralization tank. Thus, the phase separability in oil-water separation is increased, enables efficient and stable separation of the organic solvent and impurities.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an impurity removal method and an impurity removal facility in an organic solvent. More specifically, the present invention relates to an impurity removal method and an impurity removal facility for removing impurities contained in an organic solvent used for solvent extraction.

  In the hydrometallurgical process that recovers the target metal from the sulfide, the nickel matte and nickel-cobalt mixed sulfide (MS: mixed sulfide), which is the raw material, are leached with chlorine, and the liquid purification process removes impurities from the obtained leachate. After that, nickel and cobalt are recovered in the electrolysis process.

As shown in FIG. 1, the leachate obtained from the leaching step is sent to the cobalt solvent extraction step after removing copper in the cementation step and removing impurities such as iron and arsenic in the deironing step. In the cobalt solvent extraction step, nickel and cobalt are separated by solvent extraction to obtain a nickel chloride solution (NiCl ₂ ) and a cobalt chloride solution (CoCl ₂ ). Impurities are further removed from the nickel chloride solution to obtain a high purity, which is sent to the nickel electrolysis process. In the nickel electrolysis process, electric nickel is produced by electrowinning. On the other hand, the cobalt chloride solution is further purified by removing impurities and sent to the cobalt electrolysis process. In the cobalt electrolysis process, electrolytic cobalt is produced by electrowinning.

  FIG. 2 shows details of the cobalt solvent extraction step. In FIG. 2, the broken line means the flow of the organic phase, and the solid line means the flow of the aqueous phase. In the cobalt solvent extraction step, a solution after the deironing step is supplied as an extraction starting solution. The extraction starting liquid is first supplied to the extraction stage, and cobalt is extracted into the organic phase. The aqueous phase after extraction is sent to the subsequent process as a nickel chloride solution. The organic phase of the extraction stage is sent to the washing stage, and after removing nickel chloride contained in a trace amount in the organic solvent with a cobalt chloride solution, it is sent to the back extraction stage. In the back extraction stage, cobalt extracted in an organic solvent using an acidic aqueous solution such as dilute hydrochloric acid is back extracted to the aqueous phase side to produce a cobalt chloride solution. The produced cobalt chloride solution is sent to a subsequent process.

  In the extraction stage, impurities such as zinc, iron and copper are extracted into the organic phase together with cobalt. Cobalt is back extracted into the aqueous phase in the back extraction stage, but the impurities remain in the organic solvent without being back extracted. When the impurity concentration of the organic solvent increases, there arises a problem that the amount of cobalt extracted in the extraction stage decreases or impurities are eluted in the nickel chloride solution or the cobalt chloride solution. Therefore, the organic solvent after back extraction is sent to a dezincing step to remove impurities such as zinc, iron and copper.

  In the dezincing step, a part of the organic solvent after the back extraction is extracted, and a neutralizing agent is added thereto for neutralization, thereby making the impurities in the organic solvent neutralized starch (neutralization step). Next, the liquid discharged from the neutralization step is separated into a heavy liquid (an aqueous phase containing neutralized starch) and a light liquid (an organic phase containing no neutralized starch) by a decanter (for example, Patent Document 1). ). The light liquid is sent to the activation step as an organic solvent from which impurities have been removed, and after an acidic aqueous solution is added, it is repeated in the extraction stage.

  The heavy liquid contains a trace amount of organic solvent. In addition, an organic solvent is incorporated in the neutralized starch contained in the heavy liquid. Therefore, the organic solvent is recovered by adding an acidic aqueous solution to the heavy liquid to dissolve the neutralized starch. A part of the dissolved metal element is supported on the organic solvent. By repeating the organic solvent in the neutralization step, the organic solvent is reused and the metal element is recovered.

  When the decanter is continuously operated in the dezincing step, the leakage of the organic solvent into the heavy liquid and the leakage of the neutralized starch into the light liquid are gradually increased, and the phase separation may be lowered, resulting in poor separation. If it does so, there exists a problem that an organic solvent and an impurity cannot be isolate | separated efficiently.

JP 2010-196162 A

  In view of the above circumstances, an object of the present invention is to provide an impurity removal method and an impurity removal facility in an organic solvent that can efficiently and stably separate an organic solvent and impurities.

The method for removing impurities in an organic solvent according to the first aspect of the present invention includes: a neutralization step of supplying an organic solvent containing impurities to a neutralization tank; and a neutralizing agent to produce a neutralized starch; An oil-water separation step of separating the discharged liquid into a heavy liquid containing the neutralized starch and a light liquid, and supplying the heavy liquid and the acidic aqueous solution to a dissolution tank; An acid dissolving step for dissolving, and a step of temporarily storing the overflow liquid in the dissolving tank in a relay tank, and then feeding the solution to the neutralizing tank with a pump, wherein the pump is operated intermittently. To do.
The impurity removal equipment in the organic solvent of the second invention is provided with an organic solvent containing impurities and a neutralizing agent, and a neutralization tank for producing a neutralized starch, and a liquid discharged from the neutralization tank. , An oil / water separator that separates oil into water into a heavy liquid containing the neutralized starch and a light liquid, a dissolution tank in which the heavy liquid and the acidic aqueous solution are supplied and dissolves the neutralized starch, and the dissolution tank A relay tank for temporarily storing the overflow liquid, and a pump for feeding the overflow liquid from the relay tank to the neutralization tank, wherein the pump operates intermittently.

  According to the present invention, since the pump operates intermittently, it is difficult for the overflow liquid to be separated into the organic solvent and water, and only the water component can be prevented from being fed to the neutralization tank. Therefore, the phase separation in oil / water separation is improved, and the organic solvent and impurities can be separated efficiently and stably.

It is a whole process figure of a hydrometallurgical process. It is a detailed process drawing of a cobalt solvent extraction process. It is a detailed process drawing of a dezincification process. It is explanatory drawing of an impurity removal installation.

Next, an embodiment of the present invention will be described with reference to the drawings.
As described above, the cobalt solvent extraction step of the hydrometallurgical process is provided with a dezincification step in order to remove impurities such as zinc, iron, and copper contained in the organic solvent after back extraction. The impurity removal method and impurity removal equipment in an organic solvent according to an embodiment of the present invention are preferably applied to such a dezincing step.

  Here, the organic solvent is not particularly limited, but in the solvent extraction method for separating nickel and cobalt, as the organic extractant, a phosphate ester-based acidic extractant represented by Cyanex272, TNOA (Tri-n-octylamine), An amine extractant typified by TIOA (Tri-i-octylamine) is used. In general, in the case of a chloride aqueous solution having a high concentration of metal ions and chloride ions in the liquid, an amine-based extractant is preferably used. Further, when a tertiary amine having excellent selectivity between nickel and cobalt is used as the amine-based extractant, a diluent composed of an aromatic hydrocarbon or an aliphatic hydrocarbon is mixed as necessary.

In FIG. 3, the detailed process of a dezincing process is shown. In FIG. 3, the broken line means the flow of the organic phase, and the solid line means the flow of the aqueous phase.
The organic solvent after back extraction is sent to the neutralization step. The organic solvent after back extraction contains impurities such as zinc, iron and copper. In the neutralization step, a neutralized starch is generated from the impurities in the organic solvent by adding a neutralizing agent to the organic solvent containing the impurities and neutralizing the neutralized agent. Here, the neutralizing agent is not particularly limited, but an alkaline aqueous solution such as an aqueous sodium hydroxide solution, an aqueous calcium hydroxide solution, or an aqueous sodium carbonate solution is used, and an aqueous sodium hydroxide solution is preferably used.

  The liquid discharged from the neutralization step is sent to the oil / water separation step. In the oil / water separation step, the liquid discharged from the neutralization step is separated into heavy and light liquids. Here, the heavy liquid is an aqueous phase containing a neutralized starch, and the light liquid is an organic phase containing no neutralized starch. The heavy liquid contains a trace amount of organic solvent.

  The light liquid discharged from the oil / water separation step is sent to the activation step as an organic solvent from which impurities have been removed, and after being added with an acidic aqueous solution, it is repeated in the extraction stage (see FIG. 2).

  The heavy liquid discharged from the oil / water separation step is sent to the acid dissolution step. In the acid dissolving step, the neutralized starch contained in the heavy liquid is dissolved by adding an acidic aqueous solution to the heavy liquid. Here, the pH of the heavy liquid is adjusted to 1.0 or less. Although acidic aqueous solution is not specifically limited, Hydrochloric acid etc. are used.

Overflow liquid and aqueous phase are discharged from the acid dissolution step. The overflow liquid contains an organic solvent component and a water component. A part of the dissolved metal element is supported on the organic solvent component contained in the overflow liquid. By repeating the overflow liquid in the neutralization step, the organic solvent is reused and the metal element is recovered. On the other hand, the aqueous phase discharged from the acid dissolving step is treated for drainage.
In the dezincing step, impurities in the organic solvent are removed as neutralized starch by the above treatment.

Next, the impurity removal equipment 1 will be described with reference to FIG.
The impurity removal equipment 1 includes a neutralization tank 11, an oil / water separator 12, a dissolution tank 13, and a relay tank 14.

  The neutralization tank 11 is supplied with an organic solvent containing impurities (an organic solvent after back extraction) and a neutralizing agent. In the neutralization tank 11, the neutralization process which produces | generates a neutralized starch from the impurity in an organic solvent is performed. The liquid discharged from the neutralization tank 11 is supplied to the oil / water separator 12 and separated into heavy and light liquids.

  A decanter, a settler or the like is used as the oil / water separator 12. A decanter is preferably used because continuous operation is possible. An example of the decanter is a screw decanter type centrifuge. The screw decanter centrifuge includes an outer cylinder having one end formed in a conical shape and a screw provided coaxially with the outer cylinder inside the outer cylinder. By rotating the outer cylinder and the screw at a high speed in the same direction, the organic solvent supplied into the outer cylinder is separated into a heavy liquid and a light liquid by centrifugal force. Further, the outer cylinder and the screw have a difference in rotational speed, and the heavy liquid is scraped with the screw by making the rotational speed of the screw slower than that of the outer cylinder, and the heavy liquid and the light liquid can be discharged separately.

  The dissolution tank 13 is supplied with the heavy liquid discharged from the oil / water separator 12 and the acidic aqueous solution. In the dissolution tank 13, an acid dissolution step for dissolving the neutralized starch contained in the heavy liquid is performed. As described above, the heavy liquid contains a trace amount of organic solvent. Moreover, the organic solvent taken in the neutralized starch elutes by dissolving the neutralized starch. By allowing the heavy liquid to stand still in the dissolution tank 13, the organic solvent contained in the heavy liquid floats on the liquid surface. Most of the heavy liquid in the dissolution tank 13 is the water phase W, and a slight amount of the organic phase O exists on the water phase W.

  A discharge pipe is provided near the bottom of the dissolution tank 13, and the aqueous phase W is discharged. The dissolution tank 13 is provided with an overflow tank 15. The overflow liquid overflowing from the dissolution tank 13 is supplied to the relay tank 14 via the overflow tank 15. Here, the liquid level of the dissolution tank 13 is set so that the total amount of the organic phase O overflows. That is, the interface between the organic phase O and the aqueous phase W is set above the liquid level that overflows. Therefore, the overflow liquid contains an organic solvent component and a water component.

  The overflow liquid in the dissolution tank 13 is temporarily stored in the relay tank 14. The relay tank 14 is provided with a bottom pipe whose opening end is disposed near the bottom of the relay tank 14. The bottom pipe is connected to the suction side of the pump 16, and the discharge side of the pump 16 is connected to the neutralization tank 11 via a pipe. By the operation of the pump 16, the overflow liquid can be sent from the relay tank 14 to the neutralization tank 11.

  By the way, when an actual operation is performed with the impurity removal facility 1, the phase separation of the oil / water separator 12 becomes unstable, and the processing capacity of the oil / water separator 12 may suddenly decrease during the operation. In this regard, the inventor of the present application has found that the phase separation of the oil / water separator 12 decreases at the timing when the water component of the overflow liquid supplied to the neutralization tank 11 increases.

  In actual operation, the supply amount of the organic solvent to the neutralization tank 11 is not constant but varies. When the supply amount of the organic solvent is small, the amount of the liquid supplied to the oil / water separator 12 is lowered, the phase separation property of the oil / water separator 12 is increased, and the amount of the organic solvent mixed in the heavy liquid becomes very small. . If it does so, the overflow liquid of the dissolution tank 13 will contain many water components, and an organic solvent component will become very few. In some cases, most of the overflow liquid supplied to the neutralization tank 11 becomes a water component. At this timing, the phase separation of the oil / water separator 12 decreases.

  When the phase separation property of the oil / water separator 12 decreases and the amount of the organic solvent mixed in the heavy liquid increases, the organic solvent component contained in the overflow liquid increases. If it does so, the quantity of the organic solvent repeated to the neutralization tank 11 will increase, and the phase separation property of the oil-water separator 12 will become high this time. By repeating the above, the phase separation of the oil / water separator 12 becomes unstable.

The inventor of the present application confirmed the effect of supplying water to the neutralization tank 11 by the following test.
First, the organic solvent after back extraction and the aqueous phase obtained from the dissolution tank 13 were mixed in a beaker at a ratio of 9: 1. The mixture was neutralized by adding a neutralizing agent, and then centrifuged (500 rpm, 1 minute) to confirm the sedimentation state of the neutralized starch. As a result, the height of the neutralized starch was about 90% of the whole.

  Next, the organic solvent after back extraction and the organic phase obtained from the dissolution tank 13 were mixed in a beaker at a ratio of 9: 1. The mixture was neutralized by adding a neutralizing agent, and then centrifuged (500 rpm, 1 minute) to confirm the sedimentation state of the neutralized starch. As a result, the height of the neutralized starch was about 60% of the whole.

  From the above, it was confirmed that when the aqueous phase was mixed with the organic solvent after back extraction, the neutralized starch was less likely to settle. When the state after adding the neutralizing agent was confirmed, the color mixed with the aqueous phase was light and the color mixed with the organic phase was dark. From this, it is presumed that when the aqueous phase is mixed, the particle size of the neutralized starch becomes small and it is difficult to settle. From this, it was confirmed that when the proportion of the water component of the overflow liquid supplied to the neutralization tank 11 is high, the phase separation of the oil / water separator 12 is lowered.

The present embodiment is characterized in that the pump 16 for feeding the overflow liquid is operated intermittently. That is, ON / OFF of the pump 16 is repeated at a predetermined cycle.
The overflow liquid is mixed with the organic solvent component and the water component by an impact when flowing into the relay tank 14. If it is left as it is, it is separated into an organic solvent and water. However, when the pump 16 is operated intermittently, a flow occurs in the overflow liquid and it is difficult to separate the organic solvent and water. As a result, it is possible to suppress that the organic solvent component and the water component are always mixed and supplied to the neutralization tank 11 and only the water component is fed to the neutralization tank 11. As a result, phase separation in oil / water separation is improved, and organic solvent and impurities can be separated efficiently and stably.

  What is necessary is just to set the period which turns ON / OFF the pump 16 so that the organic solvent component and the water component may be supplied to the neutralization tank 11 in the mixed state. The flow rate of the organic solvent after back extraction supplied to the neutralization tank 11 may be measured, and a cycle for turning on / off the pump 16 may be set based on the flow rate.

Example 1
An operation for removing impurities from the organic solvent after back extraction in the cobalt solvent extraction step was performed using the impurity removal equipment 1 shown in FIG. The pump 16 was switched on / off at intervals of 5 minutes.
As a result, in the operation for three months, it was possible to operate continuously without causing the malfunction of the oil / water separator 12. There was no need to stop the operation in addition to the regular inspection, which improved operational efficiency. Further, when the amount of the treatment liquid was increased during the operation, the maximum could be 45 L / min.

(Comparative Example 1)
In Example 1, the pump 16 was always turned on.
As a result, one month after the start of operation, the heavy liquid discharge port of the oil-water separator 12 was clogged with neutralized starch, requiring maintenance. Since it was necessary to stop the operation without going through regular inspections, the operation efficiency decreased. Further, when the amount of the treatment liquid was increased during operation, the maximum could be 23 L / min.

DESCRIPTION OF SYMBOLS 1 Impurity removal equipment 11 Neutralization tank 12 Oil-water separator 13 Dissolution tank 14 Relay tank 15 Overflow tank 16 Pump

Claims (2)

A neutralization step of supplying an organic solvent containing impurities to the neutralization tank and a neutralizing agent to produce a neutralized starch;
An oil-water separation step of separating the liquid discharged from the neutralization step into a heavy liquid containing the neutralized starch and a light liquid;
Supplying the heavy liquid and the acidic aqueous solution to a dissolution tank, and dissolving the neutralized starch;
A step of temporarily storing the overflow liquid of the dissolution tank in the relay tank and then feeding the solution to the neutralization tank with a pump;
A method for removing impurities in an organic solvent, wherein the pump is operated intermittently. An organic solvent containing impurities and a neutralizing agent, and a neutralization tank for producing a neutralized starch;
An oil-water separator that separates the liquid discharged from the neutralization tank into a heavy liquid containing the neutralized starch and a light liquid;
A dissolving tank in which the heavy liquid and the acidic aqueous solution are supplied to dissolve the neutralized starch;
A relay tank for temporarily storing the overflow liquid of the dissolution tank;
A pump for feeding the overflow liquid from the relay tank to the neutralization tank,
The apparatus for removing impurities in an organic solvent, wherein the pump operates intermittently.

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