CA1324265C

CA1324265C - Method of recovering metals and metal alloys and a plant therefor

Info

Publication number: CA1324265C
Application number: CA000550404A
Authority: CA
Inventors: Erich Ottenschlager; Werner L. Kepplinger
Original assignee: Deutsche Voest Alpine Industrieanlagenbau GmbH
Current assignee: Deutsche Voest Alpine Industrieanlagenbau GmbH
Priority date: 1986-10-30
Filing date: 1987-10-28
Publication date: 1993-11-16
Anticipated expiration: 2010-11-16
Also published as: JP2572084B2; CN87107197A; ATA288686A; CZ769087A3; SU1582991A3; AU597737B2; BR8705781A; AT386006B; DD262676A5; KR950001909B1; DE3735966C2; CN1010325B; IN172088B; AU8000587A; KR890006831A; SK278800B6; CZ279319B6; DE3735966A1; UA2125A1; PH24466A

Abstract

ABSTRACT OF THE DISCLOSURE
Disclosed is a method for recovering a metal or metal alloy in particular a ferro-alloy, by reducing a metal oxide in a reduction zone formed by a coal bed with a reducing gas. To obtain a metal having a high affinity to oxygen, the coal bed is formed by three static bed layers including a bottom layer of degassed coal covering a liquid sump of reduced metal and slag, a middle layer and a top layer. Oxygen or an oxygen-containing gas is blown into the middle layer to form a hot reducing gas, and at a distance thereabove, fine-grain oxidic charging material is introduced into the middle layer. A
combustion gas of carbon particles and oxygen or oxygen-containing gas is fed into the top layer.

Description

1~2426~

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.
J In EP-A - O 174 291 a method of melting metals, i.e.
i; copper, lead, zinc, nickel, cobalt and tin, of oxidic fine--~ grain non-ferrous metal ores is described, wherein the charging material is charged into a reduction zone formed 10 by a coal fluidized layer in a meltdown gasifier. When , passing this reduction zone, the oxidic charging material :~ is reduced to metal, which is collected in the lower part of the meltdown gasifier.
It has shown that the method according to EP-A O
174 291 may advantageously be used for reducing oxides reacting with elementary carbon at temperatures below 1,000C, yet that problems may occur when recovering metals and metal alloys, in particular ferro-alloys, such as ferro-manganese, ferro-chromium and ferrosilicon, which 20 are recoverable from their oxides only at temperatures exceeding 1,000C using elementary carbon as the reducing agent, since 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 difficulties 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 7ii 30 ferro-alloys, such as ferro-manganese, ferro-chromium and - 1 - ;~ , s ` 1324265 ferrosilicon, from fine-grain oxidic material in a melt-down gasifier, wherein the metal has such a high affinity ;1 to oxygen that it reacts with elementary carbon at above 1,000C 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 layer 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 j essentially of Co, and at a distance thereabove, fine-grain 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, f ine-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 30 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 parti-cles 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.

, .

i32426~

The off-gas freed from carbon particles may he used as conveying medium for the fine-grain oxidic charging mate-rial.
AAs 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 10 remainder is present as undersize grain.
The method according to the invention offers the ad-vantage that all known advantages of the reduction pro-cesses in shaft furnaces heated with fossile energy are maintained, such as counterflow-heat exchange, metallurgi-cal reaction with elementary carbon in the static bed, which is necessary for the reduction of oxides of non-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 20 formed during the degassing of the coal acts as additional reducing agent to the reduction gases formed from the gasification of the degassed coal.
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 mate-rial 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, 30 e.g., silicon, chromium, manganese, can be effected without -,,, . , : , . :

13242~

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 pre-heated to 1,400C. The volume of the chamber is 12 dm3.
After cooling by flushing with cold inert gas, the grain distribution is determined.
The invention furthermore comprises a plant for car-' rying out the method with a refractorily lined shaft-shaped meltdown gasifier, which has, in its upper part, a charging opening for introducing coal as well as a gas discharge duct, the side wall of the meltdown gasifier being pene-' trated by supply ducts for carbon particles and oxygen or 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 superposed 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, :
132~26~
.~
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.
ccording to a particular embodiment, a further hot ~ cyclone is in flow-connection with this hot cyclone, a i, charging arrangement for oxidic charging material entering 3 10 into this connection duct between the two hot cyclones; the discharge end of the further hot cyclone is connected with the ring of blow in pipes for the oxidic charging material `:~ by means of a conveying duct.
The method according to the invention and the plant 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 connec-ted thereto. Fig. 2 shows the temperature profile in the meltdown gasifier.
A shaft-like meltdown gasifier denoted by 1 has a refractory lining 2. The bottom region of the meltdown ? gasifier serves for accommodating molten metal 3 and moltenslag 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 lumpycoal 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 superposed top layer C of coal particles, which is passed by gas.

i .. . . .
. . .

~3242~

he 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 q 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 s, a ring of nozzle-shaped '~ blow-in pipes 9 enters, through which fine-grain oxidic -~ charging material is blown into the middle layer s.
, 10 At a distance thereabove, i.e. in the border region between layer s and layer C, a ring of burners 10 pene-trating the side wall of the meltdown gasifier 1 is pro-i vided, into which a mixture of dust-like carbon particles i~ and oxygen or oxygen-containing gas is introduced. From the upper part of the meltdown gasifier 1 a gas discharge duct i~ 11 leads away, carrying the off-gas formed to a hot cyclone 12.
Dust-like carbon particles suspended in the off-gas are separated in the hot cyclone 12 and fed from the dis-charge end of the hot cyclone 12, in which a dosing means 13 is provided, through a duct 14 to the ring of burners 10. A duct for oxygen-containing gas leading to the burners i 10 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 charg-ing material. The gas from duct 16 serves as the conveying .

, .

` 132~6~

medium. 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 lea~s away, through which duct 22 the excess off-gas i5 3 discharged. It can be cooled and compressed and, via a duct 23, blown into duct 21 as a conveying medium.
~ The method according to tha invention advantageously 9 10 is carried out such that coal charged into the upp~r part of the meltdown gasifier 1 is degassed in static bed layer 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 oxygencon-taining 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 950C. Thereby it is ensured that tars and other condensable compounds are cracked. Thus 20 an obstruction of the static bed layer C becomes impossi-ble. In practice, a layer thickness of from 1 to 4 m has proved to be advantageous for layer C. A vertical extension of from 1 to 4 m also proves to be advantageous for static J 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 30 prove to be advantageous, because the carbon reacts with , : -132426~

the CO2 formed at the reduction by forming CO, whereby the hot gas from the meltdown gasifier 1 continues to be stron-gly rsducing. The fine-grain oxidic charging material sepa-rated after pre-reduction with fine dust is melted in layer B and is reduced by the elementary carbon. The heat re-quired 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 10 slag flow downwardly and are collected and tapped below layer A.
Fig. 2 shows the temperature profile over the height of the meltdown gasifier li 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 de-noted by 9 represents the level of the blow-in pipes 9 for 3 20 fine-grain oxidic charging material (ore), the height de-noted 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.

- a -

Claims

1. A method of recovering a metal or a metal alloy, which comprises reducing a metal oxide in a reduction zone formed by a coal bed with a reducing gas passing through the reduction zone, wherein, the coal bed comprises three static bed layers consisting of:
(i) a bottom static bed layer of degassed coal covering a liquid sump of reduced metal or metal alloy and slag, (ii) a middle static bed layer into which one of oxygen and an oxygen-containing gas is introduced so as to form a hot reducing gas consisting essentially of CO and introducing the metal oxide in a fine-grain form is introduced at a distance above where oxygen or the oxygen-containing gas is introduced, and (iii) a top static bed layer into which a combustion gas of carbon particles and one of oxygen and an oxygen-containing gas is introduced.

2. A method as set forth in claim 1, wherein the metal oxide has a grain size of up to 6 mm.

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

4. A method as set forth in claim 3, wherein the coal has a grain size of from 5 to 30 mm.

5. A method as set forth in claim 1, wherein the thickness of the middle static bed layer and the top static bed layer is maintained between 1 to 4 m.

6. A method as set forth in claim 1, which further comprises:
separating dust-like carbon particles from an off-gas that passed through the static bed layers and feeding the dust-like carbon particles together with one of oxygen and oxygen-containing gas to burners directed into the top static bed layer.

7. A method as set forth in claim 6, wherein the separated carbon particles are fed in a hot state to the burners.

8. A method as set forth in claim 6, which further comprises using the off-gas freed from the carbon particles as a conveying medium for the metal oxide.

9. A method as set forth in any one of claims 1 to 8, wherein ferro-alloy is recovered.

10. A method as set forth in claim 9, wherein the ferro-alloy is ferro-manganese, ferro-chromium or ferro-silicon.

11. A method as set forth in claim 9, wherein the reduction is carried out such that an off-gas leaving the top bed layer is maintained at a temperature of at least 950°C.

12. An apparatus for recovering a metal or a metal alloy by reducing a metal oxide in a reduction zone formed by a coal bed with a reducing gas passing through the coal bed, which comprises:
a refractorily lined shaft-like meltdown gasifier having an upper part, a side wall and a lower part, the upper part including an opening for receiving coal and a gas discharge duct, the side wall including supply ducts for carbon particles and one of oxygen and an oxygen-containing gas penetrating the said side wall, and the lower part being provided with outlets for collecting the metal or metal alloy in a molten state and liquid slag, wherein:
(a) the gasifier is adapted such that a bottom static coal-bed layer of degassed coal covering a liquid sump of reduced metal or metal alloy and slag, a middle static coal-bed layer and a top static coal-bed layer are formed within the gasifier when the apparatus is in use;
(b) in region between the bottom static bed layer and the middle static bed layer, a ring of blow-in pipes for one of oxygen and oxygen-containing gas is provided to form a hot reducing gas consisting essentially of CO;
(c) at a distance above the ring of blow-in pipes for oxygen or oxygen-containing gas, a ring of blow-in pipes for fine-grain oxidic charging material is provided; and (d) at a distance above the ring of blow-in pipes for fine-grain oxidic charging material, in the region between the middle static bed layer and the top static bed layer, a ring of burners for being charged with carbon particles and one of oxygen and oxygen-containing gas is provided.

13. An apparatus as set forth in claim 12, which further comprises a hot cyclone for separating carbon particles from an off-gas and provided in the gas discharge duct, and means flow-connecting the hot cyclone discharge end with the ring of burners.

14. An apparatus as set forth in claim 13, which further comprises a further hot cyclone having a discharge end, a connecting duct flow-connecting the hot cyclone and the said further hot cyclone, a charging means for the oxidic charging material entering into the connecting duct, and a conveying duct connecting the discharge end of said further hot cyclone with the ring of blow-in pipes for the oxidic charging material.