METHOD OF DYNAMIC CONTROL FOR BOTTOM BLOWING O2-CO2-CaO CONVERTER STEELMAKING PROCESS

Abstract

There is provided a method of dynamic control for a bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process. In the process, O.sub.2 is adopted as a top blowing gas, a mixed gas O.sub.2+CO.sub.2 is adopted as a bottom blowing carrier gas to inject lime powders into the converter from a bottom blowing tuyere. The ingredients of the molten steel in the converter steelmaking process are predicted based on the conservation of matter, in combination with the ingredient data of charged molten iron, the ingredient data of the converter gas in the converter blowing process, and working conditions of the bottom blowing device. The top blowing oxygen amount, the bottom blowing gas ratio and the flow rate of lime powder are dynamically adjusted stage by stage according to requirements for target ingredients at the end point of blowing.

Claims

1. A method of dynamic control for a bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process, comprising: dividing the bottom blowing O.sub.2—CO.sub.2—CaO converter blowing process into 3 stages, which are an early stage, a middle stage and a late stage, based on a decarburization rate ν.sub.c; calculating a blowing oxygen consumption, a CO.sub.2 ratio and a lime powder injection amount by a data calculation module, based on following parameters: a total charge amount m.sub.total, a temperature of charged molten iron T.sub.0-1, a carbon content of charged molten iron [% C].sub.0-1, a silicon content of charged molten iron [% Si].sub.0-1, a scrap-metal ratio γ, a carbon content of scrap steel [% C].sub.0-2, a silicon content of scrap steel [% Si].sub.0-2, a target carbon content [% C].sub.f and a target temperature T.sub.f; establishing a blowing operation process of the early stage of blowing by a central control system, based on a constitution of charge material, a molten bath heating rate ν.sub.r and the decarburization rate ν.sub.c; and calculating the decarburization rate ν.sub.c by a decarburization rate calculation module in the blowing process, and determining a point of starting time of the middle stage of blowing and a point of starting time of the late stage of blowing, calculating a CO.sub.2 mixing ratio by a CO.sub.2 calculation module by a calculation model for bottom blowing fire spot area temperature and a dephosphorization model, and further establishing a blowing operation process of the middle stage and a blowing operation process of the late stage, so as to decrease a fire spot area temperature, enhance stirring in a molten bath, and promote an equilibrium of slag-metal reaction in a molten bath.

2. The method of dynamic control for the bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process according to claim 1, wherein in the bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process, a bottom blowing tuyere comprises concentric tubes with an annular gap, wherein a mixed gas O.sub.2+CO.sub.2 as a carrier gas through a center tube blows lime powders from a bottom of the converter directly into the molten bath, and a cooling protective gas, including CH.sub.4, CO.sub.2, N.sub.2, Ar, blows through the annular gap; wherein ingredients and a temperature of a molten steel in the blowing process are predicted based on ingredients of charge material in the converter and ingredients of a flue gas, a CO.sub.2 mixing amount is calculated by the calculation model for bottom blowing fire spot area temperature and the dephosphorization model according to requirements for ingredients and temperature of target steel, and a ratio of CO.sub.2 in bottom blowing gas is dynamically adjusted stage by stage based on a decarburization rate in the molten bath.

3. The method of dynamic control for the bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process according to claim 1, wherein a control step is as follows: calculating a lime powder injection rate by a powder calculation module based on requirements for the total charge amount m.sub.total, silicon contents [% Si] and an alkalinity R, wherein a rate of injecting and blowing lime powders is calculated and adjusted through a formula ν.sub.cαo.Math.t={[% Si].sub.0-1.Math.(1−γ)+[% Si].sub.0-2.Math.γ}.Math.m.sub.total.Math.R; calculating a converter gas instantaneous production amount S .sub.O-gas based on feedback parameters when a top blowing device and a bottom blowing device work, and simultaneously calculating a change of the decarburization rate in the converter blowing process based on converter gas ingredient data, so as to determine a converter blowing stage and respective ingredients of the molten steel; wherein instantaneous contents of CO.sub.2, CO, O.sub.2, H.sub.2 in the converter gas are respectively P.sub.0-CO2, P.sub.0-CO, P.sub.0-O2 and P.sub.0-H2, a flow rate of top blowing oxygen is Q.sub.U-O2, a bottom blowing gas through the center tube is a mixed gas O.sub.2+CO.sub.2, a bottom blowing gas through the annular gap is CH.sub.4, and a total flow rate, a CO.sub.2 ratio and a CH.sub.4 ratio of the bottom blowing gas are respectively Q.sub.b, ε.sub.b-CO2, ε.sub.b-CH4; and calculating and confirming the converter gas flow rate S.sub.O-gas according to a formula 2Q.sub.b(ε.sub.b-CH4)=S.sub.o-gas.Math.P.sub.O-H2 and a bottom blowing working parameter, and calculating the decarburization rate by the decarburization rate calculation module.

4. The method of dynamic control for the bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process according to claim 3, wherein the decarburization rate in the converter blowing process is calculated by a formula $v_C=\frac{d_{m_c}}{d_t}=\frac{12}{22.4}\left[\left(P_{O-{\mathrm{CO}}_2}+P_{O-\mathrm{CO}}\right)⨯Q_{o-\mathrm{gas}}-Q_b⨯{\epsilon }_{b-{\mathrm{CO}}_2}\right].$

5. The method of dynamic control for the bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process according to claim 1, wherein control steps are specifically as follows: Step 1: acquiring a constitution of charge material, key ingredient data and a target parameter in the converter by a data collecting system, transmitting the constitution of charge material, the key component data and the target parameter to a data calculation module, and establishing and controlling the blowing operation process of the early stage by the central control system; Step 2: in the early stage of blowing, lowering a top blowing oxygen lance into the converter to perform oxygen blowing, blowing lime powders into the molten bath through a center tube of a bottom blowing tuyere by using the mixed gas O.sub.2+CO.sub.2 as a carrier gas, CH.sub.4 blowing as a protective gas through a annular gap of the bottom blowing tuyere, and determining an end point of the early stage of blowing based on flue gas ingredient data and the decarburization rate $v_C={\left(\frac{d_{m_c}}{d_t}\right)}_i$ obtained by the decarburization rate calculation module, according to the blowing operation process established in the step 1; Step 3: in the middle stage of blowing, determining a start time of the middle stage based on the decarburization rate $v_C={\left(\frac{d_{m_c}}{d_t}\right)}_i$ obtained in the step 2, and further establishing a middle stage operation process; Step 4: in the late stage of blowing, determining a start time of the late stage based on the decarburization rate $v_C={\left(\frac{d_{m_c}}{d_t}\right)}_i,$ calculating the CO.sub.2 ratio mixed in the late stage by using the CO.sub.2 calculation module based on the heating rate ∇.sub.T, and further establishing a late stage operation process; Step 5: at an end of blowing, determining a time point, when the blowing process ends, based on the decarburization rate $v_C={\left(\frac{d_{m_c}}{d_t}\right)}_i;$ Step 6: switching the blowing gas through the center tube to Ar at a flow rate of 2500 to 18400 Nm.sup.3/h, switching the blowing gas through the annular gap to Ar at a flow rate of 200 to 1790 Nm.sup.3/h, reducing stirring in the molten bath, accelerating separation of slag and iron, and turning the converter down for steel tapping.

6. The method of dynamic control for the bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process according to claim 5, wherein the operation process in the early stage of blowing in the Step 2 is specifically as follows: wherein a bottom lime powder injection rate is 300 to 900 kg/min; a flow rate of the top blowing oxygen is 10000 to 63000 Nm.sup.3/h, a total flow rate of bottom blowing O.sub.2+CO.sub.2 through the center tube is 3000 to 18900 Nm.sup.3/h, in which the CO.sub.2 mixing ratio is 0-100%, a flow rate of the bottom blowing CH.sub.4 through the annular gap is 300 to 1890 Nm.sup.3/h, and an end time of blowing is at 3 to 6 min.

7. The method of dynamic control for the bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process according to claim 4, wherein the operation process in the middle stage of blowing in the Step 3 is specifically as follows: wherein the bottom lime powder injection rate is 300 to 900 kg/min, and a powder injection stops at 8 to 10 min; a flow rate of the top blowing oxygen is 9000 to 62000 Nm.sup.3/h, a flow rate of the bottom blowing O.sub.2 through the center tube is 3000 to 18900 Nm.sup.3/h, in which the CO.sub.2 mixing ratio is 0, a flow rate of the bottom blowing CH.sub.4 through the annular gap is 300 to 1890 Nm.sup.3/h, and an end time of the middle stage of blowing is at 9 to 13 min.

8. The method of dynamic control for the bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process according to claim 5, wherein the operation process s in the late stage of blowing in the Step 4 is specifically as follows: wherein a bottom lime powder injection rate is 0 kg/min; a flow rate of the top blowing oxygen is 9000 to 62000 Nm.sup.3/h, a total flow rate of the bottom blowing O.sub.2+CO.sub.2 from the center tube is 3000 to 18900 Nm.sup.3/h, in which the CO.sub.2 mixing ratio is 50-100%, a flow rate of the bottom blowing CH.sub.4 through the annular gap is 300 to 1890 Nm.sup.3/h, and an end time of the late stage of blowing is at 13 to 18 min.

9. The method of dynamic control for the bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process according to claim 4, wherein control steps are specifically as follows: Step 1: acquiring a constitution of charge material, key ingredient data and a target parameter in the converter by a data collecting system, transmitting the constitution of charge material, the key component data and the target parameter to a data calculation module, and establishing and controlling the blowing operation process of the early stage by the central control system; Step 2: in the early stage of blowing, lowering a top blowing oxygen lance into the converter to perform oxygen blowing, blowing lime powders into the molten bath through a center tube of a bottom blowing tuyere by using the mixed gas O.sub.2+CO.sub.2 as a carrier gas, CH.sub.4 blowing as a protective gas through a annular gap of the bottom blowing tuyere, and determining an end point of the early stage of blowing based on flue gas ingredient data and the decarburization rate $v_C={\left(\frac{d_{m_c}}{d_t}\right)}_i$ obtained by the decarburization rate calculation module, according to the blowing operation process established in the step 1; Step 3: in the middle stage of blowing, determining a start time of the middle stage based on the decarburization rate $v_C={\left(\frac{d_{m_c}}{d_t}\right)}_i$ obtained in the step 2, and further establishing a middle stage operation process; Step 4: in the late stage of blowing, determining a start time of the late stage based on the decarburization rate $v_C={\left(\frac{d_{m_c}}{d_t}\right)}_i,$ calculating the CO.sub.2 ratio mixed in the late stage by using the CO.sub.2 calculation module based on the heating rate ν.sub.T, and further establishing a late stage operation process; Step 5: at an end of blowing, determining a time point, when the blowing process ends, based on the decarburization rate $v_C={\left(\frac{d_{m_c}}{d_t}\right)}_i;$ and Step 6: switching the blowing gas through the center tube to Ar at a flow rate of 2500 to 18400 Nm.sup.3/h, switching the blowing gas through the annular gap to Ar at a flow rate of 200 to 1790 Nm.sup.3/h, reducing stirring in the molten bath, accelerating separation of slag and iron, and turning the converter down for steel tapping.

10. The method of dynamic control for the bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process according to claim 9, wherein the operation process in the early stage of blowing in the Step 2 is specifically as follows: wherein a bottom lime powder injection rate is 300 to 900 kg/min; a flow rate of the top blowing oxygen is 10000 to 63000 Nm.sup.3/h, a total flow rate of bottom blowing O.sub.2+CO.sub.2 through the center tube is 3000 to 18900 Nm.sup.3/h, in which the CO.sub.2 mixing ratio is 0-100%, a flow rate of the bottom blowing CH.sub.4 through the annular gap is 300 to 1890 Nm.sup.3/h, and an end time of blowing is at 3 to 6 min.

11. The method of dynamic control for the bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process according to claim 9, wherein the operation process s in the late stage of blowing in the Step 4 is specifically as follows: wherein a bottom lime powder injection rate is 0 kg/min; a flow rate of the top blowing oxygen is 9000 to 62000 Nm.sup.3/h, a total flow rate of the bottom blowing O.sub.2+CO.sub.2 from the center tube is 3000 to 18900 Nm.sup.3/h, in which the CO.sub.2 mixing ratio is 50-100%, a flow rate of the bottom blowing CH.sub.4 through the annular gap is 300 to 1890 Nm.sup.3/h, and an end time of the late stage of blowing is at 13 to 18 min.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] FIG. 1 is a logic block diagram of dynamic control in a method of dynamic control for a bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process according to the present disclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

[0023] In order to make the objectives, technical solutions and advantages of the present disclosure clearer, the present disclosure will be further described in detail below in combination with embodiments. It should be understood that the specific embodiments described here are only used to explain the present disclosure, but not to limit the present disclosure.

[0024] Any alternatives, modifications, equivalent methods and schemes defined by the claims in the spirit and scope of the present disclosure are covered by the present disclosure. Further, in order to enable the public to have a better understanding of the present disclosure, in the following detailed description of the present disclosure, some specific details are described in detail. Those skilled in the art may fully understand the present disclosure without the description of these details.

Example 1

[0025] The present disclosure was applied to a 120t bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process. The top blowing gas was O.sub.2, the bottom blowing gas through the center tube contained O.sub.2+CO.sub.2, and the bottom blowing protective gas through the annular gap was CH.sub.4. Specific steps were as follows.

[0026] 1) Following parameters were acquired by a raw material parameter acquisition system and transmitted to a blowing parameter calculation module: a molten iron temperature of 1300° C., a carbon content of molten iron [% C].sub.0=4.0%, a silicon content of molten iron [% Si].sub.0=0.60%, a phosphorus content of molten iron [%1].sub.0=0.109%, a carbon content of scrap steel [% C].sub.0=0.10%, a silicon content of scrap steel [% Si].sub.0=0.25%, a phosphorus content of scrap steel [% P].sub.0=0.020%, a scrap-metal ratio of 15%, a target carbon content of 0.02%, and a target temperature of 1635° C. Then, an operation process of the early stage of blowing was established by a central control system.

[0027] 2) In the early stage of blowing, according to the operation process formulated in the step 1), oxygen blew from the top. The center tube of the bottom blowing tuyere injected CaO powders into the molten bath, by using the mixed gas O.sub.2+CO.sub.2 as the carrier gas, so as to enhance the stirring in the molten bath and promote slag fusion. CH.sub.4 blew through the annular gap of the bottom blowing tuyere to cool and protect the center tube. The decarburization rate in the molten bath was calculated by the decarburization rate calculation module, and the end time of the early stage of blowing was determined. The specific operation process was as follows. The flow rate of the top blowing oxygen was 19500 Nm.sup.3/h, the total flow rate of the bottom blowing mixed gas O.sub.2+CO.sub.2 through the center tube was 7600 Nm.sup.3/h, in which the CO.sub.2 mixing ratio was 50%, the lime powder injection rate was 300 kg/min, the flow rate of the bottom blowing gas CH.sub.4 through the annular gap was 760 Nm.sup.3/h, and the time of the early stage was at 0 to 5 min.

[0028] 3) In the middle stage, the start time of the middle stage of blowing was determined to be at 5 min based on the decarburization rate

[00006]${\left(\frac{d_{m_c}}{d_t}\right)}_i.$

Oxygen blew from the top. The center tube of the bottom blowing tuyere injected the CaO powder into the molten bath, by using pure oxygen as the carrier gas, to accelerate a decarburization reaction and enhance the stirring in the molten bath. CH.sub.4 blew through the annular gap to cool and protect the center tube. The specific operation process was as follows. The flow rate of the top blowing oxygen was 17600 Nm.sup.3/h, the flow rate of the bottom blowing pure O.sub.2 through the center tube was 7600 Nm.sup.3/h, the lime powder injection rate was 300 kg/min, the powder injection stopped at 10 min, the flow rate of the bottom blowing CH.sub.4 through the annular gap was 760 Nm.sup.3/h, and the time of the middle stage of blowing was at 5 to 13 min.

[0029] 4) In the late stage, the start time of the late stage was determined to be at 13 min based the decarburization rate

[00007]${\left(\frac{d_{m_c}}{d_t}\right)}_i.$

Oxygen blew from the top. The mixed gas O.sub.2+CO.sub.2 blew through the center tube of the bottom blowing tuyere to reduce the bottom blowing fire spot area temperature, enhance the stirring in the molten bath and promote the equilibrium of the metallurgical reaction. CH.sub.4 blew through the annular gap to cool and protect the center tube. The specific operation process was as follows. The flow rate of the top blowing oxygen was 20600 Nm.sup.3/h, the total flow rate of the bottom blowing mixed gas O.sub.2+CO.sub.2 through the center tube was 7600 Nm.sup.3/h, in which the CO.sub.2 mixing ratio was 80%. The flow rate of bottom blowing CH.sub.4 through the annular gap was 760 Nm.sup.3/h, and the end time of the late stage of blowing was at 13 to 15 min.

[0030] 5) At the end point of blowing, it was measured that the temperature was 1635° C., the carbon content of the molten bath was 0.02%, and the oxygen content was 800 PPm. The temperature and ingredients were qualified. The bottom blowing gas through the center tube was switched to pure Ar at a flow rate of 7000 Nm.sup.3/h, and the bottom blowing gas through the annular gap was switched to pure Ar at a flow rate of 600 Nm.sup.3/h, to reduce the stirring in the molten bath and accelerate a separation of slag and iron. Then the converter was turned down for steel tapping.

Example 2

[0031] The present disclosure was applied to a 300t bottom blowing O.sub.2—CO.sub.2—CaO converter steelmaking process. The top blowing gas was O.sub.2, the bottom blowing gas through the center tube contained O.sub.2+CO.sub.2, and the bottom blowing protective gas through the annular gap was CH.sub.4. Specific steps were as follows.

[0032] 1) Following parameters were acquired by a raw material parameter acquisition system and transmitted to a blowing parameter calculation module: a molten iron temperature of 1300° C., a carbon content of molten iron [% C].sub.0=4.0%, a silicon content of molten iron [% Si]o=0.50%, a phosphorus content of molten iron [% P].sub.0=0.100%, a carbon content of scrap steel [% C].sub.0=0.15%, a silicon content of scrap steel [% Si].sub.0=0.20%, a phosphorus content of scrap steel [% P].sub.0=0.020%, a scrap-metal ratio of 15%, a target carbon content of 0.02%, and a target temperature of 1635° C. Then, an operation process of the early stage of blowing was established by a central control system.

[0033] 2) In the early stage of blowing, according to the operation process formulated in the step 1), oxygen blew from the top. The center tube of the bottom blowing tuyere injected CaO powders into the molten bath, by using the mixed gas O.sub.2+CO.sub.2 as the carrier gas, so as to enhance the stirring in the molten bath and promote slag fusion. CH.sub.4 blew through the annular gap of the bottom blowing tuyere to cool and protect the center tube. The decarburization rate in the molten bath was calculated by the decarburization rate calculation module, and the end time of the early stage of blowing was determined. The specific operation process was as follows. The flow rate of the top blowing oxygen was 47800 Nm.sup.3/h, the total flow rate of the bottom blowing mixed gas O.sub.2+CO.sub.2 through the center tube was 19000 Nm.sup.3/h, in which the CO.sub.2 mixing ratio was 40%, the lime powder injection rate was 700 kg/min, the flow rate of the bottom blowing gas CH.sub.4 through the annular gap was 1900 Nm.sup.3/h, and the time of the early stage was at 0 to 6 min.

[0034] 3) In the middle stage, the start time of the middle stage of blowing was determined to be at 6 min based on the decarburization rate

[00008]${\left(\frac{d_{m_c}}{d_t}\right)}_i.$

Oxygen blew from the top. The center tube of the bottom blowing tuyere injected the CaO powder into the molten bath, by using pure oxygen as the carrier gas, to accelerate a decarburization reaction and enhance the stirring in the molten bath. CH.sub.4 blew through the annular gap to cool and protect the center tube. The specific operation process was as follows. The flow rate of the top blowing oxygen was 44000 Nm.sup.3/h, the flow rate of the bottom blowing pure O.sub.2 through the center tube was 19000 Nm.sup.3/h, the lime powder injection rate was 700 kg/min, the powder injection stopped at 9 min, the flow rate of the bottom blowing CH.sub.4 through the annular gap was 1900 Nm.sup.3/h, and the time of the middle stage of blowing was at 6 to 14 min.

[0035] 4) In the late stage, the start time of the late stage was determined to be at 14 min based the decarburization rate

[00009]${\left(\frac{d_{m_c}}{d_t}\right)}_i.$

Oxygen blew from the top. The mixed gas O.sub.2+CO.sub.2 blew through the center tube of the bottom blowing tuyere to enhance the stirring in the molten bath and promote the equilibrium of the metallurgical reaction. CH.sub.4 blew through the annular gap to cool and protect the center tube. The specific operation process was as follows. The flow rate of the top blowing oxygen was 50600 Nm.sup.3/h, the total flow rate of the bottom blowing mixed gas O.sub.2+CO.sub.2 through the center tube was 19000 Nm.sup.3/h, in which the CO.sub.2 mixing ratio was 70%. The flow rate of bottom blowing CH.sub.4 through the annular gap was 1900 Nm.sup.3/h, and the end time of the late stage of blowing was at 14 to 17 min.

[0036] 5) At the end point of blowing, it was measured that the temperature was 1637° C., the carbon content of the molten bath was 0.02%, and the oxygen content was 750 PPm. The bottom blowing gas through the center tube was switched to pure Ar at a flow rate of 49000 Nm.sup.3/h, and the bottom blowing gas through the annular gap was switched to pure Ar at a flow rate of 1300 Nm.sup.3/h, to reduce the stirring in the molten bath and accelerate a separation of slag and iron. Then the converter was turned down for steel tapping.

[0037] The specific embodiments of the present disclosure described above do not constitute a limitation on the protection scope of the present disclosure. Any other corresponding changes and modifications made according to the technical concept of the present disclosure should be included in the protection scope of the claims of the present disclosure.