RU2058395C1 - Blast furnace - Google Patents

Abstract

FIELD: ferrous metallurgy. SUBSTANCE: blast furnace has charging device installed on furnace top, stack, bosh extension, boshes, and hearth in which air tuyeres are installed. Slag and pig iron tap holes are located at different levels over hearth height at distance of 0.1-0.2 of hearth height from the level of the main pig iron tap holes. EFFECT: higher efficiency. 1 dwg, 1 tbl

Description

 The invention relates to ferrous metallurgy and can be used in the smelting of pig iron in blast furnaces operating with the periodic production of pig iron and slag.

 Iron is smelted in blast furnaces, the main elements of which are the top, shaft, steamer, shoulders and forge. The loading of bulk materials: iron ore, coke, fluxes is carried out by the filling device on the top of the blast furnace, and the supply of highly heated, oxygen-enriched air blast, injecting fuels is carried out in the furnace hearth through air lances. To produce liquid smelting products, pig-iron and slag tap holes are used, which are located in the lower part of the furnace hearth.

On furnaces with a volume of 1000 m ³ or more, two or more cast-iron doors are built. In furnaces with a volume of 3000, 3200, 5000, 5500 m ^{3, the} number of cast iron doors is increased to 3-4, and the distance between them along the circumference of the hearth is 80-90 ^about . The distance of all cast-iron notches from the bottom of the hearth (the height of the dead layer) is the same for this furnace. As the preparation of raw materials improves and the amount of slag decreases by 400-450 kg / t of pig iron and less slag tap holes lose their significance. In the conditions of blast-furnace smelting, the mining of the upper slag is practically not carried out and the construction of slag tap holes becomes optional. The production of pig iron and slag is carried out jointly periodically through pig iron notches. The melting products are released until the slag is completely removed from the furnace, as evidenced by hot gases escaping from the furnace (purge of letches). Joint production of pig iron and slag through a cast iron notch contributes to improved contact between slag and cast iron, increases the degree of utilization of the desulfurizing ability of slag, and reduces the sulfur content in cast iron.

 Closest to the design features of the claimed object is a blast furnace containing a filling apparatus, a top, a shaft, rasper, shoulders, horns, air lances installed in it, cast-iron and slag slots located in the furnace hearth.

 However, this design of the blast furnace does not provide a rational thermal and slag regime of blast furnace smelting in modern conditions and thereby leads to a deterioration in the quality of cast iron, excessive consumption of fuel and a decrease in productivity.

 In blast furnaces operating on a charge rich in iron, the output of slag is significantly reduced. So, for example, when the mixture contains 80% pellets of SSGOK and 20% agglomerates of local factories, the slag yield for the operating conditions of MMK blast furnaces is 200-230 kg / t of pig iron. The degree of achievement of the sulfur distribution coefficient is approaching unity, so it is not possible to obtain cast iron with a low sulfur content. When the slag output is less than 220 kg / t of pig iron, as the experience of the MMK blast furnaces shows, the fluctuation in the thermal regime of blast furnace smelting significantly increases, associated with a decrease in heat accumulation in the furnace and a decrease in the thermal inertia of the furnace. This reduces the regulatory effect of slag on the chemical composition of cast iron. The role of slag as one of the main regulators of heat distribution and the chemical composition of cast iron has been established in the scientific literature and is convincingly confirmed by practice.

 The purpose of the invention is to improve the quality of cast iron and its temperature when discharged from the furnace due to the separation of better quality and more physically heated cast iron from the rest of the mass of cast iron having a high sulfur content and lower temperature.

 This goal is achieved in that the blast furnace, which includes the main elements: filling apparatus, top, shaft, raspere, shoulders and forge, air tuyeres, cast-iron and slag tapes located in the furnace, unlike the prototype, is equipped with additional cast-iron notches at a distance of 0 , 1-0.2 heights of the hearth from the level of the cast iron notch.

Cast iron, produced through additional upper cast-iron notches, will be characterized by a lower sulfur content and a higher physical and chemical heating of cast iron. The bulk of the sulfur goes into slag when drops of molten iron accumulated in the furnace are filtered through a slag layer. Therefore, with the accumulation of liquid smelting products, desulfurization proceeds unevenly, first, when there is little slag in the furnace, weakly, then, as slag accumulates in the furnace, the desulfurization activity increases. In this regard, the lower layers of cast iron will have the highest sulfur content, and the upper layers will have a lower sulfur content. The temperature of the melt entering the furnace during blast furnace smelting in the accumulation-release cycle changes cyclically. With the accumulation of liquid melting products, the lowering speed of the coke nozzle decreases, as a result of which the temperature in the furnace, and therefore the liquid melting products, increase. Therefore, the upper cast iron will be 50-100 ^{° C} higher temperature than the lower iron. As calculations and research results show, as liquid smelting products accumulate in the furnace, coke is fully introduced into slag and partially into cast iron. The coke layer is in suspension, and in some cases the lower boundary of this layer can reach the region of the lower cast iron notch, i.e. substantial part of the upper iron will be in the coke nozzle that generates additional heat in the upper reserve iron in the form of heated coke mass having at 50-100 ^{° C} higher temperature than cast iron. As studies on relatively stably working furnaces show, the first servings of cast iron from the furnace are colder. In this case, the processes of reduction of silicon and manganese, as well as desulfurization, will remain incomplete and pig iron will contain less silicon and manganese and more sulfur.

With further joint production of cast iron with slag through additional cast iron notches located between slag and cast iron notches at a distance of 0.1-0.2 heights of the furnace, intensive mixing of cast iron and slag occurs, which improves mutual contact, and therefore, additional conditions for development process of desulphurization of cast iron. The processing of a smaller amount of upper cast iron with a relatively large amount of slag in the channel of the cast iron notch is also carried out at higher (50-100 ^о С) high temperature cast iron and slag, which also helps to increase the desulfurization efficiency, since the removal of sulfur from the cast iron is associated with the endothermic effect of the reaction. The proposed furnace design is most effective especially in connection with a reduction in slag yield. With a small output of slag in the case of joint production of pig iron and slag through one lower zone of cast iron notches, i.e. according to the prototype method, the degree of achievement of the sulfur distribution coefficient approaches unity and the reserves of the desulfurizing ability of slag for the entire mass of pig iron entering the furnace are used almost completely. Based on only the top cast iron of practically the same slag mass, its desulfurization ability was used to a lesser extent.

 In the subsequent period after the purge and closure of the additional cast-iron notch, the cast-iron notch of the lower belt opens and liquid products are released through this notch of cast-iron notches. At the same time, the amount of slag discharged through the lower row of the notches together with cast iron will be significantly less than the spent amount through the upper notch. Lower cast iron will, on average, have a higher sulfur content and lower physical and chemical heating.

 Thus, the proposed design of the blast furnace will provide the selection of a better composition and more physically heated cast iron, discharged through the upper zone of cast iron notches from cast iron with a high sulfur content and reduced physical heating, discharged through the lower main row of cast iron notches. There is a possibility of further increasing the desulfurization ability of slag and the regulatory effect of slag on the chemical composition of cast iron.

 The maximum distance of the cast iron notches of the upper zone relative to the existing lower zone, equal to 0.2 of the height of the hearth, is due to the following circumstance. The height of the layer of cast iron, located above the axis of the lower row of cast iron notches, largely depends on the depth of immersion in the melt of the coke column. The depth of immersion of coke in cast iron depends on the output of slag. So, with a slag output of 150 kg / t of pig iron, the depth of immersion of a coke column in cast iron is 1.2 m, and the total height of the cast iron layer above the level of the lower row of cast iron notches is 1.3 m, i.e. the lower boundary of the coke column is almost at the level of the lower row of cast-iron notches. With a slag output of 450 kg / t of pig iron, a coke column is completely submerged only in slag and to a much lesser extent in cast iron. The upper level of cast iron is located at a distance of 0.2 the height of the hearth from the level of cast-iron notches. If the upper row of cast iron notches will be located at a distance of more than 0.2 heights of the hearth, then when slag leaves 400-450 kg / t of pig iron and more, the release of cast iron through this row of notches becomes difficult, because the level of cast iron in the furnace is lower than the location of the upper row of cast iron notches. The limit value of the slag yield equal to 450 kg / t of pig iron is due to the fact that when this value is converted, the release of liquid smelting products without mining the upper slag is problematic. This is confirmed by the theory and practice of blast furnaces.

 The minimum distance of the upper belt of cast iron notches relative to the main lower belt of cast iron notches, equal to 0.1 of the height of the hearth, is due to the following circumstances. Firstly, the nature of the movement of the melt when released through a cast iron notch. It is known that in the process of exhausting from the furnace, up to about 50% of the pig iron from the area below is supplied to the tap hole. In this regard, the minimum distance is selected from the condition that through the upper row of notches, cast iron located below the axis of the lower cast-iron notch is not produced. Secondly, with a decrease in the upper row of cast iron notches, the amount of melt, including cast iron, released from the furnace through this notch belt increases. At the same time, the lower the slag yield, the deeper the coke column lowers into cast iron and a large proportion of cast iron will be released through this upper row of cast iron notches. When the slag leaves 150 kg / t of pig iron, up to 65-70% of pig iron will be produced through the upper row of notches located at the lowest possible level. Such an increase in the mass of cast iron with a small output of slag makes it difficult to achieve this goal.

 The desulfurization capacity of the slag, calculated only on the upper cast iron, will be used almost completely. As a result, the quality of the upper and lower cast iron will be the same, i.e. the allocation of better cast iron is not ensured.

 A blast furnace with an arrangement of cast-iron notches at two levels spaced apart at the claimed distance is not known, moreover, these features do not follow explicitly from the existing level of technology, therefore, this solution contributes to the criterion of "inventive step".

 The drawing shows a diagram of the proposed blast furnace.

 The blast furnace contains a loading device 1 mounted on the top 2, shaft 3, steamer 4, shoulders 5, hearth 6, in which air tuyeres 7, slag doors 8 and cast-iron doors 9 and 10 are located, located at different levels along the height of the hearth at a distance 0.1-0.2 heights of the hearth from the level of cast-iron doors.

 Blast furnace operates as follows. The loading of iron ore materials, coke, fluxes is carried out by the filling device 1 on the top of the blast furnace 2, the supply of highly heated oxygen-enriched air blast is carried out in the furnace 6 through the air lances 7. As a result of the reduction and melting of the iron ore materials, pig iron and slag are formed in the furnace, which accumulate in hearth 6 furnace.

 In the case of smelting of poor iron ore raw materials and an increased output of slag, the upper slag is preliminarily downloaded through the slag notch 8. When the slag output is reduced after the accumulation of the melt in the furnace, the upper notch 9 is opened and the pig iron and slag are jointly released. After the release of liquid products of melting and purging of this tap hole 9, it is closed. Subsequently, the lower notch 10 opens and the remaining mass of the melt is released from the furnace. After the release and closing of the lower cast-iron notch 10, the melt again accumulates in the furnace 6 and the opening and closing cycle of the notches 8, 9, 10 is repeated.

PRI me R. A description of the implementation is given in relation to the operating conditions of a blast furnace with a volume of 2014 m ³ . The furnace is equipped with two foundries, has two cast-iron notches located on the same level. The ore part of the charge consists of 60% of pellets SSGOK and 40% sinter. The furnace capacity is 4910 tons / day, the slag yield is 320 kg / ton of pig iron with a coke consumption of 410 kg / ton of pig iron. Oven worked in combination with the blast air blown into the tuyeres 120 m ³ / t of pig iron natural gas and oxygen enrichment of the blast furnace to 27% smelted pig iron with a temperature of ^about 1440 C with a silicon content of 0.57% and 0.025% sulfur Attached top slag was not made , and the joint production of pig iron and slag was carried out alternately through cast iron notches according to the 14-time schedule for the production of pig iron and slag.

The blast furnace is additionally equipped with two upper cast iron notches, located at a distance of 0.5 m above the axis of the main notches, which is 0.14 of the height of the hearth of the blast furnace. Additional slots are located under the lower cast-iron main slots with an offset of 30-90, 180 ^o (depending on the number of foundries in the furnace and the size of the foundry, if there is one). In the blast furnace casting yard two, shifted with respect to each other at ^about 180, so it is suitable one notch (lower belt) positioned at a casting yard and another notch (upper chord) on another casting yard. When the blast furnace is equipped with a cast house, the second belt with extra iron notch (lower and upper) useful to have an offset angle at least ³⁰ degrees, otherwise there will be difficulties in the distribution of equipment to service the iron notches and in the manufacture of hearth works on one of the notches in release time of smelting products on another cast-iron notch. When the furnace is equipped with a round foundry, it is advisable to arrange the upper and lower cast iron notch belts with an offset of 90 ^° relative to each other, i.e. two upper taphole, diametrically opposite, displaced by ⁹⁰ ° relative to the bottom two iron notches, also diametrically.

After the release of pig iron with slag through one of the notches of the lower level and its purge, it is closed. About 40 minutes after the closure of this notch and the accumulation of melt in the furnace, the upper notch is opened, located on the opposite side with respect to the previously closed lower cast-iron notch, and the pig iron and slag are jointly released through this upper notch for about 20-25 minutes. After the release of liquid products of melting and purging of the upper notch, it is closed. Subsequently, after a short time interval due to technological reasons, open the upper cast iron notch, which is equipped at the diametrically located foundry and release the bulk of the melt, mainly cast iron, for about 25-30 minutes. After the release, purging and closing of this upper cast-iron notch, accumulation of liquid smelting products in the furnace again occurs. Subsequently, the same cycle of opening and closing of cast-iron notches is repeated for the lower level of notches. In this case, the proportion of pig iron produced through the upper notch will be approximately 30% i.e. 70% of the mass of cast iron will be produced through the main lower notch. The sulfur content in the top iron be 0.020% and 0.027% in the bottom of the upper cast iron temperature is 1490 ^C and 1420 ^C. Lower

 Thus, the claimed technical solution provides the possibility of separating better quality and more physically heated cast iron produced through the upper notch, from cast iron with a high sulfur content and reduced physical heating, released through the lower notch, while there is the possibility of further increasing the desulfurization ability of slag and its regulatory effect on the chemical composition of cast iron.

With the location of the upper cast iron notch at a distance of 0.8 m i.e. 0.22 heights of the hearth, mainly slag will be released through the upper cast iron notch, and almost all cast iron will be released through the lower main notch. Iron temperature is equal to ^about 1440 C, and the sulfur content of the iron will be 0.025% By arranging additional top taphole at a distance of 0.3 m and height 0.08 hearth from the lower level of the tap hole through the upper taphole will produce 70-75 weight% iron accumulated in the hearth between adjacent releases. The temperatures of the upper and lower iron content of sulfur will be approximately the same and amount to ^about 1440 C, respectively, and 0.025%
Below are the calculations of the operation of the blast furnace.

The calculations were carried out in relation to the operating conditions of a blast furnace smelting pig iron, having a volume of 2014 m ³ , equipped with two cast iron notches. The area of the furnace S _g 74.6 m ² . The number of issues is 14 per day; 300 kg / t pig iron slag yield. Density of cast iron ρ _h 7.0 t / m ³ , slag ρ _sl 2.7 t / m ³ .

1. According to the data of I. S. Kulikov and A. L. Galatonov, the degree of achieving equilibrium in sulfur is determined by the ratio:
γ 22.4 / Ш ^0.6 , where γ is the degree of achievement of sulfur equilibrium; Ø slag output kg / t of pig iron.

0,73, а при Ш 220 кг/т чугуна γ

0,89; Ш=200;
γ 0,93.Then, with the existing technology, γ

0.73, and at Ш 220 kg / t of cast iron γ

0.89; W = 200;
γ 0.93.

h где β коэффициент заполнения горна β 0,41; ε 0,45 порозность слоя кокса;
Δ h расстояние между чугунной и шлаковой летками, равное 1,6 м.2. The depth of immersion of coke in liquid smelting products before their release is calculated by the ratio:
h _burr =

h where β horn fill factor β 0.41; ε 0.45 porosity of the coke layer;
Δ h the distance between the iron and slag tap holes, equal to 1.6 m

1,6=1,72 м
3. Высота слоя шлака в горне:
h_шл V_шл/(S_г ε), где V_шл объем шлака в горне.Then h _bur =

1.6 = 1.72 m
3. The height of the slag layer in the furnace:
h _sf V _sl / (S _g ε), where V _{sl is} the slag volume in the furnace.

38,1 м³; h_шл

1,13 м
4. Высота слоя чистого чугуна в горне без кокса h_чуг определяется из соотношения:
h_погрS_г ε + h_чугS_г V_Σ
или
h_чуг

0,39 м где V_Σ общий объем расплава в горне.V _shl

38.1 m ³ ; h _shl

1.13 m
4. The height of pure iron layer in the furnace without coke _Chug h determined from the relations:
h _burr S _g ε + h _{cast iron} S _g V _Σ
or
h _cast

0.39 m where V _{Σ is the} total volume of the melt in the furnace.

+

87,1 м³ где V_чуг

49 м³ объем чугуна в горне.V _Σ = V + V _{SHL Chug}

+

87.1 m ³ where V _cast

49 m ^{3 the} volume of pig iron in the furnace.

5. The height of the layer of cast iron located in the coke nozzle:
h $\genfrac{}{}{0ex}{}{\text{to}}{\text{cast <figure-callout id="1" label="iron hh" filenames="00000015.png,00000016.png" state="{{state}}">iron </figure-callout>}}$ h h _{loaders SHL} 1,72-1,13 0,59 m.

 6. The total height of the melt in the furnace above the level of the main row of cast-iron notches N 2.

h _Σ h _sml + h $\genfrac{}{}{0ex}{}{\text{to}}{\text{cast iron}}$ + h _cast 1.13 + 0.59 +
+ 0.39 2.11 m.

приl′≥ h_чуг, V $\genfrac{}{}{0ex}{}{\text{в}}{\text{чуг}}$

В данном случае l' l·h_г 0,1·3,6 0,36 м < h_чуг,
V $\genfrac{}{}{0ex}{}{\text{в}}{\text{чуг}}$

= 0,45 м³
Аналогичным образом рассчитываются указанные параметры для других условий работы печи. Результаты вычислений представлены в таблице.7. The proportion of cast iron produced through the upper row of cast iron notches:
for l′≅ h _{cast iron} , V $\genfrac{}{}{0ex}{}{\text{in}}{\text{cast iron}}$ =

for l′≥ h _{cast iron} , V $\genfrac{}{}{0ex}{}{\text{in}}{\text{cast iron}}$

In this case, l 'l · h _g 0.1 · 3.6 0.36 m <h _{cast iron} ,
V $\genfrac{}{}{0ex}{}{\text{in}}{\text{cast iron}}$

= 0.45 m ³
Similarly, these parameters are calculated for other operating conditions of the furnace. The calculation results are presented in the table.

Claims (1)

 A DOMAIN FURNACE containing a filling apparatus, a top furnace, a shaft, a steamer, shoulders, a hearth, air lances, cast iron and slag slots located in the furnace hearth, characterized in that the furnace is equipped with additional cast iron slots located at the same level between the slag and cast iron slots on distance 0.1 0.2 of the height of the hearth from the level of the main cast-iron notches.

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