A feasibility study of recycling of manganese furnace dust

This paper presents results of a feasibility study of recycling manganese furnace dust generated in production of ferromanganese and silicomanganese at Tasmanian Electrometallurgical Company, Australia. Dried manganese furnace dust contains about 20 wt% of carbon, in average 33.4 wt% of manganese and 1.3 wt% of zinc. Manganese in the dust is in the form of MnO, Mn3O4 and MnCO3; zinc is mainly in the form of ZnO and ZnSO4. Analysis of the zinc balance with dust recycling showed that to keep zinc intake at the acceptable level, it should be partly removed from the dust. In the reduction laboratory experiments, zinc oxide was reduced to zinc vapour by tar of the dust. Reduction of zinc oxide started at 800oC and zinc removal rate increased with increasing temperature; removal of zinc was close to completion at 1100oC. Optimal conditions for removing zinc from the dust include temperature in the range 1000-1150oC, inert gas atmosphere and furnace dust fraction in the furnace dust-manganese ore mixture above 60%. In the sintering of manganese ore with addition of manganese dust in the sintering pot, zinc was reoxidised and deposited in the sinter bed. Removal of zinc in the sintering pot tests was in the range 4-17%. Up to 30% zinc removal was achieved from the bottom layer of the sinter bed. It can be concluded that zinc removal will be low during the processing of manganese furnace dust in the sinter plant. The zinc removal rate will be the highest when pelletised manganese furnace dust is added to the bottom layer of the sintering bed

Microstrength, strength and microstructure of carbonaceous materials

The effect of heat treatment at 700-1500 ºC on the mechanical strength, micro strength and pore structure of carbonaceous materials, including coke, char and coals, were studied using tensile test, ultra micro indentation and image analysis. Strength of chars and pyrolysed coals was strongly enhanced by heat treatment at temperature below 1100 °C; strength of cokes was slightly degraded after heat treatment at 1500 °C. Mechanical strength of carbonaceous materials was demonstrated to be significantly affected by micro strength and porosity. Micro strength of chars and coals was significantly enhanced by heat treatment, whereas micro strength of cokes was only marginally increased by heat treatment. The major growth in the micro strength of chars and coals took place at annealing temperature below 1100 °C. Porosity of chars and coals significantly increased during annealing at temperatures below 1100 °C. Further increasing annealing temperature from 1100-1500 °C caused marginal porosity evolution in pyrolysed coals and chars. Porosity of cokes increased slightly in the temperature range of 1300-1500 °C

Strength, micro-strength and microstructure of carbonaceous materials

© 2020 INFACON.All rights reserved. The effect of heat treatment at 700-1500°C on the mechanical strength, micro strength and pore structure of carbonaceous materials, including coke, char and coals, were studied using tensile test, ultra micro indentation and image analysis. Strength of chars and pyrolysed coals was strongly enhanced by heat treatment at temperature below 1100°C; strength of cokes was slightly degraded after heat treatment at 1500°C. Mechanical strength of carbonaceous materials was demonstrated to be significantly affected by micro strength and porosity. Micro strength of chars and coals was significantly enhanced by heat treatment, whereas micro strength of cokes was only marginally increased by heat treatment. The major growth in the micro strength of chars and coals took place at annealing temperature below 1100°C. Porosity of chars and coals significantly increased during annealing at temperatures below 1100°C. Further increasing annealing temperature from 1100-1500°C caused marginal porosity evolution in pyrolysed coals and chars. Porosity of cokes increased slightly in the temperature range of 1300-1500°C

Sintering pot test of manganese ore with addition of manganese furnace dust

Manganese furnace dust is formed from volatiles and fines collected during wet scrubbing of the off-gas from manganese alloy smelting furnaces. This dust, in the form of slurry, contains tar, alkalies, zinc, manganese oxide and other elements. Impediments to the recycling of the manganese furnace dust back to the ferroalloy furnaces are the potential accumulation of zinc and alkalies, which can cause irregularities in furnace operation, and handling. This paper examines the behaviour of zinc during sintering pot tests of manganese ore with addition of manganese furnace dust. Laboratory reduction experiments showed that at temperatures above 800°C zinc oxide was reduced by carbon in tar to zinc vapour. However, zinc removal in sintering pot tests was below 30%, which was attributed to reoxidation of the zinc vapour. Zinc removal was the highest from the bottom section of the sintering pot bed