RU2009417C1 - Blast cupola - Google Patents

Abstract

FIELD: metallurgy. SUBSTANCE: cupola bottom is made at an angle of 45-60 to the shaft axis, a hearth tuyere is inserted from the side of the shaft with extension of 0.9-1.1 of the furnace radius. EFFECT: reduced lining erosion and improved reliability. 4 dwg

Description

 The invention relates to foundry, in particular to designs of cupolas, and can be used to produce high quality cast iron.

 Known cupola, having a cylindrical shaft with a mountain of smaller diameter, which has shoulders above the axis of the tuyeres at a distance of 500-600 mm. The maximum diameter of the head is 1.09-1.14 times greater than the diameter of the hearth. This design allows you to reduce the height of the lining, but the peripheral location of the combustion centers remains and the lining of the shoulder ledges burns out. A water cooling device in the area of oxygen zones leads to large heat losses and a decrease in the thermal efficiency of the furnace.

 Closest to the proposed technical essence is a cupola with a cylindrical profile, a lower horizontal bream, in the middle of which a hearth tuyere and an additional tuyere belt with side tuyeres are installed. 25-40% of the blast is fed through the bottom tuyere, the rest of the blast is fed through the side tuyeres.

The main advantage of this design cupola - even combustion bed charge throughout the volume, a good warm-hearth furnace and raising the temperature of iron 15-25 ° ^C.

 However, the known design is not effective enough. The vertical arrangement of the lance leads to its frequent pouring of metal and slag, covering the lance with the hearth of the furnace, which increases the complexity of the repair work. If the bottom tuyere fails during the smelting process, all air enters through the side tuyeres until the end of the smelting company. The lateral supply of blast leads to the peripheral arrangement of oxygen zones, where high process temperatures develop and, as a result, leads to a large swing of the lining.

 The vertical arrangement of the bottom tuyere in the design adopted as the basis does not allow to abandon the lateral, more reliable, supply of blast. In case of slagging of the bottom tuyere, it cannot be cleaned of slag mechanically, since there is no repair hole for such a tuyere. If the bottom lance has a repair peephole, then it cannot be opened during the melting period. When opening the peephole, most of the air will escape through the hole of the peephole outward into the atmosphere, the air pressure at the end of the tuyere nozzle will decrease even more and it will completely fill with metal and slag. Difficulties in the operation of bottom tuyeres forced them to abandon their use in modern cupola designs.

 The purpose of the invention is to reduce the height of the lining and increase the reliability of the bottom tuyere.

This is achieved by the fact that in the cupola, including a cylindrical shaft with a flask and a hearth lance, the flask is made at an angle of 45-60 ^about the axis of the shaft, and the hearth lance is inserted on the side of the shaft with a height of 0.9-1.1 from the radius of the furnace.

The execution of the flask at an angle to the vertical wall of the mine allows the supply of blast to the center of the furnace. The angle of incidence 45.. . 60 ^° to the vertical wall of the shaft allows the bottom tuyere to be led to the side of the shaft and it becomes possible to service it during the melting period. The lance height is 0.9. . . 1.1 radius of the furnace makes it possible to position the oxygen zone in the center of the blank spike. The recovery zone, where the coke surface temperature is T = 1100-1200 ^о С, in this case is located near the mine walls and the height of the lining decreases sharply.

 Due to the fact that distinctive signs from the prototype were not found in well-known sources in the same technical field, it can be concluded that the proposed technical solution meets the criteria of the invention "significant differences".

 In FIG. 1 shows a cupola; in FIG. 2 - single row cupola; in FIG. 3 - experimental cupola with bottom-side lance after 10.. . 12 hours of work; in FIG. 4 - experimental cupola with side supply of blast through three rows of tuyeres after 10.. . 12 hours of work.

 The proposed cupola contains a shaft 1 of the furnace with an inclined bottom 2 (flask), bottom-side tuyere 3 and tap hole 4 for the release of metal.

In addition, the drawings show the oxygen zone 5 of the combustion zone, reduction zone 6, Z is the vertical coordinate, r is the horizontal coordinate, α is the angle between the r axis and the direction of the gas flow velocity in the region δ, δ is the blank area between the top of the lance and the lower boundary of the oxygen zone, α ₁ is the angle between the bream and the vertical wall of the shaft (shaft axis), H _h.k. - the height of the idle ears, α ₂ - the angle between the direction of the lower edge of the peak and the vertical wall of the shaft; a is the characteristic region of the height on the cupola with lateral supply of blast through one row of tuyeres.

The invention is illustrated as follows. Fireclay lining consists mainly (60-76%) of SiO ₂ . It is known that silicon of the SiO ₂ is reduced only by solid carbon at 1500 ^{° C} and higher reaction.

g_в), то площадь сечения донно-боковой фурмы (S_ф) должна быть рассчитана по соотношению (см. И. Ф. Селянин. К определению площади сечения фурм в шахтных печах. В сб. Современные технологические процессы получения выосококачественных изделий методом литья в порошковой металлургии. Чебоксары, 1989, с. 84-85).SiO ₂ + C _ → SiO + CO (1)
SiO + C _ → Si + CO (2)
The cupola process surface temperature coke (T _c) is reached 1500 ^{° C} or higher only in the oxygen combustion zone of the hearth. Silicon is restored from the lining in region (a) (see Fig. 2), according to reactions (1) and (2), then it burns again in the oxygen zone by the reaction
Si + O ₂ = SiO ₂ (3) With a lateral supply of blast, the configuration of the height of the lining repeats the geometry of the combustion center 3 (Fig. 2). When blowing through the bottom-side tuyere (Fig. 1), the burning center is located in the center of the blank spike and the oxygen zone does not come into contact with the walls of the furnace shaft. Between the lining and the oxygen zone is a reduction zone 5, where the main reaction
C + CO ₂ = 2CO (4) and where the coke surface temperature T _c = 1100.. . 1200 ^about C, excluding the course of reactions (1) and (2). Since the cupola productivity P _{in is} proportional to the amount of blown air gв per unit sectional area of the furnace (P _in

g _c ), then the cross-sectional area of the bottom-side tuyere (S _f ) should be calculated by the ratio (see I. F. Selyanin. To determine the cross-sectional area of the tuyeres in shaft furnaces. In the collection Modern technological processes for producing high-quality products by casting in powder metallurgy Cheboksary, 1989, pp. 84-85).

, (5) где S_в - площадь сечения вагранки;
ε- порозность слоя кокса в холостой колоше;
T₁ - температура дутья, К;
D_в - диаметр вагранки;
T₂ - максимальная температура;
R_г - радиальная протяженность очага горения.

, (5) where S _в - sectional area of the cupola;
ε is the porosity of the coke layer in a single spike;
T ₁ is the temperature of the blast, K;
D _in - the diameter of the cupola;
T ₂ is the maximum temperature;
R _g - the radial extent of the combustion zone.

It is known (see I. S. Selyanin. Izv. Universities Ferrous metallurgy, 1991, N 2, pp. 75-76) that the gas flow in a fixed granular layer near the tuyere space of shaft furnaces is potential. Consequently, the length of the burning zone along all three coordinate axes is the same (in the radial, lateral direction and the height of the furnace) and is determined by the formula (see I. F. Selyanin, A. I. Stepanov. Izv. Universities. Ferrous Metallurgy, 1987 . N 12.p. 12-14)
R _r = 0.525 ln (1 + 0.12 V ₁ ) (6) where V ₁ is the velocity of air flow from the lance.

(8) Для вагранки диаметром D_в = 1 м при ε = 0,5, T₁ = 300К, T₂ = 1900К, dк = 0,07 м S_ф≥ ≥ 0,052 м², Dф ≥ 0,08 м.The burning center should not reach the walls of the mine by the size of a piece of coke Δ r = dк. T. about. Rr with the right choice of S _f equal
R _r = D _in / 2 - dк (7) and from equations (5) and (6) it follows
S _f ≥ S

(8) For a cupola with a diameter of D _in = 1 m at ε = 0.5, T ₁ = 300K, T ₂ = 1900K, dc = 0.07 m S _f ≥ ≥ 0.052 m ² , D f ≥ 0.08 m.

The inclination of the flask to the axis of the furnace less than 45 ^{about is} not effective, since in this case the useful height of the furnace decreases sharply. To reduce the labor costs for maintenance and repair, the bottom-side tuyere should be located at a distance of 100-150 mm from the upper bracket of the furnace bottom. With decreasing angle α _{1, the} level of air injection increases, and at a constant height of the furnace top its useful height decreases. In addition, at the lateral boundary of the oxygen zone in the region δ, two equal forces along the Z and r axes act on the gas particle due to the potential of the flow (Fig. 1). In this air jet in this area are directed at an angle α = ⁴⁵ ° to axis Z. This is confirmed by the study of the height of the cylindrical lining on conventional cupola furnaces. The angle of inclination α of the lower height line to the vertical wall of the furnace is always close to 45 ^about (Fig. 2). Therefore, with an increase in the slope angle of the bream less than 45 °, ^the upper part of the bream in the region δ will be exposed to oxygen from the air jets, partially burn out and easily eroded by the flows of liquid metal and slag.

The slope of the furnace hearth to the axis 60 ^{of the} well is not effective, ie. K. In this case, the volume of region (c) (FIG. 1), which plays the role of the hearth is reduced and there is a danger pouring lance metal and slag. When α = ₁ ^{on the} bottom tuyere 90 will lie on the hearth and are always poured metal and slag.

The bottom-side tuyere should be one. The practice of using tuyeres in the blast furnace process shows that with powerful blowers, the velocity of the outflow of blows from the tuyeres reaches 150 m / s, oxygen zones in the transverse and vertical directions 1.. . 1.5 m. The high velocity blowing lance reduces the probability of slagging and high altitude zones provides a high oxygen overheating molten iron to 1420-1450 ^o C.

The weakness of the blower on modern cupolas does not allow for the optimal supply of blast (g _in = 2. ... 2.4 m ³ / m s) through one lance. The arrangement of additional side tuyeres above the level of the bottom-side tuyere increases the total length of the oxygen zones, but the peripheral flow of air jets sharply increases the height of the lining. The practice of operating a multi-row tuyere system shows that the height of the lining increases with respect to cupolas with one row of tuyeres.

 The cupola works as follows.

 First, a single head is loaded into the furnace, coke is ignited, and the furnace is heated. They purge the furnace, load the empty spike to the optimum level, charge materials, limestone and coke of the working fuel spikes. Air, spreading potentially in the lance region, forms the oxygen zone in the center of the blank spike.

The experiments were conducted on a semi-industrial cupola of the foundry laboratory of the Siberian Metallurgical Institute. Its characteristic: useful height 3.2 m, internal diameter 500 mm, blower model VVD-8, the number of rows of tuyeres - 3 pcs. , the number of tuyeres in a row - 3 pcs. The cupboard is equipped with instrumentation for measuring the total air flow and lances of air. Cast iron lances with an inner diameter of D _f 100 mm were manufactured. The bream was stuffed with a dry molding sand and up was made of a stuffed lining at an angle of 60-45 ^about to the axis of the mine. During the repair of the cupola, all lances are lined with the exception of one hole in the second row, where the experimental lance was placed with a protrusion to the center of the furnace. For convenience, the size of the working window was increased upwards by 200 mm.

 The table shows comparative experimental data on the operation of a semi-industrial cupola with one bottom-side lance according to the claimed embodiment.

A total of 9 melts were carried out, each with a total duration of 10-12 hours. The time of each melting was composed of periods of 1.5-2 hours of continuous melting, then the cupola was knocked out. The lining before the start of a new period was not repaired, but was limited to studying the height. Lining repairs were carried out after six periods. A characteristic pattern of heat obtained after six periods of melting is shown in FIG. 3. For comparison, in FIG. Figure 4 shows the pattern of heat on a three-row cupola, obtained on a cupola with side supply of blast, after six periods of melting. The total height of the peak in this case is ≈ 170 dm ² . It should be noted that the height of the heat zone H ₁ and its length along the perimeter of the furnace is always proportional to the depth of heat Δ r. Therefore, the total height of the midst is a quantitative characteristic of the midst.

Experiments have shown that when the slope angle is higher than the optimum (65 ^o ) tuyere is often poured with metal and slag (after 15-20 minutes), the complexity of the tuyere maintenance grows. When the angle of inclination is less than the optimum (40 ^° ), the height of the lining grows. This is due to the fact that the oxygen zone in region b (Fig. 1) touches the upper edge of the bream, the printed lining burns out, the lower layers of the dry sand mixture are easily eroded by flows of liquid metal and slag, the lance is not protected by the upper layer of the bream. The end of the lance was intensively washed out by molten iron, the oxygen zone penetrated deeper into the back wall of the shaft, the height of which increased.

 If the lance height is more than optimal and is 1.2 R, then the oxygen zone reaches the opposite wall of the shaft and its height increases. When the tuyere height is less than optimal (0.8 R), the oxygen zone penetrates deeper into the back wall of the shaft and the area of its height also increases.

The device of one bottom-side tuyere according to the claimed variant on modern cupolas with turbocompressors developing an overpressure (1... 1,5) 10 ⁵ Pa allows, in comparison with the prototype, to increase the service life of the lining of the melting belt to values characteristic of higher parts mines (3-6 months), completely abandon water cooling in large cupolas and thereby increase the thermal efficiency of the furnace. (56) Evangulov E.M. Foundry-pickler, ONTI, 1936.

Claims (1)

VAGANKA, containing a cylindrical shaft with a flask and a hearth lance, characterized in that the flask is made at an angle of 45 - 60 ^o to the axis of the shaft, and a hearth lance is installed in the wall of the shaft with a height of 0.9 - 1.1 of the radius of the furnace.

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