RU2147037C1 - Process of blast-furnace melting - Google Patents

Abstract

FIELD: ferrous metallurgy. SUBSTANCE: in correspondence with process force of friction of burden against wall of stack is monitored and coefficient of active mass of burden materials is computed by balance of forces and is kept within limits of 0.30-0.60. Maximum productivity of blast furnace and low specific consumption of coke are achieved at minimal coefficient of relative consumption of energy for overcoming of friction force. EFFECT: possibility of control over blast-furnace melting over entire operation range from blowing-in to prevention of burden bridging-over under any melting conditions. 4 cl, 3 dwg, 1 tbl

Description

 The invention relates to the metallurgy of ferrous metals, in particular to methods for controlling the progress of blast furnace smelting.

 A known method of blast furnace smelting with automatic maintenance of a given total differential pressure of gas / 1 /, which allowed to reduce fluctuations in the parameters of the blast during stable operation of the furnace. However, if the melting course is disturbed, the furnace operates at low speed with incomplete loading of the mine and with precipitation, the control system for the blow mode is turned off.

 Of the known closest to the proposed is a method of controlling blast furnace with continuous monitoring and maintaining the established limits of changes in the private differential pressure of the gas / 2, p. 208-277 /. The gas pressure drops are controlled by changing the gas pressure and material distribution on the top, flow rate, temperature and humidity of the blast.

 However, the known method is applicable only for stable operation of the furnace with a good state of the profile and with a constant quality of charge materials / 2, p. 216-218 /. The reason for this is the lack of continuous information on the friction force of the charge on the shaft wall and the active weight of the charge, which determines the course of the furnace.

 The technical result of the proposed method is the ability to control the progress of the blast furnace in the entire operating range from blowing to preventing the suspension from hanging under any melting conditions.

The technical result is achieved by the fact that the method includes loading the charge materials in batches, controlling the charge charge charge, supplying hot combined blast, determining the gas pressure drop over the furnace height ΔP, influencing the melting course by changing the technological parameters of the charge and blast, while according to the invention in a controlled area the furnace is loaded into the charge materials in the measuring rod, the weight of the loaded charge materials is determined in this section of the furnace, the pressure of the materials over the cross section is calculated furnace G and the friction force of the charge materials on the wall of the furnace F in a controlled area, determine the coefficient of active weight K _a = Q _a / G according to the following ratio:
Q _a / G = 1-ΔP / GF / G,
where Q _a - the active weight of the charge materials, MPa, and support K _a in the range of 0.30-0.60. Moreover, according to the invention, the coefficient of active weight K _a is determined after each batch of charged materials, at K _a over 0.60 increase, and at K _a less than 0.30, the flow rate is reduced, and at K _a = 0.175-0.30 they are loaded with coke , and at K _a = 0.60-0.70, the peripheral part of the top is loaded with ore materials and the blast consumption is increased.

In FIG. 1 shows a graph in the form of a part of a right triangle with equal legs. For each point of this scheme, the equality of the balance of forces is valid:
K _a + K _y + K _t = 1,
where K _y = ΔP / G is the aerodynamic stability coefficient of the charge column;
K _t = F / G is the coefficient of relative energy consumption for overcoming friction forces.

A stopped furnace corresponds to K _t = 0.175 - 0.40; K _a = 0.60-0.85 and K _y = 0. When blast is supplied, K _t decreases due to a decrease in K _a and the coefficients of internal and external friction of the charge column. In this case, the actual coefficient of lateral pressure n = Q _b / Q _c (Q _b is the lateral pressure of the charge on the furnace wall) does not change significantly, since the value of K _y , increased to 0.4 and 0.5, respectively, for fields "B" and "A" increases the elasticity of the charge layer.

A further increase in K _in excess of 0.4 and 0.5 changes the nature of the lowering of the charge due to an increase in F caused by an increase in additional lateral pressure q _b with a continuing decrease in the vertical load Q _in :
F = 4Q _t f _w / πdlf _c D = (n ₀ Q _c + q _b ) f _w ,
where Q _t - the friction force between the steel rod and the mixture in a controlled area;
d and l are the diameter of the rod and the depth of its immersion in the mixture;
f _with - coefficient of friction between the steel rod and the mixture;
f _W - coefficient of friction between the wall of the furnace and the mixture;
D is the average diameter of the furnace in a controlled area;
n ₀ = 0.28 - medium over the section of the lateral pressure coefficient for extremely stressed state, provided Q _in outline diagrams of the paraboloid of revolution.

As a result, the relationship between K _t and K _y is extreme. The unequal effect of ΔP on F is caused by the ability of the gas stream to loosen the charge layer and reduce its internal friction coefficient. The positive effect of the increasing value of K _y is manifested only up to 0.4 and 0.5, when the inter-voids increase in the volume of the charge column evenly enough, facilitating the rotation and mutual movement of all particles. The porosity of the material layer under these conditions is critical, in which the mutual displacement of the particles does not change the relative volume of interclust voids.

At K _at over 0.4 and 0.5, the average porosity of the charge layer continues to increase, but the distribution of interclump voids becomes uneven due to the appearance of small channels, the volume of which increases with increasing K _at . In this regard, any displacement of even a small number of pieces, like an avalanche, quickly involves a significant mass in accelerated motion, a sudden stop of which increases K _t and for some time reduces the porosity of the charge layer. As a result, the lowering of the charge column occurs with weak shocks, which grow with increasing K _y into stronger ones with a simultaneous increase in K _t .

The range of variation of K _a is divided into three control modes:
I - bottom control (flow rate, temperature and humidity of the blast, consumption of carbon-hydrogen additives and oxygen);
II - control from above (changing the loading mode of materials, the proportion of sinter and pellets, the level of mash, gas pressure under the top);
III - optimal mode.

- образным температурным полем, подгруженной рудными материалами периферийной части колошника и развитым центральным газовым потоком. Для поля "А" режим III на 30% шире, чем для "Б", т.е. более стабильная работа на дутье повышенных параметров, обеспечивающая более высокую производительность и низкий расход кокса. Пунктирными линиями на фиг. 1 показаны поля "В" и "Г" предполагаемой работы печи на худшем качестве сырья и кокса, чем для условий в периоде 3 (таблица).In the range K _a = 0.30 - 0.60, 0.30 - 0.50, respectively, for fields "A" and "B", the blast furnace operates with the highest productivity and minimum coke consumption. Optimum mode III is achieved due to the uniform distribution of the gas flow over most of the mine section with

- a figurative temperature field loaded with ore materials of the peripheral part of the top and a developed central gas flow. For field "A", mode III is 30% wider than for "B", i.e. more stable operation on the blast of increased parameters, providing higher productivity and low coke consumption. The dashed lines in FIG. Figure 1 shows the fields "B" and "G" of the expected operation of the furnace at the worst quality of raw materials and coke than for the conditions in period 3 (table).

When K _{a is} more than 0.70 and 0, 50, the distribution of the gas flow over the mine cross section is still not uniformly enough. Melting is carried out with a developed peripheral gas flow and a W-shaped temperature field. Therefore, the degree of utilization of the chemical energy of the gas stream is not high enough and the specific consumption of coke is increased. At K _a less than 0.30, small and then larger breaks appear in the charge movement as a result of the formation of small, and later more developed channels, which lead to a deterioration in the use of chemical energy of the gas stream and a decrease in the intensity of smelting in the melted ore rash. As a result, the productivity of the furnace decreases and the specific consumption of coke increases.

In mode I, with K _a = 0.70 - 0.85 and 0.55 - 0.75, a blast furnace is blown. Values of K _a = 0.75 - 0.85 and 0.60 - 0.75 correspond to a stopped furnace. Long operation of the furnace in mode I at high values of K _a leads to the destruction of the protective layer of the skull, refractory masonry and refrigerators of the lower part of the shaft and shoulders. If K _{a is} less than 0.70 (IIA) and 0.55 (IIB), measures for controlling bottom melting (increasing the flow rate and temperature of the blast, lowering the humidity of the blasting, increasing the consumption of natural gas, fuel oil and coal fuel, as well as oxygen) are not enough for high-performance operation of the furnace, increasing the degree of utilization of the chemical energy of the gas stream and reducing the consumption of coke; therefore, it is necessary to load the peripheral part of the top with ore materials, changing the operating mode of the loading device and the level of mound, increasing the proportion of pellets and the pressure drop I am gas.

Mode I at K _a = 0-0.175 (IA) and 0-0,200 (IB) corresponds to an unstable melting course. When K _a = 0, the charge freezes with the formation of a vault resting on the walls of the mine. To resume lowering the materials, the flow rate of the blast is reduced and the melting is transferred to mode II at K _a = 0.50-0.55 (IIB) and 0.60-0.70 (IIA), due to which the arch collapses and the movement of the charge is resumed, then control “from below” and “from above” the melt is transferred to mode III. When K _{a is} less than 0.175 (IA) and 0.200 (IB), they reduce the temperature and increase the humidity of the blast, reduce the consumption of natural gas and oxygen, and when these measures become insufficient, then they reduce the flow of blast and put the heat in mode II at K _a = 0.175- 0.30 (IIA) and 0.20-0.30 (IIB), and then control "bottom" and "top" return to mode III.

The operation of the furnace in mode II with K _a over 0.175 (IIA) and 0.200 (IIB) ensures maximum productivity with coke overspending, therefore modes IIA and IIB are used only to fulfill the increased planned tasks for the production of pig iron.

The lower limit of mode II with K _a = 0.175 (IIA) and 0.20 (IIB) is the beginning of suspension of the charge (in Fig. 1 - the internal boundaries of the fields "A" and "B").

The measures taken in mode II with K _a = 0.175 - 0.30 (IIA) and 0.20 - 0.30 (IIB) when controlling the melting course "from below" and "above" are active. Reducing the flow rate of blast in mode I is a passive measure and is used in case of frustration of the melting course.

The proposed method of blast furnace smelting is implemented on a blast furnace No. 3 of the West Siberian Metallurgical Plant (usable volume of 3000 m ³ ), which includes three levels of automation in the automated process control system.

Portions of coke, agglomerate, pellets, lump ore and metal additives were loaded into the blast furnace, a combined blast with a temperature of 1050-1100 ^° C was fed, the level of charge material charge and gas pressure drops ΔP along the furnace height were continuously monitored. To determine the pressure of the charge materials G over the cross section in the controlled section of the furnace and the friction force of the materials on the wall of the furnace in the same section, a measuring steel rod with a diameter of d, length l was immersed in the charge materials and the coefficient of active weight K _a = Q _a / G was calculated.

1. Initial data (measured values):
1.1. The friction force of the charge Q _t about a steel rod, kgf (0-1000);
1.2. The charge charge level is average:
L _l + L _p ) 2 = L _cf ,
where L _l - the left level gauge;
L _p - the right level gauge;
1.3. The height of the controlled part of the charge in the furnace:
l = l _const = L _cp ,
where I _const is the distance from the cone in the lowered state to the mark of the embrasure of the gas pressure;
1.4. The upper differential pressure of the gas ΔP _in , kg / cm ² ;
1.5. The weight of the components of the charge in the feed, kg;
G _to - the weight of coke;
G _a is the weight of the agglomerate;
G _about - the weight of the pellets;
G _i - the weight of other components of the mixture;
1.6. Coefficients (which are set and can be changed):
- coefficient of friction of the charge on steel f _c = 0.460;
- the coefficient of friction of the charge on chamotte masonry f _W = 0,840;
1.7. The parameters are constant, see:
- bar diameter d = 4;
- the average radius of the furnace in the controlled zone of the furnace r = (r ₁ + r ₂ ) / 2;
- the radius of the top r ₁ = 430;
- the radius on the horizon of the embrasure for measuring ΔP _in (upper differential pressure), r ₂ = 500;
1.8. Bulk weight γ _i t / m ³ ;
- coke γ _k = 0.5
- pellets of the Kachkanar γ ₀ = 2.15;
- agglomerate ZSMK γ _a = 2,04;
- Mundybash agglomerate γ _a = 1.98;
- quartzite γ _q = 1.5;
- slag converter γ _w = 2,1.

2. Formulas
2.1. Lateral pressure of the charge on the steel rod, kgf:
Qσ = Q _t / πdlfe;
2.2. The friction force of the charge on a rod made of fireclay kgf;
F _o = Q _b • f _w
2.3. The side surface of the furnace in a controlled area, cm ²
S _pov = πl (r ₁ + r ₂ )
2.4. Controlled section of the furnace, cm ²
S _section = πr ²
2.5. The friction force of the charge on the wall of the furnace in a controlled area, kg / cm ²
F = F _about • (S _pov / S _section );
2.6. The average bulk density of the charge materials, t / m ³
γ ₀ = ΣG _i / Σ (C _i / γ _oi );
2.7. Pressure of the loaded materials, kg / cm ² ;
G = γ ₀ • 1
2.8. The vertical pressure of the mixture, kg / cm ² ;
Q _in = G- (ΔP _in + F);
2.9. The ratio of the active weight of the mixture K _a :
Q _a / G = 1- (ΔP _in / GF / G);
2.10. Coefficient of relative energy consumption for overcoming friction forces:
K _t = F / G;
2.11. The aerodynamic stability coefficient of the charge column:
K _y = ΔP _in / G;
2.12. The balance of power equation:
K _a + K _y + K _t = 1.

In FIG. Figure 2 shows three fragments of the diagram of the change in K _a on the monitor screen. Under the conditions of economical and forced blast-furnace running for field "B", the index K _a is 0.370 - 0.420 with a slight deviation from the average value. Out of nine feeds loaded into the furnace (they are shown by arrows in FIG. 2), in eight cases an even gathering of materials was recorded. Within 1 hour, there was only one case of significant compaction of materials and a decrease in K _a (Fig. 2, a).

With a less stable furnace operation in mode IIB, only eight feeds were loaded (Fig. 2, b). The lowering of each feed was accompanied by a sharp increase in K _t and a decrease in K _a , the duration of loosening of the compacted materials increased to 6-8 minutes. To improve the course of the furnace at the 52nd minute, the moving top plates were moved to position 3 (400 mm from the wall) to unload the peripheral part of the charge. As a result, the value of K _a increased and the course of melting moved to mode IIIB.

The next period of operation of the furnace (Fig. 2, c) was characterized by an even larger increase in K _t and a decrease in K _a . The upper partial drop increased, and the K value of _y became unstable, the level gauges recorded an uneven convergence of the charge. The number of feeds loaded into the furnace in 1 hour decreased to five. To prevent further deterioration of the course and suspension of the charge, at the 53rd minute, the flow rate of the blast was reduced by 8%, after which the value of K _a increased from 0.10 to 0.27 and the course of the furnace became more even. Later, when the number of direct feeds of RRKK was reduced from 7 to 5 (5RRKK + 2KRKK, P - ore rash, K - coke), the smelting course was transferred from mode IIB to mode IIIB.

The change in the productivity of the blast furnace N 3 ZSMK and the specific consumption of coke in March-April 1995, as well as the indicators K _a , K _t and K _y from the intensity of the smelting of the burnt coke (I _k ) in mode IIIA are shown in FIG. 3. The minimum value of K _t corresponds to a low consumption of coke and high productivity of the furnace.

The operation of this furnace at reduced blast parameters (K _y = 0.10-0.30 and K _a = 0.50-0.70) without controlling the melting progress “from above” and “from below” was monitored in periods 1-3 in November 1995 - February 1996 (see table) with different quality of iron ore raw materials. In period 1, the missing amount of high-quality local sinter was compensated by non-destructible pellets of the Kachkanarsky GOK with a low external friction coefficient f _w = 0.396 (versus f _w = 0.509-0.565 for the sinter), so melting was carried out in modes IA - IIA on the external branch (A) of fields K _a and K _t . A feature of the operation of the furnace in these modes is a significant expansion of the material flow zone and an increase in lateral loads on the walls of the lower part of the shaft and shoulders. In order to avoid the destruction of the refrigerators of these zones in period 2, they introduced 6.7% of the weak-strength agglomerate of the Mundybash factory instead of the 3СМК agglomerate, increased the flow rate of the blast and the degree of balancing the charge with the gas flow K _у from 0.178 to 0.240. As a result, the melting mode shifted from the outer to the inner part of the fields K _a and K _t (to the border of fields A and B), the material flow zone narrowed, creating conditions for the formation of a protective layer of a skull in the lower part of the shaft and shoulders. The course of blast-furnace smelting has become less stable; substrates and breaks of the charge, characteristic of the peripheral gas flow, have appeared. The degree of utilization of carbon monoxide η _CO decreased from 0.422 to 0.415, however, due to the intensification of smelting by blast, furnace productivity was increased by 25.8%. In period 3, due to the absence of imported pellets and agglomerate, 12.2% of non-screened Atasuysky ore was introduced, which led to a decrease in the iron content in the charge from 52.1-53.2 to 50.2%. To reduce coke consumption, we used natural gas and lean coal in an amount of 41 m ³ / t of pig iron and 18 kg / t of cast iron, respectively, and also increased the temperature of the hot blast. The melting mode IIB in period 3 was kept in the middle part of the total field K _a and K _t , but, despite this, it turned out to be more expensive in terms of total carbon due to the peripheral course and low η _CO = 0.397.

In general, the operation of the blast furnace in modes I - II at high values of K _{a is} inefficient due to the low productivity and high specific consumption of coke in comparison with the optimal mode III (Fig. 3); In addition, continuous operation of the furnace in these modes leads to a reduction in the campaign.

Operation of a powerful blast furnace at high blast parameters (K _a = 0.10-0.30 and K _y = 0.50-0.70) in unstable mode II is allowed no more than 1 hour, and in mode I with K _a less than 0 10 is generally not allowed to avoid serious breakdowns and prolonged downtime. Therefore, the use of the proposed method for controlling the progress of blast furnace smelting allows to efficiently ensure high-performance operation of the furnace, to prevent frustration and suspension of the charge, as well as to accelerate the blow-up after prolonged parking.

 The expected economic effect from the implementation of the proposed method for controlling the course of blast furnace smelting is 130.6 million rubles.

 The proposed method can be implemented on any blast furnace.

 Sources of information taken into account when compiling the description.

 1. Buklan I.Z., Bachinin A.A., Tretyak A.A. et al. / Operation of a blast furnace with automatic stabilization of the blast mode. // Steel, 1991, N 11.P. 18-21).

 2. Gimmelfarb A. A., Efimenko G. G. Automatic domain process control. M., Metallurgy, 1969 .-- 309 p.

Claims (4)

1. The method of blast furnace smelting, including loading the charge materials in batches, controlling the charge charge charge, supplying hot combined blast, determining the gas pressure drop over the furnace height ΔP, affecting the melting course by changing the technological parameters of the charge and blast, characterized in that in the controlled area the measuring rod is immersed in the furnace into the charge materials, the weight of the loaded charge materials is determined on this section of the furnace, and the material pressure is calculated over the furnace cross section G and the friction force F tovyh materials of the furnace wall in the controlled area, determine the weight coefficient of the active K _a = G _a / G according to the following relationship:
Q _a / G = 1-ΔP / GF / G,
where Q _a is the active weight of the charge materials, MPa,
and support K _a between 0.30 - 0.60. 2. The method according to claim 1, characterized in that the active weight coefficient K _a is determined after each portion of the charge materials loaded into the furnace. 3. The method according to claim 1 or 2, characterized in that at K _a over 0.60 increase, and at K _a less than 0.30 reduce the flow rate of blast. 4. The method according to claim 1 or 2, characterized in that when K _a = 0.175-0.30, they are loaded with coke, and when K _a = 0.60-0.70, the peripheral part of the top is loaded with ore materials and the blast consumption is increased.

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