JP2016113703A - Neutralization method by wet type refining of nickel oxide ore - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently use a neutralizer, in a wet type test of nickel oxide ore.SOLUTION: A neutralization method for neutralizing a slurry containing sulfuric acid and impurities, generated in wet type refining of nickel oxide ore by using lime stone and lime, comprises: a first neutralization step for generating carbon dioxide gas by adding the lime stone to the slurry; a gas removal step for removing the carbon dioxide gas generated in the first neutralization step from the slurry; and a second neutralization step for adding the lime to the slurry from which the gas has been removed, for generating a hydroxide of the impurities. The first neutralization step is performed in a first neutralization processing tank, the gas removal step is performed in a second neutralization processing tank, and the second neutralization step is performed in a third neutralization processing tank, by providing in series, the first to three neutralization processing tanks. In the gas removal step, the neutralizer is not added, and a pH meter disposed between the second neutralization processing tank and the third neutralization processing tank, measures a pH of the slurry.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a neutralization method capable of efficiently using a neutralizing agent in a final neutralization step of hydrometallurgy that recovers nickel from nickel oxide ore. This application is a divisional application of Japanese Patent Application No. 2015-552700 and claims priority on the basis of Japanese Patent Application No. 2013-259179, and these applications are incorporated herein by reference.

  In recent years, high pressure acid leaching using sulfuric acid has attracted attention as a hydrometallurgical method for nickel oxide ore. Unlike the conventional dry smelting method, which is a conventional nickel oxide ore smelting method, this method does not include dry processes such as reduction and drying processes, and is a consistent wet process. Is advantageous. Further, in this method, a sulfide containing nickel and cobalt whose nickel quality is increased to about 50% by mass (hereinafter also referred to as “nickel / cobalt mixed sulfide” or “Ni / Co mixed sulfide”) is obtained. Has the advantage of being able to

  The hydrometallurgical method of nickel oxide ore using this high-pressure acid leaching method is an ore treatment step in which nickel oxide ore is pulverized to a predetermined size to form a slurry, and sulfuric acid is added to the ore slurry under high temperature and high pressure. A leaching process (high pressure acid), a pre-neutralization process for performing a neutralization (hereinafter also referred to as “pre-neutralization”) treatment before the leaching slurry is washed in multiple stages, and a pre-neutralization process. A solid-liquid separation process (hereinafter also referred to as “CCD process”) in which the leaching slurry thus obtained is subjected to solid-liquid separation into a leaching residue and a leachate containing an impurity element together with nickel and cobalt while being washed in multiple stages. A neutralization step of adjusting the pH of the leachate to separate neutralized starch containing impurity elements and obtaining a neutralized final solution containing zinc together with nickel and cobalt, and zinc by adding a sulfurizing agent to the neutralized final solution To form and separate sulfides A zinc removal step for obtaining a nickel recovery mother liquor, a nickel recovery step for forming a mixed sulfide containing nickel and cobalt by adding a sulfiding agent to the nickel recovery mother liquor, and a drain (filtrate) in the nickel recovery step And a final neutralization step in which the residue of the CCD step is mixed and neutralized (see, for example, Patent Document 1).

  Thus, in the hydrometallurgical method using high-pressure acid leaching to recover nickel from nickel oxide ore, the leaching residue generated in the leaching process and the filtrate after recovering nickel as a mixed sulfide in the sulfidation process are final. Neutralized in the neutralization step and discharged out of the system in a detoxified state.

  In the hydrometallurgical process, nickel oxide ore contains impurities such as magnesium, aluminum, and iron in addition to nickel, and is distributed to the leachate together with nickel in the leaching step. Here, in the wet process, the concentration of free sulfuric acid in the leachate is controlled in order to leach nickel more efficiently. The leachate contains about 50 g / l of free sulfuric acid. Nickel is recovered as a mixed sulfide through a sulfurization process that is a subsequent process of the leaching process. The filtrate contains impurities such as magnesium. These leach residues and filtrates are sent to the final neutralization process, completely neutralizing the free sulfuric acid, fixing impurities as hydroxides, and then transferred to the tailing dam (waste storage site). The completely detoxified supernatant is drained.

  In this final neutralization step, a plurality of neutralization tanks equipped with a stirrer are connected in series, leaching residue and filtrate are put into the first tank, and limestone is simultaneously added to adjust the pH to about 5-6. Then, the remaining free sulfuric acid is neutralized or a hydroxide such as iron is precipitated.

  Next, the slurry discharged from the first tank is supplied to the second tank, where slaked lime is added to the second tank and the pH is adjusted to about 9 to precipitate and remove remaining impurities such as Mg. . Then, in order to perform sufficient stirring and reaction, it supplies continuously from a 3rd tank to a 4th tank. Then, the slurry is finally supplied from the fourth tank to the tailing dam. As described above, in the final neutralization step, neutralization and impurity immobilization are performed in stages by adding neutralizers having different target achievement pH values in the first tank and the second tank, respectively.

  However, the impurity quality contained in the slurry containing the leach residue and filtrate sent to the final neutralization step is greatly affected by the impurity quality of the nickel oxide ore. In particular, when ore having a high nickel quality is used to increase the nickel treatment amount in the high-pressure acid leaching process, the quality of impurities such as Mg also increases. In addition, the quality of impurities may change rapidly due to the change of nickel oxide ore species. In such a case, it becomes difficult to control the pH and impurity concentration in the final neutralization step to be constant, and it is necessary to stop the discharge to the tailing dam, resulting in a situation where the load on the previous step is reduced. . Therefore, when the impurity quality rises rapidly, the adjustment of the amount of neutralizing agent in the final neutralization process cannot catch up, so it is possible to maintain the excessive addition of neutralizing agent while monitoring the analytical value and pH. In advance, operations such as dealing with fluctuations in impurity quality are performed. Therefore, in the final neutralization step, the amount of neutralizing agent used increases, and the ratio of the actual value to the theoretical value (hereinafter referred to as the basic unit) increases. Therefore, an efficient method of using a neutralizing agent is required in the final neutralization step.

JP-A-2005-350766

  The present invention has been proposed in view of such circumstances, and even if the impurity grade of the slurry containing sulfuric acid and impurities fluctuates in the final neutralization step, the neutralization agent is appropriately added without excessive addition. It aims at providing the neutralization method in the hydrometallurgy of the nickel oxide ore which can be summed and can reduce the basic unit of the neutralizing agent.

  The neutralization method in the hydrometallurgy of nickel oxide ore according to the present invention is a neutralization method in which a slurry containing sulfuric acid and impurities generated in the hydrometallurgy of nickel oxide ore is neutralized with limestone and slaked lime. A first neutralization step for adding carbon dioxide to generate carbon dioxide, a gas removal step for removing the carbon dioxide gas generated in the first neutralization step from the slurry, and adding slaked lime to the slurry after the gas removal step A second neutralization step for producing a hydroxide of impurities, the first neutralization step is performed in the first neutralization treatment tank, and the gas removal step is performed in the second neutralization treatment tank. In order to perform the second neutralization step in the third neutralization treatment tank, a first neutralization treatment tank to a third neutralization treatment tank are provided in series. PH meter provided between the second neutralization layer and the third neutralization layer without adding And measuring the pH of the slurry.

  Moreover, it is preferable that the neutralization method in the hydrometallurgy of nickel oxide ore according to the present invention blows compressed air into the slurry at least in the gas removal step.

  In the present invention, after neutralization in the final neutralization step in the hydrometallurgy of nickel oxide ore, after removing carbon dioxide generated by adding limestone to the slurry from the slurry, by neutralizing with slaked lime, The remineralization of slaked lime can be suppressed, and the added slaked lime can be used effectively. Thereby, in this invention, even if it does not add a neutralizing agent excessively, a neutralization process can be performed appropriately and the basic unit of a neutralizing agent can be reduced.

FIG. 1 is a process diagram of a hydrometallurgical method using high pressure acid leaching of nickel oxide ore. FIG. 2 is a configuration diagram of the neutralization processing apparatus in the final neutralization step. FIG. 3 is a diagram showing changes in the amount of compressed air blown in operation example 1 and operation example 2.

  Hereinafter, the neutralization method in the hydrometallurgy of nickel oxide ore according to the present invention will be described in detail with reference to the drawings. Note that the present invention is not limited to the following embodiments, and various modifications can be made without departing from the gist of the present invention.

  The neutralization method in the hydrometallurgy of nickel oxide ore is the final step in order to discharge the wet residue generated in the hydrometallurgy by high pressure acid leaching and the filtrate after nickel recovery to the outside of the hydrometallurgical plant. It is the neutralization method in the last neutralization process to neutralize.

  First, the wet smelting of nickel oxide ore will be described. The hydrometallurgy of nickel oxide ore is a hydrometallurgical method of leaching and recovering nickel and cobalt from nickel oxide ore using, for example, a high-pressure acid leaching method (HPAL method).

  In FIG. 1, an example of the process (process) of the hydrometallurgical method by the high pressure acid leaching method of nickel oxide ore is shown. As shown in FIG. 1, a leaching step S1 in which sulfuric acid is added to a slurry of nickel oxide ore and leaching is performed under high temperature and high pressure, and preliminary neutralization is performed to adjust the pH of the obtained leaching slurry to a predetermined range. Neutralization step S2, solid-liquid separation step S3 for obtaining a leachate containing impurity elements together with nickel and cobalt by separating the residue while washing the pH-adjusted leach slurry, and adjusting the pH of the leach liquor. Neutralizing step S4 for separating the neutralized starch containing zinc to obtain a neutralized final solution containing zinc together with nickel and cobalt, and adding a sulfurizing agent to the neutralized final solution to produce zinc sulfide, A zinc removal step S5 for obtaining a nickel recovery mother liquor containing nickel and cobalt by separating and removing sulfides, and a mixed sulfide containing nickel and cobalt by adding a sulfurizing agent to the nickel recovery mother liquor And a nickel recovery step S6 described form. Furthermore, this hydrometallurgy method has a final neutralization step S7 for recovering and detoxifying the leaching residue separated in the solid-liquid separation step S3 and the filtrate discharged in the nickel recovery step S6.

(1) Leaching step In the leaching step S1, a leaching process using, for example, a high-pressure acid leaching method is performed on the nickel oxide ore. Specifically, sulfuric acid is added to ore slurry obtained by pulverizing nickel oxide ore as raw material, and the ore slurry is stirred by pressurization under a high temperature condition of 220 to 280 ° C. A leach slurry consisting of the residue is formed.

  Nickel oxide ores used in the leaching step S1 are mainly so-called laterite ores such as limonite or saprolite ores. Laterite ore usually has a nickel content of 0.8 to 2.5% by weight, and is contained as a hydroxide or siliceous clay (magnesium silicate) mineral. Further, the iron content is 10 to 50% by weight and is mainly in the form of trivalent hydroxide (goethite), but partly divalent iron is contained in the siliceous clay. In the leaching step S1, in addition to such a laterite ore, an oxidized ore containing valuable metals such as nickel, cobalt, manganese, and copper, for example, a manganese nodule that exists in the deep sea bottom is used.

  In the leaching process in the leaching step S1, a leaching reaction represented by the following formulas (1) to (3) and a high-temperature thermal hydrolysis reaction represented by the following formulas (4) and (5) occur, and nickel, cobalt, etc. Leaching as a sulfate and immobilizing the leached iron sulfate as hematite. However, since the immobilization of iron ions does not proceed completely, the leaching slurry obtained usually contains divalent and trivalent iron ions in addition to nickel, cobalt and the like.

・ Leaching reaction MO + H ₂ SO ₄ → MSO ₄ + H ₂ O (1)
(In the formula, M represents Ni, Co, Fe, Zn, Cu, Mg, Cr, Mn, etc.)
2Fe (OH) ₃ + 3H ₂ SO ₄ → Fe ₂ (SO ₄ ) ₃ + 6H ₂ O
... (2)
FeO + H ₂ SO ₄ → FeSO ₄ + H ₂ O (3)

High temperature thermal hydrolysis reaction 2FeSO ₄ + H ₂ SO ₄ + 1 / 2O ₂ → Fe ₂ (SO ₄ ) ₃ + H ₂ O
... (4)
Fe ₂ (SO ₄ ) ₃ + 3H ₂ O → Fe ₂ O ₃ + 3H ₂ SO ₄ (5)

  The amount of sulfuric acid added in the leaching step S1 is not particularly limited, and an excessive amount that allows iron in the ore to be leached is used. In the leaching step S1, the pH of the obtained leachate is adjusted to 0.1 to 1.0 from the viewpoint of the filterability of the leaching residue containing hematite produced in the subsequent solid-liquid separation step S3. It is preferable to do.

(2) Pre-neutralization step In the pre-neutralization step S2, the pH of the leaching slurry obtained in the leaching step S1 is adjusted to a predetermined range. In the leaching step S1 in which the leaching process by the high-pressure acid leaching method described above is performed, excess sulfuric acid is added from the viewpoint of improving the leaching rate. Therefore, the obtained leaching slurry contains free sulfuric acid (excess sulfuric acid not involved in the leaching reaction, hereinafter also referred to as free sulfuric acid), and its pH is very low. Therefore, in the pre-neutralization step S2, the pH of the leaching slurry is adjusted to a predetermined range so that the washing is efficiently performed at the time of the multi-stage washing in the next solid-liquid separation step S3.

  Specifically, it is preferable that the leaching slurry to be subjected to the cleaning treatment has a pH adjusted to about 2-6. When the pH is lower than 2, a cost for making the subsequent process equipment acid-resistant is required. On the other hand, if the pH is higher than 6, nickel leached in the leaching solution (slurry) may remain as a residue in the washing process (precipitate) and the washing efficiency may be reduced.

  Although it does not specifically limit as a pH adjustment method, For example, it can adjust to a predetermined range by adding neutralizing agents, such as a calcium carbonate slurry.

(3) Solid-liquid separation step In the solid-liquid separation step S3, a leaching solution containing zinc as an impurity element in addition to nickel and cobalt while washing the leached slurry after pH adjustment obtained in the preliminary neutralization step S2 in multiple stages ( Crude nickel sulfate aqueous solution) and leaching residue are separated.

  In the solid-liquid separation step S3, for example, after the leaching slurry is mixed with the cleaning liquid, the solid-liquid separation process is performed by the solid-liquid separation equipment such as a thickener using the flocculant supplied from the flocculant supply equipment. Specifically, the leaching slurry is first diluted with a cleaning liquid, and then the leaching residue in the slurry is concentrated as a thickener sediment. Thereby, the nickel content adhering to the leaching residue can be reduced according to the degree of dilution.

  In this solid-liquid separation step S3, it is preferable to use solid-liquid separation tanks such as thickeners connected in multiple stages and perform solid-liquid separation while washing the leach slurry in multiple stages. Specifically, as the multistage cleaning method, for example, a continuous countercurrent cleaning method (CCD method: Counter Current Decantation) in which the cleaning liquid is brought into contact with the leaching slurry in a countercurrent manner can be used. Thereby, the cleaning liquid newly introduced into the system can be reduced, and the recovery rate of nickel and cobalt can be improved to 95% or more.

  Although it does not specifically limit as a washing | cleaning liquid (washing water), It is preferable to use what does not contain nickel and does not affect a process. Among them, it is preferable to use an aqueous solution having a pH of 1 to 3. When the pH of the cleaning liquid is high, a bulky aluminum hydroxide is produced when aluminum is contained in the leachate, which causes poor settling of the leach residue. From this, as a washing | cleaning liquid, Preferably, it is good to repeatedly utilize the low pH (pH is about 1-3) filtrate obtained by nickel recovery process S6 which is a post process.

  The flocculant to be used is not particularly limited, and for example, an anionic flocculant can be used.

(4) Neutralization step In the neutralization step S4, the pH of the leachate (crude nickel sulfate aqueous solution) separated in the solid-liquid separation step S3 is adjusted, and the neutralized starch containing the impurity element is separated, and nickel and A neutralized final solution containing zinc together with cobalt is obtained.

  Specifically, in the neutralization step S4, the pH of the resulting neutralized final solution is 4 or less, preferably 3.0 to 3.5, more preferably 3.1 while suppressing oxidation of the separated leachate. A neutralizing agent such as calcium carbonate is added to the leachate so as to be 3.2 to form a neutralized final solution and a neutralized starch slurry containing trivalent iron as an impurity element. In the neutralization step S4, impurities such as trivalent iron ions and aluminum ions remaining in the solution are removed as neutralized starch in this way, thereby generating a neutralized final solution that is the source of the nickel recovery mother liquor. .

(5) Dezincing step In the dezincing step S5, a zinc sulfide is generated by adding a sulfiding agent such as hydrogen sulfide gas to the neutralized final solution obtained from the neutralizing step S4 and subjecting it to a sulfiding treatment. The zinc sulfide is separated and removed to obtain a nickel recovery mother liquor (dezincing final solution) containing nickel and cobalt.

  Specifically, for example, a neutralized final solution containing zinc and nickel and cobalt is introduced into a pressurized container, and hydrogen sulfide gas or the like is blown into the gas phase, so that zinc is made against nickel and cobalt. Selectively sulfides to produce zinc sulfide and nickel recovery mother liquor.

(6) Nickel recovery step In the nickel recovery step S6, a sulfur recovery agent such as hydrogen sulfide gas is blown into the nickel recovery mother liquor obtained by separating and removing zinc, which is an impurity element, as zinc sulfide in the zinc removal step S5. A sulfurization reaction is caused to produce a sulfide containing nickel and cobalt (a nickel-cobalt mixed sulfide) and a filtrate.

  The mother liquor for nickel recovery is a sulfuric acid solution in which impurity components are reduced through the leaching step S1, the neutralization step S4, and the dezincing step S5. The nickel recovery mother liquor may contain several g / L of iron, magnesium, manganese, etc. as impurity components. These impurity components are sulfides with respect to nickel and cobalt to be recovered. As a result, the resulting sulfide is not contained.

(7) Final neutralization step The final neutralization step S7 includes leaching residues containing free sulfuric acid transferred from the solid-liquid separation step S3 and impurities such as magnesium, aluminum, and iron transferred from the nickel recovery step S6. Neutralize the filtrate. The final neutralization step S7 is neutralization performed to discard the slurry to the outside from the wet smelting process, and refers to a neutralization step performed at the end of the wet smelting process. The leaching residue and filtrate are adjusted to a predetermined pH range by the neutralizing agent and become a waste slurry (tailing). The tailing produced | generated in this reaction tank is transferred to a tailing dam (waste storage place).

  Specifically, in the final neutralization step S7, the free sulfuric acid contained in the leaching residue is completely neutralized, the impurities contained in the filtrate are fixed as hydroxides, and the slurry containing the impurity hydroxides is removed from the tailing dam. To discharge.

  The final neutralization step S7 is a slurry containing a leaching residue containing free sulfuric acid transferred from the solid-liquid separation step S3 and a filtrate containing impurities such as magnesium, aluminum and iron transferred from the nickel recovery step S6. A first neutralization step in which limestone is added to neutralize sulfuric acid to generate a hydroxide of some impurities; a gas removal step in which carbon dioxide gas generated in the first neutralization step is removed from the slurry; And a second neutralization step in which slaked lime is added to the slurry after the gas removal step to generate hydroxide of remaining impurities.

  In the final neutralization step S7, for example, the leaching residue and the filtrate are neutralized by the neutralization apparatus 1 as shown in FIG. Specifically, the neutralization processing apparatus 1 has a plurality of neutralization processing tanks 2 to 5 connected in a single series.

  The first neutralization tank 2 is the first neutralization tank in a single series. The first neutralization treatment tank 2 is supplied with leaching residue and filtrate to be neutralized, added limestone to the slurry containing the leaching residue and filtrate, and neutralized the remaining free sulfuric acid, It is a tank which performs the 1st neutralization process which precipitates the hydroxide of impurities, such as iron. The 1st neutralization processing tank 2 is provided with the supply port which supplies a leaching residue and filtrate in a tank in the upper part, and supplies a neutralizing agent. The first neutralization treatment tank 2 is provided with an air supply port for supplying compressed air into the tank.

  The second neutralization treatment tank 3 is fed with the slurry to which limestone is added in the first neutralization treatment tank 2, and completes the neutralization reaction of free sulfuric acid and the formation and precipitation of hydroxides such as iron. And a gas removal step for removing carbon dioxide generated by the neutralization reaction.

  The first neutralization treatment tank 2 and the second neutralization treatment tank 3 are connected to each other at, for example, an overflow tank or an overflow pipe 6 at the upper end portion of the first neutralization treatment tank 2. Slurry is supplied to the treatment tank 3. The overflow pipe 6 is provided with a pH meter for measuring the pH of the slurry supplied to the second neutralization tank 3. In the final neutralization step S7, the pH of the slurry supplied to the second neutralization treatment tank 3 can be measured, and the presence or absence of carbon dioxide in the slurry supplied can be estimated from the pH value. Further, the second neutralization treatment tank 3 is provided with a pH meter (not shown) for measuring the pH of the slurry accommodated in the second neutralization treatment tank 3. In the final neutralization step S7, since the first neutralization reaction can be sufficiently advanced in the second neutralization treatment tank 3, the pH in a stable state after adding limestone can be confirmed. Thereby, in the 2nd neutralization processing tank 3, it is not necessary to add limestone excessively, and the usage-amount of limestone can be reduced. Therefore, in the 2nd neutralization processing tank 3, pH of the slurry in a tank is managed.

  The third neutralization treatment tank 4 is supplied with the slurry in which the first neutralization reaction and the gas removal step are completed in the second neutralization treatment tank 3. The 3rd neutralization processing tank 4 is a tank which performs the 2nd neutralization process which slaked lime is added to a slurry and produces | generates and precipitates the hydroxide of remaining impurities, such as magnesium. The second neutralization tank 3 and the third neutralization tank 4 are connected to each other by, for example, an overflow pipe 7 at the upper end of each other, and the second neutralization tank 3 to the third neutralization tank 4. The slurry is supplied to The overflow pipe 7 is provided with a pH meter for measuring the pH of the slurry supplied to the third neutralization treatment tank 4. In the final neutralization step S7, by measuring the pH of the slurry supplied to the third neutralization treatment tank 4, it can be confirmed from the pH value whether carbon dioxide in the slurry has been removed. .

  The fourth neutralization treatment tank 5 is supplied with the slurry in which the remaining impurity hydroxide is generated in the third neutralization treatment tank 4. The 3rd neutralization processing tank 4 and the 4th neutralization processing tank 5 are connected by the overflow pipe | tube 8 etc., for example by the upper end part of each other, The 3rd neutralization processing tank 4 to the 4th neutralization processing tank 5 The slurry is supplied to In the 4th neutralization processing tank 5, the hydroxide of the impurity in a slurry is precipitated. The slurry is discharged from the fourth neutralization treatment tank 5 to the tailing dam. Between the pump 9 for discharging the slurry to the tailing dam and the fourth neutralization tank 5, a pH meter for measuring the pH of the slurry discharged to the tailing dam is provided. In the final neutralization step S7, the pH of the discharged slurry is measured, and it is confirmed that the pH does not affect the environment. For example, the pH is 9.0 or less.

  The first neutralization treatment tank 2 to the fourth neutralization treatment tank 5 are provided with an air supply port for supplying compressed air into the tank at the bottom. Further, the size and shape of these neutralization treatment tanks 2 to 5 are not particularly limited, and neutralization treatment tanks generally used in wet smelting can be used.

  The neutralization processing method using the neutralization processing apparatus 1 shown in FIG. 2 will be described in more detail. In the final neutralization step S7, first, the first neutralization step is performed in the first neutralization treatment tank 2. In the first neutralization step, the leaching residue and filtrate are put into the first neutralization treatment tank 2, and limestone slurry is added as a neutralizing agent to adjust the pH to a slurry of about 5.5, for example. In the first neutralization step, the free sulfuric acid generated in the leaching step S1 is neutralized in the first neutralization treatment tank 2, and a part of impurities such as iron is generated and precipitated as a hydroxide. In the first neutralization step, carbon dioxide gas is generated by the neutralization reaction. The first neutralization step needs to be completed in the first neutralization treatment tank 2, but the increase in pH is slowed by buffering around pH 5.5. For this reason, in a 1st neutralization process, in order to raise pH, it is preferable to add limestone excessively. In the first neutralization step, it is preferable to blow a gas such as compressed air into the first neutralization treatment tank 2 in order to increase the oxidation-reduction potential. In addition, the amount of blowing in gas such as compressed air is appropriately determined.

  Then, the slurry in the first neutralization treatment tank 2 is supplied to the second neutralization treatment tank 3 through the overflow pipe 6. In the second neutralization treatment tank 3, no neutralizer is added. When supplied from the first neutralization tank 2 to the second neutralization tank 3, carbon dioxide is continuously foamed at the outlet of the first neutralization tank 2. This is because the unreacted limestone added excessively remains, and the neutralization reaction of sulfuric acid occurs also at the outlet of the first neutralization treatment tank 2. It can be estimated that the neutralization reaction of sulfuric acid is incomplete by measuring the pH of the slurry supplied from the first neutralization treatment tank 2 to the second neutralization treatment tank 3. For this reason, the neutralization reaction of sulfuric acid and precipitation of some impurities are completely completed in the second neutralization treatment tank 3 without adding a neutralizing agent. That is, in the second neutralization treatment tank 3, a gas removal step of completing the sulfuric acid neutralization reaction and removing carbon dioxide from the slurry is performed.

When the slaked lime slurry is added to the second neutralization treatment tank 3 after neutralization with the limestone slurry in the first neutralization treatment tank 2 as in the past, the slaked lime comes into contact with carbon dioxide gas. As shown in the following formula (6), calcification occurs. When slaked lime is calcified, the slaked lime cannot be used effectively in the second neutralization treatment tank 3, and the neutralization precipitation removal of impurities becomes insufficient. On the other hand, in the final neutralization step S7 to which the present invention is applied, the slaked lime slurry is not added to the second neutralization treatment tank 3, and the first neutralization step is completed in the second neutralization treatment tank 3. . In the final neutralization step S7, by adding slaked lime slurry to the third neutralization treatment tank 4, calcification of slaked lime can be prevented and slaked lime is not wasted.
Ca (OH) ₂ + CO ₂ + H ₂ O → CaCO ₃ + 2H ₂ O (6)

  In the gas removal step, it is preferable to efficiently remove carbon dioxide gas by introducing a gas such as compressed air into the second neutralization treatment tank 3 to promote aeration of carbon dioxide gas. The amount of blown gas such as compressed air is appropriately determined so that the amount of blown gas is such that carbon dioxide gas can be removed.

  Next, in the final neutralization step S <b> 7, the slurry that has completed the first neutralization reaction in the second neutralization treatment tank 3 is supplied to the third neutralization treatment tank 4 through the overflow pipe 7. In the 3rd neutralization processing tank 4, slaked lime slurry is added to a slurry as a neutralizing agent, and pH is adjusted to about 9.0, for example. The pH is adjusted by measuring the pH of the slurry with a pH meter provided between the second neutralization treatment tank 3 and the third neutralization treatment tank 4, and put into the third neutralization treatment tank 4. The slaked lime slurry is added so that the pH of the slurry becomes 9.0. In the final neutralization step S7, a second neutralization step of removing other impurities such as magnesium and aluminum in the slurry as a hydroxide in the third neutralization treatment tank 4 is performed.

  In the second neutralization step, since the sulfuric acid neutralization reaction is completed in the second neutralization treatment tank 3, the generation of carbon dioxide gas is suppressed in the third neutralization treatment tank 4, and the slaked lime slurry Even if it adds to the 3rd neutralization processing tank 4, it can prevent that slaked lime mineralizes. Thereby, in a 2nd neutralization process, slaked lime can be used effectively, slaked lime can be contributed to neutralization efficiently, it is not necessary to add slaked lime excessively beforehand, and the basic unit of slaked lime is reduced. it can.

  In the second neutralization step, it is preferable to blow a gas such as compressed air into the third neutralization treatment tank 4 in order to increase the oxidation-reduction potential. When a gas containing carbon dioxide such as compressed air is blown, it is preferable to reduce the amount blown in order to prevent slaked lime from being calcified by the blown carbon dioxide.

  In the fourth neutralization treatment tank 5, the slurry is supplied from the third neutralization treatment tank 4 through the overflow pipe 8. In the 4th neutralization processing tank 5, the hydroxide of an impurity is completed. Then, the slurry containing the hydroxide of impurities is pumped up by the pump 9 and discharged to the tailing dam.

  In the final neutralization step S7 as described above, the slaked lime is carbonated by sandwiching a gas removal step for removing carbon dioxide in the slurry without adding slaked lime after the first neutralization step using limestone. Calcification with gas can be prevented. As a result, in the final neutralization step S7, almost all of the added slaked lime can be used effectively, and the slaked lime can be efficiently contributed to the neutralization reaction. Not damaged. As a result, in the final neutralization step S7, it is possible to suppress the excessive addition of the neutralizing agent even when the quality of the impurities fluctuates, and the amount of the neutralizing agent used can be reduced, so the basic unit of the neutralizing agent Can be reduced.

  Further, in the final neutralization step S7, carbon dioxide gas generated by the neutralization reaction of sulfuric acid can be efficiently removed from the slurry by blowing a gas such as compressed air into the slurry in the gas removal step, and contact between slaked lime and carbon dioxide gas is achieved. It can be suppressed more. Thereby, in final neutralization process S7, the added slaked lime can be utilized more effectively and an impurity can fully be removed with the addition amount smaller than the conventionally added excessive amount.

  Furthermore, in the final neutralization step S7, after adding limestone, the first neutralization reaction can be sufficiently advanced in the second neutralization treatment tank 3, so that the pH of the stable state after adding limestone is increased. Can be confirmed. Thereby, in final neutralization process S7, the excessive addition of the neutralizing agent like the past can be suppressed, and the addition amount of limestone can be reduced rather than before.

  As described above, in the hydrometallurgy of nickel oxide ore, when the slurry containing the wet residue generated in the leaching step S1 and the filtrate after nickel recovery is neutralized with limestone and slaked lime in the final neutralization step S7, Without adding excessively, slaked lime added in an appropriate amount can be used efficiently. Moreover, in the hydrometallurgy of nickel oxide ore, since the pH of the stable state after adding limestone in the 2nd neutralization processing tank 3 can be confirmed, the addition amount of limestone can be reduced. Therefore, in the hydrometallurgy of nickel oxide ore, the basic unit of the neutralizing agent can be kept low.

  Embodiments to which the present invention is applied will be described. In addition, this invention is not limited to the following Example at all.

  In the operation example 1 and the operation example 2, the neutralization process was performed using the 1st neutralization processing tank thru | or the 4th neutralization processing tank as shown in FIG. In the operation example 1 and the operation example 2, the quality of impurities contained in the nickel oxide ore used in the daily operation of the nickel oxide ore always varies. For this reason, in the operation example 1 and the operation example 2, the basic unit before and behind changing the neutralization processing tank which adds slaked lime from a 2nd neutralization processing tank to the 3rd neutralization processing tank was compared correctly. That is, the evaluation was performed using the ratio of the actual unit to the theoretical unit.

  Here, the theoretical basic unit of limestone is the amount of limestone required to neutralize iron, aluminum and silicon in the wet residue discharged from the high-pressure acid wet process and the filtrate discharged from the nickel recovery process. The value is divided by (amount of nickel-cobalt mixed sulfide). The theoretical unit of slaked lime is defined as the value obtained by dividing the amount of slaked lime required to completely remove the remaining impurities such as magnesium and manganese other than iron, etc. by the production amount (the amount of nickel-cobalt mixed sulfide). .

<Operation example 1>
In Operation Example 1, first, the leaching residue and filtrate are added to the first neutralization treatment tank, limestone slurry is added to the slurry in the tank, and neutralization of free sulfuric acid and impurities such as iron are used as hydroxides. Precipitated.

  Next, in Operation Example 1, the slurry was sent to the second neutralization tank, and after a while, it was sent to the third neutralization tank.

  Next, in Operation Example 1, slaked lime slurry was added to the third neutralization treatment tank to precipitate the remaining impurity hydroxide. The operation example 1 is referred to as Example 1.

<Operation example 2>
In Operation Example 2, as shown in FIG. 3, limestone was added to the first neutralization treatment tank and slaked lime was added to the second neutralization treatment tank from May 26 to August 14. And in Operation Example 2, neutralization was performed in the same manner as in Operation Example 1 except that each neutralization tank was blown and the balance of the compressed air to be blown was adjusted as shown in FIG.

  From August 14 to September 23, limestone is added to the first neutralization tank, slaked lime is added to the third neutralization tank, and the balance of compressed air blown into each neutralization tank The neutralization was performed in the same manner as in Operation Example 1 except that was adjusted as shown in FIG. From August 14 to September 23, increase the amount blown into the second neutralization tank and reduce the amount blown into the third neutralization tank compared to before August 14 Yes. Here, the period from May 26 to August 14 is a comparative example, and the period from August 14 to September 23 is Example 2.

  In Operation Example 2, the neutralization treatment tank to which slaked lime was added was changed step by step and the compressed air was adjusted step by step, and the ratio of the actual unit consumption to the theoretical basic unit in the operation before and after the change and adjustment was determined.

  Table 1 below summarizes the basic units of Examples 1 and 2 and Comparative Example.

  From the results shown in Table 1, in Example 1, the average basic units of limestone and slaked lime were smaller than in the comparative example, and the average basic units were improved. Moreover, in Example 2, when the balance of the compressed air blown into each neutralization tank is adjusted, the average basic unit of limestone is not as good as that of Example 1, but the average basic unit of slaked lime is It improved greatly.

  On the other hand, when limestone is added to the 1st neutralization processing tank and slaked lime is added to the 2nd neutralization processing tank like a comparative example, slaked lime is calcified and the function as slaked lime is fully demonstrated. Probably not.

  DESCRIPTION OF SYMBOLS 1 Neutralization processing apparatus, 2 1st neutralization processing tank, 3rd 2nd neutralization processing tank, 4th 3rd neutralization processing tank, 5th 4th neutralization processing tank, 6-8 overflow pipe, 9 pump

Claims (2)

In the neutralization method of neutralizing the slurry containing sulfuric acid and impurities generated in the hydrometallurgy of nickel oxide ore with limestone and slaked lime,
A first neutralization step in which the limestone is added to the slurry to generate carbon dioxide;
A gas removal step of removing carbon dioxide generated in the first neutralization step from the slurry;
A second neutralization step of adding slaked lime to the slurry after the gas removal step to produce an impurity hydroxide,
The first neutralization step is performed in a first neutralization treatment tank, the gas removal step is performed in a second neutralization treatment tank, and the second neutralization step is performed in a third neutralization treatment tank. The first neutralization treatment tank to the third neutralization treatment tank are provided in series, and in the gas removal step, the neutralization agent is not added and the second neutralization treatment layer is provided. And a pH meter provided between the third neutralization treatment layer and the pH of the slurry is measured.   The neutralization method according to claim 1, wherein compressed air is blown into the slurry at least in the gas removal step.

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