JP6103017B2 - Nickel sulfate crystallization equipment and crystallization method - Google Patents
Nickel sulfate crystallization equipment and crystallization method Download PDFInfo
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Description
本発明は、硫酸ニッケルの晶析設備および晶析方法に関する。さらに詳しくは、晶析缶を備える晶析設備を用いて、硫酸ニッケル溶液を晶析することにより硫酸ニッケル結晶を得る方法に関する。 The present invention relates to a nickel sulfate crystallization facility and a crystallization method. More specifically, the present invention relates to a method for obtaining nickel sulfate crystals by crystallization of a nickel sulfate solution using a crystallization facility including a crystallization can.
晶析設備においては、晶析缶の内壁や熱交換器の伝熱面、配管などに、結晶が固着するいわゆるスケールが生じる場合がある。スケールが生じると、晶析設備の連続操業に支障が出るため、スケールの発生を抑制する種々の方法が考案されている。
例えば、熱交換器内の流速を速くすることで、伝熱面に生じるスケールを抑制する方法が知られている。しかし、熱交換器内の流速は、晶析缶の容量や結晶速度など晶析設備の条件に依存するため、スケールの抑制のみを目的として調整することは困難である。
In the crystallization equipment, there may be a so-called scale in which crystals adhere to the inner wall of the crystallization can, the heat transfer surface of the heat exchanger, piping, and the like. When the scale is generated, the continuous operation of the crystallization equipment is hindered, and various methods for suppressing the generation of the scale have been devised.
For example, a method is known in which the scale generated on the heat transfer surface is suppressed by increasing the flow rate in the heat exchanger. However, since the flow rate in the heat exchanger depends on the conditions of the crystallization equipment such as the capacity of the crystallization can and the crystallization speed, it is difficult to adjust only for the purpose of suppressing the scale.
硫酸ニッケル結晶を得る晶析設備においても、操業を継続するにしたがい熱交換器の伝熱面などに硫酸ニッケル結晶が析出してくるため、定期的に操業を停止してスケールを除去する必要がある。スケールの除去は、晶析缶内へ温水を供給して液温を上昇させつつ撹拌を行うことによりスケールを溶解し除去する洗缶操作により行われる。しかし、この洗缶操作には約10時間必要であり、従来2〜3日毎に洗缶操作が必要であったため、操業停止時間が長く、晶析設備の実稼働率が低くなるという問題がある。 Even in a crystallization facility that obtains nickel sulfate crystals, nickel sulfate crystals are deposited on the heat transfer surface of the heat exchanger as the operation continues, so it is necessary to periodically stop the operation and remove the scale. is there. Removal of the scale is performed by a can washing operation for dissolving and removing the scale by supplying warm water into the crystallization can and raising the liquid temperature while stirring. However, this can washing operation requires about 10 hours, and conventionally a can washing operation was required every 2 to 3 days, so there is a problem that the operation stop time is long and the actual operation rate of the crystallization equipment is low. .
なお、特許文献１には、多成分の不純物を含むニッケル含有スラッジから、晶析により硫酸ニッケル結晶を回収する技術が開示されているが、晶析におけるスケールの発生については開示されておらず、スケールの発生を抑制する方法も開示されていない。 Patent Document 1 discloses a technique for recovering nickel sulfate crystals by crystallization from nickel-containing sludge containing multi-component impurities, but does not disclose generation of scale in crystallization. A method for suppressing the generation of scale is not disclosed.
本発明は上記事情に鑑み、スケールの発生を抑制できる硫酸ニッケルの晶析設備および晶析方法を提供することを目的とする。 In view of the above circumstances, an object of the present invention is to provide a nickel sulfate crystallization facility and a crystallization method capable of suppressing the generation of scale.
第１発明の硫酸ニッケルの晶析設備は、ニッケル濃度が111g/L以上128g/L以下の硫酸ニッケル溶液である原液と、母液と、小粒度の硫酸ニッケル結晶とを混合する母液槽と、前記母液槽から排出された混合液が供給され、該混合液を用いて晶析する晶析缶と、前記晶析缶内のスラリーを加熱する熱交換器と、前記晶析缶から排出されたスラリーを硫酸ニッケル結晶と母液とに固液分離する固液分離装置と、前記固液分離装置で得られた前記母液を前記母液槽に供給する流路と、前記固液分離装置で得られた前記硫酸ニッケル結晶を、適正な粒度の硫酸ニッケル結晶と小粒度の硫酸ニッケル結晶とに篩分けする篩分装置と、前記篩分装置で得られた前記小粒度の硫酸ニッケル結晶を前記母液槽に供給する流路と、を備えることを特徴とする。
第２発明の硫酸ニッケルの晶析設備は、第１発明において、前記晶析缶は、液温を一定に保ちつつ、所定圧力下で硫酸ニッケル溶液中の水分を蒸発させることにより晶析するものであることを特徴とする。
第３発明の硫酸ニッケルの晶析方法は、ニッケル濃度が111g/L以上128g/L以下の硫酸ニッケル溶液である原液と、母液と、小粒度の硫酸ニッケル結晶とを母液槽で混合し、前記母液槽から排出された混合液を晶析缶に供給し、該混合液を用いて晶析し、前記晶析缶内のスラリーを熱交換器で加熱し、前記晶析缶から排出されたスラリーを硫酸ニッケル結晶と母液とに固液分離し、前記固液分離で得られた前記母液を前記母液槽に供給し、前記固液分離で得られた前記硫酸ニッケル結晶を、適正な粒度の硫酸ニッケル結晶と小粒度の硫酸ニッケル結晶とに篩分けし、前記篩分けで得られた前記小粒度の硫酸ニッケル結晶を前記母液槽に供給することを特徴とする。
第４発明の硫酸ニッケルの晶析方法は、第３発明において、前記晶析缶は、液温を一定に保ちつつ、所定圧力下で硫酸ニッケル溶液中の水分を蒸発させることにより晶析するものであることを特徴とする。
第５発明の硫酸ニッケルの晶析方法は、第３または第４発明において、前記熱交換器前後のスラリーの温度差が所定温度以上となったか否かによりスケールが発生したか否かを判断することを特徴とする。
According to a first aspect of the present invention, there is provided a nickel sulfate crystallization facility comprising a stock solution that is a nickel sulfate solution having a nickel concentration of 111 g / L or more and 128 g / L or less , a mother liquor, and a mother liquor tank in which small-sized nickel sulfate crystals are mixed. A liquid crystal discharged from the mother liquor is supplied, a crystallization can crystallized using the liquid mixture, a heat exchanger for heating the slurry in the crystallizing can, and a slurry discharged from the crystallizing can A solid-liquid separator for solid-liquid separation into nickel sulfate crystals and mother liquor, a flow path for supplying the mother liquor obtained by the solid-liquid separator to the mother liquor tank, and the above-mentioned obtained by the solid-liquid separator A sieving apparatus for sieving nickel sulfate crystals into appropriate sized nickel sulfate crystals and small sized nickel sulfate crystals, and supplying the small sized nickel sulfate crystals obtained by the sieving apparatus to the mother liquor tank And a flow path.
According to a second aspect of the present invention, there is provided the nickel sulfate crystallization facility according to the first aspect , wherein the crystallization can is crystallized by evaporating water in the nickel sulfate solution under a predetermined pressure while keeping the liquid temperature constant. It is characterized by being.
According to a third aspect of the present invention, there is provided a nickel sulfate crystallization method comprising mixing a stock solution that is a nickel sulfate solution having a nickel concentration of 111 g / L or more and 128 g / L or less , a mother solution, and small-sized nickel sulfate crystals in a mother solution tank. The mixed solution discharged from the mother liquor tank is supplied to the crystallization can, crystallized using the mixed solution, the slurry in the crystallization can is heated with a heat exchanger, and the slurry discharged from the crystallization can Is separated into a nickel sulfate crystal and a mother liquor, the mother liquor obtained by the solid-liquid separation is supplied to the mother liquor tank, and the nickel sulfate crystal obtained by the solid-liquid separation is subjected to sulfuric acid having an appropriate particle size. Sieve into nickel crystals and small-sized nickel sulfate crystals, and supply the small-sized nickel sulfate crystals obtained by the sieving to the mother liquor tank.
According to a fourth aspect of the present invention, there is provided a nickel sulfate crystallization method according to the third aspect , wherein the crystallization can is crystallized by evaporating water in the nickel sulfate solution under a predetermined pressure while keeping the liquid temperature constant. It is characterized by being.
The nickel sulfate crystallization method according to a fifth aspect of the present invention is the third or fourth aspect of the present invention, wherein whether or not a scale has occurred is determined based on whether or not the temperature difference between the slurry before and after the heat exchanger is equal to or higher than a predetermined temperature. It is characterized by that.
本発明によれば、原液中のニッケル濃度を111g/L以上128g/L以下とするので、晶析缶内のスラリーの過飽和度が高くなり、晶析缶の内壁や熱交換器の伝熱面において核が形成されにくくなるので、スケールの発生を抑制できる。 According to the present invention, since the nickel concentration in the stock solution is 111 g / L or more and 128 g / L or less , the supersaturation degree of the slurry in the crystallization can increases, the inner wall of the crystallization can and the heat transfer surface of the heat exchanger In this case, nuclei are hardly formed, and scale generation can be suppressed .
つぎに、本発明の実施形態を図面に基づき説明する。
まず、硫酸ニッケル溶液を晶析して硫酸ニッケル結晶を得るために用いられる晶析設備の一例を説明する。
図１に示すように、晶析設備１は、原液としての硫酸ニッケル溶液を一時貯留する原液槽１１と、原液槽１１から原液が供給され、その原液に後述の母液および小粒度の硫酸ニッケル結晶とを混合する母液槽１２と、母液槽１２から原液が供給される晶析缶１３とを備えている。
Next, an embodiment of the present invention will be described with reference to the drawings.
First, an example of a crystallization equipment used for crystallization of a nickel sulfate solution to obtain nickel sulfate crystals will be described.
As shown in FIG. 1, a crystallization facility 1 includes a stock solution tank 11 for temporarily storing a nickel sulfate solution as a stock solution, and a stock solution supplied from the stock solution tank 11. And a crystallization can 13 to which the stock solution is supplied from the mother liquor tank 12.
原液は、硫酸ニッケルを含有する溶液であればその組成に特に限定は無いが、例えば、ニッケル精錬法の一つであるＭＣＬＥ（Matte Chlorine Leach Electrowinning）法（特公平７−９１５９９号公報参照）の浄液工程において、粗硫酸ニッケル液から不純物を除去して得られた硫酸ニッケル純液が用いられる。なお、ＭＣＬＥ法の浄液工程において得られる硫酸ニッケル純液には、ナトリウム、塩素、マグネシウム、カルシウム、アンモニウムイオンなどの不純物が含まれている。 The stock solution is not particularly limited as long as it is a solution containing nickel sulfate. For example, the MCLE (Matte Chlorine Leach Electrowinning) method (see Japanese Patent Publication No. 7-91599), which is one of the nickel refining methods, is used. In the cleaning step, a pure nickel sulfate solution obtained by removing impurities from the crude nickel sulfate solution is used. In addition, the nickel sulfate pure solution obtained in the liquid purification process of the MCLE method contains impurities such as sodium, chlorine, magnesium, calcium, and ammonium ions.
晶析缶１３は、所定圧力下で硫酸ニッケル溶液中の水分を蒸発させることにより晶析するものであり、例えばＤＰ（ダブルプロペラ）型晶析缶が用いられる。晶析缶１３内部の圧力は、真空ポンプなどにより約7.5kPaAに制御されており、ダブルプロペラで撹拌しながら晶析が行われる。晶析缶１３内では、硫酸ニッケル溶液に硫酸ニッケル結晶が混合したスラリーとなっている。 The crystallization can 13 is crystallized by evaporating the water in the nickel sulfate solution under a predetermined pressure. For example, a DP (double propeller) type crystallization can is used. The pressure inside the crystallization can 13 is controlled to about 7.5 kPaA by a vacuum pump or the like, and crystallization is performed while stirring with a double propeller. In the crystallization can 13, a slurry in which nickel sulfate crystals are mixed with a nickel sulfate solution is formed.
晶析缶１３内のスラリーは、水分が蒸発することにより熱が奪われるため液温が低下する。晶析缶１３には熱交換器１４が設けられており、その熱交換器１４で晶析缶１３内のスラリーを加熱することにより液温が一定に保たれる。熱交換器１４としては、例えばシェルアンドチューブ型熱交換器が用いられる。また、スラリーの液温は例えば約45℃に保たれる。 The slurry in the crystallization can 13 is deprived of heat as the water evaporates, so the liquid temperature decreases. The crystallization can 13 is provided with a heat exchanger 14, and the liquid temperature is kept constant by heating the slurry in the crystallization can 13 with the heat exchanger 14. As the heat exchanger 14, for example, a shell and tube heat exchanger is used. Further, the liquid temperature of the slurry is maintained at about 45 ° C., for example.
晶析缶１３から排出されたスラリーは、遠心分離機１５で硫酸ニッケル結晶と母液とに固液分離される。母液は母液槽１２に供給され、硫酸ニッケル結晶は乾燥機１６に供給される。硫酸ニッケル結晶は、乾燥機１６で乾燥することにより水分を除去された後、振動篩機１７に供給される。振動篩機１７では、製品として適正な粒度の硫酸ニッケル結晶を選別して排出する。製品とならない小粒度の硫酸ニッケル結晶は、母液槽１２に供給される。母液槽１２では、原液槽１１から供給された硫酸ニッケル溶液と母液および小粒度の硫酸ニッケル結晶とが混合され、小粒度の硫酸ニッケル結晶が硫酸ニッケル溶液に溶解する。 The slurry discharged from the crystallization can 13 is solid-liquid separated into a nickel sulfate crystal and a mother liquor by a centrifugal separator 15. The mother liquor is supplied to the mother liquor tank 12 and the nickel sulfate crystals are supplied to the dryer 16. The nickel sulfate crystals are supplied to the vibrating sieve 17 after moisture is removed by drying with the dryer 16. In the vibration sieve 17, nickel sulfate crystals having an appropriate particle size as a product are selected and discharged. Small-sized nickel sulfate crystals that do not become a product are supplied to the mother liquor tank 12. In the mother liquor tank 12, the nickel sulfate solution supplied from the stock solution tank 11, the mother liquor, and the small-sized nickel sulfate crystals are mixed, and the small-sized nickel sulfate crystals are dissolved in the nickel sulfate solution.
以上のような晶析設備１においては、操業を継続するにしたがい晶析缶１３の内壁や熱交換器１４の伝熱面などに硫酸ニッケル結晶が析出してくる。このようなスケールが発生した場合には、操業を停止してスケールを除去する必要がある。スケールの除去は、晶析缶１３内へ温水を供給して液温を上昇させつつ撹拌を行うことによりスケールを溶解し除去する洗缶操作により行われる。 In the crystallization equipment 1 as described above, nickel sulfate crystals are deposited on the inner wall of the crystallization can 13 and the heat transfer surface of the heat exchanger 14 as the operation is continued. When such a scale occurs, it is necessary to stop the operation and remove the scale. Removal of the scale is performed by a can washing operation in which the scale is dissolved and removed by supplying warm water into the crystallization can 13 and stirring while raising the liquid temperature.
スケールが発生したか否かは、熱交換器１４前後のスラリーの温度差ΔTが所定温度以上となったか否かにより判断される。ここで、温度差ΔTは、熱交換器出口のスラリー温度から熱交換器入口のスラリー温度を減算した値である。これは、熱交換器１４内部の伝熱管にスケールが発生して閉塞してくると、熱交換器１４内の流量が減少し、スラリーの単位体積当たりに供給される熱量が多くなる結果、熱交換器１４による温度上昇が高くなるからである。例えば、ΔTが5℃以上となった時点でスケールが発生したと判断して、上記の洗缶操作が行われる。 Whether or not the scale has occurred is determined based on whether or not the temperature difference ΔT of the slurry before and after the heat exchanger 14 is equal to or higher than a predetermined temperature. Here, the temperature difference ΔT is a value obtained by subtracting the slurry temperature at the heat exchanger inlet from the slurry temperature at the heat exchanger outlet. This is because when the scale is generated in the heat transfer tube inside the heat exchanger 14 and becomes clogged, the flow rate in the heat exchanger 14 decreases and the amount of heat supplied per unit volume of the slurry increases. It is because the temperature rise by the exchanger 14 becomes high. For example, when the ΔT becomes 5 ° C. or higher, it is determined that scale has occurred, and the above-described washing operation is performed.
また、硫酸ニッケル溶液は、母液槽１２と晶析缶１３との間を循環しつつ、水分が蒸発していく。そのため、原液に不純物が含まれていると、循環を繰り返すごとに不純物濃度が上昇する。不純物濃度が高くなると硫酸ニッケル結晶中の不純物品位が高くなる。そのため、晶析缶１３内のスラリーの不純物濃度を定期的に測定し、不純物濃度が所定の基準を超えた場合に晶析缶１３内のスラリーを排出することが行われる。すなわち、スラリーとともに不純物を排出するのである。これにより、製品となる硫酸ニッケル結晶中の不純物品位を下げることができる。なお、晶析缶１３には図示しない排出口が設けられており、不純物濃度が高いスラリーはその排出口から晶析設備１の系外に排出される。 The nickel sulfate solution evaporates while circulating between the mother liquor tank 12 and the crystallization can 13. For this reason, if the stock solution contains impurities, the impurity concentration increases every time circulation is repeated. As the impurity concentration increases, the impurity quality in the nickel sulfate crystal increases. Therefore, the impurity concentration of the slurry in the crystallization can 13 is periodically measured, and when the impurity concentration exceeds a predetermined standard, the slurry in the crystallization can 13 is discharged. That is, impurities are discharged together with the slurry. Thereby, the impurity quality in the nickel sulfate crystal | crystallization used as a product can be reduced. The crystallization can 13 is provided with a discharge port (not shown), and slurry having a high impurity concentration is discharged from the discharge port to the outside of the crystallization equipment 1.
本発明に係る硫酸ニッケルの晶析方法は、上記のような晶析方法において、原液である硫酸ニッケル溶液中のニッケル濃度を90g/L以上185g/L以下、好ましくは121g/L以上140g/L以下に調整するところに特徴がある。 The nickel sulfate crystallization method according to the present invention is the above crystallization method, wherein the nickel concentration in the nickel sulfate solution as a stock solution is 90 g / L or more and 185 g / L or less, preferably 121 g / L or more and 140 g / L. It is characterized by the following adjustments.
一般に結晶化は、溶液中に分散する溶質分子が集まり核が形成される核形成と、その核が成長する結晶成長の二段階で行われる。
原液中のニッケル濃度を変化させると、晶析缶１３内のスラリーの過飽和度も同様に変化する。そして、原液中のニッケル濃度を低くすると、晶析缶１３内のスラリーの過飽和度が低くなり、核形成が行われにくくなる。この場合、流速が遅い晶析缶１３の内壁や熱交換器１４の伝熱面においては、それ以外の場所よりも相対的に核が発生しやすくなり、その核が成長するとスケールとなると考えられる。すなわち、原液中のニッケル濃度を低くすると、晶析缶１３の内壁や熱交換器１４の伝熱面にスケールが生じやすくなる。
前述のごとく、スケールが発生すると洗缶操作が行われるが、この洗缶操作には約10時間必要である。そのため、スケールが生じやすいと洗缶操作の頻度が高くなり操業停止時間が長くなるため、晶析設備１の実稼働率が低くなる。
In general, crystallization is performed in two stages: nucleation in which solute molecules dispersed in a solution gather to form nuclei and crystal growth in which the nuclei grow.
When the nickel concentration in the stock solution is changed, the degree of supersaturation of the slurry in the crystallization can 13 also changes. When the nickel concentration in the stock solution is lowered, the degree of supersaturation of the slurry in the crystallization can 13 is lowered and nucleation is difficult to be performed. In this case, on the inner wall of the crystallization can 13 with a low flow velocity and on the heat transfer surface of the heat exchanger 14, nuclei are more likely to be generated than other places, and it is considered that the scale becomes a scale when the nuclei grow. . That is, when the nickel concentration in the stock solution is lowered, scale is likely to occur on the inner wall of the crystallization can 13 and the heat transfer surface of the heat exchanger 14.
As described above, when a scale is generated, a can washing operation is performed. This can operation requires about 10 hours. For this reason, if the scale is likely to occur, the frequency of the washing operation becomes high and the operation stop time becomes long, so that the actual operation rate of the crystallization equipment 1 becomes low.
また、原液中のニッケル濃度を低くすると、ニッケルに対する不純物の比率が高くなる。そのため、製品となる硫酸ニッケル結晶中の不純物品位を低く維持するためには、晶析缶１３からのスラリーの排出量を多くする必要がある。
晶析缶１３からスラリーを排出すると、過飽和度が高められたスラリーが排出されることとなるため、過飽和度を高めるために消費されたエネルギーが無駄となる。また、不純物のみならず硫酸ニッケル溶液や硫酸ニッケル結晶も排出されるため、晶析率が低下する。ここで、晶析率とは、製品である硫酸ニッケル結晶中のニッケル重量を、原液中のニッケル重量で除算した値である。
Further, when the nickel concentration in the stock solution is lowered, the ratio of impurities to nickel is increased. Therefore, in order to keep the impurity quality in the nickel sulfate crystal as a product low, it is necessary to increase the amount of slurry discharged from the crystallization can 13.
When the slurry is discharged from the crystallization can 13, the slurry with increased supersaturation is discharged, and energy consumed to increase the supersaturation is wasted. Moreover, since not only impurities but also nickel sulfate solution and nickel sulfate crystals are discharged, the crystallization rate decreases. Here, the crystallization rate is a value obtained by dividing the nickel weight in the nickel sulfate crystal as the product by the nickel weight in the stock solution.
これに対して、原液中のニッケル濃度を90g/L以上に高くすれば、晶析缶１３内のスラリーの過飽和度が高くなり、晶析缶１３の内壁や熱交換器１４の伝熱面において核が形成されにくくなるので、スケールの発生を抑制できる。そのため、洗缶操作の頻度を低減でき、晶析設備１の実稼働率が向上する。また、晶析缶１３からのスラリーの排出量を少なくしても、硫酸ニッケル結晶中の不純物品位を低く維持することができるため、エネルギー効率が向上し、晶析率も向上する。 On the other hand, if the nickel concentration in the undiluted solution is increased to 90 g / L or more, the supersaturation degree of the slurry in the crystallization can 13 increases, and the inner wall of the crystallization can 13 and the heat transfer surface of the heat exchanger 14 are increased. Since nuclei are hardly formed, the generation of scale can be suppressed. Therefore, the frequency of the can operation can be reduced, and the actual operation rate of the crystallization equipment 1 is improved. Moreover, even if the discharge amount of the slurry from the crystallization can 13 is reduced, the impurity quality in the nickel sulfate crystal can be kept low, so that the energy efficiency is improved and the crystallization rate is improved.
さらに、原液中のニッケル濃度を121g/L以上に高くすれば、晶析缶１３内のスラリーの過飽和度がより高くなり、よりスケールの発生を抑制できる。その結果、洗缶操作の頻度を低減でき、晶析設備１の実稼働率が向上する。また、エネルギー効率が向上し、晶析率も向上する。 Furthermore, if the nickel concentration in the stock solution is increased to 121 g / L or more, the supersaturation degree of the slurry in the crystallization can 13 becomes higher, and the generation of scale can be further suppressed. As a result, the frequency of the washing operation can be reduced, and the actual operation rate of the crystallization equipment 1 is improved. Moreover, energy efficiency improves and a crystallization rate also improves.
原液中のニッケル濃度が185g/L以下であれば、晶析缶１３が処理できる許容範囲内であるので、硫酸ニッケル結晶を得ることができる。また、原液中のニッケル濃度を高くすると硫酸ニッケル溶液を晶析缶１３に供給する配管にスケールが発生しやすくなるが、原液中のニッケル濃度が140g/L以下であれば、その配管へのスケールの発生も抑制できる。 If the nickel concentration in the undiluted solution is 185 g / L or less, the crystallization can 13 is within an acceptable range that can be processed, and thus nickel sulfate crystals can be obtained. In addition, when the nickel concentration in the stock solution is increased, scales are likely to be generated in the piping for supplying the nickel sulfate solution to the crystallization can 13. Can also be suppressed.
つぎに実施例について説明する。
図１に示す晶析設備１を用いて、ＭＣＬＥ法の浄液工程において得られた硫酸ニッケル純液を原液として晶析することにより硫酸ニッケル結晶を得る操業を行った。晶析缶１３として、容量7m3のＤＰ型晶析缶（SUS製）を用いた。晶析缶１３内部の圧力は約7.5kPaAに制御した。また、熱交換器１４としてシェルアンドチューブ型熱交換器を用い、500kPaGの蒸気により晶析缶１３内のスラリーを加熱した。原液の供給量は硫酸ニッケル換算で625kg/hourとした。
Next, examples will be described.
Using the crystallization equipment 1 shown in FIG. 1, an operation for obtaining nickel sulfate crystals was performed by crystallization using a pure nickel sulfate solution obtained in the MCLE purification step as a stock solution. As the crystallization can 13, a DP-type crystallization can (made of SUS) having a capacity of 7 m 3 was used. The pressure inside the crystallization can 13 was controlled to about 7.5 kPaA. Further, a shell and tube type heat exchanger was used as the heat exchanger 14, and the slurry in the crystallization can 13 was heated with 500 kPaG steam. The supply amount of the stock solution was 625 kg / hour in terms of nickel sulfate.
実施例１〜５としてニッケル濃度を表１に示す各濃度に調整した原液を用いて、各実施例について30日の操業を行った。各実施例の操業中は、熱交換器１４前後のスラリーの温度差ΔTが5℃以上となった時点でスケールが発生したと判断して洗缶操作を行った。また、晶析缶１３内のスラリーの不純物濃度を定期的に測定し、不純物濃度が所定の基準を超えた場合に晶析缶１３内のスラリーを排出して、不純物濃度を低下させる作業を行った。各実施例における、晶析缶１３内のスラリーの比重（スラリー比重）の測定結果および洗缶操作の回数（洗缶回数）は表１の通りである。
スラリー比重はスラリーの過飽和度と相関するため、スラリー比重の推移により過飽和度の推移を知ることができる。図２（ａ）に示すように、原液中のニッケル濃度とスラリー比重との間には正の相関が見られることから、原液中のニッケル濃度を高くすると、スラリーの過飽和度が高くなることが分かる。また、原液中のニッケル濃度119g/Lと124g/Lとの間のスラリー比重の増加率が他の領域に比べて大きいことが分かる。これより、原液中のニッケル濃度119g/Lと124g/Lとの間である121g/Lに、スラリーの過飽和度が急激に上昇する変曲点があると考えられる。 Since the slurry specific gravity correlates with the supersaturation degree of the slurry, the transition of the supersaturation degree can be known from the transition of the slurry specific gravity. As shown in FIG. 2 (a), there is a positive correlation between the nickel concentration in the stock solution and the specific gravity of the slurry. Therefore, when the nickel concentration in the stock solution is increased, the degree of supersaturation of the slurry increases. I understand. It can also be seen that the rate of increase in the slurry specific gravity between the nickel concentrations in the stock solution between 119 g / L and 124 g / L is greater than in other regions. From this, it is considered that there is an inflection point at which the supersaturation degree of the slurry rapidly increases at 121 g / L, which is between the nickel concentration of 119 g / L and 124 g / L in the stock solution.
また、図２（ｂ）に示すように、原液中のニッケル濃度と洗缶回数との間には負の相関が見られたことから、原液中のニッケル濃度を高くすると、スケールの発生を抑制でき、洗缶回数を少なくできることが分かる。また、これにより晶析設備１の実稼働率が向上することが分かる（表１参照）。特に原液中のニッケル濃度を128g/L以上にすると、実稼働率が95%以上となる。 In addition, as shown in FIG. 2 (b), since a negative correlation was observed between the nickel concentration in the stock solution and the number of cans, the generation of scale was suppressed by increasing the nickel concentration in the stock solution. It can be seen that the number of cans can be reduced. Moreover, it turns out that the actual operation rate of the crystallization equipment 1 improves by this (refer Table 1). In particular, when the nickel concentration in the stock solution is set to 128 g / L or more, the actual operation rate becomes 95% or more.
原液中のニッケル濃度が119g/L以下の領域における洗缶回数の推移の傾きに比べて、124g/L以上の領域における洗缶回数の推移の傾き方が大きい。そのため、原液中のニッケル濃度119g/Lと124g/Lとの間である121g/Lに、スケール発生の変曲点があると考えられる。これは、スラリーの過飽和度の変曲点とも一致する。そして、原液中のニッケル濃度を121g/L以上に高くすればよりスケールの発生を抑制でき、洗缶回数を少なくできることが分かる。 Compared to the slope of the change in the number of cans in the region where the nickel concentration in the stock solution is 119 g / L or less, the slope of the change in the number of cans in the region of 124 g / L or more is larger. Therefore, it is considered that there is an inflection point of scale generation at 121 g / L, which is between the nickel concentration of 119 g / L and 124 g / L in the stock solution. This coincides with the inflection point of the supersaturation degree of the slurry. Then, it can be seen that if the nickel concentration in the stock solution is increased to 121 g / L or more, generation of scale can be further suppressed and the number of cans can be reduced.
表１に示すように、原液中のニッケル濃度を高くすると、晶析率が向上することが分かる。これは、硫酸ニッケル結晶中の不純物品位を低く維持するために晶析缶１３から排出されるスラリーの量が少なくなるからである。 As shown in Table 1, it can be seen that when the nickel concentration in the stock solution is increased, the crystallization rate is improved. This is because the amount of slurry discharged from the crystallization can 13 is reduced in order to keep the impurity quality in the nickel sulfate crystals low.
１ 晶析設備
１１ 原液槽
１２ 母液槽
１３ 晶析缶
１４ 熱交換器
１５ 遠心分離機
１６ 乾燥機
１７ 振動篩機
DESCRIPTION OF SYMBOLS 1 Crystallization equipment 11 Stock solution tank 12 Mother liquid tank 13 Crystallization can 14 Heat exchanger 15 Centrifuge 16 Dryer 17 Vibrating sieve machine
Claims (5)
前記母液槽から排出された混合液が供給され、該混合液を用いて晶析する晶析缶と、
前記晶析缶内のスラリーを加熱する熱交換器と、
前記晶析缶から排出されたスラリーを硫酸ニッケル結晶と母液とに固液分離する固液分離装置と、
前記固液分離装置で得られた前記母液を前記母液槽に供給する流路と、
前記固液分離装置で得られた前記硫酸ニッケル結晶を、適正な粒度の硫酸ニッケル結晶と小粒度の硫酸ニッケル結晶とに篩分けする篩分装置と、
前記篩分装置で得られた前記小粒度の硫酸ニッケル結晶を前記母液槽に供給する流路と、を備える
ことを特徴とする硫酸ニッケルの晶析設備。 A stock solution that is a nickel sulfate solution having a nickel concentration of 111 g / L or more and 128 g / L or less , a mother liquor, and a mother liquor tank in which small-sized nickel sulfate crystals are mixed;
A liquid crystal discharged from the mother liquor tank is supplied, and a crystallization can crystallized using the liquid mixture,
A heat exchanger for heating the slurry in the crystallization can;
A solid-liquid separation device for solid-liquid separation of the slurry discharged from the crystallization can into nickel sulfate crystals and mother liquor;
A flow path for supplying the mother liquor obtained by the solid-liquid separator to the mother liquor tank;
A sieving device for sieving the nickel sulfate crystals obtained by the solid-liquid separation device into nickel sulfate crystals having an appropriate particle size and nickel sulfate crystals having a small particle size;
And a flow path for supplying the small-sized nickel sulfate crystals obtained by the sieving device to the mother liquor tank.
ことを特徴とする請求項１記載の硫酸ニッケルの晶析設備。 2. The crystallization of nickel sulfate according to claim 1 , wherein the crystallization can is crystallized by evaporating water in the nickel sulfate solution under a predetermined pressure while keeping the liquid temperature constant. Facility.
前記母液槽から排出された混合液を晶析缶に供給し、該混合液を用いて晶析し、
前記晶析缶内のスラリーを熱交換器で加熱し、
前記晶析缶から排出されたスラリーを硫酸ニッケル結晶と母液とに固液分離し、
前記固液分離で得られた前記母液を前記母液槽に供給し、
前記固液分離で得られた前記硫酸ニッケル結晶を、適正な粒度の硫酸ニッケル結晶と小粒度の硫酸ニッケル結晶とに篩分けし、
前記篩分けで得られた前記小粒度の硫酸ニッケル結晶を前記母液槽に供給する
ことを特徴とする硫酸ニッケルの晶析方法。 Mixing a stock solution that is a nickel sulfate solution having a nickel concentration of 111 g / L or more and 128 g / L or less , a mother liquor, and small-sized nickel sulfate crystals in a mother liquor tank,
Supply the mixed solution discharged from the mother liquor tank to a crystallization can, crystallize using the mixed solution,
Heat the slurry in the crystallization can with a heat exchanger,
The slurry discharged from the crystallization can is solid-liquid separated into nickel sulfate crystals and mother liquor,
Supplying the mother liquor obtained by the solid-liquid separation to the mother liquor tank;
The nickel sulfate crystal obtained by the solid-liquid separation is sieved into a nickel sulfate crystal having an appropriate particle size and a nickel sulfate crystal having a small particle size,
A nickel sulfate crystallization method, wherein the nickel sulfate crystals having a small particle size obtained by the sieving are supplied to the mother liquor tank.
ことを特徴とする請求項３記載の硫酸ニッケルの晶析方法。 4. The crystallization of nickel sulfate according to claim 3 , wherein the crystallization can is crystallized by evaporating water in the nickel sulfate solution under a predetermined pressure while keeping the liquid temperature constant. Method.
ことを特徴とする請求項３または４記載の硫酸ニッケルの晶析方法。 5. The nickel sulfate crystallization method according to claim 3, wherein whether or not a scale is generated is determined based on whether or not a temperature difference between the slurry before and after the heat exchanger is equal to or higher than a predetermined temperature.
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