INFLUENCE OF STORAGE TIMES OF SLUDGE FROM THE FERROALLOY INDUSTRY ON THE PROPERTIES OF CEMENT-BASED MIXTURES

Purpose. The transition to environmentally friendly, waste-free technologies is a priority for most countries in the world. The metallurgical and construction industries make a significant contribution to the formation of large volumes of man-made waste. During the production of ferroalloys, waste is generated in the form of sludge, which is stored in sludge collectors. Sludge storage has been going on for over 25 years. In order to study the effect of the duration of storage of sludge on its properties in the compositions of dry building mixtures on a cement basis, a comparison was made of the efficiency of using sludge with different storage periods. The influence of sludge of various storage periods on the strength of dry construction is estimated. Methodology. The studies were carried out in accordance with the standard methods for determining the physical and mechanical properties of solutions from dry mixtures for the installation of self-leveling floors, specified in DSTU B V. 2.7-126: 2011 “Sludge awesome dry modified. General technical minds”. Sludge from wet gas cleaning of ferrosilicon production is stored in dumps where it is a mixture of lumps of various fractions 5…50 mm in size. To use sludge in the composition of dry building mixtures, it must be dried and crushed on a roller crusher and on a disintegrator. Findings. The best ratio of the "age" of the sludge and its percentage in the composition of the mixture was determined to increase the strength characteristics of the cement stone. Originality. The influence of the chemical nature of sludge from wet gas purifiers of ferrosilicon production on the hydration processes and strength of cement stone is analyzed. Practical value. The use of man-made waste in the formulations of dry building mixtures helps to simultaneously reduce the harmful effect on the environment of industrial enterprises and increase the mechanical and economic characteristics of cement mortars based on dry mixtures.

Fundamental Investigation of Ferrosilicon Production Using Rice Husk and Rubber Tree Bark at 1550°C: Implication for Utilization of Agricultural Waste in Steelmaking Industry

Rice husk is one of the major agricultural wastes in Thailand, which predominately consist of silica up to 90 wt%. Rubber tree bark (RTB) is an agricultural waste from the harvesting of natural rubber, composed of cellulose and rubber parts, which is a carbon-based material. This research aims to investigate the possibility of using rice husk and rubber tree bark as a silica and carbon resources for producing ferrosilicon alloy. Three different types of carbon were used for the investigation: Coal, RTB and Coal-RTB blend. Rice husk ash, iron ore and carbon were blended homogeneously according to their molar ratios. The prepared samples were heated at 1550 °C in argon atmosphere for 30 minutes and thus the metal droplets were produced. The silicon contents in the produced metal droplets were analyzed by using Inductive coupled plasma (ICP). The results show that the metal produced by this method are ferrosilicon alloy with the highest silicon contents in the metal droplets was 45.32 wt% for RTB, while it was 18.25 wt% for coal. This research unlocks the potential of utilization of agricultural waste in steelmaking industry.

Scientific and practical fundamentals of cokeless production of siliceous ferroalloys

Application of mineral carbon as carbonaceous reducing agents instead of coke for siliceous ferroalloys smelting is one of perspective ways of high efficient production of them. Results of industrial tests of expensive coke substitution by long-flame and brown coals during smelting of power-intensive ФС75 ferrosilicon presented. Tests were carried out at three ferroalloys plants of Russia and Kazakhstan. The following coals were used: long-flame coals of Shubarkol’skoe deposit (Kazakhstan), brown coals of Kajchasky open-pit mine (Kuzbass) and Majkyubenskoye deposit (Kazakhstan). The coals have Аd ash content at the level of 3–11%, high indices of reaction ability and specific electrical resistance, increased yield of volatile substances (Vdaf = 42–46%) and content of reducing components (CO, H2) up to 180–215 m3 /t (comparing with 11 m3 /t in coke). At the plant “A” the industrial tests resulted in coke substitution by 88–99% with the mixture, kg/charge: 20 – coal Б, 165–190 – coal Д and 35–60 – wood chips. Satisfactory technical and economic indices of ФС75 ferrosilicon production reached. Because of the volatile substances high yield of Д and Б coals (Vdaf = 44–46 %), an increased temperature of emitted gases (up to 240–270 °С) under the hood observed and at the gascleaning system (up to 160–170 °С). At the plant “B” during ФС75 smelting, the long-flame coal was used constantly to substitute the coke by 84%. At the plant “C”, Kazakhstan, a technological possibility of complete (100%) coke substitution by long flame coal determined. To transfer to cokeless production of siliceous ferroalloys with application of low metamorphized coals of Д and Б grades it is necessary to make considerable changes in existing mode of ferroalloys furnaces running to provide high technical and economic indices of the production. Another variant means construction of new furnaces, adapted to increased temperature of emitted gases, forming at the coals pyrolysis with high yield of volatile substances.