JP6743491B2 - Waste acid treatment method - Google Patents
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本発明は、銅製錬排ガスの処理の際に生じる廃酸の処理方法に関し、特に廃酸に含まれるカドミウムや亜鉛を分離回収することが可能な廃酸の処理方法に関する。 The present invention relates to a method for treating a waste acid generated when treating a copper smelting exhaust gas, and particularly to a method for treating a waste acid capable of separating and recovering cadmium and zinc contained in the waste acid.
銅製錬プロセスにおいて発生する銅製錬排ガスには亜硫酸ガス（ＳＯ２）が含まれるため、従来、硫酸工場に送って転化工程及び吸収工程を経て硫酸を製造することが行われている。しかし、上記銅製錬排ガスは亜硫酸ガス以外にＣｕ等の重金属の煙灰やヒュームを含んでいるため、上記転化工程で処理する前にガス精製工程で洗浄水を用いて重金属を除去した後、後段の乾燥工程で乾燥している。 Since the copper smelting exhaust gas generated in the copper smelting process contains sulfurous acid gas (SO 2 ), it has been conventionally performed to send it to a sulfuric acid factory to produce sulfuric acid through a conversion step and an absorption step. However, since the copper smelting flue gas contains fumes and fumes of heavy metals such as Cu in addition to the sulfurous acid gas, after the heavy metals are removed using the washing water in the gas purification step before the conversion step, the latter stage of It is dried in the drying process.
上記ガス精製工程で使用した重金属を含む洗浄水は、連続的又は定期的に抜き出して処理している。上記銅製錬排ガスはＳＯ２以外にＳＯ３を含んでいるため、上記の抜き出した洗浄排水は当該ＳＯ３由来の硫酸分を含んでいる。このため、硫酸分を含む上記洗浄排水（以降、廃酸と称する）の処理ではこれら硫酸分と重金属の処理が必要になる。かかる廃酸の処理方法として、特許文献１には、廃酸に炭酸カルシウムを添加して硫酸分を石膏として除去した後、水硫化ナトリウムを添加して重金属を硫化澱物として除去する技術が開示されている。また、特許文献２には、廃酸を希釈してから水硫化ナトリウムを添加して重金属を硫化澱物として除去した後、炭酸カルシウムを添加して不純物品位の低い石膏を製造する方法が開示されている。 The washing water containing heavy metals used in the gas purification step is continuously or regularly extracted and treated. Since the copper smelting exhaust gas contains SO 3 in addition to SO 2 , the extracted cleaning waste water contains the SO 3 -derived sulfuric acid content. Therefore, in the treatment of the cleaning waste water containing sulfuric acid (hereinafter referred to as waste acid), it is necessary to treat the sulfuric acid and heavy metals. As a method of treating such waste acid, Patent Document 1 discloses a technique of adding calcium carbonate to waste acid to remove sulfuric acid as gypsum, and then adding sodium hydrosulfide to remove heavy metals as sulfurized starch. Has been done. Patent Document 2 discloses a method of diluting waste acid, adding sodium hydrosulfide to remove heavy metals as sulfurized starch, and then adding calcium carbonate to produce gypsum with low impurity quality. ing.
近年、銅製錬工場では夾雑物を多く含む様々な原料を処理することが多くなってきている。これに伴い、上記の硫化澱物にはＣｕ以外の重金属の占める割合が増える傾向にある。硫化澱物は一般に銅製錬工程に繰り返して処理するため、特定の重金属については系内での循環量が増大することになり、現状の廃酸の処理装置の処理能力を超えることが懸念されている。 In recent years, copper smelting factories are increasingly processing various raw materials containing a large amount of impurities. Along with this, there is a tendency that the proportion of heavy metals other than Cu in the above-mentioned sulfurized starch increases. Since sulfurized starch is generally repeatedly treated in the copper smelting process, the amount of circulation of certain heavy metals in the system will increase, and it is feared that the current treatment capacity of waste acid treatment equipment will be exceeded. There is.
本発明は、上記した従来の廃酸の処理方法がかかえる問題点に鑑みてなされたものであり、廃酸に含まれるＣｕ以外の重金属を分離回収して製錬工程に繰り返す硫化澱物の量を減らすことが可能な廃酸の処理方法を提供することを目的としている。 The present invention has been made in view of the problems associated with the above-mentioned conventional waste acid treatment method, and the amount of sulfurized starch which is repeatedly recovered in the smelting step by separating and recovering heavy metals other than Cu contained in the waste acid. It is an object of the present invention to provide a method for treating waste acid capable of reducing the amount of waste.
本発明者らは、上記目的を達成するために検討を重ねた結果、廃酸から生成される硫化澱物には重金属（鉄以上の比重を持つ金属）として銅や砒素のほか有価金属である亜鉛やカドミウムを比較的多く含んでいるため、廃酸に対して２回に分けて硫化剤を添加して第１及び第２の硫化澱物を生成すると共に、それぞれの硫化反応条件を調整することで、第２の硫化澱物において銅や砒素の分配量を減らしつつ亜鉛とカドミウムの分配量を増やし得ることを見出し、本発明を完成するに至った。 As a result of repeated studies to achieve the above object, the present inventors have found that sulfurized starch produced from waste acid is a valuable metal in addition to copper and arsenic as heavy metals (metals having a specific gravity higher than iron). Since it contains a relatively large amount of zinc and cadmium, the sulfurizing agent is added to the waste acid in two portions to form the first and second sulfurized starch, and the respective sulfurization reaction conditions are adjusted. As a result, they have found that it is possible to increase the distribution amount of zinc and cadmium while decreasing the distribution amount of copper and arsenic in the second sulfide, and have completed the present invention.
すなわち、本発明に係る廃酸の処理方法は、銅製錬排ガスの処理の際に生じる重金属の銅、砒素、亜鉛、及びカドミウム並びに硫酸分を含む廃酸に硫化剤を添加して該重金属を硫化させた後、得られたスラリーを第１硫化澱物と第１清澄液とに固液分離する第１硫化工程と、前記第１清澄液にカルシウム系中和剤を添加して前記硫酸分から石膏を生成させた後、この石膏を含むスラリーを石膏と石膏終液に固液分離する石膏製造工程と、前記石膏終液に硫化剤を添加して残存する重金属を硫化させた後、得られたスラリーを第２硫化澱物と第２清澄液とに固液分離する第２硫化工程とを備え、前記第１硫化工程で添加する硫化剤の量を、前記第２硫化澱物の砒素品位が０.１〜３.０質量％となるように調整すること、及び前記第１硫化工程の処理液から発生するガスを捕集し、該ガスを前記廃酸の少なくとも一部と気液接触させることを特徴としている。 That is, the method for treating a waste acid according to the present invention is a method for adding a sulfidizing agent to a waste acid containing heavy metals such as copper, arsenic, zinc, cadmium and sulfuric acid , which is generated during the treatment of copper smelting exhaust gas , and sulfurizing the heavy metal. After that, a first sulfidation step of solid-liquid separating the obtained slurry into a first sulfurized starch and a first clearing solution, and a calcium-based neutralizing agent is added to the first clearing solution to remove gypsum from the sulfuric acid content. Gypsum production step of solid-liquid separating the gypsum-containing slurry into gypsum and a gypsum final liquid, and a sulfurizing agent was added to the gypsum final liquid to sulfurize the remaining heavy metal, and then obtained. A second sulfurization step of solid-liquid separating the slurry into a second sulfurized starch and a second clarified liquid, wherein the amount of the sulfurizing agent added in the first sulfurization step is the arsenic grade of the second sulfurized starch. Adjusting so as to be 0.1 to 3.0% by mass , and collecting gas generated from the treatment liquid in the first sulfiding step, and bringing the gas into gas-liquid contact with at least a part of the waste acid. It is characterized by
本発明によれば、廃酸に含まれるＣｕ以外の重金属を分離回収して製錬工程に繰り返される硫化澱物の量を減らすことができる。 According to the present invention, heavy metals other than Cu contained in waste acid can be separated and recovered to reduce the amount of sulfurized starch that is repeated in the smelting process.
以下、本発明の一具体例の廃酸の処理方法について図１を参照しながら説明する。この本発明の一具体例の処理方法は、銅製錬排ガスの処理の際に生じる重金属及び硫酸分を含む廃酸に対して硫化剤を添加して重金属から硫化澱物を生成し、これを固液分離により除去する第１硫化工程と、該第１硫化工程で除去した後の処理液に炭酸カルシウムを添加して硫酸分を石膏として回収する石膏製造工程と、該石膏製造工程で石膏を回収した後の処理液に再度硫化剤を添加して残存する重金属から硫化澱物を生成し、これを固液分離により回収する第２硫化工程と、第２硫化工程で回収した硫化澱物を処理して有価金属であるカドミウムや亜鉛を回収する有価金属回収工程とで構成される。 Hereinafter, a method for treating waste acid according to one embodiment of the present invention will be described with reference to FIG. In the treatment method of one specific example of the present invention, a sulfidizing agent is added to a waste acid containing a heavy metal and a sulfuric acid content generated during the treatment of a copper smelting exhaust gas to produce a sulfided starch from the heavy metal, which is solidified. A first sulfurization step of removing by liquid separation, a gypsum production step of adding calcium carbonate to the treatment liquid after removal in the first sulfurization step to recover sulfuric acid as gypsum, and a gypsum recovery step of the gypsum production step The sulphating agent is added again to the treated liquid after treatment to form a sulfurized starch from the remaining heavy metal, and the second sulfurization step of recovering the sulfurized solid by solid-liquid separation and the sulfurized starch recovered in the second sulfurization step are treated. And a valuable metal recovery step of recovering valuable metals such as cadmium and zinc.
各工程について具体的に説明すると、先ず第１硫化工程では、廃酸に硫化剤を添加して混合し、酸化還元電位（ＯＲＰ）約８０〜１１０ｍＶ（銀−塩化銀電極基準）の条件で硫化反応を行って硫化澱物を生成させる（第１硫化反応ステップ）。上記硫化剤には、水硫化ナトリウム（硫化水素ナトリウム）ＮａＨＳ、硫化水素Ｈ２Ｓ、硫化ナトリウムＮａ２Ｓ等の一般的な硫化剤を使用することができる。これらの中では、水硫化ナトリウムと硫化水素がコストの点で優れており、また、石膏製造に適した硫酸濃度の石膏始液が得られる点においても特に有利である。 Explaining each step in detail, first, in the first sulfurization step, a sulfidizing agent is added to waste acid and mixed, and the sulfurization is performed under the condition of redox potential (ORP) of about 80 to 110 mV (based on silver-silver chloride electrode). The reaction is performed to form a sulfurized starch (first sulfurization reaction step). As the sulfiding agent, a general sulfiding agent such as sodium hydrosulfide (sodium hydrogen sulfide) NaHS, hydrogen sulfide H 2 S, sodium sulfide Na 2 S or the like can be used. Among these, sodium hydrosulfide and hydrogen sulfide are excellent in terms of cost, and are particularly advantageous in that a gypsum starter solution having a sulfuric acid concentration suitable for gypsum production can be obtained.
上記第１硫化反応ステップで得た硫化澱物を含む第１スラリーは、次に固液分離手段によって硫化澱物に富む第１濃縮物と第１清澄液とに分離する（第１固液分離ステップ）。上記固液分離手段には比較的低コストで大量のスラリーを処理できるシックナーを用いるのが好ましい。 The first slurry containing the sulfurized starch obtained in the first sulfurization reaction step is then separated by a solid-liquid separation means into a first concentrate rich in sulfurized starch and a first clear liquid (first solid-liquid separation). Step). As the solid-liquid separation means, it is preferable to use a thickener that can process a large amount of slurry at a relatively low cost.
上記第１固液分離ステップで得た硫化澱物を含む第１濃縮物は、次に脱水手段によって含水率を低減させ（第１脱水ステップ）、その後、銅製錬工程の自熔炉、転炉などの炉に送り、熔融金属と共に処理する。上記脱水手段にはフィルタープレス、真空式ろ過機、ベルトプレス、遠心分離機等の一般的な脱水装置を使用することができる。なお、この脱水手段で上記の第１固液分離ステップと第１脱水ステップとの両方を行ってもよい。 The first concentrate containing the sulfided starch obtained in the first solid-liquid separation step is then reduced in water content by a dehydrating means (first dehydration step), and thereafter, a flash smelting furnace in a copper smelting process, a converter, etc. Sent to the furnace for processing with molten metal. As the dehydrating means, a general dehydrating device such as a filter press, a vacuum filter, a belt press, a centrifuge or the like can be used. It should be noted that this dehydrating means may perform both the first solid-liquid separation step and the first dehydrating step.
一方、上記第１固液分離ステップで得た第１清澄液は、上記固液分離手段で分離できなかった細かな固形分をろ過により除去した後、石膏始液として石膏製造工程の中和槽に送られる。この中和槽において、石膏始液にカルシウム系中和剤を添加して中和反応を行って、硫酸分を石膏として析出させる。この石膏を含むスラリーから石膏を固液分離により除去することで、硫酸分が除かれた石膏終液が得られる。上記のカルシウム系中和剤としては、炭酸カルシウム（石灰石）、水酸化カルシウム、酸化カルシウムなどを粉砕したものを用いるのがコスト的な観点から好ましい。なお、上記カルシウム系中和剤は、炭酸ナトリウムや水酸化ナトリウムを不純物として含んでいても問題なく使用することができる。 On the other hand, the first clarified liquid obtained in the first solid-liquid separation step is obtained by removing fine solids that could not be separated by the solid-liquid separation means by filtration, and then used as a gypsum starting solution in a neutralization tank in the gypsum manufacturing process. Sent to. In this neutralization tank, a calcium-based neutralizing agent is added to the gypsum starter solution to carry out a neutralization reaction to deposit sulfuric acid as gypsum. By removing the gypsum from the slurry containing this gypsum by solid-liquid separation, a gypsum final solution free of sulfuric acid is obtained. As the above-mentioned calcium-based neutralizing agent, it is preferable to use crushed calcium carbonate (limestone), calcium hydroxide, calcium oxide or the like from the viewpoint of cost. The calcium-based neutralizing agent can be used without problems even if it contains sodium carbonate or sodium hydroxide as impurities.
上記の石膏製造工程で得た石膏終液は、次に第２硫化工程において第２硫化反応ステップ、第２固液分離ステップ及び第２脱水ステップの順に処理される。即ち、第２硫化反応ステップでは、石膏終液に硫化剤として水硫化ナトリウム又は硫化水素を添加して混合し、酸化還元電位約１０ｍＶの条件で硫化反応を行って硫化澱物を含む第２スラリーを得る。この第２スラリーは第２固液分離ステップの固液分離手段で硫化澱物に富む第２濃縮物と第２清澄液とに固液分離する。この第２濃縮物は、第２脱水ステップの脱水手段で含水率を低減し、第２硫化澱物として回収する。一方、第２清澄液は活性汚泥などの一般的な排水処理工程に送って処理する。上記の第２固液分離ステップの固液分離手段及び第２脱水ステップの脱水手段には、それぞれ前述した第１固液分離ステップの固液分離手段及び第１脱水ステップの脱水手段と同様の装置を使用することが好ましい。 The gypsum final liquid obtained in the above-mentioned gypsum production process is then treated in the second sulfidation process in the order of the second sulfidation reaction step, the second solid-liquid separation step, and the second dehydration step. That is, in the second sulfidation reaction step, sodium hydrosulfide or hydrogen sulfide as a sulfiding agent is added to and mixed with the final gypsum liquid, and the sulfidation reaction is performed under the condition of redox potential of about 10 mV to obtain the second slurry containing the sulfurized precipitate. To get The second slurry is subjected to solid-liquid separation into a second concentrated liquid rich in sulphated starch and a second clarified liquid by the solid-liquid separation means in the second solid-liquid separation step. The second concentrate has its water content reduced by the dehydrating means in the second dehydrating step and is recovered as the second sulfurized starch. On the other hand, the second clarified liquid is sent to a general wastewater treatment process such as activated sludge for treatment. The solid-liquid separation means of the second solid-liquid separation step and the dehydration means of the second dehydration step are the same devices as the solid-liquid separation means of the first solid-liquid separation step and the dehydration means of the first dehydration step described above, respectively. Is preferably used.
有価金属回収工程では、先ず上記の第２脱水ステップで得た第２硫化澱物に対して硫黄除去工程又は硫黄酸化工程を行うことで、様々な亜鉛精製法やカドミウム精製法に適した亜鉛やカドミウムの濃縮物を得ることができる。硫黄除去工程は第２硫化澱物から硫黄を分離するもので、５００℃以上での焙焼や真空蒸発などの一般的な方法を用いることができる。硫黄酸化工程は第２硫化澱物を酸化して硫化物を硫酸塩又は亜硫酸塩に変えるものであり、例えば硫酸、酸素、空気などの酸化剤で硫黄を酸化する方法を挙げることができる。 In the valuable metal recovery step, first, a sulfur removal step or a sulfur oxidation step is performed on the second sulfurized starch obtained in the second dehydration step, so that zinc suitable for various zinc refining methods and cadmium refining methods can be obtained. A cadmium concentrate can be obtained. In the sulfur removal step, sulfur is separated from the second sulfurized starch, and a general method such as roasting at 500° C. or higher and vacuum evaporation can be used. The sulfur oxidation step oxidizes the second sulfurized starch to convert the sulfide into a sulfate or sulfite, and examples thereof include a method of oxidizing sulfur with an oxidizing agent such as sulfuric acid, oxygen, or air.
以降は公知の精製法を用いて該濃縮物から亜鉛やカドミウムを回収することができる。例えば硫黄除去工程又は硫黄酸化工程と同時に、あるいはその後段において、硫酸などの浸出液で亜鉛やカドミウムを浸出し、得られた亜鉛やカドミウムを含む溶解液に対して、例えば分別蒸留などの精製手段で処理することで亜鉛とカドミウムを分離して回収することができる。 After that, zinc and cadmium can be recovered from the concentrate by using a known purification method. For example, at the same time as the sulfur removal step or the sulfur oxidation step, or in the subsequent stage, zinc or cadmium is leached with a leachate such as sulfuric acid, and the obtained solution containing zinc or cadmium is purified by, for example, fractional distillation. By processing, zinc and cadmium can be separated and recovered.
ところで、上記の硫黄除去工程や硫黄酸化工程で得た亜鉛やカドミウムの濃縮物の砒素品位が高いと、その後段の亜鉛精製やカドミウム精製で砒素を除去するのが困難になる。従って上記濃縮物の砒素品位を下げるには、第２硫化澱物の砒素品位を下げるのが望ましく、そのためには、第１硫化工程で硫化剤を多めに添加し、砒素を第１硫化澱物として除去することが有効である。 By the way, if the arsenic grade of the zinc or cadmium concentrate obtained in the above-mentioned sulfur removal step or sulfur oxidation step is high, it becomes difficult to remove arsenic by the subsequent zinc purification or cadmium purification. Therefore, in order to reduce the arsenic grade of the above concentrate, it is desirable to lower the arsenic grade of the second sulphurized starch. It is effective to remove as.
そこで、本発明の一具体例の廃酸の処理方法では、第２硫化澱物の砒素品位が０.１〜３.０質量％になるように、好ましくは０.５〜２.０質量％になるように、第１硫化工程で添加する硫化剤の量の調整を行っている。廃酸中の砒素含有量が多くなると多量の硫化剤を添加する必要があるが、前述したように第１硫化工程において処理液の酸化還元電位（ＯＲＰ）を８０〜１１０ｍＶ（銀−塩化銀電極基準）となる程度に硫化剤を添加すれば、通常は上記の範囲の砒素品位に制御することができる。 Therefore, in the method for treating waste acid according to one embodiment of the present invention, the arsenic quality of the second sulfide is preferably 0.1 to 3.0% by mass, preferably 0.5 to 2.0% by mass. The amount of the sulfiding agent added in the first sulfiding step is adjusted so that When the arsenic content in the waste acid increases, it is necessary to add a large amount of sulfidizing agent, but as described above, the redox potential (ORP) of the treatment liquid in the first sulfiding step is 80 to 110 mV (silver-silver chloride electrode). If a sulfiding agent is added to the extent of the standard), the arsenic grade can be controlled usually within the above range.
上記のように、回収する亜鉛やカドミウムの純度を高めるには第１硫化工程で硫化剤を多めに添加することが有効であるが、この添加量が多すぎると、亜鉛やカドミウムが第１硫化澱物となって除去されてしまう。従って、回収する亜鉛やカドミウムの純度とその回収量とを両立させるため、上記した程度に第２硫化澱物に砒素が含まれているのが好ましい。これにより、硫化剤を節約することも可能になる。 As described above, it is effective to add a large amount of the sulfiding agent in the first sulfiding step in order to increase the purity of the recovered zinc or cadmium. It is removed as a precipitate. Therefore, in order to make both the purity of zinc and cadmium to be recovered and the amount of recovery thereof compatible, it is preferable that the second sulfide precipitate contains arsenic to the extent described above. This also makes it possible to save on the sulfiding agent.
銅製錬プロセスで処理する原料に含まれる砒素の量が増えると廃酸中の砒素量が増えるので、上記したように第１硫化工程で硫化剤を多く添加する必要が生じる。硫化剤を多く添加した結果、当該第１硫化工程やその後段の工程が行われる反応槽などの機器から硫化水素ガスが発生しやすくなるので、問題を生じるおそれがある。 When the amount of arsenic contained in the raw material treated in the copper smelting process increases, the amount of arsenic in the waste acid increases, so that it is necessary to add a large amount of the sulfiding agent in the first sulfiding step as described above. As a result of adding a large amount of the sulfiding agent, hydrogen sulfide gas is likely to be generated from equipment such as a reaction tank in which the first sulfiding step and the subsequent steps are performed, which may cause a problem.
そこで、以下に示す３つ対応策の内のいずれか１つ以上を行うのがよい。なお、図２には下記第１及び第２の対応策を含んだブロックフロー図が示されている。すなわち、第１の対応策は、第１硫化工程が行われる１つ又は複数の反応槽内の処理液から発生するガスをファン等によって捕集し、この捕集ガスが含有する硫化水素を吸収剤によって吸収するものである。吸収剤としては、例えば水酸化ナトリウムなどのアルカリを使用することができるが、硫化剤を添加する前の廃酸の少なくとも一部を吸収剤として捕集ガスに気液接触させることもできる。この場合、廃酸が含有する重金属の一部は、硫化水素の一部を吸収して硫化澱物を生成するので、この硫化水素に予硫化の役割を担わせることができる。よって、硫化水素を吸収した廃酸を第１硫化反応ステップに送ることで、第１硫化工程で使用する硫化剤を削減することができる。 Therefore, it is preferable to take one or more of the following three countermeasures. Note that FIG. 2 shows a block flow diagram including the following first and second countermeasures. That is, the first countermeasure is to collect the gas generated from the treatment liquid in the one or more reaction tanks in which the first sulfurization step is performed by a fan or the like, and absorb the hydrogen sulfide contained in the collected gas. It is absorbed by the agent. As the absorbent, for example, an alkali such as sodium hydroxide can be used, but at least a part of the waste acid before the addition of the sulfiding agent can be used as an absorbent to be brought into gas-liquid contact with the trapped gas. In this case, a part of the heavy metal contained in the waste acid absorbs a part of hydrogen sulfide to form a sulfided starch, so that this hydrogen sulfide can play a role of pre-sulfurization. Therefore, by sending the waste acid that has absorbed hydrogen sulfide to the first sulfurization reaction step, it is possible to reduce the sulfurizing agent used in the first sulfurization step.
第２の対応策は、第１硫化反応ステップで処理する廃酸に、廃酸の酸濃度を低下させるため希釈液を添加するものである。廃酸のｐＨは一般に３未満なので、廃酸よりもｐＨが高い液を使用する。希釈液としては、例えばｐＨが３〜１４の範囲内の水溶液が好ましく、硫化澱物を良好にろ過する観点からは、ｐＨが３〜８の範囲内の水溶液がより好ましい。このように希釈液で廃酸を希釈することにより、次の反応を抑制できる。 The second countermeasure is to add a diluent to the waste acid treated in the first sulfurization reaction step in order to reduce the acid concentration of the waste acid. Since the pH of waste acid is generally less than 3, a liquid having a higher pH than waste acid is used. As the diluting liquid, for example, an aqueous solution having a pH in the range of 3 to 14 is preferable, and an aqueous solution having a pH in the range of 3 to 8 is more preferable from the viewpoint of filtering the sulfurized starch well. By diluting the waste acid with the diluent as described above, the following reaction can be suppressed.
［化学式１］
２ＮａＨＳ＋Ｈ２ＳＯ４→２Ｈ２Ｓ↑＋Ｎａ２ＳＯ４
［化学式２］
ＭＳ＋Ｈ２ＳＯ４→Ｈ２Ｓ↑＋ＭＳＯ４
（式中のＭは２価の金属元素を表す）
希釈液としては、例えば他工程からの排液を用いることができ、重金属を含有している廃液であっても特に問題なく好適に用いることができる。
[Chemical formula 1]
2NaHS+H 2 SO 4 →2H 2 S↑+Na 2 SO 4
[Chemical formula 2]
MS+H 2 SO 4 →H 2 S↑+MSO 4
(M in the formula represents a divalent metal element)
As the diluting liquid, for example, a drainage liquid from another process can be used, and a waste liquid containing a heavy metal can be preferably used without any particular problem.
第３の対応策は、ファンやダクトを備えてない等の事情のある反応槽に処理液を送液する場合に好適な方法であり、該送液前に処理液をエアレーション（すなわち、処理液中に空気等のガスを吹き込む）しながら、浮上して液面から発生するガスを捕集するものである。このエアレーションによって、液中の硫化水素分圧が低下すると共に気液接触が促進されるので、溶存していた硫化水素を速やかに取り除くことができる。なお、捕集したガスは、前述した第１の対応策と同様に、吸収剤であるアルカリや廃酸の少なくとも一部に気液接触させてガス中の硫化水素を吸収すればよい。 The third countermeasure is a method suitable for feeding the treatment liquid to a reaction tank in which there is a situation such as not having a fan or a duct, and the treatment liquid is aerated (that is, the treatment liquid before the feeding). While blowing a gas such as air into it), it floats and collects the gas generated from the liquid surface. This aeration lowers the partial pressure of hydrogen sulfide in the liquid and promotes gas-liquid contact, so that the dissolved hydrogen sulfide can be quickly removed. Note that the collected gas may be brought into gas-liquid contact with at least a part of the alkali or waste acid that is the absorbent to absorb the hydrogen sulfide in the gas, as in the first countermeasure described above.
以上説明したように、本発明の廃酸の処理方法は、廃酸の浄化だけでなく亜鉛やカドミウムなどの有価金属を回収できる。特に、第２硫化工程の前段に石膏製造工程があるので石膏終液の酸濃度を低減でき、第２硫化工程において硫化水素の発生を抑えながら反応を進めることができる。また、石膏製造工程の前段に第１硫化工程があるので、石膏の品質を向上することができる。 As explained above, the waste acid treatment method of the present invention can not only purify the waste acid but also recover valuable metals such as zinc and cadmium. In particular, since the gypsum production step is provided before the second sulfurization step, the acid concentration of the final gypsum solution can be reduced, and the reaction can proceed while suppressing the generation of hydrogen sulfide in the second sulfurization step. Further, since the first sulfurization step is provided before the gypsum manufacturing step, the quality of gypsum can be improved.
［実施例］
銅製錬プラントから実際に排出された重金属及び硫酸を含むｐＨ０の廃酸を、３００Ｌ／分の流量で第１硫化反応ステップを行う反応槽に供給し、ここに濃度２５質量％の水硫化ナトリウムをＯＲＰが１１０ｍＶ（銀−塩化銀電極基準）となるように添加することにより第１硫化澱物を含む第１スラリーを得た。この第１スラリーを第１固液分離ステップのシックナーにて固液分離し、第１上澄み液と沈降濃縮した底部抜き出しの第１濃縮物とに分離した。この第１濃縮物を貯液槽に溜めた後、第１脱水ステップのフィルタープレスでろ過することにより第１硫化澱物を回収した。
[Example]
Waste acid of pH 0 containing heavy metals and sulfuric acid actually discharged from a copper smelting plant is supplied to a reaction tank for performing the first sulfurization reaction step at a flow rate of 300 L/min, and sodium hydrosulfide having a concentration of 25% by mass is added thereto. ORP was added to 110 mV (based on silver-silver chloride electrode) to obtain a first slurry containing the first sulphated starch. The first slurry was subjected to solid-liquid separation with a thickener in the first solid-liquid separation step, and separated into a first supernatant liquid and a sediment-concentrated bottom-extracted first concentrate. After the first concentrate was stored in the liquid storage tank, it was filtered with a filter press in the first dehydration step to recover the first sulfide precipitate.
一方、第１上澄み液は、微細な粒子をフィルタープレスでろ過して除いた後、得られた石膏始液を石膏製造工程へ送液した。ここで中和ステップを行うべく石膏始液に炭酸カルシウムを添加してｐＨ２.３に調整し、石膏を析出させた。この石膏を含むスラリーを固液分離して石膏と石膏終液とを得た。この石膏終液は、第２硫化工程の反応槽に送液した。 On the other hand, in the first supernatant, fine particles were filtered out with a filter press, and the obtained gypsum starting solution was sent to the gypsum manufacturing process. To perform the neutralization step, calcium carbonate was added to the gypsum initial solution to adjust the pH to 2.3, and gypsum was deposited. The slurry containing this gypsum was subjected to solid-liquid separation to obtain gypsum and gypsum final solution. This final gypsum solution was sent to the reaction tank of the second sulfiding step.
第２硫化工程の反応槽では、第２硫化反応ステップを行うべく、ＯＲＰが１０ｍＶ（銀−塩化銀電極基準）となるように調整しながら石膏終液に水硫化ナトリウムを添加して第２硫化澱物を含む第２スラリーを得た。この第２スラリーを第２固液分離ステップのシックナーで固液分離し、第２上澄み液と沈降濃縮した底部抜き出しの第２濃縮物とに分離した。この第２濃縮物を貯液槽に溜めた後、第２脱水ステップのフィルタープレスでろ過した。これにより、試料１の第２硫化澱物を回収した。得られた試料１の第２硫化澱物の砒素の含有量をＩＣＰ発光分光法を用いて分析したところ、３.０質量％であった。 In the reaction tank of the second sulfurization process, sodium hydrosulfide was added to the final gypsum solution while adjusting the ORP to 10 mV (based on silver-silver chloride electrode) in order to perform the second sulfurization reaction step. A second slurry containing starch was obtained. The second slurry was subjected to solid-liquid separation with a thickener in the second solid-liquid separation step, and separated into a second supernatant liquid and a second concentrate which was sedimented and concentrated and was withdrawn at the bottom. After the second concentrate was stored in the liquid storage tank, it was filtered by the filter press in the second dehydration step. As a result, the second sulphurized starch of Sample 1 was recovered. The content of arsenic in the second sulphurized starch of the obtained sample 1 was analyzed by ICP emission spectroscopy and found to be 3.0% by mass.
上記試料１の第２硫化澱物をビーカーに分取し、撹拌しながら空気を吹き込むと共に硫酸を徐々に添加したところ、第２硫化澱物の全量が溶解した。この溶解液に亜鉛粉末を溶けなくなるまで添加したところ、沈殿が生じた。亜鉛粉末を添加後の溶解液を５Ｃの濾紙を用いてろ過し、固形分と濾液とに分離した。濾液を乾燥したところ、結晶が得られた。この結晶をＸ線回折で分析したところ硫酸亜鉛であった。一方、固形分をＩＣＰ発光分光法を用いて分析したところ、カドミウムの含有量が８０質量％以上であり、該固形分中の砒素の含有量（質量）はカドミウムの約１／５であった。 The second sulfurized starch of Sample 1 was sampled in a beaker, air was blown into the beaker while stirring, and sulfuric acid was gradually added. As a result, the entire second sulfurized starch was dissolved. When zinc powder was added to this solution until it could not be dissolved, precipitation occurred. The solution after adding the zinc powder was filtered using a 5C filter paper to separate into a solid content and a filtrate. When the filtrate was dried, crystals were obtained. When this crystal was analyzed by X-ray diffraction, it was zinc sulfate. On the other hand, when the solid content was analyzed by ICP emission spectroscopy, the content of cadmium was 80% by mass or more, and the content (mass) of arsenic in the solid content was about 1/5 of that of cadmium. ..
次に、第１硫化工程のＯＲＰを８０ｍＶにした以外は上記試料１の場合と同様にして廃酸を処理し、試料２の第２硫化澱物を作製した。この試料２の第２硫化澱物の砒素の含有量は１.５質量％であった。得られた試料２の第２硫化澱物に対して上記試料１の場合と同様に処理して固形分と結晶を作製した。その結果、得られた結晶をＸ線回折で分析したところ硫酸亜鉛であった。また、固形分をＩＣＰ発光分光法を用いて分析したところ、カドミウムの含有量が８０質量％以上であり、該固形分中の砒素の含有量（質量）はカドミウムの約１／１０であった。 Then, the waste acid was treated in the same manner as in the case of the above-mentioned sample 1 except that the ORP of the first sulfurization step was set to 80 mV, to prepare the second sulfurized starch of the sample 2. The content of arsenic in the second sulphurized starch of Sample 2 was 1.5% by mass. The second sulfurized starch of the obtained sample 2 was treated in the same manner as in the case of the above sample 1 to prepare a solid content and crystals. As a result, the crystals obtained were analyzed by X-ray diffraction and found to be zinc sulfate. When the solid content was analyzed by ICP emission spectroscopy, the content of cadmium was 80% by mass or more, and the content (mass) of arsenic in the solid content was about 1/10 of that of cadmium. ..
更に、第１硫化工程のＯＲＰを１２０ｍＶにした以外は上記試料１の場合と同様にして廃酸を処理し、試料３の第２硫化澱物を作製した。この試料３の第２硫化澱物の砒素の含有量は３.９質量％であった。得られた試料３の第２硫化澱物に対して上記試料１の場合と同様に処理して固形分と結晶を作製した。その結果、得られた結晶をＸ線回折で分析したところ硫酸亜鉛であった。また、ＩＣＰ発光分光法を用いて固形分を分析したところ、カドミウムの含有量が８０質量％未満であり、該固形分中の砒素の含有量（質量）はカドミウムの約１／４であった。 Further, the waste acid was treated in the same manner as in the case of the above-mentioned sample 1 except that the ORP of the first sulfurization step was set to 120 mV, to prepare the second sulfurized starch of the sample 3. The arsenic content of the second starch sulfide of Sample 3 was 3.9% by mass. The second sulfurized starch of the obtained sample 3 was treated in the same manner as in the case of the above sample 1 to prepare a solid content and crystals. As a result, the crystals obtained were analyzed by X-ray diffraction and found to be zinc sulfate. Moreover, when the solid content was analyzed by ICP emission spectroscopy, the content of cadmium was less than 80 mass %, and the content (mass) of arsenic in the solid content was about ¼ of that of cadmium. ..
［参考例］
第２硫化澱物に硫酸でなく水を添加した以外は、上記実施例と同様にしたところ、第２硫化澱物はほぼ溶解しなかった。第２硫化澱物の懸濁水溶液に亜鉛粉末を添加したところ、ほとんど溶けなかったので中止した。
[Reference example]
The same procedure as in the above Example was carried out except that water was added to the second sulfurized starch instead of sulfuric acid, but the second sulfurized starch was hardly dissolved. When zinc powder was added to the suspension solution of the second sulphurised starch, it was almost insoluble, so the operation was stopped.
［実施例２］
上記試料１の第２硫化澱物をロータリーキルンに装入して１０００℃で焙焼し、煙灰を回収した。この煙灰に水を添加したところ、煙灰の全量が溶解した。この溶解液に亜鉛粉末を溶けなくなるまで添加したところ、沈殿が生じた。亜鉛粉末を添加した後の溶解液を５Ｃの濾紙を用いてろ過し、固形分と濾液とに分離した。濾液を乾燥したところ、結晶が得られた。この結晶をＸ線回折で分析したところ硫酸亜鉛であった。一方、固形分をＩＣＰ発光分光法を用いて分析したところ、カドミウムの含有量が８０質量％以上であり、該固形分中の砒素の含有量（質量）はカドミウムの約１／５であった。
[Example 2]
The second sulfurized starch of Sample 1 was charged into a rotary kiln and roasted at 1000° C. to collect smoke ash. When water was added to this smoke ash, the whole amount of the smoke ash was dissolved. When zinc powder was added to this solution until it could not be dissolved, precipitation occurred. The solution after adding the zinc powder was filtered using a 5C filter paper to separate a solid content and a filtrate. When the filtrate was dried, crystals were obtained. When this crystal was analyzed by X-ray diffraction, it was zinc sulfate. On the other hand, when the solid content was analyzed by ICP emission spectroscopy, the content of cadmium was 80% by mass or more, and the content (mass) of arsenic in the solid content was about 1/5 of that of cadmium. ..
［実施例３］
上記試料２の第２硫化澱物をロータリーキルンに装入して１４００℃で焙焼し、煙灰を回収した。この煙灰に水を添加したところ、煙灰の全量が溶解した。この溶解液に亜鉛粉末を溶けなくなるまで添加したところ、沈殿が生じた。亜鉛粉末を添加した後の溶解液を５Ｃの濾紙を用いてろ過し、固形分と濾液とに分離した。濾液を乾燥したところ、結晶が得られた。この結晶をＸ線回折で分析したところ硫酸亜鉛であった。一方、固形分をＩＣＰ発光分光法を用いて分析したところ、カドミウムの含有量が８０質量％以上であり、該固形分中の砒素の含有量（質量）はカドミウムの約１／１０であった。
[Example 3]
The second sulphurized starch of Sample 2 was charged into a rotary kiln and roasted at 1400° C. to collect smoke ash. When water was added to this smoke ash, the whole amount of the smoke ash was dissolved. When zinc powder was added to this solution until it could not be dissolved, precipitation occurred. The solution after adding the zinc powder was filtered using a 5C filter paper to separate into a solid content and a filtrate. When the filtrate was dried, crystals were obtained. When this crystal was analyzed by X-ray diffraction, it was zinc sulfate. On the other hand, when the solid content was analyzed by ICP emission spectroscopy, the content of cadmium was 80% by mass or more, and the content (mass) of arsenic in the solid content was about 1/10 of that of cadmium. ..
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| CN108285229A (en) * | 2018-02-09 | 2018-07-17 | 武汉飞博乐环保工程有限公司 | The waste acid processing method of nonferrous smelting |
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