Self-excited oscillating pulse stirring desulfurization agitator for molten iron

Abstract

The invention discloses a molten iron self-excited oscillating pulse stirring desulfurization stirrer, which comprises a stirring shaft, a stirrer connecting flange and stirring blades arranged at the top of the stirring shaft, and the stirring shaft includes a stirring shaft core and a refractory castable lining for the stirring shaft core; The stirring blades include large stirring blades and small stirring blades in an equal number, all of the large stirring blades are alternately welded to the outer peripheral surface of the stirring shaft around the circumference of the stirring shaft with all the small stirring blades, so Both the bottom surface of the large stirring blade and the bottom surface of the small stirring blade are flush with the bottom surface of the stirring shaft. The structural design of large and small stirring blades and the optimization of structural parameters can achieve comprehensive effects such as increasing the desulfurization reaction speed, improving desulfurization efficiency, shortening the stirring time, and prolonging the service life of the agitator. Finally, it can improve the dynamic conditions and desulfurization technology and economy of molten iron KR stirring desulfurization. The intended purpose of the indicator.

Description

technical field [0001] The invention relates to the field of molten iron pretreatment, in particular to a self-excited oscillation pulse stirring desulfurization agitator for molten iron. Background technique [0002] According to relevant reports, hot metal desulfurization pretreatment is the most economical process for reducing the mass fraction of sulfur in steel in the blast furnace converter-continuous casting process, and is also one of the important means to improve the operation of blast furnaces and converters. For this reason, since the 1970s, the A series of molten iron desulfurization pretreatment processes represented by injection desulfurization and KR stirring desulfurization have been popularized and applied successively. Among them, the KR mechanical stirring desulfurization process of molten iron has become the preferred process for efficient, stable and deep desulfurization of molten iron due to its excellent stirring and mixing kinetic characteristics. Th...

AI Technical Summary

Problems solved by technology

(3) Tangential flow, in a container without baffles, the fluid rotates around the stirring shaft. When the flow velocity is high, the fluid will form a vortex. At this time, the flow of the fluid from the circumference of the paddle to the paddle area is very small. poor mixing

Although this method has achieved good industrial test results in actual production, due to the large eccentric thrust of eccentric stirring, the wear of the brake system of the molten iron tanker has been promoted, and the maintenance workload of the molten iron tanker has been increased, which has brought great harm to the actual application. come difficult

The Chinese patent "Mechanical Stirring Desulfurization Method for Desulfurization Pretreatment of Hot Metal, Application Publication No.: CN106244759.A" discloses a stirring desulfurization method that uses a wall baffle to suppress the stirring tangential flow. The blocking effect of the baffle prevents the tangential flow of the agitation, strengthens the axial flow and radial flow of the agitation, and achieves the purpose of improving the mixing characteristics of the agitation. However, due to the difficulty in the installation and use of the baffle from the wall, there are no reports of practical application.

In addition, based on the improvement of mixing and dispersion performance caused by the interference of baffles, forced pulse stirring, and variable speed stirring on the stability of the stirring flow field, in view of the difficulty of implementing the above interference methods on large-scale equipment for molten iron KR stirring desulfurization, relevant scholars started from the agitator From our own point of view, we have carried out research on stirring self-pulse oscillation technology, and achieved good improvement results under water model test conditions, such as: Chinese patent "jet agitator for mechanical stirring and desulfurization of molten iron, authorized announcement number: CN102154533.B "Disclosed a new type of agitator that injects between the blades to improve the dynamic conditions of the agitation, uses the cooling nitrogen of the air-cooled tube in the metal core of the agitator shaft, and injects nitrogen into the forced vortex area of ​​the agitation through the diffuse nozzles set between the agitator blades , improve the turbulent flow in the forced vortex area, suppress the tangential flow, strengthen the axial flow and radial flow, promote stirring and mixing, and improve the kinetic conditions of stirring desulfurization. Due to the difficulty of realizing stable nitrogen injection on the rotating body agitator, currently failed to be applied in actual production

The Chinese patent "Molten Iron Global Stirring Desulfurization Agitator and Its Using Method, Application Publication No. CN 108546795 A" discloses an agitator composed of upper and lower layers of helical blades, wherein the helical direction of the upper helical blade is the same as the stirring rotation direction, The helical direction of the lower spiral blade is opposite to that of the upper layer. Through the setting and optimization of the structural parameters and layout of the upper and lower stirring blades, the design function of the upper and lower stirring blades is guaranteed, and at the same time, the entrainment and discharge cycle of the upper and lower stirring blades is strengthened. The composite effect of impact mixing and eddy current mixing between the flow can realize the direct contact and interface reaction between the solid-liquid two-phase flow of desulfurizer and molten iron entrained and discharged by the upper stirring blade and the molten iron flow entrained and discharged by the lower stirring blade, and through the upper and lower The composite eddy current and flow field interference between the two strands discharged by the stirring blade strengthen the desulfurization reaction and mass transfer process, and realize the stirring and mixing of desulfurization agent and molten iron in the whole area, but there is no report on actual production and application.

The Chinese patent "High-performance agitator for mechanical stirring and desulfurization of molten iron, application number 201610407690.1" discloses an agitator with a double-layer blade staggered arrangement structure, in which the upper and lower stirring blades are evenly distributed around the circumference of the stirring shaft, The number of upper and lower stirring blades is the same, and the upper and lower stirring blades are arranged alternately. Through the staggered arrangement of the two layers of blades, the superposition of the stirring axial flow of the two layers of blades and the interference effect of the stirring flow field are realized, improving the The depth of stirring and pulling down of desulfurizing agent can promote the mixing and dispersing of desulfurizing agent and molten iron, so as to achieve the purpose of expanding the stirring and mixing area of ​​desulfurizing agent, prolonging the entrainment and floating cycle stroke of desulfurizing agent in molten iron, and improving the degree of mixing and dispersing of desulfurizing agent particles and the desulfurization efficiency of molten iron; , Japanese Patent JP 2004-204303A also discloses a stirrer made up of double-layer blades, but the staggered distance is greater than half of the height of the blades, which is greater than the staggered distance of the above-mentioned Chinese patent, but it has not yet been seen in practice. Reports on production applications

The Chinese patent "Double-blade molten iron desulfurization composite agitator, application number 201310716672.8" discloses a double-layer blade structure agitator composed of bottom blades and upper blades, wherein the bottom blades are fixedly connected to the lower part of the central stirring shaft, and the upper blades are agitated with the center The purpose of the shaft sliding sleeve is to improve the stirring desulfurization efficiency through the compound vortex effect of the upper and lower stirring blades, but it does not limit the vortex composite conditions and vortex effect, and cannot correctly realize the global stirring of molten iron and its mixed contact reaction with the desulfurizer. At the same time, the set of upper blades cannot meet the requirements of stable stirring under the condition of molten iron. Therefore, there are no relevant application and test reports at present.

The Chinese patent "Self-pulse Stirrer for Desulfurization of Hot Metal, Application Publication No. CN 108342536 A" discloses a stirrer with a flow field interference through hole in the middle of the stirring blade along the direction of stirring rotation. , play the role of suppressing the tangential flow of stirring, strengthening the axial and radial flow of stirring, and achieving the purpose of reducing the forced vortex area, expanding the free vortex area and improving the mixing characteristics of stirring, but there are no reports of actual production and application

[0006] Based on the above, it can be seen that strengthening the axial flow and radial flow and suppressing the tangential flow is the key to improving the kinetics of the mechanical stirring desulfurization reaction of molten iron. Although domestic and foreign scholars have made a lot of efforts to this end, a series of improvement technical solutions have been formed. Some improved technologies have achieved the purpose of significantly expanding the stirring and mixing area and the mixing and dispersing effect in the water model test, but due to the limitations of high temperature, high-power stirring, intermittent production and other harsh working conditions of mechanical stirring and desulfurization of molten iron, the improvement measures are difficult. Stable implementation in actual production, such as: positive and negative rotation pulse stirring, wall-attached and off-wall baffles, eccentric stirring, etc.; in addition, there are also technologies that have been applied in actual production and have achieved good improvement effects, such as: special-shaped blade structure However, due to the local mixing characteristics of the single-layer blade structure agitator, the agitation and mixing effect does not improve the particle size significantly

Although there have been patent reports successively on the self-pulse interference of the stirred flow field, the flow field interference method is single, the influence of the stirred flow field interference on the mixing and dispersion effect needs further research, the interference strength needs further inspection, and the stability of practical application The reliability needs to be further demonstrated

Although the agitator with multi-layer blade structure can theoretically expand the axial mixing area of ​​the agitation and achieve the effect of homogenizing the desulfurization reaction in the molten iron tank, the structural parameters of the double-layer blade agitator have a great influence on the self-floating particle agitation and dispersion mixing area of ​​the molten iron agitation and desulfurization. The expansion has not been systematically studied, and further research is needed on how to apply it to actual production. At the same time, the stirring intensity of the double-blade agitator will also increase significantly, and it is difficult to implement without changing the existing equipment.

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