WO2016131445A1 - Processing method and processing device for arsenopyrite concentrates - Google Patents

Abstract

The steps provided in a refining method for removing arsenic from arsenic-containing sulphide concentrates, more particularly from arsenic- and noble-metal-containing sulphide concentrates (10) as preparation process step for subsequent isolation of noble metal, more particularly for subsequent isolation of gold, are: a) mixing the arsenic-containing sulphide concentrates (10) with a pyrite concentrate (12), where the proportion of the latter is such as to give a prescribed minimal mass ratio of sulphur in relation to the arsenic content of the sulphide concentrates; b) agglomerating the mixture obtained in step a), more particularly by briquetting or the like; c) drying the agglomerates obtained in step b); d) roasting the dried agglomerates in a neutral gas atmosphere, preferably in a vertical kiln (60) or in an indirectly heated rotary kiln; e) collecting the arsenic sulphide sublimates and the dust arising during the roasting process, and f) passing the roasted agglomerates onwards for further processing.

Description

 Processing method and processing device for arsenopyrite concentrates

The present invention relates to the field of metallurgy, and more particularly relates to de-arenization processes for arsenopyrite concentrates containing noble metals, with concomitant conversion of the arsenic into the mildly toxic sulfide product, and to apparatus formed for carrying out the process.

The purpose of the invention is the preparation of an arsenopyrite concentrate for the subsequent recovery of the precious metals with a pyro- or hydrometallurgical process while ensuring a minimum loss of precious metals and with simultaneous transfer of the arsenic in the relatively non-toxic sulfide form.

In the treatment of arsenopyrite concentrates, as it is used in particular for gold extraction nowadays, is a major challenge in the environmentally friendly and cost-saving management of the contained arsenic.

In a known method for arsenic extraction from arsenopyrite concentrates, a roasting of sulfur granulated concentrates at a temperature of 650-800 ° C and a suction of the vapors of arsenic sulfide from the reaction zone into the gas channel and a subsequent sublimation. To reduce sulfur consumption, the temperature of the granules is maintained at a gas channel height of 650-750 ° C. According to the laboratory tests carried out in the present invention, the sulfur consumption is not large when sulfur is used as the sulfiding agent; however, the sublimates may contain increased levels of metallic arsenic. In a generic method for obtaining arsenic sulphide sublimate from sulphide materials, their roasting is carried out at a temperature of 650-700 ° C. using sulphidating agents (eg pyrite) with subsequent melting of the powdery sublimates, in order to obtain them a compact, non-oxidizable airborne material To give water insoluble form.

The mass ratio of pyrite to arsenic in the layer in such a roasting is set as (1, 8-2): 1. In this process, the dust discharge from the roasting plant is very high, and also the loss of precious metal components can be very significant.

Also known is a process for deoxidizing the oxidized products from the metal industry (metal dust) in the form of less toxic sulfides, a sulfiding stage with sulfur at a temperature of 300-350 ° C. and an arsenic removal by roasting at a temperature of 500-700 ° C includes.

In order to facilitate this process, the sulphidation stage in this process is carried out at a theoretical sulfur consumption necessary for the full sulphidation of the non-ferrous oxides except the arsenic. Thereafter, the arsenic is driven off by oxidative roasting, with air passing through a layer of descent particle particles of the sulphided dust and at the same time desulfurizing the arsenic in the gas phase with a mass ratio of hydrogen sulphide to arsenic of (0.4-0.5): 1 is performed.

This method involves a difficult to control stage of oxidizing hydrogen sulfide feed roasting in the gas phase. A deviation of the hydrogen sulphide consumption from the given value may lead to the penetration of the arsenic trioxide into the sublimates, which is inadmissible.

For complex sulphide ores and concentrates containing gold, silver, iron, arsenic, antimony, bismuth and other components, an element removal drive known, however, worsens the extraction of precious metals. The Ausgangsulfidkonzentrat a thermal treatment at a temperature of 600 - 900 ° C in the gas phase at the vapor concentration of elemental sulfur at 0.2-1, 0 abs. (20-100 vol.%). For this Schweibei is admitted from an evaporator; Nitrogen is used as the carrier gas. Sulfur vapor containing impurities (arsenic, antimony, bismuth, selenium and tellurium) and carrier gas are conveyed from the sulfiding furnace to a condenser. The product resulting from the thermal treatment is cyanated. As already mentioned above, the yield of elemental sulfur in its application as a sulfiding agent for arsenopyrite concentrates is not high according to the findings of this study. The arsenic content in the calcine and the content of metallic arsenic in the sublimates is therefore increased.

For pyrite ores containing arsenic and lead, a treatment process is known which includes a partial ore oxidation in fluidized bed to remove the sulfur content. This is followed by a roasting of the burn-up in a fluidized bed in the neutral atmosphere with arsenic sublimation and an oxidizing roasting of the entarsenized material in fluidized bed to remove the residual sulfur. The roasted product represents an iron oxide burn, which is suitable for direct reduction in the metal. It should be noted that a roasting process in a fluidized bed furnace is characterized by a considerable dust discharge and a high loss of noble metal. In addition, the performance of the oxidative roasting of the arsenic-containing material can lead to transformation of the arsenic in the wastes in the form of highly toxic oxides; which makes waste recycling more difficult.

For arsenopyrite ores, a treatment process in a fluidized bed system with two zones is also known. In the first zone, the ore is combined with hot sulfur dioxide from the second zone for arsenic removal in the form of sulphide sublimate formation. In the second zone, denarsenated material is roasted in the passage of an oxygen-containing gas to form sulfur dioxide. The sulfur oxide is divided into two streams: One of the two streams is used for material heating in the first zone by a Heat exchangers used without arsenic contamination. The second stream is fed directly into the first zone and ensures the material boiling and transport of the arsenic-containing sublimate. Just as in the case of the method already described, in this case on the one hand a large loss of noble components by the dust is possible, on the other hand highly toxic arsenic oxide can be present in the waste.

For solid gold arsenic concentrates, a treatment process is known which includes granulation, drying and a two-stage roasting which in a first stage at a temperature of 500-700 ° C with the formation of arsenic-containing sublimate and in a second stage at a temperature of 800. 900 ° C in an oxidizing atmosphere in fluidized bed with recovery of sulfur dioxide and gold-containing Röstgut performed.

In order to increase the degree of arsenic emissions - in particular to improve the environmental friendliness of the process and to reduce its own costs - the roasting stage is preferably carried out in an oven. The zone of the first stage of the process is heated by the combustion exhaust of the second stage and the arsenic-containing gas phase is led out separately. The first roasting stage is in a reducing atmosphere in the relationship of the arsenic and pyrite as 1: (1.75-2.77), in the recovery of the roasted material containing not less than 15-17% sulfur, and in arsenic deposition in the sublimates , carried out.

In the second stage, first stage roasting material, which has a temperature of 500-700 ° C, is roasted. According to laboratory studies carried out on this side, the use of pyrite as a sulfiding agent in the processing of the arsenopyrite concentrates makes effective arsenic removal possible, but the presence of the stage of oxidation in the process can lead to an increase in the toxicity of the waste. Gold-arsenic-carbonaceous concentrates may be processed by a known process which includes the steps of oxidative roasting, cyanation, gold deposition on activated charcoal, roasting and smelting on the gold. According to this process, the starting material is treated at a temperature of 600-100 ° C with a residual pressure of up to about 2600 Pa (20 torr) within 15 minutes (arsenic transforms into sublimate). The residual vacuum is processed with hydrochloric acid at a temperature of 1 to 10 ° C. for 1 to 4 hours (iron is drawn out into a solution), whereby the gold-containing cake is roasted (carbon dioxide is removed).

After roasting, gold and other precious metals are extracted from the burnings. A vacuum treatment of large volumes of a concentrate with high arsenic and sulfur content is technically very difficult to realize. For the arsenopyrite concentrates which do not contain coal, the use of this method is impractical.

For desensitization of arsenopyrite concentrates, it is further known to carry out the feed roasting of the concentrate and metal-containing materials in a neutral atmosphere at 600-800 ° C. For the purpose of simplifying and facilitating the process, magnetic oxidation of the concentrate smears is used instead of metal-containing materials. The amount of oxidized concentrates in the process can lead to highly toxic waste (containing arsenic oxides). It is also known to carry out a dearsification of arsenopyrite and sulfide concentrates by roasting at 550-800 ° C. with simultaneous addition of steam with oxygen, at an oxygen-to-water ratio (1 -3): 1.

This process differs from the burn-up due to a low degree of denaturation; In addition, the presence of arsenic oxides in the sulfide sublimate can not be excluded. A detailed analysis of the known processes for the processing of arsenic-containing products has shown that it is not excluded that product contact with an oxidizing atmosphere at high temperatures can lead to a formation of toxic arsenic oxides and an increase in the hazard class of process waste.

In addition, several methods involve processing of unstirred materials, partly in a fluidized bed furnace, which involves significant dust discharge from the furnace and a need to develop complex systems for separate dedusting and sublimate recovery, as well as high loss of precious component (precious metals).

The invention is - as already mentioned - the object to enable processing of arsenopyrite concentrates containing precious metals, with minimal loss of precious components and minimal transfer of arsenic in the sublimate, preferably by forming less toxic sulfides.

To solve the above object, a method is proposed, which includes the agglomeration, in particular the briquetting, granulation or pelleting, the raw materials and subsequent roasting in a neutral atmosphere (nitrogen).

The roasting is preferably carried out batchwise in a hood furnace; Alternatively, a shaft reactor or an indirectly heated rotary kiln can be used; in the latter, a continuous process is possible.

The process according to the invention is based on the process initially described as generic in which the sulfide materials are roasted with a sulfiding agent but without sintering of the feed, preferably at 650-700 ° C. However, the method according to the invention differs by a tendency to higher consumption of sulfiding agents, which is necessary in order to exclude portions of metallic arsenic in the concentrated sublimate. In the context of a refining process according to the invention for the de-arsenicization of arsenic-containing sulfide concentrates, in particular of arsenic- and noble metal-containing sulfide concentrates as a preparatory process step for a subsequent noble metal extraction, in particular for a subsequent gold recovery, the following steps are provided:

a) mixing the arsenic sulphide concentrates with a pyrite concentrate in such a proportion that a predetermined minimum mass ratio of sulfur, based on the arsenic content of the sulphide concentrates, is adjusted;

b) agglomerating, in particular briquetting, pelleting or granulating, the mixture obtained in step a);

c) desiccation of the agglomerates obtained in step b);

d) roasting the dried agglomerates in a neutral gas atmosphere, preferably in a standing oven;

e) collecting the arsenic sulfide sublimates emitted during roasting and the dust produced during roasting, and

f) feeding the roasted agglomerates for further processing.

The corresponding process parameters are preferably adjusted so that the arsenic residue in the roasted agglomerates (eg briquettes, granules or pellets) does not reach an arsenic residual content of more than 0.5% and / or the amount of metallic arsenic in the sublimate is not more than 0.02% and / or a loss of arsenopyrite concentrate of less than 1% (absolute) occurs. In a preferred embodiment, the agglomeration (also referred to as "lumpy") in step b) is configured as briquetting with metering of lignosulfonate as a connecting substance. This is done with the goal of the formation of lumpy material and thus the formation of arsenic oxides and arsine to exclude during the heat treatment and also to increase the Brikettierfestigkeit.

Alternatively, granulation or pelleting may optionally be carried out with the addition of suitable auxiliaries or another agglomeration method may be used, with the aim of avoiding the formation of arsenic oxides and arsine and of reducing the formation of dust in the further process.

The desiccation in step c) preferably takes place as drying, preferably until the residual content of H ₂ O is not more than 0.1%.

Furthermore, the arsenic-containing sulfide concentrates preferably have an initial mass ratio As: S greater than about 2: 1, which is brought to a mass ratio As: S of about 3: 5 or less by the mixture with the pyrite concentrate in step a).

Furthermore, the roasting in step d) preferably takes place with one or more of the following parameters:

i) roasting temperature (maximum value after heating) at least about 650 ° C, preferably about 650-700 ° C, and / or

ii) roasting time 40-60 minutes, and / or

iii) the neutral gas atmosphere is formed as a nitrogen atmosphere, more preferably with a residual oxygen content of not more than 0.03%.

Furthermore, the roasting in step d) preferably takes place batchwise in a hood furnace; as an alternative, for example, a shaft reactor or an indirectly heated rotary kiln can be used, with the latter type of furnace can be made a continuous feed.

The arsenic sulfide sublimates collected in step e) are preferably stored as waste. Furthermore, the dust collected in step e) is preferably returned led into the raw material processing, ie the arsenic sulphide concentrates again struck.

In order to ensure a process-related sulfur over-supply, irrespective of fluctuations in the composition of the arsenopyrite concentrates, in step a) at least 50%, particularly preferably at least about 66% of pyrite concentrate can be admixed, based on the amount of arsenic-containing sulfide concentrate. Furthermore, to achieve the object according to the invention, a de-sizing device is proposed, which is designed to carry out the method described above. In particular, this device is characterized by the use of a stand, in particular a hood furnace or an indirectly heated rotary kiln.

The invention will be discussed in more detail below with reference to an example: Example 1 Under laboratory operations, the roasting of arsenopyrite concentrate was composed (in%): As 22.2; Fe 18.3 and S 1 1, 0 performed.

As a sulphiding agent, pyrite concentrate consisting of (in%): As 0.226; Fe 32.0 and S 39.8 applied. The consumption of pyrite concentrate was 50-66% of the amount of arsenopyrite.

The compound used was 5% lignosulfonate solution (50% dry solids, density 1, 26 g / cm ³ ) based on the total amount of dry arsenopyrite and pyrite concentrates.

Concentrate mixture and compounds were briquetted in a laboratory roller briquette press. The briquettes were dried at 150 ° C within 30 minutes.

The dry briquettes were roasted in a laboratory technical shaft reactor in a nitrogen atmosphere at 600 - 700 ° C within 60 min (see table).

According to the technical specifications, the remaining amount of arsenic in the roasting product should not exceed 0.5% of the quantity.

Table 1 - Operations and results of roasting

As can be seen, the remaining quantity of arsenic in the calcined material clearly exceeds the specifications (<0.5%) if a sufficient reserve is provided for consumption of the sulphiding agent, in particular 66% of the amount of arsenopyrite concentrates, and if the roasting temperature is not less than 650 ° C as in the case of the experiments No. 1 and No. 4.

The invention will be further explained by way of example with reference to the drawings. FIG. 1 shows a schematic block diagram of a desensitization method according to the invention, and

Figure 2 is a perspective view of a suitable for carrying out the method according to the invention hood furnace in partial sectional view. FIG. 1 shows the schematic sequence of a de-staining method according to the invention in one exemplary embodiment. The order of the individual steps is not generally mandatory. A person skilled in the art will further recognize that some processing steps - if necessary at the expense of worse process results - can in principle also be omitted without departing from the basic principle of the present invention.

According to FIG. 1, a desensitization process according to the invention begins with pyrite concentrate added in such an amount to the arsenopyrite concentrate (at 12) to be artefacts which is to be dehumidified (step 12) that a desired excess of sulfur is thereby set. Typically, based on the arsenopyrite concentrate, at least 50%, preferably more than 66%, by mass, of pyrite concentrate is fed. This mixture is then comminuted in a feed preparation and intimately mixed with each other, resulting exhaust gases 30 (in particular dusts) to an exhaust gas purification 44 explained below are supplied.

Furthermore, a feed of a briquetting system 18 takes place, in which, with the addition of lignosulfonate as binder, the mixture is brought into a lumpy, well-defined form. The geometry of the briquettes can be chosen differently. For example, the classic, particularly well stackable cuboid briquettes of about brick size or smaller can be formed. Also egg-shaped briquettes are possible. Furthermore, the introduction of holes in the briquettes (in the manner of perforated bricks) is possible to facilitate the escape of gases from the interior of the briquettes during the later Entarsenierungsroösten.

The shaped briquettes 20 are then dried in a step 24 for the purpose of solidification, for which the waste heat resulting from the subsequent roasting can be energetically co-used. The desired residual moisture is about 0.1%. The resulting in the drying exhaust gases 32 (dusts and vapors) are also the exhaust gas purification 44 fed. The dried briquettes 24 are batched in a bell-type oven where they are subjected to a denaturation roasting 26 at preferably about 650 to 700 ° C for 40 to 60 minutes under a nitrogen atmosphere with an oxygen content of less than 0.03%.

This exhaust gases escape 34, which in addition to dusts relatively high levels of arsenic sulphides in still to be sublimated steam 38. These are deposited in a special exhaust gas purification on cooled surfaces as a sublimation and can then be deposited as chemically relatively inert arsenic compounds or otherwise disposed of. The return dust 42 is filtered out and, together with the return dust 46 of the exhaust gas purification of the preceding process stages, is added back to the starting materials of the process. The cleaned and filtered exhaust gases can be released into the atmosphere at 40 and 48, respectively. The exhaust gas purifications 36 and 44 can be performed in a common device. Specific to the exhaust gases 34 of the roasting, however, are the higher arsenic sulphide contents, which is why a specific sublimate separation is expedient for these exhaust gases.

After the roasting 26 has been carried out, the roasted briquettes are available for further processing for the purpose of obtaining precious metals, in particular by a pyro- or hydrometallurgical process.

FIG. 2 shows an example of a bell-type oven 60 which can be used for the purpose of roasting, although a variety of other oven types, such as, for example, a standing oven or an indirectly heated rotary kiln, can likewise be used.

The hood furnace with a top-loading hood for loading / unloading (the opening mechanism is not shown in detail) is heated in a jacket portion 62 by means of gas burners and bottom-side combustion air supply and top exhaust gas discharge. The jacket region 62 is adjoined concentrically further inside and in a gas-tight manner by a further jacket region 64 in which inert gas (nitrogen) circulated by a blower 66 passes through the Mantle wall is heated as a heat exchanger and then passed through hole crucible 70 located on perforated plates 68. In the crucibles 70 are the briquettes (not shown). Due to the compacted form of the briquettes with a defined volume / surface ratio, the denaturing roasting can be carried out very easily and reproducibly; the accumulating return dust components are low in comparison to a roasting of the unlubricated mixture. Furthermore, it is advantageous that an uncontrolled release of arsenic compounds into the environment can be effectively ruled out by the batchwise operation in a gas-tight sealed furnace, in particular a hood furnace. A possible alternative to the above-described batchwise operation with a hood furnace may be a continuously fed, indirectly heated rotary kiln.

Claims

claims 1 . Refining process for de-arsenicization of arsenic-containing sulfide concentrates, in particular of arsenic- and noble metal-containing sulfide concentrates as a preparatory process step for subsequent precious metal extraction, in particular for subsequent gold recovery, characterized by the steps: a) mixing the arsenic-containing sulfide concentrates (10) with a pyrite concentrate (12) with a such proportion that a predetermined minimum mass ratio of sulfur based on the arsenic content of the sulfide concentrates is adjusted; b) agglomerating (18) the mixture obtained in step a); c) desiccation (22) of the agglomerates obtained in step b); d) roasting (26) the dried agglomerates in a neutral gas atmosphere, preferably in a standing furnace (60) or an indirectly heated rotary kiln; e) collecting the arsenic sulfide sublimates emitted during roasting and the dust (36) produced during roasting, and f) supplying the roasted agglomerates for further processing (28). 2. The method according to claim 1, d a d u r c h e s e n c i n e s, d a s s  the arsenic residual content of not more than 0.5% is achieved by derarening in the roasted agglomerates, and / or  the amount of metallic arsenic in the sublimate is not more than 0.02%, and / or a loss of arsenopyrite concentrate of less than 1% (absolute) occurs. 3. The method according to claim 1 or 2, characterized in that  the preferred embodiment of the agglomeration in step b) is a briquetting (18) with metered addition of lignosulfonate as compound or granulation or pelleting or another agglomeration method. 4. The method according to any one of claims 1 to 3, characterized in that the preferred design of the desiccation in step c) is a drying (22), which preferably takes place until the residual content of H ₂ O is not more than 0.1%. 5. The method according to any one of claims 1 to 4, characterized in that  the arsenic sulphide concentrates (10) have a starting mass ratio As: S of greater than about 2: 1, which, when mixed with a pyrite concentrate (12) in step a), has a mass ratio As: S of about 3: 5 or less is brought. 6. The method according to any one of claims 1 to 5, characterized in that  the roasting (26) in step d) takes place with one or more of the following parameters: i) roasting temperature (maximum value after heating up) at least approx. 650 ° C, preferably about 650 - 700 ° C, and / or ii) roasting time 40-60 minutes, and / or iii) neutral gas atmosphere formed as a nitrogen atmosphere, with a residual oxygen content of not more than 0.03%. 7. The method according to any one of claims 1 to 6, d ad urch marked that  the roasting (26) in step d) preferably takes place in batches in a hood furnace (60) or in a shaft furnace or continuously in an indirectly heated rotary kiln. 8. The method according to any one of claims 1 to 7, characterized in that  the arsenic sulphide sublimates (38) collected in step e) are stored as waste, and / or  the dust (42) collected in step e) is returned to the raw material processing. 9. The method according to any one of claims 1 to 8, characterized in that  in step a) at least 50%, preferably at least about 66%, of pyrite concentrate (12) is admixed, based on the amount of arsenic-containing sulfide concentration (10). 10. An apparatus for de-arsenicization of arsenic sulfide concentrates, characterized in that  this is designed to carry out a method according to one of the preceding claims.