DE2133860A1 - Direct reduction of iron ore - using cyclone furnace and electric arc or induction furnace - Google Patents

Abstract

Iron ore is reduced directly to pure molten iron in a continuous process. The crushed and magnetically separated material is preheated in a fluidised bed at 850-900 degrees C, where sulphur is removed. Two further fluidised beds at 700 degrees C reduce the remaining Fe2O3 to Fe and FeO. This mixture passes into the main cyclone furnace where it reacts with a mixture of H2 and CO at 1000 degrees C, granulated limestone being fed in as a flux. The remainder of the FeO is reduced to Fe and the liquid iron collects on the hearth of the electric furnace underneath, which is integral with the cyclone. P and Si are removed in the slag and the pure iron is topped off, either intermittently or continuously. The cyclone waste gases, containing H2, H2O, CO and CO2, pass through a heat exchanger and are then cleaned and reconstituted with methane to form H2 and CO for reuse in the cyclone. Removal of sulphur prevent sticking in the cyclone furnace, where the reduction is relatively rapid.

Description

Process for making iron from iron ore The invention relates to a process for making iron from iron ore. This is where the iron ore melted and it becomes pure iron, which is very easily and simply converted into steel can be made directly from iron ore.

The inventive method is through the following process steps marked: 1. Processing iron ore into a fine powder; 2. Separating part of the gangue from the iron ore in a cyclone; 3. Treatment of the remaining ore using a magnetic separation process to separate the non-ferromagnetic gait; 4. Preheating the iron ore from the magnetic Separator in a fluid bed heater; 5. Treatment of the heated iron ore with a pre-reduction process in a fluidized bed reactor; 6. Supply of the reduced Iron ore to a cyclone furnace, the carbon monoxide and hydrogen at one temperature of approx. 10000C, whereby the iron ore finally becomes "sponge iron" (sponge iron) is reduced; 7. Simultaneous supply of granular limestone to the cyclone furnace; 8. Collect the sponge iron without exposure to atmospheric influences in an electrically heated furnace in which an iron bath is formed, on the surface of which a bed of slag is formed; 9. Parting off of the molten iron from the bath as needed.

In this method according to the invention, finely ground iron ore is obtained after preliminary separation of the gangue in a cyclone by a magnetic field and the non-magnetic gangue is separated from the iron oxide particles. These iron oxide particles are then preheated in a fluid bed to remove sulfur to remove and to heat the oxide particles to 9000C in order to avoid sticky phases the subsequent reduction can be avoided. The pre-reduction will eventually completed in fluid beds. The pre-reduced sponge iron particles that are up to Contains 30% FeO, it turns into sponge iron in a cyclone oven uncontaminated CO and H2 gas reduced at 10000C. The open base of the cyclone is the top of a lowered electric arc or induction furnace. The fully reduced Sponge iron ducks from the cyclone with 10000C falling into the closed arc or induction furnace for the final Melt.

The electric furnace has a 6 - 8 "basic slag bed in which Electrodes are in place (if an arc furnace is used). Through 0 the stream a temperature of 1600 C is maintained in the molten slag bed. The sponge particles fall onto the bed of slag and melt at 156.0 ° C.

The molten iron flows through the slag and collects in the oven. Here, almost the entire phosphorus and sulfur content of the iron is used reacted with the basic slag and thereby bound. Any Silica and silica particles contained in the iron particles and have not yet been removed are also with the basic slag reacted and absorbed therein.

Further details of the method according to the invention are given below described with reference to the flow chart shown in the drawing.

(impact air mill) In a suitable 5 ubleg is made up of lumps Iron ore ground into fine particles of sufficient fineness for the Process according to the invention have (z. B. 200 mesh sizes). Part of the gait (Silicon oxide and alumina) is removed by a dust extractor of a cyclone 2, by introducing the ground iron ore particles. These ground iron ore particles are then fed to a magnetic separator 3 by the non-magnetic gait (Silicon oxide, substances containing phosphorus and manganese) from magnetic iron ore particles The cleaned iron ore particles are then placed in a preheating fluid bed 4a introduced, which is heated that with compressed air some of the waste gases from the Zy Ron furnace 6 are burned. Through the preheating fluid bed the sulfur content of the ground ore is also reduced since the bed is 0 on 850 to 900 0 is heated.

B The drawn off overflow of the preheating bed flows with one temperature of 9000C under the action of gravity in a two-stage prereduction fluid bed 4. Each bed receives reducing gases from the cyclone furnace 6, thereby making the beds be kept in the fluid state and Fe2O3 is reduced to Fe + FeO. Both reduction beds have a temperature of 7000C. The product withdrawn from the second reduction bed contains mainly Fe and up to 30% FeO.

The overflow of the second fluid bed 4 flows under the action of gravity in the cyclone furnace 6, at the entrance of which he is with a gas stream of almost pure H2 + CO meets (bubbles up to 10000C).

Granular limestone from a container 5 is also attached to this Place the cyclone 6 added so that in the electrical described in more detail below Furnace 7 sulfur, silicon dioxide and impurities not previously removed have been converted into slag.

The final FeO content is determined in the cyclone by blowing hydrogen and carbon monoxide reduced quickly. The reduced sponge iron particles fall at 100000 on the surface of the slag bed of the electric furnace 7 where they-at f5600C are melted and covered by a layer of molten basic slag (formed by the limestone) seep into the hearth of the stove. Through the slag layer Any phosphorus-containing substances or silicon dioxide and silicon oxide are absorbed.

The cyclone furnace 6 is a steel-clad container of a basic one dry cyclone lined with refractory bricks made of alumina cement and has a water-cooled or fire-resistant central exhaust duct. Of the electric furnace 7 is either an electric arc furnace or an induction furnace and forms the base. of the cyclone 6.

If an arc furnace is used, the electrodes have that are arranged in an oxygen-free, reducing atmosphere, a long time Lifespan. They are placed in a basic cinder bed with a depth of 15 up to 20 cm, which has a uniform temperature of 0 approx. 16000C above the entire furnace surface forwards.

The pure molten iron can be continuous or intermittent be drained from the electric furnace as needed.

0 The exhaust gases from the cyclone 6 have a temperature of 950 to 1000 0 and contain H2, H2O, CO, CO2, a small amount of dust (not reduced tes SiO2 Al2O3). Part of the gas is used for the pre-reduction stages in the fluidized beds 4 and 4a derived. The exhaust gases from this combine with the exhaust gases from the cyclone furnace and are then passed together through a heat exchanger s. The warmth of the Heat exchanger 8 generates steam in a steam turbine 9 to generate electrical energy can be used. The gas and dust of the heat exchanger are fed to a scrubber 10, where cooling to a temperature below 10000 takes place. The water and dust are then drawn off.

The gas containing water vapor, H2CO + CO2 is then put on a gasometer 11 supplied. Excess gas, which has a high calorific value, is used Generation of electrical energy used by being sent to a gas turbine 12 will. Part of the gas is returned and reconstituted, by pumping it by means of a fan 13 through Kieselstenöfen 14, which with Pebbles are filled from substances rich in silicon dioxide, with a coating with a catalyst, e.g. Nickel sulphate, is provided.

The pebble ovens are alternately preheated to approx. 14300C by adding Waste gas is burned. When this temperature has been reached, the gas will from the gasometer together with natural gas, volatile combustion oil or methane gas from a container 15 supplied to the recirculated gas, which by the preheated Pebble furnaces is blown through. The following reactions take place here.

CH4 + CO2 = 2CO + 2H2 CH4 + H2O = CO + 3H2 The returned gas and the volatile oils or the natural gas react with the water vapor and the carbon dioxide to CO + H2.

The KiesSeS Ln are either blown or heated. The hot gas CO + H2 is then fed to a desulfurization arrangement 17 at 11000C, where the Sulfur is removed by reaction with limestone. The calcium carbonate is in Calcium sulphate and carbon monoxide converted.

Desulfurization is only required if the sulfur content of the oil or gas makes sulfur removal necessary.

When the plant is put into operation, a gas generator 16 used to charge the system with CO gas. It is also possible to be low charcoal, coke, bone charcoal, charcoal, etc.

in connection with the recirculated gas and the natural gas respectively.

To use fuel oil.

When methane, natural gas or volatile hydrocarbons don't are freely available, cheap carbonaceous substances can be used as follows will. Part of the gas from the gasometer that was previously in the pebble ovens at 1436OC has been heated, can through a column of inferior coke, car coke (car coke), cheek charcoal etc. are passed through. The due to the gases on Column heated to 10000C reduces the C02 to 2CO. The free carbon is consumed and the hot gases are blown into the cyclone furnace, the temperature due to the endothermic reaction C + CO2 = 2CO is lower.

Since a wide range of different types of steel is desired, it is necessary for the direct production of steel from iron ore that here the necessary precautions are taken. Also because of this uses an intermittent procedure.

The main aspect of the invention is the training and the mode of operation of the Zykion furnace is of great importance in direct steel production. The reduced iron ore particles are in the electric arc furnace or melted in the induction furnace that forms the bottom of the cyclone. The melted one Iron, which is free from absorbed carbon, silica and silicon dioxide, phosphorus, Manganese and sulfur is removed from the electric furnace as a molten iron deducted high quality, to which only carbon and alloy elements are added must be made to a high or low carbon steel or an alloy steel to create.

In blast furnace operation, iron ore is reduced to pig iron. The melted one Iron absorbs carbon up to 4, 5%, as well as other impurities, sulfur, Phosphorus, manganese, silicon etc when it comes to red iron ore, limestone and coke trickles down and collects in the hearth of the stove. With the withdrawal from the blast furnace are in the pig iron both the absorbed as well as the contained Contain impurities of gout.

These impurities are subsequently found in a Bessemer pear removed in an open hearth furnace or by blowing oxygen. The amount of carbon Phosphorus, manganese, silicon, sulfur, etc., which are present in the molten iron is reduced to the minimum required for the respective steel production.

It is advantageous that, according to the invention, the impurities, such as Silicon, phosphorus and manganese and compounds containing these substances from the finely divided iron ore can be removed magnetically, while sulfur in particular is withdrawn by the preheating fluid bed and the heat present therein. By this procedure of the invention becomes the reduction of fine iron particles promoted, which takes place in a completely reducing atmosphere that is free of any impurities. Because there is no free carbon in the reducing gases is present, any problem of possible carbon absorption is caused avoided the iron.

Since the fine particles of oxide in the hot reducing gases are completely can be reduced in approx. 30 minutes, there is a very considerable time saving, since 6 to 8 hours are required when processing large lumps of iron ore in the blast furnace will. The direct steel process according to the invention thus works very quickly and can also be carried out continuously.

Another advantage is that according to the invention no expensive and extensive facilities are required, such as a blast furnace and an open hearth steel plant represent. Nitrogen and oxygen are excluded from the closed gas cycle. It is also advantageous that metallurgical Coke that is used by the conventional iron and steel plants is not an expensive raw material is required to produce a high quality steel according to the invention.

According to the invention, the following points are of particular importance.

1. Iron ore becomes metallic sponge iron through reducing gases reduced at approx. 8500C, but melting takes place at 15590C.

of 2. Lumps of iron ore require a / time up to 8 hours in a blast furnace for reduction and conversion to the melting state. However, when such lumps of iron ore are ground, e.g., to a particle size of 200 mesh sizes, there is a very large surface for the reaction gases. In addition, the heat is absorbed very quickly and there is a permanent reduction to sponge iron in 30 minutes by pure hydrogen 0 or carbon monoxide 1000 C instead.

3. Since all gases in the system are reactive (atmosphere is excluded8, only a low pressure of hot concentrated CO + H2 is required, to reduce the iron ore particles.

In comparison, in a blast furnace there is a high pressure when blowing air necessary.

4. Carbon dioxide and water vapor react with methane, natural Gas and volatile hydrocarbons to produce carbon monoxide and hydrogen at 14300C in the presence of a catalyst in the silica furnace.

5. The recycled and reconstituted gas can be used outside on the Reduction temperature of the iron ore and heated in a cyclone furnace with finely ground, pre-reduced Blown iron ore. and there is a magnetic concentration, so that pure sponge iron is produced as a raw material for steel production can be. This avoids an expensive arrangement resulting from the combination a blast furnace and an open hearth furnace for steel production.

6. The iron ore particles do not come into contact with free carbon or other impurities. Therefore, the carbon and the impurities not absorbed and therefore do not have to be removed.

7. The complete reduction of all FeO by a fluidized bed process is very difficult. The cyclone furnace not only completes this reduction, but overcomes that normally occurs in the combustion of fine hot iron particles Problems occurring in oxygen by keeping the sponge iron particles under exclusion melted by atmosphere.

8. In the Zykjofl? En, fine particles of sponge iron are controlled under bubble control reduced conditions and {what was previously considered impossible.

9. The magnetic separation of the gangue particles from the finely ground ones Elsenic oxide particles avoid the costly slag and dust problems in the cyclone furnace, while preheating these particles to 9000C in the fluidized bed effectively removes the sulfur removed and thereby adhesion problems that would otherwise occur with a reduction at lower Temperature arise, to be overcome.

Claims (6)

Claims 1. Process for the production of iron from iron ore, characterized by the following process steps: 1. The iron ore is processed into a fine powder; 2. Part of the gangue is separated from the iron ore in a cyclone; 3rd to Separating the non-ferromagnetic gangue, the remaining ore becomes a magnetic one Subject to separation process; 4. the iron ore from the magnetic separation process is preheated in a fluid bed heater; 5. The heated iron ore is in one Fluid bed reactor subjected to a pre-reduction; 6. the reduced iron ore becomes fed to a cyclone furnace, the carbon monoxide and hydrogen at one temperature of approx. 1000 ° C, the iron ore eventually becoming sponge iron is reduced; 7. At the same time granulate-like limestone is added to the cyclone furnace fed; 8. With the exclusion of the atmosphere, the sponge iron becomes electric in one heated furnace collected by forming an iron bath on its surface a slag bed forms; 9. The molten iron will ever come from the iron bath drained as needed. 2. The method according to claim 1, characterized in that the iron ore first ground in a suitable mill to 200 mesh particles will. 3. The method according to claim 1 or 2, characterized in that the fluid bed heater is heated to 850 to 9000C by using waste gases from the cyclone furnace be burned in compressed air. 4. The method according to one or more of the preceding claims, characterized in that the fluid bed in which the pre-reduction takes place is heated by waste gases from the cyclone furnace and that the reduction through this Gases is effected. 5. The method according to one or more of the preceding claims, characterized in that the electrically heated furnace is an electric arc furnace whose electrodes are immersed in a layer of slag that is on the surface of the iron collected in the furnace. 6. The method according to one or more of the preceding claims, characterized in that the cyclone furnace supplied monoxide and hydrogen through Cracking of volatile hydrocarbons are produced with gases, which are returned from the cyclone furnace to pebble furnaces, which are made with alumina pebbles are provided, wherein a catalyst coating is used and wherein further the ovens are alternately heated by burning waste gas and for cracking to be used.