CN1178261A - Method for recovering etchant from etching waste liquid containing iron chloride - Google Patents

Abstract

Method for recovering etching waste liquid containing iron chloride is disclosed, wherein iron powder is mixed with iron chloride waste solution containing copper ion, nickel ion etc. metal ions having a lesser ionization tendency than iron ion in an mixing vessel so as to cause a reaction between the iron powder and the metal ions and remove the precipitated metal. The etching waste liquid containing iron chloride or the iron chloride waste liquid which is an intermediate of the etching waste liquid containing iron chloride is supplied to the mixing vessel from the bottom of the mixing vessel, an iron-powder processed liquid is simultaneously taken out from the mixing vessel and is returned to the bottom portion of mixing vessel so as to form the fluidized bed and produce the iron-powder processed liquid in which metal ions having the lesser ionization tendency than iron ion.

Description

Regeneration method of ferric chloride corrosion waste liquid

The present invention relates to a method for regenerating an iron chloride-based waste etching solution, which is extremely suitable for the regeneration treatment of an etching solution for removing metal ions (e.g., copper and nickel) having an ionization tendency smaller than that of iron from an iron chloride-based waste etching solution generated during the etching treatment of Integrated Circuits (ICs), lead frames for large scale integrated circuits (LSIs) and shadow masks for cathode ray tubes.

Conventionally, lead frames and shields for IC and LSI use a plate-like material made of, for example, copper or an iron-nickel alloy material, which is manufactured by a method of partially etching with an etching solution containing a large amount of ferric chloride. After the etching treatment, ferric chloride contained in the etching solution is reduced to ferrous chloride, the concentration of ferric chloride is reduced, and the etching efficiency is deteriorated, so that the etching solution needs to be replaced periodically. After such corrosion treatment, the waste corrosion liquid as the waste liquid contains a considerable amount of valuable copper ions, nickel ions, and the like in addition to iron ions at a high concentration. Further, after removing these metal ions from the waste etching solution, a reusable etching solution can be obtained.

Thus, Japanese patent application laid-open No. 1-167235 discloses a method of regenerating an etching liquid, in which scrap iron or iron powder is added to anetching waste liquid to reduce metal ions (for example, copper ions and nickel ions) having a smaller ionization tendency than iron in the etching waste liquid, and copper and nickel in the waste liquid are recovered. However, the method disclosed in this publication has problems that the grade of copper and nickel recovered is low, and that the reaction rate with the waste corrosive liquid is low when the reaction is carried out using iron scrap.

Thus, Japanese patent application laid-open No. 6-127946 discloses a method for regenerating an iron chloride-based corrosive liquid, in which iron powder is added to a strong acid corrosive waste liquid containing copper, nickel and a small amount of chromium, the oxidation-reduction potential (ORP) and the iron ion concentration are controlled, copper and nickel dissolved therein are successively displaced and precipitated to obtain a purified iron chloride solution, and suspended impurities such as iron hydroxide are separated and removed therefrom.

However, in the method disclosed in japanese patent application laid-open No. 6-127946, in the reduction removal treatment of metal ions, since the stirring blade is provided in the stirring tank and the stirring is performed by rotating the stirring blade by driving a motor, there are problems described in the following (1) to (5).

(1) The indispensable conditions for treating the waste corrosive liquid are as follows: maintaining the waste corrosion liquid in the stirring tank in a good flowing state, and keeping a large amount of iron powder in a dispersed state; however, in the case of the stirring blade type mechanical stirring reactor, there is a limitation in facilities (for example, a large motor for operating a large stirring blade requires a large amount of power) to maintain the iron powder in a dispersed state in the corrosive waste liquid, and therefore, it is not suitable for the treatment of a large amount of waste liquid.

(2) In order to disperse a large amount of iron powder having a high specific gravity uniformly in the waste corrosive liquid and maintain the suspension flow state, it is necessary to drive the stirring blades with extremely high power, and therefore, the running cost is increased.

(3) Because the iron powder is stirred at a high speed by the stirring blades and the inner wall of the stirring tank and the stirring blades are in contact with the iron powder, the abrasion loss of the iron powder is increased, and the maintenance cost of the stirring tank is increased.

(4) Iron powder is retained at the corners of the stirring tank, so that a dead space in which the corrosion waste liquid cannot be sufficiently stirred can be formed, the stirring efficiency is reduced, and the time required for removing metal ions having a smaller ionization tendency than iron in the corrosion waste liquid is prolonged.

(5) It is known that in a stirring tank in which forced stirring is performed using a stirring blade, it is relatively easy to maintain a good suspension flow state using a small-particle-size iron powder, but the use of such a special-particle-size iron powder increases the raw material cost.

In addition, in the case of placing the waste corrosion liquid into a stirring tank and reducing the waste corrosion liquid by using iron powder to remove impurity metals, if ferric chloride high-valence iron ions exist, the ferric ions firstly generate reaction to consume the iron powder, and finally the total amount of the ferrous ions and the ferric ions in the waste corrosion liquid is increased; therefore, in order to make the etching solution having a predetermined concentration suitable for use, it is necessary to dilute the solution at last, so that a large amount of etching solution exceeding the required amount is formed, the storage facilities are enlarged, and there is a problem that the generated etching solution is not completely used, and the remaining etching solution which is not used is disposed.

On the other hand, a method for producing iron powder which can be used in the above-mentioned method for treating a waste corrosion liquid is disclosed in, for example, Japanese patent publication No. 57-44724, and the method comprises the following four steps.

That is, in the first step, dust generated in a converter for blowing pure oxygen steel is recovered by a wet method, and the dust is classified so that fine particles having a particle size of 44 μm or less account for 30% or less; subsequently, in the second step, impurities such as scale and slag are removed from the coarse dust by using a wet type fine powder pulverizer; in the third procedure, impurities in the dust from which the scale and the slag are removed to obtain metallic iron; in the fourth step, this metallic iron is further refined to obtain an iron powder.

However, in the method described in the above-mentioned Japanese patent publication No. 57-44724, the step of removing impurities from the dust is performed by classification, thin-flow dressing or magnetic separation, and therefore, there is a problem that the dust treatment capacity is low and the treatment of a large amount of dust is difficult. In addition, since a combined method such as iron oxide purification or dilute acid leaching purification is used in the metallic iron purification step, there is a problem of high cost.

In view of the above circumstances, an object of the present invention is to provide a method for regenerating an iron chloride-based corrosive waste liquid, which can efficiently reduce and treat a larger amount of the corrosive waste liquid with less power by using iron powder obtained by washing dust generated from a steel making furnace, and can also reduce and recover metal ions (which may be called "impurity metal ions") present in the iron chloride-based corrosive waste liquid, the metal ions having a lower ionization tendency than iron, such as copper and nickel.

Another object of the present invention is to provide a method for regenerating an iron chloride-based waste etching solution, which can reduce the amount of an excessive amount of etching solution (which is formed when iron powder is added to the waste etching solution to reduce and recover metals such as copper and nickel and finally adjust the concentration of ferric ions to a predetermined level), and can reduce the facility cost and the increase in production cost caused thereby.

The method for regenerating an iron chloride-based corrosive waste liquid according to the present invention, which comprises mixing iron powder into an iron chloride-based waste liquid containing metal ions having a lower ionization tendency than iron, such as copper and nickel, in a stirred tank, reacting the iron powder with the metal ions to precipitate and remove the metal ions, and then subjecting an iron powder-treated liquid to an oxidation treatment, is characterized in that: the iron powder-treating liquid obtained by reacting iron powder is taken out from the upper part of the agitation vessel while supplying the iron chloride-based waste liquid to the agitation vessel, and is circulated and supplied to the bottom part of the agitation vessel, thereby forming a fluidized bed in which iron powder is dispersed and suspended, and the excess iron powder-treating liquid is taken out from the upper part of the agitation vessel.

The method for regenerating an iron chloride-based corrosive waste liquid of the present invention can treat the whole iron powder treatment liquid by taking out the iron powder treatment liquid from which impurity metal ions have been removed from the upper part of a stirred tank and circulating and supplying the iron powder treatment liquid to the bottom part of the stirred tank to form a fluidized bed by this method. Therefore, even if the amount of the iron chloride-based waste liquid to be supplied changes, the fluidized bed can be stably formed, and as a result, the reaction between the iron chloride-based waste liquid and the iron powder can be performed in a stable state. Further, since a part of the iron powder treatment liquid is taken out from the upper part of the agitation vessel and fed from the bottom part, a dead space not participating in the reaction is not formed in the agitation vessel, and a fluidized bed can be formed, so that the efficiency of removing the impurity metal ions in the supplied iron chloride-based waste liquid can be improved.

In the method for regenerating an iron chloride-based waste corrosion solution of the present invention, the iron chloride-based waste corrosion solution is fed from the bottom of the agitation tank, which contributes to the formation of the fluidized bed, and it is desirable that the contact degree between the iron chloride-based waste corrosion solution and the iron powder is increased by this method, thereby increasing the treatment speed.

In the method for regenerating an iron chloride-based corrosive waste liquid according to the present invention, it is preferable that an iron powder separation region having an enlarged diameter with respect to a fluidized bed formation region forming the fluidized bed is provided in an upper part of the agitation tank, and the rising of the iron powder suspended in dispersion is suppressed by decreasing a flow velocity of the rising liquid in the enlarged diameter region. In this way, the ascending flow of the fluid in the agitation vessel is decelerated in the iron powder separation zone, and theiron powder having a particle size exceeding a predetermined particle size cannot float into the iron powder separation zone, and the upper end of the fluidized bed can be held at a fixed position even if the flow rate in the agitation vessel is changed to some extent, so that the operation of removing the impurity metal ions can be performed under stable conditions.

In the above method for regenerating an iron chloride-based corrosion waste liquid of the present invention, it is preferable that the iron chloride-based corrosion waste liquid supplied to the agitation tank is treated as a reduced iron chloride aqueous solution, that is, ferric ions in the iron chloride-based corrosion waste liquid are partially or entirely reduced to ferrous ions by a pre-electrolysis treatment, for the following reason. And electrolyzing the ferric chloride corrosion waste liquid according to the mode to reduce ferric ions into ferrous ions, wherein the total concentration of the ferrous ions and the ferric ions is unchanged. Therefore, when the ferric chloride waste liquid is subjected to oxidation treatment (for example, chlorine gas is introduced) in the final step to form ferric ions, the amount of the corrosive liquid having an applicable concentration to be regenerated does not increase because the iron content does not change. That is, when only iron powder is used for treatment according to the conventional method, since ferric ions contained therein react with the iron powder to form ferrous ions, the amount of iron component contained therein increases more than necessary, and an excess solution is generated when ferrous ions are oxidized in the final step; however, in the present invention, since iron powder is not used when reducing ferric ions to ferrous ions, the generation of an excess solution can be completely eliminated, and thus the cost incurred by treating such an excess solution can be reduced and the size of the treatment equipment can be reduced. Further, since the amountof iron powder used is reduced in the regeneration treatment of the iron chloride-based waste liquid, the treatment cost can be reduced.

In the above electrolytic treatment, the average electrolytic voltage and current density of the iron chloride-based corrosive waste liquid should be controlled to 1 to 4.5 (preferably 1.5 to 3) V and 2 to 40 (preferably 3 to 20) A/dm, respectively². According to this method, the electrolytic voltage and current density during the electrolytic treatment are controlled within specific ranges, so that the impurity metal ions such as copper and nickel contained in the iron chloride-based waste liquid are not precipitated, the desired reduction effect is ensured, and the effect is further achievedThe iron chloride waste liquid is regenerated and treated. Wherein, if the electrolytic voltage is lower than 1V, the theoretical electrolytic voltage actually required for reducing ferric ions into ferrous ions is lower than that required for reducing ferric ions into ferrous ions, and the required reduction effect cannot be obtained; on the other hand, if the electrolytic voltage exceeds 4.5V, the impurity metal ions such as copper and nickel contained in the iron chloride-based corrosive waste liquid are precipitated, which is not preferable. In addition to this, the present invention is,if the current density is less than 2A/dm²Since the treatment capacity of the iron chloride-based waste liquid is reduced, large-scale equipment is required for treating a predetermined amount of liquid; on the contrary, if the current density exceeds 40A/dm²This will increase the electrolytic voltage and increase the cost of electricity, thus being uneconomical. In addition, the load on the electrode is increased, the service life of the electrode is shortened, and the precipitation of impurity metal ions is promoted, which is not preferable.

Further, the distance between the anodeplate and the cathode plate in the electrolytic bath during the above electrolytic treatment is preferably 1.5 to 50 mm. With this configuration, since the inter-electrode distance between the anode plate and the cathode plate in the electrolytic cell is maintained within a specific range, it is possible to suppress the intrusion of chlorine gas generated at the anode plate into the cathode portion, to prevent the oxidation of divalent iron ions, and to prevent the increase in electrolytic voltage. Among them, if the inter-electrode distance is less than 1.5mm, chlorine gas generated at the anode plate easily penetrates the film and enters the cathode portion, which becomes a factor that divalent iron ions are oxidized into trivalent iron at that portion: ( ). In addition, it is actually more difficult to supply the solution to the electrode surface, and therefore metals such as copper and nickel are likely to be deposited. Further, if the inter-electrode distance is more than 50mm, the electrolytic voltage is increased, which is not preferable because the electric power cost is increased. And more preferably the interelectrode distance is 2 to 20 mm.

The electrolytic cell to be subjected to electrolytic treatment is divided into an anode chamber having an anode and a cathode chamber having a cathode by a liquid-permeable membrane, and an iron chloride-based corrosive waste liquid is supplied from a certain position of the cathode chamber, or an iron chloride-reduced aqueous solution passed through the cathode chamber and subjected to reduction treatment may be taken out from another position of the cathode chamber. By this method, the electrolytic treatment can be effectively carried out by preventing the supplied iron chloride-based corrosive waste liquid and the reduced iron chloride aqueous solution from being substantially mixed.

The concentration of ferric ions remaining inthe reduced ferric chloride aqueous solution treated by the electrolytic treatment is preferably in the range of 10 to 120 g/l. The reason is that: when the concentration of ferric ions remaining in the reduced ferric chloride aqueous solution is less than 10 g/l, the amount of ferric ions reduced to ferrous ions per unit current is reduced, and copper and nickel are also precipitated from copper and nickel ions contained in the reduced ferric chloride aqueous solution, which is not good; on the other hand, if the concentration of the ferric ions remaining in the molten reduced chloride exceeds 120g/l, the ferric ions react with the iron powder in the agitation vessel, increasing the consumption of the iron powder and the amount of the extra etching solution. Although the concentration of the ferric ion in the aqueous solution of the molten reduced chloride should be in the range of 10 to 120g/l as described above, it is preferably 100 g/l or less.

Among them, it is preferable that the chlorine gas generated from the anode during the electrolytic treatment is partially or entirely introduced into the iron powder treatment liquid taken out from the agitation vessel to oxidize a part of the divalent iron ions into trivalent iron ions. This method enables to effectively regenerate the iron chloride-based corrosive waste liquid without generating useless by-products.

The iron powder used in the present invention is preferably the refined iron powder thus prepared; that is, dust containing impurities such as calcium oxide generated in a steel making furnace is treated by a wet method, iron powder dust is recovered, and after the iron powder dust is pulverized, the impurities are washed with water, and then acid-washed. The method can effectively utilize iron powder generated by the steel-making furnace and reduce impurities such as calcium oxide in regenerated corrosive liquid.

The pickling of the iron powder dust may be performed by slowly discharging the iron powder dust through a screw conveyor provided in a settling tank in which the iron powder dust is retained and having an acid liquid inlet at an upper portion thereof. This method enables mass production at low cost by continuously treating iron powder used in the reduction treatment of the iron chloride-based waste liquid.

Wherein the hydrogen ion concentration of the acid treatment solution in the precipitation tank is preferably 0.5-3 calculated according to the pH value. Therefore, the content of impurities such as calcium oxide in the refined iron powder can reach a preset level, and meanwhile, the acid liquor cost, the treatment cost and the equipment preservation cost can be kept in a proper range, so that the regeneration treatment of the iron chloride waste liquid can be carried out at low cost. If the hydrogen ion concentration (pH) of the acid solution is less than 0.5, the corrosiveness of the acid solution increases, and special acid-resistant treatment must be performed on the equipment, so that the maintenance cost of the equipment increases. On the other hand, if the hydrogen ion concentration is more than 3, impurities including iron pieces and slag adhering to the iron powder cannot be sufficiently eluted, which is not preferable.

In the method for regenerating an iron chloride-based corrosive waste liquid of the present invention as described above, the "iron chloride-based waste liquid" means that iron chloride (FeCl) is contained therein₂) Iron chloride (FeCl)₃) The acidic aqueous solution such as the waste etching solution of (1) further contains metal ions having a lower ionization tendency than iron, such as copper, nickel and cadmium, dissolved in the etching process.

The iron powder is, for example, powdered iron having a particle size of 44 to 250 μm; the shape includes a spherical shape, a porous shape, and the like, but is not limited thereto, and iron powder, atomized iron powder, and the like can be used.

The fluidized bed is a region of high iron powder density in which the iron powder supplied into the agitation vessel flows in a suspended manner in a certain space by the balance between its own weight and viscous resistance due to the flow of the iron powder supplied from the lower portion.

The iron powder treating liquid is a liquid mainly composed of an aqueous solution in which impurity metal ions such as copper and nickel are reduced and removed from an upper region of the liquid by passing through a fluidized bed, and contains a small amount (for example, less than 20 wt%) of unseparated iron powder and suspended solids.

The iron powder separating region is a region divided in the longitudinal direction of the agitation vessel and located above the fluidized bed without being physically separated from each other. Since the upper portion of the iron powder separating region is enlarged in the horizontal cross section, the flow rate of the molten iron chloride solution supplied from the lower portion of the stirring tank is reduced, and the iron powder in the floating state does not intrude into the iron powder separating region and is substantially kept in the fluidized bed.

FIG. 1 is a schematic explanatory view of the configuration of a waste etching solution treatment apparatus used in a first embodiment of the present invention, which is suitable for regeneration of a waste etching solution of an iron chloride system.

FIG. 2 is an explanatory view of an electrolytic apparatus in the same waste liquid treatment apparatus.

FIGS. 3 to 7 are schematic views showing various arrangements among a plurality of arrangements between a supply position of the iron chloride-based corrosive waste liquid and a withdrawal position of the reduced iron chloride aqueous solution in the electrolytic apparatus.

FIG. 8 is an explanatory view of the structure of an iron powder refining apparatus in the same waste liquid treatment apparatus.

FIG. 9 is a sectional side view of a water washing apparatus and a pickling apparatus used in the fine iron powder refining apparatus.

Fig. 10 is a sectional view taken along line I-I in fig. 9.

Fig. 11 is a configuration diagram of a fine iron collecting apparatus used for obtaining fine iron dust.

FIG. 12 is a schematic diagram of an agitation tank in the same waste liquid treatment apparatus.

FIGS. 13(a), (b) and (c) are graphs showing the change of the electrolysis voltage, current density and ferric ion concentration with time in the electrolysis apparatus, respectively.

FIGS. 14(a), (b), (c) and (d) are graphs showing the change of ion concentration in the regeneration treatment of an iron chloride-based waste liquid.

Fig. 15 is a graph showing changes in the calcium oxide concentration in iron powder dust.

FIG. 16 is a schematic explanatory view of the structure of a waste etching solution treatment apparatus used in a second embodiment of the present invention, which is suitable for regeneration of a waste etching solution of ferric chloride.

FIG. 17 is a sectional view of a second agitation tank used in the same apparatus.

FIG. 18 is a sectional side view showing another form of the second agitation tank.

Fig. 19 is a view taken along line II-II of fig. 18.

The invention is explained below on the basis of the attached specific embodiments with reference to the attached drawings. These descriptions are only limited to an understanding of the present invention.

(first embodiment)

First, the structure of a waste liquid treatment apparatus 10 suitable for the regeneration method of an iron chloride-based corrosive waste liquid used in the first embodiment of the present invention will be described with reference to fig. 1 to 12.

As shown in fig. 1, the waste liquid treatment facility 10 has an electrolytic apparatus 12 for reducing ferric ions to ferrous ions in a raw material iron chloride-based corrosive waste liquid 11, an iron powder refining facility 16 for refining iron powder dust 14 discharged from a converter 13 of a specific steel making furnace example to obtain refined iron powder 15, an agitation tank 18 in which an iron reduced chloride aqueous solution 17 treated by the electrolytic apparatus 12 and the refined iron powder 15 obtained by the iron powder refining facility 16 are agitated, so that impurity metals are precipitated from the iron reduced chloride aqueous solution 17, and a chlorine gas treatment apparatus 21 for oxidizing ferrous ions in an iron powder treatment liquid 19 taken out from the agitation tank 18 to ferric ions to obtain a regenerated corrosive liquid 20. The structure of each device in the waste liquid treatment apparatus 10 having the above-described structure is explained below.

First, a specific configuration of the electrolyzer 12 will be described in detail with reference to FIGS. 2 to 7.

As shown in fig. 2, the electrolysis apparatus 12 includes: an anode plate (anode) 23 and a cathode plate (cathode) 24 are held at a predetermined distance, a liquid inlet 25 for the iron chloride-based corrosive waste liquid 11 is provided at the lower part, an electrolytic bath 27 having a liquid outlet 26 for the treated reduced iron chloride aqueous solution 17 is provided at the upper part, a DC power supply 28 for applying a voltage to the anode plate 23 and the cathode plate 24, and a control device 29 for controlling parameters such as an electrolytic voltage (E) and a supply flow rate (Q) of the iron chloride-based corrosive waste liquid 11 by inputting data such as a current density (D) of the electrolytic bath 27, a concentration (C) of ferric ions in the reduced iron chloride aqueous solution 17, and an amount of chlorine generated by the anode plate 23.

The electrolytic bath 27 is divided into an anode chamber 31 and a cathode chamber 32 by a diaphragm 30 provided around the anode plate 23, and a chlorine gas exhaust port 33 for collecting chlorine gas generated by the anode plate 23 is provided in the upper part of the anode chamber 31. In this example, the supply position of the iron chloride-based corrosive waste liquid 11 in the electrolytic bath 27 and the take-out position of the reduced iron chloride aqueous solution 17 after the treatment in the electrolytic bath 27 are shown in FIG. 2; a liquid inlet 25 of the ferric chloride system corrosive waste liquid 11 and a liquid outlet 26 of the reduced ferric chloride aqueous solution 17 are arranged on one side of the cathode chamber 32, and the method adopts a cathode liquid inlet mode and a cathode liquid outlet mode. By operating in this manner, the ferrous ions in the supplied iron chloride-based corrosive waste liquid 11 and the treated reduced iron chloride aqueous solution 17 are not oxidized by the chlorine gas generated from the anode plate 23, and the ferric ions in the iron chloride-based corrosive waste liquid 11 can be rapidly supplied to the vicinity of the surface of the cathode plate 24.

However, the liquid inlet25 of the iron chloride-based corrosive waste liquid 11 and the liquid outlet 26 of the reduced iron chloride aqueous solution 17 may be arranged as shown in the electrolytic cells 34 to 37 and 37a shown in FIG. 3 to FIG. 7. In addition, in the electrolytic cells 34 to 37 and 37a of various types, the positions of the inlet 25 for the iron chloride-based corrosive waste liquid 11 and the outlet 26 for the reduced iron chloride aqueous solution 17 may be changed as needed.

Although the electrolytic cells 27, 34 to 37, and 37a in fig. 2 to 7 are schematically shown as a combination of the pair of anode plates 23 and cathode plates 24, the electrolytic cells may be designed so that the parts divided into the anode chamber and the cathode chamber by the separators are arranged in a plurality of rows. In fig. 7, the anode plate 23 is completely separated by the separator 30, allowing chlorine gas to be discharged from the upper portion. Furthermore, the electrolytic cell of the present invention is not limited to the examples of FIGS. 2 to 7, and for example, a well-known filter press type or tank type electrolytic cell may be used; the electric power is supplied to the electrolytic cell by two types, namely, a monopolar type and a bipolar type.

The anode plate 23 is preferably an electrode whose titanium surface is partially covered with ruthenium oxide, such as a DSE electrode, DSA electrode manufactured by ペルメック, or the like. The anode plate 23 may be made of platinum-coated titanium or graphite, but a DSE electrode having a low chlorine overvoltage, a high oxygen overvoltage, and a low resistance is preferably used. As the material of the cathode plate 24, graphite, titanium, iron, stainless steel, copper, nickel alloy, etc. may be suitably used, and titanium or nickel alloy having high hydrogen overvoltage and small electric resistance is preferably used. The shape of the anode plate 23 and the cathode plate 24 maybe a shape having a structure of a plurality of small slits, a so-called cold-expansion alloy, a rod-like shape, a plate-like shape, or a curtain-like shape, which is obtained by rolling a metal plate.

The diaphragm 30 in fig. 2 separates the chlorine gas generated at the anode plate 23 from the cathode chamber 32, and prevents the oxidation reaction of ferrous chloride in the cathode chamber 32: ( ) And has the function of trapping chlorine gas. The material of the separator 30 is preferably a material that has liquid permeability, good gas barrier properties against the generated chlorine gas, and low cost. Specifically, a filter cloth or an ion exchange resin is preferably used, and among them, a filter cloth made by Kyowa Kagaku (trade name: パィレンフィラメント PF 4000) having a thickness of about 1mm is used.

In this embodiment, the inter-electrode distance L between the anode plate 23 and the cathode plate 24 is set to 8mm, but the inter-electrode distance, i.e., the inter-electrode gap, may be changed within a range of 1.5 to 50mm, preferably 2 to 20mm, if necessary.

The control device 29 is a control device composed of a program controller (program device) which inputs a predetermined processing program in advance and performs processing by the input program; however, the flow rate Q of the feed material, the electrolytic voltage E, and the like may be controlled by the operator himself or herself. Now, the function of such a control device 29 is explained as follows: the current i supplied to the electrolytic bath may be measured by an ammeter 38 provided between the dc power supply device 28 and the electrolytic bath 27, and the current density D (i/S) may be obtained by dividing the current value by the effective area S of the anode plate 23 and the cathode plate 24. And the concentration of metal ions in the reduced iron chloride aqueous solution 17 withdrawn from the electrolytic bath 27 may be measured continuously or intermittently using an ion meter.

The control device 29 receives control data of the current density D and the ferric ion concentration C, and can adjust the electrolytic voltage E and the supply flow rate Q of the iron chloride-based corrosive waste liquid 11 based on the control data.

Next, referring to fig. 8 to 10, an iron powder refining facility 16 capable of producing refined iron powder 15 by refining the iron powder dust 14 taken out of the converter 13 will be described in detail.

As shown in fig. 8, the iron powder refining apparatus 16 includes a feeder 40 for raw material of iron powder dust 14, a primary grinding ball mill 41, a prewashing augs-type classifier 42, a secondary grinding pulp mill 43, a water washing device 44, an acid washing device 45, a secondary washing augs-type classifier 46, an air dryer 47, and a vibrating screen 48; the refined iron powder 15 can be produced by arranging these apparatuses in series. Since the structures of the apparatuses other than the water washing apparatus 44 and the acid washing apparatus 45 are well known, detailed descriptions thereof will be omitted. The configurations of the water washing device 44 and the acid washing device 45, which are the main parts of the fine iron powder refining plant 16, will be described below with reference to fig. 9 and 10.

As shown in the drawing, the water washing device 44 has an inverted cone-shaped first settling tank 49 for accommodating the charged processed iron powder dust 14 and a screw conveyor 50 for washing and taking out the sediment in the first settling tank 49.

On the other hand, the pickling apparatus 45 has a second settling tank 51 of an inverted cone shape for receiving the washed fine iron discharged fromthe upper portion of the auger 50 of the washing apparatus 44, and an auger 52 for taking out the sediment in the second settling tank 51 and having washing, classifying and dewatering effects.

The lower portions of the screw feeders 50 and 52 are respectively immersed in the first settling tank 49 and the second settling tank 51, they are obliquely arranged in a direction forming an angle of 10 to 50 degrees with the horizontal direction, and the screw feeders 50 and 52 have an open channel structure at least at the upper portion.

Further, conveying screws 53 and 54 for lifting the sediments accumulated on the bottoms of the first and second settling tanks 49 and 51 and moving them upward are provided in the screw conveyors 50 and 52, respectively. The feed screws 53 and 54, not shown, are rotated by a motor or the like, so that the sediment accumulated at the bottoms of the first and second settling tanks 49 and 51 can be slowly transferred to the upper portion through the screw feeders 50 and 52.

Further, a water supply pipe 55 and an acid supply pipe 56 are provided at the upper portions of the feed screws 53 and 54 of the screw feeders 50 and 52, respectively. A drain port 57 and an acid injection port 58 are provided in the water supply pipe 55 and the acid supply pipe 56, respectively, so that washing water and acid wash can be supplied to the open portions of the upper portions of the screw feeders 50, 52, respectively.

The precipitates in the screw feeders 50, 52 which are moved upward by the rotation of the feed screws 53, 54, respectively, and the washing water and the pickling solution which are in the screw feeders 50, 52 and which respectively flow downward by gravity, are efficiently agitated and mixed, so that the particles having a small particle size in the precipitates are lowered in the screw feeders 50, 52 by the flow of the washing liquid, and accumulated in the first and second settling tanks 49, 51, and the precipitates from which the fine powder is removed are discharged from the discharge ports 59, 59a provided downward at the upper portions of the screw feeders 50, 52, respectively. In addition, the pre-washing Aijin classifier 42 and the secondary washing Aijin classifier 46 are respectively provided with a screw feeder, and the structure thereof is the same as that of the water washing device.

The iron powder dust 14 supplied to the iron powder refining facility 16 is discharged from the converter 13 and collected by using an iron powder collecting facility 60 shown in the drawing.

That is, as shown in fig. 11, a collection hood 61 for collecting dust and furnace gas discharged from the converter 13 is provided at the upper part of the converter 13, the collection hood 61 is connected to the start end of an exhaust system 62, the tail end of the exhaust system 62 is connected to a flue pipe 63, and gas subjected to dust collection and detoxification treatment described below is discharged from the flue pipe into the atmosphere.

At the upper and lower portions of the first straight pipe section 62a on the upstream side of the exhaust system 62, a first water jet 67 and a first dust capture discharge port 67a are provided, respectively. Water is sprayed into the first straight pipe section 62a from the first water spray 67, and the generated gas flowing in the exhaust system 62 is brought into contact with the water, whereby the dust containing iron powder in the generated gas is almost completely (95%) captured by the water. The captured dust can be sent to a wet classifier 64, which will be described later, through the first captured dust discharge port 67a in a state of being mixed with water.

Further, as shown in FIG. 11, the downstream side of the first straight pipe section 62a is connected to thesecond straight pipe section 62b through a horizontal section, and the upper and lower portions thereof are provided with a second water jet 65 and a second dust capture discharge port 65a, respectively. By spraying water into the second straight pipe section 62b through the second water spray 65, the generated gas flowing in the exhaust system 62 is brought into contact with the water, and the residual dust (5%) contained in the generated gas can be completely captured. Further, the blast water mixed with the captured dust is sent into the dust processing tank 66 through the second captured dust discharge port 65 a. Since this water for injection contains only a small amount of dust, it can be used as water for injection in the first straight section 62a, and is supplied to the first straight section by the pump P to be injected from the first water injection port 67, and thus can be effectively utilized.

The wet classifier 64 has a dust precipitation tank 68; also, as shown in fig. 11, the dust containing fine iron discharged from the first straight tube section 62a is sent into this dust settling tank 68 together with the blast water. Moreover, only the dust containing iron powder is precipitated as precipitated dust D at the bottom of the dust precipitation tank 68.

In the dust precipitation tank 68, a screw conveyor 70 comprising a long pipe body 69a and a conveyor screw 69 rotating in the pipe body 69a is provided, and its leading end is located in the dust precipitation tank 68 while its trailing end extends from the upper edge of the dust precipitation tank 68. And a washing water supply device 70a is provided at the rear end of the screw feeder 70.

Therefore, in the wet classifier 64, the fine powder portion of the sediment is selectively dropped and flowed out along the inner wall of the screw conveyor 70 by supplying washing water or the like from the terminal side of the screw conveyor 70, and therefore, the sediment (iron powder dust) having a relatively large particle size and from which excessive moisture is removed can be taken out from the upper portion of the screw conveyor 70.

In the present embodiment, the supernatant liquid from the upper part of the dust precipitation tank 68 is transferred to the thickener 64a arranged in parallel, and the water is used as the washing water sprayed from the second water spray 65 into the second straight pipe section 62b after the fine components (iron oxide, etc.) in the supernatant liquid are precipitated and removed. Thus, the cost required for the fine iron operation can be reduced by recycling water.

In the iron powder collecting apparatus 60, the first water jet 67 and the second water jet 65 of the exhaust system 62 are made into a constricted shape, and when water is injected by using such a constricted structure, exhaust gas or a mixing action of dust and water can be effectively generated, and the water can effectively capture captured dust.

The structure of the agitation tank 18 will be described below with reference to FIG. 12. In the agitation tank, the molten reduced iron chloride solution 17 and the refined iron powder 15 are agitated to precipitate impurity metals from the molten reduced iron chloride solution 17.

As shown in the figure, the agitation tank 18 is a reaction vessel comprising five sections including a first section 71 to a fifth section 75 having different vertical horizontal cross-sectional areas, has a total volume of 17 cubic meters and a maximum inner diameter of about 3.2 meters, and can hold the amount of the purified iron powder 15 for treating iron chloride-based waste liquid, for example, about 21 tons.

The first section 71 at the uppermost part of the agitation tank 18 is a region formed of a straight cylindrical section having the largest horizontal sectional area, and the upper end opening thereof is communicated with the atmosphere, so that the fine iron powder 15 can be charged into the agitation tank 18 from above. Further, the second section 72, which is connected to the first section 71, is a region composed of a truncated cone section that gradually decreases in diameter downward. Therefore, the first and second sections 71, 72 together form an iron powder separating region (free space) which can reduce the flow rate of the ascending stream and prevent the intrusion of iron powder flowing in suspension in the molten reduced iron chloride solution 17, i.e., in a dispersed suspended state, from a fluidized bed described later into the iron powder separating region.

At the lower part of the second section 72, there is a third section 73 formed by a straight cylindrical section having the same cross-sectional area as the second section 72, a fourth section 74 composed of an inverted truncated cone section is connected at the lower end of the third section 73, and a fifth section 75 formed by a straight cylindrical section with a small diameter is connected at the lower end of the fourth section 74. Therefore, the circulating liquid stream mainly containing the molten reduced iron chloride solution 17 can maintain the iron powder in a suspended state in the third to fifth zones 73 to 75, and a fluidized bed having a high iron powder density as indicated by the broken line in fig. 12 is formed.

In the side walls of the first section 71 and the second section 72 forming the iron powder separating region, liquid outlets 76 and 77 for taking out a part of the treatment liquid are provided, respectively, and in the side wall of the fifth section 75 forming the lower part of the fluidized bed, a treatment liquid inlet 78 is provided.

Then, the outlets 76, 77 for taking out part of the treatment liquid and the inlet 78 for the treatment liquid are connected to each other by a treatment circulation pipe 80 having a circulation pump 79 provided midway. By driving the circulation pump 79, the treatment liquid 19 containing little or no iron powder can be taken out from the first and second sections 71, 72 via the partial treatment liquid outlets 76, 77, respectively; the iron powder treatment liquid 19 is then caused to flow into the fifth section 75 by means of the treatment liquid circulation pump 80 and the treatment liquid inlet 78, thereby forming a self-circulating liquid flow in the agitation tank 18.

Further, in order to control the flow rate of the iron powder treatment liquid 19 passing through the treatment liquid circulation pump 80 via the liquid outlets 76, 77 from which the treatment liquid is taken out via two portions, first and second circulation flow rate control valves 81, 82 are provided at the upper end of the treatment liquid circulation pipe 80, and a supply flow rate control valve 83 is provided at the lower end of the treatment liquid circulation pipe 80. The first and second circulation flow rate control valves 81 and 82 and the supply flow rate control valve 83 can easily control the flow rate of the liquid to be circulated. Therefore, when the reduced iron chloride aqueous solution 17 (iron chloride-based corrosive waste liquid in some cases) is supplied to the agitation vessel 18 through the piping 85 for supplying the reduced iron chloride aqueous solution 17 (iron chloride-based corrosive waste liquid in some cases) and the treatment liquid outlet 78, which are provided with the waste liquid supply valve 84, the flow state of the refined iron powder 15 supplied to the agitation vessel 18 can be maintained within an appropriate range by the circulation flow regardless of the supply amount, and a fluidized bed is formed.

Further, by discharging a part of the iron powder treating liquid 19 in the fifth zone 75 formed of a straight cylindrical section of small diameter in which iron powder is particularly liable to settle, it is possible to move the iron powder and the like upward and suppress the formation of a dead space in the agitation tank 18.

The molten reduced iron chloride solution 17 (which may be the iron chloride-based corrosive waste liquid 11) is fed to the stirring tank 18 through a supply pipe 87 having a waste liquid supply valve 86 provided in a pipe between the supply flow control valve 83 and the circulation pump 79, or through a supply pipe 85 provided in the first section 71.

On the side walls of the first section 71 and the second section 72 forming the iron powder separating region, in addition to the above-described partially withdrawn treatment liquid outlets 76 and 77, treatment liquid discharge ports 88 and 89 are provided, respectively; the treatment liquid discharge ports 88 and 89 are connected to a treatment liquid feed pipe 91 provided with a pump 90 in the middle. The outlet side of the treatment liquid transport pipe 91 communicates with the chlorine gas treatment device 21. Therefore, the iron powder treatment liquid 19 treated in the agitation tank 18 is transported to the chlorine gas treatment apparatus or the like through the treatment liquid transport pipe 91 by the driving of the pump 90.

The iron powder treatment liquid 19 discharged from the treatment liquid discharge ports 88 and 89 can be adjusted by a first discharge flow rate control valve 92 and a second discharge flow rate control valve 93 provided at intermediate positions of a treatment liquid transport pipe 91 connected to the treatment liquid discharge ports 88 and 89, respectively.

Thus, since the iron powder treatment liquid 19 can be selected as required from different reaction zones having different treatment conditions, or the iron powder treatment liquid 19 having different characteristics can be taken out from individual zones, the iron ion concentration in the iron powder treatment liquid 19 conveyed by the pump 90 can be adjusted to control the subsequent waste liquid treatment within an appropriate range.

When the amount of the fine iron powder 15 in the agitation tank 18 is insufficient, the fine iron powder can be supplied from the upper part of the agitation tank 15. In addition, a discharge pipe 94a having a bottom discharge valve 94 is provided at the bottom of the agitation tank 18 to discharge the solid matter deposited at the bottom, and the solid matter and the like can be taken out therefrom.

The configuration of the chlorine gas treatment apparatus 21 is explained below, and the apparatus is used to oxidize ferrous iron ions in the iron powder treatment liquid 19 taken out from the stirring tank 18 into ferric iron ions, thereby producing the regenerated etching liquid 20.

The chlorine treatment device 21 is not shown in the drawing. Since the highly corrosive iron powder treatment liquid 19 must be kept in a stored state, the chlorine gas treatment device 21 should be composed of a reaction vessel made of a material having high corrosion resistance, such as FRP (fiber reinforced plastic). The regenerated etching solution 20 can be obtained by introducing or bubbling chlorine gas generated in the electrolytic apparatus 12 or the like into the iron powder treating solution 19 treated in the stirring tank 18 to oxidize part or all of the divalent iron ions in the iron powder treating solution 19 into trivalent iron ions.

Among them, such a chlorine gas treatment reaction can be realized, for example, in such a manner that it is divided into a primary chlorine gas treatment step and a secondary treatment step, so that the reaction efficiency with chlorine gas can be further improved.

Next, a method for regeneratingan iron chloride-based corrosion waste liquid, which is a first embodiment of the present invention, using the waste liquid treatment apparatus 10 having the above-described configuration will be described in detail.

First, a method of refining the iron powder dust 14 collected from the converter 3 to produce refined iron powder 15 by using the iron powder refining facility 16 shown in FIGS. 8 and 9 will be described.

As shown in fig. 8 to 10, the moisture-containing iron powder dust 14 discharged from the wet classifier 64 of fig. 11 is charged into the primary grinding ball mill 41 via the raw material feeder 40. The primary grinding ball mill 41 is a nearly cylindrical ball mill capable of handling the iron powder dust 14 continuously charged from the raw material feeder 40, and the number of revolutions of the ball mill 41 is 20 to 36rpm, and the amount of grinding balls used as a grinding medium is 3 to 5 tons.

The amount of water containing the iron powder dust 14 supplied to the primary grinding ball mill 41 is 200 to 1000 (270) l/hr on average, and the concentration of the iron powder dust 14 is 50 to 80 (65) wt% on average.

The retention time or treatment time of the iron powder dust 14 in the primary grinding ball mill 41 is about 60 to 120 minutes, and impurities contained in the iron powder dust 14 can be partially separated from the iron powder by the pulverization treatment.

The reason why the wet grinding treatment is performed is that the dust itself collected by the converter 13 is a wet powder containing a large amount of moisture as described above, and if a dry treatment is used, a drying step must be employed as a pretreatment step, and the subsequent acid treatment itself is also performed by a wet method, so that the drying treatment must be performed again after the acid treatment, which is uneconomical. Further, if the dry pulverization treatment is performed, dust is easily generated, and it is not preferable because an environmental measure must be provided for such dust, which causes extra cost.

Next, the processed product of the iron powder dust 14 discharged from the primary grinding ball mill 4 is conveyed to a pre-washing august classifier 42 having the same structure as the wet classifier 64 shown in fig. 1, and the flow washing operation is performed on the impurities peeled from the iron powder. Wherein the velocity of the ascending flow formed by ascending from the settling tank of the prewashing Aikins classifier 42 is 3 to 10 (5 on average) m/h, and the amount of washing water supplied to the open upper part of the screw feeder is 3 to 25 (5 on average) m/h. By the washing treatment using the prewashing Aikins classifier 42, impurities peeled off from the iron powder in the treated material are partially separated and removed, and the particle size distribution of the iron powder can be shifted in the direction of large particle size because the fine particles in the iron powder are removed.

The treated matter discharged from the prewashed Aikins classifier 42 is then sent to a secondary grinding pulp mill 43 to be pulverized. The secondary grinding mill 43 is a vibration type pulverizer having a capacity of 1000 liters, the supply amount of water to the iron powder dust 14 is 200 to 1000 (270 liters on average) per hour, and the concentration of the iron powder dust 14 is controlled to 50 to 80 (65 liters on average) by weight%. By the crushing treatment using the secondary grinding mill 43, the impurities adhering to the iron powder and remaining in the mixture are further crushed and finely crushed, and a treated product of the iron powder dust 14 having high efficiency of separating the iron powder from the impurities in the subsequent step can be obtained.

FIG. 15 shows changes in theconcentration of calcium oxide contained as an example of one type of impurity present in the treated iron powder; as can be seen from fig. 15, before the primary grinding ball mill 41 is charged (fig. 15 a), the calcium oxide concentration is in the range of 2 to 7 wt%; after one ore grinding washing using a pre-washing Aikins classifier 42 (FIG. 15(B)), the amount of the ore is reduced to 0.5 to 5 wt%.

However, since many impurities remain in the processed product of the iron powder dust 14, the purity is not sufficient when the processed product is used as a reducing agent in a process of recycling an iron chloride-based waste liquid, and the processed product cannot be used as it is. For this reason, the iron powder dust 14 must be further subjected to washing classification treatment using a water washing apparatus 44 and a pickling apparatus 45 as shown in fig. 9 and 10.

Therefore, the processed material of the iron powder dust 14 is fed from the upper part of the water washing apparatus 44 to the first precipitation tank 49 through the feed pipe 95. In this way, the large-particle-size iron powder portion in the iron powder dust 14 is immediately precipitated, and a precipitate layer is formed at the bottom of the first precipitation tank 49. Further, the feed screw 53 disposed in the screw feeder 50 is rotated by a driving device such as a motor.

At this time, the washing water is supplied from the water inlet 57 of the water supply pipe 55 at a water supply rate of 3 to 25 cubic meters per hour on average, the washing water forms a descending liquid flow in the screw conveyor 50, and the processed iron powder dust is supplied from the iron powder dust supply pipe 95 to the first precipitation tank 49 as described above, so that all the substances having a small specific gravity including fine iron powder and dust form an ascending liquid flow. If the rising speed of the ascending stream is adjusted to 3 to 10 (5 m/h on average), the separation and purification of the iron powder dust 14 can be performed.

With the above operation, the fine fraction in the fine iron powder dust 14 is washed out of the system in the form of an ascending stream, while the coarse fraction is selectively discharged from the upper portion of the screw conveyor 50 in the form of washed iron powder. As a result, most of the impurities in the iron powder dust are removed after the secondary grinding and washing, and thus, a clean iron powder can be obtained, and the impurities (calcium oxide) in the iron powder dust 14 are reduced to a range of 0.3 to 1.7 wt% by washing, and the particle size distribution is shifted to the coarse particle side as shown in fig. 15C.

The washed iron powder thus obtained is transferred from the discharge port 59 at the upper part of the water washing apparatus 44 to the second precipitation tank 51. By this, the portion of the washed iron powder having a relatively large specific gravity is immediately precipitated, and a precipitate layer is formed at the bottom of the second precipitation tank 51. The conveyance screw 54 in the screw conveyor 52 is rotated by the motor drive, and the sediment is discharged from the settling tank 51 to the outside. In this process, the input amount of the washed iron powder from the discharge port 59 and the discharge amount from the sediment precipitation tank 51 are adjusted so that an ascending flow is formed in the second precipitation tank 51 while the ascending speed thereof is adjusted to a range of 3 to 10 (5) m/hr on average suitable for separation and purification. Then, the post-washing liquid discharged from the secondary washing Aikins classifier 46 in the subsequent step is diluted to a dilute acid with 98 wt% concentrated sulfuric acid having a specific gravity of 1.9 and a supply rate of 30 to 100 liters/hour, and then supplied into the screw conveyer 52 through the acid injection port 58 of the acid liquid supply pipe 56, so that a downward flow of the acid liquid is formed inside the screw conveyer 52. Wherein the pH of the pickling solution in the precipitation tank 51 is 0.5 to 3, and the value thereof depends on the dilution amount of the post-washing solution from the secondary washing Aiggins classifier 46. By the above operation, since the washed iron powder is charged into the second precipitation tank 51, the fine powder portion in the washed iron powder is removed by acid washing, the coarse fraction is accumulated in the second precipitation tank 51, and the washed iron powder composed of the coarse fraction is discharged from the second precipitation tank 51 through the auger 52, and during this discharge, impurities in the washed iron powder are eluted and removed by the acid solution flowing down the auger 52 and the rising liquid flow in the liquid. Therefore, the coarse fraction containing the refined iron powder is selectively discharged from the upper discharge port 59a of the screw conveyor 52, and the supernatant liquid in the second precipitation tank 51 is simultaneously discharged from the upper portion of the second precipitation tank 51.

Next, as shown in fig. 8, the treated material after the acid washing treatment is treated by using a secondary washing aids classifier 46 having the same structure as the above-mentioned water washing apparatus 44, and the treated material which has become acidic is washed. At this time, the thickness is 1 to 10m³The residual acid solution can be removed by supplying washing water made of industrial water at a supply rate of/hr. And then, placing the treated object after acid treatment in an airflow dryer, and removing moisture by using airflow at 150-250 ℃. The particle size distribution of the dried refined iron powder 15 was measured, and the results are shown in table 1 below.

TABLE 1

Particle size G (. mu.m)	Proportion (wt%)
		150＜G≤750	0～20
105＜G≤150	5～40
		74＜G≤105	20～60
63＜G≤74	5～25
		44＜G≤63	10～30
G≤44	1～19

Representative composition of such refined iron powder 15: containing Fe, FeO, Fe₂O₃The total iron content in the steel reaches more than 96wt percent, and the metal iron is more than 92wt percent, less than 6wt percent of FeO, less than CaO0.5wt percent and SiO₂0.1 wt% or less, and carbon (C)0.7 wt% or less.

Finally, the refined iron powder 15 is classified using a vibrating screen 48 of any mesh size within the range of 100 to 150 mesh [ taylor (Tyler) standard sieve]. Thus, the fine iron powders 15 having different particle sizes can be used as required. For example, in the treatment of the waste etching solution, the oversize part may be used as a purified iron powder for copper removal, and the undersize part may be used as a purified iron powder for nickel removal.

Wherein the 100,150 mesh Tyler (Tyler) standard sieve referred to above refers to a sieve having a pore size of 147 and 104 microns, respectively.

By this method, a refined iron powder 15 can be obtained in which the impurity (CaO) is largely removed and the content thereof is in the range of 0.01 to 0.10 wt% (below the allowable value) as shown in FIG. 15D. Therefore, even in view of economy, the amounts of sulfuric acid and hydrochloric acid required for obtaining one ton of refined iron powder product should be set within the ranges of 10 to 400 liters and 25 to 700 liters, respectively.

Hereinafter, a method for obtaining a reduced iron chloride aqueous solution 17 from the iron chloride-based corrosive waste liquid 11 by using the electrolysis apparatus 12 will be described.

The operation is carried out as shown in FIG. 2, in which the waste liquid 11 after the etching treatment of the lead frame or the like, i.e., the ferric chloride-based etching waste liquid 11 is supplied from the liquid inlet 25 to the electrolytic bath 27 through the waste liquid supply tube, and ferric ions (Fe) in theferric chloride-based etching waste liquid 11 are removed³⁺) Reduction to ferrous ion (Fe)²⁺) Thus, a reduced iron chloride aqueous solution 17 is obtained. This reduction operation is carried out for the purpose of recovering and effectively utilizing chlorine gas while preventing Fe from being oxidized and eluted by the trivalent iron ions from the refined iron powder 15 in the process of removing impurity metals from the refined iron powder 15 later²⁺The concentration is significantly excessive.

Wherein the ferric chloride-based etching waste liquid 11 is an aqueous solution containing ferric ions and ferrous ions in concentrations of 100 to 250 g/L and 5 to 70 g/L, respectively, and chlorine ions (Cl)^-) And HCl, and contains metallic ions of nickel (Ni) as impurity²⁺) And copper ion (Cu)²⁺)。

The reaction of this iron chloride-based corrosive waste liquid 11 at the anode plate 23 and the cathode plate 24 in the electrolytic bath 27 is represented by the following formula:

anode:

cathode: i.e. at the anode plate 23To chlorine gas, the ferric ions are reduced to ferrous ions at the cathode plate 24, the overall reaction of which can be represented by the following formula:

the free energy change Δ G in the total reaction can be calculated from the amount of change in the free energy G of each component before and after the reaction, and Δ G is +13784 cal/mole. Then using the theoretical formula E₀Determination of the theoretical electrolysis voltage E required for the electrolysis (. DELTA.G/z F)₀. Wherein F is the normal number of particles, z is the number of moles of electrons participating in the reaction, and the theoretical electrolytic voltage E can be obtained from these values₀0.5977 volts. Then at a voltage higher than the above-mentioned theoretical electrolytic voltage E₀To FeCl at electrolytic voltage of₃The electrolysis is performed to generate chlorine gas, and the electrolysis voltage can be set within a range in which copper ions and nickel ions present in the iron chloride-based corrosive waste liquid 11 are not reduced, for example, about 1 volt.

And if each ton of chlorine gas (Cl) is to be produced, by taking into account the current efficiency, the conversion efficiency into direct current, and the electrolysis voltage of the electrolysis cell 27, etc₂) The actual amount of electricity required is set to 1000 to 3500 kWh, the scale and the design of the electrolysis apparatus 12 can be determined.

Hereinafter, the method for regenerating the iron chloride-based corrosive waste liquid will be described in further detail with reference to fig. 13 showing the change over time of the electrolytic voltage E, the current density D, and the concentration C of ferric ions in the reduced ferric chloride aqueous solution 17 in the electrolytic apparatus 12.

As shown in FIG. 2, the iron chloride-based waste etching solution 11 is supplied to the electrolytic bath 27 to a predetermined level, and after being filled with the solution, an electrolytic voltage E is applied for a certain period of time to bring the solution to a steady state.

Further, the waste liquid supply pipe and the liquid inlet 25 connected thereto are connected so that the supply flow rate Q corresponds to a pair of 1m²The iron chloride-based corrosive waste liquid 11 was supplied under the condition that the area of the electrode (i.e., one cell) was 4.6 liters/hour,and the reduced iron chloride aqueous solution 17 having a flow rate almost equal to the supply flow rate was taken out from the drain port 26 for discharging the treated liquid.

Then, as shown in FIG. 13(a), when the above-mentioned steady state is startedIs marked by t₀The electrolytic voltage E is set to 1.5V within a control range of 1-4.5V.

As shown in FIGS. 13(b) and (c), the current density D is in the range of 2-40A/dm²And the concentration C of the ferric ion is within the range of 10-120 g/l and within the range of 50-60 g/l, and then the chlorine gas is discharged from the chlorine gas discharge port 33, so that the required electrolysis state can be maintained.

As shown in FIG. 13, if the concentration C of the ferric ion is changed to be out of the prescribed range (at t)₁At that time), the electrolytic voltage E is adjusted to obtain a reduced ferric chloride aqueous solution 17 containing ferric ions at a predetermined concentration.

When an impurity metal such as copper is precipitated on the cathode plate 24, the ferric chloride-based etching waste liquid 11 is supplied to the site where copper is precipitated, and ferric ions in the solution and copper are caused to react with each other to redissolve the copper.

Alternatively, the time (t) may be as shown in FIG. 13₂～t₃) The electrolysis voltage E is maintained at 0 or at the time (t) as indicated by the interval₄～t₅) The reverse voltage was applied for a predetermined time as indicated in the interval to redissolve the precipitated copper.

Since the time (t) in FIG. 13(c) is₂) Since the stable operation is performed later, the following operationdescription is omitted.

The temperature of the electrolytic treatment liquid in the electrolytic process should be controlled within the range of 30 to 100 ℃. When the temperature of the electrolytic treatment liquid is lower than 30 ℃, the resistance is increased, and copper, nickel and the like are easily separated out; on the other hand, when the temperature of the electrolytic treatment solution is higher than 100 ℃, the treatment solution is boiled, which is not preferable.

As shown by the graphs showing the change of the ion concentrations with time in the reduced iron chloride aqueous solution 17 obtained in the electrolysis step, the ferric ion concentration in the iron chloride-based corrosive waste liquid 11 before treatment is 207g/l (FIG. 14(a)), for example, and is reduced to 50 to 60g/l (FIG. 14(b)) after treatment. And nickel ion (Ni)²⁺) And copper ion (Cu)²⁺) The isoconcentration was almost maintained at the value before treatment. Wherein the nickel ion and the copper ion are represented by M in FIG. 14ⁿ⁺Shown.

In this manner, since the concentration of the trivalent iron ions in the reduced iron chloride aqueous solution 17 is fixed at a level slightly higher than the concentration of the impurity metal ions, the impurity metal ions are not reduced during electrolysis, and thus the electrolytic treatment can be performed efficiently without consuming no electric power.

Table 2 shows the electrolysis conditions used in the steady state of the electrolysis apparatus 12 described above and the results thereof, and the ratio of the effective current for generating chlorine gas to the total current (indicating the chlorine gas recovery current efficiency) reached 67%.

TABLE 2

Electric power Solution (II) Strip for packaging articles Piece	Anode material	DSE electrode
			Cathode material	Titanium (IV)
	Separator material	PF4000
			Interpolar to polar ratioDistance L	8mm
	Electrolytic potential E	1.5V
			Current density D	5A/dm2
	Of iron chloride-based corrosive waste liquids Supply position	Cathode chamber side (cathode)
			By reducing aqueous solutions of ferric chloride Extraction site	Cathode chamber side (cathode)
	Of iron chloride-based corrosive waste liquids Supply flow rate	4.6l/hr
			Electric power Solution (II) Knot Fruit	Chlorine recovery of electricityFlow efficiency	67％
By reducing aqueous solutions of ferric chloride Concentration of ferric ion	55 g/l
		By reducing aqueous solutions of ferric chloride Concentration of ferrous ion		172 g/l

Next, as shown in fig. 12, a reduced iron chloride aqueous solution 17 obtained by subjecting an iron chloride-based corrosive waste liquid 11, which is an example of an iron chloride-based waste liquid, to electrolysis is supplied to a stirred tank 18, and impurity metal ions such as copper and nickel contained in the reduced iron chloride aqueous solution 17 are reduced and removed by a refined iron powder 15 obtained by refining an iron powder dust 14. The following is now described with respect to this method.

First, as shown in fig. 12, the refined iron powder 15 is supplied into the stirring tank 18 from the upper opening of the stirring tank 18, and the molten reduced iron chloride aqueous solution 17 is supplied into the stirring tank 18 through the waste liquid supply valve 86 and the treatment liquid inlet 78.

Thereafter, the circulating pump 79 is driven to pump the iron powder treating liquid 19 through the first circulation flow rate control valve 81 and the second circulation flow rate control valve 82 and flow the liquid through the fluidized bed, and the iron powder treating liquid 19 is supplied to the agitation tank 18 at a predetermined angle through the supply flow rate control valve 83 provided at the lowermost portion of the agitation tank 18 to flow the liquid as a bottom-up circulation in the agitation tank 18 in a swirling flow.

This makes it possible to float the iron powder, which is easily precipitated at the bottom of the vessel, up to form a fluidized bed, and to achieve effective mixing of the refined iron powder 15 and the reduced iron chloride aqueous solution 17 in a state where there is no dead space in the vessel.

Among these, the distribution state, residence time, and the like of the purified iron powder 15 are different in the first zone 71 to the third zone 73 having different horizontal cross-sectional areas. For this reason, the iron powder concentration in the iron powder treating liquid discharged from the first section 71 is lower than that in the iron powder treating liquid discharged from the second section 72.

The properties of the discharged iron powder treated liquid 19 can be controlled by adjusting the discharge amounts of the iron powder treated liquid 19 having different iron powder concentrations and different degrees of reduction reaction by using the first and second discharge flow rate control valves 92 and 93, respectively, as necessary.

In this way, while a fluidized bed having a solid-to-liquid ratio of the slurry in the range of 1: 0.6 to 1: 0.7 is formed in the agitation tank 18, the remaining ferric ions and the refined iron powder react with each other to form ferrous ions, and the metal ions having a lower ionization tendency than iron, such as copper ions and nickel ions, undergo a reduction reaction in the following manner to produce the iron powder treatment liquid 19. Chromium ions having a lower ionization tendency than iron are also reduced by the fine iron powder.

Such a reduction reaction is influenced by the iron powder concentration in the slurry, the surface area of the iron powder, the slurry temperature, and the chloride ion concentration, and therefore can be appropriately adjusted by utilizing these factors or by adding a pH adjuster.

In the step of removing the impurity metal ions, although the purified iron powder 15 is dissolved in the molten reduced iron chloride solution 17 to form divalent iron ions, the molten reduced iron chloride solution 17 is subjected to preliminary electrolysis to remove trivalent iron ions or to reduce the concentration thereof, so that the amount of the purified iron powder 15 dissolved out can be suppressed to a necessary minimum, and the removal of the impurity metal ions is not hindered, whereby the purified iron powder treatment liquid 19 can be efficiently obtained.

Therefore, the concentrations of the various metal ions in the iron powder treating liquid 19 are lower than the concentration of the impurity metal ions (Mn) in the iron chloride reduced aqueous solution 17 (FIG. 14(b)) after the electrolytic treatment, as shown in FIG. 14(c)²⁺) In a state of reduced amount.

Then, the iron powder and other impurities contained in the iron powder treatment liquid 19 discharged from the stirring tank 18 are removed to prepare an iron powder treatment liquid containing a large amount of ferrous chloride, and this iron powder treatment liquid containing a large amount of ferric chloride is supplied to the chlorine gas treatment apparatus 21, and a part or all of the contained ferrous ions are oxidized to ferric ions by blowing or bubbling with chlorine gas generated in the electrolysis apparatus 12 or the like, thereby obtaining a regenerated etching liquid 20.

That is, the chlorine gas generated in the electrolysis unit 12 is blown into the chlorine gas treatment unit 21 to serve as an oxidizing agent for divalent iron ions, thereby oxidizing the divalent iron ions remaining in the iron powder treatment liquid. Thus, a FeCl free from impurity metal ions as shown in FIG. 14(d) can be obtained₃The concentration of the regenerated corrosive liquid 20 is adjusted to 560-730 g/L. In this case, there is also an advantage that chlorine gas generated in the waste liquid treatment apparatus 10 can be effectively utilized in its own apparatus.

As described above, in the first embodiment, unlike the conventional method of reducing ferric ions using iron powder in advance, the amount of increase ofiron ions formed due to elution of iron powder in the reduction step is small, and when regenerating an etching solution having a predetermined iron ion concentration, the amount of diluent to be added for adjusting the iron ion concentration can be minimized.

Furthermore, the amount of iron powder used in the reduction removal of copper ions and nickel ions can be greatly reduced, the total amount of iron powder used in the whole process can be reduced, the cost associated with the use of iron powder can be reduced, and chlorine gas generated during electrolysis can be recovered and effectively used for chlorination in the subsequent process, so that the use cost of chlorine gas can be reduced proportionally.

Further, since the amount of the diluent used in the regeneration treatment of the iron chloride-based corrosive waste liquid 11 is not significantly increased, the waste liquid treatment apparatus 10 can be downsized.

(second embodiment)

The method for regenerating an iron chloride-based corrosive waste liquid according to the second embodiment of the present invention will be described in detail with reference to FIGS. 16 to 19; the difference from the apparatus structure shown in fig. 1 and applicable to the method for regenerating iron chloride-based corrosive waste liquid in the first embodiment is: without using the electrolysis device 12, but using the agitation tank 18 and the first and second agitation tanks 115 and 119 having a new structure; detailed description of the same parts as those of the first embodiment in terms of structure and reference numerals will be omitted. In the method for regenerating an iron chloride-based corrosive waste liquid of the second embodiment, although a conventional stirring blade type stirring tank is used as the first stirring tank 115, it is preferable to use the fluidized-bed type stirring tank 18 shown in fig. 12; as described above, in different cases, the method for regenerating an iron chloride-based corrosion waste liquid according to the second embodiment can be applied to the method for regenerating an iron chloride-based corrosion waste liquid after the iron chloride-based corrosion waste liquid is subjected to electrolytic treatment.

As shown in fig. 16, the waste corrosion solution treatment facility 110 used in the regeneration method of an iron chloride system according to the second embodiment includes a decoppering apparatus 113 for removing copper from a waste corrosion solution, a nickel-removing apparatus 122 for removing nickel and chromium from a waste corrosion solution after copper removal, a removing apparatus for removing suspended impurities such as carbon and silicon, not shown, and a chlorine gas treatment apparatus 21 for oxidizing the treated solution after impurity removal to produce a corrosive solution (see fig. 1). Each of them will be described in detail below.

The decoppering device 113 comprises: a first agitation tank 115 for mixing the etching waste liquid and a required amount of pH adjusting agent supplied from the etching waste liquid tank 111 and the pH adjusting agent tank 112, respectively, iron powder supplied from the iron powder storage tank 114 through a screw feeder 118, water added from a water source (e.g., a water supply pipe) not shown, and a part of the solid matter recovered in this decoppering apparatus 113, and discharging a suspension-like iron powder mixed liquor 1A containing reduced copper; a liquid cyclone 116 for separating the iron powder mixed solution 1A supplied from the first agitation tank 115 into a decoppering treatment liquid 1B containing relatively small particles and a copper-containing iron powder mixed solution 1C containing relatively large particles; a pump 127 for transferring the iron powder mixed liquid 1A discharged from the first stirring tank 115 to the liquid cyclone 116 through a conical tank (inverted conical tank) 121; a first aids classifier 117 for classifying and washing the copper-containing mixed solution 1C discharged from the lower part of the liquid cyclone 116 to obtain a powdery solid; and a second Aikins classifier 117a for taking out a part of the solid matter and washing it again to prepare copper powder.

The first stirring tank 115 is an approximately cylindrical FRP vessel, and is provided with a stirring blade 128 for forcibly stirring the slurry iron powder mixed liquid 1A in the tank, so that the iron powder mixed liquid 1A subjected to stirring can be discharged from an outlet 115a at the upper part of the tank.

The first and second august classifiers 117, 117a respectively include: dust settling tanks 120 and 120a for accommodating the supplied reduced copper-containing iron powder mixed solution 1A, a solids rising pipe, not shown, for rising solids in the dust settling tanks 120 and 120a by means of a screw rotating in the pipe and washing the solids while removing water, and a washing water spray device, not shown. In the first and second Aikins classifiers 117, 117a, the fine powder portion of the solids is classified in the dust precipitation tanks 120 and 120a, and the solids having a larger particle size and from which excess moisture is removed are discharged from the upper end of the solids rising pipe.

As an example of the iron chloride-based waste liquid, the nickel removing apparatus 122 includes: a second agitation tank 119 for mixing the decoppered treatment liquid 1B discharged from the liquid cyclone 116 in the decoppering apparatus 113, the iron powder supplied from the iron powder storage tank 114a, and the solid matter collected in the nickeling apparatus 122, and discharging a primary iron powder treatment liquid 2B containing reduced nickel ions, chromium ions, and the like; a screw conveyor 118a for supplying the fine iron of the fine iron storage tank 114a to the second agitating tank 119; a liquid cyclone 116a for separating the supplied primary iron powder treatment liquid 2B into a nickel-removing treatment liquid 2C containing fine-particle iron powder and a nickel-containing iron powder mixed liquid 2D containing iron powder particles from which nickel is precipitated; a pump 127a that transports the primary iron powder treating liquid 2B discharged from the second agitation tank 119 to the liquid cyclone 116a through the conical tank 121 a; an Aikins classifier 117b for washing the nickel-containing iron powder mixed solution 2D discharged from the liquid cyclone 116a with water to obtain nickel powder and nickel-attached iron powder; and a stirring adjustment tank 124 for mixing the nickel-removed treatment liquid 2C from the liquid cyclone 116a with the coagulant in the coagulant tank 125.

However, as shown by the solid line d in fig. 16, if necessary, a part or the whole of the etching waste liquid may be supplied to the copper-removing treatment liquid 1B supplied directly from the waste liquid tank 111 into the second stirring tank 119, depending on the type of the iron chloride-based etching waste liquid.

As shown in FIG. 17, the second agitation tank 119 has a volume 17M³The reaction vessel (2) is composed of five sections of a first section 130 to a fifth section 134 which are different from each other in a longitudinal horizontal cross section, and has a maximum inner diameter of about 3.2M, wherein about 21 tons of iron powder for treating a corrosive waste liquid can be held.

The second agitation tank 119 is provided therein with an agitation blade 128a for agitating the copper-removed treatment liquid 1B, which is, for example, an iron chloride-based waste liquid, and iron powder, which are supplied only at a lower position, if necessary, and is provided thereon with amotor 129 for rotating the agitation blade 128 a. In general, since the iron powder treatment liquid 2E is taken out from the upper part of the agitation tank 119 by the circulation pump 126 and supplied to the lower part thereof to form a liquid circulation as a main agitation means without agitation of the slurry by the agitation blade 128a as described below, the slurry having a solid-to-liquid ratio (weight ratio) of the iron powder to the liquid of 1: 1 has a processing capacity of 1.5 times as fast as that of a conventional reaction tank of an agitation type in which the agitation blade is driven by a motor.

The first section 130 at the uppermost portion of the second stirring tank 119 is a section composed of a straight cylindrical section having the largest horizontal cross-sectional area, and the upper end opening thereof is open to the atmosphere, so that the refined iron powder 15 produced by the above-described method can be charged into the stirring tank 119 from above. In addition, the second section 131 connected to the first section 130 is a section formed of a truncated cone portion gradually reducing in diameter from top to bottom.

A third section 132 formed of a straight cylindrical section having the same cross-sectional area as the lower end of the second section 131 is formed at the lower portion of the second section 131, a fourth section 133 formed of a truncated cone section is connected to the lower end of the third section 132, and a fifth section 134 formed of a straight cylindrical section having a small diameter is connected to the lower end of the fourth section 133. Therefore, in the third to fifth sections 132 to 134, the supplied iron powder, the iron powder treatment liquid 2E supplied from below, and the decoppering treatment liquid 1B obtained by treating the iron chloride-based corrosive waste liquid form a fluidized bed having a high iron powder density as shown by the hatching in FIG. 17. Then, in the first and second zones 130, 131 where the ascending flow rate is slow, the descending speed of the iron powder is higher than the flow rate of the processing liquid, and thus an iron powder separation region (free space) where the iron powder density is extremely small is formed.

The side walls of the first section 130 and the second section 131 forming the iron powder separation region are provided with outlets 145 and 145a for taking out a part of the treatment liquid, respectively, and the side wall of the fifth section 134 forming the lower part of the fluidized bed is provided with an inlet 145b for introducing the treatment liquid.

The part of the treatment liquid outlets 145 and 145a and the treatment liquid inlet 145b are connected to each other by a treatment liquid circulation pipe 145d having a circulation pump 126 provided in the middle. Therefore, the iron powder treating liquid 2E having a small iron powder content is taken out from the first and second sections 130 and 131 through the part of the treating liquid take-out ports 145 and 145a by the driving of the circulation pump 126, and then the iron powder treating liquid 2E is made to flow into the fifth section 134 through the treating liquid circulation pipe 145d and the treating liquid injection port 145b, so that a self-circulation flow is formed in the second stirring tank 119, and the fluidized beds are formed in the third to fifth sections 132 to 134.

First and second circulation flow control valves 135 and 136 are provided at the upper end of the treatment liquid circulation pipe 145d to control the flow rate of the iron powder treatment liquid flowing out of the respective outlet ports 145 and 145a for the upper and lower treatment liquids through the treatment liquid circulation pipe 145 d; a supply flow control valve 143 is provided at the lower end of the processing liquid circulation pipe 145 d. Theflow control of the circulating liquid can be conveniently performed by using the first and second circulation flow control valves 135, 136 and the supply flow control valve 143. Therefore, regardless of the amount of the copper removal treatment liquid 1B supplied through the copper removal treatment liquid supply pipe 147 provided with the waste liquid supply valve 142, the flow state of the iron powder supplied to the second stirring vessel 119 can be maintained within a suitable range by the circulation flow, and a fluidized bed can be formed. A stirring blade removing device not shown is further provided, and the stirring device can be removed from the second stirring tank 119 when the stirring blade 128a is not used.

Further, the iron powder treatment liquid 2E is discharged from the fifth zone 134 formed by the small-diameter straight-cylindrical portion provided at the lowermost portion of the second agitation tank 119 where iron powder is most likely to precipitate, so that the iron powder and the like can be vigorously rolled up, and the formation of a dead space in the second agitation tank 119 can be suppressed.

On the side walls of the first section 130 and the second section 131 forming the iron powder separation region, treatment liquid discharge ports 145e and 145f for discharging the primary iron powder treatment liquid 2B as the above-described treatment liquid are provided, respectively, and such treatment liquid discharge ports 145e and 145f are connected to a treatment liquid delivery pipe 127c provided with a conical tank 121a (see fig. 16) and a pump 127a in the middle, and a liquid cyclone 116a is connected to the outlet side of the treatment liquid delivery pipe 127 c. The total flow rate is adjusted by refluxing the discharge side of the fixed displacement pump 127a to the conical tank 121 a. The flow rate of the primary iron powder treatment liquid 2B discharged from the treatment liquid discharge ports 145e and 145f can be adjusted by the first discharge flow rate control valve 138 and the second discharge flow rate control valve 139 provided in the middle of the treatment liquid transfer pipe 127c connected to the treatment liquid discharge ports 145e and 145f, respectively.

In this way, the primary iron powder treatment liquid 2B can be selected from the reaction zones having different treatment conditions, or the primary iron powder treatment liquid 2B having different compositional characteristics can be taken out from a plurality of zones, as required.

When the iron powder 15 is insufficient in the second agitation tank 119, the purified iron powder 15 can be supplied from the upper part of the agitation tank 119.

The second agitation tank 119 is provided at the bottom thereof with a discharge pipe 146a having a bottom discharge valve 146 for discharging the solid matter deposited at the bottom, whereby the solid matter and the like can be discharged.

The processing conditions and the processing results of the comparative example and the second stirring tank 119 are shown in table 3 below.

TABLE 3

		Example 2	Example 2 of Variation example	Comparative example
					To Theory of things Strip for packaging articles Piece	Volume of No. 2 agitation tank m 3	17	17	11 Mechanical agitation tank
Iron powder holding amount t	21	21	6
				Processing power (note)		1.5	1.5	1
Stirring blade	Use of	None, no use	Use of
				Limitation of iron powder particle size		Small to medium	Small to medium	Small
To Theory of things Knot Fruit	Maximum flow rate of slurry (line speed)) m/s	1	0.25						6
				Amount of pH adjusting solution used (Note)	0.3	0.3	1
	Solid-to-liquid ratio	1∶0.6 ～1∶0.7	1∶1					1∶3
				Amount of wear	Small	Small	Big (a)
	Cost of raw materials	Is low in	Is low in					Height of
				Conservative cost	Is low in	Is low in	Height of

Note: the treating ability and the amount of the pH adjusting agent used were the weight ratios at which the weight in the comparative example was 1.

Next, a method for treating an iron chloride-based corrosion waste liquid using the above-described corrosion waste liquid treatment apparatus 110 in the latter half and using the method for regenerating an iron chloride-based corrosion waste liquid according to the second embodiment of the present invention will be described in more detail. In the case where the agitation treatment of the first agitation tank 115 is performed, although a conventional agitation blade is used in the illustrated example, it is needless to say that the agitation tank 18 using the fluidizedbed in the first embodiment described above may be modified, and thus a more efficient and economical method for regenerating the iron chloride-based corrosive waste liquid can be provided.

As shown in fig. 16, first, a predetermined amount of fine iron is charged from the fine iron storage tanks 114, 114a into the first and second stirring tanks 115, 119 by screw feeders 118, 118 a. For example, iron powder having a particle size of 44 to 250 μm can be used as the iron powder for reducing impurity metal ions. And ferric chloride (FeCl) in the solution after treating the shielding screen and the lead frame with corrosion₃) The concentration of the sodium hydroxide is low,the water solution contains metal ions such as copper, nickel, chromium and the like.

The iron chloride-based corrosive waste liquid is supplied from the corrosive waste liquid tank 111 to the first stirring vessel 115 by a pump, and the iron powder is suspended and mixed in the iron chloride-based corrosive waste liquid by rotating the stirring blade 128 to form a mixed slurry.

Therefore, copper ions having a lower ionization tendency than iron (Fe) are reduced and precipitated in the mixed slurry, and iron powder is dissolved out as iron ions in the solution, and is discharged as an iron powder mixed solution 1A containing only a small amount of iron powder after being treated with iron powder. If necessary, a pH adjusting agent such as hydrochloric acid is added to the mixed slurry to adjust the pH of the mixed slurry to, for example, 0.5 to 1.5, thereby maintaining the speed or efficiency of the reduction reaction within a predetermined range.

Next, this iron powder mixed liquid 1A is taken out from an outlet 115a provided at the upper portion of the first stirring tank 115 and sent to the conical receiver 121. The iron powder mixed liquid 1A in the conical stock tank 121 is supplied to the liquid cyclone 116 by a pump 127. The liquid cyclone 116 separates the iron powder mixed solution 1A into a copper-containing iron powder mixed solution 1C containing copper and containing a large amount of iron powder and a decoppering treatment liquid 1B from which copper and iron powder are mostly removed. The copper-and iron-containing powder mixed solution 1C discharged from the lower portion of the liquid cyclone 116 is washed and separated by the first and second aids classifiers 117, 117a to obtain copper powder 117 e. The slurry portion containing a large amount of iron powder, which has been treated by the first eggnostic classifier 117, may be recovered and then supplied to the first stirring tank 115.

On the other hand, the decoppering treatment liquid 1B discharged from the upper part of the liquid cyclone 116 is supplied to a nickel removal device 122, and impurity metals such as nickel and chromium are removed in the following order. As shown in fig. 16 and 17, the decoppering treatment liquid 1B is first supplied to the second agitation tank 119 via the waste liquid supply valve 142, and the fine iron powder 15 is continuously supplied from the iron powder storage tank 114a by the screw feeder 118 a. The motor 129 can also drive the stirring blade 128a to rotate at a predetermined rotational speed, for example, at a low speed of 5 to 60 rpm. However, when the second stirring tank 119 is stirred by the stirring blade 128a, the specific gravity of the iron powder in the decoppered treatment liquid 1B is significantly larger than the specific gravity of the liquid portion, and therefore the iron powder cannot be dispersed sufficiently and uniformly without any change, and therefore, the iron powder is deposited and accumulated on the bottom of the second stirring tank 119 to form a dead space, which causes a problem that the reaction efficiency between the iron powder and the decoppered treatment liquid cannot be maintained at a predetermined level. Furthermore, if the power of the motor 129 is increased to rotate the stirring blade 128a at a high speed to intensively stir the decoppering treatment liquid 1B, the dead space in the second stirring tank 119 is reduced and the iron powder can be uniformly dispersed, but the power consumed by the motor 129 is excessively increased, and the wear of the wall of the second stirring tank 119 made of FRP or the like becomes large, so that the maintenance cost of the replacement tank is increased and the stirring blade 128a is also worn.

Therefore, the stirring blade 128a is not used, and the stirring blade 128a is taken out from the second stirring tank 119 as necessary, and the circulating pump 126 is driven as shown in fig. 17 to suck the iron powder treating liquid 2E containing a small amount of iron powder through the first circulation flow control valve 135 and the second circulation flow control valve 136, and the iron powder treating liquid 2E is supplied at an angle by the supply flow control valve 143 provided at the lowermost portion of the second stirring tank 119, so that a circulation flow from the bottom to the top is generated in the second stirring tank 119. This method enables the iron powder which is liable to settle at the bottom of the second stirring tank 119 to float upward, eliminates dead space in the tank, and enables effective mixing of the iron powder with the decoppering treatment liquid 1B even when the power of the motor 126 of the circulating pump is small,

further, since the first section 130 is in a straight cylinder shape and at the upper position and the second section is in a truncated cone shape, the distribution state and the retention time of the iron powder are different, and the concentration of the iron powder in the iron powder treatment liquid discharged from the first section 130 is lower than the concentration of the iron powder in the iron powder treatment liquid discharged from the second section 131. The discharge amounts of the iron powder treating liquid, which are different in the iron powder concentration and also different in the degree of reduction reaction, are adjusted by the first and second discharge flow rate control valves 138 and 139, respectively, as necessary, so that the properties and state of the primary iron powder treating liquid 2B discharged from the conical tank 121a can be controlled. In this embodiment, the stirring blade 128a is rotated at a low speed while forming a desired circulating flow in the second stirring tank 119, and the maximum circumferential speed is maintained at 1 m/S. In this way, since a swirling flow is generated in addition to the upward flow, an improvement in stirring efficiency can be expected. At this time, if the stirring blade 128a is rotated at a medium speed or a high speed, the second stirring tank 119 and the stirring blade 128a are abraded, which is not preferable.

The iron powder, nickel ions, chromium ions, and the like undergo the following reduction reaction, and thus the primary iron powder treatment liquid 2B can be formed.

Therefore, this reduction reaction is also influenced by the concentration of iron powder in the slurry 2A in the second stirring tank 119, the surface area of the iron powder, the temperature of the slurry 2A, the concentration of chlorine ions, and the like, and therefore these parameters can be appropriately adjusted (added with a pH adjuster). In this case, the solid-liquid weight ratio of the slurry 2A in the second stirring tank 119 was 1: (0.6 to 0.7), as shown in Table 3.

The obtained primary iron powder-treated liquid 2B is sent to the conical tank 121a, and then is sent by the pump 127a, and is treated by the liquid cyclone 116a into a nickel-removed treated liquid 2C and a mixed liquid 2D containing fine iron powder. The mixed liquid 2D containing fine nickel and iron discharged from the lower portion of the liquid cyclone 116a is partially returned to the second agitation tank 119 and is mostly sent to the eggnus classifier 117b to be separated into nickel and fine iron 117f to which nickel is attached. The solution 2C discharged from the upper part of the liquid cyclone 116a is fed into the agitation adjustment tank 124, and after the coagulant supplied from the coagulant tank 125 is added, it is fed into the next suspended impurity removal apparatus not shown.

The solution 2C containing suspended impurities such as carbon and silicon (silica) is treated with a solid-liquid separator such as a decanter to separate the suspended impurities from a secondary iron powder treatment solution 2F (equivalent to the iron powder treatment solution 19 in fig. 1) which is a raw material of a corrosive solution, and the resultant is treated with chlorine gas to prepare a regenerated corrosive solution 20.

The comparative example shown in Table 3 usesStirring blade stirring type mechanical stirring tank of circulating material flow generation mechanism, wherein the volume of a reactor is 11m³The maximum flow rate (peripheral speed) of the slurry was 6m/s, and the iron powder retained a capacity of 6 tons. Compared with the comparative example shown in the table 3, the maximum flow speed in the second embodiment can be reduced from 6m/s to 1m/s, and the solid-liquid ratio can be increased from 1: 3 to 1: (0.6-0.7) in the prior art. Therefore, not only the treatment efficiency can be improved, but also the apparatus maintenance cost can be reduced due to the reduction of the abrasion of the second agitation tank 119. Further, since iron powder having a large particle size can be used, raw material cost can be reduced.

The third agitation tank 150 will be described below, and the agitation tank 150 is a modification of the second agitation tank 119 used in the above-described method for regenerating an iron chloride-based corrosive waste liquid according to the second embodiment of the present invention.

As shown in fig. 18 and 19, the third agitation tank 150 is a reaction vessel composed of three sections, i.e., a first section 151 to a third section 153, which have different vertical horizontal cross-sectional areas; a predetermined amount of iron powder for treating iron chloride-based corrosive waste liquid or purified iron powder 15 produced by the iron powder purification apparatus 16 can be held in the third agitation tank 150; the iron powder consumed by the operation of the third stirring tank 150 can be continuously replenished from an iron powder supply apparatus not shown.

A partition plate 155 for partitioning the third segment 153 and the fluid supply part 154 therebelow is provided at the bottom in the third stirring tank 150. The plurality of nozzles 156 provided on the dividing plate 155 are arranged in a staggered undulation or grid (referred to as a "screen") so that the treatment liquid supplied from the fluid supply section 154 below the dividing plate 155 is ejected from the dividing plate 155 in a horizontally distributed manner. Further, in the first section 151 of the iron powder separating zone, a discharge port 157 for discharging the amount of the iron powder treating liquid 3A required to form the fluidized bed is provided.

Next, the taken-out iron powder treating liquid 3A is supplied to a supply port 159 provided in a side surface of the fluid supply section 154 by a circulation pump 158, so that the iron powder in the third agitation tank 150 is fluidized to form a circulation flow.

Further, atthe bottom and/or side of the fluid supply region 154, a decoppering treatment liquid supply port 160 for supplying the decoppering treatment liquid 1B treated in the previous stage by the first stirring tank 115 and its accessories; in the upper first zone 151 of the third agitation tank 150, a discharge port 161 for discharging the iron powder treated liquid 3B (corresponding to the iron powder treated liquid 19 in the first embodiment) is provided.

In the case of using such a third agitation tank 150, when the circulation pump 158 is operated, the treatment liquid supplied to the fluidized bed through the nozzle 156 is taken out, so that the flow state of the iron powder in the third agitation tank 150 can be maintained.

The maximum flow rate of the slurry in this modified example was reduced from 6m/s to 0.25m/s and the solid-to-liquid ratio was increased from 1: 3 to 1: 1, enabling the treatment under these conditions, as compared with the comparative example in which iron powder and the treatment liquid were stirred using a stirring tank having stirring blades and constructed in the manner shown in Table 3.

Further, as shown in the item of the iron powder particle size in table 3, in the second embodiment and its modified example, with the circulation system in which the treatment liquid is formed inside, the stirring conditions can be easily controlled, and thus it is possible to use iron powder having a particle size ranging from small particles to medium particles. In contrast, in the case of the comparative example, only small-sized iron powder was used, which apparently increased the cost of raw materials.

In the method for regenerating an iron chloride-based corrosive waste liquid of the present invention, the iron powder fluidized bed is formed by passing the iron powder treating liquid through the fluidized bed so as to be circulated and supplied from the bottomof the agitation tank, and therefore, the following effects (1) to (4) can be obtained.

(1) In order to maintain the fluidized bed state within a proper range, the iron powder treating liquid discharged from the upper portion of the agitation tank may be supplied as a necessary amount of the fluidizing medium.

Therefore, when the supply rate of the iron chloride-based waste liquid is insufficient, the iron powder can be maintained in a good flow state by the self-circulation flow formed by a part of the iron powder treating liquid in the agitation vessel; in addition, when the supply rate of the iron chloride-based waste liquid is too high, the reduction treatment of the iron chloride-based waste liquid can be performed under a stable condition by reducing the self-circulation amount of the iron powder treating liquid.

(2) The agitation tank is formed in a shape having an enlarged diameter at the upper part thereof, and the position for taking out the iron powder treatment liquid is appropriately set, whereby the dead space of the agitation tank can be almost completely eliminated, and the efficiency of removing the impurity metal ions in the iron chloride waste liquid in the minimum facility can be improved.

(3) The movement of iron powder in the fluidized bed can be made uniform, and compared with the case of using a fluidized bed of a mechanical stirring system, the local wear phenomenon caused by the flow of iron powder is eliminated, and the service life of the apparatus can be prolonged and the maintenance cost can be reduced.

(4) Can ensure the good stirring state of the iron powder and the ferric chloride waste liquid in a fluidized bed in a narrow space, and the whole device can be miniaturized.

Among them, the iron chloride-based waste liquid supplied from the bottom of theagitation tank does not cause the problem of the mixing of the iron chloride-based waste liquid into the treatment liquid, and the formation of the fluidized bed can be promoted by the iron chloride-based waste liquid supplied in large amounts.

In the method for regenerating an iron chloride-based corrosive waste liquid of the present invention, it is preferable that the upper part of the agitation vessel is expanded in diameter relative to the main body part, so that the rising speed of the fluid in the agitation vessel is decreased to promote the precipitation of iron powder. And the upper part can form an iron powder separation area, even if the flow rate in the tank fluctuates, the upper end of the fluidized bed can be ensured not to exceed a specified position, the iron powder mixed in the iron powder treating liquid is less, the impurity metal ions can be removed under a stable condition, and the removal efficiency of the impurity metal ions can be further improved.

Therefore, in the method for regenerating an iron chloride-based corrosion waste liquid of the present invention, the supplied iron chloride-based waste liquid is subjected to a pre-electrolysis treatment, so that a part or almost all of the ferric ions in the original waste liquid can be reduced to ferrous ions. Thus, since the ferric ions are reduced by the cathode reaction, the total amount of the ferric ions and the ferrous ions in the solution is not changed. Therefore, when the ferric ion waste liquid is regenerated, a large amount of diluent (specifically, water) is not required for adjusting the concentration of the ferric ion to the specified concentration, the cost required for treating the residual liquid can be reduced, and the treatment equipment can be made smaller. Since the amount of iron powder used in the regeneration treatment of the iron chloride-based waste liquid is reduced, the treatment cost of the iron chloride-based waste liquid can be reduced.

Furthermore, in the method for regenerating an iron chloride-based corrosive waste liquid of the present invention, the electrolytic voltage of the iron chloride-based corrosive waste liquid may be controlled within a specific range during the electrolytic treatment. Therefore, it is possible to reduce trivalent iron ions without depositing impurity metal ions such as copper and nickel contained in the iron chloride-based corrosion waste liquid and to perform the regeneration treatment of the iron chloride-based waste liquid more efficiently.

In the method for regenerating an iron chloride-based corrosive waste liquid of the present invention, the inter-electrode distance between the anode plate and the cathode plate in the electrolytic cell for electrolysis can be set within a specific range, whereby not only the intrusion of chlorine gas generated at the anode plate into the cathode chamber and the oxidation of divalent iron ions can be prevented, but also the increase in electrolytic voltage can be suppressed.

In the method for regenerating an iron chloride-based corrosive waste liquid of the present invention, the iron chloride-based corrosive waste liquid can be supplied to the cathode chamber side of the electrolytic cell partitioned into the anode chamber side and the cathode chamber side by the diaphragm, and the treated reduced iron chloride aqueous solution can be taken out from the other part of the cathode chamber side. Thus, the interference of the chlorine gas generated at the anode plate and the iron chloride-based waste corrosion solution supplied is suppressed, and the electrolysis can be efficiently performed.

In the method for regenerating a waste liquid of iron chloride corrosion of the present invention, the concentration of ferric ions in the waste liquid of reduced iron chloride corrosion may be controlled to 10 to 120 g/l. Therefore,the impurity metal ions such as copper and nickel in the molten iron chloride solution are not reduced, and the subsequent regeneration treatment is not disturbed, so that the subsequent regeneration treatment cost can be reduced.

In the method for regenerating an iron chloride-based corrosive waste liquid of the present invention, since chlorine gas generated during electrolysis is blown into the iron powder treating liquid discharged from the agitation tank, part of the divalent iron ions contained in the iron powder treating liquid can be oxidized into trivalent iron ions. Therefore, the concentration of ferric ions in the iron powder treatment solution from which impurity metal ions are removed can be adjusted to a desired value without generating unnecessary by-products, and a reclaimed solution of an iron chloride aqueous solution in which both the necessary components and the concentration are adjusted can be efficiently obtained.

In the method for regenerating iron chloride-based corrosive waste liquid of the present invention, the iron powder may be a refined iron powder obtained by the following method: iron powder dust is recovered from dust containing impurities such as calcium oxide generated from a steel making furnace by a wet process, and is subjected to pulverization, water washing, and acid washing. Therefore, it is possible to regenerate the iron chloride-based waste liquid at a low cost by using a high-purity refined iron powder with few impurities obtained by treating dust generated in a steel-making furnace.

In the method for regenerating an iron chloride-based corrosive waste liquid of the present invention, the pickling of iron powder dust is carried out in a process of being discharged gradually by a screw conveyor which is disposed obliquely in a precipitation tank and has an acid liquid injection port at the upper part thereof. Therefore, since the iron powder used for the reductiontreatment of the iron chloride-based waste liquid is obtained in large quantities and at low cost as a continuous treatment, the regeneration treatment of the iron chloride-based waste liquid can be performed at low cost.

Claims (11)

1. A method for regenerating an iron chloride-based waste etching solution, which comprises mixing iron powder into an iron chloride-based waste etching solution containing metal ions having a lower ionization tendency than iron, such as copper and nickel, in a stirred tank, reacting the iron powder with the metal ions to remove the metal ions, and then oxidizing the iron powder-treated solution;

the method is characterized in that: the iron powder-treated liquid obtained by reacting the iron powder is taken out from the upper part of the agitation tank while supplying the iron chloride-based waste liquid to the agitation tank, and is circulated and supplied to the bottom of the agitation tank to form a fluidized bed in which the iron powder is dispersed and suspended, and the excess iron powder-treated liquid is taken out from the upper part of the agitation tank.

2. The method for regenerating an iron chloride-based corrosive waste liquid according to claim 1, wherein said iron chloride-based corrosive waste liquid is supplied from the bottom of said agitation tank to promote the formation of said fluidized bed.

3. The method for regenerating an iron chloride-based corrosive waste liquid according to claim 1, wherein an iron powder separation region is provided in an upper part of said agitation vessel, and said iron powder separation region is expanded in diameter with respect to a fluidized bed forming region in which said fluidized bed is formed, so that a flow velocity of the rising liquid is reduced to suppress rising of the iron powder in the dispersed suspension.

4. The method for regenerating an iron chloride-based corrosive waste liquid according to claim 1, wherein the iron chloride-based corrosive waste liquid introduced into said agitation tank is a reduced iron chloride aqueous solution in which ferric ions are partially or almost completely reduced to ferrous ions by subjecting the iron chloride-based corrosive waste liquid to electrolytic treatment.

5. The method for regenerating an iron chloride-based corrosive waste liquid according to claim 4, wherein the electrolytic voltage and current density of said iron chloride-based corrosive waste liquid are controlled to 1 to 4.5V and 2 to 40A/dm, respectively²Within the range.

6. The method for regenerating an iron chloride-based corrosive waste liquid according to claim 4, wherein an inter-electrode distance between the anode plate and the cathode plate in the electrolytic bath in which said electrolytic treatment is carried out is in the range of 1.5 to 50 mm.

7. The method for regenerating an iron chloride-based corrosive waste liquid according to claim 4, wherein said electrolytic cell for conducting electrolytic treatment is partitioned by a liquid-permeable diaphragm into an anode chamber having an anode and a cathode chamber having a cathode, said iron chloride-based corrosive waste liquid is supplied from a position in said cathode chamber, and said reduced iron chloride aqueous solution reduced in said cathode chamber is taken out from a position other than said cathode chamber.

8. Themethod for regenerating an iron chloride-based corrosive waste liquid according to claim 4, wherein the concentration of the ferric ions remaining in said reduced iron chloride aqueous solution is maintained within the range of 10 to 120 g/l.

9. The method for regenerating an iron chloride-based corrosive waste liquid according to claim 4, wherein said iron powder treating solution is subjected to oxidation treatment using part or all of chlorine gas generated from said anode during said electrolytic treatment.

10. The method for regenerating an iron chloride-based corrosive waste liquid according to claim 1, wherein said iron powder is a refined iron powder obtained by: iron powder dust contained in dust containing impurities such as calcium oxide generated in a steel making furnace is recovered by a wet method, the iron powder dust is pulverized and washed with water to remove the impurities, and the resultant is further washed with acid to obtain refined iron powder.

11. The method for regenerating an iron chloride-based corrosive waste liquid according to claim 10, wherein said pickling of the iron powder dust is carried out while gradually discharging the iron powder dust by means of a screw conveyor having an acid liquid inlet at an upper portion thereof and being disposed obliquely in a settling tank in which the iron powder dust is retained.

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