Modern technologies for preheating scrap before charging it into electric arc steelmaking furnace

There are a number of technical solutions to utilize the waste gases of electric arc furnaces (EAF) for scrap preheating thus returning back the heat into the technological process. The waste gases can be utilized also for steam or hot water production. The preliminary scrap heating before charging it into EAF is more perspective. Technical features of various types scrap heaters considered, including conveyer and shaft scrap heating technologies with continuous (Contiarc, Consteel, Comelt, BBC-Brusa) and periodic charging (Fuchs Systemtechnik, COSS, backet). It was shown that application of scrap heaters for EAF ensures saving of electric energy, increase of metal yield, decrease of dust and gases level in the shop, decrease of negative impact on environment. The disadvantages include frequent and costly repairs of the facilities, impossibility to control some factors having effect on the process of scrap heating. It was shown that when designing new EAFs with a charge exceeding 100 t, horizontal facilities are more preferrable, while for EAFs of small volumes shaft heaters suit better. At EAF modernizing it is recommended to use shaft heaters and back­et-thermos, since it is easier to construct a vertical furnace than a horizontal one with minimal length of 100 m. It was noted that hor­izontal heaters operate better in terms of technology, since ensure continuous charging by scrap, but at that occupy a considerable space in the shop. When comparing vertical heaters and backet by all the characteristics including heat-engineering and designingones, vertical shaft heaters prevail.

Briquetting of porous alumina-containing materials with organic binders

Waste from corundum production in the form of porous alumina sludge is a promising material for providing ferrous metallurgy with cheap alumina-containing slag-formers. However, the direct feeding of the pulverized materials to the steelmaking furnace generally results in a significant carryover of such materials with waste gases. This paper considers the possibility of making briquettes from porous sludge of corundum production by cold briquetting using various common binders (molasses, cement, powder based on polyacrylamide, emulsion based on polyvinyl acetate). A comparison of the features of cold briquetting of powdered porous materials (slimes from the production of electrocorundum) and dispersed crystalline materials (fines of chrome ore) was made. Experiments were carried out to determine the impact strength of briquettes on different binder (“cold” strength) and tests to determine the “hot” strength (by the “thermal shock” test method). The authors have determined the consumption of the binder required to obtain satisfactory characteristics of briquettes from corundum slimes and from chrome ore fines. A technique has been developed and a mechanism for the binding of particles of loose and crystalline materials has been determined during briquetting using polyacrylamide powder. The destruction of a briquette of loose materials occurs mainly along the grains of the most porous material, and briquettes of crystalline materials are destroyed along the boundaries of the grains glued with a binder. For porous materials, the binder consumption increases more than twice as compared to briquetting on the same binder crystalline bodies of a fine fraction, and the binder must necessarily impregnate the entire volume of the porous material.

Increasing energy efficiency of electric arc steelmaking furnace by improvement of aspiration system and recycling of melting dust.

Electric arc furnace (EAF) is considered as a basis of promising micrometallurgical complexes of Ukraine with a flexible production program. It is important to increase energy efficiency of the furnace, which depends crucially on heat loss (up to 12-20% of energy input) and iron loss (up to 20-22 kg/t of steel) with off-gas through disadvantages, inherent for EAF aspiration system, in comparison with BOF one. Purpose of the work is to reduce heat and iron loss with off-gas environment and recycling of melting dust. Research methodology consists in numerical modeling of new solutions for EAF aspiration and liquid-phase reduction of iron. The concept and basic solutions of dispersed aspiration system and liquid-phase process of carbon-thermal reduction of iron-containing wastes in heat- generating slag bath of electric resistance furnace with bottom electrodes are developed and substantiated. It has been experimentally established that increasing the aspiration surface, its distribution between the central and peripheral parts of the roof and approaching to area of electrode passage reduces unorganized emissions into electrode gaps by 40 % and air inflow into slag door by 10 %. Simulation of thermal state of a hearth with liquid cast iron under a layer of slag, which emits Joule heat, showed the need for forced mixing of the bath under conditions that multiplier, taking into account the effect of convection on coefficient of stationary thermal conductivity in the slag bath is at least 2.7. Experimentally determined power consumption is 2.12−2.29 kWh/kg of metallized product, which corresponds to the best foreign analogue "ITmk3". Estimation of expected economic effect of developments in the conditions of 120-t EAF only due to reduction of iron loss with melting dust by using of dispersed aspiration system is about 5 million UAH per year.

Physical-Chemical and Pyrometallurgical Estimation of Processing of Complex Ores with Extraction of Iron, Vanadium, Titanium

The metallurgical characteristics of pellets (reducibility, strength after reaction, softening start and end temperatures), phase composition (X-ray phase analysis), and porosity were studied. Blast furnace smelting parameters were calculated using laboratory pellets with different basicities and degrees of metallization. Pellets were obtained from complex titanium-magnetite ores. The vanadium extraction of this ore into metal did not exceed 10 % during smelting of metallized pellets in an arc steelmaking furnace, but special techniques could raise this to 85 %. According to calculations from the Institute of Metallurgy of the Ural Branch of the Russian Academy of Sciences (IMET UB RAS), vanadium extraction up to 80–90 % can be achieved by using high-base and partially metallized pellets. The influence of changes in the composition and metallurgical characteristics of titanomagnetite pellets with increasing basicity (especially relative to strength after reduction) should be taken into account.

TECHNOGENIC IMPACT OF RADIOACTIVE CONTAMINATION OF METAL SMELTING PRODUCTS ON ENVIRONMENT AND POPULATION

The analysis of the distribution of radionuclides in the products of blast furnace and steelmaking melting operation processes is carried out. It was shown that the blast furnace melting process is considerably affected by natural radionuclides whereas steelmaking furnace process - by technogenic ones. The main impact on the environment is exerted by the gas-dust fraction, which contaminates the surrounding soil, vegetation and ground water during the settling process. An additional dose of external irradiation of the population and personnel is created by slag and metal fractions. High radiation doses are possible in case of ingestion of high-intensity sources of 60Co and 137Cs into the melt. Internal irradiation of people occurs due to gas and dust emissions.