AU598237B2

AU598237B2 - Recovery of values from antimony ores and concentrates

Info

Publication number: AU598237B2
Application number: AU69707/87A
Authority: AU
Inventors: John Millice Floyd; Brian William Lightfoot
Original assignee: Ausmelt Ltd
Current assignee: Outotec Ausmelt Pty Ltd
Priority date: 1986-03-04
Filing date: 1987-03-04
Publication date: 1990-06-21
Anticipated expiration: 2007-03-04
Also published as: AU6970787A

Description

V AUSTRALIA Patents Act 09 7 COMPLETE

SPECIFICATION

(ORIGINAL)

Class Application Number: 67 O 7/cr 7.

Lodged: Int. Class Complete Specification Lodged: o 'Accepted: Published: o O Priority °Related Art: 4 *4g

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4 1 2 I i v r "'4 4 4 40, 4 44 Q 4 4* e. I 44 Name(s) of Applicant(s): Address(es) of Applicant(s): APPLICANT'S REF.: C.A.P. of PH 4861 AUSMELT PROPRIETARY LIMITED 304 High Street, Kew, Victoria 3101, Melbourne, Australia t 4 Actual Inventor(s): Address for Service is: PHILLIPS, ORMONDE AND FITZPATRICK Patent and Trade Mark Attorneys 367 Collins Street Melbourne, Australia, 3000 Complete Specification for the invention entitled: "RECOVERY OF VALUES FROM ANTIMONY ORES AND CONCENTRATES" The following statement is a full description of this invention, including the best method of performing it known to applicant(s): RECOVERY OF VALUES FROM ANTIMONY ORES AND CONCENTRATES This invention relates to the recovery of antimony and other metal values from antimony ores or concentrates.

The other metal values of particular interest are the precious metals gold and silver.

Antimony ores or concentrates often contain valuable constituents apart from antimony. The recovery of both antimony and the precious metals gold and silver is conventionally carried out in a number of stages of processing. An example of this type of multiple-pass processing is the treatment of stibnite concentrate for gold and silver recovery by leaching with cyanide or thiourea to remove the precious metals to a separate recovery circuit.

The leach residue is then treated by an antimony-recovery operation, which generally involves roasting or smelting the material to liberate antimony as the volatile sulphide or oxide, followed by oxidation and collection from the gas stream from the roaster or smelter as Sb 2 0 3 fume. This fume may be sold directly, or may be reduced to metal in a reverberatory furnace and either sold as metal or reoxidized for sale depending on market requirements and impurity levels in the materials.

These processes have inherent disadvantages in that the precious metal recovery circuit involves expensive reagents, is wasteful of reagents, produces materials which are difficult and inconvenient to handle, and often involves a low recovery.

We have found that these disadvantages can be overcome by using a novel approach involving smelting and fuming of the material in a furnace which can be operated to produce a precious metal collecting phase, and at the same time efficiently collect volatile components as fume.

According to the invention, there is provided a process for recovery of antimony and other metal values from an antimony ore or concentrate feed material, which comprises the steps of: charging the feed material into a liquid bath containing slag in a smelting furnace having means 39 for injecting fuel and oxygen-containing gas beneath

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r the surface of the bath; injecting fuel and oxygen-containing gas into the bath to maintain temperature and thereby volatilize antimony values; drawing off from the furnace a gaseous stream containing the volatilized antimony values and recovering said values from said stream; establishing a collecting phase in the liquid bath such that the other metal values are preferantially extracted from the slag into the collecting phase, terminating the charging of feed material and allowing the collecting phase containing the other metal values to settle from the slag; and recovering the collecting phase from the furnace for recovery of the other metal values therefrom The furnace to be used may be a top submerged lancing reactor. Alternatively, the furnace may be a reactor b having bottom or side twyers. These reactors have the advantage that they can be operated efficiently on a small scale and are capable of rapid response to changes in operating conditions. Such reactors have unique advantages, when operated for the recovery of precious metals as well as antimony from feed materials, which have not been previously Sappreciated and each enables a significant improvement on the prior art.

i With such reactors, the oxygen-containing gas is injected below the surface of the bath through at least one lance or twyer, while the fuel may be injected through the same or a different lance or twyer. Where the feed material S 30 is in the form of fines, it may be charged to the reactor through a lance or twyer, whether this be the same as that used for the oxygen-containing gas and/or fuel or a different lance or twyer.

The volatilized antimony values may comprise antimony sulphide and/or antimony oxides. Subject to the conditions prevailing in the furnace, some antimony metal vapour also may be present.

The antimony values preferably are recovered, by 39 cooling the gas stream, to effect their condensation. Where

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r I- reducing or neutral conditions prevail in the furnace, the volatilized values will contain antimony sulphide and possibly some antimony metal vapour. However, in such case, the gas stream may be exposed to oxidizing conditions, such as by blending with hot oxygen-containing gas, to convert the sulphide and metal vapour to antimony oxide. On cooling the stream, substantially all of the antimony values are recovered as condensed oxide.

The conditions prevailing in the furnace may be oxidizing, requiring the oxygen-containing gas to have an oxygen content in excess of that required for combustion of the fuel. Depending on that excess, the antimony values drawn off with the gaseous stream may comprise a mixture of antimony sulphide and oxide, or antimony oxide substantially free of sulphide. The excess of oxygen preferably is at least that required to burn volatilized antimony sulphide in the furnace such that the antimony values drawn off are the oxide substantially free of sulphide.

A variety of fuels can be used. However, the fuel preferably is oil, coal or natural gas.

The oxygen-containing gas may be oxygen, air or oxygen-enriched air.

The collecting phase can be established with any suitable base metal collecting agent into which the other metal values are able to be extracted. The other metal values of principal importance are gold and silver and, for extraction of these, the collecting agent may comprise copper, copper matte or iron-sulphide matte. However, other base metal collecting agents can be used.

The collecting agent may be added during smelting or, alternatively, after termination of charging the feed material. Where the agent is added after smelting, fuel and air or a neutral gas is injected into the bath during addition of the collecting agent. In either case, of adding collecting agent during or after smelting, such injection is terminated to provide a quiescent interval during which the collecting phase settles from the slag. However, this termination can be either by cutting off the supply of oxygen-containing gas and 39 fuel (with change if necessary to an auxilliary heat source)

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or, in the case of a top submerged lancing reactor, by raising the lance so that the fuel burns above the bath without preventing settling of the phases.

The collecting agent can be added under reducing, oxidizing or neutral conditions. For reducing conditions, coal, charcoal, brown coal char and coke breeze are examples of suitable reductants. Reducing conditions tend to cause any antimony values remaining in the bath to report in the collecting phase as the metal.

In the accompanying drawings: Fig. 1 is a diagrammatic representation of one type of furnace suitable for use in the process of the present invention.

Fig. 2 is a flow sheet illustrating a preferred embodiment.

'4 Q0 0** 0t 0 00 0I 4 In Fig. 1, there is shown a furnace comprising a Ott Ott submerged lancing reactor 10 in which a liquid bath 12 is maintained. Reactor 10 has a lining 14 of refractory bricks S surrounded by insulation 16, and an offtake flue 18 lined with refractory concrete 20. A lance 22, adapted to be raised or lowered as required, enters the furnace through lance hole 24. Fuel and oxidizing gas such as air may be introduced via lance 22, and solid materials may be introduced into the furnace through a feed chute 26. A slag coating 28 will normally form on lance 22. A taphole 30 is provided to draw off liquid products from reactor The submerged lancing reactor 10 can be used to generate heat efficiently with any suitable fuel and can efficiently use the heat available from smelting reactions.

It can also be used to generate oxidizing, neutral or reducing conditions in a bath. The bath 12 in the furnace acts as a medium for rapid transfer of heat and mass between injected materials and other feed materials dropped into the furnace.

Feed can be in any form which can be handled into the furnace. Fine material may be injected down the lance 22, and/or it may be wetted or agglomerated and dropped into the furnace bath through chute 26. Coarse material can be dropped into the furnace through chute 26 without the need to grind it 39 to fine sizes. The furnace, when constructed with insulated

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walls as shown, minimizes heat losses, and this gives efficiency on a small scale. However, in an alternative form, the walls can be water-cooled to minimize refractory wear and to remove excess heat.

The furnace can be readily maintained in a holding condition by raising the lance and starting a holding burner.

Start up by operating the lance is then very readily and rapidly achieved.

Sulphide materials can be efficiently oxidized to product oxides, which can be removed as fume or as an oxide slag.

In one form, the process of the invention comprises progressively feeding antimony ore or concentrate feed material into a liquid bath 12 containing slag in smelting Q furnace 10, through lance 22 (or a separate lance) and/or through chute 26. Simultaneously fuel and oxidizing gas is injected below the surface of bath 12, via lance 22, to maintain temperature and thereby promote volatilization of antimony sulphide and/or antimony oxides. A gaseous stream containing antimony values is drawn off from furnace 10 via flue 18. Optionally, when antimony sulphide is present in the gaseous stream, oxidizing conditions are provided to convert the antimony sulphide to antimony oxide. The gaseous stream Sis cooled to condense antimony oxide and antimony oxide is recovered from the gaseous stream as a solid product. In a a second stage of operation, a collecting phase is established i in liquid bath 12, such that the other metal values are preferentially extracted from the slag into the collecting phase. The collecting phase containing the other metal values is allowed to settle from the slag and the collecting phase containing the other metals is removed from furnace SWhilst lance 22 is submerged in bath 12, the conditions in furnace 10 are very turbulent and any material fed to the furnace is rapidly incorporated. By raising lance 22 above bath 12, quiescent conditions can be achieved to allow efficient separation of phases in the bath. This can allow a precious and base metal collecting agent such as copper metal, copper matte or iron-sulphide matte or other 39 concentrating phases to be charged to furnace 10 at any time

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i I to recover precious or base metals in a concentrated and easily handled form. The subsequent recovery of these metals from the product is then readily acheived in conventional smelting and refining systems. The precious metals can also be concentrated in an Sb speiss generated from sulphide feed and recovered in subsequent operations.

The features of the top submerged lancing system allow producers to operate their own upgrading systems, even on a very small scale, and thus sell material in a more favourable market.

In one variation, the invention provides a process for the recovery of antimony and precious metals from antimony-rich feed materials comprising the following two steps also depicted in Figure 2.

oi First step: Smelting the material in a top 4 submerged lancing furnace by injecting fuel and air into a bath of liquid slag in the furnace, whilst charging the feed o material together with fluxes into the furnace either as fines passed down the lance or as coarse, wet or agglomerated material added through a chute, and separating fume rich in Sb 203 from the gas phase using a suitable filtering, Sprecipitation or scrubbing system.

Second step: Stopping the feed of antimony-rich material and forming a precious metal collecting phase in the bath by either smelting under conditions where antimony metal or speiss is formed, or by adding a material such as copper, copper concentrate of pyrrhotite which will produce a metal or sulphide phase, and tapping this phase from the furnace. Slag g produced which is lean in precious metals and antimony is tapped from the furnace for discard.

In a modification of that variation, the material to produce a sulphide phase can be added during the first, smelting step.

Fluxes are also fed as desired to produce a liquid slag by known procedures. The slag required preferably is based on mixtures of silica and iron oxide and other oxides may be present.

Example i: This example illustrates the operation 39 of the process under non-oxidizing fuming conditions with -7metallic copper added to produce the collected phase. A laboratory test was carried out in which a bath cf an iron oxide-calcium oxide-silica slag was melted in an alumino-silicate crucible heated in an induction furnace.

Into this bath was injected nitrogen at 3 1/min through an alumina tube to simulate injection of a non-oxidizing fuel-air mixture in a top submerged lancing furnace; the nitrogen and induction heating providing conditions equivalent to those existing with injection of oxygen and fuel in proportion to achieve neutral or non-oxidizing conditions. 301 g of a 2 stibnite concentrate containing 66.7 wt.% Sb, 30.0 ppm Au and ppm Ag was fed as pellets over a period of 46 minutes into the bath at 1200 C. Evolved gases were passed through a ii paper bag filter. Feeding of stibnite was stopped and 20 g of copper was added to the crucible over 10 minutes, during which nitrogen injection was continued. After a settling time of minutes with no injection, the crucible was cooled to room f /temperature.

r coee A matte phase, a speiss phase and slag were recovered from the crucible and fume was collected from the filter bags. The analyses of the products are shown below: The inferred recoveries of antimony, silver and gold were greater than 95 wt.% SSb wt.% Au ppm Ag ppm slag 1.85 3.8 12 matte 2.85 315 490 speiss 6.00 3570 2300 fume 81.50 0.4 Example 2: In this example the smelting was demonstrated under oxidizing conditions and copper was added as a collector under reducing conditions. The initial bath was the same as for Example 1 and the same concentrate type and weight was fed as pellets, Air was injected at a rate of 1/min; the air and induction heating providing conditions equivalent to those existing with injection of oxygen and fuel with an excess of oxygen over requirements for fuel combustion. Feeding of antimony-concentrates was halted and 15.4 g of coal was charged over a period of 25 minutes whilst 39 injecting nitrogen at 3 1/min. in place of the injected air.

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-8- _I __J i-*l-lii- -i 40.5 g of copper was then added as a collector over 11 minutes before settling with no injection for 25 minutes. The products were slag, copper and fume of analyses shown below.

Sb wt.% Au ppm Ag ppm slag 7.3 2.3 11 copper 10.7 115 380 fume 82.0 0.4 4 The recovery of silver, gold and antimony inferred from these results were greater than 95 wt.%.

In the foregoing, it is indicated that, during and after smelting, reaction conditions prevailing in the furnace may be oxidizing, neutral or reducing. In general, it is preferred th't the oxygen-containing gas and fuel be in stoichiometric proportion. Where reducing conditions are required, such as is desirable before addition of a collecting O agent comprising a sulphidizing material, such conditions preferably are generated by the addition of a suitable reductant providing the required level of reactivity. Coal is the preferred reductant.

It will be clearly understood that the invention in its general aspects is not limited to the specific details referred to hereinabove.

0, a v a.

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Claims

2. A process according to claim i, wherein said oxygen-containing gas and fuel is injected into the bath by at least one top submerged lance.
3. A process according to claim 2, wherein at least a portion of said feed material, as fines, is injected into the bath by at least one top submerged lance. S4. A process according to claim i, wherein said oxygen-containing gas and fuel is injected into the bath by at 1 least one bottom or side twyer. A process according to claim 4, wherein at least a portion of said feed material, as fines, is injected into the bath by at least one bottom or side twyer.
6. A process according to any one of claims 1 to wherein injection into the bath, of said oxygen-containing gas plus fuel for stoichiometric combustion, is continued after terminating the charging of feed for a period of time 39 sufficient to enable the collecting phase to extract the other FY -i0- metal values.
7. A process according to claim 6, wherein the collecting phase is allowed to settle by terminating the injection of oxygen-containing gas and fuel.
8. A process according to claim 2 or claim 3, wherein said at least one lance, by which oxygen-containing gas and fuel is injected into the bath, continues to supply said gas and fuel to the reactor during a period in which the collecting phase is allowed to settle, the at least one lance being raised during said period so that the gas and fuel is not injected into the bath.
9. A process according to any one of claims 1 to 8, wherein said collecting phase is established by adding a base metal collecting agent. A process according to claim 9, wherein said collecting agent is selected from copper, copper matte or iron-sulphide matte. 11" A process according to any one of claims 1 to ,,It wherein said collecting phase is an antimony metal or speiss generated from said feed material.
12. A process according to claim 9 or claim 10, wherein said collecting agent is added during smelting of said feed material. S 13. A process according to claim 9 or claim 10, wherein said collecting agent is added on completion of smelting of said feed material.
14. A process according to claim 13, wherein said smelting is conducted under oxidizing conditions, said collecting agent is a sulphidizing agent and said bath is subjected to reducing conditions prior to adding said collecting agent. DATED: 4 March 1987 PHILLIPS ORMONDE FITZPATRICK Attorneys for: AUSMELT PTY LTD.4 -11-