阅读说明：本技术 一种确定高炉冶炼最低焦比的方法 (Method for determining minimum coke ratio in blast furnace smelting ) 是由 许俊 邹忠平 王刚 赵运建 吴开基 牛群 于 2021-08-30 设计创作，主要内容包括：本发明涉及一种确定高炉冶炼最低焦比的方法,属于高炉生产领域,包括设定原料条件和冶炼工艺条件；设定铁的直接还原度,计算吨铁直接还原耗碳、吨铁间接还原耗碳、吨铁耗热需碳、铁水中其他元素还原耗碳及铁水渗碳量；计算吨铁耗碳量,吨铁耗碳量＝吨铁间接还原耗碳和吨铁耗热需碳二者中的较大值+吨铁直接还原耗碳+铁水中其他元素还原耗碳+铁水渗碳量；选取多个直接还原度,重复上述步骤,对应得到多个吨铁耗碳量,选出其中最小值,即为该原料条件和冶炼工艺条件下的最低焦比。能够帮助操作者获得确定的减碳目标,即在特定原料条件和冶炼工艺条件下的冶炼能达到的最低焦比；并根据提供的信息制定可行的减碳措施,实现合理的减碳效果。(The invention relates to a method for determining the lowest coke ratio in blast furnace smelting, which belongs to the field of blast furnace production and comprises the steps of setting raw material conditions and smelting process conditions; setting the direct reduction degree of iron, and calculating the direct reduction carbon consumption of ton iron, the indirect reduction carbon consumption of ton iron, the heat carbon consumption of ton iron, the reduction carbon consumption of other elements in molten iron and the carburization amount of molten iron; calculating the carbon consumption of iron per ton, wherein the carbon consumption of iron per ton is the larger value of indirect reduction carbon consumption of iron per ton and heat carbon consumption of iron per ton, direct reduction carbon consumption of iron per ton, reduction carbon consumption of other elements in molten iron and carburization amount of molten iron; selecting a plurality of direct reduction degrees, repeating the steps to correspondingly obtain a plurality of tons of iron carbon consumption, and selecting the minimum value, namely the lowest coke ratio under the raw material condition and the smelting process condition. The operator can be helped to obtain a determined carbon reduction target, namely the lowest coke ratio which can be achieved by smelting under specific raw material conditions and smelting process conditions; and a feasible carbon reduction measure is made according to the provided information, so that a reasonable carbon reduction effect is realized.)

1. A method for determining the lowest coke ratio in blast furnace smelting is characterized by comprising the following steps: the method comprises the following steps:

s1, setting raw material conditions and smelting process conditions;

s2, setting the direct reduction degree of iron, and calculating the direct reduction carbon consumption of iron per ton;

s3, calculating the carbon consumption of indirect reduction of iron per ton;

s4, calculating the heat and carbon requirement of iron consumption per ton;

s5, calculating the carbon consumption of reduction of other elements in the molten iron;

s6, calculating the carburizing quantity of the molten iron;

s7, calculating the carbon consumption of each ton of iron, wherein the carbon consumption of each ton of iron is the larger value of the carbon consumption of each ton of iron in indirect reduction and the carbon consumption of each ton of iron in heat and carbon consumption of each ton of iron, the carbon consumption of each ton of iron in direct reduction, the carbon consumption of other elements in molten iron in reduction and the carburizing amount of molten iron in carburization;

s8, selecting a plurality of direct reduction degrees, repeating the steps from S2 to S7 to correspondingly obtain a plurality of tons of iron carbon consumption, and selecting the minimum value, namely the lowest coke ratio under the raw material condition and the smelting process condition.

2. The method for determining the minimum coke ratio in blast furnace smelting according to claim 1, characterized by comprising the following steps: step S2 specifically includes the following steps:

s201, setting the direct reduction degree r of iron_dAccording to the direct reduction equation FeO + C ═ Fe + CO of iron, the calculation formula M for carbon consumption in direct reduction of iron per ton is obtained_rdc＝12/56*r_d1000, calculating the carbon consumption per ton of iron direct reduction, Kg/tFe;

s202, simultaneously calculating the CO amount n generated by direct reduction_1CO＝M_rdc*1000/12，mol/tFe。

3. The method for determining the minimum coke ratio in blast furnace smelting according to claim 2, characterized by comprising the following steps: step S3 specifically includes the following steps:

s301, calculating the weight ratio of Fe₃O₄Reduction to FeO in step S2Required amount of CO n_2CO

According to Fe₃O₄Equation (1/3) Fe reduced to FeO₃O₄+n_1CO＝FeO+(n1-1/3)CO+(1/3)CO₂And its reaction equilibrium constant K_p1Calculating a CO surplus coefficient n1, mol; then Fe₃O₄The amount of CO required for reduction to FeO in step S2 is n_2CO＝1000000*r_d/56*n1，mol/tFe；

S302, calculating an excess coefficient n2 of indirectly reduced CO

According to the reaction equation FeO + n at the lower part of the indirect reduction reaction furnace body₃CO＝Fe+CO₂+ (n3-1) CO + Q and its reaction equilibrium constant K_p2Wherein Q is the heat of reaction formation, n3 is obtained, and the upper middle reaction equation (1/3) of the furnace shaft Fe₃O₄+CO₂+(n4-1)CO＝FeO+(n4-4/3)CO+(4/3)CO₂Obtaining n4, n2 ═ max (n3, n 4);

s303, calculating CO generated by direct reduction and using the CO to indirectly reduce Fe₃O₄The amount of-FeO-Fe, n5 ═ n_1CO-n_2CO，mol；

S304, calculating reducible Fe amount n of direct reduction residual CO amount_1Fe＝n5/n2，mol；

S305, calculating the residual Fe amount n needing indirect reduction_2Fe＝1000000/56*(1-rd)-n_1Fe，mol；

S306, calculating the residual Fe amount n needing indirect reduction_2FeCarbon consumption Mic ═ n_2FeN2 12/1000 Kg/tFe, namely the carbon consumption of indirect reduction of ton of iron.

4. The method for determining the minimum coke ratio in blast furnace smelting according to claim 1, characterized by comprising the following steps: step S4 specifically includes the following steps:

s401, calculating the weight ratio of Fe₂O₃Heat Q released by indirect reduction to FeO_Fe2O3-FeO；

According to Fe₂O₃Reduction to Fe₃O₄And Fe₃O₄The thermal reaction equation for reducing iron into FeO can calculate the weight of iron from Fe₂O₃Heat Q released by indirect reduction to FeO_Fe2O3-FeO；

S402, calculating the heat Qi released by the indirect reduction of FeO into Fe_FeO-Fe；

According to the thermal reaction equation of indirectly reducing FeO into Fe and the direct reduction degree r_dThe heat Qi released by the indirect reduction of FeO into Fe can be calculated_FeO-Fe；

S403, calculating the heat quantity Qd absorbed by FeO directly reduced into Fe_FeO-Fe；

According to the thermal reaction equation of FeO directly reduced into Fe and the direct reduction degree r_dThe heat quantity Qd released by the direct reduction of FeO into Fe can be calculated_FeO-Fe；

S404, calculating other heat consumption Qe in blast furnace smelting;

according to the raw material conditions, partial smelting parameters and direct reduction degree r of blast furnace smelting_dPerforming material balance and heat balance calculation to obtain reduction heat consumption Q1 of Si, Mn and P, heat quantity Q2 carried away by slag, molten iron and coal gas and physical heat Q3 carried away by hot air, and smelting other heat consumption Qe in the blast furnace, namely Q1+ Q2-Q3;

s405, calculating total heat consumption Qz of smelting

According to the energy balance, Qz is Q_Fe2O3-FeO+Qi_FeO-Fe-Qd_FeO-Fe-Qe；

S406, calculating the hot carbon requirement Mre of the iron consumption per ton

And obtaining the unit carbon combustion heat quantity q according to a thermal reaction equation of carbon combustion in front of the tuyere, and the carbon needed by the heat consumption per ton of iron, namely Mre is Qz/q.

5. The method for determining the minimum coke ratio in blast furnace smelting according to claim 4, wherein: step S5 specifically includes the following steps:

according to the material balance calculation, the carbon Mcd consumed by reducing other elements in the molten iron is further obtained_{[Si、Mn、P]}And the other elements are Si, Mn and P.

6. The method for determining the minimum coke ratio in blast furnace smelting according to claim 1, characterized by comprising the following steps: the calculation formula of the step S6 is the molten iron carburizing quantity M_[Fe]The carbon content of the molten iron is 10.

Technical Field

The invention belongs to the field of blast furnace production, and relates to a method for determining the lowest coke ratio in blast furnace smelting.

Background

Blast furnace smelting is a main process of carbon emission in the metallurgical industry, and low carbon not only can reduce the blast furnace smelting cost, but also can reduce the carbon emission, weaken the greenhouse effect and reduce the environmental pollution. The blast furnace smelting process is a complex physical and chemical reaction process, a solid raw material is heated in the process of moving downwards from the upper part of a blast furnace, high-temperature coal gas flows upwards from a tuyere along with the reduction of iron oxide, the coal gas transfers heat to descending furnace charge in the process of rising, meanwhile, the reducing gas in the coal gas reduces oxides in a grading way in the furnace charge, partial oxides which are not reduced by the reducing gas are directly reduced in a liquid area at the lower part of a furnace body, reduced metal and slag are heated and melted by the high-temperature gas in the tuyere area, simultaneously, the carburization to molten iron is completed, the formed liquid iron slag is stored in a lower furnace hearth in a layering way, and the liquid iron slag is discharged out of the furnace at regular time. As can be seen from the blast furnace smelting process, the blast furnace smelting carbon consumption mainly comprises direct reduction of low-valence metal oxides, indirect reduction of the metal oxides by reducing gas, heat consumption of molten-state iron slag and carburization of molten iron. From the viewpoint of cost reduction and environmental protection, the less the blast furnace smelting carbon consumption is, the better the consumption is, but the lower the consumption is, which needs to be explored, the blast furnace raw material condition affects the heat consumption, the direct reduction to generate CO can participate in the indirect reduction, so the direct reduction degree affects the quantity of the reducing agent and the heat consumption, and the heat carbon consumption to generate CO also participates in the indirect reduction, so the heat carbon consumption is overlapped with the indirect reducing agent, and therefore the carbon consumption is based on the raw material and is limited by the direct reduction degree. In addition to high-grade raw materials, finding the carbon consumption under the appropriate direct reduction degree is the most important task for designing and producing low-carbon smelting, and the invention provides a system and a method for determining the minimum coke ratio in blast furnace smelting based on the raw material conditions and the direct reduction degree.

Disclosure of Invention

In view of the above, the invention aims to provide a method for determining the lowest coke ratio in blast furnace smelting, which solves the problem that the lowest coke ratio in blast furnace smelting carbon consumption cannot be accurately determined under certain raw material conditions and smelting process conditions.

In order to achieve the purpose, the invention provides the following technical scheme:

a method for determining the lowest coke ratio in blast furnace smelting comprises the following steps:

s1, setting raw material conditions and smelting process conditions;

s2, setting the direct reduction degree of iron, and calculating the direct reduction carbon consumption of iron per ton;

s3, calculating the carbon consumption of indirect reduction of iron per ton;

s4, calculating the heat and carbon requirement of iron consumption per ton;

s5, calculating the carbon consumption of reduction of other elements in the molten iron;

s6, calculating the carburizing quantity of the molten iron;

s7, calculating the carbon consumption of each ton of iron, wherein the carbon consumption of each ton of iron is the larger value of the carbon consumption of each ton of iron in indirect reduction and the carbon consumption of each ton of iron in heat and carbon consumption of each ton of iron, the carbon consumption of each ton of iron in direct reduction, the carbon consumption of other elements in molten iron in reduction and the carburizing amount of molten iron in carburization;

s8, selecting a plurality of direct reduction degrees, repeating the steps from S2 to S7 to correspondingly obtain a plurality of tons of iron carbon consumption, and selecting the minimum value, namely the lowest coke ratio under the raw material condition and the smelting process condition.

Further, step S2 specifically includes the following steps:

s201, setting the direct reduction degree r of iron_dAccording to the direct reduction equation FeO + C ═ Fe + CO of iron, the calculation formula M for carbon consumption in direct reduction of iron per ton is obtained_rdc＝12/56*r_d1000, calculating the carbon consumption per ton of iron direct reduction, Kg/tFe;

s202, simultaneously calculating the CO amount n generated by direct reduction_1CO＝M_rdc*1000/12，mol/tFe。

Further, step S3 specifically includes the following steps:

S301. calculation of the amount of Fe₃O₄The amount of CO n required for reduction to FeO in step S2_2CO

According to Fe₃O₄Equation (1/3) Fe reduced to FeO₃O₄+n_1CO＝FeO+(n1-1/3)CO+(1/3)CO₂And its reaction equilibrium constant K_p1Calculating a CO surplus coefficient n1, mol; then Fe₃O₄The amount of CO required for reduction to FeO in step S2 is n_2CO＝1000000*r_d/56*n1，mol/tFe；

S302, calculating an excess coefficient n2 of indirectly reduced CO

According to the reaction equation FeO + n at the lower part of the indirect reduction reaction furnace body₃CO＝Fe+CO₂+ (n3-1) CO + Q and its reaction equilibrium constant K_p2Wherein Q is the heat of reaction formation, n3 is obtained, and the upper middle reaction equation (1/3) of the furnace shaft Fe₃O₄+CO₂+(n4-1)CO＝FeO+(n4-4/3)CO+(4/3)CO₂Obtaining n4, n2 ═ max (n3, n 4);

s303, calculating CO generated by direct reduction and using the CO to indirectly reduce Fe₃O₄The amount of-FeO-Fe, n5 ═ n_1CO-n_2CO，mol；

S304, calculating reducible Fe amount n of direct reduction residual CO amount_1Fe＝n5/n2，mol；

S305, calculating the residual Fe amount n needing indirect reduction_2Fe＝1000000/56*(1-rd)-n_1Fe，mol；

S306, calculating the residual Fe amount n needing indirect reduction_2FeCarbon consumption Mic ═ n_2Fe*n 2-12/1000 Kg/tFe, namely the carbon consumption of indirect reduction of ton of iron.

Further, step S4 specifically includes the following steps:

s401, calculating the weight ratio of Fe₂O₃Heat Q released by indirect reduction to FeO_Fe2O3-FeO；

According to Fe₂O₃Reduction to Fe₃O₄And Fe₃O₄The thermal reaction equation for reducing iron into FeO can calculate the weight of iron from Fe₂O₃Heat Q released by indirect reduction to FeO_Fe2O3-FeO；

S402, calculating the heat Qi released by the indirect reduction of FeO into Fe_FeO-Fe；

According to the thermal reaction equation of indirectly reducing FeO into Fe and the direct reduction degree r_dThe heat Qi released by the indirect reduction of FeO into Fe can be calculated_FeO-Fe；

S403, calculating the heat quantity Qd absorbed by FeO directly reduced into Fe_FeO-Fe；

According to the thermal reaction equation of FeO directly reduced into Fe and the direct reduction degree r_dThe heat quantity Qd released by the direct reduction of FeO into Fe can be calculated_FeO-Fe；

S404, calculating other heat consumption Qe in blast furnace smelting;

according to the raw material conditions, partial smelting parameters and direct reduction degree r of blast furnace smelting_dPerforming material balance and heat balance calculation to obtain reduction heat consumption Q1 of Si, Mn and P, heat quantity Q2 carried away by slag, molten iron and coal gas and physical heat Q3 carried away by hot air, and smelting other heat consumption Qe in the blast furnace, namely Q1+ Q2-Q3;

s405, calculating total heat consumption Qz of smelting

According to the energy balance, Qz is Q_Fe2O3-FeO+Qi_FeO-Fe-Qd_FeO-Fe-Qe；

S406, calculating the hot carbon requirement Mre of the iron consumption per ton

And obtaining the unit carbon combustion heat quantity q according to a thermal reaction equation of carbon combustion in front of the tuyere, and the carbon needed by the heat consumption per ton of iron, namely Mre is Qz/q.

Further, step S5 specifically includes the following steps:

according to the material balance calculation, the carbon Mcd consumed by reducing other elements in the molten iron is further obtained_{[Si、Mn、P]}And the other elements are Si, Mn and P.

Further, the calculation formula of step S6 is the amount of carburization M of molten iron_[Fe]The carbon content of the molten iron is 10.

The invention has the beneficial effects that:

the invention can help operators to obtain a determined carbon reduction target, namely the lowest coke ratio which can be achieved by smelting under specific raw material conditions and smelting process conditions; and a feasible carbon reduction measure is made according to the provided information, so that a reasonable carbon reduction effect is realized.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.

Drawings

For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:

FIG. 1 is a schematic flow chart of the present invention.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.

Wherein the showings are for the purpose of illustrating the invention only and not for the purpose of limiting the same, and in which there is shown by way of illustration only and not in the drawings in which there is no intention to limit the invention thereto; to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The same or similar reference numerals in the drawings of the embodiments of the present invention correspond to the same or similar components; in the description of the present invention, it should be understood that if there is an orientation or positional relationship indicated by terms such as "upper", "lower", "left", "right", "front", "rear", etc., based on the orientation or positional relationship shown in the drawings, it is only for convenience of description and simplification of description, but it is not an indication or suggestion that the referred device or element must have a specific orientation, be constructed in a specific orientation, and be operated, and therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes, and are not to be construed as limiting the present invention, and the specific meaning of the terms may be understood by those skilled in the art according to specific situations.

Referring to fig. 1, a method for determining the minimum coke ratio in blast furnace smelting comprises the following steps:

s1, setting raw material conditions and smelting process conditions;

the blast furnace raw material conditions are shown in the table I:

the blast furnace smelting process conditions are shown in a table II (for simplification, the coal injection amount is set as 0 in the invention, and the lowest coke ratio under the specific coal injection amount can be analyzed in the invention):

blast furnace blast parameters are shown in the third table:

s2, setting the direct reduction degree of iron, and calculating the direct reduction carbon consumption of iron per ton; the method specifically comprises the following steps:

s201, setting the direct reduction degree r of iron_d0.45, according to the direct reduction equation of iron FeO + C ═ Fe + CO, obtaining the carbon consumption M of direct reduction of iron per ton_rdc＝12/56*r_d*1000＝12/56*0.45*1000＝96.4286Kg/tFe；

S202, simultaneously calculating the CO amount n generated by direct reduction_1CO＝M_rdc*1000/12＝8035.7143mol/tFe。

S3, calculating the carbon consumption of indirect reduction of iron per ton; the method specifically comprises the following steps:

s301, calculating the weight ratio of Fe₃O₄The amount of CO n required for reduction to FeO in step S2_2CO

According to Fe₃O₄Equation (1/3) Fe reduced to FeO₃O₄+n_1CO＝FeO+(n1-1/3)CO+(1/3)CO₂And its reaction equilibrium constant K_p1＝2.5806(800℃)＝CO₂percent/CO% (1/3)/(n1-1/3), and a CO surplus coefficient n1 is calculated to be 0.4625 mol; then Fe₃O₄The amount of CO required for reduction to FeO in step S2 is n_2CO＝1000000*r_d/56*n1＝1000000*0.45/56*0.4625＝3716.7589mol/tFe；

S302, calculating an excess coefficient n2 of indirectly reduced CO

According to the reaction equation FeO + n at the lower part of the indirect reduction reaction furnace body₃CO＝Fe+CO₂+ (n3-1) CO + Q and its reaction equilibrium constant Kp 2-0.5319 (800 deg.C) CO₂percent/CO%/1/(n 3-1), wherein Q is the heat of reaction formation (obtained by subtracting the enthalpy of the reaction product from the enthalpy of the reaction product), n3 is 2.88, and the upper middle reaction equation (1/3) of the shaft is Fe₃O₄+CO₂+(n4-1)CO＝FeO+(n4-4/3)CO+(4/3)CO₂，K_p1＝2.5806＝CO₂percent/CO% (4/3)/(n4-4/3), n4 ═ 1.85, n2 ═ max (n3, n4) ═ max (2.88, 1.85) ═ 2.88 were determined;

s303, calculating CO generated by direct reduction and using the CO to indirectly reduce Fe₃O₄The amount of-FeO-Fe, n5 ═ n_1CO-n_2CO＝8035.7143-3716.7589＝4318.9554mol；

S304, calculating reducible Fe amount n of direct reduction residual CO amount_1Fe＝n5/n2＝4318.9554/2.88＝1499.6373mol；

S305, calculating the residual Fe amount n needing indirect reduction_2Fe＝1000000/56*(1-rd)-n_1Fe＝1000000/56*(1-0.45)-1499.6373＝8321.7913mol；

S306, calculating the residual Fe amount n needing indirect reduction_2FeCarbon consumption Mic ═ n_2Fe*n2*12/1000＝8321.7913*2.88*12/1000＝287.6011Kg/tFe is the carbon consumption of ton of iron by indirect reduction.

S4, calculating the heat and carbon requirement of iron consumption per ton; the method specifically comprises the following steps:

s401, calculating the weight ratio of Fe₂O₃Heat Q released by indirect reduction to FeO_Fe2O3-FeO；

According to Fe₂O₃Reduction to Fe₃O₄And Fe₃O₄Thermal reaction equation for reduction to FeO, 3Fe₂O₃+CO＝2Fe₃O₄+CO₂+24.9288KJ(800℃)，Fe₃O₄+CO＝3FeO+CO₂-3.2485KJ (800 ℃), and the iron content per ton can be calculated from Fe₂O₃Heat Q released by indirect reduction to FeO_Fe2O3-FeO＝(-24.929+3.2485*2)/6*1000000/56＝-54.854.1667KJ/tFe；

S402, calculating the heat Qi released by the indirect reduction of FeO into Fe_FeO-Fe；

According to the thermal reaction equation of FeO indirectly reduced into Fe₂-16.3125KJ (800 ℃) and degree of direct reduction r_dThe heat Qi released by the indirect reduction of FeO into Fe can be calculated_FeO-Fe＝-16.313*(1-0.45)*100000/56＝-160216.9643KJ/tFe；

S403, calculating the heat quantity Qd absorbed by FeO directly reduced into Fe_FeO-Fe；

According to the thermal reaction equation of FeO + C ═ Fe + CO-133.7155KJ for direct reduction of FeO into Fe and the direct reduction degree r_dThe heat quantity Qd released by the direct reduction of FeO into Fe can be calculated_FeO-Fe＝133.7155*0.45*1000000/56＝1074495.536KJ/tFe；

S404, calculating other heat consumption Qe in blast furnace smelting;

according to the raw material conditions, partial smelting parameters and direct reduction degree r of blast furnace smelting_dCarrying out material balance and heat balance calculation to obtain reduction heat consumption Q1-173257.572 KJ/tFe of Si, Mn and P, heat quantity Q2-2312297.843 KJ/tFe carried away by slag, molten iron and coal gas, physical heat Q3-1628015.441 KJ/tFe carried by hot air, and other heat consumption Qe-Q1 + Q2-Q3-173257.572 + 2312297.843-1628015.441-857539.974 KJ/tFe of the blast furnace;

s405, calculating total heat consumption Qz of smelting

According to the energy balance, Qz is Q_Fe2O3-FeO+Qi_FeO-Fe-Qd_FeO-Fe-Qe＝54.854.1667+160216.9643-1074495.536-857539.974＝1716963.405KJ/tFe；

S406, calculating the hot carbon requirement Mre of the iron consumption per ton

According to the thermal reaction equation of carbon combustion in front of the tuyere, the unit carbon combustion heat quantity q is 9357.9725KJ/Kg, and the carbon needed by iron consumption per ton Mre is 1716963.405/9357.9725 is 183.476 Kg/tFe.

S5, calculating the carbon consumption of reduction of other elements in the molten iron; according to the material balance calculation, the carbon Mcd consumed by reducing other elements in the molten iron is further obtained_{[Si、Mn、P]}Other elements are Si, Mn and P, 5.8 Kg/tFe.

S6, calculating the carburizing quantity of the molten iron; amount of carburization M in molten iron_[Fe]The carbon content of the molten iron is 10-4.8-10-48 Kg/tFe.

S7, calculating the carbon consumption M of iron per ton_C＝M_rdc+max(Mic，Mre)+Mcd_{[Si、Mn、P]}+M_[Fe]＝96.4286+max(287.6011，183.476)+5.8+48＝437.8297Kg/tFe。

S9, selecting a plurality of direct reduction degrees (one gradient per 0.05) within the range of 0-1, repeating the steps S2-S7, correspondingly obtaining a plurality of ton iron carbon consumption, and selecting the minimum value, namely the lowest coke ratio under the raw material condition and the smelting process condition. See table four:

as can be seen from Table four, the minimum coke ratio under the raw material conditions and the smelting conditions was 475Kg/tFe, corresponding to a degree of direct reduction of 0.55.

Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.