JP6784789B2 - Arsenic treatment method and arsenic-containing compounds - Google Patents

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 ore collected in copper mines operating all over the world has been mainly composed of primary sulfide ore, and iron, sulfur and other impurities have increased, and the copper grade has been declining. This leads to an increase in copper concentrate production costs for dry copper smelting.

Among the impurities in copper ore, arsenic is the most problematic. Arsenic, depending on its form of existence, is extremely harmful and has little use in the industrial field, so most of it needs to be disposed of or stored in a stable form.

Therefore, the pyrometallurgical smelter imposes a certain limit (usually <0.3 mass%) on the 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, for mines, efficient treatment of arsenic-rich sulfide ore is an important concern for cost reduction and extension of mine life. On the other hand, from the perspective of the pyrometallurgical smelter, there is a high possibility that it will be necessary to deal with copper concentrate containing a large amount of arsenic in the future due to the depletion of high-quality ore and the tight supply and demand of copper concentrate.

Japanese Unexamined Patent Publication No. 2009-39666 (Patent Document 1) discloses a method for treating arsenic in which an arsenic-containing compound is formed into a compact crystalline compound particle form having a low water content and then the obtained crystalline compound is coated with a resin. ..

JP-A-2009-39666

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 to a predetermined form is complicated and the processing cost is high. Considering the long-term storage of the arsenic-containing compound for several years or decades, it is possible that the resin to be coated also deteriorates and elution gradually occurs.

In view of the above problems, the present invention provides a method for treating arsenic, which can treat arsenic contained in a copper ore containing arsenic in a stable form suitable for long-term storage and storage by a simpler method.

In order to solve the above problems, the present inventor diligently studied, and found that arsenic-containing copper ore was roasted to extract arsenic-containing volatile matter from the copper ore, and the volatile matter was subjected to a predetermined treatment. Therefore, it was found that the elution of arsenic can be suppressed for a longer period of time than in the past by further performing a predetermined treatment for increasing the density of the volatile matter after the treatment to treat it in a more stable form. It was.

The present invention completed on the basis of the above findings has, in one aspect, a roasting process in which a copper ore containing arsenic is roasted in a non-oxidizing atmosphere to separate brass ore and a volatile substance containing arsenic sulfide. , The 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, the crushing step of crushing the volatile matter after the heat treatment step, and the crushing step It is a method for treating arsenic including a remelting step of heating and remelting the volatile matter of the above in a non-oxidizing atmosphere.

In one embodiment of the arsenic treatment method according to the present invention, the remelting step comprises heating the volatiles at 200-250 ° C.

In another embodiment of the arsenic treatment method according to the present invention, the remelting step is to heat the volatiles so that the density of the volatiles after remelting becomes 1.5 to 3.0 g / cm ^3. including.

In yet another embodiment, the method for treating arsenic according to the present invention further comprises adding sulfur in the heat treatment step.

In still another embodiment of the method for treating arsenic according to the present invention, sulfur is contained in a volatile substance so that the mass ratio (S / As mass ratio) of sulfur contained in the volatile matter to arsenic is 1.2 or more in the heat treatment step. Includes adjusting the content of.

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

In another aspect, the present invention is a solid arsenic-containing compound composed of arsenic and sulfur, which contains arsenic having an arsenic concentration of 1 to 40% by mass and a density of 1.5 to 3.0 g / cm ^3. It is a compound.

According to the present invention, it is possible to provide an arsenic treatment method capable of treating arsenic contained in a copper ore containing arsenic in a stable form suitable for long-term storage and storage by a simpler method.

It is a flowchart which shows the arsenic treatment method which concerns on embodiment of this invention. This is an example of a micrograph showing the properties of the heat-treated product obtained in the heat treatment step. It is a photograph which shows the appearance of the volatile matter (heat-treated matter) treated in the heat treatment process. It is a photograph which shows the appearance of the volatile matter (heat-treated matter) treated in the heat treatment process. It is a graph which shows the evaluation result of the As elution amount of the arsenic-containing compound obtained by volatilization, heat treatment, and remelting treatment.

In the method for treating arsenic according to the embodiment of the present invention, as shown in FIG. 1, copper ore containing arsenic is roasted in a non-oxidizing atmosphere to form brass ore and volatile matter containing arsenic sulfide. The roasting step S1 to be separated, the heat treatment step S2 in which the volatile matter obtained in the roasting step S1 is heat-treated in a non-oxidizing atmosphere to melt the arsenic sulfide in the volatile matter, and the volatilization after the heat treatment step S2. The crushing step S3 for crushing an object and the remelting step S4 for heating and remelting the volatile matter after the crushing step S3 are included.

The object to be treated in this embodiment is a copper ore containing arsenic. Specifically, for example, enargite (Cu ₃ AsS ₄ ), tetrahedral arsenic ore (Cu ₁₂ As ₄ S ₁₃ ), or a copper concentrate in which copper ores containing these arsenic are mixed can be used. In addition to these copper ores, it goes without saying that the ores containing arsenic and which can be treated by the following two-step treatment are not limited to the above copper ores.

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

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

-Roasting process S1-
The dried copper concentrate is roasted in a non-oxidizing atmosphere at 550 ° C. to 700 ° C. for 10 to 60 minutes. As the gas supplied to create a non-oxidizing atmosphere in the apparatus, for example, nitrogen gas is used. The treatment temperature and atmosphere control in the roasting step S1 are conditions necessary for converting copper concentrate mainly composed of enargite into arsenic sulfide, chalcopyrite, etc., and the reaction time leaves unreacted enargite. It's the time needed to not.

In the roasting step S1, the reaction for producing arsenic sulfide in the copper concentrate follows the following formula (1) or (2). If the original concentrate contains a large amount of pyrite, etc., the S added in Eq. (1) is supplemented by the S produced by the decomposition of pyrite in the treatment temperature range, as shown in Eq. (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 sulfide compound containing arsenic is produced by roasting, and the produced arsenic compound volatilizes at a vapor pressure according to the temperature and is removed from the raw material copper concentrate. Will be done.

As a result of this roasting treatment, from the raw material copper concentrate, a burnt ore mainly composed of chalcopyrite and Cubanite, and a volatile substance containing an arsenic compound (arsenic sulfide) and elemental sulfur that are volatilized and recovered can be obtained. The ratio of chalcopyrite to Cubanite in the burnt ore is added in the temperature range of 550 ° C to 700 ° C, the amount of chalcopyrite such as chalcopyrite and chalcocite contained before the reaction, the amount of pyrite contained before the reaction, and the amount added. It changes depending on the amount of chalcopyrite.

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

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

-Heat treatment step S2-
In the heat treatment step S2, the volatile particles shown in FIG. 2 are further heat-treated in a non-oxidizing atmosphere to melt the arsenic sulfide (arsenic sulfide) in the volatile matter, thereby improving the arsenic elution property of the volatile matter. Reduce more.

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

The treatment time of the heat treatment step S2 varies depending on the treatment temperature, but in order to completely proceed the reaction, it is necessary to carry out at least 30 minutes or more, more preferably 50 minutes or more from the viewpoint of the effect of reducing the amount of As elution of the heat-treated product. Is preferable.

In the heat treatment step S2, it is preferable to add sulfur to the volatile matter. This is because as the treatment temperature in the heat treatment step S2 increases, the amount of sulfur volatilized increases and the arsenic concentration in the volatile matter increases, so that the effect of suppressing the elution of arsenic 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 volatilizes and the S / As mass ratio drops to about 2.4, and at 500 ° C. In the case of treatment, the S content may volatilize and the S / As mass ratio may decrease to about 1.2. As the sulfur source to be added, elemental sulfur is preferable from the viewpoint of handling. Sulfur may be added before the heat treatment step or during the heat treatment step.

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

The upper limit of the S / As mass ratio is not particularly limited, but the higher the S / As mass ratio, the more the effect of suppressing As elution can be obtained by a short heat treatment. On the other hand, even if the amount of sulfur added is increased too much in order to increase the S / As mass ratio, the effect of suppressing As elution does not change significantly, but rather the excess sulfur content is due to the excess sulfur with respect to arsenic. Post-processing is required, which may lead to cost increase. Therefore, the upper limit of the S / As mass ratio can be set to about 6.

In the heat treatment step S2, a rubber antiaging agent may be added in addition to elemental sulfur. This makes it possible to suppress the elution of arsenic from the arsenic-containing volatile matter for a longer period of time. As the anti-aging agent for rubber, for example, any one or more anti-aging agents selected from monophenol-based, bisphenol-based, and polyphenol-based can be used. The amount of the antiaging agent added 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. 3A is a photograph showing the appearance of the volatile matter (heat-treated product) treated in the heat treatment step S2. The heat-treated product is collected as a columnar substance that is bulky in appearance. The arsenic grade of this heat-treated product is 12 to 15 mol%, and its density is about 0.6 to 1.5 g / cm ³ . Since the sample expands in the heat treatment step S2, the density of this heat-treated product is about half that of the density of arsenic sulfide, which is a pure substance. It is possible to store this heat-treated product as it is, but if the density is low, the specific surface area becomes large, so the contact area of the heat-treated product with the outside atmosphere (for example, air or liquid) becomes large, and elution is likely to occur. In some cases.

-Crushing step S3, remelting step S4-
Therefore, in the present embodiment, the heat-treated product treated in the heat treatment step S2 is crushed, and the crushed heat-treated product is reheated and remelted to increase the density of the heat-treated product. An example of the remelted product is shown in FIG. 3 (b). The pulverization method in the pulverization step S3 is not limited to a specific method, and can be carried out by a conventionally known known method. For example, the operator may crush using a predetermined tool, or a crusher may be used.

In the remelting step S4, the heat-treated product (volatile matter) after pulverization is heated in a non-oxidizing atmosphere using nitrogen or the like to melt the arsenic sulfide in the heat-treated product. The heat-treated product is preferably heated so that the density of the heat-treated product after remelting is 1.5 to 3.0 g / cm ³ . The treatment temperature of the heat-treated product in the remelting step S4 is preferably 200 to 250 ° C, more preferably 220 to 250 ° C. If the treatment temperature is lower than 200 ° C., the heat-treated product may not be sufficiently melted. If the treatment temperature is higher than 250 ° C., a part of sulfur contained in the raw material volatilizes and expands the sample, so that the density may not increase.

The remelt (sulfur-containing compound) obtained in the remelting step S4 is a solid arsenic-containing compound composed of arsenic and sulfur, and has an arsenic concentration of 1 to 40% by mass and a density of 1.5 to 3. It is 0.0 g / cm ³ . By storing this remelted product in water, arsenic contained in copper ore containing arsenic can be stored and stored in a stable form for a long period of time.

Hereinafter, the present invention will be described in more detail 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 compositions characterized for this high As grade copper concentrate using X-ray diffraction (XRD) and electron probe microanalyzer (EPMA) are chalcopyrite (CuFeS ₂ ) 11 mass%, pyrite (FeS ₂ ). It was 42 mass%, 36 mass% of enargite (Cu ₃ AsS ₄ ), and 11 mass% of vein stone component (SiO ₂ etc.).

After pre-drying 100 g of this arsenic-containing copper concentrate, it was roasted at a treatment temperature of 650 ° C. in a nitrogen gas atmosphere. As shown in Table 1, a concentrate containing chalcopyrite containing almost no arsenic (roasting). Chalcopyrite) and volatiles containing 33% by mass of arsenic and 64% by mass of sulfur could be separated.

When the volatile matter obtained in the roasting step was cooled, solidified and recovered, the S / As mass ratio of the volatile matter was 2.3. This volatile matter was heat-treated in a non-oxidizing atmosphere at a heat treatment temperature of 280 ° C. and a heat treatment time of 30 minutes to obtain a heat-treated product. The obtained heat-treated product was pulverized, and the pulverized product was heated at 240 ° C. for 10 minutes in a non-oxidizing atmosphere to obtain a remelted product.

(Example 2)
Elemental sulfur is added to the volatile matter (S / As mass ratio 2.3) obtained in the roasting step of Example 1 so that the S / As mass ratio in the volatile matter is 4.1, and further monophenolic. An anti-aging agent (2,6-di-t-butyl-4-methylphenol) was added at 0.5 mol / m ³ , and heat treatment was performed in a nitrogen gas atmosphere at a treatment temperature of 280 ° C. and a heat treatment time of 30 minutes. The obtained heat-treated product was pulverized, and the pulverized product was heated at 240 ° C. for 10 minutes to obtain a remelted product.

(Elution result)
The amount of As elution was evaluated for the volatiles, heat-treated products, and remelts obtained in each step of Example 1 and Example 2 by the elution analysis (TCLP) of soil pollutants by the US Environmental Protection Agency (EPA). .. In this elution analysis, deionized water, acetic acid or acetic acid buffer was used as the elution solvent for a sample having a particle size of less than 9.5 mm (0.5 to 5 mm) by crushing the volatiles, eluates and remelts, respectively. A liquid is used, the pH is 2.88, the liquid-solidity 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 pressurized filtration (0). The elution analysis was performed as (using a 6 to 0.8 μm GFF filter). The results are shown in FIG.

As shown in FIG. 4, the amount of As eluted decreased as the roasting, heat treatment, and remelting steps were performed. Further, in both Examples 1 and 2, the elution amount of As could be reduced to 1 mg / L or less in the finally obtained remelt.

(density)
When the densities of the heat-treated product and the remelted product of Example 1 were measured, the density of the heat-treated product was 1.0 g / cm ³ , whereas the density of the remelted product was 2.5 g / cm ^3. It was. As a result of measuring the densities of the heat-treated product and the remelted product of Example 2 to which the additive was added, the density of the heat-treated product was 1.0 g / cm ³ , whereas the density of the remelted product was 2.4 g. It was / cm ³ . That is, by increasing the density by remelting to form a lump (block shape), a more stable form with low As elution property could be obtained.

1: Inner layer 2: Outer layer

Claims (1)

A solid arsenic-containing compound consisting of arsenic and sulfur, arsenic concentration, 1 to 40 wt%, Ri density 1.5~3.0g / cm ³ der, soil in the United States Environmental Protection Agency (EPA) when measured with As elution amount by dissolution analysis of pollutants (TCLP), elution amount is 1 mg / L or less der Ru arsenic-containing compounds of As.