Aspects of the reduction of vanadium in blast fumaces and its transfer to the pig iron have been studied quite extensively by V. V. Mikhailov, P. G. Shtengel'meier, S. V. Shavrin, A. F. Chentsov, and others [1][2][3][4][5] 9]. They determined that the amount of vanadium transferred to the pig iron depends on the basicity and volume of the slag, the temperature of the pig, and other factors. These conclusions were based on the results of laboratory studies or averaged indices of trial heats conducted over a relatively long period of time. However, the averaging of the indices resulted in some "smoothing" of isolated anomalies in the data.We refined the initial relations on the basis of data from chemical analyses (more than 1000 taps on each blast furnace at the Chusovoi Metallurgical Plant). The method used to analyze data on the taps involved grouping them on the basis of various factors and determining the average index for the taps in the different groups. We then used the program Microsoft Excel to determine the relations and constructed regression curves ( Figs. 1 and 2).It was established that the amount of vanadium present in the slag in the form of V205 increases with a decrease in the temperature of the pig iron. If the temperature of the pig increases, then so does the vanadium distribution coefficient L v (Tables 1, 2, 3).It was also determined that in certain taps (V205 > 0.6) the dependence of the Si and V contents of the pig iron on the content of C205 in the slag did not conform to the general law that was established. For example, when the concentrations of these elements in the pig iron was sufficiently high, the V205 content of the slag in the corresponding heats was significantly higher than in the other groups of taps.In several of the trial heats, it was observed that vanadium could undergo sublimation in the high-temperature zones of the blast furnace [1, 8]. It can be suggested that some of the vanadium sublimes and accumulates in the form of a slag crust near the bosh. The crust begins to slide down the furnace after it has reached a certain critical mass. This is accompanied by a sudden increase in the W203 content of the slag, while the vanadium content of the pig remains nearly unchanged. The process just described is more pronounced on a small blast furnace (such as blast furnace No. 1), which may be due to the composition of the slag, the more intensive operation of the furnace, or features of its profile. This matter requires further study. When the crust slid down the furnace, the concentration of vanadium in the hearths of furnaces Nos. 1 and 2 increased by t8.2% and 19.3%, respectively. Figure 3 shows the dependence of the total mass of vanadium in the pig iron and slag on the mass of vanadium in the slag.It should be mentioned that an increase in the V203 content of the slag is accompanied by an increase in the silicon content of the pig iron, i.e., by an increase in temperature in the hearth. The rise in temperature also results in sliding of the slag crust.Analysis of the data ...
The Chusovoi Metallurgical Plant is working constantly to increase the vanadium content of its pig iron. For example, a charge that contained vanadium converter slag was used over an 8-day period in 1964 on blast furnace (BF) No. 1. The average consumption of the slag was 222 kg/ton iron (the chemical composition of the slag and the resulting pig iron are shown in Tables 1 and 2). Thus, the V20 5 content of the furnace slag was increased from 0.14 to 0.35%, while the vanadium distribution coefficient L v = [V]/(V) was decreased from 7.5 to 6.25. The vanadium content of the commercial pig iron remained at the previous level -80.53% (81% in the control period). The pig iron was processed further in accordance with the normal flow chart [ 1 ].In 1987, ash from heating and electric power plants (HPP) was used to increase the vanadium content of the iron. Ash in amounts of 20-30% was added to the charge at the local sinter plant to obtain a special sinter ( Table 1). The percentage of sinter in the charge of 225-m 3 blast furnace No. 1 was varied from 23 to 50% (Table 2). Here, the V205 content of the furnace slag was increased from 0.23 to 0.67%, while the vanadium distribution coefficient L v was raised from 4.5 to 13.4. The losses of vanadium with the top dust were large (2.89--4.60 V205). The iron was shipped to customers as a commercial product [2].In 1997, slag formed at the Nizhniy Tagil Metallurgical Combine (NTMK) in the converter production of steel from vanadium pig iron by the monoprocess [3] was used in the charge of BF No. 2. A distinguishing feature of the converter slag (CVS) is its fairly high contents ofVeO 5 and CaO. The slag also contains 10-12% scrap.Calculations showed that since the Chusovoi plant was also using unfluxed pellets from the Kachkanar Mining-Concentration Combine (KGOK) and since the consumption of raw limestone was thus very high (127 kJton pig), the introduction of CVS would make it possible to significantly reduce the content of flux in the blast-furnace charge: 100 kg of CVS should replace 41 kg of limestone, while a CVS consumption of 100 kg/ton pig was expected to increase the vanadium content of the metal from 0.484 to 0.750%.To check these calculated results, trial heats involving the use of CVS were conducted on BF No. 2 during the period Nov. [13][14][15][16][17][18][19][20] 1997. A CVS consumption of 43 kg/ton pig kept the productivity of the furnace at 1502 tons/day, the adjusted consumptions of coke and flux were reduced by 13 and 8 kg/ton, respectively, and the vanadium content of the pig iron was increased from 0.506 to 0.638% (Table 3). No complications arose in the running of the furnace. The positive results obtained from these heats made it possible to permanently institute the use of CVS in the charge of BF No. 2 beginning in January, 1998.The operating conditions of BF No. 2 improved significantly after it was subjected to a class II overhaul (April-June 1998). In addition, reconstruction of the central trough nearly eliminated the need for slow-speed operation...
The process of the reduction of vanadium in a blast furnace is determined to a significant extent by the structure of the stock, the charging regime (including the cyclicity of the charging operation), the charging sequence, stockline level, the burden ratio, and the operating regime of the revolving distributor. The profile of the charge materials and the position and height of the ore ridge in the top of the furnace are important parameters, since they determine the nonuniformity of the distribution of the gas flow and, thus, the use of the reducing potential of the gas [1][2][3].In constructing the logical-statistical balance model in [4], an attempt was made to account for the nonuniformity of the gas-flow distribution as part of the analysis of the smelting process. The nonuniformity coefficient ~t was introduced. The coefficient is equal to unity for an ideal distribution, while deviations are recorded in fractions such as 0.95. Here, some of the gas (in the given example, 0.05) is released from the furnace, by-passing the ore-bearing materials.If the nonuniformity of the gas distribution across the furnace is linked with a heat-transfer and mass-transfer characteristic of the operation of the furnace -the ratio m of the water equivalents of the charge and the gas -then the range of theoretical and practical problems that can be solved [5, 6] where n a is the number of the section in which the value of a is greatest.It follows from Eq. (1) that the gas distribution across the furnace may be ideal when a = m. Using (1) with known/.t, m, and n, we can determine a. We can then use Eq. (2) to find d and, after performing calculations with the two-dimensional model, we can analyze the work done by the gas along and across the furnace.To determine the validity of the proposed model, we studied the operation of a 1033-m 3 furnace at the Chusovoi Metallurgical Plant. During the study period (August 18-22, 1998), the iron-ore-based part of the charge consisted of 60% Kachkanar pellets, 30% imported sinter, and 10% local sinter. The productivity of the furnace was 1620 tons/day; coke rate was 546 kg/ton; the furnace was operated on an air blast heated to 892~ the consumption of natural gas was 31 m 3.Chusovoi Metallurgical Plant and the Institute of Metallurgy (in the Ural Division of the Russian Academy of Sciences).
The productivity of the blast furnaces at the Chusovoi Metallurgical Plant has decreased and coke rate has increased as a result of disruptions in the supply of charging materials, equipment wear, lengthy periods during which the furnaces were banked or were operated at slow speed, and a decline in operator skills.Blast-furnace operation was also negatively impacted when the Kachkanar Mining-Concentration Combine changed over to the production of unfluxed pellets in 1993. Given the shortage of high-basicity sinter, this change led to an increase in coke rate and a reduction in productivity. For example, just on blast furnace No. 1, where the pellet fraction was about 100%, coke rate increased by 60-70 kg/ton pig and productivity dropped by 10-20%. The same factors also led to a deterioration in the operating indices of blast furnace No. 2 [ 1, 2].Idling and slow-speed operation of the furnaces due to a shortage of coke have been serious problems, but the situation is changing dramatically (Figs. 1 and 2) thanks to the efforts of factory management, the metallurgists' union, and investors (the company AMI). Disruptions in the supply of coke have nearly been eliminated, although its quality is still less than desired.During the period April-June, 1998, a class II overhaul was performed on blast furnace No. 2 and several improvements were made. Most importantly, the cast house was partially rebuilt and a newly designed central trough was installed. The old trough had to be relined every two days and smelting rate had to be reduced accordingly, which disturbed the normal operation of the furnace and decreased the output of pig iron.The new central trough was designed by Techservice, Ltd. (Bratislava, Slovakia). Originally, the trough refractories used were also from the same company. The Chusovoi plant later changed over to refractories made by the dinas factory "Dinur." Use of the new trough has completely eliminated the need to slow the operation of the furnace for trough repairs. Also, the trough is not emptied of pig iron after each tap, as was done previously. This has significantly reduced the amount of pig iron lost with the slag and in the form of scrap, thus decreasing the consumptions of ore and coke by one ton per ton of pig.
Blast-furnace No. 2, with a useful volume of 1033 m 3, has been in operation at the Chusovoi Metallurgical Plant since a class I overhaul in 1983, i.e.. a new overhaul of the same class will be needed in the coming years. A substantial amount of reconstruction is being planned as part of that overhaul. The existing level of automation of the furnace is one reason for its inconsistent performance indices and the uneven quality of the pig iron it produces.Taking into account the capabilities of the plant as a whole and the periods of time allotted to the reconstruction of the furnace, planners have set the goal of creating an automation system which can be efficiently installed and operated. The system should also be designed so as to improve existing smelting practices, while ensuring that all operations are performed safely and that the equipment operates more reliably. In attempting to solve these problems, the planners proceeded on the basis of the following preconditions:I. The indices which characterize blast-furnace smelting depend on the coordinated operation of the hot-blast line, stove block, and stockhouse, on the prescribed changing regime, and on stabilization of the thermal state of the furnace.2. It is best if the automation system as a whole is realized in the form of information-related control subsystems based on relatively simple but reliable programmable controllers (such as the "SEMATIK $5," "VAKS 300," etc.). These devices make it possible to collect and process a large volume of raw data, operate the furnace in accordance with prescribed programs, and -most importantly -transmit information between different objects in the automation system. Duplicates of the controllers and of certain measuring instruments in the system should be provided to enhance system reliability.3. Programmable controllers, including those which contain the so-called intelligent devices, are suited only for stabilizing individual parameters and for programmed control of process operations (such as the furnace changing regime, switching of the stoves, etc.). The more complex problems of diagnosis, prediction, and control of the smelting regime require the expertise of the process engineers and blast-furnace operators. The development of methods which can solve this problem and are based on the use of information technologies and expert systems constitutes a new area of research in control theory -informatics (information technology) [I] and variantics [2, 3].4. New methods developed to solve the given problem were not considered in the design of the automatic process control systems that were installed on certain large blast furnaces. System designers also made several other serious errors of omission in developing the mathematical application software for the upper level of such systems (for example, no provision was made for evaluating and improving the reliability of the initial data, the control algorithms were based on mathematical models that are poorly suited for the given application, no "furnace-operator-compu...
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