JP5622090B2 - Method for producing zinc carbonate - Google Patents

Description

  The present invention relates to Zn-containing raw materials, particularly zinc-oxide raw materials used for pigments, medical products, etc. from Zn-containing dust generated from a reduction furnace or the like for removing Zn in steelworks and other Zn-containing products, The present invention relates to a basic zinc carbonate used as a zinc material for electrogalvanization, commonly known as a method for producing zinc carbonate.

More specifically, a Zn-containing product is dissolved in a solvent of an ammonium carbonate solution containing (NH ₄ ) ₂ CO ₃ (ammonium carbonate) and NH ₄ OH (ammonium hydroxide), and impurities in the solution are added to metal Zn. And a method for producing zinc carbonate in which zinc carbonate is crystallized from the solution after being reduced by filtration.

In the present invention, the ammonium carbonate solution refers to a solution containing (NH ₄ ) ₂ CO ₃ and NH ₄ OH.

About Zinc Carbonate Production Method Conventionally, as a method for producing zinc carbonate from a Zn-containing raw material, the Zn-containing raw material is dissolved in an ammonium carbonate solution, and ammonia in the solution is evaporated by heating or decompression to crystallize zinc carbonate. A so-called ammonium carbonate dissolution method is known.

  When zinc carbonate is produced from Zn-containing dust generated at an ironworks by this ammonium carbonate dissolution method, the Zn-containing dust at an ironworks contains a large amount of impurities such as alkalis, halogens, and heavy metals such as Fe. In order to produce pure zinc carbonate, it is important to remove these impurities.

Regarding the ion exchange method As a method for removing heavy metal impurities, for example, in Patent Document 1, Zn-containing dust is dissolved in an ammonium carbonate solution, and metal Zn is added to the solution to perform ion exchange. A method for precipitating heavy metals such as Fe and Pb and removing them as a residue is disclosed.

  Among impurities more noble than Zn, Fe has a small difference in oxidation-reduction potential from Zn, and as a result, the removal reaction rate is slower than that of noble impurity elements such as Pb. As a result, it is difficult to purify Fe, and reducing the Fe value of the product zinc carbonate is one of the difficulties in producing high-purity zinc carbonate.

Regarding Prior Art of Fe Value Reduction As a method for reducing the Fe value of product zinc carbonate, Patent Document 2 discloses partial crystallization after ion exchange and filtration, and after performing the main crystallization after removing about 10% of primary crystals, A method for reducing Fe in zinc carbonate crystals is shown.

  Patent Document 3 discloses a zinc solution microfiltration method in which a purified solution is filtered through a filter pre-coated with short fibers not containing inorganic substances, and then filtered through a membrane filter.

Furthermore, Patent Document 4 proposes a method for reducing the Fe concentration of the Zn solution itself used for ion exchange. That is, a plurality of dissolution tanks are arranged in series, a sedimentation separation tank is provided next to at least the final stage dissolution tank, and the solution is transferred from the first dissolution tank to the final dissolution tank. In this method, the Zn-containing material is fed back to the previous dissolution tank and the undissolved Zn-containing slurry in the dissolution tank excluding the precipitation separation tank and the first dissolution tank is returned to the previous dissolution tank.

  Patent Document 5 proposes an ion exchange device that reduces the Fe value. That is, a plurality of ion replacement tanks having a sedimentation section for sedimentary slurry and a clarification section for a supernatant zinc solution are arranged in series, and a zinc solution supply port is provided in the first ion exchange tank. In addition, a zinc zinc supply port is provided in the final ion replacement tank, and a clarification liquid supply path through which the clarified liquid of the zinc solution sequentially moves from the first to the final ion replacement tank is provided. The refining device is arranged so that the sedimentation slurry return path is sequentially returned to the preceding ion substitution tank over the tank.

Japanese Patent Publication No. 02-035633 Japanese Examined Patent Publication No. 01-038048 Japanese Patent Publication No. 63-046135 Japanese Patent Publication No. 01-038050 Japanese Patent Publication No. 01-039968

  In the method of Patent Document 2 which discloses a method for reducing the Fe value of zinc carbonate as a product, about 10% of the primary crystals generated by partial crystallization are removed and returned to the dissolution process. It is necessary to have an equipment capacity of 110% with respect to each process capacity corresponding to the production amount of zinc carbonate product crystals, and the equipment cost increases accordingly. In addition, the operation cost such as energy cost has a drawback that it is necessary to always add 10% in the process before partial crystallization.

  Moreover, the method of patent document 3 has the fault that an installation cost increases, in addition to the original filter which must be installed a precision filter. In general, compared with the cake filtration method, the precision membrane filtration using a membrane has a drawback that the pores of the membrane are easily blocked and the operation becomes difficult.

  Furthermore, the methods of Patent Documents 4 and 5 that proposed a method of reducing the Fe concentration of the Zn solution itself to be subjected to ion exchange are premised on the installation of continuous multistage processing tanks, and the equipment cost is high. There are disadvantages. In addition, as an example, only an example using a raw material with a relatively low impurity content such as about 1% of heavy metal impurities such as Fe and Pb is shown. When using raw materials with low purity such that the total amount is several tens of percent, sedimentation / clarification separation using a baffle plate or a draft tube may not function. Moreover, there is a problem that this method cannot be applied to a batch type processing facility.

  Moreover, as a product inspection, it is widely performed to appropriately analyze the content of Fe in zinc carbonate of a product and determine whether the product is acceptable or not based on the result. However, this is only a direct quality inspection of the product, it is only for judging the production result, and it is directly related to reducing the Fe amount stably, going back to the production process. There is no.

  As described above, there has not yet been proposed a method for reducing heavy metals in zinc carbonate as a product by an ion exchange method using metallic Zn, in particular, reducing the amount of Fe inexpensively, easily and reliably. .

The object of the present invention is to reduce the heavy metals in zinc carbonate, in particular, to reduce the amount of Fe at a low cost, easily and reliably when producing high purity zinc carbonate as a product by ion exchange with metal Zn. An object of the present invention is to provide an operation management or facility management method that can be applied regardless of the equipment form such as a continuous tank system or a batch processing system.

The present invention relates to an ion exchange reaction by dissolving Zn-containing dust generated in iron making or other Zn-containing products in an ammonium carbonate solution containing (NH ₄ ) ₂ CO ₃ and NH ₄ OH, and adding metal Zn. In the method for producing zinc carbonate in which zinc carbonate is crystallized from the solution after reducing impurities in the solution by solid separation by filtration and filtration, the Fe content in the solid separated solution or crystallized zinc carbonate is determined on-site. The basic structure is to perform periodic operation analysis using an Fe rapid analysis method, and to perform operation management or facility management by comparing the actual Fe content result value with the Fe management limit value.

  Specifically, the operation management in the method for producing zinc carbonate of the present invention involves periodically analyzing the Zn-containing solution after filtering the ion-exchanged solution on-site using an Fe rapid analysis method. When the control limit value (Cmg / l) of the resulting Fe content is 1.5 mg / l and the analysis value exceeds the control limit value, the Zn-containing solution in progress before the crystallization step of the zinc carbonate In addition, the metal Zn is added again to perform ion exchange, and then filtered again.

  Conventionally, in the production of zinc carbonate, as described in Patent Document 2 and Patent Document 3, the concentration of impurity metal in the produced zinc carbonate has been targeted at a single-digit ppm level. . As a result of the inventor's research, in order to set the amount of Fe in the produced zinc carbonate to a single-digit ppm level, the Fe content in the Zn-containing solution after filtering the ion-exchanged solution is set to 1 Since it is necessary to set to 0.5 mg / l, in the present invention, the control limit value of the Fe content is set to 1.5 in units of mg / l.

  In addition, the first of equipment management in the method for producing zinc carbonate of the present invention is to periodically analyze the Zn-containing solution after filtering the ion-exchanged solution on-site using an Fe rapid analysis method, When the control limit value (Cmg / l) of the resulting Fe content is 1.5 mg / l and the analysis value exceeds the control limit value, the operation of the zinc carbonate production facility is stopped as an abnormal value, Co-washing is performed using a solvent used for dissolution of a portion in contact with the solution of the equipment between the ion exchange step and the step of crystallizing zinc carbonate.

Here, co-washing means washing with a new solution of the ammonium carbonate solution used for dissolution. Specifically, the part in contact with the equipment solution between the ion exchange step and the step of crystallizing zinc carbonate is washed with dilute sulfuric acid and then with pure water, and then co-washed with the ammonium carbonate solution used for dissolution. Wash.

  Furthermore, the second facility management means in the method for producing zinc carbonate of the present invention is to periodically analyze the product zinc carbonate on-site by the Fe rapid analysis method, and control limit of the resulting Fe content. If the value is 0.001% by mass and the Fe content exceeds this value, the operation is stopped, and at least the portion where the solution of the equipment is in contact between the ion exchange step and the step of crystallizing zinc carbonate is washed. For final finishing, it is necessary to perform co-washing using a solvent having the same composition as that used for dissolution.

The management means further collects the solvent that has been co-washed, analyzes the solvent using an on-site Fe rapid analysis method, and confirms that Fe is not detected by the analysis method used. Then resume operation.

  INDUSTRIAL APPLICABILITY According to the present invention, Fe can be purified inexpensively, easily and reliably, generation of defective zinc carbonate products having a high Fe content can be prevented, and it contributes to quality improvement and manufacturing cost reduction.

It is a figure which shows the basic process of zinc carbonate manufacture by the ammonium carbonate melt | dissolution method. It is a figure which shows the procedure of the operation management by application of the rapid analysis of Fe in this invention. It is a figure which shows the procedure of the equipment management by application of the rapid analysis of Fe in this invention.

About the basic process of zinc carbonate production by the ammonium carbonate dissolution method The first step of the basic process shown in FIG. 1 is a cleaning step. In this washing step, the Zn-containing product to be used is washed with warm water or the like to dissolve and remove water-soluble alkali / halogen impurities such as Na, K and Cl. If the Zn-containing product used does not substantially contain water-soluble alkali / halogen impurities, it can be omitted. After the cleaning process is completed, solid-liquid separation is performed by filtration to reduce impurities contained in the attached cleaning water.

  The second step is a dissolution step. This step is a step of dissolving the Zn component in the Zn-containing product with an ammonium carbonate solution. Zn in the Zn-containing product washed in the washing step is dissolved as an ammine carbonate complex as shown in the following formula (1). After completion of the dissolution step, solid-liquid separation is performed by filtration to separate the residue, and the filtrate is subjected to the next step. At this time, most of the metal impurities such as Fe and Pb other than Zn remain undissolved.

ZnO + 2NH ₄ OH + (NH ₄ ) ₂ CO ₃ → [Zn (NH ₃ ) ₄ ] CO ₃ + 3H ₂ O (1)

The composition of the ammonium carbonate solution used in this dissolution step is not specified, but usually a (NH ₄ ) ₂ CO ₃ concentration in the range of 10 to 20% by mass and an NH ₄ OH concentration in the range of 10 to 20% by mass is used. The

  The third step is a purification step. Some of the impurity metal components such as Fe and Pb in the Zn-containing product are dissolved as an ammine carbonate complex similarly to Zn. The impurity metal component M having a higher standard electrode potential than that of Zn, that is, a noble metal component M, can be deposited by substitution by an ion substitution reaction of the formula (2) by adding metal Zn.

M ²⁺ + Zn → M ↓ + Zn ²⁺
(III) ... (2)

  Thereafter, the residue generated in this purification step is removed by filtration, and the clarified filtrate is subjected to the next fourth step.

  The fourth step is a crystallization step. Steam is blown into the purified clarified filtrate containing Zn carbonate ammine complex to separate and volatilize ammonia to crystallize zinc carbonate crystals. Thereafter, the crystallized crystal of zinc carbonate is washed, filtered, and dried to obtain a zinc carbonate product.

Problems in Fe refining in the refining process Zinc carbonate products are required to have a concentration of impurity metals such as Fe, Pb, Cd, etc. on the order of 1 ppm, from the viewpoint of their use.

  Of the reaction rates for purifying impurities by ion exchange using metal zinc for purification according to the formula (2), the reaction rate of Fe is slower than that of other impurity metals. According to the measurement by the present inventor, the reaction rate constant of the formula (2) relating to Fe was seen to be smaller by one digit or more than that of Pb or Cd. This also shows that it is more difficult to purify Fe than to reduce other impurity elements.

  In addition, Fe is likely to be generated due to scattering of rust generated in peripheral equipment or external contamination in the form of gold in moisture. Furthermore, as long as a product generated in an iron making process containing a large amount of Fe is used as a raw material for zinc carbonate production, there is a high possibility of contamination due to scattering during raw material handling in the production plant.

  Thus, when producing a high-purity zinc carbonate product by the ammonium carbonate dissolution method, one of the most notable is the purification of Fe.

  On the other hand, the impurity purification reaction by ion exchange of the metal zinc for purification cannot be performed only once. If an abnormal value is found by analysis of Fe or the like, ion exchange and filtration are performed again by adding metal zinc for purification to the purified filtrate that has been subjected to solid-liquid separation by ion exchange reaction and subsequent filtration. You can also. This is called repurification.

Operation management for producing zinc carbonate with low Fe content In FIG. 2 showing the operation management procedure by applying Fe rapid analysis, in order to produce zinc carbonate with low Fe content, ion exchange and filtration are completed. When the Fe content in the purified filtrate is measured using an Fe rapid analysis method and the measured value is less than or equal to the control limit value expressed as Cmg / l, the filtrate is directly subjected to crystallization in the next step. Provide.
Conversely, when the measured value exceeds the control limit, the filtrate is returned to the ion exchange step and re-purified as shown by the two-dot chain line in FIG.

Regarding the process of performing Fe analysis When an abnormality occurs in the ion exchange and filtration process for some reason and the Fe purification result exceeds the control limit value, it is necessary to detect it earlier and take a remedial action. For that purpose, it is preferable to perform ion analysis and Fe analysis of the purified filtrate after filtration.

Moreover, also from the point of energy saving and cost reduction, when the measured value of Fe amount exceeds the control limit, it is preferable to return to the repurification process before applying to the crystallization process using a large amount of heat energy.

Operation method for producing zinc carbonate with low Fe content For each batch (lot) of purified filtrate that has been subjected to ion exchange and filtration in a batch processing tank system, the Fe rapid analysis method is used for all batches. Analyzing is the basic operating method of the present invention. However, it is not always necessary to make all batches subject to the Fe rapid analysis method, and it is not necessary to specify the batch method as the operation method of the present invention.

  In FIG. 2, an alternate long and short dash line indicates an example of an operation method in which all lots are not subjected to the Fe rapid analysis method.

  In this method, as shown by the solid line in FIG. 2, only a part of the batch of purified filtrates subjected to batch processing is subjected to the Fe rapid analysis method. Then, as indicated by the alternate long and short dash line, analysis of other batches (lots) is omitted. If the Fe analysis value is less than the control limit value Cmg / l as a result of the rapid Fe analysis performed by sampling, all batches (lots) including unanalyzed batches (lots) in the inter-process storage tank are included. Provide the purified filtrate to the crystallization process as scheduled.

  If the Fe rapid analysis result obtained by sampling exceeds the control limit value Cmg / l, not only the batch to be analyzed but also the purified filtrate in progress before the crystallization process, for example, the process of FIG. All of the purified filtrate in the interim storage tank is again subjected to ion exchange (repurification) indicated by a two-dot chain line. The frequency of sampling for performing the Fe rapid analysis shown in FIG. 2 may be determined in consideration of the time required for analysis and the residence time in the storage tank or piping.

  The present invention can also be applied to a continuous processing tank system that performs continuous flow purification by connecting a plurality of tanks, filtration facilities, and the like.

Necessity to perform on-site and rapidly as Fe analysis Analytical method that can obtain Fe concentration in a short time with an analysis accuracy of about 0.1 to 0.2 mg / l in ammonium carbonate solution with a large amount of Zn Any analysis method can be applied.

  If the time required for the analysis is remarkably increased, it is necessary to increase the capacity of the storage tank for storing the purified filtrate in consideration of the time, which increases the equipment cost and affects the profitability. For this reason, it is necessary to obtain analytical values in a relatively short time.

  There is no clear restriction on the time required for this rapid analysis, but considering the capacity of the inter-process storage tank and the processing time for one batch, it is realistic that it takes several minutes to about one hour from the start of analysis. is there. The on-site meaning means a place where the transportation time of the sample for analysis from the manufacturing facility to the analyzer is shorter than the time required for the rapid analysis itself, and the transportation time does not become a particular problem. Specifically, it may be any place where there is an analyzer in the same side of the zinc carbonate production plant, in the same building or in a nearby building, and the sample can be transported in a very short time. The reason why on-site analysis is necessary is that it is necessary to clarify the analysis result in a short time as described above, and is a condition for realizing it.

Analytical Means Suitable for Fe Analysis Various instrumental analytical means such as ICP analysis satisfy the requirements for rapid analysis and can be installed on-site. However, these instruments are generally expensive, and there are many installation restrictions. When installed on a production line, a dedicated clean analytical instrument room is required, which can adversely affect profitability through equipment costs. High nature. For this reason, a simple analysis method in which analysis is performed with a simple instrument even if the accuracy is somewhat reduced is suitable for the present invention. One example is a colorimetric method or an absorptiometry using a simple tabletop absorptiometer.

About the first means of equipment management for producing zinc carbonate with low Fe content The first means of equipment management for producing zinc carbonate with low Fe content is a purified filtrate after ion exchange and filtration. It is to measure Fe content in Fe using an Fe rapid analysis method.

  If the measured value is less than the control limit Cmg / l, the operation is continued. Conversely, if the measured value exceeds the control limit Cmg / l, the operation is stopped immediately, and the solution of the equipment for processing the solution after the ion exchange step is obtained. The contacted part is washed with at least a solvent used for dissolution.

  There is no denying the possibility that a refined liquid with a high Fe content, a refined liquid with a high Fe content, a refined filtrate with a high Fe content remain on the inner surfaces of equipment such as piping, tanks and filtration devices. If the abnormal purified solution itself is returned and repurified as described above, the abnormal purified solution itself can be relieved, but if the operation is continued as it is, the remaining Fe in the apparatus and piping is high in the subsequent production lot. There is a possibility that secondary contamination will occur due to the purified liquid and the purified filtrate. Preventing this is the main point of equipment management for producing zinc carbonate containing less Fe.

  There is no particular limitation on the means for washing away the high-purity refined liquid and refined filtrate remaining in the part in contact with the equipment solution. Any effective method, such as clean water, pure water, acid or other chemical cleaning, or solvent used for dissolution, can be used.

However, at least for the final finishing of washing, it is necessary to use a solvent having the same composition as that used for dissolution. As the final washing solvent for washing, an unused solvent that has not yet dissolved zinc or the like is used. Since Fe is dissolved in the solvent of this composition at the time of dissolution / purification, even if there is some residual Fe in the final stage, the residual Fe can be reliably dissolved and washed by washing with a co-washing solvent. In addition, product contamination from acids and other cleaning chemicals can be prevented.

About the Fe analysis method used for the facility management method Normally, the facility management is performed using the result of the Fe analysis used for the operation management as it is. However, the analysis can be performed only for the facility management. In that case, as long as it is an analysis method which can analyze Fe in a short time similarly to the Fe analysis method used for operation management, the method is not ask | required. If the result cannot be obtained in a short time, the possibility of producing an abnormal product increases with a delay in correcting equipment that may be in an abnormal state.

Regarding the second facility management means for producing zinc carbonate with low Fe content Analytical object for recognizing abnormalities during operation in the above-mentioned first method of facility management for producing zinc carbonate with low Fe content The second facility management means is to use product zinc carbonate instead of the purified filtrate after ion exchange and filtration.

  This equipment management method detects the equipment contamination that occurs due to the intrusion of contaminants containing Fe from the outside in the subsequent processes without any abnormalities in the Fe content at the end of the ion exchange and filtration process. It is a method to do. Examples of contamination from the outside include contamination at the time of replacement of the filter of the filtration device, contamination of vapor for crystallization, and the like.

  The control limit for recognizing the abnormality is reasonable 0.001% by mass of the product crystal. The reason is that the Fe grade of the product zinc carbonate is required to be in the single digit level of ppm, and 0.001 as long as the normal operation management and equipment management state are performed in the manufacturing process for that purpose. This is because it cannot be more than mass%.

  In the first and second equipment management methods, the form of the analysis object is liquid and solid, the management value associated therewith is the former value, and Cmg / l is 1.5 mg / l. Except for the fact that the latter crystal is 0.001% by mass, the treatment method at the time of abnormality is not particularly different between the second facility management method and the first facility management method described above. Absent.

Regarding the Fe analysis for the second facility management In the second facility management, the analysis object is the product zinc carbonate crystal. Even in this case, if the crystals are dissolved in an appropriate concentration with an ammonium carbonate solvent, the on-site rapid analysis method used for the above-described operation management and first facility management method can be applied to the analytical method such as the colorimetric method. . Of course, a direct on-site rapid analysis method can be applied without dissolving the crystals.

Note that the Fe analysis of the product zinc carbonate is not limited to the purpose of facility management. That is, as long as the condition of rapidity is satisfied, the Fe value of the analysis performed for the purpose of quality control / certification / quality assurance of the product zinc carbonate can be used.

Confirmation of equipment cleaning results Check the Fe content of the Zn-containing solution or crystalline zinc carbonate after ion exchange and filtration as described above by rapid analysis. The part where the solution of the equipment is in contact between the ion exchange step and the step of crystallizing zinc carbonate is washed with the solvent used for dissolution. Then, after the co-washed solvent is recovered and Fe is analyzed to confirm that Fe is not substantially contained, the operation is resumed. This reliably prevents abnormal recurrence of the Fe value.

  The abnormality means that when the Fe content of the purified filtrate is Cmg / l as shown in FIG. 3, more specifically, 1.5 mg / l as described above, the Fe content of the product zinc carbonate crystal is 0.001 mass. The case where it exceeds%.

By applying this facility management technique, it is possible to wash away the purified solution and purified filtrate having a high Fe value remaining in the part in contact with the solution of the facility that may be contaminated with Fe. At this time, it is important to directly confirm that the residue is gone and the cleaning is completed. That is, after washing, if there is any Fe residue, it will be dissolved in the last co-washing solvent, and conversely, there will be no Fe that dissolves in the co-washing solvent. It can be said that the cause of pollution was removed.

  By this equipment management, it is judged whether or not the cleaning is completed based on whether the value within the control limit of Fe is detected from the analysis value of the solution that has been co-washed using the solvent used for dissolving the raw material. In 3, the operation resumption is determined when the value is below the limit value of the co-wash solution management indicated as Dmg / l.

  The fact that it is not substantially contained means that it is not detected by the analysis method used. Specifically, the lower limit of detection by the analysis method (shown as Dmg / l in FIG. 3, the specific value is the analysis used). Is determined by the method).

If an Fe value greater than the control limit value for the washing solution is detected, add another washing or immediately wash again with the solvent used for dissolution and recover the solution. Then, Fe analysis is performed again, and whether to resume the operation is determined based on the result.

Example 1
As an example of the method for producing zinc carbonate by the operation management of the present invention, an embodiment based on a process management analysis method in which each process shown in FIG.

The solution was a solution of ammonium carbonate 120 g / l and ammonia 120 g / l, and the filtration after ion exchange was a cake filtration method using a 1 μ filter element.

As the Fe analysis for process control, an absorptiometric method using thiocyanate which is relatively simple, quick and inexpensive can be used. After complete oxidation of Fe, color was developed by adding potassium thiocyanate, and colorimetric measurement was performed with a sample with a known value using a desktop spectrophotometer centered at a wavelength of 470 nm.

  In this example, the process control analysis using the potassium thiocyanate was performed on the purified filtrate obtained by the ion exchange reaction and subsequent filtration. As a result, the A3 lot in which the Fe value exceeded 1.5 mg / l was subjected to ion exchange again to reduce the Fe value, and then sent to the subsequent process for commercialization.

On the other hand, Comparative Examples 1 and 2 used the same solution as in the above example, and filtration after ion exchange also used a 1 μm filter element as in the above example.

Comparative Example 1 shows an example in which the process control analysis was performed, but all lots were commercialized as they were regardless of the analysis results, and Comparative Example 2 shows an example in which all lots were commercialized as they were without Fe analysis after filtration. .

In any case, the product zinc carbonate was subjected to high-precision ICP analysis as a product certification analysis for quality control.

These results are shown in Table 1. As shown in the table, 1.5 mg / l or less is continuously produced as planned, and in the case of this example where a 1.6 mg / l lot was re-purified, the Fe analysis value of the product zinc carbonate is 0 in all three lots. Both B of Comparative Example 1 which cleared 0.001% but did not re-purify the 1.6 mg / l lot and C of Comparative Example 2 which did not analyze the filtrate after purification were both produced in one lot of product carbonic acid. The analysis value of zinc Fe deviated from the control limit value.

From the above results, it was determined that 1.5 mg / l is suitable as the control limit value indicated as Cmg / l in FIG.

Example 2
As Example 2, the example of the manufacturing method of the zinc carbonate to which the equipment management of this invention is applied is shown.

  In the Fe analysis of the purified filtrate obtained by the ion exchange reaction and the subsequent filtration, when there is an abnormality exceeding the Fe control limit value, the portion where the solution of the equipment for treating the solution after the ion exchange step comes into contact is washed. The example of the present invention that was performed was compared with the comparative example in which this cleaning was not performed.

  Washing was carried out by washing the part in contact with the equipment solution from the ion exchange step to the step of crystallizing zinc carbonate with dilute sulfuric acid and then with pure water, and then co-washing with the solvent used for dissolution.

  The results are shown in Table 2. In the table, lot numbers x, x ', x + 1, and x + 2 indicate each lot according to the embodiment of the present invention. In this example, the filtrate Fe value after purification in lot x exceeded 2.2 mg / l and the control limit value 1.5 mg / l, so the operation was interrupted and the inner surface of the equipment in contact with the purified liquid was separated from the solvent. Washing including washing was performed. Thereafter, the operation was resumed from repurification of lot x. Both the next lot x + 1 and the subsequent lot x + 2 including the re-purified lot x 'passed the product zinc carbonate with an Fe value of 0.001% or less.

  In the comparative example starting from the lot number y, since the equipment was not cleaned after the abnormality, there was a slight contamination effect up to the lot next to the lot where the ion exchange reaction was abnormal. Specifically, since the filtrate Fe value after purification in lot y exceeded 2.0 mg / l and the control limit value 1.5 mg / l, repurification was performed. Lot y ′ after repurification has an Fe content of the product zinc carbonate of 0.0011 even though the Fe value of the purified filtrate is 1.3 mg / l and the control limit value is 1.5 mg / l or less. % And above the control value. It was understood that this was because the inside of the tank and the piping was not cleaned, and was affected by the high Fe contaminants remaining.

Example 3
Next, even if there is no abnormality in the Fe value in the purified filtrate, an example of application of the present invention in the case of an abnormality in the Fe value of the product zinc carbonate, which is estimated to be Fe contamination from the outside in the subsequent steps, is shown. This embodiment is a second example of facility management. The results are shown in Table 3.

  In the analysis for facility management in this example, the sampled product crystals were dissolved in the solvent used for the operation, and the Fe value was measured by the absorptiometry described above. The composition of the solvent is the same as that used in Example 1 above.

  In this example, the operation is stopped immediately after the abnormality exceeding the control limit value of the Fe value of the product zinc carbonate is found in the lot number p, and from the ion exchange process to the process of crystallizing zinc carbonate. The part in contact with the solution of the equipment was washed with dilute sulfuric acid and pure water, and then washed with a new solvent having the same composition as the solvent used for dissolution.

  At the time when the analytical value became clear, the lot (p + 1) in process and the next lot (p + 2) that were in the period from the completion of filtration after ion exchange to the crystallization step were re-purified.

  As a result of this treatment, all lots (lot number p + 1 and later) other than the lot (lot number p) in which an abnormality was found passed. Of the numerical values in Table 3, numerical values with () indicate values after re-purification.

  On the other hand, the cleaning treatment was not performed in an abnormal case (lot q) in which the Fe value of the product zinc carbonate generated at another timing as a comparative example exceeded the control limit value. As a result, Fe contamination exceeding the control limit continued in q + 1 and subsequent lots, and those lots were rejected.

Claims (4)

In an ammonium carbonate solution containing (NH ₄ ) ₂ CO ₃ and NH ₄ OH, a Zn-containing dust or other Zn-containing product generated in iron making is dissolved, and an ion exchange reaction by adding metal Zn and a solid by filtration In the method for producing zinc carbonate in which zinc carbonate is crystallized from the solution after reducing impurities in the solution by separation,
The Zn-containing solution after filtering the ion-exchanged solution is periodically analyzed on-site using an Fe rapid analysis method, and the resulting Fe content actual value is set to 1.5 mg / l as a Fe management limit value. In contrast, when the Fe content actual value is an abnormal value exceeding the Fe management limit value, metal Zn is added again to the in-process Zn-containing solution before the crystallization process of zinc carbonate, and ion exchange reaction and A method for producing zinc carbonate in which the Fe content of zinc carbonate is reduced by re-filtering . In an ammonium carbonate solution containing (NH ₄ ) ₂ CO ₃ and NH ₄ OH, a Zn-containing dust or other Zn-containing product generated in iron making is dissolved, and an ion exchange reaction by adding metal Zn and a solid by filtration In the method for producing zinc carbonate in which zinc carbonate is crystallized from the solution after reducing impurities in the solution by separation,
The Zn-containing solution after filtering the ion-exchanged solution is periodically analyzed on-site using an Fe rapid analysis method, and the resulting Fe content actual value is set to 1.5 mg / l as a Fe management limit value. In contrast, when the actual Fe content value is an abnormal value exceeding the Fe control limit value, the operation of the zinc carbonate production facility is stopped, and the equipment from the ion exchange step to the step of crystallizing zinc carbonate is performed. The manufacturing method of zinc carbonate which raises the purity of zinc carbonate by co-washing the part which the solution contact | connects using the solvent used for melt | dissolution . (NH ₄ ) ₂ CO ₃ And NH ₄ Impurities in the solution were reduced by dissolving Zn-containing dust generated in iron making or other Zn-containing products in an ammonium carbonate solution containing OH, and solid separation by ion exchange reaction and filtration by adding metal Zn. Later, in a method for producing zinc carbonate in which zinc carbonate is crystallized from a solution,
  If the product crystallized zinc carbonate is periodically analyzed on-site by the Fe rapid analysis method, the control limit value of the resulting Fe content is 0.001% by mass, and if the Fe content exceeds this, The method for producing zinc carbonate is to increase the purity of zinc carbonate by stopping the operation and washing the part in contact with the equipment solution between the ion exchange step and the step of crystallizing zinc carbonate with a solvent used for dissolution. . Claims for recovering the co-washed solvent, analyzing the solvent using an on-site Fe rapid analysis method, confirming that Fe is not substantially contained, and then restarting the operation. The method for producing zinc carbonate according to 2 or 3 .

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