CN111455136B - Method for improving energy utilization rate of carbon monoxide and hydrogen escaped from molten steel vacuum decarburization process - Google Patents
Method for improving energy utilization rate of carbon monoxide and hydrogen escaped from molten steel vacuum decarburization process Download PDFInfo
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- C21C7/068—Decarburising
Abstract
The invention discloses a method for improving the utilization rate of energy sources of carbon monoxide and hydrogen escaped from the vacuum decarburization process of molten steel, which comprises the following steps: s1, before vacuum decarburization: carrying out deep deoxidation on the molten steel to form deoxidized molten steel, wherein the deoxidized molten steel is in a low-oxygen-level state; s2, vacuumizing the RH vacuum chamber after the deoxidized molten steel enters the RH, enabling the deoxidized molten steel to circularly enter the RH vacuum chamber, controlling an oxygen lance to blow oxygen to the RH vacuum chamber, and entering a vacuum decarburization procedure; s3, in the vacuum decarburization process, controlling the lance position of the oxygen lance in real time based on the target gas component in the exhaust gas of the RH vacuum chamber so as to control the target gas component in the target range. Deeply deoxidizing the molten steel before decarburization, controlling dissolved oxygen under the condition that oxygen blowing is started at the beginning of vacuum building, and basically not generating concentrated carbon-oxygen reaction before finishing concentrated dehydrogenation; the dehydrogenation and decarburization processes are separated, the decarburization rate can be well controlled according to the oxygen blowing rate, a large amount of synchronous escape can not occur, and the serious splashing is avoided.
Description
Technical Field
The invention belongs to the technical field of external refining of steelmaking furnaces, and particularly relates to a method for improving the energy utilization rate of carbon monoxide and hydrogen escaping from a molten steel vacuum decarburization process.
Background
Among the external decarburization methods for molten steel, ladle external circulation refining devices such as RH and the like are widely applied due to the advantages of good decarburization efficiency, short treatment period, good refining effect, strong comprehensive functions and the like. Particularly, in recent years, with the development of manufacturing industries such as automobiles, home appliances, and electricians, the demand for decarburized steel has been increasing. However, the decarburization process is realized by circulating molten steel in a vacuum chamber, the refractory material and the circulating lifting gas of the vacuum chamber have relatively large requirements on heat energy consumption, and it is very important to recycle energy as much as possible in the process. The vacuum decarburization process is a process that carbon and oxygen in molten steel are reacted to generate carbon monoxide under vacuum conditions and the carbon monoxide escapes, and is divided into a natural decarburization mode and a forced decarburization mode in practice, and dissolved hydrogen in the steel can simultaneously escape in the early stage in the decarburization process. So-called natural decarburization, which is a decarburization mode in which carbon is removed to a target content by completely using dissolved oxygen already contained in molten steel, the dissolved oxygen in steel is already sufficient and does not need to be replenished, and carbon monoxide etc. released from molten steel are directly drawn out of a vacuum chamber; the forced decarbonization is a decarbonization mode that an auxiliary oxygen blowing device is adopted to supplement oxygen to dissolved oxygen which is not enough to remove carbon in steel to a target content, part of carbon monoxide which escapes from molten steel can meet the supplemented oxygen to react and release heat, heat is supplied to the molten steel and the wall of a vacuum chamber through radiation and convection, the temperature is raised, and the other part of carbon monoxide is directly pumped out of the vacuum chamber.
For a long time, it has been a common practice in the steel industry to perform vacuum decarburization by frequently using natural decarburization, and even when forced decarburization is performed, a small amount of oxygen deficiency is supplemented to the target carbon in a state of high dissolved oxygen. In this case, the combustible gases escaping during the vacuum decarburization process are only slightly, if not essentially directly, able to react with the supplemental oxygen to generate little or no exothermic heat. In addition, the amount of the available heat energy gas is related to the oxygen supply amount and the oxygen supply mode. When the dissolved oxygen in steel is high, the carbon-oxygen reaction starts as soon as the vacuum is drawn, and if the timing of oxygen blowing (particularly when the oxygen blowing flow rate is large) is not appropriate, the decarburization reaction is violent, carbon monoxide and hydrogen are instantaneously released, and the total gas generation amount is large. At this time, although the combustion reaction of carbon monoxide and hydrogen occurs, since the total amount of oxygen blowing is not large and the flow rate of oxygen blowing cannot be increased at the stage of generation of a large amount of carbon monoxide, the utilization rate of the escaping combustible gas is not high, and most of the escaping combustible gas is still discharged out of the vacuum chamber. Therefore, no matter whether the existing vacuum decarburization mode blows oxygen or not, as long as the dissolved oxygen in steel is high, the problems that reaction and escaping gas are uncontrollable, the utilization efficiency of precious combustible gas is low, and secondary energy in the process cannot be fully utilized exist.
Disclosure of Invention
The invention provides a method for improving the utilization rate of energy sources of carbon monoxide and hydrogen escaped from the vacuum decarburization process of molten steel, aiming at realizing the full utilization of combustible gases such as hydrogen, carbon monoxide and the like escaped from steel during RH decarburization so as to reduce the tapping temperature of a steelmaking furnace.
In order to achieve the purpose, the invention adopts the technical scheme that: a method for improving the utilization rate of energy sources of carbon monoxide and hydrogen escaped from the vacuum decarburization process of molten steel comprises the following steps:
s1, before vacuum decarburization: carrying out deep deoxidation on the molten steel to form deoxidized molten steel, wherein the deoxidized molten steel is in a low-oxygen-level state;
s2, vacuumizing the RH vacuum chamber after the deoxidized molten steel enters the RH, enabling the deoxidized molten steel to circularly enter the RH vacuum chamber, controlling an oxygen lance to blow oxygen to the RH vacuum chamber, and entering a vacuum decarburization procedure;
s3, in the vacuum decarburization process, controlling the lance position of the oxygen lance in real time based on the target gas component in the RH vacuum chamber exhaust gas so as to control the target gas component in the target range.
Further, the calculation of the flow of the oxygen lance specifically comprises the following steps:
calculating the oxygen blowing amount of the deoxidized molten steel;
the oxygen blowing amount consists of oxygen blowing amount of residual deoxidizing elements of the deoxidized molten steel, temperature compensation oxygen blowing amount of the deoxidized molten steel, oxygen blowing amount of decarburization in the deoxidized molten steel and oxygen blowing amount of excess oxygen for ensuring the finish of the decarburization of the deoxidized molten steel;
calculating the oxygen lance flow based on the oxygen blowing amount and the decarburization time;
wherein, the oxygen blowing amount of the residual deoxidizing elements in the deoxidized molten steel is the oxygen amount required for removing the deoxidizing elements in the deoxidized molten steel;
the temperature compensation oxygen blowing amount of the deoxidized molten steel is the oxygen amount required by heat supply through subsequent oxidation reaction with aluminum when the temperature of the deoxidized molten steel entering RH does not reach the target temperature; (ii) a
The oxygen blowing amount for decarburization in the deoxidized molten steel is the oxygen amount required for removing carbon in the deoxidized molten steel;
the oxygen blowing amount of excess oxygen at the end of decarburization of the deoxidized molten steel is an oxygen amount required for satisfying the excess oxygen at the end of decarburization. Further, the oxygen lance flow is calculated as follows:
the oxygen lance flow is divided into oxygen blowing amount and decarburization time and 60 and molten steel amount.
Furthermore, when the target gas is CO, the concentration of CO in the discharged gas of the RH vacuum value exceeds the target range, the lance position of the oxygen lance is increased by 500-1500 mm.
The beneficial effects are as follows: (1) deeply deoxidizing the molten steel before vacuum decarburization, controlling dissolved oxygen to be under the condition that oxygen blowing is started when vacuum is initially established, and basically not generating concentrated carbon-oxygen reaction before concentrated dehydrogenation is completed; (2) oxygen is blown to the molten steel at the beginning of vacuum establishment, and the oxygen blowing continuously runs through the whole decarburization process; (3) the dehydrogenation and decarburization processes are separated, the decarburization rate can be well controlled according to the oxygen blowing rate, a large amount of synchronous escape can not occur, and serious splashing is avoided; (4) the oxygen lance position is controlled by the content of the gas component of the flue gas discharged from the vacuum chamber, so that the combustion efficiency is improved;
drawings
FIG. 1 is a flow chart of a method for improving the utilization rate of carbon monoxide and hydrogen energy escaping from the vacuum decarburization process of molten steel.
Detailed Description
The following detailed description of the embodiments of the present invention will be given in order to provide those skilled in the art with a more complete, accurate and thorough understanding of the inventive concept and technical solutions of the present invention.
Controlling the molten steel to be in a low oxygen level state before vacuum decarburization treatment, blowing a large amount of oxygen into the molten steel in order to reach a decarburization target value, wherein a time process is provided for reaching the dissolved oxygen content in steel which is subjected to decarburization reaction with a large amount of carbon in the molten steel by oxygen blowing, hydrogen is intensively escaped in the process, only oxygen flow impacts the surface of the molten steel to generate a small amount of carbon monoxide, and the oxygen blowing amount is enough to fully combust the generated carbon monoxide and hydrogen; along with the gradual rise of dissolved oxygen in steel, the amount of carbon monoxide generated by oxygen flow impacting a reaction zone on the surface of molten steel is also increased, but hydrogen is not much escaped, and sufficient oxygen blowing oxygen is still available to enable combustible gas to fully react; the decarburization reaction is further carried out with the further increase of the dissolved oxygen in the steel, but because the decarburization reaction which is carried out gradually from the beginning in the early stage reduces the residual carbon in the steel, the decarburization reaction rate is not greatly increased with the increase of the oxygen content, and the oxygen blowing is enough to fully combust the generated carbon monoxide; and finally stopping blowing oxygen at the end of the decarburization reaction, so that escaped combustible gases such as hydrogen, carbon monoxide and the like are fully combusted, and secondary energy in the decarburization process is fully utilized.
FIG. 1 is a flow chart of a method for improving the utilization rate of carbon monoxide and hydrogen energy released in the vacuum decarburization process of molten steel, which is provided by the embodiment of the invention, and the method specifically comprises the following steps:
s1, before vacuum decarburization: performing deep deoxidation on the molten steel to form deoxidized molten steel, wherein the deoxidized molten steel is in a low-oxygen-level state, and for example, the deoxidized molten steel is in the low-oxygen-level state when the oxygen content is less than or equal to 100 ppm;
s2, vacuumizing the RH vacuum chamber after the deoxidized molten steel enters the RH, enabling the deoxidized molten steel to circularly enter the RH vacuum chamber, controlling an oxygen lance to blow oxygen to the RH vacuum chamber, and entering a vacuum decarburization procedure;
s3, in the vacuum decarburization process, controlling the lance position of the oxygen lance in real time based on the target gas components in the exhaust gas of the RH vacuum chamber so as to control the components of the target gas in a target range, wherein the target gas is carbon monoxide, and the corresponding target range can be defined as: the content of CO is less than or equal to 1 percent, the initial lance position of the oxygen lance is generally set to be 4500mm, when the target gas exceeds the corresponding target range, the lance position of the oxygen lance is controlled to be improved by 500mm-1500mm, the combustion of the CO is promoted, so that the content of the CO in the gas discharged from the RH vacuum chamber is controlled to be less than 1 percent, and the content of the H in the gas discharged from the RH vacuum chamber is generally less than or equal to 0.0020 percent due to the relatively small content of the H in the molten steel.
The calculation of the flow of the oxygen lance specifically comprises the following steps:
estimating the oxygen blowing amount of the deoxidized molten steel;
oxygen blowing amount which is oxygen blowing amount of residual deoxidizing elements (aluminum or silicon) in the oxidation deoxidized molten steel, temperature compensation oxygen blowing amount of the deoxidized molten steel, oxygen blowing amount of decarburization in the deoxidized molten steel and oxygen blowing amount of excess oxygen for ensuring the end of the decarburization of the deoxidized molten steel;
calculating the flow of the oxygen lance based on the oxygen blowing amount and the decarburization time, wherein the flow of the oxygen lance is divided into oxygen blowing amount and decarburization time (minutes) multiplied by 60 and divided into molten steel amount; unit of molten steel amount: t, unit of oxygen blowing amount: nm 3 The unit of oxygen lance flow is as follows: nm 3 /h·t。
Wherein, the oxygen blowing amount of the residual deoxidizing elements in the deoxidized molten steel is the oxygen amount required for removing the deoxidizing elements in the deoxidized molten steel; the required oxygen blowing amount of the deoxidized molten steel with temperature compensation is the oxygen amount required by heat supplement through subsequent oxidation reaction with aluminum when the temperature of the deoxidized molten steel entering RH does not reach the target temperature (the oxidation reaction of the aluminum releases heat for heating); the oxygen blowing amount for decarburization in the deoxidized molten steel is the oxygen amount required for removing carbon in the deoxidized molten steel; the oxygen blowing amount for ensuring the excess oxygen at the completion of decarburization of the deoxidized molten steel is an oxygen amount required for satisfying the excess oxygen at the completion of decarburization. .
The flow of the oxygen lance is 1.5Nm 3 10 Nm/h ton steel 3 A ton of steel per hour to control the time of oxygen blowing and to continue the decarburization process; the lance position of the oxygen lance is 700mm-7000mm, and the aim is to control the CO content of the flue gas analyzer to be less than or equal to 1 percent. The beneficial effects are as follows: (1) deeply deoxidizing the molten steel before vacuum decarburization, controlling dissolved oxygen to be under the condition that oxygen blowing is started when vacuum is initially established, and basically not generating concentrated carbon-oxygen reaction before concentrated dehydrogenation is completed; (2) oxygen is blown to the molten steel at the beginning of vacuum establishment, and the oxygen blowing continuously runs through the whole decarburization process; (3) the dehydrogenation and decarburization processes are separated, the decarburization rate can be well controlled according to the oxygen blowing rate, a large amount of synchronous escape can not occur, and serious splashing is avoided; (4) the oxygen lance position is controlled by the content of the gas component of the flue gas discharged from the vacuum chamber, so that the combustion efficiency is improved;
the technical scheme and the effect of the invention are described in detail by taking a 300-ton steel furnace and a 300-ton RH furnace for smelting low-carbon and ultra-low-carbon steel as examples:
example I: steel grade: low carbon steel DC 03; actual molten steel amount: 312 ton of
The chemical composition of the low-carbon steel DC03 is required to be as shown in the following table 1:
TABLE 1 Low carbon steel DC03 chemical composition Table
The tapping temperature of the steel furnace is 1621 ℃, 1382kg of aluminum and iron are added in the tapping process to carry out deep deoxidation on the molten steel, and the oxygen content of the molten steel is 3.2ppm when RH enters the station;
vacuumizing the deoxidized molten steel after entering RH, blowing oxygen into the vacuum chamber by an RH top lance after the deoxidized molten steel enters the RH vacuum chamber and starts to circulate, wherein the oxygen blowing amount is A + B + C + D-125 +157+75+ 51-408 (Nm + C + D) 3 ) The calculation process is as follows:
a: oxygen blowing amount of residual deoxidizing element (acid-soluble aluminum) of the deoxidized molten steel:
the amount of molten steel (ton) is multiplied by 0.01004 × [ Als%] Entering station ÷0.001％＝312×0.01004×0.040％÷0.001％＝125(Nm 3 ) (ii) a Wherein the molten steel amount (ton) is the weight of molten steel, [ Als%] Entering a station The content of acid-soluble aluminum in molten steel entering a station (namely entering RH), 0.01004 is the oxygen blowing amount required by acid-soluble aluminum (the content of acid-soluble aluminum: 0.001%) in per 1 ton of molten steel oxidized, and the oxygen blowing amount is determined according to the field data such as metallurgical theory calculation, oxygen yield and the like;
b: the oxygen blowing amount of the deoxidized molten steel is compensated by the temperature:
b is the amount of molten steel (ton) × 0.0373 × (T) Target temperature of arrival -T Entering station -T Temperature rise of aluminum oxidation )＝312×0.0373×(1600-1580-0.040％÷0.001％×0.37)＝157(Nm 3 ) (ii) a Wherein the molten steel amount (ton) is the molten steel weight, T Target temperature of arrival The station entering temperature of the molten steel which does not need temperature compensation in the RH process is related to steel mill equipment and process level, and 1600 ℃ is taken; t is Entering station The temperature of the molten steel is measured when the molten steel enters RH; t is Temperature rise of aluminum oxidation Is the temperature rise value T of residual acid-soluble aluminum in oxidized molten steel Heating for aluminium oxidation [Als％] Entering station 0.001% x 0.37; 0.0373 blowing required for raising the temperature of molten steel per ton to 1 DEG COxygen content is determined according to site data such as metallurgical theoretical calculation, oxygen yield and the like; 0.37 is the elevated temperature per 0.001% acid-soluble aluminum oxide; and (4) calculating according to a metallurgical theory and determining according to field measured data.
C: oxygen blowing amount for decarburization in deoxidized molten steel:
amount of molten steel (ton) × 0.1506 × ([ C%] Entering station -[C％] Target of decarburization completion )÷0.010％＝312×0.1506×(0.031％-0.0010％)÷0.010％＝75(Nm 3 )；
Wherein the molten steel amount (ton) is the weight of molten steel, [ C%] Entering station The carbon content of molten steel when entering a station; [ C ]] Target of decarburization completion In order to finish the decarburization, the target carbon content is 0.015 percent of low-carbon steel which is related to smelting steel types; 0.1506 is the oxygen blowing amount needed by removing 0.010% carbon content from each ton of molten steel, and is determined according to the metallurgical theory calculation and the field data such as oxygen yield;
d: oxygen blowing amount for ensuring excess oxygen at the end of decarburization of deoxidized molten steel:
amount of molten steel (ton) × 0.0011 × [ O ═ D] Target of decarburization completion ＝312×0.0011×150＝51(Nm 3 )
Wherein the molten steel amount (ton) is the molten steel weight, [ O ]] Target of decarburization completion In order to finish decarburization, the target oxygen content is 150ppm of low-carbon steel which is related to smelting steel types; 0.0011 is the oxygen blowing amount required by 1ppm of oxygen increase of each ton of molten steel, and is determined according to site data such as metallurgical theoretical calculation, oxygen yield and the like;
the oxygen lance flow is determined after calculation according to the following formula. Oxygen lance flow rate (Nm) is oxygen blowing rate 3 ) RH decarburization time (minutes) × 60 ÷ molten steel amount (ton) ÷ 408 ÷ 18 × 60 ÷ 312 ÷ 4.36Nm ÷ 3 H.t steel. Wherein the decarburization time is set to 18 minutes, and the setting of the decarburization time is related to the steel type;
when oxygen blowing is started, the oxygen lance position is set to be 4500 mm. During the oxygen blowing period, the content changes of CO, O, H and other gas components of the waste gas analyzer are monitored, and the purposes that the content of CO in the flue gas analyzer is less than or equal to 1 percent, the content of O in the flue gas analyzer is less than or equal to 5 percent, and the content of H in the flue gas analyzer is less than or equal to 0.0010 percent are taken as targets. In the embodiment, the content of gas components such as CO, O, H and the like of the waste gas analyzer in the early stage of oxygen blowing reaches the target, but when the oxygen blowing time is 5 minutes and 28 seconds, the content of CO in the flue gas is 1.7%, the content of O is 7.1%, and the content of H is 0%, and the content of CO in the exhaust gas exceeds the control target, so that the position of an oxygen blowing lance is increased to 5200mm, after 2 minutes, the content of CO in the exhaust gas is 0.8%, the content of O is 3.52%, and the content of H is 0.0006%, so that the control target is reached, and then the control target range fluctuates all the time, and the lance position is kept at 5200mm until the decarburization is finished;
after RH oxygen blowing is finished, molten steel is decarburized, deoxidized and alloyed, and the method is the same as the current method of a steel mill; and when the RH is out of the station, the carbon content of the molten steel is as follows: 0.022 percent.
Comparative example i: steel grade: low carbon steel DC 03; actual molten steel amount: 310 ton of
The tapping temperature of the steel-making furnace is 1665 ℃, and no deoxidation alloy is added in the tapping process;
after the molten steel enters RH, oxygen is determined, temperature measurement and sampling are carried out, the temperature of the molten steel is 1611 ℃, the oxygen content is 527ppm, and the carbon content of the molten steel is 0.028%;
RH has natural decarburization condition without oxygen blowing;
decarburization is finished after RH extraction is started for 10min, wherein the temperature of molten steel is 1585 ℃, the oxygen content is 152ppm, and the carbon content of the molten steel is 0.021%;
deoxidizing and alloying, and the total time is 12 minutes;
RH is broken, temperature is measured before breaking, and the temperature of the molten steel is 1582 ℃ at the moment.
The main process effect of example I is compared with that of comparative example I in Table 2:
the table is connected:
table 2 comparison of the main process effects of example i and comparative example i
Example II: steel grade: IF steel DC 06; actual molten steel amount: 303 ton (ton)
The chemical composition requirements of IF steel DC06 are as follows in Table 3:
TABLE 3 ultra-low carbon steel DC03 chemical composition Table
The tapping temperature of the steel furnace is 1627 ℃, 1500kg of aluminum and iron are added in the tapping process to carry out deep deoxidation on the molten steel, and when RH enters the station, the oxygen content of the molten steel is 2.8 ppm;
and vacuumizing the molten steel after RH is added. When molten steel enters an RH vacuum chamber and starts to circulate, oxygen is blown into the vacuum chamber through an RH top lance, and the oxygen blowing amount is 146+ B + C + D + 146+70+128+ 100-444 (Nm) 3 ) The calculation process is as follows:
a: oxygen blowing amount of residual deoxidizing elements (acid-soluble aluminum) of the deoxidized molten steel:
the amount of molten steel (ton) is multiplied by 0.01004 × [ Als%] Entering station ÷0.001％＝303×0.01004×0.048％÷0.001％＝146(Nm 3 ) (ii) a Wherein the molten steel amount (ton) is the weight of molten steel, [ Als%] Entering station The content of acid-soluble aluminum in molten steel entering a station; 0.01004 is the oxygen blowing amount needed by acid-soluble aluminum (acid-soluble aluminum content: 0.001%) in per 1 ton of molten steel, and is determined according to the metallurgical theory calculation and the field data such as oxygen yield;
b: the oxygen blowing amount of the deoxidized molten steel is compensated by the temperature:
b is the amount of molten steel (ton) × 0.0373 × (T) Target temperature of arrival -T Entering station -T Temperature rise of aluminum oxidation )＝303×0.0373×(1605-1597-0.048％÷0.001％×0.37)＝161(Nm 3 ) (ii) a Wherein the molten steel amount (ton) is the molten steel weight, T Target temperature of arrival The station entering temperature of the molten steel which does not need temperature compensation in the RH process is related to steel mill equipment and process level, and 1605 ℃ is taken; t is Entering station The molten steel temperature is measured when the molten steel enters RH; t is Temperature rise of aluminum oxidation Is the temperature rise value T of residual acid-soluble aluminum in oxidized molten steel Temperature rise of aluminum oxidation ＝[Als％] Entering station 0.001% x 0.37; 0.0373 per tonThe oxygen blowing amount required by the temperature rise of the molten steel at 1 ℃ is determined according to site data such as metallurgical theoretical calculation, oxygen yield and the like; 0.37 is the elevated temperature per 0.001% acid-soluble aluminum oxide; calculating according to a metallurgical theory and determining according to field measured data;
c: oxygen blowing amount for decarburization in deoxidized molten steel:
amount of molten steel (ton) × 0.1506 × ([ C%] Entering station -[C％] Target of decarburization completion )÷0.010％＝303×0.1506×(0.029％-0.0010％)÷0.010％＝128(Nm 3 ) (ii) a Wherein the molten steel amount (ton) is the weight of molten steel, [ C%] Entering station The carbon content of molten steel entering the station; [ C ]] Target of decarburization completion In order to finish the decarburization, the target carbon content is 0.0010 percent of the ultra-low carbon steel which is related to smelting steel types; 0.1506 is the oxygen blowing amount needed by removing 0.010% carbon content from each ton of molten steel, and is determined according to the metallurgical theory calculation and the field data such as oxygen yield;
d: ensuring the oxygen blowing amount of the excess oxygen after the decarburization of the deoxidized molten steel is finished;
amount of molten steel (ton) × 0.0011 × [ O ═ D] Target of decarburization completion ＝303×0.0011×300＝100(Nm 3 ) (ii) a Wherein the molten steel amount (ton) is the molten steel weight, [ O ]] Target of decarburization completion In order to finish decarburization, the target oxygen content is 300ppm of ultra-low carbon steel which is related to smelting steel; 0.0011 is the oxygen blowing amount required by increasing oxygen by 1ppm per ton of molten steel, and is determined according to site data such as metallurgical theoretical calculation, oxygen yield and the like.
The oxygen lance flow is determined after calculation according to the following formula. Oxygen lance flow rate (Nm) is oxygen blowing rate 3 ) RH decarburization time (minutes) × 60 ÷ molten steel amount (ton) ÷ 444 ÷ 28 × 60 ÷ 303 ÷ 3.14Nm ÷ 303 ÷ 3 H.t steel. Wherein the RH decarburization time was set to 28 minutes;
when oxygen blowing is started, the oxygen lance position is set to be 4500 mm. During the oxygen blowing period, the content changes of CO, O, H and other gas components of the waste gas analyzer are monitored, and the purposes that the content of CO in the flue gas analyzer is less than or equal to 1 percent, the content of O in the flue gas analyzer is less than or equal to 5 percent, and the content of H in the flue gas analyzer is less than or equal to 0.0010 percent are taken as targets. In the embodiment, the contents of gas components such as CO, O, H and the like of an exhaust gas analyzer at the early stage of oxygen blowing all reach the target, but when the oxygen blowing is carried out for 4 minutes and 07 seconds, the content of CO in the discharged gas is 1.5%, the content of O is 8.2%, the content of H is 0.0008%, and the content of CO in the discharged gas exceeds the control target, so that the oxygen blowing lance position is increased to 5600mm, after 1.5 minutes, the content of CO in the discharged gas is 0.9%, the content of O is 2.95%, and the content of H is 0.0005%, the control target is reached, and then the control target range is fluctuated, and the lance position is maintained at 5600mm until the decarburization is finished;
after RH oxygen blowing is finished, molten steel is decarburized, deoxidized and alloyed, and the method is the same as the current method of a steel mill; and when the RH is out of the station, the carbon content of the molten steel is as follows: 0.0014 percent.
Comparative example ii: steel grade: IF steel DC 06; actual molten steel amount: 308 ton of the rotary kiln
The tapping temperature of the steel-making furnace is 1678 ℃, and no deoxidation alloy is added in the tapping process;
after the molten steel enters RH, oxygen is determined, temperature measurement and sampling are carried out, the temperature of the molten steel is 1625 ℃, the oxygen content is 546ppm, and the carbon content of the molten steel is 0.026%;
RH has natural decarburization condition without oxygen blowing;
decarburization is finished 17min after RH extraction, and the temperature of the molten steel is 1581 ℃, the oxygen content is 316ppm and the carbon content of the molten steel is 0.0012 percent;
deoxidizing and alloying, and the total time is 12 minutes;
RH is broken empty, temperature is measured before breaking empty, and the temperature of molten steel is 1582 ℃ at the moment.
The main process effect of example II is compared with that of comparative example II in Table 4:
the table is connected:
table 4 comparison of main process effects of example ii and comparative example ii
The embodiment has the following positive effects:
(1) DC03 and DC06 steel grades, the highest percentage of CO in RH waste gas in the embodiment of the technical scheme of the invention is 1.7 percent and 1.5 percent respectively, and the percentage of CO in RH waste gas is reduced by 93.0 percent and 94.4 percent respectively compared with the highest percentage of CO in RH waste gas of 24.2 percent and 26.7 percent respectively;
(2) DC03 and DC06 steel grades, the maximum percentage O percentage of RH waste gas in the embodiment of the technical scheme of the invention is respectively 7.1 percent and 8.2 percent, and is respectively reduced by 35.5 percent and 33.8 percent compared with the maximum percentage O percentage of RH waste gas in the comparative examples, 11.0 percent and 12.4 percent;
(3) DC03 and DC06 steel grade, RH waste gas CO in the embodiment of the technical scheme of the invention 2 The highest percentage values are 34.6 percent and 32.5 percent respectively, and compared with RH waste gas CO of a comparative example 2 The maximum percentage values are 11.8 percent and 9.6 percent respectively increased by 193 percent and 239 percent;
(4) DC03 and DC06 steel grades, the highest percentage of H percentage of RH waste gas in the embodiment of the technical scheme of the invention is 0.0011 percent and 0.0008 percent respectively, and the highest percentage of H percentage of RH waste gas is reduced by 42.1 percent and 61.9 percent respectively compared with the highest percentage of H percentage of RH waste gas of 0.0019 percent and 0.0021 percent respectively;
(5) the steel grades of DC03 and DC06 are that the tapping temperatures of the converter in the embodiment of the technical scheme of the invention are 1621 ℃ and 1627 ℃ respectively, and are reduced by 44 ℃ and 51 ℃ respectively compared with the tapping temperatures of the converter in the comparative examples of 1665 ℃ and 1678 ℃;
(6) the molten steel temperature drop speeds of the steel grades DC03 and DC06 in the RH decarburization period of the embodiment of the invention are respectively 0.5 ℃/min and 0.11 ℃/min, and are respectively reduced by 96 percent and 81 percent compared with the molten steel temperature drop speeds of 2.60 ℃/min and 2.59 ℃/min in the RH decarburization period of the comparative example;
(7) the carbon contents of RH vacuum broken molten steel in the embodiment of the technical scheme of the invention are respectively 0.022% and 0.0014% of DC03 and DC06 steel grades, and are basically equivalent to the carbon contents of coated steel in the comparative examples, namely 0.021% and 0.0012%;
(8) the total oxygen of the continuous casting billets of the technical scheme of the invention is respectively 15ppm and 16ppm in DC03 and DC06 steel grades, and is basically equivalent to that of the continuous casting billets of the comparative examples in total oxygen of 14ppm and 15 ppm.
Therefore, the invention can obviously reduce the percentage of CO and the percentage of H in RH waste gas, greatly reduce the temperature drop speed of the molten steel, improve the combustion efficiency of hydrogen and carbon monoxide escaping from the molten steel, and does not influence the control of the carbon content of the molten steel and basically does not influence the cleanliness of the molten steel.
The invention has been described above with reference to the accompanying drawings, it is obvious that the invention is not limited to the specific implementation in the above-described manner, and it is within the scope of the invention to apply the inventive concept and solution to other applications without substantial modification.
Claims (3)
1. A method for improving the utilization rate of energy sources of carbon monoxide and hydrogen escaped from the vacuum decarburization process of molten steel is characterized by comprising the following steps:
s1, before vacuum decarburization: carrying out deep deoxidation on the molten steel to form deoxidized molten steel, wherein the deoxidized molten steel is in a low-oxygen-level state;
s2, vacuumizing the RH vacuum chamber after the deoxidized molten steel enters the RH, enabling the deoxidized molten steel to circularly enter the RH vacuum chamber, controlling an oxygen lance to blow oxygen to the RH vacuum chamber, and entering a vacuum decarburization procedure;
s3, controlling the lance position of the oxygen lance in real time based on the target gas component in the RH vacuum chamber exhaust gas in the vacuum decarburization process so as to control the target gas component in the target range;
the target gas is CO, and when the concentration of CO in the gas discharged by the RH vacuum value exceeds the target range, the target range is that the content of CO is less than or equal to 1 percent, the lance position of the oxygen lance is increased by 500-1500 mm.
2. The method for improving the energy utilization rate of the carbon monoxide and the hydrogen escaped from the vacuum decarburization process of the molten steel as claimed in claim 1, wherein the calculation of the flow rate of the oxygen lance specifically comprises the following steps:
calculating the oxygen blowing amount of the deoxidized molten steel;
the oxygen blowing amount consists of oxygen blowing amount of residual deoxidizing elements of the deoxidized molten steel, temperature compensation oxygen blowing amount of the deoxidized molten steel, oxygen blowing amount of decarburization in the deoxidized molten steel and oxygen blowing amount of excess oxygen for ensuring the finish of the decarburization of the deoxidized molten steel;
calculating the oxygen lance flow based on the oxygen blowing amount and the decarburization time;
wherein, the oxygen blowing amount of the residual deoxidizing elements in the deoxidized molten steel is the oxygen amount required for removing the deoxidizing elements in the deoxidized molten steel;
the temperature compensation oxygen blowing amount of the deoxidized molten steel is oxygen amount required by heat supplement through subsequent oxidation reaction with aluminum when the temperature of the deoxidized molten steel entering RH does not reach the target temperature;
the oxygen blowing amount for decarburization in the deoxidized molten steel is the oxygen amount required for removing carbon in the deoxidized molten steel;
the oxygen blowing amount of excess oxygen at the completion of decarburization of the deoxidized molten steel is an oxygen amount required for satisfying the excess oxygen at the completion of decarburization.
3. The method for improving the energy utilization rate of the carbon monoxide and the hydrogen escaped from the vacuum decarburization process of the molten steel as claimed in claim 2, wherein the oxygen lance flow is calculated as follows:
oxygen lance flow is divided into oxygen blowing amount and decarburization time and 60 and molten steel amount.
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