RU2082763C1 - Method of control of process of melting of iron-rich pellets in electric arc furnace - Google Patents

Abstract

FIELD: metallurgy; control of process of continuous charging and melting of iron-rich pellets in electric arc steel melting furnaces. SUBSTANCE: method includes selection of charging rate of iron-rich pellets depending on power drained from the mains and correction of changing rate proportionally to deviation of metal temperature from preset value. Selection of charging rate of iron-rich pellets in furnace is carried out depending on electric active power, and in the process of continuous charging and melting of iron-rich pellets with unstable behavior of arcs, additional correction of iron-rich charging is introduced. In so doing, if active power drops below the lower preset limit, the rate of charging is reduced, and if active power exceeds the upper preset limit, the rate of charging is increased. EFFECT: higher efficiency. 2 cl, 4 dwg

Description

 The invention relates to metallurgy, and in particular to electric steel production, and can be used to control the process of continuous loading and melting of metallized pellets in arc steel furnaces.

 A known method of controlling the process of melting metallized pellets in an arc furnace, according to which during the continuous loading of metallized pellets, their loading speed is regulated as a function of the consumed electric power.

 However, with this control method, based on the direct connection between the energy consumption and the loading speed of metallized pellets, it is impossible to accurately maintain a given temperature regime for heating the metal due to the neglect of the real situation in the furnace (heat transfer conditions in the working space, particle size and chemical composition of metallized pellets, degree of metallization, quantity and composition of waste rock), and it is also impossible to control the temperature regime of the metal bath at a given 's Permanent power level.

 The closest to the invention in technical essence and the achieved result is a method of controlling the process of melting metallized pellets in an arc furnace, according to which during the continuous loading of metallized pellets, their loading speed is controlled depending on the electric total power taken from the network, and a correction of the loading speed of metallized pellets are proportional to the deviation of the temperature of the metal from a given destination so that when the temperature of the metal rises above a predetermined value download speed increase, otherwise - decrease.

 The disadvantage of this method is that, firstly, the choice of the loading speed of metallized pellets is made depending on the total power, while the heating and melting process depends only on the active power and does not depend on reactive power, i.e. Using the choice of loading speed from the total power, it is impossible to precisely control the melting process, and, secondly, the state of the bath, which depends on the ratio of the melting speeds of the loading of metallized pellets, is not taken into account. Exceeding the loading speed over the melting rate leads to the accumulation of pellets in the molten metal bath, and thereby to expose the arcs, the intense effect of arc radiation on the lining of the walls and the roof of the furnace, reduce the lining resistance, and reduce the power. A decrease in the loading speed with respect to the melting rate of metallized pellets leads to boiling of the bath, and thereby to a sharp increase in current, the discharge of metal from the furnace.

 All this lengthens the melting time, increases the consumption of electrodes and electricity. Thus, it is not possible to achieve sustainable control of the smelting, only adjusting the loading speed of the pellets depending on the temperature.

 The technical result of the invention eliminates these drawbacks, increases the durability of the lining of the furnace, reduces the duration of melting, reduces the consumption of electrodes and electricity by eliminating the accumulation of non-molten metallized pellets on the surface of the bath or boiling it.

где Q- количество израсходованной электроэнергии, кВт•ч;
H_j изменение энтальпии загруженного в печь j-го материала при его нагреве от исходной температуры до температуры плавления, кВт•ч/т;
m_j масса загруженного в печь j-го материала, т,
в процессе непрерывной загрузки и плавления металлизованных окатышей при нестабильном поведении дуг вводя дополнительную коррекцию загрузки металлизованных окатышей, при этом при снижении активной мощности ниже нижнего заданного предела скорость загрузки уменьшают, а при превышении активной мощности выше верхнего предела увеличивают. Кроме того, при появлении нестабильного поведения дуг, выраженного соотношением
α $\genfrac{}{}{0ex}{}{\text{2}}{\text{I}}$ •α $\genfrac{}{}{0ex}{}{\text{3}}{\text{v}}$ >α_o,
где α_I коэффициент несимметрии токов;
α_v коэффициент несимметрии напряжений;
α_o граничное значение,
производят дополнительную коррекцию скорости загрузки металлизованных окатышей, при этом скорость загрузки уменьшают, если выполняется условие
P $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ < P $\genfrac{}{}{0ex}{}{\text{L}}{\text{S}}$
где P $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ текущая активная мощность на ступени напряжения s, МВт;
P $\genfrac{}{}{0ex}{}{\text{L}}{\text{S}}$ нижнее заданное граничное значение активной мощности на ступени напряжения s, МВт;
или скорость загрузки увеличивают, если выполняется условие
P $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ > P $\genfrac{}{}{0ex}{}{\text{H}}{\text{S}}$ ,
где P $\genfrac{}{}{0ex}{}{\text{H}}{\text{S}}$ верхнее заданное граничное значение активной мощности на ступени напряжения s, МВт.The technical result is achieved by the fact that in the method of controlling the process of melting metallized pellets in an arc furnace, which includes changing the loading speed of metallized pellets in the furnace depending on the electric power taken from the network, and adjusting the loading speed of the pellets is proportional to the deviation of the metal temperature from the set value, the choice of speed loading metallized pellets in the furnace is carried out depending on the electric active power, and after melting the metal filling and reaching the conditions I

where Q is the amount of consumed electricity, kW • h;
H _{j the} change in the enthalpy of the j-th material loaded into the furnace when it is heated from the initial temperature to the melting temperature, kW • h / t;
m _{j the} mass of the _jth material loaded into the furnace, t,
during the continuous loading and melting of metallized pellets with unstable behavior of the arcs, introducing an additional correction of the loading of metallized pellets, in this case, when the active power decreases below the lower predetermined limit, the download speed is reduced, and if the active power is exceeded above the upper limit, it is increased. In addition, with the appearance of unstable behavior of arcs, expressed by the relation
α $\genfrac{}{}{0ex}{}{\text{2}}{\text{I}}$ • α $\genfrac{}{}{0ex}{}{\text{3}}{\text{v}}$ > α _o ,
where α _I current asymmetry coefficient;
α _v stress asymmetry coefficient;
α _{o the} boundary value
make additional correction of the loading speed of metallized pellets, while the download speed is reduced if the condition
P $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ <P $\genfrac{}{}{0ex}{}{\text{L}}{\text{S}}$
where p $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ current active power at the voltage stage s, MW;
P $\genfrac{}{}{0ex}{}{\text{L}}{\text{S}}$ lower predetermined boundary value of active power at the voltage stage s, MW;
or download speed is increased if the condition is met
P $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ > P $\genfrac{}{}{0ex}{}{\text{H}}{\text{S}}$ ,
where p $\genfrac{}{}{0ex}{}{\text{H}}{\text{S}}$ upper specified boundary value of active power at the voltage stage s, MW.

 The fundamental difference between the proposed method and the known one, including the choice of the loading speed according to the total electric power and the correction of the loading speed according to one parameter of the bath temperature, consists in the fact that the selection of the loading speed is carried out depending on the active power and an additional correction is introduced that takes into account the state of the bath in terms of burning stability arcs.

 In FIG. 1 is a structural diagram explaining the described control method; in FIG. 2 4 plots of the probability distribution of active power values for the phenomena of accumulation and boiling: the solid line for the accumulation phenomenon is the lower limit, the dashed line for the boiling phenomenon is the upper limit (in Fig. 2 for the 20th voltage stage; in Fig. 3 for the 19th voltage stage; in Fig. 4 for the 18th voltage stage).

 In the drawings, the horizontal values of the active power are plotted, the vertical probability of the values of the active power during boiling or accumulation.

 The proposed control method is as follows.

In the inter-melting period, the signals from the scrap weight sensor 1 and the weight sensor of auxiliary materials 2 enter the control unit 3 (control mini
or microcomputers), where they are remembered.

 During the continuous loading of metallized pellets from the hopper 4 through conveyors 5 and 6 to the funnel 7 and their melting in the furnace 8, signals from the sensor of consumed active power 9 are fed to the control unit 3. Depending on the value of the active power, the control unit 3 selects the loading speed of the metallized pellets and provides a signal to the actuator of the loading system 10.

 The correction of the loading speed of the pellets according to the temperature of the metal received from the temperature sensor 11 is carried out by the control unit 3 by changing the job to the executive mechanism of the loading system 10.

и сравнивается с предварительно заданным значением, равным 1,2. При выполнении условия

блок управления 3 опрашивает датчики тока 14 и датчики напряжения 15, установленные на каждой фазе, и рассчитывает соотношение
α $\genfrac{}{}{0ex}{}{\text{2}}{\text{I}}$ •α $\genfrac{}{}{0ex}{}{\text{3}}{\text{v}}$
Это соотношение сравнивается с предварительно заданным значением, равным 1200. При выполнении условия
α $\genfrac{}{}{0ex}{}{\text{2}}{\text{I}}$ •α $\genfrac{}{}{0ex}{}{\text{3}}{\text{v}}$ > 1200
блок управления 3 сравнивает величину активной мощности с предварительно заданными значениями P $\genfrac{}{}{0ex}{}{\text{L}}{\text{S}}$ и P $\genfrac{}{}{0ex}{}{\text{H}}{\text{S}}$ . При выполнении условия
P $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ < P $\genfrac{}{}{0ex}{}{\text{L}}{\text{S}}$
блок управления 3 уменьшает скорость загрузки окатышей путем изменения задания исполнительному механизму системы загрузки 10, или, при выполнении условия
P $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ < P $\genfrac{}{}{0ex}{}{\text{H}}{\text{S}}$
увеличивает скорость загрузки окатышей.The signals from the sensor of consumed active energy 12 and from the sensor of the weight of metallized pellets 13 enter the control unit 3, where the ratio is calculated

and compared with a predefined value of 1.2. When the condition is met

the control unit 3 interrogates the current sensors 14 and voltage sensors 15 installed on each phase, and calculates the ratio
α $\genfrac{}{}{0ex}{}{\text{2}}{\text{I}}$ • α $\genfrac{}{}{0ex}{}{\text{3}}{\text{v}}$
This ratio is compared with a preset value of 1200. When the condition is met
α $\genfrac{}{}{0ex}{}{\text{2}}{\text{I}}$ • α $\genfrac{}{}{0ex}{}{\text{3}}{\text{v}}$ > 1200
control unit 3 compares the value of active power with preset values of P $\genfrac{}{}{0ex}{}{\text{L}}{\text{S}}$ and P $\genfrac{}{}{0ex}{}{\text{H}}{\text{S}}$ . When the condition is met
P $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ <P $\genfrac{}{}{0ex}{}{\text{L}}{\text{S}}$
control unit 3 reduces the loading speed of the pellets by changing the job to the executive mechanism of the loading system 10, or, if the condition
P $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ <P $\genfrac{}{}{0ex}{}{\text{H}}{\text{S}}$
increases the loading speed of pellets.

 Example 1. After filling the scrap furnace with a weight of 60 tons in the furnace, the weight of the scrap is recorded by the weight sensor 1 and the signal from the sensor 1 goes to the control unit 3 and is stored there (the change in the enthalpy of the scrap when it is heated from the initial temperature to the melting temperature is taken to be 330 kW • h / t). They light the arcs, send slag-forming materials to the furnace (lime enthalpy is taken to be 350 kW • h / t, and oxidized pellets 550 kW • h / t), the weight of the slag-forming materials is recorded by weight sensor 2 and the signal from sensor 2 is sent to control unit 3 and it is remembered there.

 Continuous loading of metallized pellets (the change in the enthalpy of metallized pellets is taken to be 450 kW • h / t) starts at a speed of 5 8 kg / min • MW and within 10-15 minutes it is brought to a speed of 23-33 kg / min • MW, determined by the value active power input, after which continuous or discrete temperature measurement begins. The signal value from the temperature sensor 11 is transmitted to the control unit 3, where the measured temperature value is compared with the set temperature value of the metal bath.

 If the temperature of the metal bath does not match the specified control unit 3 introduces the correction of the loading speed of metallized pellets by changing the setting of the actuator of the loading system of metallized pellets 10 so that when the metal temperature exceeds a predetermined value, the loading speed is increased, and if the metal temperature drops below a predetermined value, downloads reduce.

и сравнивает его со значением 1 и 2. При выполнении условия

при нестабильном поведении дуг вводят дополнительную коррекцию загрузки металлизованных окатышей. Для этого блок управления 3 опрашивает с задаваемым периодом опроса датчики тока 14 и датчики напряжения 15 и рассчитывает соотношение
α $\genfrac{}{}{0ex}{}{\text{2}}{\text{I}}$ •α $\genfrac{}{}{0ex}{}{\text{3}}{\text{v}}$
где

где A_o 100

I_A, I_B, I_C действующие значения токов фаз А, В, С (кА);

где B_o 100 константа, размерность 1/В,

где

где U_A, U_B, U_C напряжение фаз А, В, С, (В).In the process of continuous loading of metallized pellets, the control unit 3 calculates the ratio

and compares it with the value 1 and 2. When the condition is met

with unstable behavior of the arcs, an additional correction of the loading of metallized pellets is introduced. To do this, the control unit 3 polls with a specified polling period current sensors 14 and voltage sensors 15 and calculates the ratio
α $\genfrac{}{}{0ex}{}{\text{2}}{\text{I}}$ • α $\genfrac{}{}{0ex}{}{\text{3}}{\text{v}}$
Where

where A _o 100

I _A , I _B , I _C effective values of currents of phases A, B, C (kA);

where B _o 100 constant, dimension 1 / V,

Where

where U _A , U _B , U _{C the} voltage of phases A, B, C, (V).

The above ratio is compared with a predefined value of 1200. When the condition is met:
α $\genfrac{}{}{0ex}{}{\text{2}}{\text{I}}$ • α $\genfrac{}{}{0ex}{}{\text{3}}{\text{v}}$ > 1200
control unit 3 compares the value of active power with preset values of P $\genfrac{}{}{0ex}{}{\text{L}}{\text{S}}$ and P $\genfrac{}{}{0ex}{}{\text{H}}{\text{S}}$ . Under the condition
P $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ and P $\genfrac{}{}{0ex}{}{\text{L}}{\text{S}}$
control unit 3 reduces the loading speed of pellets V according to the ratio
v = v _o -Δv
where V _o the loading speed of metallized pellets, determined by the active power and the deviation of the metal temperature from the set, kg / min • MW;
Δv is the correction value of the loading speed, depending on the state of the bath, kg / min • MW.

Or when the condition is met:
P $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ > P $\genfrac{}{}{0ex}{}{\text{H}}{\text{S}}$
control unit 3 increases the loading speed of the pellets according to the ratio
v = v _o + Δv
The adjusted value of the loading speed, the control unit 3 transmits in the form of a signal to the executive mechanism of the loading system 10. The total correction for temperature and condition of the bath in order to ensure stability of the pellet loading control did not exceed 300 kg / min or 5 kg / min • MW. The duration of the correction for the state of the bath is 2 3 minutes. The control unit begins to evaluate the condition of the bath only after 3 minutes after the last correction.

 The methodology for determining the upper (when boiling the bath) and lower (during the accumulation of unmelted metallized pellets on the surface of the bath) limits of active power. In the process of continuous loading of metallized pellets, the active power level is recorded (using a computer) and at the same time the boiling of the bath or the accumulation of pellets on the surface of the bath is visually monitored. Based on the data obtained, the probability characteristics of the distribution of active power for the phenomena of accumulation and boiling are built. As the upper limit of active power, the most probable value of active power in the probability characteristic of the distribution of active power for the boiling bath phenomenon is taken, and as the lower limit of active power, the most probable value of active power in the probability characteristic of the distribution of active power for the phenomenon of accumulation of unmelted metallized pellets on the surface is taken bathtubs.

 Example 2. Under the conditions of an electric steelmaking workshop on 150-ton electric arc furnaces with a transformer capacity of 90 MVA, steel was smelted using metallized pellets in a charge. The metallization of metallized pellets was carried out at 18 to 20 voltage levels at 621,723 V.

From FIG. 2 4 it is seen that for the 18th voltage stage the upper limit of the active power P $\genfrac{}{}{0ex}{}{\text{H}}{\text{18}}$ = 60.5 MBt lower limit P $\genfrac{}{}{0ex}{}{\text{L}}{\text{18}}$ = 57.5 MB for the 19th P $\genfrac{}{}{0ex}{}{\text{H}}{\text{19}}$ = 61 MBt P $\genfrac{}{}{0ex}{}{\text{L}}{\text{19}}$ = 58 MB for the 20th P $\genfrac{}{}{0ex}{}{\text{H}}{\text{twenty}}$ = 62.5 MBt, P $\genfrac{}{}{0ex}{}{\text{H}}{\text{twenty}}$ = 59 MBt.
Using the proposed method for controlling the process of melting metallized pellets in an arc furnace provides the following advantages compared to existing methods:
more precise control of the melting process by choosing the dependence of the loading speed of metallized pellets on active power instead of the total power;
elimination of the accumulation of unmelted metallized pellets on the surface of the bath, and thereby eliminating the exposure of arcs, the intense effect of arc radiation on the lining of the walls and arch of the furnace, which increases the lining resistance, increases the active power, increases the productivity of the furnace, and reduces the duration of melting;
elimination of boiling of the bath, leading to a sharp increase in current, ejection of metal from the furnace, and thereby reduces the duration of melting;
additional correction of the state of arc burning, increasing the stability of loading control of metallized pellets, allows you to fully automate the control of the process of melting metallized pellets;
the use of metallized pellets with a wider range of parameters for the degree of metallized pellets with a wider range of parameters for the degree of metallization and carbon content, and thereby allows to increase the range of raw materials used in chemical composition;
reduction in the cost of electrodes, refractories, electricity, reduction in the cost of steel.

 Tests on 21 experimental melting showed that the specific energy consumption per ton of metal filling is on average 623 kW • h / t with a standard deviation of 19 kW • h / t, and the duration of melting under current is 108 minutes with a standard deviation of 5 minutes. On 558 industrial swimming trunks, these same indicators were respectively 627 kW • h / t at 33 kW • h / t and 110 min at 10 min. A smaller standard deviation of the energy consumption and the duration of the melting in experimental compared to industrial melts characterizes the best reproducibility of the melts, and thereby greater accuracy in controlling the melting process.

Claims (2)

1. A method of controlling the process of smelting metallized pellets in an arc furnace, comprising selecting a loading speed of metallized pellets in the furnace depending on the electric power taken from the network, and adjusting the loading speed of the pellets in proportion to the deviation of the metal temperature from the set value, characterized in that the choice of loading speed metallized pellets in the furnace are produced depending on the electric active power, after melting the metal filling and reaching the condition

where Q is the amount of consumed electricity, kW • h;
H _j - change in the enthalpy of the j-th material loaded into the furnace when it is heated from the initial temperature to the melting temperature, kW • h;
m _{j the} mass of the _jth material loaded into the furnace, t,
In the process of continuous loading and melting of metallized pellets with unstable behavior of the arcs, an additional correction of the loading of metallized pellets is introduced; in this case, when the active power decreases below the lower specified limit, the download speed is reduced, and if the active power is exceeded above the upper specified limit, the download speed is increased. 2. The method according to p. 1, characterized in that when the appearance of unstable behavior of the arcs, expressed by the ratio

where α _I is the asymmetry coefficient of currents;
α _u - stress asymmetry coefficient;
α _o is the boundary value,
make additional correction of the loading speed of metallized pellets, while the download speed is reduced if the condition
P $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ <P $\genfrac{}{}{0ex}{}{\text{L}}{\text{S}}$ ,
where p $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ - current active power at the voltage stage S, MW;
P $\genfrac{}{}{0ex}{}{\text{L}}{\text{S}}$ - lower predetermined boundary value for active power at the voltage stage S, MW,
or download speed is increased if the condition is met
P $\genfrac{}{}{0ex}{}{\text{A}}{\text{S}}$ > P $\genfrac{}{}{0ex}{}{\text{H}}{\text{S}}$ ,
where p $\genfrac{}{}{0ex}{}{\text{H}}{\text{S}}$ - the upper specified boundary value of the active power at the voltage stage S, MW.

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