Video registration of physicochemical processes in BOF cavity at bath top blowing at application oxygen lances of various designs. Report 3. The picture of bath blowing at application two-level oxygen lances

Further increase of resources- and energy-saving efficiency of BOF processes is unthinkable without development of new methods of blowing and designs of blowing devices. It requires information on the real physicochemical phenomena in the converter cavity accompanying the blowing of the converter bath using new designs of oxygen lances in order to assess the possible risks in the mastering of the proposed developments in industrial conditions. The paper presents the results of video filming of the top blowing of a 80-kg converter bath by groups of multi-pulse supersonic and sonic oxygen jets formed, respectively, by Laval and cylindrical two-level nozzles of two designs equipped with double-row tips with a circular arrangement of Laval nozzles and cylindrical ones and upper block with cylindrical nozzles. Previously unknown information was obtained on the picture of the bath blowing with the formation of a reaction zone of interaction of supersonic and sonic oxygen jets with a metal melt with a flow of carbon monoxide going out the bath and afterburning of CO to CO2 under conditions of a counter-directed double curtain of sonic oxygen jets at different levels of location of the foamed slag-metal emulsions. It was established that in the initial period of blowing during slag formation most of the thermal energy of CO to CO2 combustion flares is transferred to the surface of the bath with lumps of added lime, and the rest is transferred by forced convection to the converter walls and gases escaping from the bath to the neck. In the case of the location of the foamed slag level at the upper tier of the cylindrical nozzles of the lance, heat transfer from high-temperature flares of localized afterburning of CO to CO2 within a limited in size near-lance flow of exhaust gases from the reaction zone is carried out according to the laws of submerged combustion and is completed completely in foamed slag-metal emulsion with the prevention of aggressive action of afterburning flares and volumes of overheated slag on the converter lining. Revealed and recorded by video recording modes of blowing the converter bath, contributing to the development of such undesirable phenomena during smelting as the appearance of intense emissions of slag-metal suspension from the facility, coagulation of the slag with the cessation of dephosphorization of the metal melt, the development of intense dust formation and the removal of small metal particles and slag with the formation of crust on the lance barrel. A variant of the final stage of blowing with a transition to supplying nitrogen instead of oxygen through cylindrical nozzles of two-level lances was experimentally tested, which provides an effective reduction in the level of foamed slag-metal emulsion before the converter turning down. The data obtained were used in the development of an industrial design of a two-level lance with a double-row tip, blowing and slag modes of blowing a converter bath with its use.

Nature of dust and smoke generation during gas-oxygen blasting in converter bath

The article presents the study of the nature of dust and smoke generation during gas-oxygen blasting of a converter bath. The main reasons causing metal waste have been determined. Influence of the process main parameters on metal loss has been studied during dust removal and evaporation of iron in the reaction zone. The authors have estimated the process of metal pulverization due to CO bubbles floating, determined by the rate of their rise to the bath surface. Specifics of temperature regime of the reaction zone and heat balance have been determined when adding fuel to the oxygen flow. Adding fuel to oxygen makes it possible to increase heat input into the bath, while reducing the rate of decarburization. This enables reduction of dust discharge during rupture and crush of metal films by gas bubbles. The effect of combustion products oxygen use on metal impurities oxidation is considered. By the example of blasting carbon and alloyed steel for mill rolls, it has been shown that the degrees of CO2 and H2O decomposition in the bath are the main qualities of gas-oxygen blasting. These indicators determine the oxidizing and heating properties of the blast. Assessment of change in total, consumed heat and its losses with exhaust gases, depending on degree of the oxygen flow dilution with natural gas (methane), has been carried out. Under these conditions, use of submersible combustion torches with change in their oxidizing ability makes it possible to solve various technological tasks, including provision of an effective way to reduce dust emission in converter process.

Research on the physical model of features of the behavior of a two-phase bath at top blowing through a tip with folded nozzles

At the previous stage of research using a physical model of an oxygen converter, the results of studying the features of purging a single-phase liquid through a single composite nozzle were obtained. The aim of this work was to study the behavior of a two-phase bath using a multi-nozzle lance with folded nozzles. At this stage of the study, silicone oil was used to simulate the slag phase of a two-phase bath. The peculiarities of the influence of experimental nozzles on the processes of mixing and foaming of two phases were studied. Three variants of the experimental nozzle design were investigated: a combination of a conventional and a slit nozzle with a ratio of their areas of 1: 1, 1: 2 and 2: 1. It is established that the use of a tip with four nozzles during purging from above promotes the active formation of a two-layer foamed emulsion on the surface of the bath. Comparison of the operation of the tip with folded nozzles with a tip with a cylindrical indicates more active mixing of the two liquids and the formation of a more stable and much higher layer of foamed emulsion. The most favorable conditions for the organization of full mixing of the two phases in the converter bath are formed when using folded nozzles with a slit size of about 35% and a ratio of slot and nozzle area of 1: 2. To intensify the mixing processes in the upper zone of the unit, it is most expedient to use folded nozzles with a larger fraction of the slit (up to 65%) and the ratio of the areas of the components of the nozzle 2: 1. The use of nozzles with equal areas of components in the studied conditions does not have a positive effect on metabolic processes in the converter bath.

Physical and chemical processes in the cavity of the oxygen converter when burning the bath with the afterburning of exhaust gases

The aim of the study is to study the characteristics of physicochemical processes in the cavity of an oxygen converter when purging a bath through two-tier tuyeres of various designs. The analysis showed that the classical designs of oxygen tuyeres equipped with tips with Laval nozzles do not always satisfy the requirements of the technology. The article presents the results of laboratory high-temperature modeling of the process of purging the converter bath through two-tier tuyeres equipped with tips of various designs. The studies were carried out on a multipurpose installation mounted on the basis of a 150-kg induction furnace and a 60-kg converter manufactured at a scale of 1:18 relative to 160 tons of an industrial unit. It is shown that the use of a two-tier lance provides additional advantages for the smelting process. So, in the initial and main periods of purging the converter bath through a two-tier lance with a double-row tip, it was possible to accelerate the process of slag formation without the addition of fluorspar, to intensify the removal of phosphorus at a high carbon content. Upon completion of the initial purge period at a low metal temperature of 1300-1330 ° C and the corresponding basicity of liquid slag, the degree of dephosphorization of 73.3-79.1% is achieved. When used for blowing two-tier tuyeres with double-row tips, the efficiency of afterburning of CO exhaust gases to CO2 also increases at the same decarburization rate of the bath. Based on the data of high-temperature modeling, the rational design of the two-tier lance has been determined, which ensures: balance of the heat balance; yield increase; creating conditions for the removal of phosphorus at a high carbon content; exclusion of negative effects on the lining.

Evaluation of influence of multilevel oxygen lance constructions on blowing efficiency of converter bath with post-combustion of waste gases

The aim of the work is to carry out an economic assessment of the effect of various structures of multi-tiered oxygen lances and methods for flushing the converter bath with the afterburning of waste gases on the efficiency of the production of iron-carbon semi-products in a modern metallurgical plant. The study was conducted for the process of steel smelting in converters of combined blowing with supply of oxygen from above and neutral gas through the bottom in the conditions of using conventional and multi-tiered oxygen tuyeres. Studies on the afterburning of converter gas in the converter cavity showed that, in proportion to the increase in the proportion of CO2 in the exhaust gases, the costs of steel production are reduced. Compared with the use of tuyeres of classical construction, they amount to 3.23 US dollars / ton of steel for double-circuit, 6.81 US dollars / ton of steel for bunk, and 11.61 US dollars / ton of steel for three-tier. It was determined that when using the classic design of the upper oxygen tuyere, the lower heat of combustion of the converter gas is 10 MJ / m3. In comparison with the classical design, the two-tier, double-circuit and three-tier tuyeres ensure a reduction in the lower heat of combustion of the converter gas by 8,5; 4.4 and 27.1% (rel.), Respectively. On the basis of the data obtained, it is possible to draw a conclusion about the effectiveness of using the technology of combined blowing of the converter bath with the afterburning of exhaust gases in the converter cavity.

Development of energy efficient technology of combined blowing of converter bath by oxygen and neutral gases

The aim of the work is the development of a new technology of combined purging of the converter bath with oxygen and neutral gas, which allows to achieve a significant resource and energy saving effect. The proposed technological scheme of combined purging is based on the use of a new design of a three-tiered tuyere and a system for supplying two regulated oxygen flows to it. It is possible to completely replace oxygen with nitrogen at certain periods of melting, which allows us to significantly expand the technological capabilities of the combined purge of the converter bath. The design of a three-tiered tuyere, which eliminates the disadvantages of two-tier blowing devices, was carried out using high-temperature modeling. Processing of the materials obtained in the course of the conducted melts allowed us to obtain new information about the features of the physicochemical processes developing during the flushing of the converter bath with the afterburning of the exhaust gases. The features of the effect of oxygen jets on the removal of carbon, manganese, silicon and phosphorus from the melt are established. Based on the data of high-temperature modeling of the purge of the converter bath, the established methodology for calculating the main design parameters and experience in developing industrial structures of multi-tiered tuyeres, a three-tiered tuyere of the new design and a combined bath of oxygen and neutral gas for the 160-ton converters have been developed and proposed for industrial development . The practical implementation of the presented solutions will provide an increase in the technological and technical-economic indicators of smelting in comparison with the use of well-known developments in this field.