Kinetic Modeling of the Reaction Rate for Quartz and Carbon Black Pellet
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rg/10.1007/s11663-018-1203-1 The Minerals, Metals & Materials Society and ASM International 2018
I.
SiOðgÞ þ 2 CðsÞ ¼ SiCðsÞ þ COðgÞ
INTRODUCTION
REACTIONS in quartz and carbon pellets at high temperatures could be divided into two steps, the SiC-producing step and the SiO-producing step.[1,2] During the SiC-producing step, SiC is produced according to the Reaction [1]: SiO2 ðsÞ þ 3 CðsÞ ¼ SiCðsÞ þ 2 COðgÞ DH 1773Kð1500 CÞ ¼ 163:8 Wh=mol:
½1
It is believed that the overall reaction for the SiC-production step involves Reactions [2] and [3]. The solid-state Reaction [1] is processed using the gas intermediate of SiO. SiO2 ðsÞ þ CðsÞ ¼ SiOðsÞ þ COðgÞ DH1773Kð1500 CÞ ¼ 184:6 Wh=mol
½2
FEI LI and MERETE TANGSTAD are with the Department of Material Science and Engineering, Norwegian University of Science and Technology, 7491, Trondheim, Norway. Contact e-mail: [email protected] Manuscript submitted February 11, 2017.
METALLURGICAL AND MATERIALS TRANSACTIONS B
DH1773Kð1500 CÞ ¼ 20:8 Wh=mol:
½3
According to a previous kinetic study,[3] the reaction rate in quartz and carbon black pellets at temperatures ranging from 1848 K to 2273 K (1575 C to 2000 C) was determined by the transformation of carbon to SiC, implying that the generation of SiO(g) is fast within this temperature range. The activation energy of the reaction between quartz and carbon black was reported to be 382 kJ/mol and the particle size of carbon black in these experiments was 0.03 lm. Kuznetsova[4] studied two types of carbon black with a particle size of 0.187 and 0.385 lm, respectively. The activation energy of these two types of carbon black at temperatures ranging from 1773 K to 2073 K (1500 C to 1800 C) were 251 and 288 kJ/mol, respectively. Agarwal and Pad[5] studied the kinetics for the temperature range of 1723 K to 1873 K (1450 C to 1600 C) based on the gas-solid reaction theory. Parameters of temperature, particle size, and quartz/carbon ratio were studied. Wiik[6] studied the influence of the crucible design, and concluded that a larger opening on the crucible leads to a better mass transfer. In this study, the mathematical expression describing the reaction rate of the SiC-producing step based on the isothermal isoconversional method, which incorporates the model fitting method, will be determined. The different parameters of temperature, CO partial pressure in ambient, carbon content in the pellet, opening area of the crucible, and quartz particle size will be discussed.
II.
EXPERIMENTAL PROCEDURES AND MODELING INTERPRETATION
A. Procedures of Thermogravimetric Experiments Pellets of quartz (SiO2) and carbon black are used to study the carbothermal reduction of quartz. A series of experiments were conducted in a thermogravimetric furnace to investigate the influence of temperature [1898 K, 1923 K, and 1948 K (1625 C, 1650 C, and 1675 C)], CO partial pressure (0, 50, and 100 pct), carbon content in a mixed pellet (5, 10, 15, and 20 wt pct), and a carbon-deposited pellet (5, 11, and 20 wt pct), quartz particle
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