DE60006617T2 - Refining mineral concentrates containing precious metals by chlorination - Google Patents

Abstract

Precious metal-containing concentrates are subjected to high temperature chlorination using HCl gas, an optional reduction, an oxidation and finally a reduction, to remove most of the base metals especially the amphoteric elements.

Description

The present invention relates to Refining improvements, particularly affects one improved process for refining precious metals.

In this description is below the term "precious metal" one or more representatives from the group gold and the platinum group metals (PGM, namely Pt, Rh, Pd, Ru, Ir, Os) to understand. Silver is not supposed to be a precious metal here be considered.

After extraction from precious metal ores or as a by-product of smelting other minerals such as Nickel, or after recovery of precious metals from recycled materials, it is common to produce a concentrate the precious metal components, silver compounds and compounds contains base metals (including compounds of any other metal or one amphoteric material). The number and the quantities The individual compounds of base metal can be considerable vary depending on the origin of the concentrate. Preferred concentrates for the use according to the invention are mine concentrates, which contain about 60% by weight or more of noble metal, but can other concentrates can also be used. It is therefore envisaged that suitable starting materials for the present invention Are concentrates which are more than 50% by weight, preferably about 60% by weight Precious metal mixed with base metals, especially amphoteric Include items included. It was found that certain Elements such as Copper, nickel, iron, cobalt, sulfur, silver, Selenium, lead, tellurium, zinc, bismuth, arsenic, antimony and tin, in general harmful and are disadvantageous for the refining of precious metals and that even some of the precious metals have such a low value and in further refining Complications that would be helpful, at least to cut off part of it; Osmium is such a precious metal.

A number of methods have already been proposed where precious metal raw materials are chlorinated. So is for example in GB-A-1 502 765 (Matthey Rustenberg Refiners) a method described in which a solid concentrate with a halogen containing gas is treated to base metals and silver too remove by volatilization the corresponding halides. A preferred subsequent stage is a residue containing noble metal in hydrochloric acid contains an oxidizing agent dissolve. Another method has already been described in CA-A-2 181 369 (Prior Engineering) and this comprises the following three stages: Oxidation of the starting material at a first temperature, reduction of the residue at a second temperature and chlorination in a third stage. The first oxidation stage is a roasting stage, in which oxygen or an oxygen-containing gas is used and sulfur and amphoteric materials such as Selenium, in the form of its dioxides be removed and it is possible that some osmium evaporates in the form of its tetroxide. Part of the rest Metals are oxidized and therefore a reduction stage follows, in which is a reducing gas such as hydrogen or a gas containing hydrogen is used. In the final chlorination stage is preferred Chlorine is used and the majority of the base metals present is converted to chlorides, which are generally used in the Temperatures (800 to 1300 ° C) volatile and are removed in the gas stream. Although certainly as cheap Tests carried out have shown that even a Series of volatile Precious metal chlorides are formed, resulting in significant losses of gold, palladium and ruthenium leads. Because of this chloride formation, this process must therefore be serious consideration excrete in the refining of such precious metal concentrates. There is therefore still a need for a practical refining process where a precious metal concentrate is converted into a refined product that can be processed and with minimal losses occur in valuable precious metals.

• (1) Behandlung des Konzentrats mit Chlorwasserstoffgas bei einer Temperatur in dem Bereich von 750°C bis 1100°C unter Bildung eines ersten Rückstands,
• (2) optionale Behandlung des ersten Rückstands mit Chlorgas unter Bildung eines zweiten Rückstands,
• (3) Hochtemperaturbehandlung des ersten oder des zweiten Rückstands mit Sauerstoff bei einer Temperatur in dem Bereich von 750°C bis 1100°C unter Bildung eines dritten Rückstands, und
• (4) Behandlung des dritten Rückstands mit Wasserstoff bei einer Temperatur in dem Bereich von 750°C bis 1100°C unter Bildung eines Schlussrückstands.

The present invention relates to a process for refining a solid concentrate containing precious metals, which comprises the following steps:

• (1) treating the concentrate with hydrogen chloride gas at a temperature in the range of 750 ° C to 1100 ° C to form a first residue,
• (2) optional treatment of the first residue with chlorine gas to form a second residue,
• (3) high temperature treatment of the first or second residue with oxygen at a temperature in the range of 750 ° C to 1100 ° C to form a third residue, and
• (4) Treatment of the third residue with hydrogen at a temperature in the range of 750 ° C to 1100 ° C to form a final residue.

It is clear that the HCl gas, Cl ₂ - O ₂ - and H ₂ gas can be mixed with an inert gas or any other gas which does not interfere with the primary reactions taking place. The gas may possibly be replaced by one or more suitable precursors for the gas, such as hydrogen and chlorine, which react with one another to form HCl. It is preferred to flush each residue with an inert or other non-interfering gas between each step of the process if there is a risk of an explosive mixture being formed. In experiments, it was found that a 15-minute nitrogen purge for the its purpose is sufficient.

It was found that the stages 1, 3 and 4 of the method according to the invention at the same temperature, preferably at 850 to 1050 ° C, in particular at about 950 ° C, carried out can be. However, chlorination level 2 is preferably at a lower temperature, for example at 200 to 400 ° C, preferably at about 300 ° C. details in terms of the preferred working temperatures are given below.

Initial tests have shown that when working under the preferred conditions, the total losses of Pt, Pd, Rh and Ir are less than 1%, while removal of Se > 98%, a distance of Te of> 80% and a distance of As of> 98% is achieved. The losses of Os are of the order of magnitude from 50 to 60%, however this is not considered a serious disadvantage viewed and the losses of Ru are 2 to 4%, the greater part however, these losses can be recovered are made using known methods that are not part of the present invention are.

The starting material can be any solid concentrate from the extraction of platinum group metals or a concentrate from refining processes that are applied are on primary materials (i.e. from mine mining) or on secondary materials (i.e. from recycled Precious metals) or mixtures thereof. It is believed that inventive method is sufficiently robust to work on a wide variety of starting materials to be able to be applied. these can crushed or in agglomerated form (e.g. in the form of briquettes or pellets or similar) available. It was found that there was a physical loss Precious metal fines can occur in the gas stream when conventional Methods such as Fluid bed process or process with one upward gas flow can be applied. It is therefore preferred each of the stages with a downward gas flow in one Reactor vessel, for example in a vertical pipe. Preferably is in the reactor vessel a gas permeable Base used. The gases separated in each stage can be in conventional washers can be dealt with and the metal contents can be changed by one conventional workup can be collected. Preferably the Condensation of volatile Products in front of the washers avoided and heating the pipes and tubes may be required to avoid condensate accumulation and possible blockages.

In a first embodiment, the method is directed to minimizing the loss of the desired precious metals while removing the harmful material as much as possible. In a second embodiment, which includes the optional chlorination step, the method is directed to removing as many of the harmful elements as possible, with less emphasis on precious metal losses. The particular embodiment chosen depends largely on the individual starting materials and the refining and metal separation technology available downstream. Briefly, an example of performing the first embodiment is the following:
during the first stage of the process, the solid starting material is exposed to a chlorinating atmosphere in the form of hydrogen chloride gas. The temperature range should be kept between 750 and 1100 ° C, preferably between 850 and 1050 ° C, in particular at about 950 ° C. This atmosphere removes most of the base metal elements by forming stable base metal chlorides that evaporate. To a lesser extent, amphoteric elements are also removed.

Before the oxidative treatment the furnace is flushed with an inert gas, usually nitrogen. In present of oxygen are the problematic amphoteric elements, such as e.g. Selenium, tellurium and arsenic, removed in the form of their metal oxides.

The temperature range for this Operation should be between 750 and 1100 ° C, preferably between 850 and 1050 ° C, especially at around 950 ° C, lie.

Again, the stove has to be used Inert gas purged be before the atmosphere is converted from an oxidative to a reductive atmosphere by induction of hydrogen. The main reason for adding this Level is to take the precious metal components down to their lowest Reduce oxidation state (the metals), making them the best soluble are used in conventional refining treatment with an acidic and oxidizing Medium for the precious metal dissolution. The reduction is more effective if the temperature is not below 750 ° C, lower temperatures and longer However, treatment times are also effective. Certain materials, such as. Rhodium oxide at lower temperatures, for example of the order of magnitude from 200 to 300 ° C, be reduced. If alternative levels of dissolution or treatment carried out this sequence of steps may be not necessary anymore.

At the end of the procedure, this includes in the reaction vessel remaining solid material the bulk of platinum, palladium, gold, rhodium, iridium, Ruthenium, silicon dioxide and part of the osmium. It is one very small amount of base metal and amphoteric elements, the original contained in the starting material.

The second embodiment can be summarized briefly as follows:
During the first treatment stage, the Ma exposed to a chlorinating atmosphere in the form of hydrogen chloride gas. The temperature range must be kept between 750 and 1100 ° C, preferably between 850 and 1050 ° C, in particular at about 950 ° C. The task of this atmosphere is the same as stated above.

Before the reducing treatment the furnace is flushed with an inert gas, usually nitrogen. If desired, may include an optional reduction before level 1 or level 2 in Presence of hydrogen can be carried out, making the amphoteric Elements are reduced to their lowest oxidation states they are prepared for the easier volatilization while the subsequent treatment stage. The temperature range for this Operation should be between 750 and 1100 ° C, preferably between 850 and 1050 ° C, especially at around 950 ° C, lie.

Before the chlorination treatment the furnace is flushed and cooled with an inert gas, usually nitrogen. In The presence of chlorine becomes the amphoteric elements, such as selenium, tellurium and arsenic, mostly removed in the form of their chlorides. The temperature range for this Operation should be 250 to 500 ° C, preferably 300 to 350 ° C, be.

Before the oxidative treatment the furnace is flushed with an inert gas, usually nitrogen, and the Temperature is during this operation increases. The rest evaporate in the presence of oxygen amphoteric elements and osmium in the form of their oxides. The temperature range for this Operation should be 750 to 1100 ° C, preferably 850 to 1050 ° C, especially about 950 ° C, be.

Again, the furnace gas must be used with a Inert gas flushed out be before the atmosphere of converted from an oxidizing state to a reducing state is by introducing hydrogen. The reason for the engagement this stage is discussed above.

At the end of the thermal treatment contains that in the reaction vessel lingering solid Material the main amount of platinum, palladium, gold, rhodium, iridium, Ruthenium, silicon dioxide and part of the osmium. In the product is a very small amount of the original base metal and the original contain amphoteric elements.

The treatment times and the stoichiometric Excess gas can depending on the starting materials and the amounts contained therein various impurities can be varied.

The trend was found that the time required to treat the material is all the shorter, The higher the gas flow rate is. However, if the flow rate is too high and if there is an upward gas flow, kick significant physical loss of unreacted material that is carried along with the gas into the volatile material collection container.

The invention is illustrated below of examples of any embodiment described in more detail.

Example 1 - First embodiment

• • Erhitzen des Reaktorbehälters, der im Innern eines Ofens angeordnet ist, auf 950 °C unter Stickstoffgas
• • Umschalten auf Chlorwasserstoffgas von 950°C für 3 h und 30 min
• • Spülen mit Stickstoffgas für 15 min
• • Umschalten auf Sauerstoffgas von 950°C für 1 h
• • Spülen mit Stickstoffgas für 15 min
• • Umschalten auf Wasserstoffgas von 950°C für 1 h
• • Spülen und Abkühlen des Ofens auf Raumtemperatur unter Stickstoffgas.

After introducing a mine concentrate into the reactor vessel, the procedure described below is used:

• • Heating the reactor vessel, which is located inside an oven, to 950 ° C under nitrogen gas
• • Switch to hydrogen chloride gas of 950 ° C for 3 h and 30 min
• • purging with nitrogen gas for 15 min
• • Switch to oxygen gas at 950 ° C for 1 h
• • purging with nitrogen gas for 15 min
• • Switch to hydrogen gas at 950 ° C for 1 h
• • Rinse and cool the oven to room temperature under nitrogen gas.

The analysis of the residue after the final stage gave the following results:
Pt loss <0.25%
Pd loss <0.3%
Au loss <0.9%
Rh loss <0.35%
Ir loss <0.2%
Ru loss <2.0%
Os loss ∼ 60%
Se removal> 98%
Te removal> 80%
Ace removal> 98%
Total PGM losses ∼ 0.3% excluding Os, Ru

Example 2 - Second embodiment

• • Erhitzen des Ofens auf 950°C unter Stickstoffgas
• • Umschalten auf Chlorwasserstoffgas von 950°C für 1 h und 40 min
• • Spülen mit Stickstoffgas für 15 min } dies ist eine optionale Stufe
• • Umschalten auf Wasserstoffgas von 950°C für 30 min } dies ist eine optionale Stufe
• • Spülen mit Stickstoffgas und Abkühlen des Ofens auf 300°C
• • Umschalten auf Chlorgas von 300°C für 30 min
• • Spülen mit Stickstoffgas und Erhitzen des Ofens auf 950°C
• • Umschalten auf Sauerstoffgas von 950°C für 30 min
• • Spülen mit Stickstoffgas für 15 min
• • Umschalten auf Wasserstoffgas von 950°C für 1 h
• • Spülen und Abkühlen des Ofens auf Raumtemperatur unter Stickstoffgas

Using the same device and mine concentrate feed:

• • Heating the oven to 950 ° C under nitrogen gas
• • Switch to hydrogen chloride gas of 950 ° C for 1 h and 40 min
• • Purge with nitrogen gas for 15 min} this is an optional step
• • Switching to hydrogen gas from 950 ° C for 30 min} this is an optional step
• • Purging with nitrogen gas and cooling the oven to 300 ° C
• • Switch to chlorine gas from 300 ° C for 30 min
• • Purging with nitrogen gas and heating the oven to 950 ° C
• • Switch to oxygen gas of 950 ° C for 30 min
• • purging with nitrogen gas for 15 min
• • Switch to hydrogen gas of 950 ° C for 1 H
• • Rinse and cool the oven to room temperature under nitrogen gas

The analysis of the residue after the final stage gave the following results:
Pt loss <0.16%
Pd loss <2.16%
Au loss <2.0%
Rh loss <0.09%
Ir loss <0.3%
Ru loss <4.0 6%
Os loss ∼ 54%
Se removal> 99%
Te removal> 96.5%
Ace removal> 99%
Total PGM losses ∼ 0.81% excluding Os, Ru.

Example 3 - Comparison

• • Erhitzen des Ofens auf 450°C unter Stickstoffgas
• • Umschalten auf Sauerstoffgas von 450°C für 1 h
• • Spülen mit Stickstoffgas und Erhitzen des Ofens auf 700°C
• • Umschalten auf Wasserstoffgas für 1 h bei 700°C
• • Spülen mit Stickstoffgas und Erhitzen des Ofens auf 1000°C
• • Umschalten auf Chlorgas für 1 h und 40 min bei 1000°C
• • Spülen und Abkühlen des Ofens auf Raumtemperatur unter Stickstoffgas

The description of the method in CA-A-2 181 369 was followed using the presumed "best conditions" in the absence of exemplary embodiments and using the same device as above:

• • Heating the oven to 450 ° C under nitrogen gas
• • Switch to oxygen gas at 450 ° C for 1 h
• • Purge with nitrogen gas and heat the oven to 700 ° C
• • Switch to hydrogen gas for 1 h at 700 ° C
• • Purging with nitrogen gas and heating the oven to 1000 ° C
• • Switch to chlorine gas for 1 h and 40 min at 1000 ° C
• • Rinse and cool the oven to room temperature under nitrogen gas

The analysis of the product gave the following results:
Pt loss <0.36%
Pd loss ∼ 3.77%
Au loss ∼ 16.64%
Rh loss <2.52%
Ir loss <0.81%
Ru loss ∼ 63.64%
Os loss ∼ 84.61%
Se removal> 99%
Te removal> 98%
Ace removal> 99%
Total PGM losses - 7.38% excluding Os and ∼ 2% excluding Os and Ru.

Example 4 - Comparison

• • Erhitzen des Ofens auf 1000°C unter Stickstoffgas
• • Umschalten auf Chlorwasserstoffgas für 1 h und 40 min bei 1000°C
• • Spülen und Abkühlen des Ofens auf Raumtemperatur unter Stickstoffgas

The procedure of GB-A-1 502 765 was followed using the same device and starting material as above:

• • Heating the oven to 1000 ° C under nitrogen gas
• • Switch to hydrogen chloride gas for 1 h and 40 min at 1000 ° C
• • Rinse and cool the oven to room temperature under nitrogen gas

The analysis of the product gave the following results:
Pt loss <0.05%
Pd loss <0.03%
Au loss <0.11%
Rh loss <0.04%
Ir loss <0.05%
Ru loss <0.03%
Os loss <2.83%
Se removal <0.6%
Te removal <3%
Ace removal ∼ 47.52%
Total PGM losses <0.04% excluding Os

From the analytical results it can be seen that the examples according to the invention have good recovery values for PGM surrender while at the same time excellent reductions in problematic contaminants Se, Te and As can be achieved.

The invention can be compared to the foregoing description also on a variety of others Because of and under other conditions to be carried out in detail without thereby reducing the scope of the invention as defined in the claims is leave. becomes.

Claims (7)

Process for refining a solid precious metal Concentrate, comprising the following steps: (1) treatment of the concentrate with hydrogen chloride gas at a temperature in Range from 750 ° C to 1100 ° C below Formation of a first residue, (2) optional treatment of the first residue with chlorine gas under Formation of a second residue, (3) Treatment of the first or second residue with oxygen a temperature in the range of 750 ° C to 1100 ° C to form a third residue, and (4) Treatment of the third residue with hydrogen a temperature in the range of 750 ° C to 1100 ° C to form a last one residue; including the optional treatment of a rinse of any residue with an inert gas such as nitrogen between each process step. The method of claim 1, further comprising also as step A, treating the concentrate with hydrogen gas at a temperature in the range of 750 ° C to 1100 ° C before step (1) or step (2). The method of claim 1 or 2, wherein the temperature in steps A, (1), (3) and (4) is in the range from 850 ° C to 1050 ° C. The method of claim 3, wherein the temperature is about Is 950 ° C. A method according to any one of the preceding claims, wherein the optional chlorination step (2) is carried out at a temperature of 200 ° C to 500 ° C. The method of claim 5, wherein the chlorination step (2) at a temperature of 300 ° C up to 350 ° C carried out becomes. Method according to one of the preceding claims, the in a reaction vessel under Application of downward facing gas streams carried out becomes.