CN118406823A - Steelmaking method for directly reducing iron ore under vacuum condition - Google Patents
Steelmaking method for directly reducing iron ore under vacuum condition Download PDFInfo
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- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 title claims abstract description 148
- 229910052742 iron Inorganic materials 0.000 title claims abstract description 71
- 238000000034 method Methods 0.000 title claims abstract description 54
- 238000009628 steelmaking Methods 0.000 title claims abstract description 34
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 107
- 239000010959 steel Substances 0.000 claims abstract description 107
- 238000006722 reduction reaction Methods 0.000 claims abstract description 93
- 239000002893 slag Substances 0.000 claims abstract description 38
- 239000007791 liquid phase Substances 0.000 claims abstract description 35
- 230000009467 reduction Effects 0.000 claims abstract description 28
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 26
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 25
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 22
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 21
- 239000001257 hydrogen Substances 0.000 claims abstract description 21
- 239000000843 powder Substances 0.000 claims abstract description 20
- 230000008569 process Effects 0.000 claims abstract description 20
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 claims abstract description 16
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 16
- 239000011593 sulfur Substances 0.000 claims abstract description 16
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 13
- 239000011574 phosphorus Substances 0.000 claims abstract description 13
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 13
- 238000005275 alloying Methods 0.000 claims abstract description 10
- 238000006477 desulfuration reaction Methods 0.000 claims abstract description 9
- 230000023556 desulfurization Effects 0.000 claims abstract description 9
- 230000001105 regulatory effect Effects 0.000 claims abstract description 9
- 239000000126 substance Substances 0.000 claims abstract description 8
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 7
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims abstract description 4
- 239000001301 oxygen Substances 0.000 claims abstract description 4
- 238000010438 heat treatment Methods 0.000 claims description 43
- 239000007789 gas Substances 0.000 claims description 29
- 239000000463 material Substances 0.000 claims description 13
- 230000004907 flux Effects 0.000 claims description 11
- 239000012071 phase Substances 0.000 claims description 11
- 239000002131 composite material Substances 0.000 claims description 9
- 238000007664 blowing Methods 0.000 claims description 8
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 6
- VTYYLEPIZMXCLO-UHFFFAOYSA-L Calcium carbonate Chemical compound [Ca+2].[O-]C([O-])=O VTYYLEPIZMXCLO-UHFFFAOYSA-L 0.000 claims description 4
- 235000019738 Limestone Nutrition 0.000 claims description 3
- 239000001506 calcium phosphate Substances 0.000 claims description 3
- 229910000389 calcium phosphate Inorganic materials 0.000 claims description 3
- 235000011010 calcium phosphates Nutrition 0.000 claims description 3
- 238000000354 decomposition reaction Methods 0.000 claims description 3
- 229910000398 iron phosphate Inorganic materials 0.000 claims description 3
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims description 3
- 239000006028 limestone Substances 0.000 claims description 3
- 239000003345 natural gas Substances 0.000 claims description 3
- QORWJWZARLRLPR-UHFFFAOYSA-H tricalcium bis(phosphate) Chemical compound [Ca+2].[Ca+2].[Ca+2].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O QORWJWZARLRLPR-UHFFFAOYSA-H 0.000 claims description 3
- 229910000019 calcium carbonate Inorganic materials 0.000 claims description 2
- 230000003009 desulfurizing effect Effects 0.000 claims description 2
- 230000003247 decreasing effect Effects 0.000 claims 1
- 238000003723 Smelting Methods 0.000 abstract description 14
- 230000007613 environmental effect Effects 0.000 abstract description 6
- 239000007924 injection Substances 0.000 abstract description 6
- 238000002347 injection Methods 0.000 abstract description 6
- 238000011946 reduction process Methods 0.000 abstract description 5
- 239000000243 solution Substances 0.000 abstract description 3
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- -1 and finally Substances 0.000 abstract 1
- 239000000956 alloy Substances 0.000 description 11
- 239000007788 liquid Substances 0.000 description 11
- 229910045601 alloy Inorganic materials 0.000 description 10
- 239000000292 calcium oxide Substances 0.000 description 10
- ODINCKMPIJJUCX-UHFFFAOYSA-N calcium oxide Inorganic materials [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 10
- 230000001276 controlling effect Effects 0.000 description 8
- 238000004519 manufacturing process Methods 0.000 description 8
- 239000002994 raw material Substances 0.000 description 7
- 239000002912 waste gas Substances 0.000 description 6
- 229910004261 CaF 2 Inorganic materials 0.000 description 5
- 238000007711 solidification Methods 0.000 description 5
- 230000008023 solidification Effects 0.000 description 5
- 229910000851 Alloy steel Inorganic materials 0.000 description 4
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 4
- WUKWITHWXAAZEY-UHFFFAOYSA-L calcium difluoride Chemical compound [F-].[F-].[Ca+2] WUKWITHWXAAZEY-UHFFFAOYSA-L 0.000 description 4
- 229910001634 calcium fluoride Inorganic materials 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 229910002091 carbon monoxide Inorganic materials 0.000 description 3
- 239000003245 coal Substances 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- 229910052751 metal Inorganic materials 0.000 description 3
- 238000005272 metallurgy Methods 0.000 description 3
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- 239000001569 carbon dioxide Substances 0.000 description 2
- 229910002092 carbon dioxide Inorganic materials 0.000 description 2
- 238000004939 coking Methods 0.000 description 2
- 229910001338 liquidmetal Inorganic materials 0.000 description 2
- 230000001590 oxidative effect Effects 0.000 description 2
- 239000008188 pellet Substances 0.000 description 2
- 229910000640 Fe alloy Inorganic materials 0.000 description 1
- 241001417490 Sillaginidae Species 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 1
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- 239000002918 waste heat Substances 0.000 description 1
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- Treatment Of Steel In Its Molten State (AREA)
Abstract
The invention discloses a steelmaking method for directly reducing iron ore under vacuum condition, which comprises the steps of preheating iron ore, mixing with molten steel, and carrying out primary reduction treatment in a mode of gradually increasing vacuum degree in a sectional manner to obtain liquid-phase FeO, and regulating slag alkalinity to solidify phosphorus in slag; then, a final reduction reaction is carried out by adopting a mode of gradually increasing the vacuum degree in a sectional manner, carbon-rich powder, hydrogen-containing substances or injection H 2 are added in stages in the reduction process to accelerate the reduction reaction process until FeO is converted into molten steel, and finally, sulfur fixation, desulfurization and alloying treatment are carried out on the molten steel. The method produces clean molten steel through the direct vacuum reduction reaction of iron ore, wherein the single element S in the steel is controlled to be 5-30 ppm, the P is controlled to be 10-60 ppm, and the total oxygen is controlled to be 5-30 ppm. Compared with the traditional process, the method has the advantages of short flow, low FeO content in the final slag, high molten steel yield, reduced cost per ton of molten steel, effective reduction of carbon emission and good solution for steel smelting and environmental protection.
Description
Technical Field
The invention relates to the technical field of ferrous metallurgy, in particular to a steelmaking method for directly reducing iron ore under vacuum condition.
Background
The traditional clean steel production process mostly adopts a long-process production process mainly comprising a blast furnace and a converter, and has the advantages of high production cost, large environmental pollution and low purity of molten steel. Climate warming caused by current CO 2 emissions has become one of the great challenges facing humans. International energy agency IEA data shows that about 340 million t of carbon emissions are produced worldwide by energy production and consumption in 2023, of which about 15% are produced by the steel industry, and thus, low carbon green is a development direction of the steel industry.
The non-blast furnace ironmaking can avoid the use of coke, omits a coking link, and particularly greatly reduces the emission of harmful gas by hydrogen metallurgy based on direct reduction of a gas-based shaft furnace, so that the rapid development is achieved at present. However, the gas-based shaft furnace reduction must take high-quality oxidized pellets or lump ore as raw materials, and under the conditions of lack of high-quality lump ore and excessive price of imported lump ore in China, oxidized pellets can only be prepared through a series of procedures such as ore dressing, pelletizing, oxidizing roasting and the like, and the process flow is long and the energy consumption is high. In addition, the reducing gas must be heated to a higher temperature to provide the heat required by shaft furnace reduction, and the safety problem of the reducing gas heating process, such as carbon precipitation problem of the hydrogen-rich gas heating process, and the hydrogen corrosion problem of the pure hydrogen heating process, cannot be solved. Therefore, although the gas-based shaft furnace direct reduction process has certain superiority over the traditional iron-making and steel-making process, the gas-based shaft furnace steel-making process is difficult to popularize due to the reasons. The smelting reduction can directly utilize iron concentrate powder, and the reduction and smelting are completed synchronously, so that the process flow is greatly shortened, and the smelting reduction has superiority theoretically compared with gas-based direct reduction, but problems faced by the smelting reduction, including serious scouring of furnace top refractory materials due to high gas-phase space temperature, low heat transfer efficiency of a molten pool due to gas-phase space and the like, are difficult to overcome, and bring a certain influence to stable production.
Carbon is always the most important reducing agent for steel production, but simultaneously, a large amount of carbon dioxide is discharged, and along with the continuous enhancement of environmental awareness, the environmental problem caused by carbon dioxide discharge is urgently solved. With the development of the world steel technology and the change of resource environmental conditions, the realization of low-carbon metallurgy is increasingly focused by metallurgical workers in various countries. The invention aims to solve the defects of the traditional steel production process, and provides the optimal energy-saving and emission-reducing process method by selecting a method for directly reducing iron ore by carbon.
Disclosure of Invention
Aiming at the problems in the prior art, the invention provides a steelmaking method for directly reducing iron ore under vacuum condition, which combines an iron-steel integration method and a vacuum metallurgy method, and directly produces pure molten steel through the vacuum reduction reaction of the iron ore.
The invention is realized by the following technical scheme:
in one aspect, the present invention provides a steelmaking method for directly reducing iron ore under vacuum conditions, comprising the steps of:
Step 1, carrying out vacuum primary reduction reaction on iron ore or a mixed material of the iron ore and molten steel at 1400-1800 ℃ in a mode of gradually increasing vacuum degree in a sectional manner to obtain liquid-phase FeO;
step 2, regulating the alkalinity of slag to carry out phosphorus fixation treatment on liquid-phase FeO;
and step 3, heating the liquid-phase FeO in the step 2 to the final reduction reaction temperature of 1500-1800 ℃, carrying out the final reduction reaction in a mode of gradually increasing the vacuum degree in a sectional manner, adding carbon-rich powder and hydrogen-containing substances into the liquid-phase FeO in a sectional manner in the final reduction reaction process, and obtaining clean molten steel after the final reduction reaction is finished.
Preferably, the mass ratio of the iron ore to the molten steel in the step 1 is (20-100 percent) to (0-80 percent).
Preferably, the molten steel in the step 1 is clean molten steel prepared in the last furnace.
Preferably, in the step 1, the iron ore is preheated at 200-1200 ℃, and the preheated iron ore or the mixture of the iron ore and the molten steel is subjected to primary reduction reaction.
Preferably, the energy source for preheating the iron ore adopts O 2 generated by vacuum decomposition of the iron ore, CO gas generated by reduction reaction or/and natural gas.
Preferably, the method of the vacuum primary reduction reaction in the step 1 is as follows:
Maintaining the pressure for 0-30 min at 3000-5000 Pa, maintaining the pressure for 0-30 min at 1000-2000 Pa and maintaining the pressure for 0-30 min below 100Pa until Fe 2O3 in the furnace burden is converted into liquid-phase FeO.
Preferably, during the vacuum primary reduction reaction, the ratio of Fe 2O3 reduced to FeO is controlled to be more than 80%.
Preferably, caO is added into the slag of the primary reduction reaction in the step 2 to adjust the alkalinity of the slag to 0.8-2.0, so that the iron phosphate phase in the slag is converted into a calcium phosphate phase, and phosphorus is solidified in the slag.
Preferably, in the step 3, adding carbon-rich powder into the liquid-phase FeO in proportion in a plurality of pressure maintaining stages before the final reduction reaction, wherein the addition amount of the carbon-rich powder is gradually reduced;
and adding the hydrogen-containing substances after temperature rise into the liquid-phase FeO in a plurality of pressure maintaining stages after the final reduction reaction.
Preferably, the hydrogen-containing substance is hydrogen gas or a hydrogen-containing material.
The hydrogen is heated to 100-1000 ℃ and added into the liquid-phase FeO in a blowing mode.
Preferably, the total addition amount of the carbon-rich powder is that the molar ratio of FeO to C is more than or equal to 0.5.
Preferably, the method of the final reduction reaction is as follows:
Maintaining the pressure for 0-30 min at 3000-5000 Pa, maintaining the pressure for 0-30 min at 1000-2000 Pa and maintaining the pressure for 0-30 min below 100Pa until FeO in the furnace burden is converted into molten steel.
Preferably, the method further comprises the following steps of carrying out sulfur solidification treatment and desulfurization treatment on the molten steel;
The solidified sulfur treatment process comprises the following steps:
adding flux into clean molten steel to form composite flux, heating the molten steel to 1600-1700 ℃ by adopting an electrode heating mode, and carrying out sulfur curing treatment;
preferably, the composite flux comprises 3-20% of CaF 2,CaCO3 with the content of 0-10% and the balance of CaO according to the mass ratio.
The desulfurization treatment method comprises the following steps:
and regulating the alkalinity of the slag of the final reduction reaction to 2.0-3.5.
Preferably, the method further comprises the following steps: and carrying out alloying treatment on the clean molten steel.
The invention also provides clean molten steel, wherein the content of S element in the molten steel is 5-30 ppm, the content of P element in the molten steel is 10-60 ppm, and the total oxygen content is 5-30 ppm.
Compared with the prior art, the invention has the following beneficial technical effects:
According to the steelmaking method for directly reducing the iron ore under the vacuum condition, firstly, primary reduction reaction is carried out on the iron ore, and the primary reduction reaction is carried out by adopting a mode of increasing the vacuum degree in stages through the primary reduction temperature, so that the ratio of Fe 2O3 to FeO is controlled to be more than 80%; then carrying out final reduction reaction, adding carbon-rich powder and hydrogen-containing materials in stages in the reduction process to accelerate the reduction reaction process until FeO is converted into molten steel, and finally carrying out sulfur fixation, desulfurization and alloying treatment on the molten steel. Compared with the traditional process, the FeO content in the final slag is low, the molten steel yield is high, the cost of each ton of molten steel is reduced, the carbon emission is effectively reduced, and a good solution is provided for steel smelting and environmental protection.
Drawings
FIG. 1 is a flow chart of a steelmaking process for reducing iron ore under vacuum according to the present invention;
FIG. 2 is a graph showing the vacuum level and the reduction rate during the reduction reaction according to the present invention;
FIG. 3 is a schematic view of the structure of the steelmaking apparatus of the present invention.
Detailed Description
The invention will now be described in further detail with reference to the accompanying drawings, which illustrate but do not limit the invention.
Referring to fig. 1 and 2, a steelmaking method for directly reducing iron ore under vacuum conditions, comprising the steps of:
and step 1, performing primary reduction reaction on the mixture of the iron ore and the molten steel in a vacuum environment to obtain liquid-phase FeO.
The preparation method of the mixture furnace burden specifically comprises the following steps:
S1.1, firstly preheating the iron ore raw material, wherein the preheating temperature is 200-1200 ℃.
Optionally, adding the iron ore raw material into a rotary kiln, a shaft furnace or a rotary hearth furnace, heating to 200-1200 ℃, preheating the iron ore, and recovering O 2 generated by the thermal decomposition of the iron ore in the preheating process of the iron ore.
The iron ore raw material is lump ore or powder ore, the powder ore can be prepared into lump material by adopting a ball pressing or rotating disc granulating process, and the granularity of the ball forming of the powder ore is controlled to be 5-50 mm.
S1.2, mixing preheated iron ore or iron ore and molten steel according to a certain mass ratio, and performing vacuum primary reduction reaction at 1400-1800 ℃ in a mode of gradually increasing vacuum degree in a sectional manner to obtain liquid-phase FeO.
Adding preheated iron ore into molten steel of a reducing furnace according to the mass ratio (20-100%) (0-80%). According to the mass ratio, the method can also adopt independent iron ore to carry out reduction reaction to obtain liquid-phase FeO;
Or adding a certain amount of preheated iron ore to perform reduction reaction according to the mass of the residual molten steel in the last furnace in the reduction furnace to obtain a mixture of liquid-phase FeO and molten steel.
The method for the vacuum primary reduction reaction comprises the following steps:
and heating the iron ore or the mixture of the iron ore and molten steel to 1400-1800 ℃ by adopting an electrode heating mode, then carrying out vacuum reduction reaction in three stages, wherein the vacuum degree of reduction treatment is changed from low vacuum to high vacuum, and the pressure maintaining time in each stage is dynamically adjusted according to the concentration of O 2 in waste gas.
The three-stage vacuum reduction reaction process comprises the following steps:
Maintaining the pressure for 0-30 min at 3000-5000 Pa; maintaining the pressure for 0-30 min at 1000-2000 Pa; maintaining the pressure below 100Pa for 0-30 min until Fe 2O3 in the furnace charge is converted into liquid-phase FeO, and controlling the ratio of Fe 2O3 to FeO in the reduction treatment to be more than 80%.
S1.3, after the primary reduction reaction is finished, preparing the alkalinity of the slag to be 0.8-2.0, and treating the solidified phosphorus in the slag.
Under the oxidizing atmosphere of the slag, limestone is added into the slag to adjust the alkalinity of the slag, the iron phosphate phase in the slag is converted into a calcium phosphate phase, so that phosphorus elements are not transferred into molten steel, and the phosphorus elements are solidified in the slag to control the phosphorus content in liquid phase FeO, and the P content is controlled to be 10-60 ppm.
O 2 generated by ore vacuum decomposition and CO gas generated in the reduction process are recovered, the recovered products are used as energy sources for preheating treatment of iron ores, and the CO deficiency part can be supplemented by natural gas.
Step 2, heating liquid-phase FeO to final reduction reaction temperature under vacuum condition, and adopting a mode of gradually increasing vacuum degree in a sectional manner to perform final reduction reaction, wherein carbon-rich powder is added into the liquid-phase FeO in a sectional manner in the final reduction reaction process, and hydrogen-containing materials are added in the final reduction reaction stage to obtain molten steel, and the specific method is as follows:
S2.1, heating the reduction furnace to 1500-1800 ℃ to obtain the final reduction reaction temperature.
S2.2, under the vacuum condition, adding the carbon-rich powder into the liquid-phase FeO in proportion in different pressure maintaining stages, wherein the adding amount of the carbon-rich powder is gradually reduced.
The carbon-rich powder comprises coal dust and C-containing substances, wherein the C-containing substances are carbon-containing and iron-containing materials, and the addition amount of the carbon-rich powder is FeO and the molar ratio of C is more than or equal to 0.5.
S2.3, heating the reducing gas to 100-1000 ℃, and adding the heated reducing gas into a reducing furnace.
The reducing gas is hydrogen-containing material, preferably H 2 gas, and is added into the furnace by one or more of bottom blowing, side blowing or top gun blowing, and when the hydrogen-containing material is solid, the hydrogen-containing material is crushed into powder and blown into the furnace, for example, plastic.
S2.4, carrying out vacuum final reduction reaction in a sectional type step-by-step pressurizing mode until FeO is converted into molten steel.
The vacuum degree of the vacuum final reduction reaction is divided into three sections from low vacuum to high vacuum:
maintaining the pressure for 0-30 min at 3000-5000 Pa; maintaining the pressure for 0-30 min at 1000-2000 Pa; maintaining the pressure below 100Pa for 0-30 min until FeO in the furnace burden is converted into molten steel, dynamically adjusting the pressure maintaining time of each stage according to the concentration of CO in waste gas generated by the final reduction reaction, and adjusting the vacuum degree if the concentration is lower than 5%.
The C content in the molten steel is less than or equal to 0.01 percent.
And step 3, carrying out sulfur curing treatment on the molten steel.
Adding CaO+CaCO 3+CaF2 composite flux into molten steel, heating the molten steel to 1600-1700 deg.C by means of electrode heating, and curing sulfur treatment.
The content of CaF 2 in the composite flux is 3-20%, the content of CaCO 3 is 0-10%, and the balance is CaO.
In the reducing atmosphere of slag, the alkalinity of slag is regulated, sulfur in slag reacts with calcium oxide to form CaS, so that sulfur element is not transferred to molten steel and is solidified in slag, and the purpose of controlling the sulfur content in molten steel is achieved.
And 4, desulfurizing the molten steel obtained in the step 3.
The desulfurization treatment can be carried out under vacuum and non-vacuum conditions, and the alkalinity of slag is controlled between 2.0 and 3.5.
And 5, carrying out alloying treatment on the desulfurized molten steel to obtain liquid alloy steel.
The molten steel alloying treatment method is that various iron alloy materials are added under vacuum according to the component requirements of steel types to carry out alloying treatment, so as to obtain liquid alloy steel, wherein the single element S of the liquid alloy steel is controlled to be 5-30 ppm, the P is controlled to be 10-60 ppm, and the total oxygen is controlled to be 5-30 ppm.
Example 1
A steelmaking method for directly reducing iron ore under vacuum condition comprises the following steps:
step 1, preheating iron ore with granularity of 10-30 mm to 850 ℃ in a rotary kiln mode, wherein the heated gas is recovered gas CO and O 2.
And 2, adding the preheated iron ore into molten steel remained in the previous furnace according to the mass ratio of 1:1 to obtain mixed furnace charge.
And step 3, heating the mixed furnace burden to the reduction reaction temperature for carrying out vacuum primary reduction reaction to obtain a mixed liquid of liquid-phase FeO and molten steel.
Heating liquid-phase FeO molten steel to 1640 ℃ by adopting an electrode heating mode, and then carrying out vacuum pre-reduction treatment. Wherein, the pressure is maintained for 10min at 3000 Pa-5000 Pa; maintaining the pressure for 5min at 1000-2000 Pa; maintaining the pressure below 100Pa for 3min, and controlling the pre-reduction degree of the primary reduction treatment iron ore at 85%.
And 4, regulating the alkalinity of slag generated by the primary reduction reaction to be 1.5, and carrying out phosphorus solidification treatment.
And 5, carrying out final reduction reaction on the liquid-phase FeO in the mixed liquid to obtain molten steel.
And heating the FeO-containing molten steel to 1600 ℃ by adopting an electrode heating mode. Vacuumizing, maintaining the pressure for 10min at 3000 Pa-5000 Pa, and simultaneously adding first pulverized coal with the granularity of less than or equal to 3mm by adopting an alloy chute, wherein the adding amount is 222.94 kg/ton iron; maintaining the pressure at 1000-2000 Pa for 5min, and simultaneously adopting a top blowing mode to blow H 2,H2, and controlling the temperature at 400 ℃ after preheating treatment; maintaining the pressure below 100Pa for 3min. After the reaction is finished, measuring the temperature and sampling, wherein the content of C in the obtained molten steel is controlled to be less than or equal to 0.01 percent.
And 6, heating the molten steel to 1650 ℃ by adopting an electrode heating mode, adding CaO+CaCO 3+CaF2 composite flux into an alloy chute for sulfur curing treatment, wherein the content of CaF 2 is 15%, the content of CaCO 3 is 8%, and the balance is CaO according to the mass ratio.
And 7, adjusting the alkalinity of the slag to 3.0 for desulfurization treatment.
And 8, carrying out alloying treatment on the desulfurized molten steel to obtain alloy molten steel.
And adding alloy elements according to the component Q235B of the steel grade to obtain Q235B molten alloy steel.
Example 2
A steelmaking method for directly reducing iron ore under vacuum condition comprises the following steps:
And step 1, preheating iron ore with granularity of 10-30 mm to 1200 ℃ in a rotary kiln mode, wherein the heated gas is recovered gas CO and O 2.
And 2, adding preheated iron ore into molten steel remained in the previous furnace according to the mass ratio of 2:8, so as to obtain mixed furnace charge.
And step 3, heating the mixed furnace burden to the reduction reaction temperature for carrying out vacuum primary reduction reaction to obtain a mixed liquid of liquid-phase FeO and molten steel.
Heating liquid-phase FeO molten steel to 1400 ℃ by adopting an electrode heating mode, and then carrying out vacuum pre-reduction treatment. Wherein, the pressure is maintained for 30min at 3000 Pa-5000 Pa; maintaining the pressure for 10min at 1000-2000 Pa; maintaining the pressure below 100Pa for 30min, and controlling the pre-reduction degree of the primary reduction treatment iron ore to be 90%.
And 4, regulating the alkalinity of slag generated by the primary reduction reaction to be 2, and carrying out phosphorus solidification treatment.
And 5, carrying out final reduction reaction on the liquid-phase FeO in the mixed liquid to obtain molten steel.
And heating the FeO-containing molten steel to 1800 ℃ by adopting an electrode heating mode. Vacuumizing, maintaining the pressure for 5min at 3000 Pa-5000 Pa, and simultaneously adding first pulverized coal with the granularity of less than or equal to 3mm by adopting an alloy chute, wherein the adding amount is 222.94 kg/ton iron; maintaining the pressure for 30min at 1000-2000 Pa, and simultaneously adopting a point blowing mode to blow H 2,H2, and controlling the temperature at 400 ℃ after the preheating treatment; maintaining the pressure below 100Pa for 20min. After the reaction is finished, measuring the temperature and sampling, wherein the content of C in the obtained molten steel is controlled to be less than or equal to 0.01 percent.
And 6, heating the molten steel to 1700 ℃ by adopting an electrode heating mode, adding CaO+CaCO 3+CaF2 composite flux into an alloy chute for sulfur curing treatment, wherein the content of CaF 2 is 15%, the content of CaCO 3 is 8%, and the balance is CaO according to the mass ratio.
And 7, adjusting the alkalinity of the slag to 3.5 for desulfurization treatment.
And 8, carrying out alloying treatment on the desulfurized molten steel to obtain alloy molten steel.
Example 3
A steelmaking method for directly reducing iron ore under vacuum condition comprises the following steps:
Step 1, preheating iron ore with granularity of 10-30 mm to 200 ℃ in a rotary kiln mode, wherein the heated gas is recovered gas CO and O 2.
And 2, adding preheated iron ore into the furnace.
And step 3, heating furnace burden to the reduction reaction temperature for carrying out vacuum primary reduction reaction to obtain a mixed solution of liquid-phase FeO and molten steel.
Heating liquid-phase FeO molten steel to 1800 ℃ by adopting an electrode heating mode, and then carrying out vacuum pre-reduction treatment. Wherein, the pressure is maintained for 25min at 3000 Pa-5000 Pa; maintaining the pressure for 5min at 1000-2000 Pa; maintaining the pressure below 100Pa for 20min, and controlling the pre-reduction degree of the primary reduction treatment iron ore to be 95%.
And 4, regulating the alkalinity of slag generated by the primary reduction reaction to be 0.8, and carrying out phosphorus solidification treatment.
And 5, carrying out final reduction reaction on the liquid-phase FeO in the mixed liquid to obtain molten steel.
And heating the FeO-containing molten steel to 1500 ℃ by adopting an electrode heating mode. Vacuumizing, maintaining the pressure for 10min at 3000 Pa-5000 Pa, and simultaneously adding first pulverized coal with the granularity of less than or equal to 3mm by adopting an alloy chute, wherein the adding amount is 222.94 kg/ton iron; maintaining the pressure at 1000-2000 Pa for 5min, and simultaneously adopting a top blowing mode to blow H 2,H2, and controlling the temperature at 400 ℃ after preheating treatment; maintaining the pressure below 100Pa for 30min. After the reaction is finished, measuring the temperature and sampling, wherein the content of C in the obtained molten steel is controlled to be less than or equal to 0.01 percent.
And 6, heating the molten steel to 1600 ℃ by adopting an electrode heating mode, adding CaO+CaCO 3+CaF2 composite flux into an alloy chute for sulfur curing treatment, wherein the content of CaF 2 is 15%, the content of CaCO 3 is 8%, and the balance is CaO according to the mass ratio.
And 7, adjusting the alkalinity of the slag to 2 for desulfurization treatment.
And 8, carrying out alloying treatment on the desulfurized molten steel to obtain alloy molten steel.
The invention optimizes the existing steelmaking process, eliminates the coking, sintering and other processes of the original steel-iron smelting process, directly reduces the iron ore by utilizing a vacuum electric converter smelting device, a small amount of carbon-rich raw materials and reducing gas, and smelts the iron ore into clean molten steel in one step. A new low-cost clean steel production process flow is explored, the steel quality is effectively improved, and the smelting cost is reduced. Compared with the traditional process, the method has the advantages of low FeO content in the final slag, high molten steel yield, reduced cost per ton of molten steel, effectively reduced carbon emission, and good solution for steel smelting and environmental protection.
The invention also provides a steelmaking device which is similar to the steelmaking method for reducing iron ore under the vacuum condition, and the steelmaking device comprises a vacuum electric converter main body 1, a vacuum system 2, an electrode heating system 3, a raw material injection system 4, a reducing gas injection system 5, a charging system 6 and a metal liquid discharging system 7.
The furnace body of the vacuum electric converter main body 1 is cylindrical, the top parts of the furnace body are conical, and the furnace body is provided with a tipping system and can tilt back and forth; the vacuum system is arranged at the top of the vacuum electric converter main body 1 through a lifting device and is used for sealing a furnace body, and the electrode heating system 3 is arranged in the vacuum system 2 and is used for heating furnace burden in the furnace body in a sealing state. The charging system 6 is arranged at the top of the vacuum system 2 and is used for adding iron ore into the furnace body.
The vacuum system 2 is a steam pump vacuum system and is combined with the lower furnace body in a sealing way through a lifting device.
The electrode heating system 3 adopts a three-phase alternating current heating electrode.
The raw material injection system 4 is arranged at the bottom of the furnace body and is used for adding limestone into molten steel to carry out phosphorus solidification treatment, the raw gas injection system 5 is arranged on the side wall of the lower part of the furnace body and is used for adding reducing materials into the molten steel to accelerate the reduction reaction, and the outlet end of the reducing gas injection system 5 extending out of the bottom of the furnace body is positioned in liquid metal in the smelting furnace, so that when gas is injected, the liquid metal forms a gushing shape, and the full progress of the reduction reaction and the heat transfer are facilitated. The upper side wall of the furnace body is provided with a metal liquid discharge system 7, and molten steel flows out by tilting the furnace body.
In the one-step reduction process of iron ore, pure molten steel and molten slag phases are automatically layered due to different specific gravities, furnace charges are reduced in vacuum to obtain pure molten steel, the pure molten steel is discharged by a metal liquid discharge system, the molten slag phases are discharged by a slag discharge system, waste gas generated in the reaction is discharged from a smelting furnace through a waste gas discharge port at the top of a smelting furnace body, and waste heat of the discharged waste gas is used for carrying out preheating treatment on the iron ore or generating electricity or generating reducing gas through a waste gas reprocessing device, and the reducing gas is sprayed into the smelting furnace again for reference and reduction reaction.
The above is only for illustrating the technical idea of the present invention, and the protection scope of the present invention is not limited by this, and any modification made on the basis of the technical scheme according to the technical idea of the present invention falls within the protection scope of the claims of the present invention.
Claims (16)
1. A steelmaking method for directly reducing iron ore under vacuum conditions, comprising the steps of:
Step 1, carrying out vacuum primary reduction reaction on iron ore or a mixed material of the iron ore and molten steel at 1400-1800 ℃ in a mode of gradually increasing vacuum degree in a sectional manner to obtain liquid-phase FeO;
step 2, regulating the alkalinity of slag to carry out phosphorus fixation treatment on liquid-phase FeO;
and step 3, heating the liquid-phase FeO in the step 2 to the final reduction reaction temperature of 1500-1800 ℃, carrying out the final reduction reaction in a mode of gradually increasing the vacuum degree in a sectional manner, adding carbon-rich powder and hydrogen-containing substances into the liquid-phase FeO in a sectional manner in the final reduction reaction process, and obtaining clean molten steel after the final reduction reaction is finished.
2. The steelmaking process as claimed in claim 1, wherein the mass ratio of said iron ore to molten steel in step 1 is 20 to 100% and 0 to 80%.
3. The steel making method by directly reducing iron ore under vacuum according to claim 1, wherein said molten steel in step 1 is clean molten steel produced in the previous furnace.
4. The steelmaking process as claimed in claim 1, wherein the iron ore is preheated at 200 to 1200 ℃ in step 1, and the preheated iron ore or the mixture of the iron ore and the molten steel is subjected to primary reduction.
5. The method according to claim 4, wherein the preheated energy source of the iron ore is O 2 produced by vacuum decomposition of the iron ore, CO gas produced by reduction reaction or/and natural gas.
6. The steelmaking process as claimed in claim 1, wherein said primary vacuum reduction reaction in step 1 is carried out by:
Maintaining the pressure for 0-30 min at 3000-5000 Pa, maintaining the pressure for 0-30 min at 1000-2000 Pa and maintaining the pressure for 0-30 min below 100Pa until Fe 2O3 in the furnace burden is converted into liquid-phase FeO.
7. The steelmaking process as claimed in claim 1, wherein the ratio of Fe 2O3 to FeO is controlled to be greater than 80% during the primary vacuum reduction reaction.
8. The steelmaking process as claimed in claim 1, wherein in step 2, limestone is added to the primary reduction slag to adjust the slag basicity to 0.8 to 2.0, thereby converting the iron phosphate phase in the slag into calcium phosphate phase and solidifying the phosphorus in the slag.
9. The steelmaking process as claimed in claim 1, wherein in step 3, carbon-rich powder is added in proportion to the liquid-phase FeO in a plurality of pressure-maintaining stages before the final reduction reaction, and the addition amount of the carbon-rich powder is gradually decreased;
and adding the hydrogen-containing substances after temperature rise into the liquid-phase FeO in a plurality of pressure maintaining stages after the final reduction reaction.
10. A steelmaking process as claimed in claim 1 or 9 wherein said hydrogen-containing material is hydrogen or a hydrogen-containing material.
The hydrogen is heated to 100-1000 ℃ and added into the liquid-phase FeO in a blowing mode.
11. The steelmaking process as claimed in claim 1, wherein the carbon-rich powder is added in a total amount such that the molar ratio of FeO to C is not less than 0.5.
12. The steelmaking process as claimed in claim 1 wherein said finishing reduction is carried out by:
Maintaining the pressure for 0-30 min at 3000-5000 Pa, maintaining the pressure for 0-30 min at 1000-2000 Pa and maintaining the pressure for 0-30 min below 100Pa until FeO in the furnace burden is converted into molten steel.
13. The steelmaking process as claimed in claim 1, wherein the process comprises the steps of solidifying sulfur and desulfurizing molten steel;
The solidified sulfur treatment process comprises the following steps:
adding flux into clean molten steel to form composite flux, heating the molten steel to 1600-1700 ℃ by adopting an electrode heating mode, and carrying out sulfur curing treatment;
The desulfurization treatment method comprises the following steps:
and regulating the alkalinity of the slag of the final reduction reaction to 2.0-3.5.
14. The steelmaking process as claimed in claim 13, wherein said composite flux comprises 3 to 20% caf 2,CaCO3 by mass, 0 to 10% by mass, and the balance CaO.
15. The steelmaking process as claimed in claim 1 or 11, wherein the process further comprises the steps of: and carrying out alloying treatment on the clean molten steel.
16. The clean molten steel produced by the steel-making process of any one of claims 1-15, wherein the molten steel has an S element content of 5-30 ppm, a p element content of 10-60 ppm, and a total oxygen content of 5-30 ppm.
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