Effect of Annealing on Properties of Carbonaceous Materials. Part II: Porosity and Pore Geometry
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MERGED electrical arc furnace is a major process in the industrial production of ferroalloys, in which metal oxides are reduced by carbonaceous materials. To reduce the production cost, a variety of carbonaceous materials are used including cokes, chars, and coals. As carbonaceous materials are the only solid materials in the lower region of the submerged electric arc furnace (coke bed zone), they are required to have good mechanical strength to insure good permeability of liquid and gas phases passing the burden. The mechanical strength of carbonaceous materials strongly depends on the pore structure.[1–4] The pore structure of carbonaceous materials has been intensively studied,[5–7] with a focus on its evolution during carbonization of coals. Hays et al.[5] examined its evolution during pyrolysis of coals. Tomeczek and Gil[6] studied its evolution in the high pressure pyrolysis process and observed that both porosity and volatile release XING XING, Postdoctoral Fellow, and OLEG OSTROVSKI, Professor, are with the School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052, Australia. Contact e-mail: [email protected] GUANGQING ZHANG, Lecturer, is with the School of Mechanical, Materials & Mechatronic Engineering, University of Wollongong, Wollongong, NSW 2522. MARK DELL’AMICO, Project Scientist, is with the CSIRO Energy Centre, 10 Murray Dwyer Circuit, Steel River Estate, Mayfield West, NSW 2304. GEORGE CIEZKI, Manager Production Planning & Smelting Manganese, is with the Tasmanian Electro Metallurgical Company, PO Box 164, George Town, TAS 7253, Australia. QINGBO MENG, Vice-President, is with the Sinosteel Anshan Research Institute of Thermo-Energy Co., Ltd., Anshan, Liaoning, China. Manuscript submitted February 14, 2013. Article published online April 30, 2013. 862—VOLUME 44B, AUGUST 2013
decreased with increasing pyrolysis pressure. Heating in a furnace strongly affects the pore structure of carbonaceous materials. However, only a few papers studied the effect of heat treatment on the pore structure of carbonaceous materials,[8,9] especially under the conditions of submerged electrical arc furnaces. Gomez-Serrano et al.[9] examined the effect of heat treatment in the temperature range of 623 K to 1123 K (350 °C to 850 °C) using gas absorption and found that total porosity and microporosity developed with increasing heat treatment temperature in the temperature range of 623 K to 1023 K (350 °C to 750 °C). At higher temperature, total porosity and microporosity reduced with further increase of temperature due to micropore narrowing and pore closing.[10] Senneca et al.[8] studied the effect of heat treatment on micropore volume using porosimetric analysis and found that the micropore volume of carbonaceous materials increased significantly after heat treatment at 1173 K (900 °C), followed by a significant decrease with further increase of temperature. The measurement of micropore volume with porosimetric analysis suffers from the limitations of some micropores being inaccessible for CO2
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