RU2371484C2 - Tuyere for blowing off of alloy in oxygen-blown vessel - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to ferrous metallurgy, particularly to basic oxygen steel manufacturing. Tuyere contains concentric located pipes, forming routes for feeding of oxidant, feeding of coolant withdrawal and multiport head with Laval conical nozzles. Nozzles allows confuser, minimal section and diffuser with rectilinear generators. Between confuser and diffuser in Laval conical nozzles there are implemented cylindrical channels, length of which is defined from given correlation. Furthermore, diffuser of nozzles allows additional cylindrical outlet sections, length of which is defined from given correlation.

EFFECT: usage of invention provides increasing of effectiveness of blowing off of converter bath.

3 cl, 8 dwg

Description

The invention relates to metallurgy, mainly to oxygen-converter steel production.

Known oxygen tuyere for blowing the melt in the converter from above [1, p.164], consisting of concentrically arranged pipes forming paths for the supply of oxidizing agent (oxygen), supply and removal of cooler (water) and a head with one conical Laval nozzle having a confuser, minimum cross section and diffuser with rectilinear generators.

This ensures effective cooling of the lance head and, as a result, its high resistance.

(где F_pз, F_в - площади поперечных сечений суммарной реакционной зоны и конвертерной ванны соответственно) существенно меньше оптимальной. Имеет место неэффективная «жесткая» продувка ванны и неудовлетворительное шлакообразование, что приводит к заметалливанию оборудования, ухудшению качества выплавляемой стали, теплового баланса и технико-экономических показателей плавок. Для того чтобы уменьшить до необходимого значения относительную глубину внедрения струи дутья в ванну

(где H_рз, H_в - глубина реакционной зоны и ванны металла соответственно) необходимо поддерживать чрезмерно высокие значения высоты фурмы над ванной Н_ф, что приводит к усилению износа футеровки конвертера.However, when using the known lance, the necessary degree of dispersion of the blast along the surface of the converter bath is not provided: the value of the relative area

(where F _pз , F _в are the cross-sectional areas of the total reaction zone and the converter bath, respectively) is significantly less than optimal. There is an ineffective "hard" purge of the bathtub and unsatisfactory slag formation, which leads to the obscurity of the equipment, deterioration of the quality of the smelted steel, heat balance and technical and economic indicators of the heat. In order to reduce to the required value the relative depth of introduction of the blast jet into the bath

(where H _rz , H _in - the depth of the reaction zone and the metal bath, respectively) it is necessary to maintain excessively high values of the height of the lance above the bath N _f , which leads to increased wear of the lining of the Converter.

Known tuyere for blowing the melt in the converter from above [2, p. 74}, consisting of concentrically arranged pipes forming paths for the supply of oxidizing agent (oxygen), supply and removal of cooler (water) and a head with one nozzle having a multi-way spiral plate insert for swirling and separating the flow of oxygen.

и степень рассредоточения дутья по поверхности ванны.This ensures that several (3 ÷ 6) oxygen jets flow out from one nozzle at a small angle to the vertical axis of the lance and increases slightly

and the degree of dispersion of the blast over the surface of the bath.

не достигает оптимальных значений и режим продувки остается близким к «жесткому». Кроме того, спиралевидная вставка не имеет достаточно эффективного водяного охлаждения, быстро оплавляется и выходит из строя. При этом выходит из строя и сама фурма.However, due to the inevitable interaction and partial merger of oxygen jets flowing from a known lance, the quantity

does not reach optimal values and the purge mode remains close to “hard”. In addition, the spiral insert does not have sufficiently effective water cooling, quickly melts and fails. At the same time, the lance itself also fails.

Known tuyere for blowing the melt in the converter from above [3, p. 12-13] is a prototype consisting of concentrically arranged pipes forming paths for supplying an oxidizing agent (oxygen), supplying and discharging a cooler (water) and a multi-nozzle head with conical nozzles Davala, having a confuser, a minimum cross section and a diffuser with rectilinear generators with an opening angle γ = (5 ÷ 10) °.

и

. Это позволяет обеспечить требуемый режим продувки, т.е. степень «жесткости» дутья, которая определяется в первую очередь удельным импульсом дутьевых струй в месте встречи с металлической ванной

(Па), где I_x - избыточный импульс дутьевых струй в месте встречи с ванной, F_x - площадь поверхности ванны в зоне контакта с дутьевыми струями, м².Moreover, by changing (choosing the optimal value) the number of nozzles in the head — n _c , located at a certain angle α to the axis of the tuyere (usually α is within (15–20) ° [3, p. 13]), one can practically any combination of necessary (set) values

and

. This allows you to provide the desired purge mode, i.e. the degree of "stiffness" of the blast, which is determined primarily by the specific impulse of the blast jets at the meeting point with the metal bath

(Pa), where I _x is the excess momentum of the blast jets at the meeting point with the bathtub, F _x is the surface area of the bath in the zone of contact with the blast jets, m ² .

However, when using the well-known tuyeres to provide a “softened” purge of the converter bath (in the case of “hot” dressings of melts, redistribution of cast iron with a low Mn content, deterioration of lime quality, deficiency or the need to save fluorspar, implementation of low-slag steel smelting technology, etc. ) usually requires an increase in the number of nozzles in the head to 6 ÷ 8 or more. This significantly degrades the cooling efficiency of the lance head and reduces its resistance due to a decrease in the cross-sectional area for the passage of the cooler between the nozzles and an increase in the number of butt welds (when using a welded head design). In addition, this complicates the manufacture, increases the material consumption and cost of copper heads. When using conical Laval nozzles with the diffuser opening angle γ = (5 ÷ 10) °, there is a limited range of stable (uninterrupted) lance operation in terms of the oxygen pressure in front of the nozzles and the degree of non-design of the outflow of jets - n. At n≤1, the flow begins to separate from the nozzle diffuser walls, which leads to a “swing” (erosion) of the outlet sections of the latter, a decrease in the resistance of the tuyere heads and destabilization of the blasting mode of smelting. Therefore, when using the known tuyere, purging is carried out in the mode of under-expansion of the jets (at n = 1.3-2.0), which leads to additional losses of blast energy (at the shock waves) and a decrease in the purge efficiency (incomplete use of the potential pressure pressure energy to increase the kinetic jet energy and bath stirring power).

The aim of the present invention is to increase the efficiency of purging the converter bath, increase durability, simplify manufacturing and reduce the material consumption of the lance head and, as a result, reduce the cost of smelted steel (by reducing the unit cost of metal charge, slag-forming materials, oxygen, ferroalloys and deoxidizing agents, refractories), improving its quality and increased productivity of units (oxygen converters).

This goal is achieved by the fact that in the lance for blowing the melt in the converter from above, consisting of concentrically arranged pipes forming ducts for supplying an oxidizing agent, supply and removal of a cooler and a multi-nozzle head with conical Laval nozzles having a confuser, a minimum cross section and a diffuser with rectilinear generators, the opening angle of the nozzle diffusers is determined from the ratio.

where γ _min = 20 °

k _e - empirical coefficient equal to 0.85 ÷ 0.95;

k is the adiabatic exponent of the outgoing gas (for oxygen, k = 1.4);

P ₀ = P ₀ · σ / P _∞ - the available differential pressure at the nozzles;

P ₀ is the total oxygen braking pressure in front of the nozzles, Pa;

σ is the coefficient of restoration of the total oxygen pressure in the nozzle;

P _∞ is the static pressure in the environment (in the cavity of the converter) at the nozzle exit, Pa.

In addition, cylindrical channels are made between the confuser and the diffuser in the Laval nozzles, the length of which is determined from the relation

where l _C - the length of the cylindrical channels, m;

d _min - the diameter of the minimum section of the Laval nozzles, m

In addition, nozzle diffusers have additional cylindrical outlet sections, the length of which is determined from the ratio

where l _in - the length of the additional cylindrical output sections of the nozzle diffusers, m

и, как следствие, к эффекту «умягчения» продувки сталеплавильной ванны, что адекватно увеличению числа сопел при использовании фурмы-прототипа. Таким обрезом, применение предложенного технического решения позволяет обеспечить требуемую степень «жесткости» (степень «мягкости») дутья при использовании меньшего числа сопел в наконечнике фурмы по сравнению с прототипом. Это позволяет упростить конструкцию головки фурмы, облегчить ее изготовление, снизить материалоемкость (по меди) и существенно увеличить ее стойкость за счет увеличения площади сечений для прихода охладителя между соплами.When making conical Laval nozzles of the lance head with an opening angle of the diffuser γ, which is in the range of values (γ _min ≤γ _≤ γ _max ), a significantly different character of the expiration of the blast jets occurs compared to using the lance prototype with γ = 5 ÷ 10 °. This is due to the fact that for small values of γ (less than 15 ÷ 20 °), the influence of the radial component of the velocity of the flow of blast from the nozzle on the main parameters of the jet is insignificant, including its impulse and the diameter of the first “barrel” (or the diameter of the effective isobaric section d _ef corresponding to the full expansion of the jet), which significantly affects the characteristics (properties) of the jet at the place it meets the bath and, as a result, the mode of blowing the whole melt . At γ over 20–25 °, the radial component of the velocity of the blasting outflow increases noticeably, which leads, on the one hand, to an additional increase in the diameter of the first barrel (d _eff ), and, on the other hand, to an additional decrease in the longitudinal component of the pulse of the expiring jets i _page On the whole, the specific impulse of the jet in the effective cross section (referred to the area F _eff ) is significantly reduced. This, in turn, leads to an increase in F _x and a decrease

and, as a result, to the effect of "softening" the purge of the steelmaking bath, which is adequate to an increase in the number of nozzles when using the lance prototype. Thus, the application of the proposed technical solution allows to provide the required degree of "rigidity" (degree of "softness") of the blast when using fewer nozzles in the lance tip compared to the prototype. This allows us to simplify the design of the lance head, facilitate its manufacture, reduce material consumption (for copper) and significantly increase its resistance by increasing the cross-sectional area for the arrival of the cooler between the nozzles.

The essence of the invention is presented in figures 1-8 where in figures 1, 2, 3 are longitudinal sections of tuyeres according to claims 1, 2 and 3 of the claims, respectively; figure 4 shows the dependence of the cosine of the mass-average slope of the jet velocity vector in the output section of the nozzle on the opening angle of the cone of the conical Laval nozzle; Figures 5, 6, 7 show the dependences of the relative diameter of the jet in the effective cross section on the opening angle (solution) of the nozzle diffuser at various Mach numbers of the nozzle and at different degrees of non-design of the outflow of the jets, Fig. 8 shows the dependences of the degree of non-design of the start of flow separation from the walls nozzle from the opening angle of the nozzle diffuser at different Mach numbers of the nozzle.

(где d_эф,0 - диаметр эффективного сечения струи при угле раскрытия диффузора сопла γ, равном нулю. в случае n=1 величина и Figure 4 shows the dependence of the cosine of the mass-average slope of the jet velocity vector in the output section of the nozzle cosα [4] (which determines the longitudinal component of the jet momentum) on the opening angle of the diffuser of the conical Laval nozzle. Figure 5-7 shows the dependence of the relative diameter of the jet in the effective section

(where d _{eff, 0} is the diameter of the effective section of the jet at the nozzle diffuser angle γ equal to zero. in the case n = 1, the quantity and

d _{eff, 0} coincides with the output diameter of the nozzle d _a ) on the opening angle (solution) of the nozzle diffuser for different nozzle Mach numbers M _a (in the range used in metallurgical practice, M _a = 1.5-2.5) and for different degrees of off-design n of outflow of jets.

и cosα и малые значения параметров d_эф, d_х, F_x,

, т.е. слабое влияние величины γ на дутьевой режим конвертерной плавки в целом.From the data of FIG. 4-7 it follows that the value of γ _min is ≈15 ÷ 20 °. If γ <γ _min , then there is a weak effect of γ on

and cosα and small values of the parameters d _eff , d _x , F _x ,

, i.e. weak effect of γ on the blast mode of converter smelting as a whole.

The value of γ _{max is} determined by the maximum angle of rotation of the flow of blast in the nozzle (at a given pressure in front of it) and is described by dependence (2). In this case, the parameter k _e takes into account the design features and the manufacturing quality of the flow part of the nozzle. If γ> γ _max , then there is a separation of the flow from the walls of the diffuser in the nozzles, the “height” of the latter sharply increases and, as a result, the tuyere resistance decreases and the melting mode is destabilized.

In addition, when using conical Laval nozzles with the opening angle of the diffuser γ in the declared range of values (γ _min ≤γ≤γ _max ) in the tuyere head, the purge process is more stable. This is due to the fact that with an increase in the diameter of the first “barrel”, as well as with the radial component of the velocity of the jet, the position of the root of the jet is more resistant to external disturbances (the amplitude and frequency of the self-oscillations of the jet are less). At the same time, the range of values of n for the continuous operation of the nozzle also significantly expands (with decreasing n up to 0.6-0.7 with the nozzle Mach numbers M _a = 1.5-2.5 used in metallurgical practice) - see Fig. 8, which shows the dependences of the degree of non-design of the beginning of flow separation from the nozzle walls n _sp from the opening angle of the nozzle diffuser γ for various M _a . This leads, on the one hand, to an increase in the resistance of nozzles to erosion wear and tuyeres in general, and, on the other hand, to an increase in the purge blowing efficiency due to better organization of oxygen jets in the working space of the unit and a decrease in blast energy losses associated with “deformation” output sections of nozzles and the occurrence of separated flows. This also makes it possible to purge melts in the optimal range along n — near the calculated regime of jet outflow (for n = 0.8–1.2), which will minimize the loss of potential energy of the flow pressure in the nozzle and increase the efficiency of purging the steel bath. The increased diameter of the first "barrel" allows you to further protect the nozzle exit edge and the sub-nozzle region of the lance tip from splashing metal and slag, which helps to increase the resistance of the exit edges of the nozzles and lance tip. In addition, when using nozzles with an opening angle of the diffusers in the claimed range (γ _min ≤ γ ≤ γ _max ), (ceteris paribus) there is a significantly shorter length of the diffuser (the highest speed section) of the nozzle, which leads to a decrease in pressure loss blast in cuts and, as a result, to increase the purge efficiency.

The implementation in the Laval nozzles between the confuser and the diffuser with the opening angle γ, determined from relation (1), of a cylindrical channel with a length determined from relation (4), allows: firstly, to vary widely the length of the nozzle, and therefore the height lance heads (in accordance with the design features of the latter), and secondly, to further stabilize the process of expiration of oxygen jets and reduce the energy loss of the blast stream in the nozzles by creating a more uniform transverse velocity profile stke nozzle with a cylindrical channel. In addition, this significantly reduces the requirements for the configuration of nozzle diffusers and simplifies the manufacture of lances.

Moreover, if l _c / d _min <0.1, it is difficult to manufacture nozzles with the required accuracy and there is practically no effect of alignment of the velocity profile in the cross section of the flow in the cylindrical section of the nozzle. If l _c / d _min > 2.5 ÷ 3, the pressure loss of the blast stream in the section of the cylindrical channel of the nozzle increases significantly, the height of the lance head increases excessively, which makes it difficult to cool due to the organization of the flow of water.

The implementation of additional cylindrical outlet sections in Laval nozzles, the length of which is determined from relation (5), allows us to further increase the stability of the flow from the nozzle to separation (due to the effect of “compression” of the flow to the walls of the nozzle) and reduce the radiation heat flux to the inner surface of the nozzle exit section from the high-temperature reaction zone (by reducing the angular emissivity). This helps to increase the resistance of the outlet section of the nozzles and lance as a whole to abrasive, thermal and chemical erosion.

If l _in / d _min <0.05, it is difficult to manufacture nozzles with the necessary accuracy and there is practically no effect of the output cylindrical section on the stability of the flow from the nozzle to separation. If l _in / d _min > 0.2, then there is a noticeable decrease in the radial component of the velocity, diameter d _eff and a decrease in the effect of softening the jet.

The lance for blowing the melt in the oxygen converter consists of concentrically arranged pipes 1, forming paths for the supply of oxidizing agent (oxygen) 2, supply 3 and outlet 4 of the cooler (water) and multi-nozzle head 5 with conical Laval nozzles 6 having a confuser 7 (with length l _to ), the minimum cross section 8 and the diffuser 9 (with a length l _d ) with rectilinear generators 10, and the opening angle of the nozzle diffusers γ is determined from the relation (1) - (3) - see Fig. 1.

Between the confuser 7 and the diffuser 9 of the Laval nozzles can be made cylindrical channels 11, the length of which (l _C ) is determined from the relation (4) - see figure 2.

The diffusers 9 of the Laval nozzles can have additional cylindrical output sections 12, the length of which (l _in ) is determined from the relation (5) - see Fig. 3.

,

и др. обеспечиваются минимальным числом сопел в головке фурмы n_c, то уменьшается материалоемкость (по меди) фурмы, улучшается охлаждение головки, увеличивается стойкость и снижается ее себестоимость.The device operates as follows (see figure 1). Cooling water is supplied through the inlet path 3 to the lance head 5, circulates in it, passing the nozzle space, and is discharged from the lance along the path 4. Oxygen is supplied through the path 2 to the multi-nozzle head 5. Passing through the confusers 7 of the nozzles 6, it accelerates to a critical speed near the minimum nozzle cross section 8, and passing further through the diffusers 9 (with an opening angle γ in the declared range) - to a supersonic speed determined by the Mach number of the nozzle M _a and providing the corresponding pressure in front of the nozzles p ₀ , and expires from opel in the form of supersonic jets 13 having a substantially increased effective (isobaric) diameter d _eff 14. The process of expiration of the blast jets is characterized by a stable position of the jet root, the absence of separated flows in the outlet section of the nozzles and low losses of the potential pressure energy of the blast stream in the nozzles, which ensures stabilization and increased efficiency of purging the steelmaking bath, high resistance of nozzles to erosion wear and tuyeres in general. Since at the same time the set values of the main operating parameters of the purge

,

and others are provided with a minimum number of nozzles in the tuyere head n _c , then the material consumption (in copper) of the tuyere decreases, the cooling of the head improves, the resistance increases and its cost decreases.

When performing in the nozzles 6 of the tuyere (see FIG. 2) of cylindrical channels 11 with a length that is in the claimed range, in the blast stream during the transition from the confuser 7 to the diffuser 9 in the cylindrical channels 11 a more uniform distribution of sound velocity over the cross section at the entrance to a diffuser, which additionally stabilizes the flow of jets from the nozzles and reduces the pressure loss of the blast in the nozzles.

When the nozzles 6 of the tuyere (see FIG. 3) are executed with diffusers 9 with additional cylindrical outlet sections 12 with a length in the claimed range, the outflow resistance to separation is further increased and the heat flux to the inner surface of the nozzle decreases, which leads to stabilization of the process purge and increase lance resistance.

The use of a tuyere for blowing the melt in an oxygen converter of the indicated design by optimizing the opening angle of the nozzle diffusers and ensuring the outflow of oxygen jets with increased diameter of the first “barrel” (effective cross-section) and the radial component of the flow rate will increase the efficiency of purging the steelmaking bath, increase resistance, simplify manufacturing and reduce the material intensity of the lance head and, as a result, reduce the cost of steel smelted (by reducing specific costs atm metallic charge, the slag-forming materials, oxygen, reductants, and ferroalloys, refractory), to improve the quality and increase productivity aggregates (BOF).

INFORMATION SOURCES

1. Baptismansky V.I., Medzhibozhsky M.Ya., Okhotsky V.B. Converter steelmaking processes. Theory, technology, assembly design. - Kiev; Donetsk: Vishka school., 1984. - 343 p.

2. Afanasyev S.G. Converter quick reference. - M.: Metallurgy, 1967.

3. Starev R.V., Nagorskih V.A. Steel production in converters, - K .: Technika, 1987. - 167 p.

4. Luhtura F.I. One-dimensional theory of supersonic non-calculated gas strings. - Proceedings of the RAS. Mechanics of fluid and gas. - 1993, No. 1. - S. 48-56.

Claims (3)

1. Lance for blowing the melt in an oxygen converter, containing concentrically arranged pipes forming ducts for supplying an oxidizing agent, supply and removal of a cooler and a multi-nozzle head with conical Laval nozzles having a confuser, a minimum cross section and a diffuser with straight generators, characterized in that the opening angle nozzle diffusers determined from the relation
Y _min ≤γ≤γ _max ',
where γ _min = 20 °;

k _e - empirical coefficient equal to 0.85 ÷ 0.95,
k is the exponent of the outflowing gas adiabat, equal to 1.4 for oxygen,
P ₀ = P ₀ · σ / P _∞ - pressure drop at the nozzles,
P ₀ is the total oxygen braking pressure in front of the nozzles, Pa;
σ is the coefficient of restoration of the total oxygen pressure in the nozzle;
P _∞ is the static pressure in the cavity of the converter at the nozzle exit level, Pa. 2. The lance according to claim 1, characterized in that between the confuser and the diffuser in the Laval nozzles are made cylindrical channels, the length of which is determined from the ratio
1 _c / d _min = 0.1-3.0,
where 1 _C is the length of the cylindrical channels, m;
d _min - the diameter of the minimum section of the Laval nozzles, m 3. A lance according to any one of claims 1 and 2, characterized in that the nozzle diffusers have additional cylindrical output sections, the length of which is determined from the ratio
1 _in / d _min = 0.05-0.2,
where 1 _in - the length of the additional cylindrical outlet sections of the nozzle diffusers, m

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