RU2567424C1 - Method of steel melting out of iron-ore iron-rich pellets in electric arc furnace - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to steel melting out of iron-ore iron-rich pellets in arc furnace. are supplied continuously to the metal evaporation zone, created upon contact of the electric arcs with melted metal, and their melting is performed with assurance of the optimal waste of metal in said zone considering ratio of iron-ore iron-rich pellets consumption in said zone with parameters of heat state of slag-metal bath of the furnace.

EFFECT: reduced waste of metal in furnace, increased production of good steel, and reduced power consumption for pellets melting in the furnace.

4 cl, 1 dwg

Description

The invention relates to the field of metallurgy, and more particularly to steel electrometallurgy, in which the basis is the continuous supply of iron ore metallized pellets (LMO) to the high temperature zone in the bath of an arc steel furnace (RU 2483119, publ. 05.27.2013).

There are also known methods of steel melting using oxidized and metallized pellets with their feeding into an arc furnace (Izvestia VUZov. Ferrous metallurgy. No. 3. 2003. S. 55-59; Izvestia VUZov. Ferrous metallurgy. No. 9. 2008. S. 67- 68) for cooling the bath in order to reduce the fumes of metal formed by the action of electric arcs on the surface of liquid metal and slag using oxygen tuyeres (RU 2132394, publ. 06.27.1999).

The objective of the invention is to increase the efficiency of steel melting based on the application of methods (RU 2483119, publ. 05.27.2013; Izvestiya VUZov. Ferrous metallurgy. No. 9. 2008. S. 67-68) feeding iron ore metallized pellets (LMO) in the high temperature zone with the possibility of reducing dust and fumes of metal in the contact zone of electric arcs with liquid metal. This is due to the fact that, as a metal surface cooler in the zone of contact with it, high-temperature (up to 6000 K) electric arcs, which allows to reduce the metal evaporation temperature in this zone to an acceptable one (Izvestiya VUZov. Ferrous metallurgy. No. 3. 2003. C. 55-59; University proceedings. Ferrous metallurgy. No. 9. 2008. S. 67-68) and this circumstance leads to a decrease in metal waste (RU 2132394, publ. 06/27/1999) and increase the yield of liquid steel in the furnace.

However, despite the results achieved in reducing dust extraction (University News. Ferrous metallurgy. No. 3. 2003. P. 55-59; RU 2132394, publ. 06/27/1999) from the zone of metal evaporation in the bath of an arc steel furnace (DSP), the methods used (RU 2483119, publ. 05.27.2013; Proceedings of the universities. Ferrous metallurgy. No. 9. 2008. S. 67-68) do not significantly reduce the waste of metal, because cooled materials, such as oxidized and metallized pellets, do not directly fall on the evaporation surface of liquid metal in the contact zones of electric arcs with it and, moreover, under these conditions (RU 2483119 publ. 05.27.2013; Izvestiya VUZov. Ferrous metallurgy. No. 3. 2003. S. 55-59) a significant part of the LMO remains in the slag and does not reach the evaporation zone (Izvestia VUZov. Ferrous metallurgy. No. 9. 2008. S. 67-68; RU 2132394, publ. 06/27/1999), and therefore it is not possible to significantly reduce the waste of metal in the bath chipboard.

Closest to the invention in technical essence and the achieved result is a method (RU 2134304, publ. 10.08.1999) steel melting with the supply of oxidized and metallized pellets in the bath of an arc furnace. This method (RU 2134304, publ. 10.08.1999) allows you to feed LMOs into the high temperature zone of molten slag and metal, but outside the contact zone of the electric arcs with the surface of the liquid metal, which contributes, however, to the reduction of dust and fumes in the bath of the chipboard. In addition, a certain part of iron ore pellets is melted in slag, and not in metal, i.e. It does not contribute to cooling the metal and reducing its fumes.

The disadvantage of the prototype, i.e. of the specified method (RU 2134304, publ. 10.08.1999) is that when electrofusing steel, it is not intended to supply LMOs directly to the metal evaporation zone, i.e. on the contact surface of electric arcs with metal, which can be practically done if used (RU 2483119 publ. 05.27.2013; Izvestiya VUZov. Ferrous metallurgy. No. 9. 2008. P. 67-68), for example, the method of feeding pellets through hollow electrodes into the furnace bath, i.e. into the contact zone of the arcs with the surface of the evaporation of the metal in the unit. Therefore, to eliminate the disadvantage of the prototype (RU 2134304, publ. 10.08.1999), as well as in other methods (Izvestiya VUZov. Ferrous metallurgy. No. 3. 2003. S. 55-59; RU 2132394, publ. 27.06.1999, it is necessary solve the difficult technical problem of supplying cooling materials, such as LMOs and others to the high temperature zone.

The aim of the invention is to eliminate these drawbacks, increase the efficiency of electric steel melting using LMOs, reduce dust extraction from under electric arcs in a bath and reduce the burning of metal from the surface of a liquid metal by melting pellets on it, as well as reduce the energy consumption for the electric melting process in an arc hollow electrode furnaces.

, кг/с, где G_τ - текущая масса металла в печи, кг; $$\overline{c}$$

- средняя теплоемкость металла в печи, Дж/(кг*K); τ - время загрузки окатышей в печь, с; Т - температура жидкого металла в ванне печи, K; V_t - скорость нагрева металла в ванне печи, °C/с; G₀ - начальная масса металла в печи перед подачей окатышей в ванну печи, кг и, кроме того, способ, отличающийся тем, что тепло, генерируемое в электрической дуге, определяют по зависимости P_д=U_д*I_д, где U_д и I_д - напряжение (B) и ток дуги (A), а поверхность мениска в зоне испарения (F) рассчитывают по формуле: F=2π(L_д+r_э)*h_мен, где L_д - длина дуги, м²; r_э - радиус электрода печи, м; h_мен=r_ок/2 - глубина погружения окатыша на поверхности испарения (мениска) в расплаве под дугой в печи, м, а также тем, что скорость плавления окатышей на поверхности F=S_мен рассчитывают по выражению: V_пл=m_ок*N/τ_пл, при этом m_ок - вес окатыша, кг; τ_пл - время плавления окатыша, с; N - число окатышей на поверхности испарения, равное для трех электрических дуг N=(3*S_мен/S_ок)*0,9069, где S_мен - поверхность мениска на поверхности испарения металла м²; $$S_{ок}=\pi *r_{ок}^2$$

- площадь поверхности окатыша, м²; r_ок - радиус окатыша, м; 0,9069 - коэффициент оптимальной плотности размещения окатышей на поверхности F=S_мен и в то же время, способ, отличающийся тем, что устанавливают расход окатышей (V_ок, кг/с) в зависимости от текущей скорости их плавления (V_пл, кг/с) по неравенству: V_ок≤V_пл=m_ок*N/τ_пл, причем $${\tau }_{пл}=x_1*{\alpha }^{x_2}$$

, где α - коэффициент конвективной теплоотдачи в системе окатыш - расплав, Вт/м²*K; x₁ и x₂ - стехиометрические коэффициенты, при этом для зависимости времени плавления от коэффициента конвективной теплоотдачи (α) окатышей при их нагреве в ванне дуговой печи установлены следующие показатели для 150-т ДСП x₁=10,64 и x₂=-0,798.The technical result according to this invention is achieved by the fact that the method of electric melting of steel in an arc furnace, comprising feeding iron ore metallized pellets through hollow electrodes to the furnace bath and into the evaporation zone of the metal formed upon contact of the electric arcs with the melt, characterized in that the iron ore pellets are fed continuously through hollow electrodes in the metal evaporation zone and determine the waste of metal on the surface in this zone in accordance with the expression in the form: G _intoxication = (3P × η _{d d} -Σq FK _rad × q × _c) / L _j, where q _rad = a × ε _e ((T _d / 100) ⁴ - (T _k / 100) ^4), and q _c = [c _app (T _c -T _pl) L _pl + c _p (T _m -T _pl)] × V _c, and P _d - heat generated in the arc, W ; η _d - arc efficiency; Σq _rad - the proportion of the heat radiation from the surface of three arcs (F, m ^2), meniscal evaporation zone in contact with the melt arcs, W / m ^2; K is the fraction of pellets that melts on the surface layer of the metal in the evaporation zone; q _ok - specific heat flux for heating and melting the pellets in the melt layer under the arc, W / m ³ ; C is the emissivity of a completely black body, 5.67 W / (m ^{2 *} ); ε _e is the reduced degree of blackness of the arc-melt-pellet system, 0.9; T _d and T _c - and the surface temperature of the arc, respectively pellet for T _d = 6000 K; L _j and L _PL - specific heat of evaporation of iron and the melting of pellets, J / kg; c _ok and p _p - specific heat of the pellet and the resulting melt after the pellet is melted, J / (kg * K); T _ok , T _pl , T _m - the initial temperature of the pellet, its melting temperature and the temperature of the metal in the melt in the furnace bath, K; V _ok - the consumption of iron ore pellets in the evaporation zone of the metal in the furnace, kg / s, as well as the fact that they determine the feed rate of pellets into the evaporation zone of the furnace by the expression: $$V_{\mathrm{about}\mathrm{to}}=\left(\frac{\Delta q_{\mathrm{at}}}{\overline{c}*V_t}-G_0\right)/\tau$$

, kg / s, where G _τ is the current mass of metal in the furnace, kg; $$\overline{c}$$

- the average heat capacity of the metal in the furnace, J / (kg * K); τ — time of loading pellets into the furnace, s; T is the temperature of the molten metal in the furnace bath, K; V _t — metal heating rate in the furnace bath, ° C / s; G ₀ is the initial mass of metal in the furnace before feeding the pellets into the furnace bath, kg and, in addition, a method characterized in that the heat generated in the electric arc is determined by the dependence P _d = U _d * I _d , where U _d and I _d - voltage (B) and arc current (A), and the meniscus surface in the evaporation zone (F) is calculated by the formula: F = 2π (L _d + r _e ) * _hmen , where L _d - arc length, m ² ; r _e is the radius of the furnace electrode, m; _hmen = r _ok / 2 - the depth of immersion of the pellet on the evaporation surface (meniscus) in the melt under the arc in the furnace, m, and also the fact that the melting speed of the pellets on the surface F = _{Smen is} calculated by the expression: V _pl = m _ok * N / τ _pl , with m _ok - the weight of the pellet, kg; τ _PL - pellet melting time, s; N is the number of pellets on the evaporation surface, equal for three electric arcs N = (3 * S _men / S _ok ) * 0.9069, where S _men is the meniscus surface on the metal evaporation surface m ² ; $$S_{\mathrm{about}\mathrm{to}}=\pi *r_{\mathrm{about}\mathrm{to}}^2$$

- the surface area of the pellet, m ² ; r _ok - the radius of the pellet, m; 0.9069 is the coefficient of the optimal density of the placement of pellets on the surface F = S _men and at the same time, a method characterized in that the consumption of pellets (V _ok , kg / s) is established depending on the current rate of their melting (V _PL , kg / s) by the inequality: V _c ≤V _mp = m _c * N / τ _area, wherein $${\tau }_{Pl}=x_{\mathrm{one}}*{\mathrm{<figure-callout\; id="2"\; label="\alpha \; x"\; filenames="00000006.png"\; state="\{\{state\}\}">\alpha \; </figure-callout>}}^{x_{}}$$

where α is the convective heat transfer coefficient in the pellet-melt system, W / m ² * K; x ₁ and x ₂ are stoichiometric coefficients, while for the dependence of the melting time on the convective heat transfer coefficient (α) of the pellets when they are heated in the bath of the arc furnace, the following indicators are established for 150 t of chipboard x ₁ = 10.64 and x ₂ = -0.798 .

In FIG. Figure 1 shows the scheme for feeding pellets, their heating and melting on the surface of evaporation of liquid metal, where the feed of the furnace (1), surface of evaporation of metal (2), slag (3), position of the hollow electrode in the furnace (5), and pellet in liquid metal ( 6).

Work on the proposed method of electric steel melting in an arc furnace can be technically carried out in accordance with the scheme (Fig. 1) for placing hollow electrodes in the unit, where the LMO is continuously fed into the bath on the bottom of the chipboard (1), there is liquid metal (2) and slag ( 3), through which, through the hollow electrodes (4), pellets (6) are fed into the electric arc zone (5) onto the evaporation (meniscus) surface of the metal (7), where the formation of melting dust, heating and melting of iron ore metallized pellets takes place. The cooling effect of LMOs on the metal evaporation surface (7) leads to a decrease in dust removal, i.e. to reduce the waste of metal and increase the yield of steel in an arc furnace and at the same time, the efficiency of electric melting of steel according to this invention can be estimated according to research (RU 2483119, publ. 05.27.2013; Izvestiya VUZov. Ferrous metallurgy. No. 3. 2003. P. 55-59), from which it follows that the cooling effect (Izvestia VUZov. Ferrous metallurgy. No. 9. 2008. S. 67-68; RU 2132394, publ. 06.27.1999) the supply of pellets to the high temperature zone, and more specifically in the evaporation zone of the metal can reduce metal waste almost completely (RU 2483119, publ. 05.27.2013; Izvestia Universities. Ferrous metallurgy. No. 9. 2008. S. 67-68), if the evaporation surface) ( _Smen ) is completely covered with N quantity of pellets, which is regulated by the optimal consumption of pellets (V _okopt ) in the chipboard bath.

The efficiency of steel smelting processes using the method of supplying LMOs to the metal evaporation surface in the contact zone of the arcs with it is achieved by the optimal ratio of the speed and quantity of pellet feed with the thermal state of the arc furnace bath.

Thus, the present invention solves the complex technical problem of reducing metal waste during the melting of pellets on the evaporation surface in the contact zone of electric arcs with metal. In addition, the technical result is that the proposed method allows to reduce dust removal from particleboard, increase the yield of steel, reduce environmental pollution and energy consumption for electric melting.

Claims (4)

1. The method of melting steel from iron-ore metallized pellets (LMO) in an arc steel furnace, including their supply through hollow electrodes and melting, characterized in that the LMO is continuously fed into the evaporation zone of the metal formed upon contact of the electric arcs with the metal melt, determine the burn metal (G _carbon ) in the evaporation zone and support it during the melting process at an optimal level by regulating the consumption of LMOs in the said zone, while the metal carbon is calculated in accordance with
_Burn G = (3 P _∂ × η _∂ -Σq _rad × FK × q _c) / L _j, where
Σq _rad = a × ε _e ((T _∂ / 100) ⁴ - (T _c / 100) ⁴⁾
q _ok = [c _ok (T _pl -T _ok ) L _pl + c _p (T _m -T _pl )] × V _ok , where
P _∂ - heat generated in an electric arc, W;
η _∂ - efficiency of the arc;
Σq _rad - the proportion of the heat radiation from the surface area of the metal layer (F, ² m) in said evaporation zone W / m ^2;
K is the proportion of LMOs that is melted in the surface layer of the metal in said evaporation zone;
q _ok - specific heat flux for heating and melting the LMO in the surface layer of the metal in the mentioned evaporation zone, W / m ³ ;
c is the emissivity of a completely black body, 5.67 W / (m ^{2 *} );
ε _e is the reduced degree of blackness of the electric arc system - slag-metal melt - pellet, 0.9;
T _∂ is the temperature of the electric arc, K;
T _ok - the surface temperature of the pellet for T _∂ = 6000 K;
L _j and L _PL specific heat of evaporation of iron and melting of the pellet, J / kg;
with _ok - the specific heat of the pellet, J / (kg * K);
with _p - specific heat of the resulting melt after melting of the pellet, J / (kg * K);
T _ok , T _pl , T _m - the initial temperature of the pellet, its melting temperature and the temperature of the metal in the slag-metal melt of the furnace bath, K;
V _c - LMO flow in said evaporation zone in kg / s. 2. The method according to p. 1, characterized in that the surface layer   metal in the mentioned evaporation zone (F) is calculated by the formula:
F = 2π (L_∂  + r_uh) * h_menwhere
L_∂ - arc length, m²;
r_uh - electrode radius, m;
h_men= r_OK/ 2 - the depth of immersion of the pellet in the surface layer of the metal in the mentioned evaporation zone, m 3. The method according to p. 1, characterized in that the melting speed of the LMO on the surface of the meniscus F = S _men calculated by the expression:
V _PL = m _OK * N / τ _PL , where
m _ok - the weight of the pellet, kg;
τ _PL - pellet melting time, s;
N is the number of LMOs in the mentioned evaporation zone, equal for three electric arcs N = (3 * S _men / S _ok ) * 0.9069, where
S _men - meniscus surface area in said evaporation zone, m ² ; $$S_{\mathrm{about}\mathrm{to}}=\pi *r_{\mathrm{about}\mathrm{to}}^2$$

- the surface area of the pellet, m ² ;
r _ok - the radius of the pellet, m;
0.9069 - coefficient of the optimal density of the placement of pellets on the surface of the meniscus F = S _men . 4. The method according to p. 1, characterized in that establish the consumption of pellets (V _ok , kg / s) depending on the current rate of their melting (V _PL , kg / s) by the inequality:
V _ok ≤V _pl = m _ok * N / τ _pl , and $${\tau }_{Pl}=x_{\mathrm{one}}*{\alpha }^{x_2}$$

where
α - convection heat transfer coefficient in the pellet system - melt W / m ² * K;
x ₁ and x ₂ are stoichiometric coefficients, and for the dependence of the melting time on the convective heat transfer coefficient (α) of the pellets when they are heated in the bath of an arc furnace, the indices established for 150 t of chipboard are x ₁ = 10.64 and x ₂ = -0.798 .

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