CN87107197A

CN87107197A - Reclaim the method and apparatus of metal and metal alloy

Info

Publication number: CN87107197A
Application number: CN87107197.5A
Authority: CN
Inventors: 埃里克·奥塔斯奇拉格; 沃纳·L·凯普林格
Original assignee: Korf Engineering GmbH
Current assignee: Deutsche Voest Alpine Industrieanlagenbau GmbH
Priority date: 1986-10-30
Filing date: 1987-10-30
Publication date: 1988-08-10
Also published as: SK769087A3; KR890006831A; DE3735966C2; UA2125A1; BR8705781A; JPS63118021A; AU597737B2; KR950001909B1; JP2572084B2; PH24466A; AT386006B; SU1582991A3; CZ279319B6; DE3735966A1; DD262676A5; CN1010325B; AU8000587A; CZ769087A3; ATA288686A; IN172088B

Abstract

In this process, metals or metal alloys, especially iron alloys, are recovered after reduction in a reduction zone formed by passing metal oxides through a coal bed of reducing gas. To recover metals that have a strong affinity for oxygen, the coal bed consists of three fixed beds: a bottom layer of degassed coal, below which is a molten pool of liquid reduced metals and slag. In addition, oxygen or an oxygen-containing gas is bubbled through the interlayer to form a high temperature reducing gas, and at some distance above this, fine-grained metal oxide feedstock is added to the interlayer. Combustion gas of carbon particles and oxygen or oxygen-containing gas is added to the top fixed bed.

Description

Method and apparatus for recovering metals and metal alloys

The present invention relates to a method for recovering metals or metal alloys, in particular ferroalloys, and to a device for carrying out the method. The method utilizes a reducing gas to form a reduction zone through a coal bed to reduce the metal oxide.

EP-A-0174,291 describes ｃA process for melting certain fine-grained non-ferrous metal oxidic minerals, such as copper, lead, zinc, nickel, cobalt and tin. In the method, raw materials are fed into a reduction zone formed by a coal fluidized layer in a melting gasification reduction furnace. The metal oxide raw material is reduced into metal after passing through the reduction zone and collected through the bottom of the melting gasification reduction furnace.

EP-A-0174,291 describes that the process is advantageous when the metal oxide is reduced by reaction with elemental carbon at ｃA temperature below 1000 ℃, but that certain problems arise when used for the recovery of metals and metal alloys, particularly ferrous alloys such as iron magnesium, iron chromium and iron silicon alloys. The reason is that the oxides of these alloys can only be recovered at temperatures above 1000 c using elemental carbon as the reducing agent. At such high reaction temperatures, the contact time between the metal oxide feedstock and the carbon particles forming the fluidized layer is short.

It is an object of the present invention to overcome the above disadvantages and difficulties and to provide a method and apparatus. The original intent of such a method and apparatus was to recover metals and metal alloys from fine-grained oxides in a melter gasifier reduction furnace. Especially ferrous alloys such as iron magnesium, iron chromium and iron silicon alloys. In these oxides, the metal has a strong affinity for oxygen and therefore can only undergo a reduction reaction with elemental carbon at elevated temperatures above 1000 ℃.

The method used for this purpose is a coal bed consisting of three fixed layers:

the bottom layer is degassed coal (degassmed coal) with liquid reduced metal and slag thereunder,

-an intermediate layer into which oxygen or some oxygen-containing gas is fed to form a high temperature reducing gas, mainly consisting of CO. At a distance above the layer, a fine-grained oxide raw material is added thereto;

the top layer into which the combustion gases of carbon particles and oxygen or oxygen-containing gases are passed.

It is advantageous when the fine-grained oxide starting material used has a particle size of up to 6 mm.

The particle size of the coal suitable for forming the fixed bed layer may be 5 to 100 mm. Particularly suitable is 5-30 mm.

According to a preferred embodiment, the thickness of the middle and top layers should be kept between 1 and 4 meters.

A further embodiment of the process according to the invention is characterized in that the carbon dust in the form of dust is separated from the oxygen and the aforesaid fine carbon particles which pass through the reduction zone and are fed together with oxygen or oxygen-containing gas to burners which are directed towards the top of the fixed coal seam.

The off-gas separated from the carbon particles can be used as a transport medium for the fine-grained oxide raw material.

The coal used preferably retains its lumped characteristics after the degassing reaction. Therefore, when the size of the coal particles is within 5-100 mm, especially within 5-30 mm, at least 50% of the coal particles obtained after the degassing reaction can still maintain the original particle size range, i.e. 5-100 mm or 5-30 mm, respectively, and the particle size of the rest is less than the above value.

The advantage of the process of the invention is that it maintains all the advantages known from the reduction of a blast furnace heated with fossil fuels, such as the counter-current heat exchange, the metallurgical reaction with elementary carbon in a fixed bed necessary for the reduction of non-noble metal oxides and the good separation of metal and slag. Coking or degassing of coal can be accomplished without producing tar and other condensed components. The gas produced during coal degassing can be used as an additional reducing agent for degassing the reducing gas formed after coal gasification.

In a particular embodiment, the oxide feedstock may be pre-reduced in a pre-reduction process. This is particularly advantageous for the production of ferroalloys. In the process, the reduction of the iron oxide component in the raw material is realized.

The process also has the particular advantage that the reduction of certain non-noble elements, such as silicon, chromium and magnesium, can be carried out without consuming electrical energy. The method for adjusting the energy required for coal degassing in the method of the invention is very simple. The reason is that the pulverized coal with too small particles with the particle size of less than 5mm is discharged along with the waste gas of the melting gasification reducing furnace, separated and returned to the upper blast zone of the oxygen-containing gas and oxidized by the oxygen-containing gas to release heat.

As can be seen from the decomposition property test of the coal particles, the degassing process of the part with the size of 16-20 mm of the coal particles in the reaction chamber preheated to 1400 ℃ needs one hour. The volume of the reaction chamber is 12dm³. The particle distribution was determined after cooling by spraying cold inert gas.

The invention also includes an apparatus for carrying out the above process. I.e. a refractory lined melter gasifier furnace. The upper part of the coal feeding device is provided with a coal feeding port and an exhaust pipe. The side wall openings of the furnace are penetrated by carbon powder and oxygen or oxygen-containing gas supply pipes. The lower part of the furnace is provided with a discharge port for collecting molten metal and slag. The device is characterized by being formed by three superposed fixed beds A, B, C:

an oxygen or oxygen-containing gas blast loop is arranged between the bottom fixed bed layer A and the middle fixed bed layer B;

-providing an annular lance of fine-grained oxide raw material at a distance above the location;

above this point, between the middle fixed bed B and the top fixed bed C, an annular burner is arranged for introducing carbon particles and oxygen or an oxygen-containing gas.

Obviously, it is beneficial to arrange a high-temperature cyclone separator on the exhaust pipeline to separate carbon powder in the exhaust gas and connect the ash outlet of the high-temperature cyclone separator in series with the annular burner.

In a further special embodiment, a further high-temperature cyclone is connected in series with the above-mentioned cyclone. An oxide raw material inlet device is arranged on a connecting pipeline between the two. The ash outlet of the latter cyclone separator is connected with an annular blowing pipe for oxide raw materials by a conveying pipeline.

The method of the invention and the apparatus for carrying out the method are illustrated in detail by the accompanying drawings. Wherein FIG. 1 is a schematic view of a melter-gasifier reduction furnace and its associated equipment, and FIG. 2 is a temperature profile of the melter-gasifier reduction furnace.

In fig. 1, 1 is a melt-down gasification reduction furnace of the blast furnace type, in which a refractory lining 2 is provided. The bottom of the reduction furnace is used for containing liquid metal 3 and slag 4. 5 is a metal discharge port, and 6 is a slag discharge port. A lump coal charging opening 7 is arranged above the reducing furnace. The upper part of the liquid bath 3, 4 is then a fixed coal bed, i.e. a degassed coal bottom layer a, through which no gas passes. The upper layer is a middle layer B of aerated and degassed coal, and the upper layer is a top coal particle layer C, through which gas passes.

A lance, i.e. an annular lance 8, is introduced into the side wall of the reduction furnace 1 for introducing oxygen or oxygen-containing gas, respectively. The tubes are arranged at the intersection of the non-ventilated fixed bed a and the fixed bed B. At some distance above this, i.e. to the middle of the upper part of the fixed bed B, there is provided an annular nozzle-type lance 9, through which fine-grained oxide raw material is blown into the intermediate layer B.

And then upwards, namely at the junction of the layer B and the layer C, the annular burner 10 penetrates through the side wall of the melting gasification reduction furnace 1. From which a mixture of powdered carbon particles and oxygen or an oxygen-containing gas is passed. An exhaust pipe 11 is installed at the upper part of the reduction furnace 1, and exhaust gas generated in the furnace is introduced to a high temperature cyclone 12 through the pipe.

After the carbon particles suspended in the exhaust gas are separated from the hot air separator, the carbon particles pass through an ash outlet of the separator 12, pass through a feeding device 13 at the outlet, and enter the annular burner 10 through a feeding pipe 14. And 15 is a gas pipe for introducing oxygen-containing gas to the burner 10. The degree of filling of the high-temperature cyclone 12 can be adjusted and its separation efficiency influenced by means of the feed device 13.

The upper part of the high-temperature cyclone 12 is connected via a line 16 to a further high-temperature cyclone 17. The feeding device 18 is connected to the line 16. The feeding means is fed by a hopper 19 containing a fine oxide feed material. The gas from line 16 can then be used to export the medium with crop material. Through the ash outlet of the high-temperature cyclone 17 and the conveying pipe 20, and through the pipeline 21, the fine-grained oxide raw material is fed into the blow pipe 9.

An exhaust pipe 22 is led out from the upper end of the high-temperature cyclone 17, and the surplus exhaust gas is discharged therefrom. The discharged exhaust gas may be blown into line 21 via line 23 after cooling and compression to serve as a transport medium.

In carrying out the process of the present invention, it is advantageous to degas the coal charged into the upper part of the melter-gasifier reduction furnace 1 in a fixed bed C. The heat required for coal degassing is partly derived from the hot reducing gas rising from the fixed bed B and partly from the heat generated by the combustion of the solid carbon particles and the oxygen-containing gas in the burner 10. The thickness of the coal seam C is selected to ensure that the temperature of the gas after passing through the seam is not less than 950℃. Thereby ensuring the complete cracking of tar and other condensed components. Thus, the fixed bed layer C is not clogged. In the embodiment, the thickness of the bed layer C is preferably 1 to 4 m. The thickness of the fixed bed layer B is preferably 1-4 m. And (3) the coal in the bed layer C sinks after being degassed to form a fixed bed layer B.

The fine-grained oxide raw material is subjected to a pre-reduction treatment with hot reducing gas and dust in a second high-temperature cyclone 17 and separated again from the gas. It is advantageous to add the fine-grained carbon-containing dust simultaneously with the hot reducing gas, since the carbon is CO formed in the reduction reaction₂CO is produced by the reaction, and thus the high-temperature gas from the reduction furnace 1 is kept extremely reduced. After the pre-reduction treatment, the fine-grained oxide raw material is separated from the dust, melted in the B layer and reduced by the single carbon. The heat required for melting and reduction is provided by introducing an oxygen-containing gas into the reduction furnace through a lance 8 to gasify the high temperature deaerated coal. The molten metal and slag formed in the fixed bed layer B flow downward and are in the layer ACollected and discharged below.

Fig. 2 shows a temperature profile along the height of the melter-gasifier 1, wherein the furnace height is plotted on the ordinate and the temperature is plotted on the abscissa. The solid line indicates the change in temperature of the charged coal, and the broken line indicates the change in temperature of the generated gas. On the ordinate, the reference numeral 8 denotes the height of the

annular lance

8, 9 denotes the height of the fine-grained oxide raw material (ore)

lance

9, 10 denotes the height of the burner 10 for recycling carbon granulate, and 24 denotes the height of the highest point 24 of the fixed bed C. 11 represent the height of the exhaust pipe 11 and the charging port 7, respectively.

Claims

1. A method for recovering metals and metal alloys, such as ferroalloys, wherein metal oxides are reduced in a reduction zone formed by passing a reducing gas through a coal bed, the improvement comprising forming a coal bed having three fixed beds, namely, by

--Provide a fixed bottom bed of degassed coal, below which is a molten pool of liquid reduced metal and slag,

- Providing an intermediate fixed bed layer and introducing oxygen or oxygen-containing gas into it to form a high-temperature reducing gas mainly composed of CO, while adding fine-particle oxide raw materials to this intermediate layer from a certain distance above.

--Provide a top fixed bed layer and introduce a combustible gas consisting of carbon particles and oxygen or some oxygen-containing gas into it.

2. A process as claimed in claim 1, wherein the fine-grained oxide starting material has a particle size of up to 6 mm.

3. The method as claimed in claim 1, wherein the coal particles constituting the three fixed beds have a size of 5 to 100 mm.

4. A method as claimed in claim 3, wherein the coal has a particle size of 5 to 30 mm.

5. The method as claimed in claim 1, wherein the thickness of the middle fixed bed layer and the top fixed bed layer are maintained at 1 to 4 meters.

6. The method as claimed in claim 1, wherein the exhaust gas passes through a fixed bed forming the reduction zone, and further comprising separating pulverized carbon particles from said exhaust gas and introducing them together with oxygen or an oxygen-containing gas into a burner and passing through said top fixed bed.

7. A method as claimed in claim 6, wherein the separated carbon particles are introduced into said burner at a high temperature.

8. A method as claimed in claim 6, wherein exhaust gas from which carbon particles have been removed is used as a transport medium for said fine oxide raw material.

9. An apparatus for recovering metals and metal alloys, such as ferroalloys, wherein the method reduces metal oxides in a reduction zone formed by passing a reducing gas through a coal bed. The apparatus comprises a blast furnace-type melting and gasification reduction furnace with a refractory lining, the upper portion of which has a coal feed port and an exhaust duct, and sidewalls through which gas supply ducts for carbon particles and oxygen or an oxygen-containing gas are inserted. The lower portion of the furnace is used to collect liquid metal and slag. The improved features are:

- providing three overlapping fixed coal beds consisting of a bottom fixed coal bed, a middle fixed coal bed and a top fixed coal bed,

- providing an annular nozzle at a location between the bottom fixed coal bed and the middle fixed coal bed of degassed coal covering the liquid reducing metal and slag bath for introducing oxygen or oxygen-containing gas to form a high-temperature reducing gas mainly composed of CO,

- providing an annular nozzle at a distance above this for introducing fine-grained oxide feedstock,

- At a higher position, an annular burner is provided between the middle fixed bed layer and the top fixed bed layer, into which carbon particles and oxygen or oxygen-containing gas are introduced.

10. The apparatus as claimed in claim 9, further comprising a high temperature cyclone separator for separating carbon particles from the exhaust gas, and further comprising an exhaust duct and connecting means for connecting the separator in series with the annular burner.

11. The apparatus as claimed in claim 10, further comprising

-Another high-temperature cyclone separator with ash outlet,

-Connecting two cyclone separators in series,

- an oxide raw material feeding device connected to this connecting pipe,

- A conveying pipe connecting the ash outlet of the second cyclone separator to the annular nozzle of the oxide raw material.