CN102146491B - Method for smelting clean steel by supplementation and decarburization with CO2 at end of converter blowing - Google Patents

Abstract

The invention discloses a method for smelting clean steel by supplementation and decarburization with CO2 at the end of converter blowing. In the method, when the clean steel is smelted by using a converter, the oxygen consumption is about 80%-95% of total theoretical calculation amount and the decarburization speed is reduced to below 50% of that in a severe decarburization period, a certain proportion of CO2 gas is mixed in oxygen for decarburization, and the content of carbon in a molten bath is controlled by a furnace gas analysis system. The method has the advantages and effects that CO2 is added in the decarburization gas at the end of converter blowing, thus a decarburization purpose can be achieved and the blowing amount of oxygen can be reduced, so that the content of oxygen in steel is reduced, the loss of the temperature in the tapping process is decreased, and the increase of the oxygen activity in the molten steel is effectively controlled, thereby achieving the purposes of reducing iron loss, lowering the dosage of alloy, decreasing the quantity of impurities in the molted steel and improving the quality of the molten steel.

Description

A kind of bessemerizing adopts CO latter stage 2supplement the Clean Steel smelting process of decarburization

Technical field

The invention belongs to steelmaking technical field, relate to the end-point control method of converter non-oxygen Clean Steel Smelting in latter stage, specifically a kind of bessemerizing adopts CO latter stage ₂supplement the Clean Steel smelting process of decarburization.

Background technology

In the Clean Steel production process, often require the tapping of converter low-carbon (LC), often need to blow O for realizing the low-carbon (LC) tapping more ₂, therefore often can cause oxygen level in molten steel to exceed standard, i.e. molten steel peroxidation, so not only can cause later stage deoxygenated alloy consumption to increase, and deoxidation is mingled with and removes difficulty, indirectly causes steel product quality to descend.

In the prior art, a kind of COMI (CO ₂and O ₂mixed Injection) experimental technique, by adopting thermomechanical analysis, heat calculation and the hot experiment of metallurgical reaction, studied CO ₂with O ₂the mixed injection process for making, to the carbon rejection process in metal melt in the winding-up process, the variation of iron liquid, slag and composition of fumes and temperature has been carried out test and has been analyzed, and draws CO ₂with O ₂the feasibility conclusion of mixed injection process for making, this theory is thought, in vacuum electric induction furnace steel-smelting process, due to supplementing of electric energy heat, makes the heat requirement that can meet steelmaking process, sprays into CO ₂with O ₂mixed gas can remove the carbon in steel.Also mention and utilize CO in the COMI technology ₂reduce the exploitative experiment that fume from steel making produces, experimental result shows, along with mixed injection CO ₂the raising of ratio, the generation of flue dust gradually reduces, and iron loss is obvious downtrending.What this theory was emphasized is to be applied to electric induction furnace steel-making.

Application number 200510011479.X, denomination of invention " a kind of winding-up CO ₂the converter steelmaking process of gas ", a kind of steelmaking process is disclosed with O ₂and CO ₂or CO ₂-O ₂mixed gas is source of the gas, and amount of spraying gas is 1000-120000Nm ³/ h, pressure is 0.4-1.6MPa.This technique can be utilized the CO with waste gas acquisition after recycling of various industrial furnaces ₂, also can exploit natural natural CO ₂resource is source of the gas.Be characterized in CO ₂replace the gas of oxygen as smelting molten steel, reduced the scaling loss of smelting process iron and other metallic elements, reduced production cost, reduced the consumption of oxygen.The method adopted is that omnidistance winding-up is mixed with CO ₂mixed gas, draw CO from making steel theory ₂with carbon and iron are all thermo-negative reaction, this not only can directly cause that fire box temperature is too low, the slag making difficulty, and if omnidistance winding-up CO ₂during mixed gas that content is 13%, adding amount of scrap steel is zero substantially, does not so not only reach the original intention of " energy-saving and emission-reduction ", and need to set up gas mixing device, or set up spray gun, and operation is controlled and the base level facility all proposes requirements at the higher level.

The patent application Unexamined Patent 9-87723 of Japan, propose to be blown into CO in the later stage of converter steelmaking ₂method, what take is to add CO in the later stage of converter steelmaking in molten bath ₂, its objective is CO ₂resolve into CO and oxygen, utilize oxygen to carry out decarburization, do not discuss its reaction possibility here and occur, but the method does not have essential distinction with the minimizing oxygen supply intensity, and this method discloses CO ₂ratio between gas and oxygen and how carbon content is controlled and judged, cause this method to be difficult to realize its purpose.

In addition, the winding-up CO that a kind of application number is 200910088822.9 ₂gas is controlled the method for temperature of steelmaking melting pool of converter, belongs to the converter steelmaking field, relates to the converter dephosphorization technology.This invention adopts CO ₂gas (or CO-O ₂mixed gas) spray into converter molten pool, by regulating

ratio realizes that molten bath steadily heats up.Smelt the prometaphase (3-5min),

ratio control is at 10%-100%, and the blowing gas total flux is 100-80000Nm ³/ h, now take the bottom blowing strong mixing, and temperature is controlled in 1300-1400 ℃.Smelt and look desiliconization and dephosphorization situation and bath temperature height situation mid-term, adjust

ratio, be controlled at 10%-50%, and the blowing gas flow is 100-80000Nm ³/ h.Adopt the method, dephosphorization rate can reach 85%-95%, and after deslagging, the rephosphorization rate is less than 3%.

Also has the CO that utilizes that a kind of application number is 200810104127.2 ₂reduce the method for fume from steel making, this invention belongs to ferrous metallurgy and field of environment protection, relates to the improvement of fume from steel making.Comprise converter steelmaking and electric steelmaking process.The purpose of this invention is to adopt a kind of method that can reduce the generation of steelmaking process flue dust, reduces the scaling loss of smelting process iron and other metallic elements.Use a small amount of CO ₂gas is blended in oxygen jet, when the mixed gas jet is ejected into molten bath, has reduced “Huo Dian district, molten bath " temperature, when Dang Huodian district temperature is reduced to below 2750 ℃, the evaporation of iron will be controlled, and in the steel-making smelting process, soot emissions will reduce.In mixed gas, the content of carbonic acid gas is controlled at 1-9%, and the content of oxygen is controlled at 99%-91%.Adopt this invention, the evaporation of iron is carried and is reduced about 30-70%, and the iron loss that flue dust causes reduces 5-10kg/t.

Above several method all concentrates on and how to reduce oxygen depletion, reduces in fume amount and temperature controlled research, smelt the whole process using mixed gas, and, along with the ratio of carrying out mixed gas of smelting need to constantly be adjusted, operation is controlled for this and base level equipment is all had higher requirement.

These patent applications all do not have for how when producing Clean Steel, to adopt and to blow CO ₂carry out the elaboration of decarburization.

Summary of the invention

The present invention discloses a kind of bessemerizing and adopts CO latter stage ₂supplement the Clean Steel smelting process of decarburization, can realize the decarburization target, can effectively control again oxygen activity in molten steel increases, thereby realizes reducing iron loss, minimizing alloy consumption, minimizing inclusion content in melting steel quantity, improves the purpose of steel quality.

The object of the present invention is achieved like this, and at application converter smelting Clean Steel, when 80%～95% left and right that oxygen-consumption is the Theoretical Calculation total amount, decarbonization rate has been down to 50% when following of violent carbon period, adopts a certain proportion of CO of mixing in oxygen ₂gas carries out decarburization, by the analysis of fumes system, controls the carbon content in molten bath.

Design parameter is CO ₂content accounts for the 11%-20% of volume percent, and air supply intensity is 1.0-5.0Nm ³/ tmin.

Concrete grammar of the present invention has, the analysis of fumes system is gathered all data by acquisition system in converting process, data collecting system comprises that furnace gas under meter and composition of fumes analytical system form, utilize the furnace gas under meter to detect online the furnace gas flow, the composition of fumes analytical system is analyzed the furnace gas sample gas of obtaining simultaneously, and detected information exchange is crossed to the computer that data communication system transfers to master control room, carry out analytical calculation by mathematical model.

The present invention adopts the analysis of fumes system, and presses columns model and carry out the analytical calculation decarbonization rate:

$v_C=\frac{1}{2}\×0.1\×Q_{\mathrm{gas}}\×(x_{\mathrm{co}}+x_{{\mathrm{co}}_2})\×\frac{12}{22.4}\×\frac{1}{W_m}---\left(1\right)$

W in formula _m---steel quality, t

Q _gas---furnace gas flow, Nm ³/ s

X _co---the molar fraction of CO in furnace gas, %

Draw the molten bath carbon content by decarbonization rate:

To decarbonization rate v _ccarry out integration, can obtain summation (the ∑ C of continuous decarburized amount _de, kg):

${\mathrm{\ΣC}}_{\mathrm{de}}={\∫}_0^t\left({10W}_m{v}_C\right)\mathrm{dt}---\left(2\right)$

Carbon content while being incorporated into stove again just can calculate dynamic w[C in molten bath], %:

w[C]＝0.1×(∑C _ori-∑C _de)/W _m (3)

∑ C in formula _oriinitial carbon amount in-molten bath, kg.

Advantage of the present invention and effect be, 1, and owing to being blown into CO ₂, its reaction formula is CO ₂+ C=2CO, compared with prior art, reduce the amount of being blown into of oxygen, the reduction of oxygen content in steel, and the tapping process temperature loss reduces, so the reduction of the tapping temperature of terminal target call, although like this because of the CO that re-blows ₂cause a certain amount of temperature drop, but still do not affect adding amount of scrap steel; 2, the reduction meeting of invar water oxygen level and temperature directly reduces refractory loss; 3, in slag, FeO content reduces, and iron loss reduces; 4, Molten Steel over-oxidation alleviates, the usage quantity of deoxygenated alloy reduces, and inclusion content in melting steel quantity reduces, and improves steel quality, has real low-carbon economy meaning.

The present invention, by the combination of analysis of fumes system and mathematical model, can realize the on line real-time monitoring decarbonization rate, for accurately holding blowing gas by O ₂to O ₂with CO ₂the switching time of mixed gas provide reliable data to guarantee.

Embodiment

Below by embodiment, the invention will be further described.

Produce Clean Steel for the application converter, when steel-making oxygen-consumption 80%～95% left and right that is total amount, that is to say and bessemerize latter stage, decarbonization rate has been down to below 50% of violent carbon period, in molten steel, carbon content often<0.5%, if now further oxygen blast, not only decarburization effect descends, and molten steel oxygenation is obvious, thereby while causing follow-up refining, the deoxygenated alloy consumption increases, and deoxidation is mingled with and removes difficulty, indirectly causes steel product quality to descend, the present invention was selected this period, in the decarburization gas be blown into, added CO ₂and then supplementary decarburization, its reaction formula is CO ₂+ C=2CO, so just can reduce the amount of being blown into of oxygen, although added CO ₂can cause the decline of liquid steel temperature, but be now the latter stage of smelting, various reactions complete substantially, and supplementary decarburization completed in the very short time, can not affect the quality of tapping, the reduction due to tapping temperature can reduce refractory corrosion, the CO that the present invention is supplementary on the contrary ₂content accounts for the 11%-20% of volume percent, and air supply intensity is 1.0-5.0Nm ³/ tmin, if the CO added ₂very little, the purpose that wants to reach decarburization can cause the time lengthening of jetting to amount, affects rhythm of production; If the CO added ₂measure too greatly, molten steel temperature drop loss is too large, can't meet the tapping requirement.

The present invention is tested in the 100t converter steelmaking, and the raw material data of specific embodiment are listed in table 1,

Table 1 material condition

In order accurately to carry out the switching of mixed gas, during productive experiment, to be judged by the mathematical model of analysis of fumes system, experimental results show that and observe decarbonization rate as the preliminary basis for estimation of switching gas because can very clearly find out the variation of decarbonization rate from mathematical model so often using while testing.

Embodiment 1

(1) control the oxygen consumption total amount by mathematical model, when blowing to total oxygen-consumption 80% the time make and switch for the first time the gas judgement, now decarbonization rate does not drop to 50% of violent carbon period yet, the continuation oxygen blast;

(2) when blowing to total oxygen-consumption 88% the time make and switch for the second time gas judgement, now decarbonization rate has dropped to 50% of violent carbon period, mathematical model judges that carbon content is 0.24%, now blowing gas carries out by O ₂switch to O ₂with CO ₂mixed gas, CO ₂content accounts for 11% of air-blowing quantity, and air supply intensity is 2.0Nm ³/ tmin;

(3), when recording carbon content 0.072%, stop winding-up;

Embodiment 2

(1) control the oxygen consumption total amount by mathematical model, when blowing to total oxygen-consumption 85% the time make and switch for the first time the gas judgement, now decarbonization rate does not drop to 50% of violent carbon period yet, the continuation oxygen blast;

(2) when blowing to total oxygen-consumption 90% the time make and switch for the second time gas judgement, now decarbonization rate has dropped to 50% of violent carbon period, mathematical model judgement carbon content is 0.18%, switches gas, completes blowing gas by O ₂switch to O ₂with CO ₂mixed gas, CO ₂content accounts for 14% of air-blowing quantity, and air supply intensity is 2.0Nm ³/ tmin;

(3), when recording carbon content 0.06%, stop winding-up;

Embodiment 3

(1) control the oxygen consumption total amount by mathematical model, when blowing to total oxygen-consumption 90% the time make and switch for the first time the gas judgement, now decarbonization rate does not drop to 50% of violent carbon period yet, the continuation oxygen blast;

(2) when blowing to total oxygen-consumption 92% the time make and switch for the second time gas judgement, now decarbonization rate has dropped to below 50% of violent carbon period, mathematical model judgement carbon content is 0.12%, switches gas, completes blowing gas by O ₂switch to O ₂with CO ₂mixed gas, CO ₂content accounts for 18% of air-blowing quantity, and air supply intensity is 2.0Nm ³/ tmin;

(3), when recording carbon content 0.072%, stop winding-up;

Result of implementation is listed in table 2.Operating process is controlled blowing steadily, does not occur the spitting and getting dry phenomenon in converting process.

The test-results of table 2 patent working example

Terminal oxygen level average out to 856 * 10 in the prior art ^-6, alloy consumption silicomanganese 13.960kg/t, alumal 3.822kg/t, according to the technical essential operation of this patent, the terminal oxygen level is 600 * 10 ^-6left and right, alloy consumption silicomanganese 13.660kg/t, alumal 3.702kg/t, compare with traditional method and saved respectively 0.300kg/t and 0.120kg/t.

Claims (2)

1. bessemerize and adopt CO latter stage for one kind ₂supplement the Clean Steel smelting process of decarburization, it is characterized in that, when application converter smelting Clean Steel, when oxygen-consumption is 80% ~ 95% of Theoretical Calculation volume total amount, decarbonization rate has been down to 50% when following of violent carbon period, employing mixed C O in oxygen ₂gas carries out decarburization, by the analysis of fumes system, controls the carbon content in molten bath, CO in its mixed gas ₂content is controlled at the 11%-20% of volume percent, and air supply intensity is 1.0-5.0Nm ³/ tmin, when carbon content reaches the controlled requirement, stop winding-up.

2. a kind of bessemerizing according to claim 1 adopts CO latter stage ₂supplement the Clean Steel smelting process of decarburization, it is characterized in that, the analysis of fumes system is gathered all data according to acquisition system, utilize the furnace gas under meter to detect online the furnace gas flow, the composition of fumes analytical system is analyzed the furnace gas sample gas of obtaining simultaneously, and detected information exchange is crossed to the computer that data communication system transfers to master control room, carry out analytical calculation by mathematical model and draw corresponding analytical data

The analysis of fumes system is pressed columns model and is carried out the analytical calculation decarbonization rate:

$v_C=\frac{1}{2}\&times;0.1\&times;Q_{\mathrm{gas}}\&times;(x_{\mathrm{co}}+x_{{\mathrm{co}}_2})\&times;\frac{12}{22.4}\&times;\frac{1}{W_m}---\left(1\right)$

W in formula _m---steel quality, t

Q _gas---furnace gas flow, Nm ³/ s

X _co---the molar fraction of CO in furnace gas, %

Draw the molten bath carbon content by decarbonization rate,

To decarbonization rate v _ccarry out integration, can obtain summation (the ∑ C of continuous decarburized amount _de, kg):

$\mathrm{\&Sigma;}{C}_{\mathrm{de}}={\&Integral;}_0^t\left(10W_m{v}_C\right)\mathrm{dt}---\left(2\right)$

Carbon content while being incorporated into stove again just can calculate dynamic w[C in molten bath], %:

$w\left[C\right]=0.1\&times;(\mathrm{\&Sigma;}{C}_{\mathrm{ori}}-\mathrm{\&Sigma;}{C}_{\mathrm{de}})/W_m---\left(3\right)$

Σ C in formula _oriinitial carbon amount in-molten bath, kg.