The reliability of a steel-melting object operation depends to a considerable extent on the state of the furnace hearth refractory lining. Prolonged and partial furnace stoppages lead to loss of integrity of the sintered layer whose restoration requires performance of several necessary operations. Timely repair of the sintered layer reduces hot lost time and periclase material consumption.The hearth is one of the main elements of the workspace of an open-hearth furnace. It consists of a bottom, within whose central part there is steel delivery opening, longitudinal banks over the side of the furnace and transverse in the direction of the front and rear walls. During operation of a hearth it should exhibit sufficient impact strength in order to withstand mechanical damage during loading with charges of categories A and B of form No. 1 -3 (GOST 2787), and also physicochemical action of a gas atmosphere, slag and metal, hydrodynamic action of poured molten iron, delivered steel, etc. The lining of the hearth should be of rational thickness in order to provide sufficient heat insulation and reliable resistance to possible penetration of liquid metal.Normally a hearth consists of successively placed layers of refractory material, laid on a metal sheet. The first layer is asbestos board (GOST 2850). A layer chamotte objects (GOST 8693) is placed upon it, and then there is a layer of periclase powder, that is the so-called sintered layer. The design thickness of the furnace hearth with a capacity of 200 -300 tons is 1080 -1170 mm, including, mm: sintered layer 225 -250, layer of periclase objects 690 -805, chamotte 120, asbestos board about 20 [1]. Laying of the bottom, longitudinal and transverse banks is also made with horizontal rows. The slope of the hearth bottom surface in the direction of the steel-pouring opening is made due to the sintered layer to a value of 0.05. The axis of the steel-pouring opening is arranged at an angle of 7°to the horizontal surface. Transverse banks of the hearth of the rear and front walls to the level of the charging doors is made at an angle of 45°, and the longitudinal banks from the direction of the port are made at an angle of about 35°. Expansion joints are filled with periclase powder grade DMPK-75 with a gap.Thermal expansion joints in the hearth periclase layer have a thickness of 10 mm per running meter with laying on end and 4.5 -6.0 mm with laying at the edge. Thermal expansion joints are not considered in the layer of chamotte objects in laying the bottom and banks. In rows of periclase objects in the longitudinal bank from the direction of the port the thermal expansion joints are 9 mm per 1 running meter of laying. Joints are staggered in the banks.The temperature of the inner surface of the hearth during melting varies within wide limits. On direct contact with molten metal before delivery its rises to 1660°C and on contact with the slag to 1700°C. In the period of repairing banks and the hearth bottom the temperature falls below 1000°C. The heat resistance of the linin...
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 Chusovoi Metallurgical Plant has had a great deal of experience in using vanadium-bearing wastes in metallurgical production. For example, the plant has developed a technology that produces vanadium pig irons with high concentrations of manganese and chromium and that is based on the use of discarded sludge from the production of vanadium pentoxide.As a rule, vanadium-bearing wastes are used in the production of sinter and in the charge of oxygen converters or blast furnaces. However, their use in blast-fumace smelting has an adverse effect on the technology currently employed to convert the given elements (Mn and Cr) and increases the amount of vanadium lost with the furnace slag.Researchers have developed and tested a new method of using wastes and semifinished products (chemical wastes, sludge, top dust, and highly basic vanadium-bearing converter slags) -sintering of these materials, followed by their melting in blast furnaces in a mixture with iron-ore-based materials that do not contain titanium. This method makes it possible to alter the structure of the slag melt and stabilize its properties in the blast-furnace hearth during the smelting of vanadium pig iron. The silicon content of the pig in the trial heats reached 1%, but there were no problems with the running of the furnace or hearth operations. The coefficient characterizing the distribution of vanadium between the pig and the slag increased from 2.3 to 9.5 and the amount of vanadium recovered increased by 5.4%. The content of vanadium pentoxide in the slag decreased from 0.331 to 0.088%, i.e., the irrecoverable losses of vanadium declined by a factor of 3.8.One heat was conducted on a charge consisting of 75% pellets from the Lebedinsk Mining-Concentration Combine and 25% local sinter (sintered from a charge that included 60% vanadium pentoxide). As the control variant, we smelted vanadium pig iron on a charge containing 75% pellets and 25% sinter from the Kachkanar Mining-Concentration Combine. There was no deterioration in the technical-economic indices characterizing the operation of the furnace.The expected change in the structure of the slag melt was realized by comparing the phase composition of the slags in the control period and the trial period. Whereas the slag in the trial period consisted of mellite and the associated phases -mervenite, rankinite, oldhamite, dicalcium silicate, and glass -the mellite-based slag in the control period was fundamentally different -it contained the following related titanium-bearing minerals, % (by vol.): -baikovite Ca2(Mg 3, Ti4+A12 , Ti3+)2(SiO4)2012 -up to 35; -titanavtite m[(CaO MgO 2SiO2)]n(CaO(A1, Ti)203 SiO2] -15-20; -spinel MgA1204 -3-15; -perovskite (CaTiO3) and titanium carbides (TIC) -in small amounts.The use of mathematical models to study heat-and mass-transfer processes in the blast fumace made it possible to establish that there were no significant changes in the heating and reducing potential of the gas from in the different periods ( Fig. 1). However, the change that occurred in the com...
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...
Since there is little hope that the construction of ferroalloys shop No. 3 at the Chusovoi Metallurgical Plant will be completed anytime soon, it is important to focus on the rebuilding of ferroalloys shop No. 2. Shop No. 2, which has been in operation since 1964, is the final stage in the vanadium production cycle at the plant and yields ferrovanadium as the commercial product.The reconstmctsion program for the existing shop should be based on the following measures: -bringing shop capacity up to 7500 tons of 38% ferrovanadium per year, to ensure that the shop will be able to process at least the increasing volume of converter slag being formed in production operations at the plant;-increasing the amount of vanadium recovered by 10-12%, with a corresponding increase in the output of ferrovandium; -reinforcing the buildings and installations of the shop, which have been in use since 1964;-expanding the range of vanadium-bearing products made in the shop;-introducing new production processes and modernizing existing equipment; -mass-producing various pieces of equipment. The modernization must be carried out while the shop continues to operate, with no adverse effects on output or performance indices. Thus, the amount of work that must be done in the reconstruction and the complexity of the design changes should be evaluated in several stages. The actual reconstructsion work should also be done in stages.The order of the stages will be determined by the priority assigned to the various objectives, the financial impact, the degree to which the design changes are ready to be implemented, and whether or not the necessary planning and budget documentation has been completed. The optimum sequence for the stages in the reconstructsion program is as follows: conceptualization/setting of objectives; scientific research and experimental design work (preferably done on a competitive basis); design of the rebuilt shop, including determination of the main design features, determination of the composition of the equipment, and evaluation of the cost-effectiveness of the changes; finalization of the investment plans; development of the specifications; construction. This scheme can be modified to speed up the completion of the project, i.e., some of the stages may be executed simultaneously.Proceeding on the basis of the above scheme and an analysis of the means by which it might be implemented, we can identify the following stages and establish the following tentative schedule for reconstruction of the ferroalloys shop at the Chusovoi Metallurgical Plant.First stage: organization of the new section for filtration and leaching of the vanadium pulp, which is intended to eliminate a bottleneck in the production process and will significantly improve the performance indices of the shop in the production of vanadium pentoxide; construction of a section for removing vanadium and manganese from the waste water, in order to solve the main environmental problem facing the plant. One feature of this stage is that work on it was begun bef...
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