JP2022022852A5 - - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid matter recovery method and recovery apparatus for recovering fine solid matter contained in a liquid to be treated from the liquid to be treated.

Copper smelting methods include the wet method, in which copper is leached from copper concentrate into acid, etc., and the method in which copper concentrate is melted to produce an anode (smelting process). (electrorefining process), and a dry method. The dry process is the mainstream of copper smelting, especially for sulfide concentrates, because it enables large-scale production and is low in cost.

The dry method will be explained more specifically. First, in the smelting process, copper concentrate is melted in a flash smelting furnace to form matte, the obtained matte is oxidized in a converter to obtain blister copper, and the obtained blister copper is refined in a refining furnace to a purity of about 99%. of purified blister copper is obtained, and this purified blister copper is poured into a mold to cast an anode (anode plate) for electrolytic copper refining.

In the subsequent electrorefining step, a plurality of anodes and a plurality of separately prepared cathodes (cathode plates) are alternately arranged at regular intervals in an electrolytic cell in which a copper electrolyte is held, and these anodes and cathodes energize the As a result, copper ions are eluted from the anode into the electrolytic solution, and the copper ions are electrodeposited on the cathode to obtain electrolytic copper having a copper grade of 99.99% or more on the cathode.

In the electrorefining process, copper is eluted from the anode into the electrolytic solution as copper ions, and at the same time, impurities such as arsenic, bismuth, antimony, and nickel contained in the anode are also eluted into the electrolytic solution. Only copper ions from the electrolytic solution are electrodeposited on the cathode to obtain high-purity electrolytic copper, but impurities remain in the electrolytic solution, resulting in an increase in the concentration of impurities in the electrolytic solution.

When the concentration of impurities in the electrolytic solution increases as the electrolytic refining progresses, the impurities co-deposit with copper, lowering the copper grade of the electrolytic copper, causing scales to form in the electrolytic solution pipes, which impedes operation, and , the electric conductivity of the electrolytic solution is lowered, and the electric power cost is increased.

For this reason, part of the electrolytic solution is sent to a solution cleaning process to remove impurities, and then supplied again to the electrolytic cell. In the liquid purification process, the electrolytic solution is vacuum-evaporated to concentrate and rapidly cooled to precipitate and remove supersaturated copper as crude copper sulfate. Copper removal electrolysis process (arsenic removal electrolysis process), in which residual copper, arsenic, bismuth, and antimony are removed from the crude mother liquor, which is the filtrate, by depositing them on the cathode. A de-nickeling step or the like is performed in which nickel is separated and recovered as crude nickel sulfate from a certain decopping final solution.

In the nickel removal step, the final copper removal solution is supplied to a nickel concentration tank, and in this nickel concentration tank, a graphite electrode is immersed in the copper removal final solution and electrified, and the copper removal final solution is heated and concentrated by Joule heat ( evaporate). Next, the heat-concentrated concentrate is sent to a cooling and crystallizing tank, and crude nickel sulfate is precipitated from this concentrate due to the decrease in solubility due to cooling. Furthermore, the slurry containing precipitated crude nickel sulfate is sent to a filter by a cooling crystal tank pump, the crude nickel sulfate is recovered as a solid matter by filtration, and the filtrate is sucked by a vacuum pump and stored in a receiver tank. are paid out accordingly.

In this way, not only in the process of recovering crude nickel sulfate, but also in the process of generally recovering an object that has been solidified by using the difference in solubility to become a solid substance, the concentrated liquid that has been heated and concentrated is placed in a cooling crystallization tank. to precipitate solids by concentration and subsequent cooling to reduce solubility, and the slurry containing the precipitated solids is supplied to a filtration step. In the filtration step, the slurry is separated into solid matter (precipitate) and filtrate by a filter medium such as filter cloth, filter paper, or mesh screen. In particular, in suction filtration such as vacuum filtration, it is possible to quickly separate by suctioning the filtrate by reducing the pressure on the filtrate side of the filter medium. The sucked filtrate is stored in a receiver tank and discharged as needed.

The discharged filtrate contains the target substance in a dissolved state due to its solubility, and fine solid substances that have leaked from the filter (in the nickel removal process, nickel sulfate dissolved in the solution and fine crude nickel sulfate, respectively). are included, and these are the cause of recovery loss.

In order to reduce filtration leakage, it is conceivable to make the mesh of the filter medium finer, but this method reduces the filtration speed, so if the filter has no margin, the production volume of filtrate and solids will be reduced. is reduced.

In Japanese Patent Laid-Open No. 2020-6302, a filtrate containing fine solids that have leaked from filtration is sedimented and separated in a sedimentation tank, the solids sedimented at the bottom of the sedimentation tank are bottomed out, and cooled crystals are obtained. A method for improving the recovery rate of solids is disclosed by returning the solids to the tank for grain growth and then filtering again. According to the method described in Japanese Patent Application Laid-Open No. 2020-6302, a part of the filtrate after collecting the solid matter is treated in the cooling crystal tank compared to the case where it is directly returned from the receiver tank to the cooling crystal tank. The amount of liquid to be collected can be kept small, and mainly fine solids can be effectively recovered by circulation in the system, and the recovery rate of solids from the raw material liquid can be dramatically improved.

Japanese Patent Application Laid-Open No. 2020-6302

Slurries containing fine solids bottomed out from settling tanks have been subjected once to cooling crystallizers and are difficult to cool further. Therefore, even when the slurry extracted from the sedimentation tank is returned to the cooling crystallization tank and retained, the growth of the crystal grain size of the fine solids contained in the slurry and the solids dissolved in the slurry No new precipitation is expected. For this reason, when the slurry extracted from the cooling crystallization tank is filtered with a filter, the fine solids are supplied to the filter medium with almost the same size without growing the crystal grain size, resulting in the grain size of the filter medium. Clogging is more likely to occur. When clogging occurs in the filter medium, the filter medium needs to be cleaned or replaced, increasing the cost of collecting solids.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method and apparatus for collecting solids, which can prevent clogging of a filter medium and reduce the cost of collecting solids.

The inventors of the present invention have made various studies to solve the above problems, and found that by returning the fine solids that have not been filtered out to a process upstream of the cooling crystallization tank, the fine solids have a crystal grain size of can be prevented from being supplied to the filter medium with almost the same size without growing, and clogging of the filter medium can be made difficult to occur. The present invention has been completed based on such findings.

The solid matter recovery method of the present invention comprises:
a concentration step of heating and concentrating the liquid to be treated to obtain a concentrated liquid;
A cooling step of obtaining a first slurry containing the solids by cooling the concentrated liquid to precipitate the solids;
a filtration step of filtering the first slurry to separate it into a filtrate and the solid matter, and recovering the solid matter;
a returning step of returning the residual solid matter that is contained in the filtrate and has not been filtered through to the concentration step or a step upstream of the concentration step ;
Prepare.

In the returning step, the filtrate is put into a sedimentation tank, the residual solids in the filtrate are sedimented at the bottom of the sedimentation tank, and a second slurry containing the residual solids precipitated at the bottom is prepared. , can be recycled to the concentration step or to a step upstream of the concentration step .

In the filtering step, a rotating drum vacuum filter using a so-called Oliver filter having a cylindrical shape can be used as a filtering medium for filtering the first slurry.

The solid matter recovery device of the present invention is
a concentration tank for heating and concentrating the liquid to be treated to obtain a concentrated liquid;
a cooling crystallization tank for obtaining a first slurry containing solids by cooling the concentrated liquid sent from the thickening tank to precipitate solids;
a filter for filtering the first slurry to separate the filtrate and the solids and recovering the solids; and
a return means for returning residual solids contained in the filtrate that have leaked through filtration to the thickening tank or upstream of the thickening tank;
Prepare.

The return means is
a settling tank for settling the residual solids from the filtrate;
a return pipe for bottoming out the residual solids that have settled from the sedimentation tank and returning them upstream of the thickening tank or the thickening layer;
can have

A rotating drum type vacuum filter can be used as the filter.

According to the solid matter recovery method and recovery apparatus of the present invention, clogging of the filter media can be prevented, the frequency of cleaning and replacement of the filter media can be reduced, and the solid matter recovery cost can be reduced. .

FIG. 1 is a schematic diagram showing the overall configuration of an apparatus for recovering solid matter from a raw material liquid.

TECHNICAL FIELD The present invention relates to a process for recovering solids from a liquid to be treated, such as a de-nickel process for separating and recovering nickel as crude nickel sulfate from the de-coppering final solution produced in the liquid purification process for electrolytic refining of copper. As shown in FIG. 1, a recovery apparatus for recovering solid matter from a liquid to be treated basically comprises a concentration tank 3 for heating and concentrating a raw material liquid (liquid to be treated) 1 to obtain a concentrated liquid 2. , a first A filter 7 for filtering the slurry 5a and recovering the solid matter 4, and a filtrate 8 after recovering the solid matter 4 is separated by sedimentation, and fine residual solid matter remaining in the filtrate 8 A settling tank 9 for settling 4a and a return line 10 for returning a second slurry 5b containing residual solids 4a settled from the settling tank 9 to the thickening tank 3.

Any concentration tank can be applied to the concentration tank 3 as long as the raw material liquid 1 can be heated to a temperature equal to or higher than the boiling point of the raw material liquid 1 . For example, an electric evaporation tank is applicable. In the electric evaporation tank, a graphite electrode rod that can be energized and is immersed in the liquid to be treated is inserted into the tank. is heated by Joule heat to evaporate water, and a concentrated liquid 2 is obtained. The heating temperature depends on the type of the liquid to be treated, but in the case of the final solution for copper removal, the temperature is preferably in the range of about 150.degree. C. to 200.degree. As the thickening tank 3, a heavy oil burner may be used to heat the raw material liquid 1 directly or indirectly from the surroundings of the tank.

The cooling crystallization tank 6 also cools the concentrated liquid 2 to a temperature at which the solid matter 4 is sufficiently precipitated, for example, to about 50° C. in the case of recovery of crude nickel sulfate, depending on the type of solute contained in the concentrated liquid 2. Any possible structure can be adopted. For example, a structure in which a jacket or a corrugated tube is installed around or inside the tank and a coolant is passed through these can be applied to the cooling crystal tank 6 .

In this example, the filter 7 is a rotating drum type vacuum filter that uses a so-called Oliver filter having a cylindrical shape as a filter medium in order to recover crude nickel sulfate in the final copper removal solution. However, for the filter 7, a filter using natural filtration, vacuum filtration, pressure filtration, centrifugal filtration, or the like may be used. can be Specifically, as the filter 7, for example, a vacuum filter, a centrifuge, a centrifugal sedimentator, or the like can be used.

In this example, a solid matter 4 such as crude nickel sulfate is recovered in a filter 7 configured by a rotating drum type vacuum filter, and a filtrate 8, which is a filtrate after recovering the solid matter 4, is removed by a vacuum pump. It is sucked and put into the sedimentation tank 9 via the receiver tank 11 as needed. In the sedimentation tank 9, the filtrate 8 is retained for a sufficient period of time so that fine residual solids 4a are sedimented. Then, only the supernatant 12 generated by the precipitation of the residual solids 4a is once discharged out of the system, added to the electrolytic solution to be used for adjusting the acid concentration, etc., and a second slurry containing the precipitated residual solids 4a. 5b is bottomed out from the bottom 13 of the sedimentation tank 9 .

If the filtrate 8 contains particles of the residual solid matter 4 a with a relatively large crystal size, the particles may settle in the receiver tank 11 before reaching the sedimentation tank 9 . Therefore, it is preferable to adjust the position of the outlet pipe of the receiver tank 11 and the residence time of the filtrate 8 in the receiver tank 11 so that almost all of the particles of the residual solid matter 4a can be sent to the sedimentation tank 9.

The overall shape and size of the sedimentation tank 9 is basically sufficient as long as it can secure a residence time according to the size of the particles of the object to be sedimented. Specifically, the sedimentation tank 9 has a shape and size that can ensure a residence time longer than the settling time of particles having the same diameter as the opening of the filter media of the filter 7 . The bottom 13 of the sedimentation tank 9 is inclined downward toward the outlet for bottoming out the second slurry 5b, and preferably has a shape that narrows downward. Specifically, when the shape of the upper part of the sedimentation tank 9 is cylindrical, the shape of the bottom part 13 can have a cone shape (cone) or a mortar shape.

In order to retain the filtrate 8 for a sufficient time to settle the residual solids 4a, the settling tank 9, after receiving the filtrate 8 or before bottoming out the residual solids 4a and drawing off the supernatant 12, It has a function of providing a waiting time for only sedimentation separation of the filtrate 8 . Specifically, the sedimentation tank 9 has a function of holding (retaining) the filtrate 8 for 15 minutes or more, preferably 20 minutes or more after being introduced.

In addition, while the filtrate 8 is held (retained) by the sedimentation tank 9, the supply of the filtrate 8 from the receiver tank 11 to the sedimentation tank 9 is stopped, and the upstream process is performed as necessary. Either pause or feed the filtrate 8 to another tank (receiver tank 11 or another sedimentation tank 9). The holding time of the filtrate 8 is desirably 50 minutes or less, preferably 40 minutes or less.

As long as the sedimentation tank 9 can retain the filtrate 8 for a sufficient time and settle a sufficient amount of the residual solid matter 4a, it is sufficient to install one sedimentation tank 9 . However, in order to secure a sufficient retention time, it is effective to install two or more sedimentation tanks 9 . For example, two sedimentation tanks 9 are provided as shown in FIG. Extraction and removal of the supernatant 12 are performed, and as the second step, the work performed by one unit that received the filtrate 8 in the first step is to settle and bottom out the residual solid matter 4a, and In another unit that had done so by switching to withdrawing the supernatant 12 and settling and bottoming out the residual solids 4a in the first step and withdrawing the supernatant 12, instead of these the filtrate 8 It is preferable that the first step and the second step are alternately performed so as to receive the . As a result, after receiving the filtrate 8 or before bottoming out the residual solids 4a and drawing out the supernatant 12, it is possible to provide a sufficient waiting time for only sedimentation separation of the filtrate 8, and the residual solids The sedimentation and bottoming out of the object 4a are reliably distinguished in time. When two or more sedimentation tanks 9 are provided, a three-way valve can be arranged upstream of the sedimentation tank 9 to distribute the filtrate 8 to each of the sedimentation tanks 9. The mechanism and method for sorting the filtrate 8 are not limited to this embodiment.

A return pipe 10 returns the second slurry 5 b bottomed out from the bottom 13 of the sedimentation tank 9 to the thickening tank 3 . In this example the return line 10 has a pump 14 . That is, the suction port of the pump 14 draws in the second slurry 5b from the bottom 13 of the sedimentation tank 9, and the second slurry 5b is discharged from the discharge port of the pump 14, whereby the second slurry 5b is discharged into the thickening tank 3. send it back to In this example, the sedimentation tank 9 and the return pipe 10 constitute return means.

A method for recovering the solid matter 4 from the raw material liquid 1 using the recovery apparatus of this example will be described.

First, a predetermined amount of the raw material liquid 1 sent from the electrolytic refining process is supplied to the concentration tank 3 , heated and concentrated to obtain the concentrated liquid 2 . Next, the concentrated liquid 2 is supplied to the cooling crystal tank 6 and cooled to a predetermined temperature to precipitate the solid matter 4 . Next, the first slurry 5a containing the precipitated solid matter 4 is extracted from the cooling crystallization tank 6 and sent to the filter 7, and the first slurry 5a is filtered to remove the filtrate 8 and the solid matter. 4, and the solid matter 4 remaining on the filter medium is recovered.

Filtrate 8 containing fine residual solid matter 4 a that has leaked through the filter is supplied to sedimentation tank 9 via receiver tank 11 . In the sedimentation tank 9, the filtrate 8 is held for a predetermined time to precipitate the residual solid matter 4a. A supernatant 12 produced by the precipitation of the residual solid matter 4a is once discharged out of the system and used for adjusting the acid concentration of the electrolytic solution. On the other hand, the second slurry 5b containing the settled residual solids 4a is bottomed out from the bottom 13 of the sedimentation tank 9 and returned to the thickening tank 3 through the return line 10 .

The second slurry 5 b returned to the concentration tank 3 is mixed with the raw material liquid 1 sent from the electrorefining step, then heated and concentrated, and the resulting concentrated liquid 2 is sent to the cooling crystal tank 6 . In the cooling crystallization tank 6, the precipitation of the solid matter 4 from the concentrated liquid 2 and the growth of the crystal grain size of the solid matter 4 occur based on the decrease in solubility due to cooling. Then, the first slurry 5 a containing the solid matter 4 with sufficiently large crystal grain size is bottomed out from the cooling crystal tank 6 and supplied to the filter 7 .

According to this example, the recovery rate of the solid matter 4 from the raw material liquid 1 can be improved based on the same principle as the method described in JP-A-2020-6302. That is, in this example, the filtrate 8 is held for a predetermined time in the sedimentation tank 9 to precipitate the fine residual solids 4a, and then the second slurry 5b containing the residual solids 4a is returned to the upstream process. I'm trying Therefore, compared to the case where part of the filtrate 8 is directly returned from the receiver tank 11 to the upstream process, the amount of liquid to be treated in the upstream process can be reduced, and the residual solid matter 4a can be recovered more effectively. can do.

Particularly in this example, the return destination of the second slurry 5b containing fine residual solids 4a is the thickening tank 3 . For this reason, the fine residual solid matter 4a circulating in the system can grow, and clogging of the filter material of the filter 7 can be made difficult to occur. As a result, the frequency of cleaning and replacement of the filter medium can be kept low, the recovery efficiency of the solid matter 4 can be improved, and the recovery cost of the solid matter 4 can be reduced.

In this example, the second slurry 5b bottomed out from the bottom 13 of the sedimentation tank 9 is returned to the thickening tank 3. However, when carrying out the present invention, the second slurry is It can also be sent back to an upstream process. Specifically, for example, a mixing tank for mixing the raw material liquid sent from the electrorefining step and the second slurry is provided upstream of the concentration tank, and the second slurry is returned to the mixing tank. It can also be configured to

Tests conducted to confirm the effects of the present invention will be described below. In the following examples, an apparatus such as that shown in FIG. 1 was used to recover crude nickel sulfate from the final solution of decoppering produced in the electrolytic refining of copper. However, the present invention is not limited to the following examples.

(Example)
The final copper removal solution (copper: 0 g/L, nickel: 30 g/L to 40 g/L) generated in the electrolytic refining of copper is supplied to the concentration tank 3, and the copper removal final solution in the concentration tank 3 is applied to the graphite electrode. A concentrated liquid 2 was obtained by heating to 150° C. to 170° C. with Joule heat to evaporate water from the final decoppering liquid.

The concentrated liquid 2 was discharged from the concentrating tank 3 to the cooling crystal tank 6 by overflow, and the concentrated liquid 2 was cooled in the cooling crystal tank 6 until the liquid temperature reached 50°C. Cooling was performed by flowing industrial water into a corrugated tube provided in the cooling crystal tank 6 .

The first slurry 5a containing the produced crude nickel sulfate is supplied to a filter 7 equipped with an Oliver filter (drum diameter: 1 m, drum width: 0.4 m) equipped with a polypropylene filter cloth as a filter medium, and filtered. , the filtrate was separated into a filtrate 8 and a solid 4 . The amount of liquid treated in the filter 7 immediately after the start of test operation was 35 L/min.

The filtrate 8 is held in the sedimentation tank 9 for 30 minutes to precipitate the residual solids 4a, and the second slurry 5b containing the precipitated residual solids 4a is drained from the bottom 13 of the sedimentation tank 9. , was returned to the concentration tank 3 through the return pipe 10 .

After one month from the start of operation, the amount of treated liquid in the filter 7 was 30 L/min. After two months, the amount decreased to 20 L/min, so the filter medium was replaced.

(Comparative example)
A test operation was carried out in the same manner as in the example except that the second slurry 5b containing the residual solids 4a was returned to the cooling crystallization tank 6. The amount of treated liquid in the filter 7 decreased from 35 L/min to 20 L/min in one month from the start of operation, so the filter medium was replaced.

As is clear from the comparison between the examples and the comparative examples, in the nickel removal process, the slurry containing fine crude nickel sulfate that has leaked out of the filtration is returned to the thickening tank arranged upstream thereof, not to the cooling crystallization tank. This can cut the filter replacement frequency in half. As a result, the cost of replacing the filter medium can be reduced, and the recovery cost of crude nickel sulfate can be reduced.

1 Raw material solution (final solution for decoppering)
2 concentrated liquid 3 thickening tank 4 solid (crude nickel sulfate)
4a Residual solids 5a First slurry 5b Second slurry 6 Cooling crystal tank 7 Filter 8 Filtrate
9 sedimentation tank 10 return pipe 11 receiver tank 12 supernatant 13 bottom 14 pump

Claims (6)

a concentration step of heating and concentrating the liquid to be treated to obtain a concentrated liquid;
A cooling step of obtaining a first slurry containing the solids by cooling the concentrated liquid to precipitate the solids;
a filtration step of filtering the first slurry to separate it into a filtrate and the solid matter, and recovering the solid matter;
a returning step of returning the residual solid matter that is contained in the filtrate and has not been filtered through to the concentration step or a step upstream of the concentration step ;
A method for collecting solids, comprising: In the returning step, the filtrate is put into a sedimentation tank, the residual solids in the filtrate are sedimented at the bottom of the sedimentation tank, and a second slurry containing the residual solids precipitated at the bottom is produced. is returned to the concentration step or a step upstream of the concentration step ;
The method for recovering solids according to claim 1. In the filtering step, a rotating drum vacuum filter is used for filtering the first slurry.
3. The method for recovering solids according to claim 1 or 2. a concentration tank for heating and concentrating the liquid to be treated to obtain a concentrated liquid;
a cooling crystallization tank for obtaining a first slurry containing solids by cooling the concentrated liquid sent from the thickening tank to precipitate solids;
a filter for filtering the first slurry to separate the filtrate and the solids and recovering the solids; and
a return means for returning residual solids contained in the filtrate that have leaked through filtration to the thickening tank or upstream of the thickening tank;
A solids recovery device comprising: The return means is
a settling tank for settling the residual solids from the filtrate;
a return line for bottoming out the residual solids settled from the sedimentation tank and returning the thickening tank or upstream of the thickening tank;
having
5. The device for collecting solids according to claim 4. The filter is composed of a rotary drum vacuum filter,
6. The device for collecting solids according to claim 4 or 5.