Electric arc furnace smelting operation method

Abstract

The invention provides an electric arc furnace smelting operation method which comprises the following processes: in an arc starting stage, the secondary side voltage of a transformer is set to be 75-85% U1, and the current is set to be 90-100% Ie; in the well penetrating stage, the voltage of the secondary side of the transformer is set to be 95-100% U1, and the current of the secondary side of the transformer is set to be 80-85% Ie; in the melting stage, the voltage of the secondary side of the transformer is set to be 95-100% U1, and the current of the secondary side of the transformer is set to be 90-100% Ie; in the temperature rise stage, the voltage of the secondary side of the transformer is set to be 80-90% U1, and the current is set to be 80-90% Ie; wherein U1 is the primary voltage of the secondary side of the electric arc furnace transformer, and Ie is the maximum rated current of the electric arc furnace transformer. According to the method, the electric arc furnace steelmaking process experience and theoretical analysis are combined, a reasonable power supply system is set according to different smelting working conditions of the electric arc furnace under the condition that the electric arc furnace smelting process is stable and the power consumption per ton of steel is low, and the problems that due to manual experience operation, an electric arc violently radiates a furnace lining, the smelting period is too long, and power consumption is high are solved; high-efficiency smelting of the electric-arc furnace is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of electric arc furnace steelmaking, and in particular relates to an electric arc furnace smelting operation method. Background Art

[0002] The steel production process can generally be divided into two steelmaking processes: the long process of blast furnace-converter using iron ore and coke as raw materials and the short process of electric arc furnace using scrap steel as raw materials. The carbon emissions per ton of steel in the long process reach 1.8 tons, while the short process is only 0.6 tons. With the continuous accumulation of scrap steel in society and the strengthening of carbon emission policies, the process-oriented structural reform of the steel industry will inevitably promote the development of electric arc furnace steelmaking technology.

[0003] From the current situation, the arc furnace steelmaking process mainly presents the following problems:

[0004] (1) High electricity consumption per ton of steel. Most traditional electric arc furnaces are operated based on manual experience, and no reasonable operation plan has been formed. The smelting process system cannot be effectively combined with the furnace conditions. For example, there are differences in the ejection nodes of oxygen and carbon powder, and the matching degree between power supply intensity and smelting conditions is unreasonable, resulting in a large gap in smelting levels between different furnaces.

[0005] (2) Long smelting cycle. The normal smelting cycle of an electric furnace is about 60 minutes, while the smelting cycle of an advanced electric furnace can be less than 40 minutes. The main reason is that the non-power operation time is long. In addition, the uneven heating of the electrode causes the scrap steel in the hot zone to melt faster and the scrap steel in the cold zone to melt slower, which will increase the smelting cycle of the electric furnace. The foam slag arc burying effect is not good, and the long arc and short arc operations are unreasonable, which will reduce the thermal efficiency of the electric arc furnace smelting process. At the same time, it will also make the heat load of the water-cooled plate larger, resulting in more power outages during the smelting process, which will inevitably lead to an increase in smelting time. This is specifically manifested in the unreasonable operations of bottom blowing, flat molten pool, oxygen blowing to assist fluxing, foam slag and power supply.

[0006] (3) Short life of furnace lining. Unclear division of arc furnace smelting stages leads to unreasonable power supply system, which makes the furnace cover and furnace lining affected by strong arc radiation for a certain period of time, resulting in the life of furnace cover and furnace lining being affected; at the same time, the poor arc burying effect of foam slag will also bring the same problem.

[0007] (4) High electrode consumption. Electrode consumption is an important part of the cost of steelmaking in electric arc furnaces. During the melting process, it is hoped that the scrap steel can be melted quickly. However, once the surrounding environment of the electrode melts freely, the risk of eddy current scrap collapse will increase. The scrap steel falling along the electrode direction may cause the electrode to break. During the melting and penetration, the electric arc furnace should be operated with a higher secondary voltage and a lower current. The long arc generated can make the electrode penetrate the well quickly and achieve rapid melting of the scrap steel, thereby reducing the risk of electrode current interruption.

[0008] Therefore, developing a reasonable power supply model, formulating a reasonable smelting process system, and establishing the best arc furnace operation method can achieve high-efficiency power supply of the transformer, while improving the smelting rhythm of the electric furnace and reducing the radiation damage of the arc to the furnace lining. However, in the existing arc furnace smelting operation process, the time nodes of each power supply stage are not clearly divided, and it cannot adapt to the changes in the power supply system and oxygen supply system caused by changes in the furnace transformer and furnace capacity. Therefore, it is urgent to develop an operation method for arc furnace smelting with strong applicability. Summary of the invention

[0009] The purpose of the present invention is to provide an electric arc furnace smelting operation method, which can at least solve some of the defects existing in the prior art.

[0010] To achieve the above object, the present invention adopts the following technical solutions:

[0011] An electric arc furnace smelting operation method includes the following process:

[0012] In the arc starting stage, the transformer secondary voltage is set to 75-85% U 1 , current is set to 90~100%I e ;

[0013] During the drilling phase, the transformer secondary voltage is set to 95-100% U 1 , current is set to 80~85%I e ;

[0014] During the melting stage, the transformer secondary voltage is set to 95-100% U 1 , current is set to 90~100%I e ;

[0015] During the heating stage, the transformer secondary voltage is set to 80-90% U 1 , current is set to 80~90%I e ;

[0016] Among them, U 1 is the first-level voltage of the secondary side of the arc furnace transformer, I e It is the maximum rated current of arc furnace transformer.

[0017] Furthermore, during the melting stage, when the power consumption per ton of steel reaches 55-65% of the total power consumption per ton of steel, oxygen and carbon powder are sprayed to form foamed slag.

[0018] Furthermore, when the power consumption per ton of steel reaches 70-75% of the total power consumption per ton of steel, the melting stage ends. If multiple batches of charging operations are carried out and it is not the last basket of charge, the next batch of scrap steel will be added. If it is the last basket of charge, the secondary side voltage and current gear of the transformer will be changed to enter the heating stage.

[0019] Furthermore, the total power in the arc starting stage is 75% of the active power in the melting stage.

[0020] Furthermore, the total power in the drilling stage is 85-90% of the active power in the melting stage.

[0021] Furthermore, the total power in the temperature rising stage is 75-80% of the active power in the melting stage.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The electric arc furnace smelting operation method provided by the present invention combines the experience and theoretical analysis of the electric arc furnace steelmaking process. While ensuring the stability of the electric arc furnace smelting process and low power consumption per ton of steel, a reasonable power supply system is set according to different smelting conditions of the electric arc furnace. The problems of severe radiation of the arc to the furnace lining, long smelting cycle and high power consumption caused by manual operation are overcome, thereby achieving high-efficiency smelting in the electric arc furnace.

[0024] (2) The electric arc furnace smelting operation method provided by the present invention has good adaptability to various raw material structures and can improve oxygen utilization efficiency on the basis of setting a reasonable power supply system and coordinating a suitable oxygen blowing and carbon injection system.

[0025] The present invention will be further described in detail below with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a flow chart of the electric arc furnace smelting operation method of the present invention. DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] The steelmaking process of an electric arc furnace is divided into four stages: arc starting, well drilling, melting and heating. During the power supply process of the electric arc furnace, the effective heat source that transfers energy to the scrap steel comes from the electric arc. During the smelting process, the stability of the arc, the arc buried effect, the arc radiation to the furnace lining and the arc heat transfer efficiency should be comprehensively considered according to the different stages of smelting. That is, the parameters such as power factor, arc voltage, arc length and arc power should be considered during the smelting process; specifically, the arc voltage U of the electric arc furnace in the power supply circuit of the electric arc furnace is 弧 , arc power P 弧 , arc length L 弧 , active power P, electrical efficiency η and power factor The calculation formula is shown in formula (1)-(6):

[0029]

[0030] Where: P 弧 is the arc furnace power, kW

[0031] U 弧 is the arc voltage, V

[0032] U xop is the voltage drop caused by the operating reactance, V

[0033] U r is the voltage drop caused by the short-circuit resistor, V

[0034] I 低 is the low voltage side current of the electric furnace transformer, kA

[0035] U 0 Phase voltage of single-phase equivalent electric furnace input, V

[0036] X op is the operating reactance in the power supply circuit, Ω

[0037] r is the resistance in the power supply circuit, Ω

[0038] L 弧 =U 弧 -40 (3)

[0039] Where, L 弧 is the arc length, mm;

[0040] The active power P of the electric furnace is:

[0041]

[0042] The power supply efficiency η of the electric furnace is:

[0043]

[0044] Power factor of electric furnace power supply for:

[0045]

[0046] Where S is the apparent power, kW.

[0047] According to the theoretical calculation of the parameters to be considered in the above-mentioned electric arc furnace smelting process and combined with the experience of the electric arc furnace steelmaking process, this embodiment specifically designs an electric arc furnace smelting operation method, such as Figure 1 As shown, the process includes the following:

[0048] (1) In the arc starting stage, since the arc cannot be buried by the foam slag, the radiation of the arc to the furnace cover and furnace wall should be taken into consideration when setting the power supply parameters. That is, the heat radiation loss of the arc to the furnace wall and furnace cover should be reduced. Therefore, the secondary voltage of the transformer is designed to be 75-85% U 1 , current is set to 90~100%I e Among them, U 1 is the first-level voltage of the secondary side of the arc furnace transformer, I e is the maximum rated current of the arc furnace transformer, U 1 and I e It can be obtained from the known nameplate parameters of the arc furnace transformer.

[0049] Optimally, the total power in the arc starting stage is controlled to be about 75% of the active power in the melting stage.

[0050] (2) During the drilling stage, it is necessary to consider reducing the radiation of the arc to the furnace cover and quickly melt the scrap steel on the basis of reducing electrode loss. Therefore, a long arc and lower power are used for power supply. Therefore, the secondary side voltage of the transformer is designed to be set at 95-100% U 1 , current is set to 80~85%I e .

[0051] Preferably, the total power in the drilling stage is controlled to be about 85-90% of the active power in the melting stage.

[0052] (3) In the melting stage, the arc effect is better. In order to quickly melt the scrap steel, it is advisable to use high power, high voltage and high current for power supply. Therefore, in this stage, the secondary voltage of the transformer is designed to be set to 95-100% U 1 , current is set to 90~100%I e .

[0053] In some preferred embodiments, during this melting stage, when the electricity consumption per ton of steel reaches 55-65% of the total electricity consumption per ton of steel, oxygen and carbon powder are started to be sprayed to form foamed slag. However, through practical and theoretical analysis, it is found that spraying oxygen and carbon powder too early will affect the life of the oxygen gun and the energy utilization rate, while spraying oxygen and carbon powder too late will reduce the utilization rate of electric energy and increase the consumption of electric energy, and increase the radiation of the furnace lining. The power supply system designed in this embodiment is combined with the oxygen blowing and carbon spraying system to reduce the electricity consumption per ton of steel on the one hand, and improve the oxygen utilization rate and the smelting efficiency of the electric arc furnace on the other hand.

[0054] Furthermore, when the power consumption per ton of steel reaches 70-75% of the total power consumption per ton of steel, the melting stage ends. If multiple batches of charging operations are carried out and it is not the last basket of charge, the next batch of scrap steel will be added. If it is the last basket of charge, the secondary side voltage and current gear of the transformer will be changed to enter the heating stage.

[0055] (4) In the heating stage, due to the large amount of slag flowing at the end of melting, the slag volume is reduced, and the arc burying effect of foam slag is reduced. Therefore, it is considered to use a lower arc power to reduce the radiation of the arc to the furnace lining. Through calculation and analysis, the secondary side voltage of the transformer is designed to be 80-90% U 1 , current is set to 80~90%I e .

[0056] Preferably, the total power in the temperature rising stage is controlled to be about 75-80% of the active power in the melting stage.

[0057] The excellent effects of the arc furnace smelting operation method of the present invention are illustrated below by specific examples. The experimental methods without specifying specific conditions in the following examples are conducted according to conventional methods and conditions. The raw materials used in the following examples are all conventionally purchased from the market.

[0058] Embodiment 1:

[0059] Taking a steel plant's 120t electric furnace using all-scrap steel smelting as an example, the furnace is equipped with a 100MVA transformer and uses the existing electric arc furnace operation system and the electric arc furnace operation method optimized by the present invention. The economic index comparison results of the two smelting processes are shown in Table 1.

[0060] Table 1:

[0061] project Raw material structure Power-on time (min) Power consumption (kWh / t) Average life of furnace lining Before optimization All scrap steel 44 400 550 After optimization All scrap steel 38 385 620

[0062] It can be seen from Table 1 that after adopting the arc furnace operation method optimized by the present invention, the smelting cycle of the electric furnace is reduced by 6 minutes, the power consumption per ton of steel is reduced by 15 kWh, and the life of the furnace lining is increased by 70 furnaces.

[0063] Embodiment 2:

[0064] Taking a steel plant's 100t electric furnace using all-scrap steel smelting as an example, the electric furnace is equipped with a 90MVA transformer and uses the existing electric arc furnace operation system and the electric arc furnace operation method optimized by the present invention. The economic index comparison results of the two smelting processes are shown in Table 2.

[0065] Table 2:

[0066]

[0067]

[0068] It can be seen from Table 2 that after adopting the electric arc furnace operation method of the present invention, the smelting cycle of the electric furnace is reduced by 3 minutes, the power consumption per ton of steel is reduced by 13 kWh, and the life of the furnace lining is increased by 39 furnaces.

[0069] The above examples are merely illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. An arc furnace smelting operation method, characterized in that: The process includes the following: In the arc starting stage, the transformer secondary voltage is set to 75-85% U1, and the current is set to 90-100% I e ; During the drilling phase, the transformer secondary voltage is set to 95-100% U1 and the current is set to 80-85% I e ; In the melting stage, the transformer secondary voltage is set to 95-100% U1 and the current is set to 90-100% I e ; During the heating stage, the transformer secondary voltage is set to 80-90% U1, and the current is set to 80-90% I e ; Among them, U1 is the first-level voltage of the secondary side of the arc furnace transformer, I e It is the maximum rated current of arc furnace transformer.

2. The arc furnace smelting operation method according to claim 1, characterized in that: During the melting stage, when the power consumption per ton of steel reaches 55-65% of the total power consumption per ton of steel, oxygen and carbon powder are sprayed to form foamed slag.

3. The arc furnace smelting operation method according to claim 1, characterized in that: When the power consumption per ton of steel reaches 70-75% of the total power consumption per ton of steel, the melting stage ends. If multiple batches of charging operations are carried out and it is not the last basket of charge, the next batch of scrap steel will be added. If it is the last basket of charge, the secondary voltage and current gears of the transformer will be changed to enter the heating stage.

4. The arc furnace smelting operation method according to claim 1, characterized in that: The total power in the arc starting stage is 75% of the active power in the melting stage.

5. The arc furnace smelting operation method according to claim 1, characterized in that: The total power in the drilling stage is 85-90% of the active power in the melting stage.

6. The arc furnace smelting operation method according to claim 1, characterized in that: The total power in the temperature rising stage is 75-80% of the active power in the melting stage.

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