EFFICIENT LONG-SERVICE-LIFE BLOWING METHOD AND SYSTEM FOR VANADIUM EXTRACTION-DECARBURIZATION DUPLEX CONVERTERS

Abstract

An efficient long-service-life blowing method include the steps of introducing vanadium extraction converter flue gas and decarburization converter flue gas into an oxygen combustor; obtaining first-purity CO.sub.2N.sub.2 mixed gas through the vanadium extraction converter flue gas; obtaining second-purity CO.sub.2N.sub.2 mixed gas through the decarburization converter flue gas; obtaining O.sub.2CO.sub.2N.sub.2 mixed gas through the decarburization converter flue gas; obtaining first-purity CO.sub.2 gas through the second-purity CO.sub.2N.sub.2 mixed gas; and using the first-purity CO.sub.2N.sub.2 mixed gas for bottom blowing of the vanadium extraction converter, using the second-purity CO.sub.2N.sub.2 mixed gas as a carrier gas for blowing iron ore powder into the vanadium extraction converter, and using the O.sub.2CO.sub.2N.sub.2 mixed gas and the first-purity CO.sub.2 gas as a carrier gas for bottom blowing of the decarburization converter and bottom injecting of lime powder into the decarburization converter.

Claims

1. An efficient long-service-life blowing method for vanadium extraction-decarburization duplex converters, wherein a staged control strategy is adopted in a smelting process of a vanadium extraction converter and a decarburization converter, the proportion and flow rate of gas media with different purities are adjusted in stages, and the method comprises the following steps: introducing vanadium extraction converter flue gas and decarburization converter flue gas into an oxygen combustor separately; carrying out complete combustion on the vanadium extraction converter flue gas in an oxygen atmosphere to obtain a first-purity CO.sub.2N.sub.2 mixed gas; carrying out complete combustion on the decarburization converter flue gas in an oxygen atmosphere to obtain a second-purity CO.sub.2N.sub.2 mixed gas; carrying out oxygen-excess combustion on the decarburization converter flue gas in an oxygen atmosphere to obtain a O.sub.2CO.sub.2N.sub.2 mixed gas; introducing a first part of the second-purity CO.sub.2N.sub.2 mixed gas into a purification device to obtain a first-purity CO.sub.2 gas; and using the first-purity CO.sub.2N.sub.2 mixed gas for bottom blowing of the vanadium extraction converter, using a second part of the second-purity CO.sub.2N.sub.2 mixed gas as a carrier gas for blowing iron ore powder into the vanadium extraction converter, and using a third part of the second-purity CO.sub.2N.sub.2 mixed gas, the O.sub.2CO.sub.2N.sub.2 mixed gas and the first-purity CO.sub.2 gas for bottom blowing of the decarburization converter and as a carrier gas for bottom injecting of lime powder into the decarburization converter.

2. The method according to claim 1, wherein the gas media with different purities are respectively used in different smelting stages of the vanadium extraction converter and the decarburization converter as follows particularly: in the smelting process of the vanadium extraction converter, bottom blowing the first-purity CO.sub.2N.sub.2 mixed gas in the whole process, and the bottom blowing intensity is 0.03-0.3 Nm.sup.3/t/min; in the early smelting stage and the middle smelting stage of the vanadium extraction converter, using the second part of the second-purity CO.sub.2N.sub.2 mixed gas as a carrier gas for blowing iron ore powder into the converter, stabilizing the temperature of molten bath, the gas supply intensity is 0.1-0.5 Nm.sup.3/t/min, and the iron ore powder supply intensity is 0-2 kg/t/min; in the later smelting stage of the vanadium extraction converter, stopping blowing the iron ore powder to prevent the content of iron oxide in vanadium slag from being too high, blowing the second part of the second-purity CO.sub.2N.sub.2 mixed gas continuously, the gas supply intensity is 0.1-0.5 Nm.sup.3/t/min, enhancing stir of the molten bath, inhibiting the temperature of the molten bath from rising too fast by the heat absorption effect of CO.sub.2 for increasing the vanadium oxidation rate, and reducing the content of the iron oxide in the vanadium slag; in the early smelting stage and the middle smelting stage of the decarburization converter, when the lime powder is not blown, bottom blowing the third part of the second-purity CO.sub.2N.sub.2 mixed gas; when the lime powder is blown, blowing the lime powder by using the O.sub.2CO.sub.2N.sub.2 mixed gas as a carrier gas, inhibiting excessive growth of a mushroom-shaped loose porous medium area by the heat release effect of O.sub.2 for avoiding blockage of a bottom blowing injecting lance, the bottom blowing gas supply intensity is 0.5-1.5 Nm.sup.3/t/min, the bottom blowing powder injecting intensity is 0-5 kg/t/min, the top blowing oxygen supply intensity is 2.0-4.0 Nm.sup.3/t/min, and a top blowing lance height is 2.5-5.0 m; and in the later smelting stage of the decarburization converter, mixing the first-purity CO.sub.2 gas and industrial pure O.sub.2 as a bottom blowing gas, the bottom blowing gas supply intensity is 0.5-1.5 Nm.sup.3/t/min, the top blowing oxygen supply intensity is 2.0-4.0 Nm.sup.3/t/min, the top blowing lance height is 2.0-4.0 m, stopping top blowing oxygen supply 1-2 min before the end of blowing, and bottom blowing the first-purity CO.sub.2 gas and the industrially pure O.sub.2 to complete endpoint control.

3. The method according to claim 2, wherein, in the first-purity CO.sub.2N.sub.2 mixed gas, the volume content of CO.sub.2 is 30-50%, the volume content of N.sub.2 is 50-70%, and the total volume content of O.sub.2 and CO is not higher than 2%; in the second-purity CO.sub.2N.sub.2 mixed gas, the volume content of CO.sub.2 is 50-80%, the volume content of N.sub.2 is 20-50%, and the total volume content of O.sub.2 and CO is not higher than 2%; a gas composition of the O.sub.2CO.sub.2N.sub.2 mixed gas is controlled by adjusting the excess degree of oxygen in an oxygen combustion atmosphere, wherein the volume content of O.sub.2 is 20-60%, the volume content of CO.sub.2 is 20-65%, the volume content of N.sub.2 is 10-40%, and the volume content of CO is lower than 0.1%; and in the first-purity CO.sub.2 gas, the volume content of CO.sub.2 is higher than 99%, and the total volume content of O.sub.2 and CO is not higher than 1%.

4. The method according to claim 1, wherein disposing 2-3 groups of bottom blowing bricks on the bottom of the vanadium extraction converter, using one group of bottom blowing bricks every time, installing bottom blowing bricks by drilling, providing bottom blowing stir, after the group of bottom blowing bricks are eroded to a lower safety limit, blocking the group of bottom blowing bricks by a bottom blowing quick-change mode, using another group of bottom blowing bricks, changing bottom blowing bricks by drilling, providing bottom blowing stir, and using these groups of bottom blowing bricks alternately.

5. An efficient long-service-life blowing system for vanadium extraction-decarburization duplex converters, wherein the system comprises an oxygen combustor (1), a CO.sub.2 purification device (2), a vanadium extraction converter (3), a decarburization converter (4), an iron ore powder blowing tank (5) and a lime powder blowing tank (6), the oxygen combustor (1) comprises a first combustion chamber, a second combustion chamber and a third combustion chamber, a flue gas source of the vanadium extraction converter is connected with the first combustion chamber through a first pipeline, a flue gas source of the decarburization converter communicates with the second combustion chamber and the third combustion chamber through a second pipeline, a first industrial oxygen source communicates with the first combustion chamber, the second combustion chamber and the third combustion chamber through a third pipeline, the first combustion chamber communicates with the vanadium extraction converter (3) through a first-purity CO.sub.2N.sub.2 mixed gas pipeline, the second combustion chamber communicates with the decarburization converter (4) through an O.sub.2CO.sub.2N.sub.2 mixed gas pipeline, and a second industrial oxygen source and the lime powder blowing tank (6) communicate with the O.sub.2CO.sub.2N.sub.2 mixed gas pipeline between the second combustion chamber and the decarburization converter (4), the third combustion chamber communicates with the vanadium extraction converter (3) through a second-purity CO.sub.2N.sub.2 mixed gas pipeline, and the iron ore powder blowing tank (5) communicates with the second-purity CO.sub.2N.sub.2 mixed gas pipeline between the third combustion chamber and the vanadium extraction converter (3), the third combustion chamber also communicates with the decarburization converter (4) through the second-purity CO.sub.2N.sub.2 mixed gas pipeline, and a second industrial oxygen source and the lime powder blowing tank (6) communicate with the second-purity CO.sub.2N.sub.2 mixed gas pipeline between the third combustion chamber and the decarburization converter (4), the third combustion chamber also communicates with the CO.sub.2 purification device (2) through the second-purity CO.sub.2N.sub.2 mixed gas pipeline, the CO.sub.2 purification device (2) communicates with the decarburization converter (4) through a first-purity CO.sub.2 gas pipeline, and the second industrial oxygen source and the lime powder blowing tank (6) communicate with the first-purity CO.sub.2 gas pipeline between the CO.sub.2 purification device (2) and the decarburization converter (4).

6. The system according to claim 5, wherein the first-purity CO.sub.2N.sub.2 mixed gas pipeline communicates with a bottom blowing device of the vanadium extraction converter (3).

7. The system according to claim 5, wherein the second-purity CO.sub.2N.sub.2 mixed gas pipeline communicates with an air inlet of the iron ore powder blowing tank (5), and an iron ore powder airflow outlet of the iron ore powder blowing tank (5) is connected with an iron ore powder blowing device of the vanadium extraction converter (3) through a pipeline.

8. The system according to claim 5, wherein the O.sub.2CO.sub.2N.sub.2 mixed gas pipeline, the second-purity CO.sub.2N.sub.2 mixed gas pipeline, the first-purity CO.sub.2 gas pipeline and the second industrial oxygen source communicate with an air inlet of the lime powder blowing tank (6), and a lime powder airflow outlet of the lime powder blowing tank (6) is connected with a lime powder blowing device of the decarburization converter (4) through a pipeline.

9. The system according to claim 5, wherein a flow valve group is arranged on the first pipeline, the second pipeline and the third pipeline.

10. The system according to claim 5, wherein 2-3 groups of bottom blowing pocket bricks are arranged on the bottom of the vanadium extraction converter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0047] FIG. 1 is a flow chart illustrating an efficient long-service-life blowing method for vanadium extraction-decarburization duplex converters according to the present disclosure;

[0048] FIG. 2 is a schematic diagram of the efficient long-service-life blowing method for vanadium extraction-decarburization duplex converters according to the present disclosure; and

[0049] FIG. 3 is a schematic diagram of a structure of an oxygen combustor.

[0050] In FIG. 2: 1oxygen combustor, 2CO.sub.2 purification device, 3vanadium extraction converter, 4decarburization converter, 5iron ore powder blowing tank, and 6lime powder blowing tank.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0051] In order to enable the objects, technical schemes and advantages of the present disclosure to be clearly understood, the present disclosure will be further described with reference to specific embodiments and the accompanying drawings below.

[0052] Aiming at the problems of a vanadium extraction-decarburization duplex converter steelmaking process, the vanadium extraction converter flue gas and the decarburization converter flue gas produced by the vanadium extraction converter and the decarburization converter are utilized, CO.sub.2 gas in various purity ranges is obtained after different combustion processes are carried out, in combination with blowing process characteristics and requirements of the vanadium extraction converter and the decarburization converter, CO.sub.2 gas with different purities is respectively used for bottom blowing stirring of the vanadium extraction converter, blowing of iron ore powder into the vanadium extraction converter and bottom blowing of lime powder into the decarburization converter, in a smelting process of the vanadium extraction converter and the decarburization converter, a staged control strategy is adopted, and the proportion and flow of the CO.sub.2 gas with different purities are regulated in stages. The present disclosure is suitable for 30-350 tons of vanadium extraction-decarburization duplex converters, the vanadium extraction converter flue gas and the decarburization converter flue gas are recycled at high efficiency and low cost, and are respectively applied to different blowing procedures of the vanadium extraction converter and the decarburization converter, the vanadium oxidation rate of the vanadium extraction converter can be increased, the dephosphorization effect of the decarburization converter is improved, and meanwhile, the service lives of the vanadium extraction converter and the decarburization converter are prolonged.

[0053] As shown in FIG. 1, the efficient long-service-life blowing method for the vanadium extraction-decarburization duplex converters according to the present disclosure includes the following steps:

[0054] step 101, the vanadium extraction converter flue gas and the decarburization converter flue gas are separately introduced into the oxygen combustor.

[0055] Step 102, the vanadium extraction converter flue gas is completely combusted in an oxygen atmosphere to obtain first-purity CO.sub.2N.sub.2 mixed gas; the decarburization converter flue gas is completely combusted in an oxygen atmosphere to obtain second-purity CO.sub.2N.sub.2 mixed gas; the decarburization converter flue gas is subjected to oxygen-excess combustion in an oxygen atmosphere to obtain O.sub.2CO.sub.2N.sub.2 mixed gas; and a first part of the second-purity CO.sub.2N.sub.2 mixed gas is introduced into a purification device to obtain first-purity CO.sub.2 gas.

[0056] In the first-purity CO.sub.2N.sub.2 mixed gas, the volume content of CO.sub.2 is 30-50%, the content of N.sub.2 is 50-70%, and the total content of O.sub.2 and CO is not higher than 2%; in the second-purity CO.sub.2N.sub.2 mixed gas, the volume content of CO.sub.2 is 50-80%, the content of N.sub.2 is 20-50%, and the total content of O.sub.2 and CO is not higher than 2%; a gas composition of the O.sub.2CO.sub.2N.sub.2 mixed gas is controlled by adjusting the excess degree of oxygen, wherein the volume fraction of O.sub.2 is 20-60%, the content of CO.sub.2 is 20-65%, the content of N.sub.2 is 10-40%, and the content of CO is lower than 0.1%; and in the first-purity CO.sub.2 gas, the volume content of CO.sub.2 is higher than 99%, and the total content of O.sub.2 and CO is not higher than 1%.

[0057] Step 103, the first-purity CO.sub.2N.sub.2 mixed gas is used for bottom blowing of the vanadium extraction converter, a second part of the second-purity CO.sub.2N.sub.2 mixed gas is used as a carrier gas for blowing iron ore powder into the vanadium extraction converter, and a third part of the second-purity CO.sub.2N.sub.2 mixed gas, the O.sub.2CO.sub.2N.sub.2 mixed gas and the first-purity CO.sub.2 gas are used as a carrier gas for bottom blowing of the decarburization converter and bottom injecting of lime powder into the decarburization converter.

[0058] As shown in FIG. 2 and FIG. 3, the efficient long-service-life blowing system for vanadium extraction-decarburization duplex converters according to the present disclosure includes an oxygen combustor (1), a CO.sub.2 purification device (2), a vanadium extraction converter (3), a decarburization converter (4), an iron ore powder blowing tank (5) and a lime powder blowing tank (6), the vanadium extraction converter flue gas, the decarburization converter flue gas and industrial oxygen are connected with the oxygen combustor (1) through pipelines, the oxygen combustor (1) generates first-purity CO.sub.2N.sub.2 mixed gas, second-purity CO.sub.2N.sub.2 mixed gas and O.sub.2CO.sub.2N.sub.2 mixed gas, wherein one part of the second-purity CO.sub.2N.sub.2 mixed gas enters the CO.sub.2 purification device through a pipeline to produce first-purity CO.sub.2 gas; the first-purity CO.sub.2N.sub.2 mixed gas is connected with a bottom blowing device of the vanadium extraction converter (3) through a pipeline, one part of second-purity CO.sub.2N.sub.2 mixed gas is connected with the iron ore powder blowing tank (5) through a pipeline, and iron ore powder airflow is connected with an iron ore powder blowing device of the vanadium extraction converter (3) through a pipeline; and one part of the second-purity CO.sub.2N.sub.2 mixed gas, the O.sub.2CO.sub.2N.sub.2 mixed gas, the first-purity CO.sub.2 and the industrial oxygen are connected with the lime powder blowing tank (6) through a pipeline, and lime powder airflow is connected with a lime powder blowing device of the decarburization converter (4) through a pipeline; and the flows of a gas medium and solid powder in the system can be adjusted and metered through the valve group arranged on the pipelines.

Embodiment 1

[0059] In the embodiment, the method and system are applied to a 100-ton vanadium extraction-decarburization duplex converter process.

[0060] The converter flue gas generated by the vanadium extraction converter contains 20% CO, 15% CO.sub.2 and the rest is N.sub.2, and because the gas is low in calorific value, before the method and system are adopted, the vanadium extraction converter flue gas is diffused directly; the decarburization converter flue gas contains 60% CO, 20% CO.sub.2 and the rest is N.sub.2, and is stored in a gas cabinet. Before the method and system are adopted, eight bottom blowing air-permeable bricks are arranged on the bottom of the vanadium extraction converter, the gas supply intensity is 0.04 Nm.sup.3/t/min, two inject lances for blowing iron ore powder are arranged on a side of the converter, the gas supply intensity is 0.2 Nm.sup.3/t/min, the powder injecting intensity is 1.0 kg/t/min, and a carrier gas for bottom blowing and side blowing are N.sub.2; and four bottom blowing injecting lances for blowing lime powder are arranged on the bottom of the decarburization converter, pure O.sub.2 is used as a carrier gas for injecting powder, the bottom blowing gas supply intensity is 0.8 Nm.sup.3/t/min, and the maximum powder injecting intensity is 3.0 kg/t/min.

[0061] After the method and system are applied, the vanadium extraction converter flue gas and the decarburization converter flue gas are separately introduced into the oxygen combustor, the vanadium extraction converter flue gas is completely combusted in an oxygen atmosphere (the equivalent ratio is 1.0) to obtain the first-purity CO.sub.2N.sub.2 mixed gas, the first-purity CO.sub.2N.sub.2 mixed gas contains about 35% CO.sub.2 and the rest is N.sub.2 mainly, and the total content of CO and O.sub.2 does not exceed 2%; the decarburization converter flue gas is completely combusted in an oxygen atmosphere (the equivalent ratio is 1.0) to obtain the second-purity CO.sub.2N.sub.2 mixed gas, the second-purity CO.sub.2N.sub.2 mixed gas contains about 80% CO.sub.2 and the rest is N.sub.2 mainly, the total content of CO and O.sub.2 does not exceed 2%, and the first part of the second-purity CO.sub.2N.sub.2 mixed gas is used for preparing the first-purity CO.sub.2 gas; and the decarburization converter flue gas is subjected to oxygen-excess combustion in an oxygen atmosphere (the equivalent ratio is smaller than 1.0) to obtain O.sub.2CO.sub.2N.sub.2 mixed gas, and by adjusting the excess degree of oxygen, the O.sub.2CO.sub.2N.sub.2 mixed gas contains about 50% O.sub.2, about 40% CO.sub.2 and the rest is N.sub.2 mainly, and the content of CO is lower than 1%.

[0062] The first-purity CO.sub.2N.sub.2 mixed gas is used for bottom blowing of the vanadium extraction converter, a second part of CO.sub.2N.sub.2 mixed gas with a second concentration is used as a carrier gas for blowing iron ore powder into the vanadium extraction converter, a third part of the second-purity CO.sub.2N.sub.2 mixed gas, the O.sub.2CO.sub.2N.sub.2 mixed gas and the first-purity CO.sub.2 gas are used as a carrier gas for bottom blowing of the decarburization converter and bottom injecting of lime powder into the decarburization converter, and the specific staged control smelting process is as follows:

[0063] in the smelting process of the vanadium extraction converter, the first-purity CO.sub.2N.sub.2 mixed gas is bottom-blown in the whole process, and the bottom blowing intensity is 0.03 Nm.sup.3/t/min;

[0064] in the early smelting stage and the middle smelting stage of the vanadium extraction converter, iron ore powder is injected and blown into the converter by taking the second part of the second-purity CO.sub.2N.sub.2 mixed gas as a carrier gas, the temperature of the molten bath is stabilized, the gas supply intensity is 0.2 Nm.sup.3/t/min, and the iron ore powder supply intensity is 1.0 kg/t/min;

[0065] in the later smelting stage of the vanadium extraction converter, blowing of the iron ore powder are stopped, the content of the iron oxide in the vanadium slag is prevented from being too high, the second part of the second-purity CO.sub.2N.sub.2 mixed gas is continuously injected and blown, the gas supply intensity is 0.2 Nm.sup.3/t/min, stirring of the molten bath is enhanced, the temperature of the molten bath is inhibited from rising too fast depending on the heat absorption effect of CO.sub.2, the vanadium oxidation rate is increased, and the iron oxide in the vanadium slag is reduced;

[0066] in the early smelting stage and the middle smelting stage of the decarburization converter, when the lime powder is not injected and blown, a third part of the second-purity CO.sub.2N.sub.2 mixed gas is bottom-blown, when the lime powder is injected and blown, the O.sub.2CO.sub.2N.sub.2 mixed gas is used as a carrier gas to inject and blow the lime powder, excessive growth of a mushroom-shaped loose porous medium area is inhibited by utilizing the heat release effect of 02, blockage of a bottom blowing injecting lance is avoided, the bottom blowing gas supply intensity is 0.8 Nm.sup.3/t/min, the bottom blowing powder injecting intensity is 3.0 kg/t/min, the oxygen supply intensity of a top blowing oxygen lance is 2.5 Nm.sup.3/t/min, and a top blowing lance height is 3.5 m; and

[0067] in the later smelting stage of the decarburization converter, in order to prevent the nitrogen content of the molten steel from exceeding the standard, the first-purity CO.sub.2 gas and the industrially pure O.sub.2 are mixed as bottom blowing gas, the bottom blowing gas supply intensity is 0.8 Nm.sup.3/t/min, the top blowing oxygen supply intensity is 2.5 Nm.sup.3/t/min, the top blowing lance height is 3.0 m, top blowing oxygen supply is stopped 1.5 min before the end of blowing, and the mixed gas of the first-purity CO.sub.2 and the industrially pure O.sub.2 is bottom-blown to finish end point control.

[0068] Because the stirring effect of CO.sub.2 is superior to that of N.sub.2 under the condition that the bottom blowing flows are the same, after the first-purity CO.sub.2N.sub.2 mixed gas is used as the bottom blowing gas of the vanadium extraction converter, under the condition that the stirring effect of the molten bath is kept unchanged, the number of the bottom blowing air-permeable bricks required for the vanadium extraction converter is reduced from 8 to 6, the bottom blowing intensity is reduced from 0.04 Nm.sup.3/t/min to 0.03 Nm.sup.3/t/min, 12 bottom blowing pocket bricks are totally mounted on the bottom of the vanadium extraction converter and are divided into two groups, one group of bottom blowing pocket bricks are used every time, bottom blowing air-permeable bricks are mounted by drilling, bottom blowing stirring is provided, after the group of bottom blowing air-permeable bricks are eroded to a lower safety limit, the group of bottom blowing bricks are blocked by a bottom blowing quick-change mode, the other group of bottom blowing pocket bricks are used, bottom blowing air-permeable bricks are mounted by drilling, bottom blowing stirring is provided, the two groups of bottom blowing pocket bricks are alternately used, and the integral service life of the bottom of the vanadium extraction converter is prolonged on the premise of maintaining the stirring effect of the vanadium extraction converter.

[0069] After the method and system are adopted, the vanadium extraction converter flue gas and the decarburization converter flue gas are recycled at high efficiency and low cost, diversified CO.sub.2 gas sources are provided for smelting of the vanadium extraction converter and the decarburization converter, different process requirements of the vanadium extraction converter and the decarburization converter are respectively met, the vanadium oxidation rate of the vanadium extraction converter is improved from 89.4% to 92.0%, T.Fe in the vanadium slag is reduced from 32.1% to 29.2%, the average end phosphorus content of the decarburization converter is reduced from 0.018% to 0.012%, and the service lives of the bottom of the vanadium extraction converter and the bottom of the decarburization converter are prolonged by 30% or above.

Embodiment 2

[0070] In the embodiment, the method and system are applied to a 150-ton vanadium extraction-decarburization duplex converter process.

[0071] The converter flue gas generated by the vanadium extraction converter contains 30% CO, 20% CO.sub.2 and the rest is N.sub.2, and because the calorific value of the gas is low, before the method and system are adopted, the vanadium extraction converter flue gas is directly diffused; and the decarburization converter flue gas contains 55% CO, 25% CO.sub.2 and the rest is N.sub.2, and is stored in a gas cabinet. Before the method and system are adopted, nine bottom blowing air-permeable bricks are arranged on the bottom of the vanadium extraction converter, the gas supply intensity is 0.09 Nm.sup.3/t/min, four inject lances for blowing the iron ore powder is arranged on a side of the converter, the gas supply intensity is 0.33 Nm.sup.3/t/min, the powder injecting intensity is 2.0 kg/t/min, and the carrier gas for bottom blowing and side blowing are N.sub.2; and six bottom blowing injecting lances for blowing lime powder are arranged on the bottom of the decarburization converter, pure O.sub.2 is used as a carrier gas for injecting powder, the bottom blowing gas supply intensity is 1.0 Nm.sup.3/t/min, and the maximum powder injecting intensity is 5.0 kg/t/min.

[0072] After the method and system are applied, the vanadium extraction converter flue gas and the decarburization converter flue gas are separately introduced into the oxygen combustor, the vanadium extraction converter flue gas is completely combusted in an oxygen atmosphere (the equivalent ratio is 1.0) to obtain the first-purity CO.sub.2N.sub.2 mixed gas, the first-purity CO.sub.2N.sub.2 mixed gas contains about 50% CO.sub.2 and the rest is N.sub.2 mainly, and the total content of CO and O.sub.2 does not exceed 2%; the decarburization converter flue gas is completely combusted in an oxygen atmosphere (the equivalent ratio is 1.0) to obtain the second-purity CO.sub.2N.sub.2 mixed gas, the second-purity CO.sub.2N.sub.2 mixed gas contains about 80% CO.sub.2 and the rest is N.sub.2 mainly, the total content of CO and O.sub.2 does not exceed 2%, and the first part of the second-purity CO.sub.2N.sub.2 mixed gas is used for preparing the first-purity CO.sub.2 gas; and the decarburization converter flue gas is subjected to oxygen-excess combustion in an oxygen atmosphere (the equivalent ratio is less than 1.0) to obtain the O.sub.2CO.sub.2N.sub.2 mixed gas, by adjusting the excess degree of oxygen, the O.sub.2CO.sub.2N.sub.2 mixed gas contains about 40% O.sub.2, about 48% CO.sub.2 and the rest is N.sub.2 mainly, and the content of CO is lower than 1%.

[0073] The first-purity CO.sub.2N.sub.2 mixed gas is used for bottom blowing of the vanadium extraction converter, a second part of CO.sub.2N.sub.2 mixed gas with a second concentration is used as a carrier gas for blowing the iron ore powder into the vanadium extraction converter, a third part of the second-purity CO.sub.2N.sub.2 mixed gas, the O.sub.2CO.sub.2N.sub.2 mixed gas and the first-purity CO.sub.2 gas are used as a carrier gas for bottom blowing of the decarburization converter and bottom injecting of the lime powder into the decarburization converter, and the specific staged control smelting process is as follows:

[0074] in the smelting process of the vanadium extraction converter, the first-purity CO.sub.2N.sub.2 mixed gas is bottom-blown in the whole process, and the bottom blowing intensity is 0.06 Nm.sup.3/t/min;

[0075] in the early smelting stage and the middle smelting stage of the vanadium extraction converter, the second part of the second-purity CO.sub.2N.sub.2 mixed gas is used as a carrier gas for blowing the iron ore powder into the converter, the temperature of the molten bath is stabilized, the gas supply intensity is 0.33 Nm.sup.3/t/min, and the iron ore powder supply intensity is 2.0 kg/t/min;

[0076] in the later smelting stage of the vanadium extraction converter, blowing of the iron ore powder are stopped, the content of iron oxide in the vanadium slag is prevented from being too high, the second part of the second-purity CO.sub.2N.sub.2 mixed gas is continuously injected and blown, the gas supply intensity is 0.33 Nm.sup.3/t/min, stirring of the molten bath is enhanced, the temperature of the molten bath is inhibited from rising too fast depending on the heat absorption effect of CO.sub.2, the vanadium oxidation rate is increased, and the iron oxide in the vanadium slag is reduced;

[0077] in the early smelting stage and the middle smelting stage of the decarburization converter, when the lime powder is not injected and blown, the third part of the second-purity CO.sub.2N.sub.2 mixed gas is bottom-blown, when the lime powder is injected and blown, the O.sub.2CO.sub.2N.sub.2 mixed gas is used as a carrier gas for blowing the lime powder, excessive growth of the mushroom-shaped loose porous medium area is inhibited by utilizing the heat release effect of 02, blockage of a bottom blowing injecting lance is avoided, the bottom blowing gas supply intensity is 1.0 Nm.sup.3/t/min, the bottom blowing powder injecting intensity is 5.0 kg/t/min, the oxygen supply intensity of the top blowing oxygen lance is 3.0 Nm.sup.3/t/min, and the top blowing lance height is 4.0 m; and

[0078] in the later smelting stage of the decarburization converter, in order to prevent the nitrogen content of molten steel from exceeding the standard, the first-purity CO.sub.2 gas and the industrially pure O.sub.2 are mixed to serve as bottom blowing gas, the bottom blowing gas supply intensity is 1.0 Nm.sup.3/t/min, the top blowing oxygen supply intensity is 3.0 Nm.sup.3/t/min, the top blowing lance height is 3.5 m, top blowing oxygen supply is stopped 1.0 min before the end of blowing, and the mixed gas of the first-purity CO.sub.2 and the industrially pure O.sub.2 is bottom-blown to finish end point control.

[0079] Because the stirring effect of CO.sub.2 is superior to that of N.sub.2 under the condition that the bottom blowing flows are the same, after the first-purity CO.sub.2N.sub.2 mixed gas is used as the bottom blowing gas of the vanadium extraction converter, under the condition that the stirring effect of the molten bath is kept unchanged, the number of bottom blowing air-permeable bricks required for the vanadium extraction converter is reduced from 9 to 6, the bottom blowing intensity is reduced from 0.09 Nm.sup.3/t/min to 0.06 Nm.sup.3/t/min, twelve bottom blowing pocket bricks are mounted on the bottom of the vanadium extraction converter totally, and are divided into two groups, one group of bottom blowing pocket bricks are used every time, bottom blowing air-permeable bricks are mounted by drilling, bottom blowing stirring is provided, after the group of bottom blowing air-permeable bricks are eroded to a lower safety limit, the group of bottom blowing bricks are blocked by a bottom blowing quick-change mode, the other group of bottom blowing pocket bricks are used, bottom blowing air-permeable bricks are mounted by drilling, bottom blowing stirring is provided, the two groups of bottom blowing pocket bricks are used alternately, and the integral service life of the bottom of the vanadium extraction converter is prolonged on the premise of maintaining the stirring effect of the vanadium extraction converter.

[0080] After the method and system are adopted, the vanadium extraction converter flue gas and the decarburization converter flue gas are recycled at high efficiency and low cost, diversified CO.sub.2 gas sources are provided for smelting of the vanadium extraction converter and the decarburization converter, different process requirements of the vanadium extraction converter and the decarburization converter are respectively met, the vanadium oxidation rate of the vanadium extraction converter is improved from 90.3% to 92.8%, T.Fe in the vanadium slag is reduced from 30.8% to 28.3%, the average end phosphorus content of the decarburization converter is reduced from 0.016% to 0.009%, and the service lives of the bottom of the vanadium extraction converter and the bottom of the decarburization converter are prolonged by 20% or above.

[0081] It should be understood that the specific embodiments described below are merely illustrative of the present disclosure and are not intended to be limiting the present disclosure. Any modification, equivalent replacement, improvement and the like made according to the spirit and principle of the present disclosure shall be regarded as within the protection scope of the present disclosure.