AU597737B2

AU597737B2 - A method of recovering metals and metal alloys and a plant therefor

Info

Publication number: AU597737B2
Application number: AU80005/87A
Authority: AU
Inventors: Werner L. Dr. Kepplinger; Erich Ottenschlager
Original assignee: Voestalpine AG
Current assignee: Primetals Technologies Austria GmbH
Priority date: 1986-10-30
Filing date: 1987-10-21
Publication date: 1990-06-07
Anticipated expiration: 2007-10-21
Also published as: KR890006831A; CN1010325B; AT386006B; BR8705781A; CZ279319B6; DE3735966A1; ATA288686A; JP2572084B2; SU1582991A3; CN87107197A; CZ769087A3; IN172088B; DD262676A5; SK278800B6; CA1324265C; KR950001909B1; SK769087A3; PH24466A; DE3735966C2; UA2125A1

Description

AUSTRALIA

PATENTS ACT 1952 COMPLETE SPECIFICATION ~Bol 17 7 31 Form

(ORIGINAL)

FOR OFFICE USE Short Title: Int. Cl: Application Number: Lodged: Complete Specification-Lodged: Accepted: Lapsed: Published: Priority: Related Art: This doc.Lumtn c ontai lji aendrneimts made tndcr jection a9mnd is cornct ifol p~rinting. Y-Lsirwyk t I L) TO BE COMPLETED BY APPLICANT Name of Applicant:

VOEST-ALPINE

AKTIENGESELLSCHAFT

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0 1 Aadress of Applicant: 44 TURMSTRASSE A-4020 LINZ

AUSTRIA

Actual Inventor: Address for Service: CLEMENT HACK CO., 601 St. Kilda Road, Melbourne, Victoria 3004, Australia.

Complete Specification for the invention entitled; A METHOD OF RECOVERING METALS AND METAL ALLOYS AND A PLANT THEREFOR The following statement is a full description of this invention including the best method of performing it known to m.e:- The invention relates to a method of recovering metals or metal alloys, in particular ferro-alloys, by reducing metal oxides in a reduction zone formed by a coal bed flowed through by a reducing gas, as well as a plant for carrying out the method.

In EP-A 0 174 291 a method of melting metals, i.e.

copper, lead, zinc, nickel, cobalt and tin, of oxidic finegrain non-ferrous metal ores is described, wherein the charging material is charged into a reduction zone formed by a coal fluidized layer in a meltdown gasifier. When passing this reduction zone, the oxidic charging material 0 o Sis reduced to metal, which is collected in the lower part of the meltdown gasifier.

00a0 It has shown that the method according to EP-A 0 booo o°o 174 291 may advantageously be used for reducing oxides reacting with elementary carbon at temperatures below 1,000oC, yet that problems may occur when recovering metals 0 00 and metal alloys, in particular ferre-alloys, such as ferro-manganese, ferro-chromium and ferrosilicon, which 0000 a 20 are recoverable from their oxides only at temperatures exceeding 1,000oc using elementary carbon as the reducing 0 agent, sincs the period of contact of this oxidic charging material which reacts at higher temperatures, with the carbon particles forming the fluidized layer is relatively short.

The invention aims at avoiding these disadvantages and Sdifficulties and has as its object to provide a method and a plant of the initially defined kind which make it possible to produce metals and metal alloys, in particular ferro-alloys, such as ferro-manganese, ferro-chromium and

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ao 6, o 4 6 6 o 6 0 0 no09 0 06 0, 4 4* i 4 64 0 4 6 *4; ferrosilicon, from fine-grain oxidic material in a meltdown gasifier, wherein the metal has such a high affinity to oxygen that it reacts with elementary carbon at above 1,000 0 C only.

With a method of the initially defined kind this object is achieved in that the coal bed is formed by three static bed layers, wherein a bottom lay-r of degassed coal is provided, which covers a liquid sump of reduced metal and slag, into a middle layer, oxygen or an oxygen-containing gas is introduced so as to form a hot reducing gas consisting essentially of CO, and at a distance thereabove, finegrain oxidic charging material is introduced into the middle layer, and into a top layer, combustion gases of carbon particles and oxygen or oxygen-containing gas are introduced.

Advantageously, fine-grain oxidic charging material having a grain size of up to 6 mm is used.

For forming the static bed layers, suitably coal having a grain size of from 5 to 100 mm, in particular 5 to mm, is used.

According to a preferred embodiment, the thickness of the middle and top static bed layers is maintained between 1 and 4 m.

A further embodiment of the method according to the invention is characterised in that dust-like carbon particles are separated from the off-gas passing the reduction zones and that these carbon particles, preferably in the hot state, together with oxygen or oxygen-containing gas are fed to burners directed into the top static bed layer.

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The off-gas freed from carbon particles may be used as conveying medium for the fine-grain oxidic chargina material.

As the coal, preferably coal maintaining its lumpy character after degassing is used, so that with a grain size range of from 5 to 100 mm, preferably 5 to 30 mm, utilized, at least 50 of the degassed coal formed after degassing is present within the original grain size range of from 5 to 100 mm or 5 to 30 mm, respectively, and the remainder is present as undersize grain.

The method according to the invention offers the advantage that all known advantages of the reduction processes in shaft furnaces heated with fossile energy are 0. 4 0* maintained, such as counterflow-heat exchange, metallurgical reaction with elementary carbon in the static bed, which is necessary for the reduction of oxides of non- 1. precious metals, and a good separation of metal and slag.

Coking or degassing of coal may be carried out without the formation of tar and other condensable compounds. The gas formed during the degassing of the coal acts as additional reducing agent to the reduction gases formed from the gasification of the degassed coal.

4 According to a special embodiment, the oxidic material charged can be pre-reduced in a pre-reducing step, which has proved to be especially advantageous when producing ferro-alloys, in which the iron oxide portion of the material charged is accessible to this reduction.

A particular advantage of the method consists in that the reduction of oxides of non-precious elements, such as, silicon, chromium, manganese, can be effected without -3 !.i using electric energy. In the method according to the invention, the energy required for degassing the coal is controlled in a simple manner, because the undersize grain (smaller than 5 mm) is discharged with the hot gases of the meltdown gasifier, separated, returned into the upper blowing-in zone of oxygen-containing gases and oxidized by means of the oxygen-containing gases, heat being released.

The grain decomposition behaviour is tested such that a coal grain fraction of from 16 to 20 mm is subjected to degassing for one hour in a chamber which has been preheated to 1,400°C. The volume of the chamber is 12 dm 3 t After cooling by flushing with cold inert gas, the grain distribution is determined.

The invention furthermore comprises a plant for caro0 rying out the method with a refractorily lined shaft-shaped meltdown gasifier, which has, in its upper part, a charging o opening for introducing coal as well as a gas discharge duct, the side wall of the meltdown gasifier being penetrated by supply ducts for carbon particles and oxygen or 20 oxygen-containing gas and a lower portion being provided for collecting molten metal and liquid slag. This plant is characterised in that, under formation of three asuperposed static bed layers A, B, C in the region between the bottom static bed layer A and the middle static bed layer B, a ring of blow-in pipes for oxygen or oxygen-containing gas is provided, at a distance thereabove, a ring of blow-in pipes for fine-grain oxidic charging material, and at a distance thereabove, in the region between the middle static bed layer B and the top static bed layer C, 4

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a ring of burners charged with carbon particles and oxygen or oxygen-containing gas are provided.

Advantageously, a hot cyclone for separating carbon particles from the off-gas is provided in the gas discharge duct, and the discharge end of this hot cyclone is in flow connection with the ring of burners.

According to a particular embodiment, a further hot cyclone is in flow-connection with this hot cyclone, a charging arrangement for oxidic charging material entering into this connection duct between thetwo hot cyclones; the discharge end of the further hot cyclone is connected with the ring of blow-in pipes for the oxidic charging material t, by means of a conveying duct.

The method according to the invention and the plant 4 for carrying out the method are explained in more detail in the drawings, wherein Fig. 1 is a schematic illustration of the meltdown gasifier with additional arrangements connecoI\o ted thereto. Fig. 2 shows the temperature profile in the meltdown gasifier.

Ol a 6 A shaft-like meltdown gasifier denoted by 1 has a refractory lining 2. The bottom region of the meltdown *44441 S' gasifier serves for accommodating molten metal 3 and molten slag 4. A tap opening for metal is denoted by 5, and. a tap opening for slag is denoted by 6. In the upper part of the meltdown gasifier, a charging opening 7 for supplying lumpy coal is provided. Above the liquid sump 3, 4, the static coal bed is formed, i.e. a bottom layer A of degassed coal which is not gas-passed, a superposed gas-passed middle layer B of degassed coal and a waperposed top layer C of, coal particles, which is passed by gas.

i- Ii I 10 It Sr st The side wall of the meltdown gasifier 1 is penetrated by blow-in pipes, i.e. by a ring of blow-in pipes 8 for oxygen or oxygen-containing gases, respectively. These pipes are arranged in the border region between the non-gas-passed static bed layer A and the static bed layer B.

At a distance thereabove, i.e. in the middle to upper part of the static bed layer B, a ring of nozzle-shaped blow-in pipes 9 enters, through which fine-grain oxidic charging material is blown into the middle layer B.

At a distance thereabove, i.e. in the border region between layer B and layer C, a ring of burners 10 penetrating the side wall of the meltdown gasifier 1 is provided, into which a mixture of dust-like carbon particles and oxygen or oxygen-containing gas is introduced. From the upper part of the meltdown gasifier 1 a gas discharge duct 11 leads away, carrying the off-gas formed to a hot cyclone 12.

j a z i Dust-like carbon particles suspended in the off-gas are separated in the hot cyclone 12 and fed from the dis- 20 charge end of the hot cyclone 12, in which a dosing means 13 is provided, through a duct 14 to the ring of burners A duct for oxygen-containing gas leading to the burners is denoted by 15. With the dosing means 13 the filling degree of the hot cyclone 12 can be regulated and the separating effect of the hot cyclone 12 can be influenced.

From the upper part of the hot cyclone 12, a duct 16 leads to a further hot cyclone 17. Into the connecting duct 16 a charging device 18 enters, which charging device is charged from a bin 19 containing a fine-grain oxidic charging wmterial. The gas from duct 16 serves as the conveying 6 -rr I i~ ~~-o~cMl~r~n~ mediun. From the discharge end of the hot cyclone 17, the fine-grain oxidic charging material is discharged into a conveying duct 20 and from there is fed to the blow-in pipes 9 via a duct 21.

From the upper end of the hot cyclone 17, a duct 22 leads away, through which duct 22 the excess off-gas is discharged. It can be cooled and compressed and, via a duct 23, blown into duct 21 as a conveying medium.

The method according to the invention advantageously is carried out such that coal charged into the upper part of the meltdown gasifier 1 is degassed in static bed layer 'I C. The heat required for degassing is provided, on the one hand, by the hot reducing gases rising from the static bed layer B, and, on the other hand, by combustion heat from the solid carbon particles burned by means of oxygencontaining gases in the burners 10. The vertical extension of the layer C is selected such that the gas leaving layer C has a minimum temperature of 950 0 C. Thereby it is ensured that tars and other condensable compounds are cracked. Thus an obstruction of the static bed layer C becomes impossii ble. In practice, a iayer thickness of from 1 to 4 m has ij proved to be advantageous for layer C. A vertical extension of from 1 to 4 m also proves to be advantageous for static bed layer B. Coal degassed in layer C forms the static bed layer B when it sinks down.

The fine-grain oxidic charging material is pre-reduced by the hot reducing gas and the fine dust in the further hot cyclone 17 and re-separated from the gas. Loading the hot reducing gas with fine-grain carbon-containing dust may prove to be advantageous, because the carbon reacts with 7 r-mxr*.l~ -i-r 4Q o *r c 44 C I 4 C C9 4 0* C C C 4 C, C 4 4 040*l 4 0 DO., o 4 .4

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the CO 2 formed at the reduction by forming CO, whereby the hot gas from the meltdown gasifier 1 continues to be strongly reducing. The fine-grain oxidic charging material separated after pre-reduction with fine dust is melted in layer B and is reduced by the elementary carbon. The heat required for melting and reducing is supplied by gasifying hot degassed coal by means of oxygen-containing gases introduced into the gasifier via the blow-in pipes 8. The molten metal forming in static bed layer B and the molten slag flow downwardly and are collected and tapped below layer A.

Fig. 2 shows the temperature profile over the height of the meltdown gasifier 1, the height conditions being plotted on the ordinate and the temperatures being entered on the abscissa. The full lines illustrate the temperature course of the charged coal, and the broken lines show the temperature course of the gas forming. The height marked by 8 represents the ring of blow-in pipes 8, the height denoted by 9 represents the level of the blow-in pipes 9 for 20 fine-grain oxidic charging material (ore), the height denoted by 10 represents the carbon-particle recycling through burners 10, the height marked 24 is the static bed upper limit 24, and the height denoted by 11 represents the gas discharge duct 11 and the charging opening 7 for coal, respectively.

8 The effectiveness of the present invention is reflected in the following example relating to the method and plant shown in the drawings.

1. Ore Grain size: 0 10 mm (I#apyores) Manganese ore with about 42% Mn-content, analysis: Fe 5.7 MnO 53.2 CaO 11.8 CO 2 17.9 MgO 2.2 H 2 0 1.5 SiO 2 5.2 Al 0 0.1 ,2 3 2. Coal: 04. L Medium-volatile, bituminous, including ab. 61 C 25 volatile constituents ashes 4 H 2 0 Charge: 1,750 kg coal per ton ferromanganese 3. Ferro-manganese analysis: Mn 75 C 7 Si 0.8 S 0.02 4. 0 demand: 950 Nm 3 per ton ferro-manganese, Gas amount: 3,200 Nm 3 per ton ferro-manganese having a net calorific value nc.v. of about 2,000 cal per Nm 3 8A

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Claims

1. A method of recovering metals and metal a2loys by reducing metal oxides in a reduction zone formet by a coal bed passed through by reducing gas, the method comprising forming a coal bed of three static bed layers by providing a bottom static bed layer of degassed coal covering a liquid sump of reduced metal and slag, providing a middle static bed layer and introducing one of oxygen and an oxygen-containing gas into said middle static bed layer so as to form a hot reducing gas comprising CO, and introducing fine-grain oxidic 0 charging material at a distance thereabove into said middle static bed layer, and providing a top static bed a layer and introducing combustion gaises of carbon *t4 particles and one of oxygen and an oxygen-containing gas into said top static bed layer.

2. A method as set forth in claim 1, wherein said fine-grain oxidic charging material has a grain size of o up to 6 mm, Sel

3. A method as set forth in claim 1, wherein said three static bed layers are formed by coal having a grain size of from 5 to 100 mu

4. A method as set forth in claim 3, wherein said coal has a grain size of from 5 to 30 mm, A method as set forth in claim 1, wherein the thickness of said middle static bed layer and said top static bed layer is maintained between 1 and 4 m.

6. A method as set forth in claim 1, wherein off-gas passes the static bad laydrs constituting reduction zones, further comprising sgparating cdust-3 i ;r -T carbon particles from said off-gas and feeding said carbon particles together with one of oxygen and oxygon-containing gas to burners directed into said top static bed layer.

7. A method as set forth in claim 6, wherein said separated carbon particles are fed in the hot state to said burners. i 8. A method as set forth in claim 6, further coi prising using the off-gas freed from said carbon particles as a conveying medium for said fine-grain ioxidic charging material.

9. A plant for recovering metals and metaJ alloys Sby reducing metal oxides in a reduction zone formed by a jj coal bed passed through by reducing gas, the plant comprising, a refractorily lined shaft-like meltdown gasifier having an upper part, a side wall and a lower part, the upper part including a charging opening for charging coal as well as a gas discharge duct, supply ducts for carbon particles and one of oxygen and an oxygen-containing gas penetrating said side walls of 4' tsaid rieltdown gasifier, and said lower part being provided for collecting molten metal and liquid slag, a bottom static coal-bed layer, a middle static coal-bed jlayer and a top static coal-bed layer to form three superposed static coal-bed layers, in the region between the bottom static bed layer of degassed coal covering a liquid sump of reduced metal and slag, and the middle static bed layer, a ring of blow-in pipes for one of oxygen and oxygen-containing gas to form a hot reducing gas comprising CO, at a distance thereabove, a ring of blow-in pipes for fine-grain oxidic charging material, and at a distance thereabove, in the region between the middle static bed layer and the top static bed liyer, a i i ii~ Y-L CC ring ot burners for carbon particles and one of oxygen and oxygen-containing gas is provided. A plant as set forth in claim 9, further comprising a hot cyclone for separating carbon particles from the off-gas and provided in said gas discharge duct, and means flow-connecting said hot cyclone discharge end with said ring of burners.

11. A plant as set forth in claim 10, further comprising a further hot cyclone having a discharge end, a connecting duct flow-connecting said hot cyclone 4 i? i E 3 I 11 I r and 4 said further hot cyclone, a charging means for oxidic charging material entering into said connecting duct, and a conveying duct connecting the discharge end of said further hot cyclone with said ring of blow-in pipes for said oxidic charging material.

12. A method substantially as hereinbefore described with reference to the accompanying drawings.

13. A plant substantially as hereinbefore described with reference to the accompanying drawings. DATED THIS 21ST DAY OF OCTOBER 1987 VOEST-ALPINE AKTIENGESELLSCHAFT By its Patent Attorneys: CLEMENT HACK CO. Fellows Institute of Patent Attorneys of Australia. 4 4co 4nr 4 4 44ss 41 091 4 *4 4O IA 9 *1i i 9111 i. 4' Ir t 12