JP2015196848A - Arsenic treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an arsenic treatment method by which arsenic contained in an arsenic-containing copper ore can be treated in a shorter period of time into a stable form suitable for long-term storage and preservation.SOLUTION: The arsenic treatment method comprises: a roasting step of roasting an arsenic-containing copper ore under a non-oxidizing atmosphere to separate the ore into chalcopyrite and a volatile matter containing arsenic sulfide; a first heat treatment step of heat-treating the volatile matter obtained in the roasting step, under a non-oxidizing atmosphere and melting the arsenic sulfide in the volatile matter to obtain a heat-treated product; a coating step of producing a coated material by coating the heat-treated product with a heat-shrinkable film having a heat-resistant temperature of 120°C or more; and a second heat treatment step of heating the coated material.

Description

  The present invention relates to a method for treating arsenic, and more particularly, to a method for treating arsenic that can be used for treating copper ore containing arsenic.

  In recent years, copper ores collected at copper mines operating all over the world have become the primary sulfide ore, and iron, sulfur and other impurities have increased, and the copper quality has been on the decline. This leads to an increase in copper concentrate production costs for dry copper smelting.

  Of the impurities in copper ore, arsenic is considered the most problematic. Although arsenic depends on the form of its existence, it is extremely harmful and has few applications in the industrial field, so most of it needs to be disposed or stored in a stable form.

  For this reason, the purchase smelting smelter imposes certain restrictions (usually <about 0.3 mass%) on arsenic in the copper concentrate to be purchased. When the limit is exceeded, the mine side generally pays a penalty to the smelter according to the excess amount.

  Therefore, from the mine's point of view, an efficient method for treating sulfide ore containing a large amount of arsenic is an important concern for cost reduction and mine life extension. On the other hand, the purchase smelter is likely to need to deal with arsenic-rich copper concentrate in the future due to depletion of high-quality ore and tight supply and demand of copper concentrate.

  Japanese Patent Application Laid-Open No. 2009-39666 (Patent Document 1) discloses an arsenic treatment method in which an arsenic-containing compound is made into a compact crystalline compound particle form with less moisture and then the obtained crystalline compound is coated with a resin. .

JP 2009-39666 A

  However, the method described in Patent Document 1 has a problem that the preliminary adjustment for adjusting the arsenic-containing compound coated with the resin into a predetermined form is complicated and takes time, and the processing cost is increased.

  In view of the above problems, the present invention provides an arsenic treatment method capable of treating arsenic contained in copper ore containing arsenic in a short time and in a stable form suitable for long-term storage and preservation.

  In order to solve the above problems, the present inventors diligently studied, roasting copper ore containing arsenic, extracting volatiles containing arsenic from the copper ore, and applying heat treatment to the volatiles. On the other hand, it was found that by applying a predetermined heat treatment after coating, the arsenic-containing compound can be processed into a stable form suitable for long-term storage and preservation in a shorter time than before.

  The present invention completed on the basis of the above knowledge is, in one aspect, a roasting step of roasting copper ore containing arsenic in a non-oxidizing atmosphere and separating it into chalcopyrite and volatiles containing arsenic sulfide; A first heat treatment step of heat-treating the volatile matter obtained in the roasting step in a non-oxidizing atmosphere to melt the arsenic sulfide in the volatile matter to obtain a heat-treated product; This is a method for treating arsenic, which includes a coating step of coating with a heat-shrinkable film to produce a coating, and a second heat treatment step of heating the coating.

  In one embodiment of the method for treating arsenic according to the present invention, the first heat treatment step includes heating a volatile material at 200 to 600 ° C., and the second heat treatment step includes heating the coating to 120 ° C. to 200 ° C. Heating with.

  In another embodiment of the method for treating arsenic according to the present invention, the heat-shrinkable film contains polyvinylidene chloride.

  In another embodiment, the arsenic treatment method according to the present invention further includes adding sulfur in the first heat treatment step.

  In yet another embodiment, the method for treating arsenic according to the present invention includes further adding an anti-aging agent in the first heat treatment step.

  ADVANTAGE OF THE INVENTION According to this invention, the arsenic processing method which can process the arsenic contained in the copper ore containing arsenic in a stable form suitable for a long-term storage and preservation | save for a short time can be provided.

It is a flowchart which shows the arsenic processing method which concerns on embodiment of this invention. It is an example of the microscope picture showing the property of the heat processing thing obtained at the heat processing process. It is a photograph which shows the external appearance of the heat processing thing obtained at a 1st heat treatment process. The appearance immediately after the second heat treatment of the coating coated with the polyvinylidene chloride film is shown. The external appearance of the coating after taking out from a heating container is shown. The external appearance just after the 2nd heat processing of the coating coated with the polypropylene film is shown. The external appearance of the coating after taking out from a heating container is shown. It is a graph which shows the evaluation result of As elution amount of the arsenic containing compound obtained by roasting, 1st heat processing, and 2nd heat processing.

  As shown in FIG. 1, the arsenic treatment method according to the embodiment of the present invention roasts copper ore containing arsenic in a non-oxidizing atmosphere to convert chalcopyrite and volatiles containing arsenic sulfide. Roasting step S1 to be separated, first heat treatment step S2 to heat-treat the volatiles obtained in the roasting step in a non-oxidizing atmosphere, and melt the arsenic sulfide in the volatiles to obtain a heat-treated product; It includes a coating step S3 for coating the heat-treated product with a heat-shrinkable film having a heat-resistant temperature of 120 ° C. or higher, and a second heat-treatment step S4 for heating the coated product.

The processing object of this embodiment is a copper ore containing arsenic. Specifically, for example, copper arsenite (Cu ₃ AsS ₄ ), tetrahedral arsenite (Cu ₁₂ As ₄ S ₁₃ ), or copper concentrate in which copper ores containing these arsenic are mixed can be used. In addition to these copper ores, it is a matter of course that the present invention is not limited to the copper ores as long as they are ores containing arsenic and can be processed by the following two-stage treatment.

For example, the grade of copper concentrate mainly composed of arsenite that can be used in the present invention varies depending on the grade of coexisting pyrite (FeS ₂ ) and gangue components, but typically copper is 15 to 35% by mass. And 3-15% by mass of arsenic.

  In this embodiment, it is preferable to pre-dry the copper concentrate at a temperature at which the mineral species and quality do not change. Normally, when copper concentrate is dried with high-temperature air, the temperature of the copper concentrate at the outlet of the dryer is set to approximately 90 ° C., and the moisture content of the copper concentrate is set to 0.5 mass% or less.

-Roasting process S1-
The dried copper concentrate is roasted at 550 ° C. to 700 ° C. for 10 to 60 minutes in a non-oxidizing atmosphere. For example, nitrogen gas is used as the gas supplied to make the inside of the apparatus a non-oxidizing atmosphere. Control of the treatment temperature and atmosphere in the roasting step S1 is a condition necessary for converting the copper concentrate mainly composed of arsenite to arsenic sulfide and chalcopyrite, and the reaction time is determined based on the unreacted arsenite. This is the time required to leave no.

In the roasting step S1, the formation reaction of arsenic sulfide in the copper concentrate follows the following formula (1) or (2). If the original concentrate contains a lot of pyrite, etc., the S added in the formula (1) is compensated by the generated S by the decomposition of the pyrite in the treatment temperature zone as shown in the formula (3). Therefore, it becomes unnecessary.

4Cu ₃ AsS ₄ + 12FeS + 2S → 12CuFeS ₂ + As ₄ S ₆ (1)
4Cu ₃ AsS ₄ + 12FeS → 12CuFeS ₂ + As ₄ S ₄ (2)
FeS ₂ → FeS + S (3)

  The roasting step S1 is performed using, for example, a rotary kiln. As shown in the above formulas (1) to (3), a sulfurized compound containing arsenic is generated by roasting, and the generated arsenic compound volatilizes at a vapor pressure corresponding to the temperature and is removed from the raw copper concentrate. Is done.

  As a result of this roasting treatment, the raw copper concentrate provides a calcined ore mainly composed of chalcopyrite and Cubanite, and an arsenic compound (arsenic sulfide) recovered by volatilization and a volatile substance containing elemental sulfur. In the temperature range of 550 ° C to 700 ° C, the ratio of chalcopyrite to chalcopyrite and cuba ore is the amount of copper ore such as chalcopyrite and chalcopyrite included before the reaction, the amount of pyrite included before the reaction, and added. Varies depending on the amount of pyrite.

  Since the As sulfide and elemental sulfur volatilized in the roasting step S1 are in a gas form, they are cooled, solidified and recovered in an inert atmosphere. FIG. 2 shows an example of a photomicrograph of the recovered volatiles. The recovered volatiles include granular particles having a diameter of about 10 to 15 μm and have a two-layer structure of an inner layer 1 and an outer layer 2 having different As grades.

  The inner layer 1 of volatile particles is composed of a layer containing about 30 mol% arsenic and about 70 mol% sulfur. The outer layer 2 of volatile particles is composed of a layer containing about 5 mol% arsenic and about 95 mol% sulfur. That is, the volatile matter composed of granular particles obtained in the roasting step S1 has a two-layer structure in which the outer side of the inner layer 1 containing a large amount of arsenic inside the particles is covered with the outer layer 2 containing a large amount of sulfur.

-1st heat treatment process S2-
In the first heat treatment step S2, the volatile particles shown in FIG. 2 are further heat-treated in a non-oxidizing atmosphere to melt arsenic sulfide (arsenic sulfide) in the volatile matter, thereby arsenic of volatile matter. Reduces dissolution more.

  For example, nitrogen gas is used as a gas for making the heat treatment system non-oxidizing atmosphere. The treatment temperature in the heat treatment step S2 is preferably 200 to 600 ° C, more preferably 250 to 400 ° C. When the processing temperature is lower than 200 ° C., the arsenic sulfide in the volatile material may not be sufficiently melted, and the effect of reducing the arsenic elution amount may not be sufficiently obtained. When the processing temperature is higher than 600 ° C., hydrogen sulfide contained as arsenic sulfide in the volatiles is gasified and volatilizes, so that the heat-treated product may not be recovered.

  Although the treatment time of the heat treatment step S2 varies depending on the treatment temperature, in order to completely advance the reaction, it is preferable to carry out the treatment for at least 30 minutes or more, more preferably 50 minutes or more in terms of the effect of reducing the As elution amount of the heat treatment product. Is preferred.

  In the heat treatment step S2, sulfur is preferably added to the volatiles. This is because as the treatment temperature in the heat treatment step S2 increases, the volatilization amount of sulfur increases and the arsenic concentration in the volatile matter increases, so that the arsenic elution suppression effect due to the reaction of sulfur with arsenic decreases. . For example, when a volatile matter having an S / As mass ratio of 3.0 is treated at 400 ° C., the S content in the volatile matter is volatilized, and the S / As mass ratio is reduced to about 2.4, at 500 ° C. In the case of treatment, the S component volatilizes and the S / As mass ratio may be reduced to about 1.2. As the sulfur source to be added, simple sulfur is preferable from the viewpoint of handling. Sulfur may be added before the heat treatment step or may be added during the heat treatment step.

  In the heat treatment step S2, it is necessary that the mass ratio of sulfur to arsenic (S / As mass ratio) in the volatiles is 1.2 or more, more preferably 2.3 or more, and even more preferably 3 or more. It is preferable to adjust the concentration of sulfur and arsenic in the volatiles by adding sulfur according to the above. If the S / As mass ratio is less than 1.2, the arsenic elution reduction effect may not be sufficiently obtained even if the heat treatment time is increased.

  Although there is no particular limitation on the upper limit of the S / As mass ratio, the higher the S / As mass ratio, the more effective the As elution suppression can be achieved with a shorter heat treatment. On the other hand, if the amount of sulfur added is increased too much in order to increase the S / As mass ratio, the As elution suppression effect does not change greatly. Rather, since sulfur is excessive with respect to arsenic, excess sulfur content is not increased. Post-processing is required and may increase costs. Therefore, the upper limit of the S / As mass ratio can be about 6.

In the heat treatment step S2, an antioxidant for rubber may be added in addition to the elemental sulfur. Thereby, it can suppress that arsenic elutes from the volatile matter containing arsenic over a longer period of time. As the anti-aging agent for rubber, for example, any one or more anti-aging agents selected from monophenol, bisphenol and polyphenol can be used. The addition amount of the antioxidant is preferably 0.2 mol / m ³ or more, more preferably 0.4 mol / m ³ or more, and more specifically 0.2 to 2.0 mol / m ³ .

FIG. 3 is a photograph showing the appearance of the heat-treated product obtained in the heat treatment step S2. The heat-treated product is collected as a columnar substance that is bulky in appearance. The heat-treated product has an arsenic quality of 12 to 15 mol% and a density of about 0.6 to 1.5 g / cm ³ . Since the sample expands in the heat treatment step S2, the heat treatment product is about half the density of the pure arsenic sulfide. This heat-treated product can be stored as it is, but if the density is low, the specific surface area becomes large, so that the contact area with the atmosphere (eg, air or liquid) outside the heat-treated product becomes large and elution tends to occur. There is a case.

-Coating step S3-
Therefore, in this embodiment, the heat-treated product processed in the first heat treatment step S2 is pulverized (crushed), and the pulverized heat-treated product is coated with a heat-shrinkable film to produce a coating. By coating with a heat-shrinkable film, when the coating is heated in the second heat treatment step to be described later, the film is fixed in a state where the film partially enters the inside from the surface of the coating, thereby suppressing As elution. The effect can be expected. In addition, when the heat-treated product is not coated, the treatment time is 30 minutes or more. On the other hand, by coating the heat-treated product in the coating step S3, the time required for heating in the second heat treatment step is, for example, 5 minutes. It can be shortened to the extent.

  As the heat-shrinkable film, a heat-shrinkable film having a heat resistant temperature of 120 ° C. or higher, more preferably 130 ° C. or higher is used. As the heat-shrinkable film having a heat resistant temperature of 120 ° C. or higher, for example, polyvinylidene chloride can be used, and other examples include polyamide resins such as nylon 66, fluorine resins such as polytetrafluoroethylene, and phenol resins.

-Second heat treatment step S4-
In the second heat treatment step S4, the coating obtained in the coating step S3 is subjected to a predetermined heat treatment to dissolve the hydrogen sulfide and arsenic mixture inside the coating, and the heat shrinkable film is shrunk by heating. Get the workpiece.

In the second heat treatment step S4, the coating is heated in a non-oxidizing atmosphere using nitrogen or the like. Thereby, it heats so that the density of the coating after 2nd heat processing may be set to 1.5-3.0 g / cm < ³ >. The treatment temperature of the coating in the second heat treatment step S4 depends on the characteristics of the heat-shrinkable film to be used, but considering the properties of the arsenic-containing material (heat-treated product) contained in the coating, it is 120 to 200 ° C. It is preferable to do this. If the treatment temperature is lower than 120 ° C., the arsenic-containing material in the coating may not be sufficiently dissolved. When the treatment temperature exceeds 200 ° C., the types of heat-shrinkable films that can be used are limited, and depending on the heat-shrinkable film, breakage may occur regardless of how many times the film is wound. The heating time may be 5 minutes or longer.

The to-be-processed object obtained by 2nd heat treatment process S4 contains arsenic, The density is 1.5-3.0 g / cm < ³ >. Since the heat-shrinkable film is integrated and covered with the heat-shrinkable film so that the heat-shrinkable film adheres to the surface of the object to be processed and enters the inside from the surface, Contact can be suppressed, and oxidation of hydrogen sulfide in the workpiece can be suppressed. Furthermore, the object to be processed obtained by the second heat treatment S4 has good moldability and can be formed into a desired shape such as a lump shape, a columnar shape, or a plate shape, and is suitable for long-term storage and preservation. It can be processed into a stable form. In addition, according to the present invention, after the heat-treated product containing arsenic is coated with the heat-shrinkable film, the heat-shrinkable film is adhered to the heat-treated product and the final arsenic elution treatment is simultaneously performed. This reduces the number of processes compared to the conventional technology that stabilizes the arsenic by making it difficult to elute and then coating it with resin, and suppresses arsenic elution during the final difficult eluting process. It becomes possible to proceed with processing more safely.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited thereto.

(Example 1)
As the raw material copper concentrate, a high As grade copper concentrate having a Cu grade of 21 mass%, an Fe grade of 23 mass%, an S grade of 38 mass%, and an As grade of 6.8 mass% was used. The main mineral composition characterized using X-ray diffraction (XRD) and electron microanalyzer (EPMA) for this high As grade copper concentrate is 11 mass% of chalcopyrite (CuFeS ₂ ), pyrite (FeS ₂ ). They were 42 mass%, arsenite (Cu ₃ AsS ₄ ) 36 mass%, and gangue components (SiO ₂ etc.) 11 mass%.

  After 100 g of this copper concentrate containing arsenic was pre-dried and then baked at a processing temperature of 650 ° C. in a nitrogen gas atmosphere, as shown in Table 1, the concentrate containing the chalcopyrite containing almost no arsenic (roasted Sinter) and volatiles containing 33% by mass of arsenic and 64% by mass of sulfur.

  When the volatiles obtained in the roasting step were cooled, solidified and recovered, the S / As mass ratio of the volatiles was 2.3. The volatile matter was coated with a polyvinylidene chloride film to prepare a coating, and the coating was heat-treated at 140 ° C. for 5 minutes in a nitrogen gas atmosphere to obtain a workpiece. FIG. 4A shows the appearance of the object to be processed immediately after the heat treatment, and FIG. 4B shows the appearance of the coating after being taken out from the heating container. By the heat treatment, the compound containing arsenic was covered with the polyvinylidene chloride film, and the compound could be stored for a long time.

(Comparative Example 1)
The volatile matter obtained in the roasting step of Example 1 was coated with a polypropylene film to prepare a coating, and this coating was heat-treated at 150 ° C. for 5 minutes in a nitrogen gas atmosphere to obtain a workpiece. . FIG. 5 (a) shows the appearance of the object to be processed immediately after the heat treatment, and FIG. 5 (b) shows the appearance of the coating after taking out from the heating container. In the case of Comparative Example 1, the coating was broken by the heat treatment, and was damaged when the object to be treated was taken out from the heating container. Even when polyethylene was used in place of the polypropylene film, a phenomenon that the coating was broken by the heat treatment occurred.

(Elution results)
The volatile matter obtained in Example 1, the heat-treated product and the object to be treated, and the volatile matter obtained in the roasting step of Example 1 and the volatile matter, heat-treated product obtained by adding sulfur and an antioxidant as additives to the volatile matter, and The amount of As elution was evaluated by the soil pollution material elution analysis (TCLP) in the US Environmental Protection Agency (EPA). In this elution analysis, volatile substances, eluate and treated material are crushed and the sample is made to have a particle size of less than 9.5 mm (0.5 to 5 mm). The liquid is used, the pH is 2.88, the liquid-solid ratio is 20, the temperature is 22.3 ° C., the shaking method is rotary shaking at 30 rpm, the shaking time is 18 hours, and the solid-liquid separation is pressure filtered (0 Elution analysis was performed as 6 to 0.8 μm GFF filter). The results are shown in FIG.

  As shown in FIG. 6, the elution amount of As decreased as the roasting, the first heat treatment step, and the second heat treatment step were performed regardless of whether or not the additive was added. In any case, the processed material finally obtained was able to reduce the elution amount of As to 1 mg / L or less.

(density)
When the densities of the heat-treated product and the object to be treated in Example 1 were measured, the density of the heat-treated material was 1.0 g / cm ³ , whereas the density of the object to be treated was 2.1 g / cm ^3. It was. That is, the heat-shrinkable film was shrunk by the second heat treatment and the density of the arsenic-containing material was increased to form a block (block shape), thereby making it possible to obtain a more stable form with low As elution. .

1: Inner layer 2: Outer layer

Claims (5)

A roasting step of roasting copper ore containing arsenic in a non-oxidizing atmosphere and separating it into chalcopyrite and volatiles containing arsenic sulfide;
A first heat treatment step of heat-treating the volatile matter obtained in the roasting step in a non-oxidizing atmosphere to melt the arsenic sulfide in the volatile matter to obtain a heat-treated product;
A coating step of coating the heat-treated product with a heat-shrinkable film having a heat-resistant temperature of 120 ° C. or higher;
And a second heat treatment step of heating the coating.   The first heat treatment step includes heating the volatile material at 200 to 600 ° C, and the second heat treatment step includes heating the coating at 120 ° C to 200 ° C. The arsenic processing method as described.   The method for treating arsenic according to claim 1, wherein the heat-shrinkable film contains polyvinylidene chloride.   The method for treating arsenic according to claim 1, further comprising adding sulfur in the first heat treatment step.   The method for treating arsenic according to any one of claims 1 to 4, further comprising adding an anti-aging agent in the first heat treatment step.