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.2—N.sub.2 mixed gas through the vanadium extraction converter flue gas; obtaining second-purity CO.sub.2—N.sub.2 mixed gas through the decarburization converter flue gas; obtaining O.sub.2—CO.sub.2—N.sub.2 mixed gas through the decarburization converter flue gas; obtaining first-purity CO.sub.2 gas through the second-purity CO.sub.2—N.sub.2 mixed gas; and using the first-purity CO.sub.2—N.sub.2 mixed gas for bottom blowing of the vanadium extraction converter, using the second-purity CO.sub.2—N.sub.2 mixed gas as a carrier gas for blowing iron ore powder into the vanadium extraction converter, and using the O.sub.2—CO.sub.2—N.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. A method for vanadium extraction from molten iron, comprising: smelting a molten iron in a vanadium extraction converter; smelting a vanadium-depleted molten iron from the vanadium extraction converter in a decarburization converter; combustion on combusting a flue gas from the vanadium extraction converter to obtain a first CO.sub.2—N.sub.2 mixed gas having a first purity; combusting a flue gas from the decarburization converter to obtain a second CO.sub.2—N.sub.2 mixed gas having a second purity; combusting a flue gas from the decarburization converter flue gas to obtain an O.sub.2—CO.sub.2—N.sub.2 mixed gas; purifying a first portion of the second CO.sub.2—N.sub.2 mixed gas in a purification device to obtain a CO.sub.2 gas; bottom blowing the vanadium extraction converter with the first CO.sub.2—N.sub.2 mixed gas; blowing iron ore powder into the vanadium extraction converter with a second portion of the second CO.sub.2—N.sub.2 mixed gas; and bottom blowing the decarburization converter and/or bottom injecting lime powder into the decarburization converter with a mixture of a third portion of the second CO.sub.2—N.sub.2 mixed gas, the O.sub.2—CO.sub.2—N.sub.2 mixed gas, and the CO.sub.2 gas.

2. The method according to claim 1, wherein the smelting process of the vanadium extraction converter comprises a first smelting stage, a second smelting stage, and a third smelting stage, wherein the first CO.sub.2—N.sub.2 mixed gas is bottom blown into the vanadium extraction converter at an intensity of 0.03-0.3 Nm.sup.3/t/min throughout the smelting process in the vanadium extraction converter; wherein, in the first smelting stage and the second smelting stage in the vanadium extraction converter, the second stream of the second CO.sub.2—N.sub.2 mixed gas blows iron ore powder into the vanadium extraction converter at an intensity of 0.1-0.5 Nm.sup.3/t/min, and an iron ore powder intensity of 0-2 kg/t/min; wherein, in the third smelting stage in the vanadium extraction converter, the second portion of the second CO.sub.2—N.sub.2 mixed gas continuously blows into the vanadium extraction converter at an intensity of 0.1-0.5 Nm.sup.3/t/min; wherein the smelting process in the decarburization converter comprises a first smelting stage, a second smelting stage, and a third smelting stage, wherein, in the first smelting stage and the smelting second stage in the decarburization converter, when the lime powder is not blown, the third portion of the second CO.sub.2—N.sub.2 mixed gas is bottom blown into the decarburization converter; when the lime powder is blown, the lime powder is blown into the decarburization converter using the O.sub.2—CO.sub.2—N.sub.2 mixed gas as a carrier gas at an intensity of 0.5-1.5 Nm.sup.3/t/min and a lime powder intensity of 0-5 kg/t/min; and in the third smelting stage in the decarburization converter, the decarburization converter is bottom blown using a mixture of the CO.sub.2 gas and industrial pure O.sub.2 at a gas supply intensity 0.5-1.5 Nm.sup.3/t/min.

3. The method according to claim 2, wherein, the CO.sub.2—N.sub.2 mixed gas comprises 30-50% by volume of CO.sub.2, 50-70% by volume of N.sub.2, and not higher than 2% by volume of O.sub.2 and CO; the second CO.sub.2—N.sub.2 mixed gas comprises 50-80% by volume of CO.sub.2, 20-50% by volume of N.sub.2, and not higher than 2% by volume of O.sub.2 and CO; the O.sub.2—CO.sub.2—N.sub.2 mixed gas comprises 20-60% by volume of O.sub.2, 20-65% by volume of CO.sub.2, 10-40% by volume of N.sub.2, and less than 0.1% by volume of CO; and in the CO.sub.2 gas, comprises more than 99% by volume of CO.sub.2 and less than 1% O.sub.2 and CO.

4. The method according to claim 1, wherein the vanadium extraction converter comprises two or three groups of bottom blowing bricks, wherein the two or three groups of bottom blowing bricks are alternately in service so that only one among two or three groups of bottom blowing bricks is in service at one time.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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;

(2) 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

(3) FIG. 3 is a schematic diagram of a structure of an oxygen combustor.

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

DETAILED DESCRIPTION OF THE EMBODIMENTS

(5) 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.

(6) 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.

(7) 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:

(8) step 101, the vanadium extraction converter flue gas and the decarburization converter flue gas are separately introduced into the oxygen combustor.

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

(10) In the first-purity CO.sub.2—N.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.2—N.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.2—CO.sub.2—N.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%.

(11) Step 103, the first-purity CO.sub.2—N.sub.2 mixed gas is used for bottom blowing of the vanadium extraction converter, a second part of the second-purity CO.sub.2—N.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.2—N.sub.2 mixed gas, the O.sub.2—CO.sub.2—N.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.

(12) 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.2—N.sub.2 mixed gas, second-purity CO.sub.2—N.sub.2 mixed gas and O.sub.2—CO.sub.2—N.sub.2 mixed gas, wherein one part of the second-purity CO.sub.2—N.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.2—N.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.2—N.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.2—N.sub.2 mixed gas, the O.sub.2—CO.sub.2—N.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

(13) In the embodiment, the method and system are applied to a 100-ton vanadium extraction-decarburization duplex converter process.

(14) 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.

(15) 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.2—N.sub.2 mixed gas, the first-purity CO.sub.2—N.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.2—N.sub.2 mixed gas, the second-purity CO.sub.2—N.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.2—N.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.2—CO.sub.2—N.sub.2 mixed gas, and by adjusting the excess degree of oxygen, the O.sub.2—CO.sub.2—N.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%.

(16) The first-purity CO.sub.2—N.sub.2 mixed gas is used for bottom blowing of the vanadium extraction converter, a second part of CO.sub.2—N.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.2—N.sub.2 mixed gas, the O.sub.2—CO.sub.2—N.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:

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

(18) 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.2—N.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;

(19) 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.2—N.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;

(20) 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.2—N.sub.2 mixed gas is bottom-blown, when the lime powder is injected and blown, the O.sub.2—CO.sub.2—N.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 O.sub.2, 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

(21) 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.

(22) 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.2—N.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.

(23) 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

(24) In the embodiment, the method and system are applied to a 150-ton vanadium extraction-decarburization duplex converter process.

(25) 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.

(26) 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.2—N.sub.2 mixed gas, the first-purity CO.sub.2—N.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.2—N.sub.2 mixed gas, the second-purity CO.sub.2—N.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.2—N.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.2—CO.sub.2—N.sub.2 mixed gas, by adjusting the excess degree of oxygen, the O.sub.2—CO.sub.2—N.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%.

(27) The first-purity CO.sub.2—N.sub.2 mixed gas is used for bottom blowing of the vanadium extraction converter, a second part of CO.sub.2—N.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.2—N.sub.2 mixed gas, the O.sub.2—CO.sub.2—N.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:

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

(29) in the early smelting stage and the middle smelting stage of the vanadium extraction converter, the second part of the second-purity CO.sub.2—N.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;

(30) 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.2—N.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;

(31) 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.2—N.sub.2 mixed gas is bottom-blown, when the lime powder is injected and blown, the O.sub.2—CO.sub.2—N.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 O.sub.2, 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

(32) 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.

(33) 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.2—N.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.

(34) 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.

(35) 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.